[OpenSIPS-Users] OpenSIPS 1.7.0 Topology Hiding and NAT Traversal

[Jeremy Childs]

Thanks, for the reply, Bogdan.

I see what you're getting at, but the problem runs a little deeper that 
this, though. For the reply from the NATed UA, the dialog module needs 
to store the "fixed" contact, and it has no way of getting this 
information, as it only looks at the incoming header, not what 
fix_nated_contact has already pushed into a lump.

In your opinion, how difficult would it be to just make $ct writable? If 
it was writable, then nathelper could be coerced into putting 
$avp(contact) into $ct, where it could presumable be read normally by 
dialog.so. This assumes that modules have access to core variables that 
may have changed since the packet was received.

I recently ran into a similar problem with codec_delete and friends 
where I need to remove a codec that has no a=rtpmap entry. codec_delete 
can't find the coded to remove it, as it has no rtpmap entry, and once 
codec_delete was done removing the codecs it could find, any textops I 
ran on the SDP after that point corrupted the packet.

Any suggestions on how we can remove this one-rewrite limitation?

On 11-09-14 11:47 AM, Bogdan-Andrei Iancu wrote:
> Hi Jeremy,
>
> Indeed, seems to be an incompatibility here...What I would suggest is 
> a bit of a trick, to manually handle the NATed contact in a dialog 
> variable...Haven;t tried it, just an idea.
>
> On initial INVITE :
>
> modparam("nathelper", "received_avp", "$avp(contact)")
> ...
> topology_hiding();
> if (nat_uac_test()) {
> 	fix_nated_register(); # puts the fix contact into received avp
> 	$dlg_val(caller_contact) = $avp(contact);
> }
> ...
>
>
> And for sequential requests:
> ...
> loose_route();
> ...
> if ( match_dialog() ) {
>      # sequential request from callee to caller?
>      if ($DLG_dir=="UPSTREAM") $ru = $dlg_val(caller_contact) ;
> }
>
> Again, not tested, not sure it will work, but just an idea :)
>
> Regards,
> Bogdan
>
> On 09/13/2011 07:30 PM, Jeremy Childs wrote:
>> I'm having a problem with the dialog module's topology hiding when a 
>> UA is behind a NAT.
>>
>> If I call
>>
>> if (nat_uac_test()) {
>>     fix_nated_contact();
>> }
>> topology_hiding();
>>
>> The Contact header is rewritten twice - once by fix_nated_contact() 
>> and again by topology_hiding(). This results in an invalid contact 
>> header.
>>
>> Is there an obvious way I'm missing that could make these two modules 
>> coexist, or is the best solution to add NAT knowledge to 
>> dlg_tophiding.c? This seems like a lot of code to duplicate.
>>
>>
>> _______________________________________________
>> Users mailing list
>> Users at lists.opensips.org
>> http://lists.opensips.org/cgi-bin/mailman/listinfo/users
>
>
> -- 
> Bogdan-Andrei Iancu
> OpenSIPS eBootcamp - 19th of September 2011
> OpenSIPS solutions and "know-how"

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