move IPv6DualStack feature to stable. (#104691)

* kube-proxy

* endpoints controller

* app: kube-controller-manager

* app: cloud-controller-manager

* kubelet

* app: api-server

* node utils + registry/strategy

* api: validation (comment removal)

* api:pod strategy (util pkg)

* api: docs

* core: integration testing

* kubeadm: change feature gate to GA

* service registry and rest stack

* move feature to GA

* generated

pkg/util/iptables/iptables.go

@@ -89,6 +89,9 @@ type Interface interface {
 	// mapped to the same IP:PORT and consequently some suffer packet
 	// drops.
 	HasRandomFully() bool
+
+	// Present checks if the kernel supports the iptable interface
+	Present() bool
 }
 
 // Protocol defines the ip protocol either ipv4 or ipv6
@@ -723,6 +726,16 @@ func (runner *runner) HasRandomFully() bool {
 	return runner.hasRandomFully
 }
 
+// Present tests if iptable is supported on current kernel by checking the existence
+// of default table and chain
+func (runner *runner) Present() bool {
+	if _, err := runner.ChainExists(TableNAT, ChainPostrouting); err != nil {
+		return false
+	}
+
+	return true
+}
+
 var iptablesNotFoundStrings = []string{
 	// iptables-legacy [-A|-I] BAD-CHAIN [...]
 	// iptables-legacy [-C|-D] GOOD-CHAIN [...non-matching rule...]