Bug#25679

"Federated Denial of Service"
  Federated storage engine used to attempt to open connections within
  the ::create() and ::open() methods which are invoked while LOCK_open
  mutex is being held by mysqld. As a result, no other client sessions
  can open tables while Federated is attempting to open a connection.
  Long DNS lookup times would stall mysqld's operation and a rogue
  connection string which connects to a remote server which simply
  stalls during handshake can stall mysqld for a much longer period of
  time.
  This patch moves the opening of the connection much later, when the
  federated actually issues queries, by which time the LOCK_open mutex is
  no longer being held.

mysql-test/t/federated.test

@@ -30,25 +30,28 @@ CREATE TABLE federated.t1 (
 
 # test non-existant table
 --replace_result $SLAVE_MYPORT SLAVE_PORT
---error 1434
 eval CREATE TABLE federated.t1 (
     `id` int(20) NOT NULL,
     `name` varchar(32) NOT NULL default ''
     )
   ENGINE="FEDERATED" DEFAULT CHARSET=latin1
   CONNECTION='mysql://root@127.0.0.1:$SLAVE_MYPORT/federated/t3';
+--error 1431
+SELECT * FROM federated.t1;
+DROP TABLE federated.t1;
 
 # test bad user/password 
 --replace_result $SLAVE_MYPORT SLAVE_PORT
---error 1429
 eval CREATE TABLE federated.t1 (
     `id` int(20) NOT NULL,
     `name` varchar(32) NOT NULL default ''
     )
   ENGINE="FEDERATED" DEFAULT CHARSET=latin1
   CONNECTION='mysql://user:pass@127.0.0.1:$SLAVE_MYPORT/federated/t1';
+--error 1429
+SELECT * FROM federated.t1;
+DROP TABLE federated.t1;
 
-DROP TABLE IF EXISTS federated.t1;
 # # correct connection, same named tables
 --replace_result $SLAVE_MYPORT SLAVE_PORT
 eval CREATE TABLE federated.t1 (