Comment 6 for bug 1659376

As part of the implementation for this, currently charms often need to get the network interface related to an IP. Currently they use the network-get charm command to get the IP of the space, but then have to figure out what interface that IP is on manually. Ideally the charm API would be expanded to specifically give the interface.

Having said that there is a trap here when things change after deployment, by either juju or the system administrator. Right now juju or MAAS won't let you change network interfaces after deployment so manual changes might be made which juju may or may not know about.

On the juju side, a case it knows about is when an interface is moved to be a bridge, e.g. when a container is deployed on that interface. That can happen during inital deploy, but could also happen much later if a container was deployed for the first time.

Just some thoughts.