Re: [DNSOP] abandoning ANAME and standardizing CNAME at apex

Mukund Sivaraman <muks@mukund.org> Mon, 17 September 2018 09:30 UTC

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Date: Mon, 17 Sep 2018 15:00:28 +0530
From: Mukund Sivaraman <muks@mukund.org>
To: Ray Bellis <ray@bellis.me.uk>
Cc: dnsop@ietf.org
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References: <b73f3dc7-b378-d5d8-c7a2-42bc4326fbae@nic.cz> <20180916095655.GA11121@jurassic> <20180917071414.7pb6elbooockzaa7@nic.fr> <20180917074327.GA13046@jurassic> <409968f7-bea2-fa14-67ba-3a6ea7feb837@bellis.me.uk>
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Subject: Re: [DNSOP] abandoning ANAME and standardizing CNAME at apex
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Hi Ray

On Mon, Sep 17, 2018 at 09:47:50AM +0100, Ray Bellis wrote:
> On 17/09/2018 08:43, Mukund Sivaraman wrote:
> 
> > The suggestion is only to require support in resolvers going forward for
> > CNAME co-existing with other types for now. That should not break any
> > detail of how DNS is used today.
> 
> ....
> 
> > Although it changes current DNS protocol, AFAICT there does not seem to
> > be anything badly wrong with allowing CNAME + other types at a node,
> > where the CNAME is considered a fallback when the required type doesn't
> > exist.
> 
> This is not true.
> 
> Ondrej demonstrated at the last hackathon that permitting a CNAME
> alongside the apex can cause MX-related failures in resolvers that are
> not upgraded.

"The suggestion is only to require support in resolvers going forward
for CNAME co-existing with other types for now."

It is obvious if authoritatives did that today and a RFC 1035 resolver
cached a CNAME, it would match the cached CNAME when doing a type lookup
in cache.

		Mukund