[tor-bugs] #10418 [Tor Launcher]: Make a "Use Default Bridges" Radio button in the Tor Launcher Bridge UI

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#10418: Make a "Use Default Bridges" Radio button in the Tor Launcher Bridge UI
------------------------------+------------------------------
     Reporter:  mikeperry     |      Owner:  brade
         Type:  enhancement   |     Status:  reopened
     Priority:  major         |  Milestone:
    Component:  Tor Launcher  |    Version:
   Resolution:                |   Keywords:  MikePerry201402R
Actual Points:                |  Parent ID:
       Points:                |
------------------------------+------------------------------

Comment (by brade):

 Replying to [comment:39 mcs]:
 > I wonder if there is a race inside tor between starting the client
 transport plugins and trying to use the bridges?  As we discussed, when
 default bridges are configured, Tor Launcher always starts tor with
 DisableNetwork=1.  Then it does a SETCONF to set UseBridges=1 and to
 configure the bridges (Bridge=<list>).  Then it does a second SETCONF with
 DisableNetwork=0.

 We did a little more investigation and learned that the "can't find a
 pluggable transport proxy
 supporting 'obfs3'" warnings are emitted by tor even if tor is started
 with networking enabled and if no SETCONF commands are issued by Tor
 Launcher.

 Interestingly, if we remove cached-descriptors and cached-descriptors.new
 before starting TBB, those warnings are not emitted by tor.

 Here are some steps to reproduce the problem just by running tor at the
 command line.

 1) Download and install one of GK's TBB builds from
 https://people.torproject.org/~gk/builds/3.6-beta-1/ (we tested on Mac
 OS).

 2) edit Data/Tor/torrc and place these lines in it:
 {{{
 Bridge obfs3 83.212.101.3:60475 A09D536DD1752D542E1FBB3C9CE4449D51298239
 Bridge obfs3 109.105.109.163:47779
 844B1F53FFD548C998F8D3B01B7E19FA07C3396E
 Bridge obfs3 109.105.109.163:38980
 9D7259A696F7DAB073043B28114112A46D36CFFD
 Bridge obfs3 169.229.59.74:31493 AF9F66B7B04F8FF6F32D455F05135250A16543C9
 Bridge obfs3 208.79.90.242:35658 BA61757846841D64A83EA2514C766CB92F1FB41F
 Bridge obfs3 169.229.59.75:46328 AF9F66B7B04F8FF6F32D455F05135250A16543C9
 UseBridges 1
 }}}

 3) Run tor like this:
 {{{
 cd Tor
 ./tor --defaults-torrc ../Data/Tor/torrc-defaults -f ../Data/Tor/torrc \
       --DataDirectory ../Data/Tor GeoIPFile ../Data/Tor/geoip
 }}}

 4) Run tor a second time and you will see some "can't find a pluggable
 transport proxy
 supporting 'obfs3'" warnings.  Also, netstat will probably show outbound
 TCP connections to some of the bridges for which warnings were emitted...
 which does not make a lot of sense to me.  The warnings seem spurious.

 5) rm Data/Tor/cached-descriptors and run tor a third time.  The warnings
 will not be emitted.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/10418#comment:40>
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