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