Add SockAddrStorage type

Author: Darksonn

src/lib.rs

@@ -185,7 +185,7 @@ compile_error!("Socket2 doesn't support the compile target");
 
 use sys::c_int;
 
-pub use sockaddr::{socklen_t, SockAddr};
+pub use sockaddr::{socklen_t, SockAddr, SockAddrStorage};
 pub use socket::Socket;
 pub use sockref::SockRef;
 

src/sockaddr.rs

@@ -1,5 +1,5 @@
 use std::hash::Hash;
-use std::mem::{self, size_of, MaybeUninit};
+use std::mem::{self, size_of};
 use std::net::{SocketAddr, SocketAddrV4, SocketAddrV6};
 use std::path::Path;
 use std::{fmt, io, ptr};
@@ -17,6 +17,54 @@ use crate::Domain;
 #[allow(non_camel_case_types)]
 pub type socklen_t = crate::sys::socklen_t;
 
+/// Rust version of the [`sockaddr_storage`] type.
+///
+/// This type is intended to be used with with direct calls to the `getsockname` syscall. See the
+/// documentation of [`SockAddr::new`] for examples.
+///
+/// This crate defines its own `sockaddr_storage` type to avoid semver concerns with upgrading
+/// `windows-sys`.
+#[repr(transparent)]
+pub struct SockAddrStorage {
+    storage: sockaddr_storage,
+}
+
+impl SockAddrStorage {
+    /// Construct a new storage containing all zeros.
+    #[inline]
+    pub fn zeroed() -> Self {
+        // SAFETY: All zeros is valid for this type.
+        unsafe { mem::zeroed() }
+    }
+
+    /// Returns the size of this storage.
+    #[inline]
+    pub fn size_of(&self) -> socklen_t {
+        size_of::<Self>() as socklen_t
+    }
+
+    /// View this type as another type.
+    ///
+    /// # Safety
+    ///
+    /// The type `T` must be one of the `sockaddr_*` types defined by this platform.
+    #[inline]
+    pub unsafe fn view_as<T>(&mut self) -> &mut T {
+        assert!(size_of::<T>() <= size_of::<Self>());
+        // SAFETY: This type is repr(transparent) over `sockaddr_storage` and `T` is one of the
+        // `sockaddr_*` types defined by this platform.
+        unsafe { &mut *(self as *mut Self as *mut T) }
+    }
+}
+
+impl std::fmt::Debug for SockAddrStorage {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.debug_struct("sockaddr_storage")
+            .field("ss_family", &self.storage.ss_family)
+            .finish_non_exhaustive()
+    }
+}
+
 /// The address of a socket.
 ///
 /// `SockAddr`s may be constructed directly to and from the standard library
@@ -52,15 +100,15 @@ impl SockAddr {
     /// let socket = Socket::new(Domain::IPV4, Type::STREAM, None)?;
     ///
     /// // Initialise a `SocketAddr` byte calling `getsockname(2)`.
-    /// let mut addr_storage: libc::sockaddr_storage = unsafe { mem::zeroed() };
-    /// let mut len = mem::size_of_val(&addr_storage) as libc::socklen_t;
+    /// let mut addr_storage = SockAddrStorage::zeroed();
+    /// let mut len = addr_storage.size_of();
     ///
     /// // The `getsockname(2)` system call will intiliase `storage` for
     /// // us, setting `len` to the correct length.
     /// let res = unsafe {
     ///     libc::getsockname(
     ///         socket.as_raw_fd(),
-    ///         (&mut addr_storage as *mut libc::sockaddr_storage).cast(),
+    ///         (&mut addr_storage).cast(),
     ///         &mut len,
     ///     )
     /// };
@@ -74,8 +122,11 @@ impl SockAddr {
     /// # Ok(())
     /// # }
     /// ```
-    pub const unsafe fn new(storage: sockaddr_storage, len: socklen_t) -> SockAddr {
-        SockAddr { storage, len }
+    pub const unsafe fn new(storage: SockAddrStorage, len: socklen_t) -> SockAddr {
+        SockAddr {
+            storage: storage.storage,
+            len: len as socklen_t,
+        }
     }
 
     /// Initialise a `SockAddr` by calling the function `init`.
@@ -125,25 +176,19 @@ impl SockAddr {
     /// ```
     pub unsafe fn try_init<F, T>(init: F) -> io::Result<(T, SockAddr)>
     where
-        F: FnOnce(*mut sockaddr_storage, *mut socklen_t) -> io::Result<T>,
+        F: FnOnce(*mut SockAddrStorage, *mut socklen_t) -> io::Result<T>,
     {
         const STORAGE_SIZE: socklen_t = size_of::<sockaddr_storage>() as socklen_t;
         // NOTE: `SockAddr::unix` depends on the storage being zeroed before
         // calling `init`.
         // NOTE: calling `recvfrom` with an empty buffer also depends on the
         // storage being zeroed before calling `init` as the OS might not
         // initialise it.
-        let mut storage = MaybeUninit::<sockaddr_storage>::zeroed();
+        let mut storage = SockAddrStorage::zeroed();
         let mut len = STORAGE_SIZE;
-        init(storage.as_mut_ptr(), &mut len).map(|res| {
+        init(&mut storage, &mut len).map(|res| {
             debug_assert!(len <= STORAGE_SIZE, "overflown address storage");
-            let addr = SockAddr {
-                // Safety: zeroed-out `sockaddr_storage` is valid, caller must
-                // ensure at least `len` bytes are valid.
-                storage: storage.assume_init(),
-                len,
-            };
-            (res, addr)
+            (res, SockAddr::new(storage, len))
         })
     }
 

src/sys/unix.rs

@@ -641,9 +641,10 @@ pub(crate) fn offset_of_path(storage: &libc::sockaddr_un) -> usize {
 #[allow(unsafe_op_in_unsafe_fn)]
 pub(crate) fn unix_sockaddr(path: &Path) -> io::Result<SockAddr> {
     // SAFETY: a `sockaddr_storage` of all zeros is valid.
-    let mut storage = unsafe { mem::zeroed::<sockaddr_storage>() };
+    let mut storage = crate::SockAddrStorage::zeroed();
     let len = {
-        let storage = unsafe { &mut *ptr::addr_of_mut!(storage).cast::<libc::sockaddr_un>() };
+        // SAFETY: sockaddr_un is one of the sockaddr_* types defined by this platform.
+        let storage = unsafe { storage.view_as::<libc::sockaddr_un>() };
 
         let bytes = path.as_os_str().as_bytes();
         let too_long = match bytes.first() {