r1 - 2012-12-27 - 08:13:08 - HarlanStennYou are here: NTP >  Dev Web > TechnicalNotes
NTP users are strongly urged to take immediate action to ensure that their NTP daemons are not susceptible to being used in distributed denial-of-service (DDoS) attacks. Please also take this opportunity to defeat denial-of-service attacks by implementing Ingress and Egress filtering through BCP38.

ntp-4.2.8p15 was released on 23 June 2020. It addresses 1 medium-severity security issue in ntpd, and provides 13 non-security bugfixes over 4.2.8p13.

Please see the NTP Security Notice for vulnerability and mitigation details.

Are you using Autokey in production? If so, please contact Harlan - he's got some questions for you.

Technical Notes

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Reading the System Clock

NTP's sys_fuzz_nsec is the time it takes to read the clock in nanoseconds (it's an integer type), and sys_tick is the same thing in a floating type but in usec. sys_precision is log2 of sys_tick.

Some systems have clock_getres() and it behaves differently on different OSes. NTP generally uses CLOCK_REALTIME for its operations, but on some OSes that value will not give use the information we want:

OS sys_fuzz_nsec sys_tick CLOCK_REALTIME Other
FreeSBD7 1676 1.676 280  
Solaris10 916 0.916 1000000 83 CLOCK_HIGHRES
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