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 AcceptPendingSyncCheckpoint(uint256 hashAcceptedBlock)
  87     {
  88         if (!mapBlockIndex.count(hashAcceptedBlock))
  89             return false;
  90
  91         CRITICAL_BLOCK(cs_hashSyncCheckpoint)
  92             if ((!checkpointMessagePending.IsNull()) && checkpointMessagePending.hashCheckpoint == hashAcceptedBlock)
  93             {
  94                 if (!ValidateSyncCheckpoint(checkpointMessagePending.hashCheckpoint))
  95                 {
  96                     checkpointMessagePending.SetNull();
  97                     return false;
  98                 }
  99                 hashSyncCheckpoint = checkpointMessagePending.hashCheckpoint;
 100                 checkpointMessage = checkpointMessagePending;
 101                 checkpointMessagePending.SetNull();
 102                 return true;
 103             }
 104
 105         return false;
 106     }
 107
 108     // ppcoin: automatic checkpoint (represented by height of checkpoint)
 109     int nAutoCheckpoint = 0;
 110     int nBranchPoint = 0;    // branch point to alternative branch
 111
 112     // ppcoin: check automatic checkpoint
 113     // To pass the check:
 114     //   - All ancestors (including the block itself) have block index already
 115     //   - The immediate ancestor in main chain must not have height less than
 116     //     checkpoint height
 117     bool CheckAuto(const CBlockIndex *pindex)
 118     {
 119         while (pindex)
 120         {
 121             if (pindex->IsInMainChain())
 122             {
 123                 if (pindex->nHeight >= nAutoCheckpoint)
 124                     return true;
 125                 else
 126                 {
 127                     nBranchPoint = pindex->nHeight;
 128                     return error("Checkpoints: new block on alternative branch at height=%d before auto checkpoint at height=%d", pindex->nHeight, nAutoCheckpoint);
 129                 }
 130             }
 131             else
 132                 pindex = pindex->pprev;
 133         }
 134         return error("Checkpoints: failed to find any ancestor on main chain for the new block - internal error");
 135     }
 136
 137     // ppcoin: get next chain checkpoint
 138     int GetNextChainCheckpoint(const CBlockIndex *pindexLast)
 139     {
 140         CBigNum bnTarget;
 141         CBigNum bnTargetMax = 0;  // max target of all blocks since checkpoint
 142         CBigNum bnTargetMin = 0;  // min target of all candidate checkpoints
 143         int nMinTargetHeight = 0; // min target height of candidate checkpoints
 144         int nCheckpointMin = 0;   // minimum candidate checkpoint
 145         int nCheckpointMax = 0;   // maximum candidate checkpoint
 146         int nDepth = pindexLast->nHeight - pindexLast->nCheckpoint;
 147         const CBlockIndex *pindex = pindexLast;
 148         while (nDepth >= 0 && pindex)
 149         {
 150             bnTarget.SetCompact(pindex->nBits);
 151             if (bnTarget > bnTargetMax)
 152                 bnTargetMax = bnTarget;
 153             if (nCheckpointMax > 0 && bnTarget < bnTargetMin)
 154             {
 155                 bnTargetMin = bnTarget;
 156                 nMinTargetHeight = pindex->nHeight;
 157             }
 158             if (nCheckpointMax == 0 && pindexLast->GetBlockTime() - pindex->GetBlockTime() > AUTO_CHECKPOINT_MIN_SPAN)
 159             {
 160                 nCheckpointMax = pindex->nHeight;
 161                 bnTargetMin.SetCompact(pindex->nBits);
 162                 nMinTargetHeight = pindex->nHeight;
 163             }
 164             if (pindexLast->GetBlockTime() - pindex->GetBlockTime() < AUTO_CHECKPOINT_MAX_SPAN)
 165                 nCheckpointMin = pindex->nHeight;
 166             pindex = pindex->pprev;
 167             nDepth--;
 168         }
 169
 170         assert (nDepth == -1);  // arrive at chain checkpoint now
 171
 172         printf("Checkpoints: min=%d max=%d tminheight=%d tmin=0x%08x tmax=0x%08x\n",
 173             nCheckpointMin, nCheckpointMax, nMinTargetHeight,
 174             bnTargetMin.GetCompact(), bnTargetMax.GetCompact());
 175         if (nCheckpointMax == 0) // checkpoint stays if max candidate not found
 176             return pindexLast->nCheckpoint;
 177
 178         if (bnTargetMin * 100 > bnTargetMax * 90)
 179             return nCheckpointMax;
 180         if (bnTarget * 100 > bnTargetMax * 90)
 181             return nMinTargetHeight;
 182         else
 183             return nCheckpointMin;
 184     }
 185
 186     // ppcoin: get next auto checkpoint from the new chain checkpoint
 187     int GetNextAutoCheckpoint(int nCheckpoint)
 188     {
 189         return (std::max(nAutoCheckpoint, nCheckpoint));
 190     }
 191
 192     // ppcoin: advance to next automatic checkpoint
 193     void AdvanceAutoCheckpoint(int nCheckpoint)
 194     {
 195         nAutoCheckpoint = GetNextAutoCheckpoint(nCheckpoint);
 196         printf("Checkpoints: auto checkpoint now at height=%d\n", nAutoCheckpoint);
 197     }
 198
 199     // ppcoin: reset auto checkpoint
 200     bool ResetAutoCheckpoint(int nCheckpoint)
 201     {
 202         if (nCheckpoint <= 0 || nCheckpoint > nBestHeight)
 203             return error("ResetAutoCheckpoint() : new checkpoint invalid");
 204         if (nCheckpoint >= nAutoCheckpoint)
 205             return error("ResetAutoCheckpoint() : new checkpoint not earlier than current auto checkpoint");
 206         CTxDB txdb;
 207         txdb.TxnBegin();
 208         if (!txdb.WriteAutoCheckpoint(nCheckpoint, true))
 209             return error("ResetAutoCheckpoint() : database write failed");
 210         if (!txdb.TxnCommit())
 211             return error("ResetAutoCheckpoint() : database commit failed");
 212         nAutoCheckpoint = nCheckpoint;
 213         nBranchPoint = 0;  // clear branch point
 214
 215         // clear ban list to accept alternative branches
 216         CRITICAL_BLOCK(cs_vNodes)
 217         {
 218             BOOST_FOREACH(CNode* pnode, vNodes)
 219                 pnode->ClearBanned();
 220         }
 221
 222         return true;
 223     }
 224 }
 225
 226 // ppcoin: process synchronized checkpoint
 227 bool CSyncCheckpoint::ProcessSyncCheckpoint(CNode* pfrom)
 228 {
 229     if (!CheckSignature())
 230         return false;
 231
 232     CRITICAL_BLOCK(Checkpoints::cs_hashSyncCheckpoint)
 233     {
 234         if (!mapBlockIndex.count(hashCheckpoint))
 235         {
 236             // We haven't accepted this block, keep the checkpoint as pending
 237             Checkpoints::checkpointMessagePending = *this;
 238             // Ask this guy to fill in what we're missing
 239             if (pfrom)
 240                 pfrom->PushGetBlocks(pindexBest, hashCheckpoint);
 241             return false;
 242         }
 243         if (!Checkpoints::ValidateSyncCheckpoint(hashCheckpoint))
 244             return false;
 245         Checkpoints::hashSyncCheckpoint = this->hashCheckpoint;
 246         Checkpoints::checkpointMessage = *this;
 247         Checkpoints::checkpointMessagePending.SetNull();
 248     }
 249     return true;
 250 }