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         CRITICAL_BLOCK(cs_hashSyncCheckpoint)
  90         {
  91             if ((!checkpointMessagePending.IsNull()) && mapBlockIndex.count(checkpointMessagePending.hashCheckpoint))
  92             {
  93                 if (!ValidateSyncCheckpoint(checkpointMessagePending.hashCheckpoint))
  94                 {
  95                     checkpointMessagePending.SetNull();
  96                     return false;
  97                 }
  98
  99                 CTxDB txdb;
 100                 CBlockIndex* pindexCheckpoint = mapBlockIndex[checkpointMessagePending.hashCheckpoint];
 101                 if (!pindexCheckpoint->IsInMainChain())
 102                 {
 103                     txdb.TxnBegin();
 104                     if (!Reorganize(txdb, pindexCheckpoint))
 105                     {
 106                         txdb.TxnAbort();
 107                         return error("ProcessSyncCheckpoint: Reorganize failed for sync checkpoint %s", checkpointMessagePending.hashCheckpoint.ToString().c_str());
 108                     }
 109                 }
 110
 111                 txdb.TxnBegin();
 112                 if (!txdb.WriteSyncCheckpoint(checkpointMessagePending.hashCheckpoint))
 113                 {
 114                     txdb.TxnAbort();
 115                     return error("AcceptPendingSyncCheckpoint() : failed to write to db sync checkpoint %s\n", checkpointMessagePending.hashCheckpoint.ToString().c_str());
 116                 }
 117                 if (!txdb.TxnCommit())
 118                     return error("AcceptPendingSyncCheckpoint() : failed to commit to db sync checkpoint %s\n", checkpointMessagePending.hashCheckpoint.ToString().c_str());
 119                 txdb.Close();
 120
 121                 hashSyncCheckpoint = checkpointMessagePending.hashCheckpoint;
 122                 checkpointMessage = checkpointMessagePending;
 123                 checkpointMessagePending.SetNull();
 124                 printf("AcceptPendingSyncCheckpoint : sync-checkpoint at %s\n", hashSyncCheckpoint.ToString().c_str());
 125                 // relay the checkpoint
 126                 CRITICAL_BLOCK(cs_hashSyncCheckpoint)
 127                     BOOST_FOREACH(CNode* pnode, vNodes)
 128                         checkpointMessage.RelayTo(pnode);
 129                 return true;
 130             }
 131         }
 132
 133         return false;
 134     }
 135
 136     uint256 AutoSelectSyncCheckpoint()
 137     {
 138         // select block roughly 8 hours ago
 139         CBlockIndex *pindex = mapBlockIndex[hashSyncCheckpoint];
 140         while (pindex->pnext && pindex->pnext->GetBlockTime() + AUTO_CHECKPOINT_MIN_SPAN <= GetAdjustedTime())
 141             pindex = pindex->pnext;
 142         return pindex->GetBlockHash();
 143     }
 144
 145     // Check against synchronized checkpoint
 146     bool CheckSync(const uint256& hashBlock, const CBlockIndex* pindexPrev)
 147     {
 148         if (fTestNet) return true; // Testnet has no checkpoints
 149         int nHeight = pindexPrev->nHeight + 1;
 150
 151         CRITICAL_BLOCK(cs_hashSyncCheckpoint)
 152         {
 153             // sync-checkpoint should always be accepted block
 154             assert(mapBlockIndex.count(hashSyncCheckpoint));
 155             const CBlockIndex* pindexSync = mapBlockIndex[hashSyncCheckpoint];
 156
 157             if (nHeight > pindexSync->nHeight)
 158             {
 159                 // trace back to same height as sync-checkpoint
 160                 const CBlockIndex* pindex = pindexPrev;
 161                 while (pindex->nHeight > pindexSync->nHeight)
 162                     if (!(pindex = pindex->pprev))
 163                         return error("CheckSync: pprev null - block index structure failure");
 164                 if (pindex->nHeight < pindexSync->nHeight || pindex->GetBlockHash() != hashSyncCheckpoint)
 165                     return false; // only descendant of sync-checkpoint can pass check
 166             }
 167             if (nHeight == pindexSync->nHeight && hashBlock != hashSyncCheckpoint)
 168                 return false; // same height with sync-checkpoint
 169             if (nHeight < pindexSync->nHeight && !mapBlockIndex.count(hashBlock))
 170                 return false; // lower height than sync-checkpoint
 171         }
 172         return true;
 173     }
 174
 175     // ppcoin: automatic checkpoint (represented by height of checkpoint)
 176     int nAutoCheckpoint = 0;
 177     int nBranchPoint = 0;    // branch point to alternative branch
 178
 179     // ppcoin: check automatic checkpoint
 180     // To pass the check:
 181     //   - All ancestors (including the block itself) have block index already
 182     //   - The immediate ancestor in main chain must not have height less than
 183     //     checkpoint height
 184     bool CheckAuto(const CBlockIndex *pindex)
 185     {
 186         while (pindex)
 187         {
 188             if (pindex->IsInMainChain())
 189             {
 190                 if (pindex->nHeight >= nAutoCheckpoint)
 191                     return true;
 192                 else
 193                 {
 194                     nBranchPoint = pindex->nHeight;
 195                     return error("Checkpoints: new block on alternative branch at height=%d before auto checkpoint at height=%d", pindex->nHeight, nAutoCheckpoint);
 196                 }
 197             }
 198             else
 199                 pindex = pindex->pprev;
 200         }
 201         return error("Checkpoints: failed to find any ancestor on main chain for the new block - internal error");
 202     }
 203
 204     // ppcoin: get next chain checkpoint
 205     int GetNextChainCheckpoint(const CBlockIndex *pindexLast)
 206     {
 207         CBigNum bnTarget;
 208         CBigNum bnTargetMax = 0;  // max target of all blocks since checkpoint
 209         CBigNum bnTargetMin = 0;  // min target of all candidate checkpoints
 210         int nMinTargetHeight = 0; // min target height of candidate checkpoints
 211         int nCheckpointMin = 0;   // minimum candidate checkpoint
 212         int nCheckpointMax = 0;   // maximum candidate checkpoint
 213         int nDepth = pindexLast->nHeight - pindexLast->nCheckpoint;
 214         const CBlockIndex *pindex = pindexLast;
 215         while (nDepth >= 0 && pindex)
 216         {
 217             bnTarget.SetCompact(pindex->nBits);
 218             if (bnTarget > bnTargetMax)
 219                 bnTargetMax = bnTarget;
 220             if (nCheckpointMax > 0 && bnTarget < bnTargetMin)
 221             {
 222                 bnTargetMin = bnTarget;
 223                 nMinTargetHeight = pindex->nHeight;
 224             }
 225             if (nCheckpointMax == 0 && pindexLast->GetBlockTime() - pindex->GetBlockTime() > AUTO_CHECKPOINT_MIN_SPAN)
 226             {
 227                 nCheckpointMax = pindex->nHeight;
 228                 bnTargetMin.SetCompact(pindex->nBits);
 229                 nMinTargetHeight = pindex->nHeight;
 230             }
 231             if (pindexLast->GetBlockTime() - pindex->GetBlockTime() < AUTO_CHECKPOINT_MAX_SPAN)
 232                 nCheckpointMin = pindex->nHeight;
 233             pindex = pindex->pprev;
 234             nDepth--;
 235         }
 236
 237         assert (nDepth == -1);  // arrive at chain checkpoint now
 238
 239         printf("Checkpoints: min=%d max=%d tminheight=%d tmin=0x%08x tmax=0x%08x\n",
 240             nCheckpointMin, nCheckpointMax, nMinTargetHeight,
 241             bnTargetMin.GetCompact(), bnTargetMax.GetCompact());
 242         if (nCheckpointMax == 0) // checkpoint stays if max candidate not found
 243             return pindexLast->nCheckpoint;
 244
 245         if (bnTargetMin * 100 > bnTargetMax * 90)
 246             return nCheckpointMax;
 247         if (bnTarget * 100 > bnTargetMax * 90)
 248             return nMinTargetHeight;
 249         else
 250             return nCheckpointMin;
 251     }
 252
 253     // ppcoin: get next auto checkpoint from the new chain checkpoint
 254     int GetNextAutoCheckpoint(int nCheckpoint)
 255     {
 256         return (std::max(nAutoCheckpoint, nCheckpoint));
 257     }
 258
 259     // ppcoin: advance to next automatic checkpoint
 260     void AdvanceAutoCheckpoint(int nCheckpoint)
 261     {
 262         nAutoCheckpoint = GetNextAutoCheckpoint(nCheckpoint);
 263         printf("Checkpoints: auto checkpoint now at height=%d\n", nAutoCheckpoint);
 264     }
 265
 266     // ppcoin: reset auto checkpoint
 267     bool ResetAutoCheckpoint(int nCheckpoint)
 268     {
 269         if (nCheckpoint <= 0 || nCheckpoint > nBestHeight)
 270             return error("ResetAutoCheckpoint() : new checkpoint invalid");
 271         if (nCheckpoint >= nAutoCheckpoint)
 272             return error("ResetAutoCheckpoint() : new checkpoint not earlier than current auto checkpoint");
 273         CTxDB txdb;
 274         txdb.TxnBegin();
 275         if (!txdb.WriteAutoCheckpoint(nCheckpoint, true))
 276             return error("ResetAutoCheckpoint() : database write failed");
 277         if (!txdb.TxnCommit())
 278             return error("ResetAutoCheckpoint() : database commit failed");
 279         nAutoCheckpoint = nCheckpoint;
 280         nBranchPoint = 0;  // clear branch point
 281
 282         // clear ban list to accept alternative branches
 283         CRITICAL_BLOCK(cs_vNodes)
 284         {
 285             BOOST_FOREACH(CNode* pnode, vNodes)
 286                 pnode->ClearBanned();
 287         }
 288
 289         return true;
 290     }
 291 }
 292
 293 // ppcoin: process synchronized checkpoint
 294 bool CSyncCheckpoint::ProcessSyncCheckpoint(CNode* pfrom)
 295 {
 296     if (!CheckSignature())
 297         return false;
 298
 299     CRITICAL_BLOCK(Checkpoints::cs_hashSyncCheckpoint)
 300     {
 301         if (!mapBlockIndex.count(hashCheckpoint))
 302         {
 303             // We haven't received the checkpoint chain, keep the checkpoint as pending
 304             Checkpoints::checkpointMessagePending = *this;
 305             printf("ProcessSyncCheckpoint: pending for sync-checkpoint %s\n", hashCheckpoint.ToString().c_str());
 306             // Ask this guy to fill in what we're missing
 307             if (pfrom)
 308                 pfrom->PushGetBlocks(pindexBest, hashCheckpoint);
 309             return false;
 310         }
 311
 312         if (!Checkpoints::ValidateSyncCheckpoint(hashCheckpoint))
 313             return false;
 314
 315         CTxDB txdb;
 316         CBlockIndex* pindexCheckpoint = mapBlockIndex[hashCheckpoint];
 317         if (!pindexCheckpoint->IsInMainChain())
 318         {
 319             // checkpoint chain received but not yet main chain
 320             txdb.TxnBegin();
 321             if (!Reorganize(txdb, pindexCheckpoint))
 322             {
 323                 txdb.TxnAbort();
 324                 return error("ProcessSyncCheckpoint: Reorganize failed for sync checkpoint %s", hashCheckpoint.ToString().c_str());
 325             }
 326         }
 327
 328         txdb.TxnBegin();
 329         if (!txdb.WriteSyncCheckpoint(hashCheckpoint))
 330         {
 331             txdb.TxnAbort();
 332             return error("ProcessSyncCheckpoint(): failed to write to db sync checkpoint %s", hashCheckpoint.ToString().c_str());
 333         }
 334         if (!txdb.TxnCommit())
 335             return error("ProcessSyncCheckpoint(): failed to commit to db sync checkpoint %s", hashCheckpoint.ToString().c_str());
 336         txdb.Close();
 337
 338         Checkpoints::hashSyncCheckpoint = hashCheckpoint;
 339         Checkpoints::checkpointMessage = *this;
 340         Checkpoints::checkpointMessagePending.SetNull();
 341         printf("ProcessSyncCheckpoint: sync-checkpoint at %s\n", hashCheckpoint.ToString().c_str());
 342     }
 343     return true;
 344 }