文件列表:

ntpclient-2007 (0, 2008-07-16)
ntpclient-2007\adjtimex.1 (1621, 2008-01-01)
ntpclient-2007\adjtimex.c (4478, 2008-01-01)
ntpclient-2007\envelope (2354, 2008-01-01)
ntpclient-2007\HOWTO (9425, 2006-11-14)
ntpclient-2007\log2date.pl (320, 2003-07-06)
ntpclient-2007\Makefile (749, 2008-06-16)
ntpclient-2007\ntpclient (38670, 2008-06-16)
ntpclient-2007\ntpclient.1 (3041, 2008-01-01)
ntpclient-2007\ntpclient.c (19942, 2008-01-01)
ntpclient-2007\ntpclient.h (304, 2007-12-31)
ntpclient-2007\ntpclient.o (11148, 2008-06-16)
ntpclient-2007\phaselock.c (11235, 2007-12-31)
ntpclient-2007\phaselock.o (8744, 2008-06-16)
ntpclient-2007\rate.awk (666, 2003-07-14)
ntpclient-2007\rate2.awk (4741, 2008-01-01)
ntpclient-2007\test.dat (12762, 2006-10-28)
ntpclient-2007\todo (844, 2008-01-01)

ntpclient is an NTP (RFC-1305, RFC-4330) client for unix-alike computers. Its functionality is a small subset of xntpd, but IMHO performs better (or at least has the potential to function better) within that limited scope. Since it is much smaller than xntpd, it is also more relevant for embedded computers. ntpclient is Copyright 1997, 1999, 2000, 2003, 2006, 2007 Larry Doolittle, and may be freely copied and modified according to the terms of the GNU General Public License, version 2. If you want to distribute ntpclient under other terms, contact me. I might agree to some other arrangement, if you talk to me _before_ you start violating GPL terms. ntpclient home page: http://doolittle.icarus.com/ntpclient/ To build on Linux, type "make". Solaris and other Unix users will probably need to adjust the Makefile slightly. It's not complex. For changing the system clock frequency, only the Linux adjtimex(2) interface is implemented at this time. Non-Linux systems can only use ntpclient to measure time differences and set the system clock, by way of the POSIX 1003.1-2001 standard routines clock_gettime() and clock_settime(). Also see "Bugs", below. There are a few compile-time configurations possible, which require editing the Makefile. Either do or don't define ENABLE_DEBUG ENABLE_REPLAY USE_OBSOLETE_GETTIMEOFDAY PRECISION_SIOCGSTAMP Try it first without changing the default: that will give you a full- featured ntpclient, that uses modern POSIX time functions, and works reasonably with any Linux kernel. There are comments in ntpclient.c that you should read before experimenting with PRECISION_SIOCGSTAMP. Some older but otherwise (almost) serviceable Linux systems (e.g., Red Hat EL-3.0 and Ubuntu 4.10) have a totally broken POSIX clock_settime() implementation. If you get "clock_settime: Invalid argument" when you run ntpclient -s, rebuild with -DUSE_OBSOLETE_GETTIMEOFDAY. Linux systems that are even older won't even compile without that switch set. Usage: ntpclient [options] options: -c count stop after count time measurements (default 0 means go forever) -d print diagnostics (feature can be disabled at compile time) -g goodness causes ntpclient to stop after getting a result more accurate than goodness (microseconds, default 0 means go forever) -h hostname (mandatory) NTP server, against which to measure system time -i interval check time every interval seconds (default 600) -l attempt to lock local clock to server using adjtimex(2) -p port local NTP client UDP port (default 0 means "any available") -q min_delay minimum packet delay for transaction (default 800 microseconds) -r replay analysis code based on stdin -s simple clock set (implies -c 1) -t trust network and server, no RFC-4330 recommended cross-checks Mortal users can use this program for monitoring, but not clock setting (with the -s or -l switches). The -l switch is designed to be robust in any network environment, but has seen the most extensive testing in a low latency (less than 2 ms) Ethernet environment. Users in other environments should study ntpclient's behavior, and be prepared to adjust internal tuning parameters. A long description of how and why to use ntpclient is in the HOWTO file. ntpclient always sends packets to the server's UDP port 123. One commonly needed tuning parameter for lock mode is min_delay, the shortest possible round-trip transaction time. This can be set with the command line -q switch. The historical default of 800 microseconds was good for local Ethernet hardware a few years ago. If it is set too high, you will get a lot of "inconsistent" lines in the log file when time locking (-l switch). The only true future-proof value is 0, but that will cause the local time to wander more than it should. I use 200 on my workstation. The test.dat file has 200 lines of sample output. Its first few lines, with the output column headers that are shown when the -d option is chosen, are: day second elapsed stall skew dispersion freq 36765 00180.386 13***.0 40.3 953773.9 793.5 -1240000 36765 00780.382 1358.0 41.3 954329.0 915.5 -1240000 36765 01380.381 1439.0 56.0 954871.3 915.5 -1240000 day, second: time of measurement, UTC, relative to NTP epoch (Jan 1, 1900) elapsed: total time from query to response (microseconds) stall: time the server reports that it sat on the request (microseconds) skew: difference between local time and server time (microseconds) dispersion: reported by server, see RFC-1305 (microseconds) freq: local clock frequency adjustment (Linux only, ppm*65536) A relatively new feature is a series of sanity checks on UDP packets received, generally as recommended by RFC-4330. If it fails one of these tests, the line described above is replaced by 36765 01380.381 rejected packet or, if ENABLE_DEBUG was selected at compile time, one of 36765 01380.381 rejected packet: LI==3 36765 01380.381 rejected packet: VN<3 36765 01380.381 rejected packet: MODE!=3 36765 01380.381 rejected packet: ORG!=sent 36765 01380.381 rejected packet: XMT==0 36765 01380.381 rejected packet: abs(DELAY)>65536 36765 01380.381 rejected packet: abs(DISP)>65536 36765 01380.381 rejected packet: STRATUM==0 To see the actual values of the rejected packet, start ntpclient with the -d option; this will give a human-readable printout of every packet received, including the rejected ones. To skip these checks, use the -t switch. test.dat is suitable for piping into ntpclient -r. I have over 200000 samples (lines) archived for study, that I don't include here. They are generally spaced 10 minutes apart, representing over three years of data logging (from a variety of machines, and not continuous, unfortunately). As a special, added bonus, I also include my adjtimex(1) program. See its man page and the HOWTO file for more information. envelope is a perl script that I have used for my lock studies. It's kind of a hack and not worth documenting here. Changes since the widely distributed ntpclient_2000_345 version: -- new -g option (has had limited testing) -- changed max frequency adjustment from 91 ppm to 150 ppm -- fixed "inconsistent" bug in phaselock.c triggered by large freq errors -- new files: HOWTO, adjtimex.c, adjtimex.1, rate.awk, log2date.pl -- minor source code cleanups -- source is now as ***-bit clean as practical; tested on Alpha -- optional patches provided by Andy Warner, see andyw.patch -- optional patches provided by Linksys, see linksys.patch -- removed unreasonable 15020 day offset in date column (xntpd has this offset, which turns days-since-1900-epoch into Modified Julian Day) Changes since the widely distributed ntpclient_2003_194 version: -- default build is now -std=c99, but c89 sill works too -- switch default compile from gettimeofday() to POSIX clock_gettime() -- more sanity checking on the NTP reply packet, reference RFC-4330 -- fractional second printing in debug output changed to traditional decimal -- new -f switch to set initial frequency -- works to specify both -s and -l, will jump-set first and then phase lock -- bug fix for select() error handling, thanks to Walter Harms -- new man page, contributed by Walter Harms -- most subroutines are now flagged static to the compiler -- structural changes to the code, such as the new ntpclient.h file -- dropped (mostly) obsolete patches from Linksys and Andy Warner Changes since ntpclient_2006_318: -- adjustable min_delay parameter, used to be hard-coded 800 microseconds -- remove useless listen() call, thanks to Alexander Indenbaum -- fix length passed to recvfrom(), thanks to Alexander Indenbaum -- tidy up 32-bit integer declarations, prodding from Brian McAllister -- added rate2.awk, contributed by Lou Sortman -- provide easy way to override 15 second MIN_INTERVAL at compile time -- relax MIN_INTERVAL enforcement for one-shot use, thanks to Mihai Buha Bugs: -- Doesn't understand the LI (Leap second Indicator) field of an NTP packet -- Doesn't interact with adjtimex(2) status value -- Can't query multiple servers -- IPv4 only -- Requires Linux-style select() semantics, where timeout value is modified -- Always returns success (0) Adherence to RFC-4330 chapter 10, Best practices: 1. enforced, unless someone tinkers with the source code 2. no backoff, but no retry either; this isn't TCP 3. not in scope for the upstream source 4. not in scope for the upstream source 5. not in scope for the upstream source 6. supported 7. not supported 8. not supported (scary opportunity for DOS) - Larry Doolittle

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