Implement open file descriptor locks in fcntl

CHANGELOG.md

@@ -5,6 +5,8 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 
 ## [Unreleased] - ReleaseDate
 ### Added
+- Added support for `F_OFD_*` `fcntl` commands on Linux and Android.
+  (#[1195](https://github.com/nix-rust/nix/pull/1195))
 - Added `env::clearenv()`: calls `libc::clearenv` on platforms
   where it's available, and clears the environment of all variables
   via `std::env::vars` and `std::env::remove_var` on others.

Cargo.toml

@@ -16,7 +16,7 @@ exclude     = [
 ]
 
 [dependencies]
-libc = { version = "0.2.60", features = [ "extra_traits" ] }
+libc = { version = "0.2.68", features = [ "extra_traits" ] }
 bitflags = "1.1"
 cfg-if = "0.1.10"
 void = "1.0.2"

src/fcntl.rs

@@ -286,6 +286,12 @@ pub fn fcntl(fd: RawFd, arg: FcntlArg) -> Result<c_int> {
             F_SETLKW(flock) => libc::fcntl(fd, libc::F_SETLKW, flock),
             F_GETLK(flock) => libc::fcntl(fd, libc::F_GETLK, flock),
             #[cfg(any(target_os = "android", target_os = "linux"))]
+            F_OFD_SETLK(flock) => libc::fcntl(fd, libc::F_OFD_SETLK, flock),
+            #[cfg(any(target_os = "android", target_os = "linux"))]
+            F_OFD_SETLKW(flock) => libc::fcntl(fd, libc::F_OFD_SETLKW, flock),
+            #[cfg(any(target_os = "android", target_os = "linux"))]
+            F_OFD_GETLK(flock) => libc::fcntl(fd, libc::F_OFD_GETLK, flock),
+            #[cfg(any(target_os = "android", target_os = "linux"))]
             F_ADD_SEALS(flag) => libc::fcntl(fd, libc::F_ADD_SEALS, flag.bits()),
             #[cfg(any(target_os = "android", target_os = "linux"))]
             F_GET_SEALS => libc::fcntl(fd, libc::F_GET_SEALS),
@@ -295,8 +301,6 @@ pub fn fcntl(fd: RawFd, arg: FcntlArg) -> Result<c_int> {
             F_GETPIPE_SZ => libc::fcntl(fd, libc::F_GETPIPE_SZ),
             #[cfg(any(target_os = "linux", target_os = "android"))]
             F_SETPIPE_SZ(size) => libc::fcntl(fd, libc::F_SETPIPE_SZ, size),
-            #[cfg(any(target_os = "linux", target_os = "android"))]
-            _ => unimplemented!()
         }
     };
 

test/test_fcntl.rs

@@ -65,13 +65,15 @@ fn test_readlink() {
 
 #[cfg(any(target_os = "linux", target_os = "android"))]
 mod linux_android {
+    use std::fs::File;
     use std::io::prelude::*;
-    use std::io::SeekFrom;
+    use std::io::{BufRead, BufReader, SeekFrom};
     use std::os::unix::prelude::*;
 
     use libc::loff_t;
 
     use nix::fcntl::*;
+    use nix::sys::stat::fstat;
     use nix::sys::uio::IoVec;
     use nix::unistd::{close, pipe, read, write};
 
@@ -197,6 +199,97 @@ mod linux_android {
         let mut buf = [0u8; 200];
         assert_eq!(100, read(fd, &mut buf).unwrap());
     }
+
+    // The tests below are disabled for the listed targets
+    // due to OFD locks not being available in the kernel/libc
+    // versions used in the CI environment, probably because
+    // they run under QEMU.
+
+    #[test]
+    #[cfg(not(any(target_arch = "aarch64",
+                  target_arch = "arm",
+                  target_arch = "armv7",
+                  target_arch = "x86",
+                  target_arch = "mips",
+                  target_arch = "mips64",
+                  target_arch = "mips64el",
+                  target_arch = "powerpc64",
+                  target_arch = "powerpc64le")))]
+    fn test_ofd_write_lock() {
+        let tmp = NamedTempFile::new().unwrap();
+
+        let fd = tmp.as_raw_fd();
+        let inode = fstat(fd).expect("fstat failed").st_ino as usize;
+
+        let mut flock = libc::flock {
+            l_type: libc::F_WRLCK as libc::c_short,
+            l_whence: libc::SEEK_SET as libc::c_short,
+            l_start: 0,
+            l_len: 0,
+            l_pid: 0,
+        };
+        fcntl(fd, FcntlArg::F_OFD_SETLKW(&flock)).expect("write lock failed");
+        assert_eq!(
+            Some(("OFDLCK".to_string(), "WRITE".to_string())),
+            lock_info(inode)
+        );
+
+        flock.l_type = libc::F_UNLCK as libc::c_short;
+        fcntl(fd, FcntlArg::F_OFD_SETLKW(&flock)).expect("write unlock failed");
+        assert_eq!(None, lock_info(inode));
+    }
+
+    #[test]
+    #[cfg(not(any(target_arch = "aarch64",
+                  target_arch = "arm",
+                  target_arch = "armv7",
+                  target_arch = "x86",
+                  target_arch = "mips",
+                  target_arch = "mips64",
+                  target_arch = "mips64el",
+                  target_arch = "powerpc64",
+                  target_arch = "powerpc64le")))]
+    fn test_ofd_read_lock() {
+        let tmp = NamedTempFile::new().unwrap();
+
+        let fd = tmp.as_raw_fd();
+        let inode = fstat(fd).expect("fstat failed").st_ino as usize;
+
+        let mut flock = libc::flock {
+            l_type: libc::F_RDLCK as libc::c_short,
+            l_whence: libc::SEEK_SET as libc::c_short,
+            l_start: 0,
+            l_len: 0,
+            l_pid: 0,
+        };
+        fcntl(fd, FcntlArg::F_OFD_SETLKW(&flock)).expect("read lock failed");
+        assert_eq!(
+            Some(("OFDLCK".to_string(), "READ".to_string())),
+            lock_info(inode)
+        );
+
+        flock.l_type = libc::F_UNLCK as libc::c_short;
+        fcntl(fd, FcntlArg::F_OFD_SETLKW(&flock)).expect("read unlock failed");
+        assert_eq!(None, lock_info(inode));
+    }
+
+    fn lock_info(inode: usize) -> Option<(String, String)> {
+        let file = File::open("/proc/locks").expect("open /proc/locks failed");
+        let buf = BufReader::new(file);
+
+        for line in buf.lines() {
+            let line = line.unwrap();
+            let parts: Vec<_> = line.split_whitespace().collect();
+            let lock_type = parts[1];
+            let lock_access = parts[3];
+            let ino_parts: Vec<_> = parts[5].split(':').collect();
+            let ino: usize = ino_parts[2].parse().unwrap();
+            if ino == inode {
+                return Some((lock_type.to_string(), lock_access.to_string()));
+            }
+        }
+        None
+    }
 }
 
 #[cfg(any(target_os = "linux",