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/* virt-p2v
* Copyright (C) 2017 Red Hat Inc.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
/**
* Try to calculate Real Time Clock (RTC) offset from UTC in seconds.
* For example if the RTC is 1 hour ahead of UTC, this will return
* C<3600>. This is stored in C<config-E<gt>rtc_offset>.
*/
#include <config.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <fcntl.h>
#include <errno.h>
#include <libintl.h>
#include <time.h>
#include <sys/ioctl.h>
#include <math.h>
#ifdef HAVE_LINUX_RTC_H
#include <linux/rtc.h>
#endif
#include "getprogname.h"
#include "ignore-value.h"
#include "p2v.h"
#ifndef HAVE_LINUX_RTC_H
void
get_rtc_config (struct rtc_config *rtc)
{
fprintf (stderr, "%s: RTC: compiled without support for /dev/rtc\n",
getprogname ());
rtc->offset = 0;
rtc->basis = BASIS_UTC;
}
#else /* HAVE_LINUX_RTC_H */
/**
* Return RTC offset from UTC in seconds, positive numbers meaning
* that the RTC is running ahead of UTC.
*
* In the error case, C<rtcE<gt>offset> is updated with 0 and
* C<rtcE<gt>basis> is set to C<BASIS_UNKNOWN>.
*/
void
get_rtc_config (struct rtc_config *rtc)
{
int fd;
struct rtc_time rtm;
struct tm tm;
time_t rtc_time;
time_t system_time;
double rf;
rtc->basis = BASIS_UNKNOWN;
rtc->offset = 0;
fd = open ("/dev/rtc", O_RDONLY);
if (fd == -1) {
perror ("/dev/rtc");
return;
}
if (ioctl (fd, RTC_RD_TIME, &rtm) == -1) {
perror ("ioctl: RTC_RD_TIME");
close (fd);
return;
}
close (fd);
#ifdef DEBUG_STDERR
fprintf (stderr, "%s: RTC: %04d-%02d-%02d %02d:%02d:%02d\n",
getprogname (),
rtm.tm_year + 1900, rtm.tm_mon + 1, rtm.tm_mday,
rtm.tm_hour, rtm.tm_min, rtm.tm_sec);
#endif
/* Convert this to seconds since the epoch. */
tm.tm_sec = rtm.tm_sec;
tm.tm_min = rtm.tm_min;
tm.tm_hour = rtm.tm_hour;
tm.tm_mday = rtm.tm_mday;
tm.tm_mon = rtm.tm_mon;
tm.tm_year = rtm.tm_year;
tm.tm_isdst = 0; /* Ignore DST when calculating. */
rtc_time = timegm (&tm);
if (rtc_time == -1)
return; /* Not representable as a Unix time. */
/* Get system time in UTC. */
system_time = time (NULL);
/* Calculate the difference, rounded to the nearest 15 minutes. */
rf = rtc_time - system_time;
#ifdef DEBUG_STDERR
fprintf (stderr, "%s: RTC: %ld system time: %ld difference: %g\n",
getprogname (),
(long) rtc_time, (long) system_time, rf);
#endif
rf /= 15*60;
rf = round (rf);
rf *= 15*60;
/* If it's obviously out of range then print an error and return. */
if (rf < -12*60*60 || rf > 14*60*60) {
fprintf (stderr,
"%s: RTC: offset of RTC from UTC is out of range (%g).\n",
getprogname (), rf);
return;
}
rtc->offset = (int) rf;
#ifdef DEBUG_STDERR
fprintf (stderr, "%s: RTC: offset of RTC from UTC = %d secs\n",
getprogname (), rtc->offset);
#endif
/* Is the hardware clock set to localtime?
*
* Unfortunately it's not possible to distinguish between UTC and
* localtime in timezones that lie along the Greenwich Meridian
* (obviously including the UK), when daylight savings time is not
* in effect. In that case, prefer UTC.
*/
localtime_r (&system_time, &tm);
if (tm.tm_gmtoff != 0 && tm.tm_gmtoff != rtc->offset)
rtc->basis = BASIS_UTC;
else {
rtc->basis = BASIS_LOCALTIME;
rtc->offset = 0;
#ifdef DEBUG_STDERR
fprintf (stderr, "%s: RTC time is localtime\n", getprogname ());
#endif
}
return;
}
#endif /* HAVE_LINUX_RTC_H */
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