mqtt.fdesc

# Generic dissector for MQTT based on MQTT V3.1 Protocol Specification
# http://public.dhe.ibm.com/software/dw/webservices/ws-mqtt/mqtt-v3r1.html
#
# Johann ANGELI (02/2014)


enum4 MQTTMessageType {
    Reserved_0  0
    CONNECT     1
    CONNACK     2
    PUBLISH     3
    PUBACK      4
    PUBREC      5
    PUBREL      6
    PUBCOMP     7
    SUBSCRIBE   8
    SUBACK      9
    UNSUBSCRIBE 10
    UNSUBACK    11
    PINGREQ     12
    PINGRESP    13
    DISCONNECT  14
    Reserved_15 15
}

enum8 MQTTConnectReturnCode {
    connection_accepted                              0
    connection_refused_unacceptable_protocol_version 1
    connection_refused_identifier_rejected           2
    connection_refused_server_unavailable            3
    connection_refused_bad_username_or_password      4
    connection_refused_not_authorized                5

    #Todo : Manage reserved values
    #From 6 to 255 : reserved for future use
}

enum2 MQTTQoS {
    at_most_once    0
    at_least_once   1
    exactly_once    2
    reserved        3
}

struct  MQTTFixedHeader
{
    byte_order      big_endian;

    MQTTMessageType message_type;
    bool1           dup;
    MQTTQoS         qos;
    bool1           retain;

    hide var uint32 message_length = 1;   

    hide var uint8  multiplier = 1;
    hide var uint32 value = 0;
        
    do
    {
        hide uint8 length;
        
	set value = value + (length & 127) * multiplier;
        set multiplier = multiplier * 128;

        set message_length = message_length + 1;

     } while ( (length & 128) !=0 );

     var uint32 remaining_length = value;
     set message_length = message_length + remaining_length;

}

struct MQTTConnectFlags {

    bool1   username;
    bool1   password;
    bool1   will_retain;
    MQTTQoS will_qos;
    bool1   will;
    bool1   clean_session;
    uint1   reserved;

}

struct MQTTSubscribeQoS {

    hide uint6 reserved;
    MQTTQoS    qos;

}

struct MQTTSubScribeTopic {

    hide uint16               topic_name_length;
    string(topic_name_length) topic_name;

    hide uint6                reserved;
    MQTTQoS                   requested_qos;

}

###############################################################################
# Messages Types
###############################################################################

# Reserved 0
# Reserved message for futur use
struct MQTTMessageReserved0 {

    MQTTFixedHeader fixed_header;

    # Variable header and payload (if any)

    raw(fixed_header.remaining_length) content_of_message;

}

# CONNECT
# Message with variable header
# Message with payload
struct MQTTMessageConnect {

    MQTTFixedHeader                 fixed_header;

    # Variable header

    hide uint16                     protocol_name_length;
    string(protocol_name_length)    protocol_name;
    
    uint8                           protocol_version_number;
    MQTTConnectFlags                connect_flags;
    uint16                          keep_alive_timer;
    
    # Payload

    hide uint16                     client_id_length;
    string(client_id_length)        client_id;

    if (connect_flags.will == 1) {
        hide uint16                 will_topic_length;
	string(will_topic_length)   will_topic;

        hide uint16                 will_message_length;
	string(will_message_length) will_message;
    }

    if (connect_flags.username == 1) {
        #Todo : verify the way the username can be null
        hide uint16                 username_length;
        string(username_length)     username;
    }
    if (connect_flags.password == 1) {
        #Todo : verify the way the password can be null
        hide uint16                 password_length;
        string(password_length)     password;
    }

}

# CONNACK
# Message with variable header
# Message without payload    
struct MQTTMessageConnack {
    MQTTFixedHeader       fixed_header;

    # Variable header

    uint8                 topic_name_compression_response;
    MQTTConnectReturnCode connect_return_code;
}

# PUBLISH
# Message with variable header
# Message with payload
struct MQTTMessagePublish {

    MQTTFixedHeader     fixed_header;

    # Variable header

    hide uint16      topic_length;
    string(topic_length)   topic;
    
    hide var uint8 variable_header_length = topic_length + 2;

    if (fixed_header.qos == 1 || fixed_header.qos == 2 ) {
        uint16          message_id;
        set variable_header_length = variable_header_length + 2; 
    }

    # Payload

    raw(fixed_header.remaining_length - variable_header_length)     payload;

}

# PUBACK
# Message with variable header
# Message without payload
struct MQTTMessagePuback {

    MQTTFixedHeader fixed_header;

    # Variable header

    uint16          message_id;

}

# PUBREC
# Message with variable header
# Message without payload
struct MQTTMessagePubrec {

    MQTTFixedHeader fixed_header;

    # Variable header

    uint16          message_id;

}

# PUBREL
# Message with variable header
# Message without payload
struct MQTTMessagePubrel {

    MQTTFixedHeader fixed_header;

    # Variable header

    uint16          message_id;

}

# PUBCOMP
# Message with variable header
# Message without payload
struct MQTTMessagePubcomp {

    MQTTFixedHeader fixed_header;

    # Variable header

    uint16          message_id;

}

# SUBSCRIBE
# Message with variable header
# Message with payload
struct MQTTMessageSubscribe {
    MQTTFixedHeader       fixed_header;

    # Variable header

    uint16                message_id;
    
    # Payload

    MQTTSubScribeTopic[+] topics;

}

# SUBACK
# Message with variable header
# Message with payload
struct MQTTMessageSuback {

    MQTTFixedHeader     fixed_header;

    # Variable header

    uint16              message_id;
    
    # Payload

    MQTTSubscribeQoS[+] granted_qos;

}

# UNSUBSCRIBE
# Message with variable header
# Message without payload
struct MQTTMessageUnsubscribe {

    MQTTFixedHeader fixed_header;

    # Variable header

    uint16          message_id;

}

# UNSUBACK
# Message with variable header
# Message without payload
struct MQTTMessageUnsuback {

    MQTTFixedHeader fixed_header;   

    # Variable header

    uint16          message_id;

}

# PINGREQ
# Message without variable header
# Message without payload
struct MQTTMessagePingreq {

    MQTTFixedHeader     fixed_header;

}

# PINGRESP
# Message without variable header
# Message without payload
struct MQTTMessagePingresp {

    MQTTFixedHeader     fixed_header;

}

# DISCONNECT
# Message without variable header
# Message without payload
struct MQTTMessageDisconnect {

    MQTTFixedHeader     fixed_header;

}

# Reserved 15
# Reserved message for futur use
struct MQTTMessageReserved15 {

    MQTTFixedHeader fixed_header;

    # Variable header and payload (if any)

    raw(fixed_header.remaining_length) content_of_message;

}
  
switch MQTTMessageSwitch MQTTMessageType {

    case MQTTMessageType::Reserved_0 : MQTTMessageReserved0 "";

    case MQTTMessageType::CONNECT :     MQTTMessageConnect "";
    case MQTTMessageType::CONNACK :     MQTTMessageConnack "";

    case MQTTMessageType::PUBLISH :     MQTTMessagePublish "";
    case MQTTMessageType::PUBACK :      MQTTMessagePuback "";
    case MQTTMessageType::PUBREC :      MQTTMessagePubrec "";
    case MQTTMessageType::PUBREL :      MQTTMessagePubrel "";
    case MQTTMessageType::PUBCOMP :     MQTTMessagePubcomp "";

    case MQTTMessageType::SUBSCRIBE :   MQTTMessageSubscribe "";
    case MQTTMessageType::SUBACK :      MQTTMessageSuback "";

    case MQTTMessageType::UNSUBSCRIBE : MQTTMessageUnsubscribe "";
    case MQTTMessageType::UNSUBACK :    MQTTMessageUnsuback "";

    case MQTTMessageType::PINGREQ :     MQTTMessagePingreq "";
    case MQTTMessageType::PINGRESP :    MQTTMessagePingresp "";

    case MQTTMessageType::DISCONNECT :  MQTTMessageDisconnect "";

    case MQTTMessageType::Reserved_15 : MQTTMessageReserved15 "";

    default :
        MQTTFixedHeader  fixed_header;
        raw(fixed_header.remaining_length)  content_of_message;
}