ipproto_register
err = ipproto_register(IPPROTO_CARP, carp_input, NULL);
int ipproto_register(uint8_t, ipproto_input_t, ipproto_ctlinput_t);
error = ipproto_register(prot, input, ctl); \
error = ipproto_register(IPPROTO_SCTP, sctp_input, sctp_ctlinput);
error = ipproto_register(IPPROTO_PFSYNC, pfsync_input, NULL);