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.

If Istio is used, you can obtain the source IP address by referring to How Do I Obtain the Actual Source IP Address of a Client After a Service Is Added into Istio?

Scenarios in Which Source IP Address Can Be Obtained

Due to network model differences, CCE does not allow obtaining source IP addresses in some scenarios, as listed in Table 1. "-" in the table indicates that this scenario does not exist.

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

In Cloud Native 2.0 networks (for CCE Turbo clusters), if a shared load balancer is used, source IP addresses cannot be obtained when an ingress is associated with the NGINX Ingress Controller add-on. For details, see Scenarios in Which Source IP Address Can Be Obtained. To obtain the source IP address, uninstall the NGINX Ingress Controller add-on and use a dedicated load balancer during reinstallation.

• 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.

   Procedure for clusters of v1.23.17-r0, v1.25.12-r0, v1.27.9-r0, v1.28.7-r0, v1.29.3-r0, and later versions

   1. Log in to the CCE console and click the cluster name to access the cluster console.
   2. In the navigation pane, choose Add-ons. In the right pane, locate NGINX Ingress Controller and click Manage.
   3. Click Edit under the installed instance and enable the function of obtaining the client IP address in the load balancer configuration.

      

   4. Click OK.
      

      If backend services have been configured when you enable or disable the function of obtaining a client IP address, traffic will be interrupted. Exercise caution when performing this operation.

   Procedure for clusters earlier than v1.23.17-r0, v1.25.12-r0, v1.27.9-r0, v1.28.7-r0, and v1.29.3-r0

   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.
      Figure 2 Enabling the function
      

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

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.
      Figure 3 Enabling the function
      

Cloud Native 2.0 Network Model (CCE Turbo Clusters)

Dedicated load balancers are recommended. External access can be directly sent to containers. By default, transparent transmission of source IP addresses is enabled for dedicated load balancers. You do not need to manually enable Transfer Client IP Address on the ELB console. Instead, you only need to select a dedicated load balancer when creating a LoadBalancer Service on the CCE console.

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.

In clusters using Cloud Native 2.0 networks, if NodePort Services are used, only workloads with hostNetwork enabled support node-level service affinity. Therefore, only such workloads can obtain source IP addresses.

Figure 4 Selecting the node-level affinity