Add a systemd-resolved FallbackDNS list

The default in systemd for ubuntu in 18.04 is an empty fallback
list.

Use a reasonable list:

* Cloudflare (https://1.1.1.1/)
* Quad9 without filtering (https://www.quad9.net/)
* Google (https://developers.google.com/speed/public-dns/)
1.1.1.1
9.9.9.10
8.8.8.8
2606:4700:4700::1111
2620:fe::10
2001:4860:4860::8888

List from https://git.archlinux.org/svntogit/packages.git/tree/trunk/PKGBUILD?h=packages/systemd#n103

diff --git a/cookbooks/networking/templates/default/resolved.conf.erb b/cookbooks/networking/templates/default/resolved.conf.erb
index f749388efeb216505933b5557fb337dc2a342309..035d692dfe515ef95af13a31347d5648f83b5b95 100644 (file)
--- a/cookbooks/networking/templates/default/resolved.conf.erb
+++ b/cookbooks/networking/templates/default/resolved.conf.erb
@@ -1,4 +1,5 @@
 [Resolve]
 DNS=<%= node[:networking][:nameservers].join(" ") %>
+FallbackDNS=1.1.1.1 9.9.9.10 8.8.8.8 2606:4700:4700::1111 2620:fe::10 2001:4860:4860::8888
 Domains=<%= node[:networking][:search].join(" ") %>
 DNSSEC=allow-downgrade