From e9a98c3aefac5baebd974e8427e484e9c74bb280 Mon Sep 17 00:00:00 2001
From: David Fifield <david@bamsoftware.com>
Date: Sun, 19 Apr 2020 02:13:48 -0600
Subject: [PATCH] Avoid logging EOF and ErrClosedPipe errors.

smux Stream.WriteTo may return io.EOF, which breaks the contract of
io.Copy that says it should not return io.EOF. smux.Stream doesn't have
a unidirectional shutdown, so we always end up slamming it shut in both
directions and leave the other direction with a broken pipe.
---
 dnstt-client/main.go | 9 +++++++--
 dnstt-server/main.go | 9 +++++++--
 2 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/dnstt-client/main.go b/dnstt-client/main.go
index 9754cae..87dc302 100644
--- a/dnstt-client/main.go
+++ b/dnstt-client/main.go
@@ -110,16 +110,21 @@ func handle(local *net.TCPConn, sess *smux.Session, conv uint32) error {
 		if err != nil {
 			log.Printf("stream %08x:%d copy stream←local: %v\n", conv, stream.ID(), err)
 		}
+		local.CloseRead()
 		stream.Close()
 	}()
 	wg.Add(1)
 	go func() {
 		defer wg.Done()
 		_, err := io.Copy(local, stream)
-		if err != nil {
+		if err == io.EOF {
+			// smux Stream.WriteTo may return io.EOF.
+			err = nil
+		}
+		if err != nil && err != io.ErrClosedPipe {
 			log.Printf("stream %08x:%d copy local←stream: %v\n", conv, stream.ID(), err)
 		}
-		local.Close()
+		local.CloseWrite()
 	}()
 	wg.Wait()
 
diff --git a/dnstt-server/main.go b/dnstt-server/main.go
index 0cf1e38..bd7a4fe 100644
--- a/dnstt-server/main.go
+++ b/dnstt-server/main.go
@@ -83,16 +83,21 @@ func handleStream(stream *smux.Stream, upstream *net.TCPAddr, conv uint32) error
 		if err != nil {
 			log.Printf("stream %08x:%d copy stream←upstream: %v\n", conv, stream.ID(), err)
 		}
+		conn.CloseRead()
 		stream.Close()
 	}()
 	wg.Add(1)
 	go func() {
 		defer wg.Done()
 		_, err := io.Copy(conn, stream)
-		if err != nil {
+		if err == io.EOF {
+			// smux Stream.WriteTo may return io.EOF.
+			err = nil
+		}
+		if err != nil && err != io.ErrClosedPipe {
 			log.Printf("stream %08x:%d copy upstream←stream: %v\n", conv, stream.ID(), err)
 		}
-		conn.Close()
+		conn.CloseWrite()
 	}()
 	wg.Wait()