1 /* $OpenBSD: in_cksum.c,v 1.6 2003/12/10 07:22:43 itojun Exp $ */ 2 /* $NetBSD: in_cksum.c,v 1.11 1996/04/08 19:55:37 jonathan Exp $ */ 3 4 /* 5 * Copyright (c) 1988, 1992, 1993 6 * The Regents of the University of California. All rights reserved. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. Neither the name of the University nor the names of its contributors 17 * may be used to endorse or promote products derived from this software 18 * without specific prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30 * SUCH DAMAGE. 31 * 32 * @(#)in_cksum.c 8.1 (Berkeley) 6/10/93 33 */ 34 35 #include <sys/param.h> 36 #include <sys/mbuf.h> 37 #include <sys/systm.h> 38 #include <netinet/in.h> 39 40 /* 41 * Checksum routine for Internet Protocol family headers (Portable Version). 42 * 43 * This routine is very heavily used in the network 44 * code and should be modified for each CPU to be as fast as possible. 45 */ 46 47 #define ADDCARRY(x) (x > 65535 ? x -= 65535 : x) 48 #define REDUCE {l_util.l = sum; sum = l_util.s[0] + l_util.s[1]; ADDCARRY(sum);} 49 50 int 51 in_cksum(m, len) 52 struct mbuf *m; 53 int len; 54 { 55 u_int16_t *w; 56 int sum = 0; 57 int mlen = 0; 58 int byte_swapped = 0; 59 60 union { 61 u_int8_t c[2]; 62 u_int16_t s; 63 } s_util; 64 union { 65 u_int16_t s[2]; 66 u_int32_t l; 67 } l_util; 68 69 for (;m && len; m = m->m_next) { 70 if (m->m_len == 0) 71 continue; 72 w = mtod(m, u_int16_t *); 73 if (mlen == -1) { 74 /* 75 * The first byte of this mbuf is the continuation 76 * of a word spanning between this mbuf and the 77 * last mbuf. 78 * 79 * s_util.c[0] is already saved when scanning previous 80 * mbuf. 81 */ 82 s_util.c[1] = *(u_int8_t *)w; 83 sum += s_util.s; 84 w = (u_int16_t *)((u_int8_t *)w + 1); 85 mlen = m->m_len - 1; 86 len--; 87 } else 88 mlen = m->m_len; 89 if (len < mlen) 90 mlen = len; 91 len -= mlen; 92 /* 93 * Force to even boundary. 94 */ 95 if ((1 & (long) w) && (mlen > 0)) { 96 REDUCE; 97 sum <<= 8; 98 s_util.c[0] = *(u_int8_t *)w; 99 w = (u_int16_t *)((int8_t *)w + 1); 100 mlen--; 101 byte_swapped = 1; 102 } 103 /* 104 * Unroll the loop to make overhead from 105 * branches &c small. 106 */ 107 while ((mlen -= 32) >= 0) { 108 sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3]; 109 sum += w[4]; sum += w[5]; sum += w[6]; sum += w[7]; 110 sum += w[8]; sum += w[9]; sum += w[10]; sum += w[11]; 111 sum += w[12]; sum += w[13]; sum += w[14]; sum += w[15]; 112 w += 16; 113 } 114 mlen += 32; 115 while ((mlen -= 8) >= 0) { 116 sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3]; 117 w += 4; 118 } 119 mlen += 8; 120 if (mlen == 0 && byte_swapped == 0) 121 continue; 122 REDUCE; 123 while ((mlen -= 2) >= 0) { 124 sum += *w++; 125 } 126 if (byte_swapped) { 127 REDUCE; 128 sum <<= 8; 129 byte_swapped = 0; 130 if (mlen == -1) { 131 s_util.c[1] = *(u_int8_t *)w; 132 sum += s_util.s; 133 mlen = 0; 134 } else 135 mlen = -1; 136 } else if (mlen == -1) 137 s_util.c[0] = *(u_int8_t *)w; 138 } 139 if (len) 140 printf("cksum: out of data\n"); 141 if (mlen == -1) { 142 /* The last mbuf has odd # of bytes. Follow the 143 standard (the odd byte may be shifted left by 8 bits 144 or not as determined by endian-ness of the machine) */ 145 s_util.c[1] = 0; 146 sum += s_util.s; 147 } 148 REDUCE; 149 return (~sum & 0xffff); 150 } 151