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Refactor frame dissector to improve readability/future expansion

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Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
This commit is contained in:
Allen Hill
2026-06-11 19:21:40 -07:00
parent 83a614ed3b
commit c2440d5118
1 changed files with 305 additions and 343 deletions
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scripts/packet-analysis/avclan_plugin.lua
+109 -147
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@@ -95,37 +95,16 @@ udlt:add(wtap.USER15, iebusproto)
local avclanproto = Proto("avclan", "AVCLAN protocol")
local known_devices_names = {
["LAN"] = 0x00,
["COMM_CTRL"] = 0x01,
["COMMUNICATION v1"] = 0x11,
["COMMUNICATION v2"] = 0x12,
["SW"] = 0x21,
["SW_NAME"] = 0x23,
["SW_CONVERTING"] = 0x24,
["CMD_SW"] = 0x25,
["STATUS"] = 0x31,
["BEEP_HU"] = 0x28,
["BEEP_SPEAKERS"] = 0x29,
["FRONT_PSNG_MONITOR"] = 0x34,
["CD_CHANGER2"] = 0x43,
["BLUETOOTH_TEL"] = 0x55,
["INFO_DRAWING"] = 0x56,
["NAV_ECU"] = 0x58,
["CAMERA"] = 0x5C,
["CLIMATE_DRAWING"] = 0x5D,
["AUDIO_DRAWING"] = 0x5E,
["TRIP_INFO_DRAWING"] = 0x5F,
["TUNER"] = 0x60,
["TAPE_DECK"] = 0x61,
["CD"] = 0x62,
["CD_CHANGER"] = 0x63,
["AUDIO_AMP"] = 0x74,
["GPS"] = 0x80,
["VOICE_CTRL"] = 0x85,
["CLIMATE_CTRL_DEV"] = 0xE0,
["TRIP_INFO"] = 0xE5,
}
-- Build a reverse {value = key} lookup from a {key = value} table. Lets us keep
-- a single source-of-truth value->name table (also used as the ProtoField
-- valuestring) and derive the name->value lookup instead of hand-maintaining two.
local function invert(t)
local r = {}
for k, v in pairs(t) do
r[v] = k
end
return r
end
local known_devices = {
[0x00] = "LAN",
@@ -158,84 +137,12 @@ local known_devices = {
[0xE0] = "CLIMATE_CTRL_DEV",
[0xE5] = "TRIP_INFO",
}
local known_devices_names = invert(known_devices)
local f_from_device = ProtoField.uint8("avclan.from_device", "From device", base.HEX, known_devices)
local f_to_device = ProtoField.uint8("avclan.to_device", "To device", base.HEX, known_devices)
local f_active_device = ProtoField.uint8("avclan.active_device", "Active device", base.HEX, known_devices)
local known_actions_names = {
-- LAN related
["LIST_FUNCTIONS_REQ"] = 0x00,
["LIST_FUNCTIONS_RESP"] = 0x10,
["RESTART_LAN"] = 0x01,
["LANCHECK_END_REQ"] = 0x08,
["LANCHECK_END_RESP"] = 0x18,
["LANCHECK_SCAN_REQ"] = 0x0a,
["LANCHECK_SCAN_RESP"] = 0x1a,
["LANCHECK_REQ"] = 0x0c,
["LANCHECK_RESP"] = 0x1c,
["PING_REQ"] = 0x20,
["PING_RESP"] = 0x30,
-- Device switching
["DISABLE_FUNCTION_REQ"] = 0x43,
["DISABLE_FUNCTION_RESP"] = 0x53,
["ENABLE_FUNCTION_REQ"] = 0x42,
["ENABLE_FUNCTION_RESP"] = 0x52,
-- ADVERTISE_FUNCTION is named Current_Function in src/avclandrv.h
["ADVERTISE_FUNCTION"] = 0x45,
["GENERAL_QUERY"] = 0x46,
["SCREEN_PRESS"] = 0x78,
["BEEP"] = 0x60,
-- Physical interface
["BACKLIGHT_ADJUST"] = 0x59,
["EJECT"] = 0x80,
["DISC_UP"] = 0x90,
["DISC_DOWN"] = 0x91,
["PWRVOL_KNOB_RIGHTHAND_TURN"] = 0x9c,
["PWRVOL_KNOB_LEFTHAND_TURN"] = 0x9d,
["TRACK_SEEK_UP"] = 0x94,
["TRACK_SEEK_DOWN"] = 0x95,
["TRACK_FAST_FORWARD"] = 0x98,
["TRACK_REWIND"] = 0x99,
["CD_ENABLE_SCAN"] = 0xa6,
["CD_DISABLE_SCAN"] = 0xa7,
["CD_ENABLE_DISK_SCAN"] = 0xa9,
["CD_DISABLE_DISK_SCAN"] = 0xaa,
["CD_ENABLE_REPEAT"] = 0xa0,
["CD_DISABLE_REPEAT"] = 0xa1,
["CD_ENABLE_DISK_REPEAT"] = 0xa3,
["CD_DISABLE_DISK_REPEAT"] = 0xa4,
["CD_ENABLE_RANDOM"] = 0xb0,
["CD_DISABLE_RANDOM"] = 0xb1,
["CD_ENABLE_DISK_RANDOM"] = 0xb3,
["CD_DISABLE_DISK_RANDOM"] = 0xb4,
["TAPE_NOT_READY"] = 0x9f, -- Uncertain guess by @marcin
-- CD functions
-- Events
["INSERTION"] = 0x50,
["EJECTION"] = 0x51,
-- Requests
["INITIAL_REPORT_REQUEST"] = 0xe0,
["PLAYBACK_REQUEST"] = 0xe2,
["LOADING_REQUEST2"] = 0xe4,
["REQUEST_TRACK_NAME"] = 0xed,
-- Reports
["INITIAL_REPORT_RESPONSE"] = 0xf0,
["STATUS_REPORT"] = 0xf1,
["PLAYBACK_REPORT"] = 0xf2,
["LOADING_STATUS_REPORT"] = 0xf3,
["LOADING_RESPONSE2"] = 0xf4,
["REPORT_TOC"] = 0xf9,
["REPORT_TRACK_NAME"] = 0xfd,
}
local known_actions = {
-- LAN related
[0x00] = "LIST_FUNCTIONS_REQ",
@@ -308,6 +215,7 @@ local known_actions = {
[0xf9] = "REPORT_TOC",
[0xfd] = "REPORT_TRACK_NAME",
}
local known_actions_names = invert(known_actions)
local f_action = ProtoField.uint8("avclan.action", "Action", base.HEX, known_actions)
local f_functions = ProtoField.bytes("avclan.functions", "Functions", base.SPACE, "Device functions")
@@ -523,29 +431,20 @@ local function mark_undecoded(tree, range)
tree:add(range, "Undecoded bytes"):add_proto_expert_info(pe_unhandled_msg)
end
function avclanproto.dissector(buffer, pinfo, tree)
local length = buffer:len()
if length == 0 then
return
end
-- ---------------------------------------------------------------------------
-- Per-message decoders.
--
-- Each decoder receives the message `subtree`, the `buffer`, and `offset` (the
-- index of the `from` byte, accounting for the leading 0x00 on unicast frames).
-- Device-state decoders also receive the resolved `action`. The dissector body
-- below is just a router that selects one of these based on from/to/action,
-- preserving the historical precedence order.
-- ---------------------------------------------------------------------------
iebusproto.dissector(buffer, pinfo, tree)
local subtree = tree:add(avclanproto, buffer(7,-1), "AVCLAN message")
local offset = 7
if buffer(7,1):uint() == 0 then
offset = 8
subtree:add(f_from_device, buffer(offset+0,1))
subtree:add(f_to_device, buffer(offset+1,1))
else
subtree:add(f_from_device, buffer(offset+0,1))
subtree:add(f_to_device, buffer(offset+1,1))
end
local from_device = field_from_device().value
local to_device = field_to_device().value
if from_device == known_devices_names["CMD_SW"] then
-- CMD_SW source. Sub-commands to the amplifier (actions 0x90-0x95) set a
-- tone/level control; these codes collide with physical-interface actions, so
-- the CMD_SW -> AUDIO_AMP device pair disambiguates them.
local function decode_cmd_sw(subtree, buffer, offset, to_device)
subtree:add(f_action, buffer(offset+2,1))
local action = field_action().value
if to_device == known_devices_names["AUDIO_AMP"] then
@@ -567,8 +466,10 @@ function avclanproto.dissector(buffer, pinfo, tree)
amptree:add(f_amp_treble, param)
end
end
elseif from_device == known_devices_names["COMMUNICATION v1"] or
from_device == known_devices_names["COMMUNICATION v2"] then
end
-- COMMUNICATION v1/v2 source.
local function decode_from_comm(subtree, buffer, offset, to_device)
if to_device == known_devices_names["COMM_CTRL"] then
subtree:add(f_action, buffer(offset+2,1))
local action = field_action().value
@@ -582,9 +483,15 @@ function avclanproto.dissector(buffer, pinfo, tree)
subtree:add_proto_expert_info(pe_unhandled_msg)
end
else
-- Control actions addressed to a peripheral rather than COMM_CTRL, e.g.
-- function enable/disable (COMM_v1/v2 -> CD_CHANGER, 0x42/0x43). These
-- are understood apart from a trailing 0x01 of unknown meaning.
subtree:add(f_action, buffer(offset+2,1))
end
elseif from_device == known_devices_names["COMM_CTRL"] then
end
-- COMM_CTRL source.
local function decode_from_commctrl(subtree, buffer, offset, to_device)
if to_device == known_devices_names["COMMUNICATION v1"] or
to_device == known_devices_names["COMMUNICATION v2"] then
local action_tree = subtree:add(f_action, buffer(offset+2,1))
@@ -623,7 +530,10 @@ function avclanproto.dissector(buffer, pinfo, tree)
else
subtree:add_proto_expert_info(pe_unhandled_msg)
end
elseif to_device == known_devices_names["BEEP_SPEAKERS"] then
end
-- Beep request (any source -> BEEP_SPEAKERS), action 0x60 with a duration byte.
local function decode_beep(subtree, buffer, offset)
subtree:add(f_action, buffer(offset+2,1))
local action = field_action().value
if action == known_actions_names["BEEP"] then
@@ -631,11 +541,10 @@ function avclanproto.dissector(buffer, pinfo, tree)
else
subtree:add_proto_expert_info(pe_unhandled_msg)
end
elseif from_device == known_devices_names["STATUS"] and
known_devices[to_device] ~= nil then
subtree:add(f_action, buffer(offset+2,1))
elseif from_device == known_devices_names["TUNER"] then
subtree:add(f_action, buffer(offset+2,1))
end
-- TUNER source: radio state dump (regardless of action).
local function decode_radio(subtree, buffer, offset, action)
local radiotree = subtree:add(avclanproto, buffer(offset,10), "Device: Radio")
radiotree:add_le(f_radio_active, buffer(offset+3,1))
radiotree:add_le(f_radio_status, buffer(offset+4,1))
@@ -658,8 +567,10 @@ function avclanproto.dissector(buffer, pinfo, tree)
flags:add(f_radioflag_reg, buffer(15,1))
flags:add(f_radioflag_af, buffer(15,1))
radiotree:add(f_radio_flags2, buffer(16,1))
elseif from_device == known_devices_names["AUDIO_AMP"] then
subtree:add(f_action, buffer(offset+2,1))
end
-- AUDIO_AMP source: amplifier state dump (regardless of action).
local function decode_amp(subtree, buffer, offset, action)
local amptree = subtree:add(avclanproto, buffer(offset,10), "Device: Audio amplifier")
local vol_raw = buffer(offset+4,1):uint()
@@ -670,11 +581,10 @@ function avclanproto.dissector(buffer, pinfo, tree)
amptree:add(f_amp_bass, buffer(offset+7,1))
amptree:add(f_amp_mid, buffer(offset+8,1))
amptree:add(f_amp_treble, buffer(offset+9,1))
elseif from_device == known_devices_names["CD"] or
from_device == known_devices_names["CD_CHANGER"] then
subtree:add(f_action, buffer(offset+2,1))
local action = field_action().value
end
-- CD / CD_CHANGER source: payload depends on the report action.
local function decode_cd(subtree, buffer, offset, action)
if action == known_actions_names["STATUS_REPORT"] or
action == known_actions_names["PLAYBACK_REPORT"] then
local cdtree = subtree:add(avclanproto, buffer(offset,9), "Device: CD player")
@@ -745,16 +655,17 @@ function avclanproto.dissector(buffer, pinfo, tree)
cd_state:add(f_cd_loading, buffer(offset+9,1))
elseif action == known_actions_names["ENABLE_FUNCTION_RESP"] or
action == known_actions_names["DISABLE_FUNCTION_RESP"] then
-- Understood apart from a trailing 0x01 of unknown meaning; not flagged.
elseif buffer:len() > offset+3 then
-- Recognized CD action (initial report 0xf0, TOC 0xf9, track name
-- 0xfd, ...) whose payload layout isn't understood yet. Flag just the
-- undecoded bytes, not the whole (correctly-named) message.
mark_undecoded(subtree, buffer(offset+3))
end
elseif from_device == known_devices_names["TAPE_DECK"] then
subtree:add(f_action, buffer(offset+2,1))
local action = field_action().value
end
-- TAPE_DECK source: tape state dump on STATUS_REPORT.
local function decode_tape(subtree, buffer, offset, action)
if action == known_actions_names["STATUS_REPORT"] then
local tapetree = subtree:add(avclanproto, buffer(offset,4), "Device: Tape deck")
tapetree:add(f_tape_present, buffer(offset+3,1))
@@ -775,9 +686,10 @@ function avclanproto.dissector(buffer, pinfo, tree)
tape_flags:add(f_tape_flag3, buffer(offset+5,2))
tape_flags:add(f_tape_flag4, buffer(offset+5,2))
end
elseif from_device == known_devices_names["SW"] then
subtree:add(f_action, buffer(offset+2,1))
local action = field_action().value
end
-- SW source: touch-screen press (action 0x78) with x,y position pairs.
local function decode_touch(subtree, buffer, offset, action)
if action == known_actions_names["SCREEN_PRESS"] then
subtree:add(f_touch_x, buffer(offset+3,1))
subtree:add(f_touch_y, buffer(offset+4,1))
@@ -788,6 +700,56 @@ function avclanproto.dissector(buffer, pinfo, tree)
else
subtree:add_proto_expert_info(pe_unhandled_msg)
end
end
-- Device-state report decoders, keyed by the originating device. For these,
-- the from_device determines the payload format; the action (passed through)
-- only matters within CD/tape/touch.
local device_decoders = {
[known_devices_names["TUNER"]] = decode_radio,
[known_devices_names["AUDIO_AMP"]] = decode_amp,
[known_devices_names["CD"]] = decode_cd,
[known_devices_names["CD_CHANGER"]] = decode_cd,
[known_devices_names["TAPE_DECK"]] = decode_tape,
[known_devices_names["SW"]] = decode_touch,
}
function avclanproto.dissector(buffer, pinfo, tree)
local length = buffer:len()
if length == 0 then
return
end
iebusproto.dissector(buffer, pinfo, tree)
local subtree = tree:add(avclanproto, buffer(7,-1), "AVCLAN message")
-- Unicast device-to-device frames carry a leading 0x00 before the from/to
-- bytes; skip it so `offset` always points at the `from` byte.
local offset = 7
if buffer(7,1):uint() == 0 then
offset = 8
end
subtree:add(f_from_device, buffer(offset+0,1))
subtree:add(f_to_device, buffer(offset+1,1))
local from_device = field_from_device().value
local to_device = field_to_device().value
if from_device == known_devices_names["CMD_SW"] then
decode_cmd_sw(subtree, buffer, offset, to_device)
elseif from_device == known_devices_names["COMMUNICATION v1"] or
from_device == known_devices_names["COMMUNICATION v2"] then
decode_from_comm(subtree, buffer, offset, to_device)
elseif from_device == known_devices_names["COMM_CTRL"] then
decode_from_commctrl(subtree, buffer, offset, to_device)
elseif to_device == known_devices_names["BEEP_SPEAKERS"] then
decode_beep(subtree, buffer, offset)
elseif from_device == known_devices_names["STATUS"] and
known_devices[to_device] ~= nil then
subtree:add(f_action, buffer(offset+2,1))
elseif device_decoders[from_device] then
subtree:add(f_action, buffer(offset+2,1))
device_decoders[from_device](subtree, buffer, offset, field_action().value)
else
subtree:add_proto_expert_info(pe_unhandled_msg)
end