Run several instances of the stack

[nvelozsavino]

In a pull request I added the option to use pipes instead of the default Tun/Tap interface, the whole idea was to be able to create the interface by another means. Suppose that you can create two pipes and instead of having an interface controlling the pipes, I have another program writing and reading to the pipes.
Now, imagine that you want to have several "instances" of this programs running, and all of this instances needs to have the same IP address and the programs redirects the traffic to the correct endpoint, now if I create several instance of the stack passing a specific pipes for each, then it seems to me that starting and stopping one instance will affect the others, also the sockets are shared between all interfaces.

How can this be solved?