add wasm32-wasip2 networking support

Motivation

This adds networking support for the `wasm32-wasip2` target platform, which
includes more extensive support for sockets than `wasm32-wasip1`.

Solution

The bulk of the changes are in tokio-rs/mio#1931.  This
patch mainly tweaks a few `cfg` directives to indicate `wasm32-wasip2`'s
additional capabilities.

Note that this is a draft PR until until
tokio-rs/mio#1931 and
rust-lang/socket2#639 have been include in stable
releases of their respective projects.

Also note that I've added a `wasm32-wasip2` target to CI and triaged each test
which was previously disabled for WASI into one of three categories:

- Disabled on both WASIp1 and p2 due to not-yet-supported features such as multithreading
- Disabled on p1 but enabled on p2
- Disabled on p1 and _temporarily_ disabled on p2 due to `wasi-libc` bugfixes which have been merged but not yet included in a Rust release.  I'll open an issue to re-enable them when the fixes land in Rust.

Future Work

In the future, we could consider adding support for `tokio::net::lookup_host`.
WASIp2 natively supports asynchronous DNS lookups and is single threaded,
whereas Tokio currently assumes DNS lookups are blocking and require
multithreading to emulate async lookups.  A WASIp2-specific implementation could
do the lookup directly without multithreading.

WASIp2 also supports single-threaded, asynchronous file I/O, timers, etc.  We
could either support those directly or wait for WASIp3's multithreading support,
in which case most of `tokio::fs` (as well as `tokio::net::lookup_host`, etc.)
_should_ work unchanged via `wasi-libc` and worker threads.

Currently, building for WASIp2 requires RUSTFLAGS="--cfg tokio_unstable"`.  Once
we have a solid maintenance plan, we can remove that requirement.

Author: dicej

.github/workflows/ci.yml

@@ -1112,6 +1112,32 @@ jobs:
           CARGO_TARGET_WASM32_WASIP1_THREADS_RUNNER: "wasmtime run -W bulk-memory=y -W threads=y -W shared-memory=y -S threads=y --"
           RUSTFLAGS: --cfg tokio_unstable -Dwarnings -C target-feature=+atomics,+bulk-memory -C link-args=--max-memory=67108864
 
+  wasm32-wasip2:
+    name: test tokio for wasm32-wasip2
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+    steps:
+      - uses: actions/checkout@v4
+      - name: Install Rust ${{ env.rust_stable }}
+        uses: dtolnay/rust-toolchain@stable
+        with:
+          toolchain: ${{ env.rust_stable }}
+          targets: wasm32-wasip2
+
+      - name: Install cargo-nextest, wasmtime
+        uses: taiki-e/install-action@v2
+        with:
+          tool: cargo-nextest,wasmtime-cli
+
+      - uses: Swatinem/rust-cache@v2
+
+      - name: test tokio --target wasm32-wasip2
+        run: cargo nextest run --target wasm32-wasip2 --features net,macros,rt,io-util
+        working-directory: tokio
+        env:
+          RUSTFLAGS: --cfg tokio_unstable
+          CARGO_TARGET_WASM32_WASIP2_RUNNER: wasmtime run -Sinherit-network
+
   check-external-types:
     name: check-external-types (${{ matrix.os }})
     needs: basics

Cargo.toml

@@ -17,6 +17,9 @@ members = [
 
 [patch.crates-io]
 tokio = { path = "tokio" }
+# TODO: Remove these once new releases are available:
+mio = { git = "https://github.com/tokio-rs/mio", rev = "9a387a507a32f3bc29bd3b9c0b59edaa95ed7bd0" }
+socket2 = { git = "https://github.com/rust-lang/socket2", rev = "e47157c29446856d87370b49194ce2f998337bfa" }
 
 [workspace.metadata.spellcheck]
 config = "spellcheck.toml"

spellcheck.dic

@@ -1,4 +1,4 @@
-312
+313
 &
 +
 <
@@ -309,5 +309,6 @@ wakers
 Wakers
 wakeup
 wakeups
+WASI
 workstealing
 ZST

tokio/Cargo.toml

@@ -99,7 +99,7 @@ bytes = { version = "1.2.1", optional = true }
 mio = { version = "1.0.1", optional = true, default-features = false }
 parking_lot = { version = "0.12.0", optional = true }
 
-[target.'cfg(not(target_family = "wasm"))'.dependencies]
+[target.'cfg(any(not(target_family = "wasm"), all(target_os = "wasi", not(target_env = "p1"))))'.dependencies]
 socket2 = { version = "0.6.0", optional = true, features = ["all"] }
 
 # Currently unstable. The API exposed by these features may be broken at any time.
@@ -120,6 +120,9 @@ backtrace = { version = "0.3.58", optional = true }
 libc = { version = "0.2.168", optional = true }
 signal-hook-registry = { version = "1.1.1", optional = true }
 
+[target.'cfg(target_os = "wasi")'.dependencies]
+libc = { version = "0.2.168", optional = true }
+
 [target.'cfg(unix)'.dev-dependencies]
 libc = { version = "0.2.168" }
 nix = { version = "0.29.0", default-features = false, features = ["aio", "fs", "socket"] }

tokio/src/macros/cfg.rs

@@ -58,6 +58,18 @@ macro_rules! cfg_unix {
     }
 }
 
+/// Enables Unix-specific code, including WASI.
+/// Use this macro instead of `cfg(any(unix, target_os = "wasi"))` to generate docs properly.
+macro_rules! cfg_unix_or_wasi {
+    ($($item:item)*) => {
+        $(
+            #[cfg(any(all(doc, docsrs), unix, target_os = "wasi"))]
+            #[cfg_attr(docsrs, doc(cfg(any(unix, target_os = "wasi"))))]
+            $item
+        )*
+    }
+}
+
 /// Enables unstable Windows-specific code.
 /// Use this macro instead of `cfg(windows)` to generate docs properly.
 macro_rules! cfg_unstable_windows {
@@ -674,6 +686,15 @@ macro_rules! cfg_not_wasi {
     }
 }
 
+macro_rules! cfg_not_wasip1 {
+    ($($item:item)*) => {
+        $(
+            #[cfg(not(all(target_os = "wasi", target_env = "p1")))]
+            $item
+        )*
+    }
+}
+
 macro_rules! cfg_is_wasm_not_wasi {
     ($($item:item)*) => {
         $(

tokio/src/net/mod.rs

@@ -29,7 +29,7 @@
 //! [`AsyncFd`]: crate::io::unix::AsyncFd
 
 mod addr;
-cfg_not_wasi! {
+cfg_not_wasip1! {
     #[cfg(feature = "net")]
     pub(crate) use addr::to_socket_addrs;
 }
@@ -42,7 +42,7 @@ cfg_net! {
     pub mod tcp;
     pub use tcp::listener::TcpListener;
     pub use tcp::stream::TcpStream;
-    cfg_not_wasi! {
+    cfg_not_wasip1! {
         pub use tcp::socket::TcpSocket;
 
         mod udp;

tokio/src/net/tcp/listener.rs

@@ -2,7 +2,7 @@ use crate::io::{Interest, PollEvented};
 use crate::net::tcp::TcpStream;
 use crate::util::check_socket_for_blocking;
 
-cfg_not_wasi! {
+cfg_not_wasip1! {
     use crate::net::{to_socket_addrs, ToSocketAddrs};
 }
 
@@ -60,7 +60,7 @@ cfg_net! {
 }
 
 impl TcpListener {
-    cfg_not_wasi! {
+    cfg_not_wasip1! {
         /// Creates a new `TcpListener`, which will be bound to the specified address.
         ///
         /// The returned listener is ready for accepting connections.
@@ -292,15 +292,15 @@ impl TcpListener {
 
         #[cfg(target_os = "wasi")]
         {
-            use std::os::wasi::io::{FromRawFd, IntoRawFd};
+            use std::os::fd::{FromRawFd, IntoRawFd};
             self.io
                 .into_inner()
                 .map(|io| io.into_raw_fd())
                 .map(|raw_fd| unsafe { std::net::TcpListener::from_raw_fd(raw_fd) })
         }
     }
 
-    cfg_not_wasi! {
+    cfg_not_wasip1! {
         pub(crate) fn new(listener: mio::net::TcpListener) -> io::Result<TcpListener> {
             let io = PollEvented::new(listener)?;
             Ok(TcpListener { io })
@@ -427,7 +427,7 @@ cfg_unstable! {
     #[cfg(target_os = "wasi")]
     mod sys {
         use super::TcpListener;
-        use std::os::wasi::prelude::*;
+        use std::os::fd::{RawFd, BorrowedFd, AsRawFd, AsFd};
 
         impl AsRawFd for TcpListener {
             fn as_raw_fd(&self) -> RawFd {

tokio/src/net/tcp/mod.rs

@@ -2,7 +2,7 @@
 
 pub(crate) mod listener;
 
-cfg_not_wasi! {
+cfg_not_wasip1! {
     pub(crate) mod socket;
 }
 

tokio/src/net/tcp/socket.rs

@@ -4,8 +4,8 @@ use std::fmt;
 use std::io;
 use std::net::SocketAddr;
 
-#[cfg(unix)]
-use std::os::unix::io::{AsFd, AsRawFd, BorrowedFd, FromRawFd, IntoRawFd, RawFd};
+#[cfg(not(windows))]
+use std::os::fd::{AsFd, AsRawFd, BorrowedFd, FromRawFd, IntoRawFd, RawFd};
 use std::time::Duration;
 
 cfg_windows! {
@@ -170,7 +170,8 @@ impl TcpSocket {
             target_os = "illumos",
             target_os = "linux",
             target_os = "netbsd",
-            target_os = "openbsd"
+            target_os = "openbsd",
+            target_os = "wasi",
         ))]
         let ty = ty.nonblocking();
         let inner = socket2::Socket::new(domain, ty, Some(socket2::Protocol::TCP))?;
@@ -182,7 +183,8 @@ impl TcpSocket {
             target_os = "illumos",
             target_os = "linux",
             target_os = "netbsd",
-            target_os = "openbsd"
+            target_os = "openbsd",
+            target_os = "wasi",
         )))]
         inner.set_nonblocking(true)?;
         Ok(TcpSocket { inner })
@@ -597,7 +599,8 @@ impl TcpSocket {
         target_os = "redox",
         target_os = "solaris",
         target_os = "illumos",
-        target_os = "haiku"
+        target_os = "haiku",
+        target_os = "wasi",
     )))]
     #[cfg_attr(
         docsrs,
@@ -606,7 +609,8 @@ impl TcpSocket {
             target_os = "redox",
             target_os = "solaris",
             target_os = "illumos",
-            target_os = "haiku"
+            target_os = "haiku",
+            target_os = "wasi",
         ))))
     )]
     pub fn tos_v4(&self) -> io::Result<u32> {
@@ -625,7 +629,8 @@ impl TcpSocket {
         target_os = "redox",
         target_os = "solaris",
         target_os = "illumos",
-        target_os = "haiku"
+        target_os = "haiku",
+        target_os = "wasi",
     )))]
     #[cfg_attr(
         docsrs,
@@ -634,7 +639,8 @@ impl TcpSocket {
             target_os = "redox",
             target_os = "solaris",
             target_os = "illumos",
-            target_os = "haiku"
+            target_os = "haiku",
+            target_os = "wasi",
         ))))
     )]
     pub fn tos(&self) -> io::Result<u32> {
@@ -657,7 +663,8 @@ impl TcpSocket {
         target_os = "redox",
         target_os = "solaris",
         target_os = "illumos",
-        target_os = "haiku"
+        target_os = "haiku",
+        target_os = "wasi",
     )))]
     #[cfg_attr(
         docsrs,
@@ -666,7 +673,8 @@ impl TcpSocket {
             target_os = "redox",
             target_os = "solaris",
             target_os = "illumos",
-            target_os = "haiku"
+            target_os = "haiku",
+            target_os = "wasi",
         ))))
     )]
     pub fn set_tos_v4(&self, tos: u32) -> io::Result<()> {
@@ -685,7 +693,8 @@ impl TcpSocket {
         target_os = "redox",
         target_os = "solaris",
         target_os = "illumos",
-        target_os = "haiku"
+        target_os = "haiku",
+        target_os = "wasi",
     )))]
     #[cfg_attr(
         docsrs,
@@ -694,7 +703,8 @@ impl TcpSocket {
             target_os = "redox",
             target_os = "solaris",
             target_os = "illumos",
-            target_os = "haiku"
+            target_os = "haiku",
+            target_os = "wasi",
         ))))
     )]
     pub fn set_tos(&self, tos: u32) -> io::Result<()> {
@@ -826,7 +836,7 @@ impl TcpSocket {
     /// ```
     pub async fn connect(self, addr: SocketAddr) -> io::Result<TcpStream> {
         if let Err(err) = self.inner.connect(&addr.into()) {
-            #[cfg(unix)]
+            #[cfg(not(windows))]
             if err.raw_os_error() != Some(libc::EINPROGRESS) {
                 return Err(err);
             }
@@ -835,9 +845,9 @@ impl TcpSocket {
                 return Err(err);
             }
         }
-        #[cfg(unix)]
+        #[cfg(not(windows))]
         let mio = {
-            use std::os::unix::io::{FromRawFd, IntoRawFd};
+            use std::os::fd::{FromRawFd, IntoRawFd};
 
             let raw_fd = self.inner.into_raw_fd();
             unsafe { mio::net::TcpStream::from_raw_fd(raw_fd) }
@@ -891,9 +901,9 @@ impl TcpSocket {
     /// ```
     pub fn listen(self, backlog: u32) -> io::Result<TcpListener> {
         self.inner.listen(backlog as i32)?;
-        #[cfg(unix)]
+        #[cfg(not(windows))]
         let mio = {
-            use std::os::unix::io::{FromRawFd, IntoRawFd};
+            use std::os::fd::{FromRawFd, IntoRawFd};
 
             let raw_fd = self.inner.into_raw_fd();
             unsafe { mio::net::TcpListener::from_raw_fd(raw_fd) }
@@ -945,9 +955,9 @@ impl TcpSocket {
     /// }
     /// ```
     pub fn from_std_stream(std_stream: std::net::TcpStream) -> TcpSocket {
-        #[cfg(unix)]
+        #[cfg(not(windows))]
         {
-            use std::os::unix::io::{FromRawFd, IntoRawFd};
+            use std::os::fd::{FromRawFd, IntoRawFd};
 
             let raw_fd = std_stream.into_raw_fd();
             unsafe { TcpSocket::from_raw_fd(raw_fd) }
@@ -981,8 +991,8 @@ impl fmt::Debug for TcpSocket {
 
 // These trait implementations can't be build on Windows, so we completely
 // ignore them, even when building documentation.
-#[cfg(unix)]
-cfg_unix! {
+#[cfg(any(unix, target_os = "wasi"))]
+cfg_unix_or_wasi! {
     impl AsRawFd for TcpSocket {
         fn as_raw_fd(&self) -> RawFd {
             self.inner.as_raw_fd()

tokio/src/net/tcp/stream.rs

@@ -1,7 +1,10 @@
 cfg_not_wasi! {
+    use std::time::Duration;
+}
+
+cfg_not_wasip1! {
     use crate::net::{to_socket_addrs, ToSocketAddrs};
     use std::future::poll_fn;
-    use std::time::Duration;
 }
 
 use crate::io::{AsyncRead, AsyncWrite, Interest, PollEvented, ReadBuf, Ready};
@@ -73,7 +76,7 @@ cfg_net! {
 }
 
 impl TcpStream {
-    cfg_not_wasi! {
+    cfg_not_wasip1! {
         /// Opens a TCP connection to a remote host.
         ///
         /// `addr` is an address of the remote host. Anything which implements the
@@ -272,7 +275,7 @@ impl TcpStream {
 
         #[cfg(target_os = "wasi")]
         {
-            use std::os::wasi::io::{FromRawFd, IntoRawFd};
+            use std::os::fd::{FromRawFd, IntoRawFd};
             self.io
                 .into_inner()
                 .map(|io| io.into_raw_fd())
@@ -1564,7 +1567,7 @@ cfg_windows! {
 #[cfg(all(tokio_unstable, target_os = "wasi"))]
 mod sys {
     use super::TcpStream;
-    use std::os::wasi::prelude::*;
+    use std::os::fd::{AsFd, AsRawFd, BorrowedFd, RawFd};
 
     impl AsRawFd for TcpStream {
         fn as_raw_fd(&self) -> RawFd {