fix: do not fail mark bootstrap to gateway

src/core/ClientChainGateway.sol

@@ -71,6 +71,8 @@ contract ClientChainGateway is
 
         _whiteListFunctionSelectors[Action.REQUEST_ADD_WHITELIST_TOKENS] =
             this.afterReceiveAddWhitelistTokensRequest.selector;
+        // overwrite the bootstrap function selector
+        _whiteListFunctionSelectors[Action.REQUEST_MARK_BOOTSTRAP] = this.afterReceiveMarkBootstrapRequest.selector;
 
         bootstrapped = true;
 
@@ -82,8 +84,6 @@ contract ClientChainGateway is
 
     /// @dev Clears the bootstrap data.
     function _clearBootstrapData() internal {
-        // mandatory to clear!
-        delete _whiteListFunctionSelectors[Action.REQUEST_MARK_BOOTSTRAP];
         // the set below is recommended to clear, so that any possibilities of upgrades
         // can then be removed.
         delete customProxyAdmin;

src/core/ClientGatewayLzReceiver.sol

@@ -327,4 +327,12 @@ abstract contract ClientGatewayLzReceiver is PausableUpgradeable, OAppReceiverUp
         }
     }
 
+    /// @notice Called after a mark-bootstrap response is received.
+    /// @dev Since the contract is already bootstrapped (if we are here), there is nothing to do.
+    /// @dev Failing this, however, will cause a nonce mismatch resulting in a system halt.
+    ///      Hence, we silently ignore this call.
+    function afterReceiveMarkBootstrapRequest() public onlyCalledFromThis whenNotPaused {
+        emit BootstrappedAlready();
+    }
+
 }

test/foundry/unit/Bootstrap.t.sol

@@ -924,11 +924,8 @@ contract BootstrapTest is Test {
     function test12_MarkBootstrapped_AlreadyBootstrapped() public {
         test12_MarkBootstrapped();
         vm.startPrank(address(clientChainLzEndpoint));
-        vm.expectRevert(
-            abi.encodeWithSelector(
-                GatewayStorage.UnsupportedRequest.selector, GatewayStorage.Action.REQUEST_MARK_BOOTSTRAP
-            )
-        );
+        vm.expectEmit(address(bootstrap));
+        emit BootstrapStorage.BootstrappedAlready();
         bootstrap.lzReceive(
             Origin(exocoreChainId, bytes32(bytes20(undeployedExocoreGateway)), uint64(2)),
             generateUID(1),
@@ -955,6 +952,16 @@ contract BootstrapTest is Test {
         _markBootstrapped(2, true);
     }
 
+    function test12_MarkBootstrapped_FailThenSucceed2x() public {
+        vm.warp(spawnTime - 5);
+        _markBootstrapped(1, false);
+        vm.warp(spawnTime + 1);
+        _markBootstrapped(2, true);
+        // silently succeeds and does not block the system after bootstrapping
+        vm.warp(spawnTime + 10);
+        _markBootstrapped(3, true);
+    }
+
     function test13_OperationAllowed() public {
         vm.warp(spawnTime - offsetDuration);
         vm.startPrank(addrs[0]);