clean up and add README

1 files changed, 135 insertions, 0 deletions

diff --git a/dissectors/t937.lua b/dissectors/t937.lua
new file mode 100755
index 0000000..9d37ba6
--- /dev/null
+++ b/dissectors/t937.lua
@@ -0,0 +1,135 @@
+local proto = Proto("t937", "T-937/M Serial Control")

+

+local FUN_TABLE = {

+  [0x01] = "REQUEST_CONN",

+  [0xf1] = "CONFIRM_CONN",

+  [0x02] = "TEMP_STATUS",

+  [0x08] = "SET_HEATER",

+  [0x0d] = "SET_EXTRACTOR",

+}

+

+proto.experts.checksum = ProtoExpert.new("t937.checksum",

+  "T937 Checksum Error",

+  expert.group.CHECKSUM, expert.severity.ERROR

+)

+

+proto.fields.addr = ProtoField.uint16("t937.address", "Address", base.HEX)

+proto.fields.fun = ProtoField.uint8("t937.function", "Function", base.HEX, FUN_TABLE)

+proto.fields.len = ProtoField.uint8("t937.length", "Data Length", base.HEX)

+proto.fields.checksum = ProtoField.uint16("t937.checksum", "Message Checksum", base.HEX)

+

+proto.fields.data = ProtoField.bytes("t937.data", "Data")

+

+local function try_dissect(bytes, pinfo, tree)

+  -- minimum len is header + checksum

+  if bytes:len() < 4 + 2 then return end

+

+  local raw_len = bytes:uint(3, 1)

+  if bytes:len() < 4 + raw_len + 2 then return end

+

+  local buffer = bytes:subset(0, 4+raw_len+2):tvb("T-937 Frame")

+  local address = buffer(0, 2)

+  local fun = buffer(2, 1)

+  local len = buffer(3, 1)

+  local data = buffer(4, raw_len)

+  local checksum = buffer(4+raw_len, 2)

+

+  local sum = 0

+  for i=0,4+raw_len-1 do

+    sum = sum + buffer(i, 1):uint()

+  end

+

+  pinfo.cols.info:set("T937 " .. (FUN_TABLE[fun:uint()] or ""))

+  pinfo.cols.dst:clear_fence()

+  pinfo.cols.dst:set(address:bytes():tohex())

+

+  local sub = tree:add(proto, buffer())

+  sub:add(proto.fields.addr, address)

+  sub:add(proto.fields.fun, fun)

+  sub:add(proto.fields.len, len)

+  sub:add(proto.fields.data, data)

+

+  local cs = sub:add(proto.fields.checksum, checksum)

+  if sum ~= checksum:uint() then

+    cs:add_proto_expert_info(proto.experts.checksum, string.format(

+      "expected 0x%04x, got 0x%04x", checksum:uint(), sum

+    ))

+  end

+

+  return buffer:len()

+end

+

+local state

+

+function proto.init()

+  state = {

+    error = {},

+    rest = {

+      [P2P_DIR_SENT] = ByteArray.new(),

+      [P2P_DIR_RECV] = ByteArray.new(),

+    },

+    buffers = {},

+    last_number = -1,

+  }

+end

+

+function proto.dissector(_buf, pinfo, tree)

+  local buffers = state.buffers[pinfo.number]

+

+  if buffers then

+    for _,buffer in ipairs(buffers) do

+      try_dissect(buffer, pinfo, tree)

+    end

+    return true

+  end

+

+  local err = state.error[pinfo.p2p_dir]

+  if err then

+    if state.last_number == pinfo.number then

+      error(err)

+    else

+      return

+    end

+  end

+

+  if state.last_number >= pinfo.number then

+    error(string.format(

+      "dissection order not increasing: %d >= %d",

+      state.last_number, pinfo.number

+    ))

+  end

+

+  local rest = state.rest[pinfo.p2p_dir]

+  rest:append(_buf:bytes())

+  buffers = {}

+

+  while rest:len() > 0 do

+    local ok, len = pcall(try_dissect, rest, pinfo, tree)

+    if not ok then

+      print("GOT ERR", len, pinfo.number)

+      state.error[pinfo.p2p_dir] = len

+      state.last_number = pinfo.number

+      error(len)

+    elseif not len then

+      break

+    end

+

+    table.insert(buffers, rest:subset(0, len))

+

+    if len == rest:len() then

+      rest = ByteArray.new()

+      break

+    end

+

+    rest = rest:subset(len, rest:len() - len)

+  end

+

+  state.rest[pinfo.p2p_dir] = rest

+  state.buffers[pinfo.number] = buffers

+  state.last_number = pinfo.number

+  return true

+end

+

+pcall(proto.register_heuristic, proto, "ch340.serial_data", proto.dissector)

+pcall(proto.register_heuristic, proto, "pl2303.serial_data", proto.dissector)

+DissectorTable.get("rtacser.data"):add_for_decode_as(proto)