check_users: prefer systemd-logind over utmprefs/pull/1888/head

Prefer systemd-logind over utmp to get the number of logged in users.
utmp is not reliable for this (e.g. some terminals create utmp entries,
other not) and utmp is not Y2038 safe with glibc on Linux.

2 files changed, 26 insertions, 13 deletions

diff --git a/plugins/Makefile.am b/plugins/Makefile.am
index ab59eb7..49086b7 100644
--- a/plugins/Makefile.am
+++ b/plugins/Makefile.am
@@ -112,7 +112,7 @@ check_tcp_LDADD = $(SSLOBJS)
 check_time_LDADD = $(NETLIBS)
 check_ntp_time_LDADD = $(NETLIBS) $(MATHLIBS)
 check_ups_LDADD = $(NETLIBS)
-check_users_LDADD = $(BASEOBJS) $(WTSAPI32LIBS)
+check_users_LDADD = $(BASEOBJS) $(WTSAPI32LIBS) $(SYSTEMDLIBS)
 check_by_ssh_LDADD = $(NETLIBS)
 check_ide_smart_LDADD = $(BASEOBJS)
 negate_LDADD = $(BASEOBJS)
diff --git a/plugins/check_users.c b/plugins/check_users.c
index f6f4b36..2a9ee98 100644
--- a/plugins/check_users.c
+++ b/plugins/check_users.c
@@ -1,33 +1,33 @@
 /*****************************************************************************
-* 
+*
 * Monitoring check_users plugin
-* 
+*
 * License: GPL
 * Copyright (c) 2000-2012 Monitoring Plugins Development Team
-* 
+*
 * Description:
-* 
+*
 * This file contains the check_users plugin
-* 
+*
 * This plugin checks the number of users currently logged in on the local
 * system and generates an error if the number exceeds the thresholds
 * specified.
-* 
-* 
+*
+*
 * 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 3 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, see <http://www.gnu.org/licenses/>.
-* 
-* 
+*
+*
 *****************************************************************************/
 
 const char *progname = "check_users";
@@ -48,6 +48,11 @@ const char *email = "devel@monitoring-plugins.org";
 # include "popen.h"
 #endif
 
+#ifdef HAVE_LIBSYSTEMD
+#include <systemd/sd-daemon.h>
+#include <systemd/sd-login.h>
+#endif
+
 #define possibly_set(a,b) ((a) == 0 ? (b) : 0)
 
 int process_arguments (int, char **);
@@ -85,6 +90,11 @@ main (int argc, char **argv)
 
         users = 0;
 
+#ifdef HAVE_LIBSYSTEMD
+        if (sd_booted () > 0)
+                users = sd_get_sessions (NULL);
+        else {
+#endif
 #if HAVE_WTSAPI32_H
         if (!WTSEnumerateSessions(WTS_CURRENT_SERVER_HANDLE,
           0, 1, &wtsinfo, &wtscount)) {
@@ -156,6 +166,9 @@ main (int argc, char **argv)
         if (spclose (child_process))
                 result = possibly_set (result, STATE_UNKNOWN);
 #endif
+#ifdef HAVE_LIBSYSTEMD
+        }
+#endif
 
         /* check the user count against warning and critical thresholds */
         result = get_status((double)users, thlds);
@@ -163,7 +176,7 @@ main (int argc, char **argv)
         if (result == STATE_UNKNOWN)
                 printf ("%s\n", _("Unable to read output"));
         else {
-                printf (_("USERS %s - %d users currently logged in |%s\n"), 
+                printf (_("USERS %s - %d users currently logged in |%s\n"),
                                 state_text(result), users,
                                 sperfdata_int("users", users, "", warning_range,
                                                         critical_range, TRUE, 0, FALSE, 0));