What does the meaning of "[fixed]" string in output of ethtool command

Question

I run ethtool to query the offload features of a NIC using "ethtool -k" command, and the output is something as follows:

ethtool -k eth0

scatter-gather: on
tx-scatter-gather: on
tx-scatter-gather-fraglist: off **[fixed]**

I am wondering what the meaning of "[fixed]" is.

Answer 1

Those are the parameters that cant be changed, they are "fixed".

Here is an example. Let's take this output of ethtool :

large-receive-offload: off [fixed]
rx-vlan-offload: on
tx-vlan-offload: on

If I want to change rx-vlan-offload I would do :

$ sudo ethtool -K eth0 rxvlan off
Actual changes:
tcp-segmentation-offload: on
    tx-tcp-segmentation: on
    tx-tcp6-segmentation: on
rx-vlan-offload: off

The result will be :

$ sudo ethtool -k eth0 | grep rx-vlan
rx-vlan-offload: **off**
rx-vlan-filter: off [fixed]
rx-vlan-stag-hw-parse: off [fixed]
rx-vlan-stag-filter: off [fixed]

Now, let's try to modify a "fixed" parameter like "large-receive-offload" :

$ sudo ethtool -K eth0 lro on
Cannot change large-receive-offload
Could not change any device features

Hope this helps.