Wireshark dissector for Sonic Robo Blast 2 netplay

srb2_wireshark.lua

local srb2_proto = Proto('SRB2', 'Sonic Robo Blast 2')

srb2_proto.prefs.validate_checksum = Pref.bool('Validate checksums', false, 'Whether to validate the packet checksum')

local function add_fields(...)
	for i,v in ipairs({...}) do
		table.insert(srb2_proto.fields, v)
	end
end

-- Version 2.2.9
local packet_types = {
	[0] = 'PT_NOTHING',
	[1] = 'PT_SERVERCFG',
	[2] = 'PT_CLIENTCMD',
	[3] = 'PT_CLIENTMIS',
	[4] = 'PT_CLIENT2CMD',
	[5] = 'PT_CLIENT2MIS',
	[6] = 'PT_NODEKEEPALIVE',
	[7] = 'PT_NODEKEEPALIVEMIS',
	[8] = 'PT_SERVERTICS',
	[9] = 'PT_SERVERREFUSE',
	[10] = 'PT_SERVERSHUTDOWN',
	[11] = 'PT_CLIENTQUIT',
	[12] = 'PT_ASKINFO',
	[13] = 'PT_SERVERINFO',
	[14] = 'PT_PLAYERINFO',
	[15] = 'PT_REQUESTFILE',
	[16] = 'PT_ASKINFOVIAMS (obsolete)',
	[17] = 'PT_WILLRESENDGAMESTATE',
	[18] = 'PT_CANRECEIVEGAMESTATE',
	[19] = 'PT_RECEIVEDGAMESTATE',
	[20] = 'PT_SENDINGLUAFILE',
	[21] = 'PT_ASKLUAFILE',
	[22] = 'PT_HASLUAFILE',
	[23] = 'PT_FILEFRAGMENT',
	[24] = 'PT_FILEACK',
	[25] = 'PT_FILERECEIVED',
	[26] = 'PT_TEXTCMD',
	[27] = 'PT_TEXTCMD2',
	[28] = 'PT_CLIENTJOIN',
	[29] = 'PT_NODETIMEOUT',
	[30] = 'PT_LOGIN',
	[31] = 'PT_PING'
}

local packet_dissectors = {}

local function NetbufferChecksum(buf)
	local c = 0x1234567
	for i=4,buf:len()-1 do
		c = c + buf(i,1):uint() * (i-3)
	end
	return c
end

local f_checksum = ProtoField.uint32('srb2.checksum', 'Checksum', base.HEX)
local f_valid = ProtoField.bool('srb2.valid', 'Checksum Status')
local f_ack = ProtoField.uint8('srb2.ack', 'ACK')
local f_ackret = ProtoField.uint8('srb2.ackret', 'ACK Return')
local f_ptype = ProtoField.uint8('srb2.ptype', 'Packet Type', base.DEC, packet_types)
local f_reserved = ProtoField.uint8('srb2.reserved', 'Reserved')
local f_datalen = ProtoField.uint32('srb2.datalen', 'Data Length')
local f_data = ProtoField.bytes('srb2.data', 'Data', base.NONE)

add_fields(f_checksum, f_valid, f_ack, f_ackret, f_ptype, f_reserved, f_datalen, f_data)

-- PT_SERVERCFG
local game_states = {
	[0] = 'GS_NULL',
	[1] = 'GS_LEVEL',
	[2] = 'GS_INTERMISSION',
	[3] = 'GS_CONTINUING',
	[4] = 'GS_TITLESCREEN',
	[5] = 'GS_TIMEATTACK',
	[6] = 'GS_CREDITS',
	[7] = 'GS_EVALUATION',
	[8] = 'GS_GAMEEND',
	[9] = 'GS_INTRO',
	[10] = 'GS_ENDING',
	[11] = 'GS_CUTSCENE',
	[12] = 'GS_DEDICATEDSERVER',
	[13] = 'GS_WAITINGPLAYERS'
}
local game_types = {
	[0] = 'GT_COOP',
	[1] = 'GT_COMPETITION',
	[2] = 'GT_RACE',
	[3] = 'GT_MATCH',
	[4] = 'GT_TEAMMATCH',
	[5] = 'GT_TAG',
	[6] = 'GT_HIDEANDSEEK',
	[7] = 'GT_CTF'
}

-- PT_SERVERCFG
local f_version = ProtoField.uint8('srb2.data.version', 'Version')
local f_subversion = ProtoField.uint8('srb2.data.subversion', 'Build')
local f_serverplayer = ProtoField.uint8('srb2.data.serverplayer', 'Server Player')
local f_totalslotnum = ProtoField.uint8('srb2.data.totalslotnum', 'Total Slot Num')
local f_gametic = ProtoField.uint32('srb2.data.gametic', 'Game Tic')
local f_clientnode = ProtoField.uint8('srb2.data.clientnode', 'Client Node')
local f_gamestate = ProtoField.uint8('srb2.data.gamestate', 'Game State', base.DEC, game_states)
local f_gametype = ProtoField.uint8('srb2.data.gametype', 'Game Type', base.DEC, game_types)
local f_modifiedgame = ProtoField.uint8('srb2.data.modifiedgame', 'Modified Game')
local f_server_context = ProtoField.string('srb2.data.server_context', 'Server Context')
add_fields(f_version, f_subversion, f_serverplayer, f_totalslotnum, f_gametic, f_clientnode)
add_fields(f_gamestate, f_gametype, f_modifiedgame, f_server_context)

-- PT_SERVERREFUSE
local f_refuse_reason = ProtoField.string('srb2.data.refuse_reason', 'Refusal Reason')
add_fields(f_refuse_reason)

-- PT_REQUESTFILE
local f_fileid = ProtoField.uint8('srb2.data.fileid', 'File ID')
local f_filename = ProtoField.string('srb2.data.filename', 'Filename')
local f__255 = ProtoField.uint8('srb2.data._255', '_255')
add_fields(f_fileid, f_filename, f__255)

-- PT_FILEFRAGMENT
--    f_fileid
local f_filesize = ProtoField.uint32('srb2.data.filesize', 'File Size')
local f_iteration = ProtoField.uint8('srb2.data.iteration', 'Iteration')
local f_position = ProtoField.uint32('srb2.data.position', 'Position', base.HEX)
local f_size = ProtoField.uint16('srb2.data.fragmentsize', 'Fragment Size')
local f_fragment = ProtoField.bytes('srb2.data.fragment', 'Fragment', base.NONE)
add_fields(f_filesize, f_iteration, f_position, f_size, f_fragment)

-- PT_FILEACK
--    f_fileid
--    f_iteration
local f_numsegments = ProtoField.uint8('srb2.data.numsegments', '# of Segments')
add_fields(f_numsegments)

-- PT_FILERECEIVED
--    f_fileid

-- PT_CLIENTJOIN
--    f__255
local f_packetversion = ProtoField.uint8('srb2.data.packetversion', 'Packet Version')
local f_application = ProtoField.string('srb2.data.application', 'Application')
--    f_version
--    f_subversion
local f_localplayers = ProtoField.uint8('srb2.data.localplayers', 'Local Players')
local f_mode = ProtoField.uint8('srb2.data.mode', 'Mode')
local f_p1name = ProtoField.string('srb2.data.p1name', 'Player 1 Name')
local f_p2name = ProtoField.string('srb2.data.p2name', 'Player 2 Name')
add_fields(f_packetversion, f_application, f_localplayers, f_mode, f_p1name, f_p2name)

function srb2_proto.dissector(buffer, pinfo, tree)
	pinfo.cols.protocol = 'SRB2'

	local ptype = buffer(6,1):uint()
	local ptype_str = (packet_types[ptype] or 'Unknown')..' ('..ptype..')'
	pinfo.cols.info = ptype_str

	local cksum_expected = NetbufferChecksum(buffer)
	local cksum_given = buffer(0,4):le_uint()
	local cksum_valid = (cksum_given == cksum_expected)
	local cksum_str = 'Checksum Status: '
	if srb2_proto.prefs.validate_checksum then
		if cksum_valid then
			cksum_str = cksum_str..'OK'
		else
			cksum_str = cksum_str..string.format('should be 0x%X!', cksum_expected)
		end
	else
		cksum_str = cksum_str..'Unverified'
	end
	
	local datalen = buffer:len() - 8

	local subtree = tree:add(srb2_proto, buffer(), 'Sonic Robo Blast 2 netgame protocol')
	subtree:add_le(f_checksum, buffer(0,4))
	subtree:add(f_valid, cksum_valid):set_text(cksum_str):set_generated(true)
	subtree:add(f_ack, buffer(4,1))
	subtree:add(f_ackret, buffer(5,1))
	subtree:add(f_ptype, buffer(6,1))
	subtree:add(f_reserved, buffer(7,1))
	subtree:add(f_datalen, datalen):set_generated(true)

	local data_tree = subtree:add(f_data, buffer(8))
	local stage2 = packet_dissectors[packet_types[ptype]]
	if stage2 then
		stage2(buffer(8), datalen, pinfo, data_tree)
	end
end

local MAXAPPLICATION = 16
local MAXPLAYERNAME = 21

function packet_dissectors.PT_SERVERCFG(range, datalen, pinfo, tree)
	tree:add(f_version, range(0,1))
	tree:add(f_subversion, range(1,1))
	tree:add(f_serverplayer, range(2,1))
	tree:add(f_totalslotnum, range(3,1))
	tree:add_le(f_gametic, range(4,4))
	tree:add(f_clientnode, range(8,1))
	tree:add(f_gamestate, range(9,1))
	tree:add(f_gametype, range(10,1))
	tree:add(f_modifiedgame, range(11,1))
	tree:add(f_server_context, range(12,8))
end

function packet_dissectors.PT_SERVERREFUSE(range, datalen, pinfo, tree)
	tree:add(f_refuse_reason, range)
end

function packet_dissectors.PT_REQUESTFILE(range, datalen, pinfo, tree)
	tree:add(f_fileid, range(0,1))
	tree:add(f_filename, range(1, datalen-2))
	tree:add(f__255, range(datalen-1, 1))
end

function packet_dissectors.PT_FILEFRAGMENT(range, datalen, pinfo, tree)
	tree:add(f_fileid, range(0,1))
	tree:add_le(f_filesize, range(1,4))
	tree:add(f_iteration, range(5,1))
	tree:add_le(f_position, range(6,4))
	tree:add_le(f_size, range(10,2))
	tree:add(f_fragment, range(12))
end

function packet_dissectors.PT_FILEACK(range, datalen, pinfo, tree)
	tree:add(f_fileid, range(0,1))
	tree:add(f_iteration, range(1,1))
	tree:add(f_numsegments, range(2,1))
	local numsegments = (datalen - 3) / 8
	for i=0,numsegments-1 do
		local segstart = 3 + 8*i
		local start = range(segstart, 4):le_uint()
		local acks = range(segstart+4, 4):le_uint()
		local str = string.format('Segment %u: start=0x%X, acks=', i, start)
		for j=1,32 do
			if acks % 2 == 1 then
				str = str..'1'
			else
				str = str..'0'
			end
			acks = math.floor(acks / 2)
		end
		tree:add(range(segstart, 8), str)
	end
end

function packet_dissectors.PT_FILERECEIVED(range, datalen, pinfo, tree)
	tree:add(f_fileid, range(0,1))
end

function packet_dissectors.PT_CLIENTJOIN(range, datalen, pinfo, tree)
	tree:add(f__255, range(0,1))
	tree:add(f_packetversion, range(1,1))
	tree:add(f_application, range(2, MAXAPPLICATION))
	tree:add(f_version, range(2+MAXAPPLICATION, 1))
	tree:add(f_subversion, range(3+MAXAPPLICATION, 1))
	tree:add(f_localplayers, range(4+MAXAPPLICATION, 1))
	tree:add(f_mode, range(5+MAXAPPLICATION, 1))
	tree:add(f_p1name, range(6+MAXAPPLICATION, MAXPLAYERNAME))
	tree:add(f_p2name, range(6+MAXAPPLICATION+MAXPLAYERNAME, MAXPLAYERNAME))
end

DissectorTable.get('udp.port'):add(5029, srb2_proto)