fix

Bumps [github.com/gaissmai/bart](https://github.com/gaissmai/bart) from 0.26.0 to 0.26.1.
- [Release notes](https://github.com/gaissmai/bart/releases)
- [Commits](https://github.com/gaissmai/bart/compare/v0.26.0...v0.26.1)

---
updated-dependencies:
- dependency-name: github.com/gaissmai/bart
  dependency-version: 0.26.1
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.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
+    - name: ${{ matrix.target }}
-      run: make smoke-vagrant/freebsd-amd64
+      run: make smoke-vagrant/${{ matrix.target }}
 
-    - name: openbsd-amd64
+    timeout-minutes: 30
-      run: make smoke-vagrant/openbsd-amd64
 
-    - name: netbsd-amd64
+  # linux-386 needs VirtualBox, which conflicts with KVM/libvirt -- isolated job.
-      run: make smoke-vagrant/netbsd-amd64
+  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
+    - uses: actions/checkout@v6
-      run: make smoke-vagrant/linux-amd64-ipv6disable
 
-    # linux-386 runs last because it requires disabling KVM to use VirtualBox,
+    - uses: actions/setup-go@v6
-    # which prevents libvirt (used by the other tests) from working after this point.
+      with:
-    - name: install virtualbox for i386 test
+        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/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 }}

bits.go

@@ -2,24 +2,42 @@ package nebula
 
 import (
 	"context"
+	"fmt"
 	"log/slog"
+	"math"
+	mathbits "math/bits"
 
 	"github.com/rcrowley/go-metrics"
 )
 
+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,
+		length:             length,
-		bits:               make([]bool, bits, bits),
+		lengthMask:         length - 1,
+		bits:               make([]uint64, nWords),
 		current:            0,
 		lostCounter:        metrics.GetOrRegisterCounter("network.packets.lost", nil),
 		dupeCounter:        metrics.GetOrRegisterCounter("network.packets.duplicate", nil),
@@ -27,71 +45,194 @@ 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.bits[0] = 1
-	b.current = 0
 	return b
 }
 
+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 b.strictlyWithinWindow(i) {
-	if i > b.current-b.length || i < b.length && b.current < b.length {
+		return !b.get(i)
-		return !b.bits[i%b.length]
 	}
 
 	// Not within the window
 	if l.Enabled(context.Background(), slog.LevelDebug) {
-		l.Debug("rejected a packet (top)",
+		l.Debug("rejected a packet (top)", "current", b.current, "incoming", i)
-			"current", b.current,
-			"incoming", i,
-		)
 	}
 	return false
 }
 
+// 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 {
-	// If i is the next number, return true and update current.
+	// 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
+		pos := i & b.lengthMask
-		// The very first window can only be tracked as lost once we are on the 2nd window or greater
+		word := pos >> 6
-		if b.bits[i%b.length] == false && i > b.length {
+		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)
+		end := i
-		// Zero out the bits between the current and the new counter value, limited by the window size,
+		if end > b.current+b.length {
-		// since the window is shifting
+			end = b.current + b.length
-		for n := b.current + 1; n <= min(i, b.current+b.length); n++ {
+		}
-			if b.bits[n%b.length] == false && n > b.length {
+		count := end - b.current
-				lost++
+		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
+		// Anything past the new window can never be backfilled, so it's lost.
-		// Any loss within the new window will be accounted for in future calls
+		if i > b.current+b.length {
-		lost += max(0, int64(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,
+	// If i is within the current window but below the current counter, check to see if it's a duplicate
-	// Check to see if it's a duplicate
+	if b.strictlyWithinWindow(i) {
-	if i > b.current-b.length || i < b.length && b.current < b.length {
+		pos := i & b.lengthMask
-		if b.current == i || b.bits[i%b.length] == true {
+		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,
@@ -104,7 +245,7 @@ func (b *Bits) Update(l *slog.Logger, i uint64) bool {
 			return false
 		}
 
-		b.bits[i%b.length] = true
+		b.bits[word] = w | mask
 		return true
 	}
 

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)
+	b := NewBits(16)
-
+	assert.EqualValues(t, 16, b.length)
-	// make sure it is the right size
-	assert.Len(t, b.bits, 10)
 
 	// 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}
+	g := []bool{true, true, false, false, false, false, false, false, false, false, false, false, false, false, false, false}
-	assert.Equal(t, g, b.bits)
+	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}
+	g = []bool{true, true, true, false, false, false, false, false, false, false, false, false, false, false, false, false}
-	assert.Equal(t, g, b.bits)
+	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
+	// Jump ahead to 25, which clears the window and sets slot 25%16 = 9.
-	assert.True(t, b.Check(l, 15))
+	assert.True(t, b.Check(l, 25))
-	assert.True(t, b.Update(l, 15))
+	assert.True(t, b.Update(l, 25))
-	assert.EqualValues(t, 15, b.current)
+	assert.EqualValues(t, 25, b.current)
-	g = []bool{false, false, false, false, false, true, false, false, false, false}
+	g = []bool{false, false, false, false, false, false, false, false, false, true, false, false, false, false, false, false}
-	assert.Equal(t, g, b.bits)
+	assert.Equal(t, g, b.snapshot())
 
-	// Mark 14, which is allowed because it is in the window
+	// Mark 24, which is in window (current 25, length 16, window covers [10,25]).
-	assert.True(t, b.Check(l, 14))
+	assert.True(t, b.Check(l, 24))
-	assert.True(t, b.Update(l, 14))
+	assert.True(t, b.Update(l, 24))
-	assert.EqualValues(t, 15, b.current)
+	assert.EqualValues(t, 25, b.current)
-	g = []bool{false, false, false, false, true, true, false, false, false, false}
+	g = []bool{false, false, false, false, false, false, false, false, true, true, false, false, false, false, false, false}
-	assert.Equal(t, g, b.bits)
+	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)
+	assert.EqualValues(t, 25, b.current)
-	g = []bool{false, false, false, false, true, true, false, false, false, false}
+	g = []bool{false, false, false, false, false, false, false, false, true, true, false, false, false, false, false, false}
-	assert.Equal(t, g, b.bits)
+	assert.Equal(t, g, b.snapshot())
 
-	// make sure we handle wrapping around once to the current position
+	// Make sure we handle wrapping around once to the same slot. With
-	b = NewBits(10)
+	// 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.True(t, b.Update(l, 17))
-	assert.Equal(t, []bool{false, true, false, false, false, false, false, false, false, false}, b.bits)
+	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)
+	// Update(100): clears 16 slots starting at slot 56%16=8. Only slot 7 (for
-	b.lostCounter.Clear()
+	// packet 55) was set, so 16 - 1 = 15 evicted slots had unset bits.
-	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
+	// Plus 100 - 55 - 16 = 29 packets fell past the window. Total 44.
-	assert.Equal(t, int64(45), b.lostCounter.Count())
+	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
+	// Update(200): same shape: 16 - 1 = 15 evicted unset, plus 200 - 100 - 16 = 84 past window. Total 99.
-	assert.Equal(t, int64(89), b.lostCounter.Count())
+	assert.True(t, b.Update(l, 200))
-
+	assert.Equal(t, int64(39+44+99), 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())
 }
 
 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))
+	// 9 single-step advances, each evicts a slot whose bit was cleared during
-	assert.True(t, b.Update(l, 22))
+	// the jump above and whose value was never seen, so each contributes 1
-	assert.True(t, b.Update(l, 23))
+	// to lostCounter.
-	assert.True(t, b.Update(l, 24))
+	for n := uint64(21); n <= 29; n++ {
-	assert.True(t, b.Update(l, 25))
+		assert.True(t, b.Update(l, n))
-	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(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))
+	// Walk 20..29 like the original, just with a bigger window. Same
-	assert.True(t, b.Update(l, 21))
+	// reasoning as TestBitsOutOfWindowCounter: 4 past-window from Update(20),
-	assert.True(t, b.Update(l, 22))
+	// then 9 more from the unit advances.
-	assert.True(t, b.Update(l, 23))
+	for n := uint64(20); n <= 29; n++ {
-	assert.True(t, b.Update(l, 24))
+		assert.True(t, b.Update(l, n))
-	assert.True(t, b.Update(l, 25))
+	}
-	assert.True(t, b.Update(l, 26))
+	assert.Equal(t, int64(13), b.lostCounter.Count())
-	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
 	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))
+	// Update(15) clears the warmup window (no lost), sets slot 15.
-	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))
 	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.Equal(t, int64(1), b.lostCounter.Count())
-	assert.True(t, b.Update(l, 19))
-	assert.Equal(t, int64(8), b.lostCounter.Count())
 
-	// Jump ahead by a window size
+	// Fill in 18..30 in single steps. Each i evicts slot i%16. Slots 2..14
-	assert.True(t, b.Update(l, 29))
+	// were all cleared during Update(15), and we never re-set any of them,
-	assert.Equal(t, int64(8), b.lostCounter.Count())
+	// so each i in 18..30 is a fresh lost packet — 13 more.
-	// Now lets walk ahead normally through the window, the missed packets should fill in
+	for n := uint64(18); n <= 30; n++ {
-	assert.True(t, b.Update(l, 30))
+		assert.True(t, b.Update(l, n))
-	assert.True(t, b.Update(l, 31))
+	}
-	assert.True(t, b.Update(l, 32))
+	assert.Equal(t, int64(14), b.lostCounter.Count())
-	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())
 
-	// Jump ahead by 2 windows, should have recording 1 full window missing
+	// Jump ahead by exactly one window size.
-	assert.True(t, b.Update(l, 58))
+	assert.True(t, b.Update(l, 46))
-	assert.Equal(t, int64(27), b.lostCounter.Count())
+	// end = min(46, 30+16) = 46, count = 16, all slots cleared. Before the
-	// Now lets walk ahead normally through the window, the missed packets should fill in from this window
+	// jump every slot 0..15 had been set (Update(15), (16), (17), 18..30),
-	assert.True(t, b.Update(l, 59))
+	// so wasSet=16 and 46 == current+length means no past-window slack:
-	assert.True(t, b.Update(l, 60))
+	// lost contribution = 0.
-	assert.True(t, b.Update(l, 61))
+	assert.Equal(t, int64(14), b.lostCounter.Count())
-	assert.True(t, b.Update(l, 62))
+
-	assert.True(t, b.Update(l, 63))
+	// Walk 47..55. The Update(46) jump cleared every slot, so only slot 14
-	assert.True(t, b.Update(l, 64))
+	// (for packet 46) is set when we start. Each subsequent unit step lands
-	assert.True(t, b.Update(l, 65))
+	// on a slot that was cleared and is past warmup, so it counts as lost.
-	assert.True(t, b.Update(l, 66))
+	// 9 more = 23.
-	assert.True(t, b.Update(l, 67))
+	for n := uint64(47); n <= 55; n++ {
-	// 68 packets tracked, 32 seen, 36 missed
+		assert.True(t, b.Update(l, n))
-	assert.Equal(t, int64(36), b.lostCounter.Count())
+	}
+	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) {
+// TestBitsWarmupOvershoot exercises the jump path's warmup arm with an
-	z := NewBits(10)
+// overshoot past one full window. NewBits leaves current=0 with only slot 0
-	for n := 0; n < b.N; n++ {
+// "set" by the marker. Jumping straight to length+k must (a) clear every
-		for i := range z.bits {
+// slot the jump straddles, (b) count only past-window slack (not the
-			z.bits[i] = true
+// in-window slots, which never had a "lost" tenant during warmup), and
-		}
+// (c) leave the cursor at the new counter so subsequent unit advances
-		for i := range z.bits {
+// count from steady state. The marker bit at slot 0 is irrelevant once
-			z.bits[i] = false
+// 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")

connection_manager.go

@@ -11,7 +11,6 @@ import (
 	"sync/atomic"
 	"time"
 
-	"github.com/rcrowley/go-metrics"
 	"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 *slog.Logger
 }
 
 func newConnectionManagerFromConfig(l *slog.Logger, c *config.C, hm *HostMap, p *Punchy) *connectionManager {
 	cm := &connectionManager{
-		hostMap:         hm,
+		hostMap:       hm,
-		l:               l,
+		l:             l,
-		punchy:          p,
+		punchy:        p,
-		relayUsed:       make(map[uint32]struct{}),
+		relayUsed:     make(map[uint32]struct{}),
-		relayUsedLock:   &sync.RWMutex{},
+		relayUsedLock: &sync.RWMutex{},
-		metricsTxPunchy: metrics.GetOrRegisterCounter("messages.tx.punchy", nil),
 	}
 
 	cm.reload(c, true)
@@ -369,7 +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
@@ -400,17 +396,16 @@ func (cm *connectionManager) makeTrafficDecision(localIndex uint32, now time.Tim
 
 			// 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() {
+		// We aren't receiving traffic but we are sending it. The outbound
-			// This is similar to the old punchy behavior with a slight optimization.
+		// traffic itself refreshes the primary remote's NAT state; this
-			// We aren't receiving traffic but we are sending it, punch on all known
+		// fans out to non-primary remotes, but only if target_all_remotes
-			// ips in case we need to re-prime NAT state
+		// is configured.
-			cm.sendPunch(hostinfo)
+		cm.punchy.SendPunchToAll(hostinfo)
-		}
 
 		if cm.l.Enabled(context.Background(), slog.LevelDebug) {
 			hostinfo.logger(cm.l).Debug("Tunnel status",
@@ -512,31 +507,6 @@ 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

connection_manager_test.go

@@ -64,7 +64,7 @@ func Test_NewConnectionManagerTest(t *testing.T) {
 
 	// Create manager
 	conf := config.NewC(test.NewLogger())
-	punchy := NewPunchyFromConfig(test.NewLogger(), conf)
+	punchy := NewPunchyFromConfig(test.NewLogger(), conf, nil)
 	nc := newConnectionManagerFromConfig(test.NewLogger(), conf, hostMap, punchy)
 	nc.intf = ifce
 	p := []byte("")
@@ -146,7 +146,7 @@ func Test_NewConnectionManagerTest2(t *testing.T) {
 
 	// Create manager
 	conf := config.NewC(test.NewLogger())
-	punchy := NewPunchyFromConfig(test.NewLogger(), conf)
+	punchy := NewPunchyFromConfig(test.NewLogger(), conf, nil)
 	nc := newConnectionManagerFromConfig(test.NewLogger(), conf, hostMap, punchy)
 	nc.intf = ifce
 	p := []byte("")
@@ -233,7 +233,7 @@ func Test_NewConnectionManager_DisconnectInactive(t *testing.T) {
 	conf.Settings["tunnels"] = map[string]any{
 		"drop_inactive": true,
 	}
-	punchy := NewPunchyFromConfig(test.NewLogger(), conf)
+	punchy := NewPunchyFromConfig(test.NewLogger(), conf, nil)
 	nc := newConnectionManagerFromConfig(test.NewLogger(), conf, hostMap, punchy)
 	assert.True(t, nc.dropInactive.Load())
 	nc.intf = ifce
@@ -358,7 +358,7 @@ func Test_NewConnectionManagerTest_DisconnectInvalid(t *testing.T) {
 
 	// Create manager
 	conf := config.NewC(test.NewLogger())
-	punchy := NewPunchyFromConfig(test.NewLogger(), conf)
+	punchy := NewPunchyFromConfig(test.NewLogger(), conf, nil)
 	nc := newConnectionManagerFromConfig(test.NewLogger(), conf, hostMap, punchy)
 	nc.intf = ifce
 	ifce.connectionManager = nc

connection_state.go

@@ -7,13 +7,14 @@ import (
 
 	"github.com/slackhq/nebula/cert"
 	"github.com/slackhq/nebula/handshake"
+	"github.com/slackhq/nebula/noiseutil"
 )
 
 const ReplayWindow = 1024
 
 type ConnectionState struct {
-	eKey           *NebulaCipherState
+	eKey           noiseutil.CipherState
-	dKey           *NebulaCipherState
+	dKey           noiseutil.CipherState
 	myCert         cert.Certificate
 	peerCert       *cert.CachedCertificate
 	initiator      bool
@@ -31,8 +32,8 @@ func newConnectionStateFromResult(r *handshake.Result) *ConnectionState {
 		myCert:    r.MyCert,
 		initiator: r.Initiator,
 		peerCert:  r.RemoteCert,
-		eKey:      NewNebulaCipherState(r.EKey),
+		eKey:      noiseutil.NewCipherState(r.EKey, r.Cipher),
-		dKey:      NewNebulaCipherState(r.DKey),
+		dKey:      noiseutil.NewCipherState(r.DKey, r.Cipher),
 		window:    NewBits(ReplayWindow),
 	}
 	ci.messageCounter.Add(r.MessageIndex)

e2e/helpers_test.go

@@ -4,15 +4,13 @@
 package e2e
 
 import (
-	"io"
+	"log/slog"
 	"net/netip"
 	"os"
 	"strings"
 	"testing"
 	"time"
 
-	"log/slog"
-
 	"dario.cat/mergo"
 	"github.com/google/gopacket"
 	"github.com/google/gopacket/layers"
@@ -382,7 +380,7 @@ func getAddrs(ns []netip.Prefix) []netip.Addr {
 func NewTestLogger() *slog.Logger {
 	v := os.Getenv("TEST_LOGS")
 	if v == "" {
-		return slog.New(slog.NewTextHandler(io.Discard, nil))
+		return slog.New(slog.DiscardHandler)
 	}
 
 	level := slog.LevelInfo

e2e/leak_test.go

@@ -18,14 +18,10 @@ import (
 // retry mechanism gives the wg.Wait()-driven goroutines a moment to drain
 // before failing the assertion.
 //
-// IgnoreCurrent is necessary in the parallelized suite: other tests can
+// Intentionally NOT t.Parallel()'d: concurrent tests would have their own
-// leave goroutines mid-shutdown when this one runs (Stop is async, the
+// goroutines running and trip the assertion.
-// wg.Wait() drain is not blocking on test return). We're checking that
-// *this* test's setup tears down cleanly, not that the whole suite is
-// idle at this moment. Intentionally NOT t.Parallel()'d for the same
-// reason — concurrent test goroutines would always show up.
 func TestNoGoroutineLeaks(t *testing.T) {
-	defer goleak.VerifyNone(t, goleak.IgnoreCurrent())
+	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)

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)
+}

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

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
@@ -26,7 +26,7 @@ require (
 	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

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 v0.26.1 h1:+w4rnLGNlA2GDVn382Tfe3jOsK5vOr5n4KmigJ9lbTo=
-github.com/gaissmai/bart v0.26.0/go.mod h1:GREWQfTLRWz/c5FTOsIw+KkscuFkIV5t8Rp7Nd1Td5c=
+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=
@@ -182,8 +182,8 @@ 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 v0.53.0 h1:d+qAbo5L0orcWAr0a9JweQpjXF19LMXJE8Ey7hwOdUA=
-golang.org/x/net v0.52.0/go.mod h1:R1MAz7uMZxVMualyPXb+VaqGSa3LIaUqk0eEt3w36Sw=
+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/machine.go

@@ -31,6 +31,7 @@ type CertVerifier func(cert.Certificate) (*cert.CachedCertificate, error)
 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
@@ -105,6 +106,7 @@ func NewMachine(
 		myVersion:  version,
 		result: &Result{
 			Initiator: initiator,
+			Cipher:    cred.cipherSuite,
 		},
 	}, nil
 }

handshake_manager.go

@@ -974,6 +974,7 @@ func (hm *HandshakeManager) continueHandshake(via ViaSender, hh *HandshakeHostIn
 		nb := make([]byte, 12, 12)
 		out := make([]byte, mtu)
 		for _, cp := range hh.packetStore {
+			//todo use a sendbatcher
 			cp.callback(cp.messageType, cp.messageSubType, hostinfo, cp.packet, nb, out)
 		}
 		f.cachedPacketMetrics.sent.Inc(int64(len(hh.packetStore)))

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)

inside.go

@@ -2,6 +2,7 @@ package nebula
 
 import (
 	"context"
+	"io"
 	"log/slog"
 	"net/netip"
 
@@ -9,10 +10,16 @@ import (
 	"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/routing"
+	"github.com/slackhq/nebula/wire"
 )
 
-func (f *Interface) consumeInsidePacket(packet []byte, fwPacket *firewall.Packet, nb, out []byte, q int, localCache firewall.ConntrackCache) {
+func (f *Interface) consumeInsidePacket(pkt wire.TunPacket, fwPacket *firewall.Packet, nb []byte, sendBatch *batch.SendBatch, 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. If you must keep
+	// the packet, use pkt.Clone() to detach it
+	packet := pkt.Bytes
 	err := newPacket(packet, false, fwPacket)
 	if err != nil {
 		if f.l.Enabled(context.Background(), slog.LevelDebug) {
@@ -37,7 +44,10 @@ 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].Write(packet)
+			err := pkt.PerSegment(func(seg []byte) error {
+				_, werr := f.readers[q].Write(seg)
+				return werr
+			})
 			if err != nil {
 				f.l.Error("Failed to forward to tun", "error", err)
 			}
@@ -53,11 +63,23 @@ 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 := pkt.PerSegment(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, out, q)
+		f.rejectInside(packet, rejectBuf, q)
 		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,
@@ -73,10 +95,9 @@ func (f *Interface) consumeInsidePacket(packet []byte, fwPacket *firewall.Packet
 
 	dropReason := f.firewall.Drop(*fwPacket, false, hostinfo, f.pki.GetCAPool(), localCache)
 	if dropReason == nil {
-		f.sendNoMetrics(header.Message, 0, hostinfo.ConnectionState, hostinfo, netip.AddrPort{}, packet, nb, out, q)
+		f.sendInsideMessage(hostinfo, pkt, nb, sendBatch)
-
 	} else {
-		f.rejectInside(packet, out, q)
+		f.rejectInside(packet, rejectBuf, q)
 		if f.l.Enabled(context.Background(), slog.LevelDebug) {
 			hostinfo.logger(f.l).Debug("dropping outbound packet",
 				"fwPacket", fwPacket,
@@ -86,6 +107,124 @@ func (f *Interface) consumeInsidePacket(packet []byte, fwPacket *firewall.Packet
 	}
 }
 
+func (f *Interface) sendInsideEncrypt(hostinfo *HostInfo, ci *ConnectionState, seg, scratch, nb []byte) []byte {
+	if noiseutil.EncryptLockNeeded {
+		ci.writeLock.Lock()
+	}
+	c := ci.messageCounter.Add(1)
+
+	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: PerSegment 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 wire.TunPacket, nb []byte, sendBatch *batch.SendBatch) {
+	ci := hostinfo.ConnectionState
+	if ci.eKey == nil {
+		return
+	}
+
+	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.Enabled(context.Background(), slog.LevelDebug) {
+			hostinfo.logger(f.l).Debug("Lighthouse update triggered for punch due to rebind counter",
+				"vpnAddrs", hostinfo.vpnAddrs,
+			)
+		}
+	}
+
+	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 = pkt.PerSegment(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
+			}
+
+			sendBatch.Commit(toSend, relayHostInfo.remote, 0)
+			return nil
+		})
+		if err != nil {
+			hostinfo.logger(f.l).Error("Failed to segment superpacket for relay send", "error", err)
+		}
+		return
+	}
+
+	err := pkt.PerSegment(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
+		}
+
+		sendBatch.Commit(out, hostinfo.remote, 0)
+		return nil
+	})
+	if err != nil {
+		hostinfo.logger(f.l).Error("Failed to segment superpacket for send",
+			"error", err,
+		)
+	}
+}
+
 func (f *Interface) rejectInside(packet []byte, out []byte, q int) {
 	if !f.firewall.InSendReject {
 		return
@@ -275,21 +414,13 @@ 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
+func (f *Interface) prepareSendVia(via *HostInfo,
-// 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,
-) {
+) ([]byte, error) {
 	if noiseutil.EncryptLockNeeded {
 		// NOTE: for goboring AESGCMTLS we need to lock because of the nonce check
 		via.ConnectionState.writeLock.Lock()
@@ -311,7 +442,7 @@ func (f *Interface) SendVia(via *HostInfo,
 			"headerLen", len(out),
 			"cipherOverhead", via.ConnectionState.eKey.Overhead(),
 		)
-		return
+		return nil, io.ErrShortBuffer
 	}
 
 	// The header bytes are written to the 'out' slice; Grow the slice to hold the header and associated data payload.
@@ -331,13 +462,36 @@ func (f *Interface) SendVia(via *HostInfo,
 	}
 	if err != nil {
 		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)
+	if err != nil {
+		via.logger(f.l).Info("Failed to prepareSendVia", "error", err)
 		return
 	}
-	err = f.writers[0].WriteTo(out, via.remote)
+	err = f.writers[0].WriteTo(toSend, via.remote)
 	if err != nil {
 		via.logger(f.l).Info("Failed to WriteTo in sendVia", "error", err)
 	}
-	f.connectionManager.RelayUsed(relay.LocalIndex)
 }
 
 func (f *Interface) sendNoMetrics(t header.MessageType, st header.MessageSubType, ci *ConnectionState, hostinfo *HostInfo, remote netip.AddrPort, p, nb, out []byte, q int) {

interface.go

@@ -4,7 +4,6 @@ import (
 	"context"
 	"errors"
 	"fmt"
-	"io"
 	"log/slog"
 	"net/netip"
 	"sync"
@@ -13,11 +12,15 @@ import (
 
 	"github.com/gaissmai/bart"
 	"github.com/rcrowley/go-metrics"
+	"github.com/slackhq/nebula/util"
+	"github.com/slackhq/nebula/wire"
 
 	"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"
 )
 
@@ -37,6 +40,7 @@ type InterfaceConfig struct {
 	DropLocalBroadcast bool
 	DropMulticast      bool
 	routines           int
+	batchSize          int
 	MessageMetrics     *MessageMetrics
 	version            string
 	relayManager       *relayManager
@@ -69,6 +73,7 @@ type Interface struct {
 	dropLocalBroadcast    bool
 	dropMulticast         bool
 	routines              int
+	batchSize             int
 	disconnectInvalid     atomic.Bool
 	closed                atomic.Bool
 	relayManager          *relayManager
@@ -88,8 +93,12 @@ type Interface struct {
 
 	ctx     context.Context
 	writers []udp.Conn
-	readers []io.ReadWriteCloser
+	readers []tio.Queue
-	wg      sync.WaitGroup
+	// 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)
@@ -185,9 +194,11 @@ func NewInterface(ctx context.Context, c *InterfaceConfig) (*Interface, error) {
 		dropLocalBroadcast:    c.DropLocalBroadcast,
 		dropMulticast:         c.DropMulticast,
 		routines:              c.routines,
+		batchSize:             c.batchSize,
 		version:               c.version,
 		writers:               make([]udp.Conn, c.routines),
-		readers:               make([]io.ReadWriteCloser, c.routines),
+		readers:               make([]tio.Queue, c.routines),
+		batchers:              make([]batch.RxBatcher, c.routines),
 		myVpnNetworks:         cs.myVpnNetworks,
 		myVpnNetworksTable:    cs.myVpnNetworksTable,
 		myVpnAddrs:            cs.myVpnAddrs,
@@ -245,15 +256,17 @@ func (f *Interface) activate() error {
 	metrics.GetOrRegisterGauge("routines", nil).Update(int64(f.routines))
 
 	// Prepare n tun queues
-	var reader io.ReadWriteCloser = f.inside
 	for i := 0; i < f.routines; i++ {
 		if i > 0 {
-			reader, err = f.inside.NewMultiQueueReader()
+			if err = f.inside.NewMultiQueueReader(); err != nil {
-			if err != nil {
 				return err
 			}
 		}
-		f.readers[i] = reader
+	}
+	f.readers = f.inside.Readers()
+	for i := range f.readers {
+		arena := util.NewArena(max(f.batchSize, 1) * udp.MTU)
+		f.batchers[i] = batch.NewPassthrough(f.readers[i], f.batchSize, arena)
 	}
 
 	f.wg.Add(1) // for us to wait on Close() to return
@@ -311,14 +324,21 @@ func (f *Interface) listenOut(i int) {
 
 	ctCache := firewall.NewConntrackCacheTicker(f.ctx, f.l, f.conntrackCacheTimeout)
 	lhh := f.lightHouse.NewRequestHandler()
-	plaintext := make([]byte, udp.MTU)
 	h := &header.H{}
 	fwPacket := &firewall.Packet{}
 	nb := make([]byte, 12, 12)
 
-	err := li.ListenOut(func(fromUdpAddr netip.AddrPort, payload []byte) {
+	listener := func(fromUdpAddr netip.AddrPort, payload []byte, meta udp.RxMeta) {
-		f.readOutsidePackets(ViaSender{UdpAddr: fromUdpAddr}, plaintext[:0], payload, h, fwPacket, lhh, nb, i, ctCache.Get())
+		f.readOutsidePackets(ViaSender{UdpAddr: fromUdpAddr}, payload, h, fwPacket, lhh, nb, i, ctCache.Get())
-	})
+	}
+
+	flusher := func() {
+		if err := f.batchers[i].Flush(); err != nil {
+			f.l.Error("Failed to flush tun coalescer", "error", err)
+		}
+	}
+
+	err := li.ListenOut(listener, flusher)
 
 	if err != nil && !f.closed.Load() {
 		f.l.Error("Error while reading inbound packet, closing", "error", err)
@@ -328,28 +348,38 @@ func (f *Interface) listenOut(i int) {
 	f.l.Debug("underlay reader is done", "reader", i)
 }
 
-func (f *Interface) listenIn(reader io.ReadWriteCloser, i int) {
+func (f *Interface) listenIn(reader tio.Queue, q int) {
-	packet := make([]byte, mtu)
+	packetMem := make([]byte, mtu+16) //MTU + some leading slack space for platforms that return "bonus info"
-	out := make([]byte, mtu)
+	// TODO get the amount of bonus info from the reader
+	packets := make([]wire.TunPacket, 1)
+	rejectBuf := make([]byte, mtu)
+	arenaSize := batch.SendBatchCap * (udp.MTU + 32)
+	sb := batch.NewSendBatch(f.writers[q], batch.SendBatchCap, util.NewArena(arenaSize))
 	fwPacket := &firewall.Packet{}
 	nb := make([]byte, 12, 12)
 
 	conntrackCache := firewall.NewConntrackCacheTicker(f.ctx, f.l, f.conntrackCacheTimeout)
 
 	for {
-		n, err := reader.Read(packet)
+		n, err := reader.Read(packets, packetMem)
 		if err != nil {
 			if !f.closed.Load() {
-				f.l.Error("Error while reading outbound packet, closing", "error", err, "reader", i)
+				f.l.Error("Error while reading outbound packet, closing", "error", err, "reader", q)
 				f.onFatal(err)
 			}
 			break
 		}
 
-		f.consumeInsidePacket(packet[:n], fwPacket, nb, out, i, conntrackCache.Get())
+		ctCache := conntrackCache.Get()
+		for i := range n {
+			f.consumeInsidePacket(packets[i], fwPacket, nb, sb, rejectBuf, q, ctCache)
+		}
+		if err := sb.Flush(); err != nil {
+			f.l.Error("Failed to write outgoing batch", "error", err, "writer", q)
+		}
 	}
 
-	f.l.Debug("overlay reader is done", "reader", i)
+	f.l.Debug("overlay reader is done", "reader", q)
 }
 
 func (f *Interface) RegisterConfigChangeCallbacks(c *config.C) {

lighthouse.go

@@ -15,7 +15,6 @@ import (
 	"time"
 
 	"github.com/gaissmai/bart"
-	"github.com/rcrowley/go-metrics"
 	"github.com/slackhq/nebula/cert"
 	"github.com/slackhq/nebula/config"
 	"github.com/slackhq/nebula/header"
@@ -35,7 +34,6 @@ type LightHouse struct {
 
 	myVpnNetworks      []netip.Prefix
 	myVpnNetworksTable *bart.Lite
-	punchConn          udp.Conn
 	punchy             *Punchy
 
 	// Local cache of answers from light houses
@@ -75,9 +73,8 @@ type LightHouse struct {
 
 	calculatedRemotes atomic.Pointer[bart.Table[[]*calculatedRemote]] // Maps VpnAddr to []*calculatedRemote
 
-	metrics           *MessageMetrics
+	metrics *MessageMetrics
-	metricHolepunchTx metrics.Counter
+	l       *slog.Logger
-	l                 *slog.Logger
 }
 
 // NewLightHouseFromConfig will build a Lighthouse struct from the values provided in the config object
@@ -105,7 +102,6 @@ func NewLightHouseFromConfig(ctx context.Context, l *slog.Logger, c *config.C, 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)),
@@ -118,9 +114,6 @@ func NewLightHouseFromConfig(ctx context.Context, l *slog.Logger, c *config.C, 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)
@@ -1406,58 +1399,25 @@ func (lhh *LightHouseHandler) handleHostPunchNotification(n *NebulaMeta, fromVpn
 		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.Enabled(context.Background(), slog.LevelDebug) {
-			lhh.l.Debug("Punching",
-				"vpnPeer", vpnPeer,
-				"logVpnAddr", 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.
+	// a tunnel. ScheduleRespond is a no-op when punchy.respond is disabled.
-	if lhh.lh.punchy.GetRespond() {
+	lhh.lh.punchy.ScheduleRespond(detailsVpnAddr)
-		go func() {
-			time.Sleep(lhh.lh.punchy.GetRespondDelay())
-			if lhh.l.Enabled(context.Background(), slog.LevelDebug) {
-				lhh.l.Debug("Sending a nebula test packet",
-					"vpnAddr", 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))
-		}()
-	}
 }
 
 func protoAddrToNetAddr(addr *Addr) netip.Addr {

main.go

@@ -55,7 +55,7 @@ func Main(c *config.C, configTest bool, buildVersion string, l *slog.Logger, dev
 	}
 	l.Info("Firewall started", "firewallHashes", fw.GetRuleHashes())
 
-	ssh, err := sshd.NewSSHServer(l.With("subsystem", "sshd"))
+	ssh, err := sshd.NewSSHServer(ctx, l.With("subsystem", "sshd"))
 	if err != nil {
 		return nil, util.ContextualizeIfNeeded("Error while creating SSH server", err)
 	}
@@ -170,7 +170,7 @@ func Main(c *config.C, configTest bool, buildVersion string, l *slog.Logger, dev
 	}
 
 	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 {
@@ -215,6 +215,7 @@ func Main(c *config.C, configTest bool, buildVersion string, l *slog.Logger, dev
 		DropLocalBroadcast:    c.GetBool("tun.drop_local_broadcast", false),
 		DropMulticast:         c.GetBool("tun.drop_multicast", false),
 		routines:              routines,
+		batchSize:             c.GetInt("listen.batch", 64),
 		MessageMetrics:        messageMetrics,
 		version:               buildVersion,
 		relayManager:          NewRelayManager(ctx, l, hostMap, c),
@@ -240,6 +241,8 @@ func Main(c *config.C, configTest bool, buildVersion string, l *slog.Logger, dev
 
 		handshakeManager.f = ifce
 		go handshakeManager.Run(ctx)
+
+		punchy.Start(ctx, ifce, hostMap, lightHouse)
 	}
 
 	stats, err := newStatsServerFromConfig(ctx, l, c, buildVersion, configTest)

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),
 	}
 }
 

noise.go

@@ -1,73 +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 cipher.AEAD
-}
-
-func NewNebulaCipherState(s *noise.CipherState) *NebulaCipherState {
-	x := s.Cipher()
-	return &NebulaCipherState{c: x.(cipher.AEAD)}
-}
-
-// 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.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.Open(out, nb, ciphertext, ad)
-	} else {
-		return []byte{}, nil
-	}
-}
-
-func (s *NebulaCipherState) Overhead() int {
-	if s != nil {
-		return s.c.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 +1,222 @@
+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
+}
+
+// TestDecryptDangerRelayShapeNoAlloc covers the AD-only relay path used in
+// outside.go's handleOutsideRelayPacket: the body is AD, the trailing 16 bytes
+// are the AEAD tag, the plaintext is empty, and the caller passes nil as the
+// destination because it only needs the auth side-effect. The call must
+// succeed, return an empty plaintext, and not allocate on the hot path.
+func TestDecryptDangerRelayShapeNoAlloc(t *testing.T) {
+	cases := []struct {
+		name string
+		c    noise.CipherFunc
+		wrap func(*noise.CipherState) CipherState
+	}{
+		{"AESGCM", CipherAESGCM, func(cs *noise.CipherState) CipherState { return NewCipherStateAESGCM(cs) }},
+		{"ChaChaPoly", noise.CipherChaChaPoly, func(cs *noise.CipherState) CipherState { return NewCipherStateChaChaPoly(cs) }},
+	}
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			encCS, decCS := buildCipherStates(t, tc.c)
+			enc, dec := tc.wrap(encCS), tc.wrap(decCS)
+
+			ad := make([]byte, 1200) // typical relay packet body size
+			for i := range ad {
+				ad[i] = byte(i)
+			}
+			nb := make([]byte, 12)
+
+			// Build the "signature value" the way handleOutsideRelayPacket sees it:
+			// empty plaintext encrypted with the body as AD yields just the 16-byte tag.
+			tag, err := enc.EncryptDanger(nil, ad, nil, 1, nb)
+			require.NoError(t, err)
+			require.Len(t, tag, dec.Overhead())
+
+			// Sanity: the relay-shaped call returns empty plaintext, no error.
+			out, err := dec.DecryptDanger(nil, ad, tag, 1, nb)
+			require.NoError(t, err)
+			assert.Empty(t, out)
+
+			// Tampering with the AD must fail authentication.
+			ad[0] ^= 0xff
+			_, err = dec.DecryptDanger(nil, ad, tag, 1, nb)
+			require.Error(t, err)
+			ad[0] ^= 0xff
+
+			// The hot path must not allocate. AllocsPerRun does a warm-up run, so any
+			// one-time setup is excluded. Counter has to advance so the AEAD nonce is
+			// unique per call, but we don't care whether the auth succeeds — we only
+			// care about whether the call path allocates.
+			var counter uint64 = 2
+			allocs := testing.AllocsPerRun(100, func() {
+				_, _ = dec.DecryptDanger(nil, ad, tag, counter, nb)
+				counter++
+			})
+			assert.Equal(t, 0.0, allocs, "DecryptDanger(nil, ...) must not allocate")
+		})
+	}
+}
+
+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

@@ -20,23 +20,46 @@ const (
 	minFwPacketLen = 4
 )
 
-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) {
+var ErrOutOfWindow = errors.New("out of window packet")
+
+func (f *Interface) readOutsidePackets(via ViaSender, packet []byte, h *header.H, fwPacket *firewall.Packet, lhf *LightHouseHandler, nb []byte, q int, localCache firewall.ConntrackCache) {
 	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.Info("Error while parsing inbound packet",
+			f.messageMetrics.RxInvalid(1)
-				"from", via,
+			if f.l.Enabled(context.Background(), slog.LevelDebug) {
-				"error", err,
+				f.l.Debug("Error while parsing inbound packet",
-				"packet", 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()) {
+			f.messageMetrics.RxInvalid(1)
 			if f.l.Enabled(context.Background(), slog.LevelDebug) {
 				f.l.Debug("Refusing to process double encrypted packet", "from", via)
 			}
@@ -44,215 +67,194 @@ func (f *Interface) readOutsidePackets(via ViaSender, out []byte, packet []byte,
 		}
 	}
 
+	// 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 isMessageRelay {
-	if h.Type == header.Message && h.Subtype == header.MessageRelay {
 		hostinfo = f.hostMap.QueryRelayIndex(h.RemoteIndex)
 	} else {
 		hostinfo = f.hostMap.QueryIndex(h.RemoteIndex)
 	}
 
-	var ci *ConnectionState
+	// At this point we should have a valid existing tunnel, verify and send
-	if hostinfo != nil {
+	// recvError if necessary
-		ci = hostinfo.ConnectionState
+	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, packet, h, fwPacket, lhf, nb, q, localCache)
+		return
+	}
+
+	out := f.batchers[q].Reserve(len(packet))[:0]
+	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) {
+			f.handleOutsideMessagePacket(hostinfo, out, packet, fwPacket, nb, q, localCache)
-				return
+		default:
-			}
+			hostinfo.logger(f.l).Error("IsValidSubType was true, but unexpected message subtype seen", "from", via, "header", h)
-		case header.MessageRelay:
+			return
-			// 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).Error("HostInfo missing remote relay index",
-					"vpnAddrs", hostinfo.vpnAddrs,
-					"remoteIndex", h.RemoteIndex,
-				)
-				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).Info("Failed to find target host info by ip",
-						"relayTo", relay.PeerAddr,
-						"error", err,
-						"hostinfo.vpnAddrs", hostinfo.vpnAddrs,
-					)
-					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).Info("Unexpected target relay state",
-						"relayTo", relay.PeerAddr,
-						"relayFrom", hostinfo.vpnAddrs[0],
-						"targetRelayState", targetRelay.State,
-					)
-					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).Error("Failed to decrypt lighthouse packet",
-				"error", err,
-				"from", via,
-				"packet", packet,
-			)
-			return
-		}
-
 		//TODO: assert via is not relayed
-		lhf.HandleRequest(via.UdpAddr, hostinfo.vpnAddrs, d, f)
+		lhf.HandleRequest(via.UdpAddr, hostinfo.vpnAddrs, out, f)
-
-		// Fallthrough to the bottom to record incoming traffic
 
 	case header.Test:
-		f.messageMetrics.Rx(h.Type, h.Subtype, 1)
+		switch h.Subtype {
-		if !f.handleEncrypted(ci, via, h) {
+		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).Error("Failed to decrypt test packet",
-				"error", err,
-				"from", via,
-				"packet", 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).Error("Failed to decrypt CloseTunnel packet",
-				"error", err,
-				"from", via,
-				"packet", packet,
-			)
-			return
-		}
-
 		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) {
+		f.relayManager.HandleControlMsg(hostinfo, out, f)
-			return
-		}
-
-		d, err := f.decrypt(hostinfo, h.MessageCounter, out, packet, h, nb)
-		if err != nil {
-			hostinfo.logger(f.l).Error("Failed to decrypt Control packet",
-				"error", err,
-				"from", via,
-				"packet", packet,
-			)
-			return
-		}
-
-		f.relayManager.HandleControlMsg(hostinfo, d, f)
 
 	default:
-		f.messageMetrics.Rx(h.Type, h.Subtype, 1)
+		hostinfo.logger(f.l).Error("IsValidSubType was true, but unexpected message type seen", "from", via, "header", h)
-		if f.l.Enabled(context.Background(), slog.LevelDebug) {
+	}
-			hostinfo.logger(f.l).Debug("Unexpected packet received", "from", via)
+}
-		}
+
+func (f *Interface) handleOutsideRelayPacket(hostinfo *HostInfo, via ViaSender, packet []byte, h *header.H, fwPacket *firewall.Packet, lhf *LightHouseHandler, nb []byte, q int, localCache firewall.ConntrackCache) {
+	// 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():]
+	// The decrypted output is empty (relay packets carry their payload as AD) and unused.
+	// The recursive readOutsidePackets call below operates on signedPayload. Passing
+	// nil avoids reserving an arena slot.
+	if _, err := hostinfo.ConnectionState.dKey.DecryptDanger(nil, signedPayload, signatureValue, h.MessageCounter, nb); 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, signedPayload, h, fwPacket, lhf, nb, q, localCache)
+	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
+				out := f.batchers[q].Reserve(len(packet) + header.Len + hostinfo.ConnectionState.dKey.Overhead())[:0]
+				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
@@ -300,23 +302,6 @@ 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")
@@ -523,38 +508,20 @@ func (f *Interface) decrypt(hostinfo *HostInfo, mc uint64, out []byte, packet []
 	}
 
 	if !hostinfo.ConnectionState.window.Update(f.l, mc) {
-		if f.l.Enabled(context.Background(), slog.LevelDebug) {
+		return nil, ErrOutOfWindow
-			hostinfo.logger(f.l).Debug("dropping out of window packet", "header", h)
-		}
-		return nil, errors.New("out of window packet")
 	}
 
 	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 {
+func (f *Interface) handleOutsideMessagePacket(hostinfo *HostInfo, out []byte, packet []byte, fwPacket *firewall.Packet, nb []byte, q int, localCache firewall.ConntrackCache) {
-	var err error
+	err := newPacket(out, true, fwPacket)
-
-	out, err = hostinfo.ConnectionState.dKey.DecryptDanger(out, packet[:header.Len], packet[header.Len:], messageCounter, nb)
-	if err != nil {
-		hostinfo.logger(f.l).Error("Failed to decrypt packet", "error", err)
-		return false
-	}
-
-	err = newPacket(out, true, fwPacket)
 	if err != nil {
 		hostinfo.logger(f.l).Warn("Error while validating inbound packet",
 			"error", err,
 			"packet", out,
 		)
-		return false
+		return
-	}
-
-	if !hostinfo.ConnectionState.window.Update(f.l, messageCounter) {
-		if f.l.Enabled(context.Background(), slog.LevelDebug) {
-			hostinfo.logger(f.l).Debug("dropping out of window packet", "fwPacket", fwPacket)
-		}
-		return false
 	}
 
 	dropReason := f.firewall.Drop(*fwPacket, true, hostinfo, f.pki.GetCAPool(), localCache)
@@ -568,15 +535,13 @@ func (f *Interface) decryptToTun(hostinfo *HostInfo, messageCounter uint64, out
 				"reason", dropReason,
 			)
 		}
-		return false
+		return
 	}
 
-	f.connectionManager.In(hostinfo)
+	err = f.batchers[q].Commit(out)
-	_, err = f.readers[q].Write(out)
 	if err != nil {
 		f.l.Error("Failed to write to tun", "error", err)
 	}
-	return true
 }
 
 func (f *Interface) maybeSendRecvError(endpoint netip.AddrPort, index uint32) {

overlay/batch/coalesce_core.go

@@ -0,0 +1,42 @@
+package batch
+
+// Arena is an injectable byte-slab that hands out non-overlapping borrowed
+// slices via Reserve and releases them in bulk via Reset. Coalescers take
+// an *Arena at construction so the caller controls the slab lifetime and
+// can share one slab across multiple coalescers (MultiCoalescer hands the
+// same *Arena to every lane so the lanes don't carry their own backings).
+//
+// Reserve borrows; the slice is valid until the next Reset. The slab grows
+// (by allocating a fresh, larger backing array) if a Reserve doesn't fit;
+// pre-size the arena via NewArena to avoid that path on the hot path.
+type Arena struct {
+	buf []byte
+}
+
+// NewArena returns an Arena with a pre-allocated backing of the given
+// capacity. Pass 0 if you don't intend to call Reserve (e.g. a test that
+// only feeds the coalescer pre-made []byte packets via Commit).
+func NewArena(capacity int) *Arena {
+	return &Arena{buf: make([]byte, 0, capacity)}
+}
+
+// Reserve hands out a non-overlapping sz-byte slice from the arena. If the
+// request doesn't fit the current backing, a fresh, larger backing is
+// allocated; already-borrowed slices reference the old backing and remain
+// valid until Reset.
+func (a *Arena) Reserve(sz int) []byte {
+	if len(a.buf)+sz > cap(a.buf) {
+		newCap := max(cap(a.buf)*2, sz)
+		a.buf = make([]byte, 0, newCap)
+	}
+	start := len(a.buf)
+	a.buf = a.buf[:start+sz]
+	return a.buf[start : start+sz : start+sz]
+}
+
+// Reset releases every slice handed out since the last Reset. Callers must
+// not use any previously-borrowed slice after this returns. The underlying
+// backing array is retained so subsequent Reserves don't re-allocate.
+func (a *Arena) Reset() {
+	a.buf = a.buf[:0]
+}

overlay/batch/passthrough.go

@@ -0,0 +1,46 @@
+package batch
+
+import (
+	"io"
+
+	"github.com/slackhq/nebula/util"
+)
+
+// Passthrough is a RxBatcher that doesn't batch anything, it just accumulates and then sends packets.
+type Passthrough struct {
+	out    io.Writer
+	slots  [][]byte
+	arena  *util.Arena
+	cursor int
+}
+
+func NewPassthrough(w io.Writer, slots int, arena *util.Arena) *Passthrough {
+	return &Passthrough{
+		out:   w,
+		slots: make([][]byte, 0, slots),
+		arena: arena,
+	}
+}
+
+func (p *Passthrough) Reserve(sz int) []byte {
+	return p.arena.Reserve(sz)
+}
+
+func (p *Passthrough) Commit(pkt []byte) error {
+	p.slots = append(p.slots, pkt)
+	return nil
+}
+
+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.arena.Reset()
+	return firstErr
+}

overlay/batch/rx_batch.go

@@ -0,0 +1,12 @@
+package batch
+
+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
+	Commit(pkt []byte) 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
+}

overlay/batch/tx_batch.go

@@ -0,0 +1,60 @@
+package batch
+
+import (
+	"net/netip"
+
+	"github.com/slackhq/nebula/util"
+)
+
+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.
+// Slot bytes are borrowed from the injected Arena and remain valid until
+// Flush, which Resets the arena.
+type SendBatch struct {
+	out   batchWriter
+	bufs  [][]byte
+	dsts  []netip.AddrPort
+	ecns  []byte
+	arena *util.Arena
+}
+
+// NewSendBatch makes a SendBatch with batchCap slots backed by arena.
+func NewSendBatch(out batchWriter, batchCap int, arena *util.Arena) *SendBatch {
+	return &SendBatch{
+		out:   out,
+		bufs:  make([][]byte, 0, batchCap),
+		dsts:  make([]netip.AddrPort, 0, batchCap),
+		ecns:  make([]byte, 0, batchCap),
+		arena: arena,
+	}
+}
+
+func (b *SendBatch) Reserve(sz int) []byte {
+	return b.arena.Reserve(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.arena.Reset()
+	return err
+}

overlay/batch/tx_batch_test.go

@@ -0,0 +1,126 @@
+package batch
+
+import (
+	"net/netip"
+	"testing"
+
+	"github.com/slackhq/nebula/util"
+)
+
+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, util.NewArena(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, util.NewArena(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, util.NewArena(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/device.go

@@ -4,15 +4,21 @@ import (
 	"io"
 	"net/netip"
 
+	"github.com/slackhq/nebula/overlay/tio"
 	"github.com/slackhq/nebula/routing"
 )
 
+// defaultBatchBufSize is the per-Queue scratch size for Read on backends
+// that don't do TSO segmentation. 65535 covers any single IP packet.
+const defaultBatchBufSize = 65535
+
 type Device interface {
-	io.ReadWriteCloser
+	io.Closer
 	Activate() error
 	Networks() []netip.Prefix
 	Name() string
 	RoutesFor(netip.Addr) routing.Gateways
 	SupportsMultiqueue() bool
-	NewMultiQueueReader() (io.ReadWriteCloser, error)
+	NewMultiQueueReader() error
+	Readers() []tio.Queue
 }

overlay/network_category_windows.go

@@ -0,0 +1,358 @@
+//go:build !e2e_testing
+// +build !e2e_testing
+
+package overlay
+
+import (
+	"errors"
+	"fmt"
+	"log/slog"
+	"runtime"
+	"strings"
+	"syscall"
+	"time"
+	"unsafe"
+
+	"golang.org/x/sys/windows"
+)
+
+// networkCategory mirrors NLM_NETWORK_CATEGORY from netlistmgr.h.
+type networkCategory int32
+
+const (
+	networkCategoryPublic              networkCategory = 0
+	networkCategoryPrivate             networkCategory = 1
+	networkCategoryDomainAuthenticated networkCategory = 2
+)
+
+func (c networkCategory) String() string {
+	switch c {
+	case networkCategoryPublic:
+		return "public"
+	case networkCategoryPrivate:
+		return "private"
+	case networkCategoryDomainAuthenticated:
+		return "domain"
+	}
+	return fmt.Sprintf("unknown(%d)", c)
+}
+
+// parseNetworkCategory accepts the user-supplied tun.network_category. A
+// second return of false means "leave the category alone".
+func parseNetworkCategory(s string) (networkCategory, bool, error) {
+	switch strings.ToLower(strings.TrimSpace(s)) {
+	case "", "unset":
+		return 0, false, nil
+	case "public":
+		return networkCategoryPublic, true, nil
+	case "private":
+		return networkCategoryPrivate, true, nil
+	case "domain", "domainauthenticated":
+		return networkCategoryDomainAuthenticated, true, nil
+	}
+	return 0, false, fmt.Errorf("unknown tun.network_category %q (expected public, private, domain, or unset)", s)
+}
+
+// CLSID_NetworkListManager {DCB00C01-570F-4A9B-8D69-199FDBA5723B}
+var clsidNetworkListManager = windows.GUID{
+	Data1: 0xDCB00C01, Data2: 0x570F, Data3: 0x4A9B,
+	Data4: [8]byte{0x8D, 0x69, 0x19, 0x9F, 0xDB, 0xA5, 0x72, 0x3B},
+}
+
+// IID_INetworkListManager {DCB00000-570F-4A9B-8D69-199FDBA5723B}
+var iidINetworkListManager = windows.GUID{
+	Data1: 0xDCB00000, Data2: 0x570F, Data3: 0x4A9B,
+	Data4: [8]byte{0x8D, 0x69, 0x19, 0x9F, 0xDB, 0xA5, 0x72, 0x3B},
+}
+
+// x/sys/windows doesn't expose CoCreateInstance, so we bind it ourselves.
+var procCoCreateInstance = windows.NewLazySystemDLL("ole32.dll").NewProc("CoCreateInstance")
+
+const clsCtxAll = windows.CLSCTX_INPROC_SERVER | windows.CLSCTX_INPROC_HANDLER |
+	windows.CLSCTX_LOCAL_SERVER | windows.CLSCTX_REMOTE_SERVER
+
+const (
+	hrSFALSE          = 0x00000001
+	hrRPCEChangedMode = 0x80010106
+)
+
+type hresult uint32
+
+func (h hresult) failed() bool { return int32(h) < 0 }
+func (h hresult) String() string {
+	return fmt.Sprintf("HRESULT 0x%08x", uint32(h))
+}
+
+var errAdapterNotFound = errors.New("adapter not present in network connections enumeration")
+
+// Vtable layouts. Slot order must match the declaration order in netlistmgr.h.
+// All NLM interfaces here derive from IDispatch, which derives from IUnknown.
+
+type iUnknownVtbl struct {
+	QueryInterface uintptr
+	AddRef         uintptr
+	Release        uintptr
+}
+
+type iDispatchVtbl struct {
+	iUnknownVtbl
+	GetTypeInfoCount uintptr
+	GetTypeInfo      uintptr
+	GetIDsOfNames    uintptr
+	Invoke           uintptr
+}
+
+type iNetworkListManagerVtbl struct {
+	iDispatchVtbl
+	GetNetworks           uintptr
+	GetNetwork            uintptr
+	GetNetworkConnections uintptr
+	GetNetworkConnection  uintptr
+	IsConnectedToInternet uintptr
+	IsConnected           uintptr
+	GetConnectivity       uintptr
+}
+
+type iNetworkListManager struct{ Vtbl *iNetworkListManagerVtbl }
+
+func (n *iNetworkListManager) Release() {
+	syscall.SyscallN(n.Vtbl.Release, uintptr(unsafe.Pointer(n)))
+}
+
+func (n *iNetworkListManager) GetNetworkConnections() (*iEnumNetworkConnections, error) {
+	var enum *iEnumNetworkConnections
+	r1, _, _ := syscall.SyscallN(n.Vtbl.GetNetworkConnections,
+		uintptr(unsafe.Pointer(n)), uintptr(unsafe.Pointer(&enum)),
+	)
+	if hr := hresult(r1); hr.failed() {
+		return nil, fmt.Errorf("INetworkListManager.GetNetworkConnections: %s", hr)
+	}
+	return enum, nil
+}
+
+type iEnumNetworkConnectionsVtbl struct {
+	iDispatchVtbl
+	NewEnum uintptr
+	Next    uintptr
+	Skip    uintptr
+	Reset   uintptr
+	Clone   uintptr
+}
+
+type iEnumNetworkConnections struct{ Vtbl *iEnumNetworkConnectionsVtbl }
+
+func (e *iEnumNetworkConnections) Release() {
+	syscall.SyscallN(e.Vtbl.Release, uintptr(unsafe.Pointer(e)))
+}
+
+// Next returns the next connection, or (nil, nil) at the end of the enumeration.
+func (e *iEnumNetworkConnections) Next() (*iNetworkConnection, error) {
+	var conn *iNetworkConnection
+	var fetched uint32
+	r1, _, _ := syscall.SyscallN(e.Vtbl.Next,
+		uintptr(unsafe.Pointer(e)), 1,
+		uintptr(unsafe.Pointer(&conn)), uintptr(unsafe.Pointer(&fetched)),
+	)
+	if hr := hresult(r1); hr.failed() {
+		return nil, fmt.Errorf("IEnumNetworkConnections.Next: %s", hr)
+	}
+	if fetched == 0 {
+		return nil, nil
+	}
+	return conn, nil
+}
+
+type iNetworkConnectionVtbl struct {
+	iDispatchVtbl
+	GetNetwork            uintptr
+	IsConnectedToInternet uintptr
+	IsConnected           uintptr
+	GetConnectivity       uintptr
+	GetConnectionId       uintptr
+	GetAdapterId          uintptr
+	GetDomainType         uintptr
+}
+
+type iNetworkConnection struct{ Vtbl *iNetworkConnectionVtbl }
+
+func (c *iNetworkConnection) Release() {
+	syscall.SyscallN(c.Vtbl.Release, uintptr(unsafe.Pointer(c)))
+}
+
+func (c *iNetworkConnection) GetAdapterId() (windows.GUID, error) {
+	var g windows.GUID
+	r1, _, _ := syscall.SyscallN(c.Vtbl.GetAdapterId,
+		uintptr(unsafe.Pointer(c)), uintptr(unsafe.Pointer(&g)),
+	)
+	if hr := hresult(r1); hr.failed() {
+		return windows.GUID{}, fmt.Errorf("INetworkConnection.GetAdapterId: %s", hr)
+	}
+	return g, nil
+}
+
+func (c *iNetworkConnection) GetNetwork() (*iNetwork, error) {
+	var net *iNetwork
+	r1, _, _ := syscall.SyscallN(c.Vtbl.GetNetwork,
+		uintptr(unsafe.Pointer(c)), uintptr(unsafe.Pointer(&net)),
+	)
+	if hr := hresult(r1); hr.failed() {
+		return nil, fmt.Errorf("INetworkConnection.GetNetwork: %s", hr)
+	}
+	return net, nil
+}
+
+type iNetworkVtbl struct {
+	iDispatchVtbl
+	GetName                    uintptr
+	SetName                    uintptr
+	GetDescription             uintptr
+	SetDescription             uintptr
+	GetNetworkId               uintptr
+	GetDomainType              uintptr
+	GetNetworkConnections      uintptr
+	GetTimeCreatedAndConnected uintptr
+	IsConnectedToInternet      uintptr
+	IsConnected                uintptr
+	GetConnectivity            uintptr
+	GetCategory                uintptr
+	SetCategory                uintptr
+}
+
+type iNetwork struct{ Vtbl *iNetworkVtbl }
+
+func (n *iNetwork) Release() {
+	syscall.SyscallN(n.Vtbl.Release, uintptr(unsafe.Pointer(n)))
+}
+
+func (n *iNetwork) GetCategory() (networkCategory, error) {
+	var c networkCategory
+	r1, _, _ := syscall.SyscallN(n.Vtbl.GetCategory,
+		uintptr(unsafe.Pointer(n)), uintptr(unsafe.Pointer(&c)),
+	)
+	if hr := hresult(r1); hr.failed() {
+		return 0, fmt.Errorf("INetwork.GetCategory: %s", hr)
+	}
+	return c, nil
+}
+
+func (n *iNetwork) SetCategory(c networkCategory) error {
+	r1, _, _ := syscall.SyscallN(n.Vtbl.SetCategory,
+		uintptr(unsafe.Pointer(n)), uintptr(int32(c)),
+	)
+	if hr := hresult(r1); hr.failed() {
+		return fmt.Errorf("INetwork.SetCategory: %s", hr)
+	}
+	return nil
+}
+
+// coInit initializes COM for the current OS thread. The returned function must
+// be deferred to balance a successful init. RPC_E_CHANGED_MODE means COM is
+// already initialized in a different mode on this thread, which is still fine
+// for our calls but we must not Uninitialize in that case.
+func coInit() (func(), error) {
+	err := windows.CoInitializeEx(0, windows.COINIT_MULTITHREADED)
+	if err == nil {
+		return windows.CoUninitialize, nil
+	}
+	if e, ok := err.(syscall.Errno); ok {
+		switch uint32(e) {
+		case hrSFALSE:
+			return windows.CoUninitialize, nil
+		case hrRPCEChangedMode:
+			return func() {}, nil
+		}
+	}
+	return nil, fmt.Errorf("CoInitializeEx: %w", err)
+}
+
+func createNetworkListManager() (*iNetworkListManager, error) {
+	var nlm *iNetworkListManager
+	r1, _, _ := procCoCreateInstance.Call(
+		uintptr(unsafe.Pointer(&clsidNetworkListManager)),
+		0,
+		uintptr(clsCtxAll),
+		uintptr(unsafe.Pointer(&iidINetworkListManager)),
+		uintptr(unsafe.Pointer(&nlm)),
+	)
+	if hr := hresult(r1); hr.failed() {
+		return nil, fmt.Errorf("CoCreateInstance(NetworkListManager): %s", hr)
+	}
+	return nlm, nil
+}
+
+// setNetworkCategory locates the network connection bound to adapterGUID and
+// sets the category of its parent network. Returns errAdapterNotFound if the
+// adapter is not yet visible in the NLM enumeration.
+func setNetworkCategory(adapterGUID windows.GUID, cat networkCategory) error {
+	deinit, err := coInit()
+	if err != nil {
+		return err
+	}
+	defer deinit()
+
+	nlm, err := createNetworkListManager()
+	if err != nil {
+		return err
+	}
+	defer nlm.Release()
+
+	enum, err := nlm.GetNetworkConnections()
+	if err != nil {
+		return err
+	}
+	defer enum.Release()
+
+	for {
+		conn, err := enum.Next()
+		if err != nil {
+			return err
+		}
+		if conn == nil {
+			return errAdapterNotFound
+		}
+
+		guid, err := conn.GetAdapterId()
+		if err != nil || guid != adapterGUID {
+			conn.Release()
+			continue
+		}
+
+		net, err := conn.GetNetwork()
+		conn.Release()
+		if err != nil {
+			return err
+		}
+		err = net.SetCategory(cat)
+		net.Release()
+		return err
+	}
+}
+
+// applyNetworkCategory polls until the wintun adapter shows up in the NLM
+// enumeration, then sets the category. Intended to run in its own goroutine.
+func applyNetworkCategory(l *slog.Logger, adapterGUID windows.GUID, cat networkCategory) {
+	// COM Init/Uninit must be paired on the same OS thread.
+	runtime.LockOSThread()
+	defer runtime.UnlockOSThread()
+
+	const (
+		attempts = 30
+		interval = 500 * time.Millisecond
+	)
+	for i := 0; i < attempts; i++ {
+		err := setNetworkCategory(adapterGUID, cat)
+		if err == nil {
+			l.Info("Set Windows network category", "category", cat.String())
+			return
+		}
+		if !errors.Is(err, errAdapterNotFound) {
+			l.Warn("Failed to set Windows network category", "error", err, "category", cat.String())
+			return
+		}
+		time.Sleep(interval)
+	}
+	l.Warn("Gave up waiting for adapter to appear in NLM enumeration; network category not set",
+		"category", cat.String(),
+		"waited", time.Duration(attempts)*interval,
+	)
+}

overlay/network_category_windows_test.go

@@ -0,0 +1,109 @@
+//go:build !e2e_testing
+// +build !e2e_testing
+
+package overlay
+
+import (
+	"testing"
+)
+
+func Test_parseNetworkCategory(t *testing.T) {
+	cases := []struct {
+		in        string
+		wantCat   networkCategory
+		wantApply bool
+		wantErr   bool
+	}{
+		{"", 0, false, false},
+		{"unset", 0, false, false},
+		{"  UNSET  ", 0, false, false},
+		{"private", networkCategoryPrivate, true, false},
+		{"Private", networkCategoryPrivate, true, false},
+		{"  PRIVATE  ", networkCategoryPrivate, true, false},
+		{"public", networkCategoryPublic, true, false},
+		{"PUBLIC", networkCategoryPublic, true, false},
+		{"domain", networkCategoryDomainAuthenticated, true, false},
+		{"DomainAuthenticated", networkCategoryDomainAuthenticated, true, false},
+		{"garbage", 0, false, true},
+		{"privates", 0, false, true},
+	}
+	for _, tc := range cases {
+		cat, apply, err := parseNetworkCategory(tc.in)
+		if (err != nil) != tc.wantErr {
+			t.Errorf("parseNetworkCategory(%q) err=%v, wantErr=%v", tc.in, err, tc.wantErr)
+			continue
+		}
+		if cat != tc.wantCat || apply != tc.wantApply {
+			t.Errorf("parseNetworkCategory(%q) = (%v, %v), want (%v, %v)", tc.in, cat, apply, tc.wantCat, tc.wantApply)
+		}
+	}
+}
+
+// Test_NLM_round_trip exercises every COM call path used by setNetworkCategory
+// without mutating the host's network state. It validates the CLSID/IID
+// constants and every vtable index by enumerating connections, fetching the
+// adapter id and parent network, reading the current category, and writing it
+// back unchanged.
+//
+// Requires Windows but does not require admin or the wintun driver. Skips if
+// no network connections are available (unlikely outside of an isolated
+// container).
+func Test_NLM_round_trip(t *testing.T) {
+	deinit, err := coInit()
+	if err != nil {
+		t.Fatalf("coInit: %v", err)
+	}
+	defer deinit()
+
+	nlm, err := createNetworkListManager()
+	if err != nil {
+		t.Fatalf("createNetworkListManager: %v", err)
+	}
+	defer nlm.Release()
+
+	enum, err := nlm.GetNetworkConnections()
+	if err != nil {
+		t.Fatalf("GetNetworkConnections: %v", err)
+	}
+	defer enum.Release()
+
+	saw := 0
+	for {
+		conn, err := enum.Next()
+		if err != nil {
+			t.Fatalf("EnumNetworkConnections.Next: %v", err)
+		}
+		if conn == nil {
+			break
+		}
+		saw++
+
+		if _, err := conn.GetAdapterId(); err != nil {
+			conn.Release()
+			t.Fatalf("INetworkConnection.GetAdapterId: %v", err)
+		}
+
+		net, err := conn.GetNetwork()
+		conn.Release()
+		if err != nil {
+			t.Fatalf("INetworkConnection.GetNetwork: %v", err)
+		}
+
+		cat, err := net.GetCategory()
+		if err != nil {
+			net.Release()
+			t.Fatalf("INetwork.GetCategory: %v", err)
+		}
+		// Set to the current value so the host's NLM state is unchanged but
+		// SetCategory's vtable slot is still validated end-to-end.
+		if err := net.SetCategory(cat); err != nil {
+			net.Release()
+			t.Fatalf("INetwork.SetCategory(%v): %v", cat, err)
+		}
+		net.Release()
+	}
+
+	if saw == 0 {
+		t.Skip("no NLM network connections available; skipping round-trip")
+	}
+}

overlay/overlaytest/noop.go

@@ -4,10 +4,11 @@ package overlaytest
 
 import (
 	"errors"
-	"io"
 	"net/netip"
 
+	"github.com/slackhq/nebula/overlay/tio"
 	"github.com/slackhq/nebula/routing"
+	"github.com/slackhq/nebula/wire"
 )
 
 // NoopTun is an overlay.Device that silently discards every read and write.
@@ -15,6 +16,10 @@ import (
 // exercise the datapath.
 type NoopTun struct{}
 
+func (NoopTun) Capabilities() tio.Capabilities {
+	return tio.Capabilities{}
+}
+
 func (NoopTun) RoutesFor(addr netip.Addr) routing.Gateways {
 	return routing.Gateways{}
 }
@@ -31,7 +36,7 @@ func (NoopTun) Name() string {
 	return "noop"
 }
 
-func (NoopTun) Read([]byte) (int, error) {
+func (NoopTun) Read(p []wire.TunPacket, mem []byte) (int, error) {
 	return 0, nil
 }
 
@@ -43,8 +48,12 @@ func (NoopTun) SupportsMultiqueue() bool {
 	return false
 }
 
-func (NoopTun) NewMultiQueueReader() (io.ReadWriteCloser, error) {
+func (NoopTun) NewMultiQueueReader() error {
-	return nil, errors.New("unsupported")
+	return errors.New("unsupported")
+}
+
+func (NoopTun) Readers() []tio.Queue {
+	return []tio.Queue{NoopTun{}}
 }
 
 func (NoopTun) Close() error {

overlay/tio/queueset_poll_linux.go

@@ -0,0 +1,80 @@
+package tio
+
+import (
+	"encoding/binary"
+	"errors"
+	"fmt"
+
+	"golang.org/x/sys/unix"
+)
+
+type pollQueueSet struct {
+	pq []*Poll
+	// pqi is exactly the same as pq, but stored as the interface type
+	pqi        []Queue
+	shutdownFd int
+}
+
+func NewPollQueueSet() (QueueSet, error) {
+	shutdownFd, err := unix.Eventfd(0, unix.EFD_NONBLOCK|unix.EFD_CLOEXEC)
+	if err != nil {
+		return nil, fmt.Errorf("failed to create eventfd: %w", err)
+	}
+
+	out := &pollQueueSet{
+		pq:         []*Poll{},
+		pqi:        []Queue{},
+		shutdownFd: shutdownFd,
+	}
+
+	return out, nil
+}
+
+func (c *pollQueueSet) Queues() []Queue {
+	return c.pqi
+}
+
+func (c *pollQueueSet) Add(fd int) error {
+	x, err := newPoll(fd, c.shutdownFd)
+	if err != nil {
+		return err
+	}
+	c.pq = append(c.pq, x)
+	c.pqi = append(c.pqi, x)
+
+	return nil
+}
+
+func (c *pollQueueSet) wakeForShutdown() error {
+	var buf [8]byte
+	binary.NativeEndian.PutUint64(buf[:], 1)
+	_, err := unix.Write(c.shutdownFd, buf[:])
+	return err
+}
+
+func (c *pollQueueSet) Close() error {
+	if c.shutdownFd < 0 {
+		return nil
+	}
+
+	errs := []error{}
+
+	if err := c.wakeForShutdown(); err != nil {
+		errs = append(errs, err)
+	}
+
+	for _, x := range c.pq {
+		if err := x.Close(); err != nil {
+			errs = append(errs, err)
+		}
+	}
+
+	// All Polls reference shutdownFd in their pollfd arrays, so close it
+	// only after every Poll.Close has returned.
+	if err := unix.Close(c.shutdownFd); err != nil {
+		errs = append(errs, err)
+	}
+	c.shutdownFd = -1
+
+	return errors.Join(errs...)
+}

overlay/tio/tio.go

@@ -0,0 +1,122 @@
+package tio
+
+import (
+	"io"
+
+	"github.com/slackhq/nebula/wire"
+)
+
+// QueueSet holds one or many Queue objects and helps close them in an orderly way.
+type QueueSet interface {
+	io.Closer
+	Queues() []Queue
+
+	// Add takes a tun fd, adds it to the set, and prepares it for use as a Queue.
+	Add(fd int) error
+}
+
+// Capabilities advertises which kernel offload features a Queue successfully negotiated.
+// Callers consult this to decide which coalescers to wire onto the write path.
+type Capabilities struct {
+	// TSO means the FD was opened with IFF_VNET_HDR and the kernel agreed
+	// to TUN_F_TSO4|TSO6 — i.e. WriteGSO with GSOProtoTCP is safe.
+	TSO bool
+	// USO means the kernel additionally agreed to TUN_F_USO4|USO6, so
+	// WriteGSO with GSOProtoUDP is safe. Linux ≥ 6.2.
+	USO bool
+}
+
+// Queue is a readable/writable Poll queue. One Queue is driven by a single
+// read goroutine plus a single writer (see Write below).
+type Queue interface {
+	io.Closer
+
+	// Read will read at least 1 packet from the tun (up to len(p)).
+	// mem will be used to provide the backing for each of p[n].Bytes.
+	// Callers should size mem and p to avoid exhausting mem before p.
+	// Returns the number of packets actually read, or error.
+	Read(p []wire.TunPacket, mem []byte) (int, error)
+
+	// Write emits a single packet on the plaintext (outside→inside)
+	// delivery path.
+	Write(p []byte) (int, error)
+
+	// Capabilities returns the Queue's negotiated offload capabilities,
+	// or the zero value when q does not advertise any.
+	Capabilities() Capabilities
+}
+
+// GSOInfo describes a kernel-supplied superpacket sitting in Packet.Bytes.
+// The zero value means "not a superpacket" — Bytes is one regular IP
+// datagram and no segmentation is required.
+type GSOInfo struct {
+	// Size is the GSO segment size: max payload bytes per segment
+	// (== TCP MSS for TSO, == UDP payload chunk for USO). Zero means
+	// not a superpacket.
+	Size uint16
+	// HdrLen is the total L3+L4 header length within Bytes (already
+	// corrected via correctHdrLen, so safe to slice on).
+	HdrLen uint16
+	// CsumStart is the L4 header offset inside Bytes (== L3 header
+	// length).
+	CsumStart uint16
+	// Proto picks the L4 protocol (TCP or UDP) so the segmenter knows
+	// which checksum/header layout to apply.
+	Proto GSOProto
+}
+
+// GSOProto selects the L4 protocol for a GSO superpacket. Determines which
+// VIRTIO_NET_HDR_GSO_* type the writer stamps and which checksum offset
+// inside the transport header virtio NEEDS_CSUM expects.
+type GSOProto uint8
+
+const (
+	GSOProtoNone GSOProto = iota
+	GSOProtoTCP
+	GSOProtoUDP
+)
+
+// GSOWriter is implemented by Queues that can emit a TCP or UDP superpacket
+// assembled from a header prefix plus one or more borrowed payload
+// fragments, in a single vectored write (writev with a leading
+// virtio_net_hdr). This lets the coalescer avoid copying payload bytes
+// between the caller's decrypt buffer and the TUN. Backends without GSO
+// support do not implement this interface and coalescing is skipped.
+//
+// hdr contains the IPv4/IPv6 header prefix (mutable - callers will have
+// filled in total length and IP csum). transportHdr is the TCP or UDP
+// header (mutable - the L4 checksum field must hold the pseudo-header
+// partial, single-fold not inverted, per virtio NEEDS_CSUM semantics).
+// pays are non-overlapping payload fragments whose concatenation is the
+// full superpacket payload; they are read-only from the writer's
+// perspective and must remain valid until the call returns. Every segment
+// in pays except possibly the last is exactly the same size. proto picks
+// the L4 protocol so the writer knows which GSOType / CsumOffset to set.
+//
+// Callers should also consult CapsProvider (via SupportsGSO or
+// QueueCapabilities) for the per-protocol negotiated capability; an
+// implementation of GSOWriter is necessary but not sufficient since USO
+// may not have been negotiated even when TSO was.
+type GSOWriter interface {
+	WriteGSO(hdr []byte, transportHdr []byte, pays [][]byte, proto GSOProto) error
+}
+
+// SupportsGSO reports whether w implements GSOWriter and the underlying
+// queue advertises the negotiated capability for `want`. A writer that
+// implements GSOWriter but not CapsProvider is treated as permissive
+// (used by tests and fakes that don't negotiate).
+func SupportsGSO(w Queue, want GSOProto) (GSOWriter, bool) {
+	gw, ok := w.(GSOWriter)
+	if !ok {
+		return nil, false
+	}
+	caps := w.Capabilities()
+	switch want {
+	case GSOProtoTCP:
+		return gw, caps.TSO
+	case GSOProtoUDP:
+		return gw, caps.USO
+	default:
+		return gw, false
+	}
+}

overlay/tio/tio_poll_linux.go

@@ -0,0 +1,168 @@
+package tio
+
+import (
+	"fmt"
+	"os"
+	"sync"
+	"sync/atomic"
+
+	"github.com/slackhq/nebula/wire"
+	"golang.org/x/sys/unix"
+)
+
+type Poll struct {
+	fd int
+
+	readPoll  [2]unix.PollFd
+	writePoll [2]unix.PollFd
+	writeLock sync.Mutex
+	closed    atomic.Bool
+}
+
+func newPoll(fd int, shutdownFd int) (*Poll, error) {
+	if err := unix.SetNonblock(fd, true); err != nil {
+		_ = unix.Close(fd)
+		return nil, fmt.Errorf("failed to set Poll device as nonblocking: %w", err)
+	}
+
+	out := &Poll{
+		fd: fd,
+		readPoll: [2]unix.PollFd{
+			{Fd: int32(fd), Events: unix.POLLIN},
+			{Fd: int32(shutdownFd), Events: unix.POLLIN},
+		},
+		writePoll: [2]unix.PollFd{
+			{Fd: int32(fd), Events: unix.POLLOUT},
+			{Fd: int32(shutdownFd), Events: unix.POLLIN},
+		},
+		writeLock: sync.Mutex{},
+	}
+	return out, nil
+}
+
+// blockOnRead waits until the Poll fd is readable or shutdown has been signaled.
+// Returns os.ErrClosed if Close was called.
+func (t *Poll) blockOnRead() error {
+	const problemFlags = unix.POLLHUP | unix.POLLNVAL | unix.POLLERR
+	var err error
+	for {
+		_, err = unix.Poll(t.readPoll[:], -1)
+		if err != unix.EINTR {
+			break
+		}
+	}
+	tunEvents := t.readPoll[0].Revents
+	shutdownEvents := t.readPoll[1].Revents
+	t.readPoll[0].Revents = 0
+	t.readPoll[1].Revents = 0
+	if err != nil {
+		return err
+	}
+	if shutdownEvents&(unix.POLLIN|problemFlags) != 0 {
+		return os.ErrClosed
+	}
+	if tunEvents&problemFlags != 0 {
+		return os.ErrClosed
+	}
+	return nil
+}
+
+func (t *Poll) blockOnWrite() error {
+	const problemFlags = unix.POLLHUP | unix.POLLNVAL | unix.POLLERR
+	var err error
+	for {
+		_, err = unix.Poll(t.writePoll[:], -1)
+		if err != unix.EINTR {
+			break
+		}
+	}
+	t.writeLock.Lock()
+	tunEvents := t.writePoll[0].Revents
+	shutdownEvents := t.writePoll[1].Revents
+	t.writePoll[0].Revents = 0
+	t.writePoll[1].Revents = 0
+	t.writeLock.Unlock()
+	if err != nil {
+		return err
+	}
+	if shutdownEvents&(unix.POLLIN|problemFlags) != 0 {
+		return os.ErrClosed
+	}
+	if tunEvents&problemFlags != 0 {
+		return os.ErrClosed
+	}
+	return nil
+}
+
+func (t *Poll) Read(p []wire.TunPacket, mem []byte) (int, error) {
+	if len(p) == 0 || len(mem) == 0 {
+		return 0, nil //todo should this be an err?
+	}
+	p[0].Meta = struct{}{}
+	n, err := t.readOne(mem)
+	if err != nil {
+		return 0, err
+	}
+	p[0].Bytes = mem[:n]
+	return 1, nil
+}
+
+func (t *Poll) readOne(to []byte) (int, error) {
+	for {
+		n, errno := unix.Read(t.fd, to)
+		if errno == nil {
+			return n, nil
+		}
+		switch errno {
+		case unix.EAGAIN:
+			if err := t.blockOnRead(); err != nil {
+				return 0, err
+			}
+		case unix.EINTR:
+			// retry
+		case unix.EBADF:
+			return 0, os.ErrClosed
+		default:
+			return 0, errno
+		}
+	}
+}
+
+func (t *Poll) Write(from []byte) (int, error) {
+	for {
+		n, errno := unix.Write(t.fd, from)
+		if errno == nil {
+			return n, nil
+		}
+		switch errno {
+		case unix.EAGAIN:
+			if err := t.blockOnWrite(); err != nil {
+				return 0, err
+			}
+		case unix.EINTR:
+			// retry
+		case unix.EBADF:
+			return 0, os.ErrClosed
+		default:
+			return 0, errno
+		}
+	}
+}
+
+func (t *Poll) Close() error {
+	if t.closed.Swap(true) {
+		return nil
+	}
+	//shutdownFd is owned by the container, so we should not close it
+	var err error
+	if t.fd >= 0 {
+		err = unix.Close(t.fd)
+		t.fd = -1
+	}
+
+	return err
+}
+
+func (t *Poll) Capabilities() Capabilities {
+	return Capabilities{}
+}

overlay/tio/tun_file_linux_test.go

@@ -0,0 +1,106 @@
+//go:build linux && !android && !e2e_testing
+// +build linux,!android,!e2e_testing
+
+package tio
+
+import (
+	"errors"
+	"os"
+	"sync"
+	"testing"
+	"time"
+
+	"github.com/slackhq/nebula/wire"
+	"github.com/stretchr/testify/require"
+	"golang.org/x/sys/unix"
+)
+
+// newReadPipe returns a read fd. The matching write fd is registered for cleanup.
+// The caller takes ownership of the read fd (pass it into a QueueSet).
+func newReadPipe(t *testing.T) int {
+	t.Helper()
+	var fds [2]int
+	if err := unix.Pipe2(fds[:], unix.O_CLOEXEC); err != nil {
+		t.Fatalf("pipe2: %v", err)
+	}
+	t.Cleanup(func() { _ = unix.Close(fds[1]) })
+	return fds[0]
+}
+
+func TestPoll_WakeForShutdown_WakesFriends(t *testing.T) {
+	parent, err := NewPollQueueSet()
+	require.NoError(t, err)
+	require.NoError(t, parent.Add(newReadPipe(t)))
+	require.NoError(t, parent.Add(newReadPipe(t)))
+	// QueueSet.Close owns the read fds we Added — don't register a separate
+	// Cleanup to close them or we'll double-close whatever fd the kernel
+	// has since reused.
+
+	readers := parent.Queues()
+	errs := make([]error, len(readers))
+	var wg sync.WaitGroup
+	for i, r := range readers {
+		wg.Add(1)
+		go func(i int, r Queue) {
+			defer wg.Done()
+			pkts := make([]wire.TunPacket, 1)
+			_, errs[i] = r.Read(pkts, make([]byte, 64))
+		}(i, r)
+	}
+
+	time.Sleep(50 * time.Millisecond)
+
+	if err := parent.Close(); err != nil {
+		t.Fatalf("Close: %v", err)
+	}
+
+	done := make(chan struct{})
+	go func() { wg.Wait(); close(done) }()
+	select {
+	case <-done:
+	case <-time.After(2 * time.Second):
+		t.Fatal("readers did not wake")
+	}
+
+	for i, err := range errs {
+		if !errors.Is(err, os.ErrClosed) {
+			t.Errorf("reader %d: expected os.ErrClosed, got %v", i, err)
+		}
+	}
+}
+
+func TestPoll_Close_Idempotent(t *testing.T) {
+	shutdownFd, err := unix.Eventfd(0, unix.EFD_NONBLOCK|unix.EFD_CLOEXEC)
+	require.NoError(t, err)
+	t.Cleanup(func() { _ = unix.Close(shutdownFd) })
+
+	tf, err := newPoll(newReadPipe(t), shutdownFd)
+	require.NoError(t, err)
+	if err := tf.Close(); err != nil {
+		t.Fatalf("first Close: %v", err)
+	}
+	if err := tf.Close(); err != nil {
+		t.Fatalf("second Close should be a no-op, got %v", err)
+	}
+}
+
+func TestPollQueueSet_Close_ClosesEventfd(t *testing.T) {
+	qs, err := NewPollQueueSet()
+	require.NoError(t, err)
+	require.NoError(t, qs.Add(newReadPipe(t)))
+
+	fd := qs.(*pollQueueSet).shutdownFd
+	require.NoError(t, qs.Close())
+
+	// Closing the eventfd again should fail with EBADF, proving Close
+	// actually released it.
+	if err := unix.Close(fd); err == nil {
+		t.Fatalf("eventfd %d still open after QueueSet.Close", fd)
+	}
+
+	// Second Close must be a no-op (and must not double-close the eventfd
+	// in case the kernel handed it out to another caller in the meantime).
+	if err := qs.Close(); err != nil {
+		t.Fatalf("second Close: %v", err)
+	}
+}

overlay/tun_android.go

@@ -13,12 +13,14 @@ import (
 
 	"github.com/gaissmai/bart"
 	"github.com/slackhq/nebula/config"
+	"github.com/slackhq/nebula/overlay/tio"
 	"github.com/slackhq/nebula/routing"
 	"github.com/slackhq/nebula/util"
+	"github.com/slackhq/nebula/wire"
 )
 
 type tun struct {
-	io.ReadWriteCloser
+	rwc         io.ReadWriteCloser
 	fd          int
 	vpnNetworks []netip.Prefix
 	Routes      atomic.Pointer[[]Route]
@@ -26,16 +28,37 @@ type tun struct {
 	l           *slog.Logger
 }
 
+func (t *tun) Read(p []wire.TunPacket, mem []byte) (int, error) {
+	if len(p) == 0 || len(mem) == 0 {
+		return 0, nil //todo should this be an err?
+	}
+	p[0].Meta = struct{}{}
+	n, err := t.rwc.Read(mem)
+	if err != nil {
+		return 0, err
+	}
+	p[0].Bytes = mem[:n]
+	return 1, nil
+}
+
+func (t *tun) Write(p []byte) (int, error) {
+	return t.rwc.Write(p)
+}
+
+func (t *tun) Close() error {
+	return t.rwc.Close()
+}
+
 func newTunFromFd(c *config.C, l *slog.Logger, deviceFd int, vpnNetworks []netip.Prefix) (*tun, error) {
 	// XXX Android returns an fd in non-blocking mode which is necessary for shutdown to work properly.
 	// Be sure not to call file.Fd() as it will set the fd to blocking mode.
 	file := os.NewFile(uintptr(deviceFd), "/dev/net/tun")
 
 	t := &tun{
-		ReadWriteCloser: file,
+		rwc:         file,
-		fd:              deviceFd,
+		fd:          deviceFd,
-		vpnNetworks:     vpnNetworks,
+		vpnNetworks: vpnNetworks,
-		l:               l,
+		l:           l,
 	}
 
 	err := t.reload(c, true)
@@ -62,7 +85,7 @@ func (t *tun) RoutesFor(ip netip.Addr) routing.Gateways {
 	return r
 }
 
-func (t tun) Activate() error {
+func (t *tun) Activate() error {
 	return nil
 }
 
@@ -99,6 +122,14 @@ func (t *tun) SupportsMultiqueue() bool {
 	return false
 }
 
-func (t *tun) NewMultiQueueReader() (io.ReadWriteCloser, error) {
+func (t *tun) NewMultiQueueReader() error {
-	return nil, fmt.Errorf("TODO: multiqueue not implemented for android")
+	return fmt.Errorf("TODO: multiqueue not implemented for android")
+}
+
+func (t *tun) Readers() []tio.Queue {
+	return []tio.Queue{t}
+}
+
+func (t *tun) Capabilities() tio.Capabilities {
+	return tio.Capabilities{}
 }

overlay/tun_bypass_windows.go

@@ -0,0 +1,23 @@
+//go:build (amd64 || arm64) && !e2e_testing
+// +build amd64 arm64
+// +build !e2e_testing
+
+package overlay
+
+import (
+	"log/slog"
+
+	"github.com/slackhq/nebula/wfp"
+)
+
+// installInterfaceBypass installs a WFP PERMIT filter scoped to the wintun interface LUID so inbound traffic on the
+// nebula adapter bypasses Windows Defender Firewall.
+func installInterfaceBypass(l *slog.Logger, luid uint64) closer {
+	s, err := wfp.PermitInterface(luid)
+	if err != nil {
+		l.Warn("Failed to install WFP bypass filters on nebula interface", "error", err)
+		return nil
+	}
+	l.Info("Installed WFP filters bypassing Windows Defender Firewall on nebula interface")
+	return s
+}

overlay/tun_bypass_windows_386.go

@@ -0,0 +1,11 @@
+//go:build !e2e_testing
+// +build !e2e_testing
+
+package overlay
+
+import "log/slog"
+
+// installInterfaceBypass is a no-op on windows-386 because we don't currently build for it.
+func installInterfaceBypass(_ *slog.Logger, _ uint64) closer {
+	return nil
+}

overlay/tun_darwin.go

@@ -16,14 +16,16 @@ import (
 
 	"github.com/gaissmai/bart"
 	"github.com/slackhq/nebula/config"
+	"github.com/slackhq/nebula/overlay/tio"
 	"github.com/slackhq/nebula/routing"
 	"github.com/slackhq/nebula/util"
+	"github.com/slackhq/nebula/wire"
 	netroute "golang.org/x/net/route"
 	"golang.org/x/sys/unix"
 )
 
 type tun struct {
-	io.ReadWriteCloser
+	rwc         io.ReadWriteCloser
 	Device      string
 	vpnNetworks []netip.Prefix
 	DefaultMTU  int
@@ -124,11 +126,11 @@ func newTun(c *config.C, l *slog.Logger, vpnNetworks []netip.Prefix, _ bool) (*t
 	}
 
 	t := &tun{
-		ReadWriteCloser: os.NewFile(uintptr(fd), ""),
+		rwc:         os.NewFile(uintptr(fd), ""),
-		Device:          name,
+		Device:      name,
-		vpnNetworks:     vpnNetworks,
+		vpnNetworks: vpnNetworks,
-		DefaultMTU:      c.GetInt("tun.mtu", DefaultMTU),
+		DefaultMTU:  c.GetInt("tun.mtu", DefaultMTU),
-		l:               l,
+		l:           l,
 	}
 
 	err = t.reload(c, true)
@@ -158,8 +160,8 @@ func newTunFromFd(_ *config.C, _ *slog.Logger, _ int, _ []netip.Prefix) (*tun, e
 }
 
 func (t *tun) Close() error {
-	if t.ReadWriteCloser != nil {
+	if t.rwc != nil {
-		return t.ReadWriteCloser.Close()
+		return t.rwc.Close()
 	}
 	return nil
 }
@@ -502,13 +504,17 @@ func delRoute(prefix netip.Prefix, gateway netroute.Addr) error {
 	return nil
 }
 
-func (t *tun) Read(to []byte) (int, error) {
+func (t *tun) Read(p []wire.TunPacket, mem []byte) (int, error) {
-	buf := make([]byte, len(to)+4)
+	if len(p) == 0 || len(mem) <= 4 {
-
+		return 0, nil //todo should this be an err?
-	n, err := t.ReadWriteCloser.Read(buf)
+	}
-
+	p[0].Meta = struct{}{}
-	copy(to, buf[4:])
+	n, err := t.rwc.Read(mem)
-	return n - 4, err
+	if err != nil {
+		return 0, err
+	}
+	p[0].Bytes = mem[4:n]
+	return 1, nil
 }
 
 // Write is only valid for single threaded use
@@ -536,7 +542,7 @@ func (t *tun) Write(from []byte) (int, error) {
 
 	copy(buf[4:], from)
 
-	n, err := t.ReadWriteCloser.Write(buf)
+	n, err := t.rwc.Write(buf)
 	return n - 4, err
 }
 
@@ -552,6 +558,14 @@ func (t *tun) SupportsMultiqueue() bool {
 	return false
 }
 
-func (t *tun) NewMultiQueueReader() (io.ReadWriteCloser, error) {
+func (t *tun) NewMultiQueueReader() error {
-	return nil, fmt.Errorf("TODO: multiqueue not implemented for darwin")
+	return fmt.Errorf("TODO: multiqueue not implemented for darwin")
+}
+
+func (t *tun) Readers() []tio.Queue {
+	return []tio.Queue{t}
+}
+
+func (t *tun) Capabilities() tio.Capabilities {
+	return tio.Capabilities{}
 }

overlay/tun_disabled.go

@@ -10,7 +10,9 @@ import (
 
 	"github.com/rcrowley/go-metrics"
 	"github.com/slackhq/nebula/iputil"
+	"github.com/slackhq/nebula/overlay/tio"
 	"github.com/slackhq/nebula/routing"
+	"github.com/slackhq/nebula/wire"
 )
 
 type disabledTun struct {
@@ -18,9 +20,10 @@ type disabledTun struct {
 	vpnNetworks []netip.Prefix
 
 	// Track these metrics since we don't have the tun device to do it for us
-	tx metrics.Counter
+	tx         metrics.Counter
-	rx metrics.Counter
+	rx         metrics.Counter
-	l  *slog.Logger
+	numReaders int
+	l          *slog.Logger
 }
 
 func newDisabledTun(vpnNetworks []netip.Prefix, queueLen int, metricsEnabled bool, l *slog.Logger) *disabledTun {
@@ -28,6 +31,7 @@ func newDisabledTun(vpnNetworks []netip.Prefix, queueLen int, metricsEnabled boo
 		vpnNetworks: vpnNetworks,
 		read:        make(chan []byte, queueLen),
 		l:           l,
+		numReaders:  1,
 	}
 
 	if metricsEnabled {
@@ -57,7 +61,7 @@ func (*disabledTun) Name() string {
 	return "disabled"
 }
 
-func (t *disabledTun) Read(b []byte) (int, error) {
+func (t *disabledTun) readOne(b []byte) (int, error) {
 	r, ok := <-t.read
 	if !ok {
 		return 0, io.EOF
@@ -75,6 +79,19 @@ func (t *disabledTun) Read(b []byte) (int, error) {
 	return copy(b, r), nil
 }
 
+func (t *disabledTun) Read(p []wire.TunPacket, mem []byte) (int, error) {
+	if len(p) == 0 || len(mem) == 0 {
+		return 0, nil //todo should this be an err?
+	}
+	p[0].Meta = struct{}{}
+	n, err := t.readOne(mem)
+	if err != nil {
+		return 0, err
+	}
+	p[0].Bytes = mem[:n]
+	return 1, nil
+}
+
 func (t *disabledTun) handleICMPEchoRequest(b []byte) bool {
 	out := make([]byte, len(b))
 	out = iputil.CreateICMPEchoResponse(b, out)
@@ -110,8 +127,21 @@ func (t *disabledTun) SupportsMultiqueue() bool {
 	return true
 }
 
-func (t *disabledTun) NewMultiQueueReader() (io.ReadWriteCloser, error) {
+func (t *disabledTun) NewMultiQueueReader() error {
-	return t, nil
+	t.numReaders++
+	return nil
+}
+
+func (t *disabledTun) Readers() []tio.Queue {
+	out := make([]tio.Queue, t.numReaders)
+	for i := range t.numReaders {
+		out[i] = t
+	}
+	return out
+}
+
+func (t *disabledTun) Capabilities() tio.Capabilities {
+	return tio.Capabilities{}
 }
 
 func (t *disabledTun) Close() error {

overlay/tun_file_linux_test.go

@@ -1,120 +0,0 @@
-//go:build linux && !android && !e2e_testing
-// +build linux,!android,!e2e_testing
-
-package overlay
-
-import (
-	"errors"
-	"os"
-	"sync"
-	"testing"
-	"time"
-
-	"golang.org/x/sys/unix"
-)
-
-// newReadPipe returns a read fd. The matching write fd is registered for cleanup.
-// The caller takes ownership of the read fd (pass it to newTunFd / newFriend).
-func newReadPipe(t *testing.T) int {
-	t.Helper()
-	var fds [2]int
-	if err := unix.Pipe2(fds[:], unix.O_CLOEXEC); err != nil {
-		t.Fatalf("pipe2: %v", err)
-	}
-	t.Cleanup(func() { _ = unix.Close(fds[1]) })
-	return fds[0]
-}
-
-func TestTunFile_WakeForShutdown_UnblocksRead(t *testing.T) {
-	tf, err := newTunFd(newReadPipe(t))
-	if err != nil {
-		t.Fatalf("newTunFd: %v", err)
-	}
-	t.Cleanup(func() { _ = tf.Close() })
-
-	done := make(chan error, 1)
-	go func() {
-		_, err := tf.Read(make([]byte, 64))
-		done <- err
-	}()
-
-	// Verify Read is actually blocked in poll.
-	select {
-	case err := <-done:
-		t.Fatalf("Read returned before shutdown signal: %v", err)
-	case <-time.After(50 * time.Millisecond):
-	}
-
-	if err := tf.wakeForShutdown(); err != nil {
-		t.Fatalf("wakeForShutdown: %v", err)
-	}
-
-	select {
-	case err := <-done:
-		if !errors.Is(err, os.ErrClosed) {
-			t.Fatalf("expected os.ErrClosed, got %v", err)
-		}
-	case <-time.After(2 * time.Second):
-		t.Fatal("Read did not wake on shutdown")
-	}
-}
-
-func TestTunFile_WakeForShutdown_WakesFriends(t *testing.T) {
-	parent, err := newTunFd(newReadPipe(t))
-	if err != nil {
-		t.Fatalf("newTunFd: %v", err)
-	}
-	friend, err := parent.newFriend(newReadPipe(t))
-	if err != nil {
-		_ = parent.Close()
-		t.Fatalf("newFriend: %v", err)
-	}
-	t.Cleanup(func() {
-		_ = friend.Close()
-		_ = parent.Close()
-	})
-
-	readers := []*tunFile{parent, friend}
-	errs := make([]error, len(readers))
-	var wg sync.WaitGroup
-	for i, r := range readers {
-		wg.Add(1)
-		go func(i int, r *tunFile) {
-			defer wg.Done()
-			_, errs[i] = r.Read(make([]byte, 64))
-		}(i, r)
-	}
-
-	time.Sleep(50 * time.Millisecond)
-
-	if err := parent.wakeForShutdown(); err != nil {
-		t.Fatalf("wakeForShutdown: %v", err)
-	}
-
-	done := make(chan struct{})
-	go func() { wg.Wait(); close(done) }()
-	select {
-	case <-done:
-	case <-time.After(2 * time.Second):
-		t.Fatal("readers did not wake")
-	}
-
-	for i, err := range errs {
-		if !errors.Is(err, os.ErrClosed) {
-			t.Errorf("reader %d: expected os.ErrClosed, got %v", i, err)
-		}
-	}
-}
-
-func TestTunFile_Close_Idempotent(t *testing.T) {
-	tf, err := newTunFd(newReadPipe(t))
-	if err != nil {
-		t.Fatalf("newTunFd: %v", err)
-	}
-	if err := tf.Close(); err != nil {
-		t.Fatalf("first Close: %v", err)
-	}
-	if err := tf.Close(); err != nil {
-		t.Fatalf("second Close should be a no-op, got %v", err)
-	}
-}

overlay/tun_freebsd.go

@@ -7,7 +7,6 @@ import (
 	"bytes"
 	"errors"
 	"fmt"
-	"io"
 	"io/fs"
 	"log/slog"
 	"net/netip"
@@ -18,9 +17,10 @@ import (
 	"unsafe"
 
 	"github.com/gaissmai/bart"
+	"github.com/slackhq/nebula/wire"
 
 	"github.com/slackhq/nebula/config"
-
+	"github.com/slackhq/nebula/overlay/tio"
 	"github.com/slackhq/nebula/routing"
 	"github.com/slackhq/nebula/util"
 	netroute "golang.org/x/net/route"
@@ -157,7 +157,20 @@ func (t *tun) blockOnWrite() error {
 	return nil
 }
 
-func (t *tun) Read(to []byte) (int, error) {
+func (t *tun) Read(p []wire.TunPacket, mem []byte) (int, error) {
+	if len(p) == 0 || len(mem) == 0 {
+		return 0, nil //todo should this be an err?
+	}
+	p[0].Meta = struct{}{}
+	n, err := t.readOne(mem)
+	if err != nil {
+		return 0, err
+	}
+	p[0].Bytes = mem[:n]
+	return 1, nil
+}
+
+func (t *tun) readOne(to []byte) (int, error) {
 	// first 4 bytes is protocol family, in network byte order
 	var head [4]byte
 	iovecs := [2]syscall.Iovec{
@@ -565,8 +578,8 @@ func (t *tun) SupportsMultiqueue() bool {
 	return false
 }
 
-func (t *tun) NewMultiQueueReader() (io.ReadWriteCloser, error) {
+func (t *tun) NewMultiQueueReader() error {
-	return nil, fmt.Errorf("TODO: multiqueue not implemented for freebsd")
+	return fmt.Errorf("TODO: multiqueue not implemented for freebsd")
 }
 
 func (t *tun) addRoutes(logErrors bool) error {
@@ -593,6 +606,14 @@ func (t *tun) addRoutes(logErrors bool) error {
 	return nil
 }
 
+func (t *tun) Readers() []tio.Queue {
+	return []tio.Queue{t}
+}
+
+func (t *tun) Capabilities() tio.Capabilities {
+	return tio.Capabilities{}
+}
+
 func (t *tun) removeRoutes(routes []Route) error {
 	for _, r := range routes {
 		if !r.Install {

overlay/tun_ios.go

@@ -16,18 +16,41 @@ import (
 
 	"github.com/gaissmai/bart"
 	"github.com/slackhq/nebula/config"
+	"github.com/slackhq/nebula/overlay/tio"
 	"github.com/slackhq/nebula/routing"
 	"github.com/slackhq/nebula/util"
+	"github.com/slackhq/nebula/wire"
 )
 
 type tun struct {
-	io.ReadWriteCloser
+	rwc         io.ReadWriteCloser
 	vpnNetworks []netip.Prefix
 	Routes      atomic.Pointer[[]Route]
 	routeTree   atomic.Pointer[bart.Table[routing.Gateways]]
 	l           *slog.Logger
 }
 
+func (t *tun) Read(p []wire.TunPacket, mem []byte) (int, error) {
+	if len(p) == 0 || len(mem) <= 4 {
+		return 0, nil //todo should this be an err?
+	}
+	p[0].Meta = struct{}{}
+	n, err := t.rwc.Read(mem)
+	if err != nil {
+		return 0, err
+	}
+	p[0].Bytes = mem[4:n]
+	return 1, nil
+}
+
+func (t *tun) Write(p []byte) (int, error) {
+	return t.rwc.Write(p)
+}
+
+func (t *tun) Close() error {
+	return t.rwc.Close()
+}
+
 func newTun(_ *config.C, _ *slog.Logger, _ []netip.Prefix, _ bool) (*tun, error) {
 	return nil, fmt.Errorf("newTun not supported in iOS")
 }
@@ -35,9 +58,9 @@ func newTun(_ *config.C, _ *slog.Logger, _ []netip.Prefix, _ bool) (*tun, error)
 func newTunFromFd(c *config.C, l *slog.Logger, deviceFd int, vpnNetworks []netip.Prefix) (*tun, error) {
 	file := os.NewFile(uintptr(deviceFd), "/dev/tun")
 	t := &tun{
-		vpnNetworks:     vpnNetworks,
+		vpnNetworks: vpnNetworks,
-		ReadWriteCloser: &tunReadCloser{f: file},
+		rwc:         &tunReadCloser{f: file},
-		l:               l,
+		l:           l,
 	}
 
 	err := t.reload(c, true)
@@ -96,18 +119,9 @@ type tunReadCloser struct {
 	wBuf []byte
 }
 
+// Read returns a packet with the BSD 4-byte header, watch out!
 func (tr *tunReadCloser) Read(to []byte) (int, error) {
-	tr.rMu.Lock()
+	return tr.f.Read(to)
-	defer tr.rMu.Unlock()
-
-	if cap(tr.rBuf) < len(to)+4 {
-		tr.rBuf = make([]byte, len(to)+4)
-	}
-	tr.rBuf = tr.rBuf[:len(to)+4]
-
-	n, err := tr.f.Read(tr.rBuf)
-	copy(to, tr.rBuf[4:])
-	return n - 4, err
 }
 
 func (tr *tunReadCloser) Write(from []byte) (int, error) {
@@ -155,6 +169,14 @@ func (t *tun) SupportsMultiqueue() bool {
 	return false
 }
 
-func (t *tun) NewMultiQueueReader() (io.ReadWriteCloser, error) {
+func (t *tun) NewMultiQueueReader() error {
-	return nil, fmt.Errorf("TODO: multiqueue not implemented for ios")
+	return fmt.Errorf("TODO: multiqueue not implemented for ios")
+}
+
+func (t *tun) Readers() []tio.Queue {
+	return []tio.Queue{t}
+}
+
+func (t *tun) Capabilities() tio.Capabilities {
+	return tio.Capabilities{}
 }

overlay/tun_linux.go

@@ -4,9 +4,7 @@
 package overlay
 
 import (
-	"encoding/binary"
 	"fmt"
-	"io"
 	"log/slog"
 	"net"
 	"net/netip"
@@ -19,180 +17,15 @@ import (
 
 	"github.com/gaissmai/bart"
 	"github.com/slackhq/nebula/config"
+	"github.com/slackhq/nebula/overlay/tio"
 	"github.com/slackhq/nebula/routing"
 	"github.com/slackhq/nebula/util"
 	"github.com/vishvananda/netlink"
 	"golang.org/x/sys/unix"
 )
 
-// tunFile wraps a TUN file descriptor with poll-based reads. The FD provided will be changed to non-blocking.
-// A shared eventfd allows Close to wake all readers blocked in poll.
-type tunFile struct {
-	fd         int
-	shutdownFd int
-	lastOne    bool
-	readPoll   [2]unix.PollFd
-	writePoll  [2]unix.PollFd
-	closed     bool
-}
-
-// newFriend makes a tunFile for a MultiQueueReader that copies the shutdown eventfd from the parent tun
-func (r *tunFile) newFriend(fd int) (*tunFile, error) {
-	if err := unix.SetNonblock(fd, true); err != nil {
-		return nil, fmt.Errorf("failed to set tun fd non-blocking: %w", err)
-	}
-	return &tunFile{
-		fd:         fd,
-		shutdownFd: r.shutdownFd,
-		readPoll: [2]unix.PollFd{
-			{Fd: int32(fd), Events: unix.POLLIN},
-			{Fd: int32(r.shutdownFd), Events: unix.POLLIN},
-		},
-		writePoll: [2]unix.PollFd{
-			{Fd: int32(fd), Events: unix.POLLOUT},
-			{Fd: int32(r.shutdownFd), Events: unix.POLLIN},
-		},
-	}, nil
-}
-
-func newTunFd(fd int) (*tunFile, error) {
-	if err := unix.SetNonblock(fd, true); err != nil {
-		return nil, fmt.Errorf("failed to set tun fd non-blocking: %w", err)
-	}
-
-	shutdownFd, err := unix.Eventfd(0, unix.EFD_NONBLOCK|unix.EFD_CLOEXEC)
-	if err != nil {
-		return nil, fmt.Errorf("failed to create eventfd: %w", err)
-	}
-
-	out := &tunFile{
-		fd:         fd,
-		shutdownFd: shutdownFd,
-		lastOne:    true,
-		readPoll: [2]unix.PollFd{
-			{Fd: int32(fd), Events: unix.POLLIN},
-			{Fd: int32(shutdownFd), Events: unix.POLLIN},
-		},
-		writePoll: [2]unix.PollFd{
-			{Fd: int32(fd), Events: unix.POLLOUT},
-			{Fd: int32(shutdownFd), Events: unix.POLLIN},
-		},
-	}
-
-	return out, nil
-}
-
-func (r *tunFile) blockOnRead() error {
-	const problemFlags = unix.POLLHUP | unix.POLLNVAL | unix.POLLERR
-	var err error
-	for {
-		_, err = unix.Poll(r.readPoll[:], -1)
-		if err != unix.EINTR {
-			break
-		}
-	}
-	//always reset these!
-	tunEvents := r.readPoll[0].Revents
-	shutdownEvents := r.readPoll[1].Revents
-	r.readPoll[0].Revents = 0
-	r.readPoll[1].Revents = 0
-	//do the err check before trusting the potentially bogus bits we just got
-	if err != nil {
-		return err
-	}
-	if shutdownEvents&(unix.POLLIN|problemFlags) != 0 {
-		return os.ErrClosed
-	} else if tunEvents&problemFlags != 0 {
-		return os.ErrClosed
-	}
-	return nil
-}
-
-func (r *tunFile) blockOnWrite() error {
-	const problemFlags = unix.POLLHUP | unix.POLLNVAL | unix.POLLERR
-	var err error
-	for {
-		_, err = unix.Poll(r.writePoll[:], -1)
-		if err != unix.EINTR {
-			break
-		}
-	}
-	//always reset these!
-	tunEvents := r.writePoll[0].Revents
-	shutdownEvents := r.writePoll[1].Revents
-	r.writePoll[0].Revents = 0
-	r.writePoll[1].Revents = 0
-	//do the err check before trusting the potentially bogus bits we just got
-	if err != nil {
-		return err
-	}
-	if shutdownEvents&(unix.POLLIN|problemFlags) != 0 {
-		return os.ErrClosed
-	} else if tunEvents&problemFlags != 0 {
-		return os.ErrClosed
-	}
-	return nil
-}
-
-func (r *tunFile) Read(buf []byte) (int, error) {
-	for {
-		if n, err := unix.Read(r.fd, buf); err == nil {
-			return n, nil
-		} else if err == unix.EAGAIN {
-			if err = r.blockOnRead(); err != nil {
-				return 0, err
-			}
-			continue
-		} else if err == unix.EINTR {
-			continue
-		} else if err == unix.EBADF {
-			return 0, os.ErrClosed
-		} else {
-			return 0, err
-		}
-	}
-}
-
-func (r *tunFile) Write(buf []byte) (int, error) {
-	for {
-		if n, err := unix.Write(r.fd, buf); err == nil {
-			return n, nil
-		} else if err == unix.EAGAIN {
-			if err = r.blockOnWrite(); err != nil {
-				return 0, err
-			}
-			continue
-		} else if err == unix.EINTR {
-			continue
-		} else if err == unix.EBADF {
-			return 0, os.ErrClosed
-		} else {
-			return 0, err
-		}
-	}
-}
-
-func (r *tunFile) wakeForShutdown() error {
-	var buf [8]byte
-	binary.NativeEndian.PutUint64(buf[:], 1)
-	_, err := unix.Write(int(r.readPoll[1].Fd), buf[:])
-	return err
-}
-
-func (r *tunFile) Close() error {
-	if r.closed { // avoid closing more than once. Technically a fd could get re-used, which would be a problem
-		return nil
-	}
-	r.closed = true
-	if r.lastOne {
-		_ = unix.Close(r.shutdownFd)
-	}
-	return unix.Close(r.fd)
-}
-
 type tun struct {
-	*tunFile
+	readers     tio.QueueSet
-	readers     []*tunFile
 	closeLock   sync.Mutex
 	Device      string
 	vpnNetworks []netip.Prefix
@@ -239,7 +72,9 @@ type ifreqQLEN struct {
 }
 
 func newTunFromFd(c *config.C, l *slog.Logger, deviceFd int, vpnNetworks []netip.Prefix) (*tun, error) {
-	t, err := newTunGeneric(c, l, deviceFd, vpnNetworks)
+	// We don't know what flags the caller opened this fd with and can't turn
+	// on IFF_VNET_HDR after TUNSETIFF, so skip offload on inherited fds.
+	t, err := newTunGeneric(c, l, deviceFd, false, false, vpnNetworks)
 	if err != nil {
 		return nil, err
 	}
@@ -249,46 +84,60 @@ func newTunFromFd(c *config.C, l *slog.Logger, deviceFd int, vpnNetworks []netip
 	return t, nil
 }
 
-func newTun(c *config.C, l *slog.Logger, vpnNetworks []netip.Prefix, multiqueue bool) (*tun, error) {
+// openTunDev opens /dev/net/tun, creating the device node first if it's
+// missing (docker containers occasionally omit it).
+func openTunDev() (int, error) {
 	fd, err := unix.Open("/dev/net/tun", os.O_RDWR, 0)
-	if err != nil {
+	if err == nil {
-		// If /dev/net/tun doesn't exist, try to create it (will happen in docker)
+		return fd, nil
-		if os.IsNotExist(err) {
-			err = os.MkdirAll("/dev/net", 0755)
-			if err != nil {
-				return nil, fmt.Errorf("/dev/net/tun doesn't exist, failed to mkdir -p /dev/net: %w", err)
-			}
-			err = unix.Mknod("/dev/net/tun", unix.S_IFCHR|0600, int(unix.Mkdev(10, 200)))
-			if err != nil {
-				return nil, fmt.Errorf("failed to create /dev/net/tun: %w", err)
-			}
-
-			fd, err = unix.Open("/dev/net/tun", os.O_RDWR, 0)
-			if err != nil {
-				return nil, fmt.Errorf("created /dev/net/tun, but still failed: %w", err)
-			}
-		} else {
-			return nil, err
-		}
 	}
+	if !os.IsNotExist(err) {
+		return -1, err
+	}
+	if err = os.MkdirAll("/dev/net", 0755); err != nil {
+		return -1, fmt.Errorf("/dev/net/tun doesn't exist, failed to mkdir -p /dev/net: %w", err)
+	}
+	if err = unix.Mknod("/dev/net/tun", unix.S_IFCHR|0600, int(unix.Mkdev(10, 200))); err != nil {
+		return -1, fmt.Errorf("failed to create /dev/net/tun: %w", err)
+	}
+	fd, err = unix.Open("/dev/net/tun", os.O_RDWR, 0)
+	if err != nil {
+		return -1, fmt.Errorf("created /dev/net/tun, but still failed: %w", err)
+	}
+	return fd, nil
+}
 
+// tunSetIff runs TUNSETIFF with the given flags and returns the kernel-chosen
+// device name on success.
+func tunSetIff(fd int, name string, flags uint16) (string, error) {
 	var req ifReq
-	req.Flags = uint16(unix.IFF_TUN | unix.IFF_NO_PI)
+	req.Flags = flags
+	copy(req.Name[:], name)
+	if err := ioctl(uintptr(fd), uintptr(unix.TUNSETIFF), uintptr(unsafe.Pointer(&req))); err != nil {
+		return "", err
+	}
+	return strings.Trim(string(req.Name[:]), "\x00"), nil
+}
+
+func newTun(c *config.C, l *slog.Logger, vpnNetworks []netip.Prefix, multiqueue bool) (*tun, error) {
+	baseFlags := uint16(unix.IFF_TUN | unix.IFF_NO_PI)
 	if multiqueue {
-		req.Flags |= unix.IFF_MULTI_QUEUE
+		baseFlags |= unix.IFF_MULTI_QUEUE
 	}
 	nameStr := c.GetString("tun.dev", "")
-	copy(req.Name[:], nameStr)
-	if err = ioctl(uintptr(fd), uintptr(unix.TUNSETIFF), uintptr(unsafe.Pointer(&req))); err != nil {
-		_ = unix.Close(fd)
-		return nil, &NameError{
-			Name:       nameStr,
-			Underlying: err,
-		}
-	}
-	name := strings.Trim(string(req.Name[:]), "\x00")
 
-	t, err := newTunGeneric(c, l, fd, vpnNetworks)
+	fd, err := openTunDev()
+	if err != nil {
+		return nil, err
+	}
+
+	name, err := tunSetIff(fd, nameStr, baseFlags)
+	if err != nil {
+		_ = unix.Close(fd)
+		return nil, &NameError{Name: nameStr, Underlying: err}
+	}
+
+	t, err := newTunGeneric(c, l, fd, false, false, vpnNetworks)
 	if err != nil {
 		return nil, err
 	}
@@ -299,15 +148,21 @@ func newTun(c *config.C, l *slog.Logger, vpnNetworks []netip.Prefix, multiqueue
 }
 
 // newTunGeneric does all the stuff common to different tun initialization paths. It will close your files on error.
-func newTunGeneric(c *config.C, l *slog.Logger, fd int, vpnNetworks []netip.Prefix) (*tun, error) {
+func newTunGeneric(c *config.C, l *slog.Logger, fd int, vnetHdr, usoEnabled bool, vpnNetworks []netip.Prefix) (*tun, error) {
-	tfd, err := newTunFd(fd)
+	qs, err := tio.NewPollQueueSet()
+
 	if err != nil {
 		_ = unix.Close(fd)
 		return nil, err
 	}
+	err = qs.Add(fd)
+	if err != nil {
+		_ = unix.Close(fd)
+		return nil, err
+	}
+
 	t := &tun{
-		tunFile:                   tfd,
+		readers:                   qs,
-		readers:                   []*tunFile{tfd},
 		closeLock:                 sync.Mutex{},
 		vpnNetworks:               vpnNetworks,
 		TXQueueLen:                c.GetInt("tun.tx_queue", 500),
@@ -410,32 +265,29 @@ func (t *tun) SupportsMultiqueue() bool {
 	return true
 }
 
-func (t *tun) NewMultiQueueReader() (io.ReadWriteCloser, error) {
+func (t *tun) NewMultiQueueReader() error {
 	t.closeLock.Lock()
 	defer t.closeLock.Unlock()
 
 	fd, err := unix.Open("/dev/net/tun", os.O_RDWR, 0)
 	if err != nil {
-		return nil, err
+		return err
 	}
 
-	var req ifReq
+	flags := uint16(unix.IFF_TUN | unix.IFF_NO_PI | unix.IFF_MULTI_QUEUE)
-	req.Flags = uint16(unix.IFF_TUN | unix.IFF_NO_PI | unix.IFF_MULTI_QUEUE)
+
-	copy(req.Name[:], t.Device)
+	if _, err = tunSetIff(fd, t.Device, flags); err != nil {
-	if err = ioctl(uintptr(fd), uintptr(unix.TUNSETIFF), uintptr(unsafe.Pointer(&req))); err != nil {
 		_ = unix.Close(fd)
-		return nil, err
+		return err
 	}
 
-	out, err := t.tunFile.newFriend(fd)
+	err = t.readers.Add(fd)
 	if err != nil {
 		_ = unix.Close(fd)
-		return nil, err
+		return err
 	}
 
-	t.readers = append(t.readers, out)
+	return nil
-
-	return out, nil
 }
 
 func (t *tun) RoutesFor(ip netip.Addr) routing.Gateways {
@@ -603,6 +455,15 @@ func (t *tun) setDefaultRoute(cidr netip.Prefix) error {
 		Table:     unix.RT_TABLE_MAIN,
 		Type:      unix.RTN_UNICAST,
 	}
+	// Match the metric the kernel uses for its auto-installed connected
+	// route, so RouteReplace overwrites it in place instead of adding a
+	// second route at a worse metric. IPv6 connected routes are installed
+	// at metric 256 (IP6_RT_PRIO_KERN); IPv4 uses 0. Without this, the
+	// kernel route wins lookups and our MTU / AdvMSS / Features never
+	// apply on v6.
+	if cidr.Addr().Is6() {
+		nr.Priority = 256
+	}
 	err := netlink.RouteReplace(&nr)
 	if err != nil {
 		t.l.Warn("Failed to set default route MTU, retrying", "error", err, "cidr", cidr)
@@ -869,6 +730,10 @@ func (t *tun) updateRoutes(r netlink.RouteUpdate) {
 	t.routeTree.Store(newTree)
 }
 
+func (t *tun) Readers() []tio.Queue {
+	return t.readers.Queues()
+}
+
 func (t *tun) Close() error {
 	t.closeLock.Lock()
 	defer t.closeLock.Unlock()
@@ -878,32 +743,10 @@ func (t *tun) Close() error {
 		t.routeChan = nil
 	}
 
-	// Signal all readers blocked in poll to wake up and exit
-	_ = t.tunFile.wakeForShutdown()
-
 	if t.ioctlFd > 0 {
 		_ = unix.Close(int(t.ioctlFd))
 		t.ioctlFd = 0
 	}
 
-	for i := range t.readers {
+	return t.readers.Close()
-		if i == 0 {
-			continue //we want to close the zeroth reader last
-		}
-		err := t.readers[i].Close()
-		if err != nil {
-			t.l.Error("error closing tun reader", "reader", i, "error", err)
-		} else {
-			t.l.Info("closed tun reader", "reader", i)
-		}
-	}
-
-	//this is t.readers[0] too
-	err := t.tunFile.Close()
-	if err != nil {
-		t.l.Error("error closing tun reader", "reader", 0, "error", err)
-	} else {
-		t.l.Info("closed tun reader", "reader", 0)
-	}
-	return err
 }

overlay/tun_linux_test.go

@@ -3,7 +3,9 @@
 
 package overlay
 
-import "testing"
+import (
+	"testing"
+)
 
 var runAdvMSSTests = []struct {
 	name     string

overlay/tun_netbsd.go

@@ -6,7 +6,6 @@ package overlay
 import (
 	"errors"
 	"fmt"
-	"io"
 	"log/slog"
 	"net/netip"
 	"os"
@@ -17,8 +16,10 @@ import (
 
 	"github.com/gaissmai/bart"
 	"github.com/slackhq/nebula/config"
+	"github.com/slackhq/nebula/overlay/tio"
 	"github.com/slackhq/nebula/routing"
 	"github.com/slackhq/nebula/util"
+	"github.com/slackhq/nebula/wire"
 	netroute "golang.org/x/net/route"
 	"golang.org/x/sys/unix"
 )
@@ -68,6 +69,27 @@ type tun struct {
 	fd          int
 }
 
+func (t *tun) Read(p []wire.TunPacket, mem []byte) (int, error) {
+	if len(p) == 0 || len(mem) == 0 {
+		return 0, nil //todo should this be an err?
+	}
+	p[0].Meta = struct{}{}
+	n, err := t.readOne(mem)
+	if err != nil {
+		return 0, err
+	}
+	p[0].Bytes = mem[:n]
+	return 1, nil
+}
+
+func (t *tun) Readers() []tio.Queue {
+	return []tio.Queue{t}
+}
+
+func (t *tun) Capabilities() tio.Capabilities {
+	return tio.Capabilities{}
+}
+
 var deviceNameRE = regexp.MustCompile(`^tun[0-9]+$`)
 
 func newTunFromFd(_ *config.C, _ *slog.Logger, _ int, _ []netip.Prefix) (*tun, error) {
@@ -141,7 +163,7 @@ func (t *tun) Close() error {
 	return nil
 }
 
-func (t *tun) Read(to []byte) (int, error) {
+func (t *tun) readOne(to []byte) (int, error) {
 	rc, err := t.f.SyscallConn()
 	if err != nil {
 		return 0, fmt.Errorf("failed to get syscall conn for tun: %w", err)
@@ -394,8 +416,8 @@ func (t *tun) SupportsMultiqueue() bool {
 	return false
 }
 
-func (t *tun) NewMultiQueueReader() (io.ReadWriteCloser, error) {
+func (t *tun) NewMultiQueueReader() error {
-	return nil, fmt.Errorf("TODO: multiqueue not implemented for netbsd")
+	return fmt.Errorf("TODO: multiqueue not implemented for netbsd")
 }
 
 func (t *tun) addRoutes(logErrors bool) error {

overlay/tun_openbsd.go

@@ -6,7 +6,6 @@ package overlay
 import (
 	"errors"
 	"fmt"
-	"io"
 	"log/slog"
 	"net/netip"
 	"os"
@@ -17,8 +16,10 @@ import (
 
 	"github.com/gaissmai/bart"
 	"github.com/slackhq/nebula/config"
+	"github.com/slackhq/nebula/overlay/tio"
 	"github.com/slackhq/nebula/routing"
 	"github.com/slackhq/nebula/util"
+	"github.com/slackhq/nebula/wire"
 	netroute "golang.org/x/net/route"
 	"golang.org/x/sys/unix"
 )
@@ -61,6 +62,19 @@ type tun struct {
 	out []byte
 }
 
+func (t *tun) Read(p []wire.TunPacket, mem []byte) (int, error) {
+	if len(p) == 0 || len(mem) <= 4 {
+		return 0, nil //todo should this be an err?
+	}
+	p[0].Meta = struct{}{}
+	n, err := t.f.Read(mem)
+	if err != nil {
+		return 0, err
+	}
+	p[0].Bytes = mem[4:n]
+	return 1, nil
+}
+
 var deviceNameRE = regexp.MustCompile(`^tun[0-9]+$`)
 
 func newTunFromFd(_ *config.C, _ *slog.Logger, _ int, _ []netip.Prefix) (*tun, error) {
@@ -124,15 +138,6 @@ func (t *tun) Close() error {
 	return nil
 }
 
-func (t *tun) Read(to []byte) (int, error) {
-	buf := make([]byte, len(to)+4)
-
-	n, err := t.f.Read(buf)
-
-	copy(to, buf[4:])
-	return n - 4, err
-}
-
 // Write is only valid for single threaded use
 func (t *tun) Write(from []byte) (int, error) {
 	buf := t.out
@@ -314,8 +319,8 @@ func (t *tun) SupportsMultiqueue() bool {
 	return false
 }
 
-func (t *tun) NewMultiQueueReader() (io.ReadWriteCloser, error) {
+func (t *tun) NewMultiQueueReader() error {
-	return nil, fmt.Errorf("TODO: multiqueue not implemented for openbsd")
+	return fmt.Errorf("TODO: multiqueue not implemented for openbsd")
 }
 
 func (t *tun) addRoutes(logErrors bool) error {
@@ -366,6 +371,14 @@ func (t *tun) deviceBytes() (o [16]byte) {
 	return
 }
 
+func (t *tun) Readers() []tio.Queue {
+	return []tio.Queue{t}
+}
+
+func (t *tun) Capabilities() tio.Capabilities {
+	return tio.Capabilities{}
+}
+
 func addRoute(prefix netip.Prefix, gateways []netip.Prefix) error {
 	sock, err := unix.Socket(unix.AF_ROUTE, unix.SOCK_RAW, unix.AF_UNSPEC)
 	if err != nil {

overlay/tun_tester.go

@@ -14,8 +14,10 @@ import (
 
 	"github.com/gaissmai/bart"
 	"github.com/slackhq/nebula/config"
+	"github.com/slackhq/nebula/overlay/tio"
 	"github.com/slackhq/nebula/routing"
 	"github.com/slackhq/nebula/udp"
+	"github.com/slackhq/nebula/wire"
 )
 
 type TestTun struct {
@@ -162,7 +164,20 @@ func (t *TestTun) Close() error {
 	return nil
 }
 
-func (t *TestTun) Read(b []byte) (int, error) {
+func (t *TestTun) Read(p []wire.TunPacket, mem []byte) (int, error) {
+	if len(p) == 0 || len(mem) == 0 {
+		return 0, nil //todo should this be an err?
+	}
+	p[0].Meta = struct{}{}
+	n, err := t.read(mem)
+	if err != nil {
+		return 0, err
+	}
+	p[0].Bytes = mem[:n]
+	return 1, nil
+}
+
+func (t *TestTun) read(b []byte) (int, error) {
 	p, ok := <-t.rxPackets
 	if !ok {
 		return 0, os.ErrClosed
@@ -177,10 +192,18 @@ func (t *TestTun) Read(b []byte) (int, error) {
 	return n, nil
 }
 
+func (t *TestTun) Readers() []tio.Queue {
+	return []tio.Queue{t}
+}
+
+func (t *TestTun) Capabilities() tio.Capabilities {
+	return tio.Capabilities{}
+}
+
 func (t *TestTun) SupportsMultiqueue() bool {
 	return false
 }
 
-func (t *TestTun) NewMultiQueueReader() (io.ReadWriteCloser, error) {
+func (t *TestTun) NewMultiQueueReader() error {
-	return nil, fmt.Errorf("TODO: multiqueue not implemented")
+	return fmt.Errorf("TODO: multiqueue not implemented")
 }

overlay/tun_windows.go

@@ -6,7 +6,6 @@ package overlay
 import (
 	"crypto"
 	"fmt"
-	"io"
 	"log/slog"
 	"net/netip"
 	"os"
@@ -18,26 +17,50 @@ import (
 
 	"github.com/gaissmai/bart"
 	"github.com/slackhq/nebula/config"
+	"github.com/slackhq/nebula/overlay/tio"
 	"github.com/slackhq/nebula/routing"
 	"github.com/slackhq/nebula/util"
 	"github.com/slackhq/nebula/wintun"
+	"github.com/slackhq/nebula/wire"
 	"golang.org/x/sys/windows"
 	"golang.zx2c4.com/wireguard/windows/tunnel/winipcfg"
 )
 
+type closer interface {
+	Close()
+}
+
 const tunGUIDLabel = "Fixed Nebula Windows GUID v1"
 
 type winTun struct {
-	Device      string
+	Device          string
-	vpnNetworks []netip.Prefix
+	vpnNetworks     []netip.Prefix
-	MTU         int
+	MTU             int
-	Routes      atomic.Pointer[[]Route]
+	Routes          atomic.Pointer[[]Route]
-	routeTree   atomic.Pointer[bart.Table[routing.Gateways]]
+	routeTree       atomic.Pointer[bart.Table[routing.Gateways]]
-	l           *slog.Logger
+	guid            windows.GUID
+	networkCategory networkCategory
+	setCategory     bool
+	bypassWDF       bool
+	wdfBypass       closer
+	l               *slog.Logger
 
 	tun *wintun.NativeTun
 }
 
+func (t *winTun) Read(p []wire.TunPacket, mem []byte) (int, error) {
+	if len(p) == 0 || len(mem) == 0 {
+		return 0, nil //todo should this be an err?
+	}
+	p[0].Meta = struct{}{}
+	n, err := t.tun.Read(mem, 0)
+	if err != nil {
+		return 0, err
+	}
+	p[0].Bytes = mem[:n]
+	return 1, nil
+}
+
 func newTunFromFd(_ *config.C, _ *slog.Logger, _ int, _ []netip.Prefix) (Device, error) {
 	return nil, fmt.Errorf("newTunFromFd not supported in Windows")
 }
@@ -54,11 +77,20 @@ func newTun(c *config.C, l *slog.Logger, vpnNetworks []netip.Prefix, _ bool) (*w
 		return nil, fmt.Errorf("generate GUID failed: %w", err)
 	}
 
+	cat, setCat, err := parseNetworkCategory(c.GetString("tun.network_category", "private"))
+	if err != nil {
+		return nil, err
+	}
+
 	t := &winTun{
-		Device:      deviceName,
+		Device:          deviceName,
-		vpnNetworks: vpnNetworks,
+		vpnNetworks:     vpnNetworks,
-		MTU:         c.GetInt("tun.mtu", DefaultMTU),
+		MTU:             c.GetInt("tun.mtu", DefaultMTU),
-		l:           l,
+		guid:            *guid,
+		networkCategory: cat,
+		setCategory:     setCat,
+		bypassWDF:       c.GetBool("tun.windows_bypass_wdf", true),
+		l:               l,
 	}
 
 	err = t.reload(c, true)
@@ -142,6 +174,17 @@ func (t *winTun) Activate() error {
 		return err
 	}
 
+	if t.setCategory {
+		// The wintun adapter takes a moment to register with the Network List
+		// Manager, so we apply the category in the background and retry until
+		// it shows up.
+		go applyNetworkCategory(t.l, t.guid, t.networkCategory)
+	}
+
+	if t.bypassWDF {
+		t.wdfBypass = installInterfaceBypass(t.l, uint64(t.tun.LUID()))
+	}
+
 	return nil
 }
 
@@ -156,11 +199,8 @@ func (t *winTun) addRoutes(logErrors bool) error {
 			continue
 		}
 
-		// Add our unsafe route
+		// Add our unsafe route as an on-link route to the nebula tun device.
-		// Windows does not support multipath routes natively, so we install only a single route.
+		err := luid.AddRoute(r.Cidr, unspecifiedNextHop(r.Cidr), uint32(r.Metric))
-		// This is not a problem as traffic will always be sent to Nebula which handles the multipath routing internally.
-		// In effect this provides multipath routing support to windows supporting loadbalancing and redundancy.
-		err := luid.AddRoute(r.Cidr, r.Via[0].Addr(), uint32(r.Metric))
 		if err != nil {
 			retErr := util.NewContextualError("Failed to add route", map[string]any{"route": r}, err)
 			if logErrors {
@@ -206,7 +246,7 @@ func (t *winTun) removeRoutes(routes []Route) error {
 		}
 
 		// See comment on luid.AddRoute
-		err := luid.DeleteRoute(r.Cidr, r.Via[0].Addr())
+		err := luid.DeleteRoute(r.Cidr, unspecifiedNextHop(r.Cidr))
 		if err != nil {
 			t.l.Error("Failed to remove route", "error", err, "route", r)
 		} else {
@@ -229,10 +269,6 @@ func (t *winTun) Name() string {
 	return t.Device
 }
 
-func (t *winTun) Read(b []byte) (int, error) {
-	return t.tun.Read(b, 0)
-}
-
 func (t *winTun) Write(b []byte) (int, error) {
 	return t.tun.Write(b, 0)
 }
@@ -241,8 +277,16 @@ func (t *winTun) SupportsMultiqueue() bool {
 	return false
 }
 
-func (t *winTun) NewMultiQueueReader() (io.ReadWriteCloser, error) {
+func (t *winTun) NewMultiQueueReader() error {
-	return nil, fmt.Errorf("TODO: multiqueue not implemented for windows")
+	return fmt.Errorf("TODO: multiqueue not implemented for windows")
+}
+
+func (t *winTun) Readers() []tio.Queue {
+	return []tio.Queue{t}
+}
+
+func (t *winTun) Capabilities() tio.Capabilities {
+	return tio.Capabilities{}
 }
 
 func (t *winTun) Close() error {
@@ -258,9 +302,21 @@ func (t *winTun) Close() error {
 	_ = luid.FlushDNS(windows.AF_INET)
 	_ = luid.FlushDNS(windows.AF_INET6)
 
+	if t.wdfBypass != nil {
+		t.wdfBypass.Close()
+		t.wdfBypass = nil
+	}
+
 	return t.tun.Close()
 }
 
+func unspecifiedNextHop(p netip.Prefix) netip.Addr {
+	if p.Addr().Is4() {
+		return netip.IPv4Unspecified()
+	}
+	return netip.IPv6Unspecified()
+}
+
 func generateGUIDByDeviceName(name string) (*windows.GUID, error) {
 	// GUID is 128 bit
 	hash := crypto.MD5.New()

overlay/user.go

@@ -6,7 +6,9 @@ import (
 	"net/netip"
 
 	"github.com/slackhq/nebula/config"
+	"github.com/slackhq/nebula/overlay/tio"
 	"github.com/slackhq/nebula/routing"
+	"github.com/slackhq/nebula/wire"
 )
 
 func NewUserDeviceFromConfig(c *config.C, l *slog.Logger, vpnNetworks []netip.Prefix, routines int) (Device, error) {
@@ -23,11 +25,13 @@ func NewUserDevice(vpnNetworks []netip.Prefix) (Device, error) {
 		outboundWriter: ow,
 		inboundReader:  ir,
 		inboundWriter:  iw,
+		numReaders:     1,
 	}, nil
 }
 
 type UserDevice struct {
 	vpnNetworks []netip.Prefix
+	numReaders  int
 
 	outboundReader *io.PipeReader
 	outboundWriter *io.PipeWriter
@@ -36,6 +40,23 @@ type UserDevice struct {
 	inboundWriter *io.PipeWriter
 }
 
+func (d *UserDevice) Capabilities() tio.Capabilities {
+	return tio.Capabilities{}
+}
+
+func (d *UserDevice) Read(p []wire.TunPacket, mem []byte) (int, error) {
+	if len(p) == 0 || len(mem) == 0 {
+		return 0, nil //todo should this be an err?
+	}
+	p[0].Meta = struct{}{}
+	n, err := d.outboundReader.Read(mem)
+	if err != nil {
+		return 0, err
+	}
+	p[0].Bytes = mem[:n]
+	return 1, nil
+}
+
 func (d *UserDevice) Activate() error {
 	return nil
 }
@@ -50,20 +71,27 @@ func (d *UserDevice) SupportsMultiqueue() bool {
 	return true
 }
 
-func (d *UserDevice) NewMultiQueueReader() (io.ReadWriteCloser, error) {
+func (d *UserDevice) NewMultiQueueReader() error {
-	return d, nil
+	d.numReaders++
+	return nil
+}
+
+func (d *UserDevice) Readers() []tio.Queue {
+	out := make([]tio.Queue, d.numReaders)
+	for i := range d.numReaders {
+		out[i] = d
+	}
+	return out
 }
 
 func (d *UserDevice) Pipe() (*io.PipeReader, *io.PipeWriter) {
 	return d.inboundReader, d.outboundWriter
 }
 
-func (d *UserDevice) Read(p []byte) (n int, err error) {
-	return d.outboundReader.Read(p)
-}
 func (d *UserDevice) Write(p []byte) (n int, err error) {
 	return d.inboundWriter.Write(p)
 }
+
 func (d *UserDevice) Close() error {
 	d.inboundWriter.Close()
 	d.outboundWriter.Close()

pki.go

@@ -99,12 +99,10 @@ func (p *PKI) reloadCerts(c *config.C, initial bool) *util.ContextualError {
 	var currentState *CertState
 	if initial {
 		cipher = c.GetString("cipher", "aes")
-		//TODO: this sucks and we should make it not a global
 		switch cipher {
-		case "aes":
+		case "aes", "chachapoly":
-			noiseEndianness = binary.BigEndian
+			// Each post-handshake CipherState in noiseutil hardcodes its own
-		case "chachapoly":
+			// nonce endianness now, so there's nothing to set up here.
-			noiseEndianness = binary.LittleEndian
 		default:
 			return util.NewContextualError(
 				"unknown cipher",

punchy.go

@@ -1,24 +1,70 @@
 package nebula
 
 import (
+	"context"
 	"log/slog"
+	"net/netip"
 	"sync/atomic"
 	"time"
 
+	"github.com/rcrowley/go-metrics"
 	"github.com/slackhq/nebula/config"
+	"github.com/slackhq/nebula/header"
+	"github.com/slackhq/nebula/udp"
 )
 
+// holepunchQueueSize buffers the channel that pending holepunchJobs land on after their delay timer fires.
+const holepunchQueueSize = 64
+
+// holepunchJob is one scheduled item delivered to the worker goroutine.
+//   - target valid -> send a UDP punch to target. vpnAddr, if set, is the peer's vpn addr carried for log context.
+//   - target invalid, vpnAddr valid -> send an encrypted test packet to vpnAddr (a "punchback").
+type holepunchJob struct {
+	target  netip.AddrPort
+	vpnAddr netip.Addr
+}
+
+// lighthouseChecker is the slice of LightHouse that Punchy actually needs.
+// Defined here so Punchy doesn't take a *LightHouse dependency (LightHouse
+// already holds a *Punchy, and the bidirectional pointer reference is awkward
+// even within the same package). Tests can also substitute a fake.
+type lighthouseChecker interface {
+	IsAnyLighthouseAddr(vpnAddrs []netip.Addr) bool
+}
+
 type Punchy struct {
 	punch           atomic.Bool
 	respond         atomic.Bool
 	delay           atomic.Int64
 	respondDelay    atomic.Int64
 	punchEverything atomic.Bool
-	l               *slog.Logger
+
+	sched             *Scheduler[holepunchJob]
+	punchConn         udp.Conn
+	metricHolepunchTx metrics.Counter
+	metricPunchyTx    metrics.Counter
+
+	ctx  context.Context
+	ifce EncWriter
+	hm   *HostMap
+	lh   lighthouseChecker
+
+	l *slog.Logger
 }
 
-func NewPunchyFromConfig(l *slog.Logger, c *config.C) *Punchy {
+func NewPunchyFromConfig(l *slog.Logger, c *config.C, punchConn udp.Conn) *Punchy {
-	p := &Punchy{l: l}
+	p := &Punchy{
+		l:              l,
+		punchConn:      punchConn,
+		sched:          NewScheduler[holepunchJob](holepunchQueueSize),
+		metricPunchyTx: metrics.GetOrRegisterCounter("messages.tx.punchy", nil),
+	}
+
+	if c.GetBool("stats.lighthouse_metrics", false) {
+		p.metricHolepunchTx = metrics.GetOrRegisterCounter("messages.tx.holepunch", nil)
+	} else {
+		p.metricHolepunchTx = metrics.NilCounter{}
+	}
 
 	p.reload(c, true)
 	c.RegisterReloadCallback(func(c *config.C) {
@@ -29,7 +75,7 @@ func NewPunchyFromConfig(l *slog.Logger, c *config.C) *Punchy {
 }
 
 func (p *Punchy) reload(c *config.C, initial bool) {
-	if initial {
+	if initial || c.HasChanged("punchy.punch") || c.HasChanged("punchy") {
 		var yes bool
 		if c.IsSet("punchy.punch") {
 			yes = c.GetBool("punchy.punch", false)
@@ -38,16 +84,15 @@ func (p *Punchy) reload(c *config.C, initial bool) {
 			yes = c.GetBool("punchy", false)
 		}
 
-		p.punch.Store(yes)
+		old := p.punch.Swap(yes)
-		if yes {
+		switch {
+		case initial && yes:
 			p.l.Info("punchy enabled")
-		} else {
+		case initial:
 			p.l.Info("punchy disabled")
+		case old != yes:
+			p.l.Info("punchy.punch changed", "punch", yes)
 		}
-
-	} else if c.HasChanged("punchy.punch") || c.HasChanged("punchy") {
-		//TODO: it should be relatively easy to support this, just need to be able to cancel the goroutine and boot it up from here
-		p.l.Warn("Changing punchy.punch with reload is not supported, ignoring.")
 	}
 
 	if initial || c.HasChanged("punchy.respond") || c.HasChanged("punch_back") {
@@ -59,52 +104,132 @@ func (p *Punchy) reload(c *config.C, initial bool) {
 			yes = c.GetBool("punch_back", false)
 		}
 
-		p.respond.Store(yes)
+		old := p.respond.Swap(yes)
-
+		if !initial && old != yes {
-		if !initial {
+			p.l.Info("punchy.respond changed", "respond", yes)
-			p.l.Info("punchy.respond changed", "respond", p.GetRespond())
 		}
 	}
 
 	//NOTE: this will not apply to any in progress operations, only the next one
 	if initial || c.HasChanged("punchy.delay") {
-		p.delay.Store((int64)(c.GetDuration("punchy.delay", time.Second)))
+		newDelay := int64(c.GetDuration("punchy.delay", time.Second))
-		if !initial {
+		old := p.delay.Swap(newDelay)
-			p.l.Info("punchy.delay changed", "delay", p.GetDelay())
+		if !initial && old != newDelay {
+			p.l.Info("punchy.delay changed", "delay", time.Duration(newDelay))
 		}
 	}
 
 	if initial || c.HasChanged("punchy.target_all_remotes") {
-		p.punchEverything.Store(c.GetBool("punchy.target_all_remotes", false))
+		yes := c.GetBool("punchy.target_all_remotes", false)
-		if !initial {
+		old := p.punchEverything.Swap(yes)
-			p.l.Info("punchy.target_all_remotes changed", "target_all_remotes", p.GetTargetEverything())
+		if !initial && old != yes {
+			p.l.Info("punchy.target_all_remotes changed", "target_all_remotes", yes)
 		}
 	}
 
 	if initial || c.HasChanged("punchy.respond_delay") {
-		p.respondDelay.Store((int64)(c.GetDuration("punchy.respond_delay", 5*time.Second)))
+		newDelay := int64(c.GetDuration("punchy.respond_delay", 5*time.Second))
-		if !initial {
+		old := p.respondDelay.Swap(newDelay)
-			p.l.Info("punchy.respond_delay changed", "respond_delay", p.GetRespondDelay())
+		if !initial && old != newDelay {
+			p.l.Info("punchy.respond_delay changed", "respond_delay", time.Duration(newDelay))
 		}
 	}
 }
 
-func (p *Punchy) GetPunch() bool {
+// Schedule queues a punch packet to target, to be sent after the configured delay.
-	return p.punch.Load()
+// vpnAddr is the peer's vpn addr, used for log context when the packet actually fires.
+// No-op if target is not a valid AddrPort or if Start has not yet been called. Safe to call from any goroutine.
+func (p *Punchy) Schedule(target netip.AddrPort, vpnAddr netip.Addr) {
+	if !target.IsValid() || p.ctx == nil {
+		return
+	}
+	p.scheduleJob(holepunchJob{target: target, vpnAddr: vpnAddr}, time.Duration(p.delay.Load()))
 }
 
-func (p *Punchy) GetRespond() bool {
+// ScheduleRespond queues a punchback test packet to vpnAddr after the configured respond delay,
-	return p.respond.Load()
+// gated on punchy.respond. No-op when respond is disabled or before Start has been called.
+func (p *Punchy) ScheduleRespond(vpnAddr netip.Addr) {
+	if !p.respond.Load() || p.ctx == nil {
+		return
+	}
+	p.scheduleJob(holepunchJob{vpnAddr: vpnAddr}, time.Duration(p.respondDelay.Load()))
 }
 
-func (p *Punchy) GetDelay() time.Duration {
+// scheduleJob delegates to the pooled Scheduler.
-	return (time.Duration)(p.delay.Load())
+// The callback observes p.ctx so a job that becomes due after Stop is dropped instead of queued.
+func (p *Punchy) scheduleJob(job holepunchJob, delay time.Duration) {
+	p.sched.Schedule(p.ctx, job, delay)
 }
 
-func (p *Punchy) GetRespondDelay() time.Duration {
+// SendPunch sends an immediate keepalive punch for an idle hostinfo.
-	return (time.Duration)(p.respondDelay.Load())
+// The configured punchy.target_all_remotes mode picks the targets. Gated on punchy.punch and the lighthouse-skip rule
+// (lighthouses don't get keepalive punches because the regular update interval keeps their NAT state warm).
+func (p *Punchy) SendPunch(hostinfo *HostInfo) {
+	if !p.punch.Load() {
+		return
+	}
+	if p.lh.IsAnyLighthouseAddr(hostinfo.vpnAddrs) {
+		return
+	}
+
+	if p.punchEverything.Load() {
+		p.sendPunchToAllRemotes(hostinfo)
+	} else if hostinfo.remote.IsValid() {
+		p.metricPunchyTx.Inc(1)
+		p.punchConn.WriteTo([]byte{1}, hostinfo.remote)
+	}
 }
 
-func (p *Punchy) GetTargetEverything() bool {
+// SendPunchToAll punches every known remote for hostinfo, but only when punchy.target_all_remotes is enabled.
-	return p.punchEverything.Load()
+// The connection manager calls this during outbound-only traffic: the outbound traffic itself keeps the primary's
+// NAT state warm, but non-primary remotes need separate refresh, so we fan out to all of them (the redundant
+// primary punch is harmless). Gated on punchy.punch and the lighthouse-skip rule.
+func (p *Punchy) SendPunchToAll(hostinfo *HostInfo) {
+	if !p.punchEverything.Load() {
+		return
+	}
+	if !p.punch.Load() {
+		return
+	}
+	if p.lh.IsAnyLighthouseAddr(hostinfo.vpnAddrs) {
+		return
+	}
+	p.sendPunchToAllRemotes(hostinfo)
+}
+
+func (p *Punchy) sendPunchToAllRemotes(hostinfo *HostInfo) {
+	hostinfo.remotes.ForEach(p.hm.GetPreferredRanges(), func(addr netip.AddrPort, preferred bool) {
+		p.metricPunchyTx.Inc(1)
+		p.punchConn.WriteTo([]byte{1}, addr)
+	})
+}
+
+// Start wires the runtime dependencies and spawns the scheduler worker.
+func (p *Punchy) Start(ctx context.Context, ifce EncWriter, hm *HostMap, lh lighthouseChecker) {
+	p.ctx = ctx
+	p.ifce = ifce
+	p.hm = hm
+	p.lh = lh
+
+	nb := make([]byte, 12, 12)
+	out := make([]byte, mtu)
+	empty := []byte{0}
+
+	go p.sched.Run(ctx, func(job holepunchJob) {
+		switch {
+		case job.target.IsValid():
+			if p.l.Enabled(context.Background(), slog.LevelDebug) {
+				p.l.Debug("Punching", "target", job.target, "vpnAddr", job.vpnAddr)
+			}
+			p.metricHolepunchTx.Inc(1)
+			p.punchConn.WriteTo(empty, job.target)
+		case job.vpnAddr.IsValid():
+			// 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 p.l.Enabled(context.Background(), slog.LevelDebug) {
+				p.l.Debug("Sending a nebula test packet", "vpnAddr", job.vpnAddr)
+			}
+			p.ifce.SendMessageToVpnAddr(header.Test, header.TestRequest, job.vpnAddr, []byte(""), nb, out)
+		}
+	})
 }

punchy_test.go

@@ -17,42 +17,42 @@ func TestNewPunchyFromConfig(t *testing.T) {
 	c := config.NewC(l)
 
 	// Test defaults
-	p := NewPunchyFromConfig(test.NewLogger(), c)
+	p := NewPunchyFromConfig(test.NewLogger(), c, nil)
-	assert.False(t, p.GetPunch())
+	assert.False(t, p.punch.Load())
-	assert.False(t, p.GetRespond())
+	assert.False(t, p.respond.Load())
-	assert.Equal(t, time.Second, p.GetDelay())
+	assert.Equal(t, time.Second, time.Duration(p.delay.Load()))
-	assert.Equal(t, 5*time.Second, p.GetRespondDelay())
+	assert.Equal(t, 5*time.Second, time.Duration(p.respondDelay.Load()))
 
 	// punchy deprecation
 	c.Settings["punchy"] = true
-	p = NewPunchyFromConfig(test.NewLogger(), c)
+	p = NewPunchyFromConfig(test.NewLogger(), c, nil)
-	assert.True(t, p.GetPunch())
+	assert.True(t, p.punch.Load())
 
 	// punchy.punch
 	c.Settings["punchy"] = map[string]any{"punch": true}
-	p = NewPunchyFromConfig(test.NewLogger(), c)
+	p = NewPunchyFromConfig(test.NewLogger(), c, nil)
-	assert.True(t, p.GetPunch())
+	assert.True(t, p.punch.Load())
 
 	// punch_back deprecation
 	c.Settings["punch_back"] = true
-	p = NewPunchyFromConfig(test.NewLogger(), c)
+	p = NewPunchyFromConfig(test.NewLogger(), c, nil)
-	assert.True(t, p.GetRespond())
+	assert.True(t, p.respond.Load())
 
 	// punchy.respond
 	c.Settings["punchy"] = map[string]any{"respond": true}
 	c.Settings["punch_back"] = false
-	p = NewPunchyFromConfig(test.NewLogger(), c)
+	p = NewPunchyFromConfig(test.NewLogger(), c, nil)
-	assert.True(t, p.GetRespond())
+	assert.True(t, p.respond.Load())
 
 	// punchy.delay
 	c.Settings["punchy"] = map[string]any{"delay": "1m"}
-	p = NewPunchyFromConfig(test.NewLogger(), c)
+	p = NewPunchyFromConfig(test.NewLogger(), c, nil)
-	assert.Equal(t, time.Minute, p.GetDelay())
+	assert.Equal(t, time.Minute, time.Duration(p.delay.Load()))
 
 	// punchy.respond_delay
 	c.Settings["punchy"] = map[string]any{"respond_delay": "1m"}
-	p = NewPunchyFromConfig(test.NewLogger(), c)
+	p = NewPunchyFromConfig(test.NewLogger(), c, nil)
-	assert.Equal(t, time.Minute, p.GetRespondDelay())
+	assert.Equal(t, time.Minute, time.Duration(p.respondDelay.Load()))
 }
 
 func TestPunchy_reload(t *testing.T) {
@@ -61,35 +61,34 @@ func TestPunchy_reload(t *testing.T) {
 	delay, _ := time.ParseDuration("1m")
 	require.NoError(t, c.LoadString(`
 punchy:
+  punch: false
   delay: 1m
   respond: false
 `))
-	p := NewPunchyFromConfig(test.NewLogger(), c)
+	p := NewPunchyFromConfig(test.NewLogger(), c, nil)
-	assert.Equal(t, delay, p.GetDelay())
+	assert.False(t, p.punch.Load())
-	assert.False(t, p.GetRespond())
+	assert.Equal(t, delay, time.Duration(p.delay.Load()))
+	assert.False(t, p.respond.Load())
 
 	newDelay, _ := time.ParseDuration("10m")
 	require.NoError(t, c.ReloadConfigString(`
 punchy:
+  punch: true
   delay: 10m
   respond: true
 `))
 	p.reload(c, false)
-	assert.Equal(t, newDelay, p.GetDelay())
+	assert.True(t, p.punch.Load())
-	assert.True(t, p.GetRespond())
+	assert.Equal(t, newDelay, time.Duration(p.delay.Load()))
+	assert.True(t, p.respond.Load())
 }
 
 // The tests below pin the shape of each log line Punchy produces so changes
 // cannot silently break whatever operators are grepping for. The assertions
 // are on the structured message + attrs (e.g. "punchy.respond changed" with
-// a respond=true field) rather than a formatted string.
+// a respond=true field) rather than a formatted string. Tests filter by
-//
+// message rather than asserting total entry counts so unrelated info lines
-// Punchy.reload also emits a spurious "Changing punchy.punch with reload is
+// are tolerated without being locked into the format.
-// not supported" warning whenever any key under punchy changes, because of
-// the c.HasChanged("punchy") fallback kept for the deprecated top-level
-// punchy form. The tests filter by message rather than asserting total
-// entry counts so that warning is tolerated without being locked into
-// the format.
 
 type capturedEntry struct {
 	Level slog.Level
@@ -145,7 +144,7 @@ func TestPunchy_LogFormat_InitialEnabled(t *testing.T) {
 	c := config.NewC(test.NewLogger())
 	require.NoError(t, c.LoadString(`punchy: {punch: true}`))
 
-	NewPunchyFromConfig(l, c)
+	NewPunchyFromConfig(l, c, nil)
 
 	entry := findEntry(t, hook.entries, "punchy enabled")
 	assert.Equal(t, slog.LevelInfo, entry.Level)
@@ -157,32 +156,32 @@ func TestPunchy_LogFormat_InitialDisabled(t *testing.T) {
 	c := config.NewC(test.NewLogger())
 	require.NoError(t, c.LoadString(`punchy: {punch: false}`))
 
-	NewPunchyFromConfig(l, c)
+	NewPunchyFromConfig(l, c, nil)
 
 	entry := findEntry(t, hook.entries, "punchy disabled")
 	assert.Equal(t, slog.LevelInfo, entry.Level)
 	assert.Empty(t, entry.Attrs)
 }
 
-func TestPunchy_LogFormat_ReloadPunchUnsupported(t *testing.T) {
+func TestPunchy_LogFormat_ReloadPunch(t *testing.T) {
 	l, hook := newCapturingPunchyLogger(t)
 	c := config.NewC(test.NewLogger())
 	require.NoError(t, c.LoadString(`punchy: {punch: false}`))
-	NewPunchyFromConfig(l, c)
+	NewPunchyFromConfig(l, c, nil)
 	hook.entries = nil
 
 	require.NoError(t, c.ReloadConfigString(`punchy: {punch: true}`))
 
-	entry := findEntry(t, hook.entries, "Changing punchy.punch with reload is not supported, ignoring.")
+	entry := findEntry(t, hook.entries, "punchy.punch changed")
-	assert.Equal(t, slog.LevelWarn, entry.Level)
+	assert.Equal(t, slog.LevelInfo, entry.Level)
-	assert.Empty(t, entry.Attrs)
+	assert.Equal(t, map[string]any{"punch": true}, entry.Attrs)
 }
 
 func TestPunchy_LogFormat_ReloadRespond(t *testing.T) {
 	l, hook := newCapturingPunchyLogger(t)
 	c := config.NewC(test.NewLogger())
 	require.NoError(t, c.LoadString(`punchy: {respond: false}`))
-	NewPunchyFromConfig(l, c)
+	NewPunchyFromConfig(l, c, nil)
 	hook.entries = nil
 
 	require.NoError(t, c.ReloadConfigString(`punchy: {respond: true}`))
@@ -196,7 +195,7 @@ func TestPunchy_LogFormat_ReloadDelay(t *testing.T) {
 	l, hook := newCapturingPunchyLogger(t)
 	c := config.NewC(test.NewLogger())
 	require.NoError(t, c.LoadString(`punchy: {delay: 1s}`))
-	NewPunchyFromConfig(l, c)
+	NewPunchyFromConfig(l, c, nil)
 	hook.entries = nil
 
 	require.NoError(t, c.ReloadConfigString(`punchy: {delay: 10s}`))
@@ -210,7 +209,7 @@ func TestPunchy_LogFormat_ReloadTargetAllRemotes(t *testing.T) {
 	l, hook := newCapturingPunchyLogger(t)
 	c := config.NewC(test.NewLogger())
 	require.NoError(t, c.LoadString(`punchy: {target_all_remotes: false}`))
-	NewPunchyFromConfig(l, c)
+	NewPunchyFromConfig(l, c, nil)
 	hook.entries = nil
 
 	require.NoError(t, c.ReloadConfigString(`punchy: {target_all_remotes: true}`))
@@ -224,7 +223,7 @@ func TestPunchy_LogFormat_ReloadRespondDelay(t *testing.T) {
 	l, hook := newCapturingPunchyLogger(t)
 	c := config.NewC(test.NewLogger())
 	require.NoError(t, c.LoadString(`punchy: {respond_delay: 5s}`))
-	NewPunchyFromConfig(l, c)
+	NewPunchyFromConfig(l, c, nil)
 	hook.entries = nil
 
 	require.NoError(t, c.ReloadConfigString(`punchy: {respond_delay: 15s}`))

scheduler.go

@@ -0,0 +1,84 @@
+package nebula
+
+import (
+	"context"
+	"sync"
+	"time"
+)
+
+// Scheduler is an allocation-conscious dispatch primitive for delayed work.
+// Pending items are handed to time.AfterFunc, and ready items land on a worker
+// channel for centralized dispatch in fire-time order.
+//
+// Pick a Scheduler when fire timing matters (exact deadlines, no bucketing) or when the scheduling
+// rate is uneven enough that idle CPU matters. Each fire is a runtime-spawned goroutine running the callback before
+// delivering to the worker, which is fine at sparse rates but adds up at line rate.
+//
+// Pick a TimerWheel when scheduling is high-rate and uniform: its O(1) insert, internal item cache,
+// and bucket-batched dispatch are cheaper at scale.
+// The caller drives the tick loop (Advance/Purge) and pays for fires at bucket boundaries rather than exact deadlines.
+type Scheduler[T any] struct {
+	queue chan T
+	pool  sync.Pool
+}
+
+type schedItem[T any] struct {
+	val   T
+	ctx   context.Context
+	s     *Scheduler[T]
+	timer *time.Timer
+	fire  func()
+}
+
+// NewScheduler builds a Scheduler whose worker channel is sized to queueSize.
+// The buffer absorbs bursts of timers firing close together without
+// blocking the runtime's callback goroutines on the worker.
+func NewScheduler[T any](queueSize int) *Scheduler[T] {
+	s := &Scheduler[T]{
+		queue: make(chan T, queueSize),
+	}
+	s.pool.New = func() any {
+		si := &schedItem[T]{s: s}
+		// fire is allocated exactly once per pool-resident item.
+		// The closure captures only `si`, which stays stable for the item's lifetime.
+		si.fire = func() {
+			select {
+			case si.s.queue <- si.val:
+			case <-si.ctx.Done():
+			}
+			var zero T
+			si.val = zero
+			si.ctx = nil
+			si.s.pool.Put(si)
+		}
+		return si
+	}
+	return s
+}
+
+// Schedule arranges item to be delivered to the worker after delay.
+// The runtime's timer heap handles the wait, so the scheduler itself burns no CPU while idle.
+// The callback observes ctx: if ctx is cancelled before the timer fires, the item is dropped instead of queued.
+func (s *Scheduler[T]) Schedule(ctx context.Context, item T, delay time.Duration) {
+	si := s.pool.Get().(*schedItem[T])
+	si.val = item
+	si.ctx = ctx
+	if si.timer == nil {
+		si.timer = time.AfterFunc(delay, si.fire)
+	} else {
+		si.timer.Reset(delay)
+	}
+}
+
+// Run drains the worker queue, calling fn for each item. Returns when ctx is cancelled.
+// Tests that want deterministic timing should drive the queue directly rather than going through Schedule + Run.
+func (s *Scheduler[T]) Run(ctx context.Context, fn func(T)) {
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		case item := <-s.queue:
+			fn(item)
+		}
+	}
+}

scheduler_test.go

@@ -0,0 +1,79 @@
+package nebula
+
+import (
+	"context"
+	"testing"
+	"time"
+)
+
+func TestScheduler_PooledReuse(t *testing.T) {
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	s := NewScheduler[int](16)
+	delivered := make(chan int, 256)
+	go s.Run(ctx, func(item int) { delivered <- item })
+
+	const N = 100
+	for i := 0; i < N; i++ {
+		s.Schedule(ctx, i, time.Millisecond)
+	}
+
+	deadline := time.After(2 * time.Second)
+	got := 0
+	for got < N {
+		select {
+		case <-delivered:
+			got++
+		case <-deadline:
+			t.Fatalf("only %d/%d items delivered", got, N)
+		}
+	}
+}
+
+// BenchmarkScheduler_Schedule reports allocations per Schedule call.
+// In steady state the Scheduler's sync.Pool means we should see zero allocs per op once the pool warms up.
+func BenchmarkScheduler_Schedule(b *testing.B) {
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	s := NewScheduler[int](b.N)
+	go s.Run(ctx, func(int) {})
+
+	b.ReportAllocs()
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		s.Schedule(ctx, i, time.Microsecond)
+	}
+}
+
+// BenchmarkBareAfterFunc is the comparison baseline.
+// What we'd pay per Schedule if Punchy called time.AfterFunc directly without the pooled Scheduler.
+// Allocates a *time.Timer plus a closure each call.
+func BenchmarkBareAfterFunc(b *testing.B) {
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	queue := make(chan int, b.N)
+	go func() {
+		for {
+			select {
+			case <-ctx.Done():
+				return
+			case <-queue:
+			}
+		}
+	}()
+
+	b.ReportAllocs()
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		i := i
+		time.AfterFunc(time.Microsecond, func() {
+			select {
+			case queue <- i:
+			case <-ctx.Done():
+			}
+		})
+	}
+}

sshd/server.go

@@ -27,21 +27,20 @@ type SSHServer struct {
 	commands    *radix.Tree
 	listener    net.Listener
 
-	// Call the cancel() function to stop all active sessions
+	// ctx parents per-Run contexts. Cancelling it (e.g. via Control.Stop) tears the server down even
-	ctx    context.Context
+	// across reloads, since each Run derives a fresh child rather than reusing this one directly.
-	cancel func()
+	ctx context.Context
 }
 
-// NewSSHServer creates a new ssh server rigged with default commands and prepares to listen
+// NewSSHServer creates a new ssh server rigged with default commands and prepares to listen.
-func NewSSHServer(l *slog.Logger) (*SSHServer, error) {
+// The ssh server's context is parented off the supplied ctx so cancelling it
-
+// (e.g. on Control.Stop) tears down active sessions and closes the listener.
-	ctx, cancel := context.WithCancel(context.Background())
+func NewSSHServer(ctx context.Context, l *slog.Logger) (*SSHServer, error) {
 	s := &SSHServer{
 		trustedKeys: make(map[string]map[string]bool),
 		l:           l,
 		commands:    radix.New(),
 		ctx:         ctx,
-		cancel:      cancel,
 	}
 
 	cc := ssh.CertChecker{
@@ -151,28 +150,51 @@ func (s *SSHServer) RegisterCommand(c *Command) {
 	s.commands.Insert(c.Name, c)
 }
 
-// Run begins listening and accepting connections
+// Run begins listening and accepting connections. Each invocation derives a fresh per-Run context
+// from the constructor-supplied ctx so a Stop+Run sequence (used by config reload) starts clean
+// rather than carrying a permanently-cancelled context across runs.
 func (s *SSHServer) Run(addr string) error {
-	var err error
+	if s.ctx.Err() != nil {
-	s.listener, err = net.Listen("tcp", addr)
+		return s.ctx.Err()
+	}
+
+	listener, err := net.Listen("tcp", addr)
 	if err != nil {
 		return err
 	}
+	// s.listener is the public handle Stop uses to interrupt the active run; listener (the local) is what
+	// this run owns. They start equal but a fast reload may overwrite s.listener with the next run's
+	// listener before this run's watcher fires, so each run must close its own listener via the local
+	// reference.
+	s.listener = listener
+
+	runCtx, cancel := context.WithCancel(s.ctx)
+	defer cancel()
+
+	// Close the listener when this run's context is cancelled. That can come from the parent
+	// (Control.Stop), from Run returning normally (defer cancel above), or transitively when a sibling
+	// run cancels through Stop closing the listener. net.Listener.Close is idempotent so a duplicate
+	// close from Stop is benign.
+	go func() {
+		<-runCtx.Done()
+		if err := listener.Close(); err != nil && !errors.Is(err, net.ErrClosed) {
+			s.l.Warn("Failed to close the sshd listener", "error", err)
+		}
+	}()
 
 	s.l.Info("SSH server is listening", "sshListener", addr)
 
 	// Run loops until there is an error
-	s.run()
+	s.run(runCtx, listener)
-	s.closeSessions()
 
 	s.l.Info("SSH server stopped listening")
 	// We don't return an error because run logs for us
 	return nil
 }
 
-func (s *SSHServer) run() {
+func (s *SSHServer) run(ctx context.Context, listener net.Listener) {
 	for {
-		c, err := s.listener.Accept()
+		c, err := listener.Accept()
 		if err != nil {
 			if !errors.Is(err, net.ErrClosed) {
 				s.l.Warn("Error in listener, shutting down", "error", err)
@@ -184,7 +206,7 @@ func (s *SSHServer) run() {
 			// Ensure that a bad client doesn't hurt us by checking for the parent context
 			// cancellation before calling NewServerConn, and forcing the socket to close when
 			// the context is cancelled.
-			sessionContext, sessionCancel := context.WithCancel(s.ctx)
+			sessionContext, sessionCancel := context.WithCancel(ctx)
 			go func() {
 				<-sessionContext.Done()
 				c.Close()
@@ -227,14 +249,9 @@ func (s *SSHServer) run() {
 }
 
 func (s *SSHServer) Stop() {
-	// Close the listener, this will cause all session to terminate as well, see SSHServer.Run
 	if s.listener != nil {
 		if err := s.listener.Close(); err != nil {
 			s.l.Warn("Failed to close the sshd listener", "error", err)
 		}
 	}
 }
-
-func (s *SSHServer) closeSessions() {
-	s.cancel()
-}

timeout.go

@@ -8,6 +8,23 @@ import (
 // How many timer objects should be cached
 const timerCacheMax = 50000
 
+// TimerWheel is a hashed timing wheel: a fixed slot array indexed by (now + delay) % wheelLen,
+// with each slot a singly linked list of items due in that bucket.
+// Adds are O(1), Purges return items in arrival-within-slot order, and an internal cache of TimeoutItems
+// keeps steady-state inserts allocation-free.
+//
+// The TimerWheel does not handle concurrency or lifecycle on its own.
+// Callers drive Advance/Purge from their own ticker loop, take their own locks (or use LockingTimerWheel),
+// and decide whether to keep ticking when the wheel is empty.
+//
+// Pick a TimerWheel when scheduling is high-rate and uniform: line-rate conntrack inserts,
+// per-tunnel traffic checks at fixed intervals. O(1) insert plus the item cache means the hot path doesn't allocate.
+// Items added in the same tick are dispatched together when that slot rotates current,
+// which amortizes the cost of waking the worker.
+//
+// Pick a Scheduler when delay precision matters or scheduling is sparse or uneven.
+// The wheel rounds requested timeouts up to its tick resolution and clamps anything beyond its wheel duration;
+// both are silent in this implementation.
 type TimerWheel[T any] struct {
 	// Current tick
 	current int

udp/conn.go

@@ -8,16 +8,49 @@ import (
 
 const MTU = 9001
 
+// MaxWriteBatch is the largest batch any Conn.WriteBatch implementation is
+// required to accept. Callers SHOULD NOT pass more than this per call; Linux
+// backends preallocate sendmmsg scratch sized to this value, so exceeding it
+// only costs additional sendmmsg chunks within a single WriteBatch call.
+const MaxWriteBatch = 128
+
+// RxMeta carries per-packet metadata extracted from the RX path (ancillary
+// data, kernel offload state, etc.) and passed to EncReader callbacks.
+// Backends that do not produce a particular signal leave its zero value.
+//
+// OuterECN is the 2-bit IP-level ECN codepoint stamped on the carrier
+// datagram (extracted from IP_TOS / IPV6_TCLASS cmsg on Linux). Zero
+// means Not-ECT, which is also the value backends without ECN RX support
+// supply on every packet.
+type RxMeta struct {
+	OuterECN byte
+}
+
 type EncReader func(
 	addr netip.AddrPort,
 	payload []byte,
+	meta RxMeta,
 )
 
 type Conn interface {
 	Rebind() error
 	LocalAddr() (netip.AddrPort, error)
-	ListenOut(r EncReader) error
+	// ListenOut invokes r for each received packet. On batch-capable
+	// backends (recvmmsg), flush is called after each batch is fully
+	// delivered — callers use it to flush per-batch accumulators such as
+	// TUN write coalescers. Single-packet backends call flush after each
+	// packet. flush must not be nil.
+	ListenOut(r EncReader, flush func()) error
 	WriteTo(b []byte, addr netip.AddrPort) error
+	// WriteBatch sends a contiguous batch of packets, each with its own
+	// destination. bufs and addrs must have the same length. outerECNs may
+	// be nil (treated as all-zero / Not-ECT); when non-nil it must have the
+	// same length as bufs, and outerECNs[i] is the 2-bit IP-level ECN
+	// codepoint to set on packet i's outer header. Linux uses sendmmsg(2)
+	// for a single syscall and attaches the value as IP_TOS / IPV6_TCLASS
+	// cmsg; other backends ignore it. Returns on the first error; callers
+	// may observe a partial send if some packets went out before the error.
+	WriteBatch(bufs [][]byte, addrs []netip.AddrPort, outerECNs []byte) error
 	ReloadConfig(c *config.C)
 	SupportsMultipleReaders() bool
 	Close() error
@@ -31,7 +64,7 @@ func (NoopConn) Rebind() error {
 func (NoopConn) LocalAddr() (netip.AddrPort, error) {
 	return netip.AddrPort{}, nil
 }
-func (NoopConn) ListenOut(_ EncReader) error {
+func (NoopConn) ListenOut(_ EncReader, _ func()) error {
 	return nil
 }
 func (NoopConn) SupportsMultipleReaders() bool {
@@ -40,6 +73,9 @@ func (NoopConn) SupportsMultipleReaders() bool {
 func (NoopConn) WriteTo(_ []byte, _ netip.AddrPort) error {
 	return nil
 }
+func (NoopConn) WriteBatch(_ [][]byte, _ []netip.AddrPort, _ []byte) error {
+	return nil
+}
 func (NoopConn) ReloadConfig(_ *config.C) {
 	return
 }

udp/udp_android.go

@@ -5,12 +5,11 @@ package udp
 
 import (
 	"fmt"
+	"log/slog"
 	"net"
 	"net/netip"
 	"syscall"
 
-	"log/slog"
-
 	"golang.org/x/sys/unix"
 )
 

udp/udp_bsd.go

@@ -8,12 +8,11 @@ package udp
 
 import (
 	"fmt"
+	"log/slog"
 	"net"
 	"net/netip"
 	"syscall"
 
-	"log/slog"
-
 	"golang.org/x/sys/unix"
 )
 

udp/udp_bypass_windows.go

@@ -0,0 +1,57 @@
+//go:build (amd64 || arm64) && !e2e_testing
+// +build amd64 arm64
+// +build !e2e_testing
+
+package udp
+
+import (
+	"log/slog"
+	"sync"
+
+	"github.com/slackhq/nebula/config"
+	"github.com/slackhq/nebula/wfp"
+)
+
+// wrapWithWDFBypass wraps a Conn so that the first ReloadConfig consults listen.windows_bypass_wdf
+// and installs a WFP PERMIT filter for the listener's bound UDP port. The session is released when Close runs.
+func wrapWithWDFBypass(l *slog.Logger, conn Conn) Conn {
+	return &bypassConn{Conn: conn, l: l}
+}
+
+type bypassConn struct {
+	Conn
+
+	l           *slog.Logger
+	installOnce sync.Once
+	session     *wfp.Session
+}
+
+func (b *bypassConn) ReloadConfig(c *config.C) {
+	b.installOnce.Do(func() {
+		if !c.GetBool("listen.windows_bypass_wdf", true) {
+			return
+		}
+		addr, err := b.Conn.LocalAddr()
+		if err != nil {
+			b.l.Warn("Failed to query listener port for WFP bypass", "error", err)
+			return
+		}
+		s, err := wfp.PermitUDPPort(addr.Port())
+		if err != nil {
+			b.l.Warn("Failed to install WFP bypass filters for listener", "error", err)
+			return
+		}
+		b.l.Info("Installed WFP filters bypassing Windows Defender Firewall on UDP listener port",
+			"port", addr.Port())
+		b.session = s
+	})
+	b.Conn.ReloadConfig(c)
+}
+
+func (b *bypassConn) Close() error {
+	if b.session != nil {
+		b.session.Close()
+		b.session = nil
+	}
+	return b.Conn.Close()
+}

udp/udp_bypass_windows_386.go

@@ -0,0 +1,11 @@
+//go:build !e2e_testing
+// +build !e2e_testing
+
+package udp
+
+import "log/slog"
+
+// wrapWithWDFBypass is a no-op on windows-386 since we don't currently build for it.
+func wrapWithWDFBypass(_ *slog.Logger, conn Conn) Conn {
+	return conn
+}

udp/udp_darwin.go

@@ -140,6 +140,15 @@ func (u *StdConn) WriteTo(b []byte, ap netip.AddrPort) error {
 	}
 }
 
+func (u *StdConn) WriteBatch(bufs [][]byte, addrs []netip.AddrPort, _ []byte) error {
+	for i, b := range bufs {
+		if err := u.WriteTo(b, addrs[i]); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
 func (u *StdConn) LocalAddr() (netip.AddrPort, error) {
 	a := u.UDPConn.LocalAddr()
 
@@ -165,7 +174,7 @@ func NewUDPStatsEmitter(udpConns []Conn) func() {
 	return func() {}
 }
 
-func (u *StdConn) ListenOut(r EncReader) error {
+func (u *StdConn) ListenOut(r EncReader, flush func()) error {
 	buffer := make([]byte, MTU)
 
 	for {
@@ -179,7 +188,8 @@ func (u *StdConn) ListenOut(r EncReader) error {
 			u.l.Error("unexpected udp socket receive error", "error", err)
 		}
 
-		r(netip.AddrPortFrom(rua.Addr().Unmap(), rua.Port()), buffer[:n])
+		r(netip.AddrPortFrom(rua.Addr().Unmap(), rua.Port()), buffer[:n], RxMeta{})
+		flush()
 	}
 }
 

udp/udp_generic.go

@@ -44,6 +44,15 @@ func (u *GenericConn) WriteTo(b []byte, addr netip.AddrPort) error {
 	return err
 }
 
+func (u *GenericConn) WriteBatch(bufs [][]byte, addrs []netip.AddrPort, _ []byte) error {
+	for i, b := range bufs {
+		if _, err := u.UDPConn.WriteToUDPAddrPort(b, addrs[i]); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
 func (u *GenericConn) LocalAddr() (netip.AddrPort, error) {
 	a := u.UDPConn.LocalAddr()
 
@@ -73,7 +82,7 @@ type rawMessage struct {
 	Len uint32
 }
 
-func (u *GenericConn) ListenOut(r EncReader) error {
+func (u *GenericConn) ListenOut(r EncReader, flush func()) error {
 	buffer := make([]byte, MTU)
 
 	var lastRecvErr time.Time
@@ -93,7 +102,8 @@ func (u *GenericConn) ListenOut(r EncReader) error {
 			continue
 		}
 
-		r(netip.AddrPortFrom(rua.Addr().Unmap(), rua.Port()), buffer[:n])
+		r(netip.AddrPortFrom(rua.Addr().Unmap(), rua.Port()), buffer[:n], RxMeta{})
+		flush()
 	}
 }
 

udp/udp_linux.go

@@ -24,6 +24,22 @@ type StdConn struct {
 	isV4    bool
 	l       *slog.Logger
 	batch   int
+
+	// sendmmsg scratch. Each queue has its own StdConn, so no locking is
+	// needed. Sized to MaxWriteBatch at construction; WriteBatch chunks
+	// larger inputs.
+	writeMsgs  []rawMessage
+	writeIovs  []iovec
+	writeNames [][]byte
+
+	// sendmmsg(2) callback state. sendmmsgCB is bound once in NewListener
+	// to the sendmmsgRun method value so passing it to rawConn.Write does
+	// not allocate a fresh closure per send; sendmmsgN/Sent/Errno carry
+	// the inputs and outputs across the call without escaping locals.
+	sendmmsgCB    func(fd uintptr) bool
+	sendmmsgN     int
+	sendmmsgSent  int
+	sendmmsgErrno syscall.Errno
 }
 
 func setReusePort(network, address string, c syscall.RawConn) error {
@@ -70,9 +86,23 @@ func NewListener(l *slog.Logger, ip netip.Addr, port int, multi bool, batch int)
 	}
 	out.isV4 = af == unix.AF_INET
 
+	out.prepareWriteMessages(MaxWriteBatch)
+	out.sendmmsgCB = out.sendmmsgRun
+
 	return out, nil
 }
 
+func (u *StdConn) prepareWriteMessages(n int) {
+	u.writeMsgs = make([]rawMessage, n)
+	u.writeIovs = make([]iovec, n)
+	u.writeNames = make([][]byte, n)
+
+	for i := range u.writeMsgs {
+		u.writeNames[i] = make([]byte, unix.SizeofSockaddrInet6)
+		u.writeMsgs[i].Hdr.Name = &u.writeNames[i][0]
+	}
+}
+
 func (u *StdConn) SupportsMultipleReaders() bool {
 	return true
 }
@@ -171,7 +201,7 @@ func recvmmsg(fd uintptr, msgs []rawMessage) (int, bool, error) {
 	return int(n), true, nil
 }
 
-func (u *StdConn) listenOutSingle(r EncReader) error {
+func (u *StdConn) listenOutSingle(r EncReader, flush func()) error {
 	var err error
 	var n int
 	var from netip.AddrPort
@@ -183,16 +213,33 @@ func (u *StdConn) listenOutSingle(r EncReader) error {
 			return err
 		}
 		from = netip.AddrPortFrom(from.Addr().Unmap(), from.Port())
-		r(from, buffer[:n])
+		// listenOutSingle uses ReadFromUDPAddrPort which discards cmsgs,
+		// so the outer ECN field is not visible on this path. Zero RxMeta
+		// (Not-ECT) means RFC 6040 combine is a no-op.
+		r(from, buffer[:n], RxMeta{})
+		flush()
 	}
 }
 
-func (u *StdConn) listenOutBatch(r EncReader) error {
+// readSockaddr decodes the source address out of a recvmmsg name buffer
+func (u *StdConn) readSockaddr(name []byte) netip.AddrPort {
 	var ip netip.Addr
+	// It's ok to skip the ok check here, the slicing is the only error that can occur and it will panic
+	if u.isV4 {
+		ip, _ = netip.AddrFromSlice(name[4:8])
+	} else {
+		ip, _ = netip.AddrFromSlice(name[8:24])
+	}
+	return netip.AddrPortFrom(ip.Unmap(), binary.BigEndian.Uint16(name[2:4]))
+}
+
+func (u *StdConn) listenOutBatch(r EncReader, flush func()) error {
 	var n int
 	var operr error
 
-	msgs, buffers, names := u.PrepareRawMessages(u.batch)
+	bufSize := MTU
+	cmsgSpace := 0
+	msgs, buffers, names, _ := u.PrepareRawMessages(u.batch, bufSize, cmsgSpace)
 
 	//reader needs to capture variables from this function, since it's used as a lambda with rawConn.Read
 	//defining it outside the loop so it gets re-used
@@ -211,22 +258,18 @@ func (u *StdConn) listenOutBatch(r EncReader) error {
 		}
 
 		for i := 0; i < n; i++ {
-			// Its ok to skip the ok check here, the slicing is the only error that can occur and it will panic
+			r(u.readSockaddr(names[i]), buffers[i][:msgs[i].Len], RxMeta{})
-			if u.isV4 {
-				ip, _ = netip.AddrFromSlice(names[i][4:8])
-			} else {
-				ip, _ = netip.AddrFromSlice(names[i][8:24])
-			}
-			r(netip.AddrPortFrom(ip.Unmap(), binary.BigEndian.Uint16(names[i][2:4])), buffers[i][:msgs[i].Len])
 		}
+
+		flush()
 	}
 }
 
-func (u *StdConn) ListenOut(r EncReader) error {
+func (u *StdConn) ListenOut(r EncReader, flush func()) error {
 	if u.batch == 1 {
-		return u.listenOutSingle(r)
+		return u.listenOutSingle(r, flush)
 	} else {
-		return u.listenOutBatch(r)
+		return u.listenOutBatch(r, flush)
 	}
 }
 
@@ -235,6 +278,120 @@ func (u *StdConn) WriteTo(b []byte, ip netip.AddrPort) error {
 	return err
 }
 
+// WriteBatch sends bufs via sendmmsg(2) using the preallocated scratch on
+// StdConn. If supported, consecutive packets to the same destination with
+// matching segment sizes (all but possibly the last) are coalesced into a
+// single mmsghdr entry
+//
+// If sendmmsg returns an error and zero entries went out, we fall back to
+// per-packet WriteTo for that chunk so the caller still gets best-effort
+// delivery. On a partial send we resume at the first un-acked entry on
+// the next iteration.
+func (u *StdConn) WriteBatch(bufs [][]byte, addrs []netip.AddrPort, _ []byte) error {
+	for i := 0; i < len(bufs); {
+		chunk := min(len(bufs)-i, len(u.writeMsgs))
+
+		for k := 0; k < chunk; k++ {
+			u.writeIovs[k].Base = &bufs[i+k][0]
+			setIovLen(&u.writeIovs[k], len(bufs[i+k]))
+
+			nlen, err := writeSockaddr(u.writeNames[k], addrs[i+k], u.isV4)
+			if err != nil {
+				return err
+			}
+
+			hdr := &u.writeMsgs[k].Hdr
+			hdr.Iov = &u.writeIovs[k]
+			setMsgIovlen(hdr, 1)
+			hdr.Namelen = uint32(nlen)
+		}
+
+		sent, serr := u.sendmmsg(chunk)
+		if serr != nil && sent <= 0 {
+			// sendmmsg returns -1 / sent=0 when entry 0 itself failed; log
+			// that entry's destination and fall back to per-packet WriteTo
+			// for the whole chunk so the caller still gets best-effort
+			// delivery without duplicating packets the kernel accepted.
+			u.l.Warn("sendmmsg failed, falling back to per-packet WriteTo",
+				"err", serr,
+				"entries", chunk,
+				"entry0_dst", addrs[i],
+				"isV4", u.isV4,
+			)
+			for k := 0; k < chunk; k++ {
+				if werr := u.WriteTo(bufs[i+k], addrs[i+k]); werr != nil {
+					return werr
+				}
+			}
+			i += chunk
+			continue
+		}
+		i += sent
+	}
+	return nil
+}
+
+// sendmmsg issues sendmmsg(2) against the first n entries of u.writeMsgs.
+// The bound u.sendmmsgCB is passed to rawConn.Write so no closure is
+// allocated per call; inputs and outputs ride on the StdConn fields.
+func (u *StdConn) sendmmsg(n int) (int, error) {
+	u.sendmmsgN = n
+	u.sendmmsgSent = 0
+	u.sendmmsgErrno = 0
+	if err := u.rawConn.Write(u.sendmmsgCB); err != nil {
+		return u.sendmmsgSent, err
+	}
+	if u.sendmmsgErrno != 0 {
+		return u.sendmmsgSent, &net.OpError{Op: "sendmmsg", Err: u.sendmmsgErrno}
+	}
+	return u.sendmmsgSent, nil
+}
+
+// sendmmsgRun is the rawConn.Write callback. It is bound once into
+// u.sendmmsgCB at construction so it stays alloc-free in the hot path;
+// inputs (sendmmsgN) and outputs (sendmmsgSent, sendmmsgErrno) ride on
+// the receiver rather than escaping locals.
+func (u *StdConn) sendmmsgRun(fd uintptr) bool {
+	r1, _, errno := unix.Syscall6(unix.SYS_SENDMMSG, fd,
+		uintptr(unsafe.Pointer(&u.writeMsgs[0])), uintptr(u.sendmmsgN),
+		0, 0, 0,
+	)
+	if errno == syscall.EAGAIN || errno == syscall.EWOULDBLOCK {
+		return false
+	}
+	u.sendmmsgSent = int(r1)
+	u.sendmmsgErrno = errno
+	return true
+}
+
+// writeSockaddr encodes addr into buf (which must be at least
+// SizeofSockaddrInet6 bytes). Returns the number of bytes used. If isV4 is
+// true and addr is not a v4 (or v4-in-v6) address, returns an error.
+func writeSockaddr(buf []byte, addr netip.AddrPort, isV4 bool) (int, error) {
+	ap := addr.Addr().Unmap()
+	if isV4 {
+		if !ap.Is4() {
+			return 0, ErrInvalidIPv6RemoteForSocket
+		}
+		// struct sockaddr_in: { sa_family_t(2), in_port_t(2, BE), in_addr(4), zero(8) }
+		// sa_family is host endian.
+		binary.NativeEndian.PutUint16(buf[0:2], unix.AF_INET)
+		binary.BigEndian.PutUint16(buf[2:4], addr.Port())
+		ip4 := ap.As4()
+		copy(buf[4:8], ip4[:])
+		clear(buf[8:16])
+		return unix.SizeofSockaddrInet4, nil
+	}
+	// struct sockaddr_in6: { sa_family_t(2), in_port_t(2, BE), flowinfo(4), in6_addr(16), scope_id(4) }
+	binary.NativeEndian.PutUint16(buf[0:2], unix.AF_INET6)
+	binary.BigEndian.PutUint16(buf[2:4], addr.Port())
+	binary.NativeEndian.PutUint32(buf[4:8], 0)
+	ip6 := addr.Addr().As16()
+	copy(buf[8:24], ip6[:])
+	binary.NativeEndian.PutUint32(buf[24:28], 0)
+	return unix.SizeofSockaddrInet6, nil
+}
+
 func (u *StdConn) ReloadConfig(c *config.C) {
 	b := c.GetInt("listen.read_buffer", 0)
 	if b > 0 {

udp/udp_linux_32.go

@@ -30,13 +30,18 @@ type rawMessage struct {
 	Len uint32
 }
 
-func (u *StdConn) PrepareRawMessages(n int) ([]rawMessage, [][]byte, [][]byte) {
+func (u *StdConn) PrepareRawMessages(n, bufSize, cmsgSpace int) ([]rawMessage, [][]byte, [][]byte, []byte) {
 	msgs := make([]rawMessage, n)
 	buffers := make([][]byte, n)
 	names := make([][]byte, n)
 
+	var cmsgs []byte
+	if cmsgSpace > 0 {
+		cmsgs = make([]byte, n*cmsgSpace)
+	}
+
 	for i := range msgs {
-		buffers[i] = make([]byte, MTU)
+		buffers[i] = make([]byte, bufSize)
 		names[i] = make([]byte, unix.SizeofSockaddrInet6)
 
 		vs := []iovec{
@@ -48,7 +53,28 @@ func (u *StdConn) PrepareRawMessages(n int) ([]rawMessage, [][]byte, [][]byte) {
 
 		msgs[i].Hdr.Name = &names[i][0]
 		msgs[i].Hdr.Namelen = uint32(len(names[i]))
+
+		if cmsgSpace > 0 {
+			msgs[i].Hdr.Control = &cmsgs[i*cmsgSpace]
+			msgs[i].Hdr.Controllen = uint32(cmsgSpace)
+		}
 	}
 
-	return msgs, buffers, names
+	return msgs, buffers, names, cmsgs
+}
+
+func setIovLen(v *iovec, n int) {
+	v.Len = uint32(n)
+}
+
+func setMsgIovlen(m *msghdr, n int) {
+	m.Iovlen = uint32(n)
+}
+
+func setMsgControllen(m *msghdr, n int) {
+	m.Controllen = uint32(n)
+}
+
+func setCmsgLen(h *unix.Cmsghdr, n int) {
+	h.Len = uint32(n)
 }

udp/udp_linux_64.go

@@ -33,13 +33,18 @@ type rawMessage struct {
 	Pad0 [4]byte
 }
 
-func (u *StdConn) PrepareRawMessages(n int) ([]rawMessage, [][]byte, [][]byte) {
+func (u *StdConn) PrepareRawMessages(n, bufSize, cmsgSpace int) ([]rawMessage, [][]byte, [][]byte, []byte) {
 	msgs := make([]rawMessage, n)
 	buffers := make([][]byte, n)
 	names := make([][]byte, n)
 
+	var cmsgs []byte
+	if cmsgSpace > 0 {
+		cmsgs = make([]byte, n*cmsgSpace)
+	}
+
 	for i := range msgs {
-		buffers[i] = make([]byte, MTU)
+		buffers[i] = make([]byte, bufSize)
 		names[i] = make([]byte, unix.SizeofSockaddrInet6)
 
 		vs := []iovec{
@@ -51,7 +56,28 @@ func (u *StdConn) PrepareRawMessages(n int) ([]rawMessage, [][]byte, [][]byte) {
 
 		msgs[i].Hdr.Name = &names[i][0]
 		msgs[i].Hdr.Namelen = uint32(len(names[i]))
+
+		if cmsgSpace > 0 {
+			msgs[i].Hdr.Control = &cmsgs[i*cmsgSpace]
+			msgs[i].Hdr.Controllen = uint64(cmsgSpace)
+		}
 	}
 
-	return msgs, buffers, names
+	return msgs, buffers, names, cmsgs
+}
+
+func setIovLen(v *iovec, n int) {
+	v.Len = uint64(n)
+}
+
+func setMsgIovlen(m *msghdr, n int) {
+	m.Iovlen = uint64(n)
+}
+
+func setMsgControllen(m *msghdr, n int) {
+	m.Controllen = uint64(n)
+}
+
+func setCmsgLen(h *unix.Cmsghdr, n int) {
+	h.Len = uint64(n)
 }

udp/udp_netbsd.go

@@ -7,12 +7,11 @@ package udp
 
 import (
 	"fmt"
+	"log/slog"
 	"net"
 	"net/netip"
 	"syscall"
 
-	"log/slog"
-
 	"golang.org/x/sys/unix"
 )
 

udp/udp_rio_windows.go

@@ -140,7 +140,7 @@ func (u *RIOConn) bind(l *slog.Logger, sa windows.Sockaddr) error {
 	return nil
 }
 
-func (u *RIOConn) ListenOut(r EncReader) error {
+func (u *RIOConn) ListenOut(r EncReader, flush func()) error {
 	buffer := make([]byte, MTU)
 
 	var lastRecvErr time.Time
@@ -161,7 +161,8 @@ func (u *RIOConn) ListenOut(r EncReader) error {
 			continue
 		}
 
-		r(netip.AddrPortFrom(netip.AddrFrom16(rua.Addr).Unmap(), (rua.Port>>8)|((rua.Port&0xff)<<8)), buffer[:n])
+		r(netip.AddrPortFrom(netip.AddrFrom16(rua.Addr).Unmap(), (rua.Port>>8)|((rua.Port&0xff)<<8)), buffer[:n], RxMeta{})
+		flush()
 	}
 }
 
@@ -316,6 +317,15 @@ func (u *RIOConn) WriteTo(buf []byte, ip netip.AddrPort) error {
 	return winrio.SendEx(u.rq, dataBuffer, 1, nil, addressBuffer, nil, nil, 0, 0)
 }
 
+func (u *RIOConn) WriteBatch(bufs [][]byte, addrs []netip.AddrPort, _ []byte) error {
+	for i, b := range bufs {
+		if err := u.WriteTo(b, addrs[i]); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
 func (u *RIOConn) LocalAddr() (netip.AddrPort, error) {
 	sa, err := windows.Getsockname(u.sock)
 	if err != nil {

udp/udp_tester.go

@@ -157,15 +157,24 @@ func (u *TesterConn) WriteTo(b []byte, addr netip.AddrPort) error {
 		return nil
 	}
 }
+func (u *TesterConn) WriteBatch(bufs [][]byte, addrs []netip.AddrPort, _ []byte) error {
+	for i, b := range bufs {
+		if err := u.WriteTo(b, addrs[i]); err != nil {
+			return err
+		}
+	}
+	return nil
+}
 
-func (u *TesterConn) ListenOut(r EncReader) error {
+func (u *TesterConn) ListenOut(r EncReader, flush func()) error {
 	for {
 		select {
 		case <-u.done:
 			return os.ErrClosed
 		case p := <-u.RxPackets:
-			r(p.From, p.Data)
+			r(p.From, p.Data, RxMeta{})
 			p.Release()
+			flush()
 		}
 	}
 }

udp/udp_windows.go

@@ -19,13 +19,18 @@ func NewListener(l *slog.Logger, ip netip.Addr, port int, multi bool, batch int)
 		return nil, fmt.Errorf("multiple udp listeners not supported on windows")
 	}
 
+	var conn Conn
 	rc, err := NewRIOListener(l, ip, port)
 	if err == nil {
-		return rc, nil
+		conn = rc
+	} else {
+		l.Error("Falling back to standard udp sockets", "error", err)
+		conn, err = NewGenericListener(l, ip, port, multi, batch)
+		if err != nil {
+			return nil, err
+		}
 	}
-
+	return wrapWithWDFBypass(l, conn), nil
-	l.Error("Falling back to standard udp sockets", "error", err)
-	return NewGenericListener(l, ip, port, multi, batch)
 }
 
 func NewListenConfig(multi bool) net.ListenConfig {

wfp/wfp_windows.go

@@ -0,0 +1,377 @@
+//go:build (amd64 || arm64) && !e2e_testing
+// +build amd64 arm64
+// +build !e2e_testing
+
+// Package wfp installs Windows Filtering Platform (WFP) PERMIT filters in a dynamic, session-scoped sublayer.
+// Because WFP sits below Windows Defender Firewall, a high-weight permit at FWPM_LAYER_ALE_AUTH_RECV_ACCEPT_V4/V6 lets
+// the matching inbound traffic through regardless of WDF rules.
+//
+// Each Session owns its own engine handle. When the handle closes, every dynamic object added during the session
+// is auto-deleted by Windows, so there are no orphaned filters.
+//
+// Type definitions and constants are derived from the wireguard-windows firewall package (MIT).
+// Only the subset we exercise is reproduced.
+package wfp
+
+import (
+	"fmt"
+	"unsafe"
+
+	"golang.org/x/sys/windows"
+)
+
+// FWPM layer GUIDs (fwpmu.h).
+//
+// FWPM_LAYER_ALE_AUTH_RECV_ACCEPT_V4 = e1cd9fe7-f4b5-4273-96c0-592e487b8650
+// FWPM_LAYER_ALE_AUTH_RECV_ACCEPT_V6 = a3b42c97-9f04-4672-b87e-cee9c483257f
+var (
+	fwpmLayerAleAuthRecvAcceptV4 = windows.GUID{
+		Data1: 0xe1cd9fe7, Data2: 0xf4b5, Data3: 0x4273,
+		Data4: [8]byte{0x96, 0xc0, 0x59, 0x2e, 0x48, 0x7b, 0x86, 0x50},
+	}
+	fwpmLayerAleAuthRecvAcceptV6 = windows.GUID{
+		Data1: 0xa3b42c97, Data2: 0x9f04, Data3: 0x4672,
+		Data4: [8]byte{0xb8, 0x7e, 0xce, 0xe9, 0xc4, 0x83, 0x25, 0x7f},
+	}
+)
+
+// FWPM_CONDITION_IP_LOCAL_INTERFACE = 4cd62a49-59c3-4969-b7f3-bda5d32890a4
+var fwpmConditionIPLocalInterface = windows.GUID{
+	Data1: 0x4cd62a49, Data2: 0x59c3, Data3: 0x4969,
+	Data4: [8]byte{0xb7, 0xf3, 0xbd, 0xa5, 0xd3, 0x28, 0x90, 0xa4},
+}
+
+// FWPM_CONDITION_IP_PROTOCOL = 3971ef2b-623e-4f9a-8cb1-6e79b806b9a7
+var fwpmConditionIPProtocol = windows.GUID{
+	Data1: 0x3971ef2b, Data2: 0x623e, Data3: 0x4f9a,
+	Data4: [8]byte{0x8c, 0xb1, 0x6e, 0x79, 0xb8, 0x06, 0xb9, 0xa7},
+}
+
+// FWPM_CONDITION_IP_LOCAL_PORT = 0c1ba1af-5765-453f-af22-a8f791ac775b
+var fwpmConditionIPLocalPort = windows.GUID{
+	Data1: 0x0c1ba1af, Data2: 0x5765, Data3: 0x453f,
+	Data4: [8]byte{0xaf, 0x22, 0xa8, 0xf7, 0x91, 0xac, 0x77, 0x5b},
+}
+
+// IPPROTO_UDP from in.h.
+const ipprotoUDP uint8 = 17
+
+// FWP_ACTION_TYPE values (fwptypes.h). PERMIT is terminating.
+const fwpActionPermit uint32 = 0x00001002 // 0x2 | FWP_ACTION_FLAG_TERMINATING(0x1000)
+
+// FWP_DATA_TYPE values we use.
+const (
+	fwpEmpty  uint32 = 0
+	fwpUint8  uint32 = 1
+	fwpUint16 uint32 = 2
+	fwpUint64 uint32 = 4
+)
+
+// FWP_MATCH_TYPE values.
+const fwpMatchEqual uint32 = 0
+
+// FWPM_SESSION flags.
+const fwpmSessionFlagDynamic uint32 = 0x1
+
+// FWPM_FILTER_FLAG_CLEAR_ACTION_RIGHT prevents lower-priority filters in other sublayers,
+// notably Windows Defender Firewall's MPSSVC_WF sublayer, which shares our 0xFFFF weight from overriding this PERMIT.
+// Without it, a default WDF block at the same sublayer weight can still win arbitration.
+const fwpmFilterFlagClearActionRight uint32 = 0x8
+
+// RPC authentication.
+// RPC_C_AUTHN_WINNT works on workgroup machines with no domain context
+// RPC_C_AUTHN_DEFAULT falls back through a chain that can land on something WFP doesn't accept on a fresh box.
+const rpcCAuthnWinNT uint32 = 10
+
+// fwpByteBlob (FWP_BYTE_BLOB). 16 bytes on 64-bit.
+type fwpByteBlob struct {
+	size uint32
+	_    uint32 // padding
+	data *uint8
+}
+
+// fwpValue0 / FWP_CONDITION_VALUE0 layout. 16 bytes on 64-bit.
+// The union is pointer-sized; types <= 32 bits (UINT8/16/32, INT8/16/32, float) live inline in the low bytes
+// of `value`, while UINT64/INT64/double and aggregate types are stored *by pointer*, even on 64-bit, where the
+// union member is declared as UINT64*. So when populating an FWP_UINT64 condition, pass
+// uintptr(unsafe.Pointer(&luidVar)) instead of the LUID inline.
+type fwpValue0 struct {
+	type_ uint32
+	_     uint32 // padding before union to 8-byte alignment
+	value uintptr
+}
+
+// fwpmDisplayData0 / FWPM_DISPLAY_DATA0. 16 bytes on 64-bit.
+type fwpmDisplayData0 struct {
+	name        *uint16
+	description *uint16
+}
+
+// fwpmAction0 / FWPM_ACTION0. 20 bytes; no leading padding because actionType
+// is uint32 and GUID's first field is uint32.
+type fwpmAction0 struct {
+	actionType uint32
+	filterType windows.GUID
+}
+
+// fwpmFilterCondition0. 40 bytes on 64-bit.
+type fwpmFilterCondition0 struct {
+	fieldKey       windows.GUID // 16
+	matchType      uint32       // 4
+	_              uint32       // 4 padding
+	conditionValue fwpValue0    // 16
+}
+
+// fwpmFilter0. 200 bytes on 64-bit.
+type fwpmFilter0 struct {
+	filterKey           windows.GUID
+	displayData         fwpmDisplayData0
+	flags               uint32
+	_                   uint32 // padding before *GUID
+	providerKey         *windows.GUID
+	providerData        fwpByteBlob
+	layerKey            windows.GUID
+	subLayerKey         windows.GUID
+	weight              fwpValue0
+	numFilterConditions uint32
+	_                   uint32 // padding before pointer
+	filterCondition     *fwpmFilterCondition0
+	action              fwpmAction0
+	_                   [4]byte // layout correction
+	providerContextKey  windows.GUID
+	reserved            *windows.GUID
+	filterID            uint64
+	effectiveWeight     fwpValue0
+}
+
+// fwpmSublayer0. 72 bytes on 64-bit.
+type fwpmSublayer0 struct {
+	subLayerKey  windows.GUID
+	displayData  fwpmDisplayData0
+	flags        uint32
+	_            uint32 // padding before *GUID
+	providerKey  *windows.GUID
+	providerData fwpByteBlob
+	weight       uint16
+	_            [6]byte // padding to 72 bytes
+}
+
+// fwpmSession0. 72 bytes on 64-bit.
+type fwpmSession0 struct {
+	sessionKey           windows.GUID
+	displayData          fwpmDisplayData0
+	flags                uint32
+	txnWaitTimeoutInMSec uint32
+	processId            uint32
+	_                    uint32 // padding before *SID
+	sid                  *windows.SID
+	username             *uint16
+	kernelMode           uint8
+	_                    [7]byte // tail padding
+}
+
+// fwpuclnt.dll bindings. Only the calls we use.
+var (
+	modFwpuclnt          = windows.NewLazySystemDLL("fwpuclnt.dll")
+	procFwpmEngineOpen0  = modFwpuclnt.NewProc("FwpmEngineOpen0")
+	procFwpmEngineClose0 = modFwpuclnt.NewProc("FwpmEngineClose0")
+	procFwpmSubLayerAdd0 = modFwpuclnt.NewProc("FwpmSubLayerAdd0")
+	procFwpmFilterAdd0   = modFwpuclnt.NewProc("FwpmFilterAdd0")
+)
+
+// Session holds the WFP engine handle for a single bypass operation. The handle owns a dynamic session:
+// when it is closed, every WFP object added during the session (sublayer + filters) is automatically deleted by
+// Windows. That gives us correct cleanup even if the host process is killed hard between Permit* and Close.
+type Session struct {
+	engine uintptr
+}
+
+// Close releases the engine handle. Windows deletes every dynamic object (sublayer + filters) the session installed.
+// Safe to call on a nil receiver.
+func (s *Session) Close() {
+	if s == nil || s.engine == 0 {
+		return
+	}
+	procFwpmEngineClose0.Call(s.engine)
+	s.engine = 0
+}
+
+// PermitInterface installs PERMIT filters at FWPM_LAYER_ALE_AUTH_RECV_ACCEPT_V4 and _V6 scoped to the given network
+// interface LUID. Inbound traffic on that interface bypasses Windows Defender Firewall.
+func PermitInterface(luid uint64) (*Session, error) {
+	s, sublayerKey, err := newSession()
+	if err != nil {
+		return nil, err
+	}
+
+	if err := addInterfaceFilter(s.engine, sublayerKey, fwpmLayerAleAuthRecvAcceptV4, luid); err != nil {
+		s.Close()
+		return nil, fmt.Errorf("add v4 filter: %w", err)
+	}
+	if err := addInterfaceFilter(s.engine, sublayerKey, fwpmLayerAleAuthRecvAcceptV6, luid); err != nil {
+		s.Close()
+		return nil, fmt.Errorf("add v6 filter: %w", err)
+	}
+	return s, nil
+}
+
+// PermitUDPPort installs PERMIT filters at FWPM_LAYER_ALE_AUTH_RECV_ACCEPT_V4 and _V6 scoped to UDP traffic with the
+// given local port. Inbound UDP to that port on any interface bypasses Windows Defender Firewall.
+func PermitUDPPort(port uint16) (*Session, error) {
+	s, sublayerKey, err := newSession()
+	if err != nil {
+		return nil, err
+	}
+
+	if err := addUDPPortFilter(s.engine, sublayerKey, fwpmLayerAleAuthRecvAcceptV4, port); err != nil {
+		s.Close()
+		return nil, fmt.Errorf("add v4 filter: %w", err)
+	}
+	if err := addUDPPortFilter(s.engine, sublayerKey, fwpmLayerAleAuthRecvAcceptV6, port); err != nil {
+		s.Close()
+		return nil, fmt.Errorf("add v6 filter: %w", err)
+	}
+	return s, nil
+}
+
+func newSession() (*Session, windows.GUID, error) {
+	engine, err := openDynamicEngine()
+	if err != nil {
+		return nil, windows.GUID{}, err
+	}
+	sublayerKey, err := registerSublayer(engine)
+	if err != nil {
+		procFwpmEngineClose0.Call(engine)
+		return nil, windows.GUID{}, err
+	}
+	return &Session{engine: engine}, sublayerKey, nil
+}
+
+func openDynamicEngine() (uintptr, error) {
+	session := fwpmSession0{flags: fwpmSessionFlagDynamic}
+	var engine uintptr
+	r1, _, _ := procFwpmEngineOpen0.Call(
+		0, // serverName == NULL (local)
+		uintptr(rpcCAuthnWinNT),
+		0, // authIdentity == NULL
+		uintptr(unsafe.Pointer(&session)),
+		uintptr(unsafe.Pointer(&engine)),
+	)
+	if r1 != 0 {
+		return 0, fmt.Errorf("FwpmEngineOpen0: 0x%x", r1)
+	}
+	return engine, nil
+}
+
+// registerSublayer adds a session-scoped sublayer with a freshly generated GUID, weight 0xFFFF so its filters arbitrate
+// above WDF's default sublayer. The sublayer is dynamic (no PERSISTENT flag) and goes away when the engine handle closes.
+func registerSublayer(engine uintptr) (windows.GUID, error) {
+	key, err := windows.GenerateGUID()
+	if err != nil {
+		return windows.GUID{}, fmt.Errorf("GenerateGUID for sublayer: %w", err)
+	}
+
+	name, _ := windows.UTF16PtrFromString("Nebula WDF bypass sublayer")
+	desc, _ := windows.UTF16PtrFromString("Permit filters bypassing Windows Defender Firewall")
+	sl := fwpmSublayer0{
+		subLayerKey: key,
+		displayData: fwpmDisplayData0{name: name, description: desc},
+		weight:      0xFFFF,
+	}
+	r1, _, _ := procFwpmSubLayerAdd0.Call(
+		engine,
+		uintptr(unsafe.Pointer(&sl)),
+		0, // sd == NULL
+	)
+	if r1 != 0 {
+		return windows.GUID{}, fmt.Errorf("FwpmSubLayerAdd0: 0x%x", r1)
+	}
+	return key, nil
+}
+
+func addInterfaceFilter(engine uintptr, sublayerKey, layer windows.GUID, luid uint64) error {
+	name, _ := windows.UTF16PtrFromString("Nebula allow interface inbound")
+	desc, _ := windows.UTF16PtrFromString("Permits inbound traffic on a nebula interface")
+
+	// luid must remain addressable through the syscall -- FWP_UINT64 is stored
+	// by pointer in the FWP_VALUE0 union.
+	cond := fwpmFilterCondition0{
+		fieldKey:  fwpmConditionIPLocalInterface,
+		matchType: fwpMatchEqual,
+		conditionValue: fwpValue0{
+			type_: fwpUint64,
+			value: uintptr(unsafe.Pointer(&luid)),
+		},
+	}
+
+	filter := fwpmFilter0{
+		// filterKey left zero: WFP assigns one when the filter is added.
+		displayData:         fwpmDisplayData0{name: name, description: desc},
+		flags:               fwpmFilterFlagClearActionRight,
+		layerKey:            layer,
+		subLayerKey:         sublayerKey,
+		weight:              fwpValue0{type_: fwpUint8, value: uintptr(15)},
+		numFilterConditions: 1,
+		filterCondition:     &cond,
+		action:              fwpmAction0{actionType: fwpActionPermit},
+	}
+
+	r1, _, _ := procFwpmFilterAdd0.Call(
+		engine,
+		uintptr(unsafe.Pointer(&filter)),
+		0, // sd == NULL
+		0, // id == NULL
+	)
+	if r1 != 0 {
+		return fmt.Errorf("FwpmFilterAdd0: 0x%x", r1)
+	}
+	return nil
+}
+
+// addUDPPortFilter installs a PERMIT filter that matches (IP_PROTOCOL == UDP) AND (IP_LOCAL_PORT == port).
+// FWP_UINT8 and FWP_UINT16 are <= 32 bits so they live inline in the FWP_VALUE0 union.
+func addUDPPortFilter(engine uintptr, sublayerKey, layer windows.GUID, port uint16) error {
+	name, _ := windows.UTF16PtrFromString("Nebula allow UDP port inbound")
+	desc, _ := windows.UTF16PtrFromString("Permits inbound UDP to a nebula listener port")
+
+	conds := [2]fwpmFilterCondition0{
+		{
+			fieldKey:  fwpmConditionIPProtocol,
+			matchType: fwpMatchEqual,
+			conditionValue: fwpValue0{
+				type_: fwpUint8,
+				value: uintptr(ipprotoUDP),
+			},
+		},
+		{
+			fieldKey:  fwpmConditionIPLocalPort,
+			matchType: fwpMatchEqual,
+			conditionValue: fwpValue0{
+				type_: fwpUint16,
+				value: uintptr(port),
+			},
+		},
+	}
+
+	filter := fwpmFilter0{
+		displayData:         fwpmDisplayData0{name: name, description: desc},
+		flags:               fwpmFilterFlagClearActionRight,
+		layerKey:            layer,
+		subLayerKey:         sublayerKey,
+		weight:              fwpValue0{type_: fwpUint8, value: uintptr(15)},
+		numFilterConditions: 2,
+		filterCondition:     &conds[0],
+		action:              fwpmAction0{actionType: fwpActionPermit},
+	}
+
+	r1, _, _ := procFwpmFilterAdd0.Call(
+		engine,
+		uintptr(unsafe.Pointer(&filter)),
+		0,
+		0,
+	)
+	if r1 != 0 {
+		return fmt.Errorf("FwpmFilterAdd0: 0x%x", r1)
+	}
+	return nil
+}

wire/wire.go

@@ -0,0 +1,17 @@
+package wire
+
+// TunPacket is the unit a read from a tun device returns.
+// On supported platforms, it may be a superpacket, but a single TunPacket will never have more than one destination.
+type TunPacket struct {
+	// Bytes contains the actual packet
+	Bytes []byte
+	// Meta contains other information to help process the packet correctly, such as offsets for segmentation offloads
+	// Fields in Meta should be as portable/platform-agnostic as possible.
+	Meta struct{}
+}
+
+// PerSegment invokes fn once per segment of pkt.
+// This is a stub implementation that does not actually support segmentation
+func (t *TunPacket) PerSegment(fn func(seg []byte) error) error {
+	return fn(t.Bytes)
+}