SIP-400: Fix for underflow error when offchain price timestamp is bigger than current block timestamp

Simple Summary

Fix a bug in StalenessCircuitBreakerNode that results in an underflow error when the off-chain price update timestamp exceeds the current block timestamp.

Abstract

Propose an update to the StalenessCircuitBreakerNode script to handle situations where the off-chain price update timestamp is in the "future" for the current block. Accompany the bug fix with corresponding tests.

Motivation

Every chain mints blocks with a reasonable delay. If a fresh price update transaction retrieves a timestamp that is in the "future" relative to the current block, this results in an underflow error. Fixing this error will make the StalenessCircuitBreakerNode script more resilient and ensure its correct functioning under this particular condition.

Specification

Technical

We propose to adjust the StalenessCircuitBreakerNode contract to cater to situations where the off-chain price update timestamp exceeds the current block timestamp.

The proposed adjustment addresses the underflow error and ensures that the StalenessCircuitBreakerNode script does not fail due to this specific scenario.

In addition to the bug fix, we suggest adding new tests to the test suite that cover this particular case. Doing so will help maintain the robustness of the existing test suite and catch any future recurrences of this problem.

Incorrect implementation leading to arithmetic underflow

if (block.timestamp - priceNodeOutput.timestamp <= stalenessTolerance) {

to be fixed with

if (block.timestamp - stalenessTolerance <= priceNodeOutput.timestamp) {

This will ensure we do not get negative values when priceNodeOutput.timestamp is greater than block.timestamp