1 /* $NetBSD: in_cksum.c,v 1.16 2002/06/09 16:33:38 itojun 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. All advertising materials mentioning features or use of this software 16 * must display the following acknowledgement: 17 * This product includes software developed by the University of 18 * California, Berkeley and its contributors. 19 * 4. Neither the name of the University nor the names of its contributors 20 * may be used to endorse or promote products derived from this software 21 * without specific prior written permission. 22 * 23 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 24 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 25 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 26 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 27 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 28 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 29 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 31 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 33 * SUCH DAMAGE. 34 * 35 * @(#)in_cksum.c 8.1 (Berkeley) 6/10/93 36 */ 37 38 #include <sys/cdefs.h> 39 __KERNEL_RCSID(0, "$NetBSD: in_cksum.c,v 1.16 2002/06/09 16:33:38 itojun Exp $"); 40 41 #include <sys/param.h> 42 #include <sys/mbuf.h> 43 #include <sys/systm.h> 44 #include <netinet/in.h> 45 46 /* 47 * Checksum routine for Internet Protocol family headers (Portable Version). 48 * 49 * This routine is very heavily used in the network 50 * code and should be modified for each CPU to be as fast as possible. 51 */ 52 53 #define ADDCARRY(x) (x > 65535 ? x -= 65535 : x) 54 #define REDUCE {l_util.l = sum; sum = l_util.s[0] + l_util.s[1]; ADDCARRY(sum);} 55 56 int 57 in_cksum(m, len) 58 struct mbuf *m; 59 int len; 60 { 61 u_int16_t *w; 62 int sum = 0; 63 int mlen = 0; 64 int byte_swapped = 0; 65 66 union { 67 u_int8_t c[2]; 68 u_int16_t s; 69 } s_util; 70 union { 71 u_int16_t s[2]; 72 u_int32_t l; 73 } l_util; 74 75 for (;m && len; m = m->m_next) { 76 if (m->m_len == 0) 77 continue; 78 w = mtod(m, u_int16_t *); 79 if (mlen == -1) { 80 /* 81 * The first byte of this mbuf is the continuation 82 * of a word spanning between this mbuf and the 83 * last mbuf. 84 * 85 * s_util.c[0] is already saved when scanning previous 86 * mbuf. 87 */ 88 s_util.c[1] = *(u_int8_t *)w; 89 sum += s_util.s; 90 w = (u_int16_t *)((u_int8_t *)w + 1); 91 mlen = m->m_len - 1; 92 len--; 93 } else 94 mlen = m->m_len; 95 if (len < mlen) 96 mlen = len; 97 len -= mlen; 98 /* 99 * Force to even boundary. 100 */ 101 if ((1 & (long) w) && (mlen > 0)) { 102 REDUCE; 103 sum <<= 8; 104 s_util.c[0] = *(u_int8_t *)w; 105 w = (u_int16_t *)((int8_t *)w + 1); 106 mlen--; 107 byte_swapped = 1; 108 } 109 /* 110 * Unroll the loop to make overhead from 111 * branches &c small. 112 */ 113 while ((mlen -= 32) >= 0) { 114 sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3]; 115 sum += w[4]; sum += w[5]; sum += w[6]; sum += w[7]; 116 sum += w[8]; sum += w[9]; sum += w[10]; sum += w[11]; 117 sum += w[12]; sum += w[13]; sum += w[14]; sum += w[15]; 118 w += 16; 119 } 120 mlen += 32; 121 while ((mlen -= 8) >= 0) { 122 sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3]; 123 w += 4; 124 } 125 mlen += 8; 126 if (mlen == 0 && byte_swapped == 0) 127 continue; 128 REDUCE; 129 while ((mlen -= 2) >= 0) { 130 sum += *w++; 131 } 132 if (byte_swapped) { 133 REDUCE; 134 sum <<= 8; 135 byte_swapped = 0; 136 if (mlen == -1) { 137 s_util.c[1] = *(u_int8_t *)w; 138 sum += s_util.s; 139 mlen = 0; 140 } else 141 mlen = -1; 142 } else if (mlen == -1) 143 s_util.c[0] = *(u_int8_t *)w; 144 } 145 if (len) 146 printf("cksum: out of data\n"); 147 if (mlen == -1) { 148 /* The last mbuf has odd # of bytes. Follow the 149 standard (the odd byte may be shifted left by 8 bits 150 or not as determined by endian-ness of the machine) */ 151 s_util.c[1] = 0; 152 sum += s_util.s; 153 } 154 REDUCE; 155 return (~sum & 0xffff); 156 } 157