[RFC bpf-next v2 05/11] bpf: Implement devtx timestamp kfunc

[Stanislav Fomichev <sdf@google.com>]

Two kfuncs, one per hook point:

1. at submit time - bpf_devtx_sb_request_timestamp - to request HW
   to put TX timestamp into TX completion descriptors

2. at completion time - bpf_devtx_cp_timestamp - to read out
   TX timestamp

Cc: netdev@vger.kernel.org
Signed-off-by: Stanislav Fomichev <sdf@google.com>
---
 include/linux/netdevice.h |  4 +++
 include/net/offload.h     | 10 ++++++
 kernel/bpf/offload.c      |  8 +++++
 net/core/devtx.c          | 73 +++++++++++++++++++++++++++++++++++++++
 4 files changed, 95 insertions(+)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 08fbd4622ccf..2fdb0731eb67 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1651,10 +1651,14 @@ struct net_device_ops {
 						  bool cycles);
 };
 
+struct devtx_frame;
+
 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_sb_request_timestamp)(const struct devtx_frame *ctx);
+	int	(*xmo_cp_timestamp)(const struct devtx_frame *ctx, u64 *timestamp);
 };
 
 /**
diff --git a/include/net/offload.h b/include/net/offload.h
index 264a35881473..36899b64f4c8 100644
--- a/include/net/offload.h
+++ b/include/net/offload.h
@@ -10,9 +10,19 @@
 	NETDEV_METADATA_KFUNC(XDP_METADATA_KFUNC_RX_HASH, \
 			      bpf_xdp_metadata_rx_hash)
 
+#define DEVTX_SB_KFUNC_xxx	\
+	NETDEV_METADATA_KFUNC(DEVTX_SB_KFUNC_REQUEST_TIMESTAMP, \
+			      bpf_devtx_sb_request_timestamp)
+
+#define DEVTX_CP_KFUNC_xxx	\
+	NETDEV_METADATA_KFUNC(DEVTX_CP_KFUNC_TIMESTAMP, \
+			      bpf_devtx_cp_timestamp)
+
 enum {
 #define NETDEV_METADATA_KFUNC(name, _) name,
 XDP_METADATA_KFUNC_xxx
+DEVTX_SB_KFUNC_xxx
+DEVTX_CP_KFUNC_xxx
 #undef NETDEV_METADATA_KFUNC
 MAX_NETDEV_METADATA_KFUNC,
 };
diff --git a/kernel/bpf/offload.c b/kernel/bpf/offload.c
index f01a1aa0f627..45a243af49be 100644
--- a/kernel/bpf/offload.c
+++ b/kernel/bpf/offload.c
@@ -863,6 +863,10 @@ void *bpf_dev_bound_resolve_kfunc(struct bpf_prog *prog, u32 func_id)
 		p = ops->xmo_rx_timestamp;
 	else if (func_id == bpf_dev_bound_kfunc_id(XDP_METADATA_KFUNC_RX_HASH))
 		p = ops->xmo_rx_hash;
+	else if (func_id == bpf_dev_bound_kfunc_id(DEVTX_SB_KFUNC_REQUEST_TIMESTAMP))
+		p = ops->xmo_sb_request_timestamp;
+	else if (func_id == bpf_dev_bound_kfunc_id(DEVTX_CP_KFUNC_TIMESTAMP))
+		p = ops->xmo_cp_timestamp;
 out:
 	up_read(&bpf_devs_lock);
 
@@ -872,12 +876,16 @@ void *bpf_dev_bound_resolve_kfunc(struct bpf_prog *prog, u32 func_id)
 BTF_SET_START(dev_bound_kfunc_ids)
 #define NETDEV_METADATA_KFUNC(name, str) BTF_ID(func, str)
 XDP_METADATA_KFUNC_xxx
+DEVTX_SB_KFUNC_xxx
+DEVTX_CP_KFUNC_xxx
 #undef NETDEV_METADATA_KFUNC
 BTF_SET_END(dev_bound_kfunc_ids)
 
 BTF_ID_LIST(dev_bound_kfunc_ids_unsorted)
 #define NETDEV_METADATA_KFUNC(name, str) BTF_ID(func, str)
 XDP_METADATA_KFUNC_xxx
+DEVTX_SB_KFUNC_xxx
+DEVTX_CP_KFUNC_xxx
 #undef NETDEV_METADATA_KFUNC
 
 u32 bpf_dev_bound_kfunc_id(int id)
diff --git a/net/core/devtx.c b/net/core/devtx.c
index bad694439ae3..4267a8fe6711 100644
--- a/net/core/devtx.c
+++ b/net/core/devtx.c
@@ -74,3 +74,76 @@ void devtx_hooks_unregister(struct btf_id_set8 *set)
 	}
 	mutex_unlock(&devtx_hooks_lock);
 }
+
+__diag_push();
+__diag_ignore_all("-Wmissing-prototypes",
+		  "Global functions as their definitions will be in vmlinux BTF");
+
+/**
+ * bpf_devtx_sb_request_timestamp - Request TX timestamp on the packet.
+ * Callable only from the devtx-submit hook.
+ * @ctx: devtx context pointer.
+ *
+ * Returns 0 on success or ``-errno`` on error.
+ */
+__bpf_kfunc int bpf_devtx_sb_request_timestamp(const struct devtx_frame *ctx)
+{
+	return -EOPNOTSUPP;
+}
+
+/**
+ * bpf_devtx_cp_timestamp - Read TX timestamp of the packet. Callable
+ * only from the devtx-complete hook.
+ * @ctx: devtx context pointer.
+ * @timestamp: Return value pointer.
+ *
+ * Returns 0 on success or ``-errno`` on error.
+ */
+__bpf_kfunc int bpf_devtx_cp_timestamp(const struct devtx_frame *ctx, __u64 *timestamp)
+{
+	return -EOPNOTSUPP;
+}
+
+__diag_pop();
+
+BTF_SET8_START(devtx_sb_kfunc_ids)
+#define NETDEV_METADATA_KFUNC(_, name) BTF_ID_FLAGS(func, name, 0)
+DEVTX_SB_KFUNC_xxx
+#undef NETDEV_METADATA_KFUNC
+BTF_SET8_END(devtx_sb_kfunc_ids)
+
+static const struct btf_kfunc_id_set devtx_sb_kfunc_set = {
+	.owner = THIS_MODULE,
+	.set   = &devtx_sb_kfunc_ids,
+};
+
+BTF_SET8_START(devtx_cp_kfunc_ids)
+#define NETDEV_METADATA_KFUNC(_, name) BTF_ID_FLAGS(func, name, 0)
+DEVTX_CP_KFUNC_xxx
+#undef NETDEV_METADATA_KFUNC
+BTF_SET8_END(devtx_cp_kfunc_ids)
+
+static const struct btf_kfunc_id_set devtx_cp_kfunc_set = {
+	.owner = THIS_MODULE,
+	.set   = &devtx_cp_kfunc_ids,
+};
+
+static int __init devtx_init(void)
+{
+	int ret;
+
+	ret = register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, &devtx_sb_kfunc_set);
+	if (ret) {
+		pr_warn("failed to register devtx_sb kfuncs: %d", ret);
+		return ret;
+	}
+
+	ret = register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, &devtx_cp_kfunc_set);
+	if (ret) {
+		pr_warn("failed to register devtx_cp completion kfuncs: %d", ret);
+		return ret;
+	}
+
+	return 0;
+}
+late_initcall(devtx_init);
-- 
2.41.0.162.gfafddb0af9-goog