chan_sip: Support nat=auto_comedia or nat=force_rport,auto_comedia.

In the SIP channel driver chan_sip, auto_comedia was expected to be used in
tandem with auto_force_rport. Or stated differently: Only when auto_force_rport
was chosen (the default), auto_comedia worked. This change allows auto_comedia
to be set independently of the state of (auto_)force_rport. For example,
nat=force_rport,auto_comedia is useful for IPv4/IPv6 Dual Stack deployments
when IPv6 clients are behind a Firewall.

ASTERISK-26457 #close

Change-Id: Ib29d66c6dbb61648e371e01fc36c6978ddae5bc2

channels/chan_sip.c

@@ -30383,9 +30383,10 @@ static struct ast_channel *sip_request_call(const char *type, struct ast_format_
 	if (p->relatedpeer) {
 
 		if (!ast_strlen_zero(p->relatedpeer->fullcontact) && !p->natdetected &&
-			(ast_test_flag(&p->flags[2], SIP_PAGE3_NAT_AUTO_RPORT) && !ast_test_flag(&p->flags[0], SIP_NAT_FORCE_RPORT))) {
+		    ((ast_test_flag(&p->flags[2], SIP_PAGE3_NAT_AUTO_RPORT) && !ast_test_flag(&p->flags[0], SIP_NAT_FORCE_RPORT)) ||
+		     (ast_test_flag(&p->flags[2], SIP_PAGE3_NAT_AUTO_COMEDIA) && !ast_test_flag(&p->flags[1], SIP_PAGE2_SYMMETRICRTP)))) {
 			/* We need to make an attempt to determine if a peer is behind NAT
-			   if the peer has the auto_force_rport flag set. */
+			   if the peer has the flags auto_force_rport or auto_comedia set. */
 			struct ast_sockaddr tmpaddr;
 
 			__set_address_from_contact(p->relatedpeer->fullcontact, &tmpaddr, 0);