pf_proto_cksum_fixup
extern u_int16_t pf_proto_cksum_fixup(struct mbuf *, u_int16_t,
*pd->pcksum = pf_proto_cksum_fixup(pd->m, *pd->pcksum, po, pn, u);
*pd->pcksum = pf_proto_cksum_fixup(pd->m, *pd->pcksum, po, pn, u);
*c = pf_proto_cksum_fixup(m,
pf_proto_cksum_fixup(m, *c, ao / 65536, an / 65536, udp),
th->th_sum = pf_proto_cksum_fixup(pd->m, th->th_sum, ov, nv, 0);
th->th_sum = pf_proto_cksum_fixup(pd->m, th->th_sum, th->th_urp,