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