LDAP_SYNC

Section: C Library Functions (3)
Updated: 2018/12/19
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NAME

ldap_sync_init, ldap_sync_init_refresh_only, ldap_sync_init_refresh_and_persist, ldap_sync_poll - LDAP sync routines

LIBRARY

OpenLDAP LDAP (libldap, -lldap)

SYNOPSIS

#include <ldap.h>

int ldap_sync_init(ldap_sync_t *ls, int mode);

int ldap_sync_init_refresh_only(ldap_sync_t *ls);

int ldap_sync_init_refresh_and_persist(ldap_sync_t *ls);

int ldap_sync_poll(ldap_sync_t *ls);

ldap_sync_t * ldap_sync_initialize(ldap_sync_t *ls);

void ldap_sync_destroy(ldap_sync_t *ls, int freeit);

typedef int (*ldap_sync_search_entry_f)(ldap_sync_t *ls,
LDAPMessage *msg, struct berval *entryUUID,
ldap_sync_refresh_t phase);


typedef int (*ldap_sync_search_reference_f)(ldap_sync_t *ls,
LDAPMessage *msg);


typedef int (*ldap_sync_intermediate_f)(ldap_sync_t *ls,
LDAPMessage *msg, BerVarray syncUUIDs,
ldap_sync_refresh_t phase);


typedef int (*ldap_sync_search_result_f)(ldap_sync_t *ls,
LDAPMessage *msg, int refreshDeletes);

DESCRIPTION

These routines provide an interface to the LDAP Content Synchronization operation (RFC 4533). They require an ldap_sync_t structure to be set up with parameters required for various phases of the operation; this includes setting some handlers for special events. All handlers take a pointer to the ldap_sync_t structure as the first argument, and a pointer to the LDAPMessage structure as received from the server by the client library, plus, occasionally, other specific arguments.

The members of the ldap_sync_t structure are:

char *ls_base: The search base; by default, the BASE option in ldap.conf(5).
int ls_scope: The search scope (one of LDAP_SCOPE_BASE, LDAP_SCOPE_ONELEVEL, LDAP_SCOPE_SUBORDINATE or LDAP_SCOPE_SUBTREE; see ldap.h for details).
char *ls_filter: The filter (RFC 4515); by default, (objectClass=*).
char **ls_attrs: The requested attributes; by default NULL, indicating all user attributes.
int ls_timelimit: The requested time limit (in seconds); by default 0, to indicate no limit.
int ls_sizelimit: The requested size limit (in entries); by default 0, to indicate no limit.
int ls_timeout: The desired timeout during polling with ldap_sync_poll(3). A value of -1 means that polling is blocking, so ldap_sync_poll(3) will not return until a message is received; a value of 0 means that polling returns immediately, no matter if any response is available or not; a positive value represents the timeout the ldap_sync_poll(3) function will wait for response before returning, unless a message is received; in that case, ldap_sync_poll(3) returns as soon as the message is available.
ldap_sync_search_entry_f ls_search_entry: A function that is called whenever an entry is returned. The msg argument is the LDAPMessage that contains the searchResultEntry; it can be parsed using the regular client API routines, like ldap_get_dn(3), ldap_first_attribute(3), and so on. The entryUUID argument contains the entryUUID of the entry. The phase argument indicates the type of operation: one of LDAP_SYNC_CAPI_PRESENT, LDAP_SYNC_CAPI_ADD, LDAP_SYNC_CAPI_MODIFY, LDAP_SYNC_CAPI_DELETE; in case of LDAP_SYNC_CAPI_PRESENT or LDAP_SYNC_CAPI_DELETE, only the DN is contained in the LDAPMessage; in case of LDAP_SYNC_CAPI_MODIFY, the whole entry is contained in the LDAPMessage, and the application is responsible of determining the differences between the new view of the entry provided by the caller and the data already known.
ldap_sync_search_reference_f ls_search_reference: A function that is called whenever a search reference is returned. The msg argument is the LDAPMessage that contains the searchResultReference; it can be parsed using the regular client API routines, like ldap_parse_reference(3).
ldap_sync_intermediate_f ls_intermediate: A function that is called whenever something relevant occurs during the refresh phase of the search, which is marked by an intermediateResponse message type. The msg argument is the LDAPMessage that contains the intermediate response; it can be parsed using the regular client API routines, like ldap_parse_intermediate(3). The syncUUIDs argument contains an array of UUIDs of the entries that depends on the value of the phase argument. In case of LDAP_SYNC_CAPI_PRESENTS, the "present" phase is being entered; this means that the following sequence of results will consist in entries in "present" sync state. In case of LDAP_SYNC_CAPI_DELETES, the "deletes" phase is being entered; this means that the following sequence of results will consist in entries in "delete" sync state. In case of LDAP_SYNC_CAPI_PRESENTS_IDSET, the message contains a set of UUIDs of entries that are present; it replaces a "presents" phase. In case of LDAP_SYNC_CAPI_DELETES_IDSET, the message contains a set of UUIDs of entries that have been deleted; it replaces a "deletes" phase. In case of LDAP_SYNC_CAPI_DONE, a "presents" phase with "refreshDone" set to "TRUE" has been returned to indicate that the refresh phase of refreshAndPersist is over, and the client should start polling. Except for the LDAP_SYNC_CAPI_PRESENTS_IDSET and LDAP_SYNC_CAPI_DELETES_IDSET cases, syncUUIDs is NULL.
ldap_sync_search_result_f ls_search_result: A function that is called whenever a searchResultDone is returned. In refreshAndPersist this can only occur when the server decides that the search must be interrupted. The msg argument is the LDAPMessage that contains the response; it can be parsed using the regular client API routines, like ldap_parse_result(3). The refreshDeletes argument is not relevant in this case; it should always be -1.
void *ls_private: A pointer to private data. The client may register here a pointer to data the handlers above may need.
LDAP *ls_ld: A pointer to a LDAP structure that is used to connect to the server. It is the responsibility of the client to initialize the structure and to provide appropriate authentication and security in place.

GENERAL USE

A ldap_sync_t structure is initialized by calling ldap_sync_initialize(3). This simply clears out the contents of an already existing ldap_sync_t structure, and sets appropriate values for some members. After that, the caller is responsible for setting up the connection (member ls_ld), eventually setting up transport security (TLS), for binding and any other initialization. The caller must also fill all the documented search-related fields of the ldap_sync_t structure.

At the end of a session, the structure can be cleaned up by calling ldap_sync_destroy(3), which takes care of freeing all data assuming it was allocated by ldap_mem*(3) routines. Otherwise, the caller should take care of destroying and zeroing out the documented search-related fields, and call ldap_sync_destroy(3) to free undocumented members set by the API.

REFRESH ONLY

The refreshOnly functionality is obtained by periodically calling ldap_sync_init(3) with mode set to LDAP_SYNC_REFRESH_ONLY, or, which is equivalent, by directly calling ldap_sync_init_refresh_only(3). The state of the search, and the consistency of the search parameters, is preserved across calls by passing the ldap_sync_t structure as left by the previous call.

REFRESH AND PERSIST

The refreshAndPersist functionality is obtained by calling ldap_sync_init(3) with mode set to LDAP_SYNC_REFRESH_AND_PERSIST, or, which is equivalent, by directly calling ldap_sync_init_refresh_and_persist(3) and, after a successful return, by repeatedly polling with ldap_sync_poll(3) according to the desired pattern.

A client may insert a call to ldap_sync_poll(3) into an external loop to check if any modification was returned; in this case, it might be appropriate to set ls_timeout to 0, or to set it to a finite, small value. Otherwise, if the client's main purpose consists in waiting for responses, a timeout of -1 is most suitable, so that the function only returns after some data has been received and handled.

ERRORS

All routines return any LDAP error resulting from a lower-level error in the API calls they are based on, or LDAP_SUCCESS in case of success. ldap_sync_poll(3) may return LDAP_SYNC_REFRESH_REQUIRED if a full refresh is requested by the server. In this case, it is appropriate to call ldap_sync_init(3) again, passing the same ldap_sync_t structure as resulted from any previous call.

NOTES

AUTHOR

Designed and implemented by Pierangelo Masarati, based on RFC 4533 and loosely inspired by syncrepl code in slapd(8).

ACKNOWLEDGEMENTS

Initially developed by SysNet s.n.c. OpenLDAP is developed and maintained by The OpenLDAP Project (http://www.openldap.org/). OpenLDAP is derived from University of Michigan LDAP 3.3 Release.