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// Copyright 2020 Steven Bosnick // // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE-2.0 or // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your // option. This file may not be copied, modified, or distributed // except according to those terms use std::collections::VecDeque; use std::fmt; use std::io::{self, prelude::*, Error, ErrorKind, IoSlice, IoSliceMut}; use std::mem::size_of; use std::net::Shutdown; use std::os::unix::io::{AsRawFd, FromRawFd, IntoRawFd, RawFd}; use std::os::unix::net::{SocketAddr, UnixListener as StdUnixListner, UnixStream as StdUnixStream}; use std::path::Path; use std::slice; // needed until the MSRV is 1.43 when the associated constant becomes available use std::isize; use std::usize; use nix::cmsg_space; use nix::sys::socket::{recvmsg, sendmsg, ControlMessage, ControlMessageOwned, MsgFlags}; use nix::sys::uio::IoVec; use tracing::{trace, warn}; use crate::{DequeueFd, EnqueueFd, QueueFullError}; /// A structure representing a connected Unix socket with support for passing /// [`RawFd`][RawFd]. /// /// This is the primary implementation of `EnqueueFd` and `DequeueFd` and it is based /// on a blocking, Unix domain socket. Conceptually the key interfaces on /// `UnixStream` interact as shown in the following diagram: /// /// ```text /// EnqueueFd => Write => Read => DequeueFd /// ``` /// /// That is, you first endqueue a [`RawFd`][RawFd] to the `UnixStream` and then /// `Write` at least one byte. On the other side of the `UnixStream` you then `Read` /// at least one byte and then dequeue the [`RawFd`][RawFd]. /// /// # Examples /// /// ``` /// # use fd_queue::{EnqueueFd, DequeueFd, UnixStream}; /// # use std::io::prelude::*; /// # use std::os::unix::io::FromRawFd; /// # use tempfile::tempfile; /// use std::fs::File; /// /// let (mut sock1, mut sock2) = UnixStream::pair()?; /// /// // sender side /// # let file1: File = tempfile()?; /// // let file1: File = ... /// sock1.enqueue(&file1).expect("Can't endqueue the file descriptor."); /// sock1.write(b"a")?; /// sock1.flush()?; /// /// // receiver side /// let mut buf = [0u8; 1]; /// sock2.read(&mut buf)?; /// let fd = sock2.dequeue().expect("Can't dequeue the file descriptor."); /// let file2 = unsafe { File::from_raw_fd(fd) }; /// /// # Ok::<(),std::io::Error>(()) /// ``` /// /// [RawFd]: https://doc.rust-lang.org/stable/std/os/unix/io/type.RawFd.html #[derive(Debug)] pub struct UnixStream { inner: StdUnixStream, infd: VecDeque<RawFd>, outfd: Option<Vec<RawFd>>, cmsg_buffer: Vec<u8>, } /// A structure representing a Unix domain socket server whose connected sockets /// have support for passing [`RawFd`][RawFd]. /// /// [RawFd]: https://doc.rust-lang.org/stable/std/os/unix/io/type.RawFd.html #[derive(Debug)] pub struct UnixListener { inner: StdUnixListner, } /// An iterator over incoming connections to a `UnixListener`. /// /// It is an infinite iterator that will never return `None` #[derive(Debug)] pub struct Incoming<'a> { listener: &'a UnixListener, } #[derive(Debug)] struct CMsgTruncatedError {} // === impl UnixStream === impl UnixStream { /// The size of the bounded queue of outbound [`RawFd`][RawFd]. /// /// [RawFd]: https://doc.rust-lang.org/stable/std/os/unix/io/type.RawFd.html pub const FD_QUEUE_SIZE: usize = 2; /// Connects to the socket named by `path`. /// /// # Examples /// /// ``` /// # use std::thread; /// # use fd_queue::UnixListener; /// # use tempfile::tempdir; /// use fd_queue::UnixStream; /// /// # let dir = tempdir()?; /// # let path = dir.path().join("mysock"); /// // let path = ... /// # let listener = UnixListener::bind(&path)?; /// # thread::spawn(move || listener.accept()); /// /// let sock = match UnixStream::connect(path) { /// Ok(sock) => sock, /// Err(e) => { /// println!("Couldn't connect to a socket: {}", e); /// return Ok(()); /// } /// }; /// /// # Ok::<(), std::io::Error>(()) /// ``` pub fn connect<P: AsRef<Path>>(path: P) -> io::Result<UnixStream> { StdUnixStream::connect(path).map(|s| s.into()) } /// Creates an unnamed pair of connected sockets. /// /// Returns two `UnixStream`s which are connected to each other. /// /// # Examples /// /// ``` /// use fd_queue::UnixStream; /// /// let (sock1, sock2) = match UnixStream::pair() { /// Ok((sock1, sock2)) => (sock1, sock2), /// Err(e) => { /// println!("Couldn't create a pair of sockets: {}", e); /// return; /// } /// }; /// ``` pub fn pair() -> io::Result<(UnixStream, UnixStream)> { StdUnixStream::pair().map(|(s1, s2)| (s1.into(), s2.into())) } /// Creates a new independently owned handle to the underlying socket. /// /// The returned `UnixStream` is a reference to the same stream that this object references. /// Both handles will read and write the same stream of data, and options set on one stream /// will be propagated to the other stream. /// /// # Examples /// /// ``` /// use fd_queue::UnixStream; /// /// let (sock1, _) = UnixStream::pair()?; /// /// let sock2 = match sock1.try_clone() { /// Ok(sock) => sock, /// Err(e) => { /// println!("Couldn't clone a socket: {}", e); /// return Ok(()); /// } /// }; /// /// # Ok::<(),std::io::Error>(()) /// ``` pub fn try_clone(&self) -> io::Result<UnixStream> { self.inner.try_clone().map(|s| s.into()) } /// Returns the socket address of the local half of this connection. /// /// # Examples /// /// ``` /// # use std::thread; /// # use fd_queue::UnixListener; /// # use tempfile::tempdir; /// use fd_queue::UnixStream; /// /// # let dir = tempdir()?; /// # let path = dir.path().join("mysock"); /// // let path = ... /// # let listener = UnixListener::bind(&path)?; /// # thread::spawn(move || listener.accept()); /// # /// let sock = UnixStream::connect(path)?; /// /// let addr = match sock.local_addr() { /// Ok(addr) => addr, /// Err(e) => { /// println!("Couldn't get the local address: {}", e); /// return Ok(()); /// } /// }; /// /// # Ok::<(),std::io::Error>(()) /// ``` pub fn local_addr(&self) -> io::Result<SocketAddr> { self.inner.local_addr() } /// Returns the socket address of the remote half of this connection. /// /// # Examples /// /// ``` /// # use std::thread; /// # use fd_queue::UnixListener; /// # use tempfile::tempdir; /// use fd_queue::UnixStream; /// /// # let dir = tempdir()?; /// # let path = dir.path().join("mysock"); /// // let path = ... /// # let listener = UnixListener::bind(&path)?; /// # thread::spawn(move || listener.accept()); /// # /// let sock = UnixStream::connect(path)?; /// /// let addr = match sock.peer_addr() { /// Ok(addr) => addr, /// Err(e) => { /// println!("Couldn't get the local address: {}", e); /// return Ok(()); /// } /// }; /// /// # Ok::<(),std::io::Error>(()) /// ``` pub fn peer_addr(&self) -> io::Result<SocketAddr> { self.inner.peer_addr() } /// Returns the value of the `SO_ERROR` option. /// /// # Examples /// /// ``` /// use fd_queue::UnixStream; /// /// let (sock, _) = UnixStream::pair()?; /// /// let err = match sock.take_error() { /// Ok(Some(err)) => err, /// Ok(None) => { /// println!("No error found."); /// return Ok(()); /// } /// Err(e) => { /// println!("Couldn't take the SO_ERROR option: {}", e); /// return Ok(()); /// } /// }; /// /// # Ok::<(),std::io::Error>(()) /// ``` pub fn take_error(&self) -> io::Result<Option<Error>> { self.inner.take_error() } /// Shuts down the read, write, or both halves of this connection. /// /// This function will cause all pending and future I/O calls on the specified portions to /// immediately return with an appropriate value. /// /// # Examples /// /// ``` /// use fd_queue::UnixStream; /// use std::net::Shutdown; /// use std::io::Read; /// /// let (mut sock, _) = UnixStream::pair()?; /// /// sock.shutdown(Shutdown::Read).expect("Couldn't shutdown."); /// /// let mut buf = [0u8; 256]; /// match sock.read(buf.as_mut()) { /// Ok(0) => {}, /// _ => panic!("Read unexpectly not shut down."), /// } /// /// # Ok::<(),std::io::Error>(()) /// ``` pub fn shutdown(&self, how: Shutdown) -> io::Result<()> { self.inner.shutdown(how) } pub(crate) fn set_nonblocking(&self, nonblocking: bool) -> io::Result<()> { self.inner.set_nonblocking(nonblocking) } } /// Enqueue a [`RawFd`][RawFd] for later transmission across the `UnixStream`. /// /// The [`RawFd`][RawFd] will be transmitted on a later call to a method of `Write`. /// The number of [`RawFd`][RawFd] that can be enqueued before being transmitted is /// bounded by `FD_QUEUE_SIZE`. /// /// [RawFd]: https://doc.rust-lang.org/stable/std/os/unix/io/type.RawFd.html impl EnqueueFd for UnixStream { fn enqueue(&mut self, fd: &impl AsRawFd) -> std::result::Result<(), QueueFullError> { let outfd = self .outfd .get_or_insert_with(|| Vec::with_capacity(Self::FD_QUEUE_SIZE)); if outfd.len() >= Self::FD_QUEUE_SIZE { warn!(source = "UnixStream", event = "enqueue", condition = "full"); Err(QueueFullError::new()) } else { trace!(source = "UnixStream", event = "enqueue", count = 1); outfd.push(fd.as_raw_fd()); Ok(()) } } } /// Dequeue a [`RawFd`][RawFd] that was previously transmitted across the /// `UnixStream`. /// /// The [`RawFd`][RawFd] that are dequeued were transmitted by a previous call to a /// method of `Read`. /// /// [RawFd]: https://doc.rust-lang.org/stable/std/os/unix/io/type.RawFd.html impl DequeueFd for UnixStream { fn dequeue(&mut self) -> Option<RawFd> { let result = self.infd.pop_front(); trace!( source = "UnixStream", event = "dequeue", count = if result.is_some() { 1 } else { 0 } ); result } } /// Receive bytes and [`RawFd`][RawFd] that are transmitted across the `UnixStream`. /// /// The [`RawFd`][RawFd] that are received along with the bytes will be available /// through the method of the `DequeueFd` implementation. The number of /// [`RawFd`][RawFd] that can be received in a single call to one of the `Read` /// methods is bounded by `FD_QUEUE_SIZE`. It is an error if the other side of this /// `UnixStream` attempted to send more control messages (including [`RawFd`][RawFd]) /// than will fit in the buffer that has been sized for receiving up to /// `FD_QUEUE_SIZE` [`RawFd`][RawFd]. /// /// [RawFd]: https://doc.rust-lang.org/stable/std/os/unix/io/type.RawFd.html impl Read for UnixStream { fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> { self.read_vectored(&mut [IoSliceMut::new(buf)]) } fn read_vectored(&mut self, bufs: &mut [IoSliceMut]) -> io::Result<usize> { assert_eq!(size_of::<IoSliceMut>(), size_of::<IoVec<&mut [u8]>>()); assert!((isize::MAX as usize) / size_of::<IoVec<&mut [u8]>>() >= bufs.len()); let bufs_ptr = bufs.as_mut_ptr(); let vecs_ptr = bufs_ptr as *mut IoVec<&mut [u8]>; // Safety: from_raw_parts_mut(data, len) requires 3 things // // 1. data is valid (i.e. non-null and pointing to a single allocated // object) // 2. the memory referenced by the returned slice must not be accessed // other than through that slice for the lifetime of the slice // 3. len * size_of::<T>() <= isize::MAX // // For the first condition, vecs_ptr is is a pointer to the first byte of the // bufs slice which is bufs.len() * size_of::<IoSliceMut> bytes long. The // first assertion means that it is also bufs.len() * // size_of::<IoVec<&mut[u8]>> bytes long. vecs_ptr thus points to the single // allocated object bufs for its whole bufs.len * size_of::<IoVec<&mut[u8]> // size. Since it is pointing to the first byte of a slice, it is non-null. // It is properly aligned because it is equal to bufs_ptr (which is properly // aligned) and because both IoSliceMut and IoVec<&mut [u8]> are guarenteed // to have the same layout, specifically the layout of iovec C ABI type. // // For the second condition, all of bufs, bufs_ptr, vecs_ptr, and vecs // reference the same memory, but only vecs is used in any manner after this // call. // // For the third condition, the second assertion demonstarates that it holds // (absent a panic). let vecs = unsafe { slice::from_raw_parts_mut(vecs_ptr, bufs.len()) }; let msg = recvmsg( self.as_raw_fd(), &vecs, Some(&mut self.cmsg_buffer), MsgFlags::empty(), ) .map_err(map_error)?; if msg.flags.contains(MsgFlags::MSG_CTRUNC) { warn!( source = "UnixStream", event = "read", condition = "cmsgs truncated" ); return Err(Error::new(ErrorKind::Other, CMsgTruncatedError::new())); } let mut fds_count = 0; for c in msg.cmsgs() { if let ControlMessageOwned::ScmRights(fds) = c { self.infd.extend(fds); fds_count += 1; } } trace!( source = "UnixStream", event = "read", fds_count, byte_count = msg.bytes ); Ok(msg.bytes) } } /// Transmit bytes and [`RawFd`][RawFd] across the `UnixStream`. /// /// The [`RawFd`][RawFd] that are transmitted along with the bytes are ones that were /// previously enqueued for transmission through the method of `EnqueueFd`. /// /// [RawFd]: https://doc.rust-lang.org/stable/std/os/unix/io/type.RawFd.html impl Write for UnixStream { fn write(&mut self, buf: &[u8]) -> io::Result<usize> { self.write_vectored(&[IoSlice::new(buf)]) } fn write_vectored(&mut self, bufs: &[IoSlice]) -> io::Result<usize> { assert_eq!(size_of::<IoSlice>(), size_of::<IoVec<&[u8]>>()); assert!((isize::MAX as usize) / size_of::<IoVec<&[u8]>>() >= bufs.len()); let bufs_ptr = bufs.as_ptr(); let vecs_ptr = bufs_ptr as *const IoVec<&[u8]>; // Safety: from_raw_parts(data, len) requires three things: // // 1. data must be valid for len * size_of::<T>() bytes (non-null, // properly aligned, and the memory range from a single allocation). // 2. The memory reference by the return slice must not be mutated for // the liftime of the slice. // 3. len * size_of::<T>() <= isize::MAX // // For the first condtion vecs_ptr is non-null because it points to the first // byte of bufs. It is properly aligned for IoVec<&[u8]> because it is // properly aligned for IoSlice and IoVec<&[u8]> and IoSlice both have the // same layout: the C ABI for an iovec. The first assertion above ensures // that bufs.len() * size_of::<IoVec<&[u8]>> is the same as bufs.len() * // size_of::<IoSlice> and both are the number of bytes in bufs, which is a // single allocation. // // For the second condition, bufs, bufs_ptr, vecs, and vecs_ptr all refer to // the same memory but they are all const pointers or shared references. // There are no other references to that memory in this function and any such // references in other functions must be through shared references (becuase // bufs is a shared reference). // // For the third condition, the second assertion ensurse this is true. let vecs = unsafe { slice::from_raw_parts(vecs_ptr, bufs.len()) }; let outfd = self.outfd.take(); let fds = outfd.unwrap_or_else(Vec::new); let fds_count = fds.len(); let cmsgs = if fds.is_empty() { Vec::new() } else { vec![ControlMessage::ScmRights(&fds)] }; let byte_count: usize = vecs.iter().map(|vec| vec.as_slice().len()).sum(); trace!( source = "UnixStream", event = "write", fds_count, byte_count ); sendmsg(self.as_raw_fd(), &vecs, &cmsgs, MsgFlags::empty(), None).map_err(map_error) } fn flush(&mut self) -> io::Result<()> { self.inner.flush() } } impl AsRawFd for UnixStream { fn as_raw_fd(&self) -> RawFd { self.inner.as_raw_fd() } } impl FromRawFd for UnixStream { unsafe fn from_raw_fd(fd: RawFd) -> Self { StdUnixStream::from_raw_fd(fd).into() } } impl IntoRawFd for UnixStream { fn into_raw_fd(self) -> RawFd { self.inner.into_raw_fd() } } impl From<StdUnixStream> for UnixStream { fn from(inner: StdUnixStream) -> Self { Self { inner, infd: VecDeque::with_capacity(Self::FD_QUEUE_SIZE), outfd: None, cmsg_buffer: cmsg_space!([RawFd; Self::FD_QUEUE_SIZE]), } } } fn map_error(e: nix::Error) -> io::Error { use nix::Error::*; match e { Sys(e) => io::Error::from_raw_os_error(e as i32), _ => io::Error::new(io::ErrorKind::Other, Box::new(e)), } } // === impl UnixListener === impl UnixListener { /// Create a new `UnixListener` bound to the specified socket. /// /// # Examples /// /// ``` /// use fd_queue::UnixListener; /// # use tempfile::tempdir; /// # let dir = tempdir()?; /// # let path = dir.path().join("mysocket"); /// // let path = ... /// let listener = match UnixListener::bind(&path) { /// Ok(listener) => listener, /// Err(e) => { /// println!("Can't bind the unix socket libtest: {}", e); /// return Ok(()); /// } /// }; /// /// # Ok::<(),std::io::Error>(()) /// ``` pub fn bind(path: impl AsRef<Path>) -> io::Result<UnixListener> { StdUnixListner::bind(path).map(|s| s.into()) } /// Accepts a new incoming connection to this server. /// /// This function will block the calling thread until a new Unix connection is /// established. When established the corresponding `UnixStream` and the remote /// peer's address will be returned. /// /// # Examples /// /// ``` /// use fd_queue::UnixListener; /// # use fd_queue::UnixStream; /// # use std::thread; /// # use tempfile::tempdir; /// # let dir = tempdir()?; /// # let path = dir.path().join("mysocket"); /// /// // let path = ... /// let listener = UnixListener::bind(&path)?; /// # thread::spawn(move || UnixStream::connect(path).expect("Can't connect")); /// /// let (sock, addr) = match listener.accept() { /// Ok((sock, addr)) => (sock, addr), /// Err(e) => { /// println!("Can't accept unix stream: {}", e); /// return Ok(()); /// } /// }; /// /// # Ok::<(),std::io::Error>(()) /// ``` pub fn accept(&self) -> io::Result<(UnixStream, SocketAddr)> { self.inner.accept().map(|(s, a)| (s.into(), a)) } /// Create a new independently owned handle to the underlying socket. /// /// The returned `UnixListener` is a reference to the same socket that this /// object references. Both handles can be used to accept incoming connections /// and options set on one will affect the other. /// /// # Examples /// /// ``` /// use fd_queue::UnixListener; /// # use tempfile::tempdir; /// # let dir = tempdir()?; /// # let path = dir.path().join("mysocket"); /// /// // let path = ... /// let listener1 = UnixListener::bind(&path)?; /// /// let listener2 = match listener1.try_clone() { /// Ok(listener) => listener, /// Err(e) => { /// println!("Can't clone listener: {}", e); /// return Ok(()); /// } /// }; /// /// # Ok::<(),std::io::Error>(()) /// ``` pub fn try_clone(&self) -> io::Result<UnixListener> { self.inner.try_clone().map(|s| s.into()) } /// Returns the local address of of this listener. /// /// # Examples /// /// ``` /// use fd_queue::UnixListener; /// # use tempfile::tempdir; /// # let dir = tempdir()?; /// # let path = dir.path().join("mysocket"); /// /// // let path = ... /// let listener = UnixListener::bind(&path)?; /// /// let addr = match listener.local_addr() { /// Ok(addr) => addr, /// Err(e) => { /// println!("Couldn't get local address: {}", e); /// return Ok(()); /// } /// }; /// /// # Ok::<(),std::io::Error>(()) /// ``` pub fn local_addr(&self) -> io::Result<SocketAddr> { self.inner.local_addr() } /// Return the value of the `SO_ERROR` option. /// /// # Examples /// /// ``` /// use fd_queue::UnixListener; /// # use tempfile::tempdir; /// # let dir = tempdir()?; /// # let path = dir.path().join("mysocket"); /// /// // let path = ... /// let listener = UnixListener::bind(&path)?; /// /// let err = match listener.take_error() { /// Ok(Some(err)) => err, /// Ok(None) => { /// println!("There was no SO_ERROR option pending."); /// return Ok(()); /// } /// Err(e) => { /// println!("Couldn't get the SO_ERROR option: {}", e); /// return Ok(()) /// } /// }; /// /// # Ok::<(),std::io::Error>(()) /// ``` pub fn take_error(&self) -> io::Result<Option<Error>> { self.inner.take_error() } /// Returns an iterator over incoming connections. /// /// The iterator will never return `None` and also will not yield the peer's /// [`SocketAddr`][SocketAddr] structure. /// /// # Examples /// /// ``` /// use fd_queue::UnixListener; /// # use fd_queue::UnixStream; /// # use std::thread; /// # use tempfile::tempdir; /// # let dir = tempdir()?; /// # let path = dir.path().join("mysocket"); /// /// // let path = ... /// let listener = UnixListener::bind(&path)?; /// # thread::spawn(move || UnixStream::connect(path).expect("Can't connect")); /// /// let mut incoming = listener.incoming(); /// /// let sock = match incoming.next() { /// Some(Ok(sock)) => sock, /// Some(Err(e)) => { /// println!("Can't get the next incoming socket: {}", e); /// return Ok(()); /// } /// None => unreachable!(), /// }; /// /// # Ok::<(),std::io::Error>(()) /// ``` /// /// [SocketAddr]: https://doc.rust-lang.org/stable/std/os/unix/net/struct.SocketAddr.html pub fn incoming(&self) -> Incoming { Incoming { listener: self } } } impl AsRawFd for UnixListener { fn as_raw_fd(&self) -> RawFd { self.inner.as_raw_fd() } } impl FromRawFd for UnixListener { unsafe fn from_raw_fd(fd: RawFd) -> Self { StdUnixListner::from_raw_fd(fd).into() } } impl IntoRawFd for UnixListener { fn into_raw_fd(self) -> RawFd { self.inner.into_raw_fd() } } impl<'a> IntoIterator for &'a UnixListener { type Item = io::Result<UnixStream>; type IntoIter = Incoming<'a>; fn into_iter(self) -> Self::IntoIter { self.incoming() } } impl From<StdUnixListner> for UnixListener { fn from(inner: StdUnixListner) -> Self { UnixListener { inner } } } // === impl Incoming === impl Iterator for Incoming<'_> { type Item = io::Result<UnixStream>; fn next(&mut self) -> Option<Self::Item> { Some(self.listener.accept().map(|(s, _)| s)) } fn size_hint(&self) -> (usize, Option<usize>) { (usize::MAX, None) } } // === impl CMsgTruncatedError === impl CMsgTruncatedError { fn new() -> CMsgTruncatedError { CMsgTruncatedError {} } } impl fmt::Display for CMsgTruncatedError { fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> { write!( f, "The buffer used to receive file descriptors was too small." ) } } impl std::error::Error for CMsgTruncatedError {} #[cfg(test)] mod test { use super::*; use std::convert::AsMut; use std::ffi::c_void; use std::ptr; use std::slice; use nix::fcntl::OFlag; use nix::sys::mman::{mmap, munmap, shm_open, shm_unlink, MapFlags, ProtFlags}; use nix::sys::stat::Mode; use nix::unistd::{close, ftruncate}; struct Shm { fd: RawFd, ptr: *mut u8, len: usize, name: String, } impl Shm { fn new(name: &str, size: i64) -> Shm { let oflag = OFlag::O_CREAT | OFlag::O_RDWR; let fd = shm_open(name, oflag, Mode::S_IRUSR | Mode::S_IWUSR).expect("Can't create shm."); ftruncate(fd, size).expect("Can't ftruncate"); let len: usize = size as usize; let prot = ProtFlags::PROT_READ | ProtFlags::PROT_WRITE; let flags = MapFlags::MAP_SHARED; let ptr = unsafe { mmap(ptr::null_mut(), len, prot, flags, fd, 0).expect("Can't mmap") as *mut u8 }; Shm { fd, ptr, len, name: name.to_string(), } } fn from_raw_fd(fd: RawFd, size: usize) -> Shm { let prot = ProtFlags::PROT_READ | ProtFlags::PROT_WRITE; let flags = MapFlags::MAP_SHARED; let ptr = unsafe { mmap(ptr::null_mut(), size, prot, flags, fd, 0).expect("Can't mmap") as *mut u8 }; Shm { fd, ptr, len: size, name: String::new(), } } } impl Drop for Shm { fn drop(&mut self) { unsafe { munmap(self.ptr as *mut c_void, self.len).expect("Can't munmap"); } close(self.fd).expect("Can't close"); if !self.name.is_empty() { let name: &str = self.name.as_ref(); shm_unlink(name).expect("Can't shm_unlink"); } } } impl AsMut<[u8]> for Shm { fn as_mut(&mut self) -> &mut [u8] { unsafe { slice::from_raw_parts_mut(self.ptr, self.len) } } } impl AsRawFd for Shm { fn as_raw_fd(&self) -> RawFd { self.fd } } fn make_hello(name: &str) -> Shm { let hello = b"Hello World!\0"; let mut shm = Shm::new(name, hello.len() as i64); shm.as_mut().copy_from_slice(hello.as_ref()); shm } fn compare_hello(fd: RawFd) -> bool { let hello = b"Hello World!\0"; let mut shm = Shm::from_raw_fd(fd, hello.len()); &shm.as_mut()[..hello.len()] == hello.as_ref() } #[test] fn unix_stream_passes_fd() { let shm = make_hello("/unix_stream_passes_fd"); let mut buf = vec![0; 20]; let (mut sut1, mut sut2) = UnixStream::pair().expect("Can't make pair"); sut1.enqueue(&shm).expect("Can't enqueue"); sut1.write(b"abc").expect("Can't write"); sut1.flush().expect("Can't flush"); sut2.read(&mut buf).expect("Can't read"); let fd = sut2.dequeue().expect("Empty fd queue"); assert!(fd != shm.fd, "fd's unexpectedly equal"); assert!(compare_hello(fd), "fd didn't contain expect contents"); } }