feat: add block transaction count limit (ethereum#216)

* feat: add block transaction count limit

* add tests

* nit

consensus/errors.go

@@ -34,4 +34,7 @@ var (
 	// ErrInvalidNumber is returned if a block's number doesn't equal its parent's
 	// plus one.
 	ErrInvalidNumber = errors.New("invalid block number")
+
+	// ErrInvalidTxCount is returned if a block contains too many transactions.
+	ErrInvalidTxCount = errors.New("invalid transaction count")
 )

core/block_validator.go

@@ -54,6 +54,9 @@ func (v *BlockValidator) ValidateBody(block *types.Block) error {
 	if v.bc.HasBlockAndState(block.Hash(), block.NumberU64()) {
 		return ErrKnownBlock
 	}
+	if !v.config.IsValidTxCount(len(block.Transactions())) {
+		return consensus.ErrInvalidTxCount
+	}
 	// Header validity is known at this point, check the uncles and transactions
 	header := block.Header()
 	if err := v.engine.VerifyUncles(v.bc, block); err != nil {

core/blockchain_test.go

@@ -3177,3 +3177,64 @@ func TestFeeVault(t *testing.T) {
 		t.Fatalf("fee vault balance incorrect: expected %d, got %d", expected, actual)
 	}
 }
+
+// TestTransactionCountLimit tests that the chain reject blocks with too many transactions.
+func TestTransactionCountLimit(t *testing.T) {
+	// Create config that allows at most 1 transaction per block
+	config := params.TestChainConfig
+	config.MaxTxPerBlock = new(int)
+	*config.MaxTxPerBlock = 1
+
+	var (
+		engine  = ethash.NewFaker()
+		db      = rawdb.NewMemoryDatabase()
+		key, _  = crypto.HexToECDSA("b71c71a67e1177ad4e901695e1b4b9ee17ae16c6668d313eac2f96dbcda3f291")
+		address = crypto.PubkeyToAddress(key.PublicKey)
+		funds   = big.NewInt(1000000000000000)
+		gspec   = &Genesis{Config: config, Alloc: GenesisAlloc{address: {Balance: funds}}}
+		genesis = gspec.MustCommit(db)
+	)
+
+	addTx := func(b *BlockGen) {
+		tx := types.NewTransaction(b.TxNonce(address), address, big.NewInt(0), 50000, b.header.BaseFee, nil)
+		signed, _ := types.SignTx(tx, types.HomesteadSigner{}, key)
+		b.AddTx(signed)
+	}
+
+	// Initialize blockchain
+	blockchain, err := NewBlockChain(db, nil, config, engine, vm.Config{}, nil, nil)
+	if err != nil {
+		t.Fatalf("failed to create new chain manager: %v", err)
+	}
+	defer blockchain.Stop()
+
+	// Insert empty block
+	block1, _ := GenerateChain(config, genesis, ethash.NewFaker(), db, 1, func(i int, b *BlockGen) {
+		// empty
+	})
+
+	if _, err := blockchain.InsertChain(block1); err != nil {
+		t.Fatalf("failed to insert chain: %v", err)
+	}
+
+	// Insert block with 1 transaction
+	block2, _ := GenerateChain(config, genesis, ethash.NewFaker(), db, 1, func(i int, b *BlockGen) {
+		addTx(b)
+	})
+
+	if _, err := blockchain.InsertChain(block2); err != nil {
+		t.Fatalf("failed to insert chain: %v", err)
+	}
+
+	// Insert block with 2 transactions
+	block3, _ := GenerateChain(config, genesis, ethash.NewFaker(), db, 1, func(i int, b *BlockGen) {
+		addTx(b)
+		addTx(b)
+	})
+
+	_, err = blockchain.InsertChain(block3)
+
+	if !errors.Is(err, consensus.ErrInvalidTxCount) {
+		t.Fatalf("error mismatch: have: %v, want: %v", err, consensus.ErrInvalidTxCount)
+	}
+}

miner/worker.go

@@ -818,6 +818,11 @@ func (w *worker) commitTransactions(txs *types.TransactionsByPriceAndNonce, coin
 			}
 			return atomic.LoadInt32(interrupt) == commitInterruptNewHead
 		}
+		// If we have collected enough transactions then we're done
+		if !w.chainConfig.IsValidTxCount(w.current.tcount + 1) {
+			log.Trace("Transaction count limit reached", "have", w.current.tcount, "want", w.chainConfig.MaxTxPerBlock)
+			break
+		}
 		// If we don't have enough gas for any further transactions then we're done
 		if w.current.gasPool.Gas() < params.TxGas {
 			log.Trace("Not enough gas for further transactions", "have", w.current.gasPool, "want", params.TxGas)

params/config.go

@@ -258,16 +258,16 @@ var (
 	//
 	// This configuration is intentionally not using keyed fields to force anyone
 	// adding flags to the config to also have to set these fields.
-	AllEthashProtocolChanges = &ChainConfig{big.NewInt(1337), big.NewInt(0), nil, false, big.NewInt(0), common.Hash{}, big.NewInt(0), big.NewInt(0), big.NewInt(0), big.NewInt(0), big.NewInt(0), big.NewInt(0), big.NewInt(0), big.NewInt(0), big.NewInt(0), big.NewInt(0), nil, new(EthashConfig), nil, false, nil, true, true}
+	AllEthashProtocolChanges = &ChainConfig{big.NewInt(1337), big.NewInt(0), nil, false, big.NewInt(0), common.Hash{}, big.NewInt(0), big.NewInt(0), big.NewInt(0), big.NewInt(0), big.NewInt(0), big.NewInt(0), big.NewInt(0), big.NewInt(0), big.NewInt(0), big.NewInt(0), nil, new(EthashConfig), nil, false, nil, true, true, nil}
 
 	// AllCliqueProtocolChanges contains every protocol change (EIPs) introduced
 	// and accepted by the Ethereum core developers into the Clique consensus.
 	//
 	// This configuration is intentionally not using keyed fields to force anyone
 	// adding flags to the config to also have to set these fields.
-	AllCliqueProtocolChanges = &ChainConfig{big.NewInt(1337), big.NewInt(0), nil, false, big.NewInt(0), common.Hash{}, big.NewInt(0), big.NewInt(0), big.NewInt(0), big.NewInt(0), big.NewInt(0), big.NewInt(0), big.NewInt(0), big.NewInt(0), big.NewInt(0), nil, nil, nil, &CliqueConfig{Period: 0, Epoch: 30000}, false, nil, true, true}
+	AllCliqueProtocolChanges = &ChainConfig{big.NewInt(1337), big.NewInt(0), nil, false, big.NewInt(0), common.Hash{}, big.NewInt(0), big.NewInt(0), big.NewInt(0), big.NewInt(0), big.NewInt(0), big.NewInt(0), big.NewInt(0), big.NewInt(0), big.NewInt(0), nil, nil, nil, &CliqueConfig{Period: 0, Epoch: 30000}, false, nil, true, true, nil}
 
-	TestChainConfig = &ChainConfig{big.NewInt(1), big.NewInt(0), nil, false, big.NewInt(0), common.Hash{}, big.NewInt(0), big.NewInt(0), big.NewInt(0), big.NewInt(0), big.NewInt(0), big.NewInt(0), big.NewInt(0), big.NewInt(0), big.NewInt(0), big.NewInt(0), nil, new(EthashConfig), nil, false, &common.Address{123}, true, true}
+	TestChainConfig = &ChainConfig{big.NewInt(1), big.NewInt(0), nil, false, big.NewInt(0), common.Hash{}, big.NewInt(0), big.NewInt(0), big.NewInt(0), big.NewInt(0), big.NewInt(0), big.NewInt(0), big.NewInt(0), big.NewInt(0), big.NewInt(0), big.NewInt(0), nil, new(EthashConfig), nil, false, &common.Address{123}, true, true, nil}
 	TestRules       = TestChainConfig.Rules(new(big.Int))
 )
 
@@ -367,6 +367,9 @@ type ChainConfig struct {
 
 	// Scroll genesis extension: enable EIP-1559 in tx pool, EnableEIP2718 should be true too.
 	EnableEIP1559 bool `json:"enableEIP1559,omitempty"`
+
+	// Scroll genesis extension: Maximum number of transactions per block [optional]
+	MaxTxPerBlock *int `json:"maxTxPerBlock,omitempty"`
 }
 
 // EthashConfig is the consensus engine configs for proof-of-work based sealing.
@@ -494,6 +497,11 @@ func (c *ChainConfig) IsTerminalPoWBlock(parentTotalDiff *big.Int, totalDiff *bi
 	return parentTotalDiff.Cmp(c.TerminalTotalDifficulty) < 0 && totalDiff.Cmp(c.TerminalTotalDifficulty) >= 0
 }
 
+// IsValidTxCount returns whether the given block's transaction count is below the limit.
+func (c *ChainConfig) IsValidTxCount(count int) bool {
+	return c.MaxTxPerBlock == nil || count <= *c.MaxTxPerBlock
+}
+
 // CheckCompatible checks whether scheduled fork transitions have been imported
 // with a mismatching chain configuration.
 func (c *ChainConfig) CheckCompatible(newcfg *ChainConfig, height uint64) *ConfigCompatError {