Outbox
The Outbox
is a contract deployed on L1 that handles message passing from the rollup and to L1.
Links: Interface, Implementation.
insert()
Inserts the root of a merkle tree containing all of the L2 to L1 messages in a block specified by _l2BlockNumber.
outbox_insert
/**
* @notice Inserts the root of a merkle tree containing all of the L2 to L1 messages in
* a block specified by _l2BlockNumber.
* @dev Only callable by the rollup contract
* @dev Emits `RootAdded` upon inserting the root successfully
* @param _l2BlockNumber - The L2 Block Number in which the L2 to L1 messages reside
* @param _root - The merkle root of the tree where all the L2 to L1 messages are leaves
* @param _minHeight - The min height of the merkle tree that the root corresponds to
*/
function insert(uint256 _l2BlockNumber, bytes32 _root, uint256 _minHeight) external;
Source code: l1-contracts/src/core/interfaces/messagebridge/IOutbox.sol#L22-L33
Name | Type | Description |
---|---|---|
_l2BlockNumber | uint256 | The L2 Block Number in which the L2 to L1 messages reside |
_root | bytes32 | The merkle root of the tree where all the L2 to L1 messages are leaves |
_minHeight | uint256 | The minimum height of the merkle tree that the root corresponds to |
Edge cases
- Will revert with
Outbox__Unauthorized()
ifmsg.sender != ROLLUP_CONTRACT
. - Will revert with
Errors.Outbox__RootAlreadySetAtBlock(uint256 l2BlockNumber)
if the root for the specific block has already been set. - Will revert with
Errors.Outbox__InsertingInvalidRoot()
if the rollup is trying to insert bytes32(0) as the root.
consume()
Allows a recipient to consume a message from the Outbox
.
outbox_consume
/**
* @notice Consumes an entry from the Outbox
* @dev Only useable by portals / recipients of messages
* @dev Emits `MessageConsumed` when consuming messages
* @param _message - The L2 to L1 message
* @param _l2BlockNumber - The block number specifying the block that contains the message we want to consume
* @param _leafIndex - The index inside the merkle tree where the message is located
* @param _path - The sibling path used to prove inclusion of the message, the _path length directly depends
* on the total amount of L2 to L1 messages in the block. i.e. the length of _path is equal to the depth of the
* L1 to L2 message tree.
*/
function consume(
DataStructures.L2ToL1Msg calldata _message,
uint256 _l2BlockNumber,
uint256 _leafIndex,
bytes32[] calldata _path
) external;
Source code: l1-contracts/src/core/interfaces/messagebridge/IOutbox.sol#L35-L53
Name | Type | Description |
---|---|---|
_message | L2ToL1Msg | The L2 to L1 message we want to consume |
_l2BlockNumber | uint256 | The block number specifying the block that contains the message we want to consume |
_leafIndex | uint256 | The index inside the merkle tree where the message is located |
_path | bytes32[] | The sibling path used to prove inclusion of the message, the _path length directly depends |
Edge cases
- Will revert with
Outbox__InvalidRecipient(address expected, address actual);
ifmsg.sender != _message.recipient.actor
. - Will revert with
Outbox__InvalidChainId()
ifblock.chainid != _message.recipient.chainId
. - Will revert with
Outbox__NothingToConsumeAtBlock(uint256 l2BlockNumber)
if the root for the block has not been set yet. - Will revert with
Outbox__AlreadyNullified(uint256 l2BlockNumber, uint256 leafIndex)
if the message at leafIndex for the block has already been consumed. - Will revert with
Outbox__InvalidPathLength(uint256 expected, uint256 actual)
if the the supplied height is less than the existing minimum height of the L2 to L1 message tree, or the supplied height is greater than the maximum (minimum height + log2(maximum messages)). - Will revert with
MerkleLib__InvalidRoot(bytes32 expected, bytes32 actual, bytes32 leaf, uint256 leafIndex)
if unable to verify the message existence in the tree. It returns the message as a leaf, as well as the index of the leaf to expose more info about the error.
hasMessageBeenConsumedAtBlockAndIndex()
Checks to see if an index of the L2 to L1 message tree for a specific block has been consumed.
outbox_has_message_been_consumed_at_block_and_index
/**
* @notice Checks to see if an index of the L2 to L1 message tree for a specific block has been consumed
* @dev - This function does not throw. Out-of-bounds access is considered valid, but will always return false
* @param _l2BlockNumber - The block number specifying the block that contains the index of the message we want to check
* @param _leafIndex - The index of the message inside the merkle tree
*/
function hasMessageBeenConsumedAtBlockAndIndex(uint256 _l2BlockNumber, uint256 _leafIndex)
external
view
returns (bool);
Source code: l1-contracts/src/core/interfaces/messagebridge/IOutbox.sol#L55-L66
Name | Type | Description |
---|---|---|
_l2BlockNumber | uint256 | The block number specifying the block that contains the index of the message we want to check |
_leafIndex | uint256 | The index of the message inside the merkle tree |
Edge cases
- This function does not throw. Out-of-bounds access is considered valid, but will always return false.