net: a blocked Accept, Recv or Send on the host netdev does not return when the socket is closed #94

The host netdev uses blocking syscalls with SO_RCVTIMEO and SO_SNDTIMEO. A goroutine blocked in Accept, Recv or Send pins an OS thread and does not return when the socket is closed, so a graceful shutdown hangs instead of completing.

A deadline set while I/O is already in flight also has no effect until the next wakeup. net/http's abortPendingRead relies on that working, because it interrupts the server's background read by setting a past read deadline.

Non-blocking sockets with an epoll poller would fix both. PR #77 implements that.