Merge #717

717: WIP: USB CDC NCM (Ethernet over USB) r=Dirbaio a=Dirbaio

TODO:

- [x] Add support for string handling in `embassy-usb`, remove the MAC addr string hax
- [x] Harden parsing of incoming NTBs to avoid panics.
- [ ] Parse all datagrams in a NDP, not just the first. -- tricky, I've made it tell the host we support only one packet per NTB instead.
- [ ] Add support for all required control transfers. -- WONTFIX, seems no OS cares about those.
- [x] Works on Linux
- [x] Doesn't work on Android, make it work
- [x] Check if it works in Windows (Win10 has some sort of CDC NCM support afaict?) -- works on Win11, CDC-NCM not supported on Win10
- [x] Check if it works in MacOS (I don't know if it's supposed to) - WORKS

I won't add the `embassy-net` driver to `embassy-usb-ncm` for now because `embassy-net` buffer management will likely be refactored soon, so there's not much point to it.

Co-authored-by: Dario Nieuwenhuis <[email protected]>

10 files changed, 1032 insertions, 11 deletions

diff --git a/embassy-net/src/tcp_socket.rs b/embassy-net/src/tcp_socket.rs
index 4836f8075..5637505d4 100644
--- a/embassy-net/src/tcp_socket.rs
+++ b/embassy-net/src/tcp_socket.rs
@@ -58,7 +58,7 @@ impl<'a> TcpSocket<'a> {
         .await
     }
 
-    pub async fn listen<T>(&mut self, local_endpoint: T) -> Result<()>
+    pub async fn accept<T>(&mut self, local_endpoint: T) -> Result<()>
     where
         T: Into<IpEndpoint>,
     {
@@ -66,9 +66,7 @@ impl<'a> TcpSocket<'a> {
 
         futures::future::poll_fn(|cx| {
             self.with(|s, _| match s.state() {
-                TcpState::Closed | TcpState::TimeWait => Poll::Ready(Err(Error::Unaddressable)),
-                TcpState::Listen => Poll::Ready(Ok(())),
-                TcpState::SynSent | TcpState::SynReceived => {
+                TcpState::Listen | TcpState::SynSent | TcpState::SynReceived => {
                     s.register_send_waker(cx.waker());
                     Poll::Pending
                 }
diff --git a/embassy-usb-ncm/Cargo.toml b/embassy-usb-ncm/Cargo.toml
new file mode 100644
index 000000000..aaef01d6d
--- /dev/null
+++ b/embassy-usb-ncm/Cargo.toml
@@ -0,0 +1,19 @@
+[package]
+name = "embassy-usb-ncm"
+version = "0.1.0"
+edition = "2021"
+
+[package.metadata.embassy_docs]
+src_base = "https://github.com/embassy-rs/embassy/blob/embassy-usb-ncm-v$VERSION/embassy-usb-ncm/src/"
+src_base_git = "https://github.com/embassy-rs/embassy/blob/master/embassy-usb-ncm/src/"
+features = ["defmt"]
+flavors = [
+    { name = "default", target = "thumbv7em-none-eabihf" },
+]
+
+[dependencies]
+embassy = { version = "0.1.0", path = "../embassy" }
+embassy-usb = { version = "0.1.0", path = "../embassy-usb" }
+
+defmt = { version = "0.3", optional = true }
+log = { version = "0.4.14", optional = true }
diff --git a/embassy-usb-ncm/src/fmt.rs b/embassy-usb-ncm/src/fmt.rs
new file mode 100644
index 000000000..066970813
--- /dev/null
+++ b/embassy-usb-ncm/src/fmt.rs
@@ -0,0 +1,225 @@
+#![macro_use]
+#![allow(unused_macros)]
+
+#[cfg(all(feature = "defmt", feature = "log"))]
+compile_error!("You may not enable both `defmt` and `log` features.");
+
+macro_rules! assert {
+    ($($x:tt)*) => {
+        {
+            #[cfg(not(feature = "defmt"))]
+            ::core::assert!($($x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::assert!($($x)*);
+        }
+    };
+}
+
+macro_rules! assert_eq {
+    ($($x:tt)*) => {
+        {
+            #[cfg(not(feature = "defmt"))]
+            ::core::assert_eq!($($x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::assert_eq!($($x)*);
+        }
+    };
+}
+
+macro_rules! assert_ne {
+    ($($x:tt)*) => {
+        {
+            #[cfg(not(feature = "defmt"))]
+            ::core::assert_ne!($($x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::assert_ne!($($x)*);
+        }
+    };
+}
+
+macro_rules! debug_assert {
+    ($($x:tt)*) => {
+        {
+            #[cfg(not(feature = "defmt"))]
+            ::core::debug_assert!($($x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::debug_assert!($($x)*);
+        }
+    };
+}
+
+macro_rules! debug_assert_eq {
+    ($($x:tt)*) => {
+        {
+            #[cfg(not(feature = "defmt"))]
+            ::core::debug_assert_eq!($($x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::debug_assert_eq!($($x)*);
+        }
+    };
+}
+
+macro_rules! debug_assert_ne {
+    ($($x:tt)*) => {
+        {
+            #[cfg(not(feature = "defmt"))]
+            ::core::debug_assert_ne!($($x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::debug_assert_ne!($($x)*);
+        }
+    };
+}
+
+macro_rules! todo {
+    ($($x:tt)*) => {
+        {
+            #[cfg(not(feature = "defmt"))]
+            ::core::todo!($($x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::todo!($($x)*);
+        }
+    };
+}
+
+macro_rules! unreachable {
+    ($($x:tt)*) => {
+        {
+            #[cfg(not(feature = "defmt"))]
+            ::core::unreachable!($($x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::unreachable!($($x)*);
+        }
+    };
+}
+
+macro_rules! panic {
+    ($($x:tt)*) => {
+        {
+            #[cfg(not(feature = "defmt"))]
+            ::core::panic!($($x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::panic!($($x)*);
+        }
+    };
+}
+
+macro_rules! trace {
+    ($s:literal $(, $x:expr)* $(,)?) => {
+        {
+            #[cfg(feature = "log")]
+            ::log::trace!($s $(, $x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::trace!($s $(, $x)*);
+            #[cfg(not(any(feature = "log", feature="defmt")))]
+            let _ = ($( & $x ),*);
+        }
+    };
+}
+
+macro_rules! debug {
+    ($s:literal $(, $x:expr)* $(,)?) => {
+        {
+            #[cfg(feature = "log")]
+            ::log::debug!($s $(, $x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::debug!($s $(, $x)*);
+            #[cfg(not(any(feature = "log", feature="defmt")))]
+            let _ = ($( & $x ),*);
+        }
+    };
+}
+
+macro_rules! info {
+    ($s:literal $(, $x:expr)* $(,)?) => {
+        {
+            #[cfg(feature = "log")]
+            ::log::info!($s $(, $x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::info!($s $(, $x)*);
+            #[cfg(not(any(feature = "log", feature="defmt")))]
+            let _ = ($( & $x ),*);
+        }
+    };
+}
+
+macro_rules! warn {
+    ($s:literal $(, $x:expr)* $(,)?) => {
+        {
+            #[cfg(feature = "log")]
+            ::log::warn!($s $(, $x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::warn!($s $(, $x)*);
+            #[cfg(not(any(feature = "log", feature="defmt")))]
+            let _ = ($( & $x ),*);
+        }
+    };
+}
+
+macro_rules! error {
+    ($s:literal $(, $x:expr)* $(,)?) => {
+        {
+            #[cfg(feature = "log")]
+            ::log::error!($s $(, $x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::error!($s $(, $x)*);
+            #[cfg(not(any(feature = "log", feature="defmt")))]
+            let _ = ($( & $x ),*);
+        }
+    };
+}
+
+#[cfg(feature = "defmt")]
+macro_rules! unwrap {
+    ($($x:tt)*) => {
+        ::defmt::unwrap!($($x)*)
+    };
+}
+
+#[cfg(not(feature = "defmt"))]
+macro_rules! unwrap {
+    ($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-usb-ncm/src/lib.rs b/embassy-usb-ncm/src/lib.rs
new file mode 100644
index 000000000..3a5abee8d
--- /dev/null
+++ b/embassy-usb-ncm/src/lib.rs
@@ -0,0 +1,489 @@
+#![no_std]
+
+// This mod MUST go first, so that the others see its macros.
+pub(crate) mod fmt;
+
+use core::cell::Cell;
+use core::intrinsics::copy_nonoverlapping;
+use core::mem::{size_of, MaybeUninit};
+use embassy_usb::control::{self, ControlHandler, InResponse, OutResponse, Request};
+use embassy_usb::driver::{Endpoint, EndpointError, EndpointIn, EndpointOut};
+use embassy_usb::{driver::Driver, types::*, Builder};
+
+/// This should be used as `device_class` when building the `UsbDevice`.
+pub const USB_CLASS_CDC: u8 = 0x02;
+
+const USB_CLASS_CDC_DATA: u8 = 0x0a;
+const CDC_SUBCLASS_NCM: u8 = 0x0d;
+
+const CDC_PROTOCOL_NONE: u8 = 0x00;
+const CDC_PROTOCOL_NTB: u8 = 0x01;
+
+const CS_INTERFACE: u8 = 0x24;
+const CDC_TYPE_HEADER: u8 = 0x00;
+const CDC_TYPE_UNION: u8 = 0x06;
+const CDC_TYPE_ETHERNET: u8 = 0x0F;
+const CDC_TYPE_NCM: u8 = 0x1A;
+
+const REQ_SEND_ENCAPSULATED_COMMAND: u8 = 0x00;
+//const REQ_GET_ENCAPSULATED_COMMAND: u8 = 0x01;
+//const REQ_SET_ETHERNET_MULTICAST_FILTERS: u8 = 0x40;
+//const REQ_SET_ETHERNET_POWER_MANAGEMENT_PATTERN_FILTER: u8 = 0x41;
+//const REQ_GET_ETHERNET_POWER_MANAGEMENT_PATTERN_FILTER: u8 = 0x42;
+//const REQ_SET_ETHERNET_PACKET_FILTER: u8 = 0x43;
+//const REQ_GET_ETHERNET_STATISTIC: u8 = 0x44;
+const REQ_GET_NTB_PARAMETERS: u8 = 0x80;
+//const REQ_GET_NET_ADDRESS: u8 = 0x81;
+//const REQ_SET_NET_ADDRESS: u8 = 0x82;
+//const REQ_GET_NTB_FORMAT: u8 = 0x83;
+//const REQ_SET_NTB_FORMAT: u8 = 0x84;
+//const REQ_GET_NTB_INPUT_SIZE: u8 = 0x85;
+const REQ_SET_NTB_INPUT_SIZE: u8 = 0x86;
+//const REQ_GET_MAX_DATAGRAM_SIZE: u8 = 0x87;
+//const REQ_SET_MAX_DATAGRAM_SIZE: u8 = 0x88;
+//const REQ_GET_CRC_MODE: u8 = 0x89;
+//const REQ_SET_CRC_MODE: u8 = 0x8A;
+
+//const NOTIF_MAX_PACKET_SIZE: u16 = 8;
+//const NOTIF_POLL_INTERVAL: u8 = 20;
+
+const NTB_MAX_SIZE: usize = 2048;
+const SIG_NTH: u32 = 0x484d434e;
+const SIG_NDP_NO_FCS: u32 = 0x304d434e;
+const SIG_NDP_WITH_FCS: u32 = 0x314d434e;
+
+const ALTERNATE_SETTING_DISABLED: u8 = 0x00;
+const ALTERNATE_SETTING_ENABLED: u8 = 0x01;
+
+/// Simple NTB header (NTH+NDP all in one) for sending packets
+#[repr(packed)]
+#[allow(unused)]
+struct NtbOutHeader {
+    // NTH
+    nth_sig: u32,
+    nth_len: u16,
+    nth_seq: u16,
+    nth_total_len: u16,
+    nth_first_index: u16,
+
+    // NDP
+    ndp_sig: u32,
+    ndp_len: u16,
+    ndp_next_index: u16,
+    ndp_datagram_index: u16,
+    ndp_datagram_len: u16,
+    ndp_term1: u16,
+    ndp_term2: u16,
+}
+
+#[repr(packed)]
+#[allow(unused)]
+struct NtbParameters {
+    length: u16,
+    formats_supported: u16,
+    in_params: NtbParametersDir,
+    out_params: NtbParametersDir,
+}
+
+#[repr(packed)]
+#[allow(unused)]
+struct NtbParametersDir {
+    max_size: u32,
+    divisor: u16,
+    payload_remainder: u16,
+    out_alignment: u16,
+    max_datagram_count: u16,
+}
+
+fn byteify<T>(buf: &mut [u8], data: T) -> &[u8] {
+    let len = size_of::<T>();
+    unsafe { copy_nonoverlapping(&data as *const _ as *const u8, buf.as_mut_ptr(), len) }
+    &buf[..len]
+}
+
+pub struct State<'a> {
+    comm_control: MaybeUninit<CommControl<'a>>,
+    data_control: MaybeUninit<DataControl>,
+    shared: ControlShared,
+}
+
+impl<'a> State<'a> {
+    pub fn new() -> Self {
+        Self {
+            comm_control: MaybeUninit::uninit(),
+            data_control: MaybeUninit::uninit(),
+            shared: Default::default(),
+        }
+    }
+}
+
+/// Shared data between Control and CdcAcmClass
+struct ControlShared {
+    mac_addr: Cell<[u8; 6]>,
+}
+
+impl Default for ControlShared {
+    fn default() -> Self {
+        ControlShared {
+            mac_addr: Cell::new([0; 6]),
+        }
+    }
+}
+
+struct CommControl<'a> {
+    mac_addr_string: StringIndex,
+    shared: &'a ControlShared,
+}
+
+impl<'d> ControlHandler for CommControl<'d> {
+    fn control_out(&mut self, req: control::Request, _data: &[u8]) -> OutResponse {
+        match req.request {
+            REQ_SEND_ENCAPSULATED_COMMAND => {
+                // We don't actually support encapsulated commands but pretend we do for standards
+                // compatibility.
+                OutResponse::Accepted
+            }
+            REQ_SET_NTB_INPUT_SIZE => {
+                // TODO
+                OutResponse::Accepted
+            }
+            _ => OutResponse::Rejected,
+        }
+    }
+
+    fn control_in<'a>(&'a mut self, req: Request, buf: &'a mut [u8]) -> InResponse<'a> {
+        match req.request {
+            REQ_GET_NTB_PARAMETERS => {
+                let res = NtbParameters {
+                    length: size_of::<NtbParameters>() as _,
+                    formats_supported: 1, // only 16bit,
+                    in_params: NtbParametersDir {
+                        max_size: NTB_MAX_SIZE as _,
+                        divisor: 4,
+                        payload_remainder: 0,
+                        out_alignment: 4,
+                        max_datagram_count: 0, // not used
+                    },
+                    out_params: NtbParametersDir {
+                        max_size: NTB_MAX_SIZE as _,
+                        divisor: 4,
+                        payload_remainder: 0,
+                        out_alignment: 4,
+                        max_datagram_count: 1, // We only decode 1 packet per NTB
+                    },
+                };
+                InResponse::Accepted(byteify(buf, res))
+            }
+            _ => InResponse::Rejected,
+        }
+    }
+
+    fn get_string<'a>(
+        &'a mut self,
+        index: StringIndex,
+        _lang_id: u16,
+        buf: &'a mut [u8],
+    ) -> Option<&'a str> {
+        if index == self.mac_addr_string {
+            let mac_addr = self.shared.mac_addr.get();
+            for i in 0..12 {
+                let n = (mac_addr[i / 2] >> ((1 - i % 2) * 4)) & 0xF;
+                buf[i] = match n {
+                    0x0..=0x9 => b'0' + n,
+                    0xA..=0xF => b'A' + n - 0xA,
+                    _ => unreachable!(),
+                }
+            }
+
+            Some(unsafe { core::str::from_utf8_unchecked(&buf[..12]) })
+        } else {
+            warn!("unknown string index requested");
+            None
+        }
+    }
+}
+
+struct DataControl {}
+
+impl ControlHandler for DataControl {
+    fn set_alternate_setting(&mut self, alternate_setting: u8) {
+        match alternate_setting {
+            ALTERNATE_SETTING_ENABLED => info!("ncm: interface enabled"),
+            ALTERNATE_SETTING_DISABLED => info!("ncm: interface disabled"),
+            _ => unreachable!(),
+        }
+    }
+}
+
+pub struct CdcNcmClass<'d, D: Driver<'d>> {
+    _comm_if: InterfaceNumber,
+    comm_ep: D::EndpointIn,
+
+    data_if: InterfaceNumber,
+    read_ep: D::EndpointOut,
+    write_ep: D::EndpointIn,
+
+    _control: &'d ControlShared,
+}
+
+impl<'d, D: Driver<'d>> CdcNcmClass<'d, D> {
+    pub fn new(
+        builder: &mut Builder<'d, D>,
+        state: &'d mut State<'d>,
+        mac_address: [u8; 6],
+        max_packet_size: u16,
+    ) -> Self {
+        let control_shared = &state.shared;
+        control_shared.mac_addr.set(mac_address);
+
+        let mut func = builder.function(USB_CLASS_CDC, CDC_SUBCLASS_NCM, CDC_PROTOCOL_NONE);
+
+        // Control interface
+        let mut iface = func.interface();
+        let mac_addr_string = iface.string();
+        iface.handler(state.comm_control.write(CommControl {
+            mac_addr_string,
+            shared: &control_shared,
+        }));
+        let comm_if = iface.interface_number();
+        let mut alt = iface.alt_setting(USB_CLASS_CDC, CDC_SUBCLASS_NCM, CDC_PROTOCOL_NONE);
+
+        alt.descriptor(
+            CS_INTERFACE,
+            &[
+                CDC_TYPE_HEADER, // bDescriptorSubtype
+                0x10,
+                0x01, // bcdCDC (1.10)
+            ],
+        );
+        alt.descriptor(
+            CS_INTERFACE,
+            &[
+                CDC_TYPE_UNION,        // bDescriptorSubtype
+                comm_if.into(),        // bControlInterface
+                u8::from(comm_if) + 1, // bSubordinateInterface
+            ],
+        );
+        alt.descriptor(
+            CS_INTERFACE,
+            &[
+                CDC_TYPE_ETHERNET,      // bDescriptorSubtype
+                mac_addr_string.into(), // iMACAddress
+                0,                      // bmEthernetStatistics
+                0,                      // |
+                0,                      // |
+                0,                      // |
+                0xea,                   // wMaxSegmentSize = 1514
+                0x05,                   // |
+                0,                      // wNumberMCFilters
+                0,                      // |
+                0,                      // bNumberPowerFilters
+            ],
+        );
+        alt.descriptor(
+            CS_INTERFACE,
+            &[
+                CDC_TYPE_NCM, // bDescriptorSubtype
+                0x00,         // bcdNCMVersion
+                0x01,         // |
+                0,            // bmNetworkCapabilities
+            ],
+        );
+
+        let comm_ep = alt.endpoint_interrupt_in(8, 255);
+
+        // Data interface
+        let mut iface = func.interface();
+        iface.handler(state.data_control.write(DataControl {}));
+        let data_if = iface.interface_number();
+        let _alt = iface.alt_setting(USB_CLASS_CDC_DATA, 0x00, CDC_PROTOCOL_NTB);
+        let mut alt = iface.alt_setting(USB_CLASS_CDC_DATA, 0x00, CDC_PROTOCOL_NTB);
+        let read_ep = alt.endpoint_bulk_out(max_packet_size);
+        let write_ep = alt.endpoint_bulk_in(max_packet_size);
+
+        CdcNcmClass {
+            _comm_if: comm_if,
+            comm_ep,
+            data_if,
+            read_ep,
+            write_ep,
+            _control: control_shared,
+        }
+    }
+
+    pub fn split(self) -> (Sender<'d, D>, Receiver<'d, D>) {
+        (
+            Sender {
+                write_ep: self.write_ep,
+                seq: 0,
+            },
+            Receiver {
+                data_if: self.data_if,
+                comm_ep: self.comm_ep,
+                read_ep: self.read_ep,
+            },
+        )
+    }
+}
+
+pub struct Sender<'d, D: Driver<'d>> {
+    write_ep: D::EndpointIn,
+    seq: u16,
+}
+
+impl<'d, D: Driver<'d>> Sender<'d, D> {
+    pub async fn write_packet(&mut self, data: &[u8]) -> Result<(), EndpointError> {
+        let seq = self.seq;
+        self.seq = self.seq.wrapping_add(1);
+
+        const MAX_PACKET_SIZE: usize = 64; // TODO unhardcode
+        const OUT_HEADER_LEN: usize = 28;
+
+        let header = NtbOutHeader {
+            nth_sig: SIG_NTH,
+            nth_len: 0x0c,
+            nth_seq: seq,
+            nth_total_len: (data.len() + OUT_HEADER_LEN) as u16,
+            nth_first_index: 0x0c,
+
+            ndp_sig: SIG_NDP_NO_FCS,
+            ndp_len: 0x10,
+            ndp_next_index: 0x00,
+            ndp_datagram_index: OUT_HEADER_LEN as u16,
+            ndp_datagram_len: data.len() as u16,
+            ndp_term1: 0x00,
+            ndp_term2: 0x00,
+        };
+
+        // Build first packet on a buffer, send next packets straight from `data`.
+        let mut buf = [0; MAX_PACKET_SIZE];
+        let n = byteify(&mut buf, header);
+        assert_eq!(n.len(), OUT_HEADER_LEN);
+
+        if OUT_HEADER_LEN + data.len() < MAX_PACKET_SIZE {
+            // First packet is not full, just send it.
+            // No need to send ZLP because it's short for sure.
+            buf[OUT_HEADER_LEN..][..data.len()].copy_from_slice(data);
+            self.write_ep
+                .write(&buf[..OUT_HEADER_LEN + data.len()])
+                .await?;
+        } else {
+            let (d1, d2) = data.split_at(MAX_PACKET_SIZE - OUT_HEADER_LEN);
+
+            buf[OUT_HEADER_LEN..].copy_from_slice(d1);
+            self.write_ep.write(&buf).await?;
+
+            for chunk in d2.chunks(MAX_PACKET_SIZE) {
+                self.write_ep.write(&chunk).await?;
+            }
+
+            // Send ZLP if needed.
+            if d2.len() % MAX_PACKET_SIZE == 0 {
+                self.write_ep.write(&[]).await?;
+            }
+        }
+
+        Ok(())
+    }
+}
+
+pub struct Receiver<'d, D: Driver<'d>> {
+    data_if: InterfaceNumber,
+    comm_ep: D::EndpointIn,
+    read_ep: D::EndpointOut,
+}
+
+impl<'d, D: Driver<'d>> Receiver<'d, D> {
+    /// Reads a single packet from the OUT endpoint.
+    pub async fn read_packet(&mut self, buf: &mut [u8]) -> Result<usize, EndpointError> {
+        // Retry loop
+        loop {
+            // read NTB
+            let mut ntb = [0u8; NTB_MAX_SIZE];
+            let mut pos = 0;
+            loop {
+                let n = self.read_ep.read(&mut ntb[pos..]).await?;
+                pos += n;
+                if n < self.read_ep.info().max_packet_size as usize || pos == NTB_MAX_SIZE {
+                    break;
+                }
+            }
+
+            let ntb = &ntb[..pos];
+
+            // Process NTB header (NTH)
+            let nth = match ntb.get(..12) {
+                Some(x) => x,
+                None => {
+                    warn!("Received too short NTB");
+                    continue;
+                }
+            };
+            let sig = u32::from_le_bytes(nth[0..4].try_into().unwrap());
+            if sig != SIG_NTH {
+                warn!("Received bad NTH sig.");
+                continue;
+            }
+            let ndp_idx = u16::from_le_bytes(nth[10..12].try_into().unwrap()) as usize;
+
+            // Process NTB Datagram Pointer (NDP)
+            let ndp = match ntb.get(ndp_idx..ndp_idx + 12) {
+                Some(x) => x,
+                None => {
+                    warn!("NTH has an NDP pointer out of range.");
+                    continue;
+                }
+            };
+            let sig = u32::from_le_bytes(ndp[0..4].try_into().unwrap());
+            if sig != SIG_NDP_NO_FCS && sig != SIG_NDP_WITH_FCS {
+                warn!("Received bad NDP sig.");
+                continue;
+            }
+            let datagram_index = u16::from_le_bytes(ndp[8..10].try_into().unwrap()) as usize;
+            let datagram_len = u16::from_le_bytes(ndp[10..12].try_into().unwrap()) as usize;
+
+            if datagram_index == 0 || datagram_len == 0 {
+                // empty, ignore. This is allowed by the spec, so don't warn.
+                continue;
+            }
+
+            // Process actual datagram, finally.
+            let datagram = match ntb.get(datagram_index..datagram_index + datagram_len) {
+                Some(x) => x,
+                None => {
+                    warn!("NDP has a datagram pointer out of range.");
+                    continue;
+                }
+            };
+            buf[..datagram_len].copy_from_slice(datagram);
+
+            return Ok(datagram_len);
+        }
+    }
+
+    /// Waits for the USB host to enable this interface
+    pub async fn wait_connection(&mut self) -> Result<(), EndpointError> {
+        loop {
+            self.read_ep.wait_enabled().await;
+            self.comm_ep.wait_enabled().await;
+
+            let buf = [
+                0xA1, //bmRequestType
+                0x00, //bNotificationType = NETWORK_CONNECTION
+                0x01, // wValue = connected
+                0x00,
+                self.data_if.into(), // wIndex = interface
+                0x00,
+                0x00, // wLength
+                0x00,
+            ];
+            match self.comm_ep.write(&buf).await {
+                Ok(()) => break,                   // Done!
+                Err(EndpointError::Disabled) => {} // Got disabled again, wait again.
+                Err(e) => return Err(e),
+            }
+        }
+
+        Ok(())
+    }
+}
diff --git a/examples/nrf/Cargo.toml b/examples/nrf/Cargo.toml
index e944c171a..4258544f0 100644
--- a/examples/nrf/Cargo.toml
+++ b/examples/nrf/Cargo.toml
@@ -6,14 +6,16 @@ version = "0.1.0"
 
 [features]
 default = ["nightly"]
-nightly = ["embassy-nrf/nightly", "embassy-nrf/unstable-traits", "embassy-usb", "embassy-usb-serial", "embassy-usb-hid"]
+nightly = ["embassy-nrf/nightly", "embassy-nrf/unstable-traits", "embassy-usb", "embassy-usb-serial", "embassy-usb-hid", "embassy-usb-ncm"]
 
 [dependencies]
 embassy = { version = "0.1.0", path = "../../embassy", 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"] }
 embassy-usb = { version = "0.1.0", path = "../../embassy-usb", features = ["defmt"], optional = true }
 embassy-usb-serial = { version = "0.1.0", path = "../../embassy-usb-serial", features = ["defmt"], optional = true }
 embassy-usb-hid = { version = "0.1.0", path = "../../embassy-usb-hid", features = ["defmt"], optional = true }
+embassy-usb-ncm = { version = "0.1.0", path = "../../embassy-usb-ncm", features = ["defmt"], optional = true }
 
 defmt = "0.3"
 defmt-rtt = "0.3"
diff --git a/examples/nrf/src/bin/usb_ethernet.rs b/examples/nrf/src/bin/usb_ethernet.rs
new file mode 100644
index 000000000..70460d23c
--- /dev/null
+++ b/examples/nrf/src/bin/usb_ethernet.rs
@@ -0,0 +1,277 @@
+#![no_std]
+#![no_main]
+#![feature(generic_associated_types)]
+#![feature(type_alias_impl_trait)]
+
+use core::mem;
+use core::sync::atomic::{AtomicBool, Ordering};
+use core::task::Waker;
+use defmt::*;
+use embassy::blocking_mutex::raw::ThreadModeRawMutex;
+use embassy::channel::Channel;
+use embassy::executor::Spawner;
+use embassy::io::{AsyncBufReadExt, AsyncWriteExt};
+use embassy::util::Forever;
+use embassy_net::{PacketBox, PacketBoxExt, PacketBuf, TcpSocket};
+use embassy_nrf::pac;
+use embassy_nrf::usb::Driver;
+use embassy_nrf::Peripherals;
+use embassy_nrf::{interrupt, peripherals};
+use embassy_usb::{Builder, Config, UsbDevice};
+use embassy_usb_ncm::{CdcNcmClass, Receiver, Sender, State};
+
+use defmt_rtt as _; // global logger
+use panic_probe as _;
+
+type MyDriver = Driver<'static, peripherals::USBD>;
+
+#[embassy::task]
+async fn usb_task(mut device: UsbDevice<'static, MyDriver>) -> ! {
+    device.run().await
+}
+
+#[embassy::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::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);
+        }
+    }
+}
+
+#[embassy::task]
+async fn net_task() -> ! {
+    embassy_net::run().await
+}
+
+#[embassy::main]
+async fn main(spawner: Spawner, p: Peripherals) {
+    let clock: pac::CLOCK = unsafe { mem::transmute(()) };
+    let power: pac::POWER = unsafe { mem::transmute(()) };
+
+    info!("Enabling ext hfosc...");
+    clock.tasks_hfclkstart.write(|w| unsafe { w.bits(1) });
+    while clock.events_hfclkstarted.read().bits() != 1 {}
+
+    info!("Waiting for vbus...");
+    while !power.usbregstatus.read().vbusdetect().is_vbus_present() {}
+    info!("vbus OK");
+
+    // Create the driver, from the HAL.
+    let irq = interrupt::take!(USBD);
+    let driver = Driver::new(p.USBD, irq);
+
+    // Create embassy-usb Config
+    let mut config = Config::new(0xc0de, 0xcafe);
+    config.manufacturer = Some("Embassy");
+    config.product = Some("USB-Ethernet example");
+    config.serial_number = Some("12345678");
+    config.max_power = 100;
+    config.max_packet_size_0 = 64;
+
+    // Required for Windows support.
+    config.composite_with_iads = true;
+    config.device_class = 0xEF;
+    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>,
+    }
+    static RESOURCES: Forever<Resources> = Forever::new();
+    let res = RESOURCES.put(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,
+        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);
+
+    // 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)));
+
+    // Init embassy-net
+    struct NetResources {
+        resources: embassy_net::StackResources<1, 2, 8>,
+        configurator: embassy_net::DhcpConfigurator,
+        //configurator: StaticConfigurator,
+        device: Device,
+    }
+    static NET_RESOURCES: Forever<NetResources> = Forever::new();
+    let res = NET_RESOURCES.put(NetResources {
+        resources: embassy_net::StackResources::new(),
+        configurator: embassy_net::DhcpConfigurator::new(),
+        //configurator: embassy_net::StaticConfigurator::new(embassy_net::Config {
+        //    address: Ipv4Cidr::new(Ipv4Address::new(10, 42, 0, 1), 24),
+        //    dns_servers: Default::default(),
+        //    gateway: None,
+        //}),
+        device: Device {
+            mac_addr: our_mac_addr,
+        },
+    });
+    embassy_net::init(&mut res.device, &mut res.configurator, &mut res.resources);
+    unwrap!(spawner.spawn(net_task()));
+
+    // And now we can use it!
+
+    let mut rx_buffer = [0; 4096];
+    let mut tx_buffer = [0; 4096];
+    let mut buf = [0; 4096];
+
+    loop {
+        let mut socket = TcpSocket::new(&mut rx_buffer, &mut tx_buffer);
+        socket.set_timeout(Some(embassy_net::SmolDuration::from_secs(10)));
+
+        info!("Listening on TCP:1234...");
+        if let Err(e) = socket.accept(1234).await {
+            warn!("accept error: {:?}", e);
+            continue;
+        }
+
+        info!("Received connection from {:?}", socket.remote_endpoint());
+
+        loop {
+            let n = match socket.read(&mut buf).await {
+                Ok(0) => {
+                    warn!("read EOF");
+                    break;
+                }
+                Ok(n) => n,
+                Err(e) => {
+                    warn!("read error: {:?}", e);
+                    break;
+                }
+            };
+
+            info!("rxd {:02x}", &buf[..n]);
+
+            match socket.write_all(&buf[..n]).await {
+                Ok(()) => {}
+                Err(e) => {
+                    warn!("write error: {:?}", e);
+                    break;
+                }
+            };
+        }
+    }
+}
+
+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(&mut 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(&mut self) -> [u8; 6] {
+        self.mac_addr
+    }
+}
+
+#[no_mangle]
+fn _embassy_rand(buf: &mut [u8]) {
+    // TODO
+    buf.fill(0x42)
+}
diff --git a/examples/nrf/src/bin/usb_hid_keyboard.rs b/examples/nrf/src/bin/usb_hid_keyboard.rs
index 9fa7ab334..3852dd8da 100644
--- a/examples/nrf/src/bin/usb_hid_keyboard.rs
+++ b/examples/nrf/src/bin/usb_hid_keyboard.rs
@@ -59,8 +59,8 @@ async fn main(_spawner: Spawner, p: Peripherals) {
 
     // Create embassy-usb Config
     let mut config = Config::new(0xc0de, 0xcafe);
-    config.manufacturer = Some("Tactile Engineering");
-    config.product = Some("Testy");
+    config.manufacturer = Some("Embassy");
+    config.product = Some("HID keyboard example");
     config.serial_number = Some("12345678");
     config.max_power = 100;
     config.max_packet_size_0 = 64;
diff --git a/examples/nrf/src/bin/usb_hid_mouse.rs b/examples/nrf/src/bin/usb_hid_mouse.rs
index 92aeffda2..e70dc51a5 100644
--- a/examples/nrf/src/bin/usb_hid_mouse.rs
+++ b/examples/nrf/src/bin/usb_hid_mouse.rs
@@ -39,10 +39,11 @@ async fn main(_spawner: Spawner, p: Peripherals) {
 
     // Create embassy-usb Config
     let mut config = Config::new(0xc0de, 0xcafe);
-    config.manufacturer = Some("Tactile Engineering");
-    config.product = Some("Testy");
+    config.manufacturer = Some("Embassy");
+    config.product = Some("HID mouse example");
     config.serial_number = Some("12345678");
     config.max_power = 100;
+    config.max_packet_size_0 = 64;
 
     // Create embassy-usb DeviceBuilder using the driver and config.
     // It needs some buffers for building the descriptors.
diff --git a/examples/nrf/src/bin/usb_serial.rs b/examples/nrf/src/bin/usb_serial.rs
index 6081ee917..bc41c2acf 100644
--- a/examples/nrf/src/bin/usb_serial.rs
+++ b/examples/nrf/src/bin/usb_serial.rs
@@ -36,7 +36,12 @@ async fn main(_spawner: Spawner, p: Peripherals) {
     let driver = Driver::new(p.USBD, irq);
 
     // Create embassy-usb Config
-    let config = Config::new(0xc0de, 0xcafe);
+    let mut config = Config::new(0xc0de, 0xcafe);
+    config.manufacturer = Some("Embassy");
+    config.product = Some("USB-serial example");
+    config.serial_number = Some("12345678");
+    config.max_power = 100;
+    config.max_packet_size_0 = 64;
 
     // Create embassy-usb DeviceBuilder using the driver and config.
     // It needs some buffers for building the descriptors.
diff --git a/examples/nrf/src/bin/usb_serial_multitask.rs b/examples/nrf/src/bin/usb_serial_multitask.rs
index d4b3000e7..31e0af483 100644
--- a/examples/nrf/src/bin/usb_serial_multitask.rs
+++ b/examples/nrf/src/bin/usb_serial_multitask.rs
@@ -53,7 +53,12 @@ async fn main(spawner: Spawner, p: Peripherals) {
     let driver = Driver::new(p.USBD, irq);
 
     // Create embassy-usb Config
-    let config = Config::new(0xc0de, 0xcafe);
+    let mut config = Config::new(0xc0de, 0xcafe);
+    config.manufacturer = Some("Embassy");
+    config.product = Some("USB-serial example");
+    config.serial_number = Some("12345678");
+    config.max_power = 100;
+    config.max_packet_size_0 = 64;
 
     struct Resources {
         device_descriptor: [u8; 256],