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Re: Ping message



If you are really doing professional services then you should know how
to tell your mailer to only send a mail to the list or either insert an
appropriate comment telling me, that you also send me a unnessary copy
to my private address. 

On 01-08-08 Jeremy C. Reed wrote:
> On Wed, 8 Aug 2001, Christian Kurz wrote:
> > > > Warning: time of day goes back, taking countermeasures.

> > > I believe your ping command is using features only available in a newer
> > > kernel. Maybe upgrade your kernel (2.4.4?) or see if your ping has a -U
> > > switch to ignore this.

> > What should a feature of a kernel has to do with a message from ping
> > complaining about problems with the time measurement? 

> > I don't understand the source of ping completely, but I would say that
> > this message is a hint to a problem with the clock. This message is

> I am pretty sure it is not the return value form gettimeofday() -- it is
> the information returned via ioctl() for a SIOCGSTAM (receive timestamp of
> the last packet passed to the user) or SO_TIMESTAMP request (timestamp of
> incoming datagrams).

I don't know which source you are looking at, but I'm looking at the
source for iputils from ftp://ftp.inr.ac.ru/ip-routing/. If you look
there at the functions pr_pack and main you'll notice that pr_pack is
called with a variable containing the received_time which is as far as I
understand calculated from the time (gettimeofday). And this time value
is then used inside pr_pack to calculate the exact time for the trip. So
only when the triptime will be less then 0, ping will print the message
about the timining going back. If you are not agreeing with this, then
please tell us, which source code you are looking at and give some hints
to the code like I did now.

> I believe -U uses different functionality (old feature) and
> bypasses this problem.

-U does what? The version of ping that I use here doesn't know about
that switch.

Christian
-- 
           Debian Developer (http://www.debian.org)
1024/26CC7853 31E6 A8CA 68FC 284F 7D16  63EC A9E6 67FF 26CC 7853

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