[dns-operations] Ultra DNS responding with NXDOMAIN for "www.uber.com"

[Paul Vixie]

On Sun, Aug 08, 2021 at 03:20:24PM +0530, Shreyas Zare wrote:
> ... The resolver I have does restart for the last CNAME regardless
> of the RCODE but, the negative cache implementation based on RFC2308 and
> RFC8020 caused the NXDOMAIN response to get cached causing the issue.

that's exactly what should happen. i regularly correspond with operators
of dns-based load balancers that return NXDOMAIN for some qtypes, which
prevents a standards-conforming recursive dns server from asking about
that name for other qtypes. we have to strengthen the failure case here,
so that such authoritative responders fail earlier and more often.

-- 
Paul Vixie