LPIPHDRLEN
#if !defined(MLPIPHDRLEN) || LPIPHDRLEN > MLPIPHDRLEN
#define MLPIPHDRLEN LPIPHDRLEN
len = sc->sc_if.if_mtu + LPIPHDRLEN;
if (len <= LPIPHDRLEN)
len -= LPIPHDRLEN;
top = m_devget(sc->sc_ifbuf + LPIPHDRLEN, len, 0, &sc->sc_if);