BEP-341: Validators can produce consecutive blocks

cmd/extradump/extradump_test.go

@@ -43,7 +43,42 @@ func TestExtraParse(t *testing.T) {
 		}
 	}
 
-	// case 3, |---Extra Vanity---|---Empty---|---Vote Attestation---|---Extra Seal---|
+	// case 3, |---Extra Vanity---|---Validators Number and Validators Bytes---|---Turn Length---|---Empty---|---Extra Seal---|
+	{
+		extraData := "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"
+		extra, err := parseExtra(extraData)
+		assert.NoError(t, err)
+		{
+			var have = extra.ValidatorSize
+			var want = uint8(21)
+			if have != want {
+				t.Fatalf("extra.ValidatorSize mismatch, have %d, want %d", have, want)
+			}
+		}
+		{
+			var have = common.Bytes2Hex(extra.Validators[14].Address[:])
+			var want = "cc8e6d00c17eb431350c6c50d8b8f05176b90b11"
+			if have != want {
+				t.Fatalf("extra.Validators[14].Address mismatch, have %s, want %s", have, want)
+			}
+		}
+		{
+			var have = common.Bytes2Hex(extra.Validators[18].BLSPublicKey[:])
+			var want = "b2d4c6283c44a1c7bd503aaba7666e9f0c830e0ff016c1c750a5e48757a713d0836b1cabfd5c281b1de3b77d1c192183"
+			if have != want {
+				t.Fatalf("extra.Validators[18].BLSPublicKey mismatch, have %s, want %s", have, want)
+			}
+		}
+		{
+			var have = extra.TurnLength
+			var want = uint8(4)
+			if *have != want {
+				t.Fatalf("extra.TurnLength mismatch, have %d, want %d", *have, want)
+			}
+		}
+	}
+
+	// case 4, |---Extra Vanity---|---Empty---|---Vote Attestation---|---Extra Seal---|
 	{
 		extraData := "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"
 		extra, err := parseExtra(extraData)
@@ -64,9 +99,51 @@ func TestExtraParse(t *testing.T) {
 		}
 	}
 
-	// case 4, |---Extra Vanity---|---Validators Number and Validators Bytes---|---Vote Attestation---|---Extra Seal---|
+	// case 5, |---Extra Vanity---|---Validators Number and Validators Bytes---|---Vote Attestation---|---Extra Seal---|
+	{
+		extraData := "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"
+		extra, err := parseExtra(extraData)
+		assert.NoError(t, err)
+		{
+			var have = common.Bytes2Hex(extra.Validators[0].Address[:])
+			var want = "1284214b9b9c85549ab3d2b972df0deef66ac2c9"
+			if have != want {
+				t.Fatalf("extra.Validators[0].Address mismatch, have %s, want %s", have, want)
+			}
+		}
+		{
+			var have = common.Bytes2Hex(extra.Validators[0].BLSPublicKey[:])
+			var want = "8e82934ca974fdcd97f3309de967d3c9c43fa711a8d673af5d75465844bf8969c8d1948d903748ac7b8b1720fa64e50c"
+			if have != want {
+				t.Fatalf("extra.Validators[0].BLSPublicKey mismatch, have %s, want %s", have, want)
+			}
+		}
+		{
+			var have = extra.Validators[0].VoteIncluded
+			var want = true
+			if have != want {
+				t.Fatalf("extra.Validators[0].VoteIncluded mismatch, have %t, want %t", have, want)
+			}
+		}
+		{
+			var have = common.Bytes2Hex(extra.Data.TargetHash[:])
+			var want = "0edc71ce80105a3220a87bea2792fa340d66c59002f02b0a09349ed1ed284070"
+			if have != want {
+				t.Fatalf("extra.Data.TargetHash mismatch, have %s, want %s", have, want)
+			}
+		}
+		{
+			var have = extra.Data.TargetNumber
+			var want = uint64(32096999)
+			if have != want {
+				t.Fatalf("extra.Data.TargetNumber mismatch, have %d, want %d", have, want)
+			}
+		}
+	}
+
+	// case 6, |---Extra Vanity---|---Validators Number and Validators Bytes---|---Turn Length---|---Vote Attestation---|---Extra Seal---|
 	{
-		extraData := "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"
+		extraData := "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"
 		extra, err := parseExtra(extraData)
 		assert.NoError(t, err)
 		{
@@ -104,5 +181,12 @@ func TestExtraParse(t *testing.T) {
 				t.Fatalf("extra.Data.TargetNumber mismatch, have %d, want %d", have, want)
 			}
 		}
+		{
+			var have = extra.TurnLength
+			var want = uint8(4)
+			if *have != want {
+				t.Fatalf("extra.TurnLength mismatch, have %d, want %d", *have, want)
+			}
+		}
 	}
 }

cmd/extradump/main.go

@@ -24,7 +24,7 @@ const (
 	BLSPublicKeyLength = 48
 
 	// follow order in extra field
-	// |---Extra Vanity---|---Validators Number and Validators Bytes (or Empty)---|---Vote Attestation (or Empty)---|---Extra Seal---|
+	// |---Extra Vanity---|---Validators Number and Validators Bytes (or Empty)---|---Turn Length (or Empty)---|---Vote Attestation (or Empty)---|---Extra Seal---|
 	extraVanityLength    = 32 // Fixed number of extra-data prefix bytes reserved for signer vanity
 	validatorNumberSize  = 1  // Fixed number of extra prefix bytes reserved for validator number after Luban
 	validatorBytesLength = common.AddressLength + types.BLSPublicKeyLength
@@ -35,6 +35,7 @@ type Extra struct {
 	ExtraVanity   string
 	ValidatorSize uint8
 	Validators    validatorsAscending
+	TurnLength    *uint8
 	*types.VoteAttestation
 	ExtraSeal []byte
 }
@@ -113,6 +114,15 @@ func parseExtra(hexData string) (*Extra, error) {
 			sort.Sort(extra.Validators)
 			data = data[validatorBytesTotalLength-validatorNumberSize:]
 			dataLength = len(data)
+
+			// parse TurnLength
+			if dataLength > 0 {
+				if data[0] != '\xf8' {
+					extra.TurnLength = &data[0]
+					data = data[1:]
+					dataLength = len(data)
+				}
+			}
 		}
 
 		// parse Vote Attestation
@@ -148,6 +158,10 @@ func prettyExtra(extra Extra) {
 		}
 	}
 
+	if extra.TurnLength != nil {
+		fmt.Printf("TurnLength	:	%d\n", *extra.TurnLength)
+	}
+
 	if extra.VoteAttestation != nil {
 		fmt.Printf("Attestation	:\n")
 		fmt.Printf("\tVoteAddressSet	:	%b,	%d\n", extra.VoteAddressSet, bitset.From([]uint64{uint64(extra.VoteAddressSet)}).Count())

cmd/geth/config.go

@@ -206,6 +206,9 @@ func makeFullNode(ctx *cli.Context) (*node.Node, ethapi.Backend) {
 	if ctx.IsSet(utils.OverrideBreatheBlockInterval.Name) {
 		params.BreatheBlockInterval = ctx.Uint64(utils.OverrideBreatheBlockInterval.Name)
 	}
+	if ctx.IsSet(utils.OverrideFixedTurnLength.Name) {
+		params.FixedTurnLength = ctx.Uint64(utils.OverrideFixedTurnLength.Name)
+	}
 
 	backend, eth := utils.RegisterEthService(stack, &cfg.Eth)
 

cmd/geth/main.go

@@ -78,6 +78,7 @@ var (
 		utils.OverrideMinBlocksForBlobRequests,
 		utils.OverrideDefaultExtraReserveForBlobRequests,
 		utils.OverrideBreatheBlockInterval,
+		utils.OverrideFixedTurnLength,
 		utils.EnablePersonal,
 		utils.TxPoolLocalsFlag,
 		utils.TxPoolNoLocalsFlag,

cmd/jsutils/get_perf.js

@@ -13,6 +13,8 @@ const main = async () => {
     let gasUsedTotal = 0;
     let inturnBlocks = 0;
     let justifiedBlocks = 0;
+    let turnLength = await provider.send("parlia_getTurnLength", [
+        ethers.toQuantity(program.startNum)]);
     for (let i = program.startNum; i < program.endNum; i++) {
         let txCount = await provider.send("eth_getBlockTransactionCountByNumber", [
             ethers.toQuantity(i)]);
@@ -35,7 +37,7 @@ const main = async () => {
         } else {
             console.log("justified unexpected", "BlockNumber =", i,"justifiedNumber",justifiedNumber)    
         }
-        console.log("BlockNumber =", i, "mod =", i%4, "miner =", header.miner , "difficulty =", difficulty, "txCount =", ethers.toNumber(txCount), "gasUsed", gasUsed, "timestamp", timestamp)
+        console.log("BlockNumber =", i, "mod =", i%turnLength, "miner =", header.miner , "difficulty =", difficulty, "txCount =", ethers.toNumber(txCount), "gasUsed", gasUsed, "timestamp", timestamp)
     }
 
     let blockCount = program.endNum - program.startNum

cmd/utils/flags.go

@@ -339,6 +339,12 @@ var (
 		Value:    params.BreatheBlockInterval,
 		Category: flags.EthCategory,
 	}
+	OverrideFixedTurnLength = &cli.Uint64Flag{
+		Name:     "override.fixedturnlength",
+		Usage:    "It use fixed or random values for turn length instead of reading from the contract, only for testing purpose",
+		Value:    params.FixedTurnLength,
+		Category: flags.EthCategory,
+	}
 	SyncModeFlag = &flags.TextMarshalerFlag{
 		Name:     "syncmode",
 		Usage:    `Blockchain sync mode ("snap" or "full")`,

consensus/parlia/abi.go

@@ -2306,6 +2306,19 @@ const validatorSetABI = `
     ],
     "stateMutability": "view"
   },
+  {
+    "inputs": [],
+    "name": "getTurnLength",
+    "outputs": [
+      {
+        "internalType": "uint256",
+        "name": "",
+        "type": "uint256"
+      }
+    ],
+    "stateMutability": "view",
+    "type": "function"
+  },
   {
     "type": "function",
     "name": "getValidators",

consensus/parlia/api.go

@@ -88,6 +88,19 @@ func (api *API) GetJustifiedNumber(number *rpc.BlockNumber) (uint64, error) {
 	return snap.Attestation.TargetNumber, nil
 }
 
+func (api *API) GetTurnLength(number *rpc.BlockNumber) (uint8, error) {
+	header := api.getHeader(number)
+	// Ensure we have an actually valid block and return the validators from its snapshot
+	if header == nil {
+		return 0, errUnknownBlock
+	}
+	snap, err := api.parlia.snapshot(api.chain, header.Number.Uint64(), header.Hash(), nil)
+	if err != nil || snap.TurnLength == 0 {
+		return 0, err
+	}
+	return snap.TurnLength, nil
+}
+
 func (api *API) GetFinalizedNumber(number *rpc.BlockNumber) (uint64, error) {
 	header := api.getHeader(number)
 	// Ensure we have an actually valid block and return the validators from its snapshot

consensus/parlia/bohrFork.go

@@ -0,0 +1,91 @@
+package parlia
+
+import (
+	"context"
+	"errors"
+	"math/big"
+	mrand "math/rand"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/common/hexutil"
+	"github.com/ethereum/go-ethereum/common/math"
+	"github.com/ethereum/go-ethereum/consensus"
+	"github.com/ethereum/go-ethereum/core/systemcontracts"
+	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/internal/ethapi"
+	"github.com/ethereum/go-ethereum/log"
+	"github.com/ethereum/go-ethereum/params"
+	"github.com/ethereum/go-ethereum/rpc"
+)
+
+func (p *Parlia) getTurnLength(chain consensus.ChainHeaderReader, header *types.Header) (*uint8, error) {
+	parent := chain.GetHeaderByHash(header.ParentHash)
+	if parent == nil {
+		return nil, errors.New("parent not found")
+	}
+
+	var turnLength uint8
+	if p.chainConfig.IsBohr(parent.Number, parent.Time) {
+		turnLengthFromContract, err := p.getTurnLengthFromContract(parent)
+		if err != nil {
+			return nil, err
+		}
+		if turnLengthFromContract == nil {
+			return nil, errors.New("unexpected error when getTurnLengthFromContract")
+		}
+		turnLength = uint8(turnLengthFromContract.Int64())
+	} else {
+		turnLength = defaultTurnLength
+	}
+	log.Debug("getTurnLength", "turnLength", turnLength)
+
+	return &turnLength, nil
+}
+
+func (p *Parlia) getTurnLengthFromContract(header *types.Header) (turnLength *big.Int, err error) {
+	// mock to get turnLength from the contract
+	if params.FixedTurnLength >= 1 && params.FixedTurnLength <= 9 {
+		if params.FixedTurnLength == 2 {
+			return p.getRandTurnLength(header)
+		}
+		return big.NewInt(int64(params.FixedTurnLength)), nil
+	}
+
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	method := "getTurnLength"
+	toAddress := common.HexToAddress(systemcontracts.ValidatorContract)
+	gas := (hexutil.Uint64)(uint64(math.MaxUint64 / 2))
+
+	data, err := p.validatorSetABI.Pack(method)
+	if err != nil {
+		log.Error("Unable to pack tx for getTurnLength", "error", err)
+		return nil, err
+	}
+	msgData := (hexutil.Bytes)(data)
+
+	blockNr := rpc.BlockNumberOrHashWithHash(header.Hash(), false)
+	result, err := p.ethAPI.Call(ctx, ethapi.TransactionArgs{
+		Gas:  &gas,
+		To:   &toAddress,
+		Data: &msgData,
+	}, &blockNr, nil, nil)
+	if err != nil {
+		return nil, err
+	}
+
+	if err := p.validatorSetABI.UnpackIntoInterface(&turnLength, method, result); err != nil {
+		return nil, err
+	}
+
+	return turnLength, nil
+}
+
+// getRandTurnLength returns a random valid value, used to test switching turn length
+func (p *Parlia) getRandTurnLength(header *types.Header) (turnLength *big.Int, err error) {
+	turnLengths := [8]uint8{1, 3, 4, 5, 6, 7, 8, 9}
+	r := mrand.New(mrand.NewSource(int64(header.Time)))
+	lengthIndex := int(r.Int31n(int32(len(turnLengths))))
+	return big.NewInt(int64(turnLengths[lengthIndex])), nil
+}