$proxy_protocol_port

Description

The $proxy_protocol_port variable is utilized within NGINX to retrieve the port number specified in the PROXY protocol header for connections that have been proxied. It is primarily relevant in configurations where NGINX acts as a reverse proxy or load balancer, allowing the server to accurately identify the original port from which the client connection was made. This information can be crucial for logging, security measures, or backend server decisions. This variable is set only when the PROXY protocol is enabled in the upstream server block. If the PROXY protocol is not utilized, the variable will not hold a valid value, effectively resolving to 0. Typical values for this variable would be the original port numbers such as 80 or 443 for HTTP and HTTPS traffic. Using $proxy_protocol_port allows for greater context about the incoming request, which is especially valuable in multi-tier architectures where backend processing may depend on the original client port.

Config Example

server {
    listen 80 proxy_protocol;
    location / {
        add_header X-Proxy-Port $proxy_protocol_port;
    }
}