Help Center/ Cloud Container Engine/ User Guide (Paris Regions)/ Best Practices/ Networking/ Obtaining the Client Source IP Address for a Container
Updated on 2024-01-26 GMT+08:00
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Obtaining the Client Source IP Address for a Container

Background

There may be different types of proxy servers between a client and a container server. How can a container obtain the real source IP address of the client? This section describes several scenarios you may encounter.

Principles

Layer-7 forwarding:

Ingress: If this access mode is used, the client source IP address is saved in the X-Forwarded-For HTTP header field by default. No other configuration is required.

  • ELB ingress: A self-developed ingress to implement layer-7 network access between the internet and intranet (in the same VPC) based on ELB. If the backend Service type is NodePort, set Service Affinity to Node level.
  • Nginx ingress: An ingress that implements layer-7 networking based on the nginx-ingress add-on. The backend Service type can be either ClusterIP or NodePort. If the backend Service type is NodePort, set Service Affinity to Node level.

Layer-4 forwarding:

  • NodePort: In this access mode, the container port is mapped to the node port. If cluster-level affinity is configured, access requests will be forwarded through the node and the client source IP address cannot be obtained. If node-level affinity is configured, access requests are not forwarded and the client source IP address can be obtained.

Ingress

Configure the application server and obtain the IP address of a client from the HTTP header.

The real IP address is placed in the X-Forwarded-For HTTP header field by the load balancer in the following format:

X-Forwarded-For: IP address of the client,Proxy server 1-IP address,Proxy server 2-IP address,...

If you use this method, the first IP address obtained is the IP address of the client.

  • When adding an ingress, if the backend service is of the NodePort type, set Service Affinity to Node level, that is, set spec.externalTrafficPolicy to Local. For details, see NodePort.
  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. 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. Log in to the ELB console.
    2. Click in the upper left corner of the management console and select a region and a project.
    3. Click Service List. Under Networking, click Elastic Load Balance.
    4. On the Load Balancers page, click the name of the load balancer.
    5. Switch to the Listeners tab and click Modify on the right of the target listener. If modification protection exists, disable the protection on the basic information page of the listener and try again.
    6. Enable Obtain Client IP Address.

  3. (Perform this step only for nginx-ingress.) Edit the nginx-ingress add-on. In the nginx configuration parameter area, configure the configuration fields and information. (For details about the parameter range, see community document.) After the configuration is complete, update the add-on. 

    {
    "enable-real-ip": "true",
    "forwarded-for-header": "X-Forwarded-For",
    "proxy-real-ip-cidr": "100.125.0.0/16",
    "keep-alive-requests": "100"
}

    The proxy-real-ip-cidr parameter indicates the CIDR block of the proxy server.

    • For shared load balancers, add CIDR block 100.125.0.0/16 (reserved only for load balancers and therefore, there is no risk) and the high-defense CIDR block.
    • For dedicated load balancers, add the CIDR block of the VPC subnet where the ELB resides.

  4. 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.

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.

Parent topic: Networking