Implementing StructOps Support

[takehaya]

StructOps are used in sched_ext, mptcp, and tcp congestion control. It appears that cilium/ebpf does not support them. Why hasn't this been addressed?

If possible, I would like to work on this. Could you guide me on where to start?

[lmb]

I'm happy to help, the problem is that I don't really know how struct_ops work. Maybe you can explain them to me?

• Which program type do they use?
• How are they attached?

[shun159]

Hmm...I see, so that is probably a problem on my end. Thanks!

[ti-mo]

Could you please share some error output so we're sure we're talking about the same thing? It's hard to help without any real information.

[shun159]

The following is an error message when loading a program that includes references to .rodata.

2024/10/01 21:59:42 loading objects: field SimpleSched1: map simple_sched1: failed to load struct_ops program: simple_enable cannot load program without loading its whole collection: instruction 0: unsatisfied map reference

However, I may have figured out the cause. It's probably that the program should be loaded from NewCollectionWithOptions(), but I'm not doing that now.

[ti-mo]

It's probably that the program should be loaded from NewCollectionWithOptions(), but I'm not doing that now.

Exactly. 🙂 This is not an error related to StructOps, it goes for all ELFs. See https://ebpf-go.dev/concepts/loader/#loadandassign if you're only interested in a subset of map or program handles.

[shun159]

Thank you!

I will reconsider the implementation a bit while referring to the documentation. (I didn't know there was such a good resource available 😄)