less garbage

* firewall can distinguish if the host connecting has an overlapping network, is a VPN peer without an overlapping network, or is a unsafe network

* Cross stack subnet stuff (#1512)

* experiment with not filtering out non-common addresses in hostinfo.networks

* allow handshakes without overlaps

* unsafe network test

* change HostInfo.buildNetworks argument to reference the cert

.github/workflows/gofmt.yml

@@ -14,7 +14,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
 
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v5
 
     - uses: actions/setup-go@v6
       with:

.github/workflows/release.yml

@@ -10,7 +10,7 @@ jobs:
     name: Build Linux/BSD All
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
 
       - uses: actions/setup-go@v6
         with:
@@ -24,7 +24,7 @@ jobs:
           mv build/*.tar.gz release
 
       - name: Upload artifacts
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v5
         with:
           name: linux-latest
           path: release
@@ -33,7 +33,7 @@ jobs:
     name: Build Windows
     runs-on: windows-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
 
       - uses: actions/setup-go@v6
         with:
@@ -55,7 +55,7 @@ jobs:
           mv dist\windows\wintun build\dist\windows\
 
       - name: Upload artifacts
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v5
         with:
           name: windows-latest
           path: build
@@ -66,7 +66,7 @@ jobs:
       HAS_SIGNING_CREDS: ${{ secrets.AC_USERNAME != '' }}
     runs-on: macos-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
 
       - uses: actions/setup-go@v6
         with:
@@ -104,7 +104,7 @@ jobs:
           fi
 
       - name: Upload artifacts
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v5
         with:
           name: darwin-latest
           path: ./release/*
@@ -124,11 +124,11 @@ jobs:
       # be overwritten
       - name: Checkout code
         if: ${{ env.HAS_DOCKER_CREDS == 'true' }}
-        uses: actions/checkout@v4
+        uses: actions/checkout@v5
 
       - name: Download artifacts
         if: ${{ env.HAS_DOCKER_CREDS == 'true' }}
-        uses: actions/download-artifact@v4
+        uses: actions/download-artifact@v6
         with:
           name: linux-latest
           path: artifacts
@@ -160,10 +160,10 @@ jobs:
     needs: [build-linux, build-darwin, build-windows]
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
 
       - name: Download artifacts
-        uses: actions/download-artifact@v4
+        uses: actions/download-artifact@v6
         with:
           path: artifacts
 

.github/workflows/smoke-extra.yml

@@ -20,7 +20,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
 
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v5
 
     - uses: actions/setup-go@v6
       with:

.github/workflows/smoke.yml

@@ -18,7 +18,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
 
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v5
 
     - uses: actions/setup-go@v6
       with:

.github/workflows/test.yml

@@ -18,7 +18,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
 
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v5
 
     - uses: actions/setup-go@v6
       with:
@@ -32,7 +32,7 @@ jobs:
       run: make vet
 
     - name: golangci-lint
-      uses: golangci/golangci-lint-action@v8
+      uses: golangci/golangci-lint-action@v9
       with:
         version: v2.5
 
@@ -45,7 +45,7 @@ jobs:
     - name: Build test mobile
       run: make build-test-mobile
 
-    - uses: actions/upload-artifact@v4
+    - uses: actions/upload-artifact@v5
       with:
         name: e2e packet flow linux-latest
         path: e2e/mermaid/linux-latest
@@ -56,7 +56,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
 
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v5
 
     - uses: actions/setup-go@v6
       with:
@@ -77,7 +77,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
 
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v5
 
     - uses: actions/setup-go@v6
       with:
@@ -98,7 +98,7 @@ jobs:
         os: [windows-latest, macos-latest]
     steps:
 
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v5
 
     - uses: actions/setup-go@v6
       with:
@@ -115,7 +115,7 @@ jobs:
       run: make vet
 
     - name: golangci-lint
-      uses: golangci/golangci-lint-action@v8
+      uses: golangci/golangci-lint-action@v9
       with:
         version: v2.5
 
@@ -125,7 +125,7 @@ jobs:
     - name: End 2 end
       run: make e2evv
 
-    - uses: actions/upload-artifact@v4
+    - uses: actions/upload-artifact@v5
       with:
         name: e2e packet flow ${{ matrix.os }}
         path: e2e/mermaid/${{ matrix.os }}

bits.go

@@ -43,7 +43,7 @@ func (b *Bits) Check(l logrus.FieldLogger, i uint64) bool {
 	}
 
 	// Not within the window
-	l.Debugf("rejected a packet (top) %d %d\n", b.current, i)
+	l.Debugf("rejected a packet (top) %d %d delta %d\n", b.current, i, b.current-i)
 	return false
 }
 

cert_test/cert.go

@@ -114,6 +114,33 @@ func NewTestCert(v cert.Version, curve cert.Curve, ca cert.Certificate, key []by
 	return c, pub, cert.MarshalPrivateKeyToPEM(curve, priv), pem
 }
 
+func NewTestCertDifferentVersion(c cert.Certificate, v cert.Version, ca cert.Certificate, key []byte) (cert.Certificate, []byte) {
+	nc := &cert.TBSCertificate{
+		Version:        v,
+		Curve:          c.Curve(),
+		Name:           c.Name(),
+		Networks:       c.Networks(),
+		UnsafeNetworks: c.UnsafeNetworks(),
+		Groups:         c.Groups(),
+		NotBefore:      time.Unix(c.NotBefore().Unix(), 0),
+		NotAfter:       time.Unix(c.NotAfter().Unix(), 0),
+		PublicKey:      c.PublicKey(),
+		IsCA:           false,
+	}
+
+	c, err := nc.Sign(ca, ca.Curve(), key)
+	if err != nil {
+		panic(err)
+	}
+
+	pem, err := c.MarshalPEM()
+	if err != nil {
+		panic(err)
+	}
+
+	return c, pem
+}
+
 func X25519Keypair() ([]byte, []byte) {
 	privkey := make([]byte, 32)
 	if _, err := io.ReadFull(rand.Reader, privkey); err != nil {

cmd/nebula/main.go

@@ -3,6 +3,9 @@ package main
 import (
 	"flag"
 	"fmt"
+	"log"
+	"net/http"
+	_ "net/http/pprof"
 	"os"
 
 	"github.com/sirupsen/logrus"
@@ -58,6 +61,10 @@ func main() {
 		os.Exit(1)
 	}
 
+	go func() {
+		log.Println(http.ListenAndServe("0.0.0.0:6060", nil))
+	}()
+
 	if !*configTest {
 		ctrl.Start()
 		notifyReady(l)

config/config.go

@@ -17,7 +17,7 @@ import (
 
 	"dario.cat/mergo"
 	"github.com/sirupsen/logrus"
-	"gopkg.in/yaml.v3"
+	"go.yaml.in/yaml/v3"
 )
 
 type C struct {

config/config_test.go

@@ -10,7 +10,7 @@ import (
 	"github.com/slackhq/nebula/test"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
-	"gopkg.in/yaml.v3"
+	"go.yaml.in/yaml/v3"
 )
 
 func TestConfig_Load(t *testing.T) {

connection_manager.go

@@ -354,7 +354,6 @@ func (cm *connectionManager) makeTrafficDecision(localIndex uint32, now time.Tim
 
 		if mainHostInfo {
 			decision = tryRehandshake
-
 		} else {
 			if cm.shouldSwapPrimary(hostinfo) {
 				decision = swapPrimary
@@ -461,6 +460,10 @@ func (cm *connectionManager) shouldSwapPrimary(current *HostInfo) bool {
 	}
 
 	crt := cm.intf.pki.getCertState().getCertificate(current.ConnectionState.myCert.Version())
+	if crt == nil {
+		//my cert was reloaded away. We should definitely swap from this tunnel
+		return true
+	}
 	// If this tunnel is using the latest certificate then we should swap it to primary for a bit and see if things
 	// settle down.
 	return bytes.Equal(current.ConnectionState.myCert.Signature(), crt.Signature())
@@ -475,31 +478,34 @@ func (cm *connectionManager) swapPrimary(current, primary *HostInfo) {
 	cm.hostMap.Unlock()
 }
 
-// isInvalidCertificate will check if we should destroy a tunnel if pki.disconnect_invalid is true and
-// the certificate is no longer valid. Block listed certificates will skip the pki.disconnect_invalid
-// check and return true.
+// isInvalidCertificate decides if we should destroy a tunnel.
+// returns true if pki.disconnect_invalid is true and the certificate is no longer valid.
+// Blocklisted certificates will skip the pki.disconnect_invalid check and return true.
 func (cm *connectionManager) isInvalidCertificate(now time.Time, hostinfo *HostInfo) bool {
 	remoteCert := hostinfo.GetCert()
 	if remoteCert == nil {
-		return false
+		return false //don't tear down tunnels for handshakes in progress
 	}
 
 	caPool := cm.intf.pki.GetCAPool()
 	err := caPool.VerifyCachedCertificate(now, remoteCert)
 	if err == nil {
-		return false
-	}
-
-	if !cm.intf.disconnectInvalid.Load() && err != cert.ErrBlockListed {
+		return false //cert is still valid! yay!
+	} else if err == cert.ErrBlockListed { //avoiding errors.Is for speed
 		// Block listed certificates should always be disconnected
-		return false
-	}
-
+		hostinfo.logger(cm.l).WithError(err).
+			WithField("fingerprint", remoteCert.Fingerprint).
+			Info("Remote certificate is blocked, tearing down the tunnel")
+		return true
+	} else if cm.intf.disconnectInvalid.Load() {
 		hostinfo.logger(cm.l).WithError(err).
 			WithField("fingerprint", remoteCert.Fingerprint).
 			Info("Remote certificate is no longer valid, tearing down the tunnel")
-
 		return true
+	} else {
+		//if we reach here, the cert is no longer valid, but we're configured to keep tunnels from now-invalid certs open
+		return false
+	}
 }
 
 func (cm *connectionManager) sendPunch(hostinfo *HostInfo) {
@@ -530,15 +536,45 @@ func (cm *connectionManager) sendPunch(hostinfo *HostInfo) {
 func (cm *connectionManager) tryRehandshake(hostinfo *HostInfo) {
 	cs := cm.intf.pki.getCertState()
 	curCrt := hostinfo.ConnectionState.myCert
-	myCrt := cs.getCertificate(curCrt.Version())
-	if curCrt.Version() >= cs.initiatingVersion && bytes.Equal(curCrt.Signature(), myCrt.Signature()) == true {
-		// The current tunnel is using the latest certificate and version, no need to rehandshake.
+	curCrtVersion := curCrt.Version()
+	myCrt := cs.getCertificate(curCrtVersion)
+	if myCrt == nil {
+		cm.l.WithField("vpnAddrs", hostinfo.vpnAddrs).
+			WithField("version", curCrtVersion).
+			WithField("reason", "local certificate removed").
+			Info("Re-handshaking with remote")
+		cm.intf.handshakeManager.StartHandshake(hostinfo.vpnAddrs[0], nil)
 		return
 	}
-
+	peerCrt := hostinfo.ConnectionState.peerCert
+	if peerCrt != nil && curCrtVersion < peerCrt.Certificate.Version() {
+		// if our certificate version is less than theirs, and we have a matching version available, rehandshake?
+		if cs.getCertificate(peerCrt.Certificate.Version()) != nil {
+			cm.l.WithField("vpnAddrs", hostinfo.vpnAddrs).
+				WithField("version", curCrtVersion).
+				WithField("peerVersion", peerCrt.Certificate.Version()).
+				WithField("reason", "local certificate version lower than peer, attempting to correct").
+				Info("Re-handshaking with remote")
+			cm.intf.handshakeManager.StartHandshake(hostinfo.vpnAddrs[0], func(hh *HandshakeHostInfo) {
+				hh.initiatingVersionOverride = peerCrt.Certificate.Version()
+			})
+			return
+		}
+	}
+	if !bytes.Equal(curCrt.Signature(), myCrt.Signature()) {
 		cm.l.WithField("vpnAddrs", hostinfo.vpnAddrs).
 			WithField("reason", "local certificate is not current").
 			Info("Re-handshaking with remote")
 
 		cm.intf.handshakeManager.StartHandshake(hostinfo.vpnAddrs[0], nil)
+		return
+	}
+	if curCrtVersion < cs.initiatingVersion {
+		cm.l.WithField("vpnAddrs", hostinfo.vpnAddrs).
+			WithField("reason", "current cert version < pki.initiatingVersion").
+			Info("Re-handshaking with remote")
+
+		cm.intf.handshakeManager.StartHandshake(hostinfo.vpnAddrs[0], nil)
+		return
+	}
 }

connection_state.go

@@ -13,7 +13,7 @@ import (
 	"github.com/slackhq/nebula/noiseutil"
 )
 
-const ReplayWindow = 1024
+const ReplayWindow = 4096
 
 type ConnectionState struct {
 	eKey           *NebulaCipherState

control_tester.go

@@ -174,6 +174,10 @@ func (c *Control) GetHostmap() *HostMap {
 	return c.f.hostMap
 }
 
+func (c *Control) GetF() *Interface {
+	return c.f
+}
+
 func (c *Control) GetCertState() *CertState {
 	return c.f.pki.getCertState()
 }

e2e/handshakes_test.go

@@ -20,7 +20,7 @@ import (
 	"github.com/slackhq/nebula/udp"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
-	"gopkg.in/yaml.v3"
+	"go.yaml.in/yaml/v3"
 )
 
 func BenchmarkHotPath(b *testing.B) {
@@ -97,6 +97,41 @@ func TestGoodHandshake(t *testing.T) {
 	theirControl.Stop()
 }
 
+func TestGoodHandshakeNoOverlap(t *testing.T) {
+	ca, _, caKey, _ := cert_test.NewTestCaCert(cert.Version2, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
+	myControl, myVpnIpNet, myUdpAddr, _ := newSimpleServer(cert.Version2, ca, caKey, "me", "10.128.0.1/24", nil)
+	theirControl, theirVpnIpNet, theirUdpAddr, _ := newSimpleServer(cert.Version2, ca, caKey, "them", "2001::69/24", nil) //look ma, cross-stack!
+
+	// Put their info in our lighthouse
+	myControl.InjectLightHouseAddr(theirVpnIpNet[0].Addr(), theirUdpAddr)
+
+	// Start the servers
+	myControl.Start()
+	theirControl.Start()
+
+	empty := []byte{}
+	t.Log("do something to cause a handshake")
+	myControl.GetF().SendMessageToVpnAddr(header.Test, header.MessageNone, theirVpnIpNet[0].Addr(), empty, empty, empty)
+
+	t.Log("Have them consume my stage 0 packet. They have a tunnel now")
+	theirControl.InjectUDPPacket(myControl.GetFromUDP(true))
+
+	t.Log("Get their stage 1 packet")
+	stage1Packet := theirControl.GetFromUDP(true)
+
+	t.Log("Have me consume their stage 1 packet. I have a tunnel now")
+	myControl.InjectUDPPacket(stage1Packet)
+
+	t.Log("Wait until we see a test packet come through to make sure we give the tunnel time to complete")
+	myControl.WaitForType(header.Test, 0, theirControl)
+
+	t.Log("Make sure our host infos are correct")
+	assertHostInfoPair(t, myUdpAddr, theirUdpAddr, myVpnIpNet, theirVpnIpNet, myControl, theirControl)
+
+	myControl.Stop()
+	theirControl.Stop()
+}
+
 func TestWrongResponderHandshake(t *testing.T) {
 	ca, _, caKey, _ := cert_test.NewTestCaCert(cert.Version1, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
 
@@ -464,6 +499,35 @@ func TestRelays(t *testing.T) {
 	r.RenderHostmaps("Final hostmaps", myControl, relayControl, theirControl)
 }
 
+func TestRelaysDontCareAboutIps(t *testing.T) {
+	ca, _, caKey, _ := cert_test.NewTestCaCert(cert.Version2, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
+	myControl, myVpnIpNet, _, _ := newSimpleServer(cert.Version2, ca, caKey, "me     ", "10.128.0.1/24", m{"relay": m{"use_relays": true}})
+	relayControl, relayVpnIpNet, relayUdpAddr, _ := newSimpleServer(cert.Version2, ca, caKey, "relay  ", "2001::9999/24", m{"relay": m{"am_relay": true}})
+	theirControl, theirVpnIpNet, theirUdpAddr, _ := newSimpleServer(cert.Version2, ca, caKey, "them   ", "10.128.0.2/24", m{"relay": m{"use_relays": true}})
+
+	// Teach my how to get to the relay and that their can be reached via the relay
+	myControl.InjectLightHouseAddr(relayVpnIpNet[0].Addr(), relayUdpAddr)
+	myControl.InjectRelays(theirVpnIpNet[0].Addr(), []netip.Addr{relayVpnIpNet[0].Addr()})
+	relayControl.InjectLightHouseAddr(theirVpnIpNet[0].Addr(), theirUdpAddr)
+
+	// Build a router so we don't have to reason who gets which packet
+	r := router.NewR(t, myControl, relayControl, theirControl)
+	defer r.RenderFlow()
+
+	// Start the servers
+	myControl.Start()
+	relayControl.Start()
+	theirControl.Start()
+
+	t.Log("Trigger a handshake from me to them via the relay")
+	myControl.InjectTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me"))
+
+	p := r.RouteForAllUntilTxTun(theirControl)
+	r.Log("Assert the tunnel works")
+	assertUdpPacket(t, []byte("Hi from me"), p, myVpnIpNet[0].Addr(), theirVpnIpNet[0].Addr(), 80, 80)
+	r.RenderHostmaps("Final hostmaps", myControl, relayControl, theirControl)
+}
+
 func TestReestablishRelays(t *testing.T) {
 	ca, _, caKey, _ := cert_test.NewTestCaCert(cert.Version1, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
 	myControl, myVpnIpNet, _, _ := newSimpleServer(cert.Version1, ca, caKey, "me     ", "10.128.0.1/24", m{"relay": m{"use_relays": true}})
@@ -1227,3 +1291,109 @@ func TestV2NonPrimaryWithLighthouse(t *testing.T) {
 	myControl.Stop()
 	theirControl.Stop()
 }
+
+func TestV2NonPrimaryWithOffNetLighthouse(t *testing.T) {
+	ca, _, caKey, _ := cert_test.NewTestCaCert(cert.Version2, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
+	lhControl, lhVpnIpNet, lhUdpAddr, _ := newSimpleServer(cert.Version2, ca, caKey, "lh  ", "2001::1/64", m{"lighthouse": m{"am_lighthouse": true}})
+
+	o := m{
+		"static_host_map": m{
+			lhVpnIpNet[0].Addr().String(): []string{lhUdpAddr.String()},
+		},
+		"lighthouse": m{
+			"hosts": []string{lhVpnIpNet[0].Addr().String()},
+			"local_allow_list": m{
+				// Try and block our lighthouse updates from using the actual addresses assigned to this computer
+				// If we start discovering addresses the test router doesn't know about then test traffic cant flow
+				"10.0.0.0/24": true,
+				"::/0":        false,
+			},
+		},
+	}
+	myControl, myVpnIpNet, _, _ := newSimpleServer(cert.Version2, ca, caKey, "me  ", "10.128.0.2/24, ff::2/64", o)
+	theirControl, theirVpnIpNet, _, _ := newSimpleServer(cert.Version2, ca, caKey, "them", "10.128.0.3/24, ff::3/64", o)
+
+	// Build a router so we don't have to reason who gets which packet
+	r := router.NewR(t, lhControl, myControl, theirControl)
+	defer r.RenderFlow()
+
+	// Start the servers
+	lhControl.Start()
+	myControl.Start()
+	theirControl.Start()
+
+	t.Log("Stand up an ipv6 tunnel between me and them")
+	assert.True(t, myVpnIpNet[1].Addr().Is6())
+	assert.True(t, theirVpnIpNet[1].Addr().Is6())
+	assertTunnel(t, myVpnIpNet[1].Addr(), theirVpnIpNet[1].Addr(), myControl, theirControl, r)
+
+	lhControl.Stop()
+	myControl.Stop()
+	theirControl.Stop()
+}
+
+func TestGoodHandshakeUnsafeDest(t *testing.T) {
+	unsafePrefix := "192.168.6.0/24"
+	ca, _, caKey, _ := cert_test.NewTestCaCert(cert.Version2, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
+	theirControl, theirVpnIpNet, theirUdpAddr, _ := newSimpleServerWithUdpAndUnsafeNetworks(cert.Version2, ca, caKey, "spooky", "10.128.0.2/24", netip.MustParseAddrPort("10.64.0.2:4242"), unsafePrefix, nil)
+	route := m{"route": unsafePrefix, "via": theirVpnIpNet[0].Addr().String()}
+	myCfg := m{
+		"tun": m{
+			"unsafe_routes": []m{route},
+		},
+	}
+	myControl, myVpnIpNet, myUdpAddr, myConfig := newSimpleServer(cert.Version2, ca, caKey, "me", "10.128.0.1/24", myCfg)
+	t.Logf("my config %v", myConfig)
+	// Put their info in our lighthouse
+	myControl.InjectLightHouseAddr(theirVpnIpNet[0].Addr(), theirUdpAddr)
+
+	spookyDest := netip.MustParseAddr("192.168.6.4")
+
+	// Start the servers
+	myControl.Start()
+	theirControl.Start()
+
+	t.Log("Send a udp packet through to begin standing up the tunnel, this should come out the other side")
+	myControl.InjectTunUDPPacket(spookyDest, 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me"))
+
+	t.Log("Have them consume my stage 0 packet. They have a tunnel now")
+	theirControl.InjectUDPPacket(myControl.GetFromUDP(true))
+
+	t.Log("Get their stage 1 packet so that we can play with it")
+	stage1Packet := theirControl.GetFromUDP(true)
+
+	t.Log("I consume a garbage packet with a proper nebula header for our tunnel")
+	// this should log a statement and get ignored, allowing the real handshake packet to complete the tunnel
+	badPacket := stage1Packet.Copy()
+	badPacket.Data = badPacket.Data[:len(badPacket.Data)-header.Len]
+	myControl.InjectUDPPacket(badPacket)
+
+	t.Log("Have me consume their real stage 1 packet. I have a tunnel now")
+	myControl.InjectUDPPacket(stage1Packet)
+
+	t.Log("Wait until we see my cached packet come through")
+	myControl.WaitForType(1, 0, theirControl)
+
+	t.Log("Make sure our host infos are correct")
+	assertHostInfoPair(t, myUdpAddr, theirUdpAddr, myVpnIpNet, theirVpnIpNet, myControl, theirControl)
+
+	t.Log("Get that cached packet and make sure it looks right")
+	myCachedPacket := theirControl.GetFromTun(true)
+	assertUdpPacket(t, []byte("Hi from me"), myCachedPacket, myVpnIpNet[0].Addr(), spookyDest, 80, 80)
+
+	//reply
+	theirControl.InjectTunUDPPacket(myVpnIpNet[0].Addr(), 80, spookyDest, 80, []byte("Hi from the spookyman"))
+	//wait for reply
+	theirControl.WaitForType(1, 0, myControl)
+	theirCachedPacket := myControl.GetFromTun(true)
+	assertUdpPacket(t, []byte("Hi from the spookyman"), theirCachedPacket, spookyDest, myVpnIpNet[0].Addr(), 80, 80)
+
+	t.Log("Do a bidirectional tunnel test")
+	r := router.NewR(t, myControl, theirControl)
+	defer r.RenderFlow()
+	assertTunnel(t, myVpnIpNet[0].Addr(), theirVpnIpNet[0].Addr(), myControl, theirControl, r)
+
+	r.RenderHostmaps("Final hostmaps", myControl, theirControl)
+	myControl.Stop()
+	theirControl.Stop()
+}

e2e/helpers_test.go

@@ -22,15 +22,14 @@ import (
 	"github.com/slackhq/nebula/config"
 	"github.com/slackhq/nebula/e2e/router"
 	"github.com/stretchr/testify/assert"
-	"gopkg.in/yaml.v3"
+	"github.com/stretchr/testify/require"
+	"go.yaml.in/yaml/v3"
 )
 
 type m = map[string]any
 
 // newSimpleServer creates a nebula instance with many assumptions
 func newSimpleServer(v cert.Version, caCrt cert.Certificate, caKey []byte, name string, sVpnNetworks string, overrides m) (*nebula.Control, []netip.Prefix, netip.AddrPort, *config.C) {
-	l := NewTestLogger()
-
 	var vpnNetworks []netip.Prefix
 	for _, sn := range strings.Split(sVpnNetworks, ",") {
 		vpnIpNet, err := netip.ParsePrefix(strings.TrimSpace(sn))
@@ -56,7 +55,54 @@ func newSimpleServer(v cert.Version, caCrt cert.Certificate, caKey []byte, name
 		budpIp[3] = 239
 		udpAddr = netip.AddrPortFrom(netip.AddrFrom16(budpIp), 4242)
 	}
-	_, _, myPrivKey, myPEM := cert_test.NewTestCert(v, cert.Curve_CURVE25519, caCrt, caKey, name, time.Now(), time.Now().Add(5*time.Minute), vpnNetworks, nil, []string{})
+	return newSimpleServerWithUdp(v, caCrt, caKey, name, sVpnNetworks, udpAddr, overrides)
+}
+
+func newSimpleServerWithUdp(v cert.Version, caCrt cert.Certificate, caKey []byte, name string, sVpnNetworks string, udpAddr netip.AddrPort, overrides m) (*nebula.Control, []netip.Prefix, netip.AddrPort, *config.C) {
+	return newSimpleServerWithUdpAndUnsafeNetworks(v, caCrt, caKey, name, sVpnNetworks, udpAddr, "", overrides)
+}
+
+func newSimpleServerWithUdpAndUnsafeNetworks(v cert.Version, caCrt cert.Certificate, caKey []byte, name string, sVpnNetworks string, udpAddr netip.AddrPort, sUnsafeNetworks string, overrides m) (*nebula.Control, []netip.Prefix, netip.AddrPort, *config.C) {
+	l := NewTestLogger()
+
+	var vpnNetworks []netip.Prefix
+	for _, sn := range strings.Split(sVpnNetworks, ",") {
+		vpnIpNet, err := netip.ParsePrefix(strings.TrimSpace(sn))
+		if err != nil {
+			panic(err)
+		}
+		vpnNetworks = append(vpnNetworks, vpnIpNet)
+	}
+
+	if len(vpnNetworks) == 0 {
+		panic("no vpn networks")
+	}
+
+	firewallInbound := []m{{
+		"proto": "any",
+		"port":  "any",
+		"host":  "any",
+	}}
+
+	var unsafeNetworks []netip.Prefix
+	if sUnsafeNetworks != "" {
+		firewallInbound = []m{{
+			"proto":      "any",
+			"port":       "any",
+			"host":       "any",
+			"local_cidr": "0.0.0.0/0",
+		}}
+
+		for _, sn := range strings.Split(sUnsafeNetworks, ",") {
+			x, err := netip.ParsePrefix(strings.TrimSpace(sn))
+			if err != nil {
+				panic(err)
+			}
+			unsafeNetworks = append(unsafeNetworks, x)
+		}
+	}
+
+	_, _, myPrivKey, myPEM := cert_test.NewTestCert(v, cert.Curve_CURVE25519, caCrt, caKey, name, time.Now(), time.Now().Add(5*time.Minute), vpnNetworks, unsafeNetworks, []string{})
 
 	caB, err := caCrt.MarshalPEM()
 	if err != nil {
@@ -76,11 +122,7 @@ func newSimpleServer(v cert.Version, caCrt cert.Certificate, caKey []byte, name
 				"port":  "any",
 				"host":  "any",
 			}},
-			"inbound": []m{{
-				"proto": "any",
-				"port":  "any",
-				"host":  "any",
-			}},
+			"inbound": firewallInbound,
 		},
 		//"handshakes": m{
 		//	"try_interval": "1s",
@@ -129,6 +171,109 @@ func newSimpleServer(v cert.Version, caCrt cert.Certificate, caKey []byte, name
 	return control, vpnNetworks, udpAddr, c
 }
 
+// newServer creates a nebula instance with fewer assumptions
+func newServer(caCrt []cert.Certificate, certs []cert.Certificate, key []byte, overrides m) (*nebula.Control, []netip.Prefix, netip.AddrPort, *config.C) {
+	l := NewTestLogger()
+
+	vpnNetworks := certs[len(certs)-1].Networks()
+
+	var udpAddr netip.AddrPort
+	if vpnNetworks[0].Addr().Is4() {
+		budpIp := vpnNetworks[0].Addr().As4()
+		budpIp[1] -= 128
+		udpAddr = netip.AddrPortFrom(netip.AddrFrom4(budpIp), 4242)
+	} else {
+		budpIp := vpnNetworks[0].Addr().As16()
+		// beef for funsies
+		budpIp[2] = 190
+		budpIp[3] = 239
+		udpAddr = netip.AddrPortFrom(netip.AddrFrom16(budpIp), 4242)
+	}
+
+	caStr := ""
+	for _, ca := range caCrt {
+		x, err := ca.MarshalPEM()
+		if err != nil {
+			panic(err)
+		}
+		caStr += string(x)
+	}
+	certStr := ""
+	for _, c := range certs {
+		x, err := c.MarshalPEM()
+		if err != nil {
+			panic(err)
+		}
+		certStr += string(x)
+	}
+
+	mc := m{
+		"pki": m{
+			"ca":   caStr,
+			"cert": certStr,
+			"key":  string(key),
+		},
+		//"tun": m{"disabled": true},
+		"firewall": m{
+			"outbound": []m{{
+				"proto": "any",
+				"port":  "any",
+				"host":  "any",
+			}},
+			"inbound": []m{{
+				"proto": "any",
+				"port":  "any",
+				"host":  "any",
+			}},
+		},
+		//"handshakes": m{
+		//	"try_interval": "1s",
+		//},
+		"listen": m{
+			"host": udpAddr.Addr().String(),
+			"port": udpAddr.Port(),
+		},
+		"logging": m{
+			"timestamp_format": fmt.Sprintf("%v 15:04:05.000000", certs[0].Name()),
+			"level":            l.Level.String(),
+		},
+		"timers": m{
+			"pending_deletion_interval": 2,
+			"connection_alive_interval": 2,
+		},
+	}
+
+	if overrides != nil {
+		final := m{}
+		err := mergo.Merge(&final, overrides, mergo.WithAppendSlice)
+		if err != nil {
+			panic(err)
+		}
+		err = mergo.Merge(&final, mc, mergo.WithAppendSlice)
+		if err != nil {
+			panic(err)
+		}
+		mc = final
+	}
+
+	cb, err := yaml.Marshal(mc)
+	if err != nil {
+		panic(err)
+	}
+
+	c := config.NewC(l)
+	cStr := string(cb)
+	c.LoadString(cStr)
+
+	control, err := nebula.Main(c, false, "e2e-test", l, nil)
+
+	if err != nil {
+		panic(err)
+	}
+
+	return control, vpnNetworks, udpAddr, c
+}
+
 type doneCb func()
 
 func deadline(t *testing.T, seconds time.Duration) doneCb {
@@ -163,10 +308,10 @@ func assertHostInfoPair(t *testing.T, addrA, addrB netip.AddrPort, vpnNetsA, vpn
 	// Get both host infos
 	//TODO: CERT-V2 we may want to loop over each vpnAddr and assert all the things
 	hBinA := controlA.GetHostInfoByVpnAddr(vpnNetsB[0].Addr(), false)
-	assert.NotNil(t, hBinA, "Host B was not found by vpnAddr in controlA")
+	require.NotNil(t, hBinA, "Host B was not found by vpnAddr in controlA")
 
 	hAinB := controlB.GetHostInfoByVpnAddr(vpnNetsA[0].Addr(), false)
-	assert.NotNil(t, hAinB, "Host A was not found by vpnAddr in controlB")
+	require.NotNil(t, hAinB, "Host A was not found by vpnAddr in controlB")
 
 	// Check that both vpn and real addr are correct
 	assert.EqualValues(t, getAddrs(vpnNetsB), hBinA.VpnAddrs, "Host B VpnIp is wrong in control A")

e2e/tunnels_test.go

@@ -4,12 +4,16 @@
 package e2e
 
 import (
+	"fmt"
+	"net/netip"
 	"testing"
 	"time"
 
 	"github.com/slackhq/nebula/cert"
 	"github.com/slackhq/nebula/cert_test"
 	"github.com/slackhq/nebula/e2e/router"
+	"github.com/stretchr/testify/assert"
+	"gopkg.in/yaml.v3"
 )
 
 func TestDropInactiveTunnels(t *testing.T) {
@@ -55,3 +59,309 @@ func TestDropInactiveTunnels(t *testing.T) {
 	myControl.Stop()
 	theirControl.Stop()
 }
+
+func TestCertUpgrade(t *testing.T) {
+	// The goal of this test is to ensure the shortest inactivity timeout will close the tunnel on both sides
+	// under ideal conditions
+	ca, _, caKey, _ := cert_test.NewTestCaCert(cert.Version1, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
+	caB, err := ca.MarshalPEM()
+	if err != nil {
+		panic(err)
+	}
+	ca2, _, caKey2, _ := cert_test.NewTestCaCert(cert.Version2, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
+
+	ca2B, err := ca2.MarshalPEM()
+	if err != nil {
+		panic(err)
+	}
+	caStr := fmt.Sprintf("%s\n%s", caB, ca2B)
+
+	myCert, _, myPrivKey, _ := cert_test.NewTestCert(cert.Version1, cert.Curve_CURVE25519, ca, caKey, "me", time.Now(), time.Now().Add(5*time.Minute), []netip.Prefix{netip.MustParsePrefix("10.128.0.1/24")}, nil, []string{})
+	_, myCert2Pem := cert_test.NewTestCertDifferentVersion(myCert, cert.Version2, ca2, caKey2)
+
+	theirCert, _, theirPrivKey, _ := cert_test.NewTestCert(cert.Version1, cert.Curve_CURVE25519, ca, caKey, "them", time.Now(), time.Now().Add(5*time.Minute), []netip.Prefix{netip.MustParsePrefix("10.128.0.2/24")}, nil, []string{})
+	theirCert2, _ := cert_test.NewTestCertDifferentVersion(theirCert, cert.Version2, ca2, caKey2)
+
+	myControl, myVpnIpNet, myUdpAddr, myC := newServer([]cert.Certificate{ca, ca2}, []cert.Certificate{myCert}, myPrivKey, m{})
+	theirControl, theirVpnIpNet, theirUdpAddr, _ := newServer([]cert.Certificate{ca, ca2}, []cert.Certificate{theirCert, theirCert2}, theirPrivKey, m{})
+
+	// Share our underlay information
+	myControl.InjectLightHouseAddr(theirVpnIpNet[0].Addr(), theirUdpAddr)
+	theirControl.InjectLightHouseAddr(myVpnIpNet[0].Addr(), myUdpAddr)
+
+	// Start the servers
+	myControl.Start()
+	theirControl.Start()
+
+	r := router.NewR(t, myControl, theirControl)
+	defer r.RenderFlow()
+
+	r.Log("Assert the tunnel between me and them works")
+	assertTunnel(t, myVpnIpNet[0].Addr(), theirVpnIpNet[0].Addr(), myControl, theirControl, r)
+	r.Log("yay")
+	//todo ???
+	time.Sleep(1 * time.Second)
+	r.FlushAll()
+
+	mc := m{
+		"pki": m{
+			"ca":   caStr,
+			"cert": string(myCert2Pem),
+			"key":  string(myPrivKey),
+		},
+		//"tun": m{"disabled": true},
+		"firewall": myC.Settings["firewall"],
+		//"handshakes": m{
+		//	"try_interval": "1s",
+		//},
+		"listen":  myC.Settings["listen"],
+		"logging": myC.Settings["logging"],
+		"timers":  myC.Settings["timers"],
+	}
+
+	cb, err := yaml.Marshal(mc)
+	if err != nil {
+		panic(err)
+	}
+
+	r.Logf("reload new v2-only config")
+	err = myC.ReloadConfigString(string(cb))
+	assert.NoError(t, err)
+	r.Log("yay, spin until their sees it")
+	waitStart := time.Now()
+	for {
+		assertTunnel(t, myVpnIpNet[0].Addr(), theirVpnIpNet[0].Addr(), myControl, theirControl, r)
+		c := theirControl.GetHostInfoByVpnAddr(myVpnIpNet[0].Addr(), false)
+		if c == nil {
+			r.Log("nil")
+		} else {
+			version := c.Cert.Version()
+			r.Logf("version %d", version)
+			if version == cert.Version2 {
+				break
+			}
+		}
+		since := time.Since(waitStart)
+		if since > time.Second*10 {
+			t.Fatal("Cert should be new by now")
+		}
+		time.Sleep(time.Second)
+	}
+
+	r.RenderHostmaps("Final hostmaps", myControl, theirControl)
+
+	myControl.Stop()
+	theirControl.Stop()
+}
+
+func TestCertDowngrade(t *testing.T) {
+	// The goal of this test is to ensure the shortest inactivity timeout will close the tunnel on both sides
+	// under ideal conditions
+	ca, _, caKey, _ := cert_test.NewTestCaCert(cert.Version1, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
+	caB, err := ca.MarshalPEM()
+	if err != nil {
+		panic(err)
+	}
+	ca2, _, caKey2, _ := cert_test.NewTestCaCert(cert.Version2, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
+
+	ca2B, err := ca2.MarshalPEM()
+	if err != nil {
+		panic(err)
+	}
+	caStr := fmt.Sprintf("%s\n%s", caB, ca2B)
+
+	myCert, _, myPrivKey, myCertPem := cert_test.NewTestCert(cert.Version1, cert.Curve_CURVE25519, ca, caKey, "me", time.Now(), time.Now().Add(5*time.Minute), []netip.Prefix{netip.MustParsePrefix("10.128.0.1/24")}, nil, []string{})
+	myCert2, _ := cert_test.NewTestCertDifferentVersion(myCert, cert.Version2, ca2, caKey2)
+
+	theirCert, _, theirPrivKey, _ := cert_test.NewTestCert(cert.Version1, cert.Curve_CURVE25519, ca, caKey, "them", time.Now(), time.Now().Add(5*time.Minute), []netip.Prefix{netip.MustParsePrefix("10.128.0.2/24")}, nil, []string{})
+	theirCert2, _ := cert_test.NewTestCertDifferentVersion(theirCert, cert.Version2, ca2, caKey2)
+
+	myControl, myVpnIpNet, myUdpAddr, myC := newServer([]cert.Certificate{ca, ca2}, []cert.Certificate{myCert2}, myPrivKey, m{})
+	theirControl, theirVpnIpNet, theirUdpAddr, _ := newServer([]cert.Certificate{ca, ca2}, []cert.Certificate{theirCert, theirCert2}, theirPrivKey, m{})
+
+	// Share our underlay information
+	myControl.InjectLightHouseAddr(theirVpnIpNet[0].Addr(), theirUdpAddr)
+	theirControl.InjectLightHouseAddr(myVpnIpNet[0].Addr(), myUdpAddr)
+
+	// Start the servers
+	myControl.Start()
+	theirControl.Start()
+
+	r := router.NewR(t, myControl, theirControl)
+	defer r.RenderFlow()
+
+	r.Log("Assert the tunnel between me and them works")
+	//assertTunnel(t, theirVpnIpNet[0].Addr(), myVpnIpNet[0].Addr(), theirControl, myControl, r)
+	//r.Log("yay")
+	assertTunnel(t, myVpnIpNet[0].Addr(), theirVpnIpNet[0].Addr(), myControl, theirControl, r)
+	r.Log("yay")
+	//todo ???
+	time.Sleep(1 * time.Second)
+	r.FlushAll()
+
+	mc := m{
+		"pki": m{
+			"ca":   caStr,
+			"cert": string(myCertPem),
+			"key":  string(myPrivKey),
+		},
+		"firewall": myC.Settings["firewall"],
+		"listen":   myC.Settings["listen"],
+		"logging":  myC.Settings["logging"],
+		"timers":   myC.Settings["timers"],
+	}
+
+	cb, err := yaml.Marshal(mc)
+	if err != nil {
+		panic(err)
+	}
+
+	r.Logf("reload new v1-only config")
+	err = myC.ReloadConfigString(string(cb))
+	assert.NoError(t, err)
+	r.Log("yay, spin until their sees it")
+	waitStart := time.Now()
+	for {
+		assertTunnel(t, myVpnIpNet[0].Addr(), theirVpnIpNet[0].Addr(), myControl, theirControl, r)
+		c := theirControl.GetHostInfoByVpnAddr(myVpnIpNet[0].Addr(), false)
+		c2 := myControl.GetHostInfoByVpnAddr(theirVpnIpNet[0].Addr(), false)
+		if c == nil || c2 == nil {
+			r.Log("nil")
+		} else {
+			version := c.Cert.Version()
+			theirVersion := c2.Cert.Version()
+			r.Logf("version %d,%d", version, theirVersion)
+			if version == cert.Version1 {
+				break
+			}
+		}
+		since := time.Since(waitStart)
+		if since > time.Second*5 {
+			r.Log("it is unusual that the cert is not new yet, but not a failure yet")
+		}
+		if since > time.Second*10 {
+			r.Log("wtf")
+			t.Fatal("Cert should be new by now")
+		}
+		time.Sleep(time.Second)
+	}
+
+	r.RenderHostmaps("Final hostmaps", myControl, theirControl)
+
+	myControl.Stop()
+	theirControl.Stop()
+}
+
+func TestCertMismatchCorrection(t *testing.T) {
+	// The goal of this test is to ensure the shortest inactivity timeout will close the tunnel on both sides
+	// under ideal conditions
+	ca, _, caKey, _ := cert_test.NewTestCaCert(cert.Version1, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
+	ca2, _, caKey2, _ := cert_test.NewTestCaCert(cert.Version2, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
+
+	myCert, _, myPrivKey, _ := cert_test.NewTestCert(cert.Version1, cert.Curve_CURVE25519, ca, caKey, "me", time.Now(), time.Now().Add(5*time.Minute), []netip.Prefix{netip.MustParsePrefix("10.128.0.1/24")}, nil, []string{})
+	myCert2, _ := cert_test.NewTestCertDifferentVersion(myCert, cert.Version2, ca2, caKey2)
+
+	theirCert, _, theirPrivKey, _ := cert_test.NewTestCert(cert.Version1, cert.Curve_CURVE25519, ca, caKey, "them", time.Now(), time.Now().Add(5*time.Minute), []netip.Prefix{netip.MustParsePrefix("10.128.0.2/24")}, nil, []string{})
+	theirCert2, _ := cert_test.NewTestCertDifferentVersion(theirCert, cert.Version2, ca2, caKey2)
+
+	myControl, myVpnIpNet, myUdpAddr, _ := newServer([]cert.Certificate{ca, ca2}, []cert.Certificate{myCert2}, myPrivKey, m{})
+	theirControl, theirVpnIpNet, theirUdpAddr, _ := newServer([]cert.Certificate{ca, ca2}, []cert.Certificate{theirCert, theirCert2}, theirPrivKey, m{})
+
+	// Share our underlay information
+	myControl.InjectLightHouseAddr(theirVpnIpNet[0].Addr(), theirUdpAddr)
+	theirControl.InjectLightHouseAddr(myVpnIpNet[0].Addr(), myUdpAddr)
+
+	// Start the servers
+	myControl.Start()
+	theirControl.Start()
+
+	r := router.NewR(t, myControl, theirControl)
+	defer r.RenderFlow()
+
+	r.Log("Assert the tunnel between me and them works")
+	//assertTunnel(t, theirVpnIpNet[0].Addr(), myVpnIpNet[0].Addr(), theirControl, myControl, r)
+	//r.Log("yay")
+	assertTunnel(t, myVpnIpNet[0].Addr(), theirVpnIpNet[0].Addr(), myControl, theirControl, r)
+	r.Log("yay")
+	//todo ???
+	time.Sleep(1 * time.Second)
+	r.FlushAll()
+
+	waitStart := time.Now()
+	for {
+		assertTunnel(t, myVpnIpNet[0].Addr(), theirVpnIpNet[0].Addr(), myControl, theirControl, r)
+		c := theirControl.GetHostInfoByVpnAddr(myVpnIpNet[0].Addr(), false)
+		c2 := myControl.GetHostInfoByVpnAddr(theirVpnIpNet[0].Addr(), false)
+		if c == nil || c2 == nil {
+			r.Log("nil")
+		} else {
+			version := c.Cert.Version()
+			theirVersion := c2.Cert.Version()
+			r.Logf("version %d,%d", version, theirVersion)
+			if version == theirVersion {
+				break
+			}
+		}
+		since := time.Since(waitStart)
+		if since > time.Second*5 {
+			r.Log("wtf")
+		}
+		if since > time.Second*10 {
+			r.Log("wtf")
+			t.Fatal("Cert should be new by now")
+		}
+		time.Sleep(time.Second)
+	}
+
+	r.RenderHostmaps("Final hostmaps", myControl, theirControl)
+
+	myControl.Stop()
+	theirControl.Stop()
+}
+
+func TestCrossStackRelaysWork(t *testing.T) {
+	ca, _, caKey, _ := cert_test.NewTestCaCert(cert.Version2, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
+	myControl, myVpnIpNet, _, _ := newSimpleServer(cert.Version2, ca, caKey, "me     ", "10.128.0.1/24,fc00::1/64", m{"relay": m{"use_relays": true}})
+	relayControl, relayVpnIpNet, relayUdpAddr, _ := newSimpleServer(cert.Version2, ca, caKey, "relay  ", "10.128.0.128/24,fc00::128/64", m{"relay": m{"am_relay": true}})
+	theirUdp := netip.MustParseAddrPort("10.0.0.2:4242")
+	theirControl, theirVpnIpNet, theirUdpAddr, _ := newSimpleServerWithUdp(cert.Version2, ca, caKey, "them   ", "fc00::2/64", theirUdp, m{"relay": m{"use_relays": true}})
+
+	//myVpnV4 := myVpnIpNet[0]
+	myVpnV6 := myVpnIpNet[1]
+	relayVpnV4 := relayVpnIpNet[0]
+	relayVpnV6 := relayVpnIpNet[1]
+	theirVpnV6 := theirVpnIpNet[0]
+
+	// Teach my how to get to the relay and that their can be reached via the relay
+	myControl.InjectLightHouseAddr(relayVpnV4.Addr(), relayUdpAddr)
+	myControl.InjectLightHouseAddr(relayVpnV6.Addr(), relayUdpAddr)
+	myControl.InjectRelays(theirVpnV6.Addr(), []netip.Addr{relayVpnV6.Addr()})
+	relayControl.InjectLightHouseAddr(theirVpnV6.Addr(), theirUdpAddr)
+
+	// Build a router so we don't have to reason who gets which packet
+	r := router.NewR(t, myControl, relayControl, theirControl)
+	defer r.RenderFlow()
+
+	// Start the servers
+	myControl.Start()
+	relayControl.Start()
+	theirControl.Start()
+
+	t.Log("Trigger a handshake from me to them via the relay")
+	myControl.InjectTunUDPPacket(theirVpnV6.Addr(), 80, myVpnV6.Addr(), 80, []byte("Hi from me"))
+
+	p := r.RouteForAllUntilTxTun(theirControl)
+	r.Log("Assert the tunnel works")
+	assertUdpPacket(t, []byte("Hi from me"), p, myVpnV6.Addr(), theirVpnV6.Addr(), 80, 80)
+
+	t.Log("reply?")
+	theirControl.InjectTunUDPPacket(myVpnV6.Addr(), 80, theirVpnV6.Addr(), 80, []byte("Hi from them"))
+	p = r.RouteForAllUntilTxTun(myControl)
+	assertUdpPacket(t, []byte("Hi from them"), p, theirVpnV6.Addr(), myVpnV6.Addr(), 80, 80)
+
+	r.RenderHostmaps("Final hostmaps", myControl, relayControl, theirControl)
+	//t.Log("finish up")
+	//myControl.Stop()
+	//theirControl.Stop()
+	//relayControl.Stop()
+}

firewall.go

@@ -417,30 +417,45 @@ func AddFirewallRulesFromConfig(l *logrus.Logger, inbound bool, c *config.C, fw
 	return nil
 }
 
-var ErrInvalidRemoteIP = errors.New("remote IP is not in remote certificate subnets")
-var ErrInvalidLocalIP = errors.New("local IP is not in list of handled local IPs")
+var ErrUnknownNetworkType = errors.New("unknown network type")
+var ErrPeerRejected = errors.New("remote address is not within a network that we handle")
+var ErrInvalidRemoteIP = errors.New("remote address is not in remote certificate networks")
+var ErrInvalidLocalIP = errors.New("local address is not in list of handled local addresses")
 var ErrNoMatchingRule = errors.New("no matching rule in firewall table")
 
 // Drop returns an error if the packet should be dropped, explaining why. It
 // returns nil if the packet should not be dropped.
-func (f *Firewall) Drop(fp firewall.Packet, incoming bool, h *HostInfo, caPool *cert.CAPool, localCache firewall.ConntrackCache) error {
+func (f *Firewall) Drop(fp firewall.Packet, incoming bool, h *HostInfo, caPool *cert.CAPool, localCache firewall.ConntrackCache, now time.Time) error {
 	// Check if we spoke to this tuple, if we did then allow this packet
-	if f.inConns(fp, h, caPool, localCache) {
+	if f.inConns(fp, h, caPool, localCache, now) {
 		return nil
 	}
 
-	// Make sure remote address matches nebula certificate
-	if h.networks != nil {
-		if !h.networks.Contains(fp.RemoteAddr) {
-			f.metrics(incoming).droppedRemoteAddr.Inc(1)
-			return ErrInvalidRemoteIP
-		}
-	} else {
+	// Make sure remote address matches nebula certificate, and determine how to treat it
+	if h.networks == nil {
 		// Simple case: Certificate has one address and no unsafe networks
 		if h.vpnAddrs[0] != fp.RemoteAddr {
 			f.metrics(incoming).droppedRemoteAddr.Inc(1)
 			return ErrInvalidRemoteIP
 		}
+	} else {
+		nwType, ok := h.networks.Lookup(fp.RemoteAddr)
+		if !ok {
+			f.metrics(incoming).droppedRemoteAddr.Inc(1)
+			return ErrInvalidRemoteIP
+		}
+		switch nwType {
+		case NetworkTypeVPN:
+			break // nothing special
+		case NetworkTypeVPNPeer:
+			f.metrics(incoming).droppedRemoteAddr.Inc(1)
+			return ErrPeerRejected // reject for now, one day this may have different FW rules
+		case NetworkTypeUnsafe:
+			break // nothing special, one day this may have different FW rules
+		default:
+			f.metrics(incoming).droppedRemoteAddr.Inc(1)
+			return ErrUnknownNetworkType //should never happen
+		}
 	}
 
 	// Make sure we are supposed to be handling this local ip address
@@ -461,7 +476,7 @@ func (f *Firewall) Drop(fp firewall.Packet, incoming bool, h *HostInfo, caPool *
 	}
 
 	// We always want to conntrack since it is a faster operation
-	f.addConn(fp, incoming)
+	f.addConn(fp, incoming, now)
 
 	return nil
 }
@@ -490,7 +505,7 @@ func (f *Firewall) EmitStats() {
 	metrics.GetOrRegisterGauge("firewall.rules.hash", nil).Update(int64(f.GetRuleHashFNV()))
 }
 
-func (f *Firewall) inConns(fp firewall.Packet, h *HostInfo, caPool *cert.CAPool, localCache firewall.ConntrackCache) bool {
+func (f *Firewall) inConns(fp firewall.Packet, h *HostInfo, caPool *cert.CAPool, localCache firewall.ConntrackCache, now time.Time) bool {
 	if localCache != nil {
 		if _, ok := localCache[fp]; ok {
 			return true
@@ -502,7 +517,7 @@ func (f *Firewall) inConns(fp firewall.Packet, h *HostInfo, caPool *cert.CAPool,
 	// Purge every time we test
 	ep, has := conntrack.TimerWheel.Purge()
 	if has {
-		f.evict(ep)
+		f.evict(ep, now)
 	}
 
 	c, ok := conntrack.Conns[fp]
@@ -549,11 +564,11 @@ func (f *Firewall) inConns(fp firewall.Packet, h *HostInfo, caPool *cert.CAPool,
 
 	switch fp.Protocol {
 	case firewall.ProtoTCP:
-		c.Expires = time.Now().Add(f.TCPTimeout)
+		c.Expires = now.Add(f.TCPTimeout)
 	case firewall.ProtoUDP:
-		c.Expires = time.Now().Add(f.UDPTimeout)
+		c.Expires = now.Add(f.UDPTimeout)
 	default:
-		c.Expires = time.Now().Add(f.DefaultTimeout)
+		c.Expires = now.Add(f.DefaultTimeout)
 	}
 
 	conntrack.Unlock()
@@ -565,7 +580,7 @@ func (f *Firewall) inConns(fp firewall.Packet, h *HostInfo, caPool *cert.CAPool,
 	return true
 }
 
-func (f *Firewall) addConn(fp firewall.Packet, incoming bool) {
+func (f *Firewall) addConn(fp firewall.Packet, incoming bool, now time.Time) {
 	var timeout time.Duration
 	c := &conn{}
 
@@ -581,7 +596,7 @@ func (f *Firewall) addConn(fp firewall.Packet, incoming bool) {
 	conntrack := f.Conntrack
 	conntrack.Lock()
 	if _, ok := conntrack.Conns[fp]; !ok {
-		conntrack.TimerWheel.Advance(time.Now())
+		conntrack.TimerWheel.Advance(now)
 		conntrack.TimerWheel.Add(fp, timeout)
 	}
 
@@ -589,14 +604,14 @@ func (f *Firewall) addConn(fp firewall.Packet, incoming bool) {
 	// firewall reload
 	c.incoming = incoming
 	c.rulesVersion = f.rulesVersion
-	c.Expires = time.Now().Add(timeout)
+	c.Expires = now.Add(timeout)
 	conntrack.Conns[fp] = c
 	conntrack.Unlock()
 }
 
 // Evict checks if a conntrack entry has expired, if so it is removed, if not it is re-added to the wheel
 // Caller must own the connMutex lock!
-func (f *Firewall) evict(p firewall.Packet) {
+func (f *Firewall) evict(p firewall.Packet, now time.Time) {
 	// Are we still tracking this conn?
 	conntrack := f.Conntrack
 	t, ok := conntrack.Conns[p]
@@ -604,11 +619,11 @@ func (f *Firewall) evict(p firewall.Packet) {
 		return
 	}
 
-	newT := t.Expires.Sub(time.Now())
+	newT := t.Expires.Sub(now)
 
 	// Timeout is in the future, re-add the timer
 	if newT > 0 {
-		conntrack.TimerWheel.Advance(time.Now())
+		conntrack.TimerWheel.Advance(now)
 		conntrack.TimerWheel.Add(p, newT)
 		return
 	}

firewall_test.go

@@ -8,6 +8,8 @@ import (
 	"testing"
 	"time"
 
+	"github.com/gaissmai/bart"
+	"github.com/sirupsen/logrus"
 	"github.com/slackhq/nebula/cert"
 	"github.com/slackhq/nebula/config"
 	"github.com/slackhq/nebula/firewall"
@@ -149,7 +151,8 @@ func TestFirewall_Drop(t *testing.T) {
 	l := test.NewLogger()
 	ob := &bytes.Buffer{}
 	l.SetOutput(ob)
-
+	myVpnNetworksTable := new(bart.Lite)
+	myVpnNetworksTable.Insert(netip.MustParsePrefix("1.1.1.1/8"))
 	p := firewall.Packet{
 		LocalAddr:  netip.MustParseAddr("1.2.3.4"),
 		RemoteAddr: netip.MustParseAddr("1.2.3.4"),
@@ -174,7 +177,7 @@ func TestFirewall_Drop(t *testing.T) {
 		},
 		vpnAddrs: []netip.Addr{netip.MustParseAddr("1.2.3.4")},
 	}
-	h.buildNetworks(c.networks, c.unsafeNetworks)
+	h.buildNetworks(myVpnNetworksTable, &c)
 
 	fw := NewFirewall(l, time.Second, time.Minute, time.Hour, &c)
 	require.NoError(t, fw.AddRule(true, firewall.ProtoAny, 0, 0, []string{"any"}, "", netip.Prefix{}, netip.Prefix{}, "", ""))
@@ -226,6 +229,9 @@ func TestFirewall_DropV6(t *testing.T) {
 	ob := &bytes.Buffer{}
 	l.SetOutput(ob)
 
+	myVpnNetworksTable := new(bart.Lite)
+	myVpnNetworksTable.Insert(netip.MustParsePrefix("fd00::/7"))
+
 	p := firewall.Packet{
 		LocalAddr:  netip.MustParseAddr("fd12::34"),
 		RemoteAddr: netip.MustParseAddr("fd12::34"),
@@ -250,7 +256,7 @@ func TestFirewall_DropV6(t *testing.T) {
 		},
 		vpnAddrs: []netip.Addr{netip.MustParseAddr("fd12::34")},
 	}
-	h.buildNetworks(c.networks, c.unsafeNetworks)
+	h.buildNetworks(myVpnNetworksTable, &c)
 
 	fw := NewFirewall(l, time.Second, time.Minute, time.Hour, &c)
 	require.NoError(t, fw.AddRule(true, firewall.ProtoAny, 0, 0, []string{"any"}, "", netip.Prefix{}, netip.Prefix{}, "", ""))
@@ -453,6 +459,8 @@ func TestFirewall_Drop2(t *testing.T) {
 	l := test.NewLogger()
 	ob := &bytes.Buffer{}
 	l.SetOutput(ob)
+	myVpnNetworksTable := new(bart.Lite)
+	myVpnNetworksTable.Insert(netip.MustParsePrefix("1.1.1.1/8"))
 
 	p := firewall.Packet{
 		LocalAddr:  netip.MustParseAddr("1.2.3.4"),
@@ -478,7 +486,7 @@ func TestFirewall_Drop2(t *testing.T) {
 		},
 		vpnAddrs: []netip.Addr{network.Addr()},
 	}
-	h.buildNetworks(c.Certificate.Networks(), c.Certificate.UnsafeNetworks())
+	h.buildNetworks(myVpnNetworksTable, c.Certificate)
 
 	c1 := cert.CachedCertificate{
 		Certificate: &dummyCert{
@@ -493,7 +501,7 @@ func TestFirewall_Drop2(t *testing.T) {
 			peerCert: &c1,
 		},
 	}
-	h1.buildNetworks(c1.Certificate.Networks(), c1.Certificate.UnsafeNetworks())
+	h1.buildNetworks(myVpnNetworksTable, c1.Certificate)
 
 	fw := NewFirewall(l, time.Second, time.Minute, time.Hour, c.Certificate)
 	require.NoError(t, fw.AddRule(true, firewall.ProtoAny, 0, 0, []string{"default-group", "test-group"}, "", netip.Prefix{}, netip.Prefix{}, "", ""))
@@ -510,6 +518,8 @@ func TestFirewall_Drop3(t *testing.T) {
 	l := test.NewLogger()
 	ob := &bytes.Buffer{}
 	l.SetOutput(ob)
+	myVpnNetworksTable := new(bart.Lite)
+	myVpnNetworksTable.Insert(netip.MustParsePrefix("1.1.1.1/8"))
 
 	p := firewall.Packet{
 		LocalAddr:  netip.MustParseAddr("1.2.3.4"),
@@ -541,7 +551,7 @@ func TestFirewall_Drop3(t *testing.T) {
 		},
 		vpnAddrs: []netip.Addr{network.Addr()},
 	}
-	h1.buildNetworks(c1.Certificate.Networks(), c1.Certificate.UnsafeNetworks())
+	h1.buildNetworks(myVpnNetworksTable, c1.Certificate)
 
 	c2 := cert.CachedCertificate{
 		Certificate: &dummyCert{
@@ -556,7 +566,7 @@ func TestFirewall_Drop3(t *testing.T) {
 		},
 		vpnAddrs: []netip.Addr{network.Addr()},
 	}
-	h2.buildNetworks(c2.Certificate.Networks(), c2.Certificate.UnsafeNetworks())
+	h2.buildNetworks(myVpnNetworksTable, c2.Certificate)
 
 	c3 := cert.CachedCertificate{
 		Certificate: &dummyCert{
@@ -571,7 +581,7 @@ func TestFirewall_Drop3(t *testing.T) {
 		},
 		vpnAddrs: []netip.Addr{network.Addr()},
 	}
-	h3.buildNetworks(c3.Certificate.Networks(), c3.Certificate.UnsafeNetworks())
+	h3.buildNetworks(myVpnNetworksTable, c3.Certificate)
 
 	fw := NewFirewall(l, time.Second, time.Minute, time.Hour, c.Certificate)
 	require.NoError(t, fw.AddRule(true, firewall.ProtoAny, 1, 1, []string{}, "host1", netip.Prefix{}, netip.Prefix{}, "", ""))
@@ -597,6 +607,8 @@ func TestFirewall_Drop3V6(t *testing.T) {
 	l := test.NewLogger()
 	ob := &bytes.Buffer{}
 	l.SetOutput(ob)
+	myVpnNetworksTable := new(bart.Lite)
+	myVpnNetworksTable.Insert(netip.MustParsePrefix("fd00::/7"))
 
 	p := firewall.Packet{
 		LocalAddr:  netip.MustParseAddr("fd12::34"),
@@ -620,7 +632,7 @@ func TestFirewall_Drop3V6(t *testing.T) {
 		},
 		vpnAddrs: []netip.Addr{network.Addr()},
 	}
-	h.buildNetworks(c.Certificate.Networks(), c.Certificate.UnsafeNetworks())
+	h.buildNetworks(myVpnNetworksTable, c.Certificate)
 
 	// Test a remote address match
 	fw := NewFirewall(l, time.Second, time.Minute, time.Hour, c.Certificate)
@@ -633,6 +645,8 @@ func TestFirewall_DropConntrackReload(t *testing.T) {
 	l := test.NewLogger()
 	ob := &bytes.Buffer{}
 	l.SetOutput(ob)
+	myVpnNetworksTable := new(bart.Lite)
+	myVpnNetworksTable.Insert(netip.MustParsePrefix("1.1.1.1/8"))
 
 	p := firewall.Packet{
 		LocalAddr:  netip.MustParseAddr("1.2.3.4"),
@@ -659,7 +673,7 @@ func TestFirewall_DropConntrackReload(t *testing.T) {
 		},
 		vpnAddrs: []netip.Addr{network.Addr()},
 	}
-	h.buildNetworks(c.Certificate.Networks(), c.Certificate.UnsafeNetworks())
+	h.buildNetworks(myVpnNetworksTable, c.Certificate)
 
 	fw := NewFirewall(l, time.Second, time.Minute, time.Hour, c.Certificate)
 	require.NoError(t, fw.AddRule(true, firewall.ProtoAny, 0, 0, []string{"any"}, "", netip.Prefix{}, netip.Prefix{}, "", ""))
@@ -696,6 +710,8 @@ func TestFirewall_DropIPSpoofing(t *testing.T) {
 	l := test.NewLogger()
 	ob := &bytes.Buffer{}
 	l.SetOutput(ob)
+	myVpnNetworksTable := new(bart.Lite)
+	myVpnNetworksTable.Insert(netip.MustParsePrefix("192.0.2.1/24"))
 
 	c := cert.CachedCertificate{
 		Certificate: &dummyCert{
@@ -717,7 +733,7 @@ func TestFirewall_DropIPSpoofing(t *testing.T) {
 		},
 		vpnAddrs: []netip.Addr{c1.Certificate.Networks()[0].Addr()},
 	}
-	h1.buildNetworks(c1.Certificate.Networks(), c1.Certificate.UnsafeNetworks())
+	h1.buildNetworks(myVpnNetworksTable, c1.Certificate)
 
 	fw := NewFirewall(l, time.Second, time.Minute, time.Hour, c.Certificate)
 
@@ -1047,6 +1063,171 @@ func TestFirewall_convertRule(t *testing.T) {
 	assert.Equal(t, "group1", r.Group)
 }
 
+type testcase struct {
+	h   *HostInfo
+	p   firewall.Packet
+	c   cert.Certificate
+	err error
+}
+
+func (c *testcase) Test(t *testing.T, fw *Firewall) {
+	t.Helper()
+	cp := cert.NewCAPool()
+	resetConntrack(fw)
+	err := fw.Drop(c.p, true, c.h, cp, nil)
+	if c.err == nil {
+		require.NoError(t, err, "failed to not drop remote address %s", c.p.RemoteAddr)
+	} else {
+		require.ErrorIs(t, c.err, err, "failed to drop remote address %s", c.p.RemoteAddr)
+	}
+}
+
+func buildTestCase(setup testsetup, err error, theirPrefixes ...netip.Prefix) testcase {
+	c1 := dummyCert{
+		name:     "host1",
+		networks: theirPrefixes,
+		groups:   []string{"default-group"},
+		issuer:   "signer-shasum",
+	}
+	h := HostInfo{
+		ConnectionState: &ConnectionState{
+			peerCert: &cert.CachedCertificate{
+				Certificate:    &c1,
+				InvertedGroups: map[string]struct{}{"default-group": {}},
+			},
+		},
+		vpnAddrs: make([]netip.Addr, len(theirPrefixes)),
+	}
+	for i := range theirPrefixes {
+		h.vpnAddrs[i] = theirPrefixes[i].Addr()
+	}
+	h.buildNetworks(setup.myVpnNetworksTable, &c1)
+	p := firewall.Packet{
+		LocalAddr:  setup.c.Networks()[0].Addr(), //todo?
+		RemoteAddr: theirPrefixes[0].Addr(),
+		LocalPort:  10,
+		RemotePort: 90,
+		Protocol:   firewall.ProtoUDP,
+		Fragment:   false,
+	}
+	return testcase{
+		h:   &h,
+		p:   p,
+		c:   &c1,
+		err: err,
+	}
+}
+
+type testsetup struct {
+	c                  dummyCert
+	myVpnNetworksTable *bart.Lite
+	fw                 *Firewall
+}
+
+func newSetup(t *testing.T, l *logrus.Logger, myPrefixes ...netip.Prefix) testsetup {
+	c := dummyCert{
+		name:     "me",
+		networks: myPrefixes,
+		groups:   []string{"default-group"},
+		issuer:   "signer-shasum",
+	}
+
+	return newSetupFromCert(t, l, c)
+}
+
+func newSetupFromCert(t *testing.T, l *logrus.Logger, c dummyCert) testsetup {
+	myVpnNetworksTable := new(bart.Lite)
+	for _, prefix := range c.Networks() {
+		myVpnNetworksTable.Insert(prefix)
+	}
+	fw := NewFirewall(l, time.Second, time.Minute, time.Hour, &c)
+	require.NoError(t, fw.AddRule(true, firewall.ProtoAny, 0, 0, []string{"any"}, "", netip.Prefix{}, netip.Prefix{}, "", ""))
+
+	return testsetup{
+		c:                  c,
+		fw:                 fw,
+		myVpnNetworksTable: myVpnNetworksTable,
+	}
+}
+
+func TestFirewall_Drop_EnforceIPMatch(t *testing.T) {
+	t.Parallel()
+	l := test.NewLogger()
+	ob := &bytes.Buffer{}
+	l.SetOutput(ob)
+
+	myPrefix := netip.MustParsePrefix("1.1.1.1/8")
+	// for now, it's okay that these are all "incoming", the logic this test tries to check doesn't care about in/out
+	t.Run("allow inbound all matching", func(t *testing.T) {
+		t.Parallel()
+		setup := newSetup(t, l, myPrefix)
+		tc := buildTestCase(setup, nil, netip.MustParsePrefix("1.2.3.4/24"))
+		tc.Test(t, setup.fw)
+	})
+	t.Run("allow inbound local matching", func(t *testing.T) {
+		t.Parallel()
+		setup := newSetup(t, l, myPrefix)
+		tc := buildTestCase(setup, ErrInvalidLocalIP, netip.MustParsePrefix("1.2.3.4/24"))
+		tc.p.LocalAddr = netip.MustParseAddr("1.2.3.8")
+		tc.Test(t, setup.fw)
+	})
+	t.Run("block inbound remote mismatched", func(t *testing.T) {
+		t.Parallel()
+		setup := newSetup(t, l, myPrefix)
+		tc := buildTestCase(setup, ErrInvalidRemoteIP, netip.MustParsePrefix("1.2.3.4/24"))
+		tc.p.RemoteAddr = netip.MustParseAddr("9.9.9.9")
+		tc.Test(t, setup.fw)
+	})
+	t.Run("Block a vpn peer packet", func(t *testing.T) {
+		t.Parallel()
+		setup := newSetup(t, l, myPrefix)
+		tc := buildTestCase(setup, ErrPeerRejected, netip.MustParsePrefix("2.2.2.2/24"))
+		tc.Test(t, setup.fw)
+	})
+	twoPrefixes := []netip.Prefix{
+		netip.MustParsePrefix("1.2.3.4/24"), netip.MustParsePrefix("2.2.2.2/24"),
+	}
+	t.Run("allow inbound one matching", func(t *testing.T) {
+		t.Parallel()
+		setup := newSetup(t, l, myPrefix)
+		tc := buildTestCase(setup, nil, twoPrefixes...)
+		tc.Test(t, setup.fw)
+	})
+	t.Run("block inbound multimismatch", func(t *testing.T) {
+		t.Parallel()
+		setup := newSetup(t, l, myPrefix)
+		tc := buildTestCase(setup, ErrInvalidRemoteIP, twoPrefixes...)
+		tc.p.RemoteAddr = netip.MustParseAddr("9.9.9.9")
+		tc.Test(t, setup.fw)
+	})
+	t.Run("allow inbound 2nd one matching", func(t *testing.T) {
+		t.Parallel()
+		setup2 := newSetup(t, l, netip.MustParsePrefix("2.2.2.1/24"))
+		tc := buildTestCase(setup2, nil, twoPrefixes...)
+		tc.p.RemoteAddr = twoPrefixes[1].Addr()
+		tc.Test(t, setup2.fw)
+	})
+	t.Run("allow inbound unsafe route", func(t *testing.T) {
+		t.Parallel()
+		unsafePrefix := netip.MustParsePrefix("192.168.0.0/24")
+		c := dummyCert{
+			name:           "me",
+			networks:       []netip.Prefix{myPrefix},
+			unsafeNetworks: []netip.Prefix{unsafePrefix},
+			groups:         []string{"default-group"},
+			issuer:         "signer-shasum",
+		}
+		unsafeSetup := newSetupFromCert(t, l, c)
+		tc := buildTestCase(unsafeSetup, nil, twoPrefixes...)
+		tc.p.LocalAddr = netip.MustParseAddr("192.168.0.3")
+		tc.err = ErrNoMatchingRule
+		tc.Test(t, unsafeSetup.fw) //should hit firewall and bounce off
+		require.NoError(t, unsafeSetup.fw.AddRule(true, firewall.ProtoAny, 0, 0, []string{"any"}, "", netip.Prefix{}, unsafePrefix, "", ""))
+		tc.err = nil
+		tc.Test(t, unsafeSetup.fw) //should pass
+	})
+}
+
 type addRuleCall struct {
 	incoming  bool
 	proto     uint8

go.mod

@@ -22,18 +22,19 @@ require (
 	github.com/stefanberger/go-pkcs11uri v0.0.0-20230803200340-78284954bff6
 	github.com/stretchr/testify v1.11.1
 	github.com/vishvananda/netlink v1.3.1
-	golang.org/x/crypto v0.43.0
+	go.yaml.in/yaml/v3 v3.0.4
+	golang.org/x/crypto v0.44.0
 	golang.org/x/exp v0.0.0-20230725093048-515e97ebf090
-	golang.org/x/net v0.45.0
-	golang.org/x/sync v0.17.0
-	golang.org/x/sys v0.37.0
-	golang.org/x/term v0.36.0
+	golang.org/x/net v0.46.0
+	golang.org/x/sync v0.18.0
+	golang.org/x/sys v0.38.0
+	golang.org/x/term v0.37.0
 	golang.zx2c4.com/wintun v0.0.0-20230126152724-0fa3db229ce2
-	golang.zx2c4.com/wireguard v0.0.0-20250521234502-f333402bd9cb
+	golang.zx2c4.com/wireguard v0.0.0-20230325221338-052af4a8072b
 	golang.zx2c4.com/wireguard/windows v0.5.3
-	google.golang.org/protobuf v1.36.8
+	google.golang.org/protobuf v1.36.10
 	gopkg.in/yaml.v3 v3.0.1
-	gvisor.dev/gvisor v0.0.0-20250503011706-39ed1f5ac29c
+	gvisor.dev/gvisor v0.0.0-20240423190808-9d7a357edefe
 )
 
 require (

go.sum

@@ -155,13 +155,15 @@ go.uber.org/goleak v1.3.0 h1:2K3zAYmnTNqV73imy9J1T3WC+gmCePx2hEGkimedGto=
 go.uber.org/goleak v1.3.0/go.mod h1:CoHD4mav9JJNrW/WLlf7HGZPjdw8EucARQHekz1X6bE=
 go.yaml.in/yaml/v2 v2.4.2 h1:DzmwEr2rDGHl7lsFgAHxmNz/1NlQ7xLIrlN2h5d1eGI=
 go.yaml.in/yaml/v2 v2.4.2/go.mod h1:081UH+NErpNdqlCXm3TtEran0rJZGxAYx9hb/ELlsPU=
+go.yaml.in/yaml/v3 v3.0.4 h1:tfq32ie2Jv2UxXFdLJdh3jXuOzWiL1fo0bu/FbuKpbc=
+go.yaml.in/yaml/v3 v3.0.4/go.mod h1:DhzuOOF2ATzADvBadXxruRBLzYTpT36CKvDb3+aBEFg=
 golang.org/x/crypto v0.0.0-20180904163835-0709b304e793/go.mod h1:6SG95UA2DQfeDnfUPMdvaQW0Q7yPrPDi9nlGo2tz2b4=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
 golang.org/x/crypto v0.0.0-20191011191535-87dc89f01550/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
 golang.org/x/crypto v0.0.0-20200622213623-75b288015ac9/go.mod h1:LzIPMQfyMNhhGPhUkYOs5KpL4U8rLKemX1yGLhDgUto=
 golang.org/x/crypto v0.0.0-20210322153248-0c34fe9e7dc2/go.mod h1:T9bdIzuCu7OtxOm1hfPfRQxPLYneinmdGuTeoZ9dtd4=
-golang.org/x/crypto v0.43.0 h1:dduJYIi3A3KOfdGOHX8AVZ/jGiyPa3IbBozJ5kNuE04=
-golang.org/x/crypto v0.43.0/go.mod h1:BFbav4mRNlXJL4wNeejLpWxB7wMbc79PdRGhWKncxR0=
+golang.org/x/crypto v0.44.0 h1:A97SsFvM3AIwEEmTBiaxPPTYpDC47w720rdiiUvgoAU=
+golang.org/x/crypto v0.44.0/go.mod h1:013i+Nw79BMiQiMsOPcVCB5ZIJbYkerPrGnOa00tvmc=
 golang.org/x/exp v0.0.0-20230725093048-515e97ebf090 h1:Di6/M8l0O2lCLc6VVRWhgCiApHV8MnQurBnFSHsQtNY=
 golang.org/x/exp v0.0.0-20230725093048-515e97ebf090/go.mod h1:FXUEEKJgO7OQYeo8N01OfiKP8RXMtf6e8aTskBGqWdc=
 golang.org/x/lint v0.0.0-20200302205851-738671d3881b/go.mod h1:3xt1FjdF8hUf6vQPIChWIBhFzV8gjjsPE/fR3IyQdNY=
@@ -180,8 +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 v0.45.0 h1:RLBg5JKixCy82FtLJpeNlVM0nrSqpCRYzVU1n8kj0tM=
-golang.org/x/net v0.45.0/go.mod h1:ECOoLqd5U3Lhyeyo/QDCEVQ4sNgYsqvCZ722XogGieY=
+golang.org/x/net v0.46.0 h1:giFlY12I07fugqwPuWJi68oOnpfqFnJIJzaIIm2JVV4=
+golang.org/x/net v0.46.0/go.mod h1:Q9BGdFy1y4nkUwiLvT5qtyhAnEHgnQ/zd8PfU6nc210=
 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=
@@ -189,8 +191,8 @@ golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJ
 golang.org/x/sync v0.0.0-20190911185100-cd5d95a43a6e/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20201020160332-67f06af15bc9/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20201207232520-09787c993a3a/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
-golang.org/x/sync v0.17.0 h1:l60nONMj9l5drqw6jlhIELNv9I0A4OFgRsG9k2oT9Ug=
-golang.org/x/sync v0.17.0/go.mod h1:9KTHXmSnoGruLpwFjVSX0lNNA75CykiMECbovNTZqGI=
+golang.org/x/sync v0.18.0 h1:kr88TuHDroi+UVf+0hZnirlk8o8T+4MrK6mr60WkH/I=
+golang.org/x/sync v0.18.0/go.mod h1:9KTHXmSnoGruLpwFjVSX0lNNA75CykiMECbovNTZqGI=
 golang.org/x/sys v0.0.0-20180905080454-ebe1bf3edb33/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20181116152217-5ac8a444bdc5/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
@@ -207,11 +209,11 @@ golang.org/x/sys v0.0.0-20210603081109-ebe580a85c40/go.mod h1:oPkhp1MJrh7nUepCBc
 golang.org/x/sys v0.0.0-20220715151400-c0bba94af5f8/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.2.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.10.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.37.0 h1:fdNQudmxPjkdUTPnLn5mdQv7Zwvbvpaxqs831goi9kQ=
-golang.org/x/sys v0.37.0/go.mod h1:OgkHotnGiDImocRcuBABYBEXf8A9a87e/uXjp9XT3ks=
+golang.org/x/sys v0.38.0 h1:3yZWxaJjBmCWXqhN1qh02AkOnCQ1poK6oF+a7xWL6Gc=
+golang.org/x/sys v0.38.0/go.mod h1:OgkHotnGiDImocRcuBABYBEXf8A9a87e/uXjp9XT3ks=
 golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
-golang.org/x/term v0.36.0 h1:zMPR+aF8gfksFprF/Nc/rd1wRS1EI6nDBGyWAvDzx2Q=
-golang.org/x/term v0.36.0/go.mod h1:Qu394IJq6V6dCBRgwqshf3mPF85AqzYEzofzRdZkWss=
+golang.org/x/term v0.37.0 h1:8EGAD0qCmHYZg6J17DvsMy9/wJ7/D/4pV/wfnld5lTU=
+golang.org/x/term v0.37.0/go.mod h1:5pB4lxRNYYVZuTLmy8oR2BH8dflOR+IbTYFD8fi3254=
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/text v0.3.2/go.mod h1:bEr9sfX3Q8Zfm5fL9x+3itogRgK3+ptLWKqgva+5dAk=
 golang.org/x/text v0.3.3/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
@@ -230,8 +232,8 @@ golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8T
 golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 golang.zx2c4.com/wintun v0.0.0-20230126152724-0fa3db229ce2 h1:B82qJJgjvYKsXS9jeunTOisW56dUokqW/FOteYJJ/yg=
 golang.zx2c4.com/wintun v0.0.0-20230126152724-0fa3db229ce2/go.mod h1:deeaetjYA+DHMHg+sMSMI58GrEteJUUzzw7en6TJQcI=
-golang.zx2c4.com/wireguard v0.0.0-20250521234502-f333402bd9cb h1:whnFRlWMcXI9d+ZbWg+4sHnLp52d5yiIPUxMBSt4X9A=
-golang.zx2c4.com/wireguard v0.0.0-20250521234502-f333402bd9cb/go.mod h1:rpwXGsirqLqN2L0JDJQlwOboGHmptD5ZD6T2VmcqhTw=
+golang.zx2c4.com/wireguard v0.0.0-20230325221338-052af4a8072b h1:J1CaxgLerRR5lgx3wnr6L04cJFbWoceSK9JWBdglINo=
+golang.zx2c4.com/wireguard v0.0.0-20230325221338-052af4a8072b/go.mod h1:tqur9LnfstdR9ep2LaJT4lFUl0EjlHtge+gAjmsHUG4=
 golang.zx2c4.com/wireguard/windows v0.5.3 h1:On6j2Rpn3OEMXqBq00QEDC7bWSZrPIHKIus8eIuExIE=
 golang.zx2c4.com/wireguard/windows v0.5.3/go.mod h1:9TEe8TJmtwyQebdFwAkEWOPr3prrtqm+REGFifP60hI=
 google.golang.org/appengine v1.4.0/go.mod h1:xpcJRLb0r/rnEns0DIKYYv+WjYCduHsrkT7/EB5XEv4=
@@ -242,8 +244,8 @@ google.golang.org/protobuf v1.20.1-0.20200309200217-e05f789c0967/go.mod h1:A+miE
 google.golang.org/protobuf v1.21.0/go.mod h1:47Nbq4nVaFHyn7ilMalzfO3qCViNmqZ2kzikPIcrTAo=
 google.golang.org/protobuf v1.23.0/go.mod h1:EGpADcykh3NcUnDUJcl1+ZksZNG86OlYog2l/sGQquU=
 google.golang.org/protobuf v1.26.0-rc.1/go.mod h1:jlhhOSvTdKEhbULTjvd4ARK9grFBp09yW+WbY/TyQbw=
-google.golang.org/protobuf v1.36.8 h1:xHScyCOEuuwZEc6UtSOvPbAT4zRh0xcNRYekJwfqyMc=
-google.golang.org/protobuf v1.36.8/go.mod h1:fuxRtAxBytpl4zzqUh6/eyUujkJdNiuEkXntxiD/uRU=
+google.golang.org/protobuf v1.36.10 h1:AYd7cD/uASjIL6Q9LiTjz8JLcrh/88q5UObnmY3aOOE=
+google.golang.org/protobuf v1.36.10/go.mod h1:HTf+CrKn2C3g5S8VImy6tdcUvCska2kB7j23XfzDpco=
 gopkg.in/alecthomas/kingpin.v2 v2.2.6/go.mod h1:FMv+mEhP44yOT+4EoQTLFTRgOQ1FBLkstjWtayDeSgw=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
@@ -257,5 +259,5 @@ gopkg.in/yaml.v2 v2.3.0/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
 gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
 gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
-gvisor.dev/gvisor v0.0.0-20250503011706-39ed1f5ac29c h1:m/r7OM+Y2Ty1sgBQ7Qb27VgIMBW8ZZhT4gLnUyDIhzI=
-gvisor.dev/gvisor v0.0.0-20250503011706-39ed1f5ac29c/go.mod h1:3r5CMtNQMKIvBlrmM9xWUNamjKBYPOWyXOjmg5Kts3g=
+gvisor.dev/gvisor v0.0.0-20240423190808-9d7a357edefe h1:fre4i6mv4iBuz5lCMOzHD1rH1ljqHWSICFmZRbbgp3g=
+gvisor.dev/gvisor v0.0.0-20240423190808-9d7a357edefe/go.mod h1:sxc3Uvk/vHcd3tj7/DHVBoR5wvWT/MmRq2pj7HRJnwU=

handshake_ix.go

@@ -2,7 +2,6 @@ package nebula
 
 import (
 	"net/netip"
-	"slices"
 	"time"
 
 	"github.com/flynn/noise"
@@ -23,15 +22,19 @@ func ixHandshakeStage0(f *Interface, hh *HandshakeHostInfo) bool {
 		return false
 	}
 
-	// If we're connecting to a v6 address we must use a v2 cert
 	cs := f.pki.getCertState()
 	v := cs.initiatingVersion
+	if hh.initiatingVersionOverride != cert.VersionPre1 {
+		v = hh.initiatingVersionOverride
+	} else if v < cert.Version2 {
+		// If we're connecting to a v6 address we should encourage use of a V2 cert
 		for _, a := range hh.hostinfo.vpnAddrs {
 			if a.Is6() {
 				v = cert.Version2
 				break
 			}
 		}
+	}
 
 	crt := cs.getCertificate(v)
 	if crt == nil {
@@ -48,6 +51,7 @@ func ixHandshakeStage0(f *Interface, hh *HandshakeHostInfo) bool {
 			WithField("handshake", m{"stage": 0, "style": "ix_psk0"}).
 			WithField("certVersion", v).
 			Error("Unable to handshake with host because no certificate handshake bytes is available")
+		return false
 	}
 
 	ci, err := NewConnectionState(f.l, cs, crt, true, noise.HandshakeIX)
@@ -103,6 +107,7 @@ func ixHandshakeStage1(f *Interface, addr netip.AddrPort, via *ViaSender, packet
 			WithField("handshake", m{"stage": 0, "style": "ix_psk0"}).
 			WithField("certVersion", cs.initiatingVersion).
 			Error("Unable to handshake with host because no certificate is available")
+		return
 	}
 
 	ci, err := NewConnectionState(f.l, cs, crt, false, noise.HandshakeIX)
@@ -143,8 +148,8 @@ func ixHandshakeStage1(f *Interface, addr netip.AddrPort, via *ViaSender, packet
 
 	remoteCert, err := f.pki.GetCAPool().VerifyCertificate(time.Now(), rc)
 	if err != nil {
-		fp, err := rc.Fingerprint()
-		if err != nil {
+		fp, fperr := rc.Fingerprint()
+		if fperr != nil {
 			fp = "<error generating certificate fingerprint>"
 		}
 
@@ -163,16 +168,19 @@ func ixHandshakeStage1(f *Interface, addr netip.AddrPort, via *ViaSender, packet
 
 	if remoteCert.Certificate.Version() != ci.myCert.Version() {
 		// We started off using the wrong certificate version, lets see if we can match the version that was sent to us
-		rc := cs.getCertificate(remoteCert.Certificate.Version())
-		if rc == nil {
-			f.l.WithError(err).WithField("udpAddr", addr).
-				WithField("handshake", m{"stage": 1, "style": "ix_psk0"}).WithField("cert", remoteCert).
-				Info("Unable to handshake with host due to missing certificate version")
-			return
+		myCertOtherVersion := cs.getCertificate(remoteCert.Certificate.Version())
+		if myCertOtherVersion == nil {
+			if f.l.Level >= logrus.DebugLevel {
+				f.l.WithError(err).WithFields(m{
+					"udpAddr":   addr,
+					"handshake": m{"stage": 1, "style": "ix_psk0"},
+					"cert":      remoteCert,
+				}).Debug("Might be unable to handshake with host due to missing certificate version")
 			}
-
+		} else {
 			// Record the certificate we are actually using
-		ci.myCert = rc
+			ci.myCert = myCertOtherVersion
+		}
 	}
 
 	if len(remoteCert.Certificate.Networks()) == 0 {
@@ -183,17 +191,17 @@ func ixHandshakeStage1(f *Interface, addr netip.AddrPort, via *ViaSender, packet
 		return
 	}
 
-	var vpnAddrs []netip.Addr
-	var filteredNetworks []netip.Prefix
 	certName := remoteCert.Certificate.Name()
 	certVersion := remoteCert.Certificate.Version()
 	fingerprint := remoteCert.Fingerprint
 	issuer := remoteCert.Certificate.Issuer()
+	vpnNetworks := remoteCert.Certificate.Networks()
 
-	for _, network := range remoteCert.Certificate.Networks() {
-		vpnAddr := network.Addr()
-		if f.myVpnAddrsTable.Contains(vpnAddr) {
-			f.l.WithField("vpnAddr", vpnAddr).WithField("udpAddr", addr).
+	anyVpnAddrsInCommon := false
+	vpnAddrs := make([]netip.Addr, len(vpnNetworks))
+	for i, network := range vpnNetworks {
+		if f.myVpnAddrsTable.Contains(network.Addr()) {
+			f.l.WithField("vpnNetworks", vpnNetworks).WithField("udpAddr", addr).
 				WithField("certName", certName).
 				WithField("certVersion", certVersion).
 				WithField("fingerprint", fingerprint).
@@ -201,24 +209,10 @@ func ixHandshakeStage1(f *Interface, addr netip.AddrPort, via *ViaSender, packet
 				WithField("handshake", m{"stage": 1, "style": "ix_psk0"}).Error("Refusing to handshake with myself")
 			return
 		}
-
-		// vpnAddrs outside our vpn networks are of no use to us, filter them out
-		if !f.myVpnNetworksTable.Contains(vpnAddr) {
-			continue
+		vpnAddrs[i] = network.Addr()
+		if f.myVpnNetworksTable.Contains(network.Addr()) {
+			anyVpnAddrsInCommon = true
 		}
-
-		filteredNetworks = append(filteredNetworks, network)
-		vpnAddrs = append(vpnAddrs, vpnAddr)
-	}
-
-	if len(vpnAddrs) == 0 {
-		f.l.WithError(err).WithField("udpAddr", addr).
-			WithField("certName", certName).
-			WithField("certVersion", certVersion).
-			WithField("fingerprint", fingerprint).
-			WithField("issuer", issuer).
-			WithField("handshake", m{"stage": 1, "style": "ix_psk0"}).Error("No usable vpn addresses from host, refusing handshake")
-		return
 	}
 
 	if addr.IsValid() {
@@ -255,26 +249,30 @@ func ixHandshakeStage1(f *Interface, addr netip.AddrPort, via *ViaSender, packet
 		},
 	}
 
-	f.l.WithField("vpnAddrs", vpnAddrs).WithField("udpAddr", addr).
-		WithField("certName", certName).
-		WithField("certVersion", certVersion).
-		WithField("fingerprint", fingerprint).
-		WithField("issuer", issuer).
-		WithField("initiatorIndex", hs.Details.InitiatorIndex).WithField("responderIndex", hs.Details.ResponderIndex).
-		WithField("remoteIndex", h.RemoteIndex).WithField("handshake", m{"stage": 1, "style": "ix_psk0"}).
-		Info("Handshake message received")
+	msgRxL := f.l.WithFields(m{
+		"vpnAddrs":       vpnAddrs,
+		"udpAddr":        addr,
+		"certName":       certName,
+		"certVersion":    certVersion,
+		"fingerprint":    fingerprint,
+		"issuer":         issuer,
+		"initiatorIndex": hs.Details.InitiatorIndex,
+		"responderIndex": hs.Details.ResponderIndex,
+		"remoteIndex":    h.RemoteIndex,
+		"handshake":      m{"stage": 1, "style": "ix_psk0"},
+	})
+
+	if anyVpnAddrsInCommon {
+		msgRxL.Info("Handshake message received")
+	} else {
+		//todo warn if not lighthouse or relay?
+		msgRxL.Info("Handshake message received, but no vpnNetworks in common.")
+	}
 
 	hs.Details.ResponderIndex = myIndex
 	hs.Details.Cert = cs.getHandshakeBytes(ci.myCert.Version())
 	if hs.Details.Cert == nil {
-		f.l.WithField("vpnAddrs", vpnAddrs).WithField("udpAddr", addr).
-			WithField("certName", certName).
-			WithField("certVersion", certVersion).
-			WithField("fingerprint", fingerprint).
-			WithField("issuer", issuer).
-			WithField("initiatorIndex", hs.Details.InitiatorIndex).WithField("responderIndex", hs.Details.ResponderIndex).
-			WithField("remoteIndex", h.RemoteIndex).WithField("handshake", m{"stage": 1, "style": "ix_psk0"}).
-			WithField("certVersion", ci.myCert.Version()).
+		msgRxL.WithField("myCertVersion", ci.myCert.Version()).
 			Error("Unable to handshake with host because no certificate handshake bytes is available")
 		return
 	}
@@ -332,7 +330,7 @@ func ixHandshakeStage1(f *Interface, addr netip.AddrPort, via *ViaSender, packet
 
 	hostinfo.remotes = f.lightHouse.QueryCache(vpnAddrs)
 	hostinfo.SetRemote(addr)
-	hostinfo.buildNetworks(filteredNetworks, remoteCert.Certificate.UnsafeNetworks())
+	hostinfo.buildNetworks(f.myVpnNetworksTable, remoteCert.Certificate)
 
 	existing, err := f.handshakeManager.CheckAndComplete(hostinfo, 0, f)
 	if err != nil {
@@ -573,31 +571,22 @@ func ixHandshakeStage2(f *Interface, addr netip.AddrPort, via *ViaSender, hh *Ha
 		hostinfo.relayState.InsertRelayTo(via.relayHI.vpnAddrs[0])
 	}
 
-	var vpnAddrs []netip.Addr
-	var filteredNetworks []netip.Prefix
-	for _, network := range vpnNetworks {
-		// vpnAddrs outside our vpn networks are of no use to us, filter them out
-		vpnAddr := network.Addr()
-		if !f.myVpnNetworksTable.Contains(vpnAddr) {
-			continue
+	correctHostResponded := false
+	anyVpnAddrsInCommon := false
+	vpnAddrs := make([]netip.Addr, len(vpnNetworks))
+	for i, network := range vpnNetworks {
+		vpnAddrs[i] = network.Addr()
+		if f.myVpnNetworksTable.Contains(network.Addr()) {
+			anyVpnAddrsInCommon = true
 		}
-
-		filteredNetworks = append(filteredNetworks, network)
-		vpnAddrs = append(vpnAddrs, vpnAddr)
+		if hostinfo.vpnAddrs[0] == network.Addr() {
+			// todo is it more correct to see if any of hostinfo.vpnAddrs are in the cert? it should have len==1, but one day it might not?
+			correctHostResponded = true
 		}
-
-	if len(vpnAddrs) == 0 {
-		f.l.WithError(err).WithField("udpAddr", addr).
-			WithField("certName", certName).
-			WithField("certVersion", certVersion).
-			WithField("fingerprint", fingerprint).
-			WithField("issuer", issuer).
-			WithField("handshake", m{"stage": 2, "style": "ix_psk0"}).Error("No usable vpn addresses from host, refusing handshake")
-		return true
 	}
 
 	// Ensure the right host responded
-	if !slices.Contains(vpnAddrs, hostinfo.vpnAddrs[0]) {
+	if !correctHostResponded {
 		f.l.WithField("intendedVpnAddrs", hostinfo.vpnAddrs).WithField("haveVpnNetworks", vpnNetworks).
 			WithField("udpAddr", addr).
 			WithField("certName", certName).
@@ -609,6 +598,7 @@ func ixHandshakeStage2(f *Interface, addr netip.AddrPort, via *ViaSender, hh *Ha
 		f.handshakeManager.DeleteHostInfo(hostinfo)
 
 		// Create a new hostinfo/handshake for the intended vpn ip
+		//TODO is hostinfo.vpnAddrs[0] always the address to use?
 		f.handshakeManager.StartHandshake(hostinfo.vpnAddrs[0], func(newHH *HandshakeHostInfo) {
 			// Block the current used address
 			newHH.hostinfo.remotes = hostinfo.remotes
@@ -635,7 +625,7 @@ func ixHandshakeStage2(f *Interface, addr netip.AddrPort, via *ViaSender, hh *Ha
 	ci.window.Update(f.l, 2)
 
 	duration := time.Since(hh.startTime).Nanoseconds()
-	f.l.WithField("vpnAddrs", vpnAddrs).WithField("udpAddr", addr).
+	msgRxL := f.l.WithField("vpnAddrs", vpnAddrs).WithField("udpAddr", addr).
 		WithField("certName", certName).
 		WithField("certVersion", certVersion).
 		WithField("fingerprint", fingerprint).
@@ -643,12 +633,17 @@ func ixHandshakeStage2(f *Interface, addr netip.AddrPort, via *ViaSender, hh *Ha
 		WithField("initiatorIndex", hs.Details.InitiatorIndex).WithField("responderIndex", hs.Details.ResponderIndex).
 		WithField("remoteIndex", h.RemoteIndex).WithField("handshake", m{"stage": 2, "style": "ix_psk0"}).
 		WithField("durationNs", duration).
-		WithField("sentCachedPackets", len(hh.packetStore)).
-		Info("Handshake message received")
+		WithField("sentCachedPackets", len(hh.packetStore))
+	if anyVpnAddrsInCommon {
+		msgRxL.Info("Handshake message received")
+	} else {
+		//todo warn if not lighthouse or relay?
+		msgRxL.Info("Handshake message received, but no vpnNetworks in common.")
+	}
 
 	// Build up the radix for the firewall if we have subnets in the cert
 	hostinfo.vpnAddrs = vpnAddrs
-	hostinfo.buildNetworks(filteredNetworks, remoteCert.Certificate.UnsafeNetworks())
+	hostinfo.buildNetworks(f.myVpnNetworksTable, remoteCert.Certificate)
 
 	// Complete our handshake and update metrics, this will replace any existing tunnels for the vpnAddrs here
 	f.handshakeManager.Complete(hostinfo, f)

handshake_manager.go

@@ -70,6 +70,7 @@ type HandshakeHostInfo struct {
 
 	startTime                 time.Time        // Time that we first started trying with this handshake
 	ready                     bool             // Is the handshake ready
+	initiatingVersionOverride cert.Version     // Should we use a non-default cert version for this handshake?
 	counter                   int64            // How many attempts have we made so far
 	lastRemotes               []netip.AddrPort // Remotes that we sent to during the previous attempt
 	packetStore               []*cachedPacket  // A set of packets to be transmitted once the handshake completes
@@ -268,12 +269,12 @@ func (hm *HandshakeManager) handleOutbound(vpnIp netip.Addr, lighthouseTriggered
 		hostinfo.logger(hm.l).WithField("relays", hostinfo.remotes.relays).Info("Attempt to relay through hosts")
 		// Send a RelayRequest to all known Relay IP's
 		for _, relay := range hostinfo.remotes.relays {
-			// Don't relay to myself
+			// Don't relay through the host I'm trying to connect to
 			if relay == vpnIp {
 				continue
 			}
 
-			// Don't relay through the host I'm trying to connect to
+			// Don't relay to myself
 			if hm.f.myVpnAddrsTable.Contains(relay) {
 				continue
 			}

hostmap.go

@@ -212,6 +212,18 @@ func (rs *RelayState) InsertRelay(ip netip.Addr, idx uint32, r *Relay) {
 	rs.relayForByIdx[idx] = r
 }
 
+type NetworkType uint8
+
+const (
+	NetworkTypeUnknown NetworkType = iota
+	// NetworkTypeVPN is a network that overlaps one or more of the vpnNetworks in our certificate
+	NetworkTypeVPN
+	// NetworkTypeVPNPeer is a network that does not overlap one of our networks
+	NetworkTypeVPNPeer
+	// NetworkTypeUnsafe is a network from Certificate.UnsafeNetworks()
+	NetworkTypeUnsafe
+)
+
 type HostInfo struct {
 	remote          netip.AddrPort
 	remotes         *RemoteList
@@ -225,8 +237,8 @@ type HostInfo struct {
 	// vpn networks but were removed because they are not usable
 	vpnAddrs []netip.Addr
 
-	// networks are both all vpn and unsafe networks assigned to this host
-	networks   *bart.Lite
+	// networks is a combination of specific vpn addresses (not prefixes!) and full unsafe networks assigned to this host.
+	networks   *bart.Table[NetworkType]
 	relayState RelayState
 
 	// HandshakePacket records the packets used to create this hostinfo
@@ -730,20 +742,26 @@ func (i *HostInfo) SetRemoteIfPreferred(hm *HostMap, newRemote netip.AddrPort) b
 	return false
 }
 
-func (i *HostInfo) buildNetworks(networks, unsafeNetworks []netip.Prefix) {
-	if len(networks) == 1 && len(unsafeNetworks) == 0 {
-		// Simple case, no CIDRTree needed
-		return
+// buildNetworks fills in the networks field of HostInfo. It accepts a cert.Certificate so you never ever mix the network types up.
+func (i *HostInfo) buildNetworks(myVpnNetworksTable *bart.Lite, c cert.Certificate) {
+	if len(c.Networks()) == 1 && len(c.UnsafeNetworks()) == 0 {
+		if myVpnNetworksTable.Contains(c.Networks()[0].Addr()) {
+			return // Simple case, no BART needed
+		}
 	}
 
-	i.networks = new(bart.Lite)
-	for _, network := range networks {
+	i.networks = new(bart.Table[NetworkType])
+	for _, network := range c.Networks() {
 		nprefix := netip.PrefixFrom(network.Addr(), network.Addr().BitLen())
-		i.networks.Insert(nprefix)
+		if myVpnNetworksTable.Contains(network.Addr()) {
+			i.networks.Insert(nprefix, NetworkTypeVPN)
+		} else {
+			i.networks.Insert(nprefix, NetworkTypeVPNPeer)
+		}
 	}
 
-	for _, network := range unsafeNetworks {
-		i.networks.Insert(network)
+	for _, network := range c.UnsafeNetworks() {
+		i.networks.Insert(network, NetworkTypeUnsafe)
 	}
 }
 

inside.go

@@ -2,16 +2,18 @@ package nebula
 
 import (
 	"net/netip"
+	"time"
 
 	"github.com/sirupsen/logrus"
 	"github.com/slackhq/nebula/firewall"
 	"github.com/slackhq/nebula/header"
 	"github.com/slackhq/nebula/iputil"
 	"github.com/slackhq/nebula/noiseutil"
+	"github.com/slackhq/nebula/packet"
 	"github.com/slackhq/nebula/routing"
 )
 
-func (f *Interface) consumeInsidePacket(packet []byte, fwPacket *firewall.Packet, nb, out []byte, q int, localCache firewall.ConntrackCache) {
+func (f *Interface) consumeInsidePacket(packet []byte, fwPacket *firewall.Packet, nb []byte, out *packet.Packet, q int, localCache firewall.ConntrackCache, now time.Time) {
 	err := newPacket(packet, false, fwPacket)
 	if err != nil {
 		if f.l.Level >= logrus.DebugLevel {
@@ -33,7 +35,8 @@ 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 {
-			if err := f.writeTun(q, packet); err != nil {
+			_, err := f.readers[q].Write(packet)
+			if err != nil {
 				f.l.WithError(err).Error("Failed to forward to tun")
 			}
 		}
@@ -52,7 +55,7 @@ func (f *Interface) consumeInsidePacket(packet []byte, fwPacket *firewall.Packet
 	})
 
 	if hostinfo == nil {
-		f.rejectInside(packet, out, q)
+		f.rejectInside(packet, out.Payload, q) //todo vector?
 		if f.l.Level >= logrus.DebugLevel {
 			f.l.WithField("vpnAddr", fwPacket.RemoteAddr).
 				WithField("fwPacket", fwPacket).
@@ -65,12 +68,11 @@ func (f *Interface) consumeInsidePacket(packet []byte, fwPacket *firewall.Packet
 		return
 	}
 
-	dropReason := f.firewall.Drop(*fwPacket, false, hostinfo, f.pki.GetCAPool(), localCache)
+	dropReason := f.firewall.Drop(*fwPacket, false, hostinfo, f.pki.GetCAPool(), localCache, now)
 	if dropReason == nil {
-		f.sendNoMetrics(header.Message, 0, hostinfo.ConnectionState, hostinfo, netip.AddrPort{}, packet, nb, out, q)
-
+		f.sendNoMetricsDelayed(header.Message, 0, hostinfo.ConnectionState, hostinfo, netip.AddrPort{}, packet, nb, out, q)
 	} else {
-		f.rejectInside(packet, out, q)
+		f.rejectInside(packet, out.Payload, q) //todo vector?
 		if f.l.Level >= logrus.DebugLevel {
 			hostinfo.logger(f.l).
 				WithField("fwPacket", fwPacket).
@@ -90,7 +92,8 @@ func (f *Interface) rejectInside(packet []byte, out []byte, q int) {
 		return
 	}
 
-	if err := f.writeTun(q, out); err != nil {
+	_, err := f.readers[q].Write(out)
+	if err != nil {
 		f.l.WithError(err).Error("Failed to write to tun")
 	}
 }
@@ -118,9 +121,10 @@ func (f *Interface) rejectOutside(packet []byte, ci *ConnectionState, hostinfo *
 	f.sendNoMetrics(header.Message, 0, ci, hostinfo, netip.AddrPort{}, out, nb, packet, q)
 }
 
-// Handshake will attempt to initiate a tunnel with the provided vpn address if it is within our vpn networks. This is a no-op if the tunnel is already established or being established
+// Handshake will attempt to initiate a tunnel with the provided vpn address. This is a no-op if the tunnel is already established or being established
+// it does not check if it is within our vpn networks!
 func (f *Interface) Handshake(vpnAddr netip.Addr) {
-	f.getOrHandshakeNoRouting(vpnAddr, nil)
+	f.handshakeManager.GetOrHandshake(vpnAddr, nil)
 }
 
 // getOrHandshakeNoRouting returns nil if the vpnAddr is not routable.
@@ -136,7 +140,6 @@ func (f *Interface) getOrHandshakeNoRouting(vpnAddr netip.Addr, cacheCallback fu
 // getOrHandshakeConsiderRouting will try to find the HostInfo to handle this packet, starting a handshake if necessary.
 // If the 2nd return var is false then the hostinfo is not ready to be used in a tunnel.
 func (f *Interface) getOrHandshakeConsiderRouting(fwPacket *firewall.Packet, cacheCallback func(*HandshakeHostInfo)) (*HostInfo, bool) {
-
 	destinationAddr := fwPacket.RemoteAddr
 
 	hostinfo, ready := f.getOrHandshakeNoRouting(destinationAddr, cacheCallback)
@@ -216,7 +219,7 @@ func (f *Interface) sendMessageNow(t header.MessageType, st header.MessageSubTyp
 	}
 
 	// check if packet is in outbound fw rules
-	dropReason := f.firewall.Drop(*fp, false, hostinfo, f.pki.GetCAPool(), nil)
+	dropReason := f.firewall.Drop(*fp, false, hostinfo, f.pki.GetCAPool(), nil, time.Now())
 	if dropReason != nil {
 		if f.l.Level >= logrus.DebugLevel {
 			f.l.WithField("fwPacket", fp).
@@ -229,9 +232,10 @@ func (f *Interface) sendMessageNow(t header.MessageType, st header.MessageSubTyp
 	f.sendNoMetrics(header.Message, st, hostinfo.ConnectionState, hostinfo, netip.AddrPort{}, p, nb, out, 0)
 }
 
-// SendMessageToVpnAddr handles real addr:port lookup and sends to the current best known address for vpnAddr
+// SendMessageToVpnAddr handles real addr:port lookup and sends to the current best known address for vpnAddr.
+// This function ignores myVpnNetworksTable, and will always attempt to treat the address as a vpnAddr
 func (f *Interface) SendMessageToVpnAddr(t header.MessageType, st header.MessageSubType, vpnAddr netip.Addr, p, nb, out []byte) {
-	hostInfo, ready := f.getOrHandshakeNoRouting(vpnAddr, func(hh *HandshakeHostInfo) {
+	hostInfo, ready := f.handshakeManager.GetOrHandshake(vpnAddr, func(hh *HandshakeHostInfo) {
 		hh.cachePacket(f.l, t, st, p, f.SendMessageToHostInfo, f.cachedPacketMetrics)
 	})
 
@@ -407,3 +411,81 @@ func (f *Interface) sendNoMetrics(t header.MessageType, st header.MessageSubType
 		}
 	}
 }
+
+func (f *Interface) sendNoMetricsDelayed(t header.MessageType, st header.MessageSubType, ci *ConnectionState, hostinfo *HostInfo, remote netip.AddrPort, p, nb []byte, out *packet.Packet, q int) {
+	if ci.eKey == nil {
+		return
+	}
+	useRelay := !remote.IsValid() && !hostinfo.remote.IsValid()
+	fullOut := out.Payload
+
+	if useRelay {
+		if len(out.Payload) < header.Len {
+			// out always has a capacity of mtu, but not always a length greater than the header.Len.
+			// Grow it to make sure the next operation works.
+			out.Payload = out.Payload[:header.Len]
+		}
+		// Save a header's worth of data at the front of the 'out' buffer.
+		out.Payload = out.Payload[header.Len:]
+	}
+
+	if noiseutil.EncryptLockNeeded {
+		// NOTE: for goboring AESGCMTLS we need to lock because of the nonce check
+		ci.writeLock.Lock()
+	}
+	c := ci.messageCounter.Add(1)
+
+	//l.WithField("trace", string(debug.Stack())).Error("out Header ", &Header{Version, t, st, 0, hostinfo.remoteIndexId, c}, p)
+	out.Payload = header.Encode(out.Payload, header.Version, t, st, hostinfo.remoteIndexId, c)
+	f.connectionManager.Out(hostinfo)
+
+	// Query our LH if we haven't since the last time we've been rebound, this will cause the remote to punch against
+	// all our addrs and enable a faster roaming.
+	if t != header.CloseTunnel && hostinfo.lastRebindCount != f.rebindCount {
+		//NOTE: there is an update hole if a tunnel isn't used and exactly 256 rebinds occur before the tunnel is
+		// finally used again. This tunnel would eventually be torn down and recreated if this action didn't help.
+		f.lightHouse.QueryServer(hostinfo.vpnAddrs[0])
+		hostinfo.lastRebindCount = f.rebindCount
+		if f.l.Level >= logrus.DebugLevel {
+			f.l.WithField("vpnAddrs", hostinfo.vpnAddrs).Debug("Lighthouse update triggered for punch due to rebind counter")
+		}
+	}
+
+	var err error
+	out.Payload, err = ci.eKey.EncryptDanger(out.Payload, out.Payload, p, c, nb)
+	if noiseutil.EncryptLockNeeded {
+		ci.writeLock.Unlock()
+	}
+	if err != nil {
+		hostinfo.logger(f.l).WithError(err).
+			WithField("udpAddr", remote).WithField("counter", c).
+			WithField("attemptedCounter", c).
+			Error("Failed to encrypt outgoing packet")
+		return
+	}
+
+	if remote.IsValid() {
+		err = f.writers[q].Prep(out, remote)
+		if err != nil {
+			hostinfo.logger(f.l).WithError(err).WithField("udpAddr", remote).Error("Failed to write outgoing packet")
+		}
+	} else if hostinfo.remote.IsValid() {
+		err = f.writers[q].Prep(out, hostinfo.remote)
+		if err != nil {
+			hostinfo.logger(f.l).WithError(err).WithField("udpAddr", remote).Error("Failed to write outgoing packet")
+		}
+	} else {
+		// Try to send via a relay
+		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).WithField("relay", relayIP).WithError(err).Info("sendNoMetrics failed to find HostInfo")
+				continue
+			}
+			//todo vector!!
+			f.SendVia(relayHostInfo, relay, out.Payload, nb, fullOut[:header.Len+len(out.Payload)], true)
+			break
+		}
+	}
+}

interface.go

@@ -4,7 +4,6 @@ import (
 	"context"
 	"errors"
 	"fmt"
-	"io"
 	"net/netip"
 	"os"
 	"runtime"
@@ -18,10 +17,12 @@ import (
 	"github.com/slackhq/nebula/firewall"
 	"github.com/slackhq/nebula/header"
 	"github.com/slackhq/nebula/overlay"
+	"github.com/slackhq/nebula/packet"
 	"github.com/slackhq/nebula/udp"
 )
 
 const mtu = 9001
+const batch = 1024 //todo config!
 
 type InterfaceConfig struct {
 	HostMap            *HostMap
@@ -47,7 +48,6 @@ type InterfaceConfig struct {
 	reQueryWait     time.Duration
 
 	ConntrackCacheTimeout time.Duration
-	batchSize             int
 	l                     *logrus.Logger
 }
 
@@ -85,15 +85,20 @@ type Interface struct {
 	version     string
 
 	conntrackCacheTimeout time.Duration
-	batchSize             int
 
 	writers []udp.Conn
-	readers []io.ReadWriteCloser
+	readers []overlay.TunDev
 
 	metricHandshakes    metrics.Histogram
 	messageMetrics      *MessageMetrics
 	cachedPacketMetrics *cachedPacketMetrics
 
+	listenInN  int
+	listenOutN int
+
+	listenInMetric  metrics.Histogram
+	listenOutMetric metrics.Histogram
+
 	l *logrus.Logger
 }
 
@@ -112,16 +117,6 @@ type EncWriter interface {
 	GetCertState() *CertState
 }
 
-// BatchReader is an interface for readers that support vectorized packet reading
-type BatchReader interface {
-	BatchRead(buffers [][]byte, sizes []int) (int, error)
-}
-
-// BatchWriter is an interface for writers that support vectorized packet writing
-type BatchWriter interface {
-	BatchWrite([][]byte) (int, error)
-}
-
 type sendRecvErrorConfig uint8
 
 const (
@@ -189,7 +184,7 @@ func NewInterface(ctx context.Context, c *InterfaceConfig) (*Interface, error) {
 		routines:              c.routines,
 		version:               c.version,
 		writers:               make([]udp.Conn, c.routines),
-		readers:               make([]io.ReadWriteCloser, c.routines),
+		readers:               make([]overlay.TunDev, c.routines),
 		myVpnNetworks:         cs.myVpnNetworks,
 		myVpnNetworksTable:    cs.myVpnNetworksTable,
 		myVpnAddrs:            cs.myVpnAddrs,
@@ -198,7 +193,6 @@ func NewInterface(ctx context.Context, c *InterfaceConfig) (*Interface, error) {
 		relayManager:          c.relayManager,
 		connectionManager:     c.connectionManager,
 		conntrackCacheTimeout: c.ConntrackCacheTimeout,
-		batchSize:             c.batchSize,
 
 		metricHandshakes: metrics.GetOrRegisterHistogram("handshakes", nil, metrics.NewExpDecaySample(1028, 0.015)),
 		messageMetrics:   c.MessageMetrics,
@@ -209,6 +203,8 @@ func NewInterface(ctx context.Context, c *InterfaceConfig) (*Interface, error) {
 
 		l: c.l,
 	}
+	ifce.listenInMetric = metrics.GetOrRegisterHistogram("vhost.listenIn.n", nil, metrics.NewExpDecaySample(1028, 0.015))
+	ifce.listenOutMetric = metrics.GetOrRegisterHistogram("vhost.listenOut.n", nil, metrics.NewExpDecaySample(1028, 0.015))
 
 	ifce.tryPromoteEvery.Store(c.tryPromoteEvery)
 	ifce.reQueryEvery.Store(c.reQueryEvery)
@@ -238,7 +234,7 @@ func (f *Interface) activate() {
 	metrics.GetOrRegisterGauge("routines", nil).Update(int64(f.routines))
 
 	// Prepare n tun queues
-	var reader io.ReadWriteCloser = f.inside
+	var reader overlay.TunDev = f.inside
 	for i := 0; i < f.routines; i++ {
 		if i > 0 {
 			reader, err = f.inside.NewMultiQueueReader()
@@ -267,132 +263,98 @@ func (f *Interface) run() {
 	}
 }
 
-func (f *Interface) listenOut(i int) {
+func (f *Interface) listenOut(q int) {
 	runtime.LockOSThread()
 
 	var li udp.Conn
-	if i > 0 {
-		li = f.writers[i]
+	if q > 0 {
+		li = f.writers[q]
 	} else {
 		li = f.outside
 	}
 
 	ctCache := firewall.NewConntrackCacheTicker(f.conntrackCacheTimeout)
 	lhh := f.lightHouse.NewRequestHandler()
-	plaintext := make([]byte, udp.MTU)
+
+	outPackets := make([]*packet.OutPacket, batch)
+	for i := 0; i < batch; i++ {
+		outPackets[i] = packet.NewOut()
+	}
+
 	h := &header.H{}
 	fwPacket := &firewall.Packet{}
-	nb := make([]byte, 12)
+	nb := make([]byte, 12, 12)
+
+	toSend := make([][]byte, batch)
+
+	li.ListenOut(func(pkts []*packet.Packet) {
+		toSend = toSend[:0]
+		for i := range outPackets {
+			outPackets[i].Valid = false
+			outPackets[i].SegCounter = 0
+		}
+
+		f.readOutsidePacketsMany(pkts, outPackets, h, fwPacket, lhh, nb, q, ctCache.Get(f.l), time.Now())
+		//we opportunistically tx, but try to also send stragglers
+		if _, err := f.readers[q].WriteMany(outPackets, q); err != nil {
+			f.l.WithError(err).Error("Failed to send packets")
+		}
+		//todo I broke this
+		//n := len(toSend)
+		//if f.l.Level == logrus.DebugLevel {
+		//	f.listenOutMetric.Update(int64(n))
+		//}
+		//f.listenOutN = n
 
-	li.ListenOut(func(fromUdpAddr netip.AddrPort, payload []byte) {
-		f.readOutsidePackets(fromUdpAddr, nil, plaintext[:0], payload, h, fwPacket, lhh, nb, i, ctCache.Get(f.l))
 	})
 }
 
-func (f *Interface) listenIn(reader io.ReadWriteCloser, i int) {
+func (f *Interface) listenIn(reader overlay.TunDev, queueNum int) {
 	runtime.LockOSThread()
 
-	// Check if reader supports batch operations
-	if batchReader, ok := reader.(BatchReader); ok {
-		err := f.listenInBatch(batchReader, i)
-		if err != nil {
-			f.l.WithError(err).Error("Fatal error in batch packet reader, exiting goroutine")
-		}
-		return
-	}
-
-	// Fall back to single-packet mode
-	packet := make([]byte, mtu)
-	out := make([]byte, mtu)
 	fwPacket := &firewall.Packet{}
 	nb := make([]byte, 12, 12)
 
 	conntrackCache := firewall.NewConntrackCacheTicker(f.conntrackCacheTimeout)
 
+	packets := make([]*packet.VirtIOPacket, batch)
+	outPackets := make([]*packet.Packet, batch)
+	for i := 0; i < batch; i++ {
+		packets[i] = packet.NewVIO()
+		outPackets[i] = packet.New(false) //todo?
+	}
+
 	for {
-		n, err := reader.Read(packet)
+		n, err := reader.ReadMany(packets, queueNum)
+
+		//todo!!
 		if err != nil {
 			if errors.Is(err, os.ErrClosed) && f.closed.Load() {
 				return
 			}
 
-			f.l.WithError(err).Error("Fatal error while reading outbound packet, exiting goroutine")
-			return
+			f.l.WithError(err).Error("Error while reading outbound packet")
+			// This only seems to happen when something fatal happens to the fd, so exit.
+			os.Exit(2)
 		}
 
-		f.consumeInsidePacket(packet[:n], fwPacket, nb, out, i, conntrackCache.Get(f.l))
+		if f.l.Level == logrus.DebugLevel {
+			f.listenInMetric.Update(int64(n))
 		}
-}
+		f.listenInN = n
 
-// listenInBatch handles vectorized packet reading for improved performance
-func (f *Interface) listenInBatch(reader BatchReader, i int) error {
-	// Allocate per-packet state and buffers for batch reading
-	batchSize := f.batchSize
-	if batchSize <= 0 {
-		batchSize = 64 // Fallback to default if not configured
+		now := time.Now()
+		for i, pkt := range packets[:n] {
+			outPackets[i].OutLen = -1
+			f.consumeInsidePacket(pkt.Payload, fwPacket, nb, outPackets[i], queueNum, conntrackCache.Get(f.l), now)
+			reader.RecycleRxSeg(pkt, i == (n-1), queueNum) //todo handle err?
+			pkt.Reset()
 		}
-	fwPackets := make([]*firewall.Packet, batchSize)
-	outBuffers := make([][]byte, batchSize)
-	nbBuffers := make([][]byte, batchSize)
-	packets := make([][]byte, batchSize)
-	sizes := make([]int, batchSize)
-
-	for j := 0; j < batchSize; j++ {
-		fwPackets[j] = &firewall.Packet{}
-		outBuffers[j] = make([]byte, mtu)
-		nbBuffers[j] = make([]byte, 12)
-		packets[j] = make([]byte, mtu)
-	}
-
-	conntrackCache := firewall.NewConntrackCacheTicker(f.conntrackCacheTimeout)
-
-	for {
-		n, err := reader.BatchRead(packets, sizes)
+		_, err = f.writers[queueNum].WriteBatch(outPackets[:n])
 		if err != nil {
-			if errors.Is(err, os.ErrClosed) && f.closed.Load() {
-				return nil
-			}
-
-			return fmt.Errorf("error while batch reading outbound packets: %w", err)
-		}
-
-		// Process each packet in the batch
-		cache := conntrackCache.Get(f.l)
-		for idx := 0; idx < n; idx++ {
-			if sizes[idx] > 0 {
-				// Use modulo to reuse fw packet state if batch is larger than our pre-allocated state
-				stateIdx := idx % len(fwPackets)
-				f.consumeInsidePacket(packets[idx][:sizes[idx]], fwPackets[stateIdx], nbBuffers[stateIdx], outBuffers[stateIdx], i, cache)
+			f.l.WithError(err).Error("Error while writing outbound packets")
 		}
 	}
-	}
-}
-
-// writeTunBatch attempts to write multiple packets to the TUN device using batch operations if supported
-func (f *Interface) writeTunBatch(q int, packets [][]byte) error {
-	if len(packets) == 0 {
-		return nil
-	}
-
-	// Check if the reader/writer supports batch operations
-	if batchWriter, ok := f.readers[q].(BatchWriter); ok {
-		_, err := batchWriter.BatchWrite(packets)
-		return err
-	}
-
-	// Fall back to writing packets individually
-	for _, packet := range packets {
-		if _, err := f.readers[q].Write(packet); err != nil {
-			return err
-		}
-	}
-	return nil
-}
-
-// writeTun writes a single packet to the TUN device
-func (f *Interface) writeTun(q int, packet []byte) error {
-	_, err := f.readers[q].Write(packet)
-	return err
 }
 
 func (f *Interface) RegisterConfigChangeCallbacks(c *config.C) {
@@ -529,6 +491,11 @@ func (f *Interface) emitStats(ctx context.Context, i time.Duration) {
 			} else {
 				certMaxVersion.Update(int64(certState.v1Cert.Version()))
 			}
+			if f.l.Level != logrus.DebugLevel {
+				f.listenInMetric.Update(int64(f.listenInN))
+				f.listenOutMetric.Update(int64(f.listenOutN))
+			}
+
 		}
 	}
 }

lighthouse.go

@@ -360,7 +360,8 @@ func (lh *LightHouse) parseLighthouses(c *config.C) ([]netip.Addr, error) {
 		}
 
 		if !lh.myVpnNetworksTable.Contains(addr) {
-			return nil, util.NewContextualError("lighthouse host is not in our networks, invalid", m{"vpnAddr": addr, "networks": lh.myVpnNetworks}, nil)
+			lh.l.WithFields(m{"vpnAddr": addr, "networks": lh.myVpnNetworks}).
+				Warn("lighthouse host is not within our networks, lighthouse functionality will work but layer 3 network traffic to the lighthouse will not")
 		}
 		out[i] = addr
 	}
@@ -431,7 +432,8 @@ func (lh *LightHouse) loadStaticMap(c *config.C, staticList map[netip.Addr]struc
 		}
 
 		if !lh.myVpnNetworksTable.Contains(vpnAddr) {
-			return util.NewContextualError("static_host_map key is not in our network, invalid", m{"vpnAddr": vpnAddr, "networks": lh.myVpnNetworks, "entry": i + 1}, nil)
+			lh.l.WithFields(m{"vpnAddr": vpnAddr, "networks": lh.myVpnNetworks, "entry": i + 1}).
+				Warn("static_host_map key is not within our networks, layer 3 network traffic to this host will not work")
 		}
 
 		vals, ok := v.([]any)
@@ -1337,12 +1339,19 @@ func (lhh *LightHouseHandler) handleHostPunchNotification(n *NebulaMeta, fromVpn
 		}
 	}
 
+	remoteAllowList := lhh.lh.GetRemoteAllowList()
 	for _, a := range n.Details.V4AddrPorts {
-		punch(protoV4AddrPortToNetAddrPort(a), detailsVpnAddr)
+		b := protoV4AddrPortToNetAddrPort(a)
+		if remoteAllowList.Allow(detailsVpnAddr, b.Addr()) {
+			punch(b, detailsVpnAddr)
+		}
 	}
 
 	for _, a := range n.Details.V6AddrPorts {
-		punch(protoV6AddrPortToNetAddrPort(a), detailsVpnAddr)
+		b := protoV6AddrPortToNetAddrPort(a)
+		if remoteAllowList.Allow(detailsVpnAddr, b.Addr()) {
+			punch(b, detailsVpnAddr)
+		}
 	}
 
 	// This sends a nebula test packet to the host trying to contact us. In the case

lighthouse_test.go

@@ -14,7 +14,7 @@ import (
 	"github.com/slackhq/nebula/test"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
-	"gopkg.in/yaml.v3"
+	"go.yaml.in/yaml/v3"
 )
 
 func TestOldIPv4Only(t *testing.T) {

main.go

@@ -13,7 +13,7 @@ import (
 	"github.com/slackhq/nebula/sshd"
 	"github.com/slackhq/nebula/udp"
 	"github.com/slackhq/nebula/util"
-	"gopkg.in/yaml.v3"
+	"go.yaml.in/yaml/v3"
 )
 
 type m = map[string]any
@@ -75,7 +75,8 @@ func Main(c *config.C, configTest bool, buildVersion string, logger *logrus.Logg
 	if c.GetBool("sshd.enabled", false) {
 		sshStart, err = configSSH(l, ssh, c)
 		if err != nil {
-			return nil, util.ContextualizeIfNeeded("Error while configuring the sshd", err)
+			l.WithError(err).Warn("Failed to configure sshd, ssh debugging will not be available")
+			sshStart = nil
 		}
 	}
 
@@ -242,7 +243,6 @@ func Main(c *config.C, configTest bool, buildVersion string, logger *logrus.Logg
 		relayManager:          NewRelayManager(ctx, l, hostMap, c),
 		punchy:                punchy,
 		ConntrackCacheTimeout: conntrackCacheTimeout,
-		batchSize:             c.GetInt("tun.batch_size", 64),
 		l:                     l,
 	}
 

outside.go

@@ -7,6 +7,7 @@ import (
 	"time"
 
 	"github.com/google/gopacket/layers"
+	"github.com/slackhq/nebula/packet"
 	"golang.org/x/net/ipv6"
 
 	"github.com/sirupsen/logrus"
@@ -19,7 +20,7 @@ const (
 	minFwPacketLen = 4
 )
 
-func (f *Interface) readOutsidePackets(ip netip.AddrPort, via *ViaSender, out []byte, packet []byte, h *header.H, fwPacket *firewall.Packet, lhf *LightHouseHandler, nb []byte, q int, localCache firewall.ConntrackCache) {
+func (f *Interface) readOutsidePackets(ip netip.AddrPort, via *ViaSender, out []byte, packet []byte, h *header.H, fwPacket *firewall.Packet, lhf *LightHouseHandler, nb []byte, q int, localCache firewall.ConntrackCache, now time.Time) {
 	err := h.Parse(packet)
 	if err != nil {
 		// Hole punch packets are 0 or 1 byte big, so lets ignore printing those errors
@@ -61,7 +62,7 @@ func (f *Interface) readOutsidePackets(ip netip.AddrPort, via *ViaSender, out []
 
 		switch h.Subtype {
 		case header.MessageNone:
-			if !f.decryptToTun(hostinfo, h.MessageCounter, out, packet, fwPacket, nb, q, localCache) {
+			if !f.decryptToTun(hostinfo, h.MessageCounter, out, packet, fwPacket, nb, q, localCache, now) {
 				return
 			}
 		case header.MessageRelay:
@@ -96,7 +97,7 @@ func (f *Interface) readOutsidePackets(ip netip.AddrPort, via *ViaSender, out []
 			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.
-				f.readOutsidePackets(netip.AddrPort{}, &ViaSender{relayHI: hostinfo, remoteIdx: relay.RemoteIndex, relay: relay}, out[:0], signedPayload, h, fwPacket, lhf, nb, q, localCache)
+				f.readOutsidePackets(netip.AddrPort{}, &ViaSender{relayHI: hostinfo, remoteIdx: relay.RemoteIndex, relay: relay}, out[:0], signedPayload, h, fwPacket, lhf, nb, q, localCache, now)
 				return
 			case ForwardingType:
 				// Find the target HostInfo relay object
@@ -216,6 +217,217 @@ func (f *Interface) readOutsidePackets(ip netip.AddrPort, via *ViaSender, out []
 	f.connectionManager.In(hostinfo)
 }
 
+func (f *Interface) readOutsidePacketsMany(packets []*packet.Packet, out []*packet.OutPacket, h *header.H, fwPacket *firewall.Packet, lhf *LightHouseHandler, nb []byte, q int, localCache firewall.ConntrackCache, now time.Time) {
+	for i, pkt := range packets {
+		out[i].Scratch = out[i].Scratch[:0]
+		ip := pkt.AddrPort()
+
+		//l.Error("in packet ", header, packet[HeaderLen:])
+		if ip.IsValid() {
+			if f.myVpnNetworksTable.Contains(ip.Addr()) {
+				if f.l.Level >= logrus.DebugLevel {
+					f.l.WithField("udpAddr", ip).Debug("Refusing to process double encrypted packet")
+				}
+				return
+			}
+		}
+
+		//todo per-segment!
+		for segment := range pkt.Segments() {
+
+			err := h.Parse(segment)
+			if err != nil {
+				// Hole punch packets are 0 or 1 byte big, so lets ignore printing those errors
+				if len(segment) > 1 {
+					f.l.WithField("packet", pkt).Infof("Error while parsing inbound packet from %s: %s", ip, err)
+				}
+				return
+			}
+
+			var hostinfo *HostInfo
+			// verify if we've seen this index before, otherwise respond to the handshake initiation
+			if h.Type == header.Message && h.Subtype == header.MessageRelay {
+				hostinfo = f.hostMap.QueryRelayIndex(h.RemoteIndex)
+			} else {
+				hostinfo = f.hostMap.QueryIndex(h.RemoteIndex)
+			}
+
+			var ci *ConnectionState
+			if hostinfo != nil {
+				ci = hostinfo.ConnectionState
+			}
+
+			switch h.Type {
+			case header.Message:
+				// TODO handleEncrypted sends directly to addr on error. Handle this in the tunneling case.
+				if !f.handleEncrypted(ci, ip, h) {
+					return
+				}
+
+				switch h.Subtype {
+				case header.MessageNone:
+					if !f.decryptToTunDelayWrite(hostinfo, h.MessageCounter, out[i], pkt, segment, fwPacket, nb, q, localCache, now) {
+						return
+					}
+				case header.MessageRelay:
+					// The entire body is sent as AD, not encrypted.
+					// The packet consists of a 16-byte parsed Nebula header, Associated Data-protected payload, and a trailing 16-byte AEAD signature value.
+					// The packet is guaranteed to be at least 16 bytes at this point, b/c it got past the h.Parse() call above. If it's
+					// otherwise malformed (meaning, there is no trailing 16 byte AEAD value), then this will result in at worst a 0-length slice
+					// which will gracefully fail in the DecryptDanger call.
+					signedPayload := segment[:len(segment)-hostinfo.ConnectionState.dKey.Overhead()]
+					signatureValue := segment[len(segment)-hostinfo.ConnectionState.dKey.Overhead():]
+					out[i].Scratch, err = hostinfo.ConnectionState.dKey.DecryptDanger(out[i].Scratch, 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, ip)
+					// Track usage of both the HostInfo and the Relay for the received & authenticated packet
+					f.connectionManager.In(hostinfo)
+					f.connectionManager.RelayUsed(h.RemoteIndex)
+
+					relay, ok := hostinfo.relayState.QueryRelayForByIdx(h.RemoteIndex)
+					if !ok {
+						// The only way this happens is if hostmap has an index to the correct HostInfo, but the HostInfo is missing
+						// its internal mapping. This should never happen.
+						hostinfo.logger(f.l).WithFields(logrus.Fields{"vpnAddrs": hostinfo.vpnAddrs, "remoteIndex": h.RemoteIndex}).Error("HostInfo missing remote relay index")
+						return
+					}
+
+					switch relay.Type {
+					case TerminalType:
+						// If I am the target of this relay, process the unwrapped packet
+						// From this recursive point, all these variables are 'burned'. We shouldn't rely on them again.
+						f.readOutsidePackets(netip.AddrPort{}, &ViaSender{relayHI: hostinfo, remoteIdx: relay.RemoteIndex, relay: relay}, out[i].Scratch[:0], signedPayload, h, fwPacket, lhf, nb, q, localCache, now)
+						return
+					case ForwardingType:
+						// Find the target HostInfo relay object
+						targetHI, targetRelay, err := f.hostMap.QueryVpnAddrsRelayFor(hostinfo.vpnAddrs, relay.PeerAddr)
+						if err != nil {
+							hostinfo.logger(f.l).WithField("relayTo", relay.PeerAddr).WithError(err).WithField("hostinfo.vpnAddrs", hostinfo.vpnAddrs).Info("Failed to find target host info by ip")
+							return
+						}
+
+						// If that relay is Established, forward the payload through it
+						if targetRelay.State == Established {
+							switch targetRelay.Type {
+							case ForwardingType:
+								// Forward this packet through the relay tunnel
+								// Find the target HostInfo
+								f.SendVia(targetHI, targetRelay, signedPayload, nb, out[i].Scratch, false)
+								return
+							case TerminalType:
+								hostinfo.logger(f.l).Error("Unexpected Relay Type of Terminal")
+							}
+						} else {
+							hostinfo.logger(f.l).WithFields(logrus.Fields{"relayTo": relay.PeerAddr, "relayFrom": hostinfo.vpnAddrs[0], "targetRelayState": targetRelay.State}).Info("Unexpected target relay state")
+							return
+						}
+					}
+				}
+
+			case header.LightHouse:
+				f.messageMetrics.Rx(h.Type, h.Subtype, 1)
+				if !f.handleEncrypted(ci, ip, h) {
+					return
+				}
+
+				d, err := f.decrypt(hostinfo, h.MessageCounter, out[i].Scratch, segment, h, nb)
+				if err != nil {
+					hostinfo.logger(f.l).WithError(err).WithField("udpAddr", ip).
+						WithField("packet", segment).
+						Error("Failed to decrypt lighthouse packet")
+					return
+				}
+
+				lhf.HandleRequest(ip, hostinfo.vpnAddrs, d, f)
+
+				// Fallthrough to the bottom to record incoming traffic
+
+			case header.Test:
+				f.messageMetrics.Rx(h.Type, h.Subtype, 1)
+				if !f.handleEncrypted(ci, ip, h) {
+					return
+				}
+
+				d, err := f.decrypt(hostinfo, h.MessageCounter, out[i].Scratch, segment, h, nb)
+				if err != nil {
+					hostinfo.logger(f.l).WithError(err).WithField("udpAddr", ip).
+						WithField("packet", segment).
+						Error("Failed to decrypt test packet")
+					return
+				}
+
+				if h.Subtype == header.TestRequest {
+					// This testRequest might be from TryPromoteBest, so we should roam
+					// to the new IP address before responding
+					f.handleHostRoaming(hostinfo, ip)
+					f.send(header.Test, header.TestReply, ci, hostinfo, d, nb, out[i].Scratch)
+				}
+
+				// 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(ip, nil, segment, h)
+				return
+
+			case header.RecvError:
+				f.messageMetrics.Rx(h.Type, h.Subtype, 1)
+				f.handleRecvError(ip, h)
+				return
+
+			case header.CloseTunnel:
+				f.messageMetrics.Rx(h.Type, h.Subtype, 1)
+				if !f.handleEncrypted(ci, ip, h) {
+					return
+				}
+
+				hostinfo.logger(f.l).WithField("udpAddr", ip).
+					Info("Close tunnel received, tearing down.")
+
+				f.closeTunnel(hostinfo)
+				return
+
+			case header.Control:
+				if !f.handleEncrypted(ci, ip, h) {
+					return
+				}
+
+				d, err := f.decrypt(hostinfo, h.MessageCounter, out[i].Scratch, segment, h, nb)
+				if err != nil {
+					hostinfo.logger(f.l).WithError(err).WithField("udpAddr", ip).
+						WithField("packet", segment).
+						Error("Failed to decrypt Control packet")
+					return
+				}
+
+				f.relayManager.HandleControlMsg(hostinfo, d, f)
+
+			default:
+				f.messageMetrics.Rx(h.Type, h.Subtype, 1)
+				hostinfo.logger(f.l).Debugf("Unexpected packet received from %s", ip)
+				return
+			}
+
+			f.handleHostRoaming(hostinfo, ip)
+
+			f.connectionManager.In(hostinfo)
+
+		}
+		_, err := f.readers[q].WriteOne(out[i], false, q)
+		if err != nil {
+			f.l.WithError(err).Error("Failed to write packet")
+		}
+	}
+}
+
 // closeTunnel closes a tunnel locally, it does not send a closeTunnel packet to the remote
 func (f *Interface) closeTunnel(hostInfo *HostInfo) {
 	final := f.hostMap.DeleteHostInfo(hostInfo)
@@ -333,13 +545,12 @@ func parseV6(data []byte, incoming bool, fp *firewall.Packet) error {
 			}
 
 			fp.Protocol = uint8(proto)
-			ports := data[offset : offset+4]
 			if incoming {
-				fp.RemotePort = binary.BigEndian.Uint16(ports[0:2])
-				fp.LocalPort = binary.BigEndian.Uint16(ports[2:4])
+				fp.RemotePort = binary.BigEndian.Uint16(data[offset : offset+2])
+				fp.LocalPort = binary.BigEndian.Uint16(data[offset+2 : offset+4])
 			} else {
-				fp.LocalPort = binary.BigEndian.Uint16(ports[0:2])
-				fp.RemotePort = binary.BigEndian.Uint16(ports[2:4])
+				fp.LocalPort = binary.BigEndian.Uint16(data[offset : offset+2])
+				fp.RemotePort = binary.BigEndian.Uint16(data[offset+2 : offset+4])
 			}
 
 			fp.Fragment = false
@@ -466,7 +677,55 @@ func (f *Interface) decrypt(hostinfo *HostInfo, mc uint64, out []byte, 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) decryptToTunDelayWrite(hostinfo *HostInfo, messageCounter uint64, out *packet.OutPacket, pkt *packet.Packet, inSegment []byte, fwPacket *firewall.Packet, nb []byte, q int, localCache firewall.ConntrackCache, now time.Time) bool {
+	var err error
+
+	seg, err := f.readers[q].AllocSeg(out, q)
+	if err != nil {
+		f.l.WithError(err).Errorln("decryptToTunDelayWrite: failed to allocate segment")
+		return false
+	}
+
+	out.SegmentPayloads[seg] = out.SegmentPayloads[seg][:0]
+	out.SegmentPayloads[seg], err = hostinfo.ConnectionState.dKey.DecryptDanger(out.SegmentPayloads[seg], inSegment[:header.Len], inSegment[header.Len:], messageCounter, nb)
+	if err != nil {
+		hostinfo.logger(f.l).WithError(err).Error("Failed to decrypt packet")
+		return false
+	}
+
+	err = newPacket(out.SegmentPayloads[seg], true, fwPacket)
+	if err != nil {
+		hostinfo.logger(f.l).WithError(err).WithField("packet", out).
+			Warnf("Error while validating inbound packet")
+		return false
+	}
+
+	if !hostinfo.ConnectionState.window.Update(f.l, messageCounter) {
+		hostinfo.logger(f.l).WithField("fwPacket", fwPacket).
+			Debugln("dropping out of window packet")
+		return false
+	}
+
+	dropReason := f.firewall.Drop(*fwPacket, true, hostinfo, f.pki.GetCAPool(), localCache, now)
+	if dropReason != nil {
+		// NOTE: We give `packet` as the `out` here since we already decrypted from it and we don't need it anymore
+		// This gives us a buffer to build the reject packet in
+		f.rejectOutside(out.SegmentPayloads[seg], hostinfo.ConnectionState, hostinfo, nb, inSegment, q)
+		if f.l.Level >= logrus.DebugLevel {
+			hostinfo.logger(f.l).WithField("fwPacket", fwPacket).
+				WithField("reason", dropReason).
+				Debugln("dropping inbound packet")
+		}
+		return false
+	}
+
+	f.connectionManager.In(hostinfo)
+	pkt.OutLen += len(inSegment)
+	out.Segments[seg] = out.Segments[seg][:len(out.SegmentHeaders[seg])+len(out.SegmentPayloads[seg])]
+	return true
+}
+
+func (f *Interface) decryptToTun(hostinfo *HostInfo, messageCounter uint64, out []byte, packet []byte, fwPacket *firewall.Packet, nb []byte, q int, localCache firewall.ConntrackCache, now time.Time) bool {
 	var err error
 
 	out, err = hostinfo.ConnectionState.dKey.DecryptDanger(out, packet[:header.Len], packet[header.Len:], messageCounter, nb)
@@ -488,7 +747,7 @@ func (f *Interface) decryptToTun(hostinfo *HostInfo, messageCounter uint64, out
 		return false
 	}
 
-	dropReason := f.firewall.Drop(*fwPacket, true, hostinfo, f.pki.GetCAPool(), localCache)
+	dropReason := f.firewall.Drop(*fwPacket, true, hostinfo, f.pki.GetCAPool(), localCache, now)
 	if dropReason != nil {
 		// NOTE: We give `packet` as the `out` here since we already decrypted from it and we don't need it anymore
 		// This gives us a buffer to build the reject packet in

overlay/device.go

@@ -1,17 +1,16 @@
 package overlay
 
 import (
-	"io"
 	"net/netip"
 
 	"github.com/slackhq/nebula/routing"
 )
 
 type Device interface {
-	io.ReadWriteCloser
+	TunDev
 	Activate() error
 	Networks() []netip.Prefix
 	Name() string
 	RoutesFor(netip.Addr) routing.Gateways
-	NewMultiQueueReader() (io.ReadWriteCloser, error)
+	NewMultiQueueReader() (TunDev, error)
 }

overlay/eventfd/eventfd.go

@@ -0,0 +1,91 @@
+package eventfd
+
+import (
+	"encoding/binary"
+	"syscall"
+
+	"golang.org/x/sys/unix"
+)
+
+type EventFD struct {
+	fd  int
+	buf [8]byte
+}
+
+func New() (EventFD, error) {
+	fd, err := unix.Eventfd(0, unix.EFD_NONBLOCK)
+	if err != nil {
+		return EventFD{}, err
+	}
+	return EventFD{
+		fd:  fd,
+		buf: [8]byte{},
+	}, nil
+}
+
+func (e *EventFD) Kick() error {
+	binary.LittleEndian.PutUint64(e.buf[:], 1) //is this right???
+	_, err := syscall.Write(int(e.fd), e.buf[:])
+	return err
+}
+
+func (e *EventFD) Close() error {
+	if e.fd != 0 {
+		return unix.Close(e.fd)
+	}
+	return nil
+}
+
+func (e *EventFD) FD() int {
+	return e.fd
+}
+
+type Epoll struct {
+	fd     int
+	buf    [8]byte
+	events []syscall.EpollEvent
+}
+
+func NewEpoll() (Epoll, error) {
+	fd, err := unix.EpollCreate1(0)
+	if err != nil {
+		return Epoll{}, err
+	}
+	return Epoll{
+		fd:     fd,
+		buf:    [8]byte{},
+		events: make([]syscall.EpollEvent, 1),
+	}, nil
+}
+
+func (ep *Epoll) AddEvent(fdToAdd int) error {
+	event := syscall.EpollEvent{
+		Events: syscall.EPOLLIN,
+		Fd:     int32(fdToAdd),
+	}
+	return syscall.EpollCtl(ep.fd, syscall.EPOLL_CTL_ADD, fdToAdd, &event)
+}
+
+func (ep *Epoll) Block() (int, error) {
+	n, err := syscall.EpollWait(ep.fd, ep.events, -1)
+	if err != nil {
+		//goland:noinspection GoDirectComparisonOfErrors
+		if err == syscall.EINTR {
+			return 0, nil //??
+		}
+		return -1, err
+	}
+	return n, nil
+}
+
+func (ep *Epoll) Clear() error {
+	_, err := syscall.Read(int(ep.events[0].Fd), ep.buf[:])
+	return err
+}
+
+func (ep *Epoll) Close() error {
+	if ep.fd != 0 {
+		return unix.Close(ep.fd)
+	}
+	return nil
+}

overlay/route.go

@@ -3,6 +3,7 @@ package overlay
 import (
 	"fmt"
 	"math"
+	"net"
 	"net/netip"
 	"runtime"
 	"strconv"
@@ -304,3 +305,29 @@ func parseUnsafeRoutes(c *config.C, networks []netip.Prefix) ([]Route, error) {
 
 	return routes, nil
 }
+
+func ipWithin(o *net.IPNet, i *net.IPNet) bool {
+	// Make sure o contains the lowest form of i
+	if !o.Contains(i.IP.Mask(i.Mask)) {
+		return false
+	}
+
+	// Find the max ip in i
+	ip4 := i.IP.To4()
+	if ip4 == nil {
+		return false
+	}
+
+	last := make(net.IP, len(ip4))
+	copy(last, ip4)
+	for x := range ip4 {
+		last[x] |= ^i.Mask[x]
+	}
+
+	// Make sure o contains the max
+	if !o.Contains(last) {
+		return false
+	}
+
+	return true
+}

overlay/route_test.go

@@ -225,7 +225,6 @@ func Test_parseUnsafeRoutes(t *testing.T) {
 	// no mtu
 	c.Settings["tun"] = map[string]any{"unsafe_routes": []any{map[string]any{"via": "127.0.0.1", "route": "1.0.0.0/8"}}}
 	routes, err = parseUnsafeRoutes(c, []netip.Prefix{n})
-	require.NoError(t, err)
 	assert.Len(t, routes, 1)
 	assert.Equal(t, 0, routes[0].MTU)
 
@@ -319,7 +318,7 @@ func Test_makeRouteTree(t *testing.T) {
 
 	ip, err = netip.ParseAddr("1.1.0.1")
 	require.NoError(t, err)
-	_, ok = routeTree.Lookup(ip)
+	r, ok = routeTree.Lookup(ip)
 	assert.False(t, ok)
 }
 

overlay/tun.go

@@ -1,15 +1,30 @@
 package overlay
 
 import (
+	"fmt"
+	"io"
+	"net"
 	"net/netip"
 
 	"github.com/sirupsen/logrus"
 	"github.com/slackhq/nebula/config"
+	"github.com/slackhq/nebula/packet"
 	"github.com/slackhq/nebula/util"
 )
 
 const DefaultMTU = 1300
 
+type TunDev interface {
+	io.WriteCloser
+	ReadMany(x []*packet.VirtIOPacket, q int) (int, error)
+
+	//todo this interface sux
+	AllocSeg(pkt *packet.OutPacket, q int) (int, error)
+	WriteOne(x *packet.OutPacket, kick bool, q int) (int, error)
+	WriteMany(x []*packet.OutPacket, q int) (int, error)
+	RecycleRxSeg(pkt *packet.VirtIOPacket, kick bool, q int) error
+}
+
 // TODO: We may be able to remove routines
 type DeviceFactory func(c *config.C, l *logrus.Logger, vpnNetworks []netip.Prefix, routines int) (Device, error)
 
@@ -24,11 +39,11 @@ func NewDeviceFromConfig(c *config.C, l *logrus.Logger, vpnNetworks []netip.Pref
 	}
 }
 
-func NewFdDeviceFromConfig(fd *int) DeviceFactory {
-	return func(c *config.C, l *logrus.Logger, vpnNetworks []netip.Prefix, routines int) (Device, error) {
-		return newTunFromFd(c, l, *fd, vpnNetworks)
-	}
-}
+//func NewFdDeviceFromConfig(fd *int) DeviceFactory {
+//	return func(c *config.C, l *logrus.Logger, vpnNetworks []netip.Prefix, routines int) (Device, error) {
+//		return newTunFromFd(c, l, *fd, vpnNetworks)
+//	}
+//}
 
 func getAllRoutesFromConfig(c *config.C, vpnNetworks []netip.Prefix, initial bool) (bool, []Route, error) {
 	if !initial && !c.HasChanged("tun.routes") && !c.HasChanged("tun.unsafe_routes") {
@@ -70,3 +85,51 @@ func findRemovedRoutes(newRoutes, oldRoutes []Route) []Route {
 
 	return removed
 }
+
+func prefixToMask(prefix netip.Prefix) netip.Addr {
+	pLen := 128
+	if prefix.Addr().Is4() {
+		pLen = 32
+	}
+
+	addr, _ := netip.AddrFromSlice(net.CIDRMask(prefix.Bits(), pLen))
+	return addr
+}
+
+func flipBytes(b []byte) []byte {
+	for i := 0; i < len(b); i++ {
+		b[i] ^= 0xFF
+	}
+	return b
+}
+func orBytes(a []byte, b []byte) []byte {
+	ret := make([]byte, len(a))
+	for i := 0; i < len(a); i++ {
+		ret[i] = a[i] | b[i]
+	}
+	return ret
+}
+
+func getBroadcast(cidr netip.Prefix) netip.Addr {
+	broadcast, _ := netip.AddrFromSlice(
+		orBytes(
+			cidr.Addr().AsSlice(),
+			flipBytes(prefixToMask(cidr).AsSlice()),
+		),
+	)
+	return broadcast
+}
+
+func selectGateway(dest netip.Prefix, gateways []netip.Prefix) (netip.Prefix, error) {
+	for _, gateway := range gateways {
+		if dest.Addr().Is4() && gateway.Addr().Is4() {
+			return gateway, nil
+		}
+
+		if dest.Addr().Is6() && gateway.Addr().Is6() {
+			return gateway, nil
+		}
+	}
+
+	return netip.Prefix{}, fmt.Errorf("no gateway found for %v in the list of vpn networks", dest)
+}

overlay/tun_darwin.go

@@ -1,5 +1,5 @@
-//go:build darwin && !ios && !e2e_testing
-// +build darwin,!ios,!e2e_testing
+//go:build !ios && !e2e_testing
+// +build !ios,!e2e_testing
 
 package overlay
 
@@ -8,27 +8,48 @@ import (
 	"fmt"
 	"io"
 	"net/netip"
+	"os"
+	"sync/atomic"
+	"syscall"
 	"unsafe"
 
+	"github.com/gaissmai/bart"
 	"github.com/sirupsen/logrus"
 	"github.com/slackhq/nebula/config"
+	"github.com/slackhq/nebula/routing"
 	"github.com/slackhq/nebula/util"
 	netroute "golang.org/x/net/route"
 	"golang.org/x/sys/unix"
-	wgtun "golang.zx2c4.com/wireguard/tun"
 )
 
 type tun struct {
+	io.ReadWriteCloser
+	Device      string
+	vpnNetworks []netip.Prefix
+	DefaultMTU  int
+	Routes      atomic.Pointer[[]Route]
+	routeTree   atomic.Pointer[bart.Table[routing.Gateways]]
 	linkAddr    *netroute.LinkAddr
+	l           *logrus.Logger
+
+	// cache out buffer since we need to prepend 4 bytes for tun metadata
+	out []byte
 }
 
-// ioctl structures for Darwin network configuration
 type ifReq struct {
 	Name  [unix.IFNAMSIZ]byte
 	Flags uint16
 	pad   [8]byte
 }
 
+const (
+	_SIOCAIFADDR_IN6 = 2155899162
+	_UTUN_OPT_IFNAME = 2
+	_IN6_IFF_NODAD   = 0x0020
+	_IN6_IFF_SECURED = 0x0400
+	utunControlName  = "com.apple.net.utun_control"
+)
+
 type ifreqMTU struct {
 	Name [16]byte
 	MTU  int32
@@ -58,61 +79,60 @@ type ifreqAlias6 struct {
 	Lifetime   addrLifetime
 }
 
-const (
-	_SIOCAIFADDR_IN6 = 2155899162
-	_IN6_IFF_NODAD   = 0x0020
-)
-
-func newTunFromFd(_ *config.C, _ *logrus.Logger, _ int, _ []netip.Prefix) (*wgTun, error) {
-	return nil, fmt.Errorf("newTunFromFd not supported on Darwin")
-}
-
-func newTun(c *config.C, l *logrus.Logger, vpnNetworks []netip.Prefix, _ bool) (*wgTun, error) {
+func newTun(c *config.C, l *logrus.Logger, vpnNetworks []netip.Prefix, _ bool) (*tun, error) {
 	name := c.GetString("tun.dev", "")
-	deviceName := "utun"
-
-	// Parse device name to handle utun[0-9]+ format
-	if name != "" && name != "utun" {
 	ifIndex := -1
+	if name != "" && name != "utun" {
 		_, err := fmt.Sscanf(name, "utun%d", &ifIndex)
 		if err != nil || ifIndex < 0 {
 			// NOTE: we don't make this error so we don't break existing
 			// configs that set a name before it was used.
 			l.Warn("interface name must be utun[0-9]+ on Darwin, ignoring")
-		} else {
-			deviceName = name
+			ifIndex = -1
 		}
 	}
 
-	mtu := c.GetInt("tun.mtu", DefaultMTU)
-
-	// Create WireGuard TUN device
-	tunDevice, err := wgtun.CreateTUN(deviceName, mtu)
+	fd, err := unix.Socket(unix.AF_SYSTEM, unix.SOCK_DGRAM, unix.AF_SYS_CONTROL)
 	if err != nil {
-		return nil, fmt.Errorf("failed to create TUN device: %w", err)
+		return nil, fmt.Errorf("system socket: %v", err)
 	}
 
-	// Get the actual device name
-	actualName, err := tunDevice.Name()
+	var ctlInfo = &unix.CtlInfo{}
+	copy(ctlInfo.Name[:], utunControlName)
+
+	err = unix.IoctlCtlInfo(fd, ctlInfo)
 	if err != nil {
-		tunDevice.Close()
-		return nil, fmt.Errorf("failed to get TUN device name: %w", err)
+		return nil, fmt.Errorf("CTLIOCGINFO: %v", err)
 	}
 
-	t := &wgTun{
-		tunDevice:   tunDevice,
+	err = unix.Connect(fd, &unix.SockaddrCtl{
+		ID:   ctlInfo.Id,
+		Unit: uint32(ifIndex) + 1,
+	})
+	if err != nil {
+		return nil, fmt.Errorf("SYS_CONNECT: %v", err)
+	}
+
+	name, err = unix.GetsockoptString(fd, unix.AF_SYS_CONTROL, _UTUN_OPT_IFNAME)
+	if err != nil {
+		return nil, fmt.Errorf("failed to retrieve tun name: %w", err)
+	}
+
+	err = unix.SetNonblock(fd, true)
+	if err != nil {
+		return nil, fmt.Errorf("SetNonblock: %v", err)
+	}
+
+	t := &tun{
+		ReadWriteCloser: os.NewFile(uintptr(fd), ""),
+		Device:          name,
 		vpnNetworks:     vpnNetworks,
-		MaxMTU:      mtu,
-		DefaultMTU:  mtu,
+		DefaultMTU:      c.GetInt("tun.mtu", DefaultMTU),
 		l:               l,
 	}
 
-	// Create Darwin-specific route manager
-	t.routeManager = &tun{}
-
 	err = t.reload(c, true)
 	if err != nil {
-		tunDevice.Close()
 		return nil, err
 	}
 
@@ -123,251 +143,215 @@ func newTun(c *config.C, l *logrus.Logger, vpnNetworks []netip.Prefix, _ bool) (
 		}
 	})
 
-	l.WithField("name", actualName).Info("Created WireGuard TUN device")
-
 	return t, nil
 }
 
-func (rm *tun) Activate(t *wgTun) error {
-	name, err := t.tunDevice.Name()
-	if err != nil {
-		return fmt.Errorf("failed to get device name: %w", err)
+func (t *tun) deviceBytes() (o [16]byte) {
+	for i, c := range t.Device {
+		o[i] = byte(c)
 	}
+	return
+}
 
-	// Set the MTU
-	rm.SetMTU(t, t.MaxMTU)
+func newTunFromFd(_ *config.C, _ *logrus.Logger, _ int, _ []netip.Prefix) (*tun, error) {
+	return nil, fmt.Errorf("newTunFromFd not supported in Darwin")
+}
 
-	// Add IP addresses
-	for _, network := range t.vpnNetworks {
-		if err := rm.addIP(t, name, network); err != nil {
+func (t *tun) Close() error {
+	if t.ReadWriteCloser != nil {
+		return t.ReadWriteCloser.Close()
+	}
+	return nil
+}
+
+func (t *tun) Activate() error {
+	devName := t.deviceBytes()
+
+	s, err := unix.Socket(
+		unix.AF_INET,
+		unix.SOCK_DGRAM,
+		unix.IPPROTO_IP,
+	)
+	if err != nil {
 		return err
 	}
+	defer unix.Close(s)
+
+	fd := uintptr(s)
+
+	// Set the MTU on the device
+	ifm := ifreqMTU{Name: devName, MTU: int32(t.DefaultMTU)}
+	if err = ioctl(fd, unix.SIOCSIFMTU, uintptr(unsafe.Pointer(&ifm))); err != nil {
+		return fmt.Errorf("failed to set tun mtu: %v", err)
 	}
 
-	// Bring up the interface using ioctl
-	if err := rm.bringUpInterface(name); err != nil {
-		return fmt.Errorf("failed to bring up interface: %w", err)
+	// Get the device flags
+	ifrf := ifReq{Name: devName}
+	if err = ioctl(fd, unix.SIOCGIFFLAGS, uintptr(unsafe.Pointer(&ifrf))); err != nil {
+		return fmt.Errorf("failed to get tun flags: %s", err)
 	}
 
-	// Get the link address for routing
-	linkAddr, err := getLinkAddr(name)
+	linkAddr, err := getLinkAddr(t.Device)
 	if err != nil {
-		return fmt.Errorf("failed to get link address: %w", err)
+		return err
 	}
 	if linkAddr == nil {
 		return fmt.Errorf("unable to discover link_addr for tun interface")
 	}
-	rm.linkAddr = linkAddr
+	t.linkAddr = linkAddr
 
-	// Set the routes
-	if err := rm.AddRoutes(t, false); err != nil {
+	for _, network := range t.vpnNetworks {
+		if network.Addr().Is4() {
+			err = t.activate4(network)
+			if err != nil {
+				return err
+			}
+		} else {
+			err = t.activate6(network)
+			if err != nil {
+				return err
+			}
+		}
+	}
+
+	// Run the interface
+	ifrf.Flags = ifrf.Flags | unix.IFF_UP | unix.IFF_RUNNING
+	if err = ioctl(fd, unix.SIOCSIFFLAGS, uintptr(unsafe.Pointer(&ifrf))); err != nil {
+		return fmt.Errorf("failed to run tun device: %s", err)
+	}
+
+	// Unsafe path routes
+	return t.addRoutes(false)
+}
+
+func (t *tun) activate4(network netip.Prefix) error {
+	s, err := unix.Socket(
+		unix.AF_INET,
+		unix.SOCK_DGRAM,
+		unix.IPPROTO_IP,
+	)
+	if err != nil {
+		return err
+	}
+	defer unix.Close(s)
+
+	ifr := ifreqAlias4{
+		Name: t.deviceBytes(),
+		Addr: unix.RawSockaddrInet4{
+			Len:    unix.SizeofSockaddrInet4,
+			Family: unix.AF_INET,
+			Addr:   network.Addr().As4(),
+		},
+		DstAddr: unix.RawSockaddrInet4{
+			Len:    unix.SizeofSockaddrInet4,
+			Family: unix.AF_INET,
+			Addr:   network.Addr().As4(),
+		},
+		MaskAddr: unix.RawSockaddrInet4{
+			Len:    unix.SizeofSockaddrInet4,
+			Family: unix.AF_INET,
+			Addr:   prefixToMask(network).As4(),
+		},
+	}
+
+	if err := ioctl(uintptr(s), unix.SIOCAIFADDR, uintptr(unsafe.Pointer(&ifr))); err != nil {
+		return fmt.Errorf("failed to set tun v4 address: %s", err)
+	}
+
+	err = addRoute(network, t.linkAddr)
+	if err != nil {
 		return err
 	}
 
 	return nil
 }
 
-func (rm *tun) bringUpInterface(name string) error {
-	// Open a socket for ioctl
-	fd, err := unix.Socket(unix.AF_INET, unix.SOCK_DGRAM, 0)
+func (t *tun) activate6(network netip.Prefix) error {
+	s, err := unix.Socket(
+		unix.AF_INET6,
+		unix.SOCK_DGRAM,
+		unix.IPPROTO_IP,
+	)
 	if err != nil {
-		return fmt.Errorf("failed to create socket: %w", err)
-	}
-	defer unix.Close(fd)
-
-	// Get current flags
-	var ifrf ifReq
-	copy(ifrf.Name[:], name)
-
-	if err := ioctl(uintptr(fd), unix.SIOCGIFFLAGS, uintptr(unsafe.Pointer(&ifrf))); err != nil {
-		return fmt.Errorf("failed to get interface flags: %w", err)
-	}
-
-	// Set IFF_UP and IFF_RUNNING flags
-	ifrf.Flags = ifrf.Flags | unix.IFF_UP | unix.IFF_RUNNING
-
-	if err := ioctl(uintptr(fd), unix.SIOCSIFFLAGS, uintptr(unsafe.Pointer(&ifrf))); err != nil {
-		return fmt.Errorf("failed to set interface flags: %w", err)
-	}
-
-	return nil
-}
-
-func (rm *tun) SetMTU(t *wgTun, mtu int) {
-	name, err := t.tunDevice.Name()
-	if err != nil {
-		t.l.WithError(err).Error("Failed to get device name for MTU set")
-		return
-	}
-
-	// Open a socket for ioctl
-	fd, err := unix.Socket(unix.AF_INET, unix.SOCK_DGRAM, 0)
-	if err != nil {
-		t.l.WithError(err).Error("Failed to create socket for MTU set")
-		return
-	}
-	defer unix.Close(fd)
-
-	// Prepare the ioctl request
-	var ifr ifreqMTU
-	copy(ifr.Name[:], name)
-	ifr.MTU = int32(mtu)
-
-	// Set the MTU using ioctl
-	if err := ioctl(uintptr(fd), unix.SIOCSIFMTU, uintptr(unsafe.Pointer(&ifr))); err != nil {
-		t.l.WithError(err).Error("Failed to set tun mtu via ioctl")
-	}
-}
-
-func (rm *tun) SetDefaultRoute(t *wgTun, cidr netip.Prefix) error {
-	// On Darwin, routes are set via ifconfig and route commands
-	return nil
-}
-
-func (rm *tun) AddRoutes(t *wgTun, logErrors bool) error {
-	routes := *t.Routes.Load()
-	for _, r := range routes {
-		if !r.Install {
-			continue
-		}
-
-		err := rm.addRoute(r.Cidr)
-		if err != nil {
-			if errors.Is(err, unix.EEXIST) {
-				t.l.WithField("route", r.Cidr).
-					Warnf("unable to add unsafe_route, identical route already exists")
-			} else {
-				retErr := util.NewContextualError("Failed to add route", map[string]any{"route": r}, err)
-				if logErrors {
-					retErr.Log(t.l)
-				} else {
-					return retErr
-				}
-			}
-		} else {
-			t.l.WithField("route", r).Info("Added route")
-		}
-	}
-
-	return nil
-}
-
-func (rm *tun) RemoveRoutes(t *wgTun, routes []Route) {
-	for _, r := range routes {
-		if !r.Install {
-			continue
-		}
-
-		err := rm.delRoute(r.Cidr)
-		if err != nil {
-			t.l.WithError(err).WithField("route", r).Error("Failed to remove route")
-		} else {
-			t.l.WithField("route", r).Info("Removed route")
-		}
-	}
-}
-
-func (rm *tun) NewMultiQueueReader(t *wgTun) (io.ReadWriteCloser, error) {
-	// Darwin doesn't support multi-queue TUN devices in the same way as Linux
-	// Return a reader that wraps the same device
-	return &wgTunReader{
-		parent:    t,
-		tunDevice: t.tunDevice,
-		offset:    0,
-		l:         t.l,
-	}, nil
-}
-
-func (rm *tun) addIP(t *wgTun, name string, network netip.Prefix) error {
-	addr := network.Addr()
-
-	if addr.Is4() {
-		return rm.addIPv4(name, network)
-	} else {
-		return rm.addIPv6(name, network)
-	}
-}
-
-func (rm *tun) addIPv4(name string, network netip.Prefix) error {
-	// Open an IPv4 socket for ioctl
-	s, err := unix.Socket(unix.AF_INET, unix.SOCK_DGRAM, unix.IPPROTO_IP)
-	if err != nil {
-		return fmt.Errorf("failed to create IPv4 socket: %w", err)
+		return err
 	}
 	defer unix.Close(s)
 
-	var ifr ifreqAlias4
-	copy(ifr.Name[:], name)
-
-	// Set the address
-	ifr.Addr = unix.RawSockaddrInet4{
-		Len:    unix.SizeofSockaddrInet4,
-		Family: unix.AF_INET,
-		Addr:   network.Addr().As4(),
-	}
-
-	// Set the destination address (same as address for point-to-point)
-	ifr.DstAddr = unix.RawSockaddrInet4{
-		Len:    unix.SizeofSockaddrInet4,
-		Family: unix.AF_INET,
-		Addr:   network.Addr().As4(),
-	}
-
-	// Set the netmask
-	ifr.MaskAddr = unix.RawSockaddrInet4{
-		Len:    unix.SizeofSockaddrInet4,
-		Family: unix.AF_INET,
-		Addr:   prefixToMask(network).As4(),
-	}
-
-	if err := ioctl(uintptr(s), unix.SIOCAIFADDR, uintptr(unsafe.Pointer(&ifr))); err != nil {
-		return fmt.Errorf("failed to set IPv4 address via ioctl: %w", err)
-	}
-
-	return nil
-}
-
-func (rm *tun) addIPv6(name string, network netip.Prefix) error {
-	// Open an IPv6 socket for ioctl
-	s, err := unix.Socket(unix.AF_INET6, unix.SOCK_DGRAM, unix.IPPROTO_IP)
-	if err != nil {
-		return fmt.Errorf("failed to create IPv6 socket: %w", err)
-	}
-	defer unix.Close(s)
-
-	var ifr ifreqAlias6
-	copy(ifr.Name[:], name)
-
-	// Set the address
-	ifr.Addr = unix.RawSockaddrInet6{
+	ifr := ifreqAlias6{
+		Name: t.deviceBytes(),
+		Addr: unix.RawSockaddrInet6{
 			Len:    unix.SizeofSockaddrInet6,
 			Family: unix.AF_INET6,
 			Addr:   network.Addr().As16(),
-	}
-
-	// Set the prefix mask
-	ifr.PrefixMask = unix.RawSockaddrInet6{
+		},
+		PrefixMask: unix.RawSockaddrInet6{
 			Len:    unix.SizeofSockaddrInet6,
 			Family: unix.AF_INET6,
 			Addr:   prefixToMask(network).As16(),
-	}
-
-	// Set lifetime (never expires)
-	ifr.Lifetime = addrLifetime{
+		},
+		Lifetime: addrLifetime{
+			// never expires
 			Vltime: 0xffffffff,
 			Pltime: 0xffffffff,
+		},
+		Flags: _IN6_IFF_NODAD,
 	}
 
-	// Set flags (no DAD - Duplicate Address Detection)
-	ifr.Flags = _IN6_IFF_NODAD
-
 	if err := ioctl(uintptr(s), _SIOCAIFADDR_IN6, uintptr(unsafe.Pointer(&ifr))); err != nil {
-		return fmt.Errorf("failed to set IPv6 address via ioctl: %w", err)
+		return fmt.Errorf("failed to set tun address: %s", err)
 	}
 
 	return nil
 }
 
+func (t *tun) reload(c *config.C, initial bool) error {
+	change, routes, err := getAllRoutesFromConfig(c, t.vpnNetworks, initial)
+	if err != nil {
+		return err
+	}
+
+	if !initial && !change {
+		return nil
+	}
+
+	routeTree, err := makeRouteTree(t.l, routes, false)
+	if err != nil {
+		return err
+	}
+
+	// Teach nebula how to handle the routes before establishing them in the system table
+	oldRoutes := t.Routes.Swap(&routes)
+	t.routeTree.Store(routeTree)
+
+	if !initial {
+		// Remove first, if the system removes a wanted route hopefully it will be re-added next
+		err := t.removeRoutes(findRemovedRoutes(routes, *oldRoutes))
+		if err != nil {
+			util.LogWithContextIfNeeded("Failed to remove routes", err, t.l)
+		}
+
+		// Ensure any routes we actually want are installed
+		err = t.addRoutes(true)
+		if err != nil {
+			// Catch any stray logs
+			util.LogWithContextIfNeeded("Failed to add routes", err, t.l)
+		}
+	}
+
+	return nil
+}
+
+func (t *tun) RoutesFor(ip netip.Addr) routing.Gateways {
+	r, ok := t.routeTree.Load().Lookup(ip)
+	if ok {
+		return r
+	}
+	return routing.Gateways{}
+}
+
+// Get the LinkAddr for the interface of the given name
+// Is there an easier way to fetch this when we create the interface?
+// Maybe SIOCGIFINDEX? but this doesn't appear to exist in the darwin headers.
 func getLinkAddr(name string) (*netroute.LinkAddr, error) {
 	rib, err := netroute.FetchRIB(unix.AF_UNSPEC, unix.NET_RT_IFLIST, 0)
 	if err != nil {
@@ -393,7 +377,53 @@ func getLinkAddr(name string) (*netroute.LinkAddr, error) {
 	return nil, nil
 }
 
-func (rm *tun) addRoute(prefix netip.Prefix) error {
+func (t *tun) addRoutes(logErrors bool) error {
+	routes := *t.Routes.Load()
+
+	for _, r := range routes {
+		if len(r.Via) == 0 || !r.Install {
+			// We don't allow route MTUs so only install routes with a via
+			continue
+		}
+
+		err := addRoute(r.Cidr, t.linkAddr)
+		if err != nil {
+			if errors.Is(err, unix.EEXIST) {
+				t.l.WithField("route", r.Cidr).
+					Warnf("unable to add unsafe_route, identical route already exists")
+			} else {
+				retErr := util.NewContextualError("Failed to add route", map[string]any{"route": r}, err)
+				if logErrors {
+					retErr.Log(t.l)
+				} else {
+					return retErr
+				}
+			}
+		} else {
+			t.l.WithField("route", r).Info("Added route")
+		}
+	}
+
+	return nil
+}
+
+func (t *tun) removeRoutes(routes []Route) error {
+	for _, r := range routes {
+		if !r.Install {
+			continue
+		}
+
+		err := delRoute(r.Cidr, t.linkAddr)
+		if err != nil {
+			t.l.WithError(err).WithField("route", r).Error("Failed to remove route")
+		} else {
+			t.l.WithField("route", r).Info("Removed route")
+		}
+	}
+	return nil
+}
+
+func addRoute(prefix netip.Prefix, gateway netroute.Addr) error {
 	sock, err := unix.Socket(unix.AF_ROUTE, unix.SOCK_RAW, unix.AF_UNSPEC)
 	if err != nil {
 		return fmt.Errorf("unable to create AF_ROUTE socket: %v", err)
@@ -411,13 +441,13 @@ func (rm *tun) addRoute(prefix netip.Prefix) error {
 		route.Addrs = []netroute.Addr{
 			unix.RTAX_DST:     &netroute.Inet4Addr{IP: prefix.Masked().Addr().As4()},
 			unix.RTAX_NETMASK: &netroute.Inet4Addr{IP: prefixToMask(prefix).As4()},
-			unix.RTAX_GATEWAY: rm.linkAddr,
+			unix.RTAX_GATEWAY: gateway,
 		}
 	} else {
 		route.Addrs = []netroute.Addr{
 			unix.RTAX_DST:     &netroute.Inet6Addr{IP: prefix.Masked().Addr().As16()},
 			unix.RTAX_NETMASK: &netroute.Inet6Addr{IP: prefixToMask(prefix).As16()},
-			unix.RTAX_GATEWAY: rm.linkAddr,
+			unix.RTAX_GATEWAY: gateway,
 		}
 	}
 
@@ -434,7 +464,7 @@ func (rm *tun) addRoute(prefix netip.Prefix) error {
 	return nil
 }
 
-func (rm *tun) delRoute(prefix netip.Prefix) error {
+func delRoute(prefix netip.Prefix, gateway netroute.Addr) error {
 	sock, err := unix.Socket(unix.AF_ROUTE, unix.SOCK_RAW, unix.AF_UNSPEC)
 	if err != nil {
 		return fmt.Errorf("unable to create AF_ROUTE socket: %v", err)
@@ -451,13 +481,13 @@ func (rm *tun) delRoute(prefix netip.Prefix) error {
 		route.Addrs = []netroute.Addr{
 			unix.RTAX_DST:     &netroute.Inet4Addr{IP: prefix.Masked().Addr().As4()},
 			unix.RTAX_NETMASK: &netroute.Inet4Addr{IP: prefixToMask(prefix).As4()},
-			unix.RTAX_GATEWAY: rm.linkAddr,
+			unix.RTAX_GATEWAY: gateway,
 		}
 	} else {
 		route.Addrs = []netroute.Addr{
 			unix.RTAX_DST:     &netroute.Inet6Addr{IP: prefix.Masked().Addr().As16()},
 			unix.RTAX_NETMASK: &netroute.Inet6Addr{IP: prefixToMask(prefix).As16()},
-			unix.RTAX_GATEWAY: rm.linkAddr,
+			unix.RTAX_GATEWAY: gateway,
 		}
 	}
 
@@ -465,7 +495,6 @@ func (rm *tun) delRoute(prefix netip.Prefix) error {
 	if err != nil {
 		return fmt.Errorf("failed to create route.RouteMessage: %w", err)
 	}
-
 	_, err = unix.Write(sock, data[:])
 	if err != nil {
 		return fmt.Errorf("failed to write route.RouteMessage to socket: %w", err)
@@ -474,34 +503,52 @@ func (rm *tun) delRoute(prefix netip.Prefix) error {
 	return nil
 }
 
-func ioctl(a1, a2, a3 uintptr) error {
-	_, _, errno := unix.Syscall(unix.SYS_IOCTL, a1, a2, a3)
-	if errno != 0 {
-		return errno
-	}
-	return nil
+func (t *tun) Read(to []byte) (int, error) {
+	buf := make([]byte, len(to)+4)
+
+	n, err := t.ReadWriteCloser.Read(buf)
+
+	copy(to, buf[4:])
+	return n - 4, err
 }
 
-func prefixToMask(prefix netip.Prefix) netip.Addr {
-	bits := prefix.Bits()
-	if prefix.Addr().Is4() {
-		// Create IPv4 netmask from prefix length
-		mask := ^uint32(0) << (32 - bits)
-		return netip.AddrFrom4([4]byte{
-			byte(mask >> 24),
-			byte(mask >> 16),
-			byte(mask >> 8),
-			byte(mask),
-		})
+// Write is only valid for single threaded use
+func (t *tun) Write(from []byte) (int, error) {
+	buf := t.out
+	if cap(buf) < len(from)+4 {
+		buf = make([]byte, len(from)+4)
+		t.out = buf
+	}
+	buf = buf[:len(from)+4]
+
+	if len(from) == 0 {
+		return 0, syscall.EIO
+	}
+
+	// Determine the IP Family for the NULL L2 Header
+	ipVer := from[0] >> 4
+	if ipVer == 4 {
+		buf[3] = syscall.AF_INET
+	} else if ipVer == 6 {
+		buf[3] = syscall.AF_INET6
 	} else {
-		// Create IPv6 netmask from prefix length
-		var mask [16]byte
-		for i := 0; i < bits/8; i++ {
-			mask[i] = 0xff
-		}
-		if bits%8 != 0 {
-			mask[bits/8] = ^byte(0) << (8 - bits%8)
-		}
-		return netip.AddrFrom16(mask)
+		return 0, fmt.Errorf("unable to determine IP version from packet")
 	}
+
+	copy(buf[4:], from)
+
+	n, err := t.ReadWriteCloser.Write(buf)
+	return n - 4, err
+}
+
+func (t *tun) Networks() []netip.Prefix {
+	return t.vpnNetworks
+}
+
+func (t *tun) Name() string {
+	return t.Device
+}
+
+func (t *tun) NewMultiQueueReader() (io.ReadWriteCloser, error) {
+	return nil, fmt.Errorf("TODO: multiqueue not implemented for darwin")
 }

overlay/tun_disabled.go

@@ -9,6 +9,8 @@ import (
 	"github.com/rcrowley/go-metrics"
 	"github.com/sirupsen/logrus"
 	"github.com/slackhq/nebula/iputil"
+	"github.com/slackhq/nebula/overlay/virtqueue"
+	"github.com/slackhq/nebula/packet"
 	"github.com/slackhq/nebula/routing"
 )
 
@@ -22,6 +24,10 @@ type disabledTun struct {
 	l  *logrus.Logger
 }
 
+func (*disabledTun) RecycleRxSeg(pkt *packet.VirtIOPacket, kick bool, q int) error {
+	return nil
+}
+
 func newDisabledTun(vpnNetworks []netip.Prefix, queueLen int, metricsEnabled bool, l *logrus.Logger) *disabledTun {
 	tun := &disabledTun{
 		vpnNetworks: vpnNetworks,
@@ -40,6 +46,10 @@ func newDisabledTun(vpnNetworks []netip.Prefix, queueLen int, metricsEnabled boo
 	return tun
 }
 
+func (*disabledTun) GetQueues() []*virtqueue.SplitQueue {
+	return nil
+}
+
 func (*disabledTun) Activate() error {
 	return nil
 }
@@ -105,7 +115,23 @@ func (t *disabledTun) Write(b []byte) (int, error) {
 	return len(b), nil
 }
 
-func (t *disabledTun) NewMultiQueueReader() (io.ReadWriteCloser, error) {
+func (t *disabledTun) AllocSeg(pkt *packet.OutPacket, q int) (int, error) {
+	return 0, fmt.Errorf("tun_disabled: AllocSeg not implemented")
+}
+
+func (t *disabledTun) WriteOne(x *packet.OutPacket, kick bool, q int) (int, error) {
+	return 0, fmt.Errorf("tun_disabled: WriteOne not implemented")
+}
+
+func (t *disabledTun) WriteMany(x []*packet.OutPacket, q int) (int, error) {
+	return 0, fmt.Errorf("tun_disabled: WriteMany not implemented")
+}
+
+func (t *disabledTun) ReadMany(b []*packet.VirtIOPacket, _ int) (int, error) {
+	return t.Read(b[0].Payload)
+}
+
+func (t *disabledTun) NewMultiQueueReader() (TunDev, error) {
 	return t, nil
 }
 

overlay/tun_freebsd.go

@@ -1,77 +1,284 @@
-//go:build freebsd && !e2e_testing
-// +build freebsd,!e2e_testing
+//go:build !e2e_testing
+// +build !e2e_testing
 
 package overlay
 
 import (
+	"bytes"
+	"errors"
 	"fmt"
 	"io"
+	"io/fs"
 	"net/netip"
-	"os/exec"
-	"strconv"
-	"strings"
+	"sync/atomic"
 	"syscall"
+	"time"
 	"unsafe"
 
+	"github.com/gaissmai/bart"
 	"github.com/sirupsen/logrus"
 	"github.com/slackhq/nebula/config"
+	"github.com/slackhq/nebula/routing"
 	"github.com/slackhq/nebula/util"
+	netroute "golang.org/x/net/route"
 	"golang.org/x/sys/unix"
-	wgtun "golang.zx2c4.com/wireguard/tun"
 )
 
-type tun struct{}
+const (
+	// FIODGNAME is defined in sys/sys/filio.h on FreeBSD
+	// For 32-bit systems, use FIODGNAME_32 (not defined in this file: 0x80086678)
+	FIODGNAME        = 0x80106678
+	TUNSIFMODE       = 0x8004745e
+	TUNSIFHEAD       = 0x80047460
+	OSIOCAIFADDR_IN6 = 0x8088691b
+	IN6_IFF_NODAD    = 0x0020
+)
+
+type fiodgnameArg struct {
+	length int32
+	pad    [4]byte
+	buf    unsafe.Pointer
+}
 
-// ifreqRename is used for renaming network interfaces on FreeBSD
 type ifreqRename struct {
 	Name [unix.IFNAMSIZ]byte
 	Data uintptr
 }
 
-func newTunFromFd(_ *config.C, _ *logrus.Logger, _ int, _ []netip.Prefix) (*wgTun, error) {
-	return nil, fmt.Errorf("newTunFromFd not supported on FreeBSD")
+type ifreqDestroy struct {
+	Name [unix.IFNAMSIZ]byte
+	pad  [16]byte
 }
 
-func newTun(c *config.C, l *logrus.Logger, vpnNetworks []netip.Prefix, _ bool) (*wgTun, error) {
-	deviceName := c.GetString("tun.dev", "tun")
-	mtu := c.GetInt("tun.mtu", DefaultMTU)
+type ifReq struct {
+	Name  [unix.IFNAMSIZ]byte
+	Flags uint16
+}
 
-	// Create WireGuard TUN device
-	tunDevice, err := wgtun.CreateTUN(deviceName, mtu)
-	if err != nil {
-		return nil, fmt.Errorf("failed to create TUN device: %w", err)
+type ifreqMTU struct {
+	Name [unix.IFNAMSIZ]byte
+	MTU  int32
+}
+
+type addrLifetime struct {
+	Expire    uint64
+	Preferred uint64
+	Vltime    uint32
+	Pltime    uint32
+}
+
+type ifreqAlias4 struct {
+	Name     [unix.IFNAMSIZ]byte
+	Addr     unix.RawSockaddrInet4
+	DstAddr  unix.RawSockaddrInet4
+	MaskAddr unix.RawSockaddrInet4
+	VHid     uint32
+}
+
+type ifreqAlias6 struct {
+	Name       [unix.IFNAMSIZ]byte
+	Addr       unix.RawSockaddrInet6
+	DstAddr    unix.RawSockaddrInet6
+	PrefixMask unix.RawSockaddrInet6
+	Flags      uint32
+	Lifetime   addrLifetime
+	VHid       uint32
+}
+
+type tun struct {
+	Device      string
+	vpnNetworks []netip.Prefix
+	MTU         int
+	Routes      atomic.Pointer[[]Route]
+	routeTree   atomic.Pointer[bart.Table[routing.Gateways]]
+	linkAddr    *netroute.LinkAddr
+	l           *logrus.Logger
+	devFd       int
+}
+
+func (t *tun) Read(to []byte) (int, error) {
+	// use readv() to read from the tunnel device, to eliminate the need for copying the buffer
+	if t.devFd < 0 {
+		return -1, syscall.EINVAL
 	}
 
-	// Get the actual device name
-	actualName, err := tunDevice.Name()
+	// first 4 bytes is protocol family, in network byte order
+	head := make([]byte, 4)
+
+	iovecs := []syscall.Iovec{
+		{&head[0], 4},
+		{&to[0], uint64(len(to))},
+	}
+
+	n, _, errno := syscall.Syscall(syscall.SYS_READV, uintptr(t.devFd), uintptr(unsafe.Pointer(&iovecs[0])), uintptr(2))
+
+	var err error
+	if errno != 0 {
+		err = syscall.Errno(errno)
+	} else {
+		err = nil
+	}
+	// fix bytes read number to exclude header
+	bytesRead := int(n)
+	if bytesRead < 0 {
+		return bytesRead, err
+	} else if bytesRead < 4 {
+		return 0, err
+	} else {
+		return bytesRead - 4, err
+	}
+}
+
+// Write is only valid for single threaded use
+func (t *tun) Write(from []byte) (int, error) {
+	// use writev() to write to the tunnel device, to eliminate the need for copying the buffer
+	if t.devFd < 0 {
+		return -1, syscall.EINVAL
+	}
+
+	if len(from) <= 1 {
+		return 0, syscall.EIO
+	}
+	ipVer := from[0] >> 4
+	var head []byte
+	// first 4 bytes is protocol family, in network byte order
+	if ipVer == 4 {
+		head = []byte{0, 0, 0, syscall.AF_INET}
+	} else if ipVer == 6 {
+		head = []byte{0, 0, 0, syscall.AF_INET6}
+	} else {
+		return 0, fmt.Errorf("unable to determine IP version from packet")
+	}
+	iovecs := []syscall.Iovec{
+		{&head[0], 4},
+		{&from[0], uint64(len(from))},
+	}
+
+	n, _, errno := syscall.Syscall(syscall.SYS_WRITEV, uintptr(t.devFd), uintptr(unsafe.Pointer(&iovecs[0])), uintptr(2))
+
+	var err error
+	if errno != 0 {
+		err = syscall.Errno(errno)
+	} else {
+		err = nil
+	}
+
+	return int(n) - 4, err
+}
+
+func (t *tun) Close() error {
+	if t.devFd >= 0 {
+		err := syscall.Close(t.devFd)
 		if err != nil {
-		tunDevice.Close()
-		return nil, fmt.Errorf("failed to get TUN device name: %w", err)
+			t.l.WithError(err).Error("Error closing device")
+		}
+		t.devFd = -1
+
+		c := make(chan struct{})
+		go func() {
+			// destroying the interface can block if a read() is still pending. Do this asynchronously.
+			defer close(c)
+			s, err := syscall.Socket(syscall.AF_INET, syscall.SOCK_DGRAM, syscall.IPPROTO_IP)
+			if err == nil {
+				defer syscall.Close(s)
+				ifreq := ifreqDestroy{Name: t.deviceBytes()}
+				err = ioctl(uintptr(s), syscall.SIOCIFDESTROY, uintptr(unsafe.Pointer(&ifreq)))
+			}
+			if err != nil {
+				t.l.WithError(err).Error("Error destroying tunnel")
+			}
+		}()
+
+		// wait up to 1 second so we start blocking at the ioctl
+		select {
+		case <-c:
+		case <-time.After(1 * time.Second):
+		}
+	}
+
+	return nil
+}
+
+func newTunFromFd(_ *config.C, _ *logrus.Logger, _ int, _ []netip.Prefix) (*tun, error) {
+	return nil, fmt.Errorf("newTunFromFd not supported in FreeBSD")
+}
+
+func newTun(c *config.C, l *logrus.Logger, vpnNetworks []netip.Prefix, _ bool) (*tun, error) {
+	// Try to open existing tun device
+	var fd int
+	var err error
+	deviceName := c.GetString("tun.dev", "")
+	if deviceName != "" {
+		fd, err = syscall.Open("/dev/"+deviceName, syscall.O_RDWR, 0)
+	}
+	if errors.Is(err, fs.ErrNotExist) || deviceName == "" {
+		// If the device doesn't already exist, request a new one and rename it
+		fd, err = syscall.Open("/dev/tun", syscall.O_RDWR, 0)
+	}
+	if err != nil {
+		return nil, err
+	}
+
+	// Read the name of the interface
+	var name [16]byte
+	arg := fiodgnameArg{length: 16, buf: unsafe.Pointer(&name)}
+	ctrlErr := ioctl(uintptr(fd), FIODGNAME, uintptr(unsafe.Pointer(&arg)))
+
+	if ctrlErr == nil {
+		// set broadcast mode and multicast
+		ifmode := uint32(unix.IFF_BROADCAST | unix.IFF_MULTICAST)
+		ctrlErr = ioctl(uintptr(fd), TUNSIFMODE, uintptr(unsafe.Pointer(&ifmode)))
+	}
+
+	if ctrlErr == nil {
+		// turn on link-layer mode, to support ipv6
+		ifhead := uint32(1)
+		ctrlErr = ioctl(uintptr(fd), TUNSIFHEAD, uintptr(unsafe.Pointer(&ifhead)))
+	}
+
+	if ctrlErr != nil {
+		return nil, err
+	}
+
+	ifName := string(bytes.TrimRight(name[:], "\x00"))
+	if deviceName == "" {
+		deviceName = ifName
 	}
 
 	// If the name doesn't match the desired interface name, rename it now
-	if actualName != deviceName && deviceName != "" && deviceName != "tun" {
-		if err := renameInterface(actualName, deviceName); err != nil {
-			tunDevice.Close()
-			return nil, fmt.Errorf("failed to rename interface from %s to %s: %w", actualName, deviceName, err)
+	if ifName != deviceName {
+		s, err := unix.Socket(unix.AF_INET, unix.SOCK_DGRAM, unix.IPPROTO_IP)
+		if err != nil {
+			return nil, err
 		}
-		actualName = deviceName
+		defer syscall.Close(s)
+
+		fd := uintptr(s)
+
+		var fromName [16]byte
+		var toName [16]byte
+		copy(fromName[:], ifName)
+		copy(toName[:], deviceName)
+
+		ifrr := ifreqRename{
+			Name: fromName,
+			Data: uintptr(unsafe.Pointer(&toName)),
 		}
 
-	t := &wgTun{
-		tunDevice:   tunDevice,
+		// Set the device name
+		ioctl(fd, syscall.SIOCSIFNAME, uintptr(unsafe.Pointer(&ifrr)))
+	}
+
+	t := &tun{
+		Device:      deviceName,
 		vpnNetworks: vpnNetworks,
-		MaxMTU:      mtu,
-		DefaultMTU:  mtu,
+		MTU:         c.GetInt("tun.mtu", DefaultMTU),
 		l:           l,
+		devFd:       fd,
 	}
 
-	// Create FreeBSD-specific route manager
-	t.routeManager = &tun{}
-
 	err = t.reload(c, true)
 	if err != nil {
-		tunDevice.Close()
 		return nil, err
 	}
 
@@ -82,86 +289,180 @@ func newTun(c *config.C, l *logrus.Logger, vpnNetworks []netip.Prefix, _ bool) (
 		}
 	})
 
-	l.WithField("name", actualName).Info("Created WireGuard TUN device")
-
 	return t, nil
 }
 
-func (rm *tun) Activate(t *wgTun) error {
-	name, err := t.tunDevice.Name()
+func (t *tun) addIp(cidr netip.Prefix) error {
+	if cidr.Addr().Is4() {
+		ifr := ifreqAlias4{
+			Name: t.deviceBytes(),
+			Addr: unix.RawSockaddrInet4{
+				Len:    unix.SizeofSockaddrInet4,
+				Family: unix.AF_INET,
+				Addr:   cidr.Addr().As4(),
+			},
+			DstAddr: unix.RawSockaddrInet4{
+				Len:    unix.SizeofSockaddrInet4,
+				Family: unix.AF_INET,
+				Addr:   getBroadcast(cidr).As4(),
+			},
+			MaskAddr: unix.RawSockaddrInet4{
+				Len:    unix.SizeofSockaddrInet4,
+				Family: unix.AF_INET,
+				Addr:   prefixToMask(cidr).As4(),
+			},
+			VHid: 0,
+		}
+		s, err := unix.Socket(unix.AF_INET, unix.SOCK_DGRAM, unix.IPPROTO_IP)
 		if err != nil {
-		return fmt.Errorf("failed to get device name: %w", err)
+			return err
+		}
+		defer syscall.Close(s)
+		// Note: unix.SIOCAIFADDR corresponds to FreeBSD's OSIOCAIFADDR
+		if err := ioctl(uintptr(s), unix.SIOCAIFADDR, uintptr(unsafe.Pointer(&ifr))); err != nil {
+			return fmt.Errorf("failed to set tun address %s: %s", cidr.Addr().String(), err)
+		}
+		return nil
 	}
 
-	// Set the MTU
-	rm.SetMTU(t, t.MaxMTU)
+	if cidr.Addr().Is6() {
+		ifr := ifreqAlias6{
+			Name: t.deviceBytes(),
+			Addr: unix.RawSockaddrInet6{
+				Len:    unix.SizeofSockaddrInet6,
+				Family: unix.AF_INET6,
+				Addr:   cidr.Addr().As16(),
+			},
+			PrefixMask: unix.RawSockaddrInet6{
+				Len:    unix.SizeofSockaddrInet6,
+				Family: unix.AF_INET6,
+				Addr:   prefixToMask(cidr).As16(),
+			},
+			Lifetime: addrLifetime{
+				Expire:    0,
+				Preferred: 0,
+				Vltime:    0xffffffff,
+				Pltime:    0xffffffff,
+			},
+			Flags: IN6_IFF_NODAD,
+		}
+		s, err := syscall.Socket(syscall.AF_INET6, syscall.SOCK_DGRAM, syscall.IPPROTO_IP)
+		if err != nil {
+			return err
+		}
+		defer syscall.Close(s)
 
-	// Add IP addresses
-	for _, network := range t.vpnNetworks {
-		if err := rm.addIP(t, name, network); err != nil {
+		if err := ioctl(uintptr(s), OSIOCAIFADDR_IN6, uintptr(unsafe.Pointer(&ifr))); err != nil {
+			return fmt.Errorf("failed to set tun address %s: %s", cidr.Addr().String(), err)
+		}
+		return nil
+	}
+
+	return fmt.Errorf("unknown address type %v", cidr)
+}
+
+func (t *tun) Activate() error {
+	// Setup our default MTU
+	err := t.setMTU()
+	if err != nil {
+		return err
+	}
+
+	linkAddr, err := getLinkAddr(t.Device)
+	if err != nil {
+		return err
+	}
+	if linkAddr == nil {
+		return fmt.Errorf("unable to discover link_addr for tun interface")
+	}
+	t.linkAddr = linkAddr
+
+	for i := range t.vpnNetworks {
+		err := t.addIp(t.vpnNetworks[i])
+		if err != nil {
 			return err
 		}
 	}
 
-	// Bring up the interface
-	if err := runCommandBSD("ifconfig", name, "up"); err != nil {
-		return fmt.Errorf("failed to bring up interface: %w", err)
+	return t.addRoutes(false)
+}
+
+func (t *tun) setMTU() error {
+	// Set the MTU on the device
+	s, err := unix.Socket(unix.AF_INET, unix.SOCK_DGRAM, unix.IPPROTO_IP)
+	if err != nil {
+		return err
+	}
+	defer syscall.Close(s)
+
+	ifm := ifreqMTU{Name: t.deviceBytes(), MTU: int32(t.MTU)}
+	err = ioctl(uintptr(s), unix.SIOCSIFMTU, uintptr(unsafe.Pointer(&ifm)))
+	return err
+}
+
+func (t *tun) reload(c *config.C, initial bool) error {
+	change, routes, err := getAllRoutesFromConfig(c, t.vpnNetworks, initial)
+	if err != nil {
+		return err
 	}
 
-	// Set the routes
-	if err := rm.AddRoutes(t, false); err != nil {
+	if !initial && !change {
+		return nil
+	}
+
+	routeTree, err := makeRouteTree(t.l, routes, false)
+	if err != nil {
 		return err
 	}
 
+	// Teach nebula how to handle the routes before establishing them in the system table
+	oldRoutes := t.Routes.Swap(&routes)
+	t.routeTree.Store(routeTree)
+
+	if !initial {
+		// Remove first, if the system removes a wanted route hopefully it will be re-added next
+		err := t.removeRoutes(findRemovedRoutes(routes, *oldRoutes))
+		if err != nil {
+			util.LogWithContextIfNeeded("Failed to remove routes", err, t.l)
+		}
+
+		// Ensure any routes we actually want are installed
+		err = t.addRoutes(true)
+		if err != nil {
+			// Catch any stray logs
+			util.LogWithContextIfNeeded("Failed to add routes", err, t.l)
+		}
+	}
+
 	return nil
 }
 
-func (rm *tun) SetMTU(t *wgTun, mtu int) {
-	name, err := t.tunDevice.Name()
-	if err != nil {
-		t.l.WithError(err).Error("Failed to get device name for MTU set")
-		return
-	}
-
-	if err := runCommandBSD("ifconfig", name, "mtu", strconv.Itoa(mtu)); err != nil {
-		t.l.WithError(err).Error("Failed to set tun mtu")
-	}
+func (t *tun) RoutesFor(ip netip.Addr) routing.Gateways {
+	r, _ := t.routeTree.Load().Lookup(ip)
+	return r
 }
 
-func (rm *tun) SetDefaultRoute(t *wgTun, cidr netip.Prefix) error {
-	// On FreeBSD, routes are set via ifconfig and route commands
-	return nil
+func (t *tun) Networks() []netip.Prefix {
+	return t.vpnNetworks
 }
 
-func (rm *tun) AddRoutes(t *wgTun, logErrors bool) error {
-	name, err := t.tunDevice.Name()
-	if err != nil {
-		return fmt.Errorf("failed to get device name: %w", err)
-	}
+func (t *tun) Name() string {
+	return t.Device
+}
 
+func (t *tun) NewMultiQueueReader() (io.ReadWriteCloser, error) {
+	return nil, fmt.Errorf("TODO: multiqueue not implemented for freebsd")
+}
+
+func (t *tun) addRoutes(logErrors bool) error {
 	routes := *t.Routes.Load()
 	for _, r := range routes {
-		if !r.Install {
+		if len(r.Via) == 0 || !r.Install {
+			// We don't allow route MTUs so only install routes with a via
 			continue
 		}
 
-		// Add route using route command
-		args := []string{"add"}
-
-		if r.Cidr.Addr().Is6() {
-			args = append(args, "-inet6")
-		} else {
-			args = append(args, "-inet")
-		}
-
-		args = append(args, r.Cidr.String(), "-interface", name)
-
-		if r.Metric > 0 {
-			// FreeBSD doesn't support route metrics directly like Linux
-			t.l.WithField("route", r).Warn("Route metrics are not fully supported on FreeBSD")
-		}
-
-		err := runCommandBSD("route", args...)
+		err := addRoute(r.Cidr, t.linkAddr)
 		if err != nil {
 			retErr := util.NewContextualError("Failed to add route", map[string]any{"route": r}, err)
 			if logErrors {
@@ -177,99 +478,142 @@ func (rm *tun) AddRoutes(t *wgTun, logErrors bool) error {
 	return nil
 }
 
-func (rm *tun) RemoveRoutes(t *wgTun, routes []Route) {
-	name, err := t.tunDevice.Name()
-	if err != nil {
-		t.l.WithError(err).Error("Failed to get device name for route removal")
-		return
-	}
-
+func (t *tun) removeRoutes(routes []Route) error {
 	for _, r := range routes {
 		if !r.Install {
 			continue
 		}
 
-		args := []string{"delete"}
-
-		if r.Cidr.Addr().Is6() {
-			args = append(args, "-inet6")
-		} else {
-			args = append(args, "-inet")
-		}
-
-		args = append(args, r.Cidr.String(), "-interface", name)
-
-		err := runCommandBSD("route", args...)
+		err := delRoute(r.Cidr, t.linkAddr)
 		if err != nil {
 			t.l.WithError(err).WithField("route", r).Error("Failed to remove route")
 		} else {
 			t.l.WithField("route", r).Info("Removed route")
 		}
 	}
+	return nil
 }
 
-func (rm *tun) NewMultiQueueReader(t *wgTun) (io.ReadWriteCloser, error) {
-	// FreeBSD doesn't support multi-queue TUN devices in the same way as Linux
-	// Return a reader that wraps the same device
-	return &wgTunReader{
-		parent:    t,
-		tunDevice: t.tunDevice,
-		offset:    0,
-		l:         t.l,
-	}, nil
+func (t *tun) deviceBytes() (o [16]byte) {
+	for i, c := range t.Device {
+		o[i] = byte(c)
+	}
+	return
 }
 
-func (rm *tun) addIP(t *wgTun, name string, network netip.Prefix) error {
-	addr := network.Addr()
+func addRoute(prefix netip.Prefix, gateway netroute.Addr) error {
+	sock, err := unix.Socket(unix.AF_ROUTE, unix.SOCK_RAW, unix.AF_UNSPEC)
+	if err != nil {
+		return fmt.Errorf("unable to create AF_ROUTE socket: %v", err)
+	}
+	defer unix.Close(sock)
 
-	if addr.Is4() {
-		// For IPv4: ifconfig tun0 10.0.0.1/24
-		if err := runCommandBSD("ifconfig", name, network.String()); err != nil {
-			return fmt.Errorf("failed to add IPv4 address: %w", err)
+	route := &netroute.RouteMessage{
+		Version: unix.RTM_VERSION,
+		Type:    unix.RTM_ADD,
+		Flags:   unix.RTF_UP,
+		Seq:     1,
+	}
+
+	if prefix.Addr().Is4() {
+		route.Addrs = []netroute.Addr{
+			unix.RTAX_DST:     &netroute.Inet4Addr{IP: prefix.Masked().Addr().As4()},
+			unix.RTAX_NETMASK: &netroute.Inet4Addr{IP: prefixToMask(prefix).As4()},
+			unix.RTAX_GATEWAY: gateway,
 		}
 	} else {
-		// For IPv6: ifconfig tun0 inet6 add 2001:db8::1/64
-		if err := runCommandBSD("ifconfig", name, "inet6", "add", network.String()); err != nil {
-			return fmt.Errorf("failed to add IPv6 address: %w", err)
+		route.Addrs = []netroute.Addr{
+			unix.RTAX_DST:     &netroute.Inet6Addr{IP: prefix.Masked().Addr().As16()},
+			unix.RTAX_NETMASK: &netroute.Inet6Addr{IP: prefixToMask(prefix).As16()},
+			unix.RTAX_GATEWAY: gateway,
 		}
 	}
 
-	return nil
-}
-
-func runCommandBSD(name string, args ...string) error {
-	cmd := exec.Command(name, args...)
-	output, err := cmd.CombinedOutput()
+	data, err := route.Marshal()
 	if err != nil {
-		return fmt.Errorf("%s %s failed: %w\nOutput: %s", name, strings.Join(args, " "), err, string(output))
+		return fmt.Errorf("failed to create route.RouteMessage: %w", err)
 	}
-	return nil
-}
 
-func renameInterface(fromName, toName string) error {
-	s, err := unix.Socket(unix.AF_INET, unix.SOCK_DGRAM, unix.IPPROTO_IP)
+	_, err = unix.Write(sock, data[:])
 	if err != nil {
-		return fmt.Errorf("failed to create socket: %w", err)
+		if errors.Is(err, unix.EEXIST) {
+			// Try to do a change
+			route.Type = unix.RTM_CHANGE
+			data, err = route.Marshal()
+			if err != nil {
+				return fmt.Errorf("failed to create route.RouteMessage for change: %w", err)
 			}
-	defer syscall.Close(s)
-
-	fd := uintptr(s)
-
-	var fromNameBytes [unix.IFNAMSIZ]byte
-	var toNameBytes [unix.IFNAMSIZ]byte
-	copy(fromNameBytes[:], fromName)
-	copy(toNameBytes[:], toName)
-
-	ifrr := ifreqRename{
-		Name: fromNameBytes,
-		Data: uintptr(unsafe.Pointer(&toNameBytes)),
+			_, err = unix.Write(sock, data[:])
+			fmt.Println("DOING CHANGE")
+			return err
 		}
-
-	// Set the device name using SIOCSIFNAME ioctl
-	_, _, errno := syscall.Syscall(syscall.SYS_IOCTL, fd, syscall.SIOCSIFNAME, uintptr(unsafe.Pointer(&ifrr)))
-	if errno != 0 {
-		return fmt.Errorf("SIOCSIFNAME ioctl failed: %w", errno)
+		return fmt.Errorf("failed to write route.RouteMessage to socket: %w", err)
 	}
 
 	return nil
 }
+
+func delRoute(prefix netip.Prefix, gateway netroute.Addr) error {
+	sock, err := unix.Socket(unix.AF_ROUTE, unix.SOCK_RAW, unix.AF_UNSPEC)
+	if err != nil {
+		return fmt.Errorf("unable to create AF_ROUTE socket: %v", err)
+	}
+	defer unix.Close(sock)
+
+	route := netroute.RouteMessage{
+		Version: unix.RTM_VERSION,
+		Type:    unix.RTM_DELETE,
+		Seq:     1,
+	}
+
+	if prefix.Addr().Is4() {
+		route.Addrs = []netroute.Addr{
+			unix.RTAX_DST:     &netroute.Inet4Addr{IP: prefix.Masked().Addr().As4()},
+			unix.RTAX_NETMASK: &netroute.Inet4Addr{IP: prefixToMask(prefix).As4()},
+			unix.RTAX_GATEWAY: gateway,
+		}
+	} else {
+		route.Addrs = []netroute.Addr{
+			unix.RTAX_DST:     &netroute.Inet6Addr{IP: prefix.Masked().Addr().As16()},
+			unix.RTAX_NETMASK: &netroute.Inet6Addr{IP: prefixToMask(prefix).As16()},
+			unix.RTAX_GATEWAY: gateway,
+		}
+	}
+
+	data, err := route.Marshal()
+	if err != nil {
+		return fmt.Errorf("failed to create route.RouteMessage: %w", err)
+	}
+	_, err = unix.Write(sock, data[:])
+	if err != nil {
+		return fmt.Errorf("failed to write route.RouteMessage to socket: %w", err)
+	}
+
+	return nil
+}
+
+// getLinkAddr Gets the link address for the interface of the given name
+func getLinkAddr(name string) (*netroute.LinkAddr, error) {
+	rib, err := netroute.FetchRIB(unix.AF_UNSPEC, unix.NET_RT_IFLIST, 0)
+	if err != nil {
+		return nil, err
+	}
+	msgs, err := netroute.ParseRIB(unix.NET_RT_IFLIST, rib)
+	if err != nil {
+		return nil, err
+	}
+
+	for _, m := range msgs {
+		switch m := m.(type) {
+		case *netroute.InterfaceMessage:
+			if m.Name == name {
+				sa, ok := m.Addrs[unix.RTAX_IFP].(*netroute.LinkAddr)
+				if ok {
+					return sa, nil
+				}
+			}
+		}
+	}
+
+	return nil, nil
+}

overlay/tun_linux.go

@@ -1,113 +1,175 @@
-//go:build linux && !android && !e2e_testing
-// +build linux,!android,!e2e_testing
+//go:build !android && !e2e_testing
+// +build !android,!e2e_testing
 
 package overlay
 
 import (
 	"fmt"
-	"io"
 	"net"
 	"net/netip"
 	"os"
+	"strings"
+	"sync/atomic"
 	"time"
 	"unsafe"
 
+	"github.com/gaissmai/bart"
 	"github.com/sirupsen/logrus"
 	"github.com/slackhq/nebula/config"
+	"github.com/slackhq/nebula/overlay/vhostnet"
+	"github.com/slackhq/nebula/packet"
 	"github.com/slackhq/nebula/routing"
 	"github.com/slackhq/nebula/util"
+	"github.com/slackhq/nebula/util/virtio"
 	"github.com/vishvananda/netlink"
 	"golang.org/x/sys/unix"
-	wgtun "golang.zx2c4.com/wireguard/tun"
 )
 
 type tun struct {
+	file        *os.File
+	fd          int
+	vdev        []*vhostnet.Device
+	Device      string
+	vpnNetworks []netip.Prefix
+	MaxMTU      int
+	DefaultMTU  int
+	TXQueueLen  int
 	deviceIndex int
 	ioctlFd     uintptr
-	txQueueLen                int
+
+	Routes                    atomic.Pointer[[]Route]
+	routeTree                 atomic.Pointer[bart.Table[routing.Gateways]]
+	routeChan                 chan struct{}
 	useSystemRoutes           bool
 	useSystemRoutesBufferSize int
+
+	isV6 bool
+	l    *logrus.Logger
 }
 
-func newTun(c *config.C, l *logrus.Logger, vpnNetworks []netip.Prefix, multiqueue bool) (*wgTun, error) {
-	deviceName := c.GetString("tun.dev", "")
-	mtu := c.GetInt("tun.mtu", DefaultMTU)
-
-	// Create WireGuard TUN device
-	tunDevice, err := wgtun.CreateTUN(deviceName, mtu)
-	if err != nil {
-		return nil, fmt.Errorf("failed to create TUN device: %w", err)
-	}
-
-	// Get the actual device name
-	actualName, err := tunDevice.Name()
-	if err != nil {
-		tunDevice.Close()
-		return nil, fmt.Errorf("failed to get TUN device name: %w", err)
-	}
-
-	t := &wgTun{
-		tunDevice:   tunDevice,
-		vpnNetworks: vpnNetworks,
-		MaxMTU:      mtu,
-		DefaultMTU:  mtu,
-		l:           l,
-	}
-
-	// Create Linux-specific route manager
-	routeManager := &tun{
-		txQueueLen:                c.GetInt("tun.tx_queue", 500),
-		useSystemRoutes:           c.GetBool("tun.use_system_route_table", false),
-		useSystemRoutesBufferSize: c.GetInt("tun.use_system_route_table_buffer_size", 0),
-	}
-	t.routeManager = routeManager
-
-	err = t.reload(c, true)
-	if err != nil {
-		tunDevice.Close()
-		return nil, err
-	}
-
-	c.RegisterReloadCallback(func(c *config.C) {
-		err := t.reload(c, false)
-		if err != nil {
-			util.LogWithContextIfNeeded("failed to reload tun device", err, t.l)
-		}
-	})
-
-	l.WithField("name", actualName).Info("Created WireGuard TUN device")
-
-	return t, nil
+func (t *tun) Networks() []netip.Prefix {
+	return t.vpnNetworks
 }
 
-func newTunFromFd(c *config.C, l *logrus.Logger, deviceFd int, vpnNetworks []netip.Prefix) (*wgTun, error) {
-	// Create TUN device from file descriptor
+type ifReq struct {
+	Name  [16]byte
+	Flags uint16
+	pad   [8]byte
+}
+
+type ifreqMTU struct {
+	Name [16]byte
+	MTU  int32
+	pad  [8]byte
+}
+
+type ifreqQLEN struct {
+	Name  [16]byte
+	Value int32
+	pad   [8]byte
+}
+
+func newTunFromFd(c *config.C, l *logrus.Logger, deviceFd int, vpnNetworks []netip.Prefix) (*tun, error) {
 	file := os.NewFile(uintptr(deviceFd), "/dev/net/tun")
-	mtu := c.GetInt("tun.mtu", DefaultMTU)
-	tunDevice, err := wgtun.CreateTUNFromFile(file, mtu)
+
+	t, err := newTunGeneric(c, l, file, vpnNetworks)
 	if err != nil {
-		return nil, fmt.Errorf("failed to create TUN device from fd: %w", err)
+		return nil, err
 	}
 
-	t := &wgTun{
-		tunDevice:   tunDevice,
+	t.Device = "tun0"
+
+	return t, nil
+}
+
+func newTun(c *config.C, l *logrus.Logger, vpnNetworks []netip.Prefix, multiqueue bool) (*tun, error) {
+	fd, err := unix.Open("/dev/net/tun", os.O_RDWR, 0)
+	if err != nil {
+		// If /dev/net/tun doesn't exist, try to create it (will happen in docker)
+		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
+		}
+	}
+
+	var req ifReq
+	req.Flags = uint16(unix.IFF_TUN | unix.IFF_NO_PI | unix.IFF_TUN_EXCL | unix.IFF_VNET_HDR | unix.IFF_NAPI)
+	if multiqueue {
+		req.Flags |= unix.IFF_MULTI_QUEUE
+	}
+	copy(req.Name[:], c.GetString("tun.dev", ""))
+	if err = ioctl(uintptr(fd), uintptr(unix.TUNSETIFF), uintptr(unsafe.Pointer(&req))); err != nil {
+		return nil, err
+	}
+	name := strings.Trim(string(req.Name[:]), "\x00")
+
+	if err = unix.SetNonblock(fd, true); err != nil {
+		_ = unix.Close(fd)
+		return nil, fmt.Errorf("make file descriptor non-blocking: %w", err)
+	}
+
+	file := os.NewFile(uintptr(fd), "/dev/net/tun")
+
+	err = unix.IoctlSetPointerInt(fd, unix.TUNSETVNETHDRSZ, virtio.NetHdrSize)
+	if err != nil {
+		return nil, fmt.Errorf("set vnethdr size: %w", err)
+	}
+
+	flags := 0
+	//flags = //unix.TUN_F_CSUM //| unix.TUN_F_TSO4 | unix.TUN_F_USO4 | unix.TUN_F_TSO6 | unix.TUN_F_USO6
+	err = unix.IoctlSetInt(fd, unix.TUNSETOFFLOAD, flags)
+	if err != nil {
+		return nil, fmt.Errorf("set offloads: %w", err)
+	}
+
+	t, err := newTunGeneric(c, l, file, vpnNetworks)
+	if err != nil {
+		return nil, err
+	}
+	t.fd = fd
+	t.Device = name
+
+	vdev, err := vhostnet.NewDevice(
+		vhostnet.WithBackendFD(fd),
+		vhostnet.WithQueueSize(8192), //todo config
+	)
+	if err != nil {
+		return nil, err
+	}
+	t.vdev = []*vhostnet.Device{vdev}
+
+	return t, nil
+}
+
+func newTunGeneric(c *config.C, l *logrus.Logger, file *os.File, vpnNetworks []netip.Prefix) (*tun, error) {
+	t := &tun{
+		file:                      file,
+		fd:                        int(file.Fd()),
 		vpnNetworks:               vpnNetworks,
-		MaxMTU:      mtu,
-		DefaultMTU:  mtu,
-		l:           l,
-	}
-
-	// Create Linux-specific route manager
-	routeManager := &tun{
-		txQueueLen:                c.GetInt("tun.tx_queue", 500),
+		TXQueueLen:                c.GetInt("tun.tx_queue", 500),
 		useSystemRoutes:           c.GetBool("tun.use_system_route_table", false),
 		useSystemRoutesBufferSize: c.GetInt("tun.use_system_route_table_buffer_size", 0),
+		l:                         l,
+	}
+	if len(vpnNetworks) != 0 {
+		t.isV6 = vpnNetworks[0].Addr().Is6() //todo what about multi-IP?
 	}
-	t.routeManager = routeManager
 
-	err = t.reload(c, true)
+	err := t.reload(c, true)
 	if err != nil {
-		tunDevice.Close()
 		return nil, err
 	}
 
@@ -121,105 +183,258 @@ func newTunFromFd(c *config.C, l *logrus.Logger, deviceFd int, vpnNetworks []net
 	return t, nil
 }
 
-func (rm *tun) Activate(t *wgTun) error {
-	name, err := t.tunDevice.Name()
+func (t *tun) reload(c *config.C, initial bool) error {
+	routeChange, routes, err := getAllRoutesFromConfig(c, t.vpnNetworks, initial)
 	if err != nil {
-		return fmt.Errorf("failed to get device name: %w", err)
+		return err
 	}
 
-	if t.routeManager.useSystemRoutes {
+	if !initial && !routeChange && !c.HasChanged("tun.mtu") {
+		return nil
+	}
+
+	routeTree, err := makeRouteTree(t.l, routes, true)
+	if err != nil {
+		return err
+	}
+
+	oldDefaultMTU := t.DefaultMTU
+	oldMaxMTU := t.MaxMTU
+	newDefaultMTU := c.GetInt("tun.mtu", DefaultMTU)
+	newMaxMTU := newDefaultMTU
+	for i, r := range routes {
+		if r.MTU == 0 {
+			routes[i].MTU = newDefaultMTU
+		}
+
+		if r.MTU > t.MaxMTU {
+			newMaxMTU = r.MTU
+		}
+	}
+
+	t.MaxMTU = newMaxMTU
+	t.DefaultMTU = newDefaultMTU
+
+	// Teach nebula how to handle the routes before establishing them in the system table
+	oldRoutes := t.Routes.Swap(&routes)
+	t.routeTree.Store(routeTree)
+
+	if !initial {
+		if oldMaxMTU != newMaxMTU {
+			t.setMTU()
+			t.l.Infof("Set max MTU to %v was %v", t.MaxMTU, oldMaxMTU)
+		}
+
+		if oldDefaultMTU != newDefaultMTU {
+			for i := range t.vpnNetworks {
+				err := t.setDefaultRoute(t.vpnNetworks[i])
+				if err != nil {
+					t.l.Warn(err)
+				} else {
+					t.l.Infof("Set default MTU to %v was %v", t.DefaultMTU, oldDefaultMTU)
+				}
+			}
+		}
+
+		// Remove first, if the system removes a wanted route hopefully it will be re-added next
+		t.removeRoutes(findRemovedRoutes(routes, *oldRoutes))
+
+		// Ensure any routes we actually want are installed
+		err = t.addRoutes(true)
+		if err != nil {
+			// This should never be called since addRoutes should log its own errors in a reload condition
+			util.LogWithContextIfNeeded("Failed to refresh routes", err, t.l)
+		}
+	}
+
+	return nil
+}
+
+func (t *tun) NewMultiQueueReader() (TunDev, error) {
+	fd, err := unix.Open("/dev/net/tun", os.O_RDWR, 0)
+	if err != nil {
+		return nil, err
+	}
+
+	var req ifReq
+	req.Flags = uint16(unix.IFF_TUN | unix.IFF_NO_PI | unix.IFF_MULTI_QUEUE)
+	copy(req.Name[:], t.Device)
+	if err = ioctl(uintptr(fd), uintptr(unix.TUNSETIFF), uintptr(unsafe.Pointer(&req))); err != nil {
+		return nil, err
+	}
+
+	vdev, err := vhostnet.NewDevice(
+		vhostnet.WithBackendFD(fd),
+		vhostnet.WithQueueSize(8192), //todo config
+	)
+	if err != nil {
+		return nil, err
+	}
+
+	t.vdev = append(t.vdev, vdev)
+
+	return t, nil
+}
+
+func (t *tun) RoutesFor(ip netip.Addr) routing.Gateways {
+	r, _ := t.routeTree.Load().Lookup(ip)
+	return r
+}
+
+func (t *tun) deviceBytes() (o [16]byte) {
+	for i, c := range t.Device {
+		o[i] = byte(c)
+	}
+	return
+}
+
+func hasNetlinkAddr(al []*netlink.Addr, x netlink.Addr) bool {
+	for i := range al {
+		if al[i].Equal(x) {
+			return true
+		}
+	}
+	return false
+}
+
+// addIPs uses netlink to add all addresses that don't exist, then it removes ones that should not be there
+func (t *tun) addIPs(link netlink.Link) error {
+	newAddrs := make([]*netlink.Addr, len(t.vpnNetworks))
+	for i := range t.vpnNetworks {
+		newAddrs[i] = &netlink.Addr{
+			IPNet: &net.IPNet{
+				IP:   t.vpnNetworks[i].Addr().AsSlice(),
+				Mask: net.CIDRMask(t.vpnNetworks[i].Bits(), t.vpnNetworks[i].Addr().BitLen()),
+			},
+			Label: t.vpnNetworks[i].Addr().Zone(),
+		}
+	}
+
+	//add all new addresses
+	for i := range newAddrs {
+		//AddrReplace still adds new IPs, but if their properties change it will change them as well
+		if err := netlink.AddrReplace(link, newAddrs[i]); err != nil {
+			return err
+		}
+	}
+
+	//iterate over remainder, remove whoever shouldn't be there
+	al, err := netlink.AddrList(link, netlink.FAMILY_ALL)
+	if err != nil {
+		return fmt.Errorf("failed to get tun address list: %s", err)
+	}
+
+	for i := range al {
+		if hasNetlinkAddr(newAddrs, al[i]) {
+			continue
+		}
+		err = netlink.AddrDel(link, &al[i])
+		if err != nil {
+			t.l.WithError(err).Error("failed to remove address from tun address list")
+		} else {
+			t.l.WithField("removed", al[i].String()).Info("removed address not listed in cert(s)")
+		}
+	}
+
+	return nil
+}
+
+func (t *tun) Activate() error {
+	devName := t.deviceBytes()
+
+	if t.useSystemRoutes {
 		t.watchRoutes()
 	}
 
-	// Get the netlink device
-	link, err := netlink.LinkByName(name)
-	if err != nil {
-		return fmt.Errorf("failed to get tun device link: %s", err)
-	}
-
-	rm.deviceIndex = link.Attrs().Index
-
-	// Open socket for ioctl operations
 	s, err := unix.Socket(
-		unix.AF_INET,
+		unix.AF_INET, //because everything we use t.ioctlFd for is address family independent, this is fine
 		unix.SOCK_DGRAM,
 		unix.IPPROTO_IP,
 	)
 	if err != nil {
 		return err
 	}
-	rm.ioctlFd = uintptr(s)
+	t.ioctlFd = uintptr(s)
 
-	rm.SetMTU(t, t.MaxMTU)
+	// Set the device name
+	ifrf := ifReq{Name: devName}
+	if err = ioctl(t.ioctlFd, unix.SIOCGIFFLAGS, uintptr(unsafe.Pointer(&ifrf))); err != nil {
+		return fmt.Errorf("failed to set tun device name: %s", err)
+	}
+
+	link, err := netlink.LinkByName(t.Device)
+	if err != nil {
+		return fmt.Errorf("failed to get tun device link: %s", err)
+	}
+
+	t.deviceIndex = link.Attrs().Index
+
+	// Setup our default MTU
+	t.setMTU()
 
 	// Set the transmit queue length
-	devName := deviceBytes(name)
-	ifrq := ifreqQLEN{Name: devName, Value: int32(rm.txQueueLen)}
-	if err = ioctl(t.routeManager.ioctlFd, unix.SIOCSIFTXQLEN, uintptr(unsafe.Pointer(&ifrq))); err != nil {
+	ifrq := ifreqQLEN{Name: devName, Value: int32(t.TXQueueLen)}
+	if err = ioctl(t.ioctlFd, unix.SIOCSIFTXQLEN, uintptr(unsafe.Pointer(&ifrq))); err != nil {
 		// If we can't set the queue length nebula will still work but it may lead to packet loss
 		t.l.WithError(err).Error("Failed to set tun tx queue length")
 	}
 
-	// Disable IPv6 link-local address generation
 	const modeNone = 1
 	if err = netlink.LinkSetIP6AddrGenMode(link, modeNone); err != nil {
 		t.l.WithError(err).Warn("Failed to disable link local address generation")
 	}
 
-	// Add IP addresses
-	if err = t.routeManager.addIPs(t, link); err != nil {
+	if err = t.addIPs(link); err != nil {
 		return err
 	}
 
 	// Bring up the interface
-	if err = netlink.LinkSetUp(link); err != nil {
+	ifrf.Flags = ifrf.Flags | unix.IFF_UP
+	if err = ioctl(t.ioctlFd, unix.SIOCSIFFLAGS, uintptr(unsafe.Pointer(&ifrf))); err != nil {
 		return fmt.Errorf("failed to bring the tun device up: %s", err)
 	}
 
-	// Set route MTU
+	//set route MTU
 	for i := range t.vpnNetworks {
-		if err = t.routeManager.SetDefaultRoute(t, t.vpnNetworks[i]); err != nil {
+		if err = t.setDefaultRoute(t.vpnNetworks[i]); err != nil {
 			return fmt.Errorf("failed to set default route MTU: %w", err)
 		}
 	}
 
 	// Set the routes
-	if err = t.routeManager.AddRoutes(t, false); err != nil {
+	if err = t.addRoutes(false); err != nil {
 		return err
 	}
 
+	// Run the interface
+	ifrf.Flags = ifrf.Flags | unix.IFF_UP | unix.IFF_RUNNING
+	if err = ioctl(t.ioctlFd, unix.SIOCSIFFLAGS, uintptr(unsafe.Pointer(&ifrf))); err != nil {
+		return fmt.Errorf("failed to run tun device: %s", err)
+	}
+
 	return nil
 }
 
-func (rm *tun) SetMTU(t *wgTun, mtu int) {
-	name, err := t.tunDevice.Name()
-	if err != nil {
-		t.l.WithError(err).Error("Failed to get device name for MTU set")
-		return
-	}
-
-	link, err := netlink.LinkByName(name)
-	if err != nil {
-		t.l.WithError(err).Error("Failed to get link for MTU set")
-		return
-	}
-
-	if err := netlink.LinkSetMTU(link, mtu); err != nil {
+func (t *tun) setMTU() {
+	// Set the MTU on the device
+	ifm := ifreqMTU{Name: t.deviceBytes(), MTU: int32(t.MaxMTU)}
+	if err := ioctl(t.ioctlFd, unix.SIOCSIFMTU, uintptr(unsafe.Pointer(&ifm))); err != nil {
+		// This is currently a non fatal condition because the route table must have the MTU set appropriately as well
 		t.l.WithError(err).Error("Failed to set tun mtu")
 	}
 }
 
-func (rm *tun) SetDefaultRoute(t *wgTun, cidr netip.Prefix) error {
+func (t *tun) setDefaultRoute(cidr netip.Prefix) error {
 	dr := &net.IPNet{
 		IP:   cidr.Masked().Addr().AsSlice(),
 		Mask: net.CIDRMask(cidr.Bits(), cidr.Addr().BitLen()),
 	}
 
 	nr := netlink.Route{
-		LinkIndex: t.routeManager.deviceIndex,
+		LinkIndex: t.deviceIndex,
 		Dst:       dr,
 		MTU:       t.DefaultMTU,
-		AdvMSS:    advMSS(Route{}, t.DefaultMTU, t.MaxMTU),
+		AdvMSS:    t.advMSS(Route{}),
 		Scope:     unix.RT_SCOPE_LINK,
 		Src:       net.IP(cidr.Addr().AsSlice()),
 		Protocol:  unix.RTPROT_KERNEL,
@@ -229,7 +444,7 @@ func (rm *tun) SetDefaultRoute(t *wgTun, cidr netip.Prefix) error {
 	err := netlink.RouteReplace(&nr)
 	if err != nil {
 		t.l.WithError(err).WithField("cidr", cidr).Warn("Failed to set default route MTU, retrying")
-		// Retry twice more
+		//retry twice more -- on some systems there appears to be a race condition where if we set routes too soon, netlink says `invalid argument`
 		for i := 0; i < 2; i++ {
 			time.Sleep(100 * time.Millisecond)
 			err = netlink.RouteReplace(&nr)
@@ -247,7 +462,8 @@ func (rm *tun) SetDefaultRoute(t *wgTun, cidr netip.Prefix) error {
 	return nil
 }
 
-func (rm *tun) AddRoutes(t *wgTun, logErrors bool) error {
+func (t *tun) addRoutes(logErrors bool) error {
+	// Path routes
 	routes := *t.Routes.Load()
 	for _, r := range routes {
 		if !r.Install {
@@ -260,10 +476,10 @@ func (rm *tun) AddRoutes(t *wgTun, logErrors bool) error {
 		}
 
 		nr := netlink.Route{
-			LinkIndex: t.routeManager.deviceIndex,
+			LinkIndex: t.deviceIndex,
 			Dst:       dr,
 			MTU:       r.MTU,
-			AdvMSS:    advMSS(r, t.DefaultMTU, t.MaxMTU),
+			AdvMSS:    t.advMSS(r),
 			Scope:     unix.RT_SCOPE_LINK,
 		}
 
@@ -287,7 +503,7 @@ func (rm *tun) AddRoutes(t *wgTun, logErrors bool) error {
 	return nil
 }
 
-func (rm *tun) RemoveRoutes(t *wgTun, routes []Route) {
+func (t *tun) removeRoutes(routes []Route) {
 	for _, r := range routes {
 		if !r.Install {
 			continue
@@ -299,10 +515,10 @@ func (rm *tun) RemoveRoutes(t *wgTun, routes []Route) {
 		}
 
 		nr := netlink.Route{
-			LinkIndex: t.routeManager.deviceIndex,
+			LinkIndex: t.deviceIndex,
 			Dst:       dr,
 			MTU:       r.MTU,
-			AdvMSS:    advMSS(r, t.DefaultMTU, t.MaxMTU),
+			AdvMSS:    t.advMSS(r),
 			Scope:     unix.RT_SCOPE_LINK,
 		}
 
@@ -319,105 +535,30 @@ func (rm *tun) RemoveRoutes(t *wgTun, routes []Route) {
 	}
 }
 
-func (rm *tun) NewMultiQueueReader(t *wgTun) (io.ReadWriteCloser, error) {
-	// For Linux with WireGuard TUN, we can reuse the same device
-	// The vectorized I/O will handle batching
-	return &wgTunReader{
-		parent:    t,
-		tunDevice: t.tunDevice,
-		offset:    0,
-		l:         t.l,
-	}, nil
+func (t *tun) Name() string {
+	return t.Device
 }
 
-func deviceBytes(name string) [16]byte {
-	var o [16]byte
-	for i, c := range name {
-		if i >= 16 {
-			break
-		}
-		o[i] = byte(c)
-	}
-	return o
-}
-
-func advMSS(r Route, defaultMTU, maxMTU int) int {
+func (t *tun) advMSS(r Route) int {
 	mtu := r.MTU
 	if r.MTU == 0 {
-		mtu = defaultMTU
+		mtu = t.DefaultMTU
 	}
 
 	// We only need to set advmss if the route MTU does not match the device MTU
-	if mtu != maxMTU {
+	if mtu != t.MaxMTU {
 		return mtu - 40
 	}
 	return 0
 }
 
-type ifreqQLEN struct {
-	Name  [16]byte
-	Value int32
-	pad   [8]byte
-}
-
-func hasNetlinkAddr(al []*netlink.Addr, x netlink.Addr) bool {
-	for i := range al {
-		if al[i].Equal(x) {
-			return true
-		}
-	}
-	return false
-}
-
-func (rm *tun) addIPs(t *wgTun, link netlink.Link) error {
-	newAddrs := make([]*netlink.Addr, len(t.vpnNetworks))
-	for i := range t.vpnNetworks {
-		newAddrs[i] = &netlink.Addr{
-			IPNet: &net.IPNet{
-				IP:   t.vpnNetworks[i].Addr().AsSlice(),
-				Mask: net.CIDRMask(t.vpnNetworks[i].Bits(), t.vpnNetworks[i].Addr().BitLen()),
-			},
-			Label: t.vpnNetworks[i].Addr().Zone(),
-		}
-	}
-
-	// Add all new addresses
-	for i := range newAddrs {
-		if err := netlink.AddrReplace(link, newAddrs[i]); err != nil {
-			return err
-		}
-	}
-
-	// Iterate over remainder, remove whoever shouldn't be there
-	al, err := netlink.AddrList(link, netlink.FAMILY_ALL)
-	if err != nil {
-		return fmt.Errorf("failed to get tun address list: %s", err)
-	}
-
-	for i := range al {
-		if hasNetlinkAddr(newAddrs, al[i]) {
-			continue
-		}
-		err = netlink.AddrDel(link, &al[i])
-		if err != nil {
-			t.l.WithError(err).Error("failed to remove address from tun address list")
-		} else {
-			t.l.WithField("removed", al[i].String()).Info("removed address not listed in cert(s)")
-		}
-	}
-
-	return nil
-}
-
-// watchRoutes monitors system route changes
-func (t *wgTun) watchRoutes() {
-
+func (t *tun) watchRoutes() {
 	rch := make(chan netlink.RouteUpdate)
 	doneChan := make(chan struct{})
 
 	netlinkOptions := netlink.RouteSubscribeOptions{
-		ReceiveBufferSize:      t.routeManager.useSystemRoutesBufferSize,
-		ReceiveBufferForceSize: t.routeManager.useSystemRoutesBufferSize != 0,
+		ReceiveBufferSize:      t.useSystemRoutesBufferSize,
+		ReceiveBufferForceSize: t.useSystemRoutesBufferSize != 0,
 		ErrorCallback:          func(e error) { t.l.WithError(e).Errorf("netlink error") },
 	}
 
@@ -435,19 +576,87 @@ func (t *wgTun) watchRoutes() {
 				if ok {
 					t.updateRoutes(r)
 				} else {
+					// may be should do something here as
+					// netlink stops sending updates
 					return
 				}
 			case <-doneChan:
+				// netlink.RouteSubscriber will close the rch for us
 				return
 			}
 		}
 	}()
 }
 
-func (t *wgTun) updateRoutes(r netlink.RouteUpdate) {
-	gateways := t.getGatewaysFromRoute(&r.Route, t.routeManager.deviceIndex)
+func (t *tun) isGatewayInVpnNetworks(gwAddr netip.Addr) bool {
+	withinNetworks := false
+	for i := range t.vpnNetworks {
+		if t.vpnNetworks[i].Contains(gwAddr) {
+			withinNetworks = true
+			break
+		}
+	}
+
+	return withinNetworks
+}
+
+func (t *tun) getGatewaysFromRoute(r *netlink.Route) routing.Gateways {
+
+	var gateways routing.Gateways
+
+	link, err := netlink.LinkByName(t.Device)
+	if err != nil {
+		t.l.WithField("Devicename", t.Device).Error("Ignoring route update: failed to get link by name")
+		return gateways
+	}
+
+	// If this route is relevant to our interface and there is a gateway then add it
+	if r.LinkIndex == link.Attrs().Index && len(r.Gw) > 0 {
+		gwAddr, ok := netip.AddrFromSlice(r.Gw)
+		if !ok {
+			t.l.WithField("route", r).Debug("Ignoring route update, invalid gateway address")
+		} else {
+			gwAddr = gwAddr.Unmap()
+
+			if !t.isGatewayInVpnNetworks(gwAddr) {
+				// Gateway isn't in our overlay network, ignore
+				t.l.WithField("route", r).Debug("Ignoring route update, not in our network")
+			} else {
+				gateways = append(gateways, routing.NewGateway(gwAddr, 1))
+			}
+		}
+	}
+
+	for _, p := range r.MultiPath {
+		// If this route is relevant to our interface and there is a gateway then add it
+		if p.LinkIndex == link.Attrs().Index && len(p.Gw) > 0 {
+			gwAddr, ok := netip.AddrFromSlice(p.Gw)
+			if !ok {
+				t.l.WithField("route", r).Debug("Ignoring multipath route update, invalid gateway address")
+			} else {
+				gwAddr = gwAddr.Unmap()
+
+				if !t.isGatewayInVpnNetworks(gwAddr) {
+					// Gateway isn't in our overlay network, ignore
+					t.l.WithField("route", r).Debug("Ignoring route update, not in our network")
+				} else {
+					// p.Hops+1 = weight of the route
+					gateways = append(gateways, routing.NewGateway(gwAddr, p.Hops+1))
+				}
+			}
+		}
+	}
+
+	routing.CalculateBucketsForGateways(gateways)
+	return gateways
+}
+
+func (t *tun) updateRoutes(r netlink.RouteUpdate) {
+
+	gateways := t.getGatewaysFromRoute(&r.Route)
 
 	if len(gateways) == 0 {
+		// No gateways relevant to our network, no routing changes required.
 		t.l.WithField("route", r).Debug("Ignoring route update, no gateways")
 		return
 	}
@@ -471,6 +680,7 @@ func (t *wgTun) updateRoutes(r netlink.RouteUpdate) {
 	if r.Type == unix.RTM_NEWROUTE {
 		t.l.WithField("destination", dst).WithField("via", gateways).Info("Adding route")
 		newTree.Insert(dst, gateways)
+
 	} else {
 		t.l.WithField("destination", dst).WithField("via", gateways).Info("Removing route")
 		newTree.Delete(dst)
@@ -478,71 +688,86 @@ func (t *wgTun) updateRoutes(r netlink.RouteUpdate) {
 	t.routeTree.Store(newTree)
 }
 
-func (t *wgTun) getGatewaysFromRoute(r *netlink.Route, deviceIndex int) routing.Gateways {
-	var gateways routing.Gateways
-
-	name, err := t.tunDevice.Name()
-	if err != nil {
-		t.l.Error("Ignoring route update: failed to get device name")
-		return gateways
+func (t *tun) Close() error {
+	if t.routeChan != nil {
+		close(t.routeChan)
 	}
 
-	link, err := netlink.LinkByName(name)
-	if err != nil {
-		t.l.WithField("DeviceName", name).Error("Ignoring route update: failed to get link by name")
-		return gateways
-	}
-
-	// If this route is relevant to our interface and there is a gateway then add it
-	if r.LinkIndex == link.Attrs().Index && len(r.Gw) > 0 {
-		gwAddr, ok := netip.AddrFromSlice(r.Gw)
-		if !ok {
-			t.l.WithField("route", r).Debug("Ignoring route update, invalid gateway address")
-		} else {
-			gwAddr = gwAddr.Unmap()
-
-			if !t.isGatewayInVpnNetworks(gwAddr) {
-				t.l.WithField("route", r).Debug("Ignoring route update, not in our network")
-			} else {
-				gateways = append(gateways, routing.NewGateway(gwAddr, 1))
-			}
+	for _, v := range t.vdev {
+		if v != nil {
+			_ = v.Close()
 		}
 	}
 
-	for _, p := range r.MultiPath {
-		if p.LinkIndex == link.Attrs().Index && len(p.Gw) > 0 {
-			gwAddr, ok := netip.AddrFromSlice(p.Gw)
-			if !ok {
-				t.l.WithField("route", r).Debug("Ignoring multipath route update, invalid gateway address")
-			} else {
-				gwAddr = gwAddr.Unmap()
-
-				if !t.isGatewayInVpnNetworks(gwAddr) {
-					t.l.WithField("route", r).Debug("Ignoring route update, not in our network")
-				} else {
-					gateways = append(gateways, routing.NewGateway(gwAddr, p.Hops+1))
-				}
-			}
-		}
+	if t.file != nil {
+		_ = t.file.Close()
 	}
 
-	routing.CalculateBucketsForGateways(gateways)
-	return gateways
-}
+	if t.ioctlFd > 0 {
+		_ = os.NewFile(t.ioctlFd, "ioctlFd").Close()
+	}
 
-func (t *wgTun) isGatewayInVpnNetworks(gwAddr netip.Addr) bool {
-	for i := range t.vpnNetworks {
-		if t.vpnNetworks[i].Contains(gwAddr) {
-			return true
-		}
-	}
-	return false
-}
-
-func ioctl(a1, a2, a3 uintptr) error {
-	_, _, errno := unix.Syscall(unix.SYS_IOCTL, a1, a2, a3)
-	if errno != 0 {
-		return errno
-	}
 	return nil
 }
+
+func (t *tun) ReadMany(p []*packet.VirtIOPacket, q int) (int, error) {
+	n, err := t.vdev[q].ReceivePackets(p) //we are TXing
+	if err != nil {
+		return 0, err
+	}
+	return n, nil
+}
+
+func (t *tun) Write(b []byte) (int, error) {
+	maximum := len(b) //we are RXing
+
+	//todo garbagey
+	out := packet.NewOut()
+	x, err := t.AllocSeg(out, 0)
+	if err != nil {
+		return 0, err
+	}
+	copy(out.SegmentPayloads[x], b)
+	err = t.vdev[0].TransmitPacket(out, true)
+
+	if err != nil {
+		t.l.WithError(err).Error("Transmitting packet")
+		return 0, err
+	}
+	return maximum, nil
+}
+
+func (t *tun) AllocSeg(pkt *packet.OutPacket, q int) (int, error) {
+	idx, buf, err := t.vdev[q].GetPacketForTx()
+	if err != nil {
+		return 0, err
+	}
+	x := pkt.UseSegment(idx, buf, t.isV6)
+	return x, nil
+}
+
+func (t *tun) WriteOne(x *packet.OutPacket, kick bool, q int) (int, error) {
+	if err := t.vdev[q].TransmitPacket(x, kick); err != nil {
+		t.l.WithError(err).Error("Transmitting packet")
+		return 0, err
+	}
+	return 1, nil
+}
+
+func (t *tun) WriteMany(x []*packet.OutPacket, q int) (int, error) {
+	maximum := len(x) //we are RXing
+	if maximum == 0 {
+		return 0, nil
+	}
+
+	err := t.vdev[q].TransmitPackets(x)
+	if err != nil {
+		t.l.WithError(err).Error("Transmitting packet")
+		return 0, err
+	}
+	return maximum, nil
+}
+
+func (t *tun) RecycleRxSeg(pkt *packet.VirtIOPacket, kick bool, q int) error {
+	return t.vdev[q].ReceiveQueue.OfferDescriptorChains(pkt.Chains, kick)
+}

overlay/tun_linux_test.go

@@ -7,26 +7,25 @@ import "testing"
 
 var runAdvMSSTests = []struct {
 	name     string
-	defaultMTU int
-	maxMTU     int
+	tun      *tun
 	r        Route
 	expected int
 }{
 	// Standard case, default MTU is the device max MTU
-	{"default", 1440, 1440, Route{}, 0},
-	{"default-min", 1440, 1440, Route{MTU: 1440}, 0},
-	{"default-low", 1440, 1440, Route{MTU: 1200}, 1160},
+	{"default", &tun{DefaultMTU: 1440, MaxMTU: 1440}, Route{}, 0},
+	{"default-min", &tun{DefaultMTU: 1440, MaxMTU: 1440}, Route{MTU: 1440}, 0},
+	{"default-low", &tun{DefaultMTU: 1440, MaxMTU: 1440}, Route{MTU: 1200}, 1160},
 
 	// Case where we have a route MTU set higher than the default
-	{"route", 1440, 8941, Route{}, 1400},
-	{"route-min", 1440, 8941, Route{MTU: 1440}, 1400},
-	{"route-high", 1440, 8941, Route{MTU: 8941}, 0},
+	{"route", &tun{DefaultMTU: 1440, MaxMTU: 8941}, Route{}, 1400},
+	{"route-min", &tun{DefaultMTU: 1440, MaxMTU: 8941}, Route{MTU: 1440}, 1400},
+	{"route-high", &tun{DefaultMTU: 1440, MaxMTU: 8941}, Route{MTU: 8941}, 0},
 }
 
 func TestTunAdvMSS(t *testing.T) {
 	for _, tt := range runAdvMSSTests {
 		t.Run(tt.name, func(t *testing.T) {
-			o := advMSS(tt.r, tt.defaultMTU, tt.maxMTU)
+			o := tt.tun.advMSS(tt.r)
 			if o != tt.expected {
 				t.Errorf("got %d, want %d", o, tt.expected)
 			}

overlay/tun_netbsd.go

@@ -547,41 +547,3 @@ func delRoute(prefix netip.Prefix, gateways []netip.Prefix) error {
 
 	return nil
 }
-
-func ioctl(a1, a2, a3 uintptr) error {
-	_, _, errno := syscall.Syscall(syscall.SYS_IOCTL, a1, a2, a3)
-	if errno != 0 {
-		return errno
-	}
-	return nil
-}
-
-func prefixToMask(prefix netip.Prefix) netip.Addr {
-	bits := prefix.Bits()
-	if prefix.Addr().Is4() {
-		mask := ^uint32(0) << (32 - bits)
-		return netip.AddrFrom4([4]byte{
-			byte(mask >> 24),
-			byte(mask >> 16),
-			byte(mask >> 8),
-			byte(mask),
-		})
-	}
-	var mask [16]byte
-	for i := 0; i < bits/8; i++ {
-		mask[i] = 0xff
-	}
-	if bits%8 != 0 {
-		mask[bits/8] = ^byte(0) << (8 - bits%8)
-	}
-	return netip.AddrFrom16(mask)
-}
-
-func selectGateway(prefix netip.Prefix, gateways []netip.Prefix) (netip.Prefix, error) {
-	for _, gw := range gateways {
-		if prefix.Addr().Is4() == gw.Addr().Is4() {
-			return gw, nil
-		}
-	}
-	return netip.Prefix{}, fmt.Errorf("no suitable gateway found for prefix %v", prefix)
-}

overlay/tun_notwin.go

@@ -0,0 +1,14 @@
+//go:build !windows
+// +build !windows
+
+package overlay
+
+import "syscall"
+
+func ioctl(a1, a2, a3 uintptr) error {
+	_, _, errno := syscall.Syscall(syscall.SYS_IOCTL, a1, a2, a3)
+	if errno != 0 {
+		return errno
+	}
+	return nil
+}

overlay/tun_openbsd.go

@@ -1,59 +1,104 @@
-//go:build openbsd && !e2e_testing
-// +build openbsd,!e2e_testing
+//go:build !e2e_testing
+// +build !e2e_testing
 
 package overlay
 
 import (
+	"errors"
 	"fmt"
 	"io"
 	"net/netip"
-	"os/exec"
-	"strconv"
-	"strings"
+	"os"
+	"regexp"
+	"sync/atomic"
+	"syscall"
+	"unsafe"
 
+	"github.com/gaissmai/bart"
 	"github.com/sirupsen/logrus"
 	"github.com/slackhq/nebula/config"
+	"github.com/slackhq/nebula/routing"
 	"github.com/slackhq/nebula/util"
-	wgtun "golang.zx2c4.com/wireguard/tun"
+	netroute "golang.org/x/net/route"
+	"golang.org/x/sys/unix"
 )
 
-type tun struct{}
+const (
+	SIOCAIFADDR_IN6 = 0x8080691a
+)
 
-func newTunFromFd(_ *config.C, _ *logrus.Logger, _ int, _ []netip.Prefix) (*wgTun, error) {
-	return nil, fmt.Errorf("newTunFromFd not supported on OpenBSD")
+type ifreqAlias4 struct {
+	Name     [unix.IFNAMSIZ]byte
+	Addr     unix.RawSockaddrInet4
+	DstAddr  unix.RawSockaddrInet4
+	MaskAddr unix.RawSockaddrInet4
 }
 
-func newTun(c *config.C, l *logrus.Logger, vpnNetworks []netip.Prefix, _ bool) (*wgTun, error) {
-	deviceName := c.GetString("tun.dev", "tun")
-	mtu := c.GetInt("tun.mtu", DefaultMTU)
+type ifreqAlias6 struct {
+	Name       [unix.IFNAMSIZ]byte
+	Addr       unix.RawSockaddrInet6
+	DstAddr    unix.RawSockaddrInet6
+	PrefixMask unix.RawSockaddrInet6
+	Flags      uint32
+	Lifetime   [2]uint32
+}
 
-	// Create WireGuard TUN device
-	tunDevice, err := wgtun.CreateTUN(deviceName, mtu)
-	if err != nil {
-		return nil, fmt.Errorf("failed to create TUN device: %w", err)
+type ifreq struct {
+	Name [unix.IFNAMSIZ]byte
+	data int
+}
+
+type tun struct {
+	Device      string
+	vpnNetworks []netip.Prefix
+	MTU         int
+	Routes      atomic.Pointer[[]Route]
+	routeTree   atomic.Pointer[bart.Table[routing.Gateways]]
+	l           *logrus.Logger
+	f           *os.File
+	fd          int
+	// cache out buffer since we need to prepend 4 bytes for tun metadata
+	out []byte
+}
+
+var deviceNameRE = regexp.MustCompile(`^tun[0-9]+$`)
+
+func newTunFromFd(_ *config.C, _ *logrus.Logger, _ int, _ []netip.Prefix) (*tun, error) {
+	return nil, fmt.Errorf("newTunFromFd not supported in openbsd")
+}
+
+func newTun(c *config.C, l *logrus.Logger, vpnNetworks []netip.Prefix, _ bool) (*tun, error) {
+	// Try to open tun device
+	var err error
+	deviceName := c.GetString("tun.dev", "")
+	if deviceName == "" {
+		return nil, fmt.Errorf("a device name in the format of /dev/tunN must be specified")
+	}
+	if !deviceNameRE.MatchString(deviceName) {
+		return nil, fmt.Errorf("a device name in the format of /dev/tunN must be specified")
 	}
 
-	// Get the actual device name
-	actualName, err := tunDevice.Name()
+	fd, err := unix.Open("/dev/"+deviceName, os.O_RDWR, 0)
 	if err != nil {
-		tunDevice.Close()
-		return nil, fmt.Errorf("failed to get TUN device name: %w", err)
+		return nil, err
 	}
 
-	t := &wgTun{
-		tunDevice:   tunDevice,
+	err = unix.SetNonblock(fd, true)
+	if err != nil {
+		l.WithError(err).Warn("Failed to set the tun device as nonblocking")
+	}
+
+	t := &tun{
+		f:           os.NewFile(uintptr(fd), ""),
+		fd:          fd,
+		Device:      deviceName,
 		vpnNetworks: vpnNetworks,
-		MaxMTU:      mtu,
-		DefaultMTU:  mtu,
+		MTU:         c.GetInt("tun.mtu", DefaultMTU),
 		l:           l,
 	}
 
-	// Create OpenBSD-specific route manager
-	t.routeManager = &tun{}
-
 	err = t.reload(c, true)
 	if err != nil {
-		tunDevice.Close()
 		return nil, err
 	}
 
@@ -64,86 +109,221 @@ func newTun(c *config.C, l *logrus.Logger, vpnNetworks []netip.Prefix, _ bool) (
 		}
 	})
 
-	l.WithField("name", actualName).Info("Created WireGuard TUN device")
-
 	return t, nil
 }
 
-func (rm *tun) Activate(t *wgTun) error {
-	name, err := t.tunDevice.Name()
+func (t *tun) Close() error {
+	if t.f != nil {
+		if err := t.f.Close(); err != nil {
+			return fmt.Errorf("error closing tun file: %w", err)
+		}
+
+		// t.f.Close should have handled it for us but let's be extra sure
+		_ = unix.Close(t.fd)
+	}
+	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
+	if cap(buf) < len(from)+4 {
+		buf = make([]byte, len(from)+4)
+		t.out = buf
+	}
+	buf = buf[:len(from)+4]
+
+	if len(from) == 0 {
+		return 0, syscall.EIO
+	}
+
+	// Determine the IP Family for the NULL L2 Header
+	ipVer := from[0] >> 4
+	if ipVer == 4 {
+		buf[3] = syscall.AF_INET
+	} else if ipVer == 6 {
+		buf[3] = syscall.AF_INET6
+	} else {
+		return 0, fmt.Errorf("unable to determine IP version from packet")
+	}
+
+	copy(buf[4:], from)
+
+	n, err := t.f.Write(buf)
+	return n - 4, err
+}
+
+func (t *tun) addIp(cidr netip.Prefix) error {
+	if cidr.Addr().Is4() {
+		var req ifreqAlias4
+		req.Name = t.deviceBytes()
+		req.Addr = unix.RawSockaddrInet4{
+			Len:    unix.SizeofSockaddrInet4,
+			Family: unix.AF_INET,
+			Addr:   cidr.Addr().As4(),
+		}
+		req.DstAddr = unix.RawSockaddrInet4{
+			Len:    unix.SizeofSockaddrInet4,
+			Family: unix.AF_INET,
+			Addr:   cidr.Addr().As4(),
+		}
+		req.MaskAddr = unix.RawSockaddrInet4{
+			Len:    unix.SizeofSockaddrInet4,
+			Family: unix.AF_INET,
+			Addr:   prefixToMask(cidr).As4(),
+		}
+
+		s, err := unix.Socket(unix.AF_INET, unix.SOCK_DGRAM, unix.IPPROTO_IP)
 		if err != nil {
-		return fmt.Errorf("failed to get device name: %w", err)
+			return err
+		}
+		defer syscall.Close(s)
+
+		if err := ioctl(uintptr(s), unix.SIOCAIFADDR, uintptr(unsafe.Pointer(&req))); err != nil {
+			return fmt.Errorf("failed to set tun address %s: %s", cidr.Addr(), err)
 		}
 
-	// Set the MTU
-	rm.SetMTU(t, t.MaxMTU)
+		err = addRoute(cidr, t.vpnNetworks)
+		if err != nil {
+			return fmt.Errorf("failed to set route for vpn network %v: %w", cidr, err)
+		}
 
-	// Add IP addresses
-	for _, network := range t.vpnNetworks {
-		if err := rm.addIP(t, name, network); err != nil {
+		return nil
+	}
+
+	if cidr.Addr().Is6() {
+		var req ifreqAlias6
+		req.Name = t.deviceBytes()
+		req.Addr = unix.RawSockaddrInet6{
+			Len:    unix.SizeofSockaddrInet6,
+			Family: unix.AF_INET6,
+			Addr:   cidr.Addr().As16(),
+		}
+		req.PrefixMask = unix.RawSockaddrInet6{
+			Len:    unix.SizeofSockaddrInet6,
+			Family: unix.AF_INET6,
+			Addr:   prefixToMask(cidr).As16(),
+		}
+		req.Lifetime[0] = 0xffffffff
+		req.Lifetime[1] = 0xffffffff
+
+		s, err := unix.Socket(unix.AF_INET6, unix.SOCK_DGRAM, unix.IPPROTO_IP)
+		if err != nil {
+			return err
+		}
+		defer syscall.Close(s)
+
+		if err := ioctl(uintptr(s), SIOCAIFADDR_IN6, uintptr(unsafe.Pointer(&req))); err != nil {
+			return fmt.Errorf("failed to set tun address %s: %s", cidr.Addr().String(), err)
+		}
+
+		return nil
+	}
+
+	return fmt.Errorf("unknown address type %v", cidr)
+}
+
+func (t *tun) Activate() error {
+	err := t.doIoctlByName(unix.SIOCSIFMTU, uint32(t.MTU))
+	if err != nil {
+		return fmt.Errorf("failed to set tun mtu: %w", err)
+	}
+
+	for i := range t.vpnNetworks {
+		err = t.addIp(t.vpnNetworks[i])
+		if err != nil {
 			return err
 		}
 	}
 
-	// Bring up the interface
-	if err := runCommandBSD("ifconfig", name, "up"); err != nil {
-		return fmt.Errorf("failed to bring up interface: %w", err)
+	return t.addRoutes(false)
+}
+
+func (t *tun) doIoctlByName(ctl uintptr, value uint32) error {
+	s, err := unix.Socket(unix.AF_INET, unix.SOCK_DGRAM, unix.IPPROTO_IP)
+	if err != nil {
+		return err
+	}
+	defer syscall.Close(s)
+
+	ir := ifreq{Name: t.deviceBytes(), data: int(value)}
+	err = ioctl(uintptr(s), ctl, uintptr(unsafe.Pointer(&ir)))
+	return err
+}
+
+func (t *tun) reload(c *config.C, initial bool) error {
+	change, routes, err := getAllRoutesFromConfig(c, t.vpnNetworks, initial)
+	if err != nil {
+		return err
 	}
 
-	// Set the routes
-	if err := rm.AddRoutes(t, false); err != nil {
+	if !initial && !change {
+		return nil
+	}
+
+	routeTree, err := makeRouteTree(t.l, routes, false)
+	if err != nil {
 		return err
 	}
 
+	// Teach nebula how to handle the routes before establishing them in the system table
+	oldRoutes := t.Routes.Swap(&routes)
+	t.routeTree.Store(routeTree)
+
+	if !initial {
+		// Remove first, if the system removes a wanted route hopefully it will be re-added next
+		err := t.removeRoutes(findRemovedRoutes(routes, *oldRoutes))
+		if err != nil {
+			util.LogWithContextIfNeeded("Failed to remove routes", err, t.l)
+		}
+
+		// Ensure any routes we actually want are installed
+		err = t.addRoutes(true)
+		if err != nil {
+			// Catch any stray logs
+			util.LogWithContextIfNeeded("Failed to add routes", err, t.l)
+		}
+	}
+
 	return nil
 }
 
-func (rm *tun) SetMTU(t *wgTun, mtu int) {
-	name, err := t.tunDevice.Name()
-	if err != nil {
-		t.l.WithError(err).Error("Failed to get device name for MTU set")
-		return
-	}
-
-	if err := runCommandBSD("ifconfig", name, "mtu", strconv.Itoa(mtu)); err != nil {
-		t.l.WithError(err).Error("Failed to set tun mtu")
-	}
+func (t *tun) RoutesFor(ip netip.Addr) routing.Gateways {
+	r, _ := t.routeTree.Load().Lookup(ip)
+	return r
 }
 
-func (rm *tun) SetDefaultRoute(t *wgTun, cidr netip.Prefix) error {
-	// On OpenBSD, routes are set via ifconfig and route commands
-	return nil
+func (t *tun) Networks() []netip.Prefix {
+	return t.vpnNetworks
 }
 
-func (rm *tun) AddRoutes(t *wgTun, logErrors bool) error {
-	name, err := t.tunDevice.Name()
-	if err != nil {
-		return fmt.Errorf("failed to get device name: %w", err)
-	}
+func (t *tun) Name() string {
+	return t.Device
+}
 
+func (t *tun) NewMultiQueueReader() (io.ReadWriteCloser, error) {
+	return nil, fmt.Errorf("TODO: multiqueue not implemented for openbsd")
+}
+
+func (t *tun) addRoutes(logErrors bool) error {
 	routes := *t.Routes.Load()
+
 	for _, r := range routes {
-		if !r.Install {
+		if len(r.Via) == 0 || !r.Install {
+			// We don't allow route MTUs so only install routes with a via
 			continue
 		}
 
-		// Add route using route command
-		args := []string{"add"}
-
-		if r.Cidr.Addr().Is6() {
-			args = append(args, "-inet6")
-		} else {
-			args = append(args, "-inet")
-		}
-
-		args = append(args, r.Cidr.String(), "-interface", name)
-
-		if r.Metric > 0 {
-			// OpenBSD doesn't support route metrics directly like Linux
-			t.l.WithField("route", r).Warn("Route metrics are not fully supported on OpenBSD")
-		}
-
-		err := runCommandBSD("route", args...)
+		err := addRoute(r.Cidr, t.vpnNetworks)
 		if err != nil {
 			retErr := util.NewContextualError("Failed to add route", map[string]any{"route": r}, err)
 			if logErrors {
@@ -159,71 +339,131 @@ func (rm *tun) AddRoutes(t *wgTun, logErrors bool) error {
 	return nil
 }
 
-func (rm *tun) RemoveRoutes(t *wgTun, routes []Route) {
-	name, err := t.tunDevice.Name()
-	if err != nil {
-		t.l.WithError(err).Error("Failed to get device name for route removal")
-		return
-	}
-
+func (t *tun) removeRoutes(routes []Route) error {
 	for _, r := range routes {
 		if !r.Install {
 			continue
 		}
 
-		args := []string{"delete"}
-
-		if r.Cidr.Addr().Is6() {
-			args = append(args, "-inet6")
-		} else {
-			args = append(args, "-inet")
-		}
-
-		args = append(args, r.Cidr.String(), "-interface", name)
-
-		err := runCommandBSD("route", args...)
+		err := delRoute(r.Cidr, t.vpnNetworks)
 		if err != nil {
 			t.l.WithError(err).WithField("route", r).Error("Failed to remove route")
 		} else {
 			t.l.WithField("route", r).Info("Removed route")
 		}
 	}
+	return nil
 }
 
-func (rm *tun) NewMultiQueueReader(t *wgTun) (io.ReadWriteCloser, error) {
-	// OpenBSD doesn't support multi-queue TUN devices in the same way as Linux
-	// Return a reader that wraps the same device
-	return &wgTunReader{
-		parent:    t,
-		tunDevice: t.tunDevice,
-		offset:    0,
-		l:         t.l,
-	}, nil
+func (t *tun) deviceBytes() (o [16]byte) {
+	for i, c := range t.Device {
+		o[i] = byte(c)
+	}
+	return
 }
 
-func (rm *tun) addIP(t *wgTun, name string, network netip.Prefix) error {
-	addr := network.Addr()
+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 {
+		return fmt.Errorf("unable to create AF_ROUTE socket: %v", err)
+	}
+	defer unix.Close(sock)
 
-	if addr.Is4() {
-		// For IPv4: ifconfig tun0 10.0.0.1/24
-		if err := runCommandBSD("ifconfig", name, network.String()); err != nil {
-			return fmt.Errorf("failed to add IPv4 address: %w", err)
+	route := &netroute.RouteMessage{
+		Version: unix.RTM_VERSION,
+		Type:    unix.RTM_ADD,
+		Flags:   unix.RTF_UP | unix.RTF_GATEWAY,
+		Seq:     1,
+	}
+
+	if prefix.Addr().Is4() {
+		gw, err := selectGateway(prefix, gateways)
+		if err != nil {
+			return err
+		}
+		route.Addrs = []netroute.Addr{
+			unix.RTAX_DST:     &netroute.Inet4Addr{IP: prefix.Masked().Addr().As4()},
+			unix.RTAX_NETMASK: &netroute.Inet4Addr{IP: prefixToMask(prefix).As4()},
+			unix.RTAX_GATEWAY: &netroute.Inet4Addr{IP: gw.Addr().As4()},
 		}
 	} else {
-		// For IPv6: ifconfig tun0 inet6 add 2001:db8::1/64
-		if err := runCommandBSD("ifconfig", name, "inet6", "add", network.String()); err != nil {
-			return fmt.Errorf("failed to add IPv6 address: %w", err)
-		}
-	}
-
-	return nil
-}
-
-func runCommandBSD(name string, args ...string) error {
-	cmd := exec.Command(name, args...)
-	output, err := cmd.CombinedOutput()
+		gw, err := selectGateway(prefix, gateways)
 		if err != nil {
-		return fmt.Errorf("%s %s failed: %w\nOutput: %s", name, strings.Join(args, " "), err, string(output))
+			return err
 		}
+		route.Addrs = []netroute.Addr{
+			unix.RTAX_DST:     &netroute.Inet6Addr{IP: prefix.Masked().Addr().As16()},
+			unix.RTAX_NETMASK: &netroute.Inet6Addr{IP: prefixToMask(prefix).As16()},
+			unix.RTAX_GATEWAY: &netroute.Inet6Addr{IP: gw.Addr().As16()},
+		}
+	}
+
+	data, err := route.Marshal()
+	if err != nil {
+		return fmt.Errorf("failed to create route.RouteMessage: %w", err)
+	}
+
+	_, err = unix.Write(sock, data[:])
+	if err != nil {
+		if errors.Is(err, unix.EEXIST) {
+			// Try to do a change
+			route.Type = unix.RTM_CHANGE
+			data, err = route.Marshal()
+			if err != nil {
+				return fmt.Errorf("failed to create route.RouteMessage for change: %w", err)
+			}
+			_, err = unix.Write(sock, data[:])
+			return err
+		}
+		return fmt.Errorf("failed to write route.RouteMessage to socket: %w", err)
+	}
+
+	return nil
+}
+
+func delRoute(prefix netip.Prefix, gateways []netip.Prefix) error {
+	sock, err := unix.Socket(unix.AF_ROUTE, unix.SOCK_RAW, unix.AF_UNSPEC)
+	if err != nil {
+		return fmt.Errorf("unable to create AF_ROUTE socket: %v", err)
+	}
+	defer unix.Close(sock)
+
+	route := netroute.RouteMessage{
+		Version: unix.RTM_VERSION,
+		Type:    unix.RTM_DELETE,
+		Seq:     1,
+	}
+
+	if prefix.Addr().Is4() {
+		gw, err := selectGateway(prefix, gateways)
+		if err != nil {
+			return err
+		}
+		route.Addrs = []netroute.Addr{
+			unix.RTAX_DST:     &netroute.Inet4Addr{IP: prefix.Masked().Addr().As4()},
+			unix.RTAX_NETMASK: &netroute.Inet4Addr{IP: prefixToMask(prefix).As4()},
+			unix.RTAX_GATEWAY: &netroute.Inet4Addr{IP: gw.Addr().As4()},
+		}
+	} else {
+		gw, err := selectGateway(prefix, gateways)
+		if err != nil {
+			return err
+		}
+		route.Addrs = []netroute.Addr{
+			unix.RTAX_DST:     &netroute.Inet6Addr{IP: prefix.Masked().Addr().As16()},
+			unix.RTAX_NETMASK: &netroute.Inet6Addr{IP: prefixToMask(prefix).As16()},
+			unix.RTAX_GATEWAY: &netroute.Inet6Addr{IP: gw.Addr().As16()},
+		}
+	}
+
+	data, err := route.Marshal()
+	if err != nil {
+		return fmt.Errorf("failed to create route.RouteMessage: %w", err)
+	}
+	_, err = unix.Write(sock, data[:])
+	if err != nil {
+		return fmt.Errorf("failed to write route.RouteMessage to socket: %w", err)
+	}
+
 	return nil
 }

overlay/tun_wg.go

@@ -1,242 +0,0 @@
-//go:build !android && !netbsd && !e2e_testing
-// +build !android,!netbsd,!e2e_testing
-
-package overlay
-
-import (
-	"fmt"
-	"io"
-	"net/netip"
-	"sync/atomic"
-
-	"github.com/gaissmai/bart"
-	"github.com/sirupsen/logrus"
-	"github.com/slackhq/nebula/config"
-	"github.com/slackhq/nebula/routing"
-	"github.com/slackhq/nebula/util"
-	wgtun "golang.zx2c4.com/wireguard/tun"
-)
-
-// wgTun wraps a WireGuard TUN device and implements the overlay.Device interface
-type wgTun struct {
-	tunDevice   wgtun.Device
-	vpnNetworks []netip.Prefix
-	MaxMTU      int
-	DefaultMTU  int
-
-	Routes    atomic.Pointer[[]Route]
-	routeTree atomic.Pointer[bart.Table[routing.Gateways]]
-	routeChan chan struct{}
-
-	// Platform-specific route management
-	routeManager *tun
-
-	l *logrus.Logger
-}
-
-// BatchReader interface for readers that support vectorized I/O
-type BatchReader interface {
-	BatchRead(buffers [][]byte, sizes []int) (int, error)
-}
-
-// BatchWriter interface for writers that support vectorized I/O
-type BatchWriter interface {
-	BatchWrite(packets [][]byte) (int, error)
-}
-
-// wgTunReader wraps a single TUN queue for multi-queue support
-type wgTunReader struct {
-	parent    *wgTun
-	tunDevice wgtun.Device
-	offset    int
-	l         *logrus.Logger
-}
-
-func (t *wgTun) Networks() []netip.Prefix {
-	return t.vpnNetworks
-}
-
-func (t *wgTun) Name() string {
-	name, err := t.tunDevice.Name()
-	if err != nil {
-		t.l.WithError(err).Error("Failed to get TUN device name")
-		return "unknown"
-	}
-	return name
-}
-
-func (t *wgTun) RoutesFor(ip netip.Addr) routing.Gateways {
-	r, _ := t.routeTree.Load().Lookup(ip)
-	return r
-}
-
-func (t *wgTun) Activate() error {
-	if t.routeManager == nil {
-		return fmt.Errorf("route manager not initialized")
-	}
-	return t.routeManager.Activate(t)
-}
-
-// Read implements single-packet read for backward compatibility
-func (t *wgTun) Read(b []byte) (int, error) {
-	bufs := [][]byte{b}
-	sizes := []int{0}
-	n, err := t.tunDevice.Read(bufs, sizes, 0)
-	if err != nil {
-		return 0, err
-	}
-	if n == 0 {
-		return 0, io.ErrNoProgress
-	}
-	return sizes[0], nil
-}
-
-// Write implements single-packet write for backward compatibility
-func (t *wgTun) Write(b []byte) (int, error) {
-	bufs := [][]byte{b}
-	offset := 0
-
-	// WireGuard TUN expects the packet data to start at offset 0
-	n, err := t.tunDevice.Write(bufs, offset)
-	if err != nil {
-		return 0, err
-	}
-	if n == 0 {
-		return 0, io.ErrShortWrite
-	}
-	return len(b), nil
-}
-
-func (t *wgTun) Close() error {
-	if t.routeChan != nil {
-		close(t.routeChan)
-	}
-
-	if t.tunDevice != nil {
-		return t.tunDevice.Close()
-	}
-
-	return nil
-}
-
-func (t *wgTun) NewMultiQueueReader() (io.ReadWriteCloser, error) {
-	// For WireGuard TUN, we need to create separate TUN device instances for multi-queue
-	// The platform-specific implementation will handle this
-	if t.routeManager == nil {
-		return nil, fmt.Errorf("route manager not initialized for multi-queue reader")
-	}
-
-	return t.routeManager.NewMultiQueueReader(t)
-}
-
-func (t *wgTun) reload(c *config.C, initial bool) error {
-	routeChange, routes, err := getAllRoutesFromConfig(c, t.vpnNetworks, initial)
-	if err != nil {
-		return err
-	}
-
-	if !initial && !routeChange && !c.HasChanged("tun.mtu") {
-		return nil
-	}
-
-	routeTree, err := makeRouteTree(t.l, routes, true)
-	if err != nil {
-		return err
-	}
-
-	oldDefaultMTU := t.DefaultMTU
-	oldMaxMTU := t.MaxMTU
-	newDefaultMTU := c.GetInt("tun.mtu", DefaultMTU)
-	newMaxMTU := newDefaultMTU
-	for i, r := range routes {
-		if r.MTU == 0 {
-			routes[i].MTU = newDefaultMTU
-		}
-
-		if r.MTU > t.MaxMTU {
-			newMaxMTU = r.MTU
-		}
-	}
-
-	t.MaxMTU = newMaxMTU
-	t.DefaultMTU = newDefaultMTU
-
-	// Teach nebula how to handle the routes before establishing them in the system table
-	oldRoutes := t.Routes.Swap(&routes)
-	t.routeTree.Store(routeTree)
-
-	if !initial && t.routeManager != nil {
-		if oldMaxMTU != newMaxMTU {
-			t.routeManager.SetMTU(t, t.MaxMTU)
-			t.l.Infof("Set max MTU to %v was %v", t.MaxMTU, oldMaxMTU)
-		}
-
-		if oldDefaultMTU != newDefaultMTU {
-			for i := range t.vpnNetworks {
-				err := t.routeManager.SetDefaultRoute(t, t.vpnNetworks[i])
-				if err != nil {
-					t.l.Warn(err)
-				} else {
-					t.l.Infof("Set default MTU to %v was %v", t.DefaultMTU, oldDefaultMTU)
-				}
-			}
-		}
-
-		// Remove first, if the system removes a wanted route hopefully it will be re-added next
-		t.routeManager.RemoveRoutes(t, findRemovedRoutes(routes, *oldRoutes))
-
-		// Ensure any routes we actually want are installed
-		err = t.routeManager.AddRoutes(t, true)
-		if err != nil {
-			// This should never be called since AddRoutes should log its own errors in a reload condition
-			util.LogWithContextIfNeeded("Failed to refresh routes", err, t.l)
-		}
-	}
-
-	return nil
-}
-
-// BatchRead reads multiple packets from the TUN device using vectorized I/O
-// The caller provides buffers and sizes slices, and this function returns the number of packets read.
-func (r *wgTunReader) BatchRead(buffers [][]byte, sizes []int) (int, error) {
-	return r.tunDevice.Read(buffers, sizes, r.offset)
-}
-
-// Read implements io.Reader for wgTunReader (single packet for compatibility)
-func (r *wgTunReader) Read(b []byte) (int, error) {
-	bufs := [][]byte{b}
-	sizes := []int{0}
-	n, err := r.tunDevice.Read(bufs, sizes, r.offset)
-	if err != nil {
-		return 0, err
-	}
-	if n == 0 {
-		return 0, io.ErrNoProgress
-	}
-	return sizes[0], nil
-}
-
-// Write implements io.Writer for wgTunReader
-func (r *wgTunReader) Write(b []byte) (int, error) {
-	bufs := [][]byte{b}
-	n, err := r.tunDevice.Write(bufs, r.offset)
-	if err != nil {
-		return 0, err
-	}
-	if n == 0 {
-		return 0, io.ErrShortWrite
-	}
-	return len(b), nil
-}
-
-// BatchWrite writes multiple packets to the TUN device using vectorized I/O
-func (r *wgTunReader) BatchWrite(packets [][]byte) (int, error) {
-	return r.tunDevice.Write(packets, r.offset)
-}
-
-func (r *wgTunReader) Close() error {
-	if r.tunDevice != nil {
-		return r.tunDevice.Close()
-	}
-	return nil
-}

overlay/tun_windows.go

@@ -1,77 +1,84 @@
-//go:build windows && !e2e_testing
-// +build windows,!e2e_testing
+//go:build !e2e_testing
+// +build !e2e_testing
 
 package overlay
 
 import (
 	"crypto"
-	"encoding/binary"
 	"fmt"
 	"io"
 	"net/netip"
+	"os"
+	"path/filepath"
+	"runtime"
+	"sync/atomic"
+	"syscall"
+	"unsafe"
 
+	"github.com/gaissmai/bart"
 	"github.com/sirupsen/logrus"
 	"github.com/slackhq/nebula/config"
+	"github.com/slackhq/nebula/routing"
 	"github.com/slackhq/nebula/util"
+	"github.com/slackhq/nebula/wintun"
 	"golang.org/x/sys/windows"
-	wgtun "golang.zx2c4.com/wireguard/tun"
 	"golang.zx2c4.com/wireguard/windows/tunnel/winipcfg"
 )
 
 const tunGUIDLabel = "Fixed Nebula Windows GUID v1"
 
-type tun struct {
-	luid winipcfg.LUID
+type winTun struct {
+	Device      string
+	vpnNetworks []netip.Prefix
+	MTU         int
+	Routes      atomic.Pointer[[]Route]
+	routeTree   atomic.Pointer[bart.Table[routing.Gateways]]
+	l           *logrus.Logger
+
+	tun *wintun.NativeTun
 }
 
-func newTunFromFd(_ *config.C, _ *logrus.Logger, _ int, _ []netip.Prefix) (*wgTun, error) {
+func newTunFromFd(_ *config.C, _ *logrus.Logger, _ int, _ []netip.Prefix) (Device, error) {
 	return nil, fmt.Errorf("newTunFromFd not supported in Windows")
 }
 
-func newTun(c *config.C, l *logrus.Logger, vpnNetworks []netip.Prefix, _ bool) (*wgTun, error) {
-	deviceName := c.GetString("tun.dev", "Nebula")
-	mtu := c.GetInt("tun.mtu", DefaultMTU)
-
-	// Create WireGuard TUN device
-	tunDevice, err := wgtun.CreateTUN(deviceName, mtu)
+func newTun(c *config.C, l *logrus.Logger, vpnNetworks []netip.Prefix, _ bool) (*winTun, error) {
+	err := checkWinTunExists()
 	if err != nil {
-		return nil, fmt.Errorf("failed to create TUN device: %w", err)
+		return nil, fmt.Errorf("can not load the wintun driver: %w", err)
 	}
 
-	// Get the actual device name
-	actualName, err := tunDevice.Name()
+	deviceName := c.GetString("tun.dev", "")
+	guid, err := generateGUIDByDeviceName(deviceName)
 	if err != nil {
-		tunDevice.Close()
-		return nil, fmt.Errorf("failed to get TUN device name: %w", err)
+		return nil, fmt.Errorf("generate GUID failed: %w", err)
 	}
 
-	t := &wgTun{
-		tunDevice:   tunDevice,
+	t := &winTun{
+		Device:      deviceName,
 		vpnNetworks: vpnNetworks,
-		MaxMTU:      mtu,
-		DefaultMTU:  mtu,
+		MTU:         c.GetInt("tun.mtu", DefaultMTU),
 		l:           l,
 	}
 
-	// Create Windows-specific route manager
-	rm := &tun{}
-
-	// Get LUID from the TUN device
-	// The WireGuard TUN device on Windows should provide a LUID() method
-	if nativeTun, ok := tunDevice.(interface{ LUID() uint64 }); ok {
-		rm.luid = winipcfg.LUID(nativeTun.LUID())
-	} else {
-		tunDevice.Close()
-		return nil, fmt.Errorf("failed to get LUID from TUN device")
-	}
-	t.routeManager = rm
-
 	err = t.reload(c, true)
 	if err != nil {
-		tunDevice.Close()
 		return nil, err
 	}
 
+	var tunDevice wintun.Device
+	tunDevice, err = wintun.CreateTUNWithRequestedGUID(deviceName, guid, t.MTU)
+	if err != nil {
+		// Windows 10 has an issue with unclean shutdowns not fully cleaning up the wintun device.
+		// Trying a second time resolves the issue.
+		l.WithError(err).Debug("Failed to create wintun device, retrying")
+		tunDevice, err = wintun.CreateTUNWithRequestedGUID(deviceName, guid, t.MTU)
+		if err != nil {
+			return nil, fmt.Errorf("create TUN device failed: %w", err)
+		}
+	}
+	t.tun = tunDevice.(*wintun.NativeTun)
+
 	c.RegisterReloadCallback(func(c *config.C) {
 		err := t.reload(c, false)
 		if err != nil {
@@ -79,140 +86,206 @@ func newTun(c *config.C, l *logrus.Logger, vpnNetworks []netip.Prefix, _ bool) (
 		}
 	})
 
-	l.WithField("name", actualName).Info("Created WireGuard TUN device")
-
 	return t, nil
 }
 
-func (rm *tun) Activate(t *wgTun) error {
-	// Set MTU
-	err := rm.setMTU(t, t.MaxMTU)
+func (t *winTun) reload(c *config.C, initial bool) error {
+	change, routes, err := getAllRoutesFromConfig(c, t.vpnNetworks, initial)
 	if err != nil {
-		return fmt.Errorf("failed to set MTU: %w", err)
-	}
-
-	// Add IP addresses
-	for _, network := range t.vpnNetworks {
-		if err := rm.addIP(t, network); err != nil {
 		return err
 	}
+
+	if !initial && !change {
+		return nil
 	}
 
-	// Add routes
-	if err := rm.AddRoutes(t, false); err != nil {
+	routeTree, err := makeRouteTree(t.l, routes, false)
+	if err != nil {
+		return err
+	}
+
+	// Teach nebula how to handle the routes before establishing them in the system table
+	oldRoutes := t.Routes.Swap(&routes)
+	t.routeTree.Store(routeTree)
+
+	if !initial {
+		// Remove first, if the system removes a wanted route hopefully it will be re-added next
+		err := t.removeRoutes(findRemovedRoutes(routes, *oldRoutes))
+		if err != nil {
+			util.LogWithContextIfNeeded("Failed to remove routes", err, t.l)
+		}
+
+		// Ensure any routes we actually want are installed
+		err = t.addRoutes(true)
+		if err != nil {
+			// Catch any stray logs
+			util.LogWithContextIfNeeded("Failed to add routes", err, t.l)
+		}
+	}
+
+	return nil
+}
+
+func (t *winTun) Activate() error {
+	luid := winipcfg.LUID(t.tun.LUID())
+
+	err := luid.SetIPAddresses(t.vpnNetworks)
+	if err != nil {
+		return fmt.Errorf("failed to set address: %w", err)
+	}
+
+	err = t.addRoutes(false)
+	if err != nil {
 		return err
 	}
 
 	return nil
 }
 
-func (rm *tun) SetMTU(t *wgTun, mtu int) {
-	if err := rm.setMTU(t, mtu); err != nil {
-		t.l.WithError(err).Error("Failed to set MTU")
-	}
-}
-
-func (rm *tun) setMTU(t *wgTun, mtu int) error {
-	// Set MTU using winipcfg
-	// Note: MTU setting on Windows TUN devices may be handled by the driver
-	// For now, we'll skip explicit MTU setting as the WireGuard TUN handles it
-	return nil
-}
-
-func (rm *tun) SetDefaultRoute(t *wgTun, cidr netip.Prefix) error {
-	// On Windows, routes are managed differently
-	return nil
-}
-
-func (rm *tun) AddRoutes(t *wgTun, logErrors bool) error {
+func (t *winTun) addRoutes(logErrors bool) error {
+	luid := winipcfg.LUID(t.tun.LUID())
 	routes := *t.Routes.Load()
+	foundDefault4 := false
+
 	for _, r := range routes {
-		if !r.Install {
+		if len(r.Via) == 0 || !r.Install {
+			// We don't allow route MTUs so only install routes with a via
 			continue
 		}
 
-		if r.MTU > 0 {
-			// Windows route MTU is not directly supported
-			t.l.WithField("route", r).Debug("Route MTU is not supported on Windows")
-		}
-
-		// Use winipcfg to add the route
-		// The rm.luid should have the AddRoute method from winipcfg
-		if len(r.Via) == 0 {
-			t.l.WithField("route", r).Warn("Route has no via address, skipping")
-			continue
-		}
-
-		err := rm.luid.AddRoute(r.Cidr, r.Via[0].Addr(), uint32(r.Metric))
+		// Add our unsafe route
+		// Windows does not support multipath routes natively, so we install only a single route.
+		// 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 {
 				retErr.Log(t.l)
+				continue
 			} else {
 				return retErr
 			}
 		} else {
 			t.l.WithField("route", r).Info("Added route")
 		}
+
+		if !foundDefault4 {
+			if r.Cidr.Bits() == 0 && r.Cidr.Addr().BitLen() == 32 {
+				foundDefault4 = true
+			}
+		}
 	}
 
+	ipif, err := luid.IPInterface(windows.AF_INET)
+	if err != nil {
+		return fmt.Errorf("failed to get ip interface: %w", err)
+	}
+
+	ipif.NLMTU = uint32(t.MTU)
+	if foundDefault4 {
+		ipif.UseAutomaticMetric = false
+		ipif.Metric = 0
+	}
+
+	if err := ipif.Set(); err != nil {
+		return fmt.Errorf("failed to set ip interface: %w", err)
+	}
 	return nil
 }
 
-func (rm *tun) RemoveRoutes(t *wgTun, routes []Route) {
+func (t *winTun) removeRoutes(routes []Route) error {
+	luid := winipcfg.LUID(t.tun.LUID())
+
 	for _, r := range routes {
 		if !r.Install {
 			continue
 		}
 
-		if len(r.Via) == 0 {
-			continue
-		}
-
-		err := rm.luid.DeleteRoute(r.Cidr, r.Via[0].Addr())
+		// See comment on luid.AddRoute
+		err := luid.DeleteRoute(r.Cidr, r.Via[0].Addr())
 		if err != nil {
 			t.l.WithError(err).WithField("route", r).Error("Failed to remove route")
 		} else {
 			t.l.WithField("route", r).Info("Removed route")
 		}
 	}
-}
-
-func (rm *tun) NewMultiQueueReader(t *wgTun) (io.ReadWriteCloser, error) {
-	// Windows doesn't support multi-queue TUN devices
-	// Return a reader that wraps the same device
-	return &wgTunReader{
-		parent:    t,
-		tunDevice: t.tunDevice,
-		offset:    0,
-		l:         t.l,
-	}, nil
-}
-
-func (rm *tun) addIP(t *wgTun, network netip.Prefix) error {
-	// Add IP address using winipcfg
-	// SetIPAddresses expects a slice of prefixes
-	err := rm.luid.SetIPAddresses([]netip.Prefix{network})
-	if err != nil {
-		return fmt.Errorf("failed to add IP address %s: %w", network, err)
-	}
 	return nil
 }
 
-// generateGUIDByDeviceName generates a GUID based on the device name
-func generateGUIDByDeviceName(deviceName string) (*windows.GUID, error) {
-	// Hash the device name to create a deterministic GUID
-	h := crypto.SHA256.New()
-	h.Write([]byte(tunGUIDLabel))
-	h.Write([]byte(deviceName))
-	sum := h.Sum(nil)
-
-	guid := &windows.GUID{
-		Data1: binary.LittleEndian.Uint32(sum[0:4]),
-		Data2: binary.LittleEndian.Uint16(sum[4:6]),
-		Data3: binary.LittleEndian.Uint16(sum[6:8]),
-	}
-	copy(guid.Data4[:], sum[8:16])
-
-	return guid, nil
+func (t *winTun) RoutesFor(ip netip.Addr) routing.Gateways {
+	r, _ := t.routeTree.Load().Lookup(ip)
+	return r
+}
+
+func (t *winTun) Networks() []netip.Prefix {
+	return t.vpnNetworks
+}
+
+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)
+}
+
+func (t *winTun) NewMultiQueueReader() (io.ReadWriteCloser, error) {
+	return nil, fmt.Errorf("TODO: multiqueue not implemented for windows")
+}
+
+func (t *winTun) Close() error {
+	// It seems that the Windows networking stack doesn't like it when we destroy interfaces that have active routes,
+	// so to be certain, just remove everything before destroying.
+	luid := winipcfg.LUID(t.tun.LUID())
+	_ = luid.FlushRoutes(windows.AF_INET)
+	_ = luid.FlushIPAddresses(windows.AF_INET)
+
+	_ = luid.FlushRoutes(windows.AF_INET6)
+	_ = luid.FlushIPAddresses(windows.AF_INET6)
+
+	_ = luid.FlushDNS(windows.AF_INET)
+	_ = luid.FlushDNS(windows.AF_INET6)
+
+	return t.tun.Close()
+}
+
+func generateGUIDByDeviceName(name string) (*windows.GUID, error) {
+	// GUID is 128 bit
+	hash := crypto.MD5.New()
+
+	_, err := hash.Write([]byte(tunGUIDLabel))
+	if err != nil {
+		return nil, err
+	}
+
+	_, err = hash.Write([]byte(name))
+	if err != nil {
+		return nil, err
+	}
+
+	sum := hash.Sum(nil)
+
+	return (*windows.GUID)(unsafe.Pointer(&sum[0])), nil
+}
+
+func checkWinTunExists() error {
+	myPath, err := os.Executable()
+	if err != nil {
+		return err
+	}
+
+	arch := runtime.GOARCH
+	switch arch {
+	case "386":
+		//NOTE: wintun bundles 386 as x86
+		arch = "x86"
+	}
+
+	_, err = syscall.LoadDLL(filepath.Join(filepath.Dir(myPath), "dist", "windows", "wintun", "bin", arch, "wintun.dll"))
+	return err
 }

overlay/user.go

@@ -1,11 +1,13 @@
 package overlay
 
 import (
+	"fmt"
 	"io"
 	"net/netip"
 
 	"github.com/sirupsen/logrus"
 	"github.com/slackhq/nebula/config"
+	"github.com/slackhq/nebula/packet"
 	"github.com/slackhq/nebula/routing"
 )
 
@@ -36,6 +38,10 @@ type UserDevice struct {
 	inboundWriter *io.PipeWriter
 }
 
+func (d *UserDevice) RecycleRxSeg(pkt *packet.VirtIOPacket, kick bool, q int) error {
+	return nil
+}
+
 func (d *UserDevice) Activate() error {
 	return nil
 }
@@ -46,7 +52,7 @@ func (d *UserDevice) RoutesFor(ip netip.Addr) routing.Gateways {
 	return routing.Gateways{routing.NewGateway(ip, 1)}
 }
 
-func (d *UserDevice) NewMultiQueueReader() (io.ReadWriteCloser, error) {
+func (d *UserDevice) NewMultiQueueReader() (TunDev, error) {
 	return d, nil
 }
 
@@ -65,3 +71,19 @@ func (d *UserDevice) Close() error {
 	d.outboundWriter.Close()
 	return nil
 }
+
+func (d *UserDevice) ReadMany(b []*packet.VirtIOPacket, _ int) (int, error) {
+	return d.Read(b[0].Payload)
+}
+
+func (d *UserDevice) AllocSeg(pkt *packet.OutPacket, q int) (int, error) {
+	return 0, fmt.Errorf("user: AllocSeg not implemented")
+}
+
+func (d *UserDevice) WriteOne(x *packet.OutPacket, kick bool, q int) (int, error) {
+	return 0, fmt.Errorf("user: WriteOne not implemented")
+}
+
+func (d *UserDevice) WriteMany(x []*packet.OutPacket, q int) (int, error) {
+	return 0, fmt.Errorf("user: WriteMany not implemented")
+}

overlay/vhost/README.md

@@ -0,0 +1,23 @@
+Significant portions of this code are derived from https://pkg.go.dev/github.com/hetznercloud/virtio-go
+
+MIT License
+
+Copyright (c) 2025 Hetzner Cloud GmbH
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

overlay/vhost/doc.go

@@ -0,0 +1,4 @@
+// Package vhost implements the basic ioctl requests needed to interact with the
+// kernel-level virtio server that provides accelerated virtio devices for
+// networking and more.
+package vhost

overlay/vhost/ioctl.go

@@ -0,0 +1,218 @@
+package vhost
+
+import (
+	"fmt"
+	"unsafe"
+
+	"github.com/slackhq/nebula/overlay/virtqueue"
+	"github.com/slackhq/nebula/util/virtio"
+	"golang.org/x/sys/unix"
+)
+
+const (
+	// vhostIoctlGetFeatures can be used to retrieve the features supported by
+	// the vhost implementation in the kernel.
+	//
+	// Response payload: [virtio.Feature]
+	// Kernel name: VHOST_GET_FEATURES
+	vhostIoctlGetFeatures = 0x8008af00
+
+	// vhostIoctlSetFeatures can be used to communicate the features supported
+	// by this virtio implementation to the kernel.
+	//
+	// Request payload: [virtio.Feature]
+	// Kernel name: VHOST_SET_FEATURES
+	vhostIoctlSetFeatures = 0x4008af00
+
+	// vhostIoctlSetOwner can be used to set the current process as the
+	// exclusive owner of a control file descriptor.
+	//
+	// Request payload: none
+	// Kernel name: VHOST_SET_OWNER
+	vhostIoctlSetOwner = 0x0000af01
+
+	// vhostIoctlSetMemoryLayout can be used to set up or modify the memory
+	// layout which describes the IOTLB mappings in the kernel.
+	//
+	// Request payload: [MemoryLayout] with custom serialization
+	// Kernel name: VHOST_SET_MEM_TABLE
+	vhostIoctlSetMemoryLayout = 0x4008af03
+
+	// vhostIoctlSetQueueSize can be used to set the size of the virtqueue.
+	//
+	// Request payload: [QueueState]
+	// Kernel name: VHOST_SET_VRING_NUM
+	vhostIoctlSetQueueSize = 0x4008af10
+
+	// vhostIoctlSetQueueAddress can be used to set the addresses of the
+	// different parts of the virtqueue.
+	//
+	// Request payload: [QueueAddresses]
+	// Kernel name: VHOST_SET_VRING_ADDR
+	vhostIoctlSetQueueAddress = 0x4028af11
+
+	// vhostIoctlSetAvailableRingBase can be used to set the index of the next
+	// available ring entry the device will process.
+	//
+	// Request payload: [QueueState]
+	// Kernel name: VHOST_SET_VRING_BASE
+	vhostIoctlSetAvailableRingBase = 0x4008af12
+
+	// vhostIoctlSetQueueKickEventFD can be used to set the event file
+	// descriptor to signal the device when descriptor chains were added to the
+	// available ring.
+	//
+	// Request payload: [QueueFile]
+	// Kernel name: VHOST_SET_VRING_KICK
+	vhostIoctlSetQueueKickEventFD = 0x4008af20
+
+	// vhostIoctlSetQueueCallEventFD can be used to set the event file
+	// descriptor that gets signaled by the device when descriptor chains have
+	// been used by it.
+	//
+	// Request payload: [QueueFile]
+	// Kernel name: VHOST_SET_VRING_CALL
+	vhostIoctlSetQueueCallEventFD = 0x4008af21
+)
+
+// QueueState is an ioctl request payload that can hold a queue index and any
+// 32-bit number.
+//
+// Kernel name: vhost_vring_state
+type QueueState struct {
+	// QueueIndex is the index of the virtqueue.
+	QueueIndex uint32
+	// Num is any 32-bit number, depending on the request.
+	Num uint32
+}
+
+// QueueAddresses is an ioctl request payload that can hold the addresses of the
+// different parts of a virtqueue.
+//
+// Kernel name: vhost_vring_addr
+type QueueAddresses struct {
+	// QueueIndex is the index of the virtqueue.
+	QueueIndex uint32
+	// Flags that are not used in this implementation.
+	Flags uint32
+	// DescriptorTableAddress is the address of the descriptor table in user
+	// space memory. It must be 16-byte aligned.
+	DescriptorTableAddress uintptr
+	// UsedRingAddress is the address of the used ring in user space memory. It
+	// must be 4-byte aligned.
+	UsedRingAddress uintptr
+	// AvailableRingAddress is the address of the available ring in user space
+	// memory. It must be 2-byte aligned.
+	AvailableRingAddress uintptr
+	// LogAddress is used for an optional logging support, not supported by this
+	// implementation.
+	LogAddress uintptr
+}
+
+// QueueFile is an ioctl request payload that can hold a queue index and a file
+// descriptor.
+//
+// Kernel name: vhost_vring_file
+type QueueFile struct {
+	// QueueIndex is the index of the virtqueue.
+	QueueIndex uint32
+	// FD is the file descriptor of the file. Pass -1 to unbind from a file.
+	FD int32
+}
+
+// IoctlPtr is a copy of the similarly named unexported function from the Go
+// unix package. This is needed to do custom ioctl requests not supported by the
+// standard library.
+func IoctlPtr(fd int, req uint, arg unsafe.Pointer) error {
+	_, _, err := unix.Syscall(unix.SYS_IOCTL, uintptr(fd), uintptr(req), uintptr(arg))
+	if err != 0 {
+		return fmt.Errorf("ioctl request %d: %w", req, err)
+	}
+	return nil
+}
+
+// GetFeatures requests the supported feature bits from the virtio device
+// associated with the given control file descriptor.
+func GetFeatures(controlFD int) (virtio.Feature, error) {
+	var features virtio.Feature
+	if err := IoctlPtr(controlFD, vhostIoctlGetFeatures, unsafe.Pointer(&features)); err != nil {
+		return 0, fmt.Errorf("get features: %w", err)
+	}
+	return features, nil
+}
+
+// SetFeatures communicates the feature bits supported by this implementation
+// to the virtio device associated with the given control file descriptor.
+func SetFeatures(controlFD int, features virtio.Feature) error {
+	if err := IoctlPtr(controlFD, vhostIoctlSetFeatures, unsafe.Pointer(&features)); err != nil {
+		return fmt.Errorf("set features: %w", err)
+	}
+	return nil
+}
+
+// OwnControlFD sets the current process as the exclusive owner for the
+// given control file descriptor. This must be called before interacting with
+// the control file descriptor in any other way.
+func OwnControlFD(controlFD int) error {
+	if err := IoctlPtr(controlFD, vhostIoctlSetOwner, unsafe.Pointer(nil)); err != nil {
+		return fmt.Errorf("set control file descriptor owner: %w", err)
+	}
+	return nil
+}
+
+// SetMemoryLayout sets up or modifies the memory layout for the kernel-level
+// virtio device associated with the given control file descriptor.
+func SetMemoryLayout(controlFD int, layout MemoryLayout) error {
+	payload := layout.serializePayload()
+	if err := IoctlPtr(controlFD, vhostIoctlSetMemoryLayout, unsafe.Pointer(&payload[0])); err != nil {
+		return fmt.Errorf("set memory layout: %w", err)
+	}
+	return nil
+}
+
+// RegisterQueue registers a virtio queue with the kernel-level virtio server.
+// The virtqueue will be linked to the given control file descriptor and will
+// have the given index. The kernel will use this queue until the control file
+// descriptor is closed.
+func RegisterQueue(controlFD int, queueIndex uint32, queue *virtqueue.SplitQueue) error {
+	if err := IoctlPtr(controlFD, vhostIoctlSetQueueSize, unsafe.Pointer(&QueueState{
+		QueueIndex: queueIndex,
+		Num:        uint32(queue.Size()),
+	})); err != nil {
+		return fmt.Errorf("set queue size: %w", err)
+	}
+
+	if err := IoctlPtr(controlFD, vhostIoctlSetQueueAddress, unsafe.Pointer(&QueueAddresses{
+		QueueIndex:             queueIndex,
+		Flags:                  0,
+		DescriptorTableAddress: queue.DescriptorTable().Address(),
+		UsedRingAddress:        queue.UsedRing().Address(),
+		AvailableRingAddress:   queue.AvailableRing().Address(),
+		LogAddress:             0,
+	})); err != nil {
+		return fmt.Errorf("set queue addresses: %w", err)
+	}
+
+	if err := IoctlPtr(controlFD, vhostIoctlSetAvailableRingBase, unsafe.Pointer(&QueueState{
+		QueueIndex: queueIndex,
+		Num:        0,
+	})); err != nil {
+		return fmt.Errorf("set available ring base: %w", err)
+	}
+
+	if err := IoctlPtr(controlFD, vhostIoctlSetQueueKickEventFD, unsafe.Pointer(&QueueFile{
+		QueueIndex: queueIndex,
+		FD:         int32(queue.KickEventFD()),
+	})); err != nil {
+		return fmt.Errorf("set kick event file descriptor: %w", err)
+	}
+
+	if err := IoctlPtr(controlFD, vhostIoctlSetQueueCallEventFD, unsafe.Pointer(&QueueFile{
+		QueueIndex: queueIndex,
+		FD:         int32(queue.CallEventFD()),
+	})); err != nil {
+		return fmt.Errorf("set call event file descriptor: %w", err)
+	}
+
+	return nil
+}

overlay/vhost/ioctl_test.go

@@ -0,0 +1,21 @@
+package vhost_test
+
+import (
+	"testing"
+	"unsafe"
+
+	"github.com/slackhq/nebula/overlay/vhost"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestQueueState_Size(t *testing.T) {
+	assert.EqualValues(t, 8, unsafe.Sizeof(vhost.QueueState{}))
+}
+
+func TestQueueAddresses_Size(t *testing.T) {
+	assert.EqualValues(t, 40, unsafe.Sizeof(vhost.QueueAddresses{}))
+}
+
+func TestQueueFile_Size(t *testing.T) {
+	assert.EqualValues(t, 8, unsafe.Sizeof(vhost.QueueFile{}))
+}

overlay/vhost/memory.go

@@ -0,0 +1,73 @@
+package vhost
+
+import (
+	"encoding/binary"
+	"fmt"
+	"unsafe"
+
+	"github.com/slackhq/nebula/overlay/virtqueue"
+)
+
+// MemoryRegion describes a region of userspace memory which is being made
+// accessible to a vhost device.
+//
+// Kernel name: vhost_memory_region
+type MemoryRegion struct {
+	// GuestPhysicalAddress is the physical address of the memory region within
+	// the guest, when virtualization is used. When no virtualization is used,
+	// this should be the same as UserspaceAddress.
+	GuestPhysicalAddress uintptr
+	// Size is the size of the memory region.
+	Size uint64
+	// UserspaceAddress is the virtual address in the userspace of the host
+	// where the memory region can be found.
+	UserspaceAddress uintptr
+	// Padding and room for flags. Currently unused.
+	_ uint64
+}
+
+// MemoryLayout is a list of [MemoryRegion]s.
+type MemoryLayout []MemoryRegion
+
+// NewMemoryLayoutForQueues returns a new [MemoryLayout] that describes the
+// memory pages used by the descriptor tables of the given queues.
+func NewMemoryLayoutForQueues(queues []*virtqueue.SplitQueue) MemoryLayout {
+	regions := make([]MemoryRegion, 0)
+	for _, queue := range queues {
+		for address, size := range queue.DescriptorTable().BufferAddresses() {
+			regions = append(regions, MemoryRegion{
+				// There is no virtualization in play here, so the guest address
+				// is the same as in the host's userspace.
+				GuestPhysicalAddress: address,
+				Size:                 uint64(size),
+				UserspaceAddress:     address,
+			})
+		}
+	}
+	return regions
+}
+
+// serializePayload serializes the list of memory regions into a format that is
+// compatible to the vhost_memory kernel struct. The returned byte slice can be
+// used as a payload for the vhostIoctlSetMemoryLayout ioctl.
+func (regions MemoryLayout) serializePayload() []byte {
+	regionCount := len(regions)
+	regionSize := int(unsafe.Sizeof(MemoryRegion{}))
+	payload := make([]byte, 8+regionCount*regionSize)
+
+	// The first 32 bits contain the number of memory regions. The following 32
+	// bits are padding.
+	binary.LittleEndian.PutUint32(payload[0:4], uint32(regionCount))
+
+	if regionCount > 0 {
+		// The underlying byte array of the slice should already have the correct
+		// format, so just copy that.
+		copied := copy(payload[8:], unsafe.Slice((*byte)(unsafe.Pointer(&regions[0])), regionCount*regionSize))
+		if copied != regionCount*regionSize {
+			panic(fmt.Sprintf("copied only %d bytes of the memory regions, but expected %d",
+				copied, regionCount*regionSize))
+		}
+	}
+
+	return payload
+}

overlay/vhost/memory_internal_test.go

@@ -0,0 +1,42 @@
+package vhost
+
+import (
+	"testing"
+	"unsafe"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestMemoryRegion_Size(t *testing.T) {
+	assert.EqualValues(t, 32, unsafe.Sizeof(MemoryRegion{}))
+}
+
+func TestMemoryLayout_SerializePayload(t *testing.T) {
+	layout := MemoryLayout([]MemoryRegion{
+		{
+			GuestPhysicalAddress: 42,
+			Size:                 100,
+			UserspaceAddress:     142,
+		}, {
+			GuestPhysicalAddress: 99,
+			Size:                 100,
+			UserspaceAddress:     99,
+		},
+	})
+	payload := layout.serializePayload()
+
+	assert.Equal(t, []byte{
+		0x02, 0x00, 0x00, 0x00, // nregions
+		0x00, 0x00, 0x00, 0x00, // padding
+		// region 0
+		0x2a, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // guest_phys_addr
+		0x64, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // memory_size
+		0x8e, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // userspace_addr
+		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // flags_padding
+		// region 1
+		0x63, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // guest_phys_addr
+		0x64, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // memory_size
+		0x63, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // userspace_addr
+		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // flags_padding
+	}, payload)
+}

overlay/vhostnet/README.md

@@ -0,0 +1,23 @@
+Significant portions of this code are derived from https://pkg.go.dev/github.com/hetznercloud/virtio-go
+
+MIT License
+
+Copyright (c) 2025 Hetzner Cloud GmbH
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

overlay/vhostnet/device.go

@@ -0,0 +1,427 @@
+package vhostnet
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"os"
+	"runtime"
+
+	"github.com/slackhq/nebula/overlay/vhost"
+	"github.com/slackhq/nebula/overlay/virtqueue"
+	"github.com/slackhq/nebula/packet"
+	"github.com/slackhq/nebula/util/virtio"
+	"golang.org/x/sys/unix"
+)
+
+// ErrDeviceClosed is returned when the [Device] is closed while operations are
+// still running.
+var ErrDeviceClosed = errors.New("device was closed")
+
+// The indexes for the receive and transmit queues.
+const (
+	receiveQueueIndex  = 0
+	transmitQueueIndex = 1
+)
+
+// Device represents a vhost networking device within the kernel-level virtio
+// implementation and provides methods to interact with it.
+type Device struct {
+	initialized bool
+	controlFD   int
+
+	fullTable     bool
+	ReceiveQueue  *virtqueue.SplitQueue
+	TransmitQueue *virtqueue.SplitQueue
+}
+
+// NewDevice initializes a new vhost networking device within the
+// kernel-level virtio implementation, sets up the virtqueues and returns a
+// [Device] instance that can be used to communicate with that vhost device.
+//
+// There are multiple options that can be passed to this constructor to
+// influence device creation:
+//   - [WithQueueSize]
+//   - [WithBackendFD]
+//   - [WithBackendDevice]
+//
+// Remember to call [Device.Close] after use to free up resources.
+func NewDevice(options ...Option) (*Device, error) {
+	var err error
+	opts := optionDefaults
+	opts.apply(options)
+	if err = opts.validate(); err != nil {
+		return nil, fmt.Errorf("invalid options: %w", err)
+	}
+
+	dev := Device{
+		controlFD: -1,
+	}
+
+	// Clean up a partially initialized device when something fails.
+	defer func() {
+		if err != nil {
+			_ = dev.Close()
+		}
+	}()
+
+	// Retrieve a new control file descriptor. This will be used to configure
+	// the vhost networking device in the kernel.
+	dev.controlFD, err = unix.Open("/dev/vhost-net", os.O_RDWR, 0666)
+	if err != nil {
+		return nil, fmt.Errorf("get control file descriptor: %w", err)
+	}
+	if err = vhost.OwnControlFD(dev.controlFD); err != nil {
+		return nil, fmt.Errorf("own control file descriptor: %w", err)
+	}
+
+	// Advertise the supported features. This isn't much for now.
+	// TODO: Add feature options and implement proper feature negotiation.
+	getFeatures, err := vhost.GetFeatures(dev.controlFD) //0x1033D008000 but why
+	if err != nil {
+		return nil, fmt.Errorf("get features: %w", err)
+	}
+	if getFeatures == 0 {
+
+	}
+	//const funky = virtio.Feature(1 << 27)
+	//features := virtio.FeatureVersion1 | funky // | todo virtio.FeatureNetMergeRXBuffers
+	features := virtio.FeatureVersion1 | virtio.FeatureNetMergeRXBuffers
+	if err = vhost.SetFeatures(dev.controlFD, features); err != nil {
+		return nil, fmt.Errorf("set features: %w", err)
+	}
+
+	itemSize := os.Getpagesize() * 4 //todo config
+
+	// Initialize and register the queues needed for the networking device.
+	if dev.ReceiveQueue, err = createQueue(dev.controlFD, receiveQueueIndex, opts.queueSize, itemSize); err != nil {
+		return nil, fmt.Errorf("create receive queue: %w", err)
+	}
+	if dev.TransmitQueue, err = createQueue(dev.controlFD, transmitQueueIndex, opts.queueSize, itemSize); err != nil {
+		return nil, fmt.Errorf("create transmit queue: %w", err)
+	}
+
+	// Set up memory mappings for all buffers used by the queues. This has to
+	// happen before a backend for the queues can be registered.
+	memoryLayout := vhost.NewMemoryLayoutForQueues(
+		[]*virtqueue.SplitQueue{dev.ReceiveQueue, dev.TransmitQueue},
+	)
+	if err = vhost.SetMemoryLayout(dev.controlFD, memoryLayout); err != nil {
+		return nil, fmt.Errorf("setup memory layout: %w", err)
+	}
+
+	// Set the queue backends. This activates the queues within the kernel.
+	if err = SetQueueBackend(dev.controlFD, receiveQueueIndex, opts.backendFD); err != nil {
+		return nil, fmt.Errorf("set receive queue backend: %w", err)
+	}
+	if err = SetQueueBackend(dev.controlFD, transmitQueueIndex, opts.backendFD); err != nil {
+		return nil, fmt.Errorf("set transmit queue backend: %w", err)
+	}
+
+	// Fully populate the receive queue with available buffers which the device
+	// can write new packets into.
+	if err = dev.refillReceiveQueue(); err != nil {
+		return nil, fmt.Errorf("refill receive queue: %w", err)
+	}
+	if err = dev.refillTransmitQueue(); err != nil {
+		return nil, fmt.Errorf("refill receive queue: %w", err)
+	}
+
+	dev.initialized = true
+
+	// Make sure to clean up even when the device gets garbage collected without
+	// Close being called first.
+	devPtr := &dev
+	runtime.SetFinalizer(devPtr, (*Device).Close)
+
+	return devPtr, nil
+}
+
+// refillReceiveQueue offers as many new device-writable buffers to the device
+// as the queue can fit. The device will then use these to write received
+// packets.
+func (dev *Device) refillReceiveQueue() error {
+	for {
+		_, err := dev.ReceiveQueue.OfferInDescriptorChains()
+		if err != nil {
+			if errors.Is(err, virtqueue.ErrNotEnoughFreeDescriptors) {
+				// Queue is full, job is done.
+				return nil
+			}
+			return fmt.Errorf("offer descriptor chain: %w", err)
+		}
+	}
+}
+
+func (dev *Device) refillTransmitQueue() error {
+	//for {
+	//	desc, err := dev.TransmitQueue.DescriptorTable().CreateDescriptorForOutputs()
+	//	if err != nil {
+	//		if errors.Is(err, virtqueue.ErrNotEnoughFreeDescriptors) {
+	//			// Queue is full, job is done.
+	//			return nil
+	//		}
+	//		return fmt.Errorf("offer descriptor chain: %w", err)
+	//	} else {
+	//		dev.TransmitQueue.UsedRing().InitOfferSingle(desc, 0)
+	//	}
+	//}
+	return nil
+}
+
+// Close cleans up the vhost networking device within the kernel and releases
+// all resources used for it.
+// The implementation will try to release as many resources as possible and
+// collect potential errors before returning them.
+func (dev *Device) Close() error {
+	dev.initialized = false
+
+	// Closing the control file descriptor will unregister all queues from the
+	// kernel.
+	if dev.controlFD >= 0 {
+		if err := unix.Close(dev.controlFD); err != nil {
+			// Return an error and do not continue, because the memory used for
+			// the queues should not be released before they were unregistered
+			// from the kernel.
+			return fmt.Errorf("close control file descriptor: %w", err)
+		}
+		dev.controlFD = -1
+	}
+
+	var errs []error
+
+	if dev.ReceiveQueue != nil {
+		if err := dev.ReceiveQueue.Close(); err == nil {
+			dev.ReceiveQueue = nil
+		} else {
+			errs = append(errs, fmt.Errorf("close receive queue: %w", err))
+		}
+	}
+
+	if dev.TransmitQueue != nil {
+		if err := dev.TransmitQueue.Close(); err == nil {
+			dev.TransmitQueue = nil
+		} else {
+			errs = append(errs, fmt.Errorf("close transmit queue: %w", err))
+		}
+	}
+
+	if len(errs) == 0 {
+		// Everything was cleaned up. No need to run the finalizer anymore.
+		runtime.SetFinalizer(dev, nil)
+	}
+
+	return errors.Join(errs...)
+}
+
+// ensureInitialized is used as a guard to prevent methods to be called on an
+// uninitialized instance.
+func (dev *Device) ensureInitialized() {
+	if !dev.initialized {
+		panic("device is not initialized")
+	}
+}
+
+// createQueue creates a new virtqueue and registers it with the vhost device
+// using the given index.
+func createQueue(controlFD int, queueIndex int, queueSize int, itemSize int) (*virtqueue.SplitQueue, error) {
+	var (
+		queue *virtqueue.SplitQueue
+		err   error
+	)
+	if queue, err = virtqueue.NewSplitQueue(queueSize, itemSize); err != nil {
+		return nil, fmt.Errorf("create virtqueue: %w", err)
+	}
+	if err = vhost.RegisterQueue(controlFD, uint32(queueIndex), queue); err != nil {
+		return nil, fmt.Errorf("register virtqueue with index %d: %w", queueIndex, err)
+	}
+	return queue, nil
+}
+
+// truncateBuffers returns a new list of buffers whose combined length matches
+// exactly the specified length. When the specified length exceeds the length of
+// the buffers, this is an error. When it is smaller, the buffer list will be
+// truncated accordingly.
+func truncateBuffers(buffers [][]byte, length int) (out [][]byte) {
+	for _, buffer := range buffers {
+		if length < len(buffer) {
+			out = append(out, buffer[:length])
+			return
+		}
+		out = append(out, buffer)
+		length -= len(buffer)
+	}
+	if length > 0 {
+		panic("length exceeds the combined length of all buffers")
+	}
+	return
+}
+
+func (dev *Device) GetPacketForTx() (uint16, []byte, error) {
+	var err error
+	var idx uint16
+	if !dev.fullTable {
+
+		idx, err = dev.TransmitQueue.DescriptorTable().CreateDescriptorForOutputs()
+		if err == virtqueue.ErrNotEnoughFreeDescriptors {
+			dev.fullTable = true
+			idx, err = dev.TransmitQueue.TakeSingle(context.TODO())
+		}
+	} else {
+		idx, err = dev.TransmitQueue.TakeSingle(context.TODO())
+	}
+	if err != nil {
+		return 0, nil, fmt.Errorf("transmit queue: %w", err)
+	}
+	buf, err := dev.TransmitQueue.GetDescriptorItem(idx)
+	if err != nil {
+		return 0, nil, fmt.Errorf("get descriptor chain: %w", err)
+	}
+	return idx, buf, nil
+}
+
+func (dev *Device) TransmitPacket(pkt *packet.OutPacket, kick bool) error {
+	if len(pkt.SegmentIDs) == 0 {
+		return nil
+	}
+	for idx := range pkt.SegmentIDs {
+		segmentID := pkt.SegmentIDs[idx]
+		dev.TransmitQueue.SetDescSize(segmentID, len(pkt.Segments[idx]))
+	}
+	err := dev.TransmitQueue.OfferDescriptorChains(pkt.SegmentIDs, false)
+	if err != nil {
+		return fmt.Errorf("offer descriptor chains: %w", err)
+	}
+	pkt.Reset()
+	if kick {
+		if err := dev.TransmitQueue.Kick(); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func (dev *Device) TransmitPackets(pkts []*packet.OutPacket) error {
+	if len(pkts) == 0 {
+		return nil
+	}
+
+	for i := range pkts {
+		if err := dev.TransmitPacket(pkts[i], false); err != nil {
+			return err
+		}
+	}
+	if err := dev.TransmitQueue.Kick(); err != nil {
+		return err
+	}
+	return nil
+}
+
+// TODO: Make above methods cancelable by taking a context.Context argument?
+// TODO: Implement zero-copy variants to transmit and receive packets?
+
+// processChains processes as many chains as needed to create one packet. The number of processed chains is returned.
+func (dev *Device) processChains(pkt *packet.VirtIOPacket, chains []virtqueue.UsedElement) (int, error) {
+	//read first element to see how many descriptors we need:
+	pkt.Reset()
+
+	err := dev.ReceiveQueue.GetDescriptorInbuffers(uint16(chains[0].DescriptorIndex), &pkt.ChainRefs)
+	if err != nil {
+		return 0, fmt.Errorf("get descriptor chain: %w", err)
+	}
+	if len(pkt.ChainRefs) == 0 {
+		return 1, nil
+	}
+
+	// The specification requires that the first descriptor chain starts
+	// with a virtio-net header. It is not clear, whether it is also
+	// required to be fully contained in the first buffer of that
+	// descriptor chain, but it is reasonable to assume that this is
+	// always the case.
+	// The decode method already does the buffer length check.
+	if err = pkt.Header.Decode(pkt.ChainRefs[0][0:]); err != nil {
+		// The device misbehaved. There is no way we can gracefully
+		// recover from this, because we don't know how many of the
+		// following descriptor chains belong to this packet.
+		return 0, fmt.Errorf("decode vnethdr: %w", err)
+	}
+
+	//we have the header now: what do we need to do?
+	if int(pkt.Header.NumBuffers) > len(chains) {
+		return 0, fmt.Errorf("number of buffers is greater than number of chains %d", len(chains))
+	}
+	if int(pkt.Header.NumBuffers) != 1 {
+		return 0, fmt.Errorf("too smol-brain to handle more than one chain right now: %d chains", len(chains))
+	}
+	if chains[0].Length > 16000 {
+		//todo!
+		return 1, fmt.Errorf("too big packet length: %d", chains[0].Length)
+	}
+
+	//shift the buffer out of out:
+	pkt.Payload = pkt.ChainRefs[0][virtio.NetHdrSize:chains[0].Length]
+	pkt.Chains = append(pkt.Chains, uint16(chains[0].DescriptorIndex))
+	return 1, nil
+
+	//cursor := n - virtio.NetHdrSize
+	//
+	//if uint32(n) >= chains[0].Length && pkt.Header.NumBuffers == 1 {
+	//	pkt.Payload = pkt.Payload[:chains[0].Length-virtio.NetHdrSize]
+	//	return 1, nil
+	//}
+	//
+	//i := 1
+	//// we used chain 0 already
+	//for i = 1; i < len(chains); i++ {
+	//	n, err = dev.ReceiveQueue.GetDescriptorChainContents(uint16(chains[i].DescriptorIndex), pkt.Payload[cursor:], int(chains[i].Length))
+	//	if err != nil {
+	//		// When this fails we may miss to free some descriptor chains. We
+	//		// could try to mitigate this by deferring the freeing somehow, but
+	//		// it's not worth the hassle. When this method fails, the queue will
+	//		// be in a broken state anyway.
+	//		return i, fmt.Errorf("get descriptor chain: %w", err)
+	//	}
+	//	cursor += n
+	//}
+	////todo this has to be wrong
+	//pkt.Payload = pkt.Payload[:cursor]
+	//return i, nil
+}
+
+func (dev *Device) ReceivePackets(out []*packet.VirtIOPacket) (int, error) {
+	//todo optimize?
+	var chains []virtqueue.UsedElement
+	var err error
+	//if len(dev.extraRx) == 0 {
+	chains, err = dev.ReceiveQueue.BlockAndGetHeadsCapped(context.TODO(), len(out))
+	if err != nil {
+		return 0, err
+	}
+	if len(chains) == 0 {
+		return 0, nil
+	}
+	//} else {
+	//	chains = dev.extraRx
+	//}
+
+	numPackets := 0
+	chainsIdx := 0
+	for numPackets = 0; chainsIdx < len(chains); numPackets++ {
+		if numPackets >= len(out) {
+			return numPackets, fmt.Errorf("dropping %d packets, no room", len(chains)-numPackets)
+		}
+		numChains, err := dev.processChains(out[numPackets], chains[chainsIdx:])
+		if err != nil {
+			return 0, err
+		}
+		chainsIdx += numChains
+	}
+
+	// Now that we have copied all buffers, we can recycle the used descriptor chains
+	//if err = dev.ReceiveQueue.OfferDescriptorChains(chains); err != nil {
+	//	return 0, err
+	//}
+
+	return numPackets, nil
+}

overlay/vhostnet/doc.go

@@ -0,0 +1,3 @@
+// Package vhostnet implements methods to initialize vhost networking devices
+// within the kernel-level virtio implementation and communicate with them.
+package vhostnet

overlay/vhostnet/ioctl.go

@@ -0,0 +1,31 @@
+package vhostnet
+
+import (
+	"fmt"
+	"unsafe"
+
+	"github.com/slackhq/nebula/overlay/vhost"
+)
+
+const (
+	// vhostNetIoctlSetBackend can be used to attach a virtqueue to a RAW socket
+	// or TAP device.
+	//
+	// Request payload: [vhost.QueueFile]
+	// Kernel name: VHOST_NET_SET_BACKEND
+	vhostNetIoctlSetBackend = 0x4008af30
+)
+
+// SetQueueBackend attaches a virtqueue of the vhost networking device
+// described by controlFD to the given backend file descriptor.
+// The backend file descriptor can either be a RAW socket or a TAP device. When
+// it is -1, the queue will be detached.
+func SetQueueBackend(controlFD int, queueIndex uint32, backendFD int) error {
+	if err := vhost.IoctlPtr(controlFD, vhostNetIoctlSetBackend, unsafe.Pointer(&vhost.QueueFile{
+		QueueIndex: queueIndex,
+		FD:         int32(backendFD),
+	})); err != nil {
+		return fmt.Errorf("set queue backend file descriptor: %w", err)
+	}
+	return nil
+}

overlay/vhostnet/options.go

@@ -0,0 +1,69 @@
+package vhostnet
+
+import (
+	"errors"
+
+	"github.com/slackhq/nebula/overlay/virtqueue"
+)
+
+type optionValues struct {
+	queueSize int
+	backendFD int
+}
+
+func (o *optionValues) apply(options []Option) {
+	for _, option := range options {
+		option(o)
+	}
+}
+
+func (o *optionValues) validate() error {
+	if o.queueSize == -1 {
+		return errors.New("queue size is required")
+	}
+	if err := virtqueue.CheckQueueSize(o.queueSize); err != nil {
+		return err
+	}
+	if o.backendFD == -1 {
+		return errors.New("backend file descriptor is required")
+	}
+	return nil
+}
+
+var optionDefaults = optionValues{
+	// Required.
+	queueSize: -1,
+	// Required.
+	backendFD: -1,
+}
+
+// Option can be passed to [NewDevice] to influence device creation.
+type Option func(*optionValues)
+
+// WithQueueSize returns an [Option] that sets the size of the TX and RX queues
+// that are to be created for the device. It specifies the number of
+// entries/buffers each queue can hold. This also affects the memory
+// consumption.
+// This is required and must be an integer from 1 to 32768 that is also a power
+// of 2.
+func WithQueueSize(queueSize int) Option {
+	return func(o *optionValues) { o.queueSize = queueSize }
+}
+
+// WithBackendFD returns an [Option] that sets the file descriptor of the
+// backend that will be used for the queues of the device. The device will write
+// and read packets to/from that backend. The file descriptor can either be of a
+// RAW socket or TUN/TAP device.
+// Either this or [WithBackendDevice] is required.
+func WithBackendFD(backendFD int) Option {
+	return func(o *optionValues) { o.backendFD = backendFD }
+}
+
+//// WithBackendDevice returns an [Option] that sets the given TAP device as the
+//// backend that will be used for the queues of the device. The device will
+//// write and read packets to/from that backend. The TAP device should have been
+//// created with the [tuntap.WithVirtioNetHdr] option enabled.
+//// Either this or [WithBackendFD] is required.
+//func WithBackendDevice(dev *tuntap.Device) Option {
+//	return func(o *optionValues) { o.backendFD = int(dev.File().Fd()) }
+//}

overlay/virtqueue/README.md

@@ -0,0 +1,23 @@
+Significant portions of this code are derived from https://pkg.go.dev/github.com/hetznercloud/virtio-go
+
+MIT License
+
+Copyright (c) 2025 Hetzner Cloud GmbH
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

overlay/virtqueue/available_ring.go

@@ -0,0 +1,140 @@
+package virtqueue
+
+import (
+	"fmt"
+	"unsafe"
+)
+
+// availableRingFlag is a flag that describes an [AvailableRing].
+type availableRingFlag uint16
+
+const (
+	// availableRingFlagNoInterrupt is used by the guest to advise the host to
+	// not interrupt it when consuming a buffer. It's unreliable, so it's simply
+	// an optimization.
+	availableRingFlagNoInterrupt availableRingFlag = 1 << iota
+)
+
+// availableRingSize is the number of bytes needed to store an [AvailableRing]
+// with the given queue size in memory.
+func availableRingSize(queueSize int) int {
+	return 6 + 2*queueSize
+}
+
+// availableRingAlignment is the minimum alignment of an [AvailableRing]
+// in memory, as required by the virtio spec.
+const availableRingAlignment = 2
+
+// AvailableRing is used by the driver to offer descriptor chains to the device.
+// Each ring entry refers to the head of a descriptor chain. It is only written
+// to by the driver and read by the device.
+//
+// Because the size of the ring depends on the queue size, we cannot define a
+// Go struct with a static size that maps to the memory of the ring. Instead,
+// this struct only contains pointers to the corresponding memory areas.
+type AvailableRing struct {
+	initialized bool
+
+	// flags that describe this ring.
+	flags *availableRingFlag
+	// ringIndex indicates where the driver would put the next entry into the
+	// ring (modulo the queue size).
+	ringIndex *uint16
+	// ring references buffers using the index of the head of the descriptor
+	// chain in the [DescriptorTable]. It wraps around at queue size.
+	ring []uint16
+	// usedEvent is not used by this implementation, but we reserve it anyway to
+	// avoid issues in case a device may try to access it, contrary to the
+	// virtio specification.
+	usedEvent *uint16
+}
+
+// newAvailableRing creates an available ring that uses the given underlying
+// memory. The length of the memory slice must match the size needed for the
+// ring (see [availableRingSize]) for the given queue size.
+func newAvailableRing(queueSize int, mem []byte) *AvailableRing {
+	ringSize := availableRingSize(queueSize)
+	if len(mem) != ringSize {
+		panic(fmt.Sprintf("memory size (%v) does not match required size "+
+			"for available ring: %v", len(mem), ringSize))
+	}
+
+	return &AvailableRing{
+		initialized: true,
+		flags:       (*availableRingFlag)(unsafe.Pointer(&mem[0])),
+		ringIndex:   (*uint16)(unsafe.Pointer(&mem[2])),
+		ring:        unsafe.Slice((*uint16)(unsafe.Pointer(&mem[4])), queueSize),
+		usedEvent:   (*uint16)(unsafe.Pointer(&mem[ringSize-2])),
+	}
+}
+
+// Address returns the pointer to the beginning of the ring in memory.
+// Do not modify the memory directly to not interfere with this implementation.
+func (r *AvailableRing) Address() uintptr {
+	if !r.initialized {
+		panic("available ring is not initialized")
+	}
+	return uintptr(unsafe.Pointer(r.flags))
+}
+
+// offer adds the given descriptor chain heads to the available ring and
+// advances the ring index accordingly to make the device process the new
+// descriptor chains.
+func (r *AvailableRing) offerElements(chains []UsedElement) {
+	//always called under lock
+	//r.mu.Lock()
+	//defer r.mu.Unlock()
+
+	// Add descriptor chain heads to the ring.
+	for offset, x := range chains {
+		// The 16-bit ring index may overflow. This is expected and is not an
+		// issue because the size of the ring array (which equals the queue
+		// size) is always a power of 2 and smaller than the highest possible
+		// 16-bit value.
+		insertIndex := int(*r.ringIndex+uint16(offset)) % len(r.ring)
+		r.ring[insertIndex] = x.GetHead()
+	}
+
+	// Increase the ring index by the number of descriptor chains added to the
+	// ring.
+	*r.ringIndex += uint16(len(chains))
+}
+
+func (r *AvailableRing) offer(chains []uint16) {
+	//always called under lock
+	//r.mu.Lock()
+	//defer r.mu.Unlock()
+
+	// Add descriptor chain heads to the ring.
+	for offset, x := range chains {
+		// The 16-bit ring index may overflow. This is expected and is not an
+		// issue because the size of the ring array (which equals the queue
+		// size) is always a power of 2 and smaller than the highest possible
+		// 16-bit value.
+		insertIndex := int(*r.ringIndex+uint16(offset)) % len(r.ring)
+		r.ring[insertIndex] = x
+	}
+
+	// Increase the ring index by the number of descriptor chains added to the
+	// ring.
+	*r.ringIndex += uint16(len(chains))
+}
+
+func (r *AvailableRing) offerSingle(x uint16) {
+	//always called under lock
+	//r.mu.Lock()
+	//defer r.mu.Unlock()
+
+	offset := 0
+	// Add descriptor chain heads to the ring.
+
+	// The 16-bit ring index may overflow. This is expected and is not an
+	// issue because the size of the ring array (which equals the queue
+	// size) is always a power of 2 and smaller than the highest possible
+	// 16-bit value.
+	insertIndex := int(*r.ringIndex+uint16(offset)) % len(r.ring)
+	r.ring[insertIndex] = x
+
+	// Increase the ring index by the number of descriptor chains added to the ring.
+	*r.ringIndex += 1
+}

overlay/virtqueue/available_ring_internal_test.go

@@ -0,0 +1,71 @@
+package virtqueue
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestAvailableRing_MemoryLayout(t *testing.T) {
+	const queueSize = 2
+
+	memory := make([]byte, availableRingSize(queueSize))
+	r := newAvailableRing(queueSize, memory)
+
+	*r.flags = 0x01ff
+	*r.ringIndex = 1
+	r.ring[0] = 0x1234
+	r.ring[1] = 0x5678
+
+	assert.Equal(t, []byte{
+		0xff, 0x01,
+		0x01, 0x00,
+		0x34, 0x12,
+		0x78, 0x56,
+		0x00, 0x00,
+	}, memory)
+}
+
+func TestAvailableRing_Offer(t *testing.T) {
+	const queueSize = 8
+
+	chainHeads := []uint16{42, 33, 69}
+
+	tests := []struct {
+		name              string
+		startRingIndex    uint16
+		expectedRingIndex uint16
+		expectedRing      []uint16
+	}{
+		{
+			name:              "no overflow",
+			startRingIndex:    0,
+			expectedRingIndex: 3,
+			expectedRing:      []uint16{42, 33, 69, 0, 0, 0, 0, 0},
+		},
+		{
+			name:              "ring overflow",
+			startRingIndex:    6,
+			expectedRingIndex: 9,
+			expectedRing:      []uint16{69, 0, 0, 0, 0, 0, 42, 33},
+		},
+		{
+			name:              "index overflow",
+			startRingIndex:    65535,
+			expectedRingIndex: 2,
+			expectedRing:      []uint16{33, 69, 0, 0, 0, 0, 0, 42},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			memory := make([]byte, availableRingSize(queueSize))
+			r := newAvailableRing(queueSize, memory)
+			*r.ringIndex = tt.startRingIndex
+
+			r.offer(chainHeads)
+
+			assert.Equal(t, tt.expectedRingIndex, *r.ringIndex)
+			assert.Equal(t, tt.expectedRing, r.ring)
+		})
+	}
+}

overlay/virtqueue/descriptor.go

@@ -0,0 +1,43 @@
+package virtqueue
+
+// descriptorFlag is a flag that describes a [Descriptor].
+type descriptorFlag uint16
+
+const (
+	// descriptorFlagHasNext marks a descriptor chain as continuing via the next
+	// field.
+	descriptorFlagHasNext descriptorFlag = 1 << iota
+	// descriptorFlagWritable marks a buffer as device write-only (otherwise
+	// device read-only).
+	descriptorFlagWritable
+	// descriptorFlagIndirect means the buffer contains a list of buffer
+	// descriptors to provide an additional layer of indirection.
+	// Only allowed when the [virtio.FeatureIndirectDescriptors] feature was
+	// negotiated.
+	descriptorFlagIndirect
+)
+
+// descriptorSize is the number of bytes needed to store a [Descriptor] in
+// memory.
+const descriptorSize = 16
+
+// Descriptor describes (a part of) a buffer which is either read-only for the
+// device or write-only for the device (depending on [descriptorFlagWritable]).
+// Multiple descriptors can be chained to produce a "descriptor chain" that can
+// contain both device-readable and device-writable buffers. Device-readable
+// descriptors always come first in a chain. A single, large buffer may be
+// split up by chaining multiple similar descriptors that reference different
+// memory pages. This is required, because buffers may exceed a single page size
+// and the memory accessed by the device is expected to be continuous.
+type Descriptor struct {
+	// address is the address to the continuous memory holding the data for this
+	// descriptor.
+	address uintptr
+	// length is the amount of bytes stored at address.
+	length uint32
+	// flags that describe this descriptor.
+	flags descriptorFlag
+	// next contains the index of the next descriptor continuing this descriptor
+	// chain when the [descriptorFlagHasNext] flag is set.
+	next uint16
+}

overlay/virtqueue/descriptor_internal_test.go

@@ -0,0 +1,12 @@
+package virtqueue
+
+import (
+	"testing"
+	"unsafe"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestDescriptor_Size(t *testing.T) {
+	assert.EqualValues(t, descriptorSize, unsafe.Sizeof(Descriptor{}))
+}

overlay/virtqueue/descriptor_table.go

@@ -0,0 +1,641 @@
+package virtqueue
+
+import (
+	"errors"
+	"fmt"
+	"math"
+	"unsafe"
+
+	"golang.org/x/sys/unix"
+)
+
+var (
+	// ErrDescriptorChainEmpty is returned when a descriptor chain would contain
+	// no buffers, which is not allowed.
+	ErrDescriptorChainEmpty = errors.New("empty descriptor chains are not allowed")
+
+	// ErrNotEnoughFreeDescriptors is returned when the free descriptors are
+	// exhausted, meaning that the queue is full.
+	ErrNotEnoughFreeDescriptors = errors.New("not enough free descriptors, queue is full")
+
+	// ErrInvalidDescriptorChain is returned when a descriptor chain is not
+	// valid for a given operation.
+	ErrInvalidDescriptorChain = errors.New("invalid descriptor chain")
+)
+
+// noFreeHead is used to mark when all descriptors are in use and we have no
+// free chain. This value is impossible to occur as an index naturally, because
+// it exceeds the maximum queue size.
+const noFreeHead = uint16(math.MaxUint16)
+
+// descriptorTableSize is the number of bytes needed to store a
+// [DescriptorTable] with the given queue size in memory.
+func descriptorTableSize(queueSize int) int {
+	return descriptorSize * queueSize
+}
+
+// descriptorTableAlignment is the minimum alignment of a [DescriptorTable]
+// in memory, as required by the virtio spec.
+const descriptorTableAlignment = 16
+
+// DescriptorTable is a table that holds [Descriptor]s, addressed via their
+// index in the slice.
+type DescriptorTable struct {
+	descriptors []Descriptor
+
+	// freeHeadIndex is the index of the head of the descriptor chain which
+	// contains all currently unused descriptors. When all descriptors are in
+	// use, this has the special value of noFreeHead.
+	freeHeadIndex uint16
+	// freeNum tracks the number of descriptors which are currently not in use.
+	freeNum uint16
+
+	bufferBase uintptr
+	bufferSize int
+	itemSize   int
+}
+
+// newDescriptorTable creates a descriptor table that uses the given underlying
+// memory. The Length of the memory slice must match the size needed for the
+// descriptor table (see [descriptorTableSize]) for the given queue size.
+//
+// Before this descriptor table can be used, [initialize] must be called.
+func newDescriptorTable(queueSize int, mem []byte, itemSize int) *DescriptorTable {
+	dtSize := descriptorTableSize(queueSize)
+	if len(mem) != dtSize {
+		panic(fmt.Sprintf("memory size (%v) does not match required size "+
+			"for descriptor table: %v", len(mem), dtSize))
+	}
+
+	return &DescriptorTable{
+		descriptors: unsafe.Slice((*Descriptor)(unsafe.Pointer(&mem[0])), queueSize),
+		// We have no free descriptors until they were initialized.
+		freeHeadIndex: noFreeHead,
+		freeNum:       0,
+		itemSize:      itemSize, //todo configurable? needs to be page-aligned
+	}
+}
+
+// Address returns the pointer to the beginning of the descriptor table in
+// memory. Do not modify the memory directly to not interfere with this
+// implementation.
+func (dt *DescriptorTable) Address() uintptr {
+	if dt.descriptors == nil {
+		panic("descriptor table is not initialized")
+	}
+	//should be same as dt.bufferBase
+	return uintptr(unsafe.Pointer(&dt.descriptors[0]))
+}
+
+func (dt *DescriptorTable) Size() uintptr {
+	if dt.descriptors == nil {
+		panic("descriptor table is not initialized")
+	}
+	return uintptr(dt.bufferSize)
+}
+
+// BufferAddresses returns a map of pointer->size for all allocations used by the table
+func (dt *DescriptorTable) BufferAddresses() map[uintptr]int {
+	if dt.descriptors == nil {
+		panic("descriptor table is not initialized")
+	}
+
+	return map[uintptr]int{dt.bufferBase: dt.bufferSize}
+}
+
+// initializeDescriptors allocates buffers with the size of a full memory page
+// for each descriptor in the table. While this may be a bit wasteful, it makes
+// dealing with descriptors way easier. Without this preallocation, we would
+// have to allocate and free memory on demand, increasing complexity.
+//
+// All descriptors will be marked as free and will form a free chain. The
+// addresses of all descriptors will be populated while their length remains
+// zero.
+func (dt *DescriptorTable) initializeDescriptors() error {
+	numDescriptors := len(dt.descriptors)
+
+	// Allocate ONE large region for all buffers
+	totalSize := dt.itemSize * numDescriptors
+	basePtr, err := unix.MmapPtr(-1, 0, nil, uintptr(totalSize),
+		unix.PROT_READ|unix.PROT_WRITE,
+		unix.MAP_PRIVATE|unix.MAP_ANONYMOUS)
+	if err != nil {
+		return fmt.Errorf("allocate buffer memory for descriptors: %w", err)
+	}
+
+	// Store the base for cleanup later
+	dt.bufferBase = uintptr(basePtr)
+	dt.bufferSize = totalSize
+
+	for i := range dt.descriptors {
+		dt.descriptors[i] = Descriptor{
+			address: dt.bufferBase + uintptr(i*dt.itemSize),
+			length:  0,
+			// All descriptors should form a free chain that loops around.
+			flags: descriptorFlagHasNext,
+			next:  uint16((i + 1) % len(dt.descriptors)),
+		}
+	}
+
+	// All descriptors are free to use now.
+	dt.freeHeadIndex = 0
+	dt.freeNum = uint16(len(dt.descriptors))
+
+	return nil
+}
+
+// releaseBuffers releases all allocated buffers for this descriptor table.
+// The implementation will try to release as many buffers as possible and
+// collect potential errors before returning them.
+// The descriptor table should no longer be used after calling this.
+func (dt *DescriptorTable) releaseBuffers() error {
+	for i := range dt.descriptors {
+		descriptor := &dt.descriptors[i]
+		descriptor.address = 0
+	}
+
+	// As a safety measure, make sure no descriptors can be used anymore.
+	dt.freeHeadIndex = noFreeHead
+	dt.freeNum = 0
+
+	if dt.bufferBase != 0 {
+		// The pointer points to memory not managed by Go, so this conversion
+		// is safe. See https://github.com/golang/go/issues/58625
+		dt.bufferBase = 0
+		//goland:noinspection GoVetUnsafePointer
+		err := unix.MunmapPtr(unsafe.Pointer(dt.bufferBase), uintptr(dt.bufferSize))
+		if err != nil {
+			return fmt.Errorf("release buffer memory: %w", err)
+		}
+	}
+
+	return nil
+}
+
+// createDescriptorChain creates a new descriptor chain within the descriptor
+// table which contains a number of device-readable buffers (out buffers) and
+// device-writable buffers (in buffers).
+//
+// All buffers in the outBuffers slice will be concatenated by chaining
+// descriptors, one for each buffer in the slice. The size of the single buffers
+// must not exceed the size of a memory page (see [os.Getpagesize]).
+// When numInBuffers is greater than zero, the given number of device-writable
+// descriptors will be appended to the end of the chain, each referencing a
+// whole memory page.
+//
+// The index of the head of the new descriptor chain will be returned. Callers
+// should make sure to free the descriptor chain using [freeDescriptorChain]
+// after it was used by the device.
+//
+// When there are not enough free descriptors to hold the given number of
+// buffers, an [ErrNotEnoughFreeDescriptors] will be returned. In this case, the
+// caller should try again after some descriptor chains were used by the device
+// and returned back into the free chain.
+func (dt *DescriptorTable) createDescriptorChain(outBuffers [][]byte, numInBuffers int) (uint16, error) {
+	// Calculate the number of descriptors needed to build the chain.
+	numDesc := uint16(len(outBuffers) + numInBuffers)
+
+	// Descriptor chains must always contain at least one descriptor.
+	if numDesc < 1 {
+		return 0, ErrDescriptorChainEmpty
+	}
+
+	// Do we still have enough free descriptors?
+	if numDesc > dt.freeNum {
+		return 0, ErrNotEnoughFreeDescriptors
+	}
+
+	// Above validation ensured that there is at least one free descriptor, so
+	// the free descriptor chain head should be valid.
+	if dt.freeHeadIndex == noFreeHead {
+		panic("free descriptor chain head is unset but there should be free descriptors")
+	}
+
+	// To avoid having to iterate over the whole table to find the descriptor
+	// pointing to the head just to replace the free head, we instead always
+	// create descriptor chains from the descriptors coming after the head.
+	// This way we only have to touch the head as a last resort, when all other
+	// descriptors are already used.
+	head := dt.descriptors[dt.freeHeadIndex].next
+	next := head
+	tail := head
+	for i, buffer := range outBuffers {
+		desc := &dt.descriptors[next]
+		checkUnusedDescriptorLength(next, desc)
+
+		if len(buffer) > dt.itemSize {
+			// The caller should already prevent that from happening.
+			panic(fmt.Sprintf("out buffer %d has size %d which exceeds desc length %d", i, len(buffer), dt.itemSize))
+		}
+
+		// Copy the buffer to the memory referenced by the descriptor.
+		// The descriptor address points to memory not managed by Go, so this
+		// conversion is safe. See https://github.com/golang/go/issues/58625
+		//goland:noinspection GoVetUnsafePointer
+		copy(unsafe.Slice((*byte)(unsafe.Pointer(desc.address)), dt.itemSize), buffer)
+		desc.length = uint32(len(buffer))
+
+		// Clear the flags in case there were any others set.
+		desc.flags = descriptorFlagHasNext
+
+		tail = next
+		next = desc.next
+	}
+	for range numInBuffers {
+		desc := &dt.descriptors[next]
+		checkUnusedDescriptorLength(next, desc)
+
+		// Give the device the maximum available number of bytes to write into.
+		desc.length = uint32(dt.itemSize)
+
+		// Mark the descriptor as device-writable.
+		desc.flags = descriptorFlagHasNext | descriptorFlagWritable
+
+		tail = next
+		next = desc.next
+	}
+
+	// The last descriptor should end the chain.
+	tailDesc := &dt.descriptors[tail]
+	tailDesc.flags &= ^descriptorFlagHasNext
+	tailDesc.next = 0 // Not necessary to clear this, it's just for looks.
+
+	dt.freeNum -= numDesc
+
+	if dt.freeNum == 0 {
+		// The last descriptor in the chain should be the free chain head
+		// itself.
+		if tail != dt.freeHeadIndex {
+			panic("descriptor chain takes up all free descriptors but does not end with the free chain head")
+		}
+
+		// When this new chain takes up all remaining descriptors, we no longer
+		// have a free chain.
+		dt.freeHeadIndex = noFreeHead
+	} else {
+		// We took some descriptors out of the free chain, so make sure to close
+		// the circle again.
+		dt.descriptors[dt.freeHeadIndex].next = next
+	}
+
+	return head, nil
+}
+
+func (dt *DescriptorTable) CreateDescriptorForOutputs() (uint16, error) {
+	//todo just fill the damn table
+	// Do we still have enough free descriptors?
+
+	if 1 > dt.freeNum {
+		return 0, ErrNotEnoughFreeDescriptors
+	}
+
+	// Above validation ensured that there is at least one free descriptor, so
+	// the free descriptor chain head should be valid.
+	if dt.freeHeadIndex == noFreeHead {
+		panic("free descriptor chain head is unset but there should be free descriptors")
+	}
+
+	// To avoid having to iterate over the whole table to find the descriptor
+	// pointing to the head just to replace the free head, we instead always
+	// create descriptor chains from the descriptors coming after the head.
+	// This way we only have to touch the head as a last resort, when all other
+	// descriptors are already used.
+	head := dt.descriptors[dt.freeHeadIndex].next
+	desc := &dt.descriptors[head]
+	next := desc.next
+
+	checkUnusedDescriptorLength(head, desc)
+
+	// Give the device the maximum available number of bytes to write into.
+	desc.length = uint32(dt.itemSize)
+	desc.flags = 0 // descriptorFlagWritable
+	desc.next = 0  // Not necessary to clear this, it's just for looks.
+
+	dt.freeNum -= 1
+
+	if dt.freeNum == 0 {
+		// The last descriptor in the chain should be the free chain head
+		// itself.
+		if next != dt.freeHeadIndex {
+			panic("descriptor chain takes up all free descriptors but does not end with the free chain head")
+		}
+
+		// When this new chain takes up all remaining descriptors, we no longer
+		// have a free chain.
+		dt.freeHeadIndex = noFreeHead
+	} else {
+		// We took some descriptors out of the free chain, so make sure to close
+		// the circle again.
+		dt.descriptors[dt.freeHeadIndex].next = next
+	}
+
+	return head, nil
+}
+
+func (dt *DescriptorTable) createDescriptorForInputs() (uint16, error) {
+	// Do we still have enough free descriptors?
+	if 1 > dt.freeNum {
+		return 0, ErrNotEnoughFreeDescriptors
+	}
+
+	// Above validation ensured that there is at least one free descriptor, so
+	// the free descriptor chain head should be valid.
+	if dt.freeHeadIndex == noFreeHead {
+		panic("free descriptor chain head is unset but there should be free descriptors")
+	}
+
+	// To avoid having to iterate over the whole table to find the descriptor
+	// pointing to the head just to replace the free head, we instead always
+	// create descriptor chains from the descriptors coming after the head.
+	// This way we only have to touch the head as a last resort, when all other
+	// descriptors are already used.
+	head := dt.descriptors[dt.freeHeadIndex].next
+	desc := &dt.descriptors[head]
+	next := desc.next
+
+	checkUnusedDescriptorLength(head, desc)
+
+	// Give the device the maximum available number of bytes to write into.
+	desc.length = uint32(dt.itemSize)
+	desc.flags = descriptorFlagWritable
+	desc.next = 0 // Not necessary to clear this, it's just for looks.
+
+	dt.freeNum -= 1
+
+	if dt.freeNum == 0 {
+		// The last descriptor in the chain should be the free chain head
+		// itself.
+		if next != dt.freeHeadIndex {
+			panic("descriptor chain takes up all free descriptors but does not end with the free chain head")
+		}
+
+		// When this new chain takes up all remaining descriptors, we no longer
+		// have a free chain.
+		dt.freeHeadIndex = noFreeHead
+	} else {
+		// We took some descriptors out of the free chain, so make sure to close
+		// the circle again.
+		dt.descriptors[dt.freeHeadIndex].next = next
+	}
+
+	return head, nil
+}
+
+// TODO: Implement a zero-copy variant of createDescriptorChain?
+
+// getDescriptorChain returns the device-readable buffers (out buffers) and
+// device-writable buffers (in buffers) of the descriptor chain that starts with
+// the given head index. The descriptor chain must have been created using
+// [createDescriptorChain] and must not have been freed yet (meaning that the
+// head index must not be contained in the free chain).
+//
+// Be careful to only access the returned buffer slices when the device has not
+// yet or is no longer using them. They must not be accessed after
+// [freeDescriptorChain] has been called.
+func (dt *DescriptorTable) getDescriptorChain(head uint16) (outBuffers, inBuffers [][]byte, err error) {
+	if int(head) > len(dt.descriptors) {
+		return nil, nil, fmt.Errorf("%w: index out of range", ErrInvalidDescriptorChain)
+	}
+
+	// Iterate over the chain. The iteration is limited to the queue size to
+	// avoid ending up in an endless loop when things go very wrong.
+	next := head
+	for range len(dt.descriptors) {
+		if next == dt.freeHeadIndex {
+			return nil, nil, fmt.Errorf("%w: must not be part of the free chain", ErrInvalidDescriptorChain)
+		}
+
+		desc := &dt.descriptors[next]
+
+		// The descriptor address points to memory not managed by Go, so this
+		// conversion is safe. See https://github.com/golang/go/issues/58625
+		//goland:noinspection GoVetUnsafePointer
+		bs := unsafe.Slice((*byte)(unsafe.Pointer(desc.address)), desc.length)
+
+		if desc.flags&descriptorFlagWritable == 0 {
+			outBuffers = append(outBuffers, bs)
+		} else {
+			inBuffers = append(inBuffers, bs)
+		}
+
+		// Is this the tail of the chain?
+		if desc.flags&descriptorFlagHasNext == 0 {
+			break
+		}
+
+		// Detect loops.
+		if desc.next == head {
+			return nil, nil, fmt.Errorf("%w: contains a loop", ErrInvalidDescriptorChain)
+		}
+
+		next = desc.next
+	}
+
+	return
+}
+
+func (dt *DescriptorTable) getDescriptorItem(head uint16) ([]byte, error) {
+	if int(head) > len(dt.descriptors) {
+		return nil, fmt.Errorf("%w: index out of range", ErrInvalidDescriptorChain)
+	}
+
+	desc := &dt.descriptors[head] //todo this is a pretty nasty hack with no checks
+
+	// The descriptor address points to memory not managed by Go, so this
+	// conversion is safe. See https://github.com/golang/go/issues/58625
+	//goland:noinspection GoVetUnsafePointer
+	bs := unsafe.Slice((*byte)(unsafe.Pointer(desc.address)), desc.length)
+	return bs, nil
+}
+
+func (dt *DescriptorTable) getDescriptorInbuffers(head uint16, inBuffers *[][]byte) error {
+	if int(head) > len(dt.descriptors) {
+		return fmt.Errorf("%w: index out of range", ErrInvalidDescriptorChain)
+	}
+
+	// Iterate over the chain. The iteration is limited to the queue size to
+	// avoid ending up in an endless loop when things go very wrong.
+	next := head
+	for range len(dt.descriptors) {
+		if next == dt.freeHeadIndex {
+			return fmt.Errorf("%w: must not be part of the free chain", ErrInvalidDescriptorChain)
+		}
+
+		desc := &dt.descriptors[next]
+
+		// The descriptor address points to memory not managed by Go, so this
+		// conversion is safe. See https://github.com/golang/go/issues/58625
+		//goland:noinspection GoVetUnsafePointer
+		bs := unsafe.Slice((*byte)(unsafe.Pointer(desc.address)), desc.length)
+
+		if desc.flags&descriptorFlagWritable == 0 {
+			return fmt.Errorf("there should not be an outbuffer in %d", head)
+		} else {
+			*inBuffers = append(*inBuffers, bs)
+		}
+
+		// Is this the tail of the chain?
+		if desc.flags&descriptorFlagHasNext == 0 {
+			break
+		}
+
+		// Detect loops.
+		if desc.next == head {
+			return fmt.Errorf("%w: contains a loop", ErrInvalidDescriptorChain)
+		}
+
+		next = desc.next
+	}
+
+	return nil
+}
+
+func (dt *DescriptorTable) getDescriptorChainContents(head uint16, out []byte, maxLen int) (int, error) {
+	if int(head) > len(dt.descriptors) {
+		return 0, fmt.Errorf("%w: index out of range", ErrInvalidDescriptorChain)
+	}
+
+	// Iterate over the chain. The iteration is limited to the queue size to
+	// avoid ending up in an endless loop when things go very wrong.
+
+	length := 0
+	//find length
+	next := head
+	for range len(dt.descriptors) {
+		if next == dt.freeHeadIndex {
+			return 0, fmt.Errorf("%w: must not be part of the free chain", ErrInvalidDescriptorChain)
+		}
+
+		desc := &dt.descriptors[next]
+
+		if desc.flags&descriptorFlagWritable == 0 {
+			return 0, fmt.Errorf("receive queue contains device-readable buffer")
+		}
+		length += int(desc.length)
+
+		// Is this the tail of the chain?
+		if desc.flags&descriptorFlagHasNext == 0 {
+			break
+		}
+
+		// Detect loops.
+		if desc.next == head {
+			return 0, fmt.Errorf("%w: contains a loop", ErrInvalidDescriptorChain)
+		}
+
+		next = desc.next
+	}
+	if maxLen > 0 {
+		//todo length = min(maxLen, length)
+	}
+	//set out to length:
+	out = out[:length]
+
+	//now do the copying
+	copied := 0
+	for range len(dt.descriptors) {
+		desc := &dt.descriptors[next]
+
+		// The descriptor address points to memory not managed by Go, so this
+		// conversion is safe. See https://github.com/golang/go/issues/58625
+		//goland:noinspection GoVetUnsafePointer
+		bs := unsafe.Slice((*byte)(unsafe.Pointer(desc.address)), min(uint32(length-copied), desc.length))
+		copied += copy(out[copied:], bs)
+
+		// Is this the tail of the chain?
+		if desc.flags&descriptorFlagHasNext == 0 {
+			break
+		}
+
+		// we did this already, no need to detect loops.
+		next = desc.next
+	}
+	if copied != length {
+		panic(fmt.Sprintf("expected to copy %d bytes but only copied %d bytes", length, copied))
+	}
+
+	return length, nil
+}
+
+// freeDescriptorChain can be used to free a descriptor chain when it is no
+// longer in use. The descriptor chain that starts with the given index will be
+// put back into the free chain, so the descriptors can be used for later calls
+// of [createDescriptorChain].
+// The descriptor chain must have been created using [createDescriptorChain] and
+// must not have been freed yet (meaning that the head index must not be
+// contained in the free chain).
+func (dt *DescriptorTable) freeDescriptorChain(head uint16) error {
+	if int(head) > len(dt.descriptors) {
+		return fmt.Errorf("%w: index out of range", ErrInvalidDescriptorChain)
+	}
+
+	// Iterate over the chain. The iteration is limited to the queue size to
+	// avoid ending up in an endless loop when things go very wrong.
+	next := head
+	var tailDesc *Descriptor
+	var chainLen uint16
+	for range len(dt.descriptors) {
+		if next == dt.freeHeadIndex {
+			return fmt.Errorf("%w: must not be part of the free chain", ErrInvalidDescriptorChain)
+		}
+
+		desc := &dt.descriptors[next]
+		chainLen++
+
+		// Set the length of all unused descriptors back to zero.
+		desc.length = 0
+
+		// Unset all flags except the next flag.
+		desc.flags &= descriptorFlagHasNext
+
+		// Is this the tail of the chain?
+		if desc.flags&descriptorFlagHasNext == 0 {
+			tailDesc = desc
+			break
+		}
+
+		// Detect loops.
+		if desc.next == head {
+			return fmt.Errorf("%w: contains a loop", ErrInvalidDescriptorChain)
+		}
+
+		next = desc.next
+	}
+	if tailDesc == nil {
+		// A descriptor chain longer than the queue size but without loops
+		// should be impossible.
+		panic(fmt.Sprintf("could not find a tail for descriptor chain starting at %d", head))
+	}
+
+	// The tail descriptor does not have the next flag set, but when it comes
+	// back into the free chain, it should have.
+	tailDesc.flags = descriptorFlagHasNext
+
+	if dt.freeHeadIndex == noFreeHead {
+		// The whole free chain was used up, so we turn this returned descriptor
+		// chain into the new free chain by completing the circle and using its
+		// head.
+		tailDesc.next = head
+		dt.freeHeadIndex = head
+	} else {
+		// Attach the returned chain at the beginning of the free chain but
+		// right after the free chain head.
+		freeHeadDesc := &dt.descriptors[dt.freeHeadIndex]
+		tailDesc.next = freeHeadDesc.next
+		freeHeadDesc.next = head
+	}
+
+	dt.freeNum += chainLen
+
+	return nil
+}
+
+// checkUnusedDescriptorLength asserts that the length of an unused descriptor
+// is zero, as it should be.
+// This is not a requirement by the virtio spec but rather a thing we do to
+// notice when our algorithm goes sideways.
+func checkUnusedDescriptorLength(index uint16, desc *Descriptor) {
+	if desc.length != 0 {
+		panic(fmt.Sprintf("descriptor %d should be unused but has a non-zero length", index))
+	}
+}

overlay/virtqueue/descriptor_table_internal_test.go

@@ -0,0 +1,407 @@
+package virtqueue
+
+import (
+	"os"
+	"testing"
+	"unsafe"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestDescriptorTable_InitializeDescriptors(t *testing.T) {
+	const queueSize = 32
+
+	dt := DescriptorTable{
+		descriptors: make([]Descriptor, queueSize),
+	}
+
+	assert.NoError(t, dt.initializeDescriptors())
+	t.Cleanup(func() {
+		assert.NoError(t, dt.releaseBuffers())
+	})
+
+	for i, descriptor := range dt.descriptors {
+		assert.NotZero(t, descriptor.address)
+		assert.Zero(t, descriptor.length)
+		assert.EqualValues(t, descriptorFlagHasNext, descriptor.flags)
+		assert.EqualValues(t, (i+1)%queueSize, descriptor.next)
+	}
+}
+
+func TestDescriptorTable_DescriptorChains(t *testing.T) {
+	// Use a very short queue size to not make this test overly verbose.
+	const queueSize = 8
+
+	pageSize := os.Getpagesize() * 2
+
+	// Initialize descriptor table.
+	dt := DescriptorTable{
+		descriptors: make([]Descriptor, queueSize),
+	}
+	assert.NoError(t, dt.initializeDescriptors())
+	t.Cleanup(func() {
+		assert.NoError(t, dt.releaseBuffers())
+	})
+
+	// Some utilities for easier checking if the descriptor table looks as
+	// expected.
+	type desc struct {
+		buffer []byte
+		flags  descriptorFlag
+		next   uint16
+	}
+	assertDescriptorTable := func(expected [queueSize]desc) {
+		for i := 0; i < queueSize; i++ {
+			actualDesc := &dt.descriptors[i]
+			expectedDesc := &expected[i]
+			assert.Equal(t, uint32(len(expectedDesc.buffer)), actualDesc.length)
+			if len(expectedDesc.buffer) > 0 {
+				//goland:noinspection GoVetUnsafePointer
+				assert.EqualValues(t,
+					unsafe.Slice((*byte)(unsafe.Pointer(actualDesc.address)), actualDesc.length),
+					expectedDesc.buffer)
+			}
+			assert.Equal(t, expectedDesc.flags, actualDesc.flags)
+			if expectedDesc.flags&descriptorFlagHasNext != 0 {
+				assert.Equal(t, expectedDesc.next, actualDesc.next)
+			}
+		}
+	}
+
+	// Initial state: All descriptors are in the free chain.
+	assert.Equal(t, uint16(0), dt.freeHeadIndex)
+	assert.Equal(t, uint16(8), dt.freeNum)
+	assertDescriptorTable([queueSize]desc{
+		{
+			// Free head.
+			flags: descriptorFlagHasNext,
+			next:  1,
+		},
+		{
+			flags: descriptorFlagHasNext,
+			next:  2,
+		},
+		{
+			flags: descriptorFlagHasNext,
+			next:  3,
+		},
+		{
+			flags: descriptorFlagHasNext,
+			next:  4,
+		},
+		{
+			flags: descriptorFlagHasNext,
+			next:  5,
+		},
+		{
+			flags: descriptorFlagHasNext,
+			next:  6,
+		},
+		{
+			flags: descriptorFlagHasNext,
+			next:  7,
+		},
+		{
+			flags: descriptorFlagHasNext,
+			next:  0,
+		},
+	})
+
+	// Create the first chain.
+	firstChain, err := dt.createDescriptorChain([][]byte{
+		makeTestBuffer(t, 26),
+		makeTestBuffer(t, 256),
+	}, 1)
+	assert.NoError(t, err)
+	assert.Equal(t, uint16(1), firstChain)
+
+	// Now there should be a new chain next to the free chain.
+	assert.Equal(t, uint16(0), dt.freeHeadIndex)
+	assert.Equal(t, uint16(5), dt.freeNum)
+	assertDescriptorTable([queueSize]desc{
+		{
+			// Free head.
+			flags: descriptorFlagHasNext,
+			next:  4,
+		},
+		{
+			// Head of first chain.
+			buffer: makeTestBuffer(t, 26),
+			flags:  descriptorFlagHasNext,
+			next:   2,
+		},
+		{
+			buffer: makeTestBuffer(t, 256),
+			flags:  descriptorFlagHasNext,
+			next:   3,
+		},
+		{
+			// Tail of first chain.
+			buffer: make([]byte, pageSize),
+			flags:  descriptorFlagWritable,
+		},
+		{
+			flags: descriptorFlagHasNext,
+			next:  5,
+		},
+		{
+			flags: descriptorFlagHasNext,
+			next:  6,
+		},
+		{
+			flags: descriptorFlagHasNext,
+			next:  7,
+		},
+		{
+			flags: descriptorFlagHasNext,
+			next:  0,
+		},
+	})
+
+	// Create a second chain with only a single in buffer.
+	secondChain, err := dt.createDescriptorChain(nil, 1)
+	assert.NoError(t, err)
+	assert.Equal(t, uint16(4), secondChain)
+
+	// Now there should be two chains next to the free chain.
+	assert.Equal(t, uint16(0), dt.freeHeadIndex)
+	assert.Equal(t, uint16(4), dt.freeNum)
+	assertDescriptorTable([queueSize]desc{
+		{
+			// Free head.
+			flags: descriptorFlagHasNext,
+			next:  5,
+		},
+		{
+			// Head of the first chain.
+			buffer: makeTestBuffer(t, 26),
+			flags:  descriptorFlagHasNext,
+			next:   2,
+		},
+		{
+			buffer: makeTestBuffer(t, 256),
+			flags:  descriptorFlagHasNext,
+			next:   3,
+		},
+		{
+			// Tail of the first chain.
+			buffer: make([]byte, pageSize),
+			flags:  descriptorFlagWritable,
+		},
+		{
+			// Head and tail of the second chain.
+			buffer: make([]byte, pageSize),
+			flags:  descriptorFlagWritable,
+		},
+		{
+			flags: descriptorFlagHasNext,
+			next:  6,
+		},
+		{
+			flags: descriptorFlagHasNext,
+			next:  7,
+		},
+		{
+			flags: descriptorFlagHasNext,
+			next:  0,
+		},
+	})
+
+	// Create a third chain taking up all remaining descriptors.
+	thirdChain, err := dt.createDescriptorChain([][]byte{
+		makeTestBuffer(t, 42),
+		makeTestBuffer(t, 96),
+		makeTestBuffer(t, 33),
+		makeTestBuffer(t, 222),
+	}, 0)
+	assert.NoError(t, err)
+	assert.Equal(t, uint16(5), thirdChain)
+
+	// Now there should be three chains and no free chain.
+	assert.Equal(t, noFreeHead, dt.freeHeadIndex)
+	assert.Equal(t, uint16(0), dt.freeNum)
+	assertDescriptorTable([queueSize]desc{
+		{
+			// Tail of the third chain.
+			buffer: makeTestBuffer(t, 222),
+		},
+		{
+			// Head of the first chain.
+			buffer: makeTestBuffer(t, 26),
+			flags:  descriptorFlagHasNext,
+			next:   2,
+		},
+		{
+			buffer: makeTestBuffer(t, 256),
+			flags:  descriptorFlagHasNext,
+			next:   3,
+		},
+		{
+			// Tail of the first chain.
+			buffer: make([]byte, pageSize),
+			flags:  descriptorFlagWritable,
+		},
+		{
+			// Head and tail of the second chain.
+			buffer: make([]byte, pageSize),
+			flags:  descriptorFlagWritable,
+		},
+		{
+			// Head of the third chain.
+			buffer: makeTestBuffer(t, 42),
+			flags:  descriptorFlagHasNext,
+			next:   6,
+		},
+		{
+			buffer: makeTestBuffer(t, 96),
+			flags:  descriptorFlagHasNext,
+			next:   7,
+		},
+		{
+			buffer: makeTestBuffer(t, 33),
+			flags:  descriptorFlagHasNext,
+			next:   0,
+		},
+	})
+
+	// Free the third chain.
+	assert.NoError(t, dt.freeDescriptorChain(thirdChain))
+
+	// Now there should be two chains and a free chain again.
+	assert.Equal(t, uint16(5), dt.freeHeadIndex)
+	assert.Equal(t, uint16(4), dt.freeNum)
+	assertDescriptorTable([queueSize]desc{
+		{
+			flags: descriptorFlagHasNext,
+			next:  5,
+		},
+		{
+			// Head of the first chain.
+			buffer: makeTestBuffer(t, 26),
+			flags:  descriptorFlagHasNext,
+			next:   2,
+		},
+		{
+			buffer: makeTestBuffer(t, 256),
+			flags:  descriptorFlagHasNext,
+			next:   3,
+		},
+		{
+			// Tail of the first chain.
+			buffer: make([]byte, pageSize),
+			flags:  descriptorFlagWritable,
+		},
+		{
+			// Head and tail of the second chain.
+			buffer: make([]byte, pageSize),
+			flags:  descriptorFlagWritable,
+		},
+		{
+			// Free head.
+			flags: descriptorFlagHasNext,
+			next:  6,
+		},
+		{
+			flags: descriptorFlagHasNext,
+			next:  7,
+		},
+		{
+			flags: descriptorFlagHasNext,
+			next:  0,
+		},
+	})
+
+	// Free the first chain.
+	assert.NoError(t, dt.freeDescriptorChain(firstChain))
+
+	// Now there should be only a single chain next to the free chain.
+	assert.Equal(t, uint16(5), dt.freeHeadIndex)
+	assert.Equal(t, uint16(7), dt.freeNum)
+	assertDescriptorTable([queueSize]desc{
+		{
+			flags: descriptorFlagHasNext,
+			next:  5,
+		},
+		{
+			flags: descriptorFlagHasNext,
+			next:  2,
+		},
+		{
+			flags: descriptorFlagHasNext,
+			next:  3,
+		},
+		{
+			flags: descriptorFlagHasNext,
+			next:  6,
+		},
+		{
+			// Head and tail of the second chain.
+			buffer: make([]byte, pageSize),
+			flags:  descriptorFlagWritable,
+		},
+		{
+			// Free head.
+			flags: descriptorFlagHasNext,
+			next:  1,
+		},
+		{
+			flags: descriptorFlagHasNext,
+			next:  7,
+		},
+		{
+			flags: descriptorFlagHasNext,
+			next:  0,
+		},
+	})
+
+	// Free the second chain.
+	assert.NoError(t, dt.freeDescriptorChain(secondChain))
+
+	// Now all descriptors should be in the free chain again.
+	assert.Equal(t, uint16(5), dt.freeHeadIndex)
+	assert.Equal(t, uint16(8), dt.freeNum)
+	assertDescriptorTable([queueSize]desc{
+		{
+			flags: descriptorFlagHasNext,
+			next:  5,
+		},
+		{
+			flags: descriptorFlagHasNext,
+			next:  2,
+		},
+		{
+			flags: descriptorFlagHasNext,
+			next:  3,
+		},
+		{
+			flags: descriptorFlagHasNext,
+			next:  6,
+		},
+		{
+			flags: descriptorFlagHasNext,
+			next:  1,
+		},
+		{
+			// Free head.
+			flags: descriptorFlagHasNext,
+			next:  4,
+		},
+		{
+			flags: descriptorFlagHasNext,
+			next:  7,
+		},
+		{
+			flags: descriptorFlagHasNext,
+			next:  0,
+		},
+	})
+}
+
+func makeTestBuffer(t *testing.T, length int) []byte {
+	t.Helper()
+	buf := make([]byte, length)
+	for i := 0; i < length; i++ {
+		buf[i] = byte(length - i)
+	}
+	return buf
+}

overlay/virtqueue/doc.go

@@ -0,0 +1,7 @@
+// Package virtqueue implements the driver-side for a virtio queue as described
+// in the specification:
+// https://docs.oasis-open.org/virtio/virtio/v1.2/csd01/virtio-v1.2-csd01.html#x1-270006
+// This package does not make assumptions about the device that consumes the
+// queue. It rather just allocates the queue structures in memory and provides
+// methods to interact with it.
+package virtqueue

overlay/virtqueue/eventfd_test.go

@@ -0,0 +1,45 @@
+package virtqueue
+
+import (
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"gvisor.dev/gvisor/pkg/eventfd"
+)
+
+// Tests how an eventfd and a waiting goroutine can be gracefully closed.
+// Extends the eventfd test suite:
+// https://github.com/google/gvisor/blob/0799336d64be65eb97d330606c30162dc3440cab/pkg/eventfd/eventfd_test.go
+func TestEventFD_CancelWait(t *testing.T) {
+	efd, err := eventfd.Create()
+	require.NoError(t, err)
+	t.Cleanup(func() {
+		assert.NoError(t, efd.Close())
+	})
+
+	var stop bool
+
+	done := make(chan struct{})
+	go func() {
+		for !stop {
+			_ = efd.Wait()
+		}
+		close(done)
+	}()
+	select {
+	case <-done:
+		t.Fatalf("goroutine ended early")
+	case <-time.After(500 * time.Millisecond):
+	}
+
+	stop = true
+	assert.NoError(t, efd.Notify())
+	select {
+	case <-done:
+		break
+	case <-time.After(5 * time.Second):
+		t.Error("goroutine did not end")
+	}
+}

overlay/virtqueue/size.go

@@ -0,0 +1,33 @@
+package virtqueue
+
+import (
+	"errors"
+	"fmt"
+)
+
+// ErrQueueSizeInvalid is returned when a queue size is invalid.
+var ErrQueueSizeInvalid = errors.New("queue size is invalid")
+
+// CheckQueueSize checks if the given value would be a valid size for a
+// virtqueue and returns an [ErrQueueSizeInvalid], if not.
+func CheckQueueSize(queueSize int) error {
+	if queueSize <= 0 {
+		return fmt.Errorf("%w: %d is too small", ErrQueueSizeInvalid, queueSize)
+	}
+
+	// The queue size must always be a power of 2.
+	// This ensures that ring indexes wrap correctly when the 16-bit integers
+	// overflow.
+	if queueSize&(queueSize-1) != 0 {
+		return fmt.Errorf("%w: %d is not a power of 2", ErrQueueSizeInvalid, queueSize)
+	}
+
+	// The largest power of 2 that fits into a 16-bit integer is 32768.
+	// 2 * 32768 would be 65536 which no longer fits.
+	if queueSize > 32768 {
+		return fmt.Errorf("%w: %d is larger than the maximum possible queue size 32768",
+			ErrQueueSizeInvalid, queueSize)
+	}
+
+	return nil
+}

overlay/virtqueue/size_test.go

@@ -0,0 +1,59 @@
+package virtqueue
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestCheckQueueSize(t *testing.T) {
+	tests := []struct {
+		name        string
+		queueSize   int
+		containsErr string
+	}{
+		{
+			name:        "negative",
+			queueSize:   -1,
+			containsErr: "too small",
+		},
+		{
+			name:        "zero",
+			queueSize:   0,
+			containsErr: "too small",
+		},
+		{
+			name:        "not a power of 2",
+			queueSize:   24,
+			containsErr: "not a power of 2",
+		},
+		{
+			name:        "too large",
+			queueSize:   65536,
+			containsErr: "larger than the maximum",
+		},
+		{
+			name:      "valid 1",
+			queueSize: 1,
+		},
+		{
+			name:      "valid 256",
+			queueSize: 256,
+		},
+
+		{
+			name:      "valid 32768",
+			queueSize: 32768,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			err := CheckQueueSize(tt.queueSize)
+			if tt.containsErr != "" {
+				assert.ErrorContains(t, err, tt.containsErr)
+			} else {
+				assert.NoError(t, err)
+			}
+		})
+	}
+}

overlay/virtqueue/split_virtqueue.go

@@ -0,0 +1,530 @@
+package virtqueue
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"os"
+	"syscall"
+
+	"github.com/slackhq/nebula/overlay/eventfd"
+	"golang.org/x/sys/unix"
+)
+
+// SplitQueue is a virtqueue that consists of several parts, where each part is
+// writeable by either the driver or the device, but not both.
+type SplitQueue struct {
+	// size is the size of the queue.
+	size int
+	// buf is the underlying memory used for the queue.
+	buf []byte
+
+	descriptorTable *DescriptorTable
+	availableRing   *AvailableRing
+	usedRing        *UsedRing
+
+	// kickEventFD is used to signal the device when descriptor chains were
+	// added to the available ring.
+	kickEventFD eventfd.EventFD
+	// callEventFD is used by the device to signal when it has used descriptor
+	// chains and put them in the used ring.
+	callEventFD eventfd.EventFD
+
+	// stop is used by [SplitQueue.Close] to cancel the goroutine that handles
+	// used buffer notifications. It blocks until the goroutine ended.
+	stop func() error
+
+	itemSize int
+
+	epoll eventfd.Epoll
+	more  int
+}
+
+// NewSplitQueue allocates a new [SplitQueue] in memory. The given queue size
+// specifies the number of entries/buffers the queue can hold. This also affects
+// the memory consumption.
+func NewSplitQueue(queueSize int, itemSize int) (_ *SplitQueue, err error) {
+	if err = CheckQueueSize(queueSize); err != nil {
+		return nil, err
+	}
+
+	if itemSize%os.Getpagesize() != 0 {
+		return nil, errors.New("split queue size must be multiple of os.Getpagesize()")
+	}
+
+	sq := SplitQueue{
+		size:     queueSize,
+		itemSize: itemSize,
+	}
+
+	// Clean up a partially initialized queue when something fails.
+	defer func() {
+		if err != nil {
+			_ = sq.Close()
+		}
+	}()
+
+	// There are multiple ways for how the memory for the virtqueue could be
+	// allocated. We could use Go native structs with arrays inside them, but
+	// this wouldn't allow us to make the queue size configurable. And including
+	// a slice in the Go structs wouldn't work, because this would just put the
+	// Go slice descriptor into the memory region which the virtio device will
+	// not understand.
+	// Additionally, Go does not allow us to ensure a correct alignment of the
+	// parts of the virtqueue, as it is required by the virtio specification.
+	//
+	// To resolve this, let's just allocate the memory manually by allocating
+	// one or more memory pages, depending on the queue size. Making the
+	// virtqueue start at the beginning of a page is not strictly necessary, as
+	// the virtio specification does not require it to be continuous in the
+	// physical memory of the host (e.g. the vhost implementation in the kernel
+	// always uses copy_from_user to access it), but this makes it very easy to
+	// guarantee the alignment. Also, it is not required for the virtqueue parts
+	// to be in the same memory region, as we pass separate pointers to them to
+	// the device, but this design just makes things easier to implement.
+	//
+	// One added benefit of allocating the memory manually is, that we have full
+	// control over its lifetime and don't risk the garbage collector to collect
+	// our valuable structures while the device still works with them.
+
+	// The descriptor table is at the start of the page, so alignment is not an
+	// issue here.
+	descriptorTableStart := 0
+	descriptorTableEnd := descriptorTableStart + descriptorTableSize(queueSize)
+	availableRingStart := align(descriptorTableEnd, availableRingAlignment)
+	availableRingEnd := availableRingStart + availableRingSize(queueSize)
+	usedRingStart := align(availableRingEnd, usedRingAlignment)
+	usedRingEnd := usedRingStart + usedRingSize(queueSize)
+
+	sq.buf, err = unix.Mmap(-1, 0, usedRingEnd,
+		unix.PROT_READ|unix.PROT_WRITE,
+		unix.MAP_PRIVATE|unix.MAP_ANONYMOUS)
+	if err != nil {
+		return nil, fmt.Errorf("allocate virtqueue buffer: %w", err)
+	}
+
+	sq.descriptorTable = newDescriptorTable(queueSize, sq.buf[descriptorTableStart:descriptorTableEnd], sq.itemSize)
+	sq.availableRing = newAvailableRing(queueSize, sq.buf[availableRingStart:availableRingEnd])
+	sq.usedRing = newUsedRing(queueSize, sq.buf[usedRingStart:usedRingEnd])
+
+	sq.kickEventFD, err = eventfd.New()
+	if err != nil {
+		return nil, fmt.Errorf("create kick event file descriptor: %w", err)
+	}
+	sq.callEventFD, err = eventfd.New()
+	if err != nil {
+		return nil, fmt.Errorf("create call event file descriptor: %w", err)
+	}
+
+	if err = sq.descriptorTable.initializeDescriptors(); err != nil {
+		return nil, fmt.Errorf("initialize descriptors: %w", err)
+	}
+
+	sq.epoll, err = eventfd.NewEpoll()
+	if err != nil {
+		return nil, err
+	}
+	err = sq.epoll.AddEvent(sq.callEventFD.FD())
+	if err != nil {
+		return nil, err
+	}
+
+	// Consume used buffer notifications in the background.
+	sq.stop = sq.startConsumeUsedRing()
+
+	return &sq, nil
+}
+
+// Size returns the size of this queue, which is the number of entries/buffers
+// this queue can hold.
+func (sq *SplitQueue) Size() int {
+	return sq.size
+}
+
+// DescriptorTable returns the [DescriptorTable] behind this queue.
+func (sq *SplitQueue) DescriptorTable() *DescriptorTable {
+	return sq.descriptorTable
+}
+
+// AvailableRing returns the [AvailableRing] behind this queue.
+func (sq *SplitQueue) AvailableRing() *AvailableRing {
+	return sq.availableRing
+}
+
+// UsedRing returns the [UsedRing] behind this queue.
+func (sq *SplitQueue) UsedRing() *UsedRing {
+	return sq.usedRing
+}
+
+// KickEventFD returns the kick event file descriptor behind this queue.
+// The returned file descriptor should be used with great care to not interfere
+// with this implementation.
+func (sq *SplitQueue) KickEventFD() int {
+	return sq.kickEventFD.FD()
+}
+
+// CallEventFD returns the call event file descriptor behind this queue.
+// The returned file descriptor should be used with great care to not interfere
+// with this implementation.
+func (sq *SplitQueue) CallEventFD() int {
+	return sq.callEventFD.FD()
+}
+
+// startConsumeUsedRing starts a goroutine that runs [consumeUsedRing].
+// A function is returned that can be used to gracefully cancel it. todo rename
+func (sq *SplitQueue) startConsumeUsedRing() func() error {
+	return func() error {
+
+		// The goroutine blocks until it receives a signal on the event file
+		// descriptor, so it will never notice the context being canceled.
+		// To resolve this, we can just produce a fake-signal ourselves to wake
+		// it up.
+		if err := sq.callEventFD.Kick(); err != nil {
+			return fmt.Errorf("wake up goroutine: %w", err)
+		}
+		return nil
+	}
+}
+
+// BlockAndGetHeads waits for the device to signal that it has used descriptor chains and returns all [UsedElement]s
+func (sq *SplitQueue) BlockAndGetHeads(ctx context.Context) ([]UsedElement, error) {
+	var n int
+	var err error
+	for ctx.Err() == nil {
+
+		// Wait for a signal from the device.
+		if n, err = sq.epoll.Block(); err != nil {
+			return nil, fmt.Errorf("wait: %w", err)
+		}
+		if n > 0 {
+			stillNeedToTake, out := sq.usedRing.take(-1)
+			sq.more = stillNeedToTake
+			if stillNeedToTake == 0 {
+				_ = sq.epoll.Clear() //???
+			}
+			return out, nil
+		}
+	}
+	return nil, ctx.Err()
+}
+
+func (sq *SplitQueue) TakeSingle(ctx context.Context) (uint16, error) {
+	var n int
+	var err error
+	for ctx.Err() == nil {
+		out, ok := sq.usedRing.takeOne()
+		if ok {
+			return out, nil
+		}
+		// Wait for a signal from the device.
+		if n, err = sq.epoll.Block(); err != nil {
+			return 0, fmt.Errorf("wait: %w", err)
+		}
+
+		if n > 0 {
+			out, ok = sq.usedRing.takeOne()
+			if ok {
+				_ = sq.epoll.Clear() //???
+				return out, nil
+			} else {
+				continue //???
+			}
+		}
+	}
+	return 0, ctx.Err()
+}
+
+func (sq *SplitQueue) BlockAndGetHeadsCapped(ctx context.Context, maxToTake int) ([]UsedElement, error) {
+	var n int
+	var err error
+	for ctx.Err() == nil {
+
+		//we have leftovers in the fridge
+		if sq.more > 0 {
+			stillNeedToTake, out := sq.usedRing.take(maxToTake)
+			sq.more = stillNeedToTake
+			return out, nil
+		}
+		//look inside the fridge
+		stillNeedToTake, out := sq.usedRing.take(maxToTake)
+		if len(out) > 0 {
+			sq.more = stillNeedToTake
+			return out, nil
+		}
+		//fridge is empty I guess
+
+		// Wait for a signal from the device.
+		if n, err = sq.epoll.Block(); err != nil {
+			return nil, fmt.Errorf("wait: %w", err)
+		}
+		if n > 0 {
+			_ = sq.epoll.Clear() //???
+			stillNeedToTake, out = sq.usedRing.take(maxToTake)
+			sq.more = stillNeedToTake
+			return out, nil
+		}
+	}
+
+	return nil, ctx.Err()
+}
+
+// OfferDescriptorChain offers a descriptor chain to the device which contains a
+// number of device-readable buffers (out buffers) and device-writable buffers
+// (in buffers).
+//
+// All buffers in the outBuffers slice will be concatenated by chaining
+// descriptors, one for each buffer in the slice. When a buffer is too large to
+// fit into a single descriptor (limited by the system's page size), it will be
+// split up into multiple descriptors within the chain.
+// When numInBuffers is greater than zero, the given number of device-writable
+// descriptors will be appended to the end of the chain, each referencing a
+// whole memory page (see [os.Getpagesize]).
+//
+// When the queue is full and no more descriptor chains can be added, a wrapped
+// [ErrNotEnoughFreeDescriptors] will be returned. If you set waitFree to true,
+// this method will handle this error and will block instead until there are
+// enough free descriptors again.
+//
+// After defining the descriptor chain in the [DescriptorTable], the index of
+// the head of the chain will be made available to the device using the
+// [AvailableRing] and will be returned by this method.
+// Callers should read from the [SplitQueue.UsedDescriptorChains] channel to be
+// notified when the descriptor chain was used by the device and should free the
+// used descriptor chains again using [SplitQueue.FreeDescriptorChain] when
+// they're done with them. When this does not happen, the queue will run full
+// and any further calls to [SplitQueue.OfferDescriptorChain] will stall.
+
+func (sq *SplitQueue) OfferInDescriptorChains() (uint16, error) {
+	// Create a descriptor chain for the given buffers.
+	var (
+		head uint16
+		err  error
+	)
+	for {
+		head, err = sq.descriptorTable.createDescriptorForInputs()
+		if err == nil {
+			break
+		}
+
+		// I don't wanna use errors.Is, it's slow
+		//goland:noinspection GoDirectComparisonOfErrors
+		if err == ErrNotEnoughFreeDescriptors {
+			return 0, err
+		} else {
+			return 0, fmt.Errorf("create descriptor chain: %w", err)
+		}
+	}
+
+	// Make the descriptor chain available to the device.
+	sq.availableRing.offerSingle(head)
+
+	// Notify the device to make it process the updated available ring.
+	if err := sq.kickEventFD.Kick(); err != nil {
+		return head, fmt.Errorf("notify device: %w", err)
+	}
+
+	return head, nil
+}
+
+func (sq *SplitQueue) OfferOutDescriptorChains(prepend []byte, outBuffers [][]byte) ([]uint16, error) {
+	// TODO change this
+	// Each descriptor can only hold a whole memory page, so split large out
+	// buffers into multiple smaller ones.
+	outBuffers = splitBuffers(outBuffers, sq.itemSize)
+
+	chains := make([]uint16, len(outBuffers))
+
+	// Create a descriptor chain for the given buffers.
+	var (
+		head uint16
+		err  error
+	)
+	for i := range outBuffers {
+		for {
+			bufs := [][]byte{prepend, outBuffers[i]}
+			head, err = sq.descriptorTable.createDescriptorChain(bufs, 0)
+			if err == nil {
+				break
+			}
+
+			// I don't wanna use errors.Is, it's slow
+			//goland:noinspection GoDirectComparisonOfErrors
+			if err == ErrNotEnoughFreeDescriptors {
+				// Wait for more free descriptors to be put back into the queue.
+				// If the number of free descriptors is still not sufficient, we'll
+				// land here again.
+				//todo should never happen
+				syscall.Syscall(syscall.SYS_SCHED_YIELD, 0, 0, 0) // Cheap barrier
+				continue
+			}
+			return nil, fmt.Errorf("create descriptor chain: %w", err)
+		}
+		chains[i] = head
+	}
+
+	// Make the descriptor chain available to the device.
+	sq.availableRing.offer(chains)
+
+	// Notify the device to make it process the updated available ring.
+	if err := sq.kickEventFD.Kick(); err != nil {
+		return chains, fmt.Errorf("notify device: %w", err)
+	}
+
+	return chains, nil
+}
+
+// GetDescriptorChain returns the device-readable buffers (out buffers) and
+// device-writable buffers (in buffers) of the descriptor chain with the given
+// head index.
+// The head index must be one that was returned by a previous call to
+// [SplitQueue.OfferDescriptorChain] and the descriptor chain must not have been
+// freed yet.
+//
+// Be careful to only access the returned buffer slices when the device is no
+// longer using them. They must not be accessed after
+// [SplitQueue.FreeDescriptorChain] has been called.
+func (sq *SplitQueue) GetDescriptorChain(head uint16) (outBuffers, inBuffers [][]byte, err error) {
+	return sq.descriptorTable.getDescriptorChain(head)
+}
+
+func (sq *SplitQueue) GetDescriptorItem(head uint16) ([]byte, error) {
+	sq.descriptorTable.descriptors[head].length = uint32(sq.descriptorTable.itemSize)
+	return sq.descriptorTable.getDescriptorItem(head)
+}
+
+func (sq *SplitQueue) GetDescriptorChainContents(head uint16, out []byte, maxLen int) (int, error) {
+	return sq.descriptorTable.getDescriptorChainContents(head, out, maxLen)
+}
+
+func (sq *SplitQueue) GetDescriptorInbuffers(head uint16, inBuffers *[][]byte) error {
+	return sq.descriptorTable.getDescriptorInbuffers(head, inBuffers)
+}
+
+// FreeDescriptorChain frees the descriptor chain with the given head index.
+// The head index must be one that was returned by a previous call to
+// [SplitQueue.OfferDescriptorChain] and the descriptor chain must not have been
+// freed yet.
+//
+// This creates new room in the queue which can be used by following
+// [SplitQueue.OfferDescriptorChain] calls.
+// When there are outstanding calls for [SplitQueue.OfferDescriptorChain] that
+// are waiting for free room in the queue, they may become unblocked by this.
+func (sq *SplitQueue) FreeDescriptorChain(head uint16) error {
+	//not called under lock
+	if err := sq.descriptorTable.freeDescriptorChain(head); err != nil {
+		return fmt.Errorf("free: %w", err)
+	}
+
+	return nil
+}
+
+func (sq *SplitQueue) SetDescSize(head uint16, sz int) {
+	//not called under lock
+	sq.descriptorTable.descriptors[int(head)].length = uint32(sz)
+}
+
+func (sq *SplitQueue) OfferDescriptorChains(chains []uint16, kick bool) error {
+	//todo not doing this may break eventually?
+	//not called under lock
+	//if err := sq.descriptorTable.freeDescriptorChain(head); err != nil {
+	//	return fmt.Errorf("free: %w", err)
+	//}
+
+	// Make the descriptor chain available to the device.
+	sq.availableRing.offer(chains)
+
+	// Notify the device to make it process the updated available ring.
+	if kick {
+		return sq.Kick()
+	}
+
+	return nil
+}
+
+func (sq *SplitQueue) Kick() error {
+	if err := sq.kickEventFD.Kick(); err != nil {
+		return fmt.Errorf("notify device: %w", err)
+	}
+	return nil
+}
+
+// Close releases all resources used for this queue.
+// The implementation will try to release as many resources as possible and
+// collect potential errors before returning them.
+func (sq *SplitQueue) Close() error {
+	var errs []error
+
+	if sq.stop != nil {
+		// This has to happen before the event file descriptors may be closed.
+		if err := sq.stop(); err != nil {
+			errs = append(errs, fmt.Errorf("stop consume used ring: %w", err))
+		}
+
+		// Make sure that this code block is executed only once.
+		sq.stop = nil
+	}
+
+	if err := sq.kickEventFD.Close(); err != nil {
+		errs = append(errs, fmt.Errorf("close kick event file descriptor: %w", err))
+	}
+	if err := sq.callEventFD.Close(); err != nil {
+		errs = append(errs, fmt.Errorf("close call event file descriptor: %w", err))
+	}
+
+	if err := sq.descriptorTable.releaseBuffers(); err != nil {
+		errs = append(errs, fmt.Errorf("release descriptor buffers: %w", err))
+	}
+
+	if sq.buf != nil {
+		if err := unix.Munmap(sq.buf); err == nil {
+			sq.buf = nil
+		} else {
+			errs = append(errs, fmt.Errorf("unmap virtqueue buffer: %w", err))
+		}
+	}
+
+	return errors.Join(errs...)
+}
+
+// ensureInitialized is used as a guard to prevent methods to be called on an
+// uninitialized instance.
+func (sq *SplitQueue) ensureInitialized() {
+	if sq.buf == nil {
+		panic("used ring is not initialized")
+	}
+}
+
+func align(index, alignment int) int {
+	remainder := index % alignment
+	if remainder == 0 {
+		return index
+	}
+	return index + alignment - remainder
+}
+
+// splitBuffers processes a list of buffers and splits each buffer that is
+// larger than the size limit into multiple smaller buffers.
+// If none of the buffers are too big though, do nothing, to avoid allocation for now
+func splitBuffers(buffers [][]byte, sizeLimit int) [][]byte {
+	for i := range buffers {
+		if len(buffers[i]) > sizeLimit {
+			return reallySplitBuffers(buffers, sizeLimit)
+		}
+	}
+	return buffers
+}
+
+func reallySplitBuffers(buffers [][]byte, sizeLimit int) [][]byte {
+	result := make([][]byte, 0, len(buffers))
+	for _, buffer := range buffers {
+		for added := 0; added < len(buffer); added += sizeLimit {
+			if len(buffer)-added <= sizeLimit {
+				result = append(result, buffer[added:])
+				break
+			}
+			result = append(result, buffer[added:added+sizeLimit])
+		}
+	}
+
+	return result
+}

overlay/virtqueue/split_virtqueue_internal_test.go

@@ -0,0 +1,105 @@
+package virtqueue
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestSplitQueue_MemoryAlignment(t *testing.T) {
+	tests := []struct {
+		name      string
+		queueSize int
+	}{
+		{
+			name:      "minimal queue size",
+			queueSize: 1,
+		},
+		{
+			name:      "small queue size",
+			queueSize: 8,
+		},
+		{
+			name:      "large queue size",
+			queueSize: 256,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			sq, err := NewSplitQueue(tt.queueSize)
+			require.NoError(t, err)
+
+			assert.Zero(t, sq.descriptorTable.Address()%descriptorTableAlignment)
+			assert.Zero(t, sq.availableRing.Address()%availableRingAlignment)
+			assert.Zero(t, sq.usedRing.Address()%usedRingAlignment)
+		})
+	}
+}
+
+func TestSplitBuffers(t *testing.T) {
+	const sizeLimit = 16
+	tests := []struct {
+		name     string
+		buffers  [][]byte
+		expected [][]byte
+	}{
+		{
+			name:     "no buffers",
+			buffers:  make([][]byte, 0),
+			expected: make([][]byte, 0),
+		},
+		{
+			name: "small",
+			buffers: [][]byte{
+				make([]byte, 11),
+			},
+			expected: [][]byte{
+				make([]byte, 11),
+			},
+		},
+		{
+			name: "exact size",
+			buffers: [][]byte{
+				make([]byte, sizeLimit),
+			},
+			expected: [][]byte{
+				make([]byte, sizeLimit),
+			},
+		},
+		{
+			name: "large",
+			buffers: [][]byte{
+				make([]byte, 42),
+			},
+			expected: [][]byte{
+				make([]byte, 16),
+				make([]byte, 16),
+				make([]byte, 10),
+			},
+		},
+		{
+			name: "mixed",
+			buffers: [][]byte{
+				make([]byte, 7),
+				make([]byte, 30),
+				make([]byte, 15),
+				make([]byte, 32),
+			},
+			expected: [][]byte{
+				make([]byte, 7),
+				make([]byte, 16),
+				make([]byte, 14),
+				make([]byte, 15),
+				make([]byte, 16),
+				make([]byte, 16),
+			},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			actual := splitBuffers(tt.buffers, sizeLimit)
+			assert.Equal(t, tt.expected, actual)
+		})
+	}
+}

overlay/virtqueue/used_element.go

@@ -0,0 +1,21 @@
+package virtqueue
+
+// usedElementSize is the number of bytes needed to store a [UsedElement] in
+// memory.
+const usedElementSize = 8
+
+// UsedElement is an element of the [UsedRing] and describes a descriptor chain
+// that was used by the device.
+type UsedElement struct {
+	// DescriptorIndex is the index of the head of the used descriptor chain in
+	// the [DescriptorTable].
+	// The index is 32-bit here for padding reasons.
+	DescriptorIndex uint32
+	// Length is the number of bytes written into the device writable portion of
+	// the buffer described by the descriptor chain.
+	Length uint32
+}
+
+func (u *UsedElement) GetHead() uint16 {
+	return uint16(u.DescriptorIndex)
+}

overlay/virtqueue/used_element_internal_test.go

@@ -0,0 +1,12 @@
+package virtqueue
+
+import (
+	"testing"
+	"unsafe"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestUsedElement_Size(t *testing.T) {
+	assert.EqualValues(t, usedElementSize, unsafe.Sizeof(UsedElement{}))
+}

overlay/virtqueue/used_ring.go

@@ -0,0 +1,184 @@
+package virtqueue
+
+import (
+	"fmt"
+	"unsafe"
+)
+
+// usedRingFlag is a flag that describes a [UsedRing].
+type usedRingFlag uint16
+
+const (
+	// usedRingFlagNoNotify is used by the host to advise the guest to not
+	// kick it when adding a buffer. It's unreliable, so it's simply an
+	// optimization. Guest will still kick when it's out of buffers.
+	usedRingFlagNoNotify usedRingFlag = 1 << iota
+)
+
+// usedRingSize is the number of bytes needed to store a [UsedRing] with the
+// given queue size in memory.
+func usedRingSize(queueSize int) int {
+	return 6 + usedElementSize*queueSize
+}
+
+// usedRingAlignment is the minimum alignment of a [UsedRing] in memory, as
+// required by the virtio spec.
+const usedRingAlignment = 4
+
+// UsedRing is where the device returns descriptor chains once it is done with
+// them. Each ring entry is a [UsedElement]. It is only written to by the device
+// and read by the driver.
+//
+// Because the size of the ring depends on the queue size, we cannot define a
+// Go struct with a static size that maps to the memory of the ring. Instead,
+// this struct only contains pointers to the corresponding memory areas.
+type UsedRing struct {
+	initialized bool
+
+	// flags that describe this ring.
+	flags *usedRingFlag
+	// ringIndex indicates where the device would put the next entry into the
+	// ring (modulo the queue size).
+	ringIndex *uint16
+	// ring contains the [UsedElement]s. It wraps around at queue size.
+	ring []UsedElement
+	// availableEvent is not used by this implementation, but we reserve it
+	// anyway to avoid issues in case a device may try to write to it, contrary
+	// to the virtio specification.
+	availableEvent *uint16
+
+	// lastIndex is the internal ringIndex up to which all [UsedElement]s were
+	// processed.
+	lastIndex uint16
+
+	//mu sync.Mutex
+}
+
+// newUsedRing creates a used ring that uses the given underlying memory. The
+// length of the memory slice must match the size needed for the ring (see
+// [usedRingSize]) for the given queue size.
+func newUsedRing(queueSize int, mem []byte) *UsedRing {
+	ringSize := usedRingSize(queueSize)
+	if len(mem) != ringSize {
+		panic(fmt.Sprintf("memory size (%v) does not match required size "+
+			"for used ring: %v", len(mem), ringSize))
+	}
+
+	r := UsedRing{
+		initialized:    true,
+		flags:          (*usedRingFlag)(unsafe.Pointer(&mem[0])),
+		ringIndex:      (*uint16)(unsafe.Pointer(&mem[2])),
+		ring:           unsafe.Slice((*UsedElement)(unsafe.Pointer(&mem[4])), queueSize),
+		availableEvent: (*uint16)(unsafe.Pointer(&mem[ringSize-2])),
+	}
+	r.lastIndex = *r.ringIndex
+	return &r
+}
+
+// Address returns the pointer to the beginning of the ring in memory.
+// Do not modify the memory directly to not interfere with this implementation.
+func (r *UsedRing) Address() uintptr {
+	if !r.initialized {
+		panic("used ring is not initialized")
+	}
+	return uintptr(unsafe.Pointer(r.flags))
+}
+
+// take returns all new [UsedElement]s that the device put into the ring and
+// that weren't already returned by a previous call to this method.
+// had a lock, I removed it
+func (r *UsedRing) take(maxToTake int) (int, []UsedElement) {
+	//r.mu.Lock()
+	//defer r.mu.Unlock()
+
+	ringIndex := *r.ringIndex
+	if ringIndex == r.lastIndex {
+		// Nothing new.
+		return 0, nil
+	}
+
+	// Calculate the number new used elements that we can read from the ring.
+	// The ring index may wrap, so special handling for that case is needed.
+	count := int(ringIndex - r.lastIndex)
+	if count < 0 {
+		count += 0xffff
+	}
+
+	stillNeedToTake := 0
+
+	if maxToTake > 0 {
+		stillNeedToTake = count - maxToTake
+		if stillNeedToTake < 0 {
+			stillNeedToTake = 0
+		}
+		count = min(count, maxToTake)
+	}
+
+	// The number of new elements can never exceed the queue size.
+	if count > len(r.ring) {
+		panic("used ring contains more new elements than the ring is long")
+	}
+
+	elems := make([]UsedElement, count)
+	for i := range count {
+		elems[i] = r.ring[r.lastIndex%uint16(len(r.ring))]
+		r.lastIndex++
+	}
+
+	return stillNeedToTake, elems
+}
+
+func (r *UsedRing) takeOne() (uint16, bool) {
+	//r.mu.Lock()
+	//defer r.mu.Unlock()
+
+	ringIndex := *r.ringIndex
+	if ringIndex == r.lastIndex {
+		// Nothing new.
+		return 0xffff, false
+	}
+
+	// Calculate the number new used elements that we can read from the ring.
+	// The ring index may wrap, so special handling for that case is needed.
+	count := int(ringIndex - r.lastIndex)
+	if count < 0 {
+		count += 0xffff
+	}
+
+	// The number of new elements can never exceed the queue size.
+	if count > len(r.ring) {
+		panic("used ring contains more new elements than the ring is long")
+	}
+
+	if count == 0 {
+		return 0xffff, false
+	}
+
+	out := r.ring[r.lastIndex%uint16(len(r.ring))].GetHead()
+	r.lastIndex++
+
+	return out, true
+}
+
+// InitOfferSingle is only used to pre-fill the used queue at startup, and should not be used if the device is running!
+func (r *UsedRing) InitOfferSingle(x uint16, size int) {
+	//always called under lock
+	//r.mu.Lock()
+	//defer r.mu.Unlock()
+
+	offset := 0
+	// Add descriptor chain heads to the ring.
+
+	// The 16-bit ring index may overflow. This is expected and is not an
+	// issue because the size of the ring array (which equals the queue
+	// size) is always a power of 2 and smaller than the highest possible
+	// 16-bit value.
+	insertIndex := int(*r.ringIndex+uint16(offset)) % len(r.ring)
+	r.ring[insertIndex] = UsedElement{
+		DescriptorIndex: uint32(x),
+		Length:          uint32(size),
+	}
+
+	// Increase the ring index by the number of descriptor chains added to the ring.
+	*r.ringIndex += 1
+}

overlay/virtqueue/used_ring_internal_test.go

@@ -0,0 +1,136 @@
+package virtqueue
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestUsedRing_MemoryLayout(t *testing.T) {
+	const queueSize = 2
+
+	memory := make([]byte, usedRingSize(queueSize))
+	r := newUsedRing(queueSize, memory)
+
+	*r.flags = 0x01ff
+	*r.ringIndex = 1
+	r.ring[0] = UsedElement{
+		DescriptorIndex: 0x0123,
+		Length:          0x4567,
+	}
+	r.ring[1] = UsedElement{
+		DescriptorIndex: 0x89ab,
+		Length:          0xcdef,
+	}
+
+	assert.Equal(t, []byte{
+		0xff, 0x01,
+		0x01, 0x00,
+		0x23, 0x01, 0x00, 0x00,
+		0x67, 0x45, 0x00, 0x00,
+		0xab, 0x89, 0x00, 0x00,
+		0xef, 0xcd, 0x00, 0x00,
+		0x00, 0x00,
+	}, memory)
+}
+
+//func TestUsedRing_Take(t *testing.T) {
+//	const queueSize = 8
+//
+//	tests := []struct {
+//		name      string
+//		ring      []UsedElement
+//		ringIndex uint16
+//		lastIndex uint16
+//		expected  []UsedElement
+//	}{
+//		{
+//			name: "nothing new",
+//			ring: []UsedElement{
+//				{DescriptorIndex: 1},
+//				{DescriptorIndex: 2},
+//				{DescriptorIndex: 3},
+//				{DescriptorIndex: 4},
+//				{},
+//				{},
+//				{},
+//				{},
+//			},
+//			ringIndex: 4,
+//			lastIndex: 4,
+//			expected:  nil,
+//		},
+//		{
+//			name: "no overflow",
+//			ring: []UsedElement{
+//				{DescriptorIndex: 1},
+//				{DescriptorIndex: 2},
+//				{DescriptorIndex: 3},
+//				{DescriptorIndex: 4},
+//				{},
+//				{},
+//				{},
+//				{},
+//			},
+//			ringIndex: 4,
+//			lastIndex: 1,
+//			expected: []UsedElement{
+//				{DescriptorIndex: 2},
+//				{DescriptorIndex: 3},
+//				{DescriptorIndex: 4},
+//			},
+//		},
+//		{
+//			name: "ring overflow",
+//			ring: []UsedElement{
+//				{DescriptorIndex: 9},
+//				{DescriptorIndex: 10},
+//				{DescriptorIndex: 3},
+//				{DescriptorIndex: 4},
+//				{DescriptorIndex: 5},
+//				{DescriptorIndex: 6},
+//				{DescriptorIndex: 7},
+//				{DescriptorIndex: 8},
+//			},
+//			ringIndex: 10,
+//			lastIndex: 7,
+//			expected: []UsedElement{
+//				{DescriptorIndex: 8},
+//				{DescriptorIndex: 9},
+//				{DescriptorIndex: 10},
+//			},
+//		},
+//		{
+//			name: "index overflow",
+//			ring: []UsedElement{
+//				{DescriptorIndex: 9},
+//				{DescriptorIndex: 10},
+//				{DescriptorIndex: 3},
+//				{DescriptorIndex: 4},
+//				{DescriptorIndex: 5},
+//				{DescriptorIndex: 6},
+//				{DescriptorIndex: 7},
+//				{DescriptorIndex: 8},
+//			},
+//			ringIndex: 2,
+//			lastIndex: 65535,
+//			expected: []UsedElement{
+//				{DescriptorIndex: 8},
+//				{DescriptorIndex: 9},
+//				{DescriptorIndex: 10},
+//			},
+//		},
+//	}
+//	for _, tt := range tests {
+//		t.Run(tt.name, func(t *testing.T) {
+//			memory := make([]byte, usedRingSize(queueSize))
+//			r := newUsedRing(queueSize, memory)
+//
+//			copy(r.ring, tt.ring)
+//			*r.ringIndex = tt.ringIndex
+//			r.lastIndex = tt.lastIndex
+//
+//			assert.Equal(t, tt.expected, r.take())
+//		})
+//	}
+//}

packet/outpacket.go

@@ -0,0 +1,70 @@
+package packet
+
+import (
+	"github.com/slackhq/nebula/util/virtio"
+	"golang.org/x/sys/unix"
+)
+
+type OutPacket struct {
+	Segments        [][]byte
+	SegmentPayloads [][]byte
+	SegmentHeaders  [][]byte
+	SegmentIDs      []uint16
+	//todo virtio header?
+	SegSize      int
+	SegCounter   int
+	Valid        bool
+	wasSegmented bool
+
+	Scratch []byte
+}
+
+func NewOut() *OutPacket {
+	out := new(OutPacket)
+	out.Segments = make([][]byte, 0, 64)
+	out.SegmentHeaders = make([][]byte, 0, 64)
+	out.SegmentPayloads = make([][]byte, 0, 64)
+	out.SegmentIDs = make([]uint16, 0, 64)
+	out.Scratch = make([]byte, Size)
+	return out
+}
+
+func (pkt *OutPacket) Reset() {
+	pkt.Segments = pkt.Segments[:0]
+	pkt.SegmentPayloads = pkt.SegmentPayloads[:0]
+	pkt.SegmentHeaders = pkt.SegmentHeaders[:0]
+	pkt.SegmentIDs = pkt.SegmentIDs[:0]
+	pkt.SegSize = 0
+	pkt.Valid = false
+	pkt.wasSegmented = false
+}
+
+func (pkt *OutPacket) UseSegment(segID uint16, seg []byte, isV6 bool) int {
+	pkt.Valid = true
+	pkt.SegmentIDs = append(pkt.SegmentIDs, segID)
+	pkt.Segments = append(pkt.Segments, seg) //todo do we need this?
+
+	vhdr := virtio.NetHdr{ //todo
+		Flags:      unix.VIRTIO_NET_HDR_F_DATA_VALID,
+		GSOType:    unix.VIRTIO_NET_HDR_GSO_NONE,
+		HdrLen:     0,
+		GSOSize:    0,
+		CsumStart:  0,
+		CsumOffset: 0,
+		NumBuffers: 0,
+	}
+
+	hdr := seg[0 : virtio.NetHdrSize+14]
+	_ = vhdr.Encode(hdr)
+	if isV6 {
+		hdr[virtio.NetHdrSize+14-2] = 0x86
+		hdr[virtio.NetHdrSize+14-1] = 0xdd
+	} else {
+		hdr[virtio.NetHdrSize+14-2] = 0x08
+		hdr[virtio.NetHdrSize+14-1] = 0x00
+	}
+
+	pkt.SegmentHeaders = append(pkt.SegmentHeaders, hdr)
+	pkt.SegmentPayloads = append(pkt.SegmentPayloads, seg[virtio.NetHdrSize+14:])
+	return len(pkt.SegmentIDs) - 1
+}

packet/packet.go

@@ -0,0 +1,119 @@
+package packet
+
+import (
+	"encoding/binary"
+	"iter"
+	"net/netip"
+	"slices"
+	"syscall"
+	"unsafe"
+
+	"golang.org/x/sys/unix"
+)
+
+const Size = 0xffff
+
+type Packet struct {
+	Payload []byte
+	Control []byte
+	Name    []byte
+	SegSize int
+
+	//todo should this hold out as well?
+	OutLen int
+
+	wasSegmented bool
+	isV4         bool
+}
+
+func New(isV4 bool) *Packet {
+	return &Packet{
+		Payload: make([]byte, Size),
+		Control: make([]byte, unix.CmsgSpace(2)),
+		Name:    make([]byte, unix.SizeofSockaddrInet6),
+		isV4:    isV4,
+	}
+}
+
+func (p *Packet) AddrPort() netip.AddrPort {
+	var ip netip.Addr
+	// Its ok to skip the ok check here, the slicing is the only error that can occur and it will panic
+	if p.isV4 {
+		ip, _ = netip.AddrFromSlice(p.Name[4:8])
+	} else {
+		ip, _ = netip.AddrFromSlice(p.Name[8:24])
+	}
+	return netip.AddrPortFrom(ip.Unmap(), binary.BigEndian.Uint16(p.Name[2:4]))
+}
+
+func (p *Packet) updateCtrl(ctrlLen int) {
+	p.SegSize = len(p.Payload)
+	p.wasSegmented = false
+	if ctrlLen == 0 {
+		return
+	}
+	if len(p.Control) == 0 {
+		return
+	}
+	cmsgs, err := unix.ParseSocketControlMessage(p.Control)
+	if err != nil {
+		return // oh well
+	}
+
+	for _, c := range cmsgs {
+		if c.Header.Level == unix.SOL_UDP && c.Header.Type == unix.UDP_GRO && len(c.Data) >= 2 {
+			p.wasSegmented = true
+			p.SegSize = int(binary.LittleEndian.Uint16(c.Data[:2]))
+			return
+		}
+	}
+}
+
+// Update sets a Packet into "just received, not processed" state
+func (p *Packet) Update(ctrlLen int) {
+	p.OutLen = -1
+	p.updateCtrl(ctrlLen)
+}
+
+func (p *Packet) SetSegSizeForTX() {
+	p.SegSize = len(p.Payload)
+	hdr := (*unix.Cmsghdr)(unsafe.Pointer(&p.Control[0]))
+	hdr.Level = unix.SOL_UDP
+	hdr.Type = unix.UDP_SEGMENT
+	hdr.SetLen(syscall.CmsgLen(2))
+	binary.NativeEndian.PutUint16(p.Control[unix.CmsgLen(0):unix.CmsgLen(0)+2], uint16(p.SegSize))
+}
+
+func (p *Packet) CompatibleForSegmentationWith(otherP *Packet, currentTotalSize int) bool {
+	//same dest
+	if !slices.Equal(p.Name, otherP.Name) {
+		return false
+	}
+
+	//don't get too big
+	if len(p.Payload)+currentTotalSize >= 0xffff {
+		return false
+	}
+
+	//same body len
+	//todo allow single different size at end
+	if len(p.Payload) != len(otherP.Payload) {
+		return false //todo technically you can cram one extra in
+	}
+	return true
+}
+
+func (p *Packet) Segments() iter.Seq[[]byte] {
+	return func(yield func([]byte) bool) {
+		//cursor := 0
+		for offset := 0; offset < len(p.Payload); offset += p.SegSize {
+			end := offset + p.SegSize
+			if end > len(p.Payload) {
+				end = len(p.Payload)
+			}
+			if !yield(p.Payload[offset:end]) {
+				return
+			}
+		}
+	}
+}

packet/virtio.go

@@ -0,0 +1,37 @@
+package packet
+
+import (
+	"github.com/slackhq/nebula/util/virtio"
+)
+
+type VirtIOPacket struct {
+	Payload   []byte
+	Header    virtio.NetHdr
+	Chains    []uint16
+	ChainRefs [][]byte
+	// OfferDescriptorChains(chains []uint16, kick bool) error
+}
+
+func NewVIO() *VirtIOPacket {
+	out := new(VirtIOPacket)
+	out.Payload = nil
+	out.ChainRefs = make([][]byte, 0, 4)
+	out.Chains = make([]uint16, 0, 8)
+	return out
+}
+
+func (v *VirtIOPacket) Reset() {
+	v.Payload = nil
+	v.ChainRefs = v.ChainRefs[:0]
+	v.Chains = v.Chains[:0]
+}
+
+type VirtIOTXPacket struct {
+	VirtIOPacket
+}
+
+func NewVIOTX(isV4 bool) *VirtIOTXPacket {
+	out := new(VirtIOTXPacket)
+	out.VirtIOPacket = *NewVIO()
+	return out
+}

pki.go

@@ -100,41 +100,36 @@ func (p *PKI) reloadCerts(c *config.C, initial bool) *util.ContextualError {
 		currentState := p.cs.Load()
 		if newState.v1Cert != nil {
 			if currentState.v1Cert == nil {
-				return util.NewContextualError("v1 certificate was added, restart required", nil, err)
-			}
-
+				//adding certs is fine, actually. Networks-in-common confirmed in newCertState().
+			} else {
 				// did IP in cert change? if so, don't set
 				if !slices.Equal(currentState.v1Cert.Networks(), newState.v1Cert.Networks()) {
 					return util.NewContextualError(
 						"Networks in new cert was different from old",
-					m{"new_networks": newState.v1Cert.Networks(), "old_networks": currentState.v1Cert.Networks()},
+						m{"new_networks": newState.v1Cert.Networks(), "old_networks": currentState.v1Cert.Networks(), "cert_version": cert.Version1},
 						nil,
 					)
 				}
 
 				if currentState.v1Cert.Curve() != newState.v1Cert.Curve() {
 					return util.NewContextualError(
-					"Curve in new cert was different from old",
-					m{"new_curve": newState.v1Cert.Curve(), "old_curve": currentState.v1Cert.Curve()},
+						"Curve in new v1 cert was different from old",
+						m{"new_curve": newState.v1Cert.Curve(), "old_curve": currentState.v1Cert.Curve(), "cert_version": cert.Version1},
 						nil,
 					)
 				}
-
-		} else if currentState.v1Cert != nil {
-			//TODO: CERT-V2 we should be able to tear this down
-			return util.NewContextualError("v1 certificate was removed, restart required", nil, err)
+			}
 		}
 
 		if newState.v2Cert != nil {
 			if currentState.v2Cert == nil {
-				return util.NewContextualError("v2 certificate was added, restart required", nil, err)
-			}
-
+				//adding certs is fine, actually
+			} else {
 				// did IP in cert change? if so, don't set
 				if !slices.Equal(currentState.v2Cert.Networks(), newState.v2Cert.Networks()) {
 					return util.NewContextualError(
 						"Networks in new cert was different from old",
-					m{"new_networks": newState.v2Cert.Networks(), "old_networks": currentState.v2Cert.Networks()},
+						m{"new_networks": newState.v2Cert.Networks(), "old_networks": currentState.v2Cert.Networks(), "cert_version": cert.Version2},
 						nil,
 					)
 				}
@@ -142,13 +137,25 @@ func (p *PKI) reloadCerts(c *config.C, initial bool) *util.ContextualError {
 				if currentState.v2Cert.Curve() != newState.v2Cert.Curve() {
 					return util.NewContextualError(
 						"Curve in new cert was different from old",
-					m{"new_curve": newState.v2Cert.Curve(), "old_curve": currentState.v2Cert.Curve()},
+						m{"new_curve": newState.v2Cert.Curve(), "old_curve": currentState.v2Cert.Curve(), "cert_version": cert.Version2},
 						nil,
 					)
 				}
+			}
 
 		} else if currentState.v2Cert != nil {
-			return util.NewContextualError("v2 certificate was removed, restart required", nil, err)
+			//newState.v1Cert is non-nil bc empty certstates aren't permitted
+			if newState.v1Cert == nil {
+				return util.NewContextualError("v1 and v2 certs are nil, this should be impossible", nil, err)
+			}
+			//if we're going to v1-only, we need to make sure we didn't orphan any v2-cert vpnaddrs
+			if !slices.Equal(currentState.v2Cert.Networks(), newState.v1Cert.Networks()) {
+				return util.NewContextualError(
+					"Removing a V2 cert is not permitted unless it has identical networks to the new V1 cert",
+					m{"new_v1_networks": newState.v1Cert.Networks(), "old_v2_networks": currentState.v2Cert.Networks()},
+					nil,
+				)
+			}
 		}
 
 		// Cipher cant be hot swapped so just leave it at what it was before
@@ -516,10 +523,14 @@ func loadCAPoolFromConfig(l *logrus.Logger, c *config.C) (*cert.CAPool, error) {
 		return nil, fmt.Errorf("error while adding CA certificate to CA trust store: %s", err)
 	}
 
-	for _, fp := range c.GetStringSlice("pki.blocklist", []string{}) {
-		l.WithField("fingerprint", fp).Info("Blocklisting cert")
+	bl := c.GetStringSlice("pki.blocklist", []string{})
+	if len(bl) > 0 {
+		for _, fp := range bl {
 			caPool.BlocklistFingerprint(fp)
 		}
 
+		l.WithField("fingerprintCount", len(bl)).Info("Blocklisted certificates")
+	}
+
 	return caPool, nil
 }

service/service_test.go

@@ -16,8 +16,8 @@ import (
 	"github.com/slackhq/nebula/cert_test"
 	"github.com/slackhq/nebula/config"
 	"github.com/slackhq/nebula/overlay"
+	"go.yaml.in/yaml/v3"
 	"golang.org/x/sync/errgroup"
-	"gopkg.in/yaml.v3"
 )
 
 type m = map[string]any

udp/conn.go

@@ -4,13 +4,13 @@ import (
 	"net/netip"
 
 	"github.com/slackhq/nebula/config"
+	"github.com/slackhq/nebula/packet"
 )
 
 const MTU = 9001
 
 type EncReader func(
-	addr netip.AddrPort,
-	payload []byte,
+	[]*packet.Packet,
 )
 
 type Conn interface {
@@ -19,6 +19,8 @@ type Conn interface {
 	ListenOut(r EncReader)
 	WriteTo(b []byte, addr netip.AddrPort) error
 	ReloadConfig(c *config.C)
+	Prep(pkt *packet.Packet, addr netip.AddrPort) error
+	WriteBatch(pkt []*packet.Packet) (int, error)
 	Close() error
 }
 

udp/udp_linux.go

@@ -14,22 +14,22 @@ import (
 	"github.com/rcrowley/go-metrics"
 	"github.com/sirupsen/logrus"
 	"github.com/slackhq/nebula/config"
+	"github.com/slackhq/nebula/packet"
 	"golang.org/x/sys/unix"
 )
 
+const iovMax = 128 //1024 //no unix constant for this? from limits.h
+//todo I'd like this to be 1024 but we seem to hit errors around ~130?
+
 type StdConn struct {
 	sysFd     int
 	isV4      bool
 	l         *logrus.Logger
 	batch     int
-}
+	enableGRO bool
 
-func maybeIPV4(ip net.IP) (net.IP, bool) {
-	ip4 := ip.To4()
-	if ip4 != nil {
-		return ip4, true
-	}
-	return ip, false
+	msgs []rawMessage
+	iovs [][]iovec
 }
 
 func NewListener(l *logrus.Logger, ip netip.Addr, port int, multi bool, batch int) (Conn, error) {
@@ -69,7 +69,20 @@ func NewListener(l *logrus.Logger, ip netip.Addr, port int, multi bool, batch in
 		return nil, fmt.Errorf("unable to bind to socket: %s", err)
 	}
 
-	return &StdConn{sysFd: fd, isV4: ip.Is4(), l: l, batch: batch}, err
+	const batchSize = 8192
+	msgs := make([]rawMessage, 0, batchSize) //todo configure
+	iovs := make([][]iovec, batchSize)
+	for i := range iovs {
+		iovs[i] = make([]iovec, iovMax)
+	}
+	return &StdConn{
+		sysFd: fd,
+		isV4:  ip.Is4(),
+		l:     l,
+		batch: batch,
+		msgs:  msgs,
+		iovs:  iovs,
+	}, err
 }
 
 func (u *StdConn) Rebind() error {
@@ -119,9 +132,7 @@ func (u *StdConn) LocalAddr() (netip.AddrPort, error) {
 }
 
 func (u *StdConn) ListenOut(r EncReader) {
-	var ip netip.Addr
-
-	msgs, buffers, names := u.PrepareRawMessages(u.batch)
+	msgs, packets := u.PrepareRawMessages(u.batch, u.isV4)
 	read := u.ReadMulti
 	if u.batch == 1 {
 		read = u.ReadSingle
@@ -135,13 +146,12 @@ func (u *StdConn) ListenOut(r EncReader) {
 		}
 
 		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
-			if u.isV4 {
-				ip, _ = netip.AddrFromSlice(names[i][4:8])
-			} else {
-				ip, _ = netip.AddrFromSlice(names[i][8:24])
+			packets[i].Payload = packets[i].Payload[:msgs[i].Len]
+			packets[i].Update(getRawMessageControlLen(&msgs[i]))
 		}
-			r(netip.AddrPortFrom(ip.Unmap(), binary.BigEndian.Uint16(names[i][2:4])), buffers[i][:msgs[i].Len])
+		r(packets[:n])
+		for i := 0; i < n; i++ { //todo reset this in prev loop, but this makes debug ez
+			msgs[i].Hdr.Controllen = uint64(unix.CmsgSpace(2))
 		}
 	}
 }
@@ -194,6 +204,147 @@ func (u *StdConn) WriteTo(b []byte, ip netip.AddrPort) error {
 	return u.writeTo6(b, ip)
 }
 
+func (u *StdConn) WriteToBatch(b []byte, ip netip.AddrPort) error {
+	if u.isV4 {
+		return u.writeTo4(b, ip)
+	}
+	return u.writeTo6(b, ip)
+}
+
+func (u *StdConn) Prep(pkt *packet.Packet, addr netip.AddrPort) error {
+	nl, err := u.encodeSockaddr(pkt.Name, addr)
+	if err != nil {
+		return err
+	}
+	pkt.Name = pkt.Name[:nl]
+	pkt.OutLen = len(pkt.Payload)
+	return nil
+}
+
+func (u *StdConn) WriteBatch(pkts []*packet.Packet) (int, error) {
+	if len(pkts) == 0 {
+		return 0, nil
+	}
+
+	u.msgs = u.msgs[:0]
+	//u.iovs = u.iovs[:0]
+
+	sent := 0
+	var mostRecentPkt *packet.Packet
+	mostRecentPktSize := 0
+	//segmenting := false
+	idx := 0
+	for _, pkt := range pkts {
+		if len(pkt.Payload) == 0 || pkt.OutLen == -1 {
+			sent++
+			continue
+		}
+		lastIdx := idx - 1
+		if mostRecentPkt != nil && pkt.CompatibleForSegmentationWith(mostRecentPkt, mostRecentPktSize) && u.msgs[lastIdx].Hdr.Iovlen < iovMax {
+			u.msgs[lastIdx].Hdr.Controllen = uint64(len(mostRecentPkt.Control))
+			u.msgs[lastIdx].Hdr.Control = &mostRecentPkt.Control[0]
+
+			u.iovs[lastIdx][u.msgs[lastIdx].Hdr.Iovlen].Base = &pkt.Payload[0]
+			u.iovs[lastIdx][u.msgs[lastIdx].Hdr.Iovlen].Len = uint64(len(pkt.Payload))
+			u.msgs[lastIdx].Hdr.Iovlen++
+
+			mostRecentPktSize += len(pkt.Payload)
+			mostRecentPkt.SetSegSizeForTX()
+		} else {
+			u.msgs = append(u.msgs, rawMessage{})
+			u.iovs[idx][0] = iovec{
+				Base: &pkt.Payload[0],
+				Len:  uint64(len(pkt.Payload)),
+			}
+
+			msg := &u.msgs[idx]
+			iov := &u.iovs[idx][0]
+			idx++
+
+			msg.Hdr.Iov = iov
+			msg.Hdr.Iovlen = 1
+			setRawMessageControl(msg, nil)
+			msg.Hdr.Flags = 0
+
+			msg.Hdr.Name = &pkt.Name[0]
+			msg.Hdr.Namelen = uint32(len(pkt.Name))
+			mostRecentPkt = pkt
+			mostRecentPktSize = len(pkt.Payload)
+		}
+	}
+
+	if len(u.msgs) == 0 {
+		return sent, nil
+	}
+
+	offset := 0
+	for offset < len(u.msgs) {
+		n, _, errno := unix.Syscall6(
+			unix.SYS_SENDMMSG,
+			uintptr(u.sysFd),
+			uintptr(unsafe.Pointer(&u.msgs[offset])),
+			uintptr(len(u.msgs)-offset),
+			0,
+			0,
+			0,
+		)
+
+		if errno != 0 {
+			if errno == unix.EINTR {
+				continue
+			}
+			//for i := 0; i < len(u.msgs); i++ {
+			//	for j := 0; j < int(u.msgs[i].Hdr.Iovlen); j++ {
+			//		u.l.WithFields(logrus.Fields{
+			//			"msg_index": i,
+			//			"iov idx":   j,
+			//			"iov":       fmt.Sprintf("%+v", u.iovs[i][j]),
+			//		}).Warn("failed to send message")
+			//	}
+			//
+			//}
+			u.l.WithFields(logrus.Fields{
+				"errno":   errno,
+				"idx":     idx,
+				"len":     len(u.msgs),
+				"deets":   fmt.Sprintf("%+v", u.msgs),
+				"lastIOV": fmt.Sprintf("%+v", u.iovs[len(u.msgs)-1][u.msgs[len(u.msgs)-1].Hdr.Iovlen-1]),
+			}).Error("failed to send message")
+			return sent + offset, &net.OpError{Op: "sendmmsg", Err: errno}
+		}
+
+		if n == 0 {
+			break
+		}
+		offset += int(n)
+	}
+
+	return sent + len(u.msgs), nil
+}
+
+func (u *StdConn) encodeSockaddr(dst []byte, addr netip.AddrPort) (uint32, error) {
+	if u.isV4 {
+		if !addr.Addr().Is4() {
+			return 0, fmt.Errorf("Listener is IPv4, but writing to IPv6 remote")
+		}
+		var sa unix.RawSockaddrInet4
+		sa.Family = unix.AF_INET
+		sa.Addr = addr.Addr().As4()
+		binary.BigEndian.PutUint16((*[2]byte)(unsafe.Pointer(&sa.Port))[:], addr.Port())
+		size := unix.SizeofSockaddrInet4
+		copy(dst[:size], (*(*[unix.SizeofSockaddrInet4]byte)(unsafe.Pointer(&sa)))[:])
+		return uint32(size), nil
+	}
+
+	var sa unix.RawSockaddrInet6
+	sa.Family = unix.AF_INET6
+	sa.Addr = addr.Addr().As16()
+	binary.BigEndian.PutUint16((*[2]byte)(unsafe.Pointer(&sa.Port))[:], addr.Port())
+	size := unix.SizeofSockaddrInet6
+	copy(dst[:size], (*(*[unix.SizeofSockaddrInet6]byte)(unsafe.Pointer(&sa)))[:])
+	return uint32(size), nil
+}
+
 func (u *StdConn) writeTo6(b []byte, ip netip.AddrPort) error {
 	var rsa unix.RawSockaddrInet6
 	rsa.Family = unix.AF_INET6
@@ -294,6 +445,27 @@ func (u *StdConn) ReloadConfig(c *config.C) {
 			u.l.WithError(err).Error("Failed to set listen.so_mark")
 		}
 	}
+	u.configureGRO(true)
+}
+
+func (u *StdConn) configureGRO(enable bool) {
+	if enable == u.enableGRO {
+		return
+	}
+
+	if enable {
+		if err := unix.SetsockoptInt(u.sysFd, unix.SOL_UDP, unix.UDP_GRO, 1); err != nil {
+			u.l.WithError(err).Warn("Failed to enable UDP GRO")
+			return
+		}
+		u.enableGRO = true
+		u.l.Info("UDP GRO enabled")
+	} else {
+		if err := unix.SetsockoptInt(u.sysFd, unix.SOL_UDP, unix.UDP_GRO, 0); err != nil && err != unix.ENOPROTOOPT {
+			u.l.WithError(err).Warn("Failed to disable UDP GRO")
+		}
+		u.enableGRO = false
+	}
 }
 
 func (u *StdConn) getMemInfo(meminfo *[unix.SK_MEMINFO_VARS]uint32) error {

udp/udp_linux_64.go

@@ -7,6 +7,7 @@
 package udp
 
 import (
+	"github.com/slackhq/nebula/packet"
 	"golang.org/x/sys/unix"
 )
 
@@ -33,25 +34,59 @@ type rawMessage struct {
 	Pad0 [4]byte
 }
 
-func (u *StdConn) PrepareRawMessages(n int) ([]rawMessage, [][]byte, [][]byte) {
+func setRawMessageControl(msg *rawMessage, buf []byte) {
+	if len(buf) == 0 {
+		msg.Hdr.Control = nil
+		msg.Hdr.Controllen = 0
+		return
+	}
+	msg.Hdr.Control = &buf[0]
+	msg.Hdr.Controllen = uint64(len(buf))
+}
+
+func getRawMessageControlLen(msg *rawMessage) int {
+	return int(msg.Hdr.Controllen)
+}
+
+func setCmsgLen(h *unix.Cmsghdr, l int) {
+	h.Len = uint64(l)
+}
+
+func (u *StdConn) PrepareRawMessages(n int, isV4 bool) ([]rawMessage, []*packet.Packet) {
 	msgs := make([]rawMessage, n)
-	buffers := make([][]byte, n)
-	names := make([][]byte, n)
+	packets := make([]*packet.Packet, n)
 
 	for i := range msgs {
-		buffers[i] = make([]byte, MTU)
-		names[i] = make([]byte, unix.SizeofSockaddrInet6)
+		packets[i] = packet.New(isV4)
 
 		vs := []iovec{
-			{Base: &buffers[i][0], Len: uint64(len(buffers[i]))},
+			{Base: &packets[i].Payload[0], Len: uint64(packet.Size)},
 		}
 
 		msgs[i].Hdr.Iov = &vs[0]
 		msgs[i].Hdr.Iovlen = uint64(len(vs))
 
-		msgs[i].Hdr.Name = &names[i][0]
-		msgs[i].Hdr.Namelen = uint32(len(names[i]))
+		msgs[i].Hdr.Name = &packets[i].Name[0]
+		msgs[i].Hdr.Namelen = uint32(len(packets[i].Name))
+
+		if u.enableGRO {
+			msgs[i].Hdr.Control = &packets[i].Control[0]
+			msgs[i].Hdr.Controllen = uint64(len(packets[i].Control))
+		} else {
+			msgs[i].Hdr.Control = nil
+			msgs[i].Hdr.Controllen = 0
+		}
 	}
 
-	return msgs, buffers, names
+	return msgs, packets
+}
+
+func setIovecSlice(iov *iovec, b []byte) {
+	if len(b) == 0 {
+		iov.Base = nil
+		iov.Len = 0
+		return
+	}
+	iov.Base = &b[0]
+	iov.Len = uint64(len(b))
 }

util/virtio/doc.go

@@ -0,0 +1,3 @@
+// Package virtio contains some generic types and concepts related to the virtio
+// protocol.
+package virtio

util/virtio/features.go

@@ -0,0 +1,136 @@
+package virtio
+
+// Feature contains feature bits that describe a virtio device or driver.
+type Feature uint64
+
+// Device-independent feature bits.
+//
+// Source: https://docs.oasis-open.org/virtio/virtio/v1.2/csd01/virtio-v1.2-csd01.html#x1-6600006
+const (
+	// FeatureIndirectDescriptors indicates that the driver can use descriptors
+	// with an additional layer of indirection.
+	FeatureIndirectDescriptors Feature = 1 << 28
+
+	// FeatureVersion1 indicates compliance with version 1.0 of the virtio
+	// specification.
+	FeatureVersion1 Feature = 1 << 32
+)
+
+// Feature bits for networking devices.
+//
+// Source: https://docs.oasis-open.org/virtio/virtio/v1.2/csd01/virtio-v1.2-csd01.html#x1-2200003
+const (
+	// FeatureNetDeviceCsum indicates that the device can handle packets with
+	// partial checksum (checksum offload).
+	FeatureNetDeviceCsum Feature = 1 << 0
+
+	// FeatureNetDriverCsum indicates that the driver can handle packets with
+	// partial checksum.
+	FeatureNetDriverCsum Feature = 1 << 1
+
+	// FeatureNetCtrlDriverOffloads indicates support for dynamic offload state
+	// reconfiguration.
+	FeatureNetCtrlDriverOffloads Feature = 1 << 2
+
+	// FeatureNetMTU indicates that the device reports a maximum MTU value.
+	FeatureNetMTU Feature = 1 << 3
+
+	// FeatureNetMAC indicates that the device provides a MAC address.
+	FeatureNetMAC Feature = 1 << 5
+
+	// FeatureNetDriverTSO4 indicates that the driver supports the TCP
+	// segmentation offload for received IPv4 packets.
+	FeatureNetDriverTSO4 Feature = 1 << 7
+
+	// FeatureNetDriverTSO6 indicates that the driver supports the TCP
+	// segmentation offload for received IPv6 packets.
+	FeatureNetDriverTSO6 Feature = 1 << 8
+
+	// FeatureNetDriverECN indicates that the driver supports the TCP
+	// segmentation offload with ECN for received packets.
+	FeatureNetDriverECN Feature = 1 << 9
+
+	// FeatureNetDriverUFO indicates that the driver supports the UDP
+	// fragmentation offload for received packets.
+	FeatureNetDriverUFO Feature = 1 << 10
+
+	// FeatureNetDeviceTSO4 indicates that the device supports the TCP
+	// segmentation offload for received IPv4 packets.
+	FeatureNetDeviceTSO4 Feature = 1 << 11
+
+	// FeatureNetDeviceTSO6 indicates that the device supports the TCP
+	// segmentation offload for received IPv6 packets.
+	FeatureNetDeviceTSO6 Feature = 1 << 12
+
+	// FeatureNetDeviceECN indicates that the device supports the TCP
+	// segmentation offload with ECN for received packets.
+	FeatureNetDeviceECN Feature = 1 << 13
+
+	// FeatureNetDeviceUFO indicates that the device supports the UDP
+	// fragmentation offload for received packets.
+	FeatureNetDeviceUFO Feature = 1 << 14
+
+	// FeatureNetMergeRXBuffers indicates that the driver can handle merged
+	// receive buffers.
+	// When this feature is negotiated, devices may merge multiple descriptor
+	// chains together to transport large received packets. [NetHdr.NumBuffers]
+	// will then contain the number of merged descriptor chains.
+	FeatureNetMergeRXBuffers Feature = 1 << 15
+
+	// FeatureNetStatus indicates that the device configuration status field is
+	// available.
+	FeatureNetStatus Feature = 1 << 16
+
+	// FeatureNetCtrlVQ indicates that a control channel virtqueue is
+	// available.
+	FeatureNetCtrlVQ Feature = 1 << 17
+
+	// FeatureNetCtrlRX indicates support for RX mode control (e.g. promiscuous
+	// or all-multicast) for packet receive filtering.
+	FeatureNetCtrlRX Feature = 1 << 18
+
+	// FeatureNetCtrlVLAN indicates support for VLAN filtering through the
+	// control channel.
+	FeatureNetCtrlVLAN Feature = 1 << 19
+
+	// FeatureNetDriverAnnounce indicates that the driver can send gratuitous
+	// packets.
+	FeatureNetDriverAnnounce Feature = 1 << 21
+
+	// FeatureNetMQ indicates that the device supports multiqueue with automatic
+	// receive steering.
+	FeatureNetMQ Feature = 1 << 22
+
+	// FeatureNetCtrlMACAddr indicates that the MAC address can be set through
+	// the control channel.
+	FeatureNetCtrlMACAddr Feature = 1 << 23
+
+	// FeatureNetDeviceUSO indicates that the device supports the UDP
+	// segmentation offload for received packets.
+	FeatureNetDeviceUSO Feature = 1 << 56
+
+	// FeatureNetHashReport indicates that the device can report a per-packet
+	// hash value and type.
+	FeatureNetHashReport Feature = 1 << 57
+
+	// FeatureNetDriverHdrLen indicates that the driver can provide the exact
+	// header length value (see [NetHdr.HdrLen]).
+	// Devices may benefit from knowing the exact header length.
+	FeatureNetDriverHdrLen Feature = 1 << 59
+
+	// FeatureNetRSS indicates that the device supports RSS (receive-side
+	// scaling) with configurable hash parameters.
+	FeatureNetRSS Feature = 1 << 60
+
+	// FeatureNetRSCExt indicates that the device can process duplicated ACKs
+	// and report the number of coalesced segments and duplicated ACKs.
+	FeatureNetRSCExt Feature = 1 << 61
+
+	// FeatureNetStandby indicates that the device may act as a standby for a
+	// primary device with the same MAC address.
+	FeatureNetStandby Feature = 1 << 62
+
+	// FeatureNetSpeedDuplex indicates that the device can report link speed and
+	// duplex mode.
+	FeatureNetSpeedDuplex Feature = 1 << 63
+)

util/virtio/net_hdr.go

@@ -0,0 +1,77 @@
+package virtio
+
+import (
+	"errors"
+	"unsafe"
+
+	"golang.org/x/sys/unix"
+)
+
+// Workaround to make Go doc links work.
+var _ unix.Errno
+
+// NetHdrSize is the number of bytes needed to store a [NetHdr] in memory.
+const NetHdrSize = 12
+
+// ErrNetHdrBufferTooSmall is returned when a buffer is too small to fit a
+// virtio_net_hdr.
+var ErrNetHdrBufferTooSmall = errors.New("the buffer is too small to fit a virtio_net_hdr")
+
+// NetHdr defines the virtio_net_hdr as described by the virtio specification.
+type NetHdr struct {
+	// Flags that describe the packet.
+	// Possible values are:
+	//   - [unix.VIRTIO_NET_HDR_F_NEEDS_CSUM]
+	//   - [unix.VIRTIO_NET_HDR_F_DATA_VALID]
+	//   - [unix.VIRTIO_NET_HDR_F_RSC_INFO]
+	Flags uint8
+	// GSOType contains the type of segmentation offload that should be used for
+	// the packet.
+	// Possible values are:
+	//   - [unix.VIRTIO_NET_HDR_GSO_NONE]
+	//   - [unix.VIRTIO_NET_HDR_GSO_TCPV4]
+	//   - [unix.VIRTIO_NET_HDR_GSO_UDP]
+	//   - [unix.VIRTIO_NET_HDR_GSO_TCPV6]
+	//   - [unix.VIRTIO_NET_HDR_GSO_UDP_L4]
+	//   - [unix.VIRTIO_NET_HDR_GSO_ECN]
+	GSOType uint8
+	// HdrLen contains the length of the headers that need to be replicated by
+	// segmentation offloads. It's the number of bytes from the beginning of the
+	// packet to the beginning of the transport payload.
+	// Only used when [FeatureNetDriverHdrLen] is negotiated.
+	HdrLen uint16
+	// GSOSize contains the maximum size of each segmented packet beyond the
+	// header (payload size). In case of TCP, this is the MSS.
+	GSOSize uint16
+	// CsumStart contains the offset within the packet from which on the
+	// checksum should be computed.
+	CsumStart uint16
+	// CsumOffset specifies how many bytes after [NetHdr.CsumStart] the computed
+	// 16-bit checksum should be inserted.
+	CsumOffset uint16
+	// NumBuffers contains the number of merged descriptor chains when
+	// [FeatureNetMergeRXBuffers] is negotiated.
+	// This field is only used for packets received by the driver and should be
+	// zero for transmitted packets.
+	NumBuffers uint16
+}
+
+// Decode decodes the [NetHdr] from the given byte slice. The slice must contain
+// at least [NetHdrSize] bytes.
+func (v *NetHdr) Decode(data []byte) error {
+	if len(data) < NetHdrSize {
+		return ErrNetHdrBufferTooSmall
+	}
+	copy(unsafe.Slice((*byte)(unsafe.Pointer(v)), NetHdrSize), data[:NetHdrSize])
+	return nil
+}
+
+// Encode encodes the [NetHdr] into the given byte slice. The slice must have
+// room for at least [NetHdrSize] bytes.
+func (v *NetHdr) Encode(data []byte) error {
+	if len(data) < NetHdrSize {
+		return ErrNetHdrBufferTooSmall
+	}
+	copy(data[:NetHdrSize], unsafe.Slice((*byte)(unsafe.Pointer(v)), NetHdrSize))
+	return nil
+}

util/virtio/net_hdr_test.go

@@ -0,0 +1,43 @@
+package virtio
+
+import (
+	"testing"
+	"unsafe"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"golang.org/x/sys/unix"
+)
+
+func TestNetHdr_Size(t *testing.T) {
+	assert.EqualValues(t, NetHdrSize, unsafe.Sizeof(NetHdr{}))
+}
+
+func TestNetHdr_Encoding(t *testing.T) {
+	vnethdr := NetHdr{
+		Flags:      unix.VIRTIO_NET_HDR_F_NEEDS_CSUM,
+		GSOType:    unix.VIRTIO_NET_HDR_GSO_UDP_L4,
+		HdrLen:     42,
+		GSOSize:    1472,
+		CsumStart:  34,
+		CsumOffset: 6,
+		NumBuffers: 16,
+	}
+
+	buf := make([]byte, NetHdrSize)
+	require.NoError(t, vnethdr.Encode(buf))
+
+	assert.Equal(t, []byte{
+		0x01, 0x05,
+		0x2a, 0x00,
+		0xc0, 0x05,
+		0x22, 0x00,
+		0x06, 0x00,
+		0x10, 0x00,
+	}, buf)
+
+	var decoded NetHdr
+	require.NoError(t, decoded.Decode(buf))
+
+	assert.Equal(t, vnethdr, decoded)
+}