Tailscale: Tailscale on Windows 10 (19042) causes unexpectedly high sustained CPU load in Service Host: DNS Client

[dewitt]

Describe the bug

While Tailscale (v 1.0.4) is running, CPU load jumps from 0% to 10-20% on Windows 10 (19042).

To Reproduce

On Windows 10:

Open Task Manager and observe Service Host: DNS Client, which should show nominal CPU load / memory usage.

Launch Tailscale and connect.

Observe CPU usage associated with Service Host: DNS Client jump to 10-20%.

Disconnect Tailscale.

Observe CPU usage associated with Service Host: DNS Client drop back to 0%.

Expected behavior

No observable impact on DNS client.

Screenshots

Version information:

Windows 10.0.19042.

Tailscale 1.0.4.

Additional information

Happy to share additional debug information privately.

[bradfitz]

I looked at your logs.

Seattle and Bangalore only were running a new server binary with a TLS configuration that Windows only was rejecting so it was reconnecting often.

I've reverted them back to the old version until I figure out how to make Windows happy.

It should be happy now?

[bradfitz]

(No need to restart or anything.)

[dewitt]

Thanks for the amazingly fast turn-around! Looks back to normal with the old version. Let me know if I can help re-test.