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Bug in RTCP packet reflecting

The "ReflectorSocket::ProcessPacket()" routine (in "APIModules/QTSSReflectorModule/ReflectorStream.cpp") performs a series of tests on incoming packets, before deciding whether to 'reflect' them.

First, it calls FilterInvalidSSRCs() to check whether the incoming packet's SSRC (RTP/RTCP source id) is valid. (It does this by assuming that the SSRC of the first packet it receives is the legitimate source, and that any other SSRC it sees later is illegitimate.)

Next, for incoming RTCP packets, it checks whether the packet is a RTCP SR (Sender Report) packet, because these are the only RTCP packets that get reflected.

However, these two tests should be reversed: The RTCP SR test should come before the FilterInvalidSSRCs() test.

The reason for this is that if the first received RTCP packet is a RR (Reception Report) packet (e.g., from the DSS itself), then its SSRC (which will be different from that of the sender) will be considered the 'legitimate' source. Subsequent RTCP SR packets will then be ignored, even though they are from coming the actual data source.

I have seen this happen several times in practice. Quite often, RTCP SR packets from the source will not get reflected, because a RR (from someone else) arrived first.

Reversing the order of those two tests in "ReflectorSocket::ProcessPacket()" should fix the problem.

	Ross Finlayson
	LIVE.COM
	<http://www.live.com/>
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