tst: Add test for adjtime

  This code provides test to check if time on target machine is properly
adjusted.
The time is altered only when cross-test-ssh.sh is executed with
--allow-time-setting flag.

As the delta added to clock is only 1 sec the original time is not
restored and further tests are executed with this bias.

It is important to note that adjtime() adjusts the system time with
small ammounts in each second (it is in fact a wrapper on clock_adjtime
with modes = ADJ_OFFSET_SINGLESHOT. In other words some seconds
(may be a random value) needs to elapse until the required time offset
is added to the clock. It may take considerable time (in minutes) to
adjust clock by e.g. 1 second.

To handle that the struct timeval odelta is passed to adjtime (NULL,
&odelta) to get information of the still required delta to be added
to clock. This is done in loop until its members are equal to 0.

As a reference - CLOCK_MONOTONIC is used to check if CLOCK_REALTIME
has been adjusted. The difference between them is measured.
---
 sysdeps/unix/sysv/linux/Makefile      |  2 +-
 sysdeps/unix/sysv/linux/tst-adjtime.c | 82 +++++++++++++++++++++++++++
 2 files changed, 83 insertions(+), 1 deletion(-)
 create mode 100644 sysdeps/unix/sysv/linux/tst-adjtime.c
  

Dear Community,

> This code provides test to check if time on target machine is properly
> adjusted.
> The time is altered only when cross-test-ssh.sh is executed with
> --allow-time-setting flag.
> 
> As the delta added to clock is only 1 sec the original time is not
> restored and further tests are executed with this bias.
> 
> It is important to note that adjtime() adjusts the system time with
> small ammounts in each second (it is in fact a wrapper on
> clock_adjtime with modes = ADJ_OFFSET_SINGLESHOT. In other words some
> seconds (may be a random value) needs to elapse until the required
> time offset is added to the clock. It may take considerable time (in
> minutes) to adjust clock by e.g. 1 second.
> 
> To handle that the struct timeval odelta is passed to adjtime (NULL,
> &odelta) to get information of the still required delta to be added
> to clock. This is done in loop until its members are equal to 0.
> 
> As a reference - CLOCK_MONOTONIC is used to check if CLOCK_REALTIME
> has been adjusted. The difference between them is measured.

Feedback more than welcome. Are there any comments regarding this patch?

> ---
>  sysdeps/unix/sysv/linux/Makefile      |  2 +-
>  sysdeps/unix/sysv/linux/tst-adjtime.c | 82
> +++++++++++++++++++++++++++ 2 files changed, 83 insertions(+), 1
> deletion(-) create mode 100644 sysdeps/unix/sysv/linux/tst-adjtime.c
> 
> diff --git a/sysdeps/unix/sysv/linux/Makefile
> b/sysdeps/unix/sysv/linux/Makefile index 6a45ac820a..25d2f05183 100644
> --- a/sysdeps/unix/sysv/linux/Makefile
> +++ b/sysdeps/unix/sysv/linux/Makefile
> @@ -113,7 +113,7 @@ tests += tst-clone tst-clone2 tst-clone3
> tst-fanotify tst-personality \ tst-tgkill tst-sysvsem-linux
> tst-sysvmsg-linux tst-sysvshm-linux \ tst-timerfd tst-ppoll
> tst-futimens tst-utime tst-utimes \ tst-clock_adjtime tst-adjtimex
> tst-ntp_adjtime tst-futimes \
> -	 tst-lutimes tst-ntp_gettime tst-ntp_gettimex
> +	 tst-lutimes tst-ntp_gettime tst-ntp_gettimex tst-adjtime
>  tests-internal += tst-ofdlocks-compat tst-sigcontext-get_pc
>  tests-time64 += \
>    tst-futimes-time64\
> diff --git a/sysdeps/unix/sysv/linux/tst-adjtime.c
> b/sysdeps/unix/sysv/linux/tst-adjtime.c new file mode 100644
> index 0000000000..b381963be8
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/tst-adjtime.c
> @@ -0,0 +1,82 @@
> +/* Test for adjtime
> +   Copyright (C) 2021 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library 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
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +   <https://www.gnu.org/licenses/>.  */
> +
> +#include <time.h>
> +#include <stdlib.h>
> +#include <sys/time.h>
> +#include <sys/timerfd.h>
> +#include <support/check.h>
> +#include <support/xunistd.h>
> +#include <support/timespec.h>
> +
> +#define TIMEOUT (60*10)
> +#define ADJTIME_LOOP_SLEEP 10000
> +
> +static int
> +do_test (void)
> +{
> +  struct timespec tv_then, tv_now, tv_then_m, tv_now_m;
> +  struct timeval delta, odelta;
> +  int ret;
> +
> +  /* Check if altering target time is allowed.  */
> +  if (getenv (SETTIME_ENV_NAME) == NULL)
> +    FAIL_UNSUPPORTED ("adjtime is executed only when "\
> +                      SETTIME_ENV_NAME" is set\n");
> +
> +  tv_then = xclock_now (CLOCK_REALTIME);
> +  tv_then_m = xclock_now (CLOCK_MONOTONIC);
> +
> +  /* Setup time value to adjust - 1 sec. */
> +  delta.tv_sec = 1;
> +  delta.tv_usec = 0;
> +
> +  ret = adjtime (&delta, NULL);
> +  if (ret == -1)
> +    FAIL_EXIT1 ("adjtime failed: %m\n");
> +
> +  /* As adjtime adjust clock time gradually by some small percentage
> +     of delta in each second one needs to check if this process has
> +     been finished.  */
> +  do {
> +    ret = adjtime (NULL, &odelta);
> +    if (ret == -1)
> +      FAIL_EXIT1 ("adjtime failed: %m\n");
> +
> +    ret = usleep (ADJTIME_LOOP_SLEEP);
> +    if (ret != 0)
> +      FAIL_EXIT1 ("usleep failed: %m\n");
> +
> +  } while ( ! (odelta.tv_sec == 0 && odelta.tv_usec == 0));
> +
> +  tv_now = xclock_now (CLOCK_REALTIME);
> +  tv_now_m = xclock_now (CLOCK_MONOTONIC);
> +
> +  /* Check if adjtime adjusted the system time.  */
> +  struct timespec r = timespec_sub (tv_now, tv_then);
> +  struct timespec r_m = timespec_sub (tv_now_m, tv_then_m);
> +
> +  struct timespec r_adjtime = timespec_sub (r, r_m);
> +
> +  TEST_COMPARE (support_timespec_check_in_range
> +                ((struct timespec) { 1, 0 }, r_adjtime, 0.9, 1.1),
> 1); +
> +  return 0;
> +}
> +
> +#include <support/test-driver.c>




Best regards,

Lukasz Majewski

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