Add python bindings

[jimmylomro]

Adds python bindings for libnethogs using pybind11. Didn't touch any of the existing code, so does not break anything that already exists.

To compile/install this people will need to also install pybind11-dev deb package. It uses setuptools to install, so you need to run pip install . and it will compile everything and install.

To use:

import nethogs
import threading
def callback(action: int, record: nethogs.NethogsMonitorRecord) -> None:
    do_whatever_with_record(record)
    return
th = threading.Thread(target=nethogs.nethogsmonitor_loop, args(callback, filter, to_ms))
th.start()
do_whatever_you_need_to_do()
nethogs.nethogsmonitor_breakloop()
th.join()

As a general comment, there's some not very good use of global variables, callbacks should be std::function instead, and a lot of other things mostly related with newer c++ standards. Probably a good idea to start a ToDo list in the readme :) specially for such a widely used codebase.

There are a few things to notice:

• There are only bindings for nethogsmonitor_loop and nethogsmonitor_breakloop.
• At the moment, only one instance of the loop can be run at a time. Callbacks would get completely messed up if more than one is run.
• There is no way of setting pidsToWatch, but it is not difficult to implement if anyone wants to do it :)
• The package version is set in setup.py using the script determineVersion.sh, but it is very hacky as a PEP compatible string is needed. Something stronger should be implemented, ideally using the regex module.
• Ideally this should not be run in the main thread, stopping the nethogsmonitor_loop with a SIGINT or SIGTERM is a bit hacky and could break things.

[raboof]

Thanks for looking into this!

Might be good to add some docs?

[raboof]

Do I understand correctly that because of the way src/MakeApp.mk is set up, this file is only compiled when building the python bindings, and not when nethogs is 'regularly' compiled? Perhaps it would be neat to put it in a separate directory?

[jimmylomro]

That is right, the src/bindings.cpp file should only be compiled when building the python bindings i.e. pip install .. I see MakeApp.mk and MakeLib.mk both explicitly define the list of files to be built, so keeping src/bindings.cpp won't affect the make compilation, but I see the point, I can move it.

[jimmylomro]

I could move it to a python directory where I can add a readme with some info (will be similar to the PR original comment). The setup.py and pyproject.toml will have to stay in the root though.

[raboof]

that sounds fine to me!

I guess this makes the contrib script obsolete?

[jimmylomro]

It would, yes, but for those who still want to load the lib directly I can also move this file into the python directory.