/* $Id: cksum.c 98103 2023-01-17 14:15:46Z vboxsync $ */
/** @file
* NAT - IP checksum generation.
*/
/*
* Copyright (C) 2006-2023 Oracle and/or its affiliates.
*
* This file is part of VirtualBox base platform packages, as
* available from https://www.virtualbox.org.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation, in version 3 of the
* License.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, see .
*
* SPDX-License-Identifier: GPL-3.0-only
*/
/*
* This code is based on:
*
* Copyright (c) 1988, 1992, 1993
* The Regents of the University of California. All rights reserved.
*
* 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.
* 3. Neither the name of the University 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 REGENTS 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 REGENTS 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.
*
* @(#)in_cksum.c 8.1 (Berkeley) 6/10/93
* in_cksum.c,v 1.2 1994/08/02 07:48:16 davidg Exp
*/
#include
/*
* Checksum routine for Internet Protocol family headers (Portable Version).
*
* This routine is very heavily used in the network
* code and should be modified for each CPU to be as fast as possible.
*
* XXX Since we will never span more than 1 mbuf, we can optimise this
*/
#define ADDCARRY(x) (x > 65535 ? x -= 65535 : x)
#define REDUCE { l_util.l = sum; sum = l_util.s[0] + l_util.s[1]; ADDCARRY(sum); }
int cksum(struct mbuf *m, int len)
{
register u_int16_t *w;
register int sum = 0;
register int mlen = 0;
int byte_swapped = 0;
union
{
u_int8_t c[2];
u_int16_t s;
} s_util;
union
{
u_int16_t s[2];
u_int32_t l;
} l_util;
if (m->m_len == 0)
goto cont;
w = mtod(m, u_int16_t *);
mlen = m->m_len;
if (len < mlen)
mlen = len;
len -= mlen;
/*
* Force to even boundary.
*/
if ((1 & (long) w) && (mlen > 0))
{
REDUCE;
sum <<= 8;
s_util.c[0] = *(u_int8_t *)w;
w = (u_int16_t *)((int8_t *)w + 1);
mlen--;
byte_swapped = 1;
}
/*
* Unroll the loop to make overhead from
* branches &c small.
*/
while ((mlen -= 32) >= 0)
{
sum += w[ 0]; sum += w[ 1]; sum += w[ 2]; sum += w[ 3];
sum += w[ 4]; sum += w[ 5]; sum += w[ 6]; sum += w[ 7];
sum += w[ 8]; sum += w[ 9]; sum += w[10]; sum += w[11];
sum += w[12]; sum += w[13]; sum += w[14]; sum += w[15];
w += 16;
}
mlen += 32;
while ((mlen -= 8) >= 0)
{
sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
w += 4;
}
mlen += 8;
if (mlen == 0 && byte_swapped == 0)
goto cont;
REDUCE;
while ((mlen -= 2) >= 0)
{
sum += *w++;
}
if (byte_swapped)
{
REDUCE;
sum <<= 8;
byte_swapped = 0;
if (mlen == -1)
{
s_util.c[1] = *(u_int8_t *)w;
sum += s_util.s;
mlen = 0;
}
else
mlen = -1;
}
else if (mlen == -1)
s_util.c[0] = *(u_int8_t *)w;
cont:
#ifdef DEBUG
if (len)
Log(("cksum: out of data: len = %d\n", len));
#endif
if (mlen == -1)
{
/* The last mbuf has odd # of bytes. Follow the
standard (the odd byte may be shifted left by 8 bits
or not as determined by endian-ness of the machine) */
s_util.c[1] = 0;
sum += s_util.s;
}
REDUCE;
return (~sum & 0xffff);
}