1 /* 2 * Copyright (c) 1982, 1988 Regents of the University of California. 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms are permitted 6 * provided that this notice is preserved and that due credit is given 7 * to the University of California at Berkeley. The name of the University 8 * may not be used to endorse or promote products derived from this 9 * software without specific prior written permission. This software 10 * is provided ``as is'' without express or implied warranty. 11 * 12 * @(#)ns_cksum.c 1.2 (Berkeley) 02/25/88 13 */ 14 #include "types.h" 15 #include "mbuf.h" 16 17 /* 18 * Checksum routine for Network Systems Protocol Packets. 19 * 20 * This routine is very heavily used in the network 21 * code and should be modified for each CPU to be as fast as possible. 22 */ 23 24 #define ADDCARRY(x) (x > 65535 ? x -= 65535 : x) 25 #define FOLD(x) {l_util.l = x; x = l_util.s[0] + l_util.s[1]; ADDCARRY(x);} 26 27 u_short 28 ns_cksum(m, len) 29 register struct mbuf *m; 30 register int len; 31 { 32 register u_short *w; 33 register int sum = 0; 34 register int mlen = 0; 35 register int sum2; 36 37 union { 38 u_short s[2]; 39 long l; 40 } l_util; 41 42 for (;m && len; m = m->m_next) { 43 if (m->m_len == 0) 44 continue; 45 /* 46 * Each trip around loop adds in 47 * word from one mbuf segment. 48 */ 49 w = mtod(m, u_short *); 50 if (mlen == -1) { 51 /* 52 * There is a byte left from the last segment; 53 * ones-complement add it into the checksum. 54 */ 55 sum += *(u_char *)w; /* Big-Endian, else << 8 */ 56 sum += sum; 57 w = (u_short *)(1 + (char *)w); 58 mlen = m->m_len - 1; 59 len--; 60 FOLD(sum); 61 } else 62 mlen = m->m_len; 63 if (len < mlen) 64 mlen = len; 65 len -= mlen; 66 /* 67 * We can do a 16 bit ones complement sum using 68 * 32 bit arithmetic registers for adding, 69 * with carries from the low added 70 * into the high (by normal carry-chaining) 71 * so long as we fold back before 16 carries have occured. 72 */ 73 if (1 & (int) w) 74 goto uuuuglyy; 75 #ifndef TINY 76 /* -DTINY reduces the size from 1250 to 550, but slows it down by 22% */ 77 while ((mlen -= 32) >= 0) { 78 sum += w[0]; sum += sum; sum += w[1]; sum += sum; 79 sum += w[2]; sum += sum; sum += w[3]; sum += sum; 80 sum += w[4]; sum += sum; sum += w[5]; sum += sum; 81 sum += w[6]; sum += sum; sum += w[7]; sum += sum; 82 FOLD(sum); 83 sum += w[8]; sum += sum; sum += w[9]; sum += sum; 84 sum += w[10]; sum += sum; sum += w[11]; sum += sum; 85 sum += w[12]; sum += sum; sum += w[13]; sum += sum; 86 sum += w[14]; sum += sum; sum += w[15]; sum += sum; 87 FOLD(sum); 88 w += 16; 89 } 90 mlen += 32; 91 #endif 92 while ((mlen -= 8) >= 0) { 93 sum += w[0]; sum += sum; sum += w[1]; sum += sum; 94 sum += w[2]; sum += sum; sum += w[3]; sum += sum; 95 FOLD(sum); 96 w += 4; 97 } 98 mlen += 8; 99 while ((mlen -= 2) >= 0) { 100 sum += *w++; sum += sum; 101 } 102 goto commoncase; 103 uuuuglyy: 104 #define ww(n) (((char *)w)[n + n]) 105 #define vv(n) (((char *)w)[n + n + 1]) 106 /* Big-Endian; else reverse ww and vv */ 107 sum2 = 0; 108 #ifndef TINY 109 while ((mlen -= 32) >= 0) { 110 sum += ww(0); sum += sum; sum += ww(1); sum += sum; 111 sum += ww(2); sum += sum; sum += ww(3); sum += sum; 112 sum += ww(4); sum += sum; sum += ww(5); sum += sum; 113 sum += ww(6); sum += sum; sum += ww(7); sum += sum; 114 FOLD(sum); 115 sum += ww(8); sum += sum; sum += ww(9); sum += sum; 116 sum += ww(10); sum += sum; sum += ww(11); sum += sum; 117 sum += ww(12); sum += sum; sum += ww(13); sum += sum; 118 sum += ww(14); sum += sum; sum += ww(15); sum += sum; 119 FOLD(sum); 120 sum2 += vv(0); sum2 += sum2; sum2 += vv(1); sum2 += sum2; 121 sum2 += vv(2); sum2 += sum2; sum2 += vv(3); sum2 += sum2; 122 sum2 += vv(4); sum2 += sum2; sum2 += vv(5); sum2 += sum2; 123 sum2 += vv(6); sum2 += sum2; sum2 += vv(7); sum2 += sum2; 124 FOLD(sum2); 125 sum2 += vv(8); sum2 += sum2; sum2 += vv(9); sum2 += sum2; 126 sum2 += vv(10); sum2 += sum2; sum2 += vv(11); sum2 += sum2; 127 sum2 += vv(12); sum2 += sum2; sum2 += vv(13); sum2 += sum2; 128 sum2 += vv(14); sum2 += sum2; sum2 += vv(15); sum2 += sum2; 129 FOLD(sum2); 130 w += 16; 131 } 132 mlen += 32; 133 #endif 134 while ((mlen -= 8) >= 0) { 135 sum += ww(0); sum += sum; sum += ww(1); sum += sum; 136 sum += ww(2); sum += sum; sum += ww(3); sum += sum; 137 FOLD(sum); 138 sum2 += vv(0); sum2 += sum2; sum2 += vv(1); sum2 += sum2; 139 sum2 += vv(2); sum2 += sum2; sum2 += vv(3); sum2 += sum2; 140 FOLD(sum2); 141 w += 4; 142 } 143 mlen += 8; 144 while ((mlen -= 2) >= 0) { 145 sum += ww(0); sum += sum; 146 sum2 += vv(0); sum2 += sum2; 147 w++; 148 } 149 sum += (sum2 << 8); 150 commoncase: 151 if (mlen == -1) { 152 sum += *(u_char *)w << 8; /* Big-Endian, else no << 8 */ 153 } 154 FOLD(sum); 155 } 156 if (mlen == -1) { 157 /* We had an odd number of bytes to sum; assume a garbage 158 byte of zero and clean up */ 159 sum += sum; 160 FOLD(sum); 161 } 162 /* 163 * sum has already been kept to low sixteen bits. 164 * just examine result and exit. 165 */ 166 if(sum==0xffff) sum = 0; 167 return (sum); 168 } 169