Simple solution for #292, preventing active probing

src/relay/tcprelay/connection.rs

@@ -90,6 +90,11 @@ where
     pub fn get_ref(&self) -> &S {
         self.stream.get_ref()
     }
+
+    /// Get the internal stream and consume this Connection
+    pub fn into_inner(self) -> S {
+        self.stream.into_inner()
+    }
 }
 
 #[inline]

src/relay/tcprelay/crypto_io.rs

@@ -140,6 +140,11 @@ impl<S> CryptoStream<S> {
     pub fn get_ref(&self) -> &S {
         &self.stream
     }
+
+    /// Consume the CryptoStream and return the internal stream instance
+    pub fn into_inner(self) -> S {
+        self.stream
+    }
 }
 
 impl<S> CryptoStream<S>

src/relay/tcprelay/monitor.rs

@@ -24,6 +24,10 @@ impl<S> TcpMonStream<S> {
     pub fn new(flow_stat: SharedServerFlowStatistic, stream: S) -> TcpMonStream<S> {
         TcpMonStream { stream, flow_stat }
     }
+
+    pub fn into_inner(self) -> S {
+        self.stream
+    }
 }
 
 impl<S> AsyncRead for TcpMonStream<S>

src/relay/tcprelay/server.rs

@@ -58,6 +58,12 @@ async fn handle_client(
                 "failed to decode Address, may be wrong method or key, from client {}, error: {}",
                 peer_addr, err
             );
+
+            // Hold the TCP connection until it closes by itself for preventing active probing.
+            // Further discussion: https://github.com/shadowsocks/shadowsocks-rust/issues/292
+            let mut tcp = stream.into_inner().into_inner().into_inner();
+            let _ = super::ignore_until_end(&mut tcp).await;
+
             return Err(From::from(err));
         }
     };