Fix DNS loop when resolvconf_mode is set to host_resolvconf (#3390)

* Fix DNS loop when resolvconf_mode is set to host_resolvconf

* Make sure upstream_dns_servers is defined when using resolvconf_mode == 'host_resolvconf'

* Only set upstream dns servers on KubeDNS and CoreDNS if they are defined

* Only set upstream dns servers on KubeDNS and CoreDNS if they are defined

docs/vars.md

@@ -53,7 +53,7 @@ Kubernetes needs some parameters in order to get deployed. These are the
 following default cluster paramters:
 
 * *cluster_name* - Name of cluster (default is cluster.local)
-* *domain_name* - Name of cluster DNS domain (default is cluster.local)
+* *dns_domain* - Name of cluster DNS domain (default is cluster.local)
 * *kube_network_plugin* - Plugin to use for container networking
 * *kube_service_addresses* - Subnet for cluster IPs (default is
   10.233.0.0/18). Must not overlap with kube_pods_subnet

roles/kubernetes-apps/ansible/templates/coredns-config.yml.j2

@@ -13,10 +13,18 @@ data:
         health
         kubernetes {{ dns_domain }} in-addr.arpa ip6.arpa {
           pods insecure
+{% if resolvconf_mode == 'host_resolvconf' and upstream_dns_servers is defined and upstream_dns_servers|length > 0 %}
+          upstream {{ upstream_dns_servers|join(' ') }}
+{% else %}
           upstream /etc/resolv.conf
+{% endif %}
           fallthrough in-addr.arpa ip6.arpa
         }
         prometheus :9153
+{% if resolvconf_mode == 'host_resolvconf' and upstream_dns_servers is defined and upstream_dns_servers|length > 0 %}
+        proxy . {{ upstream_dns_servers|join(' ') }}
+{% else %}
         proxy . /etc/resolv.conf
+{% endif %}
         cache 30
     }

roles/kubernetes-apps/ansible/templates/kubedns-deploy.yml.j2

@@ -97,6 +97,9 @@ spec:
         - --dns-port=10053
         - --config-dir=/kube-dns-config
         - --v={{ kube_log_level }}
+{% if resolvconf_mode == 'host_resolvconf' and upstream_dns_servers is defined and upstream_dns_servers|length > 0 %}
+        - --nameservers={{ upstream_dns_servers|join(',') }}
+{% endif %}
         env:
         - name: PROMETHEUS_PORT
           value: "10055"