if call, ok := p.dialing[addr]; ok {
		// A dial is already in-flight. Don't start another.
		return call
	}
	call := &http2dialCall{p: p, done: make(chan struct{}), ctx: ctx}
	if p.dialing == nil {
		p.dialing = make(map[string]*http2dialCall)
	}
	p.dialing[addr] = call
	go call.dial(call.ctx, addr)
	return call
}

// run in its own goroutine.
func (c *http2dialCall) dial(ctx context.Context, addr string) {

### IPv4/IPv6 run

IPv4/IPv6 dual-stack has been reimplemented for 1.20 to support dual-stack Services, based on user and community feedback. If your cluster has dual-stack enabled, you can create Services which can use IPv4, IPv6, or both, and you can change this setting for existing Services. Details are available in updated [IPv4/IPv6 dual-stack docs](https://docs.k8s.io/concepts/services-networking/dual-stack/), which cover the nuanced array of options.

pkg net/http, type CloseNotifier //deprecated
pkg net/http, type ProtocolError //deprecated
pkg net/http, type Request struct, Cancel //deprecated
pkg net/http, type Transport struct, Dial //deprecated
pkg net/http, type Transport struct, DialTLS //deprecated
pkg net/http, var ErrHeaderTooLong //deprecated
pkg net/http, var ErrMissingContentLength //deprecated
pkg net/http, var ErrShortBody //deprecated

* etcd client add dial timeout. ([#61459](https://github.com/kubernetes/kubernetes/pull/61459), [@hzxuzhonghu](https://github.com/hzxuzhonghu))

		helpTestCreateUpdateDeleteWithFamilies(t, testCasesV4, []api.IPFamily{api.IPv4Protocol})
	})

	// Dual-stack v4,v6 cases: Covers the full matrix of:
	//    policy={nil, single, prefer, require}
	//    families={nil, single, dual}
	//    ips={nil, single, dual}
	testCasesV4V6 := []cudTestCase{{
		name: "policy:nil_families:nil_ips:nil",
		line: line(),
		create: svcTestCase{

### IPv4/IPv6 Dual-stack Networking graduates to GA

[IPv4/IPv6 dual-stack networking](https://github.com/kubernetes/enhancements/tree/master/keps/sig-network/563-dual-stack) graduates to GA.
Since 1.21, Kubernetes clusters are enabled to support dual-stack networking by default.
In 1.23, the `IPv6DualStack` feature gate is removed.
The use of dual-stack networking is not mandatory.

	// SingleStack (single IPFamily). Services can be SingleStack (single IPFamily),
	// PreferDualStack (two dual-stack IPFamilies on dual-stack clusters or single
	// IPFamily on single-stack clusters), or RequireDualStack (two dual-stack IPFamilies
	// on dual-stack configured clusters, otherwise fail). The IPFamilies and ClusterIPs assigned

	// 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"`

	IPFamilyPolicySingleStack IPFamilyPolicy = "SingleStack"
	// IPFamilyPolicyPreferDualStack indicates that this service prefers dual-stack when
	// the cluster is configured for dual-stack. If the cluster is not configured
	// for dual-stack the service will be assigned a single IPFamily. If the IPFamily is not
	// set in service.spec.ipFamilies then the service will be assigned the default IPFamily

  //
  // 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