Add test for tcp_congestion

Author: Fensteer

test/sys/test_sockopt.rs

@@ -1,5 +1,6 @@
 use rand::{thread_rng, Rng};
 use nix::sys::socket::{socket, sockopt, getsockopt, setsockopt, AddressFamily, SockType, SockFlag, SockProtocol};
+use std::ffi::OsString;
 
 #[test]
 fn test_so_buf() {
@@ -13,3 +14,19 @@ fn test_so_buf() {
     let actual = getsockopt(fd, sockopt::RcvBuf).unwrap();
     assert!(actual >= bufsize);
 }
+
+#[test]
+#[cfg(any(target_os = "freebsd", target_os = "linux"))] 
+fn test_tcp_congestion() {
+    let fd = socket(AddressFamily::Inet, SockType::Stream, SockFlag::empty(), None).unwrap();
+
+    let val = getsockopt(fd, sockopt::TcpCongestion).unwrap();
+    setsockopt(fd, sockopt::TcpCongestion, &val).unwrap();
+
+    setsockopt(fd, sockopt::TcpCongestion, &OsString::from("tcp_congestion_does_not_exist")).unwrap_err();
+
+    assert_eq!(
+        getsockopt(fd, sockopt::TcpCongestion).unwrap(),
+        val
+    );
+}