[Pdns-users] Recursor LUA - trigger additional lookups

Radoslaw Kamil Ejsmont radoslaw at ejsmont.net
Mon Feb 12 21:56:44 UTC 2018

Hi Brian

yep, reverse of DNS64 is more or less what I am trying to achieve. And I found a way - a minimal DNS lookup library for LUA that has no dependencies and runs very quickly:


It works really nicely with powerdns lua scripts. Beware though of circular queries when having query triggering a query.



Radoslaw Kamil Ejsmont, Ph.D.
http://radoslaw.ejsmont.net <http://radoslaw.ejsmont.net/>

> On 12 Feb 2018, at 18:34, Brian Candler <b.candler at pobox.com> wrote:
> On 12/02/2018 17:23, Pieter Lexis wrote:
>> If you known the (sub) domains that need this special processing, you
>> could simplify your life by adding them to a DNSSuffixMatchGroup[1] and
>> if the domain name in the AAAA query is not matched in this group, send
>> a NODATA response to let the client retry with A.
> Another way to do it would be if you know the IPv6 *prefixes* of the cloud site(s) you need to reach via the tunnel.  You could then filter out any AAAA responses which are not within those prefixes.
> It also occurs to me that what you're asking for sounds quite similar to what DNS64 does, but backwards:
> * DNS64: if AAAA query has no data then check for A record, and if it exists, embed it into AAAA response
> * What you want: if AAAA query has data then check for A record, and if it exists, change AAAA response to NODATA
> But it may not be straightforward to hack the powerdns DNS64 code to work that way.
> https://doc.powerdns.com/md/recursor/dns64/
> Cheers,
> Brian.
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