net: add UnixSocket (#6290)

tokio/src/net/mod.rs

@@ -49,6 +49,7 @@ cfg_net_unix! {
     pub use unix::datagram::socket::UnixDatagram;
     pub use unix::listener::UnixListener;
     pub use unix::stream::UnixStream;
+    pub use unix::socket::UnixSocket;
 }
 
 cfg_net_windows! {

tokio/src/net/unix/datagram/socket.rs

@@ -96,6 +96,16 @@ cfg_net_unix! {
 }
 
 impl UnixDatagram {
+    pub(crate) fn from_mio(sys: mio::net::UnixDatagram) -> io::Result<UnixDatagram> {
+        let datagram = UnixDatagram::new(sys)?;
+
+        if let Some(e) = datagram.io.take_error()? {
+            return Err(e);
+        }
+
+        Ok(datagram)
+    }
+
     /// Waits for any of the requested ready states.
     ///
     /// This function is usually paired with `try_recv()` or `try_send()`. It

tokio/src/net/unix/listener.rs

@@ -50,6 +50,11 @@ cfg_net_unix! {
 }
 
 impl UnixListener {
+    pub(crate) fn new(listener: mio::net::UnixListener) -> io::Result<UnixListener> {
+        let io = PollEvented::new(listener)?;
+        Ok(UnixListener { io })
+    }
+
     /// Creates a new `UnixListener` bound to the specified path.
     ///
     /// # Panics

tokio/src/net/unix/mod.rs

@@ -7,6 +7,8 @@ pub mod datagram;
 
 pub(crate) mod listener;
 
+pub(crate) mod socket;
+
 mod split;
 pub use split::{ReadHalf, WriteHalf};
 

tokio/src/net/unix/socket.rs

@@ -0,0 +1,271 @@
+use std::io;
+use std::path::Path;
+
+use std::os::unix::io::{AsFd, AsRawFd, BorrowedFd, FromRawFd, IntoRawFd, RawFd};
+
+use crate::net::{UnixDatagram, UnixListener, UnixStream};
+
+cfg_net_unix! {
+    /// A Unix socket that has not yet been converted to a [`UnixStream`], [`UnixDatagram`], or
+    /// [`UnixListener`].
+    ///
+    /// `UnixSocket` wraps an operating system socket and enables the caller to
+    /// configure the socket before establishing a connection or accepting
+    /// inbound connections. The caller is able to set socket option and explicitly
+    /// bind the socket with a socket address.
+    ///
+    /// The underlying socket is closed when the `UnixSocket` value is dropped.
+    ///
+    /// `UnixSocket` should only be used directly if the default configuration used
+    /// by [`UnixStream::connect`], [`UnixDatagram::bind`], and [`UnixListener::bind`]
+    /// does not meet the required use case.
+    ///
+    /// Calling `UnixStream::connect(path)` effectively performs the same function as:
+    ///
+    /// ```no_run
+    /// use tokio::net::UnixSocket;
+    /// use std::error::Error;
+    ///
+    /// #[tokio::main]
+    /// async fn main() -> Result<(), Box<dyn Error>> {
+    ///     let dir = tempfile::tempdir().unwrap();
+    ///     let path = dir.path().join("bind_path");
+    ///     let socket = UnixSocket::new_stream()?;
+    ///
+    ///     let stream = socket.connect(path).await?;
+    ///
+    ///     Ok(())
+    /// }
+    /// ```
+    ///
+    /// Calling `UnixDatagram::bind(path)` effectively performs the same function as:
+    ///
+    /// ```no_run
+    /// use tokio::net::UnixSocket;
+    /// use std::error::Error;
+    ///
+    /// #[tokio::main]
+    /// async fn main() -> Result<(), Box<dyn Error>> {
+    ///     let dir = tempfile::tempdir().unwrap();
+    ///     let path = dir.path().join("bind_path");
+    ///     let socket = UnixSocket::new_datagram()?;
+    ///     socket.bind(path)?;
+    ///
+    ///     let datagram = socket.datagram()?;
+    ///
+    ///     Ok(())
+    /// }
+    /// ```
+    ///
+    /// Calling `UnixListener::bind(path)` effectively performs the same function as:
+    ///
+    /// ```no_run
+    /// use tokio::net::UnixSocket;
+    /// use std::error::Error;
+    ///
+    /// #[tokio::main]
+    /// async fn main() -> Result<(), Box<dyn Error>> {
+    ///     let dir = tempfile::tempdir().unwrap();
+    ///     let path = dir.path().join("bind_path");
+    ///     let socket = UnixSocket::new_stream()?;
+    ///     socket.bind(path)?;
+    ///
+    ///     let listener = socket.listen(1024)?;
+    ///
+    ///     Ok(())
+    /// }
+    /// ```
+    ///
+    /// Setting socket options not explicitly provided by `UnixSocket` may be done by
+    /// accessing the [`RawFd`]/[`RawSocket`] using [`AsRawFd`]/[`AsRawSocket`] and
+    /// setting the option with a crate like [`socket2`].
+    ///
+    /// [`RawFd`]: std::os::fd::RawFd
+    /// [`RawSocket`]: https://doc.rust-lang.org/std/os/windows/io/type.RawSocket.html
+    /// [`AsRawFd`]: std::os::fd::AsRawFd
+    /// [`AsRawSocket`]: https://doc.rust-lang.org/std/os/windows/io/trait.AsRawSocket.html
+    /// [`socket2`]: https://docs.rs/socket2/
+    #[derive(Debug)]
+    pub struct UnixSocket {
+        inner: socket2::Socket,
+    }
+}
+
+impl UnixSocket {
+    fn ty(&self) -> socket2::Type {
+        self.inner.r#type().unwrap()
+    }
+
+    /// Creates a new Unix datagram socket.
+    ///
+    /// Calls `socket(2)` with `AF_UNIX` and `SOCK_DGRAM`.
+    ///
+    /// # Returns
+    ///
+    /// On success, the newly created [`UnixSocket`] is returned. If an error is
+    /// encountered, it is returned instead.
+    pub fn new_datagram() -> io::Result<UnixSocket> {
+        UnixSocket::new(socket2::Type::DGRAM)
+    }
+
+    /// Creates a new Unix stream socket.
+    ///
+    /// Calls `socket(2)` with `AF_UNIX` and `SOCK_STREAM`.
+    ///
+    /// # Returns
+    ///
+    /// On success, the newly created [`UnixSocket`] is returned. If an error is
+    /// encountered, it is returned instead.
+    pub fn new_stream() -> io::Result<UnixSocket> {
+        UnixSocket::new(socket2::Type::STREAM)
+    }
+
+    fn new(ty: socket2::Type) -> io::Result<UnixSocket> {
+        #[cfg(any(
+            target_os = "android",
+            target_os = "dragonfly",
+            target_os = "freebsd",
+            target_os = "fuchsia",
+            target_os = "illumos",
+            target_os = "linux",
+            target_os = "netbsd",
+            target_os = "openbsd"
+        ))]
+        let ty = ty.nonblocking();
+        let inner = socket2::Socket::new(socket2::Domain::UNIX, ty, None)?;
+        #[cfg(not(any(
+            target_os = "android",
+            target_os = "dragonfly",
+            target_os = "freebsd",
+            target_os = "fuchsia",
+            target_os = "illumos",
+            target_os = "linux",
+            target_os = "netbsd",
+            target_os = "openbsd"
+        )))]
+        inner.set_nonblocking(true)?;
+        Ok(UnixSocket { inner })
+    }
+
+    /// Binds the socket to the given address.
+    ///
+    /// This calls the `bind(2)` operating-system function.
+    pub fn bind(&self, path: impl AsRef<Path>) -> io::Result<()> {
+        let addr = socket2::SockAddr::unix(path)?;
+        self.inner.bind(&addr)
+    }
+
+    /// Converts the socket into a `UnixListener`.
+    ///
+    /// `backlog` defines the maximum number of pending connections are queued
+    /// by the operating system at any given time. Connection are removed from
+    /// the queue with [`UnixListener::accept`]. When the queue is full, the
+    /// operating-system will start rejecting connections.
+    ///
+    /// Calling this function on a socket created by [`new_datagram`] will return an error.
+    ///
+    /// This calls the `listen(2)` operating-system function, marking the socket
+    /// as a passive socket.
+    ///
+    /// [`new_datagram`]: `UnixSocket::new_datagram`
+    pub fn listen(self, backlog: u32) -> io::Result<UnixListener> {
+        if self.ty() == socket2::Type::DGRAM {
+            return Err(io::Error::new(
+                io::ErrorKind::Other,
+                "listen cannot be called on a datagram socket",
+            ));
+        }
+
+        self.inner.listen(backlog as i32)?;
+        let mio = {
+            use std::os::unix::io::{FromRawFd, IntoRawFd};
+
+            let raw_fd = self.inner.into_raw_fd();
+            unsafe { mio::net::UnixListener::from_raw_fd(raw_fd) }
+        };
+
+        UnixListener::new(mio)
+    }
+
+    /// Establishes a Unix connection with a peer at the specified socket address.
+    ///
+    /// The `UnixSocket` is consumed. Once the connection is established, a
+    /// connected [`UnixStream`] is returned. If the connection fails, the
+    /// encountered error is returned.
+    ///
+    /// Calling this function on a socket created by [`new_datagram`] will return an error.
+    ///
+    /// This calls the `connect(2)` operating-system function.
+    ///
+    /// [`new_datagram`]: `UnixSocket::new_datagram`
+    pub async fn connect(self, path: impl AsRef<Path>) -> io::Result<UnixStream> {
+        if self.ty() == socket2::Type::DGRAM {
+            return Err(io::Error::new(
+                io::ErrorKind::Other,
+                "connect cannot be called on a datagram socket",
+            ));
+        }
+
+        let addr = socket2::SockAddr::unix(path)?;
+        if let Err(err) = self.inner.connect(&addr) {
+            if err.raw_os_error() != Some(libc::EINPROGRESS) {
+                return Err(err);
+            }
+        }
+        let mio = {
+            use std::os::unix::io::{FromRawFd, IntoRawFd};
+
+            let raw_fd = self.inner.into_raw_fd();
+            unsafe { mio::net::UnixStream::from_raw_fd(raw_fd) }
+        };
+
+        UnixStream::connect_mio(mio).await
+    }
+
+    /// Converts the socket into a [`UnixDatagram`].
+    ///
+    /// Calling this function on a socket created by [`new_stream`] will return an error.
+    ///
+    /// [`new_stream`]: `UnixSocket::new_stream`
+    pub fn datagram(self) -> io::Result<UnixDatagram> {
+        if self.ty() == socket2::Type::STREAM {
+            return Err(io::Error::new(
+                io::ErrorKind::Other,
+                "datagram cannot be called on a stream socket",
+            ));
+        }
+        let mio = {
+            use std::os::unix::io::{FromRawFd, IntoRawFd};
+
+            let raw_fd = self.inner.into_raw_fd();
+            unsafe { mio::net::UnixDatagram::from_raw_fd(raw_fd) }
+        };
+
+        UnixDatagram::from_mio(mio)
+    }
+}
+
+impl AsRawFd for UnixSocket {
+    fn as_raw_fd(&self) -> RawFd {
+        self.inner.as_raw_fd()
+    }
+}
+
+impl AsFd for UnixSocket {
+    fn as_fd(&self) -> BorrowedFd<'_> {
+        unsafe { BorrowedFd::borrow_raw(self.as_raw_fd()) }
+    }
+}
+
+impl FromRawFd for UnixSocket {
+    unsafe fn from_raw_fd(fd: RawFd) -> UnixSocket {
+        let inner = socket2::Socket::from_raw_fd(fd);
+        UnixSocket { inner }
+    }
+}
+
+impl IntoRawFd for UnixSocket {
+    fn into_raw_fd(self) -> RawFd {
+        self.inner.into_raw_fd()
+    }
+}

tokio/src/net/unix/stream.rs

@@ -39,6 +39,24 @@ cfg_net_unix! {
 }
 
 impl UnixStream {
+    pub(crate) async fn connect_mio(sys: mio::net::UnixStream) -> io::Result<UnixStream> {
+        let stream = UnixStream::new(sys)?;
+
+        // Once we've connected, wait for the stream to be writable as
+        // that's when the actual connection has been initiated. Once we're
+        // writable we check for `take_socket_error` to see if the connect
+        // actually hit an error or not.
+        //
+        // If all that succeeded then we ship everything on up.
+        poll_fn(|cx| stream.io.registration().poll_write_ready(cx)).await?;
+
+        if let Some(e) = stream.io.take_error()? {
+            return Err(e);
+        }
+
+        Ok(stream)
+    }
+
     /// Connects to the socket named by `path`.
     ///
     /// This function will create a new Unix socket and connect to the path