https://www.kamailio.org/docs/modules/5.0.x/modules/nathelper.html#nathelper.f.fix_nated_contact ? With combination of alias and other parameter, means you can store full original contact header (encoded) in a Contact params as well.

Yes, it brakes RFC, but you can handle it manually

Le lun. 14 juil. 2025 à 14:36, Antonio via sr-users <sr-users@lists.kamailio.org> a écrit :

BUT

When Kamailio forwards REGISTER to Upstream(Asterisk), it will  contain the REAL IP of the UAC 

so later if someone will dial  UAC it will not path through  Kamailio

On Sat, Jul 12, 2025 at 9:32 PM Alex Balashov via sr-users <sr-users@lists.kamailio.org> wrote:

Hi,

Yes, that's exactly what those functions enable.

When you receive the REGISTER request, you use set_contact_alias() / add_contact_alias() to add an `;alias` parameter to the Contact, which reflects the client's external IP/port/transport. You then pass that REGISTER request onto the registrar.

When you get an incoming request from the registrar to the client, you use handle_ruri_alias() to read the `;alias` parameter and load the IP/port/transport values into the destination set ($du), while stripping the `;alias` parameter off the RURI. You then t_relay() the request, which will follow $du to the next hop read from the `;alias` parameter.

-- Alex

> On Jul 11, 2025, at 4:28 PM, Antonio <satskiy.a@gmail.com> wrote:
>
> Thanks for the reply
>
> I want to use Kamailio as a proxy, but a smart one.
> It doesn't store anything, but:
> • Modifies REGISTER requests → adds the client's IP/port to Contact
> • So when the PBX sends an INVITE back, Kamailio reads this data from the R-URI and forwards the call to the client
>
> Hope it makes sense.
>
>
> On Fri, Jul 11, 2025 at 10:14 PM Alex Balashov via sr-users <sr-users@lists.kamailio.org> wrote:
> Hi,
>
> The set_contact_alias() / handle_ruri_alias() functions from the `nathelper` module[1] are quite ready-made for this use-case, though you may need a more sophisticated approach if the upstream registrar does not support Path[2][3].
>
> -- Alex
>
> [1] https://kamailio.org/docs/modules/6.0.x/modules/nathelper.html
>
> [2] https://datatracker.ietf.org/doc/html/rfc3327
>
> [3] https://kamailio.org/docs/modules/6.0.x/modules/path.html#path.f.add_path
>
> > On Jul 11, 2025, at 6:19 AM, Antonio via sr-users <sr-users@lists.kamailio.org> wrote:
> >
> > Hi everyone,
> > Do we have a ready-to-use Kamailio role or configuration for:
> >
> > “Kamailio as a Stateless Smart SIP Proxy”,
> > Specifically one that uses Contact Header Encoding?
> >
> > That is — a proxy where Kamailio does not store registration state,
> > but encodes the client’s IP and port into the Contact header during REGISTER,
> > and later decodes it from the INVITE to forward the call back to the client.
> > Thanks in advance!
> > --
> >
> > Antony
> > satskiy.a@gmail.com
> > __________________________________________________________
> > Kamailio - Users Mailing List - Non Commercial Discussions -- sr-users@lists.kamailio.org
> > To unsubscribe send an email to sr-users-leave@lists.kamailio.org
> > Important: keep the mailing list in the recipients, do not reply only to the sender!
>
> --
> Alex Balashov
> Principal Consultant
> Evariste Systems LLC
> Web: https://evaristesys.com, https://www.csrpswitch.com
> Tel: +1-706-510-6800
>
> __________________________________________________________
> Kamailio - Users Mailing List - Non Commercial Discussions -- sr-users@lists.kamailio.org
> To unsubscribe send an email to sr-users-leave@lists.kamailio.org
> Important: keep the mailing list in the recipients, do not reply only to the sender!
>
>
> --
>
> Antony
> satskiy.a@gmail.com

--
Alex Balashov
Principal Consultant
Evariste Systems LLC
Web: https://evaristesys.com, https://www.csrpswitch.com
Tel: +1-706-510-6800

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--

Antony satskiy.a@gmail.com

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--

Best regards,

Ihor (Igor)

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