src/checkpoints.cpp

   1 // Copyright (c) 2011 The Bitcoin developers
   2 // Copyright (c) 2011-2012 The PPCoin developers
   3 // Distributed under the MIT/X11 software license, see the accompanying
   4 // file license.txt or http://www.opensource.org/licenses/mit-license.php.
   5
   6 #include <boost/assign/list_of.hpp> // for 'map_list_of()'
   7 #include <boost/foreach.hpp>
   8
   9 #include "headers.h"
  10 #include "checkpoints.h"
  11
  12 namespace Checkpoints
  13 {
  14     typedef std::map<int, uint256> MapCheckpoints;   // hardened checkpoints
  15
  16     //
  17     // What makes a good checkpoint block?
  18     // + Is surrounded by blocks with reasonable timestamps
  19     //   (no blocks before with a timestamp after, none after with
  20     //    timestamp before)
  21     // + Contains no strange transactions
  22     //
  23     static MapCheckpoints mapCheckpoints =
  24         boost::assign::map_list_of
  25         ( 0, hashGenesisBlock )
  26         ; // ppcoin: no checkpoint yet; to be created in future releases
  27
  28     bool CheckHardened(int nHeight, const uint256& hash)
  29     {
  30         if (fTestNet) return true; // Testnet has no checkpoints
  31
  32         MapCheckpoints::const_iterator i = mapCheckpoints.find(nHeight);
  33         if (i == mapCheckpoints.end()) return true;
  34         return hash == i->second;
  35     }
  36
  37     int GetTotalBlocksEstimate()
  38     {
  39         if (fTestNet) return 0;
  40
  41         return mapCheckpoints.rbegin()->first;
  42     }
  43
  44     CBlockIndex* GetLastCheckpoint(const std::map<uint256, CBlockIndex*>& mapBlockIndex)
  45     {
  46         if (fTestNet) return NULL;
  47
  48         int64 nResult;
  49         BOOST_REVERSE_FOREACH(const MapCheckpoints::value_type& i, mapCheckpoints)
  50         {
  51             const uint256& hash = i.second;
  52             std::map<uint256, CBlockIndex*>::const_iterator t = mapBlockIndex.find(hash);
  53             if (t != mapBlockIndex.end())
  54                 return t->second;
  55         }
  56         return NULL;
  57     }
  58
  59     // ppcoin: synchronized checkpoint (centrally broadcasted)
  60     uint256 hashSyncCheckpoint;
  61     CSyncCheckpoint checkpointMessage;
  62     CSyncCheckpoint checkpointMessagePending;
  63     CCriticalSection cs_hashSyncCheckpoint;
  64
  65     // ppcoin: only descendant of current sync-checkpoint is allowed
  66     bool ValidateSyncCheckpoint(uint256 hashCheckpoint)
  67     {
  68         if (!mapBlockIndex.count(hashSyncCheckpoint))
  69             return error("ValidateSyncCheckpoint: block index missing for current sync-checkpoint %s", hashSyncCheckpoint.ToString().c_str());
  70         if (!mapBlockIndex.count(hashCheckpoint))
  71             return error("ValidateSyncCheckpoint: block index missing for received sync-checkpoint %s", hashCheckpoint.ToString().c_str());
  72
  73         CBlockIndex* pindexSyncCheckpoint = mapBlockIndex[hashSyncCheckpoint];
  74         CBlockIndex* pindexCheckpointRecv = mapBlockIndex[hashCheckpoint];
  75         if (pindexCheckpointRecv->nHeight <= pindexSyncCheckpoint->nHeight)
  76             return false;  // this is an older checkpoint, ignore
  77
  78         CBlockIndex* pindex = pindexCheckpointRecv;
  79         while (pindex->nHeight > pindexSyncCheckpoint->nHeight)
  80             if (!(pindex = pindex->pprev))
  81                 return error("ValidateSyncCheckpoint: pprev null - block index structure failure");
  82         if (pindex->GetBlockHash() != hashSyncCheckpoint)
  83             return error("ValidateSyncCheckpoint: new sync-checkpoint %s is not a descendant of current sync-checkpoint %s", hashCheckpoint.ToString().c_str(), hashSyncCheckpoint.ToString().c_str());
  84         return true;
  85     }
  86
  87     bool AcceptPendingSyncCheckpoint()
  88     {
  89         bool fAccepted = false;
  90         uint256 hashCheckpoint = 0;
  91         CTxDB txdb;
  92
  93         CRITICAL_BLOCK(cs_hashSyncCheckpoint)
  94         {
  95             if ((!checkpointMessagePending.IsNull()) && mapBlockIndex.count(checkpointMessagePending.hashCheckpoint))
  96             {
  97                 if (!ValidateSyncCheckpoint(checkpointMessagePending.hashCheckpoint))
  98                 {
  99                     checkpointMessagePending.SetNull();
 100                     return false;
 101                 }
 102
 103                 txdb.TxnBegin();
 104                 if (!txdb.WriteSyncCheckpoint(checkpointMessagePending.hashCheckpoint))
 105                 {
 106                     txdb.TxnAbort();
 107                     return error("AcceptPendingSyncCheckpoint() : failed to write to db sync checkpoint %s\n", checkpointMessagePending.hashCheckpoint.ToString().c_str());
 108                 }
 109                 if (!txdb.TxnCommit())
 110                     return error("AcceptPendingSyncCheckpoint() : failed to commit to db sync checkpoint %s\n", checkpointMessagePending.hashCheckpoint.ToString().c_str());
 111
 112                 hashSyncCheckpoint = checkpointMessagePending.hashCheckpoint;
 113                 checkpointMessage = checkpointMessagePending;
 114                 checkpointMessagePending.SetNull();
 115                 printf("AcceptPendingSyncCheckpoint : sync-checkpoint at %s\n", hashSyncCheckpoint.ToString().c_str());
 116                 fAccepted = true;
 117                 hashCheckpoint = hashSyncCheckpoint;
 118             }
 119         }
 120
 121         if (fAccepted)
 122         {
 123             CBlockIndex* pindexCheckpoint = mapBlockIndex[hashCheckpoint];
 124             if (!pindexCheckpoint->IsInMainChain())
 125             {
 126                 txdb.TxnBegin();
 127                 if (!Reorganize(txdb, pindexCheckpoint))
 128                 {
 129                     txdb.TxnAbort();
 130                     return error("ProcessSyncCheckpoint: Reorganize failed for sync checkpoint %s", hashCheckpoint.ToString().c_str());
 131                 }
 132             }
 133         }
 134         txdb.Close();
 135
 136         // relay the checkpoint
 137         CRITICAL_BLOCK(cs_hashSyncCheckpoint)
 138             BOOST_FOREACH(CNode* pnode, vNodes)
 139                 checkpointMessage.RelayTo(pnode);
 140
 141         return fAccepted;
 142     }
 143
 144     uint256 AutoSelectSyncCheckpoint()
 145     {
 146         // select block roughly 8 hours ago
 147         CBlockIndex *pindex = mapBlockIndex[hashSyncCheckpoint];
 148         while (pindex->pnext && pindex->pnext->GetBlockTime() + AUTO_CHECKPOINT_MIN_SPAN <= GetAdjustedTime())
 149             pindex = pindex->pnext;
 150         return pindex->GetBlockHash();
 151     }
 152
 153     // Check against synchronized checkpoint
 154     bool CheckSync(const uint256& hashBlock, const CBlockIndex* pindexPrev)
 155     {
 156         if (fTestNet) return true; // Testnet has no checkpoints
 157         int nHeight = pindexPrev->nHeight + 1;
 158
 159         CRITICAL_BLOCK(cs_hashSyncCheckpoint)
 160         {
 161             // sync-checkpoint should always be accepted block
 162             assert(mapBlockIndex.count(hashSyncCheckpoint));
 163             const CBlockIndex* pindexSync = mapBlockIndex[hashSyncCheckpoint];
 164
 165             if (nHeight > pindexSync->nHeight)
 166             {
 167                 // trace back to same height as sync-checkpoint
 168                 const CBlockIndex* pindex = pindexPrev;
 169                 while (pindex->nHeight > pindexSync->nHeight)
 170                     if (!(pindex = pindex->pprev))
 171                         return error("CheckSync: pprev null - block index structure failure");
 172                 if (pindex->nHeight < pindexSync->nHeight || pindex->GetBlockHash() != hashSyncCheckpoint)
 173                     return false; // only descendant of sync-checkpoint can pass check
 174             }
 175             if (nHeight == pindexSync->nHeight && hashBlock != hashSyncCheckpoint)
 176                 return false; // same height with sync-checkpoint
 177             if (nHeight < pindexSync->nHeight && !mapBlockIndex.count(hashBlock))
 178                 return false; // lower height than sync-checkpoint
 179         }
 180         return true;
 181     }
 182
 183     // ppcoin: automatic checkpoint (represented by height of checkpoint)
 184     int nAutoCheckpoint = 0;
 185     int nBranchPoint = 0;    // branch point to alternative branch
 186
 187     // ppcoin: check automatic checkpoint
 188     // To pass the check:
 189     //   - All ancestors (including the block itself) have block index already
 190     //   - The immediate ancestor in main chain must not have height less than
 191     //     checkpoint height
 192     bool CheckAuto(const CBlockIndex *pindex)
 193     {
 194         while (pindex)
 195         {
 196             if (pindex->IsInMainChain())
 197             {
 198                 if (pindex->nHeight >= nAutoCheckpoint)
 199                     return true;
 200                 else
 201                 {
 202                     nBranchPoint = pindex->nHeight;
 203                     return error("Checkpoints: new block on alternative branch at height=%d before auto checkpoint at height=%d", pindex->nHeight, nAutoCheckpoint);
 204                 }
 205             }
 206             else
 207                 pindex = pindex->pprev;
 208         }
 209         return error("Checkpoints: failed to find any ancestor on main chain for the new block - internal error");
 210     }
 211
 212     // ppcoin: get next chain checkpoint
 213     int GetNextChainCheckpoint(const CBlockIndex *pindexLast)
 214     {
 215         CBigNum bnTarget;
 216         CBigNum bnTargetMax = 0;  // max target of all blocks since checkpoint
 217         CBigNum bnTargetMin = 0;  // min target of all candidate checkpoints
 218         int nMinTargetHeight = 0; // min target height of candidate checkpoints
 219         int nCheckpointMin = 0;   // minimum candidate checkpoint
 220         int nCheckpointMax = 0;   // maximum candidate checkpoint
 221         int nDepth = pindexLast->nHeight - pindexLast->nCheckpoint;
 222         const CBlockIndex *pindex = pindexLast;
 223         while (nDepth >= 0 && pindex)
 224         {
 225             bnTarget.SetCompact(pindex->nBits);
 226             if (bnTarget > bnTargetMax)
 227                 bnTargetMax = bnTarget;
 228             if (nCheckpointMax > 0 && bnTarget < bnTargetMin)
 229             {
 230                 bnTargetMin = bnTarget;
 231                 nMinTargetHeight = pindex->nHeight;
 232             }
 233             if (nCheckpointMax == 0 && pindexLast->GetBlockTime() - pindex->GetBlockTime() > AUTO_CHECKPOINT_MIN_SPAN)
 234             {
 235                 nCheckpointMax = pindex->nHeight;
 236                 bnTargetMin.SetCompact(pindex->nBits);
 237                 nMinTargetHeight = pindex->nHeight;
 238             }
 239             if (pindexLast->GetBlockTime() - pindex->GetBlockTime() < AUTO_CHECKPOINT_MAX_SPAN)
 240                 nCheckpointMin = pindex->nHeight;
 241             pindex = pindex->pprev;
 242             nDepth--;
 243         }
 244
 245         assert (nDepth == -1);  // arrive at chain checkpoint now
 246
 247         printf("Checkpoints: min=%d max=%d tminheight=%d tmin=0x%08x tmax=0x%08x\n",
 248             nCheckpointMin, nCheckpointMax, nMinTargetHeight,
 249             bnTargetMin.GetCompact(), bnTargetMax.GetCompact());
 250         if (nCheckpointMax == 0) // checkpoint stays if max candidate not found
 251             return pindexLast->nCheckpoint;
 252
 253         if (bnTargetMin * 100 > bnTargetMax * 90)
 254             return nCheckpointMax;
 255         if (bnTarget * 100 > bnTargetMax * 90)
 256             return nMinTargetHeight;
 257         else
 258             return nCheckpointMin;
 259     }
 260
 261     // ppcoin: get next auto checkpoint from the new chain checkpoint
 262     int GetNextAutoCheckpoint(int nCheckpoint)
 263     {
 264         return (std::max(nAutoCheckpoint, nCheckpoint));
 265     }
 266
 267     // ppcoin: advance to next automatic checkpoint
 268     void AdvanceAutoCheckpoint(int nCheckpoint)
 269     {
 270         nAutoCheckpoint = GetNextAutoCheckpoint(nCheckpoint);
 271         printf("Checkpoints: auto checkpoint now at height=%d\n", nAutoCheckpoint);
 272     }
 273
 274     // ppcoin: reset auto checkpoint
 275     bool ResetAutoCheckpoint(int nCheckpoint)
 276     {
 277         if (nCheckpoint <= 0 || nCheckpoint > nBestHeight)
 278             return error("ResetAutoCheckpoint() : new checkpoint invalid");
 279         if (nCheckpoint >= nAutoCheckpoint)
 280             return error("ResetAutoCheckpoint() : new checkpoint not earlier than current auto checkpoint");
 281         CTxDB txdb;
 282         txdb.TxnBegin();
 283         if (!txdb.WriteAutoCheckpoint(nCheckpoint, true))
 284             return error("ResetAutoCheckpoint() : database write failed");
 285         if (!txdb.TxnCommit())
 286             return error("ResetAutoCheckpoint() : database commit failed");
 287         nAutoCheckpoint = nCheckpoint;
 288         nBranchPoint = 0;  // clear branch point
 289
 290         // clear ban list to accept alternative branches
 291         CRITICAL_BLOCK(cs_vNodes)
 292         {
 293             BOOST_FOREACH(CNode* pnode, vNodes)
 294                 pnode->ClearBanned();
 295         }
 296
 297         return true;
 298     }
 299 }
 300
 301 // ppcoin: process synchronized checkpoint
 302 bool CSyncCheckpoint::ProcessSyncCheckpoint(CNode* pfrom)
 303 {
 304     if (!CheckSignature())
 305         return false;
 306
 307     CTxDB txdb;
 308     CRITICAL_BLOCK(Checkpoints::cs_hashSyncCheckpoint)
 309     {
 310         if (!mapBlockIndex.count(hashCheckpoint))
 311         {
 312             // We haven't accepted this block, keep the checkpoint as pending
 313             Checkpoints::checkpointMessagePending = *this;
 314             printf("ProcessSyncCheckpoint: pending for sync-checkpoint %s\n", hashCheckpoint.ToString().c_str());
 315             // Ask this guy to fill in what we're missing
 316             if (pfrom)
 317                 pfrom->PushGetBlocks(pindexBest, hashCheckpoint);
 318             return false;
 319         }
 320         if (!Checkpoints::ValidateSyncCheckpoint(hashCheckpoint))
 321             return false;
 322
 323         txdb.TxnBegin();
 324         if (!txdb.WriteSyncCheckpoint(hashCheckpoint))
 325         {
 326             txdb.TxnAbort();
 327             return error("ProcessSyncCheckpoint(): failed to write to db sync checkpoint %s", hashCheckpoint.ToString().c_str());
 328         }
 329         if (!txdb.TxnCommit())
 330             return error("ProcessSyncCheckpoint(): failed to commit to db sync checkpoint %s", hashCheckpoint.ToString().c_str());
 331
 332         Checkpoints::hashSyncCheckpoint = hashCheckpoint;
 333         Checkpoints::checkpointMessage = *this;
 334         Checkpoints::checkpointMessagePending.SetNull();
 335         printf("ProcessSyncCheckpoint: sync-checkpoint at %s\n", hashCheckpoint.ToString().c_str());
 336     }
 337
 338     CBlockIndex* pindexCheckpoint = mapBlockIndex[hashCheckpoint];
 339     if (!pindexCheckpoint->IsInMainChain())
 340     {
 341         txdb.TxnBegin();
 342         if (!Reorganize(txdb, pindexCheckpoint))
 343         {
 344             txdb.TxnAbort();
 345             return error("ProcessSyncCheckpoint: Reorganize failed for sync checkpoint %s", hashCheckpoint.ToString().c_str());
 346         }
 347     }
 348     txdb.Close();
 349     return true;
 350 }