On Mon, Jun 25, 2012 at 5:57 PM, Richard Brady <rnbrady@gmail.com> wrote:

Klaus / Daniel

Thanks again for assistance with this.

I've tried the solution based on add_contact_alias() and
handle_ruri_alias() and it works perfectly.

Richard

On 22 June 2012 13:47, Klaus Darilion <klaus.mailinglists@pernau.at> wrote:
>
>
> On 22.06.2012 13:50, Richard Brady wrote:
>>
>> Thanks guys, fantastic answers.
>>
>> You mention that NAT detection happens before save() and the flag is set
>> by lookup() which makes much more sense. However, if Kamailio is not the
>> registrar, as is the case with my current project, those functions are
>> not called, so an alternative is needed. There are clearly several
>> options.
>>
>> The solution I have gone for is to replace fix_nated_register() with
>> fix_nated_contact() so that the REGISTER request is relayed with a
>> modified Contact header containing the external ip:port of the client.
>
>
> The cleanest solution would be to use add_contact_alias() and
> handle_ruri_alias(). The do not change the contact but put the public
> address into a uri parameter. Thus, the URI seen by the client is always the
> one it sends:
> http://www.kamailio.org/docs/modules/3.2.x/modules_k/nathelper.html#id2550431
>
>
>> That is then stored by the registrar (FreeSWITCH in my case) and used
>> later to originate calls for that user. The FreeSWITCH know to send
>> those calls to Kamailio through either use of the Path header and module
>> in Kamailio, or through static configuration of fs_path or proxy
>> parameters in FreeSWITCH.
>
>
> This is fine.
>
>
>> The works for the first INVITE to the registered client behind NAT. But
>> that client sends back a 200 OK with a Contact header containing its
>> private IP address, and so fix_nated_contact() needs to be invoked on
>> that response, and normally it would be due to FLB_NATB being set, but
>> if Kamailio was not the registrar then that flag is not set. So I need
>> to detect NAT on the client at the time of receiving the reply, or
>> alternatively by having the registrar store a cookie and setting it
>> based on that.
>
>
> You are correct. For in-dialog messages received from SIP clients I would
> always use add_contact_alias() and remove the NAT flags completely.
>
>>
>> I suppose then my next question then is can I call nat_uac_test() on a
>> UAS?
>
>
> Today, almost any SIP clients are SIP symmetric. This means, that they
> receive SIP from the some port/connection where they send. Thus, skip the
> NAT tests completely and always use add_contact_alias() for messages receive
> from SIP clients and handle_ruri_alias() for messages sent to SIP clients.
>
> Depending on if you use Freeswitch also as media relay you can also remove
> the media proxy stuff from the Kamailio config.
>
> On important thing is NAT-keep-alive. This is usually done by nathelper
> module by querying the location table for contact with NAT-flag set. Thus,
> either you do NAT keep-alive by freeswitch (e.g sending OPTIONS requests) or
> do it in your Kamailio proxy (e.g. set the nat_bflag
> http://www.kamailio.org/docs/modules/3.2.x/modules_k/usrloc.html#id2541477
> and call save("location","0x02") before relaying REGISTER to freeswitch.
> Then Kamailio will do NAT-pinging. Note, if you want to keep-alive only for
> successfully registered clients, you man want to call save() in the
> reply-route of the REGISTER request).
>
> regards
> Klaus

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