rmnet_map_get_csum_field
csum_field = rmnet_map_get_csum_field(ip6h->nexthdr, txporthdr);
csum = (u16 *)rmnet_map_get_csum_field(ip4h->protocol, txphdr);
csum = (u16 *)rmnet_map_get_csum_field(ip6h->nexthdr, txphdr);
check = rmnet_map_get_csum_field(proto, trans);
csum_field = rmnet_map_get_csum_field(ip4h->protocol, txporthdr);