X-Recipient:	archive-cygwin AT delorie DOT com
DomainKey-Signature:	a=rsa-sha1; c=nofws; d=sourceware.org; h=list-id
	:list-unsubscribe:list-subscribe:list-archive:list-post
	:list-help:sender:date:from:to:subject:message-id:reply-to
	:references:mime-version:content-type:in-reply-to; q=dns; s=
	default; b=XsYw1QHs3zhulNjFCcPNHnH2wSDc+AdMrWU0fFUDd6C4KOFFkoEc+
	JvxfLMDF91Nbl90NN+iEOVS6E6xrlZSN9n5wRIMMn5tm0wXr+VixJ0EIWil9exY6
	3ghTXDXbGRflUgzGRpTc7VCQm0dqJol1LZ72SYIVC94pt0qd6eXvGI=
DKIM-Signature:	v=1; a=rsa-sha1; c=relaxed; d=sourceware.org; h=list-id
	:list-unsubscribe:list-subscribe:list-archive:list-post
	:list-help:sender:date:from:to:subject:message-id:reply-to
	:references:mime-version:content-type:in-reply-to; s=default;
	bh=RUD3hVbxne7JHDGWtEKjnQXOhvc=; b=FA21sB6hW+z+kSz4/a+zoto2bPlf
	f0VkUfzush/rQjAqWEkHuCh62iDwyCFUVd5pl0g4DKbngywciu7OLARPa/CwWafj
	CphPez+xOVnGG+yATlHWC/QXE08pPnYNybRbnX00c2lI6lJhAaiCgYKpdGeF3OTF
	ISRNDh9bL93WJFs=
Mailing-List:	contact cygwin-help AT cygwin DOT com; run by ezmlm
List-Id:	<cygwin.cygwin.com>
List-Subscribe:	<mailto:cygwin-subscribe AT cygwin DOT com>
List-Archive:	<http://sourceware.org/ml/cygwin/>
List-Post:	<mailto:cygwin AT cygwin DOT com>
List-Help:	<mailto:cygwin-help AT cygwin DOT com>, <http://sourceware.org/ml/#faqs>
Sender:	cygwin-owner AT cygwin DOT com
Mail-Followup-To:	cygwin AT cygwin DOT com
Delivered-To:	mailing list cygwin AT cygwin DOT com
Authentication-Results:	sourceware.org; auth=none
X-Virus-Found:	No
X-Spam-SWARE-Status:	No, score=-101.8 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=sake
X-HELO:	drew.franken.de
Date:	Tue, 16 Jan 2018 16:42:34 +0100
From:	Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
To:	cygwin AT cygwin DOT com
Subject:	Re: Cygwin socket option SO_REUSEADDR operates unlike Linux
Message-ID:	<20180116154234.GB3255@calimero.vinschen.de>
Reply-To:	cygwin AT cygwin DOT com
Mail-Followup-To:	cygwin AT cygwin DOT com
References:	<Pine DOT BSF DOT 4 DOT 63 DOT 1801122348420 DOT 62607 AT m0 DOT truegem DOT net> <20180113135127 DOT GA22225 AT calimero DOT vinschen DOT de> <e072e320-fca4-582d-508e-91c5c0d78bc6 AT maxrnd DOT com> <20180115200249 DOT GA3009 AT calimero DOT vinschen DOT de>
MIME-Version:	1.0
In-Reply-To:	<20180115200249.GA3009@calimero.vinschen.de>
User-Agent:	Mutt/1.9.1 (2017-09-22)

--Y7xTucakfITjPcLV
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
Content-Transfer-Encoding: quoted-printable

On Jan 15 21:02, Corinna Vinschen wrote:
> On Jan 13 13:39, Mark Geisert wrote:
> > Corinna Vinschen wrote:
> > > On Jan 13 00:36, Mark Geisert wrote:
> > > > ~ ./bindtest
> > > > 1st socket is 3
> > > > 1st bind OK
> > > > 1st connect OK
> > > > 2nd socket is 3
> > > > 2nd bind OK
> > > > 2nd connect: Address already in use
> > > >=20
> > > > ~ ./bindtest
> > > > 1st socket is 3
> > > > 1st bind OK
> > > > 1st connect: Address already in use
> > > >=20
> > > > On Fedora 27, running the same STC shows:
> > > >=20
> > > > [mark AT lux ~]$ netstat -an|grep :111
> > > > tcp        0      0 0.0.0.0:111         0.0.0.0:*        LISTEN
> > > > tcp6       0      0 :::111              :::*             LISTEN
> > > > udp        0      0 0.0.0.0:111         0.0.0.0:*
> > > > udp6       0      0 :::111              :::*
> > > > [mark AT lux ~]$ ./bindtest
> > > > 1st socket is 3
> > > > 1st bind OK
> > > > 1st connect OK
> > > > 2nd socket is 3
> > > > 2nd bind OK
> > > > 2nd connect OK
> > >=20
> > > I can't reproduce this:
> > >=20
> > > $ uname -sr
> > > Linux 4.14.13-300.fc27.x86_64
> > > $ netstat -an|grep :111
> > > tcp        0      0 0.0.0.0:111             0.0.0.0:*               L=
ISTEN
> > > tcp6       0      0 :::111                  :::*                    L=
ISTEN
> > > udp        0      0 0.0.0.0:111             0.0.0.0:*
> > > udp6       0      0 :::111                  :::*
> > > $ ./bindtest
> > > 1st socket is 3
> > > 1st bind OK
> > > 1st connect OK
> > > 2nd socket is 3
> > > 2nd bind OK
> > > 2nd connect: Cannot assign requested address
> > > [...]
> > Rats.  I'll have to investigate a couple of directions, deeper.  It mak=
es
> > sense that connect() returns EADDRINUSE rather than bind() [...]
>=20
> After some more digging it turns out that both of the above observations
> on Linux are correct.  I can reproduce the 2nd connect succeeding by
> simply adding a `sleep(1)' after the first close.  So it turns out that
> Linux has a timing issue at socket cleanup which can be alleviated
> by an extra sleep.  I opened a case about this issue.  EADDRNOTAVAIL
> sounds a bit weird in this scenario, but it's kind of ok.
>=20
> In terms of Cygwin, the EADDRINUSE is a completely different matter.
>=20
> It turns out that the second connect fails because the first socket
> connection is in TIME_WAIT state.  This is not exactly correct in POSIX
> terms.  The TIME_WAIT connection should not disallow a new socket to
> reuse the same local address.  That's what we observe on Linux (apart from
> the timing issue).
>=20
> But here's the problem:  Regardless if we actually use SO_REUSEADDR or
> not, Windows sockets apparently disallows a subsequent connect to
> succeed while the first socket is still in TIME_WAIT.  I tweaked Cygwin
> to enforce SO_REUSEADDR before bind, but connect still fails with
> EADDRINUSE as long as the first socket is in TIME_WAIT.
>=20
> It seems the code path for listen/accept is different here compared to
> connect.  Given that SO_REUSEADDR seems to cover mostly server side
> scenarios, and given that I don't see this scenario discussed at all
> in Steven's book, I wonder if bind/connect is a bit of a grey area.
>=20
> Either way, the bottom line is that this is a WinSock restriction,
> apparently.  As of today, I don't see any way around that.

For completeness sake I converted your testcase into a WinSock-only
executable, built with Mingw-w64, and the problem persists, on Windows7
as well as on Windows 10.


Corinna

--=20
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Maintainer                 cygwin AT cygwin DOT com
Red Hat

--Y7xTucakfITjPcLV
Content-Type: application/pgp-signature; name="signature.asc"

-----BEGIN PGP SIGNATURE-----
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=LQ8a
-----END PGP SIGNATURE-----

--Y7xTucakfITjPcLV--

- Raw text -