slapd-meta.5

OpenLdap是LDAP的开源项目

.TH SLAPD-META 5 "RELEASEDATE" "OpenLDAP LDVERSION"
.\" Copyright 1998-2007 The OpenLDAP Foundation, All Rights Reserved.
.\" Copying restrictions apply.  See the COPYRIGHT file.
.\" Copyright 2001, Pierangelo Masarati, All rights reserved. <[e-mail]>
.\" $OpenLDAP: pkg/ldap/doc/man/man5/slapd-meta.5,v 1.29.2.17 2007/09/13 19:33:55 ando Exp $
.\"
.\" Portions of this document should probably be moved to slapd-ldap(5)
.\" and maybe manual pages for librewrite.
.\"
.SH NAME
slapd-meta \- metadirectory backend to slapd
.SH SYNOPSIS
ETCDIR/slapd.conf
.SH DESCRIPTION
The
.B meta
backend to
.BR slapd (8)
performs basic LDAP proxying with respect to a set of remote LDAP
servers, called "targets".
The information contained in these servers can be presented as
belonging to a single Directory Information Tree (DIT).
.LP
A basic knowledge of the functionality of the
.BR slapd\-ldap (5)
backend is recommended.
This backend has been designed as an enhancement of the ldap backend.
The two backends share many features (actually they also share
portions of code).
While the
.B ldap
backend is intended to proxy operations directed to a single server, the
.B meta
backend is mainly intended for proxying of multiple servers and possibly
naming context masquerading.
These features, although useful in many scenarios, may result in
excessive overhead for some applications, so its use should be
carefully considered.
In the examples section, some typical scenarios will be discussed.

.LP
Note: When looping back to the same instance of \fBslapd\fP(8), 
each connection requires a new thread; as a consequence, \fBslapd\fP(8)
must be compiled with thread support, and the \fBthreads\fP parameter 
may need some tuning; in those cases, unless the multiple target feature
is required, one may consider using \fBslapd-relay\fP(5) instead, 
which performs the relayed operation internally and thus reuses 
the same connection.

.SH EXAMPLES
There are examples in various places in this document, as well as in the
slapd/back-meta/data/ directory in the OpenLDAP source tree.
.SH CONFIGURATION
These
.B slapd.conf
options apply to the META backend database.
That is, they must follow a "database meta" line and come before any
subsequent "backend" or "database" lines.
Other database options are described in the
.BR slapd.conf (5)
manual page.
.LP
Note: In early versions of back-ldap and back-meta it was recommended to always set
.LP
.RS
.nf
lastmod  off
.fi
.RE
.LP
for 
.B ldap
and
.B meta
databases.
This was required because operational attributes related to entry creation 
and modification should not be proxied, as they could be mistakenly written
to the target server(s), generating an error.
The current implementation automatically sets lastmod to \fBoff\fP, 
so its use is redundant and should be omitted.

.SH SPECIAL CONFIGURATION DIRECTIVES
Target configuration starts with the "uri" directive.
All the configuration directives that are not specific to targets
should be defined first for clarity, including those that are common
to all backends.
They are:

.TP
.B conn-ttl <time>
This directive causes a cached connection to be dropped an recreated
after a given ttl, regardless of being idle or not.

.TP
.B default-target none
This directive forces the backend to reject all those operations
that must resolve to a single target in case none or multiple
targets are selected.
They include: add, delete, modify, modrdn; compare is not included, as
well as bind since, as they don't alter entries, in case of multiple
matches an attempt is made to perform the operation on any candidate
target, with the constraint that at most one must succeed.
This directive can also be used when processing targets to mark a
specific target as default.

.TP
.B dncache-ttl {DISABLED|forever|<ttl>}
This directive sets the time-to-live of the DN cache.
This caches the target that holds a given DN to speed up target
selection in case multiple targets would result from an uncached
search; forever means cache never expires; disabled means no DN
caching; otherwise a valid ( > 0 ) ttl is required, in the format
illustrated for the 
.B idle-timeout
directive.

.TP
.B onerr {CONTINUE|report|stop}
This directive allows to select the behavior in case an error is returned
by one target during a search.
The default, \fBcontinue\fP, consists in continuing the operation, 
trying to return as much data as possible.
If the value is set to \fBstop\fP, the search is terminated as soon 
as an error is returned by one target, and the error is immediately 
propagated to the client.
If the value is set to \fBreport\fP, the search is continuated to the end
but, in case at least one target returned an error code, the first
non-success error code is returned.

.TP
.B protocol\-version {0,2,3}
This directive indicates what protocol version must be used to contact
the remote server.
If set to 0 (the default), the proxy uses the same protocol version 
used by the client, otherwise the requested protocol is used.
The proxy returns \fIunwillingToPerform\fP if an operation that is 
incompatible with the requested protocol is attempted.
If set before any target specification, it affects all targets, unless
overridden by any per-target directive.

.TP
.B pseudoroot-bind-defer {NO|yes}
This directive, when set to 
.BR yes ,
causes the authentication to the remote servers with the pseudo-root
identity to be deferred until actually needed by subsequent operations.

.TP
.B quarantine <interval>,<num>[;<interval>,<num>[...]]
Turns on quarantine of URIs that returned
.IR LDAP_UNAVAILABLE ,
so that an attempt to reconnect only occurs at given intervals instead
of any time a client requests an operation.
The pattern is: retry only after at least
.I interval
seconds elapsed since last attempt, for exactly
.I num
times; then use the next pattern.
If
.I num
for the last pattern is "\fB+\fP", it retries forever; otherwise, 
no more retries occur.
This directive must appear before any target specification;
it affects all targets with the same pattern.

.TP
.B rebind-as-user {NO|yes}
If this option is given, the client's bind credentials are remembered
for rebinds, when trying to re-establish a broken connection,
or when chasing a referral, if 
.B chase-referrals
is set to
.IR yes .

.TP
.B single\-conn {NO|yes}
Discards current cached connection when the client rebinds.

.TP
.B use-temporary-conn {NO|yes}
when set to 
.BR yes ,
create a temporary connection whenever competing with other threads
for a shared one; otherwise, wait until the shared connection is available.

.SH TARGET SPECIFICATION
Target specification starts with a "uri" directive:

.TP
.B uri <protocol>://[<host>]/<naming context> [...]
The <protocol> part can be anything
.BR ldap_initialize (3)
accepts ({ldap|ldaps|ldapi} and variants); the <host> may be
omitted, defaulting to whatever is set in
.BR ldap.conf (5).
The <naming context> part is \fImandatory\fP for the first URI,
but it \fImust be omitted\fP for subsequent ones, if any.
The naming context part must be within the naming context defined for the backend,
e.g.:
.LP
.RS
.nf
suffix "\fBdc=foo,dc=com\fP"
uri    "ldap://x.foo.com/dc=x,\fBdc=foo,dc=com\fP"
.fi

.RE
.RS
The <naming context> part doesn't need to be unique across the targets;
it may also match one of the values of the "suffix" directive.
Multiple URIs may be defined in a single URI statement.
The additional URIs must be separate arguments and must not have any
<naming context> part.  This causes the underlying library
to contact the first server of the list that responds.
For example, if \fIl1.foo.com\fP and \fIl2.foo.com\fP are shadows
of the same server, the directive
.LP
.nf
suffix "\fBdc=foo,dc=com\fP"
uri    "ldap://l1.foo.com/\fBdc=foo,dc=com\fP" "ldap://l2.foo.com/"
.fi

.RE
.RS
causes \fIl2.foo.com\fP to be contacted whenever \fIl1.foo.com\fP
does not respond.
In that case, the URI list is internally rearranged, by moving unavailable
URIs to the end, so that further connection attempts occur with respect to
the last URI that succeeded.
.RE

.TP
.B acl-authcDN "<administrative DN for access control purposes>"
DN which is used to query the target server for acl checking,
as in the LDAP backend; it is supposed to have read access 
on the target server to attributes used on the proxy for acl checking.
There is no risk of giving away such values; they are only used to
check permissions.
.B The acl-authcDN identity is by no means implicitly used by the proxy 
.B when the client connects anonymously.

.TP
.B acl-passwd <password>
Password used with the
.B 
acl-authcDN
above.

.TP
.B bind-timeout <microseconds>
This directive defines the timeout, in microseconds, used when polling
for response after an asynchronous bind connection.  The initial call
to ldap_result(3) is performed with a trade-off timeout of 100000 us;
if that results in a timeout exceeded, subsequent calls use the value
provided with
.BR bind-timeout .
The default value is used also for subsequent calls if
.B bind-timeout
is not specified.
If set before any target specification, it affects all targets, unless
overridden by any per-target directive.

.TP
.B chase-referrals {YES|no}
enable/disable automatic referral chasing, which is delegated to the
underlying libldap, with rebinding eventually performed if the
\fBrebind-as-user\fP directive is used.  The default is to chase referrals.
If set before any target specification, it affects all targets, unless
overridden by any per-target directive.

.TP
.B default-target [<target>]
The "default-target" directive can also be used during target specification.
With no arguments it marks the current target as the default.
The optional number marks target <target> as the default one, starting
from 1.
Target <target> must be defined.

.TP
.B idle-timeout <time>
This directive causes a cached connection to be dropped an recreated
after it has been idle for the specified time.
The value can be specified as

[<d>d][<h>h][<m>m][<s>[s]]

where <d>, <h>, <m> and <s> are respectively treated as days, hours, 
minutes and seconds.
If set before any target specification, it affects all targets, unless
overridden by any per-target directive.

.TP
.B map "{attribute|objectclass} [<local name>|*] {<foreign name>|*}"
This maps object classes and attributes as in the LDAP backend.
See
.BR slapd-ldap (5).

.TP
.B network-timeout <time>
Sets the network timeout value after which
.BR poll (2)/ select (2) 
following a 
.BR connect (2) 
returns in case of no activity.
The value is in seconds, and it can be specified as for
.BR idle-timeout .
If set before any target specification, it affects all targets, unless
overridden by any per-target directive.

.TP
.B nretries {forever|never|<nretries>}
This directive defines how many times a bind should be retried
in case of temporary failure in contacting a target.  If defined
before any target specification, it applies to all targets (by default,
.BR 3
times);
the global value can be overridden by redefinitions inside each target
specification.

.TP
.B pseudorootdn "<substitute DN in case of rootdn bind>"
This directive, if present, sets the DN that will be substituted to
the bind DN if a bind with the backend's "rootdn" succeeds.
The true "rootdn" of the target server ought not be used; an arbitrary
administrative DN should used instead.

.TP
.B pseudorootpw "<substitute password in case of rootdn bind>"
This directive sets the credential that will be used in case a bind
with the backend's "rootdn" succeeds, and the bind is propagated to
the target using the "pseudorootdn" DN.

Note: cleartext credentials must be supplied here; as a consequence,