JP Abgrall | 53f17a9 | 2014-02-12 14:02:41 -0800 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (c) 1998-2006 The TCPDUMP project |
| 3 | * |
| 4 | * Redistribution and use in source and binary forms, with or without |
| 5 | * modification, are permitted provided that: (1) source code |
| 6 | * distributions retain the above copyright notice and this paragraph |
| 7 | * in its entirety, and (2) distributions including binary code include |
| 8 | * the above copyright notice and this paragraph in its entirety in |
| 9 | * the documentation or other materials provided with the distribution. |
| 10 | * THIS SOFTWARE IS PROVIDED ``AS IS'' AND |
| 11 | * WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, WITHOUT |
| 12 | * LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS |
| 13 | * FOR A PARTICULAR PURPOSE. |
| 14 | * |
| 15 | * miscellaneous checksumming routines |
| 16 | * |
| 17 | * Original code by Hannes Gredler (hannes@juniper.net) |
| 18 | */ |
| 19 | |
| 20 | #ifndef lint |
| 21 | static const char rcsid[] _U_ = |
| 22 | "@(#) $Header: /tcpdump/master/tcpdump/checksum.c,v 1.4 2006-09-25 09:23:32 hannes Exp $"; |
| 23 | #endif |
| 24 | |
| 25 | #ifdef HAVE_CONFIG_H |
| 26 | #include "config.h" |
| 27 | #endif |
| 28 | |
| 29 | #include <tcpdump-stdinc.h> |
| 30 | |
| 31 | #include <stdio.h> |
| 32 | #include <stdlib.h> |
| 33 | #include <string.h> |
| 34 | #include <assert.h> |
| 35 | |
| 36 | #include "interface.h" |
| 37 | |
| 38 | /* |
| 39 | * CRC-10 table generated using the following Python snippet: |
| 40 | |
| 41 | import sys |
| 42 | |
| 43 | crc_table = [] |
| 44 | for i in range(256): |
| 45 | accum = i << 2 |
| 46 | for j in range(8): |
| 47 | accum <<= 1 |
| 48 | if accum & 0x400: |
| 49 | accum ^= 0x633 |
| 50 | crc_table.append(accum) |
| 51 | |
| 52 | for i in range(len(crc_table)/8): |
| 53 | for j in range(8): |
| 54 | sys.stdout.write("0x%04x, " % crc_table[i*8+j]) |
| 55 | sys.stdout.write("\n") |
| 56 | |
| 57 | */ |
| 58 | static const u_int16_t crc10_table[256] = |
| 59 | { |
| 60 | 0x0000, 0x0233, 0x0255, 0x0066, 0x0299, 0x00aa, 0x00cc, 0x02ff, |
| 61 | 0x0301, 0x0132, 0x0154, 0x0367, 0x0198, 0x03ab, 0x03cd, 0x01fe, |
| 62 | 0x0031, 0x0202, 0x0264, 0x0057, 0x02a8, 0x009b, 0x00fd, 0x02ce, |
| 63 | 0x0330, 0x0103, 0x0165, 0x0356, 0x01a9, 0x039a, 0x03fc, 0x01cf, |
| 64 | 0x0062, 0x0251, 0x0237, 0x0004, 0x02fb, 0x00c8, 0x00ae, 0x029d, |
| 65 | 0x0363, 0x0150, 0x0136, 0x0305, 0x01fa, 0x03c9, 0x03af, 0x019c, |
| 66 | 0x0053, 0x0260, 0x0206, 0x0035, 0x02ca, 0x00f9, 0x009f, 0x02ac, |
| 67 | 0x0352, 0x0161, 0x0107, 0x0334, 0x01cb, 0x03f8, 0x039e, 0x01ad, |
| 68 | 0x00c4, 0x02f7, 0x0291, 0x00a2, 0x025d, 0x006e, 0x0008, 0x023b, |
| 69 | 0x03c5, 0x01f6, 0x0190, 0x03a3, 0x015c, 0x036f, 0x0309, 0x013a, |
| 70 | 0x00f5, 0x02c6, 0x02a0, 0x0093, 0x026c, 0x005f, 0x0039, 0x020a, |
| 71 | 0x03f4, 0x01c7, 0x01a1, 0x0392, 0x016d, 0x035e, 0x0338, 0x010b, |
| 72 | 0x00a6, 0x0295, 0x02f3, 0x00c0, 0x023f, 0x000c, 0x006a, 0x0259, |
| 73 | 0x03a7, 0x0194, 0x01f2, 0x03c1, 0x013e, 0x030d, 0x036b, 0x0158, |
| 74 | 0x0097, 0x02a4, 0x02c2, 0x00f1, 0x020e, 0x003d, 0x005b, 0x0268, |
| 75 | 0x0396, 0x01a5, 0x01c3, 0x03f0, 0x010f, 0x033c, 0x035a, 0x0169, |
| 76 | 0x0188, 0x03bb, 0x03dd, 0x01ee, 0x0311, 0x0122, 0x0144, 0x0377, |
| 77 | 0x0289, 0x00ba, 0x00dc, 0x02ef, 0x0010, 0x0223, 0x0245, 0x0076, |
| 78 | 0x01b9, 0x038a, 0x03ec, 0x01df, 0x0320, 0x0113, 0x0175, 0x0346, |
| 79 | 0x02b8, 0x008b, 0x00ed, 0x02de, 0x0021, 0x0212, 0x0274, 0x0047, |
| 80 | 0x01ea, 0x03d9, 0x03bf, 0x018c, 0x0373, 0x0140, 0x0126, 0x0315, |
| 81 | 0x02eb, 0x00d8, 0x00be, 0x028d, 0x0072, 0x0241, 0x0227, 0x0014, |
| 82 | 0x01db, 0x03e8, 0x038e, 0x01bd, 0x0342, 0x0171, 0x0117, 0x0324, |
| 83 | 0x02da, 0x00e9, 0x008f, 0x02bc, 0x0043, 0x0270, 0x0216, 0x0025, |
| 84 | 0x014c, 0x037f, 0x0319, 0x012a, 0x03d5, 0x01e6, 0x0180, 0x03b3, |
| 85 | 0x024d, 0x007e, 0x0018, 0x022b, 0x00d4, 0x02e7, 0x0281, 0x00b2, |
| 86 | 0x017d, 0x034e, 0x0328, 0x011b, 0x03e4, 0x01d7, 0x01b1, 0x0382, |
| 87 | 0x027c, 0x004f, 0x0029, 0x021a, 0x00e5, 0x02d6, 0x02b0, 0x0083, |
| 88 | 0x012e, 0x031d, 0x037b, 0x0148, 0x03b7, 0x0184, 0x01e2, 0x03d1, |
| 89 | 0x022f, 0x001c, 0x007a, 0x0249, 0x00b6, 0x0285, 0x02e3, 0x00d0, |
| 90 | 0x011f, 0x032c, 0x034a, 0x0179, 0x0386, 0x01b5, 0x01d3, 0x03e0, |
| 91 | 0x021e, 0x002d, 0x004b, 0x0278, 0x0087, 0x02b4, 0x02d2, 0x00e1 |
| 92 | }; |
| 93 | |
| 94 | static void |
| 95 | init_crc10_table(void) |
| 96 | { |
| 97 | #define CRC10_POLYNOMIAL 0x633 |
| 98 | register int i, j; |
| 99 | register u_int16_t accum; |
| 100 | u_int16_t verify_crc10_table[256]; |
| 101 | |
| 102 | for ( i = 0; i < 256; i++ ) |
| 103 | { |
| 104 | accum = ((unsigned short) i << 2); |
| 105 | for ( j = 0; j < 8; j++ ) |
| 106 | { |
| 107 | if ((accum <<= 1) & 0x400) accum ^= CRC10_POLYNOMIAL; |
| 108 | } |
| 109 | verify_crc10_table[i] = accum; |
| 110 | } |
| 111 | assert(memcmp(verify_crc10_table, |
| 112 | crc10_table, |
| 113 | sizeof(verify_crc10_table)) == 0); |
| 114 | #undef CRC10_POLYNOMIAL |
| 115 | } |
| 116 | |
| 117 | u_int16_t |
| 118 | verify_crc10_cksum(u_int16_t accum, const u_char *p, int length) |
| 119 | { |
| 120 | register int i; |
| 121 | |
| 122 | for ( i = 0; i < length; i++ ) |
| 123 | { |
| 124 | accum = ((accum << 8) & 0x3ff) |
| 125 | ^ crc10_table[( accum >> 2) & 0xff] |
| 126 | ^ *p++; |
| 127 | } |
| 128 | return accum; |
| 129 | } |
| 130 | |
| 131 | /* precompute checksum tables */ |
| 132 | void |
| 133 | init_checksum(void) { |
| 134 | |
| 135 | init_crc10_table(); |
| 136 | |
| 137 | } |
| 138 | |
| 139 | /* |
| 140 | * Creates the OSI Fletcher checksum. See 8473-1, Appendix C, section C.3. |
| 141 | * The checksum field of the passed PDU does not need to be reset to zero. |
| 142 | */ |
| 143 | u_int16_t |
| 144 | create_osi_cksum (const u_int8_t *pptr, int checksum_offset, int length) |
| 145 | { |
| 146 | |
| 147 | int x; |
| 148 | int y; |
| 149 | u_int32_t mul; |
| 150 | u_int32_t c0; |
| 151 | u_int32_t c1; |
| 152 | u_int16_t checksum; |
| 153 | int index; |
| 154 | |
| 155 | c0 = 0; |
| 156 | c1 = 0; |
| 157 | |
| 158 | for (index = 0; index < length; index++) { |
| 159 | /* |
| 160 | * Ignore the contents of the checksum field. |
| 161 | */ |
| 162 | if (index == checksum_offset || |
| 163 | index == checksum_offset+1) { |
| 164 | c1 += c0; |
| 165 | pptr++; |
| 166 | } else { |
| 167 | c0 = c0 + *(pptr++); |
| 168 | c1 += c0; |
| 169 | } |
| 170 | } |
| 171 | |
| 172 | c0 = c0 % 255; |
| 173 | c1 = c1 % 255; |
| 174 | |
| 175 | mul = (length - checksum_offset)*(c0); |
| 176 | |
| 177 | x = mul - c0 - c1; |
| 178 | y = c1 - mul - 1; |
| 179 | |
| 180 | if ( y >= 0 ) y++; |
| 181 | if ( x < 0 ) x--; |
| 182 | |
| 183 | x %= 255; |
| 184 | y %= 255; |
| 185 | |
| 186 | |
| 187 | if (x == 0) x = 255; |
| 188 | if (y == 0) y = 255; |
| 189 | |
| 190 | y &= 0x00FF; |
| 191 | checksum = ((x << 8) | y); |
| 192 | |
| 193 | return checksum; |
| 194 | } |