M_CKHASH
m->m_flags |= M_CKHASH;
if ((m->m_flags & (M_HASH | M_CKHASH)) == (M_HASH | M_CKHASH) ||
m->m_flags &= ~(M_HASH | M_CKHASH);
m->m_flags &= ~(M_HASH | M_CKHASH);
M_LENCHECKED|M_HASH|M_CKHASH|M_PRIO)