linux-kernel - Re: Network isolation with RLIMIT

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Date:	Thu, 17 Dec 2009 14:35:17 -0500
From:	Bernie Innocenti <bernie@...ewiz.org>
To:	Bryan Donlan <bdonlan@...il.com>
Cc:	Mark Seaborn <mrs@...hic-beasts.com>,
	Michael Stone <michael@...top.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	linux-security-module@...r.kernel.org,
	Andi Kleen <andi@...stfloor.org>, David Lang <david@...g.hm>,
	Oliver Hartkopp <socketcan@...tkopp.net>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	Valdis Kletnieks <Valdis.Kletnieks@...edu>,
	Rémi Denis-Courmont <rdenis@...phalempin.com>,
	Evgeniy Polyakov <zbr@...emap.net>,
	"C. Scott Ananian" <cscott@...ott.net>,
	James Morris <jmorris@...ei.org>,
	Linux Containers <containers@...ts.osdl.org>
Subject: Re: Network isolation with RLIMIT_NETWORK, cont'd.

On Thu, 2009-12-17 at 13:24 -0500, Bryan Donlan wrote:
> Can this be done using openat() and friends currently? It would seem
> the natural way to implement this; open /proc/(pid)/root, then
> openat() things from there (or even chdir to it and see the mounts
> that it sees from there...)

Yeah, but /proc/<pid>/root is just a symlink. It's correct for chroots,
but I doubt it can be meaningful for per-process namespaces.

If we were to implement Mark Seaborn's idea of naming
namespaces, /proc/<pid>/rootfd would be a file descriptor providing
access to the namespace through some fancy ioctls.

Or maybe not. Could such a file-descriptor be used as the source
argument to mount(), perhaps along with a new MS_NS flag?

Alternatively, perhaps one could come up with a userspace solution:
read /proc/<pid>/mounts and repeat all mounts, perhaps with a prefix.
The downsides are that it would require superuser privs and wouldn't
automatically stay synchronized with the real namespace.

-- 
   // Bernie Innocenti - http://codewiz.org/
 \X/  Sugar Labs       - http://sugarlabs.org/

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