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As in this question, I'm looking at the output of ethtool -k eth0, and I see that some things are marked "[fixed]":

rx-checksumming: off [fixed]
tx-checksumming: off
    tx-checksum-ipv4: off [fixed]
    tx-checksum-ip-generic: off
    tx-checksum-ipv6: off [fixed]
    tx-checksum-fcoe-crc: off [fixed]
    tx-checksum-sctp: off [fixed]

I understand that this means they can't be changed, but I can't figure out where that comes from --- is it something that was compiled into my kernel?

Community
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Patrick Collins
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1 Answers1

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These features being on/off and fixed or tunable depends:

  • first on the hardware capabilities of your Ethernet adapter,
  • then on the way the kernel driver for this adapter support/use or not these hardware features.

Example: many Ethernet chips have capabilities that can ease (offload) the software job, but the kernel maintainers are reluctant to use these. See here "why" regarding TCP offloading:

http://www.linuxfoundation.org/collaborate/workgroups/networking/toe

In any case, this should not worry you. Seeing for example:

rx-checksumming: off [fixed]

...does not mean you wont have rx checksum, it just mean that it will be done by kernel code outside of your Ethernet driver code.

jbm
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