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 * 3. All advertising materials mentioning features or use of this software 14 * must display the following acknowledgement: 15 * This product includes software developed by the University of 16 * California, Berkeley and its contributors. 17 * 4. Neither the name of the University nor the names of its contributors 18 * may be used to endorse or promote products derived from this software 19 * without specific prior written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 * 33 * @(#)in_cksum.c 8.1 (Berkeley) 6/10/93 34 */ 35 36 #include <sys/param.h> 37 #include <sys/mbuf.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(m, len) 51 register struct mbuf *m; 52 register int len; 53 { 54 register u_short *w; 55 register int sum = 0; 56 register int mlen = 0; 57 int byte_swapped = 0; 58 59 union { 60 char c[2]; 61 u_short s; 62 } s_util; 63 union { 64 u_short s[2]; 65 long l; 66 } l_util; 67 68 for (;m && len; m = m->m_next) { 69 if (m->m_len == 0) 70 continue; 71 w = mtod(m, u_short *); 72 if (mlen == -1) { 73 /* 74 * The first byte of this mbuf is the continuation 75 * of a word spanning between this mbuf and the 76 * last mbuf. 77 * 78 * s_util.c[0] is already saved when scanning previous 79 * mbuf. 80 */ 81 s_util.c[1] = *(char *)w; 82 sum += s_util.s; 83 w = (u_short *)((char *)w + 1); 84 mlen = m->m_len - 1; 85 len--; 86 } else 87 mlen = m->m_len; 88 if (len < mlen) 89 mlen = len; 90 len -= mlen; 91 /* 92 * Force to even boundary. 93 */ 94 if ((1 & (int) w) && (mlen > 0)) { 95 REDUCE; 96 sum <<= 8; 97 s_util.c[0] = *(u_char *)w; 98 w = (u_short *)((char *)w + 1); 99 mlen--; 100 byte_swapped = 1; 101 } 102 /* 103 * Unroll the loop to make overhead from 104 * branches &c small. 105 */ 106 while ((mlen -= 32) >= 0) { 107 sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3]; 108 sum += w[4]; sum += w[5]; sum += w[6]; sum += w[7]; 109 sum += w[8]; sum += w[9]; sum += w[10]; sum += w[11]; 110 sum += w[12]; sum += w[13]; sum += w[14]; sum += w[15]; 111 w += 16; 112 } 113 mlen += 32; 114 while ((mlen -= 8) >= 0) { 115 sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3]; 116 w += 4; 117 } 118 mlen += 8; 119 if (mlen == 0 && byte_swapped == 0) 120 continue; 121 REDUCE; 122 while ((mlen -= 2) >= 0) { 123 sum += *w++; 124 } 125 if (byte_swapped) { 126 REDUCE; 127 sum <<= 8; 128 byte_swapped = 0; 129 if (mlen == -1) { 130 s_util.c[1] = *(char *)w; 131 sum += s_util.s; 132 mlen = 0; 133 } else 134 mlen = -1; 135 } else if (mlen == -1) 136 s_util.c[0] = *(char *)w; 137 } 138 if (len) 139 printf("cksum: out of data\n"); 140 if (mlen == -1) { 141 /* The last mbuf has odd # of bytes. Follow the 142 standard (the odd byte may be shifted left by 8 bits 143 or not as determined by endian-ness of the machine) */ 144 s_util.c[1] = 0; 145 sum += s_util.s; 146 } 147 REDUCE; 148 return (~sum & 0xffff); 149 } 150