Experimenting

cert_test/cert.go

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

connection_manager.go

@@ -153,8 +153,8 @@ func (cm *connectionManager) Start(ctx context.Context) {
 	defer clockSource.Stop()
 
 	p := []byte("")
-	nb := make([]byte, 12, 12)
+	// Long-lived buf for the traffic-check goroutine; never released.
-	out := make([]byte, mtu)
+	buf := cm.intf.bufAlloc.Acquire()
 
 	for {
 		select {
@@ -169,13 +169,13 @@ func (cm *connectionManager) Start(ctx context.Context) {
 					break
 				}
 
-				cm.doTrafficCheck(localIndex, p, nb, out, now)
+				cm.doTrafficCheck(localIndex, p, buf, now)
 			}
 		}
 	}
 }
 
-func (cm *connectionManager) doTrafficCheck(localIndex uint32, p, nb, out []byte, now time.Time) {
+func (cm *connectionManager) doTrafficCheck(localIndex uint32, p []byte, buf *WireBuffer, now time.Time) {
 	decision, hostinfo, primary := cm.makeTrafficDecision(localIndex, now)
 
 	switch decision {
@@ -199,7 +199,7 @@ func (cm *connectionManager) doTrafficCheck(localIndex uint32, p, nb, out []byte
 		cm.tryRehandshake(hostinfo)
 
 	case sendTestPacket:
-		cm.intf.SendMessageToHostInfo(header.Test, header.TestRequest, hostinfo, p, nb, out)
+		cm.intf.SendMessageToHostInfo(header.Test, header.TestRequest, hostinfo, p, buf)
 	}
 
 	cm.resetRelayTrafficCheck(hostinfo)
@@ -308,7 +308,9 @@ func (cm *connectionManager) migrateRelayUsed(oldhostinfo, newhostinfo *HostInfo
 		if err != nil {
 			cm.l.Error("failed to marshal Control message to migrate relay", "error", err)
 		} else {
-			cm.intf.SendMessageToHostInfo(header.Control, 0, newhostinfo, msg, make([]byte, 12), make([]byte, mtu))
+			migBuf := cm.intf.bufAlloc.Acquire()
+			cm.intf.SendMessageToHostInfo(header.Control, 0, newhostinfo, msg, migBuf)
+			cm.intf.bufAlloc.Release(migBuf)
 			cm.l.Info("send CreateRelayRequest",
 				"relayFrom", req.RelayFromAddr,
 				"relayTo", req.RelayToAddr,

connection_manager_test.go

@@ -7,7 +7,6 @@ import (
 	"testing"
 	"time"
 
-	"github.com/flynn/noise"
 	"github.com/slackhq/nebula/cert"
 	"github.com/slackhq/nebula/config"
 	"github.com/slackhq/nebula/overlay/overlaytest"
@@ -47,7 +46,7 @@ func Test_NewConnectionManagerTest(t *testing.T) {
 		initiatingVersion: cert.Version1,
 		privateKey:        []byte{},
 		v1Cert:            &dummyCert{version: cert.Version1},
-		v1HandshakeBytes:  []byte{},
+		v1Credential:      nil,
 	}
 
 	lh := newTestLighthouse()
@@ -68,9 +67,9 @@ func Test_NewConnectionManagerTest(t *testing.T) {
 	punchy := NewPunchyFromConfig(test.NewLogger(), conf)
 	nc := newConnectionManagerFromConfig(test.NewLogger(), conf, hostMap, punchy)
 	nc.intf = ifce
+
 	p := []byte("")
-	nb := make([]byte, 12, 12)
+	buf := NewWireBuffer(mtu, 0)
-	out := make([]byte, mtu)
 
 	// Add an ip we have established a connection w/ to hostmap
 	hostinfo := &HostInfo{
@@ -80,7 +79,6 @@ func Test_NewConnectionManagerTest(t *testing.T) {
 	}
 	hostinfo.ConnectionState = &ConnectionState{
 		myCert: &dummyCert{version: cert.Version1},
-		H:      &noise.HandshakeState{},
 	}
 	nc.hostMap.unlockedAddHostInfo(hostinfo, ifce)
 
@@ -94,7 +92,7 @@ func Test_NewConnectionManagerTest(t *testing.T) {
 	assert.True(t, hostinfo.in.Load())
 
 	// Do a traffic check tick, should not be pending deletion but should not have any in/out packets recorded
-	nc.doTrafficCheck(hostinfo.localIndexId, p, nb, out, time.Now())
+	nc.doTrafficCheck(hostinfo.localIndexId, p, buf, time.Now())
 	assert.False(t, hostinfo.pendingDeletion.Load())
 	assert.False(t, hostinfo.out.Load())
 	assert.False(t, hostinfo.in.Load())
@@ -102,7 +100,7 @@ func Test_NewConnectionManagerTest(t *testing.T) {
 	// Do another traffic check tick, this host should be pending deletion now
 	nc.Out(hostinfo)
 	assert.True(t, hostinfo.out.Load())
-	nc.doTrafficCheck(hostinfo.localIndexId, p, nb, out, time.Now())
+	nc.doTrafficCheck(hostinfo.localIndexId, p, buf, time.Now())
 	assert.True(t, hostinfo.pendingDeletion.Load())
 	assert.False(t, hostinfo.out.Load())
 	assert.False(t, hostinfo.in.Load())
@@ -110,7 +108,7 @@ func Test_NewConnectionManagerTest(t *testing.T) {
 	assert.Contains(t, nc.hostMap.Hosts, hostinfo.vpnAddrs[0])
 
 	// Do a final traffic check tick, the host should now be removed
-	nc.doTrafficCheck(hostinfo.localIndexId, p, nb, out, time.Now())
+	nc.doTrafficCheck(hostinfo.localIndexId, p, buf, time.Now())
 	assert.NotContains(t, nc.hostMap.Hosts, hostinfo.vpnAddrs)
 	assert.NotContains(t, nc.hostMap.Indexes, hostinfo.localIndexId)
 }
@@ -130,7 +128,7 @@ func Test_NewConnectionManagerTest2(t *testing.T) {
 		initiatingVersion: cert.Version1,
 		privateKey:        []byte{},
 		v1Cert:            &dummyCert{version: cert.Version1},
-		v1HandshakeBytes:  []byte{},
+		v1Credential:      nil,
 	}
 
 	lh := newTestLighthouse()
@@ -151,9 +149,9 @@ func Test_NewConnectionManagerTest2(t *testing.T) {
 	punchy := NewPunchyFromConfig(test.NewLogger(), conf)
 	nc := newConnectionManagerFromConfig(test.NewLogger(), conf, hostMap, punchy)
 	nc.intf = ifce
+
 	p := []byte("")
-	nb := make([]byte, 12, 12)
+	buf := NewWireBuffer(mtu, 0)
-	out := make([]byte, mtu)
 
 	// Add an ip we have established a connection w/ to hostmap
 	hostinfo := &HostInfo{
@@ -163,7 +161,6 @@ func Test_NewConnectionManagerTest2(t *testing.T) {
 	}
 	hostinfo.ConnectionState = &ConnectionState{
 		myCert: &dummyCert{version: cert.Version1},
-		H:      &noise.HandshakeState{},
 	}
 	nc.hostMap.unlockedAddHostInfo(hostinfo, ifce)
 
@@ -177,14 +174,14 @@ func Test_NewConnectionManagerTest2(t *testing.T) {
 	assert.Contains(t, nc.hostMap.Indexes, hostinfo.localIndexId)
 
 	// Do a traffic check tick, should not be pending deletion but should not have any in/out packets recorded
-	nc.doTrafficCheck(hostinfo.localIndexId, p, nb, out, time.Now())
+	nc.doTrafficCheck(hostinfo.localIndexId, p, buf, time.Now())
 	assert.False(t, hostinfo.pendingDeletion.Load())
 	assert.False(t, hostinfo.out.Load())
 	assert.False(t, hostinfo.in.Load())
 
 	// Do another traffic check tick, this host should be pending deletion now
 	nc.Out(hostinfo)
-	nc.doTrafficCheck(hostinfo.localIndexId, p, nb, out, time.Now())
+	nc.doTrafficCheck(hostinfo.localIndexId, p, buf, time.Now())
 	assert.True(t, hostinfo.pendingDeletion.Load())
 	assert.False(t, hostinfo.out.Load())
 	assert.False(t, hostinfo.in.Load())
@@ -193,7 +190,7 @@ func Test_NewConnectionManagerTest2(t *testing.T) {
 
 	// We saw traffic, should no longer be pending deletion
 	nc.In(hostinfo)
-	nc.doTrafficCheck(hostinfo.localIndexId, p, nb, out, time.Now())
+	nc.doTrafficCheck(hostinfo.localIndexId, p, buf, time.Now())
 	assert.False(t, hostinfo.pendingDeletion.Load())
 	assert.False(t, hostinfo.out.Load())
 	assert.False(t, hostinfo.in.Load())
@@ -215,7 +212,7 @@ func Test_NewConnectionManager_DisconnectInactive(t *testing.T) {
 		initiatingVersion: cert.Version1,
 		privateKey:        []byte{},
 		v1Cert:            &dummyCert{version: cert.Version1},
-		v1HandshakeBytes:  []byte{},
+		v1Credential:      nil,
 	}
 
 	lh := newTestLighthouse()
@@ -249,7 +246,6 @@ func Test_NewConnectionManager_DisconnectInactive(t *testing.T) {
 	}
 	hostinfo.ConnectionState = &ConnectionState{
 		myCert: &dummyCert{version: cert.Version1},
-		H:      &noise.HandshakeState{},
 	}
 	nc.hostMap.unlockedAddHostInfo(hostinfo, ifce)
 
@@ -342,7 +338,7 @@ func Test_NewConnectionManagerTest_DisconnectInvalid(t *testing.T) {
 	cs := &CertState{
 		privateKey:   []byte{},
 		v1Cert:       &dummyCert{},
-		v1HandshakeBytes: []byte{},
+		v1Credential: nil,
 	}
 
 	lh := newTestLighthouse()
@@ -372,7 +368,6 @@ func Test_NewConnectionManagerTest_DisconnectInvalid(t *testing.T) {
 		ConnectionState: &ConnectionState{
 			myCert:   &dummyCert{},
 			peerCert: cachedPeerCert,
-			H:        &noise.HandshakeState{},
 		},
 	}
 	nc.hostMap.unlockedAddHostInfo(hostinfo, ifce)

connection_state.go

@@ -1,15 +1,12 @@
 package nebula
 
 import (
-	"crypto/rand"
 	"encoding/json"
-	"fmt"
 	"sync"
 	"sync/atomic"
 
-	"github.com/flynn/noise"
 	"github.com/slackhq/nebula/cert"
-	"github.com/slackhq/nebula/noiseutil"
+	"github.com/slackhq/nebula/handshake"
 )
 
 const ReplayWindow = 1024
@@ -17,7 +14,6 @@ const ReplayWindow = 1024
 type ConnectionState struct {
 	eKey           *NebulaCipherState
 	dKey           *NebulaCipherState
-	H              *noise.HandshakeState
 	myCert         cert.Certificate
 	peerCert       *cert.CachedCertificate
 	initiator      bool
@@ -26,55 +22,24 @@ type ConnectionState struct {
 	writeLock      sync.Mutex
 }
 
-func NewConnectionState(cs *CertState, crt cert.Certificate, initiator bool, pattern noise.HandshakePattern) (*ConnectionState, error) {
+// newConnectionStateFromResult builds a fully-populated ConnectionState from a
-	var dhFunc noise.DHFunc
+// completed handshake.Result. It seeds messageCounter and the replay window so
-	switch crt.Curve() {
+// that the post-handshake message indices already used on the wire don't count
-	case cert.Curve_CURVE25519:
+// as missed traffic in the data plane.
-		dhFunc = noise.DH25519
+func newConnectionStateFromResult(r *handshake.Result) *ConnectionState {
-	case cert.Curve_P256:
-		if cs.pkcs11Backed {
-			dhFunc = noiseutil.DHP256PKCS11
-		} else {
-			dhFunc = noiseutil.DHP256
-		}
-	default:
-		return nil, fmt.Errorf("invalid curve: %s", crt.Curve())
-	}
-
-	var ncs noise.CipherSuite
-	if cs.cipher == "chachapoly" {
-		ncs = noise.NewCipherSuite(dhFunc, noise.CipherChaChaPoly, noise.HashSHA256)
-	} else {
-		ncs = noise.NewCipherSuite(dhFunc, noiseutil.CipherAESGCM, noise.HashSHA256)
-	}
-
-	static := noise.DHKey{Private: cs.privateKey, Public: crt.PublicKey()}
-	hs, err := noise.NewHandshakeState(noise.Config{
-		CipherSuite:   ncs,
-		Random:        rand.Reader,
-		Pattern:       pattern,
-		Initiator:     initiator,
-		StaticKeypair: static,
-		//NOTE: These should come from CertState (pki.go) when we finally implement it
-		PresharedKey:          []byte{},
-		PresharedKeyPlacement: 0,
-	})
-	if err != nil {
-		return nil, fmt.Errorf("NewConnectionState: %s", err)
-	}
-
-	// The queue and ready params prevent a counter race that would happen when
-	// sending stored packets and simultaneously accepting new traffic.
 	ci := &ConnectionState{
-		H:         hs,
+		myCert:    r.MyCert,
-		initiator: initiator,
+		initiator: r.Initiator,
+		peerCert:  r.RemoteCert,
+		eKey:      NewNebulaCipherState(r.EKey),
+		dKey:      NewNebulaCipherState(r.DKey),
 		window:    NewBits(ReplayWindow),
-		myCert:    crt,
 	}
-	// always start the counter from 2, as packet 1 and packet 2 are handshake packets.
+	ci.messageCounter.Add(r.MessageIndex)
-	ci.messageCounter.Add(2)
+	for i := uint64(1); i <= r.MessageIndex; i++ {
-
+		ci.window.Update(nil, i)
-	return ci, nil
+	}
+	return ci
 }
 
 func (cs *ConnectionState) MarshalJSON() ([]byte, error) {

connection_state_test.go

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

control.go

@@ -278,15 +278,9 @@ func (c *Control) CloseTunnel(vpnIp netip.Addr, localOnly bool) bool {
 	}
 
 	if !localOnly {
-		c.f.send(
+		buf := c.f.bufAlloc.Acquire()
-			header.CloseTunnel,
+		c.f.send(header.CloseTunnel, 0, hostInfo.ConnectionState, hostInfo, []byte{}, buf)
-			0,
+		c.f.bufAlloc.Release(buf)
-			hostInfo.ConnectionState,
-			hostInfo,
-			[]byte{},
-			make([]byte, 12, 12),
-			make([]byte, mtu),
-		)
 	}
 
 	c.f.closeTunnel(hostInfo)
@@ -296,11 +290,14 @@ func (c *Control) CloseTunnel(vpnIp netip.Addr, localOnly bool) bool {
 // CloseAllTunnels is just like CloseTunnel except it goes through and shuts them all down, optionally you can avoid shutting down lighthouse tunnels
 // the int returned is a count of tunnels closed
 func (c *Control) CloseAllTunnels(excludeLighthouses bool) (closed int) {
+	// One WireBuffer for the whole shutdown loop.
+	buf := c.f.bufAlloc.Acquire()
+	defer c.f.bufAlloc.Release(buf)
 	shutdown := func(h *HostInfo) {
 		if excludeLighthouses && c.f.lightHouse.IsAnyLighthouseAddr(h.vpnAddrs) {
 			return
 		}
-		c.f.send(header.CloseTunnel, 0, h.ConnectionState, h, []byte{}, make([]byte, 12, 12), make([]byte, mtu))
+		c.f.send(header.CloseTunnel, 0, h.ConnectionState, h, []byte{}, buf)
 		c.f.closeTunnel(h)
 
 		c.l.Debug("Sending close tunnel message",

control_tester.go

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

e2e/bench_test.go

@@ -0,0 +1,68 @@
+//go:build e2e_testing
+// +build e2e_testing
+
+package e2e
+
+import (
+	"testing"
+	"time"
+
+	"github.com/slackhq/nebula/cert"
+	"github.com/slackhq/nebula/cert_test"
+	"github.com/slackhq/nebula/e2e/router"
+)
+
+// BenchmarkHandshake measures end-to-end tunnel establishment time. The two
+// nodes and the router are constructed once before the loop so the timed window
+// is just the handshake itself: trigger packet -> handshake1 -> handshake2 ->
+// cached packet replay -> arrival on the remote TUN. Between iterations we
+// tear down both sides locally (no CloseTunnel notification on the wire) and
+// re-inject the lighthouse address that closeTunnel cleared, so the next
+// iteration runs through a fresh handshake against the same harness.
+func BenchmarkHandshake(b *testing.B) {
+	ca, _, caKey, _ := cert_test.NewTestCaCert(cert.Version2, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
+
+	// Default try_interval is 100ms. The handshake manager schedules handshake1
+	// on its OutboundHandshakeTimer rather than firing immediately on trigger
+	// (the trigger channel only fast-paths static hosts), so a 100ms default
+	// drowns the actual handshake cost. Drop it to 1ms so the bench reflects
+	// the computation, not the wheel cadence.
+	bovr := m{"handshakes": m{"try_interval": "1ms"}}
+	myControl, myVpnIpNet, myUdpAddr, _ := newSimpleServer(cert.Version2, ca, caKey, "me", "10.128.0.1/24", bovr)
+	theirControl, theirVpnIpNet, theirUdpAddr, _ := newSimpleServer(cert.Version2, ca, caKey, "them", "10.128.0.2/24", bovr)
+
+	myControl.InjectLightHouseAddr(theirVpnIpNet[0].Addr(), theirUdpAddr)
+	theirControl.InjectLightHouseAddr(myVpnIpNet[0].Addr(), myUdpAddr)
+
+	myControl.Start()
+	theirControl.Start()
+	defer myControl.Stop()
+	defer theirControl.Stop()
+
+	r := router.NewR(b, myControl, theirControl)
+	r.CancelFlowLogs()
+	r.EnableFanIn()
+
+	trigger := BuildTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me"))
+
+	b.ReportAllocs()
+	b.ResetTimer()
+
+	for n := 0; n < b.N; n++ {
+		myControl.InjectTunPacket(trigger)
+		// RouteForAllUntilTxTun returns the moment the cached packet arrives at
+		// the remote TUN, which is also when both sides are fully established.
+		_ = r.RouteForAllUntilTxTun(theirControl)
+
+		b.StopTimer()
+		// Local-only close removes hostmap state on both sides without putting a
+		// CloseTunnel packet on the wire that we'd then have to drain. The
+		// closeTunnel path also clears learned lighthouse state for the peer
+		// when the last hostinfo for that addr goes away, so we re-inject.
+		myControl.CloseTunnel(theirVpnIpNet[0].Addr(), true)
+		theirControl.CloseTunnel(myVpnIpNet[0].Addr(), true)
+		myControl.InjectLightHouseAddr(theirVpnIpNet[0].Addr(), theirUdpAddr)
+		theirControl.InjectLightHouseAddr(myVpnIpNet[0].Addr(), myUdpAddr)
+		b.StartTimer()
+	}
+}

e2e/handshake_manager_test.go

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

e2e/handshakes_test.go

@@ -16,6 +16,7 @@ import (
 	"github.com/slackhq/nebula/cert_test"
 	"github.com/slackhq/nebula/e2e/router"
 	"github.com/slackhq/nebula/header"
+	"github.com/slackhq/nebula/overlay"
 	"github.com/slackhq/nebula/udp"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
@@ -39,11 +40,22 @@ func BenchmarkHotPath(b *testing.B) {
 	r.CancelFlowLogs()
 
 	assertTunnel(b, myVpnIpNet[0].Addr(), theirVpnIpNet[0].Addr(), myControl, theirControl, r)
+
+	// Pre-build the IP packet bytes once so the bench measures the data plane,
+	// not gopacket SerializeLayers overhead.
+	prebuilt := BuildTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me"))
+
+	// EnableFanIn switches the router to a 0-alloc routing path. Required
+	// for hot-path benchmarks; would conflict with GetFromUDP-using tests.
+	r.EnableFanIn()
+
 	b.ResetTimer()
 
 	for n := 0; n < b.N; n++ {
-		myControl.InjectTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me"))
+		myControl.InjectTunPacket(prebuilt)
-		_ = r.RouteForAllUntilTxTun(theirControl)
+		// Release the TUN-side bytes back to the harness freelist; the bench
+		// just confirms a packet arrived, the contents aren't inspected.
+		overlay.ReleaseTunBuf(r.RouteForAllUntilTxTun(theirControl))
 	}
 
 	myControl.Stop()
@@ -71,11 +83,15 @@ func BenchmarkHotPathRelay(b *testing.B) {
 	theirControl.Start()
 
 	assertTunnel(b, theirVpnIpNet[0].Addr(), myVpnIpNet[0].Addr(), theirControl, myControl, r)
+
+	prebuilt := BuildTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me"))
+	r.EnableFanIn()
+
 	b.ResetTimer()
 
 	for n := 0; n < b.N; n++ {
-		myControl.InjectTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me"))
+		myControl.InjectTunPacket(prebuilt)
-		_ = r.RouteForAllUntilTxTun(theirControl)
+		overlay.ReleaseTunBuf(r.RouteForAllUntilTxTun(theirControl))
 	}
 
 	myControl.Stop()
@@ -84,6 +100,7 @@ func BenchmarkHotPathRelay(b *testing.B) {
 }
 
 func TestGoodHandshake(t *testing.T) {
+	t.Parallel()
 	ca, _, caKey, _ := cert_test.NewTestCaCert(cert.Version1, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
 	myControl, myVpnIpNet, myUdpAddr, _ := newSimpleServer(cert.Version1, ca, caKey, "me", "10.128.0.1/24", nil)
 	theirControl, theirVpnIpNet, theirUdpAddr, _ := newSimpleServer(cert.Version1, ca, caKey, "them", "10.128.0.2/24", nil)
@@ -96,7 +113,7 @@ func TestGoodHandshake(t *testing.T) {
 	theirControl.Start()
 
 	t.Log("Send a udp packet through to begin standing up the tunnel, this should come out the other side")
-	myControl.InjectTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me"))
+	myControl.InjectTunPacket(BuildTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me")))
 
 	t.Log("Have them consume my stage 0 packet. They have a tunnel now")
 	theirControl.InjectUDPPacket(myControl.GetFromUDP(true))
@@ -134,6 +151,7 @@ func TestGoodHandshake(t *testing.T) {
 }
 
 func TestGoodHandshakeNoOverlap(t *testing.T) {
+	t.Parallel()
 	ca, _, caKey, _ := cert_test.NewTestCaCert(cert.Version2, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
 	myControl, myVpnIpNet, myUdpAddr, _ := newSimpleServer(cert.Version2, ca, caKey, "me", "10.128.0.1/24", nil)
 	theirControl, theirVpnIpNet, theirUdpAddr, _ := newSimpleServer(cert.Version2, ca, caKey, "them", "2001::69/24", nil) //look ma, cross-stack!
@@ -147,7 +165,7 @@ func TestGoodHandshakeNoOverlap(t *testing.T) {
 
 	empty := []byte{}
 	t.Log("do something to cause a handshake")
-	myControl.GetF().SendMessageToVpnAddr(header.Test, header.MessageNone, theirVpnIpNet[0].Addr(), empty, empty, empty)
+	myControl.GetF().SendMessageToVpnAddr(header.Test, header.MessageNone, theirVpnIpNet[0].Addr(), empty, nebula.NewWireBuffer(9001, 0))
 
 	t.Log("Have them consume my stage 0 packet. They have a tunnel now")
 	theirControl.InjectUDPPacket(myControl.GetFromUDP(true))
@@ -169,6 +187,7 @@ func TestGoodHandshakeNoOverlap(t *testing.T) {
 }
 
 func TestWrongResponderHandshake(t *testing.T) {
+	t.Parallel()
 	ca, _, caKey, _ := cert_test.NewTestCaCert(cert.Version1, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
 
 	myControl, myVpnIpNet, myUdpAddr, _ := newSimpleServer(cert.Version1, ca, caKey, "me", "10.128.0.100/24", nil)
@@ -188,7 +207,7 @@ func TestWrongResponderHandshake(t *testing.T) {
 	evilControl.Start()
 
 	t.Log("Start the handshake process, we will route until we see the evil tunnel closed")
-	myControl.InjectTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me"))
+	myControl.InjectTunPacket(BuildTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me")))
 
 	h := &header.H{}
 	r.RouteForAllExitFunc(func(p *udp.Packet, c *nebula.Control) router.ExitType {
@@ -245,6 +264,7 @@ func TestWrongResponderHandshake(t *testing.T) {
 }
 
 func TestWrongResponderHandshakeStaticHostMap(t *testing.T) {
+	t.Parallel()
 	ca, _, caKey, _ := cert_test.NewTestCaCert(cert.Version1, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
 
 	theirControl, theirVpnIpNet, theirUdpAddr, _ := newSimpleServer(cert.Version1, ca, caKey, "them", "10.128.0.99/24", nil)
@@ -269,7 +289,7 @@ func TestWrongResponderHandshakeStaticHostMap(t *testing.T) {
 	evilControl.Start()
 
 	t.Log("Start the handshake process, we will route until we see the evil tunnel closed")
-	myControl.InjectTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me"))
+	myControl.InjectTunPacket(BuildTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me")))
 
 	h := &header.H{}
 	r.RouteForAllExitFunc(func(p *udp.Packet, c *nebula.Control) router.ExitType {
@@ -327,6 +347,7 @@ func TestWrongResponderHandshakeStaticHostMap(t *testing.T) {
 }
 
 func TestStage1Race(t *testing.T) {
+	t.Parallel()
 	// This tests ensures that two hosts handshaking with each other at the same time will allow traffic to flow
 	// But will eventually collapse down to a single tunnel
 
@@ -347,8 +368,8 @@ func TestStage1Race(t *testing.T) {
 	theirControl.Start()
 
 	t.Log("Trigger a handshake to start on both me and them")
-	myControl.InjectTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me"))
+	myControl.InjectTunPacket(BuildTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me")))
-	theirControl.InjectTunUDPPacket(myVpnIpNet[0].Addr(), 80, theirVpnIpNet[0].Addr(), 80, []byte("Hi from them"))
+	theirControl.InjectTunPacket(BuildTunUDPPacket(myVpnIpNet[0].Addr(), 80, theirVpnIpNet[0].Addr(), 80, []byte("Hi from them")))
 
 	t.Log("Get both stage 1 handshake packets")
 	myHsForThem := myControl.GetFromUDP(true)
@@ -407,6 +428,7 @@ func TestStage1Race(t *testing.T) {
 }
 
 func TestUncleanShutdownRaceLoser(t *testing.T) {
+	t.Parallel()
 	ca, _, caKey, _ := cert_test.NewTestCaCert(cert.Version1, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
 	myControl, myVpnIpNet, myUdpAddr, _ := newSimpleServer(cert.Version1, ca, caKey, "me  ", "10.128.0.1/24", nil)
 	theirControl, theirVpnIpNet, theirUdpAddr, _ := newSimpleServer(cert.Version1, ca, caKey, "them", "10.128.0.2/24", nil)
@@ -424,7 +446,7 @@ func TestUncleanShutdownRaceLoser(t *testing.T) {
 	theirControl.Start()
 
 	r.Log("Trigger a handshake from me to them")
-	myControl.InjectTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me"))
+	myControl.InjectTunPacket(BuildTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me")))
 
 	p := r.RouteForAllUntilTxTun(theirControl)
 	assertUdpPacket(t, []byte("Hi from me"), p, myVpnIpNet[0].Addr(), theirVpnIpNet[0].Addr(), 80, 80)
@@ -435,7 +457,7 @@ func TestUncleanShutdownRaceLoser(t *testing.T) {
 	myHostmap.Indexes = map[uint32]*nebula.HostInfo{}
 	myHostmap.RemoteIndexes = map[uint32]*nebula.HostInfo{}
 
-	myControl.InjectTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me again"))
+	myControl.InjectTunPacket(BuildTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me again")))
 	p = r.RouteForAllUntilTxTun(theirControl)
 	assertUdpPacket(t, []byte("Hi from me again"), p, myVpnIpNet[0].Addr(), theirVpnIpNet[0].Addr(), 80, 80)
 
@@ -456,6 +478,7 @@ func TestUncleanShutdownRaceLoser(t *testing.T) {
 }
 
 func TestUncleanShutdownRaceWinner(t *testing.T) {
+	t.Parallel()
 	ca, _, caKey, _ := cert_test.NewTestCaCert(cert.Version1, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
 	myControl, myVpnIpNet, myUdpAddr, _ := newSimpleServer(cert.Version1, ca, caKey, "me  ", "10.128.0.1/24", nil)
 	theirControl, theirVpnIpNet, theirUdpAddr, _ := newSimpleServer(cert.Version1, ca, caKey, "them", "10.128.0.2/24", nil)
@@ -473,7 +496,7 @@ func TestUncleanShutdownRaceWinner(t *testing.T) {
 	theirControl.Start()
 
 	r.Log("Trigger a handshake from me to them")
-	myControl.InjectTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me"))
+	myControl.InjectTunPacket(BuildTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me")))
 
 	p := r.RouteForAllUntilTxTun(theirControl)
 	assertUdpPacket(t, []byte("Hi from me"), p, myVpnIpNet[0].Addr(), theirVpnIpNet[0].Addr(), 80, 80)
@@ -485,7 +508,7 @@ func TestUncleanShutdownRaceWinner(t *testing.T) {
 	theirHostmap.Indexes = map[uint32]*nebula.HostInfo{}
 	theirHostmap.RemoteIndexes = map[uint32]*nebula.HostInfo{}
 
-	theirControl.InjectTunUDPPacket(myVpnIpNet[0].Addr(), 80, theirVpnIpNet[0].Addr(), 80, []byte("Hi from them again"))
+	theirControl.InjectTunPacket(BuildTunUDPPacket(myVpnIpNet[0].Addr(), 80, theirVpnIpNet[0].Addr(), 80, []byte("Hi from them again")))
 	p = r.RouteForAllUntilTxTun(myControl)
 	assertUdpPacket(t, []byte("Hi from them again"), p, theirVpnIpNet[0].Addr(), myVpnIpNet[0].Addr(), 80, 80)
 	r.RenderHostmaps("Derp hostmaps", myControl, theirControl)
@@ -507,6 +530,7 @@ func TestUncleanShutdownRaceWinner(t *testing.T) {
 }
 
 func TestRelays(t *testing.T) {
+	t.Parallel()
 	ca, _, caKey, _ := cert_test.NewTestCaCert(cert.Version1, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
 	myControl, myVpnIpNet, _, _ := newSimpleServer(cert.Version1, ca, caKey, "me     ", "10.128.0.1/24", m{"relay": m{"use_relays": true}})
 	relayControl, relayVpnIpNet, relayUdpAddr, _ := newSimpleServer(cert.Version1, ca, caKey, "relay  ", "10.128.0.128/24", m{"relay": m{"am_relay": true}})
@@ -527,7 +551,7 @@ func TestRelays(t *testing.T) {
 	theirControl.Start()
 
 	t.Log("Trigger a handshake from me to them via the relay")
-	myControl.InjectTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me"))
+	myControl.InjectTunPacket(BuildTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me")))
 
 	p := r.RouteForAllUntilTxTun(theirControl)
 	r.Log("Assert the tunnel works")
@@ -536,6 +560,7 @@ func TestRelays(t *testing.T) {
 }
 
 func TestRelaysDontCareAboutIps(t *testing.T) {
+	t.Parallel()
 	ca, _, caKey, _ := cert_test.NewTestCaCert(cert.Version2, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
 	myControl, myVpnIpNet, _, _ := newSimpleServer(cert.Version2, ca, caKey, "me     ", "10.128.0.1/24", m{"relay": m{"use_relays": true}})
 	relayControl, relayVpnIpNet, relayUdpAddr, _ := newSimpleServer(cert.Version2, ca, caKey, "relay  ", "2001::9999/24", m{"relay": m{"am_relay": true}})
@@ -556,7 +581,7 @@ func TestRelaysDontCareAboutIps(t *testing.T) {
 	theirControl.Start()
 
 	t.Log("Trigger a handshake from me to them via the relay")
-	myControl.InjectTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me"))
+	myControl.InjectTunPacket(BuildTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me")))
 
 	p := r.RouteForAllUntilTxTun(theirControl)
 	r.Log("Assert the tunnel works")
@@ -565,6 +590,7 @@ func TestRelaysDontCareAboutIps(t *testing.T) {
 }
 
 func TestReestablishRelays(t *testing.T) {
+	t.Parallel()
 	ca, _, caKey, _ := cert_test.NewTestCaCert(cert.Version1, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
 	myControl, myVpnIpNet, _, _ := newSimpleServer(cert.Version1, ca, caKey, "me     ", "10.128.0.1/24", m{"relay": m{"use_relays": true}})
 	relayControl, relayVpnIpNet, relayUdpAddr, _ := newSimpleServer(cert.Version1, ca, caKey, "relay  ", "10.128.0.128/24", m{"relay": m{"am_relay": true}})
@@ -585,14 +611,14 @@ func TestReestablishRelays(t *testing.T) {
 	theirControl.Start()
 
 	t.Log("Trigger a handshake from me to them via the relay")
-	myControl.InjectTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me"))
+	myControl.InjectTunPacket(BuildTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me")))
 
 	p := r.RouteForAllUntilTxTun(theirControl)
 	r.Log("Assert the tunnel works")
 	assertUdpPacket(t, []byte("Hi from me"), p, myVpnIpNet[0].Addr(), theirVpnIpNet[0].Addr(), 80, 80)
 
 	t.Log("Ensure packet traversal from them to me via the relay")
-	theirControl.InjectTunUDPPacket(myVpnIpNet[0].Addr(), 80, theirVpnIpNet[0].Addr(), 80, []byte("Hi from them"))
+	theirControl.InjectTunPacket(BuildTunUDPPacket(myVpnIpNet[0].Addr(), 80, theirVpnIpNet[0].Addr(), 80, []byte("Hi from them")))
 
 	p = r.RouteForAllUntilTxTun(myControl)
 	r.Log("Assert the tunnel works")
@@ -607,7 +633,7 @@ func TestReestablishRelays(t *testing.T) {
 	for curIndexes >= start {
 		curIndexes = len(myControl.GetHostmap().Indexes)
 		r.Logf("Wait for the dead index to go away:start=%v indexes, current=%v indexes", start, curIndexes)
-		myControl.InjectTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me should fail"))
+		myControl.InjectTunPacket(BuildTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me should fail")))
 
 		r.RouteForAllExitFunc(func(p *udp.Packet, c *nebula.Control) router.ExitType {
 			return router.RouteAndExit
@@ -624,7 +650,7 @@ func TestReestablishRelays(t *testing.T) {
 		myControl.InjectLightHouseAddr(relayVpnIpNet[0].Addr(), relayUdpAddr)
 		myControl.InjectRelays(theirVpnIpNet[0].Addr(), []netip.Addr{relayVpnIpNet[0].Addr()})
 		relayControl.InjectLightHouseAddr(theirVpnIpNet[0].Addr(), theirUdpAddr)
-		myControl.InjectTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me"))
+		myControl.InjectTunPacket(BuildTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me")))
 
 		p = r.RouteForAllUntilTxTun(theirControl)
 		r.Log("Assert the tunnel works")
@@ -659,7 +685,7 @@ func TestReestablishRelays(t *testing.T) {
 	t.Log("Assert the tunnel works the other way, too")
 	for {
 		t.Log("RouteForAllUntilTxTun")
-		theirControl.InjectTunUDPPacket(myVpnIpNet[0].Addr(), 80, theirVpnIpNet[0].Addr(), 80, []byte("Hi from them"))
+		theirControl.InjectTunPacket(BuildTunUDPPacket(myVpnIpNet[0].Addr(), 80, theirVpnIpNet[0].Addr(), 80, []byte("Hi from them")))
 
 		p = r.RouteForAllUntilTxTun(myControl)
 		r.Log("Assert the tunnel works")
@@ -696,6 +722,7 @@ func TestReestablishRelays(t *testing.T) {
 }
 
 func TestStage1RaceRelays(t *testing.T) {
+	t.Parallel()
 	//NOTE: this is a race between me and relay resulting in a full tunnel from me to them via relay
 	ca, _, caKey, _ := cert_test.NewTestCaCert(cert.Version1, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
 	myControl, myVpnIpNet, myUdpAddr, _ := newSimpleServer(cert.Version1, ca, caKey, "me     ", "10.128.0.1/24", m{"relay": m{"use_relays": true}})
@@ -728,8 +755,8 @@ func TestStage1RaceRelays(t *testing.T) {
 	assertTunnel(t, theirVpnIpNet[0].Addr(), relayVpnIpNet[0].Addr(), theirControl, relayControl, r)
 
 	r.Log("Trigger a handshake from both them and me via relay to them and me")
-	myControl.InjectTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me"))
+	myControl.InjectTunPacket(BuildTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me")))
-	theirControl.InjectTunUDPPacket(myVpnIpNet[0].Addr(), 80, theirVpnIpNet[0].Addr(), 80, []byte("Hi from them"))
+	theirControl.InjectTunPacket(BuildTunUDPPacket(myVpnIpNet[0].Addr(), 80, theirVpnIpNet[0].Addr(), 80, []byte("Hi from them")))
 
 	r.Log("Wait for a packet from them to me")
 	p := r.RouteForAllUntilTxTun(myControl)
@@ -743,6 +770,7 @@ func TestStage1RaceRelays(t *testing.T) {
 }
 
 func TestStage1RaceRelays2(t *testing.T) {
+	t.Parallel()
 	//NOTE: this is a race between me and relay resulting in a full tunnel from me to them via relay
 	ca, _, caKey, _ := cert_test.NewTestCaCert(cert.Version1, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
 	myControl, myVpnIpNet, myUdpAddr, _ := newSimpleServer(cert.Version1, ca, caKey, "me     ", "10.128.0.1/24", m{"relay": m{"use_relays": true}})
@@ -775,8 +803,8 @@ func TestStage1RaceRelays2(t *testing.T) {
 	assertTunnel(t, theirVpnIpNet[0].Addr(), relayVpnIpNet[0].Addr(), theirControl, relayControl, r)
 
 	r.Log("Trigger a handshake from both them and me via relay to them and me")
-	myControl.InjectTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me"))
+	myControl.InjectTunPacket(BuildTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me")))
-	theirControl.InjectTunUDPPacket(myVpnIpNet[0].Addr(), 80, theirVpnIpNet[0].Addr(), 80, []byte("Hi from them"))
+	theirControl.InjectTunPacket(BuildTunUDPPacket(myVpnIpNet[0].Addr(), 80, theirVpnIpNet[0].Addr(), 80, []byte("Hi from them")))
 
 	//r.RouteUntilAfterMsgType(myControl, header.Control, header.MessageNone)
 	//r.RouteUntilAfterMsgType(theirControl, header.Control, header.MessageNone)
@@ -819,6 +847,7 @@ func TestStage1RaceRelays2(t *testing.T) {
 }
 
 func TestRehandshakingRelays(t *testing.T) {
+	t.Parallel()
 	ca, _, caKey, _ := cert_test.NewTestCaCert(cert.Version1, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
 	myControl, myVpnIpNet, _, _ := newSimpleServer(cert.Version1, ca, caKey, "me     ", "10.128.0.1/24", m{"relay": m{"use_relays": true}})
 	relayControl, relayVpnIpNet, relayUdpAddr, relayConfig := newSimpleServer(cert.Version1, ca, caKey, "relay  ", "10.128.0.128/24", m{"relay": m{"am_relay": true}})
@@ -839,7 +868,7 @@ func TestRehandshakingRelays(t *testing.T) {
 	theirControl.Start()
 
 	t.Log("Trigger a handshake from me to them via the relay")
-	myControl.InjectTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me"))
+	myControl.InjectTunPacket(BuildTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me")))
 
 	p := r.RouteForAllUntilTxTun(theirControl)
 	r.Log("Assert the tunnel works")
@@ -922,6 +951,7 @@ func TestRehandshakingRelays(t *testing.T) {
 }
 
 func TestRehandshakingRelaysPrimary(t *testing.T) {
+	t.Parallel()
 	// This test is the same as TestRehandshakingRelays but one of the terminal types is a primary swap winner
 	ca, _, caKey, _ := cert_test.NewTestCaCert(cert.Version1, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
 	myControl, myVpnIpNet, _, _ := newSimpleServer(cert.Version1, ca, caKey, "me     ", "10.128.0.128/24", m{"relay": m{"use_relays": true}})
@@ -943,7 +973,7 @@ func TestRehandshakingRelaysPrimary(t *testing.T) {
 	theirControl.Start()
 
 	t.Log("Trigger a handshake from me to them via the relay")
-	myControl.InjectTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me"))
+	myControl.InjectTunPacket(BuildTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me")))
 
 	p := r.RouteForAllUntilTxTun(theirControl)
 	r.Log("Assert the tunnel works")
@@ -1026,6 +1056,7 @@ func TestRehandshakingRelaysPrimary(t *testing.T) {
 }
 
 func TestRehandshaking(t *testing.T) {
+	t.Parallel()
 	ca, _, caKey, _ := cert_test.NewTestCaCert(cert.Version1, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
 	myControl, myVpnIpNet, myUdpAddr, myConfig := newSimpleServer(cert.Version1, ca, caKey, "me  ", "10.128.0.2/24", nil)
 	theirControl, theirVpnIpNet, theirUdpAddr, theirConfig := newSimpleServer(cert.Version1, ca, caKey, "them", "10.128.0.1/24", nil)
@@ -1121,6 +1152,7 @@ func TestRehandshaking(t *testing.T) {
 }
 
 func TestRehandshakingLoser(t *testing.T) {
+	t.Parallel()
 	// The purpose of this test is that the race loser renews their certificate and rehandshakes. The final tunnel
 	// Should be the one with the new certificate
 	ca, _, caKey, _ := cert_test.NewTestCaCert(cert.Version1, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
@@ -1219,6 +1251,7 @@ func TestRehandshakingLoser(t *testing.T) {
 }
 
 func TestRaceRegression(t *testing.T) {
+	t.Parallel()
 	// This test forces stage 1, stage 2, stage 1 to be received by me from them
 	// We had a bug where we were not finding the duplicate handshake and responding to the final stage 1 which
 	// caused a cross-linked hostinfo
@@ -1242,8 +1275,8 @@ func TestRaceRegression(t *testing.T) {
 	//them rx stage:2 initiatorIndex=120607833 responderIndex=4209862089
 
 	t.Log("Start both handshakes")
-	myControl.InjectTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me"))
+	myControl.InjectTunPacket(BuildTunUDPPacket(theirVpnIpNet[0].Addr(), 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me")))
-	theirControl.InjectTunUDPPacket(myVpnIpNet[0].Addr(), 80, theirVpnIpNet[0].Addr(), 80, []byte("Hi from them"))
+	theirControl.InjectTunPacket(BuildTunUDPPacket(myVpnIpNet[0].Addr(), 80, theirVpnIpNet[0].Addr(), 80, []byte("Hi from them")))
 
 	t.Log("Get both stage 1")
 	myStage1ForThem := myControl.GetFromUDP(true)
@@ -1279,6 +1312,7 @@ func TestRaceRegression(t *testing.T) {
 }
 
 func TestV2NonPrimaryWithLighthouse(t *testing.T) {
+	t.Parallel()
 	ca, _, caKey, _ := cert_test.NewTestCaCert(cert.Version2, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
 	lhControl, lhVpnIpNet, lhUdpAddr, _ := newSimpleServer(cert.Version2, ca, caKey, "lh  ", "10.128.0.1/24, ff::1/64", m{"lighthouse": m{"am_lighthouse": true}})
 
@@ -1319,6 +1353,7 @@ func TestV2NonPrimaryWithLighthouse(t *testing.T) {
 }
 
 func TestV2NonPrimaryWithOffNetLighthouse(t *testing.T) {
+	t.Parallel()
 	ca, _, caKey, _ := cert_test.NewTestCaCert(cert.Version2, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
 	lhControl, lhVpnIpNet, lhUdpAddr, _ := newSimpleServer(cert.Version2, ca, caKey, "lh  ", "2001::1/64", m{"lighthouse": m{"am_lighthouse": true}})
 
@@ -1359,6 +1394,7 @@ func TestV2NonPrimaryWithOffNetLighthouse(t *testing.T) {
 }
 
 func TestLighthouseUpdateOnReload(t *testing.T) {
+	t.Parallel()
 	ca, _, caKey, _ := cert_test.NewTestCaCert(cert.Version2, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
 
 	// Create the lighthouse
@@ -1434,6 +1470,7 @@ func TestLighthouseUpdateOnReload(t *testing.T) {
 }
 
 func TestGoodHandshakeUnsafeDest(t *testing.T) {
+	t.Parallel()
 	unsafePrefix := "192.168.6.0/24"
 	ca, _, caKey, _ := cert_test.NewTestCaCert(cert.Version2, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
 	theirControl, theirVpnIpNet, theirUdpAddr, _ := newSimpleServerWithUdpAndUnsafeNetworks(cert.Version2, ca, caKey, "spooky", "10.128.0.2/24", netip.MustParseAddrPort("10.64.0.2:4242"), unsafePrefix, nil)
@@ -1455,7 +1492,7 @@ func TestGoodHandshakeUnsafeDest(t *testing.T) {
 	theirControl.Start()
 
 	t.Log("Send a udp packet through to begin standing up the tunnel, this should come out the other side")
-	myControl.InjectTunUDPPacket(spookyDest, 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me"))
+	myControl.InjectTunPacket(BuildTunUDPPacket(spookyDest, 80, myVpnIpNet[0].Addr(), 80, []byte("Hi from me")))
 
 	t.Log("Have them consume my stage 0 packet. They have a tunnel now")
 	theirControl.InjectUDPPacket(myControl.GetFromUDP(true))
@@ -1483,7 +1520,7 @@ func TestGoodHandshakeUnsafeDest(t *testing.T) {
 	assertUdpPacket(t, []byte("Hi from me"), myCachedPacket, myVpnIpNet[0].Addr(), spookyDest, 80, 80)
 
 	//reply
-	theirControl.InjectTunUDPPacket(myVpnIpNet[0].Addr(), 80, spookyDest, 80, []byte("Hi from the spookyman"))
+	theirControl.InjectTunPacket(BuildTunUDPPacket(myVpnIpNet[0].Addr(), 80, spookyDest, 80, []byte("Hi from the spookyman")))
 	//wait for reply
 	theirControl.WaitForType(1, 0, myControl)
 	theirCachedPacket := myControl.GetFromTun(true)

e2e/helpers_test.go

@@ -294,12 +294,12 @@ func deadline(t *testing.T, seconds time.Duration) doneCb {
 
 func assertTunnel(t testing.TB, vpnIpA, vpnIpB netip.Addr, controlA, controlB *nebula.Control, r *router.R) {
 	// Send a packet from them to me
-	controlB.InjectTunUDPPacket(vpnIpA, 80, vpnIpB, 90, []byte("Hi from B"))
+	controlB.InjectTunPacket(BuildTunUDPPacket(vpnIpA, 80, vpnIpB, 90, []byte("Hi from B")))
 	bPacket := r.RouteForAllUntilTxTun(controlA)
 	assertUdpPacket(t, []byte("Hi from B"), bPacket, vpnIpB, vpnIpA, 90, 80)
 
 	// And once more from me to them
-	controlA.InjectTunUDPPacket(vpnIpB, 80, vpnIpA, 90, []byte("Hello from A"))
+	controlA.InjectTunPacket(BuildTunUDPPacket(vpnIpB, 80, vpnIpA, 90, []byte("Hello from A")))
 	aPacket := r.RouteForAllUntilTxTun(controlB)
 	assertUdpPacket(t, []byte("Hello from A"), aPacket, vpnIpA, vpnIpB, 90, 80)
 }
@@ -408,3 +408,58 @@ func testLogLevelName() string {
 	}
 	return "info"
 }
+
+// BuildTunUDPPacket assembles an IP+UDP packet suitable for Control.InjectTunPacket.
+// Using UDP here because it's a simpler protocol.
+func BuildTunUDPPacket(toAddr netip.Addr, toPort uint16, fromAddr netip.Addr, fromPort uint16, data []byte) []byte {
+	serialize := make([]gopacket.SerializableLayer, 0)
+	var netLayer gopacket.NetworkLayer
+	if toAddr.Is6() {
+		if !fromAddr.Is6() {
+			panic("Cant send ipv6 to ipv4")
+		}
+		ip := &layers.IPv6{
+			Version:    6,
+			NextHeader: layers.IPProtocolUDP,
+			SrcIP:      fromAddr.Unmap().AsSlice(),
+			DstIP:      toAddr.Unmap().AsSlice(),
+		}
+		serialize = append(serialize, ip)
+		netLayer = ip
+	} else {
+		if !fromAddr.Is4() {
+			panic("Cant send ipv4 to ipv6")
+		}
+
+		ip := &layers.IPv4{
+			Version:  4,
+			TTL:      64,
+			Protocol: layers.IPProtocolUDP,
+			SrcIP:    fromAddr.Unmap().AsSlice(),
+			DstIP:    toAddr.Unmap().AsSlice(),
+		}
+		serialize = append(serialize, ip)
+		netLayer = ip
+	}
+
+	udp := layers.UDP{
+		SrcPort: layers.UDPPort(fromPort),
+		DstPort: layers.UDPPort(toPort),
+	}
+	if err := udp.SetNetworkLayerForChecksum(netLayer); err != nil {
+		panic(err)
+	}
+
+	buffer := gopacket.NewSerializeBuffer()
+	opt := gopacket.SerializeOptions{
+		ComputeChecksums: true,
+		FixLengths:       true,
+	}
+
+	serialize = append(serialize, &udp, gopacket.Payload(data))
+	if err := gopacket.SerializeLayers(buffer, opt, serialize...); err != nil {
+		panic(err)
+	}
+
+	return buffer.Bytes()
+}

e2e/leak_test.go

@@ -0,0 +1,51 @@
+//go:build e2e_testing
+// +build e2e_testing
+
+package e2e
+
+import (
+	"testing"
+	"time"
+
+	"github.com/slackhq/nebula/cert"
+	"github.com/slackhq/nebula/cert_test"
+	"github.com/slackhq/nebula/e2e/router"
+	"go.uber.org/goleak"
+)
+
+// TestNoGoroutineLeaks brings up two nebula instances, completes a tunnel,
+// stops both, and asserts no goroutines leak past the shutdown. goleak's
+// retry mechanism gives the wg.Wait()-driven goroutines a moment to drain
+// before failing the assertion.
+//
+// IgnoreCurrent is necessary in the parallelized suite: other tests can
+// leave goroutines mid-shutdown when this one runs (Stop is async, the
+// wg.Wait() drain is not blocking on test return). We're checking that
+// *this* test's setup tears down cleanly, not that the whole suite is
+// idle at this moment. Intentionally NOT t.Parallel()'d for the same
+// reason — concurrent test goroutines would always show up.
+func TestNoGoroutineLeaks(t *testing.T) {
+	defer goleak.VerifyNone(t, goleak.IgnoreCurrent())
+
+	ca, _, caKey, _ := cert_test.NewTestCaCert(cert.Version1, cert.Curve_CURVE25519, time.Now(), time.Now().Add(10*time.Minute), nil, nil, []string{})
+	myControl, myVpnIpNet, myUdpAddr, _ := newSimpleServer(cert.Version1, ca, caKey, "me", "10.128.0.1/24", nil)
+	theirControl, theirVpnIpNet, theirUdpAddr, _ := newSimpleServer(cert.Version1, ca, caKey, "them", "10.128.0.2/24", nil)
+
+	myControl.InjectLightHouseAddr(theirVpnIpNet[0].Addr(), theirUdpAddr)
+	theirControl.InjectLightHouseAddr(myVpnIpNet[0].Addr(), myUdpAddr)
+
+	myControl.Start()
+	theirControl.Start()
+
+	r := router.NewR(t, myControl, theirControl)
+	assertTunnel(t, myVpnIpNet[0].Addr(), theirVpnIpNet[0].Addr(), myControl, theirControl, r)
+
+	myControl.Stop()
+	theirControl.Stop()
+	r.RenderFlow()
+
+	// Settle period: Stop() is non-blocking; the wg-driven goroutines need
+	// a moment to drain. goleak retries internally too, but a short explicit
+	// settle reduces flakes when the suite is busy.
+	time.Sleep(50 * time.Millisecond)
+}

e2e/router/router.go

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

e2e/tunnels_test.go

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

firewall_test.go

@@ -1033,7 +1033,7 @@ func TestNewFirewallFromConfig(t *testing.T) {
 	l := test.NewLogger()
 	// Test a bad rule definition
 	c := &dummyCert{}
-	cs, err := newCertState(cert.Version2, nil, c, false, cert.Curve_CURVE25519, nil)
+	cs, err := newCertState(cert.Version2, nil, c, false, cert.Curve_CURVE25519, nil, "aes")
 	require.NoError(t, err)
 
 	conf := config.NewC(test.NewLogger())

go.mod

@@ -22,6 +22,7 @@ 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
+	go.uber.org/goleak v1.3.0
 	go.yaml.in/yaml/v3 v3.0.4
 	golang.org/x/crypto v0.50.0
 	golang.org/x/exp v0.0.0-20230725093048-515e97ebf090

handshake/credential.go

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

handshake/errors.go

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

handshake/handshake.proto

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

handshake/helpers_test.go

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

handshake/machine.go

@@ -0,0 +1,444 @@
+package handshake
+
+import (
+	"bytes"
+	"fmt"
+	"slices"
+	"time"
+
+	"github.com/flynn/noise"
+	"github.com/slackhq/nebula/cert"
+	"github.com/slackhq/nebula/header"
+)
+
+// IndexAllocator is called by the Machine to allocate a local index for the
+// handshake. It is called at most once, when the first outgoing message that
+// carries a payload is built.
+//
+// Implementations MUST NOT return 0. Zero is reserved as a sentinel meaning
+// "no index assigned" on the wire and in the payload-presence checks. If an
+// allocator ever returned 0, a legitimate handshake's payload could be
+// indistinguishable from an empty one and would be rejected.
+type IndexAllocator func() (uint32, error)
+
+// CertVerifier is called by the Machine after reconstructing the peer's
+// certificate from the handshake. The verifier performs all validation
+// (CA trust, expiry, policy checks, allow lists).
+type CertVerifier func(cert.Certificate) (*cert.CachedCertificate, error)
+
+// Result contains the results of a successful handshake.
+// Returned by ProcessPacket when the handshake is complete.
+type Result struct {
+	EKey          *noise.CipherState
+	DKey          *noise.CipherState
+	MyCert        cert.Certificate
+	RemoteCert    *cert.CachedCertificate
+	RemoteIndex   uint32
+	LocalIndex    uint32
+	HandshakeTime uint64
+	MessageIndex  uint64 // number of messages exchanged during the handshake
+	Initiator     bool
+}
+
+// Machine drives a Noise handshake through N messages. It handles Noise
+// protocol operations, certificate reconstruction, and payload encoding.
+// Certificate validation is delegated to the caller via CertVerifier.
+//
+// A Machine is not safe for concurrent use. The caller must ensure that
+// Initiate and ProcessPacket are not called concurrently.
+//
+// Error contract: when ProcessPacket or Initiate returns an error, callers
+// must check Failed() to decide what to do next. If Failed() is false the
+// underlying noise state was not advanced (the packet was rejected before
+// ReadMessage took effect, or the rejection is non-fatal like a stale
+// retransmit) and the Machine can accept another packet. If Failed() is
+// true the Machine is unrecoverable and the caller must abandon it.
+type Machine struct {
+	hs             *noise.HandshakeState
+	getCred        GetCredentialFunc
+	allocIndex     IndexAllocator
+	verifier       CertVerifier
+	result         *Result
+	msgs           []msgFlags
+	myVersion      cert.Version
+	subtype        header.MessageSubType
+	indexAllocated bool
+	remoteCertSet  bool
+	payloadSet     bool
+	failed         bool
+}
+
+// NewMachine creates a handshake state machine. The subtype determines both
+// the noise pattern and the per-message content layout. The credential for
+// `version` is fetched via getCred and used to seed the noise.HandshakeState.
+// IndexAllocator is called lazily when the first outgoing payload is built.
+func NewMachine(
+	version cert.Version,
+	getCred GetCredentialFunc,
+	verifier CertVerifier,
+	allocIndex IndexAllocator,
+	initiator bool,
+	subtype header.MessageSubType,
+) (*Machine, error) {
+	info, err := subtypeInfoFor(subtype)
+	if err != nil {
+		return nil, err
+	}
+
+	cred := getCred(version)
+	if cred == nil {
+		return nil, fmt.Errorf("%w: %v", ErrNoCredential, version)
+	}
+
+	hs, err := cred.buildHandshakeState(initiator, info.pattern)
+	if err != nil {
+		return nil, fmt.Errorf("build noise state: %w", err)
+	}
+
+	return &Machine{
+		hs:         hs,
+		subtype:    subtype,
+		msgs:       info.msgs,
+		getCred:    getCred,
+		allocIndex: allocIndex,
+		verifier:   verifier,
+		myVersion:  version,
+		result: &Result{
+			Initiator: initiator,
+		},
+	}, nil
+}
+
+// Failed returns true if the Machine is in an unrecoverable state.
+func (m *Machine) Failed() bool {
+	return m.failed
+}
+
+// Subtype returns the handshake subtype this Machine was built for.
+func (m *Machine) Subtype() header.MessageSubType {
+	return m.subtype
+}
+
+// MessageIndex returns the noise handshake message index, which equals the
+// wire counter of the most recently sent or received message.
+func (m *Machine) MessageIndex() int {
+	return m.hs.MessageIndex()
+}
+
+// requireComplete checks that both a peer cert and payload have been received.
+// Marks the machine as failed if not.
+func (m *Machine) requireComplete() error {
+	if !m.payloadSet || !m.remoteCertSet {
+		m.failed = true
+		return ErrIncompleteHandshake
+	}
+	return nil
+}
+
+// myMsgFlags returns the flags for the current outgoing message.
+func (m *Machine) myMsgFlags() msgFlags {
+	idx := m.hs.MessageIndex()
+	if idx < len(m.msgs) {
+		return m.msgs[idx]
+	}
+	return msgFlags{}
+}
+
+// peerMsgFlags returns the flags for the message we just read.
+func (m *Machine) peerMsgFlags() msgFlags {
+	idx := m.hs.MessageIndex() - 1
+	if idx >= 0 && idx < len(m.msgs) {
+		return m.msgs[idx]
+	}
+	return msgFlags{}
+}
+
+// Initiate produces the first handshake message. Only valid for initiators,
+// and must be called exactly once before ProcessPacket.
+//
+// out is a destination buffer the message is appended to and returned. Pass
+// nil to allocate fresh, or pass a re-used buffer sliced to length 0 (e.g.
+// buf[:0]) with sufficient capacity to avoid allocation.
+//
+// An error return may not indicate a fatal condition, check Failed() to
+// determine if the Machine can still be used.
+func (m *Machine) Initiate(out []byte) ([]byte, error) {
+	if m.failed {
+		return nil, ErrMachineFailed
+	}
+	if !m.result.Initiator {
+		m.failed = true
+		return nil, ErrInitiateOnResponder
+	}
+	if m.hs.MessageIndex() != 0 {
+		m.failed = true
+		return nil, ErrInitiateAlreadyCalled
+	}
+
+	// At MessageIndex=0 with RemoteIndex still zero, buildResponse produces
+	// header counter 1 and remote index 0, which is what the initial message needs.
+	out, _, _, err := m.buildResponse(out)
+	if err != nil {
+		m.failed = true
+		return nil, err
+	}
+	return out, nil
+}
+
+// ProcessPacket handles an incoming handshake message. It advances the Noise
+// state, validates the peer certificate via the verifier, and optionally
+// produces a response.
+//
+// out is a destination buffer the response is appended to and returned. Pass
+// nil to allocate fresh, or pass a re-used buffer sliced to length 0 (e.g.
+// buf[:0]) with sufficient capacity to avoid allocation. The returned slice
+// is nil when no outgoing message is produced (handshake complete on this
+// side, or final message of a multi-message pattern).
+//
+// Returns a non-nil Result when the handshake is complete.
+// An error return may not indicate a fatal condition, check Failed() to
+// determine if the Machine can still be used.
+func (m *Machine) ProcessPacket(out, packet []byte) ([]byte, *Result, error) {
+	if m.failed {
+		return nil, nil, ErrMachineFailed
+	}
+	if len(packet) < header.Len {
+		return nil, nil, ErrPacketTooShort
+	}
+	// Reject packets whose subtype doesn't match the one this Machine was
+	// built for. A pending handshake that suddenly receives a different
+	// subtype on its index is either a stray packet that matched by chance
+	// or a peer protocol violation; drop it without failing the Machine so
+	// the legitimate retransmit can still complete.
+	if header.MessageSubType(packet[1]) != m.subtype {
+		return nil, nil, ErrSubtypeMismatch
+	}
+	if m.result.Initiator && m.hs.MessageIndex() == 0 {
+		m.failed = true
+		return nil, nil, ErrInitiateNotCalled
+	}
+
+	// The (eKey, dKey) ordering here is correct for IX, where the initiator
+	// completes the handshake by reading the responder's stage-2 message.
+	// noise returns (cs1, cs2) where cs1 is the initiator->responder cipher.
+	// For 3-message patterns where a responder finishes by reading the final
+	// message, this ordering would be wrong; revisit when XX/pqIX lands.
+	msg, eKey, dKey, err := m.hs.ReadMessage(nil, packet[header.Len:])
+	if err != nil {
+		// Noise ReadMessage failed. The noise library checkpoints and rolls back
+		// on failure, so the Machine is still alive. The caller can retry with
+		// a different packet.
+		return nil, nil, fmt.Errorf("noise ReadMessage: %w", err)
+	}
+
+	// From here on, noise state has advanced. Any error is fatal.
+	flags := m.peerMsgFlags()
+
+	if err := m.processPayload(msg, flags); err != nil {
+		return nil, nil, err
+	}
+
+	// If ReadMessage derived keys, the handshake is complete. Noise should
+	// always produce both keys together; asymmetry is a protocol invariant
+	// violation.
+	if eKey != nil || dKey != nil {
+		if eKey == nil || dKey == nil {
+			m.failed = true
+			return nil, nil, ErrAsymmetricCipherKeys
+		}
+		if err := m.requireComplete(); err != nil {
+			return nil, nil, err
+		}
+		return nil, m.completed(eKey, dKey), nil
+	}
+
+	// ReadMessage didn't complete, produce the next outgoing message
+	out, dk, ek, err := m.buildResponse(out)
+	if err != nil {
+		m.failed = true
+		return nil, nil, err
+	}
+
+	if ek != nil || dk != nil {
+		if ek == nil || dk == nil {
+			m.failed = true
+			return nil, nil, ErrAsymmetricCipherKeys
+		}
+		if err := m.requireComplete(); err != nil {
+			return nil, nil, err
+		}
+		return out, m.completed(ek, dk), nil
+	}
+
+	return out, nil, nil
+}
+
+func (m *Machine) completed(eKey, dKey *noise.CipherState) *Result {
+	m.result.EKey = eKey
+	m.result.DKey = dKey
+	m.result.MessageIndex = uint64(m.hs.MessageIndex())
+	return m.result
+}
+
+func (m *Machine) processPayload(msg []byte, flags msgFlags) error {
+	if len(msg) == 0 {
+		if flags.expectsPayload || flags.expectsCert {
+			m.failed = true
+			return ErrMissingContent
+		}
+		return nil
+	}
+
+	payload, err := UnmarshalPayload(msg)
+	if err != nil {
+		m.failed = true
+		return fmt.Errorf("unmarshal handshake: %w", err)
+	}
+
+	// Assert the payload contains exactly what we expect
+	hasPayloadData := payload.InitiatorIndex != 0 || payload.ResponderIndex != 0 || payload.Time != 0
+	if hasPayloadData != flags.expectsPayload {
+		m.failed = true
+		return ErrUnexpectedContent
+	}
+
+	hasCertData := len(payload.Cert) > 0
+	if hasCertData != flags.expectsCert {
+		m.failed = true
+		return ErrUnexpectedContent
+	}
+
+	// Process payload
+	if flags.expectsPayload {
+		if m.result.Initiator {
+			m.result.RemoteIndex = payload.ResponderIndex
+		} else {
+			m.result.RemoteIndex = payload.InitiatorIndex
+		}
+		m.result.HandshakeTime = payload.Time
+		m.payloadSet = true
+	}
+
+	// Process certificate
+	if flags.expectsCert {
+		if err := m.validateCert(payload); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func (m *Machine) validateCert(payload Payload) error {
+	cred := m.getCred(m.myVersion)
+	if cred == nil {
+		m.failed = true
+		return fmt.Errorf("%w: %v", ErrNoCredential, m.myVersion)
+	}
+	rc, err := cert.Recombine(
+		cert.Version(payload.CertVersion),
+		payload.Cert,
+		m.hs.PeerStatic(),
+		cred.Cert.Curve(),
+	)
+	if err != nil {
+		m.failed = true
+		return fmt.Errorf("recombine cert: %w", err)
+	}
+
+	if !bytes.Equal(rc.PublicKey(), m.hs.PeerStatic()) {
+		m.failed = true
+		return ErrPublicKeyMismatch
+	}
+
+	// Version negotiation, if the peer sent a different version and we have it, switch
+	if rc.Version() != m.myVersion {
+		if m.getCred(rc.Version()) != nil {
+			m.myVersion = rc.Version()
+		}
+	}
+
+	verified, err := m.verifier(rc)
+	if err != nil {
+		m.failed = true
+		return fmt.Errorf("verify cert: %w", err)
+	}
+
+	m.result.RemoteCert = verified
+	m.remoteCertSet = true
+	return nil
+}
+
+func (m *Machine) marshalOutgoing(flags msgFlags) ([]byte, error) {
+	if !flags.expectsPayload && !flags.expectsCert {
+		return nil, nil
+	}
+
+	var p Payload
+	if flags.expectsPayload {
+		if !m.indexAllocated {
+			index, err := m.allocIndex()
+			if err != nil {
+				return nil, fmt.Errorf("%w: %w", ErrIndexAllocation, err)
+			}
+			m.result.LocalIndex = index
+			m.indexAllocated = true
+		}
+
+		if m.result.Initiator {
+			p.InitiatorIndex = m.result.LocalIndex
+		} else {
+			p.ResponderIndex = m.result.LocalIndex
+			p.InitiatorIndex = m.result.RemoteIndex
+		}
+		p.Time = uint64(time.Now().UnixNano())
+	}
+	if flags.expectsCert {
+		cred := m.getCred(m.myVersion)
+		if cred == nil {
+			return nil, fmt.Errorf("%w: %v", ErrNoCredential, m.myVersion)
+		}
+		p.Cert = cred.Bytes
+		p.CertVersion = uint32(cred.Cert.Version())
+		m.result.MyCert = cred.Cert
+	}
+
+	return MarshalPayload(nil, p), nil
+}
+
+func (m *Machine) buildResponse(out []byte) ([]byte, *noise.CipherState, *noise.CipherState, error) {
+	flags := m.myMsgFlags()
+	hsBytes, err := m.marshalOutgoing(flags)
+	if err != nil {
+		return nil, nil, nil, err
+	}
+
+	// Extend out by header.Len to make room for the header. slices.Grow is a
+	// no-op when the cap is already sufficient (the zero-copy case where the
+	// caller passed a pre-sized buffer). header.Encode overwrites the new
+	// bytes, so they don't need to be zeroed.
+	start := len(out)
+	out = slices.Grow(out, header.Len)[:start+header.Len]
+	header.Encode(
+		out[start:],
+		header.Version, header.Handshake, m.subtype,
+		m.result.RemoteIndex,
+		uint64(m.hs.MessageIndex()+1),
+	)
+
+	// noise.WriteMessage appends the encrypted handshake message to out,
+	// reusing capacity when present.
+	//
+	// The (dKey, eKey) ordering here is correct for IX, where the responder
+	// completes the handshake by writing the stage-2 message. noise returns
+	// (cs1, cs2) where cs1 is the initiator->responder cipher (which is the
+	// responder's decrypt key). For 3-message patterns where an initiator
+	// finishes by writing the final message, this ordering would be wrong;
+	// revisit when XX/pqIX lands.
+	out, dKey, eKey, err := m.hs.WriteMessage(out, hsBytes)
+	if err != nil {
+		return nil, nil, nil, fmt.Errorf("noise WriteMessage: %w", err)
+	}
+
+	return out, dKey, eKey, nil
+}

handshake/machine_test.go

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

handshake/patterns.go

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

handshake/patterns_test.go

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

handshake/payload.go

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

handshake/payload_test.go

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

handshake_ix.go

@@ -1,813 +0,0 @@
-package nebula
-
-import (
-	"bytes"
-	"context"
-	"log/slog"
-	"net/netip"
-	"time"
-
-	"github.com/flynn/noise"
-	"github.com/slackhq/nebula/cert"
-	"github.com/slackhq/nebula/header"
-)
-
-// NOISE IX Handshakes
-
-// This function constructs a handshake packet, but does not actually send it
-// Sending is done by the handshake manager
-func ixHandshakeStage0(f *Interface, hh *HandshakeHostInfo) bool {
-	err := f.handshakeManager.allocateIndex(hh)
-	if err != nil {
-		f.l.Error("Failed to generate index",
-			"error", err,
-			"vpnAddrs", hh.hostinfo.vpnAddrs,
-			"handshake", m{"stage": 0, "style": "ix_psk0"},
-		)
-		return false
-	}
-
-	cs := f.pki.getCertState()
-	v := cs.initiatingVersion
-	if hh.initiatingVersionOverride != cert.VersionPre1 {
-		v = hh.initiatingVersionOverride
-	} else if v < cert.Version2 {
-		// If we're connecting to a v6 address we should encourage use of a V2 cert
-		for _, a := range hh.hostinfo.vpnAddrs {
-			if a.Is6() {
-				v = cert.Version2
-				break
-			}
-		}
-	}
-
-	crt := cs.getCertificate(v)
-	if crt == nil {
-		f.l.Error("Unable to handshake with host because no certificate is available",
-			"vpnAddrs", hh.hostinfo.vpnAddrs,
-			"handshake", m{"stage": 0, "style": "ix_psk0"},
-			"certVersion", v,
-		)
-		return false
-	}
-
-	crtHs := cs.getHandshakeBytes(v)
-	if crtHs == nil {
-		f.l.Error("Unable to handshake with host because no certificate handshake bytes is available",
-			"vpnAddrs", hh.hostinfo.vpnAddrs,
-			"handshake", m{"stage": 0, "style": "ix_psk0"},
-			"certVersion", v,
-		)
-		return false
-	}
-
-	ci, err := NewConnectionState(cs, crt, true, noise.HandshakeIX)
-	if err != nil {
-		f.l.Error("Failed to create connection state",
-			"error", err,
-			"vpnAddrs", hh.hostinfo.vpnAddrs,
-			"handshake", m{"stage": 0, "style": "ix_psk0"},
-			"certVersion", v,
-		)
-		return false
-	}
-	hh.hostinfo.ConnectionState = ci
-
-	hs := &NebulaHandshake{
-		Details: &NebulaHandshakeDetails{
-			InitiatorIndex: hh.hostinfo.localIndexId,
-			Time:           uint64(time.Now().UnixNano()),
-			Cert:           crtHs,
-			CertVersion:    uint32(v),
-		},
-	}
-
-	hsBytes, err := hs.Marshal()
-	if err != nil {
-		f.l.Error("Failed to marshal handshake message",
-			"error", err,
-			"vpnAddrs", hh.hostinfo.vpnAddrs,
-			"certVersion", v,
-			"handshake", m{"stage": 0, "style": "ix_psk0"},
-		)
-		return false
-	}
-
-	h := header.Encode(make([]byte, header.Len), header.Version, header.Handshake, header.HandshakeIXPSK0, 0, 1)
-
-	msg, _, _, err := ci.H.WriteMessage(h, hsBytes)
-	if err != nil {
-		f.l.Error("Failed to call noise.WriteMessage",
-			"error", err,
-			"vpnAddrs", hh.hostinfo.vpnAddrs,
-			"handshake", m{"stage": 0, "style": "ix_psk0"},
-		)
-		return false
-	}
-
-	// We are sending handshake packet 1, so we don't expect to receive
-	// handshake packet 1 from the responder
-	ci.window.Update(f.l, 1)
-
-	hh.hostinfo.HandshakePacket[0] = msg
-	hh.ready = true
-	return true
-}
-
-func ixHandshakeStage1(f *Interface, via ViaSender, packet []byte, h *header.H) {
-	cs := f.pki.getCertState()
-	crt := cs.GetDefaultCertificate()
-	if crt == nil {
-		f.l.Error("Unable to handshake with host because no certificate is available",
-			"from", via,
-			"handshake", m{"stage": 0, "style": "ix_psk0"},
-			"certVersion", cs.initiatingVersion,
-		)
-		return
-	}
-
-	ci, err := NewConnectionState(cs, crt, false, noise.HandshakeIX)
-	if err != nil {
-		f.l.Error("Failed to create connection state",
-			"error", err,
-			"from", via,
-			"handshake", m{"stage": 1, "style": "ix_psk0"},
-		)
-		return
-	}
-
-	// Mark packet 1 as seen so it doesn't show up as missed
-	ci.window.Update(f.l, 1)
-
-	msg, _, _, err := ci.H.ReadMessage(nil, packet[header.Len:])
-	if err != nil {
-		f.l.Error("Failed to call noise.ReadMessage",
-			"error", err,
-			"from", via,
-			"handshake", m{"stage": 1, "style": "ix_psk0"},
-		)
-		return
-	}
-
-	hs := &NebulaHandshake{}
-	err = hs.Unmarshal(msg)
-	if err != nil || hs.Details == nil {
-		f.l.Error("Failed unmarshal handshake message",
-			"error", err,
-			"from", via,
-			"handshake", m{"stage": 1, "style": "ix_psk0"},
-		)
-		return
-	}
-
-	rc, err := cert.Recombine(cert.Version(hs.Details.CertVersion), hs.Details.Cert, ci.H.PeerStatic(), ci.Curve())
-	if err != nil {
-		f.l.Info("Handshake did not contain a certificate",
-			"error", err,
-			"from", via,
-			"handshake", m{"stage": 1, "style": "ix_psk0"},
-		)
-		return
-	}
-
-	remoteCert, err := f.pki.GetCAPool().VerifyCertificate(time.Now(), rc)
-	if err != nil {
-		fp, fperr := rc.Fingerprint()
-		if fperr != nil {
-			fp = "<error generating certificate fingerprint>"
-		}
-
-		attrs := []slog.Attr{
-			slog.Any("error", err),
-			slog.Any("from", via),
-			slog.Any("handshake", m{"stage": 1, "style": "ix_psk0"}),
-			slog.Any("certVpnNetworks", rc.Networks()),
-			slog.String("certFingerprint", fp),
-		}
-		if f.l.Enabled(context.Background(), slog.LevelDebug) {
-			attrs = append(attrs, slog.Any("cert", rc))
-		}
-
-		// LogAttrs is intentional: attrs is a pre-built []slog.Attr slice that
-		// callers grow conditionally, which has no pair-form equivalent.
-		//nolint:sloglint
-		f.l.LogAttrs(context.Background(), slog.LevelInfo, "Invalid certificate from host", attrs...)
-		return
-	}
-
-	if !bytes.Equal(remoteCert.Certificate.PublicKey(), ci.H.PeerStatic()) {
-		f.l.Info("public key mismatch between certificate and handshake",
-			"from", via,
-			"handshake", m{"stage": 1, "style": "ix_psk0"},
-			"cert", remoteCert,
-		)
-		return
-	}
-
-	if remoteCert.Certificate.Version() != ci.myCert.Version() {
-		// We started off using the wrong certificate version, lets see if we can match the version that was sent to us
-		myCertOtherVersion := cs.getCertificate(remoteCert.Certificate.Version())
-		if myCertOtherVersion == nil {
-			if f.l.Enabled(context.Background(), slog.LevelDebug) {
-				f.l.Debug("Might be unable to handshake with host due to missing certificate version",
-					"error", err,
-					"from", via,
-					"handshake", m{"stage": 1, "style": "ix_psk0"},
-					"cert", remoteCert,
-				)
-			}
-		} else {
-			// Record the certificate we are actually using
-			ci.myCert = myCertOtherVersion
-		}
-	}
-
-	if len(remoteCert.Certificate.Networks()) == 0 {
-		f.l.Info("No networks in certificate",
-			"error", err,
-			"from", via,
-			"cert", remoteCert,
-			"handshake", m{"stage": 1, "style": "ix_psk0"},
-		)
-		return
-	}
-
-	certName := remoteCert.Certificate.Name()
-	certVersion := remoteCert.Certificate.Version()
-	fingerprint := remoteCert.Fingerprint
-	issuer := remoteCert.Certificate.Issuer()
-	vpnNetworks := remoteCert.Certificate.Networks()
-
-	anyVpnAddrsInCommon := false
-	vpnAddrs := make([]netip.Addr, len(vpnNetworks))
-	for i, network := range vpnNetworks {
-		if f.myVpnAddrsTable.Contains(network.Addr()) {
-			f.l.Error("Refusing to handshake with myself",
-				"vpnNetworks", vpnNetworks,
-				"from", via,
-				"certName", certName,
-				"certVersion", certVersion,
-				"fingerprint", fingerprint,
-				"issuer", issuer,
-				"handshake", m{"stage": 1, "style": "ix_psk0"},
-			)
-			return
-		}
-		vpnAddrs[i] = network.Addr()
-		if f.myVpnNetworksTable.Contains(network.Addr()) {
-			anyVpnAddrsInCommon = true
-		}
-	}
-
-	if !via.IsRelayed {
-		// We only want to apply the remote allow list for direct tunnels here
-		if !f.lightHouse.GetRemoteAllowList().AllowAll(vpnAddrs, via.UdpAddr.Addr()) {
-			if f.l.Enabled(context.Background(), slog.LevelDebug) {
-				f.l.Debug("lighthouse.remote_allow_list denied incoming handshake",
-					"vpnAddrs", vpnAddrs,
-					"from", via,
-				)
-			}
-			return
-		}
-	}
-
-	myIndex, err := generateIndex(f.l)
-	if err != nil {
-		f.l.Error("Failed to generate index",
-			"error", err,
-			"vpnAddrs", vpnAddrs,
-			"from", via,
-			"certName", certName,
-			"certVersion", certVersion,
-			"fingerprint", fingerprint,
-			"issuer", issuer,
-			"handshake", m{"stage": 1, "style": "ix_psk0"},
-		)
-		return
-	}
-
-	hostinfo := &HostInfo{
-		ConnectionState:   ci,
-		localIndexId:      myIndex,
-		remoteIndexId:     hs.Details.InitiatorIndex,
-		vpnAddrs:          vpnAddrs,
-		HandshakePacket:   make(map[uint8][]byte, 0),
-		lastHandshakeTime: hs.Details.Time,
-		relayState: RelayState{
-			relays:         nil,
-			relayForByAddr: map[netip.Addr]*Relay{},
-			relayForByIdx:  map[uint32]*Relay{},
-		},
-	}
-
-	msgRxL := f.l.With(
-		"vpnAddrs", vpnAddrs,
-		"from", via,
-		"certName", certName,
-		"certVersion", certVersion,
-		"fingerprint", fingerprint,
-		"issuer", issuer,
-		"initiatorIndex", hs.Details.InitiatorIndex,
-		"responderIndex", hs.Details.ResponderIndex,
-		"remoteIndex", h.RemoteIndex,
-		"handshake", m{"stage": 1, "style": "ix_psk0"},
-	)
-
-	if anyVpnAddrsInCommon {
-		msgRxL.Info("Handshake message received")
-	} else {
-		//todo warn if not lighthouse or relay?
-		msgRxL.Info("Handshake message received, but no vpnNetworks in common.")
-	}
-
-	hs.Details.ResponderIndex = myIndex
-	hs.Details.Cert = cs.getHandshakeBytes(ci.myCert.Version())
-	if hs.Details.Cert == nil {
-		msgRxL.Error("Unable to handshake with host because no certificate handshake bytes is available",
-			"myCertVersion", ci.myCert.Version(),
-		)
-		return
-	}
-
-	hs.Details.CertVersion = uint32(ci.myCert.Version())
-	// Update the time in case their clock is way off from ours
-	hs.Details.Time = uint64(time.Now().UnixNano())
-
-	hsBytes, err := hs.Marshal()
-	if err != nil {
-		f.l.Error("Failed to marshal handshake message",
-			"error", err,
-			"vpnAddrs", hostinfo.vpnAddrs,
-			"from", via,
-			"certName", certName,
-			"certVersion", certVersion,
-			"fingerprint", fingerprint,
-			"issuer", issuer,
-			"handshake", m{"stage": 1, "style": "ix_psk0"},
-		)
-		return
-	}
-
-	nh := header.Encode(make([]byte, header.Len), header.Version, header.Handshake, header.HandshakeIXPSK0, hs.Details.InitiatorIndex, 2)
-	msg, dKey, eKey, err := ci.H.WriteMessage(nh, hsBytes)
-	if err != nil {
-		f.l.Error("Failed to call noise.WriteMessage",
-			"error", err,
-			"vpnAddrs", hostinfo.vpnAddrs,
-			"from", via,
-			"certName", certName,
-			"certVersion", certVersion,
-			"fingerprint", fingerprint,
-			"issuer", issuer,
-			"handshake", m{"stage": 1, "style": "ix_psk0"},
-		)
-		return
-	} else if dKey == nil || eKey == nil {
-		f.l.Error("Noise did not arrive at a key",
-			"vpnAddrs", hostinfo.vpnAddrs,
-			"from", via,
-			"certName", certName,
-			"certVersion", certVersion,
-			"fingerprint", fingerprint,
-			"issuer", issuer,
-			"handshake", m{"stage": 1, "style": "ix_psk0"},
-		)
-		return
-	}
-
-	hostinfo.HandshakePacket[0] = make([]byte, len(packet[header.Len:]))
-	copy(hostinfo.HandshakePacket[0], packet[header.Len:])
-
-	// Regardless of whether you are the sender or receiver, you should arrive here
-	// and complete standing up the connection.
-	hostinfo.HandshakePacket[2] = make([]byte, len(msg))
-	copy(hostinfo.HandshakePacket[2], msg)
-
-	// We are sending handshake packet 2, so we don't expect to receive
-	// handshake packet 2 from the initiator.
-	ci.window.Update(f.l, 2)
-
-	ci.peerCert = remoteCert
-	ci.dKey = NewNebulaCipherState(dKey)
-	ci.eKey = NewNebulaCipherState(eKey)
-
-	hostinfo.remotes = f.lightHouse.QueryCache(vpnAddrs)
-	if !via.IsRelayed {
-		hostinfo.SetRemote(via.UdpAddr)
-	}
-	hostinfo.buildNetworks(f.myVpnNetworksTable, remoteCert.Certificate)
-
-	existing, err := f.handshakeManager.CheckAndComplete(hostinfo, 0, f)
-	if err != nil {
-		switch err {
-		case ErrAlreadySeen:
-			// Update remote if preferred
-			if existing.SetRemoteIfPreferred(f.hostMap, via) {
-				// Send a test packet to ensure the other side has also switched to
-				// the preferred remote
-				f.SendMessageToVpnAddr(header.Test, header.TestRequest, vpnAddrs[0], []byte(""), make([]byte, 12, 12), make([]byte, mtu))
-			}
-
-			msg = existing.HandshakePacket[2]
-			f.messageMetrics.Tx(header.Handshake, header.MessageSubType(msg[1]), 1)
-			if !via.IsRelayed {
-				err := f.outside.WriteTo(msg, via.UdpAddr)
-				if err != nil {
-					f.l.Error("Failed to send handshake message",
-						"vpnAddrs", existing.vpnAddrs,
-						"from", via,
-						"handshake", m{"stage": 2, "style": "ix_psk0"},
-						"cached", true,
-						"error", err,
-					)
-				} else {
-					f.l.Info("Handshake message sent",
-						"vpnAddrs", existing.vpnAddrs,
-						"from", via,
-						"handshake", m{"stage": 2, "style": "ix_psk0"},
-						"cached", true,
-					)
-				}
-				return
-			} else {
-				if via.relay == nil {
-					f.l.Error("Handshake send failed: both addr and via.relay are nil.")
-					return
-				}
-				hostinfo.relayState.InsertRelayTo(via.relayHI.vpnAddrs[0])
-				f.SendVia(via.relayHI, via.relay, msg, make([]byte, 12), make([]byte, mtu), false)
-				f.l.Info("Handshake message sent",
-					"vpnAddrs", existing.vpnAddrs,
-					"relay", via.relayHI.vpnAddrs[0],
-					"handshake", m{"stage": 2, "style": "ix_psk0"},
-					"cached", true,
-				)
-				return
-			}
-		case ErrExistingHostInfo:
-			// This means there was an existing tunnel and this handshake was older than the one we are currently based on
-			f.l.Info("Handshake too old",
-				"vpnAddrs", vpnAddrs,
-				"from", via,
-				"certName", certName,
-				"certVersion", certVersion,
-				"oldHandshakeTime", existing.lastHandshakeTime,
-				"newHandshakeTime", hostinfo.lastHandshakeTime,
-				"fingerprint", fingerprint,
-				"issuer", issuer,
-				"initiatorIndex", hs.Details.InitiatorIndex,
-				"responderIndex", hs.Details.ResponderIndex,
-				"remoteIndex", h.RemoteIndex,
-				"handshake", m{"stage": 1, "style": "ix_psk0"},
-			)
-
-			// Send a test packet to trigger an authenticated tunnel test, this should suss out any lingering tunnel issues
-			f.SendMessageToVpnAddr(header.Test, header.TestRequest, vpnAddrs[0], []byte(""), make([]byte, 12, 12), make([]byte, mtu))
-			return
-		case ErrLocalIndexCollision:
-			// This means we failed to insert because of collision on localIndexId. Just let the next handshake packet retry
-			f.l.Error("Failed to add HostInfo due to localIndex collision",
-				"vpnAddrs", vpnAddrs,
-				"from", via,
-				"certName", certName,
-				"certVersion", certVersion,
-				"fingerprint", fingerprint,
-				"issuer", issuer,
-				"initiatorIndex", hs.Details.InitiatorIndex,
-				"responderIndex", hs.Details.ResponderIndex,
-				"remoteIndex", h.RemoteIndex,
-				"handshake", m{"stage": 1, "style": "ix_psk0"},
-				"localIndex", hostinfo.localIndexId,
-				"collision", existing.vpnAddrs,
-			)
-			return
-		default:
-			// Shouldn't happen, but just in case someone adds a new error type to CheckAndComplete
-			// And we forget to update it here
-			f.l.Error("Failed to add HostInfo to HostMap",
-				"error", err,
-				"vpnAddrs", vpnAddrs,
-				"from", via,
-				"certName", certName,
-				"certVersion", certVersion,
-				"fingerprint", fingerprint,
-				"issuer", issuer,
-				"initiatorIndex", hs.Details.InitiatorIndex,
-				"responderIndex", hs.Details.ResponderIndex,
-				"remoteIndex", h.RemoteIndex,
-				"handshake", m{"stage": 1, "style": "ix_psk0"},
-			)
-			return
-		}
-	}
-
-	// Do the send
-	f.messageMetrics.Tx(header.Handshake, header.MessageSubType(msg[1]), 1)
-	if !via.IsRelayed {
-		err = f.outside.WriteTo(msg, via.UdpAddr)
-		log := f.l.With(
-			"vpnAddrs", vpnAddrs,
-			"from", via,
-			"certName", certName,
-			"certVersion", certVersion,
-			"fingerprint", fingerprint,
-			"issuer", issuer,
-			"initiatorIndex", hs.Details.InitiatorIndex,
-			"responderIndex", hs.Details.ResponderIndex,
-			"remoteIndex", h.RemoteIndex,
-			"handshake", m{"stage": 2, "style": "ix_psk0"},
-		)
-		if err != nil {
-			log.Error("Failed to send handshake", "error", err)
-		} else {
-			log.Info("Handshake message sent")
-		}
-	} else {
-		if via.relay == nil {
-			f.l.Error("Handshake send failed: both addr and via.relay are nil.")
-			return
-		}
-		hostinfo.relayState.InsertRelayTo(via.relayHI.vpnAddrs[0])
-		// I successfully received a handshake. Just in case I marked this tunnel as 'Disestablished', ensure
-		// it's correctly marked as working.
-		via.relayHI.relayState.UpdateRelayForByIdxState(via.remoteIdx, Established)
-		f.SendVia(via.relayHI, via.relay, msg, make([]byte, 12), make([]byte, mtu), false)
-		f.l.Info("Handshake message sent",
-			"vpnAddrs", vpnAddrs,
-			"relay", via.relayHI.vpnAddrs[0],
-			"certName", certName,
-			"certVersion", certVersion,
-			"fingerprint", fingerprint,
-			"issuer", issuer,
-			"initiatorIndex", hs.Details.InitiatorIndex,
-			"responderIndex", hs.Details.ResponderIndex,
-			"remoteIndex", h.RemoteIndex,
-			"handshake", m{"stage": 2, "style": "ix_psk0"},
-		)
-	}
-
-	f.connectionManager.AddTrafficWatch(hostinfo)
-
-	hostinfo.remotes.RefreshFromHandshake(vpnAddrs)
-
-	// Don't wait for UpdateWorker
-	if f.lightHouse.IsAnyLighthouseAddr(vpnAddrs) {
-		f.lightHouse.TriggerUpdate()
-	}
-
-	return
-}
-
-func ixHandshakeStage2(f *Interface, via ViaSender, hh *HandshakeHostInfo, packet []byte, h *header.H) bool {
-	if hh == nil {
-		// Nothing here to tear down, got a bogus stage 2 packet
-		return true
-	}
-
-	hh.Lock()
-	defer hh.Unlock()
-
-	hostinfo := hh.hostinfo
-	if !via.IsRelayed {
-		// The vpnAddr we know about is the one we tried to handshake with, use it to apply the remote allow list.
-		if !f.lightHouse.GetRemoteAllowList().AllowAll(hostinfo.vpnAddrs, via.UdpAddr.Addr()) {
-			if f.l.Enabled(context.Background(), slog.LevelDebug) {
-				f.l.Debug("lighthouse.remote_allow_list denied incoming handshake",
-					"vpnAddrs", hostinfo.vpnAddrs,
-					"from", via,
-				)
-			}
-			return false
-		}
-	}
-
-	ci := hostinfo.ConnectionState
-	msg, eKey, dKey, err := ci.H.ReadMessage(nil, packet[header.Len:])
-	if err != nil {
-		f.l.Error("Failed to call noise.ReadMessage",
-			"error", err,
-			"vpnAddrs", hostinfo.vpnAddrs,
-			"from", via,
-			"handshake", m{"stage": 2, "style": "ix_psk0"},
-			"header", h,
-		)
-
-		// We don't want to tear down the connection on a bad ReadMessage because it could be an attacker trying
-		// to DOS us. Every other error condition after should to allow a possible good handshake to complete in the
-		// near future
-		return false
-	} else if dKey == nil || eKey == nil {
-		f.l.Error("Noise did not arrive at a key",
-			"vpnAddrs", hostinfo.vpnAddrs,
-			"from", via,
-			"handshake", m{"stage": 2, "style": "ix_psk0"},
-		)
-
-		// This should be impossible in IX but just in case, if we get here then there is no chance to recover
-		// the handshake state machine. Tear it down
-		return true
-	}
-
-	hs := &NebulaHandshake{}
-	err = hs.Unmarshal(msg)
-	if err != nil || hs.Details == nil {
-		f.l.Error("Failed unmarshal handshake message",
-			"error", err,
-			"vpnAddrs", hostinfo.vpnAddrs,
-			"from", via,
-			"handshake", m{"stage": 2, "style": "ix_psk0"},
-		)
-
-		// The handshake state machine is complete, if things break now there is no chance to recover. Tear down and start again
-		return true
-	}
-
-	rc, err := cert.Recombine(cert.Version(hs.Details.CertVersion), hs.Details.Cert, ci.H.PeerStatic(), ci.Curve())
-	if err != nil {
-		f.l.Info("Handshake did not contain a certificate",
-			"error", err,
-			"from", via,
-			"vpnAddrs", hostinfo.vpnAddrs,
-			"handshake", m{"stage": 2, "style": "ix_psk0"},
-		)
-		return true
-	}
-
-	remoteCert, err := f.pki.GetCAPool().VerifyCertificate(time.Now(), rc)
-	if err != nil {
-		fp, err := rc.Fingerprint()
-		if err != nil {
-			fp = "<error generating certificate fingerprint>"
-		}
-
-		attrs := []slog.Attr{
-			slog.Any("error", err),
-			slog.Any("from", via),
-			slog.Any("vpnAddrs", hostinfo.vpnAddrs),
-			slog.Any("handshake", m{"stage": 2, "style": "ix_psk0"}),
-			slog.String("certFingerprint", fp),
-			slog.Any("certVpnNetworks", rc.Networks()),
-		}
-		if f.l.Enabled(context.Background(), slog.LevelDebug) {
-			attrs = append(attrs, slog.Any("cert", rc))
-		}
-
-		// LogAttrs is intentional: attrs is a pre-built []slog.Attr slice that
-		// callers grow conditionally, which has no pair-form equivalent.
-		//nolint:sloglint
-		f.l.LogAttrs(context.Background(), slog.LevelInfo, "Invalid certificate from host", attrs...)
-		return true
-	}
-	if !bytes.Equal(remoteCert.Certificate.PublicKey(), ci.H.PeerStatic()) {
-		f.l.Info("public key mismatch between certificate and handshake",
-			"from", via,
-			"handshake", m{"stage": 2, "style": "ix_psk0"},
-			"cert", remoteCert,
-		)
-		return true
-	}
-
-	if len(remoteCert.Certificate.Networks()) == 0 {
-		f.l.Info("No networks in certificate",
-			"error", err,
-			"from", via,
-			"vpnAddrs", hostinfo.vpnAddrs,
-			"cert", remoteCert,
-			"handshake", m{"stage": 2, "style": "ix_psk0"},
-		)
-		return true
-	}
-
-	vpnNetworks := remoteCert.Certificate.Networks()
-	certName := remoteCert.Certificate.Name()
-	certVersion := remoteCert.Certificate.Version()
-	fingerprint := remoteCert.Fingerprint
-	issuer := remoteCert.Certificate.Issuer()
-
-	hostinfo.remoteIndexId = hs.Details.ResponderIndex
-	hostinfo.lastHandshakeTime = hs.Details.Time
-
-	// Store their cert and our symmetric keys
-	ci.peerCert = remoteCert
-	ci.dKey = NewNebulaCipherState(dKey)
-	ci.eKey = NewNebulaCipherState(eKey)
-
-	// Make sure the current udpAddr being used is set for responding
-	if !via.IsRelayed {
-		hostinfo.SetRemote(via.UdpAddr)
-	} else {
-		hostinfo.relayState.InsertRelayTo(via.relayHI.vpnAddrs[0])
-	}
-
-	correctHostResponded := false
-	anyVpnAddrsInCommon := false
-	vpnAddrs := make([]netip.Addr, len(vpnNetworks))
-	for i, network := range vpnNetworks {
-		vpnAddrs[i] = network.Addr()
-		if f.myVpnNetworksTable.Contains(network.Addr()) {
-			anyVpnAddrsInCommon = true
-		}
-		if hostinfo.vpnAddrs[0] == network.Addr() {
-			// todo is it more correct to see if any of hostinfo.vpnAddrs are in the cert? it should have len==1, but one day it might not?
-			correctHostResponded = true
-		}
-	}
-
-	// Ensure the right host responded
-	if !correctHostResponded {
-		f.l.Info("Incorrect host responded to handshake",
-			"intendedVpnAddrs", hostinfo.vpnAddrs,
-			"haveVpnNetworks", vpnNetworks,
-			"from", via,
-			"certName", certName,
-			"certVersion", certVersion,
-			"handshake", m{"stage": 2, "style": "ix_psk0"},
-		)
-
-		// Release our old handshake from pending, it should not continue
-		f.handshakeManager.DeleteHostInfo(hostinfo)
-
-		// Create a new hostinfo/handshake for the intended vpn ip
-		//TODO is hostinfo.vpnAddrs[0] always the address to use?
-		f.handshakeManager.StartHandshake(hostinfo.vpnAddrs[0], func(newHH *HandshakeHostInfo) {
-			// Block the current used address
-			newHH.hostinfo.remotes = hostinfo.remotes
-			newHH.hostinfo.remotes.BlockRemote(via)
-
-			f.l.Info("Blocked addresses for handshakes",
-				"blockedUdpAddrs", newHH.hostinfo.remotes.CopyBlockedRemotes(),
-				"vpnNetworks", vpnNetworks,
-				"remotes", newHH.hostinfo.remotes.CopyAddrs(f.hostMap.GetPreferredRanges()),
-			)
-
-			// Swap the packet store to benefit the original intended recipient
-			newHH.packetStore = hh.packetStore
-			hh.packetStore = []*cachedPacket{}
-
-			// Finally, put the correct vpn addrs in the host info, tell them to close the tunnel, and return true to tear down
-			hostinfo.vpnAddrs = vpnAddrs
-			f.sendCloseTunnel(hostinfo)
-		})
-
-		return true
-	}
-
-	// Mark packet 2 as seen so it doesn't show up as missed
-	ci.window.Update(f.l, 2)
-
-	duration := time.Since(hh.startTime).Nanoseconds()
-	msgRxL := f.l.With(
-		"vpnAddrs", vpnAddrs,
-		"from", via,
-		"certName", certName,
-		"certVersion", certVersion,
-		"fingerprint", fingerprint,
-		"issuer", issuer,
-		"initiatorIndex", hs.Details.InitiatorIndex,
-		"responderIndex", hs.Details.ResponderIndex,
-		"remoteIndex", h.RemoteIndex,
-		"handshake", m{"stage": 2, "style": "ix_psk0"},
-		"durationNs", duration,
-		"sentCachedPackets", len(hh.packetStore),
-	)
-	if anyVpnAddrsInCommon {
-		msgRxL.Info("Handshake message received")
-	} else {
-		//todo warn if not lighthouse or relay?
-		msgRxL.Info("Handshake message received, but no vpnNetworks in common.")
-	}
-
-	// Build up the radix for the firewall if we have subnets in the cert
-	hostinfo.vpnAddrs = vpnAddrs
-	hostinfo.buildNetworks(f.myVpnNetworksTable, remoteCert.Certificate)
-
-	// Complete our handshake and update metrics, this will replace any existing tunnels for the vpnAddrs here
-	f.handshakeManager.Complete(hostinfo, f)
-	f.connectionManager.AddTrafficWatch(hostinfo)
-
-	if f.l.Enabled(context.Background(), slog.LevelDebug) {
-		hostinfo.logger(f.l).Debug("Sending stored packets",
-			"count", len(hh.packetStore),
-		)
-	}
-
-	if len(hh.packetStore) > 0 {
-		nb := make([]byte, 12, 12)
-		out := make([]byte, mtu)
-		for _, cp := range hh.packetStore {
-			cp.callback(cp.messageType, cp.messageSubType, hostinfo, cp.packet, nb, out)
-		}
-		f.cachedPacketMetrics.sent.Inc(int64(len(hh.packetStore)))
-	}
-
-	hostinfo.remotes.RefreshFromHandshake(vpnAddrs)
-	f.metricHandshakes.Update(duration)
-
-	// Don't wait for UpdateWorker
-	if f.lightHouse.IsAnyLighthouseAddr(vpnAddrs) {
-		f.lightHouse.TriggerUpdate()
-	}
-
-	return false
-}

handshake_manager.go

@@ -14,6 +14,7 @@ import (
 
 	"github.com/rcrowley/go-metrics"
 	"github.com/slackhq/nebula/cert"
+	"github.com/slackhq/nebula/handshake"
 	"github.com/slackhq/nebula/header"
 	"github.com/slackhq/nebula/udp"
 )
@@ -22,7 +23,18 @@ const (
 	DefaultHandshakeTryInterval   = time.Millisecond * 100
 	DefaultHandshakeRetries       = 10
 	DefaultHandshakeTriggerBuffer = 64
-	DefaultUseRelays              = true
+
+	// maxCachedPackets is how many unsent packets we'll buffer per pending
+	// handshake before dropping further ones.
+	maxCachedPackets = 100
+
+	// HandshakePacket map keys mirror the IX protocol stage convention:
+	//   stage 0 = the initiator's first message (and what the responder
+	//             receives, stripped of header)
+	//   stage 2 = the responder's reply
+	// Other handshake patterns will need new keys when added.
+	handshakePacketStage0 uint8 = 0
+	handshakePacketStage2 uint8 = 2
 )
 
 var (
@@ -30,7 +42,6 @@ var (
 		tryInterval:   DefaultHandshakeTryInterval,
 		retries:       DefaultHandshakeRetries,
 		triggerBuffer: DefaultHandshakeTriggerBuffer,
-		useRelays:     DefaultUseRelays,
 	}
 )
 
@@ -38,7 +49,6 @@ type HandshakeConfig struct {
 	tryInterval   time.Duration
 	retries       int64
 	triggerBuffer int
-	useRelays     bool
 
 	messageMetrics *MessageMetrics
 }
@@ -76,10 +86,11 @@ type HandshakeHostInfo struct {
 	packetStore               []*cachedPacket  // A set of packets to be transmitted once the handshake completes
 
 	hostinfo *HostInfo
+	machine  *handshake.Machine // The handshake state machine, set during stage 0 (initiator) or beginHandshake (responder multi-message)
 }
 
 func (hh *HandshakeHostInfo) cachePacket(l *slog.Logger, t header.MessageType, st header.MessageSubType, packet []byte, f packetCallback, m *cachedPacketMetrics) {
-	if len(hh.packetStore) < 100 {
+	if len(hh.packetStore) < maxCachedPackets {
 		tempPacket := make([]byte, len(packet))
 		copy(tempPacket, packet)
 
@@ -137,6 +148,18 @@ func (hm *HandshakeManager) Run(ctx context.Context) {
 }
 
 func (hm *HandshakeManager) HandleIncoming(via ViaSender, packet []byte, h *header.H) {
+	// Gate on known handshake subtypes. Unknown subtypes (or future ones we
+	// don't yet support) are dropped here rather than silently routed through
+	// the IX path. Add a case when introducing a new pattern.
+	switch h.Subtype {
+	case header.HandshakeIXPSK0:
+		// supported
+	default:
+		hm.l.Debug("dropping handshake with unsupported subtype",
+			"from", via, "subtype", h.Subtype)
+		return
+	}
+
 	// First remote allow list check before we know the vpnIp
 	if !via.IsRelayed {
 		if !hm.lightHouse.GetRemoteAllowList().AllowUnknownVpnAddr(via.UdpAddr.Addr()) {
@@ -145,19 +168,27 @@ func (hm *HandshakeManager) HandleIncoming(via ViaSender, packet []byte, h *head
 		}
 	}
 
-	switch h.Subtype {
+	// First message of a new handshake. The wire format requires RemoteIndex
-	case header.HandshakeIXPSK0:
+	// to be zero here (the initiator has no responder index to fill in yet),
-		switch h.MessageCounter {
+	// and generateIndex never allocates 0, so any non-zero RemoteIndex on a
-		case 1:
+	// stage-1 packet is malformed or someone probing for an index collision.
-			ixHandshakeStage1(hm.f, via, packet, h)
+	// Drop without paying the cost of running noise on a pending Machine.
+	if h.MessageCounter == 1 {
+		if h.RemoteIndex != 0 {
+			hm.l.Debug("dropping stage-1 handshake with non-zero RemoteIndex",
+				"from", via, "remoteIndex", h.RemoteIndex)
+			return
+		}
+		hm.beginHandshake(via, packet, h)
+		return
+	}
 
-		case 2:
+	// Continuation message must match a pending handshake by index.
-			newHostinfo := hm.queryIndex(h.RemoteIndex)
+	// Anything else is an orphaned packet (e.g., late retransmit after
-			tearDown := ixHandshakeStage2(hm.f, via, newHostinfo, packet, h)
+	// timeout) and is dropped.
-			if tearDown && newHostinfo != nil {
+	if hh := hm.queryIndex(h.RemoteIndex); hh != nil {
-				hm.DeleteHostInfo(newHostinfo.hostinfo)
+		hm.continueHandshake(via, hh, packet)
-			}
+		return
-		}
 	}
 }
 
@@ -183,13 +214,22 @@ func (hm *HandshakeManager) handleOutbound(vpnIp netip.Addr, lighthouseTriggered
 	hostinfo := hh.hostinfo
 	// If we are out of time, clean up
 	if hh.counter >= hm.config.retries {
-		hh.hostinfo.logger(hm.l).Info("Handshake timed out",
+		fields := []any{
 			"udpAddrs", hh.hostinfo.remotes.CopyAddrs(hm.mainHostMap.GetPreferredRanges()),
 			"initiatorIndex", hh.hostinfo.localIndexId,
 			"remoteIndex", hh.hostinfo.remoteIndexId,
-			"handshake", m{"stage": 1, "style": "ix_psk0"},
 			"durationNs", time.Since(hh.startTime).Nanoseconds(),
-		)
+		}
+		// hh.machine can be nil here if buildStage0Packet never succeeded
+		// (e.g., no certificate available). In that case there's no useful
+		// handshake metadata to log.
+		if hh.machine != nil {
+			fields = append(fields, "handshake", m{
+				"stage": uint64(hh.machine.MessageIndex()),
+				"style": header.SubTypeName(header.Handshake, hh.machine.Subtype()),
+			})
+		}
+		hh.hostinfo.logger(hm.l).Info("Handshake timed out", fields...)
 		hm.metricTimedOut.Inc(1)
 		hm.DeleteHostInfo(hostinfo)
 		return
@@ -200,12 +240,25 @@ func (hm *HandshakeManager) handleOutbound(vpnIp netip.Addr, lighthouseTriggered
 
 	// Check if we have a handshake packet to transmit yet
 	if !hh.ready {
-		if !ixHandshakeStage0(hm.f, hh) {
+		if !hm.buildStage0Packet(hh) {
 			hm.OutboundHandshakeTimer.Add(vpnIp, hm.config.tryInterval*time.Duration(hh.counter))
 			return
 		}
 	}
 
+	// TODO: this hardcodes "always retransmit stage 0", which is correct for
+	// IX (the initiator only ever sends one packet, msg1) but wrong the
+	// moment a 3+ message pattern lands. The retry loop should resend the
+	// most recent outgoing message, not always stage 0. That implies
+	// HandshakeHostInfo tracking a single "currentOutbound" packet (bytes +
+	// header metadata) that gets replaced as the handshake progresses,
+	// instead of indexing into HandshakePacket.
+	stage0 := hostinfo.HandshakePacket[handshakePacketStage0]
+	hsFields := m{
+		"stage": uint64(hh.machine.MessageIndex()),
+		"style": header.SubTypeName(header.Handshake, hh.machine.Subtype()),
+	}
+
 	// Get a remotes object if we don't already have one.
 	// This is mainly to protect us as this should never be the case
 	// NB ^ This comment doesn't jive. It's how the thing gets initialized.
@@ -239,13 +292,13 @@ func (hm *HandshakeManager) handleOutbound(vpnIp netip.Addr, lighthouseTriggered
 	// Send the handshake to all known ips, stage 2 takes care of assigning the hostinfo.remote based on the first to reply
 	var sentTo []netip.AddrPort
 	hostinfo.remotes.ForEach(hm.mainHostMap.GetPreferredRanges(), func(addr netip.AddrPort, _ bool) {
-		hm.messageMetrics.Tx(header.Handshake, header.MessageSubType(hostinfo.HandshakePacket[0][1]), 1)
+		hm.messageMetrics.Tx(header.Handshake, hh.machine.Subtype(), 1)
-		err := hm.outside.WriteTo(hostinfo.HandshakePacket[0], addr)
+		err := hm.outside.WriteTo(stage0, addr)
 		if err != nil {
 			hostinfo.logger(hm.l).Error("Failed to send handshake message",
 				"udpAddr", addr,
 				"initiatorIndex", hostinfo.localIndexId,
-				"handshake", m{"stage": 1, "style": "ix_psk0"},
+				"handshake", hsFields,
 				"error", err,
 			)
 
@@ -260,156 +313,17 @@ func (hm *HandshakeManager) handleOutbound(vpnIp netip.Addr, lighthouseTriggered
 		hostinfo.logger(hm.l).Info("Handshake message sent",
 			"udpAddrs", sentTo,
 			"initiatorIndex", hostinfo.localIndexId,
-			"handshake", m{"stage": 1, "style": "ix_psk0"},
+			"handshake", hsFields,
 		)
 	} else if hm.l.Enabled(context.Background(), slog.LevelDebug) {
 		hostinfo.logger(hm.l).Debug("Handshake message sent",
 			"udpAddrs", sentTo,
 			"initiatorIndex", hostinfo.localIndexId,
-			"handshake", m{"stage": 1, "style": "ix_psk0"},
+			"handshake", hsFields,
 		)
 	}
 
-	if hm.config.useRelays && len(hostinfo.remotes.relays) > 0 {
+	hm.f.relayManager.StartRelays(hm.f, vpnIp, hostinfo, stage0)
-		hostinfo.logger(hm.l).Info("Attempt to relay through hosts", "relays", hostinfo.remotes.relays)
-		// Send a RelayRequest to all known Relay IP's
-		for _, relay := range hostinfo.remotes.relays {
-			// Don't relay through the host I'm trying to connect to
-			if relay == vpnIp {
-				continue
-			}
-
-			// Don't relay to myself
-			if hm.f.myVpnAddrsTable.Contains(relay) {
-				continue
-			}
-
-			relayHostInfo := hm.mainHostMap.QueryVpnAddr(relay)
-			if relayHostInfo == nil || !relayHostInfo.remote.IsValid() {
-				hostinfo.logger(hm.l).Info("Establish tunnel to relay target", "relay", relay.String())
-				hm.f.Handshake(relay)
-				continue
-			}
-			// Check the relay HostInfo to see if we already established a relay through
-			existingRelay, ok := relayHostInfo.relayState.QueryRelayForByIp(vpnIp)
-			if !ok {
-				// No relays exist or requested yet.
-				if relayHostInfo.remote.IsValid() {
-					idx, err := AddRelay(hm.l, relayHostInfo, hm.mainHostMap, vpnIp, nil, TerminalType, Requested)
-					if err != nil {
-						hostinfo.logger(hm.l).Info("Failed to add relay to hostmap", "relay", relay.String(), "error", err)
-					}
-
-					m := NebulaControl{
-						Type:                NebulaControl_CreateRelayRequest,
-						InitiatorRelayIndex: idx,
-					}
-
-					switch relayHostInfo.GetCert().Certificate.Version() {
-					case cert.Version1:
-						if !hm.f.myVpnAddrs[0].Is4() {
-							hostinfo.logger(hm.l).Error("can not establish v1 relay with a v6 network because the relay is not running a current nebula version")
-							continue
-						}
-
-						if !vpnIp.Is4() {
-							hostinfo.logger(hm.l).Error("can not establish v1 relay with a v6 remote network because the relay is not running a current nebula version")
-							continue
-						}
-
-						b := hm.f.myVpnAddrs[0].As4()
-						m.OldRelayFromAddr = binary.BigEndian.Uint32(b[:])
-						b = vpnIp.As4()
-						m.OldRelayToAddr = binary.BigEndian.Uint32(b[:])
-					case cert.Version2:
-						m.RelayFromAddr = netAddrToProtoAddr(hm.f.myVpnAddrs[0])
-						m.RelayToAddr = netAddrToProtoAddr(vpnIp)
-					default:
-						hostinfo.logger(hm.l).Error("Unknown certificate version found while creating relay")
-						continue
-					}
-
-					msg, err := m.Marshal()
-					if err != nil {
-						hostinfo.logger(hm.l).Error("Failed to marshal Control message to create relay", "error", err)
-					} else {
-						hm.f.SendMessageToHostInfo(header.Control, 0, relayHostInfo, msg, make([]byte, 12), make([]byte, mtu))
-						hm.l.Info("send CreateRelayRequest",
-							"relayFrom", hm.f.myVpnAddrs[0],
-							"relayTo", vpnIp,
-							"initiatorRelayIndex", idx,
-							"relay", relay,
-						)
-					}
-				}
-				continue
-			}
-
-			switch existingRelay.State {
-			case Established:
-				hostinfo.logger(hm.l).Info("Send handshake via relay", "relay", relay.String())
-				hm.f.SendVia(relayHostInfo, existingRelay, hostinfo.HandshakePacket[0], make([]byte, 12), make([]byte, mtu), false)
-			case Disestablished:
-				// Mark this relay as 'requested'
-				relayHostInfo.relayState.UpdateRelayForByIpState(vpnIp, Requested)
-				fallthrough
-			case Requested:
-				hostinfo.logger(hm.l).Info("Re-send CreateRelay request", "relay", relay.String())
-				// Re-send the CreateRelay request, in case the previous one was lost.
-				m := NebulaControl{
-					Type:                NebulaControl_CreateRelayRequest,
-					InitiatorRelayIndex: existingRelay.LocalIndex,
-				}
-
-				switch relayHostInfo.GetCert().Certificate.Version() {
-				case cert.Version1:
-					if !hm.f.myVpnAddrs[0].Is4() {
-						hostinfo.logger(hm.l).Error("can not establish v1 relay with a v6 network because the relay is not running a current nebula version")
-						continue
-					}
-
-					if !vpnIp.Is4() {
-						hostinfo.logger(hm.l).Error("can not establish v1 relay with a v6 remote network because the relay is not running a current nebula version")
-						continue
-					}
-
-					b := hm.f.myVpnAddrs[0].As4()
-					m.OldRelayFromAddr = binary.BigEndian.Uint32(b[:])
-					b = vpnIp.As4()
-					m.OldRelayToAddr = binary.BigEndian.Uint32(b[:])
-				case cert.Version2:
-					m.RelayFromAddr = netAddrToProtoAddr(hm.f.myVpnAddrs[0])
-					m.RelayToAddr = netAddrToProtoAddr(vpnIp)
-				default:
-					hostinfo.logger(hm.l).Error("Unknown certificate version found while creating relay")
-					continue
-				}
-				msg, err := m.Marshal()
-				if err != nil {
-					hostinfo.logger(hm.l).Error("Failed to marshal Control message to create relay", "error", err)
-				} else {
-					// This must send over the hostinfo, not over hm.Hosts[ip]
-					hm.f.SendMessageToHostInfo(header.Control, 0, relayHostInfo, msg, make([]byte, 12), make([]byte, mtu))
-					hm.l.Info("send CreateRelayRequest",
-						"relayFrom", hm.f.myVpnAddrs[0],
-						"relayTo", vpnIp,
-						"initiatorRelayIndex", existingRelay.LocalIndex,
-						"relay", relay,
-					)
-				}
-			case PeerRequested:
-				// PeerRequested only occurs in Forwarding relays, not Terminal relays, and this is a Terminal relay case.
-				fallthrough
-			default:
-				hostinfo.logger(hm.l).Error("Relay unexpected state",
-					"vpnIp", vpnIp,
-					"state", existingRelay.State,
-					"relay", relay,
-				)
-
-			}
-		}
-	}
 
 	// If a lighthouse triggered this attempt then we are still in the timer wheel and do not need to re-add
 	if !lighthouseTriggered {
@@ -587,7 +501,7 @@ func (hm *HandshakeManager) Complete(hostinfo *HostInfo, f *Interface) {
 // allocateIndex generates a unique localIndexId for this HostInfo
 // and adds it to the pendingHostMap. Will error if we are unable to generate
 // a unique localIndexId
-func (hm *HandshakeManager) allocateIndex(hh *HandshakeHostInfo) error {
+func (hm *HandshakeManager) allocateIndex(hh *HandshakeHostInfo) (uint32, error) {
 	hm.mainHostMap.RLock()
 	defer hm.mainHostMap.RUnlock()
 	hm.Lock()
@@ -596,7 +510,7 @@ func (hm *HandshakeManager) allocateIndex(hh *HandshakeHostInfo) error {
 	for range 32 {
 		index, err := generateIndex(hm.l)
 		if err != nil {
-			return err
+			return 0, err
 		}
 
 		_, inPending := hm.indexes[index]
@@ -605,11 +519,11 @@ func (hm *HandshakeManager) allocateIndex(hh *HandshakeHostInfo) error {
 		if !inMain && !inPending {
 			hh.hostinfo.localIndexId = index
 			hm.indexes[index] = hh
-			return nil
+			return index, nil
 		}
 	}
 
-	return errors.New("failed to generate unique localIndexId")
+	return 0, errors.New("failed to generate unique localIndexId")
 }
 
 func (hm *HandshakeManager) DeleteHostInfo(hostinfo *HostInfo) {
@@ -728,3 +642,530 @@ func generateIndex(l *slog.Logger) (uint32, error) {
 func hsTimeout(tries int64, interval time.Duration) time.Duration {
 	return time.Duration(tries / 2 * ((2 * int64(interval)) + (tries-1)*int64(interval)))
 }
+
+// buildStage0Packet creates the initial handshake packet for the initiator.
+func (hm *HandshakeManager) buildStage0Packet(hh *HandshakeHostInfo) bool {
+	cs := hm.f.pki.getCertState()
+	v := cs.DefaultVersion()
+	if hh.initiatingVersionOverride != cert.VersionPre1 {
+		v = hh.initiatingVersionOverride
+	} else if v < cert.Version2 {
+		for _, a := range hh.hostinfo.vpnAddrs {
+			if a.Is6() {
+				v = cert.Version2
+				break
+			}
+		}
+	}
+
+	cred := cs.GetCredential(v)
+	if cred == nil {
+		hm.f.l.Error("Unable to handshake with host because no certificate is available",
+			"vpnAddrs", hh.hostinfo.vpnAddrs, "certVersion", v)
+		return false
+	}
+
+	machine, err := handshake.NewMachine(
+		v, cs.GetCredential,
+		hm.certVerifier(), func() (uint32, error) { return hm.allocateIndex(hh) },
+		true, header.HandshakeIXPSK0,
+	)
+	if err != nil {
+		hm.f.l.Error("Failed to create handshake machine",
+			"vpnAddrs", hh.hostinfo.vpnAddrs, "error", err)
+		return false
+	}
+
+	msg, err := machine.Initiate(nil)
+	if err != nil {
+		hm.f.l.Error("Failed to initiate handshake",
+			"vpnAddrs", hh.hostinfo.vpnAddrs, "error", err)
+		return false
+	}
+
+	// hostinfo.ConnectionState stays nil until the handshake completes in
+	// continueHandshake. Pre-completion control surfaces guard with nil
+	// checks; the data plane never observes a pending hostinfo.
+	hh.hostinfo.HandshakePacket[handshakePacketStage0] = msg
+	hh.machine = machine
+	hh.ready = true
+	return true
+}
+
+// beginHandshake handles an incoming handshake packet that doesn't match any
+// existing pending handshake. It creates a new responder Machine and processes
+// the first message.
+func (hm *HandshakeManager) beginHandshake(via ViaSender, packet []byte, h *header.H) {
+	f := hm.f
+	cs := f.pki.getCertState()
+
+	v := cs.DefaultVersion()
+	if cs.GetCredential(v) == nil {
+		f.l.Error("Unable to handshake with host because no certificate is available",
+			"from", via, "certVersion", v)
+		return
+	}
+
+	machine, err := handshake.NewMachine(
+		v, cs.GetCredential,
+		hm.certVerifier(), func() (uint32, error) { return generateIndex(f.l) },
+		false, header.HandshakeIXPSK0,
+	)
+	if err != nil {
+		f.l.Error("Failed to create handshake machine", "from", via, "error", err)
+		return
+	}
+
+	response, result, err := machine.ProcessPacket(nil, packet)
+	if err != nil {
+		f.l.Error("Failed to process handshake packet", "from", via, "error", err)
+		return
+	}
+
+	if result == nil {
+		// Multi-message pattern: the responder Machine would need to be
+		// registered in hm.indexes so a future inbound packet finds it via
+		// continueHandshake. The current manager doesn't do that yet, so
+		// fail loudly rather than silently dropping the in-flight handshake.
+		// TODO: support multi-message responder flows (XX, pqIX, etc.).
+		// See also the IX-shaped cipher key assignment in handshake.Machine.
+		f.l.Error("multi-message handshake responder is not supported",
+			"from", via, "error", handshake.ErrMultiMessageUnsupported)
+		return
+	}
+
+	remoteCert := result.RemoteCert
+	if remoteCert == nil {
+		f.l.Error("Handshake did not produce a peer certificate", "from", via)
+		return
+	}
+
+	// Validate peer identity
+	vpnAddrs, anyVpnAddrsInCommon, ok := hm.validatePeerCert(via, remoteCert)
+	if !ok {
+		return
+	}
+
+	hostinfo := &HostInfo{
+		ConnectionState:   newConnectionStateFromResult(result),
+		localIndexId:      result.LocalIndex,
+		remoteIndexId:     result.RemoteIndex,
+		vpnAddrs:          vpnAddrs,
+		HandshakePacket:   make(map[uint8][]byte, 0),
+		lastHandshakeTime: result.HandshakeTime,
+		relayState: RelayState{
+			relays:         nil,
+			relayForByAddr: map[netip.Addr]*Relay{},
+			relayForByIdx:  map[uint32]*Relay{},
+		},
+	}
+
+	msg := "Handshake message received"
+	if !anyVpnAddrsInCommon {
+		msg = "Handshake message received, but no vpnNetworks in common."
+	}
+	f.l.Info(msg,
+		"vpnAddrs", vpnAddrs,
+		"from", via,
+		"certName", remoteCert.Certificate.Name(),
+		"certVersion", remoteCert.Certificate.Version(),
+		"fingerprint", remoteCert.Fingerprint,
+		"issuer", remoteCert.Certificate.Issuer(),
+		"initiatorIndex", result.RemoteIndex,
+		"responderIndex", result.LocalIndex,
+		"handshake", m{"stage": uint64(machine.MessageIndex()), "style": header.SubTypeName(header.Handshake, machine.Subtype())},
+	)
+
+	// packet aliases the listener's incoming buffer, so this copy must stay.
+	hostinfo.HandshakePacket[handshakePacketStage0] = make([]byte, len(packet[header.Len:]))
+	copy(hostinfo.HandshakePacket[handshakePacketStage0], packet[header.Len:])
+
+	// response was freshly allocated by ProcessPacket; safe to retain directly.
+	if response != nil {
+		hostinfo.HandshakePacket[handshakePacketStage2] = response
+	}
+
+	hostinfo.remotes = f.lightHouse.QueryCache(vpnAddrs)
+	if !via.IsRelayed {
+		hostinfo.SetRemote(via.UdpAddr)
+	}
+	hostinfo.buildNetworks(f.myVpnNetworksTable, remoteCert.Certificate)
+
+	existing, err := hm.CheckAndComplete(hostinfo, handshakePacketStage0, f)
+	if err != nil {
+		hm.handleCheckAndCompleteError(err, existing, hostinfo, via)
+		return
+	}
+
+	hm.sendHandshakeResponse(via, response, hostinfo, false)
+	f.connectionManager.AddTrafficWatch(hostinfo)
+	hostinfo.remotes.RefreshFromHandshake(vpnAddrs)
+
+	// Don't wait for UpdateWorker
+	if f.lightHouse.IsAnyLighthouseAddr(vpnAddrs) {
+		f.lightHouse.TriggerUpdate()
+	}
+}
+
+// continueHandshake feeds an incoming packet to an existing pending handshake Machine.
+func (hm *HandshakeManager) continueHandshake(via ViaSender, hh *HandshakeHostInfo, packet []byte) {
+	f := hm.f
+
+	hh.Lock()
+	defer hh.Unlock()
+
+	// Re-verify hh is still tracked. Between queryIndex returning and us taking
+	// hh.Lock, handleOutbound may have timed out and deleted it. Once we hold
+	// hh.Lock no other deleter can race our index: handleOutbound also takes
+	// hh.Lock first, and handleRecvError targets a main-hostmap entry with a
+	// different localIndexId.
+	hm.RLock()
+	cur, ok := hm.indexes[hh.hostinfo.localIndexId]
+	hm.RUnlock()
+	if !ok || cur != hh {
+		return
+	}
+
+	hostinfo := hh.hostinfo
+	if !via.IsRelayed {
+		if !f.lightHouse.GetRemoteAllowList().AllowAll(hostinfo.vpnAddrs, via.UdpAddr.Addr()) {
+			f.l.Debug("lighthouse.remote_allow_list denied incoming handshake",
+				"vpnAddrs", hostinfo.vpnAddrs, "from", via)
+			return
+		}
+	}
+
+	machine := hh.machine
+	if machine == nil {
+		f.l.Error("No handshake machine available for continuation",
+			"vpnAddrs", hostinfo.vpnAddrs, "from", via)
+		hm.DeleteHostInfo(hostinfo)
+		return
+	}
+
+	response, result, err := machine.ProcessPacket(nil, packet)
+	if err != nil {
+		// Recoverable errors are routine noise, log at Debug. Fatal errors get a Warn.
+		if machine.Failed() {
+			f.l.Warn("Failed to process handshake packet, abandoning",
+				"vpnAddrs", hostinfo.vpnAddrs, "from", via, "error", err)
+			hm.DeleteHostInfo(hostinfo)
+		} else {
+			f.l.Debug("Failed to process handshake packet",
+				"vpnAddrs", hostinfo.vpnAddrs, "from", via, "error", err)
+		}
+		return
+	}
+
+	if response != nil {
+		hm.sendHandshakeResponse(via, response, hostinfo, false)
+	}
+
+	if result == nil {
+		return
+	}
+
+	// Handshake complete; build the ConnectionState now that we have keys and a verified peer cert.
+	hostinfo.ConnectionState = newConnectionStateFromResult(result)
+
+	remoteCert := result.RemoteCert
+	if remoteCert == nil {
+		f.l.Error("Handshake completed without peer certificate",
+			"vpnAddrs", hostinfo.vpnAddrs, "from", via)
+		hm.DeleteHostInfo(hostinfo)
+		return
+	}
+
+	vpnNetworks := remoteCert.Certificate.Networks()
+	hostinfo.remoteIndexId = result.RemoteIndex
+	hostinfo.lastHandshakeTime = result.HandshakeTime
+
+	if !via.IsRelayed {
+		hostinfo.SetRemote(via.UdpAddr)
+	} else {
+		hostinfo.relayState.InsertRelayTo(via.relayHI.vpnAddrs[0])
+	}
+
+	// Verify correct host responded (initiator check)
+	vpnAddrs := make([]netip.Addr, len(vpnNetworks))
+	correctHostResponded := false
+	anyVpnAddrsInCommon := false
+	for i, network := range vpnNetworks {
+		// inside.go drops self-routed packets at the firewall stage, but we'd
+		// rather not let a self-handshake complete in the first place: it
+		// wastes a hostmap slot, suppresses no log, and obscures routing
+		// misconfig. Explicit refusal here mirrors the responder-side check
+		// in validatePeerCert.
+		if f.myVpnAddrsTable.Contains(network.Addr()) {
+			f.l.Error("Refusing to handshake with myself",
+				"vpnNetworks", vpnNetworks,
+				"from", via,
+				"certName", remoteCert.Certificate.Name(),
+				"certVersion", remoteCert.Certificate.Version(),
+				"fingerprint", remoteCert.Fingerprint,
+				"issuer", remoteCert.Certificate.Issuer(),
+				"handshake", m{"stage": uint64(machine.MessageIndex()), "style": header.SubTypeName(header.Handshake, machine.Subtype())},
+			)
+			hm.DeleteHostInfo(hostinfo)
+			return
+		}
+		vpnAddrs[i] = network.Addr()
+		if hostinfo.vpnAddrs[0] == network.Addr() {
+			correctHostResponded = true
+		}
+		if f.myVpnNetworksTable.Contains(network.Addr()) {
+			anyVpnAddrsInCommon = true
+		}
+	}
+
+	if !correctHostResponded {
+		f.l.Info("Incorrect host responded to handshake",
+			"intendedVpnAddrs", hostinfo.vpnAddrs,
+			"haveVpnNetworks", vpnNetworks,
+			"from", via,
+			"certName", remoteCert.Certificate.Name(),
+			"certVersion", remoteCert.Certificate.Version(),
+			"fingerprint", remoteCert.Fingerprint,
+			"issuer", remoteCert.Certificate.Issuer(),
+			"handshake", m{"stage": uint64(machine.MessageIndex()), "style": header.SubTypeName(header.Handshake, machine.Subtype())},
+		)
+
+		hm.DeleteHostInfo(hostinfo)
+		hm.StartHandshake(hostinfo.vpnAddrs[0], func(newHH *HandshakeHostInfo) {
+			newHH.hostinfo.remotes = hostinfo.remotes
+			newHH.hostinfo.remotes.BlockRemote(via)
+			newHH.packetStore = hh.packetStore
+			hh.packetStore = []*cachedPacket{}
+			hostinfo.vpnAddrs = vpnAddrs
+			f.sendCloseTunnel(hostinfo)
+		})
+		return
+	}
+
+	duration := time.Since(hh.startTime).Nanoseconds()
+	msg := "Handshake message received"
+	if !anyVpnAddrsInCommon {
+		msg = "Handshake message received, but no vpnNetworks in common."
+	}
+	f.l.Info(msg,
+		"vpnAddrs", vpnAddrs,
+		"from", via,
+		"certName", remoteCert.Certificate.Name(),
+		"certVersion", remoteCert.Certificate.Version(),
+		"fingerprint", remoteCert.Fingerprint,
+		"issuer", remoteCert.Certificate.Issuer(),
+		"initiatorIndex", result.LocalIndex,
+		"responderIndex", result.RemoteIndex,
+		"handshake", m{"stage": uint64(machine.MessageIndex()), "style": header.SubTypeName(header.Handshake, machine.Subtype())},
+		"durationNs", duration,
+		"sentCachedPackets", len(hh.packetStore),
+	)
+
+	hostinfo.vpnAddrs = vpnAddrs
+	hostinfo.buildNetworks(f.myVpnNetworksTable, remoteCert.Certificate)
+
+	hm.Complete(hostinfo, f)
+	f.connectionManager.AddTrafficWatch(hostinfo)
+
+	if len(hh.packetStore) > 0 {
+		if f.l.Enabled(context.Background(), slog.LevelDebug) {
+			hostinfo.logger(f.l).Debug("Sending stored packets", "count", len(hh.packetStore))
+		}
+		buf := f.bufAlloc.Acquire()
+		for _, cp := range hh.packetStore {
+			cp.callback(cp.messageType, cp.messageSubType, hostinfo, cp.packet, buf)
+		}
+		f.bufAlloc.Release(buf)
+		f.cachedPacketMetrics.sent.Inc(int64(len(hh.packetStore)))
+	}
+
+	hostinfo.remotes.RefreshFromHandshake(vpnAddrs)
+	f.metricHandshakes.Update(duration)
+
+	// Don't wait for UpdateWorker
+	if f.lightHouse.IsAnyLighthouseAddr(vpnAddrs) {
+		f.lightHouse.TriggerUpdate()
+	}
+}
+
+// validatePeerCert checks the peer certificate for self-connection and remote allow list.
+// Returns the VPN addrs, whether any of them fall within one of our own VPN
+// networks, and true if valid; false if rejected.
+func (hm *HandshakeManager) validatePeerCert(via ViaSender, remoteCert *cert.CachedCertificate) ([]netip.Addr, bool, bool) {
+	f := hm.f
+	vpnNetworks := remoteCert.Certificate.Networks()
+
+	// The cert package rejects host certs with no networks at parse time, so
+	// reaching this state would mean an invariant was bypassed elsewhere.
+	// Refuse explicitly so downstream code (which indexes vpnAddrs[0]) can't
+	// panic if that invariant ever changes.
+	if len(vpnNetworks) == 0 {
+		f.l.Info("No networks in certificate",
+			"from", via, "cert", remoteCert)
+		return nil, false, false
+	}
+
+	vpnAddrs := make([]netip.Addr, len(vpnNetworks))
+	anyVpnAddrsInCommon := false
+
+	for i, network := range vpnNetworks {
+		if f.myVpnAddrsTable.Contains(network.Addr()) {
+			f.l.Error("Refusing to handshake with myself",
+				"vpnNetworks", vpnNetworks,
+				"from", via,
+				"certName", remoteCert.Certificate.Name(),
+				"certVersion", remoteCert.Certificate.Version(),
+				"fingerprint", remoteCert.Fingerprint,
+				"issuer", remoteCert.Certificate.Issuer(),
+			)
+			return nil, false, false
+		}
+		vpnAddrs[i] = network.Addr()
+		if f.myVpnNetworksTable.Contains(network.Addr()) {
+			anyVpnAddrsInCommon = true
+		}
+	}
+
+	if !via.IsRelayed {
+		if !f.lightHouse.GetRemoteAllowList().AllowAll(vpnAddrs, via.UdpAddr.Addr()) {
+			f.l.Debug("lighthouse.remote_allow_list denied incoming handshake",
+				"vpnAddrs", vpnAddrs, "from", via)
+			return nil, false, false
+		}
+	}
+
+	return vpnAddrs, anyVpnAddrsInCommon, true
+}
+
+// sendHandshakeResponse sends a handshake response via the appropriate transport.
+// cached is true when msg is a stored response being retransmitted because
+// the peer's stage-1 retransmit landed (the ErrAlreadySeen path); false on a
+// fresh response.
+func (hm *HandshakeManager) sendHandshakeResponse(via ViaSender, msg []byte, hostinfo *HostInfo, cached bool) {
+	if msg == nil {
+		return
+	}
+
+	f := hm.f
+	f.messageMetrics.Tx(header.Handshake, header.MessageSubType(msg[1]), 1)
+
+	// Common log fields. peerCert may be nil during intermediate
+	// multi-message flows (handshake hasn't completed yet); skip the cert
+	// block if so.
+	logFields := []any{
+		"vpnAddrs", hostinfo.vpnAddrs,
+		"handshake", m{"stage": uint64(2), "style": header.SubTypeName(header.Handshake, header.HandshakeIXPSK0)},
+		"cached", cached,
+		"initiatorIndex", hostinfo.remoteIndexId,
+		"responderIndex", hostinfo.localIndexId,
+	}
+	if peerCert := hostinfo.ConnectionState.peerCert; peerCert != nil {
+		logFields = append(logFields,
+			"certName", peerCert.Certificate.Name(),
+			"certVersion", peerCert.Certificate.Version(),
+			"fingerprint", peerCert.Fingerprint,
+			"issuer", peerCert.Certificate.Issuer(),
+		)
+	}
+
+	if !via.IsRelayed {
+		fields := append(logFields, "from", via)
+		err := f.outside.WriteTo(msg, via.UdpAddr)
+		if err != nil {
+			f.l.Error("Failed to send handshake message", append(fields, "error", err)...)
+		} else {
+			f.l.Info("Handshake message sent", fields...)
+		}
+	} else {
+		if via.relay == nil {
+			f.l.Error("Handshake send failed: both addr and via.relay are nil.")
+			return
+		}
+		hostinfo.relayState.InsertRelayTo(via.relayHI.vpnAddrs[0])
+		// We received a valid handshake on this relay, so make sure the relay
+		// state reflects that, in case it had been marked Disestablished.
+		via.relayHI.relayState.UpdateRelayForByIdxState(via.remoteIdx, Established)
+		buf := f.bufAlloc.Acquire()
+		f.SendVia(via.relayHI, via.relay, msg, buf)
+		f.bufAlloc.Release(buf)
+		f.l.Info("Handshake message sent", append(logFields, "relay", via.relayHI.vpnAddrs[0])...)
+	}
+}
+
+// handleCheckAndCompleteError handles errors from CheckAndComplete.
+// This only fires from the responder-side beginHandshake path, after the
+// peer cert has been validated and ConnectionState populated, so peerCert
+// is always non-nil for the cases that log it.
+func (hm *HandshakeManager) handleCheckAndCompleteError(err error, existing, hostinfo *HostInfo, via ViaSender) {
+	f := hm.f
+	peerCert := hostinfo.ConnectionState.peerCert
+	hsFields := m{"stage": uint64(1), "style": header.SubTypeName(header.Handshake, header.HandshakeIXPSK0)}
+
+	switch err {
+	case ErrAlreadySeen:
+		if existing.SetRemoteIfPreferred(f.hostMap, via) {
+			buf := f.bufAlloc.Acquire()
+			f.SendMessageToVpnAddr(header.Test, header.TestRequest, hostinfo.vpnAddrs[0], []byte(""), buf)
+			f.bufAlloc.Release(buf)
+		}
+		// Resend the original response. The peer is committed to that response's
+		// ephemeral keys; a freshly-built one would have different keys and break
+		// the tunnel even though both sides "completed" the handshake.
+		if msg := existing.HandshakePacket[handshakePacketStage2]; msg != nil {
+			hm.sendHandshakeResponse(via, msg, existing, true)
+		}
+
+	case ErrExistingHostInfo:
+		f.l.Info("Handshake too old",
+			"vpnAddrs", hostinfo.vpnAddrs,
+			"from", via,
+			"certName", peerCert.Certificate.Name(),
+			"certVersion", peerCert.Certificate.Version(),
+			"fingerprint", peerCert.Fingerprint,
+			"issuer", peerCert.Certificate.Issuer(),
+			"oldHandshakeTime", existing.lastHandshakeTime,
+			"newHandshakeTime", hostinfo.lastHandshakeTime,
+			"initiatorIndex", hostinfo.remoteIndexId,
+			"responderIndex", hostinfo.localIndexId,
+			"handshake", hsFields,
+		)
+		buf := f.bufAlloc.Acquire()
+		f.SendMessageToVpnAddr(header.Test, header.TestRequest, hostinfo.vpnAddrs[0], []byte(""), buf)
+		f.bufAlloc.Release(buf)
+
+	case ErrLocalIndexCollision:
+		f.l.Error("Failed to add HostInfo due to localIndex collision",
+			"vpnAddrs", hostinfo.vpnAddrs,
+			"from", via,
+			"certName", peerCert.Certificate.Name(),
+			"certVersion", peerCert.Certificate.Version(),
+			"fingerprint", peerCert.Fingerprint,
+			"issuer", peerCert.Certificate.Issuer(),
+			"localIndex", hostinfo.localIndexId,
+			"initiatorIndex", hostinfo.remoteIndexId,
+			"responderIndex", hostinfo.localIndexId,
+			"handshake", hsFields,
+		)
+
+	default:
+		f.l.Error("Failed to add HostInfo to HostMap",
+			"vpnAddrs", hostinfo.vpnAddrs,
+			"from", via,
+			"error", err,
+			"certName", peerCert.Certificate.Name(),
+			"certVersion", peerCert.Certificate.Version(),
+			"fingerprint", peerCert.Fingerprint,
+			"issuer", peerCert.Certificate.Issuer(),
+			"initiatorIndex", hostinfo.remoteIndexId,
+			"responderIndex", hostinfo.localIndexId,
+			"handshake", hsFields,
+		)
+	}
+}
+
+// certVerifier returns a CertVerifier that validates certs against the current CA pool.
+func (hm *HandshakeManager) certVerifier() handshake.CertVerifier {
+	return func(c cert.Certificate) (*cert.CachedCertificate, error) {
+		return hm.f.pki.GetCAPool().VerifyCertificate(time.Now(), c)
+	}
+}

handshake_manager_test.go

@@ -5,6 +5,7 @@ import (
 	"testing"
 	"time"
 
+	"github.com/gaissmai/bart"
 	"github.com/slackhq/nebula/cert"
 	"github.com/slackhq/nebula/header"
 	"github.com/slackhq/nebula/test"
@@ -27,7 +28,7 @@ func Test_NewHandshakeManagerVpnIp(t *testing.T) {
 		initiatingVersion: cert.Version1,
 		privateKey:        []byte{},
 		v1Cert:            &dummyCert{version: cert.Version1},
-		v1HandshakeBytes:  []byte{},
+		v1Credential:      nil,
 	}
 
 	blah := NewHandshakeManager(l, mainHM, lh, &udp.NoopConn{}, defaultHandshakeConfig)
@@ -79,15 +80,15 @@ func testCountTimerWheelEntries(tw *LockingTimerWheel[netip.Addr]) (c int) {
 type mockEncWriter struct {
 }
 
-func (mw *mockEncWriter) SendMessageToVpnAddr(_ header.MessageType, _ header.MessageSubType, _ netip.Addr, _, _, _ []byte) {
+func (mw *mockEncWriter) SendMessageToVpnAddr(_ header.MessageType, _ header.MessageSubType, _ netip.Addr, _ []byte, _ *WireBuffer) {
 	return
 }
 
-func (mw *mockEncWriter) SendVia(_ *HostInfo, _ *Relay, _, _, _ []byte, _ bool) {
+func (mw *mockEncWriter) SendVia(_ *HostInfo, _ *Relay, _ []byte, _ *WireBuffer) {
 	return
 }
 
-func (mw *mockEncWriter) SendMessageToHostInfo(_ header.MessageType, _ header.MessageSubType, _ *HostInfo, _, _, _ []byte) {
+func (mw *mockEncWriter) SendMessageToHostInfo(_ header.MessageType, _ header.MessageSubType, _ *HostInfo, _ []byte, _ *WireBuffer) {
 	return
 }
 
@@ -100,3 +101,137 @@ func (mw *mockEncWriter) GetHostInfo(_ netip.Addr) *HostInfo {
 func (mw *mockEncWriter) GetCertState() *CertState {
 	return &CertState{initiatingVersion: cert.Version2}
 }
+
+func TestValidatePeerCert(t *testing.T) {
+	l := test.NewLogger()
+
+	myNetwork := netip.MustParsePrefix("10.0.0.1/24")
+	myAddrTable := new(bart.Lite)
+	myAddrTable.Insert(netip.PrefixFrom(myNetwork.Addr(), myNetwork.Addr().BitLen()))
+	myNetTable := new(bart.Lite)
+	myNetTable.Insert(myNetwork.Masked())
+
+	newHM := func() *HandshakeManager {
+		hm := NewHandshakeManager(l, newHostMap(l), newTestLighthouse(), &udp.NoopConn{}, defaultHandshakeConfig)
+		hm.f = &Interface{
+			handshakeManager:   hm,
+			pki:                &PKI{},
+			l:                  l,
+			myVpnAddrsTable:    myAddrTable,
+			myVpnNetworksTable: myNetTable,
+			lightHouse:         hm.lightHouse,
+		}
+		return hm
+	}
+
+	cached := func(networks ...netip.Prefix) *cert.CachedCertificate {
+		return &cert.CachedCertificate{
+			Certificate: &dummyCert{name: "peer", networks: networks},
+		}
+	}
+
+	via := ViaSender{
+		UdpAddr:   netip.MustParseAddrPort("198.51.100.7:4242"),
+		IsRelayed: true, // skip the remote allow list (covered separately)
+	}
+
+	t.Run("addr inside our networks sets anyVpnAddrsInCommon", func(t *testing.T) {
+		hm := newHM()
+		// 10.0.0.2 falls inside our 10.0.0.0/24
+		addrs, common, ok := hm.validatePeerCert(via, cached(netip.MustParsePrefix("10.0.0.2/24")))
+		assert.True(t, ok)
+		assert.True(t, common)
+		assert.Equal(t, []netip.Addr{netip.MustParseAddr("10.0.0.2")}, addrs)
+	})
+
+	t.Run("addr outside our networks leaves anyVpnAddrsInCommon false", func(t *testing.T) {
+		hm := newHM()
+		addrs, common, ok := hm.validatePeerCert(via, cached(netip.MustParsePrefix("192.168.1.5/24")))
+		assert.True(t, ok)
+		assert.False(t, common)
+		assert.Equal(t, []netip.Addr{netip.MustParseAddr("192.168.1.5")}, addrs)
+	})
+
+	t.Run("any matching network is enough", func(t *testing.T) {
+		hm := newHM()
+		addrs, common, ok := hm.validatePeerCert(via, cached(
+			netip.MustParsePrefix("192.168.1.5/24"),
+			netip.MustParsePrefix("10.0.0.42/24"),
+		))
+		assert.True(t, ok)
+		assert.True(t, common)
+		assert.Len(t, addrs, 2)
+	})
+
+	t.Run("self-handshake is rejected", func(t *testing.T) {
+		hm := newHM()
+		// 10.0.0.1 is in myVpnAddrsTable
+		addrs, common, ok := hm.validatePeerCert(via, cached(netip.MustParsePrefix("10.0.0.1/24")))
+		assert.False(t, ok)
+		assert.False(t, common)
+		assert.Nil(t, addrs)
+	})
+
+	t.Run("cert with no networks is rejected", func(t *testing.T) {
+		hm := newHM()
+		addrs, common, ok := hm.validatePeerCert(via, cached())
+		assert.False(t, ok)
+		assert.False(t, common)
+		assert.Nil(t, addrs)
+	})
+}
+
+func TestHandleIncomingDispatch(t *testing.T) {
+	l := test.NewLogger()
+
+	newHM := func() *HandshakeManager {
+		hm := NewHandshakeManager(l, newHostMap(l), newTestLighthouse(), &udp.NoopConn{}, defaultHandshakeConfig)
+		hm.f = &Interface{
+			handshakeManager: hm,
+			pki:              &PKI{},
+			l:                l,
+		}
+		return hm
+	}
+
+	via := ViaSender{
+		UdpAddr:   netip.MustParseAddrPort("198.51.100.7:4242"),
+		IsRelayed: true, // bypass remote allow list
+	}
+
+	// A packet body of zero length is fine for these tests: dispatch is
+	// gated on header fields, and we assert that we never reach noise/cert
+	// processing for any of the malformed shapes here.
+	pkt := make([]byte, header.Len)
+
+	t.Run("unsupported subtype dropped", func(t *testing.T) {
+		hm := newHM()
+		h := &header.H{Type: header.Handshake, Subtype: header.MessageSubType(99), MessageCounter: 1}
+		hm.HandleIncoming(via, pkt, h)
+		assert.Empty(t, hm.indexes, "no pending handshake should be created")
+	})
+
+	t.Run("stage-1 with non-zero RemoteIndex dropped", func(t *testing.T) {
+		hm := newHM()
+		h := &header.H{
+			Type:           header.Handshake,
+			Subtype:        header.HandshakeIXPSK0,
+			RemoteIndex:    0xdeadbeef,
+			MessageCounter: 1,
+		}
+		hm.HandleIncoming(via, pkt, h)
+		assert.Empty(t, hm.indexes, "spoofed stage-1 must not create a pending machine")
+	})
+
+	t.Run("continuation with no matching pending index dropped", func(t *testing.T) {
+		hm := newHM()
+		h := &header.H{
+			Type:           header.Handshake,
+			Subtype:        header.HandshakeIXPSK0,
+			RemoteIndex:    0xcafef00d,
+			MessageCounter: 2,
+		}
+		hm.HandleIncoming(via, pkt, h)
+		assert.Empty(t, hm.indexes, "orphan stage-2 must not create state")
+	})
+}

hostmap.go

@@ -308,7 +308,7 @@ type cachedPacket struct {
 	packet         []byte
 }
 
-type packetCallback func(t header.MessageType, st header.MessageSubType, h *HostInfo, p, nb, out []byte)
+type packetCallback func(t header.MessageType, st header.MessageSubType, h *HostInfo, p []byte, buf *WireBuffer)
 
 type cachedPacketMetrics struct {
 	sent    metrics.Counter
@@ -691,6 +691,7 @@ func (i *HostInfo) TryPromoteBest(preferredRanges []netip.Prefix, ifce *Interfac
 			}
 		}
 
+		buf := ifce.bufAlloc.Acquire()
 		i.remotes.ForEach(preferredRanges, func(addr netip.AddrPort, preferred bool) {
 			if remote.IsValid() && (!addr.IsValid() || !preferred) {
 				return
@@ -698,8 +699,9 @@ func (i *HostInfo) TryPromoteBest(preferredRanges []netip.Prefix, ifce *Interfac
 
 			// Try to send a test packet to that host, this should
 			// cause it to detect a roaming event and switch remotes
-			ifce.sendTo(header.Test, header.TestRequest, i.ConnectionState, i, addr, []byte(""), make([]byte, 12, 12), make([]byte, mtu))
+			ifce.sendTo(header.Test, header.TestRequest, i.ConnectionState, i, addr, []byte(""), buf)
 		})
+		ifce.bufAlloc.Release(buf)
 	}
 
 	// Re query our lighthouses for new remotes occasionally

inside.go

@@ -8,12 +8,13 @@ import (
 	"github.com/slackhq/nebula/firewall"
 	"github.com/slackhq/nebula/header"
 	"github.com/slackhq/nebula/iputil"
-	"github.com/slackhq/nebula/noiseutil"
 	"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(buf *WireBuffer, q int, localCache firewall.ConntrackCache) {
-	err := newPacket(packet, false, fwPacket)
+	packet := buf.IPPacket()
+
+	err := newPacket(packet, false, buf.FwPacket)
 	if err != nil {
 		if f.l.Enabled(context.Background(), slog.LevelDebug) {
 			f.l.Debug("Error while validating outbound packet",
@@ -26,12 +27,12 @@ func (f *Interface) consumeInsidePacket(packet []byte, fwPacket *firewall.Packet
 
 	// Ignore local broadcast packets
 	if f.dropLocalBroadcast {
-		if f.myBroadcastAddrsTable.Contains(fwPacket.RemoteAddr) {
+		if f.myBroadcastAddrsTable.Contains(buf.FwPacket.RemoteAddr) {
 			return
 		}
 	}
 
-	if f.myVpnAddrsTable.Contains(fwPacket.RemoteAddr) {
+	if f.myVpnAddrsTable.Contains(buf.FwPacket.RemoteAddr) {
 		// Immediately forward packets from self to self.
 		// This should only happen on Darwin-based and FreeBSD hosts, which
 		// routes packets from the Nebula addr to the Nebula addr through the Nebula
@@ -48,20 +49,20 @@ func (f *Interface) consumeInsidePacket(packet []byte, fwPacket *firewall.Packet
 	}
 
 	// Ignore multicast packets
-	if f.dropMulticast && fwPacket.RemoteAddr.IsMulticast() {
+	if f.dropMulticast && buf.FwPacket.RemoteAddr.IsMulticast() {
 		return
 	}
 
-	hostinfo, ready := f.getOrHandshakeConsiderRouting(fwPacket, func(hh *HandshakeHostInfo) {
+	hostinfo, ready := f.getOrHandshakeConsiderRouting(buf.FwPacket, func(hh *HandshakeHostInfo) {
 		hh.cachePacket(f.l, header.Message, 0, packet, f.sendMessageNow, f.cachedPacketMetrics)
 	})
 
 	if hostinfo == nil {
-		f.rejectInside(packet, out, q)
+		f.rejectInside(packet, buf.Out, q)
 		if f.l.Enabled(context.Background(), slog.LevelDebug) {
 			f.l.Debug("dropping outbound packet, vpnAddr not in our vpn networks or in unsafe networks",
-				"vpnAddr", fwPacket.RemoteAddr,
+				"vpnAddr", buf.FwPacket.RemoteAddr,
-				"fwPacket", fwPacket,
+				"fwPacket", buf.FwPacket,
 			)
 		}
 		return
@@ -71,15 +72,15 @@ 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(*buf.FwPacket, false, hostinfo, f.pki.GetCAPool(), localCache)
 	if dropReason == nil {
-		f.sendNoMetrics(header.Message, 0, hostinfo.ConnectionState, hostinfo, netip.AddrPort{}, packet, nb, out, q)
+		f.sendNoMetrics(header.Message, 0, hostinfo.ConnectionState, hostinfo, netip.AddrPort{}, packet, buf, q)
 
 	} else {
-		f.rejectInside(packet, out, q)
+		f.rejectInside(packet, buf.Out, q)
 		if f.l.Enabled(context.Background(), slog.LevelDebug) {
 			hostinfo.logger(f.l).Debug("dropping outbound packet",
-				"fwPacket", fwPacket,
+				"fwPacket", buf.FwPacket,
 				"reason", dropReason,
 			)
 		}
@@ -102,27 +103,27 @@ func (f *Interface) rejectInside(packet []byte, out []byte, q int) {
 	}
 }
 
-func (f *Interface) rejectOutside(packet []byte, ci *ConnectionState, hostinfo *HostInfo, nb, out []byte, q int) {
+func (f *Interface) rejectOutside(packet []byte, ci *ConnectionState, hostinfo *HostInfo, scratch []byte, buf *WireBuffer, q int) {
 	if !f.firewall.OutSendReject {
 		return
 	}
 
-	out = iputil.CreateRejectPacket(packet, out)
+	rejectIP := iputil.CreateRejectPacket(packet, scratch)
-	if len(out) == 0 {
+	if len(rejectIP) == 0 {
 		return
 	}
 
-	if len(out) > iputil.MaxRejectPacketSize {
+	if len(rejectIP) > iputil.MaxRejectPacketSize {
 		if f.l.Enabled(context.Background(), slog.LevelInfo) {
 			f.l.Info("rejectOutside: packet too big, not sending",
 				"packet", packet,
-				"outPacket", out,
+				"outPacket", rejectIP,
 			)
 		}
 		return
 	}
 
-	f.sendNoMetrics(header.Message, 0, ci, hostinfo, netip.AddrPort{}, out, nb, packet, q)
+	f.sendNoMetrics(header.Message, 0, ci, hostinfo, netip.AddrPort{}, rejectIP, buf, q)
 }
 
 // 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
@@ -215,7 +216,7 @@ func (f *Interface) getOrHandshakeConsiderRouting(fwPacket *firewall.Packet, cac
 
 }
 
-func (f *Interface) sendMessageNow(t header.MessageType, st header.MessageSubType, hostinfo *HostInfo, p, nb, out []byte) {
+func (f *Interface) sendMessageNow(t header.MessageType, st header.MessageSubType, hostinfo *HostInfo, p []byte, buf *WireBuffer) {
 	fp := &firewall.Packet{}
 	err := newPacket(p, false, fp)
 	if err != nil {
@@ -235,12 +236,12 @@ func (f *Interface) sendMessageNow(t header.MessageType, st header.MessageSubTyp
 		return
 	}
 
-	f.sendNoMetrics(header.Message, st, hostinfo.ConnectionState, hostinfo, netip.AddrPort{}, p, nb, out, 0)
+	f.sendNoMetrics(header.Message, st, hostinfo.ConnectionState, hostinfo, netip.AddrPort{}, p, buf, 0)
 }
 
 // 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) {
+func (f *Interface) SendMessageToVpnAddr(t header.MessageType, st header.MessageSubType, vpnAddr netip.Addr, p []byte, buf *WireBuffer) {
 	hostInfo, ready := f.handshakeManager.GetOrHandshake(vpnAddr, func(hh *HandshakeHostInfo) {
 		hh.cachePacket(f.l, t, st, p, f.SendMessageToHostInfo, f.cachedPacketMetrics)
 	})
@@ -258,113 +259,73 @@ func (f *Interface) SendMessageToVpnAddr(t header.MessageType, st header.Message
 		return
 	}
 
-	f.SendMessageToHostInfo(t, st, hostInfo, p, nb, out)
+	f.SendMessageToHostInfo(t, st, hostInfo, p, buf)
 }
 
-func (f *Interface) SendMessageToHostInfo(t header.MessageType, st header.MessageSubType, hi *HostInfo, p, nb, out []byte) {
+func (f *Interface) SendMessageToHostInfo(t header.MessageType, st header.MessageSubType, hi *HostInfo, p []byte, buf *WireBuffer) {
-	f.send(t, st, hi.ConnectionState, hi, p, nb, out)
+	f.send(t, st, hi.ConnectionState, hi, p, buf)
 }
 
-func (f *Interface) send(t header.MessageType, st header.MessageSubType, ci *ConnectionState, hostinfo *HostInfo, p, nb, out []byte) {
+func (f *Interface) send(t header.MessageType, st header.MessageSubType, ci *ConnectionState, hostinfo *HostInfo, p []byte, buf *WireBuffer) {
 	f.messageMetrics.Tx(t, st, 1)
-	f.sendNoMetrics(t, st, ci, hostinfo, netip.AddrPort{}, p, nb, out, 0)
+	f.sendNoMetrics(t, st, ci, hostinfo, netip.AddrPort{}, p, buf, 0)
 }
 
-func (f *Interface) sendTo(t header.MessageType, st header.MessageSubType, ci *ConnectionState, hostinfo *HostInfo, remote netip.AddrPort, p, nb, out []byte) {
+func (f *Interface) sendTo(t header.MessageType, st header.MessageSubType, ci *ConnectionState, hostinfo *HostInfo, remote netip.AddrPort, p []byte, buf *WireBuffer) {
 	f.messageMetrics.Tx(t, st, 1)
-	f.sendNoMetrics(t, st, ci, hostinfo, remote, p, nb, out, 0)
+	f.sendNoMetrics(t, st, ci, hostinfo, remote, p, buf, 0)
 }
 
 // SendVia sends a payload through a Relay tunnel. No authentication or encryption is done
 // to the payload for the ultimate target host, making this a useful method for sending
 // handshake messages to peers through relay tunnels.
-// via is the HostInfo through which the message is relayed.
+//
-// ad is the plaintext data to authenticate, but not encrypt
+// via is the HostInfo through which the message is relayed. ad is staged into
-// nb is a buffer used to store the nonce value, re-used for performance reasons.
+// the inner-payload slot of buf and then AAD-only sealed under via's key by
-// out is a buffer used to store the result of the Encrypt operation
+// SealRelayInPlace. The sendNoMetrics relay-forward path skips this entry
-// q indicates which writer to use to send the packet.
+// point and calls sendViaInPlace directly because its inner ciphertext is
-func (f *Interface) SendVia(via *HostInfo,
+// already in place from the encrypt step.
-	relay *Relay,
+func (f *Interface) SendVia(via *HostInfo, relay *Relay, ad []byte, buf *WireBuffer) {
-	ad,
+	if header.Len+len(ad)+via.ConnectionState.eKey.Overhead() > cap(buf.Out) {
-	nb,
-	out []byte,
-	nocopy bool,
-) {
-	if noiseutil.EncryptLockNeeded {
-		// NOTE: for goboring AESGCMTLS we need to lock because of the nonce check
-		via.ConnectionState.writeLock.Lock()
-	}
-	c := via.ConnectionState.messageCounter.Add(1)
-
-	out = header.Encode(out, header.Version, header.Message, header.MessageRelay, relay.RemoteIndex, c)
-	f.connectionManager.Out(via)
-
-	// Authenticate the header and payload, but do not encrypt for this message type.
-	// The payload consists of the inner, unencrypted Nebula header, as well as the end-to-end encrypted payload.
-	if len(out)+len(ad)+via.ConnectionState.eKey.Overhead() > cap(out) {
-		if noiseutil.EncryptLockNeeded {
-			via.ConnectionState.writeLock.Unlock()
-		}
 		via.logger(f.l).Error("SendVia out buffer not large enough for relay",
-			"outCap", cap(out),
+			"outCap", cap(buf.Out),
 			"payloadLen", len(ad),
-			"headerLen", len(out),
+			"headerLen", header.Len,
 			"cipherOverhead", via.ConnectionState.eKey.Overhead(),
 		)
 		return
 	}
+	buf.StageRelayInner(ad)
+	f.sendViaInPlace(via, relay, len(ad), buf)
+}
 
-	// The header bytes are written to the 'out' slice; Grow the slice to hold the header and associated data payload.
+// sendViaInPlace stamps the outer relay header, AAD-seals over the [outer
-	offset := len(out)
+// header | inner-already-staged] region, and writes the result to via.remote.
-	out = out[:offset+len(ad)]
+// Called from SendVia (after staging ad) and from sendNoMetrics' relay-forward
-
+// path (where the inner ciphertext is already in place from SealForRelay).
-	// In one call path, the associated data _is_ already stored in out. In other call paths, the associated data must
+func (f *Interface) sendViaInPlace(via *HostInfo, relay *Relay, innerLen int, buf *WireBuffer) {
-	// be copied into 'out'.
+	f.connectionManager.Out(via)
-	if !nocopy {
+	out, err := buf.SealRelayInPlace(via.ConnectionState, relay.RemoteIndex, innerLen)
-		copy(out[offset:], ad)
-	}
-
-	var err error
-	out, err = via.ConnectionState.eKey.EncryptDanger(out, out, nil, c, nb)
-	if noiseutil.EncryptLockNeeded {
-		via.ConnectionState.writeLock.Unlock()
-	}
 	if err != nil {
 		via.logger(f.l).Info("Failed to EncryptDanger in sendVia", "error", err)
 		return
 	}
-	err = f.writers[0].WriteTo(out, via.remote)
+	if err := f.writers[0].WriteTo(out, via.remote); err != nil {
-	if err != nil {
 		via.logger(f.l).Info("Failed to WriteTo in sendVia", "error", err)
 	}
 	f.connectionManager.RelayUsed(relay.LocalIndex)
 }
 
-func (f *Interface) sendNoMetrics(t header.MessageType, st header.MessageSubType, ci *ConnectionState, hostinfo *HostInfo, remote netip.AddrPort, p, nb, out []byte, q int) {
+// sendNoMetrics encrypts and writes one outbound nebula packet (data, control,
+// lighthouse, etc) using buf as the per-call wire scratch. When the hostinfo
+// has no direct remote we encrypt into the relay-reserved slot via
+// SealForRelay so sendViaInPlace can wrap it without an extra copy.
+func (f *Interface) sendNoMetrics(t header.MessageType, st header.MessageSubType, ci *ConnectionState, hostinfo *HostInfo, remote netip.AddrPort, p []byte, buf *WireBuffer, q int) {
 	if ci.eKey == nil {
 		return
 	}
 	useRelay := !remote.IsValid() && !hostinfo.remote.IsValid()
-	fullOut := out
 
-	if useRelay {
-		if len(out) < 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 = out[:header.Len]
-		}
-		// Save a header's worth of data at the front of the 'out' buffer.
-		out = out[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 = header.Encode(out, 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
@@ -381,50 +342,42 @@ func (f *Interface) sendNoMetrics(t header.MessageType, st header.MessageSubType
 		}
 	}
 
+	var out []byte
 	var err error
-	out, err = ci.eKey.EncryptDanger(out, out, p, c, nb)
+	if useRelay {
-	if noiseutil.EncryptLockNeeded {
+		out, err = buf.SealForRelay(ci, t, st, hostinfo.remoteIndexId, p)
-		ci.writeLock.Unlock()
+	} else {
+		out, err = buf.Seal(ci, t, st, hostinfo.remoteIndexId, p)
 	}
 	if err != nil {
 		hostinfo.logger(f.l).Error("Failed to encrypt outgoing packet",
 			"error", err,
 			"udpAddr", remote,
-			"counter", c,
-			"attemptedCounter", c,
 		)
 		return
 	}
 
-	if remote.IsValid() {
+	switch {
-		err = f.writers[q].WriteTo(out, remote)
+	case remote.IsValid():
-		if err != nil {
+		if err := f.writers[q].WriteTo(out, remote); err != nil {
-			hostinfo.logger(f.l).Error("Failed to write outgoing packet",
+			hostinfo.logger(f.l).Error("Failed to write outgoing packet", "error", err, "udpAddr", remote)
-				"error", err,
-				"udpAddr", remote,
-			)
 		}
-	} else if hostinfo.remote.IsValid() {
+	case hostinfo.remote.IsValid():
-		err = f.writers[q].WriteTo(out, hostinfo.remote)
+		if err := f.writers[q].WriteTo(out, hostinfo.remote); err != nil {
-		if err != nil {
+			hostinfo.logger(f.l).Error("Failed to write outgoing packet", "error", err, "udpAddr", hostinfo.remote)
-			hostinfo.logger(f.l).Error("Failed to write outgoing packet",
-				"error", err,
-				"udpAddr", remote,
-			)
 		}
-	} else {
+	default:
-		// Try to send via a relay
+		// SealForRelay placed the inner ciphertext at buf.Out[header.Len:],
+		// so sendViaInPlace can wrap it with the outer relay header without
+		// an extra copy.
 		for _, relayIP := range hostinfo.relayState.CopyRelayIps() {
 			relayHostInfo, relay, err := f.hostMap.QueryVpnAddrsRelayFor(hostinfo.vpnAddrs, relayIP)
 			if err != nil {
 				hostinfo.relayState.DeleteRelay(relayIP)
-				hostinfo.logger(f.l).Info("sendNoMetrics failed to find HostInfo",
+				hostinfo.logger(f.l).Info("sendNoMetrics failed to find HostInfo", "relay", relayIP, "error", err)
-					"relay", relayIP,
-					"error", err,
-				)
 				continue
 			}
-			f.SendVia(relayHostInfo, relay, out, nb, fullOut[:header.Len+len(out)], true)
+			f.sendViaInPlace(relayHostInfo, relay, len(out), buf)
 			break
 		}
 	}

interface.go

@@ -101,19 +101,19 @@ type Interface struct {
 	messageMetrics      *MessageMetrics
 	cachedPacketMetrics *cachedPacketMetrics
 
+	// bufAlloc hands out reusable WireBuffers sized for this interface's
+	// inside Device. All buf consumers (hot-path data-plane goroutines,
+	// long-lived workers, and cold callers) acquire from here so sizing
+	// is centralized and consistent. Long-lived owners just don't release.
+	bufAlloc WireBufferAllocator
+
 	l *slog.Logger
 }
 
 type EncWriter interface {
-	SendVia(via *HostInfo,
+	SendVia(via *HostInfo, relay *Relay, ad []byte, buf *WireBuffer)
-		relay *Relay,
+	SendMessageToVpnAddr(t header.MessageType, st header.MessageSubType, vpnAddr netip.Addr, p []byte, buf *WireBuffer)
-		ad,
+	SendMessageToHostInfo(t header.MessageType, st header.MessageSubType, hostinfo *HostInfo, p []byte, buf *WireBuffer)
-		nb,
-		out []byte,
-		nocopy bool,
-	)
-	SendMessageToVpnAddr(t header.MessageType, st header.MessageSubType, vpnAddr netip.Addr, p, nb, out []byte)
-	SendMessageToHostInfo(t header.MessageType, st header.MessageSubType, hostinfo *HostInfo, p, nb, out []byte)
 	Handshake(vpnAddr netip.Addr)
 	GetHostInfo(vpnAddr netip.Addr) *HostInfo
 	GetCertState() *CertState
@@ -204,6 +204,8 @@ func NewInterface(ctx context.Context, c *InterfaceConfig) (*Interface, error) {
 			dropped: metrics.GetOrRegisterCounter("hostinfo.cached_packets.dropped", nil),
 		},
 
+		bufAlloc: NewWireBufferPool(mtu, c.Inside.TunPrefixLen()),
+
 		l: c.l,
 	}
 
@@ -311,13 +313,11 @@ func (f *Interface) listenOut(i int) {
 
 	ctCache := firewall.NewConntrackCacheTicker(f.ctx, f.l, f.conntrackCacheTimeout)
 	lhh := f.lightHouse.NewRequestHandler()
-	plaintext := make([]byte, udp.MTU)
+	// Long-lived per-receive-goroutine buf; never released back to the pool.
-	h := &header.H{}
+	buf := f.bufAlloc.Acquire()
-	fwPacket := &firewall.Packet{}
-	nb := make([]byte, 12, 12)
 
 	err := li.ListenOut(func(fromUdpAddr netip.AddrPort, payload []byte) {
-		f.readOutsidePackets(ViaSender{UdpAddr: fromUdpAddr}, plaintext[:0], payload, h, fwPacket, lhh, nb, i, ctCache.Get())
+		f.readOutsidePackets(ViaSender{UdpAddr: fromUdpAddr}, buf, payload, lhh, i, ctCache.Get())
 	})
 
 	if err != nil && !f.closed.Load() {
@@ -329,15 +329,12 @@ func (f *Interface) listenOut(i int) {
 }
 
 func (f *Interface) listenIn(reader io.ReadWriteCloser, i int) {
-	packet := make([]byte, mtu)
+	// Long-lived per-tun-reader buf; never released back to the pool.
-	out := make([]byte, mtu)
+	buf := f.bufAlloc.Acquire()
-	fwPacket := &firewall.Packet{}
-	nb := make([]byte, 12, 12)
-
 	conntrackCache := firewall.NewConntrackCacheTicker(f.ctx, f.l, f.conntrackCacheTimeout)
 
 	for {
-		n, err := reader.Read(packet)
+		_, err := buf.ReadIPFromTUN(reader)
 		if err != nil {
 			if !f.closed.Load() {
 				f.l.Error("Error while reading outbound packet, closing", "error", err, "reader", i)
@@ -346,7 +343,7 @@ func (f *Interface) listenIn(reader io.ReadWriteCloser, i int) {
 			break
 		}
 
-		f.consumeInsidePacket(packet[:n], fwPacket, nb, out, i, conntrackCache.Get())
+		f.consumeInsidePacket(buf, i, conntrackCache.Get())
 	}
 
 	f.l.Debug("overlay reader is done", "reader", i)

lighthouse.go

@@ -63,6 +63,10 @@ type LightHouse struct {
 	interval     atomic.Int64
 	updateCancel context.CancelFunc
 	ifce         EncWriter
+	// bufAlloc lets the lighthouse query/update workers, request handlers
+	// and punchback goroutines acquire correctly sized WireBuffers from
+	// the same pool as the data plane. Set by main.go alongside ifce.
+	bufAlloc   WireBufferAllocator
 	nebulaPort uint32 // 32 bits because protobuf does not have a uint16
 
 	advertiseAddrs atomic.Pointer[[]netip.AddrPort]
@@ -109,6 +113,10 @@ func NewLightHouseFromConfig(ctx context.Context, l *slog.Logger, c *config.C, c
 		punchy:             p,
 		updateTrigger:      make(chan struct{}, 1),
 		queryChan:          make(chan netip.Addr, c.GetUint32("handshakes.query_buffer", 64)),
+		// Default to a no-prefix pool so the query/update workers and
+		// request handlers have a working WireBufferAllocator before
+		// main.go wires up the real one from the Interface.
+		bufAlloc: NewWireBufferPool(mtu, 0),
 		l:        l,
 	}
 	lighthouses := make([]netip.Addr, 0)
@@ -758,21 +766,22 @@ func (lh *LightHouse) startQueryWorker() {
 	}
 
 	go func() {
-		nb := make([]byte, 12, 12)
+		// Long-lived per-worker WireBuffer; reused for every lighthouse query
-		out := make([]byte, mtu)
+		// this worker issues for the life of the goroutine.
+		buf := lh.bufAlloc.Acquire()
 
 		for {
 			select {
 			case <-lh.ctx.Done():
 				return
 			case addr := <-lh.queryChan:
-				lh.innerQueryServer(addr, nb, out)
+				lh.innerQueryServer(addr, buf)
 			}
 		}
 	}()
 }
 
-func (lh *LightHouse) innerQueryServer(addr netip.Addr, nb, out []byte) {
+func (lh *LightHouse) innerQueryServer(addr netip.Addr, buf *WireBuffer) {
 	if lh.IsLighthouseAddr(addr) {
 		return
 	}
@@ -821,7 +830,7 @@ func (lh *LightHouse) innerQueryServer(addr netip.Addr, nb, out []byte) {
 				}
 			}
 
-			lh.ifce.SendMessageToVpnAddr(header.LightHouse, 0, lhVpnAddr, v1Query, nb, out)
+			lh.ifce.SendMessageToVpnAddr(header.LightHouse, 0, lhVpnAddr, v1Query, buf)
 			queried++
 
 		} else if v == cert.Version2 {
@@ -840,7 +849,7 @@ func (lh *LightHouse) innerQueryServer(addr netip.Addr, nb, out []byte) {
 				}
 			}
 
-			lh.ifce.SendMessageToVpnAddr(header.LightHouse, 0, lhVpnAddr, v2Query, nb, out)
+			lh.ifce.SendMessageToVpnAddr(header.LightHouse, 0, lhVpnAddr, v2Query, buf)
 			queried++
 
 		} else {
@@ -869,8 +878,12 @@ func (lh *LightHouse) StartUpdateWorker() {
 	go func() {
 		defer clockSource.Stop()
 
+		// Long-lived per-worker WireBuffer; reused across every periodic
+		// update for the life of this goroutine.
+		buf := lh.bufAlloc.Acquire()
+
 		for {
-			lh.SendUpdate()
+			lh.sendUpdate(buf)
 
 			select {
 			case <-updateCtx.Done():
@@ -884,6 +897,15 @@ func (lh *LightHouse) StartUpdateWorker() {
 	}()
 }
 
+// SendUpdate is the public entry point that triggers a one-shot lighthouse
+// update outside the worker loop (e.g. tests or reload paths). It allocates
+// its own WireBuffer since callers don't already own one.
+func (lh *LightHouse) SendUpdate() {
+	buf := lh.bufAlloc.Acquire()
+	defer lh.bufAlloc.Release(buf)
+	lh.sendUpdate(buf)
+}
+
 // TriggerUpdate requests an immediate lighthouse update. This is a non-blocking
 // operation intended to be called after a handshake completes with a lighthouse,
 // so the lighthouse has our current addresses without waiting for the next
@@ -895,7 +917,7 @@ func (lh *LightHouse) TriggerUpdate() {
 	}
 }
 
-func (lh *LightHouse) SendUpdate() {
+func (lh *LightHouse) sendUpdate(buf *WireBuffer) {
 	var v4 []*V4AddrPort
 	var v6 []*V6AddrPort
 
@@ -921,9 +943,6 @@ func (lh *LightHouse) SendUpdate() {
 		}
 	}
 
-	nb := make([]byte, 12, 12)
-	out := make([]byte, mtu)
-
 	var v1Update, v2Update []byte
 	var err error
 	updated := 0
@@ -974,7 +993,7 @@ func (lh *LightHouse) SendUpdate() {
 				}
 			}
 
-			lh.ifce.SendMessageToVpnAddr(header.LightHouse, 0, lhVpnAddr, v1Update, nb, out)
+			lh.ifce.SendMessageToVpnAddr(header.LightHouse, 0, lhVpnAddr, v1Update, buf)
 			updated++
 
 		} else if v == cert.Version2 {
@@ -1003,7 +1022,7 @@ func (lh *LightHouse) SendUpdate() {
 				}
 			}
 
-			lh.ifce.SendMessageToVpnAddr(header.LightHouse, 0, lhVpnAddr, v2Update, nb, out)
+			lh.ifce.SendMessageToVpnAddr(header.LightHouse, 0, lhVpnAddr, v2Update, buf)
 			updated++
 
 		} else {
@@ -1020,8 +1039,10 @@ func (lh *LightHouse) SendUpdate() {
 
 type LightHouseHandler struct {
 	lh *LightHouse
-	nb   []byte
+	// buf is the long-lived per-handler wire scratch. NewRequestHandler is
-	out  []byte
+	// called once per data-plane receive goroutine, so buf is owned by that
+	// goroutine and reused for every lighthouse send the handler issues.
+	buf  *WireBuffer
 	pb   []byte
 	meta *NebulaMeta
 	l    *slog.Logger
@@ -1030,8 +1051,7 @@ type LightHouseHandler struct {
 func (lh *LightHouse) NewRequestHandler() *LightHouseHandler {
 	lhh := &LightHouseHandler{
 		lh:  lh,
-		nb:  make([]byte, 12, 12),
+		buf: lh.bufAlloc.Acquire(),
-		out: make([]byte, mtu),
 		l:   lh.l,
 		pb:  make([]byte, mtu),
 
@@ -1168,7 +1188,7 @@ func (lhh *LightHouseHandler) handleHostQuery(n *NebulaMeta, fromVpnAddrs []neti
 	}
 
 	lhh.lh.metricTx(NebulaMeta_HostQueryReply, 1)
-	w.SendMessageToVpnAddr(header.LightHouse, 0, fromVpnAddrs[0], lhh.pb[:ln], lhh.nb, lhh.out[:0])
+	w.SendMessageToVpnAddr(header.LightHouse, 0, fromVpnAddrs[0], lhh.pb[:ln], lhh.buf)
 
 	lhh.sendHostPunchNotification(n, fromVpnAddrs, queryVpnAddr, w)
 }
@@ -1228,7 +1248,7 @@ func (lhh *LightHouseHandler) sendHostPunchNotification(n *NebulaMeta, fromVpnAd
 	}
 
 	lhh.lh.metricTx(NebulaMeta_HostPunchNotification, 1)
-	w.SendMessageToVpnAddr(header.LightHouse, 0, punchNotifDest, lhh.pb[:ln], lhh.nb, lhh.out[:0])
+	w.SendMessageToVpnAddr(header.LightHouse, 0, punchNotifDest, lhh.pb[:ln], lhh.buf)
 }
 
 func (lhh *LightHouseHandler) coalesceAnswers(v cert.Version, c *cache, n *NebulaMeta) {
@@ -1385,7 +1405,7 @@ func (lhh *LightHouseHandler) handleHostUpdateNotification(n *NebulaMeta, fromVp
 	}
 
 	lhh.lh.metricTx(NebulaMeta_HostUpdateNotificationAck, 1)
-	w.SendMessageToVpnAddr(header.LightHouse, 0, fromVpnAddrs[0], lhh.pb[:ln], lhh.nb, lhh.out[:0])
+	w.SendMessageToVpnAddr(header.LightHouse, 0, fromVpnAddrs[0], lhh.pb[:ln], lhh.buf)
 }
 
 func (lhh *LightHouseHandler) handleHostPunchNotification(n *NebulaMeta, fromVpnAddrs []netip.Addr, w EncWriter) {
@@ -1452,10 +1472,13 @@ func (lhh *LightHouseHandler) handleHostPunchNotification(n *NebulaMeta, fromVpn
 					"vpnAddr", detailsVpnAddr,
 				)
 			}
-			//NOTE: we have to allocate a new output buffer here since we are spawning a new goroutine
+			// We acquire and release a fresh buf within this goroutine so it
-			// for each punchBack packet. We should move this into a timerwheel or a single goroutine
+			// returns to the pool once the punchback send completes. We
+			// should move this into a timerwheel or a single goroutine
 			// managed by a channel.
-			w.SendMessageToVpnAddr(header.Test, header.TestRequest, detailsVpnAddr, []byte(""), make([]byte, 12, 12), make([]byte, mtu))
+			pbuf := lhh.lh.bufAlloc.Acquire()
+			defer lhh.lh.bufAlloc.Release(pbuf)
+			w.SendMessageToVpnAddr(header.Test, header.TestRequest, detailsVpnAddr, []byte(""), pbuf)
 		}()
 	}
 }

lighthouse_test.go

@@ -372,12 +372,12 @@ type testEncWriter struct {
 	protocolVersion cert.Version
 }
 
-func (tw *testEncWriter) SendVia(via *HostInfo, relay *Relay, ad, nb, out []byte, nocopy bool) {
+func (tw *testEncWriter) SendVia(via *HostInfo, relay *Relay, ad []byte, buf *WireBuffer) {
 }
 func (tw *testEncWriter) Handshake(vpnIp netip.Addr) {
 }
 
-func (tw *testEncWriter) SendMessageToHostInfo(t header.MessageType, st header.MessageSubType, hostinfo *HostInfo, p, _, _ []byte) {
+func (tw *testEncWriter) SendMessageToHostInfo(t header.MessageType, st header.MessageSubType, hostinfo *HostInfo, p []byte, _ *WireBuffer) {
 	msg := &NebulaMeta{}
 	err := msg.Unmarshal(p)
 	if tw.metaFilter == nil || msg.Type == *tw.metaFilter {
@@ -394,7 +394,7 @@ func (tw *testEncWriter) SendMessageToHostInfo(t header.MessageType, st header.M
 	}
 }
 
-func (tw *testEncWriter) SendMessageToVpnAddr(t header.MessageType, st header.MessageSubType, vpnIp netip.Addr, p, _, _ []byte) {
+func (tw *testEncWriter) SendMessageToVpnAddr(t header.MessageType, st header.MessageSubType, vpnIp netip.Addr, p []byte, _ *WireBuffer) {
 	msg := &NebulaMeta{}
 	err := msg.Unmarshal(p)
 	if tw.metaFilter == nil || msg.Type == *tw.metaFilter {

main.go

@@ -184,14 +184,10 @@ func Main(c *config.C, configTest bool, buildVersion string, l *slog.Logger, dev
 		messageMetrics = newMessageMetricsOnlyRecvError()
 	}
 
-	useRelays := c.GetBool("relay.use_relays", DefaultUseRelays) && !c.GetBool("relay.am_relay", false)
-
 	handshakeConfig := HandshakeConfig{
 		tryInterval:    c.GetDuration("handshakes.try_interval", DefaultHandshakeTryInterval),
 		retries:        int64(c.GetInt("handshakes.retries", DefaultHandshakeRetries)),
 		triggerBuffer:  c.GetInt("handshakes.trigger_buffer", DefaultHandshakeTriggerBuffer),
-		useRelays:     useRelays,
-
 		messageMetrics: messageMetrics,
 	}
 
@@ -236,6 +232,7 @@ func Main(c *config.C, configTest bool, buildVersion string, l *slog.Logger, dev
 
 		ifce.writers = udpConns
 		lightHouse.ifce = ifce
+		lightHouse.bufAlloc = ifce.bufAlloc
 
 		ifce.RegisterConfigChangeCallbacks(c)
 		ifce.reloadDisconnectInvalid(c)

nebula.pb.go

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

nebula.proto

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

noise.go

@@ -14,6 +14,19 @@ type endianness interface {
 
 var noiseEndianness endianness = binary.BigEndian
 
+// NonceSize is the AEAD nonce length used by all ciphers nebula supports
+// today (AES-GCM and ChaCha20-Poly1305 both use 96-bit nonces). Encrypt-
+// and DecryptDanger lay out the nonce as 4 zero bytes followed by an 8-byte
+// big-endian counter; if a future cipher with a different nonce size is
+// added, this constant and those layouts must change together.
+const NonceSize = 12
+
+// AEADOverhead is the AEAD authentication tag length the ciphers nebula
+// supports append to ciphertext. Both AES-GCM and ChaCha20-Poly1305 use
+// 128-bit tags. NebulaCipherState.Overhead() returns this dynamically from
+// the cipher; the constant is for sizing buffers at construction time.
+const AEADOverhead = 16
+
 type NebulaCipherState struct {
 	c cipher.AEAD
 }

outside.go

@@ -20,7 +20,8 @@ const (
 	minFwPacketLen = 4
 )
 
-func (f *Interface) readOutsidePackets(via ViaSender, out []byte, packet []byte, h *header.H, fwPacket *firewall.Packet, lhf *LightHouseHandler, nb []byte, q int, localCache firewall.ConntrackCache) {
+func (f *Interface) readOutsidePackets(via ViaSender, buf *WireBuffer, packet []byte, lhf *LightHouseHandler, q int, localCache firewall.ConntrackCache) {
+	h := buf.H
 	err := h.Parse(packet)
 	if err != nil {
 		// Hole punch packets are 0 or 1 byte big, so lets ignore printing those errors
@@ -65,7 +66,7 @@ func (f *Interface) readOutsidePackets(via ViaSender, out []byte, packet []byte,
 
 		switch h.Subtype {
 		case header.MessageNone:
-			if !f.decryptToTun(hostinfo, h.MessageCounter, out, packet, fwPacket, nb, q, localCache) {
+			if !f.decryptToTun(hostinfo, h.MessageCounter, buf, packet, q, localCache) {
 				return
 			}
 		case header.MessageRelay:
@@ -76,8 +77,9 @@ func (f *Interface) readOutsidePackets(via ViaSender, out []byte, packet []byte,
 			// which will gracefully fail in the DecryptDanger call.
 			signedPayload := packet[:len(packet)-hostinfo.ConnectionState.dKey.Overhead()]
 			signatureValue := packet[len(packet)-hostinfo.ConnectionState.dKey.Overhead():]
-			out, err = hostinfo.ConnectionState.dKey.DecryptDanger(out, signedPayload, signatureValue, h.MessageCounter, nb)
+			// AAD-only validation: passing dst=nil since there's no plaintext
-			if err != nil {
+			// to recover (ciphertext is just the trailing AEAD tag).
+			if _, err = hostinfo.ConnectionState.dKey.DecryptDanger(nil, signedPayload, signatureValue, h.MessageCounter, buf.NB); err != nil {
 				return
 			}
 			// Successfully validated the thing. Get rid of the Relay header.
@@ -110,7 +112,8 @@ func (f *Interface) readOutsidePackets(via ViaSender, out []byte, packet []byte,
 					relay:     relay,
 					IsRelayed: true,
 				}
-				f.readOutsidePackets(via, out[:0], signedPayload, h, fwPacket, lhf, nb, q, localCache)
+				buf.Reset()
+				f.readOutsidePackets(via, buf, signedPayload, lhf, q, localCache)
 				return
 			case ForwardingType:
 				// Find the target HostInfo relay object
@@ -130,7 +133,7 @@ func (f *Interface) readOutsidePackets(via ViaSender, out []byte, packet []byte,
 					case ForwardingType:
 						// Forward this packet through the relay tunnel
 						// Find the target HostInfo
-						f.SendVia(targetHI, targetRelay, signedPayload, nb, out, false)
+						f.SendVia(targetHI, targetRelay, signedPayload, buf)
 						return
 					case TerminalType:
 						hostinfo.logger(f.l).Error("Unexpected Relay Type of Terminal")
@@ -152,7 +155,7 @@ func (f *Interface) readOutsidePackets(via ViaSender, out []byte, packet []byte,
 			return
 		}
 
-		d, err := f.decrypt(hostinfo, h.MessageCounter, out, packet, h, nb)
+		d, err := f.decrypt(hostinfo, h.MessageCounter, buf, packet, h)
 		if err != nil {
 			hostinfo.logger(f.l).Error("Failed to decrypt lighthouse packet",
 				"error", err,
@@ -173,7 +176,7 @@ func (f *Interface) readOutsidePackets(via ViaSender, out []byte, packet []byte,
 			return
 		}
 
-		d, err := f.decrypt(hostinfo, h.MessageCounter, out, packet, h, nb)
+		d, err := f.decrypt(hostinfo, h.MessageCounter, buf, packet, h)
 		if err != nil {
 			hostinfo.logger(f.l).Error("Failed to decrypt test packet",
 				"error", err,
@@ -185,9 +188,9 @@ func (f *Interface) readOutsidePackets(via ViaSender, out []byte, packet []byte,
 
 		if h.Subtype == header.TestRequest {
 			// This testRequest might be from TryPromoteBest, so we should roam
-			// to the new IP address before responding
+			// to the new IP address before responding.
 			f.handleHostRoaming(hostinfo, via)
-			f.send(header.Test, header.TestReply, ci, hostinfo, d, nb, out)
+			f.send(header.Test, header.TestReply, ci, hostinfo, d, buf)
 		}
 
 		// Fallthrough to the bottom to record incoming traffic
@@ -210,7 +213,7 @@ func (f *Interface) readOutsidePackets(via ViaSender, out []byte, packet []byte,
 		if !f.handleEncrypted(ci, via, h) {
 			return
 		}
-		_, err = f.decrypt(hostinfo, h.MessageCounter, out, packet, h, nb)
+		_, err = f.decrypt(hostinfo, h.MessageCounter, buf, packet, h)
 		if err != nil {
 			hostinfo.logger(f.l).Error("Failed to decrypt CloseTunnel packet",
 				"error", err,
@@ -230,7 +233,7 @@ func (f *Interface) readOutsidePackets(via ViaSender, out []byte, packet []byte,
 			return
 		}
 
-		d, err := f.decrypt(hostinfo, h.MessageCounter, out, packet, h, nb)
+		d, err := f.decrypt(hostinfo, h.MessageCounter, buf, packet, h)
 		if err != nil {
 			hostinfo.logger(f.l).Error("Failed to decrypt Control packet",
 				"error", err,
@@ -266,7 +269,9 @@ func (f *Interface) closeTunnel(hostInfo *HostInfo) {
 
 // sendCloseTunnel is a helper function to send a proper close tunnel packet to a remote
 func (f *Interface) sendCloseTunnel(h *HostInfo) {
-	f.send(header.CloseTunnel, 0, h.ConnectionState, h, []byte{}, make([]byte, 12, 12), make([]byte, mtu))
+	buf := f.bufAlloc.Acquire()
+	defer f.bufAlloc.Release(buf)
+	f.send(header.CloseTunnel, 0, h.ConnectionState, h, []byte{}, buf)
 }
 
 func (f *Interface) handleHostRoaming(hostinfo *HostInfo, via ViaSender) {
@@ -515,9 +520,8 @@ func parseV4(data []byte, incoming bool, fp *firewall.Packet) error {
 	return nil
 }
 
-func (f *Interface) decrypt(hostinfo *HostInfo, mc uint64, out []byte, packet []byte, h *header.H, nb []byte) ([]byte, error) {
+func (f *Interface) decrypt(hostinfo *HostInfo, mc uint64, buf *WireBuffer, packet []byte, h *header.H) ([]byte, error) {
-	var err error
+	plaintext, err := buf.DecryptForHandler(hostinfo.ConnectionState, packet, mc)
-	out, err = hostinfo.ConnectionState.dKey.DecryptDanger(out, packet[:header.Len], packet[header.Len:], mc, nb)
 	if err != nil {
 		return nil, err
 	}
@@ -529,42 +533,41 @@ func (f *Interface) decrypt(hostinfo *HostInfo, mc uint64, out []byte, packet []
 		return nil, errors.New("out of window packet")
 	}
 
-	return out, nil
+	return plaintext, 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) decryptToTun(hostinfo *HostInfo, messageCounter uint64, buf *WireBuffer, packet []byte, q int, localCache firewall.ConntrackCache) bool {
-	var err error
+	if err := buf.DecryptDatagram(hostinfo.ConnectionState, packet, messageCounter); err != nil {
-
-	out, err = hostinfo.ConnectionState.dKey.DecryptDanger(out, packet[:header.Len], packet[header.Len:], messageCounter, nb)
-	if err != nil {
 		hostinfo.logger(f.l).Error("Failed to decrypt packet", "error", err)
 		return false
 	}
 
-	err = newPacket(out, true, fwPacket)
+	ipPacket := buf.IPPacket()
-	if err != nil {
+	if err := newPacket(ipPacket, true, buf.FwPacket); err != nil {
 		hostinfo.logger(f.l).Warn("Error while validating inbound packet",
 			"error", err,
-			"packet", out,
+			"packet", ipPacket,
 		)
 		return false
 	}
 
 	if !hostinfo.ConnectionState.window.Update(f.l, messageCounter) {
 		if f.l.Enabled(context.Background(), slog.LevelDebug) {
-			hostinfo.logger(f.l).Debug("dropping out of window packet", "fwPacket", fwPacket)
+			hostinfo.logger(f.l).Debug("dropping out of window packet", "fwPacket", buf.FwPacket)
 		}
 		return false
 	}
 
-	dropReason := f.firewall.Drop(*fwPacket, true, hostinfo, f.pki.GetCAPool(), localCache)
+	dropReason := f.firewall.Drop(*buf.FwPacket, true, hostinfo, f.pki.GetCAPool(), localCache)
 	if dropReason != nil {
-		// NOTE: We give `packet` as the `out` here since we already decrypted from it and we don't need it anymore
+		// NOTE: We hand `packet` (the original UDP ciphertext we already
-		// This gives us a buffer to build the reject packet in
+		// decrypted from) as the reject-IP scratch since we no longer
-		f.rejectOutside(out, hostinfo.ConnectionState, hostinfo, nb, packet, q)
+		// need its ciphertext, and it's disjoint from buf.Out where
+		// sendNoMetrics will encrypt the wire packet.
+		f.rejectOutside(ipPacket, hostinfo.ConnectionState, hostinfo, packet, buf, q)
 		if f.l.Enabled(context.Background(), slog.LevelDebug) {
 			hostinfo.logger(f.l).Debug("dropping inbound packet",
-				"fwPacket", fwPacket,
+				"fwPacket", buf.FwPacket,
 				"reason", dropReason,
 			)
 		}
@@ -572,8 +575,7 @@ func (f *Interface) decryptToTun(hostinfo *HostInfo, messageCounter uint64, out
 	}
 
 	f.connectionManager.In(hostinfo)
-	_, err = f.readers[q].Write(out)
+	if _, err := buf.WriteIPToTUN(f.readers[q]); err != nil {
-	if err != nil {
 		f.l.Error("Failed to write to tun", "error", err)
 	}
 	return true

overlay/device.go

@@ -15,4 +15,7 @@ type Device interface {
 	RoutesFor(netip.Addr) routing.Gateways
 	SupportsMultiqueue() bool
 	NewMultiQueueReader() (io.ReadWriteCloser, error)
+	// TunPrefixLen reports the number of bytes the device prepends to every IP packet on the wire.
+	// Currently only non zero for the BSD tun devices.
+	TunPrefixLen() int
 }

overlay/overlaytest/noop.go

@@ -50,3 +50,5 @@ func (NoopTun) NewMultiQueueReader() (io.ReadWriteCloser, error) {
 func (NoopTun) Close() error {
 	return nil
 }
+
+func (NoopTun) TunPrefixLen() int { return 0 }

overlay/tun_android.go

@@ -102,3 +102,5 @@ func (t *tun) SupportsMultiqueue() bool {
 func (t *tun) NewMultiQueueReader() (io.ReadWriteCloser, error) {
 	return nil, fmt.Errorf("TODO: multiqueue not implemented for android")
 }
+
+func (t *tun) TunPrefixLen() int { return 0 }

overlay/tun_bsd.go

@@ -0,0 +1,29 @@
+//go:build (darwin || ios || freebsd || openbsd || netbsd) && !e2e_testing
+
+package overlay
+
+import (
+	"fmt"
+	"syscall"
+)
+
+// StampTunPrefix writes the 4-byte AF_INET / AF_INET6 protocol-family marker into buf[0:4] in place,
+// picking the family from the first byte of the IP packet at buf[4].
+func StampTunPrefix(buf []byte) error {
+	if len(buf) < 5 {
+		return fmt.Errorf("tun write buffer too small for prefix")
+	}
+	ipVer := buf[4] >> 4
+	buf[0] = 0
+	buf[1] = 0
+	buf[2] = 0
+	switch ipVer {
+	case 4:
+		buf[3] = syscall.AF_INET
+	case 6:
+		buf[3] = syscall.AF_INET6
+	default:
+		return fmt.Errorf("unable to determine IP version from packet")
+	}
+	return nil
+}

overlay/tun_darwin.go

@@ -11,7 +11,6 @@ import (
 	"net/netip"
 	"os"
 	"sync/atomic"
-	"syscall"
 	"unsafe"
 
 	"github.com/gaissmai/bart"
@@ -31,9 +30,6 @@ type tun struct {
 	routeTree   atomic.Pointer[bart.Table[routing.Gateways]]
 	linkAddr    *netroute.LinkAddr
 	l           *slog.Logger
-
-	// cache out buffer since we need to prepend 4 bytes for tun metadata
-	out []byte
 }
 
 type ifReq struct {
@@ -502,44 +498,6 @@ func delRoute(prefix netip.Prefix, gateway netroute.Addr) error {
 	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
-}
-
-// 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.ReadWriteCloser.Write(buf)
-	return n - 4, err
-}
-
 func (t *tun) Networks() []netip.Prefix {
 	return t.vpnNetworks
 }
@@ -555,3 +513,7 @@ func (t *tun) SupportsMultiqueue() bool {
 func (t *tun) NewMultiQueueReader() (io.ReadWriteCloser, error) {
 	return nil, fmt.Errorf("TODO: multiqueue not implemented for darwin")
 }
+
+// TunPrefixLen reports the 4-byte BSD AF_INET / AF_INET6 protocol-family
+// marker the kernel prepends on read and expects on write.
+func (t *tun) TunPrefixLen() int { return 4 }

overlay/tun_disabled.go

@@ -136,3 +136,5 @@ func (p prettyPacket) String() string {
 
 	return s.String()
 }
+
+func (t *disabledTun) TunPrefixLen() int { return 0 }

overlay/tun_freebsd.go

@@ -158,74 +158,43 @@ func (t *tun) blockOnWrite() error {
 }
 
 func (t *tun) Read(to []byte) (int, error) {
-	// first 4 bytes is protocol family, in network byte order
-	var head [4]byte
-	iovecs := [2]syscall.Iovec{
-		{&head[0], 4},
-		{&to[0], uint64(len(to))},
-	}
 	for {
-		n, _, errno := syscall.Syscall(syscall.SYS_READV, uintptr(t.fd), uintptr(unsafe.Pointer(&iovecs[0])), 2)
+		n, err := unix.Read(t.fd, to)
-		if errno == 0 {
+		if err == nil {
-			bytesRead := int(n)
+			return n, nil
-			if bytesRead < 4 {
-				return 0, nil
 		}
-			return bytesRead - 4, nil
+		switch err {
-		}
-		switch errno {
 		case unix.EAGAIN:
-			if err := t.blockOnRead(); err != nil {
+			if berr := t.blockOnRead(); berr != nil {
-				return 0, err
+				return 0, berr
 			}
 		case unix.EINTR:
 			// retry
 		case unix.EBADF:
 			return 0, os.ErrClosed
 		default:
-			return 0, errno
+			return 0, err
 		}
 	}
 }
 
-// Write is only valid for single threaded use
 func (t *tun) Write(from []byte) (int, error) {
-	if len(from) <= 1 {
-		return 0, syscall.EIO
-	}
-
-	ipVer := from[0] >> 4
-	var head [4]byte
-	// first 4 bytes is protocol family, in network byte order
-	switch ipVer {
-	case 4:
-		head[3] = syscall.AF_INET
-	case 6:
-		head[3] = syscall.AF_INET6
-	default:
-		return 0, fmt.Errorf("unable to determine IP version from packet")
-	}
-
-	iovecs := [2]syscall.Iovec{
-		{&head[0], 4},
-		{&from[0], uint64(len(from))},
-	}
 	for {
-		n, _, errno := syscall.Syscall(syscall.SYS_WRITEV, uintptr(t.fd), uintptr(unsafe.Pointer(&iovecs[0])), 2)
+		n, err := unix.Write(t.fd, from)
-		if errno == 0 {
+		if err == nil {
-			return int(n) - 4, nil
+			return n, nil
 		}
-		switch errno {
+		switch err {
 		case unix.EAGAIN:
-			if err := t.blockOnWrite(); err != nil {
+			if berr := t.blockOnWrite(); berr != nil {
-				return 0, err
+				return 0, berr
 			}
 		case unix.EINTR:
 			// retry
 		case unix.EBADF:
 			return 0, os.ErrClosed
 		default:
-			return 0, errno
+			return 0, err
 		}
 	}
 }
@@ -732,3 +701,7 @@ func getLinkAddr(name string) (*netroute.LinkAddr, error) {
 
 	return nil, nil
 }
+
+// TunPrefixLen reports the 4-byte BSD AF_INET / AF_INET6 protocol-family
+// marker the kernel prepends on read and expects on write.
+func (t *tun) TunPrefixLen() int { return 4 }

overlay/tun_ios.go

@@ -4,15 +4,12 @@
 package overlay
 
 import (
-	"errors"
 	"fmt"
 	"io"
 	"log/slog"
 	"net/netip"
 	"os"
-	"sync"
 	"sync/atomic"
-	"syscall"
 
 	"github.com/gaissmai/bart"
 	"github.com/slackhq/nebula/config"
@@ -36,7 +33,7 @@ func newTunFromFd(c *config.C, l *slog.Logger, deviceFd int, vpnNetworks []netip
 	file := os.NewFile(uintptr(deviceFd), "/dev/tun")
 	t := &tun{
 		vpnNetworks:     vpnNetworks,
-		ReadWriteCloser: &tunReadCloser{f: file},
+		ReadWriteCloser: file,
 		l:               l,
 	}
 
@@ -85,64 +82,6 @@ func (t *tun) RoutesFor(ip netip.Addr) routing.Gateways {
 	return r
 }
 
-// The following is hoisted up from water, we do this so we can inject our own fd on iOS
-type tunReadCloser struct {
-	f io.ReadWriteCloser
-
-	rMu  sync.Mutex
-	rBuf []byte
-
-	wMu  sync.Mutex
-	wBuf []byte
-}
-
-func (tr *tunReadCloser) Read(to []byte) (int, error) {
-	tr.rMu.Lock()
-	defer tr.rMu.Unlock()
-
-	if cap(tr.rBuf) < len(to)+4 {
-		tr.rBuf = make([]byte, len(to)+4)
-	}
-	tr.rBuf = tr.rBuf[:len(to)+4]
-
-	n, err := tr.f.Read(tr.rBuf)
-	copy(to, tr.rBuf[4:])
-	return n - 4, err
-}
-
-func (tr *tunReadCloser) Write(from []byte) (int, error) {
-	if len(from) == 0 {
-		return 0, syscall.EIO
-	}
-
-	tr.wMu.Lock()
-	defer tr.wMu.Unlock()
-
-	if cap(tr.wBuf) < len(from)+4 {
-		tr.wBuf = make([]byte, len(from)+4)
-	}
-	tr.wBuf = tr.wBuf[:len(from)+4]
-
-	// Determine the IP Family for the NULL L2 Header
-	ipVer := from[0] >> 4
-	if ipVer == 4 {
-		tr.wBuf[3] = syscall.AF_INET
-	} else if ipVer == 6 {
-		tr.wBuf[3] = syscall.AF_INET6
-	} else {
-		return 0, errors.New("unable to determine IP version from packet")
-	}
-
-	copy(tr.wBuf[4:], from)
-
-	n, err := tr.f.Write(tr.wBuf)
-	return n - 4, err
-}
-
-func (tr *tunReadCloser) Close() error {
-	return tr.f.Close()
-}
-
 func (t *tun) Networks() []netip.Prefix {
 	return t.vpnNetworks
 }
@@ -158,3 +97,7 @@ func (t *tun) SupportsMultiqueue() bool {
 func (t *tun) NewMultiQueueReader() (io.ReadWriteCloser, error) {
 	return nil, fmt.Errorf("TODO: multiqueue not implemented for ios")
 }
+
+// TunPrefixLen reports the 4-byte BSD AF_INET / AF_INET6 protocol-family
+// marker the kernel prepends on read and expects on write.
+func (t *tun) TunPrefixLen() int { return 4 }

overlay/tun_linux.go

@@ -907,3 +907,5 @@ func (t *tun) Close() error {
 	}
 	return err
 }
+
+func (t *tun) TunPrefixLen() int { return 0 }

overlay/tun_netbsd.go

@@ -58,13 +58,13 @@ type addrLifetime struct {
 }
 
 type tun struct {
+	io.ReadWriteCloser
 	Device      string
 	vpnNetworks []netip.Prefix
 	MTU         int
 	Routes      atomic.Pointer[[]Route]
 	routeTree   atomic.Pointer[bart.Table[routing.Gateways]]
 	l           *slog.Logger
-	f           *os.File
 	fd          int
 }
 
@@ -96,7 +96,7 @@ func newTun(c *config.C, l *slog.Logger, vpnNetworks []netip.Prefix, _ bool) (*t
 	}
 
 	t := &tun{
-		f:           os.NewFile(uintptr(fd), ""),
+		ReadWriteCloser: os.NewFile(uintptr(fd), ""),
 		fd:              fd,
 		Device:          deviceName,
 		vpnNetworks:     vpnNetworks,
@@ -120,12 +120,12 @@ func newTun(c *config.C, l *slog.Logger, vpnNetworks []netip.Prefix, _ bool) (*t
 }
 
 func (t *tun) Close() error {
-	if t.f != nil {
+	if t.ReadWriteCloser != nil {
-		if err := t.f.Close(); err != nil {
+		if err := t.ReadWriteCloser.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
+		// Close on the os.File should have handled the fd for us but let's be extra sure
 		_ = unix.Close(t.fd)
 
 		s, err := syscall.Socket(syscall.AF_INET, syscall.SOCK_DGRAM, syscall.IPPROTO_IP)
@@ -141,99 +141,6 @@ func (t *tun) Close() error {
 	return nil
 }
 
-func (t *tun) Read(to []byte) (int, error) {
-	rc, err := t.f.SyscallConn()
-	if err != nil {
-		return 0, fmt.Errorf("failed to get syscall conn for tun: %w", err)
-	}
-
-	var errno syscall.Errno
-	var n uintptr
-	err = rc.Read(func(fd uintptr) bool {
-		// first 4 bytes is protocol family, in network byte order
-		head := [4]byte{}
-		iovecs := []syscall.Iovec{
-			{&head[0], 4},
-			{&to[0], uint64(len(to))},
-		}
-
-		n, _, errno = syscall.Syscall(syscall.SYS_READV, fd, uintptr(unsafe.Pointer(&iovecs[0])), uintptr(2))
-		if errno.Temporary() {
-			// We got an EAGAIN, EINTR, or EWOULDBLOCK, go again
-			return false
-		}
-		return true
-	})
-	if err != nil {
-		if err == syscall.EBADF || err.Error() == "use of closed file" {
-			// Go doesn't export poll.ErrFileClosing but happily reports it to us so here we are
-			// https://github.com/golang/go/blob/master/src/internal/poll/fd_poll_runtime.go#L121
-			return 0, os.ErrClosed
-		}
-		return 0, fmt.Errorf("failed to make read call for tun: %w", err)
-	}
-
-	if errno != 0 {
-		return 0, fmt.Errorf("failed to make inner read call for tun: %w", errno)
-	}
-
-	// fix bytes read number to exclude header
-	bytesRead := int(n)
-	if bytesRead < 0 {
-		return bytesRead, nil
-	} else if bytesRead < 4 {
-		return 0, nil
-	} else {
-		return bytesRead - 4, nil
-	}
-}
-
-// Write is only valid for single threaded use
-func (t *tun) Write(from []byte) (int, error) {
-	if len(from) <= 1 {
-		return 0, syscall.EIO
-	}
-
-	ipVer := from[0] >> 4
-	var head [4]byte
-	// first 4 bytes is protocol family, in network byte order
-	if ipVer == 4 {
-		head[3] = syscall.AF_INET
-	} else if ipVer == 6 {
-		head[3] = syscall.AF_INET6
-	} else {
-		return 0, fmt.Errorf("unable to determine IP version from packet")
-	}
-
-	rc, err := t.f.SyscallConn()
-	if err != nil {
-		return 0, err
-	}
-
-	var errno syscall.Errno
-	var n uintptr
-	err = rc.Write(func(fd uintptr) bool {
-		iovecs := []syscall.Iovec{
-			{&head[0], 4},
-			{&from[0], uint64(len(from))},
-		}
-
-		n, _, errno = syscall.Syscall(syscall.SYS_WRITEV, fd, uintptr(unsafe.Pointer(&iovecs[0])), uintptr(2))
-		// According to NetBSD documentation for TUN, writes will only return errors in which
-		// this packet will never be delivered so just go on living life.
-		return true
-	})
-	if err != nil {
-		return 0, err
-	}
-
-	if errno != 0 {
-		return 0, errno
-	}
-
-	return int(n) - 4, err
-}
-
 func (t *tun) addIp(cidr netip.Prefix) error {
 	if cidr.Addr().Is4() {
 		var req ifreqAlias4
@@ -551,3 +458,7 @@ func delRoute(prefix netip.Prefix, gateways []netip.Prefix) error {
 
 	return nil
 }
+
+// TunPrefixLen reports the 4-byte BSD AF_INET / AF_INET6 protocol-family
+// marker the kernel prepends on read and expects on write.
+func (t *tun) TunPrefixLen() int { return 4 }

overlay/tun_no_prefix.go

@@ -0,0 +1,10 @@
+//go:build (!darwin && !ios && !freebsd && !openbsd && !netbsd) || e2e_testing
+
+package overlay
+
+// StampTunPrefix is a no-op on platforms whose tun devices have no
+// protocol-family marker. WireBuffer only invokes it when its prefixLen
+// is non-zero, so this should never be reached on these platforms.
+func StampTunPrefix(buf []byte) error {
+	return nil
+}

overlay/tun_openbsd.go

@@ -49,16 +49,14 @@ type ifreq struct {
 }
 
 type tun struct {
+	io.ReadWriteCloser
 	Device      string
 	vpnNetworks []netip.Prefix
 	MTU         int
 	Routes      atomic.Pointer[[]Route]
 	routeTree   atomic.Pointer[bart.Table[routing.Gateways]]
 	l           *slog.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]+$`)
@@ -89,7 +87,7 @@ func newTun(c *config.C, l *slog.Logger, vpnNetworks []netip.Prefix, _ bool) (*t
 	}
 
 	t := &tun{
-		f:           os.NewFile(uintptr(fd), ""),
+		ReadWriteCloser: os.NewFile(uintptr(fd), ""),
 		fd:              fd,
 		Device:          deviceName,
 		vpnNetworks:     vpnNetworks,
@@ -113,55 +111,17 @@ func newTun(c *config.C, l *slog.Logger, vpnNetworks []netip.Prefix, _ bool) (*t
 }
 
 func (t *tun) Close() error {
-	if t.f != nil {
+	if t.ReadWriteCloser != nil {
-		if err := t.f.Close(); err != nil {
+		if err := t.ReadWriteCloser.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
+		// Close on the os.File should have handled the fd 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
@@ -471,3 +431,7 @@ func delRoute(prefix netip.Prefix, gateways []netip.Prefix) error {
 
 	return nil
 }
+
+// TunPrefixLen reports the 4-byte BSD AF_INET / AF_INET6 protocol-family
+// marker the kernel prepends on read and expects on write.
+func (t *tun) TunPrefixLen() int { return 4 }

overlay/tun_tester.go

@@ -15,6 +15,7 @@ import (
 	"github.com/gaissmai/bart"
 	"github.com/slackhq/nebula/config"
 	"github.com/slackhq/nebula/routing"
+	"github.com/slackhq/nebula/udp"
 )
 
 type TestTun struct {
@@ -54,9 +55,12 @@ func newTunFromFd(_ *config.C, _ *slog.Logger, _ int, _ []netip.Prefix) (*TestTu
 	return nil, fmt.Errorf("newTunFromFd not supported")
 }
 
-// Send will place a byte array onto the receive queue for nebula to consume
+// Send will place a byte array onto the receive queue for nebula to consume.
 // These are unencrypted ip layer frames destined for another nebula node.
-// packets should exit the udp side, capture them with udpConn.Get
+// packets should exit the udp side, capture them with udpConn.Get.
+//
+// Send copies the input via the freelist, so the caller is free to mutate
+// or reuse it after the call returns.
 func (t *TestTun) Send(packet []byte) {
 	if t.closed.Load() {
 		return
@@ -65,7 +69,9 @@ func (t *TestTun) Send(packet []byte) {
 	if t.l.Enabled(context.Background(), slog.LevelDebug) {
 		t.l.Debug("Tun receiving injected packet", "dataLen", len(packet))
 	}
-	t.rxPackets <- packet
+	buf := acquireTunBuf(len(packet))
+	copy(buf, packet)
+	t.rxPackets <- buf
 }
 
 // Get will pull an unencrypted ip layer frame from the transmit queue
@@ -110,12 +116,44 @@ func (t *TestTun) Write(b []byte) (n int, err error) {
 		return 0, io.ErrClosedPipe
 	}
 
-	packet := make([]byte, len(b), len(b))
+	packet := acquireTunBuf(len(b))
 	copy(packet, b)
 	t.TxPackets <- packet
 	return len(b), nil
 }
 
+// ReleaseTunBuf returns a slice from TxPackets to the harness freelist, don't use the bytes after the call.
+// Channel-backed instead of sync.Pool because putting a []byte in a sync.Pool escapes the slice header to heap.
+func ReleaseTunBuf(b []byte) {
+	if b == nil {
+		return
+	}
+	select {
+	case tunBufFreelist <- b:
+	default:
+		// Freelist full; drop the buffer for the GC.
+	}
+}
+
+// tunBufFreelist retains the backing arrays for TestTun.Write so steady-state allocation drops to zero once the
+// freelist has saturated for the current MTU.
+var tunBufFreelist = make(chan []byte, 64)
+
+func acquireTunBuf(n int) []byte {
+	var b []byte
+	select {
+	case b = <-tunBufFreelist:
+	default:
+		b = make([]byte, 0, udp.MTU)
+	}
+	if cap(b) < n {
+		b = make([]byte, n)
+	} else {
+		b = b[:n]
+	}
+	return b
+}
+
 func (t *TestTun) Close() error {
 	if t.closed.CompareAndSwap(false, true) {
 		close(t.rxPackets)
@@ -129,8 +167,14 @@ func (t *TestTun) Read(b []byte) (int, error) {
 	if !ok {
 		return 0, os.ErrClosed
 	}
+	n := len(p)
 	copy(b, p)
-	return len(p), nil
+	// Send always pushes a freelist-acquired slice, return it once we've copied the bytes into the caller's buffer.
+	select {
+	case tunBufFreelist <- p:
+	default:
+	}
+	return n, nil
 }
 
 func (t *TestTun) SupportsMultiqueue() bool {
@@ -140,3 +184,5 @@ func (t *TestTun) SupportsMultiqueue() bool {
 func (t *TestTun) NewMultiQueueReader() (io.ReadWriteCloser, error) {
 	return nil, fmt.Errorf("TODO: multiqueue not implemented")
 }
+
+func (t *TestTun) TunPrefixLen() int { return 0 }

overlay/tun_windows.go

@@ -296,3 +296,5 @@ func checkWinTunExists() error {
 	_, err = syscall.LoadDLL(filepath.Join(filepath.Dir(myPath), "dist", "windows", "wintun", "bin", arch, "wintun.dll"))
 	return err
 }
+
+func (t *winTun) TunPrefixLen() int { return 0 }

overlay/user.go

@@ -69,3 +69,5 @@ func (d *UserDevice) Close() error {
 	d.outboundWriter.Close()
 	return nil
 }
+
+func (d *UserDevice) TunPrefixLen() int { return 0 }

pki.go

@@ -15,9 +15,12 @@ import (
 	"sync/atomic"
 	"time"
 
+	"github.com/flynn/noise"
 	"github.com/gaissmai/bart"
 	"github.com/slackhq/nebula/cert"
 	"github.com/slackhq/nebula/config"
+	"github.com/slackhq/nebula/handshake"
+	"github.com/slackhq/nebula/noiseutil"
 	"github.com/slackhq/nebula/util"
 )
 
@@ -29,10 +32,10 @@ type PKI struct {
 
 type CertState struct {
 	v1Cert       cert.Certificate
-	v1HandshakeBytes []byte
+	v1Credential *handshake.Credential
 
 	v2Cert       cert.Certificate
-	v2HandshakeBytes []byte
+	v2Credential *handshake.Credential
 
 	initiatingVersion cert.Version
 	privateKey        []byte
@@ -92,13 +95,35 @@ func (p *PKI) reload(c *config.C, initial bool) error {
 }
 
 func (p *PKI) reloadCerts(c *config.C, initial bool) *util.ContextualError {
-	newState, err := newCertStateFromConfig(c)
+	var cipher string
+	var currentState *CertState
+	if initial {
+		cipher = c.GetString("cipher", "aes")
+		//TODO: this sucks and we should make it not a global
+		switch cipher {
+		case "aes":
+			noiseEndianness = binary.BigEndian
+		case "chachapoly":
+			noiseEndianness = binary.LittleEndian
+		default:
+			return util.NewContextualError(
+				"unknown cipher",
+				m{"cipher": cipher},
+				nil,
+			)
+		}
+	} else {
+		// Cipher cant be hot swapped so just leave it at what it was before
+		currentState = p.cs.Load()
+		cipher = currentState.cipher
+	}
+
+	newState, err := newCertStateFromConfig(c, cipher)
 	if err != nil {
 		return util.NewContextualError("Could not load client cert", nil, err)
 	}
 
-	if !initial {
+	if currentState != nil {
-		currentState := p.cs.Load()
 		if newState.v1Cert != nil {
 			if currentState.v1Cert == nil {
 				//adding certs is fine, actually. Networks-in-common confirmed in newCertState().
@@ -158,25 +183,6 @@ func (p *PKI) reloadCerts(c *config.C, initial bool) *util.ContextualError {
 				)
 			}
 		}
-
-		// Cipher cant be hot swapped so just leave it at what it was before
-		newState.cipher = currentState.cipher
-
-	} else {
-		newState.cipher = c.GetString("cipher", "aes")
-		//TODO: this sucks and we should make it not a global
-		switch newState.cipher {
-		case "aes":
-			noiseEndianness = binary.BigEndian
-		case "chachapoly":
-			noiseEndianness = binary.LittleEndian
-		default:
-			return util.NewContextualError(
-				"unknown cipher",
-				m{"cipher": newState.cipher},
-				nil,
-			)
-		}
 	}
 
 	p.cs.Store(newState)
@@ -208,6 +214,20 @@ func (cs *CertState) GetDefaultCertificate() cert.Certificate {
 	return c
 }
 
+// DefaultVersion returns the preferred cert version for initiating handshakes.
+func (cs *CertState) DefaultVersion() cert.Version { return cs.initiatingVersion }
+
+// GetCredential returns the pre-computed handshake credential for the given version, or nil.
+func (cs *CertState) GetCredential(v cert.Version) *handshake.Credential {
+	switch v {
+	case cert.Version1:
+		return cs.v1Credential
+	case cert.Version2:
+		return cs.v2Credential
+	}
+	return nil
+}
+
 func (cs *CertState) getCertificate(v cert.Version) cert.Certificate {
 	switch v {
 	case cert.Version1:
@@ -219,17 +239,25 @@ func (cs *CertState) getCertificate(v cert.Version) cert.Certificate {
 	return nil
 }
 
-// getHandshakeBytes returns the cached bytes to be used in a handshake message for the requested version.
+func newCipherSuite(curve cert.Curve, pkcs11backed bool, cipher string) (noise.CipherSuite, error) {
-// Callers must check if the return []byte is nil.
+	var dhFunc noise.DHFunc
-func (cs *CertState) getHandshakeBytes(v cert.Version) []byte {
+	switch curve {
-	switch v {
+	case cert.Curve_CURVE25519:
-	case cert.Version1:
+		dhFunc = noise.DH25519
-		return cs.v1HandshakeBytes
+	case cert.Curve_P256:
-	case cert.Version2:
+		if pkcs11backed {
-		return cs.v2HandshakeBytes
+			dhFunc = noiseutil.DHP256PKCS11
-	default:
+		} else {
-		return nil
+			dhFunc = noiseutil.DHP256
 		}
+	default:
+		return nil, fmt.Errorf("unsupported curve: %s", curve)
+	}
+
+	if cipher == "chachapoly" {
+		return noise.NewCipherSuite(dhFunc, noise.CipherChaChaPoly, noise.HashSHA256), nil
+	}
+	return noise.NewCipherSuite(dhFunc, noiseutil.CipherAESGCM, noise.HashSHA256), nil
 }
 
 func (cs *CertState) String() string {
@@ -261,7 +289,7 @@ func (cs *CertState) MarshalJSON() ([]byte, error) {
 	return json.Marshal(msg)
 }
 
-func newCertStateFromConfig(c *config.C) (*CertState, error) {
+func newCertStateFromConfig(c *config.C, cipher string) (*CertState, error) {
 	var err error
 
 	privPathOrPEM := c.GetString("pki.key", "")
@@ -345,13 +373,14 @@ func newCertStateFromConfig(c *config.C) (*CertState, error) {
 		return nil, fmt.Errorf("unknown pki.initiating_version: %v", rawInitiatingVersion)
 	}
 
-	return newCertState(initiatingVersion, v1, v2, isPkcs11, curve, rawKey)
+	return newCertState(initiatingVersion, v1, v2, isPkcs11, curve, rawKey, cipher)
 }
 
-func newCertState(dv cert.Version, v1, v2 cert.Certificate, pkcs11backed bool, privateKeyCurve cert.Curve, privateKey []byte) (*CertState, error) {
+func newCertState(dv cert.Version, v1, v2 cert.Certificate, pkcs11backed bool, privateKeyCurve cert.Curve, privateKey []byte, cipher string) (*CertState, error) {
 	cs := CertState{
 		privateKey:               privateKey,
 		pkcs11Backed:             pkcs11backed,
+		cipher:                   cipher,
 		myVpnNetworksTable:       new(bart.Lite),
 		myVpnAddrsTable:          new(bart.Lite),
 		myVpnBroadcastAddrsTable: new(bart.Lite),
@@ -384,10 +413,14 @@ func newCertState(dv cert.Version, v1, v2 cert.Certificate, pkcs11backed bool, p
 
 		v1hs, err := v1.MarshalForHandshakes()
 		if err != nil {
-			return nil, fmt.Errorf("error marshalling certificate for handshake: %w", err)
+			return nil, fmt.Errorf("error marshalling v1 certificate for handshake: %w", err)
+		}
+		ncs, err := newCipherSuite(v1.Curve(), pkcs11backed, cipher)
+		if err != nil {
+			return nil, err
 		}
 		cs.v1Cert = v1
-		cs.v1HandshakeBytes = v1hs
+		cs.v1Credential = handshake.NewCredential(v1, v1hs, privateKey, ncs)
 
 		if cs.initiatingVersion == 0 {
 			cs.initiatingVersion = cert.Version1
@@ -405,10 +438,14 @@ func newCertState(dv cert.Version, v1, v2 cert.Certificate, pkcs11backed bool, p
 
 		v2hs, err := v2.MarshalForHandshakes()
 		if err != nil {
-			return nil, fmt.Errorf("error marshalling certificate for handshake: %w", err)
+			return nil, fmt.Errorf("error marshalling v2 certificate for handshake: %w", err)
+		}
+		ncs, err := newCipherSuite(v2.Curve(), pkcs11backed, cipher)
+		if err != nil {
+			return nil, err
 		}
 		cs.v2Cert = v2
-		cs.v2HandshakeBytes = v2hs
+		cs.v2Credential = handshake.NewCredential(v2, v2hs, privateKey, ncs)
 
 		if cs.initiatingVersion == 0 {
 			cs.initiatingVersion = cert.Version2

relay_manager.go

@@ -18,6 +18,7 @@ type relayManager struct {
 	l         *slog.Logger
 	hostmap   *HostMap
 	amRelay   atomic.Bool
+	useRelays atomic.Bool
 }
 
 func NewRelayManager(ctx context.Context, l *slog.Logger, hostmap *HostMap, c *config.C) *relayManager {
@@ -36,8 +37,10 @@ func NewRelayManager(ctx context.Context, l *slog.Logger, hostmap *HostMap, c *c
 }
 
 func (rm *relayManager) reload(c *config.C, initial bool) error {
-	if initial || c.HasChanged("relay.am_relay") {
+	if initial || c.HasChanged("relay.am_relay") || c.HasChanged("relay.use_relays") {
-		rm.setAmRelay(c.GetBool("relay.am_relay", false))
+		amRelay := c.GetBool("relay.am_relay", false)
+		rm.amRelay.Store(amRelay)
+		rm.useRelays.Store(c.GetBool("relay.use_relays", true) && !amRelay)
 	}
 	return nil
 }
@@ -46,8 +49,160 @@ func (rm *relayManager) GetAmRelay() bool {
 	return rm.amRelay.Load()
 }
 
-func (rm *relayManager) setAmRelay(v bool) {
+func (rm *relayManager) GetUseRelays() bool {
-	rm.amRelay.Store(v)
+	return rm.useRelays.Load()
+}
+
+// StartRelays drives the relay-establishment side of an outbound handshake attempt.
+// For each candidate relay it either kicks off a handshake to the relay, sends a CreateRelayRequest, retransmits
+// one that may have been lost, or, once the relay is Established, forwards the in-progress
+// stage 0 handshake packet for vpnIp through it.
+func (rm *relayManager) StartRelays(f *Interface, vpnIp netip.Addr, hostinfo *HostInfo, stage0 []byte) {
+	if !rm.GetUseRelays() || len(hostinfo.remotes.relays) == 0 {
+		return
+	}
+
+	hostinfo.logger(rm.l).Info("Attempt to relay through hosts", "relays", hostinfo.remotes.relays)
+	// One WireBuffer for the whole relay-fanout loop.
+	buf := f.bufAlloc.Acquire()
+	defer f.bufAlloc.Release(buf)
+	// Send a RelayRequest to all known Relay IP's
+	for _, relay := range hostinfo.remotes.relays {
+		// Don't relay through the host I'm trying to connect to
+		if relay == vpnIp {
+			continue
+		}
+
+		// Don't relay to myself
+		if f.myVpnAddrsTable.Contains(relay) {
+			continue
+		}
+
+		relayHostInfo := rm.hostmap.QueryVpnAddr(relay)
+		if relayHostInfo == nil || !relayHostInfo.remote.IsValid() {
+			hostinfo.logger(rm.l).Info("Establish tunnel to relay target", "relay", relay.String())
+			f.Handshake(relay)
+			continue
+		}
+		// Check the relay HostInfo to see if we already established a relay through
+		existingRelay, ok := relayHostInfo.relayState.QueryRelayForByIp(vpnIp)
+		if !ok {
+			// No relays exist or requested yet.
+			if relayHostInfo.remote.IsValid() {
+				idx, err := AddRelay(rm.l, relayHostInfo, rm.hostmap, vpnIp, nil, TerminalType, Requested)
+				if err != nil {
+					hostinfo.logger(rm.l).Info("Failed to add relay to hostmap", "relay", relay.String(), "error", err)
+				}
+
+				m := NebulaControl{
+					Type:                NebulaControl_CreateRelayRequest,
+					InitiatorRelayIndex: idx,
+				}
+
+				switch relayHostInfo.GetCert().Certificate.Version() {
+				case cert.Version1:
+					if !f.myVpnAddrs[0].Is4() {
+						hostinfo.logger(rm.l).Error("can not establish v1 relay with a v6 network because the relay is not running a current nebula version")
+						continue
+					}
+
+					if !vpnIp.Is4() {
+						hostinfo.logger(rm.l).Error("can not establish v1 relay with a v6 remote network because the relay is not running a current nebula version")
+						continue
+					}
+
+					b := f.myVpnAddrs[0].As4()
+					m.OldRelayFromAddr = binary.BigEndian.Uint32(b[:])
+					b = vpnIp.As4()
+					m.OldRelayToAddr = binary.BigEndian.Uint32(b[:])
+				case cert.Version2:
+					m.RelayFromAddr = netAddrToProtoAddr(f.myVpnAddrs[0])
+					m.RelayToAddr = netAddrToProtoAddr(vpnIp)
+				default:
+					hostinfo.logger(rm.l).Error("Unknown certificate version found while creating relay")
+					continue
+				}
+
+				msg, err := m.Marshal()
+				if err != nil {
+					hostinfo.logger(rm.l).Error("Failed to marshal Control message to create relay", "error", err)
+				} else {
+					f.SendMessageToHostInfo(header.Control, 0, relayHostInfo, msg, buf)
+					rm.l.Info("send CreateRelayRequest",
+						"relayFrom", f.myVpnAddrs[0],
+						"relayTo", vpnIp,
+						"initiatorRelayIndex", idx,
+						"relay", relay,
+					)
+				}
+			}
+			continue
+		}
+
+		switch existingRelay.State {
+		case Established:
+			hostinfo.logger(rm.l).Info("Send handshake via relay", "relay", relay.String())
+			f.SendVia(relayHostInfo, existingRelay, stage0, buf)
+		case Disestablished:
+			// Mark this relay as 'requested'
+			relayHostInfo.relayState.UpdateRelayForByIpState(vpnIp, Requested)
+			fallthrough
+		case Requested:
+			hostinfo.logger(rm.l).Info("Re-send CreateRelay request", "relay", relay.String())
+			// Re-send the CreateRelay request, in case the previous one was lost.
+			m := NebulaControl{
+				Type:                NebulaControl_CreateRelayRequest,
+				InitiatorRelayIndex: existingRelay.LocalIndex,
+			}
+
+			switch relayHostInfo.GetCert().Certificate.Version() {
+			case cert.Version1:
+				if !f.myVpnAddrs[0].Is4() {
+					hostinfo.logger(rm.l).Error("can not establish v1 relay with a v6 network because the relay is not running a current nebula version")
+					continue
+				}
+
+				if !vpnIp.Is4() {
+					hostinfo.logger(rm.l).Error("can not establish v1 relay with a v6 remote network because the relay is not running a current nebula version")
+					continue
+				}
+
+				b := f.myVpnAddrs[0].As4()
+				m.OldRelayFromAddr = binary.BigEndian.Uint32(b[:])
+				b = vpnIp.As4()
+				m.OldRelayToAddr = binary.BigEndian.Uint32(b[:])
+			case cert.Version2:
+				m.RelayFromAddr = netAddrToProtoAddr(f.myVpnAddrs[0])
+				m.RelayToAddr = netAddrToProtoAddr(vpnIp)
+			default:
+				hostinfo.logger(rm.l).Error("Unknown certificate version found while creating relay")
+				continue
+			}
+			msg, err := m.Marshal()
+			if err != nil {
+				hostinfo.logger(rm.l).Error("Failed to marshal Control message to create relay", "error", err)
+			} else {
+				// This must send over the hostinfo, not over hm.Hosts[ip]
+				f.SendMessageToHostInfo(header.Control, 0, relayHostInfo, msg, buf)
+				rm.l.Info("send CreateRelayRequest",
+					"relayFrom", f.myVpnAddrs[0],
+					"relayTo", vpnIp,
+					"initiatorRelayIndex", existingRelay.LocalIndex,
+					"relay", relay,
+				)
+			}
+		case PeerRequested:
+			// PeerRequested only occurs in Forwarding relays, not Terminal relays, and this is a Terminal relay case.
+			fallthrough
+		default:
+			hostinfo.logger(rm.l).Error("Relay unexpected state",
+				"vpnIp", vpnIp,
+				"state", existingRelay.State,
+				"relay", relay,
+			)
+
+		}
+	}
 }
 
 // AddRelay finds an available relay index on the hostmap, and associates the relay info with it.
@@ -216,7 +371,9 @@ func (rm *relayManager) handleCreateRelayResponse(v cert.Version, h *HostInfo, f
 		if err != nil {
 			rm.l.Error("relayManager Failed to marshal Control CreateRelayResponse message to create relay", "error", err)
 		} else {
-			f.SendMessageToHostInfo(header.Control, 0, peerHostInfo, msg, make([]byte, 12), make([]byte, mtu))
+			buf := f.bufAlloc.Acquire()
+			f.SendMessageToHostInfo(header.Control, 0, peerHostInfo, msg, buf)
+			f.bufAlloc.Release(buf)
 			rm.l.Info("send CreateRelayResponse",
 				"relayFrom", resp.RelayFromAddr,
 				"relayTo", resp.RelayToAddr,
@@ -316,7 +473,9 @@ func (rm *relayManager) handleCreateRelayRequest(v cert.Version, h *HostInfo, f
 		if err != nil {
 			logMsg.Error("relayManager Failed to marshal Control CreateRelayResponse message to create relay", "error", err)
 		} else {
-			f.SendMessageToHostInfo(header.Control, 0, h, msg, make([]byte, 12), make([]byte, mtu))
+			buf := f.bufAlloc.Acquire()
+			f.SendMessageToHostInfo(header.Control, 0, h, msg, buf)
+			f.bufAlloc.Release(buf)
 			rm.l.Info("send CreateRelayResponse",
 				"relayFrom", from,
 				"relayTo", target,
@@ -386,7 +545,9 @@ func (rm *relayManager) handleCreateRelayRequest(v cert.Version, h *HostInfo, f
 		if err != nil {
 			logMsg.Error("relayManager Failed to marshal Control message to create relay", "error", err)
 		} else {
-			f.SendMessageToHostInfo(header.Control, 0, peer, msg, make([]byte, 12), make([]byte, mtu))
+			buf := f.bufAlloc.Acquire()
+			f.SendMessageToHostInfo(header.Control, 0, peer, msg, buf)
+			f.bufAlloc.Release(buf)
 			rm.l.Info("send CreateRelayRequest",
 				"relayFrom", h.vpnAddrs[0],
 				"relayTo", target,

ssh.go

@@ -632,15 +632,9 @@ func sshCloseTunnel(ifce *Interface, fs any, a []string, w sshd.StringWriter) er
 	}
 
 	if !flags.LocalOnly {
-		ifce.send(
+		buf := ifce.bufAlloc.Acquire()
-			header.CloseTunnel,
+		ifce.send(header.CloseTunnel, 0, hostInfo.ConnectionState, hostInfo, []byte{}, buf)
-			0,
+		ifce.bufAlloc.Release(buf)
-			hostInfo.ConnectionState,
-			hostInfo,
-			[]byte{},
-			make([]byte, 12, 12),
-			make([]byte, mtu),
-		)
 	}
 
 	ifce.closeTunnel(hostInfo)

udp/udp_tester.go

@@ -21,17 +21,48 @@ type Packet struct {
 	Data []byte
 }
 
+// Copy returns a fresh *Packet (from the freelist) with a duplicate Data buffer.
 func (u *Packet) Copy() *Packet {
-	n := &Packet{
+	n := acquirePacket()
-		To:   u.To,
+	n.To = u.To
-		From: u.From,
+	n.From = u.From
-		Data: make([]byte, len(u.Data)),
+	if cap(n.Data) < len(u.Data) {
+		n.Data = make([]byte, len(u.Data))
+	} else {
+		n.Data = n.Data[:len(u.Data)]
 	}
-
 	copy(n.Data, u.Data)
 	return n
 }
 
+// Release returns p to the harness packet freelist.
+// Callers that pull a *Packet from Get / TxPackets must Release when done.
+// Channel-backed instead of sync.Pool because sync.Pool's per-P caches drain badly under cross-goroutine Get/Put,
+// and putting a []byte in a Pool escapes the slice header to heap.
+func (p *Packet) Release() {
+	if p == nil {
+		return
+	}
+	p.Data = p.Data[:0]
+	select {
+	case packetFreelist <- p:
+	default:
+		// Freelist full; drop the *Packet for the GC.
+	}
+}
+
+// packetFreelist retains *Packet structs (and their backing Data arrays) so steady-state allocation drops to zero.
+var packetFreelist = make(chan *Packet, 64)
+
+func acquirePacket() *Packet {
+	select {
+	case p := <-packetFreelist:
+		return p
+	default:
+		return &Packet{}
+	}
+}
+
 type TesterConn struct {
 	Addr netip.AddrPort
 
@@ -64,13 +95,15 @@ func NewListener(l *slog.Logger, ip netip.Addr, port int, _ bool, _ int) (Conn,
 // this is an encrypted packet or a handshake message in most cases
 // packets were transmitted from another nebula node, you can send them with Tun.Send
 func (u *TesterConn) Send(packet *Packet) {
-	h := &header.H{}
+	if u.l.Enabled(context.Background(), slog.LevelDebug) {
+		// Parse the header only under debug logging, otherwise the
+		// allocation would show up in every Send call.
+		var h header.H
 		if err := h.Parse(packet.Data); err != nil {
 			panic(err)
 		}
-	if u.l.Enabled(context.Background(), slog.LevelDebug) {
 		u.l.Debug("UDP receiving injected packet",
-			"header", h,
+			"header", &h,
 			"udpAddr", packet.From,
 			"dataLen", len(packet.Data),
 		)
@@ -107,15 +140,18 @@ func (u *TesterConn) Get(block bool) *Packet {
 //********************************************************************************************************************//
 
 func (u *TesterConn) WriteTo(b []byte, addr netip.AddrPort) error {
-	p := &Packet{
+	p := acquirePacket()
-		Data: make([]byte, len(b), len(b)),
+	if cap(p.Data) < len(b) {
-		From: u.Addr,
+		p.Data = make([]byte, len(b))
-		To:   addr,
+	} else {
+		p.Data = p.Data[:len(b)]
 	}
-
 	copy(p.Data, b)
+	p.From = u.Addr
+	p.To = addr
 	select {
 	case <-u.done:
+		p.Release()
 		return io.ErrClosedPipe
 	case u.TxPackets <- p:
 		return nil
@@ -129,6 +165,7 @@ func (u *TesterConn) ListenOut(r EncReader) error {
 			return os.ErrClosed
 		case p := <-u.RxPackets:
 			r(p.From, p.Data)
+			p.Release()
 		}
 	}
 }

wire_buffer.go

@@ -0,0 +1,255 @@
+package nebula
+
+import (
+	"io"
+	"sync"
+
+	"github.com/slackhq/nebula/firewall"
+	"github.com/slackhq/nebula/header"
+	"github.com/slackhq/nebula/noiseutil"
+	"github.com/slackhq/nebula/overlay"
+)
+
+// WireBuffer is the per-goroutine working set for processing one IP packet
+// through the data plane. It owns:
+//
+//   - The IP-payload byte buffer used to hold the current inbound or
+//     outbound packet, with prefixLen bytes of slack at the front for
+//     the BSD AF_INET protocol-family marker.
+//   - The fwPacket scratch parsed by newPacket().
+//   - The 12-byte AEAD nonce scratch.
+//   - The header.H parse target used by the receive path.
+//   - An mtu-sized wire-output scratch for sendNoMetrics and for building
+//     reject packets.
+//
+// One WireBuffer is allocated per data-plane goroutine (listenIn for the
+// TUN-side, listenOut for the UDP-side) and reused for every packet. No
+// per-packet allocation. Future GRO/GSO/TSO and reliable-transport work
+// will likely extend this to carry batch state and fragment metadata.
+//
+// The TUN protocol-family prefix is handled here, not in the overlay
+// package. On BSDs the kernel writes the 4-byte marker into the slack on
+// read, and we stamp it into the slack before write. On linux/windows
+// /userspace devices prefixLen is 0 and the slack is empty.
+type WireBuffer struct {
+	// FwPacket is the parsed IP packet metadata (5-tuple, fragment flags,
+	// etc.) populated by newPacket().
+	FwPacket *firewall.Packet
+	// NB is a 12-byte scratch the AEAD uses for the nonce; reused so we
+	// don't allocate one per encrypt/decrypt.
+	NB []byte
+	// H is the parse target for inbound nebula headers. Receive path only.
+	H *header.H
+	// Out is an mtu-sized wire-output scratch passed to sendNoMetrics and
+	// rejectInside / rejectOutside. Sized to fit any single wire packet.
+	Out []byte
+
+	// ip is the IP-payload region: a slice of len 0, cap linkMTU sliced
+	// from raw at offset prefixLen. The current packet (if any) is
+	// ip[:bodyN]. The TUN prefix slack lives at raw[0:prefixLen] just
+	// before ip.
+	ip []byte
+	// raw is the backing slab. Layout:
+	//   [prefixLen bytes prefix slack | linkMTU bytes IP region | outSize bytes Out scratch]
+	// Holding it lets ReadIPFromTUN / WriteIPToTUN address the slack
+	// region directly.
+	raw       []byte
+	prefixLen int
+	bodyN     int
+}
+
+// NewWireBuffer returns a buffer sized to hold any single IP packet up to
+// linkMTU, plus a disjoint wire-output scratch sliced from the same backing
+// slab (the AEAD's Seal contract requires plaintext and dst not to partially
+// overlap, and keeping them in one slab gives a single allocation per
+// goroutine). Out is sized for the relay worst case
+// (linkMTU + 2*header.Len + 2*AEADOverhead).
+//
+// prefixLen is the number of bytes the destination tun device prepends/
+// expects on each IP packet (overlay.Device.TunPrefixLen). On BSDs this
+// is 4 (AF_INET marker); on linux/windows/userspace devices it is 0.
+func NewWireBuffer(linkMTU, prefixLen int) *WireBuffer {
+	outSize := linkMTU + 2*header.Len + 2*AEADOverhead
+	raw := make([]byte, prefixLen+linkMTU+outSize)
+	outStart := prefixLen + linkMTU
+	return &WireBuffer{
+		FwPacket:  &firewall.Packet{},
+		NB:        make([]byte, NonceSize),
+		H:         &header.H{},
+		Out:       raw[outStart : outStart : outStart+outSize],
+		ip:        raw[prefixLen:prefixLen:outStart],
+		raw:       raw,
+		prefixLen: prefixLen,
+	}
+}
+
+// Reset clears the body-length record so the buffer is ready for another
+// recv (e.g. relay-receive recursion before a nested decrypt).
+func (b *WireBuffer) Reset() { b.bodyN = 0 }
+
+// IPPacket returns the IP packet currently held in the payload region (after
+// a successful ReadIPFromTUN or DecryptDatagram). The slice aliases the
+// buffer; do not retain past the next operation.
+func (b *WireBuffer) IPPacket() []byte {
+	return b.ip[:b.bodyN]
+}
+
+// Seal stamps a nebula header at the front of buf.Out and AEAD-seals p as the
+// payload, treating the header as additional authenticated data. The lock
+// scope around counter increment + encrypt matches what goboring AESGCMTLS
+// requires; non-boring builds skip the lock.
+//
+// Returns the wire bytes (header || ciphertext || tag), aliased to buf.Out.
+// The slice is invalidated by the next Seal* call on this buffer.
+func (b *WireBuffer) Seal(ci *ConnectionState, t header.MessageType, st header.MessageSubType, remoteIndex uint32, p []byte) ([]byte, error) {
+	return b.sealInto(b.Out[:cap(b.Out)], ci, t, st, remoteIndex, p)
+}
+
+// SealForRelay is like Seal but reserves header.Len bytes of slack at the front
+// of buf.Out for an outer relay header. The inner header + ciphertext lands at
+// offset header.Len so a follow-up SealRelayInPlace can stamp the outer header
+// without copying. Use this when the caller may need to wrap the result in a
+// relay envelope after the fact.
+func (b *WireBuffer) SealForRelay(ci *ConnectionState, t header.MessageType, st header.MessageSubType, remoteIndex uint32, p []byte) ([]byte, error) {
+	return b.sealInto(b.Out[header.Len:cap(b.Out)], ci, t, st, remoteIndex, p)
+}
+
+func (b *WireBuffer) sealInto(out []byte, ci *ConnectionState, t header.MessageType, st header.MessageSubType, remoteIndex uint32, p []byte) ([]byte, error) {
+	if noiseutil.EncryptLockNeeded {
+		ci.writeLock.Lock()
+	}
+	c := ci.messageCounter.Add(1)
+	out = header.Encode(out, header.Version, t, st, remoteIndex, c)
+	out, err := ci.eKey.EncryptDanger(out, out, p, c, b.NB)
+	if noiseutil.EncryptLockNeeded {
+		ci.writeLock.Unlock()
+	}
+	return out, err
+}
+
+// SealRelayInPlace wraps an inner message that is already staged at
+// buf.Out[header.Len:header.Len+innerLen] (either from a SealForRelay encrypt
+// or from a copy via the SendVia entry point). It stamps the outer relay
+// header into buf.Out[:header.Len] and AAD-only seals over the entire region,
+// producing the wire bytes for the relay tunnel.
+//
+// Returns the wire bytes aliased to buf.Out; invalidated by the next Seal*
+// call on this buffer.
+func (b *WireBuffer) SealRelayInPlace(ci *ConnectionState, remoteIndex uint32, innerLen int) ([]byte, error) {
+	if noiseutil.EncryptLockNeeded {
+		ci.writeLock.Lock()
+	}
+	c := ci.messageCounter.Add(1)
+	out := b.Out[:cap(b.Out)]
+	out = header.Encode(out, header.Version, header.Message, header.MessageRelay, remoteIndex, c)
+	out = out[:header.Len+innerLen]
+	out, err := ci.eKey.EncryptDanger(out, out, nil, c, b.NB)
+	if noiseutil.EncryptLockNeeded {
+		ci.writeLock.Unlock()
+	}
+	return out, err
+}
+
+// StageRelayInner copies ad into the inner-payload slot at buf.Out[header.Len:]
+// so SealRelayInPlace can wrap it on the next call. Used by SendVia when ad
+// did not come from a prior SealForRelay (e.g. a handshake message being
+// forwarded through a relay tunnel without our own encryption).
+func (b *WireBuffer) StageRelayInner(ad []byte) int {
+	return copy(b.Out[header.Len:cap(b.Out)], ad)
+}
+
+// ReadIPFromTUN reads one IP packet from r into the payload region and
+// updates bodyN. On BSDs the kernel writes its 4-byte protocol-family
+// marker into the slack at raw[0:prefixLen] and the IP packet at
+// raw[prefixLen:prefixLen+n]; we hand it the slack-prefixed slice so
+// the kernel can do this in one syscall with no copy. On linux/windows/
+// userspace devices prefixLen is 0 and the slack is empty.
+func (b *WireBuffer) ReadIPFromTUN(r io.Reader) (int, error) {
+	n, err := r.Read(b.raw[:b.prefixLen+cap(b.ip)])
+	if err != nil {
+		b.bodyN = 0
+		return 0, err
+	}
+	if n < b.prefixLen {
+		b.bodyN = 0
+		return 0, nil
+	}
+	b.bodyN = n - b.prefixLen
+	return b.bodyN, nil
+}
+
+// WriteIPToTUN writes the IP packet currently in the payload region to w.
+// On BSDs we stamp the protocol-family marker into the slack at
+// raw[0:prefixLen] in place and write the entire slack+IP region in a
+// single syscall, so the kernel sees [marker][ip] back to back without a
+// userspace copy. On linux/windows/userspace devices the slack is empty
+// and we just write the IP region.
+func (b *WireBuffer) WriteIPToTUN(w io.Writer) (int, error) {
+	out := b.raw[:b.prefixLen+b.bodyN]
+	if b.prefixLen > 0 {
+		if err := overlay.StampTunPrefix(out); err != nil {
+			return 0, err
+		}
+	}
+	return w.Write(out)
+}
+
+// DecryptDatagram decrypts an inbound UDP packet into the payload region.
+func (b *WireBuffer) DecryptDatagram(ci *ConnectionState, packet []byte, mc uint64) error {
+	dst, err := ci.dKey.DecryptDanger(b.ip[:0], packet[:header.Len], packet[header.Len:], mc, b.NB)
+	if err != nil {
+		b.bodyN = 0
+		return err
+	}
+	b.bodyN = len(dst)
+	return nil
+}
+
+// DecryptForHandler decrypts an inbound UDP packet (lighthouse, test,
+// control, close-tunnel) into the payload region and returns the plaintext
+// slice for the in-process handler. Returned slice aliases the buffer.
+func (b *WireBuffer) DecryptForHandler(ci *ConnectionState, packet []byte, mc uint64) ([]byte, error) {
+	dst, err := ci.dKey.DecryptDanger(b.ip[:0], packet[:header.Len], packet[header.Len:], mc, b.NB)
+	if err != nil {
+		b.bodyN = 0
+		return nil, err
+	}
+	b.bodyN = len(dst)
+	return dst, nil
+}
+
+// WireBufferAllocator hands out reusable WireBuffers for cold callers that
+// don't own a long-lived per-goroutine buffer (control plane, relay manager,
+// connection manager teardown, etc.). Hot-path goroutines hold their own
+// buffer for the life of the goroutine and don't need to acquire one.
+type WireBufferAllocator interface {
+	Acquire() *WireBuffer
+	Release(*WireBuffer)
+}
+
+// wireBufferPool is a sync.Pool-backed WireBufferAllocator. The pool is
+// keyed off a single linkMTU and prefixLen; cold callers send across the
+// data-plane mtu and target the same Device, so we size the pool's
+// buffers the same way.
+type wireBufferPool struct {
+	pool sync.Pool
+}
+
+func NewWireBufferPool(linkMTU, prefixLen int) *wireBufferPool {
+	return &wireBufferPool{
+		pool: sync.Pool{
+			New: func() any {
+				return NewWireBuffer(linkMTU, prefixLen)
+			},
+		},
+	}
+}
+
+func (p *wireBufferPool) Acquire() *WireBuffer {
+	return p.pool.Get().(*WireBuffer)
+}
+
+func (p *wireBufferPool) Release(b *WireBuffer) {
+	b.Reset()
+	p.pool.Put(b)
+}