bpf: Add BPF-helper for accessing CLOCK_TAI
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>
Link: https://lore.kernel.org/r/20220809060803.5773-2-kurt@linutronix.de
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index f58d58e..e174ad2 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -5341,6 +5341,18 @@
* **-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 @@
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
