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-rw-r--r--leapdb.c272
1 files changed, 272 insertions, 0 deletions
diff --git a/leapdb.c b/leapdb.c
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+/*
+ chronyd/chronyc - Programs for keeping computer clocks accurate.
+
+ **********************************************************************
+ * Copyright (C) Miroslav Lichvar 2009-2018, 2020, 2022
+ * Copyright (C) Patrick Oppenlander 2023, 2024
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License as
+ * published by the Free Software Foundation.
+ *
+ * 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.
+ *
+ **********************************************************************
+
+ =======================================================================
+
+ This module provides leap second information. */
+
+#include "config.h"
+
+#include "sysincl.h"
+
+#include "conf.h"
+#include "leapdb.h"
+#include "logging.h"
+#include "util.h"
+
+/* ================================================== */
+
+/* Source of leap second data */
+enum {
+ SRC_NONE,
+ SRC_TIMEZONE,
+ SRC_LIST,
+} leap_src;
+
+/* Offset between leap-seconds.list timestamp epoch and Unix epoch.
+ leap-seconds.list epoch is 1 Jan 1900, 00:00:00 */
+#define LEAP_SEC_LIST_OFFSET 2208988800
+
+/* ================================================== */
+
+static NTP_Leap
+get_tz_leap(time_t when, int *tai_offset)
+{
+ struct tm stm, *tm;
+ time_t t;
+ char *tz_env, tz_orig[128];
+ NTP_Leap tz_leap = LEAP_Normal;
+
+ tm = gmtime(&when);
+ if (!tm)
+ return tz_leap;
+
+ stm = *tm;
+
+ /* Temporarily switch to the timezone containing leap seconds */
+ tz_env = getenv("TZ");
+ if (tz_env) {
+ if (strlen(tz_env) >= sizeof (tz_orig))
+ return tz_leap;
+ strcpy(tz_orig, tz_env);
+ }
+ setenv("TZ", CNF_GetLeapSecTimezone(), 1);
+ tzset();
+
+ /* Get the TAI-UTC offset, which started at the epoch at 10 seconds */
+ t = mktime(&stm);
+ if (t != -1)
+ *tai_offset = t - when + 10;
+
+ /* Set the time to 23:59:60 and see how it overflows in mktime() */
+ stm.tm_sec = 60;
+ stm.tm_min = 59;
+ stm.tm_hour = 23;
+
+ t = mktime(&stm);
+
+ if (tz_env)
+ setenv("TZ", tz_orig, 1);
+ else
+ unsetenv("TZ");
+ tzset();
+
+ if (t == -1)
+ return tz_leap;
+
+ if (stm.tm_sec == 60)
+ tz_leap = LEAP_InsertSecond;
+ else if (stm.tm_sec == 1)
+ tz_leap = LEAP_DeleteSecond;
+
+ return tz_leap;
+}
+
+/* ================================================== */
+
+static NTP_Leap
+get_list_leap(time_t when, int *tai_offset)
+{
+ FILE *f;
+ char line[1024];
+ NTP_Leap ret_leap = LEAP_Normal;
+ int ret_tai_offset = 0, prev_lsl_tai_offset = 10;
+ int64_t when1900, lsl_updated = 0, lsl_expiry = 0;
+ const char *leap_sec_list = CNF_GetLeapSecList();
+
+ if (!(f = UTI_OpenFile(NULL, leap_sec_list, NULL, 'r', 0))) {
+ LOG(LOGS_ERR, "Failed to open leap seconds list %s", leap_sec_list);
+ goto out;
+ }
+
+ /* Leap second happens at midnight */
+ when = (when / (24 * 3600) + 1) * (24 * 3600);
+
+ /* leap-seconds.list timestamps are relative to 1 Jan 1900, 00:00:00 */
+ when1900 = (int64_t)when + LEAP_SEC_LIST_OFFSET;
+
+ while (fgets(line, sizeof line, f) > 0) {
+ int64_t lsl_when;
+ int lsl_tai_offset;
+ char *p;
+
+ /* Ignore blank lines */
+ for (p = line; *p && isspace(*p); ++p)
+ ;
+ if (!*p)
+ continue;
+
+ if (*line == '#') {
+ /* Update time line starts with #$ */
+ if (line[1] == '$' && sscanf(line + 2, "%"SCNd64, &lsl_updated) != 1)
+ goto error;
+ /* Expiration time line starts with #@ */
+ if (line[1] == '@' && sscanf(line + 2, "%"SCNd64, &lsl_expiry) != 1)
+ goto error;
+ /* Comment or a special comment we don't care about */
+ continue;
+ }
+
+ /* Leap entry */
+ if (sscanf(line, "%"SCNd64" %d", &lsl_when, &lsl_tai_offset) != 2)
+ goto error;
+
+ if (when1900 == lsl_when) {
+ if (lsl_tai_offset > prev_lsl_tai_offset)
+ ret_leap = LEAP_InsertSecond;
+ else if (lsl_tai_offset < prev_lsl_tai_offset)
+ ret_leap = LEAP_DeleteSecond;
+ /* When is rounded to the end of the day, so offset hasn't changed yet! */
+ ret_tai_offset = prev_lsl_tai_offset;
+ } else if (when1900 > lsl_when) {
+ ret_tai_offset = lsl_tai_offset;
+ }
+
+ prev_lsl_tai_offset = lsl_tai_offset;
+ }
+
+ /* Make sure the file looks sensible */
+ if (!feof(f) || !lsl_updated || !lsl_expiry)
+ goto error;
+
+ if (when1900 >= lsl_expiry)
+ LOG(LOGS_WARN, "Leap second list %s needs update", leap_sec_list);
+
+ goto out;
+
+error:
+ if (f)
+ fclose(f);
+ LOG(LOGS_ERR, "Failed to parse leap seconds list %s", leap_sec_list);
+ return LEAP_Normal;
+
+out:
+ if (f)
+ fclose(f);
+ *tai_offset = ret_tai_offset;
+ return ret_leap;
+}
+
+/* ================================================== */
+
+static int
+check_leap_source(NTP_Leap (*src)(time_t when, int *tai_offset))
+{
+ int tai_offset = 0;
+
+ /* Check that the leap second source has good data for Jun 30 2012 and Dec 31 2012 */
+ if (src(1341014400, &tai_offset) == LEAP_InsertSecond && tai_offset == 34 &&
+ src(1356912000, &tai_offset) == LEAP_Normal && tai_offset == 35)
+ return 1;
+
+ return 0;
+}
+
+/* ================================================== */
+
+void
+LDB_Initialise(void)
+{
+ const char *leap_tzname, *leap_sec_list;
+
+ leap_tzname = CNF_GetLeapSecTimezone();
+ if (leap_tzname && !check_leap_source(get_tz_leap)) {
+ LOG(LOGS_WARN, "Timezone %s failed leap second check, ignoring", leap_tzname);
+ leap_tzname = NULL;
+ }
+
+ leap_sec_list = CNF_GetLeapSecList();
+ if (leap_sec_list && !check_leap_source(get_list_leap)) {
+ LOG(LOGS_WARN, "Leap second list %s failed check, ignoring", leap_sec_list);
+ leap_sec_list = NULL;
+ }
+
+ if (leap_sec_list) {
+ LOG(LOGS_INFO, "Using leap second list %s", leap_sec_list);
+ leap_src = SRC_LIST;
+ } else if (leap_tzname) {
+ LOG(LOGS_INFO, "Using %s timezone to obtain leap second data", leap_tzname);
+ leap_src = SRC_TIMEZONE;
+ }
+}
+
+/* ================================================== */
+
+NTP_Leap
+LDB_GetLeap(time_t when, int *tai_offset)
+{
+ static time_t last_ldb_leap_check;
+ static NTP_Leap ldb_leap;
+ static int ldb_tai_offset;
+
+ /* Do this check at most twice a day */
+ when = when / (12 * 3600) * (12 * 3600);
+ if (last_ldb_leap_check == when)
+ goto out;
+
+ last_ldb_leap_check = when;
+ ldb_leap = LEAP_Normal;
+ ldb_tai_offset = 0;
+
+ switch (leap_src) {
+ case SRC_NONE:
+ break;
+ case SRC_TIMEZONE:
+ ldb_leap = get_tz_leap(when, &ldb_tai_offset);
+ break;
+ case SRC_LIST:
+ ldb_leap = get_list_leap(when, &ldb_tai_offset);
+ break;
+ }
+
+out:
+ *tai_offset = ldb_tai_offset;
+ return ldb_leap;
+}
+
+/* ================================================== */
+
+void
+LDB_Finalise(void)
+{
+ /* Nothing to do */
+}
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