Date: Wed, 2 Jun 1999 03:00:02 -0700 (PDT) From: Brian Somers <brian@Awfulhak.org> To: freebsd-bugs@FreeBSD.org Subject: Re: kern/11988: recvmsg with a cmsghdr but no iovec is broken Message-ID: <199906021000.DAA66509@freefall.freebsd.org>
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The following reply was made to PR kern/11988; it has been noted by GNATS.
From: Brian Somers <brian@Awfulhak.org>
To: Tony Finch <dot@dotat.at>
Cc: FreeBSD-gnats-submit@freebsd.org
Subject: Re: kern/11988: recvmsg with a cmsghdr but no iovec is broken
Date: Wed, 02 Jun 1999 10:58:41 +0100
>
> >Number: 11988
> >Category: kern
> >Synopsis: recvmsg with a cmsghdr but no iovec is broken
[.....]
This has been the case for some time - since before I implemented
multi-link ppp. When I was writing it, I attempted to do exactly
what you're doing and then to write() all my link configuration data.
Things failed badly so I ended up merging everything into a single
sendmsg()/recvmsg().
I'm afraid I have nothing fantastic to say (except to confirm that
the problem exists, and has done for some time).
One other observation (a problem I suffered with for some time); you
*must* have some sort of handshake to confirm that the descriptor has
been received. If you call close(conn) while the descriptor is still
in limbo (an mbuf) the descriptor will arrive at the other end ready
to give you EBADF next time you use it.
A simple read(child, &ch, 1) after sendmsg() and before the close(conn)
and a write(3, "X", 1) after the recvmsg() will do the trick.
--
Brian <brian@Awfulhak.org> <brian@FreeBSD.org>
<http://www.Awfulhak.org>; <brian@OpenBSD.org>
Don't _EVER_ lose your sense of humour ! <brian@uk.FreeBSD.org>
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