ovsdb-idl: Return correct seqno from ovsdb_idl_db_set_condition().

If an IDL client sets the same monitor condition twice, the expected
seqno when the IDL contents are updated should be the same for both
calls.

In the following scenario:
1. Client calls ovsdb_idl_db_set_condition(db, table, cond1)
2. ovsdb_idl sends monitor_cond_change(cond1) but the server doesn't yet
   reply.
3. Client calls ovsdb_idl_db_set_condition(db, table, cond1)

At step 3 the returned expected seqno should be the same as at step 1.
Similarly, if step 2 is skipped, i.e., the client calls sets
the condition twice in the same iteration, then both
ovsdb_idl_db_set_condition() calls should return the same value.

Fixes: 46437c5 ("ovsdb-idl: Enhance conditional monitoring API")
Signed-off-by: Dumitru Ceara <[email protected]>
Signed-off-by: Ilya Maximets <[email protected]>

lib/ovsdb-idl.c

@@ -1564,7 +1564,6 @@ ovsdb_idl_db_set_condition(struct ovsdb_idl_db *db,
 {
     struct ovsdb_idl_condition *table_cond;
     struct ovsdb_idl_table *table = ovsdb_idl_db_table_from_class(db, tc);
-    unsigned int seqno = db->cond_seqno;
 
     /* Compare the new condition to the last known condition which can be
      * either "new" (not sent yet), "requested" or "acked", in this order.
@@ -1582,10 +1581,14 @@ ovsdb_idl_db_set_condition(struct ovsdb_idl_db *db,
         ovsdb_idl_condition_clone(&table->new_cond, condition);
         db->cond_changed = true;
         poll_immediate_wake();
-        return seqno + 1;
+        return db->cond_seqno + 1;
+    } else if (table_cond != table->ack_cond) {
+        /* 'condition' was already set but has not been "acked" yet.  The IDL
+         * will be up to date when db->cond_seqno gets incremented. */
+        return db->cond_seqno + 1;
     }
 
-    return seqno;
+    return db->cond_seqno;
 }
 
 /* Sets the replication condition for 'tc' in 'idl' to 'condition' and

tests/test-ovsdb.c

@@ -2407,6 +2407,10 @@ update_conditions(struct ovsdb_idl *idl, char *commands)
         if (seqno == next_seqno ) {
             ovs_fatal(0, "condition unchanged");
         }
+        unsigned int new_next_seqno = ovsdb_idl_set_condition(idl, tc, &cond);
+        if (next_seqno != new_next_seqno) {
+            ovs_fatal(0, "condition expected seqno changed");
+        }
         ovsdb_idl_condition_destroy(&cond);
         json_destroy(json);
     }