Merge #7648: BIP9 versionbits softfork for BIP68, BIP112 and BIP113

71527a0 Test of BIP9 fork activation of mtp, csv, sequence_lock (NicolasDorier)
19d73d5 Add RPC test for BIP 68/112/113 soft fork. (Alex Morcos)
12c89c9 Policy: allow transaction version 2 relay policy. (BtcDrak)
02c2435 Soft fork logic for BIP68 (BtcDrak)
478fba6 Soft fork logic for BIP113 (BtcDrak)
65751a3 Add CHECKSEQUENCEVERIFY softfork through BIP9 (Pieter Wuille)

6 files changed, 43 insertions, 7 deletions

diff --git a/src/chainparams.cpp b/src/chainparams.cpp
index 508c4de167..965d131695 100644
--- a/src/chainparams.cpp
+++ b/src/chainparams.cpp
@@ -86,7 +86,13 @@ 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
-        /** 
+
+        // Deployment of BIP68, BIP112, and BIP113.
+        consensus.vDeployments[Consensus::DEPLOYMENT_CSV].bit = 0;
+        consensus.vDeployments[Consensus::DEPLOYMENT_CSV].nStartTime = 1462060800; // May 1st, 2016
+        consensus.vDeployments[Consensus::DEPLOYMENT_CSV].nTimeout = 1493596800; // May 1st, 2017
+
+        /**
          * The message start string is designed to be unlikely to occur in normal data.
          * The characters are rarely used upper ASCII, not valid as UTF-8, and produce
          * a large 32-bit integer with any alignment.
@@ -171,6 +177,12 @@ 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
+
+        // Deployment of BIP68, BIP112, and BIP113.
+        consensus.vDeployments[Consensus::DEPLOYMENT_CSV].bit = 0;
+        consensus.vDeployments[Consensus::DEPLOYMENT_CSV].nStartTime = 1456790400; // March 1st, 2016
+        consensus.vDeployments[Consensus::DEPLOYMENT_CSV].nTimeout = 1493596800; // May 1st, 2017
+
         pchMessageStart[0] = 0x0b;
         pchMessageStart[1] = 0x11;
         pchMessageStart[2] = 0x09;
@@ -238,6 +250,9 @@ public:
         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_CSV].bit = 0;
+        consensus.vDeployments[Consensus::DEPLOYMENT_CSV].nStartTime = 0;
+        consensus.vDeployments[Consensus::DEPLOYMENT_CSV].nTimeout = 999999999999ULL;
 
         pchMessageStart[0] = 0xfa;
         pchMessageStart[1] = 0xbf;
diff --git a/src/consensus/params.h b/src/consensus/params.h
index 7c3a8e84c3..4f3480b89b 100644
--- a/src/consensus/params.h
+++ b/src/consensus/params.h
@@ -15,6 +15,7 @@ namespace Consensus {
 enum DeploymentPos
 {
     DEPLOYMENT_TESTDUMMY,
+    DEPLOYMENT_CSV, // Deployment of BIP68, BIP112, and BIP113.
     MAX_VERSION_BITS_DEPLOYMENTS
 };
 
diff --git a/src/main.cpp b/src/main.cpp
index 36189f4ffc..dfd92fa8f0 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -2286,6 +2286,13 @@ bool ConnectBlock(const CBlock& block, CValidationState& state, CBlockIndex* pin
         flags |= SCRIPT_VERIFY_CHECKLOCKTIMEVERIFY;
     }
 
+    // Start enforcing BIP68 (sequence locks) and BIP112 (CHECKSEQUENCEVERIFY) using versionbits logic.
+    int nLockTimeFlags = 0;
+    if (VersionBitsState(pindex->pprev, chainparams.GetConsensus(), Consensus::DEPLOYMENT_CSV, versionbitscache) == THRESHOLD_ACTIVE) {
+        flags |= SCRIPT_VERIFY_CHECKSEQUENCEVERIFY;
+        nLockTimeFlags |= LOCKTIME_VERIFY_SEQUENCE;
+    }
+
     int64_t nTime2 = GetTimeMicros(); nTimeForks += nTime2 - nTime1;
     LogPrint("bench", "    - Fork checks: %.2fms [%.2fs]\n", 0.001 * (nTime2 - nTime1), nTimeForks * 0.000001);
 
@@ -2294,7 +2301,6 @@ bool ConnectBlock(const CBlock& block, CValidationState& state, CBlockIndex* pin
     CCheckQueueControl<CScriptCheck> control(fScriptChecks && nScriptCheckThreads ? &scriptcheckqueue : NULL);
 
     std::vector<int> prevheights;
-    int nLockTimeFlags = 0;
     CAmount nFees = 0;
     int nInputs = 0;
     unsigned int nSigOps = 0;
@@ -3295,12 +3301,18 @@ bool ContextualCheckBlock(const CBlock& block, CValidationState& state, CBlockIn
     const int nHeight = pindexPrev == NULL ? 0 : pindexPrev->nHeight + 1;
     const Consensus::Params& consensusParams = Params().GetConsensus();
 
+    // Start enforcing BIP113 (Median Time Past) using versionbits logic.
+    int nLockTimeFlags = 0;
+    if (VersionBitsState(pindexPrev, consensusParams, Consensus::DEPLOYMENT_CSV, versionbitscache) == THRESHOLD_ACTIVE) {
+        nLockTimeFlags |= LOCKTIME_MEDIAN_TIME_PAST;
+    }
+
+    int64_t nLockTimeCutoff = (nLockTimeFlags & LOCKTIME_MEDIAN_TIME_PAST)
+                              ? pindexPrev->GetMedianTimePast()
+                              : block.GetBlockTime();
+
     // Check that all transactions are finalized
     BOOST_FOREACH(const CTransaction& tx, block.vtx) {
-        int nLockTimeFlags = 0;
-        int64_t nLockTimeCutoff = (nLockTimeFlags & LOCKTIME_MEDIAN_TIME_PAST)
-                                ? pindexPrev->GetMedianTimePast()
-                                : block.GetBlockTime();
         if (!IsFinalTx(tx, nHeight, nLockTimeCutoff)) {
             return state.DoS(10, false, REJECT_INVALID, "bad-txns-nonfinal", false, "non-final transaction");
         }
diff --git a/src/policy/policy.cpp b/src/policy/policy.cpp
index 332abc430e..e3ed7be000 100644
--- a/src/policy/policy.cpp
+++ b/src/policy/policy.cpp
@@ -55,7 +55,7 @@ bool IsStandard(const CScript& scriptPubKey, txnouttype& whichType)
 
 bool IsStandardTx(const CTransaction& tx, std::string& reason)
 {
-    if (tx.nVersion > CTransaction::CURRENT_VERSION || tx.nVersion < 1) {
+    if (tx.nVersion > CTransaction::MAX_STANDARD_VERSION || tx.nVersion < 1) {
         reason = "version";
         return false;
     }
diff --git a/src/primitives/transaction.h b/src/primitives/transaction.h
index e124dca365..149816406a 100644
--- a/src/primitives/transaction.h
+++ b/src/primitives/transaction.h
@@ -207,8 +207,15 @@ private:
     void UpdateHash() const;
 
 public:
+    // Default transaction version.
     static const int32_t CURRENT_VERSION=1;
 
+    // Changing the default transaction version requires a two step process: first
+    // adapting relay policy by bumping MAX_STANDARD_VERSION, and then later date
+    // bumping the default CURRENT_VERSION at which point both CURRENT_VERSION and
+    // MAX_STANDARD_VERSION will be equal.
+    static const int32_t MAX_STANDARD_VERSION=2;
+
     // The local variables are made const to prevent unintended modification
     // without updating the cached hash value. However, CTransaction is not
     // actually immutable; deserialization and assignment are implemented,
diff --git a/src/rpc/blockchain.cpp b/src/rpc/blockchain.cpp
index a110dff0d1..f5d75c20b3 100644
--- a/src/rpc/blockchain.cpp
+++ b/src/rpc/blockchain.cpp
@@ -681,6 +681,7 @@ UniValue getblockchaininfo(const UniValue& params, bool fHelp)
     softforks.push_back(SoftForkDesc("bip34", 2, tip, consensusParams));
     softforks.push_back(SoftForkDesc("bip66", 3, tip, consensusParams));
     softforks.push_back(SoftForkDesc("bip65", 4, tip, consensusParams));
+    bip9_softforks.push_back(BIP9SoftForkDesc("csv", consensusParams, Consensus::DEPLOYMENT_CSV));
     obj.push_back(Pair("softforks",             softforks));
     obj.push_back(Pair("bip9_softforks", bip9_softforks));