From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on inbox.vuxu.org X-Spam-Level: X-Spam-Status: No, score=-2.0 required=5.0 tests=MAILING_LIST_MULTI, RCVD_IN_DNSWL_MED,RCVD_IN_MSPIKE_H3,RCVD_IN_MSPIKE_WL, SUBJ_OBFU_PUNCT_FEW,SUBJ_OBFU_PUNCT_MANY autolearn=ham autolearn_force=no version=3.4.4 Received: (qmail 6661 invoked from network); 24 Aug 2020 21:36:34 -0000 Received: from mother.openwall.net (195.42.179.200) by inbox.vuxu.org with ESMTPUTF8; 24 Aug 2020 21:36:34 -0000 Received: (qmail 18291 invoked by uid 550); 24 Aug 2020 21:36:31 -0000 Mailing-List: contact musl-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Reply-To: musl@lists.openwall.com Received: (qmail 18273 invoked from network); 24 Aug 2020 21:36:30 -0000 Date: Mon, 24 Aug 2020 17:36:18 -0400 From: Rich Felker To: musl@lists.openwall.com Message-ID: <20200824213618.GM3265@brightrain.aerifal.cx> References: <5232EC15-7E60-4D1F-BF3B-C31BFF998C06@rb67.eu> <20200824161646.GH3265@brightrain.aerifal.cx> <20200824164326.GI3265@brightrain.aerifal.cx> <5CEB8952-4884-4FA2-ACD9-1BA118D2CB50@rb67.eu> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <5CEB8952-4884-4FA2-ACD9-1BA118D2CB50@rb67.eu> User-Agent: Mutt/1.5.21 (2010-09-15) Subject: Re: [musl] 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 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