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1 office 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 * This program is free software; you can redistribute it and/or
18 * modify it under the terms of the GNU General Public License
19 * as published by the Free Software Foundation; either version 2
20 * of the License, or (at your option) any later version.
21 *
22 * This program is distributed in the hope that it will be useful,
23 * but WITHOUT ANY WARRANTY; without even the implied warranty of
24 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
25 * GNU General Public License for more details.
26 *
27 * You should have received a copy of the GNU General Public License
28 * along with this program; if not, write to the Free Software
29 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
30 *
31 */
32  
33 #include "config.h"
34  
35 #include <glib.h>
36 #include <epan/tvbuff.h>
37 #include <epan/crc8-tvb.h>
38  
39 /**
40 * Reversed CRC table
41 *****************************************************************************/
42 static const guint8 crctable[256] = { /*reversed, 8-bit, poly=0x07*/
43 0x00, 0x91, 0xE3, 0x72, 0x07, 0x96, 0xE4, 0x75, 0x0E, 0x9F, 0xED, 0x7C, 0x09, 0x98, 0xEA, 0x7B,
44 0x1C, 0x8D, 0xFF, 0x6E, 0x1B, 0x8A, 0xF8, 0x69, 0x12, 0x83, 0xF1, 0x60, 0x15, 0x84, 0xF6, 0x67,
45 0x38, 0xA9, 0xDB, 0x4A, 0x3F, 0xAE, 0xDC, 0x4D, 0x36, 0xA7, 0xD5, 0x44, 0x31, 0xA0, 0xD2, 0x43,
46 0x24, 0xB5, 0xC7, 0x56, 0x23, 0xB2, 0xC0, 0x51, 0x2A, 0xBB, 0xC9, 0x58, 0x2D, 0xBC, 0xCE, 0x5F,
47 0x70, 0xE1, 0x93, 0x02, 0x77, 0xE6, 0x94, 0x05, 0x7E, 0xEF, 0x9D, 0x0C, 0x79, 0xE8, 0x9A, 0x0B,
48 0x6C, 0xFD, 0x8F, 0x1E, 0x6B, 0xFA, 0x88, 0x19, 0x62, 0xF3, 0x81, 0x10, 0x65, 0xF4, 0x86, 0x17,
49 0x48, 0xD9, 0xAB, 0x3A, 0x4F, 0xDE, 0xAC, 0x3D, 0x46, 0xD7, 0xA5, 0x34, 0x41, 0xD0, 0xA2, 0x33,
50 0x54, 0xC5, 0xB7, 0x26, 0x53, 0xC2, 0xB0, 0x21, 0x5A, 0xCB, 0xB9, 0x28, 0x5D, 0xCC, 0xBE, 0x2F,
51 0xE0, 0x71, 0x03, 0x92, 0xE7, 0x76, 0x04, 0x95, 0xEE, 0x7F, 0x0D, 0x9C, 0xE9, 0x78, 0x0A, 0x9B,
52 0xFC, 0x6D, 0x1F, 0x8E, 0xFB, 0x6A, 0x18, 0x89, 0xF2, 0x63, 0x11, 0x80, 0xF5, 0x64, 0x16, 0x87,
53 0xD8, 0x49, 0x3B, 0xAA, 0xDF, 0x4E, 0x3C, 0xAD, 0xD6, 0x47, 0x35, 0xA4, 0xD1, 0x40, 0x32, 0xA3,
54 0xC4, 0x55, 0x27, 0xB6, 0xC3, 0x52, 0x20, 0xB1, 0xCA, 0x5B, 0x29, 0xB8, 0xCD, 0x5C, 0x2E, 0xBF,
55 0x90, 0x01, 0x73, 0xE2, 0x97, 0x06, 0x74, 0xE5, 0x9E, 0x0F, 0x7D, 0xEC, 0x99, 0x08, 0x7A, 0xEB,
56 0x8C, 0x1D, 0x6F, 0xFE, 0x8B, 0x1A, 0x68, 0xF9, 0x82, 0x13, 0x61, 0xF0, 0x85, 0x14, 0x66, 0xF7,
57 0xA8, 0x39, 0x4B, 0xDA, 0xAF, 0x3E, 0x4C, 0xDD, 0xA6, 0x37, 0x45, 0xD4, 0xA1, 0x30, 0x42, 0xD3,
58 0xB4, 0x25, 0x57, 0xC6, 0xB3, 0x22, 0x50, 0xC1, 0xBA, 0x2B, 0x59, 0xC8, 0xBD, 0x2C, 0x5E, 0xCF
59 };
60  
61  
62 gboolean check_fcs(tvbuff_t *p, guint8 len, guint8 offset, guint8 received_fcs){
63 /*Init*/
64 guint8 FCS = 0xFF;
65 guint8 tmp = 0;
66 /*len is the number of bytes in the message, p points to message*/
67 while (len--) {
68 tmp = FCS^tvb_get_guint8(p,offset);
69 offset++;
70 FCS=crctable[tmp];
71 }
72 /*Ones complement*/
73 FCS=crctable[FCS^received_fcs];
74 /*0xCF is the reversed order of 11110011.*/
75 if (FCS==0xCF) {
76 /*FCS is OK*/
77 return TRUE;
78 }
79 else {
80 /*FCS is not OK*/
81 return FALSE;
82 }
83 }
84  
85 guint8 get_crc8_ieee8023_epon(tvbuff_t *p, guint8 len, guint8 offset) {
86 guint8 FCS = 0x00;
87 guint8 tmp = 0;
88  
89 while (len--) {
90 tmp = FCS^tvb_get_guint8(p,offset);
91 offset++;
92 FCS=crctable[tmp];
93 }
94  
95 return FCS;
96 }
97  
98 /*
99 * Editor modelines - http://www.wireshark.org/tools/modelines.html
100 *
101 * Local variables:
102 * c-basic-offset: 8
103 * tab-width: 8
104 * indent-tabs-mode: t
105 * End:
106 *
107 * vi: set shiftwidth=8 tabstop=8 noexpandtab:
108 * :indentSize=8:tabSize=8:noTabs=false:
109 */