Add support for custom gas token chains

Author: TucksonDev

packages/gas-estimation/scripts/exec.ts

@@ -1,7 +1,11 @@
 import { utils, providers } from 'ethers';
 import { NodeInterface__factory } from '@arbitrum/sdk/dist/lib/abi/factories/NodeInterface__factory';
 import { NODE_INTERFACE_ADDRESS } from '@arbitrum/sdk/dist/lib/dataEntities/constants';
-const { requireEnvVariables, addCustomNetworkFromFile } = require('arb-shared-dependencies');
+const {
+  requireEnvVariables,
+  addCustomNetworkFromFile,
+  arbLog,
+} = require('arb-shared-dependencies');
 
 // Importing configuration //
 require('dotenv').config();
@@ -24,6 +28,8 @@ const destinationAddress = '0x1234563d5de0d7198451f87bcbf15aefd00d434d';
 const txData = '0x';
 
 const gasEstimator = async () => {
+  await arbLog('Gas estimation');
+
   // ***************************
   // * Gas formula explanation *
   // ***************************
@@ -93,7 +99,9 @@ const gasEstimator = async () => {
   // -------------------------------------------------------------------------------
   // NOTE: This one might be a bit confusing, but parentChainGasEstimated (B in the formula) is calculated based on child-chain's gas fees
   const parentChainCost = parentChainGasEstimated.mul(childChainEstimatedPrice);
-  const parentChainSize = parentChainCost.div(parentChainEstimatedPrice);
+  const parentChainSize = parentChainEstimatedPrice.eq(0)
+    ? 0
+    : parentChainCost.div(parentChainEstimatedPrice);
 
   // Getting the result of the formula
   // ---------------------------------

packages/redeem-pending-retryable/contracts/parent-chain/GreeterParent.sol

@@ -3,17 +3,23 @@ pragma solidity ^0.8.0;
 
 import "@arbitrum/nitro-contracts/src/bridge/Inbox.sol";
 import "@arbitrum/nitro-contracts/src/bridge/Outbox.sol";
+import "@arbitrum/nitro-contracts/src/bridge/IERC20Inbox.sol";
+import "@arbitrum/nitro-contracts/src/bridge/IERC20Bridge.sol";
+import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
+import "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";
 import "../Greeter.sol";
 
 contract GreeterParent is Greeter {
+    using SafeERC20 for IERC20;
+
     address public childTarget;
-    IInbox public inbox;
+    address public inbox;
 
     event RetryableTicketCreated(uint256 indexed ticketId);
 
     constructor(string memory _greeting, address _childTarget, address _inbox) Greeter(_greeting) {
         childTarget = _childTarget;
-        inbox = IInbox(_inbox);
+        inbox = _inbox;
     }
 
     function updateChildTarget(address _childTarget) public {
@@ -27,24 +33,55 @@ contract GreeterParent is Greeter {
         uint256 gasPriceBid
     ) public payable returns (uint256) {
         bytes memory data = abi.encodeWithSelector(Greeter.setGreeting.selector, _greeting);
-        uint256 ticketID = inbox.createRetryableTicket{ value: msg.value }(
-            childTarget,
-            0,
-            maxSubmissionCost,
-            msg.sender,
-            msg.sender,
-            maxGas,
-            gasPriceBid,
-            data
-        );
+
+        // Find out if this chain uses a custom gas token
+        address bridge = address(IInbox(inbox).bridge());
+        address nativeToken;
+        try IERC20Bridge(bridge).nativeToken() returns (address nativeTokenAddress) {
+            nativeToken = nativeTokenAddress;
+        } catch {}
+
+        uint256 ticketID;
+        if (nativeToken == address(0)) {
+            // Chain uses ETH as the gas token
+            ticketID = IInbox(inbox).createRetryableTicket{ value: msg.value }(
+                childTarget,
+                0,
+                maxSubmissionCost,
+                msg.sender,
+                msg.sender,
+                maxGas,
+                gasPriceBid,
+                data
+            );
+        } else {
+            // Chain uses a custom gas token
+            // l2callvalue + maxSubmissionCost + execution fee
+            uint256 tokenAmount = 0 + maxSubmissionCost + (maxGas * gasPriceBid);
+
+            IERC20(nativeToken).safeTransferFrom(msg.sender, address(this), tokenAmount);
+            IERC20(nativeToken).approve(inbox, tokenAmount);
+
+            ticketID = IERC20Inbox(inbox).createRetryableTicket(
+                childTarget,
+                0,
+                maxSubmissionCost,
+                msg.sender,
+                msg.sender,
+                maxGas,
+                gasPriceBid,
+                tokenAmount,
+                data
+            );
+        }
 
         emit RetryableTicketCreated(ticketID);
         return ticketID;
     }
 
     /// @notice only childTarget can update greeting
     function setGreeting(string memory _greeting) public override {
-        IBridge bridge = inbox.bridge();
+        IBridge bridge = IInbox(inbox).bridge();
         // this prevents reentrancies on Child-to-Parent transactions
         require(msg.sender == address(bridge), "NOT_BRIDGE");
         IOutbox outbox = IOutbox(bridge.activeOutbox());

packages/redeem-pending-retryable/scripts/exec-createFailedRetryable.js

@@ -15,6 +15,7 @@ const {
   getArbitrumNetwork,
 } = require('@arbitrum/sdk');
 const { getBaseFee } = require('@arbitrum/sdk/dist/lib/utils/lib');
+const { ERC20__factory } = require('@arbitrum/sdk/dist/lib/abi/factories/ERC20__factory');
 require('dotenv').config();
 requireEnvVariables(['PRIVATE_KEY', 'CHAIN_RPC', 'PARENT_CHAIN_RPC']);
 
@@ -164,13 +165,38 @@ const main = async () => {
     `Sending greeting to the child chain with ${parentToChildMessageGasParams.deposit.toString()} callValue for child chain's fees:`,
   );
   const maxGasLimit = 10;
+
+  /**
+   * We now find out whether the child chain we are using is a custom gas token chain
+   * We need to perform an additional approve call to transfer
+   * the native tokens to pay for the gas of the retryable tickets.
+   */
+  const isCustomGasTokenChain =
+    childChainNetwork.nativeToken && childChainNetwork.nativeToken !== ethers.constants.AddressZero;
+
+  if (isCustomGasTokenChain) {
+    // Approve the gas token to be sent to the contract
+    console.log('Giving allowance to the greeter to transfer the chain native token');
+    const nativeToken = new ethers.Contract(
+      childChainNetwork.nativeToken,
+      ERC20__factory.abi,
+      parentChainWallet,
+    );
+    const approvalTransaction = await nativeToken.approve(
+      greeterParent.address,
+      ethers.utils.parseEther('1'),
+    );
+    const approvalTransactionReceipt = await approvalTransaction.wait();
+    console.log(`Approval transaction receipt is: ${approvalTransactionReceipt.transactionHash}`);
+  }
+
   const setGreetingTransaction = await greeterParent.setGreetingInChild(
     newGreeting, // string memory _greeting,
     parentToChildMessageGasParams.maxSubmissionCost,
     maxGasLimit,
     gasPriceBid,
     {
-      value: parentToChildMessageGasParams.deposit,
+      value: isCustomGasTokenChain ? 0 : parentToChildMessageGasParams.deposit,
     },
   );
   const setGreetingTransactionReceipt = await setGreetingTransaction.wait();