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SubjectRe: [PATCH 2/2] Define ENONAMESERVICE and ENAMEUNKNOWN to indicate name service errors
Date
Jim Rees <rees@umich.edu> wrote:

> > Would this be the same as NXDOMAIN? That is, does it mean the name server
> > couldn't find a record, or does it mean that the record doesn't exist?
>
> Is there a way to tell the difference? Can you store a negative record in
> the DNS? Or is it that the DNS has records for the name, just not records
> of the type you're looking for (eg. NO_ADDRESS/NO_DATA from
> gethostbyname())?
>
> It's an important distinction to the resolver if you want to avoid dns
> hijacking. See rfc2308. There doesn't seem to be a way to tell the
> difference from the gethostbyname call, which was designed before this was a
> problem. The on-the-wire dns query protocol does make the distinction.
>
> I suspect kernel dns clients won't need to know the difference, but I think
> it's useful if we decide on and document the meaning of the error codes.
> Maybe the answer is that ENAMEUNKNOWN means the same as a HOST_NOT_FOUND
> from gethostbyname().

Should I propose an extra error code? Perhaps giving:

ENONAMESERVICE "Network name service unavailable"
ENAMEUNKNOWN "Network name not known"
ENONAMERECORD "Network name query returned no records"

Note that ENONAMESERVICE covers all of: not having a name service configured,
not being able to contact the configured name server and the configured name
server not being able to chain to the authoritative name server. However, I
think this is probably okay.

David


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