[OpenSIPS-Users] Trouble with forked calls and rtpengine

[Răzvan Crainea]

Hi, Robert!

For a request, VIA 1 is always the previous hop - therefore, if you want 
to have different offer messages, you need to use something else - my 
proposal is to use the via-branch=3 and set the extra_avp to 
$T_branch_idx. You can do the same thing for replies, and that should 
cover all cases.

Best regards,

Răzvan Crainea
OpenSIPS Core Developer
http://www.opensips-solutions.com

On 1/27/22 19:23, Robert Dyck wrote:
> Opensips adds its via ( with branch info ) after script processing but before
> forwarding. Opensips branch info is not available to the script when
> processing an INVITE. I have attached some text of an INVITE with rtpengine
> and with "offer via-branch=1". What rtpengine receives is the branch parameter
> added by the upstream node. The upstream node has no knowledge of any forking
> that may occur after lookup.
> 
> The branch parameter is a legacy of rfc2543. That rfc stated that a forking
> proxy would add branch info in a via parameter called branch. This parameter
> could be added by any hop but is ignored. It was only meaningful in a response
> received by the forking proxy.
> 
> Rfc3261 retained the via parameter name, I assume for compatibility. Rfc3261
> was clear however that "branch" was now a transaction ID. This is only of
> interest to the node that added it in a request. Now in the case of a forking
> proxy the branch parameter has the dual role of being a transaction ID and a
> branch ID. Opensips does this by adding the branch index as a suffix to the
> transaction ID.
> 
> The opensips script may not have access to the eventual transaction ID but the
> branch index is available. Passing the branch index to rtpengine causes it to
> create a different profile for each branch rather than stacking the profiles.
> That stacking was causing trouble for me.
> 
> When rtpengine is simply providing a public address to relay media the
> stacking does not appear to have any consequence. However when mixing WEBRTC
> and non-WEBRTC stacking the profiles in a single entry in rtpengine gives
> inconsistent results.
> 
> On Thursday, January 27, 2022 3:57:07 A.M. PST Răzvan Crainea wrote:
>> Hi, Robert!
>>
>> Are you sure that via-branch=2 does not set different branches, and sets
>> the same param as via-branch=1?
>> If you are going to use the extra_id_pv, you should make sure that you
>> persist it over dialog, i.e. also provide it during sequential
>> offer/answer/delete commands.
>>
>> Best regards,
>>
>>
>> _______________________________________________
>> Users mailing list
>> Users at lists.opensips.org
>> http://lists.opensips.org/cgi-bin/mailman/listinfo/users