[chrony] allow specifying server, client, and command "bind addresses"

[Junien F]

Hi,

chrony can be configure to bind to specific IPs for server traffic ("bindaddress" configuration stanza), client traffic("bindacqaddress"), and "command" traffic ("bindcmdaddress).

We have a use case where we would like to specify bindaddress and bindacqaddress, but the charm doesn't allow this currently.

There are two things to consider here :
- how should that be made configurable ? three config options ? one config option which would have all 3 addresses ?

- what should the values look like ? It can't be IPs, because if multiple units are deployed they will have different IPs. It could be an interface name, but this assumes that said interfaces have a single IP (you can only have one stanza of each for IPv4, and one for IPv6). It could also be a network (e.g. 192.168.0.0/24) and then the charm would find the IP in this network that's present on the server and use that. I guess we could allow the operators to specify either an interface or a network.

And finally, this should work for IPv4 _and_ IPv6.

Thanks !

[Tom Haddon (mthaddon)]

Ok, so just to confirm we think the best approach here is to add a charm configuration option called bindaddresses that accepts yaml as follows:

juju config ntp bindaddresses='{"server": "eth1", "client": "10.10.0.0/24", "command": "-"}'

We'll need to confirm exactly what that should be translated to in terms of chrony (the default since bionic) and whether ntp supports the same for pre-bionic.