Add IPv6 support

This commits adds allows kind to create IPv6 Kubernetes clusters
and makes the code ready to implement dual stack support. For simplicity,
only one address of each ip family is considered.

It adds 2 new options to the v1alpha3 API: ipFamily and serviceSubnet

pkg/cluster/config/fuzzer/fuzzer.go

@@ -42,6 +42,8 @@ func fuzzConfig(obj *config.Cluster, c fuzz.Continue) {
 	}}
 	obj.Networking.APIServerAddress = "127.0.0.1"
 	obj.Networking.PodSubnet = "10.244.0.0/16"
+	obj.Networking.ServiceSubnet = "10.96.0.0/12"
+	obj.Networking.IPFamily = "ipv4"
 }
 
 func fuzzNode(obj *config.Node, c fuzz.Continue) {

pkg/cluster/config/types.go

@@ -88,6 +88,8 @@ const (
 
 // Networking contains cluster wide network settings
 type Networking struct {
+	// IPFamily is the network cluster model, currently it can be ipv4 or ipv6
+	IPFamily ClusterIPFamily
 	// APIServerPort is the listen port on the host for the Kubernetes API Server
 	// Defaults to a random port on the host
 	APIServerPort int32
@@ -99,7 +101,20 @@ type Networking struct {
 	// PodSubnet is the CIDR used for pod IPs
 	// kind will select a default if unspecified
 	PodSubnet string
+	// ServiceSubnet is the CIDR used for services VIPs
+	// kind will select a default if unspecified
+	ServiceSubnet string
 	// If DisableDefaultCNI is true, kind will not install the default CNI setup.
 	// Instead the user should install their own CNI after creating the cluster.
 	DisableDefaultCNI bool
 }
+
+// ClusterIPFamily defines cluster network IP family
+type ClusterIPFamily string
+
+const (
+	// IPv4Family sets ClusterIPFamily to ipv4
+	IPv4Family ClusterIPFamily = "ipv4"
+	// IPv6Family sets ClusterIPFamily to ipv6
+	IPv6Family ClusterIPFamily = "ipv6"
+)

pkg/cluster/config/v1alpha3/types.go

@@ -88,6 +88,8 @@ const (
 
 // Networking contains cluster wide network settings
 type Networking struct {
+	// IPFamily is the network cluster model, currently it can be ipv4 or ipv6
+	IPFamily ClusterIPFamily `json:"ipFamily,omitempty"`
 	// APIServerPort is the listen port on the host for the Kubernetes API Server
 	// Defaults to a random port on the host
 	APIServerPort int32 `json:"apiServerPort,omitempty"`
@@ -99,7 +101,20 @@ type Networking struct {
 	// PodSubnet is the CIDR used for pod IPs
 	// kind will select a default if unspecified
 	PodSubnet string `json:"podSubnet,omitempty"`
+	// ServiceSubnet is the CIDR used for services VIPs
+	// kind will select a default if unspecified for IPv6
+	ServiceSubnet string `json:"serviceSubnet,omitempty"`
 	// If DisableDefaultCNI is true, kind will not install the default CNI setup.
 	// Instead the user should install their own CNI after creating the cluster.
 	DisableDefaultCNI bool `json:"disableDefaultCNI,omitempty"`
 }
+
+// ClusterIPFamily defines cluster network IP family
+type ClusterIPFamily string
+
+const (
+	// IPv4Family sets ClusterIPFamily to ipv4
+	IPv4Family ClusterIPFamily = "ipv4"
+	// IPv6Family sets ClusterIPFamily to ipv6
+	IPv6Family ClusterIPFamily = "ipv6"
+)

pkg/cluster/config/validate.go

@@ -54,6 +54,10 @@ func (c *Cluster) Validate() error {
 	if _, _, err := net.ParseCIDR(c.Networking.PodSubnet); err != nil {
 		errs = append(errs, errors.Wrapf(err, "invalid podSubnet"))
 	}
+	// serviceSubnet should be a valid CIDR
+	if _, _, err := net.ParseCIDR(c.Networking.ServiceSubnet); err != nil {
+		errs = append(errs, errors.Wrapf(err, "invalid serviceSubnet"))
+	}
 
 	if len(errs) > 0 {
 		return util.NewErrors(errs)

pkg/cluster/internal/create/actions/config/config.go

@@ -65,13 +65,19 @@ func (a *Action) Execute(ctx *actions.ActionContext) error {
 		return errors.Wrap(err, "failed to get kubernetes version from node")
 	}
 
-	// get the control plane endpoint
-	controlPlaneEndpoint, err := nodes.GetControlPlaneEndpoint(allNodes)
+	// get the control plane endpoint, in case the cluster has an external load balancer in
+	// front of the control-plane nodes
+	controlPlaneEndpoint, controlPlaneEndpointIPv6, err := nodes.GetControlPlaneEndpoint(allNodes)
 	if err != nil {
 		// TODO(bentheelder): logging here
 		return err
 	}
 
+	// configure the right protocol addresses
+	if ctx.Config.Networking.IPFamily == "ipv6" {
+		controlPlaneEndpoint = controlPlaneEndpointIPv6
+	}
+
 	// create kubeadm init config
 	fns := []func() error{}
 
@@ -83,7 +89,9 @@ func (a *Action) Execute(ctx *actions.ActionContext) error {
 		APIServerAddress:     ctx.Config.Networking.APIServerAddress,
 		Token:                kubeadm.Token,
 		PodSubnet:            ctx.Config.Networking.PodSubnet,
+		ServiceSubnet:        ctx.Config.Networking.ServiceSubnet,
 		ControlPlane:         true,
+		IPv6:                 ctx.Config.Networking.IPFamily == "ipv6",
 	}
 
 	fns = append(fns, func() error {
@@ -193,12 +201,16 @@ func setPatchNames(patches []string, jsonPatches []kustomize.PatchJSON6902) ([]s
 // writeKubeadmConfig writes the kubeadm configuration in the specified node
 func writeKubeadmConfig(cfg *config.Cluster, data kubeadm.ConfigData, node *nodes.Node) error {
 	// get the node ip address
-	nodeAddress, err := node.IP()
+	nodeAddress, nodeAddressIPv6, err := node.IP()
 	if err != nil {
 		return errors.Wrap(err, "failed to get IP for node")
 	}
 
 	data.NodeAddress = nodeAddress
+	// configure the right protocol addresses
+	if cfg.Networking.IPFamily == "ipv6" {
+		data.NodeAddress = nodeAddressIPv6
+	}
 
 	kubeadmConfig, err := getKubeadmConfig(cfg, data)
 

pkg/cluster/internal/create/actions/loadbalancer/loadbalancer.go

@@ -57,6 +57,12 @@ func (a *Action) Execute(ctx *actions.ActionContext) error {
 		return nil
 	}
 
+	// obtain IP family
+	ipv6 := false
+	if ctx.Config.Networking.IPFamily == "ipv6" {
+		ipv6 = true
+	}
+
 	// otherwise notify the user
 	ctx.Status.Start("Configuring the external load balancer ⚖️")
 	defer ctx.Status.End(false)
@@ -71,17 +77,23 @@ func (a *Action) Execute(ctx *actions.ActionContext) error {
 		return err
 	}
 	for _, n := range controlPlaneNodes {
-		controlPlaneIP, err := n.IP()
+		controlPlaneIPv4, controlPlaneIPv6, err := n.IP()
 		if err != nil {
 			return errors.Wrapf(err, "failed to get IP for node %s", n.Name())
 		}
-		backendServers[n.Name()] = fmt.Sprintf("%s:%d", controlPlaneIP, kubeadm.APIServerPort)
+		if controlPlaneIPv4 != "" && !ipv6 {
+			backendServers[n.Name()] = fmt.Sprintf("%s:%d", controlPlaneIPv4, kubeadm.APIServerPort)
+		}
+		if controlPlaneIPv6 != "" && ipv6 {
+			backendServers[n.Name()] = fmt.Sprintf("[%s]:%d", controlPlaneIPv6, kubeadm.APIServerPort)
+		}
 	}
 
 	// create loadbalancer config data
 	loadbalancerConfig, err := loadbalancer.Config(&loadbalancer.ConfigData{
 		ControlPlanePort: loadbalancer.ControlPlanePort,
 		BackendServers:   backendServers,
+		IPv6:             ipv6,
 	})
 	if err != nil {
 		return errors.Wrap(err, "failed to generate loadbalancer config data")

pkg/cluster/internal/create/nodes.go

@@ -103,9 +103,16 @@ func createNodeContainers(
 		desiredNode := desiredNode // capture loop variable
 		fns = append(fns, func() error {
 			// create the node into a container (~= docker run -d)
-			_, err := desiredNode.Create(clusterLabel)
+			node, err := desiredNode.Create(clusterLabel)
+			if err != nil {
+				return err
+			}
+			if desiredNode.IPv6 {
+				err = node.EnableIPv6()
+			}
 			return err
 		})
+
 	}
 	if err := concurrent.UntilError(fns); err != nil {
 		return err
@@ -125,6 +132,7 @@ type nodeSpec struct {
 	// TODO(bentheelder): replace with a cri.PortMapping when we have that
 	APIServerPort    int32
 	APIServerAddress string
+	IPv6             bool
 }
 
 func nodesToCreate(cfg *config.Cluster, clusterName string) []nodeSpec {
@@ -154,6 +162,11 @@ func nodesToCreate(cfg *config.Cluster, clusterName string) []nodeSpec {
 		}
 	}
 	isHA := controlPlanes > 1
+	// obtain IP family
+	ipv6 := false
+	if cfg.Networking.IPFamily == "ipv6" {
+		ipv6 = true
+	}
 
 	// add all of the config nodes as desired nodes
 	for _, configNode := range configNodes {
@@ -173,6 +186,7 @@ func nodesToCreate(cfg *config.Cluster, clusterName string) []nodeSpec {
 			ExtraMounts:      configNode.ExtraMounts,
 			APIServerAddress: apiServerAddress,
 			APIServerPort:    apiServerPort,
+			IPv6:             ipv6,
 		})
 	}
 
@@ -186,6 +200,7 @@ func nodesToCreate(cfg *config.Cluster, clusterName string) []nodeSpec {
 			ExtraMounts:      []cri.Mount{},
 			APIServerAddress: cfg.Networking.APIServerAddress,
 			APIServerPort:    cfg.Networking.APIServerPort,
+			IPv6:             ipv6,
 		})
 	}