Orphan block fill-up-memory attack prevention

src/checkpoints.cpp

@@ -2,16 +2,23 @@
 // Distributed under the MIT/X11 software license, see the accompanying
 // file license.txt or http://www.opensource.org/licenses/mit-license.php.
 
-#include "checkpoints.h"
-#include "uint256.h"
-#include "util.h"
-
 #include <boost/assign/list_of.hpp> // for 'map_list_of()'
+#include <boost/foreach.hpp>
+
+#include "headers.h"
+#include "checkpoints.h"
 
 namespace Checkpoints
 {
     typedef std::map<int, uint256> MapCheckpoints;
 
+    //
+    // What makes a good checkpoint block?
+    // + Is surrounded by blocks with reasonable timestamps
+    //   (no blocks before with a timestamp after, none after with
+    //    timestamp before)
+    // + Contains no strange transactions
+    //
     static MapCheckpoints mapCheckpoints =
         boost::assign::map_list_of
         ( 11111, uint256("0x0000000069e244f73d78e8fd29ba2fd2ed618bd6fa2ee92559f542fdb26e7c1d"))
@@ -36,8 +43,23 @@ namespace Checkpoints
 
     int GetTotalBlocksEstimate()
     {
-        if (fTestNet) return 0; // Testnet has no checkpoints
+        if (fTestNet) return 0;
 
         return mapCheckpoints.rbegin()->first;
     }
+
+    CBlockIndex* GetLastCheckpoint(const std::map<uint256, CBlockIndex*>& mapBlockIndex)
+    {
+        if (fTestNet) return NULL;
+
+        int64 nResult;
+        BOOST_REVERSE_FOREACH(const MapCheckpoints::value_type& i, mapCheckpoints)
+        {
+            const uint256& hash = i.second;
+            std::map<uint256, CBlockIndex*>::const_iterator t = mapBlockIndex.find(hash);
+            if (t != mapBlockIndex.end())
+                return t->second;
+        }
+        return NULL;
+    }
 }