This is super useful! I've been hacking recently on qdisc classifiers, and trying to set a filter up with BPF, but there's a paucity of documentation on the subject. The tc tools are sorta documented here (https://man7.org/linux/man-pages/man8/tc-bpf.8.html), but it's quite hard to find docs on the underlying syscalls and the behavior of `bpf_prog_type_sched_cls`.

I bought a copy of BPF performance tools to learn more about the BPF interface, and it's really useful but quite focused on performance! I wish there was a resource of similar depth and breath about eBPF for classification/XDP.