2 * Routines for Wellfleet Compression frame disassembly
3 * Copyright 2001, Jeffrey C. Foster <jfoste@woodward.com>
5 * $Id: packet-wcp.c,v 1.27 2002/08/02 23:36:04 jmayer Exp $
7 * Ethereal - Network traffic analyzer
8 * By Gerald Combs <gerald@ethereal.com>
11 * This program is free software; you can redistribute it and/or
12 * modify it under the terms of the GNU General Public License
13 * as published by the Free Software Foundation; either version 2
14 * of the License, or (at your option) any later version.
16 * This program is distributed in the hope that it will be useful,
17 * but WITHOUT ANY WARRANTY; without even the implied warranty of
18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
19 * GNU General Public License for more details.
21 * You should have received a copy of the GNU General Public License
22 * along with this program; if not, write to the Free Software
23 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
26 * Add preference to allow/disallow decompression
27 * Calculate and verify check byte (last byte), if only we knew how!
28 * Handle Wellfleet compression over PPP links.
29 * - This will require changing the sub-dissector call
30 * routine to determine if layer 2 is frame relay or
31 * or PPP and different sub-dissector routines for each.
33 * Based upon information in the Nortel TCL based Pcaptap code.
34 *http://www.mynetworkforum.com/tools/PCAPTAP/pcaptap-Win32-3.00.exe
37 *http://www.rasip.fer.hr/research/compress/algorithms/fund/lz/lzss.html
41 * Wellfleet compression is a variation on LZSS encoding.
43 * Compression is done by keeping a sliding window of previous
44 * data transmited. The sender will use a pattern match to
45 * encode repeated data as a data pointer field. Then a stream
46 * of pointers and actual data bytes. The pointer values include
47 * an offset to previous data in the stream and the length of the
50 * The data pattern matching is done on the octects.
52 * The data is encoded as 8 field blocks with a compression flag
53 * byte at the beginning. If the bit is set in the compression
54 * flag, then that field has a compression field. If it isn't set
55 * then the byte is raw data.
57 * The compression field is either 2 or 3 bytes long. The length
58 * is determined by the length of the matching data, for short
59 * matches the match length is encoded in the high nibble of the
60 * first byte. Otherwise the third byte of the field contains
65 * High order nibble of the offset
68 * 1 = length is in 3rd byte
69 * 2-F = length of matching data - 1
72 * Lower byte of the source offset.
75 * Length of match - 1 if First byte upper nibble = 1, otherwise
76 * this byte isn't added to data stream.
79 * Uncompressed data (hex): 11 22 22 22 22 33 44 55 66 77
83 * Flag bits: 0x20 (third field is compressed)
84 * Data: 11 22 20 00 33 44 55
86 * raw data ------+--+ / /
87 * (Comp length - 1)<<4+ /
88 * Data offset ----------+
90 * Output data (hex): 20 11 22 20 00 33 44 55 66 77
92 * In this example the copy src is one byte behind the copy destination
93 * so if appears as if output is being loaded with the source byte.
106 #include <epan/packet.h>
107 #include "packet-frame.h"
108 #include <epan/conversation.h>
112 #define MAX_WIN_BUF_LEN 0x7fff /* storage size for decompressed data */
113 #define MAX_WCP_BUF_LEN 2048 /* storage size for decompressed data */
114 #define FROM_DCE 0x80 /* for direction setting */
119 guint8 buffer[MAX_WIN_BUF_LEN];
123 /*XXX do I really want the length in here */
127 guint8 buffer[MAX_WCP_BUF_LEN];
132 #define wcp_win_init_count 4
133 #define wcp_packet_init_count 10
135 #define wcp_win_length (sizeof(wcp_window_t))
136 #define wcp_packet_length (sizeof(wcp_pdata_t))
138 static GMemChunk *wcp_window = NULL;
139 static GMemChunk *wcp_pdata = NULL;
141 static int proto_wcp = -1;
142 static int hf_wcp_cmd = -1;
143 static int hf_wcp_ext_cmd = -1;
144 static int hf_wcp_seq = -1;
145 static int hf_wcp_chksum = -1;
146 static int hf_wcp_tid = -1;
147 static int hf_wcp_rev = -1;
148 static int hf_wcp_init = -1;
149 static int hf_wcp_seq_size = -1;
150 static int hf_wcp_alg = -1;
151 static int hf_wcp_alg_cnt = -1;
152 static int hf_wcp_alg_a = -1;
153 static int hf_wcp_alg_b = -1;
154 static int hf_wcp_alg_c = -1;
155 static int hf_wcp_alg_d = -1;
156 static int hf_wcp_rexmit = -1;
158 static int hf_wcp_hist_size = -1;
159 static int hf_wcp_ppc = -1;
160 static int hf_wcp_pib = -1;
162 static int hf_wcp_comp_bits = -1;
163 static int hf_wcp_comp_marker = -1;
164 static int hf_wcp_short_len = -1;
165 static int hf_wcp_long_len = -1;
166 static int hf_wcp_short_run = -1;
167 static int hf_wcp_long_run = -1;
168 static int hf_wcp_offset = -1;
170 static gint ett_wcp = -1;
171 static gint ett_wcp_field = -1;
173 static dissector_handle_t fr_uncompressed_handle;
176 * Bits in the address field.
178 #define WCP_CMD 0xf0 /* WCP Command */
179 #define WCP_EXT_CMD 0x0f /* WCP Extended Command */
180 #define WCP_SEQ 0x0fff /* WCP Sequence number */
181 #define WCP_OFFSET_MASK 0x0fff /* WCP Pattern source offset */
183 #define PPC_COMPRESSED_IND 0x0
184 #define PPC_UNCOMPRESSED_IND 0x1
185 #define PPC_TPPC_COMPRESSED_IND 0x2
186 #define PPC_TPPC_UNCOMPRESSED_IND 0x3
187 #define CONNECT_REQ 0x4
188 #define CONNECT_ACK 0x5
189 #define CONNECT_NAK 0x6
190 #define DISCONNECT_REQ 0x7
191 #define DISCONNECT_ACK 0x8
194 #define RESET_REQ 0xb
195 #define RESET_ACK 0xc
196 #define REXMIT_NAK 0xd
199 static const value_string cmd_string[] = {
200 {0, "Compressed Data"},
201 {1, "Uncompressed Data"},
206 static const value_string ext_cmd_string[] = {
207 {0, "Per Packet Compression"},
218 static tvbuff_t *wcp_uncompress( tvbuff_t *src_tvb, int offset, packet_info *pinfo, proto_tree *tree);
219 static wcp_window_t *get_wcp_window_ptr( packet_info *pinfo);
222 dissect_wcp_con_req(tvbuff_t *tvb, int offset, proto_tree *tree) {
224 /* WCP connector request message */
226 guint alg_cnt = tvb_get_guint8(tvb, 5);
228 proto_tree_add_uint(tree, hf_wcp_tid, tvb, offset, 2, tvb_get_ntohs(tvb, offset));
229 proto_tree_add_uint(tree, hf_wcp_rev, tvb, offset + 2, 1, tvb_get_guint8(tvb, offset + 2));
230 proto_tree_add_uint(tree, hf_wcp_init, tvb, offset + 3, 1, tvb_get_guint8(tvb, offset + 3));
231 proto_tree_add_uint(tree, hf_wcp_seq_size, tvb, offset + 4, 1, tvb_get_guint8(tvb, offset + 4));
232 proto_tree_add_uint(tree, hf_wcp_alg_cnt, tvb, offset + 5, 1, alg_cnt);
233 proto_tree_add_uint(tree, hf_wcp_alg_a, tvb, offset + 6, 1, tvb_get_guint8(tvb, offset + 6));
235 proto_tree_add_uint(tree, hf_wcp_alg_b, tvb, offset + 7, 1, tvb_get_guint8(tvb, offset + 7));
237 proto_tree_add_uint(tree, hf_wcp_alg_c, tvb, offset + 8, 1, tvb_get_guint8(tvb, offset + 8));
239 proto_tree_add_uint(tree, hf_wcp_alg_d, tvb, offset + 9, 1, tvb_get_guint8(tvb, offset + 9));
243 dissect_wcp_con_ack( tvbuff_t *tvb, int offset, proto_tree *tree){
245 /* WCP connector ack message */
247 proto_tree_add_uint(tree, hf_wcp_tid, tvb, offset, 2, tvb_get_ntohs(tvb, offset));
248 proto_tree_add_uint(tree, hf_wcp_rev, tvb, offset + 2, 1, tvb_get_guint8(tvb, offset + 2));
249 proto_tree_add_uint(tree, hf_wcp_seq_size, tvb, offset + 3, 1, tvb_get_guint8(tvb, offset + 3));
250 proto_tree_add_uint(tree, hf_wcp_alg, tvb, offset + 4, 1, tvb_get_guint8(tvb, offset + 4));
254 dissect_wcp_init( tvbuff_t *tvb, int offset, proto_tree *tree){
256 /* WCP Initiate Request/Ack message */
258 proto_tree_add_uint(tree, hf_wcp_tid, tvb, offset, 2, tvb_get_ntohs(tvb, offset));
259 proto_tree_add_uint(tree, hf_wcp_rev, tvb, offset + 2, 1, tvb_get_guint8(tvb, offset + 2));
260 proto_tree_add_uint(tree, hf_wcp_hist_size, tvb, offset + 3, 1, tvb_get_guint8(tvb, offset + 3));
261 proto_tree_add_uint(tree, hf_wcp_ppc, tvb, offset + 4, 1, tvb_get_guint8(tvb, offset + 4));
262 proto_tree_add_uint(tree, hf_wcp_pib, tvb, offset + 5, 1, tvb_get_guint8(tvb, offset + 5));
267 dissect_wcp_reset( tvbuff_t *tvb, int offset, proto_tree *tree){
269 /* Process WCP Reset Request/Ack message */
271 proto_tree_add_uint(tree, hf_wcp_tid, tvb, offset, 2, tvb_get_ntohs(tvb, offset));
275 static void wcp_save_data( tvbuff_t *tvb, packet_info *pinfo){
277 wcp_window_t *buf_ptr = 0;
280 /* discard first 2 bytes, header and last byte (check byte) */
281 len = tvb_reported_length( tvb)-3;
282 buf_ptr = get_wcp_window_ptr( pinfo);
284 if (( buf_ptr->buf_cur + len) <= (buf_ptr->buffer + MAX_WIN_BUF_LEN)){
285 tvb_memcpy( tvb, buf_ptr->buf_cur, 2, len);
286 buf_ptr->buf_cur = buf_ptr->buf_cur + len;
289 guint8 *buf_end = buf_ptr->buffer + MAX_WIN_BUF_LEN;
290 tvb_memcpy( tvb, buf_ptr->buf_cur, 2, buf_end - buf_ptr->buf_cur);
291 tvb_memcpy( tvb, buf_ptr->buffer, buf_end - buf_ptr->buf_cur-2,
292 len - (int)(buf_end - buf_ptr->buf_cur));
293 buf_ptr->buf_cur = buf_ptr->buf_cur + len - MAX_WIN_BUF_LEN;
299 static void dissect_wcp( tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree) {
301 proto_tree *wcp_tree;
304 guint16 temp, cmd, ext_cmd, seq;
307 if (check_col(pinfo->cinfo, COL_PROTOCOL))
308 col_set_str(pinfo->cinfo, COL_PROTOCOL, "WCP");
309 if (check_col(pinfo->cinfo, COL_INFO))
310 col_clear(pinfo->cinfo, COL_INFO);
312 temp =tvb_get_ntohs(tvb, 0);
314 cmd = (temp & 0xf000) >> 12;
315 ext_cmd = (temp & 0x0f00) >> 8;
324 /*XXX should test seq to be sure it the last + 1 !! */
326 if (check_col(pinfo->cinfo, COL_INFO)){
327 col_add_str(pinfo->cinfo, COL_INFO, val_to_str(cmd, cmd_string, "Unknown"));
329 col_append_fstr(pinfo->cinfo, COL_INFO, ", %s",
330 val_to_str(ext_cmd, ext_cmd_string, "Unknown"));
334 ti = proto_tree_add_item(tree, proto_wcp, tvb, 0, wcp_header_len, FALSE);
336 wcp_tree = proto_item_add_subtree(ti, ett_wcp);
338 proto_tree_add_uint(wcp_tree, hf_wcp_cmd, tvb, 0, 1, tvb_get_guint8( tvb, 0));
340 proto_tree_add_uint(wcp_tree, hf_wcp_ext_cmd, tvb, 1, 1,
341 tvb_get_guint8( tvb, 0));
344 dissect_wcp_con_req( tvb, 1, wcp_tree);
348 dissect_wcp_con_ack( tvb, 1, wcp_tree);
352 dissect_wcp_init( tvb, 1, wcp_tree);
356 dissect_wcp_reset( tvb, 1, wcp_tree);
362 proto_tree_add_uint(wcp_tree, hf_wcp_seq, tvb, 0, 2, seq);
371 if ( cmd != 1 && cmd != 0 && !(cmd == 0xf && ext_cmd == 0))
374 if ( cmd == 1) { /* uncompressed data */
375 if ( !pinfo->fd->flags.visited){ /* if first pass */
376 wcp_save_data( tvb, pinfo);
378 next_tvb = tvb_new_subset(tvb, wcp_header_len, -1, -1);
380 else { /* cmd == 0 || (cmd == 0xf && ext_cmd == 0) */
382 next_tvb = wcp_uncompress( tvb, wcp_header_len, pinfo, wcp_tree);
385 proto_tree_add_protocol_format(tree, proto_malformed, tvb, 0, 0,
386 "[Malformed Frame: Bad WCP compressed data]" );
391 if ( tree) /* add the check byte */
392 proto_tree_add_uint(wcp_tree, hf_wcp_chksum, tvb,
393 tvb_reported_length( tvb)-1, 1,
394 tvb_get_guint8( tvb, tvb_reported_length(tvb)-1));
396 call_dissector(fr_uncompressed_handle, next_tvb, pinfo, tree);
402 static guint8 *decompressed_entry( guint8 *src, guint8 *dst, int *len, guint8 * buf_start, guint8 *buf_end){
404 /* do the decompression for one field */
406 guint16 data_offset, data_cnt;
409 data_offset = (*(src++) & 0xf) << 8; /* get high byte */
410 data_offset += *(src++); /* add next byte */
412 if (( tmp & 0xf0) == 0x10){ /* 2 byte count */
416 }else { /* one byte count */
422 src = (dst - 1 - data_offset);
423 if ( src < buf_start)
424 src += MAX_WIN_BUF_LEN;
427 /*XXX could do some fancy memory moves, later if speed is problem */
431 if ( ++(*len) >MAX_WCP_BUF_LEN){
432 printf("decomp failed, len = %d\n", *len);
434 return NULL; /* end of buffer error */
436 if ( dst++ == buf_end)
438 if ( src++ == buf_end)
447 wcp_window_t *get_wcp_window_ptr( packet_info *pinfo){
449 /* find the conversation for this side of the DLCI, create one if needed */
450 /* and return the wcp_window data structure pointer */
452 conversation_t *conv;
453 wcp_window_t *wcp_win_data;
455 conv = find_conversation( &pinfo->dl_src, &pinfo->dl_src, PT_NONE,
456 ((pinfo->pseudo_header->x25.flags & FROM_DCE)? 1:0),
457 ((pinfo->pseudo_header->x25.flags & FROM_DCE)? 1:0), 0);
459 conv = conversation_new( &pinfo->dl_src, &pinfo->dl_src, PT_NONE,
460 ((pinfo->pseudo_header->x25.flags & FROM_DCE)? 1:0),
461 ((pinfo->pseudo_header->x25.flags & FROM_DCE)? 1:0),
464 wcp_win_data = conversation_get_proto_data(conv, proto_wcp);
466 wcp_win_data = g_mem_chunk_alloc( wcp_window);
467 wcp_win_data->buf_cur = wcp_win_data->buffer;
468 conversation_add_proto_data(conv, proto_wcp, wcp_win_data);
475 static tvbuff_t *wcp_uncompress( tvbuff_t *src_tvb, int offset, packet_info *pinfo, proto_tree *tree) {
477 /* do the packet data uncompression and load it into the dst buffer */
479 proto_tree *sub_tree;
483 int cnt = tvb_reported_length( src_tvb)-1; /* don't include check byte */
485 guint8 *buf = 0, *dst, *src, *buf_start, *buf_end, *tmp, comp_flag_bits = 0;
486 guint8 src_buf[ MAX_WCP_BUF_LEN];
487 tvbuff_t *volatile tvb = 0;
488 wcp_window_t *buf_ptr = 0;
489 wcp_pdata_t *volatile pdata_ptr;
491 buf_ptr = get_wcp_window_ptr( pinfo);
493 buf_start = buf_ptr->buffer;
494 buf_end = buf_start + MAX_WIN_BUF_LEN;
495 tmp = buf_ptr->buf_cur;
497 if (cnt - offset > MAX_WCP_BUF_LEN) {
499 proto_tree_add_text( tree, src_tvb, offset, -1,
500 "Compressed data exceeds maximum buffer length (%d > %d)",
501 cnt - offset, MAX_WCP_BUF_LEN);
505 src = tvb_memcpy(src_tvb, src_buf, offset, cnt - offset);
506 dst = buf_ptr->buf_cur;
508 while( offset++ < cnt){
511 if ( comp_flag_bits & 0x80){ /* if this is a compressed entry */
513 if ( !pinfo->fd->flags.visited){ /* if first pass */
514 dst = decompressed_entry( src, dst, &len, buf_start, buf_end);
516 if ((*src & 0xf0) == 0x10){
518 ti = proto_tree_add_item( tree, hf_wcp_long_run, src_tvb,
520 sub_tree = proto_item_add_subtree(ti, ett_wcp_field);
521 proto_tree_add_uint(sub_tree, hf_wcp_offset, src_tvb,
522 offset-1, 2, pntohs(src));
524 proto_tree_add_item( sub_tree, hf_wcp_long_len, src_tvb,
525 offset+1, 1, pntohs(src));
531 ti = proto_tree_add_item( tree, hf_wcp_short_run, src_tvb,
532 offset - 1, 2, *src);
533 sub_tree = proto_item_add_subtree(ti, ett_wcp_field);
534 proto_tree_add_item( sub_tree, hf_wcp_short_len, src_tvb,
536 proto_tree_add_uint(sub_tree, hf_wcp_offset, src_tvb,
537 offset-1, 2, pntohs(src));
543 if ( !pinfo->fd->flags.visited){ /* if first pass */
545 if ( dst++ == buf_end)
553 if ( len >MAX_WCP_BUF_LEN){
557 comp_flag_bits <<= 1;
559 }else { /* compressed data flag */
561 comp_flag_bits = *src++;
563 proto_tree_add_uint( tree, hf_wcp_comp_bits, src_tvb, offset-1, 1,
570 if ( pinfo->fd->flags.visited){ /* if not first pass */
571 /* get uncompressed data */
572 pdata_ptr = p_get_proto_data( pinfo->fd, proto_wcp);
574 if ( !pdata_ptr) /* exit if no data */
576 len = pdata_ptr->len;
579 /* save the new data as per packet data */
580 pdata_ptr = g_mem_chunk_alloc( wcp_pdata);
581 memcpy( &pdata_ptr->buffer, buf_ptr->buf_cur, len);
582 pdata_ptr->len = len;
584 p_add_proto_data( pinfo->fd, proto_wcp, (void*)pdata_ptr);
586 buf_ptr->buf_cur = dst;
591 tvb = tvb_new_real_data( pdata_ptr->buffer, pdata_ptr->len, pdata_ptr->len);
595 g_assert_not_reached();
599 CATCH(ReportedBoundsError) {
605 /* link new tvbuff into tvbuff chain so cleanup is done later */
606 tvb_set_child_real_data_tvbuff( src_tvb, tvb);
608 /* Add new data to the data source list */
609 add_new_data_source( pinfo, tvb, "Uncompressed WCP");
615 static void wcp_reinit( void){
617 /* Do the cleanup work when a new pass through the packet list is */
618 /* performed. re-initialize the memory chunks. */
621 g_mem_chunk_destroy(wcp_window);
623 wcp_window = g_mem_chunk_new("wcp_window", wcp_win_length,
624 wcp_win_init_count * wcp_win_length,
628 g_mem_chunk_destroy(wcp_pdata);
630 wcp_pdata = g_mem_chunk_new("wcp_pdata", wcp_packet_length,
631 wcp_packet_init_count * wcp_packet_length,
638 proto_register_wcp(void)
640 static hf_register_info hf[] = {
642 { "Command", "wcp.cmd", FT_UINT8, BASE_HEX, VALS(cmd_string), WCP_CMD,
643 "Compression Command", HFILL }},
645 { "Extended Command", "wcp.ext_cmd", FT_UINT8, BASE_HEX, VALS(ext_cmd_string), WCP_EXT_CMD,
646 "Extended Compression Command", HFILL }},
648 { "SEQ", "wcp.seq", FT_UINT16, BASE_HEX, NULL, WCP_SEQ,
649 "Sequence Number", HFILL }},
651 { "Checksum", "wcp.checksum", FT_UINT8, BASE_DEC, NULL, 0,
652 "Packet Checksum", HFILL }},
654 { "TID", "wcp.tid", FT_UINT16, BASE_DEC, NULL, 0,
657 { "Revision", "wcp.rev", FT_UINT8, BASE_DEC, NULL, 0,
658 "Revision", HFILL }},
660 { "Initiator", "wcp.init", FT_UINT8, BASE_DEC, NULL, 0,
661 "Initiator", HFILL }},
663 { "Seq Size", "wcp.seq_size", FT_UINT8, BASE_DEC, NULL, 0,
664 "Sequence Size", HFILL }},
666 { "Alg Count", "wcp.alg_cnt", FT_UINT8, BASE_DEC, NULL, 0,
667 "Algorithm Count", HFILL }},
669 { "Alg 1", "wcp.alg1", FT_UINT8, BASE_DEC, NULL, 0,
670 "Algorithm #1", HFILL }},
672 { "Alg 2", "wcp.alg2", FT_UINT8, BASE_DEC, NULL, 0,
673 "Algorithm #2", HFILL }},
675 { "Alg 3", "wcp.alg3", FT_UINT8, BASE_DEC, NULL, 0,
676 "Algorithm #3", HFILL }},
678 { "Alg 4", "wcp.alg4", FT_UINT8, BASE_DEC, NULL, 0,
679 "Algorithm #4", HFILL }},
681 { "Alg", "wcp.alg", FT_UINT8, BASE_DEC, NULL, 0,
682 "Algorithm", HFILL }},
684 { "Rexmit", "wcp.rexmit", FT_UINT8, BASE_DEC, NULL, 0,
685 "Retransmit", HFILL }},
687 { "History", "wcp.hist", FT_UINT8, BASE_DEC, NULL, 0,
688 "History Size", HFILL }},
690 { "PerPackComp", "wcp.ppc", FT_UINT8, BASE_DEC, NULL, 0,
691 "Per Packet Compression", HFILL }},
693 { "PIB", "wcp.pib", FT_UINT8, BASE_DEC, NULL, 0,
696 { "Compress Flag", "wcp.flag", FT_UINT8, BASE_HEX, NULL, 0,
697 "Compressed byte flag", HFILL }},
698 { &hf_wcp_comp_marker,
699 { "Compress Marker", "wcp.mark", FT_UINT8, BASE_BIN, NULL, 0,
700 "Compressed marker", HFILL }},
702 { "Source offset", "wcp.off", FT_UINT16, BASE_HEX, NULL, WCP_OFFSET_MASK,
703 "Data source offset", HFILL }},
705 { "Compress Length", "wcp.short_len", FT_UINT8, BASE_HEX, NULL, 0xf0,
706 "Compressed length", HFILL }},
708 { "Compress Length", "wcp.long_len", FT_UINT8, BASE_HEX, NULL, 0,
709 "Compressed length", HFILL }},
711 { "Long Compression", "wcp.long_comp", FT_UINT16, BASE_HEX, NULL, 0,
712 "Long Compression type", HFILL }},
714 { "Short Compression", "wcp.short_comp", FT_UINT8, BASE_HEX, NULL, 0,
715 "Short Compression type", HFILL }},
720 static gint *ett[] = {
725 proto_wcp = proto_register_protocol ("Wellfleet Compression", "WCP", "wcp");
726 proto_register_field_array (proto_wcp, hf, array_length(hf));
727 proto_register_subtree_array(ett, array_length(ett));
728 register_init_routine(&wcp_reinit);
733 proto_reg_handoff_wcp(void) {
734 dissector_handle_t wcp_handle;
737 * Get handle for the Frame Relay (uncompressed) dissector.
739 fr_uncompressed_handle = find_dissector("fr_uncompressed");
741 wcp_handle = create_dissector_handle(dissect_wcp, proto_wcp);
742 dissector_add("fr.ietf", NLPID_COMPRESSED, wcp_handle);
743 dissector_add("ethertype", ETHERTYPE_WCP, wcp_handle);