Avoid reinvite race situations with two Asterisks trying

to reinvite each other in 1.4 and trunk. 

This patch implements support for the 491 error code that
Asterisk 1.4 generates on situations where we get an 
incoming INVITE and already has one in progress.

Thanks to mavetju for reporting and to Raj Jain for an
excellent explanation of the problem.

Patch by myself. Tested with 8 Asterisk servers connected
to each other in a training network.

Closes issue #10481



git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.4@92158 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channels/chan_sip.c

@@ -986,6 +986,7 @@ static struct sip_pvt {
 	
 	int maxtime;				/*!< Max time for first response */
 	int initid;				/*!< Auto-congest ID if appropriate (scheduler) */
+	int waitid;				/*!< Wait ID for scheduler after 491 or other delays */
 	int autokillid;				/*!< Auto-kill ID (scheduler) */
 	enum transfermodes allowtransfer;	/*!< REFER: restriction scheme */
 	struct sip_refer *refer;		/*!< REFER: SIP transfer data structure */
@@ -1326,7 +1327,6 @@ static int expire_register(const void *data);
 static void *do_monitor(void *data);
 static int restart_monitor(void);
 static int sip_send_mwi_to_peer(struct sip_peer *peer);
-static void sip_destroy(struct sip_pvt *p);
 static int sip_addrcmp(char *name, struct sockaddr_in *sin);	/* Support for peer matching */
 static int sip_refer_allocate(struct sip_pvt *p);
 static void ast_quiet_chan(struct ast_channel *chan);
@@ -3043,6 +3043,8 @@ static void __sip_destroy(struct sip_pvt *p, int lockowner)
 		ast_extension_state_del(p->stateid, NULL);
 	if (p->initid > -1)
 		ast_sched_del(sched, p->initid);
+	if (p->waitid > -1)
+		ast_sched_del(sched, p->waitid);
 	if (p->autokillid > -1)
 		ast_sched_del(sched, p->autokillid);
 
@@ -3562,6 +3564,9 @@ static int sip_hangup(struct ast_channel *ast)
 				   but we can't send one while we have "INVITE" outstanding. */
 				ast_set_flag(&p->flags[0], SIP_PENDINGBYE);	
 				ast_clear_flag(&p->flags[0], SIP_NEEDREINVITE);	
+				if (p->waitid)
+					ast_sched_del(sched, p->waitid);
+				p->waitid = -1;
 				sip_cancel_destroy(p);
 			}
 		}
@@ -4366,6 +4371,7 @@ static struct sip_pvt *sip_alloc(ast_string_field callid, struct sockaddr_in *si
 
 	p->method = intended_method;
 	p->initid = -1;
+	p->waitid = -1;
 	p->autokillid = -1;
 	p->subscribed = NONE;
 	p->stateid = -1;
@@ -11892,7 +11898,7 @@ static void check_pendings(struct sip_pvt *p)
 		sip_scheddestroy(p, DEFAULT_TRANS_TIMEOUT);
 	} else if (ast_test_flag(&p->flags[0], SIP_NEEDREINVITE)) {
 		/* if we can't REINVITE, hold it for later */
-		if (p->pendinginvite || p->invitestate == INV_CALLING || p->invitestate == INV_PROCEEDING || p->invitestate == INV_EARLY_MEDIA) {
+		if (p->pendinginvite || p->invitestate == INV_CALLING || p->invitestate == INV_PROCEEDING || p->invitestate == INV_EARLY_MEDIA || p->waitid > 0) {
 			if (option_debug)
 				ast_log(LOG_DEBUG, "NOT Sending pending reinvite (yet) on '%s'\n", p->callid);
 		} else {
@@ -11905,6 +11911,20 @@ static void check_pendings(struct sip_pvt *p)
 	}
 }
 
+/*! \brief Reset the NEEDREINVITE flag after waiting when we get 491 on a Re-invite
+	to avoid race conditions between asterisk servers.
+	Called from the scheduler.
+*/
+static int sip_reinvite_retry(const void *data) 
+{
+	struct sip_pvt *p = (struct sip_pvt *) data;
+
+	ast_set_flag(&p->flags[0], SIP_NEEDREINVITE);	
+	p->waitid = -1;
+	return 0;
+}
+
+
 /*! \brief Handle SIP response to INVITE dialogue */
 static void handle_response_invite(struct sip_pvt *p, int resp, char *rest, struct sip_request *req, int seqno)
 {
@@ -12205,9 +12225,20 @@ static void handle_response_invite(struct sip_pvt *p, int resp, char *rest, stru
 			/* We should support the retry-after at some point */
 		/* At this point, we treat this as a congestion */
 		xmitres = transmit_request(p, SIP_ACK, seqno, XMIT_UNRELIABLE, FALSE);
-		if (p->owner && !ast_test_flag(req, SIP_PKT_IGNORE))
-			ast_queue_control(p->owner, AST_CONTROL_CONGESTION);
-		ast_set_flag(&p->flags[0], SIP_NEEDDESTROY);	
+		if (p->owner && !ast_test_flag(req, SIP_PKT_IGNORE)) {
+			if (p->owner->_state != AST_STATE_UP) {
+				ast_queue_control(p->owner, AST_CONTROL_CONGESTION);
+				ast_set_flag(&p->flags[0], SIP_NEEDDESTROY);	
+			} else {
+				/* This is a re-invite that failed. */
+				/* Reset the flag after a while 
+				 */
+				int wait = 3 + ast_random() % 5;
+				p->waitid = ast_sched_add(sched, wait, sip_reinvite_retry, p); 
+				if (option_debug > 2)
+					ast_log(LOG_DEBUG, "Reinvite race. Waiting %d secs before retry\n", wait);
+			}
+		}
 		break;
 
 	case 501: /* Not implemented */