On Wed, May 31, 2017 at 11:32 PM, Eric W. Biederman
[off-list ref] wrote:

Cong Wang [off-list ref] writes:

quoted

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.