MT#62266 SessionTimer: introduce `sst_strict_mode`

Introduce explicit policy for within-dialog SST support:
- whenever remote side (call leg) doesn't explicitly declare
  it supports timers (with `Supported: timer`), disable all
  previously set timers for this particular leg
- this touches request originator, as well as answerer
- requests: only UPDATE and INVITE methods are affected
- answers: only positive answers are affected
- by default this behavior is always disabled if not enabled
  explicitly in the profile's config with `sst_strict_mode`
- sst_strict_mode takes either `yes` or `no`

P.S.: the `sst_strict_mode` must not be initialized to true
by default, because RFC 4028 explicitly tells to support
the operation even when only one UA understands session timers.
So we have to be quite accurate and not enforce the strict mode.

Change-Id: Ie6647eb061a73dc052367dbd291589198487093c

apps/sbc/SBCCallProfile.cpp

@@ -234,6 +234,7 @@ bool SBCCallProfile::readFromConfiguration(const string& name,
     CP_SST_CFGVAR("", "maximum_timer", sst_b_cfg);
     CP_SST_CFGVAR("", "session_refresh_method", sst_b_cfg);
     CP_SST_CFGVAR("", "accept_501_reply", sst_b_cfg);
+    CP_SST_CFGVAR("", "sst_strict_mode", sst_b_cfg);
   }
 
   if (sst_aleg_enabled.size() && sst_aleg_enabled != "no") {
@@ -244,6 +245,7 @@ bool SBCCallProfile::readFromConfiguration(const string& name,
     CP_SST_CFGVAR("aleg_", "maximum_timer", sst_a_cfg);
     CP_SST_CFGVAR("aleg_", "session_refresh_method", sst_a_cfg);
     CP_SST_CFGVAR("aleg_", "accept_501_reply", sst_a_cfg);
+    CP_SST_CFGVAR("aleg_", "sst_strict_mode", sst_a_cfg);
   }
 #undef CP_SST_CFGVAR
 
@@ -553,6 +555,8 @@ bool SBCCallProfile::readFromConfiguration(const string& name,
 	   sst_a_cfg.getParameter("session_refresh_method").c_str());
       INFO("SBC:              accept_501_reply=%s\n",
 	   sst_a_cfg.getParameter("accept_501_reply").c_str());
+      INFO("SBC:              sst_strict_mode=%s\n",
+	   sst_a_cfg.getParameter("sst_strict_mode").c_str());
     }
     INFO("SBC:      SST on B leg enabled: '%s'\n", sst_enabled.empty() ?
 	 "no" : sst_enabled.c_str());
@@ -567,6 +571,8 @@ bool SBCCallProfile::readFromConfiguration(const string& name,
 	   sst_b_cfg.getParameter("session_refresh_method").c_str());
       INFO("SBC:              accept_501_reply=%s\n",
 	   sst_b_cfg.getParameter("accept_501_reply").c_str());
+      INFO("SBC:              sst_strict_mode=%s\n",
+	   sst_b_cfg.getParameter("sst_strict_mode").c_str());
     }
 
     INFO("SBC:      SIP auth %sabled\n", auth_enabled?"en":"dis");
@@ -776,6 +782,7 @@ void SBCCallProfile::eval_sst_config(ParamReplacerCtx& ctx,
     "maximum_timer",
     "session_refresh_method",
     "accept_501_reply",
+    "sst_strict_mode",
   };
 
   for(unsigned int i=0; i<SST_CFG_PARAM_COUNT; i++) {

apps/sbc/etc/auth_b2b.sbcprofile.conf

@@ -57,6 +57,7 @@ message_filter=transparent
 #minimum_timer=90
 #session_refresh_method=UPDATE_FALLBACK_INVITE
 #accept_501_reply=yes
+#sst_strict_mode=yes
 
 #################################################################
 #This profile implements a pure B2BUA application that does an

apps/sbc/etc/sbc.conf

@@ -69,3 +69,9 @@ active_profile=transparent
 #
 #accept_501_reply=no
 
+# sst_strict_mode - disable session timers for a leg if an INVITE/UPDATE
+# request or a positive response does not declare "Supported: timer".
+#
+# Default: yes
+#
+#sst_strict_mode=no

apps/sbc/etc/sst_b2b.sbcprofile.conf

@@ -49,6 +49,7 @@ enable_session_timer=yes
 #maximum_timer=900
 #session_refresh_method=UPDATE_FALLBACK_INVITE
 #accept_501_reply=yes
+#sst_strict_mode=yes
 
 #separate SST configuration for A (caller) leg:
 #enable_aleg_session_timer=$H(P-Enable-A-SST)
@@ -57,6 +58,7 @@ enable_session_timer=yes
 #aleg_maximum_timer=900
 #aleg_session_refresh_method=UPDATE_FALLBACK_INVITE
 #aleg_accept_501_reply=yes
+#aleg_sst_strict_mode=yes
 
 #
 #This application can be routed through for achieving 

apps/sbc/etc/transparent.sbcprofile.conf

@@ -114,6 +114,7 @@
 #minimum_timer=90
 #session_refresh_method=UPDATE_FALLBACK_INVITE
 #accept_501_reply=yes
+#sst_strict_mode=yes
 
 ##separate SST configuration for A (caller) leg, optional:
 #enable_aleg_session_timer=yes
@@ -122,6 +123,7 @@
 #aleg_maximum_timer=900
 #aleg_session_refresh_method=UPDATE_FALLBACK_INVITE
 #aleg_accept_501_reply=yes
+#aleg_sst_strict_mode=yes
 
 ## refuse call
 # refuse all calls with <code> <reason>

core/plug-in/session_timer/SessionTimer.cpp

@@ -269,8 +269,8 @@ 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) {
+    /* disable timers for this leg if not declare explicitly */
+    if (session_timer_conf.StrictMode && !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);
@@ -369,7 +369,7 @@ void SessionTimer::updateTimer(AmSession* s, const AmSipReply& reply)
   remote_timer_aware = key_in_list(getHeader(reply.hdrs, SIP_HDR_SUPPORTED, SIP_HDR_SUPPORTED_COMPACT),
                                     TIMER_OPTION_TAG);
 
-  if (!remote_timer_aware) {
+  if (session_timer_conf.StrictMode && !remote_timer_aware) {
     /* 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);
@@ -483,7 +483,8 @@ AmSessionTimerConfig::AmSessionTimerConfig()
   : EnableSessionTimer(DEFAULT_ENABLE_SESSION_TIMER), 
     SessionExpires(SESSION_EXPIRES), 
     MinimumTimer(MINIMUM_TIMER),
-    MaximumTimer(MAXIMUM_TIMER)
+    MaximumTimer(MAXIMUM_TIMER),
+    StrictMode(false)
 {
 }
 
@@ -528,6 +529,21 @@ int AmSessionTimerConfig::readFromConfig(AmConfigReader& cfg)
     MaximumTimer = (unsigned int) maximum_timer;
   }
 
+  /* SST strict mode allows to re-init timers during the session,
+   * whenever remote side with INVITE/UPDATE method doesn't
+   * declare `Supported: timer` explicitly. By default always: no.
+   */
+  if(cfg.hasParameter("sst_strict_mode")){
+    if (cfg.getParameter("sst_strict_mode", "no") == "yes") {
+      DBG("SST strict mode is enabled by profile settings (default: no).\n");
+      StrictMode = true;
+    }
+    else {
+      DBG("SST strict mode is disabled by profile settings (default: no).\n");
+      StrictMode = false;
+    }
+  }
+
   return 0;
 }
 

core/plug-in/session_timer/SessionTimer.h

@@ -85,7 +85,8 @@ class AmSessionTimerConfig
 public:
   AmSessionTimerConfig();
   ~AmSessionTimerConfig();
-  
+
+  bool StrictMode;
 
   /** Session Timer: Enable Session Timer?
       returns 0 on invalid value */