Merge pull request #39 from dextertanyj/fix/webrtc-glare

Fix webrtc glare
yjs · Jun 16, 2023 · 0cb5412 · 0cb5412
2 parents 240e793 + 45bf721
commit 0cb5412
Showing 1 changed file with 24 additions and 1 deletion.
diff --git a/src/y-webrtc.js b/src/y-webrtc.js
@@ -174,6 +174,7 @@ export class WebrtcConn {
     log('establishing connection to ', logging.BOLD, remotePeerId)
     this.room = room
     this.remotePeerId = remotePeerId
+    this.glareToken = undefined
     this.closed = false
     this.connected = false
     this.synced = false
@@ -182,7 +183,11 @@ export class WebrtcConn {
      */
     this.peer = new Peer({ initiator, ...room.provider.peerOpts })
     this.peer.on('signal', signal => {
-      publishSignalingMessage(signalingConn, room, { to: remotePeerId, from: room.peerId, type: 'signal', signal })
+      if (this.glareToken === undefined) {
+        // add some randomness to the timestamp of the offer
+        this.glareToken = Date.now() + Math.random()
+      }
+      publishSignalingMessage(signalingConn, room, { to: remotePeerId, from: room.peerId, type: 'signal', token: this.glareToken, signal })
     })
     this.peer.on('connect', () => {
       log('connected to ', logging.BOLD, remotePeerId)
@@ -515,6 +520,24 @@ export class SignalingConn extends ws.WebsocketClient {
                 }
                 break
               case 'signal':
+                if (data.signal.type === 'offer') {
+                  const existingConn = webrtcConns.get(data.from)
+                  if (existingConn) {
+                    const remoteToken = data.token
+                    const localToken = existingConn.glareToken
+                    if (localToken && localToken > remoteToken) {
+                      log('offer rejected: ', data.from)
+                      return
+                    }
+                    // if we don't reject the offer, we will be accepting it and answering it
+                    existingConn.glareToken = undefined
+                  }
+                }
+                if (data.signal.type === 'answer') {
+                  log('offer answered by: ', data.from)
+                  const existingConn = webrtcConns.get(data.from)
+                  existingConn.glareToken = undefined
+                }
                 if (data.to === peerId) {
                   map.setIfUndefined(webrtcConns, data.from, () => new WebrtcConn(this, false, data.from, room)).peer.signal(data.signal)
                   emitPeerChange()