/*

 * 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/conversation.h>

#include <epan/tfs.h>

#include <wsutil/array.h>

#include <wiretap/wtap.h>

void proto_reg_handoff_mdb(void);

void proto_register_mdb(void);

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 ett_mdb_bv;

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_bv_setup_bill_val_feature;

static int hf_mdb_bv_setup_ctry_currency_code;

static int hf_mdb_bv_setup_bill_scal_fac;

static int hf_mdb_bv_setup_dec_places;

static int hf_mdb_bv_setup_bill_stacker_cap;

static int hf_mdb_bv_setup_bill_sec_lvls;

static int hf_mdb_bv_setup_escrow;

static int hf_mdb_bv_setup_bill_type_cred;

static int hf_mdb_bv_bill_enable;

static int hf_mdb_bv_bill_escrow_enable;

static int hf_mdb_bv_poll_state;

static int hf_mdb_bv_poll_bill_routing_state;

static int hf_mdb_bv_poll_bill_type;

static int hf_mdb_bv_escrow_state;

static int hf_mdb_bv_stacker;

static int hf_mdb_bv_exp_cmd;

static int hf_mdb_bv_exp_opt_feat;

static int hf_mdb_bv_exp_opt_feat_enable;

static int hf_mdb_bv_exp_manufact_code;

static int hf_mdb_bv_exp_serial_num;

static int hf_mdb_bv_exp_model_tuning_num;

static int hf_mdb_bv_exp_software_version;

static int hf_mdb_bv_exp_bill_type_routing;

static int hf_mdb_bv_exp_manual_dispense_enable;

static int hf_mdb_bv_exp_bill_recycler_enabled;

static int hf_mdb_bv_exp_bill_count;

static int hf_mdb_bv_exp_dispenser_full_state;

static int hf_mdb_bv_exp_bill_type_dispensed;

static int hf_mdb_bv_exp_bill_type_number_bills;

static int hf_mdb_bv_exp_dispense_value_bills;

static int hf_mdb_bv_exp_payout_state;

static int hf_mdb_bv_exp_dispenser_payout_activity;

static int hf_mdb_ack;

static int hf_mdb_data;

static int hf_mdb_chk;

static int hf_mdb_chk_status;

static int hf_mdb_response_in;

static int hf_mdb_response_to;

static int hf_mdb_time;

static expert_field ei_mdb_short_packet;

static expert_field ei_mdb_bad_checksum;

static dissector_handle_t mdb_handle;

/* MDB is a master slave protocol, so per request, there is exactly one response */

typedef struct {

    uint32_t req_num, rep_num;

    nstime_t req_time;

    uint16_t cmd;   // In case of expanse cmd, 2 byte are used

} mdb_transaction_t;

typedef struct {

    wmem_tree_t* transactions;

    uint32_t last_req_packet;

    uint16_t last_cmd;

} mdb_conv_info_t;

static mdb_conv_info_t* get_mdb_conv_info(packet_info* pinfo)

{

    conversation_t* conversation;

    mdb_conv_info_t* conv_info;

    conversation = find_or_create_conversation(pinfo);

    conv_info = (mdb_conv_info_t*)conversation_get_proto_data(conversation, proto_mdb);

    if (!conv_info) {

        conv_info = wmem_new0(wmem_file_scope(), mdb_conv_info_t);

        conv_info->transactions = wmem_tree_new(wmem_file_scope());

        conversation_add_proto_data(conversation, proto_mdb, conv_info);

    }

    return conv_info;

}

#define MDB_EVT_DATA_MST_PER 0xFF

#define MDB_EVT_DATA_PER_MST 0xFE

#define MDB_EVT_BUS_RESET    0xFD

#define MDB_PSEUDO_HDR_LEN   2

static bool is_mdb_reply(uint8_t byte) {

    return (byte == 0x00 || byte == 0xAA || byte == 0xFF);

}

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

#define ADDR_BILL_VALIDATOR 0x30

#define ADDR_MASK           0xF8

#define CMD_MASK            0x07

#define SUB_CMD_OFFSET      8

static const value_string mdb_addr[] = {

    { 0x00, "Reserved for VMC" },

    { 0x08, "Changer" },

    { ADDR_CASHLESS1, "Cashless #1" },

    { ADDR_COMMS_GW, "Communications Gateway" },

    { 0x20, "Display" },

    { 0x28, "Energy Management System" },

    { ADDR_BILL_VALIDATOR, "Bill Validator" },

    { 0x38, "Reserved for Future Standard Peripheral" },

    { 0x40, "Universal Satellite Device #1" },

    { 0x48, "Universal Satellite Device #2" },

    { 0x50, "Universal Satellite Device #3" },

    { 0x58, "Coin Hopper or Tube - Dispenser 1" },

    { 0x60, "Cashless #2" },

    { 0x68, "Age Verification Device" },

    { 0x70, "Coin Hopper or Tube - Dispenser 2" },

    { 0xF0, "Vending Machine Specific Peripheral #1" },

    { 0xF8, "Vending Machine Specific Peripheral #2" },

    { 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 }

};

/*

 * Commands for Bill Validator

 */

#define MDB_BV_CMD_SETUP      0x01

#define MDB_BV_CMD_SECURITY   0x02

#define MDB_BV_CMD_POLL       0x03

#define MDB_BV_CMD_BILL_TYPE  0x04

#define MDB_BV_CMD_ESCROW     0x05

#define MDB_BV_CMD_STACKER    0x06

#define MDB_BV_CMD_EXPNS      0x07

#define MDB_BV_CMD_NONE       0xFF

static const value_string mdb_bv_cmd[] = {

    { 0x00, "Reset" },

    { MDB_BV_CMD_SETUP, "Setup" },

    { MDB_BV_CMD_SECURITY, "Security" },

    { MDB_BV_CMD_POLL, "Poll" },

    { MDB_BV_CMD_BILL_TYPE, "Bill type" },

    { MDB_BV_CMD_ESCROW, "Escrow" },

    { MDB_BV_CMD_STACKER, "Stacker" },

    { MDB_BV_CMD_EXPNS, "Expansion" },

    { 0, NULL }

};

#define MDB_BV_LVL1_WITHOUT_OPT_BITS    0x00

#define MDB_BV_LVL2_FEATURE_ENABLE      0x01

#define MDB_BV_LVL2_ID_WITH_OPTION_BITS 0x02

#define MDB_BV_RECYCL_SETUP             0x03

#define MDB_BV_RECYCL_ENABLE            0x04

#define MDB_BV_BILL_DISPENSE_STAT       0x05

#define MDB_BV_DISPENSE_BILL            0x06

#define MDB_BV_DISPENSE_VAL             0x07

#define MDB_BV_PAYOUT_STAT              0x08

#define MDB_BV_PAYOUT_VALUE_POLL        0x09

#define MDB_BV_PAYOUT_CANCEL            0x0A

static const value_string mdb_bv_exp_cmd[] = {

    { MDB_BV_LVL1_WITHOUT_OPT_BITS, "Level1 Identification without option bits" },

    { MDB_BV_LVL2_FEATURE_ENABLE, "Level2+ Feature Enable" },

    { MDB_BV_LVL2_ID_WITH_OPTION_BITS, "ID with Option Bits" },

    { MDB_BV_RECYCL_SETUP, "Recycler Setup" },

    { MDB_BV_RECYCL_ENABLE, "Recycler Enable" },

    { MDB_BV_BILL_DISPENSE_STAT, "Bill Dispense Status" },

    { MDB_BV_DISPENSE_BILL, "Dispense Bill" },

    { MDB_BV_DISPENSE_VAL, "Dispense Value" },

    { MDB_BV_PAYOUT_STAT, "Payout Status" },

    { MDB_BV_PAYOUT_VALUE_POLL, "Payout Value Poll" },

    { MDB_BV_PAYOUT_CANCEL, "Payout Cancel" },

    { 0, NULL }

};

static const true_false_string mdb_bv_escrow_state = { "Escrow Stack Bill", "Escrow Return Bill" };

// Format: 1yyyxxxx, where yyy = Bill routing, xxxx = Bill type (0 to 15)

static const value_string mdb_bv_poll_bill_routing_state[] = {

    { 0x00, "Bill Stacked" },

    { 0x01, "Escrow Position" },

    { 0x02, "Bill Returned" },

    { 0x03, "Bill to Recycler" },

    { 0x04, "Disabled Bill Rejected" },

    { 0x05, "Bill to Recycler" },

    { 0x06, "Manual Dispense" },

    { 0x07, "Transferred from Recycler to Cashbox" },

    { 0, NULL }

};

static const value_string mdb_bv_poll_state[] = {

/* Bill Validator (Only) */

    { 0x01, "Defective Motor" }, // One of the motors has failed to perform its expected assignment.

    { 0x02, "Sensor Problem" }, // One of the sensors has failed to provide its response.

    { 0x03, "Validator Busy" }, // The validator is busy and can not answer a detailed command right now.

    { 0x04, "ROM Checksum Error" }, // The validators internal checksum does not match the calculated checksum.

    { 0x05, "Validator Jammed" }, // A bill(s) has jammed in the acceptance path.

    { 0x06, "Validator was reset" }, // The validator has been reset since the last POLL.

    { 0x07, "Bill removed" }, // A bill in the escrow position has been removed by an unknown means. A BILL RETURNED message should also be sent.

    { 0x08, "Cash Box out of position" }, // The validator has detected the cash box to be open or removed.

    { 0x09, "Validator disabled" }, // The validator has been disabled, by the VMC or because of internal conditions.

    { 0x0A, "Invalid Escrow request" }, // An ESCROW command was requested for a bill not in the escrow position.

    { 0x0B, "Bill rejected" }, // A bill was detected, but rejected because it could not be identified.

    { 0x0C, "Possible Credited Bill Removal" }, // There has been an attempt to remove a credited (stacked) bill.

    { 0x40, "Disabled validator, number of attempts to input bill" }, // Format: 010xxxxx

/* Bill Recycler (Only) */

    { 0x21, "Escrow request" }, // An escrow lever activation has been detected. If a button is present and activated.

    { 0x22, "Dispenser Payout Busy" }, // The dispenser is busy activating payout devices.

    { 0x23, "Dispenser Busy" }, // The dispenser is busy and can not answer a detailed command right now

    { 0x24, "Defective Dispenser Sensor" }, // The dispenser has detected one of the dispenser sensors behaving abnormally

    { 0x26, "Dispenser did not start / motor problem" },

    { 0x27, "Dispenser Jam" }, // A dispenser payout attempt has resulted in jammed condition.

    { 0x28, "ROM Checksum Error" }, // The dispensers internal checksum does not match the calculated checksum.

                                    // (If separate from validator microprocessor.)

    { 0x29, "Dispenser Disabled" }, // dispenser disabled because of error or bill in escrow position

    { 0x2A, "Bill Waiting" },   // waiting for customer removal

    { 0x2F, "Filled key pressed" }, // The VMC should request a new DISPENSER STATUS

    { 0, NULL }

};

static const value_string mdb_bv_exp_bills_recyc_enabled[] = {

    { 0x00, "Bill type disabled" },

    { 0x01, "Only High quality bills are used" },

    { 0x02, "Only High and Medium quality bills are used" },

    { 0x03, "Use all possible bills" },

    { 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(pinfo->pool, 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 mdb_add_checksum(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, int offset, int total_len)

{

    if (total_len <= 1) return;

    uint8_t calculated_checksum = 0;

    for (int i = 0; i < total_len - 1; i++) {

        uint8_t val = tvb_get_uint8(tvb, offset + i);

        /* The MDB checksum is a simple sum modulo 256. Using uint8_t

         * causes an intentional wrap-around that perfectly matches the modulo.

         */

        calculated_checksum += val;

    }

    proto_tree_add_checksum(tree, tvb, offset + total_len - 1, hf_mdb_chk, hf_mdb_chk_status, &ei_mdb_bad_checksum, pinfo, calculated_checksum, ENC_BIG_ENDIAN, PROTO_CHECKSUM_VERIFY);

}

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 */

                pi = proto_tree_add_item_ret_uint(tree, hf_mdb_cl_max_price,

                        tvb, offset, 2, ENC_BIG_ENDIAN, &price);

                if (price == 0xFFFF) {

                    proto_item_append_text(pi, " (unknown)");

                }

                offset += 2;

                pi = proto_tree_add_item_ret_uint(tree, hf_mdb_cl_min_price,

                        tvb, offset, 2, ENC_BIG_ENDIAN, &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, mdb_conv_info_t* conv_info _U_)

{

    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, mdb_conv_info_t* conv_info _U_)

{

    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, mdb_conv_info_t* conv_info _U_)

{

    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, mdb_conv_info_t* conv_info _U_)

{

    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 int dissect_mdb_bv_setup_fields(tvbuff_t *tvb, int offset, packet_info *pinfo, proto_tree *tree)

{

    wmem_strbuf_t* bill_str = wmem_strbuf_new(pinfo->pool, "");

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

    offset += 1;

    proto_tree_add_item(tree, hf_mdb_bv_setup_ctry_currency_code, tvb, offset, 2, ENC_BIG_ENDIAN);

    offset += 2;

    proto_tree_add_item(tree, hf_mdb_bv_setup_bill_scal_fac, tvb, offset, 2, ENC_BIG_ENDIAN);

    offset += 2;

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

    offset += 1;

    proto_tree_add_item(tree, hf_mdb_bv_setup_bill_stacker_cap, tvb, offset, 2, ENC_BIG_ENDIAN);

    offset += 2;

    proto_tree_add_item(tree, hf_mdb_bv_setup_bill_sec_lvls, tvb, offset, 2, ENC_BIG_ENDIAN);

    offset += 2;

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

    offset += 1;

    uint8_t bill_val;

    for (int i = 0; i < 16; i++) {

        bill_val = tvb_get_uint8(tvb, offset + i);

        // Append each bill value to comma separated string

        wmem_strbuf_append_printf(bill_str, "%u%s", bill_val, (i < 15) ? "," : "");

    }

    // Add the formatted string to the protocol tree

    proto_tree_add_string_format_value(tree, hf_mdb_bv_setup_bill_type_cred, tvb, offset, 16,

                                        bill_str->str, "Bill values: %s", bill_str->str);

    offset += 16;

    return offset;

}

static int dissect_mdb_bv_poll_stat_bill_accept(tvbuff_t *tvb, int offset, packet_info *pinfo, proto_tree *tree)

{

    uint32_t bill_routing;

    proto_tree_add_item_ret_uint(tree, hf_mdb_bv_poll_bill_routing_state, tvb, offset, 1, ENC_NA, &bill_routing);

    proto_tree_add_item(tree, hf_mdb_bv_poll_bill_type, tvb, offset, 1, ENC_NA);

    col_add_str(pinfo->cinfo, COL_INFO,

        val_to_str(pinfo->pool, bill_routing, mdb_bv_poll_bill_routing_state, "Unknown Bill Routing: 0x%x"));

    offset += 1;

    return offset;

}

static int dissect_mdb_bv_poll_fields(tvbuff_t *tvb, int offset, packet_info *pinfo, proto_tree *tree)

{

    uint8_t cmd = tvb_get_uint8(tvb, offset);

    if (cmd & 0x80)

    {

        // Bills Accepted response

        dissect_mdb_bv_poll_stat_bill_accept(tvb, offset, pinfo, tree);

        offset += 1;

    }

    else if (cmd > 0x1A)

    {

        // File transport layer response

        offset += 1;

    }

    else

    {

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

        col_add_str(pinfo->cinfo, COL_INFO,

                val_to_str(pinfo->pool, cmd, mdb_bv_poll_state, "Unknown Poll Response 0x%x"));

        offset += 1;

    }

    return offset;

}

static int dissect_mdb_bv_bill_type(tvbuff_t *tvb, int offset, proto_tree *tree)

{

    proto_tree_add_item(tree, hf_mdb_bv_bill_enable, tvb, offset, 2, ENC_BIG_ENDIAN);

    offset += 2;

    proto_tree_add_item(tree, hf_mdb_bv_bill_escrow_enable, tvb, offset, 2, ENC_BIG_ENDIAN);

    offset += 2;

    return offset;

}

static int dissect_mdb_bv_escrow(tvbuff_t *tvb, int offset, proto_tree *tree)

{

    proto_tree_add_item(tree, hf_mdb_bv_escrow_state, tvb, offset, 1, ENC_NA);

    offset += 1;

    return offset;

}

static int dissect_mdb_bv_stacker(tvbuff_t *tvb, int offset, proto_tree *tree)

{

    proto_tree_add_item(tree, hf_mdb_bv_stacker, tvb, offset, 2, ENC_BIG_ENDIAN);

    offset += 2;

    return offset;

}

static int dissect_mdb_bv_exp_id_opt_fields(tvbuff_t *tvb, int offset,

proto_tree *tree, bool opt_features)

{

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

    offset += 3;

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

    offset += 12;

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

    offset += 12;

    proto_tree_add_item(tree, hf_mdb_bv_exp_software_version, tvb, offset, 2, ENC_BIG_ENDIAN);

    offset += 2;

    // Only for cmd 37 02

    if (opt_features) {

        proto_tree_add_item(tree, hf_mdb_bv_exp_opt_feat, tvb, offset, 4, ENC_BIG_ENDIAN);

        offset += 4;

    }

    return offset;

}