network-get returns an empty hostname

[Dmitrii Shcherbakov]

Hostnames are only populated in `network-get` output when a manual provider is used and machines are added to the model via hostname, not address.

https://github.com/juju/juju/blame/juju-2.7.1/worker/uniter/runner/jujuc/network-get.go#L197-L202

It would be good if Juju populated this field based on a reverse DNS resolution for an address done at the Unit agent's machine. The goal would be to have a canonical/primary name (don't confuse with a CNAME RR name) exposed there taken from a PTR resource record content in the IN-ADDR.ARPA domain.

https://tools.ietf.org/html/rfc1035#page-22
"Both the gateway pointers at network nodes and the normal host pointers at full address nodes use the PTR RR to point back to the primary domain names of the corresponding hosts."

Example:
    1.2.0.192.IN-ADDR.ARPA IN PTR example.com

This information is not always available because reverse lookup zones are not set up in all environments but it is useful where available.

It looks like this field was added w.r.t to this bug:
https://bugs.launchpad.net/charm-nova-compute/+bug/1721368

[Canonical Juju QA Bot (juju-qa-bot)]

This bug has not been updated in 2 years, so we're marking it Low importance. If you believe this is incorrect, please update the importance.