net: add take_error to TcpSocket and TcpStream (#4739)

Co-authored-by: Taiki Endo <te316e89@gmail.com>

tokio/src/net/tcp/socket.rs

@@ -424,6 +424,11 @@ impl TcpSocket {
         self.inner.local_addr().and_then(convert_address)
     }
 
+    /// Returns the value of the `SO_ERROR` option.
+    pub fn take_error(&self) -> io::Result<Option<io::Error>> {
+        self.inner.take_error()
+    }
+
     /// Binds the socket to the given address.
     ///
     /// This calls the `bind(2)` operating-system function. Behavior is

tokio/src/net/tcp/stream.rs

@@ -264,6 +264,11 @@ impl TcpStream {
         self.io.local_addr()
     }
 
+    /// Returns the value of the `SO_ERROR` option.
+    pub fn take_error(&self) -> io::Result<Option<io::Error>> {
+        self.io.take_error()
+    }
+
     /// Returns the remote address that this stream is connected to.
     ///
     /// # Examples