kube-proxy源码分析
Posted WaltonWang
tags:
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摘要：假设你对kube-proxy的工作原理有一定的了解，本文基于kubernetes v1.5代码对kube-proxy的源码目录结构进行了分析，并以iptables mode为例进行了完整流程的源码分析，给出了其内部实现的模块逻辑图，希望对你深入理解kube-proxy有所帮助。
kube-proxy介绍
请参考我的另一篇博文：kube-proxy工作原理
源码目录结构分析
cmd/kube-proxy //负责kube-proxy的创建，启动的入口
.
├── app
│ ├── conntrack.go //linux kernel的nf_conntrack-sysctl的interface定义，更多关于conntracker的定义请看https://www.kernel.org/doc/Documentation/networking/nf_conntrack-sysctl.txt
│ ├── options
│ │ └── options.go //kube-proxy的参数定义ProxyServerConfig及相关方法
│ ├── server.go //ProxyServer结构定义及其创建(NewProxyServerDefault)和运行(Run)的方法。
│ └── server_test.go
└── proxy.go //kube-proxy的main方法
pkg/proxy
.
├── OWNERS
├── config
│ ├── api.go //给proxy配置Service和Endpoint的Reflectors和Cache.Store
│ ├── api_test.go
│ ├── config.go //定义ServiceUpdate，EndpointUpdate结构体以及ServiceConfigHandler，EndpointConfigHandler来处理Service和Endpoint的Update
│ ├── config_test.go
│ └── doc.go
├── doc.go
├── healthcheck //负责service listener和endpoint的health check，add/delete请求。
│ ├── api.go
│ ├── doc.go
│ ├── healthcheck.go
│ ├── healthcheck_test.go
│ ├── http.go
│ ├── listener.go
│ └── worker.go
├── iptables //proxy mode为iptables的实现
│ ├── proxier.go
│ └── proxier_test.go
├── types.go
├── userspace //proxy mode为userspace的实现
│ ├── loadbalancer.go
│ ├── port_allocator.go
│ ├── port_allocator_test.go
│ ├── proxier.go
│ ├── proxier_test.go
│ ├── proxysocket.go
│ ├── rlimit.go
│ ├── rlimit_windows.go
│ ├── roundrobin.go
│ ├── roundrobin_test.go
│ └── udp_server.go
└── winuserspace //windows OS时，proxy mode为userspace的实现
├── loadbalancer.go
├── port_allocator.go
├── port_allocator_test.go
├── proxier.go
├── proxier_test.go
├── proxysocket.go
├── roundrobin.go
├── roundrobin_test.go
└── udp_server.go内部实现模块逻辑图
源码分析
main
kube-proxy的main入口在：cmd/kube-proxy/proxy.go:39
func main() {
//创建kube-proxy的默认config对象
config := options.NewProxyConfig()
//用kube-proxy命令行的参数替换默认参数
config.AddFlags(pflag.CommandLine)
flag.InitFlags()
logs.InitLogs()
defer logs.FlushLogs()
verflag.PrintAndExitIfRequested()
//根据config创建ProxyServer
s, err := app.NewProxyServerDefault(config)
if err != nil {
fmt.Fprintf(os.Stderr, "%v\\n", err)
os.Exit(1)
}
//执行Run方法让kube-proxy开始干活了
if err = s.Run(); err != nil {
fmt.Fprintf(os.Stderr, "%v\\n", err)
os.Exit(1)
}
}main方法中，我们重点关注app.NewProxyServerDefault(config)创建ProxyServer和Run方法。
创建ProxyServer
NewProxyServerDefault负责根据提供的config参数创建一个新的ProxyServer对象，其代码比较长，逻辑相对复杂，下面会挑重点说一下。
cmd/kube-proxy/app/server.go:131
func NewProxyServerDefault(config *options.ProxyServerConfig) (*ProxyServer, error) {
...
// 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)
}
...
//设置OOM_SCORE_ADJ
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)
}
}
...
// Create a Kube Client
...
// 创建event Broadcaster和event recorder
hostname := nodeutil.GetHostname(config.HostnameOverride)
eventBroadcaster := record.NewBroadcaster()
recorder := eventBroadcaster.NewRecorder(v1.EventSource{Component: "kube-proxy", Host: hostname})
//定义proxier和endpointsHandler，分别用于处理services和endpoints的update event。
var proxier proxy.ProxyProvider
var endpointsHandler proxyconfig.EndpointsConfigHandler
//从config中获取proxy mode
proxyMode := getProxyMode(string(config.Mode), client.Core().Nodes(), hostname, iptInterface, iptables.LinuxKernelCompatTester{})
// proxy mode为iptables场景
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")
}
//调用pkg/proxy/iptables/proxier.go:222中的iptables.NewProxier来创建proxier，赋值给前面定义的proxier和endpointsHandler，表示由该proxier同时负责service和endpoint的event处理。
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)
}
// proxy mode为userspace场景
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
// windows OS场景下，调用pkg/proxy/winuserspace/proxier.go:146的winuserspace.NewProxier来创建proxier。
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,
)
}
// linux OS场景下，调用pkg/proxy/userspace/proxier.go:143的userspace.NewProxier来创建proxier。
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)
// 创建serviceConfig负责service的watchforUpdates
serviceConfig := proxyconfig.NewServiceConfig()
//给serviceConfig注册proxier，既添加对应的listener用来处理service update时逻辑。
serviceConfig.RegisterHandler(proxier)
// 创建endpointsConfig负责endpoint的watchforUpdates
endpointsConfig := proxyconfig.NewEndpointsConfig()
//给endpointsConfig注册endpointsHandler，既添加对应的listener用来处理endpoint update时的逻辑。
endpointsConfig.RegisterHandler(endpointsHandler)
//NewSourceAPI creates config source that watches for changes to the services and endpoints.
//NewSourceAPI通过ListWatch apiserver的Service和endpoint，并周期性的维护serviceStore和endpointStore的更新
proxyconfig.NewSourceAPI(
client.Core().RESTClient(),
config.ConfigSyncPeriod,
serviceConfig.Channel("api"), //Service Update Channel
endpointsConfig.Channel("api"), //endpoint update channel
)
...
//把前面创建的对象作为参数，构造出ProxyServer对象。
return NewProxyServer(client, config, iptInterface, proxier, eventBroadcaster, recorder, conntracker, proxyMode)
}NewProxyServerDefault中的核心逻辑我都已经在上述代码中添加了注释，其中有几个地方需要我们再深入跟进去看看：proxyconfig.NewServiceConfig，proxyconfig.NewEndpointsConfig，serviceConfig.RegisterHandler，endpointsConfig.RegisterHandler，proxyconfig.NewSourceAPI。
proxyconfig.NewServiceConfig
我们对ServiceConfig的代码分析一遍，EndpointsConfig的代码则类似。
pkg/proxy/config/config.go:192
func NewServiceConfig() *ServiceConfig {
// 创建updates channel
updates := make(chan struct{}, 1)
// 构建serviceStore对象
store := &serviceStore{updates: updates, services: make(map[string]map[types.NamespacedName]api.Service)}
mux := config.NewMux(store)
// 新建Broadcaster，在后续的serviceConfig.RegisterHandler会注册该Broadcaster的listener。
bcaster := config.NewBroadcaster()
//启动协程，马上开始watch updates channel
go watchForUpdates(bcaster, store, updates)
return &ServiceConfig{mux, bcaster, store}
}下面我们再跟进watchForUpdates去看看。
pkg/proxy/config/config.go:292
func watchForUpdates(bcaster *config.Broadcaster, accessor config.Accessor, updates <-chan struct{}) {
for true {
<-updates
bcaster.Notify(accessor.MergedState())
}
}watchForUpdates就是一直在watch updates channel，如果有数据，则立刻由该Broadcaster Notify到注册的listeners。
Notify的代码如下，可见，它负责将数据通知给所有的listener，并调用各个listener的OnUpdate方法。
pkg/util/config/config.go:133
// Notify notifies all listeners.
func (b *Broadcaster) Notify(instance interface{}) {
b.listenerLock.RLock()
listeners := b.listeners
b.listenerLock.RUnlock()
for _, listener := range listeners {
listener.OnUpdate(instance)
}
}
func (f ListenerFunc) OnUpdate(instance interface{}) {
f(instance)
}serviceConfig.RegisterHandler
上面分析的proxyconfig.NewServiceConfig负责创建ServiceConfig，开始watch updates channel了，当从channel中取到值的时候，Broadcaster就会通知listener进行处理。serviceConfig.RegisterHandler正是负责给Broadcaster注册listener的，其代码如下。
pkg/proxy/config/config.go:205
func (c *ServiceConfig) RegisterHandler(handler ServiceConfigHandler) {
//给ServiceConfig的Broadcaster注册listener。
c.bcaster.Add(config.ListenerFunc(func(instance interface{}) {
glog.V(3).Infof("Calling handler.OnServiceUpdate()")
handler.OnServiceUpdate(instance.([]api.Service))
}))
}上面分析proxyconfig.NewServiceConfig时可知，当从updates channel中取到值的时候，最终会调用对应的ListenerFunc(instance)进行处理，在这里，也就是调用:
glog.V(3).Infof("Calling handler.OnServiceUpdate()")
handler.OnServiceUpdate(instance.([]api.Service))
}即调用到handler.OnServiceUpdate。每种proxymode对应的proxier都有对应的handler.OnServiceUpdate接口实现，我们以iptables mode为例，看看handler.OnServiceUpdate的实现：
pkg/proxy/iptables/proxier.go:428
func (proxier *Proxier) OnServiceUpdate(allServices []api.Service) {
...
proxier.syncProxyRules()
proxier.deleteServiceConnections(staleUDPServices.List())
}因此，最终关键的逻辑都转向了proxier.syncProxyRules()，从我们上面给出的内部模块交互图也能看得出来。对于proxier.syncProxyRules()，我们放到后面来详细讨论，现在你只要知道proxier.syncProxyRules()负责将proxy中缓存的service/endpoint同步更新到iptables中生成对应Chain和NAT Rules。
proxyconfig.NewEndpointsConfig
endpointsConfig的逻辑和serviceConfig的类似，在这里只给出对应代码，不再跟进分析。
pkg/proxy/config/config.go:84
func NewEndpointsConfig() *EndpointsConfig {
// The updates channel is used to send interrupts to the Endpoints handler.
// It's buffered because we never want to block for as long as there is a
// pending interrupt, but don't want to drop them if the handler is doing
// work.
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}
}endpointsConfig.RegisterHandler
pkg/proxy/config/config.go:97
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))
}))
}proxyconfig.NewSourceAPI
proxyconfig.NewSourceAPI是很关键的，它负责给service updates channel和endpoint updates channel配置数据源，它是通过周期性的List和Watch kube-apiserver中的all service and endpoint来提供数据的，发给对应的channel。默认的List周期是15min，可通过--config-sync-period修改。下面来看其具体代码：
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()
}
// NewServiceStore creates an undelta store that expands updates to the store into
// ServiceUpdate events on the channel. If no store is passed, a default store will
// be initialized. Allows reuse of a cache store across multiple components.
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,
}
}
// NewEndpointsStore creates an undelta store that expands updates to the store into
// EndpointsUpdate events on the channel. If no store is passed, a default store will
// be initialized. Allows reuse of a cache store across multiple components.
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,
}
}代码很简单，不需要过多解释。
执行Run开始工作
创建完ProxyServer后，就执行Run方法开始工作了,它主要负责周期性(default 30s)的同步proxy中的services/endpionts到iptables中生成对应Chain and NAT Rules。
cmd/kube-proxy/app/server.go:308
func (s *ProxyServer) Run() error {
...
// 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)
}
...
// Just loop forever for now...
s.Proxier.SyncLoop()
return nil
}Run方法关键代码很简单，就是执行对应proxier的SyncLoop()。我们还是以iptables mode为例，看看它是如何实现SyncLoop()的：
pkg/proxy/iptables/proxier.go:416
// SyncLoop runs periodic work. This is expected to run as a goroutine or as the main loop of the app. It does not return.
func (proxier *Proxier) SyncLoop() {
t := time.NewTicker(proxier.syncPeriod)
defer t.Stop()
for {
<-t.C
glog.V(6).Infof("Periodic sync")
proxier.Sync()
}
}SyncLoop中，通过设置定时器，默认每30s会执行一次proxier.Sync()，可以通过--iptables-sync-period修改默认时间。那我们继续跟进Sync()的代码：
pkg/proxy/iptables/proxier.go:409
// Sync is called to immediately synchronize the proxier state to iptables
func (proxier *Proxier) Sync() {
proxier.mu.Lock()
defer proxier.mu.Unlock()
proxier.syncProxyRules()
}可见，最终还是调用proxier.syncProxyRules()。前一节中创建ProxyServer的分析也是一样，最终watch到service/endpoint有更新时，都会调用到proxier.syncProxyRules()。那下面我们就来看看proxier.syncProxyRules()的代码。
proxier.syncProxyRules
下面的proxier.syncProxyRules代码是iptables mode对应的实现。userspace mode的代码我就不贴了。
pkg/proxy/iptables/proxier.go:791
// This is where all of the iptables-save/restore calls happen.
// The only other iptables rules are those that are setup in iptablesInit()
// assumes proxier.mu is held
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)
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