Outgoing TCPv6 packets are corrupted with tx-tcp6-segmentation enabled

[K900]

Windows Version

Release Preview 26100.4762

WSL Version

2.6.0

Are you using WSL 1 or WSL 2?

• WSL 2
• WSL 1

Kernel Version

No response

Distro Version

NixOS unstable

Other Software

No response

Repro Steps

Try downloading any file with curl -6 or similar inside WSL.

Expected Behavior

Download completes successfully.

Actual Behavior

WSL side reports ECONNRESET, Wireshark on the Windows side observes a corrupted TCP packet. ethtool -K <iface> tx-tcp6-segmentation off makes things work normally. Looking at hv_netsvc code in the kernel, it seems to simply pass through packets to the Windows side driver, so it could be a driver bug? Honestly no idea.

Diagnostic Logs

No response

[github-actions]

Logs are required for review from WSL team

If this a feature request, please reply with '/feature'. If this is a question, reply with '/question'.
Otherwise please attach logs by following the instructions below, your issue will not be reviewed unless they are added. These logs will help us understand what is going on in your machine.

How to collect WSL logs

Download and execute collect-wsl-logs.ps1 in an administrative powershell prompt:

Invoke-WebRequest -UseBasicParsing "https://raw.githubusercontent.com/microsoft/WSL/master/diagnostics/collect-wsl-logs.ps1" -OutFile collect-wsl-logs.ps1
Set-ExecutionPolicy Bypass -Scope Process -Force
.\collect-wsl-logs.ps1

The script will output the path of the log file once done.

If this is a networking issue, please use collect-networking-logs.ps1, following the instructions here

Once completed please upload the output files to this Github issue.

Click here for more info on logging
If you choose to email these logs instead of attaching to the bug, please send them to wsl-gh-logs@microsoft.com with the number of the github issue in the subject, and in the message a link to your comment in the github issue and reply with '/emailed-logs'.

[K900]

WslNetworkingLogs-2025-07-13_12-55-00.zip

[github-actions]

Diagnostic information

.wslconfig found
Detected appx version: 2.6.0.0
optional-components.txt not found

[zcobol]

@K900 WSL is not supporting IPv6, yet!

[craigloewen-msft]

Are you using mirrored networking mode? It does have IPv6 support

https://learn.microsoft.com/en-us/windows/wsl/networking#mirrored-mode-networking

[bmb244]

Review 26100.4762

WSL Version

2.6.0sing WSL 1 or WSL 2?

• [WSL 2
  nel sion
  _No respostro Version

Other Software

_Nteps

Try downloading any file with curl -6 or simi WSL.

Expected Behavior

ompletes successfully.

Actual Behavior

WSL side reports ECONNRESETe Windows side observes a corrupted TCP packet. ethtool -K <iface> tx-tcp6-segmentation off makes things work normally. Looking at hv_ernel, it seems to simply pass through packets to the Windows side driver, so it could be a driver bug? Honestly no idea