From: Corinna Vinschen <corinna-cygwin@cygwin.com>
To: cygwin@cygwin.com
Subject: Re: Dup'd sockets lose error information
Date: Mon, 05 May 2014 09:08:00 -0000 [thread overview]
Message-ID: <20140505090825.GA30918@calimero.vinschen.de> (raw)
In-Reply-To: <20140424141444.GR2339@calimero.vinschen.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. Since FD_SETSIZE is only 64 on
> > > Cygwin, the app uses dup()'s to lower the descriptors as it checks
> > > them for completion. There 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).
> >
> > 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.
> >
> > As for the SO_ERROR value, I have to check. Thanks for the testcase.
>
> I've applied a patch which should solve both problems.
>
> 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.
>
> 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.
>
> 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.
>
> 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.
>
> Please give the today's developer snapshot from
> http://cygwin.com/snapshots/ a try.
Any feedback? Did you test my patch?
Thanks,
Corinna
--
Corinna Vinschen Please, send mails regarding Cygwin to
Cygwin Maintainer cygwin AT cygwin DOT com
Red Hat
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prev parent reply other threads:[~2014-05-05 9:08 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-04-23 14:25 qq qq
2014-04-23 15:38 ` Corinna Vinschen
2014-04-24 14:14 ` Corinna Vinschen
2014-05-05 9:08 ` Corinna Vinschen [this message]
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