create a UDPTL structure in create_addr_from_peer() if it does not already exist for T38

This is required to create a UDPTL structure in create_addr_from_peer() to handle the
scenario where 't38pt_udptl=yes' is not defined in the [general] section of sip.conf but 
is defined the peer's context.  I tested this patch by enabling t38pt_udptl in the 
[general] section on one system and only enabling t38pt_udptl in a peer's context on
the system sending a fax.  Without the patch, the sending system will fail to initiate
T38 negotiation with the warning message, "No way to add SDP without an UDPTL structure".
When this patch is applied the sending side will successfully initiate T38 negotiation.



git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@176705 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channels/chan_sip.c

@@ -4709,6 +4709,10 @@ static int create_addr_from_peer(struct sip_pvt *dialog, struct sip_peer *peer)
 	}
 	dialog->prefs = peer->prefs;
 	if (ast_test_flag(&dialog->flags[1], SIP_PAGE2_T38SUPPORT)) {
+		if (!dialog->udptl) {
+			/* t38pt_udptl was enabled in the peer and not in [general] */
+			dialog->udptl = ast_udptl_new_with_bindaddr(sched, io, 0, bindaddr.sin_addr);
+		}
 		ast_copy_flags(&dialog->t38.t38support, &peer->flags[1], SIP_PAGE2_T38SUPPORT);
 		set_t38_capabilities(dialog);
 		dialog->t38.jointcapability = dialog->t38.capability;