Snap Sync: consensus: handle legacy pre-bedrock header verification (#…

…182)

* consensus: handle legacy pre-bedrock header verification

* consensus/beacon: Add parent hash check to OpLegacy.VerifyHeader

VerifyHeaders will be dealt with in a follow-up.

* optimism: fix historical-blocks chain-gen and TTD check

---------

Co-authored-by: Sebastian Stammler <[email protected]>

consensus/beacon/consensus.go

@@ -58,6 +58,7 @@ var (
 // is only used for necessary consensus checks. The legacy consensus engine can be any
 // engine implements the consensus interface (except the beacon itself).
 type Beacon struct {
+	// For migrated OP chains (OP mainnet, OP Goerli), ethone is a dummy legacy pre-Bedrock consensus
 	ethone consensus.Engine // Original consensus engine used in eth1, e.g. ethash or clique
 }
 
@@ -105,12 +106,27 @@ func errOut(n int, err error) chan error {
 	return errs
 }
 
+// OP-Stack Bedrock variant of splitHeaders: the total-terminal difficulty is terminated at bedrock transition, but also reset to 0.
+// So just use the bedrock fork check to split the headers, to simplify the splitting.
+// The returned slices are slices over the input. The input must be sorted.
+func (beacon *Beacon) splitBedrockHeaders(chain consensus.ChainHeaderReader, headers []*types.Header) ([]*types.Header, []*types.Header, error) {
+	for i, h := range headers {
+		if chain.Config().IsBedrock(h.Number) {
+			return headers[:i], headers[i:], nil
+		}
+	}
+	return headers, nil, nil
+}
+
 // splitHeaders splits the provided header batch into two parts according to
 // the configured ttd. It requires the parent of header batch along with its
 // td are stored correctly in chain. If ttd is not configured yet, all headers
 // will be treated legacy PoW headers.
 // Note, this function will not verify the header validity but just split them.
 func (beacon *Beacon) splitHeaders(chain consensus.ChainHeaderReader, headers []*types.Header) ([]*types.Header, []*types.Header, error) {
+	if chain.Config().Optimism != nil {
+		return beacon.splitBedrockHeaders(chain, headers)
+	}
 	// TTD is not defined yet, all headers should be in legacy format.
 	ttd := chain.Config().TerminalTotalDifficulty
 	if ttd == nil {
@@ -446,6 +462,10 @@ func (beacon *Beacon) InnerEngine() consensus.Engine {
 	return beacon.ethone
 }
 
+func (beacon *Beacon) SwapInner(inner consensus.Engine) {
+	beacon.ethone = inner
+}
+
 // SetThreads updates the mining threads. Delegate the call
 // to the eth1 engine if it's threaded.
 func (beacon *Beacon) SetThreads(threads int) {
@@ -461,6 +481,11 @@ func (beacon *Beacon) SetThreads(threads int) {
 // It depends on the parentHash already being stored in the database.
 // If the parentHash is not stored in the database a UnknownAncestor error is returned.
 func IsTTDReached(chain consensus.ChainHeaderReader, parentHash common.Hash, parentNumber uint64) (bool, error) {
+	if cfg := chain.Config(); cfg.Optimism != nil {
+		// If OP-Stack then bedrock activation number determines when TTD (eth Merge) has been reached.
+		// Note: some tests/utils will set parentNumber == max_uint64 as "parent" of the genesis block, this is fine.
+		return cfg.IsBedrock(new(big.Int).SetUint64(parentNumber + 1)), nil
+	}
 	if chain.Config().TerminalTotalDifficulty == nil {
 		return false, nil
 	}

consensus/beacon/oplegacy.go

@@ -0,0 +1,74 @@
+package beacon
+
+import (
+	"fmt"
+	"math/big"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/consensus"
+	"github.com/ethereum/go-ethereum/core/state"
+	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/rpc"
+)
+
+type OpLegacy struct{}
+
+func (o *OpLegacy) Author(header *types.Header) (common.Address, error) {
+	return header.Coinbase, nil
+}
+
+func (o *OpLegacy) VerifyHeader(chain consensus.ChainHeaderReader, header *types.Header) error {
+	// redundant check to guarantee DB consistency
+	parent := chain.GetHeader(header.ParentHash, header.Number.Uint64()-1)
+	if parent == nil {
+		return consensus.ErrUnknownAncestor
+	}
+	return nil // legacy chain is verified by block-hash reverse sync otherwise
+}
+
+func (o *OpLegacy) VerifyHeaders(chain consensus.ChainHeaderReader, headers []*types.Header) (chan<- struct{}, <-chan error) {
+	quit := make(chan struct{}, 1)
+	result := make(chan error, len(headers))
+	for _, h := range headers {
+		result <- o.VerifyHeader(chain, h)
+	}
+	return quit, result
+}
+
+func (o *OpLegacy) VerifyUncles(chain consensus.ChainReader, block *types.Block) error {
+	return nil
+}
+
+func (o *OpLegacy) Prepare(chain consensus.ChainHeaderReader, header *types.Header) error {
+	return fmt.Errorf("cannot prepare for legacy block header: %s (num %d)", header.Hash(), header.Number)
+}
+
+func (o *OpLegacy) Finalize(chain consensus.ChainHeaderReader, header *types.Header, state *state.StateDB, txs []*types.Transaction, uncles []*types.Header, withdrawals []*types.Withdrawal) {
+	panic(fmt.Errorf("cannot finalize legacy block header: %s (num %d)", header.Hash(), header.Number))
+}
+
+func (o *OpLegacy) FinalizeAndAssemble(chain consensus.ChainHeaderReader, header *types.Header, state *state.StateDB, txs []*types.Transaction, uncles []*types.Header, receipts []*types.Receipt, withdrawals []*types.Withdrawal) (*types.Block, error) {
+	return nil, fmt.Errorf("cannot finalize and assemble for legacy block header: %s (num %d)", header.Hash(), header.Number)
+}
+
+func (o *OpLegacy) Seal(chain consensus.ChainHeaderReader, block *types.Block, results chan<- *types.Block, stop <-chan struct{}) error {
+	return fmt.Errorf("cannot seal legacy block header: %s (num %d)", block.Hash(), block.Number())
+}
+
+func (o *OpLegacy) SealHash(header *types.Header) common.Hash {
+	panic(fmt.Errorf("cannot compute pow/poa seal-hash for legacy block header: %s (num %d)", header.Hash(), header.Number))
+}
+
+func (o *OpLegacy) CalcDifficulty(chain consensus.ChainHeaderReader, time uint64, parent *types.Header) *big.Int {
+	return big.NewInt(0)
+}
+
+func (o *OpLegacy) APIs(chain consensus.ChainHeaderReader) []rpc.API {
+	return nil
+}
+
+func (o *OpLegacy) Close() error {
+	return nil
+}
+
+var _ consensus.Engine = (*OpLegacy)(nil)

core/chain_makers.go

@@ -319,7 +319,7 @@ func GenerateChain(config *params.ChainConfig, parent *types.Block, engine conse
 		// to a chain, so the difficulty will be left unset (nil). Set it here to the
 		// correct value.
 		if b.header.Difficulty == nil {
-			if config.TerminalTotalDifficulty == nil {
+			if config.TerminalTotalDifficulty == nil && !config.IsOptimismBedrock(b.header.Number) {
 				// Clique chain
 				b.header.Difficulty = big.NewInt(2)
 			} else {

core/types/receipt.go

@@ -569,7 +569,7 @@ func (rs Receipts) DeriveFields(config *params.ChainConfig, hash common.Hash, nu
 			logIndex++
 		}
 	}
-	if config.Optimism != nil && len(txs) >= 2 { // need at least an info tx and a non-info tx
+	if config.Optimism != nil && len(txs) >= 2 && config.IsBedrock(new(big.Int).SetUint64(number)) { // need at least an info tx and a non-info tx
 		l1BaseFee, costFunc, feeScalar, err := extractL1GasParams(config, time, txs[0].Data())
 		if err != nil {
 			return err

core/types/receipt_test.go

@@ -34,8 +34,16 @@ import (
 )
 
 var (
+	bedrockGenesisTestConfig = func() *params.ChainConfig {
+		conf := *params.AllCliqueProtocolChanges // copy the config
+		conf.Clique = nil
+		conf.TerminalTotalDifficultyPassed = true
+		conf.BedrockBlock = big.NewInt(0)
+		conf.Optimism = &params.OptimismConfig{EIP1559Elasticity: 50, EIP1559Denominator: 10}
+		return &conf
+	}()
 	ecotoneTestConfig = func() *params.ChainConfig {
-		conf := *params.OptimismTestConfig // copy the config
+		conf := *bedrockGenesisTestConfig // copy the config
 		time := uint64(0)
 		conf.EcotoneTime = &time
 		return &conf
@@ -774,7 +782,7 @@ func TestDeriveOptimismBedrockTxReceipts(t *testing.T) {
 	// Re-derive receipts.
 	baseFee := big.NewInt(1000)
 	derivedReceipts := clearComputedFieldsOnReceipts(receipts)
-	err := Receipts(derivedReceipts).DeriveFields(params.OptimismTestConfig, blockHash, blockNumber.Uint64(), 0, baseFee, nil, txs)
+	err := Receipts(derivedReceipts).DeriveFields(bedrockGenesisTestConfig, blockHash, blockNumber.Uint64(), 0, baseFee, nil, txs)
 	if err != nil {
 		t.Fatalf("DeriveFields(...) = %v, want <nil>", err)
 	}
@@ -802,7 +810,7 @@ func TestDeriveOptimismEcotoneTxReceipts(t *testing.T) {
 	baseFee := big.NewInt(1000)
 	derivedReceipts := clearComputedFieldsOnReceipts(receipts)
 	// Should error out if we try to process this with a pre-Ecotone config
-	err := Receipts(derivedReceipts).DeriveFields(params.OptimismTestConfig, blockHash, blockNumber.Uint64(), 0, baseFee, nil, txs)
+	err := Receipts(derivedReceipts).DeriveFields(bedrockGenesisTestConfig, blockHash, blockNumber.Uint64(), 0, baseFee, nil, txs)
 	if err == nil {
 		t.Fatalf("expected error from deriving ecotone receipts with pre-ecotone config, got none")
 	}

eth/ethconfig/config.go

@@ -190,6 +190,9 @@ type Config struct {
 // Clique is allowed for now to live standalone, but ethash is forbidden and can
 // only exist on already merged networks.
 func CreateConsensusEngine(config *params.ChainConfig, db ethdb.Database) (consensus.Engine, error) {
+	if config.Optimism != nil {
+		return beacon.New(&beacon.OpLegacy{}), nil
+	}
 	// If proof-of-authority is requested, set it up
 	if config.Clique != nil {
 		return beacon.New(clique.New(config.Clique, db)), nil

ethclient/ethclient_test.go

@@ -29,6 +29,8 @@ import (
 	"time"
 
 	"github.com/ethereum/go-ethereum/common/hexutil"
+	"github.com/ethereum/go-ethereum/consensus"
+	"github.com/ethereum/go-ethereum/consensus/beacon"
 	"github.com/ethereum/go-ethereum/internal/ethapi"
 
 	"github.com/ethereum/go-ethereum"
@@ -286,21 +288,28 @@ func newMockHistoricalBackend(t *testing.T) string {
 func newTestBackend(t *testing.T, enableHistoricalState bool) (*node.Node, []*types.Block) {
 	histAddr := newMockHistoricalBackend(t)
 
-	// Generate test chain.
-	blocks := generateTestChain(enableHistoricalState)
+	var consensusEngine consensus.Engine
+	var actualGenesis *core.Genesis
+	var chainLength int
+	if enableHistoricalState {
+		actualGenesis = genesisForHistorical
+		consensusEngine = beacon.New(ethash.NewFaker())
+		chainLength = 10
+	} else {
+		actualGenesis = genesis
+		consensusEngine = ethash.NewFaker()
+		chainLength = 2
+	}
+
+	// Generate test chain
+	blocks := generateTestChain(consensusEngine, actualGenesis, chainLength)
 
 	// Create node
 	n, err := node.New(&node.Config{})
 	if err != nil {
 		t.Fatalf("can't create new node: %v", err)
 	}
 	// Create Ethereum Service
-	var actualGenesis *core.Genesis
-	if enableHistoricalState {
-		actualGenesis = genesisForHistorical
-	} else {
-		actualGenesis = genesis
-	}
 	config := &ethconfig.Config{Genesis: actualGenesis}
 	if enableHistoricalState {
 		config.RollupHistoricalRPC = histAddr
@@ -310,37 +319,39 @@ func newTestBackend(t *testing.T, enableHistoricalState bool) (*node.Node, []*ty
 	if err != nil {
 		t.Fatalf("can't create new ethereum service: %v", err)
 	}
+	if enableHistoricalState { // swap to the pre-bedrock consensus-engine that we used to generate the historical blocks
+		ethservice.BlockChain().Engine().(*beacon.Beacon).SwapInner(ethash.NewFaker())
+	}
 	// Import the test chain.
 	if err := n.Start(); err != nil {
 		t.Fatalf("can't start test node: %v", err)
 	}
 	if _, err := ethservice.BlockChain().InsertChain(blocks[1:]); err != nil {
 		t.Fatalf("can't import test blocks: %v", err)
 	}
+	if enableHistoricalState {
+		// Now that we have a filled DB, swap the pre-Bedrock consensus to OpLegacy,
+		// which does not support re-processing of pre-bedrock data.
+		ethservice.Engine().(*beacon.Beacon).SwapInner(&beacon.OpLegacy{})
+	}
 	return n, blocks
 }
 
-func generateTestChain(enableHistoricalState bool) []*types.Block {
+func generateTestChain(consensusEngine consensus.Engine, genesis *core.Genesis, length int) []*types.Block {
 	generate := func(i int, g *core.BlockGen) {
 		g.OffsetTime(5)
 		g.SetExtra([]byte("test"))
 		if i == 1 {
 			// Test transactions are included in block #2.
-			if enableHistoricalState {
+			if genesis.Config.Optimism != nil && genesis.Config.IsBedrock(big.NewInt(1)) {
 				g.AddTx(depositTx)
 			}
 			g.AddTx(testTx1)
 			g.AddTx(testTx2)
 		}
 	}
-	var actualGenesis *core.Genesis
-	if enableHistoricalState {
-		actualGenesis = genesisForHistorical
-	} else {
-		actualGenesis = genesis
-	}
-	_, blocks, _ := core.GenerateChainWithGenesis(actualGenesis, ethash.NewFaker(), 2, generate)
-	return append([]*types.Block{actualGenesis.ToBlock()}, blocks...)
+	_, blocks, _ := core.GenerateChainWithGenesis(genesis, consensusEngine, length, generate)
+	return append([]*types.Block{genesis.ToBlock()}, blocks...)
 }
 
 func TestEthClientHistoricalBackend(t *testing.T) {

fork.yaml

@@ -80,8 +80,18 @@ def:
               description: |
                 The Engine API is activated at the Merge transition, with a Total Terminal Difficulty (TTD).
                 The rollup starts post-merge, and thus sets the TTD to 0.
+                The TTD is always "reached" starting at the bedrock block.
               globs:
                 - "consensus/beacon/consensus.go"
+            - title: "Legacy OP-mainnet / OP-goerli header-verification support"
+              description: |
+                Pre-Bedrock OP-mainnet and OP-Goerli had differently formatted block-headers, loosely compatible with the geth types (since it was based on Clique).
+                However, due to differences like the extra-data length (97+ bytes), these legacy block-headers need special verification.
+                The pre-merge "consensus" fallback is set to this custom but basic verifier, to accept these headers when syncing a pre-bedrock part of the chain,
+                independent of any clique code or configuration (which may be removed from geth at a later point).
+                All the custom verifier has to do is accept the headers, as the headers are already verified by block-hash through the reverse-header-sync.
+              globs:
+                - "consensus/beacon/oplegacy.go"
         - title: "Engine API modifications"
           description: |
             The Engine API is extended to insert transactions into the block and optionally exclude the tx-pool,