[Pdns-dev] Warning regarding stricter zone parsing in 2.9.21: query overload

bert hubert bert.hubert at netherlabs.nl
Mon Apr 23 16:45:20 CEST 2007

While most users report good results with PowerDNS Authoritative Server
2.9.21, there are some important things you need to watch out for.

PowerDNS 2.9.20 and lower were very lenient with parsing malformed IP
addresses, which could not be translated into valid DNS packets. These would
be served as ''.

PowerDNS 2.9.21 is very strict, and drops the question (or more precisely,
the answer) once it finds it can't correctly parse the information from the

This leads to rapid retransmits from your client nameservers, possibly
overloading your database!

So if your database is suddenly overloaded, verify that all your database
records are correct.

A quick way of doing is is trying to AXFR all your zones, and see which ones

For MySQL, a trick is to try:

select * FROM records WHERE (type='A' AND INET_ATON(content) IS NULL);

Possibly followed by:

DELETE FROM records WHERE (type='A' AND INET_ATON(content) IS NULL);

Depending on your mood of the day.

Other interesting queries are:

select * from records where content like ' %';

So keep this in mind if your servers are suddenly overloaded after upgrading
all of them to 2.9.21!

http://www.PowerDNS.com      Open source, database driven DNS Software 
http://netherlabs.nl              Open and Closed source services

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