On Wed, Aug 12, 2015 at 01:59:55PM -0400, Andrew Sullivan wrote:
> The question, for the purposes of the protocol definition, is whether
> a message section (or maybe just the answer section) is an ordered set
> of unordered RRsets. If so, we probably ought to write that down
> somewhere, and specify the order, because as near as I can see it
> never has been specified.
>
> I'm not suggesting we try to invalidate lots of deployed software.
As another datapoint, separate from glibc, the Postfix DNS library
assumes that CNAME records in a response from recursive resolver
are ordered so that in any chain of CNAMEs such as:
A. IN CNAME B.
B. IN CNAME C.
...
L. IN CNAME M. ; logically *and* positionally last
the last CNAME RR in the response is also the logically last link
in the portion of the chain returned by the resolver. So, while
the resolver may return only an initial segment of the chain, the
last CNAME RR returned is expected to be the last in the alias
chain segment.
There is however no dependence on CNAMEs preceding the final answer
if both are returned.
--
Viktor.
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