res_pjsip: Add disable_tcp_switch option.

When a packet exceeds the MTU, pjproject will switch from UDP to TCP.  In
some circumstances (on some networks), this can cause some issues with
messages not getting sent to the correct destination - and can also cause
connections to get dropped due to quirks in pjproject deciding to
terminate TCP connections with no messages.

While fixing the routing/messaging issues is important, having a
configuration option in Asterisk that tells pjproject to not switch over
to TCP would be useful.  That way, if some glitch is discovered on some
other network/site, we can at least disable the behavior until a fix is
put into place.

AFS-197 #close

Review: https://reviewboard.asterisk.org/r/4137/
........

Merged revisions 427129 from http://svn.asterisk.org/svn/asterisk/branches/12


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/13@427130 65c4cc65-6c06-0410-ace0-fbb531ad65f3

UPGRADE.txt

@@ -21,6 +21,14 @@
 === UPGRADE-12.txt  -- Upgrade info for 11 to 12
 ===========================================================
 
+From 13.0.0 to 13.1.0:
+
+PJSIP:
+ - Added the pjsip.conf system type disable_tcp_switch option.  The option
+   allows the user to disable switching from UDP to TCP transports described
+   by RFC 3261 section 18.1.1.
+
+From 12 to 13:
 General Asterisk Changes:
  - The asterisk command line -I option and the asterisk.conf internal_timing
    option are removed and always enabled if any timing module is loaded.

configs/samples/pjsip.conf.sample

@@ -828,6 +828,10 @@
                                 ; should be disposed of (default: "60")
 ;threadpool_max_size=0  ; Maximum number of threads in the res_pjsip threadpool
                         ; A value of 0 indicates no maximum (default: "0")
+;disable_tcp_switch=no  ; Disable automatic switching from UDP to TCP transports
+                        ; if outgoing request is too large.
+                        ; See RFC 3261 section 18.1.1.
+                        ; (default: "no")
 ;type=  ; Must be of type system (default: "")
 
 ;==========================GLOBAL SECTION OPTIONS=========================

res/res_pjsip.c

@@ -1136,6 +1136,13 @@
 					<synopsis>Maximum number of threads in the res_pjsip threadpool.
 					A value of 0 indicates no maximum.</synopsis>
 				</configOption>
+				<configOption name="disable_tcp_switch" default="no">
+					<synopsis>Disable automatic switching from UDP to TCP transports.</synopsis>
+					<description><para>
+						Disable automatic switching from UDP to TCP transports if outgoing
+						request is too large.  See RFC 3261 section 18.1.1.
+					</para></description>
+				</configOption>
 				<configOption name="type">
 					<synopsis>Must be of type 'system'.</synopsis>
 				</configOption>

res/res_pjsip/config_system.c

@@ -49,6 +49,8 @@ struct system_config {
 		/*! Maxumum number of threads in the threadpool */
 		int max_size;
 	} threadpool;
+	/*! Nonzero to disable switching from UDP to TCP transport */
+	unsigned int disable_tcp_switch;
 };
 
 static struct ast_threadpool_options sip_threadpool_options = {
@@ -95,6 +97,7 @@ static int system_apply(const struct ast_sorcery *system_sorcery, void *obj)
 
 	if (system->compactheaders) {
 		extern pj_bool_t pjsip_use_compact_form;
+
 		pjsip_use_compact_form = PJ_TRUE;
 	}
 
@@ -103,6 +106,9 @@ static int system_apply(const struct ast_sorcery *system_sorcery, void *obj)
 	sip_threadpool_options.idle_timeout = system->threadpool.idle_timeout;
 	sip_threadpool_options.max_size = system->threadpool.max_size;
 
+	pjsip_cfg()->endpt.disable_tcp_switch =
+		system->disable_tcp_switch ? PJ_TRUE : PJ_FALSE;
+
 	return 0;
 }
 
@@ -141,6 +147,8 @@ int ast_sip_initialize_system(void)
 			OPT_UINT_T, 0, FLDSET(struct system_config, threadpool.idle_timeout));
 	ast_sorcery_object_field_register(system_sorcery, "system", "threadpool_max_size", "0",
 			OPT_UINT_T, 0, FLDSET(struct system_config, threadpool.max_size));
+	ast_sorcery_object_field_register(system_sorcery, "system", "disable_tcp_switch", "no",
+			OPT_BOOL_T, 1, FLDSET(struct system_config, disable_tcp_switch));
 
 	ast_sorcery_load(system_sorcery);