10 files changed, 1115 insertions, 0 deletions

diff --git a/embassy-net/src/config/dhcp.rs b/embassy-net/src/config/dhcp.rs
new file mode 100644
index 000000000..f5d598bdf
--- /dev/null
+++ b/embassy-net/src/config/dhcp.rs
@@ -0,0 +1,80 @@
+use embassy::util::Forever;
+use heapless::consts::*;
+use heapless::Vec;
+use smoltcp::dhcp::Dhcpv4Client;
+use smoltcp::socket::{RawPacketMetadata, RawSocketBuffer};
+use smoltcp::time::Instant;
+use smoltcp::wire::{Ipv4Address, Ipv4Cidr};
+
+use super::*;
+use crate::{device::LinkState, fmt::*};
+use crate::{Interface, SocketSet};
+
+pub struct DhcpResources {
+    rx_buffer: [u8; 900],
+    tx_buffer: [u8; 600],
+    rx_meta: [RawPacketMetadata; 1],
+    tx_meta: [RawPacketMetadata; 1],
+}
+
+pub struct DhcpConfigurator {
+    client: Option<Dhcpv4Client>,
+}
+
+impl DhcpConfigurator {
+    pub fn new() -> Self {
+        Self { client: None }
+    }
+}
+
+static DHCP_RESOURCES: Forever<DhcpResources> = Forever::new();
+
+impl Configurator for DhcpConfigurator {
+    fn poll(
+        &mut self,
+        iface: &mut Interface,
+        sockets: &mut SocketSet,
+        timestamp: Instant,
+    ) -> Option<Config> {
+        if self.client.is_none() {
+            let res = DHCP_RESOURCES.put(DhcpResources {
+                rx_buffer: [0; 900],
+                tx_buffer: [0; 600],
+                rx_meta: [RawPacketMetadata::EMPTY; 1],
+                tx_meta: [RawPacketMetadata::EMPTY; 1],
+            });
+            let rx_buffer = RawSocketBuffer::new(&mut res.rx_meta[..], &mut res.rx_buffer[..]);
+            let tx_buffer = RawSocketBuffer::new(&mut res.tx_meta[..], &mut res.tx_buffer[..]);
+            let dhcp = Dhcpv4Client::new(sockets, rx_buffer, tx_buffer, timestamp);
+            info!("created dhcp");
+            self.client = Some(dhcp)
+        }
+
+        let client = self.client.as_mut().unwrap();
+
+        let link_up = iface.device_mut().device.link_state() == LinkState::Up;
+        if !link_up {
+            client.reset(timestamp);
+            return Some(Config::Down);
+        }
+
+        let config = client.poll(iface, sockets, timestamp).unwrap_or(None)?;
+
+        if config.address.is_none() {
+            return Some(Config::Down);
+        }
+
+        let mut dns_servers = Vec::new();
+        for s in &config.dns_servers {
+            if let Some(addr) = s {
+                dns_servers.push(addr.clone()).unwrap();
+            }
+        }
+
+        return Some(Config::Up(UpConfig {
+            address: config.address.unwrap(),
+            gateway: config.router.unwrap_or(Ipv4Address::UNSPECIFIED),
+            dns_servers,
+        }));
+    }
+}
diff --git a/embassy-net/src/config/mod.rs b/embassy-net/src/config/mod.rs
new file mode 100644
index 000000000..596374f9e
--- /dev/null
+++ b/embassy-net/src/config/mod.rs
@@ -0,0 +1,34 @@
+use heapless::consts::*;
+use heapless::Vec;
+use smoltcp::time::Instant;
+use smoltcp::wire::{Ipv4Address, Ipv4Cidr};
+
+use crate::fmt::*;
+use crate::{Interface, SocketSet};
+
+mod dhcp;
+mod statik;
+pub use dhcp::DhcpConfigurator;
+pub use statik::StaticConfigurator;
+
+#[derive(Debug, Clone)]
+pub enum Config {
+    Down,
+    Up(UpConfig),
+}
+
+#[derive(Debug, Clone)]
+pub struct UpConfig {
+    pub address: Ipv4Cidr,
+    pub gateway: Ipv4Address,
+    pub dns_servers: Vec<Ipv4Address, U3>,
+}
+
+pub trait Configurator {
+    fn poll(
+        &mut self,
+        iface: &mut Interface,
+        sockets: &mut SocketSet,
+        timestamp: Instant,
+    ) -> Option<Config>;
+}
diff --git a/embassy-net/src/config/statik.rs b/embassy-net/src/config/statik.rs
new file mode 100644
index 000000000..52196f48a
--- /dev/null
+++ b/embassy-net/src/config/statik.rs
@@ -0,0 +1,26 @@
+use smoltcp::time::Instant;
+
+use super::*;
+use crate::fmt::*;
+use crate::{Interface, SocketSet};
+
+pub struct StaticConfigurator {
+    config: UpConfig,
+}
+
+impl StaticConfigurator {
+    pub fn new(config: UpConfig) -> Self {
+        Self { config }
+    }
+}
+
+impl Configurator for StaticConfigurator {
+    fn poll(
+        &mut self,
+        _iface: &mut Interface,
+        _sockets: &mut SocketSet,
+        _timestamp: Instant,
+    ) -> Option<Config> {
+        Some(Config::Up(self.config.clone()))
+    }
+}
diff --git a/embassy-net/src/device.rs b/embassy-net/src/device.rs
new file mode 100644
index 000000000..95a62e792
--- /dev/null
+++ b/embassy-net/src/device.rs
@@ -0,0 +1,103 @@
+use core::task::{Poll, Waker};
+use smoltcp::phy::Device as SmolDevice;
+use smoltcp::phy::DeviceCapabilities;
+use smoltcp::time::Instant as SmolInstant;
+use smoltcp::Result;
+
+use crate::fmt::*;
+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;
+}
+
+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>(mut 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..a2a320adf
--- /dev/null
+++ b/embassy-net/src/lib.rs
@@ -0,0 +1,31 @@
+#![cfg_attr(not(feature = "std"), no_std)]
+#![feature(const_fn)]
+#![feature(const_in_array_repeat_expressions)]
+#![feature(const_generics)]
+#![feature(const_evaluatable_checked)]
+#![allow(incomplete_features)]
+
+// This mod MUST go first, so that the others see its macros.
+pub(crate) mod fmt;
+
+mod pool; // TODO extract to embassy, or to own crate
+
+mod config;
+mod device;
+mod packet_pool;
+mod stack;
+mod tcp_socket;
+
+pub use config::{Config, Configurator, DhcpConfigurator, StaticConfigurator, UpConfig};
+pub use device::{Device, LinkState};
+pub use packet_pool::{Packet, PacketBox, PacketBuf};
+pub use stack::{init, is_init, run};
+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>;
diff --git a/embassy-net/src/packet_pool.rs b/embassy-net/src/packet_pool.rs
new file mode 100644
index 000000000..246356431
--- /dev/null
+++ b/embassy-net/src/packet_pool.rs
@@ -0,0 +1,88 @@
+use as_slice::{AsMutSlice, AsSlice};
+use core::ops::{Deref, DerefMut, Range};
+
+use super::pool::{BitPool, Box, StaticPool};
+
+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])
+    }
+}
+
+impl Box<PacketPool> {
+    pub 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/pool.rs b/embassy-net/src/pool.rs
new file mode 100644
index 000000000..3ab36e4cc
--- /dev/null
+++ b/embassy-net/src/pool.rs
@@ -0,0 +1,245 @@
+#![macro_use]
+
+use as_slice::{AsMutSlice, AsSlice};
+use core::cmp;
+use core::fmt;
+use core::hash::{Hash, Hasher};
+use core::mem::MaybeUninit;
+use core::ops::{Deref, DerefMut};
+use core::sync::atomic::{AtomicU32, Ordering};
+
+use crate::fmt::{assert, *};
+
+struct AtomicBitset<const N: usize>
+where
+    [AtomicU32; (N + 31) / 32]: Sized,
+{
+    used: [AtomicU32; (N + 31) / 32],
+}
+
+impl<const N: usize> AtomicBitset<N>
+where
+    [AtomicU32; (N + 31) / 32]: Sized,
+{
+    const fn new() -> Self {
+        const Z: AtomicU32 = AtomicU32::new(0);
+        Self {
+            used: [Z; (N + 31) / 32],
+        }
+    }
+
+    fn alloc(&self) -> Option<usize> {
+        for (i, val) in self.used.iter().enumerate() {
+            let res = val.fetch_update(Ordering::AcqRel, Ordering::Acquire, |val| {
+                let n = val.trailing_ones() as usize + i * 32;
+                if n >= N {
+                    None
+                } else {
+                    Some(val | (1 << n))
+                }
+            });
+            if let Ok(val) = res {
+                let n = val.trailing_ones() as usize + i * 32;
+                return Some(n);
+            }
+        }
+        None
+    }
+    fn free(&self, i: usize) {
+        assert!(i < N);
+        self.used[i / 32].fetch_and(!(1 << ((i % 32) as u32)), Ordering::AcqRel);
+    }
+}
+
+pub trait Pool<T> {
+    fn alloc(&self) -> Option<*mut T>;
+    unsafe fn free(&self, p: *mut T);
+}
+
+pub struct BitPool<T, const N: usize>
+where
+    [AtomicU32; (N + 31) / 32]: Sized,
+{
+    used: AtomicBitset<N>,
+    data: MaybeUninit<[T; N]>,
+}
+
+impl<T, const N: usize> BitPool<T, N>
+where
+    [AtomicU32; (N + 31) / 32]: Sized,
+{
+    pub const fn new() -> Self {
+        Self {
+            used: AtomicBitset::new(),
+            data: MaybeUninit::uninit(),
+        }
+    }
+}
+
+impl<T, const N: usize> Pool<T> for BitPool<T, N>
+where
+    [AtomicU32; (N + 31) / 32]: Sized,
+{
+    fn alloc(&self) -> Option<*mut T> {
+        let n = self.used.alloc()?;
+        let origin = self.data.as_ptr() as *mut T;
+        Some(unsafe { origin.add(n) })
+    }
+
+    /// safety: p must be a pointer obtained from self.alloc that hasn't been freed yet.
+    unsafe fn free(&self, p: *mut T) {
+        let origin = self.data.as_ptr() as *mut T;
+        let n = p.offset_from(origin);
+        assert!(n >= 0);
+        assert!((n as usize) < N);
+        self.used.free(n as usize);
+    }
+}
+
+pub trait StaticPool: 'static {
+    type Item: 'static;
+    type Pool: Pool<Self::Item>;
+    fn get() -> &'static Self::Pool;
+}
+
+pub struct Box<P: StaticPool> {
+    ptr: *mut P::Item,
+}
+
+impl<P: StaticPool> Box<P> {
+    pub fn new(item: P::Item) -> Option<Self> {
+        let p = match P::get().alloc() {
+            Some(p) => p,
+            None => {
+                warn!("alloc failed!");
+                return None;
+            }
+        };
+        //trace!("allocated {:u32}", p as u32);
+        unsafe { p.write(item) };
+        Some(Self { ptr: p })
+    }
+}
+
+impl<P: StaticPool> Drop for Box<P> {
+    fn drop(&mut self) {
+        unsafe {
+            //trace!("dropping {:u32}", self.ptr as u32);
+            self.ptr.drop_in_place();
+            P::get().free(self.ptr);
+        };
+    }
+}
+
+unsafe impl<P: StaticPool> Send for Box<P> where P::Item: Send {}
+
+unsafe impl<P: StaticPool> Sync for Box<P> where P::Item: Sync {}
+
+unsafe impl<P: StaticPool> stable_deref_trait::StableDeref for Box<P> {}
+
+impl<P: StaticPool> AsSlice for Box<P>
+where
+    P::Item: AsSlice,
+{
+    type Element = <P::Item as AsSlice>::Element;
+
+    fn as_slice(&self) -> &[Self::Element] {
+        self.deref().as_slice()
+    }
+}
+
+impl<P: StaticPool> AsMutSlice for Box<P>
+where
+    P::Item: AsMutSlice,
+{
+    fn as_mut_slice(&mut self) -> &mut [Self::Element] {
+        self.deref_mut().as_mut_slice()
+    }
+}
+
+impl<P: StaticPool> Deref for Box<P> {
+    type Target = P::Item;
+
+    fn deref(&self) -> &P::Item {
+        unsafe { &*self.ptr }
+    }
+}
+
+impl<P: StaticPool> DerefMut for Box<P> {
+    fn deref_mut(&mut self) -> &mut P::Item {
+        unsafe { &mut *self.ptr }
+    }
+}
+
+impl<P: StaticPool> fmt::Debug for Box<P>
+where
+    P::Item: fmt::Debug,
+{
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        <P::Item as fmt::Debug>::fmt(self, f)
+    }
+}
+
+impl<P: StaticPool> fmt::Display for Box<P>
+where
+    P::Item: fmt::Display,
+{
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        <P::Item as fmt::Display>::fmt(self, f)
+    }
+}
+
+impl<P: StaticPool> PartialEq for Box<P>
+where
+    P::Item: PartialEq,
+{
+    fn eq(&self, rhs: &Box<P>) -> bool {
+        <P::Item as PartialEq>::eq(self, rhs)
+    }
+}
+
+impl<P: StaticPool> Eq for Box<P> where P::Item: Eq {}
+
+impl<P: StaticPool> PartialOrd for Box<P>
+where
+    P::Item: PartialOrd,
+{
+    fn partial_cmp(&self, rhs: &Box<P>) -> Option<cmp::Ordering> {
+        <P::Item as PartialOrd>::partial_cmp(self, rhs)
+    }
+}
+
+impl<P: StaticPool> Ord for Box<P>
+where
+    P::Item: Ord,
+{
+    fn cmp(&self, rhs: &Box<P>) -> cmp::Ordering {
+        <P::Item as Ord>::cmp(self, rhs)
+    }
+}
+
+impl<P: StaticPool> Hash for Box<P>
+where
+    P::Item: Hash,
+{
+    fn hash<H>(&self, state: &mut H)
+    where
+        H: Hasher,
+    {
+        <P::Item as Hash>::hash(self, state)
+    }
+}
+
+macro_rules! pool {
+    ($vis:vis $name:ident: [$ty:ty; $size:expr]) => {
+        $vis struct $name;
+        impl StaticPool for $name {
+            type Item = $ty;
+            type Pool = BitPool<$ty, $size>;
+            fn get() -> &'static Self::Pool {
+                static POOL: BitPool<$ty, $size> = BitPool::new();
+                &POOL
+            }
+        }
+    };
+}
diff --git a/embassy-net/src/stack.rs b/embassy-net/src/stack.rs
new file mode 100644
index 000000000..c353f1bb1
--- /dev/null
+++ b/embassy-net/src/stack.rs
@@ -0,0 +1,212 @@
+use core::future::Future;
+use core::task::Context;
+use core::task::Poll;
+use core::{cell::RefCell, future};
+use embassy::time::{Instant, Timer};
+use embassy::util::ThreadModeMutex;
+use embassy::util::{Forever, WakerRegistration};
+use futures::pin_mut;
+use smoltcp::iface::{InterfaceBuilder, Neighbor, NeighborCache, Route, Routes};
+use smoltcp::phy::Device as _;
+use smoltcp::phy::Medium;
+use smoltcp::socket::SocketSetItem;
+use smoltcp::time::Instant as SmolInstant;
+use smoltcp::wire::{EthernetAddress, IpAddress, IpCidr, Ipv4Address};
+
+use crate::device::{Device, DeviceAdapter};
+use crate::fmt::*;
+use crate::{
+    config::{Config, Configurator},
+    device::LinkState,
+};
+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],
+    neighbor_cache: [Option<(IpAddress, Neighbor)>; NEIGHBOR_CACHE_LEN],
+    sockets: [Option<SocketSetItem<'static>>; SOCKETS_LEN],
+    routes: [Option<(IpCidr, Route)>; 1],
+}
+
+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,
+    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) {
+        if let Some(config) = self
+            .configurator
+            .poll(&mut self.iface, &mut self.sockets, timestamp)
+        {
+            let medium = self.iface.device().capabilities().medium;
+
+            let (addr, gateway) = match config {
+                Config::Up(config) => (config.address.into(), Some(config.gateway)),
+                Config::Down => (IpCidr::new(Ipv4Address::UNSPECIFIED.into(), 32), None),
+            };
+
+            self.iface.update_ip_addrs(|addrs| {
+                let curr_addr = &mut addrs[0];
+                if *curr_addr != addr {
+                    info!("IPv4 address: {:?} -> {:?}", *curr_addr, addr);
+                    *curr_addr = addr;
+                }
+            });
+
+            if medium == Medium::Ethernet {
+                self.iface.routes_mut().update(|r| {
+                    let cidr = IpCidr::new(IpAddress::v4(0, 0, 0, 0), 0);
+                    let curr_gateway = r.get(&cidr).map(|r| r.via_router);
+
+                    if curr_gateway != gateway.map(|a| a.into()) {
+                        info!("IPv4 gateway: {:?} -> {:?}", curr_gateway, gateway);
+                        if let Some(gateway) = gateway {
+                            r.insert(cidr, Route::new_ipv4_gateway(gateway)).unwrap();
+                        } else {
+                            r.remove(&cidr);
+                        }
+                    }
+                });
+            }
+        }
+    }
+
+    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(e) = 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();
+            }
+        }
+    }
+}
+
+/// Initialize embassy_net.
+/// This function must be called from thread mode.
+pub fn init(device: &'static mut dyn Device, configurator: &'static mut dyn Configurator) {
+    let res = STACK_RESOURCES.put(StackResources {
+        addresses: [IpCidr::new(Ipv4Address::UNSPECIFIED.into(), 32)],
+        neighbor_cache: [None; NEIGHBOR_CACHE_LEN],
+        sockets: [None; SOCKETS_LEN],
+        routes: [None; 1],
+    });
+
+    let ethernet_addr = EthernetAddress([0x02, 0x02, 0x02, 0x02, 0x02, 0x02]);
+
+    let medium = device.capabilities().medium;
+
+    let mut b = InterfaceBuilder::new(DeviceAdapter::new(device));
+    b = b.ip_addrs(&mut res.addresses[..]);
+
+    if medium == Medium::Ethernet {
+        b = b.ethernet_addr(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];
+        embassy::rand::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,
+        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 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)
+}
diff --git a/embassy-net/src/tcp_socket.rs b/embassy-net/src/tcp_socket.rs
new file mode 100644
index 000000000..7f4eb014c
--- /dev/null
+++ b/embassy-net/src/tcp_socket.rs
@@ -0,0 +1,178 @@
+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 smoltcp::{Error, Result};
+
+use super::stack::Stack;
+use crate::fmt::*;
+
+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(e: Error) -> io::Error {
+    warn!("smoltcp err: {:?}", e);
+    // 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))),
+        })
+    }
+}