Outdated discussion. Lua was originally just a plugin for Wireshark, but became integrated as of v0.99.4.
No Registration, just Handoff
Lua it's been added to wireshark as a plugin, its registration function doesn't do anything, it isn't until handoff that the given script is compiled and executed. The reasons for this are:
- every wireshark dissector (those in C) has already been registered. Lua resolves naming conflicts without an assertion, it just returns an error if an user tries to register a protocol that already exists, if a lua protocol named XXX was added before the wireshark XXX dissector was added there would have been a critical error.
- as all of the dissectors have already registered operations on dissector tables
to plugin or not to plugin?
While I believe it's a good thing in general that Lua is an optional module for wireshark I see few problems with this.
- It would be better that Lua's script was run *after* every other dissector has already handoff but *before* user preferences are setup. Currently wireshark loads plugins in a random order so some dissectors handoffs have not yet been called when Lua runs the script.
It is hard to specify which script to load. Right now Lua loads an script called init.lua located in the user's config directory. If the environment variable WIRESHARK_LUA_INIT is set it will look for a script located there. If Lua used a preference module for the script pathname then protocols written in Lua could not register their own preferences. The other way would be to add an -option to tell wireshark to tell lua where to look for, unfortunately we cannot use but the latin alphabet and it's too short for wireshark's options.