DNS server should have PTR records

[broder]

There's currently no way to go from an IP address (or, say, sipb-vm-##) to a VM name without having access to the database. This in particular was annoying when I was trying to come up with the names of the VMs affected by the OpenSSH bug, but there are more general cases where this could be problematic.

It would be convenient if the DNS server responded to PTR requests for IP addresses that XVM is serving.

[price]

I agree this would be good. It will require something.181.18.in-addr.arpa. to be delegated to us, so we'll have to ask Network. The request for a separate Moira network is a higher priority (e.g., we'd set the contact fields so that OpenSSH notice would go to the machines' real contacts and not to us) and probably a prerequisite, so I'll see that request through before really asking about this.

[broder]

I was thinking that we wouldn't need to get the in-addr.arpa space delegated - the server would just respond to those sorts of requests if they were pointed directly at it.

[price]

OK, sure, might as well.