[ntp:questions] ntpdate.c unsafe buffer write

David L. Mills mills at udel.edu
Tue Feb 12 15:09:33 UTC 2008


No; the server will detect that as a headway violation and drop the 
packets with, if configured, a KoD.

Come to think of it, randomization is not really required in the latest 
snapshot, since it knows about headway and will throttle accordingly. 
Only in your case where the daemon is stopped and restarted will the 
vioation be detected at the server.


Serge Bets wrote:

> Hello David,
>  On Tuesday, February 12, 2008 at 3:03:37 +0000, David L. Mills wrote:
>>The behavior after a step is deliberate. The iburst volley after a
>>step is delayed a random fraction of the poll interval to avoid
>>implosion at a busy server.
> Ah OK, I understand now! Thank you.
> This makes me wonder: When starting ntpd -gq doing a step and quitting,
> then immediatly starting ntpd daemon, this sequence sends 2 iburst
> volleys, over around 14 seconds, without the said random delay in
> between. Is that not rude to servers? The slew_sleeping script should be
> modified to sleep some time after a step. How much? 16 to 64 s?
> | /^ntpd: time set .*s$/ {
> |   sleep = 16 + int(rand() * 49)
> |   success = 1
> | }
> Serge.

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