bandwidth-file: Add relay line diagnostic KeyValues

Make Tor directory authorities avoid voting on relay bandwidths
for relays that were not successfully measured. But report diagnostics
for those relays in the Bandwidth File.

When there are not enough eligible relays, put all the relays in the file
for diagnostic purposes. But mark them so that Tor avoids voting on their
bandwidths.

Closes 29813, 29853.

bandwidth-file-spec.txt

@@ -94,6 +94,7 @@
   The following nonterminals are defined in Tor directory protocol
   sections 1.2., 2.1.1., 2.1.3.:
 
+    bool
     Int
     SP (space)
     NL (newline)
@@ -828,6 +829,70 @@
 
       This KeyValue was added in version 1.4.0 of this specification.
 
+    "under_min_report=" bool
+
+      [Zero or one time.]
+
+      If the value is 1, there are not enough eligible relays in the
+      bandwidth file, and Tor bandwidth authorities MAY NOT vote on this
+      relay. (Current Tor versions do not change their behaviour based on
+      the "under_min_report" key.)
+
+      If the value is 0 or the KeyValue is not present, there are enough
+      relays in the bandwidth file.
+
+      Because Tor versions released before April 2019 (see section 1.4. for
+      the full list of versions) ignore "vote=0", generator implementations
+      MUST NOT change the bandwidths for under_min_report relays. Using the
+      same bw value makes authorities that do not understand "vote=0"
+      or "under_min_report=1" produce votes that don't change relay weights
+      too much. It also avoids flapping when the reporting threshold is
+      reached.
+
+      This KeyValue was added in version 1.4.0 of this specification.
+
+    "unmeasured=" bool
+
+      [Zero or one time.]
+
+      If the value is 1, this relay was not successfully measured and
+      Tor bandwidth authorities MAY NOT vote on this relay.
+      (Current Tor versions do not change their behaviour based on
+      the "unmeasured" key.)
+
+      If the value is 0 or the KeyValue is not present, this relay
+      was successfully measured.
+
+      Because Tor versions released before April 2019 (see section 1.4. for
+      the full list of versions) ignore "vote=0", generator implementations
+      MUST set "bw=1" for unmeasured relays. Using the minimum bw value
+      makes authorities that do not understand "vote=0" or "unmeasured=1"
+      produce votes that don't change relay weights too much.
+
+      This KeyValue was added in version 1.4.0 of this specification.
+
+    "vote=" bool
+
+      [Zero or one time.]
+
+      If the value is 0, Tor directory authorities SHOULD ignore the relay's
+      entry in the bandwidth file. They SHOULD vote for the relay the same
+      way they would vote for a relay that is not present in the file.
+
+      This MAY be the case when this relay was not successfully measured but
+      it is included in the Bandwidth File, to diagnose why they were not
+      measured.
+
+      If the value is 1 or the KeyValue is not present, Tor directory
+      authorities MUST use the relay's bw value in any votes for that relay.
+
+      Implementations MUST also set "bw=1" for unmeasured relays.
+      But they MUST NOT change the bw for under_min_report relays.
+      (See the explanations under "unmeasured" and "under_min_report"
+      for more details.)
+
+      This KeyValue was added in version 1.4.0 of this specification.
+
 2.4.2.2. Torflow
 
   Torflow RelayLines include node_id and bw, and other KeyValue pairs [2].
@@ -948,9 +1013,10 @@ recent_priority_relay_count=6243
 scanner_country=SN
 software=sbws
 software_version=1.1.0
+time_to_report_half_network=57273
 =====
-bw=1 error_circ=1 error_destination=0 error_misc=0 error_second_relay=0 error_stream=0 master_key_ed25519=J3HQ24kOQWac3L1xlFLp7gY91qkb5NuKxjj1BhDi+m8 nick=snap269 node_id=$DC4D609F95A52614D1E69C752168AF1FCAE0B05F relay_recent_measurements_excluded_error_count=1 relay_recent_measurements_excluded_near_count=3 success=3 time=2019-03-16T18:20:57 unmeasured=1 vote=0
-bw=1 error_circ=0 error_destination=0 error_misc=0 error_second_relay=0 error_stream=0 master_key_ed25519=h6ZB1E1yBFWIMloUm9IWwjgaPXEpL5cUbuoQDgdSDKg nick=jrelay node_id=$C4544F9E209A9A9B99591D548B3E2822236C0503 relay_recent_measurements_excluded_few_count=1 success=1 time=2019-03-17T06:50:58 unmeasured=1 vote=0
+bw=1 error_circ=1 error_destination=0 error_misc=0 error_second_relay=0 error_stream=0 master_key_ed25519=J3HQ24kOQWac3L1xlFLp7gY91qkb5NuKxjj1BhDi+m8 nick=snap269 node_id=$DC4D609F95A52614D1E69C752168AF1FCAE0B05F relay_recent_measurement_attempt_count=3 relay_recent_measurements_excluded_error_count=1 relay_recent_measurements_excluded_near_count=3 relay_recent_consensus_count=3 relay_recent_priority_list_count=3 success=3 time=2019-03-16T18:20:57 unmeasured=1 vote=0
+bw=1 error_circ=0 error_destination=0 error_misc=0 error_second_relay=0 error_stream=2 master_key_ed25519=h6ZB1E1yBFWIMloUm9IWwjgaPXEpL5cUbuoQDgdSDKg nick=relay node_id=$C4544F9E209A9A9B99591D548B3E2822236C0503 relay_recent_measurement_attempt_count=3 relay_recent_measurements_excluded_error_count=2 relay_recent_measurements_excluded_few_count=1 relay_recent_consensus_count=3 relay_recent_priority_list_count=3 success=1 time=2019-03-17T06:50:58 unmeasured=1 vote=0
 
 B. Scaling bandwidths