Don't leak a ref if out of memory and can't link the linkedid

If the ao2_link fails, we are most likely out of memory and bad things
are going to happen. Before those bad things happen, make sure to clean
up the linkedid references.

This patch also adds a comment explaining why linkedid can't be passed
to both local channel allocations and combines two ao2_ref calls into 1.

Review: https://reviewboard.asterisk.org/r/1895/


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.8@365068 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channels/chan_local.c

@@ -1112,6 +1112,9 @@ static struct ast_channel *local_new(struct local_pvt *p, int state, const char
 		ama = p->owner->amaflags;
 	else
 		ama = 0;
+
+	/* Make sure that the ;2 channel gets the same linkedid as ;1. You can't pass linkedid to both
+	 * allocations since if linkedid isn't set, then each channel will generate its own linkedid. */
 	if (!(tmp = ast_channel_alloc(1, state, 0, 0, t, p->exten, p->context, linkedid, ama, "Local/%s@%s-%04x;1", p->exten, p->context, randnum)) 
 		|| !(tmp2 = ast_channel_alloc(1, AST_STATE_RING, 0, 0, t, p->exten, p->context, tmp->linkedid, ama, "Local/%s@%s-%04x;2", p->exten, p->context, randnum))) {
 		if (tmp) {

main/cel.c

@@ -377,10 +377,9 @@ void ast_cel_check_retire_linkedid(struct ast_channel *chan)
 		return;
 	}
 
-	/* We have a ref for each channel with this linkedid, the link and the above find, so if after
-	 * unreffing for the channel we have a ref of 2, we're done. Unlink and report. */
-	ao2_ref(lid, -1);
-	if (ao2_ref(lid, 0) == 2) {
+	/* We have a ref for each channel with this linkedid, the link and the above find, so if
+	 * before unreffing the channel we have a refcount of 3, we're done. Unlink and report. */
+	if (ao2_ref(lid, -1) == 3) {
 		ao2_unlink(linkedids, lid);
 		ast_cel_report_event(chan, AST_CEL_LINKEDID_END, NULL, NULL, NULL);
 	}
@@ -488,7 +487,11 @@ int ast_cel_report_event(struct ast_channel *chan, enum ast_cel_event_type event
 				return -1;
 			}
 			strcpy(lid, chan->linkedid);
-			ao2_link(linkedids, lid);
+			if (!ao2_link(linkedids, lid)) {
+				ao2_ref(lid, -1);
+				ast_mutex_unlock(&reload_lock);
+				return -1;
+			}
 			/* Leave both the link and the alloc refs to show a count of 1 + the link */
 		}
 		/* If we've found, go ahead and keep the ref to increment count of how many channels