vmm: funnel VM memory via additional connections abstraction

At this point, we are still only using a single connection.

On-behalf-of: SAP sebastian.eydam@sap.com
Signed-off-by: Sebastian Eydam <sebastian.eydam@cyberus-technology.de>

vmm/src/migration_transport.rs

@@ -72,6 +72,22 @@ impl ReceiveListener {
             Ok(None)
         }
     }
+
+    /// Tries to clone a [`ReceiveListener`].
+    pub(crate) fn try_clone(&self) -> Result<Self, MigratableError> {
+        match self {
+            ReceiveListener::Tcp(listener) => listener
+                .try_clone()
+                .map(ReceiveListener::Tcp)
+                .context("Failed to clone TCP listener")
+                .map_err(MigratableError::MigrateReceive),
+            ReceiveListener::Unix(listener) => listener
+                .try_clone()
+                .map(ReceiveListener::Unix)
+                .context("Failed to clone Unix listener")
+                .map_err(MigratableError::MigrateReceive),
+        }
+    }
 }
 
 impl AsFd for ReceiveListener {