Only try to use the invite_branch on outgoing INVITEs with auth credentials.

I have added a comment to the code to help ease understanding of the logic here
as well.



git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@199958 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channels/chan_sip.c

@@ -8967,7 +8967,11 @@ static int reqprep(struct sip_request *req, struct sip_pvt *p, int sipmethod, in
 		seqno = p->ocseq;
 	}
 	
-	if (sipmethod == SIP_CANCEL || sipmethod == SIP_INVITE) {
+	/* A CANCEL must have the same branch as the INVITE that it is canceling.
+	 * Similarly, if we need to re-send an INVITE with auth credentials, then we
+	 * need to use the same branch as we did the first time we sent the INVITE.
+	 */
+	if (sipmethod == SIP_CANCEL || (sipmethod == SIP_INVITE && !ast_strlen_zero(p->options->auth))) {
 		p->branch = p->invite_branch;
 		build_via(p);
 	} else if (newbranch) {