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kubernetes.go
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kubernetes.go
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// Package kubernetes provides the kubernetes backend.
package kubernetes
import (
"errors"
"fmt"
"net"
"strings"
"sync/atomic"
"time"
"github.com/coredns/coredns/plugin"
"github.com/coredns/coredns/plugin/etcd/msg"
"github.com/coredns/coredns/plugin/pkg/dnsutil"
"github.com/coredns/coredns/plugin/pkg/healthcheck"
"github.com/coredns/coredns/plugin/proxy"
"github.com/coredns/coredns/request"
"github.com/miekg/dns"
meta "k8s.io/apimachinery/pkg/apis/meta/v1"
"k8s.io/apimachinery/pkg/labels"
"k8s.io/client-go/kubernetes"
api "k8s.io/client-go/pkg/api/v1"
"k8s.io/client-go/rest"
"k8s.io/client-go/tools/clientcmd"
clientcmdapi "k8s.io/client-go/tools/clientcmd/api"
)
// Kubernetes implements a plugin that connects to a Kubernetes cluster.
type Kubernetes struct {
Next plugin.Handler
Zones []string
Proxy proxy.Proxy // Proxy for looking up names during the resolution process
APIServerList []string
APIProxy *apiProxy
APICertAuth string
APIClientCert string
APIClientKey string
APIConn dnsController
Namespaces map[string]bool
podMode string
Fallthrough bool
ttl uint32
primaryZoneIndex int
interfaceAddrsFunc func() net.IP
autoPathSearch []string // Local search path from /etc/resolv.conf. Needed for autopath.
}
// New returns a intialized Kubernetes. It default interfaceAddrFunc to return 127.0.0.1. All other
// values default to their zero value, primaryZoneIndex will thus point to the first zone.
func New(zones []string) *Kubernetes {
k := new(Kubernetes)
k.Zones = zones
k.Namespaces = make(map[string]bool)
k.interfaceAddrsFunc = func() net.IP { return net.ParseIP("127.0.0.1") }
k.podMode = podModeDisabled
k.Proxy = proxy.Proxy{}
k.ttl = defaultTTL
return k
}
const (
// podModeDisabled is the default value where pod requests are ignored
podModeDisabled = "disabled"
// podModeVerified is where Pod requests are answered only if they exist
podModeVerified = "verified"
// podModeInsecure is where pod requests are answered without verfying they exist
podModeInsecure = "insecure"
// DNSSchemaVersion is the schema version: https://github.com/kubernetes/dns/blob/master/docs/specification.md
DNSSchemaVersion = "1.0.1"
)
var (
errNoItems = errors.New("no items found")
errNsNotExposed = errors.New("namespace is not exposed")
errInvalidRequest = errors.New("invalid query name")
errPodsDisabled = errors.New("pod records disabled")
)
// Services implements the ServiceBackend interface.
func (k *Kubernetes) Services(state request.Request, exact bool, opt plugin.Options) (svcs []msg.Service, err error) {
// We're looking again at types, which we've already done in ServeDNS, but there are some types k8s just can't answer.
switch state.QType() {
case dns.TypeTXT:
// 1 label + zone, label must be "dns-version".
t, _ := dnsutil.TrimZone(state.Name(), state.Zone)
segs := dns.SplitDomainName(t)
if len(segs) != 1 {
return nil, fmt.Errorf("kubernetes: TXT query can only be for dns-version: %s", state.QName())
}
if segs[0] != "dns-version" {
return nil, nil
}
svc := msg.Service{Text: DNSSchemaVersion, TTL: 28800, Key: msg.Path(state.QName(), "coredns")}
return []msg.Service{svc}, nil
case dns.TypeNS:
// We can only get here if the qname equal the zone, see ServeDNS in handler.go.
ns := k.nsAddr()
svc := msg.Service{Host: ns.A.String(), Key: msg.Path(state.QName(), "coredns")}
return []msg.Service{svc}, nil
}
if state.QType() == dns.TypeA && isDefaultNS(state.Name(), state.Zone) {
// If this is an A request for "ns.dns", respond with a "fake" record for coredns.
// SOA records always use this hardcoded name
ns := k.nsAddr()
svc := msg.Service{Host: ns.A.String(), Key: msg.Path(state.QName(), "coredns")}
return []msg.Service{svc}, nil
}
s, e := k.Records(state, false)
// SRV for external services is not yet implemented, so remove those records.
if state.QType() != dns.TypeSRV {
return s, e
}
internal := []msg.Service{}
for _, svc := range s {
if t, _ := svc.HostType(); t != dns.TypeCNAME {
internal = append(internal, svc)
}
}
return internal, e
}
// primaryZone will return the first non-reverse zone being handled by this plugin
func (k *Kubernetes) primaryZone() string { return k.Zones[k.primaryZoneIndex] }
// Lookup implements the ServiceBackend interface.
func (k *Kubernetes) Lookup(state request.Request, name string, typ uint16) (*dns.Msg, error) {
return k.Proxy.Lookup(state, name, typ)
}
// IsNameError implements the ServiceBackend interface.
func (k *Kubernetes) IsNameError(err error) bool {
return err == errNoItems || err == errNsNotExposed || err == errInvalidRequest
}
func (k *Kubernetes) getClientConfig() (*rest.Config, error) {
loadingRules := &clientcmd.ClientConfigLoadingRules{}
overrides := &clientcmd.ConfigOverrides{}
clusterinfo := clientcmdapi.Cluster{}
authinfo := clientcmdapi.AuthInfo{}
// Connect to API from in cluster
if len(k.APIServerList) == 0 {
cc, err := rest.InClusterConfig()
if err != nil {
return nil, err
}
cc.ContentType = "application/vnd.kubernetes.protobuf"
return cc, err
}
// Connect to API from out of cluster
endpoint := k.APIServerList[0]
if len(k.APIServerList) > 1 {
// Use a random port for api proxy, will get the value later through listener.Addr()
listener, err := net.Listen("tcp", "127.0.0.1:0")
if err != nil {
return nil, fmt.Errorf("failed to create kubernetes api proxy: %v", err)
}
k.APIProxy = &apiProxy{
listener: listener,
handler: proxyHandler{
HealthCheck: healthcheck.HealthCheck{
FailTimeout: 3 * time.Second,
MaxFails: 1,
Path: "/",
Interval: 5 * time.Second,
},
},
}
k.APIProxy.handler.Hosts = make([]*healthcheck.UpstreamHost, len(k.APIServerList))
for i, entry := range k.APIServerList {
uh := &healthcheck.UpstreamHost{
Name: strings.TrimPrefix(entry, "http://"),
CheckDown: func(upstream *proxyHandler) healthcheck.UpstreamHostDownFunc {
return func(uh *healthcheck.UpstreamHost) bool {
fails := atomic.LoadInt32(&uh.Fails)
if fails >= upstream.MaxFails && upstream.MaxFails != 0 {
return true
}
return false
}
}(&k.APIProxy.handler),
}
k.APIProxy.handler.Hosts[i] = uh
}
k.APIProxy.Handler = &k.APIProxy.handler
// Find the random port used for api proxy
endpoint = fmt.Sprintf("http://%s", listener.Addr())
}
clusterinfo.Server = endpoint
if len(k.APICertAuth) > 0 {
clusterinfo.CertificateAuthority = k.APICertAuth
}
if len(k.APIClientCert) > 0 {
authinfo.ClientCertificate = k.APIClientCert
}
if len(k.APIClientKey) > 0 {
authinfo.ClientKey = k.APIClientKey
}
overrides.ClusterInfo = clusterinfo
overrides.AuthInfo = authinfo
clientConfig := clientcmd.NewNonInteractiveDeferredLoadingClientConfig(loadingRules, overrides)
cc, err := clientConfig.ClientConfig()
cc.ContentType = "application/vnd.kubernetes.protobuf"
return cc, err
}
// initKubeCache initializes a new Kubernetes cache.
func (k *Kubernetes) initKubeCache(opts dnsControlOpts) (err error) {
config, err := k.getClientConfig()
if err != nil {
return err
}
kubeClient, err := kubernetes.NewForConfig(config)
if err != nil {
return fmt.Errorf("failed to create kubernetes notification controller: %q", err)
}
if opts.labelSelector != nil {
var selector labels.Selector
selector, err = meta.LabelSelectorAsSelector(opts.labelSelector)
if err != nil {
return fmt.Errorf("unable to create Selector for LabelSelector '%s': %q", opts.labelSelector, err)
}
opts.selector = &selector
}
opts.initPodCache = k.podMode == podModeVerified
k.APIConn = newdnsController(kubeClient, opts)
return err
}
// Records looks up services in kubernetes.
func (k *Kubernetes) Records(state request.Request, exact bool) ([]msg.Service, error) {
r, e := parseRequest(state)
if e != nil {
return nil, e
}
if !wildcard(r.namespace) && !k.namespaceExposed(r.namespace) {
return nil, errNsNotExposed
}
if r.podOrSvc == Pod {
pods, err := k.findPods(r, state.Zone)
return pods, err
}
services, err := k.findServices(r, state.Zone)
return services, err
}
func endpointHostname(addr api.EndpointAddress) string {
if addr.Hostname != "" {
return strings.ToLower(addr.Hostname)
}
if strings.Contains(addr.IP, ".") {
return strings.Replace(addr.IP, ".", "-", -1)
}
if strings.Contains(addr.IP, ":") {
return strings.ToLower(strings.Replace(addr.IP, ":", "-", -1))
}
return ""
}
func (k *Kubernetes) findPods(r recordRequest, zone string) (pods []msg.Service, err error) {
if k.podMode == podModeDisabled {
return nil, errPodsDisabled
}
namespace := r.namespace
podname := r.service
zonePath := msg.Path(zone, "coredns")
ip := ""
err = errNoItems
if strings.Count(podname, "-") == 3 && !strings.Contains(podname, "--") {
ip = strings.Replace(podname, "-", ".", -1)
} else {
ip = strings.Replace(podname, "-", ":", -1)
}
if k.podMode == podModeInsecure {
return []msg.Service{{Key: strings.Join([]string{zonePath, Pod, namespace, podname}, "/"), Host: ip}}, nil
}
// PodModeVerified
for _, p := range k.APIConn.PodIndex(ip) {
// If namespace has a wildcard, filter results against Corefile namespace list.
if wildcard(namespace) && !k.namespaceExposed(p.Namespace) {
continue
}
// check for matching ip and namespace
if ip == p.Status.PodIP && match(namespace, p.Namespace) {
s := msg.Service{Key: strings.Join([]string{zonePath, Pod, namespace, podname}, "/"), Host: ip}
pods = append(pods, s)
err = nil
}
}
return pods, err
}
// findServices returns the services matching r from the cache.
func (k *Kubernetes) findServices(r recordRequest, zone string) (services []msg.Service, err error) {
zonePath := msg.Path(zone, "coredns")
err = errNoItems // Set to errNoItems to signal really nothing found, gets reset when name is matched.
var (
endpointsListFunc func() []*api.Endpoints
endpointsList []*api.Endpoints
serviceList []*api.Service
)
if wildcard(r.service) || wildcard(r.namespace) {
serviceList = k.APIConn.ServiceList()
endpointsListFunc = func() []*api.Endpoints { return k.APIConn.EndpointsList() }
} else {
idx := r.service + "." + r.namespace
serviceList = k.APIConn.SvcIndex(idx)
endpointsListFunc = func() []*api.Endpoints { return k.APIConn.EpIndex(idx) }
}
for _, svc := range serviceList {
if !(match(r.namespace, svc.Namespace) && match(r.service, svc.Name)) {
continue
}
// If namespace has a wildcard, filter results against Corefile namespace list.
// (Namespaces without a wildcard were filtered before the call to this function.)
if wildcard(r.namespace) && !k.namespaceExposed(svc.Namespace) {
continue
}
// Endpoint query or headless service
if svc.Spec.ClusterIP == api.ClusterIPNone || r.endpoint != "" {
if endpointsList == nil {
endpointsList = endpointsListFunc()
}
for _, ep := range endpointsList {
if ep.ObjectMeta.Name != svc.Name || ep.ObjectMeta.Namespace != svc.Namespace {
continue
}
for _, eps := range ep.Subsets {
for _, addr := range eps.Addresses {
// See comments in parse.go parseRequest about the endpoint handling.
if r.endpoint != "" {
if !match(r.endpoint, endpointHostname(addr)) {
continue
}
}
for _, p := range eps.Ports {
if !(match(r.port, p.Name) && match(r.protocol, string(p.Protocol))) {
continue
}
s := msg.Service{Host: addr.IP, Port: int(p.Port), TTL: k.ttl}
s.Key = strings.Join([]string{zonePath, Svc, svc.Namespace, svc.Name, endpointHostname(addr)}, "/")
err = nil
services = append(services, s)
}
}
}
}
continue
}
// External service
if svc.Spec.ExternalName != "" {
s := msg.Service{Key: strings.Join([]string{zonePath, Svc, svc.Namespace, svc.Name}, "/"), Host: svc.Spec.ExternalName, TTL: k.ttl}
if t, _ := s.HostType(); t == dns.TypeCNAME {
s.Key = strings.Join([]string{zonePath, Svc, svc.Namespace, svc.Name}, "/")
services = append(services, s)
err = nil
continue
}
}
// ClusterIP service
for _, p := range svc.Spec.Ports {
if !(match(r.port, p.Name) && match(r.protocol, string(p.Protocol))) {
continue
}
err = nil
s := msg.Service{Host: svc.Spec.ClusterIP, Port: int(p.Port), TTL: k.ttl}
s.Key = strings.Join([]string{zonePath, Svc, svc.Namespace, svc.Name}, "/")
services = append(services, s)
}
}
return services, err
}
// match checks if a and b are equal taking wildcards into account.
func match(a, b string) bool {
if wildcard(a) {
return true
}
if wildcard(b) {
return true
}
return strings.EqualFold(a, b)
}
// wildcard checks whether s contains a wildcard value defined as "*" or "any".
func wildcard(s string) bool {
return s == "*" || s == "any"
}
// namespaceExposed returns true when the namespace is exposed.
func (k *Kubernetes) namespaceExposed(namespace string) bool {
_, ok := k.Namespaces[namespace]
if len(k.Namespaces) > 0 && !ok {
return false
}
return true
}
const (
// Svc is the DNS schema for kubernetes services
Svc = "svc"
// Pod is the DNS schema for kubernetes pods
Pod = "pod"
// defaultTTL to apply to all answers.
defaultTTL = 5
)