Date: Fri, 4 Jun 1999 05:20:02 -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: <199906041220.FAA77921@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: Brian Somers <brian@Awfulhak.org>,
FreeBSD-gnats-submit@freebsd.org
Subject: Re: kern/11988: recvmsg with a cmsghdr but no iovec is broken
Date: Fri, 04 Jun 1999 13:12:16 +0100
> Brian Somers writes:
> >
> > 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.
>
> AIUI that shouldn't be necessary: the f_count field should be
> incremented while the descriptor is in transit so close()ing it should
> not cause the resources to be released. If the receiver of the
> descriptor gets EBADF because the sender close()d it while it was in
> transit that is a bug (but a different one from the one that started
> this PR).
I've had a poke around 'cos I recalled seeing someone else spot this.
The -current sendmsg man page mentions it in the BUGS section.
> Tony.
--
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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