-- Open Drone ID Dissector for Wireshark
-- Copyright 2021, Gabriel Cox
-- License: apache-2.0

debugMode = 0

odid_protocol = Proto("OpenDroneID",  "Open Drone ID Protocol")
odid_protocol_message_pack = Proto("OpenDroneID.message.pack",  "Open Drone ID (Message Pack)")
odid_protocol_message_basicid = Proto("OpenDroneID.message.basicid",  "Open Drone ID (Basic ID Message)")
odid_protocol_message_location = Proto("OpenDroneID.message.location",  "Open Drone ID (Location Message)")
odid_protocol_message_authentication = Proto("OpenDroneID.message.authentication",  "Open Drone ID (Authentication Message)")
odid_protocol_message_selfid = Proto("OpenDroneID.message.selfid",  "Open Drone ID (Self ID Message)")
odid_protocol_message_system = Proto("OpenDroneID.message.system",  "Open Drone ID (System Message)")
odid_protocol_message_operatorid = Proto("OpenDroneID.message.operatorid",  "Open Drone ID (Operator ID Message)")

--
-- ENUMERATIONS
--

-- Header Enumerations
local msgTypes = {
    [0]="Basic ID",
    [1]="Location/Vector",
    [2]="Authentication",
    [3]="Self ID",
    [4]="System",
    [5]="Operator ID",
    [15]="Message Pack"
}
local protoVersions = {
    [0]="F3411-19 (1.0)",
    [1]="F3411-20 (1.1)",
    [2]="F3411-22 (2.0)",
    [15]="Reserved for Private Use"
}

-- Basic ID Enumerations
local idTypes = {
    [0] = "None ",
    [1] = "Serial Number (ANSI/CTA-2063-A)",
    [2] = "CAA Assigned Registration ID ",
    [3] = "UTM Assigned UUID",
    [4] = "Specific Session ID"
}
local uaTypes = {
    [0] = "None/Not Declared",
    [1] = "Aeroplane",
    [2] = "Helicopter (or Multirotor)",
    [3] = "Gyroplane",
    [4] = "Hybrid Lift",
    [5] = "Ornithopter",
    [6] = "Glider",
    [7] = "Kite",
    [8] = "Free Balloon",
    [9] = "Captive Balloon",
    [10] = "Airship (such as a blimp)",
    [11] = "Free Fall/Parachute (unpowered)",
    [12] = "Rocket",
    [13] = "Tethered Powered Aircraft",
    [14] = "Ground Obstacle",
    [15] = "Other"
}

-- Location/Vector Enumerations
local statuses = {
    [0]="Undeclared",
    [1]="On Ground",
    [2]="Airborne",
    [3]="Emergency",
    [4]="Remote ID System Failure"
}
local heightTypes = {
    [0]="Above Takeoff",
    [1]="AGL",
}
local ewDirectionSegments = {
    [0]="East (<180)",
    [1]="West (>=180)",
}
local speedMultipliers = {
    [0]=0.25,
    [1]=0.75,
}
local horizAccuracies = {
    [0] = ">=18.52 km (10 NM) or Unknown",
    [1] = "<18.52 km (10 NM)",
    [2] = "<7.408 km (4 NM)",
    [3] = "<3.704 km (2 NM)",
    [4] = "<1852 m (1 NM)",
    [5] = "<926 m (0.5 NM)",
    [6] = "<555.6 m (0.3 NM)",
    [7] = "<185.2 m (0.1 NM)",
    [8] = "<92.6 m (0.05 NM)",
    [9] = "<30 m",
    [10] = "<10 m",
    [11] = "<3 m",
    [12] = "<1 m",
    [13] = "Reserved",
    [14] = "Reserved",
    [15] = "Reserved"
}
local vertAccuracies = {
    [0] = ">=150 m or Unknown",
    [1] = "<150 m ",
    [2] = "<45 m",
    [3] = "<25 m",
    [4] = "<10 m",
    [5] = "<3 m",
    [6] = "<1 m",
    [7] = "Reserved",
    [8] = "Reserved",
    [9] = "Reserved",
    [10] = "Reserved",
    [11] = "Reserved",
    [12] = "Reserved",
    [13] = "Reserved",
    [14] = "Reserved",
    [15] = "Reserved"
}
local speedAccuracies = {
    [0] = ">=10 m/s or Unknown",
    [1] = "<10 m/s",
    [2] = "<3 m/s",
    [3] = "<1 m/s",
    [4] = "<0.3 m/s",
    [5] = "Reserved",
    [6] = "Reserved",
    [7] = "Reserved",
    [8] = "Reserved",
    [9] = "Reserved",
    [10] = "Reserved",
    [11] = "Reserved",
    [12] = "Reserved",
    [13] = "Reserved",
    [14] = "Reserved",
    [15] = "Reserved"
}
local authTypes = {
    [0] = "None",
    [1] = "UAS ID Signature",
    [2] = "Operator ID Signature",
    [3] = "Message Set Signature",
    [4] = "Authentication Provided by Network Remote ID",
    [5] = "Specific Method",
    [6] = "Reserved",
    [7] = "Reserved",
    [8] = "Reserved",
    [9] = "Reserved",
    [10] = "Available for Private Use",
    [11] = "Available for Private Use",
    [12] = "Available for Private Use",
    [13] = "Available for Private Use",
    [14] = "Available for Private Use",
    [15] = "Available for Private Use"
}
local selfIDTypes = {
    [0] = "Text Description",
    [1] = "Emergency Description",
    [2] = "Extended Status Description"
}
local classificationTypes = {
    [0] = "Undeclared",
    [1] = "European Union",
    [2] = "Reserved",
    [3] = "Reserved",
    [4] = "Reserved",
    [5] = "Reserved",
    [6] = "Reserved",
    [7] = "Reserved"
}
local OperatorLocTypes = {
    [0] = "Take Off",
    [1] = "Dynamic",
    [2] = "Fixed"
}
local EUCats = {
    [0] = "Undefined",
    [1] = "Open",
    [2] = "Specific",
    [3] = "Certified"
}
local EUClasses = {
    [0] = "Undefined",
    [1] = "Class 0",
    [2] = "Class 1",
    [3] = "Class 2",
    [4] = "Class 3",
    [5] = "Class 4",
    [6] = "Class 5",
    [7] = "Class 6"
}
local operatorIDTypes = {
    [0] = "Operator ID"
}

--
--  Field Protocols
--

-- Frame Fields
odid_app_code    = ProtoField.uint8("OpenDroneID.appCode", "App Code", base.DEC_HEX)
odid_counter     = ProtoField.uint8("OpenDroneID.counter", "Message Counter", base.DEC_HEX)

-- Header Fields
odid_msgType     = ProtoField.uint8("OpenDroneID.msgType", "Message Type", base.DEC_HEX,msgTypes,0xf0)
odid_protoVersion  = ProtoField.uint8("OpenDroneID.protoVersion", "Protocol Version", base.DEC,protoVersions,0x0f)

-- Message Pack Fields
odid_msgPack_msgSize = ProtoField.uint8("OpenDroneID.msgPack_msgSize", "MessagePack: Message Size", base.DEC)
odid_msgPack_msgQty = ProtoField.uint8("OpenDroneID.msgPack_msgQty", "MessagePack: Message Quantity", base.DEC)

-- Basic ID Fields
odid_basicID_idType = ProtoField.uint8("OpenDroneID.basicID_idType", "ID Type", base.DEC, idTypes, 0xf0)
odid_basicID_uaType = ProtoField.uint8("OpenDroneID.basicID_uaType", "UA Type", base.DEC, uaTypes, 0x0f)
odid_basicID_id_asc = ProtoField.string("OpenDroneID.basicID_id_asc", "ID", base.ASCII)
--    if idType == 4, show binary
odid_basicID_id_bin = ProtoField.bytes("OpenDroneID.basicID_id_bin", "ID", base.SPACE)
odid_basicID_reserved = ProtoField.bytes("OpenDroneID.basicID_reserved","Reserved",base.SPACE)

-- Location/Vector Fields
odid_loc_status = ProtoField.uint8("OpenDroneID.loc_status", "Operational Status", base.DEC, statuses, 0xf0)
odid_loc_flags = ProtoField.uint8("OpenDroneID.loc_flags", "Flags", base.DEC, nil, 0x0f)

odid_loc_flag_heightType = ProtoField.uint8("OpenDroneID.loc_flag_heightType", "Height Type", base.DEC, heightTypes, 0x04)
odid_loc_flag_ewDirectionSegment = ProtoField.uint8("OpenDroneID.loc_flag_ewDirectionSegment", "East/West Direction Segment", base.DEC, ewDirectionSegments, 0x02)
odid_loc_flag_speedMultiplier = ProtoField.uint8("OpenDroneID.loc_flag_speedMultiplier", "Speed Multiplier", base.DEC, speedMultipliers, 0x01)

odid_loc_direction = ProtoField.uint8("OpenDroneID.loc_direction", "Direction", base.DEC,nil,nil,"desc")
odid_loc_speed = ProtoField.uint8("OpenDroneID.loc_speed", "Speed", base.DEC)
odid_loc_vspeed = ProtoField.uint8("OpenDroneID.loc_vspeed", "Vert Speed", base.DEC)
odid_loc_lat = ProtoField.int32("OpenDroneID.loc_lat", "UA Lattitude", base.DEC)
odid_loc_lon = ProtoField.int32("OpenDroneID.loc_lon", "UA Longitude", base.DEC)
odid_loc_pressAlt = ProtoField.uint16("OpenDroneID.loc_pressAlt","UA Pressure Altitude", base.DEC)
odid_loc_geoAlt = ProtoField.uint16("OpenDroneID.loc_geoAlt","UA Geodetic Altitude",base.DEC)
odid_loc_height = ProtoField.uint16("OpenDroneID.loc_height","UA Height AGL",base.DEC)
odid_loc_vAccuracy = ProtoField.uint8("OpenDroneID.loc_vAccuracy","Vertical Accuracy",base.DEC, vertAccuracies,0xf0)
odid_loc_hAccuracy = ProtoField.uint8("OpenDroneID.loc_hAccuracy","Horizontal Accuracy",base.DEC, horizAccuracies,0x0f)
odid_loc_baroAccuracy = ProtoField.uint8("OpenDroneID.loc_baroAccuracy","Baro Accuracy",base.DEC, vertAccuracies,0xf0)
odid_loc_speedAccuracy = ProtoField.uint8("OpenDroneID.loc_speedAccuracy","Speed Accuracy",base.DEC, speedAccuracies,0x0f)
odid_loc_timeStamp = ProtoField.uint16("OpenDroneID.loc_timeStamp","Timestamp (1/10s since hour)",base.DEC)
odid_loc_tsReserved = ProtoField.uint8("OpenDroneID.loc_tsReserved","Reserved",base.DEC,{},0xf0)
odid_loc_tsAccuracy = ProtoField.uint8("OpenDroneID.loc_tsAccuracy","Timestamp Accuracy",base.DEC,{},0x0f)
odid_loc_reserved = ProtoField.bytes("OpenDroneID.loc_reserved","Reserved",base.SPACE)

-- Authentication Fields
odid_auth_type = ProtoField.uint8("OpenDroneID.auth_type","Auth Type",base.DEC,authTypes,0xf0)
odid_auth_pageNumber = ProtoField.uint8("OpenDroneID.auth_pageNumber","Page Number",base.DEC,nil,0x0f)
odid_auth_lastPageIndex = ProtoField.uint8("OpenDroneID.auth_lastPageIndex","Last Page Index",base.DEC)
odid_auth_length = ProtoField.uint8("OpenDroneID.auth_length","Length",base.DEC)
odid_auth_timeStamp = ProtoField.uint32("OpenDroneID.auth_timeStamp","Time Stamp",base.DEC)
odid_auth_data = ProtoField.bytes("OpenDroneID.auth_data", "Auth Data", base.SPACE)

-- Self ID Fields
odid_self_type = ProtoField.uint8("OpenDroneID.self_type","Self Description Type",base.DEC,selfIDTypes)
odid_self_desc = ProtoField.string("OpenDroneID.self_desc","Self Description",base.ASCII)

-- System Fields
odid_system_flags = ProtoField.uint8("OpenDroneID.system_flags","System Flags",base.HEX)
odid_system_flag_class = ProtoField.uint8("OpenDroneID.system_flag_class","Classification Type",base.DEC,classificationTypes,0x0c)
odid_system_flag_locType = ProtoField.uint8("OpenDroneID.system_flag_locType","Operator Location Type",base.DEC,OperatorLocTypes,0x03)
odid_system_lat = ProtoField.int32("OpenDroneID.system_lat","Operator Lattitude",base.DEC)
odid_system_lon = ProtoField.int32("OpenDroneID.system_lon","Operator Longitude",base.DEC)
odid_system_areaCount = ProtoField.uint16("OpenDroneID.system_areaCount","Area Count",base.DEC)
odid_system_areaRadius = ProtoField.uint8("OpenDroneID.system_areaRadius","Area Radius",base.DEC)
odid_system_areaCeiling = ProtoField.uint16("OpenDroneID.system_areaCeiling","Area Ceiling",base.DEC)
odid_system_areaFloor = ProtoField.uint16("OpenDroneID.system_areaFloor","Area Floor",base.DEC)
odid_system_uaClass = ProtoField.uint8("OpenDroneID.system_usClass","UA Classification",base.HEX)
odid_system_uaClassEUCat = ProtoField.uint8("OpenDroneID.system_usClassEUCat","UA Classification Category",base.DEC,EUCats,0xf0)
odid_system_uaClassEUClass = ProtoField.uint8("OpenDroneID.system_usClassEUCat","UA Classification Category",base.DEC,EUClasses,0x0f)
odid_system_opGeoAlt = ProtoField.uint16("OpenDroneID.system_opGeoAlt","Operator Geodetic Alt",base.DEC)
odid_system_timeStamp = ProtoField.uint32("OpenDroneID.system_timeStamp","Message Timestamp",base.DEC)
odid_system_reserved = ProtoField.bytes("OpenDroneID.system_reserved","Reserved",base.SPACE)

-- Operator ID Fields
odid_operator_type = ProtoField.uint8("OpenDroneID.operator_type","Operator ID Type",base.DEC,operatorIDTypes)
odid_operator_id = ProtoField.string("OpenDroneID.operator_id","Operator ID",base.ASCII)
odid_operator_reserved = ProtoField.bytes("OpenDroneID.operator_reserved","Reserved",base.SPACE)

odid_protocol.fields = {
    odid_app_code, odid_counter, odid_msgType, odid_protoVersion, odid_msgPack_msgSize, odid_msgPack_msgQty,

    odid_basicID_idType, odid_basicID_uaType, odid_basicID_id_asc, odid_basicID_id_bin, odid_basicID_reserved,

    odid_loc_flag_ewDirectionSegment, odid_loc_flag_heightType, odid_loc_flag_speedMultiplier,

    odid_loc_status, odid_loc_flags, odid_loc_direction, odid_loc_speed, odid_loc_vspeed, odid_loc_lat,
    odid_loc_lon, odid_loc_pressAlt, odid_loc_geoAlt, odid_loc_height, odid_loc_hAccuracy, odid_loc_vAccuracy,
    odid_loc_baroAccuracy, odid_loc_speedAccuracy, odid_loc_timeStamp, odid_loc_tsReserved, odid_loc_tsAccuracy,
    odid_loc_reserved,

    odid_auth_type, odid_auth_pageNumber, odid_auth_lastPageIndex, odid_auth_length, odid_auth_timeStamp, odid_auth_data,

    odid_self_type, odid_self_desc,

    odid_system_flags, odid_system_flag_class, odid_system_flag_locType, odid_system_lat, odid_system_lon,
    odid_system_areaCount, odid_system_areaRadius, odid_system_areaCeiling, odid_system_areaFloor, odid_system_uaClass,
    odid_system_uaClassEUCat,odid_system_uaClassEUClass, odid_system_opGeoAlt, odid_system_timeStamp, odid_system_reserved,

    odid_operator_type, odid_operator_id, odid_operator_reserved
}

function debugPrint(pstring)
    if debugMode == 1 and pstring ~= nil then
        print(pstring)
    end
end

function odid_messageSubTree(buffer,subtree,msg_start,treeIndex,size)
    subMsgType =  bit32.extract(buffer(msg_start,1):int(),4,4)
    debugPrint("subMsgType: "..subMsgType..", size:"..size)
    if subMsgType == 0 then
        local subMsgIDType = bit32.extract(buffer(msg_start+1,1):uint(),4,4)
        subsub[treeIndex] = subtree:add(odid_protocol_message_basicid,buffer(msg_start,size), "Open Drone ID - Basic ID Message (0)")
        subsub[treeIndex]:add_le(odid_msgType, buffer(msg_start+0,1))
        subsub[treeIndex]:add_le(odid_protoVersion, buffer(msg_start+0,1))
        subsub[treeIndex]:add_le(odid_basicID_idType, buffer(msg_start+1,1))
        subsub[treeIndex]:add_le(odid_basicID_uaType, buffer(msg_start+1,1))
        if subMsgIDType == 4 then -- Specific type should be shown as binary
            subsub[treeIndex]:add_le(odid_basicID_id_bin, buffer(msg_start+2,20))
        else -- otherwise, ASCII
            subsub[treeIndex]:add_le(odid_basicID_id_asc, buffer(msg_start+2,20))
        end
        subsub[treeIndex]:add_le(odid_basicID_reserved, buffer(msg_start+22,3))
    elseif subMsgType == 1 then
        subsub[treeIndex] = subtree:add(odid_protocol_message_location,buffer(msg_start,size), "Open Drone ID - Location/Vector Message (1)")
        subsub[treeIndex]:add_le(odid_msgType, buffer(msg_start+0,1))
        subsub[treeIndex]:add_le(odid_protoVersion, buffer(msg_start+0,1))
        subsub[treeIndex]:add_le(odid_loc_status, buffer(msg_start+1,1))
        --subsub[treeIndex]:add_le(odid_loc_flags, buffer(msg_start+1,1))
        subsub[treeIndex]:add_le(odid_loc_flag_heightType, buffer(msg_start+1,1))
        subsub[treeIndex]:add_le(odid_loc_flag_ewDirectionSegment, buffer(msg_start+1,1))
        subsub[treeIndex]:add_le(odid_loc_flag_speedMultiplier, buffer(msg_start+1,1))
        subsub[treeIndex]:add_le(odid_loc_direction, buffer(msg_start+2,1))
        subsub[treeIndex]:add_le(odid_loc_speed, buffer(msg_start+3,1))
        subsub[treeIndex]:add_le(odid_loc_vspeed, buffer(msg_start+4,1))
        subsub[treeIndex]:add_le(odid_loc_lat, buffer(msg_start+5,4))
        subsub[treeIndex]:add_le(odid_loc_lon, buffer(msg_start+9,4))
        subsub[treeIndex]:add_le(odid_loc_pressAlt, buffer(msg_start+13,2))
        subsub[treeIndex]:add_le(odid_loc_geoAlt, buffer(msg_start+15,2))
        subsub[treeIndex]:add_le(odid_loc_height, buffer(msg_start+17,2))
        subsub[treeIndex]:add_le(odid_loc_hAccuracy, buffer(msg_start+19,1))
        subsub[treeIndex]:add_le(odid_loc_vAccuracy, buffer(msg_start+19,1))
        subsub[treeIndex]:add_le(odid_loc_baroAccuracy, buffer(msg_start+20,1))
        subsub[treeIndex]:add_le(odid_loc_speedAccuracy, buffer(msg_start+20,1))
        subsub[treeIndex]:add_le(odid_loc_timeStamp, buffer(msg_start+21,2))
        subsub[treeIndex]:add_le(odid_loc_tsReserved, buffer(msg_start+23,1))
        subsub[treeIndex]:add_le(odid_loc_tsAccuracy, buffer(msg_start+23,1))
        subsub[treeIndex]:add_le(odid_loc_reserved, buffer(msg_start+24,1))
    elseif subMsgType == 2 then
        subsub[treeIndex] = subtree:add(odid_protocol_message_authentication,buffer(msg_start,size), "Open Drone ID - Authentication Message (2)")
        subsub[treeIndex]:add_le(odid_msgType, buffer(msg_start+0,1))
        subsub[treeIndex]:add_le(odid_protoVersion, buffer(msg_start+0,1))
        subsub[treeIndex]:add_le(odid_auth_type, buffer(msg_start+1,1))
        subsub[treeIndex]:add_le(odid_auth_pageNumber, buffer(msg_start+1,1))
        if bit32.extract(buffer(msg_start+1,1):uint(),0,4) == 0 then
            subsub[treeIndex]:add_le(odid_auth_lastPageIndex, buffer(msg_start+2,1))
            subsub[treeIndex]:add_le(odid_auth_length, buffer(msg_start+3,1))
            subsub[treeIndex]:add_le(odid_auth_timeStamp, buffer(msg_start+4,4))
            subsub[treeIndex]:add_le(odid_auth_data, buffer(msg_start+8,17))
        else
            subsub[treeIndex]:add_le(odid_auth_data, buffer(msg_start+2,23))
        end
    elseif subMsgType == 3 then
        subsub[treeIndex] = subtree:add(odid_protocol_message_selfid,buffer(msg_start,size), "Open Drone ID - Self-ID Message (3)")
        subsub[treeIndex]:add_le(odid_msgType, buffer(msg_start+0,1))
        subsub[treeIndex]:add_le(odid_protoVersion, buffer(msg_start+0,1))
        subsub[treeIndex]:add_le(odid_self_type, buffer(msg_start+1,1))
        subsub[treeIndex]:add_le(odid_self_desc, buffer(msg_start+2,23))

    elseif subMsgType == 4 then
        subsub[treeIndex] = subtree:add(odid_protocol_message_system,buffer(msg_start,size), "Open Drone ID - System Message (4)")
        subsub[treeIndex]:add_le(odid_msgType, buffer(msg_start+0,1))
        subsub[treeIndex]:add_le(odid_protoVersion, buffer(msg_start+0,1))
        subsub[treeIndex]:add_le(odid_system_flag_class, buffer(msg_start+1,1))
        subsub[treeIndex]:add_le(odid_system_flag_locType, buffer(msg_start+1,1))
        subsub[treeIndex]:add_le(odid_system_lat, buffer(msg_start+2,4))
        subsub[treeIndex]:add_le(odid_system_lon, buffer(msg_start+6,4))
        subsub[treeIndex]:add_le(odid_system_areaCount, buffer(msg_start+10,2))
        subsub[treeIndex]:add_le(odid_system_areaRadius, buffer(msg_start+12,1))
        subsub[treeIndex]:add_le(odid_system_areaCeiling, buffer(msg_start+13,2))
        subsub[treeIndex]:add_le(odid_system_areaFloor, buffer(msg_start+15,2))
        if bit32.extract(buffer(msg_start+1,1):uint(),2,2) == 1 then
            subsub[treeIndex]:add_le(odid_system_uaClassEUCat, buffer(msg_start+17,1))
            subsub[treeIndex]:add_le(odid_system_uaClassEUClass, buffer(msg_start+17,1))
        else
            subsub[treeIndex]:add_le(odid_system_uaClass, buffer(msg_start+17,1))
        end
        subsub[treeIndex]:add_le(odid_system_opGeoAlt, buffer(msg_start+18,2))
        subsub[treeIndex]:add_le(odid_system_timeStamp, buffer(msg_start+20,4))
        subsub[treeIndex]:add_le(odid_system_reserved, buffer(msg_start+24,1))
    elseif subMsgType == 5 then
        subsub[treeIndex] = subtree:add(odid_protocol_message_operatorid,buffer(msg_start,size), "Open Drone ID - Operator ID Message (5)")
        subsub[treeIndex]:add_le(odid_msgType, buffer(msg_start+0,1))
        subsub[treeIndex]:add_le(odid_protoVersion, buffer(msg_start+0,1))
        subsub[treeIndex]:add_le(odid_operator_type, buffer(msg_start+1,1))
        subsub[treeIndex]:add_le(odid_operator_id, buffer(msg_start+2,20))
        subsub[treeIndex]:add_le(odid_operator_reserved, buffer(msg_start+22,3))
    elseif subMsgType == 15 then
        subsub[treeIndex] = subtree:add(odid_protocol_message_pack,buffer(msg_start,size), "Open Drone ID - Message Pack (15)")
        subsub[treeIndex]:add_le(odid_msgType,  buffer(msg_start+0,1))
        subsub[treeIndex]:add_le(odid_protoVersion,  buffer(msg_start+0,1))
        subsub[treeIndex]:add_le(odid_msgPack_msgSize, buffer(msg_start+1,1))
        subsub[treeIndex]:add_le(odid_msgPack_msgQty,  buffer(msg_start+2,1))
        --for m=1,buffer(msg_start+4,1):int() do
        --    sub_msg_start = start+5
        --    odid_messageSubTree(buffer,subsub[n],sub_msg_start,m)
        --end
    end
end

function findMessageOffset(buffer,len)
    -- In Wireshark/Windows, this appears to be byte 0x11, in Linux, 0x12.
    -- Either way, the offset value matches the length of the header.
    local frameTypeOffset = buffer(2,1):uint()
    -- FIX: buffer(0,1):uint() is "Com sequence(board)" in nordic_ble, is not always 3.
    if buffer(3,1):uint() == 3 then -- bluetooth nRF capture signature
        frameTypeOffset = 0x11
    end
    if frameTypeOffset > len - (25-4) then -- offset should at least be before freame
		debugPrint ("frameTypeOffset invalid ("..frameTypeOffset..") likely not BT or Wi-Fi frame")
		return 0,0
	end
    local frameOffset = {
        frameType = frameTypeOffset,
        beaconTags = frameTypeOffset+0x24,
        publicAction = frameTypeOffset+0x18,
        nanSDA = frameTypeOffset+0x1e
    }
    local frameTypes = {
        BEACON = 0x8000,
        ACTION = 0xd000,
        BT_ADV = 0x8e89bed6,
        BT_ADV_NONCONN_IND = 0x2,
        BT_ADV_SCAN_IND = 0x6,
		BT_AUX_ADV_IND = 0x7,
        BT_SVC_DATA_TYPE = 0x16,
        ASTM_UUID = 0xfffa,
        ODID_APP_CODE = 0x0d
    }
    local ouis = {
        parrot    = string.char(0x90,0x3a,0xe6),
        asdstan   = string.char(0xfa,0x0b,0xbc),
        nanParams = string.char(0x04, 0x09, 0x50, 0x6f, 0x9a, 0x13),
        nanODID   = string.char(0x88, 0x69, 0x19, 0x9d, 0x92, 0x09)
    }
    local protoLen = 0
    -- First, determine if Beacon or Action frame (reject otherwise)
    local frameType = buffer(frameOffset.frameType,2):uint()
    local frameType4 = buffer(frameOffset.frameType,4):le_uint()
    debugPrint ("frameTypeOffset: "..frameTypeOffset..", frameType: "..frameType..", frameType4="..frameType4.."("..string.format("0x%x",frameType4).."), len="..len)
    if frameType == frameTypes.BEACON then
        -- this is a beacon, so iterate through tags
        bp = frameOffset.beaconTags
        while bp < len-30 do -- If there's not at least 30 bytes left, there's no room for another RID message, so just stop looking
            if buffer(bp,1):uint() == 221 then -- vendor specific IE
                -- check that ie oui is either parrot or ASD-STAN
                if (buffer(bp+2,3):bytes():raw() == ouis.asdstan or buffer(bp+2,3):bytes():raw() == ouis.parrot) then
                    if buffer(bp+5,1):uint() == frameTypes.ODID_APP_CODE then
                        -- we have a proper odid beacon frame
                        protoLen = buffer(bp+1,1):uint() - 4
                        return bp+6,protoLen
                    else
                        -- even though OUI matches, this is not ODID
                        debugPrint ("VSIE match, OUI Match, no App Code Match")
                        bp = bp + buffer(bp+1,1):uint() + 2
                        -- continue to next tag
                    end
                else
                    -- even though this is a VSIE, it doesn't match a ODID OUI
                    debugPrint("VSIE match, no OUI match")
                    debugPrint(buffer(bp+2,3):bytes():raw())
                    bp = bp + buffer(bp+1,1):uint() + 2
                    -- continue to next tag
                end
            else
                -- skip to next tag
                debugPrint ("tag bp="..bp..",type="..buffer(bp,1):uint()..", len="..buffer(bp+1,1):uint()..", no VSIE(221) match")
                bp = bp + buffer(bp+1,1):uint() + 2
            end
        end
        -- no VSIE found
        debugPrint("This is a beacon, but no VSIE found, bp="..bp..", len="..len)
        return 0,0
    elseif frameType == frameTypes.ACTION then
        bp = frameOffset.publicAction
        if buffer(bp,6):bytes():raw() == ouis.nanParams then
            -- we have NAN, now lets check for ODID
            bp = frameOffset.nanSDA
            if buffer(bp+3,6):bytes():raw() == ouis.nanODID then
                -- all checks out
                protoLen = buffer(bp+12,1):uint()
                return bp+13, protoLen
            else
                -- we have NAN, but wrong app hash
                debugPrint("NAN, but not ODID hash")
                return 0,0
            end
        else
            -- it may be an action frame, but not NAN
            debugPrint("Action frame, but not NAN")
            return 0,0
        end
    elseif frameType4 == frameTypes.BT_ADV then
		local btOffsets = {
			btAdvLen = frameOffset.frameType+12,
			btAdvSubType = frameOffset.frameType+13,
			btAdvUUID = frameOffset.frameType+14,
			odid_app_code = frameOffset.frameType+16,
			btMsg = frameOffset.frameType+17
		}
		local btAdvType
		if bit32.extract(buffer(frameOffset.frameType+4,1):uint(),0,4) == 0 then
			-- Coded Phy, S=8 / BT5 Long Range
			btAdvType = bit32.extract(buffer(frameOffset.frameType+5,1):uint(),0,4)
			local BT5_OFF_ADDER = 5
			-- Add 5 bytes to each of the field offsets since BT5 has extra fields.
			btOffsets.btAdvLen = btOffsets.btAdvLen + BT5_OFF_ADDER
			btOffsets.btAdvSubType = btOffsets.btAdvSubType + BT5_OFF_ADDER
			btOffsets.btAdvUUID = btOffsets.btAdvUUID + BT5_OFF_ADDER
			btOffsets.odid_app_code = btOffsets.odid_app_code + BT5_OFF_ADDER
			btOffsets.btMsg = btOffsets.btMsg + BT5_OFF_ADDER
		else
			-- BT4 Legacy
			btAdvType = bit32.extract(buffer(frameOffset.frameType+4,1):uint(),0,4)
		end
        if btAdvType == frameTypes.BT_ADV_NONCONN_IND or btAdvType == frameTypes.BT_ADV_SCAN_IND or btAdvType == frameTypes.BT_AUX_ADV_IND then
            btAdvSubType = buffer(btOffsets.btAdvSubType,1):uint()
            if btAdvSubType == frameTypes.BT_SVC_DATA_TYPE then
                btAdvUUID = buffer(btOffsets.btAdvUUID,2):le_uint()
                if btAdvUUID == frameTypes.ASTM_UUID then
                    odid_app_code = buffer(btOffsets.odid_app_code,1):uint()
                    btAdvLen = buffer(btOffsets.btAdvLen,1):uint()
                    if odid_app_code == frameTypes.ODID_APP_CODE then
						debugPrint("Find Message Offset = "..btOffsets.btMsg..", "..btAdvLen)
                        return btOffsets.btMsg,btAdvLen - 4
                    else
                        debugPrint("ASTM ADV, but not ODID app code(0x0d)")
                        return 0,0
                    end
                else
                    debugPrint("BT SVC Data, but not ASTM(0xfffa)")
                    return 0,0
                end
            else
                debugPrint("BT ADV_NONCONN_IND, but not SVC_DATA_TYPE")
                return 0,0
            end
        else
            debugPrint("BT ADV, but not ADV_NONCONN_IND or AUX_ADV_IND")
            return 0,0
        end
    else
        debugPrint("Not beacon, Action Frame, or BT ADV, frametype="..frameType..", frameType4="..frameType4.."("..string.format("0x%x",frameType4)..")")
        return 0,0
    end
end

function odid_protocol.dissector(buffer, pinfo, tree)

	debugPrint("debug on")

    local length = buffer:len()
	local minLen = 0x21 + 25
    if length < minLen then
        debugPrint("too short ("..length.." < "..minLen)
        return
    end

    start, protoLen = findMessageOffset(buffer,length)
    if start == 0 then
        debugPrint("start==0")
        return
    end

    local msgTypeByte = buffer(start+1,1)
    local msgType = bit32.extract(msgTypeByte:uint(),4,4)
    debugPrint ("msgType1: "..msgType)
    subsub={}
    pinfo.cols.protocol = odid_protocol.name
    subtree = tree:add(odid_protocol, buffer(start,protoLen), "Open Drone ID")
    subtree:add_le(odid_counter,  buffer(start+0,1))

    if msgType == 15 then
        local subMsgSize = buffer(start+2,1):int()
        local subMsgQty = buffer(start+3,1):int()
        debugPrint("subMsgSize: "..subMsgSize..", subMsgQty: "..subMsgQty)
        odid_messageSubTree(buffer,subtree,start+1,0,subMsgSize*subMsgQty+3)
        local msgSize = buffer(start+2,1):int()

        for n=1,buffer(start+3,1):int() do
            local msg_start = (start+4) + (n-1)*msgSize
            odid_messageSubTree(buffer,subsub[0],msg_start,n,msgSize)
        end
    else
        msgSize=25
        odid_messageSubTree(buffer,subtree,start+1,0,msgSize)
    end
end
--local vend_specific_oui = DissectorTable.get("wlan.tag.oui")
--local wlan_pkt_type = DissectorTable.get("wtap_encap")
--wlan_pkt_type:add(wtap_encaps["IEEE_802_11_RADIOTAP"], odid_protocol)
--vend_specific_oui:add(0x903ae6, odid_protocol) -- parrot
--vend_specific_oui:add(0xfa0bbc, odid_protocol) -- ASD-STAN
--	["IEEE_802_11"] = 20,
--	["IEEE_802_11_PRISM"] = 21,
--	["IEEE_802_11_WITH_RADIO"] = 22,
--	["IEEE_802_11_RADIOTAP"] = 23,
dis = DissectorTable.get("wtap_encap")
dis:add(wtap_encaps["IEEE_802_11"],odid_protocol)
register_postdissector(odid_protocol)
