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Using trace dns
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Trace DNS queries and responses.

Screencast of the trace dns gadget

The trace dns gadget prints information about DNS queries and responses sent and received by the different pods.

On Kubernetes

Create a demo namespace:

$ kubectl create ns demo
namespace/demo created

Start the dns gadget:

$ kubectl gadget trace dns -n demo
NODE                          NAMESPACE                     POD                           QR NAMESERVER      TYPE      QTYPE      NAME

Run a pod on a different terminal and perform some DNS requests:

$ kubectl -n demo run mypod -it --image=wbitt/network-multitool -- /bin/sh
# nslookup -querytype=a inspektor-gadget.io. 8.8.4.4
# nslookup -querytype=aaaa inspektor-gadget.io. 8.8.4.4
# nslookup -querytype=mx inspektor-gadget.io. 8.8.4.4

The requests will be logged by the DNS gadget:

NODE                 NAMESPACE            POD                  PID         TID         COMM        QR NAMESERVER      TYPE      QTYPE      NAME                RCODE
minikube             demo                 mypod                1285309     1285310     isc-net-00… Q  8.8.4.4         OUTGOING  A          inspektor-gadget.i…        
minikube             demo                 mypod                1285309     1285310     isc-net-00… R  8.8.4.4         HOST      A          inspektor-gadget.i… NoError
minikube             demo                 mypod                1285594     1285595     isc-net-00… Q  8.8.4.4         OUTGOING  AAAA       inspektor-gadget.i…        
minikube             demo                 mypod                1285594     1285595     isc-net-00… R  8.8.4.4         HOST      AAAA       inspektor-gadget.i… NoError
minikube             demo                 mypod                1285655     1285656     isc-net-00… Q  8.8.4.4         OUTGOING  MX         inspektor-gadget.i…        
minikube             demo                 mypod                1285655     1285656     isc-net-00… R  8.8.4.4         HOST      MX         inspektor-gadget.i… NoError

isc-net-0000 is the name of one of the nslookup threads.

Delete the demo test namespace:

$ kubectl delete ns demo
namespace "demo" deleted

With ig

TODO

Limitations

  • The gadget is only able to capture up to 8 addresses on a DNS response. The event contains a NumAnswers field that can be used to check if the addresses reported were truncated.
  • Addresses on a response are only captured if it is compressed.