netdev - [PATCH iproute2 1/4] tc: support conversions to or from 64 bit nanosecond-based time

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Date:   Tue,  7 Nov 2017 13:16:53 -0800
From:   Dave Taht <dave.taht@...il.com>
To:     netdev@...r.kernel.org
Cc:     Dave Taht <dave.taht@...il.com>
Subject: [PATCH iproute2 1/4] tc: support conversions to or from 64 bit nanosecond-based time

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: Dave Taht <dave.taht@...il.com>
---
 tc/tc_core.h |  3 +++
 tc/tc_util.c | 56 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 tc/tc_util.h |  3 +++
 3 files changed, 62 insertions(+)

diff --git a/tc/tc_core.h b/tc/tc_core.h
index 8a63b79..e8bda8b 100644
--- a/tc/tc_core.h
+++ b/tc/tc_core.h
@@ -5,6 +5,9 @@
 #include <linux/pkt_sched.h>
 
 #define TIME_UNITS_PER_SEC	1000000
+#define USEC_PER_SEC 1000
+#define MSEC_PER_SEC (1000 * 1000)
+#define NSEC_PER_SEC (1000 * 1000 * 1000)
 
 enum link_layer {
 	LINKLAYER_UNSPEC,
diff --git a/tc/tc_util.c b/tc/tc_util.c
index b39e550..dafbbc3 100644
--- a/tc/tc_util.c
+++ b/tc/tc_util.c
@@ -323,6 +323,62 @@ 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 t;
+	char *p;
+
+	t = strtod(str, &p);
+	if (p == str)
+		return -1;
+
+	if (*p) {
+		if (strcasecmp(p, "s") == 0 ||
+		    strcasecmp(p, "sec") == 0 ||
+		    strcasecmp(p, "secs") == 0)
+			t *= NSEC_PER_SEC;
+		else if (strcasecmp(p, "ms") == 0 ||
+			 strcasecmp(p, "msec") == 0 ||
+			 strcasecmp(p, "msecs") == 0)
+			t *= MSEC_PER_SEC;
+		else if (strcasecmp(p, "us") == 0 ||
+			 strcasecmp(p, "usec") == 0 ||
+			 strcasecmp(p, "usecs") == 0)
+			t *= USEC_PER_SEC;
+		else if (strcasecmp(p, "ns") == 0 ||
+			 strcasecmp(p, "nsec") == 0 ||
+			 strcasecmp(p, "nsecs") == 0)
+			t *= 1;
+		else
+			return -1;
+	}
+
+	*time = t;
+	return 0;
+}
+
+void print_time64(char *buf, int len, __s64 time)
+{
+	double tmp = time;
+
+	if (time >= NSEC_PER_SEC)
+		snprintf(buf, len, "%.3fs", tmp/NSEC_PER_SEC);
+	else if (time >= MSEC_PER_SEC)
+		snprintf(buf, len, "%.3fms", tmp/MSEC_PER_SEC);
+	else if (time >= USEC_PER_SEC)
+		snprintf(buf, len, "%.3fus", tmp/USEC_PER_SEC);
+	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 583a21a..7a8559b 100644
--- a/tc/tc_util.h
+++ b/tc/tc_util.h
@@ -72,12 +72,14 @@ int get_rate64(__u64 *rate, const char *str);
 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);
 
 char *sprint_rate(__u64 rate, char *buf);
@@ -85,6 +87,7 @@ 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);
 
-- 
2.7.4