Kubernetes的Pod网络设置
Kubernetes的Pod网络设置
网络插件加载前
k8s.io/kubernetes/cmd/kubelet/kubelet.go:
if err := app.Run(s, nil); err != nil {
k8s.io/kubernetes/cmd/kubelet/app/server.go:
if err := run(s, kubeDeps); err != nil {
k8s.io/kubernetes/cmd/kubelet/app/server.go, run():
kubeDeps, err = UnsecuredKubeletDeps(s)
k8s.io/kubernetes/cmd/kubelet/app/server.go, UnsecuredKubeletDeps():
NetworkPlugins: ProbeNetworkPlugins(s.NetworkPluginDir, s.CNIConfDir, s.CNIBinDir),
k8s.io/kubernetes/cmd/kubelet/app/plugins.go:
// ProbeNetworkPlugins collects all compiled-in plugins
func ProbeNetworkPlugins(pluginDir, cniConfDir, cniBinDir string) []network.NetworkPlugin {
allPlugins := []network.NetworkPlugin{}
// for backwards-compat, allow pluginDir as a source of CNI config files
if cniConfDir == "" {
cniConfDir = pluginDir
}
// for each existing plugin, add to the list
allPlugins = append(allPlugins, cni.ProbeNetworkPlugins(cniConfDir, cniBinDir)...)
allPlugins = append(allPlugins, kubenet.NewPlugin(pluginDir))
return allPlugins
}
网络插件加载
k8s.io/kubernetes/pkg/kubelet/network/cni/cni.go:
func ProbeNetworkPlugins(pluginDir, binDir string) []network.NetworkPlugin {
return probeNetworkPluginsWithVendorCNIDirPrefix(pluginDir, binDir, "")
}
k8s.io/kubernetes/pkg/kubelet/network/cni/cni.go,probeNetworkPluginsWithVendorCNIDirPrefix():
func probeNetworkPluginsWithVendorCNIDirPrefix(pluginDir, binDir, vendorCNIDirPrefix string) []network.NetworkPlugin {
if binDir == "" {
binDir = DefaultCNIDir
}
plugin := &cniNetworkPlugin{
defaultNetwork: nil,
loNetwork: getLoNetwork(binDir, vendorCNIDirPrefix),
execer: utilexec.New(),
pluginDir: pluginDir,
binDir: binDir,
vendorCNIDirPrefix: vendorCNIDirPrefix,
}
// sync NetworkConfig in best effort during probing.
plugin.syncNetworkConfig()
return []network.NetworkPlugin{plugin}
}
读取cni配置文件,设置默认网络
k8s.io/kubernetes/pkg/kubelet/network/cni/cni.go:
func (plugin *cniNetworkPlugin) syncNetworkConfig() {
network, err := getDefaultCNINetwork(plugin.pluginDir, plugin.binDir, plugin.vendorCNIDirPrefix)
if err != nil {
glog.Warningf("Unable to update cni config: %s", err)
return
}
plugin.setDefaultNetwork(network)
}
k8s.io/kubernetes/pkg/kubelet/network/cni/cni.go, getDefaultCNINetwork():
//从pluginDir目录中读取所有.conf文件
files, err := libcni.ConfFiles(pluginDir)
...
for _, confFile := range files {
conf, err := libcni.ConfFromFile(confFile)
if err != nil {
glog.Warningf("Error loading CNI config file %s: %v", confFile, err)
continue
}
// Search for vendor-specific plugins as well as default plugins in the CNI codebase.
vendorDir := vendorCNIDir(vendorCNIDirPrefix, conf.Network.Type)
cninet := &libcni.CNIConfig{
Path: []string{binDir, vendorDir},
}
network := &cniNetwork{name: conf.Network.Name, NetworkConfig: conf, CNIConfig: cninet}
return network, nil
}
...
配置文件的格式为:
type NetConf struct {
Name string `json:"name,omitempty"`
Type string `json:"type,omitempty"`
IPAM struct {
Type string `json:"type,omitempty"`
} `json:"ipam,omitempty"`
DNS DNS `json:"dns"`
}
type DNS struct {
Nameservers []string `json:"nameservers,omitempty"`
Domain string `json:"domain,omitempty"`
Search []string `json:"search,omitempty"`
Options []string `json:"options,omitempty"`
}
网络插件初始化
前面的过程结束后,kubeDeps.NetworkPlugins中就设置好了指定的插件。
在k8s.io/kubernetes/pkg/kubelet/kubelet.go,NewMainKubelet()中:
if plug, err := network.InitNetworkPlugin(kubeDeps.NetworkPlugins,
kubeCfg.NetworkPluginName,
&criNetworkHost{&networkHost{klet}, &network.NoopPortMappingGetter{}},
klet.hairpinMode,
klet.nonMasqueradeCIDR,
int(kubeCfg.NetworkPluginMTU)); err != nil {
k8s.io/kubernetes/pkg/kubelet/network/plugins.go, InitNetworkPlugin()
chosenPlugin := pluginMap[networkPluginName]
if chosenPlugin != nil {
err := chosenPlugin.Init(host, hairpinMode, nonMasqueradeCIDR, mtu)
直接调用的cniNetworkPlugin
的Init()函数:
func (plugin *cniNetworkPlugin) Init(host network.Host, hairpinMode componentconfig.HairpinMode, nonMasqueradeCIDR string, mtu int) error {
var err error
plugin.nsenterPath, err = plugin.execer.LookPath("nsenter")
if err != nil {
return err
}
plugin.host = host
plugin.syncNetworkConfig()
return nil
}
网络插件的使用
cniNetworkPlugin的定义:
--cniNetworkPlugin : struct
[fields]
-binDir : string
-defaultNetwork : *cniNetwork
-execer : utilexec.Interface
-host : network.Host
-loNetwork : *cniNetwork
-nsenterPath : string //二进制文件nsenter的路径
-pluginDir : string
-vendorCNIDirPrefix : string
[embedded]
+network.NoopNetworkPlugin : network.NoopNetworkPlugin
+sync.RWMutex : sync.RWMutex
[methods]
+GetPodNetworkStatus(namespace string, name string, id kubecontainer.ContainerID) : *network.PodNetworkStatus, error
+Init(host network.Host, hairpinMode componentconfig.HairpinMode, nonMasqueradeCIDR string, mtu int) : error
+Name() : string
+SetUpPod(namespace string, name string, id kubecontainer.ContainerID, annotations map[string]string) : error
+Status() : error
+TearDownPod(namespace string, name string, id kubecontainer.ContainerID) : error
-checkInitialized() : error
-getDefaultNetwork() : *cniNetwork
-setDefaultNetwork(n *cniNetwork)
-syncNetworkConfig()
Init()
用于初始化,setUpPod
用于设置容器的网络,重点关注setUpPod。
SetUpPod()
SetUpPod()的参数分别是namespace,容器的name, pause容器的ID,注解。
这里必须要说明一下,k8s中的pod至少是包含两个容器的,其中一个容器作为infra容器,同一个pod中的其它容器和infra容器共享一个网络ns。
创建pod的时候,kubelet首先创建infra容器,得到infra容器的ID,然后创建其它容器。
k8s.io/kubernetes/pkg/kubelet/dockertools/docker_manager.go:
// If we should create infra container then we do it first.
podInfraContainerID := containerChanges.InfraContainerId
if containerChanges.StartInfraContainer && (len(containerChanges.ContainersToStart) > 0) {
glog.V(4).Infof("Creating pod infra container for %q", format.Pod(pod))
startContainerResult := kubecontainer.NewSyncResult(kubecontainer.StartContainer, PodInfraContainerName)
result.AddSyncResult(startContainerResult)
var msg string
podInfraContainerID, err, msg = dm.createPodInfraContainer(pod)
if err != nil {
startContainerResult.Fail(err, msg)
glog.Errorf("Failed to create pod infra container: %v; Skipping pod %q: %s", err, format.Pod(pod), msg)
return
}
setupNetworkResult := kubecontainer.NewSyncResult(kubecontainer.SetupNetwork, kubecontainer.GetPodFullName(pod))
result.AddSyncResult(setupNetworkResult)
if !kubecontainer.IsHostNetworkPod(pod) {
if err := dm.network.SetUpPod(pod.Namespace, pod.Name, podInfraContainerID.ContainerID(), pod.Annotations); err != nil {
setupNetworkResult.Fail(kubecontainer.ErrSetupNetwork, err.Error())
glog.Error(err)
// Delete infra container
......
所以在SetUpPod中设置好podInfraContainerID的网络即可。
将容器加入指定网络的实现
每个plugin都有一个类型为defaultNetwork
的成员cniNetwork,k8s.io/kubernetes/pkg/kubelet/network/cni/cni.go:
defaultNetwork *cniNetwork
加入、推出网络都是调用defaultNetwork的成员函数,k8s.io/kubernetes/pkg/kubelet/network/cni/cni.go
func (plugin *cniNetworkPlugin) SetUpPod(namespace string, name string, id kubecontainer.ContainerID, annotations map[string]string) error {
if err := plugin.checkInitialized(); err != nil {
return err
}
netnsPath, err := plugin.host.GetNetNS(id.ID)
if err != nil {
return fmt.Errorf("CNI failed to retrieve network namespace path: %v", err)
}
_, err = plugin.loNetwork.addToNetwork(name, namespace, id, netnsPath)
if err != nil {
glog.Errorf("Error while adding to cni lo network: %s", err)
return err
}
_, err = plugin.getDefaultNetwork().addToNetwork(name, namespace, id, netnsPath)
if err != nil {
glog.Errorf("Error while adding to cni network: %s", err)
return err
}
return err
}
k8s.io/kubernetes/pkg/kubelet/network/cni/cni.go,addToNetwork:
netconf, cninet := network.NetworkConfig, network.CNIConfig
glog.V(4).Infof("About to run with conf.Network.Type=%v", netconf.Network.Type)
res, err := cninet.AddNetwork(netconf, rt)
可以看到最终使用的是成员CNIConfig的AddNetwork()完成的。
defaultNetwork
在k8s.io/kubernetes/pkg/kubelet/network/cni/cni.go,getDefaultCNINetwork()中创建:
vendorDir := vendorCNIDir(vendorCNIDirPrefix, conf.Network.Type)
cninet := &libcni.CNIConfig{
Path: []string{binDir, vendorDir},
}
network := &cniNetwork{name: conf.Network.Name, NetworkConfig: conf, CNIConfig: cninet}
return network, nil
cninet的类型是libcni.CNIConfig:
libcni.CNIConfig
k8s.io/kubernetes/vendor/github.com/containernetworking/cni/libcni/api.go:
func (c *CNIConfig) AddNetwork(net *NetworkConfig, rt *RuntimeConf) (*types.Result, error) {
pluginPath, err := invoke.FindInPath(net.Network.Type, c.Path)
if err != nil {
return nil, err
}
return invoke.ExecPluginWithResult(pluginPath, net.Bytes, c.args("ADD", rt))
}
invoke.FindInPath在c.Path目录下寻找名为net.Network.Type的文件,返回文件的完整路径pluginPath
最后,直接使用plugin的子命令ADD
,将容器添加到指定网络中。
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