Custom wireshark disector shows value but fieldname is not visible using lua

Question

I am testing some network packets of my Organisation's product. We already have custom plugins. I am trying to add some some more fields into those existing plugins (like conversion of 2 byte code to a string and assign it to a field)

Thankyou in advance for reading my query.

--edit

Wireshark version : 2.4.5 (organization's plugins dont work on latest wireshark application)

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Problem statement: I am able to add field and show value, but fieldname is not displayed as defined.

I cannot share the entire .lua file but i will try to explain What i did:

1. Below is the image where I have a field aprint.type. this is a two byte field. In .lua file, for display purpose it is appended with corresponding description using a custom function int_to_enum.
2. I want to add one more proto field aprint.typetext which will show the text.

What I did:

1. Added a protofield f_apr_msg_type_txt = ProtoField.string("aprint.typetxt","aprint_type_text") (Tried f_apr_msg_type_txt = ProtoField.string("aprint.typetxt","aprint_type_text",FT_STRING) also)
2. Below the code where subtree aprint.type is shown, added my required field as subtree:add(f_apr_msg_type_txt, msg_type_string) (Below is image of code extract)

I am able to see the text but field Name is shown as Wireshark Lua text (_ws.lua.text)

Answer 1

Normally displaying strings based on numeric values is accomplished by a value string lookup, so you'd have something like so:

local aprint_type_vals = {
    [1] = "Foo",
    [2] = "Bar",
    [9] = "State alarm"
}

f_apr_msg_type = ProtoField.uint16("aprint.type", "Type", base.DEC, aprint_type_vals)
f_apr_msg_type_txt = ProtoField.string("aprint.typetxt","aprint_type_text", base.ASCII)

... then

local msg_type = tvb(offset, 2):le_uint()
subtree:add_le(f_apr_msg_type, tvb(offset, 2))

subtree:add(f_apr_msg_type_txt, tvb(offset, 2), (aprint_type_vals[msg_type] or "Unknown"))

--[[
Alternatively:

subtree:add(f_apr_msg_type_txt, tvb(offset, 2)):set_text("aprint_type_text: " .. (aprint_type_vals[msg_type] or "Unknown"))
--]]

I'm also not sure why you need the extra field with only the text when the text is already displayed with the existing field, but that's basically how you'd do it.