/*

 * packet-mdb.c

 * Routines for MDB dissection

 * Copyright 2023 Martin Kaiser for PayTec AG (www.paytec.ch)

 *

 * Wireshark - Network traffic analyzer

 * By Gerald Combs <gerald@wireshark.org>

 * Copyright 1998 Gerald Combs

 *

 * SPDX-License-Identifier: GPL-2.0-or-later

 */

/*

 * The MDB (Multi-Drop Bus) protocol is used inside a vending machine. MDB

 * defines the communication between the main control board (VMC = Vending

 * Machine Controller) and peripheral components, e.g. a payment terminal

 * or a bill validator.

 *

 * The VMC acts as bus master and sends a request to one peripheral at a time.

 * A peripheral may send data only in response to such a request.

 *

 * The MDB specification is maintained by the National Automatic Merchandising

 * Association (NAMA). As of August 2023, the current version of the MDB

 * specification is 4.3. It is available from

 * https://namanow.org/nama-releases-mdb-version-4-3/

 *

 * The pcap input format for this dissector is documented at

 * https://www.kaiser.cx/pcap-mdb.html

 */

#include "config.h"

#include <epan/expert.h>

#include <epan/packet.h>

#include <epan/tfs.h>

#include <wsutil/array.h>

#include <wiretap/wtap.h>

void proto_register_mdb(void);

static dissector_handle_t mdb_handle;

static int proto_mdb;

static int ett_mdb;

static int ett_mdb_hdr;

static int ett_mdb_cl;

static int ett_mdb_cgw;

static int hf_mdb_hdr_ver;

static int hf_mdb_event;

static int hf_mdb_addr;

static int hf_mdb_cmd;

static int hf_mdb_cl_setup_sub;

static int hf_mdb_cl_feat_lvl;

static int hf_mdb_cl_cols;

static int hf_mdb_cl_rows;

static int hf_mdb_cl_disp_info;

static int hf_mdb_cl_max_price;

static int hf_mdb_cl_min_price;

static int hf_mdb_cl_vend_sub;

static int hf_mdb_cl_item_price;

static int hf_mdb_cl_item_num;

static int hf_mdb_cl_reader_sub;

static int hf_mdb_cl_resp;

static int hf_mdb_cl_scale;

static int hf_mdb_cl_dec_pl;

static int hf_mdb_cl_max_rsp_time;

static int hf_mdb_cl_vend_amt;

static int hf_mdb_cl_expns_sub;

static int hf_mdb_cl_manuf_code;

static int hf_mdb_cl_ser_num;

static int hf_mdb_cl_mod_num;

static int hf_mdb_cl_opt_feat;

static int hf_mdb_cgw_feat_lvl;

static int hf_mdb_cgw_scale;

static int hf_mdb_cgw_dec_pl;

static int hf_mdb_cgw_resp;

static int hf_mdb_cgw_max_rsp_time;

static int hf_mdb_cgw_report_sub;

static int hf_mdb_cgw_dts_evt_code;

static int hf_mdb_cgw_duration;

static int hf_mdb_cgw_activity;

static int hf_mdb_cgw_expns_sub;

static int hf_mdb_cgw_opt_feat;

static int hf_mdb_cgw_manuf_code;

static int hf_mdb_cgw_ser_num;

static int hf_mdb_cgw_mod_num;

static int hf_mdb_ack;

static int hf_mdb_data;

static int hf_mdb_chk;

static expert_field ei_mdb_short_packet;

#define MDB_EVT_DATA_MST_PER 0xFF

#define MDB_EVT_DATA_PER_MST 0xFE

#define MDB_EVT_BUS_RESET    0xFD

static const value_string mdb_event[] = {

    { MDB_EVT_DATA_MST_PER, "Data transfer Master -> Peripheral" },

    { MDB_EVT_DATA_PER_MST, "Data transfer Peripheral -> Master" },

    { MDB_EVT_BUS_RESET, "Bus reset" },

    { 0, NULL }

};

#define ADDR_VMC "VMC"

#define ADDR_CASHLESS1 0x10

#define ADDR_COMMS_GW  0x18

static const value_string mdb_addr[] = {

    { 0x08, "Changer" },

    { ADDR_CASHLESS1, "Cashless #1" },

    { ADDR_COMMS_GW, "Communications Gateway" },

    { 0x30, "Bill Validator" },

    { 0x60, "Cashless #2" },

    { 0x68, "Age Verification Device" },

    { 0, NULL }

};

static const value_string mdb_ack[] = {

    { 0x00, "ACK" },

    { 0xAA, "RET" },

    { 0xFF, "NAK" },

    { 0, NULL }

};

/*

 * These are just the command bits in the address + command byte. MDB supports

 * two Cashless peripherals (Cashless #1 and #2) with different addresses,

 * both use the same commands.

 */

#define MDB_CL_CMD_SETUP  0x01

#define MDB_CL_CMD_VEND   0x03

#define MDB_CL_CMD_READER 0x04

#define MDB_CL_CMD_EXPNS  0x07

static const value_string mdb_cl_cmd[] = {

    { 0x00, "Reset" },

    { MDB_CL_CMD_SETUP, "Setup" },

    { 0x02, "Poll" },

    { MDB_CL_CMD_VEND, "Vend" },

    { MDB_CL_CMD_READER, "Reader" },

    { MDB_CL_CMD_EXPNS, "Expansion" },

    { 0, NULL }

};

#define MDB_CL_SETUP_CFG_DATA 0x00

#define MDB_CL_SETUP_MAX_MIN  0x01

static const value_string mdb_cl_setup_sub_cmd[] = {

    { MDB_CL_SETUP_CFG_DATA, "Config Data" },

    { MDB_CL_SETUP_MAX_MIN, "Max/Min Prices" },

    { 0, NULL }

};

#define MDB_CL_VEND_REQ 0x00

#define MDB_CL_VEND_SUC 0x02

static const value_string mdb_cl_vend_sub_cmd[] = {

    { MDB_CL_VEND_REQ, "Vend Request" },

    { MDB_CL_VEND_SUC, "Vend Success" },

    { 0x04, "Session Complete" },

    { 0, NULL }

};

static const value_string mdb_cl_reader_sub_cmd[] = {

    { 0x00, "Reader Disable" },

    { 0x01, "Reader Enable" },

    { 0, NULL }

};

#define MDB_CL_EXPNS_REQ_ID  0x00

#define MDB_CL_EXPNS_OPT_ENA 0x04

static const value_string mdb_cl_expns_sub_cmd[] = {

    { MDB_CL_EXPNS_REQ_ID, "Request ID" },

    { MDB_CL_EXPNS_OPT_ENA, "Optional Feature Enabled" },

    { 0, NULL }

};

#define MDB_CL_RESP_RD_CFG_DATA 0x01

#define MDB_CL_RESP_VEND_APRV   0x05

#define MDB_CL_RESP_PER_ID      0x09

static const value_string mdb_cl_resp[] = {

    { 0x00, "Just Reset" },

    { MDB_CL_RESP_RD_CFG_DATA, "Reader Config Data" },

    { 0x03, "Begin Session" },

    { MDB_CL_RESP_VEND_APRV, "Vend Approved" },

    { 0x06, "Vend Denied" },

    { 0x07, "End Session" },

    { MDB_CL_RESP_PER_ID, "Peripheral ID" },

    { 0x0b, "Cmd Out Of Sequence" },

    { 0, NULL }

};

/*

 * For the Communications Gateway, we use the complete address + command byte

 * as value for the value string. The values here match those in the MDB

 * specification.

 *

 * There's only one Communications Gateway, the address bits are always the

 * same. (This is different from the Cashless peripherals, see above.)

 */

#define MDB_CGW_ADDR_CMD_SETUP  0x19

#define MDB_CGW_ADDR_CMD_REPORT 0x1B

#define MDB_CGW_ADDR_CMD_EXPNS  0x1F

static const value_string mdb_cgw_addr_cmd[] = {

    { 0x18, "Reset" },

    { MDB_CGW_ADDR_CMD_SETUP, "Setup" },

    { 0x1A, "Poll" },

    { MDB_CGW_ADDR_CMD_REPORT, "Report" },

    { MDB_CGW_ADDR_CMD_EXPNS, "Expansion" },

    { 0, NULL }

};

#define MDB_CGW_REPORT_DTS_EVT 0x02

static const value_string mdb_cgw_report_sub_cmd[] = {

    { 0x01, "Transaction" },

    { MDB_CGW_REPORT_DTS_EVT, "DTS Event" },

    { 0, NULL }

};

#define MDB_CGW_EXPNS_FEAT_ENA 0x01

static const value_string mdb_cgw_expns_sub_cmd[] = {

    { 0x00, "Identification" },

    { MDB_CGW_EXPNS_FEAT_ENA, "Feature enable" },

    { 0x02, "Time/Date Request" },

    { 0, NULL }

};

#define MDB_CGW_RESP_CFG    0x01

#define MDB_CGW_RESP_PER_ID 0x06

static const value_string mdb_cgw_resp[] = {

    { 0x00, "Just Reset" },

    { MDB_CGW_RESP_CFG, "Comms Gateway Config" },

    { 0x05, "DTS Event Acknowledge" },

    { MDB_CGW_RESP_PER_ID, "Peripheral ID" },

    { 0, NULL }

};

static void dissect_mdb_ack(tvbuff_t *tvb, int offset,

        packet_info *pinfo, proto_tree *tree)

{

    uint32_t ack;

    proto_tree_add_item_ret_uint(tree, hf_mdb_ack, tvb, offset, 1,

                ENC_BIG_ENDIAN, &ack);

    col_set_str(pinfo->cinfo, COL_INFO,

            val_to_str_const(ack, mdb_ack, "Invalid ack byte"));

}

static void mdb_set_addrs(uint8_t event, uint8_t addr, packet_info *pinfo)

{

    const char *periph = val_to_str(addr, mdb_addr, "Unknown (0x%02x)");

    /* pinfo->p2p_dir is from the perspective of the master (VMC) */

    if (event == MDB_EVT_DATA_MST_PER) {

        set_address(&pinfo->src, AT_STRINGZ, (int)strlen(ADDR_VMC)+1, ADDR_VMC);

        set_address(&pinfo->dst, AT_STRINGZ, (int)strlen(periph)+1, periph);

        pinfo->p2p_dir = P2P_DIR_SENT;

    }

    else if (event == MDB_EVT_DATA_PER_MST) {

        set_address(&pinfo->src, AT_STRINGZ, (int)strlen(periph)+1, periph);

        set_address(&pinfo->dst, AT_STRINGZ, (int)strlen(ADDR_VMC)+1, ADDR_VMC);

        pinfo->p2p_dir = P2P_DIR_RECV;

    }

}

static void dissect_mdb_cl_setup(tvbuff_t *tvb, int offset,

        packet_info *pinfo, proto_tree *tree)

{

    uint32_t sub_cmd, price;

    const char *s;

    proto_item *pi;

    proto_tree_add_item_ret_uint(tree, hf_mdb_cl_setup_sub,

                    tvb, offset, 1, ENC_BIG_ENDIAN, &sub_cmd);

    s = try_val_to_str(sub_cmd, mdb_cl_setup_sub_cmd);

    if (s) {

        col_set_str(pinfo->cinfo, COL_INFO, s);

    }

    offset++;

    switch (sub_cmd) {

        case MDB_CL_SETUP_CFG_DATA:

            proto_tree_add_item(tree, hf_mdb_cl_feat_lvl, tvb, offset, 1,

                    ENC_BIG_ENDIAN);

            offset++;

            proto_tree_add_item(tree, hf_mdb_cl_cols, tvb, offset, 1,

                    ENC_BIG_ENDIAN);

            offset++;

            proto_tree_add_item(tree, hf_mdb_cl_rows, tvb, offset, 1,

                    ENC_BIG_ENDIAN);

            offset++;

            proto_tree_add_item(tree, hf_mdb_cl_disp_info, tvb, offset, 1,

                    ENC_BIG_ENDIAN);

            break;

        case MDB_CL_SETUP_MAX_MIN:

            if (tvb_reported_length_remaining(tvb, offset) == 5) {

                /* This is the "default version" of Max/Min Prices. */

                /* XXX - convert the scaled prices into actual amounts */

                price = tvb_get_ntohs(tvb, offset);

                pi = proto_tree_add_uint_format(tree, hf_mdb_cl_max_price,

                        tvb, offset, 2, price, "Maximum price: 0x%04x", price);

                if (price == 0xFFFF) {

                    proto_item_append_text(pi, " (unknown)");

                }

                offset += 2;

                price = tvb_get_ntohs(tvb, offset);

                pi = proto_tree_add_uint_format(tree, hf_mdb_cl_min_price,

                        tvb, offset, 2, price, "Minimum price: 0x%04x", price);

                if (price == 0x0000) {

                    proto_item_append_text(pi, " (unknown)");

                }

            }

            else if (tvb_reported_length_remaining(tvb, offset) == 11) {

                /* This is the "expanded currency version" of Max/Min Prices. */

                proto_tree_add_item(tree, hf_mdb_cl_max_price, tvb, offset, 4,

                        ENC_BIG_ENDIAN);

                offset += 4;

                proto_tree_add_item(tree, hf_mdb_cl_min_price, tvb, offset, 4,

                        ENC_BIG_ENDIAN);

            }

            /* XXX - expert info for other lengths */

            break;

    }

}

static void dissect_mdb_cl_vend(tvbuff_t *tvb, int offset,

        packet_info *pinfo, proto_tree *tree)

{

    uint32_t sub_cmd, price, item;

    const char *s;

    proto_tree_add_item_ret_uint(tree, hf_mdb_cl_vend_sub, tvb, offset, 1,

            ENC_BIG_ENDIAN, &sub_cmd);

    s = try_val_to_str(sub_cmd, mdb_cl_vend_sub_cmd);

    if (s) {

        col_set_str(pinfo->cinfo, COL_INFO, s);

    }

    offset++;

    switch (sub_cmd) {

        case MDB_CL_VEND_REQ:

            if (tvb_reported_length_remaining(tvb, offset) == 5) {

                proto_tree_add_item_ret_uint(tree, hf_mdb_cl_item_price, tvb,

                        offset, 2, ENC_BIG_ENDIAN, &price);

                offset += 2;

                proto_tree_add_item_ret_uint(tree, hf_mdb_cl_item_num, tvb,

                        offset, 2, ENC_BIG_ENDIAN, &item);

                col_append_fstr(pinfo->cinfo, COL_INFO, " (item %d, price %d)",

                        item, price);

            }

            /* XXX - dissect the longer request in Expanded Currency Mode */

            break;

        case MDB_CL_VEND_SUC:

                proto_tree_add_item(tree, hf_mdb_cl_item_num, tvb, offset, 2,

                        ENC_BIG_ENDIAN);

            break;

    }

}

static int

dissect_mdb_cl_id_fields(tvbuff_t *tvb, int offset, proto_tree *tree)

{

    proto_tree_add_item(tree, hf_mdb_cl_manuf_code, tvb, offset, 3, ENC_ASCII);

    offset += 3;

    proto_tree_add_item(tree, hf_mdb_cl_ser_num, tvb, offset, 12, ENC_ASCII);

    offset += 12;

    proto_tree_add_item(tree, hf_mdb_cl_mod_num, tvb, offset, 12, ENC_ASCII);

    offset += 12;

    /* XXX - dissect the Software Version bytes */

    offset += 2;

    return offset;

}

static void dissect_mdb_cl_expns(tvbuff_t *tvb, int offset, packet_info *pinfo,

        proto_tree *tree)

{

    uint32_t sub_cmd;

    const char *s;

    proto_tree_add_item_ret_uint(tree, hf_mdb_cl_expns_sub,

                    tvb, offset, 1, ENC_BIG_ENDIAN, &sub_cmd);

    s = try_val_to_str(sub_cmd, mdb_cl_expns_sub_cmd);

    if (s) {

        col_set_str(pinfo->cinfo, COL_INFO, s);

    }

    offset++;

    switch (sub_cmd) {

        case MDB_CL_EXPNS_REQ_ID:

            dissect_mdb_cl_id_fields(tvb, offset, tree);

            break;

        case MDB_CL_EXPNS_OPT_ENA:

            /* XXX - add a bitmask for the Optional Feature Bits */

            proto_tree_add_item(tree, hf_mdb_cl_opt_feat, tvb, offset, 4,

                    ENC_BIG_ENDIAN);

            break;

    }

}

static void dissect_mdb_cl_rd_cfg_data(tvbuff_t *tvb, int offset,

        packet_info *pinfo _U_, proto_tree *tree)

{

    proto_tree_add_item(tree, hf_mdb_cl_feat_lvl, tvb, offset, 1,

            ENC_BIG_ENDIAN);

    offset++;

    /* XXX - dissect Country/Currency Code */

    offset += 2;

    proto_tree_add_item(tree, hf_mdb_cl_scale, tvb, offset, 1, ENC_BIG_ENDIAN);

    offset++;

    proto_tree_add_item(tree, hf_mdb_cl_dec_pl, tvb, offset, 1, ENC_BIG_ENDIAN);

    offset++;

    proto_tree_add_item(tree, hf_mdb_cl_max_rsp_time, tvb, offset, 1,

            ENC_TIME_SECS | ENC_BIG_ENDIAN);

}

static void dissect_mdb_mst_per_cl( tvbuff_t *tvb, int offset, int len _U_,

        packet_info *pinfo, proto_tree *tree, proto_item *cmd_it,

        uint8_t addr_byte)

{

    uint8_t cmd = addr_byte & 0x07; /* the 3-bit command */

    proto_tree *cl_tree;

    uint32_t sub_cmd;

    const char *s;

    s = val_to_str_const(cmd, mdb_cl_cmd, "Unknown");

    proto_item_append_text(cmd_it, " (%s)", s);

    col_set_str(pinfo->cinfo, COL_INFO, s);

    cl_tree = proto_tree_add_subtree(tree, tvb, offset, len, ett_mdb_cl,

            NULL, "Cashless");

    s = NULL;

    switch (cmd) {

        case MDB_CL_CMD_SETUP:

            dissect_mdb_cl_setup(tvb, offset, pinfo, cl_tree);

            break;

        case MDB_CL_CMD_VEND:

            dissect_mdb_cl_vend(tvb, offset, pinfo, cl_tree);

            break;

        case MDB_CL_CMD_READER:

            proto_tree_add_item_ret_uint(cl_tree, hf_mdb_cl_reader_sub,

                    tvb, offset, 1, ENC_BIG_ENDIAN, &sub_cmd);

            s = try_val_to_str(sub_cmd, mdb_cl_reader_sub_cmd);

            break;

        case MDB_CL_CMD_EXPNS:

            dissect_mdb_cl_expns(tvb, offset, pinfo, cl_tree);

            break;

    }

    if (s)

        col_set_str(pinfo->cinfo, COL_INFO, s);

}

static void dissect_mdb_per_mst_cl( tvbuff_t *tvb, int offset,

        int len _U_, packet_info *pinfo, proto_tree *tree)

{

    proto_tree *cl_tree;

    uint32_t cl_resp;

    cl_tree = proto_tree_add_subtree(tree, tvb, offset, len, ett_mdb_cl,

            NULL, "Cashless");

    proto_tree_add_item_ret_uint(cl_tree, hf_mdb_cl_resp, tvb, offset, 1,

            ENC_BIG_ENDIAN, &cl_resp);

    col_set_str(pinfo->cinfo,

            COL_INFO, val_to_str_const(cl_resp, mdb_cl_resp, "Unknown"));

    offset++;

    switch (cl_resp) {

        case MDB_CL_RESP_RD_CFG_DATA:

            dissect_mdb_cl_rd_cfg_data(tvb, offset, pinfo, cl_tree);

            break;

        case MDB_CL_RESP_VEND_APRV:

            if (tvb_reported_length_remaining(tvb, offset) == 3) {

                proto_tree_add_item(cl_tree, hf_mdb_cl_vend_amt, tvb, offset,

                        2, ENC_BIG_ENDIAN);

            }

            /* XXX - dissect the longer response in Expanded Currency Mode */

            break;

        case MDB_CL_RESP_PER_ID:

            dissect_mdb_cl_id_fields(tvb, offset, tree);

            /* XXX - check if we have Optional Feature Bits */

            break;

    }

}

static void dissect_mdb_cgw_report(tvbuff_t *tvb, int offset,

        packet_info *pinfo, proto_tree *tree)

{

    uint32_t sub_cmd;

    const char *s;

    proto_tree_add_item_ret_uint(tree, hf_mdb_cgw_report_sub,

                    tvb, offset, 1, ENC_BIG_ENDIAN, &sub_cmd);

    s = try_val_to_str(sub_cmd, mdb_cgw_report_sub_cmd);

    if (s) {

        col_set_str(pinfo->cinfo, COL_INFO, s);

    }

    offset++;

    switch (sub_cmd) {

        case MDB_CGW_REPORT_DTS_EVT:

            proto_tree_add_item(tree, hf_mdb_cgw_dts_evt_code, tvb, offset, 10,

                    ENC_ASCII);

            offset += 10;

            /* XXX - dissect Date */

            offset += 4;

            /* XXX - dissect Time */

            offset += 2;

            proto_tree_add_item(tree, hf_mdb_cgw_duration, tvb, offset, 4,

                    ENC_BIG_ENDIAN);

            offset += 4;

            proto_tree_add_item(tree, hf_mdb_cgw_activity, tvb, offset, 1,

                    ENC_BIG_ENDIAN);

            break;

    }

}

static void dissect_mdb_cgw_expns(tvbuff_t *tvb, int offset,

        packet_info *pinfo, proto_tree *tree)

{

    uint32_t sub_cmd;

    const char *s;

    proto_tree_add_item_ret_uint(tree, hf_mdb_cgw_expns_sub,

                    tvb, offset, 1, ENC_BIG_ENDIAN, &sub_cmd);

    s = try_val_to_str(sub_cmd, mdb_cgw_expns_sub_cmd);

    if (s) {

        col_set_str(pinfo->cinfo, COL_INFO, s);

    }

    offset++;

    switch (sub_cmd) {

        case MDB_CGW_EXPNS_FEAT_ENA:

            proto_tree_add_item(tree, hf_mdb_cgw_opt_feat, tvb, offset, 4,

                    ENC_BIG_ENDIAN);

            break;

    }

}

static void dissect_mdb_mst_per_cgw( tvbuff_t *tvb, int offset, int len,

        packet_info *pinfo, proto_tree *tree, proto_item *cmd_it,

        uint8_t addr_cmd_byte)

{

    proto_tree *cgw_tree;

    const char *s;

    s = val_to_str_const(addr_cmd_byte, mdb_cgw_addr_cmd, "Unknown");

    proto_item_append_text(cmd_it, " (%s)", s);

    col_set_str(pinfo->cinfo, COL_INFO, s);

    cgw_tree = proto_tree_add_subtree(tree, tvb, offset, len, ett_mdb_cgw,

            NULL, "Communications Gateway");

    switch (addr_cmd_byte) {

        case MDB_CGW_ADDR_CMD_SETUP:

            proto_tree_add_item(cgw_tree, hf_mdb_cgw_feat_lvl, tvb, offset, 1,

                    ENC_BIG_ENDIAN);

            offset++;

            proto_tree_add_item(cgw_tree, hf_mdb_cgw_scale, tvb, offset, 1,

                    ENC_BIG_ENDIAN);

            offset++;

            proto_tree_add_item(cgw_tree, hf_mdb_cgw_dec_pl, tvb, offset, 1,

                    ENC_BIG_ENDIAN);

            break;

        case MDB_CGW_ADDR_CMD_REPORT:

            dissect_mdb_cgw_report(tvb, offset, pinfo, cgw_tree);

            break;

        case MDB_CGW_ADDR_CMD_EXPNS:

            dissect_mdb_cgw_expns(tvb, offset, pinfo, cgw_tree);

            break;

    }

}

static void dissect_mdb_per_mst_cgw( tvbuff_t *tvb, int offset,

        int len, packet_info *pinfo _U_, proto_tree *tree)

{

    proto_tree *cgw_tree;

    uint32_t cgw_resp;

    cgw_tree = proto_tree_add_subtree(tree, tvb, offset, len, ett_mdb_cgw,

            NULL, "Communications Gateway");

    proto_tree_add_item_ret_uint(cgw_tree, hf_mdb_cgw_resp, tvb, offset, 1,

            ENC_BIG_ENDIAN, &cgw_resp);

    col_set_str(pinfo->cinfo,

            COL_INFO, val_to_str_const(cgw_resp, mdb_cgw_resp, "Unknown"));

    offset++;

    switch (cgw_resp) {

        case MDB_CGW_RESP_CFG:

            proto_tree_add_item(cgw_tree, hf_mdb_cgw_feat_lvl, tvb, offset, 1,

                    ENC_BIG_ENDIAN);

            offset++;

            proto_tree_add_item(cgw_tree, hf_mdb_cgw_max_rsp_time, tvb, offset,

                    2, ENC_TIME_SECS | ENC_BIG_ENDIAN);

            break;

        case MDB_CGW_RESP_PER_ID:

            proto_tree_add_item(tree, hf_mdb_cgw_manuf_code, tvb, offset, 3,

                    ENC_ASCII);

            offset += 3;

            proto_tree_add_item(tree, hf_mdb_cgw_ser_num, tvb, offset, 12,

                    ENC_ASCII);

            offset += 12;

            proto_tree_add_item(tree, hf_mdb_cgw_mod_num, tvb, offset, 12,

                    ENC_ASCII);

            offset += 12;

            /* XXX - dissect the Software Version bytes */

            offset += 2;

            proto_tree_add_item(tree, hf_mdb_cgw_opt_feat, tvb, offset, 4,

                    ENC_BIG_ENDIAN);

            break;

    }

}

static void dissect_mdb_mst_per(tvbuff_t *tvb, int offset, packet_info *pinfo,

        proto_tree *tree)

{

    uint8_t addr_byte, addr;

    int mst_per_len;

    unsigned data_len;

    proto_item *cmd_it;

    mst_per_len = tvb_reported_length_remaining(tvb, offset);

    if (mst_per_len <= 0) {

        expert_add_info(pinfo, tree, &ei_mdb_short_packet);

        return;

    }

    if (mst_per_len == 1) {

        dissect_mdb_ack(tvb, offset, pinfo, tree);

        return;

    }

    /*

     * Our packet has one address byte, an optional data block and one

     * checksum byte.

     */

    data_len = mst_per_len - 2;

    /*

     * The address byte is 5-bit address | 3-bit command.

     *

     * The specification uses 8-bit addresses which are the address byte

     * with the three lowest bits set to 0.

     *

     * The commands are defined as the complete address byte (i.e. they

     * include the address part). This does not make much sense: Cashless #1

     * and #2 have different addresses but exactly the same 3-bit commands.

     *

     * In this dissector, we try to use the same values as the specification.

     */

    addr_byte = tvb_get_uint8(tvb, offset);

    addr = addr_byte & 0xF8;

    proto_tree_add_uint_bits_format_value(tree, hf_mdb_addr,

            tvb, 8*offset, 5, addr, ENC_BIG_ENDIAN, "0x%02x", addr);

    cmd_it = proto_tree_add_uint(tree, hf_mdb_cmd, tvb, offset, 1, addr_byte);

    mdb_set_addrs(MDB_EVT_DATA_MST_PER, addr, pinfo);

    offset++;

    /*

     * We call the peripheral functions even if data_len == 0 so they can fix

     * up the command with peripheral-specific info.

     */

    switch (addr) {

        case ADDR_CASHLESS1:

            dissect_mdb_mst_per_cl(tvb, offset, data_len, pinfo, tree,

                    cmd_it, addr_byte);

            break;

        case ADDR_COMMS_GW:

            dissect_mdb_mst_per_cgw(tvb, offset, data_len, pinfo, tree,

                    cmd_it, addr_byte);

            break;

        default:

            if (data_len > 0) {

                proto_tree_add_item(tree, hf_mdb_data,

                        tvb, offset, data_len, ENC_NA);

            }

            break;

    }

    offset += data_len;

    /* XXX - verify the checksum */

    proto_tree_add_item(tree, hf_mdb_chk, tvb, offset, 1, ENC_BIG_ENDIAN);

}

static void dissect_mdb_per_mst(tvbuff_t *tvb, int offset, packet_info *pinfo,

        proto_tree *tree, uint8_t addr)

{

    int per_mst_len;

    unsigned data_len;

    /*

     * A packet from peripheral to master is either a single ACK/NAK byte or

     * a non-empty data block followed by one checksum byte.

     */

    per_mst_len = tvb_reported_length_remaining(tvb, offset);

    if (per_mst_len <= 0) {

        expert_add_info(pinfo, tree, &ei_mdb_short_packet);

        return;

    }

    if (per_mst_len == 1) {

        dissect_mdb_ack(tvb, offset, pinfo, tree);

        return;

    }

    data_len = per_mst_len - 1;

    switch (addr) {

        case ADDR_CASHLESS1:

            dissect_mdb_per_mst_cl(tvb, offset, data_len, pinfo, tree);

            break;

        case ADDR_COMMS_GW:

            dissect_mdb_per_mst_cgw(tvb, offset, data_len, pinfo, tree);

            break;

        default:

            proto_tree_add_item(tree, hf_mdb_data, tvb, offset, data_len, ENC_NA);

            break;

    }

    offset += data_len;

    /* XXX - verify the checksum */

    proto_tree_add_item(tree, hf_mdb_chk, tvb, offset, 1, ENC_BIG_ENDIAN);

}

static int dissect_mdb(tvbuff_t *tvb,

        packet_info *pinfo, proto_tree *tree, void *data _U_)

{

    int offset = 0, offset_ver, offset_evt;

    uint8_t version, event, addr;

    proto_tree *mdb_tree, *hdr_tree;

    proto_item *tree_ti, *hdr_ti;

    /* We need at least the shortest possible pseudo header. */

    if (tvb_captured_length(tvb) < 3)

        return 0;

    offset_ver = offset;

    version = tvb_get_uint8(tvb, offset++);

    if (version != 0)

        return 0;

    offset_evt = offset;

    event = tvb_get_uint8(tvb, offset++);

    if (!try_val_to_str(event, mdb_event))

        return 0;

    col_set_str(pinfo->cinfo, COL_PROTOCOL, "MDB");

    col_clear(pinfo->cinfo, COL_INFO);

    tree_ti = proto_tree_add_protocol_format(tree, proto_mdb,

            tvb, 0, tvb_reported_length(tvb), "MDB");

    mdb_tree = proto_item_add_subtree(tree_ti, ett_mdb);

    hdr_tree = proto_tree_add_subtree(mdb_tree, tvb, 0, -1, ett_mdb_hdr,

            &hdr_ti, "Pseudo header");

    proto_tree_add_item(hdr_tree, hf_mdb_hdr_ver,

            tvb, offset_ver, 1, ENC_BIG_ENDIAN);

    proto_tree_add_item(hdr_tree, hf_mdb_event,

            tvb, offset_evt, 1, ENC_BIG_ENDIAN);

    /* Packets from peripheral to master always have an address byte in their

       pseudo header. */

    if (event == MDB_EVT_DATA_PER_MST) {

        /* See the comment in dissect_mdb_mst_per about MDB addresses. */

        addr = tvb_get_uint8(tvb, offset) & 0xF8;

        proto_tree_add_uint_bits_format_value(hdr_tree, hf_mdb_addr,

                tvb, 8*offset, 5, addr, ENC_BIG_ENDIAN, "0x%02x", addr);

        offset++;

        mdb_set_addrs(event, addr, pinfo);

    }

    /* We're now at the end of the pseudo header. */

    proto_item_set_len(hdr_ti, offset);

    if (event == MDB_EVT_BUS_RESET)

        return offset;

    if (event == MDB_EVT_DATA_MST_PER)

        dissect_mdb_mst_per(tvb, offset, pinfo, mdb_tree);

    else if (event == MDB_EVT_DATA_PER_MST)

        dissect_mdb_per_mst(tvb, offset, pinfo, mdb_tree, addr);

    return tvb_reported_length(tvb);

}

void proto_register_mdb(void)

{

    expert_module_t* expert_mdb;

    static int *ett[] = {

        &ett_mdb,

        &ett_mdb_hdr,

        &ett_mdb_cl,

        &ett_mdb_cgw

    };

    static hf_register_info hf[] = {

        { &hf_mdb_hdr_ver,

            { "Version", "mdb.hdr_ver",

                FT_UINT8, BASE_HEX, NULL, 0, NULL, HFILL }

        },

        { &hf_mdb_event,

            { "Event", "mdb.event",

                FT_UINT8, BASE_HEX, VALS(mdb_event), 0, NULL, HFILL }

        },

        { &hf_mdb_addr,

            { "Address", "mdb.addr",

                FT_UINT8, BASE_HEX, NULL, 0, NULL, HFILL }

        },

        { &hf_mdb_cmd,

            { "Command", "mdb.cmd",

                FT_UINT8, BASE_HEX, NULL, 0, NULL, HFILL }

        },

        { &hf_mdb_cl_setup_sub,

            { "Sub-command", "mdb.cashless.setup_sub_cmd",

                FT_UINT8, BASE_HEX, VALS(mdb_cl_setup_sub_cmd), 0, NULL, HFILL }

        },

        { &hf_mdb_cl_feat_lvl,

            { "Feature level", "mdb.cashless.feature_level",

                FT_UINT8, BASE_DEC, NULL, 0, NULL, HFILL }

        },

        { &hf_mdb_cl_cols,

            { "Columns on display", "mdb.cashless.columns",

                FT_UINT8, BASE_DEC, NULL, 0, NULL, HFILL }

        },

        { &hf_mdb_cl_rows,

            { "Rows on display", "mdb.cashless.rows",

                FT_UINT8, BASE_DEC, NULL, 0, NULL, HFILL }

        },

        { &hf_mdb_cl_disp_info,

            { "Display information", "mdb.cashless.disp_info",

                FT_UINT8, BASE_HEX, NULL, 0x07, NULL, HFILL }

        },

        { &hf_mdb_cl_max_price,

            { "Maximum price", "mdb.cashless.max_price",

                FT_UINT32, BASE_HEX, NULL, 0, NULL, HFILL }

        },

        { &hf_mdb_cl_min_price,

            { "Minimum price", "mdb.cashless.min_price",

                FT_UINT32, BASE_HEX, NULL, 0, NULL, HFILL }

        },

        { &hf_mdb_cl_vend_sub,

            { "Sub-command", "mdb.cashless.vend_sub_cmd",

                FT_UINT8, BASE_HEX, VALS(mdb_cl_vend_sub_cmd), 0, NULL, HFILL }

        },

        { &hf_mdb_cl_item_price,

            { "Item Price", "mdb.cashless.item_price",

                FT_UINT32, BASE_DEC, NULL, 0, NULL, HFILL }

        },

        { &hf_mdb_cl_item_num,

            { "Item Number", "mdb.cashless.item_number",

                FT_UINT32, BASE_DEC, NULL, 0, NULL, HFILL }

        },

        { &hf_mdb_cl_reader_sub,

            { "Sub-command", "mdb.cashless.reader_sub_cmd",

                FT_UINT8, BASE_HEX, VALS(mdb_cl_reader_sub_cmd), 0, NULL, HFILL }

        },

        { &hf_mdb_cl_resp,

            { "Response", "mdb.cashless.resp",

                FT_UINT8, BASE_HEX, VALS(mdb_cl_resp), 0, NULL, HFILL }

        },

        { &hf_mdb_cl_scale,

            { "Scale factor", "mdb.cashless.scale_factor",

                FT_UINT8, BASE_DEC, NULL, 0, NULL, HFILL }

        },

        { &hf_mdb_cl_dec_pl,

            { "Decimal places", "mdb.cashless.decimal_places",

                FT_UINT8, BASE_DEC, NULL, 0, NULL, HFILL }

        },

        { &hf_mdb_cl_max_rsp_time,

            { "Application maximum response time", "mdb.cashless.max_rsp_time",

                FT_RELATIVE_TIME, BASE_NONE, NULL, 0, NULL, HFILL }

        },

        { &hf_mdb_cl_vend_amt,

            { "Vend Amount", "mdb.cashless.vend_amount",

                FT_UINT32, BASE_DEC, NULL, 0, NULL, HFILL }

        },

        { &hf_mdb_cl_expns_sub,

            { "Sub-command", "mdb.cashless.expansion_sub_cmd",

                FT_UINT8, BASE_HEX, VALS(mdb_cl_expns_sub_cmd), 0, NULL, HFILL }

        },

        { &hf_mdb_cl_manuf_code,

            { "Manufacturer Code", "mdb.cashless.manuf_code",

                FT_STRING, BASE_NONE, NULL, 0, NULL, HFILL }

        },

        { &hf_mdb_cl_ser_num,

            { "Serial Number", "mdb.cashless.serial_number",

                FT_STRING, BASE_NONE, NULL, 0, NULL, HFILL }

        },

        { &hf_mdb_cl_mod_num,

            { "Model Number", "mdb.cashless.model_number",

                FT_STRING, BASE_NONE, NULL, 0, NULL, HFILL }

        },

        { &hf_mdb_cl_opt_feat,

            { "Optional Feature Bits", "mdb.cashless.opt_feature_bits",

                FT_UINT32, BASE_HEX, NULL, 0, NULL, HFILL }

        },

        { &hf_mdb_cgw_feat_lvl,

            { "Feature level", "mdb.comms_gw.feature_level",

                FT_UINT8, BASE_DEC, NULL, 0, NULL, HFILL }

        },

        { &hf_mdb_cgw_scale,

            { "Scale factor", "mdb.comms_gw.scale_factor",

                FT_UINT8, BASE_DEC, NULL, 0, NULL, HFILL }

        },

        { &hf_mdb_cgw_dec_pl,

            { "Decimal places", "mdb.comms_gw.decimal_places",

                FT_UINT8, BASE_DEC, NULL, 0, NULL, HFILL }

        },

        { &hf_mdb_cgw_resp,

            { "Response", "mdb.comms_gw.resp",

                FT_UINT8, BASE_HEX, VALS(mdb_cgw_resp), 0, NULL, HFILL }

        },

        { &hf_mdb_cgw_max_rsp_time,

            { "Application maximum response time", "mdb.comms_gw.max_rsp_time",

                FT_RELATIVE_TIME, BASE_NONE, NULL, 0, NULL, HFILL }

        },

        { &hf_mdb_cgw_report_sub,

            { "Sub-command", "mdb.comms_gw.report_sub_cmd", FT_UINT8,

                BASE_HEX, VALS(mdb_cgw_report_sub_cmd), 0, NULL, HFILL }

        },

        { &hf_mdb_cgw_dts_evt_code,

            { "DTS Event Code", "mdb.comms_gw.dts_event_code",

                FT_STRING, BASE_NONE, NULL, 0, NULL, HFILL }

        },

        { &hf_mdb_cgw_duration,

            { "Duration", "mdb.comms_gw.duration",

                FT_UINT32, BASE_DEC, NULL, 0, NULL, HFILL }

        },