netdev - Re: Deleting a network namespace

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Message-ID: <CAJJAcof98k+GDt88MORMz6sS-JFODeuyqYSwP6dk-ZYqFMGTWg@mail.gmail.com>
Date:	Thu, 28 Mar 2013 15:41:25 +0200
From:	David Shwatrz <dshwatrz@...il.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	netdev@...r.kernel.org
Subject: Re: Deleting a network namespace

Hello,
I checked and indeed physical hardware are moved to init_net.
I wonder how it is done, as in netns_delete() there is only
umount2() and unlink() syscalls (might these syscalls trigger this
movement to init_net)? I really could not figure how this is
implemented and where in code do we differentiate between physical and
non physical devices.

Best,
DS

On Thu, Mar 28, 2013 at 1:05 PM, Eric W. Biederman
<ebiederm@...ssion.com> wrote:
> David Shwatrz <dshwatrz@...il.com> writes:
>
>> Hello,
>> When assigning a network interface to a network namespace and
>> afterwards deleting the namespace, we will not see the network
>> interface in any other namespace (including the default namespace) anymore:
>>
>> ip netns add ns1
>> ip link set eth0 netns ns1
>> ip netns del ns1
>>
>> This means that in fact we cannot use this interface again (only after
>> rebooting)
>> Am I right on this ?
>
> Interfaces that represent physical hardware are moved to init_net.
> Interfaces that are purely software constructs are deleted.
>
>> Is moving an interface back to the default (init) namespace,
>> when deleting the namespace which contains it, can be considered?
>
> If you aren't seeing that your interface is either a purely software
> construct like the veth or dummy interfaces or something still has a
> reference to your network namespace.
>
> Eric
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