bootstrap/kubeadm: Add Ignition bootstrap format

Add support for using Ignition as the format for bootstrap data. This
allows using Ignition-based distros as the operating system for
workload cluster nodes.

Co-authored-by: Suraj Deshmukh <suraj@kinvolk.io>

Signed-off-by: Mateusz Gozdek <mateusz@kinvolk.io>
Signed-off-by: Johanan Liebermann <jliebermann@microsoft.com>

OWNERS_ALIASES

@@ -46,6 +46,16 @@ aliases:
   cluster-api-bootstrap-provider-kubeadm-maintainers:
   cluster-api-bootstrap-provider-kubeadm-reviewers:
 
+  # -----------------------------------------------------------
+  # OWNER_ALIASES for bootstrap/kubeadm/internal/ignition
+  # -----------------------------------------------------------
+
+  cluster-api-bootstrap-provider-kubeadm-ignition-maintainers:
+  cluster-api-bootstrap-provider-kubeadm-ignition-reviewers:
+  - dongsupark
+  - invidian
+  - johananl
+
   # -----------------------------------------------------------
   # OWNER_ALIASES for controlplane/kubeadm
   # -----------------------------------------------------------

bootstrap/kubeadm/api/v1alpha3/conversion.go

@@ -52,6 +52,8 @@ func (src *KubeadmConfig) ConvertTo(dstRaw conversion.Hub) error {
 		dst.Spec.InitConfiguration.NodeRegistration.IgnorePreflightErrors = restored.Spec.InitConfiguration.NodeRegistration.IgnorePreflightErrors
 	}
 
+	dst.Spec.Ignition = restored.Spec.Ignition
+
 	return nil
 }
 
@@ -109,6 +111,8 @@ func (src *KubeadmConfigTemplate) ConvertTo(dstRaw conversion.Hub) error {
 		dst.Spec.Template.Spec.InitConfiguration.NodeRegistration.IgnorePreflightErrors = restored.Spec.Template.Spec.InitConfiguration.NodeRegistration.IgnorePreflightErrors
 	}
 
+	dst.Spec.Template.Spec.Ignition = restored.Spec.Template.Spec.Ignition
+
 	return nil
 }
 
@@ -177,3 +181,9 @@ func Convert_v1beta1_JoinConfiguration_To_upstreamv1beta1_JoinConfiguration(in *
 	// NodeRegistrationOptions.IgnorePreflightErrors does not exist in kubeadm v1beta1 API
 	return upstreamv1beta1.Convert_v1beta1_JoinConfiguration_To_upstreamv1beta1_JoinConfiguration(in, out, s)
 }
+
+// Convert_v1beta1_KubeadmConfigSpec_To_v1alpha3_KubeadmConfigSpec is an autogenerated conversion function.
+func Convert_v1beta1_KubeadmConfigSpec_To_v1alpha3_KubeadmConfigSpec(in *v1beta1.KubeadmConfigSpec, out *KubeadmConfigSpec, s apiconversion.Scope) error {
+	// KubeadmConfigSpec.Ignition does not exist in kubeadm v1alpha3 API.
+	return autoConvert_v1beta1_KubeadmConfigSpec_To_v1alpha3_KubeadmConfigSpec(in, out, s)
+}

bootstrap/kubeadm/api/v1alpha4/conversion.go

@@ -17,21 +17,39 @@ limitations under the License.
 package v1alpha4
 
 import (
+	apiconversion "k8s.io/apimachinery/pkg/conversion"
 	"sigs.k8s.io/controller-runtime/pkg/conversion"
 
 	"sigs.k8s.io/cluster-api/bootstrap/kubeadm/api/v1beta1"
+	utilconversion "sigs.k8s.io/cluster-api/util/conversion"
 )
 
 func (src *KubeadmConfig) ConvertTo(dstRaw conversion.Hub) error {
 	dst := dstRaw.(*v1beta1.KubeadmConfig)
 
-	return Convert_v1alpha4_KubeadmConfig_To_v1beta1_KubeadmConfig(src, dst, nil)
+	if err := Convert_v1alpha4_KubeadmConfig_To_v1beta1_KubeadmConfig(src, dst, nil); err != nil {
+		return err
+	}
+
+	// Manually restore data.
+	restored := &v1beta1.KubeadmConfig{}
+	if ok, err := utilconversion.UnmarshalData(src, restored); err != nil || !ok {
+		return err
+	}
+
+	dst.Spec.Ignition = restored.Spec.Ignition
+
+	return nil
 }
 
 func (dst *KubeadmConfig) ConvertFrom(srcRaw conversion.Hub) error {
 	src := srcRaw.(*v1beta1.KubeadmConfig)
 
-	return Convert_v1beta1_KubeadmConfig_To_v1alpha4_KubeadmConfig(src, dst, nil)
+	if err := Convert_v1beta1_KubeadmConfig_To_v1alpha4_KubeadmConfig(src, dst, nil); err != nil {
+		return err
+	}
+	// Preserve Hub data on down-conversion except for metadata.
+	return utilconversion.MarshalData(src, dst)
 }
 
 func (src *KubeadmConfigList) ConvertTo(dstRaw conversion.Hub) error {
@@ -49,13 +67,29 @@ func (dst *KubeadmConfigList) ConvertFrom(srcRaw conversion.Hub) error {
 func (src *KubeadmConfigTemplate) ConvertTo(dstRaw conversion.Hub) error {
 	dst := dstRaw.(*v1beta1.KubeadmConfigTemplate)
 
-	return Convert_v1alpha4_KubeadmConfigTemplate_To_v1beta1_KubeadmConfigTemplate(src, dst, nil)
+	if err := Convert_v1alpha4_KubeadmConfigTemplate_To_v1beta1_KubeadmConfigTemplate(src, dst, nil); err != nil {
+		return err
+	}
+
+	// Manually restore data.
+	restored := &v1beta1.KubeadmConfigTemplate{}
+	if ok, err := utilconversion.UnmarshalData(src, restored); err != nil || !ok {
+		return err
+	}
+
+	dst.Spec.Template.Spec.Ignition = restored.Spec.Template.Spec.Ignition
+
+	return nil
 }
 
 func (dst *KubeadmConfigTemplate) ConvertFrom(srcRaw conversion.Hub) error {
 	src := srcRaw.(*v1beta1.KubeadmConfigTemplate)
 
-	return Convert_v1beta1_KubeadmConfigTemplate_To_v1alpha4_KubeadmConfigTemplate(src, dst, nil)
+	if err := Convert_v1beta1_KubeadmConfigTemplate_To_v1alpha4_KubeadmConfigTemplate(src, dst, nil); err != nil {
+		return err
+	}
+	// Preserve Hub data on down-conversion except for metadata.
+	return utilconversion.MarshalData(src, dst)
 }
 
 func (src *KubeadmConfigTemplateList) ConvertTo(dstRaw conversion.Hub) error {
@@ -69,3 +103,9 @@ func (dst *KubeadmConfigTemplateList) ConvertFrom(srcRaw conversion.Hub) error {
 
 	return Convert_v1beta1_KubeadmConfigTemplateList_To_v1alpha4_KubeadmConfigTemplateList(src, dst, nil)
 }
+
+// Convert_v1beta1_KubeadmConfigSpec_To_v1alpha4_KubeadmConfigSpec is an autogenerated conversion function.
+func Convert_v1beta1_KubeadmConfigSpec_To_v1alpha4_KubeadmConfigSpec(in *v1beta1.KubeadmConfigSpec, out *KubeadmConfigSpec, s apiconversion.Scope) error {
+	// KubeadmConfigSpec.Ignition does not exist in kubeadm v1alpha4 API.
+	return autoConvert_v1beta1_KubeadmConfigSpec_To_v1alpha4_KubeadmConfigSpec(in, out, s)
+}

bootstrap/kubeadm/api/v1alpha4/conversion_test.go

@@ -28,6 +28,11 @@ import (
 	utilconversion "sigs.k8s.io/cluster-api/util/conversion"
 )
 
+const (
+	fakeID     = "abcdef"
+	fakeSecret = "abcdef0123456789"
+)
+
 func TestFuzzyConversion(t *testing.T) {
 	t.Run("for KubeadmConfig", utilconversion.FuzzTestFunc(utilconversion.FuzzTestFuncInput{
 		Hub:         &v1beta1.KubeadmConfig{},
@@ -57,6 +62,7 @@ func fuzzFuncs(_ runtimeserializer.CodecFactory) []interface{} {
 		// the values for ID and Secret to working alphanumeric values.
 		kubeadmBootstrapTokenStringFuzzerV1UpstreamBeta1,
 		kubeadmBootstrapTokenStringFuzzerV1Beta1,
+		kubeadmBootstrapTokenStringFuzzerV1Alpha4,
 	}
 }
 
@@ -75,11 +81,16 @@ func clusterConfigurationFuzzer(obj *upstreamv1beta1.ClusterConfiguration, c fuz
 }
 
 func kubeadmBootstrapTokenStringFuzzerV1UpstreamBeta1(in *upstreamv1beta1.BootstrapTokenString, c fuzz.Continue) {
-	in.ID = "abcdef"
-	in.Secret = "abcdef0123456789"
+	in.ID = fakeID
+	in.Secret = fakeSecret
 }
 
 func kubeadmBootstrapTokenStringFuzzerV1Beta1(in *v1beta1.BootstrapTokenString, c fuzz.Continue) {
-	in.ID = "abcdef"
-	in.Secret = "abcdef0123456789"
+	in.ID = fakeID
+	in.Secret = fakeSecret
+}
+
+func kubeadmBootstrapTokenStringFuzzerV1Alpha4(in *BootstrapTokenString, c fuzz.Continue) {
+	in.ID = fakeID
+	in.Secret = fakeSecret
 }

bootstrap/kubeadm/api/v1beta1/kubeadmconfig_types.go

@@ -23,12 +23,15 @@ import (
 )
 
 // Format specifies the output format of the bootstrap data
-// +kubebuilder:validation:Enum=cloud-config
+// +kubebuilder:validation:Enum=cloud-config;ignition
 type Format string
 
 const (
 	// CloudConfig make the bootstrap data to be of cloud-config format.
 	CloudConfig Format = "cloud-config"
+
+	// Ignition make the bootstrap data to be of Ignition format.
+	Ignition Format = "ignition"
 )
 
 // KubeadmConfigSpec defines the desired state of KubeadmConfig.
@@ -95,6 +98,33 @@ type KubeadmConfigSpec struct {
 	// For more information, refer to https://github.com/kubernetes-sigs/cluster-api/pull/2763#discussion_r397306055.
 	// +optional
 	UseExperimentalRetryJoin bool `json:"useExperimentalRetryJoin,omitempty"`
+
+	// Ignition contains Ignition specific configuration.
+	// +optional
+	Ignition *IgnitionSpec `json:"ignition,omitempty"`
+}
+
+// IgnitionSpec contains Ignition specific configuration.
+type IgnitionSpec struct {
+	// ContainerLinuxConfig contains CLC specific configuration.
+	// +optional
+	ContainerLinuxConfig *ContainerLinuxConfig `json:"containerLinuxConfig,omitempty"`
+}
+
+// ContainerLinuxConfig contains CLC-specific configuration.
+//
+// We use a structured type here to allow adding additional fields, for example 'version'.
+type ContainerLinuxConfig struct {
+	// AdditionalConfig contains additional configuration to be merged with the Ignition
+	// configuration generated by the bootstrapper controller. More info: https://coreos.github.io/ignition/operator-notes/#config-merging
+	//
+	// The data format is documented here: https://kinvolk.io/docs/flatcar-container-linux/latest/provisioning/cl-config/
+	// +optional
+	AdditionalConfig string `json:"additionalConfig,omitempty"`
+
+	// Strict controls if AdditionalConfig should be strictly parsed. If so, warnings are treated as errors.
+	// +optional
+	Strict bool `json:"strict,omitempty"`
 }
 
 // KubeadmConfigStatus defines the observed state of KubeadmConfig.