From 37854ee10f7161843c338d9a9fa87f9398aacbbe Mon Sep 17 00:00:00 2001
From: Justin Israel <justinisrael@gmail.com>
Date: Tue, 6 Nov 2018 18:40:20 +1300
Subject: [PATCH] Fix panic stack trace being printed during recovery of broken
 pipe (#1089) (#1259)

---
 recovery.go      | 40 ++++++++++++++++++++++++++++++++--------
 recovery_test.go | 40 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 72 insertions(+), 8 deletions(-)

diff --git a/recovery.go b/recovery.go
index 6c28b4fa..e788cc47 100644
--- a/recovery.go
+++ b/recovery.go
@@ -10,9 +10,12 @@ import (
 	"io"
 	"io/ioutil"
 	"log"
+	"net"
 	"net/http"
 	"net/http/httputil"
+	"os"
 	"runtime"
+	"syscall"
 	"time"
 )
 
@@ -37,16 +40,37 @@ func RecoveryWithWriter(out io.Writer) HandlerFunc {
 	return func(c *Context) {
 		defer func() {
 			if err := recover(); err != nil {
-				if logger != nil {
-					stack := stack(3)
-					if IsDebugging() {
-						httprequest, _ := httputil.DumpRequest(c.Request, false)
-						logger.Printf("[Recovery] %s panic recovered:\n%s\n%s\n%s%s", timeFormat(time.Now()), string(httprequest), err, stack, reset)
-					} else {
-						logger.Printf("[Recovery] %s panic recovered:\n%s\n%s%s", timeFormat(time.Now()), err, stack, reset)
+				// Check for a broken connection, as it is not really a
+				// condition that warrants a panic stack trace.
+				var brokenPipe bool
+				if ne, ok := err.(*net.OpError); ok {
+					if se, ok := ne.Err.(*os.SyscallError); ok {
+						if se.Err == syscall.EPIPE || se.Err == syscall.ECONNRESET {
+							brokenPipe = true
+						}
 					}
 				}
-				c.AbortWithStatus(http.StatusInternalServerError)
+				if logger != nil {
+					stack := stack(3)
+					httprequest, _ := httputil.DumpRequest(c.Request, false)
+					if brokenPipe {
+						logger.Printf("%s\n%s%s", err, string(httprequest), reset)
+					} else if IsDebugging() {
+						logger.Printf("[Recovery] %s panic recovered:\n%s\n%s\n%s%s",
+							timeFormat(time.Now()), string(httprequest), err, stack, reset)
+					} else {
+						logger.Printf("[Recovery] %s panic recovered:\n%s\n%s%s",
+							timeFormat(time.Now()), err, stack, reset)
+					}
+				}
+
+				// If the connection is dead, we can't write a status to it.
+				if brokenPipe {
+					c.Error(err.(error))
+					c.Abort()
+				} else {
+					c.AbortWithStatus(http.StatusInternalServerError)
+				}
 			}
 		}()
 		c.Next()
diff --git a/recovery_test.go b/recovery_test.go
index 7d422b74..cafaee91 100644
--- a/recovery_test.go
+++ b/recovery_test.go
@@ -2,11 +2,16 @@
 // Use of this source code is governed by a MIT style
 // license that can be found in the LICENSE file.
 
+// +build go1.7
+
 package gin
 
 import (
 	"bytes"
+	"net"
 	"net/http"
+	"os"
+	"syscall"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
@@ -72,3 +77,38 @@ func TestFunction(t *testing.T) {
 	bs := function(1)
 	assert.Equal(t, []byte("???"), bs)
 }
+
+// TestPanicWithBrokenPipe asserts that recovery specifically handles
+// writing responses to broken pipes
+func TestPanicWithBrokenPipe(t *testing.T) {
+	const expectCode = 204
+
+	expectMsgs := map[syscall.Errno]string{
+		syscall.EPIPE:      "broken pipe",
+		syscall.ECONNRESET: "connection reset",
+	}
+
+	for errno, expectMsg := range expectMsgs {
+		t.Run(expectMsg, func(t *testing.T) {
+
+			var buf bytes.Buffer
+
+			router := New()
+			router.Use(RecoveryWithWriter(&buf))
+			router.GET("/recovery", func(c *Context) {
+				// Start writing response
+				c.Header("X-Test", "Value")
+				c.Status(expectCode)
+
+				// Oops. Client connection closed
+				e := &net.OpError{Err: &os.SyscallError{Err: errno}}
+				panic(e)
+			})
+			// RUN
+			w := performRequest(router, "GET", "/recovery")
+			// TEST
+			assert.Equal(t, expectCode, w.Code)
+			assert.Contains(t, buf.String(), expectMsg)
+		})
+	}
+}