wireshark/epan/dissectors/packet-dji-uav.c

/* packet-dji-uav.c
 * Routines for the disassembly of the command protocol for the
 * DJI Phantom 2 Vision+ UAV
 * http://www.dji.com/product/phantom-2-vision-plus
 * and possibly others.
 *
 * Copyright 2014,2015 Joerg Mayer (see AUTHORS file)
 *
 * Wireshark - Network traffic analyzer
 * By Gerald Combs <gerald@wireshark.org>
 * Copyright 1998 Gerald Combs
 *
 * SPDX-License-Identifier: GPL-2.0-or-later
 */

/*
 */
#include "config.h"

#include <epan/packet.h>
/* TCP desegmentation */
#include "packet-tcp.h"
/* Request Response tracking */
#include <epan/conversation.h>
#include <epan/prefs.h>

void proto_register_djiuav(void);
void proto_reg_handoff_djiuav(void);

/* Enable desegmentation of djiuav over TCP */
static gboolean djiuav_desegment = TRUE;

/* Command/Response tracking */
typedef struct _djiuav_conv_info_t {
	wmem_map_t *pdus;
} djiuav_conv_info_t;

typedef struct _djiuav_transaction_t {
	guint16	seqno;
	guint8  command;
	guint32	request_frame;
	guint32	reply_frame;
	nstime_t request_time;
} djiuav_transaction_t;

/* Finally: Protocol specific stuff */

/* protocol handles */
static int proto_djiuav = -1;

/* ett handles */
static int ett_djiuav = -1;

/* hf elements */
static int hf_djiuav_magic = -1;
static int hf_djiuav_length = -1;
static int hf_djiuav_flags = -1;
static int hf_djiuav_seqno = -1;
static int hf_djiuav_cmd = -1;
static int hf_djiuav_checksum = -1;
#if 0
static int hf_djiuav_cmd04_unknown = -1;
static int hf_djiuav_resp04_unknown = -1;
#endif
static int hf_djiuav_cmd20_unknown = -1;
#if 0
static int hf_djiuav_resp20_unknown = -1;
#endif
static int hf_djiuav_cmdunk = -1;
static int hf_djiuav_respunk = -1;
static int hf_djiuav_extradata = -1;
/* hf request/response tracking */
static int hf_djiuav_response_in = -1;
static int hf_djiuav_response_to = -1;
static int hf_djiuav_response_time = -1;

#define PROTO_SHORT_NAME "DJIUAV"
#define PROTO_LONG_NAME "DJI UAV Drone Control Protocol"

#define PORT_DJIUAV	2001 /* Not IANA registered */

static const value_string djiuav_pdu_type[] = {
	{ 0x20, "Set Time" },

	{ 0,	NULL }
};

static void
request_response_handling(tvbuff_t *tvb, packet_info *pinfo, proto_tree *djiuav_tree,
	guint32 offset)
{
	conversation_t		*conversation;
	djiuav_conv_info_t	*djiuav_info;
	djiuav_transaction_t	*djiuav_trans;

	guint16			seq_no;
	gboolean		is_cmd;
	guint8			packet_type;

	is_cmd = (pinfo->match_uint == pinfo->destport);
	seq_no = tvb_get_letohs(tvb, offset + 4);
	packet_type = tvb_get_guint8(tvb, offset + 6);

	conversation = find_or_create_conversation(pinfo);
	djiuav_info = (djiuav_conv_info_t *)conversation_get_proto_data(conversation, proto_djiuav);
	if (!djiuav_info) {
		djiuav_info = wmem_new(wmem_file_scope(), djiuav_conv_info_t);
		djiuav_info->pdus=wmem_map_new(wmem_file_scope(), g_direct_hash, g_direct_equal);

		conversation_add_proto_data(conversation, proto_djiuav, djiuav_info);
	}
	if (!pinfo->fd->visited) {
		if (is_cmd) {
			djiuav_trans=wmem_new(wmem_file_scope(), djiuav_transaction_t);
			djiuav_trans->request_frame=pinfo->num;
			djiuav_trans->reply_frame=0;
			djiuav_trans->request_time=pinfo->abs_ts;
			djiuav_trans->seqno=seq_no;
			djiuav_trans->command=packet_type;
			wmem_map_insert(djiuav_info->pdus, GUINT_TO_POINTER((guint)seq_no), (void *)djiuav_trans);
		} else {
			djiuav_trans=(djiuav_transaction_t *)wmem_map_lookup(djiuav_info->pdus, GUINT_TO_POINTER((guint)seq_no));
			if (djiuav_trans) {
				/* Special case: djiuav seems to send 0x24 replies with seqno 0 and without a request */
				if (djiuav_trans->reply_frame == 0)
					djiuav_trans->reply_frame=pinfo->num;
			}
		}
	} else {
		djiuav_trans=(djiuav_transaction_t *)wmem_map_lookup(djiuav_info->pdus, GUINT_TO_POINTER((guint)seq_no));
	}

	/* djiuav_trans may be 0 in case it's a reply without a matching request */

	if (djiuav_tree && djiuav_trans) {
		if (is_cmd) {
			if (djiuav_trans->reply_frame) {
				proto_item *it;

				it = proto_tree_add_uint(djiuav_tree, hf_djiuav_response_in,
						tvb, 0, 0, djiuav_trans->reply_frame);
				proto_item_set_generated(it);
			}
		} else {
			if (djiuav_trans->request_frame) {
				proto_item *it;
				nstime_t ns;

				it = proto_tree_add_uint(djiuav_tree, hf_djiuav_response_to,
						tvb, 0, 0, djiuav_trans->request_frame);
				proto_item_set_generated(it);

				nstime_delta(&ns, &pinfo->abs_ts, &djiuav_trans->request_time);
				it = proto_tree_add_time(djiuav_tree, hf_djiuav_response_time, tvb, 0, 0, &ns);
				proto_item_set_generated(it);
			}
		}
	}
}

static int
dissect_djiuav_pdu(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data _U_)
{
	proto_item		*ti;
	proto_tree		*djiuav_tree = NULL;
	guint32			offset = 0;
	guint32			pdu_length;
	guint8			packet_type;
	gboolean		is_cmd;

	is_cmd = (pinfo->match_uint == pinfo->destport);
	packet_type = tvb_get_guint8(tvb, 6);

	col_set_str(pinfo->cinfo, COL_PROTOCOL, PROTO_SHORT_NAME);
	col_add_str(pinfo->cinfo, COL_INFO, is_cmd?"C: ":"R: ");
	col_append_str(pinfo->cinfo, COL_INFO, val_to_str(packet_type,
			djiuav_pdu_type, "Type 0x%02x"));

	ti = proto_tree_add_item(tree, proto_djiuav, tvb, offset, -1, ENC_NA);
	djiuav_tree = proto_item_add_subtree(ti, ett_djiuav);

	request_response_handling(tvb, pinfo, djiuav_tree, offset);

	if (tree) {
		proto_tree_add_item(djiuav_tree, hf_djiuav_magic, tvb, offset, 2,
			ENC_BIG_ENDIAN);
		offset += 2;

		pdu_length = tvb_get_guint8(tvb, offset);
		proto_tree_add_item(djiuav_tree, hf_djiuav_length, tvb, offset, 1,
			ENC_NA);
		offset += 1;

		proto_tree_add_item(djiuav_tree, hf_djiuav_flags, tvb, offset, 1,
			ENC_NA);
		offset += 1;

		proto_tree_add_item(djiuav_tree, hf_djiuav_seqno, tvb, offset, 2,
			ENC_LITTLE_ENDIAN);
		offset += 2;

		proto_tree_add_item(djiuav_tree, hf_djiuav_cmd, tvb, offset, 1,
			ENC_NA);
		offset += 1;

		if (is_cmd) { /* Command */
			switch (packet_type) {
			case 0x20: /* Set time */
/* FIXME: Properly decode this: year(lo) year(hi) month date hour minute second */
				proto_tree_add_item(djiuav_tree, hf_djiuav_cmd20_unknown, tvb, offset, 7,
					ENC_NA);
				offset += 7;
				break;
			default:
				proto_tree_add_item(djiuav_tree, hf_djiuav_cmdunk, tvb, offset, pdu_length - 8,
					ENC_NA);
				offset += (pdu_length - 8);
				break;
			}
		} else { /* Response */
			switch (packet_type) {
			default:
				proto_tree_add_item(djiuav_tree, hf_djiuav_respunk, tvb,
					offset, pdu_length - 8, ENC_NA);
				offset += (pdu_length - 8);
				break;
			}
		}
		if (offset < pdu_length - 1) { /* We guessed wrong about the cmd len */
			proto_tree_add_item(djiuav_tree, hf_djiuav_extradata, tvb, offset,
				pdu_length - 1 - offset, ENC_NA);
			offset += pdu_length - 1 - offset;
		}
/* FIXME: calculate XOR and validate transmitted value */
		proto_tree_add_checksum(djiuav_tree, tvb, offset, hf_djiuav_checksum, -1, NULL, pinfo, 0, ENC_BIG_ENDIAN, PROTO_CHECKSUM_NO_FLAGS);
		offset += 1;

	}
	return offset;
}

static gboolean
test_djiuav(tvbuff_t *tvb)
{
	/* Minimum of 8 bytes, beginning with magic bytes 0x55BB */
	if ( tvb_captured_length(tvb) < 8 /* Size of a command with empty data is at least 8 */
		|| tvb_get_ntohs(tvb, 0) != 0x55BB
	) {
		return FALSE;
	}
	return TRUE;
}

/* Get the length of the full pdu */
static guint
get_djiuav_pdu_len(packet_info *pinfo _U_, tvbuff_t *tvb, int offset, void *data _U_)
{
	return tvb_get_guint8(tvb, offset + 2);
}

static int
dissect_djiuav_static(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data)
{
	if ( !test_djiuav(tvb) ) {
		return 0;
	}
	tcp_dissect_pdus(tvb, pinfo, tree, djiuav_desegment, 8,
		get_djiuav_pdu_len, dissect_djiuav_pdu, data);

	return tvb_captured_length(tvb);
}

void
proto_register_djiuav(void)
{
	static hf_register_info hf[] = {

	/* DJIUAV header */
		{ &hf_djiuav_magic,
		{ "Protocol Magic",	"djiuav.magic", FT_UINT16, BASE_HEX, NULL,
			0x0, NULL, HFILL }},

		{ &hf_djiuav_length,
		{ "PDU Length",	"djiuav.length", FT_UINT8, BASE_HEX, NULL,
			0x0, NULL, HFILL }},

		{ &hf_djiuav_flags,
		{ "Flags",	"djiuav.flags", FT_UINT8, BASE_HEX, NULL,
			0x0, NULL, HFILL }},

		{ &hf_djiuav_seqno,
		{ "Sequence No",	"djiuav.seqno", FT_UINT16, BASE_DEC, NULL,
			0x0, NULL, HFILL }},

		{ &hf_djiuav_cmd,
		{ "PDU Type",	"djiuav.pdutype", FT_UINT8, BASE_HEX, VALS(djiuav_pdu_type),
			0x0, NULL, HFILL }},

		{ &hf_djiuav_checksum,
		{ "Checksum",	"djiuav.checksum", FT_UINT8, BASE_HEX, NULL,
			0x0, NULL, HFILL }},

	/* 0x04 */
#if 0
		{ &hf_djiuav_cmd04_unknown,
		{ "C04 Unknown", "djiuav.cmd04.unknown", FT_UINT8, BASE_HEX, NULL,
				0x0, NULL, HFILL }},

		{ &hf_djiuav_resp04_unknown,
		{ "R04 Unknown", "djiuav.resp04.unknown", FT_UINT8, BASE_HEX, NULL,
				0x0, NULL, HFILL }},
#endif
	/* Set time */
		{ &hf_djiuav_cmd20_unknown,
		{ "Time in BCD", "djiuav.cmd04.bcdtime", FT_BYTES, BASE_NONE, NULL,
			0x0, NULL, HFILL }},
#if 0
		{ &hf_djiuav_resp20_unknown,
		{ "R20 Unknown", "djiuav.resp04.unknown", FT_UINT8, BASE_HEX, NULL,
			0x0, NULL, HFILL }},
#endif
	/* CMD Unknown */
		{ &hf_djiuav_cmdunk,
		{ "C Unknown", "djiuav.cmd.unknown", FT_BYTES, BASE_NONE, NULL,
			0x0, NULL, HFILL }},

	/* RESP Unknown */
		{ &hf_djiuav_respunk,
		{ "R Unknown", "djiuav.resp.unknown", FT_BYTES, BASE_NONE, NULL,
			0x0, NULL, HFILL }},

	/* Extra Data (unexpected) */
		{ &hf_djiuav_extradata,
		{ "Unexpected", "djiuav.unexpected", FT_BYTES, BASE_NONE, NULL,
			0x0, NULL, HFILL }},

	/* Request - Response tracking */
		{ &hf_djiuav_response_in,
		{ "Response In", "djiuav.response_in", FT_FRAMENUM, BASE_NONE, NULL,
			0x0, "Matching response in frame", HFILL }},

		{ &hf_djiuav_response_to,
		{ "Request In", "djiuav.response_to",
			FT_FRAMENUM, BASE_NONE, NULL,
			0x0, "Matching command in frame", HFILL }},

		{ &hf_djiuav_response_time,
		{ "Response Time", "djiuav.response_time",
			FT_RELATIVE_TIME, BASE_NONE, NULL,
			0x0, "Time between Command and matching Response", HFILL }},
	};
	static gint *ett[] = {
		&ett_djiuav,
	};
	module_t *djiuav_module;

	proto_djiuav = proto_register_protocol(PROTO_LONG_NAME, PROTO_SHORT_NAME, "djiuav");
	proto_register_field_array(proto_djiuav, hf, array_length(hf));
	proto_register_subtree_array(ett, array_length(ett));

	/* Preferences */
	djiuav_module = prefs_register_protocol(proto_djiuav, NULL);

	prefs_register_bool_preference(djiuav_module, "desegment",
		"Reassemble DJIUAV messages",
		"Whether DJIUAV should reassemble messages spanning multiple"
			" TCP segments (required to get useful results)",
		&djiuav_desegment);
}

void
proto_reg_handoff_djiuav(void)
{
	dissector_handle_t djiuav_handle;

	djiuav_handle = create_dissector_handle(dissect_djiuav_static, proto_djiuav);
	dissector_add_uint_with_preference("tcp.port", PORT_DJIUAV, djiuav_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:
 */