Implements Service Internal Traffic Policy

1. Add API definitions;
2. Add feature gate and drops the field when feature gate is not on;
3. Set default values for the field;
4. Add API Validation
5. add kube-proxy iptables and ipvs implementations
6. add tests

pkg/api/v1/service/util.go

@@ -20,7 +20,7 @@ import (
 	"fmt"
 	"strings"
 
-	"k8s.io/api/core/v1"
+	v1 "k8s.io/api/core/v1"
 	utilnet "k8s.io/utils/net"
 )
 
@@ -76,6 +76,15 @@ func RequestsOnlyLocalTraffic(service *v1.Service) bool {
 	return service.Spec.ExternalTrafficPolicy == v1.ServiceExternalTrafficPolicyTypeLocal
 }
 
+// RequestsOnlyLocalTrafficForInternal checks if service prefers Node Local
+// endpoints for internal traffic
+func RequestsOnlyLocalTrafficForInternal(service *v1.Service) bool {
+	if service.Spec.InternalTrafficPolicy == nil {
+		return false
+	}
+	return *service.Spec.InternalTrafficPolicy == v1.ServiceInternalTrafficPolicyLocal
+}
+
 // NeedsHealthCheck checks if service needs health check.
 func NeedsHealthCheck(service *v1.Service) bool {
 	if service.Spec.Type != v1.ServiceTypeLoadBalancer {

pkg/api/v1/service/util_test.go

@@ -20,7 +20,7 @@ import (
 	"strings"
 	"testing"
 
-	"k8s.io/api/core/v1"
+	v1 "k8s.io/api/core/v1"
 	utilnet "k8s.io/utils/net"
 )
 
@@ -214,3 +214,30 @@ func TestNeedsHealthCheck(t *testing.T) {
 		},
 	})
 }
+
+func TestRequestsOnlyLocalTrafficForInternal(t *testing.T) {
+	checkRequestsOnlyLocalTrafficForInternal := func(expected bool, service *v1.Service) {
+		res := RequestsOnlyLocalTrafficForInternal(service)
+		if res != expected {
+			t.Errorf("Expected internal local traffic = %v, got %v",
+				expected, res)
+		}
+	}
+
+	// default InternalTrafficPolicy is nil
+	checkRequestsOnlyLocalTrafficForInternal(false, &v1.Service{})
+
+	local := v1.ServiceInternalTrafficPolicyLocal
+	checkRequestsOnlyLocalTrafficForInternal(true, &v1.Service{
+		Spec: v1.ServiceSpec{
+			InternalTrafficPolicy: &local,
+		},
+	})
+
+	cluster := v1.ServiceInternalTrafficPolicyCluster
+	checkRequestsOnlyLocalTrafficForInternal(false, &v1.Service{
+		Spec: v1.ServiceSpec{
+			InternalTrafficPolicy: &cluster,
+		},
+	})
+}