[tor-bugs] #15500 [- Select a component]: faravahar is missing to vote HSDir and Stable too often

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#15500: faravahar is missing to vote HSDir and Stable too often
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 Reporter:  s7r                               |          Owner:
     Type:  defect                            |         Status:  new
 Priority:  normal                            |      Milestone:
Component:  - Select a component              |        Version:
 Keywords:  consensus, directory authorities  |  Actual Points:
Parent ID:                                    |         Points:
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 While asn and I were investigating the HSDir votes in the consensus for
 relays without V2Dir flag (no DirPort open) we discovered a strange
 behavior for faravahar:

 Consensus:
 network-status-version 3 microdesc
 vote-status consensus
 consensus-method 18
 valid-after 2015-03-24 23:00:00
 fresh-until 2015-03-25 00:00:00
 valid-until 2015-03-25 02:00:00
 voting-delay 300 300

 consensus: 2503 HSDir relays
 faravahar: 1376 HSDir relays

 consensus: 5302 Stable relays
 faravahar: 3236 Stable relays

 consensus: 2437 Stable and HSDir relays
 faravahar: 1309 Stable and HSDir relays

 consensus: 66 not Stable but HSDir relays
 faravahar: 67 not Stable but HSDir relays


 All HSDir relays in the consensus have also the V2Dir flag, because the
 majority of DAs haven't upgraded to mitigate #14202.

 However, faravahar voted the HSDir flag for 520 relays who do not have the
 V2Dir flag and, obviously, these relays are not in the network agreed
 consensus. So, we can say faravahar actually voted for 1376 - 520 = 856
 HSDir relays from the network agreed (useable by clients) consensus.

 (From these 520 non-V2Dir HSDir relays:
 - 23 relays are missing Stable falag.
 - 497 are Stable.)


 Results:
 faravahar missed to vote 1647 HSDir flags
 faravahar missed to vote 2066 Stable flags

 We cannot say exactly that it missed to vote, since faravahar does not
 have to agree with the rest of DAs on each and every vote - this is why we
 have a consensus based on votes / majority. Still, the difference should
 be smaller than we currently see.

 While it is normal for each DA not to vote exactly identical, we see a
 difference for the HSDir relays of 1647. This is more than 50% of all
 HSDirs voted by the rest of 8 DAs.

 For the HSDir flags missed by faravahar, we thought that it has a very
 high value for MinUptimeHidServDirectoryV2 and it only votes HSDir flag
 for relays with very high uptime. A closer look on faravahar HSDir votes
 eliminates that assumption. For reference:

 Fingerpints of relays for which faravahar voted HSDir  |  uptime at time
 of writing (24.03.2015):

 003000C32D9E16FCCAEFD89336467C01E16FB00D 5 days
 00339258B444376593E069201C4A4AA45F95AA87 15 days
 0063D0DE32C80691A0AC1A968A8CCF5ABA420E29 57 days
 0086EF7F056983D5A0EBB37F36A44CB738B16D97 20 days
 0124398EE6783F402A6FC430D0AD110982E503AC 16 days
 016DD78B2C3A468DDD48AF63F48D25660F93DAAC 4 days
 0192067CFC14F3E3022F99D32FC39016C270AC4C 9 days
 0473E3701C9EA2F8367DBAB453B6DC4EE78DEE1B 17 days
 0522B7D9FBDFA6FDA81DC6B12A8FA0BA1F7084B4 6 days
 C309A31AD772FFDD0805C9FECB6D4748A7CBF684 4 days

 5 days later the behavior did not change:
 network-status-version 3
 vote-status vote
 consensus-methods 13 14 15 16 17 18 19 20
 published 2015-03-28 21:50:01
 valid-after 2015-03-28 22:00:00
 fresh-until 2015-03-28 23:00:00
 valid-until 2015-03-29 01:00:00

 3145 HSDir relays in the consensus
 1585 HSDir relays seen by faravahar

 5165 Stable relays in the consensus
 3214 Stable relays seen by faravahar

 And, it is missing just HSDir and Stable flags, because it sees almost all
 relays in the consensus as running:
 running relays in consensus: 6623
 running relays seen by faravahar: 6443
 The difference is not so big for the running relays as it is for HSDirs
 and Stables.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/15500>
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