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cmd/k8s-operator: fix DNS reconciler for dual-stack clusters (#13057)

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* cmd/k8s-operator: fix DNS reconciler for dual-stack clusters

This fixes a bug where DNS reconciler logic was always assuming
that no more than one EndpointSlice exists for a Service.
In fact, there can be multiple, for example, in dual-stack
clusters, but also in other cases this is valid (as per kube docs).
This PR:
- allows for multiple EndpointSlices
- picks out the ones for IPv4 family
- deduplicates addresses

Updates tailscale/tailscale#13056

Signed-off-by: Irbe Krumina <irbe@tailscale.com>
Co-authored-by: Tom Proctor <tomhjp@users.noreply.github.com>
This commit is contained in:
Irbe Krumina 2024-08-13 20:42:01 +03:00 committed by GitHub
parent 9f1d9d324d
commit adbab25bac
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GPG Key ID: B5690EEEBB952194
2 changed files with 68 additions and 22 deletions
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57
cmd/k8s-operator/dnsrecords.go
View File

@ -24,6 +24,7 @@
operatorutils "tailscale.com/k8s-operator"
tsapi "tailscale.com/k8s-operator/apis/v1alpha1"
"tailscale.com/util/mak"
"tailscale.com/util/set"
)
const (
@ -167,36 +168,49 @@ func (dnsRR *dnsRecordsReconciler) maybeProvision(ctx context.Context, headlessS
}
}
// Get the Pod IP addresses for the proxy from the EndpointSlice for the
// headless Service.
// Get the Pod IP addresses for the proxy from the EndpointSlices for
// the headless Service. The Service can have multiple EndpointSlices
// associated with it, for example in dual-stack clusters.
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)
var eps = new(discoveryv1.EndpointSliceList)
if err := dnsRR.List(ctx, eps, client.InNamespace(dnsRR.tsNamespace), client.MatchingLabels(labels)); err != nil {
return fmt.Errorf("error listing EndpointSlices for the proxy's headless Service: %w", err)
}
if eps == nil {
if len(eps.Items) == 0 {
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
// Each 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)
// It is also possible that multiple EndpointSlices have overlapping addresses.
// https://kubernetes.io/docs/concepts/services-networking/endpoint-slices/#duplicate-endpoints
ips := make(set.Set[string], 0)
for _, slice := range eps.Items {
if slice.AddressType != discoveryv1.AddressTypeIPv4 {
logger.Infof("EndpointSlice is for AddressType %s, currently only IPv4 address type is supported", slice.AddressType)
continue
}
for _, ep := range slice.Endpoints {
if !epIsReady(&ep) {
logger.Debugf("Endpoint with addresses %v appears not ready to receive traffic %v", ep.Addresses, ep.Conditions.String())
continue
}
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.Add(ip)
}
}
}
}
if len(ips) == 0 {
if ips.Len() == 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)
mak.Set(&rec.IP4, fqdn, ips.Slice())
}
if err = dnsRR.updateDNSConfig(ctx, updateFunc); err != nil {
return fmt.Errorf("error updating DNS records: %w", err)
@ -204,6 +218,17 @@ func (dnsRR *dnsRecordsReconciler) maybeProvision(ctx context.Context, headlessS
return nil
}
// epIsReady reports whether the endpoint is currently in a state to receive new
// traffic. As per kube docs, only explicitly set 'false' for 'Ready' or
// 'Serving' conditions or explicitly set 'true' for 'Terminating' condition
// means that the Endpoint is NOT ready.
// https://github.com/kubernetes/kubernetes/blob/60c4c2b2521fb454ce69dee737e3eb91a25e0535/pkg/apis/discovery/types.go#L109-L131
func epIsReady(ep *discoveryv1.Endpoint) bool {
return (ep.Conditions.Ready == nil || *ep.Conditions.Ready) &&
(ep.Conditions.Serving == nil || *ep.Conditions.Serving) &&
(ep.Conditions.Terminating == nil || !*ep.Conditions.Terminating)
}
// 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

33
cmd/k8s-operator/dnsrecords_test.go
View File

@ -8,6 +8,7 @@
import (
"context"
"encoding/json"
"fmt"
"testing"
"github.com/google/go-cmp/cmp"
@ -87,13 +88,16 @@ func TestDNSRecordsReconciler(t *testing.T) {
},
}
headlessForEgressSvcFQDN := headlessSvcForParent(egressSvcFQDN, "svc") // create the proxy headless Service
ep := endpointSliceForService(headlessForEgressSvcFQDN, "10.9.8.7")
ep := endpointSliceForService(headlessForEgressSvcFQDN, "10.9.8.7", discoveryv1.AddressTypeIPv4)
epv6 := endpointSliceForService(headlessForEgressSvcFQDN, "2600:1900:4011:161:0:d:0:d", discoveryv1.AddressTypeIPv6)
mustCreate(t, fc, egressSvcFQDN)
mustCreate(t, fc, headlessForEgressSvcFQDN)
mustCreate(t, fc, ep)
mustCreate(t, fc, epv6)
expectReconciled(t, dnsRR, "tailscale", "egress-fqdn") // dns-records-reconciler reconcile the headless Service
// ConfigMap should now have a record for foo.bar.ts.net -> 10.8.8.7
wantHosts := map[string][]string{"foo.bar.ts.net": {"10.9.8.7"}}
wantHosts := map[string][]string{"foo.bar.ts.net": {"10.9.8.7"}} // IPv6 endpoint is currently ignored
expectHostsRecords(t, fc, wantHosts)
// 2. DNS record is updated if tailscale.com/tailnet-fqdn annotation's
@ -106,7 +110,7 @@ func TestDNSRecordsReconciler(t *testing.T) {
expectHostsRecords(t, fc, wantHosts)
// 3. DNS record is updated if the IP address of the proxy Pod changes.
ep = endpointSliceForService(headlessForEgressSvcFQDN, "10.6.5.4")
ep = endpointSliceForService(headlessForEgressSvcFQDN, "10.6.5.4", discoveryv1.AddressTypeIPv4)
mustUpdate(t, fc, ep.Namespace, ep.Name, func(ep *discoveryv1.EndpointSlice) {
ep.Endpoints[0].Addresses = []string{"10.6.5.4"}
})
@ -116,7 +120,7 @@ func TestDNSRecordsReconciler(t *testing.T) {
// 4. DNS record is created for an ingress proxy configured via Ingress
headlessForIngress := headlessSvcForParent(ing, "ingress")
ep = endpointSliceForService(headlessForIngress, "10.9.8.7")
ep = endpointSliceForService(headlessForIngress, "10.9.8.7", discoveryv1.AddressTypeIPv4)
mustCreate(t, fc, headlessForIngress)
mustCreate(t, fc, ep)
expectReconciled(t, dnsRR, "tailscale", "ts-ingress") // dns-records-reconciler should reconcile the headless Service
@ -140,6 +144,17 @@ func TestDNSRecordsReconciler(t *testing.T) {
expectReconciled(t, dnsRR, "tailscale", "ts-ingress")
wantHosts["another.ingress.ts.net"] = []string{"7.8.9.10"}
expectHostsRecords(t, fc, wantHosts)
// 7. A not-ready Endpoint is removed from DNS config.
mustUpdate(t, fc, ep.Namespace, ep.Name, func(ep *discoveryv1.EndpointSlice) {
ep.Endpoints[0].Conditions.Ready = ptr.To(false)
ep.Endpoints = append(ep.Endpoints, discoveryv1.Endpoint{
Addresses: []string{"1.2.3.4"},
})
})
expectReconciled(t, dnsRR, "tailscale", "ts-ingress")
wantHosts["another.ingress.ts.net"] = []string{"1.2.3.4"}
expectHostsRecords(t, fc, wantHosts)
}
func headlessSvcForParent(o client.Object, typ string) *corev1.Service {
@ -162,15 +177,21 @@ func headlessSvcForParent(o client.Object, typ string) *corev1.Service {
}
}
func endpointSliceForService(svc *corev1.Service, ip string) *discoveryv1.EndpointSlice {
func endpointSliceForService(svc *corev1.Service, ip string, fam discoveryv1.AddressType) *discoveryv1.EndpointSlice {
return &discoveryv1.EndpointSlice{
ObjectMeta: metav1.ObjectMeta{
Name: svc.Name,
Name: fmt.Sprintf("%s-%s", svc.Name, string(fam)),
Namespace: svc.Namespace,
Labels: map[string]string{discoveryv1.LabelServiceName: svc.Name},
},
AddressType: fam,
Endpoints: []discoveryv1.Endpoint{{
Addresses: []string{ip},
Conditions: discoveryv1.EndpointConditions{
Ready: ptr.To(true),
Serving: ptr.To(true),
Terminating: ptr.To(false),
},
}},
}
}