[tor-commits] [tor/master] 271: Algorithm tweak to allow multiple entry guards.

[nickm at torproject.org]

commit deb8bcadced3c54d986c526662444a46e630621d
Author: Nick Mathewson <nickm at torproject.org>
Date:   Thu Dec 8 12:47:29 2016 -0500

    271: Algorithm tweak to allow multiple entry guards.
    
    Previously, we had NumEntryGuards kind of hardwired to 1.  Now we
    have the code (but not the configuarability) to choose randomly from
    among the first N primary guards that would work, where N defaults
    to 1.
    
    Part of 20831 support for making NumEntryGuards work again.
---
 src/or/entrynodes.c | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/src/or/entrynodes.c b/src/or/entrynodes.c
index f89594b..5c64dfd 100644
--- a/src/or/entrynodes.c
+++ b/src/or/entrynodes.c
@@ -1795,6 +1795,9 @@ select_entry_guard_for_circuit(guard_selection_t *gs,
   if (!gs->primary_guards_up_to_date)
     entry_guards_update_primary(gs);
 
+  int num_entry_guards = 1;
+  smartlist_t *usable_primary_guards = smartlist_new();
+
   /* "If any entry in PRIMARY_GUARDS has {is_reachable} status of
       <maybe> or <yes>, return the first such guard." */
   SMARTLIST_FOREACH_BEGIN(gs->primary_entry_guards, entry_guard_t *, guard) {
@@ -1804,12 +1807,21 @@ select_entry_guard_for_circuit(guard_selection_t *gs,
     if (guard->is_reachable != GUARD_REACHABLE_NO) {
       *state_out = GUARD_CIRC_STATE_USABLE_ON_COMPLETION;
       guard->last_tried_to_connect = approx_time();
-      log_info(LD_GUARD, "Selected primary guard %s for circuit.",
-               entry_guard_describe(guard));
-      return guard;
+      smartlist_add(usable_primary_guards, guard);
+      if (smartlist_len(usable_primary_guards) >= num_entry_guards)
+        break;
     }
   } SMARTLIST_FOREACH_END(guard);
 
+  if (smartlist_len(usable_primary_guards)) {
+    entry_guard_t *guard = smartlist_choose(usable_primary_guards);
+    smartlist_free(usable_primary_guards);
+    log_info(LD_GUARD, "Selected primary guard %s for circuit.",
+             entry_guard_describe(guard));
+    return guard;
+  }
+  smartlist_free(usable_primary_guards);
+
   /* "Otherwise, if the ordered intersection of {CONFIRMED_GUARDS}
       and {USABLE_FILTERED_GUARDS} is nonempty, return the first
       entry in that intersection that has {is_pending} set to