1 /* $NetBSD: in_cksum.c,v 1.13 1996/10/13 02:03:03 christos 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/param.h> 39 #include <sys/mbuf.h> 40 #include <sys/systm.h> 41 #include <netinet/in.h> 42 43 /* 44 * Checksum routine for Internet Protocol family headers (Portable Version). 45 * 46 * This routine is very heavily used in the network 47 * code and should be modified for each CPU to be as fast as possible. 48 */ 49 50 #define ADDCARRY(x) (x > 65535 ? x -= 65535 : x) 51 #define REDUCE {l_util.l = sum; sum = l_util.s[0] + l_util.s[1]; ADDCARRY(sum);} 52 53 int 54 in_cksum(m, len) 55 register struct mbuf *m; 56 register int len; 57 { 58 register u_int16_t *w; 59 register int sum = 0; 60 register int mlen = 0; 61 int byte_swapped = 0; 62 63 union { 64 u_int8_t c[2]; 65 u_int16_t s; 66 } s_util; 67 union { 68 u_int16_t s[2]; 69 u_int32_t l; 70 } l_util; 71 72 for (;m && len; m = m->m_next) { 73 if (m->m_len == 0) 74 continue; 75 w = mtod(m, u_int16_t *); 76 if (mlen == -1) { 77 /* 78 * The first byte of this mbuf is the continuation 79 * of a word spanning between this mbuf and the 80 * last mbuf. 81 * 82 * s_util.c[0] is already saved when scanning previous 83 * mbuf. 84 */ 85 s_util.c[1] = *(u_int8_t *)w; 86 sum += s_util.s; 87 w = (u_int16_t *)((u_int8_t *)w + 1); 88 mlen = m->m_len - 1; 89 len--; 90 } else 91 mlen = m->m_len; 92 if (len < mlen) 93 mlen = len; 94 len -= mlen; 95 /* 96 * Force to even boundary. 97 */ 98 if ((1 & (long) w) && (mlen > 0)) { 99 REDUCE; 100 sum <<= 8; 101 s_util.c[0] = *(u_int8_t *)w; 102 w = (u_int16_t *)((int8_t *)w + 1); 103 mlen--; 104 byte_swapped = 1; 105 } 106 /* 107 * Unroll the loop to make overhead from 108 * branches &c small. 109 */ 110 while ((mlen -= 32) >= 0) { 111 sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3]; 112 sum += w[4]; sum += w[5]; sum += w[6]; sum += w[7]; 113 sum += w[8]; sum += w[9]; sum += w[10]; sum += w[11]; 114 sum += w[12]; sum += w[13]; sum += w[14]; sum += w[15]; 115 w += 16; 116 } 117 mlen += 32; 118 while ((mlen -= 8) >= 0) { 119 sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3]; 120 w += 4; 121 } 122 mlen += 8; 123 if (mlen == 0 && byte_swapped == 0) 124 continue; 125 REDUCE; 126 while ((mlen -= 2) >= 0) { 127 sum += *w++; 128 } 129 if (byte_swapped) { 130 REDUCE; 131 sum <<= 8; 132 byte_swapped = 0; 133 if (mlen == -1) { 134 s_util.c[1] = *(u_int8_t *)w; 135 sum += s_util.s; 136 mlen = 0; 137 } else 138 mlen = -1; 139 } else if (mlen == -1) 140 s_util.c[0] = *(u_int8_t *)w; 141 } 142 if (len) 143 printf("cksum: out of data\n"); 144 if (mlen == -1) { 145 /* The last mbuf has odd # of bytes. Follow the 146 standard (the odd byte may be shifted left by 8 bits 147 or not as determined by endian-ness of the machine) */ 148 s_util.c[1] = 0; 149 sum += s_util.s; 150 } 151 REDUCE; 152 return (~sum & 0xffff); 153 } 154