Implement Path use bias accounting.

Path use bias measures how often we can actually succeed using the circuits we
actually try to use. It is a subset of path bias accounting, but it is
computed as a separate statistic because the rate of client circuit use may
vary depending on use case.

1 files changed, 46 insertions, 2 deletions

diff --git a/src/or/entrynodes.c b/src/or/entrynodes.c
index 3e5837164..4ca56cbac 100644
--- a/src/or/entrynodes.c
+++ b/src/or/entrynodes.c
@@ -1098,6 +1098,40 @@ entry_guards_parse_state(or_state_t *state, int set, char **msg)
         continue;
       }
       digestmap_set(added_by, d, tor_strdup(line->value+HEX_DIGEST_LEN+1));
+    } else if (!strcasecmp(line->key, "EntryGuardPathUseBias")) {
+      const or_options_t *options = get_options();
+      double use_cnt, success_cnt;
+
+      if (!node) {
+        *msg = tor_strdup("Unable to parse entry nodes: "
+               "EntryGuardPathUseBias without EntryGuard");
+        break;
+      }
+
+      if (tor_sscanf(line->value, "%lf %lf",
+                     &use_cnt, &success_cnt) != 2) {
+        log_info(LD_GENERAL, "Malformed path use bias line for node %s",
+                 node->nickname);
+        continue;
+      }
+
+      node->use_attempts = use_cnt;
+      node->use_successes = success_cnt;
+
+      log_info(LD_GENERAL, "Read %f/%f path use bias for node %s",
+               node->use_successes, node->use_attempts, node->nickname);
+
+      /* Note: We rely on the < comparison here to allow us to set a 0
+       * rate and disable the feature entirely. If refactoring, don't
+       * change to <= */
+      if (pathbias_get_use_success_count(node)/node->use_attempts
+            < pathbias_get_extreme_use_rate(options) &&
+          pathbias_get_dropguards(options)) {
+        node->path_bias_disabled = 1;
+        log_info(LD_GENERAL,
+                 "Path use bias is too high (%f/%f); disabling node %s",
+                 node->circ_successes, node->circ_attempts, node->nickname);
+      }
     } else if (!strcasecmp(line->key, "EntryGuardPathBias")) {
       const or_options_t *options = get_options();
       double hop_cnt, success_cnt, timeouts, collapsed, successful_closed,
@@ -1144,7 +1178,7 @@ entry_guards_parse_state(or_state_t *state, int set, char **msg)
       /* Note: We rely on the < comparison here to allow us to set a 0
        * rate and disable the feature entirely. If refactoring, don't
        * change to <= */
-      if (pathbias_get_success_count(node)/node->circ_attempts
+      if (pathbias_get_close_success_count(node)/node->circ_attempts
             < pathbias_get_extreme_rate(options) &&
           pathbias_get_dropguards(options)) {
         node->path_bias_disabled = 1;
@@ -1282,10 +1316,20 @@ entry_guards_update_state(or_state_t *state)
          *                                     unusable_circuits */
         tor_asprintf(&line->value, "%f %f %f %f %f %f",
                      e->circ_attempts, e->circ_successes,
-                     pathbias_get_closed_count(e), e->collapsed_circuits,
+                     pathbias_get_close_success_count(e),
+                     e->collapsed_circuits,
                      e->unusable_circuits, e->timeouts);
         next = &(line->next);
       }
+      if (e->use_attempts > 0) {
+        *next = line = tor_malloc_zero(sizeof(config_line_t));
+        line->key = tor_strdup("EntryGuardPathUseBias");
+
+        tor_asprintf(&line->value, "%f %f",
+                     e->use_attempts,
+                     pathbias_get_use_success_count(e));
+        next = &(line->next);
+      }
 
   } SMARTLIST_FOREACH_END(e);
   if (!get_options()->AvoidDiskWrites)