[tor-commits] [tor/master] Merge remote-tracking branch 'public/bug6304_v3' into maint-0.2.4
nickm at torproject.org
nickm at torproject.org
Wed Mar 20 14:55:05 UTC 2013
commit 5b0b51ca3ff55d6e82081adf4cb1dbfa24ac4872
Merge: f1caa2f b9a8f8c
Author: Nick Mathewson <nickm at torproject.org>
Date: Wed Mar 20 10:31:28 2013 -0400
Merge remote-tracking branch 'public/bug6304_v3' into maint-0.2.4
Conflicts:
src/or/circuitbuild.c
src/or/config.c
changes/bug6304 | 4 ++++
src/or/circuitstats.c | 19 ++++++++-----------
src/or/config.c | 12 ++++++++----
3 files changed, 20 insertions(+), 15 deletions(-)
diff --cc src/or/circuitstats.c
index 73e34d9,0000000..fe9c80d
mode 100644,000000..100644
--- a/src/or/circuitstats.c
+++ b/src/or/circuitstats.c
@@@ -1,1559 -1,0 +1,1556 @@@
+/* Copyright (c) 2001 Matej Pfajfar.
+ * Copyright (c) 2001-2004, Roger Dingledine.
+ * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
+ * Copyright (c) 2007-2013, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+#define CIRCUITSTATS_PRIVATE
+
+#include "or.h"
+#include "circuitbuild.h"
+#include "circuitstats.h"
+#include "config.h"
+#include "confparse.h"
+#include "control.h"
+#include "networkstatus.h"
+#include "statefile.h"
+
+#undef log
+#include <math.h>
+
+#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.
+/* XXXX024 Make this static; add accessor functions. */
+circuit_build_times_t circ_times;
+
+/** 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;
+
+/**
+ * This function decides if CBT learning should be disabled. It returns
+ * true if one or more of the following four 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.
+ */
+int
+circuit_build_times_disabled(void)
+{
+ if (unit_tests) {
+ return 0;
+ } else {
+ int consensus_disabled = networkstatus_get_param(NULL, "cbtdisabled",
+ 0, 0, 1);
+ int config_disabled = !get_options()->LearnCircuitBuildTimeout;
+ int dirauth_disabled = get_options()->AuthoritativeDir;
+ int state_disabled = did_last_state_file_write_fail() ? 1 : 0;
+
+ if (consensus_disabled || config_disabled || dirauth_disabled ||
+ state_disabled) {
+ log_debug(LD_CIRC,
+ "CircuitBuildTime learning is disabled. "
+ "Consensus=%d, Config=%d, AuthDir=%d, StateFile=%d",
+ consensus_disabled, config_disabled, dirauth_disabled,
+ state_disabled);
+ return 1;
+ } else {
+ 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);
+ 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(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()) {
+ 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_malloc_zero(sizeof(int8_t)*num);
+ 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;
+
+ /*
+ * Check if we have LearnCircuitBuildTimeout, and if we don't,
+ * always use CircuitBuildTimeout, no questions asked.
+ */
- if (get_options()->LearnCircuitBuildTimeout) {
- if (!unit_tests && get_options()->CircuitBuildTimeout) {
- timeout = get_options()->CircuitBuildTimeout*1000;
- if (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();
++ if (!unit_tests && get_options()->CircuitBuildTimeout) {
++ timeout = get_options()->CircuitBuildTimeout*1000;
++ if (get_options()->LearnCircuitBuildTimeout &&
++ 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 = get_options()->CircuitBuildTimeout*1000;
++ timeout = circuit_build_times_initial_timeout();
+ }
+
+ return timeout;
+}
+
+/**
+ * Reset the build time state.
+ *
+ * Leave estimated parameters, timeout and network liveness intact
+ * for future use.
+ */
+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()) {
+ cbt->liveness.num_recent_circs =
+ circuit_build_times_recent_circuit_count(NULL);
+ cbt->liveness.timeouts_after_firsthop =
+ tor_malloc_zero(sizeof(int8_t)*cbt->liveness.num_recent_circs);
+ } 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();
+ 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
+
+/**
+ * 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 time)
+{
+ if (time <= 0 || time > CBT_BUILD_TIME_MAX) {
+ log_warn(LD_BUG, "Circuit build time is too large (%u)."
+ "This is probably a bug.", time);
+ tor_fragile_assert();
+ return -1;
+ }
+
+ log_debug(LD_CIRC, "Adding circuit build time %u", time);
+
+ cbt->circuit_build_times[cbt->build_times_idx] = time;
+ 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(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
+
+/**
+ * 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(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_malloc_zero(*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 = (build_time_t*)tor_malloc_zero(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(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;
+ unsigned int i;
+ build_time_t *loaded_times;
+ int err = 0;
+ circuit_build_times_init(cbt);
+
+ if (circuit_build_times_disabled()) {
+ return 0;
+ }
+
+ /* build_time_t 0 means uninitialized */
+ loaded_times = tor_malloc_zero(sizeof(build_time_t)*state->TotalBuildTimes);
+
+ 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, 0, 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, 0, 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+state->CircuitBuildAbandonedCount
+ > 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 != 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.
+ */
+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.
+ */
+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);
+
+ ret = cbt->Xm/pow(1.0-quantile,1.0/cbt->alpha);
+ if (ret > INT32_MAX) {
+ ret = INT32_MAX;
+ }
+ tor_assert(ret > 0);
+ return ret;
+}
+
+/** 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;
+}
+
+/**
+ * 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;
+}
+
+/**
+ * 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);
+}
+
+/**
+ * Returns true if we need circuits to be built
+ */
+int
+circuit_build_times_needs_circuits(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(circuit_build_times_t *cbt)
+{
+ return circuit_build_times_needs_circuits(cbt) &&
+ approx_time()-cbt->last_circ_at > circuit_build_times_test_frequency();
+}
+
+/**
+ * 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) {
+ 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)(now - cbt->liveness.network_last_live),
+ cbt->liveness.nonlive_timeouts);
+ }
+ cbt->liveness.network_last_live = now;
+ cbt->liveness.nonlive_timeouts = 0;
+}
+
+/**
+ * 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_warn(LD_BUG,
+ "Circuit somehow completed a hop while the network was "
+ "not live. Network was last live at %s, but circuit launched "
+ "at %s. It's now %s.", 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));
+ } 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(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.
+ */
+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;
+
+ /* Check to see if this has happened before. If so, double the timeout
+ * to give people on abysmally bad network connections a shot at access */
+ if (cbt->timeout_ms >= circuit_build_times_get_initial_timeout()) {
+ if (cbt->timeout_ms > INT32_MAX/2 || cbt->close_ms > INT32_MAX/2) {
+ 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();
+ }
+
+ 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()) {
+ 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()) {
+ 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())
+ 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();
+ }
+ }
+
+ 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);
+ }
+}
+/** 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;
+}
+
diff --cc src/or/config.c
index 68c0cca,b04a874..2b8eab7
--- a/src/or/config.c
+++ b/src/or/config.c
@@@ -2700,71 -3761,21 +2700,75 @@@ options_validate(or_options_t *old_opti
options->LearnCircuitBuildTimeout = 0;
}
+ if (options->Tor2webMode && options->UseEntryGuards) {
+ /* tor2web mode clients do not (and should not) use entry guards
+ * in any meaningful way. Further, tor2web mode causes the hidden
+ * service client code to do things which break the path bias
+ * detector, and it's far easier to turn off entry guards (and
+ * thus the path bias detector with it) than to figure out how to
+ * make a piece of code which cannot possibly help tor2web mode
+ * users compatible with tor2web mode.
+ */
+ log_notice(LD_CONFIG,
+ "Tor2WebMode is enabled; disabling UseEntryGuards.");
+ options->UseEntryGuards = 0;
+ }
+
+ if (!(options->UseEntryGuards) &&
+ (options->RendConfigLines != NULL)) {
+ log_warn(LD_CONFIG,
+ "UseEntryGuards is disabled, but you have configured one or more "
+ "hidden services on this Tor instance. Your hidden services "
+ "will be very easy to locate using a well-known attack -- see "
+ "http://freehaven.net/anonbib/#hs-attack06 for details.");
+ }
+
- if (!(options->LearnCircuitBuildTimeout) &&
- options->CircuitBuildTimeout < RECOMMENDED_MIN_CIRCUIT_BUILD_TIMEOUT) {
+ if (!options->LearnCircuitBuildTimeout && options->CircuitBuildTimeout &&
+ options->CircuitBuildTimeout < RECOMMENDED_MIN_CIRCUIT_BUILD_TIMEOUT) {
log_warn(LD_CONFIG,
- "CircuitBuildTimeout is shorter (%d seconds) than recommended "
- "(%d seconds), and LearnCircuitBuildTimeout is disabled. "
+ "CircuitBuildTimeout is shorter (%d seconds) than the recommended "
+ "minimum (%d seconds), and LearnCircuitBuildTimeout is disabled. "
"If tor isn't working, raise this value or enable "
"LearnCircuitBuildTimeout.",
options->CircuitBuildTimeout,
RECOMMENDED_MIN_CIRCUIT_BUILD_TIMEOUT );
+ } else if (!options->LearnCircuitBuildTimeout &&
+ !options->CircuitBuildTimeout) {
+ log_notice(LD_CONFIG, "You disabled LearnCircuitBuildTimeout, but didn't "
+ "a CircuitBuildTimeout. I'll pick a plausible default.");
}
+ if (options->PathBiasNoticeRate > 1.0) {
+ tor_asprintf(msg,
+ "PathBiasNoticeRate is too high. "
+ "It must be between 0 and 1.0");
+ return -1;
+ }
+ if (options->PathBiasWarnRate > 1.0) {
+ tor_asprintf(msg,
+ "PathBiasWarnRate is too high. "
+ "It must be between 0 and 1.0");
+ return -1;
+ }
+ if (options->PathBiasExtremeRate > 1.0) {
+ tor_asprintf(msg,
+ "PathBiasExtremeRate is too high. "
+ "It must be between 0 and 1.0");
+ return -1;
+ }
+ if (options->PathBiasNoticeUseRate > 1.0) {
+ tor_asprintf(msg,
+ "PathBiasNoticeUseRate is too high. "
+ "It must be between 0 and 1.0");
+ return -1;
+ }
+ if (options->PathBiasExtremeUseRate > 1.0) {
+ tor_asprintf(msg,
+ "PathBiasExtremeUseRate is too high. "
+ "It must be between 0 and 1.0");
+ return -1;
+ }
+
if (options->MaxCircuitDirtiness < MIN_MAX_CIRCUIT_DIRTINESS) {
log_warn(LD_CONFIG, "MaxCircuitDirtiness option is too short; "
"raising to %d seconds.", MIN_MAX_CIRCUIT_DIRTINESS);
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