Add OFTTransportAdapter to support cross-chain token transfers of USDT0 via OFT messaging protocol

contracts/AlephZero_SpokePool.sol

@@ -17,14 +17,17 @@ contract AlephZero_SpokePool is Arbitrum_SpokePool {
         uint32 _depositQuoteTimeBuffer,
         uint32 _fillDeadlineBuffer,
         IERC20 _l2Usdc,
-        ITokenMessenger _cctpTokenMessenger
+        ITokenMessenger _cctpTokenMessenger,
+        // _oftFeeCap can be set to 0 for AlephZero_SpokePool as AlephZero does not support OFT transfers.
+        uint256 _oftFeeCap
     )
         Arbitrum_SpokePool(
             _wrappedNativeTokenAddress,
             _depositQuoteTimeBuffer,
             _fillDeadlineBuffer,
             _l2Usdc,
-            _cctpTokenMessenger
+            _cctpTokenMessenger,
+            _oftFeeCap
         )
     {} // solhint-disable-line no-empty-blocks
 }

contracts/Arbitrum_SpokePool.sol

@@ -27,9 +27,11 @@ contract Arbitrum_SpokePool is SpokePool, CircleCCTPAdapter {
         uint32 _depositQuoteTimeBuffer,
         uint32 _fillDeadlineBuffer,
         IERC20 _l2Usdc,
-        ITokenMessenger _cctpTokenMessenger
+        ITokenMessenger _cctpTokenMessenger,
+        // _oftFeeCap can be set to 1 ether for Arbitrum, but has to be custom-set for other chains that might inherit this adapter, like AlephZero
+        uint256 _oftFeeCap
     )
-        SpokePool(_wrappedNativeTokenAddress, _depositQuoteTimeBuffer, _fillDeadlineBuffer)
+        SpokePool(_wrappedNativeTokenAddress, _depositQuoteTimeBuffer, _fillDeadlineBuffer, _oftFeeCap)
         CircleCCTPAdapter(_l2Usdc, _cctpTokenMessenger, CircleDomainIds.Ethereum)
     {} // solhint-disable-line no-empty-blocks
 
@@ -83,9 +85,13 @@ contract Arbitrum_SpokePool is SpokePool, CircleCCTPAdapter {
      **************************************/
 
     function _bridgeTokensToHubPool(uint256 amountToReturn, address l2TokenAddress) internal override {
+        address oftMessenger = _getOftMessenger(l2TokenAddress);
+
         // If the l2TokenAddress is UDSC, we need to use the CCTP bridge.
         if (_isCCTPEnabled() && l2TokenAddress == address(usdcToken)) {
             _transferUsdc(withdrawalRecipient, amountToReturn);
+        } else if (oftMessenger != address(0)) {
+            _transferViaOFT(IERC20(l2TokenAddress), IOFT(oftMessenger), withdrawalRecipient, amountToReturn);
         } else {
             // Check that the Ethereum counterpart of the L2 token is stored on this contract.
             address ethereumTokenToBridge = whitelistedTokens[l2TokenAddress];
@@ -112,4 +118,9 @@ contract Arbitrum_SpokePool is SpokePool, CircleCCTPAdapter {
 
     // Apply AVM-specific transformation to cross domain admin address on L1.
     function _requireAdminSender() internal override onlyFromCrossDomainAdmin {}
+
+    // Reserve storage slots for future versions of this base contract to add state variables without
+    // affecting the storage layout of child contracts. Decrement the size of __gap whenever state variables
+    // are added. This is at bottom of contract to make sure it's always at the end of storage.
+    uint256[1000] private __gap;
 }

contracts/Ethereum_SpokePool.sol

@@ -11,12 +11,15 @@ import "@openzeppelin/contracts-upgradeable/access/OwnableUpgradeable.sol";
 contract Ethereum_SpokePool is SpokePool, OwnableUpgradeable {
     using SafeERC20Upgradeable for IERC20Upgradeable;
 
+    // Ethereum_SpokePool does not use OFT messaging, setting the cap to 0
+    uint256 private constant OFT_FEE_CAP = 0;
+
     /// @custom:oz-upgrades-unsafe-allow constructor
     constructor(
         address _wrappedNativeTokenAddress,
         uint32 _depositQuoteTimeBuffer,
         uint32 _fillDeadlineBuffer
-    ) SpokePool(_wrappedNativeTokenAddress, _depositQuoteTimeBuffer, _fillDeadlineBuffer) {} // solhint-disable-line no-empty-blocks
+    ) SpokePool(_wrappedNativeTokenAddress, _depositQuoteTimeBuffer, _fillDeadlineBuffer, OFT_FEE_CAP) {} // solhint-disable-line no-empty-blocks
 
     /**
      * @notice Construct the Ethereum SpokePool.

contracts/Linea_SpokePool.sol

@@ -16,6 +16,9 @@ import "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";
 contract Linea_SpokePool is SpokePool {
     using SafeERC20 for IERC20;
 
+    // Linea_SpokePool does not use OFT messaging, setting the cap to 0
+    uint256 private constant OFT_FEE_CAP = 0;
+
     /**
      * @notice Address of Linea's Canonical Message Service contract on L2.
      */
@@ -51,7 +54,7 @@ contract Linea_SpokePool is SpokePool {
         address _wrappedNativeTokenAddress,
         uint32 _depositQuoteTimeBuffer,
         uint32 _fillDeadlineBuffer
-    ) SpokePool(_wrappedNativeTokenAddress, _depositQuoteTimeBuffer, _fillDeadlineBuffer) {} // solhint-disable-line no-empty-blocks
+    ) SpokePool(_wrappedNativeTokenAddress, _depositQuoteTimeBuffer, _fillDeadlineBuffer, OFT_FEE_CAP) {} // solhint-disable-line no-empty-blocks
 
     /**
      * @notice Initialize Linea-specific SpokePool.

contracts/Ovm_SpokePool.sol

@@ -34,6 +34,10 @@ interface IL2ERC20Bridge {
  */
 contract Ovm_SpokePool is SpokePool, CircleCCTPAdapter {
     using SafeERC20 for IERC20;
+
+    // Ovm_SpokePool does not use OFT messaging, setting the cap to 0
+    uint256 private constant OFT_FEE_CAP = 0;
+
     // "l1Gas" parameter used in call to bridge tokens from this contract back to L1 via IL2ERC20Bridge. Currently
     // unused by bridge but included for future compatibility.
     uint32 public l1Gas;
@@ -71,7 +75,7 @@ contract Ovm_SpokePool is SpokePool, CircleCCTPAdapter {
         IERC20 _l2Usdc,
         ITokenMessenger _cctpTokenMessenger
     )
-        SpokePool(_wrappedNativeTokenAddress, _depositQuoteTimeBuffer, _fillDeadlineBuffer)
+        SpokePool(_wrappedNativeTokenAddress, _depositQuoteTimeBuffer, _fillDeadlineBuffer, OFT_FEE_CAP)
         CircleCCTPAdapter(_l2Usdc, _cctpTokenMessenger, CircleDomainIds.Ethereum)
     {} // solhint-disable-line no-empty-blocks
 

contracts/PolygonZkEVM_SpokePool.sol

@@ -32,6 +32,9 @@ interface IBridgeMessageReceiver {
 contract PolygonZkEVM_SpokePool is SpokePool, IBridgeMessageReceiver {
     using SafeERC20 for IERC20;
 
+    // PolygonZkEVM_SpokePool does not use OFT messaging, setting the cap to 0
+    uint256 private constant OFT_FEE_CAP = 0;
+
     // Address of Polygon zkEVM's Canonical Bridge on L2.
     IPolygonZkEVMBridge public l2PolygonZkEVMBridge;
 
@@ -93,7 +96,7 @@ contract PolygonZkEVM_SpokePool is SpokePool, IBridgeMessageReceiver {
         address _wrappedNativeTokenAddress,
         uint32 _depositQuoteTimeBuffer,
         uint32 _fillDeadlineBuffer
-    ) SpokePool(_wrappedNativeTokenAddress, _depositQuoteTimeBuffer, _fillDeadlineBuffer) {} // solhint-disable-line no-empty-blocks
+    ) SpokePool(_wrappedNativeTokenAddress, _depositQuoteTimeBuffer, _fillDeadlineBuffer, OFT_FEE_CAP) {} // solhint-disable-line no-empty-blocks
 
     /**
      * @notice Construct the Polygon zkEVM SpokePool.

contracts/Polygon_SpokePool.sol

@@ -35,6 +35,9 @@ interface IFxMessageProcessor {
 contract Polygon_SpokePool is IFxMessageProcessor, SpokePool, CircleCCTPAdapter {
     using SafeERC20Upgradeable for PolygonIERC20Upgradeable;
 
+    // Polygon_SpokePool does not use OFT messaging, setting the cap to 0
+    uint256 private constant OFT_FEE_CAP = 0;
+
     // Address of FxChild which sends and receives messages to and from L1.
     address public fxChild;
 
@@ -87,7 +90,7 @@ contract Polygon_SpokePool is IFxMessageProcessor, SpokePool, CircleCCTPAdapter
         IERC20 _l2Usdc,
         ITokenMessenger _cctpTokenMessenger
     )
-        SpokePool(_wrappedNativeTokenAddress, _depositQuoteTimeBuffer, _fillDeadlineBuffer)
+        SpokePool(_wrappedNativeTokenAddress, _depositQuoteTimeBuffer, _fillDeadlineBuffer, OFT_FEE_CAP)
         CircleCCTPAdapter(_l2Usdc, _cctpTokenMessenger, CircleDomainIds.Ethereum)
     {} // solhint-disable-line no-empty-blocks
 

contracts/Scroll_SpokePool.sol

@@ -20,6 +20,9 @@ interface IL2GatewayRouterExtended is IL2GatewayRouter {
 contract Scroll_SpokePool is SpokePool {
     using SafeERC20Upgradeable for IERC20Upgradeable;
 
+    // Scroll_SpokePool does not use OFT messaging, setting the cap to 0
+    uint256 private constant OFT_FEE_CAP = 0;
+
     /**
      * @notice The address of the official l2GatewayRouter contract for Scroll for bridging tokens from L2 -> L1
      * @dev We can find these (main/test)net deployments here: https://docs.scroll.io/en/developers/scroll-contracts/#scroll-contracts
@@ -48,7 +51,7 @@ contract Scroll_SpokePool is SpokePool {
         address _wrappedNativeTokenAddress,
         uint32 _depositQuoteTimeBuffer,
         uint32 _fillDeadlineBuffer
-    ) SpokePool(_wrappedNativeTokenAddress, _depositQuoteTimeBuffer, _fillDeadlineBuffer) {} // solhint-disable-line no-empty-blocks
+    ) SpokePool(_wrappedNativeTokenAddress, _depositQuoteTimeBuffer, _fillDeadlineBuffer, OFT_FEE_CAP) {} // solhint-disable-line no-empty-blocks
 
     /**
      * @notice Construct the Scroll SpokePool.

contracts/SpokePool.sol

@@ -12,6 +12,7 @@ import "./upgradeable/MultiCallerUpgradeable.sol";
 import "./upgradeable/EIP712CrossChainUpgradeable.sol";
 import "./upgradeable/AddressLibUpgradeable.sol";
 import "./libraries/AddressConverters.sol";
+import "./libraries/OFTTransportAdapter.sol";
 
 import "@openzeppelin/contracts-upgradeable/token/ERC20/IERC20Upgradeable.sol";
 import "@openzeppelin/contracts-upgradeable/token/ERC20/utils/SafeERC20Upgradeable.sol";
@@ -37,7 +38,8 @@ abstract contract SpokePool is
     ReentrancyGuardUpgradeable,
     MultiCallerUpgradeable,
     EIP712CrossChainUpgradeable,
-    IDestinationSettler
+    IDestinationSettler,
+    OFTTransportAdapter
 {
     using SafeERC20Upgradeable for IERC20Upgradeable;
     using AddressLibUpgradeable for address;
@@ -111,6 +113,9 @@ abstract contract SpokePool is
     // reason (eg blacklist) to track their outstanding liability, thereby letting them claim it later.
     mapping(address => mapping(address => uint256)) public relayerRefund;
 
+    // Mapping of L2 token address to L2 IOFT messenger address. Required to support bridging via OFT standard
+    mapping(address => address) public oftMessengers;
+
     /**************************************************************
      *                CONSTANT/IMMUTABLE VARIABLES                *
      **************************************************************/
@@ -196,6 +201,7 @@ abstract contract SpokePool is
     event EmergencyDeletedRootBundle(uint256 indexed rootBundleId);
     event PausedDeposits(bool isPaused);
     event PausedFills(bool isPaused);
+    event SetOFTMessenger(address indexed token, address indexed messenger);
 
     /**
      * @notice Construct the SpokePool. Normally, logic contracts used in upgradeable proxies shouldn't
@@ -211,13 +217,15 @@ abstract contract SpokePool is
      * into the past from the block time of the deposit.
      * @param _fillDeadlineBuffer fillDeadlineBuffer to set. Fill deadlines can't be set more than this amount
      * into the future from the block time of the deposit.
+     * @param _oftFeeCap fee cap in native token when paying for cross-chain OFT transfers
      */
     /// @custom:oz-upgrades-unsafe-allow constructor
     constructor(
         address _wrappedNativeTokenAddress,
         uint32 _depositQuoteTimeBuffer,
-        uint32 _fillDeadlineBuffer
-    ) {
+        uint32 _fillDeadlineBuffer,
+        uint256 _oftFeeCap
+    ) OFTTransportAdapter(OFTEIds.Ethereum, _oftFeeCap) {
         wrappedNativeToken = WETH9Interface(_wrappedNativeTokenAddress);
         depositQuoteTimeBuffer = _depositQuoteTimeBuffer;
         fillDeadlineBuffer = _fillDeadlineBuffer;
@@ -363,6 +371,15 @@ abstract contract SpokePool is
         emit EmergencyDeletedRootBundle(rootBundleId);
     }
 
+    /**
+     * @notice Add token -> OFTMessenger relationship. Callable only by admin.
+     * @param token token address on the current chain
+     * @param messenger IOFT contract address on the current chain for the specified token. Acts as a 'mailbox'
+     */
+    function setOftMessenger(address token, address messenger) public onlyAdmin nonReentrant {
+        _setOftMessenger(token, messenger);
+    }
+
     /**************************************
      *    LEGACY DEPOSITOR FUNCTIONS      *
      **************************************/
@@ -1739,6 +1756,15 @@ abstract contract SpokePool is
         else return keccak256(message);
     }
 
+    function _setOftMessenger(address _token, address _messenger) internal {
+        oftMessengers[_token] = _messenger;
+        emit SetOFTMessenger(_token, _messenger);
+    }
+
+    function _getOftMessenger(address _token) internal view returns (address) {
+        return oftMessengers[_token];
+    }
+
     // Implementing contract needs to override this to ensure that only the appropriate cross chain admin can execute
     // certain admin functions. For L2 contracts, the cross chain admin refers to some L1 address or contract, and for
     // L1, this would just be the same admin of the HubPool.
@@ -1750,5 +1776,5 @@ abstract contract SpokePool is
     // Reserve storage slots for future versions of this base contract to add state variables without
     // affecting the storage layout of child contracts. Decrement the size of __gap whenever state variables
     // are added. This is at bottom of contract to make sure it's always at the end of storage.
-    uint256[998] private __gap;
+    uint256[997] private __gap;
 }

contracts/Succinct_SpokePool.sol

@@ -8,6 +8,9 @@ import "./external/interfaces/SuccinctInterfaces.sol";
  * @notice Succinct Spoke pool.
  */
 contract Succinct_SpokePool is SpokePool, ITelepathyHandler {
+    // Succinct_SpokePool does not use OFT messaging, setting the cap to 0
+    uint256 private constant OFT_FEE_CAP = 0;
+
     // Address of the succinct AMB contract.
     address public succinctTargetAmb;
 
@@ -47,7 +50,7 @@ contract Succinct_SpokePool is SpokePool, ITelepathyHandler {
         address _wrappedNativeTokenAddress,
         uint32 _depositQuoteTimeBuffer,
         uint32 _fillDeadlineBuffer
-    ) SpokePool(_wrappedNativeTokenAddress, _depositQuoteTimeBuffer, _fillDeadlineBuffer) {} // solhint-disable-line no-empty-blocks
+    ) SpokePool(_wrappedNativeTokenAddress, _depositQuoteTimeBuffer, _fillDeadlineBuffer, OFT_FEE_CAP) {} // solhint-disable-line no-empty-blocks
 
     /**
      * @notice Construct the Succinct SpokePool.

contracts/ZkSync_SpokePool.sol

@@ -28,6 +28,9 @@ contract ZkSync_SpokePool is SpokePool {
     // while changing only constructor parameters can lead to substantial fee savings. So, the following params
     // are all set by passing in constructor params where possible.
 
+    // ZkSync_SpokePool does not use OFT messaging, setting the cap to 0
+    uint256 private constant OFT_FEE_CAP = 0;
+
     // ETH on ZkSync implements a subset of the ERC-20 interface, with additional built-in support to bridge to L1.
     address public l2Eth;
 
@@ -41,7 +44,7 @@ contract ZkSync_SpokePool is SpokePool {
         address _wrappedNativeTokenAddress,
         uint32 _depositQuoteTimeBuffer,
         uint32 _fillDeadlineBuffer
-    ) SpokePool(_wrappedNativeTokenAddress, _depositQuoteTimeBuffer, _fillDeadlineBuffer) {} // solhint-disable-line no-empty-blocks
+    ) SpokePool(_wrappedNativeTokenAddress, _depositQuoteTimeBuffer, _fillDeadlineBuffer, OFT_FEE_CAP) {} // solhint-disable-line no-empty-blocks
 
     /**
      * @notice Construct the ZkSync SpokePool.

contracts/chain-adapters/Arbitrum_Adapter.sol

@@ -5,9 +5,12 @@
 
 import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
 import "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";
+import { IOFT } from "../interfaces/IOFT.sol";
 import "../external/interfaces/CCTPInterfaces.sol";
 import "../libraries/CircleCCTPAdapter.sol";
+import "../libraries/OFTTransportAdapter.sol";
 import { ArbitrumInboxLike as ArbitrumL1InboxLike, ArbitrumL1ERC20GatewayLike } from "../interfaces/ArbitrumBridge.sol";
+import { OFTAddressBook } from "../libraries/OFTAddressBook.sol";
 
 /**
  * @notice Contract containing logic to send messages from L1 to Arbitrum.
@@ -18,7 +21,7 @@
  */
 
 // solhint-disable-next-line contract-name-camelcase
-contract Arbitrum_Adapter is AdapterInterface, CircleCCTPAdapter {
+contract Arbitrum_Adapter is AdapterInterface, CircleCCTPAdapter, OFTTransportAdapter {
     using SafeERC20 for IERC20;
 
     // Amount of ETH allocated to pay for the base submission fee. The base submission fee is a parameter unique to
@@ -43,35 +46,46 @@
     address public constant L1_DAI = 0x6B175474E89094C44Da98b954EedeAC495271d0F;
 
     // This address on L2 receives extra ETH that is left over after relaying a message via the inbox.
     address public immutable L2_REFUND_L2_ADDRESS;
 
     // Inbox system contract to send messages to Arbitrum. Token bridges use this to send tokens to L2.
     // https://github.com/OffchainLabs/nitro-contracts/blob/f7894d3a6d4035ba60f51a7f1334f0f2d4f02dce/src/bridge/Inbox.sol
     ArbitrumL1InboxLike public immutable L1_INBOX;
 
     // Router contract to send tokens to Arbitrum. Routes to correct gateway to bridge tokens. Internally this
     // contract calls the Inbox.
     // Generic gateway: https://github.com/OffchainLabs/token-bridge-contracts/blob/main/contracts/tokenbridge/ethereum/gateway/L1ArbitrumGateway.sol
     ArbitrumL1ERC20GatewayLike public immutable L1_ERC20_GATEWAY_ROUTER;
 
+    // Helper contract to help us map token -> OFT messenger for OFT-enabled tokens
+    OFTAddressBook public immutable OFT_ADDRESS_BOOK;
+
     /**
      * @notice Constructs new Adapter.
      * @param _l1ArbitrumInbox Inbox helper contract to send messages to Arbitrum.
      * @param _l1ERC20GatewayRouter ERC20 gateway router contract to send tokens to Arbitrum.
      * @param _l2RefundL2Address L2 address to receive gas refunds on after a message is relayed.
      * @param _l1Usdc USDC address on L1.
      * @param _cctpTokenMessenger TokenMessenger contract to bridge via CCTP.
+     * @param _oftAddressBook OFTAddressBook contract to help identify token -> oftMessenger relationship for OFT bridging.
+     * @param _oftFeeCap A fee cap we apply to OFT bridge native payment. A good default is 1 ether
      */
     constructor(
         ArbitrumL1InboxLike _l1ArbitrumInbox,
         ArbitrumL1ERC20GatewayLike _l1ERC20GatewayRouter,
         address _l2RefundL2Address,
         IERC20 _l1Usdc,
-        ITokenMessenger _cctpTokenMessenger
-    ) CircleCCTPAdapter(_l1Usdc, _cctpTokenMessenger, CircleDomainIds.Arbitrum) {
+        ITokenMessenger _cctpTokenMessenger,
+        OFTAddressBook _oftAddressBook,
+        uint256 _oftFeeCap
+    )
+        CircleCCTPAdapter(_l1Usdc, _cctpTokenMessenger, CircleDomainIds.Arbitrum)
+        OFTTransportAdapter(OFTEIds.Arbitrum, _oftFeeCap)
+    {
         L1_INBOX = _l1ArbitrumInbox;
         L1_ERC20_GATEWAY_ROUTER = _l1ERC20GatewayRouter;
         L2_REFUND_L2_ADDRESS = _l2RefundL2Address;
+        OFT_ADDRESS_BOOK = _oftAddressBook;
     }
 
     /**
@@ -113,9 +127,13 @@
         uint256 amount,
         address to
     ) external payable override {
+        address oftMessenger = _getOftMessenger(l1Token);
+
         // Check if this token is USDC, which requires a custom bridge via CCTP.
         if (_isCCTPEnabled() && l1Token == address(usdcToken)) {
             _transferUsdc(to, amount);
+        } else if (oftMessenger != address(0)) {
+            _transferViaOFT(IERC20(l1Token), IOFT(oftMessenger), to, amount);
         }
         // If not, we can use the Arbitrum gateway
         else {
@@ -178,4 +196,13 @@
         require(address(this).balance >= requiredL1CallValue, "Insufficient ETH balance");
         return requiredL1CallValue;
     }
+
+    /**
+     * @notice Queries for an OFT messenger from an OFT address book contract
+     * @param _token Token to query the messenger for
+     * @return messenger OFT messenger contract
+     */
+    function _getOftMessenger(address _token) internal view returns (address) {
+        return OFT_ADDRESS_BOOK.oftMessengers(_token);
+    }
 }