MT#62266 SessionTimer: track timers support (UPDATE method)

Only for UPDATE method for now, track whether remote side
actually declares it supports timers, if not remove.

This may affect things, in case remote side expects timers
should have been declared only once during the session
origination, but all in all remote side must always add
the `Supported: timer` header to keep us explicitly aware.

Additionally: improve logs.
Change-Id: I80d4efbe38701b95549d02830392b93019cc2b85

core/plug-in/session_timer/SessionTimer.cpp

@@ -269,6 +269,15 @@ void SessionTimer::updateTimer(AmSession* s, const AmSipRequest& req) {
     remote_timer_aware = key_in_list(getHeader(req.hdrs, SIP_HDR_SUPPORTED, SIP_HDR_SUPPORTED_COMPACT),
                                       TIMER_OPTION_TAG);
 
+    /* disable timers for this leg if not declare explicitly (UPDATE only) */
+    if (req.method == SIP_METH_UPDATE && !remote_timer_aware) {
+      /* timer is not supported by originator's leg */
+      DBG("Session timer not supported by request originator's leg, remove session timer intervals");
+      session_timer_conf.setEnableSessionTimer(false);
+      removeTimers(s);
+      return;
+    }
+
     // determine session interval
     string sess_expires_hdr = getHeader(req.hdrs,
                                         SIP_HDR_SESSION_EXPIRES,
@@ -361,8 +370,8 @@ void SessionTimer::updateTimer(AmSession* s, const AmSipReply& reply)
                                     TIMER_OPTION_TAG);
 
   if (!remote_timer_aware) {
-    /* timer NOT supported by B leg */
-    DBG("Session Timer NOT supported by leg B, removing internal session timer intervals");
+    /* timer is not supported by responder's leg */
+    DBG("Session timer not supported by responder's leg, remove session timer intervals");
     session_timer_conf.setEnableSessionTimer(false);
     removeTimers(s);
     return;