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tor/src/or/circuitstats.c
Nick Mathewson 4d11a468b2 Correct two state-file variable types. 
These should have been int, but we had listed them as unsigned.
That's an easy mistake to make, since "int" corresponds with either
INT or UINT in the configuration file.

This bug cannot have actually caused a problem in practice, since we
check those fields' values on load, and ensure that they are in
range 0..INT32_MAX.
2017-09-26 12:25:01 -04:00

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/* Copyright (c) 2001 Matej Pfajfar.
* Copyright (c) 2001-2004, Roger Dingledine.
* Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
* Copyright (c) 2007-2017, The Tor Project, Inc. */
/* See LICENSE for licensing information */
/**
* \file circuitstats.c
*
* \brief Maintains and analyzes statistics about circuit built times, so we
* can tell how long we may need to wait for a fast circuit to be constructed.
*
* By keeping these statistics, a client learns when it should time out a slow
* circuit for being too slow, and when it should keep a circuit open in order
* to wait for it to complete.
*
* The information here is kept in a circuit_built_times_t structure, which is
* currently a singleton, but doesn't need to be. It's updated by calls to
* circuit_build_times_count_timeout() from circuituse.c,
* circuit_build_times_count_close() from circuituse.c, and
* circuit_build_times_add_time() from circuitbuild.c, and inspected by other
* calls into this module, mostly from circuitlist.c. Observations are
* persisted to disk via the or_state_t-related calls.
*/
#define CIRCUITSTATS_PRIVATE
#include "or.h"
#include "circuitbuild.h"
#include "circuitstats.h"
#include "config.h"
#include "confparse.h"
#include "control.h"
#include "main.h"
#include "networkstatus.h"
#include "rendclient.h"
#include "rendservice.h"
#include "statefile.h"
#undef log
#include <math.h>
static void cbt_control_event_buildtimeout_set(
const circuit_build_times_t *cbt,
buildtimeout_set_event_t type);
#define CBT_BIN_TO_MS(bin) ((bin)*CBT_BIN_WIDTH + (CBT_BIN_WIDTH/2))
/** Global list of circuit build times */
// XXXX: Add this as a member for entry_guard_t instead of global?
// Then we could do per-guard statistics, as guards are likely to
// vary in their own latency. The downside of this is that guards
// can change frequently, so we'd be building a lot more circuits
// most likely.
static circuit_build_times_t circ_times;
#ifdef TOR_UNIT_TESTS
/** If set, we're running the unit tests: we should avoid clobbering
* our state file or accessing get_options() or get_or_state() */
static int unit_tests = 0;
#else
#define unit_tests 0
#endif /* defined(TOR_UNIT_TESTS) */
/** Return a pointer to the data structure describing our current circuit
* build time history and computations. */
const circuit_build_times_t *
get_circuit_build_times(void)
{
return &circ_times;
}
/** As get_circuit_build_times, but return a mutable pointer. */
circuit_build_times_t *
get_circuit_build_times_mutable(void)
{
return &circ_times;
}
/** Return the time to wait before actually closing an under-construction, in
* milliseconds. */
double
get_circuit_build_close_time_ms(void)
{
return circ_times.close_ms;
}
/** Return the time to wait before giving up on an under-construction circuit,
* in milliseconds. */
double
get_circuit_build_timeout_ms(void)
{
return circ_times.timeout_ms;
}
/**
* This function decides if CBT learning should be disabled. It returns
* true if one or more of the following conditions are met:
*
* 1. If the cbtdisabled consensus parameter is set.
* 2. If the torrc option LearnCircuitBuildTimeout is false.
* 3. If we are a directory authority
* 4. If we fail to write circuit build time history to our state file.
* 5. If we are compiled or configured in Tor2web mode
* 6. If we are configured in Single Onion mode
*/
int
circuit_build_times_disabled(const or_options_t *options)
{
return circuit_build_times_disabled_(options, 0);
}
/** As circuit_build_times_disabled, but take options as an argument. */
int
circuit_build_times_disabled_(const or_options_t *options,
int ignore_consensus)
{
if (unit_tests) {
return 0;
} else {
int consensus_disabled =
ignore_consensus ? 0 : networkstatus_get_param(NULL, "cbtdisabled",
0, 0, 1);
int config_disabled = !options->LearnCircuitBuildTimeout;
int dirauth_disabled = options->AuthoritativeDir;
int state_disabled = did_last_state_file_write_fail() ? 1 : 0;
/* LearnCircuitBuildTimeout and Tor2web/Single Onion Services are
* incompatible in two ways:
*
* - LearnCircuitBuildTimeout results in a low CBT, which
* Single Onion use of one-hop intro and rendezvous circuits lowers
* much further, producing *far* too many timeouts.
*
* - The adaptive CBT code does not update its timeout estimate
* using build times for single-hop circuits.
*
* If we fix both of these issues someday, we should test
* these modes with LearnCircuitBuildTimeout on again. */
int tor2web_disabled = rend_client_allow_non_anonymous_connection(options);
int single_onion_disabled = rend_service_allow_non_anonymous_connection(
options);
if (consensus_disabled || config_disabled || dirauth_disabled ||
state_disabled || tor2web_disabled || single_onion_disabled) {
#if 0
log_debug(LD_CIRC,
"CircuitBuildTime learning is disabled. "
"Consensus=%d, Config=%d, AuthDir=%d, StateFile=%d",
consensus_disabled, config_disabled, dirauth_disabled,
state_disabled);
#endif /* 0 */
return 1;
} else {
#if 0
log_debug(LD_CIRC,
"CircuitBuildTime learning is not disabled. "
"Consensus=%d, Config=%d, AuthDir=%d, StateFile=%d",
consensus_disabled, config_disabled, dirauth_disabled,
state_disabled);
#endif /* 0 */
return 0;
}
}
}
/**
* Retrieve and bounds-check the cbtmaxtimeouts consensus paramter.
*
* Effect: When this many timeouts happen in the last 'cbtrecentcount'
* circuit attempts, the client should discard all of its history and
* begin learning a fresh timeout value.
*/
static int32_t
circuit_build_times_max_timeouts(void)
{
int32_t cbt_maxtimeouts;
cbt_maxtimeouts = networkstatus_get_param(NULL, "cbtmaxtimeouts",
CBT_DEFAULT_MAX_RECENT_TIMEOUT_COUNT,
CBT_MIN_MAX_RECENT_TIMEOUT_COUNT,
CBT_MAX_MAX_RECENT_TIMEOUT_COUNT);
if (!(get_options()->LearnCircuitBuildTimeout)) {
log_debug(LD_BUG,
"circuit_build_times_max_timeouts() called, cbtmaxtimeouts is"
" %d",
cbt_maxtimeouts);
}
return cbt_maxtimeouts;
}
/**
* Retrieve and bounds-check the cbtnummodes consensus paramter.
*
* Effect: This value governs how many modes to use in the weighted
* average calculation of Pareto parameter Xm. A value of 3 introduces
* some bias (2-5% of CDF) under ideal conditions, but allows for better
* performance in the event that a client chooses guard nodes of radically
* different performance characteristics.
*/
static int32_t
circuit_build_times_default_num_xm_modes(void)
{
int32_t num = networkstatus_get_param(NULL, "cbtnummodes",
CBT_DEFAULT_NUM_XM_MODES,
CBT_MIN_NUM_XM_MODES,
CBT_MAX_NUM_XM_MODES);
if (!(get_options()->LearnCircuitBuildTimeout)) {
log_debug(LD_BUG,
"circuit_build_times_default_num_xm_modes() called, cbtnummodes"
" is %d",
num);
}
return num;
}
/**
* Retrieve and bounds-check the cbtmincircs consensus paramter.
*
* Effect: This is the minimum number of circuits to build before
* computing a timeout.
*/
static int32_t
circuit_build_times_min_circs_to_observe(void)
{
int32_t num = networkstatus_get_param(NULL, "cbtmincircs",
CBT_DEFAULT_MIN_CIRCUITS_TO_OBSERVE,
CBT_MIN_MIN_CIRCUITS_TO_OBSERVE,
CBT_MAX_MIN_CIRCUITS_TO_OBSERVE);
if (!(get_options()->LearnCircuitBuildTimeout)) {
log_debug(LD_BUG,
"circuit_build_times_min_circs_to_observe() called, cbtmincircs"
" is %d",
num);
}
return num;
}
/** Return true iff <b>cbt</b> has recorded enough build times that we
* want to start acting on the timeout it implies. */
int
circuit_build_times_enough_to_compute(const circuit_build_times_t *cbt)
{
return cbt->total_build_times >= circuit_build_times_min_circs_to_observe();
}
/**
* Retrieve and bounds-check the cbtquantile consensus paramter.
*
* Effect: This is the position on the quantile curve to use to set the
* timeout value. It is a percent (10-99).
*/
double
circuit_build_times_quantile_cutoff(void)
{
int32_t num = networkstatus_get_param(NULL, "cbtquantile",
CBT_DEFAULT_QUANTILE_CUTOFF,
CBT_MIN_QUANTILE_CUTOFF,
CBT_MAX_QUANTILE_CUTOFF);
if (!(get_options()->LearnCircuitBuildTimeout)) {
log_debug(LD_BUG,
"circuit_build_times_quantile_cutoff() called, cbtquantile"
" is %d",
num);
}
return num/100.0;
}
/**
* Retrieve and bounds-check the cbtclosequantile consensus paramter.
*
* Effect: This is the position on the quantile curve to use to set the
* timeout value to use to actually close circuits. It is a percent
* (0-99).
*/
static double
circuit_build_times_close_quantile(void)
{
int32_t param;
/* Cast is safe - circuit_build_times_quantile_cutoff() is capped */
int32_t min = (int)tor_lround(100*circuit_build_times_quantile_cutoff());
param = networkstatus_get_param(NULL, "cbtclosequantile",
CBT_DEFAULT_CLOSE_QUANTILE,
CBT_MIN_CLOSE_QUANTILE,
CBT_MAX_CLOSE_QUANTILE);
if (!(get_options()->LearnCircuitBuildTimeout)) {
log_debug(LD_BUG,
"circuit_build_times_close_quantile() called, cbtclosequantile"
" is %d", param);
}
if (param < min) {
log_warn(LD_DIR, "Consensus parameter cbtclosequantile is "
"too small, raising to %d", min);
param = min;
}
return param / 100.0;
}
/**
* Retrieve and bounds-check the cbttestfreq consensus paramter.
*
* Effect: Describes how often in seconds to build a test circuit to
* gather timeout values. Only applies if less than 'cbtmincircs'
* have been recorded.
*/
static int32_t
circuit_build_times_test_frequency(void)
{
int32_t num = networkstatus_get_param(NULL, "cbttestfreq",
CBT_DEFAULT_TEST_FREQUENCY,
CBT_MIN_TEST_FREQUENCY,
CBT_MAX_TEST_FREQUENCY);
if (!(get_options()->LearnCircuitBuildTimeout)) {
log_debug(LD_BUG,
"circuit_build_times_test_frequency() called, cbttestfreq is %d",
num);
}
return num;
}
/**
* Retrieve and bounds-check the cbtmintimeout consensus parameter.
*
* Effect: This is the minimum allowed timeout value in milliseconds.
* The minimum is to prevent rounding to 0 (we only check once
* per second).
*/
static int32_t
circuit_build_times_min_timeout(void)
{
int32_t num = networkstatus_get_param(NULL, "cbtmintimeout",
CBT_DEFAULT_TIMEOUT_MIN_VALUE,
CBT_MIN_TIMEOUT_MIN_VALUE,
CBT_MAX_TIMEOUT_MIN_VALUE);
if (!(get_options()->LearnCircuitBuildTimeout)) {
log_debug(LD_BUG,
"circuit_build_times_min_timeout() called, cbtmintimeout is %d",
num);
}
return num;
}
/**
* Retrieve and bounds-check the cbtinitialtimeout consensus paramter.
*
* Effect: This is the timeout value to use before computing a timeout,
* in milliseconds.
*/
int32_t
circuit_build_times_initial_timeout(void)
{
int32_t min = circuit_build_times_min_timeout();
int32_t param = networkstatus_get_param(NULL, "cbtinitialtimeout",
CBT_DEFAULT_TIMEOUT_INITIAL_VALUE,
CBT_MIN_TIMEOUT_INITIAL_VALUE,
CBT_MAX_TIMEOUT_INITIAL_VALUE);
if (!(get_options()->LearnCircuitBuildTimeout)) {
log_debug(LD_BUG,
"circuit_build_times_initial_timeout() called, "
"cbtinitialtimeout is %d",
param);
}
if (param < min) {
log_warn(LD_DIR, "Consensus parameter cbtinitialtimeout is too small, "
"raising to %d", min);
param = min;
}
return param;
}
/**
* Retrieve and bounds-check the cbtrecentcount consensus paramter.
*
* Effect: This is the number of circuit build times to keep track of
* for deciding if we hit cbtmaxtimeouts and need to reset our state
* and learn a new timeout.
*/
static int32_t
circuit_build_times_recent_circuit_count(networkstatus_t *ns)
{
int32_t num;
num = networkstatus_get_param(ns, "cbtrecentcount",
CBT_DEFAULT_RECENT_CIRCUITS,
CBT_MIN_RECENT_CIRCUITS,
CBT_MAX_RECENT_CIRCUITS);
if (!(get_options()->LearnCircuitBuildTimeout)) {
log_debug(LD_BUG,
"circuit_build_times_recent_circuit_count() called, "
"cbtrecentcount is %d",
num);
}
return num;
}
/**
* This function is called when we get a consensus update.
*
* It checks to see if we have changed any consensus parameters
* that require reallocation or discard of previous stats.
*/
void
circuit_build_times_new_consensus_params(circuit_build_times_t *cbt,
networkstatus_t *ns)
{
int32_t num;
/*
* First check if we're doing adaptive timeouts at all; nothing to
* update if we aren't.
*/
if (!circuit_build_times_disabled(get_options())) {
num = circuit_build_times_recent_circuit_count(ns);
if (num > 0) {
if (num != cbt->liveness.num_recent_circs) {
int8_t *recent_circs;
log_notice(LD_CIRC, "The Tor Directory Consensus has changed how many "
"circuits we must track to detect network failures from %d "
"to %d.", cbt->liveness.num_recent_circs, num);
tor_assert(cbt->liveness.timeouts_after_firsthop ||
cbt->liveness.num_recent_circs == 0);
/*
* Technically this is a circular array that we are reallocating
* and memcopying. However, since it only consists of either 1s
* or 0s, and is only used in a statistical test to determine when
* we should discard our history after a sufficient number of 1's
* have been reached, it is fine if order is not preserved or
* elements are lost.
*
* cbtrecentcount should only be changing in cases of severe network
* distress anyway, so memory correctness here is paramount over
* doing acrobatics to preserve the array.
*/
recent_circs = tor_calloc(num, sizeof(int8_t));
if (cbt->liveness.timeouts_after_firsthop &&
cbt->liveness.num_recent_circs > 0) {
memcpy(recent_circs, cbt->liveness.timeouts_after_firsthop,
sizeof(int8_t)*MIN(num, cbt->liveness.num_recent_circs));
}
// Adjust the index if it needs it.
if (num < cbt->liveness.num_recent_circs) {
cbt->liveness.after_firsthop_idx = MIN(num-1,
cbt->liveness.after_firsthop_idx);
}
tor_free(cbt->liveness.timeouts_after_firsthop);
cbt->liveness.timeouts_after_firsthop = recent_circs;
cbt->liveness.num_recent_circs = num;
}
/* else no change, nothing to do */
} else { /* num == 0 */
/*
* Weird. This probably shouldn't happen, so log a warning, but try
* to do something sensible anyway.
*/
log_warn(LD_CIRC,
"The cbtrecentcircs consensus parameter came back zero! "
"This disables adaptive timeouts since we can't keep track of "
"any recent circuits.");
circuit_build_times_free_timeouts(cbt);
}
} else {
/*
* Adaptive timeouts are disabled; this might be because of the
* LearnCircuitBuildTimes config parameter, and hence permanent, or
* the cbtdisabled consensus parameter, so it may be a new condition.
* Treat it like getting num == 0 above and free the circuit history
* if we have any.
*/
circuit_build_times_free_timeouts(cbt);
}
}
/**
* Return the initial default or configured timeout in milliseconds
*/
static double
circuit_build_times_get_initial_timeout(void)
{
double timeout;
const or_options_t *options = get_options();
/*
* Check if we have LearnCircuitBuildTimeout, and if we don't,
* always use CircuitBuildTimeout, no questions asked.
*/
if (!unit_tests && options->CircuitBuildTimeout) {
timeout = options->CircuitBuildTimeout*1000;
if (!circuit_build_times_disabled(options) &&
timeout < circuit_build_times_min_timeout()) {
log_warn(LD_CIRC, "Config CircuitBuildTimeout too low. Setting to %ds",
circuit_build_times_min_timeout()/1000);
timeout = circuit_build_times_min_timeout();
}
} else {
timeout = circuit_build_times_initial_timeout();
}
return timeout;
}
/**
* Reset the build time state.
*
* Leave estimated parameters, timeout and network liveness intact
* for future use.
*/
STATIC void
circuit_build_times_reset(circuit_build_times_t *cbt)
{
memset(cbt->circuit_build_times, 0, sizeof(cbt->circuit_build_times));
cbt->total_build_times = 0;
cbt->build_times_idx = 0;
cbt->have_computed_timeout = 0;
}
/**
* Initialize the buildtimes structure for first use.
*
* Sets the initial timeout values based on either the config setting,
* the consensus param, or the default (CBT_DEFAULT_TIMEOUT_INITIAL_VALUE).
*/
void
circuit_build_times_init(circuit_build_times_t *cbt)
{
memset(cbt, 0, sizeof(*cbt));
/*
* Check if we really are using adaptive timeouts, and don't keep
* track of this stuff if not.
*/
if (!circuit_build_times_disabled(get_options())) {
cbt->liveness.num_recent_circs =
circuit_build_times_recent_circuit_count(NULL);
cbt->liveness.timeouts_after_firsthop =
tor_calloc(cbt->liveness.num_recent_circs, sizeof(int8_t));
} else {
cbt->liveness.num_recent_circs = 0;
cbt->liveness.timeouts_after_firsthop = NULL;
}
cbt->close_ms = cbt->timeout_ms = circuit_build_times_get_initial_timeout();
cbt_control_event_buildtimeout_set(cbt, BUILDTIMEOUT_SET_EVENT_RESET);
}
/**
* Free the saved timeouts, if the cbtdisabled consensus parameter got turned
* on or something.
*/
void
circuit_build_times_free_timeouts(circuit_build_times_t *cbt)
{
if (!cbt) return;
if (cbt->liveness.timeouts_after_firsthop) {
tor_free(cbt->liveness.timeouts_after_firsthop);
}
cbt->liveness.num_recent_circs = 0;
}
#if 0
/**
* Rewind our build time history by n positions.
*/
static void
circuit_build_times_rewind_history(circuit_build_times_t *cbt, int n)
{
int i = 0;
cbt->build_times_idx -= n;
cbt->build_times_idx %= CBT_NCIRCUITS_TO_OBSERVE;
for (i = 0; i < n; i++) {
cbt->circuit_build_times[(i+cbt->build_times_idx)
%CBT_NCIRCUITS_TO_OBSERVE]=0;
}
if (cbt->total_build_times > n) {
cbt->total_build_times -= n;
} else {
cbt->total_build_times = 0;
}
log_info(LD_CIRC,
"Rewound history by %d places. Current index: %d. "
"Total: %d", n, cbt->build_times_idx, cbt->total_build_times);
}
#endif /* 0 */
/**
* Add a new build time value <b>time</b> to the set of build times. Time
* units are milliseconds.
*
* circuit_build_times <b>cbt</b> is a circular array, so loop around when
* array is full.
*/
int
circuit_build_times_add_time(circuit_build_times_t *cbt, build_time_t btime)
{
if (btime <= 0 || btime > CBT_BUILD_TIME_MAX) {
log_warn(LD_BUG, "Circuit build time is too large (%u)."
"This is probably a bug.", btime);
tor_fragile_assert();
return -1;
}
log_debug(LD_CIRC, "Adding circuit build time %u", btime);
cbt->circuit_build_times[cbt->build_times_idx] = btime;
cbt->build_times_idx = (cbt->build_times_idx + 1) % CBT_NCIRCUITS_TO_OBSERVE;
if (cbt->total_build_times < CBT_NCIRCUITS_TO_OBSERVE)
cbt->total_build_times++;
if ((cbt->total_build_times % CBT_SAVE_STATE_EVERY) == 0) {
/* Save state every n circuit builds */
if (!unit_tests && !get_options()->AvoidDiskWrites)
or_state_mark_dirty(get_or_state(), 0);
}
return 0;
}
/**
* Return maximum circuit build time
*/
static build_time_t
circuit_build_times_max(const circuit_build_times_t *cbt)
{
int i = 0;
build_time_t max_build_time = 0;
for (i = 0; i < CBT_NCIRCUITS_TO_OBSERVE; i++) {
if (cbt->circuit_build_times[i] > max_build_time
&& cbt->circuit_build_times[i] != CBT_BUILD_ABANDONED)
max_build_time = cbt->circuit_build_times[i];
}
return max_build_time;
}
#if 0
/** Return minimum circuit build time */
build_time_t
circuit_build_times_min(circuit_build_times_t *cbt)
{
int i = 0;
build_time_t min_build_time = CBT_BUILD_TIME_MAX;
for (i = 0; i < CBT_NCIRCUITS_TO_OBSERVE; i++) {
if (cbt->circuit_build_times[i] && /* 0 <-> uninitialized */
cbt->circuit_build_times[i] < min_build_time)
min_build_time = cbt->circuit_build_times[i];
}
if (min_build_time == CBT_BUILD_TIME_MAX) {
log_warn(LD_CIRC, "No build times less than CBT_BUILD_TIME_MAX!");
}
return min_build_time;
}
#endif /* 0 */
/**
* Calculate and return a histogram for the set of build times.
*
* Returns an allocated array of histrogram bins representing
* the frequency of index*CBT_BIN_WIDTH millisecond
* build times. Also outputs the number of bins in nbins.
*
* The return value must be freed by the caller.
*/
static uint32_t *
circuit_build_times_create_histogram(const circuit_build_times_t *cbt,
build_time_t *nbins)
{
uint32_t *histogram;
build_time_t max_build_time = circuit_build_times_max(cbt);
int i, c;
*nbins = 1 + (max_build_time / CBT_BIN_WIDTH);
histogram = tor_calloc(*nbins, sizeof(build_time_t));
// calculate histogram
for (i = 0; i < CBT_NCIRCUITS_TO_OBSERVE; i++) {
if (cbt->circuit_build_times[i] == 0
|| cbt->circuit_build_times[i] == CBT_BUILD_ABANDONED)
continue; /* 0 <-> uninitialized */
c = (cbt->circuit_build_times[i] / CBT_BIN_WIDTH);
histogram[c]++;
}
return histogram;
}
/**
* Return the Pareto start-of-curve parameter Xm.
*
* Because we are not a true Pareto curve, we compute this as the
* weighted average of the N most frequent build time bins. N is either
* 1 if we don't have enough circuit build time data collected, or
* determined by the consensus parameter cbtnummodes (default 3).
*/
static build_time_t
circuit_build_times_get_xm(circuit_build_times_t *cbt)
{
build_time_t i, nbins;
build_time_t *nth_max_bin;
int32_t bin_counts=0;
build_time_t ret = 0;
uint32_t *histogram = circuit_build_times_create_histogram(cbt, &nbins);
int n=0;
int num_modes = circuit_build_times_default_num_xm_modes();
tor_assert(nbins > 0);
tor_assert(num_modes > 0);
// Only use one mode if < 1000 buildtimes. Not enough data
// for multiple.
if (cbt->total_build_times < CBT_NCIRCUITS_TO_OBSERVE)
num_modes = 1;
nth_max_bin = tor_calloc(num_modes, sizeof(build_time_t));
/* Determine the N most common build times */
for (i = 0; i < nbins; i++) {
if (histogram[i] >= histogram[nth_max_bin[0]]) {
nth_max_bin[0] = i;
}
for (n = 1; n < num_modes; n++) {
if (histogram[i] >= histogram[nth_max_bin[n]] &&
(!histogram[nth_max_bin[n-1]]
|| histogram[i] < histogram[nth_max_bin[n-1]])) {
nth_max_bin[n] = i;
}
}
}
for (n = 0; n < num_modes; n++) {
bin_counts += histogram[nth_max_bin[n]];
ret += CBT_BIN_TO_MS(nth_max_bin[n])*histogram[nth_max_bin[n]];
log_info(LD_CIRC, "Xm mode #%d: %u %u", n, CBT_BIN_TO_MS(nth_max_bin[n]),
histogram[nth_max_bin[n]]);
}
/* The following assert is safe, because we don't get called when we
* haven't observed at least CBT_MIN_MIN_CIRCUITS_TO_OBSERVE circuits. */
tor_assert(bin_counts > 0);
ret /= bin_counts;
tor_free(histogram);
tor_free(nth_max_bin);
return ret;
}
/**
* Output a histogram of current circuit build times to
* the or_state_t state structure.
*/
void
circuit_build_times_update_state(const circuit_build_times_t *cbt,
or_state_t *state)
{
uint32_t *histogram;
build_time_t i = 0;
build_time_t nbins = 0;
config_line_t **next, *line;
histogram = circuit_build_times_create_histogram(cbt, &nbins);
// write to state
config_free_lines(state->BuildtimeHistogram);
next = &state->BuildtimeHistogram;
*next = NULL;
state->TotalBuildTimes = cbt->total_build_times;
state->CircuitBuildAbandonedCount = 0;
for (i = 0; i < CBT_NCIRCUITS_TO_OBSERVE; i++) {
if (cbt->circuit_build_times[i] == CBT_BUILD_ABANDONED)
state->CircuitBuildAbandonedCount++;
}
for (i = 0; i < nbins; i++) {
// compress the histogram by skipping the blanks
if (histogram[i] == 0) continue;
*next = line = tor_malloc_zero(sizeof(config_line_t));
line->key = tor_strdup("CircuitBuildTimeBin");
tor_asprintf(&line->value, "%d %d",
CBT_BIN_TO_MS(i), histogram[i]);
next = &(line->next);
}
if (!unit_tests) {
if (!get_options()->AvoidDiskWrites)
or_state_mark_dirty(get_or_state(), 0);
}
tor_free(histogram);
}
/**
* Shuffle the build times array.
*
* Adapted from http://en.wikipedia.org/wiki/Fisher-Yates_shuffle
*/
static void
circuit_build_times_shuffle_and_store_array(circuit_build_times_t *cbt,
build_time_t *raw_times,
uint32_t num_times)
{
uint32_t n = num_times;
if (num_times > CBT_NCIRCUITS_TO_OBSERVE) {
log_notice(LD_CIRC, "The number of circuit times that this Tor version "
"uses to calculate build times is less than the number stored "
"in your state file. Decreasing the circuit time history from "
"%lu to %d.", (unsigned long)num_times,
CBT_NCIRCUITS_TO_OBSERVE);
}
if (n > INT_MAX-1) {
log_warn(LD_CIRC, "For some insane reasons, you had %lu circuit build "
"observations in your state file. That's far too many; probably "
"there's a bug here.", (unsigned long)n);
n = INT_MAX-1;
}
/* This code can only be run on a compact array */
while (n-- > 1) {
int k = crypto_rand_int(n + 1); /* 0 <= k <= n. */
build_time_t tmp = raw_times[k];
raw_times[k] = raw_times[n];
raw_times[n] = tmp;
}
/* Since the times are now shuffled, take a random CBT_NCIRCUITS_TO_OBSERVE
* subset (ie the first CBT_NCIRCUITS_TO_OBSERVE values) */
for (n = 0; n < MIN(num_times, CBT_NCIRCUITS_TO_OBSERVE); n++) {
circuit_build_times_add_time(cbt, raw_times[n]);
}
}
/**
* Filter old synthetic timeouts that were created before the
* new right-censored Pareto calculation was deployed.
*
* Once all clients before 0.2.1.13-alpha are gone, this code
* will be unused.
*/
static int
circuit_build_times_filter_timeouts(circuit_build_times_t *cbt)
{
int num_filtered=0, i=0;
double timeout_rate = 0;
build_time_t max_timeout = 0;
timeout_rate = circuit_build_times_timeout_rate(cbt);
max_timeout = (build_time_t)cbt->close_ms;
for (i = 0; i < CBT_NCIRCUITS_TO_OBSERVE; i++) {
if (cbt->circuit_build_times[i] > max_timeout) {
build_time_t replaced = cbt->circuit_build_times[i];
num_filtered++;
cbt->circuit_build_times[i] = CBT_BUILD_ABANDONED;
log_debug(LD_CIRC, "Replaced timeout %d with %d", replaced,
cbt->circuit_build_times[i]);
}
}
log_info(LD_CIRC,
"We had %d timeouts out of %d build times, "
"and filtered %d above the max of %u",
(int)(cbt->total_build_times*timeout_rate),
cbt->total_build_times, num_filtered, max_timeout);
return num_filtered;
}
/**
* Load histogram from <b>state</b>, shuffling the resulting array
* after we do so. Use this result to estimate parameters and
* calculate the timeout.
*
* Return -1 on error.
*/
int
circuit_build_times_parse_state(circuit_build_times_t *cbt,
or_state_t *state)
{
int tot_values = 0;
uint32_t loaded_cnt = 0, N = 0;
config_line_t *line;
int i;
build_time_t *loaded_times;
int err = 0;
circuit_build_times_init(cbt);
if (circuit_build_times_disabled(get_options())) {
return 0;
}
/* build_time_t 0 means uninitialized */
loaded_times = tor_calloc(state->TotalBuildTimes, sizeof(build_time_t));
for (line = state->BuildtimeHistogram; line; line = line->next) {
smartlist_t *args = smartlist_new();
smartlist_split_string(args, line->value, " ",
SPLIT_SKIP_SPACE|SPLIT_IGNORE_BLANK, 0);
if (smartlist_len(args) < 2) {
log_warn(LD_GENERAL, "Unable to parse circuit build times: "
"Too few arguments to CircuitBuildTime");
err = 1;
SMARTLIST_FOREACH(args, char*, cp, tor_free(cp));
smartlist_free(args);
break;
} else {
const char *ms_str = smartlist_get(args,0);
const char *count_str = smartlist_get(args,1);
uint32_t count, k;
build_time_t ms;
int ok;
ms = (build_time_t)tor_parse_ulong(ms_str, 10, 0,
CBT_BUILD_TIME_MAX, &ok, NULL);
if (!ok) {
log_warn(LD_GENERAL, "Unable to parse circuit build times: "
"Unparsable bin number");
err = 1;
SMARTLIST_FOREACH(args, char*, cp, tor_free(cp));
smartlist_free(args);
break;
}
count = (uint32_t)tor_parse_ulong(count_str, 10, 0,
UINT32_MAX, &ok, NULL);
if (!ok) {
log_warn(LD_GENERAL, "Unable to parse circuit build times: "
"Unparsable bin count");
err = 1;
SMARTLIST_FOREACH(args, char*, cp, tor_free(cp));
smartlist_free(args);
break;
}
if (loaded_cnt+count+ (unsigned)state->CircuitBuildAbandonedCount
> (unsigned) state->TotalBuildTimes) {
log_warn(LD_CIRC,
"Too many build times in state file. "
"Stopping short before %d",
loaded_cnt+count);
SMARTLIST_FOREACH(args, char*, cp, tor_free(cp));
smartlist_free(args);
break;
}
for (k = 0; k < count; k++) {
loaded_times[loaded_cnt++] = ms;
}
N++;
SMARTLIST_FOREACH(args, char*, cp, tor_free(cp));
smartlist_free(args);
}
}
log_info(LD_CIRC,
"Adding %d timeouts.", state->CircuitBuildAbandonedCount);
for (i=0; i < state->CircuitBuildAbandonedCount; i++) {
loaded_times[loaded_cnt++] = CBT_BUILD_ABANDONED;
}
if (loaded_cnt != (unsigned)state->TotalBuildTimes) {
log_warn(LD_CIRC,
"Corrupt state file? Build times count mismatch. "
"Read %d times, but file says %d", loaded_cnt,
state->TotalBuildTimes);
err = 1;
circuit_build_times_reset(cbt);
goto done;
}
circuit_build_times_shuffle_and_store_array(cbt, loaded_times, loaded_cnt);
/* Verify that we didn't overwrite any indexes */
for (i=0; i < CBT_NCIRCUITS_TO_OBSERVE; i++) {
if (!cbt->circuit_build_times[i])
break;
tot_values++;
}
log_info(LD_CIRC,
"Loaded %d/%d values from %d lines in circuit time histogram",
tot_values, cbt->total_build_times, N);
if (cbt->total_build_times != tot_values
|| cbt->total_build_times > CBT_NCIRCUITS_TO_OBSERVE) {
log_warn(LD_CIRC,
"Corrupt state file? Shuffled build times mismatch. "
"Read %d times, but file says %d", tot_values,
state->TotalBuildTimes);
err = 1;
circuit_build_times_reset(cbt);
goto done;
}
circuit_build_times_set_timeout(cbt);
if (!state->CircuitBuildAbandonedCount && cbt->total_build_times) {
circuit_build_times_filter_timeouts(cbt);
}
done:
tor_free(loaded_times);
return err ? -1 : 0;
}
/**
* Estimates the Xm and Alpha parameters using
* http://en.wikipedia.org/wiki/Pareto_distribution#Parameter_estimation
*
* The notable difference is that we use mode instead of min to estimate Xm.
* This is because our distribution is frechet-like. We claim this is
* an acceptable approximation because we are only concerned with the
* accuracy of the CDF of the tail.
*/
STATIC int
circuit_build_times_update_alpha(circuit_build_times_t *cbt)
{
build_time_t *x=cbt->circuit_build_times;
double a = 0;
int n=0,i=0,abandoned_count=0;
build_time_t max_time=0;
/* http://en.wikipedia.org/wiki/Pareto_distribution#Parameter_estimation */
/* We sort of cheat here and make our samples slightly more pareto-like
* and less frechet-like. */
cbt->Xm = circuit_build_times_get_xm(cbt);
tor_assert(cbt->Xm > 0);
for (i=0; i< CBT_NCIRCUITS_TO_OBSERVE; i++) {
if (!x[i]) {
continue;
}
if (x[i] < cbt->Xm) {
a += tor_mathlog(cbt->Xm);
} else if (x[i] == CBT_BUILD_ABANDONED) {
abandoned_count++;
} else {
a += tor_mathlog(x[i]);
if (x[i] > max_time)
max_time = x[i];
}
n++;
}
/*
* We are erring and asserting here because this can only happen
* in codepaths other than startup. The startup state parsing code
* performs this same check, and resets state if it hits it. If we
* hit it at runtime, something serious has gone wrong.
*/
if (n!=cbt->total_build_times) {
log_err(LD_CIRC, "Discrepancy in build times count: %d vs %d", n,
cbt->total_build_times);
}
tor_assert(n==cbt->total_build_times);
if (max_time <= 0) {
/* This can happen if Xm is actually the *maximum* value in the set.
* It can also happen if we've abandoned every single circuit somehow.
* In either case, tell the caller not to compute a new build timeout. */
log_warn(LD_BUG,
"Could not determine largest build time (%d). "
"Xm is %dms and we've abandoned %d out of %d circuits.", max_time,
cbt->Xm, abandoned_count, n);
return 0;
}
a += abandoned_count*tor_mathlog(max_time);
a -= n*tor_mathlog(cbt->Xm);
// Estimator comes from Eq #4 in:
// "Bayesian estimation based on trimmed samples from Pareto populations"
// by Arturo J. Fernández. We are right-censored only.
a = (n-abandoned_count)/a;
cbt->alpha = a;
return 1;
}
/**
* This is the Pareto Quantile Function. It calculates the point x
* in the distribution such that F(x) = quantile (ie quantile*100%
* of the mass of the density function is below x on the curve).
*
* We use it to calculate the timeout and also to generate synthetic
* values of time for circuits that timeout before completion.
*
* See http://en.wikipedia.org/wiki/Quantile_function,
* http://en.wikipedia.org/wiki/Inverse_transform_sampling and
* http://en.wikipedia.org/wiki/Pareto_distribution#Generating_a_
* random_sample_from_Pareto_distribution
* That's right. I'll cite wikipedia all day long.
*
* Return value is in milliseconds, clamped to INT32_MAX.
*/
STATIC double
circuit_build_times_calculate_timeout(circuit_build_times_t *cbt,
double quantile)
{
double ret;
tor_assert(quantile >= 0);
tor_assert(1.0-quantile > 0);
tor_assert(cbt->Xm > 0);
/* If either alpha or p are 0, we would divide by zero, yielding an
* infinite (double) result; which would be clamped to INT32_MAX.
* Instead, initialise ret to INT32_MAX, and skip over these
* potentially illegal/trapping divides by zero.
*/
ret = INT32_MAX;
if (cbt->alpha > 0) {
double p;
p = pow(1.0-quantile,1.0/cbt->alpha);
if (p > 0) {
ret = cbt->Xm/p;
}
}
if (ret > INT32_MAX) {
ret = INT32_MAX;
}
tor_assert(ret > 0);
return ret;
}
#ifdef TOR_UNIT_TESTS
/** Pareto CDF */
double
circuit_build_times_cdf(circuit_build_times_t *cbt, double x)
{
double ret;
tor_assert(cbt->Xm > 0);
ret = 1.0-pow(cbt->Xm/x,cbt->alpha);
tor_assert(0 <= ret && ret <= 1.0);
return ret;
}
#endif /* defined(TOR_UNIT_TESTS) */
#ifdef TOR_UNIT_TESTS
/**
* Generate a synthetic time using our distribution parameters.
*
* The return value will be within the [q_lo, q_hi) quantile points
* on the CDF.
*/
build_time_t
circuit_build_times_generate_sample(circuit_build_times_t *cbt,
double q_lo, double q_hi)
{
double randval = crypto_rand_double();
build_time_t ret;
double u;
/* Generate between [q_lo, q_hi) */
/*XXXX This is what nextafter is supposed to be for; we should use it on the
* platforms that support it. */
q_hi -= 1.0/(INT32_MAX);
tor_assert(q_lo >= 0);
tor_assert(q_hi < 1);
tor_assert(q_lo < q_hi);
u = q_lo + (q_hi-q_lo)*randval;
tor_assert(0 <= u && u < 1.0);
/* circuit_build_times_calculate_timeout returns <= INT32_MAX */
ret = (build_time_t)
tor_lround(circuit_build_times_calculate_timeout(cbt, u));
tor_assert(ret > 0);
return ret;
}
#endif /* defined(TOR_UNIT_TESTS) */
#ifdef TOR_UNIT_TESTS
/**
* Estimate an initial alpha parameter by solving the quantile
* function with a quantile point and a specific timeout value.
*/
void
circuit_build_times_initial_alpha(circuit_build_times_t *cbt,
double quantile, double timeout_ms)
{
// Q(u) = Xm/((1-u)^(1/a))
// Q(0.8) = Xm/((1-0.8))^(1/a)) = CircBuildTimeout
// CircBuildTimeout = Xm/((1-0.8))^(1/a))
// CircBuildTimeout = Xm*((1-0.8))^(-1/a))
// ln(CircBuildTimeout) = ln(Xm)+ln(((1-0.8)))*(-1/a)
// -ln(1-0.8)/(ln(CircBuildTimeout)-ln(Xm))=a
tor_assert(quantile >= 0);
tor_assert(cbt->Xm > 0);
cbt->alpha = tor_mathlog(1.0-quantile)/
(tor_mathlog(cbt->Xm)-tor_mathlog(timeout_ms));
tor_assert(cbt->alpha > 0);
}
#endif /* defined(TOR_UNIT_TESTS) */
/**
* Returns true if we need circuits to be built
*/
int
circuit_build_times_needs_circuits(const circuit_build_times_t *cbt)
{
/* Return true if < MIN_CIRCUITS_TO_OBSERVE */
return !circuit_build_times_enough_to_compute(cbt);
}
/**
* Returns true if we should build a timeout test circuit
* right now.
*/
int
circuit_build_times_needs_circuits_now(const circuit_build_times_t *cbt)
{
return circuit_build_times_needs_circuits(cbt) &&
approx_time()-cbt->last_circ_at > circuit_build_times_test_frequency();
}
/**
* How long should we be unreachable before we think we need to check if
* our published IP address has changed.
*/
#define CIRCUIT_TIMEOUT_BEFORE_RECHECK_IP (60*3)
/**
* Called to indicate that the network showed some signs of liveness,
* i.e. we received a cell.
*
* This is used by circuit_build_times_network_check_live() to decide
* if we should record the circuit build timeout or not.
*
* This function is called every time we receive a cell. Avoid
* syscalls, events, and other high-intensity work.
*/
void
circuit_build_times_network_is_live(circuit_build_times_t *cbt)
{
time_t now = approx_time();
if (cbt->liveness.nonlive_timeouts > 0) {
time_t time_since_live = now - cbt->liveness.network_last_live;
log_notice(LD_CIRC,
"Tor now sees network activity. Restoring circuit build "
"timeout recording. Network was down for %d seconds "
"during %d circuit attempts.",
(int)time_since_live,
cbt->liveness.nonlive_timeouts);
if (time_since_live > CIRCUIT_TIMEOUT_BEFORE_RECHECK_IP)
reschedule_descriptor_update_check();
}
cbt->liveness.network_last_live = now;
cbt->liveness.nonlive_timeouts = 0;
/* Tell control.c */
control_event_network_liveness_update(1);
}
/**
* Called to indicate that we completed a circuit. Because this circuit
* succeeded, it doesn't count as a timeout-after-the-first-hop.
*
* This is used by circuit_build_times_network_check_changed() to determine
* if we had too many recent timeouts and need to reset our learned timeout
* to something higher.
*/
void
circuit_build_times_network_circ_success(circuit_build_times_t *cbt)
{
/* Check for NULLness because we might not be using adaptive timeouts */
if (cbt->liveness.timeouts_after_firsthop &&
cbt->liveness.num_recent_circs > 0) {
cbt->liveness.timeouts_after_firsthop[cbt->liveness.after_firsthop_idx]
= 0;
cbt->liveness.after_firsthop_idx++;
cbt->liveness.after_firsthop_idx %= cbt->liveness.num_recent_circs;
}
}
/**
* A circuit just timed out. If it failed after the first hop, record it
* in our history for later deciding if the network speed has changed.
*
* This is used by circuit_build_times_network_check_changed() to determine
* if we had too many recent timeouts and need to reset our learned timeout
* to something higher.
*/
static void
circuit_build_times_network_timeout(circuit_build_times_t *cbt,
int did_onehop)
{
/* Check for NULLness because we might not be using adaptive timeouts */
if (cbt->liveness.timeouts_after_firsthop &&
cbt->liveness.num_recent_circs > 0) {
if (did_onehop) {
cbt->liveness.timeouts_after_firsthop[cbt->liveness.after_firsthop_idx]
= 1;
cbt->liveness.after_firsthop_idx++;
cbt->liveness.after_firsthop_idx %= cbt->liveness.num_recent_circs;
}
}
}
/**
* A circuit was just forcibly closed. If there has been no recent network
* activity at all, but this circuit was launched back when we thought the
* network was live, increment the number of "nonlive" circuit timeouts.
*
* This is used by circuit_build_times_network_check_live() to decide
* if we should record the circuit build timeout or not.
*/
static void
circuit_build_times_network_close(circuit_build_times_t *cbt,
int did_onehop, time_t start_time)
{
time_t now = time(NULL);
/*
* Check if this is a timeout that was for a circuit that spent its
* entire existence during a time where we have had no network activity.
*/
if (cbt->liveness.network_last_live < start_time) {
if (did_onehop) {
char last_live_buf[ISO_TIME_LEN+1];
char start_time_buf[ISO_TIME_LEN+1];
char now_buf[ISO_TIME_LEN+1];
format_local_iso_time(last_live_buf, cbt->liveness.network_last_live);
format_local_iso_time(start_time_buf, start_time);
format_local_iso_time(now_buf, now);
log_notice(LD_CIRC,
"A circuit somehow completed a hop while the network was "
"not live. The network was last live at %s, but the circuit "
"launched at %s. It's now %s. This could mean your clock "
"changed.", last_live_buf, start_time_buf, 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 %d "
"seconds. Disabling circuit build timeout recording.",
(int)(now - cbt->liveness.network_last_live));
/* Tell control.c */
control_event_network_liveness_update(0);
} else {
log_info(LD_CIRC,
"Got non-live timeout. Current count is: %d",
cbt->liveness.nonlive_timeouts);
}
}
}
/**
* When the network is not live, we do not record circuit build times.
*
* The network is considered not live if there has been at least one
* circuit build that began and ended (had its close_ms measurement
* period expire) since we last received a cell.
*
* Also has the side effect of rewinding the circuit time history
* in the case of recent liveness changes.
*/
int
circuit_build_times_network_check_live(const circuit_build_times_t *cbt)
{
if (cbt->liveness.nonlive_timeouts > 0) {
return 0;
}
return 1;
}
/**
* Returns true if we have seen more than MAX_RECENT_TIMEOUT_COUNT of
* the past RECENT_CIRCUITS time out after the first hop. Used to detect
* if the network connection has changed significantly, and if so,
* resets our circuit build timeout to the default.
*
* Also resets the entire timeout history in this case and causes us
* to restart the process of building test circuits and estimating a
* new timeout.
*/
STATIC int
circuit_build_times_network_check_changed(circuit_build_times_t *cbt)
{
int total_build_times = cbt->total_build_times;
int timeout_count=0;
int i;
if (cbt->liveness.timeouts_after_firsthop &&
cbt->liveness.num_recent_circs > 0) {
/* how many of our recent circuits made it to the first hop but then
* timed out? */
for (i = 0; i < cbt->liveness.num_recent_circs; i++) {
timeout_count += cbt->liveness.timeouts_after_firsthop[i];
}
}
/* If 80% of our recent circuits are timing out after the first hop,
* we need to re-estimate a new initial alpha and timeout. */
if (timeout_count < circuit_build_times_max_timeouts()) {
return 0;
}
circuit_build_times_reset(cbt);
if (cbt->liveness.timeouts_after_firsthop &&
cbt->liveness.num_recent_circs > 0) {
memset(cbt->liveness.timeouts_after_firsthop, 0,
sizeof(*cbt->liveness.timeouts_after_firsthop)*
cbt->liveness.num_recent_circs);
}
cbt->liveness.after_firsthop_idx = 0;
#define MAX_TIMEOUT ((int32_t) (INT32_MAX/2))
/* Check to see if this has happened before. If so, double the timeout
* to give clients on abysmally bad network connections a shot at access */
if (cbt->timeout_ms >= circuit_build_times_get_initial_timeout()) {
if (cbt->timeout_ms > MAX_TIMEOUT || cbt->close_ms > MAX_TIMEOUT) {
log_warn(LD_CIRC, "Insanely large circuit build timeout value. "
"(timeout = %fmsec, close = %fmsec)",
cbt->timeout_ms, cbt->close_ms);
} else {
cbt->timeout_ms *= 2;
cbt->close_ms *= 2;
}
} else {
cbt->close_ms = cbt->timeout_ms
= circuit_build_times_get_initial_timeout();
}
#undef MAX_TIMEOUT
cbt_control_event_buildtimeout_set(cbt, BUILDTIMEOUT_SET_EVENT_RESET);
log_notice(LD_CIRC,
"Your network connection speed appears to have changed. Resetting "
"timeout to %lds after %d timeouts and %d buildtimes.",
tor_lround(cbt->timeout_ms/1000), timeout_count,
total_build_times);
return 1;
}
/**
* Count the number of timeouts in a set of cbt data.
*/
double
circuit_build_times_timeout_rate(const circuit_build_times_t *cbt)
{
int i=0,timeouts=0;
for (i = 0; i < CBT_NCIRCUITS_TO_OBSERVE; i++) {
if (cbt->circuit_build_times[i] >= cbt->timeout_ms) {
timeouts++;
}
}
if (!cbt->total_build_times)
return 0;
return ((double)timeouts)/cbt->total_build_times;
}
/**
* Count the number of closed circuits in a set of cbt data.
*/
double
circuit_build_times_close_rate(const circuit_build_times_t *cbt)
{
int i=0,closed=0;
for (i = 0; i < CBT_NCIRCUITS_TO_OBSERVE; i++) {
if (cbt->circuit_build_times[i] == CBT_BUILD_ABANDONED) {
closed++;
}
}
if (!cbt->total_build_times)
return 0;
return ((double)closed)/cbt->total_build_times;
}
/**
* Store a timeout as a synthetic value.
*
* Returns true if the store was successful and we should possibly
* update our timeout estimate.
*/
int
circuit_build_times_count_close(circuit_build_times_t *cbt,
int did_onehop,
time_t start_time)
{
if (circuit_build_times_disabled(get_options())) {
cbt->close_ms = cbt->timeout_ms
= circuit_build_times_get_initial_timeout();
return 0;
}
/* Record this force-close to help determine if the network is dead */
circuit_build_times_network_close(cbt, did_onehop, start_time);
/* Only count timeouts if network is live.. */
if (!circuit_build_times_network_check_live(cbt)) {
return 0;
}
circuit_build_times_add_time(cbt, CBT_BUILD_ABANDONED);
return 1;
}
/**
* Update timeout counts to determine if we need to expire
* our build time history due to excessive timeouts.
*
* We do not record any actual time values at this stage;
* we are only interested in recording the fact that a timeout
* happened. We record the time values via
* circuit_build_times_count_close() and circuit_build_times_add_time().
*/
void
circuit_build_times_count_timeout(circuit_build_times_t *cbt,
int did_onehop)
{
if (circuit_build_times_disabled(get_options())) {
cbt->close_ms = cbt->timeout_ms
= circuit_build_times_get_initial_timeout();
return;
}
/* Register the fact that a timeout just occurred. */
circuit_build_times_network_timeout(cbt, did_onehop);
/* If there are a ton of timeouts, we should reset
* the circuit build timeout. */
circuit_build_times_network_check_changed(cbt);
}
/**
* Estimate a new timeout based on history and set our timeout
* variable accordingly.
*/
static int
circuit_build_times_set_timeout_worker(circuit_build_times_t *cbt)
{
build_time_t max_time;
if (!circuit_build_times_enough_to_compute(cbt))
return 0;
if (!circuit_build_times_update_alpha(cbt))
return 0;
cbt->timeout_ms = circuit_build_times_calculate_timeout(cbt,
circuit_build_times_quantile_cutoff());
cbt->close_ms = circuit_build_times_calculate_timeout(cbt,
circuit_build_times_close_quantile());
max_time = circuit_build_times_max(cbt);
if (cbt->timeout_ms > max_time) {
log_info(LD_CIRC,
"Circuit build timeout of %dms is beyond the maximum build "
"time we have ever observed. Capping it to %dms.",
(int)cbt->timeout_ms, max_time);
cbt->timeout_ms = max_time;
}
if (max_time < INT32_MAX/2 && cbt->close_ms > 2*max_time) {
log_info(LD_CIRC,
"Circuit build measurement period of %dms is more than twice "
"the maximum build time we have ever observed. Capping it to "
"%dms.", (int)cbt->close_ms, 2*max_time);
cbt->close_ms = 2*max_time;
}
/* Sometimes really fast guard nodes give us such a steep curve
* that this ends up being not that much greater than timeout_ms.
* Make it be at least 1 min to handle this case. */
cbt->close_ms = MAX(cbt->close_ms, circuit_build_times_initial_timeout());
cbt->have_computed_timeout = 1;
return 1;
}
/**
* Exposed function to compute a new timeout. Dispatches events and
* also filters out extremely high timeout values.
*/
void
circuit_build_times_set_timeout(circuit_build_times_t *cbt)
{
long prev_timeout = tor_lround(cbt->timeout_ms/1000);
double timeout_rate;
/*
* Just return if we aren't using adaptive timeouts
*/
if (circuit_build_times_disabled(get_options()))
return;
if (!circuit_build_times_set_timeout_worker(cbt))
return;
if (cbt->timeout_ms < circuit_build_times_min_timeout()) {
log_info(LD_CIRC, "Set buildtimeout to low value %fms. Setting to %dms",
cbt->timeout_ms, circuit_build_times_min_timeout());
cbt->timeout_ms = circuit_build_times_min_timeout();
if (cbt->close_ms < cbt->timeout_ms) {
/* This shouldn't happen because of MAX() in timeout_worker above,
* but doing it just in case */
cbt->close_ms = circuit_build_times_initial_timeout();
}
}
cbt_control_event_buildtimeout_set(cbt, BUILDTIMEOUT_SET_EVENT_COMPUTED);
timeout_rate = circuit_build_times_timeout_rate(cbt);
if (prev_timeout > tor_lround(cbt->timeout_ms/1000)) {
log_info(LD_CIRC,
"Based on %d 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 %ld seconds.",
cbt->total_build_times,
tor_lround(cbt->timeout_ms/1000));
log_info(LD_CIRC,
"Circuit timeout data: %fms, %fms, Xm: %d, a: %f, r: %f",
cbt->timeout_ms, cbt->close_ms, cbt->Xm, cbt->alpha,
timeout_rate);
} else if (prev_timeout < tor_lround(cbt->timeout_ms/1000)) {
log_info(LD_CIRC,
"Based on %d circuit times, it looks like we need to wait "
"longer for circuits to finish. We will now assume a "
"circuit is too slow to use after waiting %ld seconds.",
cbt->total_build_times,
tor_lround(cbt->timeout_ms/1000));
log_info(LD_CIRC,
"Circuit timeout data: %fms, %fms, Xm: %d, a: %f, r: %f",
cbt->timeout_ms, cbt->close_ms, cbt->Xm, cbt->alpha,
timeout_rate);
} else {
log_info(LD_CIRC,
"Set circuit build timeout to %lds (%fms, %fms, Xm: %d, a: %f,"
" r: %f) based on %d circuit times",
tor_lround(cbt->timeout_ms/1000),
cbt->timeout_ms, cbt->close_ms, cbt->Xm, cbt->alpha, timeout_rate,
cbt->total_build_times);
}
}
#ifdef TOR_UNIT_TESTS
/** Make a note that we're running unit tests (rather than running Tor
* itself), so we avoid clobbering our state file. */
void
circuitbuild_running_unit_tests(void)
{
unit_tests = 1;
}
#endif /* defined(TOR_UNIT_TESTS) */
void
circuit_build_times_update_last_circ(circuit_build_times_t *cbt)
{
cbt->last_circ_at = approx_time();
}
static void
cbt_control_event_buildtimeout_set(const circuit_build_times_t *cbt,
buildtimeout_set_event_t type)
{
char *args = NULL;
double qnt;
switch (type) {
case BUILDTIMEOUT_SET_EVENT_RESET:
case BUILDTIMEOUT_SET_EVENT_SUSPENDED:
case BUILDTIMEOUT_SET_EVENT_DISCARD:
qnt = 1.0;
break;
case BUILDTIMEOUT_SET_EVENT_COMPUTED:
case BUILDTIMEOUT_SET_EVENT_RESUME:
default:
qnt = circuit_build_times_quantile_cutoff();
break;
}
tor_asprintf(&args, "TOTAL_TIMES=%lu "
"TIMEOUT_MS=%lu XM=%lu ALPHA=%f CUTOFF_QUANTILE=%f "
"TIMEOUT_RATE=%f CLOSE_MS=%lu CLOSE_RATE=%f",
(unsigned long)cbt->total_build_times,
(unsigned long)cbt->timeout_ms,
(unsigned long)cbt->Xm, cbt->alpha, qnt,
circuit_build_times_timeout_rate(cbt),
(unsigned long)cbt->close_ms,
circuit_build_times_close_rate(cbt));
control_event_buildtimeout_set(type, args);
tor_free(args);
}
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