Apply Tailscale endpoint awareness

conn/conn.go

@@ -86,6 +86,40 @@ type Endpoint interface {
 	SrcIP() netip.Addr
 }
 
+// InitiationAwareEndpoint is an optional [Endpoint] specialization for
+// integrations that want to know when a WireGuard handshake initiation
+// message has been received, enabling just-in-time peer configuration before
+// attempted decryption.
+//
+// It's most useful when used in combination with [PeerAwareEndpoint], enabling
+// JIT peer configuration and post-decryption peer verification from a single
+// implementer.
+type InitiationAwareEndpoint interface {
+	// InitiationMessagePublicKey is called when a handshake initiation message
+	// has been received, and the sender's public key has been identified, but
+	// BEFORE an attempt has been made to verify it.
+	InitiationMessagePublicKey(peerPublicKey [32]byte)
+}
+
+// PeerAwareEndpoint is an optional Endpoint specialization for
+// integrations that want to know about the outcome of Cryptokey Routing
+// identification.
+//
+// If they receive a packet from a source they had not pre-identified,
+// to learn the identification WireGuard can derive from the session
+// or handshake.
+//
+// A [PeerAwareEndpoint] may be installed as the [conn.Endpoint] following
+// successful decryption unless endpoint roaming has been disabled for
+// the peer.
+type PeerAwareEndpoint interface {
+	// FromPeer is called at least once per successfully Cryptokey Routing ID'd
+	// [ReceiveFunc] packets batch for a given node key. wireguard-go will
+	// always call it for the latest/tail packet in the batch, only ever
+	// suppressing calls for older packets.
+	FromPeer(peerPublicKey [32]byte)
+}
+
 var (
 	ErrBindAlreadyOpen   = errors.New("bind is already open")
 	ErrWrongEndpointType = errors.New("endpoint type does not correspond with bind type")

device/noise-protocol.go

@@ -12,6 +12,7 @@ import (
 	"sync"
 	"time"
 
+	"github.com/sagernet/wireguard-go/conn"
 	"github.com/sagernet/wireguard-go/tai64n"
 	"golang.org/x/crypto/blake2s"
 	"golang.org/x/crypto/chacha20poly1305"
@@ -337,7 +338,7 @@ func (device *Device) CreateMessageInitiation(peer *Peer) (*MessageInitiation, e
 	return &msg, nil
 }
 
-func (device *Device) ConsumeMessageInitiation(msg *MessageInitiation) *Peer {
+func (device *Device) ConsumeMessageInitiation(msg *MessageInitiation, endpoint conn.Endpoint) *Peer {
 	var (
 		hash     [blake2s.Size]byte
 		chainKey [blake2s.Size]byte
@@ -371,6 +372,11 @@ func (device *Device) ConsumeMessageInitiation(msg *MessageInitiation) *Peer {
 
 	// lookup peer
 
+	initEP, ok := endpoint.(conn.InitiationAwareEndpoint)
+	if ok {
+		initEP.InitiationMessagePublicKey(peerPK)
+	}
+
 	peer := device.LookupPeer(peerPK)
 	if peer == nil || !peer.isRunning.Load() {
 		return nil

device/receive.go

@@ -359,7 +359,7 @@ func (device *Device) RoutineHandshake(id int) {
 
 			// consume initiation
 
-			peer := device.ConsumeMessageInitiation(&msg)
+			peer := device.ConsumeMessageInitiation(&msg, elem.endpoint)
 			if peer == nil {
 				device.log.Verbosef("Received invalid initiation message from %s", elem.endpoint.DstToString())
 				goto skip
@@ -459,6 +459,9 @@ func (peer *Peer) RoutineSequentialReceiver(maxBatchSize int) {
 				peer.timersHandshakeComplete()
 				peer.SendStagedPackets()
 			}
+			if ep, ok := elem.endpoint.(conn.PeerAwareEndpoint); ok {
+				ep.FromPeer(peer.handshake.remoteStatic)
+			}
 			rxBytesLen += uint64(len(elem.packet) + MinMessageSize)
 
 			if len(elem.packet) == 0 {