in4_cksum.c revision 1.8
1/* $OpenBSD: in4_cksum.c,v 1.8 2011/07/05 21:40:38 dhill Exp $ */ 2/* $KAME: in4_cksum.c,v 1.10 2001/11/30 10:06:15 itojun Exp $ */ 3/* $NetBSD: in_cksum.c,v 1.13 1996/10/13 02:03:03 christos Exp $ */ 4 5/* 6 * Copyright (C) 1999 WIDE Project. 7 * All rights reserved. 8 * 9 * Redistribution and use in source and binary forms, with or without 10 * modification, are permitted provided that the following conditions 11 * are met: 12 * 1. Redistributions of source code must retain the above copyright 13 * notice, this list of conditions and the following disclaimer. 14 * 2. Redistributions in binary form must reproduce the above copyright 15 * notice, this list of conditions and the following disclaimer in the 16 * documentation and/or other materials provided with the distribution. 17 * 3. Neither the name of the project nor the names of its contributors 18 * may be used to endorse or promote products derived from this software 19 * without specific prior written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND 22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 24 * ARE DISCLAIMED. IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE 25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 */ 33 34/* 35 * Copyright (c) 1988, 1992, 1993 36 * The Regents of the University of California. All rights reserved. 37 * 38 * Redistribution and use in source and binary forms, with or without 39 * modification, are permitted provided that the following conditions 40 * are met: 41 * 1. Redistributions of source code must retain the above copyright 42 * notice, this list of conditions and the following disclaimer. 43 * 2. Redistributions in binary form must reproduce the above copyright 44 * notice, this list of conditions and the following disclaimer in the 45 * documentation and/or other materials provided with the distribution. 46 * 3. Neither the name of the University nor the names of its contributors 47 * may be used to endorse or promote products derived from this software 48 * without specific prior written permission. 49 * 50 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 51 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 52 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 53 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 54 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 55 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 56 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 57 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 58 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 59 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 60 * SUCH DAMAGE. 61 * 62 * @(#)in_cksum.c 8.1 (Berkeley) 6/10/93 63 */ 64 65#include <sys/param.h> 66#include <sys/mbuf.h> 67#include <sys/systm.h> 68#include <sys/socket.h> 69#include <net/route.h> 70#include <netinet/in.h> 71#include <netinet/in_systm.h> 72#include <netinet/ip.h> 73#include <netinet/ip_var.h> 74 75/* 76 * Checksum routine for Internet Protocol family headers (Portable Version). 77 * This is only for IPv4 pseudo header checksum. 78 * No need to clear non-pseudo-header fields in IPv4 header. 79 * len is for actual payload size, and does not include IPv4 header and 80 * skipped header chain (off + len should be equal to the whole packet). 81 * 82 * This routine is very heavily used in the network 83 * code and should be modified for each CPU to be as fast as possible. 84 */ 85 86#define ADDCARRY(x) (x > 65535 ? x -= 65535 : x) 87#define REDUCE {l_util.l = sum; sum = l_util.s[0] + l_util.s[1]; ADDCARRY(sum);} 88 89int 90in4_cksum(struct mbuf *m, u_int8_t nxt, int off, int len) 91{ 92 u_int16_t *w; 93 int sum = 0; 94 int mlen = 0; 95 int byte_swapped = 0; 96 union { 97 struct ipovly ipov; 98 u_int16_t w[10]; 99 } u; 100 union { 101 u_int8_t c[2]; 102 u_int16_t s; 103 } s_util; 104 union { 105 u_int16_t s[2]; 106 u_int32_t l; 107 } l_util; 108 109 if (nxt != 0) { 110 /* pseudo header */ 111 if (off < sizeof(struct ipovly)) 112 panic("in4_cksum: offset too short"); 113 if (m->m_len < sizeof(struct ip)) 114 panic("in4_cksum: bad mbuf chain"); 115 bzero(&u.ipov, sizeof(u.ipov)); 116 u.ipov.ih_len = htons(len); 117 u.ipov.ih_pr = nxt; 118 u.ipov.ih_src = mtod(m, struct ip *)->ip_src; 119 u.ipov.ih_dst = mtod(m, struct ip *)->ip_dst; 120 w = u.w; 121 /* assumes sizeof(ipov) == 20 */ 122 sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3]; sum += w[4]; 123 sum += w[5]; sum += w[6]; sum += w[7]; sum += w[8]; sum += w[9]; 124 } 125 126 /* skip unnecessary part */ 127 while (m && off > 0) { 128 if (m->m_len > off) 129 break; 130 off -= m->m_len; 131 m = m->m_next; 132 } 133 134 for (;m && len; m = m->m_next) { 135 if (m->m_len == 0) 136 continue; 137 w = (u_int16_t *)(mtod(m, caddr_t) + off); 138 if (mlen == -1) { 139 /* 140 * The first byte of this mbuf is the continuation 141 * of a word spanning between this mbuf and the 142 * last mbuf. 143 * 144 * s_util.c[0] is already saved when scanning previous 145 * mbuf. 146 */ 147 s_util.c[1] = *(u_int8_t *)w; 148 sum += s_util.s; 149 w = (u_int16_t *)((u_int8_t *)w + 1); 150 mlen = m->m_len - off - 1; 151 len--; 152 } else 153 mlen = m->m_len - off; 154 off = 0; 155 if (len < mlen) 156 mlen = len; 157 len -= mlen; 158 /* 159 * Force to even boundary. 160 */ 161 if ((1 & (long) w) && (mlen > 0)) { 162 REDUCE; 163 sum <<= 8; 164 s_util.c[0] = *(u_int8_t *)w; 165 w = (u_int16_t *)((int8_t *)w + 1); 166 mlen--; 167 byte_swapped = 1; 168 } 169 /* 170 * Unroll the loop to make overhead from 171 * branches &c small. 172 */ 173 while ((mlen -= 32) >= 0) { 174 sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3]; 175 sum += w[4]; sum += w[5]; sum += w[6]; sum += w[7]; 176 sum += w[8]; sum += w[9]; sum += w[10]; sum += w[11]; 177 sum += w[12]; sum += w[13]; sum += w[14]; sum += w[15]; 178 w += 16; 179 } 180 mlen += 32; 181 while ((mlen -= 8) >= 0) { 182 sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3]; 183 w += 4; 184 } 185 mlen += 8; 186 if (mlen == 0 && byte_swapped == 0) 187 continue; 188 REDUCE; 189 while ((mlen -= 2) >= 0) { 190 sum += *w++; 191 } 192 if (byte_swapped) { 193 REDUCE; 194 sum <<= 8; 195 byte_swapped = 0; 196 if (mlen == -1) { 197 s_util.c[1] = *(u_int8_t *)w; 198 sum += s_util.s; 199 mlen = 0; 200 } else 201 mlen = -1; 202 } else if (mlen == -1) 203 s_util.c[0] = *(u_int8_t *)w; 204 } 205 if (len) 206 printf("cksum4: out of data\n"); 207 if (mlen == -1) { 208 /* The last mbuf has odd # of bytes. Follow the 209 standard (the odd byte may be shifted left by 8 bits 210 or not as determined by endian-ness of the machine) */ 211 s_util.c[1] = 0; 212 sum += s_util.s; 213 } 214 REDUCE; 215 return (~sum & 0xffff); 216} 217