[OpenSIPS-Users] How to fix contact info and RTP port in SDP? Is fix_nated_sdp function enough?

[Newlin, Ben]

Rodrigo,

What port should the module change it to? Until you receive RTP from the endpoint, there is no way to know what the correct RTP port is. It would require support on the endpoints to detect the RTP source port once RTP has been received. Most clients do not implement this, so direct media in the presence of NAT is not usually possible without other, external protocols like STUN.

Ben Newlin

From: <users-bounces at lists.opensips.org<mailto:users-bounces at lists.opensips.org>> on behalf of Rodrigo Pimenta Carvalho <pimenta at inatel.br<mailto:pimenta at inatel.br>>
Reply-To: OpenSIPS users mailling list <users at lists.opensips.org<mailto:users at lists.opensips.org>>
Date: Friday, February 5, 2016 at 2:16 PM
To: "users at lists.opensips.org<mailto:users at lists.opensips.org>" <users at lists.opensips.org<mailto:users at lists.opensips.org>>
Subject: [OpenSIPS-Users] How to fix contact info and RTP port in SDP? Is fix_nated_sdp function enough?


Dear OpenSIPS-users,


Two clients of my OpenSIPS are located behind different NATs and I have just started to search a way to mangles the SDP messages for both of them in a way that will make the parties talk directly with each other (direct media). After reading the proxy documentation (modules NATHELPER, STUN, MEDIAPROXY and NAT_TRAVERSAL) I have found the function fix_nated_sdp.


However, it seems that such function replaces the original contact IP, but not the RTP ports.

So I ask: what is the utility of the function fix_nated_sdp, if it fixes the contact info, but not the port? I mean, how can I fix the SDP in a way that contact info and RTP port will be valid to send media to a peer that is behind a NAT?


Any hint will be very very helpful!!


Best regards.



RODRIGO PIMENTA CARVALHO
Inatel Competence Center
Software
Ph: +55 35 3471 9200 RAMAL 979
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