generalize choose_random_entry()'s dirinfo parameter

Now we can specify to skip bridges that wouldn't be able to answer the
type of dir fetch we're launching.

It's still the responsibility of the rest of the code to prevent us from
launching a given dir fetch if we have no bridges that could handle it.

1 files changed, 22 insertions, 16 deletions

diff --git a/src/or/entrynodes.c b/src/or/entrynodes.c
index d029d85935..dab081d1fc 100644
--- a/src/or/entrynodes.c
+++ b/src/or/entrynodes.c
@@ -64,8 +64,7 @@ static int entry_guards_dirty = 0;
 static void bridge_free(bridge_info_t *bridge);
 static const node_t *choose_random_entry_impl(cpath_build_state_t *state,
                                               int for_directory,
-                                              dirinfo_type_t dirtype,
-                                              int prefer_microdescs);
+                                              dirinfo_type_t dirtype);
 
 /** Return the list of entry guards, creating it if necessary. */
 const smartlist_t *
@@ -844,20 +843,28 @@ node_understands_microdescriptors(const node_t *node)
   return 0;
 }
 
+/** Return true iff <b>node</b> is able to answer directory questions
+ * of type <b>dirinfo</b>. */
+static int
+node_can_handle_dirinfo(const node_t *node, dirinfo_type_t dirinfo)
+{
+  if ((dirinfo & MICRODESC_DIRINFO) &&
+      !node_understands_microdescriptors(node))
+    return 0;
+  return 1;
+}
+
 /** Pick a live (up and listed) entry guard from entry_guards. If
  * <b>state</b> is non-NULL, this is for a specific circuit --
  * make sure not to pick this circuit's exit or any node in the
  * exit's family. If <b>state</b> is NULL, we're looking for a random
- * guard (likely a bridge).
- *
- * If the prefer_microdescs flag is set, we are looking for a bridge to
- * use for directory fetching and pick a bridge that supports microdescriptors
- * if we know any that do so.
- */
+ * guard (likely a bridge).  If <b>dirinfo</b> is not NO_DIRINFO, then
+ * only select from nodes that know how to answer directory questions
+ * of that type. */
 const node_t *
-choose_random_entry(cpath_build_state_t *state, int prefer_microdescs)
+choose_random_entry(cpath_build_state_t *state, dirinfo_type_t dirinfo)
 {
-  return choose_random_entry_impl(state, 0, 0, prefer_microdescs);
+  return choose_random_entry_impl(state, 0, dirinfo);
 }
 
 /** Pick a live (up and listed) directory guard from entry_guards for
@@ -865,13 +872,13 @@ choose_random_entry(cpath_build_state_t *state, int prefer_microdescs)
 const node_t *
 choose_random_dirguard(dirinfo_type_t type)
 {
-  return choose_random_entry_impl(NULL, 1, type, 0);
+  return choose_random_entry_impl(NULL, 1, type);
 }
 
 /** Helper for choose_random{entry,dirguard}. */
 static const node_t *
 choose_random_entry_impl(cpath_build_state_t *state, int for_directory,
-                         dirinfo_type_t dirinfo_type, int prefer_microdescs)
+                         dirinfo_type_t dirinfo_type)
 {
   const or_options_t *options = get_options();
   smartlist_t *live_entry_guards = smartlist_new();
@@ -923,9 +930,8 @@ choose_random_entry_impl(cpath_build_state_t *state, int for_directory,
         continue; /* don't pick the same node for entry and exit */
       if (consider_exit_family && smartlist_contains(exit_family, node))
         continue; /* avoid relays that are family members of our exit */
-      if (prefer_microdescs &&
-          we_use_microdescriptors_for_circuits(options) &&
-          !node_understands_microdescriptors(node))
+      if (dirinfo_type != NO_DIRINFO &&
+          !node_can_handle_dirinfo(node, dirinfo_type))
         continue; /* this node won't be able to answer our dir questions */
 #if 0 /* since EntryNodes is always strict now, this clause is moot */
       if (options->EntryNodes &&
@@ -2006,7 +2012,7 @@ int
 any_bridge_descriptors_known(void)
 {
   tor_assert(get_options()->UseBridges);
-  return choose_random_entry(NULL, 0)!=NULL ? 1 : 0;
+  return choose_random_entry(NULL, NO_DIRINFO)!=NULL ? 1 : 0;
 }
 
 /** Return 1 if there are any directory conns fetching bridge descriptors