[tor-bugs] #27241 [Core Tor/Tor]: Extract information from more kinds of wedged directory connections.

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#27241: Extract information from more kinds of wedged directory connections.
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 Reporter:  nickm         |          Owner:  nickm
     Type:  enhancement   |         Status:  needs_information
 Priority:  Medium        |      Milestone:  Tor: 0.3.5.x-final
Component:  Core Tor/Tor  |        Version:
 Severity:  Normal        |     Resolution:
 Keywords:  fast-fix      |  Actual Points:
Parent ID:                |         Points:
 Reviewer:  mikeperry     |        Sponsor:  Sponsor8-can
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Comment (by nickm):

 Replying to [comment:5 mikeperry]:
 > To help me understand the consequences of this (and to figure out if I
 need to also do anything here for #25573), I have the following questions:
 >
 > 1. How do stalled dirconns translate to their linked edge_connection_ts?
 Can the edge connection "stall" first and/or get closed somewhere else, or
 will the dirconn always be the thing that stalls?

 I don't think we have any logic for an edge_connection_t to time out; in
 princple you can keep an ssh connection running over Tor indefinitely.
 Directory connections, however, do time out.


 > 2. What are the consequences to the dir conn if some other code marks
 the edge connnection is closed first?

 When one of a pair of linked connections is finally closed from
 connection_unlink in main.c, the other connection gets unlinked from it,
 and told to read all of its data from its input.

 So if something else closes the edge connection, the dir connection will
 get one last chance to handle any data queued on it before it is closed.

 > 3. When the dirconn is closed first (such as here or elsewhere in the
 code), where in the code do we decide to mark/clean up/close the
 corresponding linked edge conn? I could not find this..

 Hmm. I wonder if nothing closes it, actually. Can you think of some
 experiment we could do to find out?

 > For #25573, I'm particularly concerned about multihop hsdir dirconns.
 But if we ever make regular directory activity multihop, this could apply
 there too. Plus the linked conn close conditions may be relevant to this
 bug?

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/27241#comment:6>
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