forcibly expire previous subscriptions from a peer when they resubscribe (keeps them from building up and waiting for expiration, and stops us sending unwanted NOTIFY messages to devices)

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.2@7513 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channels/chan_sip.c

@@ -10793,12 +10793,40 @@ static int handle_request_subscribe(struct sip_pvt *p, struct sip_request *req,
 			ast_set_flag(p, SIP_NEEDDESTROY);	
 			return 0;
 		} else {
+			struct sip_pvt *p_old;
+
 			transmit_response(p, "200 OK", req);
 			transmit_state_notify(p, firststate, 1, 1);	/* Send first notification */
 			append_history(p, "Subscribestatus", ast_extension_state2str(firststate));
+
+			/* remove any old subscription from this peer for the same exten/context,
+			   as the peer has obviously forgotten about it and it's wasteful to wait
+			   for it to expire and send NOTIFY messages to the peer only to have them
+			   ignored (or generate errors)
+			*/
+			ast_mutex_lock(&iflock);
+			for (p_old = iflist; p_old; p_old = p_old->next) {
+				if (p_old == p)
+					continue;
+				if (p_old->initreq.method != SIP_SUBSCRIBE)
+					continue;
+				if (p_old->subscribed == NONE)
+					continue;
+				ast_mutex_lock(&p_old->lock);
+				if (!strcmp(p_old->username, p->username)) {
+					if (!strcmp(p_old->exten, p->exten) &&
+					    !strcmp(p_old->context, p->context)) {
+						ast_set_flag(p_old, SIP_NEEDDESTROY);
+						ast_mutex_unlock(&p_old->lock);
+						break;
+					}
+				}
+				ast_mutex_unlock(&p_old->lock);
+			}
+			ast_mutex_unlock(&iflock);
 		}
 		if (!p->expiry)
-			ast_set_flag(p, SIP_NEEDDESTROY);	
+			ast_set_flag(p, SIP_NEEDDESTROY);
 	}
 	return 1;
 }