Re: Can we remove IFCAP_RXCSUM_IPV6?

On Sat, May 10, 2025 at 01:37:47AM +0000, Bjoern A. Zeeb wrote:
> Hi,
> 
> in 356ab07e2dba0 IFCAP_RXCSUM_IPV6 was introduced along with duplicating
> all the other bits to not break hardware offload for IPv4.
> 
> Almost 13 years later I wonder if for any interface (apart from the loopback
> interface maybe) IFCAP_RXCSUM_IPV6 ever made any difference?
> 
> A driver would know what RX offload features it can do and one flag should
> fit all of them.
> 
> People might say or have said 'but if it is broken for IPv6' we
> can no longer disable it.  Well, yes we can, in the driver as it doesn't
> make sense for an admin of some hardware having to toggle off a broken
> feature manually.
> 
> So I wonder if (temporary, say for 15) we can define IFCAP_RXCSUM_IPV6
> to IFCAP_RXCSUM as well, get the bit back as "reserved" during 15 and
> then be done with it again?
> 
> I haven't done the full due diligens but a quick grep resulted in a lot
> of "same code".
> 
> What am I missing (apart from the painful to do patch)?

I think it could be a simplification.  Note that we no longer have a shortage
of the cap bits, now that there is at least IFCAP2 and full nv-based cap
passing ioctl.