all: withdrawals root in header is reused to commit to OP-Stack L2 wi…

…thdrawals storage root

beacon/engine/types.go

@@ -87,6 +87,11 @@ type ExecutableData struct {
 	Withdrawals   []*types.Withdrawal `json:"withdrawals"`
 	BlobGasUsed   *uint64             `json:"blobGasUsed"`
 	ExcessBlobGas *uint64             `json:"excessBlobGas"`
+
+	// OP-Stack Holocene specific field:
+	// instead of computing the root from a withdrawals list, set it directly.
+	// The "withdrawals" list attribute must be non-nil but empty.
+	WithdrawalsRoot *common.Hash `json:"withdrawalsRoot,omitempty"`
 }
 
 // JSON type overrides for executableData.
@@ -240,7 +245,13 @@ func ExecutableDataToBlock(data ExecutableData, versionedHashes []common.Hash, b
 	// ExecutableData before withdrawals are enabled by marshaling
 	// Withdrawals as the json null value.
 	var withdrawalsRoot *common.Hash
-	if data.Withdrawals != nil {
+	if data.WithdrawalsRoot != nil {
+		if data.Withdrawals == nil || len(data.Withdrawals) != 0 {
+			return nil, fmt.Errorf("attribute WithdrawalsRoot was set. Expecting non-nil empty withdrawals list, but got %v", data.Withdrawals)
+		}
+		h := *data.WithdrawalsRoot // copy, avoid any sharing of memory
+		withdrawalsRoot = &h
+	} else if data.Withdrawals != nil {
 		h := types.DeriveSha(types.Withdrawals(data.Withdrawals), trie.NewStackTrie(nil))
 		withdrawalsRoot = &h
 	}
@@ -293,6 +304,8 @@ func BlockToExecutableData(block *types.Block, fees *big.Int, sidecars []*types.
 		Withdrawals:   block.Withdrawals(),
 		BlobGasUsed:   block.BlobGasUsed(),
 		ExcessBlobGas: block.ExcessBlobGas(),
+		// OP-Stack addition: withdrawals list alone does not express the withdrawals storage-root.
+		WithdrawalsRoot: block.WithdrawalsRoot(),
 	}
 	bundle := BlobsBundleV1{
 		Commitments: make([]hexutil.Bytes, 0),

consensus/beacon/consensus.go

@@ -403,6 +403,15 @@ func (beacon *Beacon) FinalizeAndAssemble(chain consensus.ChainHeaderReader, hea
 	// Assign the final state root to header.
 	header.Root = state.IntermediateRoot(true)
 
+	if chain.Config().IsOptimismHolocene(header.Time) {
+		if body.Withdrawals == nil || len(body.Withdrawals) > 0 { // We verify nil/empty withdrawals in the CL pre-holocene
+			return nil, fmt.Errorf("expected non-nil empty withdrawals operation list in Holocene, but got: %v", body.Withdrawals)
+		}
+		// State-root has just been computed, we can get an accurate storage-root now.
+		h := state.GetStorageRoot(params.OptimismL2ToL1MessagePasser)
+		header.WithdrawalsHash = &h
+	}
+
 	// Assemble and return the final block.
 	return types.NewBlock(header, body, receipts, trie.NewStackTrie(nil)), nil
 }

core/block_validator.go

@@ -75,7 +75,12 @@ func (v *BlockValidator) ValidateBody(block *types.Block) error {
 		if block.Withdrawals() == nil {
 			return errors.New("missing withdrawals in block body")
 		}
-		if hash := types.DeriveSha(block.Withdrawals(), trie.NewStackTrie(nil)); hash != *header.WithdrawalsHash {
+		if v.config.IsOptimismHolocene(header.Time) {
+			if len(block.Withdrawals()) > 0 {
+				return errors.New("no withdrawal block-operations allowed, withdrawalsRoot is set to storage root")
+			}
+			// The withdrawalsHash is verified in ValidateState, like the state root, as verification requires state merkleization.
+		} else if hash := types.DeriveSha(block.Withdrawals(), trie.NewStackTrie(nil)); hash != *header.WithdrawalsHash {
 			return fmt.Errorf("withdrawals root hash mismatch (header value %x, calculated %x)", *header.WithdrawalsHash, hash)
 		}
 	} else if block.Withdrawals() != nil {
@@ -147,6 +152,15 @@ func (v *BlockValidator) ValidateState(block *types.Block, statedb *state.StateD
 	if root := statedb.IntermediateRoot(v.config.IsEIP158(header.Number)); header.Root != root {
 		return fmt.Errorf("invalid merkle root (remote: %x local: %x) dberr: %w", header.Root, root, statedb.Error())
 	}
+	if v.config.IsOptimismHolocene(block.Time()) {
+		if header.WithdrawalsHash == nil {
+			return errors.New("expected withdrawals root in OP-Stack post-Holocene block header")
+		}
+		// Validate the withdrawals root against the L2 withdrawals storage, similar to how the StateRoot is verified.
+		if root := statedb.GetStorageRoot(params.OptimismL2ToL1MessagePasser); *header.WithdrawalsHash != root {
+			return fmt.Errorf("invalid withdrawals hash (remote: %s local: %s) dberr: %w", *header.WithdrawalsHash, root, statedb.Error())
+		}
+	}
 	return nil
 }
 

core/types/block.go

@@ -391,6 +391,14 @@ func (b *Block) ReceiptHash() common.Hash { return b.header.ReceiptHash }
 func (b *Block) UncleHash() common.Hash   { return b.header.UncleHash }
 func (b *Block) Extra() []byte            { return common.CopyBytes(b.header.Extra) }
 
+func (b *Block) WithdrawalsRoot() *common.Hash {
+	if b.header.WithdrawalsHash == nil {
+		return nil
+	}
+	h := *b.header.WithdrawalsHash
+	return &h
+}
+
 func (b *Block) BaseFee() *big.Int {
 	if b.header.BaseFee == nil {
 		return nil

eth/catalyst/api.go

@@ -580,6 +580,7 @@ func (api *ConsensusAPI) newPayload(params engine.ExecutableData, versionedHashe
 			"params.ExcessBlobGas", ebg,
 			"len(params.Transactions)", len(params.Transactions),
 			"len(params.Withdrawals)", len(params.Withdrawals),
+			"params.WithdrawalsRoot", params.WithdrawalsRoot,
 			"beaconRoot", beaconRoot,
 			"error", err)
 		return api.invalid(err, nil), nil

eth/downloader/downloader.go

@@ -146,6 +146,11 @@ type Downloader struct {
 
 // BlockChain encapsulates functions required to sync a (full or snap) blockchain.
 type BlockChain interface {
+	// Config returns the chain configuration.
+	// OP-Stack diff, to adjust withdrawal-hash verification.
+	// Usage of ths in the Downloader is discouraged.
+	Config() *params.ChainConfig
+
 	// HasHeader verifies a header's presence in the local chain.
 	HasHeader(common.Hash, uint64) bool
 
@@ -201,7 +206,7 @@ func New(stateDb ethdb.Database, mux *event.TypeMux, chain BlockChain, dropPeer
 	dl := &Downloader{
 		stateDB:        stateDb,
 		mux:            mux,
-		queue:          newQueue(blockCacheMaxItems, blockCacheInitialItems),
+		queue:          newQueue(chain.Config(), blockCacheMaxItems, blockCacheInitialItems),
 		peers:          newPeerSet(),
 		blockchain:     chain,
 		dropPeer:       dropPeer,

eth/downloader/queue.go

@@ -121,6 +121,10 @@ func (f *fetchResult) Done(kind uint) bool {
 	return v&(1<<kind) == 0
 }
 
+type OPStackChainConfig interface {
+	IsOptimismHolocene(time uint64) bool
+}
+
 // queue represents hashes that are either need fetching or are being fetched
 type queue struct {
 	mode SyncMode // Synchronisation mode to decide on the block parts to schedule for fetching
@@ -156,10 +160,15 @@ type queue struct {
 	closed bool
 
 	logTime time.Time // Time instance when status was last reported
+
+	// opConfig is used for OP-Stack chain configuration checks.
+	// This may be nil if not an OP-Stack chain.
+	opConfig OPStackChainConfig
 }
 
 // newQueue creates a new download queue for scheduling block retrieval.
-func newQueue(blockCacheLimit int, thresholdInitialSize int) *queue {
+// The
+func newQueue(opConfig OPStackChainConfig, blockCacheLimit int, thresholdInitialSize int) *queue {
 	lock := new(sync.RWMutex)
 	q := &queue{
 		headerContCh:     make(chan bool, 1),
@@ -169,6 +178,7 @@ func newQueue(blockCacheLimit int, thresholdInitialSize int) *queue {
 		receiptWakeCh:    make(chan bool, 1),
 		active:           sync.NewCond(lock),
 		lock:             lock,
+		opConfig:         opConfig,
 	}
 	q.Reset(blockCacheLimit, thresholdInitialSize)
 	return q
@@ -804,7 +814,13 @@ func (q *queue) DeliverBodies(id string, txLists [][]*types.Transaction, txListH
 			if withdrawalLists[index] == nil {
 				return errInvalidBody
 			}
-			if withdrawalListHashes[index] != *header.WithdrawalsHash {
+			if q.opConfig != nil && q.opConfig.IsOptimismHolocene(header.Time) {
+				// If Holocene, we expect an empty list of withdrawal operations,
+				// but the WithdrawalsHash in the header is used for the withdrawals state storage-root.
+				if withdrawalListHashes[index] != types.EmptyWithdrawalsHash {
+					return errInvalidBody
+				}
+			} else if withdrawalListHashes[index] != *header.WithdrawalsHash {
 				return errInvalidBody
 			}
 		}

eth/downloader/queue_test.go

@@ -97,7 +97,7 @@ func TestBasics(t *testing.T) {
 	numOfBlocks := len(emptyChain.blocks)
 	numOfReceipts := len(emptyChain.blocks) / 2
 
-	q := newQueue(10, 10)
+	q := newQueue(nil, 10, 10)
 	if !q.Idle() {
 		t.Errorf("new queue should be idle")
 	}
@@ -196,7 +196,7 @@ func TestBasics(t *testing.T) {
 func TestEmptyBlocks(t *testing.T) {
 	numOfBlocks := len(emptyChain.blocks)
 
-	q := newQueue(10, 10)
+	q := newQueue(nil, 10, 10)
 
 	q.Prepare(1, SnapSync)
 
@@ -275,7 +275,7 @@ func XTestDelivery(t *testing.T) {
 	if false {
 		log.SetDefault(log.NewLogger(slog.NewTextHandler(os.Stdout, nil)))
 	}
-	q := newQueue(10, 10)
+	q := newQueue(nil, 10, 10)
 	var wg sync.WaitGroup
 	q.Prepare(1, SnapSync)
 	wg.Add(1)

params/protocol_params.go

@@ -27,6 +27,8 @@ var (
 	OptimismBaseFeeRecipient = common.HexToAddress("0x4200000000000000000000000000000000000019")
 	// The L1 portion of the transaction fee accumulates at this predeploy
 	OptimismL1FeeRecipient = common.HexToAddress("0x420000000000000000000000000000000000001A")
+	// The L2 withdrawals contract predeploy address
+	OptimismL2ToL1MessagePasser = common.HexToAddress("0x4200000000000000000000000000000000000016")
 )
 
 const (