versionbits: Add support for delayed activation

Github-Pull: #21377
Rebased-From: 73d4a706393e6dbd6b6d6b6428f8d3233ac0a2d8

8 files changed, 41 insertions, 10 deletions

diff --git a/src/chainparams.cpp b/src/chainparams.cpp
index 88cf5ef0a8..402229effa 100644
--- a/src/chainparams.cpp
+++ b/src/chainparams.cpp
@@ -85,11 +85,13 @@ public:
         consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].bit = 28;
         consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].nStartTime = 1199145601; // January 1, 2008
         consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].nTimeout = 1230767999; // December 31, 2008
+        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].min_activation_height = 0; // No activation delay
 
         // Deployment of Taproot (BIPs 340-342)
         consensus.vDeployments[Consensus::DEPLOYMENT_TAPROOT].bit = 2;
         consensus.vDeployments[Consensus::DEPLOYMENT_TAPROOT].nStartTime = 1199145601; // January 1, 2008
         consensus.vDeployments[Consensus::DEPLOYMENT_TAPROOT].nTimeout = 1230767999; // December 31, 2008
+        consensus.vDeployments[Consensus::DEPLOYMENT_TAPROOT].min_activation_height = 0; // No activation delay
 
         consensus.nMinimumChainWork = uint256S("0x00000000000000000000000000000000000000001533efd8d716a517fe2c5008");
         consensus.defaultAssumeValid = uint256S("0x0000000000000000000b9d2ec5a352ecba0592946514a92f14319dc2b367fc72"); // 654683
@@ -198,11 +200,13 @@ public:
         consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].bit = 28;
         consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].nStartTime = 1199145601; // January 1, 2008
         consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].nTimeout = 1230767999; // December 31, 2008
+        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].min_activation_height = 0; // No activation delay
 
         // Deployment of Taproot (BIPs 340-342)
         consensus.vDeployments[Consensus::DEPLOYMENT_TAPROOT].bit = 2;
         consensus.vDeployments[Consensus::DEPLOYMENT_TAPROOT].nStartTime = 1199145601; // January 1, 2008
         consensus.vDeployments[Consensus::DEPLOYMENT_TAPROOT].nTimeout = 1230767999; // December 31, 2008
+        consensus.vDeployments[Consensus::DEPLOYMENT_TAPROOT].min_activation_height = 0; // No activation delay
 
         consensus.nMinimumChainWork = uint256S("0x0000000000000000000000000000000000000000000001db6ec4ac88cf2272c6");
         consensus.defaultAssumeValid = uint256S("0x000000000000006433d1efec504c53ca332b64963c425395515b01977bd7b3b0"); // 1864000
@@ -329,11 +333,13 @@ public:
         consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].bit = 28;
         consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].nStartTime = 1199145601; // January 1, 2008
         consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].nTimeout = 1230767999; // December 31, 2008
+        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].min_activation_height = 0; // No activation delay
 
         // Activation of Taproot (BIPs 340-342)
         consensus.vDeployments[Consensus::DEPLOYMENT_TAPROOT].bit = 2;
         consensus.vDeployments[Consensus::DEPLOYMENT_TAPROOT].nStartTime = Consensus::BIP9Deployment::ALWAYS_ACTIVE;
         consensus.vDeployments[Consensus::DEPLOYMENT_TAPROOT].nTimeout = Consensus::BIP9Deployment::NO_TIMEOUT;
+        consensus.vDeployments[Consensus::DEPLOYMENT_TAPROOT].min_activation_height = 0; // No activation delay
 
         // message start is defined as the first 4 bytes of the sha256d of the block script
         CHashWriter h(SER_DISK, 0);
@@ -391,12 +397,16 @@ public:
         consensus.fPowNoRetargeting = true;
         consensus.nRuleChangeActivationThreshold = 108; // 75% for testchains
         consensus.nMinerConfirmationWindow = 144; // Faster than normal for regtest (144 instead of 2016)
+
         consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].bit = 28;
         consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].nStartTime = 0;
         consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].nTimeout = Consensus::BIP9Deployment::NO_TIMEOUT;
+        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].min_activation_height = 0; // No activation delay
+
         consensus.vDeployments[Consensus::DEPLOYMENT_TAPROOT].bit = 2;
         consensus.vDeployments[Consensus::DEPLOYMENT_TAPROOT].nStartTime = Consensus::BIP9Deployment::ALWAYS_ACTIVE;
         consensus.vDeployments[Consensus::DEPLOYMENT_TAPROOT].nTimeout = Consensus::BIP9Deployment::NO_TIMEOUT;
+        consensus.vDeployments[Consensus::DEPLOYMENT_TAPROOT].min_activation_height = 0; // No activation delay
 
         consensus.nMinimumChainWork = uint256{};
         consensus.defaultAssumeValid = uint256{};
@@ -449,10 +459,11 @@ public:
     /**
      * Allows modifying the Version Bits regtest parameters.
      */
-    void UpdateVersionBitsParameters(Consensus::DeploymentPos d, int64_t nStartTime, int64_t nTimeout)
+    void UpdateVersionBitsParameters(Consensus::DeploymentPos d, int64_t nStartTime, int64_t nTimeout, int min_activation_height)
     {
         consensus.vDeployments[d].nStartTime = nStartTime;
         consensus.vDeployments[d].nTimeout = nTimeout;
+        consensus.vDeployments[d].min_activation_height = min_activation_height;
     }
     void UpdateActivationParametersFromArgs(const ArgsManager& args);
 };
@@ -475,22 +486,26 @@ void CRegTestParams::UpdateActivationParametersFromArgs(const ArgsManager& args)
     for (const std::string& strDeployment : args.GetArgs("-vbparams")) {
         std::vector<std::string> vDeploymentParams;
         boost::split(vDeploymentParams, strDeployment, boost::is_any_of(":"));
-        if (vDeploymentParams.size() != 3) {
-            throw std::runtime_error("Version bits parameters malformed, expecting deployment:start:end");
+        if (vDeploymentParams.size() < 3 || 4 < vDeploymentParams.size()) {
+            throw std::runtime_error("Version bits parameters malformed, expecting deployment:start:end[:min_activation_height]");
         }
         int64_t nStartTime, nTimeout;
+        int min_activation_height = 0;
         if (!ParseInt64(vDeploymentParams[1], &nStartTime)) {
             throw std::runtime_error(strprintf("Invalid nStartTime (%s)", vDeploymentParams[1]));
         }
         if (!ParseInt64(vDeploymentParams[2], &nTimeout)) {
             throw std::runtime_error(strprintf("Invalid nTimeout (%s)", vDeploymentParams[2]));
         }
+        if (vDeploymentParams.size() >= 4 && !ParseInt32(vDeploymentParams[3], &min_activation_height)) {
+            throw std::runtime_error(strprintf("Invalid min_activation_height (%s)", vDeploymentParams[3]));
+        }
         bool found = false;
         for (int j=0; j < (int)Consensus::MAX_VERSION_BITS_DEPLOYMENTS; ++j) {
             if (vDeploymentParams[0] == VersionBitsDeploymentInfo[j].name) {
-                UpdateVersionBitsParameters(Consensus::DeploymentPos(j), nStartTime, nTimeout);
+                UpdateVersionBitsParameters(Consensus::DeploymentPos(j), nStartTime, nTimeout, min_activation_height);
                 found = true;
-                LogPrintf("Setting version bits activation parameters for %s to start=%ld, timeout=%ld\n", vDeploymentParams[0], nStartTime, nTimeout);
+                LogPrintf("Setting version bits activation parameters for %s to start=%ld, timeout=%ld, min_activation_height=%d\n", vDeploymentParams[0], nStartTime, nTimeout, min_activation_height);
                 break;
             }
         }
diff --git a/src/chainparamsbase.cpp b/src/chainparamsbase.cpp
index 603969aaea..be33bb94c8 100644
--- a/src/chainparamsbase.cpp
+++ b/src/chainparamsbase.cpp
@@ -23,7 +23,7 @@ void SetupChainParamsBaseOptions(ArgsManager& argsman)
                  "This is intended for regression testing tools and app development. Equivalent to -chain=regtest.", ArgsManager::ALLOW_ANY | ArgsManager::DEBUG_ONLY, OptionsCategory::CHAINPARAMS);
     argsman.AddArg("-segwitheight=<n>", "Set the activation height of segwit. -1 to disable. (regtest-only)", ArgsManager::ALLOW_ANY | ArgsManager::DEBUG_ONLY, OptionsCategory::DEBUG_TEST);
     argsman.AddArg("-testnet", "Use the test chain. Equivalent to -chain=test.", ArgsManager::ALLOW_ANY, OptionsCategory::CHAINPARAMS);
-    argsman.AddArg("-vbparams=deployment:start:end", "Use given start/end times for specified version bits deployment (regtest-only)", ArgsManager::ALLOW_ANY | ArgsManager::DEBUG_ONLY, OptionsCategory::CHAINPARAMS);
+    argsman.AddArg("-vbparams=deployment:start:end[:min_activation_height]", "Use given start/end times and min_activation_height for specified version bits deployment (regtest-only)", ArgsManager::ALLOW_ANY | ArgsManager::DEBUG_ONLY, OptionsCategory::CHAINPARAMS);
     argsman.AddArg("-signet", "Use the signet chain. Equivalent to -chain=signet. Note that the network is defined by the -signetchallenge parameter", ArgsManager::ALLOW_ANY, OptionsCategory::CHAINPARAMS);
     argsman.AddArg("-signetchallenge", "Blocks must satisfy the given script to be considered valid (only for signet networks; defaults to the global default signet test network challenge)", ArgsManager::ALLOW_STRING, OptionsCategory::CHAINPARAMS);
     argsman.AddArg("-signetseednode", "Specify a seed node for the signet network, in the hostname[:port] format, e.g. sig.net:1234 (may be used multiple times to specify multiple seed nodes; defaults to the global default signet test network seed node(s))", ArgsManager::ALLOW_STRING, OptionsCategory::CHAINPARAMS);
diff --git a/src/consensus/params.h b/src/consensus/params.h
index 0983595c6a..5d566a01b9 100644
--- a/src/consensus/params.h
+++ b/src/consensus/params.h
@@ -29,6 +29,11 @@ struct BIP9Deployment {
     int64_t nStartTime;
     /** Timeout/expiry MedianTime for the deployment attempt. */
     int64_t nTimeout;
+    /** If lock in occurs, delay activation until at least this block
+     *  height.  Note that activation will only occur on a retarget
+     *  boundary.
+     */
+    int min_activation_height{0};
 
     /** Constant for nTimeout very far in the future. */
     static constexpr int64_t NO_TIMEOUT = std::numeric_limits<int64_t>::max();
diff --git a/src/rpc/blockchain.cpp b/src/rpc/blockchain.cpp
index 392073d047..2b4d26d855 100644
--- a/src/rpc/blockchain.cpp
+++ b/src/rpc/blockchain.cpp
@@ -1247,6 +1247,7 @@ static void BIP9SoftForkDescPushBack(UniValue& softforks, const std::string &nam
         statsUV.pushKV("possible", statsStruct.possible);
         bip9.pushKV("statistics", statsUV);
     }
+    bip9.pushKV("min_activation_height", consensusParams.vDeployments[id].min_activation_height);
 
     UniValue rv(UniValue::VOBJ);
     rv.pushKV("type", "bip9");
@@ -1293,6 +1294,7 @@ RPCHelpMan getblockchaininfo()
                                     {RPCResult::Type::NUM_TIME, "start_time", "the minimum median time past of a block at which the bit gains its meaning"},
                                     {RPCResult::Type::NUM_TIME, "timeout", "the median time past of a block at which the deployment is considered failed if not yet locked in"},
                                     {RPCResult::Type::NUM, "since", "height of the first block to which the status applies"},
+                                    {RPCResult::Type::NUM, "min_activation_height", "minimum height of blocks for which the rules may be enforced"},
                                     {RPCResult::Type::OBJ, "statistics", "numeric statistics about BIP9 signalling for a softfork (only for \"started\" status)",
                                     {
                                         {RPCResult::Type::NUM, "period", "the length in blocks of the BIP9 signalling period"},
diff --git a/src/test/versionbits_tests.cpp b/src/test/versionbits_tests.cpp
index b42aaff9ad..ae0d47b2b4 100644
--- a/src/test/versionbits_tests.cpp
+++ b/src/test/versionbits_tests.cpp
@@ -255,6 +255,7 @@ static void check_computeblockversion(const Consensus::Params& params, Consensus
     int64_t bit = params.vDeployments[dep].bit;
     int64_t nStartTime = params.vDeployments[dep].nStartTime;
     int64_t nTimeout = params.vDeployments[dep].nTimeout;
+    int min_activation_height = params.vDeployments[dep].min_activation_height;
 
     // should not be any signalling for first block
     BOOST_CHECK_EQUAL(ComputeBlockVersion(nullptr, params), VERSIONBITS_TOP_BITS);
@@ -267,6 +268,7 @@ static void check_computeblockversion(const Consensus::Params& params, Consensus
     BOOST_REQUIRE(nTimeout <= std::numeric_limits<uint32_t>::max() || nTimeout == Consensus::BIP9Deployment::NO_TIMEOUT);
     BOOST_REQUIRE(0 <= bit && bit < 32);
     BOOST_REQUIRE(((1 << bit) & VERSIONBITS_TOP_MASK) == 0);
+    BOOST_REQUIRE(min_activation_height == 0);
 
     // In the first chain, test that the bit is set by CBV until it has failed.
     // In the second chain, test the bit is set by CBV while STARTED and
diff --git a/src/versionbits.cpp b/src/versionbits.cpp
index af07c67ccf..11da729596 100644
--- a/src/versionbits.cpp
+++ b/src/versionbits.cpp
@@ -9,6 +9,7 @@ ThresholdState AbstractThresholdConditionChecker::GetStateFor(const CBlockIndex*
 {
     int nPeriod = Period(params);
     int nThreshold = Threshold(params);
+    int min_activation_height = MinActivationHeight(params);
     int64_t nTimeStart = BeginTime(params);
     int64_t nTimeTimeout = EndTime(params);
 
@@ -78,8 +79,10 @@ ThresholdState AbstractThresholdConditionChecker::GetStateFor(const CBlockIndex*
                 break;
             }
             case ThresholdState::LOCKED_IN: {
-                // Always progresses into ACTIVE.
-                stateNext = ThresholdState::ACTIVE;
+                // Progresses into ACTIVE provided activation height will have been reached.
+                if (pindexPrev->nHeight + 1 >= min_activation_height) {
+                    stateNext = ThresholdState::ACTIVE;
+                }
                 break;
             }
             case ThresholdState::FAILED:
@@ -170,6 +173,7 @@ private:
 protected:
     int64_t BeginTime(const Consensus::Params& params) const override { return params.vDeployments[id].nStartTime; }
     int64_t EndTime(const Consensus::Params& params) const override { return params.vDeployments[id].nTimeout; }
+    int MinActivationHeight(const Consensus::Params& params) const override { return params.vDeployments[id].min_activation_height; }
     int Period(const Consensus::Params& params) const override { return params.nMinerConfirmationWindow; }
     int Threshold(const Consensus::Params& params) const override { return params.nRuleChangeActivationThreshold; }
 
diff --git a/src/versionbits.h b/src/versionbits.h
index b02f848b67..faf09343ea 100644
--- a/src/versionbits.h
+++ b/src/versionbits.h
@@ -25,7 +25,7 @@ static const int32_t VERSIONBITS_NUM_BITS = 29;
 enum class ThresholdState {
     DEFINED,   // First state that each softfork starts out as. The genesis block is by definition in this state for each deployment.
     STARTED,   // For blocks past the starttime.
-    LOCKED_IN, // For one retarget period after the first retarget period with STARTED blocks of which at least threshold have the associated bit set in nVersion.
+    LOCKED_IN, // For at least one retarget period after the first retarget period with STARTED blocks of which at least threshold have the associated bit set in nVersion, until min_activation_height is reached.
     ACTIVE,    // For all blocks after the LOCKED_IN retarget period (final state)
     FAILED,    // For all blocks once the first retarget period after the timeout time is hit, if LOCKED_IN wasn't already reached (final state)
 };
@@ -57,6 +57,7 @@ protected:
     virtual bool Condition(const CBlockIndex* pindex, const Consensus::Params& params) const =0;
     virtual int64_t BeginTime(const Consensus::Params& params) const =0;
     virtual int64_t EndTime(const Consensus::Params& params) const =0;
+    virtual int MinActivationHeight(const Consensus::Params& params) const { return 0; }
     virtual int Period(const Consensus::Params& params) const =0;
     virtual int Threshold(const Consensus::Params& params) const =0;
 
diff --git a/test/functional/rpc_blockchain.py b/test/functional/rpc_blockchain.py
index f965677408..79d437abd3 100755
--- a/test/functional/rpc_blockchain.py
+++ b/test/functional/rpc_blockchain.py
@@ -145,6 +145,7 @@ class BlockchainTest(BitcoinTestFramework):
                         'count': 57,
                         'possible': True,
                     },
+                    'min_activation_height': 0,
                 },
                 'active': False
             },
@@ -154,7 +155,8 @@ class BlockchainTest(BitcoinTestFramework):
                     'status': 'active',
                     'start_time': -1,
                     'timeout': 9223372036854775807,
-                    'since': 0
+                    'since': 0,
+                    'min_activation_height': 0,
                 },
                 'height': 0,
                 'active': True