Merge pull request #6931

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

1 files changed, 11 insertions, 0 deletions

diff --git a/src/main.cpp b/src/main.cpp
index f1a4527540..6e5a81f306 100644
--- a/src/main.cpp
+++ b/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());