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

Fri Nov 22 04:51:48 CET 2019

Just rectifying about the $snd variable. While the wiki tells that $snd ==
$sndfrom, I discovered that the $snd == $sndto.
So in my case, the $sndfrom(ip) gives me the local socket the message is
being sent.
However this only works from the onsend_route. I wasn't using this route at
all, so now I need to check whether a call to rtpengine_offer will properly
work from it.....

On Fri, 22 Nov 2019 at 10:01, Patrick Wakano <pwakano at gmail.com> wrote:

> Yes David, we have all sorts of weird things (specially legacy
> installations where creativity really shined....). Also, in some private
> network architectures my external interface may not have a public IP at
> all....
> Anyway, I first thought about applying some logic on the destination IP,
> but it is only reliable if I know my routing table, and this task Kamailio
> already performs when relaying.... The easiest way for now seems to save
> the info in the DB, so I explicit tell from which socket each GW is
> reachable....
>
> And for curiosity I attempted the $snd() variables but they don't have the
> socket information.... the $snd(ip) has the destination IP, not my local
> socket as the doc may suggest.....The $branch variable (
> http://www.kamailio.org/wiki/cookbooks/5.2.x/pseudovariables#branch_name_-_branch_attributes)
> was promising but I couldn't figure out when it is set. In my branch_routes
> it is always null......
>
>
> On Fri, 22 Nov 2019 at 09:15, David Villasmil <
> david.villasmil.work at gmail.com> wrote:
>
>> 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
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> Kamailio (SER) - Users Mailing List
>>>>> sr-users at lists.kamailio.org
>>>>> https://lists.kamailio.org/cgi-bin/mailman/listinfo/sr-users
>>>>>
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>> --
>> Regards,
>>
>> David Villasmil
>> email: david.villasmil.work at gmail.com
>> phone: +34669448337
>> _______________________________________________
>> Kamailio (SER) - Users Mailing List
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>>
>
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