Section (3) ldap_dup
ldap_dup, ldap_destroy — Duplicate and destroy LDAP session handles
ldap_dup() duplicates an
existing LDAP (LDAP *)
session handle. The new session handle may be used
concurrently with the original session handle. In a threaded
environment, different threads may execute concurrent
requests on the same connection/session without fear of
contamination. Each session handle manages its own private
ldap_destroy() destroys an
existing session handle.
ldap_destroy() functions are
used in conjunction with a thread safe version of
libldap_r) to enable operation thread safe
API calls, so that a single session may be simultaneously
used across multiple threads with consistent error
When a session is created through the use of one of the session creation functions including ldap_open(3), ldap_init(3), ldap_initialize(3) or ldap_init_fd(3) an LDAP * session handle is returned to the application. The session handle may be shared amongst threads, however the error codes are unique to a session handle. Multiple threads performing different operations using the same session handle will result in inconsistent error codes and return values.
To prevent this confusion,
ldap_dup() is used duplicate an existing
session handle so that multiple threads can share the
session, and maintain consistent error information and
The message queues for a session are shared between
sibling session handles. Results of operations on a sibling
session handles are accessible to all the sibling session
handles. Applications desiring results associated with a
specific operation should provide the appropriate msgid to
Applications should avoid calling
LDAP_RES_ANY as that may steal and return
results in the calling thread that another operation in a
different thread, using a different session handle, may
require to complete.
ldap_unbind() is called
on a session handle with siblings, all the siblings become
Siblings must be destroyed using
handle resources associated with the original (LDAP *) will be freed when the
last session handle is destroyed or when
ldap_unbind() is called, if no other
session handles currently exist.
If an error occurs,
ldap_dup() will return NULL and
errno should be set
will directly return the LDAP code associated to the error
LDAP_SUCCESS in case of
errno should be set as
well whenever appropriate.
This work is based on the previously proposed LDAP C API Concurrency Extensions
Software is developed and maintained by The
OpenLDAP Project <http://www.openldap.org/>. OpenLDAP Software is derived from
the University of Michigan LDAP 3.3 Release.