media-source VS opensnitch

It depends heavily on the website we're talking about but there's generally a lot going on when streaming video on the web.

Usually what happens at the core is that JavaScript will download video, audio and subtitles progressively through small chunks of data called "segments" and push them to JS-exposed buffers called 'SourceBuffer'. Deciding which chunk to download, downloading them and pushing them already require a lot of JavaScript (for example, you need to decide which video and audio quality to download through adaptive algorithms, which tend to be quite complex, moreover there's also a lot of media events that needs reaction to, like when seeking, rebuffering, changing track etc.). You also have a lot of JavaScript there to limit risks of playback stalling and if you have DRMs, a lot of JavaScript there to be able to recuperate the right decryption keys (an operation you generally wish to finish as soon as possible as it is often the last step before playback).

On some websites, you might want to play with as low latency as possible between the broadcaster and the user. In those cases, you might want to optimize your JS code, have very small checking intervals, and you might again prefer to run as much code as possible in a worker to avoid rebuffering due to the risk of the main thread being too occupied doing other things to push media segments.

Even on non-low-latency contents, some websites which already have a lot of JavaScript running beside video playback such as at least Facebook and YouTube pushed browsers for quite some time now to be able to use the main JavaScript media streaming APIs in a worker (https://github.com/w3c/media-source/issues/175), e.g. in another thread.

You could also have complex contents (lot of audio and subtitles languages, many audio and video qualities, multiple decryption keys, long duration etc.) that may lead to big performance and memory issue when parsing them on the JS-side. Those contents are usually described through a file named "manifest" or "playlist" which in this case can take a lot of resources to process (the document can be up to a huge 15MB XML where I work), often leading either the linked JavaScript to run in a worker or to use webassembly (a solution we chosed). Even more if you consider live contents, where this document might have to be regularly refreshed.

You might also want to apply some processing on the media played, for example transmuxing mpeg-ts segments to MP4 ones so they can be played by more browsers. Those are very frequent operations that can be performance-sensitive and are also often performed in another thread.

Again it very much depends on the website and I mainly know the use cases I personally encountered. Generally, adaptive media player are very complex JavaScript beasts.

Also performance issues and poor memory management from the browser-side can lead to a lot of issues. A recurring issue at my work is bad performance leading through side-effect to a very poor quality being played (due to the high overhead in loading segments, pushing them to the buffer etc.).

All these would suffer without a powerful and featureful JS engine like we generally have today on most browsers.

opensnitch has existed for a while now. I've never used it, so I can't comment on how well it works.

https://github.com/evilsocket/opensnitch

If you prefer a GUI try https://github.com/evilsocket/opensnitch

The whole BPF verifier and development process is so botched, it's ridiculous. It's like maintainers decided to make this as hard as possible out of pettiness and "they have to use C APIs instead" or something.

- Loading an eBPF module without the CAP_BPF (and in some cases without the CAP_NET_ADMIN which you need for XDP) capabilities will generate a "unknown/invalid memory access" error which is super useless as an error message.

- In my personal opinion a bytecode format for both little endian (bpfel) and big endian (bpfeb) machines is kinda unnecessary. I mean, it's a virtual bytecode format for a reason, right!?

- Compiling eBPF via clang to the bpf bytecode format without debug symbols will make every following error message down the line utterly useless. Took me a while to figure out what "unknown scalar" really means. If you forget that "-g" flag you're totally fucked.

- Anything pointer related that eBPF verifier itself doesn't support will lead to "unknown scalar" errors which are actually out of bounds errors most of the time (e.g. have to use if pointer < size(packet) around it), which only happen in the verification process and can only be shown using the bpftool. If you miss them, good luck getting a better error message out of the kernel while loading the module.

- The bpftool maintainer is kind of unfriendly, he's telling you to read a book about the bytecode format if your code doesn't compile and you're asking about examples on how to use pointers inside a BPF codebase because it seems to enforce specific rules in terms of what kind of method (__always_static) are allowed to modify or allocate memory. There's a lot of limitations that are documented _nowhere_ on the internet, and seemingly all developers are supposed to know them by reading the bpftool codebase itself!? Who's the audience for using the bpftool then? Developers of the bpftool itself?

- The BCC tools (bpf compiler collection) are still using examples that can't compile on an up-to-date kernel. [1] If you don't have the old headers, you'll find a lot of issues that show you the specific git hash where the "bpf-helpers.h" file was still inside the kernel codebase.

- The libbpf repo contain also examples that won't compile. Especially the xdp related ones [2]

- There's also an ongoing migration of all projects (?) to xdp-tools, which seems to be redundant in terms of bpf related topics, but also has only a couple examples that somehow work [3]

- Literally the only userspace eBPF generation framework that worked outside a super outdated enterprise linux environment is the cilium ebpf project [4], but only because they're using the old "bpf-helpers.h" file that are meanwhile removed from the kernel itself. [5] They're also incomplete for things like the new "__u128" and "__bpf_helper_methods" syntax which are sometimes missing.

- The only working examples that can also be used for reference on "what's available" in terms of eBPF and kernel userspace APIs is a forked repo of the bootlin project [6] which literally taught me how to use eBPF in practice.

- All other (official?) examples show you how to make a bpf_printk call, but _none_ of them show you how to even interact with bpf maps (whose syntax changed like 5 times over the course of the last years, and 4 of them don't run through the verifier, obviously). They're also somewhat documented in the wiki of the libbpf project, without further explanation on why or what [7]. Without that bootlin repo I still would have no idea other than how to make a print inside a "kretprobe". Anything more advanced is totally undocumented.

- OpenSnitch even has a workflow that copies their own codebase inside the kernel codebase, just to make it compile - because all other ways are too redundant or too broken. Not kidding you. [8]

Note that none of any BPF related projects uses any kind of reliable version scheme, and none of those project uses anything "modern" like conan (or whatever) as a package manager. Because that would have been too easy to use, and too easy on documenting on what breaks when. /s

Overall I have to say, BPF was the worst development experience I ever had. Writing a kernel module is _easier_ than writing a BPF module, because then you have at least reliable tooling. In the BPF world, anything will and can break at any unpredictable moment. If you compare that to the experience of other development environments like say, JVM or even the JS world, where debuggers that interact with JIT compilers are the norm, well ... then you've successfully been transferred back to the PTSD moments of the 90s.

Honestly I don't know how people can use BPF and say "yeah this has been a great experience and I love it" and not realize how broken the tooling is on every damn level.

I totally recommend reading the book [9] and watching the YouTube videos of Liz Rice [10]. They're awesome, and they show you how to tackle some of the problems I mentioned. I think that without her work, BPF would have had zero chance of success.

What's missing in the BPF world is definitely better tooling, better error messages (e.g. "did you forget to do this?" or even "unexpected statement" would be sooooo much better than the current state), and an easier way to debug an eBPF program. Documentation on what's available and what is not is also necessary, because it's impossible to find out right now. If I am not allowed to use pointers or whatever, then say so in the beginning.

[1] https://github.com/iovisor/bcc

[2] https://github.com/libbpf/libbpf

[3] https://github.com/xdp-project/xdp-tools

[4] https://github.com/cilium/ebpf/

[5] https://github.com/cilium/ebpf/tree/master/examples/headers

[6] https://elixir.bootlin.com/linux/latest/source/tools/testing...

[7] https://github.com/libbpf/libbpf/wiki/Libbpf-1.0-migration-g...

[8] https://github.com/evilsocket/opensnitch/blob/master/ebpf_pr...

[9] https://isovalent.com/learning-ebpf/

[10] (e.g.) https://www.youtube.com/watch?v=L3_AOFSNKK8

Close to zero most probably. If you want something different, to block/monitor what applications access the internet, block ads, etc, try https://github.com/evilsocket/opensnitch

The last thing I built from source was a suckless utility which was nothing but a treat to play with and hack on, so I felt confident I could manage this even though the project's wiki page on compilation warned that it might fail on distro's other then debain and ubuntu. First order of business was translating the apt-get command for the dependencies into an emerge command that would install the same packages. Once that was done, I went on to the go dependencies which all seemed to install without a hitch except for the first one which gave this "build constraints eliminates all Go files" message but didn't tell me that the installation had failed otherwise. I spent a good amount of time trying to decipher this message which eventually turned into just familiarizing myself with go since I hadn't really touched it before before deciding it was fine. Then I tried to build it. It didn't work.

OpenSnitch is a clone of the popular 'LittleSnitch' firewall for Mac. The main feature is that it will tell you about every single connection your computer is doing. A bit annoying for the first few days, but not too bad once you've already allowed the apps you use regularly. I think this would have been the perfect tool for the job.

take a look at opensnitch or picosnitch