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Date: Mon, 19 Sep 2022 22:57:55 +0200
From: Florian Weimer <fweimer@...hat.com>
To: Rich Felker <dalias@...c.org>
Cc: libc-coord@...ts.openwall.com
Subject: Re: EAI_NOADDR ?
* Rich Felker:
> One problem I've seen come up again and again with libc stub resolver
> API is that there's no way to distinguish between NxDomain and NODATA
> responses from DNS. These have very different meanings ("name doesn't
> exist" vs "name exists but has no address (or whatever record type you
> were looking for") and being able to distinguish them is important for
> implementing containerized-type DNS service on top of the host's
> resolver API rather than direct proxying to outside DNS (when the
> latter isn't desirable).
>
> POSIX defines EAI_NONAME as:
>
> [EAI_NONAME]
> The name does not resolve for the supplied parameters.
>
> which, under generous interpretation of "parameters", seems to cover
> both cases, although arguably it does "resolve" to just an empty list
> of addresses in the NODATA case.
>
> To address this, I'm considering proposing a new error code EAI_NOADDR
> that would be defined something like:
>
> [EAI_NOADDR]
> The name does not have any addresses for the supplied parameters.
>
> Would other implementators be on-board with such a proposal?
I think several libcs implemented this as EAI_NODATA already. I see it
documented for AIX, glibc, NetBSD, OpenBSD, QNX, Solaris. Apparently,
it's absent from FreeBSD (and Windows).
Thanks,
Florian
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