Re: Re: Problems with spf testsuite and dns specification

On Sat, 16 Jun 2007, Stefano Bagnara wrote:

> So this lead to inconsistent result when someone publishes multiple
> identical records: you cannot tell if users will receive PermError or
> they will accept it... IMHO unpredictable result is bad for a

Publishing multiple SPF records is forbidden by rfc4408, whether they
are identical or not.  The effect of your issue is that often
an implementation can't tell that multiple records were published
so as to return the required PermError.  That is the only reason that
an alternate result would be allowed in the test suite - because with
live DNS, you can't tell whether a cache combined identical records.
Ideally, you would return a Permerror because multiple records are forbidden
by the RFC, but ideals are not always attainable attainable in practice.

That is why I would like to tag tests for liveDNS vs stubbed resolver.
The stubbed resolver can test for the correct result when multiple identical
records are in fact passed through.  Just because the DNS you are testing
with happens to combine them, doesn't mean that in production you won't
run into a cache that doesn't.

The inconsistency is a red herring.  You could publish multiple non-identical
records with differing TTL and get a similar inconsistency where resolvers
could see either or both depending on timing.

-- 
	      Stuart D. Gathman <[email protected]>
    Business Management Systems Inc.  Phone: 703 591-0911 Fax: 703 591-6154
"Confutatis maledictis, flammis acribus addictis" - background song for
a Microsoft sponsored "Where do you want to go from here?" commercial.

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