Gasback

A barebones implementation of a gasback contract that implements RIP-7767.

Suggested setup for OP stack chains

Requirements

• The baseFeeVault is deployed at 0x4200000000000000000000000000000000000019.
• The WITHDRAWAL_NETWORK of the baseFeeVault is set to 1.
• The baseFeeVault recipient is set to FeeVaultSplitter.
• Gasback receives only its configured share from FeeVaultSplitter.

Via script

See script/DeployGasback.s.sol and script/DeployFeeVaultSplitter.s.sol for deployment scripts.

These scripts require you to have PRIVATE_KEY in your environment.

For more information on how to run a foundry script, see https://getfoundry.sh/guides/scripting-with-solidity.

Manual steps

1. Deploy the Gasback contract.

2. Deploy FeeVaultSplitter with Gasback as one of the payees.

3. Set the baseFeeVault recipient to the deployed FeeVaultSplitter.

4. Configure Gasback via authorized calls:

   • setBaseFeeVault(address)
0x4200000000000000000000000000000000000019
   • setBaseFeeVaultShareNumerator(uint256)
600000000000000000 (0.6 ether) and ensure it matches the splitter allocation for Gasback.
   • setGasbackRatioNumerator(uint256)
     Must be less than or equal to setBaseFeeVaultShareNumerator.
   • setGasbackMaxBaseFee(uint256)
115792089237316195423570985008687907853269984665640564039457584007913129639935

5. Put or leave some ETH in Gasback. The ETH acts as a buffer that is temporarily dished out to contracts calling Gasback in the span of a single block. The base fees collected in a block will only be accrued into the baseFeeVault at the end of a block. Try not to empty ETH from Gasback while actively serving gasback payouts.