Obtaining the Client Source IP Address for a Container

Description

Figure 1 Obtaining the source IP addresses from the containers

The method for obtaining source client IP addresses may vary with the network settings. The following shows some typical network configurations and their corresponding solutions:

• Ingress Layer-7 forwarding: When accessing an application at Layer-7, the client's source IP address is automatically saved in the X-Forwarded-For field of the HTTP header. No additional configurations are needed to obtain the client's source IP address.
• Service Layer-4 forwarding: The method and principle for obtaining the source IP addresses will depend on the type of Services being used.
  • LoadBalancer Service: A load balancer is used as the traffic entry. Both shared and dedicated load balancers are supported.
    • For a shared load balancer, you need to enable the function of obtaining client IP addresses on the listeners.
    • By default, the function of obtaining client IP addresses is enabled for a dedicated load balancer listener.
  • NodePort Service: Container ports are mapped to node ports, which are used as the entry for external services. The capability of obtaining client source IP addresses depends on the service affinity.
    • In a cluster-level service affinity for a NodePort Service, traffic is forwarded within the cluster, which means the backend containers of the Service cannot access the client's source IP address.
    • In a node-level service affinity for a NodePort Service, the traffic can directly reach the container without any forwarding. This allows the backend containers of the Service to obtain the source IP address of the client.

ELB Ingress

For the ELB Ingresses (using HTTP- or HTTPS-compliant), the function of obtaining the source IP addresses of the client is enabled by default. No other operation is required.

A client source IP address is placed in the X-Forwarded-For field of the HTTP header by the load balancer. The format is as follows:

X-Forwarded-For: <client-source-IP-address>, <proxy-server-1-IP-address>, <proxy-server-2-IP-address>, ...

The first IP address obtained from the X-Forwarded-For field is the client source IP address.

Nginx Ingress

• For an Nginx Ingress that uses a dedicated load balancer, transparent transmission of source IP addresses is enabled by default. This means that you can easily obtain the source IP address of the client without any additional configurations.
• For an Nginx Ingress that uses a shared load balancer, perform the following steps to obtain the source IP address of the client:

1. Take the Nginx workload as an example. Before configuring the source IP address, obtain the access logs. nginx-c99fd67bb-ghv4q indicates the pod name.

   kubectl logs nginx-c99fd67bb-ghv4q

   Information similar to the following is displayed:

   ...
   10.0.0.7 - - [17/Aug/2023:01:30:11 +0000] "GET / HTTP/1.1" 200 19 "http://114.114.114.114:9421/" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/115.0.0.0 Safari/537.36 Edg/115.0.1901.203" "100.125.**.**"

   100.125.**.** specifies the CIDR block of the load balancer, indicating that the traffic is forwarded through the load balancer.

2. Enable Transfer Client IP Address. This operation is required only when shared load balancers are used. For dedicated load balancers, source IP address-based transparent transmission is enabled by default.
   1. Click in the upper left corner of the management console and select a region and a project.
   2. Choose Service List > Networking > Elastic Load Balance.
   3. On the Elastic Load Balance page, click the name of the target load balancer.
   4. Click the Listeners tab, locate the row containing the target listener, and click Edit. If modification protection exists, disable the protection on the basic information page of the listener and try again.
   5. Enable Transfer Client IP Address.

3. Access the workload again and view the new access log.

   ...
   10.0.0.7 - - [17/Aug/2023:02:43:11 +0000] "GET / HTTP/1.1" 304 0 "http://114.114.114.114:9421/" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/115.0.0.0 Safari/537.36 Edg/115.0.1901.203" "124.**.**.**"

   The source IP address of the client is obtained.

You can enable WAF for the load balancers used by Nginx Ingress Controllers in clusters, but different WAF modes will affect how Nginx Ingress Controllers obtain the real client IP addresses.

• Load balancer access in WAF cloud CNAME access mode

  When using the cloud CNAME access mode, requests go through WAF and are checked for protection before being sent to the load balancer. This means that even if the load balancer has transparent transmission of source IP addresses enabled, the client will receive the back-to-source IP address of WAF. Consequently, the Nginx Ingress Controller is unable to obtain the real client IP address by default. In this case, you can edit the NGINX Ingress Controller add-on and add the following configuration to the add-on parameters:

  {
       "enable-real-ip": "true",
       "use-forwarded-headers": "true",
       "proxy-real-ip-cidr": <Back-to-source IP address you obtained from WAF> 
  }

• Load balancer access in the cloud WAF mode

  This mode is transparent access (non-inline deployment) and supports only dedicated load balancers. In this mode, Nginx Ingress Controllers can obtain the real client IP address by default.

LoadBalancer

For a LoadBalancer Service, different types of clusters obtain source IP addresses in different scenarios. In some scenarios, source IP addresses cannot be obtained currently.

VPC and Container Tunnel Network Models

To enable the function of obtaining the source IP address on the console, perform the following steps:

1. When creating a LoadBalancer Service on the CCE console, set Service Affinity to Node-level instead of Cluster-level.
2. Go to the ELB console and enable the function of obtaining the client IP address of the listener corresponding to the load balancer. Transparent transmission of source IP addresses is enabled for dedicated load balancers by default. You do not need to manually enable this function.
   1. Click in the upper left corner of the management console and select a region and a project.
   2. Choose Service List > Networking > Elastic Load Balance.
   3. On the Elastic Load Balance page, click the name of the target load balancer.
   4. Click the Listeners tab, locate the row containing the target listener, and click Edit. If modification protection exists, disable the protection on the basic information page of the listener and try again.
   5. Enable Transfer Client IP Address.

NodePort

Set the service affinity of a NodePort Service to Node-level instead of Cluster-level. That is, set spec.externalTrafficPolicy of the Service to Local.