m_pktdat
m_new->m_data = m_new->m_pktdat;
to->m_data = to->m_pktdat;
(*pr)("m_dat: %p\tm_pktdat: %p\n", m->m_dat, m->m_pktdat);
(m)->m_flags & M_PKTHDR ? (m)->m_pktdat : (m)->m_dat)
m->m_data = m->m_pktdat;
m->m_data = m->m_pktdat;
(m->m_flags & M_PKTHDR ? m->m_pktdat : m->m_dat);
if (m->m_flags & M_EXT || m->m_data - optlen < m->m_pktdat) {
(to)->m_data = (to)->m_pktdat; \