linux-kernel - Re: [PATCH,TRIVIAL] AF_UNIX, accept() and addrlen

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Message-ID: <20080324121719.GJ4434@implementation.uk.xensource.com>
Date:	Mon, 24 Mar 2008 12:17:19 +0000
From:	Samuel Thibault <samuel.thibault@...-lyon.org>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	David Miller <davem@...emloft.net>, linux-kernel@...r.kernel.org,
	akpm@...ux-foundation.org
Subject: Re: [PATCH,TRIVIAL] AF_UNIX, accept() and addrlen

Andi Kleen, le Mon 24 Mar 2008 12:50:10 +0100, a écrit :
> Samuel Thibault <samuel.thibault@...-lyon.org> writes:
> 
> > David Miller, le Sun 23 Mar 2008 21:56:41 -0700, a écrit :
> > > From: Samuel Thibault <samuel.thibault@...-lyon.org>
> > > Date: Sat, 8 Mar 2008 02:23:21 +0000
> > > 
> > > > Accept and getpeername are supposed to return the amount of bytes
> > > > written in the returned address.  However, on unnamed sockets, only
> > > > sizeof(short) is returned, while a 0 is put in the sun_path member.
> > > > This patch adds 1 for that additional byte.
> > > > 
> > > > Signed-off-by: Samuel Thibault <samuel.thibault@...-lyon.org>
> > > 
> > > This change isn't correct.  It's the fact that the
> > > length returned is sizeof(short) that tells the caller
> > > that the unix socket is unnamed.
> > 
> > Mmm, where that is documented?
> > 
> > I can't find any details about that in SUS, and man 7 unix says
> > 
> > `If sun_path starts with a null byte ('' '), then it refers to the
> > abstract namespace main- tained by the Unix protocol module.'
> 
> [I wrote unix(7) originally]. The abstract name space is a Linux
> extension and there is no written standard and whatever the kernel
> implements is the de-facto standard. If unix(7) differs in anything
> from what the code does please send patches to the manpages
> maintainer.

Oops, sorry, we are not talking about abstract namespace actually (their
sockaddr length are necessarily bigger than sizeof(sa_family_t) since
they need some data), but unamed sockets.  So the Address Format
paragraph just misses description of unnamed sockets.

Samuel
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