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     uint256 hashInvalidCheckpoint = 0;
  64     CCriticalSection cs_hashSyncCheckpoint;
  65
  66     // ppcoin: only descendant of current sync-checkpoint is allowed
  67     bool ValidateSyncCheckpoint(uint256 hashCheckpoint)
  68     {
  69         if (!mapBlockIndex.count(hashSyncCheckpoint))
  70             return error("ValidateSyncCheckpoint: block index missing for current sync-checkpoint %s", hashSyncCheckpoint.ToString().c_str());
  71         if (!mapBlockIndex.count(hashCheckpoint))
  72             return error("ValidateSyncCheckpoint: block index missing for received sync-checkpoint %s", hashCheckpoint.ToString().c_str());
  73
  74         CBlockIndex* pindexSyncCheckpoint = mapBlockIndex[hashSyncCheckpoint];
  75         CBlockIndex* pindexCheckpointRecv = mapBlockIndex[hashCheckpoint];
  76
  77         if (pindexCheckpointRecv->nHeight <= pindexSyncCheckpoint->nHeight)
  78         {
  79             // Received an older checkpoint, trace back from current checkpoint
  80             // to the same height of the received checkpoint to verify
  81             // that current checkpoint should be a descendant block
  82             CBlockIndex* pindex = pindexSyncCheckpoint;
  83             while (pindex->nHeight > pindexCheckpointRecv->nHeight)
  84                 if (!(pindex = pindex->pprev))
  85                     return error("ValidateSyncCheckpoint: pprev1 null - block index structure failure");
  86             if (pindex->GetBlockHash() != hashCheckpoint)
  87             {
  88                 hashInvalidCheckpoint = hashCheckpoint;
  89                 return error("ValidateSyncCheckpoint: new sync-checkpoint %s is conflicting with current sync-checkpoint %s", hashCheckpoint.ToString().c_str(), hashSyncCheckpoint.ToString().c_str());
  90             }
  91             return false; // ignore older checkpoint
  92         }
  93
  94         // Received checkpoint should be a descendant block of the current
  95         // checkpoint. Trace back to the same height of current checkpoint
  96         // to verify.
  97         CBlockIndex* pindex = pindexCheckpointRecv;
  98         while (pindex->nHeight > pindexSyncCheckpoint->nHeight)
  99             if (!(pindex = pindex->pprev))
 100                 return error("ValidateSyncCheckpoint: pprev2 null - block index structure failure");
 101         if (pindex->GetBlockHash() != hashSyncCheckpoint)
 102         {
 103             hashInvalidCheckpoint = hashCheckpoint;
 104             return error("ValidateSyncCheckpoint: new sync-checkpoint %s is not a descendant of current sync-checkpoint %s", hashCheckpoint.ToString().c_str(), hashSyncCheckpoint.ToString().c_str());
 105         }
 106         return true;
 107     }
 108
 109     bool AcceptPendingSyncCheckpoint()
 110     {
 111         CRITICAL_BLOCK(cs_hashSyncCheckpoint)
 112         {
 113             if ((!checkpointMessagePending.IsNull()) && mapBlockIndex.count(checkpointMessagePending.hashCheckpoint))
 114             {
 115                 if (!ValidateSyncCheckpoint(checkpointMessagePending.hashCheckpoint))
 116                 {
 117                     checkpointMessagePending.SetNull();
 118                     return false;
 119                 }
 120
 121                 CTxDB txdb;
 122                 CBlockIndex* pindexCheckpoint = mapBlockIndex[checkpointMessagePending.hashCheckpoint];
 123                 if (!pindexCheckpoint->IsInMainChain())
 124                 {
 125                     txdb.TxnBegin();
 126                     if (!Reorganize(txdb, pindexCheckpoint))
 127                     {
 128                         txdb.TxnAbort();
 129                         hashInvalidCheckpoint = checkpointMessagePending.hashCheckpoint;
 130                         return error("ProcessSyncCheckpoint: Reorganize failed for sync checkpoint %s", checkpointMessagePending.hashCheckpoint.ToString().c_str());
 131                     }
 132                 }
 133
 134                 txdb.TxnBegin();
 135                 if (!txdb.WriteSyncCheckpoint(checkpointMessagePending.hashCheckpoint))
 136                 {
 137                     txdb.TxnAbort();
 138                     return error("AcceptPendingSyncCheckpoint() : failed to write to db sync checkpoint %s\n", checkpointMessagePending.hashCheckpoint.ToString().c_str());
 139                 }
 140                 if (!txdb.TxnCommit())
 141                     return error("AcceptPendingSyncCheckpoint() : failed to commit to db sync checkpoint %s\n", checkpointMessagePending.hashCheckpoint.ToString().c_str());
 142                 txdb.Close();
 143
 144                 hashSyncCheckpoint = checkpointMessagePending.hashCheckpoint;
 145                 checkpointMessage = checkpointMessagePending;
 146                 checkpointMessagePending.SetNull();
 147                 printf("AcceptPendingSyncCheckpoint : sync-checkpoint at %s\n", hashSyncCheckpoint.ToString().c_str());
 148                 // relay the checkpoint
 149                 CRITICAL_BLOCK(cs_hashSyncCheckpoint)
 150                     BOOST_FOREACH(CNode* pnode, vNodes)
 151                         checkpointMessage.RelayTo(pnode);
 152                 return true;
 153             }
 154         }
 155
 156         return false;
 157     }
 158
 159     uint256 AutoSelectSyncCheckpoint()
 160     {
 161         // select block roughly 8 hours ago
 162         CBlockIndex *pindex = mapBlockIndex[hashSyncCheckpoint];
 163         while (pindex->pnext && pindex->pnext->GetBlockTime() + AUTO_CHECKPOINT_MIN_SPAN <= GetAdjustedTime())
 164             pindex = pindex->pnext;
 165         return pindex->GetBlockHash();
 166     }
 167
 168     // Check against synchronized checkpoint
 169     bool CheckSync(const uint256& hashBlock, const CBlockIndex* pindexPrev)
 170     {
 171         if (fTestNet) return true; // Testnet has no checkpoints
 172         int nHeight = pindexPrev->nHeight + 1;
 173
 174         CRITICAL_BLOCK(cs_hashSyncCheckpoint)
 175         {
 176             // sync-checkpoint should always be accepted block
 177             assert(mapBlockIndex.count(hashSyncCheckpoint));
 178             const CBlockIndex* pindexSync = mapBlockIndex[hashSyncCheckpoint];
 179
 180             if (nHeight > pindexSync->nHeight)
 181             {
 182                 // trace back to same height as sync-checkpoint
 183                 const CBlockIndex* pindex = pindexPrev;
 184                 while (pindex->nHeight > pindexSync->nHeight)
 185                     if (!(pindex = pindex->pprev))
 186                         return error("CheckSync: pprev null - block index structure failure");
 187                 if (pindex->nHeight < pindexSync->nHeight || pindex->GetBlockHash() != hashSyncCheckpoint)
 188                     return false; // only descendant of sync-checkpoint can pass check
 189             }
 190             if (nHeight == pindexSync->nHeight && hashBlock != hashSyncCheckpoint)
 191                 return false; // same height with sync-checkpoint
 192             if (nHeight < pindexSync->nHeight && !mapBlockIndex.count(hashBlock))
 193                 return false; // lower height than sync-checkpoint
 194         }
 195         return true;
 196     }
 197
 198     // ppcoin: automatic checkpoint (represented by height of checkpoint)
 199     int nAutoCheckpoint = 0;
 200     int nBranchPoint = 0;    // branch point to alternative branch
 201
 202     // ppcoin: check automatic checkpoint
 203     // To pass the check:
 204     //   - All ancestors (including the block itself) have block index already
 205     //   - The immediate ancestor in main chain must not have height less than
 206     //     checkpoint height
 207     bool CheckAuto(const CBlockIndex *pindex)
 208     {
 209         while (pindex)
 210         {
 211             if (pindex->IsInMainChain())
 212             {
 213                 if (pindex->nHeight >= nAutoCheckpoint)
 214                     return true;
 215                 else
 216                 {
 217                     nBranchPoint = pindex->nHeight;
 218                     return error("Checkpoints: new block on alternative branch at height=%d before auto checkpoint at height=%d", pindex->nHeight, nAutoCheckpoint);
 219                 }
 220             }
 221             else
 222                 pindex = pindex->pprev;
 223         }
 224         return error("Checkpoints: failed to find any ancestor on main chain for the new block - internal error");
 225     }
 226
 227     // ppcoin: get next chain checkpoint
 228     int GetNextChainCheckpoint(const CBlockIndex *pindexLast)
 229     {
 230         CBigNum bnTarget;
 231         CBigNum bnTargetMax = 0;  // max target of all blocks since checkpoint
 232         CBigNum bnTargetMin = 0;  // min target of all candidate checkpoints
 233         int nMinTargetHeight = 0; // min target height of candidate checkpoints
 234         int nCheckpointMin = 0;   // minimum candidate checkpoint
 235         int nCheckpointMax = 0;   // maximum candidate checkpoint
 236         int nDepth = pindexLast->nHeight - pindexLast->nCheckpoint;
 237         const CBlockIndex *pindex = pindexLast;
 238         while (nDepth >= 0 && pindex)
 239         {
 240             bnTarget.SetCompact(pindex->nBits);
 241             if (bnTarget > bnTargetMax)
 242                 bnTargetMax = bnTarget;
 243             if (nCheckpointMax > 0 && bnTarget < bnTargetMin)
 244             {
 245                 bnTargetMin = bnTarget;
 246                 nMinTargetHeight = pindex->nHeight;
 247             }
 248             if (nCheckpointMax == 0 && pindexLast->GetBlockTime() - pindex->GetBlockTime() > AUTO_CHECKPOINT_MIN_SPAN)
 249             {
 250                 nCheckpointMax = pindex->nHeight;
 251                 bnTargetMin.SetCompact(pindex->nBits);
 252                 nMinTargetHeight = pindex->nHeight;
 253             }
 254             if (pindexLast->GetBlockTime() - pindex->GetBlockTime() < AUTO_CHECKPOINT_MAX_SPAN)
 255                 nCheckpointMin = pindex->nHeight;
 256             pindex = pindex->pprev;
 257             nDepth--;
 258         }
 259
 260         assert (nDepth == -1);  // arrive at chain checkpoint now
 261
 262         printf("Checkpoints: min=%d max=%d tminheight=%d tmin=0x%08x tmax=0x%08x\n",
 263             nCheckpointMin, nCheckpointMax, nMinTargetHeight,
 264             bnTargetMin.GetCompact(), bnTargetMax.GetCompact());
 265         if (nCheckpointMax == 0) // checkpoint stays if max candidate not found
 266             return pindexLast->nCheckpoint;
 267
 268         if (bnTargetMin * 100 > bnTargetMax * 90)
 269             return nCheckpointMax;
 270         if (bnTarget * 100 > bnTargetMax * 90)
 271             return nMinTargetHeight;
 272         else
 273             return nCheckpointMin;
 274     }
 275
 276     // ppcoin: get next auto checkpoint from the new chain checkpoint
 277     int GetNextAutoCheckpoint(int nCheckpoint)
 278     {
 279         return (std::max(nAutoCheckpoint, nCheckpoint));
 280     }
 281
 282     // ppcoin: advance to next automatic checkpoint
 283     void AdvanceAutoCheckpoint(int nCheckpoint)
 284     {
 285         nAutoCheckpoint = GetNextAutoCheckpoint(nCheckpoint);
 286         printf("Checkpoints: auto checkpoint now at height=%d\n", nAutoCheckpoint);
 287     }
 288
 289     // ppcoin: reset auto checkpoint
 290     bool ResetAutoCheckpoint(int nCheckpoint)
 291     {
 292         if (nCheckpoint <= 0 || nCheckpoint > nBestHeight)
 293             return error("ResetAutoCheckpoint() : new checkpoint invalid");
 294         if (nCheckpoint >= nAutoCheckpoint)
 295             return error("ResetAutoCheckpoint() : new checkpoint not earlier than current auto checkpoint");
 296         CTxDB txdb;
 297         txdb.TxnBegin();
 298         if (!txdb.WriteAutoCheckpoint(nCheckpoint, true))
 299             return error("ResetAutoCheckpoint() : database write failed");
 300         if (!txdb.TxnCommit())
 301             return error("ResetAutoCheckpoint() : database commit failed");
 302         nAutoCheckpoint = nCheckpoint;
 303         nBranchPoint = 0;  // clear branch point
 304
 305         // clear ban list to accept alternative branches
 306         CRITICAL_BLOCK(cs_vNodes)
 307         {
 308             BOOST_FOREACH(CNode* pnode, vNodes)
 309                 pnode->ClearBanned();
 310         }
 311
 312         return true;
 313     }
 314 }
 315
 316 // ppcoin: process synchronized checkpoint
 317 bool CSyncCheckpoint::ProcessSyncCheckpoint(CNode* pfrom)
 318 {
 319     if (!CheckSignature())
 320         return false;
 321
 322     CRITICAL_BLOCK(Checkpoints::cs_hashSyncCheckpoint)
 323     {
 324         if (!mapBlockIndex.count(hashCheckpoint))
 325         {
 326             // We haven't received the checkpoint chain, keep the checkpoint as pending
 327             Checkpoints::checkpointMessagePending = *this;
 328             printf("ProcessSyncCheckpoint: pending for sync-checkpoint %s\n", hashCheckpoint.ToString().c_str());
 329             // Ask this guy to fill in what we're missing
 330             if (pfrom)
 331                 pfrom->PushGetBlocks(pindexBest, hashCheckpoint);
 332             return false;
 333         }
 334
 335         if (!Checkpoints::ValidateSyncCheckpoint(hashCheckpoint))
 336             return false;
 337
 338         CTxDB txdb;
 339         CBlockIndex* pindexCheckpoint = mapBlockIndex[hashCheckpoint];
 340         if (!pindexCheckpoint->IsInMainChain())
 341         {
 342             // checkpoint chain received but not yet main chain
 343             txdb.TxnBegin();
 344             if (!Reorganize(txdb, pindexCheckpoint))
 345             {
 346                 txdb.TxnAbort();
 347                 Checkpoints::hashInvalidCheckpoint = hashCheckpoint;
 348                 return error("ProcessSyncCheckpoint: Reorganize failed for sync checkpoint %s", hashCheckpoint.ToString().c_str());
 349             }
 350         }
 351
 352         txdb.TxnBegin();
 353         if (!txdb.WriteSyncCheckpoint(hashCheckpoint))
 354         {
 355             txdb.TxnAbort();
 356             return error("ProcessSyncCheckpoint(): failed to write to db sync checkpoint %s", hashCheckpoint.ToString().c_str());
 357         }
 358         if (!txdb.TxnCommit())
 359             return error("ProcessSyncCheckpoint(): failed to commit to db sync checkpoint %s", hashCheckpoint.ToString().c_str());
 360         txdb.Close();
 361
 362         Checkpoints::hashSyncCheckpoint = hashCheckpoint;
 363         Checkpoints::checkpointMessage = *this;
 364         Checkpoints::checkpointMessagePending.SetNull();
 365         printf("ProcessSyncCheckpoint: sync-checkpoint at %s\n", hashCheckpoint.ToString().c_str());
 366     }
 367     return true;
 368 }