Merge bitcoin#31156: test: Don't enforce BIP94 on regtest unless specified by arg

e60cecc doc: add release note for 31156 (Martin Zumsande)
fc7dfb3 test: Don't enforce BIP94 on regtest unless specified by arg (Martin Zumsande)

Pull request description:

  The added arg `-test=bip94` is only used in a functional test for BIP94. This is done because the default regtest consensus rules should follow mainnet, not testnet.

  Fixes bitcoin#31137.

ACKs for top commit:
  achow101:
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  tdb3:
    cr and light test ACK e60cecc
  rkrux:
    tACK e60cecc
  BrandonOdiwuor:
    utACK e60cecc
  laanwj:
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Tree-SHA512: ca2f322f89d8808dfc3565fe020d2615cfcc110e188a02128ad7108fef51c735b33d55b5e6a70c505d78f7291f3c635dc7dfbcd78be1348d4d6e483883be4216

Author: achow101

doc/release-notes-31156.md

@@ -0,0 +1,4 @@
+Test
+------
+
+The BIP94 timewarp attack mitigation (designed for testnet4) is no longer active on the regtest network. (#31156)

src/chainparams.cpp

@@ -44,6 +44,7 @@ void ReadSigNetArgs(const ArgsManager& args, CChainParams::SigNetOptions& option
 void ReadRegTestArgs(const ArgsManager& args, CChainParams::RegTestOptions& options)
 {
     if (auto value = args.GetBoolArg("-fastprune")) options.fastprune = *value;
+    if (HasTestOption(args, "bip94")) options.enforce_bip94 = true;
 
     for (const std::string& arg : args.GetArgs("-testactivationheight")) {
         const auto found{arg.find('@')};

src/common/args.cpp

@@ -709,6 +709,7 @@ std::string HelpMessageOpt(const std::string &option, const std::string &message
 
 const std::vector<std::string> TEST_OPTIONS_DOC{
     "addrman (use deterministic addrman)",
+    "bip94 (enforce BIP94 consensus rules)",
 };
 
 bool HasTestOption(const ArgsManager& args, const std::string& test_option)

src/kernel/chainparams.cpp

@@ -542,7 +542,7 @@ class CRegTestParams : public CChainParams
         consensus.nPowTargetTimespan = 24 * 60 * 60; // one day
         consensus.nPowTargetSpacing = 10 * 60;
         consensus.fPowAllowMinDifficultyBlocks = true;
-        consensus.enforce_BIP94 = true;
+        consensus.enforce_BIP94 = opts.enforce_bip94;
         consensus.fPowNoRetargeting = true;
         consensus.nRuleChangeActivationThreshold = 108; // 75% for testchains
         consensus.nMinerConfirmationWindow = 144; // Faster than normal for regtest (144 instead of 2016)

src/kernel/chainparams.h

@@ -155,6 +155,7 @@ class CChainParams
         std::unordered_map<Consensus::DeploymentPos, VersionBitsParameters> version_bits_parameters{};
         std::unordered_map<Consensus::BuriedDeployment, int> activation_heights{};
         bool fastprune{false};
+        bool enforce_bip94{false};
     };
 
     static std::unique_ptr<const CChainParams> RegTest(const RegTestOptions& options);

test/functional/mining_basic.py

@@ -122,6 +122,7 @@ def test_blockmintxfee_parameter(self):
     def test_timewarp(self):
         self.log.info("Test timewarp attack mitigation (BIP94)")
         node = self.nodes[0]
+        self.restart_node(0, extra_args=['-test=bip94'])
 
         self.log.info("Mine until the last block of the retarget period")
         blockchain_info = self.nodes[0].getblockchaininfo()