DHCP requests for public IPs should use DHCP options

[Mark Shuttleworth]

As described in bug #454519 it should be possible to assign public IP's for cloud instances dynamically using DHCP. The DHCP requests should include some custom dhcp options that allow for smarter configuration of the DHCP server.

For example, if the DHCP request includes custom options which identify the image used (the EMI) then it would be possible to configure the DHCP server to assign IP addresses from specific ranges to specific EMI's. If the DHCP request also included as an option an indicator of a persistent identify then the DHCP server can attempt to assign a persistent IP address. DHCP options are described in the dhcp-options(5) man page.

As an example, we could create the Canonical encapsulated option space, and then have options like:

  Canonical.UPC.mi = text (the machine image identifier)
  Canonical.UPC.id = text (some persistence identifier)

We would update the DHCP server documentation to make it very easy for people to assign ranges of IP addresses for use in their cloud, or for specific machine images etc.

[Mark Shuttleworth (sabdfl)]

There are three related bug reports in this set:

  #454519 - Eucalyptus node controllers should be able to get a DHCP address for public instances
  #454521 - The Ubuntu private cloud installation should skip public IP range question in favour of DHCP
  #454540 - Cloud DHCP requests should include some custom options to help configure IP ranges neatly