TB16/TB18 Dock: Resolving a checksum failure with systems running Ubuntu

The following article provides information about how to resolve a Hardware Checksum failure. This issue is seen on TB18 docking stations that are used with Dell systems running Ubuntu.

HW Checksum failing silently with the TB18 dock and systems running Ubuntu

The TCP (Transmission Control Protocol) rx (Receive) and tx (Transmit) checksum offloading is not working correctly. This is because both rx-checksumming and tx-checksumming are both set to ON by default.

An example of this would be: If you downloaded a large file, such as the Ubuntu ISO and then you ran a md5sum on it, it will show an incorrect md5sum return.

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Resolution Steps

Workaround

Running the following command allows the download to complete correctly:

Sudo ethtool -k <TB18 eth device> tx off rx off

Root Cause

This issue is because of the iSerial number of the USB LAN on the TB16/TB18 dock.

(The Realtek_USB_10_100_1000_LAN_000001000000 is now Realtek_USB_10_100_1000_LAN_000002000000)

Solution

The issue was reported with Linux kernel 4.15.0-34 Generic but has been resolved with kernel 4.15.0-36.39.

Update to the latest version of Ubuntu to resolve this issue.

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