Change ICE server fallback to opt-in

This changes the ICE server fallback to be disabled by default. The SDK consumer
will receive a new event in case the homeserver has no ICE servers of its own,
and can prompt the user to agree to the fallback if desired.

Part of https://github.com/vector-im/riot-web/issues/10173

src/client.js

@@ -221,6 +221,7 @@ function MatrixClient(opts) {
     this._verificationMethods = opts.verificationMethods;
 
     this._forceTURN = opts.forceTURN || false;
+    this._fallbackICEServerAllowed = false;
 
     // List of which rooms have encryption enabled: separate from crypto because
     // we still want to know which rooms are encrypted even if crypto is disabled:
@@ -3883,6 +3884,28 @@ MatrixClient.prototype.getTurnServers = function() {
     return this._turnServers || [];
 };
 
+/**
+ * Set whether to allow a fallback ICE server should be used for negotiating a
+ * WebRTC connection if the homeserver doesn't provide any servers. Defaults to
+ * false.
+ *
+ * @param {boolean} allow
+ */
+MatrixClient.prototype.setFallbackICEServerAllowed = function(allow) {
+    this._fallbackICEServerAllowed = allow;
+};
+
+/**
+ * Get whether to allow a fallback ICE server should be used for negotiating a
+ * WebRTC connection if the homeserver doesn't provide any servers. Defaults to
+ * false.
+ *
+ * @returns {boolean}
+ */
+MatrixClient.prototype.isFallbackICEServerAllowed = function() {
+    return this._fallbackICEServerAllowed;
+};
+
 // Higher level APIs
 // =================
 
@@ -4330,13 +4353,15 @@ function checkTurnServers(client) {
             client._checkTurnServersTimeoutID = setTimeout(() => {
                 checkTurnServers(client);
             }, (res.ttl || (60 * 60)) * 1000 * 0.9);
+        } else {
+            logger.warn("No TURN URIs from homeserver");
+            client.emit("Call.noTURNServers");
         }
     }, function(err) {
         logger.error("Failed to get TURN URIs");
-        client._checkTurnServersTimeoutID =
+        client._checkTurnServersTimeoutID = setTimeout(function() {
-            setTimeout(function() {
+            checkTurnServers(client);
- checkTurnServers(client);
+        }, 60000);
-}, 60000);
     });
 }
 

src/webrtc/call.js

@@ -61,9 +61,9 @@ function MatrixCall(opts) {
     this.URL = opts.URL;
     // Array of Objects with urls, username, credential keys
     this.turnServers = opts.turnServers || [];
-    if (this.turnServers.length === 0) {
+    if (this.turnServers.length === 0 && this.client.isFallbackICEServerAllowed()) {
         this.turnServers.push({
-            urls: [MatrixCall.FALLBACK_STUN_SERVER],
+            urls: [MatrixCall.FALLBACK_ICE_SERVER],
         });
     }
     utils.forEach(this.turnServers, function(server) {
@@ -92,8 +92,8 @@ function MatrixCall(opts) {
 }
 /** The length of time a call can be ringing for. */
 MatrixCall.CALL_TIMEOUT_MS = 60000;
-/** The fallback server to use for STUN. */
+/** The fallback ICE server to use for STUN or TURN protocols. */
-MatrixCall.FALLBACK_STUN_SERVER = 'stun:turn.matrix.org';
+MatrixCall.FALLBACK_ICE_SERVER = 'stun:turn.matrix.org';
 /** An error code when the local client failed to create an offer. */
 MatrixCall.ERR_LOCAL_OFFER_FAILED = "local_offer_failed";
 /**
@@ -1337,7 +1337,9 @@ module.exports.setVideoInput = function(deviceId) { videoInput = deviceId; };
  * @param {MatrixClient} client The client instance to use.
  * @param {string} roomId The room the call is in.
  * @param {Object?} options DEPRECATED optional options map.
- * @param {boolean} options.forceTURN DEPRECATED whether relay through TURN should be forced. This option is deprecated - use opts.forceTURN when creating the matrix client since it's only possible to set this option on outbound calls.
+ * @param {boolean} options.forceTURN DEPRECATED whether relay through TURN should be
+ * forced. This option is deprecated - use opts.forceTURN when creating the matrix client
+ * since it's only possible to set this option on outbound calls.
  * @return {MatrixCall} the call or null if the browser doesn't support calling.
  */
 module.exports.createNewMatrixCall = function(client, roomId, options) {