[OpenSIPS-Users] Mediaproxy wrong port, bug?

Remco . remconl87 at gmail.com
Tue Jan 8 10:49:15 CET 2013

Hi all,

I seem to experience a strange issue regarding Mediaproxy running on
OpenSIPS The following scenario:

A. UA (asterisk) <=> OpenSIPS <=> UA (asterisk) B.

I verified the following:

- Both UA's have nat=never, no re-invite is taking place (verified by
- Ports in SDP are rewritten, and match the ports Mediaproxy opens.
- Call has audio, in both directions.

After 60 seconds mediaproxy logs a conntrack_timeout, and the call loses
audio in both directions.

The following port schema is negotiated:

A. 11496 <=(capture)=> 30600 OpenSIPS 30602 <=> 17026 B.

The RTP stream is captured at (capture) between A and the proxy.

The first 3 RTP packet traverse from B => A on the correct ports over the
Then a packet is sent the other way A => B on the corect ports over the

Then the strange thing happens, the next packet going B => A is sent with a
source port of 1024 by the relay.
All subsequent packets in the stream are exchanged between A (11496/udp)
and OpenSIPS (1024/udp).

I think the loss of the call is explained by the leg between the relay and
B torn down, because of the conntrack timeout on leg A (mediaproxy sees no
RTP on the expected ports).
Also, port 1024 is not allowed by firewalls as it's not expected for media
to pass over this port.

I observe this on quite a number of calls, all being torn down after 60
seconds. Doing a random selection on them, they all seem to use port 1024
for RTP as described in the scenario above.

Any ideas?
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