[dns-operations] Adding CNAME for the root domain issue

Andrew Sullivan ajs at anvilwalrusden.com
Tue May 3 17:03:36 UTC 2016

On Tue, May 03, 2016 at 05:51:04PM +0100, Tony Finch wrote:
> I thought what would happen is just like the current per-type positive /
> negative cacheing for non-CNAME types.  When a cache gets a query for a
> type it doesn't have, query the origin, and cache positively or
> negatively. If it gets a negative result from the origin or the cache,
> look for an old-CNAME (query for it if necessary and cache positively or
> negatively per-type as usual); if it gets an old-CNAME from the origin or
> the cache, re-do the query at the target.

Given the modern semantics of CNAME, however, this won't work.  If you
got a CNAME RR, it ought to evict anything else at that owner name
from the cache, because nothing else can coexist at the location of
the CNAME RR.  No?

> The mail servers I am familiar with chase CNAME chains.

Yes, most I know do too.


Andrew Sullivan
ajs at anvilwalrusden.com

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