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NAME | SYNOPSIS | DESCRIPTION | ACCESS CONTROL | REPLICATION | FILES | SEE ALSO | AUTHOR | COLOPHON |
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SLAPO-DDS(5) File Formats Manual SLAPO-DDS(5)
slapo-dds - Dynamic Directory Services overlay to slapd
ETCDIR/slapd.conf
The dds overlay to slapd(8) implements dynamic objects as per RFC
2589. The name dds stands for Dynamic Directory Services. It
allows one to define dynamic objects, characterized by the
dynamicObject objectClass.
Dynamic objects have a limited lifetime, determined by a time-to-
live (TTL) that can be refreshed by means of a specific refresh
extended operation. This operation allows one to set the Client
Refresh Period (CRP), namely the period between refreshes that is
required to preserve the dynamic object from expiration. The
expiration time is computed by adding the requested TTL to the
current time. When dynamic objects reach the end of their
lifetime without being further refreshed, they are automatically
deleted. There is no guarantee of immediate deletion, so clients
should not count on it.
Dynamic objects can have subordinates, provided these also are
dynamic objects. RFC 2589 does not specify what the behavior of
a dynamic directory service should be when a dynamic object with
(dynamic) subordinates expires. In this implementation, the
lifetime of dynamic objects with subordinates is prolonged until
all the dynamic subordinates expire.
This slapd.conf(5) directive adds the dds overlay to the current
database:
overlay dds
The database must have a rootdn specified, otherwise, the dds
overlay will not be able to delete expired objects. The dds
overlay may be used with any backend that implements the add,
modify, search, and delete operations. Since its use may result
in many internal entry lookups, adds and deletes, it should be
best used in conjunction with backends that have reasonably good
write performances.
The config directives that are specific to the dds overlay are
prefixed by dds-, to avoid potential conflicts with directives
specific to the underlying database or to other stacked overlays.
dds-max-ttl <time>
Specifies the max TTL value. This is also the default TTL
newly created dynamic objects receive, unless
dds-default-ttl is set. When the client with a refresh
extended operation requests a TTL higher than it,
sizeLimitExceeded is returned. This value must be between
86400 (1 day, the default) and 31557600 (1 year plus 6
hours, as per RFC 2589).
dds-min-ttl <time>
Specifies the min TTL value; clients requesting a lower
TTL by means of the refresh extended operation actually
obtain this value as CRP. If set to 0 (the default), no
lower limit is set.
dds-default-ttl <time>
Specifies the default TTL value that newly created dynamic
objects get. If set to 0 (the default), the dds-max-ttl
is used.
dds-interval <time>
Specifies the interval between expiration checks; defaults
to 1 hour.
dds-tolerance <time>
Specifies an extra time that is added to the timer that
actually wakes up the thread that will delete an expired
dynamic object. So the nominal lifetime of the entry is
that specified in the entryTtl attribute, but its lifetime
will actually be entryTtl + tolerance. Note that there is
no guarantee that the lifetime of a dynamic object will be
exactly the requested TTL; due to implementation details,
it may be longer, which is allowed by RFC 2589. By
default, tolerance is 0.
dds-max-dynamicObjects <num>
Specifies the maximum number of dynamic objects that can
simultaneously exist within a naming context. This allows
one to limit the amount of resources (mostly in terms of
run-queue size) that are used by dynamic objects. By
default, no limit is set.
dds-state {TRUE|false}
Specifies if the Dynamic Directory Services feature is
enabled or not. By default it is; however, a proxy does
not need to keep track of dynamic objects itself, it only
needs to inform the frontend that support for dynamic
objects is available.
The dds overlay restricts the refresh operation by requiring
manage access to the entryTtl attribute (see slapd.access(5) for
details about the manage access privilege). Since the entryTtl
is an operational, NO-USER-MODIFICATION attribute, no direct
write access to it is possible. So the dds overlay turns refresh
extended operation into an internal modification to the value of
the entryTtl attribute with the relax control set.
RFC 2589 recommends that anonymous clients should not be allowed
to refresh a dynamic object. This can be implemented by
appropriately crafting access control to obtain the desired
effect.
Example: restrict refresh to authenticated clients
access to attrs=entryTtl
by users manage
by * read
Example: restrict refresh to the creator of the dynamic object
access to attrs=entryTtl
by dnattr=creatorsName manage
by * read
Another suggested usage of dynamic objects is to implement
dynamic meetings; in this case, all the participants to the
meeting are allowed to refresh the meeting object, but only the
creator can delete it (otherwise it will be deleted when the TTL
expires)
Example: assuming participant is a valid DN-valued attribute,
allow users to start a meeting and to join it; restrict refresh
to the participants; restrict delete to the creator
access to dn.base="cn=Meetings"
attrs=children
by users write
access to dn.onelevel="cn=Meetings"
attrs=entry
by dnattr=creatorsName write
by * read
access to dn.onelevel="cn=Meetings"
attrs=participant
by dnattr=creatorsName write
by users selfwrite
by * read
access to dn.onelevel="cn=Meetings"
attrs=entryTtl
by dnattr=participant manage
by * read
This implementation of RFC 2589 provides a restricted
interpretation of how dynamic objects replicate. Only the
provider takes care of handling dynamic object expiration, while
consumers simply see the dynamic object as a plain object.
When replicating these objects, one needs to explicitly exclude
the dynamicObject class and the entryTtl attribute. This
implementation of RFC 2589 introduces a new operational
attribute, entryExpireTimestamp, that contains the expiration
timestamp. This must be excluded from replication as well.
The quick and dirty solution is to set schemacheck=off in the
syncrepl configuration and, optionally, exclude the operational
attributes from replication, using
syncrepl ...
exattrs=entryTtl,entryExpireTimestamp
In any case the overlay must be either statically built in or
run-time loaded by the consumer, so that it is aware of the
entryExpireTimestamp operational attribute; however, it must not
be configured in the shadow database. Currently, there is no
means to remove the dynamicObject class from the entry; this may
be seen as a feature, since it allows one to see the dynamic
properties of the object.
ETCDIR/slapd.conf
default slapd configuration file
slapd.conf(5), slapd-config(5), slapd(8).
Implemented by Pierangelo Masarati.
This page is part of the OpenLDAP (an open source implementation
of the Lightweight Directory Access Protocol) project.
Information about the project can be found at
⟨http://www.openldap.org/⟩. If you have a bug report for this
manual page, see ⟨http://www.openldap.org/its/⟩. This page was
obtained from the project's upstream Git repository
⟨https://git.openldap.org/openldap/openldap.git⟩ on 2024-06-14.
(At that time, the date of the most recent commit that was found
in the repository was 2024-06-13.) If you discover any rendering
problems in this HTML version of the page, or you believe there
is a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
man-pages@man7.org
OpenLDAP LDVERSION RELEASEDATE SLAPO-DDS(5)
Pages that refer to this page: slapd.overlays(5)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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