vmm: migration: abort receive on unexpected EOF while receiving memory

This cherry-pick is needed as the new approach doesn't send the
Request::abandon() anymore.

If the sender closes the connection while the receiver is reading
memory, e.g. after a canceled migration, read_volatile_from() returns
Ok(0). The receive loop treated this as a zero-progress read and spun
forever, leaving receive-migration (and thus the destination VMM's
API) hanging indefinitely.

Found by the migration cancellation integration tests.

On-behalf-of: SAP philipp.schuster@sap.com
Signed-off-by: Philipp Schuster <philipp.schuster@cyberus-technology.de>

Author: phip1611

vmm/src/migration/transport.rs

@@ -1167,6 +1167,13 @@ pub(crate) fn receive_memory_ranges(
                         "Error receiving memory from socket: {e}"
                     ))
                 })?;
+
+            // EOF: Don't spin forever on closed connection
+            if bytes_read == 0 {
+                return Err(MigratableError::MigrateReceive(anyhow!(
+                    "Connection closed while receiving memory: EOF"
+                )));
+            }
             offset += bytes_read as u64;
 
             if offset == range.length {