MDEV-31608 - Connector/NET fails to connect since 10.10

Connector/NET does not expect collation IDs returned by "show collations"
to be NULL, runs into an exception.

The fix is to determine connector/net using its connection attributes,
then make sure "show collations" does not output NULL IDs.

The patch introduces new old_mode NO_NULL_COLLATION_IDs, that is
automatically set, once MySQL Connector/NET connection is determined.

A test was added, that uses MySql.Data from powershell - only works
if MySql.Data is installed into GAC (i.e with C/NET MSI package)

mysql-test/main/mysql_connector_net.ps1

+$assembly = [system.reflection.Assembly]::LoadWithPartialName("MySql.Data")
+if ($assembly -eq $null)
+{
+  "Can't load assembly MySql.Data"
+  exit 100
+}
+
+try
+{
+  $connectionString =[string]::Format("server=127.0.0.1;uid=root;port={0};Connection Reset=true;",$Env:MASTER_MYPORT)
+  $connection = [MySql.Data.MySqlClient.MySqlConnection]@{ConnectionString=$connectionString}
+  $connection.Open()
+
+  # Test ExecuteReader()
+  $command = New-Object MySql.Data.MySqlClient.MySqlCommand
+  $command.Connection = $connection
+  $command.CommandText = "SELECT @@old_mode"
+  $reader = $command.ExecuteReader()
+  $reader.GetName(0)
+  while ($reader.Read())
+  {
+    $reader.GetValue(0)
+  }
+
+  # Test connection reset
+  $connection.Close()
+  $connection.Open()
+  # Test ExecuteNonQuery()
+  $command.CommandText="do 1";
+  $affected_rows = $command.ExecuteNonQuery()
+  if ($affected_rows -ne 0)
+  {
+    "Expected affected rows 0, actual $affected_rows"
+    exit 1
+  }
+  # Test Prepared Statement
+  $command.CommandText = "SELECT @var";
+  [void]$command.Parameters.AddWithValue("@var", 1);
+  $command.Prepare();
+  $out = $command.ExecuteScalar();
+  if ($out -ne 1)
+  {
+    "Expected output 1, actual $out"
+    exit 1
+  }
+  $connection.Close()
+}
+catch
+{
+  # Dump exception
+  $_
+  $inner = $PSItem.Exception.InnerException
+  if ($inner -ne  $null)
+  {
+    $PSItem.Exception.InnerException.Message
+    $PSItem.Exception.InnerException.StackTrace
+  }
+}

mysql-test/main/mysql_connector_net.result

+@@old_mode
+UTF8_IS_UTF8MB3,NO_NULL_COLLATION_IDS

mysql-test/main/mysql_connector_net.test

+--source include/windows.inc
+let $sys_errno=0;
+
+# Error 100 is returned by the powershell script
+# if MySql.Data is not installed
+--error 0,100
+--exec powershell -NoLogo -NoProfile -File main\mysql_connector_net.ps1
+if ($sys_errno != 0)
+{
+  --skip Connector/NET is not installed
+}

mysql-test/main/mysqld--help,win.rdiff

-@@ -180,6 +180,7 @@
+--- main/mysqld--help.result	2023-11-30 02:21:51.951132200 +0100
++++ main/mysqld--help,win.reject	2023-11-30 02:35:44.404612300 +0100
+@@ -191,6 +191,7 @@
   --console           Write error output on screen; don't remove the console
   window on windows.
   --core-file         Write core on crashes
@@ -6,7 +8,7 @@
   -h, --datadir=name  Path to the database root directory
   --date-format=name  The DATE format (ignored)
   --datetime-format=name 
-@@ -650,6 +651,7 @@
+@@ -696,6 +697,7 @@
   Use MySQL-5.6 (instead of MariaDB-5.3) format for TIME,
   DATETIME, TIMESTAMP columns.
   (Defaults to on; use --skip-mysql56-temporal-format to disable.)
@@ -14,7 +16,7 @@
   --net-buffer-length=# 
   Buffer length for TCP/IP and socket communication
   --net-read-timeout=# 
-@@ -1327,6 +1328,10 @@
+@@ -1351,6 +1353,10 @@
   Alias for log_slow_query_file. Log slow queries to given
   log file. Defaults logging to 'hostname'-slow.log. Must
   be enabled to activate other slow log options
@@ -25,7 +27,7 @@
   --socket=name       Socket file to use for connection
   --sort-buffer-size=# 
   Each thread that needs to do a sort allocates a buffer of
-@@ -1351,6 +1356,7 @@
+@@ -1376,6 +1382,7 @@
   deleting or updating every row in a table.
   --stack-trace       Print a symbolic stack trace on failure
   (Defaults to on; use --skip-stack-trace to disable.)
@@ -33,7 +35,7 @@
   --standard-compliant-cte 
   Allow only CTEs compliant to SQL standard
   (Defaults to on; use --skip-standard-compliant-cte to disable.)
-@@ -1426,6 +1432,11 @@
+@@ -1454,6 +1461,11 @@
   --thread-pool-max-threads=# 
   Maximum allowed number of worker threads in the thread
   pool
@@ -45,7 +47,7 @@
   --thread-pool-oversubscribe=# 
   How many additional active worker threads in a group are
   allowed.
-@@ -1464,8 +1475,8 @@
+@@ -1493,8 +1505,8 @@
   automatically convert it to an on-disk MyISAM or Aria
   table.
   -t, --tmpdir=name   Path for temporary files. Several paths may be specified,
@@ -56,7 +58,7 @@
   --transaction-alloc-block-size=# 
   Allocation block size for transactions to be stored in
   binary log
-@@ -1685,6 +1696,7 @@
+@@ -1716,6 +1728,7 @@
  myisam-stats-method NULLS_UNEQUAL
  myisam-use-mmap FALSE
  mysql56-temporal-format TRUE
@@ -64,7 +66,7 @@
  net-buffer-length 16384
  net-read-timeout 30
  net-retry-count 10
-@@ -1841,6 +1853,7 @@
+@@ -1874,6 +1887,7 @@
  slave-type-conversions 
  slow-launch-time 2
  slow-query-log FALSE
@@ -72,7 +74,7 @@
  sort-buffer-size 2097152
  sql-mode STRICT_TRANS_TABLES,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION
  sql-safe-updates FALSE
-@@ -1867,6 +1880,8 @@
+@@ -1901,6 +1915,8 @@
  thread-pool-exact-stats FALSE
  thread-pool-idle-timeout 60
  thread-pool-max-threads 65536

mysql-test/main/mysqld--help.result

@@ -721,7 +721,8 @@ The following specify which files/extra groups are read (specified before remain
  MySQL versions. Any combination of: 
  NO_DUP_KEY_WARNINGS_WITH_IGNORE, NO_PROGRESS_INFO, 
  ZERO_DATE_TIME_CAST, UTF8_IS_UTF8MB3, 
- IGNORE_INDEX_ONLY_FOR_JOIN, COMPAT_5_1_CHECKSUM
+ IGNORE_INDEX_ONLY_FOR_JOIN, COMPAT_5_1_CHECKSUM, 
+ NO_NULL_COLLATION_IDS
  Use 'ALL' to set all combinations.
  --old-passwords     Use old password encryption method (needed for 4.0 and
  older clients)

mysql-test/main/old-mode.result

@@ -257,3 +257,13 @@ Warning	1264	Out of range value for column 'a' at row 2
 DROP TABLE t1;
 SET @@time_zone=DEFAULT;
 SET TIMESTAMP=DEFAULT;
+#
+# MDEV-31608 - Connector/NET fails to connect since 10.10
+#
+select count(*) > 0 from information_schema.collations where id IS NULL;
+count(*) > 0
+1
+SET old_mode=no_null_collation_ids;
+select count(*) > 0 from information_schema.collations where id IS NULL;
+count(*) > 0
+0

mysql-test/main/old-mode.test

@@ -169,3 +169,11 @@ DROP TABLE t1;
 
 SET @@time_zone=DEFAULT;
 SET TIMESTAMP=DEFAULT;
+
+--echo #
+--echo # MDEV-31608 - Connector/NET fails to connect since 10.10
+--echo #
+select count(*) > 0 from information_schema.collations where id IS NULL;
+SET old_mode=no_null_collation_ids;
+select count(*) > 0 from information_schema.collations where id IS NULL;
+

mysql-test/suite/sys_vars/r/old_mode_basic.result

@@ -114,8 +114,8 @@ SET @@global.old_mode = 4;
 SELECT @@global.old_mode;
 @@global.old_mode
 ZERO_DATE_TIME_CAST
-SET @@global.old_mode = 64;
-ERROR 42000: Variable 'old_mode' can't be set to the value of '64'
+SET @@global.old_mode = 128;
+ERROR 42000: Variable 'old_mode' can't be set to the value of '128'
 SELECT @@global.old_mode;
 @@global.old_mode
 ZERO_DATE_TIME_CAST

mysql-test/suite/sys_vars/r/sysvars_server_embedded.result

@@ -2299,7 +2299,7 @@ VARIABLE_COMMENT	Used to emulate old behavior from earlier MariaDB or MySQL vers
 NUMERIC_MIN_VALUE	NULL
 NUMERIC_MAX_VALUE	NULL
 NUMERIC_BLOCK_SIZE	NULL
-ENUM_VALUE_LIST	NO_DUP_KEY_WARNINGS_WITH_IGNORE,NO_PROGRESS_INFO,ZERO_DATE_TIME_CAST,UTF8_IS_UTF8MB3,IGNORE_INDEX_ONLY_FOR_JOIN,COMPAT_5_1_CHECKSUM
+ENUM_VALUE_LIST	NO_DUP_KEY_WARNINGS_WITH_IGNORE,NO_PROGRESS_INFO,ZERO_DATE_TIME_CAST,UTF8_IS_UTF8MB3,IGNORE_INDEX_ONLY_FOR_JOIN,COMPAT_5_1_CHECKSUM,NO_NULL_COLLATION_IDS
 READ_ONLY	NO
 COMMAND_LINE_ARGUMENT	REQUIRED
 VARIABLE_NAME	OLD_PASSWORDS

mysql-test/suite/sys_vars/r/sysvars_server_notembedded.result

@@ -2469,7 +2469,7 @@ VARIABLE_COMMENT	Used to emulate old behavior from earlier MariaDB or MySQL vers
 NUMERIC_MIN_VALUE	NULL
 NUMERIC_MAX_VALUE	NULL
 NUMERIC_BLOCK_SIZE	NULL
-ENUM_VALUE_LIST	NO_DUP_KEY_WARNINGS_WITH_IGNORE,NO_PROGRESS_INFO,ZERO_DATE_TIME_CAST,UTF8_IS_UTF8MB3,IGNORE_INDEX_ONLY_FOR_JOIN,COMPAT_5_1_CHECKSUM
+ENUM_VALUE_LIST	NO_DUP_KEY_WARNINGS_WITH_IGNORE,NO_PROGRESS_INFO,ZERO_DATE_TIME_CAST,UTF8_IS_UTF8MB3,IGNORE_INDEX_ONLY_FOR_JOIN,COMPAT_5_1_CHECKSUM,NO_NULL_COLLATION_IDS
 READ_ONLY	NO
 COMMAND_LINE_ARGUMENT	REQUIRED
 VARIABLE_NAME	OLD_PASSWORDS

mysql-test/suite/sys_vars/t/old_mode_basic.test

@@ -172,7 +172,7 @@ SET @@global.old_mode = 4;
 SELECT @@global.old_mode;
 
 --Error ER_WRONG_VALUE_FOR_VAR
-SET @@global.old_mode = 64;
+SET @@global.old_mode = 128;
 SELECT @@global.old_mode;
 
 # use of decimal values

sql/sql_acl.cc

@@ -13576,8 +13576,37 @@ static bool find_mpvio_user(MPVIO_EXT *mpvio)
   DBUG_RETURN(0);
 }
 
+
+/**
+  Determine if the client is MySQL Connector/NET.
+
+  Checks whether the given connection attributes blob corresponds to
+  MySQL Connector/NET by examining the "_client_name" attribute, which is
+  expected to be the first attribute in the blob.
+
+  @param connection_attrs - The connection attributes blob.
+  @param length - The length of the blob.
+
+  @return true if the client is MySQL Connector/NET, false otherwise.
+*/
+static inline bool is_connector_net_client(const char *connection_attrs,
+                                           size_t length)
+{
+  constexpr LEX_CSTRING prefix=
+    {STRING_WITH_LEN("\x0c_client_name\x13mysql-connector-net")};
+
+  if (length < prefix.length)
+    return false;
+
+  /* Optimization to avoid following memcmp in common cases.*/
+  if (connection_attrs[prefix.length - 1] != prefix.str[prefix.length - 1])
+    return false;
+
+  return !memcmp(connection_attrs, prefix.str, prefix.length);
+}
+
 static bool
-read_client_connect_attrs(char **ptr, char *end, CHARSET_INFO *from_cs)
+read_client_connect_attrs(char **ptr, char *end, THD* thd)
 {
   ulonglong length;
   char *ptr_save= *ptr;
@@ -13600,10 +13629,14 @@ read_client_connect_attrs(char **ptr, char *end, CHARSET_INFO *from_cs)
   if (length > 65535)
     return true;
 
-  if (PSI_CALL_set_thread_connect_attrs(*ptr, (uint)length, from_cs) &&
+  if (PSI_CALL_set_thread_connect_attrs(*ptr, (uint)length, thd->charset()) &&
       current_thd->variables.log_warnings)
     sql_print_warning("Connection attributes of length %llu were truncated",
                       length);
+
+  /* Connector/Net crashes, when "show collations" returns NULL IDs*/
+  if (is_connector_net_client(*ptr, length))
+    thd->variables.old_behavior |= OLD_MODE_NO_NULL_COLLATION_IDS;
   return false;
 }
 
@@ -13737,7 +13770,7 @@ static bool parse_com_change_user_packet(MPVIO_EXT *mpvio, uint packet_length)
   }
 
   if ((thd->client_capabilities & CLIENT_CONNECT_ATTRS) &&
-      read_client_connect_attrs(&next_field, end, thd->charset()))
+      read_client_connect_attrs(&next_field, end, thd))
   {
     my_message(ER_UNKNOWN_COM_ERROR, ER_THD(thd, ER_UNKNOWN_COM_ERROR),
                MYF(0));
@@ -13987,7 +14020,7 @@ static ulong parse_client_handshake_packet(MPVIO_EXT *mpvio,
 
   if ((thd->client_capabilities & CLIENT_CONNECT_ATTRS) &&
       read_client_connect_attrs(&next_field, ((char *)net->read_pos) + pkt_len,
-                                mpvio->auth_info.thd->charset()))
+                                mpvio->auth_info.thd))
     return packet_error;
 
   /*

sql/sql_class.h

@@ -201,6 +201,7 @@ enum enum_binlog_row_image {
 #define OLD_MODE_UTF8_IS_UTF8MB3      (1 << 3)
 #define OLD_MODE_IGNORE_INDEX_ONLY_FOR_JOIN          (1 << 4)
 #define OLD_MODE_COMPAT_5_1_CHECKSUM    (1 << 5)
+#define OLD_MODE_NO_NULL_COLLATION_IDS  (1 << 6)
 
 extern char internal_table_name[2];
 extern char empty_c_string[1];

sql/sql_show.cc

@@ -6398,7 +6398,8 @@ int fill_schema_collation(THD *thd, TABLE_LIST *tables, COND *cond)
           tmp_cl->get_collation_name(MY_COLLATION_NAME_MODE_CONTEXT);
         LEX_CSTRING full_collation_name=
           tmp_cl->get_collation_name(MY_COLLATION_NAME_MODE_FULL);
-        bool is_context= cmp(context_collation_name, full_collation_name);
+        bool is_context= cmp(context_collation_name, full_collation_name) &&
+            !(thd->variables.old_behavior & OLD_MODE_NO_NULL_COLLATION_IDS);
         /*
           Some collations are applicable to multiple character sets.
           Display them only once, with the short name (without the

sql/sys_vars.cc

@@ -3886,6 +3886,7 @@ static const char *old_mode_names[]=
   "UTF8_IS_UTF8MB3",
   "IGNORE_INDEX_ONLY_FOR_JOIN",
   "COMPAT_5_1_CHECKSUM",
+  "NO_NULL_COLLATION_IDS",
   0
 };