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()
  87     {
  88         CRITICAL_BLOCK(cs_hashSyncCheckpoint)
  89             if ((!checkpointMessagePending.IsNull()) && mapBlockIndex.count(checkpointMessagePending.hashCheckpoint))
  90             {
  91                 if (!ValidateSyncCheckpoint(checkpointMessagePending.hashCheckpoint))
  92                 {
  93                     checkpointMessagePending.SetNull();
  94                     return false;
  95                 }
  96
  97                 CTxDB txdb;
  98                 if (!txdb.WriteSyncCheckpoint(checkpointMessagePending.hashCheckpoint))
  99                     return error("AcceptPendingSyncCheckpoint() : failed to write to db sync checkpoint %s\n", checkpointMessagePending.hashCheckpoint.ToString().c_str());
 100                 txdb.Close();
 101
 102                 hashSyncCheckpoint = checkpointMessagePending.hashCheckpoint;
 103                 checkpointMessage = checkpointMessagePending;
 104                 checkpointMessagePending.SetNull();
 105                 printf("AcceptPendingSyncCheckpoint : sync-checkpoint at %s\n", hashSyncCheckpoint.ToString().c_str());
 106                 // relay the checkpoint
 107                 BOOST_FOREACH(CNode* pnode, vNodes)
 108                     checkpointMessage.RelayTo(pnode);
 109                 return true;
 110             }
 111
 112         return false;
 113     }
 114
 115     uint256 AutoSelectSyncCheckpoint()
 116     {
 117         // select block roughly 8 hours ago
 118         CBlockIndex *pindex = mapBlockIndex[hashSyncCheckpoint];
 119         while (pindex->pnext && pindex->pnext->GetBlockTime() + AUTO_CHECKPOINT_MIN_SPAN <= GetAdjustedTime())
 120             pindex = pindex->pnext;
 121         return pindex->GetBlockHash();
 122     }
 123
 124     // Check against synchronized checkpoint
 125     bool CheckSync(int nHeight, const uint256& hashBlock)
 126     {
 127         if (fTestNet) return true; // Testnet has no checkpoints
 128
 129         CRITICAL_BLOCK(cs_hashSyncCheckpoint)
 130         {
 131             CBlockIndex* pindexSync = mapBlockIndex[hashSyncCheckpoint];
 132             if (nHeight == pindexSync->nHeight && hashBlock != hashSyncCheckpoint)
 133                 return false; // same height with sync-checkpoint
 134             if (nHeight < pindexSync->nHeight && !mapBlockIndex.count(hashBlock))
 135                 return false; // lower height than sync-checkpoint
 136         }
 137         return true;
 138     }
 139
 140     // ppcoin: automatic checkpoint (represented by height of checkpoint)
 141     int nAutoCheckpoint = 0;
 142     int nBranchPoint = 0;    // branch point to alternative branch
 143
 144     // ppcoin: check automatic checkpoint
 145     // To pass the check:
 146     //   - All ancestors (including the block itself) have block index already
 147     //   - The immediate ancestor in main chain must not have height less than
 148     //     checkpoint height
 149     bool CheckAuto(const CBlockIndex *pindex)
 150     {
 151         while (pindex)
 152         {
 153             if (pindex->IsInMainChain())
 154             {
 155                 if (pindex->nHeight >= nAutoCheckpoint)
 156                     return true;
 157                 else
 158                 {
 159                     nBranchPoint = pindex->nHeight;
 160                     return error("Checkpoints: new block on alternative branch at height=%d before auto checkpoint at height=%d", pindex->nHeight, nAutoCheckpoint);
 161                 }
 162             }
 163             else
 164                 pindex = pindex->pprev;
 165         }
 166         return error("Checkpoints: failed to find any ancestor on main chain for the new block - internal error");
 167     }
 168
 169     // ppcoin: get next chain checkpoint
 170     int GetNextChainCheckpoint(const CBlockIndex *pindexLast)
 171     {
 172         CBigNum bnTarget;
 173         CBigNum bnTargetMax = 0;  // max target of all blocks since checkpoint
 174         CBigNum bnTargetMin = 0;  // min target of all candidate checkpoints
 175         int nMinTargetHeight = 0; // min target height of candidate checkpoints
 176         int nCheckpointMin = 0;   // minimum candidate checkpoint
 177         int nCheckpointMax = 0;   // maximum candidate checkpoint
 178         int nDepth = pindexLast->nHeight - pindexLast->nCheckpoint;
 179         const CBlockIndex *pindex = pindexLast;
 180         while (nDepth >= 0 && pindex)
 181         {
 182             bnTarget.SetCompact(pindex->nBits);
 183             if (bnTarget > bnTargetMax)
 184                 bnTargetMax = bnTarget;
 185             if (nCheckpointMax > 0 && bnTarget < bnTargetMin)
 186             {
 187                 bnTargetMin = bnTarget;
 188                 nMinTargetHeight = pindex->nHeight;
 189             }
 190             if (nCheckpointMax == 0 && pindexLast->GetBlockTime() - pindex->GetBlockTime() > AUTO_CHECKPOINT_MIN_SPAN)
 191             {
 192                 nCheckpointMax = pindex->nHeight;
 193                 bnTargetMin.SetCompact(pindex->nBits);
 194                 nMinTargetHeight = pindex->nHeight;
 195             }
 196             if (pindexLast->GetBlockTime() - pindex->GetBlockTime() < AUTO_CHECKPOINT_MAX_SPAN)
 197                 nCheckpointMin = pindex->nHeight;
 198             pindex = pindex->pprev;
 199             nDepth--;
 200         }
 201
 202         assert (nDepth == -1);  // arrive at chain checkpoint now
 203
 204         printf("Checkpoints: min=%d max=%d tminheight=%d tmin=0x%08x tmax=0x%08x\n",
 205             nCheckpointMin, nCheckpointMax, nMinTargetHeight,
 206             bnTargetMin.GetCompact(), bnTargetMax.GetCompact());
 207         if (nCheckpointMax == 0) // checkpoint stays if max candidate not found
 208             return pindexLast->nCheckpoint;
 209
 210         if (bnTargetMin * 100 > bnTargetMax * 90)
 211             return nCheckpointMax;
 212         if (bnTarget * 100 > bnTargetMax * 90)
 213             return nMinTargetHeight;
 214         else
 215             return nCheckpointMin;
 216     }
 217
 218     // ppcoin: get next auto checkpoint from the new chain checkpoint
 219     int GetNextAutoCheckpoint(int nCheckpoint)
 220     {
 221         return (std::max(nAutoCheckpoint, nCheckpoint));
 222     }
 223
 224     // ppcoin: advance to next automatic checkpoint
 225     void AdvanceAutoCheckpoint(int nCheckpoint)
 226     {
 227         nAutoCheckpoint = GetNextAutoCheckpoint(nCheckpoint);
 228         printf("Checkpoints: auto checkpoint now at height=%d\n", nAutoCheckpoint);
 229     }
 230
 231     // ppcoin: reset auto checkpoint
 232     bool ResetAutoCheckpoint(int nCheckpoint)
 233     {
 234         if (nCheckpoint <= 0 || nCheckpoint > nBestHeight)
 235             return error("ResetAutoCheckpoint() : new checkpoint invalid");
 236         if (nCheckpoint >= nAutoCheckpoint)
 237             return error("ResetAutoCheckpoint() : new checkpoint not earlier than current auto checkpoint");
 238         CTxDB txdb;
 239         txdb.TxnBegin();
 240         if (!txdb.WriteAutoCheckpoint(nCheckpoint, true))
 241             return error("ResetAutoCheckpoint() : database write failed");
 242         if (!txdb.TxnCommit())
 243             return error("ResetAutoCheckpoint() : database commit failed");
 244         nAutoCheckpoint = nCheckpoint;
 245         nBranchPoint = 0;  // clear branch point
 246
 247         // clear ban list to accept alternative branches
 248         CRITICAL_BLOCK(cs_vNodes)
 249         {
 250             BOOST_FOREACH(CNode* pnode, vNodes)
 251                 pnode->ClearBanned();
 252         }
 253
 254         return true;
 255     }
 256 }
 257
 258 // ppcoin: process synchronized checkpoint
 259 bool CSyncCheckpoint::ProcessSyncCheckpoint(CNode* pfrom)
 260 {
 261     if (!CheckSignature())
 262         return false;
 263
 264     CRITICAL_BLOCK(Checkpoints::cs_hashSyncCheckpoint)
 265     {
 266         if (!mapBlockIndex.count(hashCheckpoint))
 267         {
 268             // We haven't accepted this block, keep the checkpoint as pending
 269             Checkpoints::checkpointMessagePending = *this;
 270             printf("ProcessSyncCheckpoint : pending for sync-checkpoint %s\n", hashCheckpoint.ToString().c_str());
 271             // Ask this guy to fill in what we're missing
 272             if (pfrom)
 273                 pfrom->PushGetBlocks(pindexBest, hashCheckpoint);
 274             return false;
 275         }
 276         if (!Checkpoints::ValidateSyncCheckpoint(hashCheckpoint))
 277             return false;
 278
 279         CTxDB txdb;
 280         if (!txdb.WriteSyncCheckpoint(this->hashCheckpoint))
 281             return error("ProcessSyncCheckpoint() : failed to write to db sync checkpoint %s\n", this->hashCheckpoint.ToString().c_str());
 282         txdb.Close();
 283
 284         Checkpoints::hashSyncCheckpoint = this->hashCheckpoint;
 285         Checkpoints::checkpointMessage = *this;
 286         Checkpoints::checkpointMessagePending.SetNull();
 287         printf("ProcessSyncCheckpoint : sync-checkpoint at %s\n", Checkpoints::hashSyncCheckpoint.ToString().c_str());
 288     }
 289     return true;
 290 }