1 /* 2 * Copyright (c) 1988, 1992, 1993 3 * The Regents of the University of California. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 3. All advertising materials mentioning features or use of this software 14 * must display the following acknowledgement: 15 * This product includes software developed by the University of 16 * California, Berkeley and its contributors. 17 * 4. Neither the name of the University 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 REGENTS 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 REGENTS 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 * @(#)in_cksum.c 8.1 (Berkeley) 6/10/93 34 * $FreeBSD: src/sys/netinet/in_cksum.c,v 1.6 1999/08/28 00:49:16 peter Exp $ 35 * $DragonFly: src/sys/netinet/in_cksum.c,v 1.3 2003/07/26 21:00:04 rob Exp $ 36 */ 37 38 #include <sys/param.h> 39 #include <sys/mbuf.h> 40 41 /* 42 * Checksum routine for Internet Protocol family headers (Portable Version). 43 * 44 * This routine is very heavily used in the network 45 * code and should be modified for each CPU to be as fast as possible. 46 */ 47 48 #define ADDCARRY(x) (x > 65535 ? x -= 65535 : x) 49 #define REDUCE {l_util.l = sum; sum = l_util.s[0] + l_util.s[1]; ADDCARRY(sum);} 50 51 int 52 in_cksum(m, len) 53 struct mbuf *m; 54 int len; 55 { 56 u_short *w; 57 int sum = 0; 58 int mlen = 0; 59 int byte_swapped = 0; 60 61 union { 62 char c[2]; 63 u_short s; 64 } s_util; 65 union { 66 u_short s[2]; 67 long l; 68 } l_util; 69 70 for (;m && len; m = m->m_next) { 71 if (m->m_len == 0) 72 continue; 73 w = mtod(m, u_short *); 74 if (mlen == -1) { 75 /* 76 * The first byte of this mbuf is the continuation 77 * of a word spanning between this mbuf and the 78 * last mbuf. 79 * 80 * s_util.c[0] is already saved when scanning previous 81 * mbuf. 82 */ 83 s_util.c[1] = *(char *)w; 84 sum += s_util.s; 85 w = (u_short *)((char *)w + 1); 86 mlen = m->m_len - 1; 87 len--; 88 } else 89 mlen = m->m_len; 90 if (len < mlen) 91 mlen = len; 92 len -= mlen; 93 /* 94 * Force to even boundary. 95 */ 96 if ((1 & (int) w) && (mlen > 0)) { 97 REDUCE; 98 sum <<= 8; 99 s_util.c[0] = *(u_char *)w; 100 w = (u_short *)((char *)w + 1); 101 mlen--; 102 byte_swapped = 1; 103 } 104 /* 105 * Unroll the loop to make overhead from 106 * branches &c small. 107 */ 108 while ((mlen -= 32) >= 0) { 109 sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3]; 110 sum += w[4]; sum += w[5]; sum += w[6]; sum += w[7]; 111 sum += w[8]; sum += w[9]; sum += w[10]; sum += w[11]; 112 sum += w[12]; sum += w[13]; sum += w[14]; sum += w[15]; 113 w += 16; 114 } 115 mlen += 32; 116 while ((mlen -= 8) >= 0) { 117 sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3]; 118 w += 4; 119 } 120 mlen += 8; 121 if (mlen == 0 && byte_swapped == 0) 122 continue; 123 REDUCE; 124 while ((mlen -= 2) >= 0) { 125 sum += *w++; 126 } 127 if (byte_swapped) { 128 REDUCE; 129 sum <<= 8; 130 byte_swapped = 0; 131 if (mlen == -1) { 132 s_util.c[1] = *(char *)w; 133 sum += s_util.s; 134 mlen = 0; 135 } else 136 mlen = -1; 137 } else if (mlen == -1) 138 s_util.c[0] = *(char *)w; 139 } 140 if (len) 141 printf("cksum: out of data\n"); 142 if (mlen == -1) { 143 /* The last mbuf has odd # of bytes. Follow the 144 standard (the odd byte may be shifted left by 8 bits 145 or not as determined by endian-ness of the machine) */ 146 s_util.c[1] = 0; 147 sum += s_util.s; 148 } 149 REDUCE; 150 return (~sum & 0xffff); 151 } 152