Router // batch

Msg.sender

Pool

contract Pool {

    uint256 public num;
    address public msgSender;

    function setVars(uint256 _num, address onBehalfOf) public {
        num = _num;
        msgSender = onBehalfOf;
    }
}

• msgSender here will be empty 0x0, on deployment

Router

// SPDX-License-Identifier: UNLICENSED
pragma solidity 0.8.22;

contract Router {

    Pool public pool;

    /// @dev Helper function to extract a useful revert message from a failed call.
    /// If the returned data is malformed or not correctly abi encoded then this call can fail itself.
    function getRevertMsg(bytes memory returnData) internal pure returns (string memory)
    {
        // If the _res length is less than 68, then the transaction failed silently (without a revert message)
        if (returnData.length < 68) return "Transaction reverted silently";

        assembly {
            // Slice the sighash.
            returnData := add(returnData, 0x04)
        }

        return abi.decode(returnData, (string)); // All that remains is the revert string
    }

    /// @dev Allows batched call to self (this contract).
    /// @param calls An array of inputs for each call.
    function batch(bytes[] memory calls) public payable returns(bytes[] memory results) {

        results = new bytes[](calls.length);

        for (uint256 i; i < calls.length; i++) {

            (bool success, bytes memory result) = address(this).delegatecall(calls[i]);
            if (!success) revert(getRevertMsg(result));
            results[i] = result;
        }
    }


    function test(uint _num, address onBehalfOf) public {

        bytes memory payload = abi.encodeWithSignature("setVars(uint256,address)", _num, onBehalfOf);
        
        bytes[] memory allCalls = new bytes[](1);
        allCalls[0] = payload;

        batch(allCalls);
    }


    function setVars(uint _num, address onBehalfOf) external payable {
        pool.setVars(_num, onBehalfOf);
    }

    function setPool(address pool_) public {
        pool = Pool(pool_);
    }
}

• First we connect the Router to the Pool contract by calling setPool on the Router.

• Then we call test, passing in values for num and some address of choice.

• Notice that msgSender in Pool was updated with our input value.

Hence, the batch fn in Router, does pass on the correct input values through delegateCall.

Use of msg.sender in Router

What if we pass msg.sender in batch, instead of defining it as an input address?

In this example, we modify test() to use msg.sender

// SPDX-License-Identifier: UNLICENSED
pragma solidity 0.8.22;

contract Router {

    Pool public pool;


    /// @dev Helper function to extract a useful revert message from a failed call.
    /// If the returned data is malformed or not correctly abi encoded then this call can fail itself.
    function getRevertMsg(bytes memory returnData) internal pure returns (string memory)
    {
        // If the _res length is less than 68, then the transaction failed silently (without a revert message)
        if (returnData.length < 68) return "Transaction reverted silently";

        assembly {
            // Slice the sighash.
            returnData := add(returnData, 0x04)
        }

        return abi.decode(returnData, (string)); // All that remains is the revert string
    }

    /// @dev Allows batched call to self (this contract).
    /// @param calls An array of inputs for each call.
    function batch(bytes[] memory calls) public payable returns(bytes[] memory results) {

        results = new bytes[](calls.length);

        for (uint256 i; i < calls.length; i++) {

            (bool success, bytes memory result) = address(this).delegatecall(calls[i]);

            if (!success) revert(getRevertMsg(result));

            results[i] = result;
        }

    }


    function test(uint _num) public {

        bytes memory payload = abi.encodeWithSignature("setVars(uint256,address)", _num, msg.sender);
        
        bytes[] memory allCalls = new bytes[](1);
        allCalls[0] = payload;

        batch(allCalls);
    }


    function setVars(uint _num, address onBehalfOf) external payable {
        pool.setVars(_num, onBehalfOf);
    }

    function setPool(address pool_) public {
        pool = Pool(pool_);
    }
}

contract Pool {

    uint256 public num;
    address public msgSender;

    function setVars(uint256 _num, address onBehalfOf) public {
        num = _num;
        msgSender = onBehalfOf;
    }
}

• msgSender in Pool reflects the wallet address that initiated the function.

• meaning to say, batch() in Router does forward the correct msg.sender value to Pool.