Limit how often endpoint messages can be processed:

The peer discovery protocol depends on peers exchanging messages
listing IP addresses for other peers.

Under normal circumstances, these messages should not be sent
frequently; the existing code would track the earliest time a
new message should be processed, but did not actually enforce
that limit.

src/ripple/peerfinder/impl/Logic.h

@@ -782,10 +782,14 @@ class Logic
         // Must be handshaked!
         assert(slot->state() == Slot::active);
 
-        preprocess(slot, list);
-
         clock_type::time_point const now(m_clock.now());
 
+        // Limit how often we accept new endpoints
+        if (slot->whenAcceptEndpoints > now)
+            return;
+
+        preprocess(slot, list);
+
         for (auto const& ep : list)
         {
             assert(ep.hops != 0);