ArbGasInfo (0x000000000000000000000000000000000000006c)

The ArbGasInfo precompile provides essential information regarding gas scheduling, pricing components, and accounting parameters on Arbitrum Nitro. It is the primary interface for contracts and dApps to estimate L1 and L2 fees programmatically.

Configuration

The handler supports runtime configuration via a node_state/gas_config.json file. This allows for the simulation of various network conditions (e.g., congestion, high L1 fees) without restarting the local node.

Configuration Schema:

JSON
{
  "l1BaseFee": "20000000000",
  "gasPriceComponents": {
    "l2BaseFee": "100000000",
    "l1CalldataCost": "16",
    "l1StorageCost": "0",
    "congestionFee": "0"
  },
  "gasAccounting": {
    "speedLimitPerSecond": "120000000",
    "gasPoolMax": "32000000",
    "maxTxGasLimit": "32000000",
    "amortizedCostCapBips": "10000"
  }
}

Supported Functions

The handler intercepts calls to the following 4-byte function selectors:

FunctionSelectorDescription
getPricesInWei()0x41b247a8Returns a 6-tuple containing L2 base fee, L1 calldata cost, L1 byte price, active L2 base fee, congestion fee, and total L2 fee.
getPricesInArbGas()0x02199f34Returns gas prices denominated in internal ArbGas units (3-tuple).
getCurrentTxL1GasFees()0xc6f7de0eEstimates L1 gas fees for the transaction using a local compression heuristic.
getL1BaseFeeEstimate()0xf5d6ded7Returns the current estimated L1 base fee (in wei).
getL2BaseFeeEstimate()0xb246b565Returns the current L2 base fee (in wei).
getL1GasPriceEstimate()0x055f362fReturns the estimated L1 gas price (typically matches L1 base fee).
getGasAccountingParams()0x612af178Returns the Speed Limit, Gas Pool Max, and Max Tx Gas Limit.
getMinimumGasPrice()0xf918379aReturns the minimum gas price required for a transaction.
getAmortizedCostCapBips()0x7a7d6bebReturns the amortized cost cap in basis points.
getL1BlobBaseFeeEstimate()0x67037becReturns the estimated L1 blob base fee (EIP-4844 support).

L1 Cost Estimation

The getCurrentTxL1GasFees method implements a compression heuristic to approximate Mainnet behavior, where data is compressed using Brotli before posting to L1. The local simulation logic is as follows:

  1. Zero-Byte Analysis: Input calldata bytes equal to 0x00 are weighted at 4 gas per byte.
  2. Non-Zero Analysis: Non-zero bytes are weighted at the configured l1CalldataCost (default 16 gas).
  3. Compression Discount: The total calculated cost is discounted by a factor of 0.9x to simulate the average savings achieved by batch compression and metadata amortization.

Formula: $$Cost_{L1} = \lfloor (N_{zero} \times 4 + N_{nonzero} \times Cost_{calldata}) \times 0.9 \rfloor \times Fee_{L1Base}$$

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