m_xhalf
A = m_xhalf(m, k, &merr);
A = m_xhalf(m, k, &merr);
static int m_xhalf(mb_t *, int, int *);
A = m_xhalf((struct mbuf *)p, k, &merr);
A = m_xhalf((struct mbuf *)p, k, &merr);
static u_int16_t m_xhalf(struct mbuf *m, bpf_u_int32 k, int *err);