Merge pull request #1096 from embassy-rs/net-refactor2

net: remove packet pool

12 files changed, 181 insertions, 497 deletions

diff --git a/examples/nrf/Cargo.toml b/examples/nrf/Cargo.toml
index 8b95ac3a6..a980a505c 100644
--- a/examples/nrf/Cargo.toml
+++ b/examples/nrf/Cargo.toml
@@ -16,7 +16,7 @@ embassy-executor = { version = "0.1.0", path = "../../embassy-executor", feature
 embassy-time = { version = "0.1.0", path = "../../embassy-time", features = ["defmt", "defmt-timestamp-uptime"] }
 embassy-nrf = { version = "0.1.0", path = "../../embassy-nrf", features = ["defmt", "nrf52840", "time-driver-rtc1", "gpiote", "unstable-pac"] }
 embassy-net = { version = "0.1.0", path = "../../embassy-net", features = ["defmt", "tcp", "dhcpv4", "medium-ethernet", "pool-16"], optional = true }
-embassy-usb = { version = "0.1.0", path = "../../embassy-usb", features = ["defmt"], optional = true }
+embassy-usb = { version = "0.1.0", path = "../../embassy-usb", features = ["defmt", "embassy-net"], optional = true }
 embedded-io = "0.4.0"
 embassy-lora = { version = "0.1.0", path = "../../embassy-lora", features = ["sx126x", "time", "defmt"], optional = true }
 
diff --git a/examples/nrf/src/bin/usb_ethernet.rs b/examples/nrf/src/bin/usb_ethernet.rs
index de93a2b45..e5f704524 100644
--- a/examples/nrf/src/bin/usb_ethernet.rs
+++ b/examples/nrf/src/bin/usb_ethernet.rs
@@ -3,19 +3,16 @@
 #![feature(type_alias_impl_trait)]
 
 use core::mem;
-use core::sync::atomic::{AtomicBool, Ordering};
-use core::task::Waker;
 
 use defmt::*;
 use embassy_executor::Spawner;
 use embassy_net::tcp::TcpSocket;
-use embassy_net::{PacketBox, PacketBoxExt, PacketBuf, Stack, StackResources};
+use embassy_net::{Stack, StackResources};
 use embassy_nrf::rng::Rng;
 use embassy_nrf::usb::{Driver, PowerUsb};
 use embassy_nrf::{interrupt, pac, peripherals};
-use embassy_sync::blocking_mutex::raw::ThreadModeRawMutex;
-use embassy_sync::channel::Channel;
-use embassy_usb::class::cdc_ncm::{CdcNcmClass, Receiver, Sender, State};
+use embassy_usb::class::cdc_ncm::embassy_net::{Device, Runner, State as NetState};
+use embassy_usb::class::cdc_ncm::{CdcNcmClass, State};
 use embassy_usb::{Builder, Config, UsbDevice};
 use embedded_io::asynch::Write;
 use static_cell::StaticCell;
@@ -27,56 +24,25 @@ macro_rules! singleton {
     ($val:expr) => {{
         type T = impl Sized;
         static STATIC_CELL: StaticCell<T> = StaticCell::new();
-        STATIC_CELL.init_with(move || $val)
+        let (x,) = STATIC_CELL.init(($val,));
+        x
     }};
 }
 
+const MTU: usize = 1514;
+
 #[embassy_executor::task]
 async fn usb_task(mut device: UsbDevice<'static, MyDriver>) -> ! {
     device.run().await
 }
 
 #[embassy_executor::task]
-async fn usb_ncm_rx_task(mut class: Receiver<'static, MyDriver>) {
-    loop {
-        warn!("WAITING for connection");
-        LINK_UP.store(false, Ordering::Relaxed);
-
-        class.wait_connection().await.unwrap();
-
-        warn!("Connected");
-        LINK_UP.store(true, Ordering::Relaxed);
-
-        loop {
-            let mut p = unwrap!(PacketBox::new(embassy_net::Packet::new()));
-            let n = match class.read_packet(&mut p[..]).await {
-                Ok(n) => n,
-                Err(e) => {
-                    warn!("error reading packet: {:?}", e);
-                    break;
-                }
-            };
-
-            let buf = p.slice(0..n);
-            if RX_CHANNEL.try_send(buf).is_err() {
-                warn!("Failed pushing rx'd packet to channel.");
-            }
-        }
-    }
-}
-
-#[embassy_executor::task]
-async fn usb_ncm_tx_task(mut class: Sender<'static, MyDriver>) {
-    loop {
-        let pkt = TX_CHANNEL.recv().await;
-        if let Err(e) = class.write_packet(&pkt[..]).await {
-            warn!("Failed to TX packet: {:?}", e);
-        }
-    }
+async fn usb_ncm_task(class: Runner<'static, MyDriver, MTU>) -> ! {
+    class.run().await
 }
 
 #[embassy_executor::task]
-async fn net_task(stack: &'static Stack<Device>) -> ! {
+async fn net_task(stack: &'static Stack<Device<'static, MTU>>) -> ! {
     stack.run().await
 }
 
@@ -108,55 +74,32 @@ async fn main(spawner: Spawner) {
     config.device_sub_class = 0x02;
     config.device_protocol = 0x01;
 
-    struct Resources {
-        device_descriptor: [u8; 256],
-        config_descriptor: [u8; 256],
-        bos_descriptor: [u8; 256],
-        control_buf: [u8; 128],
-        serial_state: State<'static>,
-    }
-    let res: &mut Resources = singleton!(Resources {
-        device_descriptor: [0; 256],
-        config_descriptor: [0; 256],
-        bos_descriptor: [0; 256],
-        control_buf: [0; 128],
-        serial_state: State::new(),
-    });
-
     // Create embassy-usb DeviceBuilder using the driver and config.
     let mut builder = Builder::new(
         driver,
         config,
-        &mut res.device_descriptor,
-        &mut res.config_descriptor,
-        &mut res.bos_descriptor,
-        &mut res.control_buf,
+        &mut singleton!([0; 256])[..],
+        &mut singleton!([0; 256])[..],
+        &mut singleton!([0; 256])[..],
+        &mut singleton!([0; 128])[..],
         None,
     );
 
-    // WARNINGS for Android ethernet tethering:
-    // - On Pixel 4a, it refused to work on Android 11, worked on Android 12.
-    // - if the host's MAC address has the "locally-administered" bit set (bit 1 of first byte),
-    //   it doesn't work! The "Ethernet tethering" option in settings doesn't get enabled.
-    //   This is due to regex spaghetti: https://android.googlesource.com/platform/frameworks/base/+/refs/tags/android-mainline-12.0.0_r84/core/res/res/values/config.xml#417
-    //   and this nonsense in the linux kernel: https://github.com/torvalds/linux/blob/c00c5e1d157bec0ef0b0b59aa5482eb8dc7e8e49/drivers/net/usb/usbnet.c#L1751-L1757
-
     // Our MAC addr.
     let our_mac_addr = [0xCC, 0xCC, 0xCC, 0xCC, 0xCC, 0xCC];
     // Host's MAC addr. This is the MAC the host "thinks" its USB-to-ethernet adapter has.
     let host_mac_addr = [0x88, 0x88, 0x88, 0x88, 0x88, 0x88];
 
     // Create classes on the builder.
-    let class = CdcNcmClass::new(&mut builder, &mut res.serial_state, host_mac_addr, 64);
+    let class = CdcNcmClass::new(&mut builder, singleton!(State::new()), host_mac_addr, 64);
 
     // Build the builder.
     let usb = builder.build();
 
     unwrap!(spawner.spawn(usb_task(usb)));
 
-    let (tx, rx) = class.split();
-    unwrap!(spawner.spawn(usb_ncm_rx_task(rx)));
-    unwrap!(spawner.spawn(usb_ncm_tx_task(tx)));
+    let (runner, device) = class.into_embassy_net_device::<MTU, 4, 4>(singleton!(NetState::new()), our_mac_addr);
+    unwrap!(spawner.spawn(usb_ncm_task(runner)));
 
     let config = embassy_net::ConfigStrategy::Dhcp;
     //let config = embassy_net::ConfigStrategy::Static(embassy_net::Config {
@@ -172,7 +115,6 @@ async fn main(spawner: Spawner) {
     let seed = u64::from_le_bytes(seed);
 
     // Init network stack
-    let device = Device { mac_addr: our_mac_addr };
     let stack = &*singleton!(Stack::new(
         device,
         config,
@@ -225,50 +167,3 @@ async fn main(spawner: Spawner) {
         }
     }
 }
-
-static TX_CHANNEL: Channel<ThreadModeRawMutex, PacketBuf, 8> = Channel::new();
-static RX_CHANNEL: Channel<ThreadModeRawMutex, PacketBuf, 8> = Channel::new();
-static LINK_UP: AtomicBool = AtomicBool::new(false);
-
-struct Device {
-    mac_addr: [u8; 6],
-}
-
-impl embassy_net::Device for Device {
-    fn register_waker(&mut self, waker: &Waker) {
-        // loopy loopy wakey wakey
-        waker.wake_by_ref()
-    }
-
-    fn link_state(&mut self) -> embassy_net::LinkState {
-        match LINK_UP.load(Ordering::Relaxed) {
-            true => embassy_net::LinkState::Up,
-            false => embassy_net::LinkState::Down,
-        }
-    }
-
-    fn capabilities(&self) -> embassy_net::DeviceCapabilities {
-        let mut caps = embassy_net::DeviceCapabilities::default();
-        caps.max_transmission_unit = 1514; // 1500 IP + 14 ethernet header
-        caps.medium = embassy_net::Medium::Ethernet;
-        caps
-    }
-
-    fn is_transmit_ready(&mut self) -> bool {
-        true
-    }
-
-    fn transmit(&mut self, pkt: PacketBuf) {
-        if TX_CHANNEL.try_send(pkt).is_err() {
-            warn!("TX failed")
-        }
-    }
-
-    fn receive<'a>(&mut self) -> Option<PacketBuf> {
-        RX_CHANNEL.try_recv().ok()
-    }
-
-    fn ethernet_address(&self) -> [u8; 6] {
-        self.mac_addr
-    }
-}
diff --git a/examples/rp/Cargo.toml b/examples/rp/Cargo.toml
index dfbc26426..31a08cfb6 100644
--- a/examples/rp/Cargo.toml
+++ b/examples/rp/Cargo.toml
@@ -10,7 +10,7 @@ embassy-sync = { version = "0.1.0", path = "../../embassy-sync", features = ["de
 embassy-executor = { version = "0.1.0", path = "../../embassy-executor", features = ["defmt", "integrated-timers"] }
 embassy-time = { version = "0.1.0", path = "../../embassy-time", features = ["defmt", "defmt-timestamp-uptime"] }
 embassy-rp = { version = "0.1.0", path = "../../embassy-rp", features = ["defmt", "unstable-traits", "nightly", "unstable-pac", "time-driver", "pio", "critical-section-impl"] }
-embassy-usb = { version = "0.1.0", path = "../../embassy-usb", features = ["defmt"] }
+embassy-usb = { version = "0.1.0", path = "../../embassy-usb", features = ["defmt", "embassy-net"] }
 embassy-net = { version = "0.1.0", path = "../../embassy-net", features = ["defmt", "nightly", "tcp", "dhcpv4", "medium-ethernet", "pool-16"] }
 embassy-futures = { version = "0.1.0", path = "../../embassy-futures" }
 embassy-usb-logger = { version = "0.1.0", path = "../../embassy-usb-logger" }
diff --git a/examples/rp/src/bin/usb_ethernet.rs b/examples/rp/src/bin/usb_ethernet.rs
index 1057fe7fd..d0aec874a 100644
--- a/examples/rp/src/bin/usb_ethernet.rs
+++ b/examples/rp/src/bin/usb_ethernet.rs
@@ -2,18 +2,14 @@
 #![no_main]
 #![feature(type_alias_impl_trait)]
 
-use core::sync::atomic::{AtomicBool, Ordering};
-use core::task::Waker;
-
 use defmt::*;
 use embassy_executor::Spawner;
 use embassy_net::tcp::TcpSocket;
-use embassy_net::{PacketBox, PacketBoxExt, PacketBuf, Stack, StackResources};
+use embassy_net::{Stack, StackResources};
 use embassy_rp::usb::Driver;
 use embassy_rp::{interrupt, peripherals};
-use embassy_sync::blocking_mutex::raw::ThreadModeRawMutex;
-use embassy_sync::channel::Channel;
-use embassy_usb::class::cdc_ncm::{CdcNcmClass, Receiver, Sender, State};
+use embassy_usb::class::cdc_ncm::embassy_net::{Device, Runner, State as NetState};
+use embassy_usb::class::cdc_ncm::{CdcNcmClass, State};
 use embassy_usb::{Builder, Config, UsbDevice};
 use embedded_io::asynch::Write;
 use static_cell::StaticCell;
@@ -25,56 +21,25 @@ macro_rules! singleton {
     ($val:expr) => {{
         type T = impl Sized;
         static STATIC_CELL: StaticCell<T> = StaticCell::new();
-        STATIC_CELL.init_with(move || $val)
+        let (x,) = STATIC_CELL.init(($val,));
+        x
     }};
 }
 
+const MTU: usize = 1514;
+
 #[embassy_executor::task]
 async fn usb_task(mut device: UsbDevice<'static, MyDriver>) -> ! {
     device.run().await
 }
 
 #[embassy_executor::task]
-async fn usb_ncm_rx_task(mut class: Receiver<'static, MyDriver>) {
-    loop {
-        warn!("WAITING for connection");
-        LINK_UP.store(false, Ordering::Relaxed);
-
-        class.wait_connection().await.unwrap();
-
-        warn!("Connected");
-        LINK_UP.store(true, Ordering::Relaxed);
-
-        loop {
-            let mut p = unwrap!(PacketBox::new(embassy_net::Packet::new()));
-            let n = match class.read_packet(&mut p[..]).await {
-                Ok(n) => n,
-                Err(e) => {
-                    warn!("error reading packet: {:?}", e);
-                    break;
-                }
-            };
-
-            let buf = p.slice(0..n);
-            if RX_CHANNEL.try_send(buf).is_err() {
-                warn!("Failed pushing rx'd packet to channel.");
-            }
-        }
-    }
-}
-
-#[embassy_executor::task]
-async fn usb_ncm_tx_task(mut class: Sender<'static, MyDriver>) {
-    loop {
-        let pkt = TX_CHANNEL.recv().await;
-        if let Err(e) = class.write_packet(&pkt[..]).await {
-            warn!("Failed to TX packet: {:?}", e);
-        }
-    }
+async fn usb_ncm_task(class: Runner<'static, MyDriver, MTU>) -> ! {
+    class.run().await
 }
 
 #[embassy_executor::task]
-async fn net_task(stack: &'static Stack<Device>) -> ! {
+async fn net_task(stack: &'static Stack<Device<'static, MTU>>) -> ! {
     stack.run().await
 }
 
@@ -100,55 +65,32 @@ async fn main(spawner: Spawner) {
     config.device_sub_class = 0x02;
     config.device_protocol = 0x01;
 
-    struct Resources {
-        device_descriptor: [u8; 256],
-        config_descriptor: [u8; 256],
-        bos_descriptor: [u8; 256],
-        control_buf: [u8; 128],
-        serial_state: State<'static>,
-    }
-    let res: &mut Resources = singleton!(Resources {
-        device_descriptor: [0; 256],
-        config_descriptor: [0; 256],
-        bos_descriptor: [0; 256],
-        control_buf: [0; 128],
-        serial_state: State::new(),
-    });
-
     // Create embassy-usb DeviceBuilder using the driver and config.
     let mut builder = Builder::new(
         driver,
         config,
-        &mut res.device_descriptor,
-        &mut res.config_descriptor,
-        &mut res.bos_descriptor,
-        &mut res.control_buf,
+        &mut singleton!([0; 256])[..],
+        &mut singleton!([0; 256])[..],
+        &mut singleton!([0; 256])[..],
+        &mut singleton!([0; 128])[..],
         None,
     );
 
-    // WARNINGS for Android ethernet tethering:
-    // - On Pixel 4a, it refused to work on Android 11, worked on Android 12.
-    // - if the host's MAC address has the "locally-administered" bit set (bit 1 of first byte),
-    //   it doesn't work! The "Ethernet tethering" option in settings doesn't get enabled.
-    //   This is due to regex spaghetti: https://android.googlesource.com/platform/frameworks/base/+/refs/tags/android-mainline-12.0.0_r84/core/res/res/values/config.xml#417
-    //   and this nonsense in the linux kernel: https://github.com/torvalds/linux/blob/c00c5e1d157bec0ef0b0b59aa5482eb8dc7e8e49/drivers/net/usb/usbnet.c#L1751-L1757
-
     // Our MAC addr.
     let our_mac_addr = [0xCC, 0xCC, 0xCC, 0xCC, 0xCC, 0xCC];
     // Host's MAC addr. This is the MAC the host "thinks" its USB-to-ethernet adapter has.
     let host_mac_addr = [0x88, 0x88, 0x88, 0x88, 0x88, 0x88];
 
     // Create classes on the builder.
-    let class = CdcNcmClass::new(&mut builder, &mut res.serial_state, host_mac_addr, 64);
+    let class = CdcNcmClass::new(&mut builder, singleton!(State::new()), host_mac_addr, 64);
 
     // Build the builder.
     let usb = builder.build();
 
     unwrap!(spawner.spawn(usb_task(usb)));
 
-    let (tx, rx) = class.split();
-    unwrap!(spawner.spawn(usb_ncm_rx_task(rx)));
-    unwrap!(spawner.spawn(usb_ncm_tx_task(tx)));
+    let (runner, device) = class.into_embassy_net_device::<MTU, 4, 4>(singleton!(NetState::new()), our_mac_addr);
+    unwrap!(spawner.spawn(usb_ncm_task(runner)));
 
     let config = embassy_net::ConfigStrategy::Dhcp;
     //let config = embassy_net::ConfigStrategy::Static(embassy_net::Config {
@@ -161,7 +103,6 @@ async fn main(spawner: Spawner) {
     let seed = 1234; // guaranteed random, chosen by a fair dice roll
 
     // Init network stack
-    let device = Device { mac_addr: our_mac_addr };
     let stack = &*singleton!(Stack::new(
         device,
         config,
@@ -214,50 +155,3 @@ async fn main(spawner: Spawner) {
         }
     }
 }
-
-static TX_CHANNEL: Channel<ThreadModeRawMutex, PacketBuf, 8> = Channel::new();
-static RX_CHANNEL: Channel<ThreadModeRawMutex, PacketBuf, 8> = Channel::new();
-static LINK_UP: AtomicBool = AtomicBool::new(false);
-
-struct Device {
-    mac_addr: [u8; 6],
-}
-
-impl embassy_net::Device for Device {
-    fn register_waker(&mut self, waker: &Waker) {
-        // loopy loopy wakey wakey
-        waker.wake_by_ref()
-    }
-
-    fn link_state(&mut self) -> embassy_net::LinkState {
-        match LINK_UP.load(Ordering::Relaxed) {
-            true => embassy_net::LinkState::Up,
-            false => embassy_net::LinkState::Down,
-        }
-    }
-
-    fn capabilities(&self) -> embassy_net::DeviceCapabilities {
-        let mut caps = embassy_net::DeviceCapabilities::default();
-        caps.max_transmission_unit = 1514; // 1500 IP + 14 ethernet header
-        caps.medium = embassy_net::Medium::Ethernet;
-        caps
-    }
-
-    fn is_transmit_ready(&mut self) -> bool {
-        true
-    }
-
-    fn transmit(&mut self, pkt: PacketBuf) {
-        if TX_CHANNEL.try_send(pkt).is_err() {
-            warn!("TX failed")
-        }
-    }
-
-    fn receive<'a>(&mut self) -> Option<PacketBuf> {
-        RX_CHANNEL.try_recv().ok()
-    }
-
-    fn ethernet_address(&self) -> [u8; 6] {
-        self.mac_addr
-    }
-}
diff --git a/examples/std/src/tuntap.rs b/examples/std/src/tuntap.rs
index a0cace7f7..bb3e194cc 100644
--- a/examples/std/src/tuntap.rs
+++ b/examples/std/src/tuntap.rs
@@ -1,8 +1,10 @@
 use std::io;
 use std::io::{Read, Write};
 use std::os::unix::io::{AsRawFd, RawFd};
+use std::task::Context;
 
 use async_io::Async;
+use embassy_net::device::{self, Device, DeviceCapabilities, LinkState};
 use log::*;
 
 pub const SIOCGIFMTU: libc::c_ulong = 0x8921;
@@ -125,54 +127,35 @@ impl io::Write for TunTap {
 
 pub struct TunTapDevice {
     device: Async<TunTap>,
-    waker: Option<Waker>,
 }
 
 impl TunTapDevice {
     pub fn new(name: &str) -> io::Result<TunTapDevice> {
         Ok(Self {
             device: Async::new(TunTap::new(name)?)?,
-            waker: None,
         })
     }
 }
 
-use core::task::Waker;
-use std::task::Context;
-
-use embassy_net::{Device, DeviceCapabilities, LinkState, Packet, PacketBox, PacketBoxExt, PacketBuf};
-
 impl Device for TunTapDevice {
-    fn is_transmit_ready(&mut self) -> bool {
-        true
-    }
+    type RxToken<'a> = RxToken where Self: 'a;
+    type TxToken<'a> = TxToken<'a> where Self: 'a;
 
-    fn transmit(&mut self, pkt: PacketBuf) {
-        // todo handle WouldBlock
-        match self.device.get_mut().write(&pkt) {
-            Ok(_) => {}
-            Err(e) if e.kind() == io::ErrorKind::WouldBlock => {
-                info!("transmit WouldBlock");
-            }
-            Err(e) => panic!("transmit error: {:?}", e),
-        }
-    }
-
-    fn receive(&mut self) -> Option<PacketBuf> {
-        let mut pkt = PacketBox::new(Packet::new()).unwrap();
+    fn receive(&mut self, cx: &mut Context) -> Option<(Self::RxToken<'_>, Self::TxToken<'_>)> {
+        let mut buf = vec![0; self.device.get_ref().mtu];
         loop {
-            match self.device.get_mut().read(&mut pkt[..]) {
+            match self.device.get_mut().read(&mut buf) {
                 Ok(n) => {
-                    return Some(pkt.slice(0..n));
+                    buf.truncate(n);
+                    return Some((
+                        RxToken { buffer: buf },
+                        TxToken {
+                            device: &mut self.device,
+                        },
+                    ));
                 }
                 Err(e) if e.kind() == io::ErrorKind::WouldBlock => {
-                    let ready = if let Some(w) = self.waker.as_ref() {
-                        let mut cx = Context::from_waker(w);
-                        self.device.poll_readable(&mut cx).is_ready()
-                    } else {
-                        false
-                    };
-                    if !ready {
+                    if !self.device.poll_readable(cx).is_ready() {
                         return None;
                     }
                 }
@@ -181,28 +164,10 @@ impl Device for TunTapDevice {
         }
     }
 
-    fn register_waker(&mut self, w: &Waker) {
-        match self.waker {
-            // Optimization: If both the old and new Wakers wake the same task, we can simply
-            // keep the old waker, skipping the clone. (In most executor implementations,
-            // cloning a waker is somewhat expensive, comparable to cloning an Arc).
-            Some(ref w2) if (w2.will_wake(w)) => {}
-            _ => {
-                // clone the new waker and store it
-                if let Some(old_waker) = core::mem::replace(&mut self.waker, Some(w.clone())) {
-                    // We had a waker registered for another task. Wake it, so the other task can
-                    // reregister itself if it's still interested.
-                    //
-                    // If two tasks are waiting on the same thing concurrently, this will cause them
-                    // to wake each other in a loop fighting over this WakerRegistration. This wastes
-                    // CPU but things will still work.
-                    //
-                    // If the user wants to have two tasks waiting on the same thing they should use
-                    // a more appropriate primitive that can store multiple wakers.
-                    old_waker.wake()
-                }
-            }
-        }
+    fn transmit(&mut self, _cx: &mut Context) -> Option<Self::TxToken<'_>> {
+        Some(TxToken {
+            device: &mut self.device,
+        })
     }
 
     fn capabilities(&self) -> DeviceCapabilities {
@@ -211,7 +176,7 @@ impl Device for TunTapDevice {
         caps
     }
 
-    fn link_state(&mut self) -> LinkState {
+    fn link_state(&mut self, _cx: &mut Context) -> LinkState {
         LinkState::Up
     }
 
@@ -219,3 +184,41 @@ impl Device for TunTapDevice {
         [0x02, 0x03, 0x04, 0x05, 0x06, 0x07]
     }
 }
+
+#[doc(hidden)]
+pub struct RxToken {
+    buffer: Vec<u8>,
+}
+
+impl device::RxToken for RxToken {
+    fn consume<R, F>(mut self, f: F) -> R
+    where
+        F: FnOnce(&mut [u8]) -> R,
+    {
+        f(&mut self.buffer)
+    }
+}
+
+#[doc(hidden)]
+pub struct TxToken<'a> {
+    device: &'a mut Async<TunTap>,
+}
+
+impl<'a> device::TxToken for TxToken<'a> {
+    fn consume<R, F>(self, len: usize, f: F) -> R
+    where
+        F: FnOnce(&mut [u8]) -> R,
+    {
+        let mut buffer = vec![0; len];
+        let result = f(&mut buffer);
+
+        // todo handle WouldBlock with async
+        match self.device.get_mut().write(&buffer) {
+            Ok(_) => {}
+            Err(e) if e.kind() == io::ErrorKind::WouldBlock => info!("transmit WouldBlock"),
+            Err(e) => panic!("transmit error: {:?}", e),
+        }
+
+        result
+    }
+}
diff --git a/examples/stm32f7/Cargo.toml b/examples/stm32f7/Cargo.toml
index f4d674cdc..afdf87000 100644
--- a/examples/stm32f7/Cargo.toml
+++ b/examples/stm32f7/Cargo.toml
@@ -8,7 +8,7 @@ license = "MIT OR Apache-2.0"
 embassy-sync = { version = "0.1.0", path = "../../embassy-sync", features = ["defmt"] }
 embassy-executor = { version = "0.1.0", path = "../../embassy-executor", features = ["defmt", "integrated-timers"] }
 embassy-time = { version = "0.1.0", path = "../../embassy-time", features = ["defmt", "defmt-timestamp-uptime", "tick-hz-32_768"] }
-embassy-stm32 = { version = "0.1.0", path = "../../embassy-stm32", features = ["nightly", "defmt", "net", "stm32f767zi", "unstable-pac", "time-driver-any", "exti"]  }
+embassy-stm32 = { version = "0.1.0", path = "../../embassy-stm32", features = ["nightly", "defmt", "embassy-net", "stm32f767zi", "unstable-pac", "time-driver-any", "exti"]  }
 embassy-net = { path = "../../embassy-net", features = ["defmt", "nightly", "tcp", "dhcpv4", "medium-ethernet", "pool-16"] }
 embedded-io = { version = "0.4.0", features = ["async"] }
 
diff --git a/examples/stm32f7/src/bin/eth.rs b/examples/stm32f7/src/bin/eth.rs
index 5202edf62..224cc202b 100644
--- a/examples/stm32f7/src/bin/eth.rs
+++ b/examples/stm32f7/src/bin/eth.rs
@@ -7,7 +7,7 @@ use embassy_executor::Spawner;
 use embassy_net::tcp::TcpSocket;
 use embassy_net::{Ipv4Address, Stack, StackResources};
 use embassy_stm32::eth::generic_smi::GenericSMI;
-use embassy_stm32::eth::{Ethernet, State};
+use embassy_stm32::eth::{Ethernet, PacketQueue};
 use embassy_stm32::peripherals::ETH;
 use embassy_stm32::rng::Rng;
 use embassy_stm32::time::mhz;
@@ -22,11 +22,12 @@ macro_rules! singleton {
     ($val:expr) => {{
         type T = impl Sized;
         static STATIC_CELL: StaticCell<T> = StaticCell::new();
-        STATIC_CELL.init_with(move || $val)
+        let (x,) = STATIC_CELL.init(($val,));
+        x
     }};
 }
 
-type Device = Ethernet<'static, ETH, GenericSMI, 4, 4>;
+type Device = Ethernet<'static, ETH, GenericSMI>;
 
 #[embassy_executor::task]
 async fn net_task(stack: &'static Stack<Device>) -> ! {
@@ -50,25 +51,23 @@ async fn main(spawner: Spawner) -> ! {
     let eth_int = interrupt::take!(ETH);
     let mac_addr = [0x00, 0x00, 0xDE, 0xAD, 0xBE, 0xEF];
 
-    let device = unsafe {
-        Ethernet::new(
-            singleton!(State::new()),
-            p.ETH,
-            eth_int,
-            p.PA1,
-            p.PA2,
-            p.PC1,
-            p.PA7,
-            p.PC4,
-            p.PC5,
-            p.PG13,
-            p.PB13,
-            p.PG11,
-            GenericSMI,
-            mac_addr,
-            0,
-        )
-    };
+    let device = Ethernet::new(
+        singleton!(PacketQueue::<16, 16>::new()),
+        p.ETH,
+        eth_int,
+        p.PA1,
+        p.PA2,
+        p.PC1,
+        p.PA7,
+        p.PC4,
+        p.PC5,
+        p.PG13,
+        p.PB13,
+        p.PG11,
+        GenericSMI,
+        mac_addr,
+        0,
+    );
 
     let config = embassy_net::ConfigStrategy::Dhcp;
     //let config = embassy_net::ConfigStrategy::Static(embassy_net::Config {
@@ -91,8 +90,8 @@ async fn main(spawner: Spawner) -> ! {
     info!("Network task initialized");
 
     // Then we can use it!
-    let mut rx_buffer = [0; 1024];
-    let mut tx_buffer = [0; 1024];
+    let mut rx_buffer = [0; 4096];
+    let mut tx_buffer = [0; 4096];
 
     loop {
         let mut socket = TcpSocket::new(&stack, &mut rx_buffer, &mut tx_buffer);
@@ -107,8 +106,9 @@ async fn main(spawner: Spawner) -> ! {
             continue;
         }
         info!("connected!");
+        let buf = [0; 1024];
         loop {
-            let r = socket.write_all(b"Hello\n").await;
+            let r = socket.write_all(&buf).await;
             if let Err(e) = r {
                 info!("write error: {:?}", e);
                 return;
diff --git a/examples/stm32h7/Cargo.toml b/examples/stm32h7/Cargo.toml
index 11ce35053..5acf0035d 100644
--- a/examples/stm32h7/Cargo.toml
+++ b/examples/stm32h7/Cargo.toml
@@ -8,7 +8,7 @@ license = "MIT OR Apache-2.0"
 embassy-sync = { version = "0.1.0", path = "../../embassy-sync", features = ["defmt"] }
 embassy-executor = { version = "0.1.0", path = "../../embassy-executor", features = ["defmt", "integrated-timers"] }
 embassy-time = { version = "0.1.0", path = "../../embassy-time", features = ["defmt", "defmt-timestamp-uptime", "unstable-traits", "tick-hz-32_768"] }
-embassy-stm32 = { version = "0.1.0", path = "../../embassy-stm32", features = ["nightly", "defmt", "stm32h743bi", "net", "time-driver-any", "exti", "unstable-pac", "unstable-traits"] }
+embassy-stm32 = { version = "0.1.0", path = "../../embassy-stm32", features = ["nightly", "defmt", "stm32h743bi", "embassy-net", "time-driver-any", "exti", "unstable-pac", "unstable-traits"] }
 embassy-net = { path = "../../embassy-net", features = ["defmt", "nightly", "tcp", "dhcpv4", "medium-ethernet", "pool-16", "unstable-traits"] }
 embedded-io = { version = "0.4.0", features = ["async"] }
 
diff --git a/examples/stm32h7/src/bin/eth.rs b/examples/stm32h7/src/bin/eth.rs
index 4ccc0b5ef..551325ca4 100644
--- a/examples/stm32h7/src/bin/eth.rs
+++ b/examples/stm32h7/src/bin/eth.rs
@@ -7,7 +7,7 @@ use embassy_executor::Spawner;
 use embassy_net::tcp::TcpSocket;
 use embassy_net::{Ipv4Address, Stack, StackResources};
 use embassy_stm32::eth::generic_smi::GenericSMI;
-use embassy_stm32::eth::{Ethernet, State};
+use embassy_stm32::eth::{Ethernet, PacketQueue};
 use embassy_stm32::peripherals::ETH;
 use embassy_stm32::rng::Rng;
 use embassy_stm32::time::mhz;
@@ -22,11 +22,12 @@ macro_rules! singleton {
     ($val:expr) => {{
         type T = impl Sized;
         static STATIC_CELL: StaticCell<T> = StaticCell::new();
-        STATIC_CELL.init_with(move || $val)
+        let (x,) = STATIC_CELL.init(($val,));
+        x
     }};
 }
 
-type Device = Ethernet<'static, ETH, GenericSMI, 4, 4>;
+type Device = Ethernet<'static, ETH, GenericSMI>;
 
 #[embassy_executor::task]
 async fn net_task(stack: &'static Stack<Device>) -> ! {
@@ -51,25 +52,23 @@ async fn main(spawner: Spawner) -> ! {
     let eth_int = interrupt::take!(ETH);
     let mac_addr = [0x00, 0x00, 0xDE, 0xAD, 0xBE, 0xEF];
 
-    let device = unsafe {
-        Ethernet::new(
-            singleton!(State::new()),
-            p.ETH,
-            eth_int,
-            p.PA1,
-            p.PA2,
-            p.PC1,
-            p.PA7,
-            p.PC4,
-            p.PC5,
-            p.PG13,
-            p.PB13,
-            p.PG11,
-            GenericSMI,
-            mac_addr,
-            0,
-        )
-    };
+    let device = Ethernet::new(
+        singleton!(PacketQueue::<16, 16>::new()),
+        p.ETH,
+        eth_int,
+        p.PA1,
+        p.PA2,
+        p.PC1,
+        p.PA7,
+        p.PC4,
+        p.PC5,
+        p.PG13,
+        p.PB13,
+        p.PG11,
+        GenericSMI,
+        mac_addr,
+        0,
+    );
 
     let config = embassy_net::ConfigStrategy::Dhcp;
     //let config = embassy_net::ConfigStrategy::Static(embassy_net::Config {
diff --git a/examples/stm32h7/src/bin/eth_client.rs b/examples/stm32h7/src/bin/eth_client.rs
index 64fd84141..61a08ae10 100644
--- a/examples/stm32h7/src/bin/eth_client.rs
+++ b/examples/stm32h7/src/bin/eth_client.rs
@@ -7,7 +7,7 @@ use embassy_executor::Spawner;
 use embassy_net::tcp::client::{TcpClient, TcpClientState};
 use embassy_net::{Stack, StackResources};
 use embassy_stm32::eth::generic_smi::GenericSMI;
-use embassy_stm32::eth::{Ethernet, State};
+use embassy_stm32::eth::{Ethernet, PacketQueue};
 use embassy_stm32::peripherals::ETH;
 use embassy_stm32::rng::Rng;
 use embassy_stm32::time::mhz;
@@ -23,11 +23,12 @@ macro_rules! singleton {
     ($val:expr) => {{
         type T = impl Sized;
         static STATIC_CELL: StaticCell<T> = StaticCell::new();
-        STATIC_CELL.init_with(move || $val)
+        let (x,) = STATIC_CELL.init(($val,));
+        x
     }};
 }
 
-type Device = Ethernet<'static, ETH, GenericSMI, 4, 4>;
+type Device = Ethernet<'static, ETH, GenericSMI>;
 
 #[embassy_executor::task]
 async fn net_task(stack: &'static Stack<Device>) -> ! {
@@ -52,25 +53,23 @@ async fn main(spawner: Spawner) -> ! {
     let eth_int = interrupt::take!(ETH);
     let mac_addr = [0x00, 0x00, 0xDE, 0xAD, 0xBE, 0xEF];
 
-    let device = unsafe {
-        Ethernet::new(
-            singleton!(State::new()),
-            p.ETH,
-            eth_int,
-            p.PA1,
-            p.PA2,
-            p.PC1,
-            p.PA7,
-            p.PC4,
-            p.PC5,
-            p.PG13,
-            p.PB13,
-            p.PG11,
-            GenericSMI,
-            mac_addr,
-            0,
-        )
-    };
+    let device = Ethernet::new(
+        singleton!(PacketQueue::<16, 16>::new()),
+        p.ETH,
+        eth_int,
+        p.PA1,
+        p.PA2,
+        p.PC1,
+        p.PA7,
+        p.PC4,
+        p.PC5,
+        p.PG13,
+        p.PB13,
+        p.PG11,
+        GenericSMI,
+        mac_addr,
+        0,
+    );
 
     let config = embassy_net::ConfigStrategy::Dhcp;
     //let config = embassy_net::ConfigStrategy::Static(embassy_net::Config {
diff --git a/examples/stm32l5/Cargo.toml b/examples/stm32l5/Cargo.toml
index 73ad50787..bb8515312 100644
--- a/examples/stm32l5/Cargo.toml
+++ b/examples/stm32l5/Cargo.toml
@@ -11,7 +11,7 @@ embassy-sync = { version = "0.1.0", path = "../../embassy-sync", features = ["de
 embassy-executor = { version = "0.1.0", path = "../../embassy-executor", features = ["defmt", "integrated-timers"] }
 embassy-time = { version = "0.1.0", path = "../../embassy-time", features = ["defmt", "defmt-timestamp-uptime", "tick-hz-32_768"] }
 embassy-stm32 = { version = "0.1.0", path = "../../embassy-stm32", features = ["nightly", "defmt", "unstable-pac", "stm32l552ze", "time-driver-any", "exti", "unstable-traits", "memory-x"]  }
-embassy-usb = { version = "0.1.0", path = "../../embassy-usb", features = ["defmt"] }
+embassy-usb = { version = "0.1.0", path = "../../embassy-usb", features = ["defmt", "embassy-net"] }
 embassy-net = { version = "0.1.0", path = "../../embassy-net", features = ["defmt", "nightly", "tcp", "dhcpv4", "medium-ethernet", "pool-16"] }
 embassy-futures = { version = "0.1.0", path = "../../embassy-futures" }
 usbd-hid = "0.6.0"
diff --git a/examples/stm32l5/src/bin/usb_ethernet.rs b/examples/stm32l5/src/bin/usb_ethernet.rs
index 4f36d3f5a..b49329ea4 100644
--- a/examples/stm32l5/src/bin/usb_ethernet.rs
+++ b/examples/stm32l5/src/bin/usb_ethernet.rs
@@ -2,20 +2,16 @@
 #![no_main]
 #![feature(type_alias_impl_trait)]
 
-use core::sync::atomic::{AtomicBool, Ordering};
-use core::task::Waker;
-
 use defmt::*;
 use embassy_executor::Spawner;
 use embassy_net::tcp::TcpSocket;
-use embassy_net::{PacketBox, PacketBoxExt, PacketBuf, Stack, StackResources};
+use embassy_net::{Stack, StackResources};
 use embassy_stm32::rcc::*;
 use embassy_stm32::rng::Rng;
 use embassy_stm32::usb::Driver;
 use embassy_stm32::{interrupt, Config};
-use embassy_sync::blocking_mutex::raw::ThreadModeRawMutex;
-use embassy_sync::channel::Channel;
-use embassy_usb::class::cdc_ncm::{CdcNcmClass, Receiver, Sender, State};
+use embassy_usb::class::cdc_ncm::embassy_net::{Device, Runner, State as NetState};
+use embassy_usb::class::cdc_ncm::{CdcNcmClass, State};
 use embassy_usb::{Builder, UsbDevice};
 use embedded_io::asynch::Write;
 use rand_core::RngCore;
@@ -28,56 +24,25 @@ macro_rules! singleton {
     ($val:expr) => {{
         type T = impl Sized;
         static STATIC_CELL: StaticCell<T> = StaticCell::new();
-        STATIC_CELL.init_with(move || $val)
+        let (x,) = STATIC_CELL.init(($val,));
+        x
     }};
 }
 
+const MTU: usize = 1514;
+
 #[embassy_executor::task]
 async fn usb_task(mut device: UsbDevice<'static, MyDriver>) -> ! {
     device.run().await
 }
 
 #[embassy_executor::task]
-async fn usb_ncm_rx_task(mut class: Receiver<'static, MyDriver>) {
-    loop {
-        warn!("WAITING for connection");
-        LINK_UP.store(false, Ordering::Relaxed);
-
-        class.wait_connection().await.unwrap();
-
-        warn!("Connected");
-        LINK_UP.store(true, Ordering::Relaxed);
-
-        loop {
-            let mut p = unwrap!(PacketBox::new(embassy_net::Packet::new()));
-            let n = match class.read_packet(&mut p[..]).await {
-                Ok(n) => n,
-                Err(e) => {
-                    warn!("error reading packet: {:?}", e);
-                    break;
-                }
-            };
-
-            let buf = p.slice(0..n);
-            if RX_CHANNEL.try_send(buf).is_err() {
-                warn!("Failed pushing rx'd packet to channel.");
-            }
-        }
-    }
-}
-
-#[embassy_executor::task]
-async fn usb_ncm_tx_task(mut class: Sender<'static, MyDriver>) {
-    loop {
-        let pkt = TX_CHANNEL.recv().await;
-        if let Err(e) = class.write_packet(&pkt[..]).await {
-            warn!("Failed to TX packet: {:?}", e);
-        }
-    }
+async fn usb_ncm_task(class: Runner<'static, MyDriver, MTU>) -> ! {
+    class.run().await
 }
 
 #[embassy_executor::task]
-async fn net_task(stack: &'static Stack<Device>) -> ! {
+async fn net_task(stack: &'static Stack<Device<'static, MTU>>) -> ! {
     stack.run().await
 }
 
@@ -106,55 +71,32 @@ async fn main(spawner: Spawner) {
     config.device_sub_class = 0x02;
     config.device_protocol = 0x01;
 
-    struct Resources {
-        device_descriptor: [u8; 256],
-        config_descriptor: [u8; 256],
-        bos_descriptor: [u8; 256],
-        control_buf: [u8; 128],
-        serial_state: State<'static>,
-    }
-    let res: &mut Resources = singleton!(Resources {
-        device_descriptor: [0; 256],
-        config_descriptor: [0; 256],
-        bos_descriptor: [0; 256],
-        control_buf: [0; 128],
-        serial_state: State::new(),
-    });
-
     // Create embassy-usb DeviceBuilder using the driver and config.
     let mut builder = Builder::new(
         driver,
         config,
-        &mut res.device_descriptor,
-        &mut res.config_descriptor,
-        &mut res.bos_descriptor,
-        &mut res.control_buf,
+        &mut singleton!([0; 256])[..],
+        &mut singleton!([0; 256])[..],
+        &mut singleton!([0; 256])[..],
+        &mut singleton!([0; 128])[..],
         None,
     );
 
-    // WARNINGS for Android ethernet tethering:
-    // - On Pixel 4a, it refused to work on Android 11, worked on Android 12.
-    // - if the host's MAC address has the "locally-administered" bit set (bit 1 of first byte),
-    //   it doesn't work! The "Ethernet tethering" option in settings doesn't get enabled.
-    //   This is due to regex spaghetti: https://android.googlesource.com/platform/frameworks/base/+/refs/tags/android-mainline-12.0.0_r84/core/res/res/values/config.xml#417
-    //   and this nonsense in the linux kernel: https://github.com/torvalds/linux/blob/c00c5e1d157bec0ef0b0b59aa5482eb8dc7e8e49/drivers/net/usb/usbnet.c#L1751-L1757
-
     // Our MAC addr.
     let our_mac_addr = [0xCC, 0xCC, 0xCC, 0xCC, 0xCC, 0xCC];
     // Host's MAC addr. This is the MAC the host "thinks" its USB-to-ethernet adapter has.
     let host_mac_addr = [0x88, 0x88, 0x88, 0x88, 0x88, 0x88];
 
     // Create classes on the builder.
-    let class = CdcNcmClass::new(&mut builder, &mut res.serial_state, host_mac_addr, 64);
+    let class = CdcNcmClass::new(&mut builder, singleton!(State::new()), host_mac_addr, 64);
 
     // Build the builder.
     let usb = builder.build();
 
     unwrap!(spawner.spawn(usb_task(usb)));
 
-    let (tx, rx) = class.split();
-    unwrap!(spawner.spawn(usb_ncm_rx_task(rx)));
-    unwrap!(spawner.spawn(usb_ncm_tx_task(tx)));
+    let (runner, device) = class.into_embassy_net_device::<MTU, 4, 4>(singleton!(NetState::new()), our_mac_addr);
+    unwrap!(spawner.spawn(usb_ncm_task(runner)));
 
     let config = embassy_net::ConfigStrategy::Dhcp;
     //let config = embassy_net::ConfigStrategy::Static(embassy_net::Config {
@@ -168,7 +110,6 @@ async fn main(spawner: Spawner) {
     let seed = rng.next_u64();
 
     // Init network stack
-    let device = Device { mac_addr: our_mac_addr };
     let stack = &*singleton!(Stack::new(
         device,
         config,
@@ -221,50 +162,3 @@ async fn main(spawner: Spawner) {
         }
     }
 }
-
-static TX_CHANNEL: Channel<ThreadModeRawMutex, PacketBuf, 8> = Channel::new();
-static RX_CHANNEL: Channel<ThreadModeRawMutex, PacketBuf, 8> = Channel::new();
-static LINK_UP: AtomicBool = AtomicBool::new(false);
-
-struct Device {
-    mac_addr: [u8; 6],
-}
-
-impl embassy_net::Device for Device {
-    fn register_waker(&mut self, waker: &Waker) {
-        // loopy loopy wakey wakey
-        waker.wake_by_ref()
-    }
-
-    fn link_state(&mut self) -> embassy_net::LinkState {
-        match LINK_UP.load(Ordering::Relaxed) {
-            true => embassy_net::LinkState::Up,
-            false => embassy_net::LinkState::Down,
-        }
-    }
-
-    fn capabilities(&self) -> embassy_net::DeviceCapabilities {
-        let mut caps = embassy_net::DeviceCapabilities::default();
-        caps.max_transmission_unit = 1514; // 1500 IP + 14 ethernet header
-        caps.medium = embassy_net::Medium::Ethernet;
-        caps
-    }
-
-    fn is_transmit_ready(&mut self) -> bool {
-        true
-    }
-
-    fn transmit(&mut self, pkt: PacketBuf) {
-        if TX_CHANNEL.try_send(pkt).is_err() {
-            warn!("TX failed")
-        }
-    }
-
-    fn receive<'a>(&mut self) -> Option<PacketBuf> {
-        RX_CHANNEL.try_recv().ok()
-    }
-
-    fn ethernet_address(&self) -> [u8; 6] {
-        self.mac_addr
-    }
-}