__netif_set_mtu
__netif_set_mtu(slave_dev, slave->original_mtu);
__netif_set_mtu(port_dev, port->orig.mtu);
int __netif_set_mtu(struct net_device *dev, int new_mtu);
EXPORT_SYMBOL_NS_GPL(__netif_set_mtu, "NETDEV_INTERNAL");
err = __netif_set_mtu(dev, new_mtu);
__netif_set_mtu(dev, orig_mtu);