HN_CSUM_IP6_MASK
((sc)->hn_tx_ring[0].hn_csum_assist & HN_CSUM_IP6_MASK)
if (if_gethwassist(ifp) & HN_CSUM_IP6_MASK)
if_sethwassistbits(ifp, 0, (HN_CSUM_IP6_MASK | CSUM_IP6_TSO));