Merge pull request #6931

33c90cf Make skipping BIP30 check chain agnostic (Alex Morcos)
06d81ad Skip BIP30 check after BIP34 activation (Alex Morcos)

Author: sipa

src/chainparams.cpp

@@ -73,6 +73,8 @@ class CMainParams : public CChainParams {
         consensus.nMajorityEnforceBlockUpgrade = 750;
         consensus.nMajorityRejectBlockOutdated = 950;
         consensus.nMajorityWindow = 1000;
+        consensus.BIP34Height = 227931;
+        consensus.BIP34Hash = uint256S("0x000000000000024b89b42a942fe0d9fea3bb44ab7bd1b19115dd6a759c0808b8");
         consensus.powLimit = uint256S("00000000ffffffffffffffffffffffffffffffffffffffffffffffffffffffff");
         consensus.nPowTargetTimespan = 14 * 24 * 60 * 60; // two weeks
         consensus.nPowTargetSpacing = 10 * 60;
@@ -153,6 +155,8 @@ class CTestNetParams : public CChainParams {
         consensus.nMajorityEnforceBlockUpgrade = 51;
         consensus.nMajorityRejectBlockOutdated = 75;
         consensus.nMajorityWindow = 100;
+        consensus.BIP34Height = 21111;
+        consensus.BIP34Hash = uint256S("0x0000000023b3a96d3484e5abb3755c413e7d41500f8e2a5c3f0dd01299cd8ef8");
         consensus.powLimit = uint256S("00000000ffffffffffffffffffffffffffffffffffffffffffffffffffffffff");
         consensus.nPowTargetTimespan = 14 * 24 * 60 * 60; // two weeks
         consensus.nPowTargetSpacing = 10 * 60;
@@ -216,6 +220,8 @@ class CRegTestParams : public CChainParams {
         consensus.nMajorityEnforceBlockUpgrade = 750;
         consensus.nMajorityRejectBlockOutdated = 950;
         consensus.nMajorityWindow = 1000;
+        consensus.BIP34Height = -1; // BIP34 has not necessarily activated on regtest
+        consensus.BIP34Hash = uint256();
         consensus.powLimit = uint256S("7fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff");
         consensus.nPowTargetTimespan = 14 * 24 * 60 * 60; // two weeks
         consensus.nPowTargetSpacing = 10 * 60;

src/consensus/params.h

@@ -19,6 +19,9 @@ struct Params {
     int nMajorityEnforceBlockUpgrade;
     int nMajorityRejectBlockOutdated;
     int nMajorityWindow;
+    /** Block height and hash at which BIP34 becomes active */
+    int BIP34Height;
+    uint256 BIP34Hash;
     /** Proof of work parameters */
     uint256 powLimit;
     bool fPowAllowMinDifficultyBlocks;

src/main.cpp

@@ -1769,6 +1769,17 @@ bool ConnectBlock(const CBlock& block, CValidationState& state, CBlockIndex* pin
     bool fEnforceBIP30 = (!pindex->phashBlock) || // Enforce on CreateNewBlock invocations which don't have a hash.
                           !((pindex->nHeight==91842 && pindex->GetBlockHash() == uint256S("0x00000000000a4d0a398161ffc163c503763b1f4360639393e0e4c8e300e0caec")) ||
                            (pindex->nHeight==91880 && pindex->GetBlockHash() == uint256S("0x00000000000743f190a18c5577a3c2d2a1f610ae9601ac046a38084ccb7cd721")));
+
+    // Once BIP34 activated it was not possible to create new duplicate coinbases and thus other than starting
+    // with the 2 existing duplicate coinbase pairs, not possible to create overwriting txs.  But by the
+    // time BIP34 activated, in each of the existing pairs the duplicate coinbase had overwritten the first
+    // before the first had been spent.  Since those coinbases are sufficiently buried its no longer possible to create further
+    // duplicate transactions descending from the known pairs either.
+    // If we're on the known chain at height greater than where BIP34 activated, we can save the db accesses needed for the BIP30 check.
+    CBlockIndex *pindexBIP34height = pindex->pprev->GetAncestor(chainparams.GetConsensus().BIP34Height);
+    //Only continue to enforce if we're below BIP34 activation height or the block hash at that height doesn't correspond.
+    fEnforceBIP30 = fEnforceBIP30 && (!pindexBIP34height || !(pindexBIP34height->GetBlockHash() == chainparams.GetConsensus().BIP34Hash));
+
     if (fEnforceBIP30) {
         BOOST_FOREACH(const CTransaction& tx, block.vtx) {
             const CCoins* coins = view.AccessCoins(tx.GetHash());