ILLF_FIXEDMTU
if (!(ill->ill_flags & ILLF_FIXEDMTU)) {
ill->ill_flags |= ILLF_FIXEDMTU;
if (!(ill->ill_flags & ILLF_FIXEDMTU) && ill->ill_user_mtu != 0) {
if (!(ill->ill_flags & ILLF_FIXEDMTU) && (lir->lir_maxmtu != 0))