Ensure IpEchoServerMessage is not fragmented (#7214) (#7215)

automerge

net-utils/src/ip_echo_server.rs

@@ -70,6 +70,19 @@ pub fn ip_echo_server(tcp: std::net::TcpListener) -> IpEchoServer {
                         ));
                     }
 
+                    let expected_len =
+                        bincode::serialized_size(&IpEchoServerMessage::default()).unwrap() as usize;
+                    let actual_len = data[4..].len();
+                    if actual_len < expected_len {
+                        return Err(io::Error::new(
+                            io::ErrorKind::Other,
+                            format!(
+                                "Request too short, actual {} < expected {}",
+                                actual_len, expected_len
+                            ),
+                        ));
+                    }
+
                     bincode::deserialize::<IpEchoServerMessage>(&data[4..])
                         .map(Some)
                         .or_else(|err| {

net-utils/src/lib.rs

@@ -29,14 +29,15 @@ fn ip_echo_server_request(
     let timeout = Duration::new(5, 0);
     TcpStream::connect_timeout(ip_echo_server_addr, timeout)
         .and_then(|mut stream| {
-            let msg = bincode::serialize(&msg).expect("serialize IpEchoServerMessage");
+            let mut bytes = vec![0; 4]; // Start with 4 null bytes to avoid looking like an HTTP GET/POST request
-            // Start with 4 null bytes to avoid looking like an HTTP GET/POST request
-            stream.write_all(&[0; 4])?;
 
-            stream.write_all(&msg)?;
+            bytes.append(&mut bincode::serialize(&msg).expect("serialize IpEchoServerMessage"));
 
-            // Send a '\n' to make this request look HTTP-ish and tickle an error response back from an HTTP server
+            // End with '\n' to make this request look HTTP-ish and tickle an error response back
-            stream.write_all(b"\n")?;
+            // from an HTTP server
+            bytes.push(b'\n');
+
+            stream.write_all(&bytes)?;
             stream.shutdown(std::net::Shutdown::Write)?;
             stream
                 .set_read_timeout(Some(Duration::new(10, 0)))