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

From: Florian Weimer <[email-masked]>
Date: Sun, 02 Oct 2016 09:55:26 +0200

* 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).

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From: Mark Andrews <[email-masked]>
Date: Mon, 03 Oct 2016 09:10:51 +1100

In message <[email-masked]>, Florian Weimer writes:
> 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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PHONE: +61 2 9871 4742                 INTERNET: [email-masked]

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From: Florian Weimer <[email-masked]>
Date: Sun, 09 Oct 2016 13:03:32 +0200

> records for decades now skipping any records that don't match.

Okay.  Is it necessary to retain those checks and even fix them to
avoid the CNAME ordering assumption?