Configure the resolver on dnsmasq

The current options are: external (google), or internal (pointing at a
specific float service, "frontend" by default).

roles/float-base-dns-resolver/defaults/main.yml

-# How to configure resolv.conf, one of the following options:
-# 'ignore' - do nothing and leave resolv.conf alone
-# 'localhost' - use localhost as the name server (presumably a cache)
-# 'internal:NET' - use the frontend hosts as resolvers, over the
-#   specified overlay network NET
-# 'external' - use Google Public DNS.
-resolver_mode: "ignore"
+resolver:
+  # Mode should be one of 'internal', 'default'.
+  mode: internal
+  service: frontend
+  overlay_network: vpn0

roles/float-base-dns-resolver/handlers/main.yml

+---
+
+- listen: reload dnsmasq
+  command: "systemctl reload dnsmasq.service"

roles/float-base-dns-resolver/tasks/main.yml

 ---
 
-- name: Configure resolv.conf
+- name: Configure upstream resolver for dnsmasq
   template:
-    src: "resolv.conf.j2"
-    dest: "/etc/resolv.conf"
-  when: "resolver_mode != 'ignore'"
+    src: "dnsmasq.conf.j2"
+    dest: "/etc/dnsmasq.conf"
+  notify: reload dnsmasq

roles/float-base-dns-resolver/templates/dnsmasq.conf.j2

+{% if resolver.mode == 'internal' %}
+{% set dns_overlay_net = resolver.get('overlay_network', net_overlays[0].name) %}
+{% set dns_service_group = services[resolver.get('service', 'frontend')].group_name %}
+{% for h in groups[dns_service_group] | sort %}
+server={{ hostvars[h]['ip_' + dns_overlay_net] }}
+{% endfor %}
+{% else %}
+server=8.8.8.8
+server=8.8.4.4
+{% endif %}

roles/float-base-dns-resolver/templates/resolv.conf.j2

-{% if resolver_mode == 'localhost' %}
-nameserver 127.0.0.1
-options edns0
-{% elif resolver_mode.startswith('internal:') %}
-{% set dns_overlay_net = resolver_mode[9:] %}
-{% for h in services['dns'].hosts | sort %}
-nameserver {{ hostvars[h]['ip_' + dns_overlay_net] }}
-{% endfor %}
-options edns0 rotate
-{% else %}
-nameserver 8.8.8.8
-nameserver 8.8.4.4
-options edns0
-{% endif %}
-