A little while ago, I posted about this issue:
Today, with the help of a more knowledgeable friend, we tried to dig deep into this issue, testing across different servers and configurations.
What we found is this:
- There are several different CloudFlare IPs that respond to the DNS request to our domain
- When the Cloudflare IP is 126.96.36.199, this stale header issue occurs
- On other Cloudflare IPs, the CF-Connecting-IP header is updated immediately after resetting the client connection
So, this is definitely an issue on the CF side of things.