http_proxy_to_wsgi should handle the X-Forwarded-For header or the "for=" component in the Forwarded header

[Guang Yee]

The X-Forwarded-For header or the "for=" components in the Forwarded header (per RFC 7239) is essential for applications to keep track of the originating peer IP. CADF, for example, is relying on REMOTE_ADDR to keep track of the real client address.

If either header is present, http_proxy_to_wsig should properly replace the REMOTE_ADDR with the real client address.

[Ben Nemec (bnemec)]

Looks like this is done: https://github.com/openstack/oslo.middleware/blob/880f29d72e436ab3a63a62c82c2f23d2a94b1a01/oslo_middleware/http_proxy_to_wsgi.py#L73