migration: Add a semaphore to count PONGs

This is mostly useless, but useful for us to know whether the main channel
is correctly established without changing the migration protocol.

Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>

1 files changed, 6 insertions, 0 deletions

diff --git a/migration/migration.h b/migration/migration.h
index c351872360..4cb1cb6fa8 100644
--- a/migration/migration.h
+++ b/migration/migration.h
@@ -276,6 +276,12 @@ struct MigrationState {
          */
         bool          rp_thread_created;
         QemuSemaphore rp_sem;
+        /*
+         * We post to this when we got one PONG from dest. So far it's an
+         * easy way to know the main channel has successfully established
+         * on dest QEMU.
+         */
+        QemuSemaphore rp_pong_acks;
     } rp_state;
 
     double mbps;