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Fix dist_min_usec documentation and naming.

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This commit is contained in:
George Kadianakis 2019-02-25 13:46:58 +02:00
parent 341cd6ea66
commit 331a067ae3
3 changed files with 28 additions and 24 deletions
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13
src/core/or/circuitpadding.c
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@ -380,17 +380,17 @@ circpad_choose_state_length(circpad_machine_state_t *mi)
*/
static circpad_delay_t
circpad_distribution_sample_iat_delay(const circpad_state_t *state,
circpad_delay_t min_delay)
circpad_delay_t delay_shift)
{
double val = circpad_distribution_sample(state->iat_dist);
/* These comparisons are safe, because the output is in the range
* [0, 2**32), and double has a precision of 53 bits. */
val = MAX(0, val);
val = MIN(val, state->dist_max_usec);
val = MIN(val, state->dist_max_sample_usec);
/* This addition is exact: val is at most 2**32-1, min_delay
* is at most 2**32-1, and doubles have a precision of 53 bits. */
val += min_delay;
val += delay_shift;
/* Clamp the distribution at infinite delay val */
return (circpad_delay_t)MIN(tor_llround(val), CIRCPAD_DELAY_INFINITE);
@ -420,9 +420,10 @@ circpad_machine_sample_delay(circpad_machine_state_t *mi)
if (state->iat_dist.type != CIRCPAD_DIST_NONE) {
/* Sample from a fixed IAT distribution and return */
circpad_delay_t min_iat_delay = state->use_rtt_estimate ?
mi->rtt_estimate_usec + state->dist_min_usec : state->dist_min_usec;
return circpad_distribution_sample_iat_delay(state, min_iat_delay);
circpad_delay_t iat_delay_shift = state->use_rtt_estimate ?
mi->rtt_estimate_usec + state->dist_added_shift_usec :
state->dist_added_shift_usec;
return circpad_distribution_sample_iat_delay(state, iat_delay_shift);
} else if (state->token_removal != CIRCPAD_TOKEN_REMOVAL_NONE) {
/* We have a mutable histogram. Do basic sanity check and apply: */
if (BUG(!mi->histogram) ||

15
src/core/or/circuitpadding.h
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@ -309,13 +309,16 @@ typedef struct circpad_state_t {
* results of sampling from this distribution (range_sec is used as a max).
*/
circpad_distribution_t iat_dist;
/* If a delay probability distribution is used, this represents the minimum
* delay we can sample from the distribution. */
circpad_delay_t dist_min_usec;
/* If a delay probability distribution is used, this is used as the max
* delay we can sample from the distribution.
*/
circpad_delay_t dist_max_usec;
* value we can sample from the distribution. However, RTT measurements and
* dist_added_shift gets applied on top of this value to derive the final
* padding delay. */
circpad_delay_t dist_max_sample_usec;
/* If a delay probability distribution is used and this is set, we will add
* this value on top of the value sampled from the IAT distribution to
* derive the final padding delay (We also add the RTT measurement if it's
* enabled.). */
circpad_delay_t dist_added_shift_usec;
/**
* The length dist is a parameterized way of encoding how long this

24
src/test/test_circuitpadding.c
View File

@ -2098,48 +2098,48 @@ helper_circpad_circ_distribution_machine_setup(int min, int max)
zero_st->iat_dist.type = CIRCPAD_DIST_UNIFORM;
zero_st->iat_dist.param1 = min;
zero_st->iat_dist.param2 = max;
zero_st->dist_min_usec = min;
zero_st->dist_max_usec = max;
zero_st->dist_added_shift_usec = min;
zero_st->dist_max_sample_usec = max;
circpad_state_t *first_st = &circ_client_machine.states[1];
first_st->next_state[CIRCPAD_EVENT_NONPADDING_RECV] = 2;
first_st->iat_dist.type = CIRCPAD_DIST_LOGISTIC;
first_st->iat_dist.param1 = min;
first_st->iat_dist.param2 = max;
first_st->dist_min_usec = min;
first_st->dist_max_usec = max;
first_st->dist_added_shift_usec = min;
first_st->dist_max_sample_usec = max;
circpad_state_t *second_st = &circ_client_machine.states[2];
second_st->next_state[CIRCPAD_EVENT_NONPADDING_RECV] = 3;
second_st->iat_dist.type = CIRCPAD_DIST_LOG_LOGISTIC;
second_st->iat_dist.param1 = min;
second_st->iat_dist.param2 = max;
second_st->dist_min_usec = min;
second_st->dist_max_usec = max;
second_st->dist_added_shift_usec = min;
second_st->dist_max_sample_usec = max;
circpad_state_t *third_st = &circ_client_machine.states[3];
third_st->next_state[CIRCPAD_EVENT_NONPADDING_RECV] = 4;
third_st->iat_dist.type = CIRCPAD_DIST_GEOMETRIC;
third_st->iat_dist.param1 = min;
third_st->iat_dist.param2 = max;
third_st->dist_min_usec = min;
third_st->dist_max_usec = max;
third_st->dist_added_shift_usec = min;
third_st->dist_max_sample_usec = max;
circpad_state_t *fourth_st = &circ_client_machine.states[4];
fourth_st->next_state[CIRCPAD_EVENT_NONPADDING_RECV] = 5;
fourth_st->iat_dist.type = CIRCPAD_DIST_WEIBULL;
fourth_st->iat_dist.param1 = min;
fourth_st->iat_dist.param2 = max;
fourth_st->dist_min_usec = min;
fourth_st->dist_max_usec = max;
fourth_st->dist_added_shift_usec = min;
fourth_st->dist_max_sample_usec = max;
circpad_state_t *fifth_st = &circ_client_machine.states[5];
fifth_st->next_state[CIRCPAD_EVENT_NONPADDING_RECV] = 6;
fifth_st->iat_dist.type = CIRCPAD_DIST_PARETO;
fifth_st->iat_dist.param1 = min;
fifth_st->iat_dist.param2 = max;
fifth_st->dist_min_usec = min;
fifth_st->dist_max_usec = max;
fifth_st->dist_added_shift_usec = min;
fifth_st->dist_max_sample_usec = max;
}
/** Simple test that the padding delays sampled from a uniform distribution