[SR-Users] How to retrieve local socket that will be used to send a message from the branch route

[David Villasmil]

Hello,

Interesting challenge you’ve got.

 It may fail in cases where my kernel routing table has some rule where a
private IP is reachable via my external interface but different GW for
example

In this case then, the $du will be a rfc1918 ip but the outgoing interface
will be a public ip?

Have you tried $send(name) ?

The docs state:

Send Address Attributes
$sndfrom(name)

*$snd(name)* - return attributes of the address from where the request is
going to be sent (local socket).

On Thu, 21 Nov 2019 at 22:57, Patrick Wakano <pwakano at gmail.com> wrote:

> Thanks for the replies and examples! Much appreciated!
>
> I was thinking of something similar to David suggestion, but I think this
> is not 100% reliable. It may fail in cases where my kernel routing table
> has some rule where a private IP is reachable via my external interface but
> different GW for example (multiple IPs in the same interface or more
> complex network architecture with VPN or direct link with some
> endpoint).... So given Kamailio already consults the kernel looking for the
> correct interface to a given destination, I thought this is actually the
> correct information I should use in my script. The only problem is that
> apparently Kamailio is not exposing this info for the script writer....
> Karsten suggestion should probably work but in short this is just a way to
> statically save in DB the network routing information I know before hand.
> If this route changes (which should not happen often I agree) then I have
> to update the DB. And also this DB data could be replaced by some logic in
> my script if I had access to the chosen socket... That's exactly the
> purpose of having mhomed=1 in the script, I don't need to save socket info
> for all my GWs in DB because I am letting Kamailio automatically decide it.
> And it does pretty well! The only problem now is that I don't know what
> this decision was and I need it to implement the RTPEngine logic in my
> script based on the interface the INVITE will go out.
>
> Happy to hear more ideas!
> Thanks,
> Kind regards,
> Patrick Wakano
>
> On Thu, 21 Nov 2019 at 20:07, Karsten Horsmann <khorsmann at gmail.com>
> wrote:
>
>> Hi Patrick,
>>
>> If you don't use tls at this moment, the config from sbc OS is also an
>> good example of using dispatcher with the socket params to select the right
>> sendsock and using vars to give rtpengine the right internal / external
>> directions. They use numbers for internal and external. To figure out where
>> the direction is, this config use pseudo vars for receiving local socket
>>
>>
>> https://github.com/voiceboys/sbcOS/blob/master/SbcOS/configs/voice/kamailio/kamailio.cfg#L450
>>
>> Cheers
>> Karsten Horsmann
>>
>> Patrick Wakano <pwakano at gmail.com> schrieb am Do., 21. Nov. 2019, 07:11:
>>
>>> Hello list,
>>> Hope you are all doing well!
>>>
>>> I am trying to figure out a way to retrieve the local socket the
>>> t_relay() has decided to use in a mhomed=1 env. Is there a way to do that?
>>> I couldn't find any variable other than the $snd ones that maybe have this
>>> info, but I am not using onsend_route anyway.....
>>> I am after this value because this is what I can use to figure out if I
>>> need to engage RTPEngine with parameters "external, internal", "external,
>>> external", "internal, external" or "internal, internal". In my case, my
>>> server is in between two networks, and calls can traverse or can be routed
>>> back to the same interface depending on what was decide by the LCR module.
>>> Signalling is fine, but engaging the RTPEngine must be done with the
>>> correct parameters to get the correct IPs in the SDP, other else I get one
>>> way audio in the call.....
>>>
>>> Any help is much appreciated!
>>> Thank you!
>>> Kind regards,
>>> Patrick Wakano
>>>
>>>
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-- 
Regards,

David Villasmil
email: david.villasmil.work at gmail.com
phone: +34669448337
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