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@@ -11,6 +11,7 @@
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* servers.
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**/
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+#define ROUTERLIST_PRIVATE
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#include "or.h"
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#include "circuitbuild.h"
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#include "config.h"
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@@ -1652,6 +1653,53 @@ router_get_advertised_bandwidth_capped(const routerinfo_t *router)
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return result;
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}
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+/** Pick a random element of <b>n_entries</b>-element array <b>entries</b>,
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+ * choosing each element with a probability proportional to its value, and
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+ * return the index of that element. If all elements are 0, choose an index
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+ * at random. If <b>total_out</b> is provided, set it to the sum of all
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+ * elements in the array. Return -1 on error.
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+ */
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+/* private */ int
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+choose_array_element_by_weight(const uint64_t *entries, int n_entries,
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+ uint64_t *total_out)
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+{
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+ int i, i_chosen=-1, n_chosen=0;
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+ uint64_t total_so_far = 0;
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+ uint64_t rand_val;
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+ uint64_t total = 0;
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+
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+ for (i = 0; i < n_entries; ++i)
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+ total += entries[i];
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+
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+ if (total_out)
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+ *total_out = total;
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+
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+ if (n_entries < 1)
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+ return -1;
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+
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+ if (total == 0)
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+ return crypto_rand_int(n_entries);
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+
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+ rand_val = crypto_rand_uint64(total);
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+
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+ for (i = 0; i < n_entries; ++i) {
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+ total_so_far += entries[i];
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+ if (total_so_far > rand_val) {
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+ i_chosen = i;
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+ n_chosen++;
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+ /* Set rand_val to UINT_MAX rather than stopping the loop. This way,
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+ * the time we spend in the loop does not leak which element we chose. */
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+ rand_val = UINT64_MAX;
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+ }
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+ }
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+ tor_assert(total_so_far == total);
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+ tor_assert(n_chosen == 1);
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+ tor_assert(i_chosen >= 0);
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+ tor_assert(i_chosen < n_entries);
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+
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+ return i_chosen;
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+}
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+
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/** When weighting bridges, enforce these values as lower and upper
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* bound for believable bandwidth, because there is no way for us
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* to verify a bridge's bandwidth currently. */
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@@ -1702,15 +1750,10 @@ smartlist_choose_node_by_bandwidth_weights(smartlist_t *sl,
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bandwidth_weight_rule_t rule)
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{
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int64_t weight_scale;
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- uint64_t rand_bw;
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double Wg = -1, Wm = -1, We = -1, Wd = -1;
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double Wgb = -1, Wmb = -1, Web = -1, Wdb = -1;
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- uint64_t weighted_bw = 0, unweighted_bw = 0;
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+ uint64_t weighted_bw = 0;
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uint64_t *bandwidths;
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- uint64_t tmp;
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- unsigned int i;
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- unsigned int i_chosen;
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- int have_unknown = 0; /* true iff sl contains element not in consensus. */
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/* Can't choose exit and guard at same time */
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tor_assert(rule == NO_WEIGHTING ||
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@@ -1814,7 +1857,6 @@ smartlist_choose_node_by_bandwidth_weights(smartlist_t *sl,
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} else if (node->ri) {
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/* bridge or other descriptor not in our consensus */
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this_bw = bridge_get_advertised_bandwidth_bounded(node->ri);
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- have_unknown = 1;
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} else {
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/* We can't use this one. */
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continue;
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@@ -1838,69 +1880,22 @@ smartlist_choose_node_by_bandwidth_weights(smartlist_t *sl,
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weight = 0.0;
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bandwidths[node_sl_idx] = tor_llround(weight*this_bw + 0.5);
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- weighted_bw += bandwidths[node_sl_idx];
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- unweighted_bw += this_bw;
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if (is_me)
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sl_last_weighted_bw_of_me = bandwidths[node_sl_idx];
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} SMARTLIST_FOREACH_END(node);
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- /* XXXX this is a kludge to expose these values. */
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- sl_last_total_weighted_bw = weighted_bw;
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-
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log_debug(LD_CIRC, "Choosing node for rule %s based on weights "
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"Wg=%f Wm=%f We=%f Wd=%f with total bw "U64_FORMAT,
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bandwidth_weight_rule_to_string(rule),
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Wg, Wm, We, Wd, U64_PRINTF_ARG(weighted_bw));
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- /* If there is no bandwidth, choose at random */
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- if (weighted_bw == 0) {
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- /* Don't warn when using bridges/relays not in the consensus */
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- if (!have_unknown) {
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-#define ZERO_BANDWIDTH_WARNING_INTERVAL (15)
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- static ratelim_t zero_bandwidth_warning_limit =
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- RATELIM_INIT(ZERO_BANDWIDTH_WARNING_INTERVAL);
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- char *msg;
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- if ((msg = rate_limit_log(&zero_bandwidth_warning_limit,
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- approx_time()))) {
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- log_warn(LD_CIRC,
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- "Weighted bandwidth is "U64_FORMAT" in node selection for "
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- "rule %s (unweighted was "U64_FORMAT") %s",
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- U64_PRINTF_ARG(weighted_bw),
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- bandwidth_weight_rule_to_string(rule),
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- U64_PRINTF_ARG(unweighted_bw), msg);
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- }
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- }
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+ {
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+ int idx = choose_array_element_by_weight(bandwidths,
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+ smartlist_len(sl),
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+ &sl_last_total_weighted_bw);
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tor_free(bandwidths);
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- return smartlist_choose(sl);
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- }
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-
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- rand_bw = crypto_rand_uint64(weighted_bw);
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-
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- /* Last, count through sl until we get to the element we picked */
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- i_chosen = (unsigned)smartlist_len(sl);
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- tmp = 0;
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- for (i=0; i < (unsigned)smartlist_len(sl); i++) {
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- tmp += bandwidths[i];
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- if (tmp > rand_bw) {
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- i_chosen = i;
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- rand_bw = UINT64_MAX;
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- }
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- }
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- i = i_chosen;
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-
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- if (i == (unsigned)smartlist_len(sl)) {
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- /* This was once possible due to round-off error, but shouldn't be able
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- * to occur any longer. */
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- tor_fragile_assert();
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- --i;
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- log_warn(LD_BUG, "Round-off error in computing bandwidth had an effect on "
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- " which router we chose. Please tell the developers. "
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- U64_FORMAT" "U64_FORMAT" "U64_FORMAT,
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- U64_PRINTF_ARG(tmp), U64_PRINTF_ARG(rand_bw),
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- U64_PRINTF_ARG(weighted_bw));
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+ return idx < 0 ? NULL : smartlist_get(sl, idx);
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}
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- tor_free(bandwidths);
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- return smartlist_get(sl, i);
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}
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/** Helper function:
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@@ -1921,14 +1916,12 @@ smartlist_choose_node_by_bandwidth(smartlist_t *sl,
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bandwidth_weight_rule_t rule)
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{
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unsigned int i;
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- unsigned int i_chosen;
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uint64_t *bandwidths;
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int is_exit;
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int is_guard;
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int is_fast;
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- uint64_t total_nonexit_bw = 0, total_exit_bw = 0, total_bw = 0;
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+ uint64_t total_nonexit_bw = 0, total_exit_bw = 0;
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uint64_t total_nonguard_bw = 0, total_guard_bw = 0;
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- uint64_t rand_bw, tmp;
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double exit_weight;
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double guard_weight;
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int n_unknown = 0;
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@@ -2073,7 +2066,6 @@ smartlist_choose_node_by_bandwidth(smartlist_t *sl,
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if (guard_weight <= 0.0)
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guard_weight = 0.0;
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- total_bw = 0;
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sl_last_weighted_bw_of_me = 0;
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for (i=0; i < (unsigned)smartlist_len(sl); i++) {
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tor_assert(bandwidths[i] < UINT64_MAX);
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@@ -2087,15 +2079,12 @@ smartlist_choose_node_by_bandwidth(smartlist_t *sl,
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else if (is_exit)
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bandwidths[i] = tor_llround(bandwidths[i] * exit_weight);
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- total_bw += bandwidths[i];
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if (i == (unsigned) me_idx)
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sl_last_weighted_bw_of_me = bandwidths[i];
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}
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}
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- /* XXXX this is a kludge to expose these values. */
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- sl_last_total_weighted_bw = total_bw;
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-
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+#if 0
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log_debug(LD_CIRC, "Total weighted bw = "U64_FORMAT
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", exit bw = "U64_FORMAT
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", nonexit bw = "U64_FORMAT", exit weight = %f "
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@@ -2108,37 +2097,18 @@ smartlist_choose_node_by_bandwidth(smartlist_t *sl,
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exit_weight, (int)(rule == WEIGHT_FOR_EXIT),
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U64_PRINTF_ARG(total_guard_bw), U64_PRINTF_ARG(total_nonguard_bw),
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guard_weight, (int)(rule == WEIGHT_FOR_GUARD));
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+#endif
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- /* Almost done: choose a random value from the bandwidth weights. */
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- rand_bw = crypto_rand_uint64(total_bw);
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-
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- /* Last, count through sl until we get to the element we picked */
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- tmp = 0;
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- i_chosen = (unsigned)smartlist_len(sl);
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- for (i=0; i < (unsigned)smartlist_len(sl); i++) {
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- tmp += bandwidths[i];
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-
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- if (tmp > rand_bw) {
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- i_chosen = i;
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- rand_bw = UINT64_MAX;
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- }
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+ {
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+ int idx = choose_array_element_by_weight(bandwidths,
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+ smartlist_len(sl),
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+ &sl_last_total_weighted_bw);
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+ tor_free(bandwidths);
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+ tor_free(fast_bits);
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+ tor_free(exit_bits);
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+ tor_free(guard_bits);
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+ return idx < 0 ? NULL : smartlist_get(sl, idx);
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}
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- i = i_chosen;
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- if (i == (unsigned)smartlist_len(sl)) {
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- /* This was once possible due to round-off error, but shouldn't be able
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- * to occur any longer. */
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- tor_fragile_assert();
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- --i;
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- log_warn(LD_BUG, "Round-off error in computing bandwidth had an effect on "
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- " which router we chose. Please tell the developers. "
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- U64_FORMAT " " U64_FORMAT " " U64_FORMAT, U64_PRINTF_ARG(tmp),
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- U64_PRINTF_ARG(rand_bw), U64_PRINTF_ARG(total_bw));
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- }
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- tor_free(bandwidths);
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- tor_free(fast_bits);
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- tor_free(exit_bits);
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- tor_free(guard_bits);
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- return smartlist_get(sl, i);
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}
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/** Choose a random element of status list <b>sl</b>, weighted by
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