kube-proxy源码解析
ipvs相对于iptables模式具备较高的性能与稳定性, 本文讲以此模式的源码解析为主，如果想去了解iptables模式的原理，可以去参考其实现，架构上无差别。
kube-proxy主要功能是监听service和endpoint的事件，然后下放代理策略到机器上。 底层调用docker/libnetwork, 而libnetwork最终调用了netlink 与netns来实现ipvs的创建等动作
初始化配置
代码入口：cmd/kube-proxy/app/server.go Run() 函数
通过命令行参数去初始化proxyServer的配置
proxyServer, err := NewProxyServer(o)type ProxyServer struct {
// k8s client
Client clientset.Interface
EventClient v1core.EventsGetter
// ipvs 相关接口
IptInterface utiliptables.Interface
IpvsInterface utilipvs.Interface
IpsetInterface utilipset.Interface
// 处理同步时的处理器
Proxier proxy.ProxyProvider
// 代理模式，ipvs iptables userspace kernelspace(windows)四种
ProxyMode string
// 配置同步周期
ConfigSyncPeriod time.Duration
// service 与 endpoint 事件处理器
ServiceEventHandler config.ServiceHandler
EndpointsEventHandler config.EndpointsHandler
}Proxier是主要入口，抽象了两个函数：
type ProxyProvider interface {
// Sync immediately synchronizes the ProxyProvider's current state to iptables.
Sync()
// 定期执行
SyncLoop()
}ipvs 的interface 这个很重要：
type Interface interface {
// 删除所有规则
Flush() error
// 增加一个virtual server
AddVirtualServer(*VirtualServer) error
UpdateVirtualServer(*VirtualServer) error
DeleteVirtualServer(*VirtualServer) error
GetVirtualServer(*VirtualServer) (*VirtualServer, error)
GetVirtualServers() ([]*VirtualServer, error)
// 给virtual server加个realserver, 如 VirtualServer就是一个clusterip realServer就是pod(或者自定义的endpoint)
AddRealServer(*VirtualServer, *RealServer) error
GetRealServers(*VirtualServer) ([]*RealServer, error)
DeleteRealServer(*VirtualServer, *RealServer) error
}我们在下文再详细看ipvs_linux是如何实现上面接口的
virtual server与realserver, 最重要的是ip:port，然后就是一些代理的模式如sessionAffinity等:
type VirtualServer struct {
Address net.IP
Protocol string
Port uint16
Scheduler string
Flags ServiceFlags
Timeout uint32
}
type RealServer struct {
Address net.IP
Port uint16
Weight int
}创建apiserver client
client, eventClient, err := createClients(config.ClientConnection, master)创建Proxier 这是仅仅关注ipvs模式的proxier
else if proxyMode == proxyModeIPVS {
glog.V(0).Info("Using ipvs Proxier.")
proxierIPVS, err := ipvs.NewProxier(
iptInterface,
ipvsInterface,
ipsetInterface,
utilsysctl.New(),
execer,
config.IPVS.SyncPeriod.Duration,
config.IPVS.MinSyncPeriod.Duration,
config.IPTables.MasqueradeAll,
int(*config.IPTables.MasqueradeBit),
config.ClusterCIDR,
hostname,
getNodeIP(client, hostname),
recorder,
healthzServer,
config.IPVS.Scheduler,
)
...
proxier = proxierIPVS
serviceEventHandler = proxierIPVS
endpointsEventHandler = proxierIPVS这个Proxier具备以下方法：
+OnEndpointsAdd(endpoints *api.Endpoints)
+OnEndpointsDelete(endpoints *api.Endpoints)
+OnEndpointsSynced()
+OnEndpointsUpdate(oldEndpoints, endpoints *api.Endpoints)
+OnServiceAdd(service *api.Service)
+OnServiceDelete(service *api.Service)
+OnServiceSynced()
+OnServiceUpdate(oldService, service *api.Service)
+Sync()
+SyncLoop()所以ipvs的这个Proxier实现了我们需要的绝大部分接口
小结一下：
+-----------> endpointHandler
|
+-----------> serviceHandler
| ^
| | +-------------> sync 定期同步等
| | |
ProxyServer---------> Proxier --------> service 事件回调
| |
| +-------------> endpoint事件回调
| | 触发
+-----> ipvs interface ipvs handler <-----+启动proxyServer
- 检查是不是带了clean up参数，如果带了那么清除所有规则退出
- OOM adjuster貌似没实现，忽略
- resouceContainer也没实现，忽略
- 启动metrics服务器，这个挺重要，比如我们想监控时可以传入这个参数, 包含promethus的 metrics. metrics-bind-address参数
- 启动informer, 开始监听事件，分别启动协程处理。
1 2 3 4我们都不用太关注，细看5即可：
informerFactory := informers.NewSharedInformerFactory(s.Client, s.ConfigSyncPeriod)
serviceConfig := config.NewServiceConfig(informerFactory.Core().InternalVersion().Services(), s.ConfigSyncPeriod)
// 注册 service handler并启动
serviceConfig.RegisterEventHandler(s.ServiceEventHandler)
// 这里面仅仅是把ServiceEventHandler赋值给informer回调
go serviceConfig.Run(wait.NeverStop)
endpointsConfig := config.NewEndpointsConfig(informerFactory.Core().InternalVersion().Endpoints(), s.ConfigSyncPeriod)
// 注册endpoint
endpointsConfig.RegisterEventHandler(s.EndpointsEventHandler)
go endpointsConfig.Run(wait.NeverStop)
go informerFactory.Start(wait.NeverStop)serviceConfig.Run与endpointConfig.Run仅仅是给回调函数赋值, 所以注册的handler就给了informer, informer监听到事件时就会回调：
for i := range c.eventHandlers {
glog.V(3).Infof("Calling handler.OnServiceSynced()")
c.eventHandlers[i].OnServiceSynced()
}那么问题来了，注册进去的这个handler是啥？ 回顾一下上文的
serviceEventHandler = proxierIPVS
endpointsEventHandler = proxierIPVS所以都是这个proxierIPVS
handler的回调函数, informer会回调这几个函数，所以我们在自己开发时实现这个interface注册进去即可：
type ServiceHandler interface {
// OnServiceAdd is called whenever creation of new service object
// is observed.
OnServiceAdd(service *api.Service)
// OnServiceUpdate is called whenever modification of an existing
// service object is observed.
OnServiceUpdate(oldService, service *api.Service)
// OnServiceDelete is called whenever deletion of an existing service
// object is observed.
OnServiceDelete(service *api.Service)
// OnServiceSynced is called once all the initial even handlers were
// called and the state is fully propagated to local cache.
OnServiceSynced()
}开始监听
go informerFactory.Start(wait.NeverStop)这里执行后，我们创建删除service endpoint等动作都会被监听到，然后回调,回顾一下上面的图，最终都是由Proxier去实现，所以后面我们重点关注Proxier即可
s.Proxier.SyncLoop()然后开始SyncLoop,下文开讲
Proxier 实现
我们创建一个service时OnServiceAdd方法会被调用, 这里记录一下之前的状态与当前状态两个东西，然后发个信号给syncRunner让它去处理：
func (proxier *Proxier) OnServiceAdd(service *api.Service) {
namespacedName := types.NamespacedName{Namespace: service.Namespace, Name: service.Name}
if proxier.serviceChanges.update(&namespacedName, nil, service) && proxier.isInitialized() {
proxier.syncRunner.Run()
}
}记录service 信息,可以看到没做什么事，就是把service存在map里, 如果没变直接删掉map信息不做任何处理：
change, exists := scm.items[*namespacedName]
if !exists {
change = &serviceChange{}
// 老的service信息
change.previous = serviceToServiceMap(previous)
scm.items[*namespacedName] = change
}
// 当前监听到的service信息
change.current = serviceToServiceMap(current)
如果一样，直接删除
if reflect.DeepEqual(change.previous, change.current) {
delete(scm.items, *namespacedName)
}proxier.syncRunner.Run() 里面就发送了一个信号
select {
case bfr.run <- struct{}{}:
default:
}这里面处理了这个信号
s.Proxier.SyncLoop()
func (proxier *Proxier) SyncLoop() {
// Update healthz timestamp at beginning in case Sync() never succeeds.
if proxier.healthzServer != nil {
proxier.healthzServer.UpdateTimestamp()
}
proxier.syncRunner.Loop(wait.NeverStop)
}runner里收到信号执行，没收到信号会定期执行：
func (bfr *BoundedFrequencyRunner) Loop(stop <-chan struct{}) {
glog.V(3).Infof("%s Loop running", bfr.name)
bfr.timer.Reset(bfr.maxInterval)
for {
select {
case <-stop:
bfr.stop()
glog.V(3).Infof("%s Loop stopping", bfr.name)
return
case <-bfr.timer.C(): // 定期执行
bfr.tryRun()
case <-bfr.run:
bfr.tryRun() // 收到事件信号执行
}
}
}这个bfr runner里我们最需要主意的是一个回调函数，tryRun里检查这个回调是否满足被调度的条件：
type BoundedFrequencyRunner struct {
name string // the name of this instance
minInterval time.Duration // the min time between runs, modulo bursts
maxInterval time.Duration // the max time between runs
run chan struct{} // try an async run
mu sync.Mutex // guards runs of fn and all mutations
fn func() // function to run, 这个回调
lastRun time.Time // time of last run
timer timer // timer for deferred runs
limiter rateLimiter // rate limiter for on-demand runs
}
// 传入的proxier.syncProxyRules这个函数
proxier.syncRunner = async.NewBoundedFrequencyRunner("sync-runner", proxier.syncProxyRules, minSyncPeriod, syncPeriod, burstSyncs)这是个600行左右的搓逼函数，也是处理主要逻辑的地方。
syncProxyRules
- 设置一些iptables规则，如mark与comment
- 确定机器上有网卡，ipvs需要绑定地址到上面
- 确定有ipset，ipset是iptables的扩展，可以给一批地址设置iptables规则
...(又臭又长，重复代码多，看不下去了，细节问题自己去看吧) - 我们最关注的，如何去处理VirtualServer的
serv := &utilipvs.VirtualServer{
Address: net.ParseIP(ingress.IP),
Port: uint16(svcInfo.port),
Protocol: string(svcInfo.protocol),
Scheduler: proxier.ipvsScheduler,
}
if err := proxier.syncService(svcNameString, serv, false); err == nil {
if err := proxier.syncEndpoint(svcName, svcInfo.onlyNodeLocalEndpoints, serv); err != nil {
}
}看下实现, 如果没有就创建，如果已存在就更新, 给网卡绑定service的cluster ip：
func (proxier *Proxier) syncService(svcName string, vs *utilipvs.VirtualServer, bindAddr bool) error {
appliedVirtualServer, _ := proxier.ipvs.GetVirtualServer(vs)
if appliedVirtualServer == nil || !appliedVirtualServer.Equal(vs) {
if appliedVirtualServer == nil {
if err := proxier.ipvs.AddVirtualServer(vs); err != nil {
return err
}
} else {
if err := proxier.ipvs.UpdateVirtualServer(appliedVirtualServer); err != nil {
return err
}
}
}
// bind service address to dummy interface even if service not changed,
// in case that service IP was removed by other processes
if bindAddr {
_, err := proxier.netlinkHandle.EnsureAddressBind(vs.Address.String(), DefaultDummyDevice)
if err != nil {
return err
}
}
return nil
}创建service实现
现在可以去看ipvs的AddVirtualServer的实现了，主要是利用socket与内核进程通信做到的。pkg/util/ipvs/ipvs_linux.go 里 runner结构体实现了这些方法, 这里用到了 docker/libnetwork/ipvs库：
// runner implements Interface.
type runner struct {
exec utilexec.Interface
ipvsHandle *ipvs.Handle
}
// New returns a new Interface which will call ipvs APIs.
func New(exec utilexec.Interface) Interface {
ihandle, err := ipvs.New("") // github.com/docker/libnetwork/ipvs
if err != nil {
glog.Errorf("IPVS interface can't be initialized, error: %v", err)
return nil
}
return &runner{
exec: exec,
ipvsHandle: ihandle,
}
}New的时候创建了一个特殊的socket, 这里与我们普通的socket编程无差别，关键是syscall.AF_NETLINK这个参数，代表与内核进程通信：
sock, err := nl.GetNetlinkSocketAt(n, netns.None(), syscall.NETLINK_GENERIC)
func getNetlinkSocket(protocol int) (*NetlinkSocket, error) {
fd, err := syscall.Socket(syscall.AF_NETLINK, syscall.SOCK_RAW|syscall.SOCK_CLOEXEC, protocol)
if err != nil {
return nil, err
}
s := &NetlinkSocket{
fd: int32(fd),
}
s.lsa.Family = syscall.AF_NETLINK
if err := syscall.Bind(fd, &s.lsa); err != nil {
syscall.Close(fd)
return nil, err
}
return s, nil
}创建一个service, 转换成docker service格式，直接调用:
// AddVirtualServer is part of Interface.
func (runner *runner) AddVirtualServer(vs *VirtualServer) error {
eSvc, err := toBackendService(vs)
if err != nil {
return err
}
return runner.ipvsHandle.NewService(eSvc)
}然后就是把service信息打包，往socket里面写即可：
func (i *Handle) doCmdwithResponse(s *Service, d *Destination, cmd uint8) ([][]byte, error) {
req := newIPVSRequest(cmd)
req.Seq = atomic.AddUint32(&i.seq, 1)
if s == nil {
req.Flags |= syscall.NLM_F_DUMP //Flag to dump all messages
req.AddData(nl.NewRtAttr(ipvsCmdAttrService, nil)) //Add a dummy attribute
} else {
req.AddData(fillService(s))
} // 把service塞到请求中
if d == nil {
if cmd == ipvsCmdGetDest {
req.Flags |= syscall.NLM_F_DUMP
}
} else {
req.AddData(fillDestinaton(d))
}
// 给内核进程发送service信息
res, err := execute(i.sock, req, 0)
if err != nil {
return [][]byte{}, err
}
return res, nil
}构造请求
func newIPVSRequest(cmd uint8) *nl.NetlinkRequest {
return newGenlRequest(ipvsFamily, cmd)
}在构造请求时传入的是ipvs协议簇
然后构造一个与内核通信的消息头
func NewNetlinkRequest(proto, flags int) *NetlinkRequest {
return &NetlinkRequest{
NlMsghdr: syscall.NlMsghdr{
Len: uint32(syscall.SizeofNlMsghdr),
Type: uint16(proto),
Flags: syscall.NLM_F_REQUEST | uint16(flags),
Seq: atomic.AddUint32(&nextSeqNr, 1),
},
}
}给消息加Data,这个Data是个数组，需要实现两个方法：
type NetlinkRequestData interface {
Len() int // 长度
Serialize() []byte // 序列化, 内核通信也需要一定的数据格式，service信息也需要实现
}比如 header是这样序列化的, 一看愣住了，思考好久才看懂：拆下看：([unsafe.Sizeof(hdr)]byte) 一个*[]byte类型，长度就是结构体大小(unsafe.Pointer(hdr))把结构体转成byte指针类型加个*取它的值用[:]转成byte返回
func (hdr *genlMsgHdr) Serialize() []byte {
return (*(*[unsafe.Sizeof(*hdr)]byte)(unsafe.Pointer(hdr)))[:]
}发送service信息给内核
一个很普通的socket发送接收数据
func execute(s *nl.NetlinkSocket, req *nl.NetlinkRequest, resType uint16) ([][]byte, error) {
var (
err error
)
if err := s.Send(req); err != nil {
return nil, err
}
pid, err := s.GetPid()
if err != nil {
return nil, err
}
var res [][]byte
done:
for {
msgs, err := s.Receive()
if err != nil {
return nil, err
}
for _, m := range msgs {
if m.Header.Seq != req.Seq {
continue
}
if m.Header.Pid != pid {
return nil, fmt.Errorf("Wrong pid %d, expected %d", m.Header.Pid, pid)
}
if m.Header.Type == syscall.NLMSG_DONE {
break done
}
if m.Header.Type == syscall.NLMSG_ERROR {
error := int32(native.Uint32(m.Data[0:4]))
if error == 0 {
break done
}
return nil, syscall.Errno(-error)
}
if resType != 0 && m.Header.Type != resType {
continue
}
res = append(res, m.Data)
if m.Header.Flags&syscall.NLM_F_MULTI == 0 {
break done
}
}
}
return res, nil
}Service 数据打包
这里比较细，核心思想就是内核只认一定格式的标准数据，我们把service信息按其标准打包发送给内核即可。
至于怎么打包的就不详细讲了。
func fillService(s *Service) nl.NetlinkRequestData {
cmdAttr := nl.NewRtAttr(ipvsCmdAttrService, nil)
nl.NewRtAttrChild(cmdAttr, ipvsSvcAttrAddressFamily, nl.Uint16Attr(s.AddressFamily))
if s.FWMark != 0 {
nl.NewRtAttrChild(cmdAttr, ipvsSvcAttrFWMark, nl.Uint32Attr(s.FWMark))
} else {
nl.NewRtAttrChild(cmdAttr, ipvsSvcAttrProtocol, nl.Uint16Attr(s.Protocol))
nl.NewRtAttrChild(cmdAttr, ipvsSvcAttrAddress, rawIPData(s.Address))
// Port needs to be in network byte order.
portBuf := new(bytes.Buffer)
binary.Write(portBuf, binary.BigEndian, s.Port)
nl.NewRtAttrChild(cmdAttr, ipvsSvcAttrPort, portBuf.Bytes())
}
nl.NewRtAttrChild(cmdAttr, ipvsSvcAttrSchedName, nl.ZeroTerminated(s.SchedName))
if s.PEName != "" {
nl.NewRtAttrChild(cmdAttr, ipvsSvcAttrPEName, nl.ZeroTerminated(s.PEName))
}
f := &ipvsFlags{
flags: s.Flags,
mask: 0xFFFFFFFF,
}
nl.NewRtAttrChild(cmdAttr, ipvsSvcAttrFlags, f.Serialize())
nl.NewRtAttrChild(cmdAttr, ipvsSvcAttrTimeout, nl.Uint32Attr(s.Timeout))
nl.NewRtAttrChild(cmdAttr, ipvsSvcAttrNetmask, nl.Uint32Attr(s.Netmask))
return cmdAttr
}总结
Service总体来讲代码比较简单，但是觉得有些地方实现的有点绕，不够简单直接。 总体来说就是监听apiserver事件，然后比对 处理，定期也会去执行同步策略.
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