unistd: adding linux(glibc)/freebsd close_range.

Allows to close a range of file descriptors, can set close-on-exec
on these and/or unsharing (as having its own file descriptors table
 after fork for the calling process).

Author: devnexen

src/unistd.rs

@@ -3992,3 +3992,49 @@ pub fn chflags<P: ?Sized + NixPath>(path: &P, flags: FileFlag) -> Result<()> {
     Errno::result(res).map(drop)
 }
 }
+
+#[cfg(any(
+    all(target_os = "linux", target_env = "gnu"),
+    target_os = "freebsd"
+))]
+#[cfg(feature = "fs")]
+libc_bitflags! {
+    /// Options for close_range()
+    #[cfg_attr(docsrs, doc(cfg(feature = "fs")))]
+    pub struct CloseRangeFlags : c_uint {
+        #[cfg(all(target_os = "linux", target_env = "gnu"))]
+        /// Unshare the file descriptors range before closing them
+        CLOSE_RANGE_UNSHARE;
+        /// Set the close-on-exec flag on the file descriptors range
+        CLOSE_RANGE_CLOEXEC;
+    }
+}
+
+feature! {
+#![feature = "fs"]
+
+/// Close all the file descriptor from a given range.
+/// An optional flag can be applied to modify its behavior.
+#[cfg(any(
+    all(target_os = "linux", target_env = "gnu"),
+    target_os = "freebsd"
+))]
+pub fn close_range<F: std::os::fd::AsFd>(fdbegin: F, fdlast: F, flags: CloseRangeFlags) -> Result<Option<c_int>> {
+    use std::os::fd::AsRawFd;
+
+    let raw = unsafe {
+        Errno::clear();
+        libc::close_range(fdbegin.as_fd().as_raw_fd() as u32, fdlast.as_fd().as_raw_fd() as u32, flags.bits() as i32)
+    };
+    if raw == -1 {
+        if Errno::last_raw() == 0 {
+            Ok(None)
+        } else {
+            Err(Errno::last())
+        }
+    } else {
+        Ok(Some(raw))
+    }
+
+}
+}

test/test_unistd.rs

@@ -1391,3 +1391,18 @@ fn test_group_from() {
     assert_eq!(group.gid, group_id);
     assert_eq!(group.name, "wheel");
 }
+
+#[test]
+#[cfg(any(all(target_os = "linux", target_env = "gnu"), target_os = "freebsd"))]
+fn test_close_range() {
+    use tempfile::NamedTempFile;
+    const CONTENTS: &[u8] = b"abcdef123456";
+    let mut tempfile1 = NamedTempFile::new().unwrap();
+    let mut tempfile2 = NamedTempFile::new().unwrap();
+    let mut tempfile3 = NamedTempFile::new().unwrap();
+    tempfile3.write_all(CONTENTS).unwrap();
+    tempfile2.write_all(CONTENTS).unwrap();
+    tempfile1.write_all(CONTENTS).unwrap();
+    let areclosed = close_range(tempfile1, tempfile3, CloseRangeFlags::CLOSE_RANGE_CLOEXEC);
+    assert_eq!(areclosed.expect("close_range failed").expect("invalid flag"), 0);
+}