tokio-s2n-tls: Enable access to the IO instance from TcpStream (#3882)

* tokio-s2n-tls: Enable access to the IO instance from TcpStream

* Rename io_* get_* for getting the inner stream

---------

Co-authored-by: Cameron Bytheway <[email protected]>

bindings/rust/s2n-tls-tokio/src/lib.rs

@@ -166,6 +166,16 @@ where
     C: AsRef<Connection> + AsMut<Connection> + Unpin,
     S: AsyncRead + AsyncWrite + Unpin,
 {
+    ///Access a shared reference to the underlaying io stream
+    pub fn get_ref(&self) -> &S {
+        &self.stream
+    }
+
+    ///Access the mutable reference to the underlaying io stream
+    pub fn get_mut(&mut self) -> &mut S {
+        &mut self.stream
+    }
+
     async fn open(mut conn: C, stream: S) -> Result<Self, Error> {
         conn.as_mut().set_blinding(Blinding::SelfService)?;
         let mut tls = TlsStream {

bindings/rust/s2n-tls-tokio/tests/handshake.rs

@@ -185,3 +185,20 @@ async fn handshake_error_with_blinding() -> Result<(), Box<dyn std::error::Error
 
     Ok(())
 }
+
+#[tokio::test]
+async fn io_stream_access() -> Result<(), Box<dyn std::error::Error>> {
+    let (server_stream, client_stream) = common::get_streams().await?;
+
+    let client_addr = client_stream.local_addr().unwrap();
+    let client = TlsConnector::new(common::client_config()?.build()?);
+    let server = TlsAcceptor::new(common::server_config()?.build()?);
+
+    let (mut client_result, _server_result) =
+        common::run_negotiate(&client, client_stream, &server, server_stream).await?;
+
+    assert_eq!(client_result.get_ref().local_addr().unwrap(), client_addr);
+    assert_eq!(client_result.get_mut().local_addr().unwrap(), client_addr);
+
+    Ok(())
+}