path: root/epan/dissectors/packet-wcp.c

/* packet-wcp.c
 * Routines for Wellfleet Compression frame disassembly
 * Copyright 2001, Jeffrey C. Foster <jfoste@woodward.com>
 *
 * Wireshark - Network traffic analyzer
 * By Gerald Combs <gerald@wireshark.org>
 * Copyright 1998
 *
 * SPDX-License-Identifier: GPL-2.0-or-later
 *
 * ToDo:
 *	Add preference to allow/disallow decompression
 *	Calculate and verify check byte (last byte), if only we knew how!
 *	Handle Wellfleet compression over PPP links.
 *		- This will require changing the sub-dissector call
 *		  routine to determine if layer 2 is frame relay or
 *		  or PPP and different sub-dissector routines for each.
 *
 * Based upon information in the Nortel TCL based Pcaptap code.
 *http://www.mynetworkforum.com/tools/PCAPTAP/pcaptap-Win32-3.00.exe
 *
 * And lzss algorithm
 *http://www.rasip.fer.hr/research/compress/algorithms/fund/lz/lzss.html
 */

/*
 * Wellfleet compression is a variation on LZSS encoding.
 *
 * Compression is done by keeping a sliding window of previous
 * data transmited. The sender will use a pattern match to
 * encode repeated data as a data pointer field. Then a stream
 * of pointers and actual data bytes. The pointer values include
 * an offset to previous data in the stream and the length of the
 *  matching data.
 *
 * The data pattern matching is done on the octets.
 *
 * The data is encoded as 8 field blocks with a compression flag
 * byte at the beginning.  If the bit is set in the compression
 * flag, then that field has a compression field. If it isn't set
 * then the byte is raw data.
 *
 * The compression field is either 2 or 3 bytes long. The length
 * is determined by the length of the matching data, for short
 * matches the match length is encoded in the high nibble of the
 * first byte. Otherwise the third byte of the field contains
 * the match length.
 *
 * First byte -
 * lower 4 bits:
 *		High order nibble of the offset
 *
 * upper 4 bits:
 *		1   = length is in 3rd byte
 *		2-F = length of matching data - 1
 *
 * Second byte -
 *  Lower byte of the source offset.
 *
 * Third byte -
 *  Length of match - 1 if First byte upper nibble = 1, otherwise
 *  this byte isn't added to data stream.
 *
 * Example:
 * 	Uncompressed data (hex):  11 22 22 22 22 33 44 55 66 77
 *
 *
 *	Compression data :
 *			Flag bits:	0x20 (third field is compressed)
 *			Data:	11 22 20 00 33 44 55
 *				/  /  /  /
 *		raw data ------+--+  /	/
 *              (Comp length - 1)<<4+  /
 *		Data offset ----------+
 *
 *	Output data (hex):  20 11 22 20 00 33 44 55 66 77
 *
 * In this example the copy src is one byte behind the copy destination
 * so if appears as if output is being loaded with the source byte.
 *
 */



#include "config.h"


#include <epan/packet.h>
#include <epan/proto_data.h>

#include <wiretap/wtap.h>
#include <wsutil/pint.h>
#include <epan/conversation.h>
#include <epan/etypes.h>
#include <epan/nlpid.h>
#include <epan/expert.h>
#include <epan/exceptions.h>

#define MAX_WIN_BUF_LEN 0x7fff		/* storage size for decompressed data */
#define MAX_WCP_BUF_LEN 2048		/* storage size for compressed data */
#define FROM_DCE	0x80		/* for direction setting */

void proto_register_wcp(void);
void proto_reg_handoff_wcp(void);

typedef struct {
	uint8_t *buf_cur;
	uint8_t buffer[MAX_WIN_BUF_LEN];
	/* initialized bytes in the buffer (since buf_cur may wrap around) */
	uint16_t initialized;
} wcp_window_t;

typedef struct {
	wcp_window_t recv;
	wcp_window_t send;
} wcp_circuit_data_t;

/* XXX do I really want the length in here */
typedef struct {
	uint16_t len;
	uint8_t buffer[MAX_WCP_BUF_LEN];
} wcp_pdata_t;


static int proto_wcp;
static int hf_wcp_cmd;
static int hf_wcp_ext_cmd;
static int hf_wcp_seq;
static int hf_wcp_chksum;
static int hf_wcp_tid;
static int hf_wcp_rev;
static int hf_wcp_init;
static int hf_wcp_seq_size;
static int hf_wcp_alg;
static int hf_wcp_alg_cnt;
static int hf_wcp_alg_a;
static int hf_wcp_alg_b;
static int hf_wcp_alg_c;
static int hf_wcp_alg_d;
/* static int hf_wcp_rexmit; */

static int hf_wcp_hist_size;
static int hf_wcp_ppc;
static int hf_wcp_pib;

static int hf_wcp_compressed_data;
static int hf_wcp_comp_bits;
/* static int hf_wcp_comp_marker; */
static int hf_wcp_short_len;
static int hf_wcp_long_len;
static int hf_wcp_short_run;
static int hf_wcp_long_run;
static int hf_wcp_offset;

static int ett_wcp;
static int ett_wcp_comp_data;
static int ett_wcp_field;

static expert_field ei_wcp_compressed_data_exceeds;
static expert_field ei_wcp_uncompressed_data_exceeds;
static expert_field ei_wcp_invalid_window_offset;
static expert_field ei_wcp_buffer_too_long;
/* static expert_field ei_wcp_invalid_match_length; */

static dissector_handle_t wcp_handle;
static dissector_handle_t fr_uncompressed_handle;

/*
 * Bits in the address field.
 */
#define	WCP_CMD			0xf0	/* WCP Command */
#define	WCP_EXT_CMD		0x0f	/* WCP Extended Command */
#define	WCP_SEQ			0x0fff	/* WCP Sequence number */
#define	WCP_OFFSET_MASK		0x0fff	/* WCP Pattern source offset */

#define	PPC_COMPRESSED_IND		0x0
#define	PPC_UNCOMPRESSED_IND		0x1
#define	PPC_TPPC_COMPRESSED_IND		0x2
#define	PPC_TPPC_UNCOMPRESSED_IND	0x3
#define	CONNECT_REQ			0x4
#define	CONNECT_ACK			0x5
#define	CONNECT_NAK			0x6
#define	DISCONNECT_REQ			0x7
#define	DISCONNECT_ACK			0x8
#define	INIT_REQ			0x9
#define	INIT_ACK			0xa
#define	RESET_REQ			0xb
#define	RESET_ACK			0xc
#define	REXMIT_NAK			0xd


static const value_string cmd_string[] = {
	{0, "Compressed Data"},
	{1, "Uncompressed Data"},
	{15, "Extended"},
	{ 0,       NULL }
};

static const value_string ext_cmd_string[] = {
	{0, "Per Packet Compression"},
	{4, "Connect Req"},
	{5, "Connect Ack"},
	{9, "Init Req"},
	{0x0a, "Init Ack"},

	{ 0,       NULL }
};



static tvbuff_t *wcp_uncompress(tvbuff_t *src_tvb, int offset, packet_info *pinfo, proto_tree *tree);
static wcp_window_t *get_wcp_window_ptr(packet_info *pinfo);

static void
dissect_wcp_con_req(tvbuff_t *tvb, int offset, proto_tree *tree) {

/* WCP connector request message */
	uint32_t alg_cnt;

	proto_tree_add_item(tree, hf_wcp_tid, tvb, offset, 2, ENC_BIG_ENDIAN);
	proto_tree_add_item(tree, hf_wcp_rev, tvb, offset + 2, 1, ENC_NA);
	proto_tree_add_item(tree, hf_wcp_init, tvb, offset + 3, 1, ENC_NA);
	proto_tree_add_item(tree, hf_wcp_seq_size, tvb, offset + 4, 1, ENC_NA);
	proto_tree_add_item_ret_uint(tree, hf_wcp_alg_cnt, tvb, offset + 5, 1, ENC_NA, &alg_cnt);
	proto_tree_add_item(tree, hf_wcp_alg_a, tvb, offset + 6, 1, ENC_NA);
	if (alg_cnt > 1)
		proto_tree_add_item(tree, hf_wcp_alg_b, tvb, offset + 7, 1, ENC_NA);
	if (alg_cnt > 2)
		proto_tree_add_item(tree, hf_wcp_alg_c, tvb, offset + 8, 1, ENC_NA);
	if (alg_cnt > 3)
		proto_tree_add_item(tree, hf_wcp_alg_d, tvb, offset + 9, 1, ENC_NA);
}

static void
dissect_wcp_con_ack(tvbuff_t *tvb, int offset, proto_tree *tree) {

	/* WCP connector ack message */

	proto_tree_add_item(tree, hf_wcp_tid, tvb, offset, 2, ENC_BIG_ENDIAN);
	proto_tree_add_item(tree, hf_wcp_rev, tvb, offset + 2, 1, ENC_NA);
	proto_tree_add_item(tree, hf_wcp_seq_size, tvb, offset + 3, 1, ENC_NA);
	proto_tree_add_item(tree, hf_wcp_alg, tvb, offset + 4, 1, ENC_NA);
}

static void
dissect_wcp_init(tvbuff_t *tvb, int offset, proto_tree *tree) {

	/* WCP Initiate Request/Ack message */

	proto_tree_add_item(tree, hf_wcp_tid, tvb, offset, 2, ENC_BIG_ENDIAN);
	proto_tree_add_item(tree, hf_wcp_rev, tvb, offset + 2, 1, ENC_NA);
	proto_tree_add_item(tree, hf_wcp_hist_size, tvb, offset + 3, 1, ENC_NA);
	proto_tree_add_item(tree, hf_wcp_ppc, tvb, offset + 4, 1, ENC_NA);
	proto_tree_add_item(tree, hf_wcp_pib, tvb, offset + 5, 1, ENC_NA);
}


static void
dissect_wcp_reset(tvbuff_t *tvb, int offset, proto_tree *tree) {

	/* Process WCP Reset Request/Ack message */

	proto_tree_add_item(tree, hf_wcp_tid, tvb, offset, 2, ENC_BIG_ENDIAN);
}


static void wcp_save_data(tvbuff_t *tvb, packet_info *pinfo, proto_tree* tree) {

	wcp_window_t *buf_ptr = 0;
	size_t len;

	/* discard first 2 bytes, header and last byte (check byte) */
	len = tvb_reported_length(tvb) - 3;
	buf_ptr = get_wcp_window_ptr(pinfo);

	if ((buf_ptr->buf_cur + len) <= (buf_ptr->buffer + MAX_WIN_BUF_LEN)) {
		tvb_memcpy(tvb, buf_ptr->buf_cur, 2, len);
		buf_ptr->buf_cur += len;
	} else {
		uint8_t *buf_end = buf_ptr->buffer + MAX_WIN_BUF_LEN;
		tvb_memcpy(tvb, buf_ptr->buf_cur, 2, buf_end - buf_ptr->buf_cur);
		if (buf_ptr->buf_cur + len <= buf_end) {
			tvb_memcpy(tvb, buf_ptr->buffer, (int) (buf_end - buf_ptr->buf_cur-2),
				len - (buf_end - buf_ptr->buf_cur));
			buf_ptr->buf_cur += len - MAX_WIN_BUF_LEN;
		} else {
			proto_tree_add_expert(tree, pinfo, &ei_wcp_buffer_too_long, tvb, 0, -1);
		}
	}
}


static int dissect_wcp(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void* data _U_) {

	proto_tree	*wcp_tree;
	proto_item	*ti;
	int		wcp_header_len;
	uint16_t		temp, cmd, ext_cmd, seq;
	tvbuff_t	*next_tvb;

	col_set_str(pinfo->cinfo, COL_PROTOCOL, "WCP");
	col_clear(pinfo->cinfo, COL_INFO);

	temp = tvb_get_ntohs(tvb, 0);

	cmd = (temp & 0xf000) >> 12;
	ext_cmd = (temp & 0x0f00) >> 8;

	if (cmd == 0xf)
		wcp_header_len = 1;
	else
		wcp_header_len = 2;

	seq = temp & 0x0fff;

	/* XXX should test seq to be sure it the last + 1 !! */

	col_set_str(pinfo->cinfo, COL_INFO, val_to_str_const(cmd, cmd_string, "Unknown"));
	if (cmd == 0xf)
		col_append_fstr(pinfo->cinfo, COL_INFO, ", %s",
				val_to_str_const(ext_cmd, ext_cmd_string, "Unknown"));

	ti = proto_tree_add_item(tree, proto_wcp, tvb, 0, wcp_header_len, ENC_NA);
	wcp_tree = proto_item_add_subtree(ti, ett_wcp);

	proto_tree_add_item(wcp_tree, hf_wcp_cmd, tvb, 0, 1, ENC_NA);
	if (cmd == 0xf) {
		proto_tree_add_item(wcp_tree, hf_wcp_ext_cmd, tvb, 1, 1, ENC_NA);
		switch (ext_cmd) {
		case CONNECT_REQ:
			dissect_wcp_con_req(tvb, 1, wcp_tree);
			break;

		case CONNECT_ACK:
			dissect_wcp_con_ack(tvb, 1, wcp_tree);
			break;
		case INIT_REQ:
		case INIT_ACK:
			dissect_wcp_init(tvb, 1, wcp_tree);
			break;
		case RESET_REQ:
		case RESET_ACK:
			dissect_wcp_reset(tvb, 1, wcp_tree);
			break;
		default:
			break;
		}
	} else {
		proto_tree_add_uint(wcp_tree, hf_wcp_seq, tvb, 0, 2, seq);
	}


	/* exit if done */
	if (cmd != 1 && cmd != 0 && !(cmd == 0xf && ext_cmd == 0))
		return 2;

	if (cmd == 1) { /* uncompressed data */
		if (!pinfo->fd->visited) {	/* if first pass */
			wcp_save_data(tvb, pinfo, wcp_tree);
		}
		next_tvb = tvb_new_subset_remaining(tvb, wcp_header_len);
	} else { /* cmd == 0 || (cmd == 0xf && ext_cmd == 0) */

		next_tvb = wcp_uncompress(tvb, wcp_header_len, pinfo, wcp_tree);

		if (!next_tvb) {
			return tvb_captured_length(tvb);
		}
	}

	/* add the check byte */
	proto_tree_add_checksum(wcp_tree, tvb, tvb_reported_length(tvb) - 1, hf_wcp_chksum, -1, NULL, pinfo, 0, ENC_NA, PROTO_CHECKSUM_NO_FLAGS);

	call_dissector(fr_uncompressed_handle, next_tvb, pinfo, tree);

	return tvb_captured_length(tvb);
}


static uint8_t *
decompressed_entry(uint8_t *dst, uint16_t data_offset,
	uint16_t data_cnt, int *len, wcp_window_t *buf_ptr)
{
	const uint8_t *src;
	uint8_t *buf_start, *buf_end;

	buf_start = buf_ptr->buffer;
	buf_end = buf_ptr->buffer + MAX_WIN_BUF_LEN;

	/* do the decompression for one field */

	src = (dst - 1 - data_offset);
	if (src < buf_start)
		src += MAX_WIN_BUF_LEN;


	/* XXX could do some fancy memory moves, later if speed is problem */

	while(data_cnt--) {
		*dst = *src;
		if (buf_ptr->initialized < MAX_WIN_BUF_LEN)
			buf_ptr->initialized++;
		if ( ++(*len) >MAX_WCP_BUF_LEN) {
			return NULL;	/* end of buffer error */
		}
		if (dst++ == buf_end)
			dst = buf_start;
		if (src++ == buf_end)
			src = buf_start;

	}
	return dst;
}


static
wcp_window_t *get_wcp_window_ptr(packet_info *pinfo) {

	/* find the circuit for this DLCI, create one if needed */
	/* and return the wcp_window data structure pointer */
	/* for the direction of this packet */

	conversation_t *conv;
	wcp_circuit_data_t *wcp_circuit_data;

	conv = find_or_create_conversation(pinfo);

	wcp_circuit_data = (wcp_circuit_data_t *)conversation_get_proto_data(conv, proto_wcp);
	if (!wcp_circuit_data) {
		wcp_circuit_data = wmem_new0(wmem_file_scope(), wcp_circuit_data_t);
		wcp_circuit_data->recv.buf_cur = wcp_circuit_data->recv.buffer;
		wcp_circuit_data->send.buf_cur = wcp_circuit_data->send.buffer;
		conversation_add_proto_data(conv, proto_wcp, wcp_circuit_data);
	}
	if (pinfo->pseudo_header->dte_dce.flags & FROM_DCE)
		return &wcp_circuit_data->recv;
	else
		return &wcp_circuit_data->send;
}


static tvbuff_t *wcp_uncompress(tvbuff_t *src_tvb, int offset, packet_info *pinfo, proto_tree *tree) {

	/* do the packet data uncompression and load it into the dst buffer */

	proto_tree	*cd_tree, *sub_tree;
	proto_item	*cd_item, *ti;

	int len, i;
	int cnt = tvb_reported_length(src_tvb) - 1;/* don't include check byte */

	uint8_t *dst, *src, *buf_start, *buf_end, comp_flag_bits = 0;
	uint16_t data_offset, data_cnt;
	uint8_t src_buf[ MAX_WCP_BUF_LEN];
	tvbuff_t *tvb;
	wcp_window_t *buf_ptr = 0;
	wcp_pdata_t *pdata_ptr;

	buf_ptr = get_wcp_window_ptr(pinfo);

	buf_start = buf_ptr->buffer;
	buf_end = buf_start + MAX_WIN_BUF_LEN;

	cd_item = proto_tree_add_item(tree, hf_wcp_compressed_data,
		src_tvb, offset, cnt - offset, ENC_NA);
	cd_tree = proto_item_add_subtree(cd_item, ett_wcp_comp_data);
	if (cnt - offset > MAX_WCP_BUF_LEN) {
		expert_add_info_format(pinfo, cd_item, &ei_wcp_compressed_data_exceeds,
			"Compressed data exceeds maximum buffer length (%d > %d)",
			cnt - offset, MAX_WCP_BUF_LEN);
		return NULL;
	}

	/*
	 * XXX - this will throw an exception if a snapshot length cut short
	 * the data. We may want to try to dissect the data in that case,
	 * and we may even want to try to decompress it, *but* we will
	 * want to mark the buffer of decompressed data as incomplete, so
	 * that we don't try to use it for decompressing later packets.
	 */
	src = (uint8_t *)tvb_memcpy(src_tvb, src_buf, offset, cnt - offset);
	dst = buf_ptr->buf_cur;
	len = 0;
	i = -1;

	while(offset < cnt) {
		/* There are i bytes left for this byte of flag bits */
		if ( --i >= 0) {
			/*
			 * There's still at least one more byte left for
			 * the current set of compression flag bits; is
			 * it compressed data or uncompressed data?
			 */
			if (comp_flag_bits & 0x80) {
				/* This byte is compressed data */
				if (!(offset + 1 < cnt)) {
					/*
					 * The data offset runs past the
					 * end of the data.
					 */
					return NULL;
				}
				data_offset = pntoh16(src) & WCP_OFFSET_MASK;
				if ((*src & 0xf0) == 0x10) {
					/*
					 * The count of bytes to copy from
					 * the dictionary window is in the
					 * byte following the data offset.
					 */
					if (!(offset + 2 < cnt)) {
						/*
						 * The data count runs past the
						 * end of the data.
						 */
						return NULL;
					}
					data_cnt = *(src + 2) + 1;
					if (tree) {
						ti = proto_tree_add_item(cd_tree, hf_wcp_long_run, src_tvb,
							 offset, 3, ENC_NA);
						sub_tree = proto_item_add_subtree(ti, ett_wcp_field);
						proto_tree_add_uint(sub_tree, hf_wcp_offset, src_tvb,
							 offset, 2, data_offset);

						proto_tree_add_item(sub_tree, hf_wcp_long_len, src_tvb,
							 offset+2, 1, ENC_BIG_ENDIAN);
					}
					src += 3;
					offset += 3;
				} else {
					/*
					 * The count of bytes to copy from
					 * the dictionary window is in
					 * the upper 4 bits of the next
					 * byte.
					 */
					data_cnt = (*src >> 4) + 1;
					if (tree) {
						ti = proto_tree_add_item(cd_tree, hf_wcp_short_run, src_tvb,
							 offset, 2, ENC_NA);
						sub_tree = proto_item_add_subtree(ti, ett_wcp_field);
						proto_tree_add_uint(sub_tree, hf_wcp_short_len, src_tvb,
							 offset, 1, *src);
						proto_tree_add_uint(sub_tree, hf_wcp_offset, src_tvb,
							 offset, 2, data_offset);
					}
					src += 2;
					offset += 2;
				}
				if (data_offset + 1 > buf_ptr->initialized) {
					expert_add_info_format(pinfo, cd_item, &ei_wcp_invalid_window_offset,
							"Data offset exceeds valid window size (%d > %d)",
							data_offset+1, buf_ptr->initialized);
					return NULL;
				}

				if (data_offset + 1 < data_cnt) {
					expert_add_info_format(pinfo, cd_item, &ei_wcp_invalid_window_offset,
							"Data count exceeds offset (%d > %d)",
							data_cnt, data_offset+1);
					return NULL;
				}
				if ( !pinfo->fd->visited) {	/* if first pass */
					dst = decompressed_entry(dst,
						data_offset, data_cnt, &len,
						buf_ptr);
					if (dst == NULL) {
						expert_add_info_format(pinfo, cd_item, &ei_wcp_uncompressed_data_exceeds,
							"Uncompressed data exceeds maximum buffer length (%d > %d)",
							len, MAX_WCP_BUF_LEN);
						return NULL;
					}
				}
			}else {
				/*
				 * This byte is uncompressed data; is there
				 * room for it in the buffer of uncompressed
				 * data?
				 */
				if ( ++len >MAX_WCP_BUF_LEN) {
					/* No - report an error. */
					expert_add_info_format(pinfo, cd_item, &ei_wcp_uncompressed_data_exceeds,
						"Uncompressed data exceeds maximum buffer length (%d > %d)",
						len, MAX_WCP_BUF_LEN);
					return NULL;
				}

				if ( !pinfo->fd->visited) {
					/*
					 * This is the first pass through
					 * the packets, so copy it to the
					 * buffer of uncompressed data.
					 */
					*dst = *src;
					if (dst++ == buf_end)
						dst = buf_start;
					if (buf_ptr->initialized < MAX_WIN_BUF_LEN)
						buf_ptr->initialized++;
				}
				++src;
				++offset;
			}

			/* Skip to the next compression flag bit */
			comp_flag_bits <<= 1;

		}else {
			/*
			 * There are no more bytes left for the current
			 * set of compression flag bits, so this byte
			 * is another byte of compression flag bits.
			 */
			comp_flag_bits = *src++;
			proto_tree_add_uint(cd_tree, hf_wcp_comp_bits, src_tvb, offset, 1,
					comp_flag_bits);
			offset++;

			i = 8;
		}
	}

	if (pinfo->fd->visited) {	/* if not first pass */
					/* get uncompressed data */
		pdata_ptr = (wcp_pdata_t *)p_get_proto_data(wmem_file_scope(), pinfo, proto_wcp, 0);

		if (!pdata_ptr) {	/* exit if no data */
			REPORT_DISSECTOR_BUG("Can't find uncompressed data");
			return NULL;
		}
		len = pdata_ptr->len;
	} else {
		if (buf_ptr->buf_cur + len > buf_end) {
			expert_add_info_format(pinfo, cd_item, &ei_wcp_invalid_window_offset,
				"Uncompressed data exceeds available buffer length (%d > %d)",
				len, (int) (buf_end - buf_ptr->buf_cur));
			return NULL;
		}

		/* save the new data as per packet data */
		pdata_ptr = wmem_new0(wmem_file_scope(), wcp_pdata_t);
		memcpy( &pdata_ptr->buffer, buf_ptr->buf_cur, len);
		pdata_ptr->len = len;

		p_add_proto_data(wmem_file_scope(), pinfo, proto_wcp, 0, (void*)pdata_ptr);

		buf_ptr->buf_cur = dst;
	}

	tvb = tvb_new_child_real_data(src_tvb, pdata_ptr->buffer, pdata_ptr->len, pdata_ptr->len);

	/* Add new data to the data source list */
	add_new_data_source(pinfo, tvb, "Uncompressed WCP");
	return tvb;

}


void
proto_register_wcp(void)
{
	static hf_register_info hf[] = {
		{ &hf_wcp_cmd,
		  { "Command", "wcp.cmd", FT_UINT8, BASE_HEX, VALS(cmd_string), WCP_CMD,
		    "Compression Command", HFILL }},
		{ &hf_wcp_ext_cmd,
		  { "Extended Command", "wcp.ext_cmd", FT_UINT8, BASE_HEX, VALS(ext_cmd_string), WCP_EXT_CMD,
		    "Extended Compression Command", HFILL }},
		{ &hf_wcp_seq,
		  { "SEQ", "wcp.seq", FT_UINT16, BASE_HEX, NULL, WCP_SEQ,
		    "Sequence Number", HFILL }},
		{ &hf_wcp_chksum,
		  { "Checksum", "wcp.checksum", FT_UINT8, BASE_DEC, NULL, 0,
		    "Packet Checksum", HFILL }},
		{ &hf_wcp_tid,
		  { "TID", "wcp.tid", FT_UINT16, BASE_DEC, NULL, 0,
		    NULL, HFILL }},
		{ &hf_wcp_rev,
		  { "Revision", "wcp.rev", FT_UINT8, BASE_DEC, NULL, 0,
		    NULL, HFILL }},
		{ &hf_wcp_init,
		  { "Initiator", "wcp.init", FT_UINT8, BASE_DEC, NULL, 0,
		    NULL, HFILL }},
		{ &hf_wcp_seq_size,
		  { "Seq Size", "wcp.seq_size", FT_UINT8, BASE_DEC, NULL, 0,
		    "Sequence Size", HFILL }},
		{ &hf_wcp_alg_cnt,
		  { "Alg Count", "wcp.alg_cnt", FT_UINT8, BASE_DEC, NULL, 0,
		    "Algorithm Count", HFILL }},
		{ &hf_wcp_alg_a,
		  { "Alg 1", "wcp.alg1", FT_UINT8, BASE_DEC, NULL, 0,
		    "Algorithm #1", HFILL }},
		{ &hf_wcp_alg_b,
		  { "Alg 2", "wcp.alg2", FT_UINT8, BASE_DEC, NULL, 0,
		    "Algorithm #2", HFILL }},
		{ &hf_wcp_alg_c,
		  { "Alg 3", "wcp.alg3", FT_UINT8, BASE_DEC, NULL, 0,
		    "Algorithm #3", HFILL }},
		{ &hf_wcp_alg_d,
		  { "Alg 4", "wcp.alg4", FT_UINT8, BASE_DEC, NULL, 0,
		    "Algorithm #4", HFILL }},
		{ &hf_wcp_alg,
		  { "Alg", "wcp.alg", FT_UINT8, BASE_DEC, NULL, 0,
		    "Algorithm", HFILL }},
#if 0
		{ &hf_wcp_rexmit,
		  { "Rexmit", "wcp.rexmit", FT_UINT8, BASE_DEC, NULL, 0,
		    "Retransmit", HFILL }},
#endif
		{ &hf_wcp_hist_size,
		  { "History", "wcp.hist", FT_UINT8, BASE_DEC, NULL, 0,
		    "History Size", HFILL }},
		{ &hf_wcp_ppc,
		  { "PerPackComp", "wcp.ppc", FT_UINT8, BASE_DEC, NULL, 0,
		    "Per Packet Compression", HFILL }},
		{ &hf_wcp_pib,
		  { "PIB", "wcp.pib", FT_UINT8, BASE_DEC, NULL, 0,
		    NULL, HFILL }},
		{ &hf_wcp_compressed_data,
		  { "Compressed Data", "wcp.compressed_data", FT_NONE, BASE_NONE, NULL, 0,
		    "Raw compressed data", HFILL }},
		{ &hf_wcp_comp_bits,
		  { "Compress Flag", "wcp.flag", FT_UINT8, BASE_HEX, NULL, 0,
		    "Compressed byte flag", HFILL }},
#if 0
		{ &hf_wcp_comp_marker,
		  { "Compress Marker", "wcp.mark", FT_UINT8, BASE_DEC, NULL, 0,
		    "Compressed marker", HFILL }},
#endif
		{ &hf_wcp_offset,
		  { "Source offset", "wcp.off", FT_UINT16, BASE_HEX, NULL, WCP_OFFSET_MASK,
		    "Data source offset", HFILL }},
		{ &hf_wcp_short_len,
		  { "Compress Length", "wcp.short_len", FT_UINT8, BASE_HEX, NULL, 0xf0,
		    "Compressed length", HFILL }},
		{ &hf_wcp_long_len,
		  { "Compress Length", "wcp.long_len", FT_UINT8, BASE_HEX, NULL, 0,
		    "Compressed length", HFILL }},
		{ &hf_wcp_long_run,
		  { "Long Compression", "wcp.long_comp", FT_BYTES, BASE_NONE, NULL, 0,
		    "Long Compression type", HFILL }},
		{ &hf_wcp_short_run,
		  { "Short Compression", "wcp.short_comp", FT_BYTES, BASE_NONE, NULL, 0,
		    "Short Compression type", HFILL }},

	};


	static int *ett[] = {
		&ett_wcp,
		&ett_wcp_comp_data,
		&ett_wcp_field,
	};

	static ei_register_info ei[] = {
		{ &ei_wcp_compressed_data_exceeds, { "wcp.compressed_data.exceeds", PI_MALFORMED, PI_ERROR, "Compressed data exceeds maximum buffer length", EXPFILL }},
		{ &ei_wcp_uncompressed_data_exceeds, { "wcp.uncompressed_data.exceeds", PI_MALFORMED, PI_ERROR, "Uncompressed data exceeds maximum buffer length", EXPFILL }},
		{ &ei_wcp_invalid_window_offset, { "wcp.off.invalid", PI_MALFORMED, PI_ERROR, "Offset points outside of visible window", EXPFILL }},
		{ &ei_wcp_buffer_too_long, { "wcp.buffer_too_long", PI_MALFORMED, PI_ERROR, "Buffer too long", EXPFILL }},
#if 0
		{ &ei_wcp_invalid_match_length, { "wcp.len.invalid", PI_MALFORMED, PI_ERROR, "Length greater than offset", EXPFILL }},
#endif
	};

	expert_module_t* expert_wcp;

	proto_wcp = proto_register_protocol ("Wellfleet Compression", "WCP", "wcp");
	proto_register_field_array (proto_wcp, hf, array_length(hf));
	proto_register_subtree_array(ett, array_length(ett));
	expert_wcp = expert_register_protocol(proto_wcp);
	expert_register_field_array(expert_wcp, ei, array_length(ei));
	wcp_handle = register_dissector("wcp", dissect_wcp, proto_wcp);
}


void
proto_reg_handoff_wcp(void) {
	/*
	 * Get handle for the Frame Relay (uncompressed) dissector.
	 */
	fr_uncompressed_handle = find_dissector_add_dependency("fr_uncompressed", proto_wcp);

	dissector_add_uint("fr.nlpid", NLPID_COMPRESSED, wcp_handle);
	dissector_add_uint("ethertype",  ETHERTYPE_WCP, wcp_handle);
}

/*
 * Editor modelines - https://www.wireshark.org/tools/modelines.html
 *
 * Local variables:
 * c-basic-offset: 8
 * tab-width: 8
 * indent-tabs-mode: t
 * End:
 *
 * vi: set shiftwidth=8 tabstop=8 noexpandtab:
 * :indentSize=8:tabSize=8:noTabs=false:
 */