src: Add vhost-user-net backend

Create vhost-user-net backend with Tap interface, to offload network
transaction from cloud-hypervisor. The goal is to provide flexibility
about the backend being in use, but also more security as it will allow
users to isolate the backend with different security profiles since it
will run as a dedicated process on the host.

Signed-off-by: Cathy Zhang <cathy.zhang@intel.com>
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>

net_util/src/tap.rs

@@ -49,6 +49,15 @@ impl PartialEq for Tap {
     }
 }
 
+impl std::clone::Clone for Tap {
+    fn clone(&self) -> Self {
+        Tap {
+            tap_file: self.tap_file.try_clone().unwrap(),
+            if_name: self.if_name,
+        }
+    }
+}
+
 // Returns a byte vector representing the contents of a null terminated C string which
 // contains if_name.
 fn build_terminated_if_name(if_name: &str) -> Result<Vec<u8>> {