[tor-bugs] #23543 [Core Tor/Tor]: prop224: Disconnects on long-lasting HS connections (possibly because of mds)

Tor Bug Tracker & Wiki blackhole at torproject.org
Sat Sep 16 18:22:58 UTC 2017

#23543: prop224: Disconnects on long-lasting HS connections (possibly because of
 Reporter:  asn                          |          Owner:  (none)
     Type:  defect                       |         Status:  new
 Priority:  Medium                       |      Milestone:  Tor:
                                         |  0.3.2.x-final
Component:  Core Tor/Tor                 |        Version:
 Severity:  Normal                       |     Resolution:
 Keywords:  tor-hs prop224 prop224-bugs  |  Actual Points:
Parent ID:                               |         Points:  1
 Reviewer:                               |        Sponsor:

Comment (by arma):

 Replying to [ticket:23543 asn]:
 > but everytime the number of mds would decrease more and more. Then at
 some point it reached below minimum dir info, Tor stalled and then it
 started fetching mds again. It's like something expires mds while in
 memory, but there is no logic to fetch them back in before we reach the
 minimum point.

 There is something that expires the md's -- see microdesc_cache_clean().
 And if you haven't made any new socks requests lately, there won't be any
 predicted ports, so Tor won't be fetching new ones. Its list of
 descriptors *will* slowly decay, and that's ok. Or at least, that's
 intended by the current design.

 So maybe the weird bug here is that Tor cares about whether you have a
 current microdesc for your primary guard, in order to maintain the
 connection to it?

 If that's the issue, one fix would be to fix stuff so Tor doesn't break
 current connections just because a microdesc has disappeared. Another fix
 would be to prevent Tor from going dormant while it has any open
 connections. I'd be tempted to explore the former fix, since the latter
 one will (a) reduce the effectiveness of going dormant, and (b) probably
 require some fiddly bits where we say "oh but that connection was just for
 fetching a new consensus so it's not really a connection".

Ticket URL: <https://trac.torproject.org/projects/tor/ticket/23543#comment:1>
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