l3mdev_master_upper_ifindex_by_index_rcu
int l3mdev_master_upper_ifindex_by_index_rcu(struct net *net, int ifindex);
ifindex = l3mdev_master_upper_ifindex_by_index_rcu(net, ifindex);
EXPORT_SYMBOL_GPL(l3mdev_master_upper_ifindex_by_index_rcu);