Merge pull request #51937 from Lion-Wei/ipvs-readme

Automatic merge from submit-queue. If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>..

add readme file of ipvs

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**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: fixes #

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pkg/proxy/ipvs/README.md

@@ -0,0 +1,64 @@
+# How to use IPVS
+
+This document shows how to use kube-proxy ipvs mode.
+
+### What is IPVS
+
+**IPVS (IP Virtual Server)** implements transport-layer load balancing, usually called Layer 4 LAN switching, as part of
+Linux kernel.
+
+IPVS runs on a host and acts as a load balancer in front of a cluster of real servers. IPVS can direct requests for TCP
+and UDP-based services to the real servers, and make services of real servers appear as irtual services on a single IP address.
+
+### How to use
+
+##### Load IPVS kernel modules
+
+Currently the IPVS kernel module can't be loaded automatically, so first we should use the following command to load IPVS kernel
+modules manually.
+
+```shell
+modprobe ip_vs
+modprobe ip_vs_rr
+modprobe ip_vs_wrr
+modprobe ip_vs_sh
+modprobe nf_conntrack_ipv4
+```
+
+After that, use `lsmod | grep ip_vs` to make sure kernel modules are loaded.
+
+##### Run kube-proxy in ipvs mode
+
+First, [run cluster locally](https://github.com/kubernetes/community/blob/master/contributors/devel/running-locally.md). 
+
+By default kube-proxy will run in iptables mode, with configuration file `/tmp/kube-proxy.yaml`. so we need to change the
+configuration file and restart it. Here is a yaml file for reference.
+
+```yaml
+apiVersion: componentconfig/v1alpha1
+kind: KubeProxyConfiguration
+clientConnection:
+  kubeconfig: /var/run/kubernetes/kube-proxy.kubeconfig
+hostnameOverride: 127.0.0.1
+mode: ipvs
+featureGates: AllAlpha=true
+ipvs:
+  minSyncPeriod: 10s
+  syncPeriod: 60s
+```
+
+##### Test
+
+Use `ipvsadm` tool to test whether the kube-proxy start succeed. By default we may get result like:
+
+```shell
+# ipvsadm -ln
+IP Virtual Server version 1.2.1 (size=4096)
+Prot LocalAddress:Port Scheduler Flags
+  -> RemoteAddress:Port           Forward Weight ActiveConn InActConn
+TCP  10.0.0.1:443 rr persistent 10800
+  -> 10.229.43.2:6443             Masq    1      0          0         
+TCP  10.0.0.10:53 rr      
+UDP  10.0.0.10:53 rr
+```
+