add: separate mod for xdp

[syogaraj]

XDP-related operations are now added as a separate mod as discussed in #618

Closes:
#618
#205
#206
#263

[danielocfb]

Will take a look by Wednesday the latest.

[danielocfb]

Thanks for your pull request! Your change seems mostly fine. I left a few comments. I think we should think about adding more tests. Specifically, for

• query()
• forced errors for attach(), detach(), query() and query_id()
• double attach() & detach() (second one should fail, I would expect)?

What do you think?

[syogaraj]

@danielocfb,

1. test cases for query and query_id will not return any error even if the prog is not loaded to the interface. If that's the case, the returned opts struct will have the prog_id as 0.
2. Added a test case for forced error in the attach API. i.e., attach twice and expect an error.
3. Double detach doesn't seem to raise an error.
4. Some of the requested changes were made since I took references from tc.rs (ex: unnecessary casts and usage of errno). Have updated with the required changes..

[danielocfb]

Thanks for updating! I left a few more comments regarding the API. Looking closer at it I think there are some cases that we want to support but do not currently. Let me know what you think.

[danielocfb]

1. test cases for query and query_id will not return any error even if the prog is not loaded to the interface. If that's the case, the returned opts struct will have the prog_id as 0.

I think error handling for these functions is broken currently. Don't know if that will change much, though.

[danielocfb]

Seems okay. Thanks.

[syogaraj]

@danielocfb Can you please release a build for this?

[danielocfb]

Hi @syogaraj , we just released 0.22.0 and haven't accumulated much since then. Could it wait another week or so?

[syogaraj]

We really need this support in the libbpf-rs for our use case. Can we expect the release in a week? Asking to avoid manually building it from source and use them.

[danielocfb]

We can publish a new release this week.

[danielocfb]

FYI, I just pushed 0.22.1.

[syogaraj]

Thank you so much!