MDEV-8313 Got an error writing communication packets

Don't let network errors from mysql_close() leak into THD.

* remove incorrect upstream fix
** table->in_use can be NULL, must use ha_thd()
** clear_error() may remove earlier errors, don't use it
* fix the bug properly in federated and federatedx

mysql-test/suite/federated/error_on_close-8313.result

+CREATE DATABASE federated;
+CREATE DATABASE federated;
+connection slave;
+create table t1 (foo int, bar int);
+connection master;
+create server 's1' foreign data wrapper 'mysql' options
+(HOST 'localhost',
+DATABASE 'test',
+USER 'root',
+PASSWORD '',
+SOCKET 'SLAVE_MYSOCK');
+create table t1 (foo integer, bar integer) engine=federated
+connection='s1';
+select * from t1;
+foo	bar
+connection slave;
+connection master;
+drop table t1;
+drop server s1;
+connection slave;
+drop table t1;
+connection master;
+DROP TABLE IF EXISTS federated.t1;
+DROP DATABASE IF EXISTS federated;
+connection slave;
+DROP TABLE IF EXISTS federated.t1;
+DROP DATABASE IF EXISTS federated;

mysql-test/suite/federated/error_on_close-8313.test

+#
+# MDEV-8313 Got an error writing communication packets
+#
+source include/federated.inc;
+
+enable_connect_log;
+
+connection slave;
+create table t1 (foo int, bar int);
+
+connection master;
+
+--replace_result $SLAVE_MYSOCK SLAVE_MYSOCK
+eval create server 's1' foreign data wrapper 'mysql' options
+  (HOST 'localhost',
+  DATABASE 'test',
+  USER 'root',
+  PASSWORD '',
+  SOCKET '$SLAVE_MYSOCK');
+
+
+eval create table t1 (foo integer, bar integer) engine=federated
+  connection='s1';
+
+select * from t1;
+
+connection slave;
+source include/restart_mysqld.inc;
+
+connection master;
+drop table t1;
+drop server s1;
+
+connection slave;
+drop table t1;
+
+source include/federated_cleanup.inc;
+

storage/federated/ha_federated.cc

@@ -1662,6 +1662,20 @@ int ha_federated::open(const char *name, int mode, uint test_if_locked)
   DBUG_RETURN(0);
 }
 
+class Net_error_handler : public Internal_error_handler
+{
+public:
+  Net_error_handler() {}
+
+public:
+  bool handle_condition(THD *thd, uint sql_errno, const char* sqlstate,
+                        MYSQL_ERROR::enum_warning_level level,
+                        const char* msg, MYSQL_ERROR ** cond_hdl)
+  {
+    return sql_errno >= ER_ABORTING_CONNECTION &&
+           sql_errno <= ER_NET_WRITE_INTERRUPTED;
+  }
+};
 
 /*
   Closes a table. We call the free_share() function to free any resources
@@ -1683,18 +1697,15 @@ int ha_federated::close(void)
   delete_dynamic(&results);
 
   /* Disconnect from mysql */
+  THD *thd= ha_thd();
+  Net_error_handler err_handler;
+  if (thd)
+    thd->push_internal_handler(&err_handler);
   mysql_close(mysql);
-  mysql= NULL;
+  if (thd)
+    thd->pop_internal_handler();
 
-  /*
-    mysql_close() might return an error if a remote server's gone
-    for some reason. If that happens while removing a table from
-    the table cache, the error will be propagated to a client even
-    if the original query was not issued against the FEDERATED table.
-    So, don't propagate errors from mysql_close().
-  */
-  if (table->in_use)
-    table->in_use->clear_error();
+  mysql= NULL;
 
   DBUG_RETURN(free_share(share));
 }

storage/federatedx/ha_federatedx.cc

@@ -1795,6 +1795,20 @@ int ha_federatedx::open(const char *name, int mode, uint test_if_locked)
   DBUG_RETURN(0);
 }
 
+class Net_error_handler : public Internal_error_handler
+{
+public:
+  Net_error_handler() {}
+
+public:
+  bool handle_condition(THD *thd, uint sql_errno, const char* sqlstate,
+                        MYSQL_ERROR::enum_warning_level level,
+                        const char* msg, MYSQL_ERROR ** cond_hdl)
+  {
+    return sql_errno >= ER_ABORTING_CONNECTION &&
+           sql_errno <= ER_NET_WRITE_INTERRUPTED;
+  }
+};
 
 /*
   Closes a table. We call the free_share() function to free any resources
@@ -1825,7 +1839,12 @@ int ha_federatedx::close(void)
   txn->release(&io);
   DBUG_ASSERT(io == NULL);
 
+  Net_error_handler err_handler;
+  if (thd)
+    thd->push_internal_handler(&err_handler);
   free_share(txn, share);
+  if (thd)
+    thd->pop_internal_handler();
 
   DBUG_RETURN(retval);
 }