From: Tonghao Zhang <xiangxia.m.yue@xxxxxxxxx>
This patch introduce a new bpf_ktime_get_real_ns helper, which may
help us to measure the skb latency in the ingress/forwarding path:
HW/SW[1] -> ip_rcv/tcp_rcv_established -> tcp_recvmsg_locked/tcp_update_recv_tstamps
* Insert BPF kprobe into ip_rcv/tcp_rcv_established invoking this helper.
Then we can inspect how long time elapsed since HW/SW.
* If inserting BPF kprobe tcp_update_recv_tstamps invoked by tcp_recvmsg,
we can measure how much latency skb in tcp receive queue. The reason for
this can be application fetch the TCP messages too late.
[1]:
- HW drivers may set skb_hwtstamps(skb)->hwtstamp
- SW __netif_receive_skb_core set skb->tstamp with ktime_get_real()
Cc: Alexei Starovoitov <ast@xxxxxxxxxx>
Cc: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Cc: Andrii Nakryiko <andrii@xxxxxxxxxx>
Cc: Martin KaFai Lau <kafai@xxxxxx>
Cc: Song Liu <songliubraving@xxxxxx>
Cc: Yonghong Song <yhs@xxxxxx>
Cc: John Fastabend <john.fastabend@xxxxxxxxx>
Cc: KP Singh <kpsingh@xxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Dave Marchevsky <davemarchevsky@xxxxxx>
Cc: Kuniyuki Iwashima <kuniyu@xxxxxxxxxxxx>
Cc: Joanne Koong <joannekoong@xxxxxx>
Cc: Geliang Tang <geliang.tang@xxxxxxxx>
Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
Cc: Jakub Kicinski <kuba@xxxxxxxxxx>
Cc: Eric Dumazet <edumazet@xxxxxxxxxx>
Signed-off-by: Tonghao Zhang <xiangxia.m.yue@xxxxxxxxx>
---
include/uapi/linux/bpf.h | 13 +++++++++++++
kernel/bpf/core.c | 1 +
kernel/bpf/helpers.c | 14 ++++++++++++++
tools/include/uapi/linux/bpf.h | 13 +++++++++++++
4 files changed, 41 insertions(+)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index d14b10b85e51..2565c587fe1b 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -5143,6 +5143,18 @@ union bpf_attr {
* The **hash_algo** is returned on success,
* **-EOPNOTSUP** if the hash calculation failed or **-EINVAL** if
* invalid arguments are passed.
+ *
+ * u64 bpf_ktime_get_real_ns(void)
+ * Description
+ * Return a fine-grained version of the real (i.e., wall-clock) time,
+ * in nanoseconds. This clock is affected by discontinuous jumps in
+ * the system time (e.g., if the system administrator manually changes
+ * the clock), and by the incremental adjustments performed by adjtime(3)
+ * and NTP.
+ * See: **clock_gettime**\ (**CLOCK_REALTIME**)
+ * Return
+ * Current *ktime*.
+ *
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@@ -5339,6 +5351,7 @@ union bpf_attr {
FN(copy_from_user_task), \
FN(skb_set_tstamp), \
FN(ima_file_hash), \
+ FN(ktime_get_real_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 13e9dbeeedf3..acdf538b1dcd 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -2627,6 +2627,7 @@ const struct bpf_func_proto bpf_get_prandom_u32_proto __weak;
const struct bpf_func_proto bpf_get_smp_processor_id_proto __weak;
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_real_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;
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 315053ef6a75..d38548ed292f 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -159,6 +159,18 @@ const struct bpf_func_proto bpf_ktime_get_ns_proto = {
.ret_type = RET_INTEGER,
};
+BPF_CALL_0(bpf_ktime_get_real_ns)
+{
+ /* NMI safe access to clock realtime. */
+ return ktime_get_real_fast_ns();
+}
+
+const struct bpf_func_proto bpf_ktime_get_real_ns_proto = {
+ .func = bpf_ktime_get_real_ns,
+ .gpl_only = false,
+ .ret_type = RET_INTEGER,
+};
+
BPF_CALL_0(bpf_ktime_get_boot_ns)
{
/* NMI safe access to clock boottime */
@@ -1410,6 +1422,8 @@ 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_real_ns:
+ return &bpf_ktime_get_real_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 d14b10b85e51..2565c587fe1b 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -5143,6 +5143,18 @@ union bpf_attr {
* The **hash_algo** is returned on success,
* **-EOPNOTSUP** if the hash calculation failed or **-EINVAL** if
* invalid arguments are passed.
+ *
+ * u64 bpf_ktime_get_real_ns(void)
+ * Description
+ * Return a fine-grained version of the real (i.e., wall-clock) time,
+ * in nanoseconds. This clock is affected by discontinuous jumps in
+ * the system time (e.g., if the system administrator manually changes
+ * the clock), and by the incremental adjustments performed by adjtime(3)
+ * and NTP.
+ * See: **clock_gettime**\ (**CLOCK_REALTIME**)
+ * Return
+ * Current *ktime*.
+ *
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@@ -5339,6 +5351,7 @@ union bpf_attr {
FN(copy_from_user_task), \
FN(skb_set_tstamp), \
FN(ima_file_hash), \
+ FN(ktime_get_real_ns), \
/* */
/* integer value in 'imm' field of BPF_CALL instruction selects which helper
--
2.27.0
