Add exception handlers when the net interface goes down

[dugdmitry]

When the network interface (eth0, wlan0, etc.) where a routing daemon is attached to, is going down, due to either system call or physical detach - the socket.send/recv calls crash.
Need to implement exception handlers in such cases - for example, when a net interface goes down - just don't send/recv anything during that moment.
When the net interface goes up again - reattach/rebind the socket.