Role network-loopback: set internal nameserver when available

roles/network-loopback/tasks/main.yml

@@ -4,3 +4,17 @@
     src: loopback.j2
     dest: "/etc/network/interfaces.d/loopback"
   notify: reload network interfaces
+
+- name: create check-anycast.sh
+  template:
+    src: check-anycast.sh.j2
+    dest: "/usr/local/bin/check-anycast.sh"
+    owner: root
+    group: root
+    mode: 0755
+
+- name: create cronjob for check-anycast.sh"
+  cron:
+    name: "check anycast availability"
+    minute: "*/1"
+    job: "/usr/local/bin/check-anycast.sh > /dev/null 2>&1"

roles/network-loopback/templates/check-anycast.sh.j2

@@ -0,0 +1,22 @@
+#!/bin/bash
+
+LOOPBACK="loopback"
+ANYCAST="{{ anycast_ipv4 | ipaddr('address') }}"
+
+ANYCAST_PRESENT=false
+if ping -c 1 "${ANYCAST}" > /dev/null 2>&1 ; then
+   ANYCAST_PRESENT=true
+fi
+
+DNS_PRESENT=false
+if /sbin/resolvconf -l "${LOOPBACK}" > /dev/null 2>&1 ; then
+    DNS_PRESENT=true
+fi
+
+if [[ ${ANYCAST_PRESENT} == true && ${DNS_PRESENT} == true ]] ; then
+    exit 0
+elif [[ ${ANYCAST_PRESENT} == true && ${DNS_PRESENT} == false ]] ; then
+    echo "nameserver ${ANYCAST}" | /sbin/resolvconf -a "${LOOPBACK}" -m 1
+elif [[ ${ANYCAST_PRESENT} == false && ${DNS_PRESENT} == true ]] ; then
+    /sbin/resolvconf -d "${LOOPBACK}"
+fi