NH_OBSERVE
HOOK_EVENT_INIT(&ipst->ips_ip4_observe, NH_OBSERVE);
HOOK_EVENT_INIT(&ipst->ips_ip6_observe, NH_OBSERVE);
(void) net_hook_register(ipst->ips_ip4_observe_pr, NH_OBSERVE, hook);
(void) net_hook_register(ipst->ips_ip6_observe_pr, NH_OBSERVE, hook);
(void) net_hook_unregister(ipst->ips_ip4_observe_pr, NH_OBSERVE, hook);
(void) net_hook_unregister(ipst->ips_ip6_observe_pr, NH_OBSERVE, hook);
error = net_hook_register(ipst->ips_ip4_observe_pr, NH_OBSERVE,
error = net_hook_register(ipst->ips_ip6_observe_pr, NH_OBSERVE,
NH_OBSERVE, ipnet->ipnet_hook);
VERIFY(net_hook_unregister(ipst->ips_ip4_observe_pr, NH_OBSERVE,
VERIFY(net_hook_unregister(ipst->ips_ip6_observe_pr, NH_OBSERVE,