Mailing-List: contact cygwin-help AT cygwin DOT com; run by ezmlm
List-Subscribe: <mailto:cygwin-subscribe AT cygwin DOT com>
List-Archive: <http://sources.redhat.com/ml/cygwin/>
List-Post: <mailto:cygwin AT cygwin DOT com>
List-Help: <mailto:cygwin-help AT cygwin DOT com>, <http://sources.redhat.com/ml/#faqs>
Sender: cygwin-owner AT cygwin DOT com
Delivered-To: mailing list cygwin AT cygwin DOT com
Date: Thu, 24 Jan 2002 16:33:52 +0100
From: Corinna Vinschen <cygwin AT cygwin DOT com>
To: cygwin <cygwin AT cygwin DOT com>
Subject: Re: Descriptor passing between process
Message-ID: <20020124163352.Z11608@cygbert.vinschen.de>
Mail-Followup-To: cygwin <cygwin AT cygwin DOT com>
References: <002401c1a3f4$0b77e8c0$010310ac AT lyoncleitienne> <20020123120701 DOT A11608 AT cygbert DOT vinschen DOT de> <8181418335 DOT 20020124161420 AT logos-m DOT ru> <20020124142156 DOT Y11608 AT cygbert DOT vinschen DOT de> <4183271981 DOT 20020124164513 AT logos-m DOT ru> <000901c1a4e1$d967f430$010310ac AT lyoncleitienne>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <000901c1a4e1$d967f430$010310ac@lyoncleitienne>
User-Agent: Mutt/1.3.22.1i

On Thu, Jan 24, 2002 at 03:17:23PM +0100, Christophe LEITIENNE wrote:
> I found a piece of code that doesn't use all this stuff. Could it work (I
> haven't tried yet) ?
> 
> int sendfd(sockfd, fd)
> int sockfd;  /* UNIX domain socket to pass descriptor on */
> int fd;  /* the actual fd value to pass */
> {
>     struct iovec iov[1];
>     struct msghdr msg;
>     extern int errno;
> 
>     iov[0].iov_base = (char *) 0;  /* no data to send */
>     iov[0].iov_len  = 0;
>     msg.msg_iov          = iov;
>     msg.msg_iovlen       = 1;
>     msg.msg_name         = (caddr_t) 0;
>     msg.msg_accrights    = (caddr_t) &fd; /* address of descriptor */
>     msg.msg_accrightslen = sizeof(fd); /* pass 1 descriptor */
> 
>     if (sendmsg(sockfd, &msg, 0) < 0)
>         return( (errno > 0) ? errno : 255 );
> 
>     return(0);
> }

This isn't supported.  Control structure passing doesn't work at
all with the current implementation.

Btw., the above source code won't work on Linux, too.  First of all,
the msg_accrights and msg_accrightslen members doesn't exist in the 
msghdr struct (they are called msg_control and msg_controllen) and
second, file descriptors in one process have no meaning in another
process, except it's parent or child of the calling process,
coincidentally.  That's somewhat dangerous.

Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Developer                                mailto:cygwin AT cygwin DOT com
Red Hat, Inc.

--
Unsubscribe info:      http://cygwin.com/ml/#unsubscribe-simple
Bug reporting:         http://cygwin.com/bugs.html
Documentation:         http://cygwin.com/docs.html
FAQ:                   http://cygwin.com/faq/