[Serusers] Nathelper question - sr-users

2 Feb 2005

Hi,

I am new to SER and I am looking for how to determine whether the caller and the callee
are behind NAT. I found some example code from Zeus. But I do not understand how I can
distinguished whether the caller is the caller and the callee is the callee. Here is the
code:

/**************************************************************************************************************************/
Jan,

See below. Also, always CC the list so that other people can help you.

Zeus

...
  > 
 > Flag 4 is set when the caller is behind NAT.
 > Flag 5 is set when the callee is behind NAT. 

...
  Would you be so kind and tell me how do you test
messages to 
 set these 
 flags? 
        /*
        Check for UAC behind NAT
        This is done by nat_uac_test("7") which checks for
        1. RFC 1918 address in Contact - 01
        2. different src_ip and Via header - 02
        3. RFC1918 in Top Via - 04
        */
/*********************************************************************************************************************1.
Right here - it seems to me that if both the caller and the callee are behind NAT. It will
be flag as (4) and do the
force_rport.*********************************************************************************************************************/
       if (nat_uac_test("3")) {	/* 1 + 2 = 3 */
                xlog("L_NOTICE", "%rm: Client is behind NAT\n"); 
                setflag(4);     /* Flag it's a nated R-URI */
                if (method=="REGISTER" || !search("^Record-Route:"))
{
                        force_rport();
                        if (!method=="MESSAGE") {       /* MESSAGE has no
Contact header, see RFC 3428 */
                                fix_nated_contact();
                        };
                };
        } else {
                xlog("L_NOTICE", "%rm: Client is not behind a
NAT\n");
        };... Other checking
.../********************************************************************************************************************2.
Then down here - it seems to me that the caller and the callee will be mark as flag 5.
Then save into the location. Later on, how can I tell ifthe packet comes to SER is a
caller or the callee ????. I could not understand
this.********************************************************************************************************************/
        if (method=="REGISTER") {
                if (isflagset(4)) {     
                        setflag(5);     /* Turn on NAT Ping and flag it as a NAT callee
*/
                };

                if (!save("location")) {
                        xlog("L_ERR", "%rm: Failed\n");
                        sl_reply_error();
                };
                break;
        };

/********************************************************************************************************************/

I am trying to make SER works with two UAs behind a same NAT. Any help would be very
appreciated. Regards,Trong