get_random_bytes_wait
err = get_random_bytes_wait(buf, slen);
get_random_bytes_wait(dst->nonce, COOKIE_NONCE_LEN);
ret = get_random_bytes_wait(chap->challenge, chap->challenge_len);
ret = get_random_bytes_wait(&conn->stat_sn, sizeof(u32));
get_random_bytes_wait(secret, CURVE25519_KEY_SIZE);
ret = get_random_bytes_wait(enckey, CHACHA20POLY1305_KEY_SIZE);
return get_random_bytes_wait(key, key_len) ?: key_len;