Provided by: slapd_2.6.7+dfsg-1~exp1ubuntu8.2_amd64 
NAME
slapd-asyncmeta - asynchronous metadirectory backend to slapd
SYNOPSIS
/etc/ldap/slapd.conf
DESCRIPTION
The asyncmeta backend to 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).
A good knowledge of the functionality of the slapd-meta(5) backend is recommended. This backend has
been designed as an asynchronous version of the meta backend. Unlike meta , the operation handling
threads are no longer pending on the response from the remote server, thus decreasing the number of
threads necessary to handle the same load. While asyncmeta maintains the functionality of meta and has a
largely similar codebase, some changes in operation and some new configuration directives have been
added. Some configuration options, such as conn-pool-max , conn-ttl , single-conn , and
use-temporary-conn have been removed, as they are no longer relevant.
New connection handling:
Unlike meta, which caches bound connections, the asyncmeta works with a configured maximum number of
connections per target. For each request redirected to a target, a different connection is selected.
Each connection has a queue, to which the request is added before it is sent to the remote server, and is
removed after the last response for that request is received.
For each new request, a new connection is chosen using round-robin scheduling.
Overlays:
Due to implementation specifics, there is no guarantee that any of the existing OpenLDAP overlays will
work with asyncmeta backend.
EXAMPLES
Refer to slapd-meta(5) for configuration examples.
CONFIGURATION
These slapd.conf options apply to the ASYNCMETA backend database. That is, they must follow a "database
asyncmeta" line and come before any subsequent "backend" or "database" lines. Other database options are
described in the slapd.conf(5) manual page.
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:
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.
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 idle-timeout directive.
onerr {CONTINUE|report|stop}
This directive allows one to select the behavior in case an error is returned by one target during
a search. The default, continue, consists in continuing the operation, trying to return as much
data as possible. If the value is set to stop, 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 report, the search is continued to the end but, in case at least one target returned an
error code, the first non-success error code is returned.
max-timeout-ops <number>
Specify the number of consecutive timed out requests, after which the connection will be
considered faulty and dropped.
max-pending-ops <number>
The maximum number of pending requests stored in a connection's queue. The default is 128. When
this number is exceeded, LDAP_BUSY will be returned to the client.
max-target-conns <number>
The maximum number of connections per target. Unlike slapd-meta(5), no new connections will be
created once this number is reached. The default value is 255.
norefs <NO|yes>
If yes, do not return search reference responses. By default, they are returned unless request is
LDAPv2. If set before any target specification, it affects all targets, unless overridden by any
per-target directive.
noundeffilter <NO|yes>
If yes, return success instead of searching if a filter is undefined or contains undefined
portions. By default, the search is propagated after replacing undefined portions with
(!(objectClass=*)), which corresponds to the empty result set. If set before any target
specification, it affects all targets, unless overridden by any per-target directive.
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 unwillingToPerform 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.
pseudoroot-bind-defer {YES|no}
This directive, when set to yes, causes the authentication to the remote servers with the pseudo-
root identity (the identity defined in each idassert-bind directive) to be deferred until actually
needed by subsequent operations. Otherwise, all binds as the rootdn are propagated to the
targets.
quarantine <interval>,<num>[;<interval>,<num>[...]]
Turns on quarantine of URIs that returned 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 interval seconds elapsed since last attempt, for exactly num times; then
use the next pattern. If num for the last pattern is "+", it retries forever; otherwise, no more
retries occur. This directive must appear before any target specification; it affects all targets
with the same pattern.
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 chase-referrals is set to yes.
session-tracking-request {NO|yes}
Adds session tracking control for all requests. The client's IP and hostname, and the identity
associated to each request, if known, are sent to the remote server for informational purposes.
This directive is incompatible with setting protocol-version to 2. If set before any target
specification, it affects all targets, unless overridden by any per-target directive.
TARGET SPECIFICATION
Target specification starts with a "uri" directive:
uri <protocol>://[<host>]/<naming context> [...]
Identical to meta. See slapd-meta(5) for details.
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.
The acl-authcDN identity is by no means implicitly used by the proxy when the client connects
anonymously.
acl-passwd <password>
Password used with the acl-authcDN above.
bind-timeout <microseconds>
This directive defines the timeout, in microseconds, used when polling for response after an
asynchronous bind connection. See slapd-meta(5) for details.
chase-referrals {YES|no}
enable/disable automatic referral chasing, which is delegated to the underlying libldap, with
rebinding eventually performed if the rebind-as-user 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.
client-pr {accept-unsolicited|DISABLE|<size>}
This feature allows one to use RFC 2696 Paged Results control when performing search operations
with a specific target, irrespective of the client's request. See slapd-meta(5) for details.
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.
filter <pattern>
This directive allows specifying a regex(5) pattern to indicate what search filter terms are
actually served by a target.
In a search request, if the search filter matches the pattern the target is considered while
fulfilling the request; otherwise the target is ignored. There may be multiple occurrences of the
filter directive for each target.
idassert-authzFrom <authz-regexp>
if defined, selects what local identities are authorized to exploit the identity assertion
feature. The string <authz-regexp> follows the rules defined for the authzFrom attribute. See
slapd.conf(5), section related to authz-policy, for details on the syntax of this field.
idassert-bind bindmethod=none|simple|sasl [binddn=<simple DN>] [credentials=<simple password>]
[saslmech=<SASL mech>] [secprops=<properties>] [realm=<realm>] [authcId=<authentication ID>]
[authzId=<authorization ID>] [authz={native|proxyauthz}] [mode=<mode>] [flags=<flags>]
[starttls=no|yes|critical] [tls_cert=<file>] [tls_key=<file>] [tls_cacert=<file>]
[tls_cacertdir=<path>] [tls_reqcert=never|allow|try|demand] [tls_reqsan=never|allow|try|demand]
[tls_cipher_suite=<ciphers>] [tls_ecname=<names>] [tls_protocol_min=<major>[.<minor>]]
[tls_crlcheck=none|peer|all] Allows one to define the parameters of the authentication method that
is internally used by the proxy to authorize connections that are authenticated by other
databases. See slapd-meta(5) for details.
idle-timeout <time>
This directive causes a a persistent connection to be dropped after it has been idle for the
specified time. The connection will be re-created the next time it is selected for use. A
connection is considered idle if no attempts have been made by the backend to use it to send a
request to the backend server. If there are still pending requests in its queue, the connection
will be dropped after the last request one has either received a result or has timed out.
[<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.
keepalive <idle>:<probes>:<interval>
The keepalive parameter sets the values of idle, probes, and interval used to check whether a
socket is alive; idle is the number of seconds a connection needs to remain idle before TCP starts
sending keepalive probes; probes is the maximum number of keepalive probes TCP should send before
dropping the connection; interval is interval in seconds between individual keepalive probes.
Only some systems support the customization of these values; the keepalive parameter is ignored
otherwise, and system-wide settings are used.
tcp-user-timeout <milliseconds>
If non-zero, corresponds to the TCP_USER_TIMEOUT set on the target connections, overriding the
operating system setting. Only some systems support the customization of this parameter, it is
ignored otherwise and system-wide settings are used.
map {attribute|objectclass} [<local name>|*] {<foreign name>|*}
This maps object classes and attributes as in the LDAP backend. See slapd-ldap(5).
network-timeout <time>
Sets the network timeout value after which poll(2)/select(2) following a connect(2) returns in
case of no activity while sending an operation to the remote target. The value is in
milliseconds, and it can be specified as for idle-timeout. If set before any target
specification, it affects all targets, unless overridden by any per-target directive.
nretries {forever|never|<nretries>}
This directive defines how many times forwarding an operation should be retried in case of
temporary failure in contacting a target. The number of retries is per operation, so if a bind to
the target is necessary first, the remaining number is decremented. If defined before any target
specification, it applies to all targets (by default, 3 times); the global value can be overridden
by redefinitions inside each target specification.
rewrite* ...
The rewrite options are identical to the meta backend. See the REWRITING section of slapd-meta(5).
subtree-{exclude|include} <rule>
This directive allows one to indicate what subtrees are actually served by a target. See
slapd-meta(5) for details.
suffixmassage <local suffix> <remote suffix>
slapd-asyncmeta does not support the rewrite engine used by the LDAP and META backends.
suffixmassage can be used to perform DN suffix rewriting, the same way as the obsoleted
suffixmassage directive previously used by the LDAP backend.
t-f-support {NO|yes|discover}
enable if the remote server supports absolute filters (see RFC 4526 for details). If set to
discover, support is detected by reading the remote server's root DSE. If set before any target
specification, it affects all targets, unless overridden by any per-target directive.
timeout [<op>=]<val> [...]
This directive allows one to set per-operation timeouts. Operations can be
<op> ::= bind, add, delete, modrdn, modify, compare, search
By default, the timeout for all operations is 2 seconds.
See slapd-meta(5) for details.
tls {none|[try-]start|[try-]propagate|ldaps}
B [starttls=no] [tls_cert=<file>] [tls_key=<file>] [tls_cacert=<file>] [tls_cacertdir=<path>]
[tls_reqcert=never|allow|try|demand] [tls_reqsan=never|allow|try|demand]
[tls_cipher_suite=<ciphers>] [tls_ecname=<names>] [tls_crlcheck=none|peer|all]
Specify TLS settings regular connections.
If the first parameter is not "none" then this configures the TLS settings to be used for regular
connections. The StartTLS extended operation will be used when establishing the connection unless
the URI directive protocol scheme is ldaps://. In that case this keyword may only be set to
"ldaps" and the StartTLS operation will not be used.
With propagate, the proxy issues the StartTLS operation only if the original connection has a TLS
layer set up. The try- prefix instructs the proxy to continue operations if the StartTLS
operation failed; its use is not recommended.
The TLS settings default to the same as the main slapd TLS settings, except for tls_reqcert which
defaults to "demand", tls_reqsan which defaults to "allow", and starttls which is overshadowed by
the first keyword and thus ignored.
If set before any target specification, it affects all targets, unless overridden by any per-
target directive.
SCENARIOS
See slapd-meta(5) for configuration scenarios.
ACLs
ACL behavior is identical to meta. See slapd-meta(5).
ACCESS CONTROL
The asyncmeta backend does not honor all ACL semantics as described in slapd.access(5). In general,
access checking is delegated to the remote server(s). Only read (=r) access to the entry pseudo-
attribute and to the other attribute values of the entries returned by the search operation is honored,
which is performed by the frontend.
FILES
/etc/ldap/slapd.conf
default slapd configuration file
SEE ALSO
slapd.conf(5), slapd-ldap(5), slapd-meta(5), slapo-pcache(5), slapd(8), regex(7), re_format(7).
AUTHOR
Nadezhda Ivanova, based on back-meta by Pierangelo Masarati.