Hello Harry,
Thank you for sharing the API.
Please check out my comments below.
Regards,
Gregory
On Thu, 17 Apr 2025, Harry van Haaren wrote:
External email: Use caution opening links or attachments
This patch is NOT to be considered for merge, it is a demo
of the Rust APIs for Ethdev. There is no actual implementation
of the APIs against the DPDK C functions, this is Rust API only.
To test/run the code (and uncomment things to see errors)
just apply this patch, cd "rust_api_example" and run
$ cargo run
This will compile the API, and spawn 2x threads to poll on
two Rxq instances. The comments in the code explain how the
"Send" and "Sync" attributes are captured per instances of a
struct (e.g. how RxqHandle -> Rxq restricts thread movement).
Signed-off-by: Harry van Haaren <harry.van.haa...@intel.com>
---
rust_api_example/Cargo.toml | 6 ++
rust_api_example/src/main.rs | 189 +++++++++++++++++++++++++++++++++++
2 files changed, 195 insertions(+)
create mode 100644 rust_api_example/Cargo.toml
create mode 100644 rust_api_example/src/main.rs
diff --git a/rust_api_example/Cargo.toml b/rust_api_example/Cargo.toml
new file mode 100644
index 0000000000..0137826340
--- /dev/null
+++ b/rust_api_example/Cargo.toml
@@ -0,0 +1,6 @@
+[package]
+name = "rust_api_example"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
diff --git a/rust_api_example/src/main.rs b/rust_api_example/src/main.rs
new file mode 100644
index 0000000000..8d0de50c30
--- /dev/null
+++ b/rust_api_example/src/main.rs
@@ -0,0 +1,189 @@
+// Outline for safe DPDK API bindings
+// - None of the APIs are actually implemented, this is API design only
+// - This demo runs 2x threads on 2x Rxqs, and cannot accidentally poll
incorrectly
+
+pub mod dpdk {
+ pub mod eth {
+ use super::Mempool;
+
+ #[derive(Debug)]
+ pub struct TxqHandle {/* todo: but same as Rxq */}
+
+ // Handle allows moving between threads, its not polling!
+ #[derive(Debug)]
+ pub struct RxqHandle {
+ port: u16,
+ queue: u16,
+ }
+
+ impl RxqHandle {
+ pub(crate) fn new(port: u16, queue: u16) -> Self {
+ RxqHandle { port, queue }
+ }
+
+ // This function is the key to the API design: it ensures the
rx_burst()
+ // function is only available via the Rxq struct, after
enable_polling() has been called.
+ // It "consumes" (takes "self" as a parameter, not a '&'
reference!) which essentially
+ // destroys/invalidates the handle from the Application level code.
+
+ // It returns an Rxq instance, which has the PhantomData to encode
the threading requirements,
+ // and the Rxq has the rx_burst() function: this allows the
application to recieve packets.
+ pub fn enable_polling(self) -> Rxq {
+ Rxq {
+ handle: self,
+ _phantom: std::marker::PhantomData,
+ }
+ }
+ }
+
+ #[derive(Debug)]
+ pub struct Rxq {
+ handle: RxqHandle,
+ // This "PhantomData" tells the rust compiler to Pretend the
Rc<()> is in this struct
+ // but in practice it is a Zero-Sized-Type, so takes up no space.
It is a compile-time
+ // language technique to ensure the struct is not moved between
threads. This encodes
+ // the API requirement "don't poll from multiple threads without
synchronisation (e.g. Mutex)"
+ _phantom: std::marker::PhantomData<std::rc::Rc<()>>,
+ }
+
+ impl Rxq {
+ // TODO: datapath Error types should be lightweight, not String.
Here we return ().
+ pub fn rx_burst(&mut self, _mbufs: &mut [u8]) -> Result<usize, ()>
{
+ // TODO: Design the Mbuf struct wrapper, and how to best
return a batch
+ // e.g.: investigate "ArrayVec" crate for safe & fixed sized,
stack allocated arrays
+ //
+ // There is work to do here, but I want to communicate the
general DPDK/EAL/Eth/Rxq concepts
+ // now, this part is not done yet: it is likely the
hardest/most performance critical.
+ //
+ // call rte_eth_rx_burst() here
+ println!(
+ "[thread: {:?}] rx_burst: port {} queue {}",
+ std::thread::current().id(),
+ self.handle.port,
+ self.handle.queue
+ );
+ Ok(0)
+ }
+ }
+
+ #[derive(Debug)]
+ pub struct Port {
+ id: u16,
+ rxqs: Vec<RxqHandle>,
+ txqs: Vec<TxqHandle>,
+ }
+
+ impl Port {
+ // pub(crate) here ensures outside this crate users cannot call
this function
+ pub(crate) fn from_u16(id: u16) -> Self {
+ Port {
+ id,
+ rxqs: Vec::new(),
+ txqs: Vec::new(),
+ }
+ }
+
+ pub fn rxqs(&mut self, rxq_count: u16, _mempool: Mempool) ->
Result<(), String> {
+ for q in 0..rxq_count {
+ // call rte_eth_rx_queue_setup() here
+ self.rxqs.push(RxqHandle::new(self.id, q));
+ }
+ Ok(())
+ }
+
+ pub fn start(&mut self) -> (Vec<RxqHandle>, Vec<TxqHandle>) {
+ // call rte_eth_dev_start() here, then give ownership of
Rxq/Txq to app
After a call to Port::start, Rx and Tx queues are detached from it's port.
With that model how rte_eth_dev_stop() and subsequent rte_eth_dev_start()
DPDK calls can be implemented ?
+ (
+ std::mem::take(&mut self.rxqs),
+ std::mem::take(&mut self.txqs),
+ )
+ }
+ }
+ }
+
+ #[derive(Debug, Clone)]
+ // Mempool is a long-life object, which many other DPDK things refer to
(e.g. rxq config)
+ // Having a Rust lifetime attached to it (while technically correct) would
complicate the
+ // code a LOT, and for little value. This is a tradeoff - happy to discuss
more if we want.
+ // The choice here is to derive "Clone", allowing handing over multiple
instances of the
+ // same Mempool, similar to how Arc<Mempool> would work, but without the
reference counting.
+ pub struct Mempool {}
+
+ impl Mempool {
+ pub fn new(_size: usize) -> Self {
+ Self {}
+ }
+ }
+
+ #[derive(Debug)]
+ pub struct Eal {
+ eth_ports: Option<Vec<eth::Port>>,
+ }
+
+ impl Eal {
+ // allow init once,
+ pub fn init() -> Result<Self, String> {
+ // EAL init() will do PCI probe and VDev enumeration will
find/create eth ports.
+ // This code should loop over the ports, and build up Rust structs
representing them
+ let eth_port = vec![eth::Port::from_u16(0)];
+ Ok(Eal {
+ eth_ports: Some(eth_port),
+ })
+ }
+
+ // API to get eth ports, taking ownership. It can be called once.
+ // The return will be None for future calls
+ pub fn take_eth_ports(&mut self) -> Option<Vec<eth::Port>> {
+ self.eth_ports.take()
+ }
+ }
+
+ impl Drop for Eal {
+ fn drop(&mut self) {
+ // todo: rte_eal_cleanup()
+ }
+ }
+} // DPDK mod
+
+fn main() {
+ let mut dpdk = dpdk::Eal::init().expect("dpdk must init ok");
+ let rx_mempool = dpdk::Mempool::new(4096);
+
+ let mut ports = dpdk.take_eth_ports().expect("take eth ports ok");
Eal::take_eth_ports() resets EAL ports.
A call to rte_dev_probe() will ether fail, because Eal::eth_ports is None
or create another port-0, depending on implementation.
+ let mut p = ports.pop().unwrap();
+
+ p.rxqs(2, rx_mempool).expect("rxqs setup ok");
+ println!("{:?}", p);
+
+ let (mut rxqs, _txqs) = p.start();
+ println!("rxqs: {:?}", rxqs);
+
+ let rxq1 = rxqs.pop().unwrap();
+ let rxq2 = rxqs.pop().unwrap();
+
+ // spawn a new thread to use rxq1. This demonstrates that the RxqHandle
+ // type can move between threads - it is not tied to the thread that
created it.
+ std::thread::spawn(move || {
+ // Uncomment this: it fails to compile!
+ // - Rxq2 would be used by this newly-spawned thread
+ // -- specifically the variable was "moved" into this thread
+ // - it is also used below (by the main thread)
+ // "value used after move" is the error, on the below code
+ // let mut rxq = rxq2.enable_polling();
+
+ // see docs on enable_polling above to understand how the
enable_polling()
+ // function helps to achieve the thread-safety-at-compile-time goal.
+ let mut rxq = rxq1.enable_polling();
+ loop {
+ let _nb_mbufs = rxq.rx_burst(&mut [0; 32]);
+ std::thread::sleep(std::time::Duration::from_millis(1000));
+ }
+ });
+
+ // main thread polling rxq2
+ let mut rxq = rxq2.enable_polling();
+ loop {
+ let _nb_mbufs = rxq.rx_burst(&mut [0; 32]);
+ std::thread::sleep(std::time::Duration::from_millis(1000));
+ }
+}
--
2.34.1
