Add brackets around IPv6 kube-dns liveness probe addrs

When a Kubernetes cluster is instantiated in IPv6-only mode
via 'kubeadm init ...', the liveness probes that are
configured by kubeadm for kube-dns currently use IP:port
strings of "::1:53" and "::1:10053". These IP:port strings should
instead include brackets around the ::1 IPv6 loopback address, e.g.
"[::1]:53" and "[::1]:10053".

This change adds the necessary brackets around the ::1 IPv6 loopback
address.

Without this change, the kube-dns sidecar container interprets the
bracket-less strings as IPv4 IP:port strings that have too many
colons, and the kube-dns pod is restarted about once every 2 minutes.

fixes #56543

/area ipv6
/sig network

cmd/kubeadm/app/phases/addons/dns/dns.go

@@ -63,22 +63,25 @@ func kubeDNSAddon(cfg *kubeadmapi.MasterConfiguration, client clientset.Interfac
 		return err
 	}
 
-	var dnsBindAddr string
+	var dnsBindAddr, dnsProbeAddr string
 	if dnsip.To4() == nil {
 		dnsBindAddr = "::1"
+		dnsProbeAddr = "[" + dnsBindAddr + "]"
 	} else {
 		dnsBindAddr = "127.0.0.1"
+		dnsProbeAddr = dnsBindAddr
 	}
 
 	// Get the YAML manifest conditionally based on the k8s version
 	kubeDNSDeploymentBytes := GetKubeDNSManifest(k8sVersion)
 	dnsDeploymentBytes, err := kubeadmutil.ParseTemplate(kubeDNSDeploymentBytes,
-		struct{ ImageRepository, Arch, Version, DNSBindAddr, DNSDomain, DNSProbeType, MasterTaintKey string }{
+		struct{ ImageRepository, Arch, Version, DNSBindAddr, DNSProbeAddr, DNSDomain, DNSProbeType, MasterTaintKey string }{
 			ImageRepository: cfg.ImageRepository,
 			Arch:            runtime.GOARCH,
 			// Get the kube-dns version conditionally based on the k8s version
 			Version:        GetDNSVersion(k8sVersion, kubeadmconstants.KubeDNS),
 			DNSBindAddr:    dnsBindAddr,
+			DNSProbeAddr:   dnsProbeAddr,
 			DNSDomain:      cfg.Networking.DNSDomain,
 			DNSProbeType:   GetKubeDNSProbeType(k8sVersion),
 			MasterTaintKey: kubeadmconstants.LabelNodeRoleMaster,

cmd/kubeadm/app/phases/addons/dns/dns_test.go

@@ -92,11 +92,12 @@ func TestCompileManifests(t *testing.T) {
 	}{
 		{
 			manifest: v180AndAboveKubeDNSDeployment,
-			data: struct{ ImageRepository, Arch, Version, DNSBindAddr, DNSDomain, DNSProbeType, MasterTaintKey string }{
+			data: struct{ ImageRepository, Arch, Version, DNSBindAddr, DNSProbeAddr, DNSDomain, DNSProbeType, MasterTaintKey string }{
 				ImageRepository: "foo",
 				Arch:            "foo",
 				Version:         "foo",
 				DNSBindAddr:     "foo",
+				DNSProbeAddr:    "foo",
 				DNSDomain:       "foo",
 				DNSProbeType:    "foo",
 				MasterTaintKey:  "foo",

cmd/kubeadm/app/phases/addons/dns/manifests.go

@@ -156,8 +156,8 @@ spec:
         args:
         - --v=2
         - --logtostderr
-        - --probe=kubedns,{{ .DNSBindAddr }}:10053,kubernetes.default.svc.{{ .DNSDomain }},5,{{ .DNSProbeType }}
+        - --probe=kubedns,{{ .DNSProbeAddr }}:10053,kubernetes.default.svc.{{ .DNSDomain }},5,{{ .DNSProbeType }}
-        - --probe=dnsmasq,{{ .DNSBindAddr }}:53,kubernetes.default.svc.{{ .DNSDomain }},5,{{ .DNSProbeType }}
+        - --probe=dnsmasq,{{ .DNSProbeAddr }}:53,kubernetes.default.svc.{{ .DNSDomain }},5,{{ .DNSProbeType }}
         ports:
         - containerPort: 10054
           name: metrics