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 */ 31 32 #include <sys/cdefs.h> 33 __FBSDID("$FreeBSD$"); 34 35 #include <sys/param.h> 36 #include <sys/mbuf.h> 37 38 /* 39 * Checksum routine for Internet Protocol family headers (Portable Version). 40 * 41 * This routine is very heavily used in the network 42 * code and should be modified for each CPU to be as fast as possible. 43 */ 44 45 #define ADDCARRY(x) (x > 65535 ? x -= 65535 : x) 46 #define REDUCE {l_util.l = sum; sum = l_util.s[0] + l_util.s[1]; ADDCARRY(sum);} 47 48 int 49 in_cksum(struct mbuf *m, int len) 50 { 51 register u_short *w; 52 register int sum = 0; 53 register int mlen = 0; 54 int byte_swapped = 0; 55 56 union { 57 char c[2]; 58 u_short s; 59 } s_util; 60 union { 61 u_short s[2]; 62 long l; 63 } l_util; 64 65 for (;m && len; m = m->m_next) { 66 if (m->m_len == 0) 67 continue; 68 w = mtod(m, u_short *); 69 if (mlen == -1) { 70 /* 71 * The first byte of this mbuf is the continuation 72 * of a word spanning between this mbuf and the 73 * last mbuf. 74 * 75 * s_util.c[0] is already saved when scanning previous 76 * mbuf. 77 */ 78 s_util.c[1] = *(char *)w; 79 sum += s_util.s; 80 w = (u_short *)((char *)w + 1); 81 mlen = m->m_len - 1; 82 len--; 83 } else 84 mlen = m->m_len; 85 if (len < mlen) 86 mlen = len; 87 len -= mlen; 88 /* 89 * Force to even boundary. 90 */ 91 if ((1 & (uintptr_t) w) && (mlen > 0)) { 92 REDUCE; 93 sum <<= 8; 94 s_util.c[0] = *(u_char *)w; 95 w = (u_short *)((char *)w + 1); 96 mlen--; 97 byte_swapped = 1; 98 } 99 /* 100 * Unroll the loop to make overhead from 101 * branches &c small. 102 */ 103 while ((mlen -= 32) >= 0) { 104 sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3]; 105 sum += w[4]; sum += w[5]; sum += w[6]; sum += w[7]; 106 sum += w[8]; sum += w[9]; sum += w[10]; sum += w[11]; 107 sum += w[12]; sum += w[13]; sum += w[14]; sum += w[15]; 108 w += 16; 109 } 110 mlen += 32; 111 while ((mlen -= 8) >= 0) { 112 sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3]; 113 w += 4; 114 } 115 mlen += 8; 116 if (mlen == 0 && byte_swapped == 0) 117 continue; 118 REDUCE; 119 while ((mlen -= 2) >= 0) { 120 sum += *w++; 121 } 122 if (byte_swapped) { 123 REDUCE; 124 sum <<= 8; 125 byte_swapped = 0; 126 if (mlen == -1) { 127 s_util.c[1] = *(char *)w; 128 sum += s_util.s; 129 mlen = 0; 130 } else 131 mlen = -1; 132 } else if (mlen == -1) 133 s_util.c[0] = *(char *)w; 134 } 135 if (len) 136 printf("cksum: out of data\n"); 137 if (mlen == -1) { 138 /* The last mbuf has odd # of bytes. Follow the 139 standard (the odd byte may be shifted left by 8 bits 140 or not as determined by endian-ness of the machine) */ 141 s_util.c[1] = 0; 142 sum += s_util.s; 143 } 144 REDUCE; 145 return (~sum & 0xffff); 146 } 147