This is the Oracle Database backend, completely rewritten for the 3.0 release, with easily configurable SQL statements, allowing you to graft PowerDNS functionality onto any Oracle database of your choosing.
The Oracle backend is difficult, and possibly illegal, to distribute in binary form. To use it, you will probably need to compile PowerDNS from source. OCI headers are expected in
$ORACLE_HOME/rdbms/public, and OCI libraries in
$ORACLE_HOME/lib. That is where they should be with a working installation of the full Oracle Database client. Oracle InstantClient should work as well, but you will need to make the libraries and headers available in appropriate paths.
This backend uses two kinds of database connections. First, it opens a session pool. Connections from this pool are used only for queries reading DNS data from the database. Second, it opens normal (non-pooled) connections on demand for any kind of write access. The reason for this split is to allow redundancy by replication. Each DNS frontend server can have a local read-only replicated instance of your database. Open the session pool to the local replicated copy, and all data will be available with high performance, even if the main database goes down. The writing connections should go directly to the main database.
Of course, if you do not require this kind of redundancy, or want to avoid the substantial Oracle Database licensing costs, all connections can just go to the same database with the same credentials. Also, the write connections should be entirely unnecessary if you do not plan to use either master or slave mode.
The database to use for read access. OracleBackend will try to create a session pool, so make sure this database user has the necessary permissions. If your connection requires environment variables to be set, e.g.
LD_LIBRARY_PATH, make sure these are set when PowerDNS runs.
/etc/default/pdns might help.
The database to use for write access. These are normal connections, not a session pool. The backend may open more than one at a time.
Parameters for the connection pool underlying the session pool. OCI will open
session-min connections at startup, and open more connections as needed,
session-inc at a time, until
session-max connections are open.
This can be set to an arbitrary string that will be made available in the optional bind variable
:nsname for all SQL statements. You can use this to run multiple PowerDNS instances off the same database, while serving different zones.
There are many more options that are used to define the different SQL statements. These will be discussed after the reference database schema has been explained.
The Database Schema
You can find an example database schema in
schema.sql in the PowerDNS source distribution. It is intended more as a starting point to come up with a schema that works well for your organisation, than as something you should run as it is. As long as the semantics of the SQL statements still work out, you can store your DNS data any way you like.
You should read this while having
schema.sql to hand. Columns will not be specifically explained where their meaning is obvious.
Note: All FQDNs should be specified in lower case and without a trailing dot. Where things are lexicographically compared or sorted, make sure a sane ordering is used.
'NLS_LANG=AMERICAN_AMERICA.AL32UTF8' should generally work well enough; when in doubt, enforce a plain ordering with
"NLSSORT(value, 'NLS_SORT = BINARY')".
This table lists the zones for which PowerDNS is supposed to be an authoritative nameserver, plus a small amount of information related to master/slave mode.
The FQDN of the zone apex, e.g. 'example.com'.
Describes how PowerDNS should host the zone. Valid values are 'NATIVE', 'MASTER', and 'SLAVE'. PowerDNS acts as an authoritative nameserver for the zone in all modes. In slave mode, it will additionally attempt to acquire the zone's content from a master server. In master mode, it will additionally send 'NOTIFY' packets to other nameservers for the zone when its content changes.
Tip: There is a global setting to make PowerDNS send 'NOTIFY' packets in slave mode.
This value, updated by PowerDNS, is the unix timestamp of the last successful attempt to check this zone for freshness on the master.
The number of seconds PowerDNS should wait after a successful freshness check before performing another one. This value is also found in the zone's SOA record. You may want to make sure to put the same thing in both places.
The serial of the version of the zone's content we are hosting now. This value is also found in the zone's SOA record. You may want to make sure to put the same thing in both places.
The latest serial for which we have sent
NOTIFY packets. Updated by PowerDNS.
The Zonemasters and ZoneAlsoNotify Tables
These are lists of hosts PowerDNS will interact with for a zone in master/slave mode. 'Zonemasters' lists the hosts PowerDNS will attempt to pull zone transfers from, and accept 'NOTIFY' packets from. 'ZoneAlsoNotify' lists hosts PowerDNS will send 'NOTIFY' packets to, in addition to any hosts that have NS records.
Host entries can be IPv4 or IPv6 addresses, in string representation. If you need to specify a port, use
192.0.2.4:5300 notation for IPv4 and brackets for IPv6:
The Supermasters Table
In superslave mode, PowerDNS can accept 'NOTIFY' packets for zones that have not been defined in the zone table yet. PowerDNS will then create an entry for the zone and attempt a zone transfer. This table defines the list of acceptable sources for supernotifications.
An identifying string for this entry. Only used for logging.
The alleged originating IP address of the notification.
The FQDN of an authoritative nameserver.
A supernotification will be accepted if an entry is found such that the notification came from 'ip' and 'nameserver' appears in an NS record for that zone.
The ZoneMetadata Table
This is a per-zone key-value store for various things PowerDNS needs to know that are not part of the zone's content or handled by other tables. Depending on your needs, you may not want this to exist as an actual table, but simulate this in PL/SQL instead.
The currently defined metadata types are:
If set to 1, PowerDNS should assume that DNSSEC signatures for this zone exist in the database and use them instead of signing records itself. For a slave zone, this will also signal to the master that we want DNSSEC records when attempting a zone transfer.
The NSEC3 hashing parameters for the zone.
The value is the name of a TSIG key. A client will be allowed to AXFR from us if the request is signed with that key.
The value is the name of a TSIG key. Outgoing
NOTIFY packets for this zone will be signed with that key.
The Tables for Cryptographic Keys
We have two of them: 'TSIGKeys' for symmetric TSIG keys, and 'ZoneDNSKeys' for DNSSEC signing keys.
The Records Table
The actual DNS zone contents are stored here.
The zone this records belongs to. Normally, this is obvious. When you are dealing with zone delegations, you have to insert some records into the parent zone of their actual zone. See also
The owner name of this record. Again, this is lower case and without a trailing dot.
This should be a string that consists of the labels of the owner name, in reverse order, with spaces instead of dots separating them, for example:
'www.example.com' => 'com example www'
This is used as a quick and dirty way to get canonical zone ordering. You can chose a more correct and much more complicated implementation instead if you prefer. In the reference schema, this is automatically set by a trigger.
The NSEC3 hash of the owner name. The reference schema provides code and a trigger to calculate this, but they are not production quality. The recommendation is to load the dnsjava classes into your database and use their facilities for dealing with DNS names and NSEC3 hashes.
The TTL for the record set. This should be the same for all members of a record set, but PowerDNS will quietly use the minimum if it encounters different values.
The type of the record, as a canonical identification string, e.g. 'AAAA' or 'MX'. You can set this and 'content' NULL to indicate a name that exists, but doesn't carry any record (a so called empty non-terminal) for NSEC/NSEC3 ordering purposes.
The data part of the DNS record, in canonical string representation, except that if this includes FQDNs, they should be specified without a trailing dot.
The unix timestamp of the last change to this record. Used only for the deprecated autoserial feature. You can omit this unless you want to use that feature.
0 or 1 depending on whether this record is an authoritative member of the zone specified in
zone_id. These are the rules for determining that: A record is an authoritative member of the zone its owner name belongs to, except for DS records, which are authoritative members of the parent zone. Delegation records, that is, NS records and related A/AAAA glue records, are additionally non-authoritative members of the parent zone.
PowerDNS has a function to automatically set this. OracleBackend doesn't support that. Do it in the database.
The SQL Statements
Fetching DNS records
There are five queries to do this. They all share the same set of return columns:
- fqdn: The owner name of the record.
- ttl: The TTL of the record set.
- type: The type of the record.
- content: The content of the record.
- zone_id: The numerical identifier of the zone the record belongs to. A record can belong to two zones (delegations/glue), in which case it may be returned twice.
- last_change: The unix timestamp of the last time this record was changed. Can safely be set as a constant 0, unless you use the autoserial feature.
- auth: 1 or 0 depending on the zone membership (authoritative or not).
Record sets (records for the same name of the same type) must appear consecutively, which means ORDER BY clauses are needed in some places. Empty non-terminals should be suppressed.
The queries differ in which columns are restricted by 'WHERE' clauses:
Looking for records based on owner name and type. Default:
SELECT fqdn, ttl, type, content, zone_id, last_change, auth FROM Records WHERE type = :type AND fqdn = lower(:name)
Looking for records from one zone based on owner name and type. Default:
SELECT fqdn, ttl, type, content, zone_id, last_change, auth FROM Records WHERE type = :type AND fqdn = lower(:name) AND zone_id = :zoneid
Looking for records based on owner name. Default:
SELECT fqdn, ttl, type, content, zone_id, last_change, auth FROM Records WHERE fqdn = lower(:name) AND type IS NOT NULL ORDER BY type
Looking for records from one zone based on owner name. Default:
SELECT fqdn, ttl, type, content, zone_id, last_change, auth FROM Records WHERE fqdn = lower(:name) AND zone_id = :zoneid AND type IS NOT NULL ORDER BY type
Looking for all records from one zone. Default:
SELECT fqdn, ttl, type, content, zone_id, last_change, auth FROM Records WHERE zone_id = :zoneid AND type IS NOT NULL ORDER BY fqdn, type
Zone Metadata and TSIG
Fetch the content of the metadata entries of type ':kind' for the zone called ':name', in their original order. Default:
SELECT md.meta_content FROM Zones z JOIN ZoneMetadata md ON z.id = md.zone_id WHERE z.name = lower(:name) AND md.meta_type = :kind ORDER BY md.meta_ind
Delete all metadata entries of type ':kind' for the zone called ':name'. You can skip this if you do not plan to manage zones with the
pdnsutil tool. Default:
DELETE FROM ZoneMetadata md WHERE zone_id = (SELECT id FROM Zones z WHERE z.name = lower(:name)) AND md.meta_type = :kind
Create a metadata entry. You can skip this if you do not plan to manage zones with the
pdnsutil tool. Default:
INSERT INTO ZoneMetadata (zone_id, meta_type, meta_ind, meta_content) VALUES ( (SELECT id FROM Zones WHERE name = lower(:name)), :kind, :i, :content )
Retrieved the TSIG key specified by ':name'. Default:
SELECT algorithm, secret FROM TSIGKeys WHERE name = :name
Retrieve the DNSSEC signing keys for a zone. Default:
SELECT k.id, k.flags, k.active, k.keydata FROM ZoneDNSKeys k JOIN Zones z ON z.id = k.zone_id WHERE z.name = lower(:name)
Delete a DNSSEC signing key. You can skip this if you do not plan to manage zones with the
pdnsutil tool. Default:
DELETE FROM ZoneDNSKeys WHERE id = :keyid
Add a DNSSEC signing key. You can skip this if you do not plan to manage zones with the
pdnsutil tool. Default:
INSERT INTO ZoneDNSKeys (id, zone_id, flags, active, keydata) " VALUES ( zonednskeys_id_seq.NEXTVAL, (SELECT id FROM Zones WHERE name = lower(:name)), :flags, :active, :content ) RETURNING id INTO :keyid
Enable or disable a DNSSEC signing key. You can skip this if you do not plan to manage zones with the pdnsutil tool. Default:
UPDATE ZoneDNSKeys SET active = :active WHERE id = :keyid
Determine the predecessor and successor of an owner name, in canonical zone ordering. See the reference implementation for the quick and dirty way, and the RFCs for the full definition of canonical zone ordering.
This statement is a PL/SQL block that writes into two of the bind variables, not a query.
BEGIN get_canonical_prev_next(:zoneid, :name, :prev, :next); END;
Given an NSEC3 hash, this call needs to return its predecessor and successor in NSEC3 zone ordering into
:next, and the FQDN of the predecessor into
BEGIN get_hashed_prev_next(:zoneid, :hash, :unhashed, :prev, :next); END;
Get some basic information about the named zone before doing master/slave things. Default:
SELECT id, name, type, last_check, serial, notified_serial FROM Zones WHERE name = lower(:name)
Delete all records for a zone in preparation for an incoming zone transfer. This happens inside a transaction, so if the transfer fails, the old zone content will still be there. Default:
DELETE FROM Records WHERE zone_id = :zoneid
Insert a record into the zone during an incoming zone transfer. This happens inside the same transaction as delete-zone, so we will not end up with a partially transferred zone. Default:
INSERT INTO Records (id, fqdn, zone_id, ttl, type, content) VALUES (records_id_seq.NEXTVAL, lower(:name), :zoneid, :ttl, :type, :content)
A block of PL/SQL to be executed after a zone transfer has successfully completed, but before committing the transaction. A good place to locate empty non-terminals, set the
auth bit and NSEC3 hashes, and generally do any post-processing your schema requires. The do-nothing default:
DECLARE zone_id INTEGER := :zoneid; BEGIN NULL; END;
Return a list of zones that need to be checked and their master servers. Return multiple rows, identical except for the master address, for zones with more than one master. Default:
SELECT z.id, z.name, z.last_check, z.serial, zm.master FROM Zones z JOIN Zonemasters zm ON z.id = zm.zone_id WHERE z.type = 'SLAVE' AND (z.last_check IS NULL OR z.last_check + z.refresh < :ts) ORDER BY z.id
Set the last check timestamp after a successful check. Default:
UPDATE Zones SET last_check = :lastcheck WHERE id = :zoneid
Return a list of zones that need to have
NOTIFY packets sent out. Default:
SELECT id, name, serial, notified_serial FROM Zones WHERE type = 'MASTER' AND (notified_serial IS NULL OR notified_serial < serial)
Set the last notified serial after packets have been sent. Default:
UPDATE Zones SET notified_serial = :serial WHERE id = :zoneid
Return a list of hosts that should be notified, in addition to any nameservers in the NS records, when sending
NOTIFY packets for the named zone. Default:
SELECT an.hostaddr FROM Zones z JOIN ZoneAlsoNotify an ON z.id = an.zone_id WHERE z.name = lower(:name)
Return a list of masters for the zone specified by id. Default:
SELECT master FROM Zonemasters WHERE zone_id = :zoneid
Return a row if the specified host is a registered master for the named zone. Default:
SELECT zm.master FROM Zones z JOIN Zonemasters zm ON z.id = zm.zone_id WHERE z.name = lower(:name) AND zm.master = :master
If a supernotification should be accepted from ':ip', for the master nameserver ':ns', return a label for this supermaster. Default:
SELECT name FROM Supermasters WHERE ip = :ip AND nameserver = lower(:ns)
A supernotification has just been accepted, and we need to create an entry for the new zone. Default:
INSERT INTO Zones (id, name, type) VALUES (zones_id_seq.NEXTVAL, lower(:zone), 'SLAVE') RETURNING id INTO :zoneid
We need to register the first master server for the newly created zone. Default:
INSERT INTO Zonemasters (zone_id, master) VALUES (:zoneid, :ip)