如何为集群外的查询公开kube-dns服务？

Question

以前有人试图公开kube-dns服务吗？如果有，有没有其他的安装步骤或者你有什么调试建议给我？

服务定义如下：

$ kubectl get service kube-dns -o yaml --namespace kube-system
apiVersion: v1
kind: Service
metadata:
...
spec:
  clusterIP: 10.0.0.10
  ports:
  - name: dns
    nodePort: 31257
    port: 53
    protocol: UDP
    targetPort: 53
  - name: dns-tcp
    nodePort: 31605
    port: 53
    protocol: TCP
    targetPort: 53
  selector:
    k8s-app: kube-dns
  sessionAffinity: None
  type: NodePort
status:
  loadBalancer: {}

Answer 1

您是在tcp端口还是udp端口上查询？

我将kube-dns更改为NodePort服务：

$ kubectl describe services kube-dns --namespace kube-system
Name:           kube-dns
Namespace:      kube-system
Labels:         k8s-app=kube-dns
            kubernetes.io/cluster-service=true
            kubernetes.io/name=KubeDNS
Selector:       k8s-app=kube-dns
Type:           NodePort
IP:         10.171.240.10
Port:           dns 53/UDP
NodePort:       dns 30100/UDP
Endpoints:      10.168.0.6:53
Port:           dns-tcp 53/TCP
NodePort:       dns-tcp 30490/TCP
Endpoints:      10.168.0.6:53
Session Affinity:   None

然后从集群外部对udp端口进行查询，一切似乎都正常：

$ dig -p 30100 @10.240.0.4 kubernetes.default.svc.cluster.local

; <<>> DiG 9.9.5-9+deb8u6-Debian <<>> -p 30100 @10.240.0.4 kubernetes.default.svc.cluster.local
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 45472
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;kubernetes.default.svc.cluster.local. IN A

;; ANSWER SECTION:
kubernetes.default.svc.cluster.local. 30 IN A   10.171.240.1

;; Query time: 3 msec
;; SERVER: 10.240.0.4#30100(10.240.0.4)
;; WHEN: Thu May 26 18:27:32 UTC 2016
;; MSG SIZE  rcvd: 70