add wasm32-wasip2 support

This implementation currently uses a mix of POSIX-style APIs (provided by
`wasi-libc` via the `libc` crate) and WASIp2-native APIs (provided by the `wasi`
crate).

Alternatively, we could implement `Selector` using only POSIX APIs,
e.g. `poll(2)`.  However, that would add an extra layer of abstraction to
support and debug, as well as make it impossible to support polling
`wasi:io/poll/pollable` objects which cannot be represented as POSIX file
descriptors (e.g. timer events, DNS queries, HTTP requests, etc.).

Another approach would be to use _only_ the WASIp2 APIs and bypass `wasi-libc`
entirely.  However, that would break interoperability with both Rust `std` and
e.g. C libraries which expect to work with file descriptors.

Since `wasi-libc` does not yet provide a public API for converting between file
descriptors and WASIp2 resource handles, we currently use a non-public API (see
the `netc` module below) to do so.  Once
WebAssembly/wasi-libc#542 is addressed, we'll be able
to switch to a public API.

I've tested this end-to-end using https://github.com/dicej/wasi-sockets-tests,
which includes smoke tests for `mio`, `tokio`, `tokio-postgres`, etc.

add WASIp2 TODO comments

// TODO #1: Add a public, WASIp2-only API for registering
// `wasi::io::poll::Pollable`s directly (i.e. those which do not correspond to
// any `wasi-libc` file descriptor, such as `wasi:http` requests).
//
// TODO #2: Add support for binding, listening, and accepting.  This would
// involve adding cases for `TCP_SOCKET_STATE_UNBOUND`,
// `TCP_SOCKET_STATE_BOUND`, and `TCP_SOCKET_STATE_LISTENING` to the `match`
// statements in `Selector::select`.
//
// TODO #3: Add support for UDP sockets.  This would involve adding cases for
// the `UDP_SOCKET_STATE_*` tags to the `match` statements in
// `Selector::select`.

Signed-off-by: Joel Dice <[email protected]>

Author: dicej

Cargo.toml

@@ -65,8 +65,13 @@ features = [
   "Win32_System_WindowsProgramming",  # General future used for various types/funcs
 ]
 
-[target.'cfg(target_os = "wasi")'.dependencies]
+[target.'cfg(all(target_os = "wasi", not(target_env = "p2")))'.dependencies]
 wasi = "0.11.0"
+
+[target.'cfg(all(target_os = "wasi", target_env = "p2"))'.dependencies]
+wasi = "0.13.3"
+
+[target.'cfg(target_os = "wasi")'.dependencies]
 libc = "0.2.159"
 
 [dev-dependencies]
@@ -80,6 +85,7 @@ targets = [
   "aarch64-apple-ios",
   "aarch64-linux-android",
   "wasm32-wasip1",
+  "wasm32-wasip2",
   "x86_64-apple-darwin",
   "x86_64-pc-windows-gnu",
   "x86_64-pc-windows-msvc",

src/io_source.rs

@@ -104,7 +104,7 @@ impl<T> DerefMut for IoSource<T> {
     }
 }
 
-#[cfg(any(unix, target_os = "hermit"))]
+#[cfg(any(unix, target_os = "hermit", all(target_os = "wasi", target_env = "p2")))]
 impl<T> event::Source for IoSource<T>
 where
     T: AsRawFd,
@@ -175,7 +175,7 @@ where
     }
 }
 
-#[cfg(target_os = "wasi")]
+#[cfg(all(target_os = "wasi", not(target_env = "p2")))]
 impl<T> event::Source for IoSource<T>
 where
     T: AsRawFd,

src/net/tcp/stream.rs

@@ -13,7 +13,7 @@ use std::os::windows::io::{
 };
 
 use crate::io_source::IoSource;
-#[cfg(not(target_os = "wasi"))]
+#[cfg(any(not(target_os = "wasi"), target_env = "p2"))]
 use crate::sys::tcp::{connect, new_for_addr};
 use crate::{event, Interest, Registry, Token};
 
@@ -87,10 +87,10 @@ impl TcpStream {
     /// entries in the routing cache.
     ///
     /// [write interest]: Interest::WRITABLE
-    #[cfg(not(target_os = "wasi"))]
+    #[cfg(any(not(target_os = "wasi"), target_env = "p2"))]
     pub fn connect(addr: SocketAddr) -> io::Result<TcpStream> {
         let socket = new_for_addr(addr)?;
-        #[cfg(any(unix, target_os = "hermit"))]
+        #[cfg(any(unix, target_os = "hermit", all(target_os = "wasi", target_env = "p2")))]
         let stream = unsafe { TcpStream::from_raw_fd(socket) };
         #[cfg(windows)]
         let stream = unsafe { TcpStream::from_raw_socket(socket as _) };

src/sys/mod.rs

@@ -14,6 +14,7 @@
 //! * `Waker`: see [`crate::Waker`].
 
 cfg_os_poll! {
+    #[cfg(not(all(target_os = "wasi", target_env = "p2")))]
     macro_rules! debug_detail {
         (
             $type: ident ($event_type: ty), $test: path,