Re: [Doh] meta qtypes

Dave Lawrence <tale@dd.org> Mon, 19 March 2018 11:36 UTC

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Date: Mon, 19 Mar 2018 07:36:41 -0400
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Subject: Re: [Doh] meta qtypes
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Ben Schwartz writes:
> NXDOMAIN has an explicit TTL, so I don't understand
> why the "negative answer" case requires a different algorithm.

NXDOMAIN's (and pseudo-rcode NODATA's) version of "explicit TTL" is:

1) Is there an SOA in authority? Use the mininmum of the RR TTL or the
   negative TTL in rdata.
2) No SOA?  Implementation dependent.  Please try to pick a
   subjectively sane value.

And that's just NXDOMAIN/NODATA, not REFUSED, SERVFAIL, or other
non-NOERROR rcodes.

Personally I think that the best that can be hoped for when you don't
get back RRSets with clear TTLs, or an SOA for negative answers, is
probably no-cache, with "please try to pick something subjectively
sane" a not unreasonable choice.