size_to_mtu
netdev->max_mtu = size_to_mtu(9 * 1024);
netdev->max_mtu = size_to_mtu(15 * 1024);
netdev->max_mtu = size_to_mtu(16 * 1024);
#define RTL_LIMITED_TSO_SIZE (size_to_mtu(agg_buf_sz) - tp->tx_desc.size)