hhook_add_hook
error = hhook_add_hook(heads_to_hook[i], hki, flags);
error = hhook_add_hook(hhh, &h->h_hooks[i], flags);
error = hhook_add_hook(V_ipsec_hhh_in[HHOOK_IPSEC_INET],
error = hhook_add_hook(V_ipsec_hhh_out[HHOOK_IPSEC_INET],
error = hhook_add_hook(V_ipsec_hhh_in[HHOOK_IPSEC_INET6],
error = hhook_add_hook(V_ipsec_hhh_out[HHOOK_IPSEC_INET6],
int hhook_add_hook(struct hhook_head *hhh, const struct hookinfo *hki,