Add redirection for existing connections

examples/listen_server.rs

@@ -0,0 +1,76 @@
+//! A "hello world" echo server with Tokio
+//!
+//! This server will create a TCP listener, accept connections in a loop, and
+//! write back everything that's read off of each TCP connection.
+//!
+//! Because the Tokio runtime uses a thread pool, each TCP connection is
+//! processed concurrently with all other TCP connections across multiple
+//! threads.
+//!
+//! To see this server in action, you can run this in one terminal:
+//!
+//!     cargo run --example echo
+//!
+//! and in another terminal you can run:
+//!
+//!     cargo run --example connect 127.0.0.1:8080
+//!
+//! Each line you type in to the `connect` terminal should be echo'd back to
+//! you! If you open up multiple terminals running the `connect` example you
+//! should be able to see them all make progress simultaneously.
+
+#![warn(rust_2018_idioms)]
+
+use tokio::io::{AsyncReadExt};
+use tokio::net::TcpListener;
+
+use std::env;
+use std::error::Error;
+
+#[tokio::main]
+async fn main() -> Result<(), Box<dyn Error>> {
+    // Allow passing an address to listen on as the first argument of this
+    // program, but otherwise we'll just set up our TCP listener on
+    // 127.0.0.1:8080 for connections.
+    let addr = env::args()
+        .nth(1)
+        .unwrap_or_else(|| "127.0.0.1:8080".to_string());
+
+    // Next up we create a TCP listener which will listen for incoming
+    // connections. This TCP listener is bound to the address we determined
+    // above and must be associated with an event loop.
+    let listener = TcpListener::bind(&addr).await?;
+    println!("Listening on: {addr}");
+
+    loop {
+        // Asynchronously wait for an inbound socket.
+        let (mut socket, _) = listener.accept().await?;
+
+        // And this is where much of the magic of this server happens. We
+        // crucially want all clients to make progress concurrently, rather than
+        // blocking one on completion of another. To achieve this we use the
+        // `tokio::spawn` function to execute the work in the background.
+        //
+        // Essentially here we're executing a new task to run concurrently,
+        // which will allow all of our clients to be processed concurrently.
+
+        tokio::spawn(async move {
+            let mut buf = vec![0; 1024];
+
+            // In a loop, read data from the socket and write the data back.
+            loop {
+                let n = socket
+                    .read(&mut buf)
+                    .await
+                    .expect("failed to read data from socket");
+
+                if n == 0 {
+                    return;
+                }
+
+                use std::str;
+                println!("{}", str::from_utf8(&buf[0..n]).unwrap());
+            }
+        });
+    }
+}

src/lib.rs

@@ -65,7 +65,7 @@ pub async fn process_command(
     State(state): State<Arc<GlobalState>>,
     Json(payload): Json<ProxyCommand>,
 ) -> (StatusCode, Json<ProxyResponse>) {
-    tracing::error!("Received payload: {:?}", payload);
+    tracing::info!("Received payload: {:?}", payload);
     // TODO: verify signature
     match payload.command {
         Command::New {
@@ -131,17 +131,11 @@ async fn add_proxy(in_port: u16, control: Receiver<ProxyControlMessage>) -> anyh
 }
 
 async fn proxy(listener: TcpListener, mut control: Receiver<ProxyControlMessage>) {
-    let mut current_destination =
-        if let ProxyControlMessage::Open { destination } = *control.borrow() {
-            Some(destination)
-        } else {
-            None
-        };
     loop {
         tokio::select! {
             l = listener.accept()=> {
                 if let Ok((inbound, _)) = l {
-                    let transfer = transfer(inbound, current_destination.unwrap());
+                    let transfer = transfer(inbound, control.clone());
 
                     tokio::spawn(transfer);
                 }
@@ -150,7 +144,6 @@ async fn proxy(listener: TcpListener, mut control: Receiver<ProxyControlMessage>
                 match *control.borrow() {
                     ProxyControlMessage::Open { destination } => {
                         tracing::info!("destination for proxy port {} changed to {}", listener.local_addr().unwrap(), destination);
-                        current_destination=Some(destination);
                     },
                     ProxyControlMessage::Close => {
                         tracing::info!("destination for proxy port {} closed", listener.local_addr().unwrap());
@@ -162,8 +155,18 @@ async fn proxy(listener: TcpListener, mut control: Receiver<ProxyControlMessage>
     }
 }
 
-async fn transfer(mut inbound: TcpStream, destination: SocketAddrV4) -> anyhow::Result<()> {
+async fn transfer(
-    let mut outbound = TcpStream::connect(destination).await?;
+    mut inbound: TcpStream,
+    mut control: Receiver<ProxyControlMessage>,
+) -> anyhow::Result<()> {
+    loop {
+        let current_destination =
+            if let ProxyControlMessage::Open { destination } = *control.borrow() {
+                Some(destination)
+            } else {
+                break Ok(());
+            };
+        let mut outbound = TcpStream::connect(current_destination.unwrap()).await?;
 
         let (mut ri, mut wi) = inbound.split();
         let (mut ro, mut wo) = outbound.split();
@@ -178,9 +181,42 @@ async fn transfer(mut inbound: TcpStream, destination: SocketAddrV4) -> anyhow::
             wi.shutdown().await
         };
 
-    tokio::try_join!(client_to_server, server_to_client)?;
+        // Select between the copy tasks and watch channel
+        tokio::select! {
+            // Join the two copy streams and wait for the connection to clone
+            result = async move { tokio::join!(client_to_server, server_to_client) } => {
+                match result {
+                    (Ok(_), Ok(_)) => {
+                        break Ok(());
+                    }
+                    (r1, r2) => {
+                        if r1.is_err() {
+                            tracing::error!("error closing client->server of {:?}: {:?}", inbound, &r1);
+                        }
+                        if r2.is_err() {
+                            tracing::error!("error closing server->client of {:?}: {:?}", inbound, &r2);
+                        }
+                        r1?;
+                        r2?;
+                    },
+                }
+            }
+            _ = control.changed() => {
+                match *control.borrow() {
+                    ProxyControlMessage::Open { destination } => {
+                        eprintln!("Switching to new destination: {destination}");
+                        // Disconnect the current outbound connection and restart the loop
+                        drop(outbound);
+                        continue;
+                    },
+                    ProxyControlMessage::Close => {
+                        break Ok(());
+                    },
+                }
 
-    Ok(())
+            }
+        }
+    }
 }
 
 #[cfg(test)]
@@ -188,7 +224,6 @@ mod tests {
     use std::net::Ipv4Addr;
 
     use crate::{Command, ProxyCommand};
-    use serde::{Deserialize, Serialize};
     use uuid::uuid;
 
     #[test]