feat(server): support wasm32-wasi

Support the `wasm32-wasi` target, disabling unsupported components.

Signed-off-by: Richard Zak <[email protected]>

.cargo/config

@@ -0,0 +1,3 @@
+[target.wasm32-wasi]
+rustflags = ["--cfg", "tokio_unstable"]
+runner = ["wasmtime", "run", "--"]

Cargo.toml

@@ -39,7 +39,9 @@ want = "0.3"
 # Optional
 
 libc = { version = "0.2", optional = true }
-socket2 = { version = "0.4", optional = true }
+
+[target.'cfg(not(target_arch = "wasm32"))'.dependencies]
+socket2 = { version = "0.4" }
 
 [dev-dependencies]
 futures-util = { version = "0.3", default-features = false, features = ["alloc"] }
@@ -100,7 +102,6 @@ runtime = [
     "tokio/time",
 ]
 tcp = [
-    "socket2",
     "tokio/net",
     "tokio/rt",
     "tokio/time",

src/server/server.rs

@@ -74,6 +74,7 @@ impl Server<AddrIncoming, ()> {
     ///
     /// This method will panic if binding to the address fails. For a method
     /// to bind to an address and return a `Result`, see `Server::try_bind`.
+    #[cfg(not(target_os = "wasi"))]
     pub fn bind(addr: &SocketAddr) -> Builder<AddrIncoming> {
         let incoming = AddrIncoming::new(addr).unwrap_or_else(|e| {
             panic!("error binding to {}: {}", addr, e);
@@ -82,6 +83,7 @@ impl Server<AddrIncoming, ()> {
     }
 
     /// Tries to bind to the provided address, and returns a [`Builder`](Builder).
+    #[cfg(not(target_os = "wasi"))]
     pub fn try_bind(addr: &SocketAddr) -> crate::Result<Builder<AddrIncoming>> {
         AddrIncoming::new(addr).map(Server::builder)
     }

src/server/tcp.rs

@@ -4,6 +4,9 @@ use std::net::{SocketAddr, TcpListener as StdTcpListener};
 use std::time::Duration;
 use socket2::TcpKeepalive;
 
+#[cfg(target_os = "wasi")]
+use std::net::{IpAddr, Ipv4Addr};
+
 use tokio::net::TcpListener;
 use tokio::time::Sleep;
 use tracing::{debug, error, trace};
@@ -78,6 +81,7 @@ pub struct AddrIncoming {
 }
 
 impl AddrIncoming {
+    #[cfg(not(target_os = "wasi"))]
     pub(super) fn new(addr: &SocketAddr) -> crate::Result<Self> {
         let std_listener = StdTcpListener::bind(addr).map_err(crate::Error::new_listen)?;
 
@@ -94,13 +98,21 @@ impl AddrIncoming {
     }
 
     /// Creates a new `AddrIncoming` binding to provided socket address.
+    #[cfg(not(target_os = "wasi"))]
     pub fn bind(addr: &SocketAddr) -> crate::Result<Self> {
         AddrIncoming::new(addr)
     }
 
     /// Creates a new `AddrIncoming` from an existing `tokio::net::TcpListener`.
+    /// For target `wasm32-wasi`, the assumed local address is "0.0.0.0:0", since
+    /// WebAssembly-Wasi has no way to know the local address used for listening.
+    /// This could be removed, but would require refactoring a lot of code in Hyper,
+    /// and other downstream projects.
     pub fn from_listener(listener: TcpListener) -> crate::Result<Self> {
+        #[cfg(not(target_os = "wasi"))]
         let addr = listener.local_addr().map_err(crate::Error::new_listen)?;
+        #[cfg(target_os = "wasi")]
+        let addr = SocketAddr::new(IpAddr::V4(Ipv4Addr::UNSPECIFIED), 0);
         Ok(AddrIncoming {
             listener,
             addr,
@@ -172,17 +184,25 @@ impl AddrIncoming {
         loop {
             match ready!(self.listener.poll_accept(cx)) {
                 Ok((socket, remote_addr)) => {
-                    if let Some(tcp_keepalive) = &self.tcp_keepalive_config.into_socket2() {
-                        let sock_ref = socket2::SockRef::from(&socket);
-                        if let Err(e) = sock_ref.set_tcp_keepalive(tcp_keepalive) {
-                            trace!("error trying to set TCP keepalive: {}", e);
+                    #[cfg(not(target_os = "wasi"))]
+                    {
+                        if let Some(tcp_keepalive) = &self.tcp_keepalive_config.into_socket2() {
+                            let sock_ref = socket2::SockRef::from(&socket);
+                            if let Err(e) = sock_ref.set_tcp_keepalive(tcp_keepalive) {
+                                trace!("error trying to set TCP keepalive: {}", e);
+                            }
+                        }
+                        if let Err(e) = socket.set_nodelay(self.tcp_nodelay) {
+                            trace!("error trying to set TCP nodelay: {}", e);
                         }
+                        let local_addr = socket.local_addr()?;
+                        return Poll::Ready(Ok(AddrStream::new(socket, remote_addr, local_addr)));
                     }
-                    if let Err(e) = socket.set_nodelay(self.tcp_nodelay) {
-                        trace!("error trying to set TCP nodelay: {}", e);
+                    #[cfg(target_os = "wasi")]
+                    {
+                        let local_addr = SocketAddr::new(IpAddr::V4(Ipv4Addr::UNSPECIFIED), 0);
+                        return Poll::Ready(Ok(AddrStream::new(socket, remote_addr, local_addr)));
                     }
-                    let local_addr = socket.local_addr()?;
-                    return Poll::Ready(Ok(AddrStream::new(socket, remote_addr, local_addr)));
                 }
                 Err(e) => {
                     // Connection errors can be ignored directly, continue by
@@ -262,6 +282,8 @@ mod addr_stream {
     use std::net::SocketAddr;
     #[cfg(unix)]
     use std::os::unix::io::{AsRawFd, RawFd};
+    #[cfg(target_os = "wasi")]
+    use std::os::wasi::io::{AsRawFd, RawFd};
     use tokio::io::{AsyncRead, AsyncWrite, ReadBuf};
     use tokio::net::TcpStream;
 
@@ -372,7 +394,7 @@ mod addr_stream {
         }
     }
 
-    #[cfg(unix)]
+    #[cfg(any(unix, target_os = "wasi"))]
     impl AsRawFd for AddrStream {
         fn as_raw_fd(&self) -> RawFd {
             self.inner.as_raw_fd()
@@ -385,6 +407,7 @@ mod tests {
     use std::time::Duration;
     use crate::server::tcp::TcpKeepaliveConfig;
 
+    #[cfg(not(target_os = "wasi"))]
     #[test]
     fn no_tcp_keepalive_config() {
         assert!(TcpKeepaliveConfig::default().into_socket2().is_none());
@@ -401,7 +424,7 @@ mod tests {
         }
     }
 
-    #[cfg(not(any(target_os = "openbsd", target_os = "redox", target_os = "solaris")))]
+    #[cfg(not(any(target_os = "openbsd", target_os = "redox", target_os = "solaris", target_os = "wasi")))]
     #[test]
     fn tcp_keepalive_interval_config() {
         let mut kac = TcpKeepaliveConfig::default();
@@ -413,7 +436,7 @@ mod tests {
         }
     }
 
-    #[cfg(not(any(target_os = "openbsd", target_os = "redox", target_os = "solaris", target_os = "windows")))]
+    #[cfg(not(any(target_os = "openbsd", target_os = "redox", target_os = "solaris", target_os = "windows", target_os = "wasi")))]
     #[test]
     fn tcp_keepalive_retries_config() {
         let mut kac = TcpKeepaliveConfig::default();