What happened
Resolving an external domain from within a pod fails with SERVFAIL message. In the logs, i/o timeout error is mentioned.
What I expected to happen
External domains should be successfully resolved from the pods.
How to reproduce it
apiVersion: v1
kind: Pod
metadata:
name: dnsutils
namespace: default
spec:
containers:
- name: dnsutils
image: gcr.io/kubernetes-e2e-test-images/dnsutils:1.3
command:
- sleep
- "3600"
imagePullPolicy: IfNotPresent
restartPolicy: Always
Create the pod above (from Debugging DNS Resolution help page).
Run
kubectl exec dnsutils -it -- nslookup google.compig@pig202:~$ kubectl exec dnsutils -it -- nslookup google.com Server: 10.152.183.10 Address: 10.152.183.10#53 ** server can't find google.com.mshome.net: SERVFAIL command terminated with exit code 1Also run
kubectl exec dnsutils -it -- nslookup google.com.pig@pig202:~$ kubectl exec dnsutils -it -- nslookup google.com. Server: 10.152.183.10 Address: 10.152.183.10#53 ** server can't find google.com: SERVFAIL command terminated with exit code 1
Additional information
I am using microk8s environment in a Hyper-V virtual machine.
Resolving DNS from the virtual machine works, and Kubernetes is able to pull container images. It's only from within the pods that the resolution is failing meaning I cannot communicate with the Internet from within the pods.
This is OK:
pig@pig202:~$ kubectl exec dnsutils -it -- nslookup kubernetes.default
Server: 10.152.183.10
Address: 10.152.183.10#53
Name: kubernetes.default.svc.cluster.local
Address: 10.152.183.1
Environment
The version of CoreDNS
image: 'coredns/coredns:1.6.6'
Corefile (taken from ConfigMap)
Corefile: |
.:53 {
errors
health {
lameduck 5s
}
ready
log . {
class error
}
kubernetes cluster.local in-addr.arpa ip6.arpa {
pods insecure
fallthrough in-addr.arpa ip6.arpa
}
prometheus :9153
forward . 8.8.8.8 8.8.4.4
cache 30
loop
reload
loadbalance
}
Logs
pig@pig202:~$ kubectl logs --namespace=kube-system -l k8s-app=kube-dns -f
[INFO] 10.1.99.26:47204 - 29832 "AAAA IN grafana.com. udp 29 false 512" NOERROR - 0 2.0002558s
[ERROR] plugin/errors: 2 grafana.com. AAAA: read udp 10.1.99.19:52008->8.8.8.8:53: i/o timeout
[INFO] 10.1.99.26:59350 - 50446 "A IN grafana.com. udp 29 false 512" NOERROR - 0 2.0002028s
[ERROR] plugin/errors: 2 grafana.com. A: read udp 10.1.99.19:60405->8.8.8.8:53: i/o timeout
[INFO] 10.1.99.26:43050 - 13676 "AAAA IN grafana.com. udp 29 false 512" NOERROR - 0 2.0002151s
[ERROR] plugin/errors: 2 grafana.com. AAAA: read udp 10.1.99.19:45624->8.8.8.8:53: i/o timeout
[INFO] 10.1.99.26:36997 - 30359 "A IN grafana.com. udp 29 false 512" NOERROR - 0 2.0002791s
[ERROR] plugin/errors: 2 grafana.com. A: read udp 10.1.99.19:37554->8.8.4.4:53: i/o timeout
[INFO] 10.1.99.32:57927 - 53858 "A IN google.com.mshome.net. udp 39 false 512" NOERROR - 0 2.0001987s
[ERROR] plugin/errors: 2 google.com.mshome.net. A: read udp 10.1.99.19:34079->8.8.4.4:53: i/o timeout
[INFO] 10.1.99.32:38403 - 36398 "A IN google.com.mshome.net. udp 39 false 512" NOERROR - 0 2.000224s
[ERROR] plugin/errors: 2 google.com.mshome.net. A: read udp 10.1.99.19:59835->8.8.8.8:53: i/o timeout
[INFO] 10.1.99.26:57447 - 20295 "AAAA IN grafana.com.mshome.net. udp 40 false 512" NOERROR - 0 2.0001892s
[ERROR] plugin/errors: 2 grafana.com.mshome.net. AAAA: read udp 10.1.99.19:51534->8.8.8.8:53: i/o timeout
[INFO] 10.1.99.26:41052 - 56059 "A IN grafana.com.mshome.net. udp 40 false 512" NOERROR - 0 2.0001879s
[ERROR] plugin/errors: 2 grafana.com.mshome.net. A: read udp 10.1.99.19:47378->8.8.8.8:53: i/o timeout
[INFO] 10.1.99.26:56748 - 51804 "AAAA IN grafana.com.mshome.net. udp 40 false 512" NOERROR - 0 2.0003226s
[INFO] 10.1.99.26:45442 - 61916 "A IN grafana.com.mshome.net. udp 40 false 512" NOERROR - 0 2.0001922s
[ERROR] plugin/errors: 2 grafana.com.mshome.net. AAAA: read udp 10.1.99.19:35528->8.8.8.8:53: i/o timeout
[ERROR] plugin/errors: 2 grafana.com.mshome.net. A: read udp 10.1.99.19:53568->8.8.8.8:53: i/o timeout
OS
pig@pig202:~$ cat /etc/os-release
NAME="Ubuntu"
VERSION="20.04 LTS (Focal Fossa)"
ID=ubuntu
ID_LIKE=debian
PRETTY_NAME="Ubuntu 20.04 LTS"
VERSION_ID="20.04"
Tried on Ubuntu 18.04.3 LTS, same issue.
Other
mshome.net search domain comes from Hyper-V network, I assume. Perhaps this will be of help:
pig@pig202:~$ nmcli device show eth0
GENERAL.DEVICE: eth0
GENERAL.TYPE: ethernet
GENERAL.HWADDR: 00:15:5D:88:26:02
GENERAL.MTU: 1500
GENERAL.STATE: 100 (connected)
GENERAL.CONNECTION: Wired connection 1
GENERAL.CON-PATH: /org/freedesktop/NetworkManager/ActiveConnection/1
WIRED-PROPERTIES.CARRIER: on
IP4.ADDRESS[1]: 172.19.120.188/28
IP4.GATEWAY: 172.19.120.177
IP4.ROUTE[1]: dst = 0.0.0.0/0, nh = 172.19.120.177, mt = 100
IP4.ROUTE[2]: dst = 172.19.120.176/28, nh = 0.0.0.0, mt = 100
IP4.ROUTE[3]: dst = 169.254.0.0/16, nh = 0.0.0.0, mt = 1000
IP4.DNS[1]: 172.19.120.177
IP4.DOMAIN[1]: mshome.net
IP6.ADDRESS[1]: fe80::6b4a:57e2:5f1b:f739/64
IP6.GATEWAY: --
IP6.ROUTE[1]: dst = fe80::/64, nh = ::, mt = 100
IP6.ROUTE[2]: dst = ff00::/8, nh = ::, mt = 256, table=255