ipn/{ipnlocal,localapi}, wgengine/netstack: call (*LocalBackend).Shutdown when tests that create them complete

We have several places where LocalBackend instances are created for testing, but they are rarely shut down
when the tests that created them exit.

In this PR, we update newTestLocalBackend and similar functions to use testing.TB.Cleanup(lb.Shutdown)
to ensure LocalBackend instances are properly shut down during test cleanup.

Updates #12687

Signed-off-by: Nick Khyl <nickk@tailscale.com>

ipn/ipnlocal/local_test.go

@@ -458,6 +458,7 @@ func newTestLocalBackendWithSys(t testing.TB, sys *tsd.System) *LocalBackend {
 	if err != nil {
 		t.Fatalf("NewLocalBackend: %v", err)
 	}
+	t.Cleanup(lb.Shutdown)
 	return lb
 }
 
@@ -4109,6 +4110,7 @@ func newLocalBackendWithTestControl(t *testing.T, enableLogging bool, newControl
 	if err != nil {
 		t.Fatalf("NewLocalBackend: %v", err)
 	}
+	t.Cleanup(b.Shutdown)
 	b.DisablePortMapperForTest()
 
 	b.SetControlClientGetterForTesting(func(opts controlclient.Options) (controlclient.Client, error) {

ipn/ipnlocal/state_test.go

@@ -309,6 +309,7 @@ func TestStateMachine(t *testing.T) {
 	if err != nil {
 		t.Fatalf("NewLocalBackend: %v", err)
 	}
+	t.Cleanup(b.Shutdown)
 	b.DisablePortMapperForTest()
 
 	var cc, previousCC *mockControl
@@ -942,6 +943,7 @@ func TestEditPrefsHasNoKeys(t *testing.T) {
 	if err != nil {
 		t.Fatalf("NewLocalBackend: %v", err)
 	}
+	t.Cleanup(b.Shutdown)
 	b.hostinfo = &tailcfg.Hostinfo{OS: "testos"}
 	b.pm.SetPrefs((&ipn.Prefs{
 		Persist: &persist.Persist{
@@ -1023,6 +1025,7 @@ func TestWGEngineStatusRace(t *testing.T) {
 	sys.Set(eng)
 	b, err := NewLocalBackend(logf, logid.PublicID{}, sys, 0)
 	c.Assert(err, qt.IsNil)
+	t.Cleanup(b.Shutdown)
 
 	var cc *mockControl
 	b.SetControlClientGetterForTesting(func(opts controlclient.Options) (controlclient.Client, error) {

ipn/localapi/localapi_test.go

@@ -349,6 +349,7 @@ func newTestLocalBackend(t testing.TB) *ipnlocal.LocalBackend {
 	if err != nil {
 		t.Fatalf("NewLocalBackend: %v", err)
 	}
+	t.Cleanup(lb.Shutdown)
 	return lb
 }
 

wgengine/netstack/netstack_test.go

@@ -64,6 +64,7 @@ func TestInjectInboundLeak(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
+	t.Cleanup(lb.Shutdown)
 
 	ns, err := Create(logf, tunWrap, eng, sys.MagicSock.Get(), dialer, sys.DNSManager.Get(), sys.ProxyMapper())
 	if err != nil {
@@ -126,6 +127,7 @@ func makeNetstack(tb testing.TB, config func(*Impl)) *Impl {
 	if err != nil {
 		tb.Fatalf("NewLocalBackend: %v", err)
 	}
+	tb.Cleanup(lb.Shutdown)
 
 	ns.atomicIsLocalIPFunc.Store(func(netip.Addr) bool { return true })
 	if config != nil {