Goal: 

• For example: As a org with multiple IDM domains, I want new cloud VMs to automatically join the domain that matches their domain name.

Acceptance Criteria:

• When exactly one active domain registration, return that domain (i.e. the current behaviour)
• When >1 active domain registration:
  • let hostname = the enrolling VM's hostname
  • let resultSet = {}, n = 0
  • for domain in active registered domains:
    • if hostDomain is not a true subdomain of domain, continue
    • if number of components in domain = n, add domain to resultSet and continue
    • if number of components in domain > n, set n = number of components in domain, set resultSet = {domain}, continue
  • if |resultSet| = 1, succeed with info + enrollment token for that matching domain
  • if |resultSet| = 0, fail with error "no matching domain"
  • if |resultSet| > 0, fail with error "multiple matching domains"

Examples:

• 3 active domains:
  • ipa.test
  • foo.ipa.test
  • bar.ipa.test
  • xyz.test
• host h1.ipa.test matches domain ipa.test
• host hello.world.ipa.test matches domain ipa.test
• host h2.abc.foo.ipa.test matches domain foo.ipa.test
• host foo.ipa.test matches domain ipa.test
• host ipa.qq.test fails (no match)
• host xyz.test fails (no match)

Additional information:

Uncertainties:

• IPA deployments that serve multiple DNS domains
• Golang DNS library that could help with implementation?
• Testing