br_get_rx_handler
err = netdev_rx_handler_register(dev, br_get_rx_handler(dev), p);
rx_handler_func_t *br_get_rx_handler(const struct net_device *dev);
return rcu_dereference(dev->rx_handler) == br_get_rx_handler(dev);
return rcu_dereference_rtnl(dev->rx_handler) == br_get_rx_handler(dev);