LCP_HEADER_LEN
if (len > MHLEN - PKTHDRLEN - LCP_HEADER_LEN) {
m->m_pkthdr.len = m->m_len = PKTHDRLEN + LCP_HEADER_LEN + len;
lh->len = htons (LCP_HEADER_LEN + len);
if (len > MHLEN - PKTHDRLEN - LCP_HEADER_LEN)
len = MHLEN - PKTHDRLEN - LCP_HEADER_LEN;
m->m_pkthdr.len = m->m_len = PKTHDRLEN + LCP_HEADER_LEN + len;
lh->len = htons (LCP_HEADER_LEN + len);