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dnsrecords.go
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dnsrecords.go
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// Copyright (c) Tailscale Inc & AUTHORS
// SPDX-License-Identifier: BSD-3-Clause
//go:build !plan9
// tailscale-operator provides a way to expose services running in a Kubernetes
// cluster to your Tailnet and to make Tailscale nodes available to cluster
// workloads
package main
import (
"context"
"encoding/json"
"fmt"
"slices"
"go.uber.org/zap"
corev1 "k8s.io/api/core/v1"
discoveryv1 "k8s.io/api/discovery/v1"
networkingv1 "k8s.io/api/networking/v1"
apiequality "k8s.io/apimachinery/pkg/api/equality"
apierrors "k8s.io/apimachinery/pkg/api/errors"
"k8s.io/apimachinery/pkg/types"
"k8s.io/utils/net"
"sigs.k8s.io/controller-runtime/pkg/client"
"sigs.k8s.io/controller-runtime/pkg/reconcile"
operatorutils "tailscale.com/k8s-operator"
tsapi "tailscale.com/k8s-operator/apis/v1alpha1"
"tailscale.com/util/mak"
)
const (
dnsRecordsRecocilerFinalizer = "tailscale.com/dns-records-reconciler"
annotationTSMagicDNSName = "tailscale.com/magic-dnsname"
)
// dnsRecordsReconciler knows how to update dnsrecords ConfigMap with DNS
// records.
// The records that it creates are:
// - For tailscale Ingress, a mapping of the Ingress's MagicDNSName to the IP address of
// the ingress proxy Pod.
// - For egress proxies configured via tailscale.com/tailnet-fqdn annotation, a
// mapping of the tailnet FQDN to the IP address of the egress proxy Pod.
//
// Records will only be created if there is exactly one ready
// tailscale.com/v1alpha1.DNSConfig instance in the cluster (so that we know
// that there is a ts.net nameserver deployed in the cluster).
type dnsRecordsReconciler struct {
client.Client
tsNamespace string // namespace in which we provision tailscale resources
logger *zap.SugaredLogger
isDefaultLoadBalancer bool // true if operator is the default ingress controller in this cluster
}
// Reconcile takes a reconcile.Request for a headless Service fronting a
// tailscale proxy and updates DNS Records in dnsrecords ConfigMap for the
// in-cluster ts.net nameserver if required.
func (dnsRR *dnsRecordsReconciler) Reconcile(ctx context.Context, req reconcile.Request) (res reconcile.Result, err error) {
logger := dnsRR.logger.With("Service", req.NamespacedName)
logger.Debugf("starting reconcile")
defer logger.Debugf("reconcile finished")
headlessSvc := new(corev1.Service)
err = dnsRR.Client.Get(ctx, req.NamespacedName, headlessSvc)
if apierrors.IsNotFound(err) {
logger.Debugf("Service not found")
return reconcile.Result{}, nil
}
if err != nil {
return reconcile.Result{}, fmt.Errorf("failed to get Service: %w", err)
}
if !(isManagedByType(headlessSvc, "svc") || isManagedByType(headlessSvc, "ingress")) {
logger.Debugf("Service is not a headless Service for a tailscale ingress or egress proxy; do nothing")
return reconcile.Result{}, nil
}
if !headlessSvc.DeletionTimestamp.IsZero() {
logger.Debug("Service is being deleted, clean up resources")
return reconcile.Result{}, dnsRR.maybeCleanup(ctx, headlessSvc, logger)
}
// Check that there is a ts.net nameserver deployed to the cluster by
// checking that there is tailscale.com/v1alpha1.DNSConfig resource in a
// Ready state.
dnsCfgLst := new(tsapi.DNSConfigList)
if err = dnsRR.List(ctx, dnsCfgLst); err != nil {
return reconcile.Result{}, fmt.Errorf("error listing DNSConfigs: %w", err)
}
if len(dnsCfgLst.Items) == 0 {
logger.Debugf("DNSConfig does not exist, not creating DNS records")
return reconcile.Result{}, nil
}
if len(dnsCfgLst.Items) > 1 {
logger.Errorf("Invalid cluster state - more than one DNSConfig found in cluster. Please ensure no more than one exists")
return reconcile.Result{}, nil
}
dnsCfg := dnsCfgLst.Items[0]
if !operatorutils.DNSCfgIsReady(&dnsCfg) {
logger.Info("DNSConfig is not ready yet, waiting...")
return reconcile.Result{}, nil
}
return reconcile.Result{}, dnsRR.maybeProvision(ctx, headlessSvc, logger)
}
// maybeProvision ensures that dnsrecords ConfigMap contains a record for the
// proxy associated with the headless Service.
// The record is only provisioned if the proxy is for a tailscale Ingress or
// egress configured via tailscale.com/tailnet-fqdn annotation.
//
// For Ingress, the record is a mapping between the MagicDNSName of the Ingress, retrieved from
// ingress.status.loadBalancer.ingress.hostname field and the proxy Pod IP addresses
// retrieved from the EndpoinSlice associated with this headless Service, i.e
// Records{IP4: <MagicDNS name of the Ingress>: <[IPs of the ingress proxy Pods]>}
//
// For egress, the record is a mapping between tailscale.com/tailnet-fqdn
// annotation and the proxy Pod IP addresses, retrieved from the EndpointSlice
// associated with this headless Service, i.e
// Records{IP4: {<tailscale.com/tailnet-fqdn>: <[IPs of the egress proxy Pods]>}
//
// If records need to be created for this proxy, maybeProvision will also:
// - update the headless Service with a tailscale.com/magic-dnsname annotation
// - update the headless Service with a finalizer
func (dnsRR *dnsRecordsReconciler) maybeProvision(ctx context.Context, headlessSvc *corev1.Service, logger *zap.SugaredLogger) error {
if headlessSvc == nil {
logger.Info("[unexpected] maybeProvision called with a nil Service")
return nil
}
isEgressFQDNSvc, err := dnsRR.isSvcForFQDNEgressProxy(ctx, headlessSvc)
if err != nil {
return fmt.Errorf("error checking whether the Service is for an egress proxy: %w", err)
}
if !(isEgressFQDNSvc || isManagedByType(headlessSvc, "ingress")) {
logger.Debug("Service is not fronting a proxy that we create DNS records for; do nothing")
return nil
}
fqdn, err := dnsRR.fqdnForDNSRecord(ctx, headlessSvc, logger)
if err != nil {
return fmt.Errorf("error determining DNS name for record: %w", err)
}
if fqdn == "" {
logger.Debugf("MagicDNS name does not (yet) exist, not provisioning DNS record")
return nil // a new reconcile will be triggered once it's added
}
oldHeadlessSvc := headlessSvc.DeepCopy()
// Ensure that headless Service is annotated with a finalizer to help
// with records cleanup when proxy resources are deleted.
if !slices.Contains(headlessSvc.Finalizers, dnsRecordsRecocilerFinalizer) {
headlessSvc.Finalizers = append(headlessSvc.Finalizers, dnsRecordsRecocilerFinalizer)
}
// Ensure that headless Service is annotated with the current MagicDNS
// name to help with records cleanup when proxy resources are deleted or
// MagicDNS name changes.
oldFqdn := headlessSvc.Annotations[annotationTSMagicDNSName]
if oldFqdn != "" && oldFqdn != fqdn { // i.e user has changed the value of tailscale.com/tailnet-fqdn annotation
logger.Debugf("MagicDNS name has changed, remvoving record for %s", oldFqdn)
updateFunc := func(rec *operatorutils.Records) {
delete(rec.IP4, oldFqdn)
}
if err = dnsRR.updateDNSConfig(ctx, updateFunc); err != nil {
return fmt.Errorf("error removing record for %s: %w", oldFqdn, err)
}
}
mak.Set(&headlessSvc.Annotations, annotationTSMagicDNSName, fqdn)
if !apiequality.Semantic.DeepEqual(oldHeadlessSvc, headlessSvc) {
logger.Infof("provisioning DNS record for MagicDNS name: %s", fqdn) // this will be printed exactly once
if err := dnsRR.Update(ctx, headlessSvc); err != nil {
return fmt.Errorf("error updating proxy headless Service metadata: %w", err)
}
}
// Get the Pod IP addresses for the proxy from the EndpointSlice for the
// headless Service.
labels := map[string]string{discoveryv1.LabelServiceName: headlessSvc.Name} // https://kubernetes.io/docs/concepts/services-networking/endpoint-slices/#ownership
eps, err := getSingleObject[discoveryv1.EndpointSlice](ctx, dnsRR.Client, dnsRR.tsNamespace, labels)
if err != nil {
return fmt.Errorf("error getting the EndpointSlice for the proxy's headless Service: %w", err)
}
if eps == nil {
logger.Debugf("proxy's headless Service EndpointSlice does not yet exist. We will reconcile again once it's created")
return nil
}
// An EndpointSlice for a Service can have a list of endpoints that each
// can have multiple addresses - these are the IP addresses of any Pods
// selected by that Service. Pick all the IPv4 addresses.
ips := make([]string, 0)
for _, ep := range eps.Endpoints {
for _, ip := range ep.Addresses {
if !net.IsIPv4String(ip) {
logger.Infof("EndpointSlice contains IP address %q that is not IPv4, ignoring. Currently only IPv4 is supported", ip)
} else {
ips = append(ips, ip)
}
}
}
if len(ips) == 0 {
logger.Debugf("EndpointSlice for the Service contains no IPv4 addresses. We will reconcile again once they are created.")
return nil
}
updateFunc := func(rec *operatorutils.Records) {
mak.Set(&rec.IP4, fqdn, ips)
}
if err = dnsRR.updateDNSConfig(ctx, updateFunc); err != nil {
return fmt.Errorf("error updating DNS records: %w", err)
}
return nil
}
// maybeCleanup ensures that the DNS record for the proxy has been removed from
// dnsrecords ConfigMap and the tailscale.com/dns-records-reconciler finalizer
// has been removed from the Service. If the record is not found in the
// ConfigMap, the ConfigMap does not exist, or the Service does not have
// tailscale.com/magic-dnsname annotation, just remove the finalizer.
func (h *dnsRecordsReconciler) maybeCleanup(ctx context.Context, headlessSvc *corev1.Service, logger *zap.SugaredLogger) error {
ix := slices.Index(headlessSvc.Finalizers, dnsRecordsRecocilerFinalizer)
if ix == -1 {
logger.Debugf("no finalizer, nothing to do")
return nil
}
cm := &corev1.ConfigMap{}
err := h.Client.Get(ctx, types.NamespacedName{Name: operatorutils.DNSRecordsCMName, Namespace: h.tsNamespace}, cm)
if apierrors.IsNotFound(err) {
logger.Debug("'dsnrecords' ConfigMap not found")
return h.removeHeadlessSvcFinalizer(ctx, headlessSvc)
}
if err != nil {
return fmt.Errorf("error retrieving 'dnsrecords' ConfigMap: %w", err)
}
if cm.Data == nil {
logger.Debug("'dnsrecords' ConfigMap contains no records")
return h.removeHeadlessSvcFinalizer(ctx, headlessSvc)
}
_, ok := cm.Data[operatorutils.DNSRecordsCMKey]
if !ok {
logger.Debug("'dnsrecords' ConfigMap contains no records")
return h.removeHeadlessSvcFinalizer(ctx, headlessSvc)
}
fqdn, _ := headlessSvc.GetAnnotations()[annotationTSMagicDNSName]
if fqdn == "" {
return h.removeHeadlessSvcFinalizer(ctx, headlessSvc)
}
logger.Infof("removing DNS record for MagicDNS name %s", fqdn)
updateFunc := func(rec *operatorutils.Records) {
delete(rec.IP4, fqdn)
}
if err = h.updateDNSConfig(ctx, updateFunc); err != nil {
return fmt.Errorf("error updating DNS config: %w", err)
}
return h.removeHeadlessSvcFinalizer(ctx, headlessSvc)
}
func (dnsRR *dnsRecordsReconciler) removeHeadlessSvcFinalizer(ctx context.Context, headlessSvc *corev1.Service) error {
idx := slices.Index(headlessSvc.Finalizers, dnsRecordsRecocilerFinalizer)
if idx == -1 {
return nil
}
headlessSvc.Finalizers = append(headlessSvc.Finalizers[:idx], headlessSvc.Finalizers[idx+1:]...)
return dnsRR.Update(ctx, headlessSvc)
}
// fqdnForDNSRecord returns MagicDNS name associated with a given headless Service.
// If the headless Service is for a tailscale Ingress proxy, returns ingress.status.loadBalancer.ingress.hostname.
// If the headless Service is for an tailscale egress proxy configured via tailscale.com/tailnet-fqdn annotation, returns the annotation value.
// This function is not expected to be called with headless Services for other
// proxy types, or any other Services, but it just returns an empty string if
// that happens.
func (dnsRR *dnsRecordsReconciler) fqdnForDNSRecord(ctx context.Context, headlessSvc *corev1.Service, logger *zap.SugaredLogger) (string, error) {
parentName := parentFromObjectLabels(headlessSvc)
if isManagedByType(headlessSvc, "ingress") {
ing := new(networkingv1.Ingress)
if err := dnsRR.Get(ctx, parentName, ing); err != nil {
return "", err
}
if len(ing.Status.LoadBalancer.Ingress) == 0 {
return "", nil
}
return ing.Status.LoadBalancer.Ingress[0].Hostname, nil
}
if isManagedByType(headlessSvc, "svc") {
svc := new(corev1.Service)
if err := dnsRR.Get(ctx, parentName, svc); apierrors.IsNotFound(err) {
logger.Info("[unexpected] parent Service for egress proxy %s not found", headlessSvc.Name)
return "", nil
} else if err != nil {
return "", err
}
return svc.Annotations[AnnotationTailnetTargetFQDN], nil
}
return "", nil
}
// updateDNSConfig runs the provided update function against dnsrecords
// ConfigMap. At this point the in-cluster ts.net nameserver is expected to be
// successfully created together with the ConfigMap.
func (dnsRR *dnsRecordsReconciler) updateDNSConfig(ctx context.Context, update func(*operatorutils.Records)) error {
cm := &corev1.ConfigMap{}
err := dnsRR.Get(ctx, types.NamespacedName{Name: operatorutils.DNSRecordsCMName, Namespace: dnsRR.tsNamespace}, cm)
if apierrors.IsNotFound(err) {
dnsRR.logger.Info("[unexpected] dnsrecords ConfigMap not found in cluster. Not updating DNS records. Please open an isue and attach operator logs.")
return nil
}
if err != nil {
return fmt.Errorf("error retrieving dnsrecords ConfigMap: %w", err)
}
dnsRecords := operatorutils.Records{Version: operatorutils.Alpha1Version, IP4: map[string][]string{}}
if cm.Data != nil && cm.Data[operatorutils.DNSRecordsCMKey] != "" {
if err := json.Unmarshal([]byte(cm.Data[operatorutils.DNSRecordsCMKey]), &dnsRecords); err != nil {
return err
}
}
update(&dnsRecords)
dnsRecordsBs, err := json.Marshal(dnsRecords)
if err != nil {
return fmt.Errorf("error marshalling DNS records: %w", err)
}
mak.Set(&cm.Data, operatorutils.DNSRecordsCMKey, string(dnsRecordsBs))
return dnsRR.Update(ctx, cm)
}
// isSvcForFQDNEgressProxy returns true if the Service is a headless Service
// created for a proxy for a tailscale egress Service configured via
// tailscale.com/tailnet-fqdn annotation.
func (dnsRR *dnsRecordsReconciler) isSvcForFQDNEgressProxy(ctx context.Context, svc *corev1.Service) (bool, error) {
if !isManagedByType(svc, "svc") {
return false, nil
}
parentName := parentFromObjectLabels(svc)
parentSvc := new(corev1.Service)
if err := dnsRR.Get(ctx, parentName, parentSvc); apierrors.IsNotFound(err) {
return false, nil
} else if err != nil {
return false, err
}
annots := parentSvc.Annotations
return annots != nil && annots[AnnotationTailnetTargetFQDN] != "", nil
}