Router Library

Application developers looking to write their contracts once and deploy them on multiple chains should consider building with the Router pattern.

In this pattern, an instance of the application's contracts is deployed on each application-supported chain. Each instance is made aware of the addresses of instances on other chains. These instances use Hyperlane to communicate information and state to and from instances on remote chains.

Developers using this pattern can inherit from the Router mix-in contract. Router is a MailboxClient that tracks the addresses of other Router contract addresses on remote chains. This allows Routers to send messages directly to others without having to specify addresses. It also allows Routers to reject messages sent from other untrusted senders.

// SPDX-License-Identifier: MIT OR Apache-2.0
pragma solidity >=0.6.11;

// ============ Internal Imports ============
import {IMessageRecipient} from "../interfaces/IMessageRecipient.sol";
import {IPostDispatchHook} from "../interfaces/hooks/IPostDispatchHook.sol";
import {IInterchainSecurityModule} from "../interfaces/IInterchainSecurityModule.sol";
import {MailboxClient} from "./MailboxClient.sol";
import {EnumerableMapExtended} from "../libs/EnumerableMapExtended.sol";

// ============ External Imports ============
import {Strings} from "@openzeppelin/contracts/utils/Strings.sol";

abstract contract Router is MailboxClient, IMessageRecipient {
    using EnumerableMapExtended for EnumerableMapExtended.UintToBytes32Map;
    using Strings for uint32;

    // ============ Mutable Storage ============
    EnumerableMapExtended.UintToBytes32Map internal _routers;

    uint256[48] private __GAP; // gap for upgrade safety

    constructor(address _mailbox) MailboxClient(_mailbox) {}

    // ============ External functions ============
    function domains() external view returns (uint32[] memory) {
        return _routers.uint32Keys();
    }

    /**
     * @notice Returns the address of the Router contract for the given domain
     * @param _domain The remote domain ID.
     * @dev Returns 0 address if no router is enrolled for the given domain
     * @return router The address of the Router contract for the given domain
     */
    function routers(uint32 _domain) public view virtual returns (bytes32) {
        (, bytes32 _router) = _routers.tryGet(_domain);
        return _router;
    }

    /**
     * @notice Unregister the domain
     * @param _domain The domain of the remote Application Router
     */
    function unenrollRemoteRouter(uint32 _domain) external virtual onlyOwner {
        _unenrollRemoteRouter(_domain);
    }

    /**
     * @notice Register the address of a Router contract for the same Application on a remote chain
     * @param _domain The domain of the remote Application Router
     * @param _router The address of the remote Application Router
     */
    function enrollRemoteRouter(
        uint32 _domain,
        bytes32 _router
    ) external virtual onlyOwner {
        _enrollRemoteRouter(_domain, _router);
    }

    /**
     * @notice Batch version of `enrollRemoteRouter`
     * @param _domains The domains of the remote Application Routers
     * @param _addresses The addresses of the remote Application Routers
     */
    function enrollRemoteRouters(
        uint32[] calldata _domains,
        bytes32[] calldata _addresses
    ) external virtual onlyOwner {
        require(_domains.length == _addresses.length, "!length");
        uint256 length = _domains.length;
        for (uint256 i = 0; i < length; i += 1) {
            _enrollRemoteRouter(_domains[i], _addresses[i]);
        }
    }

    /**
     * @notice Batch version of `unenrollRemoteRouter`
     * @param _domains The domains of the remote Application Routers
     */
    function unenrollRemoteRouters(
        uint32[] calldata _domains
    ) external virtual onlyOwner {
        uint256 length = _domains.length;
        for (uint256 i = 0; i < length; i += 1) {
            _unenrollRemoteRouter(_domains[i]);
        }
    }

    /**
     * @notice Handles an incoming message
     * @param _origin The origin domain
     * @param _sender The sender address
     * @param _message The message
     */
    function handle(
        uint32 _origin,
        bytes32 _sender,
        bytes calldata _message
    ) external payable virtual override onlyMailbox {
        bytes32 _router = _mustHaveRemoteRouter(_origin);
        require(_router == _sender, "Enrolled router does not match sender");
        _handle(_origin, _sender, _message);
    }

    // ============ Virtual functions ============
    function _handle(
        uint32 _origin,
        bytes32 _sender,
        bytes calldata _message
    ) internal virtual;

    // ============ Internal functions ============

    /**
     * @notice Set the router for a given domain
     * @param _domain The domain
     * @param _address The new router
     */
    function _enrollRemoteRouter(
        uint32 _domain,
        bytes32 _address
    ) internal virtual {
        _routers.set(_domain, _address);
    }

    /**
     * @notice Remove the router for a given domain
     * @param _domain The domain
     */
    function _unenrollRemoteRouter(uint32 _domain) internal virtual {
        require(_routers.remove(_domain), _domainNotFoundError(_domain));
    }

    /**
     * @notice Return true if the given domain / router is the address of a remote Application Router
     * @param _domain The domain of the potential remote Application Router
     * @param _address The address of the potential remote Application Router
     */
    function _isRemoteRouter(
        uint32 _domain,
        bytes32 _address
    ) internal view returns (bool) {
        return routers(_domain) == _address;
    }

    /**
     * @notice Assert that the given domain has a Application Router registered and return its address
     * @param _domain The domain of the chain for which to get the Application Router
     * @return _router The address of the remote Application Router on _domain
     */
    function _mustHaveRemoteRouter(
        uint32 _domain
    ) internal view returns (bytes32) {
        (bool contained, bytes32 _router) = _routers.tryGet(_domain);
        if (contained) {
            return _router;
        }
        revert(_domainNotFoundError(_domain));
    }

    function _domainNotFoundError(
        uint32 _domain
    ) internal pure returns (string memory) {
        return
            string.concat(
                "No router enrolled for domain: ",
                _domain.toString()
            );
    }

    function _Router_dispatch(
        uint32 _destinationDomain,
        uint256 _value,
        bytes memory _messageBody,
        bytes memory _hookMetadata,
        address _hook
    ) internal returns (bytes32) {
        bytes32 _router = _mustHaveRemoteRouter(_destinationDomain);
        return
            mailbox.dispatch{value: _value}(
                _destinationDomain,
                _router,
                _messageBody,
                _hookMetadata,
                IPostDispatchHook(_hook)
            );
    }

    /**
     * DEPRECATED: Use `_Router_dispatch` instead
     * @dev For backward compatibility with v2 client contracts
     */
    function _dispatch(
        uint32 _destinationDomain,
        bytes memory _messageBody
    ) internal returns (bytes32) {
        return
            _Router_dispatch(
                _destinationDomain,
                msg.value,
                _messageBody,
                "",
                address(hook)
            );
    }

    function _Router_quoteDispatch(
        uint32 _destinationDomain,
        bytes memory _messageBody,
        bytes memory _hookMetadata,
        address _hook
    ) internal view returns (uint256) {
        bytes32 _router = _mustHaveRemoteRouter(_destinationDomain);
        return
            mailbox.quoteDispatch(
                _destinationDomain,
                _router,
                _messageBody,
                _hookMetadata,
                IPostDispatchHook(_hook)
            );
    }

    /**
     * DEPRECATED: Use `_Router_quoteDispatch` instead
     * @dev For backward compatibility with v2 client contracts
     */
    function _quoteDispatch(
        uint32 _destinationDomain,
        bytes memory _messageBody
    ) internal view returns (uint256) {
        return
            _Router_quoteDispatch(
                _destinationDomain,
                _messageBody,
                "",
                address(hook)
            );
    }
}