TinyDNS Backend

• Native: Yes
• Master: Yes
• Slave: No
• Superslave: No
• DNSSEC: No
• Zone caching: Yes
• Multiple Instances: Yes
• Module name: tinydns
• Launch: tinydns

The TinyDNS backend allows you to use djbdns’s data.cdb file format as the storage of your DNS records. The data.cdb file is created using tinydns-data. The backend is designed to be able to use the data.cdb files without any changes.

Configuration Parameters

These are the configuration file parameters that are available for the TinyDNS backend. It is recommended to set the tinydns-dbfile.

tinydns-dbfile

• String
• Default: data.cdb

Specifies the name of the data file to use.

tinydns-tai-adjust

• Integer
• Default: 11

This adjusts the TAI value if timestamps are used. These seconds will be added to the start point (1970) and will allow you to adjust for leap seconds. The current default is 11. The last update was on January 1st, 2017.

tinydns-notify-on-startup

• Boolean
• Default: no

Tell the TinyDNSBackend to notify all the primary nameservers on startup. This might cause broadcast storms.

tinydns-ignore-bogus-records

• Boolean
• Default: no

The tinydns-data program can create data.cdb files that have bad/corrupt RDATA. PowerDNS will crash when it tries to read that bad/corrupt data. This option (change to yes), allows you to ignore that bad RDATA to make PowerDNS operate when bad data is in your CDB file. Be aware that the records are then ignored, where tinydns would still send out the bogus data. The option is primarily useful in primary mode, as that reads all the packets in the zone to find all the SOA records.

tinydns-locations

• Boolean
• Default: yes

Enable or Disable location support in the backend. Changing the value to ‘no’ will make the backend ignore the locations. This then returns all records. When the setting is changed to ‘no’ an AXFR will also return all the records. With the setting on ‘yes’ an AXFR will only return records without a location.

Location and Timestamp support

Both timestamp and location are supported in the backend. Locations support can be changed using the tinydns-locations setting. Timestamp and location only work as expected when cache-ttl and query-cache-ttl are set to 0 (which disables these caches). Timestamp can operate with cache-ttl if cache is needed, but the TTL returned for the timestamped racked will not be totally correct. The record will expire once the cache is expired and the backend is queried again. Please note that cache-ttl is a performance related setting. See Performance and Tuning. Location support only exists for IPv4!

Primary mode

The TinyDNSBackend supports primary mode. This allows it to notify secondary nameservers of updates to a zone. You simply need to rewrite the data.cdb file with an updated/increased serial and PowerDNS will notify the secondary nameservers of that domain. The tinydns-notify-on-startup configuration setting tells the backend if it should notify all the secondary nameservers just after startup.

The CDB datafile does not allow PowerDNS to easily query for newly added domains or updated serial numbers. The CDB datafile requires us to do a full scan of all the records. When running with verbose logging, this could lead to a lot of output. The scanning of the CDB file may also take a while on systems with large files. The scan happens at an interval set by the xfr-cycle-interval. It might be useful to raise this value to limit the amount of scans on the CDB file.

The TinyDNSBackend also keeps a list of all the zones. This is needed to detect an updated serial and to give every zone a unique id. The list is updated when a zone is added, but not when a zone is removed. This leads to some memory loss.

Useful implementation Notes

This backend might solve some issues you have with the current tinydns noted on Jonathan de Boyne Pollard’s djbdns known problems page.

The data.cdb file format support all types of records. They are sometimes difficult to create because you need to specify the actual content of the rdata. Tinydns.org provides a number of links to tools/cgi-scripts that allow you to create records. Anders Brownworth also provides a number of useful record building scripts on his djbdnsRecordBuilder.

PowerDNS and TinyDNS handle wildcards differently. Looking up foo.www.example.com with the below records on TinyDNS will return 198.51.100.1, PowerDNS will return NXDOMAIN. According to RFC 4592 *.example.com should only match subdomains in under example.com, not *.*.example.com. This compatibility issue is noted on the axfr-get page for the djbdns suite.

*.example.com     A 198.51.100.1
www.example.com   A 198.51.100.1

Compiling the TinyDNS backend requires you to have tinycdb version 0.77.