1 /* $NetBSD: in_cksum.c,v 1.17 2003/08/07 16:33:10 agc Exp $ */ 2 3 /* 4 * Copyright (c) 1988, 1992, 1993 5 * The Regents of the University of California. All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 3. Neither the name of the University nor the names of its contributors 16 * may be used to endorse or promote products derived from this software 17 * without specific prior written permission. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29 * SUCH DAMAGE. 30 * 31 * @(#)in_cksum.c 8.1 (Berkeley) 6/10/93 32 */ 33 34 #include <sys/cdefs.h> 35 __KERNEL_RCSID(0, "$NetBSD: in_cksum.c,v 1.17 2003/08/07 16:33:10 agc Exp $"); 36 37 #include <sys/param.h> 38 #include <sys/mbuf.h> 39 #include <sys/systm.h> 40 #include <netinet/in.h> 41 42 /* 43 * Checksum routine for Internet Protocol family headers (Portable Version). 44 * 45 * This routine is very heavily used in the network 46 * code and should be modified for each CPU to be as fast as possible. 47 */ 48 49 #define ADDCARRY(x) (x > 65535 ? x -= 65535 : x) 50 #define REDUCE {l_util.l = sum; sum = l_util.s[0] + l_util.s[1]; ADDCARRY(sum);} 51 52 int 53 in_cksum(m, len) 54 struct mbuf *m; 55 int len; 56 { 57 u_int16_t *w; 58 int sum = 0; 59 int mlen = 0; 60 int byte_swapped = 0; 61 62 union { 63 u_int8_t c[2]; 64 u_int16_t s; 65 } s_util; 66 union { 67 u_int16_t s[2]; 68 u_int32_t l; 69 } l_util; 70 71 for (;m && len; m = m->m_next) { 72 if (m->m_len == 0) 73 continue; 74 w = mtod(m, u_int16_t *); 75 if (mlen == -1) { 76 /* 77 * The first byte of this mbuf is the continuation 78 * of a word spanning between this mbuf and the 79 * last mbuf. 80 * 81 * s_util.c[0] is already saved when scanning previous 82 * mbuf. 83 */ 84 s_util.c[1] = *(u_int8_t *)w; 85 sum += s_util.s; 86 w = (u_int16_t *)((u_int8_t *)w + 1); 87 mlen = m->m_len - 1; 88 len--; 89 } else 90 mlen = m->m_len; 91 if (len < mlen) 92 mlen = len; 93 len -= mlen; 94 /* 95 * Force to even boundary. 96 */ 97 if ((1 & (long) w) && (mlen > 0)) { 98 REDUCE; 99 sum <<= 8; 100 s_util.c[0] = *(u_int8_t *)w; 101 w = (u_int16_t *)((int8_t *)w + 1); 102 mlen--; 103 byte_swapped = 1; 104 } 105 /* 106 * Unroll the loop to make overhead from 107 * branches &c small. 108 */ 109 while ((mlen -= 32) >= 0) { 110 sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3]; 111 sum += w[4]; sum += w[5]; sum += w[6]; sum += w[7]; 112 sum += w[8]; sum += w[9]; sum += w[10]; sum += w[11]; 113 sum += w[12]; sum += w[13]; sum += w[14]; sum += w[15]; 114 w += 16; 115 } 116 mlen += 32; 117 while ((mlen -= 8) >= 0) { 118 sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3]; 119 w += 4; 120 } 121 mlen += 8; 122 if (mlen == 0 && byte_swapped == 0) 123 continue; 124 REDUCE; 125 while ((mlen -= 2) >= 0) { 126 sum += *w++; 127 } 128 if (byte_swapped) { 129 REDUCE; 130 sum <<= 8; 131 byte_swapped = 0; 132 if (mlen == -1) { 133 s_util.c[1] = *(u_int8_t *)w; 134 sum += s_util.s; 135 mlen = 0; 136 } else 137 mlen = -1; 138 } else if (mlen == -1) 139 s_util.c[0] = *(u_int8_t *)w; 140 } 141 if (len) 142 printf("cksum: out of data\n"); 143 if (mlen == -1) { 144 /* The last mbuf has odd # of bytes. Follow the 145 standard (the odd byte may be shifted left by 8 bits 146 or not as determined by endian-ness of the machine) */ 147 s_util.c[1] = 0; 148 sum += s_util.s; 149 } 150 REDUCE; 151 return (~sum & 0xffff); 152 } 153