> -----Original Message-----
> From: Vladimir Vdovin <[email protected]>
> Sent: Wednesday, July 8, 2026 10:34 PM
> To: Lorenzo Bianconi <[email protected]>; Donald Hunter
> <[email protected]>; Jakub Kicinski <[email protected]>; David S .
> Miller <[email protected]>; Eric Dumazet <[email protected]>;
> Paolo Abeni <[email protected]>; Simon Horman <[email protected]>;
> Alexei Starovoitov <[email protected]>; Daniel Borkmann
> <[email protected]>; Jesper Dangaard Brouer <[email protected]>; John
> Fastabend <[email protected]>; Stanislav Fomichev
> <[email protected]>; Andrew Lunn <[email protected]>; Nguyen,
> Anthony L <[email protected]>; Kitszel, Przemyslaw
> <[email protected]>; Lobakin, Aleksander
> <[email protected]>; Andrii Nakryiko <[email protected]>;
> Martin KaFai Lau <[email protected]>; Eduard Zingerman
> <[email protected]>; Song Liu <[email protected]>; Yonghong Song
> <[email protected]>; KP Singh <[email protected]>; Hao Luo
> <[email protected]>; Jiri Olsa <[email protected]>; Shuah Khan
> <[email protected]>; Fijalkowski, Maciej <[email protected]>
> Cc: Jakub Sitnicki <[email protected]>; Loktionov, Aleksandr
> <[email protected]>; [email protected];
> [email protected]; [email protected]; linux-
> [email protected]; Vladimir Vdovin <[email protected]>
> Subject: [PATCH bpf-next v4 1/6] netlink: specs: Add XDP RX checksum
> capability to XDP metadata specs
>
> From: Lorenzo Bianconi <[email protected]>
>
> Introduce XDP RX checksum capability to XDP metadata specs. XDP RX
> checksum will be use by devices capable of exposing receive checksum
> result via bpf_xdp_metadata_rx_checksum().
> Moreover, introduce xmo_rx_checksum netdev callback in order to allow
> the eBPF program bound to the device to retrieve the RX checksum
> result computed by the hw NIC and reported via DMA descriptors.
>
> Signed-off-by: Lorenzo Bianconi <[email protected]>
> Signed-off-by: Vladimir Vdovin <[email protected]>
> ---
> Documentation/netlink/specs/netdev.yaml | 5 ++++
> include/net/xdp.h | 18 ++++++++++++++
> include/uapi/linux/netdev.h | 3 +++
> net/core/xdp.c | 32
> +++++++++++++++++++++++++
> tools/include/uapi/linux/netdev.h | 3 +++
> 5 files changed, 61 insertions(+)
>
> diff --git a/Documentation/netlink/specs/netdev.yaml
> b/Documentation/netlink/specs/netdev.yaml
> index 5f143da7458c..6d0d90d3a614 100644
> --- a/Documentation/netlink/specs/netdev.yaml
> +++ b/Documentation/netlink/specs/netdev.yaml
> @@ -61,6 +61,11 @@ definitions:
> doc: |
> Device is capable of exposing receive packet VLAN tag via
> bpf_xdp_metadata_rx_vlan_tag().
> + -
> + name: checksum
> + doc: |
> + Device is capable of exposing receive checksum result via
> + bpf_xdp_metadata_rx_checksum().
> -
> type: flags
> name: xsk-flags
> diff --git a/include/net/xdp.h b/include/net/xdp.h index
> aa742f413c35..e255ff786131 100644
> --- a/include/net/xdp.h
> +++ b/include/net/xdp.h
> @@ -586,6 +586,10 @@ void xdp_attachment_setup(struct
> xdp_attachment_info *info,
> NETDEV_XDP_RX_METADATA_VLAN_TAG, \
> bpf_xdp_metadata_rx_vlan_tag, \
> xmo_rx_vlan_tag) \
> + XDP_METADATA_KFUNC(XDP_METADATA_KFUNC_RX_CHECKSUM, \
> + NETDEV_XDP_RX_METADATA_CHECKSUM, \
> + bpf_xdp_metadata_rx_checksum, \
> + xmo_rx_checksum)
>
> enum xdp_rx_metadata {
> #define XDP_METADATA_KFUNC(name, _, __, ___) name, @@ -643,12 +647,26
> @@ enum xdp_rss_hash_type {
> XDP_RSS_TYPE_L4_IPV6_SCTP_EX = XDP_RSS_TYPE_L4_IPV6_SCTP |
> XDP_RSS_L3_DYNHDR, };
>
> +/* Please note the driver is required to invalidate the checksum if
> the
> +NIC
> + * reports CHECKSUM_UNNECESSARY or CHECKSUM_COMPLETE and the eBPF
> +program
> + * modifies the packet since it can change some fields validated by
> the
> + * checksum.
> + */
> +enum xdp_checksum {
> + XDP_CHECKSUM_NONE = BIT(CHECKSUM_NONE),
> + XDP_CHECKSUM_UNNECESSARY = BIT(CHECKSUM_UNNECESSARY),
> + XDP_CHECKSUM_COMPLETE = BIT(CHECKSUM_COMPLETE),
> +};
> +
> struct xdp_metadata_ops {
> int (*xmo_rx_timestamp)(const struct xdp_md *ctx, u64
> *timestamp);
> int (*xmo_rx_hash)(const struct xdp_md *ctx, u32 *hash,
> enum xdp_rss_hash_type *rss_type);
> int (*xmo_rx_vlan_tag)(const struct xdp_md *ctx, __be16
> *vlan_proto,
> u16 *vlan_tci);
> + int (*xmo_rx_checksum)(const struct xdp_md *ctx,
> + enum xdp_checksum *ip_summed,
> + u32 *cksum, u8 *cksum_level);
> };
>
> #ifdef CONFIG_NET
> diff --git a/include/uapi/linux/netdev.h b/include/uapi/linux/netdev.h
> index 2f3ab75e8cc0..f8caade93c8c 100644
> --- a/include/uapi/linux/netdev.h
> +++ b/include/uapi/linux/netdev.h
> @@ -47,11 +47,14 @@ enum netdev_xdp_act {
> * hash via bpf_xdp_metadata_rx_hash().
> * @NETDEV_XDP_RX_METADATA_VLAN_TAG: Device is capable of exposing
> receive
> * packet VLAN tag via bpf_xdp_metadata_rx_vlan_tag().
> + * @NETDEV_XDP_RX_METADATA_CHECKSUM: Device is capable of exposing
> receive
> + * checksum result via bpf_xdp_metadata_rx_checksum().
> */
> enum netdev_xdp_rx_metadata {
> NETDEV_XDP_RX_METADATA_TIMESTAMP = 1,
> NETDEV_XDP_RX_METADATA_HASH = 2,
> NETDEV_XDP_RX_METADATA_VLAN_TAG = 4,
> + NETDEV_XDP_RX_METADATA_CHECKSUM = 8,
> };
>
> /**
> 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``.
> + *
> + * 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;
> +}
> +
> __bpf_kfunc_end_defs();
>
> BTF_KFUNCS_START(xdp_metadata_kfunc_ids)
> diff --git a/tools/include/uapi/linux/netdev.h
> b/tools/include/uapi/linux/netdev.h
> index 2f3ab75e8cc0..f8caade93c8c 100644
> --- a/tools/include/uapi/linux/netdev.h
> +++ b/tools/include/uapi/linux/netdev.h
> @@ -47,11 +47,14 @@ enum netdev_xdp_act {
> * hash via bpf_xdp_metadata_rx_hash().
> * @NETDEV_XDP_RX_METADATA_VLAN_TAG: Device is capable of exposing
> receive
> * packet VLAN tag via bpf_xdp_metadata_rx_vlan_tag().
> + * @NETDEV_XDP_RX_METADATA_CHECKSUM: Device is capable of exposing
> receive
> + * checksum result via bpf_xdp_metadata_rx_checksum().
> */
> enum netdev_xdp_rx_metadata {
> NETDEV_XDP_RX_METADATA_TIMESTAMP = 1,
> NETDEV_XDP_RX_METADATA_HASH = 2,
> NETDEV_XDP_RX_METADATA_VLAN_TAG = 4,
> + NETDEV_XDP_RX_METADATA_CHECKSUM = 8,
> };
>
> /**
> --
> 2.47.0
Reviewed-by: Aleksandr Loktionov <[email protected]>
