wgengine/magicsock: make lazyEndpoint load bearing for UDP relay (#16435)

Cryptokey Routing identification is now required to set an [epAddr] into
the peerMap for Geneve-encapsulated [epAddr]s.

Updates tailscale/corp#27502
Updates tailscale/corp#29422
Updates tailscale/corp#30042

Signed-off-by: Jordan Whited <jordan@tailscale.com>

go.mod

@@ -90,7 +90,7 @@ require (
 	github.com/tailscale/setec v0.0.0-20250205144240-8898a29c3fbb
 	github.com/tailscale/web-client-prebuilt v0.0.0-20250124233751-d4cd19a26976
 	github.com/tailscale/wf v0.0.0-20240214030419-6fbb0a674ee6
-	github.com/tailscale/wireguard-go v0.0.0-20250530210235-65cd6eed7d7f
+	github.com/tailscale/wireguard-go v0.0.0-20250701223756-24483d7a0003
 	github.com/tailscale/xnet v0.0.0-20240729143630-8497ac4dab2e
 	github.com/tc-hib/winres v0.2.1
 	github.com/tcnksm/go-httpstat v0.2.0

go.sum

@@ -975,8 +975,8 @@ github.com/tailscale/web-client-prebuilt v0.0.0-20250124233751-d4cd19a26976 h1:U
 github.com/tailscale/web-client-prebuilt v0.0.0-20250124233751-d4cd19a26976/go.mod h1:agQPE6y6ldqCOui2gkIh7ZMztTkIQKH049tv8siLuNQ=
 github.com/tailscale/wf v0.0.0-20240214030419-6fbb0a674ee6 h1:l10Gi6w9jxvinoiq15g8OToDdASBni4CyJOdHY1Hr8M=
 github.com/tailscale/wf v0.0.0-20240214030419-6fbb0a674ee6/go.mod h1:ZXRML051h7o4OcI0d3AaILDIad/Xw0IkXaHM17dic1Y=
-github.com/tailscale/wireguard-go v0.0.0-20250530210235-65cd6eed7d7f h1:vg3PmQdq1BbB2V81iC1VBICQtfwbVGZ/4A/p7QKXTK0=
+github.com/tailscale/wireguard-go v0.0.0-20250701223756-24483d7a0003 h1:chIzUDKxR0nXQQra0j41aqiiFNICs0FIC5ZCwDO7z3k=
-github.com/tailscale/wireguard-go v0.0.0-20250530210235-65cd6eed7d7f/go.mod h1:BOm5fXUBFM+m9woLNBoxI9TaBXXhGNP50LX/TGIvGb4=
+github.com/tailscale/wireguard-go v0.0.0-20250701223756-24483d7a0003/go.mod h1:BOm5fXUBFM+m9woLNBoxI9TaBXXhGNP50LX/TGIvGb4=
 github.com/tailscale/xnet v0.0.0-20240729143630-8497ac4dab2e h1:zOGKqN5D5hHhiYUp091JqK7DPCqSARyUfduhGUY8Bek=
 github.com/tailscale/xnet v0.0.0-20240729143630-8497ac4dab2e/go.mod h1:orPd6JZXXRyuDusYilywte7k094d7dycXXU5YnWsrwg=
 github.com/tc-hib/winres v0.2.1 h1:YDE0FiP0VmtRaDn7+aaChp1KiF4owBiJa5l964l5ujA=

wgengine/magicsock/endpoint.go

@@ -126,7 +126,6 @@ func (de *endpoint) udpRelayEndpointReady(maybeBest addrQuality) {
 	de.c.logf("magicsock: disco: node %v %v now using %v mtu=%v", de.publicKey.ShortString(), de.discoShort(), maybeBest.epAddr, maybeBest.wireMTU)
 	de.setBestAddrLocked(maybeBest)
 	de.trustBestAddrUntil = mono.Now().Add(trustUDPAddrDuration)
-	de.c.peerMap.setNodeKeyForEpAddr(maybeBest.epAddr, de.publicKey)
 }
 
 func (de *endpoint) setBestAddrLocked(v addrQuality) {

wgengine/magicsock/magicsock.go

@@ -1695,8 +1695,13 @@ func (c *Conn) receiveIP(b []byte, ipp netip.AddrPort, cache *epAddrEndpointCach
 		c.mu.Unlock()
 		if !ok {
 			if c.controlKnobs != nil && c.controlKnobs.DisableCryptorouting.Load() {
+				// Note: UDP relay is dependent on cryptorouting enablement. We
+				// only update Geneve-encapsulated [epAddr]s in the [peerMap]
+				// via [lazyEndpoint].
 				return nil, 0, false
 			}
+			// TODO(jwhited): reuse [lazyEndpoint] across calls to receiveIP()
+			//  for the same batch & [epAddr] src.
 			return &lazyEndpoint{c: c, src: src}, size, true
 		}
 		cache.epAddr = src
@@ -1704,6 +1709,8 @@ func (c *Conn) receiveIP(b []byte, ipp netip.AddrPort, cache *epAddrEndpointCach
 		cache.gen = de.numStopAndReset()
 		ep = de
 	}
+	// TODO(jwhited): consider the implications of not recording this receive
+	//  activity due to an early [lazyEndpoint] return above.
 	now := mono.Now()
 	ep.lastRecvUDPAny.StoreAtomic(now)
 	ep.noteRecvActivity(src, now)
@@ -3793,14 +3800,27 @@ func (le *lazyEndpoint) DstIP() netip.Addr   { return netip.Addr{} }
 func (le *lazyEndpoint) SrcToString() string { return le.src.String() }
 func (le *lazyEndpoint) DstToString() string { return "dst" }
 func (le *lazyEndpoint) DstToBytes() []byte  { return nil }
-func (le *lazyEndpoint) GetPeerEndpoint(peerPublicKey [32]byte) conn.Endpoint {
+
+// FromPeer implements [conn.PeerAwareEndpoint]. We return a [*lazyEndpoint] in
+// our [conn.ReceiveFunc]s when we are unable to identify the peer at WireGuard
+// packet reception time, pre-decryption. If wireguard-go successfully decrypts
+// the packet it calls us here, and we update our [peerMap] in order to
+// associate le.src with peerPublicKey.
+func (le *lazyEndpoint) FromPeer(peerPublicKey [32]byte) {
 	pubKey := key.NodePublicFromRaw32(mem.B(peerPublicKey[:]))
 	le.c.mu.Lock()
 	defer le.c.mu.Unlock()
 	ep, ok := le.c.peerMap.endpointForNodeKey(pubKey)
 	if !ok {
-		return nil
+		return
 	}
-	le.c.logf("magicsock: lazyEndpoint.GetPeerEndpoint(%v) found: %v", pubKey.ShortString(), ep.nodeAddr)
+	// TODO(jwhited): Consider [lazyEndpoint] effectiveness as a means to make
-	return ep
+	//  this the sole call site for setNodeKeyForEpAddr. If this is the sole
+	//  call site, and we always update the mapping based on successful
+	//  Cryptokey Routing identification events, then we can go ahead and make
+	//  [epAddr]s singular per peer (like they are for Geneve-encapsulated ones
+	//  already).
+	//  See http://go/corp/29422 & http://go/corp/30042
+	le.c.peerMap.setNodeKeyForEpAddr(le.src, pubKey)
+	le.c.logf("magicsock: lazyEndpoint.FromPeer(%v) setting epAddr(%v) in peerMap for node(%v)", pubKey.ShortString(), le.src, ep.nodeAddr)
 }