How to access fields in custom packet context menus?

edit

Hi nwb. It may be surprising, but the ... syntax is actually valid Lua code for handling variable arguments!

For example, here is the code from https://www.lua.org/pil/5.2.html - 5.2 – Variable Number of Arguments:

printResult = ""

function print (...)
  for i,v in ipairs(arg) do
    printResult = printResult .. tostring(v) .. "\t"
  end
  printResult = printResult .. "\n"
end

In my example, the code you can copy and paste into the lua console would be:

local function search_google(...)
    local fields =  {...}
    for i, field in ipairs( fields ) do
        if (field.name == 'http.host') then
            browser_open_url("https://www.google.com/search?q=" .. field.value)
            break
        end
    end
end

register_packet_menu("HTTP/Search host in Google", search_google, "http.host")

In your case, if you want to operate on the usb.src field, you'd likely want to do something similar:

local function usb_src_action(...)
    local fields =  {...}
    for i, field in ipairs( fields ) do
        if (field.name == 'usb.src') then
            -- Do something special
            break
        end
    end
end

register_packet_menu("USB SRC action", usb_src_action, "usb.src")

For multiple fields, as long as it's a single 'packet', you might choose to loop over the fields and extract both variables, then do your operation. However, at this time, the custom packet menu code does not support operating on multiple Wireshark packets at once.