IPPROTO_CARP
ip->ip_p = IPPROTO_CARP;
ip6->ip6_nxt = IPPROTO_CARP;
ip->ip_p = IPPROTO_CARP;
ip6->ip6_nxt = IPPROTO_CARP;
SYSCTL_NODE(_net_inet, IPPROTO_CARP, carp, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
(void)ipproto_unregister(IPPROTO_CARP);
(void)ip6proto_unregister(IPPROTO_CARP);
err = ip6proto_register(IPPROTO_CARP, carp6_input, NULL);
err = ipproto_register(IPPROTO_CARP, carp_input, NULL);
case IPPROTO_CARP: