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Date: Tue, 9 Dec 2014 08:54:15 +0100
From: Peter van Dijk <>
Subject: Re: PowerDNS Security Advisory 2014-02


On 09 Dec 2014, at 8:16 , Peter van Dijk <> wrote:

> Somebody asked me to (help him) check djbdns today, which we’ll do. Any other implementations you are interested in?

Vanilla djbdns 1.05 manages a counter called ‘loop’ (look for ‘z->loop’ in the code); if this counter hits 100, it simply aborts the current query. This is similar to the fixes now present in PowerDNS, BIND and Unbound.

Breakpoint 4, doit (z=0x611660 <u>, state=1) at query.c:452
452	  if (++z->loop == 100) goto DIE;
1: z->loop = 99
(gdb) cont

It then logs 'drop 1 input/output error’ and aborts resolution of this query. Note that it actually drops the query, the client will eventually timeout; PowerDNS Recursor sends a SERVFAIL, and I presume so do BIND and Unbound.

Kind regards,
Peter van Dijk
Netherlabs Computer Consulting BV -

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