Replace the concept of virtual block size by block cost

src/consensus/consensus.h

@@ -7,7 +7,10 @@
 #define BITCOIN_CONSENSUS_CONSENSUS_H
 
 /** The maximum allowed size for a serialized block, in bytes (network rule) */
-static const unsigned int MAX_BLOCK_SIZE = 1000000;
+static const unsigned int MAX_BLOCK_COST = 4000000;
+
+/** The maximum allowed size for a serialized block, in bytes (network rule) */
+static const unsigned int MAX_BLOCK_SIZE = MAX_BLOCK_COST/4;
 /** The maximum allowed number of signature check operations in a block (network rule) */
 static const unsigned int MAX_BLOCK_SIGOPS = MAX_BLOCK_SIZE/50;
 /** Coinbase transaction outputs can only be spent after this number of new blocks (network rule) */

src/main.cpp

@@ -3223,7 +3223,7 @@ bool ContextualCheckBlock(const CBlock& block, CValidationState& state, CBlockIn
             // Note: we aren't checking virtual size for blocks that aren't
             // witness enabled, but that's okay because CheckBlock still
             // checks the block size without any witnesses.
-            if (GetVirtualBlockSize(block) > MAX_BLOCK_SIZE) {
+            if (GetBlockCost(block) > MAX_BLOCK_COST) {
                 return state.DoS(100, error("ContextualCheckBlock(): witness size limits failed"), REJECT_INVALID, "bad-blk-wit-length");
             }
             return true;

src/primitives/block.cpp

@@ -32,12 +32,13 @@ std::string CBlock::ToString() const
     return s.str();
 }
 
-size_t GetVirtualBlockSize(const CBlock& block)
-{
-    // The intended approximate formula is: vsize = base_size + witness_size / 4.
-    // We can only serialize base or base+witness, so the formula
-    // becomes: vsize = base_size + (total_size - base_size) / 4 or
-    // vsize = (total_size + 3 * base_size) / 4, which we round up to
-    // vsize = (total_size + 3 * base_size + 3) / 4.
-    return (::GetSerializeSize(block, SER_NETWORK, 0) * 3 + ::GetSerializeSize(block, SER_NETWORK, SERIALIZE_TRANSACTION_WITNESS) + 3) / 4;
+size_t GetBlockCost(const CBlock& block)
+{    
+    // coreSize is the size of block without witness data
+    size_t coreSize = ::GetSerializeSize(block, SER_NETWORK, 0);
+    size_t totalSize = ::GetSerializeSize(block, SER_NETWORK, SERIALIZE_TRANSACTION_WITNESS);    
+    // size_t witSize = totalSize - coreSize;    
+    // return witSize + 4 * coreSize;
+    // Since totalSize == witSize + coreSize, we can avoid a substraction
+    return totalSize + 3 * coreSize;
 }

src/primitives/block.h

@@ -156,6 +156,6 @@ struct CBlockLocator
 };
 
 /** Compute the consensus-critical virtual block size. */
-size_t GetVirtualBlockSize(const CBlock& tx);
+size_t GetBlockCost(const CBlock& block);
 
 #endif // BITCOIN_PRIMITIVES_BLOCK_H

src/rpcblockchain.cpp

@@ -97,7 +97,7 @@ UniValue blockToJSON(const CBlock& block, const CBlockIndex* blockindex, bool tx
     result.push_back(Pair("confirmations", confirmations));
     result.push_back(Pair("size", (int)::GetSerializeSize(block, SER_NETWORK, PROTOCOL_VERSION)));
     result.push_back(Pair("wsize", (int)::GetSerializeSize(block, SER_NETWORK, PROTOCOL_VERSION | SERIALIZE_TRANSACTION_WITNESS)));
-    result.push_back(Pair("vsize", (int)::GetVirtualBlockSize(block)));
+    result.push_back(Pair("bcost", (int)::GetBlockCost(block)));
     result.push_back(Pair("height", blockindex->nHeight));
     result.push_back(Pair("version", block.nVersion));
     result.push_back(Pair("merkleroot", block.hashMerkleRoot.GetHex()));