From 29667c6fcc36de5cf28942bd72e5b5f5926d19f5 Mon Sep 17 00:00:00 2001 From: Jose Luis Duran Date: Fri, 6 Oct 2023 17:55:06 +0000 Subject: [PATCH] ping: Avoid reporting NaNs Avoid calculating the square root of negative zero, which can easily happen on certain architectures when calculating the population standard deviation with a sample size of one, e.g., 0.01 - (0.1 * 0.1) = -0.000000. Avoid returning a NaN by capping the minimum possible variance value to zero (positive). In the future, maybe skip reporting statistics at all for a single sample. Reported by: Jenkins Reviewed by: asomers MFC after: 1 week Pull Request: https://github.com/freebsd/freebsd-src/pull/863 Differential Revision: https://reviews.freebsd.org/D42114 (cherry picked from commit 4d348e83b738347f6aaf2b110459a01c5402d04e) --- sbin/ping/ping.c | 4 ++-- sbin/ping/ping6.c | 4 ++-- 2 files changed, 4 insertions(+), 4 deletions(-) diff --git a/sbin/ping/ping.c b/sbin/ping/ping.c index f248a0eb738c..e121ebdb19e2 100644 --- a/sbin/ping/ping.c +++ b/sbin/ping/ping.c @@ -1521,10 +1521,10 @@ finish(void) if (nreceived && timing) { double n = nreceived + nrepeats; double avg = tsum / n; - double vari = tsumsq / n - avg * avg; + double stddev = sqrt(fmax(0, tsumsq / n - avg * avg)); (void)printf( "round-trip min/avg/max/stddev = %.3f/%.3f/%.3f/%.3f ms\n", - tmin, avg, tmax, sqrt(vari)); + tmin, avg, tmax, stddev); } if (nreceived) diff --git a/sbin/ping/ping6.c b/sbin/ping/ping6.c index 432a59bf1303..0edeb01b2dc0 100644 --- a/sbin/ping/ping6.c +++ b/sbin/ping/ping6.c @@ -2349,10 +2349,10 @@ summary(void) /* Only display average to microseconds */ double num = nreceived + nrepeats; double avg = tsum / num; - double dev = sqrt(tsumsq / num - avg * avg); + double stddev = sqrt(fmax(0, tsumsq / num - avg * avg)); (void)printf( "round-trip min/avg/max/std-dev = %.3f/%.3f/%.3f/%.3f ms\n", - tmin, avg, tmax, dev); + tmin, avg, tmax, stddev); (void)fflush(stdout); } (void)fflush(stdout);