netdev - [PATCH] iputils ping,ping6: use monotonic clock to schedule pings

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Date:	Sun, 5 Sep 2010 14:58:24 +0200 (CEST)
From:	Thomas Habets <thomas@...ets.pp.se>
To:	netdev@...r.kernel.org
Subject: [PATCH] iputils ping,ping6: use monotonic clock to schedule pings


This fixes the problem where when time is set backwards 'ping' appears
to freeze until the walltime catches up with the previously set time.

Adds dependency on librt.

diff --git a/Makefile b/Makefile
index 42f8475..a6812a3 100644
--- a/Makefile
+++ b/Makefile
@@ -28,8 +28,8 @@ all: $(TARGETS)

  tftpd: tftpd.o tftpsubs.o
  arping: arping.o -lsysfs
-ping: ping.o ping_common.o
-ping6: ping6.o ping_common.o -lresolv -lcrypto
+ping: ping.o ping_common.o -lrt
+ping6: ping6.o ping_common.o -lresolv -lcrypto -lrt
  ping.o ping6.o ping_common.o: ping_common.h
  tftpd.o tftpsubs.o: tftp.h

diff --git a/ping_common.c b/ping_common.c
index e0edf39..5883e63 100644
--- a/ping_common.c
+++ b/ping_common.c
@@ -304,6 +304,20 @@ void print_timestamp(void)
         }
  }

+int
+getclock(struct timeval *tv)
+{
+#ifdef CLOCK_MONOTONIC
+       struct timespec ts;
+       if (!clock_gettime(CLOCK_MONOTONIC, &ts)) {
+               tv->tv_sec = ts.tv_sec;
+               tv->tv_usec = ts.tv_nsec / 1000;
+               return;
+       }
+#endif
+       return gettimeofday(tv, NULL);
+}
+
  /*
   * pinger --
   *     Compose and transmit an ICMP ECHO REQUEST packet.  The IP packet
@@ -324,13 +338,13 @@ int pinger(void)

         /* Check that packets < rate*time + preload */
         if (cur_time.tv_sec == 0) {
-               gettimeofday(&cur_time, NULL);
+               getclock(&cur_time);
                 tokens = interval*(preload-1);
         } else {
                 long ntokens;
                 struct timeval tv;

-               gettimeofday(&tv, NULL);
+               getclock(&tv);
                 ntokens = (tv.tv_sec - cur_time.tv_sec)*1000 +
                         (tv.tv_usec-cur_time.tv_usec)/1000;
                 if (!interval) {
--
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