Try ICE servers

kylecarbs · kylecarbs · commit 107eb968a7de · 2022-01-30T13:13:12.000Z
diff --git a/peer/conn.go b/peer/conn.go
@@ -79,6 +79,7 @@ func newWithClientOrServer(servers []webrtc.ICEServer, client bool, opts *ConnOp
 		// This channel needs to be bufferred otherwise slow consumers
 		// of this will cause a connection failure.
 		localCandidateChannel:           make(chan webrtc.ICECandidateInit, 16),
+		pendingRemoteCandidates:         make([]webrtc.ICECandidateInit, 0),
 		localSessionDescriptionChannel:  make(chan webrtc.SessionDescription, 1),
 		remoteSessionDescriptionChannel: make(chan webrtc.SessionDescription, 1),
 	}
@@ -128,6 +129,10 @@ type Conn struct {
 	localSessionDescriptionChannel  chan webrtc.SessionDescription
 	remoteSessionDescriptionChannel chan webrtc.SessionDescription
 
+	pendingRemoteCandidates  []webrtc.ICECandidateInit
+	pendingCandidatesMutex   sync.Mutex
+	pendingCandidatesFlushed bool
+
 	pingChannelID     uint16
 	pingEchoChannelID uint16
 
@@ -329,6 +334,28 @@ func (c *Conn) negotiate() {
 		return
 	}
 
+	// The RemoteDescription must be set before ICE candidates can be
+	// added to a WebRTC connection.
+	c.pendingCandidatesMutex.Lock()
+	for _, pendingCandidate := range c.pendingRemoteCandidates {
+		hash := sha256.Sum224([]byte(pendingCandidate.Candidate))
+		c.opts.Logger.Debug(context.Background(), "flushing buffered remote candidate",
+			slog.F("hash", hash),
+			slog.F("length", len(pendingCandidate.Candidate)),
+		)
+		err := c.rtc.AddICECandidate(pendingCandidate)
+		if err != nil {
+			_ = c.CloseWithError(xerrors.Errorf("flush pending remote candidate: %w", err))
+			return
+		}
+	}
+	c.opts.Logger.Debug(context.Background(), "flushed buffered remote candidates",
+		slog.F("count", len(c.pendingRemoteCandidates)),
+	)
+	c.pendingCandidatesFlushed = true
+	c.pendingRemoteCandidates = make([]webrtc.ICECandidateInit, 0)
+	c.pendingCandidatesMutex.Unlock()
+
 	if !c.offerrer {
 		answer, err := c.rtc.CreateAnswer(&webrtc.AnswerOptions{})
 		if err != nil {
@@ -362,10 +389,18 @@ func (c *Conn) LocalCandidate() <-chan webrtc.ICECandidateInit {
 
 // AddRemoteCandidate adds a remote candidate to the RTC connection.
 func (c *Conn) AddRemoteCandidate(i webrtc.ICECandidateInit) error {
-	c.opts.Logger.Debug(context.Background(), "adding remote candidate",
+	c.pendingCandidatesMutex.Lock()
+	defer c.pendingCandidatesMutex.Unlock()
+	fields := []slog.Field{
 		slog.F("hash", c.hashCandidate(i)),
 		slog.F("length", len(i.Candidate)),
-	)
+	}
+	if !c.pendingCandidatesFlushed {
+		c.opts.Logger.Debug(context.Background(), "bufferring remote candidate", fields...)
+		c.pendingRemoteCandidates = append(c.pendingRemoteCandidates, i)
+		return nil
+	}
+	c.opts.Logger.Debug(context.Background(), "adding remote candidate", fields...)
 	return c.rtc.AddICECandidate(i)
 }
 
diff --git a/peer/conn_test.go b/peer/conn_test.go
@@ -271,7 +271,9 @@ func createPair(t *testing.T) (client *peer.Conn, server *peer.Conn, wan *vnet.R
 	c1SettingEngine.SetVNet(c1Net)
 	c1SettingEngine.SetPrflxAcceptanceMinWait(0)
 	c1SettingEngine.SetICETimeouts(disconnectedTimeout, failedTimeout, keepAliveInterval)
-	channel1, err := peer.Client([]webrtc.ICEServer{}, &peer.ConnOptions{
+	channel1, err := peer.Client([]webrtc.ICEServer{{
+		URLs: []string{"stun:stun.l.google.com:19302"},
+	}}, &peer.ConnOptions{
 		SettingEngine: c1SettingEngine,
 		Logger:        slogtest.Make(t, nil).Named("client").Leveled(slog.LevelDebug),
 	})
@@ -283,7 +285,9 @@ func createPair(t *testing.T) (client *peer.Conn, server *peer.Conn, wan *vnet.R
 	c2SettingEngine.SetVNet(c2Net)
 	c2SettingEngine.SetPrflxAcceptanceMinWait(0)
 	c2SettingEngine.SetICETimeouts(disconnectedTimeout, failedTimeout, keepAliveInterval)
-	channel2, err := peer.Server([]webrtc.ICEServer{}, &peer.ConnOptions{
+	channel2, err := peer.Server([]webrtc.ICEServer{{
+		URLs: []string{"stun:stun.l.google.com:19302"},
+	}}, &peer.ConnOptions{
 		SettingEngine: c2SettingEngine,
 		Logger:        slogtest.Make(t, nil).Named("server").Leveled(slog.LevelDebug),
 	})
