On 03/17/2017 03:22 AM, Havard Eidnes wrote:
If something gets an ANY response that does not include the thing it
really needs, how is it supposed to know that it needs to ask again?
If something is unable to unambiguously ask for the exact thing it
really needs, that's their problem. It's not a concern for this WG or
the DNS protocol.
Yes, I understand that is a popular opinion. However, I would argue
that it is unhelpfully elitist.
I disagree.
This has to do with caching, so pretty fundamental to the DNS.
Can you explain a bit more about this?
The traditional understanding of ANY == ALL is well ingrained in
developers.
If the query goes directly to an authoritative name server, that
has historically been the case, yes.
If, on the other hand, you have an application making DNS queries,
it typically uses a stub resolver, so sends all its queries via a
caching recursive resolver. What you then get back as a response to
an "ANY" query will depend on what other queries has already been
resolved through that caching recursive resolver already
Yes, I know how ANY queries work. :)
You are making the assumption that those using the ANY query are sending
it to stubs, but there is no way of knowing whether that is true or not.
Therefore I'm entirely with Jim on this one: if an application
needs an MX record, it had better explicitly query for it.
I'm aware that a lot of the animosity towards ANY has come from Dan's
choice of using it to find records for qmail. I am not a Dan-fan
generally, but on this topic he has made the excellent point that the
query exists, and has well-defined semantics which meet the use case, so
it's legal to use it. I have never understood the DNS literati's
animosity towards that argument.
ANY has historically primarily been a debugging aid and isn't really
suitable for use by applications.
That's a value judgement. I don't know how to configure my name server
for that.
I find it astonishing that there is this overwhelming "We must preserve
backwards compatibility at all costs!" sentiment on so many ridiculous
topics in the DNS, and yet because people hate the ANY query (and
particularly one software author's perceived misappropriation of it) SO
MUCH y'all are willing to throw backwards compatibility out the door for
something that it's absolutely clear will break deployed applications.
Doug
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