Merge pull request #65 from cgwalters/dir-reopen-file

dirext: Add reopen_as_ownedfd helper

Author: cgwalters

src/dirext.rs

@@ -15,6 +15,7 @@ use std::ffi::OsStr;
 use std::io::Result;
 use std::io::{self, Write};
 use std::ops::Deref;
+use std::os::fd::OwnedFd;
 use std::path::Path;
 
 #[cfg(feature = "fs_utf8")]
@@ -125,6 +126,14 @@ pub trait CapStdExtDirExt {
         perms: cap_std::fs::Permissions,
     ) -> Result<()>;
 
+    /// By default, cap-std `Dir` instances are opened using `O_PATH`.
+    /// There are some operations such as `fsync` and `fsetxattr` that
+    /// cannot be performed on `O_PATH` file descriptors. Use this
+    /// function to create a non-`O_PATH` copy of the directory
+    /// file descriptor.
+    #[cfg(unix)]
+    fn reopen_as_ownedfd(&self) -> Result<OwnedFd>;
+
     #[cfg(any(target_os = "android", target_os = "linux"))]
     /// Returns `Some(true)` if the target is known to be a mountpoint, or
     /// `Some(false)` if the target is definitively known not to be a mountpoint.
@@ -532,6 +541,19 @@ impl CapStdExtDirExt for Dir {
         })
     }
 
+    #[cfg(unix)]
+    fn reopen_as_ownedfd(&self) -> Result<OwnedFd> {
+        use rustix::fs::{Mode, OFlags};
+        use std::os::fd::AsFd;
+        rustix::fs::openat(
+            self.as_fd(),
+            ".",
+            OFlags::CLOEXEC | OFlags::DIRECTORY | OFlags::RDONLY,
+            Mode::empty(),
+        )
+        .map_err(Into::into)
+    }
+
     fn is_mountpoint(&self, path: impl AsRef<Path>) -> Result<Option<bool>> {
         is_mountpoint_impl_statx(self, path.as_ref()).map_err(Into::into)
     }

tests/it/main.rs

@@ -393,6 +393,15 @@ fn test_mountpoint() -> Result<()> {
     Ok(())
 }
 
+#[test]
+#[cfg(unix)]
+fn test_reopen_as_ownedfd() -> Result<()> {
+    let td = &cap_tempfile::TempDir::new(cap_std::ambient_authority())?;
+    let fd = td.reopen_as_ownedfd()?;
+    rustix::fs::fsync(fd)?;
+    Ok(())
+}
+
 #[test]
 #[cfg(any(target_os = "android", target_os = "linux"))]
 fn test_open_noxdev() -> Result<()> {