ip6proto_register
err = ip6proto_register(IPPROTO_CARP, carp6_input, NULL);
error = ip6proto_register(IPPROTO_SCTP, sctp6_input, sctp6_ctlinput);
int ip6proto_register(uint8_t, ip6proto_input_t, ip6proto_ctlinput_t);
error = ip6proto_register(prot, input, ctl); \
error = ip6proto_register(IPPROTO_PFSYNC, pfsync6_input, NULL);