[tor-bugs] #15761 [Tor]: Bridges stop working when UseBridges is set (was: UseBridges and ExitNodes don't play together)

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#15761: Bridges stop working when UseBridges is set
------------------------+--------------------------
     Reporter:  qbi     |      Owner:
         Type:  defect  |     Status:  new
     Priority:  normal  |  Milestone:
    Component:  Tor     |    Version:  Tor: 0.2.6.7
   Resolution:          |   Keywords:
Actual Points:          |  Parent ID:
       Points:          |
------------------------+--------------------------
Description changed by qbi:

Old description:

> Tor's Q&A page has a [https://tor.stackexchange.com/q/6697/88 question]
> where someone uses bridges and `ExitNodes` and can't get a connection. So
> I tried to reproduce it:
>
> 1. Retrieve some bridges (with obfs3 in this case) and enter them into
> `torrc`.
> 2. Set `ExitNodes {US}`
> 3. restart Tor and everything is fine.
> 4. Add `UseBridges 1` and restart Tor.
>
> Now Tor can't get a connection anymore. I see the following log message
> every second:
>
> {{{
> Apr 21 19:05:42.000 [info] should_delay_dir_fetches(): Delaying dir
> fetches (no running bridges known)
> Apr 21 19:05:42.000 [info] compute_weighted_bandwidths(): Empty
> routerlist passed in to consensus weight node selection for rule weight
> as guard
> }}}
>
> When I remove `UseBridges` and restart Tor everything is fine.

New description:

 Tor's Q&A page has a [https://tor.stackexchange.com/q/6697/88 question]
 where someone uses bridges and `ExitNodes` and can't get a connection. So
 I tried to reproduce it:

 1. Retrieve some bridges (with obfs3 in this case) and enter them into
 `torrc`.
 2. Set `ExitNodes {US}`
 3. restart Tor and everything is fine.
 4. Add `UseBridges 1` and restart Tor.

 Now Tor can't get a connection anymore. I see the following log message
 every second:

 {{{
 Apr 21 19:05:42.000 [info] should_delay_dir_fetches(): Delaying dir
 fetches (no running bridges known)
 Apr 21 19:05:42.000 [info] compute_weighted_bandwidths(): Empty routerlist
 passed in to consensus weight node selection for rule weight as guard
 }}}

 When I remove `UseBridges` and restart Tor everything is fine.

 While trying to tracking it down I figured out that `ExitNodes` doesn't
 play a role here. A minimal non-working `torrc` just needs a
 `ClientTransportPlugin`, some obfs3 bridges and `UseBridges`.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/15761#comment:4>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
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