netns: Delete virtual interfaces during namespace cleanup

When physical devices are inside of network namespace and that network namespace terminates we have to keep them and moving them to the initial network namespace is the best we can do.

For virtual devices left in a network namespace that is exiting we have no need to preserve them and we now have the infrastructure that allows us to delete them. So delete virtual devices when we exit a network namespace. Keeping the necessary user space clean up after a network namespace exits much more tractable.

---
 net/core/dev.c |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)

index ea480a4..670abad 100644
@@ -4492,6 +4492,12 @@ static void __net_exit default_device_exit(struct net *net)
 		if (dev->features & NETIF_F_NETNS_LOCAL)
 			continue;
 
+		/* Delete virtual devices */
+		if (dev->rtnl_link_ops && dev->rtnl_link_ops->dellink) {
+			dev->rtnl_link_ops->dellink(dev);
+			continue;
+		}
+
 		/* Push remaing network devices to init_net */
 		snprintf(fb_name, IFNAMSIZ, "dev%d", dev->ifindex);
 		err = dev_change_net_namespace(dev, &init_net, fb_name);

1.5.3.rc6.17.g1911