A string is rewritten according to a set of rules, called a `rewrite
context'.
The rules are based on Regular Expressions (POSIX regex) with
-substring matching; extensions are planned to allow basic variable
-substitution and map resolution of substrings.
+substring matching; basic variable substitution and map resolution
+of substrings is allowed by specific mechanisms detailed in the following.
The behavior of pattern matching/substitution can be altered by a set
of flags.
.LP
for the slapd server (initially dedicated to the LDAP backend).
.SH Passes
An incoming string is matched agains a set of rules.
-Rules are made of a match pattern, a substitution pattern and a set of
-actions.
+Rules are made of a regex match pattern, a substitution pattern
+and a set of actions, described by a set of flags.
In case of match a string rewriting is performed according to the
substitution pattern that allows to refer to substrings matched in the
incoming string.
The actions, if any, are finally performed.
The substitution pattern allows map resolution of substrings.
A map is a generic object that maps a substitution pattern to a value.
+The flags are divided in "Pattern matching Flags" and "Action Flags";
+the former alter the regex match pattern behaviorm while the latter
+alter the action that is taken after substitution.
.SH "Pattern Matching Flags"
.TP
.B `C'
.TP
.B `R'
use POSIX Basic Regular Expressions (default is Extended)
+.TP
+.B `M{n}'
+allow no more than
+.B n
+recursive passes for a specific rule; does not alter the max total count
+of passes, so it can only enforce a stricter limit for a specific rule.
.SH "Action Flags"
.TP
.B `:'
apply the rule once only (default is recursive)
.TP
.B `@'
-stop applying rules in case of match.
+stop applying rules in case of match; the current rule is still applied
+recursively; combine with `:' to apply the current rule only once
+and then stop.
.TP
.B `#'
stop current operation if the rule matches, and issue an `unwilling to
perform' error.
.TP
.B `G{n}'
-jump n rules back and forth (watch for loops!).
+jump
+.B n
+rules back and forth (watch for loops!).
Note that `G{1}' is implicit in every rule.
.TP
.B `I'
ignores errors in rule; this means, in case of error, e.g. issued by a
map, the error is treated as a missed match.
The `unwilling to perform' is not overridden.
-.LP
-The ordering of the flags is significant.
+.TP
+.B `U{n}'
+uses
+.B
+n
+as return code if the rule matches; the flag does not alter the recursive
+behavior of the rule, so, to have it performed only once, it must be used
+in combination with `:', e.g.
+.B `:U{16}'
+returns the value `16' after exactly one execution of the rule, if the
+pattern matches.
+As a consequence, its behavior is equivalent to `@', with the return
+code set to
+.BR n ;
+or, in other words, `@' is equivalent to `U{0}'.
+By convention, the freely available codes are above 16 included;
+the others are reserved.
+.LP
+The ordering of the flags can be significant.
For instance: `IG{2}' means ignore errors and jump two lines ahead
both in case of match and in case of error, while `G{2}I' means ignore
-errors, but jump thwo lines ahead only in case of match.
+errors, but jump two lines ahead only in case of match.
.LP
More flags (mainly Action Flags) will be added as needed.
.SH "Pattern matching:"
In this case the alias context contains no rule, and any reference to
it will result in accessing the aliased one.
.TP
-.B rewriteRule "<regex pattern>" "<substitution pattern>" "[ <flags> ]"
-Determines how a tring can be rewritten if a pattern is matched.
+.B rewriteRule "<regex match pattern>" "<substitution pattern>" "[ <flags> ]"
+Determines how a string can be rewritten if a pattern is matched.
Examples are reported below.
.SH "Additional configuration syntax:"
.TP
Sets a value with global scope, that can be dereferenced by the
command `%{$paramName}'.
.TP
-.B rewriteMaxPasses <number of passes>
+.B rewriteMaxPasses <number of passes> [<number of passes per rule>]
Sets the maximum number of total rewriting passes that can be
performed in a single rewrite operation (to avoid loops).
+A safe default is set to 100; note that reaching this limit is still
+treated as a success; recursive invocation of rules is simply
+interrupted.
+The count applies to the rewriting operation as a whole, not
+to any single rule; an optional per-rule limit can be set.
+This limit is overridden by setting specific per-rule limits
+with the `M{n}' flag.
.SH "Configuration examples:"
.nf
# set to `off' to disable rewriting
# regular DNs, because the definition of a bindDn
# rewrite context overrides the default definition.
rewriteContext bindDn
-rewriteRule "^mail=[^,]+@[^,]+$" "%{attr2dn(%0)}" "@I"
+rewriteRule "^mail=[^,]+@[^,]+$" "%{attr2dn(%0)}" ":@I"
# This is a rather sophisticated example. It massages a
# search filter in case who performs the search has
"%{**binddn}<>%{&prefix(%1)}%{&arg(%2)}%{&suffix(%3)}"
":I"
rewriteRule "[^,]+,ou=admin,dc=home,dc=net"
- "%{*prefix}|(uid=%{*arg})(cn=%{*arg})%{*suffix}" "@I"
+ "%{*prefix}|(uid=%{*arg})(cn=%{*arg})%{*suffix}" ":@I"
rewriteRule ".*<>" "%{*prefix}uid=%{*arg}%{*suffix}" ":"
# This example shows how to strip unwanted DN-valued
# The second rule matches everything else and causes
# the value to be rejected.
rewriteContext searchResult
-rewriteRule ".*,ou=People,dc=example,dc=com" "%0" "@"
+rewriteRule ".*,ou=People,dc=example,dc=com" "%0" ":@"
rewriteRule ".*" "" "#"
.fi
.SH "LDAP Proxy resolution (a possible evolution of slapd\-ldap(5)):"
.LP
.nf
rewriteRule '^cn=root,.*' '%0' 'G{3}'
- rewriteRule '^cn=[a-l].*' 'ldap://ldap1.my.org/%0' '@'
- rewriteRule '^cn=[m-z].*' 'ldap://ldap2.my.org/%0' '@'
- rewriteRule '.*' 'ldap://ldap3.my.org/%0' '@'
+ rewriteRule '^cn=[a-l].*' 'ldap://ldap1.my.org/%0' ':@'
+ rewriteRule '^cn=[m-z].*' 'ldap://ldap2.my.org/%0' ':@'
+ rewriteRule '.*' 'ldap://ldap3.my.org/%0' ':@'
.fi
.LP
(Rule 1 is simply there to illustrate the `G{n}' action; it could have
been written:
.LP
.nf
- rewriteRule '^cn=root,.*' 'ldap://ldap3.my.org/%0' '@'
+ rewriteRule '^cn=root,.*' 'ldap://ldap3.my.org/%0' ':@'
.fi
.LP
with the advantage of saving one rewrite pass ...)
-.SH PROXY CACHE EXTENSION
-The proxy cache extension to
-.B meta
-backend allows caching of LDAP search requests (queries). For an incoming query, the
+.SH PROXY CACHE OVERLAY
+The proxy cache overlay
+allows caching of LDAP search requests (queries) in a local database.
+For an incoming query, the
proxy cache determines its corresponding \fBtemplate\fP. If the template was
-specified as cacheable using the \fBaddtemplate\fP directive and the request is
+specified as cacheable using the \fBproxytemplate\fP directive and the request is
contained in a cached request, it is answered from the proxy cache. Otherwise,
-the proxy cache obtains and caches results from target(s) specified by the
-\fBuri\fP directive.
+the search is performed as usual and cacheable search results are saved in the
+cache for use in future queries.
.LP
A template is defined by a filter string and an index identifying a set of
The following cache specific directives can be used to configure the proxy
cache:
.TP
-.B cacheparams <lo_thresh> <hi_thresh> <numattrsets> <max_entries> <cc_period>
-The directive enables proxy caching in the \fBmeta\fP backend and sets general
-cache parameters. Cache replacement is invoked when the cache size crosses the
-<hi_thresh> bytes and continues till the cache size is greater than <lo_thresh>
-bytes. <numattrsets> should be equal to the number of following \fBattrset\fP
+.B overlay proxycache
+This directive adds the proxycache overlay to the current backend. The
+proxycache overlay may be used with any backend but is intended for use
+with the
+.B ldap
+and
+.B meta
+backends.
+.TP
+.B proxycache <database> <max_entries> <numattrsets> <entry_limit> <cc_period>
+The directive enables proxy caching in the current backend and sets general
+cache parameters. A <database> backend will be used internally to maintain
+the cached entries. The chosen database will need to be configured as well,
+as shown below. Cache replacement is invoked when the cache size grows to
+<max_entries> entries and continues till the cache size drops below this size.
+<numattrsets> should be equal to the number of following \fBproxyattrset\fP
directives. Queries are cached only if they correspond to a cacheable template
-(specified by the \fBaddtemplate\fP directive) and the number of entries
-returned is less than <max_entries>. Consistency check is performed every
+(specified by the \fBproxytemplate\fP directive) and the number of entries
+returned is less than <entry_limit>. Consistency check is performed every
<cc_period> duration (specified in secs). In each cycle queries with expired
"time to live(\fBTTL\fP)" are removed. A sample cache configuration is:
.LP
.RS
-cacheparams \fB10000 150000 1 50 100\fP
+proxycache \fBbdb 10000 1 50 100\fP
.RE
.TP
-.B attrset <index> <attrs...>
+.B
proxyattrset <index> <attrs...>
Used to associate a set of attributes <attrs..> with an <index>. Each attribute
set is associated with an integer from 0 to <numattrsets>-1. These indices are
-used by the \fBaddtemplate\fP directive to define cacheable templates.
+used by the \fBproxytemplate\fP directive to define cacheable templates.
.TP
-.B
addtemplate <template_string> <attrset_index> <ttl>
+.B
proxytemplate <template_string> <attrset_index> <ttl>
Specifies a cacheable template and "time to live" (in sec) <ttl> of queries
belonging to the template.
.LP
.RS
.nf
-attrset \fB0 mail postaladdress telephonenumber\fP
-addtemplate \fB(&(sn=)(givenName=)) 0 3600\fP
+proxyattrset \fB0 mail postaladdress telephonenumber\fP
+proxytemplate \fB(&(sn=)(givenName=)) 0 3600\fP
.fi
.RE
+.LP
+Directives for configuring the underlying database must also be given, as
+shown here:
+.LP
+.RS
+.nf
+directory /var/tmp/cache
+cachesize 100
+.fi
+.RE
+.LP
+Any valid directives for the chosen database type may be used.
.SH FILES
.TP
ETCDIR/slapd.conf
projects / openldap / blobdiff