+/**
+ * dev_change_net_namespace - move device to different nethost namespace
+ * @dev: device
+ * @net: network namespace
+ * @pat: If not NULL name pattern to try if the current device name
+ * is already taken in the destination network namespace.
+ *
+ * This function shuts down a device interface and moves it
+ * to a new network namespace. On success 0 is returned, on
+ * a failure a netagive errno code is returned.
+ *
+ * Callers must hold the rtnl semaphore.
+ */
+
+int dev_change_net_namespace(struct net_device *dev, struct net *net, const char *pat)
+{
+ char buf[IFNAMSIZ];
+ const char *destname;
+ int err;
+
+ ASSERT_RTNL();
+
+ /* Don't allow namespace local devices to be moved. */
+ err = -EINVAL;
+ if (dev->features & NETIF_F_NETNS_LOCAL)
+ goto out;
+
+ /* Ensure the device has been registrered */
+ err = -EINVAL;
+ if (dev->reg_state != NETREG_REGISTERED)
+ goto out;
+
+ /* Get out if there is nothing todo */
+ err = 0;
+ if (dev->nd_net == net)
+ goto out;
+
+ /* Pick the destination device name, and ensure
+ * we can use it in the destination network namespace.
+ */
+ err = -EEXIST;
+ destname = dev->name;
+ if (__dev_get_by_name(net, destname)) {
+ /* We get here if we can't use the current device name */
+ if (!pat)
+ goto out;
+ if (!dev_valid_name(pat))
+ goto out;
+ if (strchr(pat, '%')) {
+ if (__dev_alloc_name(net, pat, buf) < 0)
+ goto out;
+ destname = buf;
+ } else
+ destname = pat;
+ if (__dev_get_by_name(net, destname))
+ goto out;
+ }
+
+ /*
+ * And now a mini version of register_netdevice unregister_netdevice.
+ */
+
+ /* If device is running close it first. */
+ if (dev->flags & IFF_UP)
+ dev_close(dev);
+
+ /* And unlink it from device chain */
+ err = -ENODEV;
+ unlist_netdevice(dev);
+
+ synchronize_net();
+
+ /* Shutdown queueing discipline. */
+ dev_shutdown(dev);
+
+ /* Notify protocols, that we are about to destroy
+ this device. They should clean all the things.
+ */
+ call_netdevice_notifiers(NETDEV_UNREGISTER, dev);
+
+ /*
+ * Flush the unicast and multicast chains
+ */
+ dev_addr_discard(dev);
+
+ /* Actually switch the network namespace */
+ dev->nd_net = net;
+
+ /* Assign the new device name */
+ if (destname != dev->name)
+ strcpy(dev->name, destname);
+
+ /* If there is an ifindex conflict assign a new one */
+ if (__dev_get_by_index(net, dev->ifindex)) {
+ int iflink = (dev->iflink == dev->ifindex);
+ dev->ifindex = dev_new_index(net);
+ if (iflink)
+ dev->iflink = dev->ifindex;
+ }
+
+ /* Fixup sysfs */
+ err = device_rename(&dev->dev, dev->name);
+ BUG_ON(err);
+
+ /* Add the device back in the hashes */
+ list_netdevice(dev);
+
+ /* Notify protocols, that a new device appeared. */
+ call_netdevice_notifiers(NETDEV_REGISTER, dev);
+
+ synchronize_net();
+ err = 0;
+out:
+ return err;
+}
+