Add polling and networking for target_os = "wasi"

Based on tokio-rs#1395

And with
* bytecodealliance/wasmtime#3711
* rust-lang/rust#93158
merged, mio can have limited support for networking for the
`wasm32-wasi` target.

Co-authored-by: Thomas de Zeeuw <thomasdezeeuw@gmail.com>
Signed-off-by: Harald Hoyer <harald@profian.com>

Cargo.toml

@@ -49,6 +49,10 @@ miow   = "0.3.6"
 winapi = { version = "0.3", features = ["winsock2", "mswsock"] }
 ntapi  = "0.3"
 
+[target.'cfg(target_os = "wasi")'.dependencies]
+wasi = "0.11.0"
+libc = "0.2.86"
+
 [dev-dependencies]
 env_logger = { version = "0.8.4", default-features = false }
 rand = "0.8"

src/io_source.rs

@@ -1,6 +1,8 @@
 use std::ops::{Deref, DerefMut};
 #[cfg(unix)]
 use std::os::unix::io::AsRawFd;
+#[cfg(target_os = "wasi")]
+use std::os::wasi::io::AsRawFd;
 #[cfg(windows)]
 use std::os::windows::io::AsRawSocket;
 #[cfg(debug_assertions)]
@@ -200,6 +202,44 @@ where
     }
 }
 
+#[cfg(target_os = "wasi")]
+impl<T> event::Source for IoSource<T>
+where
+    T: AsRawFd,
+{
+    fn register(
+        &mut self,
+        registry: &Registry,
+        token: Token,
+        interests: Interest,
+    ) -> io::Result<()> {
+        #[cfg(debug_assertions)]
+        self.selector_id.associate(registry)?;
+        registry
+            .selector()
+            .register(self.inner.as_raw_fd() as _, token, interests)
+    }
+
+    fn reregister(
+        &mut self,
+        registry: &Registry,
+        token: Token,
+        interests: Interest,
+    ) -> io::Result<()> {
+        #[cfg(debug_assertions)]
+        self.selector_id.check_association(registry)?;
+        registry
+            .selector()
+            .reregister(self.inner.as_raw_fd() as _, token, interests)
+    }
+
+    fn deregister(&mut self, registry: &Registry) -> io::Result<()> {
+        #[cfg(debug_assertions)]
+        self.selector_id.remove_association(registry)?;
+        registry.selector().deregister(self.inner.as_raw_fd() as _)
+    }
+}
+
 impl<T> fmt::Debug for IoSource<T>
 where
     T: fmt::Debug,

src/lib.rs

@@ -48,6 +48,7 @@ mod interest;
 mod poll;
 mod sys;
 mod token;
+#[cfg(not(target_os = "wasi"))]
 mod waker;
 
 pub mod event;
@@ -65,6 +66,7 @@ pub use event::Events;
 pub use interest::Interest;
 pub use poll::{Poll, Registry};
 pub use token::Token;
+#[cfg(not(target_os = "wasi"))]
 pub use waker::Waker;
 
 #[cfg(all(unix, feature = "os-ext"))]

src/net/mod.rs

@@ -28,7 +28,9 @@
 mod tcp;
 pub use self::tcp::{TcpListener, TcpStream};
 
+#[cfg(not(target_os = "wasi"))]
 mod udp;
+#[cfg(not(target_os = "wasi"))]
 pub use self::udp::UdpSocket;
 
 #[cfg(unix)]

src/net/tcp/listener.rs

@@ -1,6 +1,8 @@
 use std::net::{self, SocketAddr};
 #[cfg(unix)]
 use std::os::unix::io::{AsRawFd, FromRawFd, IntoRawFd, RawFd};
+#[cfg(target_os = "wasi")]
+use std::os::wasi::io::{AsRawFd, FromRawFd, IntoRawFd, RawFd};
 #[cfg(windows)]
 use std::os::windows::io::{AsRawSocket, FromRawSocket, IntoRawSocket, RawSocket};
 use std::{fmt, io};
@@ -9,6 +11,7 @@ use crate::io_source::IoSource;
 use crate::net::TcpStream;
 #[cfg(unix)]
 use crate::sys::tcp::set_reuseaddr;
+#[cfg(not(target_os = "wasi"))]
 use crate::sys::tcp::{bind, listen, new_for_addr};
 use crate::{event, sys, Interest, Registry, Token};
 
@@ -52,6 +55,7 @@ impl TcpListener {
     /// 2. Set the `SO_REUSEADDR` option on the socket on Unix.
     /// 3. Bind the socket to the specified address.
     /// 4. Calls `listen` on the socket to prepare it to receive new connections.
+    #[cfg(not(target_os = "wasi"))]
     pub fn bind(addr: SocketAddr) -> io::Result<TcpListener> {
         let socket = new_for_addr(addr)?;
         #[cfg(unix)]
@@ -215,3 +219,30 @@ impl FromRawSocket for TcpListener {
         TcpListener::from_std(FromRawSocket::from_raw_socket(socket))
     }
 }
+
+#[cfg(target_os = "wasi")]
+impl IntoRawFd for TcpListener {
+    fn into_raw_fd(self) -> RawFd {
+        self.inner.into_inner().into_raw_fd()
+    }
+}
+
+#[cfg(target_os = "wasi")]
+impl AsRawFd for TcpListener {
+    fn as_raw_fd(&self) -> RawFd {
+        self.inner.as_raw_fd()
+    }
+}
+
+#[cfg(target_os = "wasi")]
+impl FromRawFd for TcpListener {
+    /// Converts a `RawFd` to a `TcpListener`.
+    ///
+    /// # Notes
+    ///
+    /// The caller is responsible for ensuring that the socket is in
+    /// non-blocking mode.
+    unsafe fn from_raw_fd(fd: RawFd) -> TcpListener {
+        TcpListener::from_std(FromRawFd::from_raw_fd(fd))
+    }
+}

src/net/tcp/stream.rs

@@ -3,10 +3,13 @@ use std::io::{self, IoSlice, IoSliceMut, Read, Write};
 use std::net::{self, Shutdown, SocketAddr};
 #[cfg(unix)]
 use std::os::unix::io::{AsRawFd, FromRawFd, IntoRawFd, RawFd};
+#[cfg(target_os = "wasi")]
+use std::os::wasi::io::{AsRawFd, FromRawFd, IntoRawFd, RawFd};
 #[cfg(windows)]
 use std::os::windows::io::{AsRawSocket, FromRawSocket, IntoRawSocket, RawSocket};
 
 use crate::io_source::IoSource;
+#[cfg(not(target_os = "wasi"))]
 use crate::sys::tcp::{connect, new_for_addr};
 use crate::{event, Interest, Registry, Token};
 
@@ -73,6 +76,7 @@ impl TcpStream {
     ///  5. Now the stream can be used.
     ///
     /// [read interest]: Interest::READABLE
+    #[cfg(not(target_os = "wasi"))]
     pub fn connect(addr: SocketAddr) -> io::Result<TcpStream> {
         let socket = new_for_addr(addr)?;
         #[cfg(unix)]
@@ -332,3 +336,30 @@ impl FromRawSocket for TcpStream {
         TcpStream::from_std(FromRawSocket::from_raw_socket(socket))
     }
 }
+
+#[cfg(target_os = "wasi")]
+impl IntoRawFd for TcpStream {
+    fn into_raw_fd(self) -> RawFd {
+        self.inner.into_inner().into_raw_fd()
+    }
+}
+
+#[cfg(target_os = "wasi")]
+impl AsRawFd for TcpStream {
+    fn as_raw_fd(&self) -> RawFd {
+        self.inner.as_raw_fd()
+    }
+}
+
+#[cfg(target_os = "wasi")]
+impl FromRawFd for TcpStream {
+    /// Converts a `RawFd` to a `TcpStream`.
+    ///
+    /// # Notes
+    ///
+    /// The caller is responsible for ensuring that the socket is in
+    /// non-blocking mode.
+    unsafe fn from_raw_fd(fd: RawFd) -> TcpStream {
+        TcpStream::from_std(FromRawFd::from_raw_fd(fd))
+    }
+}

src/poll.rs

@@ -635,6 +635,7 @@ impl Registry {
     ///
     /// Event sources registered with this `Registry` will be registered with
     /// the original `Registry` and `Poll` instance.
+    #[cfg(not(target_os = "wasi"))]
     pub fn try_clone(&self) -> io::Result<Registry> {
         self.selector
             .try_clone()
@@ -643,7 +644,7 @@ impl Registry {
 
     /// Internal check to ensure only a single `Waker` is active per [`Poll`]
     /// instance.
-    #[cfg(debug_assertions)]
+    #[cfg(all(debug_assertions, not(target_os = "wasi")))]
     pub(crate) fn register_waker(&self) {
         assert!(
             !self.selector.register_waker(),
@@ -652,6 +653,7 @@ impl Registry {
     }
 
     /// Get access to the `sys::Selector`.
+    #[cfg(any(not(target_os = "wasi"), feature = "net"))]
     pub(crate) fn selector(&self) -> &sys::Selector {
         &self.selector
     }

src/sys/mod.rs

@@ -63,6 +63,12 @@ cfg_os_poll! {
     pub use self::windows::*;
 }
 
+#[cfg(target_os = "wasi")]
+cfg_os_poll! {
+    mod wasi;
+    pub(crate) use self::wasi::*;
+}
+
 cfg_not_os_poll! {
     mod shell;
     pub(crate) use self::shell::*;

src/sys/shell/mod.rs

@@ -7,7 +7,9 @@ macro_rules! os_required {
 mod selector;
 pub(crate) use self::selector::{event, Event, Events, Selector};
 
+#[cfg(not(target_os = "wasi"))]
 mod waker;
+#[cfg(not(target_os = "wasi"))]
 pub(crate) use self::waker::Waker;
 
 cfg_net! {

src/sys/shell/selector.rs

@@ -11,6 +11,7 @@ pub type Events = Vec<Event>;
 pub struct Selector {}
 
 impl Selector {
+    #[cfg(not(target_os = "wasi"))]
     pub fn try_clone(&self) -> io::Result<Selector> {
         os_required!();
     }
@@ -19,7 +20,7 @@ impl Selector {
         os_required!();
     }
 
-    #[cfg(debug_assertions)]
+    #[cfg(all(debug_assertions, not(target_os = "wasi")))]
     pub fn register_waker(&self) -> bool {
         os_required!();
     }
@@ -44,6 +45,25 @@ cfg_any_os_ext! {
     }
 }
 
+#[cfg(target_os = "wasi")]
+cfg_any_os_ext! {
+    use crate::{Interest, Token};
+
+    impl Selector {
+        pub fn register(&self, _: wasi::Fd, _: Token, _: Interest) -> io::Result<()> {
+            os_required!();
+        }
+
+        pub fn reregister(&self, _: wasi::Fd, _: Token, _: Interest) -> io::Result<()> {
+            os_required!();
+        }
+
+        pub fn deregister(&self, _: wasi::Fd) -> io::Result<()> {
+            os_required!();
+        }
+    }
+}
+
 cfg_io_source! {
     #[cfg(debug_assertions)]
     impl Selector {

src/sys/shell/tcp.rs

@@ -1,18 +1,22 @@
 use std::io;
 use std::net::{self, SocketAddr};
 
+#[cfg(not(target_os = "wasi"))]
 pub(crate) fn new_for_addr(_: SocketAddr) -> io::Result<i32> {
     os_required!();
 }
 
+#[cfg(not(target_os = "wasi"))]
 pub(crate) fn bind(_: &net::TcpListener, _: SocketAddr) -> io::Result<()> {
     os_required!();
 }
 
+#[cfg(not(target_os = "wasi"))]
 pub(crate) fn connect(_: &net::TcpStream, _: SocketAddr) -> io::Result<()> {
     os_required!();
 }
 
+#[cfg(not(target_os = "wasi"))]
 pub(crate) fn listen(_: &net::TcpListener, _: u32) -> io::Result<()> {
     os_required!();
 }

src/sys/shell/udp.rs

@@ -1,3 +1,4 @@
+#![cfg(not(target_os = "wasi"))]
 use std::io;
 use std::net::{self, SocketAddr};