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Date: Mon, 5 May 2014 11:08:25 +0200
From: Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
To: cygwin AT cygwin DOT com
Subject: Re: Dup'd sockets lose error information
Message-ID: <20140505090825.GA30918@calimero.vinschen.de>
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References: <20140423142541 DOT 156360 AT gmx DOT com> <20140423153830 DOT GN2339 AT calimero DOT vinschen DOT de> <20140424141444 DOT GR2339 AT calimero DOT vinschen DOT de>
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qq qq?

Ping?

On Apr 24 16:14, Corinna Vinschen wrote:
> On Apr 23 17:38, Corinna Vinschen wrote:
> > On Apr 23 16:25, qq qq wrote:
> > > The following code is a simplified app that was used to test-connect
> > > to local ports 55000+ (none of which were actually listening) and
> > > received false-positive "connected" results because Cygwin's dup()
> > > for socket causes SO_ERROR to be lost. =C2=A0Since FD_SETSIZE is only=
 64 on
> > > Cygwin, the app uses dup()'s to lower the descriptors as it checks
> > > them for completion. =C2=A0There is no such problem on Linux.
> > > Also, strangely that Cygwin does not accept sin_addr as 0 to connect
> > > locally (and either localhost or local host IP must be stuffed in
> > > there, otherwise resulting in the "Cannot assign requested address"
> > > error).
> >=20
> > This is Winsock at work.  Cygwin doesn't check the AF_INET address
> > when calling Winsock's connect, so Winsock's connect itself seems to
> > have this issue.
> >=20
> > As for the SO_ERROR value, I have to check.  Thanks for the testcase.
>=20
> I've applied a patch which should solve both problems.
>=20
> Cygwin is using socket events to implement select.  It turned out that,
> when using the original socket, the socket event as well as the socket's
> SO_ERROR value were set correctly.  However, when calling select with
> the dup'ed socket handle, the socket event contained the correct error
> code, but the SO_ERROR value wasn't set.  I added code to write back the
> error code from the socket event entry to the SO_ERROR socket option and
> that seems to do the trick.
>=20
> As for connecting or sending to INADDR_ANY or in6addr_any, this simply
> doesn't work with Winsock.  It just returns WSAEADDRNOTAVAIL.  I now
> added a conversion from INADDR_ANY and in6addr_any to INADDR_LOOPBACK
> and in6addr_loopback in calls to connect, sendto, and sendmsg to emulate
> the Linux behaviour.
>=20
> Apart from that it turned out that 64 bit Cygwin was suffering from a
> definition problem of a couple of Winsock types used in the Cygwin
> socket code.  As the (hopefully) only user-visible effect, this led
> to a broken address output in /proc/net/if_inet6.  This is fixed now
> as well.
>=20
> As for FD_SETSIZE, it's defined as 64 by default, but the user code
> can override the value by defining FD_SETSIZE to another value prior
> to including the standard headers.  The underlying code does not
> restrict the file descriptor values to < FD_SETSIZE.
>=20
> Please give the today's developer snapshot from=20
> http://cygwin.com/snapshots/ a try.

Any feedback?  Did you test my patch?


Thanks,
Corinna

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

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