Re: [PATCH bpf-next v5 2/8] net: veth: add xmo_rx_checksum callback to veth driver

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] veth_xdp_rx_checksum incorrectly maps CHECKSUM_PARTIAL to XDP_CHECKSUM_NONE, causing XDP programs to drop valid locally-generated packets.
--

--- Patch [2]: [PATCH bpf-next v5 2/8] net: veth: add xmo_rx_checksum callback to veth driver ---
commit 34eae1c96706424d6fb3ab7f5a60445ee0f6dd08
Author: Lorenzo Bianconi <lorenzo@kernel.org>

net: veth: add xmo_rx_checksum callback to veth driver

Implement xmo_rx_checksum callback in veth driver to report RX checksum
result to the eBPF program bounded to the veth device.

> diff --git a/drivers/net/veth.c b/drivers/net/veth.c
> index 8170bf33ccf95..dbf30089581c8 100644
> --- a/drivers/net/veth.c
> +++ b/drivers/net/veth.c
> @@ -1701,6 +1701,37 @@ static int veth_xdp_rx_vlan_tag(const struct xdp_md *ctx, __be16 *vlan_proto,
>  	return err;
>  }
>  
> +static int veth_xdp_rx_checksum(const struct xdp_md *ctx,
> +				enum xdp_checksum *ip_summed,
> +				u32 *cksum, u8 *cksum_level)
> +{
> +	const struct veth_xdp_buff *_ctx = (void *)ctx;
> +	const struct sk_buff *skb = _ctx->skb;
> +
> +	if (!skb)
> +		return -ENODATA;
> +
> +	switch (skb->ip_summed) {
> +	case CHECKSUM_COMPLETE:
> +		*ip_summed = XDP_CHECKSUM_COMPLETE;
> +		*cksum = skb->csum;
> +		*cksum_level = 0;
> +		break;
> +	case CHECKSUM_UNNECESSARY:
> +		*ip_summed = XDP_CHECKSUM_UNNECESSARY;
> +		*cksum_level = skb->csum_level;
> +		*cksum = 0;
> +		break;
> +	default:
> +		*ip_summed = XDP_CHECKSUM_NONE;
> +		*cksum_level = 0;
> +		*cksum = 0;
> +		break;
> +	}

[Severity: High]
Is there a missing case for CHECKSUM_PARTIAL in this switch statement inside
veth_xdp_rx_checksum()?

When a local process sends traffic over a veth pair with checksum offload
enabled, the packet is passed to the receiving veth with skb->ip_summed
set to CHECKSUM_PARTIAL.

By falling through to the default case, this maps CHECKSUM_PARTIAL to
XDP_CHECKSUM_NONE. An attached XDP program that validates checksums will see
XDP_CHECKSUM_NONE and attempt to compute a software checksum. The software
computation will fail because the TCP/UDP checksum field only contains a
pseudo-header checksum at this point, leading to dropped packets.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260715-bpf-xdp-meta-rxcksum-v5-0-623d5c0d0ab7@kernel.org?part=2