vL3 DNS is slow when using the DNS search path

[fr-Pursuit]

Context

We're using the interdomain vL3 example, with one of the alpine pods renamed to alpine2 to avoid confusion. The vL3 domain names of the alpine pods are therefore:

• alpine.my-interdomain-vl3-network
• alpine2.my-interdomain-vl3-network

Expected Behavior

When my-interdomain-vl3-network is in the DNS search path, DNS queries on alpine2 should take roughly the same time as explicit queries on alpine2.my-interdomain-vl3-network.

Current Behavior

DNS queries on alpine2 take around 400ms, while queries on the explicit alpine2.my-interdomain-vl3-network name take less than 50ms.

Steps to Reproduce

1. Deploy the interdomain vL3 example (while renaming one alpine pod to alpine2 to avoid confusion, setting the NSM_DNS_TEMPLATES environment variable to {{ index .Labels \"podName\" }}.my-interdomain-vl3-network. for the DNS service to work, and adding my-interdomain-vl3-network to alpine's DNS search path)
2. Open a shell in the alpine pod
3. Run time nslookup -type=a -debug alpine2.my-interdomain-vl3-network and check the time
4. Run time nslookup -type=a -debug alpine2 and check the time

Additional context

This problem was diagnosed as part of #1414

The example was deployed on three kind clusters using kind 0.17.0 and the kindest v1.25.3 image

[glazychev-art]

Hi @fr-Pursuit,
Thanks for the report!
We pushed some fixes. Could you please test this on the latest main branch?
After the fix you no longer need to add my-interdomain-vl3-network to client's DNS search path

[fr-Pursuit]

Hi @glazychev-art !

Without adding my-interdomain-vl3-network to the clients' DNS search path, here's the timings I got from the alpine pod:

/ # time nslookup -type=a -debug alpine2.my-interdomain-vl3-network
Server:         127.0.0.1
Address:        127.0.0.1:53

Query #0 completed in 3ms:
authoritative answer:
Name:   alpine2.my-interdomain-vl3-network
Address: 172.16.0.3

real    0m 0.00s
user    0m 0.00s
sys     0m 0.00s
/ # time nslookup -type=a -debug alpine2
Server:         127.0.0.1
Address:        127.0.0.1:53

Query #0 completed in 10ms:
authoritative answer:
Name:   alpine2.my-interdomain-vl3-network
Address: 172.16.0.3

real    0m 0.01s
user    0m 0.00s
sys     0m 0.00s

The issue seems to be fixed. Thanks!