src/login/logind-session.c

	logind-session.c revision ce540a24d53e1751a5b69224d5a7f5a59f2de7ad
/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/

/***
  This file is part of systemd.

  Copyright 2011 Lennart Poettering

  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 <fcntl.h>
#include <linux/vt.h>
#include <linux/kd.h>
#include <signal.h>
#include <string.h>
#include <sys/ioctl.h>
#include <unistd.h>

#include "sd-id128.h"
#include "sd-messages.h"
#include "strv.h"
#include "util.h"
#include "mkdir.h"
#include "path-util.h"
#include "fileio.h"
#include "audit.h"
#include "bus-util.h"
#include "bus-error.h"
#include "logind-session.h"

#define RELEASE_USEC (20*USEC_PER_SEC)

static void session_remove_fifo(Session *s);

Session* session_new(Manager *m, const char *id) {
        Session *s;

        assert(m);
        assert(id);
        assert(session_id_valid(id));

        s = new0(Session, 1);
        if (!s)
                return NULL;

        s->state_file = strappend("/run/systemd/sessions/", id);
        if (!s->state_file) {
                free(s);
                return NULL;
        }

        s->devices = hashmap_new(&devt_hash_ops);
        if (!s->devices) {
                free(s->state_file);
                free(s);
                return NULL;
        }

        s->id = basename(s->state_file);

        if (hashmap_put(m->sessions, s->id, s) < 0) {
                hashmap_free(s->devices);
                free(s->state_file);
                free(s);
                return NULL;
        }

        s->manager = m;
        s->fifo_fd = -1;
        s->vtfd = -1;

        return s;
}

void session_free(Session *s) {
        SessionDevice *sd;

        assert(s);

        if (s->in_gc_queue)
                LIST_REMOVE(gc_queue, s->manager->session_gc_queue, s);

        s->timer_event_source = sd_event_source_unref(s->timer_event_source);

        session_remove_fifo(s);

        session_drop_controller(s);

        while ((sd = hashmap_first(s->devices)))
                session_device_free(sd);

        hashmap_free(s->devices);

        if (s->user) {
                LIST_REMOVE(sessions_by_user, s->user->sessions, s);

                if (s->user->display == s)
                        s->user->display = NULL;
        }

        if (s->seat) {
                if (s->seat->active == s)
                        s->seat->active = NULL;
                if (s->seat->pending_switch == s)
                        s->seat->pending_switch = NULL;

                seat_evict_position(s->seat, s);
                LIST_REMOVE(sessions_by_seat, s->seat->sessions, s);
        }

        if (s->scope) {
                hashmap_remove(s->manager->session_units, s->scope);
                free(s->scope);
        }

        free(s->scope_job);

        sd_bus_message_unref(s->create_message);

        free(s->tty);
        free(s->display);
        free(s->remote_host);
        free(s->remote_user);
        free(s->service);
        free(s->desktop);

        hashmap_remove(s->manager->sessions, s->id);

        free(s->state_file);
        free(s);
}

void session_set_user(Session *s, User *u) {
        assert(s);
        assert(!s->user);

        s->user = u;
        LIST_PREPEND(sessions_by_user, u->sessions, s);
}

int session_save(Session *s) {
        _cleanup_free_ char *temp_path = NULL;
        _cleanup_fclose_ FILE *f = NULL;
        int r = 0;

        assert(s);

        if (!s->user)
                return -ESTALE;

        if (!s->started)
                return 0;

        r = mkdir_safe_label("/run/systemd/sessions", 0755, 0, 0);
        if (r < 0)
                goto finish;

        r = fopen_temporary(s->state_file, &f, &temp_path);
        if (r < 0)
                goto finish;

        assert(s->user);

        fchmod(fileno(f), 0644);

        fprintf(f,
                "# This is private data. Do not parse.\n"
                "UID="UID_FMT"\n"
                "USER=%s\n"
                "ACTIVE=%i\n"
                "STATE=%s\n"
                "REMOTE=%i\n",
                s->user->uid,
                s->user->name,
                session_is_active(s),
                session_state_to_string(session_get_state(s)),
                s->remote);

        if (s->type >= 0)
                fprintf(f, "TYPE=%s\n", session_type_to_string(s->type));

        if (s->class >= 0)
                fprintf(f, "CLASS=%s\n", session_class_to_string(s->class));

        if (s->scope)
                fprintf(f, "SCOPE=%s\n", s->scope);
        if (s->scope_job)
                fprintf(f, "SCOPE_JOB=%s\n", s->scope_job);

        if (s->fifo_path)
                fprintf(f, "FIFO=%s\n", s->fifo_path);

        if (s->seat)
                fprintf(f, "SEAT=%s\n", s->seat->id);

        if (s->tty)
                fprintf(f, "TTY=%s\n", s->tty);

        if (s->display)
                fprintf(f, "DISPLAY=%s\n", s->display);

        if (s->remote_host) {
                _cleanup_free_ char *escaped;

                escaped = cescape(s->remote_host);
                if (!escaped) {
                        r = -ENOMEM;
                        goto finish;
                }

                fprintf(f, "REMOTE_HOST=%s\n", escaped);
        }

        if (s->remote_user) {
                _cleanup_free_ char *escaped;

                escaped = cescape(s->remote_user);
                if (!escaped) {
                        r = -ENOMEM;
                        goto finish;
                }

                fprintf(f, "REMOTE_USER=%s\n", escaped);
        }

        if (s->service) {
                _cleanup_free_ char *escaped;

                escaped = cescape(s->service);
                if (!escaped) {
                        r = -ENOMEM;
                        goto finish;
                }

                fprintf(f, "SERVICE=%s\n", escaped);
        }

        if (s->desktop) {
                _cleanup_free_ char *escaped;


                escaped = cescape(s->desktop);
                if (!escaped) {
                        r = -ENOMEM;
                        goto finish;
                }

                fprintf(f, "DESKTOP=%s\n", escaped);
        }

        if (s->seat && seat_has_vts(s->seat))
                fprintf(f, "VTNR=%u\n", s->vtnr);

        if (!s->vtnr)
                fprintf(f, "POS=%u\n", s->pos);

        if (s->leader > 0)
                fprintf(f, "LEADER="PID_FMT"\n", s->leader);

        if (s->audit_id > 0)
                fprintf(f, "AUDIT=%"PRIu32"\n", s->audit_id);

        if (dual_timestamp_is_set(&s->timestamp))
                fprintf(f,
                        "REALTIME="USEC_FMT"\n"
                        "MONOTONIC="USEC_FMT"\n",
                        s->timestamp.realtime,
                        s->timestamp.monotonic);

        if (s->controller)
                fprintf(f, "CONTROLLER=%s\n", s->controller);

        fflush(f);

        if (ferror(f) || rename(temp_path, s->state_file) < 0) {
                r = -errno;
                unlink(s->state_file);
                unlink(temp_path);
        }

finish:
        if (r < 0)
                log_error("Failed to save session data %s: %s", s->state_file, strerror(-r));

        return r;
}

int session_load(Session *s) {
        _cleanup_free_ char *remote = NULL,
                *seat = NULL,
                *vtnr = NULL,
                *pos = NULL,
                *leader = NULL,
                *type = NULL,
                *class = NULL,
                *uid = NULL,
                *realtime = NULL,
                *monotonic = NULL,
                *controller = NULL;

        int k, r;

        assert(s);

        r = parse_env_file(s->state_file, NEWLINE,
                           "REMOTE",         &remote,
                           "SCOPE",          &s->scope,
                           "SCOPE_JOB",      &s->scope_job,
                           "FIFO",           &s->fifo_path,
                           "SEAT",           &seat,
                           "TTY",            &s->tty,
                           "DISPLAY",        &s->display,
                           "REMOTE_HOST",    &s->remote_host,
                           "REMOTE_USER",    &s->remote_user,
                           "SERVICE",        &s->service,
                           "DESKTOP",        &s->desktop,
                           "VTNR",           &vtnr,
                           "POS",            &pos,
                           "LEADER",         &leader,
                           "TYPE",           &type,
                           "CLASS",          &class,
                           "UID",            &uid,
                           "REALTIME",       &realtime,
                           "MONOTONIC",      &monotonic,
                           "CONTROLLER",     &controller,
                           NULL);

        if (r < 0) {
                log_error("Failed to read %s: %s", s->state_file, strerror(-r));
                return r;
        }

        if (!s->user) {
                uid_t u;
                User *user;

                if (!uid) {
                        log_error("UID not specified for session %s", s->id);
                        return -ENOENT;
                }

                r = parse_uid(uid, &u);
                if (r < 0)  {
                        log_error("Failed to parse UID value %s for session %s.", uid, s->id);
                        return r;
                }

                user = hashmap_get(s->manager->users, ULONG_TO_PTR((unsigned long) u));
                if (!user) {
                        log_error("User of session %s not known.", s->id);
                        return -ENOENT;
                }

                session_set_user(s, user);
        }

        if (remote) {
                k = parse_boolean(remote);
                if (k >= 0)
                        s->remote = k;
        }

        if (vtnr)
                safe_atou(vtnr, &s->vtnr);

        if (seat && !s->seat) {
                Seat *o;

                o = hashmap_get(s->manager->seats, seat);
                if (o)
                        r = seat_attach_session(o, s);
                if (!o || r < 0)
                        log_error("Cannot attach session %s to seat %s", s->id, seat);
        }

        if (!s->seat || !seat_has_vts(s->seat))
                s->vtnr = 0;

        if (pos && s->seat) {
                unsigned int npos;

                safe_atou(pos, &npos);
                seat_claim_position(s->seat, s, npos);
        }

        if (leader) {
                k = parse_pid(leader, &s->leader);
                if (k >= 0)
                        audit_session_from_pid(s->leader, &s->audit_id);
        }

        if (type) {
                SessionType t;

                t = session_type_from_string(type);
                if (t >= 0)
                        s->type = t;
        }

        if (class) {
                SessionClass c;

                c = session_class_from_string(class);
                if (c >= 0)
                        s->class = c;
        }

        if (s->fifo_path) {
                int fd;

                /* If we open an unopened pipe for reading we will not
                   get an EOF. to trigger an EOF we hence open it for
                   reading, but close it right-away which then will
                   trigger the EOF. */

                fd = session_create_fifo(s);
                safe_close(fd);
        }

        if (realtime) {
                unsigned long long l;
                if (sscanf(realtime, "%llu", &l) > 0)
                        s->timestamp.realtime = l;
        }

        if (monotonic) {
                unsigned long long l;
                if (sscanf(monotonic, "%llu", &l) > 0)
                        s->timestamp.monotonic = l;
        }

        if (controller) {
                if (bus_name_has_owner(s->manager->bus, controller, NULL) > 0)
                        session_set_controller(s, controller, false);
                else
                        session_restore_vt(s);
        }

        return r;
}

int session_activate(Session *s) {
        unsigned int num_pending;

        assert(s);
        assert(s->user);

        if (!s->seat)
                return -ENOTSUP;

        if (s->seat->active == s)
                return 0;

        /* on seats with VTs, we let VTs manage session-switching */
        if (seat_has_vts(s->seat)) {
                if (!s->vtnr)
                        return -ENOTSUP;

                return chvt(s->vtnr);
        }

        /* On seats without VTs, we implement session-switching in logind. We
         * try to pause all session-devices and wait until the session
         * controller acknowledged them. Once all devices are asleep, we simply
         * switch the active session and be done.
         * We save the session we want to switch to in seat->pending_switch and
         * seat_complete_switch() will perform the final switch. */

        s->seat->pending_switch = s;

        /* if no devices are running, immediately perform the session switch */
        num_pending = session_device_try_pause_all(s);
        if (!num_pending)
                seat_complete_switch(s->seat);

        return 0;
}

static int session_start_scope(Session *s) {
        int r;

        assert(s);
        assert(s->user);
        assert(s->user->slice);

        if (!s->scope) {
                _cleanup_bus_error_free_ sd_bus_error error = SD_BUS_ERROR_NULL;
                _cleanup_free_ char *description = NULL;
                char *scope, *job = NULL;

                description = strjoin("Session ", s->id, " of user ", s->user->name, NULL);
                if (!description)
                        return log_oom();

                scope = strjoin("session-", s->id, ".scope", NULL);
                if (!scope)
                        return log_oom();

                r = manager_start_scope(s->manager, scope, s->leader, s->user->slice, description, "systemd-logind.service", "systemd-user-sessions.service", &error, &job);
                if (r < 0) {
                        log_error("Failed to start session scope %s: %s %s",
                                  scope, bus_error_message(&error, r), error.name);
                        free(scope);
                        return r;
                } else {
                        s->scope = scope;

                        free(s->scope_job);
                        s->scope_job = job;
                }
        }

        if (s->scope)
                hashmap_put(s->manager->session_units, s->scope, s);

        return 0;
}

int session_start(Session *s) {
        int r;

        assert(s);

        if (!s->user)
                return -ESTALE;

        if (s->started)
                return 0;

        r = user_start(s->user);
        if (r < 0)
                return r;

        /* Create cgroup */
        r = session_start_scope(s);
        if (r < 0)
                return r;

        log_struct(s->class == SESSION_BACKGROUND ? LOG_DEBUG : LOG_INFO,
                   MESSAGE_ID(SD_MESSAGE_SESSION_START),
                   "SESSION_ID=%s", s->id,
                   "USER_ID=%s", s->user->name,
                   "LEADER="PID_FMT, s->leader,
                   "MESSAGE=New session %s of user %s.", s->id, s->user->name,
                   NULL);

        if (!dual_timestamp_is_set(&s->timestamp))
                dual_timestamp_get(&s->timestamp);

        if (s->seat)
                seat_read_active_vt(s->seat);

        s->started = true;

        user_elect_display(s->user);

        /* Save data */
        session_save(s);
        user_save(s->user);
        if (s->seat)
                seat_save(s->seat);

        /* Send signals */
        session_send_signal(s, true);
        user_send_changed(s->user, "Sessions", "Display", NULL);
        if (s->seat) {
                if (s->seat->active == s)
                        seat_send_changed(s->seat, "Sessions", "ActiveSession", NULL);
                else
                        seat_send_changed(s->seat, "Sessions", NULL);
        }

        return 0;
}

static int session_stop_scope(Session *s, bool force) {
        _cleanup_bus_error_free_ sd_bus_error error = SD_BUS_ERROR_NULL;
        char *job = NULL;
        int r;

        assert(s);

        if (!s->scope)
                return 0;

        if (force || manager_shall_kill(s->manager, s->user->name)) {
                r = manager_stop_unit(s->manager, s->scope, &error, &job);
                if (r < 0) {
                        log_error("Failed to stop session scope: %s", bus_error_message(&error, r));
                        return r;
                }

                free(s->scope_job);
                s->scope_job = job;
        } else {
                r = manager_abandon_scope(s->manager, s->scope, &error);
                if (r < 0) {
                        log_error("Failed to abandon session scope: %s", bus_error_message(&error, r));
                        return r;
                }
        }

        return 0;
}

int session_stop(Session *s, bool force) {
        int r;

        assert(s);

        if (!s->user)
                return -ESTALE;

        s->timer_event_source = sd_event_source_unref(s->timer_event_source);

        /* We are going down, don't care about FIFOs anymore */
        session_remove_fifo(s);

        /* Kill cgroup */
        r = session_stop_scope(s, force);

        s->stopping = true;

        user_elect_display(s->user);

        session_save(s);
        user_save(s->user);

        return r;
}

int session_finalize(Session *s) {
        int r = 0;
        SessionDevice *sd;

        assert(s);

        if (!s->user)
                return -ESTALE;

        if (s->started)
                log_struct(s->class == SESSION_BACKGROUND ? LOG_DEBUG : LOG_INFO,
                           MESSAGE_ID(SD_MESSAGE_SESSION_STOP),
                           "SESSION_ID=%s", s->id,
                           "USER_ID=%s", s->user->name,
                           "LEADER="PID_FMT, s->leader,
                           "MESSAGE=Removed session %s.", s->id,
                           NULL);

        s->timer_event_source = sd_event_source_unref(s->timer_event_source);

        /* Kill session devices */
        while ((sd = hashmap_first(s->devices)))
                session_device_free(sd);

        unlink(s->state_file);
        session_add_to_gc_queue(s);
        user_add_to_gc_queue(s->user);

        if (s->started) {
                session_send_signal(s, false);
                s->started = false;
        }

        if (s->seat) {
                if (s->seat->active == s)
                        seat_set_active(s->seat, NULL);

                seat_save(s->seat);
                seat_send_changed(s->seat, "Sessions", NULL);
        }

        user_save(s->user);
        user_send_changed(s->user, "Sessions", "Display", NULL);

        return r;
}

static int release_timeout_callback(sd_event_source *es, uint64_t usec, void *userdata) {
        Session *s = userdata;

        assert(es);
        assert(s);

        session_stop(s, false);
        return 0;
}

void session_release(Session *s) {
        assert(s);

        if (!s->started || s->stopping)
                return;

        if (!s->timer_event_source)
                sd_event_add_time(s->manager->event,
                                  &s->timer_event_source,
                                  CLOCK_MONOTONIC,
                                  now(CLOCK_MONOTONIC) + RELEASE_USEC, 0,
                                  release_timeout_callback, s);
}

bool session_is_active(Session *s) {
        assert(s);

        if (!s->seat)
                return true;

        return s->seat->active == s;
}

static int get_tty_atime(const char *tty, usec_t *atime) {
        _cleanup_free_ char *p = NULL;
        struct stat st;

        assert(tty);
        assert(atime);

        if (!path_is_absolute(tty)) {
                p = strappend("/dev/", tty);
                if (!p)
                        return -ENOMEM;

                tty = p;
        } else if (!path_startswith(tty, "/dev/"))
                return -ENOENT;

        if (lstat(tty, &st) < 0)
                return -errno;

        *atime = timespec_load(&st.st_atim);
        return 0;
}

static int get_process_ctty_atime(pid_t pid, usec_t *atime) {
        _cleanup_free_ char *p = NULL;
        int r;

        assert(pid > 0);
        assert(atime);

        r = get_ctty(pid, NULL, &p);
        if (r < 0)
                return r;

        return get_tty_atime(p, atime);
}

int session_get_idle_hint(Session *s, dual_timestamp *t) {
        usec_t atime = 0, n;
        int r;

        assert(s);

        /* Explicit idle hint is set */
        if (s->idle_hint) {
                if (t)
                        *t = s->idle_hint_timestamp;

                return s->idle_hint;
        }

        /* Graphical sessions should really implement a real
         * idle hint logic */
        if (s->display)
                goto dont_know;

        /* For sessions with an explicitly configured tty, let's check
         * its atime */
        if (s->tty) {
                r = get_tty_atime(s->tty, &atime);
                if (r >= 0)
                        goto found_atime;
        }

        /* For sessions with a leader but no explicitly configured
         * tty, let's check the controlling tty of the leader */
        if (s->leader > 0) {
                r = get_process_ctty_atime(s->leader, &atime);
                if (r >= 0)
                        goto found_atime;
        }

dont_know:
        if (t)
                *t = s->idle_hint_timestamp;

        return 0;

found_atime:
        if (t)
                dual_timestamp_from_realtime(t, atime);

        n = now(CLOCK_REALTIME);

        if (s->manager->idle_action_usec <= 0)
                return 0;

        return atime + s->manager->idle_action_usec <= n;
}

void session_set_idle_hint(Session *s, bool b) {
        assert(s);

        if (s->idle_hint == b)
                return;

        s->idle_hint = b;
        dual_timestamp_get(&s->idle_hint_timestamp);

        session_send_changed(s, "IdleHint", "IdleSinceHint", "IdleSinceHintMonotonic", NULL);

        if (s->seat)
                seat_send_changed(s->seat, "IdleHint", "IdleSinceHint", "IdleSinceHintMonotonic", NULL);

        user_send_changed(s->user, "IdleHint", "IdleSinceHint", "IdleSinceHintMonotonic", NULL);
        manager_send_changed(s->manager, "IdleHint", "IdleSinceHint", "IdleSinceHintMonotonic", NULL);
}

static int session_dispatch_fifo(sd_event_source *es, int fd, uint32_t revents, void *userdata) {
        Session *s = userdata;

        assert(s);
        assert(s->fifo_fd == fd);

        /* EOF on the FIFO means the session died abnormally. */

        session_remove_fifo(s);
        session_stop(s, false);

        return 1;
}

int session_create_fifo(Session *s) {
        int r;

        assert(s);

        /* Create FIFO */
        if (!s->fifo_path) {
                r = mkdir_safe_label("/run/systemd/sessions", 0755, 0, 0);
                if (r < 0)
                        return r;

                if (asprintf(&s->fifo_path, "/run/systemd/sessions/%s.ref", s->id) < 0)
                        return -ENOMEM;

                if (mkfifo(s->fifo_path, 0600) < 0 && errno != EEXIST)
                        return -errno;
        }

        /* Open reading side */
        if (s->fifo_fd < 0) {
                s->fifo_fd = open(s->fifo_path, O_RDONLY|O_CLOEXEC|O_NDELAY);
                if (s->fifo_fd < 0)
                        return -errno;

        }

        if (!s->fifo_event_source) {
                r = sd_event_add_io(s->manager->event, &s->fifo_event_source, s->fifo_fd, 0, session_dispatch_fifo, s);
                if (r < 0)
                        return r;

                r = sd_event_source_set_priority(s->fifo_event_source, SD_EVENT_PRIORITY_IDLE);
                if (r < 0)
                        return r;
        }

        /* Open writing side */
        r = open(s->fifo_path, O_WRONLY|O_CLOEXEC|O_NDELAY);
        if (r < 0)
                return -errno;

        return r;
}

static void session_remove_fifo(Session *s) {
        assert(s);

        s->fifo_event_source = sd_event_source_unref(s->fifo_event_source);
        s->fifo_fd = safe_close(s->fifo_fd);

        if (s->fifo_path) {
                unlink(s->fifo_path);
                free(s->fifo_path);
                s->fifo_path = NULL;
        }
}

bool session_check_gc(Session *s, bool drop_not_started) {
        assert(s);

        if (drop_not_started && !s->started)
                return false;

        if (!s->user)
                return false;

        if (s->fifo_fd >= 0) {
                if (pipe_eof(s->fifo_fd) <= 0)
                        return true;
        }

        if (s->scope_job && manager_job_is_active(s->manager, s->scope_job))
                return true;

        if (s->scope && manager_unit_is_active(s->manager, s->scope))
                return true;

        return false;
}

void session_add_to_gc_queue(Session *s) {
        assert(s);

        if (s->in_gc_queue)
                return;

        LIST_PREPEND(gc_queue, s->manager->session_gc_queue, s);
        s->in_gc_queue = true;
}

SessionState session_get_state(Session *s) {
        assert(s);

        /* always check closing first */
        if (s->stopping || s->timer_event_source)
                return SESSION_CLOSING;

        if (s->scope_job || s->fifo_fd < 0)
                return SESSION_OPENING;

        if (session_is_active(s))
                return SESSION_ACTIVE;

        return SESSION_ONLINE;
}

int session_kill(Session *s, KillWho who, int signo) {
        assert(s);

        if (!s->scope)
                return -ESRCH;

        return manager_kill_unit(s->manager, s->scope, who, signo, NULL);
}

static int session_open_vt(Session *s) {
        char path[sizeof("/dev/tty") + DECIMAL_STR_MAX(s->vtnr)];

        if (s->vtnr < 1)
                return -ENODEV;

        if (s->vtfd >= 0)
                return s->vtfd;

        sprintf(path, "/dev/tty%u", s->vtnr);
        s->vtfd = open(path, O_RDWR | O_CLOEXEC | O_NONBLOCK | O_NOCTTY);
        if (s->vtfd < 0) {
                log_error("cannot open VT %s of session %s: %m", path, s->id);
                return -errno;
        }

        return s->vtfd;
}

int session_prepare_vt(Session *s) {
        int vt, r;
        struct vt_mode mode = { 0 };

        if (s->vtnr < 1)
                return 0;

        vt = session_open_vt(s);
        if (vt < 0)
                return vt;

        r = fchown(vt, s->user->uid, -1);
        if (r < 0) {
                r = -errno;
                log_error("Cannot change owner of /dev/tty%u: %m", s->vtnr);
                goto error;
        }

        r = ioctl(vt, KDSKBMODE, K_OFF);
        if (r < 0) {
                r = -errno;
                log_error("Cannot set K_OFF on /dev/tty%u: %m", s->vtnr);
                goto error;
        }

        r = ioctl(vt, KDSETMODE, KD_GRAPHICS);
        if (r < 0) {
                r = -errno;
                log_error("Cannot set KD_GRAPHICS on /dev/tty%u: %m", s->vtnr);
                goto error;
        }

        /* Oh, thanks to the VT layer, VT_AUTO does not work with KD_GRAPHICS.
         * So we need a dummy handler here which just acknowledges *all* VT
         * switch requests. */
        mode.mode = VT_PROCESS;
        mode.relsig = SIGRTMIN;
        mode.acqsig = SIGRTMIN + 1;
        r = ioctl(vt, VT_SETMODE, &mode);
        if (r < 0) {
                r = -errno;
                log_error("Cannot set VT_PROCESS on /dev/tty%u: %m", s->vtnr);
                goto error;
        }

        return 0;

error:
        session_restore_vt(s);
        return r;
}

void session_restore_vt(Session *s) {
        _cleanup_free_ char *utf8 = NULL;
        int vt, kb = K_XLATE;
        struct vt_mode mode = { 0 };

        vt = session_open_vt(s);
        if (vt < 0)
                return;

        ioctl(vt, KDSETMODE, KD_TEXT);

        if (read_one_line_file("/sys/module/vt/parameters/default_utf8", &utf8) >= 0 && *utf8 == '1')
                kb = K_UNICODE;

        ioctl(vt, KDSKBMODE, kb);

        mode.mode = VT_AUTO;
        ioctl(vt, VT_SETMODE, &mode);

        fchown(vt, 0, -1);

        s->vtfd = safe_close(s->vtfd);
}

void session_leave_vt(Session *s) {
        int r;

        assert(s);

        /* This is called whenever we get a VT-switch signal from the kernel.
         * We acknowledge all of them unconditionally. Note that session are
         * free to overwrite those handlers and we only register them for
         * sessions with controllers. Legacy sessions are not affected.
         * However, if we switch from a non-legacy to a legacy session, we must
         * make sure to pause all device before acknowledging the switch. We
         * process the real switch only after we are notified via sysfs, so the
         * legacy session might have already started using the devices. If we
         * don't pause the devices before the switch, we might confuse the
         * session we switch to. */

        if (s->vtfd < 0)
                return;

        session_device_pause_all(s);
        r = ioctl(s->vtfd, VT_RELDISP, 1);
        if (r < 0)
                log_debug("Cannot release VT of session %s: %m", s->id);
}

bool session_is_controller(Session *s, const char *sender) {
        assert(s);

        return streq_ptr(s->controller, sender);
}

static void session_release_controller(Session *s, bool notify) {
        _cleanup_free_ char *name = NULL;
        SessionDevice *sd;

        if (!s->controller)
                return;

        name = s->controller;

        /* By resetting the controller before releasing the devices, we won't
         * send notification signals. This avoids sending useless notifications
         * if the controller is released on disconnects. */
        if (!notify)
                s->controller = NULL;

        while ((sd = hashmap_first(s->devices)))
                session_device_free(sd);

        s->controller = NULL;
        manager_drop_busname(s->manager, name);
}

int session_set_controller(Session *s, const char *sender, bool force) {
        _cleanup_free_ char *name = NULL;
        int r;

        assert(s);
        assert(sender);

        if (session_is_controller(s, sender))
                return 0;
        if (s->controller && !force)
                return -EBUSY;

        name = strdup(sender);
        if (!name)
                return -ENOMEM;

        r = manager_watch_busname(s->manager, name);
        if (r)
                return r;

        /* When setting a session controller, we forcibly mute the VT and set
         * it into graphics-mode. Applications can override that by changing
         * VT state after calling TakeControl(). However, this serves as a good
         * default and well-behaving controllers can now ignore VTs entirely.
         * Note that we reset the VT on ReleaseControl() and if the controller
         * exits.
         * If logind crashes/restarts, we restore the controller during restart
         * or reset the VT in case it crashed/exited, too. */
        r = session_prepare_vt(s);
        if (r < 0) {
                manager_drop_busname(s->manager, name);
                return r;
        }

        session_release_controller(s, true);
        s->controller = name;
        name = NULL;
        session_save(s);

        return 0;
}

void session_drop_controller(Session *s) {
        assert(s);

        if (!s->controller)
                return;

        session_release_controller(s, false);
        session_save(s);
        session_restore_vt(s);
}

static const char* const session_state_table[_SESSION_STATE_MAX] = {
        [SESSION_OPENING] = "opening",
        [SESSION_ONLINE] = "online",
        [SESSION_ACTIVE] = "active",
        [SESSION_CLOSING] = "closing"
};

DEFINE_STRING_TABLE_LOOKUP(session_state, SessionState);

static const char* const session_type_table[_SESSION_TYPE_MAX] = {
        [SESSION_UNSPECIFIED] = "unspecified",
        [SESSION_TTY] = "tty",
        [SESSION_X11] = "x11",
        [SESSION_WAYLAND] = "wayland",
        [SESSION_MIR] = "mir",
        [SESSION_WEB] = "web",
};

DEFINE_STRING_TABLE_LOOKUP(session_type, SessionType);

static const char* const session_class_table[_SESSION_CLASS_MAX] = {
        [SESSION_USER] = "user",
        [SESSION_GREETER] = "greeter",
        [SESSION_LOCK_SCREEN] = "lock-screen",
        [SESSION_BACKGROUND] = "background"
};

DEFINE_STRING_TABLE_LOOKUP(session_class, SessionClass);

static const char* const kill_who_table[_KILL_WHO_MAX] = {
        [KILL_LEADER] = "leader",
        [KILL_ALL] = "all"
};

DEFINE_STRING_TABLE_LOOKUP(kill_who, KillWho);