https://github.com/BtbN/FFmpeg-Builds
There's a bunch of build variants here, for various platforms, in different ways. Classic "you have to create the cartesian product of all variables" approach. Here is the single build matrix for a single "Build FFMPeg" job:
https://github.com/BtbN/FFmpeg-Builds/actions/runs/530351117...
You can look through the code and see that each of these will trigger a download.
The developer also added an interesting commit today, stopping forks from having the CI work instantly. Why? Because by default they would all share the same cron entry, and therefore launch all at the same time every night. So now new forks will need to go in and tweak/spread the Cron timer around if they want builds of their own
https://github.com/BtbN/FFmpeg-Builds/commit/78191a73a6a1959...
But there are already over 700 forks of this repository, so the current path is unsustainable.
So in short:
- This isn't an "attack", and it's unclear of the direct volume, but anyway, it doesn't matter because ultimately gmplib.org had strain caused by it.
- GitHub correctly identified the responsible user when asked, and it did not in any way seem malicious, but certainly excessive.
- The build/CI infrastructure for this project definitely hammers the project more than it probably should, exact specifics aside.
- The owner of the project put in place a small (future) mitigation for future forks, but for now IP banlists will probably remain, I'd guess?
- Please try to cache things more aggressively in your build jobs.
[1] https://gmplib.org/list-archives/gmp-devel/2023-June/006162....