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 7430 invoked from network); 24 Aug 2020 16:43:43 -0000 Received: from mother.openwall.net (195.42.179.200) by inbox.vuxu.org with ESMTPUTF8; 24 Aug 2020 16:43:43 -0000 Received: (qmail 19850 invoked by uid 550); 24 Aug 2020 16:43:39 -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 19829 invoked from network); 24 Aug 2020 16:43:39 -0000 Date: Mon, 24 Aug 2020 12:43:26 -0400 From: Rich Felker To: musl@lists.openwall.com Message-ID: <20200824164326.GI3265@brightrain.aerifal.cx> References: <5232EC15-7E60-4D1F-BF3B-C31BFF998C06@rb67.eu> <20200824161646.GH3265@brightrain.aerifal.cx> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20200824161646.GH3265@brightrain.aerifal.cx> 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 12:16:47PM -0400, Rich Felker wrote: > On Sun, Aug 23, 2020 at 11:31:32PM +0200, Daniel Neri wrote: > > Hello, > > > > > > Musl’s res_query(3) returns success for a query that results in an > > NXDOMAIN response, which disagrees with other common > > implementations. > > > > Simple test case: https://t.rb67.eu/res_query.c > > > > On Debian Linux, OpenBSD and FreeBSD this program prints: > > > > error: Unknown host > > > > but on Alpine Linux edge (musl v1.2.1): > > > > success (size 91) > > I think there's a good argument that this should be changed, but that > would require making res_* set h_errno, which would require making > h_errno thread-local -- which it probably should have been all along, > but the standard interfaces that used it, gethostby* etc., were > non-thread-safe anyway and thus it seemed unnecessary. > > FWIW I think the musl behavior is *better* here (more informative to > the application), but usually it's preferable not to break the > existing (even if informal) contracts of the interfaces being > implemented than to be "better". 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. Rich