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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"
"log"
"net"
"strings"
"time"
"github.com/coredns/coredns/middleware"
"github.com/coredns/coredns/middleware/etcd/msg"
"github.com/coredns/coredns/middleware/pkg/dnsutil"
dnsstrings "github.com/coredns/coredns/middleware/pkg/strings"
"github.com/coredns/coredns/middleware/proxy"
"github.com/coredns/coredns/request"
"github.com/miekg/dns"
"k8s.io/client-go/1.5/kubernetes"
"k8s.io/client-go/1.5/pkg/api"
unversionedapi "k8s.io/client-go/1.5/pkg/api/unversioned"
"k8s.io/client-go/1.5/pkg/labels"
"k8s.io/client-go/1.5/rest"
"k8s.io/client-go/1.5/tools/clientcmd"
clientcmdapi "k8s.io/client-go/1.5/tools/clientcmd/api"
)
// Kubernetes implements a middleware that connects to a Kubernetes cluster.
type Kubernetes struct {
Next middleware.Handler
Zones []string
primaryZone int
Proxy proxy.Proxy // Proxy for looking up names during the resolution process
APIEndpoint string
APICertAuth string
APIClientCert string
APIClientKey string
APIConn *dnsController
ResyncPeriod time.Duration
Namespaces []string
LabelSelector *unversionedapi.LabelSelector
Selector *labels.Selector
PodMode string
ReverseCidrs []net.IPNet
}
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 = "1.0.0"
)
type endpoint struct {
addr api.EndpointAddress
port api.EndpointPort
}
type service struct {
name string
namespace string
addr string
ports []api.ServicePort
endpoints []endpoint
}
type pod struct {
name string
namespace string
addr string
}
type recordRequest struct {
port, protocol, endpoint, service, namespace, typeName, zone string
}
var errNoItems = errors.New("no items found")
var errNsNotExposed = errors.New("namespace is not exposed")
var errInvalidRequest = errors.New("invalid query name")
// Services implements the ServiceBackend interface.
func (k *Kubernetes) Services(state request.Request, exact bool, opt middleware.Options) ([]msg.Service, []msg.Service, error) {
r, e := k.parseRequest(state.Name(), state.Type())
if e != nil {
return nil, nil, e
}
switch state.Type() {
case "A", "SRV":
s, e := k.Records(r)
return s, nil, e // Haven't implemented debug queries yet.
case "TXT":
s, e := k.recordsForTXT(r)
return s, nil, e
}
return nil, nil, nil
}
func (k *Kubernetes) recordsForTXT(r recordRequest) ([]msg.Service, error) {
switch r.typeName {
case "dns-version":
s := msg.Service{
Text: DNSSchemaVersion,
TTL: 28800,
Key: msg.Path(r.typeName+"."+r.zone, "coredns")}
return []msg.Service{s}, nil
}
return nil, nil
}
// PrimaryZone will return the first non-reverse zone being handled by this middleware
func (k *Kubernetes) PrimaryZone() string {
return k.Zones[k.primaryZone]
}
// Reverse implements the ServiceBackend interface.
func (k *Kubernetes) Reverse(state request.Request, exact bool, opt middleware.Options) ([]msg.Service, []msg.Service, error) {
ip := dnsutil.ExtractAddressFromReverse(state.Name())
if ip == "" {
return nil, nil, nil
}
records := k.getServiceRecordForIP(ip, state.Name())
return records, nil, nil
}
func (k *Kubernetes) isRequestInReverseRange(state request.Request) bool {
ip := dnsutil.ExtractAddressFromReverse(state.Name())
for _, c := range k.ReverseCidrs {
if c.Contains(net.ParseIP(ip)) {
return true
}
}
return false
}
// 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
}
// Debug implements the ServiceBackend interface.
func (k *Kubernetes) Debug() string {
return "debug"
}
func (k *Kubernetes) getClientConfig() (*rest.Config, error) {
// For a custom api server or running outside a k8s cluster
// set URL in env.KUBERNETES_MASTER or set endpoint in Corefile
loadingRules := clientcmd.NewDefaultClientConfigLoadingRules()
overrides := &clientcmd.ConfigOverrides{}
clusterinfo := clientcmdapi.Cluster{}
authinfo := clientcmdapi.AuthInfo{}
if len(k.APIEndpoint) > 0 {
clusterinfo.Server = k.APIEndpoint
} else {
cc, err := rest.InClusterConfig()
if err != nil {
return nil, err
}
return cc, err
}
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)
return clientConfig.ClientConfig()
}
// InitKubeCache initializes a new Kubernetes cache.
func (k *Kubernetes) InitKubeCache() 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: %v", err)
}
if k.LabelSelector != nil {
var selector labels.Selector
selector, err = unversionedapi.LabelSelectorAsSelector(k.LabelSelector)
k.Selector = &selector
if err != nil {
return fmt.Errorf("Unable to create Selector for LabelSelector '%s'.Error was: %s", k.LabelSelector, err)
}
}
if k.LabelSelector == nil {
log.Printf("[INFO] Kubernetes middleware configured without a label selector. No label-based filtering will be performed.")
} else {
log.Printf("[INFO] Kubernetes middleware configured with the label selector '%s'. Only kubernetes objects matching this label selector will be exposed.", unversionedapi.FormatLabelSelector(k.LabelSelector))
}
k.APIConn = newdnsController(kubeClient, k.ResyncPeriod, k.Selector, k.PodMode == PodModeVerified)
return err
}
func (k *Kubernetes) parseRequest(lowerCasedName, qtype string) (r recordRequest, err error) {
// 3 Possible cases
// SRV Request: _port._protocol.service.namespace.type.zone
// A Request (endpoint): endpoint.service.namespace.type.zone
// A Request (service): service.namespace.type.zone
// separate zone from rest of lowerCasedName
var segs []string
for _, z := range k.Zones {
if dns.IsSubDomain(z, lowerCasedName) {
r.zone = z
segs = dns.SplitDomainName(lowerCasedName)
segs = segs[:len(segs)-dns.CountLabel(r.zone)]
break
}
}
if r.zone == "" {
return r, errors.New("zone not found")
}
offset := 0
if qtype == "SRV" {
if len(segs) != 5 {
return r, errInvalidRequest
}
// This is a SRV style request, get first two elements as port and
// protocol, stripping leading underscores if present.
if segs[0][0] == '_' {
r.port = segs[0][1:]
} else {
r.port = segs[0]
if !symbolContainsWildcard(r.port) {
return r, errInvalidRequest
}
}
if segs[1][0] == '_' {
r.protocol = segs[1][1:]
if r.protocol != "tcp" && r.protocol != "udp" {
return r, errInvalidRequest
}
} else {
r.protocol = segs[1]
if !symbolContainsWildcard(r.protocol) {
return r, errInvalidRequest
}
}
if r.port == "" || r.protocol == "" {
return r, errInvalidRequest
}
offset = 2
}
if qtype == "A" && len(segs) == 4 {
// This is an endpoint A record request. Get first element as endpoint.
r.endpoint = segs[0]
offset = 1
}
if len(segs) == (offset + 3) {
r.service = segs[offset]
r.namespace = segs[offset+1]
r.typeName = segs[offset+2]
return r, nil
}
if len(segs) == 1 && qtype == "TXT" {
r.typeName = segs[0]
return r, nil
}
return r, errInvalidRequest
}
// Records looks up services in kubernetes. If exact is true, it will lookup
// just this name. This is used when find matches when completing SRV lookups
// for instance.
func (k *Kubernetes) Records(r recordRequest) ([]msg.Service, error) {
// Abort if the namespace does not contain a wildcard, and namespace is not published per CoreFile
// Case where namespace contains a wildcard is handled in Get(...) method.
if (!symbolContainsWildcard(r.namespace)) && (len(k.Namespaces) > 0) && (!dnsstrings.StringInSlice(r.namespace, k.Namespaces)) {
return nil, errNsNotExposed
}
services, pods, err := k.get(r)
if err != nil {
return nil, err
}
if len(services) == 0 && len(pods) == 0 {
// Did not find item in k8s
return nil, errNoItems
}
records := k.getRecordsForK8sItems(services, pods, r.zone)
return records, nil
}
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) getRecordsForK8sItems(services []service, pods []pod, zone string) []msg.Service {
var records []msg.Service
for _, svc := range services {
key := svc.name + "." + svc.namespace + ".svc." + zone
if svc.addr == api.ClusterIPNone {
// This is a headless service, create records for each endpoint
for _, ep := range svc.endpoints {
ephostname := endpointHostname(ep.addr)
s := msg.Service{
Key: msg.Path(strings.ToLower(ephostname+"."+key), "coredns"),
Host: ep.addr.IP, Port: int(ep.port.Port),
}
records = append(records, s)
}
} else {
// Create records for each exposed port...
for _, p := range svc.ports {
s := msg.Service{Key: msg.Path(strings.ToLower(key), "coredns"), Host: svc.addr, Port: int(p.Port)}
records = append(records, s)
}
}
}
for _, p := range pods {
key := p.name + "." + p.namespace + ".pod." + zone
s := msg.Service{
Key: msg.Path(strings.ToLower(key), "coredns"),
Host: p.addr,
}
records = append(records, s)
}
return records
}
func ipFromPodName(podname string) string {
if strings.Count(podname, "-") == 3 && !strings.Contains(podname, "--") {
return strings.Replace(podname, "-", ".", -1)
}
return strings.Replace(podname, "-", ":", -1)
}
func (k *Kubernetes) findPods(namespace, podname string) (pods []pod, err error) {
if k.PodMode == PodModeDisabled {
return pods, errors.New("pod records disabled")
}
var ip string
if strings.Count(podname, "-") == 3 && !strings.Contains(podname, "--") {
ip = strings.Replace(podname, "-", ".", -1)
} else {
ip = strings.Replace(podname, "-", ":", -1)
}
if k.PodMode == PodModeInsecure {
s := pod{name: podname, namespace: namespace, addr: ip}
pods = append(pods, s)
return pods, nil
}
// PodModeVerified
objList, err := k.APIConn.podLister.Indexer.ByIndex(podIPIndex, ip)
if err != nil {
return nil, err
}
nsWildcard := symbolContainsWildcard(namespace)
for _, o := range objList {
p, ok := o.(*api.Pod)
if !ok {
return nil, errors.New("expected type *api.Pod")
}
// If namespace has a wildcard, filter results against Corefile namespace list.
if nsWildcard && (len(k.Namespaces) > 0) && (!dnsstrings.StringInSlice(p.Namespace, k.Namespaces)) {
continue
}
// check for matching ip and namespace
if ip == p.Status.PodIP && symbolMatches(namespace, p.Namespace, nsWildcard) {
s := pod{name: podname, namespace: namespace, addr: ip}
pods = append(pods, s)
return pods, nil
}
}
return pods, nil
}
// get retrieves matching data from the cache.
func (k *Kubernetes) get(r recordRequest) (services []service, pods []pod, err error) {
switch {
case r.typeName == "pod":
pods, err = k.findPods(r.namespace, r.service)
return nil, pods, err
default:
services, err = k.findServices(r)
return services, nil, err
}
}
func (k *Kubernetes) findServices(r recordRequest) ([]service, error) {
serviceList := k.APIConn.ServiceList()
var resultItems []service
nsWildcard := symbolContainsWildcard(r.namespace)
serviceWildcard := symbolContainsWildcard(r.service)
portWildcard := symbolContainsWildcard(r.port) || r.port == ""
protocolWildcard := symbolContainsWildcard(r.protocol) || r.protocol == ""
for _, svc := range serviceList {
if !(symbolMatches(r.namespace, svc.Namespace, nsWildcard) && symbolMatches(r.service, svc.Name, serviceWildcard)) {
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 nsWildcard && (len(k.Namespaces) > 0) && (!dnsstrings.StringInSlice(svc.Namespace, k.Namespaces)) {
continue
}
s := service{name: svc.Name, namespace: svc.Namespace, addr: svc.Spec.ClusterIP}
if s.addr != api.ClusterIPNone {
for _, p := range svc.Spec.Ports {
if !(symbolMatches(r.port, strings.ToLower(p.Name), portWildcard) && symbolMatches(r.protocol, strings.ToLower(string(p.Protocol)), protocolWildcard)) {
continue
}
s.ports = append(s.ports, p)
}
resultItems = append(resultItems, s)
continue
}
// Headless service
endpointsList, err := k.APIConn.epLister.List()
if err != nil {
continue
}
for _, ep := range endpointsList.Items {
if ep.ObjectMeta.Name != svc.Name || ep.ObjectMeta.Namespace != svc.Namespace {
continue
}
for _, eps := range ep.Subsets {
for _, addr := range eps.Addresses {
for _, p := range eps.Ports {
ephostname := endpointHostname(addr)
if r.endpoint != "" && r.endpoint != ephostname {
continue
}
if !(symbolMatches(r.port, strings.ToLower(p.Name), portWildcard) && symbolMatches(r.protocol, strings.ToLower(string(p.Protocol)), protocolWildcard)) {
continue
}
s.endpoints = append(s.endpoints, endpoint{addr: addr, port: p})
}
}
}
}
resultItems = append(resultItems, s)
}
return resultItems, nil
}
func symbolMatches(queryString, candidateString string, wildcard bool) bool {
if wildcard {
return true
}
return queryString == candidateString
}
// getServiceRecordForIP: Gets a service record with a cluster ip matching the ip argument
// If a service cluster ip does not match, it checks all endpoints
func (k *Kubernetes) getServiceRecordForIP(ip, name string) []msg.Service {
// First check services with cluster ips
svcList, err := k.APIConn.svcLister.List(labels.Everything())
if err != nil {
return nil
}
for _, service := range svcList {
if (len(k.Namespaces) > 0) && !dnsstrings.StringInSlice(service.Namespace, k.Namespaces) {
continue
}
if service.Spec.ClusterIP == ip {
domain := service.Name + "." + service.Namespace + ".svc." + k.PrimaryZone()
return []msg.Service{{Host: domain}}
}
}
// If no cluster ips match, search endpoints
epList, err := k.APIConn.epLister.List()
if err != nil {
return nil
}
for _, ep := range epList.Items {
if (len(k.Namespaces) > 0) && !dnsstrings.StringInSlice(ep.ObjectMeta.Namespace, k.Namespaces) {
continue
}
for _, eps := range ep.Subsets {
for _, addr := range eps.Addresses {
if addr.IP == ip {
domain := endpointHostname(addr) + "." + ep.ObjectMeta.Name + "." + ep.ObjectMeta.Namespace + ".svc." + k.PrimaryZone()
return []msg.Service{{Host: domain}}
}
}
}
}
return nil
}
// symbolContainsWildcard checks whether symbol contains a wildcard value
func symbolContainsWildcard(symbol string) bool {
return (symbol == "*" || symbol == "any")
}