test_circuitpadding.c 81.7 KB
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#define TOR_CHANNEL_INTERNAL_
#define TOR_TIMERS_PRIVATE
#define CIRCUITPADDING_PRIVATE
#define NETWORKSTATUS_PRIVATE

#include "core/or/or.h"
#include "test.h"
#include "lib/testsupport/testsupport.h"
#include "core/or/connection_or.h"
#include "core/or/channel.h"
#include "core/or/channeltls.h"
#include <event.h>
#include "lib/evloop/compat_libevent.h"
#include "lib/time/compat_time.h"
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#include "lib/defs/time.h"
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#include "core/or/relay.h"
#include "core/or/circuitlist.h"
#include "core/or/circuitbuild.h"
#include "core/or/circuitpadding.h"
#include "core/crypto/relay_crypto.h"
#include "core/or/protover.h"
#include "feature/nodelist/nodelist.h"
#include "lib/evloop/compat_libevent.h"
#include "app/config/config.h"

#include "feature/nodelist/routerstatus_st.h"
#include "feature/nodelist/networkstatus_st.h"
#include "feature/nodelist/node_st.h"
#include "core/or/cell_st.h"
#include "core/or/crypt_path_st.h"
#include "core/or/or_circuit_st.h"
#include "core/or/origin_circuit_st.h"

extern smartlist_t *connection_array;

circid_t get_unique_circ_id_by_chan(channel_t *chan);
void helper_create_basic_machine(void);
static void helper_create_conditional_machines(void);

static or_circuit_t * new_fake_orcirc(channel_t *nchan, channel_t *pchan);
channel_t *new_fake_channel(void);
void test_circuitpadding_negotiation(void *arg);
void test_circuitpadding_wronghop(void *arg);
void test_circuitpadding_conditions(void *arg);

void test_circuitpadding_serialize(void *arg);
void test_circuitpadding_rtt(void *arg);
void test_circuitpadding_tokens(void *arg);

static void
simulate_single_hop_extend(circuit_t *client, circuit_t *mid_relay,
                           int padding);
void free_fake_orcirc(circuit_t *circ);
void free_fake_origin_circuit(origin_circuit_t *circ);

static int deliver_negotiated = 1;
static int64_t curr_mocked_time;

static node_t padding_node;
static node_t non_padding_node;

static channel_t dummy_channel;
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static circpad_machine_spec_t circ_client_machine;
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static void
timers_advance_and_run(int64_t msec_update)
{
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  curr_mocked_time += msec_update*TOR_NSEC_PER_MSEC;
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  monotime_coarse_set_mock_time_nsec(curr_mocked_time);
  monotime_set_mock_time_nsec(curr_mocked_time);
  timers_run_pending();
}

static void
nodes_init(void)
{
  padding_node.rs = tor_malloc_zero(sizeof(routerstatus_t));
  padding_node.rs->pv.supports_padding = 1;

  non_padding_node.rs = tor_malloc_zero(sizeof(routerstatus_t));
  non_padding_node.rs->pv.supports_padding = 0;
}

static void
nodes_free(void)
{
  tor_free(padding_node.rs);

  tor_free(non_padding_node.rs);
}

static const node_t *
node_get_by_id_mock(const char *identity_digest)
{
  if (identity_digest[0] == 1) {
    return &padding_node;
  } else if (identity_digest[0] == 0) {
    return &non_padding_node;
  }

  return NULL;
}

static or_circuit_t *
new_fake_orcirc(channel_t *nchan, channel_t *pchan)
{
  or_circuit_t *orcirc = NULL;
  circuit_t *circ = NULL;
  crypt_path_t tmp_cpath;
  char whatevs_key[CPATH_KEY_MATERIAL_LEN];

  orcirc = tor_malloc_zero(sizeof(*orcirc));
  circ = &(orcirc->base_);
  circ->magic = OR_CIRCUIT_MAGIC;

  //circ->n_chan = nchan;
  circ->n_circ_id = get_unique_circ_id_by_chan(nchan);
  circ->n_mux = NULL; /* ?? */
  cell_queue_init(&(circ->n_chan_cells));
  circ->n_hop = NULL;
  circ->streams_blocked_on_n_chan = 0;
  circ->streams_blocked_on_p_chan = 0;
  circ->n_delete_pending = 0;
  circ->p_delete_pending = 0;
  circ->received_destroy = 0;
  circ->state = CIRCUIT_STATE_OPEN;
  circ->purpose = CIRCUIT_PURPOSE_OR;
  circ->package_window = CIRCWINDOW_START_MAX;
  circ->deliver_window = CIRCWINDOW_START_MAX;
  circ->n_chan_create_cell = NULL;

  //orcirc->p_chan = pchan;
  orcirc->p_circ_id = get_unique_circ_id_by_chan(pchan);
  cell_queue_init(&(orcirc->p_chan_cells));

  circuit_set_p_circid_chan(orcirc, orcirc->p_circ_id, pchan);
  circuit_set_n_circid_chan(circ, circ->n_circ_id, nchan);

  memset(&tmp_cpath, 0, sizeof(tmp_cpath));
  if (circuit_init_cpath_crypto(&tmp_cpath, whatevs_key,
                                sizeof(whatevs_key), 0, 0)<0) {
    log_warn(LD_BUG,"Circuit initialization failed");
    return NULL;
  }
  orcirc->crypto = tmp_cpath.crypto;

  return orcirc;
}

void
free_fake_orcirc(circuit_t *circ)
{
  or_circuit_t *orcirc = TO_OR_CIRCUIT(circ);

  relay_crypto_clear(&orcirc->crypto);

  circpad_circuit_free_all_machineinfos(circ);
  tor_free(circ);
}

void
free_fake_origin_circuit(origin_circuit_t *circ)
{
  circpad_circuit_free_all_machineinfos(TO_CIRCUIT(circ));
  circuit_clear_cpath(circ);
  tor_free(circ);
}

void dummy_nop_timer(void);

//static int dont_stop_libevent = 0;

static circuit_t *client_side;
static circuit_t *relay_side;

static int n_client_cells = 0;
static int n_relay_cells = 0;

static int
circuit_package_relay_cell_mock(cell_t *cell, circuit_t *circ,
                           cell_direction_t cell_direction,
                           crypt_path_t *layer_hint, streamid_t on_stream,
                           const char *filename, int lineno);

static void
circuitmux_attach_circuit_mock(circuitmux_t *cmux, circuit_t *circ,
                               cell_direction_t direction);

static void
circuitmux_attach_circuit_mock(circuitmux_t *cmux, circuit_t *circ,
                               cell_direction_t direction)
{
  (void)cmux;
  (void)circ;
  (void)direction;

  return;
}

static int
circuit_package_relay_cell_mock(cell_t *cell, circuit_t *circ,
                           cell_direction_t cell_direction,
                           crypt_path_t *layer_hint, streamid_t on_stream,
                           const char *filename, int lineno)
{
  (void)cell; (void)on_stream; (void)filename; (void)lineno;

  if (circ == client_side) {
    if (cell->payload[0] == RELAY_COMMAND_PADDING_NEGOTIATE) {
      // Deliver to relay
      circpad_handle_padding_negotiate(relay_side, cell);
    } else {

      int is_target_hop = circpad_padding_is_from_expected_hop(circ,
                                                             layer_hint);
      tt_int_op(cell_direction, OP_EQ, CELL_DIRECTION_OUT);
      tt_int_op(is_target_hop, OP_EQ, 1);

      // No need to pretend a padding cell was sent: This event is
      // now emitted internally when the circuitpadding code sends them.
      //circpad_cell_event_padding_sent(client_side);

      // Receive padding cell at middle
      circpad_deliver_recognized_relay_cell_events(relay_side,
              cell->payload[0], NULL);
    }
    n_client_cells++;
  } else if (circ == relay_side) {
    tt_int_op(cell_direction, OP_EQ, CELL_DIRECTION_IN);

    if (cell->payload[0] == RELAY_COMMAND_PADDING_NEGOTIATED) {
      // XXX: blah need right layer_hint..
      if (deliver_negotiated)
        circpad_handle_padding_negotiated(client_side, cell,
                                          TO_ORIGIN_CIRCUIT(client_side)
                                             ->cpath->next);
    } else if (cell->payload[0] == RELAY_COMMAND_PADDING_NEGOTIATE) {
      circpad_handle_padding_negotiate(client_side, cell);
    } else {
      // No need to pretend a padding cell was sent: This event is
      // now emitted internally when the circuitpadding code sends them.
      //circpad_cell_event_padding_sent(relay_side);

      // Receive padding cell at client
      circpad_deliver_recognized_relay_cell_events(client_side,
              cell->payload[0],
              TO_ORIGIN_CIRCUIT(client_side)->cpath->next);
    }

    n_relay_cells++;
  }

 done:
  timers_advance_and_run(1);
  return 0;
}

// Test reading and writing padding to strings (or options_t + consensus)
void
test_circuitpadding_serialize(void *arg)
{
  (void)arg;
}

static signed_error_t
circpad_send_command_to_hop_mock(origin_circuit_t *circ, uint8_t hopnum,
                                 uint8_t relay_command, const uint8_t *payload,
                                 ssize_t payload_len)
{
  (void) circ;
  (void) hopnum;
  (void) relay_command;
  (void) payload;
  (void) payload_len;
  return 0;
}

void
test_circuitpadding_rtt(void *arg)
{
  /* Test Plan:
   *
   * 1. Test RTT measurement server side
   *    a. test usage of measured RTT
   * 2. Test termination of RTT measurement
   *    a. test non-update of RTT
   * 3. Test client side circuit and non-application of RTT..
   */
  circpad_delay_t rtt_estimate;
  (void)arg;

  MOCK(circuitmux_attach_circuit, circuitmux_attach_circuit_mock);
  MOCK(circpad_send_command_to_hop, circpad_send_command_to_hop_mock);

  dummy_channel.cmux = circuitmux_alloc();
  relay_side = TO_CIRCUIT(new_fake_orcirc(&dummy_channel, &dummy_channel));
  client_side = TO_CIRCUIT(origin_circuit_new());
  relay_side->purpose = CIRCUIT_PURPOSE_OR;
  client_side->purpose = CIRCUIT_PURPOSE_C_GENERAL;

  monotime_init();
  monotime_enable_test_mocking();
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  monotime_set_mock_time_nsec(1*TOR_NSEC_PER_USEC);
  monotime_coarse_set_mock_time_nsec(1*TOR_NSEC_PER_USEC);
  curr_mocked_time = 1*TOR_NSEC_PER_USEC;
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  timers_initialize();
  circpad_machines_init();
  helper_create_basic_machine();

  MOCK(circuit_package_relay_cell,
       circuit_package_relay_cell_mock);

  client_side->padding_machine[0] = &circ_client_machine;
  client_side->padding_info[0] = circpad_circuit_machineinfo_new(client_side,
                                                                 0);

  relay_side->padding_machine[0] = &circ_client_machine;
  relay_side->padding_info[0] = circpad_circuit_machineinfo_new(client_side,0);

  /* Test 1: Test measuring RTT */
  circpad_cell_event_nonpadding_received((circuit_t*)relay_side);
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  tt_u64_op(relay_side->padding_info[0]->last_received_time_usec, OP_NE, 0);
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  timers_advance_and_run(20);

  circpad_cell_event_nonpadding_sent((circuit_t*)relay_side);
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  tt_u64_op(relay_side->padding_info[0]->last_received_time_usec, OP_EQ, 0);
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  tt_int_op(relay_side->padding_info[0]->rtt_estimate_usec, OP_GE, 19000);
  tt_int_op(relay_side->padding_info[0]->rtt_estimate_usec, OP_LE, 30000);
  tt_int_op(circpad_histogram_bin_to_usec(relay_side->padding_info[0], 0),
            OP_EQ,
            relay_side->padding_info[0]->rtt_estimate_usec+
            circpad_machine_current_state(
             relay_side->padding_info[0])->start_usec);

  circpad_cell_event_nonpadding_received((circuit_t*)relay_side);
  circpad_cell_event_nonpadding_received((circuit_t*)relay_side);
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  tt_u64_op(relay_side->padding_info[0]->last_received_time_usec, OP_NE, 0);
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  timers_advance_and_run(20);
  circpad_cell_event_nonpadding_sent((circuit_t*)relay_side);
  circpad_cell_event_nonpadding_sent((circuit_t*)relay_side);
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  tt_u64_op(relay_side->padding_info[0]->last_received_time_usec, OP_EQ, 0);
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  tt_int_op(relay_side->padding_info[0]->rtt_estimate_usec, OP_GE, 20000);
  tt_int_op(relay_side->padding_info[0]->rtt_estimate_usec, OP_LE, 21000);
  tt_int_op(circpad_histogram_bin_to_usec(relay_side->padding_info[0], 0),
            OP_EQ,
            relay_side->padding_info[0]->rtt_estimate_usec+
            circpad_machine_current_state(
             relay_side->padding_info[0])->start_usec);

  /* Test 2: Termination of RTT measurement (from the previous test) */
  tt_int_op(relay_side->padding_info[0]->stop_rtt_update, OP_EQ, 1);
  rtt_estimate = relay_side->padding_info[0]->rtt_estimate_usec;

  circpad_cell_event_nonpadding_received((circuit_t*)relay_side);
  timers_advance_and_run(4);
  circpad_cell_event_nonpadding_sent((circuit_t*)relay_side);

  tt_int_op(relay_side->padding_info[0]->rtt_estimate_usec, OP_EQ,
            rtt_estimate);
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  tt_u64_op(relay_side->padding_info[0]->last_received_time_usec, OP_EQ, 0);
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  tt_int_op(relay_side->padding_info[0]->stop_rtt_update, OP_EQ, 1);
  tt_int_op(circpad_histogram_bin_to_usec(relay_side->padding_info[0], 0),
            OP_EQ,
            relay_side->padding_info[0]->rtt_estimate_usec+
            circpad_machine_current_state(
             relay_side->padding_info[0])->start_usec);

  /* Test 3: Make sure client side machine properly ignores RTT */
  circpad_cell_event_nonpadding_received((circuit_t*)client_side);
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  tt_u64_op(client_side->padding_info[0]->last_received_time_usec, OP_EQ, 0);
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  timers_advance_and_run(20);
  circpad_cell_event_nonpadding_sent((circuit_t*)client_side);
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  tt_u64_op(client_side->padding_info[0]->last_received_time_usec, OP_EQ, 0);
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  tt_int_op(client_side->padding_info[0]->rtt_estimate_usec, OP_EQ, 0);
  tt_int_op(circpad_histogram_bin_to_usec(client_side->padding_info[0], 0),
            OP_NE, client_side->padding_info[0]->rtt_estimate_usec);
  tt_int_op(circpad_histogram_bin_to_usec(client_side->padding_info[0], 0),
            OP_EQ,
            circpad_machine_current_state(
                client_side->padding_info[0])->start_usec);
 done:
  free_fake_orcirc(relay_side);
  circuitmux_detach_all_circuits(dummy_channel.cmux, NULL);
  circuitmux_free(dummy_channel.cmux);
  timers_shutdown();
  monotime_disable_test_mocking();
  UNMOCK(circuit_package_relay_cell);
  UNMOCK(circuitmux_attach_circuit);
  tor_free(circ_client_machine.states);

  return;
}

void
helper_create_basic_machine(void)
{
  /* Start, burst */
  circpad_machine_states_init(&circ_client_machine, 2);

  circ_client_machine.states[CIRCPAD_STATE_START].
      next_state[CIRCPAD_EVENT_NONPADDING_RECV] = CIRCPAD_STATE_BURST;

  circ_client_machine.states[CIRCPAD_STATE_BURST].
      next_state[CIRCPAD_EVENT_PADDING_RECV] = CIRCPAD_STATE_BURST;
  circ_client_machine.states[CIRCPAD_STATE_BURST].
      next_state[CIRCPAD_EVENT_NONPADDING_RECV] = CIRCPAD_STATE_BURST;

  circ_client_machine.states[CIRCPAD_STATE_BURST].
      next_state[CIRCPAD_EVENT_NONPADDING_SENT] = CIRCPAD_STATE_CANCEL;

  // FIXME: Is this what we want?
  circ_client_machine.states[CIRCPAD_STATE_BURST].token_removal =
      CIRCPAD_TOKEN_REMOVAL_HIGHER;

  // FIXME: Tune this histogram
  circ_client_machine.states[CIRCPAD_STATE_BURST].histogram_len = 5;
  circ_client_machine.states[CIRCPAD_STATE_BURST].start_usec = 500;
  circ_client_machine.states[CIRCPAD_STATE_BURST].range_usec = 1000000;
  circ_client_machine.states[CIRCPAD_STATE_BURST].histogram[0] = 1;
  circ_client_machine.states[CIRCPAD_STATE_BURST].histogram[1] = 0;
  circ_client_machine.states[CIRCPAD_STATE_BURST].histogram[2] = 2;
  circ_client_machine.states[CIRCPAD_STATE_BURST].histogram[3] = 2;
  circ_client_machine.states[CIRCPAD_STATE_BURST].histogram[4] = 2;
  circ_client_machine.states[CIRCPAD_STATE_BURST].histogram_total_tokens = 7;
  circ_client_machine.states[CIRCPAD_STATE_BURST].use_rtt_estimate = 1;

  return;
}

#define BIG_HISTOGRAM_LEN 10

/** Setup a machine with a big histogram */
static void
helper_create_machine_with_big_histogram(circpad_removal_t removal_strategy)
{
  const int tokens_per_bin = 2;

  /* Start, burst */
  circpad_machine_states_init(&circ_client_machine, 2);

  circpad_state_t *burst_state =
    &circ_client_machine.states[CIRCPAD_STATE_BURST];

  circ_client_machine.states[CIRCPAD_STATE_START].
    next_state[CIRCPAD_EVENT_NONPADDING_RECV] = CIRCPAD_STATE_BURST;

  burst_state->next_state[CIRCPAD_EVENT_PADDING_RECV] = CIRCPAD_STATE_BURST;
  burst_state->next_state[CIRCPAD_EVENT_NONPADDING_RECV] =CIRCPAD_STATE_BURST;

  burst_state->next_state[CIRCPAD_EVENT_NONPADDING_SENT] =CIRCPAD_STATE_CANCEL;

  burst_state->token_removal = CIRCPAD_TOKEN_REMOVAL_HIGHER;

  burst_state->histogram_len = BIG_HISTOGRAM_LEN;
  burst_state->start_usec = 0;
  burst_state->range_usec = 1000;

  int n_tokens = 0;
  for (int i = 0; i < BIG_HISTOGRAM_LEN ; i++) {
    burst_state->histogram[i] = tokens_per_bin;
    n_tokens += tokens_per_bin;
  }

  burst_state->histogram_total_tokens = n_tokens;
  burst_state->length_dist.type = CIRCPAD_DIST_UNIFORM;
  burst_state->length_dist.param1 = n_tokens;
  burst_state->length_dist.param2 = n_tokens;
  burst_state->max_length = n_tokens;
  burst_state->length_includes_nonpadding = 1;
  burst_state->use_rtt_estimate = 0;
  burst_state->token_removal = removal_strategy;
}

static circpad_decision_t
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circpad_machine_schedule_padding_mock(circpad_machine_state_t *mi)
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{
  (void)mi;
  return 0;
}

static uint64_t
mock_monotime_absolute_usec(void)
{
  return 100;
}

/** Test higher token removal strategy by bin  */
static void
test_circuitpadding_token_removal_higher(void *arg)
{
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  circpad_machine_state_t *mi;
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  (void)arg;

  /* Mock it up */
  MOCK(monotime_absolute_usec, mock_monotime_absolute_usec);
  MOCK(circpad_machine_schedule_padding,circpad_machine_schedule_padding_mock);

  /* Setup test environment (time etc.) */
  client_side = (circuit_t *)origin_circuit_new();
  client_side->purpose = CIRCUIT_PURPOSE_C_GENERAL;
  monotime_enable_test_mocking();

  /* Create test machine */
  helper_create_machine_with_big_histogram(CIRCPAD_TOKEN_REMOVAL_HIGHER);
  client_side->padding_machine[0] = &circ_client_machine;
  client_side->padding_info[0] =
    circpad_circuit_machineinfo_new(client_side, 0);

  /* move the machine to the right state */
  circpad_cell_event_nonpadding_received((circuit_t*)client_side);
  tt_int_op(client_side->padding_info[0]->current_state, OP_EQ,
            CIRCPAD_STATE_BURST);

  /* Get the machine and setup tokens */
  mi = client_side->padding_info[0];
  tt_assert(mi);

  /*************************************************************************/

  uint64_t current_time = monotime_absolute_usec();

  /* Test left boundaries of each histogram bin: */
  const circpad_delay_t bin_left_bounds[] =
    {0, 1, 7, 15, 31, 62, 125, 250, 500, CIRCPAD_DELAY_INFINITE};
  for (int i = 0; i < BIG_HISTOGRAM_LEN ; i++) {
    tt_uint_op(bin_left_bounds[i], OP_EQ,
               circpad_histogram_bin_to_usec(mi, i));
  }

  /* Check that all bins have two tokens right now */
  for (int i = 0; i < BIG_HISTOGRAM_LEN ; i++) {
    tt_int_op(mi->histogram[i], OP_EQ, 2);
  }

  /* This is the right order to remove tokens from this histogram. That is, we
   * first remove tokens from the 4th bin since 57 usec is nearest to the 4th
   * bin midpoint (31 + (62-31)/2 == 46). Then we remove from the 3rd bin for
   * the same reason, then from the 5th, etc. */
  const int bin_removal_order[] = {4, 5, 6, 7, 8};
  unsigned i;

  /* Remove all tokens from all bins apart from the infinity bin */
  for (i = 0; i < sizeof(bin_removal_order)/sizeof(int) ; i++) {
    int bin_to_remove = bin_removal_order[i];
    log_debug(LD_GENERAL, "Testing that %d attempt removes %d bin",
              i, bin_to_remove);

    tt_int_op(mi->histogram[bin_to_remove], OP_EQ, 2);

    mi->padding_scheduled_at_usec = current_time - 57;
    circpad_machine_remove_token(mi);

    tt_int_op(mi->histogram[bin_to_remove], OP_EQ, 1);

    mi->padding_scheduled_at_usec = current_time - 57;
    circpad_machine_remove_token(mi);

    /* Test that we cleaned out this bin. Don't do this in the case of the last
       bin since the tokens will get refilled */
    if (i != BIG_HISTOGRAM_LEN - 2) {
      tt_int_op(mi->histogram[bin_to_remove], OP_EQ, 0);
    }
  }

  /* Check that all lowe bins are not touched */
  for (i=0; i < 4 ; i++) {
    tt_int_op(mi->histogram[i], OP_EQ, 2);
  }

  /* Test below the lowest bin, for coverage */
  tt_int_op(client_side->padding_info[0]->current_state, OP_EQ,
            CIRCPAD_STATE_BURST);
  circ_client_machine.states[CIRCPAD_STATE_BURST].start_usec = 100;
  mi->padding_scheduled_at_usec = current_time - 1;
  circpad_machine_remove_token(mi);
  tt_int_op(mi->histogram[0], OP_EQ, 1);

 done:
  free_fake_origin_circuit(TO_ORIGIN_CIRCUIT(client_side));
  monotime_disable_test_mocking();
  tor_free(circ_client_machine.states);
}

/** Test lower token removal strategy by bin  */
static void
test_circuitpadding_token_removal_lower(void *arg)
{
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  circpad_machine_state_t *mi;
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  (void)arg;

  /* Mock it up */
  MOCK(monotime_absolute_usec, mock_monotime_absolute_usec);
  MOCK(circpad_machine_schedule_padding,circpad_machine_schedule_padding_mock);

  /* Setup test environment (time etc.) */
  client_side = (circuit_t *)origin_circuit_new();
  client_side->purpose = CIRCUIT_PURPOSE_C_GENERAL;
  monotime_enable_test_mocking();

  /* Create test machine */
  helper_create_machine_with_big_histogram(CIRCPAD_TOKEN_REMOVAL_LOWER);
  client_side->padding_machine[0] = &circ_client_machine;
  client_side->padding_info[0] =
    circpad_circuit_machineinfo_new(client_side, 0);

  /* move the machine to the right state */
  circpad_cell_event_nonpadding_received((circuit_t*)client_side);
  tt_int_op(client_side->padding_info[0]->current_state, OP_EQ,
            CIRCPAD_STATE_BURST);

  /* Get the machine and setup tokens */
  mi = client_side->padding_info[0];
  tt_assert(mi);

  /*************************************************************************/

  uint64_t current_time = monotime_absolute_usec();

  /* Test left boundaries of each histogram bin: */
  const circpad_delay_t bin_left_bounds[] =
    {0, 1, 7, 15, 31, 62, 125, 250, 500, CIRCPAD_DELAY_INFINITE};
  for (int i = 0; i < BIG_HISTOGRAM_LEN ; i++) {
    tt_uint_op(bin_left_bounds[i], OP_EQ,
               circpad_histogram_bin_to_usec(mi, i));
  }

  /* Check that all bins have two tokens right now */
  for (int i = 0; i < BIG_HISTOGRAM_LEN ; i++) {
    tt_int_op(mi->histogram[i], OP_EQ, 2);
  }

  /* This is the right order to remove tokens from this histogram. That is, we
   * first remove tokens from the 4th bin since 57 usec is nearest to the 4th
   * bin midpoint (31 + (62-31)/2 == 46). Then we remove from the 3rd bin for
   * the same reason, then from the 5th, etc. */
  const int bin_removal_order[] = {4, 3, 2, 1, 0};
  unsigned i;

  /* Remove all tokens from all bins apart from the infinity bin */
  for (i = 0; i < sizeof(bin_removal_order)/sizeof(int) ; i++) {
    int bin_to_remove = bin_removal_order[i];
    log_debug(LD_GENERAL, "Testing that %d attempt removes %d bin",
              i, bin_to_remove);

    tt_int_op(mi->histogram[bin_to_remove], OP_EQ, 2);

    mi->padding_scheduled_at_usec = current_time - 57;
    circpad_machine_remove_token(mi);

    tt_int_op(mi->histogram[bin_to_remove], OP_EQ, 1);

    mi->padding_scheduled_at_usec = current_time - 57;
    circpad_machine_remove_token(mi);

    /* Test that we cleaned out this bin. Don't do this in the case of the last
       bin since the tokens will get refilled */
    if (i != BIG_HISTOGRAM_LEN - 2) {
      tt_int_op(mi->histogram[bin_to_remove], OP_EQ, 0);
    }
  }

  /* Check that all higher bins are untouched */
  for (i = 5; i < BIG_HISTOGRAM_LEN ; i++) {
    tt_int_op(mi->histogram[i], OP_EQ, 2);
  }

  /* Test above the highest bin, for coverage */
  tt_int_op(client_side->padding_info[0]->current_state, OP_EQ,
            CIRCPAD_STATE_BURST);
  circ_client_machine.states[CIRCPAD_STATE_BURST].start_usec = 100;
  mi->padding_scheduled_at_usec = current_time - 29202;
  circpad_machine_remove_token(mi);
  tt_int_op(mi->histogram[BIG_HISTOGRAM_LEN-2], OP_EQ, 1);

 done:
  free_fake_origin_circuit(TO_ORIGIN_CIRCUIT(client_side));
  monotime_disable_test_mocking();
  tor_free(circ_client_machine.states);
}

/** Test closest token removal strategy by bin  */
static void
test_circuitpadding_closest_token_removal(void *arg)
{
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  circpad_machine_state_t *mi;
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  (void)arg;

  /* Mock it up */
  MOCK(monotime_absolute_usec, mock_monotime_absolute_usec);
  MOCK(circpad_machine_schedule_padding,circpad_machine_schedule_padding_mock);

  /* Setup test environment (time etc.) */
  client_side = (circuit_t *)origin_circuit_new();
  client_side->purpose = CIRCUIT_PURPOSE_C_GENERAL;
  monotime_enable_test_mocking();

  /* Create test machine */
  helper_create_machine_with_big_histogram(CIRCPAD_TOKEN_REMOVAL_CLOSEST);
  client_side->padding_machine[0] = &circ_client_machine;
  client_side->padding_info[0] =
    circpad_circuit_machineinfo_new(client_side, 0);

  /* move the machine to the right state */
  circpad_cell_event_nonpadding_received((circuit_t*)client_side);
  tt_int_op(client_side->padding_info[0]->current_state, OP_EQ,
            CIRCPAD_STATE_BURST);

  /* Get the machine and setup tokens */
  mi = client_side->padding_info[0];
  tt_assert(mi);

  /*************************************************************************/

  uint64_t current_time = monotime_absolute_usec();

  /* Test left boundaries of each histogram bin: */
  const circpad_delay_t bin_left_bounds[] =
    {0, 1, 7, 15, 31, 62, 125, 250, 500, CIRCPAD_DELAY_INFINITE};
  for (int i = 0; i < BIG_HISTOGRAM_LEN ; i++) {
    tt_uint_op(bin_left_bounds[i], OP_EQ,
               circpad_histogram_bin_to_usec(mi, i));
  }

  /* Check that all bins have two tokens right now */
  for (int i = 0; i < BIG_HISTOGRAM_LEN ; i++) {
    tt_int_op(mi->histogram[i], OP_EQ, 2);
  }

  /* This is the right order to remove tokens from this histogram. That is, we
   * first remove tokens from the 4th bin since 57 usec is nearest to the 4th
   * bin midpoint (31 + (62-31)/2 == 46). Then we remove from the 3rd bin for
   * the same reason, then from the 5th, etc. */
  const int bin_removal_order[] = {4, 3, 5, 2, 6, 1, 7, 0, 8, 9};

  /* Remove all tokens from all bins apart from the infinity bin */
  for (int i = 0; i < BIG_HISTOGRAM_LEN-1 ; i++) {
    int bin_to_remove = bin_removal_order[i];
    log_debug(LD_GENERAL, "Testing that %d attempt removes %d bin",
              i, bin_to_remove);

    tt_int_op(mi->histogram[bin_to_remove], OP_EQ, 2);

    mi->padding_scheduled_at_usec = current_time - 57;
    circpad_machine_remove_token(mi);

    tt_int_op(mi->histogram[bin_to_remove], OP_EQ, 1);

    mi->padding_scheduled_at_usec = current_time - 57;
    circpad_machine_remove_token(mi);

    /* Test that we cleaned out this bin. Don't do this in the case of the last
       bin since the tokens will get refilled */
    if (i != BIG_HISTOGRAM_LEN - 2) {
      tt_int_op(mi->histogram[bin_to_remove], OP_EQ, 0);
    }
  }

  /* Check that all bins have been refilled */
  for (int i = 0; i < BIG_HISTOGRAM_LEN ; i++) {
    tt_int_op(mi->histogram[i], OP_EQ, 2);
  }

  /* Test below the lowest bin, for coverage */
  tt_int_op(client_side->padding_info[0]->current_state, OP_EQ,
            CIRCPAD_STATE_BURST);
  circ_client_machine.states[CIRCPAD_STATE_BURST].start_usec = 100;
  mi->padding_scheduled_at_usec = current_time - 102;
  mi->histogram[0] = 0;
  circpad_machine_remove_token(mi);
  tt_int_op(mi->histogram[1], OP_EQ, 1);

  /* Test above the highest bin, for coverage */
  tt_int_op(client_side->padding_info[0]->current_state, OP_EQ,
            CIRCPAD_STATE_BURST);
  circ_client_machine.states[CIRCPAD_STATE_BURST].start_usec = 100;
  mi->padding_scheduled_at_usec = current_time - 29202;
  circpad_machine_remove_token(mi);
  tt_int_op(mi->histogram[BIG_HISTOGRAM_LEN-2], OP_EQ, 1);

 done:
  free_fake_origin_circuit(TO_ORIGIN_CIRCUIT(client_side));
  monotime_disable_test_mocking();
  tor_free(circ_client_machine.states);
}

/** Test closest token removal strategy with usec  */
static void
test_circuitpadding_closest_token_removal_usec(void *arg)
{
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  circpad_machine_state_t *mi;
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  (void)arg;

  /* Mock it up */
  MOCK(monotime_absolute_usec, mock_monotime_absolute_usec);
  MOCK(circpad_machine_schedule_padding,circpad_machine_schedule_padding_mock);

  /* Setup test environment (time etc.) */
  client_side = (circuit_t *)origin_circuit_new();
  client_side->purpose = CIRCUIT_PURPOSE_C_GENERAL;
  monotime_enable_test_mocking();

  /* Create test machine */
  helper_create_machine_with_big_histogram(CIRCPAD_TOKEN_REMOVAL_CLOSEST_USEC);
  client_side->padding_machine[0] = &circ_client_machine;
  client_side->padding_info[0] =
    circpad_circuit_machineinfo_new(client_side, 0);

  /* move the machine to the right state */
  circpad_cell_event_nonpadding_received((circuit_t*)client_side);
  tt_int_op(client_side->padding_info[0]->current_state, OP_EQ,
            CIRCPAD_STATE_BURST);

  /* Get the machine and setup tokens */
  mi = client_side->padding_info[0];
  tt_assert(mi);

  /*************************************************************************/

  uint64_t current_time = monotime_absolute_usec();

  /* Test left boundaries of each histogram bin: */
  const circpad_delay_t bin_left_bounds[] =
    {0, 1, 7, 15, 31, 62, 125, 250, 500, CIRCPAD_DELAY_INFINITE};
  for (int i = 0; i < BIG_HISTOGRAM_LEN ; i++) {
    tt_uint_op(bin_left_bounds[i], OP_EQ,
               circpad_histogram_bin_to_usec(mi, i));
  }

  /* XXX we want to test remove_token_exact and
     circpad_machine_remove_closest_token() with usec */

  /* Check that all bins have two tokens right now */
  for (int i = 0; i < BIG_HISTOGRAM_LEN ; i++) {
    tt_int_op(mi->histogram[i], OP_EQ, 2);
  }

  /* This is the right order to remove tokens from this histogram. That is, we
   * first remove tokens from the 4th bin since 57 usec is nearest to the 4th
   * bin midpoint (31 + (62-31)/2 == 46). Then we remove from the 3rd bin for
   * the same reason, then from the 5th, etc. */
  const int bin_removal_order[] = {4, 3, 5, 2, 1, 0, 6, 7, 8, 9};

  /* Remove all tokens from all bins apart from the infinity bin */
  for (int i = 0; i < BIG_HISTOGRAM_LEN-1 ; i++) {
    int bin_to_remove = bin_removal_order[i];
    log_debug(LD_GENERAL, "Testing that %d attempt removes %d bin",
              i, bin_to_remove);

    tt_int_op(mi->histogram[bin_to_remove], OP_EQ, 2);

    mi->padding_scheduled_at_usec = current_time - 57;
    circpad_machine_remove_token(mi);

    tt_int_op(mi->histogram[bin_to_remove], OP_EQ, 1);

    mi->padding_scheduled_at_usec = current_time - 57;
    circpad_machine_remove_token(mi);

    /* Test that we cleaned out this bin. Don't do this in the case of the last
       bin since the tokens will get refilled */
    if (i != BIG_HISTOGRAM_LEN - 2) {
      tt_int_op(mi->histogram[bin_to_remove], OP_EQ, 0);
    }
  }

  /* Check that all bins have been refilled */
  for (int i = 0; i < BIG_HISTOGRAM_LEN ; i++) {
    tt_int_op(mi->histogram[i], OP_EQ, 2);
  }

  /* Test below the lowest bin, for coverage */
  tt_int_op(client_side->padding_info[0]->current_state, OP_EQ,
            CIRCPAD_STATE_BURST);
  circ_client_machine.states[CIRCPAD_STATE_BURST].start_usec = 100;
  mi->padding_scheduled_at_usec = current_time - 102;
  mi->histogram[0] = 0;
  circpad_machine_remove_token(mi);
  tt_int_op(mi->histogram[1], OP_EQ, 1);

  /* Test above the highest bin, for coverage */
  tt_int_op(client_side->padding_info[0]->current_state, OP_EQ,
            CIRCPAD_STATE_BURST);
  circ_client_machine.states[CIRCPAD_STATE_BURST].start_usec = 100;
  mi->padding_scheduled_at_usec = current_time - 29202;
  circpad_machine_remove_token(mi);
  tt_int_op(mi->histogram[BIG_HISTOGRAM_LEN-2], OP_EQ, 1);

 done:
  free_fake_origin_circuit(TO_ORIGIN_CIRCUIT(client_side));
  monotime_disable_test_mocking();
  tor_free(circ_client_machine.states);
}

/** Test closest token removal strategy with usec  */
static void
test_circuitpadding_token_removal_exact(void *arg)
{
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  circpad_machine_state_t *mi;
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  (void)arg;

  /* Mock it up */
  MOCK(monotime_absolute_usec, mock_monotime_absolute_usec);
  MOCK(circpad_machine_schedule_padding,circpad_machine_schedule_padding_mock);

  /* Setup test environment (time etc.) */
  client_side = (circuit_t *)origin_circuit_new();
  client_side->purpose = CIRCUIT_PURPOSE_C_GENERAL;
  monotime_enable_test_mocking();

  /* Create test machine */
  helper_create_machine_with_big_histogram(CIRCPAD_TOKEN_REMOVAL_EXACT);
  client_side->padding_machine[0] = &circ_client_machine;
  client_side->padding_info[0] =
    circpad_circuit_machineinfo_new(client_side, 0);

  /* move the machine to the right state */
  circpad_cell_event_nonpadding_received((circuit_t*)client_side);
  tt_int_op(client_side->padding_info[0]->current_state, OP_EQ,
            CIRCPAD_STATE_BURST);

  /* Get the machine and setup tokens */
  mi = client_side->padding_info[0];
  tt_assert(mi);

  /**********************************************************************/
  uint64_t current_time = monotime_absolute_usec();

  /* Ensure that we will clear out bin #4 with this usec */
  mi->padding_scheduled_at_usec = current_time - 57;
  tt_int_op(mi->histogram[4], OP_EQ, 2);
  circpad_machine_remove_token(mi);
  mi->padding_scheduled_at_usec = current_time - 57;
  tt_int_op(mi->histogram[4], OP_EQ, 1);
  circpad_machine_remove_token(mi);
  tt_int_op(mi->histogram[4], OP_EQ, 0);

  /* Ensure that we will not remove any other tokens even tho we try to, since
   * this is what the exact strategy dictates */
  mi->padding_scheduled_at_usec = current_time - 57;
  circpad_machine_remove_token(mi);
  for (int i = 0; i < BIG_HISTOGRAM_LEN ; i++) {
    if (i != 4) {
      tt_int_op(mi->histogram[i], OP_EQ, 2);
    }
  }

 done:
  free_fake_origin_circuit(TO_ORIGIN_CIRCUIT(client_side));
  monotime_disable_test_mocking();
  tor_free(circ_client_machine.states);
}

#undef BIG_HISTOGRAM_LEN

void
test_circuitpadding_tokens(void *arg)
{
  const circpad_state_t *state;
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  circpad_machine_state_t *mi;
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  (void)arg;

  /** Test plan:
   *
   * 1. Test symmetry between bin_to_usec and usec_to_bin
   *    a. Test conversion
   *    b. Test edge transitions (lower, upper)
   * 2. Test remove higher on an empty bin
   *    a. Normal bin
   *    b. Infinity bin
   *    c. Bin 0
   *    d. No higher
   * 3. Test remove lower
   *    a. Normal bin
   *    b. Bin 0
   *    c. No lower
   * 4. Test remove closest
   *    a. Closest lower
   *    b. Closest higher
   *    c. Closest 0
   *    d. Closest Infinity
   */
  client_side = TO_CIRCUIT(origin_circuit_new());
  client_side->purpose = CIRCUIT_PURPOSE_C_GENERAL;

  monotime_init();
  monotime_enable_test_mocking();
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  monotime_set_mock_time_nsec(1*TOR_NSEC_PER_USEC);
  monotime_coarse_set_mock_time_nsec(1*TOR_NSEC_PER_USEC);
  curr_mocked_time = 1*TOR_NSEC_PER_USEC;
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  timers_initialize();

  helper_create_basic_machine();
  client_side->padding_machine[0] = &circ_client_machine;
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