1 /* $OpenBSD: in_cksum.c,v 1.8 2015/07/17 23:49:03 tedu 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 39 /* 40 * Checksum routine for Internet Protocol family headers (Portable Version). 41 * 42 * This routine is very heavily used in the network 43 * code and should be modified for each CPU to be as fast as possible. 44 */ 45 46 #define ADDCARRY(x) (x > 65535 ? x -= 65535 : x) 47 #define REDUCE {l_util.l = sum; sum = l_util.s[0] + l_util.s[1]; ADDCARRY(sum);} 48 49 int 50 in_cksum(struct mbuf *m, int len) 51 { 52 u_int16_t *w; 53 int sum = 0; 54 int mlen = 0; 55 int byte_swapped = 0; 56 57 union { 58 u_int8_t c[2]; 59 u_int16_t s; 60 } s_util; 61 union { 62 u_int16_t s[2]; 63 u_int32_t l; 64 } l_util; 65 66 for (;m && len; m = m->m_next) { 67 if (m->m_len == 0) 68 continue; 69 w = mtod(m, u_int16_t *); 70 if (mlen == -1) { 71 /* 72 * The first byte of this mbuf is the continuation 73 * of a word spanning between this mbuf and the 74 * last mbuf. 75 * 76 * s_util.c[0] is already saved when scanning previous 77 * mbuf. 78 */ 79 s_util.c[1] = *(u_int8_t *)w; 80 sum += s_util.s; 81 w = (u_int16_t *)((u_int8_t *)w + 1); 82 mlen = m->m_len - 1; 83 len--; 84 } else 85 mlen = m->m_len; 86 if (len < mlen) 87 mlen = len; 88 len -= mlen; 89 /* 90 * Force to even boundary. 91 */ 92 if ((1 & (long) w) && (mlen > 0)) { 93 REDUCE; 94 sum <<= 8; 95 s_util.c[0] = *(u_int8_t *)w; 96 w = (u_int16_t *)((int8_t *)w + 1); 97 mlen--; 98 byte_swapped = 1; 99 } 100 /* 101 * Unroll the loop to make overhead from 102 * branches &c small. 103 */ 104 while ((mlen -= 32) >= 0) { 105 sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3]; 106 sum += w[4]; sum += w[5]; sum += w[6]; sum += w[7]; 107 sum += w[8]; sum += w[9]; sum += w[10]; sum += w[11]; 108 sum += w[12]; sum += w[13]; sum += w[14]; sum += w[15]; 109 w += 16; 110 } 111 mlen += 32; 112 while ((mlen -= 8) >= 0) { 113 sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3]; 114 w += 4; 115 } 116 mlen += 8; 117 if (mlen == 0 && byte_swapped == 0) 118 continue; 119 REDUCE; 120 while ((mlen -= 2) >= 0) { 121 sum += *w++; 122 } 123 if (byte_swapped) { 124 REDUCE; 125 sum <<= 8; 126 byte_swapped = 0; 127 if (mlen == -1) { 128 s_util.c[1] = *(u_int8_t *)w; 129 sum += s_util.s; 130 mlen = 0; 131 } else 132 mlen = -1; 133 } else if (mlen == -1) 134 s_util.c[0] = *(u_int8_t *)w; 135 } 136 if (len) 137 printf("cksum: out of data\n"); 138 if (mlen == -1) { 139 /* The last mbuf has odd # of bytes. Follow the 140 standard (the odd byte may be shifted left by 8 bits 141 or not as determined by endian-ness of the machine) */ 142 s_util.c[1] = 0; 143 sum += s_util.s; 144 } 145 REDUCE; 146 return (~sum & 0xffff); 147 } 148