Merge branch 'maint-0.3.1'

changes/bug22400_01

@@ -0,0 +1,4 @@
+  o Major bugfixes (entry guards):
+    - When starting with an old consensus, do not add new entry guards
+      unless the consensus is "reasonably live" (under 1 day old). Fixes
+      one root cause of bug 22400; bugfix on 0.3.0.1-alpha.

src/or/entrynodes.c

@@ -1093,6 +1093,18 @@ select_and_add_guard_item_for_sample(guard_selection_t *gs,
   return added_guard;
 }
 
+/** Return true iff we need a consensus to maintain our  */
+static int
+live_consensus_is_missing(const guard_selection_t *gs)
+{
+  tor_assert(gs);
+  if (gs->type == GS_TYPE_BRIDGE) {
+    /* We don't update bridges from the consensus; they aren't there. */
+    return 0;
+  }
+  return networkstatus_get_live_consensus(approx_time()) == NULL;
+}
+
 /**
  * Add new guards to the sampled guards in <b>gs</b> until there are
  * enough usable filtered guards, but never grow the sample beyond its
@@ -1104,6 +1116,13 @@ entry_guards_expand_sample(guard_selection_t *gs)
 {
   tor_assert(gs);
   const or_options_t *options = get_options();
+
+  if (live_consensus_is_missing(gs)) {
+    log_info(LD_GUARD, "Not expanding the sample guard set; we have "
+             "no live consensus.");
+    return NULL;
+  }
+
   int n_sampled = smartlist_len(gs->sampled_entry_guards);
   entry_guard_t *added_guard = NULL;
   int n_usable_filtered_guards = num_reachable_filtered_guards(gs, NULL);
@@ -1212,18 +1231,13 @@ sampled_guards_update_from_consensus(guard_selection_t *gs)
 
   // It's important to use only a live consensus here; we don't want to
   // make changes based on anything expired or old.
-  if (gs->type != GS_TYPE_BRIDGE) {
-    networkstatus_t *ns = networkstatus_get_live_consensus(approx_time());
-
-    if (! ns) {
-      log_info(LD_GUARD, "No live consensus; can't update "
-               "sampled entry guards.");
-      return;
-    } else {
-      log_info(LD_GUARD, "Updating sampled guard status based on received "
-               "consensus.");
-    }
+  if (live_consensus_is_missing(gs)) {
+    log_info(LD_GUARD, "Not updating the sample guard set; we have "
+             "no live consensus.");
+    return;
   }
+  log_info(LD_GUARD, "Updating sampled guard status based on received "
+           "consensus.");
 
   int n_changes = 0;