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             pindex = pindex->pprev;
  81         if (pindex->GetBlockHash() != hashSyncCheckpoint)
  82             return error("ValidateSyncCheckpoint: new sync-checkpoint %s is not a descendant of current sync-checkpoint %s", hashCheckpoint.ToString().c_str(), hashSyncCheckpoint.ToString().c_str());
  83         return true;
  84     }
  85
  86     bool CSyncCheckpoint::ProcessSyncCheckpoint(CNode* pfrom)
  87     {
  88         if (!CheckSignature())
  89             return false;
  90
  91         CRITICAL_BLOCK(cs_hashSyncCheckpoint)
  92         {
  93             if (!mapBlockIndex.count(hashCheckpoint))
  94             {
  95                 // We haven't accepted this block, keep the checkpoint as pending
  96                 checkpointMessagePending = *this;
  97                 // Ask this guy to fill in what we're missing
  98                 if (pfrom)
  99                     pfrom->PushGetBlocks(pindexBest, hashCheckpoint);
 100                 return false;
 101             }
 102             if (!ValidateSyncCheckpoint(hashCheckpoint))
 103                 return false;
 104             hashSyncCheckpoint = this->hashCheckpoint;
 105             checkpointMessage = *this;
 106             checkpointMessagePending.SetNull();
 107         }
 108         return true;
 109     }
 110
 111     bool AcceptPendingSyncCheckpoint(uint256 hashAcceptedBlock)
 112     {
 113         if (!mapBlockIndex.count(hashAcceptedBlock))
 114             return false;
 115
 116         CRITICAL_BLOCK(cs_hashSyncCheckpoint)
 117             if ((!checkpointMessagePending.IsNull()) && checkpointMessagePending.hashCheckpoint == hashAcceptedBlock)
 118             {
 119                 if (!ValidateSyncCheckpoint(checkpointMessagePending.hashCheckpoint))
 120                 {
 121                     checkpointMessagePending.SetNull();
 122                     return false;
 123                 }
 124                 hashSyncCheckpoint = checkpointMessagePending.hashCheckpoint;
 125                 checkpointMessage = checkpointMessagePending;
 126                 checkpointMessagePending.SetNull();
 127                 return true;
 128             }
 129
 130         return false;
 131     }
 132
 133     // ppcoin: automatic checkpoint (represented by height of checkpoint)
 134     int nAutoCheckpoint = 0;
 135     int nBranchPoint = 0;    // branch point to alternative branch
 136
 137     // ppcoin: check automatic checkpoint
 138     // To pass the check:
 139     //   - All ancestors (including the block itself) have block index already
 140     //   - The immediate ancestor in main chain must not have height less than
 141     //     checkpoint height
 142     bool CheckAuto(const CBlockIndex *pindex)
 143     {
 144         while (pindex)
 145         {
 146             if (pindex->IsInMainChain())
 147             {
 148                 if (pindex->nHeight >= nAutoCheckpoint)
 149                     return true;
 150                 else
 151                 {
 152                     nBranchPoint = pindex->nHeight;
 153                     return error("Checkpoints: new block on alternative branch at height=%d before auto checkpoint at height=%d", pindex->nHeight, nAutoCheckpoint);
 154                 }
 155             }
 156             else
 157                 pindex = pindex->pprev;
 158         }
 159         return error("Checkpoints: failed to find any ancestor on main chain for the new block - internal error");
 160     }
 161
 162     // ppcoin: get next chain checkpoint
 163     int GetNextChainCheckpoint(const CBlockIndex *pindexLast)
 164     {
 165         CBigNum bnTarget;
 166         CBigNum bnTargetMax = 0;  // max target of all blocks since checkpoint
 167         CBigNum bnTargetMin = 0;  // min target of all candidate checkpoints
 168         int nMinTargetHeight = 0; // min target height of candidate checkpoints
 169         int nCheckpointMin = 0;   // minimum candidate checkpoint
 170         int nCheckpointMax = 0;   // maximum candidate checkpoint
 171         int nDepth = pindexLast->nHeight - pindexLast->nCheckpoint;
 172         const CBlockIndex *pindex = pindexLast;
 173         while (nDepth >= 0 && pindex)
 174         {
 175             bnTarget.SetCompact(pindex->nBits);
 176             if (bnTarget > bnTargetMax)
 177                 bnTargetMax = bnTarget;
 178             if (nCheckpointMax > 0 && bnTarget < bnTargetMin)
 179             {
 180                 bnTargetMin = bnTarget;
 181                 nMinTargetHeight = pindex->nHeight;
 182             }
 183             if (nCheckpointMax == 0 && pindexLast->GetBlockTime() - pindex->GetBlockTime() > AUTO_CHECKPOINT_MIN_SPAN)
 184             {
 185                 nCheckpointMax = pindex->nHeight;
 186                 bnTargetMin.SetCompact(pindex->nBits);
 187                 nMinTargetHeight = pindex->nHeight;
 188             }
 189             if (pindexLast->GetBlockTime() - pindex->GetBlockTime() < AUTO_CHECKPOINT_MAX_SPAN)
 190                 nCheckpointMin = pindex->nHeight;
 191             pindex = pindex->pprev;
 192             nDepth--;
 193         }
 194
 195         assert (nDepth == -1);  // arrive at chain checkpoint now
 196
 197         printf("Checkpoints: min=%d max=%d tminheight=%d tmin=0x%08x tmax=0x%08x\n",
 198             nCheckpointMin, nCheckpointMax, nMinTargetHeight,
 199             bnTargetMin.GetCompact(), bnTargetMax.GetCompact());
 200         if (nCheckpointMax == 0) // checkpoint stays if max candidate not found
 201             return pindexLast->nCheckpoint;
 202
 203         if (bnTargetMin * 100 > bnTargetMax * 90)
 204             return nCheckpointMax;
 205         if (bnTarget * 100 > bnTargetMax * 90)
 206             return nMinTargetHeight;
 207         else
 208             return nCheckpointMin;
 209     }
 210
 211     // ppcoin: get next auto checkpoint from the new chain checkpoint
 212     int GetNextAutoCheckpoint(int nCheckpoint)
 213     {
 214         return (std::max(nAutoCheckpoint, nCheckpoint));
 215     }
 216
 217     // ppcoin: advance to next automatic checkpoint
 218     void AdvanceAutoCheckpoint(int nCheckpoint)
 219     {
 220         nAutoCheckpoint = GetNextAutoCheckpoint(nCheckpoint);
 221         printf("Checkpoints: auto checkpoint now at height=%d\n", nAutoCheckpoint);
 222     }
 223
 224     // ppcoin: reset auto checkpoint
 225     bool ResetAutoCheckpoint(int nCheckpoint)
 226     {
 227         if (nCheckpoint <= 0 || nCheckpoint > nBestHeight)
 228             return error("ResetAutoCheckpoint() : new checkpoint invalid");
 229         if (nCheckpoint >= nAutoCheckpoint)
 230             return error("ResetAutoCheckpoint() : new checkpoint not earlier than current auto checkpoint");
 231         CTxDB txdb;
 232         txdb.TxnBegin();
 233         if (!txdb.WriteAutoCheckpoint(nCheckpoint, true))
 234             return error("ResetAutoCheckpoint() : database write failed");
 235         if (!txdb.TxnCommit())
 236             return error("ResetAutoCheckpoint() : database commit failed");
 237         nAutoCheckpoint = nCheckpoint;
 238         nBranchPoint = 0;  // clear branch point
 239
 240         // clear ban list to accept alternative branches
 241         CRITICAL_BLOCK(cs_vNodes)
 242         {
 243             BOOST_FOREACH(CNode* pnode, vNodes)
 244                 pnode->ClearBanned();
 245         }
 246
 247         return true;
 248     }
 249 }