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Date: Wed, 19 Jul 2023 17:42:04 -0400
From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
To: Larysa Zaremba <larysa.zaremba@...el.com>,
bpf@...r.kernel.org
Cc: Larysa Zaremba <larysa.zaremba@...el.com>,
ast@...nel.org,
daniel@...earbox.net,
andrii@...nel.org,
martin.lau@...ux.dev,
song@...nel.org,
yhs@...com,
john.fastabend@...il.com,
kpsingh@...nel.org,
sdf@...gle.com,
haoluo@...gle.com,
jolsa@...nel.org,
David Ahern <dsahern@...il.com>,
Jakub Kicinski <kuba@...nel.org>,
Willem de Bruijn <willemb@...gle.com>,
Jesper Dangaard Brouer <brouer@...hat.com>,
Anatoly Burakov <anatoly.burakov@...el.com>,
Alexander Lobakin <alexandr.lobakin@...el.com>,
Magnus Karlsson <magnus.karlsson@...il.com>,
Maryam Tahhan <mtahhan@...hat.com>,
xdp-hints@...-project.net,
netdev@...r.kernel.org
Subject: RE: [PATCH bpf-next v3 12/21] xdp: Add checksum hint
Larysa Zaremba wrote:
> Implement functionality that enables drivers to expose to XDP code checksum
> information that consists of:
>
> - Checksum status - bitfield that consists of
> - number of consecutive validated checksums. This is almost the same as
> csum_level in skb, but starts with 1. Enum names for those bits still
> use checksum level concept, so it is less confusing for driver
> developers.
> - Is checksum partial? This bit cannot coexist with any other
> - Is there a complete checksum available?
> - Additional checksum data, a union of:
> - checksum start and offset, if checksum is partial
> - complete checksum, if available
>
> Signed-off-by: Larysa Zaremba <larysa.zaremba@...el.com>
> ---
> Documentation/networking/xdp-rx-metadata.rst | 3 ++
> include/linux/netdevice.h | 3 ++
> include/net/xdp.h | 46 ++++++++++++++++++++
> kernel/bpf/offload.c | 2 +
> net/core/xdp.c | 23 ++++++++++
> 5 files changed, 77 insertions(+)
>
> diff --git a/Documentation/networking/xdp-rx-metadata.rst b/Documentation/networking/xdp-rx-metadata.rst
> index ea6dd79a21d3..7f056a44f682 100644
> --- a/Documentation/networking/xdp-rx-metadata.rst
> +++ b/Documentation/networking/xdp-rx-metadata.rst
> @@ -26,6 +26,9 @@ metadata is supported, this set will grow:
> .. kernel-doc:: net/core/xdp.c
> :identifiers: bpf_xdp_metadata_rx_vlan_tag
>
> +.. kernel-doc:: net/core/xdp.c
> + :identifiers: bpf_xdp_metadata_rx_csum
> +
> 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 1749f4f75c64..4f6da36ac123 100644
> --- a/include/linux/netdevice.h
> +++ b/include/linux/netdevice.h
> @@ -1660,6 +1660,9 @@ struct xdp_metadata_ops {
> enum xdp_rss_hash_type *rss_type);
> int (*xmo_rx_vlan_tag)(const struct xdp_md *ctx, u16 *vlan_tci,
> __be16 *vlan_proto);
> + int (*xmo_rx_csum)(const struct xdp_md *ctx,
> + enum xdp_csum_status *csum_status,
> + union xdp_csum_info *csum_info);
> };
>
> /**
> diff --git a/include/net/xdp.h b/include/net/xdp.h
> index 89c58f56ffc6..2b7a7d678ff4 100644
> --- a/include/net/xdp.h
> +++ b/include/net/xdp.h
> @@ -391,6 +391,8 @@ void xdp_attachment_setup(struct xdp_attachment_info *info,
> bpf_xdp_metadata_rx_hash) \
> XDP_METADATA_KFUNC(XDP_METADATA_KFUNC_RX_VLAN_TAG, \
> bpf_xdp_metadata_rx_vlan_tag) \
> + XDP_METADATA_KFUNC(XDP_METADATA_KFUNC_RX_CSUM, \
> + bpf_xdp_metadata_rx_csum) \
>
> enum {
> #define XDP_METADATA_KFUNC(name, _) name,
> @@ -448,6 +450,50 @@ enum xdp_rss_hash_type {
> XDP_RSS_TYPE_L4_IPV6_SCTP_EX = XDP_RSS_TYPE_L4_IPV6_SCTP | XDP_RSS_L3_DYNHDR,
> };
>
> +union xdp_csum_info {
> + /* Checksum referred to by ``csum_start + csum_offset`` is considered
> + * valid, but was never calculated, TX device has to do this,
> + * starting from csum_start packet byte.
> + * Any preceding checksums are also considered valid.
> + * Available, if ``status == XDP_CHECKSUM_PARTIAL``.
> + */
> + struct {
> + u16 csum_start;
> + u16 csum_offset;
> + };
> +
> + /* Checksum, calculated over the whole packet.
> + * Available, if ``status & XDP_CHECKSUM_COMPLETE``.
> + */
> + u32 checksum;
> +};
> +
> +enum xdp_csum_status {
> + /* HW had parsed several transport headers and validated their
> + * checksums, same as ``CHECKSUM_UNNECESSARY`` in ``sk_buff``.
> + * 3 least significat bytes contain number of consecutive checksum,
typo: significant
(I did not scan for typos, just came across this when trying to understand
the skb->csum_level + 1 trick. Probably good to run a spell check).
> + * starting with the outermost, reported by hardware as valid.
> + * ``sk_buff`` checksum level (``csum_level``) notation is provided
> + * for driver developers.
> + */
> + XDP_CHECKSUM_VALID_LVL0 = 1, /* 1 outermost checksum */
> + XDP_CHECKSUM_VALID_LVL1 = 2, /* 2 outermost checksums */
> + XDP_CHECKSUM_VALID_LVL2 = 3, /* 3 outermost checksums */
> + XDP_CHECKSUM_VALID_LVL3 = 4, /* 4 outermost checksums */
> + XDP_CHECKSUM_VALID_NUM_MASK = GENMASK(2, 0),
> + XDP_CHECKSUM_VALID = XDP_CHECKSUM_VALID_NUM_MASK,
> +
> + /* Occurs if packet is sent virtually (between Linux VMs / containers)
> + * This status cannot coexist with any other.
> + * Refer to ``csum_start`` and ``csum_offset`` in ``xdp_csum_info``
> + * for more information.
> + */
> + XDP_CHECKSUM_PARTIAL = BIT(3),
> +
> + /* Checksum, calculated over the entire packet is provided */
> + XDP_CHECKSUM_COMPLETE = BIT(4),
> +};
> +
> #ifdef CONFIG_NET
> u32 bpf_xdp_metadata_kfunc_id(int id);
> bool bpf_dev_bound_kfunc_id(u32 btf_id);
> diff --git a/kernel/bpf/offload.c b/kernel/bpf/offload.c
> index 986e7becfd42..f60a6add5273 100644
> --- a/kernel/bpf/offload.c
> +++ b/kernel/bpf/offload.c
> @@ -850,6 +850,8 @@ void *bpf_dev_bound_resolve_kfunc(struct bpf_prog *prog, u32 func_id)
> p = ops->xmo_rx_hash;
> else if (func_id == bpf_xdp_metadata_kfunc_id(XDP_METADATA_KFUNC_RX_VLAN_TAG))
> p = ops->xmo_rx_vlan_tag;
> + else if (func_id == bpf_xdp_metadata_kfunc_id(XDP_METADATA_KFUNC_RX_CSUM))
> + p = ops->xmo_rx_csum;
> out:
> up_read(&bpf_devs_lock);
>
> diff --git a/net/core/xdp.c b/net/core/xdp.c
> index 8b55419d332e..d4ea54046afc 100644
> --- a/net/core/xdp.c
> +++ b/net/core/xdp.c
> @@ -772,6 +772,29 @@ __bpf_kfunc int bpf_xdp_metadata_rx_vlan_tag(const struct xdp_md *ctx,
> return -EOPNOTSUPP;
> }
>
> +/**
> + * bpf_xdp_metadata_rx_csum - Get checksum status with additional info.
> + * @ctx: XDP context pointer.
> + * @csum_status: Destination for checksum status.
> + * @csum_info: Destination for complete checksum or partial checksum offset.
> + *
> + * Status (@csum_status) is a bitfield that informs, what checksum
> + * processing was performed. Additional results of such processing,
> + * such as complete checksum or partial checksum offsets,
> + * are passed as info (@csum_info).
> + *
> + * Return:
> + * * Returns 0 on success or ``-errno`` on error.
> + * * ``-EOPNOTSUPP`` : device driver doesn't implement kfunc
> + * * ``-ENODATA`` : Checksum status is unknown
> + */
> +__bpf_kfunc int bpf_xdp_metadata_rx_csum(const struct xdp_md *ctx,
> + enum xdp_csum_status *csum_status,
> + union xdp_csum_info *csum_info)
> +{
> + return -EOPNOTSUPP;
> +}
> +
> __diag_pop();
>
> BTF_SET8_START(xdp_metadata_kfunc_ids)
> --
> 2.41.0
>
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