Wireshark Lua解剖器没有显示树

Question

我在ixia时间戳预告片中有数据包后有拖车数据的数据包。我正在尝试为Wireshark编写一个与ixia-packet_trailer插件完全相同的解剖器。 https://raw.githubusercontent.com/boundary/wireshark/master/epan/dissectors/packet-ixiatrailer.c

但是我想用Lua写，所以最容易改变。

我使用函数is_my_trailer（在Wireshark Lua dissector plugin table error中提出）启发了lua作为启发式，它现在停止在以太网树中显示预告片，所以我相信它识别模式0xae12，但它不显示我的“我的预告片”树

-- declare our protocol
local my_trailer_proto = Proto("my_trailer","my Trailer")

-- Header fields
local timestamp  = ProtoField.uint64 ("my_trailer_proto.timestamp", "timestamp", base.HEX)
local proto_flag  = ProtoField.uint8 ("my_trailer_proto.proto_flag", "protoFlag", base.HEX)
local msg_id     = ProtoField.uint16("my_trailer_proto.msg_id"    , "msdId"    , base.HEX)

my_trailer_proto.fields = { timestamp, proto_flag, msg_id }

-- does this packet contains a trailer 
local function is_my_trailer(buffer,pinfo,tree)
    local length = buffer:len()
    if length < 12 then return 1 end
    local type = buffer(length-12, 2):uint()

    if type == 0xae12 then  return true end
    return false
end

function my_trailer_proto.dissector(buffer, pinfo, tree)
    length = buffer:len()
    if length == 0 then return end

    local subtree = tree:add(my_trailer_proto, buffer(), "my trailer")

    -- Header
    subtree:add(timestamp, buffer(length-10,8))
    subtree:add(proto_flag, buffer(length-3,1))
    subtree:add(msg_id, buffer(length-2,2))

    pinfo.cols.protocol = my_trailer_proto.name
    pinfo.cols.protocol:set("proto_flag")
    pinfo.cols.info:set("proto_flag: " .. proto_flag)
end 

my_trailer_proto:register_heuristic("eth.trailer", is_my_trailer)

这是一个带有预告片https://transfernow.net/87kwt2k0dne7的pcap文件示例

Answer 1

你忘记了一行重要的代码：

if type == 0xae12 then  return true end
return false

应该：

if type == 0xae12 then
    my_trailer_proto.dissector(buffer, pinfo, tree)
    return true
end
return false

你还有另一个bug。这一行是一个错误：

pinfo.cols.info:set("proto_flag: " .. proto_flag)

它应该是这样的：

pinfo.cols.info:set("proto_flag: " .. buffer(length-3,1):uint())