Merge pull request #50523 from rpothier/kubeadm-ipv6

Automatic merge from submit-queue

kubeadm: Add node-cidr-mask-size to pass to kube-controller-manager for IPv6

Due to the increased size of subnets with IPv6, the node-cidr-mask-size needs to be passed to kube-controller-manager. If IPv4 it will be set to 24 as it was previously, if IPv6, it will be set to 
64

**What this PR does / why we need it**:
If the user specifies the --pod-network-cidr with kubeadm init, this caused the kube-controller-manager manifest to include the "--allocate-node-cidrs" and "--cluster-cidr" flags to be set. The --node-cidr-mask-size is not set, and currently defaults to 24, which is fine for IPv4, but not appropriate for IPv6. This change passes the a value as the node-cidr-mask-size to the controller-manager. It detects if it is IPv4 or v6, and sets --node-cidr-mask-size to 24 for IPv4  as before, and to 64 for IPv6.


**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: fixes #50469

**Special notes for your reviewer**:

**Release note**:

```release-note
NONE
```

cmd/kubeadm/app/phases/controlplane/manifests.go

@@ -18,6 +18,7 @@ package controlplane
 
 import (
 	"fmt"
+	"net"
 	"os"
 	"path/filepath"
 	"strings"
@@ -230,7 +231,14 @@ func getControllerManagerCommand(cfg *kubeadmapi.MasterConfiguration, k8sVersion
 	// Let the controller-manager allocate Node CIDRs for the Pod network.
 	// Each node will get a subspace of the address CIDR provided with --pod-network-cidr.
 	if cfg.Networking.PodSubnet != "" {
-		command = append(command, "--allocate-node-cidrs=true", "--cluster-cidr="+cfg.Networking.PodSubnet)
+		maskSize := "24"
+		if ip, _, err := net.ParseCIDR(cfg.Networking.PodSubnet); err == nil {
+			if ip.To4() == nil {
+				maskSize = "64"
+			}
+		}
+		command = append(command, "--allocate-node-cidrs=true", "--cluster-cidr="+cfg.Networking.PodSubnet,
+			"--node-cidr-mask-size="+maskSize)
 	}
 	return command
 }

cmd/kubeadm/app/phases/controlplane/manifests_test.go

@@ -407,7 +407,7 @@ func TestGetControllerManagerCommand(t *testing.T) {
 		},
 		{
 			cfg: &kubeadmapi.MasterConfiguration{
-				Networking:        kubeadmapi.Networking{PodSubnet: "bar"},
+				Networking:        kubeadmapi.Networking{PodSubnet: "10.0.1.15/16"},
 				CertificatesDir:   testCertsDir,
 				KubernetesVersion: "v1.7.0",
 			},
@@ -423,7 +423,30 @@ func TestGetControllerManagerCommand(t *testing.T) {
 				"--use-service-account-credentials=true",
 				"--controllers=*,bootstrapsigner,tokencleaner",
 				"--allocate-node-cidrs=true",
-				"--cluster-cidr=bar",
+				"--cluster-cidr=10.0.1.15/16",
+				"--node-cidr-mask-size=24",
+			},
+		},
+		{
+			cfg: &kubeadmapi.MasterConfiguration{
+				Networking:        kubeadmapi.Networking{PodSubnet: "2001:101:115::/48"},
+				CertificatesDir:   testCertsDir,
+				KubernetesVersion: "v1.7.0",
+			},
+			expected: []string{
+				"kube-controller-manager",
+				"--address=127.0.0.1",
+				"--leader-elect=true",
+				"--kubeconfig=" + kubeadmconstants.KubernetesDir + "/controller-manager.conf",
+				"--root-ca-file=" + testCertsDir + "/ca.crt",
+				"--service-account-private-key-file=" + testCertsDir + "/sa.key",
+				"--cluster-signing-cert-file=" + testCertsDir + "/ca.crt",
+				"--cluster-signing-key-file=" + testCertsDir + "/ca.key",
+				"--use-service-account-credentials=true",
+				"--controllers=*,bootstrapsigner,tokencleaner",
+				"--allocate-node-cidrs=true",
+				"--cluster-cidr=2001:101:115::/48",
+				"--node-cidr-mask-size=64",
 			},
 		},
 	}