aya: Implement forget_link

[dave-tucker]

Fixes #51

Signed-off-by: Dave Tucker dave@dtucker.co.uk

[dave-tucker]

@alessandrod The impl is a bit rough, perhaps a trait would reduce the copy/paste... but this SHOULD work (and I've verified that nothing calls detach() on the link).
however, the integration test case fails because the XDP program isn't attached after the program has stopped.
Could do with some fresh set of eyes on this to see if I've missed something 👀

[dave-tucker]

@alessandrod per discussion on Discord an OwnedLink type was added to deal ensure that we detach links on drop. I've verified with strace that program::forget_link will detach on drop and that mem::forget(link) does not detach on drop....

however, the link does not stay alive after the userspace program exits.
I've tried mem::forget()ing everything (Program, Bpf, OwnedLink) and can't get the program to persist at all - even without these changes - so I've got to conclude that either something broke in the links refactor... i'm doing it wrong,... or the kernel is doing something helpful

[alessandrod]

@alessandrod per discussion on Discord an OwnedLink type was added to deal ensure that we detach links on drop. I've verified with strace that program::forget_link will detach on drop and that mem::forget(link) does not detach on drop...

Amazing! 😊 I think we should have OwnedLink::forget so that you don't have to mem::forget explicitly which seems ugly.

however, the link does not stay alive after the userspace program exits. I've tried mem::forget()ing everything (Program, Bpf, OwnedLink) and can't get the program to persist at all - even without these changes - so I've got to conclude that either something broke in the links refactor... i'm doing it wrong,... or the kernel is doing something helpful

Hrm ok, I'm going to take a look at this

[dave-tucker]

@alessandrod per discord discuission,

1, Removed the failing test as it relied on mem::forget, which won't work as we cant intentionally leak fds to make this work
2. Implemented Deref for OwnedLink

Should be ready for review now.

[alessandrod]

Smol mostly doc nits, almost there!