[Serusers] NAT Traversal using nathelper module

[Kostas Marneris]

Hello all,

I'm trying to find a solution to overcome the NAT issue using only the nathelper module.
(I've already successfully worked with 'STUN' & 'MediaProxy'
solutions but I'm trying also this).


1. OUTBOUND direction:
--- INVITE handler ---
	...
        # NAT Traversal mechanism for INVITEs
        if (nat_uac_test("19")) {
                setflag(7);
                force_rport();
                fix_nated_contact();
                fix_nated_sdp("3");
        };
        #
	...

The solution above works fine for OUTBOUND calls,
either on-net (a) or off-net (b). (For off-net calls I use a Cisco GW).

a/ SIP_UA_behind_NAT -------- SER ------- SIP_UA_on_public_IP
b/ SIP_UA_behind_NAT -------- SER ------- Cisco_PSTN_GW ------- PSTN




2. INBOUND direction:
route[1] {
        # Default Message Handler
        t_on_reply("1");
        if (!t_relay()) {
                log(1, "  - Cannot RELAY !!!");
                sl_reply_error();
        };
}

onreply_route[1] {
        if (nat_uac_test("19")) {
                log(1, " - Response behind NAT...");
                setflag(7);
                force_rport();
                fix_nated_contact();
                fix_nated_sdp("3");
        };

}


Although I have two-way audio between calling and called parties,
I get the following logging mesgs :

May  3 17:22:26 server ./ser[13705]: ERROR: extract_body: message body has length zero
May  3 17:22:26 server ./ser[13705]: ERROR: fix_nated_sdp: cannot extract body from msg!
May  3 17:22:26 server ./ser[13705]: ERROR: on_reply processing failed



My question is :
Is the above the correct way for NAT traversal of SIP Responses (200 OK) ?
Do I have to add something else somewhere in ser.cfg ?
Any idea on the log mesgs above ?


thanks in advance for any help,
Kostas