Caching and upper case issue with BIND 9.9.7-P3

Mark Andrews marka at
Wed Sep 23 23:03:27 UTC 2015

In message <alpine.LSU.2.00.1509231659080.7380 at>, Tony Fi
nch writes:
> cypher Nix <ciphernix at> wrote:
> >
> > Has anyone seen this behavior before ? Is this a bug ?
> See the CHANGES file:
> 4079.   [func]          Preserve the case of the owner name of records to
>                         the RRset level. [RT #37442]

BIND 9.9 only has 

3645.   [protocol]      Use case sensitive compression when responding to
                        queries. [RT #34737]

which returns the case of the node when it was added to the tree.
4079 adds additional data at the node that records the case of the
entire name allowing it to be returned.

For there was likely a query for "XXX.EXAMPLE.COM"
which created the nodes "EXAMPLE" and "COM".  Later on there was a
query for "" which created the nodes "foo" and
"bar".  Combining these you get "" being returned.

Even with 4079 you will see inconsistencies over time until the
authoritative servers are all upgraded to fully preserve the case
of owner names.  Until that is done you will see the case of the
initial query being reflected in later responses, however you will
see less mixed case responses as most queries are either all uppercase
or all lowercase.


> > This caused issues for certain applications on our network that did string
> > comparison and expected the answer section to be in lower case.
> That's a bug in those applications.
> Tony.
> -- 
> f.anthony.n.finch  <dot at>
> Viking, North Utsire: Easterly 4 or 5, increasing 6 at times. Slight or
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Mark Andrews, ISC
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