1// Copyright (c) 2009-2010 Satoshi Nakamoto
2// Copyright (c) 2009-present The Bitcoin Core developers
3// Distributed under the MIT software license, see the accompanying
4// file COPYING or http://www.opensource.org/licenses/mit-license.php.
5
6#ifndef BITCOIN_CONSENSUS_PARAMS_H
7#define BITCOIN_CONSENSUS_PARAMS_H
8
9#include <script/verify_flags.h>
10#include <uint256.h>
11
12#include <array>
13#include <chrono>
14#include <cstdint>
15#include <limits>
16#include <map>
17#include <vector>
18
19namespace Consensus {
20
21/**
22 * A buried deployment is one where the height of the activation has been hardcoded into
23 * the client implementation long after the consensus change has activated. See BIP 90.
24 * Consensus changes for which the new rules are enforced from genesis are not listed here.
25 */
26enum BuriedDeployment : int16_t {
27    // buried deployments get negative values to avoid overlap with DeploymentPos
28    DEPLOYMENT_HEIGHTINCB = std::numeric_limits<int16_t>::min(),
29    DEPLOYMENT_CLTV,
30    DEPLOYMENT_DERSIG,
31    DEPLOYMENT_CSV,
32    // SCRIPT_VERIFY_WITNESS is enforced from genesis, but the check for downloading
33    // missing witness data is not. BIP 147 also relies on hardcoded activation height.
34    DEPLOYMENT_SEGWIT,
35};
36constexpr bool ValidDeployment(BuriedDeployment dep) { return dep <= DEPLOYMENT_SEGWIT; }
37
38enum DeploymentPos : uint16_t {
39    DEPLOYMENT_TESTDUMMY,
40    // NOTE: Also add new deployments to VersionBitsDeploymentInfo in deploymentinfo.cpp
41    // Removing an entry may require bumping MinBIP9WarningHeight.
42    MAX_VERSION_BITS_DEPLOYMENTS
43};
44constexpr bool ValidDeployment(DeploymentPos dep) { return dep < MAX_VERSION_BITS_DEPLOYMENTS; }
45
46/**
47 * Struct for each individual consensus rule change using BIP9.
48 */
49struct BIP9Deployment {
50    /** Bit position to select the particular bit in nVersion. */
51    int bit{28};
52    /** Start MedianTime for version bits miner confirmation. Can be a date in the past */
53    int64_t nStartTime{NEVER_ACTIVE};
54    /** Timeout/expiry MedianTime for the deployment attempt. */
55    int64_t nTimeout{NEVER_ACTIVE};
56    /** If lock in occurs, delay activation until at least this block
57     *  height.  Note that activation will only occur on a retarget
58     *  boundary.
59     */
60    int min_activation_height{0};
61    /** Period of blocks to check signalling in (usually retarget period, ie params.DifficultyAdjustmentInterval()) */
62    uint32_t period{2016};
63    /**
64     * Minimum blocks including miner confirmation of the total of 2016 blocks in a retargeting period,
65     * which is also used for BIP9 deployments.
66     * Examples: 1916 for 95%, 1512 for testchains.
67     */
68    uint32_t threshold{1916};
69
70    /** Constant for nTimeout very far in the future. */
71    static constexpr int64_t NO_TIMEOUT = std::numeric_limits<int64_t>::max();
72
73    /** Special value for nStartTime indicating that the deployment is always active.
74     *  This is useful for testing, as it means tests don't need to deal with the activation
75     *  process (which takes at least 3 BIP9 intervals). Only tests that specifically test the
76     *  behaviour during activation cannot use this. */
77    static constexpr int64_t ALWAYS_ACTIVE = -1;
78
79    /** Special value for nStartTime indicating that the deployment is never active.
80     *  This is useful for integrating the code changes for a new feature
81     *  prior to deploying it on some or all networks. */
82    static constexpr int64_t NEVER_ACTIVE = -2;
83};
84
85/**
86 * Parameters that influence chain consensus.
87 */
88struct Params {
89    uint256 hashGenesisBlock;
90    int nSubsidyHalvingInterval;
91    /**
92     * Hashes of blocks that
93     * - are known to be consensus valid, and
94     * - buried in the chain, and
95     * - fail if the default script verify flags are applied.
96     */
97    std::map<uint256, script_verify_flags> script_flag_exceptions;
98    /** Block height and hash at which BIP34 becomes active */
99    int BIP34Height;
100    uint256 BIP34Hash;
101    /** Block height at which BIP65 becomes active */
102    int BIP65Height;
103    /** Block height at which BIP66 becomes active */
104    int BIP66Height;
105    /** Block height at which CSV (BIP68, BIP112 and BIP113) becomes active */
106    int CSVHeight;
107    /** Block height at which Segwit (BIP141, BIP143 and BIP147) becomes active.
108     * Note that segwit v0 script rules are enforced on all blocks except the
109     * BIP 16 exception blocks. */
110    int SegwitHeight;
111    /** Don't warn about unknown BIP 9 activations below this height.
112     * This prevents us from warning about the CSV, segwit and taproot activations. */
113    int MinBIP9WarningHeight;
114    std::array<BIP9Deployment,MAX_VERSION_BITS_DEPLOYMENTS> vDeployments;
115    /** Proof of work parameters */
116    uint256 powLimit;
117    bool fPowAllowMinDifficultyBlocks;
118    /**
119      * Enforce BIP94 timewarp attack mitigation. On testnet4 this also enforces
120      * the block storm mitigation.
121      */
122    bool enforce_BIP94;
123    bool fPowNoRetargeting;
124    int64_t nPowTargetSpacing;
125    int64_t nPowTargetTimespan;
126    std::chrono::seconds PowTargetSpacing() const
127    {
128        return std::chrono::seconds{nPowTargetSpacing};
129    }
130    int64_t DifficultyAdjustmentInterval() const { return nPowTargetTimespan / nPowTargetSpacing; }
131    /** The best chain should have at least this much work */
132    uint256 nMinimumChainWork;
133    /** By default assume that the signatures in ancestors of this block are valid */
134    uint256 defaultAssumeValid;
135
136    /**
137     * If true, witness commitments contain a payload equal to a Bitcoin Script solution
138     * to the signet challenge. See BIP325.
139     */
140    bool signet_blocks{false};
141    std::vector<uint8_t> signet_challenge;
142
143    int DeploymentHeight(BuriedDeployment dep) const
144    {
145        switch (dep) {
146        case DEPLOYMENT_HEIGHTINCB:
147            return BIP34Height;
148        case DEPLOYMENT_CLTV:
149            return BIP65Height;
150        case DEPLOYMENT_DERSIG:
151            return BIP66Height;
152        case DEPLOYMENT_CSV:
153            return CSVHeight;
154        case DEPLOYMENT_SEGWIT:
155            return SegwitHeight;
156        } // no default case, so the compiler can warn about missing cases
157        return std::numeric_limits<int>::max();
158    }
159};
160
161} // namespace Consensus
162
163#endif // BITCOIN_CONSENSUS_PARAMS_H
164