all: use Go 1.22 range-over-int

Updates #11058

Change-Id: I35e7ef9b90e83cac04ca93fd964ad00ed5b48430
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

wgengine/router/ifconfig_windows.go

@@ -265,7 +265,7 @@ func configureInterface(cfg *Config, tun *tun.NativeTun) (retErr error) {
 		// new interface has come up. Poll periodically until it
 		// does.
 		const tries = 20
-		for i := 0; i < tries; i++ {
+		for i := range tries {
 			found, err := setPrivateNetwork(luid)
 			if err != nil {
 				networkCategoryWarning.Set(fmt.Errorf("set-network-category: %w", err))
@@ -398,7 +398,7 @@ func configureInterface(cfg *Config, tun *tun.NativeTun) (retErr error) {
 	slices.SortFunc(routes, (*routeData).Compare)
 
 	deduplicatedRoutes := []*routeData{}
-	for i := 0; i < len(routes); i++ {
+	for i := range len(routes) {
 		// There's only one way to get to a given IP+Mask, so delete
 		// all matches after the first.
 		if i > 0 && routes[i].Destination == routes[i-1].Destination {

wgengine/router/ifconfig_windows_test.go

@@ -82,7 +82,7 @@ func TestRouteLess(t *testing.T) {
 }
 
 func TestRouteDataLessConsistent(t *testing.T) {
-	for i := 0; i < 10000; i++ {
+	for range 10000 {
 		ri := randRouteData()
 		rj := randRouteData()
 		if ri.Less(rj) && rj.Less(ri) {

wgengine/router/router_linux_test.go

@@ -909,7 +909,7 @@ func TestDelRouteIdempotent(t *testing.T) {
 			t.Error(err)
 			continue
 		}
-		for i := 0; i < 2; i++ {
+		for i := range 2 {
 			if err := lt.r.delRoute(cidr); err != nil {
 				t.Errorf("delRoute(i=%d): %v", i, err)
 			}

wgengine/router/router_test.go

@@ -28,7 +28,7 @@ func TestConfigEqual(t *testing.T) {
 	}
 	configType := reflect.TypeFor[Config]()
 	configFields := []string{}
-	for i := 0; i < configType.NumField(); i++ {
+	for i := range configType.NumField() {
 		configFields = append(configFields, configType.Field(i).Name)
 	}
 	if !reflect.DeepEqual(configFields, testedFields) {