DNS resolution fails in VXLAN mode.

[zhouzhifeisdcn]

calico version v3.20.2

config

dns service ip 100.123.0.10

When running dig +tcp 100.123.0.10 www.baidu.com on the host machine node, there is a response. However, running dig @100.123.0.10 www.baidu.com reports a timeout error. Running dig @100.124.48.41 works fine. Here, 100.123.0.10 is the service IP, and 100.124.48.41 is the pod IP. Since there are no issues within the pod, how can I troubleshoot this?

Expected Behavior

Using UDP, it is hoped that addresses can be parsed correctly.

Current Behavior

The address parsing works correctly in BGP mode, but there are issues with address parsing in VXLAN mode.

[tomastigera]

v3.20.2

If that version is correct, it is no longer supported and we would advice you to upgrade. The current version is 3.30.4.

Also, we do believe the the issue is happening. It would help us if you provided any additional diagnostics or a way how to reproduce the issue. The simplest is to use tcpdump and trace where your DNS requests end up and where the response end up? Check logs, check your policies, etc.

[zhouzhifeisdcn]

Based on the packet capture using tcpdump, it was found that the UDP DNS request sent from node A reached the physical network card of node B where the DNS is located, but it did not reach the vxlan.calico network card.

[zhouzhifeisdcn]

I found that running ethtool -K calico.vxlan tx off
After running ethtool -K calico.vxlan rx off, DNS resolution is normal. Could you please advise on how to configure the relevant configuration files of Calico to achieve the same effect

[lixd]

same issue in k8s 1.23.17 + calico 3.22.4 + ubuntu24.04, UDP DNS request sent from node A reached the physical network card of node B where the DNS is located, but it did not reach the vxlan.calico network card. run this command to resolve: ethtool --offload vxlan.calico rx off tx off

[tomastigera]

This issue was fixed in 3.29.0 #9091 I strongly suggest to upgrade. You can also set ChecksumOffloadBroken to true if it is available in your version.