[OpenSIPS-Users] mediaproxy bug with offer answer in different transaction

Saúl Ibarra Corretgé saul at ag-projects.com
Mon Jun 16 11:00:47 CEST 2014

Hi Eric,

On Jun 11, 2014, at 4:53 PM, Eric Tamme wrote:

> Hi Saúl, and others,
> We have discovered a bug in mediaproxy where it does not recognize an answer that is part of a different transaction, this is caused by how mediaproxy tracks offer/answer based on cseq.  Here is the example offer answer scenario from RFC3262 that does not work.
> UAC  INVITE Cseq: 1 (no SDP offer) ->
> <- 183 with SDP offer
> PRACK CSeq: 2, Rseq: 1  with SDP answer->

Wow, what an abomination of a use-case, I didn't know it was even possible to do that :-/

> Because the PRACK is a different transaction, and has a different CSeq than the offer, mediaproxy assumes it is a new offer, rather than an answer.
> Can you offer any thoughts on what might be the best way to fix this issue?  We are happy to work on a patch as well - but would like to have input from the maintainers so that we can be sure it would be accepted upstream.

The OpenSIPS mediaproxy module just takes some information and passes it to the MediaProxy dispatcher process, so the fix needs to take place in mediaproxy/mediacontrol.py, in the update_session and/or update_media functions.

Let me know how that goes!


Saúl Ibarra Corretgé
AG Projects

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