MT#62266 SST: introduce `session_timer_transparent`

Gets serialized into the bool on the profile's global level.
Isn't leg specific, but global for the whole session.

Only used to remove SST related headers and option tags
from requests and replies being sent through either
`SBCCallLeg::onSendRequest()` or `SBCCallLeg::onSendReply()`.

Transparent means - do not touch existing SST headers.
SessionTimer implementation factory isn't triggered in this case.

Change-Id: Id98a8abc957be11d140eba2394fed7ebe1302ca7

apps/sbc/SBCCallLeg.cpp

@@ -804,11 +804,19 @@ void SBCCallLeg::onSendRequest(AmSipRequest& req, int &flags) {
 
   CallLeg::onSendRequest(req, flags);
 
-  /* check whether SST related headers must be removed before sending out */
-  if (!sessionTimerSupportedByLeg(call_profile, a_leg)) {
-    ILOG_DLG(L_DBG, "SST isn't supported by '%c' leg, remove according headers and option tags.\n",
-             a_leg ? 'A' : 'B');
-    removeSessionTimerHeaders(req.hdrs);
+  /* clean SST related headers if not supported by the receiving leg
+   * but only if the mode isn't transparent */
+  if (!call_profile.sst_transparent) {
+    /* check whether SST related headers must be removed before sending out */
+    if (!sessionTimerSupportedByLeg(call_profile, a_leg)) {
+      ILOG_DLG(L_DBG, "SST isn't supported by '%c' leg, remove according headers and option tags.\n",
+              a_leg ? 'A' : 'B');
+      removeSessionTimerHeaders(req.hdrs);
+    }
+  }
+  else {
+    ILOG_DLG(L_DBG, "Transparent SST mode enabled globally, ignore SST headers for '%c' leg.\n",
+              a_leg ? 'A' : 'B');
   }
 }
 
@@ -816,11 +824,19 @@ void SBCCallLeg::onSendReply(const AmSipRequest& req, AmSipReply& reply, int &fl
 {
   CallLeg::onSendReply(req, reply, flags);
 
-  /* check whether SST related headers must be removed before sending out */
-  if (!sessionTimerSupportedByLeg(call_profile, a_leg)) {
-    ILOG_DLG(L_DBG, "SST isn't supported by '%c' leg, remove according headers and option tags.\n",
-             a_leg ? 'A' : 'B');
-    removeSessionTimerHeaders(reply.hdrs);
+  /* clean SST related headers if not supported by the receiving leg
+   * but only if the mode isn't transparent */
+  if (!call_profile.sst_transparent) {
+    /* check whether SST related headers must be removed before sending out */
+    if (!sessionTimerSupportedByLeg(call_profile, a_leg)) {
+      ILOG_DLG(L_DBG, "SST isn't supported by '%c' leg, remove according headers and option tags.\n",
+              a_leg ? 'A' : 'B');
+      removeSessionTimerHeaders(reply.hdrs);
+    }
+  }
+  else {
+    ILOG_DLG(L_DBG, "Transparent SST mode enabled globally, ignore SST headers for '%c' leg.\n",
+              a_leg ? 'A' : 'B');
   }
 }
 

apps/sbc/SBCCallProfile.cpp

@@ -204,6 +204,9 @@ bool SBCCallProfile::readFromConfiguration(const string& name,
     return false;
 
   sst_enabled = cfg.getParameter("enable_session_timer");
+
+  sst_transparent = cfg.getParameter("session_timer_transparent", "no") == "yes";
+
   if (cfg.hasParameter("enable_aleg_session_timer")) {
     sst_aleg_enabled = cfg.getParameter("enable_aleg_session_timer");
   } else {
@@ -544,6 +547,7 @@ bool SBCCallProfile::readFromConfiguration(const string& name,
 
     INFO("SBC:      SST on A leg enabled: '%s'\n", sst_aleg_enabled.empty() ?
 	 "no" : sst_aleg_enabled.c_str());
+    INFO("SBC:      SST transparent mode: %s\n", sst_transparent ? "yes" : "no");
     if (sst_aleg_enabled.size() && sst_aleg_enabled != "no") {
       INFO("SBC:              session_expires=%s\n",
 	   sst_a_cfg.getParameter("session_expires").c_str());
@@ -652,6 +656,7 @@ bool SBCCallProfile::operator==(const SBCCallProfile& rhs) const {
     sdpfilter == rhs.sdpfilter &&
     aleg_sdpfilter == rhs.aleg_sdpfilter &&
     mediafilter == rhs.mediafilter &&
+    sst_transparent == rhs.sst_transparent &&
     sst_enabled == rhs.sst_enabled &&
     sst_aleg_enabled == rhs.sst_aleg_enabled &&
     auth_enabled == rhs.auth_enabled &&

apps/sbc/SBCCallProfile.h

@@ -142,6 +142,7 @@ struct SBCCallProfile
   vector<FilterEntry> sdpalinesfilter;
   vector<FilterEntry> mediafilter;
 
+  bool sst_transparent;
   string sst_enabled;
   bool sst_enabled_value;
   string sst_aleg_enabled;
@@ -353,6 +354,7 @@ struct SBCCallProfile
     allow_subless_notify(false),
     anonymize_sdp(false),
     have_aleg_sdpfilter(false),
+    sst_transparent(false),
     sst_enabled_value(false),
     auth_aleg_enabled(false),
     uas_auth_bleg_enabled(false),

apps/sbc/etc/sbc.conf

@@ -69,6 +69,13 @@ active_profile=transparent
 #
 #accept_501_reply=no
 
+# session_timer_transparent - do not strip SST headers or timer option
+# tags while relaying SIP messages to legs without SST support.
+#
+# Default: no
+#
+#session_timer_transparent=no
+
 # sst_strict_mode - disable session timers for a leg if an INVITE/UPDATE
 # request or a positive response does not declare "Supported: timer".
 #