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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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