16 files changed, 1355 insertions, 1 deletions

diff --git a/.gitignore b/.gitignore
index 893a87368..11781dc15 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,4 +1,4 @@
 target
 Cargo.lock
 third_party
-/Cargo.toml
\ No newline at end of file
+/Cargo.toml
diff --git a/ci.sh b/ci.sh
new file mode 100755
index 000000000..f43ea5e1a
--- /dev/null
+++ b/ci.sh
@@ -0,0 +1,16 @@
+#!/bin/bash
+
+set -euxo pipefail
+
+# build for std
+(cd embassy-net; cargo build --no-default-features --features log,medium-ethernet,tcp)
+(cd embassy-net; cargo build --no-default-features --features log,medium-ethernet,tcp,dhcpv4)
+(cd embassy-net; cargo build --no-default-features --features log,medium-ip,tcp)
+(cd embassy-net; cargo build --no-default-features --features log,medium-ethernet,medium-ip,tcp,dhcpv4)
+
+# build for embedded
+(cd embassy-net; cargo build --target thumbv7em-none-eabi --no-default-features --features log,medium-ethernet,medium-ip,tcp,dhcpv4)
+(cd embassy-net; cargo build --target thumbv7em-none-eabi --no-default-features --features defmt,smoltcp/defmt,medium-ethernet,medium-ip,tcp,dhcpv4)
+
+# build examples
+(cd embassy-net-examples; cargo build)
diff --git a/embassy-net-examples/Cargo.toml b/embassy-net-examples/Cargo.toml
new file mode 100644
index 000000000..0a63a3bbd
--- /dev/null
+++ b/embassy-net-examples/Cargo.toml
@@ -0,0 +1,19 @@
+[package]
+name = "embassy-net-examples"
+version = "0.1.0"
+authors = ["Dario Nieuwenhuis <[email protected]>"]
+edition = "2018"
+
+[dependencies]
+heapless            = { version = "0.5.6", default-features = false } 
+embassy             = { version = "0.1.0", features=["std", "log"] }
+embassy-std         = { version = "0.1.0" }
+embassy-net         = { version = "0.1.0", path = "../embassy-net", features=["std", "log", "medium-ethernet", "tcp", "dhcpv4"] }
+env_logger = "0.8.2"
+log = "0.4.11"
+futures = "0.3.8"
+libc = "0.2.81"
+async-io = "1.3.1"
+smoltcp = { version = "0.7.0", default-features = false }
+clap = { version = "3.0.0-beta.2", features = ["derive"] }
+rand_core   = { version = "0.6.0", features = ["std"] }
diff --git a/embassy-net-examples/src/main.rs b/embassy-net-examples/src/main.rs
new file mode 100644
index 000000000..d1c2658dd
--- /dev/null
+++ b/embassy-net-examples/src/main.rs
@@ -0,0 +1,102 @@
+#![feature(type_alias_impl_trait)]
+#![feature(min_type_alias_impl_trait)]
+#![feature(impl_trait_in_bindings)]
+#![allow(incomplete_features)]
+
+use clap::{AppSettings, Clap};
+use embassy::executor::Spawner;
+use embassy::io::AsyncWriteExt;
+use embassy::util::Forever;
+use embassy_net::*;
+use embassy_std::Executor;
+use heapless::Vec;
+use log::*;
+
+mod tuntap;
+
+use crate::tuntap::TunTapDevice;
+
+static DEVICE: Forever<TunTapDevice> = Forever::new();
+static CONFIG: Forever<DhcpConfigurator> = Forever::new();
+
+#[derive(Clap)]
+#[clap(version = "1.0")]
+#[clap(setting = AppSettings::ColoredHelp)]
+struct Opts {
+    /// TAP device name
+    #[clap(long, default_value = "tap0")]
+    tap: String,
+}
+
+#[embassy::task]
+async fn net_task() {
+    embassy_net::run().await
+}
+
+#[embassy::task]
+async fn main_task(spawner: Spawner) {
+    let opts: Opts = Opts::parse();
+
+    // Init network device
+    let device = TunTapDevice::new(&opts.tap).unwrap();
+
+    // Static IP configuration
+    let config = StaticConfigurator::new(Config {
+        address: Ipv4Cidr::new(Ipv4Address::new(192, 168, 69, 2), 24),
+        dns_servers: Vec::new(),
+        gateway: Some(Ipv4Address::new(192, 168, 69, 1)),
+    });
+
+    // DHCP configruation
+    let config = DhcpConfigurator::new();
+
+    // Init network stack
+    embassy_net::init(DEVICE.put(device), CONFIG.put(config));
+
+    // Launch network task
+    spawner.spawn(net_task()).unwrap();
+
+    // Then we can use it!
+    let mut rx_buffer = [0; 4096];
+    let mut tx_buffer = [0; 4096];
+    let mut socket = TcpSocket::new(&mut rx_buffer, &mut tx_buffer);
+
+    socket.set_timeout(Some(embassy_net::SmolDuration::from_secs(10)));
+
+    let remote_endpoint = (Ipv4Address::new(192, 168, 69, 74), 8000);
+    info!("connecting to {:?}...", remote_endpoint);
+    let r = socket.connect(remote_endpoint).await;
+    if let Err(e) = r {
+        warn!("connect error: {:?}", e);
+        return;
+    }
+    info!("connected!");
+    loop {
+        let r = socket.write_all(b"Hello!\n").await;
+        if let Err(e) = r {
+            warn!("write error: {:?}", e);
+            return;
+        }
+    }
+}
+
+#[no_mangle]
+fn _embassy_rand(buf: &mut [u8]) {
+    use rand_core::{OsRng, RngCore};
+    OsRng.fill_bytes(buf);
+}
+
+static EXECUTOR: Forever<Executor> = Forever::new();
+
+fn main() {
+    env_logger::builder()
+        .filter_level(log::LevelFilter::Debug)
+        .filter_module("async_io", log::LevelFilter::Info)
+        .format_timestamp_nanos()
+        .init();
+
+    let executor = EXECUTOR.put(Executor::new());
+    executor.run(|spawner| {
+        spawner.spawn(main_task(spawner)).unwrap();
+    });
+}
diff --git a/embassy-net-examples/src/tuntap.rs b/embassy-net-examples/src/tuntap.rs
new file mode 100644
index 000000000..dd453deb3
--- /dev/null
+++ b/embassy-net-examples/src/tuntap.rs
@@ -0,0 +1,225 @@
+use async_io::Async;
+use libc;
+use log::*;
+use smoltcp::wire::EthernetFrame;
+use std::io;
+use std::io::{Read, Write};
+use std::os::unix::io::{AsRawFd, RawFd};
+
+pub const SIOCGIFMTU: libc::c_ulong = 0x8921;
+pub const SIOCGIFINDEX: libc::c_ulong = 0x8933;
+pub const ETH_P_ALL: libc::c_short = 0x0003;
+pub const TUNSETIFF: libc::c_ulong = 0x400454CA;
+pub const IFF_TUN: libc::c_int = 0x0001;
+pub const IFF_TAP: libc::c_int = 0x0002;
+pub const IFF_NO_PI: libc::c_int = 0x1000;
+
+#[repr(C)]
+#[derive(Debug)]
+struct ifreq {
+    ifr_name: [libc::c_char; libc::IF_NAMESIZE],
+    ifr_data: libc::c_int, /* ifr_ifindex or ifr_mtu */
+}
+
+fn ifreq_for(name: &str) -> ifreq {
+    let mut ifreq = ifreq {
+        ifr_name: [0; libc::IF_NAMESIZE],
+        ifr_data: 0,
+    };
+    for (i, byte) in name.as_bytes().iter().enumerate() {
+        ifreq.ifr_name[i] = *byte as libc::c_char
+    }
+    ifreq
+}
+
+fn ifreq_ioctl(
+    lower: libc::c_int,
+    ifreq: &mut ifreq,
+    cmd: libc::c_ulong,
+) -> io::Result<libc::c_int> {
+    unsafe {
+        let res = libc::ioctl(lower, cmd as _, ifreq as *mut ifreq);
+        if res == -1 {
+            return Err(io::Error::last_os_error());
+        }
+    }
+
+    Ok(ifreq.ifr_data)
+}
+
+#[derive(Debug)]
+pub struct TunTap {
+    fd: libc::c_int,
+    ifreq: ifreq,
+    mtu: usize,
+}
+
+impl AsRawFd for TunTap {
+    fn as_raw_fd(&self) -> RawFd {
+        self.fd
+    }
+}
+
+impl TunTap {
+    pub fn new(name: &str) -> io::Result<TunTap> {
+        unsafe {
+            let fd = libc::open(
+                "/dev/net/tun\0".as_ptr() as *const libc::c_char,
+                libc::O_RDWR | libc::O_NONBLOCK,
+            );
+            if fd == -1 {
+                return Err(io::Error::last_os_error());
+            }
+
+            let mut ifreq = ifreq_for(name);
+            ifreq.ifr_data = IFF_TAP | IFF_NO_PI;
+            ifreq_ioctl(fd, &mut ifreq, TUNSETIFF)?;
+
+            let socket = libc::socket(libc::AF_INET, libc::SOCK_DGRAM, libc::IPPROTO_IP);
+            if socket == -1 {
+                return Err(io::Error::last_os_error());
+            }
+
+            let ip_mtu = ifreq_ioctl(socket, &mut ifreq, SIOCGIFMTU);
+            libc::close(socket);
+            let ip_mtu = ip_mtu? as usize;
+
+            // SIOCGIFMTU returns the IP MTU (typically 1500 bytes.)
+            // smoltcp counts the entire Ethernet packet in the MTU, so add the Ethernet header size to it.
+            let mtu = ip_mtu + EthernetFrame::<&[u8]>::header_len();
+
+            Ok(TunTap { fd, mtu, ifreq })
+        }
+    }
+}
+
+impl Drop for TunTap {
+    fn drop(&mut self) {
+        unsafe {
+            libc::close(self.fd);
+        }
+    }
+}
+
+impl io::Read for TunTap {
+    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
+        let len = unsafe { libc::read(self.fd, buf.as_mut_ptr() as *mut libc::c_void, buf.len()) };
+        if len == -1 {
+            Err(io::Error::last_os_error())
+        } else {
+            Ok(len as usize)
+        }
+    }
+}
+
+impl io::Write for TunTap {
+    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
+        let len = unsafe { libc::write(self.fd, buf.as_ptr() as *mut libc::c_void, buf.len()) };
+        if len == -1 {
+            Err(io::Error::last_os_error())
+        } else {
+            Ok(len as usize)
+        }
+    }
+
+    fn flush(&mut self) -> io::Result<()> {
+        Ok(())
+    }
+}
+
+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 embassy_net::{DeviceCapabilities, LinkState, Packet, PacketBox, PacketBoxExt, PacketBuf};
+use std::task::Context;
+
+impl crate::Device for TunTapDevice {
+    fn is_transmit_ready(&mut self) -> bool {
+        true
+    }
+
+    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();
+        loop {
+            match self.device.get_mut().read(&mut pkt[..]) {
+                Ok(n) => {
+                    return Some(pkt.slice(0..n));
+                }
+                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);
+                        let ready = self.device.poll_readable(&mut cx).is_ready();
+                        ready
+                    } else {
+                        false
+                    };
+                    if !ready {
+                        return None;
+                    }
+                }
+                Err(e) => panic!("read error: {:?}", e),
+            }
+        }
+    }
+
+    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 capabilities(&mut self) -> DeviceCapabilities {
+        let mut caps = DeviceCapabilities::default();
+        caps.max_transmission_unit = self.device.get_ref().mtu;
+        caps
+    }
+
+    fn link_state(&mut self) -> LinkState {
+        LinkState::Up
+    }
+
+    fn ethernet_address(&mut self) -> [u8; 6] {
+        [0x02, 0x03, 0x04, 0x05, 0x06, 0x07]
+    }
+}
diff --git a/embassy-net/Cargo.toml b/embassy-net/Cargo.toml
new file mode 100644
index 000000000..36f64dbd4
--- /dev/null
+++ b/embassy-net/Cargo.toml
@@ -0,0 +1,44 @@
+[package]
+name = "embassy-net"
+version = "0.1.0"
+authors = ["Dario Nieuwenhuis <[email protected]>"]
+edition = "2018"
+
+[features]
+std = []
+defmt-trace = []
+defmt-debug = []
+defmt-info = []
+defmt-warn = []
+defmt-error = []
+
+tcp = ["smoltcp/socket-tcp"]
+dhcpv4 = ["medium-ethernet", "smoltcp/socket-dhcpv4"]
+medium-ethernet = ["smoltcp/medium-ethernet"]
+medium-ip = ["smoltcp/medium-ip"]
+
+[dependencies]
+
+defmt = { version = "0.2.0", optional = true }
+log = { version = "0.4.11", optional = true }
+
+embassy             = { version = "0.1.0" }
+
+managed             = { version = "0.8.0", default-features = false, features = [ "map" ]}
+heapless            = { version = "0.5.6", default-features = false } 
+as-slice            = { version = "0.1.4" }
+generic-array       = { version = "0.14.4", default-features = false }
+stable_deref_trait  = { version = "1.2.0", default-features = false }
+futures             = { version = "0.3.5", default-features = false, features = [ "async-await" ]}
+atomic-pool = "0.2.0"
+
+[dependencies.smoltcp]
+version = "0.7.0"
+#git = "https://github.com/akiles/smoltcp"
+#rev = "00952e2c5cdf5667a1dfb6142258055f58d3851c"
+default-features = false
+features = [
+  "proto-ipv4",
+  "socket",
+  "async",
+]
diff --git a/embassy-net/README.md b/embassy-net/README.md
new file mode 100644
index 000000000..64f656709
--- /dev/null
+++ b/embassy-net/README.md
@@ -0,0 +1,34 @@
+# embassy-net
+
+embassy-net contains an async network API based on smoltcp and embassy, designed
+for embedded systems.
+
+## Running the example
+
+First, create the tap0 interface. You only need to do this once.
+
+```sh
+sudo ip tuntap add name tap0 mode tap user $USER
+sudo ip link set tap0 up
+sudo ip addr add 192.168.69.100/24 dev tap0
+sudo ip -6 addr add fe80::100/64 dev tap0
+sudo ip -6 addr add fdaa::100/64 dev tap0
+sudo ip -6 route add fe80::/64 dev tap0
+sudo ip -6 route add fdaa::/64 dev tap0
+```
+
+Then, run it
+
+```sh
+cargo run --bin embassy-net-examples
+```
+
+## License
+
+This work is licensed under either of
+
+- Apache License, Version 2.0 ([LICENSE-APACHE](LICENSE-APACHE) or
+  http://www.apache.org/licenses/LICENSE-2.0)
+- MIT license ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT)
+
+at your option.
diff --git a/embassy-net/src/config/dhcp.rs b/embassy-net/src/config/dhcp.rs
new file mode 100644
index 000000000..f0c144321
--- /dev/null
+++ b/embassy-net/src/config/dhcp.rs
@@ -0,0 +1,59 @@
+use heapless::Vec;
+use smoltcp::socket::{Dhcpv4Event, Dhcpv4Socket, SocketHandle};
+use smoltcp::time::Instant;
+
+use super::*;
+use crate::device::LinkState;
+use crate::fmt::*;
+use crate::{Interface, SocketSet};
+
+pub struct DhcpConfigurator {
+    handle: Option<SocketHandle>,
+}
+
+impl DhcpConfigurator {
+    pub fn new() -> Self {
+        Self { handle: None }
+    }
+}
+
+impl Configurator for DhcpConfigurator {
+    fn poll(
+        &mut self,
+        iface: &mut Interface,
+        sockets: &mut SocketSet,
+        _timestamp: Instant,
+    ) -> Event {
+        if self.handle.is_none() {
+            let handle = sockets.add(Dhcpv4Socket::new());
+            self.handle = Some(handle)
+        }
+
+        let mut socket = sockets.get::<Dhcpv4Socket>(self.handle.unwrap());
+
+        let link_up = iface.device_mut().device.link_state() == LinkState::Up;
+        if !link_up {
+            socket.reset();
+            return Event::Deconfigured;
+        }
+
+        match socket.poll() {
+            None => Event::NoChange,
+            Some(Dhcpv4Event::Deconfigured) => Event::Deconfigured,
+            Some(Dhcpv4Event::Configured(config)) => {
+                let mut dns_servers = Vec::new();
+                for s in &config.dns_servers {
+                    if let Some(addr) = s {
+                        dns_servers.push(addr.clone()).unwrap();
+                    }
+                }
+
+                Event::Configured(Config {
+                    address: config.address,
+                    gateway: config.router,
+                    dns_servers,
+                })
+            }
+        }
+    }
+}
diff --git a/embassy-net/src/config/mod.rs b/embassy-net/src/config/mod.rs
new file mode 100644
index 000000000..16470f7e6
--- /dev/null
+++ b/embassy-net/src/config/mod.rs
@@ -0,0 +1,38 @@
+use heapless::consts::*;
+use heapless::Vec;
+use smoltcp::time::Instant;
+use smoltcp::wire::{Ipv4Address, Ipv4Cidr};
+
+use crate::fmt::*;
+use crate::{Interface, SocketSet};
+
+mod statik;
+pub use statik::StaticConfigurator;
+
+#[cfg(feature = "dhcpv4")]
+mod dhcp;
+#[cfg(feature = "dhcpv4")]
+pub use dhcp::DhcpConfigurator;
+
+/// Return value for the `Configurator::poll` function
+#[derive(Debug, Clone)]
+pub enum Event {
+    /// No change has occured to the configuration.
+    NoChange,
+    /// Configuration has been lost (for example, DHCP lease has expired)
+    Deconfigured,
+    /// Configuration has been newly acquired, or modified.
+    Configured(Config),
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct Config {
+    pub address: Ipv4Cidr,
+    pub gateway: Option<Ipv4Address>,
+    pub dns_servers: Vec<Ipv4Address, U3>,
+}
+
+pub trait Configurator {
+    fn poll(&mut self, iface: &mut Interface, sockets: &mut SocketSet, timestamp: Instant)
+        -> Event;
+}
diff --git a/embassy-net/src/config/statik.rs b/embassy-net/src/config/statik.rs
new file mode 100644
index 000000000..912143bff
--- /dev/null
+++ b/embassy-net/src/config/statik.rs
@@ -0,0 +1,35 @@
+use smoltcp::time::Instant;
+
+use super::*;
+use crate::fmt::*;
+use crate::{Interface, SocketSet};
+
+pub struct StaticConfigurator {
+    config: Config,
+    returned: bool,
+}
+
+impl StaticConfigurator {
+    pub fn new(config: Config) -> Self {
+        Self {
+            config,
+            returned: false,
+        }
+    }
+}
+
+impl Configurator for StaticConfigurator {
+    fn poll(
+        &mut self,
+        _iface: &mut Interface,
+        _sockets: &mut SocketSet,
+        _timestamp: Instant,
+    ) -> Event {
+        if self.returned {
+            Event::NoChange
+        } else {
+            self.returned = true;
+            Event::Configured(self.config.clone())
+        }
+    }
+}
diff --git a/embassy-net/src/device.rs b/embassy-net/src/device.rs
new file mode 100644
index 000000000..6c06b0605
--- /dev/null
+++ b/embassy-net/src/device.rs
@@ -0,0 +1,105 @@
+use core::task::Waker;
+use smoltcp::phy::Device as SmolDevice;
+use smoltcp::phy::DeviceCapabilities;
+use smoltcp::time::Instant as SmolInstant;
+
+use crate::fmt::*;
+use crate::packet_pool::PacketBoxExt;
+use crate::Result;
+use crate::{Packet, PacketBox, PacketBuf};
+
+#[derive(PartialEq, Eq, Clone, Copy)]
+pub enum LinkState {
+    Down,
+    Up,
+}
+
+pub trait Device {
+    fn is_transmit_ready(&mut self) -> bool;
+    fn transmit(&mut self, pkt: PacketBuf);
+    fn receive(&mut self) -> Option<PacketBuf>;
+
+    fn register_waker(&mut self, waker: &Waker);
+    fn capabilities(&mut self) -> DeviceCapabilities;
+    fn link_state(&mut self) -> LinkState;
+    fn ethernet_address(&mut self) -> [u8; 6];
+}
+
+pub struct DeviceAdapter {
+    pub device: &'static mut dyn Device,
+    caps: DeviceCapabilities,
+}
+
+impl DeviceAdapter {
+    pub(crate) fn new(device: &'static mut dyn Device) -> Self {
+        Self {
+            caps: device.capabilities(),
+            device,
+        }
+    }
+}
+
+impl<'a> SmolDevice<'a> for DeviceAdapter {
+    type RxToken = RxToken;
+    type TxToken = TxToken<'a>;
+
+    fn receive(&'a mut self) -> Option<(Self::RxToken, Self::TxToken)> {
+        let rx_pkt = self.device.receive()?;
+        let tx_pkt = PacketBox::new(Packet::new()).unwrap(); // TODO: not sure about unwrap
+        let rx_token = RxToken { pkt: rx_pkt };
+        let tx_token = TxToken {
+            device: self.device,
+            pkt: tx_pkt,
+        };
+
+        Some((rx_token, tx_token))
+    }
+
+    /// Construct a transmit token.
+    fn transmit(&'a mut self) -> Option<Self::TxToken> {
+        if !self.device.is_transmit_ready() {
+            return None;
+        }
+
+        let tx_pkt = PacketBox::new(Packet::new())?;
+        Some(TxToken {
+            device: self.device,
+            pkt: tx_pkt,
+        })
+    }
+
+    /// Get a description of device capabilities.
+    fn capabilities(&self) -> DeviceCapabilities {
+        self.caps.clone()
+    }
+}
+
+pub struct RxToken {
+    pkt: PacketBuf,
+}
+
+impl smoltcp::phy::RxToken for RxToken {
+    fn consume<R, F>(mut self, _timestamp: SmolInstant, f: F) -> Result<R>
+    where
+        F: FnOnce(&mut [u8]) -> Result<R>,
+    {
+        f(&mut self.pkt)
+    }
+}
+
+pub struct TxToken<'a> {
+    device: &'a mut dyn Device,
+    pkt: PacketBox,
+}
+
+impl<'a> smoltcp::phy::TxToken for TxToken<'a> {
+    fn consume<R, F>(self, _timestamp: SmolInstant, len: usize, f: F) -> Result<R>
+    where
+        F: FnOnce(&mut [u8]) -> Result<R>,
+    {
+        let mut buf = self.pkt.slice(0..len);
+        let r = f(&mut buf)?;
+        self.device.transmit(buf);
+        Ok(r)
+    }
+}
diff --git a/embassy-net/src/fmt.rs b/embassy-net/src/fmt.rs
new file mode 100644
index 000000000..4da69766c
--- /dev/null
+++ b/embassy-net/src/fmt.rs
@@ -0,0 +1,118 @@
+#![macro_use]
+
+#[cfg(all(feature = "defmt", feature = "log"))]
+compile_error!("You may not enable both `defmt` and `log` features.");
+
+pub use fmt::*;
+
+#[cfg(feature = "defmt")]
+mod fmt {
+    pub use defmt::{
+        assert, assert_eq, assert_ne, debug, debug_assert, debug_assert_eq, debug_assert_ne, error,
+        info, panic, todo, trace, unreachable, unwrap, warn,
+    };
+}
+
+#[cfg(feature = "log")]
+mod fmt {
+    pub use core::{
+        assert, assert_eq, assert_ne, debug_assert, debug_assert_eq, debug_assert_ne, panic, todo,
+        unreachable,
+    };
+    pub use log::{debug, error, info, trace, warn};
+}
+
+#[cfg(not(any(feature = "defmt", feature = "log")))]
+mod fmt {
+    #![macro_use]
+
+    pub use core::{
+        assert, assert_eq, assert_ne, debug_assert, debug_assert_eq, debug_assert_ne, panic, todo,
+        unreachable,
+    };
+
+    #[macro_export]
+    macro_rules! trace {
+        ($($msg:expr),+ $(,)?) => {
+            ()
+        };
+    }
+
+    #[macro_export]
+    macro_rules! debug {
+        ($($msg:expr),+ $(,)?) => {
+            ()
+        };
+    }
+
+    #[macro_export]
+    macro_rules! info {
+        ($($msg:expr),+ $(,)?) => {
+            ()
+        };
+    }
+
+    #[macro_export]
+    macro_rules! warn {
+        ($($msg:expr),+ $(,)?) => {
+            ()
+        };
+    }
+
+    #[macro_export]
+    macro_rules! error {
+        ($($msg:expr),+ $(,)?) => {
+            ()
+        };
+    }
+}
+
+#[cfg(not(feature = "defmt"))]
+#[macro_export]
+macro_rules! unwrap {
+    ($arg:expr) => {
+        match $crate::fmt::Try::into_result($arg) {
+            ::core::result::Result::Ok(t) => t,
+            ::core::result::Result::Err(e) => {
+                ::core::panic!("unwrap of `{}` failed: {:?}", ::core::stringify!($arg), e);
+            }
+        }
+    };
+    ($arg:expr, $($msg:expr),+ $(,)? ) => {
+        match $crate::fmt::Try::into_result($arg) {
+            ::core::result::Result::Ok(t) => t,
+            ::core::result::Result::Err(e) => {
+                ::core::panic!("unwrap of `{}` failed: {}: {:?}", ::core::stringify!($arg), ::core::format_args!($($msg,)*), e);
+            }
+        }
+    }
+}
+
+#[derive(Debug, Copy, Clone, Eq, PartialEq)]
+pub struct NoneError;
+
+pub trait Try {
+    type Ok;
+    type Error;
+    fn into_result(self) -> Result<Self::Ok, Self::Error>;
+}
+
+impl<T> Try for Option<T> {
+    type Ok = T;
+    type Error = NoneError;
+
+    #[inline]
+    fn into_result(self) -> Result<T, NoneError> {
+        self.ok_or(NoneError)
+    }
+}
+
+impl<T, E> Try for Result<T, E> {
+    type Ok = T;
+    type Error = E;
+
+    #[inline]
+    fn into_result(self) -> Self {
+        self
+    }
+}
diff --git a/embassy-net/src/lib.rs b/embassy-net/src/lib.rs
new file mode 100644
index 000000000..88dcf0aa5
--- /dev/null
+++ b/embassy-net/src/lib.rs
@@ -0,0 +1,31 @@
+#![cfg_attr(not(feature = "std"), no_std)]
+
+// This mod MUST go first, so that the others see its macros.
+pub(crate) mod fmt;
+
+mod config;
+mod device;
+mod packet_pool;
+mod stack;
+
+#[cfg(feature = "dhcpv4")]
+pub use config::DhcpConfigurator;
+pub use config::{Config, Configurator, Event as ConfigEvent, StaticConfigurator};
+
+pub use device::{Device, LinkState};
+pub use packet_pool::{Packet, PacketBox, PacketBoxExt, PacketBuf};
+pub use stack::{init, is_config_up, is_init, is_link_up, run};
+
+#[cfg(feature = "tcp")]
+mod tcp_socket;
+#[cfg(feature = "tcp")]
+pub use tcp_socket::TcpSocket;
+
+// smoltcp reexports
+pub use smoltcp::phy::{DeviceCapabilities, Medium};
+pub use smoltcp::time::Duration as SmolDuration;
+pub use smoltcp::time::Instant as SmolInstant;
+pub use smoltcp::wire::{IpAddress, IpCidr, Ipv4Address, Ipv4Cidr};
+pub type Interface = smoltcp::iface::Interface<'static, device::DeviceAdapter>;
+pub type SocketSet = smoltcp::socket::SocketSet<'static>;
+pub use smoltcp::{Error, Result};
diff --git a/embassy-net/src/packet_pool.rs b/embassy-net/src/packet_pool.rs
new file mode 100644
index 000000000..2c27d4013
--- /dev/null
+++ b/embassy-net/src/packet_pool.rs
@@ -0,0 +1,92 @@
+use as_slice::{AsMutSlice, AsSlice};
+use core::ops::{Deref, DerefMut, Range};
+
+use atomic_pool::{pool, Box};
+
+pub const MTU: usize = 1514;
+pub const PACKET_POOL_SIZE: usize = 4;
+
+pool!(pub PacketPool: [Packet; PACKET_POOL_SIZE]);
+pub type PacketBox = Box<PacketPool>;
+
+pub struct Packet(pub [u8; MTU]);
+
+impl Packet {
+    pub const fn new() -> Self {
+        Self([0; MTU])
+    }
+}
+
+pub trait PacketBoxExt {
+    fn slice(self, range: Range<usize>) -> PacketBuf;
+}
+
+impl PacketBoxExt for PacketBox {
+    fn slice(self, range: Range<usize>) -> PacketBuf {
+        PacketBuf {
+            packet: self,
+            range,
+        }
+    }
+}
+
+impl AsSlice for Packet {
+    type Element = u8;
+
+    fn as_slice(&self) -> &[Self::Element] {
+        &self.deref()[..]
+    }
+}
+
+impl AsMutSlice for Packet {
+    fn as_mut_slice(&mut self) -> &mut [Self::Element] {
+        &mut self.deref_mut()[..]
+    }
+}
+
+impl Deref for Packet {
+    type Target = [u8; MTU];
+
+    fn deref(&self) -> &[u8; MTU] {
+        &self.0
+    }
+}
+
+impl DerefMut for Packet {
+    fn deref_mut(&mut self) -> &mut [u8; MTU] {
+        &mut self.0
+    }
+}
+
+pub struct PacketBuf {
+    packet: PacketBox,
+    range: Range<usize>,
+}
+
+impl AsSlice for PacketBuf {
+    type Element = u8;
+
+    fn as_slice(&self) -> &[Self::Element] {
+        &self.packet[self.range.clone()]
+    }
+}
+
+impl AsMutSlice for PacketBuf {
+    fn as_mut_slice(&mut self) -> &mut [Self::Element] {
+        &mut self.packet[self.range.clone()]
+    }
+}
+
+impl Deref for PacketBuf {
+    type Target = [u8];
+
+    fn deref(&self) -> &[u8] {
+        &self.packet[self.range.clone()]
+    }
+}
+
+impl DerefMut for PacketBuf {
+    fn deref_mut(&mut self) -> &mut [u8] {
+        &mut self.packet[self.range.clone()]
+    }
+}
diff --git a/embassy-net/src/stack.rs b/embassy-net/src/stack.rs
new file mode 100644
index 000000000..e436beb1e
--- /dev/null
+++ b/embassy-net/src/stack.rs
@@ -0,0 +1,259 @@
+use core::cell::RefCell;
+use core::future::Future;
+use core::task::Context;
+use core::task::Poll;
+use embassy::time::{Instant, Timer};
+use embassy::util::ThreadModeMutex;
+use embassy::util::{Forever, WakerRegistration};
+use futures::pin_mut;
+use smoltcp::iface::InterfaceBuilder;
+#[cfg(feature = "medium-ethernet")]
+use smoltcp::iface::{Neighbor, NeighborCache, Route, Routes};
+use smoltcp::phy::Device as _;
+use smoltcp::phy::Medium;
+use smoltcp::socket::SocketSetItem;
+use smoltcp::time::Instant as SmolInstant;
+#[cfg(feature = "medium-ethernet")]
+use smoltcp::wire::EthernetAddress;
+use smoltcp::wire::{IpAddress, IpCidr, Ipv4Address, Ipv4Cidr};
+
+use crate::config::Configurator;
+use crate::config::Event;
+use crate::device::{Device, DeviceAdapter, LinkState};
+use crate::fmt::*;
+use crate::{Interface, SocketSet};
+
+const ADDRESSES_LEN: usize = 1;
+const NEIGHBOR_CACHE_LEN: usize = 8;
+const SOCKETS_LEN: usize = 2;
+const LOCAL_PORT_MIN: u16 = 1025;
+const LOCAL_PORT_MAX: u16 = 65535;
+
+struct StackResources {
+    addresses: [IpCidr; ADDRESSES_LEN],
+    sockets: [Option<SocketSetItem<'static>>; SOCKETS_LEN],
+
+    #[cfg(feature = "medium-ethernet")]
+    routes: [Option<(IpCidr, Route)>; 1],
+    #[cfg(feature = "medium-ethernet")]
+    neighbor_cache: [Option<(IpAddress, Neighbor)>; NEIGHBOR_CACHE_LEN],
+}
+
+static STACK_RESOURCES: Forever<StackResources> = Forever::new();
+static STACK: ThreadModeMutex<RefCell<Option<Stack>>> = ThreadModeMutex::new(RefCell::new(None));
+
+pub(crate) struct Stack {
+    iface: Interface,
+    pub sockets: SocketSet,
+    link_up: bool,
+    config_up: bool,
+    next_local_port: u16,
+    configurator: &'static mut dyn Configurator,
+    waker: WakerRegistration,
+}
+
+impl Stack {
+    pub(crate) fn with<R>(f: impl FnOnce(&mut Stack) -> R) -> R {
+        let mut stack = STACK.borrow().borrow_mut();
+        let stack = stack.as_mut().unwrap();
+        f(stack)
+    }
+
+    pub fn get_local_port(&mut self) -> u16 {
+        let res = self.next_local_port;
+        self.next_local_port = if res >= LOCAL_PORT_MAX {
+            LOCAL_PORT_MIN
+        } else {
+            res + 1
+        };
+        res
+    }
+
+    pub(crate) fn wake(&mut self) {
+        self.waker.wake()
+    }
+
+    fn poll_configurator(&mut self, timestamp: SmolInstant) {
+        let medium = self.iface.device().capabilities().medium;
+
+        match self
+            .configurator
+            .poll(&mut self.iface, &mut self.sockets, timestamp)
+        {
+            Event::NoChange => {}
+            Event::Configured(config) => {
+                debug!("Acquired IP configuration:");
+
+                debug!("   IP address:      {}", config.address);
+                set_ipv4_addr(&mut self.iface, config.address);
+
+                #[cfg(feature = "medium-ethernet")]
+                if medium == Medium::Ethernet {
+                    if let Some(gateway) = config.gateway {
+                        debug!("   Default gateway: {}", gateway);
+                        self.iface
+                            .routes_mut()
+                            .add_default_ipv4_route(gateway)
+                            .unwrap();
+                    } else {
+                        debug!("   Default gateway: None");
+                        self.iface.routes_mut().remove_default_ipv4_route();
+                    }
+                }
+                for (i, s) in config.dns_servers.iter().enumerate() {
+                    debug!("   DNS server {}:    {}", i, s);
+                }
+
+                self.config_up = true;
+            }
+            Event::Deconfigured => {
+                debug!("Lost IP configuration");
+                set_ipv4_addr(&mut self.iface, Ipv4Cidr::new(Ipv4Address::UNSPECIFIED, 0));
+                #[cfg(feature = "medium-ethernet")]
+                if medium == Medium::Ethernet {
+                    self.iface.routes_mut().remove_default_ipv4_route();
+                }
+                self.config_up = false;
+            }
+        }
+    }
+
+    fn poll(&mut self, cx: &mut Context<'_>) {
+        self.iface.device_mut().device.register_waker(cx.waker());
+        self.waker.register(cx.waker());
+
+        let timestamp = instant_to_smoltcp(Instant::now());
+        if let Err(_) = self.iface.poll(&mut self.sockets, timestamp) {
+            // If poll() returns error, it may not be done yet, so poll again later.
+            cx.waker().wake_by_ref();
+            return;
+        }
+
+        // Update link up
+        let old_link_up = self.link_up;
+        self.link_up = self.iface.device_mut().device.link_state() == LinkState::Up;
+
+        // Print when changed
+        if old_link_up != self.link_up {
+            if self.link_up {
+                info!("Link up!");
+            } else {
+                info!("Link down!");
+            }
+        }
+
+        if old_link_up || self.link_up {
+            self.poll_configurator(timestamp)
+        }
+
+        if let Some(poll_at) = self.iface.poll_at(&mut self.sockets, timestamp) {
+            let t = Timer::at(instant_from_smoltcp(poll_at));
+            pin_mut!(t);
+            if t.poll(cx).is_ready() {
+                cx.waker().wake_by_ref();
+            }
+        }
+    }
+}
+
+fn set_ipv4_addr(iface: &mut Interface, cidr: Ipv4Cidr) {
+    iface.update_ip_addrs(|addrs| {
+        let dest = addrs.iter_mut().next().unwrap();
+        *dest = IpCidr::Ipv4(cidr);
+    });
+}
+
+/// Initialize embassy_net.
+/// This function must be called from thread mode.
+pub fn init(device: &'static mut dyn Device, configurator: &'static mut dyn Configurator) {
+    const NONE_SOCKET: Option<SocketSetItem<'static>> = None;
+    let res = STACK_RESOURCES.put(StackResources {
+        addresses: [IpCidr::new(Ipv4Address::UNSPECIFIED.into(), 32)],
+        sockets: [NONE_SOCKET; SOCKETS_LEN],
+
+        #[cfg(feature = "medium-ethernet")]
+        routes: [None; 1],
+        #[cfg(feature = "medium-ethernet")]
+        neighbor_cache: [None; NEIGHBOR_CACHE_LEN],
+    });
+
+    let medium = device.capabilities().medium;
+
+    #[cfg(feature = "medium-ethernet")]
+    let ethernet_addr = if medium == Medium::Ethernet {
+        device.ethernet_address()
+    } else {
+        [0, 0, 0, 0, 0, 0]
+    };
+
+    let mut b = InterfaceBuilder::new(DeviceAdapter::new(device));
+    b = b.ip_addrs(&mut res.addresses[..]);
+
+    #[cfg(feature = "medium-ethernet")]
+    if medium == Medium::Ethernet {
+        b = b.ethernet_addr(EthernetAddress(ethernet_addr));
+        b = b.neighbor_cache(NeighborCache::new(&mut res.neighbor_cache[..]));
+        b = b.routes(Routes::new(&mut res.routes[..]));
+    }
+
+    let iface = b.finalize();
+
+    let sockets = SocketSet::new(&mut res.sockets[..]);
+
+    let local_port = loop {
+        let mut res = [0u8; 2];
+        rand(&mut res);
+        let port = u16::from_le_bytes(res);
+        if port >= LOCAL_PORT_MIN && port <= LOCAL_PORT_MAX {
+            break port;
+        }
+    };
+
+    let stack = Stack {
+        iface,
+        sockets,
+        link_up: false,
+        config_up: false,
+        configurator,
+        next_local_port: local_port,
+        waker: WakerRegistration::new(),
+    };
+
+    *STACK.borrow().borrow_mut() = Some(stack);
+}
+
+pub fn is_init() -> bool {
+    STACK.borrow().borrow().is_some()
+}
+
+pub fn is_link_up() -> bool {
+    STACK.borrow().borrow().as_ref().unwrap().link_up
+}
+
+pub fn is_config_up() -> bool {
+    STACK.borrow().borrow().as_ref().unwrap().config_up
+}
+
+pub async fn run() {
+    futures::future::poll_fn(|cx| {
+        Stack::with(|stack| stack.poll(cx));
+        Poll::<()>::Pending
+    })
+    .await
+}
+
+fn instant_to_smoltcp(instant: Instant) -> SmolInstant {
+    SmolInstant::from_millis(instant.as_millis() as i64)
+}
+
+fn instant_from_smoltcp(instant: SmolInstant) -> Instant {
+    Instant::from_millis(instant.total_millis() as u64)
+}
+
+extern "Rust" {
+    fn _embassy_rand(buf: &mut [u8]);
+}
+
+fn rand(buf: &mut [u8]) {
+    unsafe { _embassy_rand(buf) }
+}
diff --git a/embassy-net/src/tcp_socket.rs b/embassy-net/src/tcp_socket.rs
new file mode 100644
index 000000000..4f43bc611
--- /dev/null
+++ b/embassy-net/src/tcp_socket.rs
@@ -0,0 +1,177 @@
+use core::marker::PhantomData;
+use core::mem;
+use core::pin::Pin;
+use core::task::{Context, Poll};
+use embassy::io;
+use embassy::io::{AsyncBufRead, AsyncWrite};
+use smoltcp::socket::SocketHandle;
+use smoltcp::socket::TcpSocket as SyncTcpSocket;
+use smoltcp::socket::{TcpSocketBuffer, TcpState};
+use smoltcp::time::Duration;
+use smoltcp::wire::IpEndpoint;
+
+use super::stack::Stack;
+use crate::fmt::*;
+use crate::{Error, Result};
+
+pub struct TcpSocket<'a> {
+    handle: SocketHandle,
+    ghost: PhantomData<&'a mut [u8]>,
+}
+
+impl<'a> Unpin for TcpSocket<'a> {}
+
+impl<'a> TcpSocket<'a> {
+    pub fn new(rx_buffer: &'a mut [u8], tx_buffer: &'a mut [u8]) -> Self {
+        let handle = Stack::with(|stack| {
+            let rx_buffer: &'static mut [u8] = unsafe { mem::transmute(rx_buffer) };
+            let tx_buffer: &'static mut [u8] = unsafe { mem::transmute(tx_buffer) };
+            stack.sockets.add(SyncTcpSocket::new(
+                TcpSocketBuffer::new(rx_buffer),
+                TcpSocketBuffer::new(tx_buffer),
+            ))
+        });
+
+        Self {
+            handle,
+            ghost: PhantomData,
+        }
+    }
+
+    pub async fn connect<T>(&mut self, remote_endpoint: T) -> Result<()>
+    where
+        T: Into<IpEndpoint>,
+    {
+        let local_port = Stack::with(|stack| stack.get_local_port());
+        self.with(|s| s.connect(remote_endpoint, local_port))?;
+
+        futures::future::poll_fn(|cx| {
+            self.with(|s| match s.state() {
+                TcpState::Closed | TcpState::TimeWait => Poll::Ready(Err(Error::Unaddressable)),
+                TcpState::Listen => Poll::Ready(Err(Error::Illegal)),
+                TcpState::SynSent | TcpState::SynReceived => {
+                    s.register_send_waker(cx.waker());
+                    Poll::Pending
+                }
+                _ => Poll::Ready(Ok(())),
+            })
+        })
+        .await
+    }
+
+    pub fn set_timeout(&mut self, duration: Option<Duration>) {
+        self.with(|s| s.set_timeout(duration))
+    }
+
+    pub fn set_keep_alive(&mut self, interval: Option<Duration>) {
+        self.with(|s| s.set_keep_alive(interval))
+    }
+
+    pub fn set_hop_limit(&mut self, hop_limit: Option<u8>) {
+        self.with(|s| s.set_hop_limit(hop_limit))
+    }
+
+    pub fn local_endpoint(&self) -> IpEndpoint {
+        self.with(|s| s.local_endpoint())
+    }
+
+    pub fn remote_endpoint(&self) -> IpEndpoint {
+        self.with(|s| s.remote_endpoint())
+    }
+
+    pub fn state(&self) -> TcpState {
+        self.with(|s| s.state())
+    }
+
+    pub fn close(&mut self) {
+        self.with(|s| s.close())
+    }
+
+    pub fn abort(&mut self) {
+        self.with(|s| s.abort())
+    }
+
+    pub fn may_send(&self) -> bool {
+        self.with(|s| s.may_send())
+    }
+
+    pub fn may_recv(&self) -> bool {
+        self.with(|s| s.may_recv())
+    }
+
+    fn with<R>(&self, f: impl FnOnce(&mut SyncTcpSocket) -> R) -> R {
+        Stack::with(|stack| {
+            let res = {
+                let mut s = stack.sockets.get::<SyncTcpSocket>(self.handle);
+                f(&mut *s)
+            };
+            stack.wake();
+            res
+        })
+    }
+}
+
+fn to_ioerr(_err: Error) -> io::Error {
+    // todo
+    io::Error::Other
+}
+
+impl<'a> Drop for TcpSocket<'a> {
+    fn drop(&mut self) {
+        Stack::with(|stack| {
+            stack.sockets.remove(self.handle);
+        })
+    }
+}
+
+impl<'a> AsyncBufRead for TcpSocket<'a> {
+    fn poll_fill_buf<'z>(
+        self: Pin<&'z mut Self>,
+        cx: &mut Context<'_>,
+    ) -> Poll<io::Result<&'z [u8]>> {
+        self.with(|socket| match socket.peek(1 << 30) {
+            // No data ready
+            Ok(buf) if buf.len() == 0 => {
+                socket.register_recv_waker(cx.waker());
+                Poll::Pending
+            }
+            // Data ready!
+            Ok(buf) => {
+                // Safety:
+                // - User can't touch the inner TcpSocket directly at all.
+                // - The socket itself won't touch these bytes until consume() is called, which
+                //   requires the user to release this borrow.
+                let buf: &'z [u8] = unsafe { core::mem::transmute(&*buf) };
+                Poll::Ready(Ok(buf))
+            }
+            // EOF
+            Err(Error::Finished) => Poll::Ready(Ok(&[][..])),
+            // Error
+            Err(e) => Poll::Ready(Err(to_ioerr(e))),
+        })
+    }
+
+    fn consume(self: Pin<&mut Self>, amt: usize) {
+        self.with(|s| s.recv(|_| (amt, ()))).unwrap()
+    }
+}
+
+impl<'a> AsyncWrite for TcpSocket<'a> {
+    fn poll_write(
+        self: Pin<&mut Self>,
+        cx: &mut Context<'_>,
+        buf: &[u8],
+    ) -> Poll<io::Result<usize>> {
+        self.with(|s| match s.send_slice(buf) {
+            // Not ready to send (no space in the tx buffer)
+            Ok(0) => {
+                s.register_send_waker(cx.waker());
+                Poll::Pending
+            }
+            // Some data sent
+            Ok(n) => Poll::Ready(Ok(n)),
+            // Error
+            Err(e) => Poll::Ready(Err(to_ioerr(e))),
+        })
+    }
+}