netdev - [PATCH RFC bpf-next 2/6] net: xdp: Add xmo_rx

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Message-Id: <20250920-xdp-meta-rxcksum-v1-2-35e76a8a84e7@kernel.org>
Date: Sat, 20 Sep 2025 14:20:28 +0200
From: Lorenzo Bianconi <lorenzo@...nel.org>
To: Donald Hunter <donald.hunter@...il.com>, 
 Jakub Kicinski <kuba@...nel.org>, "David S. Miller" <davem@...emloft.net>, 
 Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>, 
 Simon Horman <horms@...nel.org>, Alexei Starovoitov <ast@...nel.org>, 
 Daniel Borkmann <daniel@...earbox.net>, 
 Jesper Dangaard Brouer <hawk@...nel.org>, 
 John Fastabend <john.fastabend@...il.com>, 
 Stanislav Fomichev <sdf@...ichev.me>, Andrew Lunn <andrew+netdev@...n.ch>, 
 Tony Nguyen <anthony.l.nguyen@...el.com>, 
 Przemek Kitszel <przemyslaw.kitszel@...el.com>, 
 Alexander Lobakin <aleksander.lobakin@...el.com>, 
 Andrii Nakryiko <andrii@...nel.org>, 
 Martin KaFai Lau <martin.lau@...ux.dev>, 
 Eduard Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>, 
 Yonghong Song <yonghong.song@...ux.dev>, KP Singh <kpsingh@...nel.org>, 
 Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>, 
 Shuah Khan <shuah@...nel.org>
Cc: netdev@...r.kernel.org, bpf@...r.kernel.org, 
 intel-wired-lan@...ts.osuosl.org, linux-kselftest@...r.kernel.org, 
 Lorenzo Bianconi <lorenzo@...nel.org>
Subject: [PATCH RFC bpf-next 2/6] net: xdp: Add xmo_rx_checksum callback

Introduce xmo_rx_checksum netdev callback in order allow the eBPF
program bounded to the device to retrieve the RX checksum result computed
by the hw NIC.

Signed-off-by: Lorenzo Bianconi <lorenzo@...nel.org>
---
 include/net/xdp.h |  6 ++++++
 net/core/xdp.c    | 29 +++++++++++++++++++++++++++++
 2 files changed, 35 insertions(+)

diff --git a/include/net/xdp.h b/include/net/xdp.h
index 6fd294fa6841d59c3d7dc4475e09e731996566b0..481b39976ac8c8d4db2de39055c72ba8d0d511c3 100644
--- a/include/net/xdp.h
+++ b/include/net/xdp.h
@@ -581,6 +581,10 @@ 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,
@@ -644,6 +648,8 @@ struct xdp_metadata_ops {
 			       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, u8 *ip_summed,
+				   u32 *cksum_meta);
 };

 #ifdef CONFIG_NET
diff --git a/net/core/xdp.c b/net/core/xdp.c
index 9100e160113a9a1e2cb88e7602e85c5f36a9f3b9..3edab2d5e5c7c2013b1ef98c949a83655eb94349 100644
--- a/net/core/xdp.c
+++ b/net/core/xdp.c
@@ -961,6 +961,35 @@ __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 indicating checksum result.
+ * @cksum_meta: Return value pointer indicating checksum result metadata.
+ *
+ * In case of success, ``ip_summed`` is set to the RX checksum result. Possible
+ * values are:
+ * ``CHECKSUM_NONE``
+ * ``CHECKSUM_UNNECESSARY``
+ * ``CHECKSUM_COMPLETE``
+ * ``CHECKSUM_PARTIAL``
+ *
+ * In case of success, ``cksum_meta`` contains the hw computed checksum value
+ * for ``CHECKSUM_COMPLETE`` or the ``csum_level`` for
+ * ``CHECKSUM_UNNECESSARY``. It is set to 0 for ``CHECKSUM_NONE`` and
+ * ``CHECKSUM_PARTIAL``.
+ *
+ * Return:
+ * * Returns 0 on success or ``-errno`` on error.
+ * * ``-EOPNOTSUPP`` : means device driver does not implement kfunc
+ * * ``-ENODATA``    : means no RX-timestamp available for this frame
+ */
+__bpf_kfunc int bpf_xdp_metadata_rx_checksum(const struct xdp_md *ctx,
+					     u8 *ip_summed, u32 *cksum_meta)
+{
+	return -EOPNOTSUPP;
+}
+
 __bpf_kfunc_end_defs();

 BTF_KFUNCS_START(xdp_metadata_kfunc_ids)

-- 
2.51.0