CoreDNS pod definition and Corefile template for control plane

For cloud platforms where customers are allowed to bring their own
DNS post cluster install, an in-cluster DNS solution is required
for the installation to be successful.
Adding the manifest containing CoreDNS pod definition and Corefile
template to be used by the MCO instance running on the control plane.

pkg/controller/template/render.go

@@ -334,6 +334,7 @@ func renderTemplate(config RenderConfig, path string, b []byte) ([]byte, error)
 	funcs["urlHost"] = urlHost
 	funcs["urlPort"] = urlPort
 	funcs["isOpenShiftManagedDefaultLB"] = isOpenShiftManagedDefaultLB
+	funcs["cloudPlatformShortName"] = cloudPlatformShortName
 	tmpl, err := template.New(path).Funcs(funcs).Parse(string(b))
 	if err != nil {
 		return nil, fmt.Errorf("failed to parse template %s: %w", path, err)
@@ -687,3 +688,15 @@ func isOpenShiftManagedDefaultLB(cfg RenderConfig) bool {
 	}
 	return false
 }
+
+func cloudPlatformShortName(cfg RenderConfig) interface{} {
+	if cfg.Infra.Status.PlatformStatus != nil {
+		switch cfg.Infra.Status.PlatformStatus.Type {
+		case configv1.GCPPlatformType:
+			return "gcp"
+		default:
+			return ""
+		}
+	}
+	return ""
+}

templates/common/cloud-platform-alt-dns/files/coredns-corefile.yaml

@@ -0,0 +1,40 @@
+mode: 0644
+path: "/etc/kubernetes/static-pod-resources/coredns/Corefile.tmpl"
+contents:
+  inline: |
+    . {
+        errors
+        bufsize 512
+        health :18080
+        forward . {{`{{- range $upstream := .DNSUpstreams}} {{$upstream}}{{- end}}`}} {
+            policy sequential
+        }
+        cache 30
+        reload
+        template IN {{`{{ .Cluster.CloudLBRecordType }}`}} {{ .DNS.Spec.BaseDomain }} {
+            match ^api.{{ .DNS.Spec.BaseDomain }}
+            answer "{{`{{"{{ .Name }}"}}`}} 60 in {{`{{"{{ .Type }}"}}`}} {{ if gt (len (.Cluster.APILBIPs )) 0 }}{{ index (.Cluster.APILBIPs) 0 }}{{ end }}"
+            fallthrough
+        }
+        template IN {{`{{ .Cluster.CloudLBEmptyType }}`}} {{ .DNS.Spec.BaseDomain }} {
+            match ^api.{{ .DNS.Spec.BaseDomain }}
+            {{ if gt (len (.Cluster.APILBIPs )) 1 }}answer "{{`{{"{{ .Name }}"}}`}} 60 in {{`{{"{{ .Type }}"}}`}} {{ index (.Cluster.APILBIPs) 1 }}"{{ end }}
+            fallthrough
+        }
+        template IN {{`{{ .Cluster.CloudLBRecordType }}`}} {{ .DNS.Spec.BaseDomain }} {
+            match ^api-int.{{ .DNS.Spec.BaseDomain }}
+            answer "{{`{{"{{ .Name }}"}}`}} 60 in {{`{{"{{ .Type }}"}}`}} {{ if gt (len (.Cluster.APIIntLBIPs)) 0 }}{{ index (.Cluster.APIIntLBIPs) 0 }}{{ end }}"
+            fallthrough
+        }
+        template IN {{`{{ .Cluster.CloudLBEmptyType }}`}} {{ .DNS.Spec.BaseDomain }} {
+            match ^api-int.{{ .DNS.Spec.BaseDomain }}
+            {{ if gt (len (.Cluster.APIIntLBIPs)) 1 }}answer "{{`{{"{{ .Name }}"}}`}} 60 in {{`{{"{{ .Type }}"}}`}} {{ index (.Cluster.APIIntLBIPs) 1 }}"{{ end }}
+            fallthrough
+        }
+        hosts {
+            {{`{{- range .Cluster.NodeAddresses }}
+            {{ .Address }} {{ .Name }} {{ .Name }}.{{ $.Cluster.Name }}.{{ $.Cluster.Domain }}
+            {{- end }}`}}
+            fallthrough
+        }
+    }

templates/common/cloud-platform-alt-dns/files/coredns.yaml

@@ -0,0 +1,109 @@
+mode: 0644
+path: {{ if gt (len (.CloudIntLBIPs)) 0 -}} "/etc/kubernetes/manifests/coredns.yaml" {{ else }} "/etc/kubernetes/disabled-manifests/coredns.yaml" {{ end }}
+contents:
+  inline: |
+    kind: Pod
+    apiVersion: v1
+    metadata:
+      name: coredns
+      namespace: openshift-{{ cloudPlatformShortName . }}-infra
+      creationTimestamp:
+      deletionGracePeriodSeconds: 65
+      labels:
+        app: {{ cloudPlatformShortName . }}-infra-coredns
+    spec:
+      volumes:
+      - name: resource-dir
+        hostPath:
+          path: "/etc/kubernetes/static-pod-resources/coredns"
+      - name: kubeconfig
+        hostPath:
+          path: "/var/lib/kubelet"
+      - name: conf-dir
+        hostPath:
+          path: "/etc/coredns"
+      initContainers:
+      - name: render-config-coredns
+        image: {{ .Images.baremetalRuntimeCfgImage }}
+        command:
+        - runtimecfg
+        - render
+        - "/var/lib/kubelet/kubeconfig"
+        - "--cloud-ext-lb-ips"
+        - "{{- range $index, $ip := .CloudExtLBIPs }}{{ if gt $index 0 }},{{end}}{{$ip}}{{end}}"
+        - "--cloud-int-lb-ips"
+        - "{{- range $index, $ip := .CloudIntLBIPs }}{{ if gt $index 0 }},{{end}}{{$ip}}{{end}}"
+        - "/config"
+        - "--out-dir"
+        - "/etc/coredns"
+        resources: {}
+        volumeMounts:
+        - name: kubeconfig
+          mountPath: "/var/lib/kubelet"
+          mountPropagation: HostToContainer
+        - name: resource-dir
+          mountPath: "/config"
+          mountPropagation: HostToContainer
+        - name: conf-dir
+          mountPath: "/etc/coredns"
+          mountPropagation: HostToContainer
+        imagePullPolicy: IfNotPresent
+      containers:
+      - name: coredns
+        securityContext:
+          privileged: true
+        image: {{.Images.corednsImage}}
+        args:
+        - "--conf"
+        - "/etc/coredns/Corefile"
+        resources:
+          requests:
+            cpu: 100m
+            memory: 200Mi
+        volumeMounts:
+        - name: conf-dir
+          mountPath: "/etc/coredns"
+        livenessProbe:
+          httpGet:
+            path: /health
+            port: 18080
+            scheme: HTTP
+          initialDelaySeconds: 60
+          timeoutSeconds: 5
+          successThreshold: 1
+          failureThreshold: 5
+        terminationMessagePolicy: FallbackToLogsOnError
+        imagePullPolicy: IfNotPresent
+      - name: coredns-monitor
+        securityContext:
+          privileged: true
+        image: {{ .Images.baremetalRuntimeCfgImage }}
+        command:
+        - corednsmonitor
+        - "/var/lib/kubelet/kubeconfig"
+        - "/config/Corefile.tmpl"
+        - "/etc/coredns/Corefile"
+        - "--cloud-ext-lb-ips"
+        - "{{- range $index, $ip := .CloudExtLBIPs }}{{ if gt $index 0 }},{{end}}{{$ip}}{{end}}"
+        - "--cloud-int-lb-ips"
+        - "{{- range $index, $ip := .CloudIntLBIPs }}{{ if gt $index 0 }},{{end}}{{$ip}}{{end}}"
+        resources:
+          requests:
+            cpu: 100m
+            memory: 200Mi          
+        volumeMounts:
+        - name: kubeconfig
+          mountPath: "/var/lib/kubelet"
+          mountPropagation: HostToContainer
+        - name: resource-dir
+          mountPath: "/config"
+          mountPropagation: HostToContainer
+        - name: conf-dir
+          mountPath: "/etc/coredns"
+          mountPropagation: HostToContainer
+        imagePullPolicy: IfNotPresent        
+      hostNetwork: true
+      tolerations:
+      - operator: Exists
+      priorityClassName: system-node-critical
+    status: {}