[tor-bugs] #3443 [Tor Client]: Client with low CBT can't switch to a bridge if it's slow

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#3443: Client with low CBT can't switch to a bridge if it's slow
------------------------+---------------------------------------------------
 Reporter:  arma        |          Owner:                    
     Type:  defect      |         Status:  new               
 Priority:  major       |      Milestone:  Tor: 0.2.3.x-final
Component:  Tor Client  |        Version:                    
 Keywords:              |         Parent:                    
   Points:              |   Actualpoints:                    
------------------------+---------------------------------------------------
 I ran my Tor client on my laptop for a while in a stable place. It ended
 up thinking my connection is super-fast:
 {{{
 Jun 21 01:49:15.786 [info] circuit_build_times_parse_state(): Loaded
 1000/1000 values from 136 lines in circuit time histogram
 Jun 21 01:49:15.786 [info] circuit_build_times_get_xm(): Xm mode #0: 575
 55
 Jun 21 01:49:15.786 [info] circuit_build_times_get_xm(): Xm mode #1: 625
 51
 Jun 21 01:49:15.786 [info] circuit_build_times_get_xm(): Xm mode #2: 575
 55
 Jun 21 01:49:15.786 [notice] Based on 1000 circuit times, it looks like we
 don't need to wait so long for circuits to finish. We will now assume a
 circuit is too slow to use after waiting 2 seconds.
 Jun 21 01:49:15.786 [info] circuit_build_times_set_timeout(): Circuit
 timeout data: 2025.978516ms, 60000.000000ms, Xm: 590, a: 1.304577, r:
 0.199000
 }}}

 But then I restarted my Tor, this time with a bridge that is in .za:
 {{{
 Jun 21 01:49:16.968 [debug] onion_pick_cpath_exit(): Launching a one-hop
 circuit for dir tunnel.
 ...
 Jun 21 01:49:16.968 [notice] Bootstrapped 5%: Connecting to directory
 server.
 ...
 Jun 21 01:49:16.968 [debug] circuit_handle_first_hop(): connecting in
 progress (or finished). Good.
 ...
 Jun 21 01:49:17.256 [debug] connection_or_finished_connecting(): OR
 connect() to router at 196.x.x.x:10000 finished.
 Jun 21 01:49:17.256 [notice] Bootstrapped 10%: Finishing handshake with
 directory server.
 ...
 Jun 21 01:49:17.851 [debug] connection_tls_continue_handshake(): Done with
 initial SSL handshake (client-side). Requesting renegotiation.
 ...
 Jun 21 01:49:18.448 [debug] connection_tls_finish_handshake(): tls
 handshake with 196.x.x.x done. verifying.
 ...
 Jun 21 01:49:18.741 [info] command_process_versions_cell(): Negotiated
 version 2 with 196.x.x.x:10000; sending NETINFO.
 ...
 Jun 21 01:49:18.741 [debug] circuit_send_next_onion_skin(): First skin;
 sending create cell.
 Jun 21 01:49:18.741 [notice] Bootstrapped 15%: Establishing an encrypted
 directory connection.
 ...
 Jun 21 01:49:18.969 [info] circuit_expire_building(): Abandoning circ
 196.x.x.x:10000:54967 (state 0:doing handshakes, purpose 5)
 Jun 21 01:49:18.969 [info] exit circ (length 1, last hop
 0000000000000000000000000000000000000000):
 $0000000000000000000000000000000000000000(waiting for keys)
 Jun 21 01:49:18.969 [info] circuit_build_failed(): Our circuit failed to
 get a response from the first hop (196.x.x.x:10000). I'm going to try to
 rotate to a better connection.
 Jun 21 01:49:18.969 [info] connection_ap_fail_onehop(): Closing one-hop
 stream to '$0000000000000000000000000000000000000000/196.x.x.x' because
 the OR conn just failed.
 ...
 Jun 21 01:49:18.970 [info] connection_dir_request_failed(): Giving up on
 directory server at '196.x.x.x'; retrying
 ...
 Jun 21 01:49:27.978 [info] should_delay_dir_fetches(): delaying dir
 fetches (no running bridges known)
 }}}

 And now my Tor client is dead in the water.

-- 
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/3443>
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