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