Re: Wireshark-dev: Re: Lua embedded into C++

[Peter Wu <peter () lekensteyn nl>]

On Mon, Mar 13, 2017 at 10:25:17PM +0000, Kunal Thakrar wrote:
> My aim for my module is to create a web browser agnostic developer's
> tools, similar to Chrome and Firefox. When a user opens my module they
> will see all the current TCP conversations occurring on their system
> (this works in a similar way to the Conversation dialog). A user will
> be able to choose a conversation. From there I want to be able to use
> listeners to see all the packets to do with that conversation which
> they selected on a new GUI window, and hopefully be able to implement
> some sort of check whether there are HTTP or https packets etc.
>
>
> In my previous email thread Peter Wu mentioned
>
> "The classes included with the WSLUA API are not designed to be
>
> registered with multiple users. If you are lucky, it sometimes does not
> work as expected (due to shared global variables, registrations to other
> parts of the dissector APIs), if you are unlucky it will just crash."
>
> Which seems to be the problem I am running into. So my question is, is
> there a way to get around these problems with the Lua stack or would
> it be easier to create/register listeners and post dissectors in C and
> C++ and if it is, how would I go about doing it?

I think you can still use Lua as long as you load it through the
"normal" methods (putting the Lua script in the plugins directory or
using -Xlua_script:path/to/alert.lua). This will allow your Lua code to
be executed as post-dissector or listener. Note that the Wireshark core
will then invoke your Lua code, you should not call the Lua code from
your C++ module.

To trigger the post-dissector, I think your best chance will be invoking
the redissection routines. Some grepping around points to something like
MainWindow::redissectPackets (no idea whether it works for you, ymmv).

If you have some functionality to expose to the Lua script, maybe you
could register a class as usual (luaL_newmetatable, luaL_setfuncs,
etc.), but you have to be careful to leave the Lua stack pointer
unchanged.
-- 
Kind regards,
Peter Wu
https://lekensteyn.nl
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