feat(clique): allow shadowforking a clique network (#828)

Author: omerfirmak

cmd/geth/main.go

@@ -169,6 +169,7 @@ var (
 		utils.L1DeploymentBlockFlag,
 		utils.CircuitCapacityCheckEnabledFlag,
 		utils.RollupVerifyEnabledFlag,
+		utils.ShadowforkPeersFlag,
 	}
 
 	rpcFlags = []cli.Flag{

cmd/geth/usage.go

@@ -237,6 +237,7 @@ var AppHelpFlagGroups = []flags.FlagGroup{
 			utils.BloomFilterSizeFlag,
 			cli.HelpFlag,
 			utils.CatalystFlag,
+			utils.ShadowforkPeersFlag,
 		},
 	},
 }

cmd/utils/flags.go

@@ -858,6 +858,12 @@ var (
 		Name:  "rpc.getlogs.maxrange",
 		Usage: "Limit max fetched block range for `eth_getLogs` method",
 	}
+
+	// Shadowfork peers
+	ShadowforkPeersFlag = cli.StringSliceFlag{
+		Name:  "net.shadowforkpeers",
+		Usage: "peer ids of shadow fork peers",
+	}
 )
 
 // MakeDataDir retrieves the currently requested data directory, terminating
@@ -1651,6 +1657,10 @@ func SetEthConfig(ctx *cli.Context, stack *node.Node, cfg *ethconfig.Config) {
 	setCircuitCapacityCheck(ctx, cfg)
 	setEnableRollupVerify(ctx, cfg)
 	setMaxBlockRange(ctx, cfg)
+	if ctx.GlobalIsSet(ShadowforkPeersFlag.Name) {
+		cfg.ShadowForkPeerIDs = ctx.GlobalStringSlice(ShadowforkPeersFlag.Name)
+		log.Info("Shadow fork peers", "ids", cfg.ShadowForkPeerIDs)
+	}
 
 	// Cap the cache allowance and tune the garbage collector
 	mem, err := gopsutil.VirtualMemory()

consensus/clique/clique.go

@@ -66,8 +66,9 @@ var (
 
 	uncleHash = types.CalcUncleHash(nil) // Always Keccak256(RLP([])) as uncles are meaningless outside of PoW.
 
-	diffInTurn = big.NewInt(2) // Block difficulty for in-turn signatures
-	diffNoTurn = big.NewInt(1) // Block difficulty for out-of-turn signatures
+	diffInTurn     = big.NewInt(2) // Block difficulty for in-turn signatures
+	diffNoTurn     = big.NewInt(1) // Block difficulty for out-of-turn signatures
+	diffShadowFork = diffNoTurn
 )
 
 // Various error messages to mark blocks invalid. These should be private to
@@ -195,6 +196,7 @@ func New(config *params.CliqueConfig, db ethdb.Database) *Clique {
 	if conf.Epoch == 0 {
 		conf.Epoch = epochLength
 	}
+
 	// Allocate the snapshot caches and create the engine
 	recents, _ := lru.NewARC(inmemorySnapshots)
 	signatures, _ := lru.NewARC(inmemorySignatures)
@@ -291,7 +293,7 @@ func (c *Clique) verifyHeader(chain consensus.ChainHeaderReader, header *types.H
 	}
 	// Ensure that the block's difficulty is meaningful (may not be correct at this point)
 	if number > 0 {
-		if header.Difficulty == nil || (header.Difficulty.Cmp(diffInTurn) != 0 && header.Difficulty.Cmp(diffNoTurn) != 0) {
+		if header.Difficulty == nil || (header.Difficulty.Cmp(diffInTurn) != 0 && header.Difficulty.Cmp(diffNoTurn) != 0 && header.Difficulty.Cmp(diffShadowFork) != 0) {
 			return errInvalidDifficulty
 		}
 	}
@@ -375,6 +377,14 @@ func (c *Clique) snapshot(chain consensus.ChainHeaderReader, number uint64, hash
 		snap    *Snapshot
 	)
 	for snap == nil {
+		if c.config.ShadowForkHeight > 0 && number == c.config.ShadowForkHeight {
+			c.signatures.Purge()
+			c.recents.Purge()
+			c.proposals = make(map[common.Address]bool)
+			snap = newSnapshot(c.config, c.signatures, number, hash, []common.Address{c.config.ShadowForkSigner})
+			break
+		}
+
 		// If an in-memory snapshot was found, use that
 		if s, ok := c.recents.Get(hash); ok {
 			snap = s.(*Snapshot)
@@ -485,11 +495,8 @@ func (c *Clique) verifySeal(snap *Snapshot, header *types.Header, parents []*typ
 	}
 	// Ensure that the difficulty corresponds to the turn-ness of the signer
 	if !c.fakeDiff {
-		inturn := snap.inturn(header.Number.Uint64(), signer)
-		if inturn && header.Difficulty.Cmp(diffInTurn) != 0 {
-			return errWrongDifficulty
-		}
-		if !inturn && header.Difficulty.Cmp(diffNoTurn) != 0 {
+		expected := c.calcDifficulty(snap, signer)
+		if header.Difficulty.Cmp(expected) != 0 {
 			return errWrongDifficulty
 		}
 	}
@@ -534,7 +541,7 @@ func (c *Clique) Prepare(chain consensus.ChainHeaderReader, header *types.Header
 	c.lock.RUnlock()
 
 	// Set the correct difficulty
-	header.Difficulty = calcDifficulty(snap, signer)
+	header.Difficulty = c.calcDifficulty(snap, signer)
 
 	// Ensure the extra data has all its components
 	if len(header.Extra) < extraVanity {
@@ -678,10 +685,14 @@ func (c *Clique) CalcDifficulty(chain consensus.ChainHeaderReader, time uint64,
 	c.lock.RLock()
 	signer := c.signer
 	c.lock.RUnlock()
-	return calcDifficulty(snap, signer)
+	return c.calcDifficulty(snap, signer)
 }
 
-func calcDifficulty(snap *Snapshot, signer common.Address) *big.Int {
+func (c *Clique) calcDifficulty(snap *Snapshot, signer common.Address) *big.Int {
+	if c.config.ShadowForkHeight > 0 && snap.Number >= c.config.ShadowForkHeight {
+		// if we are past shadow fork point, set a low difficulty so that mainnet nodes don't try to switch to forked chain
+		return new(big.Int).Set(diffShadowFork)
+	}
 	if snap.inturn(snap.Number+1, signer) {
 		return new(big.Int).Set(diffInTurn)
 	}

consensus/clique/clique_test.go

@@ -17,7 +17,9 @@
 package clique
 
 import (
+	"bytes"
 	"math/big"
+	"strings"
 	"testing"
 
 	"github.com/scroll-tech/go-ethereum/common"
@@ -125,3 +127,90 @@ func TestSealHash(t *testing.T) {
 		t.Errorf("have %x, want %x", have, want)
 	}
 }
+
+func TestShadowFork(t *testing.T) {
+	engineConf := *params.AllCliqueProtocolChanges.Clique
+	engineConf.Epoch = 2
+	forkedEngineConf := engineConf
+	forkedEngineConf.ShadowForkHeight = 3
+	shadowForkKey, _ := crypto.HexToECDSA(strings.Repeat("11", 32))
+	shadowForkAddr := crypto.PubkeyToAddress(shadowForkKey.PublicKey)
+	forkedEngineConf.ShadowForkSigner = shadowForkAddr
+
+	// Initialize a Clique chain with a single signer
+	var (
+		db           = rawdb.NewMemoryDatabase()
+		key, _       = crypto.HexToECDSA("b71c71a67e1177ad4e901695e1b4b9ee17ae16c6668d313eac2f96dbcda3f291")
+		addr         = crypto.PubkeyToAddress(key.PublicKey)
+		engine       = New(&engineConf, db)
+		signer       = new(types.HomesteadSigner)
+		forkedEngine = New(&forkedEngineConf, db)
+	)
+	genspec := &core.Genesis{
+		ExtraData: make([]byte, extraVanity+common.AddressLength+extraSeal),
+		Alloc: map[common.Address]core.GenesisAccount{
+			addr: {Balance: big.NewInt(10000000000000000)},
+		},
+		BaseFee: big.NewInt(params.InitialBaseFee),
+	}
+	copy(genspec.ExtraData[extraVanity:], addr[:])
+	genesis := genspec.MustCommit(db)
+
+	// Generate a batch of blocks, each properly signed
+	chain, _ := core.NewBlockChain(db, nil, params.AllCliqueProtocolChanges, engine, vm.Config{}, nil, nil)
+	defer chain.Stop()
+
+	forkedChain, _ := core.NewBlockChain(db, nil, params.AllCliqueProtocolChanges, forkedEngine, vm.Config{}, nil, nil)
+	defer forkedChain.Stop()
+
+	blocks, _ := core.GenerateChain(params.AllCliqueProtocolChanges, genesis, forkedEngine, db, 16, func(i int, block *core.BlockGen) {
+		// The chain maker doesn't have access to a chain, so the difficulty will be
+		// lets unset (nil). Set it here to the correct value.
+		if block.Number().Uint64() > forkedEngineConf.ShadowForkHeight {
+			block.SetDifficulty(diffShadowFork)
+		} else {
+			block.SetDifficulty(diffInTurn)
+		}
+
+		tx, err := types.SignTx(types.NewTransaction(block.TxNonce(addr), common.Address{0x00}, new(big.Int), params.TxGas, block.BaseFee(), nil), signer, key)
+		if err != nil {
+			panic(err)
+		}
+		block.AddTxWithChain(chain, tx)
+	})
+	for i, block := range blocks {
+		header := block.Header()
+		if i > 0 {
+			header.ParentHash = blocks[i-1].Hash()
+		}
+
+		signingAddr, signingKey := addr, key
+		if header.Number.Uint64() > forkedEngineConf.ShadowForkHeight {
+			// start signing with shadow fork authority key
+			signingAddr, signingKey = shadowForkAddr, shadowForkKey
+		}
+
+		header.Extra = make([]byte, extraVanity)
+		if header.Number.Uint64()%engineConf.Epoch == 0 {
+			header.Extra = append(header.Extra, signingAddr.Bytes()...)
+		}
+		header.Extra = append(header.Extra, bytes.Repeat([]byte{0}, extraSeal)...)
+
+		sig, _ := crypto.Sign(SealHash(header).Bytes(), signingKey)
+		copy(header.Extra[len(header.Extra)-extraSeal:], sig)
+		blocks[i] = block.WithSeal(header)
+	}
+
+	if _, err := chain.InsertChain(blocks); err == nil {
+		t.Fatalf("should've failed to insert some blocks to canonical chain")
+	}
+	if chain.CurrentHeader().Number.Uint64() != forkedEngineConf.ShadowForkHeight {
+		t.Fatalf("unexpected canonical chain height")
+	}
+	if _, err := forkedChain.InsertChain(blocks); err != nil {
+		t.Fatalf("failed to insert blocks to forked chain: %v %d", err, forkedChain.CurrentHeader().Number)
+	}
+	if forkedChain.CurrentHeader().Number.Uint64() != uint64(len(blocks)) {
+		t.Fatalf("unexpected forked chain height")
+	}
+}

consensus/misc/eip1559.go

@@ -51,6 +51,9 @@ func VerifyEip1559Header(config *params.ChainConfig, parent, header *types.Heade
 
 // CalcBaseFee calculates the basefee of the header.
 func CalcBaseFee(config *params.ChainConfig, parent *types.Header, parentL1BaseFee *big.Int) *big.Int {
+	if config.Clique != nil && config.Clique.ShadowForkHeight != 0 && parent.Number.Uint64() >= config.Clique.ShadowForkHeight {
+		return big.NewInt(10000000) // 0.01 Gwei
+	}
 	l2SequencerFee := big.NewInt(1000000) // 0.001 Gwei
 	provingFee := big.NewInt(47700000)    // 0.0477 Gwei
 

eth/backend.go

@@ -239,15 +239,16 @@ func New(stack *node.Node, config *ethconfig.Config, l1Client sync_service.EthCl
 		checkpoint = params.TrustedCheckpoints[genesisHash]
 	}
 	if eth.handler, err = newHandler(&handlerConfig{
-		Database:   chainDb,
-		Chain:      eth.blockchain,
-		TxPool:     eth.txPool,
-		Network:    config.NetworkId,
-		Sync:       config.SyncMode,
-		BloomCache: uint64(cacheLimit),
-		EventMux:   eth.eventMux,
-		Checkpoint: checkpoint,
-		Whitelist:  config.Whitelist,
+		Database:          chainDb,
+		Chain:             eth.blockchain,
+		TxPool:            eth.txPool,
+		Network:           config.NetworkId,
+		Sync:              config.SyncMode,
+		BloomCache:        uint64(cacheLimit),
+		EventMux:          eth.eventMux,
+		Checkpoint:        checkpoint,
+		Whitelist:         config.Whitelist,
+		ShadowForkPeerIDs: config.ShadowForkPeerIDs,
 	}); err != nil {
 		return nil, err
 	}

eth/ethconfig/config.go

@@ -214,6 +214,9 @@ type Config struct {
 
 	// Max block range for eth_getLogs api method
 	MaxBlockRange int64
+
+	// List of peer ids that take part in the shadow-fork
+	ShadowForkPeerIDs []string
 }
 
 // CreateConsensusEngine creates a consensus engine for the given chain configuration.