DNS packets seemingly randomly dropped

[regner]

Windows Version

Microsoft Windows [Version 10.0.19045.2965]

WSL Version

0.0.0.0

Are you using WSL 1 or WSL 2?

• WSL 2
• WSL 1

Kernel Version

5.10.102.1

Distro Version

Ubuntu-22.04

Other Software

Docker Desktop (Windows): v4.21.1

Repro Steps

regner@WORKSTATION:/$ for i in {1..200}; do time nslookup compute.googleapis.com 8.8.8.8; done 2>&1 | grep ^real | sed -e s/.*m// | sort -r | head -10
5.027s
5.026s
5.025s
0.032s
0.031s
0.025s
0.024s
0.024s
0.024s
0.024s

Expected Behavior

All DNS response times should be around the 0.030s mark.

Actual Behavior

On average, around 1 in 70-80 DNS packets time out and require being retransmitted.

In my diagnostics I have found that the issue appears to be something between WSL and my physical NIC. Possibly in the Hyper-V virtual switch.

If I run tcpdump within WSL I can see the DNS requests going out, including the packets that don't get a response and require a retransmission. If I run Wireshark on the host machine I can see the DNS packets on the WSL interface, but the packets which appear to be getting dropped are not seen on the physical interface.

Here are two Wireshark captures. The left is capturing the vEthernet (WSL) NIC, and the right is capturing the Ethernet 2 NIC.

In the above screenshot we can see that there are two DNS requests that appear to leave the WSL distro. The first packet however never gets to the physical NIC, only the retransmission gets there.

We have tested on other machines in the office, and everyone who is on WSL2 has the same issue. However those who are on WSL1 do not appear to have this issue.

I did my best to review all the other DNS related issues, and non of them seem to be linked to this issue.

Diagnostic Logs

No response

[Edstub207]

Can confirm we have experienced this issue as well on:

• Windows 10 - Ubuntu 20.04.4 LTS (GNU/Linux 5.10.102.1-microsoft-standard-WSL2 x86_64)
• Windows 11- Ubuntu 20.04.6 LTS (GNU/Linux 5.15.90.1-microsoft-standard-WSL2 x86_64)

[craigloewen-msft]

Are you able to update your Windows and WSL version to try the new networking features? This might resolve you: https://devblogs.microsoft.com/commandline/windows-subsystem-for-linux-september-2023-update/

These features will be coming to Windows 11 22H2 very soon.

[craigloewen-msft]

Closing this due to lack of response, if you're still seeing this issue please reopen it as a new issue. Thank you!