Subject: Re: [PATCH RESEND bpf-next 11/15] xdp: Add checksum level hint

From: Stanislav Fomichev <[email-masked]>
Date: Fri, 12 May 2023 11:34:21 -0700

On 05/12, Larysa Zaremba wrote:
> Implement functionality that enables drivers to expose to XDP code,
> whether checksums was checked and on what level.
> 
> Signed-off-by: Larysa Zaremba <[email-masked]>
> ---
>  Documentation/networking/xdp-rx-metadata.rst |  3 +++
>  include/linux/netdevice.h                    |  1 +
>  include/net/xdp.h                            |  2 ++
>  kernel/bpf/offload.c                         |  2 ++
>  net/core/xdp.c                               | 12 ++++++++++++
>  5 files changed, 20 insertions(+)
> 
> diff --git a/Documentation/networking/xdp-rx-metadata.rst b/Documentation/networking/xdp-rx-metadata.rst
> index 73a78029c596..f74f0e283097 100644
> --- a/Documentation/networking/xdp-rx-metadata.rst
> +++ b/Documentation/networking/xdp-rx-metadata.rst
> @@ -29,6 +29,9 @@ metadata is supported, this set will grow:
>  .. kernel-doc:: net/core/xdp.c
>     :identifiers: bpf_xdp_metadata_rx_stag
>  
> +.. kernel-doc:: net/core/xdp.c
> +   :identifiers: bpf_xdp_metadata_rx_csum_lvl
> +
>  An XDP program can use these kfuncs to read the metadata into stack
>  variables for its own consumption. Or, to pass the metadata on to other
>  consumers, an XDP program can store it into the metadata area carried
> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> index fdae37fe11f5..ddade3a15366 100644
> --- a/include/linux/netdevice.h
> +++ b/include/linux/netdevice.h
> @@ -1657,6 +1657,7 @@ struct xdp_metadata_ops {
>  			       enum xdp_rss_hash_type *rss_type);
>  	int	(*xmo_rx_ctag)(const struct xdp_md *ctx, u16 *vlan_tag);
>  	int	(*xmo_rx_stag)(const struct xdp_md *ctx, u16 *vlan_tag);
> +	int	(*xmo_rx_csum_lvl)(const struct xdp_md *ctx, u8 *csum_level);
>  };
>  
>  /**
> diff --git a/include/net/xdp.h b/include/net/xdp.h
> index 2db7439fc60f..0fbd25616241 100644
> --- a/include/net/xdp.h
> +++ b/include/net/xdp.h
> @@ -393,6 +393,8 @@ void xdp_attachment_setup(struct xdp_attachment_info *info,
>  			   bpf_xdp_metadata_rx_ctag) \
>  	XDP_METADATA_KFUNC(XDP_METADATA_KFUNC_RX_STAG, \
>  			   bpf_xdp_metadata_rx_stag) \
> +	XDP_METADATA_KFUNC(XDP_METADATA_KFUNC_RX_CSUM_LVL, \
> +			   bpf_xdp_metadata_rx_csum_lvl) \
>  
>  enum {
>  #define XDP_METADATA_KFUNC(name, _) name,
> diff --git a/kernel/bpf/offload.c b/kernel/bpf/offload.c
> index 2c6b6e82cfac..8bd54fb4ac63 100644
> --- a/kernel/bpf/offload.c
> +++ b/kernel/bpf/offload.c
> @@ -852,6 +852,8 @@ void *bpf_dev_bound_resolve_kfunc(struct bpf_prog *prog, u32 func_id)
>  		p = ops->xmo_rx_ctag;
>  	else if (func_id == bpf_xdp_metadata_kfunc_id(XDP_METADATA_KFUNC_RX_STAG))
>  		p = ops->xmo_rx_stag;
> +	else if (func_id == bpf_xdp_metadata_kfunc_id(XDP_METADATA_KFUNC_RX_CSUM_LVL))
> +		p = ops->xmo_rx_csum_lvl;
>  out:
>  	up_read(&bpf_devs_lock);
>  
> diff --git a/net/core/xdp.c b/net/core/xdp.c
> index eff21501609f..7dd45fd62983 100644
> --- a/net/core/xdp.c
> +++ b/net/core/xdp.c
> @@ -762,6 +762,18 @@ __bpf_kfunc int bpf_xdp_metadata_rx_stag(const struct xdp_md *ctx, u16 *vlan_tag
>  	return -EOPNOTSUPP;
>  }
>  
> +/**
> + * bpf_xdp_metadata_rx_csum_lvl - Get depth at which HW has checked the checksum.
> + * @ctx: XDP context pointer.
> + * @csum_level: Return value pointer.

Let's maybe clarify what the level means here? For example, do we start
counting from 0 or 1?

> + *
> + * Returns 0 on success (HW has checked the checksum) or ``-errno`` on error.
> + */
> +__bpf_kfunc int bpf_xdp_metadata_rx_csum_lvl(const struct xdp_md *ctx, u8 *csum_level)
> +{
> +	return -EOPNOTSUPP;
> +}
> +
>  __diag_pop();
>  
>  BTF_SET8_START(xdp_metadata_kfunc_ids)
> -- 
> 2.35.3
>