aboutsummaryrefslogtreecommitdiff
path: root/src/txmempool.h
blob: a1867eb895ae65b90bdfcfa97d1cb35c6b060f51 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
// 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 <atomic>
#include <map>
#include <optional>
#include <set>
#include <string>
#include <string_view>
#include <utility>
#include <vector>

#include <kernel/mempool_limits.h>
#include <kernel/mempool_options.h>

#include <coins.h>
#include <consensus/amount.h>
#include <indirectmap.h>
#include <kernel/cs_main.h>
#include <kernel/mempool_entry.h>
#include <policy/feerate.h>
#include <policy/packages.h>
#include <primitives/transaction.h>
#include <random.h>
#include <sync.h>
#include <util/epochguard.h>
#include <util/hasher.h>
#include <util/result.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>

class CBlockIndex;
class CChain;
class Chainstate;

/** Fake height value used in Coin to signify they are only in the memory pool (since 0.8) */
static const uint32_t MEMPOOL_HEIGHT = 0x7FFFFFFF;

/**
 * Test whether the LockPoints height and time are still valid on the current chain
 */
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
 *
 *  Sort an entry by max(score/size of entry's tx, score/size with all descendants).
 */
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
 *
 *  Sort by feerate of entry (fee/size) in descending order
 *  This is only used for transaction relay, so we use GetFee()
 *  instead of GetModifiedFee() to avoid leaking prioritization
 *  information via the sort order.
 */
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 CompareTxMemPoolEntryByAncestorScore
 *
 *  Sort an entry by min(score/size of entry's tx, score/size with all ancestors).
 */
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 {};

class CBlockPolicyEstimator;

/**
 * Information about a mempool transaction.
 */
struct TxMempoolInfo
{
    /** The transaction itself */
    CTransactionRef tx;

    /** Time the transaction entered the mempool. */
    std::chrono::seconds m_time;

    /** Fee of the transaction. */
    CAmount fee;

    /** Virtual size of the transaction. */
    int32_t vsize;

    /** The fee delta. */
    int64_t nFeeDelta;
};

/** Reason why a transaction was removed from the mempool,
 * this is passed to the notification signal.
 */
enum class MemPoolRemovalReason {
    EXPIRY,      //!< Expired from mempool
    SIZELIMIT,   //!< Removed in size limiting
    REORG,       //!< Removed for reorganization
    BLOCK,       //!< Removed for block
    CONFLICT,    //!< Removed for conflict with in-block transaction
    REPLACED,    //!< Removed for replacement
};

std::string RemovalReasonToString(const MemPoolRemovalReason& r) noexcept;

/**
 * CTxMemPool stores valid-according-to-the-current-best-chain transactions
 * that may be included in the next block.
 *
 * Transactions are added when they are seen on the network (or created by the
 * local node), but not all transactions seen are added to the pool. For
 * example, the following new transactions will not be added to the mempool:
 * - a transaction which doesn't meet the minimum fee requirements.
 * - a new transaction that double-spends an input of a transaction already in
 * the pool where the new transaction does not meet the Replace-By-Fee
 * requirements as defined in doc/policy/mempool-replacements.md.
 * - a non-standard transaction.
 *
 * CTxMemPool::mapTx, and CTxMemPoolEntry bookkeeping:
 *
 * mapTx is a boost::multi_index that sorts the mempool on 5 criteria:
 * - transaction hash (txid)
 * - witness-transaction hash (wtxid)
 * - descendant feerate [we use max(feerate of tx, feerate of tx with all descendants)]
 * - time in mempool
 * - ancestor feerate [we use min(feerate of tx, feerate of tx with all unconfirmed ancestors)]
 *
 * Note: the term "descendant" refers to in-mempool transactions that depend on
 * this one, while "ancestor" refers to in-mempool transactions that a given
 * transaction depends on.
 *
 * In order for the feerate sort to remain correct, we must update transactions
 * in the mempool when new descendants arrive.  To facilitate this, we track
 * the set of in-mempool direct parents and direct children in mapLinks.  Within
 * each CTxMemPoolEntry, we track the size and fees of all descendants.
 *
 * Usually when a new transaction is added to the mempool, it has no in-mempool
 * children (because any such children would be an orphan).  So in
 * addUnchecked(), we:
 * - update a new entry's setMemPoolParents to include all in-mempool parents
 * - update the new entry's direct parents to include the new tx as a child
 * - update all ancestors of the transaction to include the new tx's size/fee
 *
 * When a transaction is removed from the mempool, we must:
 * - update all in-mempool parents to not track the tx in setMemPoolChildren
 * - update all ancestors to not include the tx's size/fees in descendant state
 * - update all in-mempool children to not include it as a parent
 *
 * These happen in UpdateForRemoveFromMempool().  (Note that when removing a
 * transaction along with its descendants, we must calculate that set of
 * transactions to be removed before doing the removal, or else the mempool can
 * be in an inconsistent state where it's impossible to walk the ancestors of
 * a transaction.)
 *
 * In the event of a reorg, the assumption that a newly added tx has no
 * in-mempool children is false.  In particular, the mempool is in an
 * inconsistent state while new transactions are being added, because there may
 * be descendant transactions of a tx coming from a disconnected block that are
 * unreachable from just looking at transactions in the mempool (the linking
 * transactions may also be in the disconnected block, waiting to be added).
 * Because of this, there's not much benefit in trying to search for in-mempool
 * children in addUnchecked().  Instead, in the special case of transactions
 * being added from a disconnected block, we require the caller to clean up the
 * state, to account for in-mempool, out-of-block descendants for all the
 * in-block transactions by calling UpdateTransactionsFromBlock().  Note that
 * until this is called, the mempool state is not consistent, and in particular
 * mapLinks may not be correct (and therefore functions like
 * CalculateMemPoolAncestors() and CalculateDescendants() that rely
 * on them to walk the mempool are not generally safe to use).
 *
 * Computational limits:
 *
 * Updating all in-mempool ancestors of a newly added transaction can be slow,
 * if no bound exists on how many in-mempool ancestors there may be.
 * CalculateMemPoolAncestors() takes configurable limits that are designed to
 * prevent these calculations from being too CPU intensive.
 *
 */
class CTxMemPool
{
protected:
    const int m_check_ratio; //!< Value n means that 1 times in n we check.
    std::atomic<unsigned int> nTransactionsUpdated{0}; //!< Used by getblocktemplate to trigger CreateNewBlock() invocation
    CBlockPolicyEstimator* const minerPolicyEstimator;

    uint64_t totalTxSize GUARDED_BY(cs){0};      //!< sum of all mempool tx's virtual sizes. Differs from serialized tx size since witness data is discounted. Defined in BIP 141.
    CAmount m_total_fee GUARDED_BY(cs){0};       //!< sum of all mempool tx's fees (NOT modified fee)
    uint64_t cachedInnerUsage GUARDED_BY(cs){0}; //!< sum of dynamic memory usage of all the map elements (NOT the maps themselves)

    mutable int64_t lastRollingFeeUpdate GUARDED_BY(cs){GetTime()};
    mutable bool blockSinceLastRollingFeeBump GUARDED_BY(cs){false};
    mutable double rollingMinimumFeeRate GUARDED_BY(cs){0}; //!< minimum fee to get into the pool, decreases exponentially
    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

    typedef boost::multi_index_container<
        CTxMemPoolEntry,
        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
            >
        >
    > indexed_transaction_set;

    /**
     * This mutex needs to be locked when accessing `mapTx` or other members
     * that are guarded by it.
     *
     * @par Consistency guarantees
     *
     * By design, it is guaranteed that:
     *
     * 1. Locking both `cs_main` and `mempool.cs` will give a view of mempool
     *    that is consistent with current chain tip (`ActiveChain()` and
     *    `CoinsTip()`) and is fully populated. Fully populated means that if the
     *    current active chain is missing transactions that were present in a
     *    previously active chain, all the missing transactions will have been
     *    re-added to the mempool and should be present if they meet size and
     *    consistency constraints.
     *
     * 2. Locking `mempool.cs` without `cs_main` will give a view of a mempool
     *    consistent with some chain that was active since `cs_main` was last
     *    locked, and that is fully populated as described above. It is ok for
     *    code that only needs to query or remove transactions from the mempool
     *    to lock just `mempool.cs` without `cs_main`.
     *
     * To provide these guarantees, it is necessary to lock both `cs_main` and
     * `mempool.cs` whenever adding transactions to the mempool and whenever
     * changing the chain tip. It's necessary to keep both mutexes locked until
     * the mempool is consistent with the new chain tip and fully populated.
     */
    mutable RecursiveMutex cs;
    indexed_transaction_set mapTx GUARDED_BY(cs);

    using txiter = indexed_transaction_set::nth_index<0>::type::const_iterator;
    std::vector<std::pair<uint256, txiter>> vTxHashes GUARDED_BY(cs); //!< All tx witness hashes/entries in mapTx, in random order

    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);

    /**
     * Track locally submitted transactions to periodically retry initial broadcast.
     */
    std::set<uint256> m_unbroadcast_txids GUARDED_BY(cs);


    /**
     * Helper function to calculate all in-mempool ancestors of staged_ancestors and apply ancestor
     * and descendant limits (including staged_ancestors themselves, entry_size and entry_count).
     *
     * @param[in]   entry_size          Virtual size to include in the limits.
     * @param[in]   entry_count         How many entries to include in the limits.
     * @param[in]   staged_ancestors    Should contain entries in the mempool.
     * @param[in]   limits              Maximum number and size of ancestors and descendants
     *
     * @return all in-mempool ancestors, or an error if any ancestor or descendant limits were hit
     */
    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 int64_t m_max_size_bytes;
    const std::chrono::seconds m_expiry;
    const CFeeRate m_incremental_relay_feerate;
    const CFeeRate m_min_relay_feerate;
    const CFeeRate m_dust_relay_feerate;
    const bool m_permit_bare_multisig;
    const std::optional<unsigned> m_max_datacarrier_bytes;
    const bool m_require_standard;
    const bool m_full_rbf;

    const Limits m_limits;

    /** Create a new CTxMemPool.
     * Sanity checks will be off by default for performance, because otherwise
     * accepting transactions becomes O(N^2) where N is the number of transactions
     * in the pool.
     */
    explicit CTxMemPool(const Options& opts);

    /**
     * If sanity-checking is turned on, check makes sure the pool is
     * consistent (does not contain two transactions that spend the same inputs,
     * all inputs are in the mapNextTx array). If sanity-checking is turned off,
     * check does nothing.
     */
    void check(const CCoinsViewCache& active_coins_tip, int64_t spendheight) const EXCLUSIVE_LOCKS_REQUIRED(::cs_main);

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

    void removeRecursive(const CTransaction& tx, MemPoolRemovalReason reason) EXCLUSIVE_LOCKS_REQUIRED(cs);
    /** After reorg, filter the entries that would no longer be valid in the next block, and update
     * the entries' cached LockPoints if needed.  The mempool does not have any knowledge of
     * consensus rules. It just appplies the callable function and removes the ones for which it
     * returns true.
     * @param[in]   filter_final_and_mature   Predicate that checks the relevant validation rules
     *                                        and updates an entry's LockPoints.
     * */
    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);
    void queryHashes(std::vector<uint256>& vtxid) const;
    bool isSpent(const COutPoint& outpoint) const;
    unsigned int GetTransactionsUpdated() const;
    void AddTransactionsUpdated(unsigned int n);
    /**
     * Check that none of this transactions inputs are in the mempool, and thus
     * the tx is not dependent on other mempool transactions to be included in a block.
     */
    bool HasNoInputsOf(const CTransaction& tx) const EXCLUSIVE_LOCKS_REQUIRED(cs);

    /** Affect CreateNewBlock prioritisation of transactions */
    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 {
        /** Whether this transaction is in the mempool. */
        const bool in_mempool;
        /** The fee delta added using PrioritiseTransaction(). */
        const CAmount delta;
        /** The modified fee (base fee + delta) of this entry. Only present if in_mempool=true. */
        std::optional<CAmount> modified_fee;
        /** The prioritised transaction's txid. */
        const uint256 txid;
    };
    /** Return a vector of all entries in mapDeltas with their corresponding delta_info. */
    std::vector<delta_info> GetPrioritisedTransactions() const EXCLUSIVE_LOCKS_REQUIRED(!cs);

    /** Get the transaction in the pool that spends the same prevout */
    const CTransaction* GetConflictTx(const COutPoint& prevout) const EXCLUSIVE_LOCKS_REQUIRED(cs);

    /** Returns an iterator to the given hash, if found */
    std::optional<txiter> GetIter(const uint256& txid) const EXCLUSIVE_LOCKS_REQUIRED(cs);

    /** Translate a set of hashes into a set of pool iterators to avoid repeated lookups.
     * Does not require that all of the hashes correspond to actual transactions in the mempool,
     * only returns the ones that exist. */
    setEntries GetIterSet(const std::set<uint256>& hashes) const EXCLUSIVE_LOCKS_REQUIRED(cs);

    /** Translate a list of hashes into a list of mempool iterators to avoid repeated lookups.
     * The nth element in txids becomes the nth element in the returned vector. If any of the txids
     * don't actually exist in the mempool, returns an empty vector. */
    std::vector<txiter> GetIterVec(const std::vector<uint256>& txids) const EXCLUSIVE_LOCKS_REQUIRED(cs);

    /** Remove a set of transactions from the mempool.
     *  If a transaction is in this set, then all in-mempool descendants must
     *  also be in the set, unless this transaction is being removed for being
     *  in a block.
     *  Set updateDescendants to true when removing a tx that was in a block, so
     *  that any in-mempool descendants have their ancestor state updated.
     */
    void RemoveStaged(setEntries& stage, bool updateDescendants, MemPoolRemovalReason reason) EXCLUSIVE_LOCKS_REQUIRED(cs);

    /** UpdateTransactionsFromBlock is called when adding transactions from a
     * disconnected block back to the mempool, new mempool entries may have
     * children in the mempool (which is generally not the case when otherwise
     * adding transactions).
     *  @post updated descendant state for descendants of each transaction in
     *        vHashesToUpdate (excluding any child transactions present in
     *        vHashesToUpdate, which are already accounted for). Updated state
     *        includes add fee/size information for such descendants to the
     *        parent and updated ancestor state to include the parent.
     *
     * @param[in] vHashesToUpdate          The set of txids from the
     *     disconnected block that have been accepted back into the mempool.
     */
    void UpdateTransactionsFromBlock(const std::vector<uint256>& vHashesToUpdate) EXCLUSIVE_LOCKS_REQUIRED(cs, cs_main) LOCKS_EXCLUDED(m_epoch);

    /**
     * Try to calculate all in-mempool ancestors of entry.
     * (these are all calculated including the tx itself)
     *
     * @param[in]   entry               CTxMemPoolEntry of which all in-mempool ancestors are calculated
     * @param[in]   limits              Maximum number and size of ancestors and descendants
     * @param[in]   fSearchForParents   Whether to search a tx's vin for in-mempool parents, or look
     *                                  up parents from mapLinks. Must be true for entries not in
     *                                  the mempool
     *
     * @return all in-mempool ancestors, or an error if any ancestor or descendant limits were hit
     */
    util::Result<setEntries> CalculateMemPoolAncestors(const CTxMemPoolEntry& entry,
                                   const Limits& limits,
                                   bool fSearchForParents = true) const EXCLUSIVE_LOCKS_REQUIRED(cs);

    /**
     * Same as CalculateMemPoolAncestors, but always returns a (non-optional) setEntries.
     * Should only be used when it is assumed CalculateMemPoolAncestors would not fail. If
     * CalculateMemPoolAncestors does unexpectedly fail, an empty setEntries is returned and the
     * error is logged to BCLog::MEMPOOL with level BCLog::Level::Error. In debug builds, failure
     * of CalculateMemPoolAncestors will lead to shutdown due to assertion failure.
     *
     * @param[in]   calling_fn_name     Name of calling function so we can properly log the call site
     *
     * @return a setEntries corresponding to the result of CalculateMemPoolAncestors or an empty
     *         setEntries if it failed
     *
     * @see CTXMemPool::CalculateMemPoolAncestors()
     */
    setEntries AssumeCalculateMemPoolAncestors(
        std::string_view calling_fn_name,
        const CTxMemPoolEntry &entry,
        const Limits& limits,
        bool fSearchForParents = true) const EXCLUSIVE_LOCKS_REQUIRED(cs);

    /** Collect the entire cluster of connected transactions for each transaction in txids.
     * All txids must correspond to transaction entries in the mempool, otherwise this returns an
     * empty vector. This call will also exit early and return an empty vector if it collects 500 or
     * more transactions as a DoS protection. */
    std::vector<txiter> GatherClusters(const std::vector<uint256>& txids) const EXCLUSIVE_LOCKS_REQUIRED(cs);

    /** Calculate all in-mempool ancestors of a set of transactions not already in the mempool and
     * check ancestor and descendant limits. Heuristics are used to estimate the ancestor and
     * descendant count of all entries if the package were to be added to the mempool.  The limits
     * are applied to the union of all package transactions. For example, if the package has 3
     * transactions and limits.ancestor_count = 25, the union of all 3 sets of ancestors (including the
     * transactions themselves) must be <= 22.
     * @param[in]       package                 Transaction package being evaluated for acceptance
     *                                          to mempool. The transactions need not be direct
     *                                          ancestors/descendants of each other.
     * @param[in]       limits                  Maximum number and size of ancestors and descendants
     * @param[out]      errString               Populated with error reason if a limit is hit.
     */
    bool CheckPackageLimits(const Package& package,
                            const Limits& limits,
                            std::string &errString) const EXCLUSIVE_LOCKS_REQUIRED(cs);

    /** Populate setDescendants with all in-mempool descendants of hash.
     *  Assumes that setDescendants includes all in-mempool descendants of anything
     *  already in it.  */
    void CalculateDescendants(txiter it, setEntries& setDescendants) const EXCLUSIVE_LOCKS_REQUIRED(cs);

    /** The minimum fee to get into the mempool, which may itself not be enough
     *  for larger-sized transactions.
     *  The m_incremental_relay_feerate policy variable is used to bound the time it
     *  takes the fee rate to go back down all the way to 0. When the feerate
     *  would otherwise be half of this, it is set to 0 instead.
     */
    CFeeRate GetMinFee() const {
        return GetMinFee(m_max_size_bytes);
    }

    /** Remove transactions from the mempool until its dynamic size is <= sizelimit.
      *  pvNoSpendsRemaining, if set, will be populated with the list of outpoints
      *  which are not in mempool which no longer have any spends in this mempool.
      */
    void TrimToSize(size_t sizelimit, std::vector<COutPoint>* pvNoSpendsRemaining = nullptr) EXCLUSIVE_LOCKS_REQUIRED(cs);

    /** Expire all transaction (and their dependencies) in the mempool older than time. Return the number of removed transactions. */
    int Expire(std::chrono::seconds time) EXCLUSIVE_LOCKS_REQUIRED(cs);

    /**
     * Calculate the ancestor and descendant count for the given transaction.
     * The counts include the transaction itself.
     * When ancestors is non-zero (ie, the transaction itself is in the mempool),
     * ancestorsize and ancestorfees will also be set to the appropriate values.
     */
    void GetTransactionAncestry(const uint256& txid, size_t& ancestors, size_t& descendants, size_t* ancestorsize = nullptr, CAmount* ancestorfees = nullptr) const;

    /**
     * @returns true if we've made an attempt to load the mempool regardless of
     *          whether the attempt was successful or not
     */
    bool GetLoadTried() const;

    /**
     * Set whether or not we've made an attempt to load the mempool (regardless
     * of whether the attempt was successful or not)
     */
    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);
    }

    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;
    std::vector<TxMempoolInfo> infoAll() const;

    size_t DynamicMemoryUsage() const;

    /** Adds a transaction to the unbroadcast set */
    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);
    };

    /** Removes a transaction from the unbroadcast set */
    void RemoveUnbroadcastTx(const uint256& txid, const bool unchecked = false);

    /** Returns transactions in unbroadcast set */
    std::set<uint256> GetUnbroadcastTxs() const
    {
        LOCK(cs);
        return m_unbroadcast_txids;
    }

    /** Returns whether a txid is in the unbroadcast set */
    bool IsUnbroadcastTx(const uint256& txid) const EXCLUSIVE_LOCKS_REQUIRED(cs)
    {
        AssertLockHeld(cs);
        return m_unbroadcast_txids.count(txid) != 0;
    }

    /** Guards this internal counter for external reporting */
    uint64_t GetAndIncrementSequence() const EXCLUSIVE_LOCKS_REQUIRED(cs) {
        return m_sequence_number++;
    }

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

private:
    /** UpdateForDescendants is used by UpdateTransactionsFromBlock to update
     *  the descendants for a single transaction that has been added to the
     *  mempool but may have child transactions in the mempool, eg during a
     *  chain reorg.
     *
     * @pre CTxMemPoolEntry::m_children is correct for the given tx and all
     *      descendants.
     * @pre cachedDescendants is an accurate cache where each entry has all
     *      descendants of the corresponding key, including those that should
     *      be removed for violation of ancestor limits.
     * @post if updateIt has any non-excluded descendants, cachedDescendants has
     *       a new cache line for updateIt.
     * @post descendants_to_remove has a new entry for any descendant which exceeded
     *       ancestor limits relative to updateIt.
     *
     * @param[in] updateIt the entry to update for its descendants
     * @param[in,out] cachedDescendants a cache where each line corresponds to all
     *     descendants. It will be updated with the descendants of the transaction
     *     being updated, so that future invocations don't need to walk the same
     *     transaction again, if encountered in another transaction chain.
     * @param[in] setExclude the set of descendant transactions in the mempool
     *     that must not be accounted for (because any descendants in setExclude
     *     were added to the mempool after the transaction being updated and hence
     *     their state is already reflected in the parent state).
     * @param[out] descendants_to_remove Populated with the txids of entries that
     *     exceed ancestor limits. It's the responsibility of the caller to
     *     removeRecursive them.
     */
    void UpdateForDescendants(txiter updateIt, cacheMap& cachedDescendants,
                              const std::set<uint256>& setExclude, std::set<uint256>& descendants_to_remove) EXCLUSIVE_LOCKS_REQUIRED(cs);
    /** Update ancestors of hash to add/remove it as a descendant transaction. */
    void UpdateAncestorsOf(bool add, txiter hash, setEntries &setAncestors) EXCLUSIVE_LOCKS_REQUIRED(cs);
    /** Set ancestor state for an entry */
    void UpdateEntryForAncestors(txiter it, const setEntries &setAncestors) EXCLUSIVE_LOCKS_REQUIRED(cs);
    /** For each transaction being removed, update ancestors and any direct children.
      * If updateDescendants is true, then also update in-mempool descendants'
      * ancestor state. */
    void UpdateForRemoveFromMempool(const setEntries &entriesToRemove, bool updateDescendants) EXCLUSIVE_LOCKS_REQUIRED(cs);
    /** Sever link between specified transaction and direct children. */
    void UpdateChildrenForRemoval(txiter entry) EXCLUSIVE_LOCKS_REQUIRED(cs);

    /** Before calling removeUnchecked for a given transaction,
     *  UpdateForRemoveFromMempool must be called on the entire (dependent) set
     *  of transactions being removed at the same time.  We use each
     *  CTxMemPoolEntry's setMemPoolParents in order to walk ancestors of a
     *  given transaction that is removed, so we can't remove intermediate
     *  transactions in a chain before we've updated all the state for the
     *  removal.
     */
    void removeUnchecked(txiter entry, MemPoolRemovalReason reason) EXCLUSIVE_LOCKS_REQUIRED(cs);
public:
    /** visited marks a CTxMemPoolEntry as having been traversed
     * during the lifetime of the most recently created Epoch::Guard
     * and returns false if we are the first visitor, true otherwise.
     *
     * An Epoch::Guard must be held when visited is called or an assert will be
     * triggered.
     *
     */
    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);
    }
};

/**
 * CCoinsView that brings transactions from a mempool into view.
 * It does not check for spendings by memory pool transactions.
 * Instead, it provides access to all Coins which are either unspent in the
 * base CCoinsView, are outputs from any mempool transaction, or are
 * tracked temporarily to allow transaction dependencies in package validation.
 * This allows transaction replacement to work as expected, as you want to
 * have all inputs "available" to check signatures, and any cycles in the
 * dependency graph are checked directly in AcceptToMemoryPool.
 * It also allows you to sign a double-spend directly in
 * signrawtransactionwithkey and signrawtransactionwithwallet,
 * as long as the conflicting transaction is not yet confirmed.
 */
class CCoinsViewMemPool : public CCoinsViewBacked
{
    /**
    * Coins made available by transactions being validated. Tracking these allows for package
    * validation, since we can access transaction outputs without submitting them to mempool.
    */
    std::unordered_map<COutPoint, Coin, SaltedOutpointHasher> m_temp_added;
protected:
    const CTxMemPool& mempool;

public:
    CCoinsViewMemPool(CCoinsView* baseIn, const CTxMemPool& mempoolIn);
    bool GetCoin(const COutPoint &outpoint, Coin &coin) const override;
    /** Add the coins created by this transaction. These coins are only temporarily stored in
     * m_temp_added and cannot be flushed to the back end. Only used for package validation. */
    void PackageAddTransaction(const CTransactionRef& tx);
};

/**
 * DisconnectedBlockTransactions

 * During the reorg, it's desirable to re-add previously confirmed transactions
 * to the mempool, so that anything not re-confirmed in the new chain is
 * available to be mined. However, it's more efficient to wait until the reorg
 * is complete and process all still-unconfirmed transactions at that time,
 * since we expect most confirmed transactions to (typically) still be
 * confirmed in the new chain, and re-accepting to the memory pool is expensive
 * (and therefore better to not do in the middle of reorg-processing).
 * Instead, store the disconnected transactions (in order!) as we go, remove any
 * that are included in blocks in the new chain, and then process the remaining
 * still-unconfirmed transactions at the end.
 */

// multi_index tag names
struct txid_index {};
struct insertion_order {};

struct DisconnectedBlockTransactions {
    typedef boost::multi_index_container<
        CTransactionRef,
        boost::multi_index::indexed_by<
            // sorted by txid
            boost::multi_index::hashed_unique<
                boost::multi_index::tag<txid_index>,
                mempoolentry_txid,
                SaltedTxidHasher
            >,
            // sorted by order in the blockchain
            boost::multi_index::sequenced<
                boost::multi_index::tag<insertion_order>
            >
        >
    > indexed_disconnected_transactions;

    // It's almost certainly a logic bug if we don't clear out queuedTx before
    // destruction, as we add to it while disconnecting blocks, and then we
    // need to re-process remaining transactions to ensure mempool consistency.
    // For now, assert() that we've emptied out this object on destruction.
    // This assert() can always be removed if the reorg-processing code were
    // to be refactored such that this assumption is no longer true (for
    // instance if there was some other way we cleaned up the mempool after a
    // reorg, besides draining this object).
    ~DisconnectedBlockTransactions() { assert(queuedTx.empty()); }

    indexed_disconnected_transactions queuedTx;
    uint64_t cachedInnerUsage = 0;

    // Estimate the overhead of queuedTx to be 6 pointers + an allocation, as
    // no exact formula for boost::multi_index_contained is implemented.
    size_t DynamicMemoryUsage() const {
        return memusage::MallocUsage(sizeof(CTransactionRef) + 6 * sizeof(void*)) * queuedTx.size() + cachedInnerUsage;
    }

    void addTransaction(const CTransactionRef& tx)
    {
        queuedTx.insert(tx);
        cachedInnerUsage += RecursiveDynamicUsage(tx);
    }

    // Remove entries based on txid_index, and update memory usage.
    void removeForBlock(const std::vector<CTransactionRef>& vtx)
    {
        // Short-circuit in the common case of a block being added to the tip
        if (queuedTx.empty()) {
            return;
        }
        for (auto const &tx : vtx) {
            auto it = queuedTx.find(tx->GetHash());
            if (it != queuedTx.end()) {
                cachedInnerUsage -= RecursiveDynamicUsage(*it);
                queuedTx.erase(it);
            }
        }
    }

    // Remove an entry by insertion_order index, and update memory usage.
    void removeEntry(indexed_disconnected_transactions::index<insertion_order>::type::iterator entry)
    {
        cachedInnerUsage -= RecursiveDynamicUsage(*entry);
        queuedTx.get<insertion_order>().erase(entry);
    }

    void clear()
    {
        cachedInnerUsage = 0;
        queuedTx.clear();
    }
};

#endif // BITCOIN_TXMEMPOOL_H