npf_ext_register
npf_ext_log_id = npf_ext_register(npf, "log", &npf_log_ops);
npf_ext_normalize_id = npf_ext_register(npf,
npf_ext_rndblock_id = npf_ext_register(npf, "rndblock",
npf_ext_route_id = npf_ext_register(npf, "route", &npf_route_ops);
void * npf_ext_register(npf_t *, const char *, const npf_ext_ops_t *);