BIND started replying to queries for .com with .COM
marka at isc.org
Wed Mar 30 11:25:15 UTC 2016
In message <56FBB385.5070203 at imperial.ac.uk>, Phil Mayers writes:
> On 30/03/16 01:19, Mark Andrews wrote:
> > Your monitoring probe is broken.
> > STD 13 says that that the DNS is case preserving. The problem is
> > that lots of servers aren't case preserving instead they echo back
> > the query case in the owner names of records returned which named
> > then records.
> Can I be clear on what you think would be the correct behaviour here?
> Presumably the question section should exactly match what the client
> sent always, bit-for-bit, so we're talking about the ans/auth/add
> sections - they should, in your reading of the standards, match the case
> of the on-disk authoritative data, not what the client sent, yes?
> Am I correct in assuming that, by case-sensitively compressing labels
> for many years, bind has been doing the opposite (the label compression
> effectively throwing away the carefully case-preserved data)?
It was doing case insensitive compression. It now does case sensitive
compression. The rdata was fixed long ago when we went from 1
record per message in a zone transfer to many records as that
resulted in rdata having different case than what was entered.
AXFR/IXFR have been using case sensitive compression for over a
The recent change was to record and return the learnt case of
ownernames (to the RRset level) rather than use whatever was used
to build the red-black tree names.
> I'm curious why this has come to the fore now, if you're able to say?
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Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742 INTERNET: marka at isc.org
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