Isolate extra data modification to builder module

builder/builder.go

@@ -61,6 +61,8 @@ type Builder struct {
 	bestBlockMu sync.Mutex
 	bestBlock   *builderTypes.VersionedBuilderPayloadResponse
 
+	extraData []byte
+
 	stop chan struct{}
 }
 
@@ -74,6 +76,7 @@ type BuilderArgs struct {
 	eth                         IEthereumService
 	ignoreLatePayloadAttributes bool
 	beaconClient                IBeaconClient
+	extraData                   []byte
 }
 
 // SubmitBlockOpts is a struct that contains all the arguments needed to submit a block to the relay
@@ -101,6 +104,8 @@ func NewBuilder(args BuilderArgs) (*Builder, error) {
 		slotCtx:       slotCtx,
 		slotCtxCancel: slotCtxCancel,
 
+		extraData: args.extraData,
+
 		stop: make(chan struct{}, 1),
 	}, nil
 }
@@ -369,6 +374,8 @@ func (b *Builder) handlePayloadAttributes(attrs *builderTypes.PayloadAttributes)
 		b.slotCtxCancel()
 	}
 
+	attrs.ExtraData = b.extraData
+
 	slotCtx, slotCtxCancel := context.WithTimeout(context.Background(), b.builderBlockTime)
 	b.slotAttrs = *attrs
 	b.slotCtx = slotCtx

builder/config.go

@@ -17,6 +17,7 @@ type Config struct {
 	RetryInterval               string        `toml:",omitempty"`
 	BlockTime                   time.Duration `toml:",omitempty"`
 	ProposerAddress             string        `toml:",omitempty"`
+	ExtraData                   string        `toml:",omitempty"`
 }
 
 // DefaultConfig is the default config for the builder.
@@ -29,4 +30,5 @@ var DefaultConfig = Config{
 	BeaconEndpoints:             []string{"http://127.0.0.1:5052"},
 	RetryInterval:               RetryIntervalDefault.String(),
 	BlockTime:                   BlockTimeDefault,
+	ExtraData:                   "",
 }

builder/eth_service.go

@@ -46,6 +46,7 @@ func (s *EthereumService) BuildBlock(attrs *builderTypes.PayloadAttributes) (*en
 		BeaconRoot:   attrs.ParentBeaconBlockRoot,
 		Transactions: attrs.Transactions,
 		NoTxPool:     attrs.NoTxPool,
+		ExtraData:    attrs.ExtraData,
 	}
 
 	payload, err := s.eth.Miner().BuildPayload(args)

builder/service.go

@@ -113,6 +113,7 @@ func Register(stack *node.Node, backend *eth.Ethereum, cfg *Config) error {
 		ignoreLatePayloadAttributes: cfg.IgnoreLatePayloadAttributes,
 		beaconClient:                beaconClient,
 		blockTime:                   cfg.BlockTime,
+		extraData:                   []byte(cfg.ExtraData),
 	}
 
 	builderBackend, err := NewBuilder(builderArgs)

builder/types/attributes.go

@@ -19,6 +19,8 @@ type PayloadAttributes struct {
 
 	NoTxPool     bool                 `json:"noTxPool,omitempty"` // Optimism addition: option to disable tx pool contents from being included
 	Transactions []*types.Transaction `json:"transactions"`       // Optimism addition: txs forced into the block via engine API
+
+	ExtraData []byte `json:"extraData,omitempty"` // Flashbots addition: extra data to include in the block
 }
 
 func (attrs *PayloadAttributes) Equal(other *PayloadAttributes) bool {
@@ -41,5 +43,9 @@ func (attrs *PayloadAttributes) Equal(other *PayloadAttributes) bool {
 		return false
 	}
 
+	if !slices.Equal(attrs.ExtraData, other.ExtraData) {
+		return false
+	}
+
 	return true
 }

cmd/geth/main.go

@@ -185,6 +185,7 @@ var (
 		utils.BuilderBlockRetryInterval,
 		utils.BuilderBlockTime,
 		utils.BuilderProposerSigningAddress,
+		utils.BuilderExtraData,
 	}
 
 	rpcFlags = []cli.Flag{

cmd/utils/flags.go

@@ -724,6 +724,12 @@ var (
 		EnvVars:  []string{"BUILDER_PROPOSER_SIGNING_ADDRESS"},
 		Category: flags.BuilderCategory,
 	}
+	BuilderExtraData = &cli.StringFlag{
+		Name:     "builder.extra_data",
+		Usage:    "Extra data to include in the block",
+		EnvVars:  []string{"BUILDER_EXTRA_DATA"},
+		Category: flags.BuilderCategory,
+	}
 
 	CustomChainFlag = &cli.StringFlag{
 		Name:     "chain",
@@ -1589,6 +1595,7 @@ func SetBuilderConfig(ctx *cli.Context, cfg *builder.Config) {
 	cfg.RetryInterval = ctx.String(BuilderBlockRetryInterval.Name)
 	cfg.BlockTime = ctx.Duration(BuilderBlockTime.Name)
 	cfg.ProposerAddress = ctx.String(BuilderProposerSigningAddress.Name)
+	cfg.ExtraData = ctx.String(BuilderExtraData.Name)
 }
 
 // SetNodeConfig applies node-related command line flags to the config.

miner/payload_building.go

@@ -47,6 +47,8 @@ type BuildPayloadArgs struct {
 	NoTxPool     bool                 // Optimism addition: option to disable tx pool contents from being included
 	Transactions []*types.Transaction // Optimism addition: txs forced into the block via engine API
 	GasLimit     *uint64              // Optimism addition: override gas limit of the block to build
+
+	ExtraData []byte // Flashbots addition: extra data to include in the block
 }
 
 // Id computes an 8-byte identifier by hashing the components of the payload arguments.
@@ -261,6 +263,7 @@ func (miner *Miner) buildPayload(args *BuildPayloadArgs) (*Payload, error) {
 			noTxs:       true,
 			txs:         args.Transactions,
 			gasLimit:    args.GasLimit,
+			extraData:   args.ExtraData,
 		}
 		empty := miner.generateWork(emptyParams)
 		if empty.err != nil {
@@ -285,6 +288,7 @@ func (miner *Miner) buildPayload(args *BuildPayloadArgs) (*Payload, error) {
 		noTxs:       false,
 		txs:         args.Transactions,
 		gasLimit:    args.GasLimit,
+		extraData:   args.ExtraData,
 	}
 
 	// Since we skip building the empty block when using the tx pool, we need to explicitly

miner/worker.go

@@ -101,6 +101,8 @@ type generateParams struct {
 	gasLimit  *uint64            // Optional gas limit override
 	interrupt *atomic.Int32      // Optional interruption signal to pass down to worker.generateWork
 	isUpdate  bool               // Optional flag indicating that this is building a discardable update
+
+	extraData []byte // Extra data to include in the block
 }
 
 // generateWork generates a sealing block based on the given parameters.
@@ -197,9 +199,10 @@ func (miner *Miner) prepareWork(genParams *generateParams) (*environment, error)
 		Time:       timestamp,
 		Coinbase:   genParams.coinbase,
 	}
-	// Set the extra field.
-	if len(miner.config.ExtraData) != 0 && miner.chainConfig.Optimism == nil { // Optimism chains must not set any extra data.
-		header.Extra = miner.config.ExtraData
+	// Set the extra field if specified.
+	if len(genParams.extraData) != 0 {
+		log.Debug("Setting extra data", "extraData", genParams.extraData)
+		header.Extra = genParams.extraData
 	}
 	// Set the randomness field from the beacon chain if it's available.
 	if genParams.random != (common.Hash{}) {