🐛 BUG: missing network request header causes IP address conflict when hitting Cloudflare-proxied domain in

[woodypowr5]

Which Cloudflare product(s) does this pertain to?

Wrangler

What versions are you using?

3.101.0

What operating system and version are you using?

Mac Sonoma 14.2.1

Please provide a link to a minimal reproduction

No response

Describe the Bug

Starting in v3.101, when a request is made to another domain that is proxied by Cloudflare, the request fails with the following error:

DNS points to prohibited IP

What happened?

You've requested a page on a website ({domain}) that is on the Cloudflare
network. Unfortunately, it is resolving to an IP address that is creating a conflict within Cloudflare's system.

Here’s is our original worker code that fails on v3.101.0 because we are proxying to another domain which is proxied by Cloudflare:

/**
 * Open API Reverse Proxy
 *
 * A Cloudflare Pages function that acts as a reverse proxy for Open API.
 * <cloudflare-address>/openapi/* calls are transformed into <open-api-address>/* calls
 *
 * @param context
 * @returns
 */
export const onRequest: PagesFunction<Env> = async (context) => {
    function removePrefix(string0, prefix: string): string {
        const hasPrefix = string0.indexOf(prefix) === 0;
        return hasPrefix ? string0.substr(prefix.length) : string0;
    }

    const { request, env } = context
    const { pathname, searchParams } = new URL(request.url)
    const openApiRequestUrl = env.VITE_OPEN_API_BASE_URL + removePrefix(pathname, "/openapi")

    return await fetch(
        new Request(
            searchParams.size > 0 ? `${openApiRequestUrl}?${searchParams}` : openApiRequestUrl,
            request
        )
    )
}

We were able to fix the issue by adding the following line before the fetch call:

request.headers.set("cf-connecting-ip", "")

We were inspired to attempt the given fix by looking the following pr, which for some reason on its own did not resolve the issue for us: #7712
10:48

reverting to v3.100.0 also fixes the issue for us

Please provide any relevant error logs

No response