AGE_CSUM_FEATURES
if ((m->m_pkthdr.csum_flags & AGE_CSUM_FEATURES) != 0) {
ifp->if_hwassist |= AGE_CSUM_FEATURES;
ifp->if_hwassist &= ~AGE_CSUM_FEATURES;
ifp->if_hwassist = AGE_CSUM_FEATURES;