kubeadm: apply the new "control-plane" taint on CP nodes

- Apply "control-plane" taint during init/join by adding the
taint in SetNodeRegistrationDynamicDefaults(). The old
taint "master" is still applied.
- Clarify API docs (v1beta2 and v1beta3) for nodeRegistration.Taint
to not mention "master" taint and be more generic. Remove
example for taints that includes the word "master".
- Update unit tests.

cmd/kubeadm/app/apis/kubeadm/types.go

@@ -212,9 +212,9 @@ type NodeRegistrationOptions struct {
 	// CRISocket is used to retrieve container runtime info. This information will be annotated to the Node API object, for later re-use
 	CRISocket string
 
-	// Taints specifies the taints the Node API object should be registered with. If this field is unset, i.e. nil, in the `kubeadm init` process
-	// it will be defaulted to []v1.Taint{'node-role.kubernetes.io/master=""'}. If you don't want to taint your control-plane node, set this field to an
-	// empty slice, i.e. `taints: []` in the YAML file. This field is solely used for Node registration.
+	// Taints specifies the taints the Node API object should be registered with. If this field is unset, i.e. nil,
+	// it will be defaulted with a control-plane taint for control-plane nodes. If you don't want to taint your control-plane
+	// node, set this field to an empty slice, i.e. `taints: []` in the YAML file. This field is solely used for Node registration.
 	Taints []v1.Taint
 
 	// KubeletExtraArgs passes through extra arguments to the kubelet. The arguments here are passed to the kubelet command line via the environment file

cmd/kubeadm/app/apis/kubeadm/v1beta2/doc.go

@@ -172,7 +172,7 @@ limitations under the License.
 // 	  criSocket: "unix:///var/run/dockershim.sock"
 // 	  taints:
 // 	  - key: "kubeadmNode"
-// 	    value: "master"
+// 	    value: "someValue"
 // 	    effect: "NoSchedule"
 // 	  kubeletExtraArgs:
 // 	    v: 4

cmd/kubeadm/app/apis/kubeadm/v1beta2/types.go

@@ -201,9 +201,9 @@ type NodeRegistrationOptions struct {
 	// CRISocket is used to retrieve container runtime info. This information will be annotated to the Node API object, for later re-use
 	CRISocket string `json:"criSocket,omitempty"`
 
-	// Taints specifies the taints the Node API object should be registered with. If this field is unset, i.e. nil, in the `kubeadm init` process
-	// it will be defaulted to []v1.Taint{'node-role.kubernetes.io/master=""'}. If you don't want to taint your control-plane node, set this field to an
-	// empty slice, i.e. `taints: []` in the YAML file. This field is solely used for Node registration.
+	// Taints specifies the taints the Node API object should be registered with. If this field is unset, i.e. nil,
+	// it will be defaulted with a control-plane taint for control-plane nodes. If you don't want to taint your control-plane
+	// node, set this field to an empty slice, i.e. `taints: []` in the YAML file. This field is solely used for Node registration.
 	Taints []v1.Taint `json:"taints"`
 
 	// KubeletExtraArgs passes through extra arguments to the kubelet. The arguments here are passed to the kubelet command line via the environment file

cmd/kubeadm/app/apis/kubeadm/v1beta3/doc.go

@@ -176,7 +176,7 @@ limitations under the License.
 // 	  criSocket: "unix:///var/run/dockershim.sock"
 // 	  taints:
 // 	  - key: "kubeadmNode"
-// 	    value: "master"
+// 	    value: "someValue"
 // 	    effect: "NoSchedule"
 // 	  kubeletExtraArgs:
 // 	    v: 4

cmd/kubeadm/app/apis/kubeadm/v1beta3/types.go

@@ -215,9 +215,9 @@ type NodeRegistrationOptions struct {
 	// +optional
 	CRISocket string `json:"criSocket,omitempty"`
 
-	// Taints specifies the taints the Node API object should be registered with. If this field is unset, i.e. nil, in the `kubeadm init` process
-	// it will be defaulted to []v1.Taint{'node-role.kubernetes.io/master=""'}. If you don't want to taint your control-plane node, set this field to an
-	// empty slice, i.e. `taints: []` in the YAML file. This field is solely used for Node registration.
+	// Taints specifies the taints the Node API object should be registered with. If this field is unset, i.e. nil,
+	// it will be defaulted with a control-plane taint for control-plane nodes. If you don't want to taint your control-plane
+	// node, set this field to an empty slice, i.e. `taints: []` in the YAML file. This field is solely used for Node registration.
 	Taints []corev1.Taint `json:"taints"`
 
 	// KubeletExtraArgs passes through extra arguments to the kubelet. The arguments here are passed to the kubelet command line via the environment file

cmd/kubeadm/app/util/config/initconfiguration.go

@@ -106,7 +106,7 @@ func SetNodeRegistrationDynamicDefaults(cfg *kubeadmapi.NodeRegistrationOptions,
 	// Only if the slice is nil, we should append the control-plane taint. This allows the user to specify an empty slice for no default control-plane taint
 	if controlPlaneTaint && cfg.Taints == nil {
 		// TODO: https://github.com/kubernetes/kubeadm/issues/2200
-		cfg.Taints = []v1.Taint{kubeadmconstants.OldControlPlaneTaint}
+		cfg.Taints = []v1.Taint{kubeadmconstants.OldControlPlaneTaint, kubeadmconstants.ControlPlaneTaint}
 	}
 
 	if cfg.CRISocket == "" {

cmd/kubeadm/app/util/config/initconfiguration_test.go

@@ -116,17 +116,17 @@ func TestDefaultTaintsMarshaling(t *testing.T) {
 		expectedTaintCnt int
 	}{
 		{
-			desc: "Uninitialized nodeRegistration field produces a single taint (the master one)",
+			desc: "Uninitialized nodeRegistration field produces expected taints",
 			cfg: kubeadmapiv1.InitConfiguration{
 				TypeMeta: metav1.TypeMeta{
 					APIVersion: kubeadmapiv1.SchemeGroupVersion.String(),
 					Kind:       constants.InitConfigurationKind,
 				},
 			},
-			expectedTaintCnt: 1,
+			expectedTaintCnt: 2,
 		},
 		{
-			desc: "Uninitialized taints field produces a single taint (the master one)",
+			desc: "Uninitialized taints field produces expected taints",
 			cfg: kubeadmapiv1.InitConfiguration{
 				TypeMeta: metav1.TypeMeta{
 					APIVersion: kubeadmapiv1.SchemeGroupVersion.String(),
@@ -134,7 +134,7 @@ func TestDefaultTaintsMarshaling(t *testing.T) {
 				},
 				NodeRegistration: kubeadmapiv1.NodeRegistrationOptions{},
 			},
-			expectedTaintCnt: 1,
+			expectedTaintCnt: 2,
 		},
 		{
 			desc: "Forsing taints to an empty slice produces no taints",