MySQL Bugs: #60405: mysql_real_connect fails when trying to use shared memory

Bug #60405	mysql_real_connect fails when trying to use shared memory
Submitted:	9 Mar 2011 17:13	Modified:	22 Mar 2011 19:12
Reporter:	Attila Bódy	Email Updates:
Status:	Verified	Impact on me:	None
Category:	Connector / C	Severity:	S2 (Serious)
Version:	6.0.2	OS:	Windows (windows 7 enterprise N)
Assigned to:		CPU Architecture:	Any
Tags:	shared-memory

Description:
MySQL server configured to support shared memory connection, mysql "factroy" client connects without any problem using "--protocol=memory" option.

When we try to connect to the server using shared memory (either specifying "localhost" or NULL as host string and/or setting MYSQL_OPT_PROTOCOL to MYSQL_PROTOCOL_MEMORY calling mysql_options call mysql_real_connect fails, then mysql_error() returns "Lost connection to MySQL server at 'waiting for initial communication packet', system error: 0" message.
The connection builds up successfully (using TCP/IP) if we use 127.0.0.1 as host string (and not forcing the connection to use shared memory)

mysql_real_connect(m_mysql,"localhost",user,password,database,0,NULL,0) fails
mysql_real_connect(m_mysql,"127.0.0.1",user,password,database,3306,NULL,0) succeeds (using TCP/IP)

We experienced similar behavior when tried to connect using named pipe

How to repeat:
see description

Could you please provide your C test case?. Thanks in advance.

#include <winsock2.h>
#include <windows.h>
#include "mysql.h"

#pragma comment( lib, "libmysql" )

int _tmain(int argc, _TCHAR* argv[])
{
	MYSQL	*mysql( mysql_init( NULL ) );
	const char	*strerr;

	if( mysql_real_connect(
		mysql, "localhost",
		"user", "password",
		"testdb",
		0, NULL, 0
	) != mysql ) {
		strerr = mysql_error( mysql );
	}

	mysql_close( mysql );

	return 0;
}

the above fails with "Lost connection to MySQL server at 'waiting for initial communication packet', system error: 0" message.

if I replace "localhost" to "127.0.0.1" the connection succeeds (but uses TCP/IP)

Some additional info:
-----------------------------------------------------------------------------
C:\SDKs\MySQL Connector C 6.0.2 64bit\bin>mysql_client_test.exe --host=localhost
 --user=user --password=password

#####################################
client_connect
#####################################

 Establishing a connection to 'localhost' ...
 [MySQL][2013] Lost connection to MySQL server at 'waiting for initial communica
tion packet', system error: 2

 Check the connection options using --help or -?
-----------------------------------------------------------------------------
mysql --protocol=memory --user=user --password=password

still connects flawlessly anyway

If we run mysqld from the console (instead of running it as service), SHM connection builds up without any problem. Running as service under a real user account instead of localsystem, does not help .

Interesting.  Services running under 'localsystem' account have several restrictions.  For instance they cannot access shares using the mapped drive letter.

Did you try 'networkservice' account? No guarantee, but worth trying (and I believe it is what SQL Server does).

Peter
(not a MySQL person)

It cannot be started with networkservice user as it has no acces to files on the default install path. I tried two usert (created user MySQL just for this purpose which i made sure has rights for the necessary files) but there is no luck except we start mysqld using a cmd shell in the same session we try to connect via SHM.

Thank you for the bug report.

C:\DBS>5.1\bin\bug60405
Error: Lost connection to MySQL server at 'waiting for initial communication packet', system error: 0