flow, repair: Wait for a short while for passt-repair to connect

...and time out after that. This will be needed because of an upcoming
change to passt-repair enabling it to start before passt is started,
on both source and target, by means of an inotify watch.

Once the inotify watch triggers, passt-repair will connect right away,
but we have no guarantees that the connection completes before we
start the migration process, so wait for it (for a reasonable amount
of time).

Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
(cherry picked from commit c8b520c062)

flow.c

@@ -930,6 +930,22 @@ static int flow_migrate_source_rollback(struct ctx *c, unsigned max_flow,
 	return ret;
 }
 
+/**
+ * flow_migrate_need_repair() - Do we need to set repair mode for any flow?
+ *
+ * Return: true if repair mode is needed, false otherwise
+ */
+static bool flow_migrate_need_repair(void)
+{
+	union flow *flow;
+	unsigned i;
+
+	foreach_established_tcp_flow(i, flow, FLOW_MAX)
+		return true;
+
+	return false;
+}
+
 /**
  * flow_migrate_repair_all() - Turn repair mode on or off for all flows
  * @c:		Execution context
@@ -985,6 +1001,9 @@ int flow_migrate_source_pre(struct ctx *c, const struct migrate_stage *stage,
 	(void)stage;
 	(void)fd;
 
+	if (flow_migrate_need_repair())
+		repair_wait(c);
+
 	if ((rc = flow_migrate_repair_all(c, true)))
 		return -rc;
 
@@ -1101,6 +1120,8 @@ int flow_migrate_target(struct ctx *c, const struct migrate_stage *stage,
 	if (!count)
 		return 0;
 
+	repair_wait(c);
+
 	if ((rc = flow_migrate_repair_all(c, true)))
 		return -rc;