From e4dc2883efea932f1da62ef35c3e88806aed9eea Mon Sep 17 00:00:00 2001
From: David Fifield <david@bamsoftware.com>
Date: Tue, 3 Aug 2021 21:00:45 -0600
Subject: [PATCH] Use errors.Is to compare against ErrClosedPipe.

I was still getting "io: read/write on closed pipe" errors in the logs,
even after comparing errors against io.ErrClosedPipe to skip logging
them. It turns out that kcp-go wraps many of its errors in another type.
The actual type of the errors was *errors.withStack, where errors is
https://github.com/pkg/errors. We can use the go1.13 errors interface
(https://blog.golang.org/go1.13-errors) to get at the value inside.
---
 dnstt-client/main.go |  5 +++--
 dnstt-server/main.go | 11 ++++-------
 go.mod               |  2 +-
 3 files changed, 8 insertions(+), 10 deletions(-)

diff --git a/dnstt-client/main.go b/dnstt-client/main.go
index f73d97e..19b05f6 100644
--- a/dnstt-client/main.go
+++ b/dnstt-client/main.go
@@ -26,6 +26,7 @@
 package main
 
 import (
+	"errors"
 	"flag"
 	"fmt"
 	"io"
@@ -95,7 +96,7 @@ func handle(local *net.TCPConn, sess *smux.Session, conv uint32) error {
 			// smux Stream.Write may return io.EOF.
 			err = nil
 		}
-		if err != nil && err != io.ErrClosedPipe {
+		if err != nil && !errors.Is(err, io.ErrClosedPipe) {
 			log.Printf("stream %08x:%d copy stream←local: %v", conv, stream.ID(), err)
 		}
 		local.CloseRead()
@@ -108,7 +109,7 @@ func handle(local *net.TCPConn, sess *smux.Session, conv uint32) error {
 			// smux Stream.WriteTo may return io.EOF.
 			err = nil
 		}
-		if err != nil && err != io.ErrClosedPipe {
+		if err != nil && !errors.Is(err, io.ErrClosedPipe) {
 			log.Printf("stream %08x:%d copy local←stream: %v", conv, stream.ID(), err)
 		}
 		local.CloseWrite()
diff --git a/dnstt-server/main.go b/dnstt-server/main.go
index 4bfa6cd..753fdff 100644
--- a/dnstt-server/main.go
+++ b/dnstt-server/main.go
@@ -38,6 +38,7 @@ import (
 	"bytes"
 	"encoding/base32"
 	"encoding/binary"
+	"errors"
 	"flag"
 	"fmt"
 	"io"
@@ -205,7 +206,7 @@ func handleStream(stream *smux.Stream, upstream string, conv uint32) error {
 			// smux Stream.Write may return io.EOF.
 			err = nil
 		}
-		if err != nil && err != io.ErrClosedPipe {
+		if err != nil && !errors.Is(err, io.ErrClosedPipe) {
 			log.Printf("stream %08x:%d copy stream←upstream: %v", conv, stream.ID(), err)
 		}
 		upstreamTCPConn.CloseRead()
@@ -218,7 +219,7 @@ func handleStream(stream *smux.Stream, upstream string, conv uint32) error {
 			// smux Stream.WriteTo may return io.EOF.
 			err = nil
 		}
-		if err != nil && err != io.ErrClosedPipe {
+		if err != nil && !errors.Is(err, io.ErrClosedPipe) {
 			log.Printf("stream %08x:%d copy upstream←stream: %v", conv, stream.ID(), err)
 		}
 		upstreamTCPConn.CloseWrite()
@@ -302,11 +303,7 @@ func acceptSessions(ln *kcp.Listener, privkey []byte, mtu int, upstream string)
 				conn.Close()
 			}()
 			err := acceptStreams(conn, privkey, upstream)
-			if err == io.ErrClosedPipe {
-				// We don't want to report this error.
-				err = nil
-			}
-			if err != nil {
+			if err != nil && !errors.Is(err, io.ErrClosedPipe) {
 				log.Printf("session %08x acceptStreams: %v", conn.GetConv(), err)
 			}
 		}()
diff --git a/go.mod b/go.mod
index b8750f3..b959c4e 100644
--- a/go.mod
+++ b/go.mod
@@ -1,6 +1,6 @@
 module www.bamsoftware.com/git/dnstt.git
 
-go 1.11
+go 1.13
 
 require (
 	github.com/flynn/noise v1.0.0