From: ebiederm@xmission•com (Eric W. Biederman)
To: Cong Wang <xiyou.wangcong@gmail•com>
Cc: Harald Welte <laforge@gnumonks•org>,
Linux Kernel Network Developers <netdev@vger•kernel.org>
Subject: Re: loosing netdevices with namespaces and unshare?
Date: Sat, 03 Jun 2017 05:53:48 -0500 [thread overview]
Message-ID: <8760gd735v.fsf@xmission.com> (raw)
In-Reply-To: <CAM_iQpWaJ7WKOEQe=00AX35x_gCKHoHikVTGH6UQTPw+3oD_pw@mail.gmail.com> (Cong Wang's message of "Fri, 2 Jun 2017 16:25:44 -0700")
Cong Wang <xiyou.wangcong@gmail•com> writes:
> On Wed, May 31, 2017 at 11:32 PM, Eric W. Biederman
> <ebiederm@xmission•com> wrote:
>> Cong Wang <xiyou.wangcong@gmail•com> writes:
>>> Network namespace does not special-case the physical devices,
>>> it treats them all equally as abstract net devices.
>>
>> Absolutely not true.
>>
>> The relevant code is in net/core/dev.c:default_device_exit
>>
>> If a network device does not implement rntl_link_ops it is returned to
>> the initial network namespace. Anything else will loose physical
>> devices.
>
> Hmm, I never noticed that if check...
>
>>
>> Only for pure software based devices do we delete them. Perhaps your
>> sub interface implements rtnl_link_ops? Either that or something is
>> still holding a reference to your network namespace, which would prevent
>> the network device from being returned.
>>
>
> But this simply sucks:
>
> snprintf(fb_name, IFNAMSIZ, "dev%d", dev->ifindex);
> err = dev_change_net_namespace(dev, &init_net, fb_name);
> if (err) {
> pr_emerg("%s: failed to move %s to init_net: %d\n",
> __func__, dev->name, err);
> BUG();
> }
>
> It is essentially hard to handle the error here, but it is quite easy to
> trigger such BUG() by naming other device devX, it is no better
> than just losing it.
The rename only happens if there is a conflicting device name.
Beyond that there is the entire hotplug functionality so it should be
possible to automatically detect a new device in your network namespace
and do something with it.
Eric
next prev parent reply other threads:[~2017-06-03 11:00 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-05-30 22:07 loosing netdevices with namespaces and unshare? Harald Welte
2017-05-30 23:18 ` Cong Wang
2017-05-31 12:27 ` Harald Welte
2017-05-31 17:44 ` Cong Wang
2017-05-31 18:11 ` Harald Welte
2017-05-31 22:40 ` Cong Wang
2017-05-31 23:13 ` Harald Welte
2017-06-01 6:32 ` Eric W. Biederman
2017-06-01 7:00 ` Harald Welte
2017-06-01 7:48 ` Eric W. Biederman
2017-06-02 23:25 ` Cong Wang
2017-06-03 10:53 ` Eric W. Biederman [this message]
2017-05-30 23:41 ` David Ahern
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