5 files changed, 221 insertions, 3 deletions

diff --git a/embassy-net/Cargo.toml b/embassy-net/Cargo.toml
index 4ec340b7a..6b3468283 100644
--- a/embassy-net/Cargo.toml
+++ b/embassy-net/Cargo.toml
@@ -13,7 +13,7 @@ target = "thumbv7em-none-eabi"
 
 [features]
 default = []
-std = []
+std = ["smoltcp/alloc", "managed/std"]
 
 defmt = ["dep:defmt", "smoltcp/defmt", "embassy-net-driver/defmt"]
 
@@ -22,7 +22,7 @@ unstable-traits = []
 
 udp = ["smoltcp/socket-udp"]
 tcp = ["smoltcp/socket-tcp"]
-dns = ["smoltcp/socket-dns"]
+dns = ["smoltcp/socket-dns", "smoltcp/proto-dns"]
 dhcpv4 = ["medium-ethernet", "smoltcp/socket-dhcpv4"]
 proto-ipv6 = ["smoltcp/proto-ipv6"]
 medium-ethernet = ["smoltcp/medium-ethernet"]
diff --git a/embassy-net/src/dns.rs b/embassy-net/src/dns.rs
new file mode 100644
index 000000000..f18750cc3
--- /dev/null
+++ b/embassy-net/src/dns.rs
@@ -0,0 +1,114 @@
+//! DNS socket with async support.
+use core::cell::RefCell;
+use core::future::poll_fn;
+use core::mem;
+use core::task::Poll;
+
+use embassy_net_driver::Driver;
+use heapless::Vec;
+use managed::ManagedSlice;
+use smoltcp::iface::{Interface, SocketHandle};
+pub use smoltcp::socket::dns::DnsQuery;
+use smoltcp::socket::dns::{self, GetQueryResultError, StartQueryError, MAX_ADDRESS_COUNT};
+pub use smoltcp::wire::{DnsQueryType, IpAddress};
+
+use crate::{SocketStack, Stack};
+
+/// Errors returned by DnsSocket.
+#[derive(Debug, PartialEq, Eq, Clone, Copy)]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+pub enum Error {
+    /// No available query slot
+    NoFreeSlot,
+    /// Invalid name
+    InvalidName,
+    /// Name too long
+    NameTooLong,
+    /// Name lookup failed
+    Failed,
+}
+
+impl From<GetQueryResultError> for Error {
+    fn from(_: GetQueryResultError) -> Self {
+        Self::Failed
+    }
+}
+
+impl From<StartQueryError> for Error {
+    fn from(e: StartQueryError) -> Self {
+        match e {
+            StartQueryError::NoFreeSlot => Self::NoFreeSlot,
+            StartQueryError::InvalidName => Self::InvalidName,
+            StartQueryError::NameTooLong => Self::NameTooLong,
+        }
+    }
+}
+
+/// Async socket for making DNS queries.
+pub struct DnsSocket<'a> {
+    stack: &'a RefCell<SocketStack>,
+    handle: SocketHandle,
+}
+
+impl<'a> DnsSocket<'a> {
+    /// Create a new DNS socket using the provided stack and query storage.
+    ///
+    /// DNS servers are derived from the stack configuration.
+    ///
+    /// NOTE: If using DHCP, make sure it has reconfigured the stack to ensure the DNS servers are updated.
+    pub fn new<D, Q>(stack: &'a Stack<D>, queries: Q) -> Self
+    where
+        D: Driver + 'static,
+        Q: Into<ManagedSlice<'a, Option<DnsQuery>>>,
+    {
+        let servers = stack
+            .config()
+            .map(|c| {
+                let v: Vec<IpAddress, 3> = c.dns_servers.iter().map(|c| IpAddress::Ipv4(*c)).collect();
+                v
+            })
+            .unwrap_or(Vec::new());
+        let s = &mut *stack.socket.borrow_mut();
+        let queries: ManagedSlice<'static, Option<DnsQuery>> = unsafe { mem::transmute(queries.into()) };
+
+        let handle = s.sockets.add(dns::Socket::new(&servers[..], queries));
+        Self {
+            stack: &stack.socket,
+            handle,
+        }
+    }
+
+    fn with_mut<R>(&mut self, f: impl FnOnce(&mut dns::Socket, &mut Interface) -> R) -> R {
+        let s = &mut *self.stack.borrow_mut();
+        let socket = s.sockets.get_mut::<dns::Socket>(self.handle);
+        let res = f(socket, &mut s.iface);
+        s.waker.wake();
+        res
+    }
+
+    /// Make a query for a given name and return the corresponding IP addresses.
+    pub async fn query(&mut self, name: &str, qtype: DnsQueryType) -> Result<Vec<IpAddress, MAX_ADDRESS_COUNT>, Error> {
+        let query = match { self.with_mut(|s, i| s.start_query(i.context(), name, qtype)) } {
+            Ok(handle) => handle,
+            Err(e) => return Err(e.into()),
+        };
+
+        poll_fn(|cx| {
+            self.with_mut(|s, _| match s.get_query_result(query) {
+                Ok(addrs) => Poll::Ready(Ok(addrs)),
+                Err(GetQueryResultError::Pending) => {
+                    s.register_query_waker(query, cx.waker());
+                    Poll::Pending
+                }
+                Err(e) => Poll::Ready(Err(e.into())),
+            })
+        })
+        .await
+    }
+}
+
+impl<'a> Drop for DnsSocket<'a> {
+    fn drop(&mut self) {
+        self.stack.borrow_mut().sockets.remove(self.handle);
+    }
+}
diff --git a/embassy-net/src/lib.rs b/embassy-net/src/lib.rs
index 0f694ee70..ae447d063 100644
--- a/embassy-net/src/lib.rs
+++ b/embassy-net/src/lib.rs
@@ -11,6 +11,8 @@ pub(crate) mod fmt;
 pub use embassy_net_driver as driver;
 
 mod device;
+#[cfg(feature = "dns")]
+pub mod dns;
 #[cfg(feature = "tcp")]
 pub mod tcp;
 #[cfg(feature = "udp")]
diff --git a/examples/std/Cargo.toml b/examples/std/Cargo.toml
index af1481e08..8087df09a 100644
--- a/examples/std/Cargo.toml
+++ b/examples/std/Cargo.toml
@@ -8,7 +8,7 @@ license = "MIT OR Apache-2.0"
 embassy-sync = { version = "0.1.0", path = "../../embassy-sync", features = ["log"] }
 embassy-executor = { version = "0.1.0", path = "../../embassy-executor", features = ["log", "std", "nightly", "integrated-timers"] }
 embassy-time = { version = "0.1.0", path = "../../embassy-time", features = ["log", "std", "nightly"] }
-embassy-net = { version = "0.1.0", path = "../../embassy-net", features=[ "std", "nightly", "log", "medium-ethernet", "tcp", "udp", "dhcpv4"] }
+embassy-net = { version = "0.1.0", path = "../../embassy-net", features=[ "std", "nightly", "log", "medium-ethernet", "tcp", "udp", "dns", "dhcpv4", "unstable-traits", "proto-ipv6"] }
 embassy-net-driver = { version = "0.1.0", path = "../../embassy-net-driver" }
 embedded-io = { version = "0.4.0", features = ["async", "std", "futures"] }
 critical-section = { version = "1.1", features = ["std"] }
diff --git a/examples/std/src/bin/net_dns.rs b/examples/std/src/bin/net_dns.rs
new file mode 100644
index 000000000..6203f8370
--- /dev/null
+++ b/examples/std/src/bin/net_dns.rs
@@ -0,0 +1,102 @@
+#![feature(type_alias_impl_trait)]
+
+use std::default::Default;
+
+use clap::Parser;
+use embassy_executor::{Executor, Spawner};
+use embassy_net::dns::{DnsQueryType, DnsSocket};
+use embassy_net::{Config, Ipv4Address, Ipv4Cidr, Stack, StackResources};
+use heapless::Vec;
+use log::*;
+use rand_core::{OsRng, RngCore};
+use static_cell::StaticCell;
+
+#[path = "../tuntap.rs"]
+mod tuntap;
+
+use crate::tuntap::TunTapDevice;
+
+macro_rules! singleton {
+    ($val:expr) => {{
+        type T = impl Sized;
+        static STATIC_CELL: StaticCell<T> = StaticCell::new();
+        STATIC_CELL.init_with(move || $val)
+    }};
+}
+
+#[derive(Parser)]
+#[clap(version = "1.0")]
+struct Opts {
+    /// TAP device name
+    #[clap(long, default_value = "tap0")]
+    tap: String,
+    /// use a static IP instead of DHCP
+    #[clap(long)]
+    static_ip: bool,
+}
+
+#[embassy_executor::task]
+async fn net_task(stack: &'static Stack<TunTapDevice>) -> ! {
+    stack.run().await
+}
+
+#[embassy_executor::task]
+async fn main_task(spawner: Spawner) {
+    let opts: Opts = Opts::parse();
+
+    // Init network device
+    let device = TunTapDevice::new(&opts.tap).unwrap();
+
+    // Choose between dhcp or static ip
+    let config = if opts.static_ip {
+        Config::Static(embassy_net::StaticConfig {
+            address: Ipv4Cidr::new(Ipv4Address::new(192, 168, 69, 1), 24),
+            dns_servers: Vec::from_slice(&[Ipv4Address::new(8, 8, 4, 4).into(), Ipv4Address::new(8, 8, 8, 8).into()])
+                .unwrap(),
+            gateway: Some(Ipv4Address::new(192, 168, 69, 100)),
+        })
+    } else {
+        Config::Dhcp(Default::default())
+    };
+
+    // Generate random seed
+    let mut seed = [0; 8];
+    OsRng.fill_bytes(&mut seed);
+    let seed = u64::from_le_bytes(seed);
+
+    // Init network stack
+    let stack = &*singleton!(Stack::new(device, config, singleton!(StackResources::<2>::new()), seed));
+
+    // Launch network task
+    spawner.spawn(net_task(stack)).unwrap();
+
+    // Then we can use it!
+
+    let mut socket = DnsSocket::new(stack, vec![]);
+
+    let host = "example.com";
+    info!("querying host {:?}...", host);
+    match socket.query(host, DnsQueryType::A).await {
+        Ok(r) => {
+            info!("query response: {:?}", r);
+        }
+        Err(e) => {
+            warn!("query error: {:?}", e);
+        }
+    };
+}
+
+static EXECUTOR: StaticCell<Executor> = StaticCell::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.init(Executor::new());
+    executor.run(|spawner| {
+        spawner.spawn(main_task(spawner)).unwrap();
+    });
+}