[metrics-bugs] #18342 [Metrics/Onionoo]: Provide more accurate reverse DNS results

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#18342: Provide more accurate reverse DNS results
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 Reporter:  cypherpunks      |          Owner:  irl
     Type:  defect           |         Status:  accepted
 Priority:  Medium           |      Milestone:
Component:  Metrics/Onionoo  |        Version:
 Severity:  Normal           |     Resolution:
 Keywords:  metrics-2018     |  Actual Points:
Parent ID:                   |         Points:
 Reviewer:                   |        Sponsor:
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Comment (by irl):

 The DNS specification does not actually prohibit the presence of multiple
 PTR records. ):

 This means it can be perfectly valid for an IP address to have multiple
 reverse names which could all be validated using forward names
 successfully.

 I have found at least 3 relays that have more than one PTR record that
 validate with a forward record.

 Alternative proposal:

 * For `host_name` we implement the spec as it is (actually omitting the
 field instead of returning IP addresses), but also deprecate the field.
 * Add a new `verified_host_names` field with an **array** of strings, this
 will include the DNS PTR record's names. It would be updated at the same
 time as the host_name record. Omitted if the host name was verified by
 looking up an A record, or if no PTR record was found.
 * Add a new `unverified_host_names` field with an **array** of strings,
 this will include the DNS PTR record's names. It would be updated at the
 same time as the host_name record. Omitted if the host name was verified
 by looking up an A record, or if no PTR record was found.

 It would be possible to have either, both, or neither verified and
 unverified host names for each relay.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/18342#comment:18>
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