migrate ether on upgrade

contracts/src/Agent.sol

@@ -20,8 +20,7 @@ contract Agent {
     }
 
     /// @dev Agents can receive ether permissionlessly.
-    /// This is important, as agents for top-level parachains also act as sovereign accounts from which message relayers
-    /// are rewarded.
+    /// This is important, as agents are used to lock ether.
     receive() external payable {}
 
     /// @dev Allow the gateway to invoke some code within the context of this agent

contracts/src/AgentExecutor.sol

@@ -6,6 +6,7 @@ import {AgentExecuteCommand, ParaID} from "./Types.sol";
 import {SubstrateTypes} from "./SubstrateTypes.sol";
 
 import {IERC20} from "./interfaces/IERC20.sol";
+import {IGateway} from "./interfaces/IGateway.sol";
 import {SafeTokenTransfer, SafeNativeTransfer} from "./utils/SafeTransfer.sol";
 
 /// @title Code which will run within an `Agent` using `delegatecall`.
@@ -16,11 +17,15 @@ contract AgentExecutor {
 
     /// @dev Transfer ether to `recipient`. Unlike `_transferToken` This logic is not nested within `execute`,
     /// as the gateway needs to control an agent's ether balance directly.
-    ///
     function transferNative(address payable recipient, uint256 amount) external {
         recipient.safeNativeTransfer(amount);
     }
 
+    /// @dev Transfer ether to Gateway. Used once off for migration purposes. Can be removed after version 1.
+    function transferNativeToGateway(address payable gateway, uint256 amount) external {
+        IGateway(gateway).depositEther{value: amount}();
+    }
+
     /// @dev Transfer ERC20 to `recipient`. Only callable via `execute`.
     function transferToken(address token, address recipient, uint128 amount) external {
         _transferToken(token, recipient, amount);

contracts/src/Gateway.sol

@@ -281,6 +281,17 @@ contract Gateway is IGateway, IInitializable, IUpgradable {
         return ERC1967.load();
     }
 
+    function version() public view returns (uint64) {
+        return CoreStorage.layout().version;
+    }
+
+    /**
+     * Fee management
+     */
+    function depositEther() external payable {
+        emit EtherDeposited(msg.sender, msg.value);
+    }
+
     /**
      * Handlers
      */

contracts/src/GatewayProxy.sol

@@ -37,6 +37,9 @@ contract GatewayProxy is IInitializable {
         }
     }
 
-    // Allow the Gateway proxy to receive ether in order to pay out rewards and refunds
-    receive() external payable {}
+    // Prevent users from unwittingly sending ether to the gateway, as these funds
+    // would otherwise be lost forever.
+    receive() external payable {
+        revert NativeCurrencyNotAccepted();
+    }
 }

contracts/src/interfaces/IGateway.sol

@@ -38,6 +38,9 @@ interface IGateway {
     // Emitted when foreign token from polkadot registed
     event ForeignTokenRegistered(bytes32 indexed tokenID, address token);
 
+    // Emitted when ether is deposited
+    event EtherDeposited(address who, uint256 amount);
+
     /**
      * Getters
      */
@@ -53,6 +56,13 @@ interface IGateway {
 
     function implementation() external view returns (address);
 
+    function version() external view returns (uint64);
+
+    /**
+     * Fee management
+     */
+    function depositEther() external payable;
+
     /**
      * Messaging
      */

contracts/src/storage/CoreStorage.sol

@@ -14,6 +14,8 @@ library CoreStorage {
         mapping(bytes32 agentID => address) agents;
         // Agent addresses
         mapping(address agent => bytes32 agentID) agentAddresses;
+        // Version of the Gateway Implementation
+        uint64 version;
     }
 
     bytes32 internal constant SLOT = keccak256("org.snowbridge.storage.core");

contracts/src/upgrades/Gateway202410.sol

@@ -25,10 +25,23 @@ contract Gateway202410 is Gateway {
     {}
 
     // Override parent initializer to prevent re-initialization of storage.
-    function initialize(bytes memory) external view override {
+    function initialize(bytes memory) external override {
         // Ensure that arbitrary users cannot initialize storage in this logic contract.
         if (ERC1967.load() == address(0)) {
             revert Unauthorized();
         }
+
+        // We expect version 0, deploying version 1.
+        CoreStorage.Layout storage $ = CoreStorage.layout();
+        if ($.version != 0) {
+            revert Unauthorized();
+        }
+        $.version = 1;
+
+        // migrate asset hub agent
+        address agent = _ensureAgent(hex"81c5ab2571199e3188135178f3c2c8e2d268be1313d029b30f534fa579b69b79");
+        bytes memory call =
+            abi.encodeCall(AgentExecutor.transferNativeToGateway, (payable(address(this)), agent.balance));
+        _invokeOnAgent(agent, call);
     }
 }

contracts/test/ForkUpgrade.t.sol → contracts/test/ForkUpgrade202410.t.sol

@@ -16,6 +16,7 @@ contract ForkUpgradeTest is Test {
     address private constant GatewayProxy = 0x27ca963C279c93801941e1eB8799c23f407d68e7;
     address private constant BeefyClient = 0x6eD05bAa904df3DE117EcFa638d4CB84e1B8A00C;
     bytes32 private constant BridgeHubAgent = 0x03170a2e7597b7b7e3d84c05391d139a62b157e78786d8c082f29dcf4c111314;
+    bytes32 private constant AssetHubAgent = 0x81c5ab2571199e3188135178f3c2c8e2d268be1313d029b30f534fa579b69b79;
 
     function setUp() public {
         vm.createSelectFork("https://rpc.tenderly.co/fork/b77e07b8-ad6d-4e83-b5be-30a2001964aa", 20645700);
@@ -33,10 +34,20 @@ contract ForkUpgradeTest is Test {
         UpgradeParams memory params =
             UpgradeParams({impl: address(newLogic), implCodeHash: address(newLogic).codehash, initParams: bytes("")});
 
-        vm.expectEmit(true, false, false, false);
+        Gateway gateway = Gateway(GatewayProxy);
+
+        // Check pre-migration of ETH from Asset Hub agent
+        assertGt(IGateway(GatewayProxy).agentOf(AssetHubAgent).balance, 0);
+        // Check pre-migration of ETH to Gateway
+        assertEq(address(GatewayProxy).balance, 0);
+
+        vm.expectEmit();
+        emit IGateway.EtherDeposited(gateway.agentOf(AssetHubAgent), 587928061927368450);
+
+        vm.expectEmit();
         emit IUpgradable.Upgraded(address(newLogic));
 
-        Gateway(GatewayProxy).upgrade(abi.encode(params));
+        gateway.upgrade(abi.encode(params));
     }
 
     function checkLegacyToken() public {
@@ -60,6 +71,12 @@ contract ForkUpgradeTest is Test {
     }
 
     function testSanityCheck() public {
+        // Check that the version is correctly set.
+        assertEq(IGateway(GatewayProxy).version(), 1);
+        // Check migration of ETH from Asset Hub agent
+        assertEq(IGateway(GatewayProxy).agentOf(AssetHubAgent).balance, 0);
+        // Check migration of ETH to Gateway
+        assertGt(address(GatewayProxy).balance, 0);
         // Check AH channel nonces as expected
         (uint64 inbound, uint64 outbound) = IGateway(GatewayProxy).channelNoncesOf(
             ChannelID.wrap(0xc173fac324158e77fb5840738a1a541f633cbec8884c6a601c567d2b376a0539)

contracts/test/Gateway.t.sol

@@ -401,8 +401,11 @@ contract GatewayTest is Test {
 
         assertEq(address(gateway).balance, 0);
 
+        vm.expectRevert(GatewayProxy.NativeCurrencyNotAccepted.selector);
         SafeNativeTransfer.safeNativeTransfer(payable(gateway), amount);
 
+        IGateway(address(gateway)).depositEther{value: amount}();
+
         assertEq(address(gateway).balance, amount);
     }