From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 11858 invoked by alias); 5 Feb 2018 20:15:37 -0000 Mailing-List: contact cygwin-help@cygwin.com; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: cygwin-owner@cygwin.com Mail-Followup-To: cygwin@cygwin.com Received: (qmail 11504 invoked by uid 89); 5 Feb 2018 20:15:24 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-101.9 required=5.0 tests=AWL,BAYES_00,GOOD_FROM_CORINNA_CYGWIN,KAM_LAZY_DOMAIN_SECURITY,RCVD_IN_DNSWL_LOW,SPF_HELO_PASS autolearn=ham version=3.3.2 spammy=Hx-languages-length:2524, reserved X-HELO: drew.franken.de Received: from mail-n.franken.de (HELO drew.franken.de) (193.175.24.27) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Mon, 05 Feb 2018 20:15:22 +0000 Received: from aqua.hirmke.de (aquarius.franken.de [193.175.24.89]) (Authenticated sender: aquarius) by mail-n.franken.de (Postfix) with ESMTPSA id 55544721E281A for ; Mon, 5 Feb 2018 21:15:12 +0100 (CET) Received: from calimero.vinschen.de (calimero.vinschen.de [192.168.129.6]) by aqua.hirmke.de (Postfix) with ESMTP id F28E25E0418 for ; Mon, 5 Feb 2018 21:15:11 +0100 (CET) Received: by calimero.vinschen.de (Postfix, from userid 500) id DC732A8076E; Mon, 5 Feb 2018 21:15:11 +0100 (CET) Date: Mon, 05 Feb 2018 20:15:00 -0000 From: Corinna Vinschen To: cygwin@cygwin.com Subject: Re: RPC clnt_create() adress already in use Message-ID: <20180205201511.GC13050@calimero.vinschen.de> Reply-To: cygwin@cygwin.com Mail-Followup-To: cygwin@cygwin.com References: <59D90AF8D70E9740907BACDE2BCB520836E325EF@RESW102.resdom01.local> <5b897ca4-9a7d-df90-e7a0-dbdedbd1f179@maxrnd.com> <20180205112617.GB2912@calimero.vinschen.de> <20180205133450.GJ2912@calimero.vinschen.de> <20180205140623.GK2912@calimero.vinschen.de> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="mYCpIKhGyMATD0i+" Content-Disposition: inline In-Reply-To: <20180205140623.GK2912@calimero.vinschen.de> User-Agent: Mutt/1.9.1 (2017-09-22) X-SW-Source: 2018-02/txt/msg00049.txt.bz2 --mYCpIKhGyMATD0i+ Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Content-length: 2571 On Feb 5 15:06, Corinna Vinschen wrote: > On Feb 5 14:34, Corinna Vinschen wrote: > > On Feb 5 12:26, Corinna Vinschen wrote: > > > To reiterate the problem we observe: > > >=20 > > > - socket() > > > - setsockopt (SO_REUSEADDR) > > > - bind() succeeds > > > - connect() fails with EADDRINUSE while socket is still in TIME_WAIT > > >=20 > > > using bindresvport in place of bind only marginally changes the > > > situation, in particular if the second parameter is set and requests a > > > port number !=3D 0. What happens in that case is that bindresvport c= alls > > > bind with this port number and checks if bind returns EADDRINUSE. > > >=20 > > > Only then it tries to bind other port numbers in the reserved range. > > > But we now know that bind will never return EADDINUSE if the SO_REUSE= ADDR > > > socket option has been set. > > >=20 > > > Even assuming the process calls bindresvport(sock, NULL) we may end up > > > returning a port number already in use if the process is the only Cyg= win > > > process on the system. The reason is that Cygwin uses a round robin > > > approach which relies on having a globally shared value called > > > last_used_bindresvport. If the process is the only Cygwin process on > > > the system, this information is lost after exiting the process, so the > > > next process will start with the same start port number and bind will > > > again fail to notice the client with EADDRINUSE. > > >=20 > > > What potential solutions to this problem do we have? > > >=20 > > > - bindresvport could enforce SO_EXCLUSIVEADDRUSE temporarily to make > > > sure bind fails. > >=20 > > Nope, no way. Even enforcing SO_EXCLUSIVEADDRUSE results in the > > second bind succeeding and the subsequent connect failing. The > > entire SO_REUSEADDR/SO_EXCLUSIVEADDRUSE semantics only works as > > desired on the server side apparently > >=20 > > > - bindresvport could check every local address for being free prior > > > to calling bind. However, there's a potential race here. > > >=20 > > > - DisconnectEx? Never tried this Winsock extension but it might be > > > worth a shot. >=20 > I think I have a very simple solution for the scenario which calls > bindresvport with port number. Still looking for a solution for > the second problem... I've pushed a few patches and uploaded new developer snapshots to https://cygwin.com/snapshots. Please give them a try. Thanks, Corinna --=20 Corinna Vinschen Please, send mails regarding Cygwin to Cygwin Maintainer cygwin AT cygwin DOT com Red Hat --mYCpIKhGyMATD0i+ Content-Type: application/pgp-signature; name="signature.asc" Content-length: 833 -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEEoVYPmneWZnwT6kwF9TYGna5ET6AFAlp4u08ACgkQ9TYGna5E T6CgXQ/8DcpiNzVSUATpWXABNSaXLERdX7+X9cnUFSIRlBhdWL6K0xqLbLE0T64X sCgOJ0+bB0/HItWNIG+IFiRthBF0M3SefeM2OsA2EXxsawUTcR9sFqpvWTelcjOM jRwacGQHkUbe+e5RMlValXWzcoqKRsWMtCAj2qm4DGNjzaOIkpOA7tR4N8z2Bzlt VKML+j14fSb7Mthuql8wKonoa5x95bbZy2uN+VlfaRWY6MQUjvHgCIRky7epII4F xmlSPLs+yhiZp3Xg/YjYFTyEGNQByGbyaraeJym4IdeYvev0gptdDlzpRlekRfVd 0swq5oi+cTd8lefiAwDbrRBHcKomDF6dweXUU7E31UxuMIugs7yMSTjUK8auNCqY Mzs8CUfDT3tqi7kqHgo7UN39al9UFl7m7fUu+qcbjJs1pDLkJ5yeET8PWXx28vsA 01wr7PfL0FKPiroipFm4JdsG/rf3ef4uLU5UG3NiVwmfmSCvbIwv4bpvg6qvm3Bu kKfi52Sj5xy/GLisPVUaE2WuMBhUDhL1m8tQP7HgsBkAwDgq5v0v5s6bkdFoIyvd 3+xyOJ+c5PYWtsNP1ezPHF6astbPwjD4rGv+7i6rleePMXtsvASViBX8i8c3wajz kgv0u+EZ9moy254RKI4sutKQMWc3TSSfZUKs+DsfjyNvFQpy/fE= =gxTz -----END PGP SIGNATURE----- --mYCpIKhGyMATD0i+--