From Bugzilla Helper: User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; .NET CLR 1.0.3705) Description of problem: When pinging hosts, intermittently, the error 'Warning: time of day goes back, taking countermeasures.' Countermeasures, in this case, appears to be returning a trip time of 0 usecs. I just recently upgraded the machine from kernel-2.4.9-31 to kernel-2.4.18- 17.7.x (both RH7.2 errata kernels, stock). The problem did not exist before the upgrade. Version-Release number of selected component (if applicable): How reproducible: Sometimes Steps to Reproduce: 1. upgrade kernel 2. ping -U -s 56 host 10 3. Actual Results: Warning given, ping returns bad 0 value for the time. After first return, subsequent warnings take a long time (> 5secs) to appear. Expected Results: Ping doesn't give warning and gives correct ping times. Additional info: This bug has been filed under 19952 (CLOSED) for RH7.0 and as a duplicate of that bug (60765) for RH 7.2. I'm filing separately because the old bug has been closed for over six months, and the kernel was released in October. This may be different issue, or it may be a regression, but I want it seen.
I upgraded to the latest rawhide version of iputils (I normally don't like to upgrade past anything outside the distro and its errata, but I really need this), and the warnings have gone away (presumably because they're only printed in verbose mode now; see changelog). I'm still extremely nervous about those 0usec ping times, though, when the errors was printed. We're measuring ping times for latency calculations, so 0usec ping times are actually a big deal to us.
Example output showing what we're seeing, even with the new code: $ ping -U -v -s 56 209.99.41.93 PING 209.99.41.93 (209.99.41.93) from 216.166.60.79 : 56(84) bytes of data. 64 bytes from 209.99.41.93: icmp_seq=1 ttl=254 time=0.609 ms 64 bytes from 209.99.41.93: icmp_seq=2 ttl=254 time=0.756 ms 64 bytes from 209.99.41.93: icmp_seq=3 ttl=254 time=0.664 ms 64 bytes from 209.99.41.93: icmp_seq=4 ttl=254 time=0.635 ms 64 bytes from 209.99.41.93: icmp_seq=5 ttl=254 time=0.744 ms 64 bytes from 209.99.41.93: icmp_seq=6 ttl=254 time=0.906 ms 64 bytes from 209.99.41.93: icmp_seq=7 ttl=254 time=0.616 ms 64 bytes from 209.99.41.93: icmp_seq=8 ttl=254 time=0.695 ms 64 bytes from 209.99.41.93: icmp_seq=9 ttl=254 time=0.634 ms 64 bytes from 209.99.41.93: icmp_seq=10 ttl=254 time=0.720 ms Warning: time of day goes back (-7806011us), taking countermeasures. 64 bytes from 209.99.41.93: icmp_seq=11 ttl=254 time=0.000 ms Warning: time of day goes back (-7806078us), taking countermeasures. 64 bytes from 209.99.41.93: icmp_seq=12 ttl=254 time=0.000 ms 64 bytes from 209.99.41.93: icmp_seq=13 ttl=254 time=0.722 ms 64 bytes from 209.99.41.93: icmp_seq=14 ttl=254 time=0.833 ms 64 bytes from 209.99.41.93: icmp_seq=15 ttl=254 time=0.630 ms
Do you have ntp running on that host by chance? This might affect the time setting of your machine and cause the effect. With the latest iputils on a RH 9 i haven't see the effect at all anymore (where i was able to reproduce it with older releases and kernels). As you've been using the latest iputils package i can only think of 2 causes: either ntp running on your machine or that the 7.2 errata kernel still has issues with the precise time interface. Read ya, Phil
I've tried various setups and installations over the last few months and the bug didn't appear on any of the systems anymore, so i'm closing the bug as fixed in the current release. Read ya, Phil