Date: Mon, 24 Aug 2020 17:36:18 -0400 From: Rich Felker <dalias@...c.org> To: musl@...ts.openwall.com Subject: Re: Incompatible behaviour of res_query(3) w.r.t. NXDOMAIN On Mon, Aug 24, 2020 at 10:39:30PM +0200, Daniel Neri wrote: > On 24 Aug 2020, at 18:43, Rich Felker <dalias@...c.org> wrote: > > > > Hmm, I think in this case the "better" might be sufficient that we > > want to keep it and pressure other implementations to change too. A > > program performing a lookup where the result is NxDomain may very well > > want to know whether that's an authenticated (by DNSSEC) NxDomain or > > one in an insecure zone. Returning an error to the caller with no > > packet contents discards this critical data. > > In that case, it’d be better to add a new resolver API, or implement > an already existing one that supports this usecase. The other > implementations I mentioned also support option flags (in global > state) that can change the behaviour. > > res_query(3) is almost as old as DNS itself — it doesn’t seem likely > that everyone else, both libraries and applications, are going to > make incompatible changes at this point. If it were really incompatible behavior I would agree, but the behaviors aren't incompatible. Either is compatible with the same underspecified documentation, and a reasonable caller will easily deal with both -- the nxdomain reply looks very similar to nodata, which it also needs to be able to handle, except for the different error code (3 vs 0). A caller can't assume just because res_query succeeded that ancount>0. Rich
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