[tor-bugs] #19166 [Core Tor/Tor]: HS connections randomly fail

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#19166: HS connections randomly fail
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     Reporter:  TvdW          |      Owner:
         Type:  defect        |     Status:  new
     Priority:  Medium        |  Milestone:
    Component:  Core Tor/Tor  |    Version:  Tor: 0.2.7.6
     Severity:  Normal        |   Keywords:
Actual Points:                |  Parent ID:
       Points:                |   Reviewer:
      Sponsor:                |
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 For the sake of checking whether my bridges are running properly, a
 regular nagios job tries to establish a tcp connection to a HS running on
 each bridge, every 5 minutes. This is done through 'torsocks check_ssh -H
 abcdef.onion -p 22' but the issue in this ticket is reproducible with
 'torsocks nc abcdef.onion 22' as well.

 Connections randomly fail, causing a lot of monitoring noise, though I bet
 that for other users this manifests as hosts being unavailable completely.

 As a test, I restarted tor and waited for a nagios check to fail. I then
 stopped nagios completely, causing tor to be idle, and manually ran a
 single check. The tor debug log, trimmed to the rough timeframe in which I
 ran the check, can be found at https://tvdw.eu/tor-
 debug-20160524220000.log

 torsocks says: [May 24 22:00:33] ERROR torsocks[28974]: General SOCKS
 server failure (in socks5_recv_connect_reply() at socks5.c:516)
 (note the timestamp, this failure is visible in tor's logs)

 In my test the client ran Tor 0.2.7.6, and the HS ran 0.2.8.2, though I
 have been able to reproduce this with various tor versions on the HS side.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/19166>
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