Merge pull request #17 from btc1/2017_bip91

BIP91 SegWit2x activation

Author: jgarzik

src/chainparams.cpp

@@ -96,6 +96,11 @@ class CMainParams : public CChainParams {
         consensus.vDeployments[Consensus::DEPLOYMENT_SEGWIT].nStartTime = 1479168000; // November 15th, 2016.
         consensus.vDeployments[Consensus::DEPLOYMENT_SEGWIT].nTimeout = 1510704000; // November 15th, 2017.
 
+        // Deployment of SEGWIT2X
+        consensus.vDeployments[Consensus::DEPLOYMENT_SEGWIT2X].bit = 4;
+        consensus.vDeployments[Consensus::DEPLOYMENT_SEGWIT2X].nStartTime = 1496275200; // June 1st, 2017.
+        consensus.vDeployments[Consensus::DEPLOYMENT_SEGWIT2X].nTimeout = 1510704000; // November 15th, 2017.
+
         // The best chain should have at least this much work.
         consensus.nMinimumChainWork = uint256S("0x0000000000000000000000000000000000000000003f94d1ad391682fe038bf5");
 

src/consensus/params.h

@@ -17,6 +17,7 @@ enum DeploymentPos
     DEPLOYMENT_TESTDUMMY,
     DEPLOYMENT_CSV, // Deployment of BIP68, BIP112, and BIP113.
     DEPLOYMENT_SEGWIT, // Deployment of BIP141, BIP143, and BIP147.
+    DEPLOYMENT_SEGWIT2X, // Deployment of SEGWIT2X
     // NOTE: Also add new deployments to VersionBitsDeploymentInfo in versionbits.cpp
     MAX_VERSION_BITS_DEPLOYMENTS
 };

src/rpc/blockchain.cpp

@@ -1135,6 +1135,7 @@ UniValue getblockchaininfo(const JSONRPCRequest& request)
     softforks.push_back(SoftForkDesc("bip65", 4, tip, consensusParams));
     BIP9SoftForkDescPushBack(bip9_softforks, "csv", consensusParams, Consensus::DEPLOYMENT_CSV);
     BIP9SoftForkDescPushBack(bip9_softforks, "segwit", consensusParams, Consensus::DEPLOYMENT_SEGWIT);
+    BIP9SoftForkDescPushBack(bip9_softforks, "segwit2x", consensusParams, Consensus::DEPLOYMENT_SEGWIT2X);
     obj.push_back(Pair("softforks",             softforks));
     obj.push_back(Pair("bip9_softforks", bip9_softforks));
 

src/validation.cpp

@@ -1851,6 +1851,18 @@ bool ConnectBlock(const CBlock& block, CValidationState& state, CBlockIndex* pin
         flags |= SCRIPT_VERIFY_NULLDUMMY;
     }
 
+    // SEGWIT2X signalling.
+    if ( VersionBitsState(pindex->pprev, chainparams.GetConsensus(), Consensus::DEPLOYMENT_SEGWIT2X, versionbitscache) == THRESHOLD_ACTIVE &&
+         !IsWitnessLockedIn(pindex->pprev, chainparams.GetConsensus()) &&  // Segwit is not locked in
+         !IsWitnessEnabled(pindex->pprev, chainparams.GetConsensus()) ) // and is not active.
+    {
+        bool fVersionBits = (pindex->nVersion & VERSIONBITS_TOP_MASK) == VERSIONBITS_TOP_BITS;
+        bool fSegbit = (pindex->nVersion & VersionBitsMask(chainparams.GetConsensus(), Consensus::DEPLOYMENT_SEGWIT)) != 0;
+        if (!(fVersionBits && fSegbit)) {
+            return state.DoS(0, error("ConnectBlock(): relayed block must signal for segwit, please upgrade"), REJECT_INVALID, "bad-no-segwit");
+        }
+    }
+
     int64_t nTime2 = GetTimeMicros(); nTimeForks += nTime2 - nTime1;
     LogPrint("bench", "    - Fork checks: %.2fms [%.2fs]\n", 0.001 * (nTime2 - nTime1), nTimeForks * 0.000001);
 
@@ -2918,6 +2930,13 @@ bool IsWitnessEnabled(const CBlockIndex* pindexPrev, const Consensus::Params& pa
     return (VersionBitsState(pindexPrev, params, Consensus::DEPLOYMENT_SEGWIT, versionbitscache) == THRESHOLD_ACTIVE);
 }
 
+// Check if Segregated Witness is Locked In
+bool IsWitnessLockedIn(const CBlockIndex* pindexPrev, const Consensus::Params& params)
+{
+    LOCK(cs_main);
+    return (VersionBitsState(pindexPrev, params, Consensus::DEPLOYMENT_SEGWIT, versionbitscache) == THRESHOLD_LOCKED_IN);
+}
+
 // Compute at which vout of the block's coinbase transaction the witness
 // commitment occurs, or -1 if not found.
 static int GetWitnessCommitmentIndex(const CBlock& block)

src/validation.h

@@ -503,6 +503,9 @@ bool TestBlockValidity(CValidationState& state, const CChainParams& chainparams,
 /** Check whether witness commitments are required for block. */
 bool IsWitnessEnabled(const CBlockIndex* pindexPrev, const Consensus::Params& params);
 
+/** Check whether witness commitments are required for block. */
+bool IsWitnessLockedIn(const CBlockIndex* pindexPrev, const Consensus::Params& params);
+
 /** When there are blocks in the active chain with missing data, rewind the chainstate and remove them from the block index */
 bool RewindBlockIndex(const CChainParams& params);
 

src/versionbits.cpp

@@ -18,6 +18,10 @@ const struct BIP9DeploymentInfo VersionBitsDeploymentInfo[Consensus::MAX_VERSION
     {
         /*.name =*/ "segwit",
         /*.gbt_force =*/ true,
+    },
+    {
+        /*.name =*/ "segwit2x",
+        /*.gbt_force =*/ true,
     }
 };
 
@@ -148,7 +152,14 @@ class VersionBitsConditionChecker : public AbstractThresholdConditionChecker {
     int64_t BeginTime(const Consensus::Params& params) const { return params.vDeployments[id].nStartTime; }
     int64_t EndTime(const Consensus::Params& params) const { return params.vDeployments[id].nTimeout; }
     int Period(const Consensus::Params& params) const { return params.nMinerConfirmationWindow; }
-    int Threshold(const Consensus::Params& params) const { return params.nRuleChangeActivationThreshold; }
+    int Threshold(const Consensus::Params& params) const {
+        if (params.nRuleChangeActivationThreshold == 1916 && params.nMinerConfirmationWindow == 2016 &&
+            params.vDeployments[id].bit == params.vDeployments[Consensus::DEPLOYMENT_SEGWIT2X].bit &&
+            params.vDeployments[id].nStartTime == params.vDeployments[Consensus::DEPLOYMENT_SEGWIT2X].nStartTime) {
+            return 1612; // 80% threshold for SEGWIT2X only
+        }
+        return params.nRuleChangeActivationThreshold;
+    }
 
     bool Condition(const CBlockIndex* pindex, const Consensus::Params& params) const
     {