epan/crc8-tvb.c

   1 /* crc8.c
   2  *
   3  * Checks the checksum (FCS) of the 3G TS 27.010 Multiplexing protocol.
   4  * The algorithm to check the FCS is described in "3G TS 27.010 V2.0.0 (1999-06)"
   5  * See: www.3gpp.org/ftp/tsg_t/TSG_T/TSGT_04/docs/PDFs/TP-99119.pdf
   6  * or: http://www.3gpp.org/ftp/Specs/html-info/27010.htm
   7  *
   8  * Polynom: (x^8 + x^2 + x^1 + 1)
   9  *
  10  * 2011 Hans-Christoph Schemmel <hans-christoph.schemmel[AT]cinterion.com>
  11  *
  12  *
  13  * Wireshark - Network traffic analyzer
  14  * By Gerald Combs <gerald@wireshark.org>
  15  * Copyright 1998 Gerald Combs
  16  *
  17  * SPDX-License-Identifier: GPL-2.0-or-later
  18  *
  19 */
  20
  21 #include "config.h"
  22
  23 #include <glib.h>
  24 #include <epan/tvbuff.h>
  25 #include <epan/crc8-tvb.h>
  26
  27 /**
  28  * Reversed CRC table
  29  *****************************************************************************/
  30 static const uint8_t crctable[256] = { /*reversed, 8-bit, poly=0x07*/
  31         0x00, 0x91, 0xE3, 0x72, 0x07, 0x96, 0xE4, 0x75, 0x0E, 0x9F, 0xED, 0x7C, 0x09, 0x98, 0xEA, 0x7B,
  32         0x1C, 0x8D, 0xFF, 0x6E, 0x1B, 0x8A, 0xF8, 0x69, 0x12, 0x83, 0xF1, 0x60, 0x15, 0x84, 0xF6, 0x67,
  33         0x38, 0xA9, 0xDB, 0x4A, 0x3F, 0xAE, 0xDC, 0x4D, 0x36, 0xA7, 0xD5, 0x44, 0x31, 0xA0, 0xD2, 0x43,
  34         0x24, 0xB5, 0xC7, 0x56, 0x23, 0xB2, 0xC0, 0x51, 0x2A, 0xBB, 0xC9, 0x58, 0x2D, 0xBC, 0xCE, 0x5F,
  35         0x70, 0xE1, 0x93, 0x02, 0x77, 0xE6, 0x94, 0x05, 0x7E, 0xEF, 0x9D, 0x0C, 0x79, 0xE8, 0x9A, 0x0B,
  36         0x6C, 0xFD, 0x8F, 0x1E, 0x6B, 0xFA, 0x88, 0x19, 0x62, 0xF3, 0x81, 0x10, 0x65, 0xF4, 0x86, 0x17,
  37         0x48, 0xD9, 0xAB, 0x3A, 0x4F, 0xDE, 0xAC, 0x3D, 0x46, 0xD7, 0xA5, 0x34, 0x41, 0xD0, 0xA2, 0x33,
  38         0x54, 0xC5, 0xB7, 0x26, 0x53, 0xC2, 0xB0, 0x21, 0x5A, 0xCB, 0xB9, 0x28, 0x5D, 0xCC, 0xBE, 0x2F,
  39         0xE0, 0x71, 0x03, 0x92, 0xE7, 0x76, 0x04, 0x95, 0xEE, 0x7F, 0x0D, 0x9C, 0xE9, 0x78, 0x0A, 0x9B,
  40         0xFC, 0x6D, 0x1F, 0x8E, 0xFB, 0x6A, 0x18, 0x89, 0xF2, 0x63, 0x11, 0x80, 0xF5, 0x64, 0x16, 0x87,
  41         0xD8, 0x49, 0x3B, 0xAA, 0xDF, 0x4E, 0x3C, 0xAD, 0xD6, 0x47, 0x35, 0xA4, 0xD1, 0x40, 0x32, 0xA3,
  42         0xC4, 0x55, 0x27, 0xB6, 0xC3, 0x52, 0x20, 0xB1, 0xCA, 0x5B, 0x29, 0xB8, 0xCD, 0x5C, 0x2E, 0xBF,
  43         0x90, 0x01, 0x73, 0xE2, 0x97, 0x06, 0x74, 0xE5, 0x9E, 0x0F, 0x7D, 0xEC, 0x99, 0x08, 0x7A, 0xEB,
  44         0x8C, 0x1D, 0x6F, 0xFE, 0x8B, 0x1A, 0x68, 0xF9, 0x82, 0x13, 0x61, 0xF0, 0x85, 0x14, 0x66, 0xF7,
  45         0xA8, 0x39, 0x4B, 0xDA, 0xAF, 0x3E, 0x4C, 0xDD, 0xA6, 0x37, 0x45, 0xD4, 0xA1, 0x30, 0x42, 0xD3,
  46         0xB4, 0x25, 0x57, 0xC6, 0xB3, 0x22, 0x50, 0xC1, 0xBA, 0x2B, 0x59, 0xC8, 0xBD, 0x2C, 0x5E, 0xCF
  47 };
  48
  49
  50 bool check_fcs(tvbuff_t *p, uint8_t len, uint8_t offset, uint8_t received_fcs){
  51         /*Init*/
  52         uint8_t FCS = 0xFF;
  53         /*len is the number of bytes in the message, p points to message*/
  54         while (len--) {
  55                 uint8_t tmp;
  56
  57                 tmp = FCS^tvb_get_uint8(p,offset);
  58                 offset++;
  59                 FCS=crctable[tmp];
  60         }
  61         /*Ones complement*/
  62         FCS=crctable[FCS^received_fcs];
  63         /*0xCF is the reversed order of 11110011.*/
  64         if (FCS==0xCF) {
  65                 /*FCS is OK*/
  66                 return true;
  67         }
  68         else {
  69                 /*FCS is not OK*/
  70                 return false;
  71         }
  72 }
  73
  74 uint8_t get_crc8_ieee8023_epon(tvbuff_t *p, uint8_t len, uint8_t offset) {
  75         uint8_t FCS = 0x00;
  76
  77         while (len--) {
  78                 uint8_t tmp;
  79
  80                 tmp = FCS^tvb_get_uint8(p,offset);
  81                 offset++;
  82                 FCS=crctable[tmp];
  83         }
  84
  85   return FCS;
  86 }
  87
  88 /*
  89  * Editor modelines  -  https://www.wireshark.org/tools/modelines.html
  90  *
  91  * Local variables:
  92  * c-basic-offset: 8
  93  * tab-width: 8
  94  * indent-tabs-mode: t
  95  * End:
  96  *
  97  * vi: set shiftwidth=8 tabstop=8 noexpandtab:
  98  * :indentSize=8:tabSize=8:noTabs=false:
  99  */