Re: [PATCH net] ice: Fix missing 1's complement negation in GCS raw checksum

[Simon Horman]

On Wed, Apr 08, 2026 at 08:02:14PM +0100, Matt Fleming wrote:
> From: Matt Fleming <mfleming@xxxxxxxxxxxxxx>
> 
> Commit 905d1a220e8d ("ice: Add E830 checksum offload support") added
> Generic Checksum (GCS) support for E830 NICs but omitted the 1's
> complement negation (~) when converting the hardware raw_csum to
> skb->csum for CHECKSUM_COMPLETE.
> 
> Without the negation, every CHECKSUM_COMPLETE packet fails the
> fast-path validation in nf_ip_checksum() and falls through to software
> checksumming via __skb_checksum_complete(), which triggers the
> rate-limited "hw csum failure" warning. Packets are still accepted
> (the software recheck passes) but hardware checksum offload is
> effectively disabled and the warning floods dmesg on systems running
> nf_conntrack on VLAN sub-interfaces.
> 
> Multiple other drivers (idpf, ehea, iwlwifi, cassini, sunhme, enetc)
> also apply ~ for CHECKSUM_COMPLETE. The ice driver was the only in-tree
> user of csum_unfold() for CHECKSUM_COMPLETE that omitted it.
> 
> Fixes: 905d1a220e8d ("ice: Add E830 checksum offload support")
> Signed-off-by: Matt Fleming <mfleming@xxxxxxxxxxxxxx>

Reviewed-by: Simon Horman <horms@xxxxxxxxxx>