[core] adds back the ability to reply to VIA (and not to network src)

This is a rework of #3327 (credits go to @carstenbock).
Even more, we merged:
* force_rport()
* this new reply_to_via PR
* add_local_rport()
* force_tcp_alias()
as a single VIA related function:
  set_via_handling("force-rport|add-local-rport|reply-to-via|force-tcp-alias")

Closes #3327

core_cmds.c

@@ -39,6 +39,7 @@
 #include "status_report.h"
 #include "cachedb/cachedb.h"
 #include "msg_translator.h"
+#include "mod_fix.h"
 /* needed by tcpconn_add_alias() */
 #include "net/tcp_conn_defs.h"
 
@@ -64,6 +65,7 @@ static int fixup_format_string(void** param);
 static int fixup_nt_string(void** param);
 static int fixup_nt_str(void** param);
 static int fixup_nt_str_free(void** param);
+static int fixup_via_hdl(void** param);
 
 static int w_forward(struct sip_msg *msg, struct proxy_l *dest);
 static int w_send(struct sip_msg *msg, struct proxy_l *dest, str *headers);
@@ -127,6 +129,7 @@ static int w_script_trace(struct sip_msg *msg, int *log_level,
 					pv_elem_t *fmt_string, void *info_str);
 static int w_is_myself(struct sip_msg *msg, str *host, int *port);
 static int w_print_avps(struct sip_msg* msg, char* foo, char *bar);
+static int w_set_via_handling(struct sip_msg* msg, int* flags);
 
 #ifndef FUZZ_BUILD
 static
@@ -362,6 +365,9 @@ const cmd_export_t core_cmds[]={
 		ALL_ROUTES},
 	{"avp_print", (cmd_function)w_print_avps, {{0, 0, 0}},
 		ALL_ROUTES},
+	{"set_via_handling", (cmd_function)w_set_via_handling, {
+		{CMD_PARAM_STR, fixup_via_hdl, 0}, {0,0,0}},
+		ALL_ROUTES},
 	{0,0,{{0,0,0}},0}
 };
 
@@ -1463,3 +1469,38 @@ static int w_print_avps(struct sip_msg* msg, char* foo, char *bar)
 }
 
 
+static str via_hdl_flag_names[] = {
+	str_init("force-rport"),
+	str_init("add-local-rport"),
+	str_init("reply-to-via"),
+	str_init("force-tcp-alias"),
+	STR_NULL
+};
+enum via_hdl_flags {
+	VIA_HDL_FORCE_RPORT,
+	VIA_HDL_ADD_LOCAL_RPORT,
+	VIA_HDL_REPLY_TO_VIA,
+	VIA_HDL_FORCE_TCP_ALIAS,
+};
+static int fixup_via_hdl(void** param)
+{
+	return fixup_named_flags(param, via_hdl_flag_names, NULL, NULL);
+}
+
+static int w_set_via_handling(struct sip_msg* msg, int* flags)
+{
+	if (*flags & VIA_HDL_FORCE_RPORT)
+		msg->msg_flags |= FL_FORCE_RPORT;
+
+	if (*flags & VIA_HDL_ADD_LOCAL_RPORT)
+		msg->msg_flags|=FL_FORCE_LOCAL_RPORT;
+
+	if (*flags & VIA_HDL_REPLY_TO_VIA)
+		msg->msg_flags |= FL_REPLY_TO_VIA;
+
+	if (*flags & VIA_HDL_FORCE_TCP_ALIAS)
+		w_force_tcp_alias( msg, 0);
+
+	return 1;
+}
+

modules/sl/sl_funcs.c

@@ -154,7 +154,15 @@ int sl_send_reply_helper(struct sip_msg *msg ,int code, const str *text)
 	if ( msg->REQ_METHOD==METHOD_ACK)
 		return 1;
 
-	update_sock_struct_from_ip( &to, msg );
+	if (msg->msg_flags&FL_REPLY_TO_VIA) {
+		if (update_sock_struct_from_via( &to, msg, msg->via1 )==-1) {
+			LM_ERR("cannot lookup reply dst: %.*s\n",
+					msg->via1->host.len, msg->via1->host.s);
+			goto error;
+		}
+	} else {
+		update_sock_struct_from_ip( &to, msg );
+	}
 
 	/* if that is a redirection message, dump current message set to it */
 	if (code>=300 && code<400) {

modules/tm/t_lookup.c

@@ -942,8 +942,18 @@ int init_rb( struct retr_buf *rb, struct sip_msg *msg)
 {
 	int proto;
 
-	update_sock_struct_from_ip( &rb->dst.to, msg );
 	proto=msg->rcv.proto;
+
+	if (msg->msg_flags&FL_REPLY_TO_VIA) {
+		if (update_sock_struct_from_via( &(rb->dst.to), msg, msg->via1 )==-1) {
+			LM_ERR("cannot lookup reply dst: %.*s\n",
+					msg->via1->host.len, msg->via1->host.s );
+			ser_error=E_BAD_VIA;
+			return 0;
+		}
+	} else {
+		update_sock_struct_from_ip( &rb->dst.to, msg );
+	}
 	rb->dst.proto=proto;
 	rb->dst.proto_reserved1=msg->rcv.proto_reserved1;
 	/* use for sending replies the incoming interface of the request -bogdan */

parser/msg_parser.h

@@ -88,7 +88,8 @@ enum request_method {
 };
 
 #define FL_FORCE_RPORT       (1<<0)  /* force rport (top via) */
-#define FL_FORCE_ACTIVE      (1<<1)  /* force active SDP */
+#define FL_REPLY_TO_VIA      (1<<1)  /* force replying to VIA ip:port */
+#define FL_FORCE_ACTIVE      (1<<1)  /* force active SDP (deprecated) */
 #define FL_FORCE_LOCAL_RPORT (1<<2)  /* force local rport (local via) */
 #define FL_SDP_IP_AFS        (1<<3)  /* SDP IP rewritten */
 #define FL_SDP_PORT_AFS      (1<<4)  /* SDP port rewritten */