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eProsima / Micro-XRCE-DDS

An XRCE DDS implementation. Looking for commercial support? Contact info@eprosima.com
Apache License 2.0
158 stars 15 forks source link

Wireshark dissector? #101

Open gavanderhoorn opened 3 years ago

gavanderhoorn commented 3 years ago

A quick search using Google returned https://gist.github.com/driftregion/ee12af4ef4e202ef5111d4c9987a9382 by @driftregion.

It does dissect some traffic, but the payloads don't seem to be dissected.

Would you internally perhaps also use Wireshark and have something you could share? It would make debugging client <-> agent interactions a lot easier.

pablogs9 commented 3 years ago

Hello, @gavanderhoorn I was not aware of this. I'll check that and maybe we create a complete version.

Thanks for sharing.

gavanderhoorn commented 3 years ago

I'd write one myself normally, but seeing as you guys are most likely much more up-to-speed on the workings of the protocol, I expect it to be less work for you.

If you do decide to extend the skeleton dissector, I'd be interested.

gavanderhoorn commented 3 years ago

@pablogs9: did you guys end up extending the dissector?

Edit: I guess you did: https://github.com/eProsima/Micro-XRCE-DDS/compare/develop...wireshark_plugin

C plugins are logistically more difficult to get to work btw. They require users to build them locally on their own machines. Getting a dissector into Wireshark itself is also not that easy.

jseldent commented 2 years ago

Just in case anyone is interested, this is a more extensive Wireshark dissector for DDS-XRCE. It dissects everything apart from binary QoS profiles and of course the serialized user messages. It currently expects the agent and client to use port 2018. You can change that on line 281. To use the dissector, save the file as ~/.local/lib/wireshark/plugins/dds-xrce.lua.

-- DDS-XRCE protocol dissector for Wireshark
--
-- Copyright 2022 Lely Industries N.V.
--
-- Licensed under the Apache License, Version 2.0 (the "License");
-- you may not use this file except in compliance with the License.
-- You may obtain a copy of the License at
--
--     http://www.apache.org/licenses/LICENSE-2.0
--
-- Unless required by applicable law or agreed to in writing, software
-- distributed under the License is distributed on an "AS IS" BASIS,
-- WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-- See the License for the specific language governing permissions and
-- limitations under the License.

local p_dds_xrce = Proto("DDS-XRCE", "DDS for eXtremely Resource Constrained Environments")

local f_session_id = ProtoField.uint8("dds-xrce.session_id", "sessionId", base.HEX)
local f_stream_id = ProtoField.uint8("dds-xrce.stream_id", "streamId", base.HEX)
local f_sequence_nr = ProtoField.uint16("dds-xrce.sequence_nr", "sequenceNr", base.DEC)
local f_client_key = ProtoField.uint32("dds-xrce.client_key", "clientKey", base.HEX)

local f_submessage = ProtoField.none("dds-xrce.submessage", "submessage")
local f_submessage_id = ProtoField.uint8("dds-xrce.submessage.id", "submessageId", base.DEC)
local f_flags = ProtoField.uint8("dds-xrce.submessage.flags", "flags", base.HEX)
local f_flags_endianness =
    ProtoField.uint8(
    "dds-xrce.submessage.flags.endianness",
    "Endianness bit",
    base.HEX,
    {[0] = "Not set", [1] = "Set"},
    0x01
)
local f_flags_reuse =
    ProtoField.uint8("dds-xrce.submessage.flags.reuse", "Reuse bit", base.HEX, {[0] = "Not set", [1] = "Set"}, 0x02)
local f_flags_replace =
    ProtoField.uint8("dds-xrce.submessage.flags.replace", "Replace bit", base.HEX, {[0] = "Not set", [1] = "Set"}, 0x04)
local f_flags_data_format =
    ProtoField.uint8(
    "dds-xrce.submessage.flags.data_format",
    "DataFormat",
    base.HEX,
    {
        [0x0] = "FORMAT_DATA",
        [0x2] = "FORMAT_SAMPLE",
        [0x8] = "FORMAT_DATA_SEQ",
        [0xA] = "FORMAT_SAMPLE_SEQ",
        [0xE] = "FORMAT_PACKED_SAMPLES"
    },
    0x0E
)
local f_flags_last_fragment =
    ProtoField.uint8(
    "dds-xrce.submessage.flags.last_fragment",
    "Last Fragment bit",
    base.HEX,
    {[0] = "Not set", [1] = "Set"},
    0x04
)
local f_submessage_length = ProtoField.uint16("dds-xrce.submessage.length", "submessageLength", base.DEC)
local f_payload = ProtoField.bytes("dds-xrce.submessage.payload", "payload", base.SPACE)

p_dds_xrce.fields = {
    f_session_id,
    f_stream_id,
    f_sequence_nr,
    f_client_key,
    f_submessage,
    f_submessage_id,
    f_flags,
    f_flags_endianness,
    f_flags_reuse,
    f_flags_replace,
    f_flags_data_format,
    f_flags_last_fragment,
    f_submessage_length,
    f_payload
}

function p_dds_xrce.dissector(tvb, pinfo, tree)
    pinfo.cols.protocol = "DDS-XRCE"

    local t_dds_xrce = tree:add(p_dds_xrce, tvb(), "DDS-XRCE Protocol")
    local offset = 0

    local session_id = tvb(offset, 1):uint()
    local t_session_id = t_dds_xrce:add(f_session_id, tvb(offset, 1))
    if session_id == 0x00 then
        t_session_id:append_text(" (SESSION_ID_NONE_WITH_CLIENT_KEY)")
    elseif session_id == 0x80 then
        t_session_id:append_text(" (SESSION_ID_NONE_WITHOUT_CLIENT_KEY)")
    end
    offset = offset + 1

    local stream_id = tvb(offset, 1):uint()
    local t_stream_id = t_dds_xrce:add(f_stream_id, tvb(offset, 1))
    if stream_id == 0x00 then
        t_stream_id:append_text(" (STREAMID_NONE)")
    elseif stream_id == 0x01 then
        t_stream_id:append_text(" (STREAMID_BUILTIN_BEST_EFFORTS)")
    elseif stream_id == 0x80 then
        t_stream_id:append_text(" (STREAMID_BUILTIN_RELIABLE)")
    end
    if stream_id >= 0x80 then
        t_stream_id:add(tvb(offset, 1), "reliability:", "RELIABLE")
    elseif stream_id >= 0x01 then
        t_stream_id:add(tvb(offset, 1), "reliability:", "BEST_EFFORTS")
    end
    offset = offset + 1

    t_dds_xrce:add_le(f_sequence_nr, tvb(offset, 2))
    offset = offset + 2

    if session_id < 0x80 then
        t_dds_xrce:add_le(f_client_key, tvb(offset, 4))
        offset = offset + 4
    end

    while offset < tvb:len() do
        local t_submessage = t_dds_xrce:add(f_submessage, tvb(offset))

        local submessage_id = tvb(offset, 1):uint()
        t_submessage:add(f_submessage_id, tvb(offset, 1))
        offset = offset + 1

        local flags = tvb(offset, 1):uint()
        local t_flags = t_submessage:add(f_flags, tvb(offset, 1))
        if submessage_id == 1 then
            -- CREATE
            if bit.band(flags, 0x04) == 0x04 then
                t_flags:append_text(", Replace bit")
            end
            t_flags:add(f_flags_replace, tvb(offset, 1))
            if bit.band(flags, 0x02) == 0x02 then
                t_flags:append_text(", Reuse bit")
            end
            t_flags:add(f_flags_reuse, tvb(offset, 1))
        elseif submessage_id == 7 or submessage_id == 9 then
            -- WRITE_DATA or DATA
            if bit.band(flags, 0x0E) == 0x00 then
                t_flags:append_text(", FORMAT_DATA")
            elseif bit.band(flags, 0x0E) == 0x02 then
                t_flags:append_text(", FORMAT_SAMPLE")
            elseif bit.band(flags, 0x0E) == 0x08 then
                t_flags:append_text(", FORMAT_DATA_SEQ")
            elseif bit.band(flags, 0x0E) == 0x0A then
                t_flags:append_text(", FORMAT_SAMPLE_SEQ")
            elseif bit.band(flags, 0x0E) == 0x0E then
                t_flags:append_text(", FORMAT_PACKED_SAMPLES")
            end
            t_flags:add(f_flags_data_format, tvb(offset, 1))
        elseif submessage_id == 13 then
            -- FRAGMENT
            if bit.band(flags, 0x02) == 0x02 then
                t_flags:append_text(", Last Fragment bit")
            end
            t_flags:add(f_flags_last_fragment, tvb(offset, 1))
        end
        local encoding = ENC_BIG_ENDIAN
        if bit.band(flags, 0x01) == 0x01 then
            t_flags:append_text(", Endianness bit")
            encoding = ENC_LITTLE_ENDIAN
        end
        t_flags:add(f_flags_endianness, tvb(offset, 1))
        offset = offset + 1

        submessage_length = tvb(offset, 2):le_uint()
        t_submessage:add_le(f_submessage_length, tvb(offset, 2))
        offset = offset + 2

        t_submessage:set_len(4 + submessage_length)

        local t_payload = t_submessage:add(f_payload, tvb(offset, submessage_length))

        if submessage_id == 0 then
            t_submessage:set_text("CREATE_CLIENT")
            t_payload:set_text("CREATE_CLIENT_Payload")
            idl_create_client_payload(t_payload, tvb(offset, submessage_length), 0, encoding)
        elseif submessage_id == 1 then
            t_submessage:set_text("CREATE")
            t_payload:set_text("CREATE_Payload")
            idl_create_payload(t_payload, tvb(offset, submessage_length), 0, encoding)
        elseif submessage_id == 2 then
            t_submessage:set_text("GET_INFO")
            t_payload:set_text("GET_INFO_Payload")
            idl_get_info_payload(t_payload, tvb(offset, submessage_length), 0, encoding)
        elseif submessage_id == 3 then
            t_submessage:set_text("DELETE")
            t_payload:set_text("DELETE_Payload")
            idl_delete_payload(t_payload, tvb(offset, submessage_length), 0, encoding)
        elseif submessage_id == 4 then
            t_submessage:set_text("STATUS_AGENT")
            t_payload:set_text("STATUS_AGENT_Payload")
            idl_status_agent_payload(t_payload, tvb(offset, submessage_length), 0, encoding)
        elseif submessage_id == 5 then
            t_submessage:set_text("STATUS")
            t_payload:set_text("STATUS_Payload")
            idl_status_payload(t_payload, tvb(offset, submessage_length), 0, encoding)
        elseif submessage_id == 6 then
            t_submessage:set_text("INFO")
            t_payload:set_text("INFO_Payload")
            idl_info_payload(t_payload, tvb(offset, submessage_length), 0, encoding)
        elseif submessage_id == 7 then
            t_submessage:set_text("WRITE_DATA")
            if bit.band(flags, 0x0E) == 0x00 then
                -- FORMAT_DATA
                t_payload:set_text("WRITE_DATA_Payload_Data")
                idl_write_data_payload_data(t_payload, tvb(offset, submessage_length), 0, encoding)
            elseif bit.band(flags, 0x0E) == 0x02 then
                -- FORMAT_SAMPLE
                t_payload:set_text("WRITE_DATA_Payload_Sample")
                idl_write_data_payload_sample(t_payload, tvb(offset, submessage_length), 0, encoding)
            elseif bit.band(flags, 0x0E) == 0x08 then
                -- FORMAT_DATA_SEQ
                t_payload:set_text("WRITE_DATA_Payload_DataSeq")
                idl_write_data_payload_data_seq(t_payload, tvb(offset, submessage_length), 0, encoding)
            elseif bit.band(flags, 0x0E) == 0x0A then
                -- FORMAT_SAMPLE_SEQ
                t_payload:set_text("WRITE_DATA_Payload_SampleSeq")
                idl_write_data_payload_sample_seq(t_payload, tvb(offset, submessage_length), 0, encoding)
            elseif bit.band(flags, 0x0E) == 0x0E then
                -- FORMAT_PACKED_SAMPLES
                t_payload:set_text("WRITE_DATA_Payload_PackedSamples")
                idl_write_data_payload_packed_samples(t_payload, tvb(offset, submessage_length), 0, encoding)
            end
        elseif submessage_id == 8 then
            t_submessage:set_text("READ_DATA")
            t_payload:set_text("READ_DATA_Payload")
            idl_read_data_payload(t_payload, tvb(offset, submessage_length), 0, encoding)
        elseif submessage_id == 9 then
            t_submessage:set_text("DATA")
            if bit.band(flags, 0x0E) == 0x00 then
                -- FORMAT_DATA
                t_payload:set_text("DATA_Payload_Data")
                idl_data_payload_data(t_payload, tvb(offset, submessage_length), 0, encoding)
            elseif bit.band(flags, 0x0E) == 0x02 then
                -- FORMAT_SAMPLE
                t_payload:set_text("DATA_Payload_Sample")
                idl_data_payload_sample(t_payload, tvb(offset, submessage_length), 0, encoding)
            elseif bit.band(flags, 0x0E) == 0x08 then
                -- FORMAT_DATA_SEQ
                t_payload:set_text("DATA_Payload_DataSeq")
                idl_data_payload_data_seq(t_payload, tvb(offset, submessage_length), 0, encoding)
            elseif bit.band(flags, 0x0E) == 0x0A then
                -- FORMAT_SAMPLE_SEQ
                t_payload:set_text("DATA_Payload_SampleSeq")
                idl_data_payload_sample_seq(t_payload, tvb(offset, submessage_length), 0, encoding)
            elseif bit.band(flags, 0x0E) == 0x0E then
                -- FORMAT_PACKED_SAMPLES
                t_payload:set_text("DATA_Payload_PackedSamples")
                idl_data_payload_packed_samples(t_payload, tvb(offset, submessage_length), 0, encoding)
            end
        elseif submessage_id == 10 then
            t_submessage:set_text("ACKNACK")
            t_payload:set_text("ACKNACK_Payload")
            idl_acknack_payload(t_payload, tvb(offset, submessage_length), 0, encoding)
        elseif submessage_id == 11 then
            t_submessage:set_text("HEARTBEAT")
            t_payload:set_text("HEARTBEAT_Payload")
            idl_heartbeat_payload(t_payload, tvb(offset, submessage_length), 0, encoding)
        elseif submessage_id == 12 then
            t_submessage:set_text("RESET")
        elseif submessage_id == 13 then
            t_submessage:set_text("FRAGMENT")
        elseif submessage_id == 14 then
            t_submessage:set_text("TIMESTAMP")
            t_payload:set_text("TIMESTAMP_Payload")
            idl_timestamp_payload(t_payload, tvb(offset, submessage_length), 0, encoding)
        elseif submessage_id == 15 then
            t_submessage:set_text("TIMESTAMP_REPLY")
            t_payload:set_text("TIMESTAMP_REPLY_Payload")
            idl_timestamp_reply_payload(t_payload, tvb(offset, submessage_length), 0, encoding)
        end

        offset = offset + align(submessage_length, 4)
    end
end

local udp_table = DissectorTable.get("udp.port")
udp_table:add(2018, p_dds_xrce)

function align(x, a)
    return bit.band(x + a - 1, bit.bnot(a - 1))
end

function tvb_int(tvb, encoding)
    encoding = encoding or ENC_BIG_ENDIAN
    local value = 0
    if encoding == ENC_BIG_ENDIAN then
        if tvb:len() <= 4 then
            value = tvb:int()
        else
            value = tvb:int64()
        end
    elseif encoding == ENC_LITTLE_ENDIAN then
        if tvb:len() <= 4 then
            value = tvb:le_int()
        else
            value = tvb:le_int64()
        end
    end
    return value
end

function tvb_uint(tvb, encoding)
    encoding = encoding or ENC_BIG_ENDIAN
    local value = 0
    if encoding == ENC_BIG_ENDIAN then
        if tvb:len() <= 4 then
            value = tvb:uint()
        else
            value = tvb:uint64()
        end
    elseif encoding == ENC_LITTLE_ENDIAN then
        if tvb:len() <= 4 then
            value = tvb:le_uint()
        else
            value = tvb:le_uint64()
        end
    end
    return value
end

function tvb_format_uint(tvb, encoding, b)
    b = b or base.DEC

    value = tvb_uint(tvb, encoding)
    if b == base.DEC then
        return string.format("%u", value)
    elseif b == base.HEX then
        return string.format("0x%0" .. tostring(tvb:len() * 2) .. "x", value)
    end
end

function idl_client_key(tree, tvb, offset, encoding, label)
    label = label or "client_key:"

    tree:add(tvb(offset, 4), label, tvb(offset, 4):bytes():tohex(true))
    offset = offset + 4

    return offset
end

function idl_object_id(tree, tvb, offset, encoding, label)
    label = label or "object_id:"

    local object_id_0 = tvb(offset, 1):uint()
    local object_id_1 = tvb(offset + 1, 1):uint()
    local t_object_id = tree:add(tvb(offset, 2), label, tvb(offset, 2):bytes():tohex(true))
    if object_id_0 == 0x00 and object_id_1 == 0x00 then
        t_object_id:append_text(" (INVALID)")
    elseif object_id_0 == 0xff then
        if object_id_1 == 0xfd then
            t_object_id:append_text(" (AGENT)")
        elseif object_id_1 == 0xfe then
            t_object_id:append_text(" (CLIENT)")
        elseif object_id_1 == 0xff then
            t_object_id:append_text(" (SESSION)")
        end
    end
    offset = offset + 2

    return offset
end

function idl_xrce_cookie(tree, tvb, offset, encoding, label)
    label = label or "xrce_cookie:"

    tree:add(tvb(offset, 4), label, tvb(offset, 4):string())
    offset = offset + 4

    return offset
end

function idl_xrce_version(tree, tvb, offset, encoding, label)
    label = label or "xrce_version:"

    local xrce_version_major = tvb(offset, 1):uint()
    local xrce_version_minor = tvb(offset + 1, 1):uint()
    local xrce_version = tostring(xrce_version_major) .. "." .. tostring(xrce_version_minor)
    local t_xrce_version = tree:add(tvb(offset, 2), label, xrce_version)
    t_xrce_version:add(tvb(offset, 1), "major:", xrce_version_major)
    t_xrce_version:add(tvb(offset + 1, 1), "minor:", xrce_version_minor)
    offset = offset + 2

    return offset
end

function idl_xrce_vendor_id(tree, tvb, offset, encoding, label)
    label = label or "xrce_vendor_id:"

    local xrce_vendor_id_major = tvb(offset, 1):uint()
    local xrce_vendor_id_minor = tvb(offset + 1, 1):uint()
    local xrce_vendor_id = tostring(xrce_vendor_id_major) .. "." .. tostring(xrce_vendor_id_minor)
    if xrce_vendor_id_major == 0 and xrce_vendor_id_minor == 0 then
        xrce_vendor_id = xrce_vendor_id .. " (INVALID)"
    elseif xrce_vendor_id_major == 1 and xrce_vendor_id_minor == 15 then
        xrce_vendor_id = xrce_vendor_id .. " (eProsima)"
    end
    tree:add(tvb(offset, 2), label, xrce_vendor_id)
    offset = offset + 2

    return offset
end

function idl_time_t(tree, tvb, offset, encoding, label)
    label = label or "timestamp:"

    offset = align(offset, 4)

    local seconds = tvb_int(tvb(offset, 4), encoding)
    local nanoseconds = tvb_uint(tvb(offset, 4), encoding)
    local t_time_t = tree:add(tvb(offset, 8), label, seconds + 1e-9 * nanoseconds)
    t_time_t:add(tvb(offset, 4), "seconds:", seconds)
    offset = offset + 4
    t_time_t:add(tvb(offset, 4), "nanoseconds:", nanoseconds)
    offset = offset + 4

    return offset
end

function idl_session_id(tree, tvb, offset, encoding, label)
    label = label or "session_id:"

    local session_id = tvb(offset, 1):uint()
    local t_session_id = tree:add(tvb(offset, 1), label, tvb_format_uint(tvb(offset, 1), encoding, base.HEX))
    if session_id == 0x00 then
        t_session_id:append_text(" (SESSION_ID_NONE_WITH_CLIENT_KEY)")
    elseif session_id == 0x80 then
        t_session_id:append_text(" (SESSION_ID_NONE_WITHOUT_CLIENT_KEY)")
    end
    offset = offset + 1

    return offset
end

function idl_stream_id(tree, tvb, offset, encoding, label)
    label = label or "stream_id:"

    local stream_id = tvb(offset, 1):uint()
    local t_stream_id = tree:add(tvb(offset, 1), label, tvb_format_uint(tvb(offset, 1), encoding, base.HEX))
    if stream_id == 0x00 then
        t_stream_id:append_text(" (STREAMID_NONE)")
    elseif session_id == 0x01 then
        t_stream_id:append_text(" (STREAMID_BUILTIN_BEST_EFFORTS)")
    elseif session_id == 0x80 then
        t_stream_id:append_text(" (STREAMID_BUILTIN_RELIABLE)")
    end
    if stream_id >= 0x80 then
        t_stream_id:add(tvb(offset, 1), "reliability:", "RELIABLE")
    elseif stream_id >= 0x01 then
        t_stream_id:add(tvb(offset, 1), "reliability:", "BEST_EFFORTS")
    end
    offset = offset + 1

    return offset
end

function idl_transport_locator(tree, tvb, offset, encoding, label)
    label = label or "address"

    local begin = offset

    local t_transport_locator = tree:add(tvb(offset), label)

    local transport_locator_format = tvb(offset, 1):uint()
    offset = offset + 1

    if transport_locator_format == 0x00 then
        -- ADDRES_FORMAT_SMALL
        tree:add(tvb(offset, 2), "address:", tvb(offset, 2):bytes():tohex(true))
        offset = offset + 2
        t_transport_locator:add(tvb(offset, 1), "locator_port:", tvb_uint(tvb(offset, 1), encoding))
        offset = offset + 1
    elseif transport_locator_format == 0x01 then
        -- ADDRES_FORMAT_MEDIUM
        t_transport_locator:add(
            tvb(offset, 4),
            "address:",
            string.format("%u.%u.%u.%u", tvb(offset, 1), tvb(offset + 1, 1), tvb(offset + 2, 1), tvb(offset + 3, 1))
        )
        offset = offset + 4
        offset = align(offset, 2)
        t_transport_locator:add(tvb(offset, 2), "locator_port:", tvb_uint(tvb(offset, 2), encoding))
        offset = offset + 2
    elseif transport_locator_format == 0x02 then
        -- ADDRES_FORMAT_LARGE
        address_0 = tvb_uint(tvb(offset, 2), encoding)
        address_1 = tvb_uint(tvb(offset + 2, 2), encoding)
        address_2 = tvb_uint(tvb(offset + 4, 2), encoding)
        address_3 = tvb_uint(tvb(offset + 6, 2), encoding)
        address_4 = tvb_uint(tvb(offset + 8, 2), encoding)
        address_5 = tvb_uint(tvb(offset + 10, 2), encoding)
        address_6 = tvb_uint(tvb(offset + 12, 2), encoding)
        address_7 = tvb_uint(tvb(offset + 14, 2), encoding)
        t_transport_locator:add(
            tvb(offset, 16),
            "address:",
            string.format(
                "%04x:%04x:%04x:%04x:%04x:%04x:%04x:%04x",
                address_0,
                address_1,
                address_2,
                address_3,
                address_4,
                address_5,
                address_6,
                address_7
            )
        )
        offset = offset + 16
        offset = align(offset, 4)
        t_transport_locator:add(tvb(offset, 4), "locator_port:", tvb_uint(tvb(offset, 4), encoding))
        offset = offset + 4
    elseif transport_locator_format == 0x03 then
        -- ADDRES_FORMAT_STRING
        offset = align(offset, 4)
        local size = tvb_uint(tvb(offset, 4), encoding)
        offset = offset + 4
        t_transport_locator:add(tvb(offset, size), "string_locator:", tvb(offset, size):stringz())
        offset = offset + size
    end

    t_transport_locator:set_len(offset - begin)

    return offset
end

function idl_transport_locator_seq(tree, tvb, offset, encoding, label)
    label = label or "address_seq"

    offset = align(offset, 4)
    local begin = offset

    local t_address_seq = tree:add(tvb(offset), label)

    local size = tvb_uint(tvb(offset, 4), encoding)
    offset = offset + 4

    if size == 0 then
        t_address_seq:append_text(" [empty]")
    else
        for i = 1, size do
            offset = idl_transport_locator(t_address_seq, tvb, offset, encoding, "[" .. tostring(i - 1) .. "]")
        end
    end

    t_address_seq:set_len(offset - begin)

    return offset
end

function idl_property(tree, tvb, offset, encoding)
    offset = align(offset, 4)
    local begin = offset
    local name_size = tvb_uint(tvb(offset, 4), encoding)
    offset = offset + 4
    local name = tvb(offset, name_size):stringz()
    offset = offset + name_size

    offset = align(offset, 4)
    local value_size = tvb_uint(tvb(offset, 4), encoding)
    offset = offset + 4
    local value = tvb(offset, value_size):stringz()
    offset = offset + value_size

    tree:add(tvb(begin, offset - begin), name .. ":", value)

    return offset
end

function idl_property_seq(tree, tvb, offset, encoding, label)
    label = label or "properties"

    offset = align(offset, 4)
    local begin = offset

    local t_properties = tree:add(tvb(offset), label)

    local size = tvb_uint(tvb(offset, 4), encoding)
    offset = offset + 4

    if size == 0 then
        t_properties:append_text(" [empty]")
    else
        for i = 1, size do
            offset = idl_property(t_properties, tvb, offset, encoding)
        end
    end

    t_properties:set_len(offset - begin)

    return offset
end

function idl_objk_representation_base(tree, tvb, offset, encoding)
    local format = tvb(offset, 1):uint()
    local t_format = tree:add(tvb(offset, 1), "format:", tvb_format_uint(tvb(offset, 1), encoding, base.HEX))
    offset = offset + 1

    if format == 0x01 then
        --- REPRESENTATION_BY_REFERENCE
        t_format:append_text(" (REPRESENTATION_BY_REFERENCE)")
        offset = align(offset, 4)
        local size = tvb_uint(tvb(offset, 4), encoding)
        offset = offset + 4
        tree:add(tvb(offset, size), "object_reference:", tvb(offset, size):stringz())
        offset = offset + size
    elseif format == 0x02 then
        --- REPRESENTATION_AS_XML_STRING
        t_format:append_text(" (REPRESENTATION_BY_REFERENCE)")
        offset = align(offset, 4)
        local size = tvb_uint(tvb(offset, 4), encoding)
        offset = offset + 4
        tree:add(tvb(offset, size), "xml_string_representation:", tvb(offset, size):stringz())
        offset = offset + size
    elseif format == 0x03 then
        --- REPRESENTATION_IN_BINARY
        t_format:append_text(" (REPRESENTATION_BY_REFERENCE)")
        offset = align(offset, 4)
        local size = tvb_uint(tvb(offset, 4), encoding)
        offset = offset + 4
        tree:add(tvb(offset, size), "binary_representation:", tvb(offset, size):bytes():tohex(true))
        offset = offset + size
    end

    return offset
end

function idl_objk_qos_profile_representation(tree, tvb, offset, encoding, label)
    label = label or "qos_profile"

    local begin = offset

    local t_qos_profile = tree:add(tvb(offset), label)

    offset = idl_objk_representation_base(t_qos_profile, tvb, offset, encoding)

    t_qos_profile:set_len(offset - begin)

    return offset
end

function idl_objk_type_representation(tree, tvb, offset, encoding, label)
    label = label or "type"

    local begin = offset

    local t_type = tree:add(tvb(offset), label)

    offset = idl_objk_representation_base(t_type, tvb, offset, encoding)

    t_type:set_len(offset - begin)

    return offset
end

function idl_objk_application_representation(tree, tvb, offset, encoding, label)
    label = label or "application"

    local begin = offset

    local t_application = tree:add(tvb(offset), label)

    offset = idl_objk_representation_base(t_application, tvb, offset, encoding)

    t_application:set_len(offset - begin)

    return offset
end

function idl_objk_publisher_representation(tree, tvb, offset, encoding, label)
    label = label or "publisher"

    local begin = offset

    local t_publisher = tree:add(tvb(offset), label)

    offset = idl_objk_representation_base(t_publisher, tvb, offset, encoding)
    offset = idl_object_id(t_publisher, tvb, offset, encoding, "participant_id:")

    t_publisher:set_len(offset - begin)

    return offset
end

function idl_objk_subscriber_representation(tree, tvb, offset, encoding, label)
    label = label or "subscriber"

    local begin = offset

    local t_subscriber = tree:add(tvb(offset), label)

    offset = idl_objk_representation_base(t_subscriber, tvb, offset, encoding)
    offset = idl_object_id(t_subscriber, tvb, offset, encoding, "participant_id:")

    t_subscriber:set_len(offset - begin)

    return offset
end

function idl_objk_data_writer_representation(tree, tvb, offset, encoding, label)
    label = label or "data_writer"

    local begin = offset

    local t_data_writer = tree:add(tvb(offset), label)

    offset = idl_objk_representation_base(t_data_writer, tvb, offset, encoding)
    offset = idl_object_id(t_data_writer, tvb, offset, encoding, "publisher_id:")

    t_data_writer:set_len(offset - begin)

    return offset
end

function idl_objk_data_reader_representation(tree, tvb, offset, encoding, label)
    label = label or "data_reader"

    local begin = offset

    local t_data_reader = tree:add(tvb(offset), label)

    offset = idl_objk_representation_base(t_data_reader, tvb, offset, encoding)
    offset = idl_object_id(t_data_reader, tvb, offset, encoding, "subscriber_id:")

    t_data_reader:set_len(offset - begin)

    return offset
end

function idl_objk_participant_representation(tree, tvb, offset, encoding, label)
    label = label or "participant"

    local begin = offset

    local t_participant = tree:add(tvb(offset), label)

    offset = idl_objk_representation_base(t_participant, tvb, offset, encoding)

    offset = align(offset, 2)
    t_participant:add(tvb(offset, 2), "domain_id:", tvb_int(tvb(offset, 2), encoding))
    offset = offset + 2

    t_participant:set_len(offset - begin)

    return offset
end

function idl_objk_topic_representation(tree, tvb, offset, encoding, label)
    label = label or "topic"

    local begin = offset

    local t_topic = tree:add(tvb(offset), label)

    offset = idl_objk_representation_base(t_topic, tvb, offset, encoding)
    offset = idl_object_id(t_topic, tvb, offset, encoding, "participant_id:")

    t_topic:set_len(offset - begin)

    return offset
end

function idl_object_variant(tree, tvb, offset, encoding, label)
    label = label or "object_variant"

    local begin = offset

    local t_object_variant = tree:add(tvb(offset), label)

    local kind = tvb(offset, 1):uint()
    local t_kind = t_object_variant:add(tvb(offset, 1), "kind:", tvb_format_uint(tvb(offset, 1), encoding, base.HEX))
    offset = offset + 1

    if kind == 0x0D then
        -- OBJK_AGENT
        t_kind:append_text(" (OBJK_AGENT)")
        offset = idl_agent_representation(t_object_variant, tvb, offset, encoding, "agent")
    elseif kind == 0x0E then
        -- OBJK_CLIENT
        t_kind:append_text(" (OBJK_CLIENT)")
        offset = idl_client_representation(t_object_variant, tvb, offset, encoding, "client")
    elseif kind == 0x0C then
        -- OBJK_APPLICATION
        t_kind:append_text(" (OBJK_APPLICATION)")
        offset = idl_objk_application_representation(t_object_variant, tvb, offset, encoding)
    elseif kind == 0x01 then
        -- OBJK_PARTICIPANT
        t_kind:append_text(" (OBJK_PARTICIPANT)")
        offset = idl_objk_participant_representation(t_object_variant, tvb, offset, encoding)
    elseif kind == 0x0B then
        -- OBJK_QOSPROFILE
        t_kind:append_text(" (OBJK_QOSPROFILE)")
        offset = idl_objk_qos_profile_representation(t_object_variant, tvb, offset, encoding)
    elseif kind == 0x0A then
        -- OBJK_TYPE
        t_kind:append_text(" (OBJK_TYPE)")
        offset = idl_objk_type_representation(t_object_variant, tvb, offset, encoding)
    elseif kind == 0x02 then
        -- OBJK_TOPIC
        t_kind:append_text(" (OBJK_TOPIC)")
        offset = idl_objk_topic_representation(t_object_variant, tvb, offset, encoding)
    elseif kind == 0x03 then
        -- OBJK_PUBLISHER
        t_kind:append_text(" (OBJK_PUBLISHER)")
        offset = idl_objk_publisher_representation(t_object_variant, tvb, offset, encoding)
    elseif kind == 0x04 then
        -- OBJK_SUBSCRIBER
        t_kind:append_text(" (OBJK_SUBSCRIBER)")
        offset = idl_objk_subscriber_representation(t_object_variant, tvb, offset, encoding)
    elseif kind == 0x05 then
        -- OBJK_DATAWRITER
        t_kind:append_text(" (OBJK_DATAWRITER)")
        offset = idl_objk_data_writer_representation(t_object_variant, tvb, offset, encoding)
    elseif kind == 0x06 then
        -- OBJK_DATAREADER
        t_kind:append_text(" (OBJK_DATAREADER)")
        offset = idl_objk_data_reader_representation(t_object_variant, tvb, offset, encoding)
    end

    t_object_variant:set_len(offset - begin)

    return offset
end

function idl_request_id(tree, tvb, offset, encoding, label)
    label = label or "request_id:"

    tree:add(tvb(offset, 2), label, tvb(offset, 2):bytes():tohex(true))
    offset = offset + 2

    return offset
end

function idl_result_status(tree, tvb, offset, encoding, label)
    label = label or "result_status"

    local t_result_status = tree:add(tvb(offset, 2), label)

    local status = tvb_uint(tvb(offset, 1), encoding)
    local t_status = t_result_status:add(tvb(offset, 1), "status", tvb_format_uint(tvb(offset, 1), encoding, base.HEX))
    if status == 0x00 then
        t_status:append_text(" (STATUS_OK)")
    elseif status == 0x01 then
        t_status:append_text(" (STATUS_OK_MATCHED)")
    elseif status == 0x80 then
        t_status:append_text(" (STATUS_ERR_DDS_ERROR)")
    elseif status == 0x81 then
        t_status:append_text(" (STATUS_ERR_MISMATCH)")
    elseif status == 0x82 then
        t_status:append_text(" (STATUS_ERR_ALREADY_EXISTS)")
    elseif status == 0x83 then
        t_status:append_text(" (STATUS_ERR_DENIED)")
    elseif status == 0x84 then
        t_status:append_text(" (STATUS_ERR_UNKNOWN_REFERENEC)")
    elseif status == 0x85 then
        t_status:append_text(" (STATUS_ERR_INVALID_DATA)")
    elseif status == 0x86 then
        t_status:append_text(" (STATUS_ERR_INCOMPATIBLE)")
    elseif status == 0x87 then
        t_status:append_text(" (STATUS_ERR_RESOURCES)")
    end
    offset = offset + 1

    t_result_status:add(tvb(offset, 1), "implementation_status", tvb_format_uint(tvb(offset, 1), encoding, base.HEX))
    offset = offset + 1

    return offset
end

function idl_info_mask(tree, tvb, offset, encoding, label)
    label = label or "info_mask:"

    local info_mask = tvb_uint(tvb(offset, 4), encoding)
    local t_info_mask = tree:add(tvb(offset, 1), label, tvb_format_uint(tvb(offset, 4), encoding, base.HEX))
    if bit.band(info_mask, 0x2) == 0x2 then
        t_info_mask:append_text(", INFO_ACTIVITY")
        t_info_mask:add(tvb(offset, 4), ".... .... .... .... .... .... .... ..1. = INFO_ACTIVITY:", "Set")
    else
        t_info_mask:add(tvb(offset, 4), ".... .... .... .... .... .... .... ..0. = INFO_ACTIVITY:", "Not set")
    end
    if bit.band(info_mask, 0x1) == 0x1 then
        t_info_mask:append_text(", INFO_CONFIGURATION")
        t_info_mask:add(tvb(offset, 4), ".... .... .... .... .... .... .... ...1 = INFO_CONFIGURATION:", "Set")
    else
        t_info_mask:add(tvb(offset, 4), ".... .... .... .... .... .... .... ...0 = INFO_CONFIGURATION:", "Not set")
    end
    offset = offset + 4

    return offset
end

function idl_object_info(tree, tvb, offset, encoding, label)
    label = label or "object_info"

    local begin = offset

    local t_object_info = tree:add(tvb(offset), label)

    local has_config = tvb(offset, 1):uint()
    offset = offset + 1
    if has_config > 0 then
        offset = idl_object_variant(t_object_info, tvb, offset, encoding, "config")
    end

    local has_activity = tvb(offset, 1):uint()
    offset = offset + 1
    if has_activity > 0 then
        local begin_activity = offset
        local t_activity = t_object_info:add(tvb(offset), "activity")

        -- ActivityInfoVariant
        local kind = tvb(offset, 1):uint()
        local t_kind = t_activity:add(tvb(offset, 1), "kind:", tvb_format_uint(tvb(offset, 1), encoding, base.HEX))
        offset = offset + 1
        if kind == 0x0D then
            -- OBJK_AGENT
            t_kind:append_text(" (OBJK_AGENT)")
            offset = align(offset, 2)
            local begin_agent = offset
            local t_agent = t_activity:add(tvb(offset, 2), "agent")
            t_agent:add(tvb(offset, 2), "availability:", tvb_int(tvb(offset, 2), encoding))
            offset = offset + 2
            offset = idl_transport_locator_seq(t_agent, tvb, offset, encoding)
            t_agent:set_len(offset - begin_agent)
        elseif kind == 0x05 then
            -- OBJK_DATAWRITER
            t_kind:append_text(" (OBJK_DATAWRITER)")
            offset = align(offset, 8)
            local t_data_writer = t_activity:add(tvb(offset, 2), "data_writer")
            t_data_reader:add(tvb(offset, 8), "sample_seq_num:", tvb_int(tvb(offset, 8), encoding))
            offset = offset + 8
            t_data_reader:add(tvb(offset, 2), "stream_seq_num:", tvb_int(tvb(offset, 2), encoding))
            offset = offset + 2
        elseif kind == 0x06 then
            -- OBJK_DATAREADER
            t_kind:append_text(" (OBJK_DATAREADER)")
            offset = align(offset, 2)
            local t_data_reader = t_activity:add(tvb(offset, 2), "data_reader")
            t_data_reader:add(tvb(offset, 2), "highest_acked_num:", tvb_int(tvb(offset, 2), encoding))
            offset = offset + 2
        end

        t_activity:set_len(offset - begin_activity)
    end

    t_object_info:set_len(offset - begin)

    return offset
end

function idl_base_object_request(tree, tvb, offset, encoding)
    offset = idl_request_id(tree, tvb, offset, encoding)
    offset = idl_object_id(tree, tvb, offset, encoding)

    return offset
end

function idl_base_object_reply(tree, tvb, offset, encoding)
    local begin = offset

    local t_related_request = tree:add(tvb(offset), "related_request")
    offset = idl_base_object_request(t_related_request, tvb, offset, encoding)
    t_related_request:set_len(offset - begin)

    offset = idl_result_status(tree, tvb, offset, encoding)

    return offset
end

function idl_data_format(tree, tvb, offset, encoding, label)
    label = label or "data_format:"

    local data_format = tvb(offset, 1):uint()
    local t_data_format = tree:add(tvb(offset, 1), label, tvb_format_uint(tvb(offset, 1), encoding, base.HEX))
    if data_format == 0x00 then
        t_data_format:append_text(" (FORMAT_DATA)")
    elseif session_id == 0x02 then
        t_data_format:append_text(" (FORMAT_SAMPLE)")
    elseif session_id == 0x08 then
        t_data_format:append_text(" (FORMAT_DATA_SEQ)")
    elseif session_id == 0x0A then
        t_data_format:append_text(" (FORMAT_SAMPLE_SEQ)")
    elseif session_id == 0x0E then
        t_data_format:append_text(" (FORMAT_PACKED_SAMPLES)")
    end
    offset = offset + 1

    return offset
end

function idl_read_specification(tree, tvb, offset, encoding, label)
    label = label or "read_specification"

    local begin = offset

    local t_read_specification = tree:add(tvb(offset), label)

    offset = idl_stream_id(t_read_specification, tvb, offset, encoding, "preferred_stream_id:")
    offset = idl_data_format(t_read_specification, tvb, offset, encoding)

    local has_content_filter_expression = tvb(offset, 1):uint()
    offset = offset + 1
    if has_content_filter_expression > 0 then
        offset = align(offset, 4)
        local size = tvb_uint(tvb(offset, 4), encoding)
        offset = offset + 4
        t_read_specification:add(tvb(offset, size), "content_filter_expression:", tvb(offset, size):stringz())
        offset = offset + size
    end

    local has_delivery_control = tvb(offset, 1):uint()
    offset = offset + 1
    if has_delivery_control > 0 then
        offset = align(offset, 2)
        local t_delivery_control = t_read_specification:add(tvb(offset, 8), "delivery_control")
        t_delivery_control:add(tvb(offset, 2), "max_samples:", tvb_uint(tvb(offset, 2), encoding))
        offset = offset + 2
        t_delivery_control:add(tvb(offset, 2), "max_elapsed_time:", tvb_uint(tvb(offset, 2), encoding))
        offset = offset + 2
        t_delivery_control:add(tvb(offset, 2), "max_bytes_per_second:", tvb_uint(tvb(offset, 2), encoding))
        offset = offset + 2
        t_delivery_control:add(tvb(offset, 2), "min_pace_period:", tvb_uint(tvb(offset, 2), encoding))
        offset = offset + 2
    end

    t_read_specification:set_len(offset - begin)

    return offset
end

function idl_sample_info_flags(tree, tvb, offset, encoding, label)
    label = label or "state"

    local samsample_info_flagsple_info_flags = tvb(offset, 1):uint()
    local t_sample_info_flags = tree:add(tvb(offset, 1), label, tvb_format_uint(tvb(offset, 1), encoding, base.HEX))
    if bit.band(sample_info_flags, 0x8) == 0x8 then
        t_sample_info_flags:append_text(", SAMPLE_STATE_READ")
        t_sample_info_flags:add(tvb(offset, 1), ".... 1... = SAMPLE_STATE_READ:", "Set")
    else
        t_sample_info_flags:add(tvb(offset, 1), ".... 0... = SAMPLE_STATE_READ:", "Not set")
    end
    if bit.band(sample_info_flags, 0x4) == 0x4 then
        t_sample_info_flags:append_text(", VIEW_STATE_NEW")
        t_sample_info_flags:add(tvb(offset, 1), ".... .1.. = VIEW_STATE_NEW:", "Set")
    else
        t_sample_info_flags:add(tvb(offset, 1), ".... .0.. = VIEW_STATE_NEW:", "Not set")
    end
    if bit.band(sample_info_flags, 0x2) == 0x2 then
        t_sample_info_flags:append_text(", INSTANCE_STATE_DISPOSED")
        t_sample_info_flags:add(tvb(offset, 1), ".... ..1. = INSTANCE_STATE_DISPOSED:", "Set")
    else
        t_sample_info_flags:add(tvb(offset, 1), ".... ..0. = INSTANCE_STATE_DISPOSED:", "Not set")
    end
    if bit.band(sample_info_flags, 0x1) == 0x1 then
        t_sample_info_flags:append_text(", INSTANCE_STATE_UNREGISTERED")
        t_sample_info_flags:add(tvb(offset, 1), ".... ...1 = INSTANCE_STATE_UNREGISTERED:", "Set")
    else
        t_sample_info_flags:add(tvb(offset, 1), ".... ...0 = INSTANCE_STATE_UNREGISTERED:", "Not set")
    end
    offset = offset + 1

    return offset
end

function idl_sample_info(tree, tvb, offset, encoding, label)
    label = label or "info"

    local begin = offset

    local t_sample_info = tree:add(tvb(offset), label)

    offset = idl_sample_info_flags(t_sample_info, tvb, offset, encoding)

    -- SampleInfoDetail
    local format = tvb(offset, 1):uint()
    local t_format = t_sample_info:add(tvb(offset, 1), "format:", tvb_format_uint(tvb(offset, 1), encoding, base.HEX))
    offset = offset + 1
    if format == 0x00 then
        -- FORMAT_EMPTY
        t_format:append_text(" (FORMAT_EMPTY)")
    elseif format == 0x01 then
        -- FORMAT_SEQNUM
        t_format:append_text(" (FORMAT_SEQNUM)")
        offset = align(offset, 4)
        t_sample_info:add(tvb(offset, 4), "sequence_number:", tvb_uint(tvb(offset, 4), encoding))
        offset = offset + 4
    elseif format == 0x02 then
        -- FORMAT_TIMESTAMP
        t_format:append_text(" (FORMAT_TIMESTAMP)")
        offset = align(offset, 4)
        t_sample_info:add(tvb(offset, 4), "session_time_offset:", tvb_uint(tvb(offset, 4), encoding))
        offset = offset + 4
    elseif format == 0x03 then
        -- FORMAT_SEQN_TIMS
        t_format:append_text(" (FORMAT_SEQN_TIMS)")
        offset = align(offset, 4)
        local t_seqnum_n_timestamp = t_sample_info:add(tvb(offset, 8), "seqnum_n_timestamp")
        t_seqnum_n_timestamp:add(tvb(offset, 4), "sequence_number:", tvb_uint(tvb(offset, 4), encoding))
        offset = offset + 4
        t_seqnum_n_timestamp:add(tvb(offset, 4), "session_time_offset:", tvb_uint(tvb(offset, 4), encoding))
        offset = offset + 4
    end

    t_sample_info:set_len(offset - begin)

    return offset
end

function idl_sample_data(tree, tvb, offset, encoding, label)
    label = label or "data"

    tree:add(tvb(offset), label):add(tvb(offset), "serialized_data:", tvb(offset):bytes():tohex(true, " "))
    offset = tvb:len()

    return offset
end

function idl_sample_data_seq(tree, tvb, offset, encoding, label)
    label = label or "data_seq"

    offset = align(offset, 4)
    local begin = offset

    local t_sample_data_seq = tree:add(tvb(offset), label)

    local size = tvb_uint(tvb(offset, 4), encoding)
    offset = offset + 4

    if size == 0 then
        t_sample_data_seq:append_text(" [empty]")
    else
        local sample_data_size = math.ceil((tvb:len() - offset) / size)
        for i = 1, size do
            offset =
                idl_sample_data(
                t_sample_data_seq,
                tvb(0, offset + sample_data_size),
                offset,
                encoding,
                "[" .. tostring(i - 1) .. "]"
            )
        end
    end

    t_sample_data_seq:set_len(offset - begin)

    return offset
end

function idl_sample_seq(tree, tvb, offset, encoding, label)
    label = label or "sample_seq"

    offset = align(offset, 4)
    local begin = offset

    local t_sample_seq = tree:add(tvb(offset), label)

    local size = tvb_uint(tvb(offset, 4), encoding)
    offset = offset + 4

    if size == 0 then
        t_sample_seq:append_text(" [empty]")
    else
        local sample_size = math.ceil((tvb:len() - offset) / size)
        for i = 1, size do
            offset =
                idl_sample(t_sample_seq, tvb(0, offset + sample_size), offset, encoding, "[" .. tostring(i - 1) .. "]")
        end
    end

    t_sample_seq:set_len(offset - begin)

    return offset
end

function idl_sample(tree, tvb, offset, encoding, label)
    label = label or "sample"

    local begin = offset

    local t_sample = tree:add(tvb(offset), label)

    offset = idl_sample_info(t_sample, tvb, offset, encoding)
    offset = idl_sample_data(t_sample, tvb, offset, encoding)

    t_sample:set_len(offset - begin)

    return offset
end

function idl_sample_delta(tree, tvb, offset, encoding, label)
    label = label or "idl_sample_delta"

    local begin = offset

    local t_sample_delta = tree:add(tvb(offset), label)

    -- SampleInfoDelta
    local t_sample_info_delta = t_sample_delta:add(tvb(offset, align(offset + 2, 2) + 2), "info_delta")
    offset = t_sample_info_flags(t_sample_info_delta, tvb, offset, encoding)
    t_sample_info_delta:add(tvb(offset, 1), "seq_number_delta:", tvb_int(tvb(offset, 1), encoding))
    offset = offset + 1
    offset = align(offset, 2)
    t_sample_info_delta:add(tvb(offset, 1), "timestamp_delta:", tvb_uint(tvb(offset, 2), encoding))
    offset = offset + 2

    offset = idl_sample_data(tree, tvb, offset, encoding)

    t_sample_delta:set_len(offset - begin)

    return offset
end

function idl_packed_samples(tree, tvb, offset, encoding, label)
    label = label or "packed_samples"

    local begin = offset

    local t_packed_samples = tree:add(tvb(offset), label)

    offset = t_sample_info(t_packed_samples, tvb, offset, encoding, "info_base")

    offset = align(offset, 4)
    local begin_sample_delta_seq = offset

    local t_sample_delta_seq = tree:add(tvb(offset), "sample_delta_seq")

    local size = tvb_uint(tvb(offset, 4), encoding)
    offset = offset + 4

    if size == 0 then
        t_sample_delta_seq:append_text(" [empty]")
    else
        local sample_delta_size = math.ceil((tvb:len() - offset) / size)
        for i = 1, size do
            offset =
                idl_sample_delta(
                t_sample_seq,
                tvb(0, offset + sample_delta_size),
                offset,
                encoding,
                "[" .. tostring(i - 1) .. "]"
            )
        end
    end

    t_sample_delta_seq:set_len(offset - begin_sample_delta_seq)

    t_packed_samples:set_len(offset - begin)

    return offset
end

function idl_client_representation(tree, tvb, offset, encoding, label)
    label = label or "client_representation"

    local begin = offset

    local t_client_representation = tree:add(tvb(offset), label)
    offset = idl_xrce_cookie(t_client_representation, tvb, offset, encoding)
    offset = idl_xrce_version(t_client_representation, tvb, offset, encoding)
    offset = idl_xrce_vendor_id(t_client_representation, tvb, offset, encoding)
    offset = idl_client_key(t_client_representation, tvb, offset, encoding)
    offset = idl_session_id(t_client_representation, tvb, offset, encoding)
    local has_properties = tvb(offset, 1):uint()
    offset = offset + 1
    if has_properties > 0 then
        offset = idl_property_seq(t_client_representation, tvb, offset, encoding)
    end
    t_client_representation:set_len(offset - begin)

    return offset
end

function idl_agent_representation(tree, tvb, offset, encoding, label)
    label = label or "agent_representation"

    local begin = offset

    local t_agent_representation = tree:add(tvb(offset), label)
    offset = idl_xrce_cookie(t_agent_representation, tvb, offset, encoding)
    offset = idl_xrce_version(t_agent_representation, tvb, offset, encoding)
    offset = idl_xrce_vendor_id(t_agent_representation, tvb, offset, encoding)
    local has_properties = tvb(offset, 1):uint()
    offset = offset + 1
    if has_properties > 0 then
        offset = idl_property_seq(t_agent_representation, tvb, offset, encoding)
    end
    t_agent_representation:set_len(offset - begin)

    return offset
end

function idl_create_client_payload(tree, tvb, offset, encoding)
    return idl_client_representation(tree, tvb, offset, encoding)
end

function idl_create_payload(tree, tvb, offset, encoding)
    offset = idl_base_object_request(tree, tvb, offset, encoding)
    offset = idl_object_variant(tree, tvb, offset, encoding, "object_representation")

    return offset
end

function idl_get_info_payload(tree, tvb, offset, encoding)
    offset = idl_base_object_request(tree, tvb, offset, encoding)
    offset = idl_info_mask(tree, tvb, offset, encoding)

    return offset
end

function idl_delete_payload(tree, tvb, offset, encoding)
    return idl_base_object_request(tree, tvb, offset, encoding)
end

function idl_status_agent_payload(tree, tvb, offset, encoding)
    offset = idl_result_status(tree, tvb, offset, encoding, "result")
    offset = idl_agent_representation(tree, tvb, offset, encoding, "agent_info")

    return offset
end

function idl_status_payload(tree, tvb, offset, encoding)
    return idl_base_object_reply(tree, tvb, offset, encoding)
end

function idl_info_payload(tree, tvb, offset, encoding)
    offset = idl_base_object_reply(tree, tvb, offset, encoding)
    offset = idl_object_info(tree, tvb, offset, encoding)

    return offset
end

function idl_read_data_payload(tree, tvb, offset, encoding)
    offset = idl_base_object_request(tree, tvb, offset, encoding)
    offset = idl_read_specification(tree, tvb, offset, encoding)

    return offset
end

function idl_write_data_payload_data(tree, tvb, offset, encoding)
    offset = idl_base_object_request(tree, tvb, offset, encoding)
    offset = idl_sample_data(tree, tvb, offset, encoding)

    return offset
end

function idl_write_data_payload_sample(tree, tvb, offset, encoding)
    offset = idl_base_object_request(tree, tvb, offset, encoding)
    offset = idl_sample(tree, tvb, offset, encoding)

    return offset
end

function idl_write_data_payload_data_seq(tree, tvb, offset, encoding)
    offset = idl_base_object_request(tree, tvb, offset, encoding)
    offset = idl_sample_data_seq(tree, tvb, offset, encoding)

    return offset
end

function idl_write_data_payload_sample_seq(tree, tvb, offset, encoding)
    offset = idl_base_object_request(tree, tvb, offset, encoding)
    offset = idl_sample_seq(tree, tvb, offset, encoding)

    return offset
end

function idl_write_data_payload_packed_samples(tree, tvb, offset, encoding)
    offset = idl_base_object_request(tree, tvb, offset, encoding)
    offset = idl_packed_samples(tree, tvb, offset, encoding)

    return offset
end

function idl_data_payload_data(tree, tvb, offset, encoding)
    offset = idl_base_object_request(tree, tvb, offset, encoding)
    offset = idl_sample_data(tree, tvb, offset, encoding)

    return offset
end

function idl_data_payload_sample(tree, tvb, offset, encoding)
    offset = idl_base_object_request(tree, tvb, offset, encoding)
    offset = idl_sample(tree, tvb, offset, encoding)

    return offset
end

function idl_data_payload_data_seq(tree, tvb, offset, encoding)
    offset = idl_base_object_request(tree, tvb, offset, encoding)
    offset = idl_sample_data_seq(tree, tvb, offset, encoding)

    return offset
end

function idl_data_payload_sample_seq(tree, tvb, offset, encoding)
    offset = idl_base_object_request(tree, tvb, offset, encoding)
    offset = idl_sample_seq(tree, tvb, offset, encoding)

    return offset
end

function idl_data_payload_packed_samples(tree, tvb, offset, encoding)
    offset = idl_base_object_request(tree, tvb, offset, encoding)
    offset = idl_packed_samples(tree, tvb, offset, encoding)

    return offset
end

function idl_acknack_payload(tree, tvb, offset, encoding)
    offset = align(offset, 2)

    tree:add(tvb(offset, 2), "first_unacked_seq_num:", tvb_format_uint(tvb(offset, 2), encoding, base.DEC))
    offset = offset + 2

    tree:add(tvb(offset, 2), "nack_bitmap:", tvb_format_uint(tvb(offset, 2), encoding, base.HEX))
    offset = offset + 2

    tree:add(tvb(offset, 1), "stream_id:", tvb_format_uint(tvb(offset, 1), encoding, base.HEX))
    offset = offset + 1

    return offset
end

function idl_heartbeat_payload(tree, tvb, offset, encoding)
    offset = align(offset, 2)

    tree:add(tvb(offset, 2), "first_unacked_seq_nr:", tvb_format_uint(tvb(offset, 2), encoding, base.DEC))
    offset = offset + 2

    tree:add(tvb(offset, 2), "last_unacked_seq_nr:", tvb_format_uint(tvb(offset, 2), encoding, base.DEC))
    offset = offset + 2

    tree:add(tvb(offset, 1), "stream_id:", tvb_format_uint(tvb(offset, 1), encoding, base.HEX))
    offset = offset + 1

    return offset
end

function idl_timestamp_payload(tree, tvb, offset, encoding)
    return idl_time_t(tree, tvb, offset, encoding, "transmit_timestamp:")
end

function idl_timestamp_reply_payload(tree, tvb, offset, encoding)
    offset = idl_time_t(tree, tvb, offset, encoding, "transmit_timestamp:")
    offset = idl_time_t(tree, tvb, offset, encoding, "receive_timestamp:")
    offset = idl_time_t(tree, tvb, offset, encoding, "originate_timestamp:")

    return offset
end
gavanderhoorn commented 2 years ago

Nice. Thanks Jos :+1:

Edit: is this hosted in a repository somewhere? That would make tracking updates possible/easier.

pablogs9 commented 2 years ago

@jseldent would you mind if we add this code to the repo?

jseldent commented 2 years ago

@jseldent would you mind if we add this code to the repo?

Not at all. Go ahead.

Edit: is this hosted in a repository somewhere? That would make tracking updates possible/easier.

Not yet. But see above :)

pablogs9 commented 2 years ago

I have added it to this branch: https://github.com/eProsima/Micro-XRCE-DDS/tree/wireshark_plugin

I have there a basic Lua version, a C plugin, and this new version. When we have some time we will order and document this and add it to the mainline. If you need to make changes I would appreciate it if you use this branch.

Thanks for the contribution!

gavanderhoorn commented 2 years ago

@jseldent's dissector is quite extensive. Thanks again @jseldent :+1:

@pablogs9: any ideas about dissecting payload?

I could imagine that'd be difficult with a plain .lua dissector, but a C-based one could potentially use Micro-CDR.

Would that need access to the message definitions / type-supports which generated those serialised payloads? Or would you see a possibility to deserialise without access to that information?

pablogs9 commented 2 years ago

@gavanderhoorn you will need to have access to the generated type support so I guess that deserializing payloads is not an easy task.

jseldent commented 2 years ago

@gavanderhoorn and it would require the dissector to track the creation of DDS entities to know which topics use which data types. And depending on how they are created, that might also require access to the QoS XML file used by MicroXRCEAgent. I don't think that's really feasible.

gavanderhoorn commented 2 years ago

I'd sort-of understood that myself, but one can always hope.

As much as I like (XRCE-)DDS, this is one aspect which isn't very nice. It makes debugging the applications built upon it much more difficult. Especially in embedded environments.

(this is not directed at any of you here of course)

Edit:

it would require the dissector to track the creation of DDS entities to know which topics use which data types.

there are dissectors which do similar things though for other protocols. So while it would be quite a bit of work, it would not be impossible.

jseldent commented 2 years ago

I'd sort-of understood that myself, but one can always hope.

As much as I like (XRCE-)DDS, this is one aspect which isn't very nice. It makes debugging the applications built upon it much more difficult. Especially in embedded environments.

(this is not directed at any of you here of course)

I agree that it makes debugging quite a bit harder. But making this easier would generally require that the protocol is self-describing. And the overhead is usually not acceptable for embedded applications.

Edit:

it would require the dissector to track the creation of DDS entities to know which topics use which data types.

there are dissectors which do similar things though for other protocols. So while it would be quite a bit of work, it would not be impossible.

The tracking itself is not that difficult to add. Parsing and interpreting external IDL and XML files would be the real challenge.

But that's for a fully generic and automated solution. It might be possible to allow the dissector to be extended with user-defined deserializers. In our projects we use QoS references when creating DDS-XRCE entities. It's not that hard to track those. And we might be able to use those as keys in a table of user-defined dissector functions. You'd still have to write dissectors for your own message types. But that's not that hard. Especially with a few good examples. I'll look into that.

gavanderhoorn commented 2 years ago

But making this easier would generally require that the protocol is self-describing.

or make the descriptions available in some form or other which is easily consumed by external tooling.

But that's for a fully generic and automated solution. It might be possible to allow the dissector to be extended with user-defined deserializers. In our projects we use QoS references when creating DDS-XRCE entities. It's not that hard to track those. And we might be able to use those as keys in a table of user-defined dissector functions. You'd still have to write dissectors for your own message types. But that's not that hard. Especially with a few good examples. I'll look into that.

what about 'abusing' the type-support generator infrastructure to -- in addition to C/C++/Python/what-have-you -- also generate those dissector functions?

Or alternatively: use something stand-alone (Python script?) which consumes the IDL and XML files you mention and generates them that way.

pablogs9 commented 2 years ago

what about 'abusing' the type-support generator infrastructure to -- in addition to C/C++/Python/what-have-you -- also generate those dissector functions?

That would be a matter of modifying some EmPy templates... Good idea.

jseldent commented 2 years ago

Good idea! It would still require some extra work to register the dissector functions, since the mapping from data type to datareader/datawriter is not part of the IDL. But even for that we might be able to make a small tool that does that from the QoS XML.

gavanderhoorn commented 2 years ago

the mapping from data type to datareader/datawriter is not part of the IDL.

@pablogs9: how does Micro-ROS do this now, if there is no custom XML file supplied? Does it use a default one, generate something or is it all in-memory?

jseldent commented 2 years ago

If no XML file is supplied to MicroXRCEAgent, the QoS XML string has to be specified when creating the entity. In that case the string ends up in the CREATE message.

pablogs9 commented 2 years ago

If no XML file is supplied to MicroXRCEAgent, the QoS XML string has to be specified when creating the entity. In that case, the string ends up in the CREATE message.

And also there is a Binary entity creation mode. Take a look here: https://micro-xrce-dds.docs.eprosima.com/en/latest/client.html#creation-mode-client

In summary nor XRCE-DDS Client or Agent knows anything about how to serialize or deserialize types. In fact in the XRCE Agent, data readers and data writers are created with empty type support (just a topic name and type name) that retransmits raw data from DDS to XRCE and from XRCE to DDS.

When using a bare XRCE-DDS application, the user has to provide the type of support on the client-side. Probably it will be generated with Micro XRCE-DDS Gen.

On the other hand, when micro-ROS is used on top of XRCE-DDS the ROS 2 type support and Micro XRCE-DDS type support take care of serializing and deserializing the data.

jseldent commented 2 years ago

Adding support for user-defined data types was easier than expected. The dissector currently supports it if you use profile references or QoS XML strings when creating DDS entities. And Wireshark needs to capture the creation of the DDS entities for it to work.

You can find the new version here. The README shows how to deserialize the HelloWorld messages from the examples.

gavanderhoorn commented 2 years ago

Nice.

So that "just" leaves generating those dissection functions, instead of having to write them by hand.

jseldent commented 2 years ago

The dissector now also supports binary entity creation.

So that "just" leaves generating those dissection functions, instead of having to write them by hand.

Yes. It would be nice if we can add that to microxrceddsgen. But in the mean time, it's not that hard to do it yourself. Deserialization functions for the basic data types are provided in dds-xrce.lua. Using those it's quite straightforward to write them for your own types.

jseldent commented 2 years ago

It now also supports Agent discovery, the TCP and CANFD transports and it can reassemble (and deserialize) fragmented messages.

pablogs9 commented 2 years ago

The dissector now also supports binary entity creation.

It now also supports Agent discovery, the TCP and CANFD transports and it can reassemble (and deserialize) fragmented messages.

Where are hosted those new versions?

jseldent commented 2 years ago

Where are hosted those new versions?

https://github.com/jseldent/wireshark-dds-xrce

gavanderhoorn commented 2 years ago

Not yet automatically generated (would be more work than it saved right now), but I've made some dissector functions available over at gavanderhoorn/micro_xrce_dds_ros_idl_dissectors.

Together with the enhancements @jseldent recently merged, this makes using Wireshark to capture and analyse XRCE-DDS traffic pretty OK.