Add configurable threshold for 'future block' check

cmd/geth/main.go

@@ -145,6 +145,7 @@ var (
 		utils.EmitCheckpointsFlag,
 		utils.IstanbulRequestTimeoutFlag,
 		utils.IstanbulBlockPeriodFlag,
+		utils.IstanbulAllowedFutureBlockTimeFlag,
 		utils.PluginSettingsFlag,
 		utils.PluginSkipVerifyFlag,
 		utils.PluginLocalVerifyFlag,

cmd/geth/usage.go

@@ -269,6 +269,7 @@ var AppHelpFlagGroups = []flagGroup{
 		Flags: []cli.Flag{
 			utils.IstanbulRequestTimeoutFlag,
 			utils.IstanbulBlockPeriodFlag,
+			utils.IstanbulAllowedFutureBlockTimeFlag,
 		},
 	},
 	{

cmd/utils/flags.go

@@ -647,6 +647,11 @@ var (
 		Usage: "Default minimum difference between two consecutive block's timestamps in seconds",
 		Value: eth.DefaultConfig.Istanbul.BlockPeriod,
 	}
+	IstanbulAllowedFutureBlockTimeFlag = cli.Uint64Flag{
+		Name:  "istanbul.allowedfutureblocktime",
+		Usage: "Time threshold allowed when detecting future blocks in seconds",
+		Value: eth.DefaultConfig.Istanbul.AllowedFutureBlockTime,
+	}
 
 	// Metrics flags
 	MetricsEnabledFlag = cli.BoolFlag{
@@ -1201,6 +1206,9 @@ func setIstanbul(ctx *cli.Context, cfg *eth.Config) {
 	if ctx.GlobalIsSet(IstanbulBlockPeriodFlag.Name) {
 		cfg.Istanbul.BlockPeriod = ctx.GlobalUint64(IstanbulBlockPeriodFlag.Name)
 	}
+	if ctx.GlobalIsSet(IstanbulAllowedFutureBlockTimeFlag.Name) {
+		cfg.Istanbul.AllowedFutureBlockTime = ctx.GlobalUint64(IstanbulAllowedFutureBlockTimeFlag.Name)
+	}
 }
 
 // checkExclusive verifies that only a single instance of the provided flags was

consensus/istanbul/backend/engine.go

@@ -144,8 +144,9 @@ func (sb *backend) verifyHeader(chain consensus.ChainReader, header *types.Heade
 		return errUnknownBlock
 	}
 
-	// Don't waste time checking blocks from the future
-	if header.Time.Cmp(big.NewInt(now().Unix())) > 0 {
+	// Don't waste time checking blocks from the future (adjusting for allowed threshold)
+	adjustedTimeNow := now().Add(time.Duration(sb.config.AllowedFutureBlockTime) * time.Second).Unix()
+	if header.Time.Cmp(big.NewInt(adjustedTimeNow)) > 0 {
 		return consensus.ErrFutureBlock
 	}
 

consensus/istanbul/backend/engine_test.go

@@ -325,6 +325,18 @@ func TestVerifyHeader(t *testing.T) {
 		t.Errorf("error mismatch: have %v, want %v", err, consensus.ErrFutureBlock)
 	}
 
+	// future block which is within AllowedFutureBlockTime
+	block = makeBlockWithoutSeal(chain, engine, chain.Genesis())
+	header = block.Header()
+	header.Time = new(big.Int).Add(big.NewInt(now().Unix()), new(big.Int).SetUint64(10))
+	priorValue := engine.config.AllowedFutureBlockTime
+	engine.config.AllowedFutureBlockTime = 10
+	err = engine.VerifyHeader(chain, header, false)
+	engine.config.AllowedFutureBlockTime = priorValue //restore changed value
+	if err == consensus.ErrFutureBlock {
+		t.Errorf("error mismatch: have %v, want nil", err)
+	}
+
 	// invalid nonce
 	block = makeBlockWithoutSeal(chain, engine, chain.Genesis())
 	header = block.Header()

consensus/istanbul/config.go

@@ -26,11 +26,12 @@ const (
 )
 
 type Config struct {
-	RequestTimeout uint64         `toml:",omitempty"` // The timeout for each Istanbul round in milliseconds.
-	BlockPeriod    uint64         `toml:",omitempty"` // Default minimum difference between two consecutive block's timestamps in second
-	ProposerPolicy ProposerPolicy `toml:",omitempty"` // The policy for proposer selection
-	Epoch          uint64         `toml:",omitempty"` // The number of blocks after which to checkpoint and reset the pending votes
-	Ceil2Nby3Block *big.Int       `toml:",omitempty"` // Number of confirmations required to move from one state to next [2F + 1 to Ceil(2N/3)]
+	RequestTimeout         uint64         `toml:",omitempty"` // The timeout for each Istanbul round in milliseconds.
+	BlockPeriod            uint64         `toml:",omitempty"` // Default minimum difference between two consecutive block's timestamps in second
+	ProposerPolicy         ProposerPolicy `toml:",omitempty"` // The policy for proposer selection
+	Epoch                  uint64         `toml:",omitempty"` // The number of blocks after which to checkpoint and reset the pending votes
+	Ceil2Nby3Block         *big.Int       `toml:",omitempty"` // Number of confirmations required to move from one state to next [2F + 1 to Ceil(2N/3)]
+	AllowedFutureBlockTime uint64         `toml:",omitempty"` // Time threshold allowed when detecting future blocks, in seconds
 }
 
 var DefaultConfig = &Config{
@@ -39,4 +40,5 @@ var DefaultConfig = &Config{
 	ProposerPolicy: RoundRobin,
 	Epoch:          30000,
 	Ceil2Nby3Block: big.NewInt(0),
+	AllowedFutureBlockTime: 1,
 }