[xdp-hints] [RFC bpf-next v3 07/14] bpf: Introduce tx checksum devtx kfuncs

[Stanislav Fomichev <sdf@google.com>]

Add new kfunc that will be used for tx checksum offloading.
The API mirrors existing one from sk_buff:
- csum_start - checksum the packet starting from this position
- csum_offset - put checksum at this offset

Signed-off-by: Stanislav Fomichev <sdf@google.com>
---
 include/linux/netdevice.h |  2 ++
 include/net/offload.h     |  5 ++++-
 net/core/devtx.c          | 17 +++++++++++++++++
 3 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 5be6649ea3fa..aeb1fa024d65 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1662,6 +1662,8 @@ struct xdp_metadata_ops {
 			       enum xdp_rss_hash_type *rss_type);
 	int	(*xmo_request_tx_timestamp)(const struct devtx_ctx *ctx);
 	int	(*xmo_tx_timestamp)(const struct devtx_ctx *ctx, u64 *timestamp);
+	int	(*xmo_request_l4_checksum)(const struct devtx_ctx *ctx,
+					   u16 csum_start, u16 csum_offset);
 };
 
 /**
diff --git a/include/net/offload.h b/include/net/offload.h
index 7e2c19c5aaef..d8f908af9e59 100644
--- a/include/net/offload.h
+++ b/include/net/offload.h
@@ -15,7 +15,10 @@
 #define DEVTX_SUBMIT_KFUNC_xxx	\
 	NETDEV_METADATA_KFUNC(DEVTX_KFUNC_REQUEST_TX_TIMESTAMP, \
 			      bpf_devtx_request_tx_timestamp, \
-			      xmo_request_tx_timestamp)
+			      xmo_request_tx_timestamp) \
+	NETDEV_METADATA_KFUNC(DEVTX_KFUNC_REQUEST_L4_CHECKSUM, \
+			      bpf_devtx_request_l4_csum, \
+			      xmo_request_l4_checksum)
 
 #define DEVTX_COMPLETE_KFUNC_xxx	\
 	NETDEV_METADATA_KFUNC(DEVTX_KFUNC_TX_TIMESTAMP, \
diff --git a/net/core/devtx.c b/net/core/devtx.c
index 991a52fe81a3..fd8a9ea125db 100644
--- a/net/core/devtx.c
+++ b/net/core/devtx.c
@@ -106,6 +106,23 @@ __bpf_kfunc int bpf_devtx_tx_timestamp(const struct devtx_ctx *ctx, __u64 *times
 	return -EOPNOTSUPP;
 }
 
+/**
+ * bpf_devtx_request_l4_csum - Request TX checksum offload on the packet.
+ * Callable only from the devtx-submit hook.
+ * @ctx: devtx context pointer.
+ * @csum_start: start checksumming from given position
+ * @csum_offset: add resulting checksum at given offset
+ *
+ * Note, this checksum offload doesn't calculate pseudo-header part.
+ *
+ * Returns 0 on success or ``-errno`` on error.
+ */
+__bpf_kfunc int bpf_devtx_request_l4_csum(const struct devtx_ctx *ctx,
+					  u16 csum_start, u16 csum_offset)
+{
+	return -EOPNOTSUPP;
+}
+
 __diag_pop();
 
 BTF_SET8_START(devtx_sb_kfunc_ids)
-- 
2.41.0.255.g8b1d071c50-goog