MLPIPHDRLEN
#if !defined(MLPIPHDRLEN) || LPIPHDRLEN > MLPIPHDRLEN
sc->sc_ifbuf = malloc(if_getmtu(sc->sc_ifp) + MLPIPHDRLEN,
ptr = malloc(ifr->ifr_mtu + MLPIPHDRLEN, M_DEVBUF,
if (len > if_getmtu(sc->sc_ifp) + MLPIPHDRLEN)