[asterisk-dev] pjsip: SDP port reuse timeout?

[Michael Maier]

Hello all!

I think I encountered a local sdp port problem (no audio after call setup), because the time delta between the previously ended call and the following new call (75 s) was too short to drop the previously used NAT conntrack (in case of a stream per default 120 s / 
nf_conntrack_udp_timeout_stream [1]), because unfortunately, the same local sdp port for the following new call was used (but a different remote sdp port).

If I got it correctly, rtp_allocate_transport() randomly finds new rtp ports based on the given port range - but it doesn't respect system based timeouts. Therefore, it seems to be possible, that a port is reused though it hasn't been timed out in conntrack, e.g.

How should this problem be handled to ensure, that a port isn't reused too fast (previously used rtp ports should be blocked for nf_conntrack_udp_timeout_stream e.g. until being reused)?


Thanks
Michael

[1] https://www.kernel.org/doc/html/latest/networking/nf_conntrack-sysctl.html