logind: add code for UTMP wall messages

Add a timer to print UTMP wall messages so that it repeatedly informs users
about a scheduled shutdown:

 * every 1 minute with less than 10 minutes to go
 * every 15 minutes with less than 60 minutes to go
 * every 30 minutes with less than 180 minutes (3 hours) to go
 * every 60 minutes if more than that to go

This functionality only active if the .EnableWallMessages DBus property
is set to true. Also, a custom string can be added to the wall message,
set through the WallMessagePrefix property.

4 files changed, 234 insertions, 0 deletions

diff --git a/src/login/logind-dbus.c b/src/login/logind-dbus.c
index 0fcf2cc96..80514f3d2 100644
--- a/src/login/logind-dbus.c
+++ b/src/login/logind-dbus.c
@@ -43,6 +43,7 @@
 #include "formats-util.h"
 #include "process-util.h"
 #include "terminal-util.h"
+#include "utmp-wtmp.h"
 
 int manager_get_session_from_creds(Manager *m, sd_bus_message *message, const char *name, sd_bus_error *error, Session **ret) {
         _cleanup_bus_creds_unref_ sd_bus_creds *creds = NULL;
@@ -1800,6 +1801,7 @@ static int manager_scheduled_shutdown_handler(
 
 static int method_schedule_shutdown(sd_bus *bus, sd_bus_message *message, void *userdata, sd_bus_error *error) {
         Manager *m = userdata;
+        _cleanup_bus_creds_unref_ sd_bus_creds *creds = NULL;
         const char *action_multiple_sessions = NULL;
         const char *action_ignore_inhibit = NULL;
         const char *action = NULL;
@@ -1857,6 +1859,24 @@ static int method_schedule_shutdown(sd_bus *bus, sd_bus_message *message, void *
 
         m->scheduled_shutdown_timeout = elapse;
 
+        r = sd_bus_query_sender_creds(message, SD_BUS_CREDS_AUGMENT|SD_BUS_CREDS_TTY|SD_BUS_CREDS_UID, &creds);
+        if (r >= 0) {
+                const char *tty;
+
+                (void) sd_bus_creds_get_uid(creds, &m->scheduled_shutdown_uid);
+                (void) sd_bus_creds_get_tty(creds, &tty);
+
+                r = free_and_strdup(&m->scheduled_shutdown_tty, tty);
+                if (r < 0) {
+                        m->scheduled_shutdown_timeout_source = sd_event_source_unref(m->scheduled_shutdown_timeout_source);
+                        return log_oom();
+                }
+        }
+
+        r = manager_setup_wall_message_timer(m);
+        if (r < 0)
+                return r;
+
         return sd_bus_reply_method_return(message, NULL);
 }
 
@@ -1870,10 +1890,27 @@ static int method_cancel_scheduled_shutdown(sd_bus *bus, sd_bus_message *message
         cancelled = m->scheduled_shutdown_type != NULL;
 
         m->scheduled_shutdown_timeout_source = sd_event_source_unref(m->scheduled_shutdown_timeout_source);
+        m->wall_message_timeout_source = sd_event_source_unref(m->wall_message_timeout_source);
         free(m->scheduled_shutdown_type);
         m->scheduled_shutdown_type = NULL;
         m->scheduled_shutdown_timeout = 0;
 
+        if (cancelled) {
+                _cleanup_bus_creds_unref_ sd_bus_creds *creds = NULL;
+                const char *tty = NULL;
+                uid_t uid = 0;
+                int r;
+
+                r = sd_bus_query_sender_creds(message, SD_BUS_CREDS_AUGMENT|SD_BUS_CREDS_TTY|SD_BUS_CREDS_UID, &creds);
+                if (r >= 0) {
+                        (void) sd_bus_creds_get_uid(creds, &uid);
+                        (void) sd_bus_creds_get_tty(creds, &tty);
+                }
+
+                utmp_wall("The system shutdown has been cancelled",
+                          lookup_uid(uid), tty, logind_wall_tty_filter, m);
+        }
+
         return sd_bus_reply_method_return(message, "b", cancelled);
 }
 
@@ -2275,6 +2312,9 @@ fail:
 const sd_bus_vtable manager_vtable[] = {
         SD_BUS_VTABLE_START(0),
 
+        SD_BUS_WRITABLE_PROPERTY("EnableWallMessages", "b", NULL, NULL, offsetof(Manager, enable_wall_messages), 0),
+        SD_BUS_WRITABLE_PROPERTY("WallMessage", "s", NULL, NULL, offsetof(Manager, wall_message), 0),
+
         SD_BUS_PROPERTY("NAutoVTs", "u", NULL, offsetof(Manager, n_autovts), SD_BUS_VTABLE_PROPERTY_CONST),
         SD_BUS_PROPERTY("KillOnlyUsers", "as", NULL, offsetof(Manager, kill_only_users), SD_BUS_VTABLE_PROPERTY_CONST),
         SD_BUS_PROPERTY("KillExcludeUsers", "as", NULL, offsetof(Manager, kill_exclude_users), SD_BUS_VTABLE_PROPERTY_CONST),
diff --git a/src/login/logind-utmp.c b/src/login/logind-utmp.c
new file mode 100644
index 000000000..9bbffe34c
--- /dev/null
+++ b/src/login/logind-utmp.c
@@ -0,0 +1,182 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+  This file is part of systemd.
+
+  Copyright 2015 Daniel Mack
+
+  systemd 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.
+
+  systemd 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 systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <errno.h>
+#include <string.h>
+#include <unistd.h>
+#include <pwd.h>
+
+#include "sd-messages.h"
+#include "strv.h"
+#include "special.h"
+#include "unit-name.h"
+#include "audit.h"
+#include "bus-util.h"
+#include "bus-error.h"
+#include "bus-common-errors.h"
+#include "logind.h"
+#include "formats-util.h"
+#include "utmp-wtmp.h"
+
+_const_ static usec_t when_wall(usec_t n, usec_t elapse) {
+
+        usec_t left;
+        unsigned int i;
+        static const int wall_timers[] = {
+                0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10,
+                25, 40, 55, 70, 100, 130, 150, 180,
+        };
+
+        /* If the time is already passed, then don't announce */
+        if (n >= elapse)
+                return 0;
+
+        left = elapse - n;
+
+        for (i = 1; i < ELEMENTSOF(wall_timers); i++)
+                if (wall_timers[i] * USEC_PER_MINUTE >= left)
+                        return left - wall_timers[i-1] * USEC_PER_MINUTE;
+
+        return left % USEC_PER_HOUR;
+}
+
+bool logind_wall_tty_filter(const char *tty, void *userdata) {
+
+        Manager *m = userdata;
+
+        assert(m);
+
+        if (!startswith(tty, "/dev/"))
+                return true;
+
+        return !streq(tty + 5, m->scheduled_shutdown_tty);
+}
+
+static int warn_wall(Manager *m, usec_t n) {
+        char date[FORMAT_TIMESTAMP_MAX] = {};
+        _cleanup_free_ char *l = NULL;
+        usec_t left;
+        int r;
+
+        assert(m);
+
+        if (!m->enable_wall_messages)
+                return 0;
+
+        left = m->scheduled_shutdown_timeout > n;
+
+        r = asprintf(&l, "%s%sThe system is going down for %s %s%s!",
+                     strempty(m->wall_message),
+                     isempty(m->wall_message) ? "" : "\n",
+                     m->scheduled_shutdown_type,
+                     left ? "at " : "NOW",
+                     left ? format_timestamp(date, sizeof(date), m->scheduled_shutdown_timeout) : "");
+        if (r < 0) {
+                log_oom();
+                return 0;
+        }
+
+        utmp_wall(l, lookup_uid(m->scheduled_shutdown_uid),
+                  m->scheduled_shutdown_tty, logind_wall_tty_filter, m);
+
+        return 1;
+}
+
+static int wall_message_timeout_handler(
+                        sd_event_source *s,
+                        uint64_t usec,
+                        void *userdata) {
+
+        Manager *m = userdata;
+        usec_t n, next;
+        int r;
+
+        assert(m);
+        assert(s == m->wall_message_timeout_source);
+
+        n = now(CLOCK_REALTIME);
+
+        r = warn_wall(m, n);
+        if (r == 0)
+                return 0;
+
+        next = when_wall(n, m->scheduled_shutdown_timeout);
+        if (next > 0) {
+                r = sd_event_source_set_time(s, n + next);
+                if (r < 0)
+                        return log_error_errno(r, "sd_event_source_set_time() failed. %m\n");
+
+                r = sd_event_source_set_enabled(s, SD_EVENT_ONESHOT);
+                if (r < 0)
+                        return log_error_errno(r, "sd_event_source_set_enabled() failed. %m\n");
+        }
+
+        return 0;
+}
+
+int manager_setup_wall_message_timer(Manager *m) {
+
+        usec_t n, elapse;
+        int r;
+
+        assert(m);
+
+        n = now(CLOCK_REALTIME);
+        elapse = m->scheduled_shutdown_timeout;
+
+        /* wall message handling */
+
+        if (isempty(m->scheduled_shutdown_type)) {
+                warn_wall(m, n);
+                return 0;
+        }
+
+        if (elapse < n)
+                return 0;
+
+        /* Warn immediately if less than 15 minutes are left */
+        if (elapse - n < 15 * USEC_PER_MINUTE) {
+                r = warn_wall(m, n);
+                if (r == 0)
+                        return 0;
+        }
+
+        elapse = when_wall(n, elapse);
+        if (elapse == 0)
+                return 0;
+
+        if (m->wall_message_timeout_source) {
+                r = sd_event_source_set_time(m->wall_message_timeout_source, n + elapse);
+                if (r < 0)
+                        return log_error_errno(r, "sd_event_source_set_time() failed. %m\n");
+
+                r = sd_event_source_set_enabled(m->wall_message_timeout_source, SD_EVENT_ONESHOT);
+                if (r < 0)
+                        return log_error_errno(r, "sd_event_source_set_enabled() failed. %m\n");
+        } else {
+                r = sd_event_add_time(m->event, &m->wall_message_timeout_source,
+                                      CLOCK_REALTIME, n + elapse, 0, wall_message_timeout_handler, m);
+                if (r < 0)
+                        return log_error_errno(r, "sd_event_add_time() failed. %m\n");
+        }
+
+        return 0;
+}
diff --git a/src/login/logind.c b/src/login/logind.c
index 3a4afdd26..0d96bbdaa 100644
--- a/src/login/logind.c
+++ b/src/login/logind.c
@@ -145,6 +145,7 @@ static void manager_free(Manager *m) {
         sd_event_source_unref(m->idle_action_event_source);
         sd_event_source_unref(m->inhibit_timeout_source);
         sd_event_source_unref(m->scheduled_shutdown_timeout_source);
+        sd_event_source_unref(m->wall_message_timeout_source);
 
         sd_event_source_unref(m->console_active_event_source);
         sd_event_source_unref(m->udev_seat_event_source);
@@ -178,6 +179,8 @@ static void manager_free(Manager *m) {
         strv_free(m->kill_exclude_users);
 
         free(m->scheduled_shutdown_type);
+        free(m->scheduled_shutdown_tty);
+        free(m->wall_message);
         free(m->action_job);
         free(m);
 }
diff --git a/src/login/logind.h b/src/login/logind.h
index 6fc77d1ca..906c8ba40 100644
--- a/src/login/logind.h
+++ b/src/login/logind.h
@@ -95,6 +95,12 @@ struct Manager {
         char *scheduled_shutdown_type;
         usec_t scheduled_shutdown_timeout;
         sd_event_source *scheduled_shutdown_timeout_source;
+        uid_t scheduled_shutdown_uid;
+        char *scheduled_shutdown_tty;
+
+        char *wall_message;
+        unsigned enable_wall_messages;
+        sd_event_source *wall_message_timeout_source;
 
         sd_event_source *idle_action_event_source;
         usec_t idle_action_usec;
@@ -171,3 +177,6 @@ int config_parse_tmpfs_size(const char *unit, const char *filename, unsigned lin
 int manager_get_session_from_creds(Manager *m, sd_bus_message *message, const char *name, sd_bus_error *error, Session **ret);
 int manager_get_user_from_creds(Manager *m, sd_bus_message *message, uid_t uid, sd_bus_error *error, User **ret);
 int manager_get_seat_from_creds(Manager *m, sd_bus_message *message, const char *name, sd_bus_error *error, Seat **ret);
+
+int manager_setup_wall_message_timer(Manager *m);
+bool logind_wall_tty_filter(const char *tty, void *userdata);