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...instead of recursively locking unconditionally
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// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2020 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or
#include <validation.h>
#include <arith_uint256.h>
#include <chain.h>
#include <chainparams.h>
#include <checkqueue.h>
#include <consensus/consensus.h>
#include <consensus/merkle.h>
#include <consensus/tx_check.h>
#include <consensus/tx_verify.h>
#include <consensus/validation.h>
#include <cuckoocache.h>
#include <flatfile.h>
#include <hash.h>
#include <index/blockfilterindex.h>
#include <index/txindex.h>
#include <logging.h>
#include <logging/timer.h>
#include <node/coinstats.h>
#include <node/ui_interface.h>
#include <optional.h>
#include <policy/policy.h>
#include <policy/settings.h>
#include <pow.h>
#include <primitives/block.h>
#include <primitives/transaction.h>
#include <random.h>
#include <reverse_iterator.h>
#include <script/script.h>
#include <script/sigcache.h>
#include <shutdown.h>
#include <signet.h>
#include <timedata.h>
#include <tinyformat.h>
#include <txdb.h>
#include <txmempool.h>
#include <uint256.h>
#include <undo.h>
#include <util/check.h> // For NDEBUG compile time check
#include <util/moneystr.h>
#include <util/rbf.h>
#include <util/strencodings.h>
#include <util/system.h>
#include <util/translation.h>
#include <validationinterface.h>
#include <warnings.h>
#include <string>
#include <boost/algorithm/string/replace.hpp>
#define MICRO 0.000001
#define MILLI 0.001
* An extra transaction can be added to a package, as long as it only has one
* ancestor and is no larger than this. Not really any reason to make this
* configurable as it doesn't materially change DoS parameters.
static const unsigned int EXTRA_DESCENDANT_TX_SIZE_LIMIT = 10000;
/** Maximum kilobytes for transactions to store for processing during reorg */
static const unsigned int MAX_DISCONNECTED_TX_POOL_SIZE = 20000;
/** The pre-allocation chunk size for blk?????.dat files (since 0.8) */
static const unsigned int BLOCKFILE_CHUNK_SIZE = 0x1000000; // 16 MiB
/** The pre-allocation chunk size for rev?????.dat files (since 0.8) */
static const unsigned int UNDOFILE_CHUNK_SIZE = 0x100000; // 1 MiB
/** Time to wait between writing blocks/block index to disk. */
static constexpr std::chrono::hours DATABASE_WRITE_INTERVAL{1};
/** Time to wait between flushing chainstate to disk. */
static constexpr std::chrono::hours DATABASE_FLUSH_INTERVAL{24};
/** Maximum age of our tip for us to be considered current for fee estimation */
static constexpr std::chrono::hours MAX_FEE_ESTIMATION_TIP_AGE{3};
const std::vector<std::string> CHECKLEVEL_DOC {
"level 0 reads the blocks from disk",
"level 1 verifies block validity",
"level 2 verifies undo data",
"level 3 checks disconnection of tip blocks",
"level 4 tries to reconnect the blocks",
"each level includes the checks of the previous levels",
bool CBlockIndexWorkComparator::operator()(const CBlockIndex *pa, const CBlockIndex *pb) const {
// 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;
ChainstateManager g_chainman;
CChainState& ChainstateActive()
return *g_chainman.m_active_chainstate;
CChain& ChainActive()
return ::ChainstateActive().m_chain;
* Mutex to guard access to validation specific variables, such as reading
* or changing the chainstate.
* This may also need to be locked when updating the transaction pool, e.g. on
* AcceptToMemoryPool. See CTxMemPool::cs comment for details.
* The transaction pool has a separate lock to allow reading from it and the
* chainstate at the same time.
RecursiveMutex cs_main;
CBlockIndex *pindexBestHeader = nullptr;
Mutex g_best_block_mutex;
std::condition_variable g_best_block_cv;
uint256 g_best_block;
bool g_parallel_script_checks{false};
std::atomic_bool fImporting(false);
std::atomic_bool fReindex(false);
bool fHavePruned = false;
bool fPruneMode = false;
bool fRequireStandard = true;
bool fCheckBlockIndex = false;
bool fCheckpointsEnabled = DEFAULT_CHECKPOINTS_ENABLED;
uint64_t nPruneTarget = 0;
int64_t nMaxTipAge = DEFAULT_MAX_TIP_AGE;
uint256 hashAssumeValid;
arith_uint256 nMinimumChainWork;
CFeeRate minRelayTxFee = CFeeRate(DEFAULT_MIN_RELAY_TX_FEE);
// Internal stuff
namespace {
CBlockIndex* pindexBestInvalid = nullptr;
RecursiveMutex cs_LastBlockFile;
std::vector<CBlockFileInfo> vinfoBlockFile;
int nLastBlockFile = 0;
/** Global flag to indicate we should check to see if there are
* block/undo files that should be deleted. Set on startup
* or if we allocate more file space when we're in prune mode
bool fCheckForPruning = false;
/** Dirty block index entries. */
std::set<CBlockIndex*> setDirtyBlockIndex;
/** Dirty block file entries. */
std::set<int> setDirtyFileInfo;
} // anon namespace
CBlockIndex* BlockManager::LookupBlockIndex(const uint256& hash)
assert(std::addressof(g_chainman.BlockIndex()) == std::addressof(m_block_index));
BlockMap::const_iterator it = m_block_index.find(hash);
return it == m_block_index.end() ? nullptr : it->second;
CBlockIndex* BlockManager::FindForkInGlobalIndex(const CChain& chain, const CBlockLocator& locator)
assert(std::addressof(g_chainman.m_blockman) == std::addressof(*this));
// Find the latest block common to locator and chain - we expect that
// locator.vHave is sorted descending by height.
for (const uint256& hash : locator.vHave) {
CBlockIndex* pindex = LookupBlockIndex(hash);
if (pindex) {
if (chain.Contains(pindex))
return pindex;
if (pindex->GetAncestor(chain.Height()) == chain.Tip()) {
return chain.Tip();
return chain.Genesis();
std::unique_ptr<CBlockTreeDB> pblocktree;
bool CheckInputScripts(const CTransaction& tx, TxValidationState& state,
const CCoinsViewCache& inputs, unsigned int flags, bool cacheSigStore,
bool cacheFullScriptStore, PrecomputedTransactionData& txdata,
std::vector<CScriptCheck>* pvChecks = nullptr)
static FILE* OpenUndoFile(const FlatFilePos &pos, bool fReadOnly = false);
static FlatFileSeq BlockFileSeq();
static FlatFileSeq UndoFileSeq();
bool CheckFinalTx(const CBlockIndex* active_chain_tip, const CTransaction &tx, int flags)
assert(active_chain_tip); // TODO: Make active_chain_tip a reference
assert(std::addressof(*::ChainActive().Tip()) == std::addressof(*active_chain_tip));
// By convention a negative value for flags indicates that the
// current network-enforced consensus rules should be used. In
// a future soft-fork scenario that would mean checking which
// rules would be enforced for the next block and setting the
// appropriate flags. At the present time no soft-forks are
// scheduled, so no flags are set.
flags = std::max(flags, 0);
// CheckFinalTx() uses active_chain_tip.Height()+1 to evaluate
// nLockTime because 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 active_chain_tip.Height().
const int nBlockHeight = active_chain_tip->nHeight + 1;
// BIP113 requires that time-locked transactions have nLockTime set to
// less than the median time of the previous block they're contained in.
// When the next block is created its previous block will be the current
// chain tip, so we use that to calculate the median time passed to
// IsFinalTx() if LOCKTIME_MEDIAN_TIME_PAST is set.
const int64_t nBlockTime = (flags & LOCKTIME_MEDIAN_TIME_PAST)
? active_chain_tip->GetMedianTimePast()
: GetAdjustedTime();
return IsFinalTx(tx, nBlockHeight, nBlockTime);
bool TestLockPointValidity(CChain& active_chain, const LockPoints* lp)
// If there are relative lock times then the maxInputBlock will be set
// If there are no relative lock times, the LockPoints don't depend on the chain
if (lp->maxInputBlock) {
// Check whether ::ChainActive() is an extension of the block at which the LockPoints
// calculation was valid. If not LockPoints are no longer valid
assert(std::addressof(::ChainActive()) == std::addressof(active_chain));
if (!active_chain.Contains(lp->maxInputBlock)) {
return false;
// LockPoints still valid
return true;
bool CheckSequenceLocks(CChainState& active_chainstate,
const CTxMemPool& pool,
const CTransaction& tx,
int flags,
LockPoints* lp,
bool useExistingLockPoints)
assert(std::addressof(::ChainstateActive()) == std::addressof(active_chainstate));
CBlockIndex* tip = active_chainstate.m_chain.Tip();
assert(tip != nullptr);
CBlockIndex index;
index.pprev = tip;
// CheckSequenceLocks() uses active_chainstate.m_chain.Height()+1 to evaluate
// height based locks because when SequenceLocks() is called within
// ConnectBlock(), 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 use one more than active_chainstate.m_chain.Height()
index.nHeight = tip->nHeight + 1;
std::pair<int, int64_t> lockPair;
if (useExistingLockPoints) {
lockPair.first = lp->height;
lockPair.second = lp->time;
else {
// CoinsTip() contains the UTXO set for active_chainstate.m_chain.Tip()
CCoinsViewMemPool viewMemPool(&active_chainstate.CoinsTip(), pool);
std::vector<int> prevheights;
for (size_t txinIndex = 0; txinIndex <; txinIndex++) {
const CTxIn& txin =[txinIndex];
Coin coin;
if (!viewMemPool.GetCoin(txin.prevout, coin)) {
return error("%s: Missing input", __func__);
if (coin.nHeight == MEMPOOL_HEIGHT) {
// Assume all mempool transaction confirm in the next block
prevheights[txinIndex] = tip->nHeight + 1;
} else {
prevheights[txinIndex] = coin.nHeight;
lockPair = CalculateSequenceLocks(tx, flags, prevheights, index);
if (lp) {
lp->height = lockPair.first;
lp->time = lockPair.second;
// Also store the hash of the block with the highest height of
// all the blocks which have sequence locked prevouts.
// This hash needs to still be on the chain
// for these LockPoint calculations to be valid
// Note: It is impossible to correctly calculate a maxInputBlock
// if any of the sequence locked inputs depend on unconfirmed txs,
// except in the special case where the relative lock time/height
// is 0, which is equivalent to no sequence lock. Since we assume
// input height of tip+1 for mempool txs and test the resulting
// lockPair from CalculateSequenceLocks against tip+1. We know
// EvaluateSequenceLocks will fail if there was a non-zero sequence
// lock on a mempool input, so we can use the return value of
// CheckSequenceLocks to indicate the LockPoints validity
int maxInputHeight = 0;
for (const int height : prevheights) {
// Can ignore mempool inputs since we'll fail if they had non-zero locks
if (height != tip->nHeight+1) {
maxInputHeight = std::max(maxInputHeight, height);
lp->maxInputBlock = tip->GetAncestor(maxInputHeight);
return EvaluateSequenceLocks(index, lockPair);
// Returns the script flags which should be checked for a given block
static unsigned int GetBlockScriptFlags(const CBlockIndex* pindex, const Consensus::Params& chainparams);
static void LimitMempoolSize(CTxMemPool& pool, CCoinsViewCache& coins_cache, size_t limit, std::chrono::seconds age)
EXCLUSIVE_LOCKS_REQUIRED(pool.cs, ::cs_main)
int expired = pool.Expire(GetTime<std::chrono::seconds>() - age);
if (expired != 0) {
LogPrint(BCLog::MEMPOOL, "Expired %i transactions from the memory pool\n", expired);
std::vector<COutPoint> vNoSpendsRemaining;
pool.TrimToSize(limit, &vNoSpendsRemaining);
assert(std::addressof(::ChainstateActive().CoinsTip()) == std::addressof(coins_cache));
for (const COutPoint& removed : vNoSpendsRemaining)
static bool IsCurrentForFeeEstimation(CChainState& active_chainstate) EXCLUSIVE_LOCKS_REQUIRED(cs_main)
assert(std::addressof(::ChainstateActive()) == std::addressof(active_chainstate));
if (active_chainstate.IsInitialBlockDownload())
return false;
if (active_chainstate.m_chain.Tip()->GetBlockTime() < count_seconds(GetTime<std::chrono::seconds>() - MAX_FEE_ESTIMATION_TIP_AGE))
return false;
if (active_chainstate.m_chain.Height() < pindexBestHeader->nHeight - 1)
return false;
return true;
/* Make mempool consistent after a reorg, by re-adding or recursively erasing
* disconnected block transactions from the mempool, and also removing any
* other transactions from the mempool that are no longer valid given the new
* tip/height.
* Note: we assume that disconnectpool only contains transactions that are NOT
* confirmed in the current chain nor already in the mempool (otherwise,
* in-mempool descendants of such transactions would be removed).
* Passing fAddToMempool=false will skip trying to add the transactions back,
* and instead just erase from the mempool as needed.
static void UpdateMempoolForReorg(CChainState& active_chainstate, CTxMemPool& mempool, DisconnectedBlockTransactions& disconnectpool, bool fAddToMempool) EXCLUSIVE_LOCKS_REQUIRED(cs_main, mempool.cs)
assert(std::addressof(::ChainstateActive()) == std::addressof(active_chainstate));
std::vector<uint256> vHashUpdate;
// disconnectpool's insertion_order index sorts the entries from
// oldest to newest, but the oldest entry will be the last tx from the
// latest mined block that was disconnected.
// Iterate disconnectpool in reverse, so that we add transactions
// back to the mempool starting with the earliest transaction that had
// been previously seen in a block.
auto it = disconnectpool.queuedTx.get<insertion_order>().rbegin();
while (it != disconnectpool.queuedTx.get<insertion_order>().rend()) {
// ignore validation errors in resurrected transactions
if (!fAddToMempool || (*it)->IsCoinBase() ||
AcceptToMemoryPool(active_chainstate, mempool, *it, true /* bypass_limits */).m_result_type != MempoolAcceptResult::ResultType::VALID) {
// If the transaction doesn't make it in to the mempool, remove any
// transactions that depend on it (which would now be orphans).
mempool.removeRecursive(**it, MemPoolRemovalReason::REORG);
} else if (mempool.exists((*it)->GetHash())) {
// AcceptToMemoryPool/addUnchecked all assume that new mempool entries have
// no in-mempool children, which is generally not true when adding
// previously-confirmed transactions back to the mempool.
// UpdateTransactionsFromBlock finds descendants of any transactions in
// the disconnectpool that were added back and cleans up the mempool state.
// We also need to remove any now-immature transactions
mempool.removeForReorg(active_chainstate, STANDARD_LOCKTIME_VERIFY_FLAGS);
// Re-limit mempool size, in case we added any transactions
LimitMempoolSize(mempool, active_chainstate.CoinsTip(), gArgs.GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) * 1000000, std::chrono::hours{gArgs.GetArg("-mempoolexpiry", DEFAULT_MEMPOOL_EXPIRY)});
* Checks to avoid mempool polluting consensus critical paths since cached
* signature and script validity results will be reused if we validate this
* transaction again during block validation.
* */
static bool CheckInputsFromMempoolAndCache(const CTransaction& tx, TxValidationState& state,
const CCoinsViewCache& view, const CTxMemPool& pool,
unsigned int flags, PrecomputedTransactionData& txdata, CCoinsViewCache& coins_tip)
for (const CTxIn& txin : {
const Coin& coin = view.AccessCoin(txin.prevout);
// This coin was checked in PreChecks and MemPoolAccept
// has been holding cs_main since then.
if (coin.IsSpent()) return false;
// If the Coin is available, there are 2 possibilities:
// it is available in our current ChainstateActive UTXO set,
// or it's a UTXO provided by a transaction in our mempool.
// Ensure the scriptPubKeys in Coins from CoinsView are correct.
const CTransactionRef& txFrom = pool.get(txin.prevout.hash);
if (txFrom) {
assert(txFrom->GetHash() == txin.prevout.hash);
assert(txFrom->vout.size() > txin.prevout.n);
assert(txFrom->vout[txin.prevout.n] == coin.out);
} else {
assert(std::addressof(::ChainstateActive().CoinsTip()) == std::addressof(coins_tip));
const Coin& coinFromUTXOSet = coins_tip.AccessCoin(txin.prevout);
assert(coinFromUTXOSet.out == coin.out);
// Call CheckInputScripts() to cache signature and script validity against current tip consensus rules.
return CheckInputScripts(tx, state, view, flags, /* cacheSigStore = */ true, /* cacheFullSciptStore = */ true, txdata);
namespace {
class MemPoolAccept
explicit MemPoolAccept(CTxMemPool& mempool, CChainState& active_chainstate) : m_pool(mempool), m_view(&m_dummy), m_viewmempool(&active_chainstate.CoinsTip(), m_pool), m_active_chainstate(active_chainstate),
m_limit_ancestors(gArgs.GetArg("-limitancestorcount", DEFAULT_ANCESTOR_LIMIT)),
m_limit_ancestor_size(gArgs.GetArg("-limitancestorsize", DEFAULT_ANCESTOR_SIZE_LIMIT)*1000),
m_limit_descendants(gArgs.GetArg("-limitdescendantcount", DEFAULT_DESCENDANT_LIMIT)),
m_limit_descendant_size(gArgs.GetArg("-limitdescendantsize", DEFAULT_DESCENDANT_SIZE_LIMIT)*1000) {
assert(std::addressof(::ChainstateActive()) == std::addressof(m_active_chainstate));
// We put the arguments we're handed into a struct, so we can pass them
// around easier.
struct ATMPArgs {
const CChainParams& m_chainparams;
const int64_t m_accept_time;
const bool m_bypass_limits;
* Return any outpoints which were not previously present in the coins
* cache, but were added as a result of validating the tx for mempool
* acceptance. This allows the caller to optionally remove the cache
* additions if the associated transaction ends up being rejected by
* the mempool.
std::vector<COutPoint>& m_coins_to_uncache;
const bool m_test_accept;
// Single transaction acceptance
MempoolAcceptResult AcceptSingleTransaction(const CTransactionRef& ptx, ATMPArgs& args) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
// All the intermediate state that gets passed between the various levels
// of checking a given transaction.
struct Workspace {
explicit Workspace(const CTransactionRef& ptx) : m_ptx(ptx), m_hash(ptx->GetHash()) {}
std::set<uint256> m_conflicts;
CTxMemPool::setEntries m_all_conflicting;
CTxMemPool::setEntries m_ancestors;
std::unique_ptr<CTxMemPoolEntry> m_entry;
std::list<CTransactionRef> m_replaced_transactions;
bool m_replacement_transaction;
CAmount m_base_fees;
CAmount m_modified_fees;
CAmount m_conflicting_fees;
size_t m_conflicting_size;
const CTransactionRef& m_ptx;
const uint256& m_hash;
TxValidationState m_state;
// Run the policy checks on a given transaction, excluding any script checks.
// Looks up inputs, calculates feerate, considers replacement, evaluates
// package limits, etc. As this function can be invoked for "free" by a peer,
// only tests that are fast should be done here (to avoid CPU DoS).
bool PreChecks(ATMPArgs& args, Workspace& ws) EXCLUSIVE_LOCKS_REQUIRED(cs_main, m_pool.cs);
// Run the script checks using our policy flags. As this can be slow, we should
// only invoke this on transactions that have otherwise passed policy checks.
bool PolicyScriptChecks(const ATMPArgs& args, Workspace& ws, PrecomputedTransactionData& txdata) EXCLUSIVE_LOCKS_REQUIRED(cs_main, m_pool.cs);
// Re-run the script checks, using consensus flags, and try to cache the
// result in the scriptcache. This should be done after
// PolicyScriptChecks(). This requires that all inputs either be in our
// utxo set or in the mempool.
bool ConsensusScriptChecks(const ATMPArgs& args, Workspace& ws, PrecomputedTransactionData &txdata) EXCLUSIVE_LOCKS_REQUIRED(cs_main, m_pool.cs);
// Try to add the transaction to the mempool, removing any conflicts first.
// Returns true if the transaction is in the mempool after any size
// limiting is performed, false otherwise.
bool Finalize(const ATMPArgs& args, Workspace& ws) EXCLUSIVE_LOCKS_REQUIRED(cs_main, m_pool.cs);
// Compare a package's feerate against minimum allowed.
bool CheckFeeRate(size_t package_size, CAmount package_fee, TxValidationState& state) EXCLUSIVE_LOCKS_REQUIRED(cs_main, m_pool.cs)
CAmount mempoolRejectFee = m_pool.GetMinFee(gArgs.GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) * 1000000).GetFee(package_size);
if (mempoolRejectFee > 0 && package_fee < mempoolRejectFee) {
return state.Invalid(TxValidationResult::TX_MEMPOOL_POLICY, "mempool min fee not met", strprintf("%d < %d", package_fee, mempoolRejectFee));
if (package_fee < ::minRelayTxFee.GetFee(package_size)) {
return state.Invalid(TxValidationResult::TX_MEMPOOL_POLICY, "min relay fee not met", strprintf("%d < %d", package_fee, ::minRelayTxFee.GetFee(package_size)));
return true;
CTxMemPool& m_pool;
CCoinsViewCache m_view;
CCoinsViewMemPool m_viewmempool;
CCoinsView m_dummy;
CChainState& m_active_chainstate;
// The package limits in effect at the time of invocation.
const size_t m_limit_ancestors;
const size_t m_limit_ancestor_size;
// These may be modified while evaluating a transaction (eg to account for
// in-mempool conflicts; see below).
size_t m_limit_descendants;
size_t m_limit_descendant_size;
bool MemPoolAccept::PreChecks(ATMPArgs& args, Workspace& ws)
const CTransactionRef& ptx = ws.m_ptx;
const CTransaction& tx = *ws.m_ptx;
const uint256& hash = ws.m_hash;
// Copy/alias what we need out of args
const int64_t nAcceptTime = args.m_accept_time;
const bool bypass_limits = args.m_bypass_limits;
std::vector<COutPoint>& coins_to_uncache = args.m_coins_to_uncache;
// Alias what we need out of ws
TxValidationState& state = ws.m_state;
std::set<uint256>& setConflicts = ws.m_conflicts;
CTxMemPool::setEntries& allConflicting = ws.m_all_conflicting;
CTxMemPool::setEntries& setAncestors = ws.m_ancestors;
std::unique_ptr<CTxMemPoolEntry>& entry = ws.m_entry;
bool& fReplacementTransaction = ws.m_replacement_transaction;
CAmount& nModifiedFees = ws.m_modified_fees;
CAmount& nConflictingFees = ws.m_conflicting_fees;
size_t& nConflictingSize = ws.m_conflicting_size;
if (!CheckTransaction(tx, state)) {
return false; // state filled in by CheckTransaction
// Coinbase is only valid in a block, not as a loose transaction
if (tx.IsCoinBase())
return state.Invalid(TxValidationResult::TX_CONSENSUS, "coinbase");
// Rather not work on nonstandard transactions (unless -testnet/-regtest)
std::string reason;
if (fRequireStandard && !IsStandardTx(tx, reason))
return state.Invalid(TxValidationResult::TX_NOT_STANDARD, reason);
// Do not work on transactions that are too small.
// A transaction with 1 segwit input and 1 P2WPHK output has non-witness size of 82 bytes.
// Transactions smaller than this are not relayed to mitigate CVE-2017-12842 by not relaying
// 64-byte transactions.
return state.Invalid(TxValidationResult::TX_NOT_STANDARD, "tx-size-small");
// Only accept nLockTime-using transactions that can be mined in the next
// block; we don't want our mempool filled up with transactions that can't
// be mined yet.
assert(std::addressof(::ChainActive()) == std::addressof(m_active_chainstate.m_chain));
if (!CheckFinalTx(m_active_chainstate.m_chain.Tip(), tx, STANDARD_LOCKTIME_VERIFY_FLAGS))
return state.Invalid(TxValidationResult::TX_PREMATURE_SPEND, "non-final");
// is it already in the memory pool?
if (m_pool.exists(hash)) {
return state.Invalid(TxValidationResult::TX_CONFLICT, "txn-already-in-mempool");
// Check for conflicts with in-memory transactions
for (const CTxIn &txin :
const CTransaction* ptxConflicting = m_pool.GetConflictTx(txin.prevout);
if (ptxConflicting) {
if (!setConflicts.count(ptxConflicting->GetHash()))
// Allow opt-out of transaction replacement by setting
// nSequence > MAX_BIP125_RBF_SEQUENCE (SEQUENCE_FINAL-2) on all inputs.
// SEQUENCE_FINAL-1 is picked to still allow use of nLockTime by
// non-replaceable transactions. All inputs rather than just one
// is for the sake of multi-party protocols, where we don't
// want a single party to be able to disable replacement.
// The opt-out ignores descendants as anyone relying on
// first-seen mempool behavior should be checking all
// unconfirmed ancestors anyway; doing otherwise is hopelessly
// insecure.
bool fReplacementOptOut = true;
for (const CTxIn &_txin : ptxConflicting->vin)
if (_txin.nSequence <= MAX_BIP125_RBF_SEQUENCE)
fReplacementOptOut = false;
if (fReplacementOptOut) {
return state.Invalid(TxValidationResult::TX_MEMPOOL_POLICY, "txn-mempool-conflict");
LockPoints lp;
assert(std::addressof(::ChainstateActive().CoinsTip()) == std::addressof(m_active_chainstate.CoinsTip()));
const CCoinsViewCache& coins_cache = m_active_chainstate.CoinsTip();
// do all inputs exist?
for (const CTxIn& txin : {
if (!coins_cache.HaveCoinInCache(txin.prevout)) {
// Note: this call may add txin.prevout to the coins cache
// (coins_cache.cacheCoins) by way of FetchCoin(). It should be removed
// later (via coins_to_uncache) if this tx turns out to be invalid.
if (!m_view.HaveCoin(txin.prevout)) {
// Are inputs missing because we already have the tx?
for (size_t out = 0; out < tx.vout.size(); out++) {
// Optimistically just do efficient check of cache for outputs
if (coins_cache.HaveCoinInCache(COutPoint(hash, out))) {
return state.Invalid(TxValidationResult::TX_CONFLICT, "txn-already-known");
// Otherwise assume this might be an orphan tx for which we just haven't seen parents yet
return state.Invalid(TxValidationResult::TX_MISSING_INPUTS, "bad-txns-inputs-missingorspent");
// Bring the best block into scope
// we have all inputs cached now, so switch back to dummy (to protect
// against bugs where we pull more inputs from disk that miss being added
// to coins_to_uncache)
// Only accept BIP68 sequence locked transactions that can be mined in the next
// block; we don't want our mempool filled up with transactions that can't
// be mined yet.
// Must keep pool.cs for this unless we change CheckSequenceLocks to take a
// CoinsViewCache instead of create its own
assert(std::addressof(::ChainstateActive()) == std::addressof(m_active_chainstate));
if (!CheckSequenceLocks(m_active_chainstate, m_pool, tx, STANDARD_LOCKTIME_VERIFY_FLAGS, &lp))
return state.Invalid(TxValidationResult::TX_PREMATURE_SPEND, "non-BIP68-final");
assert(std::addressof(g_chainman.m_blockman) == std::addressof(m_active_chainstate.m_blockman));
if (!Consensus::CheckTxInputs(tx, state, m_view, m_active_chainstate.m_blockman.GetSpendHeight(m_view), ws.m_base_fees)) {
return false; // state filled in by CheckTxInputs
// Check for non-standard pay-to-script-hash in inputs
const auto& params = args.m_chainparams.GetConsensus();
assert(std::addressof(::ChainActive()) == std::addressof(m_active_chainstate.m_chain));
auto taproot_state = VersionBitsState(m_active_chainstate.m_chain.Tip(), params, Consensus::DEPLOYMENT_TAPROOT, versionbitscache);
if (fRequireStandard && !AreInputsStandard(tx, m_view, taproot_state == ThresholdState::ACTIVE)) {
return state.Invalid(TxValidationResult::TX_INPUTS_NOT_STANDARD, "bad-txns-nonstandard-inputs");
// Check for non-standard witnesses.
if (tx.HasWitness() && fRequireStandard && !IsWitnessStandard(tx, m_view))
return state.Invalid(TxValidationResult::TX_WITNESS_MUTATED, "bad-witness-nonstandard");
int64_t nSigOpsCost = GetTransactionSigOpCost(tx, m_view, STANDARD_SCRIPT_VERIFY_FLAGS);
// nModifiedFees includes any fee deltas from PrioritiseTransaction
nModifiedFees = ws.m_base_fees;
m_pool.ApplyDelta(hash, nModifiedFees);
// Keep track of transactions that spend a coinbase, which we re-scan
// during reorgs to ensure COINBASE_MATURITY is still met.
bool fSpendsCoinbase = false;
for (const CTxIn &txin : {
const Coin &coin = m_view.AccessCoin(txin.prevout);
if (coin.IsCoinBase()) {
fSpendsCoinbase = true;
assert(std::addressof(::ChainActive()) == std::addressof(m_active_chainstate.m_chain));
entry.reset(new CTxMemPoolEntry(ptx, ws.m_base_fees, nAcceptTime, m_active_chainstate.m_chain.Height(),
fSpendsCoinbase, nSigOpsCost, lp));
unsigned int nSize = entry->GetTxSize();
return state.Invalid(TxValidationResult::TX_NOT_STANDARD, "bad-txns-too-many-sigops",
strprintf("%d", nSigOpsCost));
// No transactions are allowed below minRelayTxFee except from disconnected
// blocks
if (!bypass_limits && !CheckFeeRate(nSize, nModifiedFees, state)) return false;
const CTxMemPool::setEntries setIterConflicting = m_pool.GetIterSet(setConflicts);
// Calculate in-mempool ancestors, up to a limit.
if (setConflicts.size() == 1) {
// In general, when we receive an RBF transaction with mempool conflicts, we want to know whether we
// would meet the chain limits after the conflicts have been removed. However, there isn't a practical
// way to do this short of calculating the ancestor and descendant sets with an overlay cache of
// changed mempool entries. Due to both implementation and runtime complexity concerns, this isn't
// very realistic, thus we only ensure a limited set of transactions are RBF'able despite mempool
// conflicts here. Importantly, we need to ensure that some transactions which were accepted using
// the below carve-out are able to be RBF'ed, without impacting the security the carve-out provides
// for off-chain contract systems (see link in the comment below).
// Specifically, the subset of RBF transactions which we allow despite chain limits are those which
// conflict directly with exactly one other transaction (but may evict children of said transaction),
// and which are not adding any new mempool dependencies. Note that the "no new mempool dependencies"
// check is accomplished later, so we don't bother doing anything about it here, but if BIP 125 is
// amended, we may need to move that check to here instead of removing it wholesale.
// Such transactions are clearly not merging any existing packages, so we are only concerned with
// ensuring that (a) no package is growing past the package size (not count) limits and (b) we are
// not allowing something to effectively use the (below) carve-out spot when it shouldn't be allowed
// to.
// To check these we first check if we meet the RBF criteria, above, and increment the descendant
// limits by the direct conflict and its descendants (as these are recalculated in
// CalculateMempoolAncestors by assuming the new transaction being added is a new descendant, with no
// removals, of each parent's existing dependent set). The ancestor count limits are unmodified (as
// the ancestor limits should be the same for both our new transaction and any conflicts).
// We don't bother incrementing m_limit_descendants by the full removal count as that limit never comes
// into force here (as we're only adding a single transaction).
assert(setIterConflicting.size() == 1);
CTxMemPool::txiter conflict = *setIterConflicting.begin();
m_limit_descendants += 1;
m_limit_descendant_size += conflict->GetSizeWithDescendants();
std::string errString;
if (!m_pool.CalculateMemPoolAncestors(*entry, setAncestors, m_limit_ancestors, m_limit_ancestor_size, m_limit_descendants, m_limit_descendant_size, errString)) {
// If CalculateMemPoolAncestors fails second time, we want the original error string.
std::string dummy_err_string;
// Contracting/payment channels CPFP carve-out:
// If the new transaction is relatively small (up to 40k weight)
// and has at most one ancestor (ie ancestor limit of 2, including
// the new transaction), allow it if its parent has exactly the
// descendant limit descendants.
// This allows protocols which rely on distrusting counterparties
// being able to broadcast descendants of an unconfirmed transaction
// to be secure by simply only having two immediately-spendable
// outputs - one for each counterparty. For more info on the uses for
// this, see
!m_pool.CalculateMemPoolAncestors(*entry, setAncestors, 2, m_limit_ancestor_size, m_limit_descendants + 1, m_limit_descendant_size + EXTRA_DESCENDANT_TX_SIZE_LIMIT, dummy_err_string)) {
return state.Invalid(TxValidationResult::TX_MEMPOOL_POLICY, "too-long-mempool-chain", errString);
// A transaction that spends outputs that would be replaced by it is invalid. Now
// that we have the set of all ancestors we can detect this
// pathological case by making sure setConflicts and setAncestors don't
// intersect.
for (CTxMemPool::txiter ancestorIt : setAncestors)
const uint256 &hashAncestor = ancestorIt->GetTx().GetHash();
if (setConflicts.count(hashAncestor))
return state.Invalid(TxValidationResult::TX_CONSENSUS, "bad-txns-spends-conflicting-tx",
strprintf("%s spends conflicting transaction %s",
// Check if it's economically rational to mine this transaction rather
// than the ones it replaces.
nConflictingFees = 0;
nConflictingSize = 0;
uint64_t nConflictingCount = 0;
// If we don't hold the lock allConflicting might be incomplete; the
// subsequent RemoveStaged() and addUnchecked() calls don't guarantee
// mempool consistency for us.
fReplacementTransaction = setConflicts.size();
if (fReplacementTransaction)
CFeeRate newFeeRate(nModifiedFees, nSize);
std::set<uint256> setConflictsParents;
const int maxDescendantsToVisit = 100;
for (const auto& mi : setIterConflicting) {
// Don't allow the replacement to reduce the feerate of the
// mempool.
// We usually don't want to accept replacements with lower
// feerates than what they replaced as that would lower the
// feerate of the next block. Requiring that the feerate always
// be increased is also an easy-to-reason about way to prevent
// DoS attacks via replacements.
// We only consider the feerates of transactions being directly
// replaced, not their indirect descendants. While that does
// mean high feerate children are ignored when deciding whether
// or not to replace, we do require the replacement to pay more
// overall fees too, mitigating most cases.
CFeeRate oldFeeRate(mi->GetModifiedFee(), mi->GetTxSize());
if (newFeeRate <= oldFeeRate)
return state.Invalid(TxValidationResult::TX_MEMPOOL_POLICY, "insufficient fee",
strprintf("rejecting replacement %s; new feerate %s <= old feerate %s",
for (const CTxIn &txin : mi->GetTx().vin)
nConflictingCount += mi->GetCountWithDescendants();
// This potentially overestimates the number of actual descendants
// but we just want to be conservative to avoid doing too much
// work.
if (nConflictingCount <= maxDescendantsToVisit) {
// If not too many to replace, then calculate the set of
// transactions that would have to be evicted
for (CTxMemPool::txiter it : setIterConflicting) {
m_pool.CalculateDescendants(it, allConflicting);
for (CTxMemPool::txiter it : allConflicting) {
nConflictingFees += it->GetModifiedFee();
nConflictingSize += it->GetTxSize();
} else {
return state.Invalid(TxValidationResult::TX_MEMPOOL_POLICY, "too many potential replacements",
strprintf("rejecting replacement %s; too many potential replacements (%d > %d)\n",
for (unsigned int j = 0; j <; j++)
// We don't want to accept replacements that require low
// feerate junk to be mined first. Ideally we'd keep track of
// the ancestor feerates and make the decision based on that,
// but for now requiring all new inputs to be confirmed works.
// Note that if you relax this to make RBF a little more useful,
// this may break the CalculateMempoolAncestors RBF relaxation,
// above. See the comment above the first CalculateMempoolAncestors
// call for more info.
if (!setConflictsParents.count([j].prevout.hash))
// Rather than check the UTXO set - potentially expensive -
// it's cheaper to just check if the new input refers to a
// tx that's in the mempool.
if (m_pool.exists([j].prevout.hash)) {
return state.Invalid(TxValidationResult::TX_MEMPOOL_POLICY, "replacement-adds-unconfirmed",
strprintf("replacement %s adds unconfirmed input, idx %d",
hash.ToString(), j));
// The replacement must pay greater fees than the transactions it
// replaces - if we did the bandwidth used by those conflicting
// transactions would not be paid for.
if (nModifiedFees < nConflictingFees)
return state.Invalid(TxValidationResult::TX_MEMPOOL_POLICY, "insufficient fee",
strprintf("rejecting replacement %s, less fees than conflicting txs; %s < %s",
hash.ToString(), FormatMoney(nModifiedFees), FormatMoney(nConflictingFees)));
// Finally in addition to paying more fees than the conflicts the
// new transaction must pay for its own bandwidth.
CAmount nDeltaFees = nModifiedFees - nConflictingFees;
if (nDeltaFees < ::incrementalRelayFee.GetFee(nSize))
return state.Invalid(TxValidationResult::TX_MEMPOOL_POLICY, "insufficient fee",
strprintf("rejecting replacement %s, not enough additional fees to relay; %s < %s",
return true;
bool MemPoolAccept::PolicyScriptChecks(const ATMPArgs& args, Workspace& ws, PrecomputedTransactionData& txdata)
const CTransaction& tx = *ws.m_ptx;
TxValidationState& state = ws.m_state;
constexpr unsigned int scriptVerifyFlags = STANDARD_SCRIPT_VERIFY_FLAGS;
// Check input scripts and signatures.
// This is done last to help prevent CPU exhaustion denial-of-service attacks.
if (!CheckInputScripts(tx, state, m_view, scriptVerifyFlags, true, false, txdata)) {
// need to turn both off, and compare against just turning off CLEANSTACK
// to see if the failure is specifically due to witness validation.
TxValidationState state_dummy; // Want reported failures to be from first CheckInputScripts
if (!tx.HasWitness() && CheckInputScripts(tx, state_dummy, m_view, scriptVerifyFlags & ~(SCRIPT_VERIFY_WITNESS | SCRIPT_VERIFY_CLEANSTACK), true, false, txdata) &&
!CheckInputScripts(tx, state_dummy, m_view, scriptVerifyFlags & ~SCRIPT_VERIFY_CLEANSTACK, true, false, txdata)) {
// Only the witness is missing, so the transaction itself may be fine.
state.GetRejectReason(), state.GetDebugMessage());
return false; // state filled in by CheckInputScripts
return true;
bool MemPoolAccept::ConsensusScriptChecks(const ATMPArgs& args, Workspace& ws, PrecomputedTransactionData& txdata)
const CTransaction& tx = *ws.m_ptx;
const uint256& hash = ws.m_hash;
TxValidationState& state = ws.m_state;
const CChainParams& chainparams = args.m_chainparams;
// Check again against the current block tip's script verification
// flags to cache our script execution flags. This is, of course,
// useless if the next block has different script flags from the
// previous one, but because the cache tracks script flags for us it
// will auto-invalidate and we'll just have a few blocks of extra
// misses on soft-fork activation.
// This is also useful in case of bugs in the standard flags that cause
// transactions to pass as valid when they're actually invalid. For
// instance the STRICTENC flag was incorrectly allowing certain
// CHECKSIG NOT scripts to pass, even though they were invalid.
// There is a similar check in CreateNewBlock() to prevent creating
// invalid blocks (using TestBlockValidity), however allowing such
// transactions into the mempool can be exploited as a DoS attack.
assert(std::addressof(::ChainActive()) == std::addressof(m_active_chainstate.m_chain));
unsigned int currentBlockScriptVerifyFlags = GetBlockScriptFlags(m_active_chainstate.m_chain.Tip(), chainparams.GetConsensus());
assert(std::addressof(::ChainstateActive().CoinsTip()) == std::addressof(m_active_chainstate.CoinsTip()));
if (!CheckInputsFromMempoolAndCache(tx, state, m_view, m_pool, currentBlockScriptVerifyFlags, txdata, m_active_chainstate.CoinsTip())) {
return error("%s: BUG! PLEASE REPORT THIS! CheckInputScripts failed against latest-block but not STANDARD flags %s, %s",
__func__, hash.ToString(), state.ToString());
return true;
bool MemPoolAccept::Finalize(const ATMPArgs& args, Workspace& ws)
const CTransaction& tx = *ws.m_ptx;
const uint256& hash = ws.m_hash;
TxValidationState& state = ws.m_state;
const bool bypass_limits = args.m_bypass_limits;
CTxMemPool::setEntries& allConflicting = ws.m_all_conflicting;
CTxMemPool::setEntries& setAncestors = ws.m_ancestors;
const CAmount& nModifiedFees = ws.m_modified_fees;
const CAmount& nConflictingFees = ws.m_conflicting_fees;
const size_t& nConflictingSize = ws.m_conflicting_size;
const bool fReplacementTransaction = ws.m_replacement_transaction;
std::unique_ptr<CTxMemPoolEntry>& entry = ws.m_entry;
// Remove conflicting transactions from the mempool
for (CTxMemPool::txiter it : allConflicting)
LogPrint(BCLog::MEMPOOL, "replacing tx %s with %s for %s additional fees, %d delta bytes\n",
FormatMoney(nModifiedFees - nConflictingFees),
(int)entry->GetTxSize() - (int)nConflictingSize);
m_pool.RemoveStaged(allConflicting, false, MemPoolRemovalReason::REPLACED);
// This transaction should only count for fee estimation if:
// - it isn't a BIP 125 replacement transaction (may not be widely supported)
// - it's not being re-added during a reorg which bypasses typical mempool fee limits
// - the node is not behind
// - the transaction is not dependent on any other transactions in the mempool
assert(std::addressof(::ChainstateActive()) == std::addressof(m_active_chainstate));
bool validForFeeEstimation = !fReplacementTransaction && !bypass_limits && IsCurrentForFeeEstimation(m_active_chainstate) && m_pool.HasNoInputsOf(tx);
// Store transaction in memory
m_pool.addUnchecked(*entry, setAncestors, validForFeeEstimation);
// trim mempool and check if tx was trimmed
if (!bypass_limits) {
assert(std::addressof(::ChainstateActive().CoinsTip()) == std::addressof(m_active_chainstate.CoinsTip()));
LimitMempoolSize(m_pool, m_active_chainstate.CoinsTip(), gArgs.GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) * 1000000, std::chrono::hours{gArgs.GetArg("-mempoolexpiry", DEFAULT_MEMPOOL_EXPIRY)});
if (!m_pool.exists(hash))
return state.Invalid(TxValidationResult::TX_MEMPOOL_POLICY, "mempool full");
return true;
MempoolAcceptResult MemPoolAccept::AcceptSingleTransaction(const CTransactionRef& ptx, ATMPArgs& args)
LOCK(m_pool.cs); // mempool "read lock" (held through GetMainSignals().TransactionAddedToMempool())
Workspace ws(ptx);
if (!PreChecks(args, ws)) return MempoolAcceptResult(ws.m_state);
// Only compute the precomputed transaction data if we need to verify
// scripts (ie, other policy checks pass). We perform the inexpensive
// checks first and avoid hashing and signature verification unless those
// checks pass, to mitigate CPU exhaustion denial-of-service attacks.
PrecomputedTransactionData txdata;
if (!PolicyScriptChecks(args, ws, txdata)) return MempoolAcceptResult(ws.m_state);
if (!ConsensusScriptChecks(args, ws, txdata)) return MempoolAcceptResult(ws.m_state);
// Tx was accepted, but not added
if (args.m_test_accept) {
return MempoolAcceptResult(std::move(ws.m_replaced_transactions), ws.m_base_fees);
if (!Finalize(args, ws)) return MempoolAcceptResult(ws.m_state);
GetMainSignals().TransactionAddedToMempool(ptx, m_pool.GetAndIncrementSequence());
return MempoolAcceptResult(std::move(ws.m_replaced_transactions), ws.m_base_fees);
} // anon namespace
/** (try to) add transaction to memory pool with a specified acceptance time **/
static MempoolAcceptResult AcceptToMemoryPoolWithTime(const CChainParams& chainparams, CTxMemPool& pool,
CChainState& active_chainstate,
const CTransactionRef &tx, int64_t nAcceptTime,
bool bypass_limits, bool test_accept)
std::vector<COutPoint> coins_to_uncache;
MemPoolAccept::ATMPArgs args { chainparams, nAcceptTime, bypass_limits, coins_to_uncache, test_accept };
assert(std::addressof(::ChainstateActive()) == std::addressof(active_chainstate));
const MempoolAcceptResult result = MemPoolAccept(pool, active_chainstate).AcceptSingleTransaction(tx, args);
if (result.m_result_type != MempoolAcceptResult::ResultType::VALID) {
// Remove coins that were not present in the coins cache before calling ATMPW;
// this is to prevent memory DoS in case we receive a large number of
// invalid transactions that attempt to overrun the in-memory coins cache
// (`CCoinsViewCache::cacheCoins`).
for (const COutPoint& hashTx : coins_to_uncache)
// After we've (potentially) uncached entries, ensure our coins cache is still within its size limits
BlockValidationState state_dummy;
active_chainstate.FlushStateToDisk(chainparams, state_dummy, FlushStateMode::PERIODIC);
return result;
MempoolAcceptResult AcceptToMemoryPool(CChainState& active_chainstate, CTxMemPool& pool, const CTransactionRef& tx,
bool bypass_limits, bool test_accept)
assert(std::addressof(::ChainstateActive()) == std::addressof(active_chainstate));
return AcceptToMemoryPoolWithTime(Params(), pool, active_chainstate, tx, GetTime(), bypass_limits, test_accept);
CTransactionRef GetTransaction(const CBlockIndex* const block_index, const CTxMemPool* const mempool, const uint256& hash, const Consensus::Params& consensusParams, uint256& hashBlock)
if (block_index) {
CBlock block;
if (ReadBlockFromDisk(block, block_index, consensusParams)) {
for (const auto& tx : block.vtx) {
if (tx->GetHash() == hash) {
hashBlock = block_index->GetBlockHash();
return tx;
return nullptr;
if (mempool) {
CTransactionRef ptx = mempool->get(hash);
if (ptx) return ptx;
if (g_txindex) {
CTransactionRef tx;
if (g_txindex->FindTx(hash, hashBlock, tx)) return tx;
return nullptr;
// CBlock and CBlockIndex
static bool WriteBlockToDisk(const CBlock& block, FlatFilePos& pos, const CMessageHeader::MessageStartChars& messageStart)
// Open history file to append
CAutoFile fileout(OpenBlockFile(pos), SER_DISK, CLIENT_VERSION);
if (fileout.IsNull())
return error("WriteBlockToDisk: OpenBlockFile failed");
// Write index header
unsigned int nSize = GetSerializeSize(block, fileout.GetVersion());
fileout << messageStart << nSize;
// Write block
long fileOutPos = ftell(fileout.Get());
if (fileOutPos < 0)
return error("WriteBlockToDisk: ftell failed");
pos.nPos = (unsigned int)fileOutPos;
fileout << block;
return true;
bool ReadBlockFromDisk(CBlock& block, const FlatFilePos& pos, const Consensus::Params& consensusParams)
// Open history file to read
CAutoFile filein(OpenBlockFile(pos, true), SER_DISK, CLIENT_VERSION);
if (filein.IsNull())
return error("ReadBlockFromDisk: OpenBlockFile failed for %s", pos.ToString());
// Read block
try {
filein >> block;
catch (const std::exception& e) {
return error("%s: Deserialize or I/O error - %s at %s", __func__, e.what(), pos.ToString());
// Check the header
if (!CheckProofOfWork(block.GetHash(), block.nBits, consensusParams))
return error("ReadBlockFromDisk: Errors in block header at %s", pos.ToString());
// Signet only: check block solution
if (consensusParams.signet_blocks && !CheckSignetBlockSolution(block, consensusParams)) {
return error("ReadBlockFromDisk: Errors in block solution at %s", pos.ToString());
return true;
bool ReadBlockFromDisk(CBlock& block, const CBlockIndex* pindex, const Consensus::Params& consensusParams)
FlatFilePos blockPos;
blockPos = pindex->GetBlockPos();
if (!ReadBlockFromDisk(block, blockPos, consensusParams))
return false;
if (block.GetHash() != pindex->GetBlockHash())
return error("ReadBlockFromDisk(CBlock&, CBlockIndex*): GetHash() doesn't match index for %s at %s",
pindex->ToString(), pindex->GetBlockPos().ToString());
return true;
bool ReadRawBlockFromDisk(std::vector<uint8_t>& block, const FlatFilePos& pos, const CMessageHeader::MessageStartChars& message_start)
FlatFilePos hpos = pos;
hpos.nPos -= 8; // Seek back 8 bytes for meta header
CAutoFile filein(OpenBlockFile(hpos, true), SER_DISK, CLIENT_VERSION);
if (filein.IsNull()) {
return error("%s: OpenBlockFile failed for %s", __func__, pos.ToString());
try {
CMessageHeader::MessageStartChars blk_start;
unsigned int blk_size;
filein >> blk_start >> blk_size;
if (memcmp(blk_start, message_start, CMessageHeader::MESSAGE_START_SIZE)) {
return error("%s: Block magic mismatch for %s: %s versus expected %s", __func__, pos.ToString(),
if (blk_size > MAX_SIZE) {
return error("%s: Block data is larger than maximum deserialization size for %s: %s versus %s", __func__, pos.ToString(),
blk_size, MAX_SIZE);
block.resize(blk_size); // Zeroing of memory is intentional here*), blk_size);
} catch(const std::exception& e) {
return error("%s: Read from block file failed: %s for %s", __func__, e.what(), pos.ToString());
return true;
bool ReadRawBlockFromDisk(std::vector<uint8_t>& block, const CBlockIndex* pindex, const CMessageHeader::MessageStartChars& message_start)
FlatFilePos block_pos;
block_pos = pindex->GetBlockPos();
return ReadRawBlockFromDisk(block, block_pos, message_start);
CAmount GetBlockSubsidy(int nHeight, const Consensus::Params& consensusParams)
int halvings = nHeight / consensusParams.nSubsidyHalvingInterval;
// Force block reward to zero when right shift is undefined.
if (halvings >= 64)
return 0;
CAmount nSubsidy = 50 * COIN;
// Subsidy is cut in half every 210,000 blocks which will occur approximately every 4 years.
nSubsidy >>= halvings;
return nSubsidy;
std::string ldb_name,
size_t cache_size_bytes,
bool in_memory,
bool should_wipe) : m_dbview(
GetDataDir() / ldb_name, cache_size_bytes, in_memory, should_wipe),
m_catcherview(&m_dbview) {}
void CoinsViews::InitCache()
m_cacheview = MakeUnique<CCoinsViewCache>(&m_catcherview);
CChainState::CChainState(CTxMemPool& mempool, BlockManager& blockman, uint256 from_snapshot_blockhash)
: m_mempool(mempool),
m_from_snapshot_blockhash(from_snapshot_blockhash) {}
void CChainState::InitCoinsDB(
size_t cache_size_bytes,
bool in_memory,
bool should_wipe,
std::string leveldb_name)
if (!m_from_snapshot_blockhash.IsNull()) {
leveldb_name += "_" + m_from_snapshot_blockhash.ToString();
m_coins_views = MakeUnique<CoinsViews>(
leveldb_name, cache_size_bytes, in_memory, should_wipe);
void CChainState::InitCoinsCache(size_t cache_size_bytes)
assert(m_coins_views != nullptr);
m_coinstip_cache_size_bytes = cache_size_bytes;
// Note that though this is marked const, we may end up modifying `m_cached_finished_ibd`, which
// is a performance-related implementation detail. This function must be marked
// `const` so that `CValidationInterface` clients (which are given a `const CChainState*`)
// can call it.
bool CChainState::IsInitialBlockDownload() const
// Optimization: pre-test latch before taking the lock.
if (m_cached_finished_ibd.load(std::memory_order_relaxed))
return false;
if (m_cached_finished_ibd.load(std::memory_order_relaxed))
return false;
if (fImporting || fReindex)
return true;
if (m_chain.Tip() == nullptr)
return true;
if (m_chain.Tip()->nChainWork < nMinimumChainWork)
return true;
if (m_chain.Tip()->GetBlockTime() < (GetTime() - nMaxTipAge))
return true;
LogPrintf("Leaving InitialBlockDownload (latching to false)\n");, std::memory_order_relaxed);
return false;
static void AlertNotify(const std::string& strMessage)
std::string strCmd = gArgs.GetArg("-alertnotify", "");
if (strCmd.empty()) return;
// Alert text should be plain ascii coming from a trusted source, but to
// be safe we first strip anything not in safeChars, then add single quotes around
// the whole string before passing it to the shell:
std::string singleQuote("'");
std::string safeStatus = SanitizeString(strMessage);
safeStatus = singleQuote+safeStatus+singleQuote;
boost::replace_all(strCmd, "%s", safeStatus);
std::thread t(runCommand, strCmd);
t.detach(); // thread runs free
void CChainState::CheckForkWarningConditions()
assert(std::addressof(::ChainstateActive()) == std::addressof(*this));
// Before we get past initial download, we cannot reliably alert about forks
// (we assume we don't get stuck on a fork before finishing our initial sync)
if (IsInitialBlockDownload()) {
if (pindexBestInvalid && pindexBestInvalid->nChainWork > m_chain.Tip()->nChainWork + (GetBlockProof(*m_chain.Tip()) * 6)) {
LogPrintf("%s: Warning: Found invalid chain at least ~6 blocks longer than our best chain.\nChain state database corruption likely.\n", __func__);
} else {
// Called both upon regular invalid block discovery *and* InvalidateBlock
void CChainState::InvalidChainFound(CBlockIndex* pindexNew)
assert(std::addressof(::ChainstateActive()) == std::addressof(*this));
if (!pindexBestInvalid || pindexNew->nChainWork > pindexBestInvalid->nChainWork)
pindexBestInvalid = pindexNew;
if (pindexBestHeader != nullptr && pindexBestHeader->GetAncestor(pindexNew->nHeight) == pindexNew) {
pindexBestHeader = m_chain.Tip();
LogPrintf("%s: invalid block=%s height=%d log2_work=%f date=%s\n", __func__,
pindexNew->GetBlockHash().ToString(), pindexNew->nHeight,
log(pindexNew->nChainWork.getdouble())/log(2.0), FormatISO8601DateTime(pindexNew->GetBlockTime()));
CBlockIndex *tip = m_chain.Tip();
assert (tip);
LogPrintf("%s: current best=%s height=%d log2_work=%f date=%s\n", __func__,
tip->GetBlockHash().ToString(), m_chain.Height(), log(tip->nChainWork.getdouble())/log(2.0),
// Same as InvalidChainFound, above, except not called directly from InvalidateBlock,
// which does its own setBlockIndexCandidates manageent.
void CChainState::InvalidBlockFound(CBlockIndex *pindex, const BlockValidationState &state) {
if (state.GetResult() != BlockValidationResult::BLOCK_MUTATED) {
pindex->nStatus |= BLOCK_FAILED_VALID;
void UpdateCoins(const CTransaction& tx, CCoinsViewCache& inputs, CTxUndo &txundo, int nHeight)
// mark inputs spent
if (!tx.IsCoinBase()) {
for (const CTxIn &txin : {
bool is_spent = inputs.SpendCoin(txin.prevout, &txundo.vprevout.back());
// add outputs
AddCoins(inputs, tx, nHeight);
void UpdateCoins(const CTransaction& tx, CCoinsViewCache& inputs, int nHeight)
CTxUndo txundo;
UpdateCoins(tx, inputs, txundo, nHeight);
bool CScriptCheck::operator()() {
const CScript &scriptSig = ptxTo->vin[nIn].scriptSig;
const CScriptWitness *witness = &ptxTo->vin[nIn].scriptWitness;
return VerifyScript(scriptSig, m_tx_out.scriptPubKey, witness, nFlags, CachingTransactionSignatureChecker(ptxTo, nIn, m_tx_out.nValue, cacheStore, *txdata), &error);
int BlockManager::GetSpendHeight(const CCoinsViewCache& inputs)
assert(std::addressof(g_chainman.m_blockman) == std::addressof(*this));
CBlockIndex* pindexPrev = LookupBlockIndex(inputs.GetBestBlock());
return pindexPrev->nHeight + 1;
static CuckooCache::cache<uint256, SignatureCacheHasher> g_scriptExecutionCache;
static CSHA256 g_scriptExecutionCacheHasher;
void InitScriptExecutionCache() {
// Setup the salted hasher
uint256 nonce = GetRandHash();
// We want the nonce to be 64 bytes long to force the hasher to process
// this chunk, which makes later hash computations more efficient. We
// just write our 32-byte entropy twice to fill the 64 bytes.
g_scriptExecutionCacheHasher.Write(nonce.begin(), 32);
g_scriptExecutionCacheHasher.Write(nonce.begin(), 32);
// nMaxCacheSize is unsigned. If -maxsigcachesize is set to zero,
// setup_bytes creates the minimum possible cache (2 elements).
size_t nMaxCacheSize = std::min(std::max((int64_t)0, gArgs.GetArg("-maxsigcachesize", DEFAULT_MAX_SIG_CACHE_SIZE) / 2), MAX_MAX_SIG_CACHE_SIZE) * ((size_t) 1 << 20);
size_t nElems = g_scriptExecutionCache.setup_bytes(nMaxCacheSize);
LogPrintf("Using %zu MiB out of %zu/2 requested for script execution cache, able to store %zu elements\n",
(nElems*sizeof(uint256)) >>20, (nMaxCacheSize*2)>>20, nElems);
* Check whether all of this transaction's input scripts succeed.
* This involves ECDSA signature checks so can be computationally intensive. This function should
* only be called after the cheap sanity checks in CheckTxInputs passed.
* If pvChecks is not nullptr, script checks are pushed onto it instead of being performed inline. Any
* script checks which are not necessary (eg due to script execution cache hits) are, obviously,
* not pushed onto pvChecks/run.
* Setting cacheSigStore/cacheFullScriptStore to false will remove elements from the corresponding cache
* which are matched. This is useful for checking blocks where we will likely never need the cache
* entry again.
* Note that we may set state.reason to NOT_STANDARD for extra soft-fork flags in flags, block-checking
* callers should probably reset it to CONSENSUS in such cases.
* Non-static (and re-declared) in src/test/txvalidationcache_tests.cpp
bool CheckInputScripts(const CTransaction& tx, TxValidationState& state,
const CCoinsViewCache& inputs, unsigned int flags, bool cacheSigStore,
bool cacheFullScriptStore, PrecomputedTransactionData& txdata,
std::vector<CScriptCheck>* pvChecks)
if (tx.IsCoinBase()) return true;
if (pvChecks) {
// First check if script executions have been cached with the same
// flags. Note that this assumes that the inputs provided are
// correct (ie that the transaction hash which is in tx's prevouts
// properly commits to the scriptPubKey in the inputs view of that
// transaction).
uint256 hashCacheEntry;
CSHA256 hasher = g_scriptExecutionCacheHasher;
hasher.Write(tx.GetWitnessHash().begin(), 32).Write((unsigned char*)&flags, sizeof(flags)).Finalize(hashCacheEntry.begin());
AssertLockHeld(cs_main); //TODO: Remove this requirement by making CuckooCache not require external locks
if (g_scriptExecutionCache.contains(hashCacheEntry, !cacheFullScriptStore)) {
return true;
if (!txdata.m_spent_outputs_ready) {
std::vector<CTxOut> spent_outputs;
for (const auto& txin : {
const COutPoint& prevout = txin.prevout;
const Coin& coin = inputs.AccessCoin(prevout);
txdata.Init(tx, std::move(spent_outputs));
assert(txdata.m_spent_outputs.size() ==;
for (unsigned int i = 0; i <; i++) {
// We very carefully only pass in things to CScriptCheck which
// are clearly committed to by tx' witness hash. This provides
// a sanity check that our caching is not introducing consensus
// failures through additional data in, eg, the coins being
// spent being checked as a part of CScriptCheck.
// Verify signature
CScriptCheck check(txdata.m_spent_outputs[i], tx, i, flags, cacheSigStore, &txdata);
if (pvChecks) {
} else if (!check()) {
// Check whether the failure was caused by a
// non-mandatory script verification check, such as
// non-standard DER encodings or non-null dummy
// arguments; if so, ensure we return NOT_STANDARD
// instead of CONSENSUS to avoid downstream users
// splitting the network between upgraded and
// non-upgraded nodes by banning CONSENSUS-failing
// data providers.
CScriptCheck check2(txdata.m_spent_outputs[i], tx, i,
flags & ~STANDARD_NOT_MANDATORY_VERIFY_FLAGS, cacheSigStore, &txdata);
if (check2())
return state.Invalid(TxValidationResult::TX_NOT_STANDARD, strprintf("non-mandatory-script-verify-flag (%s)", ScriptErrorString(check.GetScriptError())));
// MANDATORY flag failures correspond to
// TxValidationResult::TX_CONSENSUS. Because CONSENSUS
// failures are the most serious case of validation
// failures, we may need to consider using
// RECENT_CONSENSUS_CHANGE for any script failure that
// could be due to non-upgraded nodes which we may want to
// support, to avoid splitting the network (but this
// depends on the details of how net_processing handles
// such errors).
return state.Invalid(TxValidationResult::TX_CONSENSUS, strprintf("mandatory-script-verify-flag-failed (%s)", ScriptErrorString(check.GetScriptError())));
if (cacheFullScriptStore && !pvChecks) {
// We executed all of the provided scripts, and were told to
// cache the result. Do so now.
return true;
static bool UndoWriteToDisk(const CBlockUndo& blockundo, FlatFilePos& pos, const uint256& hashBlock, const CMessageHeader::MessageStartChars& messageStart)
// Open history file to append
CAutoFile fileout(OpenUndoFile(pos), SER_DISK, CLIENT_VERSION);
if (fileout.IsNull())
return error("%s: OpenUndoFile failed", __func__);
// Write index header
unsigned int nSize = GetSerializeSize(blockundo, fileout.GetVersion());
fileout << messageStart << nSize;
// Write undo data
long fileOutPos = ftell(fileout.Get());
if (fileOutPos < 0)
return error("%s: ftell failed", __func__);
pos.nPos = (unsigned int)fileOutPos;
fileout << blockundo;
// calculate & write checksum
hasher << hashBlock;
hasher << blockundo;
fileout << hasher.GetHash();
return true;
bool UndoReadFromDisk(CBlockUndo& blockundo, const CBlockIndex* pindex)
FlatFilePos pos = pindex->GetUndoPos();
if (pos.IsNull()) {
return error("%s: no undo data available", __func__);
// Open history file to read
CAutoFile filein(OpenUndoFile(pos, true), SER_DISK, CLIENT_VERSION);
if (filein.IsNull())
return error("%s: OpenUndoFile failed", __func__);
// Read block
uint256 hashChecksum;
CHashVerifier<CAutoFile> verifier(&filein); // We need a CHashVerifier as reserializing may lose data
try {
verifier << pindex->pprev->GetBlockHash();
verifier >> blockundo;
filein >> hashChecksum;
catch (const std::exception& e) {
return error("%s: Deserialize or I/O error - %s", __func__, e.what());
// Verify checksum
if (hashChecksum != verifier.GetHash())
return error("%s: Checksum mismatch", __func__);
return true;
/** Abort with a message */
static bool AbortNode(const std::string& strMessage, bilingual_str user_message = bilingual_str())
LogPrintf("*** %s\n", strMessage);
if (user_message.empty()) {
user_message = _("A fatal internal error occurred, see debug.log for details");
return false;
static bool AbortNode(BlockValidationState& state, const std::string& strMessage, const bilingual_str& userMessage = bilingual_str())
AbortNode(strMessage, userMessage);
return state.Error(strMessage);
* Restore the UTXO in a Coin at a given COutPoint
* @param undo The Coin to be restored.
* @param view The coins view to which to apply the changes.
* @param out The out point that corresponds to the tx input.
* @return A DisconnectResult as an int
int ApplyTxInUndo(Coin&& undo, CCoinsViewCache& view, const COutPoint& out)
bool fClean = true;
if (view.HaveCoin(out)) fClean = false; // overwriting transaction output
if (undo.nHeight == 0) {
// Missing undo metadata (height and coinbase). Older versions included this
// information only in undo records for the last spend of a transactions'
// outputs. This implies that it must be present for some other output of the same tx.
const Coin& alternate = AccessByTxid(view, out.hash);
if (!alternate.IsSpent()) {
undo.nHeight = alternate.nHeight;
undo.fCoinBase = alternate.fCoinBase;
} else {
return DISCONNECT_FAILED; // adding output for transaction without known metadata
// If the coin already exists as an unspent coin in the cache, then the
// possible_overwrite parameter to AddCoin must be set to true. We have
// already checked whether an unspent coin exists above using HaveCoin, so
// we don't need to guess. When fClean is false, an unspent coin already
// existed and it is an overwrite.
view.AddCoin(out, std::move(undo), !fClean);
/** Undo the effects of this block (with given index) on the UTXO set represented by coins.
* When FAILED is returned, view is left in an indeterminate state. */
DisconnectResult CChainState::DisconnectBlock(const CBlock& block, const CBlockIndex* pindex, CCoinsViewCache& view)
bool fClean = true;
CBlockUndo blockUndo;
if (!UndoReadFromDisk(blockUndo, pindex)) {
error("DisconnectBlock(): failure reading undo data");
if (blockUndo.vtxundo.size() + 1 != block.vtx.size()) {
error("DisconnectBlock(): block and undo data inconsistent");
// undo transactions in reverse order
for (int i = block.vtx.size() - 1; i >= 0; i--) {
const CTransaction &tx = *(block.vtx[i]);
uint256 hash = tx.GetHash();
bool is_coinbase = tx.IsCoinBase();
// Check that all outputs are available and match the outputs in the block itself
// exactly.
for (size_t o = 0; o < tx.vout.size(); o++) {
if (!tx.vout[o].scriptPubKey.IsUnspendable()) {
COutPoint out(hash, o);
Coin coin;
bool is_spent = view.SpendCoin(out, &coin);
if (!is_spent || tx.vout[o] != coin.out || pindex->nHeight != coin.nHeight || is_coinbase != coin.fCoinBase) {
fClean = false; // transaction output mismatch
// restore inputs
if (i > 0) { // not coinbases
CTxUndo &txundo = blockUndo.vtxundo[i-1];
if (txundo.vprevout.size() != {
error("DisconnectBlock(): transaction and undo data inconsistent");
for (unsigned int j =; j-- > 0;) {
const COutPoint &out =[j].prevout;
int res = ApplyTxInUndo(std::move(txundo.vprevout[j]), view, out);
fClean = fClean && res != DISCONNECT_UNCLEAN;
// At this point, all of txundo.vprevout should have been moved out.
// move best block pointer to prevout block
static void FlushUndoFile(int block_file, bool finalize = false)
FlatFilePos undo_pos_old(block_file, vinfoBlockFile[block_file].nUndoSize);
if (!UndoFileSeq().Flush(undo_pos_old, finalize)) {
AbortNode("Flushing undo file to disk failed. This is likely the result of an I/O error.");
static void FlushBlockFile(bool fFinalize = false, bool finalize_undo = false)
FlatFilePos block_pos_old(nLastBlockFile, vinfoBlockFile[nLastBlockFile].nSize);
if (!BlockFileSeq().Flush(block_pos_old, fFinalize)) {
AbortNode("Flushing block file to disk failed. This is likely the result of an I/O error.");
// we do not always flush the undo file, as the chain tip may be lagging behind the incoming blocks,
// e.g. during IBD or a sync after a node going offline
if (!fFinalize || finalize_undo) FlushUndoFile(nLastBlockFile, finalize_undo);
static bool FindUndoPos(BlockValidationState &state, int nFile, FlatFilePos &pos, unsigned int nAddSize);
static bool WriteUndoDataForBlock(const CBlockUndo& blockundo, BlockValidationState& state, CBlockIndex* pindex, const CChainParams& chainparams)
// Write undo information to disk
if (pindex->GetUndoPos().IsNull()) {
FlatFilePos _pos;
if (!FindUndoPos(state, pindex->nFile, _pos, ::GetSerializeSize(blockundo, CLIENT_VERSION) + 40))
return error("ConnectBlock(): FindUndoPos failed");
if (!UndoWriteToDisk(blockundo, _pos, pindex->pprev->GetBlockHash(), chainparams.MessageStart()))
return AbortNode(state, "Failed to write undo data");
// rev files are written in block height order, whereas blk files are written as blocks come in (often out of order)
// we want to flush the rev (undo) file once we've written the last block, which is indicated by the last height
// in the block file info as below; note that this does not catch the case where the undo writes are keeping up
// with the block writes (usually when a synced up node is getting newly mined blocks) -- this case is caught in
// the FindBlockPos function
if (_pos.nFile < nLastBlockFile && static_cast<uint32_t>(pindex->nHeight) == vinfoBlockFile[_pos.nFile].nHeightLast) {
FlushUndoFile(_pos.nFile, true);
// update nUndoPos in block index
pindex->nUndoPos = _pos.nPos;
pindex->nStatus |= BLOCK_HAVE_UNDO;
return true;
static CCheckQueue<CScriptCheck> scriptcheckqueue(128);
void StartScriptCheckWorkerThreads(int threads_num)
void StopScriptCheckWorkerThreads()
VersionBitsCache versionbitscache GUARDED_BY(cs_main);
int32_t ComputeBlockVersion(const CBlockIndex* pindexPrev, const Consensus::Params& params)
int32_t nVersion = VERSIONBITS_TOP_BITS;
for (int i = 0; i < (int)Consensus::MAX_VERSION_BITS_DEPLOYMENTS; i++) {
ThresholdState state = VersionBitsState(pindexPrev, params, static_cast<Consensus::DeploymentPos>(i), versionbitscache);
if (state == ThresholdState::LOCKED_IN || state == ThresholdState::STARTED) {
nVersion |= VersionBitsMask(params, static_cast<Consensus::DeploymentPos>(i));
return nVersion;
* Threshold condition checker that triggers when unknown versionbits are seen on the network.
class WarningBitsConditionChecker : public AbstractThresholdConditionChecker
int bit;
explicit WarningBitsConditionChecker(int bitIn) : bit(bitIn) {}
int64_t BeginTime(const Consensus::Params& params) const override { return 0; }
int64_t EndTime(const Consensus::Params& params) const override { return std::numeric_limits<int64_t>::max(); }
int Period(const Consensus::Params& params) const override { return params.nMinerConfirmationWindow; }
int Threshold(const Consensus::Params& params) const override { return params.nRuleChangeActivationThreshold; }
bool Condition(const CBlockIndex* pindex, const Consensus::Params& params) const override
return pindex->nHeight >= params.MinBIP9WarningHeight &&
((pindex->nVersion >> bit) & 1) != 0 &&
((ComputeBlockVersion(pindex->pprev, params) >> bit) & 1) == 0;
static ThresholdConditionCache warningcache[VERSIONBITS_NUM_BITS] GUARDED_BY(cs_main);
// 0.13.0 was shipped with a segwit deployment defined for testnet, but not for
// mainnet. We no longer need to support disabling the segwit deployment
// except for testing purposes, due to limitations of the functional test
// environment. See test/functional/
static bool IsScriptWitnessEnabled(const Consensus::Params& params)
return params.SegwitHeight != std::numeric_limits<int>::max();
static unsigned int GetBlockScriptFlags(const CBlockIndex* pindex, const Consensus::Params& consensusparams) EXCLUSIVE_LOCKS_REQUIRED(cs_main) {
unsigned int flags = SCRIPT_VERIFY_NONE;
// BIP16 didn't become active until Apr 1 2012 (on mainnet, and
// retroactively applied to testnet)
// However, only one historical block violated the P2SH rules (on both
// mainnet and testnet), so for simplicity, always leave P2SH
// on except for the one violating block.
if (consensusparams.BIP16Exception.IsNull() || // no bip16 exception on this chain
pindex->phashBlock == nullptr || // this is a new candidate block, eg from TestBlockValidity()
*pindex->phashBlock != consensusparams.BIP16Exception) // this block isn't the historical exception
// Enforce WITNESS rules whenever P2SH is in effect (and the segwit
// deployment is defined).
if (flags & SCRIPT_VERIFY_P2SH && IsScriptWitnessEnabled(consensusparams)) {
// Start enforcing the DERSIG (BIP66) rule
if (pindex->nHeight >= consensusparams.BIP66Height) {
// Start enforcing CHECKLOCKTIMEVERIFY (BIP65) rule
if (pindex->nHeight >= consensusparams.BIP65Height) {
// Start enforcing BIP112 (CHECKSEQUENCEVERIFY)
if (pindex->nHeight >= consensusparams.CSVHeight) {
// Start enforcing Taproot using versionbits logic.
if (VersionBitsState(pindex->pprev, consensusparams, Consensus::DEPLOYMENT_TAPROOT, versionbitscache) == ThresholdState::ACTIVE) {
// Start enforcing BIP147 NULLDUMMY (activated simultaneously with segwit)
if (IsWitnessEnabled(pindex->pprev, consensusparams)) {
return flags;
static int64_t nTimeCheck = 0;
static int64_t nTimeForks = 0;
static int64_t nTimeVerify = 0;
static int64_t nTimeConnect = 0;
static int64_t nTimeIndex = 0;
static int64_t nTimeCallbacks = 0;
static int64_t nTimeTotal = 0;
static int64_t nBlocksTotal = 0;
/** Apply the effects of this block (with given index) on the UTXO set represented by coins.
* Validity checks that depend on the UTXO set are also done; ConnectBlock()
* can fail if those validity checks fail (among other reasons). */
bool CChainState::ConnectBlock(const CBlock& block, BlockValidationState& state, CBlockIndex* pindex,
CCoinsViewCache& view, const CChainParams& chainparams, bool fJustCheck)
assert(*pindex->phashBlock == block.GetHash());
int64_t nTimeStart = GetTimeMicros();
// Check it again in case a previous version let a bad block in
// NOTE: We don't currently (re-)invoke ContextualCheckBlock() or
// ContextualCheckBlockHeader() here. This means that if we add a new
// consensus rule that is enforced in one of those two functions, then we
// may have let in a block that violates the rule prior to updating the
// software, and we would NOT be enforcing the rule here. Fully solving
// upgrade from one software version to the next after a consensus rule
// change is potentially tricky and issue-specific (see RewindBlockIndex()
// for one general approach that was used for BIP 141 deployment).
// Also, currently the rule against blocks more than 2 hours in the future
// is enforced in ContextualCheckBlockHeader(); we wouldn't want to
// re-enforce that rule here (at least until we make it impossible for
// GetAdjustedTime() to go backward).
if (!CheckBlock(block, state, chainparams.GetConsensus(), !fJustCheck, !fJustCheck)) {
if (state.GetResult() == BlockValidationResult::BLOCK_MUTATED) {
// We don't write down blocks to disk if they may have been
// corrupted, so this should be impossible unless we're having hardware
// problems.
return AbortNode(state, "Corrupt block found indicating potential hardware failure; shutting down");
return error("%s: Consensus::CheckBlock: %s", __func__, state.ToString());
// verify that the view's current state corresponds to the previous block
uint256 hashPrevBlock = pindex->pprev == nullptr ? uint256() : pindex->pprev->GetBlockHash();
assert(hashPrevBlock == view.GetBestBlock());
// Special case for the genesis block, skipping connection of its transactions
// (its coinbase is unspendable)
if (block.GetHash() == chainparams.GetConsensus().hashGenesisBlock) {
if (!fJustCheck)
return true;
bool fScriptChecks = true;
if (!hashAssumeValid.IsNull()) {
// We've been configured with the hash of a block which has been externally verified to have a valid history.
// A suitable default value is included with the software and updated from time to time. Because validity
// relative to a piece of software is an objective fact these defaults can be easily reviewed.
// This setting doesn't force the selection of any particular chain but makes validating some faster by
// effectively caching the result of part of the verification.
BlockMap::const_iterator it = m_blockman.m_block_index.find(hashAssumeValid);
if (it != m_blockman.m_block_index.end()) {
if (it->second->GetAncestor(pindex->nHeight) == pindex &&
pindexBestHeader->GetAncestor(pindex->nHeight) == pindex &&
pindexBestHeader->nChainWork >= nMinimumChainWork) {
// This block is a member of the assumed verified chain and an ancestor of the best header.
// Script verification is skipped when connecting blocks under the
// assumevalid block. Assuming the assumevalid block is valid this
// is safe because block merkle hashes are still computed and checked,
// Of course, if an assumed valid block is invalid due to false scriptSigs
// this optimization would allow an invalid chain to be accepted.
// The equivalent time check discourages hash power from extorting the network via DOS attack
// into accepting an invalid block through telling users they must manually set assumevalid.
// Requiring a software change or burying the invalid block, regardless of the setting, makes
// it hard to hide the implication of the demand. This also avoids having release candidates
// that are hardly doing any signature verification at all in testing without having to
// artificially set the default assumed verified block further back.
// The test against nMinimumChainWork prevents the skipping when denied access to any chain at
// least as good as the expected chain.
fScriptChecks = (GetBlockProofEquivalentTime(*pindexBestHeader, *pindex, *pindexBestHeader, chainparams.GetConsensus()) <= 60 * 60 * 24 * 7 * 2);
int64_t nTime1 = GetTimeMicros(); nTimeCheck += nTime1 - nTimeStart;
LogPrint(BCLog::BENCH, " - Sanity checks: %.2fms [%.2fs (%.2fms/blk)]\n", MILLI * (nTime1 - nTimeStart), nTimeCheck * MICRO, nTimeCheck * MILLI / nBlocksTotal);
// Do not allow blocks that contain transactions which 'overwrite' older transactions,
// unless those are already completely spent.
// If such overwrites are allowed, coinbases and transactions depending upon those
// can be duplicated to remove the ability to spend the first instance -- even after
// being sent to another address.
// See BIP30, CVE-2012-1909, and for more information.
// This logic is not necessary for memory pool transactions, as AcceptToMemoryPool
// already refuses previously-known transaction ids entirely.
// This rule was originally applied to all blocks with a timestamp after March 15, 2012, 0:00 UTC.
// Now that the whole chain is irreversibly beyond that time it is applied to all blocks except the
// two in the chain that violate it. This prevents exploiting the issue against nodes during their
// initial block download.
bool fEnforceBIP30 = !((pindex->nHeight==91842 && pindex->GetBlockHash() == uint256S("0x00000000000a4d0a398161ffc163c503763b1f4360639393e0e4c8e300e0caec")) ||
(pindex->nHeight==91880 && pindex->GetBlockHash() == uint256S("0x00000000000743f190a18c5577a3c2d2a1f610ae9601ac046a38084ccb7cd721")));
// Once BIP34 activated it was not possible to create new duplicate coinbases and thus other than starting
// with the 2 existing duplicate coinbase pairs, not possible to create overwriting txs. But by the
// time BIP34 activated, in each of the existing pairs the duplicate coinbase had overwritten the first
// before the first had been spent. Since those coinbases are sufficiently buried it's no longer possible to create further
// duplicate transactions descending from the known pairs either.
// If we're on the known chain at height greater than where BIP34 activated, we can save the db accesses needed for the BIP30 check.
// BIP34 requires that a block at height X (block X) has its coinbase
// scriptSig start with a CScriptNum of X (indicated height X). The above
// logic of no longer requiring BIP30 once BIP34 activates is flawed in the
// case that there is a block X before the BIP34 height of 227,931 which has
// an indicated height Y where Y is greater than X. The coinbase for block
// X would also be a valid coinbase for block Y, which could be a BIP30
// violation. An exhaustive search of all mainnet coinbases before the
// BIP34 height which have an indicated height greater than the block height
// reveals many occurrences. The 3 lowest indicated heights found are
// 209,921, 490,897, and 1,983,702 and thus coinbases for blocks at these 3
// heights would be the first opportunity for BIP30 to be violated.
// The search reveals a great many blocks which have an indicated height
// greater than 1,983,702, so we simply remove the optimization to skip
// BIP30 checking for blocks at height 1,983,702 or higher. Before we reach
// that block in another 25 years or so, we should take advantage of a
// future consensus change to do a new and improved version of BIP34 that
// will actually prevent ever creating any duplicate coinbases in the
// future.
static constexpr int BIP34_IMPLIES_BIP30_LIMIT = 1983702;
// There is no potential to create a duplicate coinbase at block 209,921
// because this is still before the BIP34 height and so explicit BIP30
// checking is still active.
// The final case is block 176,684 which has an indicated height of
// 490,897. Unfortunately, this issue was not discovered until about 2 weeks
// before block 490,897 so there was not much opportunity to address this
// case other than to carefully analyze it and determine it would not be a
// problem. Block 490,897 was, in fact, mined with a different coinbase than
// block 176,684, but it is important to note that even if it hadn't been or
// is remined on an alternate fork with a duplicate coinbase, we would still
// not run into a BIP30 violation. This is because the coinbase for 176,684
// is spent in block 185,956 in transaction
// d4f7fbbf92f4a3014a230b2dc70b8058d02eb36ac06b4a0736d9d60eaa9e8781. This
// spending transaction can't be duplicated because it also spends coinbase
// 0328dd85c331237f18e781d692c92de57649529bd5edf1d01036daea32ffde29. This
// coinbase has an indicated height of over 4.2 billion, and wouldn't be
// duplicatable until that height, and it's currently impossible to create a
// chain that long. Nevertheless we may wish to consider a future soft fork
// which retroactively prevents block 490,897 from creating a duplicate
// coinbase. The two historical BIP30 violations often provide a confusing
// edge case when manipulating the UTXO and it would be simpler not to have
// another edge case to deal with.
// testnet3 has no blocks before the BIP34 height with indicated heights
// post BIP34 before approximately height 486,000,000 and presumably will
// be reset before it reaches block 1,983,702 and starts doing unnecessary
// BIP30 checking again.
CBlockIndex *pindexBIP34height = pindex->pprev->GetAncestor(chainparams.GetConsensus().BIP34Height);
//Only continue to enforce if we're below BIP34 activation height or the block hash at that height doesn't correspond.
fEnforceBIP30 = fEnforceBIP30 && (!pindexBIP34height || !(pindexBIP34height->GetBlockHash() == chainparams.GetConsensus().BIP34Hash));
// TODO: Remove BIP30 checking from block height 1,983,702 on, once we have a
// consensus change that ensures coinbases at those heights can not
// duplicate earlier coinbases.
if (fEnforceBIP30 || pindex->nHeight >= BIP34_IMPLIES_BIP30_LIMIT) {
for (const auto& tx : block.vtx) {
for (size_t o = 0; o < tx->vout.size(); o++) {
if (view.HaveCoin(COutPoint(tx->GetHash(), o))) {
LogPrintf("ERROR: ConnectBlock(): tried to overwrite transaction\n");
return state.Invalid(BlockValidationResult::BLOCK_CONSENSUS, "bad-txns-BIP30");
// Start enforcing BIP68 (sequence locks)
int nLockTimeFlags = 0;
if (pindex->nHeight >= chainparams.GetConsensus().CSVHeight) {
// Get the script flags for this block
unsigned int flags = GetBlockScriptFlags(pindex, chainparams.GetConsensus());
int64_t nTime2 = GetTimeMicros(); nTimeForks += nTime2 - nTime1;
LogPrint(BCLog::BENCH, " - Fork checks: %.2fms [%.2fs (%.2fms/blk)]\n", MILLI * (nTime2 - nTime1), nTimeForks * MICRO, nTimeForks * MILLI / nBlocksTotal);
CBlockUndo blockundo;
// Precomputed transaction data pointers must not be invalidated
// until after `control` has run the script checks (potentially
// in multiple threads). Preallocate the vector size so a new allocation
// doesn't invalidate pointers into the vector, and keep txsdata in scope
// for as long as `control`.
CCheckQueueControl<CScriptCheck> control(fScriptChecks && g_parallel_script_checks ? &scriptcheckqueue : nullptr);
std::vector<PrecomputedTransactionData> txsdata(block.vtx.size());
std::vector<int> prevheights;
CAmount nFees = 0;
int nInputs = 0;
int64_t nSigOpsCost = 0;
blockundo.vtxundo.reserve(block.vtx.size() - 1);
for (unsigned int i = 0; i < block.vtx.size(); i++)
const CTransaction &tx = *(block.vtx[i]);
nInputs +=;
if (!tx.IsCoinBase())
CAmount txfee = 0;
TxValidationState tx_state;
if (!Consensus::CheckTxInputs(tx, tx_state, view, pindex->nHeight, txfee)) {
// Any transaction validation failure in ConnectBlock is a block consensus failure
tx_state.GetRejectReason(), tx_state.GetDebugMessage());
return error("%s: Consensus::CheckTxInputs: %s, %s", __func__, tx.GetHash().ToString(), state.ToString());
nFees += txfee;
if (!MoneyRange(nFees)) {
LogPrintf("ERROR: %s: accumulated fee in the block out of range.\n", __func__);
return state.Invalid(BlockValidationResult::BLOCK_CONSENSUS, "bad-txns-accumulated-fee-outofrange");
// Check that transaction is BIP68 final
// BIP68 lock checks (as opposed to nLockTime checks) must
// be in ConnectBlock because they require the UTXO set
for (size_t j = 0; j <; j++) {
prevheights[j] = view.AccessCoin([j].prevout).nHeight;
if (!SequenceLocks(tx, nLockTimeFlags, prevheights, *pindex)) {
LogPrintf("ERROR: %s: contains a non-BIP68-final transaction\n", __func__);
return state.Invalid(BlockValidationResult::BLOCK_CONSENSUS, "bad-txns-nonfinal");
// GetTransactionSigOpCost counts 3 types of sigops:
// * legacy (always)
// * p2sh (when P2SH enabled in flags and excludes coinbase)
// * witness (when witness enabled in flags and excludes coinbase)
nSigOpsCost += GetTransactionSigOpCost(tx, view, flags);
if (nSigOpsCost > MAX_BLOCK_SIGOPS_COST) {
LogPrintf("ERROR: ConnectBlock(): too many sigops\n");
return state.Invalid(BlockValidationResult::BLOCK_CONSENSUS, "bad-blk-sigops");
if (!tx.IsCoinBase())
std::vector<CScriptCheck> vChecks;
bool fCacheResults = fJustCheck; /* Don't cache results if we're actually connecting blocks (still consult the cache, though) */
TxValidationState tx_state;
if (fScriptChecks && !CheckInputScripts(tx, tx_state, view, flags, fCacheResults, fCacheResults, txsdata[i], g_parallel_script_checks ? &vChecks : nullptr)) {
// Any transaction validation failure in ConnectBlock is a block consensus failure
tx_state.GetRejectReason(), tx_state.GetDebugMessage());
return error("ConnectBlock(): CheckInputScripts on %s failed with %s",
tx.GetHash().ToString(), state.ToString());
CTxUndo undoDummy;
if (i > 0) {
UpdateCoins(tx, view, i == 0 ? undoDummy : blockundo.vtxundo.back(), pindex->nHeight);
int64_t nTime3 = GetTimeMicros(); nTimeConnect += nTime3 - nTime2;
LogPrint(BCLog::BENCH, " - Connect %u transactions: %.2fms (%.3fms/tx, %.3fms/txin) [%.2fs (%.2fms/blk)]\n", (unsigned)block.vtx.size(), MILLI * (nTime3 - nTime2), MILLI * (nTime3 - nTime2) / block.vtx.size(), nInputs <= 1 ? 0 : MILLI * (nTime3 - nTime2) / (nInputs-1), nTimeConnect * MICRO, nTimeConnect * MILLI / nBlocksTotal);
CAmount blockReward = nFees + GetBlockSubsidy(pindex->nHeight, chainparams.GetConsensus());
if (block.vtx[0]->GetValueOut() > blockReward) {
LogPrintf("ERROR: ConnectBlock(): coinbase pays too much (actual=%d vs limit=%d)\n", block.vtx[0]->GetValueOut(), blockReward);
return state.Invalid(BlockValidationResult::BLOCK_CONSENSUS, "bad-cb-amount");
if (!control.Wait()) {
LogPrintf("ERROR: %s: CheckQueue failed\n", __func__);
return state.Invalid(BlockValidationResult::BLOCK_CONSENSUS, "block-validation-failed");
int64_t nTime4 = GetTimeMicros(); nTimeVerify += nTime4 - nTime2;
LogPrint(BCLog::BENCH, " - Verify %u txins: %.2fms (%.3fms/txin) [%.2fs (%.2fms/blk)]\n", nInputs - 1, MILLI * (nTime4 - nTime2), nInputs <= 1 ? 0 : MILLI * (nTime4 - nTime2) / (nInputs-1), nTimeVerify * MICRO, nTimeVerify * MILLI / nBlocksTotal);
if (fJustCheck)
return true;
if (!WriteUndoDataForBlock(blockundo, state, pindex, chainparams))
return false;
if (!pindex->IsValid(BLOCK_VALID_SCRIPTS)) {
// add this block to the view's block chain
int64_t nTime5 = GetTimeMicros(); nTimeIndex += nTime5 - nTime4;
LogPrint(BCLog::BENCH, " - Index writing: %.2fms [%.2fs (%.2fms/blk)]\n", MILLI * (nTime5 - nTime4), nTimeIndex * MICRO, nTimeIndex * MILLI / nBlocksTotal);
int64_t nTime6 = GetTimeMicros(); nTimeCallbacks += nTime6 - nTime5;
LogPrint(BCLog::BENCH, " - Callbacks: %.2fms [%.2fs (%.2fms/blk)]\n", MILLI * (nTime6 - nTime5), nTimeCallbacks * MICRO, nTimeCallbacks * MILLI / nBlocksTotal);
return true;
CoinsCacheSizeState CChainState::GetCoinsCacheSizeState(const CTxMemPool* tx_pool)
return this->GetCoinsCacheSizeState(
gArgs.GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) * 1000000);
CoinsCacheSizeState CChainState::GetCoinsCacheSizeState(
const CTxMemPool* tx_pool,
size_t max_coins_cache_size_bytes,
size_t max_mempool_size_bytes)
const int64_t nMempoolUsage = tx_pool ? tx_pool->DynamicMemoryUsage() : 0;
int64_t cacheSize = CoinsTip().DynamicMemoryUsage();
int64_t nTotalSpace =
max_coins_cache_size_bytes + std::max<int64_t>(max_mempool_size_bytes - nMempoolUsage, 0);
//! No need to periodic flush if at least this much space still available.
static constexpr int64_t MAX_BLOCK_COINSDB_USAGE_BYTES = 10 * 1024 * 1024; // 10MB
int64_t large_threshold =
std::max((9 * nTotalSpace) / 10, nTotalSpace - MAX_BLOCK_COINSDB_USAGE_BYTES);
if (cacheSize > nTotalSpace) {
LogPrintf("Cache size (%s) exceeds total space (%s)\n", cacheSize, nTotalSpace);
return CoinsCacheSizeState::CRITICAL;
} else if (cacheSize > large_threshold) {
return CoinsCacheSizeState::LARGE;
return CoinsCacheSizeState::OK;
bool CChainState::FlushStateToDisk(
const CChainParams& chainparams,
BlockValidationState &state,
FlushStateMode mode,
int nManualPruneHeight)
static std::chrono::microseconds nLastWrite{0};
static std::chrono::microseconds nLastFlush{0};
std::set<int> setFilesToPrune;
bool full_flush_completed = false;
const size_t coins_count = CoinsTip().GetCacheSize();
const size_t coins_mem_usage = CoinsTip().DynamicMemoryUsage();
try {
bool fFlushForPrune = false;
bool fDoFullFlush = false;
CoinsCacheSizeState cache_state = GetCoinsCacheSizeState(&m_mempool);
if (fPruneMode && (fCheckForPruning || nManualPruneHeight > 0) && !fReindex) {
// make sure we don't prune above the blockfilterindexes bestblocks
// pruning is height-based
int last_prune = m_chain.Height(); // last height we can prune
ForEachBlockFilterIndex([&](BlockFilterIndex& index) {
last_prune = std::max(1, std::min(last_prune, index.GetSummary().best_block_height));
if (nManualPruneHeight > 0) {
LOG_TIME_MILLIS_WITH_CATEGORY("find files to prune (manual)", BCLog::BENCH);
m_blockman.FindFilesToPruneManual(setFilesToPrune, std::min(last_prune, nManualPruneHeight), m_chain.Height());
} else {
LOG_TIME_MILLIS_WITH_CATEGORY("find files to prune", BCLog::BENCH);
m_blockman.FindFilesToPrune(setFilesToPrune, chainparams.PruneAfterHeight(), m_chain.Height(), last_prune, IsInitialBlockDownload());
fCheckForPruning = false;
if (!setFilesToPrune.empty()) {
fFlushForPrune = true;
if (!fHavePruned) {
pblocktree->WriteFlag("prunedblockfiles", true);
fHavePruned = true;
const auto nNow = GetTime<std::chrono::microseconds>();
// Avoid writing/flushing immediately after startup.
if (nLastWrite.count() == 0) {
nLastWrite = nNow;
if (nLastFlush.count() == 0) {
nLastFlush = nNow;
// The cache is large and we're within 10% and 10 MiB of the limit, but we have time now (not in the middle of a block processing).
bool fCacheLarge = mode == FlushStateMode::PERIODIC && cache_state >= CoinsCacheSizeState::LARGE;
// The cache is over the limit, we have to write now.
bool fCacheCritical = mode == FlushStateMode::IF_NEEDED && cache_state >= CoinsCacheSizeState::CRITICAL;
// It's been a while since we wrote the block index to disk. Do this frequently, so we don't need to redownload after a crash.
bool fPeriodicWrite = mode == FlushStateMode::PERIODIC && nNow > nLastWrite + DATABASE_WRITE_INTERVAL;
// It's been very long since we flushed the cache. Do this infrequently, to optimize cache usage.
bool fPeriodicFlush = mode == FlushStateMode::PERIODIC && nNow > nLastFlush + DATABASE_FLUSH_INTERVAL;
// Combine all conditions that result in a full cache flush.
fDoFullFlush = (mode == FlushStateMode::ALWAYS) || fCacheLarge || fCacheCritical || fPeriodicFlush || fFlushForPrune;
// Write blocks and block index to disk.
if (fDoFullFlush || fPeriodicWrite) {
// Depend on nMinDiskSpace to ensure we can write block index
if (!CheckDiskSpace(GetBlocksDir())) {
return AbortNode(state, "Disk space is too low!", _("Disk space is too low!"));
LOG_TIME_MILLIS_WITH_CATEGORY("write block and undo data to disk", BCLog::BENCH);
// First make sure all block and undo data is flushed to disk.
// Then update all block file information (which may refer to block and undo files).
LOG_TIME_MILLIS_WITH_CATEGORY("write block index to disk", BCLog::BENCH);
std::vector<std::pair<int, const CBlockFileInfo*> > vFiles;
for (std::set<int>::iterator it = setDirtyFileInfo.begin(); it != setDirtyFileInfo.end(); ) {
vFiles.push_back(std::make_pair(*it, &vinfoBlockFile[*it]));
std::vector<const CBlockIndex*> vBlocks;
for (std::set<CBlockIndex*>::iterator it = setDirtyBlockIndex.begin(); it != setDirtyBlockIndex.end(); ) {
if (!pblocktree->WriteBatchSync(vFiles, nLastBlockFile, vBlocks)) {
return AbortNode(state, "Failed to write to block index database");
// Finally remove any pruned files
if (fFlushForPrune) {
LOG_TIME_MILLIS_WITH_CATEGORY("unlink pruned files", BCLog::BENCH);
nLastWrite = nNow;
// Flush best chain related state. This can only be done if the blocks / block index write was also done.
if (fDoFullFlush && !CoinsTip().GetBestBlock().IsNull()) {
LOG_TIME_SECONDS(strprintf("write coins cache to disk (%d coins, %.2fkB)",
coins_count, coins_mem_usage / 1000));
// Typical Coin structures on disk are around 48 bytes in size.
// Pushing a new one to the database can cause it to be written
// twice (once in the log, and once in the tables). This is already
// an overestimation, as most will delete an existing entry or
// overwrite one. Still, use a conservative safety factor of 2.
if (!CheckDiskSpace(GetDataDir(), 48 * 2 * 2 * CoinsTip().GetCacheSize())) {
return AbortNode(state, "Disk space is too low!", _("Disk space is too low!"));
// Flush the chainstate (which may refer to block index entries).
if (!CoinsTip().Flush())
return AbortNode(state, "Failed to write to coin database");
nLastFlush = nNow;
full_flush_completed = true;
if (full_flush_completed) {
// Update best block in wallet (so we can detect restored wallets).
} catch (const std::runtime_error& e) {
return AbortNode(state, std::string("System error while flushing: ") + e.what());
return true;
void CChainState::ForceFlushStateToDisk() {
BlockValidationState state;
const CChainParams& chainparams = Params();
if (!this->FlushStateToDisk(chainparams, state, FlushStateMode::ALWAYS)) {
LogPrintf("%s: failed to flush state (%s)\n", __func__, state.ToString());
void CChainState::PruneAndFlush() {
BlockValidationState state;
fCheckForPruning = true;
const CChainParams& chainparams = Params();
if (!this->FlushStateToDisk(chainparams, state, FlushStateMode::NONE)) {
LogPrintf("%s: failed to flush state (%s)\n", __func__, state.ToString());
static void DoWarning(const bilingual_str& warning)
static bool fWarned = false;
if (!fWarned) {
fWarned = true;
/** Private helper function that concatenates warning messages. */
static void AppendWarning(bilingual_str& res, const bilingual_str& warn)
if (!res.empty()) res += Untranslated(", ");
res += warn;
/** Check warning conditions and do some notifications on new chain tip set. */
static void UpdateTip(CTxMemPool& mempool, const CBlockIndex* pindexNew, const CChainParams& chainParams, CChainState& active_chainstate)
// New best block
g_best_block = pindexNew->GetBlockHash();
bilingual_str warning_messages;
assert(std::addressof(::ChainstateActive()) == std::addressof(active_chainstate));
if (!active_chainstate.IsInitialBlockDownload()) {
const CBlockIndex* pindex = pindexNew;
for (int bit = 0; bit < VERSIONBITS_NUM_BITS; bit++) {
WarningBitsConditionChecker checker(bit);
ThresholdState state = checker.GetStateFor(pindex, chainParams.GetConsensus(), warningcache[bit]);
if (state == ThresholdState::ACTIVE || state == ThresholdState::LOCKED_IN) {
const bilingual_str warning = strprintf(_("Warning: unknown new rules activated (versionbit %i)"), bit);
if (state == ThresholdState::ACTIVE) {
} else {
AppendWarning(warning_messages, warning);
assert(std::addressof(::ChainstateActive()) == std::addressof(active_chainstate));
LogPrintf("%s: new best=%s height=%d version=0x%08x log2_work=%f tx=%lu date='%s' progress=%f cache=%.1fMiB(%utxo)%s\n", __func__,
pindexNew->GetBlockHash().ToString(), pindexNew->nHeight, pindexNew->nVersion,
log(pindexNew->nChainWork.getdouble())/log(2.0), (unsigned long)pindexNew->nChainTx,
GuessVerificationProgress(chainParams.TxData(), pindexNew), active_chainstate.CoinsTip().DynamicMemoryUsage() * (1.0 / (1<<20)), active_chainstate.CoinsTip().GetCacheSize(),
!warning_messages.empty() ? strprintf(" warning='%s'", warning_messages.original) : "");
/** Disconnect m_chain's tip.
* After calling, the mempool will be in an inconsistent state, with
* transactions from disconnected blocks being added to disconnectpool. You
* should make the mempool consistent again by calling UpdateMempoolForReorg.
* with cs_main held.
* If disconnectpool is nullptr, then no disconnected transactions are added to
* disconnectpool (note that the caller is responsible for mempool consistency
* in any case).
bool CChainState::DisconnectTip(BlockValidationState& state, const CChainParams& chainparams, DisconnectedBlockTransactions* disconnectpool)
CBlockIndex *pindexDelete = m_chain.Tip();
// Read block from disk.
std::shared_ptr<CBlock> pblock = std::make_shared<CBlock>();
CBlock& block = *pblock;
if (!ReadBlockFromDisk(block, pindexDelete, chainparams.GetConsensus()))
return error("DisconnectTip(): Failed to read block");
// Apply the block atomically to the chain state.
int64_t nStart = GetTimeMicros();
CCoinsViewCache view(&CoinsTip());
assert(view.GetBestBlock() == pindexDelete->GetBlockHash());
if (DisconnectBlock(block, pindexDelete, view) != DISCONNECT_OK)
return error("DisconnectTip(): DisconnectBlock %s failed", pindexDelete->GetBlockHash().ToString());
bool flushed = view.Flush();
LogPrint(BCLog::BENCH, "- Disconnect block: %.2fms\n", (GetTimeMicros() - nStart) * MILLI);
// Write the chain state to disk, if necessary.
if (!FlushStateToDisk(chainparams, state, FlushStateMode::IF_NEEDED))
return false;
if (disconnectpool) {
// Save transactions to re-add to mempool at end of reorg
for (auto it = block.vtx.rbegin(); it != block.vtx.rend(); ++it) {
while (disconnectpool->DynamicMemoryUsage() > MAX_DISCONNECTED_TX_POOL_SIZE * 1000) {
// Drop the earliest entry, and remove its children from the mempool.
auto it = disconnectpool->queuedTx.get<insertion_order>().begin();
m_mempool.removeRecursive(**it, MemPoolRemovalReason::REORG);
UpdateTip(m_mempool, pindexDelete->pprev, chainparams, *this);
// Let wallets know transactions went from 1-confirmed to
// 0-confirmed or conflicted:
GetMainSignals().BlockDisconnected(pblock, pindexDelete);
return true;
static int64_t nTimeReadFromDisk = 0;
static int64_t nTimeConnectTotal = 0;
static int64_t nTimeFlush = 0;
static int64_t nTimeChainState = 0;
static int64_t nTimePostConnect = 0;
struct PerBlockConnectTrace {
CBlockIndex* pindex = nullptr;
std::shared_ptr<const CBlock> pblock;
PerBlockConnectTrace() {}
* Used to track blocks whose transactions were applied to the UTXO state as a
* part of a single ActivateBestChainStep call.
* This class is single-use, once you call GetBlocksConnected() you have to throw
* it away and make a new one.
class ConnectTrace {
std::vector<PerBlockConnectTrace> blocksConnected;
explicit ConnectTrace() : blocksConnected(1) {}
void BlockConnected(CBlockIndex* pindex, std::shared_ptr<const CBlock> pblock) {
blocksConnected.back().pindex = pindex;
blocksConnected.back().pblock = std::move(pblock);
std::vector<PerBlockConnectTrace>& GetBlocksConnected() {
// We always keep one extra block at the end of our list because
// blocks are added after all the conflicted transactions have
// been filled in. Thus, the last entry should always be an empty
// one waiting for the transactions from the next block. We pop
// the last entry here to make sure the list we return is sane.
return blocksConnected;
* Connect a new block to m_chain. pblock is either nullptr or a pointer to a CBlock
* corresponding to pindexNew, to bypass loading it again from disk.
* The block is added to connectTrace if connection succeeds.
bool CChainState::ConnectTip(BlockValidationState& state, const CChainParams& chainparams, CBlockIndex* pindexNew, const std::shared_ptr<const CBlock>& pblock, ConnectTrace& connectTrace, DisconnectedBlockTransactions &disconnectpool)
assert(pindexNew->pprev == m_chain.Tip());
// Read block from disk.
int64_t nTime1 = GetTimeMicros();
std::shared_ptr<const CBlock> pthisBlock;
if (!pblock) {
std::shared_ptr<CBlock> pblockNew = std::make_shared<CBlock>();
if (!ReadBlockFromDisk(*pblockNew, pindexNew, chainparams.GetConsensus()))
return AbortNode(state, "Failed to read block");
pthisBlock = pblockNew;
} else {
pthisBlock = pblock;
const CBlock& blockConnecting = *pthisBlock;
// Apply the block atomically to the chain state.
int64_t nTime2 = GetTimeMicros(); nTimeReadFromDisk += nTime2 - nTime1;
int64_t nTime3;
LogPrint(BCLog::BENCH, " - Load block from disk: %.2fms [%.2fs]\n", (nTime2 - nTime1) * MILLI, nTimeReadFromDisk * MICRO);
CCoinsViewCache view(&CoinsTip());
bool rv = ConnectBlock(blockConnecting, state, pindexNew, view, chainparams);
GetMainSignals().BlockChecked(blockConnecting, state);
if (!rv) {
if (state.IsInvalid())
InvalidBlockFound(pindexNew, state);
return error("%s: ConnectBlock %s failed, %s", __func__, pindexNew->GetBlockHash().ToString(), state.ToString());
nTime3 = GetTimeMicros(); nTimeConnectTotal += nTime3 - nTime2;
assert(nBlocksTotal > 0);
LogPrint(BCLog::BENCH, " - Connect total: %.2fms [%.2fs (%.2fms/blk)]\n", (nTime3 - nTime2) * MILLI, nTimeConnectTotal * MICRO, nTimeConnectTotal * MILLI / nBlocksTotal);
bool flushed = view.Flush();
int64_t nTime4 = GetTimeMicros(); nTimeFlush += nTime4 - nTime3;
LogPrint(BCLog::BENCH, " - Flush: %.2fms [%.2fs (%.2fms/blk)]\n", (nTime4 - nTime3) * MILLI, nTimeFlush * MICRO, nTimeFlush * MILLI / nBlocksTotal);
// Write the chain state to disk, if necessary.
if (!FlushStateToDisk(chainparams, state, FlushStateMode::IF_NEEDED))
return false;
int64_t nTime5 = GetTimeMicros(); nTimeChainState += nTime5 - nTime4;
LogPrint(BCLog::BENCH, " - Writing chainstate: %.2fms [%.2fs (%.2fms/blk)]\n", (nTime5 - nTime4) * MILLI, nTimeChainState * MICRO, nTimeChainState * MILLI / nBlocksTotal);
// Remove conflicting transactions from the mempool.;
m_mempool.removeForBlock(blockConnecting.vtx, pindexNew->nHeight);
// Update m_chain & related variables.
UpdateTip(m_mempool, pindexNew, chainparams, *this);
int64_t nTime6 = GetTimeMicros(); nTimePostConnect += nTime6 - nTime5; nTimeTotal += nTime6 - nTime1;
LogPrint(BCLog::BENCH, " - Connect postprocess: %.2fms [%.2fs (%.2fms/blk)]\n", (nTime6 - nTime5) * MILLI, nTimePostConnect * MICRO, nTimePostConnect * MILLI / nBlocksTotal);
LogPrint(BCLog::BENCH, "- Connect block: %.2fms [%.2fs (%.2fms/blk)]\n", (nTime6 - nTime1) * MILLI, nTimeTotal * MICRO, nTimeTotal * MILLI / nBlocksTotal);
connectTrace.BlockConnected(pindexNew, std::move(pthisBlock));
return true;
* Return the tip of the chain with the most work in it, that isn't
* known to be invalid (it's however far from certain to be valid).
CBlockIndex* CChainState::FindMostWorkChain() {
do {
CBlockIndex *pindexNew = nullptr;
// Find the best candidate header.
std::set<CBlockIndex*, CBlockIndexWorkComparator>::reverse_iterator it = setBlockIndexCandidates.rbegin();
if (it == setBlockIndexCandidates.rend())
return nullptr;
pindexNew = *it;
// Check whether all blocks on the path between the currently active chain and the candidate are valid.
// Just going until the active chain is an optimization, as we know all blocks in it are valid already.
CBlockIndex *pindexTest = pindexNew;
bool fInvalidAncestor = false;
while (pindexTest && !m_chain.Contains(pindexTest)) {
assert(pindexTest->HaveTxsDownloaded() || pindexTest->nHeight == 0);
// Pruned nodes may have entries in setBlockIndexCandidates for
// which block files have been deleted. Remove those as candidates
// for the most work chain if we come across them; we can't switch
// to a chain unless we have all the non-active-chain parent blocks.
bool fFailedChain = pindexTest->nStatus & BLOCK_FAILED_MASK;
bool fMissingData = !(pindexTest->nStatus & BLOCK_HAVE_DATA);
if (fFailedChain || fMissingData) {
// Candidate chain is not usable (either invalid or missing data)
if (fFailedChain && (pindexBestInvalid == nullptr || pindexNew->nChainWork > pindexBestInvalid->nChainWork))
pindexBestInvalid = pindexNew;
CBlockIndex *pindexFailed = pindexNew;
// Remove the entire chain from the set.
while (pindexTest != pindexFailed) {
if (fFailedChain) {
pindexFailed->nStatus |= BLOCK_FAILED_CHILD;
} else if (fMissingData) {
// If we're missing data, then add back to m_blocks_unlinked,
// so that if the block arrives in the future we can try adding
// to setBlockIndexCandidates again.
std::make_pair(pindexFailed->pprev, pindexFailed));
pindexFailed = pindexFailed->pprev;
fInvalidAncestor = true;
pindexTest = pindexTest->pprev;
if (!fInvalidAncestor)
return pindexNew;
} while(true);
/** Delete all entries in setBlockIndexCandidates that are worse than the current tip. */
void CChainState::PruneBlockIndexCandidates() {
// Note that we can't delete the current block itself, as we may need to return to it later in case a
// reorganization to a better block fails.
std::set<CBlockIndex*, CBlockIndexWorkComparator>::iterator it = setBlockIndexCandidates.begin();
while (it != setBlockIndexCandidates.end() && setBlockIndexCandidates.value_comp()(*it, m_chain.Tip())) {
// Either the current tip or a successor of it we're working towards is left in setBlockIndexCandidates.
* Try to make some progress towards making pindexMostWork the active block.
* pblock is either nullptr or a pointer to a CBlock corresponding to pindexMostWork.
* @returns true unless a system error occurred
bool CChainState::ActivateBestChainStep(BlockValidationState& state, const CChainParams& chainparams, CBlockIndex* pindexMostWork, const std::shared_ptr<const CBlock>& pblock, bool& fInvalidFound, ConnectTrace& connectTrace)
assert(std::addressof(::ChainstateActive()) == std::addressof(*this));
const CBlockIndex* pindexOldTip = m_chain.Tip();
const CBlockIndex* pindexFork = m_chain.FindFork(pindexMostWork);
// Disconnect active blocks which are no longer in the best chain.
bool fBlocksDisconnected = false;
DisconnectedBlockTransactions disconnectpool;
while (m_chain.Tip() && m_chain.Tip() != pindexFork) {
if (!DisconnectTip(state, chainparams, &disconnectpool)) {
// This is likely a fatal error, but keep the mempool consistent,
// just in case. Only remove from the mempool in this case.
UpdateMempoolForReorg(*this, m_mempool, disconnectpool, false);
// If we're unable to disconnect a block during normal operation,
// then that is a failure of our local system -- we should abort
// rather than stay on a less work chain.
AbortNode(state, "Failed to disconnect block; see debug.log for details");
return false;
fBlocksDisconnected = true;
// Build list of new blocks to connect (in descending height order).
std::vector<CBlockIndex*> vpindexToConnect;
bool fContinue = true;
int nHeight = pindexFork ? pindexFork->nHeight : -1;
while (fContinue && nHeight != pindexMostWork->nHeight) {
// Don't iterate the entire list of potential improvements toward the best tip, as we likely only need
// a few blocks along the way.
int nTargetHeight = std::min(nHeight + 32, pindexMostWork->nHeight);
vpindexToConnect.reserve(nTargetHeight - nHeight);
CBlockIndex* pindexIter = pindexMostWork->GetAncestor(nTargetHeight);
while (pindexIter && pindexIter->nHeight != nHeight) {
pindexIter = pindexIter->pprev;
nHeight = nTargetHeight;
// Connect new blocks.
for (CBlockIndex* pindexConnect : reverse_iterate(vpindexToConnect)) {
if (!ConnectTip(state, chainparams, pindexConnect, pindexConnect == pindexMostWork ? pblock : std::shared_ptr<const CBlock>(), connectTrace, disconnectpool)) {
if (state.IsInvalid()) {
// The block violates a consensus rule.
if (state.GetResult() != BlockValidationResult::BLOCK_MUTATED) {
state = BlockValidationState();
fInvalidFound = true;
fContinue = false;
} else {
// A system error occurred (disk space, database error, ...).
// Make the mempool consistent with the current tip, just in case
// any observers try to use it before shutdown.
UpdateMempoolForReorg(*this, m_mempool, disconnectpool, false);
return false;
} else {
if (!pindexOldTip || m_chain.Tip()->nChainWork > pindexOldTip->nChainWork) {
// We're in a better position than we were. Return temporarily to release the lock.
fContinue = false;
if (fBlocksDisconnected) {
// If any blocks were disconnected, disconnectpool may be non empty. Add
// any disconnected transactions back to the mempool.
UpdateMempoolForReorg(*this, m_mempool, disconnectpool, true);
return true;
static SynchronizationState GetSynchronizationState(bool init)
if (!init) return SynchronizationState::POST_INIT;
if (::fReindex) return SynchronizationState::INIT_REINDEX;
return SynchronizationState::INIT_DOWNLOAD;
static bool NotifyHeaderTip(CChainState& chainstate) LOCKS_EXCLUDED(cs_main) {
bool fNotify = false;
bool fInitialBlockDownload = false;
static CBlockIndex* pindexHeaderOld = nullptr;
CBlockIndex* pindexHeader = nullptr;
pindexHeader = pindexBestHeader;
if (pindexHeader != pindexHeaderOld) {
fNotify = true;
assert(std::addressof(::ChainstateActive()) == std::addressof(chainstate));
fInitialBlockDownload = chainstate.IsInitialBlockDownload();
pindexHeaderOld = pindexHeader;
// Send block tip changed notifications without cs_main
if (fNotify) {
uiInterface.NotifyHeaderTip(GetSynchronizationState(fInitialBlockDownload), pindexHeader);
return fNotify;
static void LimitValidationInterfaceQueue() LOCKS_EXCLUDED(cs_main) {
if (GetMainSignals().CallbacksPending() > 10) {
bool CChainState::ActivateBestChain(BlockValidationState &state, const CChainParams& chainparams, std::shared_ptr<const CBlock> pblock) {
// Note that while we're often called here from ProcessNewBlock, this is
// far from a guarantee. Things in the P2P/RPC will often end up calling
// us in the middle of ProcessNewBlock - do not assume pblock is set
// sanely for performance or correctness!
// ABC maintains a fair degree of expensive-to-calculate internal state
// because this function periodically releases cs_main so that it does not lock up other threads for too long
// during large connects - and to allow for e.g. the callback queue to drain
// we use m_cs_chainstate to enforce mutual exclusion so that only one caller may execute this function at a time
CBlockIndex *pindexMostWork = nullptr;
CBlockIndex *pindexNewTip = nullptr;
int nStopAtHeight = gArgs.GetArg("-stopatheight", DEFAULT_STOPATHEIGHT);
do {
// Block until the validation queue drains. This should largely
// never happen in normal operation, however may happen during
// reindex, causing memory blowup if we run too far ahead.
// Note that if a validationinterface callback ends up calling
// ActivateBestChain this may lead to a deadlock! We should
// probably have a DEBUG_LOCKORDER test for this in the future.
LOCK(m_mempool.cs); // Lock transaction pool for at least as long as it takes for connectTrace to be consumed
CBlockIndex* starting_tip = m_chain.Tip();
bool blocks_connected = false;
do {
// We absolutely may not unlock cs_main until we've made forward progress
// (with the exception of shutdown due to hardware issues, low disk space, etc).
ConnectTrace connectTrace; // Destructed before cs_main is unlocked
if (pindexMostWork == nullptr) {
pindexMostWork = FindMostWorkChain();
// Whether we have anything to do at all.
if (pindexMostWork == nullptr || pindexMostWork == m_chain.Tip()) {
bool fInvalidFound = false;
std::shared_ptr<const CBlock> nullBlockPtr;
if (!ActivateBestChainStep(state, chainparams, pindexMostWork, pblock && pblock->GetHash() == pindexMostWork->GetBlockHash() ? pblock : nullBlockPtr, fInvalidFound, connectTrace)) {
// A system error occurred
return false;
blocks_connected = true;
if (fInvalidFound) {
// Wipe cache, we may need another branch now.
pindexMostWork = nullptr;
pindexNewTip = m_chain.Tip();
for (const PerBlockConnectTrace& trace : connectTrace.GetBlocksConnected()) {
assert(trace.pblock && trace.pindex);
GetMainSignals().BlockConnected(trace.pblock, trace.pindex);
} while (!m_chain.Tip() || (starting_tip && CBlockIndexWorkComparator()(m_chain.Tip(), starting_tip)));
if (!blocks_connected) return true;
const CBlockIndex* pindexFork = m_chain.FindFork(starting_tip);
bool fInitialDownload = IsInitialBlockDownload();
// Notify external listeners about the new tip.
// Enqueue while holding cs_main to ensure that UpdatedBlockTip is called in the order in which blocks are connected
if (pindexFork != pindexNewTip) {
// Notify ValidationInterface subscribers
GetMainSignals().UpdatedBlockTip(pindexNewTip, pindexFork, fInitialDownload);
// Always notify the UI if a new block tip was connected
uiInterface.NotifyBlockTip(GetSynchronizationState(fInitialDownload), pindexNewTip);
// When we reach this point, we switched to a new tip (stored in pindexNewTip).
if (nStopAtHeight && pindexNewTip && pindexNewTip->nHeight >= nStopAtHeight) StartShutdown();
// We check shutdown only after giving ActivateBestChainStep a chance to run once so that we
// never shutdown before connecting the genesis block during LoadChainTip(). Previously this
// caused an assert() failure during shutdown in such cases as the UTXO DB flushing checks
// that the best block hash is non-null.
if (ShutdownRequested()) break;
} while (pindexNewTip != pindexMostWork);
// Write changes periodically to disk, after relay.
if (!FlushStateToDisk(chainparams, state, FlushStateMode::PERIODIC)) {
return false;
return true;
bool CChainState::PreciousBlock(BlockValidationState& state, const CChainParams& params, CBlockIndex *pindex)
if (pindex->nChainWork < m_chain.Tip()->nChainWork) {
// Nothing to do, this block is not at the tip.
return true;
if (m_chain.Tip()->nChainWork > nLastPreciousChainwork) {
// The chain has been extended since the last call, reset the counter.
nBlockReverseSequenceId = -1;
nLastPreciousChainwork = m_chain.Tip()->nChainWork;
pindex->nSequenceId = nBlockReverseSequenceId;
if (nBlockReverseSequenceId > std::numeric_limits<int32_t>::min()) {
// We can't keep reducing the counter if somebody really wants to
// call preciousblock 2**31-1 times on the same set of tips...
if (pindex->IsValid(BLOCK_VALID_TRANSACTIONS) && pindex->HaveTxsDownloaded()) {
return ActivateBestChain(state, params, std::shared_ptr<const CBlock>());
bool CChainState::InvalidateBlock(BlockValidationState& state, const CChainParams& chainparams, CBlockIndex *pindex)
CBlockIndex* to_mark_failed = pindex;
bool pindex_was_in_chain = false;
int disconnected = 0;
// We do not allow ActivateBestChain() to run while InvalidateBlock() is
// running, as that could cause the tip to change while we disconnect
// blocks.
// We'll be acquiring and releasing cs_main below, to allow the validation
// callbacks to run. However, we should keep the block index in a
// consistent state as we disconnect blocks -- in particular we need to
// add equal-work blocks to setBlockIndexCandidates as we disconnect.
// To avoid walking the block index repeatedly in search of candidates,
// build a map once so that we can look up candidate blocks by chain
// work as we go.
std::multimap<const arith_uint256, CBlockIndex *> candidate_blocks_by_work;
for (const auto& entry : m_blockman.m_block_index) {
CBlockIndex *candidate = entry.second;
// We don't need to put anything in our active chain into the
// multimap, because those candidates will be found and considered
// as we disconnect.
// Instead, consider only non-active-chain blocks that have at
// least as much work as where we expect the new tip to end up.
if (!m_chain.Contains(candidate) &&
!CBlockIndexWorkComparator()(candidate, pindex->pprev) &&
candidate->HaveTxsDownloaded()) {
candidate_blocks_by_work.insert(std::make_pair(candidate->nChainWork, candidate));
// Disconnect (descendants of) pindex, and mark them invalid.
while (true) {
if (ShutdownRequested()) break;
// Make sure the queue of validation callbacks doesn't grow unboundedly.
LOCK(m_mempool.cs); // Lock for as long as disconnectpool is in scope to make sure UpdateMempoolForReorg is called after DisconnectTip without unlocking in between
if (!m_chain.Contains(pindex)) break;
pindex_was_in_chain = true;
CBlockIndex *invalid_walk_tip = m_chain.Tip();
// ActivateBestChain considers blocks already in m_chain
// unconditionally valid already, so force disconnect away from it.
DisconnectedBlockTransactions disconnectpool;
bool ret = DisconnectTip(state, chainparams, &disconnectpool);
// DisconnectTip will add transactions to disconnectpool.
// Adjust the mempool to be consistent with the new tip, adding
// transactions back to the mempool if disconnecting was successful,
// and we're not doing a very deep invalidation (in which case
// keeping the mempool up to date is probably futile anyway).
assert(std::addressof(::ChainstateActive()) == std::addressof(*this));
UpdateMempoolForReorg(*this, m_mempool, disconnectpool, /* fAddToMempool = */ (++disconnected <= 10) && ret);
if (!ret) return false;
assert(invalid_walk_tip->pprev == m_chain.Tip());
// We immediately mark the disconnected blocks as invalid.
// This prevents a case where pruned nodes may fail to invalidateblock
// and be left unable to start as they have no tip candidates (as there
// are no blocks that meet the "have data and are not invalid per
// nStatus" criteria for inclusion in setBlockIndexCandidates).
invalid_walk_tip->nStatus |= BLOCK_FAILED_VALID;
if (invalid_walk_tip->pprev == to_mark_failed && (to_mark_failed->nStatus & BLOCK_FAILED_VALID)) {
// We only want to mark the last disconnected block as BLOCK_FAILED_VALID; its children
// need to be BLOCK_FAILED_CHILD instead.
to_mark_failed->nStatus = (to_mark_failed->nStatus ^ BLOCK_FAILED_VALID) | BLOCK_FAILED_CHILD;
// Add any equal or more work headers to setBlockIndexCandidates
auto candidate_it = candidate_blocks_by_work.lower_bound(invalid_walk_tip->pprev->nChainWork);
while (candidate_it != candidate_blocks_by_work.end()) {
if (!CBlockIndexWorkComparator()(candidate_it->second, invalid_walk_tip->pprev)) {
candidate_it = candidate_blocks_by_work.erase(candidate_it);
} else {
// Track the last disconnected block, so we can correct its BLOCK_FAILED_CHILD status in future
// iterations, or, if it's the last one, call InvalidChainFound on it.
to_mark_failed = invalid_walk_tip;
if (m_chain.Contains(to_mark_failed)) {
// If the to-be-marked invalid block is in the active chain, something is interfering and we can't proceed.
return false;
// Mark pindex (or the last disconnected block) as invalid, even when it never was in the main chain
to_mark_failed->nStatus |= BLOCK_FAILED_VALID;
// If any new blocks somehow arrived while we were disconnecting
// (above), then the pre-calculation of what should go into
// setBlockIndexCandidates may have missed entries. This would
// technically be an inconsistency in the block index, but if we clean
// it up here, this should be an essentially unobservable error.
// Loop back over all block index entries and add any missing entries
// to setBlockIndexCandidates.
BlockMap::iterator it = m_blockman.m_block_index.begin();
while (it != m_blockman.m_block_index.end()) {
if (it->second->IsValid(BLOCK_VALID_TRANSACTIONS) && it->second->HaveTxsDownloaded() && !setBlockIndexCandidates.value_comp()(it->second, m_chain.Tip())) {
// Only notify about a new block tip if the active chain was modified.
if (pindex_was_in_chain) {
uiInterface.NotifyBlockTip(GetSynchronizationState(IsInitialBlockDownload()), to_mark_failed->pprev);
return true;
void CChainState::ResetBlockFailureFlags(CBlockIndex *pindex) {
int nHeight = pindex->nHeight;
// Remove the invalidity flag from this block and all its descendants.
BlockMap::iterator it = m_blockman.m_block_index.begin();
while (it != m_blockman.m_block_index.end()) {
if (!it->second->IsValid() && it->second->GetAncestor(nHeight) == pindex) {
it->second->nStatus &= ~BLOCK_FAILED_MASK;
if (it->second->IsValid(BLOCK_VALID_TRANSACTIONS) && it->second->HaveTxsDownloaded() && setBlockIndexCandidates.value_comp()(m_chain.Tip(), it->second)) {
if (it->second == pindexBestInvalid) {
// Reset invalid block marker if it was pointing to one of those.
pindexBestInvalid = nullptr;
// Remove the invalidity flag from all ancestors too.
while (pindex != nullptr) {
if (pindex->nStatus & BLOCK_FAILED_MASK) {
pindex->nStatus &= ~BLOCK_FAILED_MASK;
pindex = pindex->pprev;
CBlockIndex* BlockManager::AddToBlockIndex(const CBlockHeader& block)
// Check for duplicate
uint256 hash = block.GetHash();
BlockMap::iterator it = m_block_index.find(hash);
if (it != m_block_index.end())
return it->second;
// Construct new block index object
CBlockIndex* pindexNew = new CBlockIndex(block);
// We assign the sequence id to blocks only when the full data is available,
// to avoid miners withholding blocks but broadcasting headers, to get a
// competitive advantage.
pindexNew->nSequenceId = 0;
BlockMap::iterator mi = m_block_index.insert(std::make_pair(hash, pindexNew)).first;
pindexNew->phashBlock = &((*mi).first);
BlockMap::iterator miPrev = m_block_index.find(block.hashPrevBlock);
if (miPrev != m_block_index.end())
pindexNew->pprev = (*miPrev).second;
pindexNew->nHeight = pindexNew->pprev->nHeight + 1;
pindexNew->nTimeMax = (pindexNew->pprev ? std::max(pindexNew->pprev->nTimeMax, pindexNew->nTime) : pindexNew->nTime);
pindexNew->nChainWork = (pindexNew->pprev ? pindexNew->pprev->nChainWork : 0) + GetBlockProof(*pindexNew);
if (pindexBestHeader == nullptr || pindexBestHeader->nChainWork < pindexNew->nChainWork)
pindexBestHeader = pindexNew;
return pindexNew;
/** Mark a block as having its data received and checked (up to BLOCK_VALID_TRANSACTIONS). */
void CChainState::ReceivedBlockTransactions(const CBlock& block, CBlockIndex* pindexNew, const FlatFilePos& pos, const Consensus::Params& consensusParams)
pindexNew->nTx = block.vtx.size();
pindexNew->nChainTx = 0;
pindexNew->nFile = pos.nFile;
pindexNew->nDataPos = pos.nPos;
pindexNew->nUndoPos = 0;
pindexNew->nStatus |= BLOCK_HAVE_DATA;
if (IsWitnessEnabled(pindexNew->pprev, consensusParams)) {
pindexNew->nStatus |= BLOCK_OPT_WITNESS;
if (pindexNew->pprev == nullptr || pindexNew->pprev->HaveTxsDownloaded()) {
// If pindexNew is the genesis block or all parents are BLOCK_VALID_TRANSACTIONS.
std::deque<CBlockIndex*> queue;
// Recursively process any descendant blocks that now may be eligible to be connected.
while (!queue.empty()) {
CBlockIndex *pindex = queue.front();
pindex->nChainTx = (pindex->pprev ? pindex->pprev->nChainTx : 0) + pindex->nTx;
pindex->nSequenceId = nBlockSequenceId++;
if (m_chain.Tip() == nullptr || !setBlockIndexCandidates.value_comp()(pindex, m_chain.Tip())) {
std::pair<std::multimap<CBlockIndex*, CBlockIndex*>::iterator, std::multimap<CBlockIndex*, CBlockIndex*>::iterator> range = m_blockman.m_blocks_unlinked.equal_range(pindex);
while (range.first != range.second) {
std::multimap<CBlockIndex*, CBlockIndex*>::iterator it = range.first;
} else {
if (pindexNew->pprev && pindexNew->pprev->IsValid(BLOCK_VALID_TREE)) {
m_blockman.m_blocks_unlinked.insert(std::make_pair(pindexNew->pprev, pindexNew));
static bool FindBlockPos(FlatFilePos &pos, unsigned int nAddSize, unsigned int nHeight, CChain& active_chain, uint64_t nTime, bool fKnown = false)
unsigned int nFile = fKnown ? pos.nFile : nLastBlockFile;
if (vinfoBlockFile.size() <= nFile) {
vinfoBlockFile.resize(nFile + 1);
bool finalize_undo = false;
if (!fKnown) {
while (vinfoBlockFile[nFile].nSize + nAddSize >= (gArgs.GetBoolArg("-fastprune", false) ? 0x10000 /* 64kb */ : MAX_BLOCKFILE_SIZE)) {
// when the undo file is keeping up with the block file, we want to flush it explicitly
// when it is lagging behind (more blocks arrive than are being connected), we let the
// undo block write case handle it
assert(std::addressof(::ChainActive()) == std::addressof(active_chain));
finalize_undo = (vinfoBlockFile[nFile].nHeightLast == (unsigned int)active_chain.Tip()->nHeight);
if (vinfoBlockFile.size() <= nFile) {
vinfoBlockFile.resize(nFile + 1);
pos.nFile = nFile;
pos.nPos = vinfoBlockFile[nFile].nSize;
if ((int)nFile != nLastBlockFile) {
if (!fKnown) {
LogPrint(BCLog::VALIDATION, "Leaving block file %i: %s\n", nLastBlockFile, vinfoBlockFile[nLastBlockFile].ToString());
FlushBlockFile(!fKnown, finalize_undo);
nLastBlockFile = nFile;
vinfoBlockFile[nFile].AddBlock(nHeight, nTime);
if (fKnown)
vinfoBlockFile[nFile].nSize = std::max(pos.nPos + nAddSize, vinfoBlockFile[nFile].nSize);
vinfoBlockFile[nFile].nSize += nAddSize;
if (!fKnown) {
bool out_of_space;
size_t bytes_allocated = BlockFileSeq().Allocate(pos, nAddSize, out_of_space);
if (out_of_space) {
return AbortNode("Disk space is too low!", _("Disk space is too low!"));
if (bytes_allocated != 0 && fPruneMode) {
fCheckForPruning = true;
return true;
static bool FindUndoPos(BlockValidationState &state, int nFile, FlatFilePos &pos, unsigned int nAddSize)
pos.nFile = nFile;
pos.nPos = vinfoBlockFile[nFile].nUndoSize;
vinfoBlockFile[nFile].nUndoSize += nAddSize;
bool out_of_space;
size_t bytes_allocated = UndoFileSeq().Allocate(pos, nAddSize, out_of_space);
if (out_of_space) {
return AbortNode(state, "Disk space is too low!", _("Disk space is too low!"));
if (bytes_allocated != 0 && fPruneMode) {
fCheckForPruning = true;
return true;
static bool CheckBlockHeader(const CBlockHeader& block, BlockValidationState& state, const Consensus::Params& consensusParams, bool fCheckPOW = true)
// Check proof of work matches claimed amount
if (fCheckPOW && !CheckProofOfWork(block.GetHash(), block.nBits, consensusParams))
return state.Invalid(BlockValidationResult::BLOCK_INVALID_HEADER, "high-hash", "proof of work failed");
return true;
bool CheckBlock(const CBlock& block, BlockValidationState& state, const Consensus::Params& consensusParams, bool fCheckPOW, bool fCheckMerkleRoot)
// These are checks that are independent of context.
if (block.fChecked)
return true;
// Check that the header is valid (particularly PoW). This is mostly
// redundant with the call in AcceptBlockHeader.
if (!CheckBlockHeader(block, state, consensusParams, fCheckPOW))
return false;
// Signet only: check block solution
if (consensusParams.signet_blocks && fCheckPOW && !CheckSignetBlockSolution(block, consensusParams)) {
return state.Invalid(BlockValidationResult::BLOCK_CONSENSUS, "bad-signet-blksig", "signet block signature validation failure");
// Check the merkle root.
if (fCheckMerkleRoot) {
bool mutated;
uint256 hashMerkleRoot2 = BlockMerkleRoot(block, &mutated);
if (block.hashMerkleRoot != hashMerkleRoot2)
return state.Invalid(BlockValidationResult::BLOCK_MUTATED, "bad-txnmrklroot", "hashMerkleRoot mismatch");
// Check for merkle tree malleability (CVE-2012-2459): repeating sequences
// of transactions in a block without affecting the merkle root of a block,
// while still invalidating it.
if (mutated)
return state.Invalid(BlockValidationResult::BLOCK_MUTATED, "bad-txns-duplicate", "duplicate transaction");
// All potential-corruption validation must be done before we do any
// transaction validation, as otherwise we may mark the header as invalid
// because we receive the wrong transactions for it.
// Note that witness malleability is checked in ContextualCheckBlock, so no
// checks that use witness data may be performed here.
// Size limits
return state.Invalid(BlockValidationResult::BLOCK_CONSENSUS, "bad-blk-length", "size limits failed");
// First transaction must be coinbase, the rest must not be
if (block.vtx.empty() || !block.vtx[0]->IsCoinBase())
return state.Invalid(BlockValidationResult::BLOCK_CONSENSUS, "bad-cb-missing", "first tx is not coinbase");
for (unsigned int i = 1; i < block.vtx.size(); i++)
if (block.vtx[i]->IsCoinBase())
return state.Invalid(BlockValidationResult::BLOCK_CONSENSUS, "bad-cb-multiple", "more than one coinbase");
// Check transactions
// Must check for duplicate inputs (see CVE-2018-17144)
for (const auto& tx : block.vtx) {
TxValidationState tx_state;
if (!CheckTransaction(*tx, tx_state)) {
// CheckBlock() does context-free validation checks. The only
// possible failures are consensus failures.
assert(tx_state.GetResult() == TxValidationResult::TX_CONSENSUS);
return state.Invalid(BlockValidationResult::BLOCK_CONSENSUS, tx_state.GetRejectReason(),
strprintf("Transaction check failed (tx hash %s) %s", tx->GetHash().ToString(), tx_state.GetDebugMessage()));
unsigned int nSigOps = 0;
for (const auto& tx : block.vtx)
nSigOps += GetLegacySigOpCount(*tx);
return state.Invalid(BlockValidationResult::BLOCK_CONSENSUS, "bad-blk-sigops", "out-of-bounds SigOpCount");
if (fCheckPOW && fCheckMerkleRoot)
block.fChecked = true;
return true;
bool IsWitnessEnabled(const CBlockIndex* pindexPrev, const Consensus::Params& params)
int height = pindexPrev == nullptr ? 0 : pindexPrev->nHeight + 1;
return (height >= params.SegwitHeight);
void UpdateUncommittedBlockStructures(CBlock& block, const CBlockIndex* pindexPrev, const Consensus::Params& consensusParams)
int commitpos = GetWitnessCommitmentIndex(block);
static const std::vector<unsigned char> nonce(32, 0x00);
if (commitpos != NO_WITNESS_COMMITMENT && IsWitnessEnabled(pindexPrev, consensusParams) && !block.vtx[0]->HasWitness()) {
CMutableTransaction tx(*block.vtx[0]);[0].scriptWitness.stack.resize(1);[0].scriptWitness.stack[0] = nonce;
block.vtx[0] = MakeTransactionRef(std::move(tx));
std::vector<unsigned char> GenerateCoinbaseCommitment(CBlock& block, const CBlockIndex* pindexPrev, const Consensus::Params& consensusParams)
std::vector<unsigned char> commitment;