net: don't call forceCloseSockets in non-TestMain functions

forceCloseSockets is just designed as a kingston valve for TestMain
function and is not suitable to keep track of inflight sockets.

Fixes #15525.

Change-Id: Id967fe5b8da99bb08b699cc45e07bbc3dfc3ae3d
Reviewed-on: https://go-review.googlesource.com/23505
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Mikio Hara <mikioh.mikioh@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/net/dial_test.go

@@ -87,17 +87,14 @@ func TestDialTimeoutFDLeak(t *testing.T) {
 	// socktest.Switch.
 	// It may happen when the Dial call bumps against TCP
 	// simultaneous open. See selfConnect in tcpsock_posix.go.
-	defer func() {
-		sw.Set(socktest.FilterClose, nil)
-		forceCloseSockets()
-	}()
+	defer func() { sw.Set(socktest.FilterClose, nil) }()
 	var mu sync.Mutex
 	var attempts int
 	sw.Set(socktest.FilterClose, func(so *socktest.Status) (socktest.AfterFilter, error) {
 		mu.Lock()
 		attempts++
 		mu.Unlock()
-		return nil, errTimedout
+		return nil, nil
 	})
 
 	const N = 100

src/net/main_plan9_test.go

@@ -8,6 +8,7 @@ func installTestHooks() {}
 
 func uninstallTestHooks() {}
 
+// forceCloseSockets must be called only from TestMain.
 func forceCloseSockets() {}
 
 func enableSocketConnect() {}

src/net/main_unix_test.go

@@ -45,6 +45,7 @@ func uninstallTestHooks() {
 	}
 }
 
+// forceCloseSockets must be called only from TestMain.
 func forceCloseSockets() {
 	for s := range sw.Sockets() {
 		closeFunc(s)

src/net/main_windows_test.go

@@ -32,6 +32,7 @@ func uninstallTestHooks() {
 	acceptFunc = origAccept
 }
 
+// forceCloseSockets must be called only from TestMain.
 func forceCloseSockets() {
 	for s := range sw.Sockets() {
 		closeFunc(s)

src/net/timeout_test.go

@@ -41,19 +41,6 @@ func TestDialTimeout(t *testing.T) {
 	defer func() { testHookDialChannel = origTestHookDialChannel }()
 	defer sw.Set(socktest.FilterConnect, nil)
 
-	// Avoid tracking open-close jitterbugs between netFD and
-	// socket that leads to confusion of information inside
-	// socktest.Switch.
-	// It may happen when the Dial call bumps against TCP
-	// simultaneous open. See selfConnect in tcpsock_posix.go.
-	defer func() {
-		sw.Set(socktest.FilterClose, nil)
-		forceCloseSockets()
-	}()
-	sw.Set(socktest.FilterClose, func(so *socktest.Status) (socktest.AfterFilter, error) {
-		return nil, errTimedout
-	})
-
 	for i, tt := range dialTimeoutTests {
 		switch runtime.GOOS {
 		case "plan9", "windows":