[dns-operations] DNSSEC and qmail

[Tony Finch]

On Thu, 8 Oct 2009, Roy Arends wrote:
>
> This is odd.
>
> What cname?

It's asking for cam.ac.uk. IN ANY when trying to canonicalize the
recipient domain.

> Second, I'd expect qmail to talk to resolver. resolvers generally trip the
> response to stubs to fit a 512 udp message.

They do?

Looking at the code I think what is happening is that the stub resolver is
getting a truncated UDP response, and retrying with TCP. The stub resolver
truncates responses that don't fit in the caller's buffer by just chopping
off the end (much less gracefully than a recursive server truncates a UDP
response) and when qmail tries to parse the chopped packet it fails with a
temporary error.

Tony.
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