Clock debugging script.

clockdbg.py

#!/usr/bin/env python

import ctypes
import ntplib # wget https://ntplib.googlecode.com/hg/ntplib.py
import sys
import time

# struct timespec {
#     time_t   tv_sec;        /* seconds */
#     long     tv_nsec;       /* nanoseconds */
# };
class TimeSpec(ctypes.Structure):
    _fields_ = [
        ('tv_sec', ctypes.c_long),
        ('tv_nsec', ctypes.c_long),
    ]

librt = ctypes.CDLL('librt.so.1', use_errno=True)
clock_gettime_raw = librt.clock_gettime

clock_gettime_raw.argtypes = [ ctypes.c_int, ctypes.POINTER(TimeSpec) ]
clock_gettime_raw.restype = ctypes.c_int

def clock_gettime(clock):
    ts = TimeSpec()
    res = clock_gettime_raw(clock, ctypes.pointer(ts))
    if res < 0:
        raise Exception('Error calling clock_gettime({clock}): {errno}'.format(clock=clock, errno=ctypes.get_errno()))
    return ts.tv_sec + ts.tv_nsec / 1000000000.0

CLOCK_REALTIME = 0
CLOCK_MONOTONIC	= 1
CLOCK_MONOTONIC_RAW = 4
CLOCK_BOOTTIME = 7

def ntp_timegetter(server):
    nc = ntplib.NTPClient()
    try:
        res = nc.request(server, timeout=1)
        offset = res.offset
    except:
        offset = None
    def get():
        if offset is None:
            return None
        return offset + time.time()
    return get

def fmt_ts(ts):
    if ts is None:
        return '-                             '

    secs = int(ts)
    nsecs = int((ts - secs) * 1000000000)
    return time.strftime('%Y-%m-%dT%H:%M:%S', time.gmtime(secs)) + '.%09dZ' % nsecs

def fmt_mt(ts):
    return '%020.9f' % (ts)

print 'FL OFFSET REALTIME                       MONOTONIC            MONOTONIC_RAW        NTP1                           NTP2                          '
while True:
    ntp1 = ntp_timegetter('0.pool.ntp.org')
    ntp2 = ntp_timegetter('1.pool.ntp.org')

    realtime = clock_gettime(CLOCK_REALTIME)
    monotonic = clock_gettime(CLOCK_MONOTONIC)
    monotonic_raw = clock_gettime(CLOCK_MONOTONIC_RAW)
    ntp1 = ntp1()
    ntp2 = ntp2()

    if ntp1 is not None and ntp2 is not None:
        offset = (ntp1 + ntp2) / 2.0 - realtime
    elif ntp1 is not None:
        offset = ntp1 - realtime
    elif ntp2 is not None:
        offset = ntp2 - realtime
    else:
        offset = None

    flag = '!' if offset is not None and abs(offset) > 0.5 else ' '
    offset = '% 7.3f' % offset

    print flag, offset, fmt_ts(realtime), fmt_mt(monotonic), fmt_mt(monotonic_raw), fmt_ts(ntp1), fmt_ts(ntp2)
    sys.stdout.flush()
    time.sleep(1)