Disable Checksum offload

[alopez@ac.upc.edu]

Hi everyone,

I would like to disable the checksum offload of my network card. I have found this command that should solve my problem:


ethtool -K eth0 tx off rx off

When I query the status of the network card with ethtool -k eth0 everything seems ok, but when I use wireshark, the TCP packets have errors in the checksum. The connectivity is ok so I suppose that the checksum offload is not disabled.



rx-checksumming: off
tx-checksumming: off


I am using Ubuntu 12.04




Thanks in advance

[Sergius14]

You can also turn off checksum validation at Wireshark Preferences...

[alopez@ac.upc.edu]

Thanks for your replay. We are developing a new protocol that encapsulates the packets. If the checksum is calculated by the network card, it will just calculate the correct cheksum for the external packet and not the internal one. When the packet is decapsulated, the internal packet has a wrong checksum and the packet is discarded.
I have noticed that when I turn off the checksum offload using the ethtool command, the only packets that wireshark detects with wrong checksum are SYN and ACK tcp packets. The other ones are correctly detected. I need that the checksum of these packets (SYN, ACK) are also calculated by the cpu.