1 /* 2 * Copyright (c) 1982, 1992, 1993 3 * The Regents of the University of California. All rights reserved. 4 * 5 * %sccs.include.redist.c% 6 * 7 * @(#)ns_cksum.c 8.1 (Berkeley) 06/10/93 8 */ 9 10 #include <sys/param.h> 11 #include <sys/mbuf.h> 12 13 /* 14 * Checksum routine for Network Systems Protocol Packets (Big-Endian). 15 * 16 * This routine is very heavily used in the network 17 * code and should be modified for each CPU to be as fast as possible. 18 */ 19 20 #define ADDCARRY(x) { if ((x) > 65535) (x) -= 65535; } 21 #define FOLD(x) {l_util.l = (x); (x) = l_util.s[0] + l_util.s[1]; ADDCARRY(x);} 22 23 u_short 24 ns_cksum(m, len) 25 register struct mbuf *m; 26 register int len; 27 { 28 register u_short *w; 29 register int sum = 0; 30 register int mlen = 0; 31 register int sum2; 32 33 union { 34 u_short s[2]; 35 long l; 36 } l_util; 37 38 for (;m && len; m = m->m_next) { 39 if (m->m_len == 0) 40 continue; 41 /* 42 * Each trip around loop adds in 43 * word from one mbuf segment. 44 */ 45 w = mtod(m, u_short *); 46 if (mlen == -1) { 47 /* 48 * There is a byte left from the last segment; 49 * ones-complement add it into the checksum. 50 */ 51 #if BYTE_ORDER == BIG_ENDIAN 52 sum += *(u_char *)w; 53 #else 54 sum += *(u_char *)w << 8; 55 #endif 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 #if BYTE_ORDER == BIG_ENDIAN 105 #define ww(n) (((u_char *)w)[n + n + 1]) 106 #define vv(n) (((u_char *)w)[n + n]) 107 #else 108 #if BYTE_ORDER == LITTLE_ENDIAN 109 #define vv(n) (((u_char *)w)[n + n + 1]) 110 #define ww(n) (((u_char *)w)[n + n]) 111 #endif 112 #endif 113 sum2 = 0; 114 #ifndef TINY 115 while ((mlen -= 32) >= 0) { 116 sum += ww(0); sum += sum; sum += ww(1); sum += sum; 117 sum += ww(2); sum += sum; sum += ww(3); sum += sum; 118 sum += ww(4); sum += sum; sum += ww(5); sum += sum; 119 sum += ww(6); sum += sum; sum += ww(7); sum += sum; 120 FOLD(sum); 121 sum += ww(8); sum += sum; sum += ww(9); sum += sum; 122 sum += ww(10); sum += sum; sum += ww(11); sum += sum; 123 sum += ww(12); sum += sum; sum += ww(13); sum += sum; 124 sum += ww(14); sum += sum; sum += ww(15); sum += sum; 125 FOLD(sum); 126 sum2 += vv(0); sum2 += sum2; sum2 += vv(1); sum2 += sum2; 127 sum2 += vv(2); sum2 += sum2; sum2 += vv(3); sum2 += sum2; 128 sum2 += vv(4); sum2 += sum2; sum2 += vv(5); sum2 += sum2; 129 sum2 += vv(6); sum2 += sum2; sum2 += vv(7); sum2 += sum2; 130 FOLD(sum2); 131 sum2 += vv(8); sum2 += sum2; sum2 += vv(9); sum2 += sum2; 132 sum2 += vv(10); sum2 += sum2; sum2 += vv(11); sum2 += sum2; 133 sum2 += vv(12); sum2 += sum2; sum2 += vv(13); sum2 += sum2; 134 sum2 += vv(14); sum2 += sum2; sum2 += vv(15); sum2 += sum2; 135 FOLD(sum2); 136 w += 16; 137 } 138 mlen += 32; 139 #endif 140 while ((mlen -= 8) >= 0) { 141 sum += ww(0); sum += sum; sum += ww(1); sum += sum; 142 sum += ww(2); sum += sum; sum += ww(3); sum += sum; 143 FOLD(sum); 144 sum2 += vv(0); sum2 += sum2; sum2 += vv(1); sum2 += sum2; 145 sum2 += vv(2); sum2 += sum2; sum2 += vv(3); sum2 += sum2; 146 FOLD(sum2); 147 w += 4; 148 } 149 mlen += 8; 150 while ((mlen -= 2) >= 0) { 151 sum += ww(0); sum += sum; 152 sum2 += vv(0); sum2 += sum2; 153 w++; 154 } 155 sum += (sum2 << 8); 156 commoncase: 157 if (mlen == -1) { 158 #if BYTE_ORDER == BIG_ENDIAN 159 sum += *(u_char *)w << 8; 160 #else 161 sum += *(u_char *)w; 162 #endif 163 } 164 FOLD(sum); 165 } 166 if (mlen == -1) { 167 /* We had an odd number of bytes to sum; assume a garbage 168 byte of zero and clean up */ 169 sum += sum; 170 FOLD(sum); 171 } 172 /* 173 * sum has already been kept to low sixteen bits. 174 * just examine result and exit. 175 */ 176 if(sum==0xffff) sum = 0; 177 return (sum); 178 } 179