Re: my purpose [for building with support for Lua in Linux (Ubuntu 20.04)]

[Guy Harris <gharris () sonic net>]

On May 22, 2021, at 1:46 PM, Vincent Randal <vtrandal () gmail com> wrote:

> On Sat, May 22, 2021 at 3:51 AM Guy Harris <gharris () sonic net> wrote:
> > On May 21, 2021, at 8:03 PM, Vincent Randal <vtrandal () gmail com> wrote:
> >
> > > 1. Before running cmake how can I tell the appropriate "with-lua" sort of switch is enabled?
> >
> > By making sure that the appropriate package for Lua is installed.  That's liblua5.2-dev.
> >
> > The easiest way to make sure it's installed is to run
> >
> >         tools/debian-setup.sh --install-optional
>
> Thank you. Graham had the same suggestion. This helped tremendously. I was doing it the hard way trying to manage 
> dependencies myself.

The UNIX section (which should perhaps be called "UN*X" or "UNIX and UNIX-like", as it also applies to systems such as 
most Linux distributions and the *BSDs that aren't licensed for the UNIX trademark):

        https://www.wireshark.org/docs/wsdg_html_chunked/ChapterSetup.html#ChSetupUNIX

has been expanded recently to give ore instructions on setting up a development environment (it's not quite at the 
"IKEA motorcycle engine", to quote our illustrious founder, level that Windows is at, but it *does* involve some work 
for which we should and now do give some help).

It mentions the "set up the development environment scripts" for Debian-flavored Linux distributions, RPM-based Linux 
distributions, Alpine Linux, the *BSDs, and macOS.

> > > 3. If it does not find Lua how do I fix that?
> >
> > Make sure liblua5.2-dev is installed.  (If you've already run CMake before running tools/debian-setup.sh 
> > --install-optional, you *might* have to remove the directory in which you ran it, create a new directory in which to 
> > do the build, and re-run CMake, so that there isn't any cached "sorry, I didn't find Lua" indication left around.)
>
> Thank you. I did have to remove the build directory and re-run cmake in a fresh new (empty) directory.

CMake leaves a bunch of cache information around so it doesn't redo tests that it's already done and that "shouldn't" 
give different results when redone; if you change things that CMake doesn't realize *will* change those results, it 
won't retry them.

There may be less "nuke it from orbit, it's the only way to be sure" solutions, e.g. removing some specific cache files.

> > > 4. When the build succeeds how do I compensate for the difference sudo and non-sudo seem to have on tshark? 
> > > Non-sudo invokation runs my lua scripts. Sudo invocations don't.
> >
> > Don't run with sudo.  You should *NEVER* run TShark or Wireshark under sudo.  To quote section 3.11.1 "Packaging 
> > Guidelines":
> >
> >      ...
> >
> > Instead, run CMake with the option -DDUMPCAP_INSTALL_OPTION=capabilities.  Then, if you install Wireshark with "sudo 
> > cmake install", it will install the dumpcap program with sufficient Linux capabilities to do capturing on network 
> > interfaces.
>
> Thank you. That works. And -DDUMPCAP_INSTALL_OPTION=suid also seems to work.

It also works.  If you don't care about capturing raw USB traffic, -DDUMPCAP_INSTALL_OPTION=capabilities is sufficient, 
and doesn't grant dumpcap quite as much privilege when it starts up (it relinquishes privileges as soon as it can, but 
the less privilege, the better); annoyingly, the devices for snooping raw USB traffic require root privilege (at least 
it's not as annoying as macOS Big Sur, where it requires sufficient privilege *and* disabling System Integrity 
Protection - I guess some vendors of USB peripherals asked Apple to protect them from reverse engineers or something 
such as that).

> > 5. And assuming (with some help) I get past the above issues, how much control can lua scripts expert over tshark 
> > and Wireshark?
> >
> > To see what Lua scripts can do, see Chapter 10 "Lua Support in Wireshark":
> >
> >      ...
> >
> > If what you want to do is *not* there, then a Lua script probably *can't* do it.
>
> Exactly. I should set my expectations accordingly. Thank you. 

And if there's something you'd *like* it to be able to do, please file an enhancement request as an issue at the 
Wireshark issue list:

        https://gitlab.com/wireshark/wireshark/-/issues
___________________________________________________________________________
Sent via:    Wireshark-dev mailing list <wireshark-dev () wireshark org>
Archives:    https://www.wireshark.org/lists/wireshark-dev
Unsubscribe: https://www.wireshark.org/mailman/options/wireshark-dev
             mailto:wireshark-dev-request () wireshark org?subject=unsubscribe