consensus: add a CTV deployment for regtest only

Co-authored-by: Jeremy Rubin <j@rubin.io>

Author: jamesob

src/consensus/params.h

@@ -33,6 +33,7 @@ enum DeploymentPos : uint16_t {
     DEPLOYMENT_TESTDUMMY,
     DEPLOYMENT_TAPROOT, // Deployment of Schnorr/Taproot (BIPs 340-342)
     // NOTE: Also add new deployments to VersionBitsDeploymentInfo in deploymentinfo.cpp
+    DEPLOYMENT_CTV,  // Deployment of CHECKTEMPLATEVERIFY (BIP 119) (regtest only)
     MAX_VERSION_BITS_DEPLOYMENTS
 };
 constexpr bool ValidDeployment(DeploymentPos dep) { return dep < MAX_VERSION_BITS_DEPLOYMENTS; }

src/deploymentinfo.cpp

@@ -17,6 +17,10 @@ const struct VBDeploymentInfo VersionBitsDeploymentInfo[Consensus::MAX_VERSION_B
         /*.name =*/ "taproot",
         /*.gbt_force =*/ true,
     },
+    {
+        /*.name =*/ "ctv",
+        /*.gbt_force =*/ true,
+    },
 };
 
 std::string DeploymentName(Consensus::BuriedDeployment dep)

src/kernel/chainparams.cpp

@@ -557,6 +557,11 @@ class CRegTestParams : public CChainParams
         consensus.vDeployments[Consensus::DEPLOYMENT_TAPROOT].nTimeout = Consensus::BIP9Deployment::NO_TIMEOUT;
         consensus.vDeployments[Consensus::DEPLOYMENT_TAPROOT].min_activation_height = 0; // No activation delay
 
+        consensus.vDeployments[Consensus::DEPLOYMENT_CTV].bit = 1;
+        consensus.vDeployments[Consensus::DEPLOYMENT_CTV].nStartTime = Consensus::BIP9Deployment::ALWAYS_ACTIVE;
+        consensus.vDeployments[Consensus::DEPLOYMENT_CTV].nTimeout = Consensus::BIP9Deployment::NO_TIMEOUT;
+        consensus.vDeployments[Consensus::DEPLOYMENT_CTV].min_activation_height = 0; // No activation delay
+
         consensus.nMinimumChainWork = uint256{};
         consensus.defaultAssumeValid = uint256{};
 

src/policy/policy.h

@@ -125,9 +125,7 @@ static constexpr unsigned int STANDARD_SCRIPT_VERIFY_FLAGS{MANDATORY_SCRIPT_VERI
                                                              SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_TAPROOT_VERSION |
                                                              SCRIPT_VERIFY_DISCOURAGE_OP_SUCCESS |
                                                              SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_PUBKEYTYPE |
-                                                             SCRIPT_VERIFY_DISCOURAGE_CHECKTEMPLATEVERIFY |
-                                                             SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_CHECKTEMPLATEVERIFY |
-                                                             SCRIPT_VERIFY_CHECKTEMPLATEVERIFY};
+                                                             SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_CHECKTEMPLATEVERIFY};
 
 
 /** For convenience, standard but not mandatory verify flags. */

src/rpc/blockchain.cpp

@@ -1408,6 +1408,10 @@ UniValue DeploymentInfo(const CBlockIndex* blockindex, const ChainstateManager&
     SoftForkDescPushBack(blockindex, softforks, chainman, Consensus::DEPLOYMENT_SEGWIT);
     SoftForkDescPushBack(blockindex, softforks, chainman, Consensus::DEPLOYMENT_TESTDUMMY);
     SoftForkDescPushBack(blockindex, softforks, chainman, Consensus::DEPLOYMENT_TAPROOT);
+
+    if (chainman.GetParams().GetChainType() == ChainType::REGTEST) {
+        SoftForkDescPushBack(blockindex, softforks, chainman, Consensus::DEPLOYMENT_CTV);
+    }
     return softforks;
 }
 } // anon namespace

src/test/versionbits_tests.cpp

@@ -435,6 +435,12 @@ BOOST_FIXTURE_TEST_CASE(versionbits_computeblockversion, BlockVersionTest)
             // the same bit might overlap, even when non-overlapping start-end
             // times are picked.
             const uint32_t dep_mask{vbcache.Mask(chainParams->GetConsensus(), dep)};
+
+            if (chain_type != ChainType::REGTEST && dep == Consensus::DEPLOYMENT_CTV) {
+                // CTV only exists as a deployment on regtest, so skip over it for other
+                // chains.
+                continue;
+            }
             BOOST_CHECK(!(chain_all_vbits & dep_mask));
             chain_all_vbits |= dep_mask;
             check_computeblockversion(vbcache, chainParams->GetConsensus(), dep);

src/validation.cpp

@@ -1231,7 +1231,12 @@ bool MemPoolAccept::PolicyScriptChecks(const ATMPArgs& args, Workspace& ws)
     const CTransaction& tx = *ws.m_ptx;
     TxValidationState& state = ws.m_state;
 
-    constexpr unsigned int scriptVerifyFlags = STANDARD_SCRIPT_VERIFY_FLAGS;
+    unsigned int scriptVerifyFlags = STANDARD_SCRIPT_VERIFY_FLAGS;
+
+    // CHECKTEMPLATEVERIFY (BIP119) is always active on regtest, but no other chain.
+    if (args.m_chainparams.GetChainType() == ChainType::REGTEST) {
+        scriptVerifyFlags |= SCRIPT_VERIFY_CHECKTEMPLATEVERIFY;
+    }
 
     // Check input scripts and signatures.
     // This is done last to help prevent CPU exhaustion denial-of-service attacks.
@@ -2410,6 +2415,11 @@ static unsigned int GetBlockScriptFlags(const CBlockIndex& block_index, const Ch
         flags = it->second;
     }
 
+    // Enforce CHECKLOCKTIMEVERIFY (BIP119)
+    if (DeploymentActiveAt(block_index, chainman, Consensus::DEPLOYMENT_CTV)) {
+        flags |= SCRIPT_VERIFY_CHECKTEMPLATEVERIFY;
+    }
+
     // Enforce the DERSIG (BIP66) rule
     if (DeploymentActiveAt(block_index, chainman, Consensus::DEPLOYMENT_DERSIG)) {
         flags |= SCRIPT_VERIFY_DERSIG;