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@@ -99,6 +99,15 @@ static int onion_append_hop(crypt_path_t **head_ptr, extend_info_t *choice);
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static void entry_guards_changed(void);
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+/**
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+ * This function decides if CBT learning should be disabled. It returns
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+ * true if one or more of the following four conditions are met:
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+ *
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+ * 1. If the cbtdisabled consensus parameter is set.
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+ * 2. If the torrc option LearnCircuitBuildTimeout is false.
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+ * 3. If we are a directory authority
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+ * 4. If we fail to write circuit build time history to our state file.
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+ */
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static int
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circuit_build_times_disabled(void)
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{
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@@ -125,6 +134,13 @@ circuit_build_times_disabled(void)
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}
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}
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+/**
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+ * Retrieve and bounds-check the cbtmaxtimeouts consensus paramter.
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+ *
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+ * Effect: When this many timeouts happen in the last 'cbtrecentcount'
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+ * circuit attempts, the client should discard all of its history and
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+ * begin learning a fresh timeout value.
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+ */
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static int32_t
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circuit_build_times_max_timeouts(void)
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{
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@@ -134,6 +150,15 @@ circuit_build_times_max_timeouts(void)
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CBT_MAX_MAX_RECENT_TIMEOUT_COUNT);
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}
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+/**
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+ * Retrieve and bounds-check the cbtnummodes consensus paramter.
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+ *
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+ * Effect: This value governs how many modes to use in the weighted
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+ * average calculation of Pareto parameter Xm. A value of 3 introduces
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+ * some bias (2-5% of CDF) under ideal conditions, but allows for better
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+ * performance in the event that a client chooses guard nodes of radically
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+ * different performance characteristics.
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+ */
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static int32_t
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circuit_build_times_default_num_xm_modes(void)
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{
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@@ -144,6 +169,12 @@ circuit_build_times_default_num_xm_modes(void)
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return num;
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}
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+/**
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+ * Retrieve and bounds-check the cbtmincircs consensus paramter.
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+ *
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+ * Effect: This is the minimum number of circuits to build before
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+ * computing a timeout.
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+ */
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static int32_t
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circuit_build_times_min_circs_to_observe(void)
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{
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@@ -162,6 +193,12 @@ circuit_build_times_enough_to_compute(circuit_build_times_t *cbt)
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return cbt->total_build_times >= circuit_build_times_min_circs_to_observe();
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}
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+/**
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+ * Retrieve and bounds-check the cbtquantile consensus paramter.
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+ *
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+ * Effect: This is the position on the quantile curve to use to set the
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+ * timeout value. It is a percent (10-99).
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+ */
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double
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circuit_build_times_quantile_cutoff(void)
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{
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@@ -181,6 +218,13 @@ circuit_build_times_get_bw_scale(networkstatus_t *ns)
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BW_MAX_WEIGHT_SCALE);
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}
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+/**
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+ * Retrieve and bounds-check the cbtclosequantile consensus paramter.
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+ *
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+ * Effect: This is the position on the quantile curve to use to set the
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+ * timeout value to use to actually close circuits. It is a percent
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+ * (0-99).
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+ */
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static double
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circuit_build_times_close_quantile(void)
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{
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@@ -199,6 +243,13 @@ circuit_build_times_close_quantile(void)
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return param / 100.0;
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}
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+/**
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+ * Retrieve and bounds-check the cbttestfreq consensus paramter.
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+ *
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+ * Effect: Describes how often in seconds to build a test circuit to
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+ * gather timeout values. Only applies if less than 'cbtmincircs'
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+ * have been recorded.
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+ */
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static int32_t
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circuit_build_times_test_frequency(void)
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{
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@@ -209,6 +260,13 @@ circuit_build_times_test_frequency(void)
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return num;
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}
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+/**
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+ * Retrieve and bounds-check the cbtmintimeout consensus paramter.
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+ *
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+ * Effect: This is the minimum allowed timeout value in milliseconds.
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+ * The minimum is to prevent rounding to 0 (we only check once
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+ * per second).
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+ */
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static int32_t
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circuit_build_times_min_timeout(void)
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{
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@@ -219,6 +277,12 @@ circuit_build_times_min_timeout(void)
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return num;
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}
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+/**
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+ * Retrieve and bounds-check the cbtinitialtimeout consensus paramter.
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+ *
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+ * Effect: This is the timeout value to use before computing a timeout,
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+ * in milliseconds.
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+ */
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int32_t
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circuit_build_times_initial_timeout(void)
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{
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@@ -235,6 +299,13 @@ circuit_build_times_initial_timeout(void)
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return param;
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}
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+/**
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+ * Retrieve and bounds-check the cbtrecentcount consensus paramter.
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+ *
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+ * Effect: This is the number of circuit build times to keep track of
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+ * for deciding if we hit cbtmaxtimeouts and need to reset our state
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+ * and learn a new timeout.
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+ */
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static int32_t
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circuit_build_times_recent_circuit_count(networkstatus_t *ns)
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{
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