fix after rebase

grr heap usage!

.github/actions/code-sign/action.yml

@@ -0,0 +1,113 @@
+name: Code-sign Windows binaries
+description: >
+  Sign every .exe under a given path in place via the DefinedNet code-signer
+  Lambda. If `role` or `bucket` is empty, logs a notice and skips signing so
+  forks and dev branches without AWS access still produce usable builds.
+
+inputs:
+  path:
+    description: "Directory whose .exe files should be signed in place"
+    required: true
+  role:
+    description: "IAM role ARN to assume via OIDC; empty disables signing"
+    required: false
+    default: ""
+  bucket:
+    description: "S3 staging bucket the code-signer Lambda reads from; empty disables signing"
+    required: false
+    default: ""
+  region:
+    description: "AWS region for the role and Lambda"
+    required: false
+    default: "us-east-2"
+  function-name:
+    description: "Code-signer Lambda function name"
+    required: false
+    default: "code-signer"
+  key-prefix:
+    description: "S3 key prefix the caller is authorized to write under"
+    required: false
+    default: "code-signing/slackhq/nebula"
+
+runs:
+  using: composite
+  steps:
+    - name: Skip notice
+      if: inputs.role == '' || inputs.bucket == ''
+      shell: sh
+      run: echo "::notice::code-signer role or bucket not set; skipping code signing."
+
+    - name: Configure AWS credentials
+      if: inputs.role != '' && inputs.bucket != ''
+      uses: aws-actions/configure-aws-credentials@v6
+      with:
+        role-to-assume: ${{ inputs.role }}
+        aws-region: ${{ inputs.region }}
+        # Default is 12 retries to ride out IAM trust-policy propagation; once
+        # the role is stable we want a real misconfiguration to fail fast.
+        retry-max-attempts: 5
+
+    - name: Sign .exe files
+      if: inputs.role != '' && inputs.bucket != ''
+      shell: sh
+      env:
+        SIGN_PATH: ${{ inputs.path }}
+        BUCKET: ${{ inputs.bucket }}
+        FUNCTION_NAME: ${{ inputs.function-name }}
+        KEY_PREFIX: ${{ inputs.key-prefix }}
+      run: |
+        set -eu
+        RUN="${GITHUB_RUN_ID}-${GITHUB_RUN_ATTEMPT}"
+
+        find "$SIGN_PATH" -name '*.exe' -print | while read -r path
+        do
+            rel=${path#"$SIGN_PATH"/}
+            file=$(basename "$path")
+            name=${file%.exe}
+            prefix="${KEY_PREFIX}/${RUN}"
+            src="${prefix}/unsigned/${rel}"
+            dst="${prefix}/signed/${rel}"
+
+            echo "::group::Sign ${rel}"
+            echo "Uploading unsigned to s3://${BUCKET}/${src}"
+            aws s3 cp --no-progress "$path" "s3://${BUCKET}/${src}" >/dev/null
+
+            echo "Invoking ${FUNCTION_NAME} Lambda"
+            payload=$(jq -nc \
+                --arg s "$src" \
+                --arg d "$dst" \
+                --arg p "$name" \
+                '{source_key: $s, dest_key: $d, program_name: $p}')
+            meta=$(aws lambda invoke \
+                --function-name "$FUNCTION_NAME" \
+                --cli-binary-format raw-in-base64-out \
+                --payload "$payload" \
+                --output json \
+                /tmp/sign-resp.json)
+            if echo "$meta" | jq -e '.FunctionError != null' >/dev/null
+            then
+                echo "::endgroup::"
+                echo "::error::code-signer Lambda failed for ${rel}"
+                cat /tmp/sign-resp.json >&2
+                exit 1
+            fi
+
+            echo "Downloading signed back to ${path}"
+            aws s3 cp --no-progress "s3://${BUCKET}/${dst}" "$path" >/dev/null
+
+            aws s3 rm "s3://${BUCKET}/${src}" >/dev/null 2>&1 || true
+            aws s3 rm "s3://${BUCKET}/${dst}" >/dev/null 2>&1 || true
+
+            # Sanity-check the bytes we got back actually carry an Authenticode
+            # signature that this machine can validate end to end.
+            status=$(powershell -NoProfile -Command "(Get-AuthenticodeSignature -FilePath '$path').Status" | tr -d '\r')
+            if [ "$status" != "Valid" ]
+            then
+                echo "::endgroup::"
+                echo "::error::${rel} signature status: ${status} (expected Valid)"
+                exit 1
+            fi
+
+            echo "Signed ${rel} (sha256=$(jq -r '.sha256' /tmp/sign-resp.json), status=${status})"
+            echo "::endgroup::"
+        done

.github/workflows/release.yml

@@ -24,7 +24,7 @@ jobs:
           mv build/*.tar.gz release
 
       - name: Upload artifacts
-        uses: actions/upload-artifact@v6
+        uses: actions/upload-artifact@v7
         with:
           name: linux-latest
           path: release
@@ -32,6 +32,9 @@ jobs:
   build-windows:
     name: Build Windows
     runs-on: windows-latest
+    permissions:
+      id-token: write
+      contents: read
     steps:
       - uses: actions/checkout@v6
 
@@ -54,8 +57,15 @@ jobs:
           mkdir build\dist\windows
           mv dist\windows\wintun build\dist\windows\
 
+      - name: Code-sign
+        uses: ./.github/actions/code-sign
+        with:
+          path: build
+          role: ${{ secrets.DEFINED_CODE_SIGNER_ROLE }}
+          bucket: ${{ secrets.DEFINED_CODE_SIGNER_BUCKET }}
+
       - name: Upload artifacts
-        uses: actions/upload-artifact@v6
+        uses: actions/upload-artifact@v7
         with:
           name: windows-latest
           path: build
@@ -75,7 +85,7 @@ jobs:
 
       - name: Import certificates
         if: env.HAS_SIGNING_CREDS == 'true'
-        uses: Apple-Actions/import-codesign-certs@v6
+        uses: Apple-Actions/import-codesign-certs@v7
         with:
           p12-file-base64: ${{ secrets.APPLE_DEVELOPER_CERTIFICATE_P12_BASE64 }}
           p12-password: ${{ secrets.APPLE_DEVELOPER_CERTIFICATE_PASSWORD }}
@@ -104,7 +114,7 @@ jobs:
           fi
 
       - name: Upload artifacts
-        uses: actions/upload-artifact@v6
+        uses: actions/upload-artifact@v7
         with:
           name: darwin-latest
           path: ./release/*
@@ -128,21 +138,21 @@ jobs:
 
       - name: Download artifacts
         if: ${{ env.HAS_DOCKER_CREDS == 'true' }}
-        uses: actions/download-artifact@v7
+        uses: actions/download-artifact@v8
         with:
           name: linux-latest
           path: artifacts
 
       - name: Login to Docker Hub
         if: ${{ env.HAS_DOCKER_CREDS == 'true' }}
-        uses: docker/login-action@v3
+        uses: docker/login-action@v4
         with:
           username: ${{ vars.DOCKERHUB_USERNAME }}
           password: ${{ secrets.DOCKERHUB_TOKEN }}
 
       - name: Set up Docker Buildx
         if: ${{ env.HAS_DOCKER_CREDS == 'true' }}
-        uses: docker/setup-buildx-action@v3
+        uses: docker/setup-buildx-action@v4
 
       - name: Build and push images
         if: ${{ env.HAS_DOCKER_CREDS == 'true' }}
@@ -163,7 +173,7 @@ jobs:
       - uses: actions/checkout@v6
 
       - name: Download artifacts
-        uses: actions/download-artifact@v7
+        uses: actions/download-artifact@v8
         with:
           path: artifacts
 

.github/workflows/smoke-extra.yml

@@ -14,10 +14,18 @@ on:
       - 'go.sum'
 jobs:
 
-  smoke-extra:
+  smoke-extra-libvirt:
     if: github.ref == 'refs/heads/master' || contains(github.event.pull_request.labels.*.name, 'smoke-test-extra')
-    name: Run extra smoke tests
+    name: ${{ matrix.target }}
     runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        target:
+          - freebsd-amd64
+          - openbsd-amd64
+          - netbsd-amd64
+          - linux-amd64-ipv6disable
     env:
       VAGRANT_DEFAULT_PROVIDER: libvirt
     steps:
@@ -40,28 +48,85 @@ jobs:
         sudo chmod 666 /var/run/libvirt/libvirt-sock
         vagrant plugin install vagrant-libvirt
 
-    - name: freebsd-amd64
-      run: make smoke-vagrant/freebsd-amd64
+    - name: ${{ matrix.target }}
+      run: make smoke-vagrant/${{ matrix.target }}
 
-    - name: openbsd-amd64
-      run: make smoke-vagrant/openbsd-amd64
+    timeout-minutes: 30
 
-    - name: netbsd-amd64
-      run: make smoke-vagrant/netbsd-amd64
+  # linux-386 needs VirtualBox, which conflicts with KVM/libvirt -- isolated job.
+  smoke-extra-virtualbox:
+    if: github.ref == 'refs/heads/master' || contains(github.event.pull_request.labels.*.name, 'smoke-test-extra')
+    name: linux-386
+    runs-on: ubuntu-latest
+    env:
+      VAGRANT_DEFAULT_PROVIDER: virtualbox
+    steps:
 
-    - name: linux-amd64-ipv6disable
-      run: make smoke-vagrant/linux-amd64-ipv6disable
+    - uses: actions/checkout@v6
 
-    # linux-386 runs last because it requires disabling KVM to use VirtualBox,
-    # which prevents libvirt (used by the other tests) from working after this point.
-    - name: install virtualbox for i386 test
+    - uses: actions/setup-go@v6
+      with:
+        go-version: '1.25'
+        check-latest: true
+
+    - name: add hashicorp source
+      run: wget -O- https://apt.releases.hashicorp.com/gpg | gpg --dearmor | sudo tee /usr/share/keyrings/hashicorp-archive-keyring.gpg && echo "deb [signed-by=/usr/share/keyrings/hashicorp-archive-keyring.gpg] https://apt.releases.hashicorp.com $(lsb_release -cs) main" | sudo tee /etc/apt/sources.list.d/hashicorp.list
+
+    - name: install vagrant and virtualbox
       run: |
-        sudo apt-get install -y virtualbox
+        sudo apt-get update && sudo apt-get install -y vagrant virtualbox
         sudo rmmod kvm_amd kvm_intel kvm 2>/dev/null || true
 
     - name: linux-386
-      env:
-        VAGRANT_DEFAULT_PROVIDER: virtualbox
       run: make smoke-vagrant/linux-386
 
     timeout-minutes: 30
+
+  smoke-windows:
+    if: github.ref == 'refs/heads/master' || contains(github.event.pull_request.labels.*.name, 'smoke-test-extra')
+    name: Run windows smoke test
+    runs-on: windows-latest
+    steps:
+
+    - uses: actions/checkout@v6
+
+    - uses: actions/setup-go@v6
+      with:
+        go-version: '1.25'
+        check-latest: true
+
+    # WSL2 + Ubuntu so the smoke can run a real linux peer with its own
+    # netns. iputils-ping is needed for the in-WSL ping check. WSL1 has no
+    # real kernel and would lack /dev/net/tun, so we have to force WSL2.
+    - uses: Vampire/setup-wsl@v3
+      with:
+        distribution: Ubuntu-24.04
+        additional-packages: iputils-ping iproute2
+
+    # Vampire/setup-wsl provisions WSL1 even when the WSL2 platform is present.
+    # Convert the distro to WSL2 explicitly before we try to use /dev/net/tun.
+    - name: convert distro to WSL2
+      shell: pwsh
+      run: |
+        wsl --set-version Ubuntu-24.04 2
+        wsl --shutdown
+        wsl --list --verbose
+
+    - name: build windows nebula
+      run: make bin-windows
+
+    - name: build linux nebula for WSL
+      shell: bash
+      env:
+        GOOS: linux
+        GOARCH: amd64
+      run: |
+        mkdir -p build/linux-amd64
+        go build -o build/linux-amd64/nebula ./cmd/nebula
+
+    - name: run smoke-windows
+      shell: pwsh
+      working-directory: ./.github/workflows/smoke
+      run: ./smoke-windows.ps1
+
+    timeout-minutes: 15

.github/workflows/smoke/smoke-windows.ps1

@@ -0,0 +1,272 @@
+#!/usr/bin/env pwsh
+# Windows smoke test for the nebula tun + UDP + NLM code paths.
+#
+# Topology:
+#   - lighthouse runs natively on the Windows host (wintun + windows UDP)
+#   - peer runs inside WSL2 (Linux build of nebula, /dev/net/tun)
+#
+# WSL2 gives us a real netns boundary so the loopback fast-path on Windows
+# does not short-circuit the overlay -- when WSL pings the lighthouse VPN IP,
+# Linux has no idea that IP is local to the Windows host, so the packet is
+# forced through nebula. Same in reverse.
+
+$ErrorActionPreference = 'Stop'
+
+# wsl.exe emits UTF-16 LE by default which PowerShell reads as bytes, mangling
+# every captured string. WSL_UTF8 makes wsl.exe emit UTF-8 instead.
+$env:WSL_UTF8 = '1'
+
+$RepoRoot = Resolve-Path "$PSScriptRoot\..\..\.."
+$Nebula = Join-Path $RepoRoot 'nebula.exe'
+$NebulaCert = Join-Path $RepoRoot 'nebula-cert.exe'
+$NebulaLinux = Join-Path $RepoRoot 'build\linux-amd64\nebula'
+
+if (-not (Test-Path $Nebula)) { throw "missing $Nebula; run 'make bin-windows' first" }
+if (-not (Test-Path $NebulaCert)) { throw "missing $NebulaCert; run 'make bin-windows' first" }
+if (-not (Test-Path $NebulaLinux)) { throw "missing $NebulaLinux; build the linux nebula first" }
+
+# Matches the distro installed by Vampire/setup-wsl in smoke-extra.yml.
+$Distro = 'Ubuntu-24.04'
+$listed = (wsl --list --quiet 2>$null) -join "`n"
+if ($listed -notmatch [regex]::Escape($Distro)) {
+    throw "WSL distro $Distro not registered. Got: $listed"
+}
+Write-Host "Using WSL distro: $Distro"
+
+# Windows host as seen from inside WSL: WSL's default-route gateway. We extract
+# it with a regex rather than awk fields so PowerShell does not eat any '$N'
+# tokens, and tabs/double-spaces in `ip route` output do not confuse a cut.
+$ipCmd = 'ip route show default | grep -oE "([0-9]+\.){3}[0-9]+" | head -1'
+$WindowsIp = (wsl -d $Distro -- bash -c $ipCmd).Trim()
+if (-not $WindowsIp) { throw "could not determine Windows host IP from WSL" }
+Write-Host "Windows host IP from WSL: $WindowsIp"
+
+$WorkDir = Join-Path $env:TEMP 'nebula-smoke-windows'
+if (Test-Path $WorkDir) { Remove-Item -Recurse -Force $WorkDir }
+New-Item -ItemType Directory -Path $WorkDir | Out-Null
+
+$WslDir = '/tmp/nebula-smoke'
+wsl -d $Distro -- bash -c "rm -rf $WslDir && mkdir -p $WslDir" | Out-Null
+
+$DevName = 'nebula-smoke'
+$Ip1 = '192.168.241.1'
+$Ip2 = '192.168.241.2'
+$Port = 4242
+
+& $NebulaCert ca -name 'smoke-ca' -out-crt "$WorkDir\ca.crt" -out-key "$WorkDir\ca.key"
+if ($LASTEXITCODE -ne 0) { throw "nebula-cert ca failed (exit $LASTEXITCODE)" }
+
+& $NebulaCert sign -name 'lighthouse' -networks "$Ip1/24" -ca-crt "$WorkDir\ca.crt" -ca-key "$WorkDir\ca.key" -out-crt "$WorkDir\lighthouse.crt" -out-key "$WorkDir\lighthouse.key"
+if ($LASTEXITCODE -ne 0) { throw "nebula-cert sign lighthouse failed (exit $LASTEXITCODE)" }
+
+& $NebulaCert sign -name 'peer' -networks "$Ip2/24" -ca-crt "$WorkDir\ca.crt" -ca-key "$WorkDir\ca.key" -out-crt "$WorkDir\peer.crt" -out-key "$WorkDir\peer.key"
+if ($LASTEXITCODE -ne 0) { throw "nebula-cert sign peer failed (exit $LASTEXITCODE)" }
+
+# Windows lighthouse config.
+@"
+pki:
+  ca: $WorkDir\ca.crt
+  cert: $WorkDir\lighthouse.crt
+  key: $WorkDir\lighthouse.key
+static_host_map: {}
+lighthouse:
+  am_lighthouse: true
+  interval: 60
+  hosts: []
+listen:
+  host: 0.0.0.0
+  port: $Port
+tun:
+  disabled: false
+  dev: $DevName
+  drop_local_broadcast: false
+  drop_multicast: false
+  tx_queue: 500
+  mtu: 1300
+  network_category: private
+logging:
+  level: info
+  format: text
+firewall:
+  outbound_action: drop
+  inbound_action: drop
+  conntrack:
+    tcp_timeout: 12m
+    udp_timeout: 3m
+    default_timeout: 10m
+  outbound:
+    - port: any
+      proto: any
+      host: any
+  inbound:
+    - port: any
+      proto: any
+      host: any
+"@ | Out-File -FilePath "$WorkDir\lighthouse.yml" -Encoding utf8
+
+# WSL peer config (paths are POSIX, deliberately).
+@"
+pki:
+  ca: $WslDir/ca.crt
+  cert: $WslDir/peer.crt
+  key: $WslDir/peer.key
+static_host_map:
+  "${Ip1}": ["${WindowsIp}:$Port"]
+lighthouse:
+  am_lighthouse: false
+  interval: 60
+  hosts:
+    - "${Ip1}"
+listen:
+  host: 0.0.0.0
+  port: 0
+tun:
+  disabled: false
+  dev: nebula1
+  drop_local_broadcast: false
+  drop_multicast: false
+  tx_queue: 500
+  mtu: 1300
+logging:
+  level: info
+  format: text
+firewall:
+  outbound_action: drop
+  inbound_action: drop
+  conntrack:
+    tcp_timeout: 12m
+    udp_timeout: 3m
+    default_timeout: 10m
+  outbound:
+    - port: any
+      proto: any
+      host: any
+  inbound:
+    - port: any
+      proto: any
+      host: any
+"@ | Out-File -FilePath "$WorkDir\peer.yml" -Encoding utf8
+
+# Stage WSL artifacts. Convert Windows paths to WSL paths ourselves rather than
+# calling `wslpath`, because PowerShell's argument-passing to external EXEs
+# strips backslashes from path arguments in ways that are hard to escape around.
+function ConvertTo-WslPath {
+    param([string]$WindowsPath)
+    if ($WindowsPath -notmatch '^([A-Za-z]):\\(.*)$') {
+        throw "cannot convert path to WSL: $WindowsPath"
+    }
+    return "/mnt/$($matches[1].ToLower())/$($matches[2].Replace('\','/'))"
+}
+
+$WslWorkDir = ConvertTo-WslPath $WorkDir
+$WslNebulaPath = ConvertTo-WslPath $NebulaLinux
+wsl -d $Distro -- bash -c "cp '$WslWorkDir/ca.crt' '$WslWorkDir/peer.crt' '$WslWorkDir/peer.key' '$WslWorkDir/peer.yml' $WslDir/ && cp '$WslNebulaPath' $WslDir/nebula && chmod +x $WslDir/nebula"
+
+# Make sure WSL has tun support and /dev/net/tun is usable before starting
+# nebula. Diagnostics first so a fail here points at the real problem (e.g.
+# WSL1 distros do not have a real kernel and will not have tun).
+Write-Host '=== WSL diagnostic ==='
+wsl --version 2>&1 | Out-Host
+wsl --list --verbose 2>&1 | Out-Host
+wsl -d $Distro -u root -- uname -a | Out-Host
+wsl -d $Distro -u root -- bash -c "modprobe tun 2>&1 || true; mkdir -p /dev/net; [ -c /dev/net/tun ] || mknod /dev/net/tun c 10 200; chmod 600 /dev/net/tun; ls -l /dev/net/tun"
+if ($LASTEXITCODE -ne 0) { throw "failed to prepare /dev/net/tun in WSL (TUN support missing?)" }
+
+# Deliberately no New-NetFirewallRule calls here -- nebula's windows_bypass_wdf
+# feature is supposed to install WFP permit filters that let inbound traffic
+# through Windows Defender Firewall on its own. If this smoke regresses, that
+# feature regressed.
+
+$lhOut = Join-Path $WorkDir 'lighthouse.out.log'
+$lhErr = Join-Path $WorkDir 'lighthouse.err.log'
+$lhProc = Start-Process -FilePath $Nebula -ArgumentList @('-config', "$WorkDir\lighthouse.yml") `
+    -PassThru -NoNewWindow `
+    -RedirectStandardOutput $lhOut `
+    -RedirectStandardError $lhErr
+
+# Run nebula in WSL as root with no sudo + no shell wrapper. PowerShell's
+# Start-Process arg quoting mangles `bash -c "..."` strings that contain
+# spaces/redirections, so we skip bash entirely and let Start-Process do the
+# stdout/stderr capture itself.
+$peerOut = Join-Path $WorkDir 'peer.out.log'
+$peerErr = Join-Path $WorkDir 'peer.err.log'
+$peerProc = Start-Process -FilePath 'wsl' `
+    -ArgumentList @('-d', $Distro, '-u', 'root', '--', "$WslDir/nebula", '-config', "$WslDir/peer.yml") `
+    -PassThru -NoNewWindow `
+    -RedirectStandardOutput $peerOut `
+    -RedirectStandardError $peerErr
+
+function Wait-Until {
+    param([scriptblock]$Predicate, [int]$TimeoutSec, [string]$What)
+    $deadline = (Get-Date).AddSeconds($TimeoutSec)
+    while ((Get-Date) -lt $deadline) {
+        if (& $Predicate) { return }
+        Start-Sleep -Milliseconds 500
+    }
+    throw "timed out waiting for: $What"
+}
+
+try {
+    Wait-Until -TimeoutSec 30 -What "windows wintun adapter $DevName with NetworkCategory=Private" -Predicate {
+        if ($lhProc.HasExited) { throw "lighthouse exited (code $($lhProc.ExitCode)) before tun was ready" }
+        $p = Get-NetConnectionProfile -InterfaceAlias $DevName -ErrorAction SilentlyContinue
+        $p -and ("$($p.NetworkCategory)" -ieq 'Private')
+    }
+    Write-Host "OK: $DevName NetworkCategory=Private"
+
+    Wait-Until -TimeoutSec 30 -What "WSL nebula1 with $Ip2" -Predicate {
+        if ($peerProc.HasExited) { throw "peer exited (code $($peerProc.ExitCode)) before tun was ready" }
+        $r = wsl -d $Distro -u root -- bash -c "ip -o addr show nebula1 2>/dev/null | grep -q 'inet $Ip2' && echo yes"
+        ("$r").Trim() -eq 'yes'
+    }
+    Write-Host "OK: WSL nebula1 has $Ip2"
+
+    Wait-Until -TimeoutSec 30 -What "ping from WSL peer to windows lighthouse ($Ip1)" -Predicate {
+        if ($peerProc.HasExited) { throw "peer exited (code $($peerProc.ExitCode)) before ping succeeded" }
+        $r = wsl -d $Distro -u root -- bash -c "ping -c1 -W1 $Ip1 >/dev/null 2>&1 && echo OK"
+        ("$r").Trim() -eq 'OK'
+    }
+    Write-Host "OK: WSL peer -> windows lighthouse"
+
+    Wait-Until -TimeoutSec 30 -What "ping from windows lighthouse to WSL peer ($Ip2)" -Predicate {
+        $null = & ping.exe -n 1 -w 1000 $Ip2
+        $LASTEXITCODE -eq 0
+    }
+    Write-Host "OK: windows lighthouse -> WSL peer"
+
+    Write-Host ''
+    Write-Host 'All smoke checks passed.'
+}
+catch {
+    Write-Host ''
+    Write-Host '=== lighthouse stdout ==='
+    Get-Content $lhOut -ErrorAction SilentlyContinue | Out-Host
+    Write-Host '=== lighthouse stderr ==='
+    Get-Content $lhErr -ErrorAction SilentlyContinue | Out-Host
+    Write-Host '=== peer stdout ==='
+    Get-Content $peerOut -ErrorAction SilentlyContinue | Out-Host
+    Write-Host '=== peer stderr ==='
+    Get-Content $peerErr -ErrorAction SilentlyContinue | Out-Host
+    Write-Host '=== nebula WFP filters ==='
+    # Dump nebula-installed filters so we can verify they got registered with
+    # the conditions we expect.
+    $wfpDump = Join-Path $WorkDir 'wfp.xml'
+    netsh wfp show filters file=$wfpDump 2>&1 | Out-Null
+    if (Test-Path $wfpDump) {
+        Select-String -Path $wfpDump -Pattern 'Nebula' -Context 0,80 -ErrorAction SilentlyContinue | Out-Host
+    }
+    throw
+}
+finally {
+    if (-not $lhProc.HasExited) {
+        Stop-Process -Id $lhProc.Id -Force -ErrorAction SilentlyContinue
+        $lhProc.WaitForExit(5000) | Out-Null
+    }
+    wsl -d $Distro -u root -- bash -c "pkill -f $WslDir/nebula 2>/dev/null; true" | Out-Null
+    # pkill returns 1 when no match and wsl propagates that; the smoke is done
+    # so we don't want it to leak into the script's exit code.
+    $global:LASTEXITCODE = 0
+    if ($peerProc -and -not $peerProc.HasExited) {
+        Stop-Process -Id $peerProc.Id -Force -ErrorAction SilentlyContinue
+    }
+}

.github/workflows/smoke/smoke.sh

@@ -82,7 +82,7 @@ docker exec host4 tcpdump -i eth0 -q -w - -U 2>logs/host4.outside.log >logs/host
 
 docker exec host2 ncat -nklv 0.0.0.0 2000 &
 docker exec host3 ncat -nklv 0.0.0.0 2000 &
-docker exec host4 ncat -nkluv 0.0.0.0 4000 &
+docker exec host4 ncat -e '/usr/bin/echo helloagainfromhost4' -nkluv 0.0.0.0 4000 &
 docker exec host2 ncat -e '/usr/bin/echo host2' -nkluv 0.0.0.0 3000 &
 docker exec host3 ncat -e '/usr/bin/echo host3' -nkluv 0.0.0.0 3000 &
 
@@ -155,11 +155,11 @@ echo " *** Testing conntrack"
 echo
 set -x
 
-# host2 speaking to host4 on UDP 4000 should allow it to reply, when firewall rules would normally not permit this
-docker exec host2 sh -c "/usr/bin/echo host2 | ncat -nuv 192.168.100.4 4000"
-docker exec host2 ncat -e '/usr/bin/echo helloagainfromhost2' -nkluv 0.0.0.0 4000 &
-sleep 1
-docker exec host4 sh -c "/usr/bin/echo host4 | ncat -nuv 192.168.100.2 4000"
+# host4's outbound firewall only allows ICMP to the lighthouse, so host4
+# cannot initiate UDP to host2. Once host2 initiates a flow to host4:4000,
+# conntrack must let host4's listener reply on that flow. If it doesn't,
+# the echo back from host4 never reaches host2.
+docker exec host2 sh -c "(/usr/bin/echo host2; sleep 2) | ncat -nuv 192.168.100.4 4000" | grep -q helloagainfromhost4
 
 docker exec host4 sh -c 'kill 1'
 docker exec host3 sh -c 'kill 1'

.github/workflows/smoke/vagrant-netbsd-amd64/Vagrantfile

@@ -1,7 +1,7 @@
 # -*- mode: ruby -*-
 # vi: set ft=ruby :
 Vagrant.configure("2") do |config|
-  config.vm.box = "generic/netbsd9"
+  config.vm.box = "DefinedNet/netbsd10"
 
   config.vm.synced_folder "../build", "/nebula", type: "rsync"
 end

.github/workflows/test.yml

@@ -45,7 +45,7 @@ jobs:
     - name: Build test mobile
       run: make build-test-mobile
 
-    - uses: actions/upload-artifact@v6
+    - uses: actions/upload-artifact@v7
       with:
         name: e2e packet flow linux-latest
         path: e2e/mermaid/linux-latest
@@ -125,7 +125,7 @@ jobs:
     - name: End 2 end
       run: make e2evv
 
-    - uses: actions/upload-artifact@v6
+    - uses: actions/upload-artifact@v7
       with:
         name: e2e packet flow ${{ matrix.os }}
         path: e2e/mermaid/${{ matrix.os }}

.golangci.yaml

@@ -2,7 +2,21 @@ version: "2"
 linters:
   default: none
   enable:
+    - sloglint
     - testifylint
+  settings:
+    sloglint:
+      # Enforce key-value pair form for Info/Debug/Warn/Error/Log/With and
+      # the package-level slog equivalents. Use l.Log(ctx, level, ...) for
+      # custom levels instead of LogAttrs when you can.
+      #
+      # LogAttrs is also flagged by this rule because it takes ...slog.Attr;
+      # the few legitimate sites (where attrs is built up as a []slog.Attr)
+      # carry a //nolint:sloglint with rationale.
+      kv-only: true
+      # no-mixed-args is on by default: forbids mixing kv and attrs in one call.
+      # discard-handler is on by default (since Go 1.24): suggests
+      # slog.DiscardHandler over slog.NewTextHandler(io.Discard, nil).
   exclusions:
     generated: lax
     presets:

batch.go

@@ -1,70 +0,0 @@
-package nebula
-
-import "net/netip"
-
-// sendBatchCap is the maximum number of encrypted packets accumulated before a
-// flush is forced. TSO superpackets segment to at most ~45 packets on
-// reasonable MTUs, so 128 leaves headroom without bloating the backing
-// allocation.
-const sendBatchCap = 128
-
-// sendBatch accumulates encrypted UDP packets for a single sendmmsg flush.
-// One sendBatch is owned by each listenIn goroutine; no locking is needed.
-// The backing storage holds up to batchCap packets of slotCap bytes each;
-// bufs and dsts are parallel slices of committed slots.
-type sendBatch struct {
-	bufs     [][]byte
-	dsts     []netip.AddrPort
-	backing  []byte
-	slotCap  int
-	batchCap int
-	nextSlot int
-}
-
-func newSendBatch(batchCap, slotCap int) *sendBatch {
-	return &sendBatch{
-		bufs:     make([][]byte, 0, batchCap),
-		dsts:     make([]netip.AddrPort, 0, batchCap),
-		backing:  make([]byte, batchCap*slotCap),
-		slotCap:  slotCap,
-		batchCap: batchCap,
-	}
-}
-
-// Next returns a zero-length slice with slotCap capacity over the next unused
-// slot's backing bytes. The caller writes into the returned slice and then
-// calls Commit with the final length and destination. Next returns nil when
-// the batch is full.
-func (b *sendBatch) Next() []byte {
-	if b.nextSlot >= b.batchCap {
-		return nil
-	}
-	start := b.nextSlot * b.slotCap
-	return b.backing[start : start : start+b.slotCap]
-}
-
-// Commit records the slot just returned by Next as a packet of length n
-// destined for dst.
-func (b *sendBatch) Commit(n int, dst netip.AddrPort) {
-	start := b.nextSlot * b.slotCap
-	b.bufs = append(b.bufs, b.backing[start:start+n])
-	b.dsts = append(b.dsts, dst)
-	b.nextSlot++
-}
-
-// Reset clears committed slots; backing storage is retained for reuse.
-func (b *sendBatch) Reset() {
-	b.bufs = b.bufs[:0]
-	b.dsts = b.dsts[:0]
-	b.nextSlot = 0
-}
-
-// Len returns the number of committed packets.
-func (b *sendBatch) Len() int {
-	return len(b.bufs)
-}
-
-// Cap returns the maximum number of slots in the batch.
-func (b *sendBatch) Cap() int {
-	return b.batchCap
-}

batch_test.go

@@ -1,137 +0,0 @@
-package nebula
-
-import (
-	"net/netip"
-	"testing"
-)
-
-func TestSendBatchBookkeeping(t *testing.T) {
-	b := newSendBatch(4, 32)
-	if b.Len() != 0 || b.Cap() != 4 {
-		t.Fatalf("fresh batch: len=%d cap=%d", b.Len(), b.Cap())
-	}
-
-	ap := netip.MustParseAddrPort("10.0.0.1:4242")
-	for i := 0; i < 4; i++ {
-		slot := b.Next()
-		if slot == nil {
-			t.Fatalf("slot %d: Next returned nil before cap", i)
-		}
-		if cap(slot) != 32 || len(slot) != 0 {
-			t.Fatalf("slot %d: got len=%d cap=%d want len=0 cap=32", i, len(slot), cap(slot))
-		}
-		// Write a marker byte.
-		slot = append(slot, byte(i), byte(i+1), byte(i+2))
-		b.Commit(len(slot), ap)
-	}
-	if b.Next() != nil {
-		t.Fatalf("Next should return nil when full")
-	}
-	if b.Len() != 4 {
-		t.Fatalf("Len=%d want 4", b.Len())
-	}
-	for i, buf := range b.bufs {
-		if len(buf) != 3 || buf[0] != byte(i) {
-			t.Errorf("buf %d: %x", i, buf)
-		}
-		if b.dsts[i] != ap {
-			t.Errorf("dst %d: got %v want %v", i, b.dsts[i], ap)
-		}
-	}
-
-	// Reset returns empty and Next works again.
-	b.Reset()
-	if b.Len() != 0 {
-		t.Fatalf("after Reset Len=%d want 0", b.Len())
-	}
-	slot := b.Next()
-	if slot == nil || cap(slot) != 32 {
-		t.Fatalf("after Reset Next nil or wrong cap: %v cap=%d", slot == nil, cap(slot))
-	}
-}
-
-func TestBatchSegmentable(t *testing.T) {
-	ap := netip.MustParseAddrPort("10.0.0.1:4242")
-	other := netip.MustParseAddrPort("10.0.0.2:4242")
-
-	mk := func(addrs []netip.AddrPort, sizes []int) *sendBatch {
-		b := newSendBatch(len(addrs), 64)
-		for i, a := range addrs {
-			s := b.Next()
-			for j := 0; j < sizes[i]; j++ {
-				s = append(s, byte(j))
-			}
-			b.Commit(len(s), a)
-		}
-		return b
-	}
-
-	t.Run("uniform same dst", func(t *testing.T) {
-		b := mk([]netip.AddrPort{ap, ap, ap}, []int{10, 10, 10})
-		seg, ok := batchSegmentable(b)
-		if !ok || seg != 10 {
-			t.Fatalf("got seg=%d ok=%v", seg, ok)
-		}
-	})
-
-	t.Run("last segment short ok", func(t *testing.T) {
-		b := mk([]netip.AddrPort{ap, ap, ap}, []int{10, 10, 4})
-		seg, ok := batchSegmentable(b)
-		if !ok || seg != 10 {
-			t.Fatalf("got seg=%d ok=%v", seg, ok)
-		}
-	})
-
-	t.Run("mixed dst rejected", func(t *testing.T) {
-		b := mk([]netip.AddrPort{ap, other, ap}, []int{10, 10, 10})
-		if _, ok := batchSegmentable(b); ok {
-			t.Fatalf("expected rejection for mixed dst")
-		}
-	})
-
-	t.Run("mid-batch short rejected", func(t *testing.T) {
-		b := mk([]netip.AddrPort{ap, ap, ap}, []int{10, 4, 10})
-		if _, ok := batchSegmentable(b); ok {
-			t.Fatalf("expected rejection for short mid-batch")
-		}
-	})
-
-	t.Run("mid-batch longer rejected", func(t *testing.T) {
-		b := mk([]netip.AddrPort{ap, ap, ap}, []int{10, 11, 10})
-		if _, ok := batchSegmentable(b); ok {
-			t.Fatalf("expected rejection for longer mid-batch")
-		}
-	})
-
-	t.Run("last longer rejected", func(t *testing.T) {
-		b := mk([]netip.AddrPort{ap, ap, ap}, []int{10, 10, 11})
-		if _, ok := batchSegmentable(b); ok {
-			t.Fatalf("expected rejection for longer last segment")
-		}
-	})
-
-	t.Run("first zero rejected", func(t *testing.T) {
-		b := mk([]netip.AddrPort{ap, ap}, []int{0, 10})
-		if _, ok := batchSegmentable(b); ok {
-			t.Fatalf("expected rejection for zero first")
-		}
-	})
-}
-
-func TestSendBatchSlotsDoNotOverlap(t *testing.T) {
-	b := newSendBatch(3, 8)
-	ap := netip.MustParseAddrPort("10.0.0.1:80")
-
-	// Fill three slots, each with its own sentinel byte.
-	for i := 0; i < 3; i++ {
-		s := b.Next()
-		s = append(s, byte(0xA0+i), byte(0xB0+i))
-		b.Commit(len(s), ap)
-	}
-
-	for i, buf := range b.bufs {
-		if buf[0] != byte(0xA0+i) || buf[1] != byte(0xB0+i) {
-			t.Errorf("slot %d corrupted: %x", i, buf)
-		}
-	}
-}

bits.go

@@ -1,23 +1,43 @@
 package nebula
 
 import (
+	"context"
+	"fmt"
+	"log/slog"
+	"math"
+	mathbits "math/bits"
+
 	"github.com/rcrowley/go-metrics"
-	"github.com/sirupsen/logrus"
 )
 
+const bitsPerWord = 64
+
+// Bits is a sliding-window anti-replay tracker. The window is stored as a
+// circular bitmap packed into uint64 words (8x denser than a []bool), so a
+// length-N window costs N/8 bytes. length must be a power of two.
 type Bits struct {
 	length             uint64
+	lengthMask         uint64
 	current            uint64
-	bits               []bool
+	bits               []uint64
 	lostCounter        metrics.Counter
 	dupeCounter        metrics.Counter
 	outOfWindowCounter metrics.Counter
 }
 
-func NewBits(bits uint64) *Bits {
+func NewBits(length uint64) *Bits {
+	if length == 0 || length&(length-1) != 0 {
+		panic(fmt.Sprintf("Bits length must be a power of two, got %d", length))
+	}
+
+	nWords := length / bitsPerWord
+	if nWords == 0 {
+		nWords = 1
+	}
 	b := &Bits{
-		length:             bits,
-		bits:               make([]bool, bits, bits),
+		length:             length,
+		lengthMask:         length - 1,
+		bits:               make([]uint64, nWords),
 		current:            0,
 		lostCounter:        metrics.GetOrRegisterCounter("network.packets.lost", nil),
 		dupeCounter:        metrics.GetOrRegisterCounter("network.packets.duplicate", nil),
@@ -25,88 +45,219 @@ func NewBits(bits uint64) *Bits {
 	}
 
 	// There is no counter value 0, mark it to avoid counting a lost packet later.
-	b.bits[0] = true
-	b.current = 0
+	b.bits[0] = 1
 	return b
 }
 
-func (b *Bits) Check(l *logrus.Logger, i uint64) bool {
+func (b *Bits) get(i uint64) bool {
+	pos := i & b.lengthMask
+	//bit-shifting by 6 because i is a bit index, not a u64 index, and we need to find the u64 without bit in it
+	return b.bits[pos>>6]&(uint64(1)<<(pos&63)) != 0
+}
+
+func (b *Bits) set(i uint64) {
+	pos := i & b.lengthMask
+	b.bits[pos>>6] |= uint64(1) << (pos & 63)
+}
+
+// clearRange clears `count` bits starting at circular position `startPos`
+// (already masked to [0, length)) and returns how many of them were set
+// before the clear. count must be in [1, length].
+func (b *Bits) clearRange(startPos, count uint64) uint64 {
+	wasSet := uint64(0)
+	if count >= b.length {
+		for _, w := range b.bits {
+			wasSet += uint64(mathbits.OnesCount64(w))
+		}
+		clear(b.bits)
+		return wasSet
+	}
+
+	pos := startPos
+	remaining := count
+
+	// handle the potential partial word before pos becomes u64 aligned
+	word := pos >> 6
+	bit := pos & 63
+	take := uint64(64) - bit
+	if take > remaining {
+		take = remaining
+	}
+	if take > b.length-pos {
+		take = b.length - pos
+	}
+	var mask uint64
+	if take == 64 {
+		mask = math.MaxUint64
+	} else {
+		mask = ((uint64(1) << take) - 1) << bit
+	}
+	wasSet += uint64(mathbits.OnesCount64(b.bits[word] & mask))
+	b.bits[word] &^= mask
+	remaining -= take
+	pos = (pos + take) & b.lengthMask
+
+	// Clear whole words, keeping track of the number of set bits
+	for remaining >= 64 {
+		word = pos >> 6
+		wasSet += uint64(mathbits.OnesCount64(b.bits[word]))
+		b.bits[word] = 0
+		remaining -= 64
+		pos = (pos + 64) & b.lengthMask
+	}
+
+	// Clear the remaining partial word
+	if remaining > 0 {
+		word = pos >> 6
+		mask = (uint64(1) << remaining) - 1
+		wasSet += uint64(mathbits.OnesCount64(b.bits[word] & mask))
+		b.bits[word] &^= mask
+	}
+
+	return wasSet
+}
+
+func (b *Bits) strictlyWithinWindow(i uint64) bool {
+	// Handle the case where the window hasn't slid yet. This avoids u64 underflow.
+	inWarmup := b.current < b.length
+	if i < b.length && inWarmup {
+		return true
+	}
+
+	// Next, if the packet is in-window, see if we've seen it before
+	if i > b.current-b.length {
+		return true
+	}
+	return false //not within window!
+}
+
+// Check returns true if i is within (or way out in front of) the window, and not a replay
+func (b *Bits) Check(l *slog.Logger, i uint64) bool {
 	// If i is the next number, return true.
 	if i > b.current {
 		return true
 	}
 
-	// If i is within the window, check if it's been set already.
-	if i > b.current-b.length || i < b.length && b.current < b.length {
-		return !b.bits[i%b.length]
+	if b.strictlyWithinWindow(i) {
+		return !b.get(i)
 	}
 
 	// Not within the window
-	if l.Level >= logrus.DebugLevel {
-		l.Debugf("rejected a packet (top) %d %d\n", b.current, i)
+	if l.Enabled(context.Background(), slog.LevelDebug) {
+		l.Debug("rejected a packet (top)", "current", b.current, "incoming", i)
 	}
 	return false
 }
 
-func (b *Bits) Update(l *logrus.Logger, i uint64) bool {
-	// If i is the next number, return true and update current.
+// Update has three branches:
+//   - i == b.current+1: fast path; advance the cursor by one and lose-count
+//     the slot we just stomped (only past warmup; see the i > b.length guard
+//     below).
+//   - i  >  b.current+1: jump path; clear all slots between current and i
+//     (or up to a full window's worth, whichever is smaller) via clearRange,
+//     then mark i. Two arms here: a warmup arm that handles the very first
+//     window before the cursor has slid, and a steady-state arm that treats
+//     every cleared empty slot as a lost packet.
+//   - i  <= b.current: in-window check for duplicates; out-of-window otherwise.
+//
+// NewBits seeds bits[0]=1 so counter 0 looks "received" — Update never
+// clears that marker during warmup (clearRange skips position 0 when
+// startPos=1), and once b.current >= b.length the marker is no longer
+// consulted. The marker prevents a fictitious "lost" hit on the first real
+// counter.
+func (b *Bits) Update(l *slog.Logger, i uint64) bool {
+	// Fast path: i is the next expected counter. Split out so the function
+	// stays small and avoids paying for the slow paths' slog argument-build
+	// stack frame on every call. The bit read/test/write is inlined to
+	// touch the backing word once.
 	if i == b.current+1 {
-		// Check if the oldest bit was lost since we are shifting the window by 1 and occupying it with this counter
-		// The very first window can only be tracked as lost once we are on the 2nd window or greater
-		if b.bits[i%b.length] == false && i > b.length {
+		pos := i & b.lengthMask
+		word := pos >> 6
+		mask := uint64(1) << (pos & 63)
+		w := b.bits[word]
+		if i > b.length && w&mask == 0 {
 			b.lostCounter.Inc(1)
 		}
-		b.bits[i%b.length] = true
+		b.bits[word] = w | mask
 		b.current = i
 		return true
 	}
+	return b.updateSlow(l, i)
+}
 
+// updateSlow handles jumps, in-window backfill, dupes, and out-of-window.
+func (b *Bits) updateSlow(l *slog.Logger, i uint64) bool {
 	// If i is a jump, adjust the window, record lost, update current, and return true
 	if i > b.current {
-		lost := int64(0)
-		// Zero out the bits between the current and the new counter value, limited by the window size,
-		// since the window is shifting
-		for n := b.current + 1; n <= min(i, b.current+b.length); n++ {
-			if b.bits[n%b.length] == false && n > b.length {
-				lost++
+		end := i
+		if end > b.current+b.length {
+			end = b.current + b.length
+		}
+		count := end - b.current
+		startPos := (b.current + 1) & b.lengthMask
+
+		var lost int64
+		if b.current >= b.length {
+			// Steady state: every cleared slot is past warmup, so any unset
+			// bit we evict is a lost packet from the previous cycle.
+			wasSet := b.clearRange(startPos, count)
+			lost = int64(count) - int64(wasSet)
+		} else {
+			// Warmup (the very first window). Some cleared slots represent
+			// packets <= length where eviction is not "lost" in the usual
+			// sense. This branch is taken at most once per connection so we
+			// don't bother optimizing it.
+			for n := b.current + 1; n <= end; n++ {
+				if !b.get(n) && n > b.length {
+					lost++
+				}
 			}
-			b.bits[n%b.length] = false
+			b.clearRange(startPos, count)
 		}
 
-		// Only record any skipped packets as a result of the window moving further than the window length
-		// Any loss within the new window will be accounted for in future calls
-		lost += max(0, int64(i-b.current-b.length))
+		// Anything past the new window can never be backfilled, so it's lost.
+		if i > b.current+b.length {
+			lost += int64(i - b.current - b.length)
+		}
 		b.lostCounter.Inc(lost)
 
-		b.bits[i%b.length] = true
+		b.set(i)
 		b.current = i
 		return true
 	}
 
-	// If i is within the current window but below the current counter,
-	// Check to see if it's a duplicate
-	if i > b.current-b.length || i < b.length && b.current < b.length {
-		if b.current == i || b.bits[i%b.length] == true {
-			if l.Level >= logrus.DebugLevel {
-				l.WithField("receiveWindow", m{"accepted": false, "currentCounter": b.current, "incomingCounter": i, "reason": "duplicate"}).
-					Debug("Receive window")
+	// If i is within the current window but below the current counter, check to see if it's a duplicate
+	if b.strictlyWithinWindow(i) {
+		pos := i & b.lengthMask
+		word := pos >> 6
+		mask := uint64(1) << (pos & 63)
+		w := b.bits[word]
+		if b.current == i || w&mask != 0 {
+			if l.Enabled(context.Background(), slog.LevelDebug) {
+				l.Debug("Receive window",
+					"accepted", false,
+					"currentCounter", b.current,
+					"incomingCounter", i,
+					"reason", "duplicate",
+				)
 			}
 			b.dupeCounter.Inc(1)
 			return false
 		}
 
-		b.bits[i%b.length] = true
+		b.bits[word] = w | mask
 		return true
 	}
 
 	// In all other cases, fail and don't change current.
 	b.outOfWindowCounter.Inc(1)
-	if l.Level >= logrus.DebugLevel {
-		l.WithField("accepted", false).
-			WithField("currentCounter", b.current).
-			WithField("incomingCounter", i).
-			WithField("reason", "nonsense").
-			Debug("Receive window")
+	if l.Enabled(context.Background(), slog.LevelDebug) {
+		l.Debug("Receive window",
+			"accepted", false,
+			"currentCounter", b.current,
+			"incomingCounter", i,
+			"reason", "nonsense",
+		)
 	}
 	return false
 }

bits_test.go

@@ -7,61 +7,79 @@ import (
 	"github.com/stretchr/testify/assert"
 )
 
+// snapshot returns the bitmap as a []bool of length b.length, for readable
+// test assertions against the now-packed []uint64 storage.
+func (b *Bits) snapshot() []bool {
+	out := make([]bool, b.length)
+	for i := uint64(0); i < b.length; i++ {
+		out[i] = b.get(i)
+	}
+	return out
+}
+
+func TestBitsRequiresPowerOfTwo(t *testing.T) {
+	assert.Panics(t, func() { NewBits(10) })
+	assert.Panics(t, func() { NewBits(0) })
+	assert.NotPanics(t, func() { NewBits(1) })
+	assert.NotPanics(t, func() { NewBits(16) })
+	assert.NotPanics(t, func() { NewBits(1024) })
+	assert.NotPanics(t, func() { NewBits(16384) })
+}
+
 func TestBits(t *testing.T) {
 	l := test.NewLogger()
-	b := NewBits(10)
-
-	// make sure it is the right size
-	assert.Len(t, b.bits, 10)
+	b := NewBits(16)
+	assert.EqualValues(t, 16, b.length)
 
 	// This is initialized to zero - receive one. This should work.
 	assert.True(t, b.Check(l, 1))
 	assert.True(t, b.Update(l, 1))
 	assert.EqualValues(t, 1, b.current)
-	g := []bool{true, true, false, false, false, false, false, false, false, false}
-	assert.Equal(t, g, b.bits)
+	g := []bool{true, true, false, false, false, false, false, false, false, false, false, false, false, false, false, false}
+	assert.Equal(t, g, b.snapshot())
 
 	// Receive two
 	assert.True(t, b.Check(l, 2))
 	assert.True(t, b.Update(l, 2))
 	assert.EqualValues(t, 2, b.current)
-	g = []bool{true, true, true, false, false, false, false, false, false, false}
-	assert.Equal(t, g, b.bits)
+	g = []bool{true, true, true, false, false, false, false, false, false, false, false, false, false, false, false, false}
+	assert.Equal(t, g, b.snapshot())
 
 	// Receive two again - it will fail
 	assert.False(t, b.Check(l, 2))
 	assert.False(t, b.Update(l, 2))
 	assert.EqualValues(t, 2, b.current)
 
-	// Jump ahead to 15, which should clear everything and set the 6th element
-	assert.True(t, b.Check(l, 15))
-	assert.True(t, b.Update(l, 15))
-	assert.EqualValues(t, 15, b.current)
-	g = []bool{false, false, false, false, false, true, false, false, false, false}
-	assert.Equal(t, g, b.bits)
+	// Jump ahead to 25, which clears the window and sets slot 25%16 = 9.
+	assert.True(t, b.Check(l, 25))
+	assert.True(t, b.Update(l, 25))
+	assert.EqualValues(t, 25, b.current)
+	g = []bool{false, false, false, false, false, false, false, false, false, true, false, false, false, false, false, false}
+	assert.Equal(t, g, b.snapshot())
 
-	// Mark 14, which is allowed because it is in the window
-	assert.True(t, b.Check(l, 14))
-	assert.True(t, b.Update(l, 14))
-	assert.EqualValues(t, 15, b.current)
-	g = []bool{false, false, false, false, true, true, false, false, false, false}
-	assert.Equal(t, g, b.bits)
+	// Mark 24, which is in window (current 25, length 16, window covers [10,25]).
+	assert.True(t, b.Check(l, 24))
+	assert.True(t, b.Update(l, 24))
+	assert.EqualValues(t, 25, b.current)
+	g = []bool{false, false, false, false, false, false, false, false, true, true, false, false, false, false, false, false}
+	assert.Equal(t, g, b.snapshot())
 
-	// Mark 5, which is not allowed because it is not in the window
+	// Mark 5, not allowed because 5 <= current-length (25-16=9).
 	assert.False(t, b.Check(l, 5))
 	assert.False(t, b.Update(l, 5))
-	assert.EqualValues(t, 15, b.current)
-	g = []bool{false, false, false, false, true, true, false, false, false, false}
-	assert.Equal(t, g, b.bits)
+	assert.EqualValues(t, 25, b.current)
+	g = []bool{false, false, false, false, false, false, false, false, true, true, false, false, false, false, false, false}
+	assert.Equal(t, g, b.snapshot())
 
-	// make sure we handle wrapping around once to the current position
-	b = NewBits(10)
+	// Make sure we handle wrapping around once to the same slot. With
+	// length=16, packets 1 and 17 share slot 1.
+	b = NewBits(16)
 	assert.True(t, b.Update(l, 1))
-	assert.True(t, b.Update(l, 11))
-	assert.Equal(t, []bool{false, true, false, false, false, false, false, false, false, false}, b.bits)
+	assert.True(t, b.Update(l, 17))
+	assert.Equal(t, []bool{false, true, false, false, false, false, false, false, false, false, false, false, false, false, false, false}, b.snapshot())
 
 	// Walk through a few windows in order
-	b = NewBits(10)
+	b = NewBits(16)
 	for i := uint64(1); i <= 100; i++ {
 		assert.True(t, b.Check(l, i), "Error while checking %v", i)
 		assert.True(t, b.Update(l, i), "Error while updating %v", i)
@@ -72,24 +90,31 @@ func TestBits(t *testing.T) {
 
 func TestBitsLargeJumps(t *testing.T) {
 	l := test.NewLogger()
-	b := NewBits(10)
+
+	// length=16. Update(55) from current=0:
+	//   warmup, per-bit loop sees no n>16 with unset bits (slot 0 was set by
+	//   NewBits and gets re-evaluated when n=16; n=16 is not strictly > 16),
+	//   so the loop contributes 0. The jump exceeds the window so we record
+	//   55 - 0 - 16 = 39 packets fell out the back.
+	b := NewBits(16)
 	b.lostCounter.Clear()
+	assert.True(t, b.Update(l, 55))
+	assert.Equal(t, int64(39), b.lostCounter.Count())
 
-	b = NewBits(10)
-	b.lostCounter.Clear()
-	assert.True(t, b.Update(l, 55)) // We saw packet 55 and can still track 45,46,47,48,49,50,51,52,53,54
-	assert.Equal(t, int64(45), b.lostCounter.Count())
+	// Update(100): clears 16 slots starting at slot 56%16=8. Only slot 7 (for
+	// packet 55) was set, so 16 - 1 = 15 evicted slots had unset bits.
+	// Plus 100 - 55 - 16 = 29 packets fell past the window. Total 44.
+	assert.True(t, b.Update(l, 100))
+	assert.Equal(t, int64(39+44), b.lostCounter.Count())
 
-	assert.True(t, b.Update(l, 100)) // We saw packet 55 and 100 and can still track 90,91,92,93,94,95,96,97,98,99
-	assert.Equal(t, int64(89), b.lostCounter.Count())
-
-	assert.True(t, b.Update(l, 200)) // We saw packet 55, 100, and 200 and can still track 190,191,192,193,194,195,196,197,198,199
-	assert.Equal(t, int64(188), b.lostCounter.Count())
+	// Update(200): same shape: 16 - 1 = 15 evicted unset, plus 200 - 100 - 16 = 84 past window. Total 99.
+	assert.True(t, b.Update(l, 200))
+	assert.Equal(t, int64(39+44+99), b.lostCounter.Count())
 }
 
 func TestBitsDupeCounter(t *testing.T) {
 	l := test.NewLogger()
-	b := NewBits(10)
+	b := NewBits(16)
 	b.lostCounter.Clear()
 	b.dupeCounter.Clear()
 	b.outOfWindowCounter.Clear()
@@ -114,120 +139,117 @@ func TestBitsDupeCounter(t *testing.T) {
 
 func TestBitsOutOfWindowCounter(t *testing.T) {
 	l := test.NewLogger()
-	b := NewBits(10)
+	b := NewBits(16)
 	b.lostCounter.Clear()
 	b.dupeCounter.Clear()
 	b.outOfWindowCounter.Clear()
 
+	// Jump to 20 (warmup branch + 4 past-window packets).
 	assert.True(t, b.Update(l, 20))
 	assert.Equal(t, int64(0), b.outOfWindowCounter.Count())
 
-	assert.True(t, b.Update(l, 21))
-	assert.True(t, b.Update(l, 22))
-	assert.True(t, b.Update(l, 23))
-	assert.True(t, b.Update(l, 24))
-	assert.True(t, b.Update(l, 25))
-	assert.True(t, b.Update(l, 26))
-	assert.True(t, b.Update(l, 27))
-	assert.True(t, b.Update(l, 28))
-	assert.True(t, b.Update(l, 29))
+	// 9 single-step advances, each evicts a slot whose bit was cleared during
+	// the jump above and whose value was never seen, so each contributes 1
+	// to lostCounter.
+	for n := uint64(21); n <= 29; n++ {
+		assert.True(t, b.Update(l, n))
+	}
 	assert.Equal(t, int64(0), b.outOfWindowCounter.Count())
 
+	// 0 is below current-length (29-16=13) so it falls outside the window.
 	assert.False(t, b.Update(l, 0))
 	assert.Equal(t, int64(1), b.outOfWindowCounter.Count())
 
-	assert.Equal(t, int64(19), b.lostCounter.Count()) // packet 0 wasn't lost
+	// 4 from the Update(20) jump + 9 from 21..29.
+	assert.Equal(t, int64(13), b.lostCounter.Count())
 	assert.Equal(t, int64(0), b.dupeCounter.Count())
 	assert.Equal(t, int64(1), b.outOfWindowCounter.Count())
 }
 
 func TestBitsLostCounter(t *testing.T) {
 	l := test.NewLogger()
-	b := NewBits(10)
+	b := NewBits(16)
 	b.lostCounter.Clear()
 	b.dupeCounter.Clear()
 	b.outOfWindowCounter.Clear()
 
-	assert.True(t, b.Update(l, 20))
-	assert.True(t, b.Update(l, 21))
-	assert.True(t, b.Update(l, 22))
-	assert.True(t, b.Update(l, 23))
-	assert.True(t, b.Update(l, 24))
-	assert.True(t, b.Update(l, 25))
-	assert.True(t, b.Update(l, 26))
-	assert.True(t, b.Update(l, 27))
-	assert.True(t, b.Update(l, 28))
-	assert.True(t, b.Update(l, 29))
-	assert.Equal(t, int64(19), b.lostCounter.Count()) // packet 0 wasn't lost
+	// Walk 20..29 like the original, just with a bigger window. Same
+	// reasoning as TestBitsOutOfWindowCounter: 4 past-window from Update(20),
+	// then 9 more from the unit advances.
+	for n := uint64(20); n <= 29; n++ {
+		assert.True(t, b.Update(l, n))
+	}
+	assert.Equal(t, int64(13), b.lostCounter.Count())
 	assert.Equal(t, int64(0), b.dupeCounter.Count())
 	assert.Equal(t, int64(0), b.outOfWindowCounter.Count())
 
-	b = NewBits(10)
+	b = NewBits(16)
 	b.lostCounter.Clear()
 	b.dupeCounter.Clear()
 	b.outOfWindowCounter.Clear()
 
-	assert.True(t, b.Update(l, 9))
-	assert.Equal(t, int64(0), b.lostCounter.Count())
-	// 10 will set 0 index, 0 was already set, no lost packets
-	assert.True(t, b.Update(l, 10))
-	assert.Equal(t, int64(0), b.lostCounter.Count())
-	// 11 will set 1 index, 1 was missed, we should see 1 packet lost
-	assert.True(t, b.Update(l, 11))
-	assert.Equal(t, int64(1), b.lostCounter.Count())
-	// Now let's fill in the window, should end up with 8 lost packets
-	assert.True(t, b.Update(l, 12))
-	assert.True(t, b.Update(l, 13))
-	assert.True(t, b.Update(l, 14))
+	// Update(15) clears the warmup window (no lost), sets slot 15.
 	assert.True(t, b.Update(l, 15))
+	assert.Equal(t, int64(0), b.lostCounter.Count())
+
+	// Update(16): slot 0 was already set (NewBits seeded it), and 16 is not
+	// strictly > length, so nothing is recorded as lost.
 	assert.True(t, b.Update(l, 16))
+	assert.Equal(t, int64(0), b.lostCounter.Count())
+
+	// Update(17): we jumped straight from 0 to 15, so slot 1 was cleared
+	// (and never re-set). 17 > 16 is past warmup, so packet 1 is recorded lost.
 	assert.True(t, b.Update(l, 17))
-	assert.True(t, b.Update(l, 18))
-	assert.True(t, b.Update(l, 19))
-	assert.Equal(t, int64(8), b.lostCounter.Count())
+	assert.Equal(t, int64(1), b.lostCounter.Count())
 
-	// Jump ahead by a window size
-	assert.True(t, b.Update(l, 29))
-	assert.Equal(t, int64(8), b.lostCounter.Count())
-	// Now lets walk ahead normally through the window, the missed packets should fill in
-	assert.True(t, b.Update(l, 30))
-	assert.True(t, b.Update(l, 31))
-	assert.True(t, b.Update(l, 32))
-	assert.True(t, b.Update(l, 33))
-	assert.True(t, b.Update(l, 34))
-	assert.True(t, b.Update(l, 35))
-	assert.True(t, b.Update(l, 36))
-	assert.True(t, b.Update(l, 37))
-	assert.True(t, b.Update(l, 38))
-	// 39 packets tracked, 22 seen, 17 lost
-	assert.Equal(t, int64(17), b.lostCounter.Count())
+	// Fill in 18..30 in single steps. Each i evicts slot i%16. Slots 2..14
+	// were all cleared during Update(15), and we never re-set any of them,
+	// so each i in 18..30 is a fresh lost packet — 13 more.
+	for n := uint64(18); n <= 30; n++ {
+		assert.True(t, b.Update(l, n))
+	}
+	assert.Equal(t, int64(14), b.lostCounter.Count())
 
-	// Jump ahead by 2 windows, should have recording 1 full window missing
-	assert.True(t, b.Update(l, 58))
-	assert.Equal(t, int64(27), b.lostCounter.Count())
-	// Now lets walk ahead normally through the window, the missed packets should fill in from this window
-	assert.True(t, b.Update(l, 59))
-	assert.True(t, b.Update(l, 60))
-	assert.True(t, b.Update(l, 61))
-	assert.True(t, b.Update(l, 62))
-	assert.True(t, b.Update(l, 63))
-	assert.True(t, b.Update(l, 64))
-	assert.True(t, b.Update(l, 65))
-	assert.True(t, b.Update(l, 66))
-	assert.True(t, b.Update(l, 67))
-	// 68 packets tracked, 32 seen, 36 missed
-	assert.Equal(t, int64(36), b.lostCounter.Count())
+	// Jump ahead by exactly one window size.
+	assert.True(t, b.Update(l, 46))
+	// end = min(46, 30+16) = 46, count = 16, all slots cleared. Before the
+	// jump every slot 0..15 had been set (Update(15), (16), (17), 18..30),
+	// so wasSet=16 and 46 == current+length means no past-window slack:
+	// lost contribution = 0.
+	assert.Equal(t, int64(14), b.lostCounter.Count())
+
+	// Walk 47..55. The Update(46) jump cleared every slot, so only slot 14
+	// (for packet 46) is set when we start. Each subsequent unit step lands
+	// on a slot that was cleared and is past warmup, so it counts as lost.
+	// 9 more = 23.
+	for n := uint64(47); n <= 55; n++ {
+		assert.True(t, b.Update(l, n))
+	}
+	assert.Equal(t, int64(23), b.lostCounter.Count())
+
+	// Jump ahead by two windows: clears the window plus past-window loss.
+	assert.True(t, b.Update(l, 87))
+	// current=55, length=16. end = min(87, 71) = 71. count=16, all slots
+	// cleared. Slots set before the clear are slots 14,15,0..7 (10 total).
+	// Lost from clear = 16 - 10 = 6. Past window: 87 - 55 - 16 = 16. +22.
+	assert.Equal(t, int64(45), b.lostCounter.Count())
 	assert.Equal(t, int64(0), b.dupeCounter.Count())
 	assert.Equal(t, int64(0), b.outOfWindowCounter.Count())
 }
 
 func TestBitsLostCounterIssue1(t *testing.T) {
 	l := test.NewLogger()
-	b := NewBits(10)
+	b := NewBits(16)
 	b.lostCounter.Clear()
 	b.dupeCounter.Clear()
 	b.outOfWindowCounter.Clear()
 
+	// Receive 4, backfill 1, then 9, 2, 3, 5, 6, 7 (skip 8), 10, 11, 14.
+	// Then jump to 25 — slot 25%16=9 is being evicted, but it had been set
+	// (we received packet 9), so no spurious lost increment. The original
+	// regression was about double-counting a missing packet when its slot
+	// got cleared on a jump. With the jump path now using clearRange's
+	// word-level wasSet count, the same semantics hold.
 	assert.True(t, b.Update(l, 4))
 	assert.Equal(t, int64(0), b.lostCounter.Count())
 	assert.True(t, b.Update(l, 1))
@@ -244,7 +266,7 @@ func TestBitsLostCounterIssue1(t *testing.T) {
 	assert.Equal(t, int64(0), b.lostCounter.Count())
 	assert.True(t, b.Update(l, 7))
 	assert.Equal(t, int64(0), b.lostCounter.Count())
-	// assert.True(t, b.Update(l, 8))
+	// Skip packet 8.
 	assert.True(t, b.Update(l, 10))
 	assert.Equal(t, int64(0), b.lostCounter.Count())
 	assert.True(t, b.Update(l, 11))
@@ -252,9 +274,23 @@ func TestBitsLostCounterIssue1(t *testing.T) {
 
 	assert.True(t, b.Update(l, 14))
 	assert.Equal(t, int64(0), b.lostCounter.Count())
-	// Issue seems to be here, we reset missing packet 8 to false here and don't increment the lost counter
-	assert.True(t, b.Update(l, 19))
+
+	// Jump to 25. With length=16, slot 25%16=9 corresponds to packet 9
+	// (which we DID receive), so its bit is set and no lost++ from that
+	// eviction. The trace below shows the only loss is packet 8.
+	assert.True(t, b.Update(l, 25))
+	// current was 14, i=25. end=min(25,30)=25. count=11. startPos=15.
+	// steady? current=14<16, so warmup branch: per-bit n=15..25, count those
+	// with !get(n) AND n>16. n=17..25 are >16. Among slots 17%16=1..25%16=9
+	// did we set slots 1..9 (packets 1..9)? Yes for all but slot 8 (packet 8
+	// was skipped). n=24 maps to slot 8 which is FALSE → lost++. All other
+	// n in 17..25 map to slots that are set. n=16 is not strictly > 16. So
+	// lost = 1.
 	assert.Equal(t, int64(1), b.lostCounter.Count())
+
+	// Fill in 12, 13, 15, 16. Each is below current=25 (in-window). 16 must
+	// recheck slot 0 — it was set by NewBits and then cleared by the
+	// Update(25) jump, so 16 backfills cleanly.
 	assert.True(t, b.Update(l, 12))
 	assert.Equal(t, int64(1), b.lostCounter.Count())
 	assert.True(t, b.Update(l, 13))
@@ -263,29 +299,140 @@ func TestBitsLostCounterIssue1(t *testing.T) {
 	assert.Equal(t, int64(1), b.lostCounter.Count())
 	assert.True(t, b.Update(l, 16))
 	assert.Equal(t, int64(1), b.lostCounter.Count())
-	assert.True(t, b.Update(l, 17))
-	assert.Equal(t, int64(1), b.lostCounter.Count())
-	assert.True(t, b.Update(l, 18))
-	assert.Equal(t, int64(1), b.lostCounter.Count())
-	assert.True(t, b.Update(l, 20))
-	assert.Equal(t, int64(1), b.lostCounter.Count())
-	assert.True(t, b.Update(l, 21))
 
-	// We missed packet 8 above
+	// We missed packet 8 above and that loss is still recorded once, never
+	// double-counted, never zeroed.
 	assert.Equal(t, int64(1), b.lostCounter.Count())
 	assert.Equal(t, int64(0), b.dupeCounter.Count())
 	assert.Equal(t, int64(0), b.outOfWindowCounter.Count())
 }
 
-func BenchmarkBits(b *testing.B) {
-	z := NewBits(10)
-	for n := 0; n < b.N; n++ {
-		for i := range z.bits {
-			z.bits[i] = true
-		}
-		for i := range z.bits {
-			z.bits[i] = false
-		}
+// TestBitsWarmupOvershoot exercises the jump path's warmup arm with an
+// overshoot past one full window. NewBits leaves current=0 with only slot 0
+// "set" by the marker. Jumping straight to length+k must (a) clear every
+// slot the jump straddles, (b) count only past-window slack (not the
+// in-window slots, which never had a "lost" tenant during warmup), and
+// (c) leave the cursor at the new counter so subsequent unit advances
+// count from steady state. The marker bit at slot 0 is irrelevant once
+// current >= length.
+func TestBitsWarmupOvershoot(t *testing.T) {
+	l := test.NewLogger()
+	b := NewBits(16)
+	b.lostCounter.Clear()
 
+	// Jump from current=0 to i=20 (length=16, overshoot=4).
+	// Warmup arm: counts slots in [1..16] where bit unset and n>length.
+	// Only n=16 was unset and >length: but slot 16%16=0 is the marker,
+	// so b.get(16) reads bits[0]=1 and skips. Result: 0 lost from the loop.
+	// Past-window: i - current - length = 20 - 0 - 16 = 4 lost.
+	assert.True(t, b.Update(l, 20))
+	assert.Equal(t, int64(4), b.lostCounter.Count())
+	assert.Equal(t, uint64(20), b.current)
+
+	// Steady state now (current=20 >= length=16). Unit advance to 21
+	// stomps slot 21%16=5, which was cleared by the jump and not reset,
+	// so this is +1 lost.
+	assert.True(t, b.Update(l, 21))
+	assert.Equal(t, int64(5), b.lostCounter.Count())
+}
+
+// TestBitsCheckAcrossWarmupBoundary pins the underflow trick in Check's
+// in-window clause. While in warmup, b.current-b.length underflows uint64
+// to a huge value so the first OR-clause is always false; the second
+// clause (i < length && current < length) carries the in-window check.
+// Once current >= length the regimes flip cleanly.
+func TestBitsCheckAcrossWarmupBoundary(t *testing.T) {
+	l := test.NewLogger()
+	b := NewBits(16)
+
+	// Warmup: current=0. Check(0) must read the marker (set) and return false.
+	assert.False(t, b.Check(l, 0), "marker slot should look already-received")
+	// Warmup: any 0 < i < length is in-window and unset → accepted.
+	for i := uint64(1); i < 16; i++ {
+		assert.True(t, b.Check(l, i), "warmup in-window i=%d should be accepted", i)
+	}
+	// Warmup: i >= length but > current is "next number" so accepted.
+	assert.True(t, b.Check(l, 16))
+	assert.True(t, b.Check(l, 1_000_000))
+
+	// Cross into steady state.
+	assert.True(t, b.Update(l, 100))
+	// Now current=100, length=16. In-window range is [85..100].
+	// 84 is just outside: the underflow clause activates; 84 > 100-16=84 is false.
+	// And the warmup clause is false (current >= length). So out of window.
+	assert.False(t, b.Check(l, 84))
+	// 85 sits at the boundary. 85 > 84 is true → in window, unset → accept.
+	assert.True(t, b.Check(l, 85))
+	// 100 is current itself; not strictly greater, in-window, but already set.
+	assert.False(t, b.Check(l, 100))
+	// Way out: clearly out of window.
+	assert.False(t, b.Check(l, 50))
+}
+
+// TestBitsMarkerInvariant verifies the seeded bits[0]=1 marker behaves
+// correctly across warmup and beyond. Update should never clear the marker
+// during warmup (clearRange skips position 0 when startPos=1), and once
+// current >= length the marker is no longer consulted by Check/Update on
+// the live path — but it must still report counter 0 as a duplicate while
+// we are in warmup.
+func TestBitsMarkerInvariant(t *testing.T) {
+	l := test.NewLogger()
+	b := NewBits(8)
+
+	// Counter 0 is the seeded marker; Check sees it as already received.
+	assert.False(t, b.Check(l, 0))
+	// Update(0) at current=0 hits the duplicate branch.
+	b.dupeCounter.Clear()
+	assert.False(t, b.Update(l, 0))
+	assert.Equal(t, int64(1), b.dupeCounter.Count())
+
+	// Walk forward through warmup; the marker must remain set.
+	for n := uint64(1); n <= 7; n++ {
+		assert.True(t, b.Update(l, n))
+	}
+	// Position 0 (the marker) should still read as set because we never
+	// cleared it; Update(0) still looks like a duplicate.
+	assert.False(t, b.Check(l, 0))
+
+	// Cross into steady state with a unit advance to 8: pos=0, evicts the
+	// marker bit. The lost-counter guard (i > b.length) is false (8 == 8),
+	// so this advance does NOT charge a lost packet — exactly what the
+	// marker is there to prevent.
+	b.lostCounter.Clear()
+	assert.True(t, b.Update(l, 8))
+	assert.Equal(t, int64(0), b.lostCounter.Count())
+	// The slot at pos 0 is now occupied by counter 8.
+	assert.False(t, b.Check(l, 8))
+}
+
+// BenchmarkBitsUpdateInOrder is the steady-state hot path: each call is
+// i == current+1.
+func BenchmarkBitsUpdateInOrder(b *testing.B) {
+	l := test.NewLogger()
+	z := NewBits(16384)
+	for n := 0; n < b.N; n++ {
+		z.Update(l, uint64(n)+1)
+	}
+}
+
+// BenchmarkBitsUpdateReorder simulates light reorder within the window:
+// every other packet arrives one slot behind its predecessor (forces the
+// in-window backfill branch).
+func BenchmarkBitsUpdateReorder(b *testing.B) {
+	l := test.NewLogger()
+	z := NewBits(16384)
+	for n := 0; n < b.N; n++ {
+		base := uint64(n) * 2
+		z.Update(l, base+2)
+		z.Update(l, base+1)
+	}
+}
+
+// BenchmarkBitsUpdateLargeJumps stresses the clearRange word-level path.
+func BenchmarkBitsUpdateLargeJumps(b *testing.B) {
+	l := test.NewLogger()
+	z := NewBits(16384)
+	for n := 0; n < b.N; n++ {
+		z.Update(l, uint64(n+1)*1000)
 	}
 }

cert/ca_pool.go

@@ -217,6 +217,10 @@ func (ncp *CAPool) verify(c Certificate, now time.Time, certFp string, signerFp
 		return nil, err
 	}
 
+	if signer.Certificate.Curve() != c.Curve() {
+		return nil, ErrCurveMismatch
+	}
+
 	if signer.Certificate.Expired(now) {
 		return nil, ErrRootExpired
 	}

cert/ca_pool_test.go

@@ -654,3 +654,31 @@ func TestCertificateV2_Verify_Subnets(t *testing.T) {
 	_, err = caPool.VerifyCertificate(time.Now(), c)
 	require.NoError(t, err)
 }
+
+func TestCertificateV2_CurveMismatch(t *testing.T) {
+	caIp1 := mustParsePrefixUnmapped("10.0.0.0/16")
+	caIp2 := mustParsePrefixUnmapped("192.168.0.0/24")
+	ca, _, caKey, _ := NewTestCaCert(Version2, Curve_P256, time.Now(), time.Now().Add(10*time.Minute), []netip.Prefix{caIp1, caIp2}, nil, []string{"test"})
+
+	caPem, err := ca.MarshalPEM()
+	require.NoError(t, err)
+
+	caPool := NewCAPool()
+	b, err := caPool.AddCAFromPEM(caPem)
+	require.NoError(t, err)
+	assert.Empty(t, b)
+
+	// ip is outside the network
+	cIp1 := mustParsePrefixUnmapped("10.0.0.1/24")
+	c, _, _, _ := NewTestCert(Version2, Curve_P256, ca, caKey, "test", time.Now(), time.Now().Add(5*time.Minute), []netip.Prefix{cIp1}, nil, []string{"test"})
+
+	fp, _ := c.Fingerprint()
+	_, err = caPool.verify(c, time.Now(), fp, c.Issuer())
+	require.NoError(t, err)
+	//
+	c2 := c.(*certificateV2)
+	c2.curve = Curve_CURVE25519
+	fp, _ = c.Fingerprint()
+	_, err = caPool.verify(c, time.Now(), fp, c.Issuer())
+	require.Error(t, err)
+}

cert/cert_v1.go

@@ -112,6 +112,9 @@ func (c *certificateV1) CheckSignature(key []byte) bool {
 	}
 	switch c.details.curve {
 	case Curve_CURVE25519:
+		if len(key) != ed25519.PublicKeySize {
+			return false //avoids a panic internal to ed25519
+		}
 		return ed25519.Verify(key, b, c.signature)
 	case Curve_P256:
 		pubKey, err := ecdsa.ParseUncompressedPublicKey(elliptic.P256(), key)

cert/cert_v2.go

@@ -151,6 +151,9 @@ func (c *certificateV2) CheckSignature(key []byte) bool {
 
 	switch c.curve {
 	case Curve_CURVE25519:
+		if len(key) != ed25519.PublicKeySize {
+			return false //avoids a panic internal to ed25519
+		}
 		return ed25519.Verify(key, b, c.signature)
 	case Curve_P256:
 		pubKey, err := ecdsa.ParseUncompressedPublicKey(elliptic.P256(), key)

cert/errors.go

@@ -22,6 +22,7 @@ var (
 	ErrCaNotFound                 = errors.New("could not find ca for the certificate")
 	ErrUnknownVersion             = errors.New("certificate version unrecognized")
 	ErrCertPubkeyPresent          = errors.New("certificate has unexpected pubkey present")
+	ErrCurveMismatch              = errors.New("certificate curve does not match CA")
 
 	ErrInvalidPEMBlock                   = errors.New("input did not contain a valid PEM encoded block")
 	ErrInvalidPEMCertificateBanner       = errors.New("bytes did not contain a proper certificate banner")

cert_test/cert.go

@@ -163,3 +163,55 @@ func P256Keypair() ([]byte, []byte) {
 	pubkey := privkey.PublicKey()
 	return pubkey.Bytes(), privkey.Bytes()
 }
+
+// DummyCert is a minimal cert.Certificate implementation for testing error paths.
+type DummyCert struct {
+	Version_        cert.Version
+	Curve_          cert.Curve
+	Groups_         []string
+	IsCA_           bool
+	Issuer_         string
+	Name_           string
+	Networks_       []netip.Prefix
+	NotAfter_       time.Time
+	NotBefore_      time.Time
+	PublicKey_      []byte
+	Signature_      []byte
+	UnsafeNetworks_ []netip.Prefix
+}
+
+func (d *DummyCert) Version() cert.Version                         { return d.Version_ }
+func (d *DummyCert) Curve() cert.Curve                             { return d.Curve_ }
+func (d *DummyCert) Groups() []string                              { return d.Groups_ }
+func (d *DummyCert) IsCA() bool                                    { return d.IsCA_ }
+func (d *DummyCert) Issuer() string                                { return d.Issuer_ }
+func (d *DummyCert) Name() string                                  { return d.Name_ }
+func (d *DummyCert) Networks() []netip.Prefix                      { return d.Networks_ }
+func (d *DummyCert) NotAfter() time.Time                           { return d.NotAfter_ }
+func (d *DummyCert) NotBefore() time.Time                          { return d.NotBefore_ }
+func (d *DummyCert) PublicKey() []byte                             { return d.PublicKey_ }
+func (d *DummyCert) Signature() []byte                             { return d.Signature_ }
+func (d *DummyCert) UnsafeNetworks() []netip.Prefix                { return d.UnsafeNetworks_ }
+func (d *DummyCert) Fingerprint() (string, error)                  { return "", nil }
+func (d *DummyCert) CheckSignature(key []byte) bool                { return false }
+func (d *DummyCert) MarshalForHandshakes() ([]byte, error)         { return nil, nil }
+func (d *DummyCert) MarshalPEM() ([]byte, error)                   { return nil, nil }
+func (d *DummyCert) MarshalJSON() ([]byte, error)                  { return nil, nil }
+func (d *DummyCert) Marshal() ([]byte, error)                      { return nil, nil }
+func (d *DummyCert) String() string                                { return "dummy" }
+func (d *DummyCert) Copy() cert.Certificate                        { return d }
+func (d *DummyCert) VerifyPrivateKey(c cert.Curve, k []byte) error { return nil }
+func (d *DummyCert) Expired(time.Time) bool                        { return false }
+func (d *DummyCert) MarshalPublicKeyPEM() []byte                   { return nil }
+func (d *DummyCert) PublicKeyPEM() []byte                          { return nil }
+
+// NewTestCAPool creates a CAPool from the given CA certificates, panicking on error.
+func NewTestCAPool(cas ...cert.Certificate) *cert.CAPool {
+	pool := cert.NewCAPool()
+	for _, ca := range cas {
+		if err := pool.AddCA(ca); err != nil {
+			panic(err)
+		}
+	}
+	return pool
+}

cmd/nebula-service/logs_generic.go

@@ -3,8 +3,15 @@
 
 package main
 
-import "github.com/sirupsen/logrus"
+import (
+	"log/slog"
+	"os"
 
-func HookLogger(l *logrus.Logger) {
-	// Do nothing, let the logs flow to stdout/stderr
+	"github.com/slackhq/nebula/logging"
+)
+
+// newPlatformLogger returns a *slog.Logger that writes to stdout. Non-Windows
+// platforms have no special sink to integrate with.
+func newPlatformLogger() *slog.Logger {
+	return logging.NewLogger(os.Stdout)
 }

cmd/nebula-service/logs_windows.go

@@ -1,54 +1,86 @@
 package main
 
 import (
-	"fmt"
-	"io/ioutil"
-	"os"
+	"context"
+	"log/slog"
+	"strings"
+	"sync"
 
-	"github.com/kardianos/service"
-	"github.com/sirupsen/logrus"
+	"github.com/slackhq/nebula/logging"
 )
 
-// HookLogger routes the logrus logs through the service logger so that they end up in the Windows Event Viewer
-// logrus output will be discarded
-func HookLogger(l *logrus.Logger) {
-	l.AddHook(newLogHook(logger))
-	l.SetOutput(ioutil.Discard)
+// newPlatformLogger returns a *slog.Logger that routes every log record
+// through the Windows service logger so records end up in the Windows
+// Event Log. All the heavy lifting (level management, format swap,
+// timestamp toggle, WithAttrs/WithGroup) comes from logging.NewHandler;
+// this file only contributes:
+//
+//   - an io.Writer that forwards each formatted line to the service
+//     logger at the current record's Event Log severity, and
+//   - a thin severityTag that embeds *logging.Handler and overrides
+//     only Handle / WithAttrs / WithGroup, so Event Viewer's severity
+//     column and severity-based filters keep working the way they did
+//     before the slog migration.
+//
+// Format (text vs json) is carried by the embedded *logging.Handler, so
+// logging.format: json in config still produces JSON lines in Event
+// Viewer, same as the pre-slog logrus setup.
+func newPlatformLogger() *slog.Logger {
+	w := &eventLogWriter{}
+	return slog.New(&severityTag{Handler: logging.NewHandler(w), w: w})
 }
 
-type logHook struct {
-	sl service.Logger
+// eventLogWriter forwards slog-formatted lines to the Windows service
+// logger at the severity most recently stashed by severityTag.Handle.
+// The mutex serializes the stash + inner.Handle + Write cycle per record
+// across all concurrent goroutines; slog's builtin text/json handlers
+// each hold their own mutex around Write, but that only protects the
+// Write call itself, not our stash-then-handle sequence.
+type eventLogWriter struct {
+	mu    sync.Mutex
+	level slog.Level
 }
 
-func newLogHook(sl service.Logger) *logHook {
-	return &logHook{sl: sl}
-}
-
-func (h *logHook) Fire(entry *logrus.Entry) error {
-	line, err := entry.String()
-	if err != nil {
-		fmt.Fprintf(os.Stderr, "Unable to read entry, %v", err)
-		return err
-	}
-
-	switch entry.Level {
-	case logrus.PanicLevel:
-		return h.sl.Error(line)
-	case logrus.FatalLevel:
-		return h.sl.Error(line)
-	case logrus.ErrorLevel:
-		return h.sl.Error(line)
-	case logrus.WarnLevel:
-		return h.sl.Warning(line)
-	case logrus.InfoLevel:
-		return h.sl.Info(line)
-	case logrus.DebugLevel:
-		return h.sl.Info(line)
+func (w *eventLogWriter) Write(p []byte) (int, error) {
+	line := strings.TrimRight(string(p), "\n")
+	switch {
+	case w.level >= slog.LevelError:
+		return len(p), logger.Error(line)
+	case w.level >= slog.LevelWarn:
+		return len(p), logger.Warning(line)
 	default:
-		return nil
+		return len(p), logger.Info(line)
 	}
 }
 
-func (h *logHook) Levels() []logrus.Level {
-	return logrus.AllLevels
+// severityTag embeds *logging.Handler to pick up everything it does for
+// free (Enabled, SetLevel, GetLevel, SetFormat, GetFormat,
+// SetDisableTimestamp) and overrides only Handle / WithAttrs / WithGroup
+// so each record's slog.Level is stashed on the writer before formatting
+// and so derived handlers stay wrapped as severityTag rather than
+// downgrading to bare *logging.Handler.
+type severityTag struct {
+	*logging.Handler
+	w *eventLogWriter
+}
+
+func (s *severityTag) Handle(ctx context.Context, r slog.Record) error {
+	s.w.mu.Lock()
+	defer s.w.mu.Unlock()
+	s.w.level = r.Level
+	return s.Handler.Handle(ctx, r)
+}
+
+func (s *severityTag) WithAttrs(attrs []slog.Attr) slog.Handler {
+	if len(attrs) == 0 {
+		return s
+	}
+	return &severityTag{Handler: s.Handler.WithAttrs(attrs).(*logging.Handler), w: s.w}
+}
+
+func (s *severityTag) WithGroup(name string) slog.Handler {
+	if name == "" {
+		return s
+	}
+	return &severityTag{Handler: s.Handler.WithGroup(name).(*logging.Handler), w: s.w}
 }

cmd/nebula-service/main.go

@@ -7,9 +7,9 @@ import (
 	"runtime/debug"
 	"strings"
 
-	"github.com/sirupsen/logrus"
 	"github.com/slackhq/nebula"
 	"github.com/slackhq/nebula/config"
+	"github.com/slackhq/nebula/logging"
 	"github.com/slackhq/nebula/util"
 )
 
@@ -50,9 +50,14 @@ func main() {
 		os.Exit(0)
 	}
 
+	l := logging.NewLogger(os.Stdout)
+
 	if *serviceFlag != "" {
-		doService(configPath, configTest, Build, serviceFlag)
-		os.Exit(1)
+		if err := doService(configPath, configTest, Build, serviceFlag); err != nil {
+			l.Error("Service command failed", "error", err)
+			os.Exit(1)
+		}
+		return
 	}
 
 	if *configPath == "" {
@@ -61,9 +66,6 @@ func main() {
 		os.Exit(1)
 	}
 
-	l := logrus.New()
-	l.Out = os.Stdout
-
 	c := config.NewC(l)
 	err := c.Load(*configPath)
 	if err != nil {
@@ -71,6 +73,16 @@ func main() {
 		os.Exit(1)
 	}
 
+	if err := logging.ApplyConfig(l, c); err != nil {
+		fmt.Printf("failed to apply logging config: %s", err)
+		os.Exit(1)
+	}
+	c.RegisterReloadCallback(func(c *config.C) {
+		if err := logging.ApplyConfig(l, c); err != nil {
+			l.Error("Failed to reconfigure logger on reload", "error", err)
+		}
+	})
+
 	ctrl, err := nebula.Main(c, *configTest, Build, l, nil)
 	if err != nil {
 		util.LogWithContextIfNeeded("Failed to start", err, l)
@@ -87,7 +99,7 @@ func main() {
 		go ctrl.ShutdownBlock()
 
 		if err := wait(); err != nil {
-			l.WithError(err).Error("Nebula stopped due to fatal error")
+			l.Error("Nebula stopped due to fatal error", "error", err)
 			os.Exit(2)
 		}
 

cmd/nebula-service/service.go

@@ -7,9 +7,9 @@ import (
 	"path/filepath"
 
 	"github.com/kardianos/service"
-	"github.com/sirupsen/logrus"
 	"github.com/slackhq/nebula"
 	"github.com/slackhq/nebula/config"
+	"github.com/slackhq/nebula/logging"
 )
 
 var logger service.Logger
@@ -25,8 +25,7 @@ func (p *program) Start(s service.Service) error {
 	// Start should not block.
 	logger.Info("Nebula service starting.")
 
-	l := logrus.New()
-	HookLogger(l)
+	l := newPlatformLogger()
 
 	c := config.NewC(l)
 	err := c.Load(*p.configPath)
@@ -34,6 +33,15 @@ func (p *program) Start(s service.Service) error {
 		return fmt.Errorf("failed to load config: %s", err)
 	}
 
+	if err := logging.ApplyConfig(l, c); err != nil {
+		return fmt.Errorf("failed to apply logging config: %s", err)
+	}
+	c.RegisterReloadCallback(func(c *config.C) {
+		if err := logging.ApplyConfig(l, c); err != nil {
+			l.Error("Failed to reconfigure logger on reload", "error", err)
+		}
+	})
+
 	p.control, err = nebula.Main(c, *p.configTest, Build, l, nil)
 	if err != nil {
 		return err
@@ -57,11 +65,11 @@ func fileExists(filename string) bool {
 	return true
 }
 
-func doService(configPath *string, configTest *bool, build string, serviceFlag *string) {
+func doService(configPath *string, configTest *bool, build string, serviceFlag *string) error {
 	if *configPath == "" {
 		ex, err := os.Executable()
 		if err != nil {
-			panic(err)
+			return err
 		}
 		*configPath = filepath.Dir(ex) + "/config.yaml"
 		if !fileExists(*configPath) {
@@ -85,16 +93,16 @@ func doService(configPath *string, configTest *bool, build string, serviceFlag *
 	// Here are what the different loggers are doing:
 	// - `log` is the standard go log utility, meant to be used while the process is still attached to stdout/stderr
 	// - `logger` is the service log utility that may be attached to a special place depending on OS (Windows will have it attached to the event log)
-	// - above, in `Run` we create a `logrus.Logger` which is what nebula expects to use
+	// - in program.Start we build a *slog.Logger via newPlatformLogger; on non-Windows that is a stdout-backed slog logger, on Windows it routes records through the service logger
 	s, err := service.New(prg, svcConfig)
 	if err != nil {
-		log.Fatal(err)
+		return err
 	}
 
 	errs := make(chan error, 5)
 	logger, err = s.Logger(errs)
 	if err != nil {
-		log.Fatal(err)
+		return err
 	}
 
 	go func() {
@@ -109,18 +117,16 @@ func doService(configPath *string, configTest *bool, build string, serviceFlag *
 
 	switch *serviceFlag {
 	case "run":
-		err = s.Run()
-		if err != nil {
+		if err := s.Run(); err != nil {
 			// Route any errors to the system logger
 			logger.Error(err)
 		}
 	default:
-		err := service.Control(s, *serviceFlag)
-		if err != nil {
+		if err := service.Control(s, *serviceFlag); err != nil {
 			log.Printf("Valid actions: %q\n", service.ControlAction)
-			log.Fatal(err)
+			return err
 		}
-		return
 	}
 
+	return nil
 }

cmd/nebula/main.go

@@ -7,9 +7,9 @@ import (
 	"runtime/debug"
 	"strings"
 
-	"github.com/sirupsen/logrus"
 	"github.com/slackhq/nebula"
 	"github.com/slackhq/nebula/config"
+	"github.com/slackhq/nebula/logging"
 	"github.com/slackhq/nebula/util"
 )
 
@@ -55,8 +55,7 @@ func main() {
 		os.Exit(1)
 	}
 
-	l := logrus.New()
-	l.Out = os.Stdout
+	l := logging.NewLogger(os.Stdout)
 
 	c := config.NewC(l)
 	err := c.Load(*configPath)
@@ -65,6 +64,16 @@ func main() {
 		os.Exit(1)
 	}
 
+	if err := logging.ApplyConfig(l, c); err != nil {
+		fmt.Printf("failed to apply logging config: %s", err)
+		os.Exit(1)
+	}
+	c.RegisterReloadCallback(func(c *config.C) {
+		if err := logging.ApplyConfig(l, c); err != nil {
+			l.Error("Failed to reconfigure logger on reload", "error", err)
+		}
+	})
+
 	ctrl, err := nebula.Main(c, *configTest, Build, l, nil)
 	if err != nil {
 		util.LogWithContextIfNeeded("Failed to start", err, l)
@@ -82,7 +91,7 @@ func main() {
 		notifyReady(l)
 
 		if err := wait(); err != nil {
-			l.WithError(err).Error("Nebula stopped due to fatal error")
+			l.Error("Nebula stopped due to fatal error", "error", err)
 			os.Exit(2)
 		}
 

cmd/nebula/notify_linux.go

@@ -1,11 +1,10 @@
 package main
 
 import (
+	"log/slog"
 	"net"
 	"os"
 	"time"
-
-	"github.com/sirupsen/logrus"
 )
 
 // SdNotifyReady tells systemd the service is ready and dependent services can now be started
@@ -13,30 +12,30 @@ import (
 // https://www.freedesktop.org/software/systemd/man/systemd.service.html
 const SdNotifyReady = "READY=1"
 
-func notifyReady(l *logrus.Logger) {
+func notifyReady(l *slog.Logger) {
 	sockName := os.Getenv("NOTIFY_SOCKET")
 	if sockName == "" {
-		l.Debugln("NOTIFY_SOCKET systemd env var not set, not sending ready signal")
+		l.Debug("NOTIFY_SOCKET systemd env var not set, not sending ready signal")
 		return
 	}
 
 	conn, err := net.DialTimeout("unixgram", sockName, time.Second)
 	if err != nil {
-		l.WithError(err).Error("failed to connect to systemd notification socket")
+		l.Error("failed to connect to systemd notification socket", "error", err)
 		return
 	}
 	defer conn.Close()
 
 	err = conn.SetWriteDeadline(time.Now().Add(time.Second))
 	if err != nil {
-		l.WithError(err).Error("failed to set the write deadline for the systemd notification socket")
+		l.Error("failed to set the write deadline for the systemd notification socket", "error", err)
 		return
 	}
 
 	if _, err = conn.Write([]byte(SdNotifyReady)); err != nil {
-		l.WithError(err).Error("failed to signal the systemd notification socket")
+		l.Error("failed to signal the systemd notification socket", "error", err)
 		return
 	}
 
-	l.Debugln("notified systemd the service is ready")
+	l.Debug("notified systemd the service is ready")
 }

cmd/nebula/notify_notlinux.go

@@ -3,8 +3,8 @@
 
 package main
 
-import "github.com/sirupsen/logrus"
+import "log/slog"
 
-func notifyReady(_ *logrus.Logger) {
+func notifyReady(_ *slog.Logger) {
 	// No init service to notify
 }

config/config.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"log/slog"
 	"math"
 	"os"
 	"os/signal"
@@ -16,7 +17,6 @@ import (
 	"time"
 
 	"dario.cat/mergo"
-	"github.com/sirupsen/logrus"
 	"go.yaml.in/yaml/v3"
 )
 
@@ -26,11 +26,11 @@ type C struct {
 	Settings    map[string]any
 	oldSettings map[string]any
 	callbacks   []func(*C)
-	l           *logrus.Logger
+	l           *slog.Logger
 	reloadLock  sync.Mutex
 }
 
-func NewC(l *logrus.Logger) *C {
+func NewC(l *slog.Logger) *C {
 	return &C{
 		Settings: make(map[string]any),
 		l:        l,
@@ -107,12 +107,18 @@ func (c *C) HasChanged(k string) bool {
 
 	newVals, err := yaml.Marshal(nv)
 	if err != nil {
-		c.l.WithField("config_path", k).WithError(err).Error("Error while marshaling new config")
+		c.l.Error("Error while marshaling new config",
+			"config_path", k,
+			"error", err,
+		)
 	}
 
 	oldVals, err := yaml.Marshal(ov)
 	if err != nil {
-		c.l.WithField("config_path", k).WithError(err).Error("Error while marshaling old config")
+		c.l.Error("Error while marshaling old config",
+			"config_path", k,
+			"error", err,
+		)
 	}
 
 	return string(newVals) != string(oldVals)
@@ -154,7 +160,10 @@ func (c *C) ReloadConfig() {
 
 	err := c.Load(c.path)
 	if err != nil {
-		c.l.WithField("config_path", c.path).WithError(err).Error("Error occurred while reloading config")
+		c.l.Error("Error occurred while reloading config",
+			"config_path", c.path,
+			"error", err,
+		)
 		return
 	}
 

connection_manager.go

@@ -5,13 +5,12 @@ import (
 	"context"
 	"encoding/binary"
 	"fmt"
+	"log/slog"
 	"net/netip"
 	"sync"
 	"sync/atomic"
 	"time"
 
-	"github.com/rcrowley/go-metrics"
-	"github.com/sirupsen/logrus"
 	"github.com/slackhq/nebula/cert"
 	"github.com/slackhq/nebula/config"
 	"github.com/slackhq/nebula/header"
@@ -45,19 +44,16 @@ type connectionManager struct {
 	inactivityTimeout       atomic.Int64
 	dropInactive            atomic.Bool
 
-	metricsTxPunchy metrics.Counter
-
-	l *logrus.Logger
+	l *slog.Logger
 }
 
-func newConnectionManagerFromConfig(l *logrus.Logger, c *config.C, hm *HostMap, p *Punchy) *connectionManager {
+func newConnectionManagerFromConfig(l *slog.Logger, c *config.C, hm *HostMap, p *Punchy) *connectionManager {
 	cm := &connectionManager{
-		hostMap:         hm,
-		l:               l,
-		punchy:          p,
-		relayUsed:       make(map[uint32]struct{}),
-		relayUsedLock:   &sync.RWMutex{},
-		metricsTxPunchy: metrics.GetOrRegisterCounter("messages.tx.punchy", nil),
+		hostMap:       hm,
+		l:             l,
+		punchy:        p,
+		relayUsed:     make(map[uint32]struct{}),
+		relayUsedLock: &sync.RWMutex{},
 	}
 
 	cm.reload(c, true)
@@ -85,9 +81,10 @@ func (cm *connectionManager) reload(c *config.C, initial bool) {
 		old := cm.getInactivityTimeout()
 		cm.inactivityTimeout.Store((int64)(c.GetDuration("tunnels.inactivity_timeout", 10*time.Minute)))
 		if !initial {
-			cm.l.WithField("oldDuration", old).
-				WithField("newDuration", cm.getInactivityTimeout()).
-				Info("Inactivity timeout has changed")
+			cm.l.Info("Inactivity timeout has changed",
+				"oldDuration", old,
+				"newDuration", cm.getInactivityTimeout(),
+			)
 		}
 	}
 
@@ -95,9 +92,10 @@ func (cm *connectionManager) reload(c *config.C, initial bool) {
 		old := cm.dropInactive.Load()
 		cm.dropInactive.Store(c.GetBool("tunnels.drop_inactive", false))
 		if !initial {
-			cm.l.WithField("oldBool", old).
-				WithField("newBool", cm.dropInactive.Load()).
-				Info("Drop inactive setting has changed")
+			cm.l.Info("Drop inactive setting has changed",
+				"oldBool", old,
+				"newBool", cm.dropInactive.Load(),
+			)
 		}
 	}
 }
@@ -256,7 +254,7 @@ func (cm *connectionManager) migrateRelayUsed(oldhostinfo, newhostinfo *HostInfo
 			var err error
 			index, err = AddRelay(cm.l, newhostinfo, cm.hostMap, r.PeerAddr, nil, r.Type, Requested)
 			if err != nil {
-				cm.l.WithError(err).Error("failed to migrate relay to new hostinfo")
+				cm.l.Error("failed to migrate relay to new hostinfo", "error", err)
 				continue
 			}
 			switch r.Type {
@@ -304,16 +302,16 @@ func (cm *connectionManager) migrateRelayUsed(oldhostinfo, newhostinfo *HostInfo
 
 		msg, err := req.Marshal()
 		if err != nil {
-			cm.l.WithError(err).Error("failed to marshal Control message to migrate relay")
+			cm.l.Error("failed to marshal Control message to migrate relay", "error", err)
 		} else {
 			cm.intf.SendMessageToHostInfo(header.Control, 0, newhostinfo, msg, make([]byte, 12), make([]byte, mtu))
-			cm.l.WithFields(logrus.Fields{
-				"relayFrom":           req.RelayFromAddr,
-				"relayTo":             req.RelayToAddr,
-				"initiatorRelayIndex": req.InitiatorRelayIndex,
-				"responderRelayIndex": req.ResponderRelayIndex,
-				"vpnAddrs":            newhostinfo.vpnAddrs}).
-				Info("send CreateRelayRequest")
+			cm.l.Info("send CreateRelayRequest",
+				"relayFrom", req.RelayFromAddr,
+				"relayTo", req.RelayToAddr,
+				"initiatorRelayIndex", req.InitiatorRelayIndex,
+				"responderRelayIndex", req.ResponderRelayIndex,
+				"vpnAddrs", newhostinfo.vpnAddrs,
+			)
 		}
 	}
 }
@@ -325,7 +323,7 @@ func (cm *connectionManager) makeTrafficDecision(localIndex uint32, now time.Tim
 
 	hostinfo := cm.hostMap.Indexes[localIndex]
 	if hostinfo == nil {
-		cm.l.WithField("localIndex", localIndex).Debugln("Not found in hostmap")
+		cm.l.Debug("Not found in hostmap", "localIndex", localIndex)
 		return doNothing, nil, nil
 	}
 
@@ -345,10 +343,10 @@ func (cm *connectionManager) makeTrafficDecision(localIndex uint32, now time.Tim
 	// A hostinfo is determined alive if there is incoming traffic
 	if inTraffic {
 		decision := doNothing
-		if cm.l.Level >= logrus.DebugLevel {
-			hostinfo.logger(cm.l).
-				WithField("tunnelCheck", m{"state": "alive", "method": "passive"}).
-				Debug("Tunnel status")
+		if cm.l.Enabled(context.Background(), slog.LevelDebug) {
+			hostinfo.logger(cm.l).Debug("Tunnel status",
+				"tunnelCheck", m{"state": "alive", "method": "passive"},
+			)
 		}
 		hostinfo.pendingDeletion.Store(false)
 
@@ -367,7 +365,7 @@ func (cm *connectionManager) makeTrafficDecision(localIndex uint32, now time.Tim
 
 		if !outTraffic {
 			// Send a punch packet to keep the NAT state alive
-			cm.sendPunch(hostinfo)
+			cm.punchy.SendPunch(hostinfo)
 		}
 
 		return decision, hostinfo, primary
@@ -375,9 +373,9 @@ func (cm *connectionManager) makeTrafficDecision(localIndex uint32, now time.Tim
 
 	if hostinfo.pendingDeletion.Load() {
 		// We have already sent a test packet and nothing was returned, this hostinfo is dead
-		hostinfo.logger(cm.l).
-			WithField("tunnelCheck", m{"state": "dead", "method": "active"}).
-			Info("Tunnel status")
+		hostinfo.logger(cm.l).Info("Tunnel status",
+			"tunnelCheck", m{"state": "dead", "method": "active"},
+		)
 
 		return deleteTunnel, hostinfo, nil
 	}
@@ -388,40 +386,39 @@ func (cm *connectionManager) makeTrafficDecision(localIndex uint32, now time.Tim
 			inactiveFor, isInactive := cm.isInactive(hostinfo, now)
 			if isInactive {
 				// Tunnel is inactive, tear it down
-				hostinfo.logger(cm.l).
-					WithField("inactiveDuration", inactiveFor).
-					WithField("primary", mainHostInfo).
-					Info("Dropping tunnel due to inactivity")
+				hostinfo.logger(cm.l).Info("Dropping tunnel due to inactivity",
+					"inactiveDuration", inactiveFor,
+					"primary", mainHostInfo,
+				)
 
 				return closeTunnel, hostinfo, primary
 			}
 
 			// If we aren't sending or receiving traffic then its an unused tunnel and we don't to test the tunnel.
 			// Just maintain NAT state if configured to do so.
-			cm.sendPunch(hostinfo)
+			cm.punchy.SendPunch(hostinfo)
 			cm.trafficTimer.Add(hostinfo.localIndexId, cm.checkInterval)
 			return doNothing, nil, nil
 		}
 
-		if cm.punchy.GetTargetEverything() {
-			// This is similar to the old punchy behavior with a slight optimization.
-			// We aren't receiving traffic but we are sending it, punch on all known
-			// ips in case we need to re-prime NAT state
-			cm.sendPunch(hostinfo)
-		}
+		// We aren't receiving traffic but we are sending it. The outbound
+		// traffic itself refreshes the primary remote's NAT state; this
+		// fans out to non-primary remotes, but only if target_all_remotes
+		// is configured.
+		cm.punchy.SendPunchToAll(hostinfo)
 
-		if cm.l.Level >= logrus.DebugLevel {
-			hostinfo.logger(cm.l).
-				WithField("tunnelCheck", m{"state": "testing", "method": "active"}).
-				Debug("Tunnel status")
+		if cm.l.Enabled(context.Background(), slog.LevelDebug) {
+			hostinfo.logger(cm.l).Debug("Tunnel status",
+				"tunnelCheck", m{"state": "testing", "method": "active"},
+			)
 		}
 
 		// Send a test packet to trigger an authenticated tunnel test, this should suss out any lingering tunnel issues
 		decision = sendTestPacket
 
 	} else {
-		if cm.l.Level >= logrus.DebugLevel {
-			hostinfo.logger(cm.l).Debugf("Hostinfo sadness")
+		if cm.l.Enabled(context.Background(), slog.LevelDebug) {
+			hostinfo.logger(cm.l).Debug("Hostinfo sadness")
 		}
 	}
 
@@ -493,14 +490,16 @@ func (cm *connectionManager) isInvalidCertificate(now time.Time, hostinfo *HostI
 		return false //cert is still valid! yay!
 	} else if err == cert.ErrBlockListed { //avoiding errors.Is for speed
 		// Block listed certificates should always be disconnected
-		hostinfo.logger(cm.l).WithError(err).
-			WithField("fingerprint", remoteCert.Fingerprint).
-			Info("Remote certificate is blocked, tearing down the tunnel")
+		hostinfo.logger(cm.l).Info("Remote certificate is blocked, tearing down the tunnel",
+			"error", err,
+			"fingerprint", remoteCert.Fingerprint,
+		)
 		return true
 	} else if cm.intf.disconnectInvalid.Load() {
-		hostinfo.logger(cm.l).WithError(err).
-			WithField("fingerprint", remoteCert.Fingerprint).
-			Info("Remote certificate is no longer valid, tearing down the tunnel")
+		hostinfo.logger(cm.l).Info("Remote certificate is no longer valid, tearing down the tunnel",
+			"error", err,
+			"fingerprint", remoteCert.Fingerprint,
+		)
 		return true
 	} else {
 		//if we reach here, the cert is no longer valid, but we're configured to keep tunnels from now-invalid certs open
@@ -508,41 +507,17 @@ func (cm *connectionManager) isInvalidCertificate(now time.Time, hostinfo *HostI
 	}
 }
 
-func (cm *connectionManager) sendPunch(hostinfo *HostInfo) {
-	if !cm.punchy.GetPunch() {
-		// Punching is disabled
-		return
-	}
-
-	if cm.intf.lightHouse.IsAnyLighthouseAddr(hostinfo.vpnAddrs) {
-		// Do not punch to lighthouses, we assume our lighthouse update interval is good enough.
-		// In the event the update interval is not sufficient to maintain NAT state then a publicly available lighthouse
-		// would lose the ability to notify us and punchy.respond would become unreliable.
-		return
-	}
-
-	if cm.punchy.GetTargetEverything() {
-		hostinfo.remotes.ForEach(cm.hostMap.GetPreferredRanges(), func(addr netip.AddrPort, preferred bool) {
-			cm.metricsTxPunchy.Inc(1)
-			cm.intf.outside.WriteTo([]byte{1}, addr)
-		})
-
-	} else if hostinfo.remote.IsValid() {
-		cm.metricsTxPunchy.Inc(1)
-		cm.intf.outside.WriteTo([]byte{1}, hostinfo.remote)
-	}
-}
-
 func (cm *connectionManager) tryRehandshake(hostinfo *HostInfo) {
 	cs := cm.intf.pki.getCertState()
 	curCrt := hostinfo.ConnectionState.myCert
 	curCrtVersion := curCrt.Version()
 	myCrt := cs.getCertificate(curCrtVersion)
 	if myCrt == nil {
-		cm.l.WithField("vpnAddrs", hostinfo.vpnAddrs).
-			WithField("version", curCrtVersion).
-			WithField("reason", "local certificate removed").
-			Info("Re-handshaking with remote")
+		cm.l.Info("Re-handshaking with remote",
+			"vpnAddrs", hostinfo.vpnAddrs,
+			"version", curCrtVersion,
+			"reason", "local certificate removed",
+		)
 		cm.intf.handshakeManager.StartHandshake(hostinfo.vpnAddrs[0], nil)
 		return
 	}
@@ -550,11 +525,12 @@ func (cm *connectionManager) tryRehandshake(hostinfo *HostInfo) {
 	if peerCrt != nil && curCrtVersion < peerCrt.Certificate.Version() {
 		// if our certificate version is less than theirs, and we have a matching version available, rehandshake?
 		if cs.getCertificate(peerCrt.Certificate.Version()) != nil {
-			cm.l.WithField("vpnAddrs", hostinfo.vpnAddrs).
-				WithField("version", curCrtVersion).
-				WithField("peerVersion", peerCrt.Certificate.Version()).
-				WithField("reason", "local certificate version lower than peer, attempting to correct").
-				Info("Re-handshaking with remote")
+			cm.l.Info("Re-handshaking with remote",
+				"vpnAddrs", hostinfo.vpnAddrs,
+				"version", curCrtVersion,
+				"peerVersion", peerCrt.Certificate.Version(),
+				"reason", "local certificate version lower than peer, attempting to correct",
+			)
 			cm.intf.handshakeManager.StartHandshake(hostinfo.vpnAddrs[0], func(hh *HandshakeHostInfo) {
 				hh.initiatingVersionOverride = peerCrt.Certificate.Version()
 			})
@@ -562,17 +538,19 @@ func (cm *connectionManager) tryRehandshake(hostinfo *HostInfo) {
 		}
 	}
 	if !bytes.Equal(curCrt.Signature(), myCrt.Signature()) {
-		cm.l.WithField("vpnAddrs", hostinfo.vpnAddrs).
-			WithField("reason", "local certificate is not current").
-			Info("Re-handshaking with remote")
+		cm.l.Info("Re-handshaking with remote",
+			"vpnAddrs", hostinfo.vpnAddrs,
+			"reason", "local certificate is not current",
+		)
 
 		cm.intf.handshakeManager.StartHandshake(hostinfo.vpnAddrs[0], nil)
 		return
 	}
 	if curCrtVersion < cs.initiatingVersion {
-		cm.l.WithField("vpnAddrs", hostinfo.vpnAddrs).
-			WithField("reason", "current cert version < pki.initiatingVersion").
-			Info("Re-handshaking with remote")
+		cm.l.Info("Re-handshaking with remote",
+			"vpnAddrs", hostinfo.vpnAddrs,
+			"reason", "current cert version < pki.initiatingVersion",
+		)
 
 		cm.intf.handshakeManager.StartHandshake(hostinfo.vpnAddrs[0], nil)
 		return

connection_manager_test.go

@@ -7,10 +7,9 @@ import (
 	"testing"
 	"time"
 
-	"github.com/flynn/noise"
 	"github.com/slackhq/nebula/cert"
 	"github.com/slackhq/nebula/config"
-	"github.com/slackhq/nebula/overlay"
+	"github.com/slackhq/nebula/overlay/overlaytest"
 	"github.com/slackhq/nebula/test"
 	"github.com/slackhq/nebula/udp"
 	"github.com/stretchr/testify/assert"
@@ -47,13 +46,13 @@ func Test_NewConnectionManagerTest(t *testing.T) {
 		initiatingVersion: cert.Version1,
 		privateKey:        []byte{},
 		v1Cert:            &dummyCert{version: cert.Version1},
-		v1HandshakeBytes:  []byte{},
+		v1Credential:      nil,
 	}
 
 	lh := newTestLighthouse()
 	ifce := &Interface{
 		hostMap:          hostMap,
-		inside:           &overlay.NoopTun{},
+		inside:           &overlaytest.NoopTun{},
 		outside:          &udp.NoopConn{},
 		firewall:         &Firewall{},
 		lightHouse:       lh,
@@ -64,9 +63,9 @@ func Test_NewConnectionManagerTest(t *testing.T) {
 	ifce.pki.cs.Store(cs)
 
 	// Create manager
-	conf := config.NewC(l)
-	punchy := NewPunchyFromConfig(l, conf)
-	nc := newConnectionManagerFromConfig(l, conf, hostMap, punchy)
+	conf := config.NewC(test.NewLogger())
+	punchy := NewPunchyFromConfig(test.NewLogger(), conf, nil)
+	nc := newConnectionManagerFromConfig(test.NewLogger(), conf, hostMap, punchy)
 	nc.intf = ifce
 	p := []byte("")
 	nb := make([]byte, 12, 12)
@@ -80,7 +79,6 @@ func Test_NewConnectionManagerTest(t *testing.T) {
 	}
 	hostinfo.ConnectionState = &ConnectionState{
 		myCert: &dummyCert{version: cert.Version1},
-		H:      &noise.HandshakeState{},
 	}
 	nc.hostMap.unlockedAddHostInfo(hostinfo, ifce)
 
@@ -130,13 +128,13 @@ func Test_NewConnectionManagerTest2(t *testing.T) {
 		initiatingVersion: cert.Version1,
 		privateKey:        []byte{},
 		v1Cert:            &dummyCert{version: cert.Version1},
-		v1HandshakeBytes:  []byte{},
+		v1Credential:      nil,
 	}
 
 	lh := newTestLighthouse()
 	ifce := &Interface{
 		hostMap:          hostMap,
-		inside:           &overlay.NoopTun{},
+		inside:           &overlaytest.NoopTun{},
 		outside:          &udp.NoopConn{},
 		firewall:         &Firewall{},
 		lightHouse:       lh,
@@ -147,9 +145,9 @@ func Test_NewConnectionManagerTest2(t *testing.T) {
 	ifce.pki.cs.Store(cs)
 
 	// Create manager
-	conf := config.NewC(l)
-	punchy := NewPunchyFromConfig(l, conf)
-	nc := newConnectionManagerFromConfig(l, conf, hostMap, punchy)
+	conf := config.NewC(test.NewLogger())
+	punchy := NewPunchyFromConfig(test.NewLogger(), conf, nil)
+	nc := newConnectionManagerFromConfig(test.NewLogger(), conf, hostMap, punchy)
 	nc.intf = ifce
 	p := []byte("")
 	nb := make([]byte, 12, 12)
@@ -163,7 +161,6 @@ func Test_NewConnectionManagerTest2(t *testing.T) {
 	}
 	hostinfo.ConnectionState = &ConnectionState{
 		myCert: &dummyCert{version: cert.Version1},
-		H:      &noise.HandshakeState{},
 	}
 	nc.hostMap.unlockedAddHostInfo(hostinfo, ifce)
 
@@ -215,13 +212,13 @@ func Test_NewConnectionManager_DisconnectInactive(t *testing.T) {
 		initiatingVersion: cert.Version1,
 		privateKey:        []byte{},
 		v1Cert:            &dummyCert{version: cert.Version1},
-		v1HandshakeBytes:  []byte{},
+		v1Credential:      nil,
 	}
 
 	lh := newTestLighthouse()
 	ifce := &Interface{
 		hostMap:          hostMap,
-		inside:           &overlay.NoopTun{},
+		inside:           &overlaytest.NoopTun{},
 		outside:          &udp.NoopConn{},
 		firewall:         &Firewall{},
 		lightHouse:       lh,
@@ -232,12 +229,12 @@ func Test_NewConnectionManager_DisconnectInactive(t *testing.T) {
 	ifce.pki.cs.Store(cs)
 
 	// Create manager
-	conf := config.NewC(l)
+	conf := config.NewC(test.NewLogger())
 	conf.Settings["tunnels"] = map[string]any{
 		"drop_inactive": true,
 	}
-	punchy := NewPunchyFromConfig(l, conf)
-	nc := newConnectionManagerFromConfig(l, conf, hostMap, punchy)
+	punchy := NewPunchyFromConfig(test.NewLogger(), conf, nil)
+	nc := newConnectionManagerFromConfig(test.NewLogger(), conf, hostMap, punchy)
 	assert.True(t, nc.dropInactive.Load())
 	nc.intf = ifce
 
@@ -249,7 +246,6 @@ func Test_NewConnectionManager_DisconnectInactive(t *testing.T) {
 	}
 	hostinfo.ConnectionState = &ConnectionState{
 		myCert: &dummyCert{version: cert.Version1},
-		H:      &noise.HandshakeState{},
 	}
 	nc.hostMap.unlockedAddHostInfo(hostinfo, ifce)
 
@@ -340,15 +336,15 @@ func Test_NewConnectionManagerTest_DisconnectInvalid(t *testing.T) {
 	cachedPeerCert, err := ncp.VerifyCertificate(now.Add(time.Second), peerCert)
 
 	cs := &CertState{
-		privateKey:       []byte{},
-		v1Cert:           &dummyCert{},
-		v1HandshakeBytes: []byte{},
+		privateKey:   []byte{},
+		v1Cert:       &dummyCert{},
+		v1Credential: nil,
 	}
 
 	lh := newTestLighthouse()
 	ifce := &Interface{
 		hostMap:          hostMap,
-		inside:           &overlay.NoopTun{},
+		inside:           &overlaytest.NoopTun{},
 		outside:          &udp.NoopConn{},
 		firewall:         &Firewall{},
 		lightHouse:       lh,
@@ -361,9 +357,9 @@ func Test_NewConnectionManagerTest_DisconnectInvalid(t *testing.T) {
 	ifce.disconnectInvalid.Store(true)
 
 	// Create manager
-	conf := config.NewC(l)
-	punchy := NewPunchyFromConfig(l, conf)
-	nc := newConnectionManagerFromConfig(l, conf, hostMap, punchy)
+	conf := config.NewC(test.NewLogger())
+	punchy := NewPunchyFromConfig(test.NewLogger(), conf, nil)
+	nc := newConnectionManagerFromConfig(test.NewLogger(), conf, hostMap, punchy)
 	nc.intf = ifce
 	ifce.connectionManager = nc
 
@@ -372,7 +368,6 @@ func Test_NewConnectionManagerTest_DisconnectInvalid(t *testing.T) {
 		ConnectionState: &ConnectionState{
 			myCert:   &dummyCert{},
 			peerCert: cachedPeerCert,
-			H:        &noise.HandshakeState{},
 		},
 	}
 	nc.hostMap.unlockedAddHostInfo(hostinfo, ifce)

connection_state.go

@@ -1,24 +1,20 @@
 package nebula
 
 import (
-	"crypto/rand"
 	"encoding/json"
-	"fmt"
 	"sync"
 	"sync/atomic"
 
-	"github.com/flynn/noise"
-	"github.com/sirupsen/logrus"
 	"github.com/slackhq/nebula/cert"
+	"github.com/slackhq/nebula/handshake"
 	"github.com/slackhq/nebula/noiseutil"
 )
 
-const ReplayWindow = 1024
+const ReplayWindow = 8192
 
 type ConnectionState struct {
-	eKey           *NebulaCipherState
-	dKey           *NebulaCipherState
-	H              *noise.HandshakeState
+	eKey           noiseutil.CipherState
+	dKey           noiseutil.CipherState
 	myCert         cert.Certificate
 	peerCert       *cert.CachedCertificate
 	initiator      bool
@@ -27,55 +23,24 @@ type ConnectionState struct {
 	writeLock      sync.Mutex
 }
 
-func NewConnectionState(l *logrus.Logger, cs *CertState, crt cert.Certificate, initiator bool, pattern noise.HandshakePattern) (*ConnectionState, error) {
-	var dhFunc noise.DHFunc
-	switch crt.Curve() {
-	case cert.Curve_CURVE25519:
-		dhFunc = noise.DH25519
-	case cert.Curve_P256:
-		if cs.pkcs11Backed {
-			dhFunc = noiseutil.DHP256PKCS11
-		} else {
-			dhFunc = noiseutil.DHP256
-		}
-	default:
-		return nil, fmt.Errorf("invalid curve: %s", crt.Curve())
-	}
-
-	var ncs noise.CipherSuite
-	if cs.cipher == "chachapoly" {
-		ncs = noise.NewCipherSuite(dhFunc, noise.CipherChaChaPoly, noise.HashSHA256)
-	} else {
-		ncs = noise.NewCipherSuite(dhFunc, noiseutil.CipherAESGCM, noise.HashSHA256)
-	}
-
-	static := noise.DHKey{Private: cs.privateKey, Public: crt.PublicKey()}
-	hs, err := noise.NewHandshakeState(noise.Config{
-		CipherSuite:   ncs,
-		Random:        rand.Reader,
-		Pattern:       pattern,
-		Initiator:     initiator,
-		StaticKeypair: static,
-		//NOTE: These should come from CertState (pki.go) when we finally implement it
-		PresharedKey:          []byte{},
-		PresharedKeyPlacement: 0,
-	})
-	if err != nil {
-		return nil, fmt.Errorf("NewConnectionState: %s", err)
-	}
-
-	// The queue and ready params prevent a counter race that would happen when
-	// sending stored packets and simultaneously accepting new traffic.
+// newConnectionStateFromResult builds a fully-populated ConnectionState from a
+// completed handshake.Result. It seeds messageCounter and the replay window so
+// that the post-handshake message indices already used on the wire don't count
+// as missed traffic in the data plane.
+func newConnectionStateFromResult(r *handshake.Result) *ConnectionState {
 	ci := &ConnectionState{
-		H:         hs,
-		initiator: initiator,
+		myCert:    r.MyCert,
+		initiator: r.Initiator,
+		peerCert:  r.RemoteCert,
+		eKey:      noiseutil.NewCipherState(r.EKey, r.Cipher),
+		dKey:      noiseutil.NewCipherState(r.DKey, r.Cipher),
 		window:    NewBits(ReplayWindow),
-		myCert:    crt,
 	}
-	// always start the counter from 2, as packet 1 and packet 2 are handshake packets.
-	ci.messageCounter.Add(2)
-
-	return ci, nil
+	ci.messageCounter.Add(r.MessageIndex)
+	for i := uint64(1); i <= r.MessageIndex; i++ {
+		ci.window.Update(nil, i)
+	}
+	return ci
 }
 
 func (cs *ConnectionState) MarshalJSON() ([]byte, error) {

connection_state_test.go

@@ -0,0 +1,114 @@
+package nebula
+
+import (
+	"net/netip"
+	"testing"
+	"time"
+
+	"github.com/flynn/noise"
+	"github.com/slackhq/nebula/cert"
+	ct "github.com/slackhq/nebula/cert_test"
+	"github.com/slackhq/nebula/handshake"
+	"github.com/slackhq/nebula/header"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+// runTestHandshake runs a complete IX handshake between two freshly-built
+// peers and returns the initiator and responder Results. Used to produce
+// real cipher states for tests that need to exercise post-handshake glue.
+func runTestHandshake(t *testing.T) (initR, respR *handshake.Result) {
+	t.Helper()
+
+	ca, _, caKey, _ := ct.NewTestCaCert(
+		cert.Version2, cert.Curve_CURVE25519, time.Time{}, time.Time{}, nil, nil, nil,
+	)
+	caPool := ct.NewTestCAPool(ca)
+
+	makeCreds := func(name string, networks []netip.Prefix) handshake.GetCredentialFunc {
+		c, _, rawKey, _ := ct.NewTestCert(
+			cert.Version2, cert.Curve_CURVE25519, ca, caKey,
+			name, ca.NotBefore(), ca.NotAfter(), networks, nil, nil,
+		)
+		priv, _, _, err := cert.UnmarshalPrivateKeyFromPEM(rawKey)
+		require.NoError(t, err)
+		hsBytes, err := c.MarshalForHandshakes()
+		require.NoError(t, err)
+		ncs := noise.NewCipherSuite(noise.DH25519, noise.CipherChaChaPoly, noise.HashSHA256)
+		cred := handshake.NewCredential(c, hsBytes, priv, ncs)
+		return func(v cert.Version) *handshake.Credential {
+			if v == cert.Version2 {
+				return cred
+			}
+			return nil
+		}
+	}
+
+	verifier := func(c cert.Certificate) (*cert.CachedCertificate, error) {
+		return caPool.VerifyCertificate(time.Now(), c)
+	}
+
+	initCreds := makeCreds("initiator", []netip.Prefix{netip.MustParsePrefix("10.0.0.1/24")})
+	respCreds := makeCreds("responder", []netip.Prefix{netip.MustParsePrefix("10.0.0.2/24")})
+
+	initM, err := handshake.NewMachine(
+		cert.Version2, initCreds, verifier,
+		func() (uint32, error) { return 1000, nil },
+		true, header.HandshakeIXPSK0,
+	)
+	require.NoError(t, err)
+
+	respM, err := handshake.NewMachine(
+		cert.Version2, respCreds, verifier,
+		func() (uint32, error) { return 2000, nil },
+		false, header.HandshakeIXPSK0,
+	)
+	require.NoError(t, err)
+
+	msg1, err := initM.Initiate(nil)
+	require.NoError(t, err)
+
+	resp, respR, err := respM.ProcessPacket(nil, msg1)
+	require.NoError(t, err)
+	require.NotNil(t, respR)
+
+	_, initR, err = initM.ProcessPacket(nil, resp)
+	require.NoError(t, err)
+	require.NotNil(t, initR)
+
+	return initR, respR
+}
+
+func TestNewConnectionStateFromResult(t *testing.T) {
+	initR, respR := runTestHandshake(t)
+
+	t.Run("initiator", func(t *testing.T) {
+		ci := newConnectionStateFromResult(initR)
+		assert.True(t, ci.initiator)
+		assert.Equal(t, initR.MyCert, ci.myCert)
+		assert.Equal(t, initR.RemoteCert, ci.peerCert)
+		assert.NotNil(t, ci.eKey)
+		assert.NotNil(t, ci.dKey)
+
+		// IX has 2 handshake messages; the next data-plane send is counter=3.
+		assert.Equal(t, uint64(2), ci.messageCounter.Load(),
+			"messageCounter must equal Result.MessageIndex so the next send is N+1")
+
+		// Both handshake counters must be marked seen so they don't appear lost.
+		// Check returns false if an index has already been recorded.
+		assert.False(t, ci.window.Check(nil, 1), "counter 1 must already be seen")
+		assert.False(t, ci.window.Check(nil, 2), "counter 2 must already be seen")
+		// Counter 3 is the next data-plane message and must NOT be pre-marked.
+		assert.True(t, ci.window.Check(nil, 3), "counter 3 must not be pre-seeded")
+	})
+
+	t.Run("responder", func(t *testing.T) {
+		ci := newConnectionStateFromResult(respR)
+		assert.False(t, ci.initiator)
+		assert.Equal(t, respR.MyCert, ci.myCert)
+		assert.Equal(t, respR.RemoteCert, ci.peerCert)
+		assert.NotNil(t, ci.eKey)
+		assert.NotNil(t, ci.dKey)
+		assert.Equal(t, uint64(2), ci.messageCounter.Load())
+	})
+}

control.go

@@ -3,13 +3,13 @@ package nebula
 import (
 	"context"
 	"errors"
+	"log/slog"
 	"net/netip"
 	"os"
 	"os/signal"
 	"sync"
 	"syscall"
 
-	"github.com/sirupsen/logrus"
 	"github.com/slackhq/nebula/cert"
 	"github.com/slackhq/nebula/header"
 	"github.com/slackhq/nebula/overlay"
@@ -46,7 +46,7 @@ type Control struct {
 	state     RunState
 
 	f                      *Interface
-	l                      *logrus.Logger
+	l                      *slog.Logger
 	ctx                    context.Context
 	cancel                 context.CancelFunc
 	sshStart               func()
@@ -151,7 +151,7 @@ func (c *Control) Stop() {
 
 	c.CloseAllTunnels(false)
 	if err := c.f.Close(); err != nil {
-		c.l.WithError(err).Error("Close interface failed")
+		c.l.Error("Close interface failed", "error", err)
 	}
 	c.stateLock.Lock()
 	c.state = StateStopped
@@ -166,7 +166,7 @@ func (c *Control) ShutdownBlock() {
 
 	rawSig := <-sigChan
 	sig := rawSig.String()
-	c.l.WithField("signal", sig).Info("Caught signal, shutting down")
+	c.l.Info("Caught signal, shutting down", "signal", sig)
 	c.Stop()
 }
 
@@ -303,8 +303,10 @@ func (c *Control) CloseAllTunnels(excludeLighthouses bool) (closed int) {
 		c.f.send(header.CloseTunnel, 0, h.ConnectionState, h, []byte{}, make([]byte, 12, 12), make([]byte, mtu))
 		c.f.closeTunnel(h)
 
-		c.l.WithField("vpnAddrs", h.vpnAddrs).WithField("udpAddr", h.remote).
-			Debug("Sending close tunnel message")
+		c.l.Debug("Sending close tunnel message",
+			"vpnAddrs", h.vpnAddrs,
+			"udpAddr", h.remote,
+		)
 		closed++
 	}
 

control_test.go

@@ -6,7 +6,6 @@ import (
 	"reflect"
 	"testing"
 
-	"github.com/sirupsen/logrus"
 	"github.com/slackhq/nebula/cert"
 	"github.com/slackhq/nebula/test"
 	"github.com/stretchr/testify/assert"
@@ -83,7 +82,7 @@ func TestControl_GetHostInfoByVpnIp(t *testing.T) {
 		f: &Interface{
 			hostMap: hm,
 		},
-		l: logrus.New(),
+		l: test.NewLogger(),
 	}
 
 	thi := c.GetHostInfoByVpnAddr(vpnIp, false)

control_tester.go

@@ -5,8 +5,6 @@ package nebula
 import (
 	"net/netip"
 
-	"github.com/google/gopacket"
-	"github.com/google/gopacket/layers"
 	"github.com/slackhq/nebula/header"
 	"github.com/slackhq/nebula/overlay"
 	"github.com/slackhq/nebula/udp"
@@ -22,7 +20,9 @@ func (c *Control) WaitForType(msgType header.MessageType, subType header.Message
 			panic(err)
 		}
 		pipeTo.InjectUDPPacket(p)
-		if h.Type == msgType && h.Subtype == subType {
+		match := h.Type == msgType && h.Subtype == subType
+		p.Release()
+		if match {
 			return
 		}
 	}
@@ -38,7 +38,9 @@ func (c *Control) WaitForTypeByIndex(toIndex uint32, msgType header.MessageType,
 			panic(err)
 		}
 		pipeTo.InjectUDPPacket(p)
-		if h.RemoteIndex == toIndex && h.Type == msgType && h.Subtype == subType {
+		match := h.RemoteIndex == toIndex && h.Type == msgType && h.Subtype == subType
+		p.Release()
+		if match {
 			return
 		}
 	}
@@ -90,65 +92,15 @@ func (c *Control) GetTunTxChan() <-chan []byte {
 	return c.f.inside.(*overlay.TestTun).TxPackets
 }
 
-// InjectUDPPacket will inject a packet into the udp side of nebula
+// InjectUDPPacket injects a packet into the udp side. We copy internally so the caller keeps ownership of p.
+// The copy comes from the freelist so steady-state alloc is zero.
 func (c *Control) InjectUDPPacket(p *udp.Packet) {
-	c.f.outside.(*udp.TesterConn).Send(p)
+	c.f.outside.(*udp.TesterConn).Send(p.Copy())
 }
 
-// InjectTunUDPPacket puts a udp packet on the tun interface. Using UDP here because it's a simpler protocol
-func (c *Control) InjectTunUDPPacket(toAddr netip.Addr, toPort uint16, fromAddr netip.Addr, fromPort uint16, data []byte) {
-	serialize := make([]gopacket.SerializableLayer, 0)
-	var netLayer gopacket.NetworkLayer
-	if toAddr.Is6() {
-		if !fromAddr.Is6() {
-			panic("Cant send ipv6 to ipv4")
-		}
-		ip := &layers.IPv6{
-			Version:    6,
-			NextHeader: layers.IPProtocolUDP,
-			SrcIP:      fromAddr.Unmap().AsSlice(),
-			DstIP:      toAddr.Unmap().AsSlice(),
-		}
-		serialize = append(serialize, ip)
-		netLayer = ip
-	} else {
-		if !fromAddr.Is4() {
-			panic("Cant send ipv4 to ipv6")
-		}
-
-		ip := &layers.IPv4{
-			Version:  4,
-			TTL:      64,
-			Protocol: layers.IPProtocolUDP,
-			SrcIP:    fromAddr.Unmap().AsSlice(),
-			DstIP:    toAddr.Unmap().AsSlice(),
-		}
-		serialize = append(serialize, ip)
-		netLayer = ip
-	}
-
-	udp := layers.UDP{
-		SrcPort: layers.UDPPort(fromPort),
-		DstPort: layers.UDPPort(toPort),
-	}
-	err := udp.SetNetworkLayerForChecksum(netLayer)
-	if err != nil {
-		panic(err)
-	}
-
-	buffer := gopacket.NewSerializeBuffer()
-	opt := gopacket.SerializeOptions{
-		ComputeChecksums: true,
-		FixLengths:       true,
-	}
-
-	serialize = append(serialize, &udp, gopacket.Payload(data))
-	err = gopacket.SerializeLayers(buffer, opt, serialize...)
-	if err != nil {
-		panic(err)
-	}
-
-	c.f.inside.(*overlay.TestTun).Send(buffer.Bytes())
+// InjectTunPacket pushes an IP packet onto the tun interface.
+func (c *Control) InjectTunPacket(packet []byte) {
+	c.f.inside.(*overlay.TestTun).Send(packet)
 }
 
 func (c *Control) GetVpnAddrs() []netip.Addr {

dns_server.go

@@ -1,63 +1,249 @@
 package nebula
 
 import (
+	"context"
 	"fmt"
+	"log/slog"
 	"net"
 	"net/netip"
 	"strconv"
 	"strings"
 	"sync"
+	"sync/atomic"
 
 	"github.com/gaissmai/bart"
 	"github.com/miekg/dns"
-	"github.com/sirupsen/logrus"
 	"github.com/slackhq/nebula/config"
 )
 
-// This whole thing should be rewritten to use context
-
-var dnsR *dnsRecords
-var dnsServer *dns.Server
-var dnsAddr string
-
-type dnsRecords struct {
+type dnsServer struct {
 	sync.RWMutex
-	l               *logrus.Logger
+	l               *slog.Logger
+	ctx             context.Context
 	dnsMap4         map[string]netip.Addr
 	dnsMap6         map[string]netip.Addr
 	hostMap         *HostMap
 	myVpnAddrsTable *bart.Lite
+
+	mux *dns.ServeMux
+
+	// enabled mirrors `lighthouse.serve_dns && lighthouse.am_lighthouse`.
+	// Start, Add, and reload consult it so callers don't need to know the
+	// gating rules. When it toggles off via reload, accumulated records are
+	// cleared so a later re-enable starts with a fresh map populated from
+	// new handshakes.
+	enabled atomic.Bool
+
+	serverMu sync.Mutex
+	server   *dns.Server
+	// started is closed once `server` has finished binding (or after
+	// ListenAndServe returns on a bind failure). Stop waits on it before
+	// calling Shutdown to avoid the miekg/dns "server not started" race
+	// where a Shutdown that arrives before bind completes is silently
+	// ignored, leaving the listener running forever.
+	started chan struct{}
+	addr    string
 }
 
-func newDnsRecords(l *logrus.Logger, cs *CertState, hostMap *HostMap) *dnsRecords {
-	return &dnsRecords{
+// newDnsServerFromConfig builds a dnsServer, applies the initial config, and
+// registers a reload callback. The reload callback is registered before the
+// initial config is applied, so a SIGHUP can later enable, fix, or disable
+// DNS even if the initial application failed.
+//
+// The dnsServer internally gates on `lighthouse.serve_dns &&
+// lighthouse.am_lighthouse`. Start and Add are safe to call unconditionally,
+// they no-op when DNS isn't enabled. Each Start invocation owns a ctx-cancel
+// watcher that tears the listener down on nebula shutdown. The returned
+// pointer is always non-nil, even on error.
+func newDnsServerFromConfig(ctx context.Context, l *slog.Logger, cs *CertState, hostMap *HostMap, c *config.C) (*dnsServer, error) {
+	ds := &dnsServer{
 		l:               l,
+		ctx:             ctx,
 		dnsMap4:         make(map[string]netip.Addr),
 		dnsMap6:         make(map[string]netip.Addr),
 		hostMap:         hostMap,
 		myVpnAddrsTable: cs.myVpnAddrsTable,
 	}
+	ds.mux = dns.NewServeMux()
+	ds.mux.HandleFunc(".", ds.handleDnsRequest)
+
+	c.RegisterReloadCallback(func(c *config.C) {
+		if err := ds.reload(c, false); err != nil {
+			ds.l.Error("Failed to reload DNS responder from config", "error", err)
+		}
+	})
+
+	if err := ds.reload(c, true); err != nil {
+		return ds, err
+	}
+	return ds, nil
 }
 
-func (d *dnsRecords) Query(q uint16, data string) netip.Addr {
+// reload applies the latest config and reconciles the running state with it:
+//   - enabled toggled on  -> spawn a runner
+//   - enabled toggled off -> stop the runner
+//   - listen address changed (while running) -> restart on the new address
+//   - everything else     -> no-op
+//
+// On the initial call it only records configuration; Control.Start is what
+// launches the first runner via dnsStart.
+func (d *dnsServer) reload(c *config.C, initial bool) error {
+	wantsDns := c.GetBool("lighthouse.serve_dns", false)
+	amLighthouse := c.GetBool("lighthouse.am_lighthouse", false)
+	enabled := wantsDns && amLighthouse
+	newAddr := getDnsServerAddr(c)
+
+	d.serverMu.Lock()
+	running := d.server
+	runningStarted := d.started
+	sameAddr := d.addr == newAddr
+	d.addr = newAddr
+	d.enabled.Store(enabled)
+	d.serverMu.Unlock()
+
+	if initial {
+		if wantsDns && !amLighthouse {
+			d.l.Warn("DNS server refusing to run because this host is not a lighthouse.")
+		}
+		return nil
+	}
+
+	if !enabled {
+		if running != nil {
+			d.Stop()
+		}
+		// Drop any records that accumulated while enabled; a later re-enable
+		// will repopulate from fresh handshakes.
+		d.clearRecords()
+		return nil
+	}
+
+	if running == nil {
+		// Was disabled (or never started); bring it up now.
+		go d.Start()
+		return nil
+	}
+
+	if sameAddr {
+		return nil
+	}
+
+	d.shutdownServer(running, runningStarted, "reload")
+	// Old Start goroutine has now exited; bring up a fresh listener on the
+	// new address.
+	go d.Start()
+	return nil
+}
+
+// shutdownServer waits for the server to finish binding (so Shutdown actually
+// stops it rather than no-oping) and then shuts it down.
+func (d *dnsServer) shutdownServer(srv *dns.Server, started chan struct{}, reason string) {
+	if srv == nil {
+		return
+	}
+	if started != nil {
+		<-started
+	}
+	if err := srv.Shutdown(); err != nil {
+		d.l.Warn("Failed to shut down the DNS responder", "reason", reason, "error", err)
+	}
+}
+
+// Start binds and serves the DNS responder. Blocks until Stop is called or
+// the listener errors. Safe to call when DNS is disabled (returns
+// immediately). This is what Control.dnsStart points at.
+//
+// Must be invoked after the tun device is active so that lighthouse.dns.host
+// may bind to a nebula IP.
+func (d *dnsServer) Start() {
+	if !d.enabled.Load() {
+		return
+	}
+
+	started := make(chan struct{})
+	d.serverMu.Lock()
+	if d.ctx.Err() != nil {
+		d.serverMu.Unlock()
+		return
+	}
+	addr := d.addr
+	server := &dns.Server{
+		Addr:              addr,
+		Net:               "udp",
+		Handler:           d.mux,
+		NotifyStartedFunc: func() { close(started) },
+	}
+	d.server = server
+	d.started = started
+	d.serverMu.Unlock()
+
+	// Per-invocation ctx watcher. Exits when Start does, so we don't leak a
+	// watcher per reload-driven restart.
+	done := make(chan struct{})
+	go func() {
+		select {
+		case <-d.ctx.Done():
+			d.shutdownServer(server, started, "shutdown")
+		case <-done:
+		}
+	}()
+
+	d.l.Info("Starting DNS responder", "dnsListener", addr)
+	err := server.ListenAndServe()
+	close(done)
+
+	// If the listener never bound (bind error) NotifyStartedFunc never fires,
+	// so close started here to release any Stop caller waiting on it.
+	select {
+	case <-started:
+	default:
+		close(started)
+	}
+
+	if err != nil {
+		d.l.Warn("Failed to run the DNS responder", "error", err)
+	}
+}
+
+// Stop shuts down the active server, if any. Idempotent.
+func (d *dnsServer) Stop() {
+	d.serverMu.Lock()
+	srv := d.server
+	started := d.started
+	d.server = nil
+	d.started = nil
+	d.serverMu.Unlock()
+	d.shutdownServer(srv, started, "stop")
+}
+
+// Query returns the address for the given name and query type. The second
+// return value reports whether the name is known at all (in either A or AAAA),
+// which lets callers distinguish NODATA from NXDOMAIN.
+func (d *dnsServer) Query(q uint16, data string) (netip.Addr, bool) {
 	data = strings.ToLower(data)
 	d.RLock()
 	defer d.RUnlock()
+	addr4, haveV4 := d.dnsMap4[data]
+	addr6, haveV6 := d.dnsMap6[data]
+	nameExists := haveV4 || haveV6
 	switch q {
 	case dns.TypeA:
-		if r, ok := d.dnsMap4[data]; ok {
-			return r
+		if haveV4 {
+			return addr4, nameExists
 		}
 	case dns.TypeAAAA:
-		if r, ok := d.dnsMap6[data]; ok {
-			return r
+		if haveV6 {
+			return addr6, nameExists
 		}
 	}
 
-	return netip.Addr{}
+	return netip.Addr{}, nameExists
 }
 
-func (d *dnsRecords) QueryCert(data string) string {
+func (d *dnsServer) QueryCert(data string) string {
+	if len(data) < 2 {
+		return ""
+	}
 	ip, err := netip.ParseAddr(data[:len(data)-1])
 	if err != nil {
 		return ""
@@ -80,8 +266,19 @@ func (d *dnsRecords) QueryCert(data string) string {
 	return string(b)
 }
 
+// clearRecords drops all DNS records.
+func (d *dnsServer) clearRecords() {
+	d.Lock()
+	defer d.Unlock()
+	clear(d.dnsMap4)
+	clear(d.dnsMap6)
+}
+
 // Add adds the first IPv4 and IPv6 address that appears in `addresses` as the record for `host`
-func (d *dnsRecords) Add(host string, addresses []netip.Addr) {
+func (d *dnsServer) Add(host string, addresses []netip.Addr) {
+	if !d.enabled.Load() {
+		return
+	}
 	host = strings.ToLower(host)
 	d.Lock()
 	defer d.Unlock()
@@ -101,7 +298,7 @@ func (d *dnsRecords) Add(host string, addresses []netip.Addr) {
 	}
 }
 
-func (d *dnsRecords) isSelfNebulaOrLocalhost(addr string) bool {
+func (d *dnsServer) isSelfNebulaOrLocalhost(addr string) bool {
 	a, _, _ := net.SplitHostPort(addr)
 	b, err := netip.ParseAddr(a)
 	if err != nil {
@@ -116,13 +313,24 @@ func (d *dnsRecords) isSelfNebulaOrLocalhost(addr string) bool {
 	return d.myVpnAddrsTable.Contains(b)
 }
 
-func (d *dnsRecords) parseQuery(m *dns.Msg, w dns.ResponseWriter) {
+func (d *dnsServer) parseQuery(m *dns.Msg, w dns.ResponseWriter) {
+	debugEnabled := d.l.Enabled(context.Background(), slog.LevelDebug)
+	// Per RFC 2308 §2.2, a name that exists but has no record of the requested
+	// type must be answered with NOERROR and an empty answer section (NODATA),
+	// not NXDOMAIN (RFC 2308 §2.1), which is reserved for names that do not
+	// exist at all.
+	anyNameExists := false
 	for _, q := range m.Question {
 		switch q.Qtype {
 		case dns.TypeA, dns.TypeAAAA:
 			qType := dns.TypeToString[q.Qtype]
-			d.l.Debugf("Query for %s %s", qType, q.Name)
-			ip := d.Query(q.Qtype, q.Name)
+			if debugEnabled {
+				d.l.Debug("DNS query", "type", qType, "name", q.Name)
+			}
+			ip, nameExists := d.Query(q.Qtype, q.Name)
+			if nameExists {
+				anyNameExists = true
+			}
 			if ip.IsValid() {
 				rr, err := dns.NewRR(fmt.Sprintf("%s %s %s", q.Name, qType, ip))
 				if err == nil {
@@ -134,7 +342,9 @@ func (d *dnsRecords) parseQuery(m *dns.Msg, w dns.ResponseWriter) {
 			if !d.isSelfNebulaOrLocalhost(w.RemoteAddr().String()) {
 				return
 			}
-			d.l.Debugf("Query for TXT %s", q.Name)
+			if debugEnabled {
+				d.l.Debug("DNS query", "type", "TXT", "name", q.Name)
+			}
 			ip := d.QueryCert(q.Name)
 			if ip != "" {
 				rr, err := dns.NewRR(fmt.Sprintf("%s TXT %s", q.Name, ip))
@@ -145,12 +355,12 @@ func (d *dnsRecords) parseQuery(m *dns.Msg, w dns.ResponseWriter) {
 		}
 	}
 
-	if len(m.Answer) == 0 {
+	if len(m.Answer) == 0 && !anyNameExists {
 		m.Rcode = dns.RcodeNameError
 	}
 }
 
-func (d *dnsRecords) handleDnsRequest(w dns.ResponseWriter, r *dns.Msg) {
+func (d *dnsServer) handleDnsRequest(w dns.ResponseWriter, r *dns.Msg) {
 	m := new(dns.Msg)
 	m.SetReply(r)
 	m.Compress = false
@@ -163,21 +373,6 @@ func (d *dnsRecords) handleDnsRequest(w dns.ResponseWriter, r *dns.Msg) {
 	w.WriteMsg(m)
 }
 
-func dnsMain(l *logrus.Logger, cs *CertState, hostMap *HostMap, c *config.C) func() {
-	dnsR = newDnsRecords(l, cs, hostMap)
-
-	// attach request handler func
-	dns.HandleFunc(".", dnsR.handleDnsRequest)
-
-	c.RegisterReloadCallback(func(c *config.C) {
-		reloadDns(l, c)
-	})
-
-	return func() {
-		startDns(l, c)
-	}
-}
-
 func getDnsServerAddr(c *config.C) string {
 	dnsHost := strings.TrimSpace(c.GetString("lighthouse.dns.host", ""))
 	// Old guidance was to provide the literal `[::]` in `lighthouse.dns.host` but that won't resolve.
@@ -186,25 +381,3 @@ func getDnsServerAddr(c *config.C) string {
 	}
 	return net.JoinHostPort(dnsHost, strconv.Itoa(c.GetInt("lighthouse.dns.port", 53)))
 }
-
-func startDns(l *logrus.Logger, c *config.C) {
-	dnsAddr = getDnsServerAddr(c)
-	dnsServer = &dns.Server{Addr: dnsAddr, Net: "udp"}
-	l.WithField("dnsListener", dnsAddr).Info("Starting DNS responder")
-	err := dnsServer.ListenAndServe()
-	defer dnsServer.Shutdown()
-	if err != nil {
-		l.Errorf("Failed to start server: %s\n ", err.Error())
-	}
-}
-
-func reloadDns(l *logrus.Logger, c *config.C) {
-	if dnsAddr == getDnsServerAddr(c) {
-		l.Debug("No DNS server config change detected")
-		return
-	}
-
-	l.Debug("Restarting DNS server")
-	dnsServer.Shutdown()
-	go startDns(l, c)
-}

dns_server_test.go

@@ -1,19 +1,43 @@
 package nebula
 
 import (
+	"context"
+	"log/slog"
+	"net"
 	"net/netip"
+	"strconv"
 	"testing"
+	"time"
 
 	"github.com/miekg/dns"
-	"github.com/sirupsen/logrus"
 	"github.com/slackhq/nebula/config"
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 )
 
+type stubDNSWriter struct{}
+
+func (stubDNSWriter) LocalAddr() net.Addr { return &net.UDPAddr{} }
+func (stubDNSWriter) RemoteAddr() net.Addr {
+	return &net.UDPAddr{IP: net.ParseIP("127.0.0.1"), Port: 5353}
+}
+func (stubDNSWriter) Write([]byte) (int, error) { return 0, nil }
+func (stubDNSWriter) WriteMsg(*dns.Msg) error   { return nil }
+func (stubDNSWriter) Close() error              { return nil }
+func (stubDNSWriter) TsigStatus() error         { return nil }
+func (stubDNSWriter) TsigTimersOnly(bool)       {}
+func (stubDNSWriter) Hijack()                   {}
+
 func TestParsequery(t *testing.T) {
-	l := logrus.New()
+	l := slog.New(slog.DiscardHandler)
 	hostMap := &HostMap{}
-	ds := newDnsRecords(l, &CertState{}, hostMap)
+	ds := &dnsServer{
+		l:       l,
+		dnsMap4: make(map[string]netip.Addr),
+		dnsMap6: make(map[string]netip.Addr),
+		hostMap: hostMap,
+	}
+	ds.enabled.Store(true)
 	addrs := []netip.Addr{
 		netip.MustParseAddr("1.2.3.4"),
 		netip.MustParseAddr("1.2.3.5"),
@@ -21,18 +45,56 @@ func TestParsequery(t *testing.T) {
 		netip.MustParseAddr("fd01::25"),
 	}
 	ds.Add("test.com.com", addrs)
+	ds.Add("v4only.com.com", []netip.Addr{netip.MustParseAddr("1.2.3.6")})
+	ds.Add("v6only.com.com", []netip.Addr{netip.MustParseAddr("fd01::26")})
 
 	m := &dns.Msg{}
 	m.SetQuestion("test.com.com", dns.TypeA)
 	ds.parseQuery(m, nil)
 	assert.NotNil(t, m.Answer)
 	assert.Equal(t, "1.2.3.4", m.Answer[0].(*dns.A).A.String())
+	assert.Equal(t, dns.RcodeSuccess, m.Rcode)
 
 	m = &dns.Msg{}
 	m.SetQuestion("test.com.com", dns.TypeAAAA)
 	ds.parseQuery(m, nil)
 	assert.NotNil(t, m.Answer)
 	assert.Equal(t, "fd01::24", m.Answer[0].(*dns.AAAA).AAAA.String())
+	assert.Equal(t, dns.RcodeSuccess, m.Rcode)
+
+	// A known name with no record of the requested type should return NODATA
+	// (NOERROR with empty answer), not NXDOMAIN.
+	m = &dns.Msg{}
+	m.SetQuestion("v4only.com.com", dns.TypeAAAA)
+	ds.parseQuery(m, nil)
+	assert.Empty(t, m.Answer)
+	assert.Equal(t, dns.RcodeSuccess, m.Rcode)
+
+	m = &dns.Msg{}
+	m.SetQuestion("v6only.com.com", dns.TypeA)
+	ds.parseQuery(m, nil)
+	assert.Empty(t, m.Answer)
+	assert.Equal(t, dns.RcodeSuccess, m.Rcode)
+
+	// An unknown name should still return NXDOMAIN.
+	m = &dns.Msg{}
+	m.SetQuestion("unknown.com.com", dns.TypeA)
+	ds.parseQuery(m, nil)
+	assert.Empty(t, m.Answer)
+	assert.Equal(t, dns.RcodeNameError, m.Rcode)
+
+	// short lookups should not fail
+	m = &dns.Msg{}
+	m.Question = []dns.Question{{Name: "", Qtype: dns.TypeTXT, Qclass: dns.ClassINET}}
+	ds.parseQuery(m, stubDNSWriter{})
+	assert.Empty(t, m.Answer)
+	assert.Equal(t, dns.RcodeNameError, m.Rcode)
+
+	m = &dns.Msg{}
+	m.Question = []dns.Question{{Name: ".", Qtype: dns.TypeTXT, Qclass: dns.ClassINET}}
+	ds.parseQuery(m, stubDNSWriter{})
+	assert.Empty(t, m.Answer)
+	assert.Equal(t, dns.RcodeNameError, m.Rcode)
 }
 
 func Test_getDnsServerAddr(t *testing.T) {
@@ -71,3 +133,208 @@ func Test_getDnsServerAddr(t *testing.T) {
 	}
 	assert.Equal(t, "[::]:1", getDnsServerAddr(c))
 }
+
+func newTestDnsServer(t *testing.T) (*dnsServer, *config.C) {
+	t.Helper()
+	sl := slog.New(slog.DiscardHandler)
+	ds := &dnsServer{
+		l:       sl,
+		ctx:     context.Background(),
+		dnsMap4: make(map[string]netip.Addr),
+		dnsMap6: make(map[string]netip.Addr),
+		hostMap: &HostMap{},
+	}
+	ds.mux = dns.NewServeMux()
+	ds.mux.HandleFunc(".", ds.handleDnsRequest)
+	return ds, config.NewC(nil)
+}
+
+func setDnsConfig(c *config.C, host string, port string, amLighthouse, serveDns bool) {
+	c.Settings["lighthouse"] = map[string]any{
+		"am_lighthouse": amLighthouse,
+		"serve_dns":     serveDns,
+		"dns": map[string]any{
+			"host": host,
+			"port": port,
+		},
+	}
+}
+
+func TestDnsServer_reload_initial_disabled(t *testing.T) {
+	ds, c := newTestDnsServer(t)
+	setDnsConfig(c, "127.0.0.1", "0", true, false)
+
+	require.NoError(t, ds.reload(c, true))
+	assert.False(t, ds.enabled.Load())
+	assert.Equal(t, "127.0.0.1:0", ds.addr)
+	assert.Nil(t, ds.server)
+}
+
+func TestDnsServer_reload_initial_enabled(t *testing.T) {
+	ds, c := newTestDnsServer(t)
+	setDnsConfig(c, "127.0.0.1", "0", true, true)
+
+	require.NoError(t, ds.reload(c, true))
+	assert.True(t, ds.enabled.Load())
+	assert.Equal(t, "127.0.0.1:0", ds.addr)
+	// initial never starts a runner; that's Control.Start's job
+	assert.Nil(t, ds.server)
+}
+
+func TestDnsServer_reload_initial_serveDnsWithoutLighthouse(t *testing.T) {
+	ds, c := newTestDnsServer(t)
+	setDnsConfig(c, "127.0.0.1", "0", false, true)
+
+	require.NoError(t, ds.reload(c, true))
+	// Wants DNS but isn't a lighthouse: gated off, no runner.
+	assert.False(t, ds.enabled.Load())
+}
+
+func TestDnsServer_reload_sameAddr_noOp(t *testing.T) {
+	ds, c := newTestDnsServer(t)
+	setDnsConfig(c, "127.0.0.1", "0", true, true)
+
+	require.NoError(t, ds.reload(c, true))
+	// No server running yet, no addr change. Reload should not spawn anything.
+	require.NoError(t, ds.reload(c, false))
+	assert.True(t, ds.enabled.Load())
+	assert.Nil(t, ds.server)
+}
+
+func TestDnsServer_StartStop_lifecycle(t *testing.T) {
+	// Bind to a real (random) UDP port so we exercise the actual
+	// ListenAndServe + Shutdown plumbing including the started-chan race fix.
+	port := freeUDPPort(t)
+
+	ds, c := newTestDnsServer(t)
+	setDnsConfig(c, "127.0.0.1", port, true, true)
+	require.NoError(t, ds.reload(c, true))
+
+	done := make(chan struct{})
+	go func() {
+		ds.Start()
+		close(done)
+	}()
+
+	waitFor(t, func() bool {
+		ds.serverMu.Lock()
+		started := ds.started
+		ds.serverMu.Unlock()
+		if started == nil {
+			return false
+		}
+		select {
+		case <-started:
+			return true
+		default:
+			return false
+		}
+	})
+
+	ds.Stop()
+	select {
+	case <-done:
+	case <-time.After(5 * time.Second):
+		t.Fatal("Start did not return after Stop")
+	}
+}
+
+func TestDnsServer_Stop_beforeBind_doesNotHang(t *testing.T) {
+	// Stop called immediately after Start should not deadlock even if bind
+	// hasn't completed yet. This exercises the started-chan close-on-bind-fail
+	// path: by binding to an obviously bad port (privileged) we get a fast
+	// bind error before NotifyStartedFunc fires.
+	ds, c := newTestDnsServer(t)
+	// Use a port that should fail to bind (negative would be invalid, use a
+	// host that won't resolve to ensure listenUDP fails quickly).
+	setDnsConfig(c, "256.256.256.256", "53", true, true)
+	require.NoError(t, ds.reload(c, true))
+
+	done := make(chan struct{})
+	go func() {
+		ds.Start()
+		close(done)
+	}()
+
+	// Give Start a moment to attempt the bind and fail.
+	select {
+	case <-done:
+		// Bind failed and Start returned; Stop should be a no-op.
+	case <-time.After(time.Second):
+		t.Fatal("Start did not return after a bad bind")
+	}
+
+	stopped := make(chan struct{})
+	go func() {
+		ds.Stop()
+		close(stopped)
+	}()
+	select {
+	case <-stopped:
+	case <-time.After(time.Second):
+		t.Fatal("Stop hung after a failed bind")
+	}
+}
+
+func TestDnsServer_reload_disable_stopsRunningServer(t *testing.T) {
+	port := freeUDPPort(t)
+	ds, c := newTestDnsServer(t)
+	setDnsConfig(c, "127.0.0.1", port, true, true)
+	require.NoError(t, ds.reload(c, true))
+
+	startReturned := make(chan struct{})
+	go func() {
+		ds.Start()
+		close(startReturned)
+	}()
+	waitForBind(t, ds)
+
+	// Toggle serve_dns off; reload should shut the running server down.
+	setDnsConfig(c, "127.0.0.1", port, true, false)
+	require.NoError(t, ds.reload(c, false))
+	select {
+	case <-startReturned:
+	case <-time.After(5 * time.Second):
+		t.Fatal("Start did not return after reload disabled DNS")
+	}
+	assert.False(t, ds.enabled.Load())
+}
+
+func freeUDPPort(t *testing.T) string {
+	t.Helper()
+	conn, err := net.ListenPacket("udp", "127.0.0.1:0")
+	require.NoError(t, err)
+	port := conn.LocalAddr().(*net.UDPAddr).Port
+	require.NoError(t, conn.Close())
+	return strconv.Itoa(port)
+}
+
+func waitForBind(t *testing.T, ds *dnsServer) {
+	t.Helper()
+	waitFor(t, func() bool {
+		ds.serverMu.Lock()
+		started := ds.started
+		ds.serverMu.Unlock()
+		if started == nil {
+			return false
+		}
+		select {
+		case <-started:
+			return true
+		default:
+			return false
+		}
+	})
+}
+
+func waitFor(t *testing.T, cond func() bool) {
+	t.Helper()
+	deadline := time.Now().Add(5 * time.Second)
+	for time.Now().Before(deadline) {
+		if cond() {
+			return
+		}
+		time.Sleep(5 * time.Millisecond)
+	}
+	t.Fatal("timed out waiting for condition")
+}

e2e/handshake_manager_test.go

@@ -28,6 +28,7 @@ func makeHandshakePacket(from, to netip.AddrPort, subtype header.MessageSubType,
 }
 
 func TestHandshakeRetransmitDuplicate(t *testing.T) {
+	t.Parallel()
 	// Verify the responder correctly handles receiving the same msg1 multiple times
 	// (retransmission). The duplicate goes through CheckAndComplete -> ErrAlreadySeen
 	// and the cached response is resent.
@@ -46,7 +47,7 @@ func TestHandshakeRetransmitDuplicate(t *testing.T) {
 	defer r.RenderFlow()
 
 	t.Log("Trigger handshake from me to them")
-	myControl.InjectTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi"))
+	myControl.InjectTunPacket(BuildTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi")))
 
 	t.Log("Grab my msg1")
 	msg1 := myControl.GetFromUDP(true)
@@ -78,6 +79,7 @@ func TestHandshakeRetransmitDuplicate(t *testing.T) {
 }
 
 func TestHandshakeTruncatedPacketRecovery(t *testing.T) {
+	t.Parallel()
 	// Verify that a truncated handshake packet is ignored and the real
 	// packet can still complete the handshake.
 
@@ -95,7 +97,7 @@ func TestHandshakeTruncatedPacketRecovery(t *testing.T) {
 	defer r.RenderFlow()
 
 	t.Log("Trigger handshake")
-	myControl.InjectTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi"))
+	myControl.InjectTunPacket(BuildTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi")))
 
 	t.Log("Get msg1 and deliver to responder")
 	msg1 := myControl.GetFromUDP(true)
@@ -126,6 +128,7 @@ func TestHandshakeTruncatedPacketRecovery(t *testing.T) {
 }
 
 func TestHandshakeOrphanedMsg2Dropped(t *testing.T) {
+	t.Parallel()
 	// A msg2 arriving with no matching pending index should be silently dropped
 	// with no response sent and no state changes.
 
@@ -143,7 +146,7 @@ func TestHandshakeOrphanedMsg2Dropped(t *testing.T) {
 	defer r.RenderFlow()
 
 	t.Log("Complete a normal handshake")
-	myControl.InjectTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi"))
+	myControl.InjectTunPacket(BuildTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi")))
 	r.RouteForAllUntilTxTun(theirControl)
 	assertTunnel(t, myVpnIpNet[0].Addr(), theirVpnIpNet[0].Addr(), myControl, theirControl, r)
 
@@ -168,6 +171,7 @@ func TestHandshakeOrphanedMsg2Dropped(t *testing.T) {
 }
 
 func TestHandshakeUnknownMessageCounter(t *testing.T) {
+	t.Parallel()
 	// A handshake packet with an unexpected message counter should be silently
 	// dropped with no side effects and no UDP response.
 
@@ -199,6 +203,7 @@ func TestHandshakeUnknownMessageCounter(t *testing.T) {
 }
 
 func TestHandshakeUnknownSubtype(t *testing.T) {
+	t.Parallel()
 	// A handshake packet with an unknown subtype should be silently dropped.
 
 	ca, _, caKey, _ := cert_test.NewTestCaCert(cert.Version1, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
@@ -224,6 +229,7 @@ func TestHandshakeUnknownSubtype(t *testing.T) {
 }
 
 func TestHandshakeLateResponse(t *testing.T) {
+	t.Parallel()
 	// After a handshake times out, a late response should be silently ignored
 	// with no new tunnels created.
 
@@ -242,7 +248,7 @@ func TestHandshakeLateResponse(t *testing.T) {
 	theirControl.Start()
 
 	t.Log("Trigger handshake from me")
-	myControl.InjectTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi"))
+	myControl.InjectTunPacket(BuildTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi")))
 
 	t.Log("Grab msg1 but don't deliver")
 	msg1 := myControl.GetFromUDP(true)
@@ -273,6 +279,7 @@ func TestHandshakeLateResponse(t *testing.T) {
 }
 
 func TestHandshakeSelfConnectionRejected(t *testing.T) {
+	t.Parallel()
 	// Verify that a node rejects a handshake containing its own VPN IP in the
 	// peer cert. We do this by sending the initiator's own msg1 back to itself.
 
@@ -285,7 +292,7 @@ func TestHandshakeSelfConnectionRejected(t *testing.T) {
 	myControl.Start()
 
 	t.Log("Trigger handshake from me")
-	myControl.InjectTunUDPPacket(netip.MustParseAddr("10.128.0.2"), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi"))
+	myControl.InjectTunPacket(BuildTunUDPPacket(netip.MustParseAddr("10.128.0.2"), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi")))
 	msg1 := myControl.GetFromUDP(true)
 
 	t.Log("Drain any handshake retransmits before injecting")
@@ -321,6 +328,7 @@ func TestHandshakeSelfConnectionRejected(t *testing.T) {
 }
 
 func TestHandshakeMessageCounter0Dropped(t *testing.T) {
+	t.Parallel()
 	// MessageCounter=0 is not a valid handshake message and should be dropped.
 
 	ca, _, caKey, _ := cert_test.NewTestCaCert(cert.Version1, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
@@ -341,6 +349,7 @@ func TestHandshakeMessageCounter0Dropped(t *testing.T) {
 }
 
 func TestHandshakeRemoteAllowList(t *testing.T) {
+	t.Parallel()
 	// Verify that a handshake from a blocked underlay IP is dropped with no
 	// response and no state changes. Then verify the same packet from an
 	// allowed IP succeeds.
@@ -366,7 +375,7 @@ func TestHandshakeRemoteAllowList(t *testing.T) {
 	defer r.RenderFlow()
 
 	t.Log("Trigger handshake from them")
-	theirControl.InjectTunUDPPacket(myVpnIpNet[0].Addr(), 80, theirVpnIpNet[0].Addr(), 80, []byte("Hi"))
+	theirControl.InjectTunPacket(BuildTunUDPPacket(myVpnIpNet[0].Addr(), 80, theirVpnIpNet[0].Addr(), 80, []byte("Hi")))
 	msg1 := theirControl.GetFromUDP(true)
 
 	t.Log("Rewrite the source to a blocked IP and inject")
@@ -399,6 +408,7 @@ func TestHandshakeRemoteAllowList(t *testing.T) {
 }
 
 func TestHandshakeAlreadySeenPreferredRemote(t *testing.T) {
+	t.Parallel()
 	// When a duplicate msg1 arrives via ErrAlreadySeen, verify the tunnel
 	// remains functional and hostmap index count is stable.
 
@@ -416,7 +426,7 @@ func TestHandshakeAlreadySeenPreferredRemote(t *testing.T) {
 	defer r.RenderFlow()
 
 	t.Log("Complete a normal handshake via the router")
-	myControl.InjectTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi"))
+	myControl.InjectTunPacket(BuildTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi")))
 	r.RouteForAllUntilTxTun(theirControl)
 	assertTunnel(t, myVpnIpNet[0].Addr(), theirVpnIpNet[0].Addr(), myControl, theirControl, r)
 
@@ -427,7 +437,7 @@ func TestHandshakeAlreadySeenPreferredRemote(t *testing.T) {
 	originalRemote := hi.CurrentRemote
 
 	t.Log("Re-trigger traffic to cause a new handshake attempt (ErrAlreadySeen)")
-	myControl.InjectTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("roam"))
+	myControl.InjectTunPacket(BuildTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("roam")))
 	r.RouteForAllUntilTxTun(theirControl)
 
 	t.Log("Verify tunnel still works")
@@ -445,6 +455,7 @@ func TestHandshakeAlreadySeenPreferredRemote(t *testing.T) {
 }
 
 func TestHandshakeWrongResponderPacketStore(t *testing.T) {
+	t.Parallel()
 	// Verify that when the wrong host responds, the cached packets are
 	// transferred to the new handshake, the evil tunnel is closed, evil's
 	// address is blocked, and the correct tunnel is eventually established.
@@ -464,8 +475,8 @@ func TestHandshakeWrongResponderPacketStore(t *testing.T) {
 	evilControl.Start()
 
 	t.Log("Send multiple packets to them (cached during handshake)")
-	myControl.InjectTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("packet1"))
-	myControl.InjectTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("packet2"))
+	myControl.InjectTunPacket(BuildTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("packet1")))
+	myControl.InjectTunPacket(BuildTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("packet2")))
 
 	t.Log("Route until evil tunnel is closed")
 	h := &header.H{}
@@ -508,6 +519,7 @@ func TestHandshakeWrongResponderPacketStore(t *testing.T) {
 }
 
 func TestHandshakeRelayComplete(t *testing.T) {
+	t.Parallel()
 	// Verify that a relay handshake completes correctly and relay state is
 	// properly maintained on all three nodes.
 
@@ -528,7 +540,7 @@ func TestHandshakeRelayComplete(t *testing.T) {
 	theirControl.Start()
 
 	t.Log("Trigger handshake via relay")
-	myControl.InjectTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi via relay"))
+	myControl.InjectTunPacket(BuildTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi via relay")))
 
 	p := r.RouteForAllUntilTxTun(theirControl)
 	assertUdpPacket(t, []byte("Hi via relay"), p, myVpnIpNet[0].Addr(), theirVpnIpNet[0].Addr(), 80, 80)
@@ -556,7 +568,7 @@ func TestHandshakeRelayComplete(t *testing.T) {
 }
 
 // NOTE: Relay V1 cert + IPv6 rejection is not tested here because
-// InjectTunUDPPacket from a V4 node to a V6 address panics in the test
+// BuildTunUDPPacket from a V4 node to a V6 address panics in the test
 // framework. The check is in handshake_manager.go handleOutbound relay
 // logic (lines ~304-313): if the relay host has a V1 cert and either
 // address is IPv6, the relay is skipped.

e2e/handshakes_test.go

@@ -11,12 +11,12 @@ import (
 
 	"github.com/google/gopacket"
 	"github.com/google/gopacket/layers"
-	"github.com/sirupsen/logrus"
 	"github.com/slackhq/nebula"
 	"github.com/slackhq/nebula/cert"
 	"github.com/slackhq/nebula/cert_test"
 	"github.com/slackhq/nebula/e2e/router"
 	"github.com/slackhq/nebula/header"
+	"github.com/slackhq/nebula/overlay"
 	"github.com/slackhq/nebula/udp"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
@@ -40,11 +40,22 @@ func BenchmarkHotPath(b *testing.B) {
 	r.CancelFlowLogs()
 
 	assertTunnel(b, myVpnIpNet[0].Addr(), theirVpnIpNet[0].Addr(), myControl, theirControl, r)
+
+	// Pre-build the IP packet bytes once so the bench measures the data plane,
+	// not gopacket SerializeLayers overhead.
+	prebuilt := BuildTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me"))
+
+	// EnableFanIn switches the router to a 0-alloc routing path. Required
+	// for hot-path benchmarks; would conflict with GetFromUDP-using tests.
+	r.EnableFanIn()
+
 	b.ResetTimer()
 
 	for n := 0; n < b.N; n++ {
-		myControl.InjectTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me"))
-		_ = r.RouteForAllUntilTxTun(theirControl)
+		myControl.InjectTunPacket(prebuilt)
+		// Release the TUN-side bytes back to the harness freelist; the bench
+		// just confirms a packet arrived, the contents aren't inspected.
+		overlay.ReleaseTunBuf(r.RouteForAllUntilTxTun(theirControl))
 	}
 
 	myControl.Stop()
@@ -72,11 +83,15 @@ func BenchmarkHotPathRelay(b *testing.B) {
 	theirControl.Start()
 
 	assertTunnel(b, theirVpnIpNet[0].Addr(), myVpnIpNet[0].Addr(), theirControl, myControl, r)
+
+	prebuilt := BuildTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me"))
+	r.EnableFanIn()
+
 	b.ResetTimer()
 
 	for n := 0; n < b.N; n++ {
-		myControl.InjectTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me"))
-		_ = r.RouteForAllUntilTxTun(theirControl)
+		myControl.InjectTunPacket(prebuilt)
+		overlay.ReleaseTunBuf(r.RouteForAllUntilTxTun(theirControl))
 	}
 
 	myControl.Stop()
@@ -85,6 +100,7 @@ func BenchmarkHotPathRelay(b *testing.B) {
 }
 
 func TestGoodHandshake(t *testing.T) {
+	t.Parallel()
 	ca, _, caKey, _ := cert_test.NewTestCaCert(cert.Version1, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
 	myControl, myVpnIpNet, myUdpAddr, _ := newSimpleServer(cert.Version1, ca, caKey, "me", "10.128.0.1/24", nil)
 	theirControl, theirVpnIpNet, theirUdpAddr, _ := newSimpleServer(cert.Version1, ca, caKey, "them", "10.128.0.2/24", nil)
@@ -97,7 +113,7 @@ func TestGoodHandshake(t *testing.T) {
 	theirControl.Start()
 
 	t.Log("Send a udp packet through to begin standing up the tunnel, this should come out the other side")
-	myControl.InjectTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me"))
+	myControl.InjectTunPacket(BuildTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me")))
 
 	t.Log("Have them consume my stage 0 packet. They have a tunnel now")
 	theirControl.InjectUDPPacket(myControl.GetFromUDP(true))
@@ -135,6 +151,7 @@ func TestGoodHandshake(t *testing.T) {
 }
 
 func TestGoodHandshakeNoOverlap(t *testing.T) {
+	t.Parallel()
 	ca, _, caKey, _ := cert_test.NewTestCaCert(cert.Version2, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
 	myControl, myVpnIpNet, myUdpAddr, _ := newSimpleServer(cert.Version2, ca, caKey, "me", "10.128.0.1/24", nil)
 	theirControl, theirVpnIpNet, theirUdpAddr, _ := newSimpleServer(cert.Version2, ca, caKey, "them", "2001::69/24", nil) //look ma, cross-stack!
@@ -170,6 +187,7 @@ func TestGoodHandshakeNoOverlap(t *testing.T) {
 }
 
 func TestWrongResponderHandshake(t *testing.T) {
+	t.Parallel()
 	ca, _, caKey, _ := cert_test.NewTestCaCert(cert.Version1, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
 
 	myControl, myVpnIpNet, myUdpAddr, _ := newSimpleServer(cert.Version1, ca, caKey, "me", "10.128.0.100/24", nil)
@@ -189,7 +207,7 @@ func TestWrongResponderHandshake(t *testing.T) {
 	evilControl.Start()
 
 	t.Log("Start the handshake process, we will route until we see the evil tunnel closed")
-	myControl.InjectTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me"))
+	myControl.InjectTunPacket(BuildTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me")))
 
 	h := &header.H{}
 	r.RouteForAllExitFunc(func(p *udp.Packet, c *nebula.Control) router.ExitType {
@@ -246,6 +264,7 @@ func TestWrongResponderHandshake(t *testing.T) {
 }
 
 func TestWrongResponderHandshakeStaticHostMap(t *testing.T) {
+	t.Parallel()
 	ca, _, caKey, _ := cert_test.NewTestCaCert(cert.Version1, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
 
 	theirControl, theirVpnIpNet, theirUdpAddr, _ := newSimpleServer(cert.Version1, ca, caKey, "them", "10.128.0.99/24", nil)
@@ -270,7 +289,7 @@ func TestWrongResponderHandshakeStaticHostMap(t *testing.T) {
 	evilControl.Start()
 
 	t.Log("Start the handshake process, we will route until we see the evil tunnel closed")
-	myControl.InjectTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me"))
+	myControl.InjectTunPacket(BuildTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me")))
 
 	h := &header.H{}
 	r.RouteForAllExitFunc(func(p *udp.Packet, c *nebula.Control) router.ExitType {
@@ -328,6 +347,7 @@ func TestWrongResponderHandshakeStaticHostMap(t *testing.T) {
 }
 
 func TestStage1Race(t *testing.T) {
+	t.Parallel()
 	// This tests ensures that two hosts handshaking with each other at the same time will allow traffic to flow
 	// But will eventually collapse down to a single tunnel
 
@@ -348,8 +368,8 @@ func TestStage1Race(t *testing.T) {
 	theirControl.Start()
 
 	t.Log("Trigger a handshake to start on both me and them")
-	myControl.InjectTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me"))
-	theirControl.InjectTunUDPPacket(myVpnIpNet[0].Addr(), 80, theirVpnIpNet[0].Addr(), 80, []byte("Hi from them"))
+	myControl.InjectTunPacket(BuildTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me")))
+	theirControl.InjectTunPacket(BuildTunUDPPacket(myVpnIpNet[0].Addr(), 80, theirVpnIpNet[0].Addr(), 80, []byte("Hi from them")))
 
 	t.Log("Get both stage 1 handshake packets")
 	myHsForThem := myControl.GetFromUDP(true)
@@ -408,6 +428,7 @@ func TestStage1Race(t *testing.T) {
 }
 
 func TestUncleanShutdownRaceLoser(t *testing.T) {
+	t.Parallel()
 	ca, _, caKey, _ := cert_test.NewTestCaCert(cert.Version1, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
 	myControl, myVpnIpNet, myUdpAddr, _ := newSimpleServer(cert.Version1, ca, caKey, "me  ", "10.128.0.1/24", nil)
 	theirControl, theirVpnIpNet, theirUdpAddr, _ := newSimpleServer(cert.Version1, ca, caKey, "them", "10.128.0.2/24", nil)
@@ -425,7 +446,7 @@ func TestUncleanShutdownRaceLoser(t *testing.T) {
 	theirControl.Start()
 
 	r.Log("Trigger a handshake from me to them")
-	myControl.InjectTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me"))
+	myControl.InjectTunPacket(BuildTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me")))
 
 	p := r.RouteForAllUntilTxTun(theirControl)
 	assertUdpPacket(t, []byte("Hi from me"), p, myVpnIpNet[0].Addr(), theirVpnIpNet[0].Addr(), 80, 80)
@@ -436,7 +457,7 @@ func TestUncleanShutdownRaceLoser(t *testing.T) {
 	myHostmap.Indexes = map[uint32]*nebula.HostInfo{}
 	myHostmap.RemoteIndexes = map[uint32]*nebula.HostInfo{}
 
-	myControl.InjectTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me again"))
+	myControl.InjectTunPacket(BuildTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me again")))
 	p = r.RouteForAllUntilTxTun(theirControl)
 	assertUdpPacket(t, []byte("Hi from me again"), p, myVpnIpNet[0].Addr(), theirVpnIpNet[0].Addr(), 80, 80)
 
@@ -457,6 +478,7 @@ func TestUncleanShutdownRaceLoser(t *testing.T) {
 }
 
 func TestUncleanShutdownRaceWinner(t *testing.T) {
+	t.Parallel()
 	ca, _, caKey, _ := cert_test.NewTestCaCert(cert.Version1, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
 	myControl, myVpnIpNet, myUdpAddr, _ := newSimpleServer(cert.Version1, ca, caKey, "me  ", "10.128.0.1/24", nil)
 	theirControl, theirVpnIpNet, theirUdpAddr, _ := newSimpleServer(cert.Version1, ca, caKey, "them", "10.128.0.2/24", nil)
@@ -474,7 +496,7 @@ func TestUncleanShutdownRaceWinner(t *testing.T) {
 	theirControl.Start()
 
 	r.Log("Trigger a handshake from me to them")
-	myControl.InjectTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me"))
+	myControl.InjectTunPacket(BuildTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me")))
 
 	p := r.RouteForAllUntilTxTun(theirControl)
 	assertUdpPacket(t, []byte("Hi from me"), p, myVpnIpNet[0].Addr(), theirVpnIpNet[0].Addr(), 80, 80)
@@ -486,7 +508,7 @@ func TestUncleanShutdownRaceWinner(t *testing.T) {
 	theirHostmap.Indexes = map[uint32]*nebula.HostInfo{}
 	theirHostmap.RemoteIndexes = map[uint32]*nebula.HostInfo{}
 
-	theirControl.InjectTunUDPPacket(myVpnIpNet[0].Addr(), 80, theirVpnIpNet[0].Addr(), 80, []byte("Hi from them again"))
+	theirControl.InjectTunPacket(BuildTunUDPPacket(myVpnIpNet[0].Addr(), 80, theirVpnIpNet[0].Addr(), 80, []byte("Hi from them again")))
 	p = r.RouteForAllUntilTxTun(myControl)
 	assertUdpPacket(t, []byte("Hi from them again"), p, theirVpnIpNet[0].Addr(), myVpnIpNet[0].Addr(), 80, 80)
 	r.RenderHostmaps("Derp hostmaps", myControl, theirControl)
@@ -508,6 +530,7 @@ func TestUncleanShutdownRaceWinner(t *testing.T) {
 }
 
 func TestRelays(t *testing.T) {
+	t.Parallel()
 	ca, _, caKey, _ := cert_test.NewTestCaCert(cert.Version1, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
 	myControl, myVpnIpNet, _, _ := newSimpleServer(cert.Version1, ca, caKey, "me     ", "10.128.0.1/24", m{"relay": m{"use_relays": true}})
 	relayControl, relayVpnIpNet, relayUdpAddr, _ := newSimpleServer(cert.Version1, ca, caKey, "relay  ", "10.128.0.128/24", m{"relay": m{"am_relay": true}})
@@ -528,7 +551,7 @@ func TestRelays(t *testing.T) {
 	theirControl.Start()
 
 	t.Log("Trigger a handshake from me to them via the relay")
-	myControl.InjectTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me"))
+	myControl.InjectTunPacket(BuildTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me")))
 
 	p := r.RouteForAllUntilTxTun(theirControl)
 	r.Log("Assert the tunnel works")
@@ -537,6 +560,7 @@ func TestRelays(t *testing.T) {
 }
 
 func TestRelaysDontCareAboutIps(t *testing.T) {
+	t.Parallel()
 	ca, _, caKey, _ := cert_test.NewTestCaCert(cert.Version2, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
 	myControl, myVpnIpNet, _, _ := newSimpleServer(cert.Version2, ca, caKey, "me     ", "10.128.0.1/24", m{"relay": m{"use_relays": true}})
 	relayControl, relayVpnIpNet, relayUdpAddr, _ := newSimpleServer(cert.Version2, ca, caKey, "relay  ", "2001::9999/24", m{"relay": m{"am_relay": true}})
@@ -557,7 +581,7 @@ func TestRelaysDontCareAboutIps(t *testing.T) {
 	theirControl.Start()
 
 	t.Log("Trigger a handshake from me to them via the relay")
-	myControl.InjectTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me"))
+	myControl.InjectTunPacket(BuildTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me")))
 
 	p := r.RouteForAllUntilTxTun(theirControl)
 	r.Log("Assert the tunnel works")
@@ -566,6 +590,7 @@ func TestRelaysDontCareAboutIps(t *testing.T) {
 }
 
 func TestReestablishRelays(t *testing.T) {
+	t.Parallel()
 	ca, _, caKey, _ := cert_test.NewTestCaCert(cert.Version1, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
 	myControl, myVpnIpNet, _, _ := newSimpleServer(cert.Version1, ca, caKey, "me     ", "10.128.0.1/24", m{"relay": m{"use_relays": true}})
 	relayControl, relayVpnIpNet, relayUdpAddr, _ := newSimpleServer(cert.Version1, ca, caKey, "relay  ", "10.128.0.128/24", m{"relay": m{"am_relay": true}})
@@ -586,14 +611,14 @@ func TestReestablishRelays(t *testing.T) {
 	theirControl.Start()
 
 	t.Log("Trigger a handshake from me to them via the relay")
-	myControl.InjectTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me"))
+	myControl.InjectTunPacket(BuildTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me")))
 
 	p := r.RouteForAllUntilTxTun(theirControl)
 	r.Log("Assert the tunnel works")
 	assertUdpPacket(t, []byte("Hi from me"), p, myVpnIpNet[0].Addr(), theirVpnIpNet[0].Addr(), 80, 80)
 
 	t.Log("Ensure packet traversal from them to me via the relay")
-	theirControl.InjectTunUDPPacket(myVpnIpNet[0].Addr(), 80, theirVpnIpNet[0].Addr(), 80, []byte("Hi from them"))
+	theirControl.InjectTunPacket(BuildTunUDPPacket(myVpnIpNet[0].Addr(), 80, theirVpnIpNet[0].Addr(), 80, []byte("Hi from them")))
 
 	p = r.RouteForAllUntilTxTun(myControl)
 	r.Log("Assert the tunnel works")
@@ -608,7 +633,7 @@ func TestReestablishRelays(t *testing.T) {
 	for curIndexes >= start {
 		curIndexes = len(myControl.GetHostmap().Indexes)
 		r.Logf("Wait for the dead index to go away:start=%v indexes, current=%v indexes", start, curIndexes)
-		myControl.InjectTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me should fail"))
+		myControl.InjectTunPacket(BuildTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me should fail")))
 
 		r.RouteForAllExitFunc(func(p *udp.Packet, c *nebula.Control) router.ExitType {
 			return router.RouteAndExit
@@ -625,7 +650,7 @@ func TestReestablishRelays(t *testing.T) {
 		myControl.InjectLightHouseAddr(relayVpnIpNet[0].Addr(), relayUdpAddr)
 		myControl.InjectRelays(theirVpnIpNet[0].Addr(), []netip.Addr{relayVpnIpNet[0].Addr()})
 		relayControl.InjectLightHouseAddr(theirVpnIpNet[0].Addr(), theirUdpAddr)
-		myControl.InjectTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me"))
+		myControl.InjectTunPacket(BuildTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me")))
 
 		p = r.RouteForAllUntilTxTun(theirControl)
 		r.Log("Assert the tunnel works")
@@ -660,7 +685,7 @@ func TestReestablishRelays(t *testing.T) {
 	t.Log("Assert the tunnel works the other way, too")
 	for {
 		t.Log("RouteForAllUntilTxTun")
-		theirControl.InjectTunUDPPacket(myVpnIpNet[0].Addr(), 80, theirVpnIpNet[0].Addr(), 80, []byte("Hi from them"))
+		theirControl.InjectTunPacket(BuildTunUDPPacket(myVpnIpNet[0].Addr(), 80, theirVpnIpNet[0].Addr(), 80, []byte("Hi from them")))
 
 		p = r.RouteForAllUntilTxTun(myControl)
 		r.Log("Assert the tunnel works")
@@ -697,6 +722,7 @@ func TestReestablishRelays(t *testing.T) {
 }
 
 func TestStage1RaceRelays(t *testing.T) {
+	t.Parallel()
 	//NOTE: this is a race between me and relay resulting in a full tunnel from me to them via relay
 	ca, _, caKey, _ := cert_test.NewTestCaCert(cert.Version1, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
 	myControl, myVpnIpNet, myUdpAddr, _ := newSimpleServer(cert.Version1, ca, caKey, "me     ", "10.128.0.1/24", m{"relay": m{"use_relays": true}})
@@ -729,8 +755,8 @@ func TestStage1RaceRelays(t *testing.T) {
 	assertTunnel(t, theirVpnIpNet[0].Addr(), relayVpnIpNet[0].Addr(), theirControl, relayControl, r)
 
 	r.Log("Trigger a handshake from both them and me via relay to them and me")
-	myControl.InjectTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me"))
-	theirControl.InjectTunUDPPacket(myVpnIpNet[0].Addr(), 80, theirVpnIpNet[0].Addr(), 80, []byte("Hi from them"))
+	myControl.InjectTunPacket(BuildTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me")))
+	theirControl.InjectTunPacket(BuildTunUDPPacket(myVpnIpNet[0].Addr(), 80, theirVpnIpNet[0].Addr(), 80, []byte("Hi from them")))
 
 	r.Log("Wait for a packet from them to me")
 	p := r.RouteForAllUntilTxTun(myControl)
@@ -744,12 +770,12 @@ func TestStage1RaceRelays(t *testing.T) {
 }
 
 func TestStage1RaceRelays2(t *testing.T) {
+	t.Parallel()
 	//NOTE: this is a race between me and relay resulting in a full tunnel from me to them via relay
 	ca, _, caKey, _ := cert_test.NewTestCaCert(cert.Version1, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
 	myControl, myVpnIpNet, myUdpAddr, _ := newSimpleServer(cert.Version1, ca, caKey, "me     ", "10.128.0.1/24", m{"relay": m{"use_relays": true}})
 	relayControl, relayVpnIpNet, relayUdpAddr, _ := newSimpleServer(cert.Version1, ca, caKey, "relay  ", "10.128.0.128/24", m{"relay": m{"am_relay": true}})
 	theirControl, theirVpnIpNet, theirUdpAddr, _ := newSimpleServer(cert.Version1, ca, caKey, "them   ", "10.128.0.2/24", m{"relay": m{"use_relays": true}})
-	l := NewTestLogger()
 
 	// Teach my how to get to the relay and that their can be reached via the relay
 	myControl.InjectLightHouseAddr(relayVpnIpNet[0].Addr(), relayUdpAddr)
@@ -771,49 +797,41 @@ func TestStage1RaceRelays2(t *testing.T) {
 	theirControl.Start()
 
 	r.Log("Get a tunnel between me and relay")
-	l.Info("Get a tunnel between me and relay")
 	assertTunnel(t, myVpnIpNet[0].Addr(), relayVpnIpNet[0].Addr(), myControl, relayControl, r)
 
 	r.Log("Get a tunnel between them and relay")
-	l.Info("Get a tunnel between them and relay")
 	assertTunnel(t, theirVpnIpNet[0].Addr(), relayVpnIpNet[0].Addr(), theirControl, relayControl, r)
 
 	r.Log("Trigger a handshake from both them and me via relay to them and me")
-	l.Info("Trigger a handshake from both them and me via relay to them and me")
-	myControl.InjectTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me"))
-	theirControl.InjectTunUDPPacket(myVpnIpNet[0].Addr(), 80, theirVpnIpNet[0].Addr(), 80, []byte("Hi from them"))
+	myControl.InjectTunPacket(BuildTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me")))
+	theirControl.InjectTunPacket(BuildTunUDPPacket(myVpnIpNet[0].Addr(), 80, theirVpnIpNet[0].Addr(), 80, []byte("Hi from them")))
 
 	//r.RouteUntilAfterMsgType(myControl, header.Control, header.MessageNone)
 	//r.RouteUntilAfterMsgType(theirControl, header.Control, header.MessageNone)
 
-	r.Log("Wait for a packet from them to me")
-	l.Info("Wait for a packet from them to me; myControl")
+	r.Log("Wait for a packet from them to me; myControl")
 	r.RouteForAllUntilTxTun(myControl)
-	l.Info("Wait for a packet from them to me; theirControl")
+	r.Log("Wait for a packet from them to me; theirControl")
 	r.RouteForAllUntilTxTun(theirControl)
 
 	r.Log("Assert the tunnel works")
-	l.Info("Assert the tunnel works")
 	assertTunnel(t, theirVpnIpNet[0].Addr(), myVpnIpNet[0].Addr(), theirControl, myControl, r)
 
 	t.Log("Wait until we remove extra tunnels")
-	l.Info("Wait until we remove extra tunnels")
-	l.WithFields(
-		logrus.Fields{
-			"myControl":    len(myControl.GetHostmap().Indexes),
-			"theirControl": len(theirControl.GetHostmap().Indexes),
-			"relayControl": len(relayControl.GetHostmap().Indexes),
-		}).Info("Waiting for hostinfos to be removed...")
+	t.Logf("Waiting for hostinfos to be removed... myControl=%d theirControl=%d relayControl=%d",
+		len(myControl.GetHostmap().Indexes),
+		len(theirControl.GetHostmap().Indexes),
+		len(relayControl.GetHostmap().Indexes),
+	)
 	hostInfos := len(myControl.GetHostmap().Indexes) + len(theirControl.GetHostmap().Indexes) + len(relayControl.GetHostmap().Indexes)
 	retries := 60
 	for hostInfos > 6 && retries > 0 {
 		hostInfos = len(myControl.GetHostmap().Indexes) + len(theirControl.GetHostmap().Indexes) + len(relayControl.GetHostmap().Indexes)
-		l.WithFields(
-			logrus.Fields{
-				"myControl":    len(myControl.GetHostmap().Indexes),
-				"theirControl": len(theirControl.GetHostmap().Indexes),
-				"relayControl": len(relayControl.GetHostmap().Indexes),
-			}).Info("Waiting for hostinfos to be removed...")
+		t.Logf("Waiting for hostinfos to be removed... myControl=%d theirControl=%d relayControl=%d",
+			len(myControl.GetHostmap().Indexes),
+			len(theirControl.GetHostmap().Indexes),
+			len(relayControl.GetHostmap().Indexes),
+		)
 		assertTunnel(t, myVpnIpNet[0].Addr(), theirVpnIpNet[0].Addr(), myControl, theirControl, r)
 		t.Log("Connection manager hasn't ticked yet")
 		time.Sleep(time.Second)
@@ -821,7 +839,6 @@ func TestStage1RaceRelays2(t *testing.T) {
 	}
 
 	r.Log("Assert the tunnel works")
-	l.Info("Assert the tunnel works")
 	assertTunnel(t, theirVpnIpNet[0].Addr(), myVpnIpNet[0].Addr(), theirControl, myControl, r)
 
 	myControl.Stop()
@@ -830,6 +847,7 @@ func TestStage1RaceRelays2(t *testing.T) {
 }
 
 func TestRehandshakingRelays(t *testing.T) {
+	t.Parallel()
 	ca, _, caKey, _ := cert_test.NewTestCaCert(cert.Version1, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
 	myControl, myVpnIpNet, _, _ := newSimpleServer(cert.Version1, ca, caKey, "me     ", "10.128.0.1/24", m{"relay": m{"use_relays": true}})
 	relayControl, relayVpnIpNet, relayUdpAddr, relayConfig := newSimpleServer(cert.Version1, ca, caKey, "relay  ", "10.128.0.128/24", m{"relay": m{"am_relay": true}})
@@ -850,7 +868,7 @@ func TestRehandshakingRelays(t *testing.T) {
 	theirControl.Start()
 
 	t.Log("Trigger a handshake from me to them via the relay")
-	myControl.InjectTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me"))
+	myControl.InjectTunPacket(BuildTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me")))
 
 	p := r.RouteForAllUntilTxTun(theirControl)
 	r.Log("Assert the tunnel works")
@@ -933,6 +951,7 @@ func TestRehandshakingRelays(t *testing.T) {
 }
 
 func TestRehandshakingRelaysPrimary(t *testing.T) {
+	t.Parallel()
 	// This test is the same as TestRehandshakingRelays but one of the terminal types is a primary swap winner
 	ca, _, caKey, _ := cert_test.NewTestCaCert(cert.Version1, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
 	myControl, myVpnIpNet, _, _ := newSimpleServer(cert.Version1, ca, caKey, "me     ", "10.128.0.128/24", m{"relay": m{"use_relays": true}})
@@ -954,7 +973,7 @@ func TestRehandshakingRelaysPrimary(t *testing.T) {
 	theirControl.Start()
 
 	t.Log("Trigger a handshake from me to them via the relay")
-	myControl.InjectTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me"))
+	myControl.InjectTunPacket(BuildTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me")))
 
 	p := r.RouteForAllUntilTxTun(theirControl)
 	r.Log("Assert the tunnel works")
@@ -1037,6 +1056,7 @@ func TestRehandshakingRelaysPrimary(t *testing.T) {
 }
 
 func TestRehandshaking(t *testing.T) {
+	t.Parallel()
 	ca, _, caKey, _ := cert_test.NewTestCaCert(cert.Version1, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
 	myControl, myVpnIpNet, myUdpAddr, myConfig := newSimpleServer(cert.Version1, ca, caKey, "me  ", "10.128.0.2/24", nil)
 	theirControl, theirVpnIpNet, theirUdpAddr, theirConfig := newSimpleServer(cert.Version1, ca, caKey, "them", "10.128.0.1/24", nil)
@@ -1132,6 +1152,7 @@ func TestRehandshaking(t *testing.T) {
 }
 
 func TestRehandshakingLoser(t *testing.T) {
+	t.Parallel()
 	// The purpose of this test is that the race loser renews their certificate and rehandshakes. The final tunnel
 	// Should be the one with the new certificate
 	ca, _, caKey, _ := cert_test.NewTestCaCert(cert.Version1, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
@@ -1230,6 +1251,7 @@ func TestRehandshakingLoser(t *testing.T) {
 }
 
 func TestRaceRegression(t *testing.T) {
+	t.Parallel()
 	// This test forces stage 1, stage 2, stage 1 to be received by me from them
 	// We had a bug where we were not finding the duplicate handshake and responding to the final stage 1 which
 	// caused a cross-linked hostinfo
@@ -1253,8 +1275,8 @@ func TestRaceRegression(t *testing.T) {
 	//them rx stage:2 initiatorIndex=120607833 responderIndex=4209862089
 
 	t.Log("Start both handshakes")
-	myControl.InjectTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me"))
-	theirControl.InjectTunUDPPacket(myVpnIpNet[0].Addr(), 80, theirVpnIpNet[0].Addr(), 80, []byte("Hi from them"))
+	myControl.InjectTunPacket(BuildTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me")))
+	theirControl.InjectTunPacket(BuildTunUDPPacket(myVpnIpNet[0].Addr(), 80, theirVpnIpNet[0].Addr(), 80, []byte("Hi from them")))
 
 	t.Log("Get both stage 1")
 	myStage1ForThem := myControl.GetFromUDP(true)
@@ -1290,6 +1312,7 @@ func TestRaceRegression(t *testing.T) {
 }
 
 func TestV2NonPrimaryWithLighthouse(t *testing.T) {
+	t.Parallel()
 	ca, _, caKey, _ := cert_test.NewTestCaCert(cert.Version2, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
 	lhControl, lhVpnIpNet, lhUdpAddr, _ := newSimpleServer(cert.Version2, ca, caKey, "lh  ", "10.128.0.1/24, ff::1/64", m{"lighthouse": m{"am_lighthouse": true}})
 
@@ -1330,6 +1353,7 @@ func TestV2NonPrimaryWithLighthouse(t *testing.T) {
 }
 
 func TestV2NonPrimaryWithOffNetLighthouse(t *testing.T) {
+	t.Parallel()
 	ca, _, caKey, _ := cert_test.NewTestCaCert(cert.Version2, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
 	lhControl, lhVpnIpNet, lhUdpAddr, _ := newSimpleServer(cert.Version2, ca, caKey, "lh  ", "2001::1/64", m{"lighthouse": m{"am_lighthouse": true}})
 
@@ -1369,7 +1393,84 @@ func TestV2NonPrimaryWithOffNetLighthouse(t *testing.T) {
 	theirControl.Stop()
 }
 
+func TestLighthouseUpdateOnReload(t *testing.T) {
+	t.Parallel()
+	ca, _, caKey, _ := cert_test.NewTestCaCert(cert.Version2, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
+
+	// Create the lighthouse
+	lhControl, lhVpnIpNet, lhUdpAddr, _ := newSimpleServer(cert.Version2, ca, caKey, "lh", "10.128.0.1/24", m{"lighthouse": m{"am_lighthouse": true}})
+
+	// Create a client with NO lighthouse configured and a long update interval.
+	// The initial SendUpdate at startup will be a no-op since no lighthouses are known.
+	myControl, myVpnIpNet, _, myConfig := newSimpleServer(cert.Version2, ca, caKey, "me", "10.128.0.2/24", m{
+		"lighthouse": m{
+			"interval": 600,
+			"local_allow_list": m{
+				"10.0.0.0/24": true,
+				"::/0":        false,
+			},
+		},
+	})
+
+	r := router.NewR(t, lhControl, myControl)
+	defer r.RenderFlow()
+
+	lhControl.Start()
+	myControl.Start()
+
+	// Drain any startup packets (there should be none meaningful)
+	r.FlushAll()
+
+	// Verify lighthouse has no knowledge of the client
+	assert.Nil(t, lhControl.QueryLighthouse(myVpnIpNet[0].Addr()))
+
+	// Build a new config that adds the lighthouse
+	newSettings := make(m)
+	for k, v := range myConfig.Settings {
+		newSettings[k] = v
+	}
+	newSettings["static_host_map"] = m{
+		lhVpnIpNet[0].Addr().String(): []any{lhUdpAddr.String()},
+	}
+	newSettings["lighthouse"] = m{
+		"hosts":    []any{lhVpnIpNet[0].Addr().String()},
+		"interval": 600,
+		"local_allow_list": m{
+			"10.0.0.0/24": true,
+			"::/0":        false,
+		},
+	}
+	newCfg, err := yaml.Marshal(newSettings)
+	require.NoError(t, err)
+
+	// Reload the config. The lighthouse.hosts change triggers TriggerUpdate,
+	// which wakes the update worker. It calls SendUpdate, initiating a
+	// handshake to the new lighthouse and caching the HostUpdateNotification.
+	require.NoError(t, myConfig.ReloadConfigString(string(newCfg)))
+
+	// Route until the lighthouse receives the HostUpdateNotification.
+	// This covers: handshake stage 1, stage 2, then the cached update.
+	done := make(chan struct{})
+	go func() {
+		r.RouteForAllUntilAfterMsgTypeTo(lhControl, header.LightHouse, 0)
+		close(done)
+	}()
+	select {
+	case <-done:
+	case <-time.After(5 * time.Second):
+		t.Fatal("timed out waiting for lighthouse update after config reload")
+	}
+
+	// Verify lighthouse now has the client's addresses
+	assert.NotNil(t, lhControl.QueryLighthouse(myVpnIpNet[0].Addr()))
+
+	r.RenderHostmaps("Final hostmaps", lhControl, myControl)
+	lhControl.Stop()
+	myControl.Stop()
+}
+
 func TestGoodHandshakeUnsafeDest(t *testing.T) {
+	t.Parallel()
 	unsafePrefix := "192.168.6.0/24"
 	ca, _, caKey, _ := cert_test.NewTestCaCert(cert.Version2, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
 	theirControl, theirVpnIpNet, theirUdpAddr, _ := newSimpleServerWithUdpAndUnsafeNetworks(cert.Version2, ca, caKey, "spooky", "10.128.0.2/24", netip.MustParseAddrPort("10.64.0.2:4242"), unsafePrefix, nil)
@@ -1391,7 +1492,7 @@ func TestGoodHandshakeUnsafeDest(t *testing.T) {
 	theirControl.Start()
 
 	t.Log("Send a udp packet through to begin standing up the tunnel, this should come out the other side")
-	myControl.InjectTunUDPPacket(spookyDest, 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me"))
+	myControl.InjectTunPacket(BuildTunUDPPacket(spookyDest, 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me")))
 
 	t.Log("Have them consume my stage 0 packet. They have a tunnel now")
 	theirControl.InjectUDPPacket(myControl.GetFromUDP(true))
@@ -1419,7 +1520,7 @@ func TestGoodHandshakeUnsafeDest(t *testing.T) {
 	assertUdpPacket(t, []byte("Hi from me"), myCachedPacket, myVpnIpNet[0].Addr(), spookyDest, 80, 80)
 
 	//reply
-	theirControl.InjectTunUDPPacket(myVpnIpNet[0].Addr(), 80, spookyDest, 80, []byte("Hi from the spookyman"))
+	theirControl.InjectTunPacket(BuildTunUDPPacket(myVpnIpNet[0].Addr(), 80, spookyDest, 80, []byte("Hi from the spookyman")))
 	//wait for reply
 	theirControl.WaitForType(1, 0, myControl)
 	theirCachedPacket := myControl.GetFromTun(true)

e2e/helpers_test.go

@@ -4,7 +4,6 @@
 package e2e
 
 import (
-	"fmt"
 	"io"
 	"net/netip"
 	"os"
@@ -12,15 +11,18 @@ import (
 	"testing"
 	"time"
 
+	"log/slog"
+
 	"dario.cat/mergo"
 	"github.com/google/gopacket"
 	"github.com/google/gopacket/layers"
-	"github.com/sirupsen/logrus"
+
 	"github.com/slackhq/nebula"
 	"github.com/slackhq/nebula/cert"
 	"github.com/slackhq/nebula/cert_test"
 	"github.com/slackhq/nebula/config"
 	"github.com/slackhq/nebula/e2e/router"
+	"github.com/slackhq/nebula/logging"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 	"go.yaml.in/yaml/v3"
@@ -132,8 +134,7 @@ func newSimpleServerWithUdpAndUnsafeNetworks(v cert.Version, caCrt cert.Certific
 			"port": udpAddr.Port(),
 		},
 		"logging": m{
-			"timestamp_format": fmt.Sprintf("%v 15:04:05.000000", name),
-			"level":            l.Level.String(),
+			"level": testLogLevelName(),
 		},
 		"timers": m{
 			"pending_deletion_interval": 2,
@@ -234,8 +235,7 @@ func newServer(caCrt []cert.Certificate, certs []cert.Certificate, key []byte, o
 			"port": udpAddr.Port(),
 		},
 		"logging": m{
-			"timestamp_format": fmt.Sprintf("%v 15:04:05.000000", certs[0].Name()),
-			"level":            l.Level.String(),
+			"level": testLogLevelName(),
 		},
 		"timers": m{
 			"pending_deletion_interval": 2,
@@ -294,12 +294,12 @@ func deadline(t *testing.T, seconds time.Duration) doneCb {
 
 func assertTunnel(t testing.TB, vpnIpA, vpnIpB netip.Addr, controlA, controlB *nebula.Control, r *router.R) {
 	// Send a packet from them to me
-	controlB.InjectTunUDPPacket(vpnIpA, 80, vpnIpB, 90, []byte("Hi from B"))
+	controlB.InjectTunPacket(BuildTunUDPPacket(vpnIpA, 80, vpnIpB, 90, []byte("Hi from B")))
 	bPacket := r.RouteForAllUntilTxTun(controlA)
 	assertUdpPacket(t, []byte("Hi from B"), bPacket, vpnIpB, vpnIpA, 90, 80)
 
 	// And once more from me to them
-	controlA.InjectTunUDPPacket(vpnIpB, 80, vpnIpA, 90, []byte("Hello from A"))
+	controlA.InjectTunPacket(BuildTunUDPPacket(vpnIpB, 80, vpnIpA, 90, []byte("Hello from A")))
 	aPacket := r.RouteForAllUntilTxTun(controlB)
 	assertUdpPacket(t, []byte("Hello from A"), aPacket, vpnIpA, vpnIpB, 90, 80)
 }
@@ -379,24 +379,87 @@ func getAddrs(ns []netip.Prefix) []netip.Addr {
 	return a
 }
 
-func NewTestLogger() *logrus.Logger {
-	l := logrus.New()
-
+func NewTestLogger() *slog.Logger {
 	v := os.Getenv("TEST_LOGS")
 	if v == "" {
-		l.SetOutput(io.Discard)
-		l.SetLevel(logrus.PanicLevel)
-		return l
+		return slog.New(slog.NewTextHandler(io.Discard, nil))
 	}
 
+	level := slog.LevelInfo
 	switch v {
 	case "2":
-		l.SetLevel(logrus.DebugLevel)
+		level = slog.LevelDebug
 	case "3":
-		l.SetLevel(logrus.TraceLevel)
-	default:
-		l.SetLevel(logrus.InfoLevel)
+		level = logging.LevelTrace
+	}
+	return slog.New(slog.NewTextHandler(os.Stderr, &slog.HandlerOptions{Level: level}))
+}
+
+// testLogLevelName returns the level name string accepted by logging.ApplyConfig
+// for the current TEST_LOGS setting. Kept in sync with NewTestLogger.
+func testLogLevelName() string {
+	switch os.Getenv("TEST_LOGS") {
+	case "2":
+		return "debug"
+	case "3":
+		return "trace"
+	case "":
+		return "info"
+	}
+	return "info"
+}
+
+// BuildTunUDPPacket assembles an IP+UDP packet suitable for Control.InjectTunPacket.
+// Using UDP here because it's a simpler protocol.
+func BuildTunUDPPacket(toAddr netip.Addr, toPort uint16, fromAddr netip.Addr, fromPort uint16, data []byte) []byte {
+	serialize := make([]gopacket.SerializableLayer, 0)
+	var netLayer gopacket.NetworkLayer
+	if toAddr.Is6() {
+		if !fromAddr.Is6() {
+			panic("Cant send ipv6 to ipv4")
+		}
+		ip := &layers.IPv6{
+			Version:    6,
+			NextHeader: layers.IPProtocolUDP,
+			SrcIP:      fromAddr.Unmap().AsSlice(),
+			DstIP:      toAddr.Unmap().AsSlice(),
+		}
+		serialize = append(serialize, ip)
+		netLayer = ip
+	} else {
+		if !fromAddr.Is4() {
+			panic("Cant send ipv4 to ipv6")
+		}
+
+		ip := &layers.IPv4{
+			Version:  4,
+			TTL:      64,
+			Protocol: layers.IPProtocolUDP,
+			SrcIP:    fromAddr.Unmap().AsSlice(),
+			DstIP:    toAddr.Unmap().AsSlice(),
+		}
+		serialize = append(serialize, ip)
+		netLayer = ip
 	}
 
-	return l
+	udp := layers.UDP{
+		SrcPort: layers.UDPPort(fromPort),
+		DstPort: layers.UDPPort(toPort),
+	}
+	if err := udp.SetNetworkLayerForChecksum(netLayer); err != nil {
+		panic(err)
+	}
+
+	buffer := gopacket.NewSerializeBuffer()
+	opt := gopacket.SerializeOptions{
+		ComputeChecksums: true,
+		FixLengths:       true,
+	}
+
+	serialize = append(serialize, &udp, gopacket.Payload(data))
+	if err := gopacket.SerializeLayers(buffer, opt, serialize...); err != nil {
+		panic(err)
+	}
+
+	return buffer.Bytes()
 }

e2e/leak_test.go

@@ -0,0 +1,47 @@
+//go:build e2e_testing
+// +build e2e_testing
+
+package e2e
+
+import (
+	"testing"
+	"time"
+
+	"github.com/slackhq/nebula/cert"
+	"github.com/slackhq/nebula/cert_test"
+	"github.com/slackhq/nebula/e2e/router"
+	"go.uber.org/goleak"
+)
+
+// TestNoGoroutineLeaks brings up two nebula instances, completes a tunnel,
+// stops both, and asserts no goroutines leak past the shutdown. goleak's
+// retry mechanism gives the wg.Wait()-driven goroutines a moment to drain
+// before failing the assertion.
+//
+// Intentionally NOT t.Parallel()'d: concurrent tests would have their own
+// goroutines running and trip the assertion.
+func TestNoGoroutineLeaks(t *testing.T) {
+	defer goleak.VerifyNone(t)
+
+	ca, _, caKey, _ := cert_test.NewTestCaCert(cert.Version1, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
+	myControl, myVpnIpNet, myUdpAddr, _ := newSimpleServer(cert.Version1, ca, caKey, "me", "10.128.0.1/24", nil)
+	theirControl, theirVpnIpNet, theirUdpAddr, _ := newSimpleServer(cert.Version1, ca, caKey, "them", "10.128.0.2/24", nil)
+
+	myControl.InjectLightHouseAddr(theirVpnIpNet[0].Addr(), theirUdpAddr)
+	theirControl.InjectLightHouseAddr(myVpnIpNet[0].Addr(), myUdpAddr)
+
+	myControl.Start()
+	theirControl.Start()
+
+	r := router.NewR(t, myControl, theirControl)
+	assertTunnel(t, myVpnIpNet[0].Addr(), theirVpnIpNet[0].Addr(), myControl, theirControl, r)
+
+	myControl.Stop()
+	theirControl.Stop()
+	r.RenderFlow()
+
+	// Settle period: Stop() is non-blocking; the wg-driven goroutines need
+	// a moment to drain. goleak retries internally too, but a short explicit
+	// settle reduces flakes when the suite is busy.
+	time.Sleep(50 * time.Millisecond)
+}

e2e/router/router.go

@@ -13,6 +13,7 @@ import (
 	"regexp"
 	"sort"
 	"sync"
+	"sync/atomic"
 	"testing"
 	"time"
 
@@ -24,6 +25,19 @@ import (
 	"golang.org/x/exp/maps"
 )
 
+// outNatKey is the (from, to) pair used by outNat. Comparable struct, so it works as a map key without the
+// allocation cost of a string-concat key.
+type outNatKey struct {
+	from, to netip.AddrPort
+}
+
+// fannedPacket pairs a UDP TX packet with its source control so the router can route it after popping from
+// the fan-in channel.
+type fannedPacket struct {
+	from *nebula.Control
+	pkt  *udp.Packet
+}
+
 type R struct {
 	// Simple map of the ip:port registered on a control to the control
 	// Basically a router, right?
@@ -34,12 +48,28 @@ type R struct {
 
 	// A last used map, if an inbound packet hit the inNat map then
 	// all return packets should use the same last used inbound address for the outbound sender
-	// map[from address + ":" + to address] => ip:port to rewrite in the udp packet to receiver
-	outNat map[string]netip.AddrPort
+	outNat map[outNatKey]netip.AddrPort
 
 	// A map of vpn ip to the nebula control it belongs to
 	vpnControls map[netip.Addr]*nebula.Control
 
+	// Cached select infrastructure for RouteForAllUntilTxTun.
+	// The controls map is immutable after NewR so the cases are good for the test lifetime.
+	// We only rebuild if a different receiver is asked.
+	selRecvCtl *nebula.Control
+	selCases   []reflect.SelectCase
+	selCtls    []*nebula.Control
+
+	// Optional fan-in mode for hot-path benchmarks: one forwarder goroutine per control drains UDP TX into udpFanIn,
+	// so RouteForAllUntilTxTun can do a fixed 2-way native select instead of paying reflect.Select per call.
+	// Off by default (would otherwise interleave with tests that use GetFromUDP directly on the same control).
+	// Enabled by EnableFanIn.
+	udpFanIn  chan fannedPacket
+	stopFanIn chan struct{}
+	fanInWG   sync.WaitGroup
+	fanInMu   sync.Mutex
+	fanInOn   atomic.Bool
+
 	ignoreFlows []ignoreFlow
 	flow        []flowEntry
 
@@ -119,7 +149,7 @@ func NewR(t testing.TB, controls ...*nebula.Control) *R {
 		controls:     make(map[netip.AddrPort]*nebula.Control),
 		vpnControls:  make(map[netip.Addr]*nebula.Control),
 		inNat:        make(map[netip.AddrPort]*nebula.Control),
-		outNat:       make(map[string]netip.AddrPort),
+		outNat:       make(map[outNatKey]netip.AddrPort),
 		flow:         []flowEntry{},
 		ignoreFlows:  []ignoreFlow{},
 		fn:           filepath.Join("mermaid", fmt.Sprintf("%s.md", t.Name())),
@@ -153,8 +183,10 @@ func NewR(t testing.TB, controls ...*nebula.Control) *R {
 			case <-ctx.Done():
 				return
 			case <-clockSource.C:
+				r.Lock()
 				r.renderHostmaps("clock tick")
 				r.renderFlow()
+				r.Unlock()
 			}
 		}
 	}()
@@ -180,15 +212,21 @@ func (r *R) AddRoute(ip netip.Addr, port uint16, c *nebula.Control) {
 // RenderFlow renders the packet flow seen up until now and stops further automatic renders from happening.
 func (r *R) RenderFlow() {
 	r.cancelRender()
+	r.Lock()
+	defer r.Unlock()
 	r.renderFlow()
 }
 
 // CancelFlowLogs stops flow logs from being tracked and destroys any logs already collected
 func (r *R) CancelFlowLogs() {
 	r.cancelRender()
+	r.Lock()
 	r.flow = nil
+	r.Unlock()
 }
 
+// renderFlow writes the flow log to disk. Caller must hold r.Lock. renderFlow reads r.flow / r.additionalGraphs and
+// the *packet pointers stashed inside, all of which are mutated under the same lock by routing paths.
 func (r *R) renderFlow() {
 	if r.flow == nil {
 		return
@@ -434,68 +472,157 @@ func (r *R) RouteUntilTxTun(sender *nebula.Control, receiver *nebula.Control) []
 				panic("No control for udp tx " + a.String())
 			}
 			fp := r.unlockedInjectFlow(sender, c, p, false)
-			c.InjectUDPPacket(p)
+			c.InjectUDPPacket(p) // copies internally; original is ours to release
 			fp.WasReceived()
 			r.Unlock()
+			p.Release()
 		}
 	}
 }
 
-// RouteForAllUntilTxTun will route for everyone and return when a packet is seen on receivers tun
-// If the router doesn't have the nebula controller for that address, we panic
+// RouteForAllUntilTxTun will route for everyone and return when a packet is seen on the receiver's tun.
+// If a control's UDP TX address can't be matched to a registered control, we panic.
+//
+// For allocation-sensitive callers (hot-path benchmarks, in particular relay
+// benches with 3+ controls), call EnableFanIn() first.
 func (r *R) RouteForAllUntilTxTun(receiver *nebula.Control) []byte {
+	if r.fanInOn.Load() {
+		return r.routeFanIn(receiver)
+	}
+	return r.routeReflect(receiver)
+}
+
+// routeFanIn is the alloc-free path used when EnableFanIn is in effect.
+func (r *R) routeFanIn(receiver *nebula.Control) []byte {
+	tunTx := receiver.GetTunTxChan()
+	for {
+		select {
+		case p := <-tunTx:
+			r.Lock()
+			if r.flow != nil {
+				np := udp.Packet{Data: make([]byte, len(p))}
+				copy(np.Data, p)
+				r.unlockedInjectFlow(receiver, receiver, &np, true)
+			}
+			r.Unlock()
+			return p
+		case fp := <-r.udpFanIn:
+			r.routeUDP(fp.from, fp.pkt)
+		}
+	}
+}
+
+// routeReflect is the default reflect.Select-based path. Pays the boxing allocation per call but doesn't interfere
+// with tests that pull packets directly from controls' UDP TX channels via GetFromUDP.
+func (r *R) routeReflect(receiver *nebula.Control) []byte {
+	sc, cm := r.selectCasesFor(receiver)
+	for {
+		x, rx, _ := reflect.Select(sc)
+		if x == 0 {
+			p := rx.Interface().([]byte)
+			r.Lock()
+			if r.flow != nil {
+				np := udp.Packet{Data: make([]byte, len(p))}
+				copy(np.Data, p)
+				r.unlockedInjectFlow(cm[x], cm[x], &np, true)
+			}
+			r.Unlock()
+			return p
+		}
+		r.routeUDP(cm[x], rx.Interface().(*udp.Packet))
+	}
+}
+
+// EnableFanIn switches RouteForAllUntilTxTun to the alloc-free fan-in path.
+// One forwarder goroutine per registered control drains UDP TX into a shared channel that RouteForAllUntilTxTun selects
+// on alongside the receiver's TUN TX channel.
+func (r *R) EnableFanIn() {
+	r.fanInMu.Lock()
+	defer r.fanInMu.Unlock()
+	if r.fanInOn.Load() {
+		return
+	}
+	r.udpFanIn = make(chan fannedPacket, 32)
+	r.stopFanIn = make(chan struct{})
+	for _, c := range r.controls {
+		r.startFanInWorker(c)
+	}
+	r.fanInOn.Store(true)
+	r.t.Cleanup(r.stopFanInWorkers)
+}
+
+// startFanInWorker spawns a goroutine that drains c's UDP TX into r.udpFanIn.
+func (r *R) startFanInWorker(c *nebula.Control) {
+	r.fanInWG.Add(1)
+	udpTx := c.GetUDPTxChan()
+	go func() {
+		defer r.fanInWG.Done()
+		for {
+			select {
+			case <-r.stopFanIn:
+				return
+			case p := <-udpTx:
+				select {
+				case <-r.stopFanIn:
+					p.Release()
+					return
+				case r.udpFanIn <- fannedPacket{from: c, pkt: p}:
+				}
+			}
+		}
+	}()
+}
+
+// stopFanInWorkers signals the fan-in goroutines to exit and waits for them.
+func (r *R) stopFanInWorkers() {
+	r.fanInMu.Lock()
+	wasOn := r.fanInOn.Swap(false)
+	r.fanInMu.Unlock()
+	if !wasOn {
+		return
+	}
+	close(r.stopFanIn)
+	r.fanInWG.Wait()
+}
+
+// routeUDP forwards a UDP TX packet from the named source control to the destination control derived from p.To,
+// releasing the source packet after InjectUDPPacket has copied its bytes into a fresh pool slot.
+func (r *R) routeUDP(from *nebula.Control, p *udp.Packet) {
+	r.Lock()
+	defer r.Unlock()
+	a := from.GetUDPAddr()
+	c := r.getControl(a, p.To, p)
+	if c == nil {
+		panic(fmt.Sprintf("No control for udp tx %s", p.To))
+	}
+	fp := r.unlockedInjectFlow(from, c, p, false)
+	c.InjectUDPPacket(p) // copies internally; original is ours to release
+	fp.WasReceived()
+	p.Release()
+}
+
+// selectCasesFor returns the SelectCase array used by routeReflect: one slot for the receiver's TUN TX channel followed
+// by one per control's UDP TX channel. Cached for the test lifetime, only rebuilt if the receiver changes.
+func (r *R) selectCasesFor(receiver *nebula.Control) ([]reflect.SelectCase, []*nebula.Control) {
+	r.Lock()
+	defer r.Unlock()
+	if r.selRecvCtl == receiver && r.selCases != nil {
+		return r.selCases, r.selCtls
+	}
 	sc := make([]reflect.SelectCase, len(r.controls)+1)
 	cm := make([]*nebula.Control, len(r.controls)+1)
-
-	i := 0
-	sc[i] = reflect.SelectCase{
-		Dir:  reflect.SelectRecv,
-		Chan: reflect.ValueOf(receiver.GetTunTxChan()),
-		Send: reflect.Value{},
-	}
-	cm[i] = receiver
-
-	i++
+	sc[0] = reflect.SelectCase{Dir: reflect.SelectRecv, Chan: reflect.ValueOf(receiver.GetTunTxChan())}
+	cm[0] = receiver
+	i := 1
 	for _, c := range r.controls {
-		sc[i] = reflect.SelectCase{
-			Dir:  reflect.SelectRecv,
-			Chan: reflect.ValueOf(c.GetUDPTxChan()),
-			Send: reflect.Value{},
-		}
-
+		sc[i] = reflect.SelectCase{Dir: reflect.SelectRecv, Chan: reflect.ValueOf(c.GetUDPTxChan())}
 		cm[i] = c
 		i++
 	}
-
-	for {
-		x, rx, _ := reflect.Select(sc)
-		r.Lock()
-
-		if x == 0 {
-			// we are the tun tx, we can exit
-			p := rx.Interface().([]byte)
-			np := udp.Packet{Data: make([]byte, len(p))}
-			copy(np.Data, p)
-
-			r.unlockedInjectFlow(cm[x], cm[x], &np, true)
-			r.Unlock()
-			return p
-
-		} else {
-			// we are a udp tx, route and continue
-			p := rx.Interface().(*udp.Packet)
-			a := cm[x].GetUDPAddr()
-			c := r.getControl(a, p.To, p)
-			if c == nil {
-				r.Unlock()
-				panic(fmt.Sprintf("No control for udp tx %s", p.To))
-			}
-			fp := r.unlockedInjectFlow(cm[x], c, p, false)
-			c.InjectUDPPacket(p)
-			fp.WasReceived()
-		}
-		r.Unlock()
-	}
+	r.selRecvCtl = receiver
+	r.selCases = sc
+	r.selCtls = cm
+	return sc, cm
 }
 
 // RouteExitFunc will call the whatDo func with each udp packet from sender.
@@ -522,6 +649,7 @@ func (r *R) RouteExitFunc(sender *nebula.Control, whatDo ExitFunc) {
 		switch e {
 		case ExitNow:
 			r.Unlock()
+			p.Release()
 			return
 
 		case RouteAndExit:
@@ -529,6 +657,7 @@ func (r *R) RouteExitFunc(sender *nebula.Control, whatDo ExitFunc) {
 			receiver.InjectUDPPacket(p)
 			fp.WasReceived()
 			r.Unlock()
+			p.Release()
 			return
 
 		case KeepRouting:
@@ -541,6 +670,7 @@ func (r *R) RouteExitFunc(sender *nebula.Control, whatDo ExitFunc) {
 		}
 
 		r.Unlock()
+		p.Release()
 	}
 }
 
@@ -641,6 +771,7 @@ func (r *R) RouteForAllExitFunc(whatDo ExitFunc) {
 		switch e {
 		case ExitNow:
 			r.Unlock()
+			p.Release()
 			return
 
 		case RouteAndExit:
@@ -648,6 +779,7 @@ func (r *R) RouteForAllExitFunc(whatDo ExitFunc) {
 			receiver.InjectUDPPacket(p)
 			fp.WasReceived()
 			r.Unlock()
+			p.Release()
 			return
 
 		case KeepRouting:
@@ -659,6 +791,7 @@ func (r *R) RouteForAllExitFunc(whatDo ExitFunc) {
 			panic(fmt.Sprintf("Unknown exitFunc return: %v", e))
 		}
 		r.Unlock()
+		p.Release()
 	}
 }
 
@@ -702,19 +835,20 @@ func (r *R) FlushAll() {
 		}
 		receiver.InjectUDPPacket(p)
 		r.Unlock()
+		p.Release()
 	}
 }
 
 // getControl performs or seeds NAT translation and returns the control for toAddr, p from fields may change
 // This is an internal router function, the caller must hold the lock
 func (r *R) getControl(fromAddr, toAddr netip.AddrPort, p *udp.Packet) *nebula.Control {
-	if newAddr, ok := r.outNat[fromAddr.String()+":"+toAddr.String()]; ok {
+	if newAddr, ok := r.outNat[outNatKey{from: fromAddr, to: toAddr}]; ok {
 		p.From = newAddr
 	}
 
 	c, ok := r.inNat[toAddr]
 	if ok {
-		r.outNat[c.GetUDPAddr().String()+":"+fromAddr.String()] = toAddr
+		r.outNat[outNatKey{from: c.GetUDPAddr(), to: fromAddr}] = toAddr
 		return c
 	}
 

e2e/sshd_test.go

@@ -0,0 +1,125 @@
+//go:build e2e_testing
+// +build e2e_testing
+
+package e2e
+
+import (
+	"crypto/ed25519"
+	"crypto/rand"
+	"encoding/pem"
+	"net"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/slackhq/nebula/cert"
+	"github.com/slackhq/nebula/cert_test"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"golang.org/x/crypto/ssh"
+)
+
+func TestSSHDLifecycle(t *testing.T) {
+	// TestSSHDLifecycle exercises the in-process sshd through several config reloads and a Control.Stop.
+	ca, _, caKey, _ := cert_test.NewTestCaCert(
+		cert.Version1, cert.Curve_CURVE25519,
+		time.Now(), time.Now().Add(10*time.Minute),
+		nil, nil, []string{},
+	)
+
+	hostKeyPEM := generateSSHHostKey(t)
+	clientSigner, clientAuthKey := generateSSHClientKey(t)
+	sshdAddr := allocLoopbackPort(t)
+
+	overrides := m{
+		"sshd": m{
+			"enabled":  true,
+			"listen":   sshdAddr,
+			"host_key": hostKeyPEM,
+			"authorized_users": []m{{
+				"user": "tester",
+				"keys": []string{clientAuthKey},
+			}},
+		},
+	}
+	control, _, _, _ := newSimpleServer(cert.Version1, ca, caKey, "sshd-test", "10.222.0.1/24", overrides)
+	control.Start()
+	t.Cleanup(func() { control.Stop() })
+
+	// sshd binds in a goroutine after Start returns; wait for it.
+	require.Eventually(t, func() bool { return canDial(sshdAddr) }, 2*time.Second, 25*time.Millisecond,
+		"sshd never started listening")
+
+	for i := 1; i <= 3; i++ {
+		out := sshExecReload(t, sshdAddr, clientSigner)
+		assert.Contains(t, out, "Reloading config", "reload cycle %d", i)
+		require.Eventually(t, func() bool { return canDial(sshdAddr) }, 2*time.Second, 25*time.Millisecond,
+			"sshd not listening after reload cycle %d", i)
+	}
+
+	control.Stop()
+	require.Eventually(t, func() bool { return !canDial(sshdAddr) }, 2*time.Second, 25*time.Millisecond,
+		"sshd still listening after Control.Stop")
+}
+
+func canDial(addr string) bool {
+	c, err := net.DialTimeout("tcp", addr, 100*time.Millisecond)
+	if err != nil {
+		return false
+	}
+	_ = c.Close()
+	return true
+}
+
+// allocLoopbackPort grabs an unused TCP port on 127.0.0.1, closes it, and returns the address. There
+// is a small race between releasing the port and the sshd reclaiming it; in practice the OS keeps the
+// port available long enough for the test to bind it.
+func allocLoopbackPort(t *testing.T) string {
+	t.Helper()
+	l, err := net.Listen("tcp", "127.0.0.1:0")
+	require.NoError(t, err)
+	addr := l.Addr().String()
+	require.NoError(t, l.Close())
+	return addr
+}
+
+func generateSSHHostKey(t *testing.T) string {
+	t.Helper()
+	_, priv, err := ed25519.GenerateKey(rand.Reader)
+	require.NoError(t, err)
+	block, err := ssh.MarshalPrivateKey(priv, "nebula-e2e-host")
+	require.NoError(t, err)
+	return string(pem.EncodeToMemory(block))
+}
+
+func generateSSHClientKey(t *testing.T) (ssh.Signer, string) {
+	t.Helper()
+	_, priv, err := ed25519.GenerateKey(rand.Reader)
+	require.NoError(t, err)
+	signer, err := ssh.NewSignerFromKey(priv)
+	require.NoError(t, err)
+	auth := strings.TrimSpace(string(ssh.MarshalAuthorizedKey(signer.PublicKey())))
+	return signer, auth
+}
+
+func sshExecReload(t *testing.T, addr string, signer ssh.Signer) string {
+	t.Helper()
+	cfg := &ssh.ClientConfig{
+		User:            "tester",
+		Auth:            []ssh.AuthMethod{ssh.PublicKeys(signer)},
+		HostKeyCallback: ssh.InsecureIgnoreHostKey(),
+		Timeout:         2 * time.Second,
+	}
+	client, err := ssh.Dial("tcp", addr, cfg)
+	require.NoError(t, err)
+	defer client.Close()
+
+	sess, err := client.NewSession()
+	require.NoError(t, err)
+	defer sess.Close()
+
+	// reload tears the channel down before sending exit-status, so Output returns an error on the
+	// channel close. The output buffer still has whatever the reload callback wrote before that.
+	out, _ := sess.Output("reload")
+	return string(out)
+}

e2e/tunnels_test.go

@@ -19,6 +19,7 @@ import (
 )
 
 func TestDropInactiveTunnels(t *testing.T) {
+	t.Parallel()
 	// The goal of this test is to ensure the shortest inactivity timeout will close the tunnel on both sides
 	// under ideal conditions
 	ca, _, caKey, _ := cert_test.NewTestCaCert(cert.Version1, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
@@ -63,6 +64,7 @@ func TestDropInactiveTunnels(t *testing.T) {
 }
 
 func TestCertUpgrade(t *testing.T) {
+	t.Parallel()
 	// The goal of this test is to ensure the shortest inactivity timeout will close the tunnel on both sides
 	// under ideal conditions
 	ca, _, caKey, _ := cert_test.NewTestCaCert(cert.Version1, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
@@ -157,6 +159,7 @@ func TestCertUpgrade(t *testing.T) {
 }
 
 func TestCertDowngrade(t *testing.T) {
+	t.Parallel()
 	// The goal of this test is to ensure the shortest inactivity timeout will close the tunnel on both sides
 	// under ideal conditions
 	ca, _, caKey, _ := cert_test.NewTestCaCert(cert.Version1, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
@@ -255,6 +258,7 @@ func TestCertDowngrade(t *testing.T) {
 }
 
 func TestCertMismatchCorrection(t *testing.T) {
+	t.Parallel()
 	// The goal of this test is to ensure the shortest inactivity timeout will close the tunnel on both sides
 	// under ideal conditions
 	ca, _, caKey, _ := cert_test.NewTestCaCert(cert.Version1, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
@@ -322,6 +326,7 @@ func TestCertMismatchCorrection(t *testing.T) {
 }
 
 func TestCrossStackRelaysWork(t *testing.T) {
+	t.Parallel()
 	ca, _, caKey, _ := cert_test.NewTestCaCert(cert.Version2, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
 	myControl, myVpnIpNet, _, _ := newSimpleServer(cert.Version2, ca, caKey, "me     ", "10.128.0.1/24,fc00::1/64", m{"relay": m{"use_relays": true}})
 	relayControl, relayVpnIpNet, relayUdpAddr, _ := newSimpleServer(cert.Version2, ca, caKey, "relay  ", "10.128.0.128/24,fc00::128/64", m{"relay": m{"am_relay": true}})
@@ -350,14 +355,14 @@ func TestCrossStackRelaysWork(t *testing.T) {
 	theirControl.Start()
 
 	t.Log("Trigger a handshake from me to them via the relay")
-	myControl.InjectTunUDPPacket(theirVpnV6.Addr(), 80, myVpnV6.Addr(), 80, []byte("Hi from me"))
+	myControl.InjectTunPacket(BuildTunUDPPacket(theirVpnV6.Addr(), 80, myVpnV6.Addr(), 80, []byte("Hi from me")))
 
 	p := r.RouteForAllUntilTxTun(theirControl)
 	r.Log("Assert the tunnel works")
 	assertUdpPacket(t, []byte("Hi from me"), p, myVpnV6.Addr(), theirVpnV6.Addr(), 80, 80)
 
 	t.Log("reply?")
-	theirControl.InjectTunUDPPacket(myVpnV6.Addr(), 80, theirVpnV6.Addr(), 80, []byte("Hi from them"))
+	theirControl.InjectTunPacket(BuildTunUDPPacket(myVpnV6.Addr(), 80, theirVpnV6.Addr(), 80, []byte("Hi from them")))
 	p = r.RouteForAllUntilTxTun(myControl)
 	assertUdpPacket(t, []byte("Hi from them"), p, theirVpnV6.Addr(), myVpnV6.Addr(), 80, 80)
 
@@ -369,6 +374,7 @@ func TestCrossStackRelaysWork(t *testing.T) {
 }
 
 func TestCloseTunnelAuthenticated(t *testing.T) {
+	t.Parallel()
 	ca, _, caKey, _ := cert_test.NewTestCaCert(cert.Version1, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
 	myControl, myVpnIpNet, myUdpAddr, _ := newSimpleServer(cert.Version1, ca, caKey, "me", "10.128.0.1/24", m{"tunnels": m{"drop_inactive": true, "inactivity_timeout": "5s"}})
 	theirControl, theirVpnIpNet, theirUdpAddr, _ := newSimpleServer(cert.Version1, ca, caKey, "them", "10.128.0.2/24", m{"tunnels": m{"drop_inactive": true, "inactivity_timeout": "10m"}})

ecn_inner_test.go

@@ -0,0 +1,125 @@
+package nebula
+
+import (
+	"io"
+	"log/slog"
+	"testing"
+)
+
+func TestInnerECN(t *testing.T) {
+	cases := []struct {
+		name string
+		pkt  []byte
+		want byte
+	}{
+		{"empty", nil, 0},
+		{"v4_NotECT", v4WithToS(0x00), 0x00},
+		{"v4_ECT0", v4WithToS(0x02), 0x02},
+		{"v4_ECT1", v4WithToS(0x01), 0x01},
+		{"v4_CE", v4WithToS(0x03), 0x03},
+		{"v4_DSCP_then_NotECT", v4WithToS(0x88 | 0x00), 0x00},
+		{"v4_DSCP_then_CE", v4WithToS(0x88 | 0x03), 0x03},
+		{"v6_NotECT", v6WithTC(0x00), 0x00},
+		{"v6_ECT0", v6WithTC(0x02), 0x02},
+		{"v6_CE", v6WithTC(0x03), 0x03},
+		{"v6_DSCP_then_CE", v6WithTC(0x88 | 0x03), 0x03},
+		{"unknown_version", []byte{0xa5, 0xff}, 0},
+	}
+	for _, c := range cases {
+		t.Run(c.name, func(t *testing.T) {
+			got := innerECN(c.pkt)
+			if got != c.want {
+				t.Errorf("innerECN=0x%02x want 0x%02x", got, c.want)
+			}
+		})
+	}
+}
+
+// v4WithToS returns a 2-byte slice tall enough for innerECN: byte 0 carries
+// version=4 in the high nibble, byte 1 is the full ToS so we exercise both
+// the DSCP and ECN portions through the byte 1 mask.
+func v4WithToS(tos byte) []byte {
+	return []byte{0x45, tos}
+}
+
+// v6WithTC builds a 2-byte slice that places a known traffic class value
+// across bytes 0 (high nibble of TC) and 1 (low nibble of TC). innerECN
+// extracts ECN as (b[1]>>4)&0x03, which corresponds to TC[1:0].
+func v6WithTC(tc byte) []byte {
+	return []byte{0x60 | (tc>>4)&0x0f, (tc & 0x0f) << 4}
+}
+
+func TestApplyOuterECN(t *testing.T) {
+	silent := slog.New(slog.NewTextHandler(io.Discard, nil))
+	hi := &HostInfo{}
+
+	// Build a v4 packet helper with a given inner ECN field.
+	v4 := func(innerECN byte) []byte {
+		// 20-byte minimal IPv4 header with ToS = innerECN (DSCP zeroed).
+		return []byte{
+			0x45, innerECN, 0, 28,
+			0, 0, 0x40, 0,
+			64, 6, 0, 0,
+			10, 0, 0, 1,
+			10, 0, 0, 2,
+		}
+	}
+	// Build a v6 packet helper with a given inner ECN field. ECN occupies
+	// TC[1:0] which sit at byte 1 mask 0x30.
+	v6 := func(innerECN byte) []byte {
+		// 40-byte minimal IPv6 header with TC[1:0] = innerECN.
+		pkt := make([]byte, 40)
+		pkt[0] = 0x60                   // version=6, TC[7:4]=0
+		pkt[1] = (innerECN & 0x03) << 4 // TC[3:0]: low 2 bits = ECN, top 2 = DSCP-low (0)
+		return pkt
+	}
+
+	type cell struct {
+		outer    byte
+		inner    byte
+		wantECN  byte
+		wantSame bool // expect inner unchanged (true => verify the byte didn't move)
+	}
+
+	// RFC 6040 normal-mode combine table. Only outer==CE causes mutation.
+	table := []cell{
+		{ecnNotECT, ecnNotECT, ecnNotECT, true},
+		{ecnNotECT, ecnECT0, ecnECT0, true},
+		{ecnNotECT, ecnECT1, ecnECT1, true},
+		{ecnNotECT, ecnCE, ecnCE, true},
+
+		{ecnECT0, ecnNotECT, ecnNotECT, true},
+		{ecnECT0, ecnECT0, ecnECT0, true},
+		{ecnECT0, ecnECT1, ecnECT1, true},
+		{ecnECT0, ecnCE, ecnCE, true},
+
+		{ecnECT1, ecnNotECT, ecnNotECT, true},
+		{ecnECT1, ecnECT0, ecnECT0, true},
+		{ecnECT1, ecnECT1, ecnECT1, true},
+		{ecnECT1, ecnCE, ecnCE, true},
+
+		{ecnCE, ecnNotECT, ecnNotECT, true}, // legacy: log, leave alone
+		{ecnCE, ecnECT0, ecnCE, false},      // CE folded in
+		{ecnCE, ecnECT1, ecnCE, false},
+		{ecnCE, ecnCE, ecnCE, true},
+	}
+
+	for _, c := range table {
+		t.Run("v4", func(t *testing.T) {
+			pkt := v4(c.inner)
+			applyOuterECN(pkt, c.outer, hi, silent)
+			got := pkt[1] & 0x03
+			if got != c.wantECN {
+				t.Errorf("v4 outer=0x%02x inner=0x%02x: got 0x%02x want 0x%02x", c.outer, c.inner, got, c.wantECN)
+			}
+		})
+		t.Run("v6", func(t *testing.T) {
+			pkt := v6(c.inner)
+			applyOuterECN(pkt, c.outer, hi, silent)
+			got := (pkt[1] >> 4) & 0x03
+			if got != c.wantECN {
+				t.Errorf("v6 outer=0x%02x inner=0x%02x: got 0x%02x want 0x%02x", c.outer, c.inner, got, c.wantECN)
+			}
+		})
+	}
+}

examples/config.yml

@@ -138,6 +138,14 @@ listen:
   # max, net.core.rmem_max and net.core.wmem_max
   #read_buffer: 10485760
   #write_buffer: 10485760
+
+  # On Windows only
+  # When true, Nebula installs a WFP (Windows Filtering Platform) PERMIT filter scoped to UDP at the listener port.
+  # WFP sits below Windows Defender Firewall, so this lets peer handshakes reach Nebula's outside socket regardless
+  # of WDF's inbound rules.
+  # Default true; set to false to leave WDF in charge of inbound decisions on the listener port. Not reloadable.
+  #windows_bypass_wdf: true
+
   # By default, Nebula replies to packets it has no tunnel for with a "recv_error" packet. This packet helps speed up reconnection
   # in the case that Nebula on either side did not shut down cleanly. This response can be abused as a way to discover if Nebula is running
   # on a host though. This option lets you configure if you want to send "recv_error" packets always, never, or only to private network remotes.
@@ -163,17 +171,21 @@ listen:
 
 punchy:
   # Continues to punch inbound/outbound at a regular interval to avoid expiration of firewall nat mappings
+  # This setting is reloadable.
   punch: true
 
   # respond means that a node you are trying to reach will connect back out to you if your hole punching fails
   # this is extremely useful if one node is behind a difficult nat, such as a symmetric NAT
   # Default is false
+  # This setting is reloadable.
   #respond: true
 
   # delays a punch response for misbehaving NATs, default is 1 second.
+  # This setting is reloadable.
   #delay: 1s
 
   # set the delay before attempting punchy.respond. Default is 5 seconds. respond must be true to take effect.
+  # This setting is reloadable.
   #respond_delay: 5s
 
 # Cipher allows you to choose between the available ciphers for your network. Options are chachapoly or aes
@@ -282,6 +294,24 @@ tun:
     #  metric: 100
     #  install: true
 
+  # On Windows only, sets the network category of the nebula interface. Without this, Windows often
+  # leaves the network as "Unidentified" and treats it as Public, which makes the host firewall more
+  # restrictive than you usually want for an overlay between trusted peers. Valid values:
+  #   private             - treat the nebula network as a private/trusted network (default)
+  #   public              - treat it as a public/untrusted network
+  #   domain              - treat it as a domain-authenticated network
+  #   unset               - leave whatever Windows decided alone
+  # Not reloadable.
+  #network_category: private
+
+  # On Windows only
+  # When true, Nebula installs a WFP (Windows Filtering Platform) PERMIT filter scoped to the nebula adapter LUID.
+  # WFP sits below Windows Defender Firewall, so this lets inbound traffic through regardless of WDF rules.
+  # Filters are auto-removed when the adapter goes away.
+  # See listen.windows_bypass_wdf for the matching control over inbound to nebula's outside UDP listener.
+  # Default true; set to false to leave WDF in charge of inbound decisions on the nebula interface. Not reloadable.
+  #windows_bypass_wdf: true
+
   # On linux only, set to true to manage unsafe routes directly on the system route table with gateway routes instead of
   # in nebula configuration files. Default false, not reloadable.
   #use_system_route_table: false
@@ -292,24 +322,21 @@ tun:
 
 # Configure logging level
 logging:
-  # panic, fatal, error, warning, info, or debug. Default is info and is reloadable.
-  #NOTE: Debug mode can log remotely controlled/untrusted data which can quickly fill a disk in some
-  # scenarios. Debug logging is also CPU intensive and will decrease performance overall.
-  # Only enable debug logging while actively investigating an issue.
+  # trace, debug, info, warn, or error. Default is info and is reloadable.
+  # fatal and panic are accepted for backwards compatibility and map to error.
+  #NOTE: Debug and trace modes can log remotely controlled/untrusted data which can quickly fill a disk in some
+  # scenarios. Debug and trace logging are also CPU intensive and will decrease performance overall.
+  # Only enable debug or trace logging while actively investigating an issue.
   level: info
-  # json or text formats currently available. Default is text
+  # json or text formats currently available. Default is text.
   format: text
-  # Disable timestamp logging. useful when output is redirected to logging system that already adds timestamps. Default is false
+  # Disable timestamp logging. Useful when output is redirected to a logging system that already adds timestamps. Default is false.
   #disable_timestamp: true
-  # timestamp format is specified in Go time format, see:
-  #     https://golang.org/pkg/time/#pkg-constants
-  # default when `format: json`: "2006-01-02T15:04:05Z07:00" (RFC3339)
-  # default when `format: text`:
-  #     when TTY attached: seconds since beginning of execution
-  #     otherwise: "2006-01-02T15:04:05Z07:00" (RFC3339)
-  # As an example, to log as RFC3339 with millisecond precision, set to:
-  #timestamp_format: "2006-01-02T15:04:05.000Z07:00"
+  # Timestamps use RFC3339Nano ("2006-01-02T15:04:05.999999999Z07:00") and are not configurable.
 
+# The stats section is reloadable. A HUP may change the backend, toggle stats
+# on or off, switch the listen/host address, or pick up new DNS for the
+# configured graphite host.
 #stats:
   #type: graphite
   #prefix: nebula
@@ -327,10 +354,12 @@ logging:
   # enables counter metrics for meta packets
   #   e.g.: `messages.tx.handshake`
   # NOTE: `message.{tx,rx}.recv_error` is always emitted
+  # Not reloadable.
   #message_metrics: false
 
   # enables detailed counter metrics for lighthouse packets
   #   e.g.: `lighthouse.rx.HostQuery`
+  # Not reloadable.
   #lighthouse_metrics: false
 
 # Handshake Manager Settings

examples/go_service/main.go

@@ -7,9 +7,9 @@ import (
 	"net"
 	"os"
 
-	"github.com/sirupsen/logrus"
 	"github.com/slackhq/nebula"
 	"github.com/slackhq/nebula/config"
+	"github.com/slackhq/nebula/logging"
 	"github.com/slackhq/nebula/overlay"
 	"github.com/slackhq/nebula/service"
 )
@@ -64,8 +64,7 @@ pki:
 		return err
 	}
 
-	logger := logrus.New()
-	logger.Out = os.Stdout
+	logger := logging.NewLogger(os.Stdout)
 
 	ctrl, err := nebula.Main(&cfg, false, "custom-app", logger, overlay.NewUserDeviceFromConfig)
 	if err != nil {

firewall.go

@@ -1,11 +1,13 @@
 package nebula
 
 import (
+	"context"
 	"crypto/sha256"
 	"encoding/hex"
 	"errors"
 	"fmt"
 	"hash/fnv"
+	"log/slog"
 	"net/netip"
 	"reflect"
 	"slices"
@@ -16,7 +18,6 @@ import (
 
 	"github.com/gaissmai/bart"
 	"github.com/rcrowley/go-metrics"
-	"github.com/sirupsen/logrus"
 	"github.com/slackhq/nebula/cert"
 	"github.com/slackhq/nebula/config"
 	"github.com/slackhq/nebula/firewall"
@@ -67,7 +68,7 @@ type Firewall struct {
 	incomingMetrics     firewallMetrics
 	outgoingMetrics     firewallMetrics
 
-	l *logrus.Logger
+	l *slog.Logger
 }
 
 type firewallMetrics struct {
@@ -79,8 +80,8 @@ type firewallMetrics struct {
 type FirewallConntrack struct {
 	sync.Mutex
 
-	Conns      map[firewall.Packet]*conn
-	TimerWheel *TimerWheel[firewall.Packet]
+	Conns      map[firewall.PacketKey]*conn
+	TimerWheel *TimerWheel[firewall.PacketKey]
 }
 
 // FirewallTable is the entry point for a rule, the evaluation order is:
@@ -131,7 +132,7 @@ type firewallLocalCIDR struct {
 
 // NewFirewall creates a new Firewall object. A TimerWheel is created for you from the provided timeouts.
 // The certificate provided should be the highest version loaded in memory.
-func NewFirewall(l *logrus.Logger, tcpTimeout, UDPTimeout, defaultTimeout time.Duration, c cert.Certificate) *Firewall {
+func NewFirewall(l *slog.Logger, tcpTimeout, UDPTimeout, defaultTimeout time.Duration, c cert.Certificate) *Firewall {
 	//TODO: error on 0 duration
 	var tmin, tmax time.Duration
 
@@ -165,8 +166,8 @@ func NewFirewall(l *logrus.Logger, tcpTimeout, UDPTimeout, defaultTimeout time.D
 
 	return &Firewall{
 		Conntrack: &FirewallConntrack{
-			Conns:      make(map[firewall.Packet]*conn),
-			TimerWheel: NewTimerWheel[firewall.Packet](tmin, tmax),
+			Conns:      make(map[firewall.PacketKey]*conn),
+			TimerWheel: NewTimerWheel[firewall.PacketKey](tmin, tmax),
 		},
 		InRules:           newFirewallTable(),
 		OutRules:          newFirewallTable(),
@@ -191,7 +192,7 @@ func NewFirewall(l *logrus.Logger, tcpTimeout, UDPTimeout, defaultTimeout time.D
 	}
 }
 
-func NewFirewallFromConfig(l *logrus.Logger, cs *CertState, c *config.C) (*Firewall, error) {
+func NewFirewallFromConfig(l *slog.Logger, cs *CertState, c *config.C) (*Firewall, error) {
 	certificate := cs.getCertificate(cert.Version2)
 	if certificate == nil {
 		certificate = cs.getCertificate(cert.Version1)
@@ -219,7 +220,7 @@ func NewFirewallFromConfig(l *logrus.Logger, cs *CertState, c *config.C) (*Firew
 	case "drop":
 		fw.InSendReject = false
 	default:
-		l.WithField("action", inboundAction).Warn("invalid firewall.inbound_action, defaulting to `drop`")
+		l.Warn("invalid firewall.inbound_action, defaulting to `drop`", "action", inboundAction)
 		fw.InSendReject = false
 	}
 
@@ -230,7 +231,7 @@ func NewFirewallFromConfig(l *logrus.Logger, cs *CertState, c *config.C) (*Firew
 	case "drop":
 		fw.OutSendReject = false
 	default:
-		l.WithField("action", outboundAction).Warn("invalid firewall.outbound_action, defaulting to `drop`")
+		l.Warn("invalid firewall.outbound_action, defaulting to `drop`", "action", outboundAction)
 		fw.OutSendReject = false
 	}
 
@@ -268,7 +269,7 @@ func (f *Firewall) AddRule(incoming bool, proto uint8, startPort int32, endPort
 	case firewall.ProtoICMP, firewall.ProtoICMPv6:
 		//ICMP traffic doesn't have ports, so we always coerce to "any", even if a value is provided
 		if startPort != firewall.PortAny {
-			f.l.WithField("startPort", startPort).Warn("ignoring port specification for ICMP firewall rule")
+			f.l.Warn("ignoring port specification for ICMP firewall rule", "startPort", startPort)
 		}
 		startPort = firewall.PortAny
 		endPort = firewall.PortAny
@@ -290,8 +291,9 @@ func (f *Firewall) AddRule(incoming bool, proto uint8, startPort int32, endPort
 	if !incoming {
 		direction = "outgoing"
 	}
-	f.l.WithField("firewallRule", m{"direction": direction, "proto": proto, "startPort": startPort, "endPort": endPort, "groups": groups, "host": host, "cidr": cidr, "localCidr": localCidr, "caName": caName, "caSha": caSha}).
-		Info("Firewall rule added")
+	f.l.Info("Firewall rule added",
+		"firewallRule", m{"direction": direction, "proto": proto, "startPort": startPort, "endPort": endPort, "groups": groups, "host": host, "cidr": cidr, "localCidr": localCidr, "caName": caName, "caSha": caSha},
+	)
 
 	return fp.addRule(f, startPort, endPort, groups, host, cidr, localCidr, caName, caSha)
 }
@@ -314,7 +316,7 @@ func (f *Firewall) GetRuleHashes() string {
 	return "SHA:" + f.GetRuleHash() + ",FNV:" + strconv.FormatUint(uint64(f.GetRuleHashFNV()), 10)
 }
 
-func AddFirewallRulesFromConfig(l *logrus.Logger, inbound bool, c *config.C, fw FirewallInterface) error {
+func AddFirewallRulesFromConfig(l *slog.Logger, inbound bool, c *config.C, fw FirewallInterface) error {
 	var table string
 	if inbound {
 		table = "firewall.inbound"
@@ -372,7 +374,7 @@ func AddFirewallRulesFromConfig(l *logrus.Logger, inbound bool, c *config.C, fw
 			startPort = firewall.PortAny
 			endPort = firewall.PortAny
 			if sPort != "" {
-				l.WithField("port", sPort).Warn("ignoring port specification for ICMP firewall rule")
+				l.Warn("ignoring port specification for ICMP firewall rule", "port", sPort)
 			}
 		default:
 			return fmt.Errorf("%s rule #%v; proto was not understood; `%s`", table, i, r.Proto)
@@ -396,7 +398,11 @@ func AddFirewallRulesFromConfig(l *logrus.Logger, inbound bool, c *config.C, fw
 		}
 
 		if warning := r.sanity(); warning != nil {
-			l.Warnf("%s rule #%v; %s", table, i, warning)
+			l.Warn("firewall rule sanity check",
+				"table", table,
+				"rule", i,
+				"warning", warning,
+			)
 		}
 
 		err = fw.AddRule(inbound, proto, startPort, endPort, r.Groups, r.Host, r.Cidr, r.LocalCidr, r.CAName, r.CASha)
@@ -416,12 +422,27 @@ var ErrNoMatchingRule = errors.New("no matching rule in firewall table")
 
 // Drop returns an error if the packet should be dropped, explaining why. It
 // returns nil if the packet should not be dropped.
-func (f *Firewall) Drop(fp firewall.Packet, incoming bool, h *HostInfo, caPool *cert.CAPool, localCache firewall.ConntrackCache) error {
-	// Check if we spoke to this tuple, if we did then allow this packet
-	if f.inConns(fp, h, caPool, localCache) {
+//
+// key is the dense conntrack key — used as-is for the inConns fast path
+// without touching fp at all. fp is the rich Packet form rule matching
+// needs (CIDR lookups, family checks); on the conntrack-miss slow path
+// Drop ensures fp is hydrated from key (idempotent if the caller already
+// filled fp). On accept-via-conntrack the caller's fp is left untouched.
+func (f *Firewall) Drop(key firewall.PacketKey, fp *firewall.Packet, incoming bool, h *HostInfo, caPool *cert.CAPool, localCache firewall.ConntrackCache) error {
+	// Check if we spoke to this tuple, if we did then allow this packet.
+	// Hot path: only the dense key is touched.
+	if f.inConns(key, h, caPool, localCache) {
 		return nil
 	}
 
+	// Conntrack miss → rule matching needs the rich Packet form. Hydrate
+	// from the key if the caller passed a zero-valued fp (the inbound path
+	// after batch.ParsePacket). Outbound callers Hydrate themselves and
+	// skip this hop.
+	if !fp.LocalAddr.IsValid() {
+		key.Hydrate(fp)
+	}
+
 	// Make sure remote address matches nebula certificate, and determine how to treat it
 	if h.networks == nil {
 		// Simple case: Certificate has one address and no unsafe networks
@@ -461,13 +482,13 @@ func (f *Firewall) Drop(fp firewall.Packet, incoming bool, h *HostInfo, caPool *
 	}
 
 	// We now know which firewall table to check against
-	if !table.match(fp, incoming, h.ConnectionState.peerCert, caPool) {
+	if !table.match(*fp, incoming, h.ConnectionState.peerCert, caPool) {
 		f.metrics(incoming).droppedNoRule.Inc(1)
 		return ErrNoMatchingRule
 	}
 
 	// We always want to conntrack since it is a faster operation
-	f.addConn(fp, incoming)
+	f.addConn(key, fp.Protocol, incoming)
 
 	return nil
 }
@@ -496,9 +517,9 @@ func (f *Firewall) EmitStats() {
 	metrics.GetOrRegisterGauge("firewall.rules.hash", nil).Update(int64(f.GetRuleHashFNV()))
 }
 
-func (f *Firewall) inConns(fp firewall.Packet, h *HostInfo, caPool *cert.CAPool, localCache firewall.ConntrackCache) bool {
+func (f *Firewall) inConns(key firewall.PacketKey, h *HostInfo, caPool *cert.CAPool, localCache firewall.ConntrackCache) bool {
 	if localCache != nil {
-		if _, ok := localCache[fp]; ok {
+		if _, ok := localCache[key]; ok {
 			return true
 		}
 	}
@@ -511,7 +532,7 @@ func (f *Firewall) inConns(fp firewall.Packet, h *HostInfo, caPool *cert.CAPool,
 		f.evict(ep)
 	}
 
-	c, ok := conntrack.Conns[fp]
+	c, ok := conntrack.Conns[key]
 
 	if !ok {
 		conntrack.Unlock()
@@ -520,7 +541,11 @@ func (f *Firewall) inConns(fp firewall.Packet, h *HostInfo, caPool *cert.CAPool,
 
 	if c.rulesVersion != f.rulesVersion {
 		// This conntrack entry was for an older rule set, validate
-		// it still passes with the current rule set
+		// it still passes with the current rule set. Rule matching needs
+		// the rich Packet form, so hydrate from key.
+		var fp firewall.Packet
+		key.Hydrate(&fp)
+
 		table := f.OutRules
 		if c.incoming {
 			table = f.InRules
@@ -528,32 +553,32 @@ func (f *Firewall) inConns(fp firewall.Packet, h *HostInfo, caPool *cert.CAPool,
 
 		// We now know which firewall table to check against
 		if !table.match(fp, c.incoming, h.ConnectionState.peerCert, caPool) {
-			if f.l.Level >= logrus.DebugLevel {
-				h.logger(f.l).
-					WithField("fwPacket", fp).
-					WithField("incoming", c.incoming).
-					WithField("rulesVersion", f.rulesVersion).
-					WithField("oldRulesVersion", c.rulesVersion).
-					Debugln("dropping old conntrack entry, does not match new ruleset")
+			if f.l.Enabled(context.Background(), slog.LevelDebug) {
+				h.logger(f.l).Debug("dropping old conntrack entry, does not match new ruleset",
+					"fwPacket", fp,
+					"incoming", c.incoming,
+					"rulesVersion", f.rulesVersion,
+					"oldRulesVersion", c.rulesVersion,
+				)
 			}
-			delete(conntrack.Conns, fp)
+			delete(conntrack.Conns, key)
 			conntrack.Unlock()
 			return false
 		}
 
-		if f.l.Level >= logrus.DebugLevel {
-			h.logger(f.l).
-				WithField("fwPacket", fp).
-				WithField("incoming", c.incoming).
-				WithField("rulesVersion", f.rulesVersion).
-				WithField("oldRulesVersion", c.rulesVersion).
-				Debugln("keeping old conntrack entry, does match new ruleset")
+		if f.l.Enabled(context.Background(), slog.LevelDebug) {
+			h.logger(f.l).Debug("keeping old conntrack entry, does match new ruleset",
+				"fwPacket", fp,
+				"incoming", c.incoming,
+				"rulesVersion", f.rulesVersion,
+				"oldRulesVersion", c.rulesVersion,
+			)
 		}
 
 		c.rulesVersion = f.rulesVersion
 	}
 
-	switch fp.Protocol {
+	switch key.Protocol {
 	case firewall.ProtoTCP:
 		c.Expires = time.Now().Add(f.TCPTimeout)
 	case firewall.ProtoUDP:
@@ -565,17 +590,17 @@ func (f *Firewall) inConns(fp firewall.Packet, h *HostInfo, caPool *cert.CAPool,
 	conntrack.Unlock()
 
 	if localCache != nil {
-		localCache[fp] = struct{}{}
+		localCache[key] = struct{}{}
 	}
 
 	return true
 }
 
-func (f *Firewall) addConn(fp firewall.Packet, incoming bool) {
+func (f *Firewall) addConn(key firewall.PacketKey, protocol uint8, incoming bool) {
 	var timeout time.Duration
 	c := &conn{}
 
-	switch fp.Protocol {
+	switch protocol {
 	case firewall.ProtoTCP:
 		timeout = f.TCPTimeout
 	case firewall.ProtoUDP:
@@ -586,9 +611,9 @@ func (f *Firewall) addConn(fp firewall.Packet, incoming bool) {
 
 	conntrack := f.Conntrack
 	conntrack.Lock()
-	if _, ok := conntrack.Conns[fp]; !ok {
+	if _, ok := conntrack.Conns[key]; !ok {
 		conntrack.TimerWheel.Advance(time.Now())
-		conntrack.TimerWheel.Add(fp, timeout)
+		conntrack.TimerWheel.Add(key, timeout)
 	}
 
 	// Record which rulesVersion allowed this connection, so we can retest after
@@ -596,16 +621,16 @@ func (f *Firewall) addConn(fp firewall.Packet, incoming bool) {
 	c.incoming = incoming
 	c.rulesVersion = f.rulesVersion
 	c.Expires = time.Now().Add(timeout)
-	conntrack.Conns[fp] = c
+	conntrack.Conns[key] = c
 	conntrack.Unlock()
 }
 
 // Evict checks if a conntrack entry has expired, if so it is removed, if not it is re-added to the wheel
 // Caller must own the connMutex lock!
-func (f *Firewall) evict(p firewall.Packet) {
+func (f *Firewall) evict(key firewall.PacketKey) {
 	// Are we still tracking this conn?
 	conntrack := f.Conntrack
-	t, ok := conntrack.Conns[p]
+	t, ok := conntrack.Conns[key]
 	if !ok {
 		return
 	}
@@ -615,12 +640,12 @@ func (f *Firewall) evict(p firewall.Packet) {
 	// Timeout is in the future, re-add the timer
 	if newT > 0 {
 		conntrack.TimerWheel.Advance(time.Now())
-		conntrack.TimerWheel.Add(p, newT)
+		conntrack.TimerWheel.Add(key, newT)
 		return
 	}
 
 	// This conn is done
-	delete(conntrack.Conns, p)
+	delete(conntrack.Conns, key)
 }
 
 func (ft *FirewallTable) match(p firewall.Packet, incoming bool, c *cert.CachedCertificate, caPool *cert.CAPool) bool {
@@ -935,7 +960,7 @@ type rule struct {
 	CASha     string
 }
 
-func convertRule(l *logrus.Logger, p any, table string, i int) (rule, error) {
+func convertRule(l *slog.Logger, p any, table string, i int) (rule, error) {
 	r := rule{}
 
 	m, ok := p.(map[string]any)
@@ -966,7 +991,10 @@ func convertRule(l *logrus.Logger, p any, table string, i int) (rule, error) {
 			return r, errors.New("group should contain a single value, an array with more than one entry was provided")
 		}
 
-		l.Warnf("%s rule #%v; group was an array with a single value, converting to simple value", table, i)
+		l.Warn("group was an array with a single value, converting to simple value",
+			"table", table,
+			"rule", i,
+		)
 		m["group"] = v[0]
 	}
 

firewall/cache.go

@@ -1,55 +1,67 @@
 package firewall
 
 import (
+	"context"
+	"log/slog"
 	"sync/atomic"
 	"time"
 
-	"github.com/sirupsen/logrus"
+	"github.com/slackhq/nebula/logging"
 )
 
 // ConntrackCache is used as a local routine cache to know if a given flow
-// has been seen in the conntrack table.
-type ConntrackCache map[Packet]struct{}
+// has been seen in the conntrack table. Keyed on PacketKey (dense form)
+// rather than Packet so the lookup hashes raw bytes instead of the
+// unique.Handle each netip.Addr in Packet carries.
+type ConntrackCache map[PacketKey]struct{}
 
 type ConntrackCacheTicker struct {
 	cacheV    uint64
 	cacheTick atomic.Uint64
 
+	l     *slog.Logger
 	cache ConntrackCache
 }
 
-func NewConntrackCacheTicker(d time.Duration) *ConntrackCacheTicker {
+func NewConntrackCacheTicker(ctx context.Context, l *slog.Logger, d time.Duration) *ConntrackCacheTicker {
 	if d == 0 {
 		return nil
 	}
 
 	c := &ConntrackCacheTicker{
+		l:     l,
 		cache: ConntrackCache{},
 	}
 
-	go c.tick(d)
+	go c.tick(ctx, d)
 
 	return c
 }
 
-func (c *ConntrackCacheTicker) tick(d time.Duration) {
+func (c *ConntrackCacheTicker) tick(ctx context.Context, d time.Duration) {
+	t := time.NewTicker(d)
+	defer t.Stop()
 	for {
-		time.Sleep(d)
-		c.cacheTick.Add(1)
+		select {
+		case <-ctx.Done():
+			return
+		case <-t.C:
+			c.cacheTick.Add(1)
+		}
 	}
 }
 
 // Get checks if the cache ticker has moved to the next version before returning
 // the map. If it has moved, we reset the map.
-func (c *ConntrackCacheTicker) Get(l *logrus.Logger) ConntrackCache {
+func (c *ConntrackCacheTicker) Get() ConntrackCache {
 	if c == nil {
 		return nil
 	}
 	if tick := c.cacheTick.Load(); tick != c.cacheV {
 		c.cacheV = tick
 		if ll := len(c.cache); ll > 0 {
-			if l.Level == logrus.DebugLevel {
-				l.WithField("len", ll).Debug("resetting conntrack cache")
+			if c.l.Enabled(context.Background(), logging.LevelTrace) {
+				c.l.Log(context.Background(), logging.LevelTrace, "resetting conntrack cache", "len", ll)
 			}
 			c.cache = make(ConntrackCache, ll)
 		}

firewall/cache_test.go

@@ -0,0 +1,70 @@
+package firewall
+
+import (
+	"bytes"
+	"log/slog"
+	"strings"
+	"testing"
+
+	"github.com/slackhq/nebula/logging"
+	"github.com/slackhq/nebula/test"
+	"github.com/stretchr/testify/assert"
+)
+
+// The tests below pin the log format produced by ConntrackCacheTicker.Get
+// so changes cannot silently break what operators are grepping for. The
+// ticker's internal state (cache + cacheTick) is poked directly to avoid
+// racing a goroutine-driven tick in tests.
+
+func newFixedTicker(t *testing.T, l *slog.Logger, cacheLen int) *ConntrackCacheTicker {
+	t.Helper()
+	c := &ConntrackCacheTicker{
+		l:     l,
+		cache: make(ConntrackCache, cacheLen),
+	}
+	for i := 0; i < cacheLen; i++ {
+		c.cache[PacketKey{LocalPort: uint16(i) + 1}] = struct{}{}
+	}
+	c.cacheTick.Store(1) // cacheV starts at 0, so Get() takes the reset path
+	return c
+}
+
+func TestConntrackCacheTicker_Get_TextFormat(t *testing.T) {
+	buf := &bytes.Buffer{}
+	l := test.NewLoggerWithOutputAndLevel(buf, logging.LevelTrace)
+
+	c := newFixedTicker(t, l, 3)
+	c.Get()
+
+	assert.Equal(t, "level=DEBUG-4 msg=\"resetting conntrack cache\" len=3\n", buf.String())
+}
+
+func TestConntrackCacheTicker_Get_JSONFormat(t *testing.T) {
+	buf := &bytes.Buffer{}
+	l := test.NewJSONLoggerWithOutput(buf, logging.LevelTrace)
+
+	c := newFixedTicker(t, l, 2)
+	c.Get()
+
+	assert.JSONEq(t, `{"level":"DEBUG-4","msg":"resetting conntrack cache","len":2}`, strings.TrimSpace(buf.String()))
+}
+
+func TestConntrackCacheTicker_Get_QuietBelowTrace(t *testing.T) {
+	buf := &bytes.Buffer{}
+	l := test.NewLoggerWithOutputAndLevel(buf, slog.LevelDebug)
+
+	c := newFixedTicker(t, l, 5)
+	c.Get()
+
+	assert.Empty(t, buf.String())
+}
+
+func TestConntrackCacheTicker_Get_QuietWhenCacheEmpty(t *testing.T) {
+	buf := &bytes.Buffer{}
+	l := test.NewLoggerWithOutputAndLevel(buf, logging.LevelTrace)
+
+	c := newFixedTicker(t, l, 0)
+	c.Get()
+
+	assert.Empty(t, buf.String())
+}

firewall/packet.go

@@ -19,6 +19,25 @@ const (
 	PortFragment = -1 // Special value for matching `port: fragment`
 )
 
+// PacketKey is the firewall's conntrack and ConntrackCache map key — the
+// dense form of the 5-tuple plus the protocol and fragment flag the
+// firewall actually discriminates flows on. Kept separate from Packet so
+// the conntrack-hit fast path doesn't pay for hashing the unique.Handle
+// each netip.Addr carries, and so the inbound parser can skip the
+// AddrFrom4/AddrFrom16 calls until rule matching actually needs them.
+//
+// Superset of the coalescer's flowKey shape (same 5-tuple, just in
+// Local/Remote orientation rather than wire src/dst).
+type PacketKey struct {
+	LocalAddr  [16]byte
+	RemoteAddr [16]byte
+	LocalPort  uint16
+	RemotePort uint16
+	IsV6       bool
+	Protocol   uint8
+	Fragment   bool
+}
+
 type Packet struct {
 	LocalAddr  netip.Addr
 	RemoteAddr netip.Addr
@@ -31,6 +50,61 @@ type Packet struct {
 	Fragment   bool
 }
 
+// Key derives a PacketKey from a populated Packet. Used by the few code
+// paths that have a Packet but no Key in hand (e.g. tests). Both inbound
+// and outbound production parsers write straight into a PacketKey via
+// batch.ParsePacket, so this function is rarely on the hot path.
+func (fp *Packet) Key() PacketKey {
+	k := PacketKey{
+		Protocol: fp.Protocol,
+		Fragment: fp.Fragment,
+	}
+	k.LocalPort = fp.LocalPort
+	k.RemotePort = fp.RemotePort
+	k.IsV6 = !fp.LocalAddr.Is4()
+	if k.IsV6 {
+		k.LocalAddr = fp.LocalAddr.As16()
+		k.RemoteAddr = fp.RemoteAddr.As16()
+	} else {
+		v4 := fp.LocalAddr.As4()
+		copy(k.LocalAddr[:4], v4[:])
+		v4 = fp.RemoteAddr.As4()
+		copy(k.RemoteAddr[:4], v4[:])
+	}
+	return k
+}
+
+// Hydrate fills fp's netip.Addr fields and copies the rest from k. Called
+// by the firewall slow path when conntrack misses and rule matching needs
+// the rich Packet form (CIDR lookups, family checks). The fast path skips
+// this entirely.
+func (k *PacketKey) Hydrate(fp *Packet) {
+	fp.LocalPort = k.LocalPort
+	fp.RemotePort = k.RemotePort
+	fp.Protocol = k.Protocol
+	fp.Fragment = k.Fragment
+	if k.IsV6 {
+		fp.LocalAddr = netip.AddrFrom16(k.LocalAddr)
+		fp.RemoteAddr = netip.AddrFrom16(k.RemoteAddr)
+	} else {
+		var v4 [4]byte
+		copy(v4[:], k.LocalAddr[:4])
+		fp.LocalAddr = netip.AddrFrom4(v4)
+		copy(v4[:], k.RemoteAddr[:4])
+		fp.RemoteAddr = netip.AddrFrom4(v4)
+	}
+}
+
+func (k *PacketKey) GetRemoteAddr() netip.Addr {
+	if k.IsV6 {
+		return netip.AddrFrom16(k.RemoteAddr)
+	} else {
+		var v4 [4]byte
+		copy(v4[:], k.RemoteAddr[:4])
+		return netip.AddrFrom4(v4)
+	}
+}
+
 func (fp *Packet) Copy() *Packet {
 	return &Packet{
 		LocalAddr:  fp.LocalAddr,

firewall_test.go

@@ -3,13 +3,13 @@ package nebula
 import (
 	"bytes"
 	"errors"
+	"log/slog"
 	"math"
 	"net/netip"
 	"testing"
 	"time"
 
 	"github.com/gaissmai/bart"
-	"github.com/sirupsen/logrus"
 	"github.com/slackhq/nebula/cert"
 	"github.com/slackhq/nebula/config"
 	"github.com/slackhq/nebula/firewall"
@@ -58,9 +58,8 @@ func TestNewFirewall(t *testing.T) {
 }
 
 func TestFirewall_AddRule(t *testing.T) {
-	l := test.NewLogger()
 	ob := &bytes.Buffer{}
-	l.SetOutput(ob)
+	l := test.NewLoggerWithOutput(ob)
 
 	c := &dummyCert{}
 	fw := NewFirewall(l, time.Second, time.Minute, time.Hour, c)
@@ -177,9 +176,8 @@ func TestFirewall_AddRule(t *testing.T) {
 }
 
 func TestFirewall_Drop(t *testing.T) {
-	l := test.NewLogger()
 	ob := &bytes.Buffer{}
-	l.SetOutput(ob)
+	l := test.NewLoggerWithOutput(ob)
 	myVpnNetworksTable := new(bart.Lite)
 	myVpnNetworksTable.Insert(netip.MustParsePrefix("1.1.1.1/8"))
 	p := firewall.Packet{
@@ -213,50 +211,49 @@ func TestFirewall_Drop(t *testing.T) {
 	cp := cert.NewCAPool()
 
 	// Drop outbound
-	assert.Equal(t, ErrNoMatchingRule, fw.Drop(p, false, &h, cp, nil))
+	assert.Equal(t, ErrNoMatchingRule, fw.Drop(p.Key(), &p, false, &h, cp, nil))
 	// Allow inbound
 	resetConntrack(fw)
-	require.NoError(t, fw.Drop(p, true, &h, cp, nil))
+	require.NoError(t, fw.Drop(p.Key(), &p, true, &h, cp, nil))
 	// Allow outbound because conntrack
-	require.NoError(t, fw.Drop(p, false, &h, cp, nil))
+	require.NoError(t, fw.Drop(p.Key(), &p, false, &h, cp, nil))
 
 	// test remote mismatch
 	oldRemote := p.RemoteAddr
 	p.RemoteAddr = netip.MustParseAddr("1.2.3.10")
-	assert.Equal(t, fw.Drop(p, false, &h, cp, nil), ErrInvalidRemoteIP)
+	assert.Equal(t, fw.Drop(p.Key(), &p, false, &h, cp, nil), ErrInvalidRemoteIP)
 	p.RemoteAddr = oldRemote
 
 	// ensure signer doesn't get in the way of group checks
 	fw = NewFirewall(l, time.Second, time.Minute, time.Hour, &c)
 	require.NoError(t, fw.AddRule(true, firewall.ProtoAny, 0, 0, []string{"nope"}, "", "", "", "", "signer-shasum"))
 	require.NoError(t, fw.AddRule(true, firewall.ProtoAny, 0, 0, []string{"default-group"}, "", "", "", "", "signer-shasum-bad"))
-	assert.Equal(t, fw.Drop(p, true, &h, cp, nil), ErrNoMatchingRule)
+	assert.Equal(t, fw.Drop(p.Key(), &p, true, &h, cp, nil), ErrNoMatchingRule)
 
 	// test caSha doesn't drop on match
 	fw = NewFirewall(l, time.Second, time.Minute, time.Hour, &c)
 	require.NoError(t, fw.AddRule(true, firewall.ProtoAny, 0, 0, []string{"nope"}, "", "", "", "", "signer-shasum-bad"))
 	require.NoError(t, fw.AddRule(true, firewall.ProtoAny, 0, 0, []string{"default-group"}, "", "", "", "", "signer-shasum"))
-	require.NoError(t, fw.Drop(p, true, &h, cp, nil))
+	require.NoError(t, fw.Drop(p.Key(), &p, true, &h, cp, nil))
 
 	// ensure ca name doesn't get in the way of group checks
 	cp.CAs["signer-shasum"] = &cert.CachedCertificate{Certificate: &dummyCert{name: "ca-good"}}
 	fw = NewFirewall(l, time.Second, time.Minute, time.Hour, &c)
 	require.NoError(t, fw.AddRule(true, firewall.ProtoAny, 0, 0, []string{"nope"}, "", "", "", "ca-good", ""))
 	require.NoError(t, fw.AddRule(true, firewall.ProtoAny, 0, 0, []string{"default-group"}, "", "", "", "ca-good-bad", ""))
-	assert.Equal(t, fw.Drop(p, true, &h, cp, nil), ErrNoMatchingRule)
+	assert.Equal(t, fw.Drop(p.Key(), &p, true, &h, cp, nil), ErrNoMatchingRule)
 
 	// test caName doesn't drop on match
 	cp.CAs["signer-shasum"] = &cert.CachedCertificate{Certificate: &dummyCert{name: "ca-good"}}
 	fw = NewFirewall(l, time.Second, time.Minute, time.Hour, &c)
 	require.NoError(t, fw.AddRule(true, firewall.ProtoAny, 0, 0, []string{"nope"}, "", "", "", "ca-good-bad", ""))
 	require.NoError(t, fw.AddRule(true, firewall.ProtoAny, 0, 0, []string{"default-group"}, "", "", "", "ca-good", ""))
-	require.NoError(t, fw.Drop(p, true, &h, cp, nil))
+	require.NoError(t, fw.Drop(p.Key(), &p, true, &h, cp, nil))
 }
 
 func TestFirewall_DropV6(t *testing.T) {
-	l := test.NewLogger()
 	ob := &bytes.Buffer{}
-	l.SetOutput(ob)
+	l := test.NewLoggerWithOutput(ob)
 
 	myVpnNetworksTable := new(bart.Lite)
 	myVpnNetworksTable.Insert(netip.MustParsePrefix("fd00::/7"))
@@ -292,44 +289,44 @@ func TestFirewall_DropV6(t *testing.T) {
 	cp := cert.NewCAPool()
 
 	// Drop outbound
-	assert.Equal(t, ErrNoMatchingRule, fw.Drop(p, false, &h, cp, nil))
+	assert.Equal(t, ErrNoMatchingRule, fw.Drop(p.Key(), &p, false, &h, cp, nil))
 	// Allow inbound
 	resetConntrack(fw)
-	require.NoError(t, fw.Drop(p, true, &h, cp, nil))
+	require.NoError(t, fw.Drop(p.Key(), &p, true, &h, cp, nil))
 	// Allow outbound because conntrack
-	require.NoError(t, fw.Drop(p, false, &h, cp, nil))
+	require.NoError(t, fw.Drop(p.Key(), &p, false, &h, cp, nil))
 
 	// test remote mismatch
 	oldRemote := p.RemoteAddr
 	p.RemoteAddr = netip.MustParseAddr("fd12::56")
-	assert.Equal(t, fw.Drop(p, false, &h, cp, nil), ErrInvalidRemoteIP)
+	assert.Equal(t, fw.Drop(p.Key(), &p, false, &h, cp, nil), ErrInvalidRemoteIP)
 	p.RemoteAddr = oldRemote
 
 	// ensure signer doesn't get in the way of group checks
 	fw = NewFirewall(l, time.Second, time.Minute, time.Hour, &c)
 	require.NoError(t, fw.AddRule(true, firewall.ProtoAny, 0, 0, []string{"nope"}, "", "", "", "", "signer-shasum"))
 	require.NoError(t, fw.AddRule(true, firewall.ProtoAny, 0, 0, []string{"default-group"}, "", "", "", "", "signer-shasum-bad"))
-	assert.Equal(t, fw.Drop(p, true, &h, cp, nil), ErrNoMatchingRule)
+	assert.Equal(t, fw.Drop(p.Key(), &p, true, &h, cp, nil), ErrNoMatchingRule)
 
 	// test caSha doesn't drop on match
 	fw = NewFirewall(l, time.Second, time.Minute, time.Hour, &c)
 	require.NoError(t, fw.AddRule(true, firewall.ProtoAny, 0, 0, []string{"nope"}, "", "", "", "", "signer-shasum-bad"))
 	require.NoError(t, fw.AddRule(true, firewall.ProtoAny, 0, 0, []string{"default-group"}, "", "", "", "", "signer-shasum"))
-	require.NoError(t, fw.Drop(p, true, &h, cp, nil))
+	require.NoError(t, fw.Drop(p.Key(), &p, true, &h, cp, nil))
 
 	// ensure ca name doesn't get in the way of group checks
 	cp.CAs["signer-shasum"] = &cert.CachedCertificate{Certificate: &dummyCert{name: "ca-good"}}
 	fw = NewFirewall(l, time.Second, time.Minute, time.Hour, &c)
 	require.NoError(t, fw.AddRule(true, firewall.ProtoAny, 0, 0, []string{"nope"}, "", "", "", "ca-good", ""))
 	require.NoError(t, fw.AddRule(true, firewall.ProtoAny, 0, 0, []string{"default-group"}, "", "", "", "ca-good-bad", ""))
-	assert.Equal(t, fw.Drop(p, true, &h, cp, nil), ErrNoMatchingRule)
+	assert.Equal(t, fw.Drop(p.Key(), &p, true, &h, cp, nil), ErrNoMatchingRule)
 
 	// test caName doesn't drop on match
 	cp.CAs["signer-shasum"] = &cert.CachedCertificate{Certificate: &dummyCert{name: "ca-good"}}
 	fw = NewFirewall(l, time.Second, time.Minute, time.Hour, &c)
 	require.NoError(t, fw.AddRule(true, firewall.ProtoAny, 0, 0, []string{"nope"}, "", "", "", "ca-good-bad", ""))
 	require.NoError(t, fw.AddRule(true, firewall.ProtoAny, 0, 0, []string{"default-group"}, "", "", "", "ca-good", ""))
-	require.NoError(t, fw.Drop(p, true, &h, cp, nil))
+	require.NoError(t, fw.Drop(p.Key(), &p, true, &h, cp, nil))
 }
 
 func BenchmarkFirewallTable_match(b *testing.B) {
@@ -485,9 +482,8 @@ func BenchmarkFirewallTable_match(b *testing.B) {
 }
 
 func TestFirewall_Drop2(t *testing.T) {
-	l := test.NewLogger()
 	ob := &bytes.Buffer{}
-	l.SetOutput(ob)
+	l := test.NewLoggerWithOutput(ob)
 	myVpnNetworksTable := new(bart.Lite)
 	myVpnNetworksTable.Insert(netip.MustParsePrefix("1.1.1.1/8"))
 
@@ -537,16 +533,15 @@ func TestFirewall_Drop2(t *testing.T) {
 	cp := cert.NewCAPool()
 
 	// h1/c1 lacks the proper groups
-	require.ErrorIs(t, fw.Drop(p, true, &h1, cp, nil), ErrNoMatchingRule)
+	require.ErrorIs(t, fw.Drop(p.Key(), &p, true, &h1, cp, nil), ErrNoMatchingRule)
 	// c has the proper groups
 	resetConntrack(fw)
-	require.NoError(t, fw.Drop(p, true, &h, cp, nil))
+	require.NoError(t, fw.Drop(p.Key(), &p, true, &h, cp, nil))
 }
 
 func TestFirewall_Drop3(t *testing.T) {
-	l := test.NewLogger()
 	ob := &bytes.Buffer{}
-	l.SetOutput(ob)
+	l := test.NewLoggerWithOutput(ob)
 	myVpnNetworksTable := new(bart.Lite)
 	myVpnNetworksTable.Insert(netip.MustParsePrefix("1.1.1.1/8"))
 
@@ -618,24 +613,23 @@ func TestFirewall_Drop3(t *testing.T) {
 	cp := cert.NewCAPool()
 
 	// c1 should pass because host match
-	require.NoError(t, fw.Drop(p, true, &h1, cp, nil))
+	require.NoError(t, fw.Drop(p.Key(), &p, true, &h1, cp, nil))
 	// c2 should pass because ca sha match
 	resetConntrack(fw)
-	require.NoError(t, fw.Drop(p, true, &h2, cp, nil))
+	require.NoError(t, fw.Drop(p.Key(), &p, true, &h2, cp, nil))
 	// c3 should fail because no match
 	resetConntrack(fw)
-	assert.Equal(t, fw.Drop(p, true, &h3, cp, nil), ErrNoMatchingRule)
+	assert.Equal(t, fw.Drop(p.Key(), &p, true, &h3, cp, nil), ErrNoMatchingRule)
 
 	// Test a remote address match
 	fw = NewFirewall(l, time.Second, time.Minute, time.Hour, c.Certificate)
 	require.NoError(t, fw.AddRule(true, firewall.ProtoAny, 1, 1, []string{}, "", "1.2.3.4/24", "", "", ""))
-	require.NoError(t, fw.Drop(p, true, &h1, cp, nil))
+	require.NoError(t, fw.Drop(p.Key(), &p, true, &h1, cp, nil))
 }
 
 func TestFirewall_Drop3V6(t *testing.T) {
-	l := test.NewLogger()
 	ob := &bytes.Buffer{}
-	l.SetOutput(ob)
+	l := test.NewLoggerWithOutput(ob)
 	myVpnNetworksTable := new(bart.Lite)
 	myVpnNetworksTable.Insert(netip.MustParsePrefix("fd00::/7"))
 
@@ -667,13 +661,12 @@ func TestFirewall_Drop3V6(t *testing.T) {
 	fw := NewFirewall(l, time.Second, time.Minute, time.Hour, c.Certificate)
 	cp := cert.NewCAPool()
 	require.NoError(t, fw.AddRule(true, firewall.ProtoAny, 1, 1, []string{}, "", "fd12::34/120", "", "", ""))
-	require.NoError(t, fw.Drop(p, true, &h, cp, nil))
+	require.NoError(t, fw.Drop(p.Key(), &p, true, &h, cp, nil))
 }
 
 func TestFirewall_DropConntrackReload(t *testing.T) {
-	l := test.NewLogger()
 	ob := &bytes.Buffer{}
-	l.SetOutput(ob)
+	l := test.NewLoggerWithOutput(ob)
 	myVpnNetworksTable := new(bart.Lite)
 	myVpnNetworksTable.Insert(netip.MustParsePrefix("1.1.1.1/8"))
 
@@ -709,12 +702,12 @@ func TestFirewall_DropConntrackReload(t *testing.T) {
 	cp := cert.NewCAPool()
 
 	// Drop outbound
-	assert.Equal(t, fw.Drop(p, false, &h, cp, nil), ErrNoMatchingRule)
+	assert.Equal(t, fw.Drop(p.Key(), &p, false, &h, cp, nil), ErrNoMatchingRule)
 	// Allow inbound
 	resetConntrack(fw)
-	require.NoError(t, fw.Drop(p, true, &h, cp, nil))
+	require.NoError(t, fw.Drop(p.Key(), &p, true, &h, cp, nil))
 	// Allow outbound because conntrack
-	require.NoError(t, fw.Drop(p, false, &h, cp, nil))
+	require.NoError(t, fw.Drop(p.Key(), &p, false, &h, cp, nil))
 
 	oldFw := fw
 	fw = NewFirewall(l, time.Second, time.Minute, time.Hour, c.Certificate)
@@ -723,7 +716,7 @@ func TestFirewall_DropConntrackReload(t *testing.T) {
 	fw.rulesVersion = oldFw.rulesVersion + 1
 
 	// Allow outbound because conntrack and new rules allow port 10
-	require.NoError(t, fw.Drop(p, false, &h, cp, nil))
+	require.NoError(t, fw.Drop(p.Key(), &p, false, &h, cp, nil))
 
 	oldFw = fw
 	fw = NewFirewall(l, time.Second, time.Minute, time.Hour, c.Certificate)
@@ -732,13 +725,12 @@ func TestFirewall_DropConntrackReload(t *testing.T) {
 	fw.rulesVersion = oldFw.rulesVersion + 1
 
 	// Drop outbound because conntrack doesn't match new ruleset
-	assert.Equal(t, fw.Drop(p, false, &h, cp, nil), ErrNoMatchingRule)
+	assert.Equal(t, fw.Drop(p.Key(), &p, false, &h, cp, nil), ErrNoMatchingRule)
 }
 
 func TestFirewall_ICMPPortBehavior(t *testing.T) {
-	l := test.NewLogger()
 	ob := &bytes.Buffer{}
-	l.SetOutput(ob)
+	l := test.NewLoggerWithOutput(ob)
 	myVpnNetworksTable := new(bart.Lite)
 	myVpnNetworksTable.Insert(netip.MustParsePrefix("1.1.1.1/8"))
 
@@ -778,12 +770,12 @@ func TestFirewall_ICMPPortBehavior(t *testing.T) {
 			p.LocalPort = 0
 			p.RemotePort = 0
 			// Drop outbound
-			assert.Equal(t, fw.Drop(*p, false, &h, cp, nil), ErrNoMatchingRule)
+			assert.Equal(t, fw.Drop(p.Key(), p, false, &h, cp, nil), ErrNoMatchingRule)
 			// Allow inbound
 			resetConntrack(fw)
-			require.NoError(t, fw.Drop(*p, true, &h, cp, nil))
+			require.NoError(t, fw.Drop(p.Key(), p, true, &h, cp, nil))
 			//now also allow outbound
-			require.NoError(t, fw.Drop(*p, false, &h, cp, nil))
+			require.NoError(t, fw.Drop(p.Key(), p, false, &h, cp, nil))
 		})
 
 		t.Run("nonzero ports", func(t *testing.T) {
@@ -791,12 +783,12 @@ func TestFirewall_ICMPPortBehavior(t *testing.T) {
 			p.LocalPort = 0xabcd
 			p.RemotePort = 0x1234
 			// Drop outbound
-			assert.Equal(t, fw.Drop(*p, false, &h, cp, nil), ErrNoMatchingRule)
+			assert.Equal(t, fw.Drop(p.Key(), p, false, &h, cp, nil), ErrNoMatchingRule)
 			// Allow inbound
 			resetConntrack(fw)
-			require.NoError(t, fw.Drop(*p, true, &h, cp, nil))
+			require.NoError(t, fw.Drop(p.Key(), p, true, &h, cp, nil))
 			//now also allow outbound
-			require.NoError(t, fw.Drop(*p, false, &h, cp, nil))
+			require.NoError(t, fw.Drop(p.Key(), p, false, &h, cp, nil))
 		})
 	})
 
@@ -808,12 +800,12 @@ func TestFirewall_ICMPPortBehavior(t *testing.T) {
 			p.LocalPort = 0
 			p.RemotePort = 0
 			// Drop outbound
-			assert.Equal(t, fw.Drop(*p, false, &h, cp, nil), ErrNoMatchingRule)
+			assert.Equal(t, fw.Drop(p.Key(), p, false, &h, cp, nil), ErrNoMatchingRule)
 			// Allow inbound
 			resetConntrack(fw)
-			assert.Equal(t, fw.Drop(*p, true, &h, cp, nil), ErrNoMatchingRule)
+			assert.Equal(t, fw.Drop(p.Key(), p, true, &h, cp, nil), ErrNoMatchingRule)
 			//now also allow outbound
-			assert.Equal(t, fw.Drop(*p, false, &h, cp, nil), ErrNoMatchingRule)
+			assert.Equal(t, fw.Drop(p.Key(), p, false, &h, cp, nil), ErrNoMatchingRule)
 		})
 
 		t.Run("nonzero ports, still blocked", func(t *testing.T) {
@@ -821,12 +813,12 @@ func TestFirewall_ICMPPortBehavior(t *testing.T) {
 			p.LocalPort = 0xabcd
 			p.RemotePort = 0x1234
 			// Drop outbound
-			assert.Equal(t, fw.Drop(*p, false, &h, cp, nil), ErrNoMatchingRule)
+			assert.Equal(t, fw.Drop(p.Key(), p, false, &h, cp, nil), ErrNoMatchingRule)
 			// Allow inbound
 			resetConntrack(fw)
-			assert.Equal(t, fw.Drop(*p, true, &h, cp, nil), ErrNoMatchingRule)
+			assert.Equal(t, fw.Drop(p.Key(), p, true, &h, cp, nil), ErrNoMatchingRule)
 			//now also allow outbound
-			assert.Equal(t, fw.Drop(*p, false, &h, cp, nil), ErrNoMatchingRule)
+			assert.Equal(t, fw.Drop(p.Key(), p, false, &h, cp, nil), ErrNoMatchingRule)
 		})
 
 		t.Run("nonzero, matching ports, still blocked", func(t *testing.T) {
@@ -834,12 +826,12 @@ func TestFirewall_ICMPPortBehavior(t *testing.T) {
 			p.LocalPort = 80
 			p.RemotePort = 80
 			// Drop outbound
-			assert.Equal(t, fw.Drop(*p, false, &h, cp, nil), ErrNoMatchingRule)
+			assert.Equal(t, fw.Drop(p.Key(), p, false, &h, cp, nil), ErrNoMatchingRule)
 			// Allow inbound
 			resetConntrack(fw)
-			assert.Equal(t, fw.Drop(*p, true, &h, cp, nil), ErrNoMatchingRule)
+			assert.Equal(t, fw.Drop(p.Key(), p, true, &h, cp, nil), ErrNoMatchingRule)
 			//now also allow outbound
-			assert.Equal(t, fw.Drop(*p, false, &h, cp, nil), ErrNoMatchingRule)
+			assert.Equal(t, fw.Drop(p.Key(), p, false, &h, cp, nil), ErrNoMatchingRule)
 		})
 	})
 	t.Run("Any proto, any port", func(t *testing.T) {
@@ -851,12 +843,12 @@ func TestFirewall_ICMPPortBehavior(t *testing.T) {
 			p.LocalPort = 0
 			p.RemotePort = 0
 			// Drop outbound
-			assert.Equal(t, fw.Drop(*p, false, &h, cp, nil), ErrNoMatchingRule)
+			assert.Equal(t, fw.Drop(p.Key(), p, false, &h, cp, nil), ErrNoMatchingRule)
 			// Allow inbound
 			resetConntrack(fw)
-			require.NoError(t, fw.Drop(*p, true, &h, cp, nil))
+			require.NoError(t, fw.Drop(p.Key(), p, true, &h, cp, nil))
 			//now also allow outbound
-			require.NoError(t, fw.Drop(*p, false, &h, cp, nil))
+			require.NoError(t, fw.Drop(p.Key(), p, false, &h, cp, nil))
 		})
 
 		t.Run("nonzero ports, allowed", func(t *testing.T) {
@@ -865,24 +857,23 @@ func TestFirewall_ICMPPortBehavior(t *testing.T) {
 			p.LocalPort = 0xabcd
 			p.RemotePort = 0x1234
 			// Drop outbound
-			assert.Equal(t, fw.Drop(*p, false, &h, cp, nil), ErrNoMatchingRule)
+			assert.Equal(t, fw.Drop(p.Key(), p, false, &h, cp, nil), ErrNoMatchingRule)
 			// Allow inbound
 			resetConntrack(fw)
-			require.NoError(t, fw.Drop(*p, true, &h, cp, nil))
+			require.NoError(t, fw.Drop(p.Key(), p, true, &h, cp, nil))
 			//now also allow outbound
-			require.NoError(t, fw.Drop(*p, false, &h, cp, nil))
+			require.NoError(t, fw.Drop(p.Key(), p, false, &h, cp, nil))
 			//different ID is blocked
 			p.RemotePort++
-			require.Equal(t, fw.Drop(*p, false, &h, cp, nil), ErrNoMatchingRule)
+			require.Equal(t, fw.Drop(p.Key(), p, false, &h, cp, nil), ErrNoMatchingRule)
 		})
 	})
 
 }
 
 func TestFirewall_DropIPSpoofing(t *testing.T) {
-	l := test.NewLogger()
 	ob := &bytes.Buffer{}
-	l.SetOutput(ob)
+	l := test.NewLoggerWithOutput(ob)
 	myVpnNetworksTable := new(bart.Lite)
 	myVpnNetworksTable.Insert(netip.MustParsePrefix("192.0.2.1/24"))
 
@@ -922,7 +913,7 @@ func TestFirewall_DropIPSpoofing(t *testing.T) {
 		Protocol:   firewall.ProtoUDP,
 		Fragment:   false,
 	}
-	assert.Equal(t, fw.Drop(p, true, &h1, cp, nil), ErrInvalidRemoteIP)
+	assert.Equal(t, fw.Drop(p.Key(), &p, true, &h1, cp, nil), ErrInvalidRemoteIP)
 }
 
 func BenchmarkLookup(b *testing.B) {
@@ -1042,28 +1033,28 @@ func TestNewFirewallFromConfig(t *testing.T) {
 	l := test.NewLogger()
 	// Test a bad rule definition
 	c := &dummyCert{}
-	cs, err := newCertState(cert.Version2, nil, c, false, cert.Curve_CURVE25519, nil)
+	cs, err := newCertState(cert.Version2, nil, c, false, cert.Curve_CURVE25519, nil, "aes")
 	require.NoError(t, err)
 
-	conf := config.NewC(l)
+	conf := config.NewC(test.NewLogger())
 	conf.Settings["firewall"] = map[string]any{"outbound": "asdf"}
 	_, err = NewFirewallFromConfig(l, cs, conf)
 	require.EqualError(t, err, "firewall.outbound failed to parse, should be an array of rules")
 
 	// Test both port and code
-	conf = config.NewC(l)
+	conf = config.NewC(test.NewLogger())
 	conf.Settings["firewall"] = map[string]any{"outbound": []any{map[string]any{"port": "1", "code": "2"}}}
 	_, err = NewFirewallFromConfig(l, cs, conf)
 	require.EqualError(t, err, "firewall.outbound rule #0; only one of port or code should be provided")
 
 	// Test missing host, group, cidr, ca_name and ca_sha
-	conf = config.NewC(l)
+	conf = config.NewC(test.NewLogger())
 	conf.Settings["firewall"] = map[string]any{"outbound": []any{map[string]any{}}}
 	_, err = NewFirewallFromConfig(l, cs, conf)
 	require.EqualError(t, err, "firewall.outbound rule #0; at least one of host, group, cidr, local_cidr, ca_name, or ca_sha must be provided")
 
 	// Test code/port error
-	conf = config.NewC(l)
+	conf = config.NewC(test.NewLogger())
 	conf.Settings["firewall"] = map[string]any{"outbound": []any{map[string]any{"code": "a", "host": "testh", "proto": "any"}}}
 	_, err = NewFirewallFromConfig(l, cs, conf)
 	require.EqualError(t, err, "firewall.outbound rule #0; code was not a number; `a`")
@@ -1073,25 +1064,25 @@ func TestNewFirewallFromConfig(t *testing.T) {
 	require.EqualError(t, err, "firewall.outbound rule #0; port was not a number; `a`")
 
 	// Test proto error
-	conf = config.NewC(l)
+	conf = config.NewC(test.NewLogger())
 	conf.Settings["firewall"] = map[string]any{"outbound": []any{map[string]any{"code": "1", "host": "testh"}}}
 	_, err = NewFirewallFromConfig(l, cs, conf)
 	require.EqualError(t, err, "firewall.outbound rule #0; proto was not understood; ``")
 
 	// Test cidr parse error
-	conf = config.NewC(l)
+	conf = config.NewC(test.NewLogger())
 	conf.Settings["firewall"] = map[string]any{"outbound": []any{map[string]any{"code": "1", "cidr": "testh", "proto": "any"}}}
 	_, err = NewFirewallFromConfig(l, cs, conf)
 	require.EqualError(t, err, "firewall.outbound rule #0; cidr did not parse; netip.ParsePrefix(\"testh\"): no '/'")
 
 	// Test local_cidr parse error
-	conf = config.NewC(l)
+	conf = config.NewC(test.NewLogger())
 	conf.Settings["firewall"] = map[string]any{"outbound": []any{map[string]any{"code": "1", "local_cidr": "testh", "proto": "any"}}}
 	_, err = NewFirewallFromConfig(l, cs, conf)
 	require.EqualError(t, err, "firewall.outbound rule #0; local_cidr did not parse; netip.ParsePrefix(\"testh\"): no '/'")
 
 	// Test both group and groups
-	conf = config.NewC(l)
+	conf = config.NewC(test.NewLogger())
 	conf.Settings["firewall"] = map[string]any{"inbound": []any{map[string]any{"port": "1", "proto": "any", "group": "a", "groups": []string{"b", "c"}}}}
 	_, err = NewFirewallFromConfig(l, cs, conf)
 	require.EqualError(t, err, "firewall.inbound rule #0; only one of group or groups should be defined, both provided")
@@ -1100,35 +1091,35 @@ func TestNewFirewallFromConfig(t *testing.T) {
 func TestAddFirewallRulesFromConfig(t *testing.T) {
 	l := test.NewLogger()
 	// Test adding tcp rule
-	conf := config.NewC(l)
+	conf := config.NewC(test.NewLogger())
 	mf := &mockFirewall{}
 	conf.Settings["firewall"] = map[string]any{"outbound": []any{map[string]any{"port": "1", "proto": "tcp", "host": "a"}}}
 	require.NoError(t, AddFirewallRulesFromConfig(l, false, conf, mf))
 	assert.Equal(t, addRuleCall{incoming: false, proto: firewall.ProtoTCP, startPort: 1, endPort: 1, groups: nil, host: "a", ip: "", localIp: ""}, mf.lastCall)
 
 	// Test adding udp rule
-	conf = config.NewC(l)
+	conf = config.NewC(test.NewLogger())
 	mf = &mockFirewall{}
 	conf.Settings["firewall"] = map[string]any{"outbound": []any{map[string]any{"port": "1", "proto": "udp", "host": "a"}}}
 	require.NoError(t, AddFirewallRulesFromConfig(l, false, conf, mf))
 	assert.Equal(t, addRuleCall{incoming: false, proto: firewall.ProtoUDP, startPort: 1, endPort: 1, groups: nil, host: "a", ip: "", localIp: ""}, mf.lastCall)
 
 	// Test adding icmp rule
-	conf = config.NewC(l)
+	conf = config.NewC(test.NewLogger())
 	mf = &mockFirewall{}
 	conf.Settings["firewall"] = map[string]any{"outbound": []any{map[string]any{"port": "1", "proto": "icmp", "host": "a"}}}
 	require.NoError(t, AddFirewallRulesFromConfig(l, false, conf, mf))
 	assert.Equal(t, addRuleCall{incoming: false, proto: firewall.ProtoICMP, startPort: firewall.PortAny, endPort: firewall.PortAny, groups: nil, host: "a", ip: "", localIp: ""}, mf.lastCall)
 
 	// Test adding icmp rule no port
-	conf = config.NewC(l)
+	conf = config.NewC(test.NewLogger())
 	mf = &mockFirewall{}
 	conf.Settings["firewall"] = map[string]any{"outbound": []any{map[string]any{"proto": "icmp", "host": "a"}}}
 	require.NoError(t, AddFirewallRulesFromConfig(l, false, conf, mf))
 	assert.Equal(t, addRuleCall{incoming: false, proto: firewall.ProtoICMP, startPort: firewall.PortAny, endPort: firewall.PortAny, groups: nil, host: "a", ip: "", localIp: ""}, mf.lastCall)
 
 	// Test adding any rule
-	conf = config.NewC(l)
+	conf = config.NewC(test.NewLogger())
 	mf = &mockFirewall{}
 	conf.Settings["firewall"] = map[string]any{"inbound": []any{map[string]any{"port": "1", "proto": "any", "host": "a"}}}
 	require.NoError(t, AddFirewallRulesFromConfig(l, true, conf, mf))
@@ -1136,14 +1127,14 @@ func TestAddFirewallRulesFromConfig(t *testing.T) {
 
 	// Test adding rule with cidr
 	cidr := netip.MustParsePrefix("10.0.0.0/8")
-	conf = config.NewC(l)
+	conf = config.NewC(test.NewLogger())
 	mf = &mockFirewall{}
 	conf.Settings["firewall"] = map[string]any{"inbound": []any{map[string]any{"port": "1", "proto": "any", "cidr": cidr.String()}}}
 	require.NoError(t, AddFirewallRulesFromConfig(l, true, conf, mf))
 	assert.Equal(t, addRuleCall{incoming: true, proto: firewall.ProtoAny, startPort: 1, endPort: 1, groups: nil, ip: cidr.String(), localIp: ""}, mf.lastCall)
 
 	// Test adding rule with local_cidr
-	conf = config.NewC(l)
+	conf = config.NewC(test.NewLogger())
 	mf = &mockFirewall{}
 	conf.Settings["firewall"] = map[string]any{"inbound": []any{map[string]any{"port": "1", "proto": "any", "local_cidr": cidr.String()}}}
 	require.NoError(t, AddFirewallRulesFromConfig(l, true, conf, mf))
@@ -1151,82 +1142,82 @@ func TestAddFirewallRulesFromConfig(t *testing.T) {
 
 	// Test adding rule with cidr ipv6
 	cidr6 := netip.MustParsePrefix("fd00::/8")
-	conf = config.NewC(l)
+	conf = config.NewC(test.NewLogger())
 	mf = &mockFirewall{}
 	conf.Settings["firewall"] = map[string]any{"inbound": []any{map[string]any{"port": "1", "proto": "any", "cidr": cidr6.String()}}}
 	require.NoError(t, AddFirewallRulesFromConfig(l, true, conf, mf))
 	assert.Equal(t, addRuleCall{incoming: true, proto: firewall.ProtoAny, startPort: 1, endPort: 1, groups: nil, ip: cidr6.String(), localIp: ""}, mf.lastCall)
 
 	// Test adding rule with any cidr
-	conf = config.NewC(l)
+	conf = config.NewC(test.NewLogger())
 	mf = &mockFirewall{}
 	conf.Settings["firewall"] = map[string]any{"inbound": []any{map[string]any{"port": "1", "proto": "any", "cidr": "any"}}}
 	require.NoError(t, AddFirewallRulesFromConfig(l, true, conf, mf))
 	assert.Equal(t, addRuleCall{incoming: true, proto: firewall.ProtoAny, startPort: 1, endPort: 1, groups: nil, ip: "any", localIp: ""}, mf.lastCall)
 
 	// Test adding rule with junk cidr
-	conf = config.NewC(l)
+	conf = config.NewC(test.NewLogger())
 	mf = &mockFirewall{}
 	conf.Settings["firewall"] = map[string]any{"inbound": []any{map[string]any{"port": "1", "proto": "any", "cidr": "junk/junk"}}}
 	require.EqualError(t, AddFirewallRulesFromConfig(l, true, conf, mf), "firewall.inbound rule #0; cidr did not parse; netip.ParsePrefix(\"junk/junk\"): ParseAddr(\"junk\"): unable to parse IP")
 
 	// Test adding rule with local_cidr ipv6
-	conf = config.NewC(l)
+	conf = config.NewC(test.NewLogger())
 	mf = &mockFirewall{}
 	conf.Settings["firewall"] = map[string]any{"inbound": []any{map[string]any{"port": "1", "proto": "any", "local_cidr": cidr6.String()}}}
 	require.NoError(t, AddFirewallRulesFromConfig(l, true, conf, mf))
 	assert.Equal(t, addRuleCall{incoming: true, proto: firewall.ProtoAny, startPort: 1, endPort: 1, groups: nil, ip: "", localIp: cidr6.String()}, mf.lastCall)
 
 	// Test adding rule with any local_cidr
-	conf = config.NewC(l)
+	conf = config.NewC(test.NewLogger())
 	mf = &mockFirewall{}
 	conf.Settings["firewall"] = map[string]any{"inbound": []any{map[string]any{"port": "1", "proto": "any", "local_cidr": "any"}}}
 	require.NoError(t, AddFirewallRulesFromConfig(l, true, conf, mf))
 	assert.Equal(t, addRuleCall{incoming: true, proto: firewall.ProtoAny, startPort: 1, endPort: 1, groups: nil, localIp: "any"}, mf.lastCall)
 
 	// Test adding rule with junk local_cidr
-	conf = config.NewC(l)
+	conf = config.NewC(test.NewLogger())
 	mf = &mockFirewall{}
 	conf.Settings["firewall"] = map[string]any{"inbound": []any{map[string]any{"port": "1", "proto": "any", "local_cidr": "junk/junk"}}}
 	require.EqualError(t, AddFirewallRulesFromConfig(l, true, conf, mf), "firewall.inbound rule #0; local_cidr did not parse; netip.ParsePrefix(\"junk/junk\"): ParseAddr(\"junk\"): unable to parse IP")
 
 	// Test adding rule with ca_sha
-	conf = config.NewC(l)
+	conf = config.NewC(test.NewLogger())
 	mf = &mockFirewall{}
 	conf.Settings["firewall"] = map[string]any{"inbound": []any{map[string]any{"port": "1", "proto": "any", "ca_sha": "12312313123"}}}
 	require.NoError(t, AddFirewallRulesFromConfig(l, true, conf, mf))
 	assert.Equal(t, addRuleCall{incoming: true, proto: firewall.ProtoAny, startPort: 1, endPort: 1, groups: nil, ip: "", localIp: "", caSha: "12312313123"}, mf.lastCall)
 
 	// Test adding rule with ca_name
-	conf = config.NewC(l)
+	conf = config.NewC(test.NewLogger())
 	mf = &mockFirewall{}
 	conf.Settings["firewall"] = map[string]any{"inbound": []any{map[string]any{"port": "1", "proto": "any", "ca_name": "root01"}}}
 	require.NoError(t, AddFirewallRulesFromConfig(l, true, conf, mf))
 	assert.Equal(t, addRuleCall{incoming: true, proto: firewall.ProtoAny, startPort: 1, endPort: 1, groups: nil, ip: "", localIp: "", caName: "root01"}, mf.lastCall)
 
 	// Test single group
-	conf = config.NewC(l)
+	conf = config.NewC(test.NewLogger())
 	mf = &mockFirewall{}
 	conf.Settings["firewall"] = map[string]any{"inbound": []any{map[string]any{"port": "1", "proto": "any", "group": "a"}}}
 	require.NoError(t, AddFirewallRulesFromConfig(l, true, conf, mf))
 	assert.Equal(t, addRuleCall{incoming: true, proto: firewall.ProtoAny, startPort: 1, endPort: 1, groups: []string{"a"}, ip: "", localIp: ""}, mf.lastCall)
 
 	// Test single groups
-	conf = config.NewC(l)
+	conf = config.NewC(test.NewLogger())
 	mf = &mockFirewall{}
 	conf.Settings["firewall"] = map[string]any{"inbound": []any{map[string]any{"port": "1", "proto": "any", "groups": "a"}}}
 	require.NoError(t, AddFirewallRulesFromConfig(l, true, conf, mf))
 	assert.Equal(t, addRuleCall{incoming: true, proto: firewall.ProtoAny, startPort: 1, endPort: 1, groups: []string{"a"}, ip: "", localIp: ""}, mf.lastCall)
 
 	// Test multiple AND groups
-	conf = config.NewC(l)
+	conf = config.NewC(test.NewLogger())
 	mf = &mockFirewall{}
 	conf.Settings["firewall"] = map[string]any{"inbound": []any{map[string]any{"port": "1", "proto": "any", "groups": []string{"a", "b"}}}}
 	require.NoError(t, AddFirewallRulesFromConfig(l, true, conf, mf))
 	assert.Equal(t, addRuleCall{incoming: true, proto: firewall.ProtoAny, startPort: 1, endPort: 1, groups: []string{"a", "b"}, ip: "", localIp: ""}, mf.lastCall)
 
 	// Test Add error
-	conf = config.NewC(l)
+	conf = config.NewC(test.NewLogger())
 	mf = &mockFirewall{}
 	mf.nextCallReturn = errors.New("test error")
 	conf.Settings["firewall"] = map[string]any{"inbound": []any{map[string]any{"port": "1", "proto": "any", "host": "a"}}}
@@ -1234,9 +1225,8 @@ func TestAddFirewallRulesFromConfig(t *testing.T) {
 }
 
 func TestFirewall_convertRule(t *testing.T) {
-	l := test.NewLogger()
 	ob := &bytes.Buffer{}
-	l.SetOutput(ob)
+	l := test.NewLoggerWithOutput(ob)
 
 	// Ensure group array of 1 is converted and a warning is printed
 	c := map[string]any{
@@ -1244,7 +1234,9 @@ func TestFirewall_convertRule(t *testing.T) {
 	}
 
 	r, err := convertRule(l, c, "test", 1)
-	assert.Contains(t, ob.String(), "test rule #1; group was an array with a single value, converting to simple value")
+	assert.Contains(t, ob.String(), "group was an array with a single value, converting to simple value")
+	assert.Contains(t, ob.String(), "table=test")
+	assert.Contains(t, ob.String(), "rule=1")
 	require.NoError(t, err)
 	assert.Equal(t, []string{"group1"}, r.Groups)
 
@@ -1270,9 +1262,8 @@ func TestFirewall_convertRule(t *testing.T) {
 }
 
 func TestFirewall_convertRuleSanity(t *testing.T) {
-	l := test.NewLogger()
 	ob := &bytes.Buffer{}
-	l.SetOutput(ob)
+	l := test.NewLoggerWithOutput(ob)
 
 	noWarningPlease := []map[string]any{
 		{"group": "group1"},
@@ -1336,7 +1327,7 @@ func (c *testcase) Test(t *testing.T, fw *Firewall) {
 	t.Helper()
 	cp := cert.NewCAPool()
 	resetConntrack(fw)
-	err := fw.Drop(c.p, true, c.h, cp, nil)
+	err := fw.Drop(c.p.Key(), &c.p, true, c.h, cp, nil)
 	if c.err == nil {
 		require.NoError(t, err, "failed to not drop remote address %s", c.p.RemoteAddr)
 	} else {
@@ -1386,7 +1377,7 @@ type testsetup struct {
 	fw                 *Firewall
 }
 
-func newSetup(t *testing.T, l *logrus.Logger, myPrefixes ...netip.Prefix) testsetup {
+func newSetup(t *testing.T, l *slog.Logger, myPrefixes ...netip.Prefix) testsetup {
 	c := dummyCert{
 		name:     "me",
 		networks: myPrefixes,
@@ -1397,7 +1388,7 @@ func newSetup(t *testing.T, l *logrus.Logger, myPrefixes ...netip.Prefix) testse
 	return newSetupFromCert(t, l, c)
 }
 
-func newSetupFromCert(t *testing.T, l *logrus.Logger, c dummyCert) testsetup {
+func newSetupFromCert(t *testing.T, l *slog.Logger, c dummyCert) testsetup {
 	myVpnNetworksTable := new(bart.Lite)
 	for _, prefix := range c.Networks() {
 		myVpnNetworksTable.Insert(prefix)
@@ -1414,9 +1405,8 @@ func newSetupFromCert(t *testing.T, l *logrus.Logger, c dummyCert) testsetup {
 
 func TestFirewall_Drop_EnforceIPMatch(t *testing.T) {
 	t.Parallel()
-	l := test.NewLogger()
 	ob := &bytes.Buffer{}
-	l.SetOutput(ob)
+	l := test.NewLoggerWithOutput(ob)
 
 	myPrefix := netip.MustParsePrefix("1.1.1.1/8")
 	// for now, it's okay that these are all "incoming", the logic this test tries to check doesn't care about in/out
@@ -1529,6 +1519,6 @@ func (mf *mockFirewall) AddRule(incoming bool, proto uint8, startPort int32, end
 
 func resetConntrack(fw *Firewall) {
 	fw.Conntrack.Lock()
-	fw.Conntrack.Conns = map[firewall.Packet]*conn{}
+	fw.Conntrack.Conns = map[firewall.PacketKey]*conn{}
 	fw.Conntrack.Unlock()
 }

go.mod

@@ -9,7 +9,7 @@ require (
 	github.com/armon/go-radix v1.0.0
 	github.com/cyberdelia/go-metrics-graphite v0.0.0-20161219230853-39f87cc3b432
 	github.com/flynn/noise v1.1.0
-	github.com/gaissmai/bart v0.26.0
+	github.com/gaissmai/bart v0.26.1
 	github.com/gogo/protobuf v1.3.2
 	github.com/google/gopacket v1.1.19
 	github.com/kardianos/service v1.2.4
@@ -18,15 +18,15 @@ require (
 	github.com/nbrownus/go-metrics-prometheus v0.0.0-20210712211119-974a6260965f
 	github.com/prometheus/client_golang v1.23.2
 	github.com/rcrowley/go-metrics v0.0.0-20201227073835-cf1acfcdf475
-	github.com/sirupsen/logrus v1.9.4
 	github.com/skip2/go-qrcode v0.0.0-20200617195104-da1b6568686e
 	github.com/stefanberger/go-pkcs11uri v0.0.0-20230803200340-78284954bff6
 	github.com/stretchr/testify v1.11.1
 	github.com/vishvananda/netlink v1.3.1
+	go.uber.org/goleak v1.3.0
 	go.yaml.in/yaml/v3 v3.0.4
 	golang.org/x/crypto v0.50.0
 	golang.org/x/exp v0.0.0-20230725093048-515e97ebf090
-	golang.org/x/net v0.52.0
+	golang.org/x/net v0.53.0
 	golang.org/x/sync v0.20.0
 	golang.org/x/sys v0.43.0
 	golang.org/x/term v0.42.0
@@ -43,6 +43,7 @@ require (
 	github.com/cespare/xxhash/v2 v2.3.0 // indirect
 	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/google/btree v1.1.2 // indirect
+	github.com/guptarohit/asciigraph v0.9.0 // indirect
 	github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
 	github.com/prometheus/client_model v0.6.2 // indirect

go.sum

@@ -26,8 +26,8 @@ github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/flynn/noise v1.1.0 h1:KjPQoQCEFdZDiP03phOvGi11+SVVhBG2wOWAorLsstg=
 github.com/flynn/noise v1.1.0/go.mod h1:xbMo+0i6+IGbYdJhF31t2eR1BIU0CYc12+BNAKwUTag=
-github.com/gaissmai/bart v0.26.0 h1:xOZ57E9hJLBiQaSyeZa9wgWhGuzfGACgqp4BE77OkO0=
-github.com/gaissmai/bart v0.26.0/go.mod h1:GREWQfTLRWz/c5FTOsIw+KkscuFkIV5t8Rp7Nd1Td5c=
+github.com/gaissmai/bart v0.26.1 h1:+w4rnLGNlA2GDVn382Tfe3jOsK5vOr5n4KmigJ9lbTo=
+github.com/gaissmai/bart v0.26.1/go.mod h1:GREWQfTLRWz/c5FTOsIw+KkscuFkIV5t8Rp7Nd1Td5c=
 github.com/go-kit/kit v0.8.0/go.mod h1:xBxKIO96dXMWWy0MnWVtmwkA9/13aqxPnvrjFYMA2as=
 github.com/go-kit/kit v0.9.0/go.mod h1:xBxKIO96dXMWWy0MnWVtmwkA9/13aqxPnvrjFYMA2as=
 github.com/go-kit/log v0.1.0/go.mod h1:zbhenjAZHb184qTLMA9ZjW7ThYL0H2mk7Q6pNt4vbaY=
@@ -60,6 +60,8 @@ github.com/google/go-cmp v0.7.0/go.mod h1:pXiqmnSA92OHEEa9HXL2W4E7lf9JzCmGVUdgjX
 github.com/google/gofuzz v1.0.0/go.mod h1:dBl0BpW6vV/+mYPU4Po3pmUjxk6FQPldtuIdl/M65Eg=
 github.com/google/gopacket v1.1.19 h1:ves8RnFZPGiFnTS0uPQStjwru6uO6h+nlr9j6fL7kF8=
 github.com/google/gopacket v1.1.19/go.mod h1:iJ8V8n6KS+z2U1A8pUwu8bW5SyEMkXJB8Yo/Vo+TKTo=
+github.com/guptarohit/asciigraph v0.9.0 h1:MvCSRRVkT2XvU1IO6n92o7l7zqx1DiFaoszOUZQztbY=
+github.com/guptarohit/asciigraph v0.9.0/go.mod h1:dYl5wwK4gNsnFf9Zp+l06rFiDZ5YtXM6x7SRWZ3KGag=
 github.com/jpillora/backoff v1.0.0/go.mod h1:J/6gKK9jxlEcS3zixgDgUAsiuZ7yrSoa/FX5e0EB2j4=
 github.com/json-iterator/go v1.1.6/go.mod h1:+SdeFBvtyEkXs7REEP0seUULqWtbJapLOCVDaaPEHmU=
 github.com/json-iterator/go v1.1.10/go.mod h1:KdQUCv79m/52Kvf8AW2vK1V8akMuk1QjK/uOdHXbAo4=
@@ -133,8 +135,6 @@ github.com/rogpeppe/go-internal v1.10.0/go.mod h1:UQnix2H7Ngw/k4C5ijL5+65zddjncj
 github.com/sirupsen/logrus v1.2.0/go.mod h1:LxeOpSwHxABJmUn/MG1IvRgCAasNZTLOkJPxbbu5VWo=
 github.com/sirupsen/logrus v1.4.2/go.mod h1:tLMulIdttU9McNUspp0xgXVQah82FyeX6MwdIuYE2rE=
 github.com/sirupsen/logrus v1.6.0/go.mod h1:7uNnSEd1DgxDLC74fIahvMZmmYsHGZGEOFrfsX/uA88=
-github.com/sirupsen/logrus v1.9.4 h1:TsZE7l11zFCLZnZ+teH4Umoq5BhEIfIzfRDZ1Uzql2w=
-github.com/sirupsen/logrus v1.9.4/go.mod h1:ftWc9WdOfJ0a92nsE2jF5u5ZwH8Bv2zdeOC42RjbV2g=
 github.com/skip2/go-qrcode v0.0.0-20200617195104-da1b6568686e h1:MRM5ITcdelLK2j1vwZ3Je0FKVCfqOLp5zO6trqMLYs0=
 github.com/skip2/go-qrcode v0.0.0-20200617195104-da1b6568686e/go.mod h1:XV66xRDqSt+GTGFMVlhk3ULuV0y9ZmzeVGR4mloJI3M=
 github.com/stefanberger/go-pkcs11uri v0.0.0-20230803200340-78284954bff6 h1:pnnLyeX7o/5aX8qUQ69P/mLojDqwda8hFOCBTmP/6hw=
@@ -184,8 +184,8 @@ golang.org/x/net v0.0.0-20200226121028-0de0cce0169b/go.mod h1:z5CRVTTTmAJ677TzLL
 golang.org/x/net v0.0.0-20200625001655-4c5254603344/go.mod h1:/O7V0waA8r7cgGh81Ro3o1hOxt32SMVPicZroKQ2sZA=
 golang.org/x/net v0.0.0-20201021035429-f5854403a974/go.mod h1:sp8m0HH+o8qH0wwXwYZr8TS3Oi6o0r6Gce1SSxlDquU=
 golang.org/x/net v0.0.0-20210226172049-e18ecbb05110/go.mod h1:m0MpNAwzfU5UDzcl9v0D8zg8gWTRqZa9RBIspLL5mdg=
-golang.org/x/net v0.52.0 h1:He/TN1l0e4mmR3QqHMT2Xab3Aj3L9qjbhRm78/6jrW0=
-golang.org/x/net v0.52.0/go.mod h1:R1MAz7uMZxVMualyPXb+VaqGSa3LIaUqk0eEt3w36Sw=
+golang.org/x/net v0.53.0 h1:d+qAbo5L0orcWAr0a9JweQpjXF19LMXJE8Ey7hwOdUA=
+golang.org/x/net v0.53.0/go.mod h1:JvMuJH7rrdiCfbeHoo3fCQU24Lf5JJwT9W3sJFulfgs=
 golang.org/x/oauth2 v0.0.0-20190226205417-e64efc72b421/go.mod h1:gOpvHmFTYa4IltrdGE7lF6nIHvwfUNPOp7c8zoXwtLw=
 golang.org/x/sync v0.0.0-20181108010431-42b317875d0f/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20181221193216-37e7f081c4d4/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=

handshake/credential.go

@@ -0,0 +1,57 @@
+package handshake
+
+import (
+	"crypto/rand"
+
+	"github.com/flynn/noise"
+	"github.com/slackhq/nebula/cert"
+)
+
+// Credential holds everything needed to participate in a handshake
+// at a given cert version. Version and Curve are read from Cert; the public
+// half of the static keypair likewise comes from Cert.PublicKey().
+type Credential struct {
+	Cert        cert.Certificate  // the certificate
+	Bytes       []byte            // pre-marshaled certificate bytes
+	privateKey  []byte            // static private key (public half lives in Cert)
+	cipherSuite noise.CipherSuite // pre-built cipher suite (DH + cipher + hash)
+}
+
+// NewCredential creates a Credential with all material needed for handshake
+// participation. The cipherSuite should be pre-built by the caller with the
+// appropriate DH function, cipher, and hash.
+func NewCredential(
+	c cert.Certificate,
+	hsBytes []byte,
+	privateKey []byte,
+	cipherSuite noise.CipherSuite,
+) *Credential {
+	return &Credential{
+		Cert:        c,
+		Bytes:       hsBytes,
+		privateKey:  privateKey,
+		cipherSuite: cipherSuite,
+	}
+}
+
+// buildHandshakeState creates a noise.HandshakeState from this credential.
+func (hc *Credential) buildHandshakeState(initiator bool, pattern noise.HandshakePattern) (*noise.HandshakeState, error) {
+	return noise.NewHandshakeState(noise.Config{
+		CipherSuite:           hc.cipherSuite,
+		Random:                rand.Reader,
+		Pattern:               pattern,
+		Initiator:             initiator,
+		StaticKeypair:         noise.DHKey{Private: hc.privateKey, Public: hc.Cert.PublicKey()},
+		PresharedKey:          []byte{},
+		PresharedKeyPlacement: 0,
+	})
+}
+
+// GetCredentialFunc returns the handshake credential for the given version,
+// or nil if that version is not available.
+//
+// Implementations must return credentials drawn from a snapshot stable for
+// the lifetime of any single Machine. The Machine may call this multiple
+// times during a handshake (e.g. when negotiating to the peer's version)
+// and assumes the underlying static keypair is consistent across calls.
+type GetCredentialFunc func(v cert.Version) *Credential

handshake/errors.go

@@ -0,0 +1,21 @@
+package handshake
+
+import "errors"
+
+var (
+	ErrInitiateOnResponder     = errors.New("initiate called on responder")
+	ErrInitiateAlreadyCalled   = errors.New("initiate already called")
+	ErrInitiateNotCalled       = errors.New("initiate must be called before ProcessPacket for initiators")
+	ErrPacketTooShort          = errors.New("packet too short")
+	ErrPublicKeyMismatch       = errors.New("public key mismatch between certificate and handshake")
+	ErrIncompleteHandshake     = errors.New("handshake completed without receiving required content")
+	ErrMachineFailed           = errors.New("handshake machine has failed")
+	ErrUnknownSubtype          = errors.New("unknown handshake subtype")
+	ErrMissingContent          = errors.New("expected handshake content but message was empty")
+	ErrUnexpectedContent       = errors.New("received unexpected handshake content")
+	ErrIndexAllocation         = errors.New("failed to allocate local index")
+	ErrNoCredential            = errors.New("no handshake credential available for cert version")
+	ErrAsymmetricCipherKeys    = errors.New("noise produced only one cipher key")
+	ErrMultiMessageUnsupported = errors.New("multi-message handshake patterns are not yet supported by the manager")
+	ErrSubtypeMismatch         = errors.New("packet subtype does not match handshake machine subtype")
+)

handshake/handshake.proto

@@ -0,0 +1,29 @@
+// This file documents the wire format the nebula handshake speaks. It is
+// not run through protoc; the encoder/decoder in payload.go is hand-written
+// against this shape directly to keep the parser narrow and panic-free.
+//
+// Any change to the wire format must be reflected here, and adding a new
+// field requires updating MarshalPayload / unmarshalPayloadDetails together
+// with the field-uniqueness and wire-type checks in those functions.
+
+syntax = "proto3";
+package nebula.handshake;
+
+message NebulaHandshake {
+  NebulaHandshakeDetails Details = 1;
+  bytes Hmac = 2;
+}
+
+message NebulaHandshakeDetails {
+  bytes Cert = 1;
+  uint32 InitiatorIndex = 2;
+  uint32 ResponderIndex = 3;
+  // Cookie was reserved for an anti-DoS mechanism that was never
+  // implemented. No released version of nebula has ever populated it; the
+  // hand-written parser silently skips it on read.
+  uint64 Cookie = 4 [deprecated = true];
+  uint64 Time = 5;
+  uint32 CertVersion = 8;
+  // reserved for WIP multiport
+  reserved 6, 7;
+}

handshake/helpers_test.go

@@ -0,0 +1,116 @@
+package handshake
+
+import (
+	"net/netip"
+	"testing"
+	"time"
+
+	"github.com/flynn/noise"
+	"github.com/slackhq/nebula/cert"
+	ct "github.com/slackhq/nebula/cert_test"
+	"github.com/slackhq/nebula/header"
+	"github.com/stretchr/testify/require"
+)
+
+// testCertState holds cert material for a test peer.
+type testCertState struct {
+	version cert.Version
+	creds   map[cert.Version]*Credential
+}
+
+func (s *testCertState) getCredential(v cert.Version) *Credential {
+	return s.creds[v]
+}
+
+func newTestCertState(
+	t *testing.T, ca cert.Certificate, caKey []byte, name string, networks []netip.Prefix,
+) *testCertState {
+	return newTestCertStateWithCipher(t, ca, caKey, name, networks, noise.CipherChaChaPoly)
+}
+
+func newTestCertStateWithCipher(
+	t *testing.T, ca cert.Certificate, caKey []byte, name string, networks []netip.Prefix,
+	cipher noise.CipherFunc,
+) *testCertState {
+	t.Helper()
+	c, _, rawPrivKey, _ := ct.NewTestCert(
+		cert.Version2, cert.Curve_CURVE25519, ca, caKey,
+		name, ca.NotBefore(), ca.NotAfter(), networks, nil, nil,
+	)
+
+	priv, _, _, err := cert.UnmarshalPrivateKeyFromPEM(rawPrivKey)
+	require.NoError(t, err)
+
+	hsBytes, err := c.MarshalForHandshakes()
+	require.NoError(t, err)
+
+	ncs := noise.NewCipherSuite(noise.DH25519, cipher, noise.HashSHA256)
+	return &testCertState{
+		version: cert.Version2,
+		creds: map[cert.Version]*Credential{
+			cert.Version2: NewCredential(c, hsBytes, priv, ncs),
+		},
+	}
+}
+
+func testVerifier(pool *cert.CAPool) CertVerifier {
+	return func(c cert.Certificate) (*cert.CachedCertificate, error) {
+		return pool.VerifyCertificate(time.Now(), c)
+	}
+}
+
+func newTestMachine(
+	t *testing.T,
+	cs *testCertState,
+	verifier CertVerifier,
+	initiator bool,
+	localIndex uint32,
+) *Machine {
+	t.Helper()
+	m, err := NewMachine(
+		cs.version, cs.getCredential,
+		verifier, func() (uint32, error) { return localIndex, nil },
+		initiator, header.HandshakeIXPSK0,
+	)
+	require.NoError(t, err)
+	return m
+}
+
+func initiateHandshake(
+	t *testing.T,
+	initCS *testCertState, initVerifier CertVerifier,
+	respCS *testCertState, respVerifier CertVerifier,
+) (initM, respM *Machine, respResult *Result, resp []byte, err error) {
+	t.Helper()
+	initM = newTestMachine(t, initCS, initVerifier, true, 100)
+	msg1, merr := initM.Initiate(nil)
+	require.NoError(t, merr)
+
+	respM = newTestMachine(t, respCS, respVerifier, false, 200)
+	resp, respResult, err = respM.ProcessPacket(nil, msg1)
+	return
+}
+
+func doFullHandshake(
+	t *testing.T, initCS, respCS *testCertState, caPool *cert.CAPool,
+) (initResult, respResult *Result) {
+	t.Helper()
+	v := testVerifier(caPool)
+
+	initM := newTestMachine(t, initCS, v, true, 1000)
+	respM := newTestMachine(t, respCS, v, false, 2000)
+
+	msg1, err := initM.Initiate(nil)
+	require.NoError(t, err)
+
+	resp, respResult, err := respM.ProcessPacket(nil, msg1)
+	require.NoError(t, err)
+	require.NotNil(t, respResult)
+	require.NotEmpty(t, resp)
+
+	_, initResult, err = initM.ProcessPacket(nil, resp)
+	require.NoError(t, err)
+	require.NotNil(t, initResult)
+
+	return initResult, respResult
+}

handshake/machine.go

@@ -0,0 +1,446 @@
+package handshake
+
+import (
+	"bytes"
+	"fmt"
+	"slices"
+	"time"
+
+	"github.com/flynn/noise"
+	"github.com/slackhq/nebula/cert"
+	"github.com/slackhq/nebula/header"
+)
+
+// IndexAllocator is called by the Machine to allocate a local index for the
+// handshake. It is called at most once, when the first outgoing message that
+// carries a payload is built.
+//
+// Implementations MUST NOT return 0. Zero is reserved as a sentinel meaning
+// "no index assigned" on the wire and in the payload-presence checks. If an
+// allocator ever returned 0, a legitimate handshake's payload could be
+// indistinguishable from an empty one and would be rejected.
+type IndexAllocator func() (uint32, error)
+
+// CertVerifier is called by the Machine after reconstructing the peer's
+// certificate from the handshake. The verifier performs all validation
+// (CA trust, expiry, policy checks, allow lists).
+type CertVerifier func(cert.Certificate) (*cert.CachedCertificate, error)
+
+// Result contains the results of a successful handshake.
+// Returned by ProcessPacket when the handshake is complete.
+type Result struct {
+	EKey          *noise.CipherState
+	DKey          *noise.CipherState
+	Cipher        noise.CipherFunc // identifies which post-handshake CipherState the data plane should wrap EKey/DKey in
+	MyCert        cert.Certificate
+	RemoteCert    *cert.CachedCertificate
+	RemoteIndex   uint32
+	LocalIndex    uint32
+	HandshakeTime uint64
+	MessageIndex  uint64 // number of messages exchanged during the handshake
+	Initiator     bool
+}
+
+// Machine drives a Noise handshake through N messages. It handles Noise
+// protocol operations, certificate reconstruction, and payload encoding.
+// Certificate validation is delegated to the caller via CertVerifier.
+//
+// A Machine is not safe for concurrent use. The caller must ensure that
+// Initiate and ProcessPacket are not called concurrently.
+//
+// Error contract: when ProcessPacket or Initiate returns an error, callers
+// must check Failed() to decide what to do next. If Failed() is false the
+// underlying noise state was not advanced (the packet was rejected before
+// ReadMessage took effect, or the rejection is non-fatal like a stale
+// retransmit) and the Machine can accept another packet. If Failed() is
+// true the Machine is unrecoverable and the caller must abandon it.
+type Machine struct {
+	hs             *noise.HandshakeState
+	getCred        GetCredentialFunc
+	allocIndex     IndexAllocator
+	verifier       CertVerifier
+	result         *Result
+	msgs           []msgFlags
+	myVersion      cert.Version
+	subtype        header.MessageSubType
+	indexAllocated bool
+	remoteCertSet  bool
+	payloadSet     bool
+	failed         bool
+}
+
+// NewMachine creates a handshake state machine. The subtype determines both
+// the noise pattern and the per-message content layout. The credential for
+// `version` is fetched via getCred and used to seed the noise.HandshakeState.
+// IndexAllocator is called lazily when the first outgoing payload is built.
+func NewMachine(
+	version cert.Version,
+	getCred GetCredentialFunc,
+	verifier CertVerifier,
+	allocIndex IndexAllocator,
+	initiator bool,
+	subtype header.MessageSubType,
+) (*Machine, error) {
+	info, err := subtypeInfoFor(subtype)
+	if err != nil {
+		return nil, err
+	}
+
+	cred := getCred(version)
+	if cred == nil {
+		return nil, fmt.Errorf("%w: %v", ErrNoCredential, version)
+	}
+
+	hs, err := cred.buildHandshakeState(initiator, info.pattern)
+	if err != nil {
+		return nil, fmt.Errorf("build noise state: %w", err)
+	}
+
+	return &Machine{
+		hs:         hs,
+		subtype:    subtype,
+		msgs:       info.msgs,
+		getCred:    getCred,
+		allocIndex: allocIndex,
+		verifier:   verifier,
+		myVersion:  version,
+		result: &Result{
+			Initiator: initiator,
+			Cipher:    cred.cipherSuite,
+		},
+	}, nil
+}
+
+// Failed returns true if the Machine is in an unrecoverable state.
+func (m *Machine) Failed() bool {
+	return m.failed
+}
+
+// Subtype returns the handshake subtype this Machine was built for.
+func (m *Machine) Subtype() header.MessageSubType {
+	return m.subtype
+}
+
+// MessageIndex returns the noise handshake message index, which equals the
+// wire counter of the most recently sent or received message.
+func (m *Machine) MessageIndex() int {
+	return m.hs.MessageIndex()
+}
+
+// requireComplete checks that both a peer cert and payload have been received.
+// Marks the machine as failed if not.
+func (m *Machine) requireComplete() error {
+	if !m.payloadSet || !m.remoteCertSet {
+		m.failed = true
+		return ErrIncompleteHandshake
+	}
+	return nil
+}
+
+// myMsgFlags returns the flags for the current outgoing message.
+func (m *Machine) myMsgFlags() msgFlags {
+	idx := m.hs.MessageIndex()
+	if idx < len(m.msgs) {
+		return m.msgs[idx]
+	}
+	return msgFlags{}
+}
+
+// peerMsgFlags returns the flags for the message we just read.
+func (m *Machine) peerMsgFlags() msgFlags {
+	idx := m.hs.MessageIndex() - 1
+	if idx >= 0 && idx < len(m.msgs) {
+		return m.msgs[idx]
+	}
+	return msgFlags{}
+}
+
+// Initiate produces the first handshake message. Only valid for initiators,
+// and must be called exactly once before ProcessPacket.
+//
+// out is a destination buffer the message is appended to and returned. Pass
+// nil to allocate fresh, or pass a re-used buffer sliced to length 0 (e.g.
+// buf[:0]) with sufficient capacity to avoid allocation.
+//
+// An error return may not indicate a fatal condition, check Failed() to
+// determine if the Machine can still be used.
+func (m *Machine) Initiate(out []byte) ([]byte, error) {
+	if m.failed {
+		return nil, ErrMachineFailed
+	}
+	if !m.result.Initiator {
+		m.failed = true
+		return nil, ErrInitiateOnResponder
+	}
+	if m.hs.MessageIndex() != 0 {
+		m.failed = true
+		return nil, ErrInitiateAlreadyCalled
+	}
+
+	// At MessageIndex=0 with RemoteIndex still zero, buildResponse produces
+	// header counter 1 and remote index 0, which is what the initial message needs.
+	out, _, _, err := m.buildResponse(out)
+	if err != nil {
+		m.failed = true
+		return nil, err
+	}
+	return out, nil
+}
+
+// ProcessPacket handles an incoming handshake message. It advances the Noise
+// state, validates the peer certificate via the verifier, and optionally
+// produces a response.
+//
+// out is a destination buffer the response is appended to and returned. Pass
+// nil to allocate fresh, or pass a re-used buffer sliced to length 0 (e.g.
+// buf[:0]) with sufficient capacity to avoid allocation. The returned slice
+// is nil when no outgoing message is produced (handshake complete on this
+// side, or final message of a multi-message pattern).
+//
+// Returns a non-nil Result when the handshake is complete.
+// An error return may not indicate a fatal condition, check Failed() to
+// determine if the Machine can still be used.
+func (m *Machine) ProcessPacket(out, packet []byte) ([]byte, *Result, error) {
+	if m.failed {
+		return nil, nil, ErrMachineFailed
+	}
+	if len(packet) < header.Len {
+		return nil, nil, ErrPacketTooShort
+	}
+	// Reject packets whose subtype doesn't match the one this Machine was
+	// built for. A pending handshake that suddenly receives a different
+	// subtype on its index is either a stray packet that matched by chance
+	// or a peer protocol violation; drop it without failing the Machine so
+	// the legitimate retransmit can still complete.
+	if header.MessageSubType(packet[1]) != m.subtype {
+		return nil, nil, ErrSubtypeMismatch
+	}
+	if m.result.Initiator && m.hs.MessageIndex() == 0 {
+		m.failed = true
+		return nil, nil, ErrInitiateNotCalled
+	}
+
+	// The (eKey, dKey) ordering here is correct for IX, where the initiator
+	// completes the handshake by reading the responder's stage-2 message.
+	// noise returns (cs1, cs2) where cs1 is the initiator->responder cipher.
+	// For 3-message patterns where a responder finishes by reading the final
+	// message, this ordering would be wrong; revisit when XX/pqIX lands.
+	msg, eKey, dKey, err := m.hs.ReadMessage(nil, packet[header.Len:])
+	if err != nil {
+		// Noise ReadMessage failed. The noise library checkpoints and rolls back
+		// on failure, so the Machine is still alive. The caller can retry with
+		// a different packet.
+		return nil, nil, fmt.Errorf("noise ReadMessage: %w", err)
+	}
+
+	// From here on, noise state has advanced. Any error is fatal.
+	flags := m.peerMsgFlags()
+
+	if err := m.processPayload(msg, flags); err != nil {
+		return nil, nil, err
+	}
+
+	// If ReadMessage derived keys, the handshake is complete. Noise should
+	// always produce both keys together; asymmetry is a protocol invariant
+	// violation.
+	if eKey != nil || dKey != nil {
+		if eKey == nil || dKey == nil {
+			m.failed = true
+			return nil, nil, ErrAsymmetricCipherKeys
+		}
+		if err := m.requireComplete(); err != nil {
+			return nil, nil, err
+		}
+		return nil, m.completed(eKey, dKey), nil
+	}
+
+	// ReadMessage didn't complete, produce the next outgoing message
+	out, dk, ek, err := m.buildResponse(out)
+	if err != nil {
+		m.failed = true
+		return nil, nil, err
+	}
+
+	if ek != nil || dk != nil {
+		if ek == nil || dk == nil {
+			m.failed = true
+			return nil, nil, ErrAsymmetricCipherKeys
+		}
+		if err := m.requireComplete(); err != nil {
+			return nil, nil, err
+		}
+		return out, m.completed(ek, dk), nil
+	}
+
+	return out, nil, nil
+}
+
+func (m *Machine) completed(eKey, dKey *noise.CipherState) *Result {
+	m.result.EKey = eKey
+	m.result.DKey = dKey
+	m.result.MessageIndex = uint64(m.hs.MessageIndex())
+	return m.result
+}
+
+func (m *Machine) processPayload(msg []byte, flags msgFlags) error {
+	if len(msg) == 0 {
+		if flags.expectsPayload || flags.expectsCert {
+			m.failed = true
+			return ErrMissingContent
+		}
+		return nil
+	}
+
+	payload, err := UnmarshalPayload(msg)
+	if err != nil {
+		m.failed = true
+		return fmt.Errorf("unmarshal handshake: %w", err)
+	}
+
+	// Assert the payload contains exactly what we expect
+	hasPayloadData := payload.InitiatorIndex != 0 || payload.ResponderIndex != 0 || payload.Time != 0
+	if hasPayloadData != flags.expectsPayload {
+		m.failed = true
+		return ErrUnexpectedContent
+	}
+
+	hasCertData := len(payload.Cert) > 0
+	if hasCertData != flags.expectsCert {
+		m.failed = true
+		return ErrUnexpectedContent
+	}
+
+	// Process payload
+	if flags.expectsPayload {
+		if m.result.Initiator {
+			m.result.RemoteIndex = payload.ResponderIndex
+		} else {
+			m.result.RemoteIndex = payload.InitiatorIndex
+		}
+		m.result.HandshakeTime = payload.Time
+		m.payloadSet = true
+	}
+
+	// Process certificate
+	if flags.expectsCert {
+		if err := m.validateCert(payload); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func (m *Machine) validateCert(payload Payload) error {
+	cred := m.getCred(m.myVersion)
+	if cred == nil {
+		m.failed = true
+		return fmt.Errorf("%w: %v", ErrNoCredential, m.myVersion)
+	}
+	rc, err := cert.Recombine(
+		cert.Version(payload.CertVersion),
+		payload.Cert,
+		m.hs.PeerStatic(),
+		cred.Cert.Curve(),
+	)
+	if err != nil {
+		m.failed = true
+		return fmt.Errorf("recombine cert: %w", err)
+	}
+
+	if !bytes.Equal(rc.PublicKey(), m.hs.PeerStatic()) {
+		m.failed = true
+		return ErrPublicKeyMismatch
+	}
+
+	// Version negotiation, if the peer sent a different version and we have it, switch
+	if rc.Version() != m.myVersion {
+		if m.getCred(rc.Version()) != nil {
+			m.myVersion = rc.Version()
+		}
+	}
+
+	verified, err := m.verifier(rc)
+	if err != nil {
+		m.failed = true
+		return fmt.Errorf("verify cert: %w", err)
+	}
+
+	m.result.RemoteCert = verified
+	m.remoteCertSet = true
+	return nil
+}
+
+func (m *Machine) marshalOutgoing(flags msgFlags) ([]byte, error) {
+	if !flags.expectsPayload && !flags.expectsCert {
+		return nil, nil
+	}
+
+	var p Payload
+	if flags.expectsPayload {
+		if !m.indexAllocated {
+			index, err := m.allocIndex()
+			if err != nil {
+				return nil, fmt.Errorf("%w: %w", ErrIndexAllocation, err)
+			}
+			m.result.LocalIndex = index
+			m.indexAllocated = true
+		}
+
+		if m.result.Initiator {
+			p.InitiatorIndex = m.result.LocalIndex
+		} else {
+			p.ResponderIndex = m.result.LocalIndex
+			p.InitiatorIndex = m.result.RemoteIndex
+		}
+		p.Time = uint64(time.Now().UnixNano())
+	}
+	if flags.expectsCert {
+		cred := m.getCred(m.myVersion)
+		if cred == nil {
+			return nil, fmt.Errorf("%w: %v", ErrNoCredential, m.myVersion)
+		}
+		p.Cert = cred.Bytes
+		p.CertVersion = uint32(cred.Cert.Version())
+		m.result.MyCert = cred.Cert
+	}
+
+	return MarshalPayload(nil, p), nil
+}
+
+func (m *Machine) buildResponse(out []byte) ([]byte, *noise.CipherState, *noise.CipherState, error) {
+	flags := m.myMsgFlags()
+	hsBytes, err := m.marshalOutgoing(flags)
+	if err != nil {
+		return nil, nil, nil, err
+	}
+
+	// Extend out by header.Len to make room for the header. slices.Grow is a
+	// no-op when the cap is already sufficient (the zero-copy case where the
+	// caller passed a pre-sized buffer). header.Encode overwrites the new
+	// bytes, so they don't need to be zeroed.
+	start := len(out)
+	out = slices.Grow(out, header.Len)[:start+header.Len]
+	header.Encode(
+		out[start:],
+		header.Version, header.Handshake, m.subtype,
+		m.result.RemoteIndex,
+		uint64(m.hs.MessageIndex()+1),
+	)
+
+	// noise.WriteMessage appends the encrypted handshake message to out,
+	// reusing capacity when present.
+	//
+	// The (dKey, eKey) ordering here is correct for IX, where the responder
+	// completes the handshake by writing the stage-2 message. noise returns
+	// (cs1, cs2) where cs1 is the initiator->responder cipher (which is the
+	// responder's decrypt key). For 3-message patterns where an initiator
+	// finishes by writing the final message, this ordering would be wrong;
+	// revisit when XX/pqIX lands.
+	out, dKey, eKey, err := m.hs.WriteMessage(out, hsBytes)
+	if err != nil {
+		return nil, nil, nil, fmt.Errorf("noise WriteMessage: %w", err)
+	}
+
+	return out, dKey, eKey, nil
+}

handshake/machine_test.go

@@ -0,0 +1,662 @@
+package handshake
+
+import (
+	"net/netip"
+	"testing"
+	"time"
+
+	"github.com/flynn/noise"
+	"github.com/slackhq/nebula/cert"
+	ct "github.com/slackhq/nebula/cert_test"
+	"github.com/slackhq/nebula/header"
+	"github.com/slackhq/nebula/noiseutil"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestMachineIXHappyPath(t *testing.T) {
+	ca, _, caKey, _ := ct.NewTestCaCert(
+		cert.Version2, cert.Curve_CURVE25519, time.Time{}, time.Time{}, nil, nil, nil,
+	)
+	caPool := ct.NewTestCAPool(ca)
+
+	initCS := newTestCertState(t, ca, caKey, "initiator", []netip.Prefix{netip.MustParsePrefix("10.0.0.1/24")})
+	respCS := newTestCertState(t, ca, caKey, "responder", []netip.Prefix{netip.MustParsePrefix("10.0.0.2/24")})
+
+	initR, respR := doFullHandshake(t, initCS, respCS, caPool)
+
+	assert.Equal(t, "responder", initR.RemoteCert.Certificate.Name())
+	assert.Equal(t, "initiator", respR.RemoteCert.Certificate.Name())
+
+	assert.Equal(t, uint32(1000), initR.LocalIndex)
+	assert.Equal(t, uint32(2000), initR.RemoteIndex)
+	assert.Equal(t, uint32(2000), respR.LocalIndex)
+	assert.Equal(t, uint32(1000), respR.RemoteIndex)
+
+	assert.Equal(t, uint64(2), initR.MessageIndex, "IX has 2 messages")
+	assert.Equal(t, uint64(2), respR.MessageIndex, "IX has 2 messages")
+
+	ct1, err := initR.EKey.Encrypt(nil, nil, []byte("hello"))
+	require.NoError(t, err)
+	pt1, err := respR.DKey.Decrypt(nil, nil, ct1)
+	require.NoError(t, err)
+	assert.Equal(t, []byte("hello"), pt1)
+
+	ct2, err := respR.EKey.Encrypt(nil, nil, []byte("world"))
+	require.NoError(t, err)
+	pt2, err := initR.DKey.Decrypt(nil, nil, ct2)
+	require.NoError(t, err)
+	assert.Equal(t, []byte("world"), pt2)
+}
+
+func TestMachineInitiateErrors(t *testing.T) {
+	ca, _, caKey, _ := ct.NewTestCaCert(
+		cert.Version2, cert.Curve_CURVE25519, time.Time{}, time.Time{}, nil, nil, nil,
+	)
+	caPool := ct.NewTestCAPool(ca)
+	cs := newTestCertState(t, ca, caKey, "test", []netip.Prefix{netip.MustParsePrefix("10.0.0.1/24")})
+	v := testVerifier(caPool)
+
+	t.Run("initiate on responder", func(t *testing.T) {
+		m := newTestMachine(t, cs, v, false, 100)
+		_, err := m.Initiate(nil)
+		require.ErrorIs(t, err, ErrInitiateOnResponder)
+		assert.True(t, m.Failed())
+	})
+
+	t.Run("initiate called twice", func(t *testing.T) {
+		m := newTestMachine(t, cs, v, true, 100)
+		_, err := m.Initiate(nil)
+		require.NoError(t, err)
+		_, err = m.Initiate(nil)
+		require.ErrorIs(t, err, ErrInitiateAlreadyCalled)
+		assert.True(t, m.Failed())
+	})
+
+	t.Run("process packet before initiate on initiator", func(t *testing.T) {
+		m := newTestMachine(t, cs, v, true, 100)
+		_, _, err := m.ProcessPacket(nil, make([]byte, 100))
+		require.ErrorIs(t, err, ErrInitiateNotCalled)
+		assert.True(t, m.Failed())
+	})
+
+	t.Run("calling failed machine", func(t *testing.T) {
+		m := newTestMachine(t, cs, v, false, 100)
+		_, err := m.Initiate(nil) // fails: responder
+		require.Error(t, err)
+		_, err = m.Initiate(nil) // fails: already failed
+		require.ErrorIs(t, err, ErrMachineFailed)
+	})
+}
+
+func TestMachineProcessPacketErrors(t *testing.T) {
+	ca, _, caKey, _ := ct.NewTestCaCert(
+		cert.Version2, cert.Curve_CURVE25519, time.Time{}, time.Time{}, nil, nil, nil,
+	)
+	caPool := ct.NewTestCAPool(ca)
+	cs := newTestCertState(t, ca, caKey, "test", []netip.Prefix{netip.MustParsePrefix("10.0.0.1/24")})
+	v := testVerifier(caPool)
+
+	t.Run("packet too short", func(t *testing.T) {
+		m := newTestMachine(t, cs, v, false, 100)
+		_, _, err := m.ProcessPacket(nil, []byte{1, 2, 3})
+		require.ErrorIs(t, err, ErrPacketTooShort)
+		assert.False(t, m.Failed(), "short packet should not kill machine")
+	})
+
+	t.Run("noise decryption failure is recoverable", func(t *testing.T) {
+		initCS := newTestCertState(t, ca, caKey, "init", []netip.Prefix{netip.MustParsePrefix("10.0.0.1/24")})
+		initM := newTestMachine(t, initCS, v, true, 100)
+		msg1, err := initM.Initiate(nil)
+		require.NoError(t, err)
+
+		respM := newTestMachine(t, cs, v, false, 200)
+		resp, _, err := respM.ProcessPacket(nil, msg1)
+		require.NoError(t, err)
+
+		corrupted := make([]byte, len(resp))
+		copy(corrupted, resp)
+		for i := header.Len; i < len(corrupted); i++ {
+			corrupted[i] ^= 0xff
+		}
+		_, _, err = initM.ProcessPacket(nil, corrupted)
+		require.Error(t, err)
+		assert.False(t, initM.Failed(), "noise failure should be recoverable")
+
+		// And the machine should still complete a real handshake afterward.
+		_, result, err := initM.ProcessPacket(nil, resp)
+		require.NoError(t, err)
+		require.NotNil(t, result, "initiator should complete on the legitimate response")
+	})
+
+	t.Run("invalid cert is fatal", func(t *testing.T) {
+		otherCA, _, otherCAKey, _ := ct.NewTestCaCert(
+			cert.Version2, cert.Curve_CURVE25519, time.Time{}, time.Time{}, nil, nil, nil,
+		)
+		otherCS := newTestCertState(t, otherCA, otherCAKey, "other", []netip.Prefix{netip.MustParsePrefix("10.0.0.2/24")})
+
+		initM := newTestMachine(t, otherCS, testVerifier(ct.NewTestCAPool(otherCA)), true, 100)
+		msg1, err := initM.Initiate(nil)
+		require.NoError(t, err)
+
+		respM := newTestMachine(t, cs, v, false, 200)
+		_, _, err = respM.ProcessPacket(nil, msg1)
+		require.Error(t, err)
+		assert.True(t, respM.Failed(), "cert validation failure should kill machine")
+	})
+
+	t.Run("subtype mismatch is recoverable", func(t *testing.T) {
+		initCS := newTestCertState(t, ca, caKey, "init", []netip.Prefix{netip.MustParsePrefix("10.0.0.1/24")})
+		initM := newTestMachine(t, initCS, v, true, 100)
+		msg1, err := initM.Initiate(nil)
+		require.NoError(t, err)
+
+		// Mutate the subtype byte (offset 1 in the header) to a value the
+		// responder Machine wasn't built for.
+		bad := make([]byte, len(msg1))
+		copy(bad, msg1)
+		bad[1] = 0xff
+
+		respM := newTestMachine(t, cs, v, false, 200)
+		_, _, err = respM.ProcessPacket(nil, bad)
+		require.ErrorIs(t, err, ErrSubtypeMismatch)
+		assert.False(t, respM.Failed(), "subtype mismatch should not kill the machine")
+
+		// And the machine should still complete a real handshake afterward.
+		resp, result, err := respM.ProcessPacket(nil, msg1)
+		require.NoError(t, err)
+		require.NotNil(t, result, "responder should complete on the legitimate stage-1 packet")
+		assert.NotEmpty(t, resp, "responder should produce a stage-2 reply")
+	})
+}
+
+// TestMachineProcessPayload exercises processPayload's internal validation
+// directly. Most of these failure modes can't be reached black-box once the
+// subtype check at the top of ProcessPacket gates external callers, so we
+// drive them by hand here for coverage.
+func TestMachineProcessPayload(t *testing.T) {
+	ca, _, caKey, _ := ct.NewTestCaCert(
+		cert.Version2, cert.Curve_CURVE25519, time.Time{}, time.Time{}, nil, nil, nil,
+	)
+	caPool := ct.NewTestCAPool(ca)
+	cs := newTestCertState(t, ca, caKey, "test", []netip.Prefix{netip.MustParsePrefix("10.0.0.1/24")})
+	v := testVerifier(caPool)
+
+	t.Run("empty message with expects fails", func(t *testing.T) {
+		m := newTestMachine(t, cs, v, false, 100)
+		err := m.processPayload(nil, msgFlags{expectsPayload: true, expectsCert: true})
+		require.ErrorIs(t, err, ErrMissingContent)
+		assert.True(t, m.Failed())
+	})
+
+	t.Run("empty message with no expects passes", func(t *testing.T) {
+		m := newTestMachine(t, cs, v, false, 100)
+		err := m.processPayload(nil, msgFlags{})
+		require.NoError(t, err)
+		assert.False(t, m.Failed())
+	})
+
+	t.Run("malformed protobuf is fatal", func(t *testing.T) {
+		m := newTestMachine(t, cs, v, false, 100)
+		err := m.processPayload([]byte{0xff, 0xff, 0xff}, msgFlags{expectsPayload: true, expectsCert: true})
+		require.Error(t, err)
+		assert.True(t, m.Failed())
+	})
+
+	t.Run("unexpected payload data is fatal", func(t *testing.T) {
+		m := newTestMachine(t, cs, v, false, 100)
+		// A payload with index data when none was expected.
+		bytes := MarshalPayload(nil, Payload{InitiatorIndex: 42, Time: 1})
+		err := m.processPayload(bytes, msgFlags{expectsPayload: false, expectsCert: false})
+		require.ErrorIs(t, err, ErrUnexpectedContent)
+		assert.True(t, m.Failed())
+	})
+
+	t.Run("unexpected cert data is fatal", func(t *testing.T) {
+		m := newTestMachine(t, cs, v, false, 100)
+		// A payload with cert when none was expected.
+		bytes := MarshalPayload(nil, Payload{Cert: []byte{1, 2, 3}, CertVersion: 2})
+		err := m.processPayload(bytes, msgFlags{expectsPayload: false, expectsCert: false})
+		require.ErrorIs(t, err, ErrUnexpectedContent)
+		assert.True(t, m.Failed())
+	})
+
+	t.Run("missing payload data when expected is fatal", func(t *testing.T) {
+		m := newTestMachine(t, cs, v, false, 100)
+		// Cert present, but no index/time fields.
+		bytes := MarshalPayload(nil, Payload{Cert: []byte{1, 2, 3}, CertVersion: 2})
+		err := m.processPayload(bytes, msgFlags{expectsPayload: true, expectsCert: true})
+		require.ErrorIs(t, err, ErrUnexpectedContent)
+		assert.True(t, m.Failed())
+	})
+}
+
+// TestMachineRequireComplete checks the fail-on-incomplete-handshake path
+// directly. Like processPayload above this isn't reachable from a normal IX
+// flow, so we drive it by hand.
+func TestMachineRequireComplete(t *testing.T) {
+	ca, _, caKey, _ := ct.NewTestCaCert(
+		cert.Version2, cert.Curve_CURVE25519, time.Time{}, time.Time{}, nil, nil, nil,
+	)
+	caPool := ct.NewTestCAPool(ca)
+	cs := newTestCertState(t, ca, caKey, "test", []netip.Prefix{netip.MustParsePrefix("10.0.0.1/24")})
+	v := testVerifier(caPool)
+
+	t.Run("missing both fails", func(t *testing.T) {
+		m := newTestMachine(t, cs, v, false, 100)
+		err := m.requireComplete()
+		require.ErrorIs(t, err, ErrIncompleteHandshake)
+		assert.True(t, m.Failed())
+	})
+
+	t.Run("payload only fails", func(t *testing.T) {
+		m := newTestMachine(t, cs, v, false, 100)
+		m.payloadSet = true
+		err := m.requireComplete()
+		require.ErrorIs(t, err, ErrIncompleteHandshake)
+		assert.True(t, m.Failed())
+	})
+
+	t.Run("cert only fails", func(t *testing.T) {
+		m := newTestMachine(t, cs, v, false, 100)
+		m.remoteCertSet = true
+		err := m.requireComplete()
+		require.ErrorIs(t, err, ErrIncompleteHandshake)
+		assert.True(t, m.Failed())
+	})
+
+	t.Run("both set passes", func(t *testing.T) {
+		m := newTestMachine(t, cs, v, false, 100)
+		m.payloadSet = true
+		m.remoteCertSet = true
+		err := m.requireComplete()
+		require.NoError(t, err)
+		assert.False(t, m.Failed())
+	})
+}
+
+func TestMachineAESCipher(t *testing.T) {
+	ca, _, caKey, _ := ct.NewTestCaCert(
+		cert.Version2, cert.Curve_CURVE25519, time.Time{}, time.Time{}, nil, nil, nil,
+	)
+	caPool := ct.NewTestCAPool(ca)
+
+	initCS := newTestCertStateWithCipher(
+		t, ca, caKey, "init",
+		[]netip.Prefix{netip.MustParsePrefix("10.0.0.1/24")},
+		noiseutil.CipherAESGCM,
+	)
+	respCS := newTestCertStateWithCipher(
+		t, ca, caKey, "resp",
+		[]netip.Prefix{netip.MustParsePrefix("10.0.0.2/24")},
+		noiseutil.CipherAESGCM,
+	)
+
+	initR, respR := doFullHandshake(t, initCS, respCS, caPool)
+
+	ct1, err := initR.EKey.Encrypt(nil, nil, []byte("works"))
+	require.NoError(t, err)
+	pt1, err := respR.DKey.Decrypt(nil, nil, ct1)
+	require.NoError(t, err)
+	assert.Equal(t, []byte("works"), pt1)
+
+	ct2, err := respR.EKey.Encrypt(nil, nil, []byte("back"))
+	require.NoError(t, err)
+	pt2, err := initR.DKey.Decrypt(nil, nil, ct2)
+	require.NoError(t, err)
+	assert.Equal(t, []byte("back"), pt2)
+}
+
+func TestResultFields(t *testing.T) {
+	ca, _, caKey, _ := ct.NewTestCaCert(
+		cert.Version2, cert.Curve_CURVE25519, time.Time{}, time.Time{}, nil, nil, nil,
+	)
+	caPool := ct.NewTestCAPool(ca)
+	initCS := newTestCertState(t, ca, caKey, "init", []netip.Prefix{netip.MustParsePrefix("10.0.0.1/24")})
+	respCS := newTestCertState(t, ca, caKey, "resp", []netip.Prefix{netip.MustParsePrefix("10.0.0.2/24")})
+
+	initR, respR := doFullHandshake(t, initCS, respCS, caPool)
+
+	assert.True(t, initR.Initiator)
+	assert.False(t, respR.Initiator)
+	assert.NotZero(t, initR.HandshakeTime)
+	assert.NotZero(t, respR.HandshakeTime)
+	assert.NotNil(t, initR.RemoteCert)
+	assert.NotNil(t, respR.RemoteCert)
+}
+
+func TestMachineBufferReuse(t *testing.T) {
+	ca, _, caKey, _ := ct.NewTestCaCert(
+		cert.Version2, cert.Curve_CURVE25519, time.Time{}, time.Time{}, nil, nil, nil,
+	)
+	caPool := ct.NewTestCAPool(ca)
+	initCS := newTestCertState(t, ca, caKey, "init", []netip.Prefix{netip.MustParsePrefix("10.0.0.1/24")})
+	respCS := newTestCertState(t, ca, caKey, "resp", []netip.Prefix{netip.MustParsePrefix("10.0.0.2/24")})
+	v := testVerifier(caPool)
+
+	initM := newTestMachine(t, initCS, v, true, 1000)
+	respM := newTestMachine(t, respCS, v, false, 2000)
+
+	msg1, err := initM.Initiate(nil)
+	require.NoError(t, err)
+
+	t.Run("response writes into provided buffer", func(t *testing.T) {
+		buf := make([]byte, 0, 4096)
+		resp, result, err := respM.ProcessPacket(buf, msg1)
+		require.NoError(t, err)
+		require.NotNil(t, result)
+
+		assert.NotEmpty(t, resp, "response should have content")
+		assert.Equal(t, &buf[:1][0], &resp[:1][0],
+			"response should reuse the provided buffer's backing array")
+	})
+
+	t.Run("initiate writes into provided buffer", func(t *testing.T) {
+		initM2 := newTestMachine(t, initCS, v, true, 3000)
+		buf := make([]byte, 0, 4096)
+		msg, err := initM2.Initiate(buf)
+		require.NoError(t, err)
+
+		assert.NotEmpty(t, msg, "initiate should have content")
+		assert.Equal(t, &buf[:1][0], &msg[:1][0],
+			"initiate should reuse the provided buffer's backing array")
+	})
+
+	t.Run("nil out still works", func(t *testing.T) {
+		initM2 := newTestMachine(t, initCS, v, true, 4000)
+		respM2 := newTestMachine(t, respCS, v, false, 5000)
+
+		msg1, err := initM2.Initiate(nil)
+		require.NoError(t, err)
+
+		resp, _, err := respM2.ProcessPacket(nil, msg1)
+		require.NoError(t, err)
+
+		out, result, err := initM2.ProcessPacket(nil, resp)
+		require.NoError(t, err)
+		assert.NotNil(t, result)
+		assert.Nil(t, out, "initiator should have no response for IX msg2")
+	})
+}
+
+func TestMachineMsgIndexTracking(t *testing.T) {
+	ca, _, caKey, _ := ct.NewTestCaCert(
+		cert.Version2, cert.Curve_CURVE25519, time.Time{}, time.Time{}, nil, nil, nil,
+	)
+	caPool := ct.NewTestCAPool(ca)
+	initCS := newTestCertState(t, ca, caKey, "init", []netip.Prefix{netip.MustParsePrefix("10.0.0.1/24")})
+	respCS := newTestCertState(t, ca, caKey, "resp", []netip.Prefix{netip.MustParsePrefix("10.0.0.2/24")})
+	v := testVerifier(caPool)
+
+	initM := newTestMachine(t, initCS, v, true, 100)
+	respM := newTestMachine(t, respCS, v, false, 200)
+
+	msg1, err := initM.Initiate(nil)
+	require.NoError(t, err)
+
+	resp1, result1, err := respM.ProcessPacket(nil, msg1)
+	require.NoError(t, err)
+	assert.NotNil(t, result1)
+
+	_, result2, err := initM.ProcessPacket(nil, resp1)
+	require.NoError(t, err)
+	assert.NotNil(t, result2)
+}
+
+func TestMachineThreeMessagePattern(t *testing.T) {
+	registerTestXXInfo(t)
+
+	// Use HandshakeXX (3 messages) to verify the Machine handles multi-message
+	// patterns correctly. XX flow:
+	//   msg1 (I->R): [E]           - payload only, no cert
+	//   msg2 (R->I): [E, ee, S, es] - payload + cert
+	//   msg3 (I->R): [S, se]       - cert only (no payload, not first two)
+
+	ca, _, caKey, _ := ct.NewTestCaCert(
+		cert.Version2, cert.Curve_CURVE25519, time.Time{}, time.Time{}, nil, nil, nil,
+	)
+	caPool := ct.NewTestCAPool(ca)
+	v := testVerifier(caPool)
+
+	initCS := newTestCertState(t, ca, caKey, "init", []netip.Prefix{netip.MustParsePrefix("10.0.0.1/24")})
+	respCS := newTestCertState(t, ca, caKey, "resp", []netip.Prefix{netip.MustParsePrefix("10.0.0.2/24")})
+
+	initM, err := NewMachine(
+		cert.Version2,
+		initCS.getCredential, v,
+		func() (uint32, error) { return 1000, nil },
+		true, header.HandshakeXXPSK0,
+	)
+	require.NoError(t, err)
+
+	respM, err := NewMachine(
+		cert.Version2,
+		respCS.getCredential, v,
+		func() (uint32, error) { return 2000, nil },
+		false, header.HandshakeXXPSK0,
+	)
+	require.NoError(t, err)
+
+	// msg1: initiator -> responder (E only, no cert)
+	msg1, err := initM.Initiate(nil)
+	require.NoError(t, err)
+	assert.NotEmpty(t, msg1)
+
+	// Responder processes msg1, should not complete yet, should produce msg2
+	msg2, result, err := respM.ProcessPacket(nil, msg1)
+	require.NoError(t, err)
+	assert.Nil(t, result, "XX should not complete on msg1")
+	assert.NotEmpty(t, msg2, "responder should produce msg2")
+
+	// Initiator processes msg2: gets responder's cert, produces msg3, and
+	// completes (WriteMessage for msg3 derives keys)
+	msg3, initResult, err := initM.ProcessPacket(nil, msg2)
+	require.NoError(t, err)
+	require.NotNil(t, initResult, "XX initiator should complete after reading msg2 and writing msg3")
+	assert.NotEmpty(t, msg3, "initiator should produce msg3")
+	assert.Equal(t, "resp", initResult.RemoteCert.Certificate.Name())
+
+	// Responder processes msg3: gets initiator's cert and completes
+	_, respResult, err := respM.ProcessPacket(nil, msg3)
+	require.NoError(t, err)
+	require.NotNil(t, respResult, "XX responder should complete on msg3")
+	assert.Equal(t, "init", respResult.RemoteCert.Certificate.Name())
+
+	assert.Equal(t, uint64(3), initResult.MessageIndex, "XX has 3 messages")
+	assert.Equal(t, uint64(3), respResult.MessageIndex, "XX has 3 messages")
+
+	// Verify keys work
+	ct1, err := initResult.EKey.Encrypt(nil, nil, []byte("three messages"))
+	require.NoError(t, err)
+	pt1, err := respResult.DKey.Decrypt(nil, nil, ct1)
+	require.NoError(t, err)
+	assert.Equal(t, []byte("three messages"), pt1)
+}
+
+// NOTE: ErrIncompleteHandshake is tested implicitly. It can't be triggered with
+// IX since the cert is always in the payload. A 3-message pattern test (HybridIX)
+// should exercise the case where cert arrives in msg3 and verify that completing
+// without it fails.
+
+func TestMachineExpiredCert(t *testing.T) {
+	ca, _, caKey, _ := ct.NewTestCaCert(
+		cert.Version2, cert.Curve_CURVE25519,
+		time.Now().Add(-24*time.Hour), time.Now().Add(24*time.Hour),
+		nil, nil, nil,
+	)
+	caPool := ct.NewTestCAPool(ca)
+
+	expCert, _, expKeyPEM, _ := ct.NewTestCert(
+		cert.Version2, cert.Curve_CURVE25519, ca, caKey,
+		"expired", time.Now().Add(-2*time.Hour), time.Now().Add(-1*time.Hour),
+		[]netip.Prefix{netip.MustParsePrefix("10.0.0.1/24")}, nil, nil,
+	)
+	expKey, _, _, err := cert.UnmarshalPrivateKeyFromPEM(expKeyPEM)
+	require.NoError(t, err)
+	expHsBytes, err := expCert.MarshalForHandshakes()
+	require.NoError(t, err)
+	ncs := noise.NewCipherSuite(noise.DH25519, noise.CipherChaChaPoly, noise.HashSHA256)
+
+	expiredCS := &testCertState{
+		version: cert.Version2,
+		creds: map[cert.Version]*Credential{
+			cert.Version2: NewCredential(expCert, expHsBytes, expKey, ncs),
+		},
+	}
+
+	respCS := newTestCertState(
+		t, ca, caKey, "responder",
+		[]netip.Prefix{netip.MustParsePrefix("10.0.0.2/24")},
+	)
+
+	_, respM, _, _, err := initiateHandshake(
+		t, expiredCS, testVerifier(caPool),
+		respCS, testVerifier(caPool),
+	)
+	require.ErrorContains(t, err, "verify cert")
+	assert.True(t, respM.Failed())
+}
+
+func TestMachineNoCertNetworks(t *testing.T) {
+	ca, _, caKey, _ := ct.NewTestCaCert(
+		cert.Version2, cert.Curve_CURVE25519, time.Time{}, time.Time{}, nil, nil, nil,
+	)
+	caPool := ct.NewTestCAPool(ca)
+
+	caHsBytes, err := ca.MarshalForHandshakes()
+	require.NoError(t, err)
+	ncs := noise.NewCipherSuite(noise.DH25519, noise.CipherChaChaPoly, noise.HashSHA256)
+
+	noNetCS := &testCertState{
+		version: cert.Version2,
+		creds: map[cert.Version]*Credential{
+			cert.Version2: NewCredential(ca, caHsBytes, caKey, ncs),
+		},
+	}
+
+	respCS := newTestCertState(
+		t, ca, caKey, "responder",
+		[]netip.Prefix{netip.MustParsePrefix("10.0.0.2/24")},
+	)
+
+	_, respM, _, _, err := initiateHandshake(
+		t, noNetCS, testVerifier(caPool),
+		respCS, testVerifier(caPool),
+	)
+	require.Error(t, err)
+	assert.True(t, respM.Failed())
+}
+
+func TestMachineDifferentCAs(t *testing.T) {
+	ca1, _, caKey1, _ := ct.NewTestCaCert(
+		cert.Version2, cert.Curve_CURVE25519, time.Time{}, time.Time{}, nil, nil, nil,
+	)
+	ca2, _, caKey2, _ := ct.NewTestCaCert(
+		cert.Version2, cert.Curve_CURVE25519, time.Time{}, time.Time{}, nil, nil, nil,
+	)
+
+	initCS := newTestCertState(
+		t, ca1, caKey1, "init",
+		[]netip.Prefix{netip.MustParsePrefix("10.0.0.1/24")},
+	)
+	respCS := newTestCertState(
+		t, ca2, caKey2, "resp",
+		[]netip.Prefix{netip.MustParsePrefix("10.0.0.2/24")},
+	)
+
+	_, respM, _, _, err := initiateHandshake(
+		t, initCS, testVerifier(ct.NewTestCAPool(ca1)),
+		respCS, testVerifier(ct.NewTestCAPool(ca2)),
+	)
+	require.ErrorContains(t, err, "verify cert")
+	assert.True(t, respM.Failed())
+}
+
+func TestMachineVersionNegotiation(t *testing.T) {
+	ca1, _, caKey1, _ := ct.NewTestCaCert(
+		cert.Version1, cert.Curve_CURVE25519, time.Time{}, time.Time{}, nil, nil, nil,
+	)
+	ca2, _, caKey2, _ := ct.NewTestCaCert(
+		cert.Version2, cert.Curve_CURVE25519, time.Time{}, time.Time{}, nil, nil, nil,
+	)
+	caPool := ct.NewTestCAPool(ca1, ca2)
+
+	makeMultiVersionResp := func(t *testing.T) *testCertState {
+		t.Helper()
+		respCertV1, _, respKeyPEM, _ := ct.NewTestCert(
+			cert.Version1, cert.Curve_CURVE25519, ca1, caKey1, "resp",
+			ca1.NotBefore(), ca1.NotAfter(),
+			[]netip.Prefix{netip.MustParsePrefix("10.0.0.2/24")}, nil, nil,
+		)
+		respKey, _, _, _ := cert.UnmarshalPrivateKeyFromPEM(respKeyPEM)
+		respCertV2, _ := ct.NewTestCertDifferentVersion(respCertV1, cert.Version2, ca2, caKey2)
+		respHsV1, _ := respCertV1.MarshalForHandshakes()
+		respHsV2, _ := respCertV2.MarshalForHandshakes()
+		ncs := noise.NewCipherSuite(noise.DH25519, noise.CipherChaChaPoly, noise.HashSHA256)
+		return &testCertState{
+			version: cert.Version1,
+			creds: map[cert.Version]*Credential{
+				cert.Version1: NewCredential(respCertV1, respHsV1, respKey, ncs),
+				cert.Version2: NewCredential(respCertV2, respHsV2, respKey, ncs),
+			},
+		}
+	}
+
+	t.Run("responder matches initiator version", func(t *testing.T) {
+		initCS := newTestCertState(
+			t, ca2, caKey2, "init",
+			[]netip.Prefix{netip.MustParsePrefix("10.0.0.1/24")},
+		)
+		respCS := makeMultiVersionResp(t)
+		v := testVerifier(caPool)
+
+		initM, _, respResult, resp, err := initiateHandshake(
+			t, initCS, v,
+			respCS, v,
+		)
+		require.NoError(t, err)
+		require.NotNil(t, respResult)
+
+		assert.Equal(t, cert.Version2, respResult.MyCert.Version(),
+			"responder should negotiate to initiator's version")
+
+		_, initResult, err := initM.ProcessPacket(nil, resp)
+		require.NoError(t, err)
+		require.NotNil(t, initResult)
+		assert.Equal(t, cert.Version2, initResult.RemoteCert.Certificate.Version(),
+			"initiator should see V2 cert from responder")
+	})
+
+	t.Run("responder keeps version when no match available", func(t *testing.T) {
+		initCS := newTestCertState(
+			t, ca2, caKey2, "init",
+			[]netip.Prefix{netip.MustParsePrefix("10.0.0.1/24")},
+		)
+
+		respCert, _, respKeyPEM, _ := ct.NewTestCert(
+			cert.Version1, cert.Curve_CURVE25519, ca1, caKey1, "resp",
+			ca1.NotBefore(), ca1.NotAfter(),
+			[]netip.Prefix{netip.MustParsePrefix("10.0.0.2/24")}, nil, nil,
+		)
+		respKey, _, _, _ := cert.UnmarshalPrivateKeyFromPEM(respKeyPEM)
+		respHs, _ := respCert.MarshalForHandshakes()
+		ncs := noise.NewCipherSuite(noise.DH25519, noise.CipherChaChaPoly, noise.HashSHA256)
+		respCS := &testCertState{
+			version: cert.Version1,
+			creds: map[cert.Version]*Credential{
+				cert.Version1: NewCredential(respCert, respHs, respKey, ncs),
+			},
+		}
+
+		v := testVerifier(caPool)
+		_, _, respResult, _, err := initiateHandshake(
+			t, initCS, v,
+			respCS, v,
+		)
+		require.NoError(t, err)
+		require.NotNil(t, respResult)
+
+		assert.Equal(t, cert.Version1, respResult.MyCert.Version(),
+			"responder should keep V1 when V2 not available")
+	})
+}

handshake/patterns.go

@@ -0,0 +1,54 @@
+package handshake
+
+import (
+	"fmt"
+
+	"github.com/flynn/noise"
+	"github.com/slackhq/nebula/header"
+)
+
+// msgFlags tracks what application data a handshake message carries.
+type msgFlags struct {
+	expectsPayload bool // message carries indexes and time
+	expectsCert    bool // message carries the certificate
+}
+
+// subtypeInfo bundles the noise pattern with the per-message flags for a
+// given handshake subtype.
+type subtypeInfo struct {
+	pattern noise.HandshakePattern
+	msgs    []msgFlags
+}
+
+// subtypeInfos defines the noise pattern and message content layout for each
+// handshake subtype.
+var subtypeInfos = map[header.MessageSubType]subtypeInfo{
+	// IX: 2 messages, both carry payload and cert
+	header.HandshakeIXPSK0: {
+		pattern: noise.HandshakeIX,
+		msgs: []msgFlags{
+			{expectsPayload: true, expectsCert: true},
+			{expectsPayload: true, expectsCert: true},
+		},
+	},
+
+	// XX: 3 messages
+	//   msg1 (I->R): payload only
+	//   msg2 (R->I): payload + cert
+	//   msg3 (I->R): cert only
+	//header.HandshakeXXPSK0: {
+	//	pattern: noise.HandshakeXX,
+	//	msgs: []msgFlags{
+	//		{expectsPayload: true, expectsCert: false},
+	//		{expectsPayload: true, expectsCert: true},
+	//		{expectsPayload: false, expectsCert: true},
+	//	},
+	//},
+}
+
+func subtypeInfoFor(subtype header.MessageSubType) (subtypeInfo, error) {
+	if info, ok := subtypeInfos[subtype]; ok {
+		return info, nil
+	}
+	return subtypeInfo{}, fmt.Errorf("%w: %d", ErrUnknownSubtype, subtype)
+}

handshake/patterns_test.go

@@ -0,0 +1,63 @@
+package handshake
+
+import (
+	"testing"
+
+	"github.com/flynn/noise"
+	"github.com/slackhq/nebula/header"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestSubtypeInfo(t *testing.T) {
+	t.Run("IX", func(t *testing.T) {
+		info, err := subtypeInfoFor(header.HandshakeIXPSK0)
+		require.NoError(t, err)
+		assert.Equal(t, noise.HandshakeIX.Name, info.pattern.Name)
+		require.Len(t, info.msgs, 2)
+		// msg1: payload + cert
+		assert.True(t, info.msgs[0].expectsPayload)
+		assert.True(t, info.msgs[0].expectsCert)
+		// msg2: payload + cert
+		assert.True(t, info.msgs[1].expectsPayload)
+		assert.True(t, info.msgs[1].expectsCert)
+	})
+
+	t.Run("XX", func(t *testing.T) {
+		registerTestXXInfo(t)
+		info, err := subtypeInfoFor(header.HandshakeXXPSK0)
+		require.NoError(t, err)
+		assert.Equal(t, noise.HandshakeXX.Name, info.pattern.Name)
+		require.Len(t, info.msgs, 3)
+		// msg1: payload only
+		assert.True(t, info.msgs[0].expectsPayload)
+		assert.False(t, info.msgs[0].expectsCert)
+		// msg2: payload + cert
+		assert.True(t, info.msgs[1].expectsPayload)
+		assert.True(t, info.msgs[1].expectsCert)
+		// msg3: cert only
+		assert.False(t, info.msgs[2].expectsPayload)
+		assert.True(t, info.msgs[2].expectsCert)
+	})
+
+	t.Run("unknown subtype returns error", func(t *testing.T) {
+		_, err := subtypeInfoFor(99)
+		require.ErrorIs(t, err, ErrUnknownSubtype)
+	})
+}
+
+// registerTestXXInfo temporarily registers XX subtype info for testing.
+func registerTestXXInfo(t *testing.T) {
+	t.Helper()
+	subtypeInfos[header.HandshakeXXPSK0] = subtypeInfo{
+		pattern: noise.HandshakeXX,
+		msgs: []msgFlags{
+			{expectsPayload: true, expectsCert: false},
+			{expectsPayload: true, expectsCert: true},
+			{expectsPayload: false, expectsCert: true},
+		},
+	}
+	t.Cleanup(func() {
+		delete(subtypeInfos, header.HandshakeXXPSK0)
+	})
+}

handshake/payload.go

@@ -0,0 +1,173 @@
+package handshake
+
+import (
+	"errors"
+	"math"
+
+	"google.golang.org/protobuf/encoding/protowire"
+)
+
+var (
+	errInvalidHandshakeMessage = errors.New("invalid handshake message")
+	errInvalidHandshakeDetails = errors.New("invalid handshake details")
+)
+
+// Payload represents the decoded fields of a handshake message.
+// Wire format is protobuf-compatible with NebulaHandshake{Details: NebulaHandshakeDetails{...}}.
+type Payload struct {
+	Cert           []byte
+	InitiatorIndex uint32
+	ResponderIndex uint32
+	Time           uint64
+	CertVersion    uint32
+}
+
+// Proto field numbers for NebulaHandshakeDetails
+const (
+	fieldCert           = 1 // bytes
+	fieldInitiatorIndex = 2 // uint32
+	fieldResponderIndex = 3 // uint32
+	fieldTime           = 5 // uint64
+	fieldCertVersion    = 8 // uint32
+)
+
+// MarshalPayload encodes a handshake payload in protobuf wire format compatible
+// with NebulaHandshake{Details: NebulaHandshakeDetails{...}}.
+// Returns out (which may be nil), with the marshalled Payload appended to it.
+func MarshalPayload(out []byte, p Payload) []byte {
+	var details []byte
+
+	if len(p.Cert) > 0 {
+		details = protowire.AppendTag(details, fieldCert, protowire.BytesType)
+		details = protowire.AppendBytes(details, p.Cert)
+	}
+	if p.InitiatorIndex != 0 {
+		details = protowire.AppendTag(details, fieldInitiatorIndex, protowire.VarintType)
+		details = protowire.AppendVarint(details, uint64(p.InitiatorIndex))
+	}
+	if p.ResponderIndex != 0 {
+		details = protowire.AppendTag(details, fieldResponderIndex, protowire.VarintType)
+		details = protowire.AppendVarint(details, uint64(p.ResponderIndex))
+	}
+	if p.Time != 0 {
+		details = protowire.AppendTag(details, fieldTime, protowire.VarintType)
+		details = protowire.AppendVarint(details, p.Time)
+	}
+	if p.CertVersion != 0 {
+		details = protowire.AppendTag(details, fieldCertVersion, protowire.VarintType)
+		details = protowire.AppendVarint(details, uint64(p.CertVersion))
+	}
+
+	out = protowire.AppendTag(out, 1, protowire.BytesType)
+	out = protowire.AppendBytes(out, details)
+
+	return out
+}
+
+// UnmarshalPayload decodes a protobuf-encoded NebulaHandshake message.
+func UnmarshalPayload(b []byte) (Payload, error) {
+	var p Payload
+
+	for len(b) > 0 {
+		num, typ, n := protowire.ConsumeTag(b)
+		if n < 0 {
+			return p, errInvalidHandshakeMessage
+		}
+		b = b[n:]
+
+		switch {
+		case num == 1 && typ == protowire.BytesType:
+			details, n := protowire.ConsumeBytes(b)
+			if n < 0 {
+				return p, errInvalidHandshakeMessage
+			}
+			b = b[n:]
+			if err := unmarshalPayloadDetails(&p, details); err != nil {
+				return p, err
+			}
+		default:
+			n := protowire.ConsumeFieldValue(num, typ, b)
+			if n < 0 {
+				return p, errInvalidHandshakeMessage
+			}
+			b = b[n:]
+		}
+	}
+
+	return p, nil
+}
+
+func unmarshalPayloadDetails(p *Payload, b []byte) error {
+	for len(b) > 0 {
+		num, typ, n := protowire.ConsumeTag(b)
+		if n < 0 {
+			return errInvalidHandshakeDetails
+		}
+		b = b[n:]
+
+		// For known field numbers, reject any non-matching wire type as a
+		// hard error rather than silently skipping. The caller will catch
+		// missing-field cases downstream, but a wire-type mismatch on a tag
+		// we know is a peer protocol violation worth flagging here.
+		// Repeated occurrences of a singular field follow proto3 last-wins.
+		switch num {
+		case fieldCert:
+			if typ != protowire.BytesType {
+				return errInvalidHandshakeDetails
+			}
+			v, n := protowire.ConsumeBytes(b)
+			if n < 0 {
+				return errInvalidHandshakeDetails
+			}
+			p.Cert = append([]byte(nil), v...)
+			b = b[n:]
+		case fieldInitiatorIndex:
+			if typ != protowire.VarintType {
+				return errInvalidHandshakeDetails
+			}
+			v, n := protowire.ConsumeVarint(b)
+			if n < 0 || v > math.MaxUint32 {
+				return errInvalidHandshakeDetails
+			}
+			p.InitiatorIndex = uint32(v)
+			b = b[n:]
+		case fieldResponderIndex:
+			if typ != protowire.VarintType {
+				return errInvalidHandshakeDetails
+			}
+			v, n := protowire.ConsumeVarint(b)
+			if n < 0 || v > math.MaxUint32 {
+				return errInvalidHandshakeDetails
+			}
+			p.ResponderIndex = uint32(v)
+			b = b[n:]
+		case fieldTime:
+			if typ != protowire.VarintType {
+				return errInvalidHandshakeDetails
+			}
+			v, n := protowire.ConsumeVarint(b)
+			if n < 0 {
+				return errInvalidHandshakeDetails
+			}
+			p.Time = v
+			b = b[n:]
+		case fieldCertVersion:
+			if typ != protowire.VarintType {
+				return errInvalidHandshakeDetails
+			}
+			v, n := protowire.ConsumeVarint(b)
+			if n < 0 || v > math.MaxUint32 {
+				return errInvalidHandshakeDetails
+			}
+			p.CertVersion = uint32(v)
+			b = b[n:]
+		default:
+			n := protowire.ConsumeFieldValue(num, typ, b)
+			if n < 0 {
+				return errInvalidHandshakeDetails
+			}
+			b = b[n:]
+		}
+	}
+	return nil
+}

handshake/payload_test.go

@@ -0,0 +1,361 @@
+package handshake
+
+import (
+	"bytes"
+	"math"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"google.golang.org/protobuf/encoding/protowire"
+)
+
+func TestPayloadRoundTrip(t *testing.T) {
+	t.Run("all fields set", func(t *testing.T) {
+		data := MarshalPayload(nil, Payload{
+			Cert:           []byte("test-cert-bytes"),
+			CertVersion:    2,
+			InitiatorIndex: 12345,
+			ResponderIndex: 67890,
+			Time:           1234567890,
+		})
+
+		got, err := UnmarshalPayload(data)
+		require.NoError(t, err)
+
+		assert.Equal(t, []byte("test-cert-bytes"), got.Cert)
+		assert.Equal(t, uint32(12345), got.InitiatorIndex)
+		assert.Equal(t, uint32(67890), got.ResponderIndex)
+		assert.Equal(t, uint64(1234567890), got.Time)
+		assert.Equal(t, uint32(2), got.CertVersion)
+	})
+
+	t.Run("minimal fields", func(t *testing.T) {
+		data := MarshalPayload(nil, Payload{InitiatorIndex: 1})
+
+		got, err := UnmarshalPayload(data)
+		require.NoError(t, err)
+
+		assert.Equal(t, uint32(1), got.InitiatorIndex)
+		assert.Equal(t, uint32(0), got.ResponderIndex)
+		assert.Equal(t, uint64(0), got.Time)
+		assert.Nil(t, got.Cert)
+	})
+
+	t.Run("empty payload", func(t *testing.T) {
+		data := MarshalPayload(nil, Payload{})
+
+		got, err := UnmarshalPayload(data)
+		require.NoError(t, err)
+
+		assert.Equal(t, uint32(0), got.InitiatorIndex)
+	})
+
+	t.Run("large cert bytes", func(t *testing.T) {
+		bigCert := make([]byte, 4096)
+		for i := range bigCert {
+			bigCert[i] = byte(i % 256)
+		}
+
+		data := MarshalPayload(nil, Payload{
+			Cert:           bigCert,
+			CertVersion:    2,
+			InitiatorIndex: 999,
+		})
+
+		got, err := UnmarshalPayload(data)
+		require.NoError(t, err)
+
+		assert.Equal(t, bigCert, got.Cert)
+		assert.Equal(t, uint32(999), got.InitiatorIndex)
+	})
+
+	t.Run("append to existing buffer", func(t *testing.T) {
+		prefix := []byte("prefix")
+		data := MarshalPayload(prefix, Payload{InitiatorIndex: 42})
+
+		assert.Equal(t, []byte("prefix"), data[:6])
+
+		got, err := UnmarshalPayload(data[6:])
+		require.NoError(t, err)
+		assert.Equal(t, uint32(42), got.InitiatorIndex)
+	})
+}
+
+func TestPayloadUnknownFields(t *testing.T) {
+	t.Run("unknown field in outer message is skipped", func(t *testing.T) {
+		// Marshal a normal payload then append an unknown field (field 99, varint)
+		data := MarshalPayload(nil, Payload{InitiatorIndex: 42})
+		data = protowire.AppendTag(data, 99, protowire.VarintType)
+		data = protowire.AppendVarint(data, 12345)
+
+		got, err := UnmarshalPayload(data)
+		require.NoError(t, err)
+		assert.Equal(t, uint32(42), got.InitiatorIndex)
+	})
+
+	t.Run("unknown field in details is skipped", func(t *testing.T) {
+		// Build details with a known field + unknown field
+		var details []byte
+		details = protowire.AppendTag(details, fieldInitiatorIndex, protowire.VarintType)
+		details = protowire.AppendVarint(details, 77)
+		// Unknown field 50, varint
+		details = protowire.AppendTag(details, 50, protowire.VarintType)
+		details = protowire.AppendVarint(details, 9999)
+		// Another known field after the unknown one
+		details = protowire.AppendTag(details, fieldResponderIndex, protowire.VarintType)
+		details = protowire.AppendVarint(details, 88)
+
+		// Wrap in outer message
+		var data []byte
+		data = protowire.AppendTag(data, 1, protowire.BytesType)
+		data = protowire.AppendBytes(data, details)
+
+		got, err := UnmarshalPayload(data)
+		require.NoError(t, err)
+		assert.Equal(t, uint32(77), got.InitiatorIndex)
+		assert.Equal(t, uint32(88), got.ResponderIndex)
+	})
+
+	t.Run("reserved fields 6 and 7 are skipped", func(t *testing.T) {
+		// Fields 6 and 7 are reserved in the proto definition
+		var details []byte
+		details = protowire.AppendTag(details, fieldInitiatorIndex, protowire.VarintType)
+		details = protowire.AppendVarint(details, 100)
+		details = protowire.AppendTag(details, 6, protowire.VarintType)
+		details = protowire.AppendVarint(details, 1)
+		details = protowire.AppendTag(details, 7, protowire.VarintType)
+		details = protowire.AppendVarint(details, 2)
+
+		var data []byte
+		data = protowire.AppendTag(data, 1, protowire.BytesType)
+		data = protowire.AppendBytes(data, details)
+
+		got, err := UnmarshalPayload(data)
+		require.NoError(t, err)
+		assert.Equal(t, uint32(100), got.InitiatorIndex)
+	})
+}
+
+func TestPayloadBytesConsumed(t *testing.T) {
+	t.Run("all bytes consumed on valid input", func(t *testing.T) {
+		original := Payload{
+			Cert:           []byte("cert"),
+			CertVersion:    2,
+			InitiatorIndex: 100,
+			ResponderIndex: 200,
+			Time:           999,
+		}
+		data := MarshalPayload(nil, original)
+
+		got, err := UnmarshalPayload(data)
+		require.NoError(t, err)
+
+		// Re-marshal and compare — proves we consumed and reproduced all fields
+		remarshaled := MarshalPayload(nil, got)
+		assert.Equal(t, data, remarshaled)
+	})
+}
+
+// wrapDetails wraps raw detail bytes in the outer NebulaHandshake envelope
+// so UnmarshalPayload can reach unmarshalPayloadDetails.
+func wrapDetails(details []byte) []byte {
+	var out []byte
+	out = protowire.AppendTag(out, 1, protowire.BytesType)
+	out = protowire.AppendBytes(out, details)
+	return out
+}
+
+func TestPayloadUnmarshalErrors(t *testing.T) {
+	t.Run("nil input", func(t *testing.T) {
+		got, err := UnmarshalPayload(nil)
+		require.NoError(t, err)
+		assert.Equal(t, uint32(0), got.InitiatorIndex)
+	})
+
+	t.Run("truncated outer tag", func(t *testing.T) {
+		_, err := UnmarshalPayload([]byte{0x80})
+		assert.Error(t, err)
+	})
+
+	t.Run("truncated outer details field", func(t *testing.T) {
+		_, err := UnmarshalPayload([]byte{0x0a, 0x64, 0x01, 0x02, 0x03, 0x04, 0x05})
+		assert.Error(t, err)
+	})
+
+	t.Run("truncated outer unknown field", func(t *testing.T) {
+		// Valid tag for unknown field 99 varint, but no value follows
+		var data []byte
+		data = protowire.AppendTag(data, 99, protowire.VarintType)
+		_, err := UnmarshalPayload(data)
+		assert.Error(t, err)
+	})
+
+	t.Run("truncated details tag", func(t *testing.T) {
+		_, err := UnmarshalPayload(wrapDetails([]byte{0x80}))
+		assert.Error(t, err)
+	})
+
+	t.Run("truncated cert bytes", func(t *testing.T) {
+		// Field 1 (cert), bytes type, length 10 but only 2 bytes
+		var details []byte
+		details = protowire.AppendTag(details, fieldCert, protowire.BytesType)
+		details = append(details, 0x0a, 0x01, 0x02) // length 10, only 2 bytes
+		_, err := UnmarshalPayload(wrapDetails(details))
+		assert.Error(t, err)
+	})
+
+	t.Run("truncated initiator index varint", func(t *testing.T) {
+		var details []byte
+		details = protowire.AppendTag(details, fieldInitiatorIndex, protowire.VarintType)
+		details = append(details, 0x80) // incomplete varint
+		_, err := UnmarshalPayload(wrapDetails(details))
+		assert.Error(t, err)
+	})
+
+	t.Run("truncated responder index varint", func(t *testing.T) {
+		var details []byte
+		details = protowire.AppendTag(details, fieldResponderIndex, protowire.VarintType)
+		details = append(details, 0x80)
+		_, err := UnmarshalPayload(wrapDetails(details))
+		assert.Error(t, err)
+	})
+
+	t.Run("truncated time varint", func(t *testing.T) {
+		var details []byte
+		details = protowire.AppendTag(details, fieldTime, protowire.VarintType)
+		details = append(details, 0x80)
+		_, err := UnmarshalPayload(wrapDetails(details))
+		assert.Error(t, err)
+	})
+
+	t.Run("truncated cert version varint", func(t *testing.T) {
+		var details []byte
+		details = protowire.AppendTag(details, fieldCertVersion, protowire.VarintType)
+		details = append(details, 0x80)
+		_, err := UnmarshalPayload(wrapDetails(details))
+		assert.Error(t, err)
+	})
+
+	t.Run("truncated unknown field in details", func(t *testing.T) {
+		var details []byte
+		details = protowire.AppendTag(details, 50, protowire.VarintType)
+		details = append(details, 0x80) // incomplete varint
+		_, err := UnmarshalPayload(wrapDetails(details))
+		assert.Error(t, err)
+	})
+
+	t.Run("cert with wrong wire type rejected", func(t *testing.T) {
+		// fieldCert as Varint instead of Bytes.
+		var details []byte
+		details = protowire.AppendTag(details, fieldCert, protowire.VarintType)
+		details = protowire.AppendVarint(details, 42)
+		_, err := UnmarshalPayload(wrapDetails(details))
+		assert.Error(t, err)
+	})
+
+	t.Run("initiator index with wrong wire type rejected", func(t *testing.T) {
+		// fieldInitiatorIndex as Bytes instead of Varint.
+		var details []byte
+		details = protowire.AppendTag(details, fieldInitiatorIndex, protowire.BytesType)
+		details = protowire.AppendBytes(details, []byte{1, 2, 3})
+		_, err := UnmarshalPayload(wrapDetails(details))
+		assert.Error(t, err)
+	})
+
+	t.Run("time with wrong wire type rejected", func(t *testing.T) {
+		var details []byte
+		details = protowire.AppendTag(details, fieldTime, protowire.BytesType)
+		details = protowire.AppendBytes(details, []byte{1, 2, 3})
+		_, err := UnmarshalPayload(wrapDetails(details))
+		assert.Error(t, err)
+	})
+
+	t.Run("cert version with wrong wire type rejected", func(t *testing.T) {
+		var details []byte
+		details = protowire.AppendTag(details, fieldCertVersion, protowire.BytesType)
+		details = protowire.AppendBytes(details, []byte{1, 2, 3})
+		_, err := UnmarshalPayload(wrapDetails(details))
+		assert.Error(t, err)
+	})
+
+	t.Run("repeated singular field follows proto3 last-wins", func(t *testing.T) {
+		// Per proto3, multiple instances of a singular field are accepted and
+		// the last value wins. We keep this behavior so that peers using
+		// alternative encoders aren't rejected.
+		var details []byte
+		details = protowire.AppendTag(details, fieldInitiatorIndex, protowire.VarintType)
+		details = protowire.AppendVarint(details, 1)
+		details = protowire.AppendTag(details, fieldInitiatorIndex, protowire.VarintType)
+		details = protowire.AppendVarint(details, 42)
+		got, err := UnmarshalPayload(wrapDetails(details))
+		require.NoError(t, err)
+		assert.Equal(t, uint32(42), got.InitiatorIndex)
+	})
+
+	t.Run("initiator index varint overflow rejected", func(t *testing.T) {
+		var details []byte
+		details = protowire.AppendTag(details, fieldInitiatorIndex, protowire.VarintType)
+		details = protowire.AppendVarint(details, math.MaxUint32+1)
+		_, err := UnmarshalPayload(wrapDetails(details))
+		assert.Error(t, err)
+	})
+
+	t.Run("cert version varint overflow rejected", func(t *testing.T) {
+		var details []byte
+		details = protowire.AppendTag(details, fieldCertVersion, protowire.VarintType)
+		details = protowire.AppendVarint(details, math.MaxUint32+1)
+		_, err := UnmarshalPayload(wrapDetails(details))
+		assert.Error(t, err)
+	})
+
+}
+
+// FuzzPayload feeds arbitrary bytes through UnmarshalPayload to confirm it
+// never panics, and for any input that parses cleanly, that re-marshal +
+// re-parse is a fix-point. Inputs come from an authenticated peer (post-
+// noise-decrypt), so the threat model is "valid peer behaving arbitrarily,"
+// not "unauthenticated injection."
+func FuzzPayload(f *testing.F) {
+	// Seed corpus with a handful of known-good shapes.
+	f.Add(MarshalPayload(nil, Payload{}))
+	f.Add(MarshalPayload(nil, Payload{Cert: []byte{1, 2, 3}, CertVersion: 2}))
+	f.Add(MarshalPayload(nil, Payload{InitiatorIndex: 42, Time: 1}))
+	f.Add(MarshalPayload(nil, Payload{
+		Cert:           []byte("seed-cert"),
+		InitiatorIndex: 1,
+		ResponderIndex: 2,
+		Time:           3,
+		CertVersion:    2,
+	}))
+	f.Add([]byte{})
+	f.Add([]byte{0xff})
+
+	f.Fuzz(func(t *testing.T, data []byte) {
+		p1, err := UnmarshalPayload(data)
+		if err != nil {
+			return
+		}
+
+		// For any input that parses, re-marshaling and re-parsing must
+		// yield an equivalent Payload. This catches dispatch bugs (e.g.
+		// emitting a field on marshal that we don't accept on parse) and
+		// any non-idempotent parsing behavior.
+		b2 := MarshalPayload(nil, p1)
+		p2, err := UnmarshalPayload(b2)
+		if err != nil {
+			t.Fatalf("re-parse of self-marshaled payload failed: %v\nintermediate: %x\n", err, b2)
+		}
+		if !payloadsEqual(p1, p2) {
+			t.Fatalf("re-marshal not idempotent\nfirst:  %+v\nsecond: %+v", p1, p2)
+		}
+	})
+}
+
+func payloadsEqual(a, b Payload) bool {
+	return bytes.Equal(a.Cert, b.Cert) &&
+		a.InitiatorIndex == b.InitiatorIndex &&
+		a.ResponderIndex == b.ResponderIndex &&
+		a.Time == b.Time &&
+		a.CertVersion == b.CertVersion
+}

handshake_ix.go

@@ -1,678 +0,0 @@
-package nebula
-
-import (
-	"bytes"
-	"net/netip"
-	"time"
-
-	"github.com/flynn/noise"
-	"github.com/sirupsen/logrus"
-	"github.com/slackhq/nebula/cert"
-	"github.com/slackhq/nebula/header"
-)
-
-// NOISE IX Handshakes
-
-// This function constructs a handshake packet, but does not actually send it
-// Sending is done by the handshake manager
-func ixHandshakeStage0(f *Interface, hh *HandshakeHostInfo) bool {
-	err := f.handshakeManager.allocateIndex(hh)
-	if err != nil {
-		f.l.WithError(err).WithField("vpnAddrs", hh.hostinfo.vpnAddrs).
-			WithField("handshake", m{"stage": 0, "style": "ix_psk0"}).Error("Failed to generate index")
-		return false
-	}
-
-	cs := f.pki.getCertState()
-	v := cs.initiatingVersion
-	if hh.initiatingVersionOverride != cert.VersionPre1 {
-		v = hh.initiatingVersionOverride
-	} else if v < cert.Version2 {
-		// If we're connecting to a v6 address we should encourage use of a V2 cert
-		for _, a := range hh.hostinfo.vpnAddrs {
-			if a.Is6() {
-				v = cert.Version2
-				break
-			}
-		}
-	}
-
-	crt := cs.getCertificate(v)
-	if crt == nil {
-		f.l.WithField("vpnAddrs", hh.hostinfo.vpnAddrs).
-			WithField("handshake", m{"stage": 0, "style": "ix_psk0"}).
-			WithField("certVersion", v).
-			Error("Unable to handshake with host because no certificate is available")
-		return false
-	}
-
-	crtHs := cs.getHandshakeBytes(v)
-	if crtHs == nil {
-		f.l.WithField("vpnAddrs", hh.hostinfo.vpnAddrs).
-			WithField("handshake", m{"stage": 0, "style": "ix_psk0"}).
-			WithField("certVersion", v).
-			Error("Unable to handshake with host because no certificate handshake bytes is available")
-		return false
-	}
-
-	ci, err := NewConnectionState(f.l, cs, crt, true, noise.HandshakeIX)
-	if err != nil {
-		f.l.WithError(err).WithField("vpnAddrs", hh.hostinfo.vpnAddrs).
-			WithField("handshake", m{"stage": 0, "style": "ix_psk0"}).
-			WithField("certVersion", v).
-			Error("Failed to create connection state")
-		return false
-	}
-	hh.hostinfo.ConnectionState = ci
-
-	hs := &NebulaHandshake{
-		Details: &NebulaHandshakeDetails{
-			InitiatorIndex: hh.hostinfo.localIndexId,
-			Time:           uint64(time.Now().UnixNano()),
-			Cert:           crtHs,
-			CertVersion:    uint32(v),
-		},
-	}
-
-	hsBytes, err := hs.Marshal()
-	if err != nil {
-		f.l.WithError(err).WithField("vpnAddrs", hh.hostinfo.vpnAddrs).
-			WithField("certVersion", v).
-			WithField("handshake", m{"stage": 0, "style": "ix_psk0"}).Error("Failed to marshal handshake message")
-		return false
-	}
-
-	h := header.Encode(make([]byte, header.Len), header.Version, header.Handshake, header.HandshakeIXPSK0, 0, 1)
-
-	msg, _, _, err := ci.H.WriteMessage(h, hsBytes)
-	if err != nil {
-		f.l.WithError(err).WithField("vpnAddrs", hh.hostinfo.vpnAddrs).
-			WithField("handshake", m{"stage": 0, "style": "ix_psk0"}).Error("Failed to call noise.WriteMessage")
-		return false
-	}
-
-	// We are sending handshake packet 1, so we don't expect to receive
-	// handshake packet 1 from the responder
-	ci.window.Update(f.l, 1)
-
-	hh.hostinfo.HandshakePacket[0] = msg
-	hh.ready = true
-	return true
-}
-
-func ixHandshakeStage1(f *Interface, via ViaSender, packet []byte, h *header.H) {
-	cs := f.pki.getCertState()
-	crt := cs.GetDefaultCertificate()
-	if crt == nil {
-		f.l.WithField("from", via).
-			WithField("handshake", m{"stage": 0, "style": "ix_psk0"}).
-			WithField("certVersion", cs.initiatingVersion).
-			Error("Unable to handshake with host because no certificate is available")
-		return
-	}
-
-	ci, err := NewConnectionState(f.l, cs, crt, false, noise.HandshakeIX)
-	if err != nil {
-		f.l.WithError(err).WithField("from", via).
-			WithField("handshake", m{"stage": 1, "style": "ix_psk0"}).
-			Error("Failed to create connection state")
-		return
-	}
-
-	// Mark packet 1 as seen so it doesn't show up as missed
-	ci.window.Update(f.l, 1)
-
-	msg, _, _, err := ci.H.ReadMessage(nil, packet[header.Len:])
-	if err != nil {
-		f.l.WithError(err).WithField("from", via).
-			WithField("handshake", m{"stage": 1, "style": "ix_psk0"}).
-			Error("Failed to call noise.ReadMessage")
-		return
-	}
-
-	hs := &NebulaHandshake{}
-	err = hs.Unmarshal(msg)
-	if err != nil || hs.Details == nil {
-		f.l.WithError(err).WithField("from", via).
-			WithField("handshake", m{"stage": 1, "style": "ix_psk0"}).
-			Error("Failed unmarshal handshake message")
-		return
-	}
-
-	rc, err := cert.Recombine(cert.Version(hs.Details.CertVersion), hs.Details.Cert, ci.H.PeerStatic(), ci.Curve())
-	if err != nil {
-		f.l.WithError(err).WithField("from", via).
-			WithField("handshake", m{"stage": 1, "style": "ix_psk0"}).
-			Info("Handshake did not contain a certificate")
-		return
-	}
-
-	remoteCert, err := f.pki.GetCAPool().VerifyCertificate(time.Now(), rc)
-	if err != nil {
-		fp, fperr := rc.Fingerprint()
-		if fperr != nil {
-			fp = "<error generating certificate fingerprint>"
-		}
-
-		e := f.l.WithError(err).WithField("from", via).
-			WithField("handshake", m{"stage": 1, "style": "ix_psk0"}).
-			WithField("certVpnNetworks", rc.Networks()).
-			WithField("certFingerprint", fp)
-
-		if f.l.Level >= logrus.DebugLevel {
-			e = e.WithField("cert", rc)
-		}
-
-		e.Info("Invalid certificate from host")
-		return
-	}
-
-	if !bytes.Equal(remoteCert.Certificate.PublicKey(), ci.H.PeerStatic()) {
-		f.l.WithField("from", via).
-			WithField("handshake", m{"stage": 1, "style": "ix_psk0"}).
-			WithField("cert", remoteCert).Info("public key mismatch between certificate and handshake")
-		return
-	}
-
-	if remoteCert.Certificate.Version() != ci.myCert.Version() {
-		// We started off using the wrong certificate version, lets see if we can match the version that was sent to us
-		myCertOtherVersion := cs.getCertificate(remoteCert.Certificate.Version())
-		if myCertOtherVersion == nil {
-			if f.l.Level >= logrus.DebugLevel {
-				f.l.WithError(err).WithFields(m{
-					"from":      via,
-					"handshake": m{"stage": 1, "style": "ix_psk0"},
-					"cert":      remoteCert,
-				}).Debug("Might be unable to handshake with host due to missing certificate version")
-			}
-		} else {
-			// Record the certificate we are actually using
-			ci.myCert = myCertOtherVersion
-		}
-	}
-
-	if len(remoteCert.Certificate.Networks()) == 0 {
-		f.l.WithError(err).WithField("from", via).
-			WithField("cert", remoteCert).
-			WithField("handshake", m{"stage": 1, "style": "ix_psk0"}).
-			Info("No networks in certificate")
-		return
-	}
-
-	certName := remoteCert.Certificate.Name()
-	certVersion := remoteCert.Certificate.Version()
-	fingerprint := remoteCert.Fingerprint
-	issuer := remoteCert.Certificate.Issuer()
-	vpnNetworks := remoteCert.Certificate.Networks()
-
-	anyVpnAddrsInCommon := false
-	vpnAddrs := make([]netip.Addr, len(vpnNetworks))
-	for i, network := range vpnNetworks {
-		if f.myVpnAddrsTable.Contains(network.Addr()) {
-			f.l.WithField("vpnNetworks", vpnNetworks).WithField("from", via).
-				WithField("certName", certName).
-				WithField("certVersion", certVersion).
-				WithField("fingerprint", fingerprint).
-				WithField("issuer", issuer).
-				WithField("handshake", m{"stage": 1, "style": "ix_psk0"}).Error("Refusing to handshake with myself")
-			return
-		}
-		vpnAddrs[i] = network.Addr()
-		if f.myVpnNetworksTable.Contains(network.Addr()) {
-			anyVpnAddrsInCommon = true
-		}
-	}
-
-	if !via.IsRelayed {
-		// We only want to apply the remote allow list for direct tunnels here
-		if !f.lightHouse.GetRemoteAllowList().AllowAll(vpnAddrs, via.UdpAddr.Addr()) {
-			f.l.WithField("vpnAddrs", vpnAddrs).WithField("from", via).
-				Debug("lighthouse.remote_allow_list denied incoming handshake")
-			return
-		}
-	}
-
-	myIndex, err := generateIndex(f.l)
-	if err != nil {
-		f.l.WithError(err).WithField("vpnAddrs", vpnAddrs).WithField("from", via).
-			WithField("certName", certName).
-			WithField("certVersion", certVersion).
-			WithField("fingerprint", fingerprint).
-			WithField("issuer", issuer).
-			WithField("handshake", m{"stage": 1, "style": "ix_psk0"}).Error("Failed to generate index")
-		return
-	}
-
-	hostinfo := &HostInfo{
-		ConnectionState:   ci,
-		localIndexId:      myIndex,
-		remoteIndexId:     hs.Details.InitiatorIndex,
-		vpnAddrs:          vpnAddrs,
-		HandshakePacket:   make(map[uint8][]byte, 0),
-		lastHandshakeTime: hs.Details.Time,
-		relayState: RelayState{
-			relays:         nil,
-			relayForByAddr: map[netip.Addr]*Relay{},
-			relayForByIdx:  map[uint32]*Relay{},
-		},
-	}
-
-	msgRxL := f.l.WithFields(m{
-		"vpnAddrs":       vpnAddrs,
-		"from":           via,
-		"certName":       certName,
-		"certVersion":    certVersion,
-		"fingerprint":    fingerprint,
-		"issuer":         issuer,
-		"initiatorIndex": hs.Details.InitiatorIndex,
-		"responderIndex": hs.Details.ResponderIndex,
-		"remoteIndex":    h.RemoteIndex,
-		"handshake":      m{"stage": 1, "style": "ix_psk0"},
-	})
-
-	if anyVpnAddrsInCommon {
-		msgRxL.Info("Handshake message received")
-	} else {
-		//todo warn if not lighthouse or relay?
-		msgRxL.Info("Handshake message received, but no vpnNetworks in common.")
-	}
-
-	hs.Details.ResponderIndex = myIndex
-	hs.Details.Cert = cs.getHandshakeBytes(ci.myCert.Version())
-	if hs.Details.Cert == nil {
-		msgRxL.WithField("myCertVersion", ci.myCert.Version()).
-			Error("Unable to handshake with host because no certificate handshake bytes is available")
-		return
-	}
-
-	hs.Details.CertVersion = uint32(ci.myCert.Version())
-	// Update the time in case their clock is way off from ours
-	hs.Details.Time = uint64(time.Now().UnixNano())
-
-	hsBytes, err := hs.Marshal()
-	if err != nil {
-		f.l.WithError(err).WithField("vpnAddrs", hostinfo.vpnAddrs).WithField("from", via).
-			WithField("certName", certName).
-			WithField("certVersion", certVersion).
-			WithField("fingerprint", fingerprint).
-			WithField("issuer", issuer).
-			WithField("handshake", m{"stage": 1, "style": "ix_psk0"}).Error("Failed to marshal handshake message")
-		return
-	}
-
-	nh := header.Encode(make([]byte, header.Len), header.Version, header.Handshake, header.HandshakeIXPSK0, hs.Details.InitiatorIndex, 2)
-	msg, dKey, eKey, err := ci.H.WriteMessage(nh, hsBytes)
-	if err != nil {
-		f.l.WithError(err).WithField("vpnAddrs", hostinfo.vpnAddrs).WithField("from", via).
-			WithField("certName", certName).
-			WithField("certVersion", certVersion).
-			WithField("fingerprint", fingerprint).
-			WithField("issuer", issuer).
-			WithField("handshake", m{"stage": 1, "style": "ix_psk0"}).Error("Failed to call noise.WriteMessage")
-		return
-	} else if dKey == nil || eKey == nil {
-		f.l.WithField("vpnAddrs", hostinfo.vpnAddrs).WithField("from", via).
-			WithField("certName", certName).
-			WithField("certVersion", certVersion).
-			WithField("fingerprint", fingerprint).
-			WithField("issuer", issuer).
-			WithField("handshake", m{"stage": 1, "style": "ix_psk0"}).Error("Noise did not arrive at a key")
-		return
-	}
-
-	hostinfo.HandshakePacket[0] = make([]byte, len(packet[header.Len:]))
-	copy(hostinfo.HandshakePacket[0], packet[header.Len:])
-
-	// Regardless of whether you are the sender or receiver, you should arrive here
-	// and complete standing up the connection.
-	hostinfo.HandshakePacket[2] = make([]byte, len(msg))
-	copy(hostinfo.HandshakePacket[2], msg)
-
-	// We are sending handshake packet 2, so we don't expect to receive
-	// handshake packet 2 from the initiator.
-	ci.window.Update(f.l, 2)
-
-	ci.peerCert = remoteCert
-	ci.dKey = NewNebulaCipherState(dKey)
-	ci.eKey = NewNebulaCipherState(eKey)
-
-	hostinfo.remotes = f.lightHouse.QueryCache(vpnAddrs)
-	if !via.IsRelayed {
-		hostinfo.SetRemote(via.UdpAddr)
-	}
-	hostinfo.buildNetworks(f.myVpnNetworksTable, remoteCert.Certificate)
-
-	existing, err := f.handshakeManager.CheckAndComplete(hostinfo, 0, f)
-	if err != nil {
-		switch err {
-		case ErrAlreadySeen:
-			// Update remote if preferred
-			if existing.SetRemoteIfPreferred(f.hostMap, via) {
-				// Send a test packet to ensure the other side has also switched to
-				// the preferred remote
-				f.SendMessageToVpnAddr(header.Test, header.TestRequest, vpnAddrs[0], []byte(""), make([]byte, 12, 12), make([]byte, mtu))
-			}
-
-			msg = existing.HandshakePacket[2]
-			f.messageMetrics.Tx(header.Handshake, header.MessageSubType(msg[1]), 1)
-			if !via.IsRelayed {
-				err := f.outside.WriteTo(msg, via.UdpAddr)
-				if err != nil {
-					f.l.WithField("vpnAddrs", existing.vpnAddrs).WithField("from", via).
-						WithField("handshake", m{"stage": 2, "style": "ix_psk0"}).WithField("cached", true).
-						WithError(err).Error("Failed to send handshake message")
-				} else {
-					f.l.WithField("vpnAddrs", existing.vpnAddrs).WithField("from", via).
-						WithField("handshake", m{"stage": 2, "style": "ix_psk0"}).WithField("cached", true).
-						Info("Handshake message sent")
-				}
-				return
-			} else {
-				if via.relay == nil {
-					f.l.Error("Handshake send failed: both addr and via.relay are nil.")
-					return
-				}
-				hostinfo.relayState.InsertRelayTo(via.relayHI.vpnAddrs[0])
-				f.SendVia(via.relayHI, via.relay, msg, make([]byte, 12), make([]byte, mtu), false)
-				f.l.WithField("vpnAddrs", existing.vpnAddrs).WithField("relay", via.relayHI.vpnAddrs[0]).
-					WithField("handshake", m{"stage": 2, "style": "ix_psk0"}).WithField("cached", true).
-					Info("Handshake message sent")
-				return
-			}
-		case ErrExistingHostInfo:
-			// This means there was an existing tunnel and this handshake was older than the one we are currently based on
-			f.l.WithField("vpnAddrs", vpnAddrs).WithField("from", via).
-				WithField("certName", certName).
-				WithField("certVersion", certVersion).
-				WithField("oldHandshakeTime", existing.lastHandshakeTime).
-				WithField("newHandshakeTime", hostinfo.lastHandshakeTime).
-				WithField("fingerprint", fingerprint).
-				WithField("issuer", issuer).
-				WithField("initiatorIndex", hs.Details.InitiatorIndex).WithField("responderIndex", hs.Details.ResponderIndex).
-				WithField("remoteIndex", h.RemoteIndex).WithField("handshake", m{"stage": 1, "style": "ix_psk0"}).
-				Info("Handshake too old")
-
-			// Send a test packet to trigger an authenticated tunnel test, this should suss out any lingering tunnel issues
-			f.SendMessageToVpnAddr(header.Test, header.TestRequest, vpnAddrs[0], []byte(""), make([]byte, 12, 12), make([]byte, mtu))
-			return
-		case ErrLocalIndexCollision:
-			// This means we failed to insert because of collision on localIndexId. Just let the next handshake packet retry
-			f.l.WithField("vpnAddrs", vpnAddrs).WithField("from", via).
-				WithField("certName", certName).
-				WithField("certVersion", certVersion).
-				WithField("fingerprint", fingerprint).
-				WithField("issuer", issuer).
-				WithField("initiatorIndex", hs.Details.InitiatorIndex).WithField("responderIndex", hs.Details.ResponderIndex).
-				WithField("remoteIndex", h.RemoteIndex).WithField("handshake", m{"stage": 1, "style": "ix_psk0"}).
-				WithField("localIndex", hostinfo.localIndexId).WithField("collision", existing.vpnAddrs).
-				Error("Failed to add HostInfo due to localIndex collision")
-			return
-		default:
-			// Shouldn't happen, but just in case someone adds a new error type to CheckAndComplete
-			// And we forget to update it here
-			f.l.WithError(err).WithField("vpnAddrs", vpnAddrs).WithField("from", via).
-				WithField("certName", certName).
-				WithField("certVersion", certVersion).
-				WithField("fingerprint", fingerprint).
-				WithField("issuer", issuer).
-				WithField("initiatorIndex", hs.Details.InitiatorIndex).WithField("responderIndex", hs.Details.ResponderIndex).
-				WithField("remoteIndex", h.RemoteIndex).WithField("handshake", m{"stage": 1, "style": "ix_psk0"}).
-				Error("Failed to add HostInfo to HostMap")
-			return
-		}
-	}
-
-	// Do the send
-	f.messageMetrics.Tx(header.Handshake, header.MessageSubType(msg[1]), 1)
-	if !via.IsRelayed {
-		err = f.outside.WriteTo(msg, via.UdpAddr)
-		log := f.l.WithField("vpnAddrs", vpnAddrs).WithField("from", via).
-			WithField("certName", certName).
-			WithField("certVersion", certVersion).
-			WithField("fingerprint", fingerprint).
-			WithField("issuer", issuer).
-			WithField("initiatorIndex", hs.Details.InitiatorIndex).WithField("responderIndex", hs.Details.ResponderIndex).
-			WithField("remoteIndex", h.RemoteIndex).WithField("handshake", m{"stage": 2, "style": "ix_psk0"})
-		if err != nil {
-			log.WithError(err).Error("Failed to send handshake")
-		} else {
-			log.Info("Handshake message sent")
-		}
-	} else {
-		if via.relay == nil {
-			f.l.Error("Handshake send failed: both addr and via.relay are nil.")
-			return
-		}
-		hostinfo.relayState.InsertRelayTo(via.relayHI.vpnAddrs[0])
-		// I successfully received a handshake. Just in case I marked this tunnel as 'Disestablished', ensure
-		// it's correctly marked as working.
-		via.relayHI.relayState.UpdateRelayForByIdxState(via.remoteIdx, Established)
-		f.SendVia(via.relayHI, via.relay, msg, make([]byte, 12), make([]byte, mtu), false)
-		f.l.WithField("vpnAddrs", vpnAddrs).WithField("relay", via.relayHI.vpnAddrs[0]).
-			WithField("certName", certName).
-			WithField("certVersion", certVersion).
-			WithField("fingerprint", fingerprint).
-			WithField("issuer", issuer).
-			WithField("initiatorIndex", hs.Details.InitiatorIndex).WithField("responderIndex", hs.Details.ResponderIndex).
-			WithField("remoteIndex", h.RemoteIndex).WithField("handshake", m{"stage": 2, "style": "ix_psk0"}).
-			Info("Handshake message sent")
-	}
-
-	f.connectionManager.AddTrafficWatch(hostinfo)
-
-	hostinfo.remotes.RefreshFromHandshake(vpnAddrs)
-
-	return
-}
-
-func ixHandshakeStage2(f *Interface, via ViaSender, hh *HandshakeHostInfo, packet []byte, h *header.H) bool {
-	if hh == nil {
-		// Nothing here to tear down, got a bogus stage 2 packet
-		return true
-	}
-
-	hh.Lock()
-	defer hh.Unlock()
-
-	hostinfo := hh.hostinfo
-	if !via.IsRelayed {
-		// The vpnAddr we know about is the one we tried to handshake with, use it to apply the remote allow list.
-		if !f.lightHouse.GetRemoteAllowList().AllowAll(hostinfo.vpnAddrs, via.UdpAddr.Addr()) {
-			f.l.WithField("vpnAddrs", hostinfo.vpnAddrs).WithField("from", via).Debug("lighthouse.remote_allow_list denied incoming handshake")
-			return false
-		}
-	}
-
-	ci := hostinfo.ConnectionState
-	msg, eKey, dKey, err := ci.H.ReadMessage(nil, packet[header.Len:])
-	if err != nil {
-		f.l.WithError(err).WithField("vpnAddrs", hostinfo.vpnAddrs).WithField("from", via).
-			WithField("handshake", m{"stage": 2, "style": "ix_psk0"}).WithField("header", h).
-			Error("Failed to call noise.ReadMessage")
-
-		// We don't want to tear down the connection on a bad ReadMessage because it could be an attacker trying
-		// to DOS us. Every other error condition after should to allow a possible good handshake to complete in the
-		// near future
-		return false
-	} else if dKey == nil || eKey == nil {
-		f.l.WithField("vpnAddrs", hostinfo.vpnAddrs).WithField("from", via).
-			WithField("handshake", m{"stage": 2, "style": "ix_psk0"}).
-			Error("Noise did not arrive at a key")
-
-		// This should be impossible in IX but just in case, if we get here then there is no chance to recover
-		// the handshake state machine. Tear it down
-		return true
-	}
-
-	hs := &NebulaHandshake{}
-	err = hs.Unmarshal(msg)
-	if err != nil || hs.Details == nil {
-		f.l.WithError(err).WithField("vpnAddrs", hostinfo.vpnAddrs).WithField("from", via).
-			WithField("handshake", m{"stage": 2, "style": "ix_psk0"}).Error("Failed unmarshal handshake message")
-
-		// The handshake state machine is complete, if things break now there is no chance to recover. Tear down and start again
-		return true
-	}
-
-	rc, err := cert.Recombine(cert.Version(hs.Details.CertVersion), hs.Details.Cert, ci.H.PeerStatic(), ci.Curve())
-	if err != nil {
-		f.l.WithError(err).WithField("from", via).
-			WithField("vpnAddrs", hostinfo.vpnAddrs).
-			WithField("handshake", m{"stage": 2, "style": "ix_psk0"}).
-			Info("Handshake did not contain a certificate")
-		return true
-	}
-
-	remoteCert, err := f.pki.GetCAPool().VerifyCertificate(time.Now(), rc)
-	if err != nil {
-		fp, err := rc.Fingerprint()
-		if err != nil {
-			fp = "<error generating certificate fingerprint>"
-		}
-
-		e := f.l.WithError(err).WithField("from", via).
-			WithField("vpnAddrs", hostinfo.vpnAddrs).
-			WithField("handshake", m{"stage": 2, "style": "ix_psk0"}).
-			WithField("certFingerprint", fp).
-			WithField("certVpnNetworks", rc.Networks())
-
-		if f.l.Level >= logrus.DebugLevel {
-			e = e.WithField("cert", rc)
-		}
-
-		e.Info("Invalid certificate from host")
-		return true
-	}
-	if !bytes.Equal(remoteCert.Certificate.PublicKey(), ci.H.PeerStatic()) {
-		f.l.WithField("from", via).
-			WithField("handshake", m{"stage": 2, "style": "ix_psk0"}).
-			WithField("cert", remoteCert).Info("public key mismatch between certificate and handshake")
-		return true
-	}
-
-	if len(remoteCert.Certificate.Networks()) == 0 {
-		f.l.WithError(err).WithField("from", via).
-			WithField("vpnAddrs", hostinfo.vpnAddrs).
-			WithField("cert", remoteCert).
-			WithField("handshake", m{"stage": 2, "style": "ix_psk0"}).
-			Info("No networks in certificate")
-		return true
-	}
-
-	vpnNetworks := remoteCert.Certificate.Networks()
-	certName := remoteCert.Certificate.Name()
-	certVersion := remoteCert.Certificate.Version()
-	fingerprint := remoteCert.Fingerprint
-	issuer := remoteCert.Certificate.Issuer()
-
-	hostinfo.remoteIndexId = hs.Details.ResponderIndex
-	hostinfo.lastHandshakeTime = hs.Details.Time
-
-	// Store their cert and our symmetric keys
-	ci.peerCert = remoteCert
-	ci.dKey = NewNebulaCipherState(dKey)
-	ci.eKey = NewNebulaCipherState(eKey)
-
-	// Make sure the current udpAddr being used is set for responding
-	if !via.IsRelayed {
-		hostinfo.SetRemote(via.UdpAddr)
-	} else {
-		hostinfo.relayState.InsertRelayTo(via.relayHI.vpnAddrs[0])
-	}
-
-	correctHostResponded := false
-	anyVpnAddrsInCommon := false
-	vpnAddrs := make([]netip.Addr, len(vpnNetworks))
-	for i, network := range vpnNetworks {
-		vpnAddrs[i] = network.Addr()
-		if f.myVpnNetworksTable.Contains(network.Addr()) {
-			anyVpnAddrsInCommon = true
-		}
-		if hostinfo.vpnAddrs[0] == network.Addr() {
-			// todo is it more correct to see if any of hostinfo.vpnAddrs are in the cert? it should have len==1, but one day it might not?
-			correctHostResponded = true
-		}
-	}
-
-	// Ensure the right host responded
-	if !correctHostResponded {
-		f.l.WithField("intendedVpnAddrs", hostinfo.vpnAddrs).WithField("haveVpnNetworks", vpnNetworks).
-			WithField("from", via).
-			WithField("certName", certName).
-			WithField("certVersion", certVersion).
-			WithField("handshake", m{"stage": 2, "style": "ix_psk0"}).
-			Info("Incorrect host responded to handshake")
-
-		// Release our old handshake from pending, it should not continue
-		f.handshakeManager.DeleteHostInfo(hostinfo)
-
-		// Create a new hostinfo/handshake for the intended vpn ip
-		//TODO is hostinfo.vpnAddrs[0] always the address to use?
-		f.handshakeManager.StartHandshake(hostinfo.vpnAddrs[0], func(newHH *HandshakeHostInfo) {
-			// Block the current used address
-			newHH.hostinfo.remotes = hostinfo.remotes
-			newHH.hostinfo.remotes.BlockRemote(via)
-
-			f.l.WithField("blockedUdpAddrs", newHH.hostinfo.remotes.CopyBlockedRemotes()).
-				WithField("vpnNetworks", vpnNetworks).
-				WithField("remotes", newHH.hostinfo.remotes.CopyAddrs(f.hostMap.GetPreferredRanges())).
-				Info("Blocked addresses for handshakes")
-
-			// Swap the packet store to benefit the original intended recipient
-			newHH.packetStore = hh.packetStore
-			hh.packetStore = []*cachedPacket{}
-
-			// Finally, put the correct vpn addrs in the host info, tell them to close the tunnel, and return true to tear down
-			hostinfo.vpnAddrs = vpnAddrs
-			f.sendCloseTunnel(hostinfo)
-		})
-
-		return true
-	}
-
-	// Mark packet 2 as seen so it doesn't show up as missed
-	ci.window.Update(f.l, 2)
-
-	duration := time.Since(hh.startTime).Nanoseconds()
-	msgRxL := f.l.WithField("vpnAddrs", vpnAddrs).WithField("from", via).
-		WithField("certName", certName).
-		WithField("certVersion", certVersion).
-		WithField("fingerprint", fingerprint).
-		WithField("issuer", issuer).
-		WithField("initiatorIndex", hs.Details.InitiatorIndex).WithField("responderIndex", hs.Details.ResponderIndex).
-		WithField("remoteIndex", h.RemoteIndex).WithField("handshake", m{"stage": 2, "style": "ix_psk0"}).
-		WithField("durationNs", duration).
-		WithField("sentCachedPackets", len(hh.packetStore))
-	if anyVpnAddrsInCommon {
-		msgRxL.Info("Handshake message received")
-	} else {
-		//todo warn if not lighthouse or relay?
-		msgRxL.Info("Handshake message received, but no vpnNetworks in common.")
-	}
-
-	// Build up the radix for the firewall if we have subnets in the cert
-	hostinfo.vpnAddrs = vpnAddrs
-	hostinfo.buildNetworks(f.myVpnNetworksTable, remoteCert.Certificate)
-
-	// Complete our handshake and update metrics, this will replace any existing tunnels for the vpnAddrs here
-	f.handshakeManager.Complete(hostinfo, f)
-	f.connectionManager.AddTrafficWatch(hostinfo)
-
-	if f.l.Level >= logrus.DebugLevel {
-		hostinfo.logger(f.l).Debugf("Sending %d stored packets", len(hh.packetStore))
-	}
-
-	if len(hh.packetStore) > 0 {
-		nb := make([]byte, 12, 12)
-		out := make([]byte, mtu)
-		for _, cp := range hh.packetStore {
-			cp.callback(cp.messageType, cp.messageSubType, hostinfo, cp.packet, nb, out)
-		}
-		f.cachedPacketMetrics.sent.Inc(int64(len(hh.packetStore)))
-	}
-
-	hostinfo.remotes.RefreshFromHandshake(vpnAddrs)
-	f.metricHandshakes.Update(duration)
-
-	return false
-}

handshake_manager_test.go

@@ -5,6 +5,7 @@ import (
 	"testing"
 	"time"
 
+	"github.com/gaissmai/bart"
 	"github.com/slackhq/nebula/cert"
 	"github.com/slackhq/nebula/header"
 	"github.com/slackhq/nebula/test"
@@ -27,7 +28,7 @@ func Test_NewHandshakeManagerVpnIp(t *testing.T) {
 		initiatingVersion: cert.Version1,
 		privateKey:        []byte{},
 		v1Cert:            &dummyCert{version: cert.Version1},
-		v1HandshakeBytes:  []byte{},
+		v1Credential:      nil,
 	}
 
 	blah := NewHandshakeManager(l, mainHM, lh, &udp.NoopConn{}, defaultHandshakeConfig)
@@ -100,3 +101,137 @@ func (mw *mockEncWriter) GetHostInfo(_ netip.Addr) *HostInfo {
 func (mw *mockEncWriter) GetCertState() *CertState {
 	return &CertState{initiatingVersion: cert.Version2}
 }
+
+func TestValidatePeerCert(t *testing.T) {
+	l := test.NewLogger()
+
+	myNetwork := netip.MustParsePrefix("10.0.0.1/24")
+	myAddrTable := new(bart.Lite)
+	myAddrTable.Insert(netip.PrefixFrom(myNetwork.Addr(), myNetwork.Addr().BitLen()))
+	myNetTable := new(bart.Lite)
+	myNetTable.Insert(myNetwork.Masked())
+
+	newHM := func() *HandshakeManager {
+		hm := NewHandshakeManager(l, newHostMap(l), newTestLighthouse(), &udp.NoopConn{}, defaultHandshakeConfig)
+		hm.f = &Interface{
+			handshakeManager:   hm,
+			pki:                &PKI{},
+			l:                  l,
+			myVpnAddrsTable:    myAddrTable,
+			myVpnNetworksTable: myNetTable,
+			lightHouse:         hm.lightHouse,
+		}
+		return hm
+	}
+
+	cached := func(networks ...netip.Prefix) *cert.CachedCertificate {
+		return &cert.CachedCertificate{
+			Certificate: &dummyCert{name: "peer", networks: networks},
+		}
+	}
+
+	via := ViaSender{
+		UdpAddr:   netip.MustParseAddrPort("198.51.100.7:4242"),
+		IsRelayed: true, // skip the remote allow list (covered separately)
+	}
+
+	t.Run("addr inside our networks sets anyVpnAddrsInCommon", func(t *testing.T) {
+		hm := newHM()
+		// 10.0.0.2 falls inside our 10.0.0.0/24
+		addrs, common, ok := hm.validatePeerCert(via, cached(netip.MustParsePrefix("10.0.0.2/24")))
+		assert.True(t, ok)
+		assert.True(t, common)
+		assert.Equal(t, []netip.Addr{netip.MustParseAddr("10.0.0.2")}, addrs)
+	})
+
+	t.Run("addr outside our networks leaves anyVpnAddrsInCommon false", func(t *testing.T) {
+		hm := newHM()
+		addrs, common, ok := hm.validatePeerCert(via, cached(netip.MustParsePrefix("192.168.1.5/24")))
+		assert.True(t, ok)
+		assert.False(t, common)
+		assert.Equal(t, []netip.Addr{netip.MustParseAddr("192.168.1.5")}, addrs)
+	})
+
+	t.Run("any matching network is enough", func(t *testing.T) {
+		hm := newHM()
+		addrs, common, ok := hm.validatePeerCert(via, cached(
+			netip.MustParsePrefix("192.168.1.5/24"),
+			netip.MustParsePrefix("10.0.0.42/24"),
+		))
+		assert.True(t, ok)
+		assert.True(t, common)
+		assert.Len(t, addrs, 2)
+	})
+
+	t.Run("self-handshake is rejected", func(t *testing.T) {
+		hm := newHM()
+		// 10.0.0.1 is in myVpnAddrsTable
+		addrs, common, ok := hm.validatePeerCert(via, cached(netip.MustParsePrefix("10.0.0.1/24")))
+		assert.False(t, ok)
+		assert.False(t, common)
+		assert.Nil(t, addrs)
+	})
+
+	t.Run("cert with no networks is rejected", func(t *testing.T) {
+		hm := newHM()
+		addrs, common, ok := hm.validatePeerCert(via, cached())
+		assert.False(t, ok)
+		assert.False(t, common)
+		assert.Nil(t, addrs)
+	})
+}
+
+func TestHandleIncomingDispatch(t *testing.T) {
+	l := test.NewLogger()
+
+	newHM := func() *HandshakeManager {
+		hm := NewHandshakeManager(l, newHostMap(l), newTestLighthouse(), &udp.NoopConn{}, defaultHandshakeConfig)
+		hm.f = &Interface{
+			handshakeManager: hm,
+			pki:              &PKI{},
+			l:                l,
+		}
+		return hm
+	}
+
+	via := ViaSender{
+		UdpAddr:   netip.MustParseAddrPort("198.51.100.7:4242"),
+		IsRelayed: true, // bypass remote allow list
+	}
+
+	// A packet body of zero length is fine for these tests: dispatch is
+	// gated on header fields, and we assert that we never reach noise/cert
+	// processing for any of the malformed shapes here.
+	pkt := make([]byte, header.Len)
+
+	t.Run("unsupported subtype dropped", func(t *testing.T) {
+		hm := newHM()
+		h := &header.H{Type: header.Handshake, Subtype: header.MessageSubType(99), MessageCounter: 1}
+		hm.HandleIncoming(via, pkt, h)
+		assert.Empty(t, hm.indexes, "no pending handshake should be created")
+	})
+
+	t.Run("stage-1 with non-zero RemoteIndex dropped", func(t *testing.T) {
+		hm := newHM()
+		h := &header.H{
+			Type:           header.Handshake,
+			Subtype:        header.HandshakeIXPSK0,
+			RemoteIndex:    0xdeadbeef,
+			MessageCounter: 1,
+		}
+		hm.HandleIncoming(via, pkt, h)
+		assert.Empty(t, hm.indexes, "spoofed stage-1 must not create a pending machine")
+	})
+
+	t.Run("continuation with no matching pending index dropped", func(t *testing.T) {
+		hm := newHM()
+		h := &header.H{
+			Type:           header.Handshake,
+			Subtype:        header.HandshakeIXPSK0,
+			RemoteIndex:    0xcafef00d,
+			MessageCounter: 2,
+		}
+		hm.HandleIncoming(via, pkt, h)
+		assert.Empty(t, hm.indexes, "orphan stage-2 must not create state")
+	})
+}

header/header.go

@@ -174,6 +174,10 @@ func (h *H) SubTypeName() string {
 	return SubTypeName(h.Type, h.Subtype)
 }
 
+func (h *H) IsValidSubType() bool {
+	return IsValidSubType(h.Type, h.Subtype)
+}
+
 // SubTypeName will transform a nebula message sub type into a human string
 func SubTypeName(t MessageType, s MessageSubType) string {
 	if n, ok := subTypeMap[t]; ok {
@@ -185,6 +189,16 @@ func SubTypeName(t MessageType, s MessageSubType) string {
 	return "unknown"
 }
 
+func IsValidSubType(t MessageType, s MessageSubType) bool {
+	if n, ok := subTypeMap[t]; ok {
+		if _, ok := (*n)[s]; ok {
+			return true
+		}
+	}
+
+	return false
+}
+
 // NewHeader turns bytes into a header
 func NewHeader(b []byte) (*H, error) {
 	h := new(H)

hostmap.go

@@ -1,9 +1,11 @@
 package nebula
 
 import (
+	"context"
 	"encoding/json"
 	"errors"
 	"fmt"
+	"log/slog"
 	"net"
 	"net/netip"
 	"slices"
@@ -13,10 +15,10 @@ import (
 
 	"github.com/gaissmai/bart"
 	"github.com/rcrowley/go-metrics"
-	"github.com/sirupsen/logrus"
 	"github.com/slackhq/nebula/cert"
 	"github.com/slackhq/nebula/config"
 	"github.com/slackhq/nebula/header"
+	"github.com/slackhq/nebula/logging"
 )
 
 const defaultPromoteEvery = 1000       // Count of packets sent before we try moving a tunnel to a preferred underlay ip address
@@ -60,7 +62,7 @@ type HostMap struct {
 	RemoteIndexes   map[uint32]*HostInfo
 	Hosts           map[netip.Addr]*HostInfo
 	preferredRanges atomic.Pointer[[]netip.Prefix]
-	l               *logrus.Logger
+	l               *slog.Logger
 }
 
 // For synchronization, treat the pointed-to Relay struct as immutable. To edit the Relay
@@ -313,7 +315,7 @@ type cachedPacketMetrics struct {
 	dropped metrics.Counter
 }
 
-func NewHostMapFromConfig(l *logrus.Logger, c *config.C) *HostMap {
+func NewHostMapFromConfig(l *slog.Logger, c *config.C) *HostMap {
 	hm := newHostMap(l)
 
 	hm.reload(c, true)
@@ -321,13 +323,12 @@ func NewHostMapFromConfig(l *logrus.Logger, c *config.C) *HostMap {
 		hm.reload(c, false)
 	})
 
-	l.WithField("preferredRanges", hm.GetPreferredRanges()).
-		Info("Main HostMap created")
+	l.Info("Main HostMap created", "preferredRanges", hm.GetPreferredRanges())
 
 	return hm
 }
 
-func newHostMap(l *logrus.Logger) *HostMap {
+func newHostMap(l *slog.Logger) *HostMap {
 	return &HostMap{
 		Indexes:       map[uint32]*HostInfo{},
 		Relays:        map[uint32]*HostInfo{},
@@ -346,7 +347,10 @@ func (hm *HostMap) reload(c *config.C, initial bool) {
 			preferredRange, err := netip.ParsePrefix(rawPreferredRange)
 
 			if err != nil {
-				hm.l.WithError(err).WithField("range", rawPreferredRanges).Warn("Failed to parse preferred ranges, ignoring")
+				hm.l.Warn("Failed to parse preferred ranges, ignoring",
+					"error", err,
+					"range", rawPreferredRanges,
+				)
 				continue
 			}
 
@@ -355,7 +359,10 @@ func (hm *HostMap) reload(c *config.C, initial bool) {
 
 		oldRanges := hm.preferredRanges.Swap(&preferredRanges)
 		if !initial {
-			hm.l.WithField("oldPreferredRanges", *oldRanges).WithField("newPreferredRanges", preferredRanges).Info("preferred_ranges changed")
+			hm.l.Info("preferred_ranges changed",
+				"oldPreferredRanges", *oldRanges,
+				"newPreferredRanges", preferredRanges,
+			)
 		}
 	}
 }
@@ -488,10 +495,11 @@ func (hm *HostMap) unlockedInnerDeleteHostInfo(hostinfo *HostInfo, addr netip.Ad
 		hm.Indexes = map[uint32]*HostInfo{}
 	}
 
-	if hm.l.Level >= logrus.DebugLevel {
-		hm.l.WithField("hostMap", m{"mapTotalSize": len(hm.Hosts),
-			"vpnAddrs": hostinfo.vpnAddrs, "indexNumber": hostinfo.localIndexId, "remoteIndexNumber": hostinfo.remoteIndexId}).
-			Debug("Hostmap hostInfo deleted")
+	if hm.l.Enabled(context.Background(), slog.LevelDebug) {
+		hm.l.Debug("Hostmap hostInfo deleted",
+			"hostMap", m{"mapTotalSize": len(hm.Hosts),
+				"vpnAddrs": hostinfo.vpnAddrs, "indexNumber": hostinfo.localIndexId, "remoteIndexNumber": hostinfo.remoteIndexId},
+		)
 	}
 
 	if isLastHostinfo {
@@ -604,9 +612,9 @@ func (hm *HostMap) queryVpnAddr(vpnIp netip.Addr, promoteIfce *Interface) *HostI
 // unlockedAddHostInfo assumes you have a write-lock and will add a hostinfo object to the hostmap Indexes and RemoteIndexes maps.
 // If an entry exists for the Hosts table (vpnIp -> hostinfo) then the provided hostinfo will be made primary
 func (hm *HostMap) unlockedAddHostInfo(hostinfo *HostInfo, f *Interface) {
-	if f.serveDns {
+	if f.dnsServer != nil {
 		remoteCert := hostinfo.ConnectionState.peerCert
-		dnsR.Add(remoteCert.Certificate.Name()+".", hostinfo.vpnAddrs)
+		f.dnsServer.Add(remoteCert.Certificate.Name()+".", hostinfo.vpnAddrs)
 	}
 	for _, addr := range hostinfo.vpnAddrs {
 		hm.unlockedInnerAddHostInfo(addr, hostinfo, f)
@@ -615,10 +623,11 @@ func (hm *HostMap) unlockedAddHostInfo(hostinfo *HostInfo, f *Interface) {
 	hm.Indexes[hostinfo.localIndexId] = hostinfo
 	hm.RemoteIndexes[hostinfo.remoteIndexId] = hostinfo
 
-	if hm.l.Level >= logrus.DebugLevel {
-		hm.l.WithField("hostMap", m{"vpnAddrs": hostinfo.vpnAddrs, "mapTotalSize": len(hm.Hosts),
-			"hostinfo": m{"existing": true, "localIndexId": hostinfo.localIndexId, "vpnAddrs": hostinfo.vpnAddrs}}).
-			Debug("Hostmap vpnIp added")
+	if hm.l.Enabled(context.Background(), slog.LevelDebug) {
+		hm.l.Debug("Hostmap vpnIp added",
+			"hostMap", m{"vpnAddrs": hostinfo.vpnAddrs, "mapTotalSize": len(hm.Hosts),
+				"hostinfo": m{"existing": true, "localIndexId": hostinfo.localIndexId, "vpnAddrs": hostinfo.vpnAddrs}},
+		)
 	}
 }
 
@@ -784,18 +793,21 @@ func (i *HostInfo) buildNetworks(myVpnNetworksTable *bart.Lite, c cert.Certifica
 	}
 }
 
-func (i *HostInfo) logger(l *logrus.Logger) *logrus.Entry {
+// logger returns a derived slog.Logger with per-hostinfo fields pre-bound.
+func (i *HostInfo) logger(l *slog.Logger) *slog.Logger {
 	if i == nil {
-		return logrus.NewEntry(l)
+		return l
 	}
 
-	li := l.WithField("vpnAddrs", i.vpnAddrs).
-		WithField("localIndex", i.localIndexId).
-		WithField("remoteIndex", i.remoteIndexId)
+	li := l.With(
+		"vpnAddrs", i.vpnAddrs,
+		"localIndex", i.localIndexId,
+		"remoteIndex", i.remoteIndexId,
+	)
 
 	if connState := i.ConnectionState; connState != nil {
 		if peerCert := connState.peerCert; peerCert != nil {
-			li = li.WithField("certName", peerCert.Certificate.Name())
+			li = li.With("certName", peerCert.Certificate.Name())
 		}
 	}
 
@@ -804,14 +816,17 @@ func (i *HostInfo) logger(l *logrus.Logger) *logrus.Entry {
 
 // Utility functions
 
-func localAddrs(l *logrus.Logger, allowList *LocalAllowList) []netip.Addr {
+func localAddrs(l *slog.Logger, allowList *LocalAllowList) []netip.Addr {
 	//FIXME: This function is pretty garbage
 	var finalAddrs []netip.Addr
 	ifaces, _ := net.Interfaces()
 	for _, i := range ifaces {
 		allow := allowList.AllowName(i.Name)
-		if l.Level >= logrus.TraceLevel {
-			l.WithField("interfaceName", i.Name).WithField("allow", allow).Trace("localAllowList.AllowName")
+		if l.Enabled(context.Background(), logging.LevelTrace) {
+			l.Log(context.Background(), logging.LevelTrace, "localAllowList.AllowName",
+				"interfaceName", i.Name,
+				"allow", allow,
+			)
 		}
 
 		if !allow {
@@ -829,8 +844,8 @@ func localAddrs(l *logrus.Logger, allowList *LocalAllowList) []netip.Addr {
 			}
 
 			if !addr.IsValid() {
-				if l.Level >= logrus.DebugLevel {
-					l.WithField("localAddr", rawAddr).Debug("addr was invalid")
+				if l.Enabled(context.Background(), slog.LevelDebug) {
+					l.Debug("addr was invalid", "localAddr", rawAddr)
 				}
 				continue
 			}
@@ -838,8 +853,11 @@ func localAddrs(l *logrus.Logger, allowList *LocalAllowList) []netip.Addr {
 
 			if addr.IsLoopback() == false && addr.IsLinkLocalUnicast() == false {
 				isAllowed := allowList.Allow(addr)
-				if l.Level >= logrus.TraceLevel {
-					l.WithField("localAddr", addr).WithField("allowed", isAllowed).Trace("localAllowList.Allow")
+				if l.Enabled(context.Background(), logging.LevelTrace) {
+					l.Log(context.Background(), logging.LevelTrace, "localAllowList.Allow",
+						"localAddr", addr,
+						"allowed", isAllowed,
+					)
 				}
 				if !isAllowed {
 					continue

hostmap_test.go

@@ -196,7 +196,7 @@ func TestHostMap_DeleteHostInfo(t *testing.T) {
 
 func TestHostMap_reload(t *testing.T) {
 	l := test.NewLogger()
-	c := config.NewC(l)
+	c := config.NewC(test.NewLogger())
 
 	hm := NewHostMapFromConfig(l, c)
 

inside.go

@@ -1,25 +1,46 @@
 package nebula
 
 import (
+	"context"
+	"io"
+	"log/slog"
 	"net/netip"
 
-	"github.com/sirupsen/logrus"
 	"github.com/slackhq/nebula/firewall"
 	"github.com/slackhq/nebula/header"
 	"github.com/slackhq/nebula/iputil"
 	"github.com/slackhq/nebula/noiseutil"
+	"github.com/slackhq/nebula/overlay/batch"
+	"github.com/slackhq/nebula/overlay/tio"
 	"github.com/slackhq/nebula/routing"
 )
 
-func (f *Interface) consumeInsidePacket(packet []byte, fwPacket *firewall.Packet, nb []byte, batch *sendBatch, rejectBuf []byte, q int, localCache firewall.ConntrackCache) {
-	err := newPacket(packet, false, fwPacket)
-	if err != nil {
-		if f.l.Level >= logrus.DebugLevel {
-			f.l.WithField("packet", packet).Debugf("Error while validating outbound packet: %s", err)
+func (f *Interface) consumeInsidePacket(pkt tio.Packet, fwPacket *firewall.Packet, nb []byte, sendBatch batch.TxBatcher, rejectBuf []byte, q int, localCache firewall.ConntrackCache) {
+	// borrowed: pkt.Bytes is owned by the originating tio.Queue and is
+	// only valid until the next Read on that queue. Every consumer below
+	// (parse, self-forward, handshake cache, sendInsideMessage) reads it
+	// synchronously; do not retain pkt outside this call. If a future
+	// caller needs to keep the packet, use pkt.Clone() to detach it from
+	// the borrow.
+	//
+	// pkt.Bytes is either one IP datagram (GSO zero) or a TSO/USO
+	// superpacket. In both cases the L3+L4 headers at the start describe
+	// the same 5-tuple every segment will share, so a single parse +
+	// firewall check covers the whole superpacket.
+	packet := pkt.Bytes
+	var parsed batch.RxParsed
+	if err := batch.ParsePacket(packet, false, &parsed); err != nil {
+		if f.l.Enabled(context.Background(), slog.LevelDebug) {
+			f.l.Debug("Error while validating outbound packet",
+				"packet", packet,
+				"error", err,
+			)
 		}
 		return
 	}
 
+	parsed.Key.Hydrate(fwPacket)
+
 	// Ignore local broadcast packets
 	if f.dropLocalBroadcast {
 		if f.myBroadcastAddrsTable.Contains(fwPacket.RemoteAddr) {
@@ -33,9 +54,16 @@ func (f *Interface) consumeInsidePacket(packet []byte, fwPacket *firewall.Packet
 		// routes packets from the Nebula addr to the Nebula addr through the Nebula
 		// TUN device.
 		if immediatelyForwardToSelf {
-			_, err := f.readers[q].WriteReject(packet)
+			// Write copies into the kernel queue synchronously, so seg's lifetime ends at return.
+			// A self-forwarded superpacket would be re-handed to the
+			// kernel as one giant blob; segment first so the loopback
+			// path sees one IP datagram per Write.
+			err := tio.SegmentSuperpacket(pkt, func(seg []byte) error {
+				_, werr := f.readers[q].Write(seg)
+				return werr
+			})
 			if err != nil {
-				f.l.WithError(err).Error("Failed to forward to tun")
+				f.l.Error("Failed to forward to tun", "error", err)
 			}
 		}
 		// Otherwise, drop. On linux, we should never see these packets - Linux
@@ -49,15 +77,28 @@ func (f *Interface) consumeInsidePacket(packet []byte, fwPacket *firewall.Packet
 	}
 
 	hostinfo, ready := f.getOrHandshakeConsiderRouting(fwPacket, func(hh *HandshakeHostInfo) {
-		hh.cachePacket(f.l, header.Message, 0, packet, f.sendMessageNow, f.cachedPacketMetrics)
+		// borrowed: SegmentSuperpacket builds each segment in the kernel-supplied pkt
+		// bytes underneath. cachePacket explicitly copies its argument (handshake_manager.go cachePacket),
+		// so retaining segments past the loop is safe.
+		err := tio.SegmentSuperpacket(pkt, func(seg []byte) error {
+			hh.cachePacket(f.l, header.Message, 0, seg, f.sendMessageNow, f.cachedPacketMetrics)
+			return nil
+		})
+		if err != nil && f.l.Enabled(context.Background(), slog.LevelDebug) {
+			f.l.Debug("Failed to segment superpacket for handshake cache",
+				"error", err,
+				"vpnAddr", fwPacket.RemoteAddr,
+			)
+		}
 	})
 
 	if hostinfo == nil {
 		f.rejectInside(packet, rejectBuf, q)
-		if f.l.Level >= logrus.DebugLevel {
-			f.l.WithField("vpnAddr", fwPacket.RemoteAddr).
-				WithField("fwPacket", fwPacket).
-				Debugln("dropping outbound packet, vpnAddr not in our vpn networks or in unsafe networks")
+		if f.l.Enabled(context.Background(), slog.LevelDebug) {
+			f.l.Debug("dropping outbound packet, vpnAddr not in our vpn networks or in unsafe networks",
+				"vpnAddr", fwPacket.RemoteAddr,
+				"fwPacket", fwPacket,
+			)
 		}
 		return
 	}
@@ -66,46 +107,21 @@ func (f *Interface) consumeInsidePacket(packet []byte, fwPacket *firewall.Packet
 		return
 	}
 
-	dropReason := f.firewall.Drop(*fwPacket, false, hostinfo, f.pki.GetCAPool(), localCache)
+	dropReason := f.firewall.Drop(parsed.Key, fwPacket, false, hostinfo, f.pki.GetCAPool(), localCache)
 	if dropReason == nil {
-		f.sendInsideMessage(hostinfo, packet, nb, batch, rejectBuf, q)
-
+		f.sendInsideMessage(hostinfo, pkt, nb, sendBatch, rejectBuf, q)
 	} else {
 		f.rejectInside(packet, rejectBuf, q)
-		if f.l.Level >= logrus.DebugLevel {
-			hostinfo.logger(f.l).
-				WithField("fwPacket", fwPacket).
-				WithField("reason", dropReason).
-				Debugln("dropping outbound packet")
+		if f.l.Enabled(context.Background(), slog.LevelDebug) {
+			hostinfo.logger(f.l).Debug("dropping outbound packet",
+				"fwPacket", fwPacket,
+				"reason", dropReason,
+			)
 		}
 	}
 }
 
-// sendInsideMessage encrypts a firewall-approved inside packet into the
-// caller's batch slot for later sendmmsg flush. When hostinfo.remote is not
-// valid we fall through to the relay slow path via the unbatched sendNoMetrics
-// so relay behavior is unchanged.
-func (f *Interface) sendInsideMessage(hostinfo *HostInfo, p, nb []byte, batch *sendBatch, rejectBuf []byte, q int) {
-	ci := hostinfo.ConnectionState
-	if ci.eKey == nil {
-		return
-	}
-
-	if !hostinfo.remote.IsValid() {
-		// Slow path: relay fallback. Reuse rejectBuf as the ciphertext
-		// scratch; sendNoMetrics arranges header space for SendVia.
-		f.sendNoMetrics(header.Message, 0, ci, hostinfo, netip.AddrPort{}, p, nb, rejectBuf, q)
-		return
-	}
-
-	scratch := batch.Next()
-	if scratch == nil {
-		// Batch full: bypass batching and send this packet directly so we
-		// never drop traffic on over-subscribed iterations.
-		f.sendNoMetrics(header.Message, 0, ci, hostinfo, netip.AddrPort{}, p, nb, rejectBuf, q)
-		return
-	}
-
+func (f *Interface) sendInsideEncrypt(hostinfo *HostInfo, ci *ConnectionState, seg, scratch, nb []byte) []byte {
 	if noiseutil.EncryptLockNeeded {
 		ci.writeLock.Lock()
 	}
@@ -114,28 +130,138 @@ func (f *Interface) sendInsideMessage(hostinfo *HostInfo, p, nb []byte, batch *s
 	out := header.Encode(scratch, header.Version, header.Message, 0, hostinfo.remoteIndexId, c)
 	f.connectionManager.Out(hostinfo)
 
+	out, encErr := ci.eKey.EncryptDanger(out, out, seg, c, nb)
+	if noiseutil.EncryptLockNeeded {
+		ci.writeLock.Unlock()
+	}
+	if encErr != nil {
+		hostinfo.logger(f.l).Error("Failed to encrypt outgoing packet",
+			"error", encErr,
+			"udpAddr", hostinfo.remote,
+			"counter", c,
+		)
+		// Skip this segment; the rest of the superpacket can still
+		// go out — TCP will retransmit anything we drop here.
+		return nil
+	}
+
+	return out
+}
+
+// sendInsideMessage encrypts a firewall-approved inside packet (or every
+// segment of a TSO/USO superpacket) into the caller's batch slot for
+// later sendmmsg flush. Segmentation is fused with encryption here so the
+// kernel-supplied superpacket bytes never get written into a separate
+// scratch arena: SegmentSuperpacket builds each segment's plaintext in
+// segScratch[:segLen] in turn, and we encrypt directly into a fresh
+// SendBatch slot.
+func (f *Interface) sendInsideMessage(hostinfo *HostInfo, pkt tio.Packet, nb []byte, sendBatch batch.TxBatcher, rejectBuf []byte, q int) {
+	ci := hostinfo.ConnectionState
+	if ci.eKey == nil {
+		return
+	}
+
+	ecnEnabled := f.ecnEnabled.Load()
 	if hostinfo.lastRebindCount != f.rebindCount {
 		//NOTE: there is an update hole if a tunnel isn't used and exactly 256 rebinds occur before the tunnel is
 		// finally used again. This tunnel would eventually be torn down and recreated if this action didn't help.
 		f.lightHouse.QueryServer(hostinfo.vpnAddrs[0])
 		hostinfo.lastRebindCount = f.rebindCount
-		if f.l.Level >= logrus.DebugLevel {
-			f.l.WithField("vpnAddrs", hostinfo.vpnAddrs).Debug("Lighthouse update triggered for punch due to rebind counter")
+		if f.l.Enabled(context.Background(), slog.LevelDebug) {
+			hostinfo.logger(f.l).Debug("Lighthouse update triggered for punch due to rebind counter",
+				"vpnAddrs", hostinfo.vpnAddrs,
+			)
 		}
 	}
 
-	out, err := ci.eKey.EncryptDanger(out, out, p, c, nb)
-	if noiseutil.EncryptLockNeeded {
-		ci.writeLock.Unlock()
-	}
-	if err != nil {
-		hostinfo.logger(f.l).WithError(err).
-			WithField("udpAddr", hostinfo.remote).WithField("counter", c).
-			Error("Failed to encrypt outgoing packet")
+	if !hostinfo.remote.IsValid() { //the relay path
+		//first, find our relay hostinfo:
+		var relayHostInfo *HostInfo
+		var relay *Relay
+		var err error
+		for _, relayIP := range hostinfo.relayState.CopyRelayIps() {
+			relayHostInfo, relay, err = f.hostMap.QueryVpnAddrsRelayFor(hostinfo.vpnAddrs, relayIP)
+			if err != nil {
+				hostinfo.relayState.DeleteRelay(relayIP)
+				hostinfo.logger(f.l).Info("sendNoMetrics failed to find HostInfo",
+					"relay", relayIP,
+					"error", err,
+				)
+				continue
+			}
+			break
+		}
+		if relayHostInfo == nil || relay == nil {
+			//failure already logged
+			return
+		}
+
+		err = tio.SegmentSuperpacket(pkt, func(seg []byte) error {
+			//relay header + header + plaintext + AEAD tag (16 bytes for both AES-GCM and ChaCha20-Poly1305) + relay tag
+			scratch := sendBatch.Reserve(header.Len + header.Len + len(seg) + 16 + 16)
+
+			innerPacket := f.sendInsideEncrypt(hostinfo, ci, seg, scratch[header.Len:], nb)
+			if innerPacket == nil {
+				return nil
+			}
+
+			//now we need to do a relay-encrypt:
+			toSend, err := f.prepareSendVia(relayHostInfo, relay, innerPacket, nb, scratch, true)
+			if err != nil {
+				//already logged
+				return nil
+			}
+
+			var ecn byte
+			if ecnEnabled {
+				ecn = innerECN(seg)
+			}
+			sendBatch.Commit(toSend, relayHostInfo.remote, ecn)
+			return nil
+		})
+		if err != nil {
+			hostinfo.logger(f.l).Error("Failed to segment superpacket for relay send", "error", err)
+		}
 		return
 	}
 
-	batch.Commit(len(out), hostinfo.remote)
+	err := tio.SegmentSuperpacket(pkt, func(seg []byte) error {
+		// header + plaintext + AEAD tag (16 bytes for both AES-GCM and ChaCha20-Poly1305)
+		scratch := sendBatch.Reserve(header.Len + len(seg) + 16)
+
+		out := f.sendInsideEncrypt(hostinfo, ci, seg, scratch, nb)
+		if out == nil {
+			return nil
+		}
+
+		var ecn byte
+		if ecnEnabled {
+			ecn = innerECN(seg)
+		}
+		sendBatch.Commit(out, hostinfo.remote, ecn)
+		return nil
+	})
+	if err != nil {
+		hostinfo.logger(f.l).Error("Failed to segment superpacket for send",
+			"error", err,
+		)
+	}
+}
+
+// innerECN returns the 2-bit IP-level ECN codepoint of an inner IPv4 or IPv6
+// packet, or 0 if pkt is too short or its IP version is unrecognized. Used at
+// encap to copy the inner codepoint onto the outer carrier per RFC 6040.
+func innerECN(pkt []byte) byte {
+	if len(pkt) < 2 {
+		return 0
+	}
+	switch pkt[0] >> 4 {
+	case 4:
+		return pkt[1] & 0x03
+	case 6:
+		return (pkt[1] >> 4) & 0x03
+	}
+	return 0
 }
 
 func (f *Interface) rejectInside(packet []byte, out []byte, q int) {
@@ -148,9 +274,9 @@ func (f *Interface) rejectInside(packet []byte, out []byte, q int) {
 		return
 	}
 
-	_, err := f.readers[q].WriteReject(out)
+	_, err := f.readers[q].Write(out)
 	if err != nil {
-		f.l.WithError(err).Error("Failed to write to tun")
+		f.l.Error("Failed to write to tun", "error", err)
 	}
 }
 
@@ -165,11 +291,11 @@ func (f *Interface) rejectOutside(packet []byte, ci *ConnectionState, hostinfo *
 	}
 
 	if len(out) > iputil.MaxRejectPacketSize {
-		if f.l.GetLevel() >= logrus.InfoLevel {
-			f.l.
-				WithField("packet", packet).
-				WithField("outPacket", out).
-				Info("rejectOutside: packet too big, not sending")
+		if f.l.Enabled(context.Background(), slog.LevelInfo) {
+			f.l.Info("rejectOutside: packet too big, not sending",
+				"packet", packet,
+				"outPacket", out,
+			)
 		}
 		return
 	}
@@ -241,10 +367,11 @@ func (f *Interface) getOrHandshakeConsiderRouting(fwPacket *firewall.Packet, cac
 		// This would also need to interact with unsafe_route updates through reloading the config or
 		// use of the use_system_route_table option
 
-		if f.l.Level >= logrus.DebugLevel {
-			f.l.WithField("destination", destinationAddr).
-				WithField("originalGateway", gatewayAddr).
-				Debugln("Calculated gateway for ECMP not available, attempting other gateways")
+		if f.l.Enabled(context.Background(), slog.LevelDebug) {
+			f.l.Debug("Calculated gateway for ECMP not available, attempting other gateways",
+				"destination", destinationAddr,
+				"originalGateway", gatewayAddr,
+			)
 		}
 
 		for i := range gateways {
@@ -267,20 +394,22 @@ func (f *Interface) getOrHandshakeConsiderRouting(fwPacket *firewall.Packet, cac
 }
 
 func (f *Interface) sendMessageNow(t header.MessageType, st header.MessageSubType, hostinfo *HostInfo, p, nb, out []byte) {
-	fp := &firewall.Packet{}
-	err := newPacket(p, false, fp)
-	if err != nil {
-		f.l.Warnf("error while parsing outgoing packet for firewall check; %v", err)
+	var parsed batch.RxParsed
+	if err := batch.ParsePacket(p, false, &parsed); err != nil {
+		f.l.Warn("error while parsing outgoing packet for firewall check", "error", err)
 		return
 	}
+	fp := &firewall.Packet{}
+	parsed.Key.Hydrate(fp)
 
 	// check if packet is in outbound fw rules
-	dropReason := f.firewall.Drop(*fp, false, hostinfo, f.pki.GetCAPool(), nil)
+	dropReason := f.firewall.Drop(parsed.Key, fp, false, hostinfo, f.pki.GetCAPool(), nil)
 	if dropReason != nil {
-		if f.l.Level >= logrus.DebugLevel {
-			f.l.WithField("fwPacket", fp).
-				WithField("reason", dropReason).
-				Debugln("dropping cached packet")
+		if f.l.Enabled(context.Background(), slog.LevelDebug) {
+			f.l.Debug("dropping cached packet",
+				"fwPacket", fp,
+				"reason", dropReason,
+			)
 		}
 		return
 	}
@@ -296,9 +425,10 @@ func (f *Interface) SendMessageToVpnAddr(t header.MessageType, st header.Message
 	})
 
 	if hostInfo == nil {
-		if f.l.Level >= logrus.DebugLevel {
-			f.l.WithField("vpnAddr", vpnAddr).
-				Debugln("dropping SendMessageToVpnAddr, vpnAddr not in our vpn networks or in unsafe routes")
+		if f.l.Enabled(context.Background(), slog.LevelDebug) {
+			f.l.Debug("dropping SendMessageToVpnAddr, vpnAddr not in our vpn networks or in unsafe routes",
+				"vpnAddr", vpnAddr,
+			)
 		}
 		return
 	}
@@ -324,21 +454,13 @@ func (f *Interface) sendTo(t header.MessageType, st header.MessageSubType, ci *C
 	f.sendNoMetrics(t, st, ci, hostinfo, remote, p, nb, out, 0)
 }
 
-// SendVia sends a payload through a Relay tunnel. No authentication or encryption is done
-// to the payload for the ultimate target host, making this a useful method for sending
-// handshake messages to peers through relay tunnels.
-// via is the HostInfo through which the message is relayed.
-// ad is the plaintext data to authenticate, but not encrypt
-// nb is a buffer used to store the nonce value, re-used for performance reasons.
-// out is a buffer used to store the result of the Encrypt operation
-// q indicates which writer to use to send the packet.
-func (f *Interface) SendVia(via *HostInfo,
+func (f *Interface) prepareSendVia(via *HostInfo,
 	relay *Relay,
 	ad,
 	nb,
 	out []byte,
 	nocopy bool,
-) {
+) ([]byte, error) {
 	if noiseutil.EncryptLockNeeded {
 		// NOTE: for goboring AESGCMTLS we need to lock because of the nonce check
 		via.ConnectionState.writeLock.Lock()
@@ -354,13 +476,13 @@ func (f *Interface) SendVia(via *HostInfo,
 		if noiseutil.EncryptLockNeeded {
 			via.ConnectionState.writeLock.Unlock()
 		}
-		via.logger(f.l).
-			WithField("outCap", cap(out)).
-			WithField("payloadLen", len(ad)).
-			WithField("headerLen", len(out)).
-			WithField("cipherOverhead", via.ConnectionState.eKey.Overhead()).
-			Error("SendVia out buffer not large enough for relay")
-		return
+		via.logger(f.l).Error("SendVia out buffer not large enough for relay",
+			"outCap", cap(out),
+			"payloadLen", len(ad),
+			"headerLen", len(out),
+			"cipherOverhead", via.ConnectionState.eKey.Overhead(),
+		)
+		return nil, io.ErrShortBuffer
 	}
 
 	// The header bytes are written to the 'out' slice; Grow the slice to hold the header and associated data payload.
@@ -379,14 +501,33 @@ func (f *Interface) SendVia(via *HostInfo,
 		via.ConnectionState.writeLock.Unlock()
 	}
 	if err != nil {
-		via.logger(f.l).WithError(err).Info("Failed to EncryptDanger in sendVia")
-		return
-	}
-	err = f.writers[0].WriteTo(out, via.remote)
-	if err != nil {
-		via.logger(f.l).WithError(err).Info("Failed to WriteTo in sendVia")
+		via.logger(f.l).Info("Failed to EncryptDanger in sendVia", "error", err)
+		return nil, err
 	}
 	f.connectionManager.RelayUsed(relay.LocalIndex)
+	return out, nil
+}
+
+// SendVia sends a payload through a Relay tunnel. No authentication or encryption is done
+// to the payload for the ultimate target host, making this a useful method for sending
+// handshake messages to peers through relay tunnels.
+// via is the HostInfo through which the message is relayed.
+// ad is the plaintext data to authenticate, but not encrypt
+// nb is a buffer used to store the nonce value, re-used for performance reasons.
+// out is a buffer used to store the result of the Encrypt operation
+// q indicates which writer to use to send the packet.
+func (f *Interface) SendVia(via *HostInfo,
+	relay *Relay,
+	ad,
+	nb,
+	out []byte,
+	nocopy bool,
+) {
+	toSend, err := f.prepareSendVia(via, relay, ad, nb, out, nocopy)
+	err = f.writers[0].WriteTo(toSend, via.remote)
+	if err != nil {
+		via.logger(f.l).Info("Failed to WriteTo in sendVia", "error", err)
+	}
 }
 
 func (f *Interface) sendNoMetrics(t header.MessageType, st header.MessageSubType, ci *ConnectionState, hostinfo *HostInfo, remote netip.AddrPort, p, nb, out []byte, q int) {
@@ -423,8 +564,10 @@ func (f *Interface) sendNoMetrics(t header.MessageType, st header.MessageSubType
 		// finally used again. This tunnel would eventually be torn down and recreated if this action didn't help.
 		f.lightHouse.QueryServer(hostinfo.vpnAddrs[0])
 		hostinfo.lastRebindCount = f.rebindCount
-		if f.l.Level >= logrus.DebugLevel {
-			f.l.WithField("vpnAddrs", hostinfo.vpnAddrs).Debug("Lighthouse update triggered for punch due to rebind counter")
+		if f.l.Enabled(context.Background(), slog.LevelDebug) {
+			f.l.Debug("Lighthouse update triggered for punch due to rebind counter",
+				"vpnAddrs", hostinfo.vpnAddrs,
+			)
 		}
 	}
 
@@ -434,24 +577,30 @@ func (f *Interface) sendNoMetrics(t header.MessageType, st header.MessageSubType
 		ci.writeLock.Unlock()
 	}
 	if err != nil {
-		hostinfo.logger(f.l).WithError(err).
-			WithField("udpAddr", remote).WithField("counter", c).
-			WithField("attemptedCounter", c).
-			Error("Failed to encrypt outgoing packet")
+		hostinfo.logger(f.l).Error("Failed to encrypt outgoing packet",
+			"error", err,
+			"udpAddr", remote,
+			"counter", c,
+			"attemptedCounter", c,
+		)
 		return
 	}
 
 	if remote.IsValid() {
 		err = f.writers[q].WriteTo(out, remote)
 		if err != nil {
-			hostinfo.logger(f.l).WithError(err).
-				WithField("udpAddr", remote).Error("Failed to write outgoing packet")
+			hostinfo.logger(f.l).Error("Failed to write outgoing packet",
+				"error", err,
+				"udpAddr", remote,
+			)
 		}
 	} else if hostinfo.remote.IsValid() {
 		err = f.writers[q].WriteTo(out, hostinfo.remote)
 		if err != nil {
-			hostinfo.logger(f.l).WithError(err).
-				WithField("udpAddr", remote).Error("Failed to write outgoing packet")
+			hostinfo.logger(f.l).Error("Failed to write outgoing packet",
+				"error", err,
+				"udpAddr", remote,
+			)
 		}
 	} else {
 		// Try to send via a relay
@@ -459,7 +608,10 @@ func (f *Interface) sendNoMetrics(t header.MessageType, st header.MessageSubType
 			relayHostInfo, relay, err := f.hostMap.QueryVpnAddrsRelayFor(hostinfo.vpnAddrs, relayIP)
 			if err != nil {
 				hostinfo.relayState.DeleteRelay(relayIP)
-				hostinfo.logger(f.l).WithField("relay", relayIP).WithError(err).Info("sendNoMetrics failed to find HostInfo")
+				hostinfo.logger(f.l).Info("sendNoMetrics failed to find HostInfo",
+					"relay", relayIP,
+					"error", err,
+				)
 				continue
 			}
 			f.SendVia(relayHostInfo, relay, out, nb, fullOut[:header.Len+len(out)], true)

interface.go

@@ -4,18 +4,23 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"log/slog"
 	"net/netip"
+	"runtime"
 	"sync"
 	"sync/atomic"
 	"time"
 
 	"github.com/gaissmai/bart"
 	"github.com/rcrowley/go-metrics"
-	"github.com/sirupsen/logrus"
+	"github.com/slackhq/nebula/util"
+
 	"github.com/slackhq/nebula/config"
 	"github.com/slackhq/nebula/firewall"
 	"github.com/slackhq/nebula/header"
 	"github.com/slackhq/nebula/overlay"
+	"github.com/slackhq/nebula/overlay/batch"
+	"github.com/slackhq/nebula/overlay/tio"
 	"github.com/slackhq/nebula/udp"
 )
 
@@ -28,7 +33,7 @@ type InterfaceConfig struct {
 	pki                *PKI
 	Cipher             string
 	Firewall           *Firewall
-	ServeDns           bool
+	DnsServer          *dnsServer
 	HandshakeManager   *HandshakeManager
 	lightHouse         *LightHouse
 	connectionManager  *connectionManager
@@ -45,7 +50,14 @@ type InterfaceConfig struct {
 	reQueryWait     time.Duration
 
 	ConntrackCacheTimeout time.Duration
-	l                     *logrus.Logger
+
+	// CpuAffinity, when non-empty, names the CPUs each TUN reader goroutine
+	// should pin to. Queue i pins to CpuAffinity[i % len(CpuAffinity)] —
+	// shorter lists than `routines` cycle. Empty list keeps the default
+	// pin-to-(i % NumCPU) behavior.
+	CpuAffinity []int
+
+	l *slog.Logger
 }
 
 type Interface struct {
@@ -56,7 +68,7 @@ type Interface struct {
 	firewall              *Firewall
 	connectionManager     *connectionManager
 	handshakeManager      *HandshakeManager
-	serveDns              bool
+	dnsServer             *dnsServer
 	createTime            time.Time
 	lightHouse            *LightHouse
 	myBroadcastAddrsTable *bart.Lite
@@ -69,7 +81,16 @@ type Interface struct {
 	routines              int
 	disconnectInvalid     atomic.Bool
 	closed                atomic.Bool
-	relayManager          *relayManager
+	// cpuAffinity, when non-empty, names the CPUs each TUN reader goroutine
+	// should pin to. Queue i pins to cpuAffinity[i % len(cpuAffinity)].
+	// Empty falls back to the default pin-to-(i % NumCPU) behavior.
+	cpuAffinity []int
+	// ecnEnabled gates RFC 6040 underlay ECN propagation. When true,
+	// inside.go copies the inner ECN onto the outer carrier on encap and
+	// decryptToTun folds outer CE into the inner header on decap. Toggle
+	// via tunnels.ecn (default true).
+	ecnEnabled   atomic.Bool
+	relayManager *relayManager
 
 	tryPromoteEvery atomic.Uint32
 	reQueryEvery    atomic.Uint32
@@ -84,13 +105,14 @@ type Interface struct {
 
 	conntrackCacheTimeout time.Duration
 
+	ctx     context.Context
 	writers []udp.Conn
-	readers []overlay.Queue
-	// tunCoalescers is one tcpCoalescer per tun queue, wrapping readers[i].
-	// decryptToTun sends plaintext into the coalescer; listenOut calls its
-	// Flush at the end of each UDP recvmmsg batch.
-	tunCoalescers []*tcpCoalescer
-	wg            sync.WaitGroup
+	readers []tio.Queue
+	// batchers is one per tun queue, wrapping readers[i].
+	// decryptToTun sends plaintext into the batch.RxBatcher;
+	// listenOut calls its Flush at the end of each UDP recvmmsg batch.
+	batchers []batch.RxBatcher
+	wg       sync.WaitGroup
 
 	// fatalErr holds the first unexpected reader error that caused shutdown.
 	// nil means "no fatal error" (yet)
@@ -102,7 +124,7 @@ type Interface struct {
 	messageMetrics      *MessageMetrics
 	cachedPacketMetrics *cachedPacketMetrics
 
-	l *logrus.Logger
+	l *slog.Logger
 }
 
 type EncWriter interface {
@@ -173,12 +195,13 @@ func NewInterface(ctx context.Context, c *InterfaceConfig) (*Interface, error) {
 
 	cs := c.pki.getCertState()
 	ifce := &Interface{
+		ctx:                   ctx,
 		pki:                   c.pki,
 		hostMap:               c.HostMap,
 		outside:               c.Outside,
 		inside:                c.Inside,
 		firewall:              c.Firewall,
-		serveDns:              c.ServeDns,
+		dnsServer:             c.DnsServer,
 		handshakeManager:      c.HandshakeManager,
 		createTime:            time.Now(),
 		lightHouse:            c.lightHouse,
@@ -187,8 +210,8 @@ func NewInterface(ctx context.Context, c *InterfaceConfig) (*Interface, error) {
 		routines:              c.routines,
 		version:               c.version,
 		writers:               make([]udp.Conn, c.routines),
-		readers:               make([]overlay.Queue, c.routines),
-		tunCoalescers:         make([]*tcpCoalescer, c.routines),
+		readers:               make([]tio.Queue, c.routines),
+		batchers:              make([]batch.RxBatcher, c.routines),
 		myVpnNetworks:         cs.myVpnNetworks,
 		myVpnNetworksTable:    cs.myVpnNetworksTable,
 		myVpnAddrs:            cs.myVpnAddrs,
@@ -197,6 +220,7 @@ func NewInterface(ctx context.Context, c *InterfaceConfig) (*Interface, error) {
 		relayManager:          c.relayManager,
 		connectionManager:     c.connectionManager,
 		conntrackCacheTimeout: c.ConntrackCacheTimeout,
+		cpuAffinity:           c.CpuAffinity,
 
 		metricHandshakes: metrics.GetOrRegisterHistogram("handshakes", nil, metrics.NewExpDecaySample(1028, 0.015)),
 		messageMetrics:   c.MessageMetrics,
@@ -225,13 +249,16 @@ func (f *Interface) activate() error {
 
 	addr, err := f.outside.LocalAddr()
 	if err != nil {
-		f.l.WithError(err).Error("Failed to get udp listen address")
+		f.l.Error("Failed to get udp listen address", "error", err)
 	}
 
-	f.l.WithField("interface", f.inside.Name()).WithField("networks", f.myVpnNetworks).
-		WithField("build", f.version).WithField("udpAddr", addr).
-		WithField("boringcrypto", boringEnabled()).
-		Info("Nebula interface is active")
+	f.l.Info("Nebula interface is active",
+		"interface", f.inside.Name(),
+		"networks", f.myVpnNetworks,
+		"build", f.version,
+		"udpAddr", addr,
+		"boringcrypto", boringEnabled(),
+	)
 
 	if f.routines > 1 {
 		if !f.inside.SupportsMultiqueue() || !f.outside.SupportsMultipleReaders() {
@@ -243,16 +270,25 @@ func (f *Interface) activate() error {
 	metrics.GetOrRegisterGauge("routines", nil).Update(int64(f.routines))
 
 	// Prepare n tun queues
-	var reader overlay.Queue = f.inside
 	for i := 0; i < f.routines; i++ {
 		if i > 0 {
-			reader, err = f.inside.NewMultiQueueReader()
-			if err != nil {
+			if err = f.inside.NewMultiQueueReader(); err != nil {
 				return err
 			}
 		}
-		f.readers[i] = reader
-		f.tunCoalescers[i] = newTCPCoalescer(reader)
+	}
+	f.readers = f.inside.Readers()
+	for i := range f.readers {
+		caps := tio.QueueCapabilities(f.readers[i])
+		if caps.TSO || caps.USO {
+			// Multi-lane: TCP gets coalesced when TSO is on, UDP when USO
+			// is on, everything else (and either lane disabled) falls
+			// through to passthrough so non-IP / non-TCP-UDP traffic still
+			// reaches the TUN.
+			f.batchers[i] = batch.NewMultiCoalescer(f.readers[i], caps.TSO, caps.USO)
+		} else {
+			f.batchers[i] = batch.NewPassthrough(f.readers[i])
+		}
 	}
 
 	f.wg.Add(1) // for us to wait on Close() to return
@@ -308,121 +344,80 @@ func (f *Interface) listenOut(i int) {
 		li = f.outside
 	}
 
-	ctCache := firewall.NewConntrackCacheTicker(f.conntrackCacheTimeout)
+	ctCache := firewall.NewConntrackCacheTicker(f.ctx, f.l, f.conntrackCacheTimeout)
 	lhh := f.lightHouse.NewRequestHandler()
 	h := &header.H{}
 	fwPacket := &firewall.Packet{}
+	parsedRx := &batch.RxParsed{}
 	nb := make([]byte, 12, 12)
 
-	// plaintexts is a ring of decrypt scratches, one per packet in a UDP
-	// recvmmsg batch. The coalescer borrows payload slices from here and
-	// requires they stay valid until Flush — so we rotate each packet and
-	// reset only in the batch-end flush callback.
-	var plaintexts [][]byte
-	idx := 0
-	coalescer := f.tunCoalescers[i]
-	err := li.ListenOut(func(fromUdpAddr netip.AddrPort, payload []byte) {
-		if idx >= len(plaintexts) {
-			plaintexts = append(plaintexts, make([]byte, udp.MTU))
+	listener := func(fromUdpAddr netip.AddrPort, payload []byte, meta udp.RxMeta) {
+		plaintext := f.batchers[i].Reserve(len(payload))
+		f.readOutsidePackets(ViaSender{UdpAddr: fromUdpAddr}, plaintext[:0], payload, h, fwPacket, parsedRx, lhh, nb, i, ctCache.Get(), meta)
+	}
+
+	flusher := func() {
+		if err := f.batchers[i].Flush(); err != nil {
+			f.l.Error("Failed to flush tun coalescer", "error", err)
 		}
-		f.readOutsidePackets(ViaSender{UdpAddr: fromUdpAddr}, plaintexts[idx][:0], payload, h, fwPacket, lhh, nb, i, ctCache.Get(f.l))
-		idx++
-	}, func() {
-		if err := coalescer.Flush(); err != nil {
-			f.l.WithError(err).Error("Failed to flush tun coalescer")
-		}
-		idx = 0
-	})
+	}
+
+	err := li.ListenOut(listener, flusher)
 
 	if err != nil && !f.closed.Load() {
-		f.l.WithError(err).Error("Error while reading inbound packet, closing")
+		f.l.Error("Error while reading inbound packet, closing", "error", err)
 		f.onFatal(err)
 	}
 
-	f.l.Debugf("underlay reader %v is done", i)
+	f.l.Debug("underlay reader is done", "reader", i)
 }
 
-func (f *Interface) listenIn(reader overlay.Queue, i int) {
+func (f *Interface) listenIn(reader tio.Queue, i int) {
+	// Pin this goroutine to one CPU. LockOSThread alone keeps the goroutine
+	// on a single OS thread but the kernel can still migrate that thread
+	// across CPUs — XPS reads smp_processor_id() at sendmmsg time and picks
+	// the TX ring from the current CPU's xps_cpus map, so an unpinned
+	// thread bouncing between CPUs spreads one nebula flow's packets across
+	// multiple TX rings, which the rings then drain at independent rates
+	// and the wire delivers reordered.
+	//
+	// Pinning keeps every sendmmsg from this goroutine going through the
+	// same TX ring, so the wire sees per-flow order. Cost: less scheduler
+	// flexibility — if i % NumCPU collides between two TUN reader
+	// goroutines they share a CPU.
+	cpu := i % runtime.NumCPU()
+	if n := len(f.cpuAffinity); n > 0 {
+		cpu = f.cpuAffinity[i%n]
+	}
+	if err := util.PinThreadToCPU(cpu); err != nil {
+		f.l.Warn("failed to pin tun reader to CPU", "queue", i, "cpu", cpu, "err", err)
+	}
 	rejectBuf := make([]byte, mtu)
-	batch := newSendBatch(sendBatchCap, udp.MTU+32)
+	sb := batch.NewSendBatch(f.writers[i], batch.SendBatchCap, udp.MTU+32)
 	fwPacket := &firewall.Packet{}
 	nb := make([]byte, 12, 12)
 
-	conntrackCache := firewall.NewConntrackCacheTicker(f.conntrackCacheTimeout)
+	conntrackCache := firewall.NewConntrackCacheTicker(f.ctx, f.l, f.conntrackCacheTimeout)
 
 	for {
 		pkts, err := reader.Read()
 		if err != nil {
 			if !f.closed.Load() {
-				f.l.WithError(err).WithField("reader", i).Error("Error while reading outbound packet, closing")
+				f.l.Error("Error while reading outbound packet, closing", "error", err, "reader", i)
 				f.onFatal(err)
 			}
 			break
 		}
 
-		batch.Reset()
 		for _, pkt := range pkts {
-			if batch.Len() >= batch.Cap() {
-				f.flushBatch(batch, i)
-				batch.Reset()
-			}
-			f.consumeInsidePacket(pkt, fwPacket, nb, batch, rejectBuf, i, conntrackCache.Get(f.l))
+			f.consumeInsidePacket(pkt, fwPacket, nb, sb, rejectBuf, i, conntrackCache.Get())
 		}
-		if batch.Len() > 0 {
-			f.flushBatch(batch, i)
+		if err := sb.Flush(); err != nil {
+			f.l.Error("Failed to write outgoing batch", "error", err, "writer", i)
 		}
 	}
 
-	f.l.Debugf("overlay reader %v is done", i)
-}
-
-func (f *Interface) flushBatch(batch *sendBatch, q int) {
-	//if len(batch.bufs) == 1 {
-	//	if err := f.writers[q].WriteTo(batch.bufs[0], batch.dsts[0]); err != nil {
-	//		f.l.WithError(err).WithField("writer", q).Error("Failed to write outgoing single-batch")
-	//	}
-	//	return
-	//}
-	w := f.writers[q]
-	if w.SupportsGSO() {
-		if segSize, ok := batchSegmentable(batch); ok {
-			if err := w.WriteSegmented(batch.bufs, batch.dsts[0], segSize); err != nil {
-				f.l.WithError(err).WithField("writer", q).Error("Failed to write outgoing GSO batch")
-			}
-			return
-		}
-	}
-	if err := w.WriteBatch(batch.bufs, batch.dsts); err != nil {
-		f.l.WithError(err).WithField("writer", q).Error("Failed to write outgoing batch")
-	}
-}
-
-// batchSegmentable reports whether a batch can be emitted as a single UDP GSO
-// superpacket: all packets go to the same destination, and every packet
-// except possibly the last has the same length. Returns the segment size on
-// success. The single-packet case is handled in flushBatch before this runs.
-func batchSegmentable(b *sendBatch) (int, bool) {
-	segSize := len(b.bufs[0])
-	if segSize == 0 {
-		return 0, false
-	}
-	dst := b.dsts[0]
-	last := len(b.bufs) - 1
-	for i := 1; i <= last; i++ {
-		if b.dsts[i] != dst {
-			return 0, false
-		}
-		if i < last {
-			if len(b.bufs[i]) != segSize {
-				return 0, false
-			}
-		} else {
-			if len(b.bufs[i]) == 0 || len(b.bufs[i]) > segSize {
-				return 0, false
-			}
-		}
-	}
-	return segSize, true
+	f.l.Debug("overlay reader is done", "reader", i)
 }
 
 func (f *Interface) RegisterConfigChangeCallbacks(c *config.C) {
@@ -431,6 +426,7 @@ func (f *Interface) RegisterConfigChangeCallbacks(c *config.C) {
 	c.RegisterReloadCallback(f.reloadAcceptRecvError)
 	c.RegisterReloadCallback(f.reloadDisconnectInvalid)
 	c.RegisterReloadCallback(f.reloadMisc)
+	c.RegisterReloadCallback(f.reloadEcn)
 
 	for _, udpConn := range f.writers {
 		c.RegisterReloadCallback(udpConn.ReloadConfig)
@@ -442,7 +438,7 @@ func (f *Interface) reloadDisconnectInvalid(c *config.C) {
 	if initial || c.HasChanged("pki.disconnect_invalid") {
 		f.disconnectInvalid.Store(c.GetBool("pki.disconnect_invalid", true))
 		if !initial {
-			f.l.Infof("pki.disconnect_invalid changed to %v", f.disconnectInvalid.Load())
+			f.l.Info("pki.disconnect_invalid changed", "value", f.disconnectInvalid.Load())
 		}
 	}
 }
@@ -456,7 +452,7 @@ func (f *Interface) reloadFirewall(c *config.C) {
 
 	fw, err := NewFirewallFromConfig(f.l, f.pki.getCertState(), c)
 	if err != nil {
-		f.l.WithError(err).Error("Error while creating firewall during reload")
+		f.l.Error("Error while creating firewall during reload", "error", err)
 		return
 	}
 
@@ -469,10 +465,11 @@ func (f *Interface) reloadFirewall(c *config.C) {
 	// If rulesVersion is back to zero, we have wrapped all the way around. Be
 	// safe and just reset conntrack in this case.
 	if fw.rulesVersion == 0 {
-		f.l.WithField("firewallHashes", fw.GetRuleHashes()).
-			WithField("oldFirewallHashes", oldFw.GetRuleHashes()).
-			WithField("rulesVersion", fw.rulesVersion).
-			Warn("firewall rulesVersion has overflowed, resetting conntrack")
+		f.l.Warn("firewall rulesVersion has overflowed, resetting conntrack",
+			"firewallHashes", fw.GetRuleHashes(),
+			"oldFirewallHashes", oldFw.GetRuleHashes(),
+			"rulesVersion", fw.rulesVersion,
+		)
 	} else {
 		fw.Conntrack = conntrack
 	}
@@ -480,10 +477,11 @@ func (f *Interface) reloadFirewall(c *config.C) {
 	f.firewall = fw
 
 	oldFw.Destroy()
-	f.l.WithField("firewallHashes", fw.GetRuleHashes()).
-		WithField("oldFirewallHashes", oldFw.GetRuleHashes()).
-		WithField("rulesVersion", fw.rulesVersion).
-		Info("New firewall has been installed")
+	f.l.Info("New firewall has been installed",
+		"firewallHashes", fw.GetRuleHashes(),
+		"oldFirewallHashes", oldFw.GetRuleHashes(),
+		"rulesVersion", fw.rulesVersion,
+	)
 }
 
 func (f *Interface) reloadSendRecvError(c *config.C) {
@@ -505,8 +503,7 @@ func (f *Interface) reloadSendRecvError(c *config.C) {
 			}
 		}
 
-		f.l.WithField("sendRecvError", f.sendRecvErrorConfig.String()).
-			Info("Loaded send_recv_error config")
+		f.l.Info("Loaded send_recv_error config", "sendRecvError", f.sendRecvErrorConfig.String())
 	}
 }
 
@@ -529,8 +526,7 @@ func (f *Interface) reloadAcceptRecvError(c *config.C) {
 			}
 		}
 
-		f.l.WithField("acceptRecvError", f.acceptRecvErrorConfig.String()).
-			Info("Loaded accept_recv_error config")
+		f.l.Info("Loaded accept_recv_error config", "acceptRecvError", f.acceptRecvErrorConfig.String())
 	}
 }
 
@@ -554,6 +550,20 @@ func (f *Interface) reloadMisc(c *config.C) {
 	}
 }
 
+// reloadEcn syncs Interface.ecnEnabled with the tunnels.ecn config knob.
+// Default is enabled (RFC 6040 normal mode); set false on the rare path
+// where an underlay middlebox rewrites or drops ECN bits unpredictably.
+func (f *Interface) reloadEcn(c *config.C) {
+	initial := c.InitialLoad()
+	if initial || c.HasChanged("tunnels.ecn") {
+		v := c.GetBool("tunnels.ecn", true)
+		f.ecnEnabled.Store(v)
+		if !initial {
+			f.l.Info("tunnels.ecn changed", "enabled", v)
+		}
+	}
+}
+
 func (f *Interface) emitStats(ctx context.Context, i time.Duration) {
 	ticker := time.NewTicker(i)
 	defer ticker.Stop()
@@ -604,7 +614,7 @@ func (f *Interface) Close() error {
 	for i, u := range f.writers {
 		err := u.Close()
 		if err != nil {
-			f.l.WithError(err).WithField("writer", i).Error("Error while closing udp socket")
+			f.l.Error("Error while closing udp socket", "error", err, "writer", i)
 			errs = append(errs, err)
 		}
 	}

lighthouse.go

@@ -5,6 +5,7 @@ import (
 	"encoding/binary"
 	"errors"
 	"fmt"
+	"log/slog"
 	"net"
 	"net/netip"
 	"slices"
@@ -14,11 +15,10 @@ import (
 	"time"
 
 	"github.com/gaissmai/bart"
-	"github.com/rcrowley/go-metrics"
-	"github.com/sirupsen/logrus"
 	"github.com/slackhq/nebula/cert"
 	"github.com/slackhq/nebula/config"
 	"github.com/slackhq/nebula/header"
+	"github.com/slackhq/nebula/logging"
 	"github.com/slackhq/nebula/udp"
 	"github.com/slackhq/nebula/util"
 )
@@ -34,7 +34,6 @@ type LightHouse struct {
 
 	myVpnNetworks      []netip.Prefix
 	myVpnNetworksTable *bart.Lite
-	punchConn          udp.Conn
 	punchy             *Punchy
 
 	// Local cache of answers from light houses
@@ -69,18 +68,18 @@ type LightHouse struct {
 	// Addr's of relays that can be used by peers to access me
 	relaysForMe atomic.Pointer[[]netip.Addr]
 
-	queryChan chan netip.Addr
+	updateTrigger chan struct{}
+	queryChan     chan netip.Addr
 
 	calculatedRemotes atomic.Pointer[bart.Table[[]*calculatedRemote]] // Maps VpnAddr to []*calculatedRemote
 
-	metrics           *MessageMetrics
-	metricHolepunchTx metrics.Counter
-	l                 *logrus.Logger
+	metrics *MessageMetrics
+	l       *slog.Logger
 }
 
 // NewLightHouseFromConfig will build a Lighthouse struct from the values provided in the config object
 // addrMap should be nil unless this is during a config reload
-func NewLightHouseFromConfig(ctx context.Context, l *logrus.Logger, c *config.C, cs *CertState, pc udp.Conn, p *Punchy) (*LightHouse, error) {
+func NewLightHouseFromConfig(ctx context.Context, l *slog.Logger, c *config.C, cs *CertState, pc udp.Conn, p *Punchy) (*LightHouse, error) {
 	amLighthouse := c.GetBool("lighthouse.am_lighthouse", false)
 	nebulaPort := uint32(c.GetInt("listen.port", 0))
 	if amLighthouse && nebulaPort == 0 {
@@ -103,8 +102,8 @@ func NewLightHouseFromConfig(ctx context.Context, l *logrus.Logger, c *config.C,
 		myVpnNetworksTable: cs.myVpnNetworksTable,
 		addrMap:            make(map[netip.Addr]*RemoteList),
 		nebulaPort:         nebulaPort,
-		punchConn:          pc,
 		punchy:             p,
+		updateTrigger:      make(chan struct{}, 1),
 		queryChan:          make(chan netip.Addr, c.GetUint32("handshakes.query_buffer", 64)),
 		l:                  l,
 	}
@@ -115,9 +114,6 @@ func NewLightHouseFromConfig(ctx context.Context, l *logrus.Logger, c *config.C,
 
 	if c.GetBool("stats.lighthouse_metrics", false) {
 		h.metrics = newLighthouseMetrics()
-		h.metricHolepunchTx = metrics.GetOrRegisterCounter("messages.tx.holepunch", nil)
-	} else {
-		h.metricHolepunchTx = metrics.NilCounter{}
 	}
 
 	err := h.reload(c, true)
@@ -131,7 +127,7 @@ func NewLightHouseFromConfig(ctx context.Context, l *logrus.Logger, c *config.C,
 		case *util.ContextualError:
 			v.Log(l)
 		case error:
-			l.WithError(err).Error("failed to reload lighthouse")
+			l.Error("failed to reload lighthouse", "error", err)
 		}
 	})
 
@@ -203,8 +199,10 @@ func (lh *LightHouse) reload(c *config.C, initial bool) error {
 			//TODO: we could technically insert all returned addrs instead of just the first one if a dns lookup was used
 			addr := addrs[0].Unmap()
 			if lh.myVpnNetworksTable.Contains(addr) {
-				lh.l.WithField("addr", rawAddr).WithField("entry", i+1).
-					Warn("Ignoring lighthouse.advertise_addrs report because it is within the nebula network range")
+				lh.l.Warn("Ignoring lighthouse.advertise_addrs report because it is within the nebula network range",
+					"addr", rawAddr,
+					"entry", i+1,
+				)
 				continue
 			}
 
@@ -222,7 +220,9 @@ func (lh *LightHouse) reload(c *config.C, initial bool) error {
 		lh.interval.Store(int64(c.GetInt("lighthouse.interval", 10)))
 
 		if !initial {
-			lh.l.Infof("lighthouse.interval changed to %v", lh.interval.Load())
+			lh.l.Info("lighthouse.interval changed",
+				"interval", lh.interval.Load(),
+			)
 
 			if lh.updateCancel != nil {
 				// May not always have a running routine
@@ -316,6 +316,7 @@ func (lh *LightHouse) reload(c *config.C, initial bool) error {
 		if !initial {
 			//NOTE: we are not tearing down existing lighthouse connections because they might be used for non lighthouse traffic
 			lh.l.Info("lighthouse.hosts has changed")
+			lh.TriggerUpdate()
 		}
 	}
 
@@ -333,9 +334,12 @@ func (lh *LightHouse) reload(c *config.C, initial bool) error {
 			for _, v := range c.GetStringSlice("relay.relays", nil) {
 				configRIP, err := netip.ParseAddr(v)
 				if err != nil {
-					lh.l.WithField("relay", v).WithError(err).Warn("Parse relay from config failed")
+					lh.l.Warn("Parse relay from config failed",
+						"relay", v,
+						"error", err,
+					)
 				} else {
-					lh.l.WithField("relay", v).Info("Read relay from config")
+					lh.l.Info("Read relay from config", "relay", v)
 					relaysForMe = append(relaysForMe, configRIP)
 				}
 			}
@@ -360,8 +364,10 @@ func (lh *LightHouse) parseLighthouses(c *config.C) ([]netip.Addr, error) {
 		}
 
 		if !lh.myVpnNetworksTable.Contains(addr) {
-			lh.l.WithFields(m{"vpnAddr": addr, "networks": lh.myVpnNetworks}).
-				Warn("lighthouse host is not within our networks, lighthouse functionality will work but layer 3 network traffic to the lighthouse will not")
+			lh.l.Warn("lighthouse host is not within our networks, lighthouse functionality will work but layer 3 network traffic to the lighthouse will not",
+				"vpnAddr", addr,
+				"networks", lh.myVpnNetworks,
+			)
 		}
 		out[i] = addr
 	}
@@ -432,8 +438,11 @@ func (lh *LightHouse) loadStaticMap(c *config.C, staticList map[netip.Addr]struc
 		}
 
 		if !lh.myVpnNetworksTable.Contains(vpnAddr) {
-			lh.l.WithFields(m{"vpnAddr": vpnAddr, "networks": lh.myVpnNetworks, "entry": i + 1}).
-				Warn("static_host_map key is not within our networks, layer 3 network traffic to this host will not work")
+			lh.l.Warn("static_host_map key is not within our networks, layer 3 network traffic to this host will not work",
+				"vpnAddr", vpnAddr,
+				"networks", lh.myVpnNetworks,
+				"entry", i+1,
+			)
 		}
 
 		vals, ok := v.([]any)
@@ -534,12 +543,13 @@ func (lh *LightHouse) DeleteVpnAddrs(allVpnAddrs []netip.Addr) {
 	lh.Lock()
 	rm, ok := lh.addrMap[allVpnAddrs[0]]
 	if ok {
+		debugEnabled := lh.l.Enabled(context.Background(), slog.LevelDebug)
 		for _, addr := range allVpnAddrs {
 			srm := lh.addrMap[addr]
 			if srm == rm {
 				delete(lh.addrMap, addr)
-				if lh.l.Level >= logrus.DebugLevel {
-					lh.l.Debugf("deleting %s from lighthouse.", addr)
+				if debugEnabled {
+					lh.l.Debug("deleting from lighthouse", "vpnAddr", addr)
 				}
 			}
 		}
@@ -656,9 +666,12 @@ func (lh *LightHouse) unlockedGetRemoteList(allAddrs []netip.Addr) *RemoteList {
 
 func (lh *LightHouse) shouldAdd(vpnAddrs []netip.Addr, to netip.Addr) bool {
 	allow := lh.GetRemoteAllowList().AllowAll(vpnAddrs, to)
-	if lh.l.Level >= logrus.TraceLevel {
-		lh.l.WithField("vpnAddrs", vpnAddrs).WithField("udpAddr", to).WithField("allow", allow).
-			Trace("remoteAllowList.Allow")
+	if lh.l.Enabled(context.Background(), logging.LevelTrace) {
+		lh.l.Log(context.Background(), logging.LevelTrace, "remoteAllowList.Allow",
+			"vpnAddrs", vpnAddrs,
+			"udpAddr", to,
+			"allow", allow,
+		)
 	}
 	if !allow {
 		return false
@@ -675,9 +688,12 @@ func (lh *LightHouse) shouldAdd(vpnAddrs []netip.Addr, to netip.Addr) bool {
 func (lh *LightHouse) unlockedShouldAddV4(vpnAddr netip.Addr, to *V4AddrPort) bool {
 	udpAddr := protoV4AddrPortToNetAddrPort(to)
 	allow := lh.GetRemoteAllowList().Allow(vpnAddr, udpAddr.Addr())
-	if lh.l.Level >= logrus.TraceLevel {
-		lh.l.WithField("vpnAddr", vpnAddr).WithField("udpAddr", udpAddr).WithField("allow", allow).
-			Trace("remoteAllowList.Allow")
+	if lh.l.Enabled(context.Background(), logging.LevelTrace) {
+		lh.l.Log(context.Background(), logging.LevelTrace, "remoteAllowList.Allow",
+			"vpnAddr", vpnAddr,
+			"udpAddr", udpAddr,
+			"allow", allow,
+		)
 	}
 
 	if !allow {
@@ -695,9 +711,12 @@ func (lh *LightHouse) unlockedShouldAddV4(vpnAddr netip.Addr, to *V4AddrPort) bo
 func (lh *LightHouse) unlockedShouldAddV6(vpnAddr netip.Addr, to *V6AddrPort) bool {
 	udpAddr := protoV6AddrPortToNetAddrPort(to)
 	allow := lh.GetRemoteAllowList().Allow(vpnAddr, udpAddr.Addr())
-	if lh.l.Level >= logrus.TraceLevel {
-		lh.l.WithField("vpnAddr", vpnAddr).WithField("udpAddr", udpAddr).WithField("allow", allow).
-			Trace("remoteAllowList.Allow")
+	if lh.l.Enabled(context.Background(), logging.LevelTrace) {
+		lh.l.Log(context.Background(), logging.LevelTrace, "remoteAllowList.Allow",
+			"vpnAddr", vpnAddr,
+			"udpAddr", udpAddr,
+			"allow", allow,
+		)
 	}
 
 	if !allow {
@@ -772,8 +791,10 @@ func (lh *LightHouse) innerQueryServer(addr netip.Addr, nb, out []byte) {
 
 		if v == cert.Version1 {
 			if !addr.Is4() {
-				lh.l.WithField("queryVpnAddr", addr).WithField("lighthouseAddr", lhVpnAddr).
-					Error("Can't query lighthouse for v6 address using a v1 protocol")
+				lh.l.Error("Can't query lighthouse for v6 address using a v1 protocol",
+					"queryVpnAddr", addr,
+					"lighthouseAddr", lhVpnAddr,
+				)
 				continue
 			}
 
@@ -784,9 +805,11 @@ func (lh *LightHouse) innerQueryServer(addr netip.Addr, nb, out []byte) {
 
 				v1Query, err = msg.Marshal()
 				if err != nil {
-					lh.l.WithError(err).WithField("queryVpnAddr", addr).
-						WithField("lighthouseAddr", lhVpnAddr).
-						Error("Failed to marshal lighthouse v1 query payload")
+					lh.l.Error("Failed to marshal lighthouse v1 query payload",
+						"error", err,
+						"queryVpnAddr", addr,
+						"lighthouseAddr", lhVpnAddr,
+					)
 					continue
 				}
 			}
@@ -801,9 +824,11 @@ func (lh *LightHouse) innerQueryServer(addr netip.Addr, nb, out []byte) {
 
 				v2Query, err = msg.Marshal()
 				if err != nil {
-					lh.l.WithError(err).WithField("queryVpnAddr", addr).
-						WithField("lighthouseAddr", lhVpnAddr).
-						Error("Failed to marshal lighthouse v2 query payload")
+					lh.l.Error("Failed to marshal lighthouse v2 query payload",
+						"error", err,
+						"queryVpnAddr", addr,
+						"lighthouseAddr", lhVpnAddr,
+					)
 					continue
 				}
 			}
@@ -812,7 +837,11 @@ func (lh *LightHouse) innerQueryServer(addr netip.Addr, nb, out []byte) {
 			queried++
 
 		} else {
-			lh.l.Debugf("Can not query lighthouse for %v using unknown protocol version: %v", addr, v)
+			lh.l.Debug("unsupported protocol version",
+				"op", "query",
+				"queryVpnAddr", addr,
+				"version", v,
+			)
 			continue
 		}
 	}
@@ -841,11 +870,24 @@ func (lh *LightHouse) StartUpdateWorker() {
 				return
 			case <-clockSource.C:
 				continue
+			case <-lh.updateTrigger:
+				continue
 			}
 		}
 	}()
 }
 
+// TriggerUpdate requests an immediate lighthouse update. This is a non-blocking
+// operation intended to be called after a handshake completes with a lighthouse,
+// so the lighthouse has our current addresses without waiting for the next
+// periodic update.
+func (lh *LightHouse) TriggerUpdate() {
+	select {
+	case lh.updateTrigger <- struct{}{}:
+	default:
+	}
+}
+
 func (lh *LightHouse) SendUpdate() {
 	var v4 []*V4AddrPort
 	var v6 []*V6AddrPort
@@ -891,8 +933,9 @@ func (lh *LightHouse) SendUpdate() {
 		if v == cert.Version1 {
 			if v1Update == nil {
 				if !lh.myVpnNetworks[0].Addr().Is4() {
-					lh.l.WithField("lighthouseAddr", lhVpnAddr).
-						Warn("cannot update lighthouse using v1 protocol without an IPv4 address")
+					lh.l.Warn("cannot update lighthouse using v1 protocol without an IPv4 address",
+						"lighthouseAddr", lhVpnAddr,
+					)
 					continue
 				}
 				var relays []uint32
@@ -916,8 +959,10 @@ func (lh *LightHouse) SendUpdate() {
 
 				v1Update, err = msg.Marshal()
 				if err != nil {
-					lh.l.WithError(err).WithField("lighthouseAddr", lhVpnAddr).
-						Error("Error while marshaling for lighthouse v1 update")
+					lh.l.Error("Error while marshaling for lighthouse v1 update",
+						"error", err,
+						"lighthouseAddr", lhVpnAddr,
+					)
 					continue
 				}
 			}
@@ -943,8 +988,10 @@ func (lh *LightHouse) SendUpdate() {
 
 				v2Update, err = msg.Marshal()
 				if err != nil {
-					lh.l.WithError(err).WithField("lighthouseAddr", lhVpnAddr).
-						Error("Error while marshaling for lighthouse v2 update")
+					lh.l.Error("Error while marshaling for lighthouse v2 update",
+						"error", err,
+						"lighthouseAddr", lhVpnAddr,
+					)
 					continue
 				}
 			}
@@ -953,7 +1000,10 @@ func (lh *LightHouse) SendUpdate() {
 			updated++
 
 		} else {
-			lh.l.Debugf("Can not update lighthouse using unknown protocol version: %v", v)
+			lh.l.Debug("unsupported protocol version",
+				"op", "update",
+				"version", v,
+			)
 			continue
 		}
 	}
@@ -967,7 +1017,7 @@ type LightHouseHandler struct {
 	out  []byte
 	pb   []byte
 	meta *NebulaMeta
-	l    *logrus.Logger
+	l    *slog.Logger
 }
 
 func (lh *LightHouse) NewRequestHandler() *LightHouseHandler {
@@ -1016,14 +1066,19 @@ func (lhh *LightHouseHandler) HandleRequest(rAddr netip.AddrPort, fromVpnAddrs [
 	n := lhh.resetMeta()
 	err := n.Unmarshal(p)
 	if err != nil {
-		lhh.l.WithError(err).WithField("vpnAddrs", fromVpnAddrs).WithField("udpAddr", rAddr).
-			Error("Failed to unmarshal lighthouse packet")
+		lhh.l.Error("Failed to unmarshal lighthouse packet",
+			"error", err,
+			"vpnAddrs", fromVpnAddrs,
+			"udpAddr", rAddr,
+		)
 		return
 	}
 
 	if n.Details == nil {
-		lhh.l.WithField("vpnAddrs", fromVpnAddrs).WithField("udpAddr", rAddr).
-			Error("Invalid lighthouse update")
+		lhh.l.Error("Invalid lighthouse update",
+			"vpnAddrs", fromVpnAddrs,
+			"udpAddr", rAddr,
+		)
 		return
 	}
 
@@ -1051,25 +1106,29 @@ func (lhh *LightHouseHandler) HandleRequest(rAddr netip.AddrPort, fromVpnAddrs [
 func (lhh *LightHouseHandler) handleHostQuery(n *NebulaMeta, fromVpnAddrs []netip.Addr, addr netip.AddrPort, w EncWriter) {
 	// Exit if we don't answer queries
 	if !lhh.lh.amLighthouse {
-		if lhh.l.Level >= logrus.DebugLevel {
-			lhh.l.Debugln("I don't answer queries, but received from: ", addr)
+		if lhh.l.Enabled(context.Background(), slog.LevelDebug) {
+			lhh.l.Debug("I don't answer queries, but received one", "from", addr)
 		}
 		return
 	}
 
 	queryVpnAddr, useVersion, err := n.Details.GetVpnAddrAndVersion()
 	if err != nil {
-		if lhh.l.Level >= logrus.DebugLevel {
-			lhh.l.WithField("from", fromVpnAddrs).WithField("details", n.Details).
-				Debugln("Dropping malformed HostQuery")
+		if lhh.l.Enabled(context.Background(), slog.LevelDebug) {
+			lhh.l.Debug("Dropping malformed HostQuery",
+				"from", fromVpnAddrs,
+				"details", n.Details,
+			)
 		}
 		return
 	}
 	if useVersion == cert.Version1 && queryVpnAddr.Is6() {
 		// this case really shouldn't be possible to represent, but reject it anyway.
-		if lhh.l.Level >= logrus.DebugLevel {
-			lhh.l.WithField("vpnAddrs", fromVpnAddrs).WithField("queryVpnAddr", queryVpnAddr).
-				Debugln("invalid vpn addr for v1 handleHostQuery")
+		if lhh.l.Enabled(context.Background(), slog.LevelDebug) {
+			lhh.l.Debug("invalid vpn addr for v1 handleHostQuery",
+				"vpnAddrs", fromVpnAddrs,
+				"queryVpnAddr", queryVpnAddr,
+			)
 		}
 		return
 	}
@@ -1094,7 +1153,10 @@ func (lhh *LightHouseHandler) handleHostQuery(n *NebulaMeta, fromVpnAddrs []neti
 	}
 
 	if err != nil {
-		lhh.l.WithError(err).WithField("vpnAddrs", fromVpnAddrs).Error("Failed to marshal lighthouse host query reply")
+		lhh.l.Error("Failed to marshal lighthouse host query reply",
+			"error", err,
+			"vpnAddrs", fromVpnAddrs,
+		)
 		return
 	}
 
@@ -1122,8 +1184,10 @@ func (lhh *LightHouseHandler) sendHostPunchNotification(n *NebulaMeta, fromVpnAd
 			if ok {
 				whereToPunch = newDest
 			} else {
-				if lhh.l.Level >= logrus.DebugLevel {
-					lhh.l.WithField("to", crt.Networks()).Debugln("unable to punch to host, no addresses in common")
+				if lhh.l.Enabled(context.Background(), slog.LevelDebug) {
+					lhh.l.Debug("unable to punch to host, no addresses in common",
+						"to", crt.Networks(),
+					)
 				}
 			}
 		}
@@ -1149,7 +1213,10 @@ func (lhh *LightHouseHandler) sendHostPunchNotification(n *NebulaMeta, fromVpnAd
 	}
 
 	if err != nil {
-		lhh.l.WithError(err).WithField("vpnAddrs", fromVpnAddrs).Error("Failed to marshal lighthouse host was queried for")
+		lhh.l.Error("Failed to marshal lighthouse host was queried for",
+			"error", err,
+			"vpnAddrs", fromVpnAddrs,
+		)
 		return
 	}
 
@@ -1191,8 +1258,11 @@ func (lhh *LightHouseHandler) coalesceAnswers(v cert.Version, c *cache, n *Nebul
 				n.Details.RelayVpnAddrs = append(n.Details.RelayVpnAddrs, netAddrToProtoAddr(r))
 			}
 		} else {
-			if lhh.l.Level >= logrus.DebugLevel {
-				lhh.l.WithField("version", v).Debug("unsupported protocol version")
+			if lhh.l.Enabled(context.Background(), slog.LevelDebug) {
+				lhh.l.Debug("unsupported protocol version",
+					"op", "coalesceAnswers",
+					"version", v,
+				)
 			}
 		}
 	}
@@ -1205,8 +1275,11 @@ func (lhh *LightHouseHandler) handleHostQueryReply(n *NebulaMeta, fromVpnAddrs [
 
 	certVpnAddr, _, err := n.Details.GetVpnAddrAndVersion()
 	if err != nil {
-		if lhh.l.Level >= logrus.DebugLevel {
-			lhh.l.WithError(err).WithField("vpnAddrs", fromVpnAddrs).Error("dropping malformed HostQueryReply")
+		if lhh.l.Enabled(context.Background(), slog.LevelDebug) {
+			lhh.l.Error("dropping malformed HostQueryReply",
+				"error", err,
+				"vpnAddrs", fromVpnAddrs,
+			)
 		}
 		return
 	}
@@ -1231,8 +1304,8 @@ func (lhh *LightHouseHandler) handleHostQueryReply(n *NebulaMeta, fromVpnAddrs [
 
 func (lhh *LightHouseHandler) handleHostUpdateNotification(n *NebulaMeta, fromVpnAddrs []netip.Addr, w EncWriter) {
 	if !lhh.lh.amLighthouse {
-		if lhh.l.Level >= logrus.DebugLevel {
-			lhh.l.Debugln("I am not a lighthouse, do not take host updates: ", fromVpnAddrs)
+		if lhh.l.Enabled(context.Background(), slog.LevelDebug) {
+			lhh.l.Debug("I am not a lighthouse, do not take host updates", "from", fromVpnAddrs)
 		}
 		return
 	}
@@ -1255,8 +1328,11 @@ func (lhh *LightHouseHandler) handleHostUpdateNotification(n *NebulaMeta, fromVp
 
 	//Simple check that the host sent this not someone else, if detailsVpnAddr is filled
 	if detailsVpnAddr.IsValid() && !slices.Contains(fromVpnAddrs, detailsVpnAddr) {
-		if lhh.l.Level >= logrus.DebugLevel {
-			lhh.l.WithField("vpnAddrs", fromVpnAddrs).WithField("answer", detailsVpnAddr).Debugln("Host sent invalid update")
+		if lhh.l.Enabled(context.Background(), slog.LevelDebug) {
+			lhh.l.Debug("Host sent invalid update",
+				"vpnAddrs", fromVpnAddrs,
+				"answer", detailsVpnAddr,
+			)
 		}
 		return
 	}
@@ -1278,7 +1354,9 @@ func (lhh *LightHouseHandler) handleHostUpdateNotification(n *NebulaMeta, fromVp
 	switch useVersion {
 	case cert.Version1:
 		if !fromVpnAddrs[0].Is4() {
-			lhh.l.WithField("vpnAddrs", fromVpnAddrs).Error("Can not send HostUpdateNotificationAck for a ipv6 vpn ip in a v1 message")
+			lhh.l.Error("Can not send HostUpdateNotificationAck for a ipv6 vpn ip in a v1 message",
+				"vpnAddrs", fromVpnAddrs,
+			)
 			return
 		}
 		vpnAddrB := fromVpnAddrs[0].As4()
@@ -1286,13 +1364,16 @@ func (lhh *LightHouseHandler) handleHostUpdateNotification(n *NebulaMeta, fromVp
 	case cert.Version2:
 		// do nothing, we want to send a blank message
 	default:
-		lhh.l.WithField("useVersion", useVersion).Error("invalid protocol version")
+		lhh.l.Error("invalid protocol version", "useVersion", useVersion)
 		return
 	}
 
 	ln, err := n.MarshalTo(lhh.pb)
 	if err != nil {
-		lhh.l.WithError(err).WithField("vpnAddrs", fromVpnAddrs).Error("Failed to marshal lighthouse host update ack")
+		lhh.l.Error("Failed to marshal lighthouse host update ack",
+			"error", err,
+			"vpnAddrs", fromVpnAddrs,
+		)
 		return
 	}
 
@@ -1309,59 +1390,34 @@ func (lhh *LightHouseHandler) handleHostPunchNotification(n *NebulaMeta, fromVpn
 
 	detailsVpnAddr, _, err := n.Details.GetVpnAddrAndVersion()
 	if err != nil {
-		if lhh.l.Level >= logrus.DebugLevel {
-			lhh.l.WithField("details", n.Details).WithError(err).Debugln("dropping invalid HostPunchNotification")
+		if lhh.l.Enabled(context.Background(), slog.LevelDebug) {
+			lhh.l.Debug("dropping invalid HostPunchNotification",
+				"details", n.Details,
+				"error", err,
+			)
 		}
 		return
 	}
 
-	empty := []byte{0}
-	punch := func(vpnPeer netip.AddrPort, logVpnAddr netip.Addr) {
-		if !vpnPeer.IsValid() {
-			return
-		}
-
-		go func() {
-			time.Sleep(lhh.lh.punchy.GetDelay())
-			lhh.lh.metricHolepunchTx.Inc(1)
-			lhh.lh.punchConn.WriteTo(empty, vpnPeer)
-		}()
-
-		if lhh.l.Level >= logrus.DebugLevel {
-			lhh.l.Debugf("Punching on %v for %v", vpnPeer, logVpnAddr)
-		}
-	}
-
 	remoteAllowList := lhh.lh.GetRemoteAllowList()
 	for _, a := range n.Details.V4AddrPorts {
 		b := protoV4AddrPortToNetAddrPort(a)
 		if remoteAllowList.Allow(detailsVpnAddr, b.Addr()) {
-			punch(b, detailsVpnAddr)
+			lhh.lh.punchy.Schedule(b, detailsVpnAddr)
 		}
 	}
 
 	for _, a := range n.Details.V6AddrPorts {
 		b := protoV6AddrPortToNetAddrPort(a)
 		if remoteAllowList.Allow(detailsVpnAddr, b.Addr()) {
-			punch(b, detailsVpnAddr)
+			lhh.lh.punchy.Schedule(b, detailsVpnAddr)
 		}
 	}
 
 	// This sends a nebula test packet to the host trying to contact us. In the case
 	// of a double nat or other difficult scenario, this may help establish
-	// a tunnel.
-	if lhh.lh.punchy.GetRespond() {
-		go func() {
-			time.Sleep(lhh.lh.punchy.GetRespondDelay())
-			if lhh.l.Level >= logrus.DebugLevel {
-				lhh.l.Debugf("Sending a nebula test packet to vpn addr %s", detailsVpnAddr)
-			}
-			//NOTE: we have to allocate a new output buffer here since we are spawning a new goroutine
-			// for each punchBack packet. We should move this into a timerwheel or a single goroutine
-			// managed by a channel.
-			w.SendMessageToVpnAddr(header.Test, header.TestRequest, detailsVpnAddr, []byte(""), make([]byte, 12, 12), make([]byte, mtu))
-		}()
-	}
+	// a tunnel. ScheduleRespond is a no-op when punchy.respond is disabled.
+	lhh.lh.punchy.ScheduleRespond(detailsVpnAddr)
 }
 
 func protoAddrToNetAddr(addr *Addr) netip.Addr {

logger.go

@@ -1,45 +0,0 @@
-package nebula
-
-import (
-	"fmt"
-	"strings"
-	"time"
-
-	"github.com/sirupsen/logrus"
-	"github.com/slackhq/nebula/config"
-)
-
-func configLogger(l *logrus.Logger, c *config.C) error {
-	// set up our logging level
-	logLevel, err := logrus.ParseLevel(strings.ToLower(c.GetString("logging.level", "info")))
-	if err != nil {
-		return fmt.Errorf("%s; possible levels: %s", err, logrus.AllLevels)
-	}
-	l.SetLevel(logLevel)
-
-	disableTimestamp := c.GetBool("logging.disable_timestamp", false)
-	timestampFormat := c.GetString("logging.timestamp_format", "")
-	fullTimestamp := (timestampFormat != "")
-	if timestampFormat == "" {
-		timestampFormat = time.RFC3339
-	}
-
-	logFormat := strings.ToLower(c.GetString("logging.format", "text"))
-	switch logFormat {
-	case "text":
-		l.Formatter = &logrus.TextFormatter{
-			TimestampFormat:  timestampFormat,
-			FullTimestamp:    fullTimestamp,
-			DisableTimestamp: disableTimestamp,
-		}
-	case "json":
-		l.Formatter = &logrus.JSONFormatter{
-			TimestampFormat:  timestampFormat,
-			DisableTimestamp: disableTimestamp,
-		}
-	default:
-		return fmt.Errorf("unknown log format `%s`. possible formats: %s", logFormat, []string{"text", "json"})
-	}
-
-	return nil
-}

logging/logger.go

@@ -0,0 +1,233 @@
+// Package logging wires the nebula runtime-reconfigurable slog handler used
+// by nebula.Main and the nebula CLI binaries. Callers build a logger with
+// NewLogger, then call ApplyConfig at startup and from a config reload
+// callback to push logging.level, logging.format, and
+// logging.disable_timestamp changes onto the logger without rebuilding it.
+package logging
+
+import (
+	"context"
+	"fmt"
+	"io"
+	"log/slog"
+	"strings"
+	"sync/atomic"
+	"time"
+)
+
+// Config is the subset of *config.C that ApplyConfig reads. Declaring it
+// here keeps the logging package from depending on config directly, which
+// would cycle through the shared test helpers (test.NewLogger imports
+// logging, and config's tests import test). *config.C satisfies this
+// interface structurally with no adapter.
+type Config interface {
+	GetString(key, def string) string
+	GetBool(key string, def bool) bool
+}
+
+// LevelTrace is a custom slog level below Debug, used when logging.level is
+// "trace". slog has no builtin trace level; the value is one step below
+// slog.LevelDebug in slog's 4-point spacing.
+const LevelTrace = slog.Level(-8)
+
+// NewLogger returns a *slog.Logger whose level, format, and timestamp
+// emission can be reconfigured at runtime via ApplyConfig and the SSH debug
+// commands. The default configuration is info-level text output so log
+// calls made before ApplyConfig runs still produce output. Timestamps
+// follow slog's default RFC3339Nano format; set logging.disable_timestamp
+// in config to suppress them.
+//
+// ApplyConfig and the SSH commands discover the reconfig surface via
+// structural type-assertion on l.Handler(), so replacement implementations
+// (tests, platform-specific sinks) need only implement the subset of
+// {SetLevel(slog.Level), SetFormat(string) error, SetDisableTimestamp(bool)}
+// they care about. Callers that pass a plain *slog.Logger without these
+// methods get a silent no-op; reconfiguration is always opt-in.
+func NewLogger(w io.Writer) *slog.Logger {
+	return slog.New(NewHandler(w))
+}
+
+// NewHandler builds the *Handler that NewLogger wraps. Exported for
+// platform-specific sinks (notably cmd/nebula-service/logs_windows.go)
+// that want to wrap the handler with extra behavior, such as tagging each
+// record with its Event Log severity, while still benefiting from all the
+// level / format / timestamp / WithAttrs machinery implemented here.
+func NewHandler(w io.Writer) *Handler {
+	root := &handlerRoot{}
+	root.level.Set(slog.LevelInfo)
+	opts := &slog.HandlerOptions{Level: &root.level}
+	return &Handler{
+		root: root,
+		text: slog.NewTextHandler(w, opts),
+		json: slog.NewJSONHandler(w, opts),
+	}
+}
+
+// handlerRoot carries the reconfiguration state shared by every logger
+// derived from a NewHandler call. All fields are consulted on the log
+// path and updated lock-free.
+type handlerRoot struct {
+	level            slog.LevelVar
+	disableTimestamp atomic.Bool
+	// jsonMode picks which of the pre-derived inner handlers Handler.Handle
+	// dispatches to. Flipping it propagates instantly to every derived logger
+	// without rebuilding or chain-replaying anything.
+	jsonMode atomic.Bool
+}
+
+// Handler is the slog.Handler returned by NewHandler. It holds two
+// pre-derived slog handlers -- one text, one json -- both built from the
+// same accumulated WithAttrs/WithGroup state. Handle picks which one to
+// dispatch to based on handlerRoot.jsonMode, so a SetFormat call takes
+// effect immediately across the whole process without having to rebuild
+// any derived loggers.
+type Handler struct {
+	root *handlerRoot
+	text slog.Handler
+	json slog.Handler
+}
+
+func (h *Handler) Enabled(_ context.Context, l slog.Level) bool {
+	return h.root.level.Level() <= l
+}
+
+func (h *Handler) Handle(ctx context.Context, r slog.Record) error {
+	if h.root.disableTimestamp.Load() {
+		r.Time = time.Time{}
+	}
+	if h.root.jsonMode.Load() {
+		return h.json.Handle(ctx, r)
+	}
+	return h.text.Handle(ctx, r)
+}
+
+func (h *Handler) WithAttrs(attrs []slog.Attr) slog.Handler {
+	if len(attrs) == 0 {
+		return h
+	}
+	return &Handler{
+		root: h.root,
+		text: h.text.WithAttrs(attrs),
+		json: h.json.WithAttrs(attrs),
+	}
+}
+
+func (h *Handler) WithGroup(name string) slog.Handler {
+	if name == "" {
+		return h
+	}
+	return &Handler{
+		root: h.root,
+		text: h.text.WithGroup(name),
+		json: h.json.WithGroup(name),
+	}
+}
+
+// SetLevel updates the effective log level. Propagates to every derived
+// logger via the shared LevelVar.
+func (h *Handler) SetLevel(level slog.Level) { h.root.level.Set(level) }
+
+// GetLevel reports the current log level.
+func (h *Handler) GetLevel() slog.Level { return h.root.level.Level() }
+
+// SetFormat flips the output format atomically. Valid formats are "text"
+// and "json". Every derived logger sees the new format on its next Handle
+// call; no rebuild or registration is required.
+func (h *Handler) SetFormat(format string) error {
+	switch format {
+	case "text":
+		h.root.jsonMode.Store(false)
+	case "json":
+		h.root.jsonMode.Store(true)
+	default:
+		return fmt.Errorf("unknown log format `%s`. possible formats: %s", format, []string{"text", "json"})
+	}
+	return nil
+}
+
+// GetFormat reports the currently selected format name.
+func (h *Handler) GetFormat() string {
+	if h.root.jsonMode.Load() {
+		return "json"
+	}
+	return "text"
+}
+
+// SetDisableTimestamp toggles whether Handle zeroes r.Time before
+// dispatching (slog's builtin text/json handlers skip emitting the time
+// attribute on a zero time).
+func (h *Handler) SetDisableTimestamp(v bool) { h.root.disableTimestamp.Store(v) }
+
+// ApplyConfig reads logging.level, logging.format, and (optionally)
+// logging.disable_timestamp from c and applies them to l. The reconfig
+// surface is discovered via structural type-assertion on l.Handler(), so
+// foreign handlers silently opt out of whichever capabilities they do not
+// implement.
+//
+// nebula.Main does NOT call this function on your behalf; callers that want
+// config-driven log level / format / timestamp updates invoke it at
+// startup and register it as a reload callback themselves. This keeps the
+// library from mutating an embedder's logger without their say-so.
+func ApplyConfig(l *slog.Logger, c Config) error {
+	h := l.Handler()
+
+	lvl, err := ParseLevel(strings.ToLower(c.GetString("logging.level", "info")))
+	if err != nil {
+		return err
+	}
+	if ls, ok := h.(interface{ SetLevel(slog.Level) }); ok {
+		ls.SetLevel(lvl)
+	}
+
+	format := strings.ToLower(c.GetString("logging.format", "text"))
+	if fs, ok := h.(interface{ SetFormat(string) error }); ok {
+		if err := fs.SetFormat(format); err != nil {
+			return err
+		}
+	}
+
+	if ts, ok := h.(interface{ SetDisableTimestamp(bool) }); ok {
+		ts.SetDisableTimestamp(c.GetBool("logging.disable_timestamp", false))
+	}
+	return nil
+}
+
+// ParseLevel converts a config-string level name ("trace", "debug", "info",
+// "warn"/"warning", "error", "fatal"/"panic") to a slog.Level. "fatal" and
+// "panic" are accepted for backwards compatibility with pre-slog configs
+// and both map to slog.LevelError.
+func ParseLevel(s string) (slog.Level, error) {
+	switch s {
+	case "trace":
+		return LevelTrace, nil
+	case "debug":
+		return slog.LevelDebug, nil
+	case "info":
+		return slog.LevelInfo, nil
+	case "warn", "warning":
+		return slog.LevelWarn, nil
+	case "error":
+		return slog.LevelError, nil
+	case "fatal", "panic":
+		return slog.LevelError, nil
+	default:
+		return 0, fmt.Errorf("not a valid logging level: %q", s)
+	}
+}
+
+// LevelName returns a human-readable name for a slog.Level matching the
+// strings accepted by ParseLevel.
+func LevelName(l slog.Level) string {
+	switch {
+	case l <= LevelTrace:
+		return "trace"
+	case l <= slog.LevelDebug:
+		return "debug"
+	case l <= slog.LevelInfo:
+		return "info"
+	case l <= slog.LevelWarn:
+		return "warn"
+	default:
+		return "error"
+	}
+}

logging/logger_bench_test.go

@@ -0,0 +1,90 @@
+package logging
+
+import (
+	"context"
+	"io"
+	"log/slog"
+	"testing"
+)
+
+// BenchmarkLogger_* compare the handler returned by NewLogger against a
+// stock slog text handler. The key thing we care about is the per-log
+// cost on a logger that has been derived via .With(), because that is the
+// shape subsystems store on their structs (HostInfo.logger(),
+// lh.l.With("subsystem", ...), etc.) and call from hot paths.
+
+func BenchmarkLogger_Stock_RootInfo(b *testing.B) {
+	l := slog.New(slog.DiscardHandler)
+	b.ReportAllocs()
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		l.Info("hello", "i", i)
+	}
+}
+
+func BenchmarkLogger_Nebula_RootInfo(b *testing.B) {
+	l := NewLogger(io.Discard)
+	b.ReportAllocs()
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		l.Info("hello", "i", i)
+	}
+}
+
+func BenchmarkLogger_Stock_DerivedInfo(b *testing.B) {
+	l := slog.New(slog.DiscardHandler).With(
+		"subsystem", "bench",
+		"localIndex", 1234,
+	)
+	b.ReportAllocs()
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		l.Info("hello", "i", i)
+	}
+}
+
+func BenchmarkLogger_Nebula_DerivedInfo(b *testing.B) {
+	l := NewLogger(io.Discard).With(
+		"subsystem", "bench",
+		"localIndex", 1234,
+	)
+	b.ReportAllocs()
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		l.Info("hello", "i", i)
+	}
+}
+
+// Gated-off-path benchmarks: mimic the typical hot-path shape
+// `if l.Enabled(ctx, slog.LevelDebug) { ... }` where the log is gated below
+// the active level. This is the dominant pattern in inside.go/outside.go and
+// what we pay on every packet.
+func BenchmarkLogger_Stock_DerivedEnabledGateMiss(b *testing.B) {
+	l := slog.New(slog.DiscardHandler).With(
+		"subsystem", "bench",
+		"localIndex", 1234,
+	)
+	ctx := context.Background()
+	b.ReportAllocs()
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		if l.Enabled(ctx, slog.LevelDebug) {
+			l.Debug("hello", "i", i)
+		}
+	}
+}
+
+func BenchmarkLogger_Nebula_DerivedEnabledGateMiss(b *testing.B) {
+	l := NewLogger(io.Discard).With(
+		"subsystem", "bench",
+		"localIndex", 1234,
+	)
+	ctx := context.Background()
+	b.ReportAllocs()
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		if l.Enabled(ctx, slog.LevelDebug) {
+			l.Debug("hello", "i", i)
+		}
+	}
+}

main.go

@@ -3,13 +3,16 @@ package nebula
 import (
 	"context"
 	"fmt"
+	"log/slog"
 	"net"
+	"net/http"
+	_ "net/http/pprof"
 	"net/netip"
+	"runtime"
 	"runtime/debug"
 	"strings"
 	"time"
 
-	"github.com/sirupsen/logrus"
 	"github.com/slackhq/nebula/config"
 	"github.com/slackhq/nebula/overlay"
 	"github.com/slackhq/nebula/sshd"
@@ -20,7 +23,7 @@ import (
 
 type m = map[string]any
 
-func Main(c *config.C, configTest bool, buildVersion string, logger *logrus.Logger, deviceFactory overlay.DeviceFactory) (retcon *Control, reterr error) {
+func Main(c *config.C, configTest bool, buildVersion string, l *slog.Logger, deviceFactory overlay.DeviceFactory) (retcon *Control, reterr error) {
 	ctx, cancel := context.WithCancel(context.Background())
 	// Automatically cancel the context if Main returns an error, to signal all created goroutines to quit.
 	defer func() {
@@ -33,10 +36,8 @@ func Main(c *config.C, configTest bool, buildVersion string, logger *logrus.Logg
 		buildVersion = moduleVersion()
 	}
 
-	l := logger
-	l.Formatter = &logrus.TextFormatter{
-		FullTimestamp: true,
-	}
+	//todo no merge
+	go http.ListenAndServe(":6060", nil)
 
 	// Print the config if in test, the exit comes later
 	if configTest {
@@ -46,21 +47,9 @@ func Main(c *config.C, configTest bool, buildVersion string, logger *logrus.Logg
 		}
 
 		// Print the final config
-		l.Println(string(b))
+		l.Info(string(b))
 	}
 
-	err := configLogger(l, c)
-	if err != nil {
-		return nil, util.ContextualizeIfNeeded("Failed to configure the logger", err)
-	}
-
-	c.RegisterReloadCallback(func(c *config.C) {
-		err := configLogger(l, c)
-		if err != nil {
-			l.WithError(err).Error("Failed to configure the logger")
-		}
-	})
-
 	pki, err := NewPKIFromConfig(l, c)
 	if err != nil {
 		return nil, util.ContextualizeIfNeeded("Failed to load PKI from config", err)
@@ -70,9 +59,9 @@ func Main(c *config.C, configTest bool, buildVersion string, logger *logrus.Logg
 	if err != nil {
 		return nil, util.ContextualizeIfNeeded("Error while loading firewall rules", err)
 	}
-	l.WithField("firewallHashes", fw.GetRuleHashes()).Info("Firewall started")
+	l.Info("Firewall started", "firewallHashes", fw.GetRuleHashes())
 
-	ssh, err := sshd.NewSSHServer(l.WithField("subsystem", "sshd"))
+	ssh, err := sshd.NewSSHServer(ctx, l.With("subsystem", "sshd"))
 	if err != nil {
 		return nil, util.ContextualizeIfNeeded("Error while creating SSH server", err)
 	}
@@ -81,7 +70,7 @@ func Main(c *config.C, configTest bool, buildVersion string, logger *logrus.Logg
 	if c.GetBool("sshd.enabled", false) {
 		sshStart, err = configSSH(l, ssh, c)
 		if err != nil {
-			l.WithError(err).Warn("Failed to configure sshd, ssh debugging will not be available")
+			l.Warn("Failed to configure sshd, ssh debugging will not be available", "error", err)
 			sshStart = nil
 		}
 	}
@@ -99,7 +88,7 @@ func Main(c *config.C, configTest bool, buildVersion string, logger *logrus.Logg
 			routines = 1
 		}
 		if routines > 1 {
-			l.WithField("routines", routines).Info("Using multiple routines")
+			l.Info("Using multiple routines", "routines", routines)
 		}
 	} else {
 		// deprecated and undocumented
@@ -107,7 +96,7 @@ func Main(c *config.C, configTest bool, buildVersion string, logger *logrus.Logg
 		udpQueues := c.GetInt("listen.routines", 1)
 		routines = max(tunQueues, udpQueues)
 		if routines != 1 {
-			l.WithField("routines", routines).Warn("Setting tun.routines and listen.routines is deprecated. Use `routines` instead")
+			l.Warn("Setting tun.routines and listen.routines is deprecated. Use `routines` instead", "routines", routines)
 		}
 	}
 
@@ -120,7 +109,7 @@ func Main(c *config.C, configTest bool, buildVersion string, logger *logrus.Logg
 		conntrackCacheTimeout = 1 * time.Second
 	}
 	if conntrackCacheTimeout > 0 {
-		l.WithField("duration", conntrackCacheTimeout).Info("Using routine-local conntrack cache")
+		l.Info("Using routine-local conntrack cache", "duration", conntrackCacheTimeout)
 	}
 
 	var tun overlay.Device
@@ -166,7 +155,7 @@ func Main(c *config.C, configTest bool, buildVersion string, logger *logrus.Logg
 		}
 
 		for i := 0; i < routines; i++ {
-			l.Infof("listening on %v", netip.AddrPortFrom(listenHost, uint16(port)))
+			l.Info("listening", "addr", netip.AddrPortFrom(listenHost, uint16(port)))
 			udpServer, err := udp.NewListener(l, listenHost, port, routines > 1, c.GetInt("listen.batch", 64))
 			if err != nil {
 				return nil, util.NewContextualError("Failed to open udp listener", m{"queue": i}, err)
@@ -187,7 +176,7 @@ func Main(c *config.C, configTest bool, buildVersion string, logger *logrus.Logg
 	}
 
 	hostMap := NewHostMapFromConfig(l, c)
-	punchy := NewPunchyFromConfig(l, c)
+	punchy := NewPunchyFromConfig(l, c, udpConns[0])
 	connManager := newConnectionManagerFromConfig(l, c, hostMap, punchy)
 	lightHouse, err := NewLightHouseFromConfig(ctx, l, c, pki.getCertState(), udpConns[0], punchy)
 	if err != nil {
@@ -201,27 +190,19 @@ func Main(c *config.C, configTest bool, buildVersion string, logger *logrus.Logg
 		messageMetrics = newMessageMetricsOnlyRecvError()
 	}
 
-	useRelays := c.GetBool("relay.use_relays", DefaultUseRelays) && !c.GetBool("relay.am_relay", false)
-
 	handshakeConfig := HandshakeConfig{
-		tryInterval:   c.GetDuration("handshakes.try_interval", DefaultHandshakeTryInterval),
-		retries:       int64(c.GetInt("handshakes.retries", DefaultHandshakeRetries)),
-		triggerBuffer: c.GetInt("handshakes.trigger_buffer", DefaultHandshakeTriggerBuffer),
-		useRelays:     useRelays,
-
+		tryInterval:    c.GetDuration("handshakes.try_interval", DefaultHandshakeTryInterval),
+		retries:        int64(c.GetInt("handshakes.retries", DefaultHandshakeRetries)),
+		triggerBuffer:  c.GetInt("handshakes.trigger_buffer", DefaultHandshakeTriggerBuffer),
 		messageMetrics: messageMetrics,
 	}
 
 	handshakeManager := NewHandshakeManager(l, hostMap, lightHouse, udpConns[0], handshakeConfig)
 	lightHouse.handshakeTrigger = handshakeManager.trigger
 
-	serveDns := false
-	if c.GetBool("lighthouse.serve_dns", false) {
-		if c.GetBool("lighthouse.am_lighthouse", false) {
-			serveDns = true
-		} else {
-			l.Warn("DNS server refusing to run because this host is not a lighthouse.")
-		}
+	ds, err := newDnsServerFromConfig(ctx, l, pki.getCertState(), hostMap, c)
+	if err != nil {
+		l.Warn("Failed to start DNS responder", "error", err)
 	}
 
 	ifConfig := &InterfaceConfig{
@@ -230,7 +211,7 @@ func Main(c *config.C, configTest bool, buildVersion string, logger *logrus.Logg
 		Outside:               udpConns[0],
 		pki:                   pki,
 		Firewall:              fw,
-		ServeDns:              serveDns,
+		DnsServer:             ds,
 		HandshakeManager:      handshakeManager,
 		connectionManager:     connManager,
 		lightHouse:            lightHouse,
@@ -245,6 +226,7 @@ func Main(c *config.C, configTest bool, buildVersion string, logger *logrus.Logg
 		relayManager:          NewRelayManager(ctx, l, hostMap, c),
 		punchy:                punchy,
 		ConntrackCacheTimeout: conntrackCacheTimeout,
+		CpuAffinity:           parseCpuAffinity(c, l, routines),
 		l:                     l,
 	}
 
@@ -262,12 +244,15 @@ func Main(c *config.C, configTest bool, buildVersion string, logger *logrus.Logg
 		ifce.reloadDisconnectInvalid(c)
 		ifce.reloadSendRecvError(c)
 		ifce.reloadAcceptRecvError(c)
+		ifce.reloadEcn(c)
 
 		handshakeManager.f = ifce
 		go handshakeManager.Run(ctx)
+
+		punchy.Start(ctx, ifce, hostMap, lightHouse)
 	}
 
-	statsStart, err := startStats(l, c, buildVersion, configTest)
+	stats, err := newStatsServerFromConfig(ctx, l, c, buildVersion, configTest)
 	if err != nil {
 		return nil, util.ContextualizeIfNeeded("Failed to start stats emitter", err)
 	}
@@ -280,13 +265,6 @@ func Main(c *config.C, configTest bool, buildVersion string, logger *logrus.Logg
 
 	attachCommands(l, c, ssh, ifce)
 
-	// Start DNS server last to allow using the nebula IP as lighthouse.dns.host
-	var dnsStart func()
-	if lightHouse.amLighthouse && serveDns {
-		l.Debugln("Starting dns server")
-		dnsStart = dnsMain(l, pki.getCertState(), hostMap, c)
-	}
-
 	return &Control{
 		state:                  StateReady,
 		f:                      ifce,
@@ -294,13 +272,60 @@ func Main(c *config.C, configTest bool, buildVersion string, logger *logrus.Logg
 		ctx:                    ctx,
 		cancel:                 cancel,
 		sshStart:               sshStart,
-		statsStart:             statsStart,
-		dnsStart:               dnsStart,
+		statsStart:             stats.Start,
+		dnsStart:               ds.Start,
 		lighthouseStart:        lightHouse.StartUpdateWorker,
 		connectionManagerStart: connManager.Start,
 	}, nil
 }
 
+// parseCpuAffinity reads `tun.cpu_affinity` from the config — a list of
+// integer CPU IDs, one per TUN reader goroutine. Empty / unset returns nil
+// (listenIn falls back to its default `i % NumCPU` pinning). Length
+// mismatch with `routines` is a warning, not an error: shorter lists are
+// modulo-cycled across queues, longer lists' tail is ignored. Invalid
+// entries (non-integer, out of range) are also a warning and disable the
+// override entirely so we don't silently pin to the wrong CPU.
+func parseCpuAffinity(c *config.C, l *slog.Logger, routines int) []int {
+	raw := c.Get("tun.cpu_affinity")
+	if raw == nil {
+		return nil
+	}
+	rv, ok := raw.([]any)
+	if !ok {
+		l.Warn("tun.cpu_affinity must be a list of integers; ignoring", "value", raw)
+		return nil
+	}
+	nCPU := runtime.NumCPU()
+	cpus := make([]int, 0, len(rv))
+	for i, e := range rv {
+		var cpu int
+		switch v := e.(type) {
+		case int:
+			cpu = v
+		case int64:
+			cpu = int(v)
+		case float64:
+			cpu = int(v)
+		default:
+			l.Warn("tun.cpu_affinity entry not an integer; ignoring affinity",
+				"index", i, "value", e)
+			return nil
+		}
+		if cpu < 0 || cpu >= nCPU {
+			l.Warn("tun.cpu_affinity entry out of range; ignoring affinity",
+				"index", i, "cpu", cpu, "num_cpu", nCPU)
+			return nil
+		}
+		cpus = append(cpus, cpu)
+	}
+	if len(cpus) != routines {
+		l.Warn("tun.cpu_affinity length doesn't match routines; queues will modulo-cycle through the list",
+			"affinity_len", len(cpus), "routines", routines)
+	}
+	return cpus
+}
+
 func moduleVersion() string {
 	info, ok := debug.ReadBuildInfo()
 	if !ok {

message_metrics.go

@@ -13,6 +13,8 @@ type MessageMetrics struct {
 
 	rxUnknown metrics.Counter
 	txUnknown metrics.Counter
+
+	rxInvalid metrics.Counter
 }
 
 func (m *MessageMetrics) Rx(t header.MessageType, s header.MessageSubType, i int64) {
@@ -33,6 +35,11 @@ func (m *MessageMetrics) Tx(t header.MessageType, s header.MessageSubType, i int
 		}
 	}
 }
+func (m *MessageMetrics) RxInvalid(i int64) {
+	if m != nil && m.rxInvalid != nil {
+		m.rxInvalid.Inc(i)
+	}
+}
 
 func newMessageMetrics() *MessageMetrics {
 	gen := func(t string) [][]metrics.Counter {
@@ -56,6 +63,7 @@ func newMessageMetrics() *MessageMetrics {
 
 		rxUnknown: metrics.GetOrRegisterCounter("messages.rx.other", nil),
 		txUnknown: metrics.GetOrRegisterCounter("messages.tx.other", nil),
+		rxInvalid: metrics.GetOrRegisterCounter("messages.rx.invalid", nil),
 	}
 }
 

nebula.pb.go

@@ -124,7 +124,7 @@ func (x NebulaControl_MessageType) String() string {
 }
 
 func (NebulaControl_MessageType) EnumDescriptor() ([]byte, []int) {
-	return fileDescriptor_2d65afa7693df5ef, []int{8, 0}
+	return fileDescriptor_2d65afa7693df5ef, []int{6, 0}
 }
 
 type NebulaMeta struct {
@@ -489,142 +489,6 @@ func (m *NebulaPing) GetTime() uint64 {
 	return 0
 }
 
-type NebulaHandshake struct {
-	Details *NebulaHandshakeDetails `protobuf:"bytes,1,opt,name=Details,proto3" json:"Details,omitempty"`
-	Hmac    []byte                  `protobuf:"bytes,2,opt,name=Hmac,proto3" json:"Hmac,omitempty"`
-}
-
-func (m *NebulaHandshake) Reset()         { *m = NebulaHandshake{} }
-func (m *NebulaHandshake) String() string { return proto.CompactTextString(m) }
-func (*NebulaHandshake) ProtoMessage()    {}
-func (*NebulaHandshake) Descriptor() ([]byte, []int) {
-	return fileDescriptor_2d65afa7693df5ef, []int{6}
-}
-func (m *NebulaHandshake) XXX_Unmarshal(b []byte) error {
-	return m.Unmarshal(b)
-}
-func (m *NebulaHandshake) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
-	if deterministic {
-		return xxx_messageInfo_NebulaHandshake.Marshal(b, m, deterministic)
-	} else {
-		b = b[:cap(b)]
-		n, err := m.MarshalToSizedBuffer(b)
-		if err != nil {
-			return nil, err
-		}
-		return b[:n], nil
-	}
-}
-func (m *NebulaHandshake) XXX_Merge(src proto.Message) {
-	xxx_messageInfo_NebulaHandshake.Merge(m, src)
-}
-func (m *NebulaHandshake) XXX_Size() int {
-	return m.Size()
-}
-func (m *NebulaHandshake) XXX_DiscardUnknown() {
-	xxx_messageInfo_NebulaHandshake.DiscardUnknown(m)
-}
-
-var xxx_messageInfo_NebulaHandshake proto.InternalMessageInfo
-
-func (m *NebulaHandshake) GetDetails() *NebulaHandshakeDetails {
-	if m != nil {
-		return m.Details
-	}
-	return nil
-}
-
-func (m *NebulaHandshake) GetHmac() []byte {
-	if m != nil {
-		return m.Hmac
-	}
-	return nil
-}
-
-type NebulaHandshakeDetails struct {
-	Cert           []byte `protobuf:"bytes,1,opt,name=Cert,proto3" json:"Cert,omitempty"`
-	InitiatorIndex uint32 `protobuf:"varint,2,opt,name=InitiatorIndex,proto3" json:"InitiatorIndex,omitempty"`
-	ResponderIndex uint32 `protobuf:"varint,3,opt,name=ResponderIndex,proto3" json:"ResponderIndex,omitempty"`
-	Cookie         uint64 `protobuf:"varint,4,opt,name=Cookie,proto3" json:"Cookie,omitempty"`
-	Time           uint64 `protobuf:"varint,5,opt,name=Time,proto3" json:"Time,omitempty"`
-	CertVersion    uint32 `protobuf:"varint,8,opt,name=CertVersion,proto3" json:"CertVersion,omitempty"`
-}
-
-func (m *NebulaHandshakeDetails) Reset()         { *m = NebulaHandshakeDetails{} }
-func (m *NebulaHandshakeDetails) String() string { return proto.CompactTextString(m) }
-func (*NebulaHandshakeDetails) ProtoMessage()    {}
-func (*NebulaHandshakeDetails) Descriptor() ([]byte, []int) {
-	return fileDescriptor_2d65afa7693df5ef, []int{7}
-}
-func (m *NebulaHandshakeDetails) XXX_Unmarshal(b []byte) error {
-	return m.Unmarshal(b)
-}
-func (m *NebulaHandshakeDetails) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
-	if deterministic {
-		return xxx_messageInfo_NebulaHandshakeDetails.Marshal(b, m, deterministic)
-	} else {
-		b = b[:cap(b)]
-		n, err := m.MarshalToSizedBuffer(b)
-		if err != nil {
-			return nil, err
-		}
-		return b[:n], nil
-	}
-}
-func (m *NebulaHandshakeDetails) XXX_Merge(src proto.Message) {
-	xxx_messageInfo_NebulaHandshakeDetails.Merge(m, src)
-}
-func (m *NebulaHandshakeDetails) XXX_Size() int {
-	return m.Size()
-}
-func (m *NebulaHandshakeDetails) XXX_DiscardUnknown() {
-	xxx_messageInfo_NebulaHandshakeDetails.DiscardUnknown(m)
-}
-
-var xxx_messageInfo_NebulaHandshakeDetails proto.InternalMessageInfo
-
-func (m *NebulaHandshakeDetails) GetCert() []byte {
-	if m != nil {
-		return m.Cert
-	}
-	return nil
-}
-
-func (m *NebulaHandshakeDetails) GetInitiatorIndex() uint32 {
-	if m != nil {
-		return m.InitiatorIndex
-	}
-	return 0
-}
-
-func (m *NebulaHandshakeDetails) GetResponderIndex() uint32 {
-	if m != nil {
-		return m.ResponderIndex
-	}
-	return 0
-}
-
-func (m *NebulaHandshakeDetails) GetCookie() uint64 {
-	if m != nil {
-		return m.Cookie
-	}
-	return 0
-}
-
-func (m *NebulaHandshakeDetails) GetTime() uint64 {
-	if m != nil {
-		return m.Time
-	}
-	return 0
-}
-
-func (m *NebulaHandshakeDetails) GetCertVersion() uint32 {
-	if m != nil {
-		return m.CertVersion
-	}
-	return 0
-}
-
 type NebulaControl struct {
 	Type                NebulaControl_MessageType `protobuf:"varint,1,opt,name=Type,proto3,enum=nebula.NebulaControl_MessageType" json:"Type,omitempty"`
 	InitiatorRelayIndex uint32                    `protobuf:"varint,2,opt,name=InitiatorRelayIndex,proto3" json:"InitiatorRelayIndex,omitempty"`
@@ -639,7 +503,7 @@ func (m *NebulaControl) Reset()         { *m = NebulaControl{} }
 func (m *NebulaControl) String() string { return proto.CompactTextString(m) }
 func (*NebulaControl) ProtoMessage()    {}
 func (*NebulaControl) Descriptor() ([]byte, []int) {
-	return fileDescriptor_2d65afa7693df5ef, []int{8}
+	return fileDescriptor_2d65afa7693df5ef, []int{6}
 }
 func (m *NebulaControl) XXX_Unmarshal(b []byte) error {
 	return m.Unmarshal(b)
@@ -729,65 +593,55 @@ func init() {
 	proto.RegisterType((*V4AddrPort)(nil), "nebula.V4AddrPort")
 	proto.RegisterType((*V6AddrPort)(nil), "nebula.V6AddrPort")
 	proto.RegisterType((*NebulaPing)(nil), "nebula.NebulaPing")
-	proto.RegisterType((*NebulaHandshake)(nil), "nebula.NebulaHandshake")
-	proto.RegisterType((*NebulaHandshakeDetails)(nil), "nebula.NebulaHandshakeDetails")
 	proto.RegisterType((*NebulaControl)(nil), "nebula.NebulaControl")
 }
 
 func init() { proto.RegisterFile("nebula.proto", fileDescriptor_2d65afa7693df5ef) }
 
 var fileDescriptor_2d65afa7693df5ef = []byte{
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 }
 
 func (m *NebulaMeta) Marshal() (dAtA []byte, err error) {
@@ -1072,103 +926,6 @@ func (m *NebulaPing) MarshalToSizedBuffer(dAtA []byte) (int, error) {
 	return len(dAtA) - i, nil
 }
 
-func (m *NebulaHandshake) Marshal() (dAtA []byte, err error) {
-	size := m.Size()
-	dAtA = make([]byte, size)
-	n, err := m.MarshalToSizedBuffer(dAtA[:size])
-	if err != nil {
-		return nil, err
-	}
-	return dAtA[:n], nil
-}
-
-func (m *NebulaHandshake) MarshalTo(dAtA []byte) (int, error) {
-	size := m.Size()
-	return m.MarshalToSizedBuffer(dAtA[:size])
-}
-
-func (m *NebulaHandshake) MarshalToSizedBuffer(dAtA []byte) (int, error) {
-	i := len(dAtA)
-	_ = i
-	var l int
-	_ = l
-	if len(m.Hmac) > 0 {
-		i -= len(m.Hmac)
-		copy(dAtA[i:], m.Hmac)
-		i = encodeVarintNebula(dAtA, i, uint64(len(m.Hmac)))
-		i--
-		dAtA[i] = 0x12
-	}
-	if m.Details != nil {
-		{
-			size, err := m.Details.MarshalToSizedBuffer(dAtA[:i])
-			if err != nil {
-				return 0, err
-			}
-			i -= size
-			i = encodeVarintNebula(dAtA, i, uint64(size))
-		}
-		i--
-		dAtA[i] = 0xa
-	}
-	return len(dAtA) - i, nil
-}
-
-func (m *NebulaHandshakeDetails) Marshal() (dAtA []byte, err error) {
-	size := m.Size()
-	dAtA = make([]byte, size)
-	n, err := m.MarshalToSizedBuffer(dAtA[:size])
-	if err != nil {
-		return nil, err
-	}
-	return dAtA[:n], nil
-}
-
-func (m *NebulaHandshakeDetails) MarshalTo(dAtA []byte) (int, error) {
-	size := m.Size()
-	return m.MarshalToSizedBuffer(dAtA[:size])
-}
-
-func (m *NebulaHandshakeDetails) MarshalToSizedBuffer(dAtA []byte) (int, error) {
-	i := len(dAtA)
-	_ = i
-	var l int
-	_ = l
-	if m.CertVersion != 0 {
-		i = encodeVarintNebula(dAtA, i, uint64(m.CertVersion))
-		i--
-		dAtA[i] = 0x40
-	}
-	if m.Time != 0 {
-		i = encodeVarintNebula(dAtA, i, uint64(m.Time))
-		i--
-		dAtA[i] = 0x28
-	}
-	if m.Cookie != 0 {
-		i = encodeVarintNebula(dAtA, i, uint64(m.Cookie))
-		i--
-		dAtA[i] = 0x20
-	}
-	if m.ResponderIndex != 0 {
-		i = encodeVarintNebula(dAtA, i, uint64(m.ResponderIndex))
-		i--
-		dAtA[i] = 0x18
-	}
-	if m.InitiatorIndex != 0 {
-		i = encodeVarintNebula(dAtA, i, uint64(m.InitiatorIndex))
-		i--
-		dAtA[i] = 0x10
-	}
-	if len(m.Cert) > 0 {
-		i -= len(m.Cert)
-		copy(dAtA[i:], m.Cert)
-		i = encodeVarintNebula(dAtA, i, uint64(len(m.Cert)))
-		i--
-		dAtA[i] = 0xa
-	}
-	return len(dAtA) - i, nil
-}
-
 func (m *NebulaControl) Marshal() (dAtA []byte, err error) {
 	size := m.Size()
 	dAtA = make([]byte, size)
@@ -1375,51 +1132,6 @@ func (m *NebulaPing) Size() (n int) {
 	return n
 }
 
-func (m *NebulaHandshake) Size() (n int) {
-	if m == nil {
-		return 0
-	}
-	var l int
-	_ = l
-	if m.Details != nil {
-		l = m.Details.Size()
-		n += 1 + l + sovNebula(uint64(l))
-	}
-	l = len(m.Hmac)
-	if l > 0 {
-		n += 1 + l + sovNebula(uint64(l))
-	}
-	return n
-}
-
-func (m *NebulaHandshakeDetails) Size() (n int) {
-	if m == nil {
-		return 0
-	}
-	var l int
-	_ = l
-	l = len(m.Cert)
-	if l > 0 {
-		n += 1 + l + sovNebula(uint64(l))
-	}
-	if m.InitiatorIndex != 0 {
-		n += 1 + sovNebula(uint64(m.InitiatorIndex))
-	}
-	if m.ResponderIndex != 0 {
-		n += 1 + sovNebula(uint64(m.ResponderIndex))
-	}
-	if m.Cookie != 0 {
-		n += 1 + sovNebula(uint64(m.Cookie))
-	}
-	if m.Time != 0 {
-		n += 1 + sovNebula(uint64(m.Time))
-	}
-	if m.CertVersion != 0 {
-		n += 1 + sovNebula(uint64(m.CertVersion))
-	}
-	return n
-}
-
 func (m *NebulaControl) Size() (n int) {
 	if m == nil {
 		return 0
@@ -2236,305 +1948,6 @@ func (m *NebulaPing) Unmarshal(dAtA []byte) error {
 	}
 	return nil
 }
-func (m *NebulaHandshake) Unmarshal(dAtA []byte) error {
-	l := len(dAtA)
-	iNdEx := 0
-	for iNdEx < l {
-		preIndex := iNdEx
-		var wire uint64
-		for shift := uint(0); ; shift += 7 {
-			if shift >= 64 {
-				return ErrIntOverflowNebula
-			}
-			if iNdEx >= l {
-				return io.ErrUnexpectedEOF
-			}
-			b := dAtA[iNdEx]
-			iNdEx++
-			wire |= uint64(b&0x7F) << shift
-			if b < 0x80 {
-				break
-			}
-		}
-		fieldNum := int32(wire >> 3)
-		wireType := int(wire & 0x7)
-		if wireType == 4 {
-			return fmt.Errorf("proto: NebulaHandshake: wiretype end group for non-group")
-		}
-		if fieldNum <= 0 {
-			return fmt.Errorf("proto: NebulaHandshake: illegal tag %d (wire type %d)", fieldNum, wire)
-		}
-		switch fieldNum {
-		case 1:
-			if wireType != 2 {
-				return fmt.Errorf("proto: wrong wireType = %d for field Details", wireType)
-			}
-			var msglen int
-			for shift := uint(0); ; shift += 7 {
-				if shift >= 64 {
-					return ErrIntOverflowNebula
-				}
-				if iNdEx >= l {
-					return io.ErrUnexpectedEOF
-				}
-				b := dAtA[iNdEx]
-				iNdEx++
-				msglen |= int(b&0x7F) << shift
-				if b < 0x80 {
-					break
-				}
-			}
-			if msglen < 0 {
-				return ErrInvalidLengthNebula
-			}
-			postIndex := iNdEx + msglen
-			if postIndex < 0 {
-				return ErrInvalidLengthNebula
-			}
-			if postIndex > l {
-				return io.ErrUnexpectedEOF
-			}
-			if m.Details == nil {
-				m.Details = &NebulaHandshakeDetails{}
-			}
-			if err := m.Details.Unmarshal(dAtA[iNdEx:postIndex]); err != nil {
-				return err
-			}
-			iNdEx = postIndex
-		case 2:
-			if wireType != 2 {
-				return fmt.Errorf("proto: wrong wireType = %d for field Hmac", wireType)
-			}
-			var byteLen int
-			for shift := uint(0); ; shift += 7 {
-				if shift >= 64 {
-					return ErrIntOverflowNebula
-				}
-				if iNdEx >= l {
-					return io.ErrUnexpectedEOF
-				}
-				b := dAtA[iNdEx]
-				iNdEx++
-				byteLen |= int(b&0x7F) << shift
-				if b < 0x80 {
-					break
-				}
-			}
-			if byteLen < 0 {
-				return ErrInvalidLengthNebula
-			}
-			postIndex := iNdEx + byteLen
-			if postIndex < 0 {
-				return ErrInvalidLengthNebula
-			}
-			if postIndex > l {
-				return io.ErrUnexpectedEOF
-			}
-			m.Hmac = append(m.Hmac[:0], dAtA[iNdEx:postIndex]...)
-			if m.Hmac == nil {
-				m.Hmac = []byte{}
-			}
-			iNdEx = postIndex
-		default:
-			iNdEx = preIndex
-			skippy, err := skipNebula(dAtA[iNdEx:])
-			if err != nil {
-				return err
-			}
-			if (skippy < 0) || (iNdEx+skippy) < 0 {
-				return ErrInvalidLengthNebula
-			}
-			if (iNdEx + skippy) > l {
-				return io.ErrUnexpectedEOF
-			}
-			iNdEx += skippy
-		}
-	}
-
-	if iNdEx > l {
-		return io.ErrUnexpectedEOF
-	}
-	return nil
-}
-func (m *NebulaHandshakeDetails) Unmarshal(dAtA []byte) error {
-	l := len(dAtA)
-	iNdEx := 0
-	for iNdEx < l {
-		preIndex := iNdEx
-		var wire uint64
-		for shift := uint(0); ; shift += 7 {
-			if shift >= 64 {
-				return ErrIntOverflowNebula
-			}
-			if iNdEx >= l {
-				return io.ErrUnexpectedEOF
-			}
-			b := dAtA[iNdEx]
-			iNdEx++
-			wire |= uint64(b&0x7F) << shift
-			if b < 0x80 {
-				break
-			}
-		}
-		fieldNum := int32(wire >> 3)
-		wireType := int(wire & 0x7)
-		if wireType == 4 {
-			return fmt.Errorf("proto: NebulaHandshakeDetails: wiretype end group for non-group")
-		}
-		if fieldNum <= 0 {
-			return fmt.Errorf("proto: NebulaHandshakeDetails: illegal tag %d (wire type %d)", fieldNum, wire)
-		}
-		switch fieldNum {
-		case 1:
-			if wireType != 2 {
-				return fmt.Errorf("proto: wrong wireType = %d for field Cert", wireType)
-			}
-			var byteLen int
-			for shift := uint(0); ; shift += 7 {
-				if shift >= 64 {
-					return ErrIntOverflowNebula
-				}
-				if iNdEx >= l {
-					return io.ErrUnexpectedEOF
-				}
-				b := dAtA[iNdEx]
-				iNdEx++
-				byteLen |= int(b&0x7F) << shift
-				if b < 0x80 {
-					break
-				}
-			}
-			if byteLen < 0 {
-				return ErrInvalidLengthNebula
-			}
-			postIndex := iNdEx + byteLen
-			if postIndex < 0 {
-				return ErrInvalidLengthNebula
-			}
-			if postIndex > l {
-				return io.ErrUnexpectedEOF
-			}
-			m.Cert = append(m.Cert[:0], dAtA[iNdEx:postIndex]...)
-			if m.Cert == nil {
-				m.Cert = []byte{}
-			}
-			iNdEx = postIndex
-		case 2:
-			if wireType != 0 {
-				return fmt.Errorf("proto: wrong wireType = %d for field InitiatorIndex", wireType)
-			}
-			m.InitiatorIndex = 0
-			for shift := uint(0); ; shift += 7 {
-				if shift >= 64 {
-					return ErrIntOverflowNebula
-				}
-				if iNdEx >= l {
-					return io.ErrUnexpectedEOF
-				}
-				b := dAtA[iNdEx]
-				iNdEx++
-				m.InitiatorIndex |= uint32(b&0x7F) << shift
-				if b < 0x80 {
-					break
-				}
-			}
-		case 3:
-			if wireType != 0 {
-				return fmt.Errorf("proto: wrong wireType = %d for field ResponderIndex", wireType)
-			}
-			m.ResponderIndex = 0
-			for shift := uint(0); ; shift += 7 {
-				if shift >= 64 {
-					return ErrIntOverflowNebula
-				}
-				if iNdEx >= l {
-					return io.ErrUnexpectedEOF
-				}
-				b := dAtA[iNdEx]
-				iNdEx++
-				m.ResponderIndex |= uint32(b&0x7F) << shift
-				if b < 0x80 {
-					break
-				}
-			}
-		case 4:
-			if wireType != 0 {
-				return fmt.Errorf("proto: wrong wireType = %d for field Cookie", wireType)
-			}
-			m.Cookie = 0
-			for shift := uint(0); ; shift += 7 {
-				if shift >= 64 {
-					return ErrIntOverflowNebula
-				}
-				if iNdEx >= l {
-					return io.ErrUnexpectedEOF
-				}
-				b := dAtA[iNdEx]
-				iNdEx++
-				m.Cookie |= uint64(b&0x7F) << shift
-				if b < 0x80 {
-					break
-				}
-			}
-		case 5:
-			if wireType != 0 {
-				return fmt.Errorf("proto: wrong wireType = %d for field Time", wireType)
-			}
-			m.Time = 0
-			for shift := uint(0); ; shift += 7 {
-				if shift >= 64 {
-					return ErrIntOverflowNebula
-				}
-				if iNdEx >= l {
-					return io.ErrUnexpectedEOF
-				}
-				b := dAtA[iNdEx]
-				iNdEx++
-				m.Time |= uint64(b&0x7F) << shift
-				if b < 0x80 {
-					break
-				}
-			}
-		case 8:
-			if wireType != 0 {
-				return fmt.Errorf("proto: wrong wireType = %d for field CertVersion", wireType)
-			}
-			m.CertVersion = 0
-			for shift := uint(0); ; shift += 7 {
-				if shift >= 64 {
-					return ErrIntOverflowNebula
-				}
-				if iNdEx >= l {
-					return io.ErrUnexpectedEOF
-				}
-				b := dAtA[iNdEx]
-				iNdEx++
-				m.CertVersion |= uint32(b&0x7F) << shift
-				if b < 0x80 {
-					break
-				}
-			}
-		default:
-			iNdEx = preIndex
-			skippy, err := skipNebula(dAtA[iNdEx:])
-			if err != nil {
-				return err
-			}
-			if (skippy < 0) || (iNdEx+skippy) < 0 {
-				return ErrInvalidLengthNebula
-			}
-			if (iNdEx + skippy) > l {
-				return io.ErrUnexpectedEOF
-			}
-			iNdEx += skippy
-		}
-	}
-
-	if iNdEx > l {
-		return io.ErrUnexpectedEOF
-	}
-	return nil
-}
 func (m *NebulaControl) Unmarshal(dAtA []byte) error {
 	l := len(dAtA)
 	iNdEx := 0

nebula.proto

@@ -60,21 +60,9 @@ message NebulaPing {
 	uint64 Time = 2;
 }
 
-message NebulaHandshake {
-  NebulaHandshakeDetails Details = 1;
-  bytes Hmac = 2;
-}
-
-message NebulaHandshakeDetails {
-  bytes Cert = 1;
-  uint32 InitiatorIndex = 2;
-  uint32 ResponderIndex = 3;
-  uint64 Cookie = 4;
-  uint64 Time = 5;
-  uint32 CertVersion = 8;
-  // reserved for WIP multiport
-  reserved 6, 7;
-}
+// NebulaHandshake / NebulaHandshakeDetails moved to
+// handshake/handshake.proto. The handshake package speaks that wire format
+// directly via a hand-written encoder/decoder.
 
 message NebulaControl {
   enum MessageType {

noise.go

@@ -1,75 +0,0 @@
-package nebula
-
-import (
-	"crypto/cipher"
-	"encoding/binary"
-	"errors"
-
-	"github.com/flynn/noise"
-)
-
-type endianness interface {
-	PutUint64(b []byte, v uint64)
-}
-
-var noiseEndianness endianness = binary.BigEndian
-
-type NebulaCipherState struct {
-	c noise.Cipher
-	//k [32]byte
-	//n uint64
-}
-
-func NewNebulaCipherState(s *noise.CipherState) *NebulaCipherState {
-	return &NebulaCipherState{c: s.Cipher()}
-
-}
-
-// EncryptDanger encrypts and authenticates a given payload.
-//
-// out is a destination slice to hold the output of the EncryptDanger operation.
-//   - ad is additional data, which will be authenticated and appended to out, but not encrypted.
-//   - plaintext is encrypted, authenticated and appended to out.
-//   - n is a nonce value which must never be re-used with this key.
-//   - nb is a buffer used for temporary storage in the implementation of this call, which should
-//     be re-used by callers to minimize garbage collection.
-func (s *NebulaCipherState) EncryptDanger(out, ad, plaintext []byte, n uint64, nb []byte) ([]byte, error) {
-	if s != nil {
-		// TODO: Is this okay now that we have made messageCounter atomic?
-		// Alternative may be to split the counter space into ranges
-		//if n <= s.n {
-		//	return nil, errors.New("CRITICAL: a duplicate counter value was used")
-		//}
-		//s.n = n
-		nb[0] = 0
-		nb[1] = 0
-		nb[2] = 0
-		nb[3] = 0
-		noiseEndianness.PutUint64(nb[4:], n)
-		out = s.c.(cipher.AEAD).Seal(out, nb, plaintext, ad)
-		//l.Debugf("Encryption: outlen: %d, nonce: %d, ad: %s, plainlen %d", len(out), n, ad, len(plaintext))
-		return out, nil
-	} else {
-		return nil, errors.New("no cipher state available to encrypt")
-	}
-}
-
-func (s *NebulaCipherState) DecryptDanger(out, ad, ciphertext []byte, n uint64, nb []byte) ([]byte, error) {
-	if s != nil {
-		nb[0] = 0
-		nb[1] = 0
-		nb[2] = 0
-		nb[3] = 0
-		noiseEndianness.PutUint64(nb[4:], n)
-		return s.c.(cipher.AEAD).Open(out, nb, ciphertext, ad)
-	} else {
-		return []byte{}, nil
-	}
-}
-
-func (s *NebulaCipherState) Overhead() int {
-	if s != nil {
-		return s.c.(cipher.AEAD).Overhead()
-	}
-	return 0
-}

noiseutil/aesgcm.go

@@ -0,0 +1,53 @@
+package noiseutil
+
+import (
+	"crypto/cipher"
+	"encoding/binary"
+	"errors"
+
+	"github.com/flynn/noise"
+)
+
+// CipherStateAESGCM is the data-plane wrapper for the AES-GCM AEAD cipher.
+// AES-GCM uses big-endian nonce encoding per the Noise spec.
+type CipherStateAESGCM struct {
+	c cipher.AEAD
+}
+
+// NewCipherStateAESGCM extracts the underlying AEAD from the post-handshake noise.CipherState.
+// The caller is responsible for ensuring the noise cipher is actually AES-GCM,
+// otherwise the type assertion still succeeds but the nonce endianness will be wrong on the wire.
+func NewCipherStateAESGCM(s *noise.CipherState) *CipherStateAESGCM {
+	return &CipherStateAESGCM{c: s.Cipher().(cipher.AEAD)}
+}
+
+func (s *CipherStateAESGCM) EncryptDanger(out, ad, plaintext []byte, n uint64, nb []byte) ([]byte, error) {
+	if s == nil {
+		return nil, errors.New("no cipher state available to encrypt")
+	}
+	nb[0] = 0
+	nb[1] = 0
+	nb[2] = 0
+	nb[3] = 0
+	binary.BigEndian.PutUint64(nb[4:], n)
+	return s.c.Seal(out, nb, plaintext, ad), nil
+}
+
+func (s *CipherStateAESGCM) DecryptDanger(out, ad, ciphertext []byte, n uint64, nb []byte) ([]byte, error) {
+	if s == nil {
+		return []byte{}, nil
+	}
+	nb[0] = 0
+	nb[1] = 0
+	nb[2] = 0
+	nb[3] = 0
+	binary.BigEndian.PutUint64(nb[4:], n)
+	return s.c.Open(out, nb, ciphertext, ad)
+}
+
+func (s *CipherStateAESGCM) Overhead() int {
+	if s == nil {
+		return 0
+	}
+	return s.c.Overhead()
+}

noiseutil/chachapoly.go

@@ -0,0 +1,52 @@
+package noiseutil
+
+import (
+	"crypto/cipher"
+	"encoding/binary"
+	"errors"
+
+	"github.com/flynn/noise"
+)
+
+// CipherStateChaChaPoly is the data-plane wrapper for the ChaCha20-Poly1305 AEAD cipher.
+// ChaCha20-Poly1305 uses little-endian nonce encoding per the Noise spec.
+type CipherStateChaChaPoly struct {
+	c cipher.AEAD
+}
+
+// NewCipherStateChaChaPoly extracts the underlying AEAD from the post-handshake noise.CipherState.
+// The caller is responsible for ensuring the noise cipher is actually ChaCha20-Poly1305.
+func NewCipherStateChaChaPoly(s *noise.CipherState) *CipherStateChaChaPoly {
+	return &CipherStateChaChaPoly{c: s.Cipher().(cipher.AEAD)}
+}
+
+func (s *CipherStateChaChaPoly) EncryptDanger(out, ad, plaintext []byte, n uint64, nb []byte) ([]byte, error) {
+	if s == nil {
+		return nil, errors.New("no cipher state available to encrypt")
+	}
+	nb[0] = 0
+	nb[1] = 0
+	nb[2] = 0
+	nb[3] = 0
+	binary.LittleEndian.PutUint64(nb[4:], n)
+	return s.c.Seal(out, nb, plaintext, ad), nil
+}
+
+func (s *CipherStateChaChaPoly) DecryptDanger(out, ad, ciphertext []byte, n uint64, nb []byte) ([]byte, error) {
+	if s == nil {
+		return []byte{}, nil
+	}
+	nb[0] = 0
+	nb[1] = 0
+	nb[2] = 0
+	nb[3] = 0
+	binary.LittleEndian.PutUint64(nb[4:], n)
+	return s.c.Open(out, nb, ciphertext, ad)
+}
+
+func (s *CipherStateChaChaPoly) Overhead() int {
+	if s == nil {
+		return 0
+	}
+	return s.c.Overhead()
+}

noiseutil/cipher_state.go

@@ -0,0 +1,40 @@
+package noiseutil
+
+import (
+	"fmt"
+
+	"github.com/flynn/noise"
+)
+
+// CipherState is the post-handshake AEAD cipher used for the data plane.
+// Each supported cipher has its own concrete implementation in this package with the nonce endianness hardcoded,
+// so the encrypt/decrypt fast path avoids interface dispatch on the byte order.
+type CipherState interface {
+	// EncryptDanger encrypts and authenticates a given payload.
+	//
+	// out is a destination slice to hold the output of the EncryptDanger operation.
+	//   - ad is additional data, which will be authenticated and appended to out, but not encrypted.
+	//   - plaintext is encrypted, authenticated and appended to out.
+	//   - n is a nonce value which must never be re-used with this key.
+	//   - nb is a scratch buffer used to assemble the nonce.
+	EncryptDanger(out, ad, plaintext []byte, n uint64, nb []byte) ([]byte, error)
+
+	// DecryptDanger authenticates and decrypts a given payload, with the same argument shape as EncryptDanger.
+	DecryptDanger(out, ad, ciphertext []byte, n uint64, nb []byte) ([]byte, error)
+
+	// Overhead returns the AEAD tag size, or 0 if the receiver is nil.
+	Overhead() int
+}
+
+// NewCipherState wraps the post-handshake noise.CipherState in the per-cipher type that matches cipherFunc.
+// cipherFunc must be the same cipher used to build the noise CipherSuite that produced s.
+func NewCipherState(s *noise.CipherState, cipherFunc noise.CipherFunc) CipherState {
+	switch cipherFunc.CipherName() {
+	case CipherAESGCM.CipherName():
+		return NewCipherStateAESGCM(s)
+	case noise.CipherChaChaPoly.CipherName():
+		return NewCipherStateChaChaPoly(s)
+	default:
+		panic(fmt.Sprintf("noiseutil: unsupported cipher %q", cipherFunc.CipherName()))
+	}
+}

noiseutil/cipher_state_test.go

@@ -0,0 +1,166 @@
+package noiseutil
+
+import (
+	"testing"
+
+	"github.com/flynn/noise"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestCipherStateAESGCMRoundtrip(t *testing.T) {
+	enc, dec := buildCipherStates(t, CipherAESGCM)
+	roundtrip(t, NewCipherStateAESGCM(enc), NewCipherStateAESGCM(dec))
+}
+
+func TestCipherStateChaChaPolyRoundtrip(t *testing.T) {
+	enc, dec := buildCipherStates(t, noise.CipherChaChaPoly)
+	roundtrip(t, NewCipherStateChaChaPoly(enc), NewCipherStateChaChaPoly(dec))
+}
+
+func TestNewCipherStateDispatch(t *testing.T) {
+	encA, _ := buildCipherStates(t, CipherAESGCM)
+	encC, _ := buildCipherStates(t, noise.CipherChaChaPoly)
+
+	assert.IsType(t, &CipherStateAESGCM{}, NewCipherState(encA, CipherAESGCM))
+	assert.IsType(t, &CipherStateChaChaPoly{}, NewCipherState(encC, noise.CipherChaChaPoly))
+}
+
+func TestNewCipherStateUnsupportedPanics(t *testing.T) {
+	enc, _ := buildCipherStates(t, CipherAESGCM)
+	assert.Panics(t, func() {
+		NewCipherState(enc, fakeCipher{})
+	})
+}
+
+type fakeCipher struct{}
+
+func (fakeCipher) Cipher(k [32]byte) noise.Cipher { return nil }
+func (fakeCipher) CipherName() string             { return "Fake" }
+
+// buildCipherStates runs an in-memory NN handshake with the requested cipher
+// to produce a pair of post-handshake CipherStates that share keys.
+func buildCipherStates(t *testing.T, c noise.CipherFunc) (*noise.CipherState, *noise.CipherState) {
+	t.Helper()
+	suite := noise.NewCipherSuite(noise.DH25519, c, noise.HashSHA256)
+	cfg := noise.Config{CipherSuite: suite, Pattern: noise.HandshakeNN}
+	cfg.Initiator = true
+	hsI, err := noise.NewHandshakeState(cfg)
+	require.NoError(t, err)
+	cfg.Initiator = false
+	hsR, err := noise.NewHandshakeState(cfg)
+	require.NoError(t, err)
+
+	msg, _, _, err := hsI.WriteMessage(nil, nil)
+	require.NoError(t, err)
+	_, _, _, err = hsR.ReadMessage(nil, msg)
+	require.NoError(t, err)
+
+	msg, dR, _, err := hsR.WriteMessage(nil, nil)
+	require.NoError(t, err)
+	_, eI, _, err := hsI.ReadMessage(nil, msg)
+	require.NoError(t, err)
+	require.NotNil(t, eI)
+	require.NotNil(t, dR)
+
+	// noise returns (cs1, cs2) where cs1 is the initiator->responder cipher.
+	return eI, dR
+}
+
+func roundtrip(t *testing.T, enc, dec CipherState) {
+	t.Helper()
+	plaintext := []byte("nebula cipher state roundtrip")
+	ad := []byte("aad")
+	nb := make([]byte, 12)
+
+	ct, err := enc.EncryptDanger(nil, ad, plaintext, 1, nb)
+	require.NoError(t, err)
+	assert.NotEqual(t, plaintext, ct)
+
+	pt, err := dec.DecryptDanger(nil, ad, ct, 1, nb)
+	require.NoError(t, err)
+	assert.Equal(t, plaintext, pt)
+
+	// Wrong nonce must fail authentication.
+	_, err = dec.DecryptDanger(nil, ad, ct, 2, nb)
+	require.Error(t, err)
+
+	assert.Equal(t, enc.Overhead(), dec.Overhead())
+	assert.Equal(t, 16, enc.Overhead())
+}
+
+func BenchmarkCipherStateEncryptAESGCM(b *testing.B) {
+	enc, _ := buildCipherStatesB(b, CipherAESGCM)
+	benchEncryptCipherState(b, NewCipherState(enc, CipherAESGCM))
+}
+
+func BenchmarkCipherStateEncryptChaChaPoly(b *testing.B) {
+	enc, _ := buildCipherStatesB(b, noise.CipherChaChaPoly)
+	benchEncryptCipherState(b, NewCipherState(enc, noise.CipherChaChaPoly))
+}
+
+func benchEncryptCipherState(b *testing.B, cs CipherState) {
+	plaintext := make([]byte, 1280)
+	ad := make([]byte, 16)
+	nb := make([]byte, 12)
+	out := make([]byte, 0, len(plaintext)+cs.Overhead())
+	b.ResetTimer()
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		var err error
+		out, err = cs.EncryptDanger(out[:0], ad, plaintext, uint64(i+1), nb)
+		if err != nil {
+			b.Fatal(err)
+		}
+	}
+}
+
+func buildCipherStatesB(b *testing.B, c noise.CipherFunc) (*noise.CipherState, *noise.CipherState) {
+	b.Helper()
+	suite := noise.NewCipherSuite(noise.DH25519, c, noise.HashSHA256)
+	cfg := noise.Config{CipherSuite: suite, Pattern: noise.HandshakeNN}
+	cfg.Initiator = true
+	hsI, err := noise.NewHandshakeState(cfg)
+	if err != nil {
+		b.Fatal(err)
+	}
+	cfg.Initiator = false
+	hsR, err := noise.NewHandshakeState(cfg)
+	if err != nil {
+		b.Fatal(err)
+	}
+	msg, _, _, err := hsI.WriteMessage(nil, nil)
+	if err != nil {
+		b.Fatal(err)
+	}
+	if _, _, _, err := hsR.ReadMessage(nil, msg); err != nil {
+		b.Fatal(err)
+	}
+	msg, dR, _, err := hsR.WriteMessage(nil, nil)
+	if err != nil {
+		b.Fatal(err)
+	}
+	_, eI, _, err := hsI.ReadMessage(nil, msg)
+	if err != nil {
+		b.Fatal(err)
+	}
+	return eI, dR
+}
+
+func TestCipherStateNilSafety(t *testing.T) {
+	var aes *CipherStateAESGCM
+	_, err := aes.EncryptDanger(nil, nil, nil, 0, make([]byte, 12))
+	require.Error(t, err)
+	out, err := aes.DecryptDanger(nil, nil, nil, 0, make([]byte, 12))
+	require.NoError(t, err)
+	assert.Empty(t, out)
+	assert.Equal(t, 0, aes.Overhead())
+
+	var cc *CipherStateChaChaPoly
+	_, err = cc.EncryptDanger(nil, nil, nil, 0, make([]byte, 12))
+	require.Error(t, err)
+	out, err = cc.DecryptDanger(nil, nil, nil, 0, make([]byte, 12))
+	require.NoError(t, err)
+	assert.Empty(t, out)
+	assert.Equal(t, 0, cc.Overhead())
+}

outside.go

@@ -1,233 +1,252 @@
 package nebula
 
 import (
-	"encoding/binary"
+	"context"
 	"errors"
+	"log/slog"
 	"net/netip"
 	"time"
 
-	"github.com/google/gopacket/layers"
-	"golang.org/x/net/ipv6"
-
-	"github.com/sirupsen/logrus"
 	"github.com/slackhq/nebula/firewall"
 	"github.com/slackhq/nebula/header"
-	"golang.org/x/net/ipv4"
+	"github.com/slackhq/nebula/overlay/batch"
+	"github.com/slackhq/nebula/udp"
 )
 
-const (
-	minFwPacketLen = 4
-)
+var ErrOutOfWindow = errors.New("out of window packet")
 
-func (f *Interface) readOutsidePackets(via ViaSender, out []byte, packet []byte, h *header.H, fwPacket *firewall.Packet, lhf *LightHouseHandler, nb []byte, q int, localCache firewall.ConntrackCache) {
+func (f *Interface) readOutsidePackets(via ViaSender, out []byte, packet []byte, h *header.H, fwPacket *firewall.Packet, parsedRx *batch.RxParsed, lhf *LightHouseHandler, nb []byte, q int, localCache firewall.ConntrackCache, meta udp.RxMeta) {
 	err := h.Parse(packet)
 	if err != nil {
 		// Hole punch packets are 0 or 1 byte big, so lets ignore printing those errors
+		// TODO: record metrics for rx holepunch/punchy packets?
 		if len(packet) > 1 {
-			f.l.WithField("packet", packet).Infof("Error while parsing inbound packet from %s: %s", via, err)
+			f.messageMetrics.RxInvalid(1)
+			if f.l.Enabled(context.Background(), slog.LevelDebug) {
+				f.l.Debug("Error while parsing inbound packet",
+					"from", via,
+					"error", err,
+					"packet", packet,
+				)
+			}
+		}
+		return
+	}
+
+	if h.Version != header.Version {
+		f.messageMetrics.RxInvalid(1)
+		if f.l.Enabled(context.Background(), slog.LevelDebug) {
+			f.l.Debug("Unexpected header version received", "from", via)
+		}
+		return
+	}
+
+	// Check before processing to see if this is a expected type/subtype
+	if !h.IsValidSubType() {
+		f.messageMetrics.RxInvalid(1)
+		if f.l.Enabled(context.Background(), slog.LevelDebug) {
+			f.l.Debug("Unexpected packet received", "from", via)
 		}
 		return
 	}
 
-	//l.Error("in packet ", header, packet[HeaderLen:])
 	if !via.IsRelayed {
 		if f.myVpnNetworksTable.Contains(via.UdpAddr.Addr()) {
-			if f.l.Level >= logrus.DebugLevel {
-				f.l.WithField("from", via).Debug("Refusing to process double encrypted packet")
+			f.messageMetrics.RxInvalid(1)
+			if f.l.Enabled(context.Background(), slog.LevelDebug) {
+				f.l.Debug("Refusing to process double encrypted packet", "from", via)
 			}
 			return
 		}
 	}
 
+	// don't keep Rx metrics for message type, since you can see those in the tun metrics
+	if h.Type != header.Message {
+		f.messageMetrics.Rx(h.Type, h.Subtype, 1)
+	}
+
+	// Unencrypted packets
+	switch h.Type {
+	case header.Handshake:
+		f.handshakeManager.HandleIncoming(via, packet, h)
+		return
+
+	case header.RecvError:
+		f.handleRecvError(via.UdpAddr, h)
+		return
+	}
+
+	// Relay packets are special
+	isMessageRelay := (h.Type == header.Message && h.Subtype == header.MessageRelay)
+
 	var hostinfo *HostInfo
-	// verify if we've seen this index before, otherwise respond to the handshake initiation
-	if h.Type == header.Message && h.Subtype == header.MessageRelay {
+	if isMessageRelay {
 		hostinfo = f.hostMap.QueryRelayIndex(h.RemoteIndex)
 	} else {
 		hostinfo = f.hostMap.QueryIndex(h.RemoteIndex)
 	}
 
-	var ci *ConnectionState
-	if hostinfo != nil {
-		ci = hostinfo.ConnectionState
+	// At this point we should have a valid existing tunnel, verify and send
+	// recvError if necessary
+	if hostinfo == nil || hostinfo.ConnectionState == nil {
+		if !via.IsRelayed {
+			f.maybeSendRecvError(via.UdpAddr, h.RemoteIndex)
+		}
+		return
 	}
 
+	// All remaining packets are encrypted
+	ci := hostinfo.ConnectionState
+	if !ci.window.Check(f.l, h.MessageCounter) {
+		return
+	}
+
+	// Relay packets are special
+	if isMessageRelay {
+		f.handleOutsideRelayPacket(hostinfo, via, out, packet, h, fwPacket, parsedRx, lhf, nb, q, localCache, meta)
+
+		return
+	}
+
+	out, err = f.decrypt(hostinfo, h.MessageCounter, out, packet, h, nb)
+	if err != nil {
+		if f.l.Enabled(context.Background(), slog.LevelDebug) {
+			hostinfo.logger(f.l).Debug("Failed to decrypt packet",
+				"error", err,
+				"from", via,
+				"header", h,
+			)
+		}
+		return
+	}
+
+	// Roam before we respond
+	f.handleHostRoaming(hostinfo, via)
+	f.connectionManager.In(hostinfo)
+
 	switch h.Type {
 	case header.Message:
-		if !f.handleEncrypted(ci, via, h) {
-			return
-		}
-
 		switch h.Subtype {
 		case header.MessageNone:
-			if !f.decryptToTun(hostinfo, h.MessageCounter, out, packet, fwPacket, nb, q, localCache) {
-				return
-			}
-		case header.MessageRelay:
-			// The entire body is sent as AD, not encrypted.
-			// The packet consists of a 16-byte parsed Nebula header, Associated Data-protected payload, and a trailing 16-byte AEAD signature value.
-			// The packet is guaranteed to be at least 16 bytes at this point, b/c it got past the h.Parse() call above. If it's
-			// otherwise malformed (meaning, there is no trailing 16 byte AEAD value), then this will result in at worst a 0-length slice
-			// which will gracefully fail in the DecryptDanger call.
-			signedPayload := packet[:len(packet)-hostinfo.ConnectionState.dKey.Overhead()]
-			signatureValue := packet[len(packet)-hostinfo.ConnectionState.dKey.Overhead():]
-			out, err = hostinfo.ConnectionState.dKey.DecryptDanger(out, signedPayload, signatureValue, h.MessageCounter, nb)
-			if err != nil {
-				return
-			}
-			// Successfully validated the thing. Get rid of the Relay header.
-			signedPayload = signedPayload[header.Len:]
-			// Pull the Roaming parts up here, and return in all call paths.
-			f.handleHostRoaming(hostinfo, via)
-			// Track usage of both the HostInfo and the Relay for the received & authenticated packet
-			f.connectionManager.In(hostinfo)
-			f.connectionManager.RelayUsed(h.RemoteIndex)
-
-			relay, ok := hostinfo.relayState.QueryRelayForByIdx(h.RemoteIndex)
-			if !ok {
-				// The only way this happens is if hostmap has an index to the correct HostInfo, but the HostInfo is missing
-				// its internal mapping. This should never happen.
-				hostinfo.logger(f.l).WithFields(logrus.Fields{"vpnAddrs": hostinfo.vpnAddrs, "remoteIndex": h.RemoteIndex}).Error("HostInfo missing remote relay index")
-				return
-			}
-
-			switch relay.Type {
-			case TerminalType:
-				// If I am the target of this relay, process the unwrapped packet
-				// From this recursive point, all these variables are 'burned'. We shouldn't rely on them again.
-				via = ViaSender{
-					UdpAddr:   via.UdpAddr,
-					relayHI:   hostinfo,
-					remoteIdx: relay.RemoteIndex,
-					relay:     relay,
-					IsRelayed: true,
-				}
-				f.readOutsidePackets(via, out[:0], signedPayload, h, fwPacket, lhf, nb, q, localCache)
-				return
-			case ForwardingType:
-				// Find the target HostInfo relay object
-				targetHI, targetRelay, err := f.hostMap.QueryVpnAddrsRelayFor(hostinfo.vpnAddrs, relay.PeerAddr)
-				if err != nil {
-					hostinfo.logger(f.l).WithField("relayTo", relay.PeerAddr).WithError(err).WithField("hostinfo.vpnAddrs", hostinfo.vpnAddrs).Info("Failed to find target host info by ip")
-					return
-				}
-
-				// If that relay is Established, forward the payload through it
-				if targetRelay.State == Established {
-					switch targetRelay.Type {
-					case ForwardingType:
-						// Forward this packet through the relay tunnel
-						// Find the target HostInfo
-						f.SendVia(targetHI, targetRelay, signedPayload, nb, out, false)
-						return
-					case TerminalType:
-						hostinfo.logger(f.l).Error("Unexpected Relay Type of Terminal")
-					}
-				} else {
-					hostinfo.logger(f.l).WithFields(logrus.Fields{"relayTo": relay.PeerAddr, "relayFrom": hostinfo.vpnAddrs[0], "targetRelayState": targetRelay.State}).Info("Unexpected target relay state")
-					return
-				}
-			}
+			f.handleOutsideMessagePacket(hostinfo, out, packet, fwPacket, parsedRx, nb, q, localCache, meta)
+		default:
+			hostinfo.logger(f.l).Error("IsValidSubType was true, but unexpected message subtype seen", "from", via, "header", h)
+			return
 		}
 
 	case header.LightHouse:
-		f.messageMetrics.Rx(h.Type, h.Subtype, 1)
-		if !f.handleEncrypted(ci, via, h) {
-			return
-		}
-
-		d, err := f.decrypt(hostinfo, h.MessageCounter, out, packet, h, nb)
-		if err != nil {
-			hostinfo.logger(f.l).WithError(err).WithField("from", via).
-				WithField("packet", packet).
-				Error("Failed to decrypt lighthouse packet")
-			return
-		}
-
 		//TODO: assert via is not relayed
-		lhf.HandleRequest(via.UdpAddr, hostinfo.vpnAddrs, d, f)
-
-		// Fallthrough to the bottom to record incoming traffic
+		lhf.HandleRequest(via.UdpAddr, hostinfo.vpnAddrs, out, f)
 
 	case header.Test:
-		f.messageMetrics.Rx(h.Type, h.Subtype, 1)
-		if !f.handleEncrypted(ci, via, h) {
+		switch h.Subtype {
+		case header.TestReply:
+			// No-op, useful for the Roaming and connectionManager side-effects above
+		case header.TestRequest:
+			f.send(header.Test, header.TestReply, ci, hostinfo, out, nb, out)
+		default:
+			hostinfo.logger(f.l).Error("IsValidSubType was true, but unexpected test subtype seen", "from", via, "header", h)
 			return
 		}
 
-		d, err := f.decrypt(hostinfo, h.MessageCounter, out, packet, h, nb)
-		if err != nil {
-			hostinfo.logger(f.l).WithError(err).WithField("from", via).
-				WithField("packet", packet).
-				Error("Failed to decrypt test packet")
-			return
-		}
-
-		if h.Subtype == header.TestRequest {
-			// This testRequest might be from TryPromoteBest, so we should roam
-			// to the new IP address before responding
-			f.handleHostRoaming(hostinfo, via)
-			f.send(header.Test, header.TestReply, ci, hostinfo, d, nb, out)
-		}
-
-		// Fallthrough to the bottom to record incoming traffic
-
-		// Non encrypted messages below here, they should not fall through to avoid tracking incoming traffic since they
-		// are unauthenticated
-
-	case header.Handshake:
-		f.messageMetrics.Rx(h.Type, h.Subtype, 1)
-		f.handshakeManager.HandleIncoming(via, packet, h)
-		return
-
-	case header.RecvError:
-		f.messageMetrics.Rx(h.Type, h.Subtype, 1)
-		f.handleRecvError(via.UdpAddr, h)
-		return
-
 	case header.CloseTunnel:
-		f.messageMetrics.Rx(h.Type, h.Subtype, 1)
-		if !f.handleEncrypted(ci, via, h) {
-			return
-		}
-		_, err = f.decrypt(hostinfo, h.MessageCounter, out, packet, h, nb)
-		if err != nil {
-			hostinfo.logger(f.l).WithError(err).WithField("from", via).
-				WithField("packet", packet).
-				Error("Failed to decrypt CloseTunnel packet")
-			return
-		}
-
-		hostinfo.logger(f.l).WithField("from", via).
-			Info("Close tunnel received, tearing down.")
-
+		hostinfo.logger(f.l).Info("Close tunnel received, tearing down.", "from", via)
 		f.closeTunnel(hostinfo)
-		return
 
 	case header.Control:
-		if !f.handleEncrypted(ci, via, h) {
-			return
-		}
-
-		d, err := f.decrypt(hostinfo, h.MessageCounter, out, packet, h, nb)
-		if err != nil {
-			hostinfo.logger(f.l).WithError(err).WithField("from", via).
-				WithField("packet", packet).
-				Error("Failed to decrypt Control packet")
-			return
-		}
-
-		f.relayManager.HandleControlMsg(hostinfo, d, f)
+		f.relayManager.HandleControlMsg(hostinfo, out, f)
 
 	default:
-		f.messageMetrics.Rx(h.Type, h.Subtype, 1)
-		hostinfo.logger(f.l).Debugf("Unexpected packet received from %s", via)
+		hostinfo.logger(f.l).Error("IsValidSubType was true, but unexpected message type seen", "from", via, "header", h)
+	}
+}
+
+func (f *Interface) handleOutsideRelayPacket(hostinfo *HostInfo, via ViaSender, out []byte, packet []byte, h *header.H, fwPacket *firewall.Packet, parsedRx *batch.RxParsed, lhf *LightHouseHandler, nb []byte, q int, localCache firewall.ConntrackCache, meta udp.RxMeta) {
+	// The entire body is sent as AD, not encrypted.
+	// The packet consists of a 16-byte parsed Nebula header, Associated Data-protected payload, and a trailing 16-byte AEAD signature value.
+	// The packet is guaranteed to be at least 16 bytes at this point, b/c it got past the h.Parse() call above. If it's
+	// otherwise malformed (meaning, there is no trailing 16 byte AEAD value), then this will result in at worst a 0-length slice
+	// which will gracefully fail in the DecryptDanger call.
+	signedPayload := packet[:len(packet)-hostinfo.ConnectionState.dKey.Overhead()]
+	signatureValue := packet[len(packet)-hostinfo.ConnectionState.dKey.Overhead():]
+	var err error
+	out, err = hostinfo.ConnectionState.dKey.DecryptDanger(out, signedPayload, signatureValue, h.MessageCounter, nb)
+	if err != nil {
+		return
+	}
+	// Successfully validated the thing. Get rid of the Relay header.
+	signedPayload = signedPayload[header.Len:]
+	// Pull the Roaming parts up here, and return in all call paths.
+	f.handleHostRoaming(hostinfo, via)
+	// Track usage of both the HostInfo and the Relay for the received & authenticated packet
+	f.connectionManager.In(hostinfo)
+	f.connectionManager.RelayUsed(h.RemoteIndex)
+
+	relay, ok := hostinfo.relayState.QueryRelayForByIdx(h.RemoteIndex)
+	if !ok {
+		// The only way this happens is if hostmap has an index to the correct HostInfo, but the HostInfo is missing
+		// its internal mapping. This should never happen.
+		hostinfo.logger(f.l).Error("HostInfo missing remote relay index",
+			"vpnAddrs", hostinfo.vpnAddrs,
+			"remoteIndex", h.RemoteIndex,
+		)
 		return
 	}
 
-	f.handleHostRoaming(hostinfo, via)
+	switch relay.Type {
+	case TerminalType:
+		// If I am the target of this relay, process the unwrapped packet
+		// From this recursive point, all these variables are 'burned'. We shouldn't rely on them again.
+		via = ViaSender{
+			UdpAddr:   via.UdpAddr,
+			relayHI:   hostinfo,
+			remoteIdx: relay.RemoteIndex,
+			relay:     relay,
+			IsRelayed: true,
+		}
+		f.readOutsidePackets(via, out[:0], signedPayload, h, fwPacket, parsedRx, lhf, nb, q, localCache, meta)
+		return
+	case ForwardingType:
+		// Find the target HostInfo relay object
+		targetHI, targetRelay, err := f.hostMap.QueryVpnAddrsRelayFor(hostinfo.vpnAddrs, relay.PeerAddr)
+		if err != nil {
+			hostinfo.logger(f.l).Info("Failed to find target host info by ip",
+				"relayTo", relay.PeerAddr,
+				"error", err,
+				"hostinfo.vpnAddrs", hostinfo.vpnAddrs,
+			)
+			return
+		}
 
-	f.connectionManager.In(hostinfo)
+		// If that relay is Established, forward the payload through it
+		if targetRelay.State == Established {
+			switch targetRelay.Type {
+			case ForwardingType:
+				// Forward this packet through the relay tunnel
+				// Find the target HostInfo //todo it would potentially be nice to batch these
+				f.SendVia(targetHI, targetRelay, signedPayload, nb, out, false)
+			case TerminalType:
+				hostinfo.logger(f.l).Error("Unexpected Relay Type of Terminal")
+				return
+			default:
+				if f.l.Enabled(context.Background(), slog.LevelDebug) {
+					hostinfo.logger(f.l).Debug("Unexpected targetRelay Type", "from", via, "relayType", targetRelay.Type)
+				}
+				return
+			}
+		} else {
+			hostinfo.logger(f.l).Info("Unexpected target relay state",
+				"relayTo", relay.PeerAddr,
+				"relayFrom", hostinfo.vpnAddrs[0],
+				"targetRelayState", targetRelay.State,
+			)
+			return
+		}
+	default:
+		if f.l.Enabled(context.Background(), slog.LevelDebug) {
+			hostinfo.logger(f.l).Debug("Unexpected relay type", "from", via, "relayType", relay.Type)
+		}
+	}
 }
 
 // closeTunnel closes a tunnel locally, it does not send a closeTunnel packet to the remote
@@ -247,20 +266,27 @@ func (f *Interface) sendCloseTunnel(h *HostInfo) {
 func (f *Interface) handleHostRoaming(hostinfo *HostInfo, via ViaSender) {
 	if !via.IsRelayed && hostinfo.remote != via.UdpAddr {
 		if !f.lightHouse.GetRemoteAllowList().AllowAll(hostinfo.vpnAddrs, via.UdpAddr.Addr()) {
-			hostinfo.logger(f.l).WithField("newAddr", via.UdpAddr).Debug("lighthouse.remote_allow_list denied roaming")
-			return
-		}
-
-		if !hostinfo.lastRoam.IsZero() && via.UdpAddr == hostinfo.lastRoamRemote && time.Since(hostinfo.lastRoam) < RoamingSuppressSeconds*time.Second {
-			if f.l.Level >= logrus.DebugLevel {
-				hostinfo.logger(f.l).WithField("udpAddr", hostinfo.remote).WithField("newAddr", via.UdpAddr).
-					Debugf("Suppressing roam back to previous remote for %d seconds", RoamingSuppressSeconds)
+			if f.l.Enabled(context.Background(), slog.LevelDebug) {
+				hostinfo.logger(f.l).Debug("lighthouse.remote_allow_list denied roaming", "newAddr", via.UdpAddr)
 			}
 			return
 		}
 
-		hostinfo.logger(f.l).WithField("udpAddr", hostinfo.remote).WithField("newAddr", via.UdpAddr).
-			Info("Host roamed to new udp ip/port.")
+		if !hostinfo.lastRoam.IsZero() && via.UdpAddr == hostinfo.lastRoamRemote && time.Since(hostinfo.lastRoam) < RoamingSuppressSeconds*time.Second {
+			if f.l.Enabled(context.Background(), slog.LevelDebug) {
+				hostinfo.logger(f.l).Debug("Suppressing roam back to previous remote",
+					"suppressSeconds", RoamingSuppressSeconds,
+					"udpAddr", hostinfo.remote,
+					"newAddr", via.UdpAddr,
+				)
+			}
+			return
+		}
+
+		hostinfo.logger(f.l).Info("Host roamed to new udp ip/port.",
+			"udpAddr", hostinfo.remote,
+			"newAddr", via.UdpAddr,
+		)
 		hostinfo.lastRoam = time.Now()
 		hostinfo.lastRoamRemote = hostinfo.remote
 		hostinfo.SetRemote(via.UdpAddr)
@@ -268,23 +294,6 @@ func (f *Interface) handleHostRoaming(hostinfo *HostInfo, via ViaSender) {
 
 }
 
-// handleEncrypted returns true if a packet should be processed, false otherwise
-func (f *Interface) handleEncrypted(ci *ConnectionState, via ViaSender, h *header.H) bool {
-	// If connectionstate does not exist, send a recv error, if possible, to encourage a fast reconnect
-	if ci == nil {
-		if !via.IsRelayed {
-			f.maybeSendRecvError(via.UdpAddr, h.RemoteIndex)
-		}
-		return false
-	}
-	// If the window check fails, refuse to process the packet, but don't send a recv error
-	if !ci.window.Check(f.l, h.MessageCounter) {
-		return false
-	}
-
-	return true
-}
-
 var (
 	ErrPacketTooShort          = errors.New("packet is too short")
 	ErrUnknownIPVersion        = errors.New("packet is an unknown ip version")
@@ -295,191 +304,16 @@ var (
 )
 
 // newPacket validates and parses the interesting bits for the firewall out of the ip and sub protocol headers
+// newPacket parses data into a fully-hydrated firewall.Packet — kept as a
+// thin wrapper around newPacketKey + Hydrate so there's one source of
+// parse logic. Callers that don't need the netip.Addr-rich form (e.g.
+// conntrack-only paths) should use newPacketKey directly.
 func newPacket(data []byte, incoming bool, fp *firewall.Packet) error {
-	if len(data) < 1 {
-		return ErrPacketTooShort
+	var parsed batch.RxParsed
+	if err := batch.ParsePacket(data, incoming, &parsed); err != nil {
+		return err
 	}
-
-	version := int((data[0] >> 4) & 0x0f)
-	switch version {
-	case ipv4.Version:
-		return parseV4(data, incoming, fp)
-	case ipv6.Version:
-		return parseV6(data, incoming, fp)
-	}
-	return ErrUnknownIPVersion
-}
-
-func parseV6(data []byte, incoming bool, fp *firewall.Packet) error {
-	dataLen := len(data)
-	if dataLen < ipv6.HeaderLen {
-		return ErrIPv6PacketTooShort
-	}
-
-	if incoming {
-		fp.RemoteAddr, _ = netip.AddrFromSlice(data[8:24])
-		fp.LocalAddr, _ = netip.AddrFromSlice(data[24:40])
-	} else {
-		fp.LocalAddr, _ = netip.AddrFromSlice(data[8:24])
-		fp.RemoteAddr, _ = netip.AddrFromSlice(data[24:40])
-	}
-
-	protoAt := 6             // NextHeader is at 6 bytes into the ipv6 header
-	offset := ipv6.HeaderLen // Start at the end of the ipv6 header
-	next := 0
-	for {
-		if protoAt >= dataLen {
-			break
-		}
-		proto := layers.IPProtocol(data[protoAt])
-
-		switch proto {
-		case layers.IPProtocolESP, layers.IPProtocolNoNextHeader:
-			fp.Protocol = uint8(proto)
-			fp.RemotePort = 0
-			fp.LocalPort = 0
-			fp.Fragment = false
-			return nil
-
-		case layers.IPProtocolICMPv6:
-			if dataLen < offset+6 {
-				return ErrIPv6PacketTooShort
-			}
-			fp.Protocol = uint8(proto)
-			fp.LocalPort = 0 //incoming vs outgoing doesn't matter for icmpv6
-			icmptype := data[offset+1]
-			switch icmptype {
-			case layers.ICMPv6TypeEchoRequest, layers.ICMPv6TypeEchoReply:
-				fp.RemotePort = binary.BigEndian.Uint16(data[offset+4 : offset+6]) //identifier
-			default:
-				fp.RemotePort = 0
-			}
-			fp.Fragment = false
-			return nil
-
-		case layers.IPProtocolTCP, layers.IPProtocolUDP:
-			if dataLen < offset+4 {
-				return ErrIPv6PacketTooShort
-			}
-
-			fp.Protocol = uint8(proto)
-			if incoming {
-				fp.RemotePort = binary.BigEndian.Uint16(data[offset : offset+2])
-				fp.LocalPort = binary.BigEndian.Uint16(data[offset+2 : offset+4])
-			} else {
-				fp.LocalPort = binary.BigEndian.Uint16(data[offset : offset+2])
-				fp.RemotePort = binary.BigEndian.Uint16(data[offset+2 : offset+4])
-			}
-
-			fp.Fragment = false
-			return nil
-
-		case layers.IPProtocolIPv6Fragment:
-			// Fragment header is 8 bytes, need at least offset+4 to read the offset field
-			if dataLen < offset+8 {
-				return ErrIPv6PacketTooShort
-			}
-
-			// Check if this is the first fragment
-			fragmentOffset := binary.BigEndian.Uint16(data[offset+2:offset+4]) &^ uint16(0x7) // Remove the reserved and M flag bits
-			if fragmentOffset != 0 {
-				// Non-first fragment, use what we have now and stop processing
-				fp.Protocol = data[offset]
-				fp.Fragment = true
-				fp.RemotePort = 0
-				fp.LocalPort = 0
-				return nil
-			}
-
-			// The next loop should be the transport layer since we are the first fragment
-			next = 8 // Fragment headers are always 8 bytes
-
-		case layers.IPProtocolAH:
-			// Auth headers, used by IPSec, have a different meaning for header length
-			if dataLen <= offset+1 {
-				break
-			}
-
-			next = int(data[offset+1]+2) << 2
-
-		default:
-			// Normal ipv6 header length processing
-			if dataLen <= offset+1 {
-				break
-			}
-
-			next = int(data[offset+1]+1) << 3
-		}
-
-		if next <= 0 {
-			// Safety check, each ipv6 header has to be at least 8 bytes
-			next = 8
-		}
-
-		protoAt = offset
-		offset = offset + next
-	}
-
-	return ErrIPv6CouldNotFindPayload
-}
-
-func parseV4(data []byte, incoming bool, fp *firewall.Packet) error {
-	// Do we at least have an ipv4 header worth of data?
-	if len(data) < ipv4.HeaderLen {
-		return ErrIPv4PacketTooShort
-	}
-
-	// Adjust our start position based on the advertised ip header length
-	ihl := int(data[0]&0x0f) << 2
-
-	// Well-formed ip header length?
-	if ihl < ipv4.HeaderLen {
-		return ErrIPv4InvalidHeaderLength
-	}
-
-	// Check if this is the second or further fragment of a fragmented packet.
-	flagsfrags := binary.BigEndian.Uint16(data[6:8])
-	fp.Fragment = (flagsfrags & 0x1FFF) != 0
-
-	// Firewall handles protocol checks
-	fp.Protocol = data[9]
-
-	// Accounting for a variable header length, do we have enough data for our src/dst tuples?
-	minLen := ihl
-	if !fp.Fragment {
-		if fp.Protocol == firewall.ProtoICMP {
-			minLen += minFwPacketLen + 2
-		} else {
-			minLen += minFwPacketLen
-		}
-	}
-
-	if len(data) < minLen {
-		return ErrIPv4InvalidHeaderLength
-	}
-
-	if incoming { // Firewall packets are locally oriented
-		fp.RemoteAddr, _ = netip.AddrFromSlice(data[12:16])
-		fp.LocalAddr, _ = netip.AddrFromSlice(data[16:20])
-	} else {
-		fp.LocalAddr, _ = netip.AddrFromSlice(data[12:16])
-		fp.RemoteAddr, _ = netip.AddrFromSlice(data[16:20])
-	}
-
-	if fp.Fragment {
-		fp.RemotePort = 0
-		fp.LocalPort = 0
-	} else if fp.Protocol == firewall.ProtoICMP { //note that orientation doesn't matter on ICMP
-		fp.RemotePort = binary.BigEndian.Uint16(data[ihl+4 : ihl+6]) //identifier
-		fp.LocalPort = 0                                             //code would be uint16(data[ihl+1])
-	} else if incoming {
-		fp.RemotePort = binary.BigEndian.Uint16(data[ihl : ihl+2])  //src port
-		fp.LocalPort = binary.BigEndian.Uint16(data[ihl+2 : ihl+4]) //dst port
-	} else {
-		fp.LocalPort = binary.BigEndian.Uint16(data[ihl : ihl+2])    //src port
-		fp.RemotePort = binary.BigEndian.Uint16(data[ihl+2 : ihl+4]) //dst port
-	}
-
+	parsed.Key.Hydrate(fp)
 	return nil
 }
 
@@ -491,55 +325,100 @@ func (f *Interface) decrypt(hostinfo *HostInfo, mc uint64, out []byte, packet []
 	}
 
 	if !hostinfo.ConnectionState.window.Update(f.l, mc) {
-		hostinfo.logger(f.l).WithField("header", h).
-			Debugln("dropping out of window packet")
-		return nil, errors.New("out of window packet")
+		return nil, ErrOutOfWindow
 	}
 
 	return out, nil
 }
 
-func (f *Interface) decryptToTun(hostinfo *HostInfo, messageCounter uint64, out []byte, packet []byte, fwPacket *firewall.Packet, nb []byte, q int, localCache firewall.ConntrackCache) bool {
-	var err error
+// 2-bit IP-level ECN codepoints (lower bits of IPv4 ToS / IPv6 TC).
+const (
+	ecnNotECT = 0x00
+	ecnECT1   = 0x01
+	ecnECT0   = 0x02
+	ecnCE     = 0x03
+)
 
-	out, err = hostinfo.ConnectionState.dKey.DecryptDanger(out, packet[:header.Len], packet[header.Len:], messageCounter, nb)
+// applyOuterECN folds an outer CE mark from the underlay into the inner
+// IP header per RFC 6040 normal mode. It mutates pkt[1] in place. Other
+// codepoints are advisory only and leave the inner unchanged.
+//
+// Merge cases (outer × inner → action):
+//
+//	outer != CE                : no-op (inner is authoritative)
+//	outer == CE, inner Not-ECT : log; cannot propagate to a non-ECN host
+//	outer == CE, inner ECT/CE  : rewrite inner ECN to CE
+func applyOuterECN(pkt []byte, outerECN byte, hostinfo *HostInfo, l *slog.Logger) {
+	if outerECN&ecnCE != ecnCE || len(pkt) < 2 {
+		return
+	}
+	switch pkt[0] >> 4 {
+	case 4:
+		switch pkt[1] & 0x03 {
+		case ecnNotECT:
+			if l.Enabled(context.Background(), slog.LevelDebug) {
+				hostinfo.logger(l).Debug("RFC 6040: outer CE on inner Not-ECT, leaving inner unchanged")
+			}
+		case ecnCE:
+			// Already CE.
+		default:
+			pkt[1] = (pkt[1] &^ 0x03) | ecnCE
+		}
+	case 6:
+		switch (pkt[1] >> 4) & 0x03 {
+		case ecnNotECT:
+			if l.Enabled(context.Background(), slog.LevelDebug) {
+				hostinfo.logger(l).Debug("RFC 6040: outer CE on inner Not-ECT, leaving inner unchanged")
+			}
+		case ecnCE:
+			// Already CE.
+		default:
+			pkt[1] = (pkt[1] &^ 0x30) | (ecnCE << 4)
+		}
+	}
+}
+
+func (f *Interface) handleOutsideMessagePacket(hostinfo *HostInfo, out []byte, packet []byte, fwPacket *firewall.Packet, parsedRx *batch.RxParsed, nb []byte, q int, localCache firewall.ConntrackCache, meta udp.RxMeta) {
+	// RFC 6040 normal-mode combine: fold any outer CE mark stamped by the
+	// underlay into the inner header before firewall + TUN write. Other
+	// outer codepoints are advisory only — we keep the inner unchanged.
+	if f.ecnEnabled.Load() {
+		applyOuterECN(out, meta.OuterECN, hostinfo, f.l)
+	}
+
+	// Single IP+L4 walk feeds the firewall conntrack key (parsedRx.Key)
+	// and the batcher hint (parsedRx.tcp/udp). Replaces newPacket — and
+	// pointedly does NOT fill fwPacket.LocalAddr/RemoteAddr, since
+	// firewall.Drop's fast path uses Key alone and only hydrates fwPacket
+	// from Key on the slow path.
+	*fwPacket = firewall.Packet{}
+	err := batch.ParsePacket(out, true, parsedRx)
 	if err != nil {
-		hostinfo.logger(f.l).WithError(err).Error("Failed to decrypt packet")
-		return false
+		hostinfo.logger(f.l).Warn("Error while validating inbound packet",
+			"error", err,
+			"packet", out,
+		)
+		return
 	}
 
-	err = newPacket(out, true, fwPacket)
-	if err != nil {
-		hostinfo.logger(f.l).WithError(err).WithField("packet", out).
-			Warnf("Error while validating inbound packet")
-		return false
-	}
-
-	if !hostinfo.ConnectionState.window.Update(f.l, messageCounter) {
-		hostinfo.logger(f.l).WithField("fwPacket", fwPacket).
-			Debugln("dropping out of window packet")
-		return false
-	}
-
-	dropReason := f.firewall.Drop(*fwPacket, true, hostinfo, f.pki.GetCAPool(), localCache)
+	dropReason := f.firewall.Drop(parsedRx.Key, fwPacket, true, hostinfo, f.pki.GetCAPool(), localCache)
 	if dropReason != nil {
 		// NOTE: We give `packet` as the `out` here since we already decrypted from it and we don't need it anymore
 		// This gives us a buffer to build the reject packet in
 		f.rejectOutside(out, hostinfo.ConnectionState, hostinfo, nb, packet, q)
-		if f.l.Level >= logrus.DebugLevel {
-			hostinfo.logger(f.l).WithField("fwPacket", fwPacket).
-				WithField("reason", dropReason).
-				Debugln("dropping inbound packet")
+		if f.l.Enabled(context.Background(), slog.LevelDebug) {
+			hostinfo.logger(f.l).Debug("dropping inbound packet",
+				"fwPacket", fwPacket,
+				"reason", dropReason,
+			)
 		}
-		return false
+		return
 	}
 
-	f.connectionManager.In(hostinfo)
-	err = f.tunCoalescers[q].Add(out)
+	err = f.batchers[q].CommitInbound(out, parsedRx)
 	if err != nil {
-		f.l.WithError(err).Error("Failed to write to tun")
+		f.l.Error("Failed to write to tun", "error", err)
 	}
-	return true
 }
 
 func (f *Interface) maybeSendRecvError(endpoint netip.AddrPort, index uint32) {
@@ -553,35 +432,41 @@ func (f *Interface) sendRecvError(endpoint netip.AddrPort, index uint32) {
 
 	b := header.Encode(make([]byte, header.Len), header.Version, header.RecvError, 0, index, 0)
 	_ = f.outside.WriteTo(b, endpoint)
-	if f.l.Level >= logrus.DebugLevel {
-		f.l.WithField("index", index).
-			WithField("udpAddr", endpoint).
-			Debug("Recv error sent")
+	if f.l.Enabled(context.Background(), slog.LevelDebug) {
+		f.l.Debug("Recv error sent",
+			"index", index,
+			"udpAddr", endpoint,
+		)
 	}
 }
 
 func (f *Interface) handleRecvError(addr netip.AddrPort, h *header.H) {
 	if !f.acceptRecvErrorConfig.ShouldRecvError(addr) {
-		f.l.WithField("index", h.RemoteIndex).
-			WithField("udpAddr", addr).
-			Debug("Recv error received, ignoring")
+		f.l.Debug("Recv error received, ignoring",
+			"index", h.RemoteIndex,
+			"udpAddr", addr,
+		)
 		return
 	}
 
-	if f.l.Level >= logrus.DebugLevel {
-		f.l.WithField("index", h.RemoteIndex).
-			WithField("udpAddr", addr).
-			Debug("Recv error received")
+	if f.l.Enabled(context.Background(), slog.LevelDebug) {
+		f.l.Debug("Recv error received",
+			"index", h.RemoteIndex,
+			"udpAddr", addr,
+		)
 	}
 
 	hostinfo := f.hostMap.QueryReverseIndex(h.RemoteIndex)
 	if hostinfo == nil {
-		f.l.WithField("remoteIndex", h.RemoteIndex).Debugln("Did not find remote index in main hostmap")
+		f.l.Debug("Did not find remote index in main hostmap", "remoteIndex", h.RemoteIndex)
 		return
 	}
 
 	if hostinfo.remote.IsValid() && hostinfo.remote != addr {
-		f.l.Infoln("Someone spoofing recv_errors? ", addr, hostinfo.remote)
+		f.l.Info("Someone spoofing recv_errors?",
+			"addr", addr,
+			"hostinfoRemote", hostinfo.remote,
+		)
 		return
 	}
 

outside_test.go

@@ -11,6 +11,7 @@ import (
 	"github.com/google/gopacket/layers"
 
 	"github.com/slackhq/nebula/firewall"
+	"github.com/slackhq/nebula/overlay/batch"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 	"golang.org/x/net/ipv4"
@@ -21,13 +22,13 @@ func Test_newPacket(t *testing.T) {
 
 	// length fails
 	err := newPacket([]byte{}, true, p)
-	require.ErrorIs(t, err, ErrPacketTooShort)
+	require.ErrorIs(t, err, batch.ErrPacketTooShort)
 
 	err = newPacket([]byte{0x40}, true, p)
-	require.ErrorIs(t, err, ErrIPv4PacketTooShort)
+	require.ErrorIs(t, err, batch.ErrIPv4PacketTooShort)
 
 	err = newPacket([]byte{0x60}, true, p)
-	require.ErrorIs(t, err, ErrIPv6PacketTooShort)
+	require.ErrorIs(t, err, batch.ErrIPv6PacketTooShort)
 
 	// length fail with ip options
 	h := ipv4.Header{
@@ -40,15 +41,15 @@ func Test_newPacket(t *testing.T) {
 
 	b, _ := h.Marshal()
 	err = newPacket(b, true, p)
-	require.ErrorIs(t, err, ErrIPv4InvalidHeaderLength)
+	require.ErrorIs(t, err, batch.ErrIPv4InvalidHeaderLength)
 
 	// not an ipv4 packet
 	err = newPacket([]byte{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, true, p)
-	require.ErrorIs(t, err, ErrUnknownIPVersion)
+	require.ErrorIs(t, err, batch.ErrUnknownIPVersion)
 
 	// invalid ihl
 	err = newPacket([]byte{4<<4 | (8 >> 2 & 0x0f), 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, true, p)
-	require.ErrorIs(t, err, ErrIPv4InvalidHeaderLength)
+	require.ErrorIs(t, err, batch.ErrIPv4InvalidHeaderLength)
 
 	// account for variable ip header length - incoming
 	h = ipv4.Header{
@@ -115,7 +116,7 @@ func Test_newPacket_v6(t *testing.T) {
 	require.NoError(t, err)
 
 	err = newPacket(buffer.Bytes(), true, p)
-	require.ErrorIs(t, err, ErrIPv6CouldNotFindPayload)
+	require.ErrorIs(t, err, batch.ErrIPv6CouldNotFindPayload)
 
 	// A v6 packet with a hop-by-hop extension
 	// ICMPv6 Payload (Echo Request)
@@ -149,12 +150,12 @@ func Test_newPacket_v6(t *testing.T) {
 	// A full IPv6 header and 1 byte in the first extension, but missing
 	// the length byte.
 	err = newPacket(buffer.Bytes()[:41], true, p)
-	require.ErrorIs(t, err, ErrIPv6CouldNotFindPayload)
+	require.ErrorIs(t, err, batch.ErrIPv6CouldNotFindPayload)
 
 	// A full IPv6 header plus 1 full extension, but only 1 byte of the
 	// next layer, missing length byte
 	err = newPacket(buffer.Bytes()[:49], true, p)
-	require.ErrorIs(t, err, ErrIPv6CouldNotFindPayload)
+	require.ErrorIs(t, err, batch.ErrIPv6CouldNotFindPayload)
 	err = nil
 
 	// A good ICMP packet
@@ -217,7 +218,7 @@ func Test_newPacket_v6(t *testing.T) {
 	b = buffer.Bytes()
 	b[6] = 255 // 255 is a reserved protocol number
 	err = newPacket(b, true, p)
-	require.ErrorIs(t, err, ErrIPv6CouldNotFindPayload)
+	require.ErrorIs(t, err, batch.ErrIPv6CouldNotFindPayload)
 
 	// A good UDP packet
 	ip = layers.IPv6{
@@ -264,7 +265,7 @@ func Test_newPacket_v6(t *testing.T) {
 
 	// Too short UDP packet
 	err = newPacket(b[:len(b)-10], false, p) // pull off the last 10 bytes
-	require.ErrorIs(t, err, ErrIPv6PacketTooShort)
+	require.ErrorIs(t, err, batch.ErrIPv6PacketTooShort)
 
 	// A good TCP packet
 	b[6] = byte(layers.IPProtocolTCP)
@@ -291,7 +292,7 @@ func Test_newPacket_v6(t *testing.T) {
 
 	// Too short TCP packet
 	err = newPacket(b[:len(b)-10], false, p) // pull off the last 10 bytes
-	require.ErrorIs(t, err, ErrIPv6PacketTooShort)
+	require.ErrorIs(t, err, batch.ErrIPv6PacketTooShort)
 
 	// A good UDP packet with an AH header
 	ip = layers.IPv6{
@@ -336,12 +337,12 @@ func Test_newPacket_v6(t *testing.T) {
 
 	// Ensure buffer bounds checking during processing
 	err = newPacket(b[:41], true, p)
-	require.ErrorIs(t, err, ErrIPv6PacketTooShort)
+	require.ErrorIs(t, err, batch.ErrIPv6PacketTooShort)
 
 	// Invalid AH header
 	b = buffer.Bytes()
 	err = newPacket(b, true, p)
-	require.ErrorIs(t, err, ErrIPv6CouldNotFindPayload)
+	require.ErrorIs(t, err, batch.ErrIPv6CouldNotFindPayload)
 }
 
 func Test_newPacket_ipv6Fragment(t *testing.T) {
@@ -448,7 +449,7 @@ func Test_newPacket_ipv6Fragment(t *testing.T) {
 
 	// Too short of a fragment packet
 	err = newPacket(secondFrag[:len(secondFrag)-10], false, p)
-	require.ErrorIs(t, err, ErrIPv6PacketTooShort)
+	require.ErrorIs(t, err, batch.ErrIPv6PacketTooShort)
 }
 
 func BenchmarkParseV6(b *testing.B) {
@@ -529,7 +530,7 @@ func BenchmarkParseV6(b *testing.B) {
 
 	b.Run("Normal", func(b *testing.B) {
 		for i := 0; i < b.N; i++ {
-			if err = parseV6(normalPacket, true, fp); err != nil {
+			if err = newPacket(normalPacket, true, fp); err != nil {
 				b.Fatal(err)
 			}
 		}
@@ -537,7 +538,7 @@ func BenchmarkParseV6(b *testing.B) {
 
 	b.Run("FirstFragment", func(b *testing.B) {
 		for i := 0; i < b.N; i++ {
-			if err = parseV6(firstFrag, true, fp); err != nil {
+			if err = newPacket(firstFrag, true, fp); err != nil {
 				b.Fatal(err)
 			}
 		}
@@ -545,7 +546,7 @@ func BenchmarkParseV6(b *testing.B) {
 
 	b.Run("SecondFragment", func(b *testing.B) {
 		for i := 0; i < b.N; i++ {
-			if err = parseV6(secondFrag, true, fp); err != nil {
+			if err = newPacket(secondFrag, true, fp); err != nil {
 				b.Fatal(err)
 			}
 		}
@@ -590,7 +591,7 @@ func BenchmarkParseV6(b *testing.B) {
 
 	b.Run("200 HopByHop headers", func(b *testing.B) {
 		for i := 0; i < b.N; i++ {
-			if err = parseV6(evilBytes, false, fp); err != nil {
+			if err = newPacket(evilBytes, false, fp); err != nil {
 				b.Fatal(err)
 			}
 		}

overlay/batch/batch.go

@@ -0,0 +1,35 @@
+package batch
+
+import "net/netip"
+
+type RxBatcher interface {
+	// Reserve creates a pkt to borrow
+	Reserve(sz int) []byte
+	// Commit borrows pkt. The caller must keep pkt valid until the next Flush.
+	// Walks IP+L4 headers itself; prefer CommitInbound when the caller already
+	// has an RxParsed in hand from ParsePacket.
+	Commit(pkt []byte) error
+	// CommitInbound is Commit with a hint produced by ParsePacket, so the
+	// batcher can skip the IP+L4 re-parse. Borrowed slice contract is the
+	// same as Commit. Implementations that don't coalesce may delegate to
+	// Commit.
+	CommitInbound(pkt []byte, parsed *RxParsed) error
+	// Flush emits every queued packet in arrival order. Returns the
+	// first error observed; keeps draining so one bad packet doesn't hold up
+	// the rest. After Flush returns, borrowed payload slices may be recycled.
+	Flush() error
+}
+
+type TxBatcher interface {
+	// Reserve creates a pkt to borrow
+	Reserve(sz int) []byte
+	// Commit borrows pkt and records its destination plus the 2-bit
+	// IP-level ECN codepoint to set on the outer (carrier) header. The
+	// caller must keep pkt valid until the next Flush. Pass 0 (Not-ECT)
+	// to leave the outer ECN field unset.
+	Commit(pkt []byte, dst netip.AddrPort, outerECN byte)
+	// Flush emits every queued packet via the underlying batch writer in
+	// arrival order. Returns an errors.Join of one or more errors. After Flush returns,
+	// borrowed payload slices may be recycled.
+	Flush() error
+}

overlay/batch/coalesce_core.go

@@ -0,0 +1,163 @@
+package batch
+
+import (
+	"bytes"
+	"encoding/binary"
+)
+
+// flowKey identifies a transport flow by {src, dst, sport, dport, family}.
+// Comparable, so map lookups and linear scans over the slot list stay tight.
+// Shared by the TCP and UDP coalescers; each coalescer keeps its own
+// openSlots map, so a TCP and UDP flow on the same 5-tuple-without-proto
+// never alias.
+type flowKey struct {
+	src, dst     [16]byte
+	sport, dport uint16
+	isV6         bool
+}
+
+// initialSlots is the starting capacity of the slot pool. One flow per
+// packet is the worst case so this matches a typical carrier-side
+// recvmmsg batch on the encrypted UDP socket.
+const initialSlots = 64
+
+// parsedIP is the IP-level result of parseIPPrologue. The caller layers
+// L4-specific parsing (TCP / UDP) on top.
+type parsedIP struct {
+	fk       flowKey
+	ipHdrLen int
+	// pkt is the original buffer trimmed to the IP-declared total length.
+	// Anything below the IP layer (transport parsers) should slice into
+	// pkt rather than the unbounded original.
+	pkt []byte
+}
+
+// parseIPPrologue extracts the IP-level fields the coalescers care about:
+// IHL/payload length, version, src/dst addresses, and the L4 protocol byte.
+// Returns ok=false for malformed input, IPv4 with options or fragmentation,
+// or IPv6 with extension headers (all rejected by both coalescers in
+// identical ways before this refactor).
+//
+// On success, p.pkt is len-trimmed to the IP-declared length so callers
+// don't have to repeat the trim. wantProto is the IANA protocol number to
+// require (6 for TCP, 17 for UDP); ok=false for any other value.
+func parseIPPrologue(pkt []byte, wantProto byte) (parsedIP, bool) {
+	var p parsedIP
+	if len(pkt) < 20 {
+		return p, false
+	}
+	v := pkt[0] >> 4
+	switch v {
+	case 4:
+		ihl := int(pkt[0]&0x0f) * 4
+		if ihl != 20 {
+			return p, false
+		}
+		if pkt[9] != wantProto {
+			return p, false
+		}
+		// Reject actual fragmentation (MF or non-zero frag offset).
+		if binary.BigEndian.Uint16(pkt[6:8])&0x3fff != 0 {
+			return p, false
+		}
+		totalLen := int(binary.BigEndian.Uint16(pkt[2:4]))
+		if totalLen > len(pkt) || totalLen < ihl {
+			return p, false
+		}
+		p.ipHdrLen = 20
+		p.fk.isV6 = false
+		copy(p.fk.src[:4], pkt[12:16])
+		copy(p.fk.dst[:4], pkt[16:20])
+		p.pkt = pkt[:totalLen]
+	case 6:
+		if len(pkt) < 40 {
+			return p, false
+		}
+		if pkt[6] != wantProto {
+			return p, false
+		}
+		payloadLen := int(binary.BigEndian.Uint16(pkt[4:6]))
+		if 40+payloadLen > len(pkt) {
+			return p, false
+		}
+		p.ipHdrLen = 40
+		p.fk.isV6 = true
+		copy(p.fk.src[:], pkt[8:24])
+		copy(p.fk.dst[:], pkt[24:40])
+		p.pkt = pkt[:40+payloadLen]
+	default:
+		return p, false
+	}
+	return p, true
+}
+
+// ipHeadersMatch compares the IP portion of two packet header prefixes for
+// byte-for-byte equality on every field that must be identical across
+// coalesced segments. Size/IPID/IPCsum and the 2-bit IP-level ECN field are
+// masked out — the appendPayload step merges CE into the seed.
+//
+// The transport (L4) portion of the header is checked separately by the
+// per-protocol matcher.
+func ipHeadersMatch(a, b []byte, isV6 bool) bool {
+	if isV6 {
+		// IPv6: byte 0 = version/TC[7:4], byte 1 = TC[3:0]/flow[19:16],
+		// bytes [2:4] = flow[15:0], [6:8] = next_hdr/hop, [8:40] = src+dst.
+		// ECN lives in TC[1:0] = byte 1 mask 0x30. Skip [4:6] payload_len.
+		if a[0] != b[0] {
+			return false
+		}
+		if a[1]&^0x30 != b[1]&^0x30 {
+			return false
+		}
+		if !bytes.Equal(a[2:4], b[2:4]) {
+			return false
+		}
+		if !bytes.Equal(a[6:40], b[6:40]) {
+			return false
+		}
+		return true
+	}
+	// IPv4: byte 0 = version/IHL, byte 1 = DSCP(6)|ECN(2),
+	// [6:10] flags/fragoff/TTL/proto, [12:20] src+dst.
+	// Skip [2:4] total len, [4:6] id, [10:12] csum.
+	if a[0] != b[0] {
+		return false
+	}
+	if a[1]&^0x03 != b[1]&^0x03 {
+		return false
+	}
+	if !bytes.Equal(a[6:10], b[6:10]) {
+		return false
+	}
+	if !bytes.Equal(a[12:20], b[12:20]) {
+		return false
+	}
+	return true
+}
+
+// mergeECNIntoSeed ORs the 2-bit IP-level ECN field of pkt's IP header
+// onto the seed's IP header, so a CE mark on any coalesced segment
+// propagates to the final superpacket. (CE is 0b11; ORing yields CE if
+// any segment carried it.) Used by both TCP and UDP coalescers, so the
+// invariant lives in one place.
+func mergeECNIntoSeed(seedHdr, pktHdr []byte, isV6 bool) {
+	if isV6 {
+		seedHdr[1] |= pktHdr[1] & 0x30
+	} else {
+		seedHdr[1] |= pktHdr[1] & 0x03
+	}
+}
+
+// reserveFromBacking implements the Reserve half of the RxBatcher contract
+// shared by TCP and UDP coalescers. The backing slice grows on demand;
+// already-committed slices reference the old array and remain valid until
+// Flush resets backing.
+func reserveFromBacking(backing *[]byte, sz int) []byte {
+	if len(*backing)+sz > cap(*backing) {
+		newCap := max(cap(*backing)*2, sz)
+		*backing = make([]byte, 0, newCap)
+	}
+	start := len(*backing)
+	*backing = (*backing)[:start+sz]
+	return (*backing)[start : start+sz : start+sz]
+}

overlay/batch/inbound.go

@@ -0,0 +1,443 @@
+package batch
+
+import (
+	"encoding/binary"
+	"errors"
+
+	"github.com/slackhq/nebula/firewall"
+)
+
+// IANA protocol numbers we recognise during the inbound parse. Kept local
+// (rather than reaching for the firewall constants for every one of these)
+// so the byte-comparison hot path doesn't depend on cross-package values.
+const (
+	ipProtoICMP         = 1
+	ipProtoIPv6Fragment = 44
+	ipProtoESP          = 50
+	ipProtoAH           = 51
+	ipProtoICMPv6       = 58
+	ipProtoNoNextHdr    = 59
+
+	icmpv6TypeEchoRequest = 128
+	icmpv6TypeEchoReply   = 129
+)
+
+// Packet parse errors — the canonical sentinel set for IP+L4 parsing.
+// Both inbound and outbound callers share this surface, so any code path
+// that ends up at firewall.PacketKey reports drops with the same errors.
+var (
+	ErrPacketTooShort          = errors.New("packet is too short")
+	ErrUnknownIPVersion        = errors.New("packet is an unknown ip version")
+	ErrIPv4InvalidHeaderLength = errors.New("invalid ipv4 header length")
+	ErrIPv4PacketTooShort      = errors.New("ipv4 packet is too short")
+	ErrIPv6PacketTooShort      = errors.New("ipv6 packet is too short")
+	ErrIPv6CouldNotFindPayload = errors.New("could not find payload in ipv6 packet")
+)
+
+// RxKind discriminates how an inbound plaintext packet should be committed
+// after its firewall.Packet has been built. RxKindPassthrough means the
+// IP shape is valid (firewall could match on it) but the coalescer's
+// strict checks reject it — caller should still write it via the
+// passthrough lane.
+type RxKind uint8
+
+const (
+	RxKindPassthrough RxKind = iota
+	RxKindTCP
+	RxKindUDP
+)
+
+// RxParsed is the unified result of one IP+L4 walk:
+//   - Key: the firewall's conntrack/cache lookup key. The dense form lets
+//     firewall.Drop hit conntrack without ever filling the rich Packet's
+//     netip.Addr fields. On a conntrack miss, Drop hydrates the caller's
+//     Packet from Key.
+//   - tcp/udp: the coalescer hint so commitParsed doesn't re-walk the
+//     headers. Meaningful only when Kind is RxKindTCP / RxKindUDP.
+type RxParsed struct {
+	Kind RxKind
+	Key  firewall.PacketKey
+	tcp  parsedTCP
+	udp  parsedUDP
+}
+
+// ParsePacket walks an IP packet once and fills parsed.Key. When incoming
+// is true and the L4 shape is coalesce-eligible, also fills parsed.tcp /
+// parsed.udp so CommitInbound can dispatch into the coalescer without
+// re-walking the headers.
+//
+// Direction selects the Key orientation:
+//
+//	incoming=true  → wire src → Key.RemoteAddr/Port, wire dst → Key.LocalAddr/Port
+//	incoming=false → wire src → Key.LocalAddr/Port,  wire dst → Key.RemoteAddr/Port
+//
+// ICMP always lands the identifier in Key.RemotePort, regardless of direction.
+//
+// Eligibility rules for the coalescer hint match the coalescer's own
+// parseTCPBase/parseUDP:
+//   - IPv4 strict: IHL == 20, no fragmentation (MF or offset), proto TCP/UDP.
+//   - IPv6 strict: NextHeader is directly TCP or UDP (no extension headers).
+//
+// The hint is only filled for incoming packets, since the outbound path
+// does not feed an inbound coalescer. Outbound callers see Kind stay at
+// RxKindPassthrough and parsed.tcp/udp stay zero.
+func ParsePacket(pkt []byte, incoming bool, parsed *RxParsed) error {
+	parsed.Kind = RxKindPassthrough
+	// Reset Key in full: v4 only writes the low 4 bytes of each address
+	// field, so without this a v6 call followed by a v4 reusing the same
+	// RxParsed would inherit the high 12 bytes — breaking the conntrack
+	// map equality for v4 flows.
+	parsed.Key = firewall.PacketKey{}
+	if len(pkt) < 1 {
+		return ErrPacketTooShort
+	}
+	switch pkt[0] >> 4 {
+	case 4:
+		return parsePacketV4(pkt, incoming, parsed)
+	case 6:
+		return parsePacketV6(pkt, incoming, parsed)
+	}
+	return ErrUnknownIPVersion
+}
+
+// parsePacketV4 fills parsed.Key from an IPv4 packet. Direction selects
+// Local/Remote orientation. When incoming and the shape is strict, also
+// fills the coalescer hint.
+func parsePacketV4(pkt []byte, incoming bool, parsed *RxParsed) error {
+	if len(pkt) < 20 {
+		return ErrIPv4PacketTooShort
+	}
+	ihl := int(pkt[0]&0x0f) << 2
+	if ihl < 20 {
+		return ErrIPv4InvalidHeaderLength
+	}
+	flagsfrags := binary.BigEndian.Uint16(pkt[6:8])
+	parsed.Key.Fragment = (flagsfrags & 0x1FFF) != 0
+	parsed.Key.Protocol = pkt[9]
+	parsed.Key.IsV6 = false
+
+	// minFwPacketLen (4) is the L4-header prefix the firewall needs to pull
+	// ports; ICMP needs two extra bytes for the identifier.
+	minLen := ihl
+	if !parsed.Key.Fragment {
+		if parsed.Key.Protocol == firewall.ProtoICMP {
+			minLen += 4 + 2
+		} else {
+			minLen += 4
+		}
+	}
+	if len(pkt) < minLen {
+		return ErrIPv4InvalidHeaderLength
+	}
+
+	if incoming {
+		copy(parsed.Key.RemoteAddr[:4], pkt[12:16])
+		copy(parsed.Key.LocalAddr[:4], pkt[16:20])
+	} else {
+		copy(parsed.Key.LocalAddr[:4], pkt[12:16])
+		copy(parsed.Key.RemoteAddr[:4], pkt[16:20])
+	}
+
+	switch {
+	case parsed.Key.Fragment:
+		parsed.Key.RemotePort = 0
+		parsed.Key.LocalPort = 0
+	case parsed.Key.Protocol == firewall.ProtoICMP:
+		parsed.Key.RemotePort = binary.BigEndian.Uint16(pkt[ihl+4 : ihl+6])
+		parsed.Key.LocalPort = 0
+	case incoming:
+		parsed.Key.RemotePort = binary.BigEndian.Uint16(pkt[ihl : ihl+2])
+		parsed.Key.LocalPort = binary.BigEndian.Uint16(pkt[ihl+2 : ihl+4])
+	default:
+		parsed.Key.LocalPort = binary.BigEndian.Uint16(pkt[ihl : ihl+2])
+		parsed.Key.RemotePort = binary.BigEndian.Uint16(pkt[ihl+2 : ihl+4])
+	}
+
+	// Coalescer hint is inbound-only: no inbound coalescer fires on outgoing.
+	if !incoming {
+		return nil
+	}
+	// Coalescer-eligible? Strict shape: IHL==20, no MF/offset, TCP or UDP.
+	if ihl != 20 || (flagsfrags&0x3FFF) != 0 {
+		return nil
+	}
+	if parsed.Key.Protocol != ipProtoTCP && parsed.Key.Protocol != ipProtoUDP {
+		return nil
+	}
+	totalLen := int(binary.BigEndian.Uint16(pkt[2:4]))
+	if totalLen > len(pkt) || totalLen < 20 {
+		return nil
+	}
+	pktTrim := pkt[:totalLen]
+
+	switch parsed.Key.Protocol {
+	case ipProtoTCP:
+		fillParsedTCPv4(pktTrim, parsed)
+	case ipProtoUDP:
+		fillParsedUDPv4(pktTrim, parsed)
+	}
+	return nil
+}
+
+// fillParsedTCPv4 fills parsed.tcp from a strict-shape IPv4+TCP packet
+// already validated to have IHL==20 and to be totalLen-trimmed.
+func fillParsedTCPv4(pkt []byte, parsed *RxParsed) {
+	if len(pkt) < 40 { // IPv4(20) + min TCP(20)
+		return
+	}
+	tcpOff := int(pkt[32]>>4) * 4
+	if tcpOff < 20 || tcpOff > 60 {
+		return
+	}
+	if len(pkt) < 20+tcpOff {
+		return
+	}
+	p := &parsed.tcp
+	p.ipHdrLen = 20
+	p.tcpHdrLen = tcpOff
+	p.hdrLen = 20 + tcpOff
+	p.payLen = len(pkt) - p.hdrLen
+	p.seq = binary.BigEndian.Uint32(pkt[24:28])
+	p.flags = pkt[33]
+	p.fk.isV6 = false
+	p.fk.sport = parsed.Key.RemotePort
+	p.fk.dport = parsed.Key.LocalPort
+	copy(p.fk.src[:4], pkt[12:16])
+	copy(p.fk.dst[:4], pkt[16:20])
+	parsed.Kind = RxKindTCP
+}
+
+// fillParsedUDPv4 fills parsed.udp from a strict-shape IPv4+UDP packet.
+func fillParsedUDPv4(pkt []byte, parsed *RxParsed) {
+	if len(pkt) < 28 { // IPv4(20) + UDP(8)
+		return
+	}
+	udpLen := int(binary.BigEndian.Uint16(pkt[24:26]))
+	if udpLen < 8 || udpLen > len(pkt)-20 {
+		return
+	}
+	p := &parsed.udp
+	p.ipHdrLen = 20
+	p.hdrLen = 28
+	p.payLen = udpLen - 8
+	p.fk.isV6 = false
+	p.fk.sport = parsed.Key.RemotePort
+	p.fk.dport = parsed.Key.LocalPort
+	copy(p.fk.src[:4], pkt[12:16])
+	copy(p.fk.dst[:4], pkt[16:20])
+	parsed.Kind = RxKindUDP
+}
+
+// parsePacketV6 fills parsed.Key from an IPv6 packet. Direction selects
+// Local/Remote orientation. The coalescer hint fast path only triggers
+// when NextHeader is directly TCP or UDP — any extension header chain
+// falls into the lenient walk below, and the hint stays unfilled.
+func parsePacketV6(pkt []byte, incoming bool, parsed *RxParsed) error {
+	if len(pkt) < 40 {
+		return ErrIPv6PacketTooShort
+	}
+	parsed.Key.IsV6 = true
+	if incoming {
+		copy(parsed.Key.RemoteAddr[:], pkt[8:24])
+		copy(parsed.Key.LocalAddr[:], pkt[24:40])
+	} else {
+		copy(parsed.Key.LocalAddr[:], pkt[8:24])
+		copy(parsed.Key.RemoteAddr[:], pkt[24:40])
+	}
+
+	if proto := pkt[6]; proto == ipProtoTCP || proto == ipProtoUDP {
+		// Strict v6: ports are at the IP header end. Always fill key; only
+		// fill the coalescer hint if the L4 shape passes.
+		if len(pkt) < 44 {
+			return ErrIPv6PacketTooShort
+		}
+		parsed.Key.Protocol = proto
+		parsed.Key.Fragment = false
+		if incoming {
+			parsed.Key.RemotePort = binary.BigEndian.Uint16(pkt[40:42])
+			parsed.Key.LocalPort = binary.BigEndian.Uint16(pkt[42:44])
+		} else {
+			parsed.Key.LocalPort = binary.BigEndian.Uint16(pkt[40:42])
+			parsed.Key.RemotePort = binary.BigEndian.Uint16(pkt[42:44])
+		}
+
+		// Coalescer hint is inbound-only.
+		if !incoming {
+			return nil
+		}
+		payloadLen := int(binary.BigEndian.Uint16(pkt[4:6]))
+		if 40+payloadLen > len(pkt) {
+			return nil
+		}
+		pktTrim := pkt[:40+payloadLen]
+
+		switch proto {
+		case ipProtoTCP:
+			fillParsedTCPv6(pktTrim, parsed)
+		case ipProtoUDP:
+			fillParsedUDPv6(pktTrim, parsed)
+		}
+		return nil
+	}
+
+	// Slow path: walk extension header chain. Coalescer hint never fires
+	// here, so direction only matters for L4 port orientation.
+	return walkV6Headers(pkt, incoming, parsed)
+}
+
+func fillParsedTCPv6(pkt []byte, parsed *RxParsed) {
+	if len(pkt) < 60 { // IPv6(40) + min TCP(20)
+		return
+	}
+	tcpOff := int(pkt[52]>>4) * 4
+	if tcpOff < 20 || tcpOff > 60 {
+		return
+	}
+	if len(pkt) < 40+tcpOff {
+		return
+	}
+	p := &parsed.tcp
+	p.ipHdrLen = 40
+	p.tcpHdrLen = tcpOff
+	p.hdrLen = 40 + tcpOff
+	p.payLen = len(pkt) - p.hdrLen
+	p.seq = binary.BigEndian.Uint32(pkt[44:48])
+	p.flags = pkt[53]
+	p.fk.isV6 = true
+	p.fk.sport = parsed.Key.RemotePort
+	p.fk.dport = parsed.Key.LocalPort
+	copy(p.fk.src[:], pkt[8:24])
+	copy(p.fk.dst[:], pkt[24:40])
+	parsed.Kind = RxKindTCP
+}
+
+func fillParsedUDPv6(pkt []byte, parsed *RxParsed) {
+	if len(pkt) < 48 { // IPv6(40) + UDP(8)
+		return
+	}
+	udpLen := int(binary.BigEndian.Uint16(pkt[44:46]))
+	if udpLen < 8 || udpLen > len(pkt)-40 {
+		return
+	}
+	p := &parsed.udp
+	p.ipHdrLen = 40
+	p.hdrLen = 48
+	p.payLen = udpLen - 8
+	p.fk.isV6 = true
+	p.fk.sport = parsed.Key.RemotePort
+	p.fk.dport = parsed.Key.LocalPort
+	copy(p.fk.src[:], pkt[8:24])
+	copy(p.fk.dst[:], pkt[24:40])
+	parsed.Kind = RxKindUDP
+}
+
+// walkV6Headers handles every IPv6 case the strict "NextHeader == TCP/UDP"
+// fast path doesn't: ESP, NoNextHeader, ICMPv6, fragment headers (first vs
+// later), AH, generic extension headers. Coalescer eligibility is always
+// RxKindPassthrough on this path (parsed already initialised that way).
+// Direction matters only for the L4 port orientation when the chain
+// terminates at TCP/UDP.
+func walkV6Headers(pkt []byte, incoming bool, parsed *RxParsed) error {
+	dataLen := len(pkt)
+	protoAt := 6
+	offset := 40
+	next := 0
+	for {
+		if protoAt >= dataLen {
+			break
+		}
+		proto := pkt[protoAt]
+		switch proto {
+		case ipProtoESP, ipProtoNoNextHdr:
+			parsed.Key.Protocol = proto
+			parsed.Key.RemotePort = 0
+			parsed.Key.LocalPort = 0
+			parsed.Key.Fragment = false
+			return nil
+
+		case ipProtoICMPv6:
+			if dataLen < offset+6 {
+				return ErrIPv6PacketTooShort
+			}
+			parsed.Key.Protocol = proto
+			parsed.Key.LocalPort = 0
+			switch pkt[offset+1] {
+			case icmpv6TypeEchoRequest, icmpv6TypeEchoReply:
+				parsed.Key.RemotePort = binary.BigEndian.Uint16(pkt[offset+4 : offset+6])
+			default:
+				parsed.Key.RemotePort = 0
+			}
+			parsed.Key.Fragment = false
+			return nil
+
+		case ipProtoTCP, ipProtoUDP:
+			// Reachable when an extension-header chain ends at TCP/UDP. The
+			// strict-eligible fast path above already handled the no-extension
+			// case; here we only fill firewall ports and stay passthrough.
+			if dataLen < offset+4 {
+				return ErrIPv6PacketTooShort
+			}
+			parsed.Key.Protocol = proto
+			if incoming {
+				parsed.Key.RemotePort = binary.BigEndian.Uint16(pkt[offset : offset+2])
+				parsed.Key.LocalPort = binary.BigEndian.Uint16(pkt[offset+2 : offset+4])
+			} else {
+				parsed.Key.LocalPort = binary.BigEndian.Uint16(pkt[offset : offset+2])
+				parsed.Key.RemotePort = binary.BigEndian.Uint16(pkt[offset+2 : offset+4])
+			}
+			parsed.Key.Fragment = false
+			return nil
+
+		case ipProtoIPv6Fragment:
+			if dataLen < offset+8 {
+				return ErrIPv6PacketTooShort
+			}
+			fragmentOffset := binary.BigEndian.Uint16(pkt[offset+2:offset+4]) &^ uint16(0x7)
+			if fragmentOffset != 0 {
+				// Non-first fragment: report the fragment flag and stop.
+				parsed.Key.Protocol = pkt[offset]
+				parsed.Key.Fragment = true
+				parsed.Key.RemotePort = 0
+				parsed.Key.LocalPort = 0
+				return nil
+			}
+			next = 8
+
+		case ipProtoAH:
+			if dataLen <= offset+1 {
+				break
+			}
+			next = int(pkt[offset+1]+2) << 2
+
+		default:
+			if dataLen <= offset+1 {
+				break
+			}
+			next = int(pkt[offset+1]+1) << 3
+		}
+
+		if next <= 0 {
+			next = 8
+		}
+		protoAt = offset
+		offset = offset + next
+	}
+	return ErrIPv6CouldNotFindPayload
+}
+
+// CommitInbound dispatches pkt to the appropriate lane using parsed.Kind,
+// skipping the IP+L4 re-parse that MultiCoalescer.Commit would otherwise
+// do. Borrowed slice contract is identical to MultiCoalescer.Commit.
+func (m *MultiCoalescer) CommitInbound(pkt []byte, parsed *RxParsed) error {
+	switch parsed.Kind {
+	case RxKindTCP:
+		if m.tcp != nil {
+			return m.tcp.commitParsed(pkt, parsed.tcp)
+		}
+	case RxKindUDP:
+		if m.udp != nil {
+			return m.udp.commitParsed(pkt, parsed.udp)
+		}
+	}
+	return m.pt.Commit(pkt)
+}

overlay/batch/inbound_bench_test.go

@@ -0,0 +1,394 @@
+package batch
+
+import (
+	"encoding/binary"
+	"net/netip"
+	"testing"
+
+	"github.com/slackhq/nebula/firewall"
+)
+
+// parseV4InboundBaseline mirrors what outside.go's parseV4(incoming=true)
+// does, so the "split" bench measures the *current* state: firewall-side
+// parse, then m.Commit re-parses inside the coalescer. Two walks per
+// packet. Kept faithful in shape (one read per field, AddrFromSlice for
+// the addrs) so the CPU profile matches the production parseV4.
+func parseV4InboundBaseline(pkt []byte, fp *firewall.Packet) bool {
+	if len(pkt) < 20 {
+		return false
+	}
+	ihl := int(pkt[0]&0x0f) << 2
+	if ihl < 20 {
+		return false
+	}
+	flagsfrags := binary.BigEndian.Uint16(pkt[6:8])
+	fp.Fragment = (flagsfrags & 0x1FFF) != 0
+	fp.Protocol = pkt[9]
+	minLen := ihl
+	if !fp.Fragment {
+		if fp.Protocol == firewall.ProtoICMP {
+			minLen += 4 + 2
+		} else {
+			minLen += 4
+		}
+	}
+	if len(pkt) < minLen {
+		return false
+	}
+	fp.RemoteAddr, _ = netip.AddrFromSlice(pkt[12:16])
+	fp.LocalAddr, _ = netip.AddrFromSlice(pkt[16:20])
+	switch {
+	case fp.Fragment:
+		fp.RemotePort = 0
+		fp.LocalPort = 0
+	case fp.Protocol == firewall.ProtoICMP:
+		fp.RemotePort = binary.BigEndian.Uint16(pkt[ihl+4 : ihl+6])
+		fp.LocalPort = 0
+	default:
+		fp.RemotePort = binary.BigEndian.Uint16(pkt[ihl : ihl+2])
+		fp.LocalPort = binary.BigEndian.Uint16(pkt[ihl+2 : ihl+4])
+	}
+	return true
+}
+
+// parseV6InboundBaseline is the v6 analogue: replicates parseV6's
+// extension-header walk so the split bench captures its true cost.
+func parseV6InboundBaseline(pkt []byte, fp *firewall.Packet) bool {
+	dataLen := len(pkt)
+	if dataLen < 40 {
+		return false
+	}
+	fp.RemoteAddr, _ = netip.AddrFromSlice(pkt[8:24])
+	fp.LocalAddr, _ = netip.AddrFromSlice(pkt[24:40])
+
+	protoAt := 6
+	offset := 40
+	next := 0
+	for {
+		if protoAt >= dataLen {
+			return false
+		}
+		proto := pkt[protoAt]
+		switch proto {
+		case ipProtoESP, ipProtoNoNextHdr:
+			fp.Protocol = proto
+			fp.RemotePort = 0
+			fp.LocalPort = 0
+			fp.Fragment = false
+			return true
+		case ipProtoICMPv6:
+			if dataLen < offset+6 {
+				return false
+			}
+			fp.Protocol = proto
+			fp.LocalPort = 0
+			switch pkt[offset+1] {
+			case icmpv6TypeEchoRequest, icmpv6TypeEchoReply:
+				fp.RemotePort = binary.BigEndian.Uint16(pkt[offset+4 : offset+6])
+			default:
+				fp.RemotePort = 0
+			}
+			fp.Fragment = false
+			return true
+		case ipProtoTCP, ipProtoUDP:
+			if dataLen < offset+4 {
+				return false
+			}
+			fp.Protocol = proto
+			fp.RemotePort = binary.BigEndian.Uint16(pkt[offset : offset+2])
+			fp.LocalPort = binary.BigEndian.Uint16(pkt[offset+2 : offset+4])
+			fp.Fragment = false
+			return true
+		case ipProtoIPv6Fragment:
+			if dataLen < offset+8 {
+				return false
+			}
+			fragmentOffset := binary.BigEndian.Uint16(pkt[offset+2:offset+4]) &^ uint16(0x7)
+			if fragmentOffset != 0 {
+				fp.Protocol = pkt[offset]
+				fp.Fragment = true
+				fp.RemotePort = 0
+				fp.LocalPort = 0
+				return true
+			}
+			next = 8
+		case ipProtoAH:
+			if dataLen <= offset+1 {
+				return false
+			}
+			next = int(pkt[offset+1]+2) << 2
+		default:
+			if dataLen <= offset+1 {
+				return false
+			}
+			next = int(pkt[offset+1]+1) << 3
+		}
+		if next <= 0 {
+			next = 8
+		}
+		protoAt = offset
+		offset = offset + next
+	}
+}
+
+// runRxSplit drives the split path: faithful inbound parse for the firewall
+// side, then m.Commit re-parses to coalesce. v6 controls which baseline
+// parser we run.
+func runRxSplit(b *testing.B, pkts [][]byte, batchSize int, v6 bool) {
+	b.Helper()
+	m := NewMultiCoalescer(nopTunWriter{}, true, true)
+	var fp firewall.Packet
+	b.ReportAllocs()
+	b.SetBytes(int64(len(pkts[0])))
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		pkt := pkts[i%len(pkts)]
+		var ok bool
+		if v6 {
+			ok = parseV6InboundBaseline(pkt, &fp)
+		} else {
+			ok = parseV4InboundBaseline(pkt, &fp)
+		}
+		if !ok {
+			b.Fatal("baseline parse failed")
+		}
+		if err := m.Commit(pkt); err != nil {
+			b.Fatal(err)
+		}
+		if (i+1)%batchSize == 0 {
+			if err := m.Flush(); err != nil {
+				b.Fatal(err)
+			}
+		}
+	}
+	_ = m.Flush()
+}
+
+// runRxUnified drives the unified path: ParseInbound walks once, filling
+// the conntrack key + coalescer hint in parsed; CommitInbound dispatches
+// without re-parsing.
+func runRxUnified(b *testing.B, pkts [][]byte, batchSize int) {
+	b.Helper()
+	m := NewMultiCoalescer(nopTunWriter{}, true, true)
+	var parsed RxParsed
+	b.ReportAllocs()
+	b.SetBytes(int64(len(pkts[0])))
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		pkt := pkts[i%len(pkts)]
+		if err := ParsePacket(pkt, true, &parsed); err != nil {
+			b.Fatal(err)
+		}
+		if err := m.CommitInbound(pkt, &parsed); err != nil {
+			b.Fatal(err)
+		}
+		if (i+1)%batchSize == 0 {
+			if err := m.Flush(); err != nil {
+				b.Fatal(err)
+			}
+		}
+	}
+	_ = m.Flush()
+}
+
+// buildUDPv4Bulk returns N UDP packets on a single 5-tuple suitable for the
+// UDP coalescer's append path.
+func buildUDPv4Bulk(n, payloadLen int) [][]byte {
+	pkts := make([][]byte, n)
+	pay := make([]byte, payloadLen)
+	for i := range n {
+		pkts[i] = buildUDPv4(1000, 53, pay)
+	}
+	return pkts
+}
+
+func buildTCPv6Bulk(n, payloadLen int) [][]byte {
+	pkts := make([][]byte, n)
+	pay := make([]byte, payloadLen)
+	seq := uint32(1000)
+	for i := range n {
+		pkts[i] = buildTCPv6(0, seq, tcpAck, pay)
+		seq += uint32(payloadLen)
+	}
+	return pkts
+}
+
+func buildICMPv4Bulk(n int) [][]byte {
+	pkts := make([][]byte, n)
+	for i := range pkts {
+		pkts[i] = buildICMPv4()
+	}
+	return pkts
+}
+
+// === TCPv4 ===
+
+func BenchmarkRxSplitTCPv4(b *testing.B) {
+	pkts := buildTCPv4BulkFlow(tcpCoalesceMaxSegs, 1200)
+	runRxSplit(b, pkts, tcpCoalesceMaxSegs, false)
+}
+
+func BenchmarkRxUnifiedTCPv4(b *testing.B) {
+	pkts := buildTCPv4BulkFlow(tcpCoalesceMaxSegs, 1200)
+	runRxUnified(b, pkts, tcpCoalesceMaxSegs)
+}
+
+// === TCPv4 interleaved (4 flows) ===
+
+func BenchmarkRxSplitTCPv4Interleaved4(b *testing.B) {
+	pkts := buildTCPv4Interleaved(4, tcpCoalesceMaxSegs, 1200)
+	runRxSplit(b, pkts, len(pkts), false)
+}
+
+func BenchmarkRxUnifiedTCPv4Interleaved4(b *testing.B) {
+	pkts := buildTCPv4Interleaved(4, tcpCoalesceMaxSegs, 1200)
+	runRxUnified(b, pkts, len(pkts))
+}
+
+// === UDPv4 ===
+
+func BenchmarkRxSplitUDPv4(b *testing.B) {
+	pkts := buildUDPv4Bulk(udpCoalesceMaxSegs, 1200)
+	runRxSplit(b, pkts, udpCoalesceMaxSegs, false)
+}
+
+func BenchmarkRxUnifiedUDPv4(b *testing.B) {
+	pkts := buildUDPv4Bulk(udpCoalesceMaxSegs, 1200)
+	runRxUnified(b, pkts, udpCoalesceMaxSegs)
+}
+
+// === TCPv6 ===
+
+func BenchmarkRxSplitTCPv6(b *testing.B) {
+	pkts := buildTCPv6Bulk(tcpCoalesceMaxSegs, 1200)
+	runRxSplit(b, pkts, tcpCoalesceMaxSegs, true)
+}
+
+func BenchmarkRxUnifiedTCPv6(b *testing.B) {
+	pkts := buildTCPv6Bulk(tcpCoalesceMaxSegs, 1200)
+	runRxUnified(b, pkts, tcpCoalesceMaxSegs)
+}
+
+// === ICMPv4 (passthrough) — measures the unified parser on the coalescer-
+// rejected path, where both lenient and unified must still fill fp. ===
+
+func BenchmarkRxSplitICMPv4(b *testing.B) {
+	pkts := buildICMPv4Bulk(64)
+	runRxSplit(b, pkts, 64, false)
+}
+
+func BenchmarkRxUnifiedICMPv4(b *testing.B) {
+	pkts := buildICMPv4Bulk(64)
+	runRxUnified(b, pkts, 64)
+}
+
+// === Firewall fast-path (conntrack-hit) — exercises the savings from the
+// dense PacketKey: smaller hash key for the per-routine ConntrackCache,
+// and skipping the AddrFrom4 calls that the old path needed to fill the
+// netip.Addr-rich firewall.Packet up-front. ===
+//
+// The "split" baseline simulates the legacy path: parseV4InboundBaseline
+// fills a netip.Addr-rich Packet, then we probe a localCache keyed on
+// Packet. The "unified" path: ParseInbound fills only the dense PacketKey,
+// and we probe a localCache keyed on PacketKey. Both paths follow with
+// the coalescer Commit so the bench captures end-to-end RX-side cost.
+
+// runRxSplitWithCache mirrors runRxSplit but runs the legacy-style
+// firewall fast path (localCache keyed on firewall.Packet) on every
+// packet so we can compare against the unified path.
+func runRxSplitWithCache(b *testing.B, pkts [][]byte, batchSize int) {
+	b.Helper()
+	m := NewMultiCoalescer(nopTunWriter{}, true, true)
+	var fp firewall.Packet
+
+	// Pre-warm a per-packet cache keyed on the netip.Addr-rich Packet form.
+	cache := make(map[firewall.Packet]struct{}, len(pkts))
+	for _, pkt := range pkts {
+		var seedFp firewall.Packet
+		if !parseV4InboundBaseline(pkt, &seedFp) {
+			b.Fatal("seed parse failed")
+		}
+		cache[seedFp] = struct{}{}
+	}
+
+	b.ReportAllocs()
+	b.SetBytes(int64(len(pkts[0])))
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		pkt := pkts[i%len(pkts)]
+		if !parseV4InboundBaseline(pkt, &fp) {
+			b.Fatal("baseline parse failed")
+		}
+		if _, ok := cache[fp]; !ok {
+			b.Fatal("cache miss")
+		}
+		if err := m.Commit(pkt); err != nil {
+			b.Fatal(err)
+		}
+		if (i+1)%batchSize == 0 {
+			if err := m.Flush(); err != nil {
+				b.Fatal(err)
+			}
+		}
+	}
+	_ = m.Flush()
+}
+
+// runRxUnifiedWithCache: unified path with a PacketKey-keyed localCache.
+// Each iteration: ParseInbound → conntrack-cache hit → CommitInbound.
+func runRxUnifiedWithCache(b *testing.B, pkts [][]byte, batchSize int) {
+	b.Helper()
+	m := NewMultiCoalescer(nopTunWriter{}, true, true)
+	var parsed RxParsed
+
+	cache := make(firewall.ConntrackCache, len(pkts))
+	for _, pkt := range pkts {
+		var seed RxParsed
+		if err := ParsePacket(pkt, true, &seed); err != nil {
+			b.Fatal(err)
+		}
+		cache[seed.Key] = struct{}{}
+	}
+
+	b.ReportAllocs()
+	b.SetBytes(int64(len(pkts[0])))
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		pkt := pkts[i%len(pkts)]
+		if err := ParsePacket(pkt, true, &parsed); err != nil {
+			b.Fatal(err)
+		}
+		if _, ok := cache[parsed.Key]; !ok {
+			b.Fatal("cache miss")
+		}
+		if err := m.CommitInbound(pkt, &parsed); err != nil {
+			b.Fatal(err)
+		}
+		if (i+1)%batchSize == 0 {
+			if err := m.Flush(); err != nil {
+				b.Fatal(err)
+			}
+		}
+	}
+	_ = m.Flush()
+}
+
+func BenchmarkRxSplitTCPv4WithCache(b *testing.B) {
+	pkts := buildTCPv4BulkFlow(tcpCoalesceMaxSegs, 1200)
+	runRxSplitWithCache(b, pkts, tcpCoalesceMaxSegs)
+}
+
+func BenchmarkRxUnifiedTCPv4WithCache(b *testing.B) {
+	pkts := buildTCPv4BulkFlow(tcpCoalesceMaxSegs, 1200)
+	runRxUnifiedWithCache(b, pkts, tcpCoalesceMaxSegs)
+}
+
+func BenchmarkRxSplitInterleaved4WithCache(b *testing.B) {
+	pkts := buildTCPv4Interleaved(4, tcpCoalesceMaxSegs, 1200)
+	runRxSplitWithCache(b, pkts, len(pkts))
+}
+
+func BenchmarkRxUnifiedInterleaved4WithCache(b *testing.B) {
+	pkts := buildTCPv4Interleaved(4, tcpCoalesceMaxSegs, 1200)
+	runRxUnifiedWithCache(b, pkts, len(pkts))
+}

overlay/batch/inbound_test.go

@@ -0,0 +1,174 @@
+package batch
+
+import (
+	"net/netip"
+	"testing"
+
+	"github.com/slackhq/nebula/firewall"
+)
+
+// TestParseInboundParity asserts that ParseInbound + Key.Hydrate produces
+// the same firewall.Packet that the lenient baseline parsers (which
+// mirror outside.go's parseV4/parseV6 with incoming=true) produce for
+// every shape we care about. Catches drift between the unified
+// parse-then-hydrate flow and the production newPacket behavior so
+// swapping one for the other is observably safe.
+func TestParseInboundParity(t *testing.T) {
+	cases := []struct {
+		name string
+		pkt  []byte
+		v6   bool
+	}{
+		{"tcp_v4", buildTCPv4Ports(1234, 443, 1000, tcpAck, []byte("payload")), false},
+		{"tcp_v4_psh", buildTCPv4Ports(1234, 443, 2000, tcpAckPsh, make([]byte, 1200)), false},
+		{"udp_v4", buildUDPv4(40000, 53, []byte("dnsquery")), false},
+		{"icmp_v4", buildICMPv4(), false},
+		{"tcp_v6", buildTCPv6(0, 5000, tcpAck, make([]byte, 800)), true},
+		{"udp_v6", buildUDPv6(40001, 53, []byte("v6dns")), true},
+	}
+
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			var fpUnified, fpBaseline firewall.Packet
+			var parsed RxParsed
+
+			if err := ParsePacket(tc.pkt, true, &parsed); err != nil {
+				t.Fatalf("ParsePacket: %v", err)
+			}
+			parsed.Key.Hydrate(&fpUnified)
+			var ok bool
+			if tc.v6 {
+				ok = parseV6InboundBaseline(tc.pkt, &fpBaseline)
+			} else {
+				ok = parseV4InboundBaseline(tc.pkt, &fpBaseline)
+			}
+			if !ok {
+				t.Fatalf("baseline parse failed")
+			}
+
+			if fpUnified != fpBaseline {
+				t.Errorf("firewall.Packet mismatch:\n  unified:  %+v\n  baseline: %+v", fpUnified, fpBaseline)
+			}
+		})
+	}
+}
+
+// TestParseInboundFlowKey checks that the coalescer hint the unified parser
+// produces matches what parseTCPBase/parseUDP would produce on the same
+// packet — same flowKey, ipHdrLen, payLen, etc. The hint is only valid
+// when Kind is RxKindTCP/RxKindUDP.
+func TestParseInboundFlowKey(t *testing.T) {
+	t.Run("tcp_v4", func(t *testing.T) {
+		pkt := buildTCPv4Ports(1234, 443, 5000, tcpAck, make([]byte, 800))
+		var parsed RxParsed
+		if err := ParsePacket(pkt, true, &parsed); err != nil {
+			t.Fatal(err)
+		}
+		if parsed.Kind != RxKindTCP {
+			t.Fatalf("kind=%v want TCP", parsed.Kind)
+		}
+		ref, ok := parseTCPBase(pkt)
+		if !ok {
+			t.Fatal("parseTCPBase failed")
+		}
+		if parsed.tcp != ref {
+			t.Errorf("parsedTCP mismatch:\n  unified: %+v\n  ref:     %+v", parsed.tcp, ref)
+		}
+	})
+
+	t.Run("udp_v4", func(t *testing.T) {
+		pkt := buildUDPv4(40000, 53, []byte("dnsquery"))
+		var parsed RxParsed
+		if err := ParsePacket(pkt, true, &parsed); err != nil {
+			t.Fatal(err)
+		}
+		if parsed.Kind != RxKindUDP {
+			t.Fatalf("kind=%v want UDP", parsed.Kind)
+		}
+		ref, ok := parseUDP(pkt)
+		if !ok {
+			t.Fatal("parseUDP failed")
+		}
+		if parsed.udp != ref {
+			t.Errorf("parsedUDP mismatch:\n  unified: %+v\n  ref:     %+v", parsed.udp, ref)
+		}
+	})
+
+	t.Run("tcp_v6", func(t *testing.T) {
+		pkt := buildTCPv6(0, 9000, tcpAck, make([]byte, 800))
+		var parsed RxParsed
+		if err := ParsePacket(pkt, true, &parsed); err != nil {
+			t.Fatal(err)
+		}
+		if parsed.Kind != RxKindTCP {
+			t.Fatalf("kind=%v want TCP", parsed.Kind)
+		}
+		ref, ok := parseTCPBase(pkt)
+		if !ok {
+			t.Fatal("parseTCPBase failed")
+		}
+		if parsed.tcp != ref {
+			t.Errorf("parsedTCP mismatch:\n  unified: %+v\n  ref:     %+v", parsed.tcp, ref)
+		}
+	})
+}
+
+// TestParseInboundICMPPassthrough confirms ICMP packets populate the
+// conntrack key (including the ICMP identifier in RemotePort) but stay
+// RxKindPassthrough so the batcher writes them verbatim. After Hydrate
+// the firewall.Packet form should match what the legacy parseV4 produced.
+func TestParseInboundICMPPassthrough(t *testing.T) {
+	pkt := buildICMPv4()
+	// Stamp a non-zero identifier into the ICMP header so we can check
+	// RemotePort gets it.
+	pkt[20] = 8 // type=echo
+	pkt[24] = 0xab
+	pkt[25] = 0xcd
+
+	var parsed RxParsed
+	if err := ParsePacket(pkt, true, &parsed); err != nil {
+		t.Fatal(err)
+	}
+	if parsed.Kind != RxKindPassthrough {
+		t.Errorf("kind=%v want Passthrough", parsed.Kind)
+	}
+	var fp firewall.Packet
+	parsed.Key.Hydrate(&fp)
+	if fp.Protocol != firewall.ProtoICMP {
+		t.Errorf("Protocol=%d want %d", fp.Protocol, firewall.ProtoICMP)
+	}
+	if fp.RemotePort != 0xabcd {
+		t.Errorf("RemotePort=0x%x want 0xabcd", fp.RemotePort)
+	}
+	if fp.LocalPort != 0 {
+		t.Errorf("LocalPort=%d want 0", fp.LocalPort)
+	}
+	wantRemote := netip.MustParseAddr("10.0.0.1")
+	wantLocal := netip.MustParseAddr("10.0.0.2")
+	if fp.RemoteAddr != wantRemote || fp.LocalAddr != wantLocal {
+		t.Errorf("addrs: remote=%v local=%v want %v/%v", fp.RemoteAddr, fp.LocalAddr, wantRemote, wantLocal)
+	}
+}
+
+// TestParseInboundV4Fragment confirms a fragmented v4 packet fills the
+// conntrack key with Fragment=true and falls into Passthrough on the
+// coalescer side.
+func TestParseInboundV4Fragment(t *testing.T) {
+	// Build a TCP packet then twiddle the IP flags to make it look like a
+	// non-first fragment (offset != 0).
+	pkt := buildTCPv4Ports(1234, 443, 1000, tcpAck, []byte("payload"))
+	// Set a non-zero fragment offset (bytes 6-7, low 13 bits).
+	pkt[6] = 0x00
+	pkt[7] = 0x10 // offset = 16 (in 8-byte units)
+
+	var parsed RxParsed
+	if err := ParsePacket(pkt, true, &parsed); err != nil {
+		t.Fatal(err)
+	}
+	if !parsed.Key.Fragment {
+		t.Error("Fragment=false, want true")
+	}
+	if parsed.Kind != RxKindPassthrough {
+		t.Errorf("kind=%v want Passthrough", parsed.Kind)
+	}
+}

overlay/batch/multi_coalesce.go

@@ -0,0 +1,133 @@
+package batch
+
+import (
+	"errors"
+	"io"
+)
+
+// MultiCoalescer fans plaintext packets out to lane-specific batchers based
+// on the IP/L4 protocol of the packet, sharing a single Reserve arena
+// across lanes so the caller's allocation pattern is unchanged.
+//
+// Lanes are processed independently: the TCP coalescer only sees TCP, the
+// UDP coalescer only sees UDP, and the passthrough lane handles everything
+// else. Per-flow arrival order is preserved because a single 5-tuple only
+// ever lands in one lane and each lane preserves its own slot order.
+//
+// Cross-lane order is NOT preserved across the TCP/UDP/passthrough split.
+// This is acceptable because the carrier-side recvmmsg path already
+// stable-sorts by (peer, message counter) before delivering plaintext
+// here, so replay-window invariants are unaffected, and apps observe
+// correct per-flow ordering — which is all the IP layer guarantees anyway.
+// Do not "fix" this by interleaving lane outputs at flush time; that
+// negates the entire point of coalescing (each lane needs to see runs of
+// adjacent same-flow packets to coalesce them).
+type MultiCoalescer struct {
+	tcp *TCPCoalescer
+	udp *UDPCoalescer
+	pt  *Passthrough
+
+	// arena shared across all lanes so a single Reserve grows one backing
+	// slice; lane Commit calls borrow into this same arena.
+	backing []byte
+}
+
+// NewMultiCoalescer builds a multi-lane batcher. tcpEnabled lets the caller
+// opt out of TCP coalescing (e.g. when the queue can't do TSO); udpEnabled
+// likewise gates UDP coalescing (only enable when USO was negotiated).
+// Either lane disabled redirects its traffic into the passthrough lane.
+func NewMultiCoalescer(w io.Writer, tcpEnabled, udpEnabled bool) *MultiCoalescer {
+	m := &MultiCoalescer{
+		pt:      NewPassthrough(w),
+		backing: make([]byte, 0, initialSlots*65535),
+	}
+	if tcpEnabled {
+		m.tcp = NewTCPCoalescer(w)
+	}
+	if udpEnabled {
+		m.udp = NewUDPCoalescer(w)
+	}
+	return m
+}
+
+func (m *MultiCoalescer) Reserve(sz int) []byte {
+	if len(m.backing)+sz > cap(m.backing) {
+		newCap := max(cap(m.backing)*2, sz)
+		m.backing = make([]byte, 0, newCap)
+	}
+	start := len(m.backing)
+	m.backing = m.backing[:start+sz]
+	return m.backing[start : start+sz : start+sz]
+}
+
+// Commit dispatches pkt to the appropriate lane based on IP version + L4
+// proto. Borrowed slice contract is identical to the single-lane batchers,
+// pkt must remain valid until the next Flush.
+//
+// On the success path the IP/TCP-or-UDP parse happens here once and the
+// parsed struct is handed to the lane via commitParsed so the lane doesn't
+// re-walk the header.
+func (m *MultiCoalescer) Commit(pkt []byte) error {
+	if len(pkt) < 20 {
+		return m.pt.Commit(pkt)
+	}
+	v := pkt[0] >> 4
+	var proto byte
+	switch v {
+	case 4:
+		proto = pkt[9]
+	case 6:
+		if len(pkt) < 40 {
+			return m.pt.Commit(pkt)
+		}
+		proto = pkt[6]
+	default:
+		return m.pt.Commit(pkt)
+	}
+	switch proto {
+	case ipProtoTCP:
+		if m.tcp != nil {
+			info, ok := parseTCPBase(pkt)
+			if !ok {
+				// Malformed/unsupported TCP shape (IP options, fragments, ...).
+				// Handle this via passthrough support in the TCP coalescer, to attempt to preserve flow order.
+				m.tcp.addPassthrough(pkt)
+				return nil
+			}
+			return m.tcp.commitParsed(pkt, info)
+		}
+	case ipProtoUDP:
+		if m.udp != nil {
+			info, ok := parseUDP(pkt)
+			if !ok {
+				m.udp.addPassthrough(pkt) //we could also m.pt.Commit() here I guess?
+				return nil
+			}
+			return m.udp.commitParsed(pkt, info)
+		}
+	}
+	return m.pt.Commit(pkt)
+}
+
+// Flush drains every lane in a fixed order: TCP, UDP, passthrough. Errors
+// from a lane do not stop subsequent lanes from flushing, we keep
+// draining and return the first observed error so a single bad packet
+// doesn't strand the others.
+func (m *MultiCoalescer) Flush() error {
+	var errs []error
+	if m.tcp != nil {
+		if err := m.tcp.Flush(); err != nil {
+			errs = append(errs, err)
+		}
+	}
+	if m.udp != nil {
+		if err := m.udp.Flush(); err != nil {
+			errs = append(errs, err)
+		}
+	}
+	if err := m.pt.Flush(); err != nil {
+		errs = append(errs, err)
+	}
+	m.backing = m.backing[:0]
+	return errors.Join(errs...)
+}

overlay/batch/multi_coalesce_test.go

@@ -0,0 +1,94 @@
+package batch
+
+import (
+	"testing"
+)
+
+// TestMultiCoalescerRoutesByProto confirms TCP/UDP/other land in the right
+// lane: TCP and UDP get coalesced when their lanes are enabled, anything
+// else (ICMP here) falls through to plain Write.
+func TestMultiCoalescerRoutesByProto(t *testing.T) {
+	w := &fakeTunWriter{gsoEnabled: true}
+	m := NewMultiCoalescer(w, true, true)
+
+	tcpPay := make([]byte, 1200)
+	udpPay := make([]byte, 1200)
+	icmp := make([]byte, 28)
+	icmp[0] = 0x45
+	icmp[2] = 0
+	icmp[3] = 28
+	icmp[9] = 1
+
+	if err := m.Commit(buildTCPv4(1000, tcpAck, tcpPay)); err != nil {
+		t.Fatal(err)
+	}
+	if err := m.Commit(buildTCPv4(2200, tcpAck, tcpPay)); err != nil {
+		t.Fatal(err)
+	}
+	if err := m.Commit(buildUDPv4(2000, 53, udpPay)); err != nil {
+		t.Fatal(err)
+	}
+	if err := m.Commit(buildUDPv4(2000, 53, udpPay)); err != nil {
+		t.Fatal(err)
+	}
+	if err := m.Commit(icmp); err != nil {
+		t.Fatal(err)
+	}
+	if err := m.Flush(); err != nil {
+		t.Fatal(err)
+	}
+	// 1 TCP super (2 segments) + 1 UDP super (2 segments) = 2 gso writes.
+	if len(w.gsoWrites) != 2 {
+		t.Fatalf("want 2 gso writes (one TCP + one UDP), got %d", len(w.gsoWrites))
+	}
+	if len(w.writes) != 1 {
+		t.Fatalf("want 1 plain write (ICMP), got %d", len(w.writes))
+	}
+}
+
+// TestMultiCoalescerDisabledUDPFallsThrough verifies that when the UDP lane
+// is disabled (e.g. kernel doesn't support USO), UDP packets still reach
+// the kernel via the passthrough lane rather than being lost.
+func TestMultiCoalescerDisabledUDPFallsThrough(t *testing.T) {
+	w := &fakeTunWriter{gsoEnabled: true}
+	m := NewMultiCoalescer(w, true, false) // TSO on, USO off
+
+	if err := m.Commit(buildUDPv4(1000, 53, make([]byte, 800))); err != nil {
+		t.Fatal(err)
+	}
+	if err := m.Commit(buildUDPv4(1000, 53, make([]byte, 800))); err != nil {
+		t.Fatal(err)
+	}
+	if err := m.Flush(); err != nil {
+		t.Fatal(err)
+	}
+	if len(w.gsoWrites) != 0 {
+		t.Errorf("UDP must NOT be coalesced when USO disabled, got %d gso writes", len(w.gsoWrites))
+	}
+	if len(w.writes) != 2 {
+		t.Errorf("UDP must pass through as 2 plain writes, got %d", len(w.writes))
+	}
+}
+
+// TestMultiCoalescerDisabledTCPFallsThrough mirrors the TSO=off case.
+func TestMultiCoalescerDisabledTCPFallsThrough(t *testing.T) {
+	w := &fakeTunWriter{gsoEnabled: true}
+	m := NewMultiCoalescer(w, false, true) // TSO off, USO on
+
+	pay := make([]byte, 1200)
+	if err := m.Commit(buildTCPv4(1000, tcpAck, pay)); err != nil {
+		t.Fatal(err)
+	}
+	if err := m.Commit(buildTCPv4(2200, tcpAck, pay)); err != nil {
+		t.Fatal(err)
+	}
+	if err := m.Flush(); err != nil {
+		t.Fatal(err)
+	}
+	if len(w.gsoWrites) != 0 {
+		t.Errorf("TCP must NOT be coalesced when TSO disabled, got %d gso writes", len(w.gsoWrites))
+	}
+	if len(w.writes) != 2 {
+		t.Errorf("TCP must pass through as 2 plain writes, got %d", len(w.writes))
+	}
+}

overlay/batch/passthrough.go

@@ -0,0 +1,62 @@
+package batch
+
+import (
+	"io"
+
+	"github.com/slackhq/nebula/udp"
+)
+
+// Passthrough is a RxBatcher that doesn't batch anything, it just accumulates and then sends packets.
+type Passthrough struct {
+	out     io.Writer
+	slots   [][]byte
+	backing []byte
+	cursor  int
+}
+
+func NewPassthrough(w io.Writer) *Passthrough {
+	const baseNumSlots = 128
+	return &Passthrough{
+		out:     w,
+		slots:   make([][]byte, 0, baseNumSlots),
+		backing: make([]byte, 0, baseNumSlots*udp.MTU),
+	}
+}
+
+func (p *Passthrough) Reserve(sz int) []byte {
+	if len(p.backing)+sz > cap(p.backing) {
+		// Grow: allocate a fresh backing. Already-committed slices still
+		// reference the old array and remain valid until Flush drops them.
+		newCap := max(cap(p.backing)*2, sz)
+		p.backing = make([]byte, 0, newCap)
+	}
+	start := len(p.backing)
+	p.backing = p.backing[:start+sz]
+	return p.backing[start : start+sz : start+sz] //return zero length, sz-cap slice
+}
+
+func (p *Passthrough) Commit(pkt []byte) error {
+	p.slots = append(p.slots, pkt)
+	return nil
+}
+
+// CommitInbound ignores the hint — Passthrough never coalesces, so there's
+// no IP/L4 re-parse to skip. Present so Passthrough satisfies the RxBatcher
+// interface alongside MultiCoalescer.
+func (p *Passthrough) CommitInbound(pkt []byte, _ *RxParsed) error {
+	return p.Commit(pkt)
+}
+
+func (p *Passthrough) Flush() error {
+	var firstErr error
+	for _, s := range p.slots {
+		_, err := p.out.Write(s)
+		if err != nil && firstErr == nil {
+			firstErr = err
+		}
+	}
+	clear(p.slots)
+	p.slots = p.slots[:0]
+	p.backing = p.backing[:0]
+	return firstErr
+}

overlay/batch/tcp_coalesce.go

@@ -0,0 +1,731 @@
+package batch
+
+import (
+	"bytes"
+	"encoding/binary"
+	"io"
+	"log/slog"
+	"net/netip"
+	"slices"
+
+	"github.com/slackhq/nebula/overlay/tio"
+)
+
+// ipProtoTCP is the IANA protocol number for TCP. Hardcoded instead of
+// reaching for golang.org/x/sys/unix — that package doesn't define the
+// constant on Windows, which would break cross-compiles even though this
+// file runs unchanged on every platform.
+const ipProtoTCP = 6
+
+// tcpCoalesceBufSize caps total bytes per superpacket. Mirrors the kernel's
+// sk_gso_max_size of ~64KiB; anything beyond this would be rejected anyway.
+const tcpCoalesceBufSize = 65535
+
+// tcpCoalesceMaxSegs caps how many segments we'll coalesce into a single
+// superpacket. Keeping this well below the kernel's TSO ceiling bounds
+// latency.
+const tcpCoalesceMaxSegs = 64
+
+// tcpCoalesceHdrCap is the scratch space we copy a seed's IP+TCP header
+// into. IPv6 (40) + TCP with full options (60) = 100 bytes.
+const tcpCoalesceHdrCap = 100
+
+// coalesceSlot is one entry in the coalescer's ordered event queue. When
+// passthrough is true the slot holds a single borrowed packet that must be
+// emitted verbatim (non-TCP, non-admissible TCP, or oversize seed). When
+// passthrough is false the slot is an in-progress coalesced superpacket:
+// hdrBuf is a mutable copy of the seed's IP+TCP header (we patch total
+// length and pseudo-header partial at flush), and payIovs are *borrowed*
+// slices from the caller's plaintext buffers — no payload is ever copied.
+// The caller (listenOut) must keep those buffers alive until Flush.
+type coalesceSlot struct {
+	passthrough bool
+	rawPkt      []byte // borrowed when passthrough
+
+	fk       flowKey
+	hdrBuf   [tcpCoalesceHdrCap]byte
+	hdrLen   int
+	ipHdrLen int
+	isV6     bool
+	gsoSize  int
+	numSeg   int
+	totalPay int
+	nextSeq  uint32
+	// psh closes the chain: set when the last-accepted segment had PSH or
+	// was sub-gsoSize. No further appends after that.
+	psh     bool
+	payIovs [][]byte
+}
+
+// TCPCoalescer accumulates adjacent in-flow TCP data segments across
+// multiple concurrent flows and emits each flow's run as a single TSO
+// superpacket via tio.GSOWriter. All output — coalesced or not — is
+// deferred until Flush so arrival order is preserved on the wire. Owns
+// no locks; one coalescer per TUN write queue.
+type TCPCoalescer struct {
+	plainW io.Writer
+	gsoW   tio.GSOWriter // nil when the queue doesn't support TSO
+
+	// slots is the ordered event queue. Flush walks it once and emits each
+	// entry as either a WriteGSO (coalesced) or a plainW.Write (passthrough).
+	slots []*coalesceSlot
+	// openSlots maps a flow key to its most recent non-sealed slot, so new
+	// segments can extend an in-progress superpacket in O(1). Slots are
+	// removed from this map when they close (PSH or short-last-segment),
+	// when a non-admissible packet for that flow arrives, or in Flush.
+	openSlots map[flowKey]*coalesceSlot
+	// lastSlot caches the most recently touched open slot. Steady-state
+	// bulk traffic is dominated by a single flow, so comparing the
+	// incoming key against the cached slot's own fk lets the hot path
+	// skip the map lookup (and the aeshash of a 38-byte key) entirely.
+	// Kept in lockstep with openSlots: nil whenever the slot it pointed
+	// at is removed/sealed.
+	lastSlot *coalesceSlot
+	pool     []*coalesceSlot // free list for reuse
+
+	backing []byte
+}
+
+func NewTCPCoalescer(w io.Writer) *TCPCoalescer {
+	c := &TCPCoalescer{
+		plainW:    w,
+		slots:     make([]*coalesceSlot, 0, initialSlots),
+		openSlots: make(map[flowKey]*coalesceSlot, initialSlots),
+		pool:      make([]*coalesceSlot, 0, initialSlots),
+		backing:   make([]byte, 0, initialSlots*65535),
+	}
+	if gw, ok := tio.SupportsGSO(w, tio.GSOProtoTCP); ok {
+		c.gsoW = gw
+	}
+	return c
+}
+
+// parsedTCP holds the fields extracted from a single parse so later steps
+// (admission, slot lookup, canAppend) don't re-walk the header.
+type parsedTCP struct {
+	fk        flowKey
+	ipHdrLen  int
+	tcpHdrLen int
+	hdrLen    int
+	payLen    int
+	seq       uint32
+	flags     byte
+}
+
+// parseTCPBase extracts the flow key and IP/TCP offsets for any TCP packet,
+// regardless of whether it's admissible for coalescing. Returns ok=false
+// for non-TCP or malformed input. Accepts IPv4 (no options, no fragmentation)
+// and IPv6 (no extension headers).
+func parseTCPBase(pkt []byte) (parsedTCP, bool) {
+	var p parsedTCP
+	ip, ok := parseIPPrologue(pkt, ipProtoTCP)
+	if !ok {
+		return p, false
+	}
+	pkt = ip.pkt
+	p.fk = ip.fk
+	p.ipHdrLen = ip.ipHdrLen
+
+	if len(pkt) < p.ipHdrLen+20 {
+		return p, false
+	}
+	tcpOff := int(pkt[p.ipHdrLen+12]>>4) * 4
+	if tcpOff < 20 || tcpOff > 60 {
+		return p, false
+	}
+	if len(pkt) < p.ipHdrLen+tcpOff {
+		return p, false
+	}
+	p.tcpHdrLen = tcpOff
+	p.hdrLen = p.ipHdrLen + tcpOff
+	p.payLen = len(pkt) - p.hdrLen
+	p.seq = binary.BigEndian.Uint32(pkt[p.ipHdrLen+4 : p.ipHdrLen+8])
+	p.flags = pkt[p.ipHdrLen+13]
+	p.fk.sport = binary.BigEndian.Uint16(pkt[p.ipHdrLen : p.ipHdrLen+2])
+	p.fk.dport = binary.BigEndian.Uint16(pkt[p.ipHdrLen+2 : p.ipHdrLen+4])
+	return p, true
+}
+
+// TCP flag bits (byte 13 of the TCP header). Only the bits actually consulted
+// by the coalescer are named; FIN/SYN/RST/URG/CWR are rejected via the
+// negative mask in coalesceable, not by name.
+const (
+	tcpFlagPsh = 0x08
+	tcpFlagAck = 0x10
+	tcpFlagEce = 0x40
+)
+
+// coalesceable reports whether a parsed TCP segment is eligible for
+// coalescing. Accepts ACK, ACK|PSH, ACK|ECE, ACK|PSH|ECE with a
+// non-empty payload. CWR is excluded because it marks a one-shot
+// congestion-window-reduced transition the receiver must observe at a
+// segment boundary.
+func (p parsedTCP) coalesceable() bool {
+	if p.flags&tcpFlagAck == 0 {
+		return false
+	}
+	if p.flags&^(tcpFlagAck|tcpFlagPsh|tcpFlagEce) != 0 {
+		return false
+	}
+	return p.payLen > 0
+}
+
+func (c *TCPCoalescer) Reserve(sz int) []byte {
+	return reserveFromBacking(&c.backing, sz)
+}
+
+// Commit borrows pkt. The caller must keep pkt valid until the next Flush,
+// whether or not the packet was coalesced — passthrough (non-admissible)
+// packets are queued and written at Flush time, not synchronously.
+func (c *TCPCoalescer) Commit(pkt []byte) error {
+	if c.gsoW == nil {
+		c.addPassthrough(pkt)
+		return nil
+	}
+	info, ok := parseTCPBase(pkt)
+	if !ok {
+		c.addPassthrough(pkt)
+		return nil
+	}
+	return c.commitParsed(pkt, info)
+}
+
+// commitParsed is the post-parse half of Commit. The caller must have
+// already verified parseTCPBase succeeded (info is a valid TCP parse).
+// Used by MultiCoalescer.Commit to avoid re-walking the IP/TCP header
+// after the dispatcher has already done so.
+func (c *TCPCoalescer) commitParsed(pkt []byte, info parsedTCP) error {
+	if c.gsoW == nil {
+		c.addPassthrough(pkt)
+		return nil
+	}
+	if !info.coalesceable() {
+		// TCP but not admissible (SYN/FIN/RST/URG/CWR or zero-payload).
+		// Seal this flow's open slot so later in-flow packets don't extend
+		// it and accidentally reorder past this passthrough.
+		if last := c.lastSlot; last != nil && last.fk == info.fk {
+			c.lastSlot = nil
+		}
+		delete(c.openSlots, info.fk)
+		c.addPassthrough(pkt)
+		return nil
+	}
+
+	// Single-flow fast path: with only one open flow the cache hits every
+	// packet, and len(openSlots)==1 lets us skip the 38-byte fk compare
+	// when there are multiple flows in flight (where the hit rate would
+	// be ~0 and the compare is pure overhead).
+	var open *coalesceSlot
+	if last := c.lastSlot; last != nil && len(c.openSlots) == 1 && last.fk == info.fk {
+		open = last
+	} else {
+		open = c.openSlots[info.fk]
+	}
+	if open != nil {
+		if c.canAppend(open, pkt, info) {
+			c.appendPayload(open, pkt, info)
+			if open.psh {
+				delete(c.openSlots, info.fk)
+				c.lastSlot = nil
+			} else {
+				c.lastSlot = open
+			}
+			return nil
+		}
+		// Can't extend — seal it and fall through to seed a fresh slot.
+		delete(c.openSlots, info.fk)
+		if c.lastSlot == open {
+			c.lastSlot = nil
+		}
+	}
+	c.seed(pkt, info)
+	return nil
+}
+
+// Flush emits every queued event in (per-flow) seq order. Coalesced slots
+// go out via WriteGSO; passthrough slots go out via plainW.Write.
+// reorderForFlush first sorts each flow's slots into TCP-seq order within
+// passthrough-bounded segments and merges contiguous adjacent slots, so
+// any wire-side reorder that crossed an rxOrder batch boundary doesn't
+// get amplified into kernel-visible reorder by the slot machinery.
+// Returns the first error observed; keeps draining so one bad packet
+// doesn't hold up the rest. After Flush returns, borrowed payload slices
+// may be recycled.
+func (c *TCPCoalescer) Flush() error {
+	c.reorderForFlush()
+	var first error
+	for _, s := range c.slots {
+		var err error
+		if s.passthrough {
+			_, err = c.plainW.Write(s.rawPkt)
+		} else {
+			err = c.flushSlot(s)
+		}
+		if err != nil && first == nil {
+			first = err
+		}
+		c.release(s)
+	}
+	clear(c.slots)
+	c.slots = c.slots[:0]
+	clear(c.openSlots)
+	c.lastSlot = nil
+
+	c.backing = c.backing[:0]
+	return first
+}
+
+func (c *TCPCoalescer) addPassthrough(pkt []byte) {
+	s := c.take()
+	s.passthrough = true
+	s.rawPkt = pkt
+	c.slots = append(c.slots, s)
+}
+
+func (c *TCPCoalescer) seed(pkt []byte, info parsedTCP) {
+	if info.hdrLen > tcpCoalesceHdrCap || info.hdrLen+info.payLen > tcpCoalesceBufSize {
+		// Pathological shape — can't fit our scratch, emit as-is.
+		c.addPassthrough(pkt)
+		return
+	}
+	s := c.take()
+	s.passthrough = false
+	s.rawPkt = nil
+	copy(s.hdrBuf[:], pkt[:info.hdrLen])
+	s.hdrLen = info.hdrLen
+	s.ipHdrLen = info.ipHdrLen
+	s.isV6 = info.fk.isV6
+	s.fk = info.fk
+	s.gsoSize = info.payLen
+	s.numSeg = 1
+	s.totalPay = info.payLen
+	s.nextSeq = info.seq + uint32(info.payLen)
+	s.psh = info.flags&tcpFlagPsh != 0
+	s.payIovs = append(s.payIovs[:0], pkt[info.hdrLen:info.hdrLen+info.payLen])
+	c.slots = append(c.slots, s)
+	if !s.psh {
+		c.openSlots[info.fk] = s
+		c.lastSlot = s
+	} else if last := c.lastSlot; last != nil && last.fk == info.fk {
+		// PSH-on-seed seals the slot immediately. Any prior cached open
+		// slot for this flow has just been sealed-and-replaced by this
+		// passthrough-shaped seed, so drop the cache too.
+		c.lastSlot = nil
+	}
+}
+
+// canAppend reports whether info's packet extends the slot's seed: same
+// header shape and stable contents, adjacent seq, not oversized, chain not
+// closed.
+func (c *TCPCoalescer) canAppend(s *coalesceSlot, pkt []byte, info parsedTCP) bool {
+	if s.psh {
+		return false
+	}
+	if info.hdrLen != s.hdrLen {
+		return false
+	}
+	if info.seq != s.nextSeq {
+		return false
+	}
+	if s.numSeg >= tcpCoalesceMaxSegs {
+		return false
+	}
+	if info.payLen > s.gsoSize {
+		return false
+	}
+	if s.hdrLen+s.totalPay+info.payLen > tcpCoalesceBufSize {
+		return false
+	}
+	// ECE state must be stable across a burst — receivers expect the
+	// flag set on every segment of a CE-echoing window or none.
+	seedFlags := s.hdrBuf[s.ipHdrLen+13]
+	if (seedFlags^info.flags)&tcpFlagEce != 0 {
+		return false
+	}
+	if !headersMatch(s.hdrBuf[:s.hdrLen], pkt[:info.hdrLen], s.isV6, s.ipHdrLen) {
+		return false
+	}
+	return true
+}
+
+func (c *TCPCoalescer) appendPayload(s *coalesceSlot, pkt []byte, info parsedTCP) {
+	s.payIovs = append(s.payIovs, pkt[info.hdrLen:info.hdrLen+info.payLen])
+	s.numSeg++
+	s.totalPay += info.payLen
+	s.nextSeq = info.seq + uint32(info.payLen)
+	if info.flags&tcpFlagPsh != 0 {
+		// Propagate PSH into the seed header so kernel TSO sets it on the
+		// last segment. Without this the sender's push signal is dropped.
+		s.hdrBuf[s.ipHdrLen+13] |= tcpFlagPsh
+	}
+	// Merge IP-level CE marks into the seed: headersMatch ignores ECN, so
+	// this is the one place the signal is preserved.
+	mergeECNIntoSeed(s.hdrBuf[:s.ipHdrLen], pkt[:s.ipHdrLen], s.isV6)
+	if info.payLen < s.gsoSize || info.flags&tcpFlagPsh != 0 {
+		s.psh = true
+	}
+}
+
+func (c *TCPCoalescer) take() *coalesceSlot {
+	if n := len(c.pool); n > 0 {
+		s := c.pool[n-1]
+		c.pool[n-1] = nil
+		c.pool = c.pool[:n-1]
+		return s
+	}
+	return &coalesceSlot{}
+}
+
+func (c *TCPCoalescer) release(s *coalesceSlot) {
+	s.passthrough = false
+	s.rawPkt = nil
+	clear(s.payIovs)
+	s.payIovs = s.payIovs[:0]
+	s.numSeg = 0
+	s.totalPay = 0
+	s.psh = false
+	c.pool = append(c.pool, s)
+}
+
+// flushSlot patches the header and calls WriteGSO. Does not remove the
+// slot from c.slots.
+func (c *TCPCoalescer) flushSlot(s *coalesceSlot) error {
+	total := s.hdrLen + s.totalPay
+	l4Len := total - s.ipHdrLen
+	hdr := s.hdrBuf[:s.hdrLen]
+
+	if s.isV6 {
+		binary.BigEndian.PutUint16(hdr[4:6], uint16(l4Len))
+	} else {
+		binary.BigEndian.PutUint16(hdr[2:4], uint16(total))
+		hdr[10] = 0
+		hdr[11] = 0
+		binary.BigEndian.PutUint16(hdr[10:12], ipv4HdrChecksum(hdr[:s.ipHdrLen]))
+	}
+
+	var psum uint32
+	if s.isV6 {
+		psum = pseudoSumIPv6(hdr[8:24], hdr[24:40], ipProtoTCP, l4Len)
+	} else {
+		psum = pseudoSumIPv4(hdr[12:16], hdr[16:20], ipProtoTCP, l4Len)
+	}
+	tcsum := s.ipHdrLen + 16
+	binary.BigEndian.PutUint16(hdr[tcsum:tcsum+2], foldOnceNoInvert(psum))
+
+	return c.gsoW.WriteGSO(hdr[:s.ipHdrLen], hdr[s.ipHdrLen:], s.payIovs, tio.GSOProtoTCP)
+}
+
+// headersMatch compares two IP+TCP header prefixes for byte-for-byte
+// equality on every field that must be identical across coalesced
+// segments. Size/IPID/IPCsum/seq/flags/tcpCsum are masked out, as is the
+// 2-bit IP-level ECN field — appendPayload merges CE into the seed.
+func headersMatch(a, b []byte, isV6 bool, ipHdrLen int) bool {
+	if len(a) != len(b) {
+		return false
+	}
+	if !ipHeadersMatch(a, b, isV6) {
+		return false
+	}
+	// TCP: compare [0:4] ports, [8:13] ack+dataoff, [14:16] window,
+	// [18:tcpHdrLen] options (incl. urgent).
+	tcp := ipHdrLen
+	if !bytes.Equal(a[tcp:tcp+4], b[tcp:tcp+4]) {
+		return false
+	}
+	if !bytes.Equal(a[tcp+8:tcp+13], b[tcp+8:tcp+13]) {
+		return false
+	}
+	if !bytes.Equal(a[tcp+14:tcp+16], b[tcp+14:tcp+16]) {
+		return false
+	}
+	if !bytes.Equal(a[tcp+18:], b[tcp+18:]) {
+		return false
+	}
+	return true
+}
+
+// reorderForFlush neutralizes wire-side reorder that the rxOrder buffer
+// couldn't catch (anything crossing a recvmmsg batch boundary). Without
+// this pass a small wire reorder — counter 250 arriving in batch K when
+// 200..249 are coming in batch K+1 — would seed an out-of-seq slot first
+// and emit it ahead of the lower-seq slot, manifesting at the inner TCP
+// receiver as a much larger reorder than the wire actually had.
+//
+// Two phases:
+//  1. Sort each passthrough-bounded segment of c.slots by (flow, seq).
+//     Cross-flow ordering inside a segment isn't preserved (it never was
+//     and doesn't matter for any single flow's TCP correctness).
+//  2. Sweep once and merge adjacent same-flow slots whose ranges are now
+//     contiguous AND whose tail is gsoSize-aligned. The tail constraint
+//     matters because the kernel TSO splitter chops at gsoSize from the
+//     start of the merged payload — a short segment in the middle would
+//     desynchronize every later segment.
+//
+// Passthrough slots act as barriers: the merge check skips them on either
+// side, so a SYN/FIN/RST/CWR is never reordered relative to its flow's
+// data.
+func (c *TCPCoalescer) reorderForFlush() {
+	if len(c.slots) <= 1 {
+		return
+	}
+	runStart := 0
+	for i := 0; i <= len(c.slots); i++ {
+		if i < len(c.slots) && !c.slots[i].passthrough {
+			continue
+		}
+		c.sortRun(c.slots[runStart:i])
+		runStart = i + 1
+	}
+	out := c.slots[:0]
+	logged := false
+	for _, s := range c.slots {
+		if n := len(out); n > 0 {
+			prev := out[n-1]
+			if !prev.passthrough && !s.passthrough && prev.fk == s.fk {
+				// Same-flow neighbors after sort. If they aren't seq-
+				// contiguous it's a real gap — packets the wire reordered
+				// across batches, or actual loss before nebula. Log it so
+				// the operator can quantify how often it happens; the data
+				// itself still emits in seq order, kernel TCP handles the
+				// gap via its OOO queue.
+				if prev.nextSeq != slotSeedSeq(s) {
+					logged = true
+					gap := int64(slotSeedSeq(s)) - int64(prev.nextSeq)
+					slog.Default().Warn("tcp coalesce: cross-slot seq gap",
+						"src", flowKeyAddr(s.fk, false),
+						"dst", flowKeyAddr(s.fk, true),
+						"sport", s.fk.sport,
+						"dport", s.fk.dport,
+						"prev_seed_seq", slotSeedSeq(prev),
+						"prev_next_seq", prev.nextSeq,
+						"this_seed_seq", slotSeedSeq(s),
+						"gap_bytes", gap,
+						"prev_seg_count", prev.numSeg,
+						"prev_total_pay", prev.totalPay,
+					)
+				}
+				if canMergeSlots(prev, s) {
+					mergeSlots(prev, s)
+					c.release(s)
+					continue
+				}
+			}
+		}
+		out = append(out, s)
+	}
+	if logged {
+		slog.Default().Warn("==== end of batch ====")
+	}
+	c.slots = out
+}
+
+// flowKeyAddr returns the src or dst address from fk as a netip.Addr for
+// logging. Only used on the cold gap-log path so the netip allocation
+// doesn't matter.
+func flowKeyAddr(fk flowKey, dst bool) netip.Addr {
+	src := fk.src
+	if dst {
+		src = fk.dst
+	}
+	if fk.isV6 {
+		return netip.AddrFrom16(src)
+	}
+	var v4 [4]byte
+	copy(v4[:], src[:4])
+	return netip.AddrFrom4(v4)
+}
+
+// sortRun stable-sorts run by (flowKey, seedSeq) so each flow's slots
+// cluster together in seq order, ready for the merge sweep. Stable so
+// equal-key slots keep their original relative position (defensive — a
+// duplicate seedSeq would already mean something's wrong upstream).
+func (c *TCPCoalescer) sortRun(run []*coalesceSlot) {
+	if len(run) <= 1 {
+		return
+	}
+	// slices.SortStableFunc with a free, non-capturing comparator avoids the
+	// reflection + closure-escape allocations that sort.SliceStable forces.
+	slices.SortStableFunc(run, compareCoalesceSlots)
+}
+
+func compareCoalesceSlots(a, b *coalesceSlot) int {
+	if cmp := flowKeyCompare(a.fk, b.fk); cmp != 0 {
+		return cmp
+	}
+	aSeq, bSeq := slotSeedSeq(a), slotSeedSeq(b)
+	if aSeq == bSeq {
+		return 0
+	}
+	if tcpSeqLess(aSeq, bSeq) {
+		return -1
+	}
+	return 1
+}
+
+// slotSeedSeq returns the TCP seq of the slot's seed (first segment).
+// nextSeq tracks the seq just past the last appended byte; subtracting
+// totalPay walks back to the seed. uint32 wraparound is the right TCP
+// arithmetic so no special-casing is needed.
+func slotSeedSeq(s *coalesceSlot) uint32 {
+	return s.nextSeq - uint32(s.totalPay)
+}
+
+// tcpSeqLess reports whether a precedes b in TCP serial-number arithmetic
+// (RFC 1323 §2.3). The signed int32 cast turns the modular subtraction
+// into the right comparison even across the 2^32 wrap.
+func tcpSeqLess(a, b uint32) bool {
+	return int32(a-b) < 0
+}
+
+// flowKeyCompare orders flowKeys deterministically. The exact ordering
+// is irrelevant — only that same-flow slots cluster together so the
+// post-sort sweep can merge contiguous pairs.
+func flowKeyCompare(a, b flowKey) int {
+	// Cheap scalar fields first so most non-matching keys short-circuit
+	// without ever calling bytes.Compare. sport is the ephemeral port on
+	// egress flows and discriminates fastest. For matching keys (same
+	// flow), array equality on src/dst inlines to word-sized compares,
+	// so we only pay bytes.Compare when the arrays actually differ.
+	if a.sport != b.sport {
+		if a.sport < b.sport {
+			return -1
+		}
+		return 1
+	}
+	if a.dport != b.dport {
+		if a.dport < b.dport {
+			return -1
+		}
+		return 1
+	}
+	if a.dst != b.dst {
+		return bytes.Compare(a.dst[:], b.dst[:])
+	}
+	if a.src != b.src {
+		return bytes.Compare(a.src[:], b.src[:])
+	}
+	if a.isV6 != b.isV6 {
+		if !a.isV6 {
+			return -1
+		}
+		return 1
+	}
+	return 0
+}
+
+// canMergeSlots reports whether s can fold into prev as one merged TSO
+// superpacket. Same flow, contiguous TCP byte range, equal gsoSize, and
+// fits within the kernel TSO limits. The tail-of-prev check rejects any
+// merge whose first slot ended on a sub-gsoSize segment — kernel TSO
+// would split the merged skb at gsoSize boundaries from the start, so a
+// short segment in the middle would corrupt every later segment. PSH and
+// ECE state must agree across both slots: PSH is a semantic delimiter
+// (preserving the sender's push boundary) and ECE state must be uniform
+// across a window (the same rule canAppend enforces for in-flow appends).
+//
+// Note: a slot sealed by reorder (canAppend returned false on seq
+// mismatch) keeps psh=false, so this restriction does not block the
+// reorder-fix merge — only legitimate PSH-set seals.
+func canMergeSlots(prev, s *coalesceSlot) bool {
+	if prev.psh {
+		return false
+	}
+	if prev.fk != s.fk {
+		return false
+	}
+	if prev.gsoSize != s.gsoSize {
+		return false
+	}
+	if prev.nextSeq != slotSeedSeq(s) {
+		return false
+	}
+	if prev.numSeg+s.numSeg > tcpCoalesceMaxSegs {
+		return false
+	}
+	if prev.hdrLen+prev.totalPay+s.totalPay > tcpCoalesceBufSize {
+		return false
+	}
+	if len(prev.payIovs[len(prev.payIovs)-1]) != prev.gsoSize {
+		return false
+	}
+	prevFlags := prev.hdrBuf[prev.ipHdrLen+13]
+	sFlags := s.hdrBuf[s.ipHdrLen+13]
+	if (prevFlags^sFlags)&tcpFlagEce != 0 {
+		return false
+	}
+	if !headersMatch(prev.hdrBuf[:prev.hdrLen], s.hdrBuf[:s.hdrLen], prev.isV6, prev.ipHdrLen) {
+		return false
+	}
+	return true
+}
+
+// mergeSlots folds src into dst in place: payIovs concatenated, counters
+// and totals updated, PSH and IP-level CE bits OR'd into the seed header
+// so neither the push signal nor a CE mark is lost. The seed header's
+// seq, gsoSize, and fk are unchanged. Caller is responsible for releasing
+// src (it's no longer in c.slots after this call).
+func mergeSlots(dst, src *coalesceSlot) {
+	dst.payIovs = append(dst.payIovs, src.payIovs...)
+	dst.numSeg += src.numSeg
+	dst.totalPay += src.totalPay
+	dst.nextSeq = src.nextSeq
+	if src.psh {
+		dst.psh = true
+		dst.hdrBuf[dst.ipHdrLen+13] |= tcpFlagPsh
+	}
+	mergeECNIntoSeed(dst.hdrBuf[:dst.ipHdrLen], src.hdrBuf[:src.ipHdrLen], dst.isV6)
+}
+
+// ipv4HdrChecksum computes the IPv4 header checksum over hdr (which must
+// already have its checksum field zeroed) and returns the folded/inverted
+// 16-bit value to store.
+func ipv4HdrChecksum(hdr []byte) uint16 {
+	var sum uint32
+	for i := 0; i+1 < len(hdr); i += 2 {
+		sum += uint32(binary.BigEndian.Uint16(hdr[i : i+2]))
+	}
+	if len(hdr)%2 == 1 {
+		sum += uint32(hdr[len(hdr)-1]) << 8
+	}
+	for sum>>16 != 0 {
+		sum = (sum & 0xffff) + (sum >> 16)
+	}
+	return ^uint16(sum)
+}
+
+// pseudoSumIPv4 / pseudoSumIPv6 build the L4 pseudo-header partial sum
+// expected by the virtio NEEDS_CSUM kernel path: the 32-bit accumulator
+// before folding. proto selects the L4 (TCP or UDP); the UDP coalescer
+// reuses these helpers.
+func pseudoSumIPv4(src, dst []byte, proto byte, l4Len int) uint32 {
+	var sum uint32
+	sum += uint32(binary.BigEndian.Uint16(src[0:2]))
+	sum += uint32(binary.BigEndian.Uint16(src[2:4]))
+	sum += uint32(binary.BigEndian.Uint16(dst[0:2]))
+	sum += uint32(binary.BigEndian.Uint16(dst[2:4]))
+	sum += uint32(proto)
+	sum += uint32(l4Len)
+	return sum
+}
+
+func pseudoSumIPv6(src, dst []byte, proto byte, l4Len int) uint32 {
+	var sum uint32
+	for i := 0; i < 16; i += 2 {
+		sum += uint32(binary.BigEndian.Uint16(src[i : i+2]))
+		sum += uint32(binary.BigEndian.Uint16(dst[i : i+2]))
+	}
+	sum += uint32(l4Len >> 16)
+	sum += uint32(l4Len & 0xffff)
+	sum += uint32(proto)
+	return sum
+}
+
+// foldOnceNoInvert folds the 32-bit accumulator to 16 bits and returns it
+// unchanged (no one's complement). This is what virtio NEEDS_CSUM wants in
+// the L4 checksum field — the kernel will add the payload sum and invert.
+func foldOnceNoInvert(sum uint32) uint16 {
+	for sum>>16 != 0 {
+		sum = (sum & 0xffff) + (sum >> 16)
+	}
+	return uint16(sum)
+}

overlay/batch/tcp_coalesce_bench_test.go

@@ -0,0 +1,239 @@
+package batch
+
+import (
+	"encoding/binary"
+	"runtime"
+	"testing"
+
+	"github.com/slackhq/nebula/overlay/tio"
+)
+
+// nopTunWriter is a zero-alloc tio.GSOWriter for benchmarks. Discards
+// everything but satisfies the interface the coalescer detects.
+type nopTunWriter struct{}
+
+func (nopTunWriter) Write(p []byte) (int, error) { return len(p), nil }
+func (nopTunWriter) WriteGSO(hdr []byte, transportHdr []byte, pays [][]byte, _ tio.GSOProto) error {
+	return nil
+}
+func (nopTunWriter) Capabilities() tio.Capabilities {
+	return tio.Capabilities{TSO: true, USO: true}
+}
+
+// buildTCPv4BulkFlow returns a slice of N adjacent ACK-only TCP segments
+// on a single 5-tuple, each carrying payloadLen bytes. Seq numbers are
+// contiguous so every packet is coalesceable onto the previous one.
+func buildTCPv4BulkFlow(n, payloadLen int) [][]byte {
+	pkts := make([][]byte, n)
+	pay := make([]byte, payloadLen)
+	seq := uint32(1000)
+	for i := range n {
+		pkts[i] = buildTCPv4(seq, tcpAck, pay)
+		seq += uint32(payloadLen)
+	}
+	return pkts
+}
+
+// buildTCPv4Interleaved returns nFlows * perFlow packets with per-flow
+// seq continuity but round-robin across flows — worst case for any
+// "last-slot" cache.
+func buildTCPv4Interleaved(nFlows, perFlow, payloadLen int) [][]byte {
+	pay := make([]byte, payloadLen)
+	seqs := make([]uint32, nFlows)
+	for i := range seqs {
+		seqs[i] = uint32(1000 + i*1000000)
+	}
+	pkts := make([][]byte, 0, nFlows*perFlow)
+	for range perFlow {
+		for f := range nFlows {
+			sport := uint16(10000 + f)
+			pkts = append(pkts, buildTCPv4Ports(sport, 2000, seqs[f], tcpAck, pay))
+			seqs[f] += uint32(payloadLen)
+		}
+	}
+	return pkts
+}
+
+// buildICMPv4 returns a minimal non-TCP packet that takes the passthrough
+// branch in Commit.
+func buildICMPv4() []byte {
+	pkt := make([]byte, 28)
+	pkt[0] = 0x45
+	binary.BigEndian.PutUint16(pkt[2:4], 28)
+	pkt[9] = 1 // ICMP
+	copy(pkt[12:16], []byte{10, 0, 0, 1})
+	copy(pkt[16:20], []byte{10, 0, 0, 2})
+	return pkt
+}
+
+// runCommitBench drives Commit over pkts batchSize at a time, flushing
+// between batches, and reports per-packet cost.
+func runCommitBench(b *testing.B, pkts [][]byte, batchSize int) {
+	b.Helper()
+	c := NewTCPCoalescer(nopTunWriter{})
+	b.ReportAllocs()
+	b.SetBytes(int64(len(pkts[0])))
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		pkt := pkts[i%len(pkts)]
+		if err := c.Commit(pkt); err != nil {
+			b.Fatal(err)
+		}
+		if (i+1)%batchSize == 0 {
+			if err := c.Flush(); err != nil {
+				b.Fatal(err)
+			}
+		}
+	}
+	// Drain any trailing partial batch so slot state doesn't leak across runs.
+	_ = c.Flush()
+}
+
+// BenchmarkCommitSingleFlow is the bulk-TCP steady state: one flow,
+// contiguous seq, 1200-byte payloads. Every packet past the seed should
+// append onto the open slot. This is the case we most care about.
+func BenchmarkCommitSingleFlow(b *testing.B) {
+	pkts := buildTCPv4BulkFlow(tcpCoalesceMaxSegs, 1200)
+	runCommitBench(b, pkts, tcpCoalesceMaxSegs)
+}
+
+// BenchmarkCommitInterleaved4 has 4 concurrent bulk flows round-robined.
+// A single-entry fast-path cache will miss on every packet; an N-way
+// cache or map lookup carries the weight.
+func BenchmarkCommitInterleaved4(b *testing.B) {
+	pkts := buildTCPv4Interleaved(4, tcpCoalesceMaxSegs, 1200)
+	runCommitBench(b, pkts, len(pkts))
+}
+
+// BenchmarkCommitInterleaved16 stresses the map at higher flow counts.
+func BenchmarkCommitInterleaved16(b *testing.B) {
+	pkts := buildTCPv4Interleaved(16, tcpCoalesceMaxSegs, 1200)
+	runCommitBench(b, pkts, len(pkts))
+}
+
+// BenchmarkCommitPassthrough exercises the non-TCP branch: parseTCPBase
+// bails early and addPassthrough is the only work.
+func BenchmarkCommitPassthrough(b *testing.B) {
+	pkt := buildICMPv4()
+	pkts := make([][]byte, 64)
+	for i := range pkts {
+		pkts[i] = pkt
+	}
+	runCommitBench(b, pkts, 64)
+}
+
+// BenchmarkCommitNonCoalesceableTCP sends SYN|ACK packets on one flow.
+// Each packet takes the "TCP but not admissible" branch which does a
+// map delete + passthrough. Measures the seal-without-slot cost.
+func BenchmarkCommitNonCoalesceableTCP(b *testing.B) {
+	pay := make([]byte, 0)
+	pkts := make([][]byte, 64)
+	for i := range pkts {
+		pkts[i] = buildTCPv4(uint32(1000+i), tcpSyn|tcpAck, pay)
+	}
+	runCommitBench(b, pkts, 64)
+}
+
+// runMultiCommitBench drives MultiCoalescer.Commit. The dispatcher does
+// the IP/L4 parse once and passes the parsed struct to the lane, so this
+// is the bench that shows the savings of skipping the lane's re-parse.
+func runMultiCommitBench(b *testing.B, pkts [][]byte, batchSize int) {
+	b.Helper()
+	m := NewMultiCoalescer(nopTunWriter{}, true, true)
+	b.ReportAllocs()
+	b.SetBytes(int64(len(pkts[0])))
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		pkt := pkts[i%len(pkts)]
+		if err := m.Commit(pkt); err != nil {
+			b.Fatal(err)
+		}
+		if (i+1)%batchSize == 0 {
+			if err := m.Flush(); err != nil {
+				b.Fatal(err)
+			}
+		}
+	}
+	_ = m.Flush()
+}
+
+// BenchmarkMultiCommitSingleFlow is the multi-lane analogue of
+// BenchmarkCommitSingleFlow — same workload but routed through the
+// dispatcher. The delta vs the single-lane bench measures dispatcher
+// overhead.
+func BenchmarkMultiCommitSingleFlow(b *testing.B) {
+	pkts := buildTCPv4BulkFlow(tcpCoalesceMaxSegs, 1200)
+	runMultiCommitBench(b, pkts, tcpCoalesceMaxSegs)
+}
+
+// BenchmarkMultiCommitInterleaved4 mirrors BenchmarkCommitInterleaved4
+// through the dispatcher.
+func BenchmarkMultiCommitInterleaved4(b *testing.B) {
+	pkts := buildTCPv4Interleaved(4, tcpCoalesceMaxSegs, 1200)
+	runMultiCommitBench(b, pkts, len(pkts))
+}
+
+// flowKeyPair is one comparison input for the flowKeyCompare bench.
+type flowKeyPair struct{ a, b flowKey }
+
+// makeFlowKey builds an IPv4 flowKey from compact inputs.
+func makeFlowKey(srcLow, dstLow uint32, sport, dport uint16) flowKey {
+	var fk flowKey
+	binary.BigEndian.PutUint32(fk.src[12:16], srcLow)
+	binary.BigEndian.PutUint32(fk.dst[12:16], dstLow)
+	fk.sport = sport
+	fk.dport = dport
+	return fk
+}
+
+// flowKeyCases are the workload mixes flowKeyCompare sees in practice.
+//   - sameFlow: equal keys; tests the equal-path cost (sort runs hit this
+//     repeatedly when many segments share a flow).
+//   - sportDiffers: same src/dst/dport, different sport — the typical
+//     "sibling flows from one host to one server" pattern.
+//   - dstDiffers: same src/sport/dport, different dst — outbound to many
+//     servers from a fixed local port.
+//   - allDiffer: every field differs; worst case for short-circuiting.
+func flowKeyCases() map[string][]flowKeyPair {
+	const n = 64
+	cases := map[string][]flowKeyPair{
+		"sameFlow":     make([]flowKeyPair, n),
+		"sportDiffers": make([]flowKeyPair, n),
+		"dstDiffers":   make([]flowKeyPair, n),
+		"allDiffer":    make([]flowKeyPair, n),
+	}
+	for i := range n {
+		base := makeFlowKey(0x0a000001, 0x0a000002, 40000, 443)
+		cases["sameFlow"][i] = flowKeyPair{a: base, b: base}
+		cases["sportDiffers"][i] = flowKeyPair{
+			a: base,
+			b: makeFlowKey(0x0a000001, 0x0a000002, uint16(40001+i), 443),
+		}
+		cases["dstDiffers"][i] = flowKeyPair{
+			a: base,
+			b: makeFlowKey(0x0a000001, uint32(0x0a000002+i+1), 40000, 443),
+		}
+		cases["allDiffer"][i] = flowKeyPair{
+			a: makeFlowKey(uint32(0x0a000001+i), uint32(0x0a000002+i), uint16(40000+i), uint16(80+i)),
+			b: makeFlowKey(uint32(0x0b000001+i), uint32(0x0b000002+i), uint16(50000+i), uint16(443+i)),
+		}
+	}
+	return cases
+}
+
+// BenchmarkFlowKeyCompare measures flowKeyCompare across the workloads
+// the sort step actually sees. Use this to compare reorderings.
+func BenchmarkFlowKeyCompare(b *testing.B) {
+	for name, pairs := range flowKeyCases() {
+		b.Run(name, func(b *testing.B) {
+			b.ReportAllocs()
+			b.ResetTimer()
+			var sink int
+			for i := 0; i < b.N; i++ {
+				p := pairs[i&(len(pairs)-1)]
+				sink += flowKeyCompare(p.a, p.b)
+			}
+			runtime.KeepAlive(sink)
+		})
+	}
+}

overlay/batch/tx_batch.go

@@ -0,0 +1,64 @@
+package batch
+
+import "net/netip"
+
+const SendBatchCap = 128
+
+// batchWriter is the minimal subset of udp.Conn needed by SendBatch to flush.
+type batchWriter interface {
+	WriteBatch(bufs [][]byte, addrs []netip.AddrPort, outerECNs []byte) error
+}
+
+// SendBatch accumulates encrypted UDP packets and flushes them via WriteBatch.
+// One SendBatch is owned by each listenIn goroutine; no locking is needed.
+// The backing arena grows on demand: when there isn't room for the next slot
+// we allocate a fresh backing array. Already-committed slices keep referencing
+// the old array and remain valid until Flush drops them.
+type SendBatch struct {
+	out     batchWriter
+	bufs    [][]byte
+	dsts    []netip.AddrPort
+	ecns    []byte
+	backing []byte
+}
+
+func NewSendBatch(out batchWriter, batchCap, slotCap int) *SendBatch {
+	return &SendBatch{
+		out:     out,
+		bufs:    make([][]byte, 0, batchCap),
+		dsts:    make([]netip.AddrPort, 0, batchCap),
+		ecns:    make([]byte, 0, batchCap),
+		backing: make([]byte, 0, batchCap*slotCap),
+	}
+}
+
+func (b *SendBatch) Reserve(sz int) []byte {
+	if len(b.backing)+sz > cap(b.backing) {
+		// Grow: allocate a fresh backing. Already-committed slices still
+		// reference the old array and remain valid until Flush drops them.
+		newCap := max(cap(b.backing)*2, sz)
+		b.backing = make([]byte, 0, newCap)
+	}
+	start := len(b.backing)
+	b.backing = b.backing[:start+sz]
+	return b.backing[start : start+sz : start+sz]
+}
+
+func (b *SendBatch) Commit(pkt []byte, dst netip.AddrPort, outerECN byte) {
+	b.bufs = append(b.bufs, pkt)
+	b.dsts = append(b.dsts, dst)
+	b.ecns = append(b.ecns, outerECN)
+}
+
+func (b *SendBatch) Flush() error {
+	var err error
+	if len(b.bufs) > 0 {
+		err = b.out.WriteBatch(b.bufs, b.dsts, b.ecns)
+	}
+	clear(b.bufs)
+	b.bufs = b.bufs[:0]
+	b.dsts = b.dsts[:0]
+	b.ecns = b.ecns[:0]
+	b.backing = b.backing[:0]
+	return err
+}

overlay/batch/tx_batch_test.go

@@ -0,0 +1,124 @@
+package batch
+
+import (
+	"net/netip"
+	"testing"
+)
+
+type fakeBatchWriter struct {
+	bufs  [][]byte
+	addrs []netip.AddrPort
+	ecns  []byte
+}
+
+func (w *fakeBatchWriter) WriteBatch(bufs [][]byte, addrs []netip.AddrPort, ecns []byte) error {
+	// Snapshot — SendBatch.Flush nils its slot pointers right after WriteBatch
+	// returns, so tests must capture data before that happens.
+	w.bufs = make([][]byte, len(bufs))
+	for i, b := range bufs {
+		cp := make([]byte, len(b))
+		copy(cp, b)
+		w.bufs[i] = cp
+	}
+	w.addrs = append(w.addrs[:0], addrs...)
+	w.ecns = append(w.ecns[:0], ecns...)
+	return nil
+}
+
+func TestSendBatchReserveCommitFlush(t *testing.T) {
+	fw := &fakeBatchWriter{}
+	b := NewSendBatch(fw, 4, 32)
+
+	ap := netip.MustParseAddrPort("10.0.0.1:4242")
+	for i := 0; i < 4; i++ {
+		slot := b.Reserve(32)
+		if cap(slot) != 32 {
+			t.Fatalf("slot %d: cap=%d want 32", i, cap(slot))
+		}
+		pkt := append(slot[:0], byte(i), byte(i+1), byte(i+2))
+		b.Commit(pkt, ap, 0)
+	}
+	if err := b.Flush(); err != nil {
+		t.Fatalf("Flush: %v", err)
+	}
+	if len(fw.bufs) != 4 {
+		t.Fatalf("WriteBatch got %d bufs want 4", len(fw.bufs))
+	}
+	for i, buf := range fw.bufs {
+		if len(buf) != 3 || buf[0] != byte(i) {
+			t.Errorf("buf %d: %x", i, buf)
+		}
+		if fw.addrs[i] != ap {
+			t.Errorf("addr %d: got %v want %v", i, fw.addrs[i], ap)
+		}
+	}
+
+	// Flush again with nothing committed — should be a no-op.
+	fw.bufs = nil
+	if err := b.Flush(); err != nil {
+		t.Fatalf("empty Flush: %v", err)
+	}
+	if fw.bufs != nil {
+		t.Fatalf("empty Flush triggered WriteBatch")
+	}
+
+	// Reuse after Flush.
+	slot := b.Reserve(32)
+	if cap(slot) != 32 {
+		t.Fatalf("after Flush Reserve wrong cap: %d", cap(slot))
+	}
+}
+
+func TestSendBatchSlotsDoNotOverlap(t *testing.T) {
+	fw := &fakeBatchWriter{}
+	b := NewSendBatch(fw, 3, 8)
+	ap := netip.MustParseAddrPort("10.0.0.1:80")
+
+	for i := 0; i < 3; i++ {
+		s := b.Reserve(8)
+		pkt := append(s[:0], byte(0xA0+i), byte(0xB0+i))
+		b.Commit(pkt, ap, 0)
+	}
+	if err := b.Flush(); err != nil {
+		t.Fatalf("Flush: %v", err)
+	}
+
+	for i, buf := range fw.bufs {
+		if buf[0] != byte(0xA0+i) || buf[1] != byte(0xB0+i) {
+			t.Errorf("slot %d corrupted: %x", i, buf)
+		}
+	}
+}
+
+func TestSendBatchGrowPreservesCommitted(t *testing.T) {
+	fw := &fakeBatchWriter{}
+	// Tiny initial backing forces a grow on the second Reserve.
+	b := NewSendBatch(fw, 1, 4)
+	ap := netip.MustParseAddrPort("10.0.0.1:80")
+
+	s1 := b.Reserve(4)
+	pkt1 := append(s1[:0], 0x11, 0x22, 0x33, 0x44)
+	b.Commit(pkt1, ap, 0)
+
+	s2 := b.Reserve(8) // exceeds remaining cap, triggers grow
+	pkt2 := append(s2[:0], 0xA, 0xB, 0xC, 0xD, 0xE)
+	b.Commit(pkt2, ap, 0)
+
+	// pkt1 must still be intact even though backing reallocated.
+	if pkt1[0] != 0x11 || pkt1[3] != 0x44 {
+		t.Fatalf("first packet corrupted by grow: %x", pkt1)
+	}
+
+	if err := b.Flush(); err != nil {
+		t.Fatalf("Flush: %v", err)
+	}
+	if len(fw.bufs) != 2 {
+		t.Fatalf("got %d bufs want 2", len(fw.bufs))
+	}
+	if fw.bufs[0][0] != 0x11 || fw.bufs[0][3] != 0x44 {
+		t.Errorf("first packet on the wire: %x", fw.bufs[0])
+	}
+	if fw.bufs[1][0] != 0xA || fw.bufs[1][4] != 0xE {
+		t.Errorf("second packet on the wire: %x", fw.bufs[1])
+	}
+}

overlay/batch/udp_coalesce.go

@@ -0,0 +1,336 @@
+package batch
+
+import (
+	"encoding/binary"
+	"io"
+
+	"github.com/slackhq/nebula/overlay/tio"
+)
+
+// ipProtoUDP is the IANA protocol number for UDP.
+const ipProtoUDP = 17
+
+// udpCoalesceBufSize caps total bytes per UDP superpacket. Mirrors the
+// kernel's gso_max_size; payloads beyond this are emitted as-is.
+const udpCoalesceBufSize = 65535
+
+// udpCoalesceMaxSegs caps how many segments we'll coalesce. Kernel UDP-GSO
+// accepts up to 64 segments per skb (UDP_MAX_SEGMENTS); stay under that.
+const udpCoalesceMaxSegs = 64
+
+// udpCoalesceHdrCap is the scratch space we copy a seed's IP+UDP header
+// into. IPv6 (40) + UDP (8) = 48; round up for safety.
+const udpCoalesceHdrCap = 64
+
+// udpSlot is one entry in the UDPCoalescer's ordered event queue. Same
+// passthrough-vs-coalesced shape as the TCP coalescer's slot, but no
+// seq/PSH/CWR bookkeeping — UDP segments only need 5-tuple + length
+// matching to coalesce.
+type udpSlot struct {
+	passthrough bool
+	rawPkt      []byte // borrowed when passthrough
+
+	fk       flowKey
+	hdrBuf   [udpCoalesceHdrCap]byte
+	hdrLen   int
+	ipHdrLen int
+	isV6     bool
+	gsoSize  int // per-segment UDP payload length
+	numSeg   int
+	totalPay int
+	// sealed closes the chain: set when a sub-gsoSize segment is appended
+	// (kernel UDP-GSO requires every segment but the last to be exactly
+	// gsoSize) or when limits are hit. No further appends after.
+	sealed  bool
+	payIovs [][]byte
+}
+
+// UDPCoalescer accumulates adjacent in-flow UDP datagrams across multiple
+// concurrent flows and emits each flow's run as a single GSO_UDP_L4
+// superpacket via tio.GSOWriter. Falls back to per-packet writes when the
+// underlying writer doesn't support USO.
+//
+// All output — coalesced or not — is deferred until Flush so per-flow
+// arrival order is preserved on the wire. Cross-flow order is NOT preserved
+// across the TCP/UDP/passthrough split when this coalescer runs alongside
+// others — see multi_coalesce.go. Per-flow order is preserved because a
+// single 5-tuple only ever lands in one lane and each lane preserves its
+// own slot order.
+//
+// Owns no locks; one coalescer per TUN write queue.
+type UDPCoalescer struct {
+	plainW io.Writer
+	gsoW   tio.GSOWriter // nil when the queue can't accept GSO_UDP_L4
+
+	slots     []*udpSlot
+	openSlots map[flowKey]*udpSlot
+	pool      []*udpSlot
+
+	backing []byte
+}
+
+// NewUDPCoalescer wraps w. The caller is responsible for only constructing
+// this when the underlying Queue's Capabilities advertise USO; otherwise
+// the kernel may reject GSO_UDP_L4 writes. If w does not implement
+// tio.GSOWriter at all (single-packet Queue), the coalescer degrades to
+// plain Writes — same defensive shape as the TCP coalescer.
+func NewUDPCoalescer(w io.Writer) *UDPCoalescer {
+	c := &UDPCoalescer{
+		plainW:    w,
+		slots:     make([]*udpSlot, 0, initialSlots),
+		openSlots: make(map[flowKey]*udpSlot, initialSlots),
+		pool:      make([]*udpSlot, 0, initialSlots),
+		backing:   make([]byte, 0, initialSlots*udpCoalesceBufSize),
+	}
+	if gw, ok := tio.SupportsGSO(w, tio.GSOProtoUDP); ok {
+		c.gsoW = gw
+	}
+	return c
+}
+
+// parsedUDP holds the fields extracted from a single parse so later steps
+// (admission, slot lookup, canAppend) don't re-walk the header.
+type parsedUDP struct {
+	fk       flowKey
+	ipHdrLen int
+	hdrLen   int // ipHdrLen + 8
+	payLen   int
+}
+
+// parseUDP extracts the flow key and IP/UDP offsets for a UDP packet.
+// Returns ok=false for non-UDP, malformed, or unsupported header shapes
+// (IPv4 with options/fragmentation, IPv6 with extension headers).
+func parseUDP(pkt []byte) (parsedUDP, bool) {
+	var p parsedUDP
+	ip, ok := parseIPPrologue(pkt, ipProtoUDP)
+	if !ok {
+		return p, false
+	}
+	pkt = ip.pkt
+	p.fk = ip.fk
+	p.ipHdrLen = ip.ipHdrLen
+
+	if len(pkt) < p.ipHdrLen+8 {
+		return p, false
+	}
+	p.hdrLen = p.ipHdrLen + 8
+	// UDP `length` field: must equal IP-derived length-of-UDP-header-plus-payload.
+	udpLen := int(binary.BigEndian.Uint16(pkt[p.ipHdrLen+4 : p.ipHdrLen+6]))
+	if udpLen < 8 || udpLen > len(pkt)-p.ipHdrLen {
+		return p, false
+	}
+	p.payLen = udpLen - 8
+	p.fk.sport = binary.BigEndian.Uint16(pkt[p.ipHdrLen : p.ipHdrLen+2])
+	p.fk.dport = binary.BigEndian.Uint16(pkt[p.ipHdrLen+2 : p.ipHdrLen+4])
+	return p, true
+}
+
+func (c *UDPCoalescer) Reserve(sz int) []byte {
+	return reserveFromBacking(&c.backing, sz)
+}
+
+// Commit borrows pkt. The caller must keep pkt valid until the next Flush.
+func (c *UDPCoalescer) Commit(pkt []byte) error {
+	if c.gsoW == nil {
+		c.addPassthrough(pkt)
+		return nil
+	}
+	info, ok := parseUDP(pkt)
+	if !ok {
+		c.addPassthrough(pkt)
+		return nil
+	}
+	return c.commitParsed(pkt, info)
+}
+
+// commitParsed is the post-parse half of Commit. The caller must have
+// already verified parseUDP succeeded. Used by MultiCoalescer.Commit to
+// avoid re-walking the IP/UDP header.
+func (c *UDPCoalescer) commitParsed(pkt []byte, info parsedUDP) error {
+	if c.gsoW == nil {
+		c.addPassthrough(pkt)
+		return nil
+	}
+	if open := c.openSlots[info.fk]; open != nil {
+		if c.canAppend(open, pkt, info) {
+			c.appendPayload(open, pkt, info)
+			if open.sealed {
+				delete(c.openSlots, info.fk)
+			}
+			return nil
+		}
+		// Can't extend — seal it and fall through to seed a fresh slot.
+		delete(c.openSlots, info.fk)
+	}
+	c.seed(pkt, info)
+	return nil
+}
+
+func (c *UDPCoalescer) Flush() error {
+	var first error
+	for _, s := range c.slots {
+		var err error
+		if s.passthrough {
+			_, err = c.plainW.Write(s.rawPkt)
+		} else {
+			err = c.flushSlot(s)
+		}
+		if err != nil && first == nil {
+			first = err
+		}
+		c.release(s)
+	}
+	clear(c.slots)
+	c.slots = c.slots[:0]
+	clear(c.openSlots)
+	c.backing = c.backing[:0]
+	return first
+}
+
+func (c *UDPCoalescer) addPassthrough(pkt []byte) {
+	s := c.take()
+	s.passthrough = true
+	s.rawPkt = pkt
+	c.slots = append(c.slots, s)
+}
+
+func (c *UDPCoalescer) seed(pkt []byte, info parsedUDP) {
+	if info.hdrLen > udpCoalesceHdrCap || info.hdrLen+info.payLen > udpCoalesceBufSize {
+		c.addPassthrough(pkt)
+		return
+	}
+	s := c.take()
+	s.passthrough = false
+	s.rawPkt = nil
+	copy(s.hdrBuf[:], pkt[:info.hdrLen])
+	s.hdrLen = info.hdrLen
+	s.ipHdrLen = info.ipHdrLen
+	s.isV6 = info.fk.isV6
+	s.fk = info.fk
+	s.gsoSize = info.payLen
+	s.numSeg = 1
+	s.totalPay = info.payLen
+	s.sealed = false
+	s.payIovs = append(s.payIovs[:0], pkt[info.hdrLen:info.hdrLen+info.payLen])
+	c.slots = append(c.slots, s)
+	c.openSlots[info.fk] = s
+}
+
+// canAppend reports whether info's packet extends the slot's seed.
+// Kernel UDP-GSO requires every segment except possibly the last to be
+// exactly gsoSize, and the last may be shorter (≤ gsoSize).
+func (c *UDPCoalescer) canAppend(s *udpSlot, pkt []byte, info parsedUDP) bool {
+	if s.sealed {
+		return false
+	}
+	if info.hdrLen != s.hdrLen {
+		return false
+	}
+	if s.numSeg >= udpCoalesceMaxSegs {
+		return false
+	}
+	if info.payLen > s.gsoSize {
+		return false
+	}
+	if s.hdrLen+s.totalPay+info.payLen > udpCoalesceBufSize {
+		return false
+	}
+	if !udpHeadersMatch(s.hdrBuf[:s.hdrLen], pkt[:info.hdrLen], s.isV6, s.ipHdrLen) {
+		return false
+	}
+	return true
+}
+
+func (c *UDPCoalescer) appendPayload(s *udpSlot, pkt []byte, info parsedUDP) {
+	s.payIovs = append(s.payIovs, pkt[info.hdrLen:info.hdrLen+info.payLen])
+	s.numSeg++
+	s.totalPay += info.payLen
+	// Merge IP-level CE marks into the seed (same trick TCP coalescer uses).
+	mergeECNIntoSeed(s.hdrBuf[:s.ipHdrLen], pkt[:s.ipHdrLen], s.isV6)
+	if info.payLen < s.gsoSize {
+		// Last-segment-can-be-shorter: this seals the chain.
+		s.sealed = true
+	}
+}
+
+func (c *UDPCoalescer) take() *udpSlot {
+	if n := len(c.pool); n > 0 {
+		s := c.pool[n-1]
+		c.pool[n-1] = nil
+		c.pool = c.pool[:n-1]
+		return s
+	}
+	return &udpSlot{}
+}
+
+func (c *UDPCoalescer) release(s *udpSlot) {
+	s.passthrough = false
+	s.rawPkt = nil
+	clear(s.payIovs)
+	s.payIovs = s.payIovs[:0]
+	s.numSeg = 0
+	s.totalPay = 0
+	s.sealed = false
+	c.pool = append(c.pool, s)
+}
+
+// flushSlot patches the IP header total length / IPv6 payload length and
+// the UDP length to the *total* across all coalesced segments, then seeds
+// the UDP checksum field with the pseudo-header partial (single-fold, not
+// inverted) per virtio NEEDS_CSUM. The kernel's ip_rcv_core (v4) and
+// ip6_rcv_core (v6) trim the skb to those length fields, so per-segment
+// values would silently drop everything but the first segment. The kernel
+// then walks each segment in __udp_gso_segment, recomputing per-segment
+// uh->len / iph->tot_len / IPv6 plen and adjusting the checksum via
+// `check = csum16_add(csum16_sub(uh->check, uh->len), newlen)` — meaning
+// our seed's uh->check must be consistent with the seed's uh->len, which
+// is what passing the total to both pseudoSum and the UDP length field
+// guarantees.
+func (c *UDPCoalescer) flushSlot(s *udpSlot) error {
+	hdr := s.hdrBuf[:s.hdrLen]
+	total := s.hdrLen + s.totalPay // full IP+UDP+all_payloads bytes
+	l4Len := total - s.ipHdrLen    // total UDP (8 + sum of payloads)
+
+	if s.isV6 {
+		binary.BigEndian.PutUint16(hdr[4:6], uint16(l4Len))
+	} else {
+		binary.BigEndian.PutUint16(hdr[2:4], uint16(total))
+		hdr[10] = 0
+		hdr[11] = 0
+		binary.BigEndian.PutUint16(hdr[10:12], ipv4HdrChecksum(hdr[:s.ipHdrLen]))
+	}
+
+	// UDP length field (offset 4 inside the UDP header) = total UDP size.
+	binary.BigEndian.PutUint16(hdr[s.ipHdrLen+4:s.ipHdrLen+6], uint16(l4Len))
+
+	var psum uint32
+	if s.isV6 {
+		psum = pseudoSumIPv6(hdr[8:24], hdr[24:40], ipProtoUDP, l4Len)
+	} else {
+		psum = pseudoSumIPv4(hdr[12:16], hdr[16:20], ipProtoUDP, l4Len)
+	}
+	udpCsumOff := s.ipHdrLen + 6
+	binary.BigEndian.PutUint16(hdr[udpCsumOff:udpCsumOff+2], foldOnceNoInvert(psum))
+
+	return c.gsoW.WriteGSO(hdr[:s.ipHdrLen], hdr[s.ipHdrLen:], s.payIovs, tio.GSOProtoUDP)
+}
+
+// udpHeadersMatch compares two IP+UDP header prefixes for byte-equality on
+// every field that must be identical across coalesced segments. Length
+// fields and the ECN bits in IP TOS/TC are masked out — appendPayload
+// merges CE into the seed; flushSlot rewrites lengths.
+func udpHeadersMatch(a, b []byte, isV6 bool, ipHdrLen int) bool {
+	if len(a) != len(b) {
+		return false
+	}
+	if !ipHeadersMatch(a, b, isV6) {
+		return false
+	}
+	// UDP: compare sport+dport ([0:4]). Skip length [4:6] and checksum [6:8] —
+	// length varies (we rewrite at flush) and the checksum will be redone.
+	udp := ipHdrLen
+	if a[udp] != b[udp] || a[udp+1] != b[udp+1] || a[udp+2] != b[udp+2] || a[udp+3] != b[udp+3] {
+		return false
+	}
+	return true
+}

overlay/batch/udp_coalesce_test.go

@@ -0,0 +1,383 @@
+package batch
+
+import (
+	"encoding/binary"
+	"testing"
+)
+
+// buildUDPv4 builds a minimal IPv4+UDP packet with the given payload and ports.
+func buildUDPv4(sport, dport uint16, payload []byte) []byte {
+	const ipHdrLen = 20
+	const udpHdrLen = 8
+	total := ipHdrLen + udpHdrLen + len(payload)
+	pkt := make([]byte, total)
+
+	pkt[0] = 0x45
+	pkt[1] = 0x00
+	binary.BigEndian.PutUint16(pkt[2:4], uint16(total))
+	binary.BigEndian.PutUint16(pkt[4:6], 0)
+	binary.BigEndian.PutUint16(pkt[6:8], 0x4000)
+	pkt[8] = 64
+	pkt[9] = ipProtoUDP
+	copy(pkt[12:16], []byte{10, 0, 0, 1})
+	copy(pkt[16:20], []byte{10, 0, 0, 2})
+
+	binary.BigEndian.PutUint16(pkt[20:22], sport)
+	binary.BigEndian.PutUint16(pkt[22:24], dport)
+	binary.BigEndian.PutUint16(pkt[24:26], uint16(udpHdrLen+len(payload)))
+	binary.BigEndian.PutUint16(pkt[26:28], 0)
+
+	copy(pkt[28:], payload)
+	return pkt
+}
+
+// buildUDPv6 builds a minimal IPv6+UDP packet.
+func buildUDPv6(sport, dport uint16, payload []byte) []byte {
+	const ipHdrLen = 40
+	const udpHdrLen = 8
+	total := ipHdrLen + udpHdrLen + len(payload)
+	pkt := make([]byte, total)
+
+	pkt[0] = 0x60
+	binary.BigEndian.PutUint16(pkt[4:6], uint16(udpHdrLen+len(payload)))
+	pkt[6] = ipProtoUDP
+	pkt[7] = 64
+	pkt[8] = 0xfe
+	pkt[9] = 0x80
+	pkt[23] = 1
+	pkt[24] = 0xfe
+	pkt[25] = 0x80
+	pkt[39] = 2
+
+	binary.BigEndian.PutUint16(pkt[40:42], sport)
+	binary.BigEndian.PutUint16(pkt[42:44], dport)
+	binary.BigEndian.PutUint16(pkt[44:46], uint16(udpHdrLen+len(payload)))
+	binary.BigEndian.PutUint16(pkt[46:48], 0)
+
+	copy(pkt[48:], payload)
+	return pkt
+}
+
+func TestUDPCoalescerPassthroughWhenGSOUnavailable(t *testing.T) {
+	w := &fakeTunWriter{gsoEnabled: false}
+	c := NewUDPCoalescer(w)
+	pkt := buildUDPv4(1000, 53, make([]byte, 100))
+	if err := c.Commit(pkt); err != nil {
+		t.Fatal(err)
+	}
+	if len(w.writes) != 0 || len(w.gsoWrites) != 0 {
+		t.Fatalf("no Add-time writes: writes=%d gso=%d", len(w.writes), len(w.gsoWrites))
+	}
+	if err := c.Flush(); err != nil {
+		t.Fatal(err)
+	}
+	if len(w.writes) != 1 || len(w.gsoWrites) != 0 {
+		t.Fatalf("want single plain write, got writes=%d gso=%d", len(w.writes), len(w.gsoWrites))
+	}
+}
+
+func TestUDPCoalescerNonUDPPassthrough(t *testing.T) {
+	w := &fakeTunWriter{gsoEnabled: true}
+	c := NewUDPCoalescer(w)
+	// ICMP packet
+	pkt := make([]byte, 28)
+	pkt[0] = 0x45
+	binary.BigEndian.PutUint16(pkt[2:4], 28)
+	pkt[9] = 1
+	copy(pkt[12:16], []byte{10, 0, 0, 1})
+	copy(pkt[16:20], []byte{10, 0, 0, 2})
+	if err := c.Commit(pkt); err != nil {
+		t.Fatal(err)
+	}
+	if err := c.Flush(); err != nil {
+		t.Fatal(err)
+	}
+	if len(w.writes) != 1 || len(w.gsoWrites) != 0 {
+		t.Fatalf("ICMP must pass through unchanged: writes=%d gso=%d", len(w.writes), len(w.gsoWrites))
+	}
+}
+
+func TestUDPCoalescerSeedThenFlushAlone(t *testing.T) {
+	w := &fakeTunWriter{gsoEnabled: true}
+	c := NewUDPCoalescer(w)
+	pkt := buildUDPv4(1000, 53, make([]byte, 800))
+	if err := c.Commit(pkt); err != nil {
+		t.Fatal(err)
+	}
+	if err := c.Flush(); err != nil {
+		t.Fatal(err)
+	}
+	// Single-segment flush goes through WriteGSO; the writer infers GSO_NONE
+	// from len(pays)==1 and the kernel fills in the UDP csum (NEEDS_CSUM).
+	if len(w.gsoWrites) != 1 || len(w.writes) != 0 {
+		t.Fatalf("single-seg flush: writes=%d gso=%d", len(w.writes), len(w.gsoWrites))
+	}
+}
+
+func TestUDPCoalescerCoalescesEqualSized(t *testing.T) {
+	w := &fakeTunWriter{gsoEnabled: true}
+	c := NewUDPCoalescer(w)
+	pay := make([]byte, 1200)
+	for i := 0; i < 3; i++ {
+		if err := c.Commit(buildUDPv4(1000, 53, pay)); err != nil {
+			t.Fatal(err)
+		}
+	}
+	if err := c.Flush(); err != nil {
+		t.Fatal(err)
+	}
+	if len(w.gsoWrites) != 1 {
+		t.Fatalf("want 1 gso write, got %d (plain=%d)", len(w.gsoWrites), len(w.writes))
+	}
+	g := w.gsoWrites[0]
+	if g.gsoSize != 1200 {
+		t.Errorf("gsoSize=%d want 1200", g.gsoSize)
+	}
+	if len(g.pays) != 3 {
+		t.Errorf("pay count=%d want 3", len(g.pays))
+	}
+	if g.csumStart != 20 {
+		t.Errorf("csumStart=%d want 20", g.csumStart)
+	}
+	// IP totalLen and UDP length must be the TOTAL across all segments —
+	// the kernel's ip_rcv_core trims skbs to iph->tot_len, so a per-segment
+	// value would silently drop everything but the first segment. Total =
+	// IP(20) + UDP(8) + 3*1200 = 3628.
+	gotTotalLen := binary.BigEndian.Uint16(g.hdr[2:4])
+	if gotTotalLen != 3628 {
+		t.Errorf("ipv4 total_len=%d want 3628 (must be total across segments)", gotTotalLen)
+	}
+	gotUDPLen := binary.BigEndian.Uint16(g.hdr[20+4 : 20+6])
+	if gotUDPLen != 8+3*1200 {
+		t.Errorf("udp len=%d want %d", gotUDPLen, 8+3*1200)
+	}
+}
+
+// Last segment may be shorter, sealing the chain.
+func TestUDPCoalescerShortLastSegmentSeals(t *testing.T) {
+	w := &fakeTunWriter{gsoEnabled: true}
+	c := NewUDPCoalescer(w)
+	full := make([]byte, 1200)
+	tail := make([]byte, 600)
+	if err := c.Commit(buildUDPv4(1000, 53, full)); err != nil {
+		t.Fatal(err)
+	}
+	if err := c.Commit(buildUDPv4(1000, 53, full)); err != nil {
+		t.Fatal(err)
+	}
+	if err := c.Commit(buildUDPv4(1000, 53, tail)); err != nil {
+		t.Fatal(err)
+	}
+	// A 4th packet, even same-sized, must NOT join — chain is sealed.
+	if err := c.Commit(buildUDPv4(1000, 53, full)); err != nil {
+		t.Fatal(err)
+	}
+	if err := c.Flush(); err != nil {
+		t.Fatal(err)
+	}
+	if len(w.gsoWrites) != 2 {
+		t.Fatalf("want 2 gso writes (sealed + new seed), got %d", len(w.gsoWrites))
+	}
+	if len(w.gsoWrites[0].pays) != 3 {
+		t.Errorf("first super: want 3 pays, got %d", len(w.gsoWrites[0].pays))
+	}
+	if len(w.gsoWrites[1].pays) != 1 {
+		t.Errorf("second super: want 1 pay (re-seed), got %d", len(w.gsoWrites[1].pays))
+	}
+}
+
+// A larger-than-gsoSize packet cannot extend the slot — it reseeds.
+func TestUDPCoalescerLargerThanSeedReseeds(t *testing.T) {
+	w := &fakeTunWriter{gsoEnabled: true}
+	c := NewUDPCoalescer(w)
+	if err := c.Commit(buildUDPv4(1000, 53, make([]byte, 800))); err != nil {
+		t.Fatal(err)
+	}
+	if err := c.Commit(buildUDPv4(1000, 53, make([]byte, 1200))); err != nil {
+		t.Fatal(err)
+	}
+	if err := c.Flush(); err != nil {
+		t.Fatal(err)
+	}
+	if len(w.gsoWrites) != 2 {
+		t.Fatalf("want 2 separate seeds, got %d", len(w.gsoWrites))
+	}
+}
+
+// Different 5-tuples must not coalesce.
+func TestUDPCoalescerDifferentFlowsKeepSeparate(t *testing.T) {
+	w := &fakeTunWriter{gsoEnabled: true}
+	c := NewUDPCoalescer(w)
+	pay := make([]byte, 800)
+	if err := c.Commit(buildUDPv4(1000, 53, pay)); err != nil {
+		t.Fatal(err)
+	}
+	if err := c.Commit(buildUDPv4(2000, 53, pay)); err != nil {
+		t.Fatal(err)
+	}
+	if err := c.Commit(buildUDPv4(1000, 53, pay)); err != nil {
+		t.Fatal(err)
+	}
+	if err := c.Commit(buildUDPv4(2000, 53, pay)); err != nil {
+		t.Fatal(err)
+	}
+	if err := c.Flush(); err != nil {
+		t.Fatal(err)
+	}
+	// Two flows × 2 datagrams each = 2 superpackets of 2 segments.
+	if len(w.gsoWrites) != 2 {
+		t.Fatalf("want 2 gso writes (one per flow), got %d", len(w.gsoWrites))
+	}
+	for i, g := range w.gsoWrites {
+		if len(g.pays) != 2 {
+			t.Errorf("super %d: want 2 pays, got %d", i, len(g.pays))
+		}
+	}
+}
+
+// Caps at udpCoalesceMaxSegs.
+func TestUDPCoalescerCapsAtMaxSegs(t *testing.T) {
+	w := &fakeTunWriter{gsoEnabled: true}
+	c := NewUDPCoalescer(w)
+	pay := make([]byte, 100)
+	for i := 0; i < udpCoalesceMaxSegs+5; i++ {
+		if err := c.Commit(buildUDPv4(1000, 53, pay)); err != nil {
+			t.Fatal(err)
+		}
+	}
+	if err := c.Flush(); err != nil {
+		t.Fatal(err)
+	}
+	// First superpacket holds udpCoalesceMaxSegs segments; the spillover
+	// reseeds a new one.
+	if len(w.gsoWrites) != 2 {
+		t.Fatalf("want 2 gso writes (cap then reseed), got %d", len(w.gsoWrites))
+	}
+	if len(w.gsoWrites[0].pays) != udpCoalesceMaxSegs {
+		t.Errorf("first super: pays=%d want %d", len(w.gsoWrites[0].pays), udpCoalesceMaxSegs)
+	}
+	if len(w.gsoWrites[1].pays) != 5 {
+		t.Errorf("second super: pays=%d want 5", len(w.gsoWrites[1].pays))
+	}
+}
+
+// CE marks on appended segments must be merged into the seed's IP TOS.
+func TestUDPCoalescerMergesCEMark(t *testing.T) {
+	w := &fakeTunWriter{gsoEnabled: true}
+	c := NewUDPCoalescer(w)
+	pay := make([]byte, 800)
+	pkt0 := buildUDPv4(1000, 53, pay) // ECN=00
+	pkt1 := buildUDPv4(1000, 53, pay)
+	pkt1[1] = 0x03 // CE
+	pkt2 := buildUDPv4(1000, 53, pay)
+	if err := c.Commit(pkt0); err != nil {
+		t.Fatal(err)
+	}
+	if err := c.Commit(pkt1); err != nil {
+		t.Fatal(err)
+	}
+	if err := c.Commit(pkt2); err != nil {
+		t.Fatal(err)
+	}
+	if err := c.Flush(); err != nil {
+		t.Fatal(err)
+	}
+	if len(w.gsoWrites) != 1 {
+		t.Fatalf("want 1 merged gso write, got %d (plain=%d)", len(w.gsoWrites), len(w.writes))
+	}
+	if w.gsoWrites[0].hdr[1]&0x03 != 0x03 {
+		t.Errorf("CE not merged into seed (tos=%#x)", w.gsoWrites[0].hdr[1])
+	}
+}
+
+// IPv6 path: same flow, equal-sized → coalesced.
+func TestUDPCoalescerIPv6Coalesces(t *testing.T) {
+	w := &fakeTunWriter{gsoEnabled: true}
+	c := NewUDPCoalescer(w)
+	pay := make([]byte, 1200)
+	for i := 0; i < 3; i++ {
+		if err := c.Commit(buildUDPv6(1000, 53, pay)); err != nil {
+			t.Fatal(err)
+		}
+	}
+	if err := c.Flush(); err != nil {
+		t.Fatal(err)
+	}
+	if len(w.gsoWrites) != 1 {
+		t.Fatalf("want 1 gso write, got %d", len(w.gsoWrites))
+	}
+	g := w.gsoWrites[0]
+	if !g.isV6 {
+		t.Errorf("expected v6 write")
+	}
+	if g.csumStart != 40 {
+		t.Errorf("csumStart=%d want 40", g.csumStart)
+	}
+	// IPv6 payload_len and UDP length must be TOTAL — kernel's
+	// ip6_rcv_core trims to payload_len + ipv6 hdr size. Total UDP = 8 +
+	// 3*1200 = 3608.
+	gotPlen := binary.BigEndian.Uint16(g.hdr[4:6])
+	if gotPlen != 8+3*1200 {
+		t.Errorf("ipv6 payload_len=%d want %d (must be total)", gotPlen, 8+3*1200)
+	}
+	gotUDPLen := binary.BigEndian.Uint16(g.hdr[40+4 : 40+6])
+	if gotUDPLen != 8+3*1200 {
+		t.Errorf("udp len=%d want %d", gotUDPLen, 8+3*1200)
+	}
+}
+
+// DSCP differences must reseed (headers don't match outside ECN).
+func TestUDPCoalescerDSCPMismatchReseeds(t *testing.T) {
+	w := &fakeTunWriter{gsoEnabled: true}
+	c := NewUDPCoalescer(w)
+	pay := make([]byte, 800)
+	pkt0 := buildUDPv4(1000, 53, pay)
+	pkt1 := buildUDPv4(1000, 53, pay)
+	pkt1[1] = 0xb8 // EF DSCP, ECN=0
+	if err := c.Commit(pkt0); err != nil {
+		t.Fatal(err)
+	}
+	if err := c.Commit(pkt1); err != nil {
+		t.Fatal(err)
+	}
+	if err := c.Flush(); err != nil {
+		t.Fatal(err)
+	}
+	if len(w.gsoWrites) != 2 {
+		t.Fatalf("want 2 separate seeds (different DSCP), got %d", len(w.gsoWrites))
+	}
+}
+
+// Fragmented IPv4 must not be coalesced.
+func TestUDPCoalescerFragmentedIPv4PassesThrough(t *testing.T) {
+	w := &fakeTunWriter{gsoEnabled: true}
+	c := NewUDPCoalescer(w)
+	pkt := buildUDPv4(1000, 53, make([]byte, 200))
+	binary.BigEndian.PutUint16(pkt[6:8], 0x2000) // MF=1
+	if err := c.Commit(pkt); err != nil {
+		t.Fatal(err)
+	}
+	if err := c.Flush(); err != nil {
+		t.Fatal(err)
+	}
+	if len(w.writes) != 1 || len(w.gsoWrites) != 0 {
+		t.Fatalf("frag must pass through plain, got writes=%d gso=%d", len(w.writes), len(w.gsoWrites))
+	}
+}
+
+// IPv4 with options is not admissible (we require IHL=5).
+func TestUDPCoalescerIPv4WithOptionsPassesThrough(t *testing.T) {
+	w := &fakeTunWriter{gsoEnabled: true}
+	c := NewUDPCoalescer(w)
+	pkt := buildUDPv4(1000, 53, make([]byte, 200))
+	pkt[0] = 0x46 // IHL = 6 (24-byte IPv4 header — has options)
+	if err := c.Commit(pkt); err != nil {
+		t.Fatal(err)
+	}
+	if err := c.Flush(); err != nil {
+		t.Fatal(err)
+	}
+	if len(w.writes) != 1 || len(w.gsoWrites) != 0 {
+		t.Fatalf("ipv4-with-options must pass through plain, got writes=%d gso=%d", len(w.writes), len(w.gsoWrites))
+	}
+}