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I would like to find out if my Ubuntu VM uses tcp-offloading to increase the performance of VXLAN encapsulation. Where can I find this information on my machine?

arne.z
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3 Answers3

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NIC properties and settings are typically displayed with the ethtool command. In this case the --show-offload option may provide insightful details.

But please bear in mind that you're using a virtual server with (para-) virtualised hardware and the features a virtual network adapter shows not necessarily correspond to what is done by the hypervisor which actually controls the hardware.

HBruijn
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  • Great! That was what I was looking for. And thank you for mentioning to treat the output with care. – arne.z May 02 '16 at 23:21
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Maybe 4 years ago that was the default for Wireshark but in 2020 you must check the box under Edit->Preferences->Protocols->TCP called Validate the TCP checksum if possible. This will display TCP CHECKSUM INCORRECT for longish outgoing packets. You may then want to disable TCP Offload so that only TCP packets with invalid TCP checksums are displayed, if ever.

On MACOS this can be done inside a user's .bash_profile to re-enable after a new boot:

sudo sysctl net.link.generic.system.hwcksum_tx=0
sudo sysctl net.link.generic.system.hwcksum_rx=0
Stuggi
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Jeff Rhodes
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I saw this was answered already, but if you run Wireshark on a machine using TCP offloading, in the packet details it'll say that the checksum is incorrect for everything exiting the machine.

Some Linux Nerd
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