Remove drop messages function

contracts/contracts/l1/IL1CrossDomainMessenger.sol

@@ -37,10 +37,6 @@ interface IL1CrossDomainMessenger is ICrossDomainMessenger {
         bytes message
     );
 
-    /// @notice Emitted when have message dropped.
-    /// @param nonce The index of the message to be dropped.
-    event DropMessage(uint256 indexed nonce);
-
     /*****************************
      * Public Mutating Functions *
      *****************************/
@@ -80,12 +76,4 @@ interface IL1CrossDomainMessenger is ICrossDomainMessenger {
         uint32 newGasLimit,
         address refundAddress
     ) external payable;
-
-    /// @notice Drop a skipped message.
-    /// @param from The address of the sender of the message.
-    /// @param to The address of the recipient of the message.
-    /// @param value The msg.value passed to the message call.
-    /// @param messageNonce The nonce for the message to drop.
-    /// @param message The content of the message.
-    function dropMessage(address from, address to, uint256 value, uint256 messageNonce, bytes memory message) external;
 }

contracts/contracts/l1/L1CrossDomainMessenger.sol

@@ -42,7 +42,7 @@ contract L1CrossDomainMessenger is IL1CrossDomainMessenger, CrossDomainMessenger
     mapping(bytes32 => uint256) public messageSendTimestamp;
 
     /// @notice Mapping from L1 message hash to drop status.
-    mapping(bytes32 => bool) public isL1MessageDropped;
+    mapping(bytes32 => bool) public __isL1MessageDropped;
 
     /// @notice The address of Rollup contract.
     address public rollup;
@@ -192,7 +192,7 @@ contract L1CrossDomainMessenger is IL1CrossDomainMessenger, CrossDomainMessenger
 
         require(messageSendTimestamp[_xDomainCalldataHash] > 0, "Provided message has not been enqueued");
         // cannot replay dropped message
-        require(!isL1MessageDropped[_xDomainCalldataHash], "Message already dropped");
+        require(!__isL1MessageDropped[_xDomainCalldataHash], "Message already dropped");
 
         // compute and deduct the messaging fee to fee vault.
         uint256 _fee = IL1MessageQueue(_messageQueue).estimateCrossDomainMessageFee(_from, _newGasLimit);
@@ -243,61 +243,6 @@ contract L1CrossDomainMessenger is IL1CrossDomainMessenger, CrossDomainMessenger
         }
     }
 
-    /// @inheritdoc IL1CrossDomainMessenger
-    function dropMessage(
-        address _from,
-        address _to,
-        uint256 _value,
-        uint256 _messageNonce,
-        bytes memory _message
-    ) external override whenNotPaused notInExecution {
-        // The criteria for dropping a message:
-        // 1. The message is a L1 message.
-        // 2. The message has not been dropped before.
-        // 3. the message and all of its replacement are finalized in L1.
-        // 4. the message and all of its replacement are skipped.
-        //
-        // Possible denial of service attack:
-        // + replayMessage is called every time someone want to drop the message.
-        // + replayMessage is called so many times for a skipped message, thus results a long list.
-        //
-        // We limit the number of `replayMessage` calls of each message, which may solve the above problem.
-
-        address _messageQueue = messageQueue;
-
-        // check message exists
-        bytes memory _xDomainCalldata = _encodeXDomainCalldata(_from, _to, _value, _messageNonce, _message);
-        bytes32 _xDomainCalldataHash = keccak256(_xDomainCalldata);
-        require(messageSendTimestamp[_xDomainCalldataHash] > 0, "Provided message has not been enqueued");
-
-        // check message not dropped
-        require(!isL1MessageDropped[_xDomainCalldataHash], "Message already dropped");
-
-        // check message is finalized
-        uint256 _lastIndex = replayStates[_xDomainCalldataHash].lastIndex;
-        if (_lastIndex == 0) _lastIndex = _messageNonce;
-
-        // check message is skipped and drop it.
-        // @note If the list is very long, the message may never be dropped.
-        while (true) {
-            IL1MessageQueue(_messageQueue).dropCrossDomainMessage(_lastIndex);
-            _lastIndex = prevReplayIndex[_lastIndex];
-            if (_lastIndex == 0) break;
-            unchecked {
-                _lastIndex = _lastIndex - 1;
-            }
-        }
-
-        isL1MessageDropped[_xDomainCalldataHash] = true;
-        emit DropMessage(_messageNonce);
-
-        // set execution context
-        xDomainMessageSender = Constants.DROP_XDOMAIN_MESSAGE_SENDER;
-        IMessageDropCallback(_from).onDropMessage{value: _value}(_message);
-        // clear execution context
-        xDomainMessageSender = Constants.DEFAULT_XDOMAIN_MESSAGE_SENDER;
-    }
-
     /************************
      * Restricted Functions *
      ************************/

contracts/contracts/l1/rollup/IL1MessageQueue.sol

@@ -35,10 +35,6 @@ interface IL1MessageQueue {
     /// @param count The number of messages popped.
     event DequeueTransaction(uint256 startIndex, uint256 count);
 
-    /// @notice Emitted when a message is dropped from L1.
-    /// @param index The index of message dropped.
-    event DropTransaction(uint256 index);
-
     /// @notice Emitted when owner updates gas oracle contract.
     /// @param _oldGasOracle The address of old gas oracle contract.
     /// @param _newGasOracle The address of new gas oracle contract.
@@ -95,10 +91,6 @@ interface IL1MessageQueue {
         bytes calldata data
     ) external view returns (bytes32);
 
-    /// @notice Return whether the message is dropped.
-    /// @param queueIndex The queue index of the message to check.
-    function isMessageDropped(uint256 queueIndex) external view returns (bool);
-
     /*****************************
      * Public Mutating Functions *
      *****************************/
@@ -132,7 +124,4 @@ interface IL1MessageQueue {
     /// @param startIndex The start index to pop.
     /// @param count The number of messages to pop.
     function popCrossDomainMessage(uint256 startIndex, uint256 count) external;
-
-    /// @notice Drop a skipped message from the queue.
-    function dropCrossDomainMessage(uint256 index) external;
 }

contracts/contracts/l1/rollup/L1MessageQueueWithGasPriceOracle.sol

@@ -48,8 +48,8 @@ contract L1MessageQueueWithGasPriceOracle is OwnableUpgradeable, IL1MessageQueue
     /// @notice The max gas limit of L1 transactions.
     uint256 public maxGasLimit;
 
-    /// @dev The bitmap for dropped messages, where `droppedMessageBitmap[i]` keeps the bits from `[i*256, (i+1)*256)`.
-    BitMapsUpgradeable.BitMap private droppedMessageBitmap;
+    /// @dev The bitmap for dropped messages, where `droppedMessageBitmap[i]` keeps the bits from `[i*256, (i+1)*256)`. Deprecated.
+    BitMapsUpgradeable.BitMap private __droppedMessageBitmap;
 
     /// @dev The bitmap for skipped messages, where `skippedMessageBitmap[i]` keeps the bits from `[i*256, (i+1)*256)`. Deprecated.
     mapping(uint256 => uint256) private __skippedMessageBitmap;
@@ -260,11 +260,6 @@ contract L1MessageQueueWithGasPriceOracle is OwnableUpgradeable, IL1MessageQueue
         return hash;
     }
 
-    /// @inheritdoc IL1MessageQueue
-    function isMessageDropped(uint256 _queueIndex) external view returns (bool) {
-        return droppedMessageBitmap.get(_queueIndex);
-    }
-
     /*****************************
      * Public Mutating Functions *
      *****************************/
@@ -325,16 +320,6 @@ contract L1MessageQueueWithGasPriceOracle is OwnableUpgradeable, IL1MessageQueue
         emit DequeueTransaction(_startIndex, _count);
     }
 
-    /// @inheritdoc IL1MessageQueue
-    function dropCrossDomainMessage(uint256 _index) external onlyMessenger {
-        require(_index < pendingQueueIndex, "cannot drop pending message");
-
-        require(!droppedMessageBitmap.get(_index), "message already dropped");
-        droppedMessageBitmap.set(_index);
-
-        emit DropTransaction(_index);
-    }
-
     /************************
      * Restricted Functions *
      ************************/