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From: ebiederm@xmission.com (Eric W. Biederman)
To: Pavel Emelyanov <xemul@openvz.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
       David Miller <davem@davemloft.net>,
       Linux Netdev List <netdev@vger.kernel.org>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       Alexey Dobriyan <adobriyan@openvz.org>
Subject: Re: [PATCH] Make /proc/net a symlink on /proc/self/net
References: <47CE8FF7.7000701@openvz.org>
Date: Wed, 05 Mar 2008 17:24:10 -0700
In-Reply-To: <47CE8FF7.7000701@openvz.org> (Pavel Emelyanov's message of "Wed,
	05 Mar 2008 15:20:07 +0300")
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Pavel Emelyanov <xemul@openvz.org> writes:

> Current /proc/net is done with so called "shadows", but current
> implementation is broken and has little chances to get fixed.
>
> The problem is that dentries subtree of /proc/net directory has
> fancy revalidation rules to make processes living in different
> net namespaces see different entries in /proc/net subtree, but
> currently, tasks see in the /proc/net subdir the contents of any
> other namespace, depending on who opened the file first.
>
> The proposed fix is to turn /proc/net into a symlink, which points
> to /proc/self/net, which in turn shows what previously was in
> /proc/net - the network-related info, from the net namespace the
> appropriate task lives in.
>
> # ls -l /proc/net
> lrwxrwxrwx  1 root root 8 Mar  5 15:17 /proc/net -> self/net
>
> In other words - this behaves like /proc/mounts, but unlike
> "mounts", "net" is not a file, but a directory.

Overall this looks good, thanks.


As a follow on patch this should be moved from /proc/<pid>/net
into /proc/<pid>/task/<tid>/net.

We don't have anything that currently forces network namespaces to be
the same between different tasks of the same task group (I just
looked), nor do we have a technical reason to require that.

So we should fix our infrastructure to include the companion of
/proc/self, a /proc/current (which points at the current task)
after which it should be about a two line change to move this
from the tgid to the task directory.

Eric
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