I've been looking at the behavior of the RTSP alg extension. When it parses
a RTSP Transport that contains a RTP/AVP/UDP port range, it creates a
conntrack update for the RTP port (low port), but not the RTCP port (high
port). This prevents the server side from sending RTCP sender reports.
+ case pb_range:
+ for (loport = prtspexp->loport; loport != 0; loport += 2) /* XXX:
improper wrap? */
+ {
+ t.dst.u.udp.port = htons(loport);
+ if (ip_conntrack_change_expect(exp, &t) == 0)
+ {
+ hiport = loport + ~exp->mask.dst.u.udp.port;
+ DEBUGP("using ports %hu-%hu\n", loport, hiport);
+ break;
+ }
+ }
+ if (loport != 0)
+ {
+ rbuf1len = sprintf(rbuf1, "%hu", loport);
+ rbufalen = sprintf(rbufa, "%hu-%hu", loport, loport+1);
+ }
+ break;
It looks like RTSP clients can still function without this behind a NAT
device - at least real player.
Has anyone created a setup that is allowing RTCP packets from the server to
the client?
Regards,
Joe
