vm-virtio: Create virtio-net device

In order to provide connectivity through network interface between
host and guest, this patch introduces the virtio-net backend.

This code is based on Firecracker commit
d4a89cdc0bd2867f821e3678328dabad6dd8b767

It is a trimmed down version of the original files as it removes the
rate limiter support. It has been ported to support vm-memory crate
and the epoll handler has been modified in order to run a dedicated
epoll loop from the device itself. This epoll loop runs in its own
dedicated thread.

Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>

vm-virtio/src/lib.rs

@@ -22,12 +22,14 @@ use std::io;
 
 mod block;
 mod device;
+pub mod net;
 mod queue;
 
 pub mod transport;
 
 pub use self::block::*;
 pub use self::device::*;
+pub use self::net::*;
 pub use self::queue::*;
 
 const DEVICE_INIT: u32 = 0x00;