aya: Add from_pin for Programs #496

dave-tucker · 2023-01-19T22:52:59Z

This commit adds from_pin() which allows the creation of a Program from a path on bpffs. This is useful to be able to call attach or other APIs for programs that are already loaded to the kernel.

This differs from #444 since it implements this on the concrete program type, not the Program enum, allowing the user to pass in any additional context that isn't available from bpf_prog_info.

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

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alessandrod

This seems largely ok! See comments

aya/src/programs/cgroup_skb.rs

aya/src/programs/cgroup_sock.rs

aya/src/programs/mod.rs

aya/src/programs/lirc_mode2.rs

aya/src/programs/perf_event.rs

aya/src/programs/socket_filter.rs

dave-tucker · 2023-02-08T19:17:02Z

@alessandrod changes addressed.

Path was moved to ProgramData and program_data_from_path was made a function instead of a macro
from_pin was added using a macro impl_from_pin for simple cases and manually otherwise

dave-tucker · 2023-02-08T22:58:53Z

Updated to fix CI...
I had to move the Drop trait from the Program enum to the concrete program type (i.e XDP) for this to behave as expected. For example:

{
    let prog = Xdp::from_pin("/path/to/prog").unwrap();
    prog.attach("eth0");
}
// Link should get detached here and program fd should be closed

When I moved Drop, clippy was kind enough to point out that we have both Program::unload and Xdp::unload - the latter was pub where the former was pub (crate) and only called via the drop implementation. I went ahead and made Program::unload public since to me it makes sense to have it there as a convenience.

alessandrod · 2023-02-08T23:06:35Z

Updated to fix CI... I had to move the Drop trait from the Program enum to the concrete program type (i.e XDP) for this to behave as expected. For example:
{
    let prog = Xdp::from_pin("/path/to/prog").unwrap();
    prog.attach("eth0");
}
// Link should get detached here and program fd should be closed
When I moved Drop, clippy was kind enough to point out that we have both Program::unload and Xdp::unload - the latter was pub where the former was pub (crate) and only called via the drop implementation. I went ahead and made Program::unload public since to me it makes sense to have it there as a convenience.

This now will not drop programs unless you access them through concrete program types tho right? Eg if you Bpf::load and never create a concrete program

aya/src/programs/mod.rs

alessandrod · 2023-02-08T23:39:18Z

aya/src/programs/mod.rs

+    pub(crate) fn from_pinned_path<P: AsRef<Path>>(
+        path: P,
+    ) -> Result<ProgramData<T>, ProgramError> {
+        let path_string = std::ffi::CString::new(path.as_ref().to_str().unwrap()).unwrap();


I think we should use to_string_lossy here

also import types, don't use full qualified paths

Ugh, so Path -> Cstring isn't exactly easy, but this is what I settled on.

CString::new(path.as_ref().as_os_str().to_string_lossy().as_bytes())

aya/src/programs/mod.rs

test/integration-test/src/tests/load.rs

alessandrod

Almost there!

This commit adds from_pin() which allows the creation of a Program from a path on bpffs. This is useful to be able to call `attach` or other APIs for programs that are already loaded to the kernel. This differs from aya-rs#444 since it implements this on the concrete program type, not the Program enum, allowing the user to pass in any additional context that isn't available from bpf_prog_info. Signed-off-by: Dave Tucker <dave@dtucker.co.uk>

alessandrod

LGTM! Feel free to merge on green

dave-tucker force-pushed the program-from-pinned3 branch from ea44857 to 662548d Compare January 31, 2023 21:57

alessandrod reviewed Jan 31, 2023

View reviewed changes

dave-tucker force-pushed the program-from-pinned3 branch 2 times, most recently from 3027156 to 6289b77 Compare February 8, 2023 19:14

dave-tucker force-pushed the program-from-pinned3 branch 2 times, most recently from 45923f6 to 75e6444 Compare February 8, 2023 22:56

dave-tucker force-pushed the program-from-pinned3 branch from 75e6444 to 0806b9e Compare February 8, 2023 23:33