Re: Re: Problems with spf testsuite and dns specification

On Sat, 16 Jun 2007, Julian Mehnle wrote:

> I don't see that as a good idea.  Stub resolvers should always try to 
> conform to the same RFCs as live resolvers, and any ambiguities in those 
> RFCs must be considered legal by the RFC 4408 test suite, i.e., it must 
> NOT test them.

The point is, a live resolver *just might* return multiple identical
records.  In that case (as unlikely as it may be in practice), rfc4408 says the
result is PermError.  So this is a legitimate thing to test for.  The
more unlikely, the more important to test for it.  (More likely bugs will show
up in operation right away anyhow.)  The fact that jSPF is unable to
test this scenario is a deficiency in the test setup.  The stub
resolver has different deficiencies.  No test setup is perfect.

> > 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.
> 
> So what?

So you should produce the rfc mandated result given multiple identical records.

> > 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.
> 
> That's true.  But it still doesn't mean that the RFC 4408 test suite 
> should, implicitly or explicitly, test for compliance with some "should" 
> in RFC 2181.

The MUST is in RFC 4408.  The only difficulty is that a particular test setup
has trouble reproducing the multiple identical records scenario.

Now if you feel that RFC 4408 didn't really mean to mandate a permerror
for multiple records when they are identical (in light of 2181), then we can
discuss that.  We can also allow both results in the test suite to reflect
that lack of consensus.

-- 
	      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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