The Proxy Protocol, which operates beneath at the TCP layer, fills this gap, expanding coverage to any upper layer protocol-SMTP, IMAP, FTP, the Minecraft protocol, proprietary database protocols, etc.-that transmits messages over TCP/IP. With HTTP, a proxy can add a Forwarded HTTP header, or the non-standard X-Forwarded-For header, to store the client’s original IP address so that the server can retrieve it, but other protocols lack a similar fix. Some higher-level protocols, such as HTTP, have a solution for this. This distorts the logs of upstream servers because the logs incorrectly indicate that all traffic originated at the proxy.

Without such a mechanism, proxies lose this information because they act as a surrogate for the client, relaying messages to the server, but replacing the client’s IP address with their own.

What is the Proxy Protocol? It is a network protocol for preserving a client’s IP address when the client’s TCP connection passes through a proxy.

You will also find resources for how to integrate the protocol into your own proxy or web server software. In this blog post, you’ll learn how the Proxy Protocol preserves a client’s IP address when that client’s connection passes through a proxy.

Wireshark http proxy