Forward DNS via ingress

- Forward UDP DNS requests from maas-ingress to the region pod
  for PXE networks that do not have access to upstream DNS servers.

Change-Id: Icf88bac4c0df1a351a5bd246e3fa8bf28135d37e

charts/maas/templates/bin/_maas-ingress.sh.tpl

@@ -32,7 +32,8 @@ function start () {
       --ingress-class=maas-ingress \
       --default-backend-service=${POD_NAMESPACE}/${ERROR_PAGE_SERVICE} \
       --configmap=${POD_NAMESPACE}/maas-ingress-config \
-      --tcp-services-configmap=${POD_NAMESPACE}/maas-ingress-services-tcp
+      --tcp-services-configmap=${POD_NAMESPACE}/maas-ingress-services-tcp \
+      --udp-services-configmap=${POD_NAMESPACE}/maas-ingress-services-udp
 }
 
 function stop () {

charts/maas/templates/configmap-ingress.yaml

@@ -27,6 +27,14 @@ data:
 ---
 apiVersion: v1
 kind: ConfigMap
+metadata:
+  name: maas-ingress-services-udp
+data:
+  '53': "{{- .Release.Namespace -}}/{{- tuple "maas_region" "internal" . | include "helm-toolkit.endpoints.hostname_short_endpoint_lookup" -}}:region-dns"
+...
+---
+apiVersion: v1
+kind: ConfigMap
 metadata:
   name: maas-ingress-config
 data:

charts/maas/templates/service-region.yaml

@@ -34,6 +34,9 @@ spec:
       {{ if .Values.network.region_proxy.node_port.enabled }}
       nodePort:  {{ tuple "maas_region" "nodeport" "region_proxy" $envAll | include "helm-toolkit.endpoints.endpoint_port_lookup" }}
       {{ end }}
+    - name: region-dns
+      port: 53
+      targetPort: 53
   selector:
 {{ tuple $envAll "maas" "region" | include "helm-toolkit.snippets.kubernetes_metadata_labels" | indent 4 }}
   {{ if or .Values.network.region_proxy.node_port.enabled .Values.network.region_api.node_port.enabled }}