[dns-operations] Name server turning off RD bit in response - just curious

Robert Edmonds edmonds at isc.org
Tue Aug 7 19:05:20 UTC 2012

Peter Koch wrote:
> On Tue, Aug 07, 2012 at 01:39:32PM -0400, Robert Edmonds wrote:
> > indeed, and for an example of the opposite behavior, see
> > ns[1-4].google.com, which set the RD bit in responses regardless of the
> > RD bit in the query.
> Well, at least my version of "dig" breaks insofar as it emits a warning
> that is only based on the response: ";; WARNING: recursion requested but not available",
> even with "+norec".

right, dig is comparing the response-RD bit against the response-RA bit,
with the assumption that response-RD == query-RD.  i believe that
warning was introduced in this change:

1908.   [func]          dig now warns if 'RA' is not set in the answer when
                        'RD' was set in the query.  host/nslookup skip servers
                        that fail to set 'RA' when 'RD' is set unless a server
                        is explicitly set.  [RT #15005]

Robert Edmonds
edmonds at isc.org

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