/*-
 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
 *
 * Copyright (c) 2019 Conrad Meyer <cem@FreeBSD.org>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * $FreeBSD$
 */
#pragma once

#include <sys/systm.h>

/*
 * The root BRNG seed version, or generation.
 *
 * FenestrasX-aware downstream CSPRNGs (i.e., arc4random(9)) should track the
 * generation number they seeded from, using the read_random_key(9) API below.
 * If their current seed version is older than the root generation, they should
 * reseed before producing output.
 *
 * The variable is read-only outside of the fenestrasX implementation and
 * should be accessed using 'atomic_load_acq_64(&fxrng_root_generation)'.
 * Reseeds are extremely infrequent, so callers may wish to hint to the
 * compiler that a matching generation is the expected case, with
 * __predict_true() or __predict_false().
 */
extern uint64_t __read_mostly fxrng_root_generation;

/*
 * A routine for generating seed/key material 
 * Bypasses random(4) for now, but conceivably could be incorporated into that.
 */
void read_random_key(void *buf, size_t nbytes, uint64_t *seed_version_out);