Merge #1342

1342: feat(unistd): Add getpeereid(3) r=asomers a=woodruffw

`getpeereid(3)` is not POSIX, but it's present on many BSD-derived Unices. It's also the standard mechanism on those OSes for retrieving socket peer credentials (compare `getsockopt` + `SO_PEERCRED` on Linux, which `nix` already supports).

Closes #1339.

Co-authored-by: William Woodruff <william@yossarian.net>

1 files changed, 20 insertions, 0 deletions

diff --git a/src/unistd.rs b/src/unistd.rs
index 20d7c79a..dd335596 100644
--- a/src/unistd.rs
+++ b/src/unistd.rs
@@ -2804,3 +2804,23 @@ pub fn ttyname(fd: RawFd) -> Result<PathBuf> {
     buf.truncate(nul);
     Ok(OsString::from_vec(buf).into())
 }
+
+/// Get the effective user ID and group ID associated with a Unix domain socket.
+///
+/// See also [getpeereid(3)](https://www.freebsd.org/cgi/man.cgi?query=getpeereid)
+#[cfg(any(
+    target_os = "macos",
+    target_os = "ios",
+    target_os = "freebsd",
+    target_os = "openbsd",
+    target_os = "netbsd",
+    target_os = "dragonfly",
+))]
+pub fn getpeereid(fd: RawFd) -> Result<(Uid, Gid)> {
+    let mut uid = 1;
+    let mut gid = 1;
+
+    let ret = unsafe { libc::getpeereid(fd, &mut uid, &mut gid) };
+
+    Errno::result(ret).map(|_| (Uid(uid), Gid(gid)))
+}