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From Julian Cable: 

New dissector for ETSI DCP (ETSI TS 102 821).

Code rearranged to look more like other Wireshark dissectors and some warnings/errors
on Windows fixed.

svn path=/trunk/; revision=19981
This commit is contained in:
Anders Broman 2006-11-25 13:03:48 +00:00
parent 643dc7099d
commit 1509562c0f
7 changed files with 1698 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
epan/Makefile.common
View File

@ -40,6 +40,7 @@ LIBWIRESHARK_SRC = \
conversation.c \
crc16.c \
crc32.c \
crcdrm.c \
crypt-des.c \
crypt-md4.c \
crypt-md5.c \
@ -73,6 +74,7 @@ LIBWIRESHARK_SRC = \
radius_dict.c \
range.c \
reassemble.c \
reedsolomon.c \
req_resp_hdrs.c \
sha1.c \
sigcomp_state_hdlr.c \
@ -119,6 +121,7 @@ LIBWIRESHARK_INCLUDES = \
conversation.h \
crc16.h \
crc32.h \
crcdrm.h \
crypt-des.h \
crypt-md4.h \
crypt-md5.h \
@ -168,6 +171,7 @@ LIBWIRESHARK_INCLUDES = \
ptvcursor.h \
range.h \
reassemble.h \
reedsolomon.h \
report_err.h \
req_resp_hdrs.h \
rtp_pt.h \

50
epan/crcdrm.c Normal file
View File

@ -0,0 +1,50 @@
/* drmcrc.c
* another CRC 16
* Copyright 2006, British Broadcasting Corporation
*
* $Id$
*
* 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*/
#include "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;
}

7
epan/crcdrm.h Normal file
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@ -0,0 +1,7 @@
#ifndef _CRCDRM_H
#include <stdlib.h>
unsigned long crc_drm(const char *data, size_t bytesize,
unsigned short num_crc_bits, unsigned long crc_gen, int invert);
#endif

1
epan/dissectors/Makefile.common
View File

@ -255,6 +255,7 @@ DISSECTOR_SRC = \
packet-dcom-remact.c \
packet-dcom-remunkn.c \
packet-dcom-sysact.c \
packet-dcp-etsi.c \
packet-ddtp.c \
packet-dec-bpdu.c \
packet-dec-dnart.c \

878
epan/dissectors/packet-dcp-etsi.c Normal file
View File

@ -0,0 +1,878 @@
/* packet-dcp-etsi.c
* Routines for ETSI Distribution & Communication Protocol
* Copyright 2006, British Broadcasting Corporation
*
* $Id:$
*
* 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*
* Protocol info
* Ref: ETSI DCP (ETSI TS 102 821)
*/
#ifdef HAVE_CONFIG_H
# include "config.h"
#endif
#include <gmodule.h>
#include <epan/packet.h>
#include <epan/prefs.h>
#include <epan/reassemble.h>
#include <epan/crcdrm.h>
#include <epan/reedsolomon.h>
#include <string.h>
/* forward reference */
static gboolean dissect_dcp_etsi (tvbuff_t * tvb, packet_info * pinfo, proto_tree * tree);
static void dissect_af (tvbuff_t * tvb, packet_info * pinfo, proto_tree * tree);
static void dissect_pft (tvbuff_t * tvb, packet_info * pinfo, proto_tree * tree);
static void dissect_tpl(tvbuff_t * tvb, packet_info * pinfo, proto_tree * tree);
static dissector_table_t dcp_dissector_table;
static dissector_table_t af_dissector_table;
static dissector_table_t tpl_dissector_table;
static int proto_dcp_etsi = -1;
static int proto_af = -1;
static int proto_pft = -1;
static int proto_tpl = -1;
static dissector_handle_t af_handle;
static dissector_handle_t pft_handle;
static dissector_handle_t tpl_handle;
static int hf_edcp_sync = -1;
static int hf_edcp_len = -1;
static int hf_edcp_seq = -1;
static int hf_edcp_crcflag = -1;
static int hf_edcp_maj = -1;
static int hf_edcp_min = -1;
static int hf_edcp_pt = -1;
static int hf_edcp_crc = -1;
static int hf_edcp_crc_ok = -1;
static int hf_edcp_pft_pt = -1;
static int hf_edcp_pseq = -1;
static int hf_edcp_findex = -1;
static int hf_edcp_fcount = -1;
static int hf_edcp_fecflag = -1;
static int hf_edcp_addrflag = -1;
static int hf_edcp_plen = -1;
static int hf_edcp_rsk = -1;
static int hf_edcp_rsz = -1;
static int hf_edcp_source = -1;
static int hf_edcp_dest = -1;
static int hf_edcp_hcrc = -1;
static int hf_edcp_hcrc_ok = -1;
static int hf_edcp_c_max = -1;
static int hf_edcp_rx_min = -1;
static int hf_edcp_rs_corrected = -1;
static int hf_edcp_rs_ok = -1;
static int hf_edcp_pft_payload = -1;
static int hf_tpl_tlv = -1;
static int hf_tpl_ptr = -1;
static int hf_edcp_fragments = -1;
static int hf_edcp_fragment = -1;
static int hf_edcp_fragment_overlap = -1;
static int hf_edcp_fragment_overlap_conflicts = -1;
static int hf_edcp_fragment_multiple_tails = -1;
static int hf_edcp_fragment_too_long_fragment = -1;
static int hf_edcp_fragment_error = -1;
static int hf_edcp_reassembled_in = -1;
/* Initialize the subtree pointers */
static gint ett_edcp = -1;
static gint ett_af = -1;
static gint ett_pft = -1;
static gint ett_tpl = -1;
static gint ett_edcp_fragment = -1;
static gint ett_edcp_fragments = -1;
static GHashTable *dcp_fragment_table = NULL;
static GHashTable *dcp_reassembled_table = NULL;
static const fragment_items dcp_frag_items = {
/* Fragment subtrees */
&ett_edcp_fragment,
&ett_edcp_fragments,
/* Fragment fields */
&hf_edcp_fragments,
&hf_edcp_fragment,
&hf_edcp_fragment_overlap,
&hf_edcp_fragment_overlap_conflicts,
&hf_edcp_fragment_multiple_tails,
&hf_edcp_fragment_too_long_fragment,
&hf_edcp_fragment_error,
/* Reassembled in field */
&hf_edcp_reassembled_in,
/* Tag */
"Message fragments"
};
/** initialise the DCP protocol. Details follow
* here.
*/
static void
dcp_init_protocol(void)
{
fragment_table_init (&dcp_fragment_table);
reassembled_table_init (&dcp_reassembled_table);
}
/** Dissect a DCP packet. Details follow
* here.
* \param[in,out] tvb The buffer containing the packet
* \param[in,out] pinfo The packet info structure
* \param[in,out] tree The structure containing the details which will be displayed, filtered, etc.
static void
*/
static gboolean
dissect_dcp_etsi (tvbuff_t * tvb, packet_info * pinfo, proto_tree * tree)
{
guint8 *sync;
proto_tree *dcp_tree = NULL;
sync = tvb_get_string (tvb, 0, 2);
if((sync[0]!='A' && sync[0]!='P') || sync[1]!='F')
return FALSE;
pinfo->current_proto = "DCP (ETSI)";
/* Clear out stuff in the info column */
if (check_col (pinfo->cinfo, COL_INFO)) {
col_clear (pinfo->cinfo, COL_INFO);
}
if (check_col (pinfo->cinfo, COL_PROTOCOL)) {
col_set_str (pinfo->cinfo, COL_PROTOCOL, "DCP (ETSI)");
/*col_append_fstr (pinfo->cinfo, COL_INFO, " tvb %d", tvb_length(tvb));*/
}
if(tree) {
proto_item *ti = NULL;
ti = proto_tree_add_item (tree, proto_dcp_etsi, tvb, 0, -1, FALSE);
dcp_tree = proto_item_add_subtree (ti, ett_edcp);
}
dissector_try_string(dcp_dissector_table, (char*)sync, tvb, pinfo, dcp_tree);
g_free (sync);
return TRUE;
}
#define PFT_RS_N_MAX 207
#define PFT_RS_K 255
#define PFT_RS_P (PFT_RS_K - PFT_RS_N_MAX)
static
void rs_deinterleave(const guint8 *input, guint8 *output, guint16 plen, guint32 fcount)
{
guint fidx;
for(fidx=0; fidx<fcount; fidx++)
{
int r;
for (r=0; r<plen; r++)
{
output[fidx+r*fcount] = input[fidx*plen+r];
}
}
}
static
gboolean rs_correct_data(guint8 *deinterleaved, guint8 *output,
guint32 c_max, guint16 rsk, guint16 rsz)
{
guint32 i, index_coded = 0, index_out = 0;
int err_corr;
for (i=0; i<c_max; i++)
{
memcpy(output+index_out, deinterleaved+index_coded, rsk);
index_coded += rsk;
memcpy(output+index_out+PFT_RS_N_MAX, deinterleaved+index_coded, PFT_RS_P);
index_coded += PFT_RS_P;
err_corr = eras_dec_rs(output+index_out, NULL, 0);
if (err_corr<0) {
return FALSE;
}
index_out += rsk;
}
return TRUE;
}
static tvbuff_t *
dissect_pft_fec_detailed(tvbuff_t * tvb, packet_info * pinfo, proto_tree * tree,
guint32 findex,
guint32 fcount,
guint16 seq,
gint offset,
guint16 plen,
gboolean fec,
guint16 rsk,
guint16 rsz,
fragment_data *fd
)
{
guint16 decoded_size;
guint32 c_max;
guint32 rx_min;
gboolean first, last, decoded = TRUE;
tvbuff_t *new_tvb=NULL;
first = findex == 0;
last = fcount == (findex+1);
decoded_size = fcount*plen;
c_max = fcount*plen/(rsk+PFT_RS_P); /* rounded down */
rx_min = c_max*rsk/plen;
if(rx_min*plen<c_max*rsk)
rx_min++;
if (fd)
new_tvb = process_reassembled_data (tvb, offset, pinfo,
"Reassembled Message",
fd, &dcp_frag_items,
NULL, tree);
else {
guint fragments=0;
guint32 *got = g_malloc(fcount*sizeof(guint32));
fragment_data *fd = fragment_get(pinfo, seq, dcp_fragment_table);
fragment_data *fd_head;
for (fd_head = fd; fd_head != NULL; fd_head = fd_head->next) {
if(fd_head->data) {
got[fragments] = fd_head->offset;
fragments++;
}
}
if(fragments>=rx_min) {
guint i,j;
fragment_data *frag=NULL;
guint8 *dummy_data = (guint8*) g_malloc (plen);
tvbuff_t *dummytvb = tvb_new_real_data(dummy_data, plen, plen);
/* try and decode with missing fragments */
if(tree)
proto_tree_add_text (tree, tvb, 0, -1, "want %d, got %d need %d",
fcount, fragments, rx_min
);
memset(dummy_data, 0, plen);
for(i=0,j=0; i<fragments; i++,j++) {
while(j<got[i]) {
frag = fragment_add_seq_check (dummytvb, 0, pinfo, seq,
dcp_fragment_table, dcp_reassembled_table, j, plen, (j+1!=fcount));
if(tree) {
proto_tree_add_text (tree, tvb, 0, -1, "missing %d", j);
if(frag) {
proto_tree_add_text (tree, tvb, 0, -1, "fragment %d was what we needed", j);
break;
} else {
proto_tree_add_text (tree, tvb, 0, -1, "added %d but still not reassembled", j);
}
}
j++;
}
}
if(frag)
new_tvb = process_reassembled_data (tvb, offset, pinfo,
"Reassembled Message",
frag, &dcp_frag_items,
NULL, tree);
}
g_free(got);
}
if(new_tvb) {
tvbuff_t *dtvb = NULL;
const guint8 *input = tvb_get_ptr(new_tvb, 0, -1);
guint16 reassembled_size = tvb_length(new_tvb);
guint8 *deinterleaved = (guint8*) g_malloc (reassembled_size);
guint8 *output = (guint8*) g_malloc (decoded_size);
rs_deinterleave(input, deinterleaved, plen, fcount);
dtvb = tvb_new_real_data(deinterleaved, reassembled_size, reassembled_size);
tvb_set_child_real_data_tvbuff(tvb, dtvb);
add_new_data_source(pinfo, dtvb, "Deinterleaved");
tvb_set_free_cb(dtvb, g_free);
decoded = rs_correct_data(deinterleaved, output, c_max, rsk, rsz);
if(tree)
proto_tree_add_boolean (tree, hf_edcp_rs_ok, tvb, offset, 2, decoded);
new_tvb = tvb_new_real_data(output, decoded_size, decoded_size);
tvb_set_child_real_data_tvbuff(dtvb, new_tvb);
add_new_data_source(pinfo, new_tvb, "RS Error Corrected Data");
tvb_set_free_cb(new_tvb, g_free);
}
return new_tvb;
}
/** Handle a PFT packet which has the fragmentation header. This uses the
* standard ethereal methods for reassembling fragments. If FEC is used,
* the FEC is handled too. For the moment, all the fragments must be
* available but this could be improved.
* \param[in,out] tvb The buffer containing the current fragment
* \param[in,out] pinfo The packet info structure
* \param[in,out] tree The structure containing the details which will be displayed, filtered, etc.
* \param[in] findex the fragment count
* \param[in] fcount the number of fragments
* \param[in] seq the sequence number of the reassembled packet
* \param[in] offset the offset into the tvb of the fragment
* \param[in] plen the length of each fragment
* \param[in] fec is fec used
* \param[in] rsk the number of useful bytes in each chunk
* \param[in] rsz the number of padding bytes in each chunk
*/
static tvbuff_t *
dissect_pft_fragmented(tvbuff_t * tvb, packet_info * pinfo, proto_tree * tree,
guint32 findex,
guint32 fcount,
guint16 seq,
gint offset,
guint16 plen,
gboolean fec,
guint16 rsk,
guint16 rsz
)
{
gboolean first, last;
tvbuff_t *new_tvb=NULL;
fragment_data *frag_edcp = NULL;
pinfo->fragmented = TRUE;
first = findex == 0;
last = fcount == (findex+1);
frag_edcp = fragment_add_seq_check (
tvb, offset, pinfo,
seq,
dcp_fragment_table, dcp_reassembled_table,
findex,
plen,
!last);
if(fec) {
new_tvb = dissect_pft_fec_detailed(
tvb, pinfo, tree, findex, fcount, seq, offset, plen, fec, rsk, rsz, frag_edcp
);
} else {
new_tvb = process_reassembled_data (tvb, offset, pinfo,
"Reassembled Message",
frag_edcp, &dcp_frag_items,
NULL, tree);
}
if (check_col (pinfo->cinfo, COL_INFO)) {
if(new_tvb) {
col_append_str (pinfo->cinfo, COL_INFO, " (Message Reassembled)");
} else {
if(last) {
col_append_str (pinfo->cinfo, COL_INFO, " (Message Reassembly failure)");
} else {
col_append_fstr (pinfo->cinfo, COL_INFO, " (Message fragment %u)", findex);
}
}
if(first)
col_append_str (pinfo->cinfo, COL_INFO, " (first)");
if(last)
col_append_str (pinfo->cinfo, COL_INFO, " (last)");
}
return new_tvb;
}
/** Dissect a PFT packet. Details follow
* here.
* \param[in,out] tvb The buffer containing the packet
* \param[in,out] pinfo The packet info structure
* \param[in,out] tree The structure containing the details which will be displayed, filtered, etc.
*/
static void
dissect_pft(tvbuff_t * tvb, packet_info * pinfo, proto_tree * tree)
{
guint16 plen;
gint offset = 0;
guint16 seq, payload_len, hcrc;
guint32 findex, fcount;
proto_tree *pft_tree = NULL;
proto_item *ti = NULL, *li = NULL;
tvbuff_t *next_tvb = NULL;
gboolean fec = FALSE;
guint16 rsk=0, rsz=0;
pinfo->current_proto = "DCP-PFT";
if (check_col (pinfo->cinfo, COL_PROTOCOL)) {
col_set_str (pinfo->cinfo, COL_PROTOCOL, "DCP-PFT");
}
if (tree) { /* we are being asked for details */
ti = proto_tree_add_item (tree, proto_pft, tvb, 0, -1, FALSE);
pft_tree = proto_item_add_subtree (ti, ett_pft);
proto_tree_add_item (pft_tree, hf_edcp_sync, tvb, offset, 2, FALSE);
}
offset += 2;
seq = tvb_get_ntohs (tvb, offset);
if (tree) {
proto_tree_add_item (pft_tree, hf_edcp_pseq, tvb, offset, 2, FALSE);
}
offset += 2;
findex = tvb_get_ntoh24 (tvb, offset);
if (tree) {
proto_tree_add_item (pft_tree, hf_edcp_findex, tvb, offset, 3, FALSE);
}
offset += 3;
fcount = tvb_get_ntoh24 (tvb, offset);
if (tree) {
proto_tree_add_item (pft_tree, hf_edcp_fcount, tvb, offset, 3, FALSE);
}
offset += 3;
plen = tvb_get_ntohs (tvb, offset);
payload_len = plen & 0x3fff;
if (tree) {
proto_tree_add_item (pft_tree, hf_edcp_fecflag, tvb, offset, 2, FALSE);
proto_tree_add_item (pft_tree, hf_edcp_addrflag, tvb, offset, 2, FALSE);
li = proto_tree_add_item (pft_tree, hf_edcp_plen, tvb, offset, 2, FALSE);
}
offset += 2;
if (plen & 0x8000) {
fec = TRUE;
rsk = tvb_get_guint8 (tvb, offset);
if (tree)
proto_tree_add_item (pft_tree, hf_edcp_rsk, tvb, offset, 1, FALSE);
offset += 1;
rsz = tvb_get_guint8 (tvb, offset);
if (tree)
proto_tree_add_item (pft_tree, hf_edcp_rsz, tvb, offset, 1, FALSE);
offset += 1;
}
if (plen & 0x4000) {
if (tree)
proto_tree_add_item (pft_tree, hf_edcp_source, tvb, offset, 2, FALSE);
offset += 2;
if (tree)
proto_tree_add_item (pft_tree, hf_edcp_dest, tvb, offset, 2, FALSE);
offset += 2;
}
if (tree) {
proto_item *ci = NULL;
guint header_len = offset+2;
const guint8 *crc_buf = tvb_get_ptr(tvb, 0, header_len);
unsigned long c = crc_drm(crc_buf, header_len, 16, 0x11021, 1);
ci = proto_tree_add_item (pft_tree, hf_edcp_hcrc, tvb, offset, 2, FALSE);
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);
}
hcrc = tvb_get_ntohs (tvb, offset);
offset += 2;
if (fcount > 1) { /* fragmented*/
gboolean save_fragmented = pinfo->fragmented;
guint16 real_len = tvb_length(tvb)-offset;
proto_tree_add_item (pft_tree, hf_edcp_pft_payload, tvb, offset, real_len, FALSE);
if(real_len != payload_len) {
if(li)
proto_item_append_text(li, " (length error (%d))", real_len);
}
next_tvb = dissect_pft_fragmented(tvb, pinfo, pft_tree,
findex, fcount, seq, offset, real_len,
fec, rsk, rsz
);
pinfo->fragmented = save_fragmented;
} else {
next_tvb = tvb_new_subset (tvb, offset, -1, -1);
}
if(next_tvb) {
dissect_af(next_tvb, pinfo, tree);
}
}
/** Dissect an AF Packet. Parse an AF packet, checking the CRC if the CRC valid
* flag is set and calling any registered sub dissectors on the payload type.
* Currently only a payload type 'T' is defined which is the tag packet layer.
* If any others are defined then they can register themselves.
* \param[in,out] tvb The buffer containing the packet
* \param[in,out] pinfo The packet info structure
* \param[in,out] tree The structure containing the details which will be displayed, filtered, etc.
*/
static void
dissect_af (tvbuff_t * tvb, packet_info * pinfo, proto_tree * tree)
{
gint offset = 0;
proto_item *ti = NULL;
proto_item *li = NULL;
proto_item *ci = NULL;
proto_tree *af_tree = NULL;
guint8 ver, pt;
guint32 payload_len;
tvbuff_t *next_tvb = NULL;
pinfo->current_proto = "DCP-AF";
if (check_col (pinfo->cinfo, COL_PROTOCOL)) {
col_set_str (pinfo->cinfo, COL_PROTOCOL, "DCP-AF");
}
if (tree) { /* we are being asked for details */
ti = proto_tree_add_item (tree, proto_af, tvb, 0, -1, FALSE);
af_tree = proto_item_add_subtree (ti, ett_af);
proto_tree_add_item (af_tree, hf_edcp_sync, tvb, offset, 2, FALSE);
}
offset += 2;
payload_len = tvb_get_ntohl(tvb, offset);
if (tree) {
guint32 real_payload_len = tvb_length(tvb)-12;
li = proto_tree_add_item (af_tree, hf_edcp_len, tvb, offset, 4, FALSE);
if(real_payload_len < payload_len) {
proto_item_append_text (li, " (wrong len claims %d is %d)",
payload_len, real_payload_len
);
} else if(real_payload_len > payload_len) {
proto_item_append_text (li, " (%d bytes in packet after end of AF frame)",
real_payload_len-payload_len
);
}
}
offset += 4;
if (tree)
proto_tree_add_item (af_tree, hf_edcp_seq, tvb, offset, 2, FALSE);
offset += 2;
ver = tvb_get_guint8 (tvb, offset);
if (tree) {
proto_tree_add_item (af_tree, hf_edcp_crcflag, tvb, offset, 1, FALSE);
proto_tree_add_item (af_tree, hf_edcp_maj, tvb, offset, 1, FALSE);
proto_tree_add_item (af_tree, hf_edcp_min, tvb, offset, 1, FALSE);
}
offset += 1;
pt = tvb_get_guint8 (tvb, offset);
if (tree)
proto_tree_add_item (af_tree, hf_edcp_pt, tvb, offset, 1, FALSE);
offset += 1;
next_tvb = tvb_new_subset (tvb, offset, payload_len, -1);
offset += payload_len;
if (tree)
ci = proto_tree_add_item (af_tree, hf_edcp_crc, tvb, offset, 2, FALSE);
if (ver & 0x80) { /* crc valid */
guint len = offset+2;
const guint8 *crc_buf = tvb_get_ptr(tvb, 0, len);
unsigned long c = crc_drm(crc_buf, len, 16, 0x11021, 1);
if (tree) {
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);
}
}
offset += 2;
dissector_try_port(af_dissector_table, pt, next_tvb, pinfo, tree);
}
/** Dissect the Tag Packet Layer.
* Split the AF packet into its tag items. Each tag item has a 4 character
* tag, a length in bits and a value. The *ptr tag is dissected in the routine.
* All other tags are listed and may be handled by other dissectors.
* Child dissectors are tied to the parent tree, not to this tree, so that
* they appear at the same level as DCP.
* \param[in,out] tvb The buffer containing the packet
* \param[in,out] pinfo The packet info structure
* \param[in,out] tree The structure containing the details which will be displayed, filtered, etc.
*/
static void
dissect_tpl(tvbuff_t * tvb, packet_info * pinfo, proto_tree * tree)
{
proto_tree *tpl_tree = NULL;
guint offset=0;
char *prot=NULL;
guint16 maj, min;
pinfo->current_proto = "DCP-TPL";
if (check_col (pinfo->cinfo, COL_PROTOCOL)) {
col_set_str (pinfo->cinfo, COL_PROTOCOL, "DCP-TPL");
}
if(tree) {
proto_item *ti = NULL;
ti = proto_tree_add_item (tree, proto_tpl, tvb, 0, -1, FALSE);
tpl_tree = proto_item_add_subtree (ti, ett_tpl);
}
while(offset<tvb_length(tvb)) {
guint32 bits;
guint32 bytes;
char *tag = (char*)tvb_get_string (tvb, offset, 4); offset += 4;
bits = tvb_get_ntohl(tvb, offset); offset += 4;
bytes = bits / 8;
if(bits % 8)
bytes++;
if(tree) {
proto_item *i = NULL;
const guint8 *p = tvb_get_ptr(tvb, offset, bytes);
if(strcmp(tag, "*ptr")==0) {
prot = (char*)tvb_get_string (tvb, offset, 4);
maj = tvb_get_ntohs(tvb, offset+4);
min = tvb_get_ntohs(tvb, offset+6);
i = proto_tree_add_bytes_format(tpl_tree, hf_tpl_tlv, tvb,
offset-8, bytes+8, p, "%s %s rev %d.%d", tag, prot, maj, min);
} else {
i = proto_tree_add_bytes_format(tpl_tree, hf_tpl_tlv, tvb,
offset-8, bytes+8, p, "%s (%u bits)", tag, bits);
}
}
offset += bytes;
}
if(prot) {
if(tree) {
dissector_try_string(tpl_dissector_table, prot, tvb, pinfo, tree->parent);
} else {
dissector_try_string(tpl_dissector_table, prot, tvb, pinfo, NULL);
}
}
}
void
proto_reg_handoff_dcp_etsi (void)
{
static int Initialized = FALSE;
if (!Initialized) {
af_handle = create_dissector_handle(dissect_af, proto_af);
pft_handle = create_dissector_handle(dissect_pft, proto_pft);
tpl_handle = create_dissector_handle(dissect_tpl, proto_tpl);
heur_dissector_add("udp", dissect_dcp_etsi, proto_dcp_etsi);
dissector_add_string("dcp-etsi.sync", "AF", af_handle);
dissector_add_string("dcp-etsi.sync", "PF", pft_handle);
/* if there are ever other payload types ...*/
dissector_add("dcp-af.pt", 'T', tpl_handle);
}
}
void
proto_register_dcp_etsi (void)
{
module_t *dcp_module;
static hf_register_info hf_edcp[] = {
{&hf_edcp_sync,
{"sync", "dcp-etsi.sync",
FT_STRING, BASE_NONE, NULL, 0,
"AF or PF", HFILL}
}
};
static hf_register_info hf_af[] = {
{&hf_edcp_len,
{"length", "dcp-af.len",
FT_UINT32, BASE_DEC, NULL, 0,
"length in bytes of the payload", HFILL}
},
{&hf_edcp_seq,
{"frame count", "dcp-af.seq",
FT_UINT16, BASE_DEC, NULL, 0,
"Logical Frame Number", HFILL}
},
{&hf_edcp_crcflag,
{"crc flag", "dcp-af.crcflag",
FT_BOOLEAN, BASE_NONE, NULL, 0x80,
"Frame is protected by CRC", HFILL}
},
{&hf_edcp_maj,
{"Major Revision", "dcp-af.maj",
FT_UINT8, BASE_DEC, NULL, 0x70,
"Major Protocol Revision", HFILL}
},
{&hf_edcp_min,
{"Minor Revision", "dcp-af.min",
FT_UINT8, BASE_DEC, NULL, 0x0f,
"Minor Protocol Revision", HFILL}
},
{&hf_edcp_pt,
{"Payload Type", "dcp-af.pt",
FT_STRING, BASE_NONE, NULL, 0,
"T means Tag Packets, all other values reserved", HFILL}
},
{&hf_edcp_crc,
{"CRC", "dcp-af.crc",
FT_UINT16, BASE_HEX, NULL, 0,
"CRC", HFILL}
},
{&hf_edcp_crc_ok,
{"CRC OK", "dcp-af.crc_ok",
FT_BOOLEAN, BASE_NONE, NULL, 0,
"AF CRC OK", HFILL}
}
};
static hf_register_info hf_pft[] = {
{&hf_edcp_pft_pt,
{"Sub-protocol", "dcp-pft.pt",
FT_UINT8, BASE_DEC, NULL, 0,
"Always AF", HFILL}
},
{&hf_edcp_pseq,
{"Sequence No", "dcp-pft.seq",
FT_UINT16, BASE_DEC, NULL, 0,
"PFT Sequence No", HFILL}
},
{&hf_edcp_findex,
{"Fragment Index", "dcp-pft.findex",
FT_UINT24, BASE_DEC, NULL, 0,
"Index of the fragment within one AF Packet", HFILL}
},
{&hf_edcp_fcount,
{"Fragment Count", "dcp-pft.fcount",
FT_UINT24, BASE_DEC, NULL, 0,
"Number of fragments produced from this AF Packet", HFILL}
},
{&hf_edcp_fecflag,
{"FEC", "dcp-pft.fec",
FT_BOOLEAN, BASE_NONE, NULL, 0x8000,
"When set the optional RS header is present", HFILL}
},
{&hf_edcp_addrflag,
{"Addr", "dcp-pft.addr",
FT_BOOLEAN, BASE_NONE, NULL, 0x4000,
"When set the optional transport header is present", HFILL}
},
{&hf_edcp_plen,
{"fragment length", "dcp-pft.len",
FT_UINT16, BASE_DEC, NULL, 0x3fff,
"length in bytes of the payload of this fragment", HFILL}
},
{&hf_edcp_rsk,
{"RSk", "dcp-pft.rsk",
FT_UINT8, BASE_DEC, NULL, 0,
"The length of the Reed Solomon data word", HFILL}
},
{&hf_edcp_rsz,
{"RSz", "dcp-pft.rsz",
FT_UINT8, BASE_DEC, NULL, 0,
"The number of padding bytes in the last Reed Solomon block", HFILL}
},
{&hf_edcp_source,
{"source addr", "dcp-pft.source",
FT_UINT16, BASE_DEC, NULL, 0,
"PFT source identifier", HFILL}
},
{&hf_edcp_dest,
{"dest addr", "dcp-pft.dest",
FT_UINT16, BASE_DEC, NULL, 0,
"PFT destination identifier", HFILL}
},
{&hf_edcp_hcrc,
{"header CRC", "dcp-pft.crc",
FT_UINT16, BASE_HEX, NULL, 0,
"PFT Header CRC", HFILL}
},
{&hf_edcp_hcrc_ok,
{"PFT CRC OK", "dcp-pft.crc_ok",
FT_BOOLEAN, BASE_NONE, NULL, 0,
"PFT Header CRC OK", HFILL}
},
{&hf_edcp_fragments,
{"Message fragments", "dcp-pft.fragments",
FT_NONE, BASE_NONE, NULL, 0x00, NULL, HFILL}},
{&hf_edcp_fragment,
{"Message fragment", "dcp-pft.fragment",
FT_FRAMENUM, BASE_NONE, NULL, 0x00, NULL, HFILL}},
{&hf_edcp_fragment_overlap,
{"Message fragment overlap", "dcp-pft.fragment.overlap",
FT_BOOLEAN, BASE_NONE, NULL, 0x00, NULL, HFILL}},
{&hf_edcp_fragment_overlap_conflicts,
{"Message fragment overlapping with conflicting data",
"dcp-pft.fragment.overlap.conflicts",
FT_BOOLEAN, BASE_NONE, NULL, 0x00, NULL, HFILL}},
{&hf_edcp_fragment_multiple_tails,
{"Message has multiple tail fragments",
"dcp-pft.fragment.multiple_tails",
FT_BOOLEAN, BASE_NONE, NULL, 0x00, NULL, HFILL}},
{&hf_edcp_fragment_too_long_fragment,
{"Message fragment too long", "dcp-pft.fragment.too_long_fragment",
FT_BOOLEAN, BASE_NONE, NULL, 0x00, NULL, HFILL}},
{&hf_edcp_fragment_error,
{"Message defragmentation error", "dcp-pft.fragment.error",
FT_FRAMENUM, BASE_NONE, NULL, 0x00, NULL, HFILL}},
{&hf_edcp_reassembled_in,
{"Reassembled in", "dcp-pft.reassembled.in",
FT_FRAMENUM, BASE_NONE, NULL, 0x00, NULL, HFILL}},
{&hf_edcp_c_max,
{"C max", "dcp-pft.cmax",
FT_UINT16, BASE_DEC, NULL, 0,
"Maximum number of RS chunks sent", HFILL}
},
{&hf_edcp_rx_min,
{"Rx min", "dcp-pft.rxmin",
FT_UINT16, BASE_DEC, NULL, 0,
"Minimum number of fragments needed for RS decode", HFILL}
},
{&hf_edcp_rs_corrected,
{"RS Symbols Corrected", "dcp-pft.rs_corrected",
FT_INT16, BASE_DEC, NULL, 0,
"Number of symbols corrected by RS decode or -1 for failure", HFILL}
},
{&hf_edcp_rs_ok,
{"RS decode OK", "dcp-pft.rs_ok",
FT_BOOLEAN, BASE_NONE, NULL, 0,
"successfully decoded RS blocks", HFILL}
},
{&hf_edcp_pft_payload,
{"payload", "dcp-pft.payload",
FT_BYTES, BASE_HEX, NULL, 0,
"PFT Payload", HFILL}
}
};
static hf_register_info hf_tpl[] = {
{&hf_tpl_tlv,
{"tag", "dcp-tpl.tlv",
FT_BYTES, BASE_HEX, NULL, 0,
"Tag Packet", HFILL}
},
{&hf_tpl_ptr,
{"Type", "dcp-tpl.ptr",
FT_STRING, BASE_NONE, NULL, 0,
"Protocol Type & Revision", HFILL}
}
};
/* Setup protocol subtree array */
static gint *ett[] = {
&ett_edcp,
&ett_af,
&ett_pft,
&ett_tpl,
&ett_edcp_fragment,
&ett_edcp_fragments
};
if (proto_dcp_etsi == -1) {
proto_dcp_etsi = proto_register_protocol ("ETSI Distribution & Communication Protocol (for DRM)", /* name */
"DCP (ETSI)", /* short name */
"dcp-etsi" /* abbrev */
);
proto_af = proto_register_protocol ("DCP Application Framing Layer", "DCP-AF", "dcp-af");
proto_pft = proto_register_protocol ("DCP Protection, Fragmentation & Transport Layer", "DCP-PFT", "dcp-pft");
proto_tpl = proto_register_protocol ("DCP Tag Packet Layer", "DCP-TPL", "dcp-tpl");
}
dcp_module = prefs_register_protocol (proto_dcp_etsi, proto_reg_handoff_dcp_etsi);
proto_register_field_array (proto_dcp_etsi, hf_edcp, array_length (hf_edcp));
proto_register_field_array (proto_af, hf_af, array_length (hf_af));
proto_register_field_array (proto_pft, hf_pft, array_length (hf_pft));
proto_register_field_array (proto_tpl, hf_tpl, array_length (hf_tpl));
proto_register_subtree_array (ett, array_length (ett));
/* subdissector code */
dcp_dissector_table = register_dissector_table("dcp-etsi.sync",
"DCP Sync", FT_STRING, BASE_NONE);
af_dissector_table = register_dissector_table("dcp-af.pt",
"AF Payload Type", FT_UINT8, BASE_DEC);
tpl_dissector_table = register_dissector_table("dcp-tpl.ptr",
"AF Payload Type", FT_STRING, BASE_NONE);
register_init_routine(dcp_init_protocol);
}

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/*
* Reed-Solomon coding and decoding
* Phil Karn (karn@ka9q.ampr.org) September 1996
* Separate CCSDS version create Dec 1998, merged into this version May 1999
*
* This file is derived from my generic RS encoder/decoder, which is
* in turn based on the program "new_rs_erasures.c" by Robert
* Morelos-Zaragoza (robert@spectra.eng.hawaii.edu) and Hari Thirumoorthy
* (harit@spectra.eng.hawaii.edu), Aug 1995
* Copyright 1999 Phil Karn, KA9Q
* May be used under the terms of the GNU public license
*/
#include <stdio.h>
#include "reedsolomon.h"
#ifdef CCSDS
/* CCSDS field generator polynomial: 1+x+x^2+x^7+x^8 */
int Pp[MM+1] = { 1, 1, 1, 0, 0, 0, 0, 1, 1 };
#else /* not CCSDS */
/* MM, KK, B0, PRIM are user-defined in rs.h */
/* Primitive polynomials - see Lin & Costello, Appendix A,
* and Lee & Messerschmitt, p. 453.
*/
#if(MM == 2)/* Admittedly silly */
int Pp[MM+1] = { 1, 1, 1 };
#elif(MM == 3)
/* 1 + x + x^3 */
int Pp[MM+1] = { 1, 1, 0, 1 };
#elif(MM == 4)
/* 1 + x + x^4 */
int Pp[MM+1] = { 1, 1, 0, 0, 1 };
#elif(MM == 5)
/* 1 + x^2 + x^5 */
int Pp[MM+1] = { 1, 0, 1, 0, 0, 1 };
#elif(MM == 6)
/* 1 + x + x^6 */
int Pp[MM+1] = { 1, 1, 0, 0, 0, 0, 1 };
#elif(MM == 7)
/* 1 + x^3 + x^7 */
int Pp[MM+1] = { 1, 0, 0, 1, 0, 0, 0, 1 };
#elif(MM == 8)
/* 1+x^2+x^3+x^4+x^8 */
int Pp[MM+1] = { 1, 0, 1, 1, 1, 0, 0, 0, 1 };
#elif(MM == 9)
/* 1+x^4+x^9 */
int Pp[MM+1] = { 1, 0, 0, 0, 1, 0, 0, 0, 0, 1 };
#elif(MM == 10)
/* 1+x^3+x^10 */
int Pp[MM+1] = { 1, 0, 0, 1, 0, 0, 0, 0, 0, 0, 1 };
#elif(MM == 11)
/* 1+x^2+x^11 */
int Pp[MM+1] = { 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1 };
#elif(MM == 12)
/* 1+x+x^4+x^6+x^12 */
int Pp[MM+1] = { 1, 1, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1 };
#elif(MM == 13)
/* 1+x+x^3+x^4+x^13 */
int Pp[MM+1] = { 1, 1, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1 };
#elif(MM == 14)
/* 1+x+x^6+x^10+x^14 */
int Pp[MM+1] = { 1, 1, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1 };
#elif(MM == 15)
/* 1+x+x^15 */
int Pp[MM+1] = { 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1 };
#elif(MM == 16)
/* 1+x+x^3+x^12+x^16 */
int Pp[MM+1] = { 1, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1 };
#else
#error "Either CCSDS must be defined, or MM must be set in range 2-16"
#endif
#endif
#ifdef STANDARD_ORDER /* first byte transmitted is index of x**(KK-1) in message poly*/
/* definitions used in the encode routine*/
#define MESSAGE(i) data[KK-(i)-1]
#define REMAINDER(i) bb[NN-KK-(i)-1]
/* definitions used in the decode routine*/
#define RECEIVED(i) data[NN-1-(i)]
#define ERAS_INDEX(i) (NN-1-eras_pos[i])
#define INDEX_TO_POS(i) (NN-1-(i))
#else /* first byte transmitted is index of x**0 in message polynomial*/
/* definitions used in the encode routine*/
#define MESSAGE(i) data[i]
#define REMAINDER(i) bb[i]
/* definitions used in the decode routine*/
#define RECEIVED(i) data[i]
#define ERAS_INDEX(i) eras_pos[i]
#define INDEX_TO_POS(i) i
#endif
/* This defines the type used to store an element of the Galois Field
* used by the code. Make sure this is something larger than a char if
* if anything larger than GF(256) is used.
*
* Note: unsigned char will work up to GF(256) but int seems to run
* faster on the Pentium.
*/
typedef int gf;
/* index->polynomial form conversion table */
static gf Alpha_to[NN + 1];
/* Polynomial->index form conversion table */
static gf Index_of[NN + 1];
/* No legal value in index form represents zero, so
* we need a special value for this purpose
*/
#define A0 (NN)
/* Generator polynomial g(x) in index form */
static gf Gg[NN - KK + 1];
static int RS_init; /* Initialization flag */
/* Compute x % NN, where NN is 2**MM - 1,
* without a slow divide
*/
/* static inline gf*/
static gf
modnn(int x)
{
while (x >= NN) {
x -= NN;
x = (x >> MM) + (x & NN);
}
return x;
}
#define min_(a,b) ((a) < (b) ? (a) : (b))
#define CLEAR(a,n) {\
int ci;\
for(ci=(n)-1;ci >=0;ci--)\
(a)[ci] = 0;\
}
#define COPY(a,b,n) {\
int ci;\
for(ci=(n)-1;ci >=0;ci--)\
(a)[ci] = (b)[ci];\
}
#define COPYDOWN(a,b,n) {\
int ci;\
for(ci=(n)-1;ci >=0;ci--)\
(a)[ci] = (b)[ci];\
}
static void init_rs(void);
#ifdef CCSDS
/* Conversion lookup tables from conventional alpha to Berlekamp's
* dual-basis representation. Used in the CCSDS version only.
* taltab[] -- convert conventional to dual basis
* tal1tab[] -- convert dual basis to conventional
* Note: the actual RS encoder/decoder works with the conventional basis.
* So data is converted from dual to conventional basis before either
* encoding or decoding and then converted back.
*/
static unsigned char taltab[NN+1],tal1tab[NN+1];
static unsigned char tal[] = { 0x8d, 0xef, 0xec, 0x86, 0xfa, 0x99, 0xaf, 0x7b };
/* Generate conversion lookup tables between conventional alpha representation
* (@**7, @**6, ...@**0)
* and Berlekamp's dual basis representation
* (l0, l1, ...l7)
*/
static void
gen_ltab(void)
{
int i,j,k;
for(i=0;i<256;i++){/* For each value of input */
taltab[i] = 0;
for(j=0;j<8;j++) /* for each column of matrix */
for(k=0;k<8;k++){ /* for each row of matrix */
if(i & (1<<k))
taltab[i] ^= tal[7-k] & (1<<j);
}
tal1tab[taltab[i]] = i;
}
}
#endif /* CCSDS */
#if PRIM != 1
static int Ldec;/* Decrement for aux location variable in Chien search */
static void
gen_ldec(void)
{
for(Ldec=1;(Ldec % PRIM) != 0;Ldec+= NN)
;
Ldec /= PRIM;
}
#else
#define Ldec 1
#endif
/* generate GF(2**m) from the irreducible polynomial p(X) in Pp[0]..Pp[m]
lookup tables: index->polynomial form alpha_to[] contains j=alpha**i;
polynomial form -> index form index_of[j=alpha**i] = i
alpha=2 is the primitive element of GF(2**m)
HARI's COMMENT: (4/13/94) alpha_to[] can be used as follows:
Let @ represent the primitive element commonly called "alpha" that
is the root of the primitive polynomial p(x). Then in GF(2^m), for any
0 <= i <= 2^m-2,
@^i = a(0) + a(1) @ + a(2) @^2 + ... + a(m-1) @^(m-1)
where the binary vector (a(0),a(1),a(2),...,a(m-1)) is the representation
of the integer "alpha_to[i]" with a(0) being the LSB and a(m-1) the MSB. Thus for
example the polynomial representation of @^5 would be given by the binary
representation of the integer "alpha_to[5]".
Similarily, index_of[] can be used as follows:
As above, let @ represent the primitive element of GF(2^m) that is
the root of the primitive polynomial p(x). In order to find the power
of @ (alpha) that has the polynomial representation
a(0) + a(1) @ + a(2) @^2 + ... + a(m-1) @^(m-1)
we consider the integer "i" whose binary representation with a(0) being LSB
and a(m-1) MSB is (a(0),a(1),...,a(m-1)) and locate the entry
"index_of[i]". Now, @^index_of[i] is that element whose polynomial
representation is (a(0),a(1),a(2),...,a(m-1)).
NOTE:
The element alpha_to[2^m-1] = 0 always signifying that the
representation of "@^infinity" = 0 is (0,0,0,...,0).
Similarily, the element index_of[0] = A0 always signifying
that the power of alpha which has the polynomial representation
(0,0,...,0) is "infinity".
*/
static void
generate_gf(void)
{
register int i, mask;
mask = 1;
Alpha_to[MM] = 0;
for (i = 0; i < MM; i++) {
Alpha_to[i] = mask;
Index_of[Alpha_to[i]] = i;
/* If Pp[i] == 1 then, term @^i occurs in poly-repr of @^MM */
if (Pp[i] != 0)
Alpha_to[MM] ^= mask; /* Bit-wise EXOR operation */
mask <<= 1; /* single left-shift */
}
Index_of[Alpha_to[MM]] = MM;
/*
* Have obtained poly-repr of @^MM. Poly-repr of @^(i+1) is given by
* poly-repr of @^i shifted left one-bit and accounting for any @^MM
* term that may occur when poly-repr of @^i is shifted.
*/
mask >>= 1;
for (i = MM + 1; i < NN; i++) {
if (Alpha_to[i - 1] >= mask)
Alpha_to[i] = Alpha_to[MM] ^ ((Alpha_to[i - 1] ^ mask) << 1);
else
Alpha_to[i] = Alpha_to[i - 1] << 1;
Index_of[Alpha_to[i]] = i;
}
Index_of[0] = A0;
Alpha_to[NN] = 0;
}
/*
* Obtain the generator polynomial of the TT-error correcting, length
* NN=(2**MM -1) Reed Solomon code from the product of (X+@**(B0+i)), i = 0,
* ... ,(2*TT-1)
*
* Examples:
*
* If B0 = 1, TT = 1. deg(g(x)) = 2*TT = 2.
* g(x) = (x+@) (x+@**2)
*
* If B0 = 0, TT = 2. deg(g(x)) = 2*TT = 4.
* g(x) = (x+1) (x+@) (x+@**2) (x+@**3)
*/
static void
gen_poly(void)
{
register int i, j;
Gg[0] = 1;
for (i = 0; i < NN - KK; i++) {
Gg[i+1] = 1;
/*
* Below multiply (Gg[0]+Gg[1]*x + ... +Gg[i]x^i) by
* (@**(B0+i)*PRIM + x)
*/
for (j = i; j > 0; j--)
if (Gg[j] != 0)
Gg[j] = Gg[j - 1] ^ Alpha_to[modnn((Index_of[Gg[j]]) + (B0 + i) *PRIM)];
else
Gg[j] = Gg[j - 1];
/* Gg[0] can never be zero */
Gg[0] = Alpha_to[modnn(Index_of[Gg[0]] + (B0 + i) * PRIM)];
}
/* convert Gg[] to index form for quicker encoding */
for (i = 0; i <= NN - KK; i++)
Gg[i] = Index_of[Gg[i]];
}
/*
* take the string of symbols in data[i], i=0..(k-1) and encode
* systematically to produce NN-KK parity symbols in bb[0]..bb[NN-KK-1] data[]
* is input and bb[] is output in polynomial form. Encoding is done by using
* a feedback shift register with appropriate connections specified by the
* elements of Gg[], which was generated above. Codeword is c(X) =
* data(X)*X**(NN-KK)+ b(X)
*/
int
encode_rs(dtype data[KK], dtype bb[NN-KK])
{
register int i, j;
gf feedback;
#if DEBUG >= 1 && MM != 8
/* Check for illegal input values */
for(i=0;i<KK;i++)
if(MESSAGE(i) > NN)
return -1;
#endif
if(!RS_init)
init_rs();
CLEAR(bb,NN-KK);
#ifdef CCSDS
/* Convert to conventional basis */
for(i=0;i<KK;i++)
MESSAGE(i) = tal1tab[MESSAGE(i)];
#endif
for(i = KK - 1; i >= 0; i--) {
feedback = Index_of[MESSAGE(i) ^ REMAINDER(NN - KK - 1)];
if (feedback != A0) { /* feedback term is non-zero */
for (j = NN - KK - 1; j > 0; j--)
if (Gg[j] != A0)
REMAINDER(j) = REMAINDER(j - 1) ^ Alpha_to[modnn(Gg[j] + feedback)];
else
REMAINDER(j) = REMAINDER(j - 1);
REMAINDER(0) = Alpha_to[modnn(Gg[0] + feedback)];
} else { /* feedback term is zero. encoder becomes a
* single-byte shifter */
for (j = NN - KK - 1; j > 0; j--)
REMAINDER(j) = REMAINDER(j - 1);
REMAINDER(0) = 0;
}
}
#ifdef CCSDS
/* Convert to l-basis */
for(i=0;i<NN;i++)
MESSAGE(i) = taltab[MESSAGE(i)];
#endif
return 0;
}
/*
* Performs ERRORS+ERASURES decoding of RS codes. If decoding is successful,
* writes the codeword into data[] itself. Otherwise data[] is unaltered.
*
* Return number of symbols corrected, or -1 if codeword is illegal
* or uncorrectable. If eras_pos is non-null, the detected error locations
* are written back. NOTE! This array must be at least NN-KK elements long.
*
* First "no_eras" erasures are declared by the calling program. Then, the
* maximum # of errors correctable is t_after_eras = floor((NN-KK-no_eras)/2).
* If the number of channel errors is not greater than "t_after_eras" the
* transmitted codeword will be recovered. Details of algorithm can be found
* in R. Blahut's "Theory ... of Error-Correcting Codes".
* Warning: the eras_pos[] array must not contain duplicate entries; decoder failure
* will result. The decoder *could* check for this condition, but it would involve
* extra time on every decoding operation.
*/
int
eras_dec_rs(dtype data[NN], int eras_pos[NN-KK], int no_eras)
{
int deg_lambda, el, deg_omega;
int i, j, r,k;
gf u,q,tmp,num1,num2,den,discr_r;
gf lambda[NN-KK + 1], s[NN-KK + 1]; /* Err+Eras Locator poly
* and syndrome poly */
gf b[NN-KK + 1], t[NN-KK + 1], omega[NN-KK + 1];
gf root[NN-KK], reg[NN-KK + 1], loc[NN-KK];
int syn_error, count;
if(!RS_init)
init_rs();
#ifdef CCSDS
/* Convert to conventional basis */
for(i=0;i<NN;i++)
RECEIVED(i) = tal1tab[RECEIVED(i)];
#endif
#if DEBUG >= 1 && MM != 8
/* Check for illegal input values */
for(i=0;i<NN;i++)
if(RECEIVED(i) > NN)
return -1;
#endif
/* form the syndromes; i.e., evaluate data(x) at roots of g(x)
* namely @**(B0+i)*PRIM, i = 0, ... ,(NN-KK-1)
*/
for(i=1;i<=NN-KK;i++){
s[i] = RECEIVED(0);
}
for(j=1;j<NN;j++){
if(RECEIVED(j) == 0)
continue;
tmp = Index_of[RECEIVED(j)];
/* s[i] ^= Alpha_to[modnn(tmp + (B0+i-1)*j)]; */
for(i=1;i<=NN-KK;i++)
s[i] ^= Alpha_to[modnn(tmp + (B0+i-1)*PRIM*j)];
}
/* Convert syndromes to index form, checking for nonzero condition */
syn_error = 0;
for(i=1;i<=NN-KK;i++){
syn_error |= s[i];
/*printf("syndrome %d = %x\n",i,s[i]);*/
s[i] = Index_of[s[i]];
}
if (!syn_error) {
/* if syndrome is zero, data[] is a codeword and there are no
* errors to correct. So return data[] unmodified
*/
count = 0;
goto finish;
}
CLEAR(&lambda[1],NN-KK);
lambda[0] = 1;
if (no_eras > 0) {
/* Init lambda to be the erasure locator polynomial */
lambda[1] = Alpha_to[modnn(PRIM * ERAS_INDEX(0))];
for (i = 1; i < no_eras; i++) {
u = modnn(PRIM*ERAS_INDEX(i));
for (j = i+1; j > 0; j--) {
tmp = Index_of[lambda[j - 1]];
if(tmp != A0)
lambda[j] ^= Alpha_to[modnn(u + tmp)];
}
}
#if DEBUG >= 1
/* Test code that verifies the erasure locator polynomial just constructed
Needed only for decoder debugging. */
/* find roots of the erasure location polynomial */
for(i=1;i<=no_eras;i++)
reg[i] = Index_of[lambda[i]];
count = 0;
for (i = 1,k=NN-Ldec; i <= NN; i++,k = modnn(NN+k-Ldec)) {
q = 1;
for (j = 1; j <= no_eras; j++)
if (reg[j] != A0) {
reg[j] = modnn(reg[j] + j);
q ^= Alpha_to[reg[j]];
}
if (q != 0)
continue;
/* store root and error location number indices */
root[count] = i;
loc[count] = k;
count++;
}
if (count != no_eras) {
printf("\n lambda(x) is WRONG\n");
count = -1;
goto finish;
}
#if DEBUG >= 2
printf("\n Erasure positions as determined by roots of Eras Loc Poly:\n");
for (i = 0; i < count; i++)
printf("%d ", loc[i]);
printf("\n");
#endif
#endif
}
for(i=0;i<NN-KK+1;i++)
b[i] = Index_of[lambda[i]];
/*
* Begin Berlekamp-Massey algorithm to determine error+erasure
* locator polynomial
*/
r = no_eras;
el = no_eras;
while (++r <= NN-KK) { /* r is the step number */
/* Compute discrepancy at the r-th step in poly-form */
discr_r = 0;
for (i = 0; i < r; i++){
if ((lambda[i] != 0) && (s[r - i] != A0)) {
discr_r ^= Alpha_to[modnn(Index_of[lambda[i]] + s[r - i])];
}
}
discr_r = Index_of[discr_r]; /* Index form */
if (discr_r == A0) {
/* 2 lines below: B(x) <-- x*B(x) */
COPYDOWN(&b[1],b,NN-KK);
b[0] = A0;
} else {
/* 7 lines below: T(x) <-- lambda(x) - discr_r*x*b(x) */
t[0] = lambda[0];
for (i = 0 ; i < NN-KK; i++) {
if(b[i] != A0)
t[i+1] = lambda[i+1] ^ Alpha_to[modnn(discr_r + b[i])];
else
t[i+1] = lambda[i+1];
}
if (2 * el <= r + no_eras - 1) {
el = r + no_eras - el;
/*
* 2 lines below: B(x) <-- inv(discr_r) *
* lambda(x)
*/
for (i = 0; i <= NN-KK; i++)
b[i] = (lambda[i] == 0) ? A0 : modnn(Index_of[lambda[i]] - discr_r + NN);
} else {
/* 2 lines below: B(x) <-- x*B(x) */
COPYDOWN(&b[1],b,NN-KK);
b[0] = A0;
}
COPY(lambda,t,NN-KK+1);
}
}
/* Convert lambda to index form and compute deg(lambda(x)) */
deg_lambda = 0;
for(i=0;i<NN-KK+1;i++){
lambda[i] = Index_of[lambda[i]];
if(lambda[i] != A0)
deg_lambda = i;
}
/*
* Find roots of the error+erasure locator polynomial by Chien
* Search
*/
COPY(&reg[1],&lambda[1],NN-KK);
count = 0; /* Number of roots of lambda(x) */
for (i = 1,k=NN-Ldec; i <= NN; i++,k = modnn(NN+k-Ldec)) {
q = 1;
for (j = deg_lambda; j > 0; j--){
if (reg[j] != A0) {
reg[j] = modnn(reg[j] + j);
q ^= Alpha_to[reg[j]];
}
}
if (q != 0)
continue;
/* store root (index-form) and error location number */
root[count] = i;
loc[count] = k;
/* If we've already found max possible roots,
* abort the search to save time
*/
if(++count == deg_lambda)
break;
}
if (deg_lambda != count) {
/*
* deg(lambda) unequal to number of roots => uncorrectable
* error detected
*/
count = -1;
goto finish;
}
/*
* Compute err+eras evaluator poly omega(x) = s(x)*lambda(x) (modulo
* x**(NN-KK)). in index form. Also find deg(omega).
*/
deg_omega = 0;
for (i = 0; i < NN-KK;i++){
tmp = 0;
j = (deg_lambda < i) ? deg_lambda : i;
for(;j >= 0; j--){
if ((s[i + 1 - j] != A0) && (lambda[j] != A0))
tmp ^= Alpha_to[modnn(s[i + 1 - j] + lambda[j])];
}
if(tmp != 0)
deg_omega = i;
omega[i] = Index_of[tmp];
}
omega[NN-KK] = A0;
/*
* Compute error values in poly-form. num1 = omega(inv(X(l))), num2 =
* inv(X(l))**(B0-1) and den = lambda_pr(inv(X(l))) all in poly-form
*/
for (j = count-1; j >=0; j--) {
num1 = 0;
for (i = deg_omega; i >= 0; i--) {
if (omega[i] != A0)
num1 ^= Alpha_to[modnn(omega[i] + i * root[j])];
}
num2 = Alpha_to[modnn(root[j] * (B0 - 1) + NN)];
den = 0;
/* lambda[i+1] for i even is the formal derivative lambda_pr of lambda[i] */
for (i = min_(deg_lambda,NN-KK-1) & ~1; i >= 0; i -=2) {
if(lambda[i+1] != A0)
den ^= Alpha_to[modnn(lambda[i+1] + i * root[j])];
}
if (den == 0) {
#if DEBUG >= 1
printf("\n ERROR: denominator = 0\n");
#endif
/* Convert to dual- basis */
count = -1;
goto finish;
}
/* Apply error to data */
if (num1 != 0) {
RECEIVED(loc[j]) ^= Alpha_to[modnn(Index_of[num1] + Index_of[num2] + NN - Index_of[den])];
}
}
finish:
#ifdef CCSDS
/* Convert to dual- basis */
for(i=0;i<NN;i++)
RECEIVED(i) = taltab[RECEIVED(i)];
#endif
if(eras_pos != NULL){
for(i=0;i<count;i++){
if(eras_pos!= NULL)
eras_pos[i] = INDEX_TO_POS(loc[i]);
}
}
return count;
}
/* Encoder/decoder initialization - call this first! */
static void
init_rs(void)
{
generate_gf();
gen_poly();
#ifdef CCSDS
gen_ltab();
#endif
#if PRIM != 1
gen_ldec();
#endif
RS_init = 1;
}

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#ifdef __cplusplus
extern "C" {
#endif
/* Global definitions for Reed-Solomon encoder/decoder
* Phil Karn KA9Q, September 1996
*/
/* Set one of these to enable encoder/decoder debugging and error checking,
* at the expense of speed */
/* #undef DEBUG 1*/
/* #undef DEBUG 2*/
#undef DEBUG
/* To select the CCSDS standard (255,223) code, define CCSDS. This
* implies standard values for MM, KK, B0 and PRIM.
*/
/* #undef CCSDS 1*/
#undef CCSDS
#ifndef CCSDS
/* Otherwise, leave CCSDS undefined and set the parameters below:
*
* Set MM to be the size of each code symbol in bits. The Reed-Solomon
* block size will then be NN = 2**M - 1 symbols. Supported values are
* defined in rs.c.
*/
#define MM 8 /* Symbol size in bits */
/*
* Set KK to be the number of data symbols in each block, which must be
* less than the block size. The code will then be able to correct up
* to NN-KK erasures or (NN-KK)/2 errors, or combinations thereof with
* each error counting as two erasures.
*/
#define KK 207 /* Number of data symbols per block */
/* Set B0 to the first root of the generator polynomial, in alpha form, and
* set PRIM to the power of alpha used to generate the roots of the
* generator polynomial. The generator polynomial will then be
* @**PRIM*B0, @**PRIM*(B0+1), @**PRIM*(B0+2)...@**PRIM*(B0+NN-KK)
* where "@" represents a lower case alpha.
*/
#define B0 1 /* First root of generator polynomial, alpha form */
#define PRIM 1 /* power of alpha used to generate roots of generator poly */
#define STANDARD_ORDER
/* If you want to select your own field generator polynomial, you'll have
* to edit that in rs.c.
*/
#else /* CCSDS */
/* Don't change these, they're CCSDS standard */
#define MM 8
#define KK 223
#define B0 112
#define PRIM 11
#endif
#define NN ((1 << MM) - 1)
#if MM <= 8
typedef unsigned char dtype;
#else
typedef unsigned int dtype;
#endif
/* Reed-Solomon encoding
* data[] is the input block, parity symbols are placed in bb[]
* bb[] may lie past the end of the data, e.g., for (255,223):
* encode_rs(&data[0],&data[223]);
*/
int encode_rs(dtype data[], dtype bb[]);
/* Reed-Solomon erasures-and-errors decoding
* The received block goes into data[], and a list of zero-origin
* erasure positions, if any, goes in eras_pos[] with a count in no_eras.
*
* The decoder corrects the symbols in place, if possible and returns
* the number of corrected symbols. If the codeword is illegal or
* uncorrectible, the data array is unchanged and -1 is returned
*/
int eras_dec_rs(dtype data[], int eras_pos[], int no_eras);
#ifdef __cplusplus
}
#endif