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LayerZero

LayerZero V1 Solidity Examples

Important

LayerZero V2 is now available here, offering improvements in cross-chain transaction speed, gas efficiency, and more.

Review the LayerZero V2 Documentation for a comprehensive overview of the new feature set.

For these reasons, we recommend deploying to LayerZero V2 instead of LayerZero V1.

All of the contracts available in this repo should be considered legacy for Endpoint V1.

Welcome to the solidity-examples repository, showcasing various contract examples utilizing LayerZero. LayerZero is an Omnichain Interoperability Protocol, facilitating reliable, trustless communication between different blockchain networks.

Disclaimer: This repository contains example contracts to demonstrate the capabilities and usage of LayerZero. For actual implementation in your projects, it's recommended to use the official LayerZero contracts (such as LZApp, OFT, OFTV1.2, etc.) directly from the npm package.

You can find instructions for inheriting, deploying, and best practices for the provided contracts in the LayerZero V1 Documentation.

  • Formal audit(s) (May 21, 2022) can be found in audit

Install & Run tests

yarn install
yarn test

The code in the contracts folder demonstrates LayerZero contract behaviours:

  • NonblockingLzApp provides a generic message passing interface to send and receive arbitrary pieces of data between contracts existing on different blockchain networks. Take a look at how OmniCounter inherits NonblockingLzApp to easily handle omnichain messaging.

  • The OFTV1 Standard allows ERC20 tokens to be transferred across multiple EVM-compatible blockchains without asset wrapping or middlechains.

  • The OFTV1.2 Standard allows fungible tokens to be transferred across both EVM and non-EVM compatible blockchains supported by LayerZero.

  • The ONFT721 Standard allows ERC721 NFTs to be moved across EVM chains.

  • The ONFT1155 Standard allows ERC1155 tokens to be sent to EVM chains.

Notice: Each of the above standards comes with a Proxy variant for sending tokens that have already been deployed cross-chain.

There can only be one Proxy per deployment. Multiple Proxies break omnichain unified liquidity by effectively creating token pools. If you create Proxies on multiple chains, you have no way to guarantee finality for token transfers due to the fact that the source chain has no knowledge of the destination pool's supply (or lack of supply). This can create race conditions where if a sent amount exceeds the available supply on the destination chain, those sent tokens will be permanently lost.

  • Always audit your own code and test extensively on testnet before going to mainnet 🙏

The examples below use two chains, however you could substitute any LayerZero supported chain!

OmniCounter.sol

OmniCounter is a simple example of NonblockingLzApp contract that increments a counter on multiple chains. You can only remotely increment the counter!

  1. Deploy both OmniCounters:
npx hardhat --network bsc-testnet deploy --tags OmniCounter
npx hardhat --network fuji deploy --tags OmniCounter
  1. Set the remote addresses, so each contract can receive messages
npx hardhat --network bsc-testnet setTrustedRemote --target-network fuji --contract OmniCounter
npx hardhat --network fuji setTrustedRemote --target-network bsc-testnet --contract OmniCounter
  1. Send a cross chain message from bsc-testnet to fuji !
npx hardhat --network bsc-testnet incrementCounter --target-network fuji

Optionally use this command in a separate terminal to watch the counter increment in real-time.

npx hardhat --network fuji ocPoll

Check your setTrustedRemote's are wired up correctly

Just use our checkWireUpAll task to check if your contracts are wired up correctly. You can use it on the example contracts deployed above.

  1. UniversalONFT
npx hardhat checkWireUpAll --e testnet --contract ONFT721Mock
  1. OmniCounter
npx hardhat checkWireUpAll --e testnet --contract OmniCounter

See some examples in /contracts 🙌

Many of the example contracts make use of LayerZeroEndpointMock.sol which is a nice way to test LayerZero locally!

For further reading, and a list of endpoint ids and deployed LayerZero contract addresses please take a look at the Documentation here: https://docs.layerzero.network/v1/developers/evm/build/what-you-can-build

OmnichainFungibleToken (OFT)

About OFTV1.2

NOTE: the OFTV1.2 uses uint64 to encode value transfer for compatibility of Aptos and Solana. 

The deployer is expected to set a lower decimal points like 6 or 8. 

If the decimal point is 18, then uint64 can only represent approximately 18 tokens (uint64.max ~= 18 * 10^18).

Deploy Setup

  1. Add a .env file (to the root project directory) with your MNEMONIC="your mnemonic" and fund your wallet in order to deploy!
  2. Follow any of the tutorials below

OFTV2Mock.sol - an omnichain ERC20

⚠️ You must perform setTrustedRemote() (step 2). This is a mock deployment that auto mints tokens to msg.sender

  1. Deploy two contracts:
npx hardhat --network goerli deploy --tags ExampleOFTV2
npx hardhat --network fuji deploy --tags ExampleOFTV2
  1. Set the "trusted remotes" (ie: your contracts) so each of them can receive messages from one another, and only one another.
npx hardhat --network goerli setTrustedRemote --target-network fuji --contract OFTV2Mock
npx hardhat --network fuji setTrustedRemote --target-network goerli --contract OFTV2Mock
  1. Set the "minDstGas" required on the destination chain.
npx hardhat --network goerli setMinDstGas --packet-type 0 --target-network fuji --contract OFTV2Mock --min-gas 100000
npx hardhat --network fuji setMinDstGas --packet-type 0 --target-network goerli --contract OFTV2Mock --min-gas 100000

⚠️ Although 100000 is used for min-gas in this example, you should set this value based on careful gas consumption analysis.

  1. Send tokens from goerli to fuji
npx hardhat --network goerli oftv2Send --target-network fuji --qty 42 --contract OFTV2Mock

Pro-tip: Check the ERC20 transactions tab of the destination chain block explorer and await your tokens!

OmnichainNonFungibleToken721 (ONFT721)

This ONFT contract allows minting of nftIds on separate chains. To ensure two chains can not mint the same nftId each contract on each chain is only allowed to mintnftIds in certain ranges. Check the ONFT_ARGS constant defined in ONFT721 deploy script for the specific test configuration used in this demo.

ONFT721Mock.sol

⚠️ You must perform the setTrustedRemote() (step 2).

  1. Deploy two contracts:
npx hardhat --network bsc-testnet deploy --tags ONFT721
npx hardhat --network fuji deploy --tags ONFT721
  1. Set the "trusted remotes", so each contract can send & receive messages from one another, and only one another.
npx hardhat --network bsc-testnet setTrustedRemote --target-network fuji --contract ONFT721Mock
npx hardhat --network fuji setTrustedRemote --target-network bsc-testnet --contract ONFT721Mock
  1. Set the min gas required on the destination
npx hardhat --network bsc-testnet setMinDstGas --target-network fuji --contract ONFT721Mock --packet-type 1 --min-gas 100000
npx hardhat --network fuji setMinDstGas --target-network bsc-testnet --contract ONFT721Mock --packet-type 1 --min-gas 100000
  1. Mint an NFT on each chain!
npx hardhat --network bsc-testnet onftMint --contract ONFT721Mock --to-address <address> --token-id 1
npx hardhat --network fuji onftMint --contract ONFT721Mock --to-address <address> --token-id 11
  1. [Optional] Show the token owner(s)
npx hardhat --network bsc-testnet ownerOf --token-id 1 --contract ONFT721Mock
npx hardhat --network fuji ownerOf --token-id 11 --contract ONFT721Mock
  1. Send ONFT across chains
npx hardhat --network bsc-testnet onftSend --target-network fuji --token-id 1 --contract ONFT721Mock
npx hardhat --network fuji onftSend --target-network bsc-testnet --token-id 11 --contract ONFT721Mock
  1. Verify your token no longer exists in your wallet on the source chain & wait for it to reach the destination side.
npx hardhat --network bsc-testnet ownerOf --token-id 1 --contract ONFT721Mock
npx hardhat --network fuji ownerOf --token-id 1 --contract ONFT721Mock

See testnet and mainnet chainIds and addresses, and the format for connecting contracts on different chains:

https://github.com/LayerZero-Labs/set-trusted-remotes

https://docs.layerzero.network/v1/developers/evm/technical-reference/testnet/testnet-addresses

https://docs.layerzero.network/v1/developers/evm/technical-reference/mainnet/mainnet-addresses

Most recently tested with node version 18.16.0