Re: Kamailio as a Stateless Smart SIP Proxy

route[REGISTER] {
if (!is_method("REGISTER")) return;
if (nat_uac_test("19")) {
xlog("L_INFO", "NAT detected for REGISTER request\n");
fix_nated_contact();
msg_apply_changes();
}
encode_contact("proxy_ip", ADV_HOST);
t_relay();
exit;
}


I have found this but ima little bit confused that i have to use
msg_apply_changes();
before doing encode_contact()
because otherwise kama respond that buffer is overloded





On Fri, Jul 18, 2025 at 9:31 AM Ihor Olkhovskyi via sr-users <
[email protected]> wrote:

>
> 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 <
> [email protected]> 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 <
>> [email protected]> 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 <[email protected]> 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 <
>>> [email protected]> 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 <
>>> [email protected]> 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
>>> > > [email protected]
>>> > > __________________________________________________________
>>> > > Kamailio - Users Mailing List - Non Commercial Discussions --
>>> [email protected]
>>> > > To unsubscribe send an email to [email protected]
>>> > > 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 --
>>> [email protected]
>>> > To unsubscribe send an email to [email protected]
>>> > Important: keep the mailing list in the recipients, do not reply only
>>> to the sender!
>>> >
>>> >
>>> > --
>>> >
>>> > Antony
>>> > [email protected]
>>>
>>> --
>>> 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 --
>>> [email protected]
>>> To unsubscribe send an email to [email protected]
>>> Important: keep the mailing list in the recipients, do not reply only to
>>> the sender!
>>>
>>
>>
>> --
>>
>> *Antony*
>> [email protected]
>>
>> __________________________________________________________
>> Kamailio - Users Mailing List - Non Commercial Discussions --
>> [email protected]
>> To unsubscribe send an email to [email protected]
>> Important: keep the mailing list in the recipients, do not reply only to
>> the sender!
>>
>
>
> --
> Best regards,
> Ihor (Igor)
> __________________________________________________________
> Kamailio - Users Mailing List - Non Commercial Discussions --
> [email protected]
> To unsubscribe send an email to [email protected]
> Important: keep the mailing list in the recipients, do not reply only to
> the sender!
>


-- 

*Antony*
[email protected]

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