ipsec6_check_policy
sp = ipsec6_check_policy(m, NULL, 0, &needipsec, &error);
sp = ipsec6_check_policy(m, inp, flags, &needipsec, &error);
struct secpolicy *ipsec6_check_policy(struct mbuf *, struct inpcb *,
__weak_alias(ipsec6_check_policy,rumpnet_stub);