netdev - [PATCH iproute2-next 1/3] tc: support conversions to or from 64 bit nanosecond-based time

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Date:   Mon,  6 Aug 2018 10:09:51 -0700
From:   Yousuk Seung <ysseung@...gle.com>
To:     netdev@...r.kernel.org
Cc:     Stephen Hemminger <stephen@...workplumber.org>,
        David Ahern <dsahern@...il.com>,
        Michael McLennan <nefario@...gle.com>,
        Priyaranjan Jha <priyarjha@...gle.com>,
        Dave Taht <dave.taht@...il.com>,
        Yousuk Seung <ysseung@...gle.com>,
        Neal Cardwell <ncardwell@...gle.com>
Subject: [PATCH iproute2-next 1/3] tc: support conversions to or from 64 bit
 nanosecond-based time

From: Dave Taht <dave.taht@...il.com>

Using a 32 bit field to represent time in nanoseconds results in a
maximum value of about 4.3 seconds, which is well below many observed
delays in WiFi and LTE, and barely in the ballpark for a trip past the
Earth's moon, Luna.

Using 64 bit time fields in nanoseconds allows us to simulate
network diameters of several hundred light-years. However, only
conversions to and from ns, us, ms, and seconds are provided.

Signed-off-by: Yousuk Seung <ysseung@...gle.com>
Signed-off-by: Dave Taht <dave.taht@...il.com>
Signed-off-by: Neal Cardwell <ncardwell@...gle.com>
---
 tc/tc_core.h |  4 ++++
 tc/tc_util.c | 55 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 tc/tc_util.h |  3 +++
 3 files changed, 62 insertions(+)

diff --git a/tc/tc_core.h b/tc/tc_core.h
index 1dfa9a4f773b..a0fe0923d171 100644
--- a/tc/tc_core.h
+++ b/tc/tc_core.h
@@ -7,6 +7,10 @@
 
 #define TIME_UNITS_PER_SEC	1000000
 
+#define NSEC_PER_USEC 1000
+#define NSEC_PER_MSEC 1000000
+#define NSEC_PER_SEC 1000000000LL
+
 enum link_layer {
 	LINKLAYER_UNSPEC,
 	LINKLAYER_ETHERNET,
diff --git a/tc/tc_util.c b/tc/tc_util.c
index d7578528a31b..c39c9046dcae 100644
--- a/tc/tc_util.c
+++ b/tc/tc_util.c
@@ -385,6 +385,61 @@ char *sprint_ticks(__u32 ticks, char *buf)
 	return sprint_time(tc_core_tick2time(ticks), buf);
 }
 
+/* 64 bit times are represented internally in nanoseconds */
+int get_time64(__s64 *time, const char *str)
+{
+	double nsec;
+	char *p;
+
+	nsec = strtod(str, &p);
+	if (p == str)
+		return -1;
+
+	if (*p) {
+		if (strcasecmp(p, "s") == 0 ||
+		    strcasecmp(p, "sec") == 0 ||
+		    strcasecmp(p, "secs") == 0)
+			nsec *= NSEC_PER_SEC;
+		else if (strcasecmp(p, "ms") == 0 ||
+			 strcasecmp(p, "msec") == 0 ||
+			 strcasecmp(p, "msecs") == 0)
+			nsec *= NSEC_PER_MSEC;
+		else if (strcasecmp(p, "us") == 0 ||
+			 strcasecmp(p, "usec") == 0 ||
+			 strcasecmp(p, "usecs") == 0)
+			nsec *= NSEC_PER_USEC;
+		else if (strcasecmp(p, "ns") == 0 ||
+			 strcasecmp(p, "nsec") == 0 ||
+			 strcasecmp(p, "nsecs") == 0)
+			nsec *= 1;
+		else
+			return -1;
+	}
+
+	*time = nsec;
+	return 0;
+}
+
+void print_time64(char *buf, int len, __s64 time)
+{
+	double nsec = time;
+
+	if (time >= NSEC_PER_SEC)
+		snprintf(buf, len, "%.3fs", nsec/NSEC_PER_SEC);
+	else if (time >= NSEC_PER_MSEC)
+		snprintf(buf, len, "%.3fms", nsec/NSEC_PER_MSEC);
+	else if (time >= NSEC_PER_USEC)
+		snprintf(buf, len, "%.3fus", nsec/NSEC_PER_USEC);
+	else
+		snprintf(buf, len, "%lldns", time);
+}
+
+char *sprint_time64(__s64 time, char *buf)
+{
+	print_time64(buf, SPRINT_BSIZE-1, time);
+	return buf;
+}
+
 int get_size(unsigned int *size, const char *str)
 {
 	double sz;
diff --git a/tc/tc_util.h b/tc/tc_util.h
index 6632c4f9c528..87be951c622d 100644
--- a/tc/tc_util.h
+++ b/tc/tc_util.h
@@ -82,12 +82,14 @@ int get_percent_rate64(__u64 *rate, const char *str, const char *dev);
 int get_size(unsigned int *size, const char *str);
 int get_size_and_cell(unsigned int *size, int *cell_log, char *str);
 int get_time(unsigned int *time, const char *str);
+int get_time64(__s64 *time, const char *str);
 int get_linklayer(unsigned int *val, const char *arg);
 
 void print_rate(char *buf, int len, __u64 rate);
 void print_size(char *buf, int len, __u32 size);
 void print_qdisc_handle(char *buf, int len, __u32 h);
 void print_time(char *buf, int len, __u32 time);
+void print_time64(char *buf, int len, __s64 time);
 void print_linklayer(char *buf, int len, unsigned int linklayer);
 void print_devname(enum output_type type, int ifindex);
 
@@ -96,6 +98,7 @@ char *sprint_size(__u32 size, char *buf);
 char *sprint_qdisc_handle(__u32 h, char *buf);
 char *sprint_tc_classid(__u32 h, char *buf);
 char *sprint_time(__u32 time, char *buf);
+char *sprint_time64(__s64 time, char *buf);
 char *sprint_ticks(__u32 ticks, char *buf);
 char *sprint_linklayer(unsigned int linklayer, char *buf);
 
-- 
2.18.0.597.ga71716f1ad-goog