OffchainNext.sol

Automatically randomize CCIP-Read endpoints and conditionally choose to accept a response without terminating the request session. Calls will succeed as long as one endpoint produces a valid response.

Testing Requirements

1. foundryup
2. npm i

Setup

• Abstract Contract Base: OffchainNext.sol
• Test: node test/test.js

Usage

• inherit OffchainNext
• use offchainLookup(...) instead of revert OffchainLookup(...) (same arguments)
• use revert OffchainTryNext() during callback to reject responses and proceed to the next endpoint
• will revert OffchainLookupUnanswered() if all endpoints attempted without success
• override _shouldTryNext(bytes) to control which exceptions should retry

---

☠️ Failed Idea: Shuffle

This approach works but cannot determine which endpoint failed so calls may take infinite time.

1. revert OffchainLookup(shuffled([a, b, c, ...]), ...)
2. callback fires if any endpoint responds
3. since we don't know which endpoint answered, must retry all endpoints again

Setup

• Abstract Contract Base: OffchainShuffle.sol
• Test: node test/shuffle.js

Usage

• inherit OffchainShuffle
• use offchainLookup(...) instead of revert OffchainLookup(...) (same arguments)
• on valid response, decode original carry using extractCarry(carry)
• to reject response, call offchainLookup(carry)

☠️ Failed Idea: Trampoline

This approach is not allowed by EIP-3668, specifically: Client Lookup Protocol: Rule #5

If the sender field does not match the address of the contract that was called, return an error to the caller and stop.

Setup

• Singleton Contract: OffchainTrampoline.sol
• Interface: IOffchainTrampoline.sol
• Test: node test/trampoline.js

Usage

• deploy IOffchainTrampoline
• use: IOffchainTrampoline().offchainLookup(...) instead of revert OffchainLookup(...) (same arguments)
  • minimal contract code
  • avoids stack issues
• by default, any revert during callback will try next endpoint
• (optional) implement IOffchainNext.isOffchainLookupRevertFatal(bytes) to allow specific errors to terminate the request session
  • eg. invalid proof vs exclusion proof
• use revert OffchainTryNext() to always try next endpoint
• will revert OffchainLookupUnanswered() if all endpoints attempted without success

FisherYates.sol

• Library: FisherYates.sol
• Test: node test/FisherYates.js