LDAP_OPEN(3) OpenLDAP LDVERSION LDAP_OPEN(3)
RELEASEDATE
NAME
ldap_init, ldap_initialize, ldap_open - Initialize the LDAP library
and open a connection to an LDAP server
LIBRARY
OpenLDAP LDAP (libldap, -lldap)
SYNOPSIS
#include <ldap.h>
LDAP *ldap_open(host, port)
char *host;
int port;
LDAP *ldap_init(host, port)
char *host;
int port;
int ldap_initialize(ldp, uri)
LDAP **ldp;
char *uri;
int ldap_set_urllist_proc(ld, proc, params)
LDAP *ld;
LDAP_URLLIST_PROC *proc;
void *params;
int (LDAP_URLLIST_PROC)(ld, urllist, url, params);
LDAP *ld;
LDAPURLDesc **urllist;
LDAPURLDesc **url;
void *params;
#include <ldap_pvt.h>
int ldap_init_fd(fd, proto, uri, ldp)
ber_socket_t fd;
int proto;
char *uri;
LDAP **ldp;
DESCRIPTION
ldap_open() opens a connection to an LDAP server and allocates an LDAP
structure which is used to identify the connection and to maintain
per-connection information. ldap_init() allocates an LDAP structure
but does not open an initial connection. ldap_initialize() allocates
an LDAP structure but does not open an initial connection.
ldap_init_fd() allocates an LDAP structure using an existing
connection on the provided socket. One of these routines must be
called before any operations are attempted. ldap_open() takes host,
the hostname on which the LDAP server is running, and port, the port
number to which to connect. If the default IANA-assigned port of 389
is desired, LDAP_PORT should be specified for port. The host
parameter may contain a blank-separated list of hosts to try to
connect to, and each host may optionally by of the form host:port. If
present, the :port overrides the port parameter to ldap_open(). Upon
successfully making a connection to an LDAP server, ldap_open()
returns a pointer to an opaque LDAP structure, which should be passed
- 1 - Formatted: December 16, 2025
LDAP_OPEN(3) OpenLDAP LDVERSION LDAP_OPEN(3)
RELEASEDATE
to subsequent calls to ldap_bind(), ldap_search(), etc. Certain fields
in the LDAP structure can be set to indicate size limit, time limit,
and how aliases are handled during operations; read and write access
to those fields must occur by calling ldap_get_option(3) and
ldap_set_option(3) respectively, whenever possible. ldap_init() acts
just like ldap_open(), but does not open a connection to the LDAP
server. The actual connection open will occur when the first
operation is attempted. ldap_initialize() acts like ldap_init(), but
it returns an integer indicating either success or the failure reason,
and it allows to specify details for the connection in the schema
portion of the URI. The uri parameter may be a comma- or whitespace-
separated list of URIs containing only the schema, the host, and the
port fields. Apart from ldap, other (non-standard) recognized values
of the schema field are ldaps (LDAP over TLS), ldapi (LDAP over IPC),
and cldap (connectionless LDAP). If other fields are present, the
behavior is undefined. At this time, ldap_open() and ldap_init() are
deprecated in favor of ldap_initialize(), essentially because the
latter allows to specify a schema in the URI and it explicitly returns
an error code. ldap_init_fd() allows an LDAP structure to be
initialized using an already-opened connection. The proto parameter
should be one of LDAP_PROTO_TCP, LDAP_PROTO_UDP, or LDAP_PROTO_IPC for
a connection using TCP, UDP, or IPC, respectively. The value
LDAP_PROTO_EXT may also be specified if user-supplied sockbuf handlers
are going to be used. Note that support for UDP is not implemented
unless libldap was built with LDAP_CONNECTIONLESS defined. The uri
parameter may optionally be provided for informational purposes.
ldap_set_urllist_proc() allows to set a function proc of type
LDAP_URLLIST_PROC that is called when a successful connection can be
established. This function receives the list of URIs parsed from the
uri string originally passed to ldap_initialize(), and the one that
successfully connected. The function may manipulate the URI list; the
typical use consists in moving the successful URI to the head of the
list, so that subsequent attempts to connect to one of the URIs using
the same LDAP handle will try it first. If ld is null, proc is set as
a global parameter that is inherited by all handlers within the
process that are created after the call to ldap_set_urllist_proc().
By default, no LDAP_URLLIST_PROC is set. In a multithreaded
environment, ldap_set_urllist_proc() must be called before any
concurrent operation using the LDAP handle is started.
Note: the first call into the LDAP library also initializes the global
options for the library. As such the first call should be single-
threaded or otherwise protected to insure that only one call is
active. It is recommended that ldap_get_option() or ldap_set_option()
be used in the program's main thread before any additional threads are
created. See ldap_get_option(3).
ERRORS
If an error occurs, ldap_open() and ldap_init() will return NULL and
errno should be set appropriately. ldap_initialize() and
- 2 - Formatted: December 16, 2025
LDAP_OPEN(3) OpenLDAP LDVERSION LDAP_OPEN(3)
RELEASEDATE
ldap_init_fd() will directly return the LDAP code associated to the
error (or LDAP_SUCCESS in case of success); errno should be set as
well whenever appropriate. ldap_set_urllist_proc() returns
LDAP_OPT_ERROR on error, and LDAP_OPT_SUCCESS on success.
SEE ALSO
ldap(3), ldap_bind(3), ldap_get_option(3), ldap_set_option(3), lber-
sockbuf(3), errno(3)
ACKNOWLEDGEMENTS
- 3 - Formatted: December 16, 2025
