Flash Loans

Flash loans are handled through contracts implementing the following two interfaces: IBorrower and IFlashLoanRouter.

IFlashLoanRouter contract

This contract manages all flash-loan requests and is eventually responsible for executing the settlement.

Data Types and Storage

interface IFlashLoanRouter {
    function flashLoanAndSettle(Loan.Data[] calldata loans, bytes calldata settlement) external;
    function borrowerCallBack(bytes calldata encodedLoansWithSettlement) external;
    function settlementContract() external returns (ICowSettlement);
    function settlementAuthentication() external returns (ICowAuthentication);
}

Functions

flashLoanAndSettle

Request all flash loan specified in the input and, after that, executes the specified settlement.

flashLoanAndSettle(Loan.Data[] calldata loans, bytes calldata settlement) external;

Parameter	Description
loans	The list of flash loans to be requested before the settlement is executed. The loans will be requested in the specified order
settlement	The ABI-encoded bytes for a call to settle() (as in abi.encodeCall)

borrowerCallBack

Once a borrower has received the proceeds of a flash loan, it calls back the router through this function.

borrowerCallBack(bytes calldata encodedLoansWithSettlement) external;

Parameter	Description
encodedLoansWithSettlement	The data the borrower received when it was called, without any modification

settlementContract

The settlement contract supported by this router. This is the contract that will be called when the settlement is executed.

settlementContract() external returns (ICowSettlement);

settlementAuthentication

The settlement authenticator contract for CoW Protocol. This contract determines whether CoW protocol considers an address an eligible solver.

settlementAuthentication() external returns (ICowAuthentication);

IBorrower contract

IBorrower is an abstraction around specific flash-loan providers. Each provider has slightly different syntax for the loan request, as well as for the function that is called back. The borrower contract abstracts this away for the router.

Data Types and Storage

interface IBorrower {
    function flashLoanAndCallBack(address lender, IERC20 token, uint256 amount, bytes calldata callBackData) external;
    function approve(IERC20 token, address target, uint256 amount) external;
    function settlementContract() external view returns (ICowSettlement);
    function router() external view returns (IFlashLoanRouter);
}

Functions

flashLoanAndCallBack

Requests a flash loan with the specified parameters from the lender and, once the funds have been received, call back the router while passing through the specified custom data. The flash-loan repayment is expected to take place during the final settlement in the router.

flashLoanAndCallBack(address lender, IERC20 token, uint256 amount, bytes calldata callBackData) external;

Parameter	Description
lender	The address of the flash-loan lender from which to borrow
token	The token that is requested in the flash loan
amount	The amount of funds requested from the lender
callBackData	The data to send back when calling the router once the loan is received

approve

Approves the target address to spend the specified token on behalf of the Borrower up to the specified amount.

approve(IERC20 token, address target, uint256 amount) external;

Parameter	Description
token	The token to approve for transferring
target	The address that will be allowed to spend the token
amount	The amount of tokens to set as the allowance

settlementContract

The settlement contract supported by this contract.

settlementContract() external view returns (ICowSettlement);

router

The router contract that manages this borrower contract. It will be called back once the flash-loan proceeds are received and is the only address that can trigger a flash loan request.

router() external view returns (IFlashLoanRouter);