[dns-operations] Cloudflare considered harmful?

Alexander Dupuy alexdupuy at google.com
Thu Apr 9 22:44:50 UTC 2020


FWIW, Google Public DNS doesn't make any attempt to try to check for or
handle CNAMEs at apex, either in regular lookup or DNSSEC validation.
There's not much point, since it's not legal zone data, and there is no
possibility of consistent behavior.

SERVFAILing the NODATA responses for domains with CNAME and other records,
as Paul Vixie suggested, won't help in the case of the domain served from
gslb01.nlm.nih.gov since the NSEC3 records don't have the CNAME, and even
if they were present, only breaks negative responses, which has little
operational effect.

A case similar to the unsigned Cloudflare one was reported against Google
Public DNS on our issue tracker over a year ago – I closed it in
https://issuetracker.google.com/122204067#comment3 as Works as Intended and
suggested they file an issue with Cloudflare.

My best guess about the problem is that they allow users on paid plans to
create CNAME at apex (since it is flattened, it works correctly). When
users drop back to free plans (or free trials expire), the CNAME flattening
is turned off, and then you see the CNAME at apex configuration.
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