[PATCH bpf-next v2 0/2] Add BPF-helper for accessing CLOCK_TAI

[PATCH bpf-next v2 0/2] Add BPF-helper for accessing CLOCK_TAI

[Kurt Kanzenbach]

Hi,

add a BPF-helper for accessing CLOCK_TAI. Use cases for such a BPF helper
include functionalities such as Tx launch time (e.g. ETF and TAPRIO Qdiscs),
timestamping and policing.

Patch #1 - Introduce BPF helper
Patch #2 - Add test case (skb based)

Changes since v1:

 * Update changelog (Alexei Starovoitov)
 * Add test case (Alexei Starovoitov, Andrii Nakryiko)
 * Add missing function prototype (netdev ci)

Previous versions:

 * v1: https://lore.kernel.org/r/20220606103734.92423-1-kurt@linutronix.de/

Jesper Dangaard Brouer (1):
  bpf: Add BPF-helper for accessing CLOCK_TAI

Kurt Kanzenbach (1):
  selftests/bpf: Add BPF-helper test for CLOCK_TAI access

 include/linux/bpf.h                           |  1 +
 include/uapi/linux/bpf.h                      | 13 ++++
 kernel/bpf/core.c                             |  1 +
 kernel/bpf/helpers.c                          | 14 ++++
 tools/include/uapi/linux/bpf.h                | 13 ++++
 .../selftests/bpf/prog_tests/time_tai.c       | 74 +++++++++++++++++++
 .../selftests/bpf/progs/test_time_tai.c       | 24 ++++++
 7 files changed, 140 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/time_tai.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_time_tai.c

-- 
2.30.2

[PATCH bpf-next v2 1/2] bpf: Add BPF-helper for accessing CLOCK_TAI

[Kurt Kanzenbach]

From: Jesper Dangaard Brouer <brouer@redhat.com>

Commit 3dc6ffae2da2 ("timekeeping: Introduce fast accessor to clock tai")
introduced a fast and NMI-safe accessor for CLOCK_TAI. Especially in time
sensitive networks (TSN), where all nodes are synchronized by Precision Time
Protocol (PTP), it's helpful to have the possibility to generate timestamps
based on CLOCK_TAI instead of CLOCK_MONOTONIC. With a BPF helper for TAI in
place, it becomes very convenient to correlate activity across different
machines in the network.

Use cases for such a BPF helper include functionalities such as Tx launch
time (e.g. ETF and TAPRIO Qdiscs) and timestamping.

Note: CLOCK_TAI is nothing new per se, only the NMI-safe variant of it is.

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
[Kurt: Wrote changelog and renamed helper]
Signed-off-by: Kurt Kanzenbach <kurt@linutronix.de>
---
 include/linux/bpf.h            |  1 +
 include/uapi/linux/bpf.h       | 13 +++++++++++++
 kernel/bpf/core.c              |  1 +
 kernel/bpf/helpers.c           | 14 ++++++++++++++
 tools/include/uapi/linux/bpf.h | 13 +++++++++++++
 5 files changed, 42 insertions(+)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 20c26aed7896..a627a02cf8ab 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -2349,6 +2349,7 @@ extern const struct bpf_func_proto bpf_get_numa_node_id_proto;
 extern const struct bpf_func_proto bpf_tail_call_proto;
 extern const struct bpf_func_proto bpf_ktime_get_ns_proto;
 extern const struct bpf_func_proto bpf_ktime_get_boot_ns_proto;
+extern const struct bpf_func_proto bpf_ktime_get_tai_ns_proto;
 extern const struct bpf_func_proto bpf_get_current_pid_tgid_proto;
 extern const struct bpf_func_proto bpf_get_current_uid_gid_proto;
 extern const struct bpf_func_proto bpf_get_current_comm_proto;
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 534e33fb1029..7d1e2794d83e 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -5341,6 +5341,18 @@ union bpf_attr {
  *		**-EACCES** if the SYN cookie is not valid.
  *
  *		**-EPROTONOSUPPORT** if CONFIG_IPV6 is not builtin.
+ *
+ * u64 bpf_ktime_get_tai_ns(void)
+ *	Description
+ *		A nonsettable system-wide clock derived from wall-clock time but
+ *		ignoring leap seconds.  This clock does not experience
+ *		discontinuities and backwards jumps caused by NTP inserting leap
+ *		seconds as CLOCK_REALTIME does.
+ *
+ *		See: **clock_gettime**\ (**CLOCK_TAI**)
+ *	Return
+ *		Current *ktime*.
+ *
  */
 #define __BPF_FUNC_MAPPER(FN)		\
 	FN(unspec),			\
@@ -5551,6 +5563,7 @@ union bpf_attr {
 	FN(tcp_raw_gen_syncookie_ipv6),	\
 	FN(tcp_raw_check_syncookie_ipv4),	\
 	FN(tcp_raw_check_syncookie_ipv6),	\
+	FN(ktime_get_tai_ns),		\
 	/* */
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index c1e10d088dbb..639437f36928 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -2623,6 +2623,7 @@ const struct bpf_func_proto bpf_get_numa_node_id_proto __weak;
 const struct bpf_func_proto bpf_ktime_get_ns_proto __weak;
 const struct bpf_func_proto bpf_ktime_get_boot_ns_proto __weak;
 const struct bpf_func_proto bpf_ktime_get_coarse_ns_proto __weak;
+const struct bpf_func_proto bpf_ktime_get_tai_ns_proto __weak;
 
 const struct bpf_func_proto bpf_get_current_pid_tgid_proto __weak;
 const struct bpf_func_proto bpf_get_current_uid_gid_proto __weak;
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 1f961f9982d2..a95eb9fb01ff 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -198,6 +198,18 @@ const struct bpf_func_proto bpf_ktime_get_coarse_ns_proto = {
 	.ret_type	= RET_INTEGER,
 };
 
+BPF_CALL_0(bpf_ktime_get_tai_ns)
+{
+	/* NMI safe access to clock tai */
+	return ktime_get_tai_fast_ns();
+}
+
+const struct bpf_func_proto bpf_ktime_get_tai_ns_proto = {
+	.func		= bpf_ktime_get_tai_ns,
+	.gpl_only	= false,
+	.ret_type	= RET_INTEGER,
+};
+
 BPF_CALL_0(bpf_get_current_pid_tgid)
 {
 	struct task_struct *task = current;
@@ -1617,6 +1629,8 @@ bpf_base_func_proto(enum bpf_func_id func_id)
 		return &bpf_ktime_get_ns_proto;
 	case BPF_FUNC_ktime_get_boot_ns:
 		return &bpf_ktime_get_boot_ns_proto;
+	case BPF_FUNC_ktime_get_tai_ns:
+		return &bpf_ktime_get_tai_ns_proto;
 	case BPF_FUNC_ringbuf_output:
 		return &bpf_ringbuf_output_proto;
 	case BPF_FUNC_ringbuf_reserve:
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index f58d58e1d547..e174ad28aeb7 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -5341,6 +5341,18 @@ union bpf_attr {
  *		**-EACCES** if the SYN cookie is not valid.
  *
  *		**-EPROTONOSUPPORT** if CONFIG_IPV6 is not builtin.
+ *
+ * u64 bpf_ktime_get_tai_ns(void)
+ *	Description
+ *		A nonsettable system-wide clock derived from wall-clock time but
+ *		ignoring leap seconds.  This clock does not experience
+ *		discontinuities and backwards jumps caused by NTP inserting leap
+ *		seconds as CLOCK_REALTIME does.
+ *
+ *		See: **clock_gettime**\ (**CLOCK_TAI**)
+ *	Return
+ *		Current *ktime*.
+ *
  */
 #define __BPF_FUNC_MAPPER(FN)		\
 	FN(unspec),			\
@@ -5551,6 +5563,7 @@ union bpf_attr {
 	FN(tcp_raw_gen_syncookie_ipv6),	\
 	FN(tcp_raw_check_syncookie_ipv4),	\
 	FN(tcp_raw_check_syncookie_ipv6),	\
+	FN(ktime_get_tai_ns),		\
 	/* */
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper
-- 
2.30.2

[PATCH bpf-next v2 2/2] selftests/bpf: Add BPF-helper test for CLOCK_TAI access

[Kurt Kanzenbach]

Add BPF-helper test case for CLOCK_TAI access. The added test verifies that:

 * Timestamps are generated
 * Timestamps are moving forward
 * Timestamps are reasonable

Signed-off-by: Kurt Kanzenbach <kurt@linutronix.de>
---
 .../selftests/bpf/prog_tests/time_tai.c       | 74 +++++++++++++++++++
 .../selftests/bpf/progs/test_time_tai.c       | 24 ++++++
 2 files changed, 98 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/time_tai.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_time_tai.c

diff --git a/tools/testing/selftests/bpf/prog_tests/time_tai.c b/tools/testing/selftests/bpf/prog_tests/time_tai.c
new file mode 100644
index 000000000000..a31119823666
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/time_tai.c
@@ -0,0 +1,74 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (C) 2022 Linutronix GmbH */
+
+#include <test_progs.h>
+#include <network_helpers.h>
+
+#include "test_time_tai.skel.h"
+
+#include <time.h>
+#include <stdint.h>
+
+#define TAI_THRESHOLD	1000000000ULL /* 1s */
+#define NSEC_PER_SEC	1000000000ULL
+
+static __u64 ts_to_ns(const struct timespec *ts)
+{
+	return ts->tv_sec * NSEC_PER_SEC + ts->tv_nsec;
+}
+
+void test_time_tai(void)
+{
+	struct __sk_buff skb = {
+		.cb[0] = 0,
+		.cb[1] = 0,
+		.tstamp = 0,
+	};
+	LIBBPF_OPTS(bpf_test_run_opts, topts,
+		.data_in = &pkt_v4,
+		.data_size_in = sizeof(pkt_v4),
+		.ctx_in = &skb,
+		.ctx_size_in = sizeof(skb),
+		.ctx_out = &skb,
+		.ctx_size_out = sizeof(skb),
+	);
+	struct test_time_tai *skel;
+	struct timespec now_tai;
+	__u64 ts1, ts2, now;
+	int ret, prog_fd;
+
+	/* Open and load */
+	skel = test_time_tai__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "tai_open"))
+		return;
+
+	/* Run test program */
+	prog_fd = bpf_program__fd(skel->progs.time_tai);
+	ret = bpf_prog_test_run_opts(prog_fd, &topts);
+	ASSERT_OK(ret, "test_run");
+
+	/* Retrieve generated TAI timestamps */
+	ts1 = skb.tstamp;
+	ts2 = skb.cb[0] | ((__u64)skb.cb[1] << 32);
+
+	/* TAI != 0 */
+	ASSERT_NEQ(ts1, 0, "tai_ts1");
+	ASSERT_NEQ(ts2, 0, "tai_ts2");
+
+	/* TAI is moving forward only */
+	ASSERT_GT(ts2, ts1, "tai_forward");
+
+	/* Check for future */
+	ret = clock_gettime(CLOCK_TAI, &now_tai);
+	ASSERT_EQ(ret, 0, "tai_gettime");
+	now = ts_to_ns(&now_tai);
+
+	ASSERT_TRUE(now > ts1, "tai_future_ts1");
+	ASSERT_TRUE(now > ts2, "tai_future_ts2");
+
+	/* Check for reasonable range */
+	ASSERT_TRUE(now - ts1 < TAI_THRESHOLD, "tai_range_ts1");
+	ASSERT_TRUE(now - ts2 < TAI_THRESHOLD, "tai_range_ts2");
+
+	test_time_tai__destroy(skel);
+}
diff --git a/tools/testing/selftests/bpf/progs/test_time_tai.c b/tools/testing/selftests/bpf/progs/test_time_tai.c
new file mode 100644
index 000000000000..7ea0863f3ddb
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_time_tai.c
@@ -0,0 +1,24 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (C) 2022 Linutronix GmbH */
+
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+
+char _license[] SEC("license") = "GPL";
+
+SEC("tc")
+int time_tai(struct __sk_buff *skb)
+{
+	__u64 ts1, ts2;
+
+	/* Get TAI timestamps */
+	ts1 = bpf_ktime_get_tai_ns();
+	ts2 = bpf_ktime_get_tai_ns();
+
+	/* Save TAI timestamps (Note: skb->hwtstamp is read-only) */
+	skb->tstamp = ts1;
+	skb->cb[0] = ts2 & 0xffffffff;
+	skb->cb[1] = ts2 >> 32;
+
+	return 0;
+}
-- 
2.30.2

Re: [PATCH bpf-next v2 0/2] Add BPF-helper for accessing CLOCK_TAI

[patchwork-bot+netdevbpf]

Hello:

This series was applied to bpf/bpf-next.git (master)
by Alexei Starovoitov <ast@kernel.org>:

On Tue,  9 Aug 2022 08:08:01 +0200 you wrote:
> Hi,
> 
> add a BPF-helper for accessing CLOCK_TAI. Use cases for such a BPF helper
> include functionalities such as Tx launch time (e.g. ETF and TAPRIO Qdiscs),
> timestamping and policing.
> 
> Patch #1 - Introduce BPF helper
> Patch #2 - Add test case (skb based)
> 
> [...]

Here is the summary with links:
  - [bpf-next,v2,1/2] bpf: Add BPF-helper for accessing CLOCK_TAI
    https://git.kernel.org/bpf/bpf-next/c/c8996c98f703
  - [bpf-next,v2,2/2] selftests/bpf: Add BPF-helper test for CLOCK_TAI access
    https://git.kernel.org/bpf/bpf-next/c/64e15820b987

You are awesome, thank you!
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