feat(opn): expose GasUsed in BlockInfo type

Exposes the GasUsed field in the BlockInfo type. This has no impact on
the op-node for Optimism Mainnet, but it will be used in the OP Stack
Getting Started guide.

op-node/eth/block_info.go

@@ -20,6 +20,7 @@ type BlockInfo interface {
 	MixDigest() common.Hash
 	BaseFee() *big.Int
 	ReceiptHash() common.Hash
+	GasUsed() uint64
 }
 
 func InfoToL1BlockRef(info BlockInfo) L1BlockRef {
@@ -79,6 +80,10 @@ func (h headerBlockInfo) ReceiptHash() common.Hash {
 	return h.Header.ReceiptHash
 }
 
+func (h headerBlockInfo) GasUsed() uint64 {
+	return h.Header.GasUsed
+}
+
 // HeaderBlockInfo returns h as a BlockInfo implementation.
 func HeaderBlockInfo(h *types.Header) BlockInfo {
 	return headerBlockInfo{h}

op-node/sources/types.go

@@ -46,6 +46,7 @@ type HeaderInfo struct {
 	baseFee     *big.Int
 	txHash      common.Hash
 	receiptHash common.Hash
+	gasUsed     uint64
 }
 
 var _ eth.BlockInfo = (*HeaderInfo)(nil)
@@ -90,6 +91,10 @@ func (info *HeaderInfo) ReceiptHash() common.Hash {
 	return info.receiptHash
 }
 
+func (info *HeaderInfo) GasUsed() uint64 {
+	return info.gasUsed
+}
+
 type rpcHeader struct {
 	ParentHash  common.Hash      `json:"parentHash"`
 	UncleHash   common.Hash      `json:"sha3Uncles"`
@@ -182,6 +187,7 @@ func (hdr *rpcHeader) Info(trustCache bool, mustBePostMerge bool) (*HeaderInfo,
 		baseFee:     (*big.Int)(hdr.BaseFee),
 		txHash:      hdr.TxHash,
 		receiptHash: hdr.ReceiptHash,
+		gasUsed:     uint64(hdr.GasUsed),
 	}
 	return &info, nil
 }

op-node/testutils/l1info.go

@@ -21,6 +21,7 @@ type MockBlockInfo struct {
 	InfoMixDigest   [32]byte
 	InfoBaseFee     *big.Int
 	InfoReceiptRoot common.Hash
+	InfoGasUsed     uint64
 }
 
 func (l *MockBlockInfo) Hash() common.Hash {
@@ -59,6 +60,10 @@ func (l *MockBlockInfo) ReceiptHash() common.Hash {
 	return l.InfoReceiptRoot
 }
 
+func (l *MockBlockInfo) GasUsed() uint64 {
+	return l.InfoGasUsed
+}
+
 func (l *MockBlockInfo) ID() eth.BlockID {
 	return eth.BlockID{Hash: l.InfoHash, Number: l.InfoNum}
 }
@@ -81,6 +86,7 @@ func RandomBlockInfo(rng *rand.Rand) *MockBlockInfo {
 		InfoBaseFee:     big.NewInt(rng.Int63n(1000_000 * 1e9)), // a million GWEI
 		InfoReceiptRoot: types.EmptyRootHash,
 		InfoRoot:        RandomHash(rng),
+		InfoGasUsed:     rng.Uint64(),
 	}
 }