replace "SERVFAIL" to "NXDOMAIN" with rpz

Mon Jun 19 09:03:08 UTC 2023

Hi Sami.
Firstly, a couple of definitions:
NXDOMAIN is a response from an authoritative server (or a resolver because
it cached it). It is a positive confirmation that "this name does not
exist". It means that the QNAME in the query cannot be found, for any
record type.
SERVFAIL is a response from a recursive server meaning "I tried my best to
get a response to your query but I just failed".

So if your monitoring tool, whatever it is, is receiving SERVFAIL responses
from your DNS server then you need to fix whatever is causing those in the
server.
Causes of SERVFAIL could be that your server cannot contact the
authoritative server(s) that should know the answer. Or it might be because
your server is trying to do DNSSEC validation and that is failing.
The best way to know *why* you are getting SERVFAIL would be to take a
packet capture that includes the client queries to the server and any
queries the server makes to try and get answers, plus all the responses.
Please do that and share the results, using real domains, not examples.

Hope that helps, Greg

On Mon, 19 Jun 2023 at 09:39, <sami.rahal at sofrecom.com> wrote:

> Hello Thank you for your feedback,
> yes it works like that!  for that does not work for a domain name that
> already has the return code "SERVFAIL" and we want to change this code by
> "NXDDOMAIN" like this domain name "antlauncher.com"
> regards Rahal
>
> -----Message d'origine-----
> De : bind-users <bind-users-bounces at lists.isc.org> De la part de
> bind-users-request at lists.isc.org
> Envoyé : samedi 17 juin 2023 06:23
> À : bind-users at lists.isc.org
> Objet : bind-users Digest, Vol 4262, Issue 1
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> Today's Topics:
>
>    1. replace "SERVFAIL"  to "NXDOMAIN"  with rpz
>       (sami.rahal at sofrecom.com)
>    2. Re: replace "SERVFAIL" to "NXDOMAIN" with rpz (Crist Clark)
>    3. Re: replace "SERVFAIL" to "NXDOMAIN" with rpz (Fred Morris)
>    4. Re: replace "SERVFAIL" to "NXDOMAIN" with rpz (Ond?ej Sur?)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Fri, 16 Jun 2023 20:39:43 +0000
> From: sami.rahal at sofrecom.com
> To: "bind-users at lists.isc.org" <bind-users at lists.isc.org>
> Subject: replace "SERVFAIL"  to "NXDOMAIN"  with rpz
> Message-ID: <9c4465dc103645149093f4d3f60cf89a at sofrecom.com>
> Content-Type: text/plain; charset="us-ascii"
>
>
> Hello
> For monitoring reasons I try to change the return code of a domain name
> from "SERVFAIL" to "NXDOMAIN" with the rpz classic configuration of
> BIND9.16.42 as follows:
> example.com IN CNAME.
> *.example.com IN CNAME .
> But it still doesn't work, I still have the message  " SERVFAIL", is it
> feasible or not please ?
> Kind regards
>
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> Message: 2
> Date: Fri, 16 Jun 2023 20:29:16 -0700
> From: Crist Clark <cjc+bind-users at pumpky.net>
> To: sami.rahal at sofrecom.com
> Cc: "bind-users at lists.isc.org" <bind-users at lists.isc.org>
> Subject: Re: replace "SERVFAIL" to "NXDOMAIN" with rpz
> Message-ID:
>         <CAAcrURK2=+uqQ+_AvVbiAV2jpagOhd=
> ozRfQ_SCazBn-rUZXig at mail.gmail.com>
> Content-Type: text/plain; charset="utf-8"
>
> That should return a NXDOMAIN. Returning SERVFAIL is never a normal RPZ
> action. Something is wrong with your configuration.
>
> On Fri, Jun 16, 2023 at 1:39?PM <sami.rahal at sofrecom.com> wrote:
>
> >
> >
> > Hello
> >
> > For monitoring reasons I try to change the return code of a domain
> > name from "SERVFAIL" to "NXDOMAIN" with the rpz classic configuration
> > of
> > BIND9.16.42 as follows:
> >
> > example.com IN CNAME.
> >
> > *.example.com IN CNAME .
> >
> > But it still doesn't work, I still have the message  " SERVFAIL", is
> > it feasible or not please ?
> >
> > Kind regards
> >
> >
> > --
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> ------------------------------
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> Message: 3
> Date: Fri, 16 Jun 2023 21:40:11 -0700 (PDT)
> From: Fred Morris <m3047 at m3047.net>
> To: "bind-users at lists.isc.org" <bind-users at lists.isc.org>
> Subject: Re: replace "SERVFAIL" to "NXDOMAIN" with rpz
> Message-ID: <alpine.LSU.2.21.2306162134190.27806 at flame.m3047>
> Content-Type: text/plain; charset="utf-8"; Format="flowed"
>
> Admittedly, since I'm writing software to do "off label" stuff with DNS I
> make mistakes. But I have seen things along this line (interactions between
> RPZ and regular resolution in the context of "broken" domains): in some
> cases it has seemed impossible to ameliorate / mitigate SERVFAIL utilizing
> RPZ.
>
> I'll try to pay more attention and see if I can isolate a test case if the
> problem recurs. (I was kind of hoping someone would have a solution!)
>
> --
>
> Fred Morris
>
> On Fri, 16 Jun 2023, Crist Clark wrote:
> >
> > That should return a NXDOMAIN. Returning SERVFAIL is never a normal
> > RPZ action. Something is wrong with your configuration.
> >
> > On Fri, Jun 16, 2023 at 1:39?PM <sami.rahal at sofrecom.com> wrote:
> >>
> >> For monitoring reasons I try to change the return code of a domain
> >> name from "SERVFAIL" to "NXDOMAIN" with the rpz classic configuration
> >> of
> >> BIND9.16.42 as follows:
> >>
> >> example.com IN CNAME.
> >>
> >> *.example.com IN CNAME .
> >>
> >> But it still doesn't work, I still have the message  " SERVFAIL", is
> >> it feasible or not please ?
> >>
>
> ------------------------------
>
> Message: 4
> Date: Sat, 17 Jun 2023 07:22:50 +0200
> From: Ond?ej Sur? <ondrej at isc.org>
> To: Fred Morris <m3047 at m3047.net>
> Cc: bind-users at lists.isc.org
> Subject: Re: replace "SERVFAIL" to "NXDOMAIN" with rpz
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