Date: Fri, 10 Aug 2012 20:28:18 +0100
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: "J. Bruce Fields" <bfields@fieldses.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>,
        Stanislav Kinsbursky <skinsbursky@parallels.com>,
        Trond.Myklebust@netapp.com, davem@davemloft.net,
        linux-nfs@vger.kernel.org, eric.dumazet@gmail.com, xemul@parallels.com,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
        viro@zeniv.linux.org.uk, tim.c.chen@linux.intel.com, devel@openvz.org
Subject: Re: [RFC PATCH 0/2] net: connect to UNIX sockets from specified
 root
Message-ID: <20120810202818.06236f46@pyramind.ukuu.org.uk>
In-Reply-To: <20120810191149.GA17985@fieldses.org>
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	<50254FA6.3060806@zytor.com>
	<20120810192628.79a34d28@pyramind.ukuu.org.uk>
	<20120810191149.GA17985@fieldses.org>
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On Fri, 10 Aug 2012 15:11:50 -0400
"J. Bruce Fields" <bfields@fieldses.org> wrote:

> On Fri, Aug 10, 2012 at 07:26:28PM +0100, Alan Cox wrote:
> > > On that whole subject...
> > > 
> > > Do we need a Unix domain socket equivalent to openat()?
> > 
> > I don't think so. The name is just a file system indexing trick, it's not
> > really the socket proper. It's little more than "ascii string with
> > permissions attached"
> 
> That's overstating the case.  As I understand it the address is resolved
> by a pathname lookup like any other--it can follow symlinks, is relative
> to the current working directory and filesystem namespace, etc. 

Explicitly for Linux yes - this is not generally true of the AF_UNIX
socket domain and even the permissions aspect isn't guaranteed to be
supported on some BSD environments !

The name is however just a proxy for the socket itself. You don't even
get a device node in the usual sense or the same inode in the file system
space.

Alan