/* packet-mqtt-sn.c

 *

 * Routines for MQTT-SN v1.2 <http://mqtt.org>

 * https://mqtt.org/mqtt-specification/

 * https://groups.oasis-open.org/higherlogic/ws/public/download/66091/MQTT-SN_spec_v1.2.pdf

 *

 * Copyright (c) 2015, Jan-Hendrik Bolte <jabolte@uni-osnabrueck.de>

 * Copyright (c) 2015, University of Osnabrueck

 *

 * 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>

#include <epan/tfs.h>

#include <wsutil/array.h>

/* MQTT-SN message types. */

#define MQTTSN_ADVERTISE              0x00

#define MQTTSN_SEARCHGW               0x01

#define MQTTSN_GWINFO                 0x02

#define MQTTSN_RESERVED_03            0x03

#define MQTTSN_CONNECT                0x04

#define MQTTSN_CONNACK                0x05

#define MQTTSN_WILLTOPICREQ           0x06

#define MQTTSN_WILLTOPIC              0x07

#define MQTTSN_WILLMSGREQ             0x08

#define MQTTSN_WILLMSG                0x09

#define MQTTSN_REGISTER               0x0A

#define MQTTSN_REGACK                 0x0B

#define MQTTSN_PUBLISH                0x0C

#define MQTTSN_PUBACK                 0x0D

#define MQTTSN_PUBCOMP                0x0E

#define MQTTSN_PUBREC                 0x0F

#define MQTTSN_PUBREL                 0x10

#define MQTTSN_RESERVED_11            0x11

#define MQTTSN_SUBSCRIBE              0x12

#define MQTTSN_SUBACK                 0x13

#define MQTTSN_UNSUBSCRIBE            0x14

#define MQTTSN_UNSUBACK               0x15

#define MQTTSN_PINGREQ                0x16

#define MQTTSN_PINGRESP               0x17

#define MQTTSN_DISCONNECT             0x18

#define MQTTSN_RESERVED_19            0x19

#define MQTTSN_WILLTOPICUPD           0x1A

#define MQTTSN_WILLTOPICRESP          0x1B

#define MQTTSN_WILLMSGUPD             0x1C

#define MQTTSN_WILLMSGRESP            0x1D

#define MQTTSN_ENCAPSULATED_MSG       0xFE

/* Masks to extract flag values. */

#define MQTTSN_MASK_DUP_FLAG          0x80

#define MQTTSN_MASK_QOS               0x60

#define MQTTSN_MASK_RETAIN            0x10

#define MQTTSN_MASK_WILL              0x08

#define MQTTSN_MASK_CLEAN             0x04

#define MQTTSN_MASK_TOPIC_ID_TYPE     0x03

/* Mask to extract radius from control. */

#define MQTTSN_MASK_CONTROL           0x03

/* MQTT-SN QoS levels. */

#define MQTTSN_QOS_ATMOST_ONCE      0x00

#define MQTTSN_QOS_ATLEAST_ONCE     0x01

#define MQTTSN_QOS_EXACTLY_ONCE     0x02

#define MQTTSN_QOS_NO_CONNECTION    0x03

/* MQTT-SN topic types. */

#define MQTTSN_TOPIC_NORMAL_ID      0x00

#define MQTTSN_TOPIC_PREDEF_ID      0x01

#define MQTTSN_TOPIC_SHORT_NAME     0x02

#define MQTTSN_TOPIC_RESERVED       0x03

/* MQTT-SN connection return types. */

#define MQTTSN_CON_ACCEPTED                   0x00

#define MQTTSN_CON_REFUSED_CONGESTION         0x01

#define MQTTSN_CON_REFUSED_INVALID_TOPIC_ID   0x02

#define MQTTSN_CON_REFUSED_NOT_SUPPORTED      0x03

void proto_register_mqttsn(void);

void proto_reg_handoff_mqttsn(void);

/* MQTT-SN message type values. */

static const value_string mqttsn_msgtype_vals[] = {

    { MQTTSN_ADVERTISE,           "Advertise Gateway" },

    { MQTTSN_SEARCHGW,            "Search Gateway" },

    { MQTTSN_GWINFO,              "Gateway Info" },

    { MQTTSN_RESERVED_03,         "Reserved_03" },

    { MQTTSN_CONNECT,             "Connect Command" },

    { MQTTSN_CONNACK,             "Connect Ack" },

    { MQTTSN_WILLTOPICREQ,        "Will Topic Request" },

    { MQTTSN_WILLTOPIC,           "Will Topic" },

    { MQTTSN_WILLMSGREQ,          "Will Message Request" },

    { MQTTSN_WILLMSG,             "Will Message" },

    { MQTTSN_REGISTER,            "Register" },

    { MQTTSN_REGACK,              "Register Ack" },

    { MQTTSN_PUBLISH,             "Publish Message" },

    { MQTTSN_PUBACK,              "Publish Ack" },

    { MQTTSN_PUBCOMP,             "Publish Complete" },

    { MQTTSN_PUBREC,              "Publish Received" },

    { MQTTSN_PUBREL,              "Publish Release" },

    { MQTTSN_RESERVED_11,         "Reserved_11" },

    { MQTTSN_SUBSCRIBE,           "Subscribe Request" },

    { MQTTSN_SUBACK,              "Subscribe Ack" },

    { MQTTSN_UNSUBSCRIBE,         "Unsubscribe Request" },

    { MQTTSN_UNSUBACK,            "Unsubscribe Ack" },

    { MQTTSN_PINGREQ,             "Ping Request" },

    { MQTTSN_PINGRESP,            "Ping Response" },

    { MQTTSN_DISCONNECT,          "Disconnect Req" },

    { MQTTSN_RESERVED_19,         "Reserved_19" },

    { MQTTSN_WILLTOPICUPD,        "Will Topic Update" },

    { MQTTSN_WILLTOPICRESP,       "Will Topic Response" },

    { MQTTSN_WILLMSGUPD,          "Will Message Update" },

    { MQTTSN_WILLMSGRESP,         "Will Message Response" },

    { MQTTSN_ENCAPSULATED_MSG,    "Encapsulated Message" },

    { 0,                          NULL }

};

static value_string_ext mqttsn_msgtype_vals_ext = VALUE_STRING_EXT_INIT(mqttsn_msgtype_vals);

/* MQTT-SN QoS level values. */

static const value_string mqttsn_qos_vals[] = {

    { MQTTSN_QOS_ATMOST_ONCE,         "Fire and Forget" },

    { MQTTSN_QOS_ATLEAST_ONCE,        "Acknowledged deliver" },

    { MQTTSN_QOS_EXACTLY_ONCE,        "Assured Delivery" },

    { MQTTSN_QOS_NO_CONNECTION,       "No Connection required" },

    { 0,                              NULL }

};

/* MQTT-SN topic type values. */

static const value_string mqttsn_typeid_vals[] = {

    { MQTTSN_TOPIC_NORMAL_ID,         "Normal ID" },

    { MQTTSN_TOPIC_PREDEF_ID,         "Pre-defined ID" },

    { MQTTSN_TOPIC_SHORT_NAME,        "Short Topic Name" },

    { MQTTSN_TOPIC_RESERVED,          "Reserved" },

    { 0,                              NULL }

};

/* MQTT-SN connection return type values. */

static const value_string mqttsn_return_vals[] = {

    { MQTTSN_CON_ACCEPTED,                      "Accepted" },

    { MQTTSN_CON_REFUSED_CONGESTION,            "Rejected: Congestion" },

    { MQTTSN_CON_REFUSED_INVALID_TOPIC_ID,      "Rejected: invalid topic ID" },

    { MQTTSN_CON_REFUSED_NOT_SUPPORTED,         "Rejected: not supported" },

    { 0,                                        NULL }

};

/* MQTT-SN Handle */

static dissector_handle_t mqttsn_handle;

/* Initialize the protocol and registered fields. */

static int proto_mqttsn;

static int hf_mqttsn_msg;

static int hf_mqttsn_msg_len;

static int hf_mqttsn_msg_type;

static int hf_mqttsn_flags;

static int hf_mqttsn_dup;

static int hf_mqttsn_qos;

static int hf_mqttsn_retain;

static int hf_mqttsn_will;

static int hf_mqttsn_clean_session;

static int hf_mqttsn_topic_id_type;

static int hf_mqttsn_return_code;

static int hf_mqttsn_gw_id;

static int hf_mqttsn_gw_addr;

static int hf_mqttsn_adv_interv;

static int hf_mqttsn_radius;

static int hf_mqttsn_protocol_id;

static int hf_mqttsn_topic_id;

static int hf_mqttsn_msg_id;

static int hf_mqttsn_topic;

static int hf_mqttsn_sleep_timer;

static int hf_mqttsn_will_topic;

static int hf_mqttsn_will_msg;

static int hf_mqttsn_pub_msg;

static int hf_mqttsn_client_id;

static int hf_mqttsn_keep_alive;

static int hf_mqttsn_control_info;

static int hf_mqttsn_wireless_node_id;

/* Initialize subtree pointers. */

static int ett_mqttsn_hdr;

static int ett_mqttsn_msg;

static int ett_mqttsn_flags;

/* Dissect a single MQTT-SN packet. */

// NOLINTNEXTLINE(misc-no-recursion)

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

{

    /* Various variables. */

    int long_hdr_len = 0;

    uint8_t mqttsn_msg_type_id;

    uint16_t mqttsn_msg_len;

    int8_t mqttsn_topic_id_type = MQTTSN_TOPIC_NORMAL_ID;

    /* Get the message length. */

    mqttsn_msg_len = tvb_get_uint8(tvb, offset);

    /* If the message length is equal to 1 then the next two bytes define the real message length. */

    if (mqttsn_msg_len == 1)

    {

        long_hdr_len = 1;

        mqttsn_msg_len = tvb_get_ntohs(tvb, offset + 1);

    }

    /* If this is an encapsulated message, we need to add the offset of the previous packet. */

    mqttsn_msg_len += offset;

    /* Get the message type id (in byte 1 or 3 - depending on the message length). */

    mqttsn_msg_type_id = tvb_get_uint8(tvb, offset + (long_hdr_len ? 3 : 1));

    if (tree)

    {

        /* Variables for the message items and trees. */

        proto_item *ti = NULL;

        proto_item *ti_mqttsn = NULL;

        proto_tree *mqttsn_tree = NULL;

        proto_tree *mqttsn_msg_tree = NULL;

        /* Add MQTT-SN subtree to the main tree. */

        if (offset == 0)

        {

            ti = proto_tree_add_item(tree, proto_mqttsn, tvb, 0, -1, ENC_NA);

            mqttsn_tree = proto_item_add_subtree(ti, ett_mqttsn_hdr);

        }

        /* If this is an encapsulated message, we add the message to the existing subtree. */

        else

        {

            mqttsn_tree = tree;

        }

        /* Add message subtree. */

        ti_mqttsn = proto_tree_add_item(mqttsn_tree, hf_mqttsn_msg, tvb, offset + (long_hdr_len ? 3 : 1), -1, ENC_NA);

        mqttsn_msg_tree = proto_item_add_subtree(ti_mqttsn, ett_mqttsn_msg);

        /* | Message type (1 octet) | */

        proto_tree_add_item(mqttsn_msg_tree, hf_mqttsn_msg_type, tvb, offset + (long_hdr_len ? 3 : 1), 1, ENC_BIG_ENDIAN);

        offset += 1;

        /* | Message length (1 - 2 octets) | */

        proto_tree_add_item(mqttsn_msg_tree, hf_mqttsn_msg_len, tvb, offset - 1 + (long_hdr_len ? 1 : 0), (long_hdr_len ? 2 : 1), ENC_BIG_ENDIAN);

        offset += (long_hdr_len ? 3 : 1);

        /*

         * Only some message types contain flags (1 octet).

         * ______________________________________________________________________________________

         * |         |           |            |          |                  |                   |

         * |  bit 7  | bit 6 + 5 |    bit 4   |   bit 3  |      bit 2       |     bit 1 + 0     |

         * |   DUP   |    QoS    |   Retain   |   Will   |   CleanSession   |    TopicIdType    |

         * |_________|___________|____________|__________|__________________|___________________|

         */

        static int * const connect_flags[] = {

            &hf_mqttsn_will,

            &hf_mqttsn_clean_session,

            NULL

        };

        static int * const willtopic_flags[] = {

            &hf_mqttsn_qos,

            &hf_mqttsn_retain,

            NULL

        };

        static int * const publish_flags[] = {

            &hf_mqttsn_dup,

            &hf_mqttsn_qos,

            &hf_mqttsn_retain,

            &hf_mqttsn_topic_id_type,

            NULL

        };

        static int * const subscribe_flags[] = {

            &hf_mqttsn_dup,

            &hf_mqttsn_qos,

            &hf_mqttsn_topic_id_type,

            NULL

        };

        static int * const suback_flags[] = {

            &hf_mqttsn_qos,

            NULL

        };

        static int * const unsubscribe_flags[] = {

            &hf_mqttsn_topic_id_type,

            NULL

        };

        switch (mqttsn_msg_type_id)

        {

            /* Connect */

            case MQTTSN_CONNECT:

                /* Add Will and CleanSession Type flags. */

                proto_tree_add_bitmask(mqttsn_msg_tree, tvb, offset, hf_mqttsn_flags, ett_mqttsn_flags, connect_flags, ENC_BIG_ENDIAN);

                offset += 1;

                break;

            /* Publish */

            case MQTTSN_PUBLISH:

                /* Add DUP, QoS, Retain and Topic ID Type flags. */

                mqttsn_topic_id_type = tvb_get_uint8(tvb, offset) & MQTTSN_MASK_TOPIC_ID_TYPE;

                proto_tree_add_bitmask(mqttsn_msg_tree, tvb, offset, hf_mqttsn_flags, ett_mqttsn_flags, publish_flags, ENC_BIG_ENDIAN);

                offset += 1;

                break;

            case MQTTSN_SUBSCRIBE:

                mqttsn_topic_id_type = tvb_get_uint8(tvb, offset) & MQTTSN_MASK_TOPIC_ID_TYPE;

                proto_tree_add_bitmask(mqttsn_msg_tree, tvb, offset, hf_mqttsn_flags, ett_mqttsn_flags, subscribe_flags, ENC_BIG_ENDIAN);

                offset += 1;

                break;

            case MQTTSN_SUBACK:

                proto_tree_add_bitmask(mqttsn_msg_tree, tvb, offset, hf_mqttsn_flags, ett_mqttsn_flags, suback_flags, ENC_BIG_ENDIAN);

                offset += 1;

                break;

            case MQTTSN_UNSUBSCRIBE:

                mqttsn_topic_id_type = tvb_get_uint8(tvb, offset) & MQTTSN_MASK_TOPIC_ID_TYPE;

                proto_tree_add_bitmask(mqttsn_msg_tree, tvb, offset, hf_mqttsn_flags, ett_mqttsn_flags, unsubscribe_flags, ENC_BIG_ENDIAN);

                offset += 1;

                break;

            case MQTTSN_WILLTOPIC:

            case MQTTSN_WILLTOPICUPD:

                /* "An empty WILLTOPIC[UPD] message is a message without Flags

                 * and WillTopic field (i.e. it is exactly 2 octets long)." */

                if (mqttsn_msg_len > 2) {

                    proto_tree_add_bitmask(mqttsn_msg_tree, tvb, offset, hf_mqttsn_flags, ett_mqttsn_flags, willtopic_flags, ENC_BIG_ENDIAN);

                    offset += 1;

                }

                break;

            /* Default Case */

            default:

                break;

        }

        /* Add message specific informations. */

        switch (mqttsn_msg_type_id)

        {

            /* Advertise Gateway */

            case MQTTSN_ADVERTISE:

                /* | 1 - Gateway ID | 2,3 - Duration until next Advertise | */

                proto_tree_add_item(mqttsn_msg_tree, hf_mqttsn_gw_id, tvb, offset, 1, ENC_BIG_ENDIAN);

                offset += 1;

                proto_tree_add_item(mqttsn_msg_tree, hf_mqttsn_adv_interv, tvb, offset, 2, ENC_BIG_ENDIAN);

                break;

            /* Search Gateway */

            case MQTTSN_SEARCHGW:

                /* | 1 - Broadcast Radius | */

                proto_tree_add_item(mqttsn_msg_tree, hf_mqttsn_radius, tvb, offset, 1, ENC_BIG_ENDIAN);

                break;

            /* Gateway Information */

            case MQTTSN_GWINFO:

                /* | 1 - Gateway ID | 2:n - Gateway Address (optional) | */

                proto_tree_add_item(mqttsn_msg_tree, hf_mqttsn_gw_id, tvb, offset, 1, ENC_BIG_ENDIAN);

                offset += 1;

                /* Gateway Address is only present if message is sent by client. */

                if (offset < mqttsn_msg_len)

                {

                    proto_tree_add_item(mqttsn_msg_tree, hf_mqttsn_gw_addr, tvb, offset, (mqttsn_msg_len - offset), ENC_ASCII);

                }

                break;

            /* Connect */

            case MQTTSN_CONNECT:

                /* | 1 - Protocol ID | 2,3 - Keep Alive Duration | 4:n - Client ID | */

                proto_tree_add_item(mqttsn_msg_tree, hf_mqttsn_protocol_id, tvb, offset, 1, ENC_BIG_ENDIAN);

                offset += 1;

                proto_tree_add_item(mqttsn_msg_tree, hf_mqttsn_keep_alive, tvb, offset, 2, ENC_BIG_ENDIAN);

                offset += 2;

                proto_tree_add_item(mqttsn_msg_tree, hf_mqttsn_client_id, tvb, offset, (mqttsn_msg_len - offset), ENC_ASCII);

                break;

            /* Connection Acknowledgement */

            case MQTTSN_CONNACK:

                /* | 1 - Return code | */

                proto_tree_add_item(mqttsn_msg_tree, hf_mqttsn_return_code, tvb, offset, 1, ENC_BIG_ENDIAN);

                break;

            /* Will Topic Request + Will Message Request */

            case MQTTSN_WILLTOPICREQ:

            case MQTTSN_WILLMSGREQ:

                /* Will topic/message requests don't have a variable header. */

                break;

            /* Will Topic */

            case MQTTSN_WILLTOPIC:

                /* | 1:n - Will topic | */

                if (mqttsn_msg_len > 2) {

                    proto_tree_add_item(mqttsn_msg_tree, hf_mqttsn_will_topic, tvb, offset, (mqttsn_msg_len - offset), ENC_ASCII);

                }

                break;

            /* Will Message */

            case MQTTSN_WILLMSG:

                /* | 1:n - Will message | */

                proto_tree_add_item(mqttsn_msg_tree, hf_mqttsn_will_msg, tvb, offset, (mqttsn_msg_len - offset), ENC_ASCII);

                break;

            /* Register */

            case MQTTSN_REGISTER:

                /* | 1,2 - Topic ID | 3,4 - Message ID | 5:n - Topic name | */

                proto_tree_add_item(mqttsn_msg_tree, hf_mqttsn_topic_id, tvb, offset, 2, ENC_BIG_ENDIAN);

                offset += 2;

                proto_tree_add_item(mqttsn_msg_tree, hf_mqttsn_msg_id, tvb, offset, 2, ENC_BIG_ENDIAN);

                offset += 2;

                proto_tree_add_item(mqttsn_msg_tree, hf_mqttsn_topic, tvb, offset, (mqttsn_msg_len - offset), ENC_ASCII);

                break;

            /* Register Acknowledgement */

            case MQTTSN_REGACK:

                /* | 1,2 - Topic ID | 3,4 - Message ID | 5 - Return code | */

                proto_tree_add_item(mqttsn_msg_tree, hf_mqttsn_topic_id, tvb, offset, 2, ENC_BIG_ENDIAN);

                offset += 2;

                proto_tree_add_item(mqttsn_msg_tree, hf_mqttsn_msg_id, tvb, offset, 2, ENC_BIG_ENDIAN);

                offset += 2;

                proto_tree_add_item(mqttsn_msg_tree, hf_mqttsn_return_code, tvb, offset, 1, ENC_BIG_ENDIAN);

                break;

            /* Publish */

            case MQTTSN_PUBLISH:

                /* | 1,2 - Topic ID | 3,4 - Message ID | 5:n - Publish data | */

                if (mqttsn_topic_id_type == MQTTSN_TOPIC_SHORT_NAME) {

                    proto_tree_add_item(mqttsn_msg_tree, hf_mqttsn_topic, tvb, offset, 2, ENC_ASCII);

                } else {

                    proto_tree_add_item(mqttsn_msg_tree, hf_mqttsn_topic_id, tvb, offset, 2, ENC_BIG_ENDIAN);

                }

                offset += 2;

                proto_tree_add_item(mqttsn_msg_tree, hf_mqttsn_msg_id, tvb, offset, 2, ENC_BIG_ENDIAN);

                offset += 2;

                proto_tree_add_item(mqttsn_msg_tree, hf_mqttsn_pub_msg, tvb, offset, (mqttsn_msg_len - offset), ENC_ASCII);

                break;

            /* Publish Acknowledgement */

            case MQTTSN_PUBACK:

                /* | 1,2 - Topic ID | 3,4 - Message ID | 5 - Return code | */

                proto_tree_add_item(mqttsn_msg_tree, hf_mqttsn_topic_id, tvb, offset, 2, ENC_BIG_ENDIAN);

                offset += 2;

                proto_tree_add_item(mqttsn_msg_tree, hf_mqttsn_msg_id, tvb, offset, 2, ENC_BIG_ENDIAN);

                offset += 2;

                proto_tree_add_item(mqttsn_msg_tree, hf_mqttsn_return_code, tvb, offset, 1, ENC_BIG_ENDIAN);

                break;

            /* Publish Complete + Publish Received + Publish Released */

            case MQTTSN_PUBCOMP:

            case MQTTSN_PUBREC:

            case MQTTSN_PUBREL:

                /* | 1,2 - Message ID | */

                proto_tree_add_item(mqttsn_msg_tree, hf_mqttsn_msg_id, tvb, offset, 2, ENC_BIG_ENDIAN);

                break;

            /* Subscribe + Unsubscribe */

            case MQTTSN_SUBSCRIBE:

            case MQTTSN_UNSUBSCRIBE:

                /* | 1,2 - Message ID | 5:n - Topic name _OR_ 5,6 - Topic ID | */

                proto_tree_add_item(mqttsn_msg_tree, hf_mqttsn_msg_id, tvb, offset, 2, ENC_BIG_ENDIAN);

                offset += 2;

                if (mqttsn_topic_id_type == MQTTSN_TOPIC_PREDEF_ID) {

                    proto_tree_add_item(mqttsn_msg_tree, hf_mqttsn_topic_id, tvb, offset, 2, ENC_BIG_ENDIAN);

                } else if (mqttsn_topic_id_type == MQTTSN_TOPIC_SHORT_NAME) {

                    proto_tree_add_item(mqttsn_msg_tree, hf_mqttsn_topic, tvb, offset, 2, ENC_ASCII);

                } else {

                    proto_tree_add_item(mqttsn_msg_tree, hf_mqttsn_topic, tvb, offset, (mqttsn_msg_len - offset), ENC_ASCII);

                }

                break;

            /* Subscribe Acknowledgment */

            case MQTTSN_SUBACK:

                /* | 1,2 - Topic ID | 3,4 - Message ID | 5 - Return code | */

                proto_tree_add_item(mqttsn_msg_tree, hf_mqttsn_topic_id, tvb, offset, 2, ENC_BIG_ENDIAN);

                offset += 2;

                proto_tree_add_item(mqttsn_msg_tree, hf_mqttsn_msg_id, tvb, offset, 2, ENC_BIG_ENDIAN);

                offset += 2;

                proto_tree_add_item(mqttsn_msg_tree, hf_mqttsn_return_code, tvb, offset, 1, ENC_BIG_ENDIAN);

                break;

            /* Unsubscribe Acknowledgement */

            case MQTTSN_UNSUBACK:

                /* | 1,2 - Message ID | */

                proto_tree_add_item(mqttsn_msg_tree, hf_mqttsn_msg_id, tvb, offset, 2, ENC_BIG_ENDIAN);

                break;

            /* Ping Request */

            case MQTTSN_PINGREQ:

                /* | 1:n - Client ID (optional) | */

                if (offset < mqttsn_msg_len)

                {

                    proto_tree_add_item(mqttsn_msg_tree, hf_mqttsn_client_id, tvb, offset, (mqttsn_msg_len - offset), ENC_ASCII);

                }

                break;

            /* Ping Response */

            case MQTTSN_PINGRESP:

                /* Ping responses don't have a variable header. */

                break;

            /* Disconnect */

            case MQTTSN_DISCONNECT:

                /* | 1,2 - Sleep Time Duration (optional) | */

                if (offset < mqttsn_msg_len)

                {

                    proto_tree_add_item(mqttsn_msg_tree, hf_mqttsn_sleep_timer, tvb, offset, 2, ENC_BIG_ENDIAN);

                }

                break;

            /* Will Topic Update */

            case MQTTSN_WILLTOPICUPD:

                /* | 1:n - Will topic | */

                if (mqttsn_msg_len > 2) {

                    proto_tree_add_item(mqttsn_msg_tree, hf_mqttsn_will_topic, tvb, offset, (mqttsn_msg_len - offset), ENC_ASCII);

                }

                break;

            /* Will Message Update */

            case MQTTSN_WILLMSGUPD:

                /* | 1:n - Will message | */

                proto_tree_add_item(mqttsn_msg_tree, hf_mqttsn_will_msg, tvb, offset, (mqttsn_msg_len - offset), ENC_ASCII);

                break;

            /* Will Topic Response + Will Message Response */

            case MQTTSN_WILLTOPICRESP:

            case MQTTSN_WILLMSGRESP:

                /* | 1 - Return code | */

                proto_tree_add_item(mqttsn_msg_tree, hf_mqttsn_return_code, tvb, offset, 1, ENC_BIG_ENDIAN);

                break;

            case MQTTSN_ENCAPSULATED_MSG:

                /* | 1 - Control information | 2:n - Wireless Node ID | n+1:m - MQTT-SN message | */

                proto_tree_add_item(mqttsn_msg_tree, hf_mqttsn_control_info, tvb, offset, 1, ENC_BIG_ENDIAN);

                offset += 1;

                proto_tree_add_item(mqttsn_msg_tree, hf_mqttsn_wireless_node_id, tvb, offset, (mqttsn_msg_len - offset), ENC_BIG_ENDIAN);

                offset += (mqttsn_msg_len - offset);

                /* Dissect encapsulated message (if present). */

                if (tvb_reported_length_remaining(tvb, offset) > 0)

                {

                    increment_dissection_depth(pinfo);

                    dissect_mqttsn_packet(tvb, pinfo, mqttsn_msg_tree, offset);

                    decrement_dissection_depth(pinfo);

                }

            /* Default Case */

            default:

                break;

        }

    }

}

/* Dissect a complete MQTT-SN message. */

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

{

    /* Various variables. */

    unsigned offset = 0;

    uint8_t mqttsn_msg_type_id;

    /*

     * If the value in byte 0 is unequal to 1 then the value defines the

     * message length and the message type id is contained in byte 1.

     */

    if (tvb_get_uint8(tvb, 0) != 1)

    {

        mqttsn_msg_type_id = tvb_get_uint8(tvb, 1);

    }

    /*

     * If the value in byte 0 is equal to 1 then the next two bytes define

     * the real message length and the message type id is contained in byte 3.

     */

    else

    {

        mqttsn_msg_type_id = tvb_get_uint8(tvb, 3);

    }

    /* Add the protocol name to the protocol column. */

    col_set_str(pinfo->cinfo, COL_PROTOCOL, "MQTT-SN");

    /* Add the message type to the info column. */

    col_clear(pinfo->cinfo, COL_INFO);

    col_add_str(pinfo->cinfo, COL_INFO, val_to_str_ext(pinfo->pool, mqttsn_msg_type_id, &mqttsn_msgtype_vals_ext, "Unknown (0x%02x)"));

    /* Dissect a MQTT-SN packet. */

    dissect_mqttsn_packet(tvb, pinfo, tree, offset);

    return tvb_captured_length(tvb);

}

/* Register the protocol with Wireshark. */

void proto_register_mqttsn(void)

{

    static hf_register_info hf_mqttsn[] = {

        { &hf_mqttsn_msg,

            { "Message", "mqttsn.msg",

                FT_NONE, BASE_NONE, NULL, 0,

                NULL, HFILL }

        },

        { &hf_mqttsn_msg_len,

            { "Message Length", "mqttsn.msg.len",

                FT_UINT16, BASE_DEC, NULL, 0x0,

                NULL, HFILL }

        },

        { &hf_mqttsn_msg_type,

            { "Message Type", "mqttsn.msg.type",

                FT_UINT8, BASE_HEX | BASE_EXT_STRING, &mqttsn_msgtype_vals_ext, 0,

                NULL, HFILL }

        },

        { &hf_mqttsn_flags,

            { "Flags", "mqttsn.flags",

                FT_UINT8, BASE_HEX, NULL, 0,

                NULL, HFILL }

        },

        { &hf_mqttsn_dup,

            { "DUP", "mqttsn.dup",

                FT_BOOLEAN, 8, TFS(&tfs_yes_no), MQTTSN_MASK_DUP_FLAG,

                NULL, HFILL }

        },

        { &hf_mqttsn_will,

            { "Will", "mqttsn.will",

                FT_BOOLEAN, 8, TFS(&tfs_yes_no), MQTTSN_MASK_WILL,

                NULL, HFILL }

        },

        { &hf_mqttsn_clean_session,

            { "Clean Session", "mqttsn.clean.session",

                FT_BOOLEAN, 8, TFS(&tfs_yes_no), MQTTSN_MASK_CLEAN,

                NULL, HFILL }

        },

        { &hf_mqttsn_topic_id_type,

            { "Topic ID Type", "mqttsn.topic.id.type",

                FT_UINT8, BASE_HEX, VALS(mqttsn_typeid_vals), MQTTSN_MASK_TOPIC_ID_TYPE,

                NULL, HFILL }

        },

        { &hf_mqttsn_qos,

            { "QoS", "mqttsn.qos",

                FT_UINT8, BASE_HEX, VALS(mqttsn_qos_vals), MQTTSN_MASK_QOS,

                NULL, HFILL }

        },

        { &hf_mqttsn_retain,

            { "Retain", "mqttsn.retain",

                FT_BOOLEAN, 8, TFS(&tfs_yes_no), MQTTSN_MASK_RETAIN,

                NULL, HFILL }

        },

        { &hf_mqttsn_return_code,

            { "Return Code", "mqttsn.return.code",

                FT_UINT8, BASE_HEX, VALS(mqttsn_return_vals), 0x0,

                NULL, HFILL }

        },

        { &hf_mqttsn_gw_id,

            { "Gateway ID", "mqttsn.gw.id",

                FT_UINT8, BASE_DEC, NULL, 0x0,

                NULL, HFILL }

        },

        { &hf_mqttsn_gw_addr,

            { "Gateway Address", "mqttsn.gw.addr",

                FT_STRING, BASE_NONE, NULL, 0x0,

                NULL, HFILL }

        },

        { &hf_mqttsn_adv_interv,

            { "Advertise Interval", "mqttsn.adv.interv",

                FT_UINT16, BASE_DEC, NULL, 0x0,

                NULL, HFILL }

        },

        { &hf_mqttsn_radius,

            { "Broadcast Radius", "mqttsn.radius",

                FT_UINT8, BASE_DEC, NULL, 0x0,

                NULL, HFILL }

        },

        { &hf_mqttsn_protocol_id,

            { "Protocol ID", "mqttsn.protocol.id",

                FT_UINT8, BASE_HEX, NULL, 0x0,

                NULL, HFILL }

        },

        { &hf_mqttsn_topic_id,

            { "Topic ID", "mqttsn.topic.id",

                FT_UINT16, BASE_DEC, NULL, 0x0,

                NULL, HFILL }

        },

        { &hf_mqttsn_msg_id,

            { "Message ID", "mqttsn.msg.id",

                FT_UINT16, BASE_DEC, NULL, 0x0,

                NULL, HFILL }

        },

        { &hf_mqttsn_topic,

            { "Topic Name", "mqttsn.topic",

                FT_STRING, BASE_NONE, NULL, 0x0,

                NULL, HFILL }

        },

        { &hf_mqttsn_sleep_timer,

            { "Sleep Timer", "mqttsn.sleep.timer",

                FT_UINT16, BASE_DEC, NULL, 0x0,

                NULL, HFILL }

        },

        { &hf_mqttsn_will_topic,

            { "Will Topic", "mqttsn.will.topic",

                FT_STRING, BASE_NONE, NULL, 0x0,

                NULL, HFILL }

        },

        { &hf_mqttsn_will_msg,

            { "Will Message", "mqttsn.will.msg",

                FT_STRING, BASE_NONE, NULL, 0x0,

                NULL, HFILL }

        },

        { &hf_mqttsn_pub_msg,

            { "Message", "mqttsn.pub.msg",

                FT_STRING, BASE_NONE, NULL, 0x0,

                NULL, HFILL }

        },

        { &hf_mqttsn_client_id,

            { "Client ID", "mqttsn.client.id",

                FT_STRING, BASE_NONE, NULL, 0x0,

                NULL, HFILL }

        },

        { &hf_mqttsn_keep_alive,

            { "Keep Alive", "mqttsn.keep.alive",

                FT_UINT16, BASE_DEC, NULL, 0x0,

                NULL, HFILL }

        },

        { &hf_mqttsn_control_info,

            { "Control", "mqttsn.control.info",

                FT_UINT8, BASE_HEX, NULL, MQTTSN_MASK_CONTROL,

                NULL, HFILL }

        },

        { &hf_mqttsn_wireless_node_id,

            { "Wireless Node ID", "mqttsn.wireless.node.id",

                FT_UINT16, BASE_DEC, NULL, 0x0,

                NULL, HFILL }

        }

    };

    /* Setup protocol subtree arrays. */

    static int* ett_mqttsn[] = {

        &ett_mqttsn_hdr,

        &ett_mqttsn_msg,

        &ett_mqttsn_flags

    };

    /* Register protocol names and descriptions. */

    proto_mqttsn = proto_register_protocol("MQ Telemetry Transport Protocol for Sensor Networks", "MQTT-SN", "mqttsn");

    /* Create the dissector handle. */

    mqttsn_handle = register_dissector("mqttsn", dissect_mqttsn, proto_mqttsn);

    /* Register fields and subtrees. */

    proto_register_field_array(proto_mqttsn, hf_mqttsn, array_length(hf_mqttsn));

    proto_register_subtree_array(ett_mqttsn, array_length(ett_mqttsn));

}

/* Dissector Handoff */

void proto_reg_handoff_mqttsn(void)

{

    dissector_add_for_decode_as_with_preference("udp.port", mqttsn_handle);

}

/*

 * Editor modelines  -  https://www.wireshark.org/tools/modelines.html

 *

 * Local variables:

 * c-basic-offset: 4

 * tab-width: 8

 * indent-tabs-mode: nil

 * End:

 *

 * vi: set shiftwidth=4 tabstop=8 expandtab:

 * :indentSize=4:tabSize=8:noTabs=true:

 */