Unable to connect to any external services

Installation Home Assistant OS
1

Since updating to 0.81.6 all of my external services have stopped working.
Hive component will not connect to the Hive servers
Trying to update Hass.io to 0.82.0 (the offered version) fails without an error message (it tries for a while then the update button briefly flashes red)
Connecting to the HA Cloud was stuck at “connecting”. I tried logging in again but now it just says, “Unable to reach the Home Assistant cloud.”
Trying to add an add-on from the add-on store fails without an error message (same symptoms as trying to update hass.io above)

Having searched for similar problems it looks like a dns resolution problem but I’m able to resolve addresses through docker from the command line using docker exec -it homeassistant ping websitename.

Can anyone shed any light on this?

Thanks,

Steve

2

And as if by magic… It started working again about half an hour after I posted this. No idea what the problem was, it’s been down for at least a week, maybe two.

3

And down again.

I think I’ve traced it to the DNS server setting in /etc/resolv.conf
Docker has this set to 127.0.0.11. I changed it to my internal router address (which acts as a dns server for the lan) and everything’s working.
I need to see why Docker sets it’s DNS server as some sort of loopback now to see what I may have broken by implementing this workaround.