HTTP registry: for

IP-address of client making a request through a proxy

HTTP parameter values extend negotiation, framing, preferences, range handling, or other protocol components. for is registered in HTTP Forwarded Parameters. Defining reference: rfc7239.

httpregistryhttp-parametersforwarded

Identifier (http)

for

IP-address of client making a request through a proxy

Interpret parameters only in the context that defines them; unknown parameters must not silently change security or framing behavior.

This registry value is currently marked active by IANA. Follow the defining specification before sending, accepting, or proxying it.

IANA registry: http-parameters/forwarded

Registry reference: rfc7239

Sources

HTTP Forwarded Parameters
rfc7239