txmempool.h

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// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2022 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#ifndef BITCOIN_TXMEMPOOL_H
#define BITCOIN_TXMEMPOOL_H

#include <coins.h>
#include <consensus/amount.h>
#include <indirectmap.h>
#include <kernel/cs_main.h>
#include <kernel/mempool_entry.h>          // IWYU pragma: export
#include <kernel/mempool_limits.h>         // IWYU pragma: export
#include <kernel/mempool_options.h>        // IWYU pragma: export
#include <kernel/mempool_removal_reason.h> // IWYU pragma: export
#include <policy/feerate.h>
#include <policy/packages.h>
#include <primitives/transaction.h>
#include <sync.h>
#include <util/epochguard.h>
#include <util/hasher.h>
#include <util/result.h>
#include <util/feefrac.h>

#include <boost/multi_index/hashed_index.hpp>
#include <boost/multi_index/identity.hpp>
#include <boost/multi_index/indexed_by.hpp>
#include <boost/multi_index/ordered_index.hpp>
#include <boost/multi_index/sequenced_index.hpp>
#include <boost/multi_index/tag.hpp>
#include <boost/multi_index_container.hpp>

#include <atomic>
#include <map>
#include <optional>
#include <set>
#include <string>
#include <string_view>
#include <utility>
#include <vector>

class CChain;
class ValidationSignals;

struct bilingual_str;

static const uint32_t MEMPOOL_HEIGHT = 0x7FFFFFFF;

bool TestLockPointValidity(CChain& active_chain, const LockPoints& lp) EXCLUSIVE_LOCKS_REQUIRED(cs_main);

// extracts a transaction hash from CTxMemPoolEntry or CTransactionRef
struct mempoolentry_txid
{
    typedef uint256 result_type;
    result_type operator() (const CTxMemPoolEntry &entry) const
    {
        return entry.GetTx().GetHash();
    }

    result_type operator() (const CTransactionRef& tx) const
    {
        return tx->GetHash();
    }
};

// extracts a transaction witness-hash from CTxMemPoolEntry or CTransactionRef
struct mempoolentry_wtxid
{
    typedef uint256 result_type;
    result_type operator() (const CTxMemPoolEntry &entry) const
    {
        return entry.GetTx().GetWitnessHash();
    }

    result_type operator() (const CTransactionRef& tx) const
    {
        return tx->GetWitnessHash();
    }
};


class CompareTxMemPoolEntryByDescendantScore
{
public:
    bool operator()(const CTxMemPoolEntry& a, const CTxMemPoolEntry& b) const
    {
        double a_mod_fee, a_size, b_mod_fee, b_size;

        GetModFeeAndSize(a, a_mod_fee, a_size);
        GetModFeeAndSize(b, b_mod_fee, b_size);

        // Avoid division by rewriting (a/b > c/d) as (a*d > c*b).
        double f1 = a_mod_fee * b_size;
        double f2 = a_size * b_mod_fee;

        if (f1 == f2) {
            return a.GetTime() >= b.GetTime();
        }
        return f1 < f2;
    }

    // Return the fee/size we're using for sorting this entry.
    void GetModFeeAndSize(const CTxMemPoolEntry &a, double &mod_fee, double &size) const
    {
        // Compare feerate with descendants to feerate of the transaction, and
        // return the fee/size for the max.
        double f1 = (double)a.GetModifiedFee() * a.GetSizeWithDescendants();
        double f2 = (double)a.GetModFeesWithDescendants() * a.GetTxSize();

        if (f2 > f1) {
            mod_fee = a.GetModFeesWithDescendants();
            size = a.GetSizeWithDescendants();
        } else {
            mod_fee = a.GetModifiedFee();
            size = a.GetTxSize();
        }
    }
};

class CompareTxMemPoolEntryByScore
{
public:
    bool operator()(const CTxMemPoolEntry& a, const CTxMemPoolEntry& b) const
    {
        double f1 = (double)a.GetFee() * b.GetTxSize();
        double f2 = (double)b.GetFee() * a.GetTxSize();
        if (f1 == f2) {
            return b.GetTx().GetHash() < a.GetTx().GetHash();
        }
        return f1 > f2;
    }
};

class CompareTxMemPoolEntryByEntryTime
{
public:
    bool operator()(const CTxMemPoolEntry& a, const CTxMemPoolEntry& b) const
    {
        return a.GetTime() < b.GetTime();
    }
};

class CompareTxMemPoolEntryByAncestorFee
{
public:
    template<typename T>
    bool operator()(const T& a, const T& b) const
    {
        double a_mod_fee, a_size, b_mod_fee, b_size;

        GetModFeeAndSize(a, a_mod_fee, a_size);
        GetModFeeAndSize(b, b_mod_fee, b_size);

        // Avoid division by rewriting (a/b > c/d) as (a*d > c*b).
        double f1 = a_mod_fee * b_size;
        double f2 = a_size * b_mod_fee;

        if (f1 == f2) {
            return a.GetTx().GetHash() < b.GetTx().GetHash();
        }
        return f1 > f2;
    }

    // Return the fee/size we're using for sorting this entry.
    template <typename T>
    void GetModFeeAndSize(const T &a, double &mod_fee, double &size) const
    {
        // Compare feerate with ancestors to feerate of the transaction, and
        // return the fee/size for the min.
        double f1 = (double)a.GetModifiedFee() * a.GetSizeWithAncestors();
        double f2 = (double)a.GetModFeesWithAncestors() * a.GetTxSize();

        if (f1 > f2) {
            mod_fee = a.GetModFeesWithAncestors();
            size = a.GetSizeWithAncestors();
        } else {
            mod_fee = a.GetModifiedFee();
            size = a.GetTxSize();
        }
    }
};

// Multi_index tag names
struct descendant_score {};
struct entry_time {};
struct ancestor_score {};
struct index_by_wtxid {};

struct TxMempoolInfo
{
    CTransactionRef tx;

    std::chrono::seconds m_time;

    CAmount fee;

    int32_t vsize;

    int64_t nFeeDelta;
};

class CTxMemPool
{
protected:
    std::atomic<unsigned int> nTransactionsUpdated{0}; 

    uint64_t totalTxSize GUARDED_BY(cs){0};      
    CAmount m_total_fee GUARDED_BY(cs){0};       
    uint64_t cachedInnerUsage GUARDED_BY(cs){0}; 

    mutable int64_t lastRollingFeeUpdate GUARDED_BY(cs){GetTime()};
    mutable bool blockSinceLastRollingFeeBump GUARDED_BY(cs){false};
    mutable double rollingMinimumFeeRate GUARDED_BY(cs){0}; 
    mutable Epoch m_epoch GUARDED_BY(cs){};

    // In-memory counter for external mempool tracking purposes.
    // This number is incremented once every time a transaction
    // is added or removed from the mempool for any reason.
    mutable uint64_t m_sequence_number GUARDED_BY(cs){1};

    void trackPackageRemoved(const CFeeRate& rate) EXCLUSIVE_LOCKS_REQUIRED(cs);

    bool m_load_tried GUARDED_BY(cs){false};

    CFeeRate GetMinFee(size_t sizelimit) const;

public:

    static const int ROLLING_FEE_HALFLIFE = 60 * 60 * 12; // public only for testing

    struct CTxMemPoolEntry_Indices final : boost::multi_index::indexed_by<
            // sorted by txid
            boost::multi_index::hashed_unique<mempoolentry_txid, SaltedTxidHasher>,
            // sorted by wtxid
            boost::multi_index::hashed_unique<
                boost::multi_index::tag<index_by_wtxid>,
                mempoolentry_wtxid,
                SaltedTxidHasher
            >,
            // sorted by fee rate
            boost::multi_index::ordered_non_unique<
                boost::multi_index::tag<descendant_score>,
                boost::multi_index::identity<CTxMemPoolEntry>,
                CompareTxMemPoolEntryByDescendantScore
            >,
            // sorted by entry time
            boost::multi_index::ordered_non_unique<
                boost::multi_index::tag<entry_time>,
                boost::multi_index::identity<CTxMemPoolEntry>,
                CompareTxMemPoolEntryByEntryTime
            >,
            // sorted by fee rate with ancestors
            boost::multi_index::ordered_non_unique<
                boost::multi_index::tag<ancestor_score>,
                boost::multi_index::identity<CTxMemPoolEntry>,
                CompareTxMemPoolEntryByAncestorFee
            >
        >
        {};
    typedef boost::multi_index_container<
        CTxMemPoolEntry,
        CTxMemPoolEntry_Indices
    > indexed_transaction_set;

    mutable RecursiveMutex cs;
    indexed_transaction_set mapTx GUARDED_BY(cs);

    using txiter = indexed_transaction_set::nth_index<0>::type::const_iterator;
    std::vector<CTransactionRef> txns_randomized GUARDED_BY(cs); 

    typedef std::set<txiter, CompareIteratorByHash> setEntries;

    using Limits = kernel::MemPoolLimits;

    uint64_t CalculateDescendantMaximum(txiter entry) const EXCLUSIVE_LOCKS_REQUIRED(cs);
private:
    typedef std::map<txiter, setEntries, CompareIteratorByHash> cacheMap;


    void UpdateParent(txiter entry, txiter parent, bool add) EXCLUSIVE_LOCKS_REQUIRED(cs);
    void UpdateChild(txiter entry, txiter child, bool add) EXCLUSIVE_LOCKS_REQUIRED(cs);

    std::vector<indexed_transaction_set::const_iterator> GetSortedDepthAndScore() const EXCLUSIVE_LOCKS_REQUIRED(cs);

    std::set<uint256> m_unbroadcast_txids GUARDED_BY(cs);


    util::Result<setEntries> CalculateAncestorsAndCheckLimits(int64_t entry_size,
                                                              size_t entry_count,
                                                              CTxMemPoolEntry::Parents &staged_ancestors,
                                                              const Limits& limits
                                                              ) const EXCLUSIVE_LOCKS_REQUIRED(cs);

public:
    indirectmap<COutPoint, const CTransaction*> mapNextTx GUARDED_BY(cs);
    std::map<uint256, CAmount> mapDeltas GUARDED_BY(cs);

    using Options = kernel::MemPoolOptions;

    const Options m_opts;

    explicit CTxMemPool(Options opts, bilingual_str& error);

    void check(const CCoinsViewCache& active_coins_tip, int64_t spendheight) const EXCLUSIVE_LOCKS_REQUIRED(::cs_main);


    void removeRecursive(const CTransaction& tx, MemPoolRemovalReason reason) EXCLUSIVE_LOCKS_REQUIRED(cs);
    void removeForReorg(CChain& chain, std::function<bool(txiter)> filter_final_and_mature) EXCLUSIVE_LOCKS_REQUIRED(cs, cs_main);
    void removeConflicts(const CTransaction& tx) EXCLUSIVE_LOCKS_REQUIRED(cs);
    void removeForBlock(const std::vector<CTransactionRef>& vtx, unsigned int nBlockHeight) EXCLUSIVE_LOCKS_REQUIRED(cs);

    bool CompareDepthAndScore(const uint256& hasha, const uint256& hashb, bool wtxid=false);
    bool isSpent(const COutPoint& outpoint) const;
    unsigned int GetTransactionsUpdated() const;
    void AddTransactionsUpdated(unsigned int n);
    bool HasNoInputsOf(const CTransaction& tx) const EXCLUSIVE_LOCKS_REQUIRED(cs);

    void PrioritiseTransaction(const uint256& hash, const CAmount& nFeeDelta);
    void ApplyDelta(const uint256& hash, CAmount &nFeeDelta) const EXCLUSIVE_LOCKS_REQUIRED(cs);
    void ClearPrioritisation(const uint256& hash) EXCLUSIVE_LOCKS_REQUIRED(cs);

    struct delta_info {
        const bool in_mempool;
        const CAmount delta;
        std::optional<CAmount> modified_fee;
        const uint256 txid;
    };
    std::vector<delta_info> GetPrioritisedTransactions() const EXCLUSIVE_LOCKS_REQUIRED(!cs);

    const CTransaction* GetConflictTx(const COutPoint& prevout) const EXCLUSIVE_LOCKS_REQUIRED(cs);

    std::optional<txiter> GetIter(const uint256& txid) const EXCLUSIVE_LOCKS_REQUIRED(cs);

    setEntries GetIterSet(const std::set<Txid>& hashes) const EXCLUSIVE_LOCKS_REQUIRED(cs);

    std::vector<txiter> GetIterVec(const std::vector<uint256>& txids) const EXCLUSIVE_LOCKS_REQUIRED(cs);

    void UpdateTransactionsFromBlock(const std::vector<uint256>& vHashesToUpdate) EXCLUSIVE_LOCKS_REQUIRED(cs, cs_main) LOCKS_EXCLUDED(m_epoch);

    util::Result<setEntries> CalculateMemPoolAncestors(const CTxMemPoolEntry& entry,
                                   const Limits& limits,
                                   bool fSearchForParents = true) const EXCLUSIVE_LOCKS_REQUIRED(cs);

    setEntries AssumeCalculateMemPoolAncestors(
        std::string_view calling_fn_name,
        const CTxMemPoolEntry &entry,
        const Limits& limits,
        bool fSearchForParents = true) const EXCLUSIVE_LOCKS_REQUIRED(cs);

    std::vector<txiter> GatherClusters(const std::vector<uint256>& txids) const EXCLUSIVE_LOCKS_REQUIRED(cs);

    util::Result<void> CheckPackageLimits(const Package& package,
                                          int64_t total_vsize) const EXCLUSIVE_LOCKS_REQUIRED(cs);

    void CalculateDescendants(txiter it, setEntries& setDescendants) const EXCLUSIVE_LOCKS_REQUIRED(cs);

    CFeeRate GetMinFee() const {
        return GetMinFee(m_opts.max_size_bytes);
    }

    void TrimToSize(size_t sizelimit, std::vector<COutPoint>* pvNoSpendsRemaining = nullptr) EXCLUSIVE_LOCKS_REQUIRED(cs);

    int Expire(std::chrono::seconds time) EXCLUSIVE_LOCKS_REQUIRED(cs);

    void GetTransactionAncestry(const uint256& txid, size_t& ancestors, size_t& descendants, size_t* ancestorsize = nullptr, CAmount* ancestorfees = nullptr) const;

    bool GetLoadTried() const;

    void SetLoadTried(bool load_tried);

    unsigned long size() const
    {
        LOCK(cs);
        return mapTx.size();
    }

    uint64_t GetTotalTxSize() const EXCLUSIVE_LOCKS_REQUIRED(cs)
    {
        AssertLockHeld(cs);
        return totalTxSize;
    }

    CAmount GetTotalFee() const EXCLUSIVE_LOCKS_REQUIRED(cs)
    {
        AssertLockHeld(cs);
        return m_total_fee;
    }

    bool exists(const GenTxid& gtxid) const
    {
        LOCK(cs);
        if (gtxid.IsWtxid()) {
            return (mapTx.get<index_by_wtxid>().count(gtxid.GetHash()) != 0);
        }
        return (mapTx.count(gtxid.GetHash()) != 0);
    }

    const CTxMemPoolEntry* GetEntry(const Txid& txid) const LIFETIMEBOUND EXCLUSIVE_LOCKS_REQUIRED(cs);

    CTransactionRef get(const uint256& hash) const;
    txiter get_iter_from_wtxid(const uint256& wtxid) const EXCLUSIVE_LOCKS_REQUIRED(cs)
    {
        AssertLockHeld(cs);
        return mapTx.project<0>(mapTx.get<index_by_wtxid>().find(wtxid));
    }
    TxMempoolInfo info(const GenTxid& gtxid) const;

    TxMempoolInfo info_for_relay(const GenTxid& gtxid, uint64_t last_sequence) const;

    std::vector<CTxMemPoolEntryRef> entryAll() const EXCLUSIVE_LOCKS_REQUIRED(cs);
    std::vector<TxMempoolInfo> infoAll() const;

    size_t DynamicMemoryUsage() const;

    void AddUnbroadcastTx(const uint256& txid)
    {
        LOCK(cs);
        // Sanity check the transaction is in the mempool & insert into
        // unbroadcast set.
        if (exists(GenTxid::Txid(txid))) m_unbroadcast_txids.insert(txid);
    };

    void RemoveUnbroadcastTx(const uint256& txid, const bool unchecked = false);

    std::set<uint256> GetUnbroadcastTxs() const
    {
        LOCK(cs);
        return m_unbroadcast_txids;
    }

    bool IsUnbroadcastTx(const uint256& txid) const EXCLUSIVE_LOCKS_REQUIRED(cs)
    {
        AssertLockHeld(cs);
        return m_unbroadcast_txids.count(txid) != 0;
    }

    uint64_t GetAndIncrementSequence() const EXCLUSIVE_LOCKS_REQUIRED(cs) {
        return m_sequence_number++;
    }

    uint64_t GetSequence() const EXCLUSIVE_LOCKS_REQUIRED(cs) {
        return m_sequence_number;
    }

    /* Check that all direct conflicts are in a cluster size of two or less. Each
     * direct conflict may be in a separate cluster.
     */
    std::optional<std::string> CheckConflictTopology(const setEntries& direct_conflicts);

private:
    void RemoveStaged(setEntries& stage, bool updateDescendants, MemPoolRemovalReason reason) EXCLUSIVE_LOCKS_REQUIRED(cs);

    void UpdateForDescendants(txiter updateIt, cacheMap& cachedDescendants,
                              const std::set<uint256>& setExclude, std::set<uint256>& descendants_to_remove) EXCLUSIVE_LOCKS_REQUIRED(cs);
    void UpdateAncestorsOf(bool add, txiter hash, setEntries &setAncestors) EXCLUSIVE_LOCKS_REQUIRED(cs);
    void UpdateEntryForAncestors(txiter it, const setEntries &setAncestors) EXCLUSIVE_LOCKS_REQUIRED(cs);
    void UpdateForRemoveFromMempool(const setEntries &entriesToRemove, bool updateDescendants) EXCLUSIVE_LOCKS_REQUIRED(cs);
    void UpdateChildrenForRemoval(txiter entry) EXCLUSIVE_LOCKS_REQUIRED(cs);

    void removeUnchecked(txiter entry, MemPoolRemovalReason reason) EXCLUSIVE_LOCKS_REQUIRED(cs);
public:
    bool visited(const txiter it) const EXCLUSIVE_LOCKS_REQUIRED(cs, m_epoch)
    {
        return m_epoch.visited(it->m_epoch_marker);
    }

    bool visited(std::optional<txiter> it) const EXCLUSIVE_LOCKS_REQUIRED(cs, m_epoch)
    {
        assert(m_epoch.guarded()); // verify guard even when it==nullopt
        return !it || visited(*it);
    }

    /*
     * CTxMemPool::ChangeSet:
     *
     * This class is used for all mempool additions and associated removals (eg
     * due to rbf). Removals that don't need to be evaluated for acceptance,
     * such as removing transactions that appear in a block, or due to reorg,
     * or removals related to mempool limiting or expiry do not need to use
     * this.
     *
     * Callers can interleave calls to StageAddition()/StageRemoval(), and
     * removals may be invoked in any order, but additions must be done in a
     * topological order in the case of transaction packages (ie, parents must
     * be added before children).
     *
     * CalculateChunksForRBF() can be used to calculate the feerate diagram of
     * the proposed set of new transactions and compare with the existing
     * mempool.
     *
     * CalculateMemPoolAncestors() calculates the in-mempool (not including
     * what is in the change set itself) ancestors of a given transaction.
     *
     * Apply() will apply the removals and additions that are staged into the
     * mempool.
     *
     * Only one changeset may exist at a time. While a changeset is
     * outstanding, no removals or additions may be made directly to the
     * mempool.
     */
    class ChangeSet {
    public:
        explicit ChangeSet(CTxMemPool* pool) : m_pool(pool) {}
        ~ChangeSet() EXCLUSIVE_LOCKS_REQUIRED(m_pool->cs) { m_pool->m_have_changeset = false; }

        ChangeSet(const ChangeSet&) = delete;
        ChangeSet& operator=(const ChangeSet&) = delete;

        using TxHandle = CTxMemPool::txiter;

        TxHandle StageAddition(const CTransactionRef& tx, const CAmount fee, int64_t time, unsigned int entry_height, uint64_t entry_sequence, bool spends_coinbase, int64_t sigops_cost, LockPoints lp);
        void StageRemoval(CTxMemPool::txiter it) { m_to_remove.insert(it); }

        const CTxMemPool::setEntries& GetRemovals() const { return m_to_remove; }

        util::Result<CTxMemPool::setEntries> CalculateMemPoolAncestors(TxHandle tx, const Limits& limits)
        {
            // Look up transaction in our cache first
            auto it = m_ancestors.find(tx);
            if (it != m_ancestors.end()) return it->second;

            // If not found, try to have the mempool calculate it, and cache
            // for later.
            LOCK(m_pool->cs);
            auto ret{m_pool->CalculateMemPoolAncestors(*tx, limits)};
            if (ret) m_ancestors.try_emplace(tx, *ret);
            return ret;
        }

        std::vector<CTransactionRef> GetAddedTxns() const {
            std::vector<CTransactionRef> ret;
            ret.reserve(m_entry_vec.size());
            for (const auto& entry : m_entry_vec) {
                ret.emplace_back(entry->GetSharedTx());
            }
            return ret;
        }

        util::Result<std::pair<std::vector<FeeFrac>, std::vector<FeeFrac>>> CalculateChunksForRBF();

        size_t GetTxCount() const { return m_entry_vec.size(); }
        const CTransaction& GetAddedTxn(size_t index) const { return m_entry_vec.at(index)->GetTx(); }

        void Apply() EXCLUSIVE_LOCKS_REQUIRED(cs_main);

    private:
        CTxMemPool* m_pool;
        CTxMemPool::indexed_transaction_set m_to_add;
        std::vector<CTxMemPool::txiter> m_entry_vec; // track the added transactions' insertion order
        // map from the m_to_add index to the ancestors for the transaction
        std::map<CTxMemPool::txiter, CTxMemPool::setEntries, CompareIteratorByHash> m_ancestors;
        CTxMemPool::setEntries m_to_remove;

        friend class CTxMemPool;
    };

    std::unique_ptr<ChangeSet> GetChangeSet() EXCLUSIVE_LOCKS_REQUIRED(cs) {
        Assume(!m_have_changeset);
        m_have_changeset = true;
        return std::make_unique<ChangeSet>(this);
    }

    bool m_have_changeset GUARDED_BY(cs){false};

    friend class CTxMemPool::ChangeSet;

private:
    // Apply the given changeset to the mempool, by removing transactions in
    // the to_remove set and adding transactions in the to_add set.
    void Apply(CTxMemPool::ChangeSet* changeset) EXCLUSIVE_LOCKS_REQUIRED(cs);

    // addNewTransaction must update state for all ancestors of a given transaction,
    // to track size/count of descendant transactions.  First version of
    // addNewTransaction can be used to have it call CalculateMemPoolAncestors(), and
    // then invoke the second version.
    // Note that addNewTransaction is ONLY called (via Apply()) from ATMP
    // outside of tests and any other callers may break wallet's in-mempool
    // tracking (due to lack of CValidationInterface::TransactionAddedToMempool
    // callbacks).
    void addNewTransaction(CTxMemPool::txiter it) EXCLUSIVE_LOCKS_REQUIRED(cs);
    void addNewTransaction(CTxMemPool::txiter it, CTxMemPool::setEntries& setAncestors) EXCLUSIVE_LOCKS_REQUIRED(cs);
};

class CCoinsViewMemPool : public CCoinsViewBacked
{
    std::unordered_map<COutPoint, Coin, SaltedOutpointHasher> m_temp_added;

    mutable std::unordered_set<COutPoint, SaltedOutpointHasher> m_non_base_coins;
protected:
    const CTxMemPool& mempool;

public:
    CCoinsViewMemPool(CCoinsView* baseIn, const CTxMemPool& mempoolIn);
    std::optional<Coin> GetCoin(const COutPoint& outpoint) const override;
    void PackageAddTransaction(const CTransactionRef& tx);
    std::unordered_set<COutPoint, SaltedOutpointHasher> GetNonBaseCoins() const { return m_non_base_coins; }
    void Reset();
};
#endif // BITCOIN_TXMEMPOOL_H