Bug #33831 mysql_real_connect() connects again if

           given an already connected MYSQL handle

mysql_real_connect() did not check whether the MYSQL connection
handler was already connected and connected again even if so. 
Now a CR_ALREADY_CONNECTED error is returned.

include/errmsg.h

@@ -97,6 +97,7 @@ extern const char *client_errors[];	/* Error messages */
 #define CR_SERVER_LOST_EXTENDED			2055
 #define CR_STMT_CLOSED				2056
 #define CR_NEW_STMT_METADATA                    2057
-#define CR_ERROR_LAST  /*Copy last error nr:*/  2057
+#define CR_ALREADY_CONNECTED                    2058
+#define CR_ERROR_LAST  /*Copy last error nr:*/  2058
 /* Add error numbers before CR_ERROR_LAST and change it accordingly. */
 

libmysql/errmsg.c

@@ -85,6 +85,7 @@ const char *client_errors[]=
   "Lost connection to MySQL server at '%s', system error: %d",
   "Statement closed indirectly because of a preceeding %s() call",
   "The number of columns in the result set differs from the number of bound buffers. You must reset the statement, rebind the result set columns, and execute the statement again",
+  "This handle is already connected. Use a separate handle for each connection."
   ""
 };
 
@@ -151,6 +152,7 @@ const char *client_errors[]=
   "Lost connection to MySQL server at '%s', system error: %d",
   "Statement closed indirectly because of a preceeding %s() call",
   "The number of columns in the result set differs from the number of bound buffers. You must reset the statement, rebind the result set columns, and execute the statement again",
+  "This handle is already connected. Use a separate handle for each connection."
   ""
 };
 
@@ -215,6 +217,7 @@ const char *client_errors[]=
   "Lost connection to MySQL server at '%s', system error: %d",
   "Statement closed indirectly because of a preceeding %s() call",
   "The number of columns in the result set differs from the number of bound buffers. You must reset the statement, rebind the result set columns, and execute the statement again",
+  "This handle is already connected. Use a separate handle for each connection."
   ""
 };
 #endif

libmysqld/libmysqld.c

@@ -28,6 +28,7 @@
 #include <sys/stat.h>
 #include <signal.h>
 #include <time.h>
+#include <sql_common.h>
 #include "client_settings.h"
 #ifdef	 HAVE_PWD_H
 #include <pwd.h>
@@ -77,17 +78,6 @@ static my_bool is_NT(void)
 }
 #endif
 
-/**************************************************************************
-** Shut down connection
-**************************************************************************/
-
-static void end_server(MYSQL *mysql)
-{
-  DBUG_ENTER("end_server");
-  free_old_query(mysql);
-  DBUG_VOID_RETURN;
-}
-
 
 int mysql_init_character_set(MYSQL *mysql);
 
@@ -104,6 +94,13 @@ mysql_real_connect(MYSQL *mysql,const char *host, const char *user,
 		      db ? db : "(Null)",
 		      user ? user : "(Null)"));
 
+  /* Test whether we're already connected */
+  if (mysql->server_version)
+  {
+    set_mysql_error(mysql, CR_ALREADY_CONNECTED, unknown_sqlstate);
+    DBUG_RETURN(0);
+  }
+
   if (!host || !host[0])
     host= mysql->options.host;
 
@@ -215,7 +212,7 @@ error:
   {
     /* Free alloced memory */
     my_bool free_me=mysql->free_me;
-    end_server(mysql);
+    free_old_query(mysql); 
     mysql->free_me=0;
     mysql_close(mysql);
     mysql->free_me=free_me;

sql-common/client.c

@@ -1919,6 +1919,13 @@ CLI_MYSQL_REAL_CONNECT(MYSQL *mysql,const char *host, const char *user,
 		      db ? db : "(Null)",
 		      user ? user : "(Null)"));
 
+  /* Test whether we're already connected */
+  if (net->vio)
+  {
+    set_mysql_error(mysql, CR_ALREADY_CONNECTED, unknown_sqlstate);
+    DBUG_RETURN(0);
+  }
+
   /* Don't give sigpipe errors if the client doesn't want them */
   set_sigpipe(mysql);
   mysql->methods= &client_methods;

tests/mysql_client_test.c

@@ -18026,6 +18026,49 @@ static void test_bug44495()
   DBUG_VOID_RETURN;
 }
 
+
+/**
+     Bug# 33831 mysql_real_connect() should fail if
+     given an already connected MYSQL handle.
+*/
+
+static void test_bug33831(void)
+{
+  MYSQL *l_mysql;
+  my_bool error;
+
+  DBUG_ENTER("test_bug33831");
+  
+  error= 0;
+
+  if (!(l_mysql= mysql_init(NULL)))
+  {
+    myerror("mysql_init() failed");
+    DIE_UNLESS(0);
+  }
+  if (!(mysql_real_connect(l_mysql, opt_host, opt_user,
+                           opt_password, current_db, opt_port,
+                           opt_unix_socket, 0)))
+  {
+    myerror("connection failed");
+    DIE_UNLESS(0);
+  }
+
+  if (mysql_real_connect(l_mysql, opt_host, opt_user,
+                         opt_password, current_db, opt_port,
+                         opt_unix_socket, 0))
+  {
+    myerror("connection should have failed");
+    DIE_UNLESS(0);
+  }
+
+
+  mysql_close(l_mysql);
+  
+  DBUG_VOID_RETURN;
+}
+
+
 /*
   Read and parse arguments and MySQL options from my.cnf
 */
@@ -18336,6 +18379,7 @@ static struct my_tests_st my_tests[]= {
   { "test_wl4166_1", test_wl4166_1 },
   { "test_wl4166_2", test_wl4166_2 },
   { "test_bug38486", test_bug38486 },
+  { "test_bug33831", test_bug33831 },
   { "test_bug40365", test_bug40365 },
   { "test_bug43560", test_bug43560 },
 #ifdef HAVE_QUERY_CACHE