On Wed, May 31, 2017 at 11:11 AM, Harald Welte [off-list ref] 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.