1// Copyright (c) 2021-present The Bitcoin Core developers
2// Distributed under the MIT software license, see the accompanying
3// file COPYING or http://www.opensource.org/licenses/mit-license.php.
4
5#ifndef BITCOIN_POLICY_PACKAGES_H
6#define BITCOIN_POLICY_PACKAGES_H
7
8#include <consensus/consensus.h>
9#include <consensus/validation.h>
10#include <policy/policy.h>
11#include <primitives/transaction.h>
12#include <util/hasher.h>
13
14#include <cstdint>
15#include <unordered_set>
16#include <vector>
17
18/** Default maximum number of transactions in a package. */
19inline constexpr uint32_t MAX_PACKAGE_COUNT{25};
20/** Default maximum total weight of transactions in a package in weight
21    to allow for context-less checks. This must allow a superset of sigops
22    weighted vsize limited transactions to not disallow transactions we would
23    have otherwise accepted individually. */
24inline constexpr uint32_t MAX_PACKAGE_WEIGHT = 404'000;
25static_assert(MAX_PACKAGE_WEIGHT >= MAX_STANDARD_TX_WEIGHT);
26
27// Packages are part of a single cluster, so ensure that the package limits are
28// set within the mempool's cluster size limits.
29static_assert(DEFAULT_CLUSTER_LIMIT >= MAX_PACKAGE_COUNT);
30static_assert(MAX_PACKAGE_WEIGHT <= DEFAULT_CLUSTER_SIZE_LIMIT_KVB * WITNESS_SCALE_FACTOR * 1000);
31
32/** A "reason" why a package was invalid. It may be that one or more of the included
33 * transactions is invalid or the package itself violates our rules.
34 * We don't distinguish between consensus and policy violations right now.
35 */
36enum class PackageValidationResult {
37    PCKG_RESULT_UNSET = 0,        //!< Initial value. The package has not yet been rejected.
38    PCKG_POLICY,                  //!< The package itself is invalid (e.g. too many transactions).
39    PCKG_TX,                      //!< At least one tx is invalid.
40    PCKG_MEMPOOL_ERROR,           //!< Mempool logic error.
41};
42
43/** A package is an ordered list of transactions. The transactions cannot conflict with (spend the
44 * same inputs as) one another. */
45using Package = std::vector<CTransactionRef>;
46
47class PackageValidationState : public ValidationState<PackageValidationResult> {};
48
49/** If any direct dependencies exist between transactions (i.e. a child spending the output of a
50 * parent), checks that all parents appear somewhere in the list before their respective children.
51 * No other ordering is enforced. This function cannot detect indirect dependencies (e.g. a
52 * transaction's grandparent if its parent is not present).
53 * @returns true if sorted. False if any tx spends the output of a tx that appears later in txns.
54 */
55bool IsTopoSortedPackage(const Package& txns);
56
57/** Checks that these transactions don't conflict, i.e., spend the same prevout. This includes
58 * checking that there are no duplicate transactions. Since these checks require looking at the inputs
59 * of a transaction, returns false immediately if any transactions have empty vin.
60 *
61 * Does not check consistency of a transaction with oneself; does not check if a transaction spends
62 * the same prevout multiple times (see bad-txns-inputs-duplicate in CheckTransaction()).
63 *
64 * @returns true if there are no conflicts. False if any two transactions spend the same prevout.
65 * */
66bool IsConsistentPackage(const Package& txns);
67
68/** Context-free package policy checks:
69 * 1. The number of transactions cannot exceed MAX_PACKAGE_COUNT.
70 * 2. The total weight cannot exceed MAX_PACKAGE_WEIGHT.
71 * 3. If any dependencies exist between transactions, parents must appear before children.
72 * 4. Transactions cannot conflict, i.e., spend the same inputs.
73 */
74bool IsWellFormedPackage(const Package& txns, PackageValidationState& state);
75
76/** Context-free check that a package is exactly one child and its parents; not all parents need to
77 * be present, but the package must not contain any transactions that are not the child's parents.
78 * It is expected to be sorted, which means the last transaction must be the child.
79 */
80bool IsChildWithParents(const Package& package);
81
82/** Context-free check that a package IsChildWithParents() and none of the parents depend on each
83 * other (the package is a "tree").
84 */
85bool IsChildWithParentsTree(const Package& package);
86
87/** Get the hash of the concatenated wtxids of transactions, with wtxids
88 * treated as a little-endian numbers and sorted in ascending numeric order.
89 */
90uint256 GetPackageHash(const std::vector<CTransactionRef>& transactions);
91
92#endif // BITCOIN_POLICY_PACKAGES_H
93