Merge #11389: Support having SegWit always active in regtest (sipa, ajtowns, jnewbery)

d61845818 Have SegWit active by default (Pieter Wuille)
4bd89210a Unit tests for always-active versionbits. (Anthony Towns)
d07ee77ab Always-active versionbits support (Pieter Wuille)
18e071841 [consensus] Pin P2SH activation to block 173805 on mainnet (John Newbery)
526023aa7 Improve handling of BIP9Deployment limits (Anthony Towns)

Pull request description:

  Most tests shouldn't have to deal with the now-historical SegWit activation transition (and other deployments, but SegWit is certainly the hardest one to accomodate).

  This PR makes a versionbits starttime of -1 equal to "always active", and enables it by default for SegWit on regtest. Individual tests can override this by using the existing `-vbparams` option.

  A few unit tests and functional tests are adapted to indeed override vbparams, as they specifically test the transition.

  This is in preparation for wallet SegWit support, but I thought having earlier eyes on it would be useful.

Tree-SHA512: 3f07a7b41cf46476e6c7a5c43244e68c9f41d223482cedaa4c02a3a7b7cd0e90cbd06b84a1f3704620559636a2268f5767d4c52d09c1b354945737046f618fe5

7 files changed, 70 insertions, 25 deletions

diff --git a/src/chainparams.cpp b/src/chainparams.cpp
index afdac16da4..950bdd945c 100644
--- a/src/chainparams.cpp
+++ b/src/chainparams.cpp
@@ -75,6 +75,7 @@ public:
     CMainParams() {
         strNetworkID = "main";
         consensus.nSubsidyHalvingInterval = 210000;
+        consensus.BIP16Height = 173805; // 00000000000000ce80a7e057163a4db1d5ad7b20fb6f598c9597b9665c8fb0d4 - April 1, 2012
         consensus.BIP34Height = 227931;
         consensus.BIP34Hash = uint256S("0x000000000000024b89b42a942fe0d9fea3bb44ab7bd1b19115dd6a759c0808b8");
         consensus.BIP65Height = 388381; // 000000000000000004c2b624ed5d7756c508d90fd0da2c7c679febfa6c4735f0
@@ -181,6 +182,7 @@ public:
     CTestNetParams() {
         strNetworkID = "test";
         consensus.nSubsidyHalvingInterval = 210000;
+        consensus.BIP16Height = 514; // 00000000040b4e986385315e14bee30ad876d8b47f748025b26683116d21aa65
         consensus.BIP34Height = 21111;
         consensus.BIP34Hash = uint256S("0x0000000023b3a96d3484e5abb3755c413e7d41500f8e2a5c3f0dd01299cd8ef8");
         consensus.BIP65Height = 581885; // 00000000007f6655f22f98e72ed80d8b06dc761d5da09df0fa1dc4be4f861eb6
@@ -270,6 +272,7 @@ public:
     CRegTestParams() {
         strNetworkID = "regtest";
         consensus.nSubsidyHalvingInterval = 150;
+        consensus.BIP16Height = 0; // always enforce P2SH BIP16 on regtest
         consensus.BIP34Height = 100000000; // BIP34 has not activated on regtest (far in the future so block v1 are not rejected in tests)
         consensus.BIP34Hash = uint256();
         consensus.BIP65Height = 1351; // BIP65 activated on regtest (Used in rpc activation tests)
@@ -283,13 +286,13 @@ public:
         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 = 999999999999ULL;
+        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].nTimeout = Consensus::BIP9Deployment::NO_TIMEOUT;
         consensus.vDeployments[Consensus::DEPLOYMENT_CSV].bit = 0;
         consensus.vDeployments[Consensus::DEPLOYMENT_CSV].nStartTime = 0;
-        consensus.vDeployments[Consensus::DEPLOYMENT_CSV].nTimeout = 999999999999ULL;
+        consensus.vDeployments[Consensus::DEPLOYMENT_CSV].nTimeout = Consensus::BIP9Deployment::NO_TIMEOUT;
         consensus.vDeployments[Consensus::DEPLOYMENT_SEGWIT].bit = 1;
-        consensus.vDeployments[Consensus::DEPLOYMENT_SEGWIT].nStartTime = 0;
-        consensus.vDeployments[Consensus::DEPLOYMENT_SEGWIT].nTimeout = 999999999999ULL;
+        consensus.vDeployments[Consensus::DEPLOYMENT_SEGWIT].nStartTime = Consensus::BIP9Deployment::ALWAYS_ACTIVE;
+        consensus.vDeployments[Consensus::DEPLOYMENT_SEGWIT].nTimeout = Consensus::BIP9Deployment::NO_TIMEOUT;
 
         // The best chain should have at least this much work.
         consensus.nMinimumChainWork = uint256S("0x00");
diff --git a/src/consensus/params.h b/src/consensus/params.h
index 6240e82857..fd0946a612 100644
--- a/src/consensus/params.h
+++ b/src/consensus/params.h
@@ -7,6 +7,7 @@
 #define BITCOIN_CONSENSUS_PARAMS_H
 
 #include "uint256.h"
+#include <limits>
 #include <map>
 #include <string>
 
@@ -31,6 +32,15 @@ struct BIP9Deployment {
     int64_t nStartTime;
     /** Timeout/expiry MedianTime for the deployment attempt. */
     int64_t nTimeout;
+
+    /** Constant for nTimeout very far in the future. */
+    static constexpr int64_t NO_TIMEOUT = std::numeric_limits<int64_t>::max();
+
+    /** Special value for nStartTime indicating that the deployment is always active.
+     *  This is useful for testing, as it means tests don't need to deal with the activation
+     *  process (which takes at least 3 BIP9 intervals). Only tests that specifically test the
+     *  behaviour during activation cannot use this. */
+    static constexpr int64_t ALWAYS_ACTIVE = -1;
 };
 
 /**
@@ -39,6 +49,8 @@ struct BIP9Deployment {
 struct Params {
     uint256 hashGenesisBlock;
     int nSubsidyHalvingInterval;
+    /** Block height at which BIP16 becomes active */
+    int BIP16Height;
     /** Block height and hash at which BIP34 becomes active */
     int BIP34Height;
     uint256 BIP34Hash;
diff --git a/src/test/miner_tests.cpp b/src/test/miner_tests.cpp
index 41e0626eb9..2851808cf4 100644
--- a/src/test/miner_tests.cpp
+++ b/src/test/miner_tests.cpp
@@ -335,23 +335,6 @@ BOOST_AUTO_TEST_CASE(CreateNewBlock_validity)
     BOOST_CHECK_THROW(AssemblerForTest(chainparams).CreateNewBlock(scriptPubKey), std::runtime_error);
     mempool.clear();
 
-    // invalid (pre-p2sh) txn in mempool, template creation fails
-    tx.vin[0].prevout.hash = txFirst[0]->GetHash();
-    tx.vin[0].prevout.n = 0;
-    tx.vin[0].scriptSig = CScript() << OP_1;
-    tx.vout[0].nValue = BLOCKSUBSIDY-LOWFEE;
-    script = CScript() << OP_0;
-    tx.vout[0].scriptPubKey = GetScriptForDestination(CScriptID(script));
-    hash = tx.GetHash();
-    mempool.addUnchecked(hash, entry.Fee(LOWFEE).Time(GetTime()).SpendsCoinbase(true).FromTx(tx));
-    tx.vin[0].prevout.hash = hash;
-    tx.vin[0].scriptSig = CScript() << std::vector<unsigned char>(script.begin(), script.end());
-    tx.vout[0].nValue -= LOWFEE;
-    hash = tx.GetHash();
-    mempool.addUnchecked(hash, entry.Fee(LOWFEE).Time(GetTime()).SpendsCoinbase(false).FromTx(tx));
-    BOOST_CHECK_THROW(AssemblerForTest(chainparams).CreateNewBlock(scriptPubKey), std::runtime_error);
-    mempool.clear();
-
     // double spend txn pair in mempool, template creation fails
     tx.vin[0].prevout.hash = txFirst[0]->GetHash();
     tx.vin[0].scriptSig = CScript() << OP_1;
@@ -391,6 +374,24 @@ BOOST_AUTO_TEST_CASE(CreateNewBlock_validity)
         chainActive.SetTip(next);
     }
     BOOST_CHECK(pblocktemplate = AssemblerForTest(chainparams).CreateNewBlock(scriptPubKey));
+
+    // invalid p2sh txn in mempool, template creation fails
+    tx.vin[0].prevout.hash = txFirst[0]->GetHash();
+    tx.vin[0].prevout.n = 0;
+    tx.vin[0].scriptSig = CScript() << OP_1;
+    tx.vout[0].nValue = BLOCKSUBSIDY-LOWFEE;
+    script = CScript() << OP_0;
+    tx.vout[0].scriptPubKey = GetScriptForDestination(CScriptID(script));
+    hash = tx.GetHash();
+    mempool.addUnchecked(hash, entry.Fee(LOWFEE).Time(GetTime()).SpendsCoinbase(true).FromTx(tx));
+    tx.vin[0].prevout.hash = hash;
+    tx.vin[0].scriptSig = CScript() << std::vector<unsigned char>(script.begin(), script.end());
+    tx.vout[0].nValue -= LOWFEE;
+    hash = tx.GetHash();
+    mempool.addUnchecked(hash, entry.Fee(LOWFEE).Time(GetTime()).SpendsCoinbase(false).FromTx(tx));
+    BOOST_CHECK_THROW(AssemblerForTest(chainparams).CreateNewBlock(scriptPubKey), std::runtime_error);
+    mempool.clear();
+
     // Delete the dummy blocks again.
     while (chainActive.Tip()->nHeight > nHeight) {
         CBlockIndex* del = chainActive.Tip();
diff --git a/src/test/test_bitcoin.cpp b/src/test/test_bitcoin.cpp
index 85476b6da2..f9ce52c594 100644
--- a/src/test/test_bitcoin.cpp
+++ b/src/test/test_bitcoin.cpp
@@ -118,6 +118,9 @@ TestingSetup::~TestingSetup()
 
 TestChain100Setup::TestChain100Setup() : TestingSetup(CBaseChainParams::REGTEST)
 {
+    // CreateAndProcessBlock() does not support building SegWit blocks, so don't activate in these tests.
+    // TODO: fix the code to support SegWit blocks.
+    UpdateVersionBitsParameters(Consensus::DEPLOYMENT_SEGWIT, 0, Consensus::BIP9Deployment::NO_TIMEOUT);
     // Generate a 100-block chain:
     coinbaseKey.MakeNewKey(true);
     CScript scriptPubKey = CScript() <<  ToByteVector(coinbaseKey.GetPubKey()) << OP_CHECKSIG;
diff --git a/src/test/versionbits_tests.cpp b/src/test/versionbits_tests.cpp
index 882afb2e20..db537d3932 100644
--- a/src/test/versionbits_tests.cpp
+++ b/src/test/versionbits_tests.cpp
@@ -32,6 +32,12 @@ public:
     int GetStateSinceHeightFor(const CBlockIndex* pindexPrev) const { return AbstractThresholdConditionChecker::GetStateSinceHeightFor(pindexPrev, paramsDummy, cache); }
 };
 
+class TestAlwaysActiveConditionChecker : public TestConditionChecker
+{
+public:
+    int64_t BeginTime(const Consensus::Params& params) const override { return Consensus::BIP9Deployment::ALWAYS_ACTIVE; }
+};
+
 #define CHECKERS 6
 
 class VersionBitsTester
@@ -43,6 +49,8 @@ class VersionBitsTester
     // The first one performs all checks, the second only 50%, the third only 25%, etc...
     // This is to test whether lack of cached information leads to the same results.
     TestConditionChecker checker[CHECKERS];
+    // Another 6 that assume always active activation
+    TestAlwaysActiveConditionChecker checker_always[CHECKERS];
 
     // Test counter (to identify failures)
     int num;
@@ -56,6 +64,7 @@ public:
         }
         for (unsigned int  i = 0; i < CHECKERS; i++) {
             checker[i] = TestConditionChecker();
+            checker_always[i] = TestAlwaysActiveConditionChecker();
         }
         vpblock.clear();
         return *this;
@@ -82,6 +91,7 @@ public:
         for (int i = 0; i < CHECKERS; i++) {
             if (InsecureRandBits(i) == 0) {
                 BOOST_CHECK_MESSAGE(checker[i].GetStateSinceHeightFor(vpblock.empty() ? nullptr : vpblock.back()) == height, strprintf("Test %i for StateSinceHeight", num));
+                BOOST_CHECK_MESSAGE(checker_always[i].GetStateSinceHeightFor(vpblock.empty() ? nullptr : vpblock.back()) == 0, strprintf("Test %i for StateSinceHeight (always active)", num));
             }
         }
         num++;
@@ -92,6 +102,7 @@ public:
         for (int i = 0; i < CHECKERS; i++) {
             if (InsecureRandBits(i) == 0) {
                 BOOST_CHECK_MESSAGE(checker[i].GetStateFor(vpblock.empty() ? nullptr : vpblock.back()) == THRESHOLD_DEFINED, strprintf("Test %i for DEFINED", num));
+                BOOST_CHECK_MESSAGE(checker_always[i].GetStateFor(vpblock.empty() ? nullptr : vpblock.back()) == THRESHOLD_ACTIVE, strprintf("Test %i for ACTIVE (always active)", num));
             }
         }
         num++;
@@ -102,6 +113,7 @@ public:
         for (int i = 0; i < CHECKERS; i++) {
             if (InsecureRandBits(i) == 0) {
                 BOOST_CHECK_MESSAGE(checker[i].GetStateFor(vpblock.empty() ? nullptr : vpblock.back()) == THRESHOLD_STARTED, strprintf("Test %i for STARTED", num));
+                BOOST_CHECK_MESSAGE(checker_always[i].GetStateFor(vpblock.empty() ? nullptr : vpblock.back()) == THRESHOLD_ACTIVE, strprintf("Test %i for ACTIVE (always active)", num));
             }
         }
         num++;
@@ -112,6 +124,7 @@ public:
         for (int i = 0; i < CHECKERS; i++) {
             if (InsecureRandBits(i) == 0) {
                 BOOST_CHECK_MESSAGE(checker[i].GetStateFor(vpblock.empty() ? nullptr : vpblock.back()) == THRESHOLD_LOCKED_IN, strprintf("Test %i for LOCKED_IN", num));
+                BOOST_CHECK_MESSAGE(checker_always[i].GetStateFor(vpblock.empty() ? nullptr : vpblock.back()) == THRESHOLD_ACTIVE, strprintf("Test %i for ACTIVE (always active)", num));
             }
         }
         num++;
@@ -122,6 +135,7 @@ public:
         for (int i = 0; i < CHECKERS; i++) {
             if (InsecureRandBits(i) == 0) {
                 BOOST_CHECK_MESSAGE(checker[i].GetStateFor(vpblock.empty() ? nullptr : vpblock.back()) == THRESHOLD_ACTIVE, strprintf("Test %i for ACTIVE", num));
+                BOOST_CHECK_MESSAGE(checker_always[i].GetStateFor(vpblock.empty() ? nullptr : vpblock.back()) == THRESHOLD_ACTIVE, strprintf("Test %i for ACTIVE (always active)", num));
             }
         }
         num++;
@@ -132,6 +146,7 @@ public:
         for (int i = 0; i < CHECKERS; i++) {
             if (InsecureRandBits(i) == 0) {
                 BOOST_CHECK_MESSAGE(checker[i].GetStateFor(vpblock.empty() ? nullptr : vpblock.back()) == THRESHOLD_FAILED, strprintf("Test %i for FAILED", num));
+                BOOST_CHECK_MESSAGE(checker_always[i].GetStateFor(vpblock.empty() ? nullptr : vpblock.back()) == THRESHOLD_ACTIVE, strprintf("Test %i for ACTIVE (always active)", num));
             }
         }
         num++;
diff --git a/src/validation.cpp b/src/validation.cpp
index 83cbcb42cb..a98036f03c 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -1611,11 +1611,12 @@ static ThresholdConditionCache warningcache[VERSIONBITS_NUM_BITS];
 static unsigned int GetBlockScriptFlags(const CBlockIndex* pindex, const Consensus::Params& consensusparams) {
     AssertLockHeld(cs_main);
 
-    // BIP16 didn't become active until Apr 1 2012
-    int64_t nBIP16SwitchTime = 1333238400;
-    bool fStrictPayToScriptHash = (pindex->GetBlockTime() >= nBIP16SwitchTime);
+    unsigned int flags = SCRIPT_VERIFY_NONE;
 
-    unsigned int flags = fStrictPayToScriptHash ? SCRIPT_VERIFY_P2SH : SCRIPT_VERIFY_NONE;
+    // Start enforcing P2SH (BIP16)
+    if (pindex->nHeight >= consensusparams.BIP16Height) {
+        flags |= SCRIPT_VERIFY_P2SH;
+    }
 
     // Start enforcing the DERSIG (BIP66) rule
     if (pindex->nHeight >= consensusparams.BIP66Height) {
diff --git a/src/versionbits.cpp b/src/versionbits.cpp
index 64ae939672..fc1acb3258 100644
--- a/src/versionbits.cpp
+++ b/src/versionbits.cpp
@@ -27,6 +27,11 @@ ThresholdState AbstractThresholdConditionChecker::GetStateFor(const CBlockIndex*
     int64_t nTimeStart = BeginTime(params);
     int64_t nTimeTimeout = EndTime(params);
 
+    // Check if this deployment is always active.
+    if (nTimeStart == Consensus::BIP9Deployment::ALWAYS_ACTIVE) {
+        return THRESHOLD_ACTIVE;
+    }
+
     // A block's state is always the same as that of the first of its period, so it is computed based on a pindexPrev whose height equals a multiple of nPeriod - 1.
     if (pindexPrev != nullptr) {
         pindexPrev = pindexPrev->GetAncestor(pindexPrev->nHeight - ((pindexPrev->nHeight + 1) % nPeriod));
@@ -136,6 +141,11 @@ BIP9Stats AbstractThresholdConditionChecker::GetStateStatisticsFor(const CBlockI
 
 int AbstractThresholdConditionChecker::GetStateSinceHeightFor(const CBlockIndex* pindexPrev, const Consensus::Params& params, ThresholdConditionCache& cache) const
 {
+    int64_t start_time = BeginTime(params);
+    if (start_time == Consensus::BIP9Deployment::ALWAYS_ACTIVE) {
+        return 0;
+    }
+
     const ThresholdState initialState = GetStateFor(pindexPrev, params, cache);
 
     // BIP 9 about state DEFINED: "The genesis block is by definition in this state for each deployment."