Introduction

Google Container Engine, now known as Google Kubernetes Engine (GKE), offers a powerful platform for deploying containerized applications in the cloud. When deploying applications using GKE, it is often necessary to track the originating IP address of client requests for security and logging purposes. In an HTTPS scenario, this can be complex due to SSL termination at the load balancer or ingress level in GKE. This article will explore methods to forward the client IP address in a GKE environment.

Understanding SSL Termination

When you deploy an application in GKE behind a Google Cloud Load Balancer, SSL termination usually occurs at the load balancer level. This means that the SSL connection is decrypted there before forwarding to your backend services. While this ensures efficient load distribution and security management, it poses challenges in transmitting the original client IP to your application.

How SSL Termination Works

1. Client to Load Balancer: The client initiates an SSL handshake and establishes a secure connection with the load balancer.
2. Load Balancer: The load balancer decrypts the incoming traffic and terminates the SSL.
3. Load Balancer to Backend: Unencrypted traffic is forwarded to the backend services.

Forwarding the Client IP

To forward the client IP to your application, you need to handle the incoming HTTP headers correctly. The `X-Forwarded-For` header is instrumental in this process.

X-Forwarded-For Header

The `X-Forwarded-For` (XFF) header is an HTTP header used to identify the originating IP address of a client connecting to a web server through a proxy or load balancer. In most GKE setups, this header is automatically added by the Google Cloud Load Balancer.

Example of an XFF Header:

• host: example.com
  • path: /
• from:
  • ipBlock: