SASL(-4): no mechanism available

[Robin SP Zhang <RobinZhang@pek.destiny.com.cn>]

Hi,
      I want to use TLS to connect to LDAP server, but it failed.
the debug info is

...
TLS trace: SSL_connect:SSLv3 read finished A
ldap_interactive_sasl_bind_s: user selected: EXTERNAL
ldap_int_sasl_bind: EXTERNAL
SASL/EXTERNAL authentication started
ldap_perror
ldap_sasl_interactive_bind_s: Unknown authentication method (86)
        additional info: SASL(-4): no mechanism available:

I traced the routine, and found that it is failed because  auth_id of
external
is NULL, auth_id seems come from certificate, then I found that 
SSL_get_certificate return NULL in tls.c, so I doubted that
my configuration about TLS client has some error.
I configure it in ldap.conf as
 
TLS_CACERT 		E:\\OpenLDAP\\SYSCONF\\server.pem
SASL_SECPROPS none

Is it right ? or I created a wrong certificate? 

thanks

Best Regards,
Robin Zhang
BNC,#538,