| 1 | /* $Id: cksum.c 98103 2023-01-17 14:15:46Z vboxsync $ */
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| 2 | /** @file
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| 3 | * NAT - IP checksum generation.
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| 4 | */
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| 5 |
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| 6 | /*
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| 7 | * Copyright (C) 2006-2023 Oracle and/or its affiliates.
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| 8 | *
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| 9 | * This file is part of VirtualBox base platform packages, as
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| 10 | * available from https://www.virtualbox.org.
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| 11 | *
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| 12 | * This program is free software; you can redistribute it and/or
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| 13 | * modify it under the terms of the GNU General Public License
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| 14 | * as published by the Free Software Foundation, in version 3 of the
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| 15 | * License.
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| 16 | *
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| 17 | * This program is distributed in the hope that it will be useful, but
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| 18 | * WITHOUT ANY WARRANTY; without even the implied warranty of
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| 19 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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| 20 | * General Public License for more details.
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| 21 | *
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| 22 | * You should have received a copy of the GNU General Public License
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| 23 | * along with this program; if not, see <https://www.gnu.org/licenses>.
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| 24 | *
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| 25 | * SPDX-License-Identifier: GPL-3.0-only
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| 26 | */
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| 27 |
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| 28 | /*
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| 29 | * This code is based on:
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| 30 | *
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| 31 | * Copyright (c) 1988, 1992, 1993
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| 32 | * The Regents of the University of California. All rights reserved.
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| 33 | *
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| 34 | * Redistribution and use in source and binary forms, with or without
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| 35 | * modification, are permitted provided that the following conditions
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| 36 | * are met:
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| 37 | * 1. Redistributions of source code must retain the above copyright
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| 38 | * notice, this list of conditions and the following disclaimer.
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| 39 | * 2. Redistributions in binary form must reproduce the above copyright
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| 40 | * notice, this list of conditions and the following disclaimer in the
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| 41 | * documentation and/or other materials provided with the distribution.
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| 42 | * 3. Neither the name of the University nor the names of its contributors
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| 43 | * may be used to endorse or promote products derived from this software
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| 44 | * without specific prior written permission.
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| 45 | *
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| 46 | * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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| 47 | * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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| 48 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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| 49 | * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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| 50 | * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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| 51 | * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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| 52 | * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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| 53 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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| 54 | * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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| 55 | * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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| 56 | * SUCH DAMAGE.
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| 57 | *
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| 58 | * @(#)in_cksum.c 8.1 (Berkeley) 6/10/93
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| 59 | * in_cksum.c,v 1.2 1994/08/02 07:48:16 davidg Exp
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| 60 | */
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| 61 |
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| 62 | #include <slirp.h>
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| 63 |
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| 64 | /*
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| 65 | * Checksum routine for Internet Protocol family headers (Portable Version).
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| 66 | *
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| 67 | * This routine is very heavily used in the network
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| 68 | * code and should be modified for each CPU to be as fast as possible.
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| 69 | *
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| 70 | * XXX Since we will never span more than 1 mbuf, we can optimise this
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| 71 | */
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| 72 |
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| 73 | #define ADDCARRY(x) (x > 65535 ? x -= 65535 : x)
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| 74 | #define REDUCE { l_util.l = sum; sum = l_util.s[0] + l_util.s[1]; ADDCARRY(sum); }
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| 75 |
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| 76 | int cksum(struct mbuf *m, int len)
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| 77 | {
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| 78 | register u_int16_t *w;
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| 79 | register int sum = 0;
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| 80 | register int mlen = 0;
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| 81 | int byte_swapped = 0;
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| 82 |
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| 83 | union
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| 84 | {
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| 85 | u_int8_t c[2];
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| 86 | u_int16_t s;
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| 87 | } s_util;
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| 88 | union
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| 89 | {
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| 90 | u_int16_t s[2];
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| 91 | u_int32_t l;
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| 92 | } l_util;
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| 93 |
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| 94 | if (m->m_len == 0)
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| 95 | goto cont;
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| 96 | w = mtod(m, u_int16_t *);
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| 97 |
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| 98 | mlen = m->m_len;
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| 99 |
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| 100 | if (len < mlen)
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| 101 | mlen = len;
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| 102 | len -= mlen;
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| 103 | /*
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| 104 | * Force to even boundary.
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| 105 | */
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| 106 | if ((1 & (long) w) && (mlen > 0))
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| 107 | {
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| 108 | REDUCE;
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| 109 | sum <<= 8;
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| 110 | s_util.c[0] = *(u_int8_t *)w;
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| 111 | w = (u_int16_t *)((int8_t *)w + 1);
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| 112 | mlen--;
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| 113 | byte_swapped = 1;
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| 114 | }
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| 115 | /*
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| 116 | * Unroll the loop to make overhead from
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| 117 | * branches &c small.
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| 118 | */
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| 119 | while ((mlen -= 32) >= 0)
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| 120 | {
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| 121 | sum += w[ 0]; sum += w[ 1]; sum += w[ 2]; sum += w[ 3];
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| 122 | sum += w[ 4]; sum += w[ 5]; sum += w[ 6]; sum += w[ 7];
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| 123 | sum += w[ 8]; sum += w[ 9]; sum += w[10]; sum += w[11];
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| 124 | sum += w[12]; sum += w[13]; sum += w[14]; sum += w[15];
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| 125 | w += 16;
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| 126 | }
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| 127 | mlen += 32;
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| 128 | while ((mlen -= 8) >= 0)
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| 129 | {
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| 130 | sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
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| 131 | w += 4;
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| 132 | }
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| 133 | mlen += 8;
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| 134 | if (mlen == 0 && byte_swapped == 0)
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| 135 | goto cont;
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| 136 | REDUCE;
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| 137 | while ((mlen -= 2) >= 0)
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| 138 | {
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| 139 | sum += *w++;
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| 140 | }
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| 141 |
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| 142 | if (byte_swapped)
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| 143 | {
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| 144 | REDUCE;
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| 145 | sum <<= 8;
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| 146 | byte_swapped = 0;
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| 147 | if (mlen == -1)
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| 148 | {
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| 149 | s_util.c[1] = *(u_int8_t *)w;
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| 150 | sum += s_util.s;
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| 151 | mlen = 0;
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| 152 | }
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| 153 | else
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| 154 | mlen = -1;
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| 155 | }
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| 156 | else if (mlen == -1)
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| 157 | s_util.c[0] = *(u_int8_t *)w;
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| 158 |
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| 159 | cont:
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| 160 | #ifdef DEBUG
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| 161 | if (len)
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| 162 | Log(("cksum: out of data: len = %d\n", len));
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| 163 | #endif
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| 164 | if (mlen == -1)
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| 165 | {
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| 166 | /* The last mbuf has odd # of bytes. Follow the
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| 167 | standard (the odd byte may be shifted left by 8 bits
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| 168 | or not as determined by endian-ness of the machine) */
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| 169 | s_util.c[1] = 0;
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| 170 | sum += s_util.s;
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| 171 | }
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| 172 | REDUCE;
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| 173 | return (~sum & 0xffff);
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| 174 | }
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