Commit 11910cf5 authored by Mike Perry's avatar Mike Perry
Browse files

Do away with the complexity of the network liveness detection. 

We really should ignore any timeouts that have *no* network activity for their
entire measured lifetime, now that we have the 95th percentile measurement
changes. Usually this is up to a minute, even on fast connections.
parent 0744a175

src/or/circuitbuild.c

+21 −50
Original line number Diff line number Diff line
@@ -306,6 +306,7 @@ circuit_build_times_init(circuit_build_times_t *cbt) 
  control_event_buildtimeout_set(cbt, BUILDTIMEOUT_SET_EVENT_RESET);

}



#if 0

/**

 * Rewind our build time history by n positions.

 */
@@ -332,6 +333,7 @@ circuit_build_times_rewind_history(circuit_build_times_t *cbt, int n) 
          "Rewound history by %d places. Current index: %d. "

          "Total: %d", n, cbt->build_times_idx, cbt->total_build_times);

}

#endif



/**

 * Add a new build time value <b>time</b> to the set of build times. Time
@@ -941,8 +943,16 @@ circuit_build_times_needs_circuits_now(circuit_build_times_t *cbt) 
void

circuit_build_times_network_is_live(circuit_build_times_t *cbt)

{

  cbt->liveness.network_last_live = approx_time();

  cbt->liveness.nonlive_discarded = 0;

  time_t now = approx_time();

  if (cbt->liveness.nonlive_timeouts > 0) {

    log_notice(LD_CIRC,

               "Tor now sees network activity. Restoring circuit build "

               "timeout recording. Network was down for %ld seconds "

               "during %d circuit attempts.",

               (long int)now - cbt->liveness.network_last_live,

               cbt->liveness.nonlive_timeouts);

  }

  cbt->liveness.network_last_live = now;

  cbt->liveness.nonlive_timeouts = 0;

}
@@ -1002,11 +1012,18 @@ circuit_build_times_network_close(circuit_build_times_t *cbt, 
               now_buf);

    }

    cbt->liveness.nonlive_timeouts++;

    if (cbt->liveness.nonlive_timeouts == 1) {

      log_notice(LD_CIRC,

                 "Tor has not observed any network activity for the past %ld "

                 "seconds. Disabling circuit build timeout code.",

                 (long int)now - cbt->liveness.network_last_live);

    } else {

      log_info(LD_CIRC,

             "Got non-live timeout. Current count is: %d",

             cbt->liveness.nonlive_timeouts);

    }

  }

}



/**

 * Returns false if the network has not received a cell or tls handshake
@@ -1018,54 +1035,8 @@ circuit_build_times_network_close(circuit_build_times_t *cbt, 
int

circuit_build_times_network_check_live(circuit_build_times_t *cbt)

{

  time_t now = approx_time();

  if (cbt->liveness.nonlive_timeouts >= CBT_NETWORK_NONLIVE_DISCARD_COUNT) {

    if (!cbt->liveness.nonlive_discarded) {

      cbt->liveness.nonlive_discarded = 1;

      log_notice(LD_CIRC, "Network is no longer live (too many recent "

                "circuit timeouts). Dead for %ld seconds.",

                (long int)(now - cbt->liveness.network_last_live));

      /* Only discard NETWORK_NONLIVE_TIMEOUT_COUNT-1 because we stopped

       * counting after that */

      circuit_build_times_rewind_history(cbt,

                     CBT_NETWORK_NONLIVE_TIMEOUT_COUNT-1);

      control_event_buildtimeout_set(cbt, BUILDTIMEOUT_SET_EVENT_DISCARD);

    }

  if (cbt->liveness.nonlive_timeouts > 0) {

    return 0;

  } else if (cbt->liveness.nonlive_timeouts >=

                CBT_NETWORK_NONLIVE_TIMEOUT_COUNT) {

    if (cbt->liveness.suspended_timeout <= 0) {

      cbt->liveness.suspended_timeout = cbt->timeout_ms;

      cbt->liveness.suspended_close_timeout = cbt->close_ms;



      if (cbt->timeout_ms < circuit_build_times_get_initial_timeout())

        cbt->timeout_ms = circuit_build_times_get_initial_timeout();

      else

        cbt->timeout_ms *= 2;



      if (cbt->close_ms < circuit_build_times_get_initial_timeout())

        cbt->close_ms = circuit_build_times_get_initial_timeout();

      else

        cbt->close_ms *= 2;



      log_notice(LD_CIRC,

                "Network is flaky. No activity for %ld seconds. "

                "Temporarily raising timeout to %lds.",

                (long int)(now - cbt->liveness.network_last_live),

                tor_lround(cbt->timeout_ms/1000));

      control_event_buildtimeout_set(cbt, BUILDTIMEOUT_SET_EVENT_SUSPENDED);

    }



    return 0;

  } else if (cbt->liveness.suspended_timeout > 0) {

    log_notice(LD_CIRC,

              "Network activity has resumed. "

              "Resuming circuit timeout calculations.");

    cbt->timeout_ms = cbt->liveness.suspended_timeout;

    cbt->close_ms = cbt->liveness.suspended_close_timeout;

    cbt->liveness.suspended_timeout = 0;

    cbt->liveness.suspended_close_timeout = 0;

    control_event_buildtimeout_set(cbt, BUILDTIMEOUT_SET_EVENT_RESUME);

  }



  return 1;

src/or/or.h

+1 −31
Original line number Diff line number Diff line
@@ -2961,26 +2961,6 @@ typedef uint32_t build_time_t; 
/** Save state every 10 circuits */

#define CBT_SAVE_STATE_EVERY 10



/* Circuit Build Timeout network liveness constants */



/**

 * Have we received a cell in the last N circ attempts?

 *

 * This tells us when to temporarily switch back to

 * BUILD_TIMEOUT_INITIAL_VALUE until we start getting cells,

 * at which point we switch back to computing the timeout from

 * our saved history.

 */

#define CBT_NETWORK_NONLIVE_TIMEOUT_COUNT 3



/**

 * This tells us when to toss out the last streak of N timeouts.

 *

 * If instead we start getting cells, we switch back to computing the timeout

 * from our saved history.

 */

#define CBT_NETWORK_NONLIVE_DISCARD_COUNT (CBT_NETWORK_NONLIVE_TIMEOUT_COUNT*2)



/* Circuit build times consensus parameters */



/**
@@ -3021,9 +3001,7 @@ double circuit_build_times_quantile_cutoff(void); 
#define CBT_DEFAULT_TIMEOUT_INITIAL_VALUE (60*1000)

int32_t circuit_build_times_initial_timeout(void);



#if CBT_DEFAULT_MAX_RECENT_TIMEOUT_COUNT < 1 || \

    CBT_NETWORK_NONLIVE_DISCARD_COUNT < 1 || \

    CBT_NETWORK_NONLIVE_TIMEOUT_COUNT < 1

#if CBT_DEFAULT_MAX_RECENT_TIMEOUT_COUNT < 1

#error "RECENT_CIRCUITS is set too low."

#endif
@@ -3033,8 +3011,6 @@ typedef struct { 
  time_t network_last_live;

  /** If the network is not live, how many timeouts has this caused? */

  int nonlive_timeouts;

  /** If the network is not live, have we yet discarded our history? */

  int nonlive_discarded;

  /** Circular array of circuits that have made it to the first hop. Slot is

   * 1 if circuit timed out, 0 if circuit succeeded */

  int8_t *timeouts_after_firsthop;
@@ -3042,12 +3018,6 @@ typedef struct { 
  int num_recent_circs;

  /** Index into circular array. */

  int after_firsthop_idx;

  /** Timeout gathering is suspended if non-zero. The old timeout value

    * is stored here in that case. */

  double suspended_timeout;

  /** Timeout gathering is suspended if non-zero. The old close value

    * is stored here in that case. */

  double suspended_close_timeout;

} network_liveness_t;



/** Structure for circuit build times history */

src/test/test.c

+6 −20
Original line number Diff line number Diff line
@@ -499,7 +499,7 @@ test_circuit_timeout(void) 


    build_times_idx = estimate.build_times_idx;

    total_build_times = estimate.total_build_times;

    for (i = 0; i < CBT_NETWORK_NONLIVE_TIMEOUT_COUNT; i++) {



    test_assert(circuit_build_times_network_check_live(&estimate));

    test_assert(circuit_build_times_network_check_live(&final));
@@ -507,20 +507,6 @@ test_circuit_timeout(void) 
            (time_t)(approx_time()-estimate.close_ms/1000.0-1));

    circuit_build_times_count_close(&final, 0,

            (time_t)(approx_time()-final.close_ms/1000.0-1));

    }



    test_assert(!circuit_build_times_network_check_live(&estimate));

    test_assert(!circuit_build_times_network_check_live(&final));



    for ( ; i < CBT_NETWORK_NONLIVE_DISCARD_COUNT; i++) {

      circuit_build_times_count_close(&estimate, 0,

                (time_t)(approx_time()-estimate.close_ms/1000.0-1));



      if (i < CBT_NETWORK_NONLIVE_DISCARD_COUNT-1) {

        circuit_build_times_count_close(&final, 0,

                (time_t)(approx_time()-final.close_ms/1000.0-1));

      }

    }



    test_assert(!circuit_build_times_network_check_live(&estimate));

    test_assert(!circuit_build_times_network_check_live(&final));