Check for "the right descriptor", not just "any descriptor".

This patch adds a new node_has_preferred_descriptor() function, and
replaces most users of node_has_descriptor() with it.  That's an
important change, since as of d1874b433953f64 (our fix for #25213),
we are willing to say that a node has _some_ descriptor, but not the
_right_ descriptor for a particular use case.

Part of a fix for 25691 and 25692.

1 files changed, 4 insertions, 3 deletions

diff --git a/src/or/entrynodes.c b/src/or/entrynodes.c
index 2b6ff38c9c..54638810fa 100644
--- a/src/or/entrynodes.c
+++ b/src/or/entrynodes.c
@@ -185,14 +185,14 @@ should_apply_guardfraction(const networkstatus_t *ns)
   return options->UseGuardFraction;
 }
 
-/** Return true iff we know a descriptor for <b>guard</b> */
+/** Return true iff we know a preferred descriptor for <b>guard</b> */
 static int
 guard_has_descriptor(const entry_guard_t *guard)
 {
   const node_t *node = node_get_by_id(guard->identity);
   if (!node)
     return 0;
-  return node_has_descriptor(node);
+  return node_has_preferred_descriptor(node, 1);
 }
 
 /**
@@ -2269,7 +2269,8 @@ entry_guard_pick_for_circuit(guard_selection_t *gs,
   // XXXX #20827 check Ed ID.
   if (! node)
     goto fail;
-  if (BUG(usage != GUARD_USAGE_DIRGUARD && !node_has_descriptor(node)))
+  if (BUG(usage != GUARD_USAGE_DIRGUARD &&
+          !node_has_preferred_descriptor(node, 1)))
     goto fail;
 
   *chosen_node_out = node;