Improvements to 2xx retransmission behaviour

Fixes #131

Author: Gavin Llewellyn

src/RTCSession.js

@@ -197,34 +197,33 @@ RTCSession.prototype.answer = function(options) {
       var
         // run for reply success callback
         replySucceeded = function() {
+          var timeout = JsSIP.Timers.T1;
+
           self.status = C.STATUS_WAITING_FOR_ACK;
 
           /**
            * RFC3261 13.3.1.4
            * Response retransmissions cannot be accomplished by transaction layer
            *  since it is destroyed when receiving the first 2xx answer
            */
-          self.timers.invite2xxTimer = window.setTimeout(function invite2xxRetransmission(retransmissions) {
-              retransmissions = retransmissions || 1;
-
-              var timeout = JsSIP.Timers.T1 * (Math.pow(2, retransmissions));
-
-              if((retransmissions * JsSIP.Timers.T1) <= JsSIP.Timers.T2) {
-                retransmissions += 1;
+          self.timers.invite2xxTimer = window.setTimeout(function invite2xxRetransmission() {
+              if (self.status !== C.STATUS_WAITING_FOR_ACK) {
+                return;
+              }
 
-                request.reply(200, null, ['Contact: '+ self.contact], body);
+              request.reply(200, null, ['Contact: '+ self.contact], body);
 
-                self.timers.invite2xxTimer = window.setTimeout(
-                  function() {
-                    invite2xxRetransmission(retransmissions);
-                  },
-                  timeout
-                );
-              } else {
-                window.clearTimeout(self.timers.invite2xxTimer);
+              if (timeout < JsSIP.Timers.T2) {
+                timeout = timeout * 2;
+                if (timeout > JsSIP.Timers.T2) {
+                  timeout = JsSIP.Timers.T2;
+                }
               }
+              self.timers.invite2xxTimer = window.setTimeout(
+                invite2xxRetransmission, timeout
+              );
             },
-            JsSIP.Timers.T1
+            timeout
           );
 
           /**