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// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2014 The Bitcoin developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
#include "main.h"
#include "addrman.h"
#include "alert.h"
#include "chainparams.h"
#include "checkpoints.h"
#include "checkqueue.h"
#include "init.h"
#include "merkleblock.h"
#include "net.h"
#include "pow.h"
#include "txdb.h"
#include "txmempool.h"
11 years ago
#include "ui_interface.h"
#include "util.h"
#include "utilmoneystr.h"
#include <sstream>
#include <boost/algorithm/string/replace.hpp>
#include <boost/filesystem.hpp>
#include <boost/filesystem/fstream.hpp>
#include <boost/thread.hpp>
using namespace boost;
using namespace std;
#if defined(NDEBUG)
# error "Bitcoin cannot be compiled without assertions."
#endif
/**
* Global state
*/
CCriticalSection cs_main;
BlockMap mapBlockIndex;
CChain chainActive;
CBlockIndex *pindexBestHeader = NULL;
int64_t nTimeBestReceived = 0;
CWaitableCriticalSection csBestBlock;
CConditionVariable cvBlockChange;
int nScriptCheckThreads = 0;
bool fImporting = false;
bool fReindex = false;
bool fTxIndex = false;
bool fIsBareMultisigStd = true;
unsigned int nCoinCacheSize = 5000;
/** Fees smaller than this (in satoshi) are considered zero fee (for relaying and mining) */
CFeeRate minRelayTxFee = CFeeRate(1000);
CTxMemPool mempool(::minRelayTxFee);
struct COrphanTx {
CTransaction tx;
NodeId fromPeer;
};
map<uint256, COrphanTx> mapOrphanTransactions;
map<uint256, set<uint256> > mapOrphanTransactionsByPrev;
void EraseOrphansFor(NodeId peer);
/**
* Returns true if there are nRequired or more blocks of minVersion or above
* in the last Params().ToCheckBlockUpgradeMajority() blocks, starting at pstart
* and going backwards.
*/
static bool IsSuperMajority(int minVersion, const CBlockIndex* pstart, unsigned int nRequired);
/** Constant stuff for coinbase transactions we create: */
CScript COINBASE_FLAGS;
const string strMessageMagic = "Bitcoin Signed Message:\n";
// Internal stuff
namespace {
struct CBlockIndexWorkComparator
{
bool operator()(CBlockIndex *pa, CBlockIndex *pb) {
// First sort by most total work, ...
if (pa->nChainWork > pb->nChainWork) return false;
if (pa->nChainWork < pb->nChainWork) return true;
// ... then by earliest time received, ...
if (pa->nSequenceId < pb->nSequenceId) return false;
if (pa->nSequenceId > pb->nSequenceId) return true;
// Use pointer address as tie breaker (should only happen with blocks
// loaded from disk, as those all have id 0).
if (pa < pb) return false;
if (pa > pb) return true;
// Identical blocks.
return false;
}
};
CBlockIndex *pindexBestInvalid;
/**
* The set of all CBlockIndex entries with BLOCK_VALID_TRANSACTIONS or better that are at least
* as good as our current tip. Entries may be failed, though.
*/
set<CBlockIndex*, CBlockIndexWorkComparator> setBlockIndexCandidates;
/** Number of nodes with fSyncStarted. */
int nSyncStarted = 0;
/** All pairs A->B, where A (or one if its ancestors) misses transactions, but B has transactions. */
multimap<CBlockIndex*, CBlockIndex*> mapBlocksUnlinked;
CCriticalSection cs_LastBlockFile;
std::vector<CBlockFileInfo> vinfoBlockFile;
int nLastBlockFile = 0;
/**
* Every received block is assigned a unique and increasing identifier, so we
* know which one to give priority in case of a fork.
*/
CCriticalSection cs_nBlockSequenceId;
/** Blocks loaded from disk are assigned id 0, so start the counter at 1. */
uint32_t nBlockSequenceId = 1;
/**
* Sources of received blocks, to be able to send them reject messages or ban
* them, if processing happens afterwards. Protected by cs_main.
*/
map<uint256, NodeId> mapBlockSource;
/** Blocks that are in flight, and that are in the queue to be downloaded. Protected by cs_main. */
struct QueuedBlock {
uint256 hash;
CBlockIndex *pindex; //! Optional.
int64_t nTime; //! Time of "getdata" request in microseconds.
};
map<uint256, pair<NodeId, list<QueuedBlock>::iterator> > mapBlocksInFlight;
/** Number of preferable block download peers. */
int nPreferredDownload = 0;
/** Dirty block index entries. */
set<CBlockIndex*> setDirtyBlockIndex;
/** Dirty block file entries. */
set<int> setDirtyFileInfo;
} // anon namespace
//////////////////////////////////////////////////////////////////////////////
//
// dispatching functions
//
// These functions dispatch to one or all registered wallets
namespace {
struct CMainSignals {
/** Notifies listeners of updated transaction data (transaction, and optionally the block it is found in. */
boost::signals2::signal<void (const CTransaction &, const CBlock *)> SyncTransaction;
/** Notifies listeners of an erased transaction (currently disabled, requires transaction replacement). */
boost::signals2::signal<void (const uint256 &)> EraseTransaction;
/** Notifies listeners of an updated transaction without new data (for now: a coinbase potentially becoming visible). */
boost::signals2::signal<void (const uint256 &)> UpdatedTransaction;
/** Notifies listeners of a new active block chain. */
boost::signals2::signal<void (const CBlockLocator &)> SetBestChain;
/** Notifies listeners about an inventory item being seen on the network. */
boost::signals2::signal<void (const uint256 &)> Inventory;
/** Tells listeners to broadcast their data. */
boost::signals2::signal<void ()> Broadcast;
/** Notifies listeners of a block validation result */
boost::signals2::signal<void (const CBlock&, const CValidationState&)> BlockChecked;
} g_signals;
} // anon namespace
void RegisterValidationInterface(CValidationInterface* pwalletIn) {
g_signals.SyncTransaction.connect(boost::bind(&CValidationInterface::SyncTransaction, pwalletIn, _1, _2));
g_signals.EraseTransaction.connect(boost::bind(&CValidationInterface::EraseFromWallet, pwalletIn, _1));
g_signals.UpdatedTransaction.connect(boost::bind(&CValidationInterface::UpdatedTransaction, pwalletIn, _1));
g_signals.SetBestChain.connect(boost::bind(&CValidationInterface::SetBestChain, pwalletIn, _1));
g_signals.Inventory.connect(boost::bind(&CValidationInterface::Inventory, pwalletIn, _1));
g_signals.Broadcast.connect(boost::bind(&CValidationInterface::ResendWalletTransactions, pwalletIn));
g_signals.BlockChecked.connect(boost::bind(&CValidationInterface::BlockChecked, pwalletIn, _1, _2));
}
void UnregisterValidationInterface(CValidationInterface* pwalletIn) {
g_signals.BlockChecked.disconnect(boost::bind(&CValidationInterface::BlockChecked, pwalletIn, _1, _2));
g_signals.Broadcast.disconnect(boost::bind(&CValidationInterface::ResendWalletTransactions, pwalletIn));
g_signals.Inventory.disconnect(boost::bind(&CValidationInterface::Inventory, pwalletIn, _1));
g_signals.SetBestChain.disconnect(boost::bind(&CValidationInterface::SetBestChain, pwalletIn, _1));
g_signals.UpdatedTransaction.disconnect(boost::bind(&CValidationInterface::UpdatedTransaction, pwalletIn, _1));
g_signals.EraseTransaction.disconnect(boost::bind(&CValidationInterface::EraseFromWallet, pwalletIn, _1));
g_signals.SyncTransaction.disconnect(boost::bind(&CValidationInterface::SyncTransaction, pwalletIn, _1, _2));
}
void UnregisterAllValidationInterfaces() {
g_signals.BlockChecked.disconnect_all_slots();
g_signals.Broadcast.disconnect_all_slots();
g_signals.Inventory.disconnect_all_slots();
g_signals.SetBestChain.disconnect_all_slots();
g_signals.UpdatedTransaction.disconnect_all_slots();
g_signals.EraseTransaction.disconnect_all_slots();
g_signals.SyncTransaction.disconnect_all_slots();
}
void SyncWithWallets(const CTransaction &tx, const CBlock *pblock) {
g_signals.SyncTransaction(tx, pblock);
}
//////////////////////////////////////////////////////////////////////////////
//
// Registration of network node signals.
//
namespace {
struct CBlockReject {
unsigned char chRejectCode;
string strRejectReason;
uint256 hashBlock;
};
/**
* Maintain validation-specific state about nodes, protected by cs_main, instead
* by CNode's own locks. This simplifies asynchronous operation, where
* processing of incoming data is done after the ProcessMessage call returns,
* and we're no longer holding the node's locks.
*/
struct CNodeState {
//! Accumulated misbehaviour score for this peer.
int nMisbehavior;
//! Whether this peer should be disconnected and banned (unless whitelisted).
bool fShouldBan;
//! String name of this peer (debugging/logging purposes).
std::string name;
//! List of asynchronously-determined block rejections to notify this peer about.
std::vector<CBlockReject> rejects;
//! The best known block we know this peer has announced.
CBlockIndex *pindexBestKnownBlock;
//! The hash of the last unknown block this peer has announced.
uint256 hashLastUnknownBlock;
//! The last full block we both have.
CBlockIndex *pindexLastCommonBlock;
//! Whether we've started headers synchronization with this peer.
bool fSyncStarted;
//! Since when we're stalling block download progress (in microseconds), or 0.
int64_t nStallingSince;
list<QueuedBlock> vBlocksInFlight;
int nBlocksInFlight;
//! Whether we consider this a preferred download peer.
bool fPreferredDownload;
CNodeState() {
nMisbehavior = 0;
fShouldBan = false;
pindexBestKnownBlock = NULL;
hashLastUnknownBlock = uint256(0);
pindexLastCommonBlock = NULL;
fSyncStarted = false;
nStallingSince = 0;
nBlocksInFlight = 0;
fPreferredDownload = false;
}
};
/** Map maintaining per-node state. Requires cs_main. */
map<NodeId, CNodeState> mapNodeState;
// Requires cs_main.
CNodeState *State(NodeId pnode) {
map<NodeId, CNodeState>::iterator it = mapNodeState.find(pnode);
if (it == mapNodeState.end())
return NULL;
return &it->second;
}
int GetHeight()
{
LOCK(cs_main);
return chainActive.Height();
}
void UpdatePreferredDownload(CNode* node, CNodeState* state)
{
nPreferredDownload -= state->fPreferredDownload;
// Whether this node should be marked as a preferred download node.
state->fPreferredDownload = (!node->fInbound || node->fWhitelisted) && !node->fOneShot && !node->fClient;
nPreferredDownload += state->fPreferredDownload;
}
void InitializeNode(NodeId nodeid, const CNode *pnode) {
LOCK(cs_main);
CNodeState &state = mapNodeState.insert(std::make_pair(nodeid, CNodeState())).first->second;
state.name = pnode->addrName;
}
void FinalizeNode(NodeId nodeid) {
LOCK(cs_main);
CNodeState *state = State(nodeid);
if (state->fSyncStarted)
nSyncStarted--;
BOOST_FOREACH(const QueuedBlock& entry, state->vBlocksInFlight)
mapBlocksInFlight.erase(entry.hash);
EraseOrphansFor(nodeid);
nPreferredDownload -= state->fPreferredDownload;
mapNodeState.erase(nodeid);
}
// Requires cs_main.
void MarkBlockAsReceived(const uint256& hash) {
map<uint256, pair<NodeId, list<QueuedBlock>::iterator> >::iterator itInFlight = mapBlocksInFlight.find(hash);
if (itInFlight != mapBlocksInFlight.end()) {
CNodeState *state = State(itInFlight->second.first);
state->vBlocksInFlight.erase(itInFlight->second.second);
state->nBlocksInFlight--;
state->nStallingSince = 0;
mapBlocksInFlight.erase(itInFlight);
}
}
// Requires cs_main.
void MarkBlockAsInFlight(NodeId nodeid, const uint256& hash, CBlockIndex *pindex = NULL) {
CNodeState *state = State(nodeid);
assert(state != NULL);
// Make sure it's not listed somewhere already.
MarkBlockAsReceived(hash);
QueuedBlock newentry = {hash, pindex, GetTimeMicros()};
list<QueuedBlock>::iterator it = state->vBlocksInFlight.insert(state->vBlocksInFlight.end(), newentry);
state->nBlocksInFlight++;
mapBlocksInFlight[hash] = std::make_pair(nodeid, it);
}
/** Check whether the last unknown block a peer advertized is not yet known. */
void ProcessBlockAvailability(NodeId nodeid) {
CNodeState *state = State(nodeid);
assert(state != NULL);
if (state->hashLastUnknownBlock != 0) {
BlockMap::iterator itOld = mapBlockIndex.find(state->hashLastUnknownBlock);
if (itOld != mapBlockIndex.end() && itOld->second->nChainWork > 0) {
if (state->pindexBestKnownBlock == NULL || itOld->second->nChainWork >= state->pindexBestKnownBlock->nChainWork)
state->pindexBestKnownBlock = itOld->second;
state->hashLastUnknownBlock = uint256(0);
}
}
}
/** Update tracking information about which blocks a peer is assumed to have. */
void UpdateBlockAvailability(NodeId nodeid, const uint256 &hash) {
CNodeState *state = State(nodeid);
assert(state != NULL);
ProcessBlockAvailability(nodeid);
BlockMap::iterator it = mapBlockIndex.find(hash);
if (it != mapBlockIndex.end() && it->second->nChainWork > 0) {
// An actually better block was announced.
if (state->pindexBestKnownBlock == NULL || it->second->nChainWork >= state->pindexBestKnownBlock->nChainWork)
state->pindexBestKnownBlock = it->second;
} else {
// An unknown block was announced; just assume that the latest one is the best one.
state->hashLastUnknownBlock = hash;
}
}
/** Find the last common ancestor two blocks have.
* Both pa and pb must be non-NULL. */
CBlockIndex* LastCommonAncestor(CBlockIndex* pa, CBlockIndex* pb) {
if (pa->nHeight > pb->nHeight) {
pa = pa->GetAncestor(pb->nHeight);
} else if (pb->nHeight > pa->nHeight) {
pb = pb->GetAncestor(pa->nHeight);
}
while (pa != pb && pa && pb) {
pa = pa->pprev;
pb = pb->pprev;
}
// Eventually all chain branches meet at the genesis block.
assert(pa == pb);
return pa;
}
/** Update pindexLastCommonBlock and add not-in-flight missing successors to vBlocks, until it has
* at most count entries. */
void FindNextBlocksToDownload(NodeId nodeid, unsigned int count, std::vector<CBlockIndex*>& vBlocks, NodeId& nodeStaller) {
if (count == 0)
return;
vBlocks.reserve(vBlocks.size() + count);
CNodeState *state = State(nodeid);
assert(state != NULL);
// Make sure pindexBestKnownBlock is up to date, we'll need it.
ProcessBlockAvailability(nodeid);
if (state->pindexBestKnownBlock == NULL || state->pindexBestKnownBlock->nChainWork < chainActive.Tip()->nChainWork) {
// This peer has nothing interesting.
return;
}
if (state->pindexLastCommonBlock == NULL) {
// Bootstrap quickly by guessing a parent of our best tip is the forking point.
// Guessing wrong in either direction is not a problem.
state->pindexLastCommonBlock = chainActive[std::min(state->pindexBestKnownBlock->nHeight, chainActive.Height())];
}
// If the peer reorganized, our previous pindexLastCommonBlock may not be an ancestor
// of their current tip anymore. Go back enough to fix that.
state->pindexLastCommonBlock = LastCommonAncestor(state->pindexLastCommonBlock, state->pindexBestKnownBlock);
if (state->pindexLastCommonBlock == state->pindexBestKnownBlock)
return;
std::vector<CBlockIndex*> vToFetch;
CBlockIndex *pindexWalk = state->pindexLastCommonBlock;
8 years ago
// Never fetch further than the best block we know the peer has, or more than BLOCK_DOWNLOAD_WINDOW + 1 beyond the last
// linked block we have in common with this peer. The +1 is so we can detect stalling, namely if we would be able to
// download that next block if the window were 1 larger.
int nWindowEnd = state->pindexLastCommonBlock->nHeight + BLOCK_DOWNLOAD_WINDOW;
int nMaxHeight = std::min<int>(state->pindexBestKnownBlock->nHeight, nWindowEnd + 1);
NodeId waitingfor = -1;
while (pindexWalk->nHeight < nMaxHeight) {
// Read up to 128 (or more, if more blocks than that are needed) successors of pindexWalk (towards
// pindexBestKnownBlock) into vToFetch. We fetch 128, because CBlockIndex::GetAncestor may be as expensive
// as iterating over ~100 CBlockIndex* entries anyway.
int nToFetch = std::min(nMaxHeight - pindexWalk->nHeight, std::max<int>(count - vBlocks.size(), 128));
vToFetch.resize(nToFetch);
pindexWalk = state->pindexBestKnownBlock->GetAncestor(pindexWalk->nHeight + nToFetch);
vToFetch[nToFetch - 1] = pindexWalk;
for (unsigned int i = nToFetch - 1; i > 0; i--) {
vToFetch[i - 1] = vToFetch[i]->pprev;
}
// Iterate over those blocks in vToFetch (in forward direction), adding the ones that
// are not yet downloaded and not in flight to vBlocks. In the mean time, update
// pindexLastCommonBlock as long as all ancestors are already downloaded.
BOOST_FOREACH(CBlockIndex* pindex, vToFetch) {
if (pindex->nStatus & BLOCK_HAVE_DATA) {
if (pindex->nChainTx)
state->pindexLastCommonBlock = pindex;
} else if (mapBlocksInFlight.count(pindex->GetBlockHash()) == 0) {
// The block is not already downloaded, and not yet in flight.
8 years ago
if (pindex->nHeight > nWindowEnd) {
// We reached the end of the window.
if (vBlocks.size() == 0 && waitingfor != nodeid) {
// We aren't able to fetch anything, but we would be if the download window was one larger.
nodeStaller = waitingfor;
}
return;
}
vBlocks.push_back(pindex);
if (vBlocks.size() == count) {
return;
}
} else if (waitingfor == -1) {
// This is the first already-in-flight block.
waitingfor = mapBlocksInFlight[pindex->GetBlockHash()].first;
}
}
}
}
} // anon namespace
bool GetNodeStateStats(NodeId nodeid, CNodeStateStats &stats) {
LOCK(cs_main);
CNodeState *state = State(nodeid);
if (state == NULL)
return false;
stats.nMisbehavior = state->nMisbehavior;
stats.nSyncHeight = state->pindexBestKnownBlock ? state->pindexBestKnownBlock->nHeight : -1;
stats.nCommonHeight = state->pindexLastCommonBlock ? state->pindexLastCommonBlock->nHeight : -1;
BOOST_FOREACH(const QueuedBlock& queue, state->vBlocksInFlight) {
if (queue.pindex)
stats.vHeightInFlight.push_back(queue.pindex->nHeight);
}
return true;
}
void RegisterNodeSignals(CNodeSignals& nodeSignals)
{
nodeSignals.GetHeight.connect(&GetHeight);
nodeSignals.ProcessMessages.connect(&ProcessMessages);
nodeSignals.SendMessages.connect(&SendMessages);
nodeSignals.InitializeNode.connect(&InitializeNode);
nodeSignals.FinalizeNode.connect(&FinalizeNode);
}
void UnregisterNodeSignals(CNodeSignals& nodeSignals)
{
nodeSignals.GetHeight.disconnect(&GetHeight);
nodeSignals.ProcessMessages.disconnect(&ProcessMessages);
nodeSignals.SendMessages.disconnect(&SendMessages);
nodeSignals.InitializeNode.disconnect(&InitializeNode);
nodeSignals.FinalizeNode.disconnect(&FinalizeNode);
}
CBlockIndex* FindForkInGlobalIndex(const CChain& chain, const CBlockLocator& locator)
{
// Find the first block the caller has in the main chain
BOOST_FOREACH(const uint256& hash, locator.vHave) {
BlockMap::iterator mi = mapBlockIndex.find(hash);
if (mi != mapBlockIndex.end())
{
CBlockIndex* pindex = (*mi).second;
if (chain.Contains(pindex))
return pindex;
}
}
return chain.Genesis();
}
CCoinsViewCache *pcoinsTip = NULL;
CBlockTreeDB *pblocktree = NULL;
Ultraprune This switches bitcoin's transaction/block verification logic to use a "coin database", which contains all unredeemed transaction output scripts, amounts and heights. The name ultraprune comes from the fact that instead of a full transaction index, we only (need to) keep an index with unspent outputs. For now, the blocks themselves are kept as usual, although they are only necessary for serving, rescanning and reorganizing. The basic datastructures are CCoins (representing the coins of a single transaction), and CCoinsView (representing a state of the coins database). There are several implementations for CCoinsView. A dummy, one backed by the coins database (coins.dat), one backed by the memory pool, and one that adds a cache on top of it. FetchInputs, ConnectInputs, ConnectBlock, DisconnectBlock, ... now operate on a generic CCoinsView. The block switching logic now builds a single cached CCoinsView with changes to be committed to the database before any changes are made. This means no uncommitted changes are ever read from the database, and should ease the transition to another database layer which does not support transactions (but does support atomic writes), like LevelDB. For the getrawtransaction() RPC call, access to a txid-to-disk index would be preferable. As this index is not necessary or even useful for any other part of the implementation, it is not provided. Instead, getrawtransaction() uses the coin database to find the block height, and then scans that block to find the requested transaction. This is slow, but should suffice for debug purposes.
11 years ago
//////////////////////////////////////////////////////////////////////////////
//
// mapOrphanTransactions
//
bool AddOrphanTx(const CTransaction& tx, NodeId peer)
{
uint256 hash = tx.GetHash();
if (mapOrphanTransactions.count(hash))
return false;
// Ignore big transactions, to avoid a
// send-big-orphans memory exhaustion attack. If a peer has a legitimate
// large transaction with a missing parent then we assume
// it will rebroadcast it later, after the parent transaction(s)
// have been mined or received.
// 10,000 orphans, each of which is at most 5,000 bytes big is
// at most 500 megabytes of orphans:
unsigned int sz = tx.GetSerializeSize(SER_NETWORK, CTransaction::CURRENT_VERSION);
if (sz > 5000)
{
LogPrint("mempool", "ignoring large orphan tx (size: %u, hash: %s)\n", sz, hash.ToString());
return false;
}
mapOrphanTransactions[hash].tx = tx;
mapOrphanTransactions[hash].fromPeer = peer;
BOOST_FOREACH(const CTxIn& txin, tx.vin)
mapOrphanTransactionsByPrev[txin.prevout.hash].insert(hash);
LogPrint("mempool", "stored orphan tx %s (mapsz %u prevsz %u)\n", hash.ToString(),
mapOrphanTransactions.size(), mapOrphanTransactionsByPrev.size());
return true;
}
void static EraseOrphanTx(uint256 hash)
{
map<uint256, COrphanTx>::iterator it = mapOrphanTransactions.find(hash);
if (it == mapOrphanTransactions.end())
return;
BOOST_FOREACH(const CTxIn& txin, it->second.tx.vin)
{
map<uint256, set<uint256> >::iterator itPrev = mapOrphanTransactionsByPrev.find(txin.prevout.hash);
if (itPrev == mapOrphanTransactionsByPrev.end())
continue;
itPrev->second.erase(hash);
if (itPrev->second.empty())
mapOrphanTransactionsByPrev.erase(itPrev);
}
mapOrphanTransactions.erase(it);
}
void EraseOrphansFor(NodeId peer)
{
int nErased = 0;
map<uint256, COrphanTx>::iterator iter = mapOrphanTransactions.begin();
while (iter != mapOrphanTransactions.end())
{
map<uint256, COrphanTx>::iterator maybeErase = iter++; // increment to avoid iterator becoming invalid
if (maybeErase->second.fromPeer == peer)
{
EraseOrphanTx(maybeErase->second.tx.GetHash());
++nErased;
}
}
if (nErased > 0) LogPrint("mempool", "Erased %d orphan tx from peer %d\n", nErased, peer);
}
unsigned int LimitOrphanTxSize(unsigned int nMaxOrphans)
{
unsigned int nEvicted = 0;
while (mapOrphanTransactions.size() > nMaxOrphans)
{
// Evict a random orphan:
uint256 randomhash = GetRandHash();
map<uint256, COrphanTx>::iterator it = mapOrphanTransactions.lower_bound(randomhash);
if (it == mapOrphanTransactions.end())
it = mapOrphanTransactions.begin();
EraseOrphanTx(it->first);
++nEvicted;
}
return nEvicted;
}
bool IsStandardTx(const CTransaction& tx, string& reason)
{
AssertLockHeld(cs_main);
if (tx.nVersion > CTransaction::CURRENT_VERSION || tx.nVersion < 1) {
reason = "version";
return false;
}
// Treat non-final transactions as non-standard to prevent a specific type
// of double-spend attack, as well as DoS attacks. (if the transaction
// can't be mined, the attacker isn't expending resources broadcasting it)
// Basically we don't want to propagate transactions that can't be included in
// the next block.
//
// However, IsFinalTx() is confusing... Without arguments, it uses
// chainActive.Height() to evaluate nLockTime; when a block is accepted, chainActive.Height()
// is set to the value of nHeight in the block. However, when IsFinalTx()
// is called within CBlock::AcceptBlock(), the height of the block *being*
// evaluated is what is used. Thus if we want to know if a transaction can
// be part of the *next* block, we need to call IsFinalTx() with one more
// than chainActive.Height().
//
// Timestamps on the other hand don't get any special treatment, because we
// can't know what timestamp the next block will have, and there aren't
// timestamp applications where it matters.
if (!IsFinalTx(tx, chainActive.Height() + 1)) {
reason = "non-final";
return false;
}