From 68911f677864795751025175578953b24bc6cfd6 Mon Sep 17 00:00:00 2001
From: Josh Bleecher Snyder <josh@tailscale.com>
Date: Tue, 11 May 2021 11:14:53 -0700
Subject: [PATCH] wgengine/bench: ignore "engine closing" errors

On benchmark completion, we shut down the wgengine.
If we happen to poll for status during shutdown,
we get an "engine closing" error.
It doesn't hurt anything; ignore it.

Fixes tailscale/corp#1776

Signed-off-by: Josh Bleecher Snyder <josh@tailscale.com>
---
 wgengine/bench/wg.go  | 7 +++++++
 wgengine/userspace.go | 4 +++-
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/wgengine/bench/wg.go b/wgengine/bench/wg.go
index 412799e15..f4275d674 100644
--- a/wgengine/bench/wg.go
+++ b/wgengine/bench/wg.go
@@ -5,6 +5,7 @@
 package main
 
 import (
+	"errors"
 	"io"
 	"log"
 	"os"
@@ -89,6 +90,9 @@ func setupWGTest(b *testing.B, logf logger.Logf, traf *TrafficGen, a1, a2 netadd
 
 	var e1waitDoneOnce sync.Once
 	e1.SetStatusCallback(func(st *wgengine.Status, err error) {
+		if errors.Is(err, wgengine.ErrEngineClosing) {
+			return
+		}
 		if err != nil {
 			log.Fatalf("e1 status err: %v", err)
 		}
@@ -124,6 +128,9 @@ func setupWGTest(b *testing.B, logf logger.Logf, traf *TrafficGen, a1, a2 netadd
 
 	var e2waitDoneOnce sync.Once
 	e2.SetStatusCallback(func(st *wgengine.Status, err error) {
+		if errors.Is(err, wgengine.ErrEngineClosing) {
+			return
+		}
 		if err != nil {
 			log.Fatalf("e2 status err: %v", err)
 		}
diff --git a/wgengine/userspace.go b/wgengine/userspace.go
index d90cb8533..4a7f56545 100644
--- a/wgengine/userspace.go
+++ b/wgengine/userspace.go
@@ -880,6 +880,8 @@ func (e *userspaceEngine) getStatusCallback() StatusCallback {
 
 var singleNewline = []byte{'\n'}
 
+var ErrEngineClosing = errors.New("engine closing; no status")
+
 func (e *userspaceEngine) getStatus() (*Status, error) {
 	// Grab derpConns before acquiring wgLock to not violate lock ordering;
 	// the DERPs method acquires magicsock.Conn.mu.
@@ -893,7 +895,7 @@ func (e *userspaceEngine) getStatus() (*Status, error) {
 	closing := e.closing
 	e.mu.Unlock()
 	if closing {
-		return nil, errors.New("engine closing; no status")
+		return nil, ErrEngineClosing
 	}
 
 	if e.wgdev == nil {