miner: add --miner.maxblobs flag (#33129)

Adds a flag to specify how many blobs a node is willing to include in
their locally build block as specified in
https://eips.ethereum.org/EIPS/eip-7872

I deviated from the EIP in one case, I allowed for specifying 0 as the
minimum blobs/block

cmd/geth/main.go

@@ -118,6 +118,7 @@ var (
 		utils.MinerGasPriceFlag,
 		utils.MinerEtherbaseFlag, // deprecated
 		utils.MinerExtraDataFlag,
+		utils.MinerMaxBlobsFlag,
 		utils.MinerRecommitIntervalFlag,
 		utils.MinerPendingFeeRecipientFlag,
 		utils.MinerNewPayloadTimeoutFlag, // deprecated

cmd/utils/flags.go

@@ -553,6 +553,11 @@ var (
 		Usage:    "0x prefixed public address for the pending block producer (not used for actual block production)",
 		Category: flags.MinerCategory,
 	}
+	MinerMaxBlobsFlag = &cli.IntFlag{
+		Name:     "miner.maxblobs",
+		Usage:    "Maximum number of blobs per block (falls back to protocol maximum if unspecified)",
+		Category: flags.MinerCategory,
+	}
 
 	// Account settings
 	PasswordFileFlag = &cli.PathFlag{
@@ -1571,6 +1576,10 @@ func setMiner(ctx *cli.Context, cfg *miner.Config) {
 		log.Warn("The flag --miner.newpayload-timeout is deprecated and will be removed, please use --miner.recommit")
 		cfg.Recommit = ctx.Duration(MinerNewPayloadTimeoutFlag.Name)
 	}
+	if ctx.IsSet(MinerMaxBlobsFlag.Name) {
+		maxBlobs := ctx.Int(MinerMaxBlobsFlag.Name)
+		cfg.MaxBlobsPerBlock = &maxBlobs
+	}
 }
 
 func setRequiredBlocks(ctx *cli.Context, cfg *ethconfig.Config) {

miner/miner.go

@@ -48,6 +48,7 @@ type Config struct {
 	GasCeil             uint64         // Target gas ceiling for mined blocks.
 	GasPrice            *big.Int       // Minimum gas price for mining a transaction
 	Recommit            time.Duration  // The time interval for miner to re-create mining work.
+	MaxBlobsPerBlock    *int           // Maximum number of blobs per block (unset uses protocol default)
 }
 
 // DefaultConfig contains default settings for miner.

miner/worker.go

@@ -43,6 +43,16 @@ var (
 	errBlockInterruptedByTimeout  = errors.New("timeout while building block")
 )
 
+// maxBlobsPerBlock returns the maximum number of blobs per block.
+// Users can specify the maximum number of blobs per block if necessary.
+func (miner *Miner) maxBlobsPerBlock(time uint64) int {
+	maxBlobs := eip4844.MaxBlobsPerBlock(miner.chainConfig, time)
+	if miner.config.MaxBlobsPerBlock != nil {
+		maxBlobs = *miner.config.MaxBlobsPerBlock
+	}
+	return maxBlobs
+}
+
 // environment is the worker's current environment and holds all
 // information of the sealing block generation.
 type environment struct {
@@ -309,7 +319,7 @@ func (miner *Miner) commitBlobTransaction(env *environment, tx *types.Transactio
 	// isn't really a better place right now. The blob gas limit is checked at block validation time
 	// and not during execution. This means core.ApplyTransaction will not return an error if the
 	// tx has too many blobs. So we have to explicitly check it here.
-	maxBlobs := eip4844.MaxBlobsPerBlock(miner.chainConfig, env.header.Time)
+	maxBlobs := miner.maxBlobsPerBlock(env.header.Time)
 	if env.blobs+len(sc.Blobs) > maxBlobs {
 		return errors.New("max data blobs reached")
 	}
@@ -364,7 +374,7 @@ func (miner *Miner) commitTransactions(env *environment, plainTxs, blobTxs *tran
 		}
 		// If we don't have enough blob space for any further blob transactions,
 		// skip that list altogether
-		if !blobTxs.Empty() && env.blobs >= eip4844.MaxBlobsPerBlock(miner.chainConfig, env.header.Time) {
+		if !blobTxs.Empty() && env.blobs >= miner.maxBlobsPerBlock(env.header.Time) {
 			log.Trace("Not enough blob space for further blob transactions")
 			blobTxs.Clear()
 			// Fall though to pick up any plain txs
@@ -403,7 +413,7 @@ func (miner *Miner) commitTransactions(env *environment, plainTxs, blobTxs *tran
 		// blobs or not, however the max check panics when called on a chain without
 		// a defined schedule, so we need to verify it's safe to call.
 		if isCancun {
-			left := eip4844.MaxBlobsPerBlock(miner.chainConfig, env.header.Time) - env.blobs
+			left := miner.maxBlobsPerBlock(env.header.Time) - env.blobs
 			if left < int(ltx.BlobGas/params.BlobTxBlobGasPerBlob) {
 				log.Trace("Not enough blob space left for transaction", "hash", ltx.Hash, "left", left, "needed", ltx.BlobGas/params.BlobTxBlobGasPerBlob)
 				txs.Pop()