Re: Needless DNS queries

From	Dieter Rohlfing <dr-erc@gmx.net>
Newsgroups	linux.debian.user
Subject	Re: Needless DNS queries
Date	2022-06-14 15:10 +0200
Message-ID	<EyesV-4Lmc-37@gated-at.bofh.it> (permalink)
References	<EvJ0d-3dZZ-11@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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Thanks to everybody, who replied.

After some more reading and tinkering I've made the following
observations:

The response code NXDOMAIN means: domain name did not resolve. In
this case the search option becomes important. Whenever a domain name
does not resolve, the client's resolver (at least in Linux) suffixes the
original domain name with each item in the search list until the new
domain name resolves.

So this is regular behaviour and it explains the needless DNS queries.

AdguardHome uses the response code NXDOMAIN to signal the client "this
is a forbidden domain". For this signal "this is a forbidden domain"
you can configure AdguardHome to use the IPv4 0.0.0.0 and the response
code NOERROR. Now the (forbidden) domain is resolved without an error
and the IPv4 of 0.0.0.0. So there's no need to use the search list and
the needless DNS queries vanish.

Thanks for reading and have a nice day.

Dieter

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Thread

Needless DNS queries Dieter Rohlfing <dr-erc@gmx.net> - 2022-06-07 17:10 +0200
  Re: Needless DNS queries David Wright <deblis@lionunicorn.co.uk> - 2022-06-07 17:30 +0200
  Re: Needless DNS queries Dan Ritter <dsr@randomstring.org> - 2022-06-07 17:40 +0200
    Re: Needless DNS queries Tim Woodall <debianuser@woodall.me.uk> - 2022-06-07 18:10 +0200
    Re: Needless DNS queries Greg Wooledge <greg@wooledge.org> - 2022-06-07 19:00 +0200
      Re: Needless DNS queries Darac Marjal <mailinglist@darac.org.uk> - 2022-06-07 19:40 +0200
        Re: Needless DNS queries Lee <ler762@gmail.com> - 2022-06-08 00:10 +0200
      Re: Needless DNS queries Tim Woodall <debianuser@woodall.me.uk> - 2022-06-08 00:20 +0200
        Re: Needless DNS queries Lee <ler762@gmail.com> - 2022-06-08 03:00 +0200
          Re: Needless DNS queries Greg Wooledge <greg@wooledge.org> - 2022-06-08 03:10 +0200
            Re: Needless DNS queries Lee <ler762@gmail.com> - 2022-06-08 07:30 +0200
  Re: Needless DNS queries Dieter Rohlfing <dr-erc@gmx.net> - 2022-06-14 15:10 +0200

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