hash_update
void hash_update(struct iked_hash *, void *, size_t);
hash_update(sa->sa_prf, IKEV2_KEYPAD, strlen(IKEV2_KEYPAD));
hash_update(prf, ibuf_data(dhsecret), ibuf_size(dhsecret));
hash_update(prf, ibuf_data(t2), ibuf_size(t2));
hash_update(sa->sa_integr, ibuf_data(src),
hash_update(sa->sa_integr, ibuf_data(msg),
hash_update(sa->sa_prf, ibuf_data(id->id_buf), ibuf_size(id->id_buf));