Sending offer from the endpoint which needs negotiation.

The offer side and answer side used to be fixed during a session. It's a
problem as we changed to unified plan because there might be more than
one m section in SDP, but the answer side cannot add more m sections
when it is needed.

Author: jianjunz

src/sdk/p2p/peerconnection-channel.js

@@ -48,11 +48,6 @@ const SignalingType = {
   UA: 'chat-ua',
 };
 
-const offerOptions = {
-  'offerToReceiveAudio': true,
-  'offerToReceiveVideo': true,
-};
-
 const sysInfo = Utils.sysInfo();
 
 /**
@@ -83,7 +78,6 @@ class P2PPeerConnectionChannel extends EventDispatcher {
     this._publishingStreamTracks = new Map(); // Key is MediaStream's ID, value is an array of the ID of its MediaStreamTracks that haven't been acked.
     this._publishedStreamTracks = new Map(); // Key is MediaStream's ID, value is an array of the ID of its MediaStreamTracks that haven't been removed.
     this._isNegotiationNeeded = false;
-    this._negotiating = false;
     this._remoteSideSupportsRemoveStream = true;
     this._remoteSideSupportsPlanB = true;
     this._remoteSideSupportsUnifiedPlan = true;
@@ -122,7 +116,10 @@ class P2PPeerConnectionChannel extends EventDispatcher {
       this._sendStreamInfo(stream)]).then(() => {
       return new Promise((resolve, reject) => {
         // Replace |addStream| with PeerConnection.addTrack when all browsers are ready.
-        this._pc.addStream(stream.mediaStream);
+        for (const track of stream.mediaStream.getTracks()) {
+          this._pc.addTrack(track, stream.mediaStream);
+        }
+        this._onNegotiationneeded();
         this._publishingStreams.push(stream);
         const trackIds = Array.from(stream.mediaStream.getTracks(),
             (track) => track.id);
@@ -132,9 +129,6 @@ class P2PPeerConnectionChannel extends EventDispatcher {
           resolve: resolve,
           reject: reject,
         });
-        if (!this._dataChannels.has(DataChannelLabel.MESSAGE)) {
-          this._createDataChannel(DataChannelLabel.MESSAGE);
-        }
       });
     });
   }
@@ -264,9 +258,6 @@ class P2PPeerConnectionChannel extends EventDispatcher {
       case SignalingType.CLOSED:
         this._chatClosedHandler(message.data);
         break;
-      case SignalingType.NEGOTIATION_NEEDED:
-        this._doNegotiate();
-        break;
       default:
         Logger.error('Invalid signaling message received. Type: ' +
             message.type);
@@ -538,12 +529,14 @@ class P2PPeerConnectionChannel extends EventDispatcher {
   }
 
   _onNegotiationneeded() {
+    // This is intented to be executed when onnegotiationneeded event is fired.
+    // However, onnegotiationneeded may fire mutiple times when more than one
+    // track is added/removed. So we manually execute this function after
+    // adding/removing track and creating data channel.
     Logger.debug('On negotiation needed.');
 
-    if (this._pc.signalingState === 'stable' && this._negotiating === false) {
-      this._negotiating = true;
+    if (this._pc.signalingState === 'stable') {
       this._doNegotiate();
-      this._isNegotiationNeeded = false;
     } else {
       this._isNegotiationNeeded = true;
     }
@@ -667,9 +660,6 @@ class P2PPeerConnectionChannel extends EventDispatcher {
         this._onRemoteTrackAdded.apply(this, [event]);
       };
     }
-    this._pc.onnegotiationneeded = (event)=>{
-      this._onNegotiationneeded.apply(this, [event]);
-    };
     this._pc.onicecandidate = (event) => {
       this._onLocalIceCandidate.apply(this, [event]);
     };
@@ -709,6 +699,7 @@ class P2PPeerConnectionChannel extends EventDispatcher {
   }
 
   _drainPendingStreams() {
+    let negotiationNeeded = false;
     Logger.debug('Draining pending streams.');
     if (this._pc && this._pc.signalingState === 'stable') {
       Logger.debug('Peer connection is ready for draining pending streams.');
@@ -721,7 +712,10 @@ class P2PPeerConnectionChannel extends EventDispatcher {
         if (!stream.mediaStream) {
           continue;
         }
-        this._pc.addStream(stream.mediaStream);
+        for (const track of stream.mediaStream.getTracks()) {
+          this._pc.addTrack(track, stream.mediaStream);
+          negotiationNeeded = true;
+        }
         Logger.debug('Added stream to peer connection.');
         this._publishingStreams.push(stream);
       }
@@ -731,13 +725,17 @@ class P2PPeerConnectionChannel extends EventDispatcher {
           continue;
         }
         this._pc.removeStream(this._pendingUnpublishStreams[j].mediaStream);
+        negotiationNeeded = true;
         this._unpublishPromises.get(
             this._pendingUnpublishStreams[j].mediaStream.id).resolve();
         this._publishedStreams.delete(this._pendingUnpublishStreams[j]);
         Logger.debug('Remove stream.');
       }
       this._pendingUnpublishStreams.length = 0;
     }
+    if (negotiationNeeded) {
+      this._onNegotiationneeded();
+    }
   }
 
   _drainPendingRemoteIceCandidates() {
@@ -762,7 +760,7 @@ class P2PPeerConnectionChannel extends EventDispatcher {
         dc.send(JSON.stringify(this._pendingMessages[i]));
       }
       this._pendingMessages.length = 0;
-    } else if (this._pc&&!dc) {
+    } else if (this._pc && !dc) {
       this._createDataChannel(DataChannelLabel.MESSAGE);
     }
   }
@@ -822,11 +820,7 @@ class P2PPeerConnectionChannel extends EventDispatcher {
   }
 
   _doNegotiate() {
-    if (this._isCaller) {
-      this._createAndSendOffer();
-    } else {
-      this._sendSignalingMessage(SignalingType.NEGOTIATION_NEEDED);
-    }
+    this._createAndSendOffer();
   }
 
   _setCodecOrder(sdp) {
@@ -871,12 +865,14 @@ class P2PPeerConnectionChannel extends EventDispatcher {
     this._isNegotiationNeeded = false;
     this._isCaller = true;
     let localDesc;
-    this._pc.createOffer(offerOptions).then((desc) => {
+    this._pc.createOffer().then((desc) => {
       desc.sdp = this._setRtpReceiverOptions(desc.sdp);
       localDesc = desc;
-      return this._pc.setLocalDescription(desc);
-    }).then(() => {
-      return this._sendSdp(localDesc);
+      if(this._pc.signalingState==='stable'){
+        return this._pc.setLocalDescription(desc).then(()=>{
+          return this._sendSdp(localDesc);
+        });
+      }
     }).catch((e) => {
       Logger.error(e.message + ' Please check your codec settings.');
       const error = new ErrorModule.P2PError(ErrorModule.errors.P2P_WEBRTC_SDP,
@@ -893,6 +889,7 @@ class P2PPeerConnectionChannel extends EventDispatcher {
     this._pc.createAnswer().then((desc) => {
       desc.sdp = this._setRtpReceiverOptions(desc.sdp);
       localDesc=desc;
+      this._logCurrentAndPendingLocalDescription();
       return this._pc.setLocalDescription(desc);
     }).then(()=>{
       return this._sendSdp(localDesc);
@@ -904,6 +901,10 @@ class P2PPeerConnectionChannel extends EventDispatcher {
     });
   }
 
+  _logCurrentAndPendingLocalDescription(){
+    Logger.info('Current description: '+this._pc.currentLocalDescription);
+    Logger.info('Pending description: '+this._pc.pendingLocalDescription);
+  }
 
   _getAndDeleteTrackSourceInfo(tracks) {
     if (tracks.length > 0) {
@@ -955,6 +956,7 @@ class P2PPeerConnectionChannel extends EventDispatcher {
     const dc = this._pc.createDataChannel(label);
     this._bindEventsToDataChannel(dc);
     this._dataChannels.set(DataChannelLabel.MESSAGE, dc);
+    this._onNegotiationneeded();
   }
 
   _bindEventsToDataChannel(dc) {