From 598c53724f1dc8eeec4dd4087865a377b4cac4e0 Mon Sep 17 00:00:00 2001
From: chrysn <chrysn@fsfe.org>
Date: Tue, 2 Jul 2024 22:40:23 +0200
Subject: [PATCH 01/10] refactor(coap): Move server/client mechanism from
 example into coapcore

---
 Cargo.lock                  |  5 ++-
 examples/coap/Cargo.toml    |  1 -
 examples/coap/src/main.rs   | 89 +++++++++++++++++--------------------
 src/lib/coapcore/Cargo.toml |  8 ++++
 src/lib/coapcore/src/lib.rs | 42 +++++++++++++++--
 5 files changed, 90 insertions(+), 55 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index d78519177..0a9af9bd2 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -449,7 +449,6 @@ dependencies = [
  "coap-scroll-ring-server",
  "coapcore",
  "embassy-executor",
- "embassy-futures",
  "embassy-net",
  "embassy-time",
  "embedded-io-async",
@@ -598,6 +597,9 @@ dependencies = [
  "coap-message-implementations",
  "coap-message-utils",
  "coap-numbers",
+ "embassy-futures",
+ "embedded-nal-async",
+ "embedded-nal-coap",
  "heapless 0.8.0",
  "hexlit",
  "lakers",
@@ -605,6 +607,7 @@ dependencies = [
  "liboscore",
  "liboscore-msgbackend",
  "minicbor 0.23.0",
+ "rand_core",
 ]
 
 [[package]]
diff --git a/examples/coap/Cargo.toml b/examples/coap/Cargo.toml
index 6db682ec5..b6dc44ca3 100644
--- a/examples/coap/Cargo.toml
+++ b/examples/coap/Cargo.toml
@@ -28,7 +28,6 @@ smoltcp = { version = "0.11", default-features = false }
 embedded-nal-coap = "0.1.0-alpha.2"
 coap-request = "0.2.0-alpha.2"
 coap-message = "0.3.2"
-embassy-futures = "0.1.1"
 coap-message-demos = { version = "0.4.0", default-features = false }
 coap-request-implementations = "0.1.0-alpha.4"
 lakers = { version = "0.6.0", default-features = false }
diff --git a/examples/coap/src/main.rs b/examples/coap/src/main.rs
index 201a9806d..c7ec871ad 100644
--- a/examples/coap/src/main.rs
+++ b/examples/coap/src/main.rs
@@ -107,57 +107,48 @@ where
 
     println!("Server is ready.");
 
-    let coap = embedded_nal_coap::CoAPShared::<3>::new();
-    let (client, server) = coap.split();
-
-    // going with an embassy_futures join instead of an async_std::task::spawn b/c CoAPShared is not
-    // Sync, and async_std expects to work in multiple threads
-    embassy_futures::join::join(
-        async {
-            server
-                .run(&mut sock, &mut handler, &mut riot_rs::random::fast_rng())
-                .await
-                .expect("UDP error")
-        },
-        run_client_operations(client),
-    )
-    .await;
+    // FIXME: We may want to have a very slim wrapper around this for riot-rs that provides our RNG
+    // … or maybe less slim and it handles the sock creation as well.
+    let mut rng = riot_rs::random::fast_rng();
+    coapcore::coap_task(&mut sock, &mut handler, &mut rng, Client).await;
 }
 
-/// In parallel to server operation, this function performs some operations as a client.
-///
-/// This doubles as an experimentation ground for the client side of embedded_nal_coap and
-/// coap-request in general.
-async fn run_client_operations<const N: usize>(
-    client: embedded_nal_coap::CoAPRuntimeClient<'_, N>,
-) {
-    // shame
-    let demoserver = "10.42.0.1:1234".parse().unwrap();
-
-    use coap_request::Stack;
-    println!("Sending GET to {}...", demoserver);
-    let response = client
-        .to(demoserver)
-        .request(
-            coap_request_implementations::Code::get()
-                .with_path("/other/separate")
+struct Client;
+
+impl coapcore::ClientRunner<3> for Client {
+    /// In parallel to server operation, this function performs some operations as a client.
+    ///
+    /// This doubles as an experimentation ground for the client side of embedded_nal_coap and
+    /// coap-request in general.
+    async fn run(self, client: embedded_nal_coap::CoAPRuntimeClient<'_, 3>) {
+        // shame
+        let demoserver = "10.42.0.1:1234".parse().unwrap();
+
+        use coap_request::Stack;
+        println!("Sending GET to {}...", demoserver);
+        let response = client
+            .to(demoserver)
+            .request(
+                coap_request_implementations::Code::get()
+                    .with_path("/other/separate")
+                    .processing_response_payload_through(|p| {
+                        println!("Got payload {:?}", p);
+                    }),
+            )
+            .await;
+        println!("Response {:?}", response);
+
+        let req = coap_request_implementations::Code::post().with_path("/uppercase");
+
+        println!("Sending POST...");
+        let mut response = client.to(demoserver);
+        let response = response.request(
+            req.with_request_payload_slice(b"Set time to 1955-11-05")
                 .processing_response_payload_through(|p| {
-                    println!("Got payload {:?}", p);
+                    println!("Uppercase is {}", core::str::from_utf8(p).unwrap())
                 }),
-        )
-        .await;
-    println!("Response {:?}", response);
-
-    let req = coap_request_implementations::Code::post().with_path("/uppercase");
-
-    println!("Sending POST...");
-    let mut response = client.to(demoserver);
-    let response = response.request(
-        req.with_request_payload_slice(b"Set time to 1955-11-05")
-            .processing_response_payload_through(|p| {
-                println!("Uppercase is {}", core::str::from_utf8(p).unwrap())
-            }),
-    );
-    let response = response.await;
-    println!("Response {:?}", response);
+        );
+        let response = response.await;
+        println!("Response {:?}", response);
+    }
 }
diff --git a/src/lib/coapcore/Cargo.toml b/src/lib/coapcore/Cargo.toml
index 3b7f3a113..1fbd868bf 100644
--- a/src/lib/coapcore/Cargo.toml
+++ b/src/lib/coapcore/Cargo.toml
@@ -14,7 +14,14 @@ description = "A CoAP stack for embedded devices with built-in OSCORE/EDHOC supp
 # public
 coap-handler = "0.2.0"
 coap-message = "0.3.2"
+# public because we take a credential
 lakers = { version = "0.6.0", default-features = false }
+# public because the callback provides a type from there
+embedded-nal-coap = "0.1.0-alpha.2"
+# public because we take a socket
+embedded-nal-async = "0.7"
+# public because we take a RngCor
+rand_core = "0.6.4"
 
 # private
 arrayvec = { version = "0.7.4", default-features = false }
@@ -29,3 +36,4 @@ liboscore-msgbackend = { git = "https://gitlab.com/oscore/liboscore/", features
 ], rev = "e7a4ecd037cbb9c7f085047fec5896f4bdc68d50" }
 minicbor = "0.23.0"
 heapless = "0.8.0"
+embassy-futures = "0.1.1"
diff --git a/src/lib/coapcore/src/lib.rs b/src/lib/coapcore/src/lib.rs
index 049a19300..0b0470546 100644
--- a/src/lib/coapcore/src/lib.rs
+++ b/src/lib/coapcore/src/lib.rs
@@ -5,11 +5,9 @@
 //! the application as an `embedded-nal` socket, and processes CoAP along with its security
 //! components OSCORE and EDHOC before passing on authorized requests to the application.
 //!
-//! The crate is under heavy development: Its API is in flux, and so far it does not yet provide
-//! the CoAP server itself, but merely a middleware. (Providing the full CoAP will be a requirement
-//! for at least as long as the OSCORE component is tightly coupled to a particular implementation
-//! of [`coap-message`]).
+//! The crate is under heavy development.
 #![no_std]
+#![feature(lint_reasons)]
 
 // Might warrant a standalone crate at some point
 //
@@ -17,3 +15,39 @@
 // anyway)
 pub mod oluru;
 pub mod seccontext;
+
+// This is a trait because I haven't managed to work out any lifetimes for a single client
+// callback; tried
+// pub async fn coap_task<ClientOps, ClientFuture>(
+//     sock: &mut impl embedded_nal_async::UnconnectedUdp,
+//     handler: &mut impl coap_handler::Handler,
+//     rng: &mut impl rand_core::RngCore,
+//     run_client_operations: ClientOps,
+// ) where
+//     for<'a> ClientOps: Fn(embedded_nal_coap::CoAPRuntimeClient<'a, 3>) -> ClientFuture,
+//     ClientFuture: core::future::Future<Output = ()>,
+// {
+// which typechecks on its own, but won't take a static async fn (or closure that returns an async
+// block) as input.
+pub trait ClientRunner<const N: usize> {
+    #[allow(async_fn_in_trait, reason = "We explicitly expect this to not be send")]
+    async fn run(self, client: embedded_nal_coap::CoAPRuntimeClient<'_, N>);
+}
+
+pub async fn coap_task<const N: usize>(
+    sock: &mut impl embedded_nal_async::UnconnectedUdp,
+    handler: &mut impl coap_handler::Handler,
+    rng: &mut impl rand_core::RngCore,
+    client_runner: impl ClientRunner<N>,
+) {
+    let coap = embedded_nal_coap::CoAPShared::<N>::new();
+    let (client, server) = coap.split();
+
+    // going with an embassy_futures join instead of an async_std::task::spawn b/c CoAPShared is not
+    // Sync, and async_std expects to work in multiple threads
+    embassy_futures::join::join(
+        async { server.run(sock, handler, rng).await.expect("UDP error") },
+        client_runner.run(client),
+    )
+    .await;
+}

From 65021053233e4f8dd68ee16437819a3a5580cff6 Mon Sep 17 00:00:00 2001
From: chrysn <chrysn@fsfe.org>
Date: Tue, 2 Jul 2024 22:46:15 +0200
Subject: [PATCH 02/10] fix(coap): Minor lint fixes

---
 examples/coap/src/main.rs          | 2 +-
 examples/coap/src/udp_nal/mod.rs   | 2 +-
 src/lib/coapcore/src/seccontext.rs | 3 ++-
 3 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/examples/coap/src/main.rs b/examples/coap/src/main.rs
index c7ec871ad..253ce43f9 100644
--- a/examples/coap/src/main.rs
+++ b/examples/coap/src/main.rs
@@ -94,7 +94,7 @@ where
         R,
         );
 
-    let mut handler = coap_message_demos::full_application_tree(log)
+    let handler = coap_message_demos::full_application_tree(log)
         .at(
             &["stdout"],
             coap_scroll_ring_server::BufferHandler::new(&buffer),
diff --git a/examples/coap/src/udp_nal/mod.rs b/examples/coap/src/udp_nal/mod.rs
index bd0ad3871..8464ef08b 100644
--- a/examples/coap/src/udp_nal/mod.rs
+++ b/examples/coap/src/udp_nal/mod.rs
@@ -78,7 +78,7 @@ impl<'a> ConnectedUdp<'a> {
     /// unconnected.
     pub async fn connect(socket: udp::UdpSocket<'a>, /*, ... */) -> Result<Self, udp::BindError> {
         // This is really just a copy of the provided `embedded_nal::udp::UdpStack::connect` method
-        todo!()
+        todo!("use {:p}", &socket)
     }
 }
 
diff --git a/src/lib/coapcore/src/seccontext.rs b/src/lib/coapcore/src/seccontext.rs
index 396c75786..e4d1f5d84 100644
--- a/src/lib/coapcore/src/seccontext.rs
+++ b/src/lib/coapcore/src/seccontext.rs
@@ -615,7 +615,8 @@ impl<'a, H: coap_handler::Handler, L: Write, Crypto: lakers::Crypto> coap_handle
                                 self.log,
                                 "Got credential by value: {:?}..",
                                 &id_cred_i.value.get_slice(0, 5)
-                            );
+                            )
+                            .unwrap();
 
                             cred_i = lakers::CredentialRPK::new(id_cred_i.value)
                                 // FIXME What kind of error do we send here?

From 30f1716e9abdf10f2982b9561b9b03ca4a31e1e4 Mon Sep 17 00:00:00 2001
From: chrysn <chrysn@fsfe.org>
Date: Wed, 3 Jul 2024 10:23:44 +0200
Subject: [PATCH 03/10] build: Add riot-rs{-,::}coap

---
 Cargo.lock                  |  8 ++++++++
 Cargo.toml                  |  1 +
 examples/coap/Cargo.toml    |  2 ++
 src/riot-rs-coap/Cargo.toml | 12 ++++++++++++
 src/riot-rs-coap/src/lib.rs |  8 ++++++++
 src/riot-rs/Cargo.toml      |  3 +++
 src/riot-rs/src/lib.rs      |  3 +++
 7 files changed, 37 insertions(+)
 create mode 100644 src/riot-rs-coap/Cargo.toml
 create mode 100644 src/riot-rs-coap/src/lib.rs

diff --git a/Cargo.lock b/Cargo.lock
index 0a9af9bd2..f31af7d0b 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -3363,6 +3363,7 @@ dependencies = [
  "linkme",
  "riot-rs-bench",
  "riot-rs-boards",
+ "riot-rs-coap",
  "riot-rs-debug",
  "riot-rs-embassy",
  "riot-rs-macros",
@@ -3409,6 +3410,13 @@ dependencies = [
  "stm32f4xx",
 ]
 
+[[package]]
+name = "riot-rs-coap"
+version = "0.1.0"
+dependencies = [
+ "coapcore",
+]
+
 [[package]]
 name = "riot-rs-debug"
 version = "0.1.0"
diff --git a/Cargo.toml b/Cargo.toml
index 3a2bdbe24..a1256adc2 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -12,6 +12,7 @@ members = [
   "src/riot-rs-boards/nrf52840dk",
   "src/riot-rs-boards/nucleo-f401re",
   "src/riot-rs-chips",
+  "src/riot-rs-coap",
   "src/riot-rs-debug",
   "src/riot-rs-macros",
   "src/riot-rs-random",
diff --git a/examples/coap/Cargo.toml b/examples/coap/Cargo.toml
index b6dc44ca3..f20f8105a 100644
--- a/examples/coap/Cargo.toml
+++ b/examples/coap/Cargo.toml
@@ -13,6 +13,8 @@ embedded-io-async = "0.6.1"
 heapless = { workspace = true }
 riot-rs = { path = "../../src/riot-rs", features = [
   "override-network-config",
+  "coap",
+  # to be removed later once coap pulls them in
   "random",
   "csprng",
 ] }
diff --git a/src/riot-rs-coap/Cargo.toml b/src/riot-rs-coap/Cargo.toml
new file mode 100644
index 000000000..cfd8900b6
--- /dev/null
+++ b/src/riot-rs-coap/Cargo.toml
@@ -0,0 +1,12 @@
+[package]
+name = "riot-rs-coap"
+version.workspace = true
+authors.workspace = true
+edition.workspace = true
+repository.workspace = true
+
+[dependencies]
+coapcore.path = "../lib/coapcore"
+
+[lints]
+workspace = true
diff --git a/src/riot-rs-coap/src/lib.rs b/src/riot-rs-coap/src/lib.rs
new file mode 100644
index 000000000..04ead5746
--- /dev/null
+++ b/src/riot-rs-coap/src/lib.rs
@@ -0,0 +1,8 @@
+//! A CoAP stack preconfigured for RIOT-rs
+//! ======================================
+//!
+//! This crate mainly provides easy-to-use wrappers around the [`coapcore`] crate, with presets
+//! tailored towards RIOT-rs: It utilizes [`embassy-net`] to open a network accessible CoAP socket,
+//! [`riot-rs-random`] as a source of randomness, and [`lakers-crypto-rustcrypto`] for the
+//! cryptographic algorithm implementations.
+#![no_std]
diff --git a/src/riot-rs/Cargo.toml b/src/riot-rs/Cargo.toml
index 9b3154651..1e453af32 100644
--- a/src/riot-rs/Cargo.toml
+++ b/src/riot-rs/Cargo.toml
@@ -12,6 +12,7 @@ document-features = { workspace = true }
 linkme = { workspace = true }
 riot-rs-bench = { workspace = true, optional = true }
 riot-rs-boards = { path = "../riot-rs-boards" }
+riot-rs-coap = { path = "../riot-rs-coap", optional = true }
 riot-rs-debug = { workspace = true }
 riot-rs-embassy = { path = "../riot-rs-embassy" }
 riot-rs-macros = { path = "../riot-rs-macros" }
@@ -40,6 +41,8 @@ random = ["riot-rs-random"]
 csprng = ["riot-rs-random/csprng"]
 ## Enables seeding the random number generator from hardware.
 hwrng = ["riot-rs-embassy/hwrng"]
+## Enables the [`coap`] module
+coap = ["riot-rs-coap", "random", "csprng"]
 
 #! ## Wired communication
 ## Enables USB support.
diff --git a/src/riot-rs/src/lib.rs b/src/riot-rs/src/lib.rs
index a9093d316..564131e1f 100644
--- a/src/riot-rs/src/lib.rs
+++ b/src/riot-rs/src/lib.rs
@@ -16,6 +16,9 @@ pub mod buildinfo;
 #[cfg(feature = "bench")]
 #[doc(inline)]
 pub use riot_rs_bench as bench;
+#[cfg(feature = "coap")]
+#[doc(inline)]
+pub use riot_rs_coap as coap;
 #[doc(inline)]
 pub use riot_rs_debug as debug;
 #[doc(inline)]

From 09a3cb05ce2df2bb22cee46df03064425f05e8af Mon Sep 17 00:00:00 2001
From: chrysn <chrysn@fsfe.org>
Date: Wed, 3 Jul 2024 10:44:27 +0200
Subject: [PATCH 04/10] refactor: Move CoAP stack setup into riot-rs-coap
 module

The security setup is not moved in yet.

Choices of address families are propagated into smoltcp to avoid
mismatches.
---
 Cargo.lock                                    | 10 ++--
 examples/coap/Cargo.toml                      | 12 -----
 examples/coap/src/main.rs                     | 51 ++-----------------
 src/riot-rs-coap/Cargo.toml                   | 20 ++++++++
 src/riot-rs-coap/src/lib.rs                   | 37 ++++++++++++++
 .../riot-rs-coap}/src/udp_nal/mod.rs          |  2 +-
 .../riot-rs-coap}/src/udp_nal/util.rs         |  2 +-
 7 files changed, 71 insertions(+), 63 deletions(-)
 rename {examples/coap => src/riot-rs-coap}/src/udp_nal/mod.rs (99%)
 rename {examples/coap => src/riot-rs-coap}/src/udp_nal/util.rs (99%)

diff --git a/Cargo.lock b/Cargo.lock
index f31af7d0b..b283186f7 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -451,8 +451,6 @@ dependencies = [
  "embassy-executor",
  "embassy-net",
  "embassy-time",
- "embedded-io-async",
- "embedded-nal-async",
  "embedded-nal-coap",
  "heapless 0.8.0",
  "hexlit",
@@ -461,7 +459,6 @@ dependencies = [
  "riot-rs",
  "riot-rs-boards",
  "scroll-ring",
- "smoltcp",
  "static-alloc",
 ]
 
@@ -3414,7 +3411,14 @@ dependencies = [
 name = "riot-rs-coap"
 version = "0.1.0"
 dependencies = [
+ "coap-handler",
  "coapcore",
+ "embedded-io-async",
+ "embedded-nal-async",
+ "embedded-nal-coap",
+ "riot-rs-embassy",
+ "riot-rs-random",
+ "smoltcp",
 ]
 
 [[package]]
diff --git a/examples/coap/Cargo.toml b/examples/coap/Cargo.toml
index f20f8105a..5bcfa7d15 100644
--- a/examples/coap/Cargo.toml
+++ b/examples/coap/Cargo.toml
@@ -9,7 +9,6 @@ publish = false
 embassy-executor = { workspace = true, default-features = false }
 embassy-net = { workspace = true, features = ["udp"] }
 embassy-time = { workspace = true, default-features = false }
-embedded-io-async = "0.6.1"
 heapless = { workspace = true }
 riot-rs = { path = "../../src/riot-rs", features = [
   "override-network-config",
@@ -22,11 +21,6 @@ riot-rs-boards = { path = "../../src/riot-rs-boards" }
 
 coapcore.path = "../../src/lib/coapcore/"
 
-# for the udp_nal mod
-embedded-nal-async = "0.7"
-# actually patched with https://github.com/smoltcp-rs/smoltcp/pull/904 but
-# patch.crates-io takes care of that
-smoltcp = { version = "0.11", default-features = false }
 embedded-nal-coap = "0.1.0-alpha.2"
 coap-request = "0.2.0-alpha.2"
 coap-message = "0.3.2"
@@ -41,9 +35,3 @@ hexlit = "0.5.5"
 static-alloc = "0.2.5"
 coap-scroll-ring-server = "0.2.0"
 scroll-ring = "0.1.1"
-
-[features]
-default = ["proto-ipv4"] # shame
-# actually embedded-nal features, we have to match them here while developing udp_nal in here
-proto-ipv4 = []
-proto-ipv6 = []
diff --git a/examples/coap/src/main.rs b/examples/coap/src/main.rs
index 253ce43f9..bb2d89c56 100644
--- a/examples/coap/src/main.rs
+++ b/examples/coap/src/main.rs
@@ -5,10 +5,7 @@
 
 use riot_rs::{debug::println, embassy::network};
 
-use embassy_net::udp::{PacketMetadata, UdpSocket};
-
-// Moving work from https://github.com/embassy-rs/embassy/pull/2519 in here for the time being
-mod udp_nal;
+use riot_rs::embassy::embassy_net;
 
 use coapcore::seccontext;
 
@@ -19,36 +16,6 @@ use static_alloc::Bump;
 #[global_allocator]
 static A: Bump<[u8; 1 << 16]> = Bump::uninit();
 
-#[riot_rs::task(autostart)]
-async fn coap_run() {
-    let stack = network::network_stack().await.unwrap();
-
-    // FIXME trim to CoAP requirements
-    let mut rx_meta = [PacketMetadata::EMPTY; 16];
-    let mut rx_buffer = [0; 4096];
-    let mut tx_meta = [PacketMetadata::EMPTY; 16];
-    let mut tx_buffer = [0; 4096];
-
-    let socket = UdpSocket::new(
-        stack,
-        &mut rx_meta,
-        &mut rx_buffer,
-        &mut tx_meta,
-        &mut tx_buffer,
-    );
-
-    println!("Starting up CoAP server");
-
-    // Can't that even bind to the Any address??
-    // let local_any = "0.0.0.0:5683".parse().unwrap(); // shame
-    let local_any = "10.42.0.61:5683".parse().unwrap(); // shame
-    let unconnected = udp_nal::UnconnectedUdp::bind_multiple(socket, local_any)
-        .await
-        .unwrap();
-
-    run(unconnected).await;
-}
-
 // FIXME: So far, this is necessary boiler plate; see ../README.md#networking for details
 #[riot_rs::config(network)]
 fn network_config() -> embassy_net::Config {
@@ -61,15 +28,10 @@ fn network_config() -> embassy_net::Config {
     })
 }
 
-// Rest is from coap-message-demos/examples/std_embedded_nal_coap.rs
+// This is adjusted from coap-message-demos/examples/std_embedded_nal_coap.rs
 
-/// This function works on *any* UdpFullStack, including embedded ones -- only main() is what makes
-/// this use POSIX sockets. (It does make use of a std based RNG, but that could be passed in just
-/// as well for no_std operation).
-async fn run<S>(mut sock: S)
-where
-    S: embedded_nal_async::UnconnectedUdp,
-{
+#[riot_rs::task(autostart)]
+async fn run() {
     use coap_handler_implementations::{HandlerBuilder, ReportingHandlerBuilder};
 
     let log = None;
@@ -107,10 +69,7 @@ where
 
     println!("Server is ready.");
 
-    // FIXME: We may want to have a very slim wrapper around this for riot-rs that provides our RNG
-    // … or maybe less slim and it handles the sock creation as well.
-    let mut rng = riot_rs::random::fast_rng();
-    coapcore::coap_task(&mut sock, &mut handler, &mut rng, Client).await;
+    riot_rs::coap::coap_task(&mut handler, Client).await;
 }
 
 struct Client;
diff --git a/src/riot-rs-coap/Cargo.toml b/src/riot-rs-coap/Cargo.toml
index cfd8900b6..513d08cfb 100644
--- a/src/riot-rs-coap/Cargo.toml
+++ b/src/riot-rs-coap/Cargo.toml
@@ -7,6 +7,26 @@ repository.workspace = true
 
 [dependencies]
 coapcore.path = "../lib/coapcore"
+riot-rs-random.path = "../riot-rs-random"
+riot-rs-embassy.path = "../riot-rs-embassy"
+
+# actually patched with https://github.com/smoltcp-rs/smoltcp/pull/904 but
+# patch.crates-io takes care of that
+smoltcp = { version = "0.11", default-features = false }
+
+embedded-nal-coap = "0.1.0-alpha.2"
+coap-handler = "0.2.0"
+
+# for the udp_nal mod
+embedded-nal-async = "0.7"
+embedded-io-async = "0.6.1"
 
 [lints]
 workspace = true
+
+[features]
+# all for udp_nal
+default = ["proto-ipv4"] # shame
+# actually embedded-nal features, we have to match them here while developing udp_nal in here
+proto-ipv4 = ["smoltcp/proto-ipv4"]
+proto-ipv6 = ["smoltcp/proto-ipv6"]
diff --git a/src/riot-rs-coap/src/lib.rs b/src/riot-rs-coap/src/lib.rs
index 04ead5746..2bb6c3f82 100644
--- a/src/riot-rs-coap/src/lib.rs
+++ b/src/riot-rs-coap/src/lib.rs
@@ -6,3 +6,40 @@
 //! [`riot-rs-random`] as a source of randomness, and [`lakers-crypto-rustcrypto`] for the
 //! cryptographic algorithm implementations.
 #![no_std]
+
+// Moving work from https://github.com/embassy-rs/embassy/pull/2519 in here for the time being
+mod udp_nal;
+
+use riot_rs_embassy::embassy_net::udp::{PacketMetadata, UdpSocket};
+
+pub async fn coap_task<const N: usize>(
+    handler: &mut impl coap_handler::Handler,
+    client_runner: impl coapcore::ClientRunner<N>,
+) {
+    let stack = riot_rs_embassy::network::network_stack().await.unwrap();
+
+    // FIXME trim to CoAP requirements
+    let mut rx_meta = [PacketMetadata::EMPTY; 16];
+    let mut rx_buffer = [0; 4096];
+    let mut tx_meta = [PacketMetadata::EMPTY; 16];
+    let mut tx_buffer = [0; 4096];
+
+    let socket = UdpSocket::new(
+        stack,
+        &mut rx_meta,
+        &mut rx_buffer,
+        &mut tx_meta,
+        &mut tx_buffer,
+    );
+
+    // Can't that even bind to the Any address??
+    // let local_any = "0.0.0.0:5683".parse().unwrap(); // shame
+    let local_any = "10.42.0.61:5683".parse().unwrap(); // shame
+    let mut sock = udp_nal::UnconnectedUdp::bind_multiple(socket, local_any)
+        .await
+        .unwrap();
+
+    let mut rng = riot_rs_random::fast_rng();
+
+    coapcore::coap_task(&mut sock, handler, &mut rng, client_runner).await;
+}
diff --git a/examples/coap/src/udp_nal/mod.rs b/src/riot-rs-coap/src/udp_nal/mod.rs
similarity index 99%
rename from examples/coap/src/udp_nal/mod.rs
rename to src/riot-rs-coap/src/udp_nal/mod.rs
index 8464ef08b..b468933b3 100644
--- a/examples/coap/src/udp_nal/mod.rs
+++ b/src/riot-rs-coap/src/udp_nal/mod.rs
@@ -21,7 +21,7 @@ use core::future::poll_fn;
 use embedded_nal_async as nal;
 use smoltcp::wire::{IpAddress, IpEndpoint};
 
-use embassy_net::udp;
+use riot_rs_embassy::embassy_net::udp;
 
 mod util;
 pub use util::Error;
diff --git a/examples/coap/src/udp_nal/util.rs b/src/riot-rs-coap/src/udp_nal/util.rs
similarity index 99%
rename from examples/coap/src/udp_nal/util.rs
rename to src/riot-rs-coap/src/udp_nal/util.rs
index fc8b532f4..5c0e0a3a6 100644
--- a/examples/coap/src/udp_nal/util.rs
+++ b/src/riot-rs-coap/src/udp_nal/util.rs
@@ -1,7 +1,7 @@
 //! Helpers for udp_nal -- conversion and error types
 
-use embassy_net::udp;
 use embedded_nal_async as nal;
+use riot_rs_embassy::embassy_net::udp;
 use smoltcp::wire::{IpAddress, IpEndpoint};
 
 pub(super) fn sockaddr_nal2smol(sockaddr: nal::SocketAddr) -> Result<IpEndpoint, Error> {

From bf57daf810a5102153c5d69611578ff06b10bb6b Mon Sep 17 00:00:00 2001
From: chrysn <chrysn@fsfe.org>
Date: Wed, 3 Jul 2024 10:56:59 +0200
Subject: [PATCH 05/10] refactor(coap): Move crypto setup into riot-rs-coap

---
 Cargo.lock                  |  6 +++---
 examples/coap/Cargo.toml    |  3 ---
 examples/coap/src/main.rs   | 17 ++---------------
 src/riot-rs-coap/Cargo.toml |  5 ++++-
 src/riot-rs-coap/src/lib.rs | 18 ++++++++++++++++--
 5 files changed, 25 insertions(+), 24 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index b283186f7..7e5045982 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -453,9 +453,6 @@ dependencies = [
  "embassy-time",
  "embedded-nal-coap",
  "heapless 0.8.0",
- "hexlit",
- "lakers",
- "lakers-crypto-rustcrypto",
  "riot-rs",
  "riot-rs-boards",
  "scroll-ring",
@@ -3416,6 +3413,9 @@ dependencies = [
  "embedded-io-async",
  "embedded-nal-async",
  "embedded-nal-coap",
+ "hexlit",
+ "lakers",
+ "lakers-crypto-rustcrypto",
  "riot-rs-embassy",
  "riot-rs-random",
  "smoltcp",
diff --git a/examples/coap/Cargo.toml b/examples/coap/Cargo.toml
index 5bcfa7d15..5cb825b89 100644
--- a/examples/coap/Cargo.toml
+++ b/examples/coap/Cargo.toml
@@ -26,11 +26,8 @@ coap-request = "0.2.0-alpha.2"
 coap-message = "0.3.2"
 coap-message-demos = { version = "0.4.0", default-features = false }
 coap-request-implementations = "0.1.0-alpha.4"
-lakers = { version = "0.6.0", default-features = false }
-lakers-crypto-rustcrypto = "0.6.0"
 coap-handler = "0.2.0"
 coap-handler-implementations = "0.5.0"
-hexlit = "0.5.5"
 
 static-alloc = "0.2.5"
 coap-scroll-ring-server = "0.2.0"
diff --git a/examples/coap/src/main.rs b/examples/coap/src/main.rs
index bb2d89c56..0bb8b83a4 100644
--- a/examples/coap/src/main.rs
+++ b/examples/coap/src/main.rs
@@ -3,12 +3,10 @@
 #![feature(type_alias_impl_trait)]
 #![feature(used_with_arg)]
 
-use riot_rs::{debug::println, embassy::network};
+use riot_rs::debug::println;
 
 use riot_rs::embassy::embassy_net;
 
-use coapcore::seccontext;
-
 // because coapcore depends on it temporarily
 extern crate alloc;
 use static_alloc::Bump;
@@ -49,13 +47,6 @@ async fn run() {
     writeln!(stdout, "We have our own stdout now.").unwrap();
     writeln!(stdout, "With rings and atomics.").unwrap();
 
-    use hexlit::hex;
-    const R: &[u8] = &hex!("72cc4761dbd4c78f758931aa589d348d1ef874a7e303ede2f140dcf3e6aa4aac");
-    let own_identity = (
-        &lakers::CredentialRPK::new(lakers::EdhocMessageBuffer::new_from_slice(&hex!("A2026008A101A5010202410A2001215820BBC34960526EA4D32E940CAD2A234148DDC21791A12AFBCBAC93622046DD44F02258204519E257236B2A0CE2023F0931F1F386CA7AFDA64FCDE0108C224C51EABF6072")).expect("Credential should be small enough")).expect("Credential should be processable"),
-        R,
-        );
-
     let handler = coap_message_demos::full_application_tree(log)
         .at(
             &["stdout"],
@@ -63,13 +54,9 @@ async fn run() {
         )
         .with_wkc();
 
-    let mut handler = seccontext::OscoreEdhocHandler::new(own_identity, handler, stdout, || {
-        lakers_crypto_rustcrypto::Crypto::new(riot_rs::random::crypto_rng())
-    });
-
     println!("Server is ready.");
 
-    riot_rs::coap::coap_task(&mut handler, Client).await;
+    riot_rs::coap::coap_task(handler, Client, &mut stdout).await;
 }
 
 struct Client;
diff --git a/src/riot-rs-coap/Cargo.toml b/src/riot-rs-coap/Cargo.toml
index 513d08cfb..349548b4d 100644
--- a/src/riot-rs-coap/Cargo.toml
+++ b/src/riot-rs-coap/Cargo.toml
@@ -7,7 +7,7 @@ repository.workspace = true
 
 [dependencies]
 coapcore.path = "../lib/coapcore"
-riot-rs-random.path = "../riot-rs-random"
+riot-rs-random = { path = "../riot-rs-random", features = ["csprng"] }
 riot-rs-embassy.path = "../riot-rs-embassy"
 
 # actually patched with https://github.com/smoltcp-rs/smoltcp/pull/904 but
@@ -16,6 +16,9 @@ smoltcp = { version = "0.11", default-features = false }
 
 embedded-nal-coap = "0.1.0-alpha.2"
 coap-handler = "0.2.0"
+hexlit = "0.5.5"
+lakers = { version = "0.6.0", default-features = false }
+lakers-crypto-rustcrypto = "0.6.0"
 
 # for the udp_nal mod
 embedded-nal-async = "0.7"
diff --git a/src/riot-rs-coap/src/lib.rs b/src/riot-rs-coap/src/lib.rs
index 2bb6c3f82..1bb26a679 100644
--- a/src/riot-rs-coap/src/lib.rs
+++ b/src/riot-rs-coap/src/lib.rs
@@ -12,9 +12,12 @@ mod udp_nal;
 
 use riot_rs_embassy::embassy_net::udp::{PacketMetadata, UdpSocket};
 
+use coapcore::seccontext;
+
 pub async fn coap_task<const N: usize>(
-    handler: &mut impl coap_handler::Handler,
+    handler: impl coap_handler::Handler,
     client_runner: impl coapcore::ClientRunner<N>,
+    logger: &mut impl core::fmt::Write,
 ) {
     let stack = riot_rs_embassy::network::network_stack().await.unwrap();
 
@@ -41,5 +44,16 @@ pub async fn coap_task<const N: usize>(
 
     let mut rng = riot_rs_random::fast_rng();
 
-    coapcore::coap_task(&mut sock, handler, &mut rng, client_runner).await;
+    use hexlit::hex;
+    const R: &[u8] = &hex!("72cc4761dbd4c78f758931aa589d348d1ef874a7e303ede2f140dcf3e6aa4aac");
+    let own_identity = (
+        &lakers::CredentialRPK::new(lakers::EdhocMessageBuffer::new_from_slice(&hex!("A2026008A101A5010202410A2001215820BBC34960526EA4D32E940CAD2A234148DDC21791A12AFBCBAC93622046DD44F02258204519E257236B2A0CE2023F0931F1F386CA7AFDA64FCDE0108C224C51EABF6072")).expect("Credential should be small enough")).expect("Credential should be processable"),
+        R,
+        );
+
+    let mut handler = seccontext::OscoreEdhocHandler::new(own_identity, handler, logger, || {
+        lakers_crypto_rustcrypto::Crypto::new(riot_rs_random::crypto_rng())
+    });
+
+    coapcore::coap_task(&mut sock, &mut handler, &mut rng, client_runner).await;
 }

From 83d39d953bc18ec800e09d565cb4e17ba5a3bab8 Mon Sep 17 00:00:00 2001
From: chrysn <chrysn@fsfe.org>
Date: Wed, 3 Jul 2024 11:37:43 +0200
Subject: [PATCH 06/10] ci(doc): Enable CoAP module

---
 .github/workflows/build-deploy-docs.yml | 2 +-
 .github/workflows/main.yml              | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/.github/workflows/build-deploy-docs.yml b/.github/workflows/build-deploy-docs.yml
index 1487d1f62..c00738b4c 100644
--- a/.github/workflows/build-deploy-docs.yml
+++ b/.github/workflows/build-deploy-docs.yml
@@ -48,7 +48,7 @@ jobs:
 
       - name: Build rustdoc docs
         run: |
-          cargo doc -p riot-rs --features no-boards,bench,threading,random,csprng,hwrng
+          cargo doc -p riot-rs --features no-boards,bench,threading,random,csprng,hwrng,coap
           echo "<meta http-equiv=\"refresh\" content=\"0; url=riot_rs\">" > target/doc/index.html
           mkdir -p ./_site/dev/docs/api && mv target/doc/* ./_site/dev/docs/api
 
diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 93a87cd13..5fe59ded9 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -141,7 +141,7 @@ jobs:
           args: --verbose --locked --features no-boards -p riot-rs -p riot-rs-boards -p riot-rs-chips -p riot-rs-debug -p riot-rs-embassy -p riot-rs-macros -p riot-rs-random -p riot-rs-rt -p riot-rs-utils
 
       - name: rustdoc
-        run: RUSTDOCFLAGS='-D warnings' cargo doc -p riot-rs --features no-boards,bench,threading,random,csprng,hwrng
+        run: RUSTDOCFLAGS='-D warnings' cargo doc -p riot-rs --features no-boards,bench,threading,random,csprng,hwrng,coap
 
       - name: rustfmt
         run: cargo fmt --check --all

From ed56c4189ec2def9f83b4e4f752b7f4d0d6c366e Mon Sep 17 00:00:00 2001
From: chrysn <chrysn@fsfe.org>
Date: Wed, 3 Jul 2024 13:20:28 +0200
Subject: [PATCH 07/10] fix(coap): Split and simplify example client code to
 avoid unwraps and enhance error handling

---
 examples/coap/src/main.rs | 87 ++++++++++++++++++++++-----------------
 1 file changed, 50 insertions(+), 37 deletions(-)

diff --git a/examples/coap/src/main.rs b/examples/coap/src/main.rs
index 0bb8b83a4..1063f9c97 100644
--- a/examples/coap/src/main.rs
+++ b/examples/coap/src/main.rs
@@ -3,7 +3,7 @@
 #![feature(type_alias_impl_trait)]
 #![feature(used_with_arg)]
 
-use riot_rs::debug::println;
+use core::fmt::Write;
 
 use riot_rs::embassy::embassy_net;
 
@@ -28,22 +28,23 @@ fn network_config() -> embassy_net::Config {
 
 // This is adjusted from coap-message-demos/examples/std_embedded_nal_coap.rs
 
+// FIXME: Why doesn't scroll_ring provide that?
+#[derive(Clone)]
+struct Stdout<'a>(&'a scroll_ring::Buffer<512>);
+impl<'a> Write for Stdout<'a> {
+    fn write_str(&mut self, s: &str) -> Result<(), core::fmt::Error> {
+        self.0.write(s.as_bytes());
+        Ok(())
+    }
+}
+
 #[riot_rs::task(autostart)]
 async fn run() {
     use coap_handler_implementations::{HandlerBuilder, ReportingHandlerBuilder};
 
     let log = None;
     let buffer = scroll_ring::Buffer::<512>::default();
-    // FIXME: Why doesn't scroll_ring provide that?
-    struct Stdout<'a>(&'a scroll_ring::Buffer<512>);
-    impl<'a> core::fmt::Write for Stdout<'a> {
-        fn write_str(&mut self, s: &str) -> Result<(), core::fmt::Error> {
-            self.0.write(s.as_bytes());
-            Ok(())
-        }
-    }
     let mut stdout = Stdout(&buffer);
-    use core::fmt::Write;
     writeln!(stdout, "We have our own stdout now.").unwrap();
     writeln!(stdout, "With rings and atomics.").unwrap();
 
@@ -54,47 +55,59 @@ async fn run() {
         )
         .with_wkc();
 
-    println!("Server is ready.");
+    writeln!(stdout, "Server is ready.").unwrap();
 
-    riot_rs::coap::coap_task(handler, Client, &mut stdout).await;
+    riot_rs::coap::coap_task(handler, Client(stdout.clone()), &mut stdout).await;
 }
 
-struct Client;
+struct Client<'s>(Stdout<'s>);
 
-impl coapcore::ClientRunner<3> for Client {
-    /// In parallel to server operation, this function performs some operations as a client.
-    ///
-    /// This doubles as an experimentation ground for the client side of embedded_nal_coap and
-    /// coap-request in general.
-    async fn run(self, client: embedded_nal_coap::CoAPRuntimeClient<'_, 3>) {
+impl<'s> Client<'s> {
+    async fn run_logging(
+        mut self,
+        client: embedded_nal_coap::CoAPRuntimeClient<'_, 3>,
+    ) -> Result<(), &'static str> {
         // shame
-        let demoserver = "10.42.0.1:1234".parse().unwrap();
+        let demoserver = "10.42.0.1:1234"
+            .parse()
+            .map_err(|_| "Error parsing demo server address")?;
 
         use coap_request::Stack;
-        println!("Sending GET to {}...", demoserver);
+        writeln!(self.0, "Sending GET to {}...", demoserver).unwrap();
+
         let response = client
             .to(demoserver)
             .request(
                 coap_request_implementations::Code::get()
                     .with_path("/other/separate")
                     .processing_response_payload_through(|p| {
-                        println!("Got payload {:?}", p);
+                        writeln!(
+                            self.0,
+                            "Got payload {:?} length {}",
+                            &p[..core::cmp::min(10, p.len())],
+                            p.len()
+                        )
+                        .unwrap();
                     }),
             )
-            .await;
-        println!("Response {:?}", response);
-
-        let req = coap_request_implementations::Code::post().with_path("/uppercase");
-
-        println!("Sending POST...");
-        let mut response = client.to(demoserver);
-        let response = response.request(
-            req.with_request_payload_slice(b"Set time to 1955-11-05")
-                .processing_response_payload_through(|p| {
-                    println!("Uppercase is {}", core::str::from_utf8(p).unwrap())
-                }),
-        );
-        let response = response.await;
-        println!("Response {:?}", response);
+            .await
+            .map_err(|_| "Error while trying to GET /other/separate")?;
+        writeln!(self.0, "Response {:?}", response).unwrap();
+
+        Ok(())
+    }
+}
+
+impl<'s> coapcore::ClientRunner<3> for Client<'s> {
+    /// In parallel to server operation, this function performs some operations as a client.
+    ///
+    /// This doubles as an experimentation ground for the client side of embedded_nal_coap and
+    /// coap-request in general.
+    async fn run(self, client: embedded_nal_coap::CoAPRuntimeClient<'_, 3>) {
+        let mut stdout = self.0.clone();
+        match self.run_logging(client).await {
+            Ok(_) => writeln!(stdout, "Client process completed").unwrap(),
+            Err(e) => writeln!(stdout, "Client process erred out: {e}").unwrap(),
+        }
     }
 }

From 000d917f090a41575df328c194131c6831703a64 Mon Sep 17 00:00:00 2001
From: chrysn <chrysn@fsfe.org>
Date: Wed, 3 Jul 2024 13:43:06 +0200
Subject: [PATCH 08/10] fix(coap): Restore building with IPv6 enabled

---
 src/riot-rs-coap/src/udp_nal/util.rs | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/riot-rs-coap/src/udp_nal/util.rs b/src/riot-rs-coap/src/udp_nal/util.rs
index 5c0e0a3a6..1048510d3 100644
--- a/src/riot-rs-coap/src/udp_nal/util.rs
+++ b/src/riot-rs-coap/src/udp_nal/util.rs
@@ -39,7 +39,8 @@ pub(super) fn sockaddr_smol2nal(endpoint: IpEndpoint) -> nal::SocketAddr {
         }
         #[cfg(feature = "proto-ipv6")]
         IpAddress::Ipv6(addr) => {
-            embedded_nal_async::SocketAddrV6::new(addr.0.into(), endpoint.port).into()
+            // FIXME: Where is smoltcp's zone identifier?
+            embedded_nal_async::SocketAddrV6::new(addr.0.into(), endpoint.port, 0, 0).into()
         }
     }
 }

From 764adb28f1f72e6b202ddfc62313331ad2812de3 Mon Sep 17 00:00:00 2001
From: chrysn <chrysn@fsfe.org>
Date: Fri, 16 Aug 2024 22:11:25 +0200
Subject: [PATCH 09/10] refactor(coap): Generalize to make buffer size more
 flexible

---
 examples/coap/src/main.rs | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/examples/coap/src/main.rs b/examples/coap/src/main.rs
index 1063f9c97..b3efd412c 100644
--- a/examples/coap/src/main.rs
+++ b/examples/coap/src/main.rs
@@ -30,8 +30,8 @@ fn network_config() -> embassy_net::Config {
 
 // FIXME: Why doesn't scroll_ring provide that?
 #[derive(Clone)]
-struct Stdout<'a>(&'a scroll_ring::Buffer<512>);
-impl<'a> Write for Stdout<'a> {
+struct Stdout<'a, const N: usize>(&'a scroll_ring::Buffer<N>);
+impl<'a, const N: usize> Write for Stdout<'a, N> {
     fn write_str(&mut self, s: &str) -> Result<(), core::fmt::Error> {
         self.0.write(s.as_bytes());
         Ok(())
@@ -60,9 +60,9 @@ async fn run() {
     riot_rs::coap::coap_task(handler, Client(stdout.clone()), &mut stdout).await;
 }
 
-struct Client<'s>(Stdout<'s>);
+struct Client<W: core::fmt::Write + Clone>(W);
 
-impl<'s> Client<'s> {
+impl<W: core::fmt::Write + Clone> Client<W> {
     async fn run_logging(
         mut self,
         client: embedded_nal_coap::CoAPRuntimeClient<'_, 3>,
@@ -98,7 +98,7 @@ impl<'s> Client<'s> {
     }
 }
 
-impl<'s> coapcore::ClientRunner<3> for Client<'s> {
+impl<W: core::fmt::Write + Clone> coapcore::ClientRunner<3> for Client<W> {
     /// In parallel to server operation, this function performs some operations as a client.
     ///
     /// This doubles as an experimentation ground for the client side of embedded_nal_coap and

From 796181a3173e54770a123f7bfa5fd4c825e62dcd Mon Sep 17 00:00:00 2001
From: chrysn <chrysn@fsfe.org>
Date: Fri, 16 Aug 2024 22:23:18 +0200
Subject: [PATCH 10/10] fix(build): Close gaps that resulted in lint stage
 failures

---
 .github/workflows/main.yml     | 2 +-
 src/riot-rs-coap/Cargo.toml    | 2 +-
 src/riot-rs-embassy/Cargo.toml | 4 ++++
 3 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 3384a52dd..7b0be0c01 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -141,7 +141,7 @@ jobs:
           args: --verbose --locked --features no-boards -p riot-rs -p riot-rs-boards -p riot-rs-chips -p riot-rs-debug -p riot-rs-embassy -p riot-rs-macros -p riot-rs-random -p riot-rs-rt -p riot-rs-threads -p riot-rs-utils
 
       - name: rustdoc
-        run: RUSTDOCFLAGS='-D warnings' cargo doc -p riot-rs --features no-boards,bench,external-interrupts,threading,random,csprng,hwrng,coap
+        run: RUSTDOCFLAGS='-D warnings' cargo doc -p riot-rs --features no-boards,bench,external-interrupts,threading,random,csprng,hwrng,coap,net,usb-ethernet
 
       - name: rustfmt
         run: cargo fmt --check --all
diff --git a/src/riot-rs-coap/Cargo.toml b/src/riot-rs-coap/Cargo.toml
index 349548b4d..879925744 100644
--- a/src/riot-rs-coap/Cargo.toml
+++ b/src/riot-rs-coap/Cargo.toml
@@ -8,7 +8,7 @@ repository.workspace = true
 [dependencies]
 coapcore.path = "../lib/coapcore"
 riot-rs-random = { path = "../riot-rs-random", features = ["csprng"] }
-riot-rs-embassy.path = "../riot-rs-embassy"
+riot-rs-embassy = { path = "../riot-rs-embassy", features = ["udp"] }
 
 # actually patched with https://github.com/smoltcp-rs/smoltcp/pull/904 but
 # patch.crates-io takes care of that
diff --git a/src/riot-rs-embassy/Cargo.toml b/src/riot-rs-embassy/Cargo.toml
index 5fe769e15..8d834e4f9 100644
--- a/src/riot-rs-embassy/Cargo.toml
+++ b/src/riot-rs-embassy/Cargo.toml
@@ -166,3 +166,7 @@ defmt = [
 # usb peripheral support.
 stm32-usb = []
 stm32-usb-synopsis = []
+
+# Made available so that downsteram crates such as riot-rs-coap don't need to
+# pull in embassy-net just to enable a feature they use through a pub-use.
+udp = ["net", "embassy-net/udp"]