Implement XDP map types #527

Tuetuopay · 2023-02-20T22:11:35Z

This PR is an update of @dave-tucker’s #292 updated for the current Aya main.

It adds implementations for:

xskmap
cpumap
devmap
devmap_hash

All of those can be used to redirect XDP packets to various notations. Note that the userspace part (umem ans socket) of xskmap (i.e. AF_XDP) is not handled by this PR and requires other libraries (like libbpf, xsk-rs, …). For this, see #507.

All map types have been tested working.

TODO:

integration tests
~~add bindings to struct xdp_sock to implement aya::maps::XskMap::get~~
Cancelled: contrary to what the kernel documentation say, XskMap does not support element lookup from the userspace (https://elixir.bootlin.com/linux/v6.2/source/net/xdp/xskmap.c#L148).
frags support (xdp.frags/devmap et al)

Closes: #193 #194 #195 #199

This change is

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dave-tucker

Some comments so far... and can you please make this a draft PR if you're still working on it? That way I can hold of doing another review until you're done 😆

aya/src/maps/mod.rs

aya/src/maps/xdp/cpu_map.rs

aya/src/maps/xdp/dev_map_hash.rs

aya-bpf-macros/src/expand.rs

aya-obj/src/obj.rs

aya/src/maps/xdp/dev_map.rs

Tuetuopay · 2023-02-23T12:00:18Z

Some comments so far... and can you please make this a draft PR if you're still working on it? That way I can hold of doing another review until you're done 😆

Whooops sorry. Done for the draft! I always find additionnal stuff to shove in a PR 😅

I’ll apply your suggestions this afternoon.

Tuetuopay · 2023-02-23T23:50:36Z

@dave-tucker I now consider this PR as ready, I shoved everything I could think of as far as maps are concerned. It just needs #532 first to be "canonically" built with the additional bindings generated by bors.

The last pain point are the integration tests somehow not passing in the CI while they run fine locally. I'll try to troubleshoot it but I'm not able to reproduce it...

aya/src/maps/mod.rs

bpf/aya-bpf/src/maps/xdp/cpu_map.rs

bpf/aya-bpf/src/maps/xdp/dev_map.rs

bpf/aya-bpf/src/maps/xdp/dev_map_hash.rs

bpf/aya-bpf/src/maps/xdp/xsk_map.rs

set/insert functions can now take an optional bpf program fd to run once the packet has been redirected from the main probe

Values in those map are small enough to return copied values instead of reference to values.

Not having a generic here allows to pass `None` without specifying the actual type you don't care about.

Use our own type that: - is stable as not from bindgen - does not have an union inside

On startup, the kernel is probed for support of chained program ids for CpuMap, DevMap and DevMapHash, and will patch maps at load time to have the proper size. Then, at runtime, the support is checked and will error out if a program id is passed when the kernel does not support it.

alessandrod

Some more comments!

aya/src/maps/xdp/mod.rs

aya/src/maps/xdp/cpu_map.rs

aya/src/maps/xdp/dev_map.rs

alessandrod · 2023-09-22T12:05:41Z

aya-bpf-macros/src/lib.rs

@@ -128,6 +128,35 @@ pub fn sk_msg(attrs: TokenStream, item: TokenStream) -> TokenStream {
    }
 }

+/// Marks a function as an eBPF XDP program that can be attached to a network interface.
+///
+/// On some NIC drivers, XDP probes are compatible with jumbo frames through the use of


I don't think so? Maybe it depends on the attach mode? On aws I've definitely
worked with 9001 bytes large frames with regular (no frags) xdp programs

aya-obj/src/obj.rs

alessandrod · 2023-09-22T13:47:08Z

bpf/aya-bpf/src/maps/xdp/cpu_map.rs

+    /// }
+    /// ```
+    #[inline(always)]
+    pub fn redirect(&self, index: u32, flags: u64) -> u32 {


Yes but that's a C API :P A rusty equivalent would be

MAP.redirect(0, 0).or(Ok(XDP_DROP))

And if you make it return Result<i32, i32> I guess this also works

MAP.redirect(0, XDP_DROP as u64)

and then in the caller

match try_thing(ctx) { Ok(res) => res, Err(res) => res, }

So I don't see a reason not to return Result?

alessandrod · 2023-09-22T13:50:44Z

bpf/aya-bpf/src/maps/xdp/dev_map.rs

+
+#[derive(Clone, Copy)]
+pub struct DevMapValue {
+    pub ifindex: u32,


if_index (search ifindex PR-wide :P)

aya/src/maps/mod.rs

alessandrod · 2023-09-22T16:02:38Z

bpf/aya-bpf/src/maps/xdp/dev_map.rs

+pub struct DevMapValue {
+    /// Target interface index to redirect to.
+    pub if_index: u32,
+    pub prog_id: u32,


No docs for prog_id?

doh. fixed.

also changed the u32 -> Option<NonZeroU32> to reflect the userspace API (and the fact that there's not necessarily a chained program)

alessandrod · 2023-09-22T16:05:50Z

couple smol nits, then it's ready to go!

tamird

Reviewed 31 of 31 files at r14, 32 of 32 files at r17, 13 of 13 files at r19, all commit messages.
Reviewable status: all files reviewed, 56 unresolved discussions (waiting on @alessandrod, @astoycos, @dave-tucker, @Tuetuopay, and @vadorovsky)

aya/src/maps/xdp/cpu_map.rs line 51 at r17 (raw file):

/// # See also
///
/// Kernel documentation: <https://docs.kernel.org/next/bpf/map_cpumap.html>

why the angle brackets?

aya/src/maps/xdp/dev_map.rs line 43 at r17 (raw file):

/// # See also
///
/// Kernel documentation: <https://docs.kernel.org/next/bpf/map_devmap.html>

ditto

aya/src/maps/xdp/dev_map_hash.rs line 43 at r17 (raw file):

/// # See also
///
/// Kernel documentation: <https://docs.kernel.org/next/bpf/map_devmap.html>

ditto

aya/src/maps/xdp/mod.rs line 16 at r17 (raw file):

#[derive(Error, Debug)]
/// Errors occuring from working with XDP Maps

period?

aya/src/maps/xdp/xsk_map.rs line 36 at r17 (raw file):

/// # See also
///
/// Kernel documentation: <https://docs.kernel.org/next/bpf/map_xskmap.html>

ditto

bpf/aya-bpf/src/maps/xdp/cpu_map.rs line 120 at r19 (raw file):

        match ret.unsigned_abs() as u32 {
            XDP_REDIRECT => Ok(XDP_REDIRECT),
            // Return XDP_REDIRECT on success, or the value of the two lower bits of the flags

this comment should probably on top of the match?

EDIT: there are many instances of this - consider extracting at least some of this logic so it can be documented just once.

bpf/aya-bpf/src/maps/xdp/dev_map.rs line 145 at r19 (raw file):

        match ret.unsigned_abs() as u32 {
            XDP_REDIRECT => Ok(XDP_REDIRECT),
            // Return XDP_REDIRECT on success, or the value of the two lower bits of the flags

ditto

bpf/aya-bpf/src/maps/xdp/dev_map_hash.rs line 147 at r19 (raw file):

        match ret.unsigned_abs() as u32 {
            XDP_REDIRECT => Ok(XDP_REDIRECT),
            // Return XDP_REDIRECT on success, or the value of the two lower bits of the flags

ditto

bpf/aya-bpf/src/maps/xdp/xsk_map.rs line 163 at r19 (raw file):

        match ret.unsigned_abs() as u32 {
            XDP_REDIRECT => Ok(XDP_REDIRECT),
            // Return XDP_REDIRECT on success, or the value of the two lower bits of the flags

one more

Tuetuopay

Reviewable status: 31 of 34 files reviewed, 57 unresolved discussions (waiting on @alessandrod, @astoycos, @dave-tucker, @tamird, and @vadorovsky)

aya/src/maps/xdp/cpu_map.rs line 51 at r17 (raw file):