netdev - Re: loosing netdevices with namespaces and unshare?

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Date:   Wed, 31 May 2017 15:40:33 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Harald Welte <laforge@...monks.org>
Cc:     Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: loosing netdevices with namespaces and unshare?

On Wed, May 31, 2017 at 11:11 AM, Harald Welte <laforge@...monks.org> wrote:
> I mean, what is the *use case* for loosing any refrence to a physical
> network device and unregistering it from the stack?  Is there any API by
> which a new netdevice structure can be instantiated on the actual
> hardware?  Registering the netdev is what the driver does during
> discovering the system hardware.  If there's a method to "automagically"
> loose devices, at the very least I wold expect some reasonable method to
> resurrect them.  Unloading the kernel module and reloading it is for
> sure not elegant, particularly not if you have multiple Ethernet
> devices/ports sharing the same driver.
>
> One could e.g. also think of something like a special namespace that
> collects all the "orphan" netdevices.  Something analogous to the old
> Unix tradition of "pid 1" collecting all the orphan tasks whose parents
> died.  Transferring them into that "netdev orphanage" could
> automatically set the link down so that no accidential
> routing/forwarding of traffic between the devices is possible.

Understand.

But you have other choices than using the physical interface
directly in non-root ns, for example, creating a virtual pair and
connect it with the physical one with a bridge. There are various
ways to achieve this.