[Users] UA behind NAT puts public IP in Contact, Via - help

[Arek Bekiersz]

...and I answer myself.

Of course I don't need the Via value. It's not the private IP I want , but
obviously the received, public one. Come on, I was tired, sorry :-)))

For this UA I will try to solve the problem using AVP module, or I will
write some custom functions elsewhere. I just need to store real, public
(received) IP in 'location' table,  together with NAT-ed flag. Could be done
either with appending Contact HF with received IP, by some clever avp
"store-retrieve" usage or otherwise.


--
Regards,
Arek Bekiersz


----- Original Message ----- 
From: "Arek Bekiersz" <arek at perceval.net>
To: "Bogdan-Andrei Iancu" <bogdan at voice-system.ro>
Cc: "Openser-Users" <users at openser.org>
Sent: Tuesday, March 21, 2006 8:03 PM
Subject: Re: [Users] UA behind NAT puts public IP in Contact, Via - help


> Hi Bogdan,
>
> I think it should be possible by some flag manipulation, with some help
> from registrar module. I can:
>
> 1. Set NAT-ed flag (flag 1) on first REGISTER, that comes with private
> IP in Via
> 2. If flag (1) is set, store "temporary" registration in "location"
> table, with  flag (let's say flag 10)
> 3. challenge user
> 4. when second REGISTER comes (with public IP Via ,so there is no (1)
> flag) check if UA is "already" in "location" table and the flag (10) was
> stored
> 5. If yes, set flag (1) (UA wanted to cheat us, he is NATed), answer
> '200 OK' and store in "location" table, this time with flag (1)
> 6. Next actions will assume that user is NAT-ed, by checking (1) flag in
> "location". He will also be pinged from SER. Pretty standard stuff.
>
>
> However, the problem is there is no "Contact" in first REGISTER. So I
> cannot store temporary entry in "location" database.. But the true
> (private) IP of user is still in Via. So maybe I could append "Contact"
> header field with IP value from Via. It would allow me to store this
> "temporary" registration.
>
> QUESTION: Do we have any access to Via value from ser.cfg, to append
> Contact HF with Via value? And not the topmost, but the last Via, as
> this will probably contain true private IP of UA?
>
> Help!!!
>
> I don't want to write another custom module or database for this stupid
> UA. In fact last year I had to write custom module for SDP manipulation.
> It was impossible to set codec preference in the SAME vendor's devices.
> I had preferred system codec and I had to force it using brute force...
> works until today...
>
>
>
> -- 
> Regards,
> Arek Bekiersz
>
>
> Bogdan-Andrei Iancu wrote:
> > it's not about RFC compliance here, but about making it work, about the
> > logic used to detect and traverse NATS , things that are not specified
> > by RFC.
> > I guess it should be reasonable from them to accept to make this auto
> > NAT detection configurable in order to disable it.
> > alternative solutions will be (1) to consider all these UAC as nated -
> > by looking at UA hdr- or (2) to try to remember the NAT flag from the
> > non-authenticated REGISTER until the auth-ed one - the first
> > (challenged) register will reveal the true status of the clients (nated
> > or not) as it's also used by client for nat detection....but I guess it
> > will be quite complicated