Implementing connection tracking in userspace?

Question

Programming

The task is next.
It is necessary to analyze the passing traffic, and drop packets according to some rules, say with the Skype protocol.
There are no problems with the analysis of the protocol.
The question arises of how to store the result, and if stored, then how much, and even so that there is enough memory, and if there are a lot of small connections.
In general, connection tracking suggests itself, which is implemented in kernel linux (netfilter), because will allow you to delete the connection that has closed in time, and once again not analyze the traffic if the protocol is already known.
Actually, the question is, maybe someone has seen / knows some implementations of this very connection tracking in order to use it in the userspace application, otherwise you really don’t want to pick it out of netfilter.
PS: I can't use core connections. packets are processed before entering the kernel.