kubeadm: add support for patching a corednsdeployment target

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

@@ -468,7 +468,7 @@ type HostPathMount struct {
 type Patches struct {
 	// Directory is a path to a directory that contains files named "target[suffix][+patchtype].extension".
 	// For example, "kube-apiserver0+merge.yaml" or just "etcd.json". "target" can be one of
-	// "kube-apiserver", "kube-controller-manager", "kube-scheduler", "etcd", "kubeletconfiguration".
+	// "kube-apiserver", "kube-controller-manager", "kube-scheduler", "etcd", "kubeletconfiguration", "corednsdeployment".
 	// "patchtype" can be one of "strategic" "merge" or "json" and they match the patch formats supported by kubectl.
 	// The default "patchtype" is "strategic". "extension" must be either "json" or "yaml".
 	// "suffix" is an optional string that can be used to determine which patches are applied

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

@@ -438,7 +438,7 @@ type HostPathMount struct {
 type Patches struct {
 	// Directory is a path to a directory that contains files named "target[suffix][+patchtype].extension".
 	// For example, "kube-apiserver0+merge.yaml" or just "etcd.json". "target" can be one of
-	// "kube-apiserver", "kube-controller-manager", "kube-scheduler", "etcd", "kubeletconfiguration".
+	// "kube-apiserver", "kube-controller-manager", "kube-scheduler", "etcd", "kubeletconfiguration", "corednsdeployment".
 	// "patchtype" can be one of "strategic" "merge" or "json" and they match the patch formats supported by kubectl.
 	// The default "patchtype" is "strategic". "extension" must be either "json" or "yaml".
 	// "suffix" is an optional string that can be used to determine which patches are applied

cmd/kubeadm/app/apis/kubeadm/v1beta4/types.go

@@ -487,7 +487,7 @@ type HostPathMount struct {
 type Patches struct {
 	// Directory is a path to a directory that contains files named "target[suffix][+patchtype].extension".
 	// For example, "kube-apiserver0+merge.yaml" or just "etcd.json". "target" can be one of
-	// "kube-apiserver", "kube-controller-manager", "kube-scheduler", "etcd", "kubeletconfiguration".
+	// "kube-apiserver", "kube-controller-manager", "kube-scheduler", "etcd", "kubeletconfiguration", "corednsdeployment".
 	// "patchtype" can be one of "strategic" "merge" or "json" and they match the patch formats supported by kubectl.
 	// The default "patchtype" is "strategic". "extension" must be either "json" or "yaml".
 	// "suffix" is an optional string that can be used to determine which patches are applied

cmd/kubeadm/app/cmd/options/generic.go

@@ -99,7 +99,7 @@ func AddPatchesFlag(fs *pflag.FlagSet, patchesDir *string) {
 	const usage = `Path to a directory that contains files named ` +
 		`"target[suffix][+patchtype].extension". For example, ` +
 		`"kube-apiserver0+merge.yaml" or just "etcd.json". ` +
-		`"target" can be one of "kube-apiserver", "kube-controller-manager", "kube-scheduler", "etcd", "kubeletconfiguration". ` +
+		`"target" can be one of "kube-apiserver", "kube-controller-manager", "kube-scheduler", "etcd", "kubeletconfiguration", "corednsdeployment". ` +
 		`"patchtype" can be one of "strategic", "merge" or "json" and they match the patch formats ` +
 		`supported by kubectl. The default "patchtype" is "strategic". "extension" must be either ` +
 		`"json" or "yaml". "suffix" is an optional string that can be used to determine ` +

cmd/kubeadm/app/cmd/phases/init/addons.go

@@ -84,10 +84,10 @@ func NewAddonPhase() workflow.Phase {
 	}
 }
 
-func getInitData(c workflow.RunData) (*kubeadmapi.InitConfiguration, clientset.Interface, io.Writer, error) {
+func getInitData(c workflow.RunData) (*kubeadmapi.InitConfiguration, clientset.Interface, string, io.Writer, error) {
 	data, ok := c.(InitData)
 	if !ok {
-		return nil, nil, nil, errors.New("addon phase invoked with an invalid data struct")
+		return nil, nil, "", nil, errors.New("addon phase invoked with an invalid data struct")
 	}
 	cfg := data.Cfg()
 	var client clientset.Interface
@@ -95,26 +95,27 @@ func getInitData(c workflow.RunData) (*kubeadmapi.InitConfiguration, clientset.I
 	if !printManifest {
 		client, err = data.Client()
 		if err != nil {
-			return nil, nil, nil, err
+			return nil, nil, "", nil, err
 		}
 	}
 
 	out := data.OutputWriter()
-	return cfg, client, out, err
+	patchesDir := data.PatchesDir()
+	return cfg, client, patchesDir, out, err
 }
 
 // runCoreDNSAddon installs CoreDNS addon to a Kubernetes cluster
 func runCoreDNSAddon(c workflow.RunData) error {
-	cfg, client, out, err := getInitData(c)
+	cfg, client, patchesDir, out, err := getInitData(c)
 	if err != nil {
 		return err
 	}
-	return dnsaddon.EnsureDNSAddon(&cfg.ClusterConfiguration, client, out, printManifest)
+	return dnsaddon.EnsureDNSAddon(&cfg.ClusterConfiguration, client, patchesDir, out, printManifest)
 }
 
 // runKubeProxyAddon installs KubeProxy addon to a Kubernetes cluster
 func runKubeProxyAddon(c workflow.RunData) error {
-	cfg, client, out, err := getInitData(c)
+	cfg, client, _, out, err := getInitData(c)
 	if err != nil {
 		return err
 	}

cmd/kubeadm/app/cmd/phases/upgrade/node/controlplane.go

@@ -78,7 +78,7 @@ func runControlPlane() func(c workflow.RunData) error {
 			return errors.Wrap(err, "couldn't complete the static pod upgrade")
 		}
 
-		if err := upgrade.PerformAddonsUpgrade(client, cfg, data.OutputWriter()); err != nil {
+		if err := upgrade.PerformAddonsUpgrade(client, cfg, data.PatchesDir(), data.OutputWriter()); err != nil {
 			return errors.Wrap(err, "failed to perform addons upgrade")
 		}
 

cmd/kubeadm/app/phases/addons/dns/dns.go

@@ -35,6 +35,7 @@ import (
 	clientset "k8s.io/client-go/kubernetes"
 	clientsetscheme "k8s.io/client-go/kubernetes/scheme"
 	"k8s.io/klog/v2"
+	"sigs.k8s.io/yaml"
 
 	kubeadmapi "k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm"
 	kubeadmconstants "k8s.io/kubernetes/cmd/kubeadm/app/constants"
@@ -42,6 +43,7 @@ import (
 	kubeadmutil "k8s.io/kubernetes/cmd/kubeadm/app/util"
 	"k8s.io/kubernetes/cmd/kubeadm/app/util/apiclient"
 	"k8s.io/kubernetes/cmd/kubeadm/app/util/image"
+	"k8s.io/kubernetes/cmd/kubeadm/app/util/patches"
 )
 
 const (
@@ -85,7 +87,7 @@ func deployedDNSReplicas(client clientset.Interface, replicas int32) (*int32, er
 }
 
 // EnsureDNSAddon creates the CoreDNS addon
-func EnsureDNSAddon(cfg *kubeadmapi.ClusterConfiguration, client clientset.Interface, out io.Writer, printManifest bool) error {
+func EnsureDNSAddon(cfg *kubeadmapi.ClusterConfiguration, client clientset.Interface, patchesDir string, out io.Writer, printManifest bool) error {
 	var replicas *int32
 	var err error
 	if !printManifest {
@@ -97,10 +99,10 @@ func EnsureDNSAddon(cfg *kubeadmapi.ClusterConfiguration, client clientset.Inter
 		var defaultReplicas int32 = coreDNSReplicas
 		replicas = &defaultReplicas
 	}
-	return coreDNSAddon(cfg, client, replicas, out, printManifest)
+	return coreDNSAddon(cfg, client, replicas, patchesDir, out, printManifest)
 }
 
-func coreDNSAddon(cfg *kubeadmapi.ClusterConfiguration, client clientset.Interface, replicas *int32, out io.Writer, printManifest bool) error {
+func coreDNSAddon(cfg *kubeadmapi.ClusterConfiguration, client clientset.Interface, replicas *int32, patchesDir string, out io.Writer, printManifest bool) error {
 	// Get the YAML manifest
 	coreDNSDeploymentBytes, err := kubeadmutil.ParseTemplate(CoreDNSDeployment, struct {
 		DeploymentName, Image, ControlPlaneTaintKey string
@@ -115,6 +117,14 @@ func coreDNSAddon(cfg *kubeadmapi.ClusterConfiguration, client clientset.Interfa
 		return errors.Wrap(err, "error when parsing CoreDNS deployment template")
 	}
 
+	// Apply patches to the CoreDNS Deployment
+	if len(patchesDir) != 0 {
+		coreDNSDeploymentBytes, err = applyCoreDNSDeploymentPatches(coreDNSDeploymentBytes, patchesDir, out)
+		if err != nil {
+			return errors.Wrap(err, "could not apply patches to the CoreDNS Deployment")
+		}
+	}
+
 	// Get the config file for CoreDNS
 	coreDNSConfigMapBytes, err := kubeadmutil.ParseTemplate(CoreDNSConfigMap, struct{ DNSDomain, UpstreamNameserver, StubDomain string }{
 		DNSDomain: cfg.Networking.DNSDomain,
@@ -377,3 +387,27 @@ func setCorefile(client clientset.Interface, coreDNSCorefileName string) error {
 	}
 	return nil
 }
+
+// applyCoreDNSDeploymentPatches reads patches from a directory and applies them over the input coreDNSDeploymentBytes
+func applyCoreDNSDeploymentPatches(coreDNSDeploymentBytes []byte, patchesDir string, output io.Writer) ([]byte, error) {
+	patchManager, err := patches.GetPatchManagerForPath(patchesDir, patches.KnownTargets(), output)
+	if err != nil {
+		return nil, err
+	}
+
+	patchTarget := &patches.PatchTarget{
+		Name:                      patches.CoreDNSDeployment,
+		StrategicMergePatchObject: apps.Deployment{},
+		Data:                      coreDNSDeploymentBytes,
+	}
+	if err := patchManager.ApplyPatchesToTarget(patchTarget); err != nil {
+		return nil, err
+	}
+
+	coreDNSDeploymentBytes, err = yaml.JSONToYAML(patchTarget.Data)
+	if err != nil {
+		return nil, err
+	}
+
+	return coreDNSDeploymentBytes, nil
+}

cmd/kubeadm/app/phases/addons/dns/dns_test.go

@@ -865,7 +865,7 @@ metadata:
 		t.Run(tt.name, func(t *testing.T) {
 			out := &bytes.Buffer{}
 			var replicas int32 = 3
-			if err := coreDNSAddon(tt.args.cfg, tt.args.client, &replicas, out, tt.args.printManifest); (err != nil) != tt.wantErr {
+			if err := coreDNSAddon(tt.args.cfg, tt.args.client, &replicas, "", out, tt.args.printManifest); (err != nil) != tt.wantErr {
 				t.Errorf("coreDNSAddon() error = %v, wantErr %v", err, tt.wantErr)
 				return
 			}
@@ -1148,7 +1148,7 @@ metadata:
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
 			out := &bytes.Buffer{}
-			if err := EnsureDNSAddon(tt.args.cfg, tt.args.client, out, tt.args.printManifest); (err != nil) != tt.wantErr {
+			if err := EnsureDNSAddon(tt.args.cfg, tt.args.client, "", out, tt.args.printManifest); (err != nil) != tt.wantErr {
 				t.Errorf("EnsureDNSAddon() error = %v, wantErr %v", err, tt.wantErr)
 				return
 			}

cmd/kubeadm/app/phases/upgrade/postupgrade.go

@@ -105,7 +105,7 @@ func PerformPostUpgradeTasks(client clientset.Interface, cfg *kubeadmapi.InitCon
 		errs = append(errs, err)
 	}
 
-	if err := PerformAddonsUpgrade(client, cfg, out); err != nil {
+	if err := PerformAddonsUpgrade(client, cfg, patchesDir, out); err != nil {
 		errs = append(errs, err)
 	}
 
@@ -113,7 +113,7 @@ func PerformPostUpgradeTasks(client clientset.Interface, cfg *kubeadmapi.InitCon
 }
 
 // PerformAddonsUpgrade performs the upgrade of the coredns and kube-proxy addons.
-func PerformAddonsUpgrade(client clientset.Interface, cfg *kubeadmapi.InitConfiguration, out io.Writer) error {
+func PerformAddonsUpgrade(client clientset.Interface, cfg *kubeadmapi.InitConfiguration, patchesDir string, out io.Writer) error {
 	unupgradedControlPlanes, err := unupgradedControlPlaneInstances(client, cfg.NodeRegistration.Name)
 	if err != nil {
 		return errors.Wrapf(err, "failed to determine whether all the control plane instances have been upgraded")
@@ -147,7 +147,7 @@ func PerformAddonsUpgrade(client clientset.Interface, cfg *kubeadmapi.InitConfig
 			metav1.NamespaceSystem)
 	} else {
 		// Upgrade CoreDNS
-		if err := dns.EnsureDNSAddon(&cfg.ClusterConfiguration, client, out, false); err != nil {
+		if err := dns.EnsureDNSAddon(&cfg.ClusterConfiguration, client, patchesDir, out, false); err != nil {
 			errs = append(errs, err)
 		}
 	}

cmd/kubeadm/app/util/patches/patches.go

@@ -75,8 +75,12 @@ func (ps *patchSet) String() string {
 	)
 }
 
-// KubeletConfiguration defines the kubeletconfiguration patch target.
+const (
-const KubeletConfiguration = "kubeletconfiguration"
+	// KubeletConfiguration defines the kubeletconfiguration patch target.
+	KubeletConfiguration = "kubeletconfiguration"
+	// CoreDNSDeployment defines the corednsdeployment patch target.
+	CoreDNSDeployment = "corednsdeployment"
+)
 
 var (
 	pathLock  = &sync.RWMutex{}
@@ -100,6 +104,7 @@ var (
 		kubeadmconstants.KubeControllerManager,
 		kubeadmconstants.KubeScheduler,
 		KubeletConfiguration,
+		CoreDNSDeployment,
 	}
 )