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.
6 #include <boost/assign/list_of.hpp> // for 'map_list_of()'
7 #include <boost/foreach.hpp>
10 #include "checkpoints.h"
14 typedef std::map<int, uint256> MapCheckpoints; // hardened checkpoints
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
21 // + Contains no strange transactions
23 static MapCheckpoints mapCheckpoints =
24 boost::assign::map_list_of
25 ( 0, hashGenesisBlock )
26 ; // ppcoin: no checkpoint yet; to be created in future releases
28 bool CheckHardened(int nHeight, const uint256& hash)
30 if (fTestNet) return true; // Testnet has no checkpoints
32 MapCheckpoints::const_iterator i = mapCheckpoints.find(nHeight);
33 if (i == mapCheckpoints.end()) return true;
34 return hash == i->second;
37 int GetTotalBlocksEstimate()
39 if (fTestNet) return 0;
41 return mapCheckpoints.rbegin()->first;
44 CBlockIndex* GetLastCheckpoint(const std::map<uint256, CBlockIndex*>& mapBlockIndex)
46 if (fTestNet) return NULL;
49 BOOST_REVERSE_FOREACH(const MapCheckpoints::value_type& i, mapCheckpoints)
51 const uint256& hash = i.second;
52 std::map<uint256, CBlockIndex*>::const_iterator t = mapBlockIndex.find(hash);
53 if (t != mapBlockIndex.end())
59 // ppcoin: synchronized checkpoint (centrally broadcasted)
60 uint256 hashSyncCheckpoint;
61 CSyncCheckpoint checkpointMessage;
62 CSyncCheckpoint checkpointMessagePending;
63 CCriticalSection cs_hashSyncCheckpoint;
65 // ppcoin: only descendant of current sync-checkpoint is allowed
66 bool ValidateSyncCheckpoint(uint256 hashCheckpoint)
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());
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
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());
87 bool AcceptPendingSyncCheckpoint()
89 CRITICAL_BLOCK(cs_hashSyncCheckpoint)
90 if ((!checkpointMessagePending.IsNull()) && mapBlockIndex.count(checkpointMessagePending.hashCheckpoint))
92 if (!ValidateSyncCheckpoint(checkpointMessagePending.hashCheckpoint))
94 checkpointMessagePending.SetNull();
99 if (!txdb.WriteSyncCheckpoint(checkpointMessagePending.hashCheckpoint))
100 return error("AcceptPendingSyncCheckpoint() : failed to write to db sync checkpoint %s\n", checkpointMessagePending.hashCheckpoint.ToString().c_str());
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);
116 uint256 AutoSelectSyncCheckpoint()
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();
125 // Check against synchronized checkpoint
126 bool CheckSync(const uint256& hashBlock, const CBlockIndex* pindexPrev)
128 if (fTestNet) return true; // Testnet has no checkpoints
129 int nHeight = pindexPrev->nHeight + 1;
131 CRITICAL_BLOCK(cs_hashSyncCheckpoint)
133 // sync-checkpoint should always be accepted block
134 assert(mapBlockIndex.count(hashSyncCheckpoint));
135 const CBlockIndex* pindexSync = mapBlockIndex[hashSyncCheckpoint];
137 if (nHeight > pindexSync->nHeight)
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
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
155 // ppcoin: automatic checkpoint (represented by height of checkpoint)
156 int nAutoCheckpoint = 0;
157 int nBranchPoint = 0; // branch point to alternative branch
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
164 bool CheckAuto(const CBlockIndex *pindex)
168 if (pindex->IsInMainChain())
170 if (pindex->nHeight >= nAutoCheckpoint)
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);
179 pindex = pindex->pprev;
181 return error("Checkpoints: failed to find any ancestor on main chain for the new block - internal error");
184 // ppcoin: get next chain checkpoint
185 int GetNextChainCheckpoint(const CBlockIndex *pindexLast)
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)
197 bnTarget.SetCompact(pindex->nBits);
198 if (bnTarget > bnTargetMax)
199 bnTargetMax = bnTarget;
200 if (nCheckpointMax > 0 && bnTarget < bnTargetMin)
202 bnTargetMin = bnTarget;
203 nMinTargetHeight = pindex->nHeight;
205 if (nCheckpointMax == 0 && pindexLast->GetBlockTime() - pindex->GetBlockTime() > AUTO_CHECKPOINT_MIN_SPAN)
207 nCheckpointMax = pindex->nHeight;
208 bnTargetMin.SetCompact(pindex->nBits);
209 nMinTargetHeight = pindex->nHeight;
211 if (pindexLast->GetBlockTime() - pindex->GetBlockTime() < AUTO_CHECKPOINT_MAX_SPAN)
212 nCheckpointMin = pindex->nHeight;
213 pindex = pindex->pprev;
217 assert (nDepth == -1); // arrive at chain checkpoint now
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;
225 if (bnTargetMin * 100 > bnTargetMax * 90)
226 return nCheckpointMax;
227 if (bnTarget * 100 > bnTargetMax * 90)
228 return nMinTargetHeight;
230 return nCheckpointMin;
233 // ppcoin: get next auto checkpoint from the new chain checkpoint
234 int GetNextAutoCheckpoint(int nCheckpoint)
236 return (std::max(nAutoCheckpoint, nCheckpoint));
239 // ppcoin: advance to next automatic checkpoint
240 void AdvanceAutoCheckpoint(int nCheckpoint)
242 nAutoCheckpoint = GetNextAutoCheckpoint(nCheckpoint);
243 printf("Checkpoints: auto checkpoint now at height=%d\n", nAutoCheckpoint);
246 // ppcoin: reset auto checkpoint
247 bool ResetAutoCheckpoint(int nCheckpoint)
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");
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
262 // clear ban list to accept alternative branches
263 CRITICAL_BLOCK(cs_vNodes)
265 BOOST_FOREACH(CNode* pnode, vNodes)
266 pnode->ClearBanned();
273 // ppcoin: process synchronized checkpoint
274 bool CSyncCheckpoint::ProcessSyncCheckpoint(CNode* pfrom)
276 if (!CheckSignature())
279 CRITICAL_BLOCK(Checkpoints::cs_hashSyncCheckpoint)
281 if (!mapBlockIndex.count(hashCheckpoint))
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
288 pfrom->PushGetBlocks(pindexBest, hashCheckpoint);
291 if (!Checkpoints::ValidateSyncCheckpoint(hashCheckpoint))
295 if (!txdb.WriteSyncCheckpoint(this->hashCheckpoint))
296 return error("ProcessSyncCheckpoint() : failed to write to db sync checkpoint %s\n", this->hashCheckpoint.ToString().c_str());
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());