logind: log wall messages to the journal

Currently kde installs a fake utmp session to listen for this. This provides an
alternative mechanism as discussed in #23574.

Example with 'shutdown 6 -r' and shutdown -c':
    PRIORITY=6
    SYSLOG_FACILITY=4
    SYSLOG_IDENTIFIER=systemd-logind
    ...
    CODE_FILE=src/login/logind-utmp.c
    CODE_LINE=90
    CODE_FUNC=warn_wall
    MESSAGE_ID=9e7066279dc8403da79ce4b1a69064b2
    OPERATOR=root
    MESSAGE=The system will reboot at Thu 2022-06-30 12:16:43 CEST!
    ACTION=reboot

    PRIORITY=5
    SYSLOG_FACILITY=4
    SYSLOG_IDENTIFIER=systemd-logind
    ...
    OPERATOR=root
    CODE_FILE=src/login/logind-dbus.c
    CODE_LINE=2407
    CODE_FUNC=method_cancel_scheduled_shutdown
    MESSAGE=System shutdown has been cancelled
    MESSAGE_ID=249f6fb9e6e2428c96f3f0875681ffa3
    ACTION=reboot

1 files changed, 8 insertions, 2 deletions

diff --git a/src/login/logind-dbus.c b/src/login/logind-dbus.c
index 031b96e9f1..a426842bbb 100644
--- a/src/login/logind-dbus.c
+++ b/src/login/logind-dbus.c
@@ -2347,7 +2347,6 @@ static int method_cancel_scheduled_shutdown(sd_bus_message *message, void *userd
 
         if (m->enable_wall_messages) {
                 _cleanup_(sd_bus_creds_unrefp) sd_bus_creds *creds = NULL;
-                _cleanup_free_ char *username = NULL;
                 const char *tty = NULL;
                 uid_t uid = 0;
 
@@ -2357,7 +2356,14 @@ static int method_cancel_scheduled_shutdown(sd_bus_message *message, void *userd
                         (void) sd_bus_creds_get_tty(creds, &tty);
                 }
 
-                username = uid_to_name(uid);
+                _cleanup_free_ char *username = uid_to_name(uid);
+
+                log_struct(LOG_INFO,
+                           LOG_MESSAGE("System shutdown has been cancelled"),
+                           "ACTION=%s", handle_action_to_string(a->handle),
+                           "MESSAGE_ID=" SD_MESSAGE_LOGIND_SHUTDOWN_CANCELED_STR,
+                           username ? "OPERATOR=%s" : NULL, username);
+
                 utmp_wall("System shutdown has been cancelled",
                           username, tty, logind_wall_tty_filter, m);
         }