commit 14a3c17ce658c47ae9a0b8e689970efe37ca3b22 Author: George Kadianakis desnacked@riseup.net Date: Thu Jan 29 15:05:30 2015 +0000
Calculate the guardfraction bandwidth of a guard. --- src/or/entrynodes.c | 36 ++++++++++++++++++++++++++++++++++++ src/or/entrynodes.h | 14 ++++++++++++++ 2 files changed, 50 insertions(+)
diff --git a/src/or/entrynodes.c b/src/or/entrynodes.c index a766f6c..93b23f6 100644 --- a/src/or/entrynodes.c +++ b/src/or/entrynodes.c @@ -1715,6 +1715,42 @@ should_apply_guardfraction(const networkstatus_t *ns)
return options->UseGuardFraction; } + +/* Given the original bandwidth of a guard and its guardfraction, + * calculate how much bandwidth the guard should have as a guard and + * as a non-guard. + * + * Quoting from proposal236: + * + * Let Wpf denote the weight from the 'bandwidth-weights' line a + * client would apply to N for position p if it had the guard + * flag, Wpn the weight if it did not have the guard flag, and B the + * measured bandwidth of N in the consensus. Then instead of choosing + * N for position p proportionally to Wpf*B or Wpn*B, clients should + * choose N proportionally to F*Wpf*B + (1-F)*Wpn*B. + * + * This function fills the <b>guardfraction_bw</b> structure. It sets + * <b>guard_bw</b> to F*B and <b>non_guard_bw</b> to (1-F)*B. + */ +void +guard_get_guardfraction_bandwidth(guardfraction_bandwidth_t *guardfraction_bw, + int orig_bandwidth, + uint32_t guardfraction_percentage) +{ + double guardfraction_fraction; + + /* Turn the percentage into a fraction. */ + tor_assert(guardfraction_percentage <= 100); + guardfraction_fraction = guardfraction_percentage / 100.0; + + long guard_bw = tor_lround(guardfraction_fraction * orig_bandwidth); + tor_assert(guard_bw <= INT_MAX); + + guardfraction_bw->guard_bw = (int) guard_bw; + + guardfraction_bw->non_guard_bw = orig_bandwidth - guard_bw; +} + /** A list of configured bridges. Whenever we actually get a descriptor * for one, we add it as an entry guard. Note that the order of bridges * in this list does not necessarily correspond to the order of bridges diff --git a/src/or/entrynodes.h b/src/or/entrynodes.h index 96d832e..35bd748 100644 --- a/src/or/entrynodes.h +++ b/src/or/entrynodes.h @@ -160,7 +160,21 @@ int validate_pluggable_transports_config(void); double pathbias_get_close_success_count(entry_guard_t *guard); double pathbias_get_use_success_count(entry_guard_t *guard);
+/** Contains the bandwidth of a relay as a guard and as a non-guard + * after the guardfraction has been considered. */ +typedef struct guardfraction_bandwidth_t { + /* Bandwidth as a guard after guardfraction has been considered. */ + int guard_bw; + /* Bandwidth as a non-guard after guardfraction has been considered. */ + int non_guard_bw; +} guardfraction_bandwidth_t; + int should_apply_guardfraction(const networkstatus_t *ns);
+void +guard_get_guardfraction_bandwidth(guardfraction_bandwidth_t *guardfraction_bw, + int orig_bandwidth, + uint32_t guardfraction_percentage); + #endif