From a26f669e341664aec752095000b8c7a1d5741b7c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?P=C3=A9ter=20Szil=C3=A1gyi?= <peterke@gmail.com>
Date: Tue, 3 Oct 2017 15:08:58 +0300
Subject: [PATCH] core: verify state too when deduping existing blocks

---
 core/blockchain.go | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/core/blockchain.go b/core/blockchain.go
index 235c1f3da2..c896408b33 100644
--- a/core/blockchain.go
+++ b/core/blockchain.go
@@ -792,15 +792,14 @@ func (bc *BlockChain) WriteBlockAndState(block *types.Block, receipts []*types.R
 	if ptd == nil {
 		return NonStatTy, consensus.ErrUnknownAncestor
 	}
+	// If the block is already known, skip it
+	if bc.HasBlockAndState(block.Hash()) {
+		return SideStatTy, nil
+	}
 	// Make sure no inconsistent state is leaked during insertion
 	bc.mu.Lock()
 	defer bc.mu.Unlock()
 
-	if bc.HasBlock(block.Hash(), block.NumberU64()) {
-		log.Trace("Block existed", "hash", block.Hash())
-		return
-	}
-
 	localTd := bc.GetTd(bc.currentBlock.Hash(), bc.currentBlock.NumberU64())
 	externTd := new(big.Int).Add(block.Difficulty(), ptd)