From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 98827 invoked by alias); 5 Feb 2018 14:06:29 -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 98812 invoked by uid 89); 5 Feb 2018 14:06:28 -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=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 14:06:27 +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 237D1721E281A for ; Mon, 5 Feb 2018 15:06:24 +0100 (CET) Received: from calimero.vinschen.de (calimero.vinschen.de [192.168.129.6]) by aqua.hirmke.de (Postfix) with ESMTP id A20935E009F for ; Mon, 5 Feb 2018 15:06:23 +0100 (CET) Received: by calimero.vinschen.de (Postfix, from userid 500) id 8F7C0A8066D; Mon, 5 Feb 2018 15:06:23 +0100 (CET) Date: Mon, 05 Feb 2018 14:06:00 -0000 From: Corinna Vinschen To: cygwin@cygwin.com Subject: Re: RPC clnt_create() adress already in use Message-ID: <20180205140623.GK2912@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> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="GLp9dJVi+aaipsRk" Content-Disposition: inline In-Reply-To: <20180205133450.GJ2912@calimero.vinschen.de> User-Agent: Mutt/1.9.1 (2017-09-22) X-SW-Source: 2018-02/txt/msg00035.txt.bz2 --GLp9dJVi+aaipsRk Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Content-length: 2304 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 cal= ls > > 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_REUSEAD= DR > > 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 Cygwin > > 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. 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... Corinna --=20 Corinna Vinschen Please, send mails regarding Cygwin to Cygwin Maintainer cygwin AT cygwin DOT com Red Hat --GLp9dJVi+aaipsRk Content-Type: application/pgp-signature; name="signature.asc" Content-length: 833 -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEEoVYPmneWZnwT6kwF9TYGna5ET6AFAlp4ZN8ACgkQ9TYGna5E T6B81w/9Fd/UhMDs6gnT4/0eeVLL5Mb0ZSWXtaDvGnNoCWoQy3xHXxoDVrpZojtP arS4vUx+94e6eEpA80+yI5TSBdlwQWHxuqjdu8lEwWWGaHKq3HdyW8uzW+Hq58X8 Z3Bxs1w9RFoMxsO1hqLdtsk9NEr5s9dYFNvWcn6PdRLzKK21BFL433F8TK0fhE8G bvlPUKqGSesCK/GKCW0Q4uAp60cMOayah6JCyYvAHvRwz9Vka2YhqedsANH9IfyH 4XuyTvtbs0wzNqgZKdqTE3D9Fe+8EywxV8T8Pn/Xb0rIVYQucPB5fABgZRcPRaQN x6dP9G+pmAKUioC0Xu3/4UQoO8ZPicqy1T+OS/kUjEiD51V6BrZMuC0wrFW0S3Cr Vw8YVvfC2VaFnKbRt7wEp8rKqI8c9MLpMsOKHOJe1iQ+CswN/oFNjG4trlmT618c 4O6DZeaFtqUG9Cp8qFWimIKF1cwm8+lrz4BglInoKCHoiyn+qBrnfJPo7O5tDOAe CC/hgjBfv5znGzFI17tpojnur5kUvh6RTqbQdLJfqUgsmHwfk+YxbdV5w7NqPahP ONFzd7r2XteCQJobRnpU3BHdaxjtxmnxYBfkdoMJE46N0UoxK/kRa4TF196wMn84 LkggRI5muP3028bm7jpenorGLw74AtlyvyEmZFv60+W5DYmMgcc= =jS2I -----END PGP SIGNATURE----- --GLp9dJVi+aaipsRk--