[dns-operations] CloudFlare policy on ANY records changing

[Mark Andrews]

In message <CAGmQtQJrpx_XG_OJTShsW5YqAeFKZwdMa16XW7iry9PR0_FT+A at mail.gmail.com>
, Yunhong Gu writes:
> 
> Returning NOTIMP may confuse resolvers as it is not clear "what is not
> implemented".

Which is why you only change one thing at a time when trying to
determine what is covered by NOTIMP.

> A NOTIMP response to an ANY query with EDNS0 option could
> cause a retry-without-EDNS0 query, or mislead the resolver to believe that
> the nameserver does not support EDNS0.

And if you retry w/o a OPT record you will still get NOTIMP, move
onto the next nameserver and enventually return SERVFAIL.

Note there really is nothing special w.r.t. ANY here.  We have
nameservers that return NOTIMP to TXT, MX, NS, SOA, DNSKEY etc.
About the only query type that doesn't get NOTIMP is A.

Mark

-- 
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: marka at isc.org