[Users] clienst behind same NAT

Daniel-Constantin Mierla daniel at voice-system.ro
Thu Aug 18 13:17:22 CEST 2005



On 08/18/05 13:24, Klaus Darilion wrote:

> If oyu use fix_nated_contact for REGISTER messages, than it should work.
>
> If ouy use fix_nated_register, it will not work. We would need a 
> pseudo variable which points to the received-socket. Maybe the core 
> developers can help you on this.

There is a pseudo variable $du that points to destination uri (dst_uri 
filed of sip_msg structure - the address where the sip message will be 
sent after a loose_route() or lookup() request for callee behind the nat).

So, if the callee is behind the nat, the dst_uri is set to the address 
and port of the NAT. To check it, copy $du in an avp, use avp_subst() to 
extract the ip address and and compare it with src_ip.

avp_printf("i:20","$du");
avp_subst("i:20/d","/.*([1-9][0-9]{1,2}\.[1-9][0-9]{1,2}\.[1-9][0-9]{1,2}\.[1-9][0-9]{1,2}).*"/\1/);
if(avp_check("i:20","eq/$src_ip")) {
    # src_ip is the same with destination ip
}

Looking at this issue, I am wondering if worth to add the 
pseudovariables $dh and $dp for destination host and port ... Also I am 
considering to change a bit the $du reference so when the dst_uri is not 
set to point to request URI. Would be these changes usefully?

Daniel

>
> regards
> klaus
>
> jayesh nambiar wrote:
>
>> hi all,
>> Thanx Klaus.
>> Sorry to ask a question again related to the same problem. I had 
>> already tried writing the avp_write after lookup but even that causes 
>> a problem.
>> When avp_write is done it writes the private IP address of the callee 
>> while the source_ip is the IP address of the NAT. I beleive this IP 
>> address is written because of the fix_nated_contact.
>> Again, when avp_check is done, it returns false and again the RTP 
>> session gets started. IS there any way out to this problem.
>> Thanx again..
>> Jayesh
>>
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