copying the question section

[Andreas Gustafsson]

Paul Vixie writes:
> bind has always copied the question section into the response.  some versions
> (notably the ill-fated 4.9.2) demanded to see this, but earlier and current
> versions only demand that the question section in the response match the one
> from the query if it's present at all -- an empty question section in a
> response is not treated as an error.

I beg to differ.  All versions of BIND 9 treats an empty question
section in a response as an error - see the following code in
same_question() in lib/dns/resolver.c:

        if (message->counts[DNS_SECTION_QUESTION] != 1)
                return (DNS_R_FORMERR);

> some non-bind servers have been sending
> back empty question sections for years now and it's been seen to cause no
> trouble.

Which ones would that be?  If such servers were actually deployed, I
would expect BIND 9 users to have reported it.
-- 
Andreas Gustafsson, gson at nominum.com