Re: [DNSOP] Mandated order of CNAME records in a CNAME chain?

Mark Andrews <marka@isc.org> Sun, 02 October 2016 22:10 UTC

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To: Florian Weimer <fw@deneb.enyo.de>
From: Mark Andrews <marka@isc.org>
References: <20160929123532.GD22645@laperouse.bortzmeyer.org> <20160929130333.qsrjntfgmrobj7i2@mycre.ws> <87bmz3p4lt.fsf@mid.deneb.enyo.de>
In-reply-to: Your message of "Sun, 02 Oct 2016 09:55:26 +0200." <87bmz3p4lt.fsf@mid.deneb.enyo.de>
Date: Mon, 03 Oct 2016 09:10:51 +1100
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Archived-At: <https://mailarchive.ietf.org/arch/msg/dnsop/M4M13a3cUMyn8erjLAmMfMtEOEo>
Cc: Robert Edmonds <edmonds@mycre.ws>, dnsop@ietf.org
Subject: Re: [DNSOP] Mandated order of CNAME records in a CNAME chain?
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In message <87bmz3p4lt.fsf@mid.deneb.enyo.de>de>, Florian Weimer writes:
> * Robert Edmonds:
>
> > I think there was already a thread on this topic recently on this list
> > ("Order of CNAME and A in Authoritative Reply" from August 2015). There
> > was some discussion over "adding" versus "appending" and it was pointed
> > out that a lot of existing code (e.g., the BSD stub resolver) was
> > written using the "add at the end" meaning.
>
> Are there stub resolvers which actually chase the CNAME chain?
>
> I assume it is quite common just to check the QNAME, and then extract
> A/AAAA records from the answer section without matching their owner
> names (but potentially recording their owner name as the canonical
> name of the host, even though that's rarely useful these days).

No.  libresolv has checked the owner names of the A (and AAAA)
records for decades now skipping any records that don't match.

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Mark Andrews, ISC
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