netdev - Re: Namespaces and devices

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Message-ID: <4BF935F6.2050907@free.fr>
Date:	Sun, 23 May 2010 16:04:38 +0200
From:	Daniel Lezcano <daniel.lezcano@...e.fr>
To:	Martín Ferrari <martin.ferrari@...il.com>
CC:	netdev <netdev@...r.kernel.org>,
	Mathieu Lacage <mathieu.lacage@...hia.inria.fr>
Subject: Re: Namespaces and devices

On 05/21/2010 06:27 PM, Martín Ferrari wrote:
> Hi,
>
> Sorry if this is a dumb question, but I couldn't find any
> documentation that matches the current behaviour... So I don't know if
> what I see is what is intended, or if it's a bug.
>
> I would like to know what is the exact behaviour re. devices when a
> netns is destroyed, and which kind of devices can be moved.
>
> According to http://lxc.sourceforge.net/network/configuration.php,
> devices assigned to a netns should move to the main netns when the
> former is destroyed. What I see is that the devices are deleted, at
> least for veth and dummy devices. I also see a bug I previously
> reported that caused an oops in some cases.
>    

The documentation on this website is a bit out dated. That was the 
initial behavior but was changed as the following.

All the virtual devices are destroyed with the network namespace. The 
destroyable virtual devices are identified when they have the dellink 
ops defined. If you can do the 'ip link del' command on this device, 
then this device type will be destroyed by a netns.

About the oops,  was the it "kernel panic when using 
netns+bridges+tc(netem)" ?

> Also, I have read somewhere (now I cannot find it) that supposedly, I
> should be able to move real devices to a netns, but I always get
> Invalid argument errors.

Yes, that was previously the case with the proof of concept, because 
sysfs per namespace was enabled. But this feature is not merged upstream 
yet (but is on the way), so physical devices are not movable across 
namespaces.

Hope that helps
   -- Daniel
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