Don't build circuits till primary guards have descriptors

In addition to not wanting to build circuits until we can see most
of the paths in the network, and in addition to not wanting to build
circuits until we have a consensus ... we shouldn't build circuits
till all of our (in-use) primary guards have descriptors that we can
use for them.

This is another bug 21242 fix.

1 files changed, 37 insertions, 0 deletions

diff --git a/src/or/entrynodes.c b/src/or/entrynodes.c
index 1cf1ff2c8e..6249e847a9 100644
--- a/src/or/entrynodes.c
+++ b/src/or/entrynodes.c
@@ -3335,6 +3335,43 @@ guards_retry_optimistic(const or_options_t *options)
   return 1;
 }
 
+/**
+ * Return true iff we know enough directory information to construct
+ * circuits through all of the primary guards we'd currently use.
+ */
+int
+guard_selection_have_enough_dir_info_to_build_circuits(guard_selection_t *gs)
+{
+  if (!gs->primary_guards_up_to_date)
+    entry_guards_update_primary(gs);
+
+  const int num_primary = get_n_primary_guards_to_use(GUARD_USAGE_TRAFFIC);
+  int n_missing_descriptors = 0;
+  int n_considered = 0;
+
+  SMARTLIST_FOREACH_BEGIN(gs->primary_entry_guards, entry_guard_t *, guard) {
+    entry_guard_consider_retry(guard);
+    if (guard->is_reachable == GUARD_REACHABLE_NO)
+      continue;
+    n_considered++;
+    if (!guard_has_descriptor(guard))
+      n_missing_descriptors++;
+    if (n_considered >= num_primary)
+      break;
+  } SMARTLIST_FOREACH_END(guard);
+
+  return n_missing_descriptors == 0;
+}
+
+/** As guard_selection_have_enough_dir_info_to_build_circuits, but uses
+ * the default guard selection. */
+int
+entry_guards_have_enough_dir_info_to_build_circuits(void)
+{
+  return guard_selection_have_enough_dir_info_to_build_circuits(
+                                        get_guard_selection_info());
+}
+
 /** Free one guard selection context */
 STATIC void
 guard_selection_free(guard_selection_t *gs)