> diff --git a/net/core/xdp.c b/net/core/xdp.c
> index 9890a30584ba..9bcaa423ad17 100644
> --- a/net/core/xdp.c
> +++ b/net/core/xdp.c
> @@ -961,6 +961,38 @@ __bpf_kfunc int bpf_xdp_metadata_rx_vlan_tag(const
> struct xdp_md *ctx,
> return -EOPNOTSUPP;
> }
>
> +/**
> + * bpf_xdp_metadata_rx_checksum - Read XDP frame RX checksum.
> + * @ctx: XDP context pointer.
> + * @ip_summed: Return value pointer to a bitmask indicating available
> checksums.
> + * @cksum: Return value pointer indicating the hw checksum value.
> + * @cksum_level: Return value pointer indicating the checksum level result.
> + *
> + * In case of success, ``ip_summed`` is set to the RX checksum result.
> Possible
> + * values are:
> + * ``XDP_CHECKSUM_NONE``
> + * ``XDP_CHECKSUM_UNNECESSARY``
> + * ``XDP_CHECKSUM_COMPLETE``
> + * ``XDP_CHECKSUM_COMPLETE`` | ``XDP_CHECKSUM_UNNECESSARY``
> + *
> + * In case of success, ``cksum`` contains the checksum value calculated by
> the
> + * NIC. ``cksum`` is valid only if ``XDP_CHECKSUM_COMPLETE`` is set in
> + * ``ip_summed``. ``cksum_level`` contains the checksum level reported by the
> + * hw. ``cksum_level`` can be considered valid only if
> + * ``XDP_CHECKSUM_UNNECESSARY`` is set in ``ip_summed``.
Earlier review of this series raised the case where the NIC reports
COMPLETE or UNNECESSARY, the XDP program then modifies the packet and
returns XDP_PASS. In that situation the reported checksum is stale.
It was noted on the list that drivers today do not invalidate the
checksum in this case, they only stop reporting COMPLETE while an XDP
program is attached.
Would it help to document that expected driver behavior here (how it
works today versus what is expected), and possibly add a kselftest that
checks it? If this is handled in a later patch of the series, please
disregard.
> + *
> + * Return:
> + * * Returns 0 on success or ``-errno`` on error.
> + * * ``-EOPNOTSUPP`` : means device driver does not implement kfunc
> + * * ``-ENODATA`` : means no RX-checksum available for this frame
> + */
> +__bpf_kfunc int bpf_xdp_metadata_rx_checksum(const struct xdp_md *ctx,
> + enum xdp_checksum *ip_summed,
> + u32 *cksum, u8 *cksum_level)
> +{
> + return -EOPNOTSUPP;
> +}
---
AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md
CI run summary: https://github.com/kernel-patches/bpf/actions/runs/29453967825
