Added max_user_connections

BUILD/compile-pentium-debug

@@ -11,7 +11,8 @@ extra_configs="$pentium_configs $debug_configs"
 # Use the debug version if it exists
 if test -d /usr/local/BerkeleyDB-dbug/
 then
- extra_configs="$extra_configs --with-berkeley-db=/usr/local/BerkeleyDB-dbug/ --with-innobase"
+ extra_configs="$extra_configs --with-berkeley-db=/usr/local/BerkeleyDB-dbug/"
 fi
+extra_configs="$extra_configs --with-innobase"
 
 . "$path/FINISH.sh"

Docs/manual.texi

@@ -9579,6 +9579,7 @@ uses:
 
 @findex command-line options
 @cindex options, command-line
+@cindex mysqld options
 @node Command-line options, Option files, Automatic start, Post-installation
 @subsection Command-line Options
 
@@ -11522,6 +11523,11 @@ in the grant tables.  In principle, the @code{--secure} option to
 @code{mysqld} should make hostnames safe.  In any case, you should be very
 careful about creating grant table entries using hostname values that
 contain wild cards!
+
+@item
+If you want to restrict the number of connections for a single user, you
+can do this by setting the @code{max_user_connections} variable in
+@code{mysqld}.
 @end itemize
 
 @node Privileges options, What Privileges, Security, Privilege system
@@ -21048,6 +21054,9 @@ The number of bytes to use when sorting @code{BLOB} or @code{TEXT}
 values (only the first @code{max_sort_length} bytes of each value
 are used; the rest are ignored).
 
+@item @code{max_user_connections}
+The maximum number of active connections for a single user (0 = no limit).
+
 @item @code{max_tmp_tables}
 (This option doesn't yet do anything.)
 Maximum number of temporary tables a client can keep open at the same time.
@@ -41585,6 +41594,8 @@ not yet 100 % confident in this code.
 @appendixsubsec Changes in release 3.23.34
 @itemize @bullet
 @item
+Added option @code{max_user_connections} to @code{mysqld}.
+@item
 Limit query length for replication by max_allowed_packet, not the arbitrary
 limit of 4 MB
 @item

innobase/os/os0sync.c

@@ -19,14 +19,14 @@ Created 9/6/1995 Heikki Tuuri
 #include "ut0mem.h"
 
 /* Type definition for an operating system mutex struct */
-struct os_mutex_struct{ 
+struct os_mutex_struct{
 	void*		handle;	/* OS handle to mutex */
 	ulint		count;	/* we use this counter to check
 				that the same thread does not
 				recursively lock the mutex: we
 				do not assume that the OS mutex
 				supports recursive locking, though
-				NT seems to do that */				
+				NT seems to do that */
 };
 
 /*************************************************************
@@ -44,7 +44,7 @@ os_event_create(
 {
 #ifdef __WIN__
 	HANDLE	event;
-	
+
 	event = CreateEvent(NULL,	/* No security attributes */
 			TRUE,		/* Manual reset */
 			FALSE,		/* Initial state nonsignaled */
@@ -60,9 +60,9 @@ os_event_create(
 	event = ut_malloc(sizeof(struct os_event_struct));
 
 	os_fast_mutex_init(&(event->os_mutex));
-	os_fast_mutex_init(&(event->wait_mutex));
+	pthread_cond_init(&(event->cond_var), NULL);
 
-	event->is_set = TRUE;
+	event->is_set = FALSE;
 
 	return(event);
 #endif
@@ -108,7 +108,7 @@ os_event_set(
 /*=========*/
 	os_event_t	event)	/* in: event to set */
 {
-#ifdef __WIN__	
+#ifdef __WIN__
 	ut_a(event);
 	ut_a(SetEvent(event));
 #else
@@ -119,12 +119,12 @@ os_event_set(
 	if (event->is_set) {
 		/* Do nothing */
 	} else {
-		os_fast_mutex_unlock(&(event->wait_mutex));
 		event->is_set = TRUE;
+		pthread_cond_broadcast(&(event->cond_var));
 	}
 
 	os_fast_mutex_unlock(&(event->os_mutex));
-#endif		
+#endif
 }
 
 /**************************************************************
@@ -148,7 +148,6 @@ os_event_reset(
 	if (!event->is_set) {
 		/* Do nothing */
 	} else {
-		os_fast_mutex_lock(&(event->wait_mutex));
 		event->is_set = FALSE;
 	}
 
@@ -163,7 +162,7 @@ void
 os_event_free(
 /*==========*/
 	os_event_t	event)	/* in: event to free */
-	
+
 {
 #ifdef __WIN__
 	ut_a(event);
@@ -173,7 +172,7 @@ os_event_free(
 	ut_a(event);
 
 	os_fast_mutex_free(&(event->os_mutex));
-	os_fast_mutex_free(&(event->wait_mutex));
+	pthread_cond_destroy(&(event->cond_var));
 
 	ut_free(event);
 #endif
@@ -197,8 +196,22 @@ os_event_wait(
 
 	ut_a(err == WAIT_OBJECT_0);
 #else
-	os_fast_mutex_lock(&(event->wait_mutex));
+	os_fast_mutex_lock(&(event->os_mutex));
-	os_fast_mutex_unlock(&(event->wait_mutex));
+loop:
+	if (event->is_set == TRUE) {
+		os_fast_mutex_unlock(&(event->os_mutex));
+
+		/* Ok, we may return */
+
+		return;
+	}
+
+	pthread_cond_wait(&(event->cond_var), &(event->os_mutex));
+
+	/* Solaris manual said that spurious wakeups may occur: we have
+	to check the 'is_set' variable again */
+
+	goto loop;
 #endif
 }
 
@@ -225,7 +238,7 @@ os_event_wait_time(
 	} else {
 		err = WaitForSingleObject(event, INFINITE);
 	}
-	
+
 	if (err == WAIT_OBJECT_0) {
 
 		return(0);
@@ -237,7 +250,7 @@ os_event_wait_time(
 	}
 #else
 	UT_NOT_USED(time);
-	
+
 	/* In Posix this is just an ordinary, infinite wait */
 
 	os_event_wait(event);
@@ -277,7 +290,7 @@ os_event_wait_multiple(
 	return(index - WAIT_OBJECT_0);
 #else
 	ut_a(n == 0);
-	
+
 	/* In Posix we can only wait for a single event */
 
 	os_event_wait(*event_array);
@@ -318,7 +331,7 @@ os_mutex_create(
 	os_mutex_t		mutex_str;
 
 	UT_NOT_USED(name);
-	
+
 	os_mutex = ut_malloc(sizeof(os_fast_mutex_t));
 
 	os_fast_mutex_init(os_mutex);
@@ -329,7 +342,7 @@ os_mutex_create(
 	mutex_str->count = 0;
 
 	return(mutex_str);
-#endif	
+#endif
 }
 
 /**************************************************************
@@ -385,7 +398,7 @@ os_mutex_exit(
 	(mutex->count)--;
 
 	os_fast_mutex_unlock(mutex->handle);
-#endif	
+#endif
 }
 
 /**************************************************************
@@ -419,7 +432,7 @@ os_fast_mutex_init(
 {
 #ifdef __WIN__
 	ut_a(fast_mutex);
-	
+
 	InitializeCriticalSection((LPCRITICAL_SECTION) fast_mutex);
 #else
 	pthread_mutex_init(fast_mutex, NULL);

sql/mysql_priv.h

@@ -521,7 +521,7 @@ extern uint protocol_version,dropping_tables;
 extern ulong keybuff_size,sortbuff_size,max_item_sort_length,table_cache_size,
 	     max_join_size,join_buff_size,tmp_table_size,
 	     max_connections,max_connect_errors,long_query_time,
-	     max_insert_delayed_threads,
+	     max_insert_delayed_threads, max_user_connections,
 	     long_query_count,net_wait_timeout,net_interactive_timeout,
 	     net_read_timeout,net_write_timeout,
 	     what_to_log,flush_time,

sql/sql_parse.cc

@@ -22,6 +22,7 @@
 #include <thr_alarm.h>
 #include <myisam.h>
 #include <my_dir.h>
+#include <assert.h>
 
 #define SCRAMBLE_LENGTH 8
 
@@ -32,6 +33,9 @@ extern "C" pthread_mutex_t THR_LOCK_keycache;
 extern "C" int gethostname(char *name, int namelen);
 #endif
 
+static int check_for_max_user_connections(const char *user, int u_length,
+					  const char *host);
+static void decrease_user_connections(const char *user, const char *host);
 static bool check_table_access(THD *thd,uint want_access, TABLE_LIST *tables);
 static bool check_db_used(THD *thd,TABLE_LIST *tables);
 static bool check_merge_table_access(THD *thd, char *db, TABLE_LIST *tables);
@@ -145,13 +149,134 @@ static bool check_user(THD *thd,enum_server_command command, const char *user,
 		  thd->host ? thd->host : thd->ip ? thd->ip : "unknown ip",
 		  db ? db : (char*) "");
   thd->db_access=0;
+  if (max_user_connections &&
+      check_for_max_user_connections(user, strlen(user), thd->host))
+    return -1;
   if (db && db[0])
-    return test(mysql_change_db(thd,db));
+  {
+    bool error=test(mysql_change_db(thd,db));
+    if (error)
+      decrease_user_connections(user,thd->host);
+    return error;
+  }
   else
     send_ok(net);				// Ready to handle questions
   return 0;					// ok
 }
 
+/*
+** check for maximum allowable user connections
+** if mysql server is started with corresponding
+** variable that is greater then 0
+*/
+
+static HASH hash_user_connections;
+static DYNAMIC_ARRAY  user_conn_array;
+extern  pthread_mutex_t LOCK_user_conn;
+
+struct  user_conn {
+  char user[USERNAME_LENGTH+HOSTNAME_LENGTH+2];
+  int connections, len;
+};
+
+static byte* get_key_conn(user_conn *buff, uint *length,
+			  my_bool not_used __attribute__((unused)))
+{
+  *length=buff->len;
+  return (byte*) buff->user;
+}
+
+#define DEF_USER_COUNT 50
+
+void init_max_user_conn(void) 
+{
+  (void) hash_init(&hash_user_connections,DEF_USER_COUNT,0,0,
+		   (hash_get_key) get_key_conn,0, 0);
+  (void) init_dynamic_array(&user_conn_array,sizeof(user_conn),
+			    DEF_USER_COUNT, DEF_USER_COUNT);
+}
+
+
+static int check_for_max_user_connections(const char *user, int u_length,
+					  const char *host) 
+{
+  uint temp_len;
+  char temp_user[USERNAME_LENGTH+HOSTNAME_LENGTH+2];
+  struct  user_conn *uc;
+  if (!user)
+    user="";
+  if (!host)
+    host="";
+  temp_len= (uint) (strxnmov(temp_user, sizeof(temp_user), user, "@", host,
+			     NullS) - temp_user);
+  (void) pthread_mutex_lock(&LOCK_user_conn);
+  uc = (struct  user_conn *) hash_search(&hash_user_connections,
+					 (byte*) temp_user, temp_len);
+  if (uc) /* user found ; check for no. of connections */
+  {
+    if (max_user_connections ==  uc->connections) 
+    {
+      net_printf(&(current_thd->net),ER_TOO_MANY_USER_CONNECTIONS, temp_user);
+      pthread_mutex_unlock(&LOCK_user_conn);
+      return 1;
+    }
+    uc->connections++; 
+  }
+  else
+  {
+    /* the user is not found in the cache; Insert it */
+    struct user_conn uc;
+    memcpy(uc.user,temp_user,temp_len+1);
+    uc.len = temp_len;
+    uc.connections = 1;
+    if (!insert_dynamic(&user_conn_array, (char *) &uc))
+    {
+      hash_insert(&hash_user_connections,
+		  (byte *) dynamic_array_ptr(&user_conn_array,
+					     user_conn_array.elements - 1));
+    }
+  }
+  (void) pthread_mutex_unlock(&LOCK_user_conn);
+  return 0;
+}
+
+
+static void decrease_user_connections(const char *user, const char *host)
+{
+  char temp_user[USERNAME_LENGTH+HOSTNAME_LENGTH+2];
+  int temp_len;
+  struct user_conn uucc, *uc;
+  if (!user)
+    user="";
+  if (!host)
+    host="";
+  temp_len= (uint) (strxnmov(temp_user, sizeof(temp_user), user, "@", host,
+			     NullS) - temp_user);
+  (void) pthread_mutex_lock(&LOCK_user_conn);
+
+  uc = (struct  user_conn *) hash_search(&hash_user_connections,
+					 (byte*) temp_user, temp_len);
+  dbug_assert(uc != 0);			// We should always find the user
+  if (!uc)
+    goto end;				// Safety; Something went wrong
+  if (! --uc->connections)
+  {
+    /* Last connection for user; Delete it */
+    (void) hash_delete(&hash_user_connections,(char *) uc);
+    uint element= ((uint) ((byte*) uc - (byte*) user_conn_array.buffer) /
+		   user_conn_array.size_of_element);
+    delete_dynamic_element(&user_conn_array,element);
+  }
+end:
+  (void) pthread_mutex_unlock(&LOCK_user_conn);
+}
+
+void free_max_user_conn(void)
+{
+  delete_dynamic(&user_conn_array);
+  hash_free(&hash_user_connections);
+}
+
 
 /*
 ** check connnetion and get priviliges
@@ -417,6 +542,8 @@ pthread_handler_decl(handle_one_connection,arg)
       thread_safe_increment(aborted_threads,&LOCK_thread_count);
     }
 
+    if (max_user_connections)
+      decrease_user_connections(thd->user,thd->host);
 end_thread:
     close_connection(net);
     end_thread(thd,1);
@@ -512,7 +639,7 @@ int mysql_table_dump(THD* thd, char* db, char* tbl_name, int fd)
   DBUG_ENTER("mysql_table_dump");
   db = (db && db[0]) ? db : thd->db;
   if (!(table_list = (TABLE_LIST*) sql_calloc(sizeof(TABLE_LIST))))
-     DBUG_RETURN(1); // out of memory
+    DBUG_RETURN(1); // out of memory
   table_list->db = db;
   table_list->real_name = table_list->name = tbl_name;
   table_list->lock_type = TL_READ_NO_INSERT;
@@ -641,7 +768,7 @@ bool do_command(THD *thd)
       send_error(net, ER_UNKNOWN_COM_ERROR);
       break;
     }
-    if (check_user(thd, COM_CHANGE_USER, user, passwd, db,0))
+    if (check_user(thd, COM_CHANGE_USER, user, passwd, db, 0))
     {						// Restore old user
       x_free(thd->user);
       x_free(thd->db);
@@ -652,6 +779,7 @@ bool do_command(THD *thd)
       thd->priv_user=save_priv_user;
       break;
     }
+    decrease_user_connections (save_user, thd->host);
     x_free((gptr) save_db);
     x_free((gptr) save_user);
     thd->password=test(passwd[0]);