wgengine/magicsock: disable some code paths when relay server is removed from build

Saves 90 KB.

Updates #12614

Change-Id: I47c6b8541c4069fcc5dfcc9763da50f827ad28c7
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

wgengine/magicsock/endpoint.go

@@ -24,6 +24,7 @@ import (
 	"golang.org/x/net/ipv4"
 	"golang.org/x/net/ipv6"
 	"tailscale.com/disco"
+	"tailscale.com/feature/buildfeatures"
 	"tailscale.com/ipn/ipnstate"
 	"tailscale.com/net/packet"
 	"tailscale.com/net/stun"
@@ -896,7 +897,7 @@ func (de *endpoint) discoverUDPRelayPathsLocked(now mono.Time) {
 // wantUDPRelayPathDiscoveryLocked reports whether we should kick off UDP relay
 // path discovery.
 func (de *endpoint) wantUDPRelayPathDiscoveryLocked(now mono.Time) bool {
-	if runtime.GOOS == "js" {
+	if runtime.GOOS == "js" || !buildfeatures.HasRelayServer {
 		return false
 	}
 	if !de.relayCapable {
@@ -2000,8 +2001,10 @@ func (de *endpoint) handleCallMeMaybe(m *disco.CallMeMaybe) {
 	// path discovery can also trigger disco ping transmission, which *could*
 	// lead to an infinite loop of peer relay path discovery between two peers,
 	// absent intended triggers.
-	if de.wantUDPRelayPathDiscoveryLocked(monoNow) {
-		de.discoverUDPRelayPathsLocked(monoNow)
+	if buildfeatures.HasRelayServer {
+		if de.wantUDPRelayPathDiscoveryLocked(monoNow) {
+			de.discoverUDPRelayPathsLocked(monoNow)
+		}
 	}
 }
 

wgengine/magicsock/magicsock.go

@@ -644,7 +644,11 @@ func (c *Conn) consumeEventbusTopics(cli *eventbus.Client) func(*eventbus.Client
 	nodeViewsSub := eventbus.Subscribe[NodeViewsUpdate](cli)
 	nodeMutsSub := eventbus.Subscribe[NodeMutationsUpdate](cli)
 	syncSub := eventbus.Subscribe[syncPoint](cli)
-	allocRelayEndpointSub := eventbus.Subscribe[UDPRelayAllocResp](cli)
+
+	var relayCh <-chan UDPRelayAllocResp
+	if buildfeatures.HasRelayServer {
+		relayCh = eventbus.Subscribe[UDPRelayAllocResp](cli).Events()
+	}
 	return func(cli *eventbus.Client) {
 		for {
 			select {
@@ -661,8 +665,10 @@ func (c *Conn) consumeEventbusTopics(cli *eventbus.Client) func(*eventbus.Client
 			case syncPoint := <-syncSub.Events():
 				c.dlogf("magicsock: received sync point after reconfig")
 				syncPoint.Signal()
-			case allocResp := <-allocRelayEndpointSub.Events():
-				c.onUDPRelayAllocResp(allocResp)
+			case allocResp := <-relayCh:
+				if buildfeatures.HasRelayServer {
+					c.onUDPRelayAllocResp(allocResp)
+				}
 			}
 		}
 	}
@@ -1945,11 +1951,13 @@ func (c *Conn) sendDiscoMessage(dst epAddr, dstKey key.NodePublic, dstDisco key.
 	var di *discoInfo
 	switch {
 	case isRelayHandshakeMsg:
-		var ok bool
-		di, ok = c.relayManager.discoInfo(dstDisco)
-		if !ok {
-			c.mu.Unlock()
-			return false, errors.New("unknown relay server")
+		if buildfeatures.HasRelayServer {
+			var ok bool
+			di, ok = c.relayManager.discoInfo(dstDisco)
+			if !ok {
+				c.mu.Unlock()
+				return false, errors.New("unknown relay server")
+			}
 		}
 	case c.peerMap.knownPeerDiscoKey(dstDisco):
 		di = c.discoInfoForKnownPeerLocked(dstDisco)
@@ -2169,13 +2177,15 @@ func (c *Conn) handleDiscoMessage(msg []byte, src epAddr, shouldBeRelayHandshake
 	var di *discoInfo
 	switch {
 	case shouldBeRelayHandshakeMsg:
-		var ok bool
-		di, ok = c.relayManager.discoInfo(sender)
-		if !ok {
-			if debugDisco() {
-				c.logf("magicsock: disco: ignoring disco-looking relay handshake frame, no active handshakes with key %v over %v", sender.ShortString(), src)
+		if buildfeatures.HasRelayServer {
+			var ok bool
+			di, ok = c.relayManager.discoInfo(sender)
+			if !ok {
+				if debugDisco() {
+					c.logf("magicsock: disco: ignoring disco-looking relay handshake frame, no active handshakes with key %v over %v", sender.ShortString(), src)
+				}
+				return
 			}
-			return
 		}
 	case c.peerMap.knownPeerDiscoKey(sender):
 		di = c.discoInfoForKnownPeerLocked(sender)
@@ -2894,6 +2904,9 @@ func (c *Conn) onFilterUpdate(f FilterUpdate) {
 //  2. Moving this work upstream into [nodeBackend] or similar, and publishing
 //     the computed result over the eventbus instead.
 func (c *Conn) updateRelayServersSet(filt *filter.Filter, self tailcfg.NodeView, peers views.Slice[tailcfg.NodeView]) {
+	if !buildfeatures.HasRelayServer {
+		return
+	}
 	relayServers := make(set.Set[candidatePeerRelay])
 	nodes := append(peers.AsSlice(), self)
 	for _, maybeCandidate := range nodes {

wgengine/magicsock/relaymanager.go

@@ -12,6 +12,7 @@ import (
 	"time"
 
 	"tailscale.com/disco"
+	"tailscale.com/feature/buildfeatures"
 	"tailscale.com/net/packet"
 	"tailscale.com/net/stun"
 	udprelay "tailscale.com/net/udprelay/endpoint"
@@ -419,6 +420,9 @@ func (r *relayManager) handleCallMeMaybeVia(ep *endpoint, lastBest addrQuality,
 // [*disco.AllocateUDPRelayEndpointResponse] then relayServerNodeKey must be
 // nonzero.
 func (r *relayManager) handleRxDiscoMsg(conn *Conn, dm disco.Message, relayServerNodeKey key.NodePublic, discoKey key.DiscoPublic, src epAddr) {
+	if !buildfeatures.HasRelayServer {
+		return
+	}
 	relayManagerInputEvent(r, nil, &r.rxDiscoMsgCh, relayDiscoMsgEvent{
 		conn:               conn,
 		msg:                dm,
@@ -445,6 +449,9 @@ func (r *relayManager) handleRelayServersSet(servers set.Set[candidatePeerRelay]
 // goroutine to return, i.e. the calling goroutine was birthed by runLoop and is
 // cancelable via 'ctx'. 'ctx' may be nil.
 func relayManagerInputEvent[T any](r *relayManager, ctx context.Context, eventCh *chan T, event T) {
+	if !buildfeatures.HasRelayServer {
+		return
+	}
 	r.init()
 	var ctxDoneCh <-chan struct{}
 	if ctx != nil {