ReplayDetector is shared among multiple SSRCs

[at-wat]

srtp.Context is shared among multiple SSRCs, but roll over counter and replay detector must not be shared.
Shared ROC causes decryption failure when the difference of actual ROCs is more than 1.
(Packet rate of each stream can be different.)
And, replay detector causes false positive detection.

ref: pion/webrtc#1095 (comment)

[Sean-Der]

It has been a while since I have worked on this package, but rolloverCounter is a member of ssrcState. So maybe we just need to push the reploy detector into this as well?

[Sean-Der]

https://github.com/pion/srtp/blob/master/context.go#L43

[at-wat]

That's true. Thanks!

[Sean-Der]

One thing I do think we should do is get rid of all the stream stuff in this package, it was a bad design on my part :(

I would rather see demuxing in pion/rtp and a Session then we can do Congestion Control and JitterBuffer in there. I just have hit the second systems problem, just anxious to make mistakes when refactoring.

[at-wat]

I would rather see demuxing in pion/rtp and a Session then we can do Congestion Control and JitterBuffer in there.

That sounds better.
I think all of congestion controller, JitterBuffer, and also SRTP decoder can be represented as a kind of interceptor interface that input and output RTP packet.
https://github.com/pion/webrtc/wiki/PlanningV3/_compare/ff1af1c4ae536549a0355c0eb64236ada391c234