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Overview

The Ethereum_SpokePool is the L1-specific SpokePool variant deployed on Ethereum mainnet. Unlike L2 SpokePools that bridge tokens across chains, this contract facilitates L2→L1 transfers by directly transferring tokens to the withdrawal recipient (HubPool). Contract: contracts/Ethereum_SpokePool.sol

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Key Characteristics

  • Same-chain deployment: Deployed on the same network as HubPool (Ethereum L1)
  • Direct ownership: Owned directly by HubPool via OwnableUpgradeable
  • No cross-chain bridging: Uses simple ERC20 transfers instead of bridge contracts
  • No OFT messaging: Does not use LayerZero OFT; both oftDstEid and oftFeeCap set to 0

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Inheritance

contract Ethereum_SpokePool is SpokePool, OwnableUpgradeable
  • Inherits base SpokePool functionality
  • Uses OwnableUpgradeable for simple admin control (no cross-chain verification needed)

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Constructor

constructor(
    address _wrappedNativeTokenAddress,
    uint32 _depositQuoteTimeBuffer,
    uint32 _fillDeadlineBuffer
)
    SpokePool(
        _wrappedNativeTokenAddress,
        _depositQuoteTimeBuffer,
        _fillDeadlineBuffer,
        // Ethereum_SpokePool does not use OFT messaging
        0, // oftDstEid
        0  // oftFeeCap
    )
Parameters:
  • _wrappedNativeTokenAddress: Address of WETH on Ethereum
  • _depositQuoteTimeBuffer: Max age for deposit quote timestamps
  • _fillDeadlineBuffer: Max future offset for fill deadlines

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Initialization

function initialize(
    uint32 _initialDepositId,
    address _withdrawalRecipient
) public initializer
Parameters:
  • _initialDepositId: Starting deposit nonce (0 for new deployments, incremented for re-deployments to avoid relay hash collisions)
  • _withdrawalRecipient: Recipient of token withdrawals (typically the HubPool address)
Note: crossDomainAdmin parameter is unused on Ethereum and set equal to _withdrawalRecipient.

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Admin Verification

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_requireAdminSender()

function _requireAdminSender() internal override onlyOwner {}
Implementation: Uses OpenZeppelin’s onlyOwner modifier to verify the caller is the contract owner (HubPool). Why it’s different: Since this SpokePool is deployed on the same chain as HubPool, no cross-chain message verification is needed. The owner can call admin functions directly.

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Token Bridging

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_bridgeTokensToHubPool()

function _bridgeTokensToHubPool(
    uint256 amountToReturn,
    address l2TokenAddress
) internal override {
    IERC20Upgradeable(l2TokenAddress).safeTransfer(
        withdrawalRecipient,
        amountToReturn
    );
}
Implementation: Performs a simple ERC20 transfer to the withdrawalRecipient (HubPool). Why it’s different: No canonical bridge interaction required since tokens are already on L1. This is the simplest implementation among all SpokePool variants.

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Unique Features

  1. Simplest variant: Minimal code due to same-chain deployment
  2. Direct transfers: No bridge contracts or cross-chain messages
  3. Standard ownership: Uses standard Ownable pattern instead of cross-domain admin verification
  4. L2→L1 facilitator: Primary purpose is to receive tokens bridged from L2s and transfer them to HubPool

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Architecture Notes

  • The Ethereum_SpokePool is owned by the HubPool contract
  • Admin functions are called directly by HubPool without cross-chain relaying
  • This contract serves as the final destination for tokens bridged from L2 SpokePools
  • The crossDomainAdmin variable exists for interface compatibility but is unused