Fix broken reinvite glare scenario.

To make a long story short, reinvite glares were broken
because Asterisk would invert the To and From headers
when ACKing a 491 response.

The reason was because the initreq of the dialog was being
changed to the incoming glared reinvite instead of being
set to the outgoing glared reinvite. This change has three
parts

* In handle_incoming, we never will reject an ACK because it
has a to-tag present, even if we think the request may be out
of dialog.
* In handle_request_invite, we do not change the initreq when
receiving a reinvite to which we will respond with a 491.
* In handle_request_invite, several superflous settings up
pendinginvite have been removed since this is dones automatically
by transmit_response_reliable

Review: https://reviewboard.asterisk.org/r/1911


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.8@366389 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channels/chan_sip.c

@@ -22354,9 +22354,7 @@ static int handle_request_invite(struct sip_pvt *p, struct sip_request *req, int
 				}
 			}
 			transmit_response_reliable(p, "491 Request Pending", req);
-			p->pendinginvite = seqno;
 			check_via(p, req);
-			copy_request(&p->initreq, req);
 			ast_debug(1, "Got INVITE on call where we already have pending INVITE, deferring that - %s\n", p->callid);
 			/* Don't destroy dialog here */
 			res = 0;
@@ -22376,7 +22374,6 @@ static int handle_request_invite(struct sip_pvt *p, struct sip_request *req, int
 		if (p->owner) {
 			ast_debug(3, "INVITE w Replaces on existing call? Refusing action. [%s]\n", p->callid);
 			transmit_response_reliable(p, "400 Bad request", req);	/* The best way to not not accept the transfer */
-			p->pendinginvite = seqno;
 			check_via(p, req);
 			copy_request(&p->initreq, req);
 			/* Do not destroy existing call */
@@ -22395,7 +22392,6 @@ static int handle_request_invite(struct sip_pvt *p, struct sip_request *req, int
 			append_history(p, "Xfer", "INVITE/Replace Failed. Out of memory.");
 			sip_scheddestroy(p, DEFAULT_TRANS_TIMEOUT);
 			p->invitestate = INV_COMPLETED;
-			p->pendinginvite = seqno;
 			check_via(p, req);
 			copy_request(&p->initreq, req);
 			res = -1;
@@ -22500,7 +22496,6 @@ static int handle_request_invite(struct sip_pvt *p, struct sip_request *req, int
 			}
 			refer_locked = 0;
 			p->invitestate = INV_COMPLETED;
-			p->pendinginvite = seqno;
 			check_via(p, req);
 			copy_request(&p->initreq, req);
 			res = -1;
@@ -25192,13 +25187,13 @@ static int handle_incoming(struct sip_pvt *p, struct sip_request *req, struct as
 			if (!req->ignore && req->method == SIP_INVITE) {
 				transmit_response_reliable(p, "481 Call/Transaction Does Not Exist", req);
 				/* Will cease to exist after ACK */
+				return res;
 			} else if (req->method != SIP_ACK) {
 				transmit_response(p, "481 Call/Transaction Does Not Exist", req);
 				sip_scheddestroy(p, DEFAULT_TRANS_TIMEOUT);
-			} else {
+				return res;
-				ast_debug(1, "Got ACK for unknown dialog... strange.\n");
 			}
-			return res;
+			/* Otherwise, this is an ACK. It will always have a to-tag */
 		}
 	}