net: avoid racing on port reuse in TestListenConfigControl

Fixes #52798.
Fixes #51441 (until proven otherwise 😅).

Change-Id: Ic1eadebd0d41c5cbe37340190f8b2bde4b6c5673
Reviewed-on: https://go-review.googlesource.com/c/go/+/405214
Run-TryBot: Bryan Mills <bcmills@google.com>
Auto-Submit: Bryan Mills <bcmills@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@google.com>

2 files changed, 29 insertions, 33 deletions

diff --git a/src/net/listen_test.go b/src/net/listen_test.go
index 59c0112122..df3cadfa1a 100644
--- a/src/net/listen_test.go
+++ b/src/net/listen_test.go
@@ -7,7 +7,6 @@
 package net
 
 import (
-	"context"
 	"fmt"
 	"internal/testenv"
 	"os"
@@ -735,17 +734,7 @@ func TestListenConfigControl(t *testing.T) {
 			if !testableNetwork(network) {
 				continue
 			}
-			ln := newLocalListener(t, network)
-			address := ln.Addr().String()
-			// TODO: This is racy. The selected address could be reused in between
-			// this Close and the subsequent Listen.
-			ln.Close()
-			lc := ListenConfig{Control: controlOnConnSetup}
-			ln, err := lc.Listen(context.Background(), network, address)
-			if err != nil {
-				t.Error(err)
-				continue
-			}
+			ln := newLocalListener(t, network, &ListenConfig{Control: controlOnConnSetup})
 			ln.Close()
 		}
 	})
@@ -754,24 +743,8 @@ func TestListenConfigControl(t *testing.T) {
 			if !testableNetwork(network) {
 				continue
 			}
-			c := newLocalPacketListener(t, network)
-			address := c.LocalAddr().String()
-			// TODO: This is racy. The selected address could be reused in between
-			// this Close and the subsequent ListenPacket.
-			c.Close()
-			if network == "unixgram" {
-				os.Remove(address)
-			}
-			lc := ListenConfig{Control: controlOnConnSetup}
-			c, err := lc.ListenPacket(context.Background(), network, address)
-			if err != nil {
-				t.Error(err)
-				continue
-			}
+			c := newLocalPacketListener(t, network, &ListenConfig{Control: controlOnConnSetup})
 			c.Close()
-			if network == "unixgram" {
-				os.Remove(address)
-			}
 		}
 	})
 }
diff --git a/src/net/mockserver_test.go b/src/net/mockserver_test.go
index 186bd330b2..61c17530c2 100644
--- a/src/net/mockserver_test.go
+++ b/src/net/mockserver_test.go
@@ -7,6 +7,7 @@
 package net
 
 import (
+	"context"
 	"errors"
 	"fmt"
 	"os"
@@ -33,9 +34,20 @@ func testUnixAddr(t testing.TB) string {
 	return filepath.Join(d, "sock")
 }
 
-func newLocalListener(t testing.TB, network string) Listener {
+func newLocalListener(t testing.TB, network string, lcOpt ...*ListenConfig) Listener {
+	var lc *ListenConfig
+	switch len(lcOpt) {
+	case 0:
+		lc = new(ListenConfig)
+	case 1:
+		lc = lcOpt[0]
+	default:
+		t.Helper()
+		t.Fatal("too many ListenConfigs passed to newLocalListener: want 0 or 1")
+	}
+
 	listen := func(net, addr string) Listener {
-		ln, err := Listen(net, addr)
+		ln, err := lc.Listen(context.Background(), net, addr)
 		if err != nil {
 			t.Helper()
 			t.Fatal(err)
@@ -306,9 +318,20 @@ func transceiver(c Conn, wb []byte, ch chan<- error) {
 	}
 }
 
-func newLocalPacketListener(t testing.TB, network string) PacketConn {
+func newLocalPacketListener(t testing.TB, network string, lcOpt ...*ListenConfig) PacketConn {
+	var lc *ListenConfig
+	switch len(lcOpt) {
+	case 0:
+		lc = new(ListenConfig)
+	case 1:
+		lc = lcOpt[0]
+	default:
+		t.Helper()
+		t.Fatal("too many ListenConfigs passed to newLocalListener: want 0 or 1")
+	}
+
 	listenPacket := func(net, addr string) PacketConn {
-		c, err := ListenPacket(net, addr)
+		c, err := lc.ListenPacket(context.Background(), net, addr)
 		if err != nil {
 			t.Helper()
 			t.Fatal(err)