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cmux: Make EWMA policy mandatory
To achieve this, a default value for the CircuitPriorityHalflife option was needed. We still look in the options and then the consensus but in case no value can be found, the default CircuitPriorityHalflifeMsec=30000 is used. It it the value we've been using since 0.2.4.4-alpha. This means that EWMA, our only policy, can not be disabled anymore fallbacking to the round robin algorithm. Unneeded code to control that is removed in this commit. Part of #25268 Signed-off-by: David Goulet <dgoulet@torproject.org>
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@ -2108,21 +2108,6 @@ channel_listener_dumpstats(int severity)
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}
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}
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/**
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* Set the cmux policy on all active channels.
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*/
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void
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channel_set_cmux_policy_everywhere(circuitmux_policy_t *pol)
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{
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if (!active_channels) return;
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SMARTLIST_FOREACH_BEGIN(active_channels, channel_t *, curr) {
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if (curr->cmux) {
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circuitmux_set_policy(curr->cmux, pol);
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}
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} SMARTLIST_FOREACH_END(curr);
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}
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/**
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* Clean up channels.
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*
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@ -422,9 +422,6 @@ void channel_free_all(void);
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void channel_dumpstats(int severity);
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void channel_listener_dumpstats(int severity);
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/* Set the cmux policy on all active channels */
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void channel_set_cmux_policy_everywhere(circuitmux_policy_t *pol);
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#ifdef TOR_CHANNEL_INTERNAL_
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#ifdef CHANNEL_PRIVATE_
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@ -160,9 +160,8 @@ channel_tls_common_init(channel_tls_t *tlschan)
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chan->write_var_cell = channel_tls_write_var_cell_method;
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chan->cmux = circuitmux_alloc();
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if (cell_ewma_enabled()) {
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circuitmux_set_policy(chan->cmux, &ewma_policy);
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}
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/* We only have one policy for now so always set it to EWMA. */
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circuitmux_set_policy(chan->cmux, &ewma_policy);
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}
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/**
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@ -223,8 +223,6 @@ ewma_cmp_cmux(circuitmux_t *cmux_1, circuitmux_policy_data_t *pol_data_1,
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* has value ewma_scale_factor ** N.)
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*/
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static double ewma_scale_factor = 0.1;
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/* DOCDOC ewma_enabled */
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static int ewma_enabled = 0;
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/*** EWMA circuitmux_policy_t method table ***/
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@ -612,13 +610,6 @@ cell_ewma_tick_from_timeval(const struct timeval *now,
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return res;
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}
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/** Tell the caller whether ewma_enabled is set */
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int
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cell_ewma_enabled(void)
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{
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return ewma_enabled;
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}
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/** Compute and return the current cell_ewma tick. */
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unsigned int
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cell_ewma_get_tick(void)
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@ -626,45 +617,79 @@ cell_ewma_get_tick(void)
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return ((unsigned)approx_time() / EWMA_TICK_LEN);
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}
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/* Default value for the CircuitPriorityHalflifeMsec consensus parameter in
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* msec. */
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#define CMUX_PRIORITY_HALFLIFE_MSEC_DEFAULT 30000
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/* Minimum and maximum value for the CircuitPriorityHalflifeMsec consensus
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* parameter. */
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#define CMUX_PRIORITY_HALFLIFE_MSEC_MIN 1
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#define CMUX_PRIORITY_HALFLIFE_MSEC_MAX INT32_MAX
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/* Return the value of the circuit priority halflife from the options if
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* available or else from the consensus (in that order). If none can be found,
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* a default value is returned.
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*
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* The source_msg points to a string describing from where the value was
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* picked so it can be used for logging. */
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static double
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get_circuit_priority_halflife(const or_options_t *options,
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const networkstatus_t *consensus,
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const char **source_msg)
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{
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int32_t halflife_ms;
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double halflife;
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/* Compute the default value now. We might need it. */
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double halflife_default =
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((double) CMUX_PRIORITY_HALFLIFE_MSEC_DEFAULT) / 1000.0;
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/* Try to get it from configuration file first. */
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if (options && options->CircuitPriorityHalflife < EPSILON) {
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halflife = options->CircuitPriorityHalflife;
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*source_msg = "CircuitPriorityHalflife in configuration";
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goto end;
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}
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/* Try to get the msec value from the consensus. */
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halflife_ms = networkstatus_get_param(consensus,
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"CircuitPriorityHalflifeMsec",
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CMUX_PRIORITY_HALFLIFE_MSEC_DEFAULT,
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CMUX_PRIORITY_HALFLIFE_MSEC_MIN,
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CMUX_PRIORITY_HALFLIFE_MSEC_MAX);
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halflife = ((double) halflife_ms) / 1000.0;
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*source_msg = "CircuitPriorityHalflifeMsec in consensus";
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end:
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/* We should never go below the EPSILON else we would consider it disabled
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* and we can't have that. */
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if (halflife < EPSILON) {
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log_warn(LD_CONFIG, "CircuitPriorityHalflife is too small (%f). "
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"Adjusting to the smallest value allowed: %f.",
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halflife, halflife_default);
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halflife = halflife_default;
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}
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return halflife;
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}
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/** Adjust the global cell scale factor based on <b>options</b> */
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void
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cell_ewma_set_scale_factor(const or_options_t *options,
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const networkstatus_t *consensus)
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{
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int32_t halflife_ms;
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double halflife;
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const char *source;
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if (options && options->CircuitPriorityHalflife >= -EPSILON) {
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halflife = options->CircuitPriorityHalflife;
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source = "CircuitPriorityHalflife in configuration";
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} else if (consensus && (halflife_ms = networkstatus_get_param(
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consensus, "CircuitPriorityHalflifeMsec",
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-1, -1, INT32_MAX)) >= 0) {
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halflife = ((double)halflife_ms)/1000.0;
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source = "CircuitPriorityHalflifeMsec in consensus";
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} else {
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halflife = EWMA_DEFAULT_HALFLIFE;
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source = "Default value";
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}
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if (halflife <= EPSILON) {
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/* The cell EWMA algorithm is disabled. */
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ewma_scale_factor = 0.1;
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ewma_enabled = 0;
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log_info(LD_OR,
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"Disabled cell_ewma algorithm because of value in %s",
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source);
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} else {
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/* convert halflife into halflife-per-tick. */
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halflife /= EWMA_TICK_LEN;
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/* compute per-tick scale factor. */
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ewma_scale_factor = exp( LOG_ONEHALF / halflife );
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ewma_enabled = 1;
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log_info(LD_OR,
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"Enabled cell_ewma algorithm because of value in %s; "
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"scale factor is %f per %d seconds",
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source, ewma_scale_factor, EWMA_TICK_LEN);
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}
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/* Both options and consensus can be NULL. This assures us to either get a
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* valid configured value or the default one. */
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halflife = get_circuit_priority_halflife(options, consensus, &source);
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/* convert halflife into halflife-per-tick. */
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halflife /= EWMA_TICK_LEN;
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/* compute per-tick scale factor. */
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ewma_scale_factor = exp( LOG_ONEHALF / halflife );
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log_info(LD_OR,
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"Enabled cell_ewma algorithm because of value in %s; "
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"scale factor is %f per %d seconds",
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source, ewma_scale_factor, EWMA_TICK_LEN);
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}
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/** Return the multiplier necessary to convert the value of a cell sent in
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@ -15,7 +15,6 @@
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extern circuitmux_policy_t ewma_policy;
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/* Externally visible EWMA functions */
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int cell_ewma_enabled(void);
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unsigned int cell_ewma_get_tick(void);
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void cell_ewma_set_scale_factor(const or_options_t *options,
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const networkstatus_t *consensus);
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@ -1799,7 +1799,6 @@ options_act(const or_options_t *old_options)
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char *msg=NULL;
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const int transition_affects_workers =
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old_options && options_transition_affects_workers(old_options, options);
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int old_ewma_enabled;
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const int transition_affects_guards =
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old_options && options_transition_affects_guards(old_options, options);
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@ -2073,16 +2072,8 @@ options_act(const or_options_t *old_options)
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if (accounting_is_enabled(options))
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configure_accounting(time(NULL));
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old_ewma_enabled = cell_ewma_enabled();
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/* Change the cell EWMA settings */
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cell_ewma_set_scale_factor(options, networkstatus_get_latest_consensus());
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/* If we just enabled ewma, set the cmux policy on all active channels */
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if (cell_ewma_enabled() && !old_ewma_enabled) {
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channel_set_cmux_policy_everywhere(&ewma_policy);
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} else if (!cell_ewma_enabled() && old_ewma_enabled) {
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/* Turn it off everywhere */
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channel_set_cmux_policy_everywhere(NULL);
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}
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/* Update the BridgePassword's hashed version as needed. We store this as a
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* digest so that we can do side-channel-proof comparisons on it.
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@ -1779,7 +1779,6 @@ networkstatus_set_current_consensus(const char *consensus,
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consensus_waiting_for_certs_t *waiting = NULL;
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time_t current_valid_after = 0;
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int free_consensus = 1; /* Free 'c' at the end of the function */
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int old_ewma_enabled;
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int checked_protocols_already = 0;
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if (flav < 0) {
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@ -2003,17 +2002,8 @@ networkstatus_set_current_consensus(const char *consensus,
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/* XXXXNM Microdescs: needs a non-ns variant. ???? NM*/
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update_consensus_networkstatus_fetch_time(now);
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/* Update ewma and adjust policy if needed; first cache the old value */
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old_ewma_enabled = cell_ewma_enabled();
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/* Change the cell EWMA settings */
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cell_ewma_set_scale_factor(options, c);
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/* If we just enabled ewma, set the cmux policy on all active channels */
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if (cell_ewma_enabled() && !old_ewma_enabled) {
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channel_set_cmux_policy_everywhere(&ewma_policy);
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} else if (!cell_ewma_enabled() && old_ewma_enabled) {
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/* Turn it off everywhere */
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channel_set_cmux_policy_everywhere(NULL);
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}
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/* XXXX this call might be unnecessary here: can changing the
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* current consensus really alter our view of any OR's rate limits? */
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@ -575,7 +575,7 @@ test_channel_outbound_cell(void *arg)
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channel_register(chan);
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tt_int_op(chan->registered, OP_EQ, 1);
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/* Set EWMA policy so we can pick it when flushing. */
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channel_set_cmux_policy_everywhere(&ewma_policy);
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circuitmux_set_policy(chan->cmux, &ewma_policy);
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tt_ptr_op(circuitmux_get_policy(chan->cmux), OP_EQ, &ewma_policy);
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/* Register circuit to the channel circid map which will attach the circuit
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