Replace changed connections.

We used to destroy and recreate connections, we now replace them atomically.

static/sfu.js

@@ -139,14 +139,10 @@ document.getElementById('unpresentbutton').onclick = function(e) {
 };
 
 function changePresentation() {
-    let found = false;
-    for(let id in up) {
-        if(up[id].kind === 'local')
-            found = true;
+    let id = findUpMedia('local');
+    if(id) {
+        addLocalMedia(id);
     }
-    delUpMediaKind('local');
-    if(found)
-        addLocalMedia();
 }
 
 function setVisibility(id, visible) {
@@ -158,8 +154,8 @@ function setVisibility(id, visible) {
 }
 
 function setButtonsVisibility() {
-    let local = findUpMedia('local');
-    let share = findUpMedia('screenshare')
+    let local = !!findUpMedia('local');
+    let share = !!findUpMedia('screenshare')
     // don't allow multiple presentations
     setVisibility('presentbutton', permissions.present && !local);
     setVisibility('unpresentbutton', local);
@@ -344,15 +340,21 @@ async function setMediaChoices() {
     mediaChoicesDone = true;
 }
 
-async function addLocalMedia() {
+async function addLocalMedia(id) {
     if(!getUserPass())
         return;
 
     let audio = mapMediaOption(document.getElementById('audioselect').value);
     let video = mapMediaOption(document.getElementById('videoselect').value);
 
-    if(!audio && !video)
+    if(!audio && !video) {
+        if(id)
+            delUpMedia(id);
         return;
+    }
+
+    if(id)
+        stopUpMedia(id);
 
     let constraints = {audio: audio, video: video};
     let stream = null;
@@ -360,13 +362,16 @@ async function addLocalMedia() {
         stream = await navigator.mediaDevices.getUserMedia(constraints);
     } catch(e) {
         console.error(e);
+        if(id)
+            delUpMedia(id);
         return;
     }
 
     setMediaChoices();
 
-    let id = await newUpStream();
+    id = await newUpStream(id);
     let c = up[id];
+
     c.kind = 'local';
     c.stream = stream;
     stream.getTracks().forEach(t => {
@@ -418,16 +423,32 @@ async function addShareMedia(setup) {
     setButtonsVisibility()
 }
 
+function stopUpMedia(id) {
+    let c = up[id];
+    if(!c) {
+        console.error('Stopping unknown up media');
+        return;
+    }
+    if(!c.stream)
+        return;
+    c.stream.getTracks().forEach(t => {
+        try {
+            t.stop();
+        } catch(e) {
+        }
+    });
+}
+
 function delUpMedia(id) {
     let c = up[id];
     if(!c) {
-        console.error("Deleting unknown up media");
+        console.error('Deleting unknown up media');
         return;
     }
-    c.close(true);
+    stopUpMedia(id);
     delMedia(id);
+    c.close(true);
     delete(up[id]);
-
     setButtonsVisibility()
 }
 
@@ -447,9 +468,9 @@ function delUpMediaKind(kind) {
 function findUpMedia(kind) {
     for(let id in up) {
         if(up[id].kind === kind)
-            return true;
+            return id;
     }
-    return false;
+    return null;
 }
 
 function muteLocalTracks(mute) {
@@ -680,6 +701,14 @@ function sendRequest(value) {
 
 async function gotOffer(id, labels, offer) {
     let c = down[id];
+    if(c) {
+        // a new offer with a known id does not indicate renegotiation,
+        // but a new connection that replaces the old one.
+        delete(down[id])
+        c.close(false);
+        c = null;
+    }
+
     if(!c) {
         let pc = new RTCPeerConnection({
             iceServers: iceServers,
@@ -1113,15 +1142,20 @@ function chatResizer(e) {
 
 document.getElementById('resizer').addEventListener('mousedown', chatResizer, false);
 
-async function newUpStream() {
-    let id = randomid();
+async function newUpStream(id) {
+    if(!id) {
+        id = randomid();
         if(up[id])
             throw new Error('Eek!');
+    }
     let pc = new RTCPeerConnection({
         iceServers: iceServers,
     });
     if(!pc)
         throw new Error("Couldn't create peer connection");
+    if(up[id]) {
+        up[id].close(false);
+    }
     up[id] = new Connection(id, pc);
 
     pc.onnegotiationneeded = async e => {

webclient.go

@@ -221,10 +221,17 @@ func addUpConn(c *webClient, id string) (*rtpUpConnection, error) {
 	if c.up == nil {
 		c.up = make(map[string]*rtpUpConnection)
 	}
-	if c.up[id] != nil || (c.down != nil && c.down[id] != nil) {
+	if c.down != nil && c.down[id] != nil {
 		conn.pc.Close()
 		return nil, errors.New("Adding duplicate connection")
 	}
+
+	old := c.up[id]
+	if old != nil {
+		decrementVideoTracks(c, old)
+		old.pc.Close()
+	}
+
 	c.up[id] = conn
 
 	conn.pc.OnICECandidate(func(candidate *webrtc.ICECandidate) {
@@ -248,7 +255,21 @@ func delUpConn(c *webClient, id string) bool {
 	delete(c.up, id)
 	c.mu.Unlock()
 
+	decrementVideoTracks(c, conn)
+
+	go func(clients []client) {
+		for _, c := range clients {
+			c.pushConn(conn.id, nil, nil, "")
+		}
+	}(c.Group().getClients(c))
+
+	conn.pc.Close()
+	return true
+}
+
+func decrementVideoTracks(c *webClient, conn *rtpUpConnection) {
 	conn.mu.Lock()
+	defer conn.mu.Unlock()
 	for _, track := range conn.tracks {
 		if track.track.Kind() == webrtc.RTPCodecTypeVideo {
 			count := atomic.AddUint32(&c.group.videoCount,
@@ -259,17 +280,6 @@ func delUpConn(c *webClient, id string) bool {
 			}
 		}
 	}
-	conn.mu.Unlock()
-
-	go func(clients []client) {
-		for _, c := range clients {
-			c.pushConn(conn.id, nil, nil, "")
-		}
-	}(c.Group().getClients(c))
-
-	conn.pc.Close()
-
-	return true
 }
 
 func getDownConn(c *webClient, id string) *rtpDownConnection {
@@ -307,13 +317,18 @@ func addDownConn(c *webClient, id string, remote upConnection) (*rtpDownConnecti
 	c.mu.Lock()
 	defer c.mu.Unlock()
 
+	if c.up != nil && c.up[id] != nil {
+		conn.pc.Close()
+		return nil, errors.New("Adding duplicate connection")
+	}
+
 	if c.down == nil {
 		c.down = make(map[string]*rtpDownConnection)
 	}
 
-	if c.down[id] != nil || (c.up != nil && c.up[id] != nil) {
-		conn.pc.Close()
-		return nil, errors.New("Adding duplicate connection")
+	old := c.down[id]
+	if old != nil {
+		old.pc.Close()
 	}
 
 	conn.pc.OnICECandidate(func(candidate *webrtc.ICECandidate) {
@@ -441,14 +456,10 @@ func sendICE(c *webClient, id string, candidate *webrtc.ICECandidate) error {
 }
 
 func gotOffer(c *webClient, id string, offer webrtc.SessionDescription, labels map[string]string) error {
-	var err error
-	up, ok := c.up[id]
-	if !ok {
-		up, err = addUpConn(c, id)
+	up, err := addUpConn(c, id)
 	if err != nil {
 		return err
 	}
-	}
 	if c.username != "" {
 		up.label = c.username
 	}
@@ -718,13 +729,16 @@ func clientLoop(c *webClient, conn *websocket.Conn) error {
 		case a := <-c.actionCh:
 			switch a := a.(type) {
 			case pushConnAction:
-				found := delDownConn(c, a.id)
 				if a.conn == nil {
+					found := delDownConn(c, a.id)
 					if found {
 						c.write(clientMessage{
 							Type: "close",
 							Id:   a.id,
 						})
+					} else {
+						log.Printf("Deleting unknown " +
+							"down connection")
 					}
 					continue
 				}