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The DRM DCP CRC-16 is the same as the X.25 CRC-16. 

So just use crc16_x25_ccitt_tvb(), which goes a byte at a time rather
than a bit at a time, and which takes a tvbuff rather than requiring you
to call tvb_get_ptr().

It also doesn't 1's-complement the result, so we can compare it against the
0x1D0F in ETSI TS 102 821 V1.4.1 (2012-10) rather than against a
1's-complement version, 0xE2F0.

Change-Id: Ia513f851f0a8ff1e7853278ddf3618c532fb2aba
Reviewed-on: https://code.wireshark.org/review/3507
Reviewed-by: Guy Harris <guy@alum.mit.edu>
This commit is contained in:
Guy Harris 2014-08-08 10:10:36 -07:00
parent 57927c8a56
commit 9b9005eb94
5 changed files with 7 additions and 95 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

16
epan/dissectors/packet-dcp-etsi.c
View File

@ -28,7 +28,7 @@
#include <epan/packet.h>
#include <epan/reassemble.h>
#include <wsutil/crcdrm.h>
#include <epan/crc16-tvb.h>
#include <epan/reedsolomon.h>
#include <epan/wmem/wmem.h>
#include <string.h>
@ -494,11 +494,10 @@ dissect_pft(tvbuff_t * tvb, packet_info * pinfo, proto_tree * tree)
if (tree) {
proto_item *ci = NULL;
guint header_len = offset+2;
const char *crc_buf = (const char *) tvb_get_ptr(tvb, 0, header_len);
unsigned long c = crc_drm(crc_buf, header_len, 16, 0x11021, 1);
guint16 c = crc16_x25_ccitt_tvb(tvb, header_len);
ci = proto_tree_add_item (pft_tree, hf_edcp_hcrc, tvb, offset, 2, ENC_BIG_ENDIAN);
proto_item_append_text(ci, " (%s)", (c==0xe2f0)?"Ok":"bad");
proto_tree_add_boolean(pft_tree, hf_edcp_hcrc_ok, tvb, offset, 2, c==0xe2f0);
proto_item_append_text(ci, " (%s)", (c==0x1D0F)?"Ok":"bad");
proto_tree_add_boolean(pft_tree, hf_edcp_hcrc_ok, tvb, offset, 2, c==0x1D0F);
}
offset += 2;
if (fcount > 1) { /* fragmented*/
@ -580,10 +579,9 @@ dissect_af (tvbuff_t * tvb, packet_info * pinfo, proto_tree * tree)
ci = proto_tree_add_item (af_tree, hf_edcp_crc, tvb, offset, 2, ENC_BIG_ENDIAN);
if (ver & 0x80) { /* crc valid */
guint len = offset+2;
const char *crc_buf = (const char *) tvb_get_ptr(tvb, 0, len);
unsigned long c = crc_drm(crc_buf, len, 16, 0x11021, 1);
proto_item_append_text(ci, " (%s)", (c==0xe2f0)?"Ok":"bad");
proto_tree_add_boolean(af_tree, hf_edcp_crc_ok, tvb, offset, 2, c==0xe2f0);
guint16 c = crc16_x25_ccitt_tvb(tvb, len);
proto_item_append_text(ci, " (%s)", (c==0x1D0F)?"Ok":"bad");
proto_tree_add_boolean(af_tree, hf_edcp_crc_ok, tvb, offset, 2, c==0x1D0F);
}
/*offset += 2;*/

1
wsutil/CMakeLists.txt
View File

@ -60,7 +60,6 @@ set(WSUTIL_FILES
crc7.c
crc8.c
crc11.c
crcdrm.c
des.c
eax.c
filesystem.c

2
wsutil/Makefile.common
View File

@ -48,7 +48,6 @@ LIBWSUTIL_SRC = \
crc16.c \
crc16-plain.c \
crc32.c \
crcdrm.c \
des.c \
eax.c \
filesystem.c \
@ -101,7 +100,6 @@ libwsutil_nonrepl_INCLUDES = \
crc16.h \
crc16-plain.h \
crc32.h \
crcdrm.h \
des.h \
eax.h \
filesystem.h \

49
wsutil/crcdrm.c
View File

@ -1,49 +0,0 @@
/* crcdrm.c
* another CRC 16
* Copyright 2006, British Broadcasting Corporation
*
* Wireshark - Network traffic analyzer
* By Gerald Combs <gerald@wireshark.org>
* Copyright 1998 Gerald Combs
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#include <stdlib.h>
#include <wsutil/crcdrm.h>
unsigned long crc_drm(const char *data, size_t bytesize,
unsigned short num_crc_bits, unsigned long crc_gen, int invert)
{
unsigned long crc_holder, ones, i, msb, databit;
signed short j;
ones = (1 << num_crc_bits) - 1;
crc_holder = ones;
for (i=0; i<bytesize; i++)
for (j=7; j>=0; j--)
{
crc_holder <<= 1;
msb = crc_holder >> num_crc_bits;
databit = (data[i] >> j) & 1;
if ((msb ^ databit) != 0)
crc_holder = crc_holder ^ crc_gen;
crc_holder = crc_holder & ones;
}
if (invert)
crc_holder = crc_holder ^ ones; /* invert checksum */
return crc_holder;
}

34
wsutil/crcdrm.h
View File

@ -1,34 +0,0 @@
/* crcdrm.h
* another CRC 16
* Copyright 2006, British Broadcasting Corporation
*
* Wireshark - Network traffic analyzer
* By Gerald Combs <gerald@wireshark.org>
* Copyright 1998 Gerald Combs
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#ifndef __CRCDRM_H__
#define __CRCDRM_H__
#include "ws_symbol_export.h"
WS_DLL_PUBLIC
unsigned long crc_drm(const char *data, size_t bytesize,
unsigned short num_crc_bits, unsigned long crc_gen, int invert);
#endif /* __CRCDRM_H__ */