本代码分析基于kubernetes v1.5.0
功能描述
kube-proxy应该是k8s所有服务里面最简单的服务，它的功能很单一，主要用来管理service，包括service的负载均衡。每个service都有一个cluster ip，service依靠selector label，对应后台的Pod，这个工作主要有kube-controller-manager的endpoint-controller完成，这个controller会生成与service相对应的endpoint。
kube-proxy运行于每一个node节点，它的主要工作就是对service、endpoint进行watch，然后在每一个节点建立相关的iptables表项，这样我们就可以在任意一个node上访问service，同时，假如一个service包含多个endpoint，它还起着负载均衡的作用，流量将平均分配到一个endpoint。
一、服务函数入口
和其他服务一致，kube-proxy的主要位于kubernetes/cmd/kube-proxy。首先options.NewProxyConfig()创建一个配置文件，然后利用配置文件创建服务app.NewProxyServerDefault(config)，最后运行这个服务。
kubernetes/cmd/kube-proxy/proxy.go +55
func init() {
healthz.DefaultHealthz()
}
func main() {
config := options.NewProxyConfig()
config.AddFlags(pflag.CommandLine)
flag.InitFlags()
logs.InitLogs()
defer logs.FlushLogs()
verflag.PrintAndExitIfRequested()
s, err := app.NewProxyServerDefault(config)
if err != nil {
fmt.Fprintf(os.Stderr, "%v\n", err)
os.Exit(1)
}
if err = s.Run(); err != nil {
fmt.Fprintf(os.Stderr, "%v\n", err)
os.Exit(1)
}
}二、创建服务
1、proxier和endpointsHandler的创建
kube-proxy的主要代码就位于创建服务，我们现在解析app.NewProxyServerDefault(config)这个函数。
func NewProxyServerDefault(config *options.ProxyServerConfig) (*ProxyServer, error) {
if c, err := configz.New("componentconfig"); err == nil {
c.Set(config.KubeProxyConfiguration)
} else {
glog.Errorf("unable to register configz: %s", err)
}
protocol := utiliptables.ProtocolIpv4
if net.ParseIP(config.BindAddress).To4() == nil {
protocol = utiliptables.ProtocolIpv6
}
var netshInterface utilnetsh.Interface
var iptInterface utiliptables.Interface
var dbus utildbus.Interface
// Create a iptables utils.
execer := exec.New()
if runtime.GOOS == "windows" {
netshInterface = utilnetsh.New(execer)
} else {
dbus = utildbus.New()
iptInterface = utiliptables.New(execer, dbus, protocol)
}
// We omit creation of pretty much everything if we run in cleanup mode
if config.CleanupAndExit {
return &ProxyServer{
Config: config,
IptInterface: iptInterface,
}, nil
}
// TODO(vmarmol): Use container config for this.
var oomAdjuster *oom.OOMAdjuster
if config.OOMScoreAdj != nil {
oomAdjuster = oom.NewOOMAdjuster()
if err := oomAdjuster.ApplyOOMScoreAdj(0, int(*config.OOMScoreAdj)); err != nil {
glog.V(2).Info(err)
}
}
if config.ResourceContainer != "" {
// Run in its own container.
if err := resourcecontainer.RunInResourceContainer(config.ResourceContainer); err != nil {
glog.Warningf("Failed to start in resource-only container %q: %v", config.ResourceContainer, err)
} else {
glog.V(2).Infof("Running in resource-only container %q", config.ResourceContainer)
}
}
// Create a Kube Client
// define api config source
if config.Kubeconfig == "" && config.Master == "" {
glog.Warningf("Neither --kubeconfig nor --master was specified. Using default API client. This might not work.")
}
// This creates a client, first loading any specified kubeconfig
// file, and then overriding the Master flag, if non-empty.
kubeconfig, err := clientcmd.NewNonInteractiveDeferredLoadingClientConfig(
&clientcmd.ClientConfigLoadingRules{ExplicitPath: config.Kubeconfig},
&clientcmd.ConfigOverrides{ClusterInfo: clientcmdapi.Cluster{Server: config.Master}}).ClientConfig()
if err != nil {
return nil, err
}
kubeconfig.ContentType = config.ContentType
// Override kubeconfig qps/burst settings from flags
kubeconfig.QPS = config.KubeAPIQPS
kubeconfig.Burst = int(config.KubeAPIBurst)
client, err := clientset.NewForConfig(kubeconfig)
if err != nil {
glog.Fatalf("Invalid API configuration: %v", err)
}
// Create event recorder
hostname := nodeutil.GetHostname(config.HostnameOverride)
eventBroadcaster := record.NewBroadcaster()
recorder := eventBroadcaster.NewRecorder(api.EventSource{Component: "kube-proxy", Host: hostname})
var proxier proxy.ProxyProvider
var endpointsHandler proxyconfig.EndpointsConfigHandler
proxyMode := getProxyMode(string(config.Mode), client.Core().Nodes(), hostname, iptInterface, iptables.LinuxKernelCompatTester{})
if proxyMode == proxyModeIPTables {
glog.V(0).Info("Using iptables Proxier.")
if config.IPTablesMasqueradeBit == nil {
// IPTablesMasqueradeBit must be specified or defaulted.
return nil, fmt.Errorf("Unable to read IPTablesMasqueradeBit from config")
}
proxierIPTables, err := iptables.NewProxier(iptInterface, utilsysctl.New(), execer, config.IPTablesSyncPeriod.Duration, config.IPTablesMinSyncPeriod.Duration, config.MasqueradeAll, int(*config.IPTablesMasqueradeBit), config.ClusterCIDR, hostname, getNodeIP(client, hostname))
if err != nil {
glog.Fatalf("Unable to create proxier: %v", err)
}
proxier = proxierIPTables
endpointsHandler = proxierIPTables
// No turning back. Remove artifacts that might still exist from the userspace Proxier.
glog.V(0).Info("Tearing down userspace rules.")
userspace.CleanupLeftovers(iptInterface)
} else {
glog.V(0).Info("Using userspace Proxier.")
// This is a proxy.LoadBalancer which NewProxier needs but has methods we don't need for
// our config.EndpointsConfigHandler.
loadBalancer := userspace.NewLoadBalancerRR()
// set EndpointsConfigHandler to our loadBalancer
endpointsHandler = loadBalancer
var proxierUserspace proxy.ProxyProvider
if runtime.GOOS == "windows" {
proxierUserspace, err = winuserspace.NewProxier(
loadBalancer,
net.ParseIP(config.BindAddress),
netshInterface,
*utilnet.ParsePortRangeOrDie(config.PortRange),
// TODO @pires replace below with default values, if applicable
config.IPTablesSyncPeriod.Duration,
config.UDPIdleTimeout.Duration,
)
} else {
proxierUserspace, err = userspace.NewProxier(
loadBalancer,
net.ParseIP(config.BindAddress),
iptInterface,
*utilnet.ParsePortRangeOrDie(config.PortRange),
config.IPTablesSyncPeriod.Duration,
config.IPTablesMinSyncPeriod.Duration,
config.UDPIdleTimeout.Duration,
)
}
if err != nil {
glog.Fatalf("Unable to create proxier: %v", err)
}
proxier = proxierUserspace
// Remove artifacts from the pure-iptables Proxier, if not on Windows.
if runtime.GOOS != "windows" {
glog.V(0).Info("Tearing down pure-iptables proxy rules.")
iptables.CleanupLeftovers(iptInterface)
}
}
// Add iptables reload function, if not on Windows.
if runtime.GOOS != "windows" {
iptInterface.AddReloadFunc(proxier.Sync)
}
// Create configs (i.e. Watches for Services and Endpoints)
// Note: RegisterHandler() calls need to happen before creation of Sources because sources
// only notify on changes, and the initial update (on process start) may be lost if no handlers
// are registered yet.
serviceConfig := proxyconfig.NewServiceConfig()
serviceConfig.RegisterHandler(proxier)
endpointsConfig := proxyconfig.NewEndpointsConfig()
endpointsConfig.RegisterHandler(endpointsHandler)
proxyconfig.NewSourceAPI(
client.Core().RESTClient(),
config.ConfigSyncPeriod,
serviceConfig.Channel("api"),
endpointsConfig.Channel("api"),
)
config.NodeRef = &api.ObjectReference{
Kind: "Node",
Name: hostname,
UID: types.UID(hostname),
Namespace: "",
}
conntracker := realConntracker{}
return NewProxyServer(client, config, iptInterface, proxier, eventBroadcaster, recorder, conntracker, proxyMode)
}kube-proxy有两种运行模式，一种是基于用户态proxy，另一种是基于内核态的iptables。基于iptables，效率更高。这里我们主要讨论基于iptables的工作模式。
进入 if proxyMode == proxyModeIptables 函数，这个函数内部主要构建了两个对象，一个是proxier，另一个是endpointsHandler，他们都是proxierIptables。
2、serviceconfig创建
NewServiceConfig首先创建了一个channel，然后创建一个serviceStore，这个serviceStore主要用于存储从api-service watch的service，当然之前还有一些过滤操作。然后创建了一个mux和bcaster，然后启动一个goroutine,运行函数watchForUpdates，假如updates可读，则立即执行bcaster.Notify(accessor.MergedState())。其实这里利用了broadcaster这一套框架，其实主要是我们可以向broadcaster注册listeners，broadcaster有更新时，调用notify通知所有的listener。
serviceConfig.RegisterHandler(proxier)其实就是注册了一个listener，到收到通知时，它会执行handler.OnServiceUpdate(instance.([]api.Service))函数。
只有updates可读时，才会触发bcaster.Notify，进而促发handler.OnServiceUpdate(instance.([]api.Service)),那么谁会往updates这个channel里面写入东西呢？
kubernetes/cmd/kube-proxy/app/server.go +280
serviceConfig := proxyconfig.NewServiceConfig()
serviceConfig.RegisterHandler(proxier)kubernetes/pkg/proxy/config/config.go +193
func NewServiceConfig() *ServiceConfig {
updates := make(chan struct{}, 1)
store := &serviceStore{updates: updates, services: make(map[string]map[types.NamespacedName]api.Service)}
mux := config.NewMux(store)
bcaster := config.NewBroadcaster()
go watchForUpdates(bcaster, store, updates)
return &ServiceConfig{mux, bcaster, store}
}
func (c *ServiceConfig) RegisterHandler(handler ServiceConfigHandler) {
c.bcaster.Add(config.ListenerFunc(func(instance interface{}) {
glog.V(3).Infof("Calling handler.OnServiceUpdate()")
handler.OnServiceUpdate(instance.([]api.Service))
}))
}
...
func watchForUpdates(bcaster *config.Broadcaster, accessor config.Accessor, updates <-chan struct{}) {
for true {
<-updates
bcaster.Notify(accessor.MergedState())
}
}3、endpointsConfig的创建
逻辑和serviceConfig的创建完全一样，只是将service换成了endpoint。
kubernetes/cmd/kube-proxy/app/server.go +283
endpointsConfig := proxyconfig.NewEndpointsConfig()
endpointsConfig.RegisterHandler(endpointsHandler)kubernetes/pkg/proxy/config/config.go +84
func NewEndpointsConfig() *EndpointsConfig {
updates := make(chan struct{}, 1)
store := &endpointsStore{updates: updates, endpoints: make(map[string]map[types.NamespacedName]api.Endpoints)}
mux := config.NewMux(store)
bcaster := config.NewBroadcaster()
go watchForUpdates(bcaster, store, updates)
return &EndpointsConfig{mux, bcaster, store}
}
func (c *EndpointsConfig) RegisterHandler(handler EndpointsConfigHandler) {
c.bcaster.Add(config.ListenerFunc(func(instance interface{}) {
glog.V(3).Infof("Calling handler.OnEndpointsUpdate()")
handler.OnEndpointsUpdate(instance.([]api.Endpoints))
}))
}4、 service和endpoint的真实来源
service、endpoint肯定来源于apiserver，kube-proxy如何获取呢？获取的关键代码是proxyconfig.NewSourceAPI这个函数。我们看看这个函数传入的几个参数，主要看后两个，serviceConfig.Channel(“api”)和endpointsConfig.Channel(“api”)，这里以service为例。
kubernetes/cmd/kube-proxy/app/server.go +286
proxyconfig.NewSourceAPI(
client,
config.ConfigSyncPeriod,
serviceConfig.Channel("api"),
endpointsConfig.Channel("api"),
)首先调用c.mux.Channel构建创建了ch，ch本质上是一个channel，然后又创建了一个serviceCh。启动一个goroutine，这个goroutine的作用就是从serviceCh读取东西，然后写入ch。最后返回这个serviceCh
kubernetes/pkg/proxy/config/config.go +213
func (c *ServiceConfig) Channel(source string) chan ServiceUpdate {
ch := c.mux.Channel(source)
serviceCh := make(chan ServiceUpdate)
go func() {
for update := range serviceCh {
ch <- update
}
close(ch)
}()
return serviceCh
}返回的serviceCh被传入proxyconfig.NewSourceAPI函数。我们看一下这个函数，其实主要创建了两个reflector，用来从kube-apiserver同步service和endpoint信息，同步的信息会写入serviceCh和endpointCh。这些信息进而会写入ch这个channel。那么谁会从ch读取信息呢。问题的关键是ch := c.mux.Channel(source)
kubernetes/pkg/proxy/config/api.go +28
func NewSourceAPI(c cache.Getter, period time.Duration, servicesChan chan<- ServiceUpdate, endpointsChan chan<- EndpointsUpdate) {
servicesLW := cache.NewListWatchFromClient(c, "services", api.NamespaceAll, fields.Everything())
cache.NewReflector(servicesLW, &api.Service{}, NewServiceStore(nil, servicesChan), period).Run()
endpointsLW := cache.NewListWatchFromClient(c, "endpoints", api.NamespaceAll, fields.Everything())
cache.NewReflector(endpointsLW, &api.Endpoints{}, NewEndpointsStore(nil, endpointsChan), period).Run()
}
func NewServiceStore(store cache.Store, ch chan<- ServiceUpdate) cache.Store {
fn := func(objs []interface{}) {
var services []api.Service
for _, o := range objs {
services = append(services, *(o.(*api.Service)))
}
ch <- ServiceUpdate{Op: SET, Services: services}
}
if store == nil {
store = cache.NewStore(cache.MetaNamespaceKeyFunc)
}
return &cache.UndeltaStore{
Store: store,
PushFunc: fn,
}
}
func NewEndpointsStore(store cache.Store, ch chan<- EndpointsUpdate) cache.Store {
fn := func(objs []interface{}) {
var endpoints []api.Endpoints
for _, o := range objs {
endpoints = append(endpoints, *(o.(*api.Endpoints)))
}
ch <- EndpointsUpdate{Op: SET, Endpoints: endpoints}
}
if store == nil {
store = cache.NewStore(cache.MetaNamespaceKeyFunc)
}
return &cache.UndeltaStore{
Store: store,
PushFunc: fn,
}
}5、Mux框架
Mux框架代码的位于kubernetes/pkg/util/config/config.go。它的主要作用是合并多个数据源，每一次调用Channel(source)都会注册一个数据源，同时返回一个channel，我们可以往返回的channel中写入数据，一旦写入数据就会促发Merge函数。上面的ch这个channel，就是调用Channel返回的。我们看看service的Merge函数，endpoint类似
kubernetes/pkg/proxy/config/config.go +235
func (s *serviceStore) Merge(source string, change interface{}) error {
s.serviceLock.Lock()
services := s.services[source]
if services == nil {
services = make(map[types.NamespacedName]api.Service)
}
update := change.(ServiceUpdate)
switch update.Op {
case ADD:
glog.V(5).Infof("Adding new service from source %s : %s", source, spew.Sdump(update.Services))
for _, value := range update.Services {
name := types.NamespacedName{Namespace: value.Namespace, Name: value.Name}
services[name] = value
}
case REMOVE:
glog.V(5).Infof("Removing a service %s", spew.Sdump(update))
for _, value := range update.Services {
name := types.NamespacedName{Namespace: value.Namespace, Name: value.Name}
delete(services, name)
}
case SET:
glog.V(5).Infof("Setting services %s", spew.Sdump(update))
// Clear the old map entries by just creating a new map
services = make(map[types.NamespacedName]api.Service)
for _, value := range update.Services {
name := types.NamespacedName{Namespace: value.Namespace, Name: value.Name}
services[name] = value
}
default:
glog.V(4).Infof("Received invalid update type: %s", spew.Sdump(update))
}
s.services[source] = services
s.serviceLock.Unlock()
if s.updates != nil {
// Since we record the snapshot before sending this signal, it's
// possible that the consumer ends up performing an extra update.
select {
case s.updates <- struct{}{}:
default:
glog.V(4).Infof("Service handler already has a pending interrupt.")
}
}
return nil
}这个函数的作用写将获取的service写到serviceStore.services，然后往updates写入一个空的结构体，updates变成可读的，这样就将前面的东西串联起来了。
6、OnServiceUpdate和OnEndpointsUpdate
以OnServiceUpdate函数为例
func (proxier *Proxier) OnServiceUpdate(allServices []api.Service) {
start := time.Now()
defer func() {
glog.V(4).Infof("OnServiceUpdate took %v for %d services", time.Since(start), len(allServices))
}()
proxier.mu.Lock()
defer proxier.mu.Unlock()
proxier.haveReceivedServiceUpdate = true
activeServices := make(map[proxy.ServicePortName]bool) // use a map as a set
for i := range allServices {
service := &allServices[i]
svcName := types.NamespacedName{
Namespace: service.Namespace,
Name: service.Name,
}
// if ClusterIP is "None" or empty, skip proxying
if !api.IsServiceIPSet(service) {
glog.V(3).Infof("Skipping service %s due to clusterIP = %q", svcName, service.Spec.ClusterIP)
continue
}
for i := range service.Spec.Ports {
servicePort := &service.Spec.Ports[i]
serviceName := proxy.ServicePortName{
NamespacedName: svcName,
Port: servicePort.Name,
}
activeServices[serviceName] = true
info, exists := proxier.serviceMap[serviceName]
if exists && proxier.sameConfig(info, service, servicePort) {
// Nothing changed.
continue
}
if exists {
// Something changed.
glog.V(3).Infof("Something changed for service %q: removing it", serviceName)
delete(proxier.serviceMap, serviceName)
}
serviceIP := net.ParseIP(service.Spec.ClusterIP)
glog.V(1).Infof("Adding new service %q at %s:%d/%s", serviceName, serviceIP, servicePort.Port, servicePort.Protocol)
info = newServiceInfo(serviceName)
info.clusterIP = serviceIP
info.port = int(servicePort.Port)
info.protocol = servicePort.Protocol
info.nodePort = int(servicePort.NodePort)
info.externalIPs = service.Spec.ExternalIPs
// Deep-copy in case the service instance changes
info.loadBalancerStatus = *api.LoadBalancerStatusDeepCopy(&service.Status.LoadBalancer)
info.sessionAffinityType = service.Spec.SessionAffinity
info.loadBalancerSourceRanges = service.Spec.LoadBalancerSourceRanges
proxier.serviceMap[serviceName] = info
glog.V(4).Infof("added serviceInfo(%s): %s", serviceName, spew.Sdump(info))
}
}
staleUDPServices := sets.NewString()
// Remove services missing from the update.
for name := range proxier.serviceMap {
if !activeServices[name] {
glog.V(1).Infof("Removing service %q", name)
if proxier.serviceMap[name].protocol == api.ProtocolUDP {
staleUDPServices.Insert(proxier.serviceMap[name].clusterIP.String())
}
delete(proxier.serviceMap, name)
}
}
proxier.syncProxyRules()
proxier.deleteServiceConnections(staleUDPServices.List())
}代码的核心是根据获取的service信息，构建proxier.serviceMap，然后调用proxier.syncProxyRules()去同步iptables信息。
从上述的分析可知，一旦service、endpoint有变化，相应的iptables规则就会得到更新。
三、运行服务
kubernetes/cmd/kube-proxy/app/server.go +306
func (s *ProxyServer) Run() error {
// remove iptables rules and exit
if s.Config.CleanupAndExit {
encounteredError := userspace.CleanupLeftovers(s.IptInterface)
encounteredError = iptables.CleanupLeftovers(s.IptInterface) || encounteredError
if encounteredError {
return errors.New("Encountered an error while tearing down rules.")
}
return nil
}
s.Broadcaster.StartRecordingToSink(s.Client.Events(""))
// Start up a webserver if requested
if s.Config.HealthzPort > 0 {
http.HandleFunc("/proxyMode", func(w http.ResponseWriter, r *http.Request) {
fmt.Fprintf(w, "%s", s.ProxyMode)
})
configz.InstallHandler(http.DefaultServeMux)
go wait.Until(func() {
err := http.ListenAndServe(s.Config.HealthzBindAddress+":"+strconv.Itoa(int(s.Config.HealthzPort)), nil)
if err != nil {
glog.Errorf("Starting health server failed: %v", err)
}
}, 5*time.Second, wait.NeverStop)
}
// Tune conntrack, if requested
if s.Conntracker != nil {
max, err := getConntrackMax(s.Config)
if err != nil {
return err
}
if max > 0 {
err := s.Conntracker.SetMax(max)
if err != nil {
if err != readOnlySysFSError {
return err
}
const message = "DOCKER RESTART NEEDED (docker issue #24000): /sys is read-only: can't raise conntrack limits, problems may arise later."
s.Recorder.Eventf(s.Config.NodeRef, api.EventTypeWarning, err.Error(), message)
}
}
if s.Config.ConntrackTCPEstablishedTimeout.Duration > 0 {
if err := s.Conntracker.SetTCPEstablishedTimeout(int(s.Config.ConntrackTCPEstablishedTimeout.Duration / time.Second)); err != nil {
return err
}
}
}
// Birth Cry after the birth is successful
s.birthCry()
// Just loop forever for now...
s.Proxier.SyncLoop()
return nil
}
kubernetes/pkg/proxy/iptables/proxier.go +385
func (proxier *Proxier) SyncLoop() {
t := time.NewTicker(proxier.syncPeriod)
defer t.Stop()
for {
<-t.C
glog.V(6).Infof("Periodic sync")
proxier.Sync()
}
}
func (proxier *Proxier) Sync() {
proxier.mu.Lock()
defer proxier.mu.Unlock()
proxier.syncProxyRules()
}code url:
k8s.io/kubernetes/pkg/proxy/iptables/proxier.go
Run()的作用主要是每隔proxier.syncPeriod，会调用一次proxier.Sync()，进而调用proxier.syncProxyRules()。proxier.syncPeriod的默认值为30秒
至于怎么更新iptables，查看synxProxyRules即可。
func (proxier *Proxier) syncProxyRules() {
if proxier.throttle != nil {
proxier.throttle.Accept()
}
start := time.Now()
defer func() {
glog.V(4).Infof("syncProxyRules took %v", time.Since(start))
}()
// don't sync rules till we've received services and endpoints
if !proxier.haveReceivedEndpointsUpdate || !proxier.haveReceivedServiceUpdate {
glog.V(2).Info("Not syncing iptables until Services and Endpoints have been received from master")
return
}
glog.V(3).Infof("Syncing iptables rules")
// Create and link the kube services chain.
{
tablesNeedServicesChain := []utiliptables.Table{utiliptables.TableFilter, utiliptables.TableNAT}
for _, table := range tablesNeedServicesChain {
if _, err := proxier.iptables.EnsureChain(table, kubeServicesChain); err != nil {
glog.Errorf("Failed to ensure that %s chain %s exists: %v", table, kubeServicesChain, err)
return
}
}
tableChainsNeedJumpServices := []struct {
table utiliptables.Table
chain utiliptables.Chain
}{
{utiliptables.TableFilter, utiliptables.ChainOutput},
{utiliptables.TableNAT, utiliptables.ChainOutput},
{utiliptables.TableNAT, utiliptables.ChainPrerouting},
}
comment := "kubernetes service portals"
args := []string{"-m", "comment", "--comment", comment, "-j", string(kubeServicesChain)}
for _, tc := range tableChainsNeedJumpServices {
if _, err := proxier.iptables.EnsureRule(utiliptables.Prepend, tc.table, tc.chain, args...); err != nil {
glog.Errorf("Failed to ensure that %s chain %s jumps to %s: %v", tc.table, tc.chain, kubeServicesChain, err)
return
}
}
}
// Create and link the kube postrouting chain.
{
if _, err := proxier.iptables.EnsureChain(utiliptables.TableNAT, kubePostroutingChain); err != nil {
glog.Errorf("Failed to ensure that %s chain %s exists: %v", utiliptables.TableNAT, kubePostroutingChain, err)
return
}
comment := "kubernetes postrouting rules"
args := []string{"-m", "comment", "--comment", comment, "-j", string(kubePostroutingChain)}
if _, err := proxier.iptables.EnsureRule(utiliptables.Prepend, utiliptables.TableNAT, utiliptables.ChainPostrouting, args...); err != nil {
glog.Errorf("Failed to ensure that %s chain %s jumps to %s: %v", utiliptables.TableNAT, utiliptables.ChainPostrouting, kubePostroutingChain, err)
return
}
}
// Get iptables-save output so we can check for existing chains and rules.
// This will be a map of chain name to chain with rules as stored in iptables-save/iptables-restore
existingFilterChains := make(map[utiliptables.Chain]string)
iptablesSaveRaw, err := proxier.iptables.Save(utiliptables.TableFilter)
if err != nil { // if we failed to get any rules
glog.Errorf("Failed to execute iptables-save, syncing all rules: %v", err)
} else { // otherwise parse the output
existingFilterChains = utiliptables.GetChainLines(utiliptables.TableFilter, iptablesSaveRaw)
}
existingNATChains := make(map[utiliptables.Chain]string)
iptablesSaveRaw, err = proxier.iptables.Save(utiliptables.TableNAT)
if err != nil { // if we failed to get any rules
glog.Errorf("Failed to execute iptables-save, syncing all rules: %v", err)
} else { // otherwise parse the output
existingNATChains = utiliptables.GetChainLines(utiliptables.TableNAT, iptablesSaveRaw)
}
filterChains := bytes.NewBuffer(nil)
filterRules := bytes.NewBuffer(nil)
natChains := bytes.NewBuffer(nil)
natRules := bytes.NewBuffer(nil)
// Write table headers.
writeLine(filterChains, "*filter")
writeLine(natChains, "*nat")
// Make sure we keep stats for the top-level chains, if they existed
// (which most should have because we created them above).
if chain, ok := existingFilterChains[kubeServicesChain]; ok {
writeLine(filterChains, chain)
} else {
writeLine(filterChains, utiliptables.MakeChainLine(kubeServicesChain))
}
if chain, ok := existingNATChains[kubeServicesChain]; ok {
writeLine(natChains, chain)
} else {
writeLine(natChains, utiliptables.MakeChainLine(kubeServicesChain))
}
if chain, ok := existingNATChains[kubeNodePortsChain]; ok {
writeLine(natChains, chain)
} else {
writeLine(natChains, utiliptables.MakeChainLine(kubeNodePortsChain))
}
if chain, ok := existingNATChains[kubePostroutingChain]; ok {
writeLine(natChains, chain)
} else {
writeLine(natChains, utiliptables.MakeChainLine(kubePostroutingChain))
}
if chain, ok := existingNATChains[KubeMarkMasqChain]; ok {
writeLine(natChains, chain)
} else {
writeLine(natChains, utiliptables.MakeChainLine(KubeMarkMasqChain))
}
// Install the kubernetes-specific postrouting rules. We use a whole chain for
// this so that it is easier to flush and change, for example if the mark
// value should ever change.
writeLine(natRules, []string{
"-A", string(kubePostroutingChain),
"-m", "comment", "--comment", `"kubernetes service traffic requiring SNAT"`,
"-m", "mark", "--mark", proxier.masqueradeMark,
"-j", "MASQUERADE",
}...)
// Install the kubernetes-specific masquerade mark rule. We use a whole chain for
// this so that it is easier to flush and change, for example if the mark
// value should ever change.
writeLine(natRules, []string{
"-A", string(KubeMarkMasqChain),
"-j", "MARK", "--set-xmark", proxier.masqueradeMark,
}...)
// Accumulate NAT chains to keep.
activeNATChains := map[utiliptables.Chain]bool{} // use a map as a set
// Accumulate the set of local ports that we will be holding open once this update is complete
replacementPortsMap := map[localPort]closeable{}
// Build rules for each service.
for svcName, svcInfo := range proxier.serviceMap {
protocol := strings.ToLower(string(svcInfo.protocol))
// Create the per-service chain, retaining counters if possible.
svcChain := servicePortChainName(svcName, protocol)
if chain, ok := existingNATChains[svcChain]; ok {
writeLine(natChains, chain)
} else {
writeLine(natChains, utiliptables.MakeChainLine(svcChain))
}
activeNATChains[svcChain] = true
svcXlbChain := serviceLBChainName(svcName, protocol)
if svcInfo.onlyNodeLocalEndpoints {
// Only for services with the externalTraffic annotation set to OnlyLocal
// create the per-service LB chain, retaining counters if possible.
if lbChain, ok := existingNATChains[svcXlbChain]; ok {
writeLine(natChains, lbChain)
} else {
writeLine(natChains, utiliptables.MakeChainLine(svcXlbChain))
}
activeNATChains[svcXlbChain] = true
} else if activeNATChains[svcXlbChain] {
// Cleanup the previously created XLB chain for this service
delete(activeNATChains, svcXlbChain)
}
// Capture the clusterIP.
args := []string{
"-A", string(kubeServicesChain),
"-m", "comment", "--comment", fmt.Sprintf(`"%s cluster IP"`, svcName.String()),
"-m", protocol, "-p", protocol,
"-d", fmt.Sprintf("%s/32", svcInfo.clusterIP.String()),
"--dport", fmt.Sprintf("%d", svcInfo.port),
}
if proxier.masqueradeAll {
writeLine(natRules, append(args, "-j", string(KubeMarkMasqChain))...)
}
if len(proxier.clusterCIDR) > 0 {
writeLine(natRules, append(args, "! -s", proxier.clusterCIDR, "-j", string(KubeMarkMasqChain))...)
}
writeLine(natRules, append(args, "-j", string(svcChain))...)
// Capture externalIPs.
for _, externalIP := range svcInfo.externalIPs {
// If the "external" IP happens to be an IP that is local to this
// machine, hold the local port open so no other process can open it
// (because the socket might open but it would never work).
if local, err := isLocalIP(externalIP); err != nil {
glog.Errorf("can't determine if IP is local, assuming not: %v", err)
} else if local {
lp := localPort{
desc: "externalIP for " + svcName.String(),
ip: externalIP,
port: svcInfo.port,
protocol: protocol,
}
if proxier.portsMap[lp] != nil {
glog.V(4).Infof("Port %s was open before and is still needed", lp.String())
replacementPortsMap[lp] = proxier.portsMap[lp]
} else {
socket, err := proxier.portMapper.OpenLocalPort(&lp)
if err != nil {
glog.Errorf("can't open %s, skipping this externalIP: %v", lp.String(), err)
continue
}
replacementPortsMap[lp] = socket
}
} // We're holding the port, so it's OK to install iptables rules.
args := []string{
"-A", string(kubeServicesChain),
"-m", "comment", "--comment", fmt.Sprintf(`"%s external IP"`, svcName.String()),
"-m", protocol, "-p", protocol,
"-d", fmt.Sprintf("%s/32", externalIP),
"--dport", fmt.Sprintf("%d", svcInfo.port),
}
// We have to SNAT packets to external IPs.
writeLine(natRules, append(args, "-j", string(KubeMarkMasqChain))...)
// Allow traffic for external IPs that does not come from a bridge (i.e. not from a container)
// nor from a local process to be forwarded to the service.
// This rule roughly translates to "all traffic from off-machine".
// This is imperfect in the face of network plugins that might not use a bridge, but we can revisit that later.
externalTrafficOnlyArgs := append(args,
"-m", "physdev", "!", "--physdev-is-in",
"-m", "addrtype", "!", "--src-type", "LOCAL")
writeLine(natRules, append(externalTrafficOnlyArgs, "-j", string(svcChain))...)
dstLocalOnlyArgs := append(args, "-m", "addrtype", "--dst-type", "LOCAL")
// Allow traffic bound for external IPs that happen to be recognized as local IPs to stay local.
// This covers cases like GCE load-balancers which get added to the local routing table.
writeLine(natRules, append(dstLocalOnlyArgs, "-j", string(svcChain))...)
}
// Capture load-balancer ingress.
for _, ingress := range svcInfo.loadBalancerStatus.Ingress {
if ingress.IP != "" {
// create service firewall chain
fwChain := serviceFirewallChainName(svcName, protocol)
if chain, ok := existingNATChains[fwChain]; ok {
writeLine(natChains, chain)
} else {
writeLine(natChains, utiliptables.MakeChainLine(fwChain))
}
activeNATChains[fwChain] = true
// The service firewall rules are created based on ServiceSpec.loadBalancerSourceRanges field.
// This currently works for loadbalancers that preserves source ips.
// For loadbalancers which direct traffic to service NodePort, the firewall rules will not apply.
args := []string{
"-A", string(kubeServicesChain),
"-m", "comment", "--comment", fmt.Sprintf(`"%s loadbalancer IP"`, svcName.String()),
"-m", protocol, "-p", protocol,
"-d", fmt.Sprintf("%s/32", ingress.IP),
"--dport", fmt.Sprintf("%d", svcInfo.port),
}
// jump to service firewall chain
writeLine(natRules, append(args, "-j", string(fwChain))...)
args = []string{
"-A", string(fwChain),
"-m", "comment", "--comment", fmt.Sprintf(`"%s loadbalancer IP"`, svcName.String()),
}
// Each source match rule in the FW chain may jump to either the SVC or the XLB chain
chosenChain := svcXlbChain
// If we are proxying globally, we need to masquerade in case we cross nodes.
// If we are proxying only locally, we can retain the source IP.
if !svcInfo.onlyNodeLocalEndpoints {
writeLine(natRules, append(args, "-j", string(KubeMarkMasqChain))...)
chosenChain = svcChain
}
if len(svcInfo.loadBalancerSourceRanges) == 0 {
// allow all sources, so jump directly to the KUBE-SVC or KUBE-XLB chain
writeLine(natRules, append(args, "-j", string(chosenChain))...)
} else {
// firewall filter based on each source range
allowFromNode := false
for _, src := range svcInfo.loadBalancerSourceRanges {
writeLine(natRules, append(args, "-s", src, "-j", string(chosenChain))...)
// ignore error because it has been validated
_, cidr, _ := net.ParseCIDR(src)
if cidr.Contains(proxier.nodeIP) {
allowFromNode = true
}
}
// generally, ip route rule was added to intercept request to loadbalancer vip from the
// loadbalancer's backend hosts. In this case, request will not hit the loadbalancer but loop back directly.
// Need to add the following rule to allow request on host.
if allowFromNode {
writeLine(natRules, append(args, "-s", fmt.Sprintf("%s/32", ingress.IP), "-j", string(chosenChain))...)
}
}
// If the packet was able to reach the end of firewall chain, then it did not get DNATed.
// It means the packet cannot go thru the firewall, then mark it for DROP
writeLine(natRules, append(args, "-j", string(KubeMarkDropChain))...)
}
}
// Capture nodeports. If we had more than 2 rules it might be
// worthwhile to make a new per-service chain for nodeport rules, but
// with just 2 rules it ends up being a waste and a cognitive burden.
if svcInfo.nodePort != 0 {
// Hold the local port open so no other process can open it
// (because the socket might open but it would never work).
lp := localPort{
desc: "nodePort for " + svcName.String(),
ip: "",
port: svcInfo.nodePort,
protocol: protocol,
}
if proxier.portsMap[lp] != nil {
glog.V(4).Infof("Port %s was open before and is still needed", lp.String())
replacementPortsMap[lp] = proxier.portsMap[lp]
} else {
socket, err := proxier.portMapper.OpenLocalPort(&lp)
if err != nil {
glog.Errorf("can't open %s, skipping this nodePort: %v", lp.String(), err)
continue
}
replacementPortsMap[lp] = socket
} // We're holding the port, so it's OK to install iptables rules.
args := []string{
"-A", string(kubeNodePortsChain),
"-m", "comment", "--comment", svcName.String(),
"-m", protocol, "-p", protocol,
"--dport", fmt.Sprintf("%d", svcInfo.nodePort),
}
if !svcInfo.onlyNodeLocalEndpoints {
// Nodeports need SNAT, unless they're local.
writeLine(natRules, append(args, "-j", string(KubeMarkMasqChain))...)
// Jump to the service chain.
writeLine(natRules, append(args, "-j", string(svcChain))...)
} else {
// TODO: Make all nodePorts jump to the firewall chain.
// Currently we only create it for loadbalancers (#33586).
writeLine(natRules, append(args, "-j", string(svcXlbChain))...)
}
}
// If the service has no endpoints then reject packets.
if len(proxier.endpointsMap[svcName]) == 0 {
writeLine(filterRules,
"-A", string(kubeServicesChain),
"-m", "comment", "--comment", fmt.Sprintf(`"%s has no endpoints"`, svcName.String()),
"-m", protocol, "-p", protocol,
"-d", fmt.Sprintf("%s/32", svcInfo.clusterIP.String()),
"--dport", fmt.Sprintf("%d", svcInfo.port),
"-j", "REJECT",
)
continue
}
// Generate the per-endpoint chains. We do this in multiple passes so we
// can group rules together.
// These two slices parallel each other - keep in sync
endpoints := make([]*endpointsInfo, 0)
endpointChains := make([]utiliptables.Chain, 0)
for _, ep := range proxier.endpointsMap[svcName] {
endpoints = append(endpoints, ep)
endpointChain := servicePortEndpointChainName(svcName, protocol, ep.ip)
endpointChains = append(endpointChains, endpointChain)
// Create the endpoint chain, retaining counters if possible.
if chain, ok := existingNATChains[utiliptables.Chain(endpointChain)]; ok {
writeLine(natChains, chain)
} else {
writeLine(natChains, utiliptables.MakeChainLine(endpointChain))
}
activeNATChains[endpointChain] = true
}
// First write session affinity rules, if applicable.
if svcInfo.sessionAffinityType == api.ServiceAffinityClientIP {
for _, endpointChain := range endpointChains {
writeLine(natRules,
"-A", string(svcChain),
"-m", "comment", "--comment", svcName.String(),
"-m", "recent", "--name", string(endpointChain),
"--rcheck", "--seconds", fmt.Sprintf("%d", svcInfo.stickyMaxAgeMinutes*60), "--reap",
"-j", string(endpointChain))
}
}
// Now write loadbalancing & DNAT rules.
n := len(endpointChains)
for i, endpointChain := range endpointChains {
// Balancing rules in the per-service chain.
args := []string{
"-A", string(svcChain),
"-m", "comment", "--comment", svcName.String(),
}
if i < (n - 1) {
// Each rule is a probabilistic match.
args = append(args,
"-m", "statistic",
"--mode", "random",
"--probability", fmt.Sprintf("%0.5f", 1.0/float64(n-i)))
}
// The final (or only if n == 1) rule is a guaranteed match.
args = append(args, "-j", string(endpointChain))
writeLine(natRules, args...)
// Rules in the per-endpoint chain.
args = []string{
"-A", string(endpointChain),
"-m", "comment", "--comment", svcName.String(),
}
// Handle traffic that loops back to the originator with SNAT.
writeLine(natRules, append(args,
"-s", fmt.Sprintf("%s/32", strings.Split(endpoints[i].ip, ":")[0]),
"-j", string(KubeMarkMasqChain))...)
// Update client-affinity lists.
if svcInfo.sessionAffinityType == api.ServiceAffinityClientIP {
args = append(args, "-m", "recent", "--name", string(endpointChain), "--set")
}
// DNAT to final destination.
args = append(args, "-m", protocol, "-p", protocol, "-j", "DNAT", "--to-destination", endpoints[i].ip)
writeLine(natRules, args...)
}
// The logic below this applies only if this service is marked as OnlyLocal
if !svcInfo.onlyNodeLocalEndpoints {
continue
}
// Now write ingress loadbalancing & DNAT rules only for services that have a localOnly annotation
// TODO - This logic may be combinable with the block above that creates the svc balancer chain
localEndpoints := make([]*endpointsInfo, 0)
localEndpointChains := make([]utiliptables.Chain, 0)
for i := range endpointChains {
if endpoints[i].localEndpoint {
// These slices parallel each other; must be kept in sync
localEndpoints = append(localEndpoints, endpoints[i])
localEndpointChains = append(localEndpointChains, endpointChains[i])
}
}
// First rule in the chain redirects all pod -> external vip traffic to the
// Service's ClusterIP instead. This happens whether or not we have local
// endpoints; only if clusterCIDR is specified
if len(proxier.clusterCIDR) > 0 {
args = []string{
"-A", string(svcXlbChain),
"-m", "comment", "--comment",
fmt.Sprintf(`"Redirect pods trying to reach external loadbalancer VIP to clusterIP"`),
"-s", proxier.clusterCIDR,
"-j", string(svcChain),
}
writeLine(natRules, args...)
}
numLocalEndpoints := len(localEndpointChains)
if numLocalEndpoints == 0 {
// Blackhole all traffic since there are no local endpoints
args := []string{
"-A", string(svcXlbChain),
"-m", "comment", "--comment",
fmt.Sprintf(`"%s has no local endpoints"`, svcName.String()),
"-j",
string(KubeMarkDropChain),
}
writeLine(natRules, args...)
} else {
// Setup probability filter rules only over local endpoints
for i, endpointChain := range localEndpointChains {
// Balancing rules in the per-service chain.
args := []string{
"-A", string(svcXlbChain),
"-m", "comment", "--comment",
fmt.Sprintf(`"Balancing rule %d for %s"`, i, svcName.String()),
}
if i < (numLocalEndpoints - 1) {
// Each rule is a probabilistic match.
args = append(args,
"-m", "statistic",
"--mode", "random",
"--probability", fmt.Sprintf("%0.5f", 1.0/float64(numLocalEndpoints-i)))
}
// The final (or only if n == 1) rule is a guaranteed match.
args = append(args, "-j", string(endpointChain))
writeLine(natRules, args...)
}
}
}
// Delete chains no longer in use.
for chain := range existingNATChains {
if !activeNATChains[chain] {
chainString := string(chain)
if !strings.HasPrefix(chainString, "KUBE-SVC-") && !strings.HasPrefix(chainString, "KUBE-SEP-") && !strings.HasPrefix(chainString, "KUBE-FW-") && !strings.HasPrefix(chainString, "KUBE-XLB-") {
// Ignore chains that aren't ours.
continue
}
// We must (as per iptables) write a chain-line for it, which has
// the nice effect of flushing the chain. Then we can remove the
// chain.
writeLine(natChains, existingNATChains[chain])
writeLine(natRules, "-X", chainString)
}
}
// Finally, tail-call to the nodeports chain. This needs to be after all
// other service portal rules.
writeLine(natRules,
"-A", string(kubeServicesChain),
"-m", "comment", "--comment", `"kubernetes service nodeports; NOTE: this must be the last rule in this chain"`,
"-m", "addrtype", "--dst-type", "LOCAL",
"-j", string(kubeNodePortsChain))
// Write the end-of-table markers.
writeLine(filterRules, "COMMIT")
writeLine(natRules, "COMMIT")
// Sync rules.
// NOTE: NoFlushTables is used so we don't flush non-kubernetes chains in the table.
filterLines := append(filterChains.Bytes(), filterRules.Bytes()...)
natLines := append(natChains.Bytes(), natRules.Bytes()...)
lines := append(filterLines, natLines...)
glog.V(3).Infof("Restoring iptables rules: %s", lines)
err = proxier.iptables.RestoreAll(lines, utiliptables.NoFlushTables, utiliptables.RestoreCounters)
if err != nil {
glog.Errorf("Failed to execute iptables-restore: %v\nRules:\n%s", err, lines)
// Revert new local ports.
revertPorts(replacementPortsMap, proxier.portsMap)
return
}
// Close old local ports and save new ones.
for k, v := range proxier.portsMap {
if replacementPortsMap[k] == nil {
v.Close()
}
}
proxier.portsMap = replacementPortsMap
}四、总结
kube-proxy的功能较为单一，其核心思想是同kube-apiserver同步service和endpoint信息，然后更新到iptables。
本文章为转载内容，我们尊重原作者对文章享有的著作权。如有内容错误或侵权问题，欢迎原作者联系我们进行内容更正或删除文章。
