fn forwarded_caller(headers: &HeaderMap) -> Option<IpAddr>Expand description
The address the reverse proxy in front of this server saw the request arrive from, for a deployment that has opted into trusting it.
The rightmost X-Forwarded-For element, because a proxy appends:
nginx’s proxy_add_x_forwarded_for and an AWS ALB both put the peer they
saw at the right-hand end and keep whatever the client sent to its left.
The leftmost element is therefore the client’s own text, and reading it is
what let a caller send a different value on every request and get a fresh
budget against every limiter each time.
None when neither header holds an address: an unparseable value is not a
caller’s name, and the TCP peer is.