In containers, multiple types of proxy servers may exist between a client and the container servers. After an external request is forwarded for multiple times, the source IP address of the client cannot be transmitted to the containers. As a result, Services in the containers cannot obtain the real source IP addresses of the client.

Description

Layer-7 forwarding:

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

LoadBalancer Ingresses use ELB for Layer 7 network access between the Internet and internal network (in the same VPC) based on the ELB service.

Layer-4 forwarding:

LoadBalancer: Use ELB to achieve load balancing. You can manually enable the Transfer Client IP Address option for TCP and UDP listeners of shared load balancers. By default, the Transfer Client IP Address option is enabled for TCP and UDP listeners of dedicated load balancers. You do not need to manually enable it.
NodePort: The container port is mapped to the node port. If the cluster-level affinity is selected, access requests will be forwarded through the node and the client source IP address cannot be obtained. If the node-level affinity is selected, access requests will not be forwarded and the client source IP address can be obtained.

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.

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.

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.
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. 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.
6. Enable Transfer Client IP Address.
(Perform this step only for Nginx ingresses.) 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.
For details, see How Can I Transfer the IP Address of a Client?

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.

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.

CCE Clusters (using VPC or Tunnel network): Source IP addresses can be obtained when either a shared or dedicated load balancer is used.
CCE Turbo Clusters (using the Cloud Native Network 2.0): Source IP addresses can be obtained for dedicated load balancers, and for shared load balancers with hostNetwork enabled.

VPC and Container Tunnel Network Models

To obtain source IP addresses, perform the following steps:

When creating a LoadBalancer Service on the CCE console, set Service Affinity to Node-level instead of Cluster-level.
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. 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.
6. Enable Transfer Client IP Address.

Cloud Native Network 2.0 Model (CCE Turbo Clusters)

In the Cloud Native Network 2.0 model, when a shared load balancer is used for load balancing, the service affinity cannot be set to Node-level. As a result, source IP addresses cannot be obtained. To obtain a source IP address, you must use a dedicated load balancer. External access to the container does not need to pass through the forwarding plane.

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 an ENI 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.

When a node (using Cloud Native Network 2.0) accesses a NodePort Service, source IP addresses can be obtained only when hostNetwork is enabled for workloads.

Obtaining the Client Source IP Address for a Container

Description

ELB Ingress

LoadBalancer

NodePort