This document is about PowerDNS 4.X. If you have PowerDNS 3.X, please see the PowerDNS 3.X documentation

LDAP backend

As of PowerDNS Authoritative Server 4.0.0, the LDAP backend is fully supported.

Warning: Grégory Oestreicher has forked the LDAP backend shortly before our 3.2 release, after which a lot of development happened in a short time. We are working to upstream this work.

The original author for this module is Norbert Sendetzky. This page is based on the content from his LDAPbackend wiki section as copied in February 2016, and edited from there.

Warning: Host names and the MNAME of a SOA records are NEVER terminated with a '.' in PowerDNS storage! If a trailing '.' is present it will inevitably cause problems, problems that may be hard to debug.

Native Yes
Master No
Slave No
Superslave No
Autoserial No
DNSSEC No

Introduction

Rationale

This HOWTO documents the steps necessary to build and use the LDAP DNS backend I've written for PowerDNS, an extremely versatile name server. This backend enables PowerDNS to retrieve DNS information from any standard compliant LDAP server. This is extremely handy if you have already stored information about your hosts in your LDAP tree.

Schemas

The schema is based on the 'uninett' dnszone schema, with a few types added by number as designed in that schema.

# A schema for storing DNS zones in LDAP
#
# ORDERING is not necessary, and some servers don't support
# integerOrderingMatch. Omit or change if you like

attributetype ( 1.3.6.1.4.1.2428.20.0.0  NAME 'dNSTTL'
    DESC 'An integer denoting time to live'
    EQUALITY integerMatch
    ORDERING integerOrderingMatch
    SYNTAX 1.3.6.1.4.1.1466.115.121.1.27 )

attributetype ( 1.3.6.1.4.1.2428.20.0.1 NAME 'dNSClass'
    DESC 'The class of a resource record'
    EQUALITY caseIgnoreIA5Match
    SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )

attributetype ( 1.3.6.1.4.1.2428.20.1.11 NAME 'wKSRecord'
    DESC 'a well known service description, RFC 1035'
    EQUALITY caseIgnoreIA5Match
    SUBSTR caseIgnoreIA5SubstringsMatch
    SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )

attributetype ( 1.3.6.1.4.1.2428.20.1.12 NAME 'pTRRecord'
    DESC 'domain name pointer, RFC 1035'
    EQUALITY caseIgnoreIA5Match
    SUBSTR caseIgnoreIA5SubstringsMatch
    SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )

attributetype ( 1.3.6.1.4.1.2428.20.1.13 NAME 'hInfoRecord'
    DESC 'host information, RFC 1035'
    EQUALITY caseIgnoreIA5Match
    SUBSTR caseIgnoreIA5SubstringsMatch
    SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )

attributetype ( 1.3.6.1.4.1.2428.20.1.14 NAME 'mInfoRecord'
    DESC 'mailbox or mail list information, RFC 1035'
    EQUALITY caseIgnoreIA5Match
    SUBSTR caseIgnoreIA5SubstringsMatch
    SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )

attributetype ( 1.3.6.1.4.1.2428.20.1.16 NAME 'tXTRecord'
    DESC 'text string, RFC 1035'
    EQUALITY caseIgnoreIA5Match
    SUBSTR caseIgnoreIA5SubstringsMatch
    SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )

attributetype ( 1.3.6.1.4.1.2428.20.1.17 NAME 'rPRecord'
    DESC 'for Responsible Person, RFC 1183'
    EQUALITY caseIgnoreIA5Match
    SUBSTR caseIgnoreIA5SubstringsMatch
    SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )

attributetype ( 1.3.6.1.4.1.2428.20.1.18 NAME 'aFSDBRecord'
    DESC 'for AFS Data Base location, RFC 1183'
    EQUALITY caseIgnoreIA5Match
    SUBSTR caseIgnoreIA5SubstringsMatch
    SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )

attributetype ( 1.3.6.1.4.1.2428.20.1.24 NAME 'SigRecord'
    DESC 'Signature, RFC 2535'
    EQUALITY caseIgnoreIA5Match
    SUBSTR caseIgnoreIA5SubstringsMatch
    SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )

attributetype ( 1.3.6.1.4.1.2428.20.1.25 NAME 'KeyRecord'
    DESC 'Key, RFC 2535'
    EQUALITY caseIgnoreIA5Match
    SUBSTR caseIgnoreIA5SubstringsMatch
    SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )

attributetype ( 1.3.6.1.4.1.2428.20.1.27 NAME 'gPosRecord'
    DESC 'Geographical Position, RFC 1712'
    EQUALITY caseIgnoreIA5Match
    SUBSTR caseIgnoreIA5SubstringsMatch
    SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )

attributetype ( 1.3.6.1.4.1.2428.20.1.28 NAME 'aAAARecord'
    DESC 'IPv6 address, RFC 1886'
    EQUALITY caseIgnoreIA5Match
    SUBSTR caseIgnoreIA5SubstringsMatch
    SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )

attributetype ( 1.3.6.1.4.1.2428.20.1.29 NAME 'LocRecord'
    DESC 'Location, RFC 1876'
    EQUALITY caseIgnoreIA5Match
    SUBSTR caseIgnoreIA5SubstringsMatch
    SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )

attributetype ( 1.3.6.1.4.1.2428.20.1.30 NAME 'nXTRecord'
    DESC 'non-existant, RFC 2535'
    EQUALITY caseIgnoreIA5Match
    SUBSTR caseIgnoreIA5SubstringsMatch
    SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )

attributetype ( 1.3.6.1.4.1.2428.20.1.33 NAME 'sRVRecord'
    DESC 'service location, RFC 2782'
    EQUALITY caseIgnoreIA5Match
    SUBSTR caseIgnoreIA5SubstringsMatch
    SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )

attributetype ( 1.3.6.1.4.1.2428.20.1.35 NAME 'nAPTRRecord'
    DESC 'Naming Authority Pointer, RFC 2915'
    EQUALITY caseIgnoreIA5Match
    SUBSTR caseIgnoreIA5SubstringsMatch
    SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )

attributetype ( 1.3.6.1.4.1.2428.20.1.36 NAME 'kXRecord'
    DESC 'Key Exchange Delegation, RFC 2230'
    EQUALITY caseIgnoreIA5Match
    SUBSTR caseIgnoreIA5SubstringsMatch
    SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )

attributetype ( 1.3.6.1.4.1.2428.20.1.37 NAME 'certRecord'
    DESC 'certificate, RFC 2538'
    EQUALITY caseIgnoreIA5Match
    SUBSTR caseIgnoreIA5SubstringsMatch
    SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )

attributetype ( 1.3.6.1.4.1.2428.20.1.38 NAME 'a6Record'
    DESC 'A6 Record Type, RFC 2874'
    EQUALITY caseIgnoreIA5Match
    SUBSTR caseIgnoreIA5SubstringsMatch
    SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )

attributetype ( 1.3.6.1.4.1.2428.20.1.39 NAME 'dNameRecord'
    DESC 'Non-Terminal DNS Name Redirection, RFC 2672'
    EQUALITY caseIgnoreIA5Match
    SUBSTR caseIgnoreIA5SubstringsMatch
    SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )

attributetype ( 1.3.6.1.4.1.2428.20.1.42 NAME 'aPLRecord'
    DESC 'Lists of Address Prefixes, RFC 3123'
    EQUALITY caseIgnoreIA5Match
    SUBSTR caseIgnoreIA5SubstringsMatch
    SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )

attributetype ( 1.3.6.1.4.1.2428.20.1.43 NAME 'dSRecord'
    DESC 'Delegation Signer, RFC 3658'
    EQUALITY caseIgnoreIA5Match
    SUBSTR caseIgnoreIA5SubstringsMatch
    SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )

attributetype ( 1.3.6.1.4.1.2428.20.1.44 NAME 'sSHFPRecord'
    DESC 'SSH Key Fingerprint, RFC 4255'
    EQUALITY caseIgnoreIA5Match
    SUBSTR caseIgnoreIA5SubstringsMatch
    SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )

attributetype ( 1.3.6.1.4.1.2428.20.1.45 NAME 'iPSecKeyRecord'
    DESC 'SSH Key Fingerprint, RFC 4025'
    EQUALITY caseIgnoreIA5Match
    SUBSTR caseIgnoreIA5SubstringsMatch
    SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )

attributetype ( 1.3.6.1.4.1.2428.20.1.46 NAME 'rRSIGRecord'
    DESC 'RRSIG, RFC 3755'
    EQUALITY caseIgnoreIA5Match
    SUBSTR caseIgnoreIA5SubstringsMatch
    SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )

attributetype ( 1.3.6.1.4.1.2428.20.1.47 NAME 'nSECRecord'
    DESC 'NSEC, RFC 3755'
    EQUALITY caseIgnoreIA5Match
    SUBSTR caseIgnoreIA5SubstringsMatch
    SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )

attributetype ( 1.3.6.1.4.1.2428.20.1.48 NAME 'dNSKeyRecord'
    DESC 'DNSKEY, RFC 3755'
    EQUALITY caseIgnoreIA5Match
    SUBSTR caseIgnoreIA5SubstringsMatch
    SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )

attributetype ( 1.3.6.1.4.1.2428.20.1.49 NAME 'dHCIDRecord'
    DESC 'DHCID, RFC 4701'
    EQUALITY caseIgnoreIA5Match
    SUBSTR caseIgnoreIA5SubstringsMatch
    SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )

attributetype ( 1.3.6.1.4.1.2428.20.1.99 NAME 'sPFRecord'
    DESC 'Sender Policy Framework, RFC 4408'
    EQUALITY caseIgnoreIA5Match
    SUBSTR caseIgnoreIA5SubstringsMatch
    SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )

attributetype ( 1.3.6.1.4.1.2428.20.1.65534 NAME 'TYPE65534Record'
    DESC ''
    EQUALITY caseIgnoreIA5Match
    SUBSTR caseIgnoreIA5SubstringsMatch
    SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )

attributetype ( 1.3.6.1.4.1.2428.20.1.108 NAME 'EUI48Record'
    DESC ''
    EQUALITY caseIgnoreIA5Match
    SUBSTR caseIgnoreIA5SubstringsMatch
    SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )

attributetype ( 1.3.6.1.4.1.2428.20.1.109 NAME 'EUI64Record'
    DESC ''
    EQUALITY caseIgnoreIA5Match
    SUBSTR caseIgnoreIA5SubstringsMatch
    SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )

attributetype ( 1.3.6.1.4.1.2428.20.1.65226 NAME 'TYPE65226Record'
    DESC ''
    EQUALITY caseIgnoreIA5Match
    SUBSTR caseIgnoreIA5SubstringsMatch
    SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )

objectclass ( 1.3.6.1.4.1.2428.20.2 NAME 'dNSDomain2'
    SUP 'dNSDomain' STRUCTURAL
    MAY ( DNSTTL $ DNSClass $ WKSRecord $ PTRRecord $
        HINFORecord $ MINFORecord $ TXTRecord $ RPRecord $
        AFSDBRecord $ SIGRecord $ KEYRecord $ GPOSRecord $
        AAAARecord $ LOCRecord $ NXTRecord $ SRVRecord $
        NAPTRRecord $ KXRecord $ CERTRecord $ A6Record $
        DNAMERecord $ APLRecord $ DSRecord $ SSHFPRecord $
        IPSECKEYRecord $ RRSIGRecord $ NSECRecord $
        DNSKEYRecord $ DHCIDRecord $ SPFRecord $ TYPE65534Record $
        TYPE65226Record $ EUI48Record $ EUI64Record
    ) )

The LDAP dnsdomain2 schema contains the additional object descriptions which are required by the LDAP server to check the validity of entries when they are added. Please consult the documentation of your LDAP server to find out how to add this schema to the server.

Installation

Configuration options

There are a few options through the LDAP DNS backend can be configured for your environment. Add them to the pdns.conf file located in /etc/powerdns or /usr/local/etc/ (depends on your configuration while compiling):

launch=ldap

You'll have to add the LDAP DNS backend to the PowerDNS backends first by altering the launch declaration in the pdns.conf file. Otherwise the options below won't have any effect.

ldap-host (default "") : The values assigned to this parameter can be LDAP URIs (e.g. or ) describing the connection to the LDAP server. There can be multiple LDAP URIs specified for load balancing and high availability if they are separated by spaces. In case the used LDAP client library doesn't support LDAP URIs as connection parameter, use plain host names or IP addresses instead (both may optionally be followed by a colon and the port).

ldap-starttls

(default "no") : Use TLS encrypted connections to the LDAP server. This is only allowed if ldap-host is a URI or a host name / IP address.

ldap-basedn

(default "") : The PowerDNS LDAP DNS backend searches below this path for objects containing the specified DNS information. The retrieval of attributes is limited to this subtree. This option must be set to the path according to the layout of your LDAP tree, e.g. ou=hosts,o=linuxnetworks,c=de is the DN to my objects containing the DNS information.

ldap-binddn

(default "") : Path to the object to authenticate against. Should only be used, if the LDAP server doesn't support anonymous binds.

ldap-secret

(default "") : Password for authentication against the object specified by ldap-binddn

ldap-method

(default "simple") :

ldap-filter-axfr

(default "(:target:)" ) : LDAP filter for limiting AXFR results (zone transfers), e.g. (&(:target:)(active=yes)) for returning only entries whose attribute "active" is set to "yes".

ldap-filter-lookup

(default "(:target:)" ) : LDAP filter for limiting IP or name lookups, e.g. (&(:target:)(active=yes)) for returning only entries whose attribute "active" is set to "yes".

Example

Tree design

The DNS LDAP tree should be designed carefully to prevent mistakes, which are hard to correct afterwards. The best solution is to create a subtree for all host entries which will contain the DNS records. You can do this the simple way or in a tree style.

DN of a simple style example record (e.g. myhost.linuxnetworks.de):

dn: dc=myhost,dc=linuxnetworks,ou=hosts,...

DN of a tree style example record (e.g. myhost.test.linuxnetworks.de):

dn: dc=myhost,dc=test,dc=linuxnetworks,dc=de,ou=hosts,...

Basic objects

Each domain (or zone for BIND users) must include one object containing a SOA (Start Of Authority) record. This object can also contain the attribute for a MX (Mail eXchange) and a NS (Name Server) record. These attributes allow one or more values, e.g. for a backup mail or name server:

dn: dc=linuxnetworks,ou=hosts,o=linuxnetworks,c=de
objectclass: top
objectclass: dcobject
objectclass: dnsdomain
objectclass: domainrelatedobject
dc: linuxnetworks
soarecord: ns.linuxnetworks.de me@linuxnetworks.de 1 1800 3600 86400 7200
nsrecord: ns.linuxnetworks.de
mxrecord: 10 mail.linuxnetworks.de
mxrecord: 20 mail2.linuxnetworks.de
associateddomain: linuxnetworks.de

A simple mapping between name and IP address can be specified by an object containing an arecord and an associateddomain. You don't have to bother about a reverse mapping (ip address to name) if you don't want to, because this can be done automagically by the LDAP DNS backend if you set ldap-method=strict in pdns.conf.

dn: dc=server,dc=linuxnetworks,ou=hosts,o=linuxnetworks,c=de
objectclass: top
objectclass: dnsdomain
objectclass: domainrelatedobject
dc: server
arecord: 10.1.0.1
arecord: 192.168.0.1
associateddomain: server.linuxnetworks.de

Be aware of the fact that these examples work if ldap-method is simple or strict. For tree mode you have to modify all DNs according to the algorithm described in the section above.

Wildcards

Wild-card domains are possible by using the asterisk in the associatedDomain value like it is used in the bind zone files. The "dc" attribute can be set to any value in simple or strict mode - this doesn't matter.

dn: dc=any,dc=linuxnetworks,ou=hosts,o=linuxnetworks,c=de objectclass: top objectclass: dnsdomain objectclass: domainrelatedobject dc: any arecord: 192.168.0.1 associateddomain: *.linuxnetworks.de

In tree mode wild-card entries has to look like this instead:

dn: dc=*,dc=linuxnetworks,dc=de,ou=hosts,o=linuxnetworks,c=de
objectclass: top
objectclass: dnsdomain
objectclass: domainrelatedobject
dc: *
arecord: 192.168.0.1
associateddomain: *.linuxnetworks.de

Aliases

Aliases for an existing DNS object have to be defined in a separate LDAP object. You can create one object per alias (this is a must in tree mode) or add all aliases (as values of associateddomain) to one object. The only thing which is not allowed is to create loops by using the same name in associateddomain and in cnamerecord

dn: dc=server-aliases,dc=linuxnetworks,ou=hosts,o=linuxnetworks,c=de
objectclass: top
objectclass: dnsdomain
objectclass: domainrelatedobject
dc: server-aliases
cnamerecord: server.linuxnetworks.de
associateddomain: proxy.linuxnetworks.de
associateddomain: mail2.linuxnetworks.de
associateddomain: ns.linuxnetworks.de

Aliases are optional. You can also add all alias domains to the associateddomain attribute. The only difference is that these additional domains aren't recognized as aliases anymore, but instead as a normal arecord:

dn: dc=server,dc=linuxnetworks,ou=hosts,o=linuxnetworks,c=de
objectclass: top
objectclass: dnsdomain
objectclass: domainrelatedobject
dc: server
arecord: 10.1.0.1
associateddomain: server.linuxnetworks.de
associateddomain: proxy.linuxnetworks.de
associateddomain: mail2.linuxnetworks.de
associateddomain: ns.linuxnetworks.de

Reverse lookups

Currently you have two options: Either reverse lookups handled by the code automagically or you have to add PTR records to your LDAP directory. If you want to derive PTR records from A records, you have set "ldap-method" to "strict". Otherwise add objects like below to your directory:

dn: dc=1.10.in-addr.arpa,ou=hosts,o=linuxnetworks,c=de
objectclass: top
objectclass: dnsdomain2
objectclass: domainrelatedobject
dc: 1.10.in-addr.arpa
soarecord: ns.linuxnetworks.de me@linuxnetworks.de 1 1800 3600 86400 7200
nsrecord: ns.linuxnetworks.de
associateddomain: 1.10.in-addr.arpa

dn: dc=1.0,dc=1.10.in-addr.arpa,ou=hosts,o=linuxnetworks,c=de
objectclass: top
objectclass: dnsdomain2
objectclass: domainrelatedobject
dc: 1.0
ptrrecord: server.linuxnetworks.de
associateddomain: 1.0.1.10.in-addr.arpa

Tree mode requires each component to be a dc element of its own:

dn: dc=1,dc=0,dc=1,dc=10,dc=in-addr,dc=arpa,ou=hosts,o=linuxnetworks,c=de
objectclass: top
objectclass: dnsdomain2
objectclass: domainrelatedobject
dc: 1
ptrrecord: server.linuxnetworks.de
associateddomain: 1.0.1.10.in-addr.arpa

To use this kind of record, you also have to add the dnsdomain2 schema to the configuration of your LDAP server.

CAUTION:

You can't use "ldap-method=strict" if you need zone transfers (AXFR) to other name servers. Distributing zones can only be done directly via LDAP replication in this case, because for a full zone transfer the reverse records are missing

Migration

BIND zone files

There is a small utility in the PowerDNS distribution available called "zone2ldap", which can convert zone files used by BIND to the ldif format. Ldif is a text file format containing information about LDAP objects and can be read by every standard compliant LDAP server. Zone2ldap needs the BIND named.conf (usually located in /etc) as input and writes the dns record entries in ldif format to stdout:

Usage:

zone2ldap
   --basedn=`<your-basedn
   --named-conf=`<file
   --resume
   > zones.ldif

Alternatively zone2ldap can be used to convert only single zone files instead all zones:

Usage:

zone2ldap
   --basedn=`<your-basedn
   --zone-file=`<file
   --zone-name=`<file
   --resume
   > zone.ldif

See its manpage for a complete list of options.

Bind LDAP backend

If you are using the Bind LDAP sdb backend, you can keep the records in the LDAP tree also for the PowerDNS LDAP backend. The schemas both backends utilize is almost the same except for one important thing: Domains for PowerDNS are stored in the attribute "associatedDomain" whereas Bind stores them split in "relativeDomainName" and "zoneName".

There is a migration script which creates a file in LDIF format with the necessary LDAP updates including the "associatedDomain" and "dc" attributes. The utility is executed on the command line by:

./bind2pdns-ldap
 --host=<host name or IP>
 --basedn=<subtree dn>
 --binddn=<admin dn>
 > update.ldif

The parameter "host" and "basedn" are mandatory, "binddn" is optional. If "binddn" is given, you will be asked for a password, otherwise an anonymous bind is executed. The updates in LDIF format are written to stdout and can be redirected to a file.

The script requires Perl and the Perl Net::LDAP module and can be downloaded from /pdnsldap/bind2pdns-ldap.

Updating the entries in the LDAP tree requires to make the dnsdomain2 schema known to the LDAP server. Unfortunately, both schemas (dnsdomain2 and dnszone) share the same record types and use the same OIDs so the LDAP server can't use both schemas at the same time. The solution is to add the dnsdomain2 schema and replace the dnszone schema by the dnszone-migrate schema. After restarting the LDAP server you can use attributes from both schemas and updating the objects in the LDAP tree using the LDIF file generated from bind2pdns-ldap will work without errors.

Other name server

The easiest way for migrating DNS records is to use the output of a zone transfer (AXFR). Save the output of the "dig" program provided by bind into a file and call zone2ldap with the file name as option to the --zone-file parameter. This will generate you an appropriate ldif file, which you can import into your LDAP tree. The bash script except below automates this for you.

DNSSERVER=127.0.0.1
DOMAINS="linuxnetworks.de 10.10.in-addr.arpa"

for DOMAIN in $DOMAINS; do
   dig @$DNSSERVER $DOMAIN AXFR> $DOMAIN.zone;
   zone2ldap --zone-name=$DOMAIN --zone-file=$DOMAIN.zone> $DOMAIN.ldif;
done

Optimization

LDAP indices

To improve performance, you can tell the LDAP server to maintain indices on certain attributes. This leads to much faster searches for these type of attributes.

The LDAP DNS backend mainly searches for values in associatedDomain, so maintaining an index (pres,eq,sub) on this attribute is a big performance improvement:

index associatedDomain pres,eq,sub

Furthermore if you set ldap-method=strict, it uses the aRecord and aAAARecord attribute for reverse mapping of IP addresses to names. To maintain an index (pres,eq) on these attributes also improves performance of the LDAP server:

index aAAARecord pres,eq
index aRecord pres,eq

All other attributes than associatedDomain, aRecord or aAAARecord are only read if the object matches the specified criteria. Thus, maintaining an index on these attributes is useless.

If you've inserted your entries before adding these statements to your slapd.conf, you have to stop your LDAP server and call slapindex on the command line. This will generate the indices for already existing attributes

dNSTTL attribute

Converting the string in the dNSTTL attribute to an integer is a time consuming task. If you don't use a separate TTL value for each entry and use the default-ttl parameter in pdns.conf instead, you will gain a approx. 7% better performance for entries that aren't cached. You can still add a dNSTTL attribute to entries that should have a different TTL than the default TTL

Access method

The method of accessing the entries in the directory affects the performance too. By default, the "simple" method is used search for entries by using their associatedDomain attribute. Alternatively you can choose the "tree" method, whereby the search is done along the directory tree, e.g. "host.example.dom" is translated into "dc=host,dc=example,dc=dom,...". This requires your LDAP DNS subtree layout to be 1:1 to the DNS tree, but then you will gain additional 7% better performance values.

Troubleshooting

No reverse zone transfer

Your LDAP tree must contain a separate subtree of PTR records (e.g. for 1.1.10.10.in-addr.arpa) and you can't set "ldap-method" to "strict".

IPv6 reverse lookup doesn't work in strict mode

For automatically generated reverse IPv6 records your aAAARecord entries must follow two restrictions: They have to be fully expanded ("FFFF::1" is not allowed and it must be "FFFF:0:0:0:0:0:0:1" instead) and they must not contain leading zeros, e.g. an entry containing "002A" is incorrect - use "2A" without zeros instead. These restrictions are due to the fact that LDAP DNS AAAA entries are pure text and doesn't allow searching by wild-cards.

Bad search filter

The release of PowerDNS 2.9.20 contains a bug in ldap-filter-{axfr,lookup}. A user provided string with ":target:" is replaced with "(associatedDomain=QUERYDATA)" and braces ARE added. So if you create some filter like

ldap-filter-lookup=(&(:target:)(active=yes))

it will result as

ldap-filter-lookup=(&((associatedDomain=QUERYDATA))(active=yes))

which results with bad search filter. To circumvent the bug temporarily you can add instead

ldap-filter-lookup=(&:target:(active=yes))

The bug will be fixed in version 2.9.21 and later versions.


Feel free to add your own tips

Future

DNS notification support

As soon as the LDAP server implementations begin to provide the features of the LDAP client update protocol (LCUP, RFC 3928), it will be possible to support the DNS notification feature for the LDAP DNS backend in case a record in the LDAP directory was changed.

SASL support

Support for more authentication methods would be handy. Anyone interested and willing to contribute?