/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 2001-2007, by Cisco Systems, Inc. All rights reserved.
 * Copyright (c) 2008-2012, by Randall Stewart. All rights reserved.
 * Copyright (c) 2008-2012, by Michael Tuexen. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * a) Redistributions of source code must retain the above copyright notice,
 *   this list of conditions and the following disclaimer.
 *
 * b) 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.
 *
 * c) Neither the name of Cisco Systems, Inc. nor the names of its
 *    contributors may be used to endorse or promote products derived
 *    from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS 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 COPYRIGHT OWNER 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.
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD: releng/12.0/sys/netinet/sctp_crc32.c 336508 2018-07-19 20:11:14Z tuexen $");

#include "opt_sctp.h"

#ifdef SCTP
#include <netinet/sctp_os.h>
#include <netinet/sctp.h>
#include <netinet/sctp_crc32.h>
#include <netinet/sctp_pcb.h>
#else
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/mbuf.h>

#include <netinet/sctp_crc32.h>
#endif

static uint32_t
sctp_finalize_crc32c(uint32_t crc32c)
{
	uint32_t result;
#if BYTE_ORDER == BIG_ENDIAN
	uint8_t byte0, byte1, byte2, byte3;
#endif

	/* Complement the result */
	result = ~crc32c;
#if BYTE_ORDER == BIG_ENDIAN
	/*
	 * For BIG-ENDIAN platforms the result is in little-endian form. So
	 * we must swap the bytes to return the result in network byte
	 * order.
	 */
	byte0 = result & 0x000000ff;
	byte1 = (result >> 8) & 0x000000ff;
	byte2 = (result >> 16) & 0x000000ff;
	byte3 = (result >> 24) & 0x000000ff;
	crc32c = ((byte0 << 24) | (byte1 << 16) | (byte2 << 8) | byte3);
#else
	/*
	 * For LITTLE ENDIAN platforms the result is in already in network
	 * byte order.
	 */
	crc32c = result;
#endif
	return (crc32c);
}

/*
 * Compute the SCTP checksum in network byte order for a given mbuf chain m
 * which contains an SCTP packet starting at offset.
 * Since this function is also called by ipfw, don't assume that
 * it is compiled on a kernel with SCTP support.
 */
uint32_t
sctp_calculate_cksum(struct mbuf *m, uint32_t offset)
{
	uint32_t base = 0xffffffff;

	while (offset > 0) {
		KASSERT(m != NULL, ("sctp_calculate_cksum, offset > length of mbuf chain"));
		if (offset < (uint32_t)m->m_len) {
			break;
		}
		offset -= m->m_len;
		m = m->m_next;
	}
	if (offset > 0) {
		base = calculate_crc32c(base,
		    (unsigned char *)(m->m_data + offset),
		    (unsigned int)(m->m_len - offset));
		m = m->m_next;
	}
	while (m != NULL) {
		base = calculate_crc32c(base,
		    (unsigned char *)m->m_data,
		    (unsigned int)m->m_len);
		m = m->m_next;
	}
	base = sctp_finalize_crc32c(base);
	return (base);
}

#ifdef SCTP
/*
 * Compute and insert the SCTP checksum in network byte order for a given
 * mbuf chain m which contains an SCTP packet starting at offset.
 */
void
sctp_delayed_cksum(struct mbuf *m, uint32_t offset)
{
	uint32_t checksum;

	checksum = sctp_calculate_cksum(m, offset);
	SCTP_STAT_DECR(sctps_sendhwcrc);
	SCTP_STAT_INCR(sctps_sendswcrc);
	offset += offsetof(struct sctphdr, checksum);

	if (offset + sizeof(uint32_t) > (uint32_t)(m->m_len)) {
#ifdef INVARIANTS
		panic("sctp_delayed_cksum(): m->m_len: %d, offset: %u.",
		    m->m_len, offset);
#else
		SCTP_PRINTF("sctp_delayed_cksum(): m->m_len: %d, offset: %u.\n",
		    m->m_len, offset);
#endif
		return;
	}
	*(uint32_t *)(m->m_data + offset) = checksum;
}
#endif
