cmd/{k8s-nameserver,k8s-operator},k8s-operator: add a kube nameserver, make operator deploy it (#11919)

* cmd/k8s-nameserver,k8s-operator: add a nameserver that can resolve ts.net DNS names in cluster.

Adds a simple nameserver that can respond to A record queries for ts.net DNS names.
It can respond to queries from in-memory records, populated from a ConfigMap
mounted at /config. It dynamically updates its records as the ConfigMap
contents changes.
It will respond with NXDOMAIN to queries for any other record types
(AAAA to be implemented in the future).
It can respond to queries over UDP or TCP. It runs a miekg/dns
DNS server with a single registered handler for ts.net domain names.
Queries for other domain names will be refused.

The intended use of this is:
1) to allow non-tailnet cluster workloads to talk to HTTPS tailnet
services exposed via Tailscale operator egress over HTTPS
2) to allow non-tailnet cluster workloads to talk to workloads in
the same cluster that have been exposed to tailnet over their
MagicDNS names but on their cluster IPs.

DNSConfig CRD can be used to configure
the operator to deploy kube nameserver (./cmd/k8s-nameserver) to cluster.

Updates tailscale/tailscale#10499

Signed-off-by: Irbe Krumina <irbe@tailscale.com>

k8s-operator/apis/v1alpha1/register.go

@@ -49,7 +49,7 @@ func init() {
 
 // Adds the list of known types to api.Scheme.
 func addKnownTypes(scheme *runtime.Scheme) error {
-	scheme.AddKnownTypes(SchemeGroupVersion, &Connector{}, &ConnectorList{}, &ProxyClass{}, &ProxyClassList{})
+	scheme.AddKnownTypes(SchemeGroupVersion, &Connector{}, &ConnectorList{}, &ProxyClass{}, &ProxyClassList{}, &DNSConfig{}, &DNSConfigList{})
 
 	metav1.AddToGroupVersion(scheme, SchemeGroupVersion)
 	return nil

k8s-operator/apis/v1alpha1/types_tsdnsconfig.go

@@ -0,0 +1,71 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build !plan9
+
+package v1alpha1
+
+import (
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+)
+
+// Code comments on these types should be treated as user facing documentation-
+// they will appear on the DNSConfig CRD i.e if someone runs kubectl explain dnsconfig.
+
+var DNSConfigKind = "DNSConfig"
+
+// +kubebuilder:object:root=true
+// +kubebuilder:subresource:status
+// +kubebuilder:resource:scope=Cluster,shortName=dc
+// +kubebuilder:printcolumn:name="NameserverIP",type="string",JSONPath=`.status.nameserverStatus.ip`,description="Service IP address of the nameserver"
+
+type DNSConfig struct {
+	metav1.TypeMeta   `json:",inline"`
+	metav1.ObjectMeta `json:"metadata,omitempty"`
+
+	Spec DNSConfigSpec `json:"spec"`
+
+	// +optional
+	Status DNSConfigStatus `json:"status"`
+}
+
+// +kubebuilder:object:root=true
+
+type DNSConfigList struct {
+	metav1.TypeMeta `json:",inline"`
+	metav1.ListMeta `json:"metadata"`
+
+	Items []DNSConfig `json:"items"`
+}
+
+type DNSConfigSpec struct {
+	Nameserver *Nameserver `json:"nameserver"`
+}
+
+type Nameserver struct {
+	// +optional
+	Image *Image `json:"image,omitempty"`
+}
+
+type Image struct {
+	// +optional
+	Repo string `json:"repo,omitempty"`
+	// +optional
+	Tag string `json:"tag,omitempty"`
+}
+
+type DNSConfigStatus struct {
+	// +listType=map
+	// +listMapKey=type
+	// +optional
+	Conditions []ConnectorCondition `json:"conditions"`
+	// +optional
+	NameserverStatus *NameserverStatus `json:"nameserverStatus"`
+}
+
+type NameserverStatus struct {
+	// +optional
+	IP string `json:"ip"`
+}
+
+const NameserverReady ConnectorConditionType = `NameserverReady`

k8s-operator/apis/v1alpha1/zz_generated.deepcopy.go

@@ -163,6 +163,112 @@ func (in *Container) DeepCopy() *Container {
 	return out
 }
 
+// DeepCopyInto is an autogenerated deepcopy function, copying the receiver, writing into out. in must be non-nil.
+func (in *DNSConfig) DeepCopyInto(out *DNSConfig) {
+	*out = *in
+	out.TypeMeta = in.TypeMeta
+	in.ObjectMeta.DeepCopyInto(&out.ObjectMeta)
+	in.Spec.DeepCopyInto(&out.Spec)
+	in.Status.DeepCopyInto(&out.Status)
+}
+
+// DeepCopy is an autogenerated deepcopy function, copying the receiver, creating a new DNSConfig.
+func (in *DNSConfig) DeepCopy() *DNSConfig {
+	if in == nil {
+		return nil
+	}
+	out := new(DNSConfig)
+	in.DeepCopyInto(out)
+	return out
+}
+
+// DeepCopyObject is an autogenerated deepcopy function, copying the receiver, creating a new runtime.Object.
+func (in *DNSConfig) DeepCopyObject() runtime.Object {
+	if c := in.DeepCopy(); c != nil {
+		return c
+	}
+	return nil
+}
+
+// DeepCopyInto is an autogenerated deepcopy function, copying the receiver, writing into out. in must be non-nil.
+func (in *DNSConfigList) DeepCopyInto(out *DNSConfigList) {
+	*out = *in
+	out.TypeMeta = in.TypeMeta
+	in.ListMeta.DeepCopyInto(&out.ListMeta)
+	if in.Items != nil {
+		in, out := &in.Items, &out.Items
+		*out = make([]DNSConfig, len(*in))
+		for i := range *in {
+			(*in)[i].DeepCopyInto(&(*out)[i])
+		}
+	}
+}
+
+// DeepCopy is an autogenerated deepcopy function, copying the receiver, creating a new DNSConfigList.
+func (in *DNSConfigList) DeepCopy() *DNSConfigList {
+	if in == nil {
+		return nil
+	}
+	out := new(DNSConfigList)
+	in.DeepCopyInto(out)
+	return out
+}
+
+// DeepCopyObject is an autogenerated deepcopy function, copying the receiver, creating a new runtime.Object.
+func (in *DNSConfigList) DeepCopyObject() runtime.Object {
+	if c := in.DeepCopy(); c != nil {
+		return c
+	}
+	return nil
+}
+
+// DeepCopyInto is an autogenerated deepcopy function, copying the receiver, writing into out. in must be non-nil.
+func (in *DNSConfigSpec) DeepCopyInto(out *DNSConfigSpec) {
+	*out = *in
+	if in.Nameserver != nil {
+		in, out := &in.Nameserver, &out.Nameserver
+		*out = new(Nameserver)
+		(*in).DeepCopyInto(*out)
+	}
+}
+
+// DeepCopy is an autogenerated deepcopy function, copying the receiver, creating a new DNSConfigSpec.
+func (in *DNSConfigSpec) DeepCopy() *DNSConfigSpec {
+	if in == nil {
+		return nil
+	}
+	out := new(DNSConfigSpec)
+	in.DeepCopyInto(out)
+	return out
+}
+
+// DeepCopyInto is an autogenerated deepcopy function, copying the receiver, writing into out. in must be non-nil.
+func (in *DNSConfigStatus) DeepCopyInto(out *DNSConfigStatus) {
+	*out = *in
+	if in.Conditions != nil {
+		in, out := &in.Conditions, &out.Conditions
+		*out = make([]ConnectorCondition, len(*in))
+		for i := range *in {
+			(*in)[i].DeepCopyInto(&(*out)[i])
+		}
+	}
+	if in.NameserverStatus != nil {
+		in, out := &in.NameserverStatus, &out.NameserverStatus
+		*out = new(NameserverStatus)
+		**out = **in
+	}
+}
+
+// DeepCopy is an autogenerated deepcopy function, copying the receiver, creating a new DNSConfigStatus.
+func (in *DNSConfigStatus) DeepCopy() *DNSConfigStatus {
+	if in == nil {
+		return nil
+	}
+	out := new(DNSConfigStatus)
+	in.DeepCopyInto(out)
+	return out
+}
+
 // DeepCopyInto is an autogenerated deepcopy function, copying the receiver, writing into out. in must be non-nil.
 func (in *Env) DeepCopyInto(out *Env) {
 	*out = *in
@@ -178,6 +284,21 @@ func (in *Env) DeepCopy() *Env {
 	return out
 }
 
+// DeepCopyInto is an autogenerated deepcopy function, copying the receiver, writing into out. in must be non-nil.
+func (in *Image) DeepCopyInto(out *Image) {
+	*out = *in
+}
+
+// DeepCopy is an autogenerated deepcopy function, copying the receiver, creating a new Image.
+func (in *Image) DeepCopy() *Image {
+	if in == nil {
+		return nil
+	}
+	out := new(Image)
+	in.DeepCopyInto(out)
+	return out
+}
+
 // DeepCopyInto is an autogenerated deepcopy function, copying the receiver, writing into out. in must be non-nil.
 func (in *Metrics) DeepCopyInto(out *Metrics) {
 	*out = *in
@@ -193,6 +314,41 @@ func (in *Metrics) DeepCopy() *Metrics {
 	return out
 }
 
+// DeepCopyInto is an autogenerated deepcopy function, copying the receiver, writing into out. in must be non-nil.
+func (in *Nameserver) DeepCopyInto(out *Nameserver) {
+	*out = *in
+	if in.Image != nil {
+		in, out := &in.Image, &out.Image
+		*out = new(Image)
+		**out = **in
+	}
+}
+
+// DeepCopy is an autogenerated deepcopy function, copying the receiver, creating a new Nameserver.
+func (in *Nameserver) DeepCopy() *Nameserver {
+	if in == nil {
+		return nil
+	}
+	out := new(Nameserver)
+	in.DeepCopyInto(out)
+	return out
+}
+
+// DeepCopyInto is an autogenerated deepcopy function, copying the receiver, writing into out. in must be non-nil.
+func (in *NameserverStatus) DeepCopyInto(out *NameserverStatus) {
+	*out = *in
+}
+
+// DeepCopy is an autogenerated deepcopy function, copying the receiver, creating a new NameserverStatus.
+func (in *NameserverStatus) DeepCopy() *NameserverStatus {
+	if in == nil {
+		return nil
+	}
+	out := new(NameserverStatus)
+	in.DeepCopyInto(out)
+	return out
+}
+
 // DeepCopyInto is an autogenerated deepcopy function, copying the receiver, writing into out. in must be non-nil.
 func (in *Pod) DeepCopyInto(out *Pod) {
 	*out = *in