pjsip: Ignore state changes from old transactions.

When we fail over to a new target we create a new transaction
and it becomes the current INVITE transaction. This does not
prevent the previous transaction from raising state changes
and causing the session to be prematurely disconnected if a
transport error occurs immediately.

This change backports a fix from PJSIP that eliminates the
incorrect state change and reduces when they would be raised
in the first place.

ASTERISK-27408

Change-Id: Id22d087591782eee31311753d11e7eca4b95ef34

third-party/pjproject/patches/0050-dont_terminate_session_early.patch

@@ -0,0 +1,71 @@
+commit ca0b723e92bd76bbda1bbd14477a829eaeeb675e
+Author: Joshua Colp <jcolp@digium.com>
+Date:   Wed Dec 13 10:58:57 2017 +0000
+
+    Ignore transport error on completed transaction.
+    Don't disconnect call if transport error happens on transaction that is not initial INVITE transaction.
+    
+    Scenario:
+    
+    DNS lookup returning two servers.
+    Sending INVITE to first server over TCP.
+    Response received with code 503 (Service Unavailable).
+    Failover to second server, sending second INVITE after restarting the session.
+    TCP connection for the first INVITE getting disconnected and causing call disconnection (while second INVITE is still outstanding).
+    
+    This is a backport of 5714 from upstream PJSIP.
+
+diff --git a/pjsip/src/pjsip-ua/sip_inv.c b/pjsip/src/pjsip-ua/sip_inv.c
+index ac4d1949..0173cb4c 100644
+--- a/pjsip/src/pjsip-ua/sip_inv.c
++++ b/pjsip/src/pjsip-ua/sip_inv.c
+@@ -4254,8 +4254,7 @@ static void inv_on_state_calling( pjsip_inv_session *inv, pjsip_event *e)
+ 	if ((tsx->status_code == PJSIP_SC_CALL_TSX_DOES_NOT_EXIST &&
+ 		tsx->method.id != PJSIP_CANCEL_METHOD) ||
+ 	    tsx->status_code == PJSIP_SC_REQUEST_TIMEOUT ||
+-	    tsx->status_code == PJSIP_SC_TSX_TIMEOUT ||
+-	    tsx->status_code == PJSIP_SC_TSX_TRANSPORT_ERROR)
++	    tsx->status_code == PJSIP_SC_TSX_TIMEOUT)
+ 	{
+ 	    inv_set_cause(inv, tsx->status_code, &tsx->status_text);
+ 	    inv_set_state(inv, PJSIP_INV_STATE_DISCONNECTED, e);
+diff --git a/pjsip/src/pjsip/sip_transaction.c b/pjsip/src/pjsip/sip_transaction.c
+index 7ac3d1b7..d52b12a7 100644
+--- a/pjsip/src/pjsip/sip_transaction.c
++++ b/pjsip/src/pjsip/sip_transaction.c
+@@ -2044,9 +2044,14 @@ static void transport_callback(void *token, pjsip_tx_data *tdata,
+ 	 */
+ 	lock_timer(tsx);
+ 	tsx->transport_err = (pj_status_t)-sent;
+-	tsx_cancel_timer(tsx, &tsx->timeout_timer);
+-	tsx_schedule_timer(tsx, &tsx->timeout_timer, &delay,
+-	                   TRANSPORT_ERR_TIMER);
++	/* Don't cancel timeout timer if tsx state is already
++	 * PJSIP_TSX_STATE_COMPLETED (see #2076).
++	 */
++	if (tsx->state < PJSIP_TSX_STATE_COMPLETED) {
++	    tsx_cancel_timer(tsx, &tsx->timeout_timer);
++	    tsx_schedule_timer(tsx, &tsx->timeout_timer, &delay,
++			       TRANSPORT_ERR_TIMER);
++	}
+ 	unlock_timer(tsx);
+    }
+ 
+@@ -2077,9 +2082,14 @@ static void tsx_tp_state_callback( pjsip_transport *tp,
+ 	 */
+ 	lock_timer(tsx);
+ 	tsx->transport_err = info->status;
+-	tsx_cancel_timer(tsx, &tsx->timeout_timer);
+-	tsx_schedule_timer(tsx, &tsx->timeout_timer, &delay,
+-	                   TRANSPORT_ERR_TIMER);
++	/* Don't cancel timeout timer if tsx state is already
++	 * PJSIP_TSX_STATE_COMPLETED (see #2076).
++	 */
++	if (tsx->state < PJSIP_TSX_STATE_COMPLETED) {
++	    tsx_cancel_timer(tsx, &tsx->timeout_timer);
++	    tsx_schedule_timer(tsx, &tsx->timeout_timer, &delay,
++			       TRANSPORT_ERR_TIMER);
++	}
+ 	unlock_timer(tsx);
+     }
+ }