From dfdca9f595d5fd1d1dd3d1aa5bbf41f540deba80 Mon Sep 17 00:00:00 2001
From: Adrian Lopez <adrianlzt@gmail.com>
Date: Fri, 15 Mar 2019 14:16:37 +0100
Subject: [PATCH] Handle correctly servers not initiating close

If we use the default handler to a Redis server, Switcher will keep the
connection open forever, because Redis server is not going to initiate
the close of the connection.

With this new scheme, as soon as one channel has finished sending data,
the two connections are closed and Shovel could finish.

This follows the pattern seen in https://github.com/google/tcpproxy/blob/master/tcpproxy.go#L386
---
 shovel.go | 21 ++++++++++++++-------
 1 file changed, 14 insertions(+), 7 deletions(-)

diff --git a/shovel.go b/shovel.go
index 04dd184..a84aed7 100644
--- a/shovel.go
+++ b/shovel.go
@@ -2,27 +2,34 @@ package main
 
 import (
 	"io"
+	"log"
+	"strings"
 )
 
 // proxy between two sockets
 func Shovel(local, remote io.ReadWriteCloser) error {
 	errch := make(chan error, 1)
 
+	defer func() {
+		go local.Close()
+	}()
+
+	defer func() {
+		go remote.Close()
+	}()
+
 	go chanCopy(errch, local, remote)
 	go chanCopy(errch, remote, local)
 
-	for i := 0; i < 2; i++ {
-		if err := <-errch; err != nil {
-			// If this returns early the second func will push into the
-			// buffer, and the GC will clean up
-			return err
-		}
-	}
+	<-errch
 	return nil
 }
 
 // copy between pipes, sending errors to channel
 func chanCopy(e chan error, dst, src io.ReadWriter) {
 	_, err := io.Copy(dst, src)
+	if err != nil && !strings.HasSuffix(err.Error(), ": use of closed network connection") {
+		log.Printf("[ERROR] chanCopy: %v\n", err)
+	}
 	e <- err
 }