Caching and upper case issue with BIND 9.9.7-P3

Evan Hunt each at
Wed Sep 23 16:18:30 UTC 2015

On Wed, Sep 23, 2015 at 08:18:45AM -0700, cypher Nix wrote:
> After upgrading BIND from BIND 9.9.7-P2 to BIND 9.9.7-P3 on about a dozen

... that's odd, the new case compression behavior was introduced a fair
bit earlier than that; are you sure you weren't upgrading a few servers
older than 9.9.7-P2?

> Has anyone seen this behavior before ? Is this a bug ?
> [...]
> This caused issues for certain applications on our network that did string
> comparison and expected the answer section to be in lower case.

Those applications should be changed to use strcasecmp() not strcmp().
However, if that's not practical, you can configure named to work the way
it used to for selected clients, or for all clients.

The case of the question is preserved in responses, but the case of the
answer can change. BIND (and most other DNS implementations) used to
compress names in responses in a way that forced the the answer to
conform to the case of the question.  But the specification actually
says to preserve the original owner's case whenever possible, so we
changed it.

If you need the old behavior back for a particular client, add
"no-case-compress { <address> ; };" to your options. If you
want it back for all clients, then use "no-case-compress { any; };".

Evan Hunt -- each at
Internet Systems Consortium, Inc.

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