connections leaks of tcpdump plugin

[Vlad Lesin]

Tcpdump plugin breaks connection with server only when it meets FIN/RST packets in input file during parsing. But that packets can be dropped by tcpdump during capturing what can lead to connection leaks during playback.

There may be several ways to solve this problem.

The first we could throttle the interface during capturing to avoid packets dropping. I don't think it's a good idea because capturing will influent on production workload. But we could implement it as an option which would be helpful for certain cases.

The next solution is to manage connections inside the tool. For example we could use some kind of LRU algorithm. We could have the limit for connections count and if that limit was reached we could release last recently used connection to create new one. This would make some small additional workload but I think it isn't so important.