}
		if tc.expectStackDowngrade && len(want.Spec.IPFamilies) > len(got.Spec.ClusterIPs) {
			want.Spec.IPFamilies = want.Spec.IPFamilies[0:1]
		} else if len(got.Spec.IPFamilies) > len(want.Spec.IPFamilies) {
			want.Spec.IPFamilies = append(want.Spec.IPFamilies, got.Spec.IPFamilies[len(want.Spec.IPFamilies):]...)
		}
	}

	if tc.expectNodePorts {
		for i := range want.Spec.Ports {

  //
  // This field may hold a maximum of two entries (dual-stack families, in
  // either order).  These families must correspond to the values of the
  // clusterIPs field, if specified. Both clusterIPs and ipFamilies are
  // governed by the ipFamilyPolicy field.
  // +listType=atomic
  // +optional
  repeated string ipFamilies = 19;

  // IPFamilyPolicy represents the dual-stack-ness requested or required by

	"ipFamilyPolicy":                "IPFamilyPolicy represents the dual-stack-ness requested or required by this Service. If there...

		}
	}

	// match clusterIPs to their families, if they were provided
	if !isHeadlessService(service) && len(service.Spec.ClusterIPs) > 0 && len(service.Spec.IPFamilies) > 0 {
		for i, ip := range service.Spec.ClusterIPs {
			if i > (len(service.Spec.IPFamilies) - 1) {
				break // no more families to check
			}

			// 4=>6
			if service.Spec.IPFamilies[i] == core.IPv4Protocol && netutils.IsIPv6String(ip) {

  //
  // This field may hold a maximum of two entries (dual-stack families, in
  // either order).  These families must correspond to the values of the
  // clusterIPs field, if specified. Both clusterIPs and ipFamilies are
  // governed by the ipFamilyPolicy field.
  // +listType=atomic
  // +optional
  repeated string ipFamilies = 19;

  // IPFamilyPolicy represents the dual-stack-ness requested or required by

	// This field may hold a maximum of two entries (dual-stack families, in
	// either order).  These families must correspond to the values of the
	// clusterIPs field, if specified. Both clusterIPs and ipFamilies are
	// governed by the ipFamilyPolicy field.
	// +listType=atomic
	// +optional
	IPFamilies []IPFamily `json:"ipFamilies,omitempty" protobuf:"bytes,19,opt,name=ipFamilies,casttype=IPFamily"`

	// Defines which IP family to use for single stack or the order of IP families for dual-stack.
	// Valid list items are "IPv4", "IPv6".
	// More info: https://kubernetes.io/docs/concepts/services-networking/dual-stack/#services
	IpFamilies []string `protobuf:"bytes,29,rep,name=ipFamilies,proto3" json:"ipFamilies,omitempty"`
	// Controls whether Services are configured to use IPv4, IPv6, or both. Valid options

- Kubenet: added HostPort IPv6 support.  HostPortManager: operates only with one IP family, failing if receives port mapping entries with different IP families.  HostPortSyncer: operates only with one IP family, skipping portmap entries with different IP families ([#80854](https://github.com/kubernetes/kubernetes/pull/80854), [@aojea](https://github.com/aojea))

  It changes the dual-stack API wrt Service from a single ipFamily field to 3
  fields: ipFamilyPolicy (SingleStack, PreferDualStack, RequireDualStack),
  ipFamilies (a list of families assigned), and clusterIPs (inclusive of
  clusterIP).  Most users do not need to set anything at all, defaulting will
  handle it for them.  Services are single-stack unless the user asks for

			intrinsics[intrinsicKey{a, pkg, fn}] = b
		}
	}
	// addF does the same as add but operates on architecture families.
	addF := func(pkg, fn string, b intrinsicBuilder, archFamilies ...sys.ArchFamily) {
		m := 0
		for _, f := range archFamilies {
			if f >= 32 {
				panic("too many architecture families")
			}
			m |= 1 << uint(f)
		}
		for _, a := range all {
			if m>>uint(a.Family)&1 != 0 {