Add a test that passes a CmsgSpace that is too large

Author: jonas-schievink

test/sys/test_socket.rs

@@ -303,12 +303,30 @@ fn test_scm_credentials() {
 #[cfg(any(target_os = "android", target_os = "linux"))]
 #[test]
 fn test_scm_credentials_and_rights() {
+    use nix::sys::socket::CmsgSpace;
+    use libc;
+
+    test_impl_scm_credentials_and_rights(CmsgSpace::<(libc::ucred, CmsgSpace<RawFd>)>::new());
+}
+
+/// Ensure that passing a `CmsgSpace` with too much space for the received
+/// messages still works.
+#[cfg(any(target_os = "android", target_os = "linux"))]
+#[test]
+fn test_too_large_cmsgspace() {
+    use nix::sys::socket::CmsgSpace;
+
+    test_impl_scm_credentials_and_rights(CmsgSpace::<[u8; 1024]>::new());
+}
+
+#[cfg(any(target_os = "android", target_os = "linux"))]
+fn test_impl_scm_credentials_and_rights<T>(mut space: ::nix::sys::socket::CmsgSpace<T>) {
     use libc;
     use nix::sys::uio::IoVec;
     use nix::unistd::{pipe, read, write, close, getpid, getuid, getgid};
     use nix::sys::socket::{socketpair, sendmsg, recvmsg, setsockopt,
                            AddressFamily, SockType, SockFlag,
-                           ControlMessage, CmsgSpace, MsgFlags};
+                           ControlMessage, MsgFlags};
     use nix::sys::socket::sockopt::PassCred;
 
     let (send, recv) = socketpair(AddressFamily::Unix, SockType::Stream, None, SockFlag::empty())
@@ -338,8 +356,7 @@ fn test_scm_credentials_and_rights() {
     {
         let mut buf = [0u8; 5];
         let iov = [IoVec::from_mut_slice(&mut buf[..])];
-        let mut cmsgspace: CmsgSpace<(libc::ucred, CmsgSpace<RawFd>)> = CmsgSpace::new();
-        let msg = recvmsg(recv, &iov, Some(&mut cmsgspace), MsgFlags::empty()).unwrap();
+        let msg = recvmsg(recv, &iov, Some(&mut space), MsgFlags::empty()).unwrap();
         let mut received_cred = None;
 
         assert_eq!(msg.cmsgs().count(), 2);