[Pdns-users] Possible DNS DOS?

bert hubert bert.hubert at netherlabs.nl
Tue Jun 23 06:17:25 UTC 2009

On Tue, Jun 23, 2009 at 12:27 AM, Chris Modesitt<chris at veracitycom.net> wrote:
> I have an interesting problem that has been happening for about 2 weeks.
> First a little about my setup, currently I am running the following:

Ok - this issue has probably been fixed in commits 1364 and 1365.

What happened was that during the attempt to restart PowerDNS it
either crashed, or blocked.

This in turn happened because a restart attempts to do a full cleanup
of the packet cache, which had problems if it happened under high
query load (which does not stop for the restart).

I've now modified the code not to do a full cleanup when attempting to
restart for such purposes. In addition, the packet cache should now be
able to deal with a cleanup in progress during queries, but that
should not happen anymore.

The quick workaround is to raise the 5000 query limit to 50000, and
hope the problem goes away, or to run one of the 2.9.23 snapshots I'll
be generating shortly.


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