Improve error handling when the user mixes up gossip (8001) and RPC (8899) ports (#7158)

automerge

net-utils/src/lib.rs

@@ -30,7 +30,13 @@ fn ip_echo_server_request(
     TcpStream::connect_timeout(ip_echo_server_addr, timeout)
         .and_then(|mut stream| {
             let msg = bincode::serialize(&msg).expect("serialize IpEchoServerMessage");
+            // Start with 4 null bytes to avoid looking like an HTTP GET/POST request
+            stream.write_all(&[0; 4])?;
+
             stream.write_all(&msg)?;
+
+            // Send a '\n' to make this request look HTTP-ish and tickle an error response back from an HTTP server
+            stream.write_all(b"\n")?;
             stream.shutdown(std::net::Shutdown::Write)?;
             stream
                 .set_read_timeout(Some(Duration::new(10, 0)))
@@ -38,7 +44,38 @@ fn ip_echo_server_request(
             stream.read_to_end(&mut data)
         })
         .and_then(|_| {
-            bincode::deserialize(&data).map_err(|err| {
+            // It's common for users to accidentally confuse the validator's gossip port and JSON
+            // RPC port.  Attempt to detect when this occurs by looking for the standard HTTP
+            // response header and provide the user with a helpful error message
+            if data.len() < 4 {
+                return Err(io::Error::new(
+                    io::ErrorKind::Other,
+                    format!("Response too short, received {} bytes", data.len()),
+                ));
+            }
+
+            let response_header: String = data[0..4].iter().map(|b| *b as char).collect();
+            if response_header != "\0\0\0\0" {
+                if response_header == "HTTP" {
+                    let http_response = data.iter().map(|b| *b as char).collect::<String>();
+                    return Err(io::Error::new(
+                        io::ErrorKind::Other,
+                        format!(
+                            "Invalid gossip entrypoint. {} looks to be an HTTP port: {}",
+                            ip_echo_server_addr, http_response
+                        ),
+                    ));
+                }
+                return Err(io::Error::new(
+                    io::ErrorKind::Other,
+                    format!(
+                        "Invalid gossip entrypoint. {} provided an invalid response header: '{}'",
+                        ip_echo_server_addr, response_header
+                    ),
+                ));
+            }
+
+            bincode::deserialize(&data[3..]).map_err(|err| {
                 io::Error::new(
                     io::ErrorKind::Other,
                     format!("Failed to deserialize: {:?}", err),
@@ -435,6 +472,7 @@ mod tests {
 
     #[test]
     fn test_get_public_ip_addr() {
+        solana_logger::setup();
         let (_server_port, (server_udp_socket, server_tcp_listener)) =
             bind_common_in_range((3200, 3250)).unwrap();
         let (client_port, (client_udp_socket, client_tcp_listener)) =