logind: add option to stop idle sessions after specified timeout

Thanks to Jan Pazdziora <jpazdziora@redhat.com> for providing a patch
which implemeted a PoC of this feature.

man/logind.conf.xml

@@ -344,6 +344,17 @@
         are excluded from the effect of this setting. Defaults to <literal>yes</literal>.</para></listitem>
       </varlistentry>
 
+      <varlistentry>
+        <term><varname>StopIdleSessionSec=</varname></term>
+
+        <listitem><para>Specifies a timeout in seconds, or a time span value after which
+        <filename>systemd-logind</filename> checks the idle state of all sessions. Every session that is idle for
+        longer then the timeout will be stopped. Defaults to <literal>infinity</literal>
+        (<filename>systemd-logind</filename> is not checking the idle state of sessions). For details about the syntax
+        of time spans, see
+        <citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>7</manvolnum></citerefentry>.
+        </para></listitem>
+      </varlistentry>
     </variablelist>
   </refsect1>
 

man/org.freedesktop.login1.xml

@@ -245,6 +245,8 @@ node /org/freedesktop/login1 {
       readonly t SessionsMax = ...;
       @org.freedesktop.DBus.Property.EmitsChangedSignal("false")
       readonly t NCurrentSessions = ...;
+      @org.freedesktop.DBus.Property.EmitsChangedSignal("const")
+      readonly t StopIdleSessionUSec = ...;
   };
   interface org.freedesktop.DBus.Peer { ... };
   interface org.freedesktop.DBus.Introspectable { ... };
@@ -262,6 +264,8 @@ node /org/freedesktop/login1 {
 
     <!--property HandleHibernateKeyLongPress is not documented!-->
 
+    <!--property StopIdleSessionUSec is not documented!-->
+
     <!--Autogenerated cross-references for systemd.directives, do not edit-->
 
     <variablelist class="dbus-interface" generated="True" extra-ref="org.freedesktop.login1.Manager"/>
@@ -490,6 +494,8 @@ node /org/freedesktop/login1 {
 
     <variablelist class="dbus-property" generated="True" extra-ref="NCurrentSessions"/>
 
+    <variablelist class="dbus-property" generated="True" extra-ref="StopIdleSessionUSec"/>
+
     <!--End of Autogenerated section-->
 
     <refsect2>

src/login/logind-core.c

@@ -71,6 +71,8 @@ void manager_reset_config(Manager *m) {
 
         m->kill_only_users = strv_free(m->kill_only_users);
         m->kill_exclude_users = strv_free(m->kill_exclude_users);
+
+        m->stop_idle_session_usec = USEC_INFINITY;
 }
 
 int manager_parse_config_file(Manager *m) {

src/login/logind-dbus.c

@@ -3402,6 +3402,7 @@ static const sd_bus_vtable manager_vtable[] = {
         SD_BUS_PROPERTY("SessionsMax", "t", NULL, offsetof(Manager, sessions_max), SD_BUS_VTABLE_PROPERTY_CONST),
         SD_BUS_PROPERTY("NCurrentSessions", "t", property_get_hashmap_size, offsetof(Manager, sessions), 0),
         SD_BUS_PROPERTY("UserTasksMax", "t", property_get_compat_user_tasks_max, 0, SD_BUS_VTABLE_PROPERTY_CONST|SD_BUS_VTABLE_HIDDEN),
+        SD_BUS_PROPERTY("StopIdleSessionUSec", "t", NULL, offsetof(Manager, stop_idle_session_usec), SD_BUS_VTABLE_PROPERTY_CONST),
 
         SD_BUS_METHOD_WITH_ARGS("GetSession",
                                 SD_BUS_ARGS("s", session_id),

src/login/logind-gperf.gperf

@@ -50,3 +50,4 @@ Login.RemoveIPC,                    config_parse_bool,                  0, offse
 Login.InhibitorsMax,                config_parse_uint64,                0, offsetof(Manager, inhibitors_max)
 Login.SessionsMax,                  config_parse_uint64,                0, offsetof(Manager, sessions_max)
 Login.UserTasksMax,                 config_parse_compat_user_tasks_max, 0, 0
+Login.StopIdleSessionSec,           config_parse_sec_fix_0,             0, offsetof(Manager, stop_idle_session_usec)

src/login/logind-session.c

@@ -152,6 +152,8 @@ Session* session_free(Session *s) {
         free(s->state_file);
         free(s->fifo_path);
 
+        sd_event_source_unref(s->stop_on_idle_event_source);
+
         return mfree(s);
 }
 
@@ -697,6 +699,55 @@ static int session_start_scope(Session *s, sd_bus_message *properties, sd_bus_er
         return 0;
 }
 
+static int session_dispatch_stop_on_idle(sd_event_source *source, uint64_t t, void *userdata) {
+        Session *s = userdata;
+        dual_timestamp ts;
+        int r, idle;
+
+        assert(s);
+
+        if (s->stopping)
+                return 0;
+
+        idle = session_get_idle_hint(s, &ts);
+        if (idle) {
+                log_debug("Session \"%s\" of user \"%s\" is idle, stopping.", s->id, s->user->user_record->user_name);
+
+                return session_stop(s, /* force */ true);
+        }
+
+        r = sd_event_source_set_time(source, usec_add(ts.monotonic, s->manager->stop_idle_session_usec));
+        if (r < 0)
+                return log_error_errno(r, "Failed to configure stop on idle session event source: %m");
+
+        r = sd_event_source_set_enabled(source, SD_EVENT_ONESHOT);
+        if (r < 0)
+                return log_error_errno(r, "Failed to enable stop on idle session event source: %m");
+
+        return 1;
+}
+
+static int session_setup_stop_on_idle_timer(Session *s) {
+        int r;
+
+        assert(s);
+
+        if (s->manager->stop_idle_session_usec == USEC_INFINITY)
+                return 0;
+
+        r = sd_event_add_time_relative(
+                        s->manager->event,
+                        &s->stop_on_idle_event_source,
+                        CLOCK_MONOTONIC,
+                        s->manager->stop_idle_session_usec,
+                        0,
+                        session_dispatch_stop_on_idle, s);
+        if (r < 0)
+                return log_error_errno(r, "Failed to add stop on idle session event source: %m");
+
+        return 0;
+}
+
 int session_start(Session *s, sd_bus_message *properties, sd_bus_error *error) {
         int r;
 
@@ -719,6 +770,10 @@ int session_start(Session *s, sd_bus_message *properties, sd_bus_error *error) {
         if (r < 0)
                 return r;
 
+        r = session_setup_stop_on_idle_timer(s);
+        if (r < 0)
+                return r;
+
         log_struct(s->class == SESSION_BACKGROUND ? LOG_DEBUG : LOG_INFO,
                    "MESSAGE_ID=" SD_MESSAGE_SESSION_START_STR,
                    "SESSION_ID=%s", s->id,
@@ -959,7 +1014,7 @@ static int get_process_ctty_atime(pid_t pid, usec_t *atime) {
 }
 
 int session_get_idle_hint(Session *s, dual_timestamp *t) {
-        usec_t atime = 0;
+        usec_t atime = 0, dtime = 0;
         int r;
 
         assert(s);
@@ -996,10 +1051,16 @@ found_atime:
         if (t)
                 dual_timestamp_from_realtime(t, atime);
 
-        if (s->manager->idle_action_usec <= 0)
+        if (s->manager->idle_action_usec > 0 && s->manager->stop_idle_session_usec != USEC_INFINITY)
+                dtime = MIN(s->manager->idle_action_usec, s->manager->stop_idle_session_usec);
+        else if (s->manager->idle_action_usec > 0)
+                dtime = s->manager->idle_action_usec;
+        else if (s->manager->stop_idle_session_usec != USEC_INFINITY)
+                dtime = s->manager->stop_idle_session_usec;
+        else
                 return false;
 
-        return usec_add(atime, s->manager->idle_action_usec) <= now(CLOCK_REALTIME);
+        return usec_add(atime, dtime) <= now(CLOCK_REALTIME);
 }
 
 int session_set_idle_hint(Session *s, bool b) {

src/login/logind-session.h

@@ -115,6 +115,8 @@ struct Session {
         Hashmap *devices;
         sd_bus_track *track;
 
+        sd_event_source *stop_on_idle_event_source;
+
         LIST_FIELDS(Session, sessions_by_user);
         LIST_FIELDS(Session, sessions_by_seat);
 

src/login/logind.conf.in

@@ -46,3 +46,4 @@
 #RemoveIPC=yes
 #InhibitorsMax=8192
 #SessionsMax=8192
+#StopIdleSessionSec=infinity

src/login/logind.h

@@ -96,6 +96,8 @@ struct Manager {
         HandleAction idle_action;
         bool was_idle;
 
+        usec_t stop_idle_session_usec;
+
         HandleAction handle_power_key;
         HandleAction handle_power_key_long_press;
         HandleAction handle_reboot_key;