On 14/09/2022 22:32, Dmitry Pasiukevich via Dnsmasq-discuss wrote:
Hi,
TLDR: DNS request to dnsmasq with upper-case domain is handled
differently if request is sent over TCP vs UDP
I run a server to forward "cluster.local" queries to another process:
/usr/sbin/dnsmasq-k--cache-size=1000--no-negcache--dns-forward-max=1500--log-facility=---server=/cluster.local/127.0.0.1#10053--log-queries=extra--log-debug
<http://127.0.0.1/#10053--log-queries=extra--log-debug>
dnsmasq 2.86 with IP 10.64.0.7
1. When I run:
dig +tcp kubernetes.default.svc.cluster.LOCAL @10.64.0.7 <http://10.64.0.7/>
I get NOERROR but no data in the response. dnsmasq logs:
I0913 06:15:04.790606 1 nanny.go:146] dnsmasq[86]: 44065
10.64.1.4/33015 <http://10.64.1.4/33015> query[A]
kubernetes.default.svc.CLUSTER.LOCAL from 10.64.1.4
I0913 06:15:04.851065 1 nanny.go:146] dnsmasq[86]: 44065
10.64.1.4/33015 <http://10.64.1.4/33015> forwarded
kubernetes.default.svc.CLUSTER.LOCAL to 169.254.169.254
As you can see dnsmasq doesn't modify the domain. Because it's a
"CLUSTER.LOCAL" and not a "cluster.local" it's forwarded to the server
169.254.169.254 set in the /etc/resolv.conf. And not the
--server=/cluster.local/127.0.0.1#10053 <http://127.0.0.1/#10053>
2. When I run exactly the same query but over UDP not TCP:
dig kubernetes.default.svc.CLUSTER.LOCAL @10.64.0.7 <http://10.64.0.7/>
I get NOERROR and correct response:
kubernetes.default.svc.CLUSTER.LOCAL. 30 IN A 10.68.0.1
dnsmasq logs in this case:
I0913 06:19:20.820425 1 nanny.go:146] dnsmasq[11]: 44471
10.64.1.4/49622 <http://10.64.1.4/49622> query[A]
kubernetes.default.svc.CLUSTER.LOCAL from 10.64.1.4
I0913 06:19:20.820866 1 nanny.go:146] dnsmasq[11]: 44471
10.64.1.4/49622 <http://10.64.1.4/49622> forwarded
kubernetes.default.svc.cluster.local to 127.0.0.1
In this case the domain in the query is changed to the lower-case and it
matches "cluster.local" and forwards to 127.0.0.1 as expected.
3. When I run exactly the same query over TCP but fully lower-case it
works as well.
Is this a bug or intended behaviour or maybe I misunderstood the logs?
Thanks!
Definitely not intended behaviour.
Also not immediately reproducible in the current development code,
though I don't recall fixing anything that might cause this. Would it be
easy for you to repeat the tests using the git HEAD branch for a quick
win? If that fails for you I'll try harder to reproduce the problem.
Cheers,
Simon.
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