logind: use named pipes instead of fifos to keep track of sessions so that we can reconnect later

7 files changed, 105 insertions, 61 deletions

diff --git a/src/logind-dbus.c b/src/logind-dbus.c
index 5997fb5d7a..ff500f3c6b 100644
--- a/src/logind-dbus.c
+++ b/src/logind-dbus.c
@@ -191,7 +191,7 @@ static int bus_manager_create_session(Manager *m, DBusMessage *message, DBusMess
         int r;
         char *id = NULL, *p;
         uint32_t vtnr = 0;
-        int pipe_fds[2] = { -1, -1 };
+        int fifo_fd = -1;
         DBusMessage *reply = NULL;
         bool b;
 
@@ -353,6 +353,12 @@ static int bus_manager_create_session(Manager *m, DBusMessage *message, DBusMess
 
                 if (session) {
 
+                        fifo_fd = session_create_fifo(session);
+                        if (fifo_fd < 0) {
+                                r = fifo_fd;
+                                goto fail;
+                        }
+
                         /* Session already exists, client is probably
                          * something like "su" which changes uid but
                          * is still the same audit session */
@@ -363,15 +369,6 @@ static int bus_manager_create_session(Manager *m, DBusMessage *message, DBusMess
                                 goto fail;
                         }
 
-                        /* Create a throw-away fd */
-                        if (pipe(pipe_fds) < 0) {
-                                r = -errno;
-                                goto fail;
-                        }
-
-                        close_nointr_nofail(pipe_fds[0]);
-                        pipe_fds[0] = -1;
-
                         p = session_bus_path(session);
                         if (!p) {
                                 r = -ENOMEM;
@@ -383,7 +380,7 @@ static int bus_manager_create_session(Manager *m, DBusMessage *message, DBusMess
                                         DBUS_TYPE_STRING, &session->id,
                                         DBUS_TYPE_OBJECT_PATH, &p,
                                         DBUS_TYPE_STRING, &session->user->runtime_path,
-                                        DBUS_TYPE_UNIX_FD, &pipe_fds[1],
+                                        DBUS_TYPE_UNIX_FD, &fifo_fd,
                                         DBUS_TYPE_INVALID);
                         free(p);
 
@@ -392,7 +389,7 @@ static int bus_manager_create_session(Manager *m, DBusMessage *message, DBusMess
                                 goto fail;
                         }
 
-                        close_nointr_nofail(pipe_fds[1]);
+                        close_nointr_nofail(fifo_fd);
                         *_reply = reply;
 
                         return 0;
@@ -467,16 +464,12 @@ static int bus_manager_create_session(Manager *m, DBusMessage *message, DBusMess
                 }
         }
 
-        if (pipe(pipe_fds) < 0) {
-                r = -errno;
+        fifo_fd = session_create_fifo(session);
+        if (fifo_fd < 0) {
+                r = fifo_fd;
                 goto fail;
         }
 
-        r = session_set_pipe_fd(session, pipe_fds[0]);
-        if (r < 0)
-                goto fail;
-        pipe_fds[0] = -1;
-
         if (s) {
                 r = seat_attach_session(s, session);
                 if (r < 0)
@@ -504,7 +497,7 @@ static int bus_manager_create_session(Manager *m, DBusMessage *message, DBusMess
                         DBUS_TYPE_STRING, &session->id,
                         DBUS_TYPE_OBJECT_PATH, &p,
                         DBUS_TYPE_STRING, &session->user->runtime_path,
-                        DBUS_TYPE_UNIX_FD, &pipe_fds[1],
+                        DBUS_TYPE_UNIX_FD, &fifo_fd,
                         DBUS_TYPE_INVALID);
         free(p);
 
@@ -513,7 +506,7 @@ static int bus_manager_create_session(Manager *m, DBusMessage *message, DBusMess
                 goto fail;
         }
 
-        close_nointr_nofail(pipe_fds[1]);
+        close_nointr_nofail(fifo_fd);
         *_reply = reply;
 
         return 0;
@@ -528,7 +521,8 @@ fail:
         if (user)
                 user_add_to_gc_queue(user);
 
-        close_pipe(pipe_fds);
+        if (fifo_fd >= 0)
+                close_nointr_nofail(fifo_fd);
 
         if (reply)
                 dbus_message_unref(reply);
@@ -611,7 +605,7 @@ static int attach_device(Manager *m, const char *seat, const char *sysfs) {
                 const char *p;
 
                 p = udev_list_entry_get_name(item);
-                if (!startswith(p, sysfs))
+                if (!path_startswith(p, sysfs))
                         continue;
 
                 t = strappend(p, "/uevent");
diff --git a/src/logind-seat.c b/src/logind-seat.c
index 5663aeea4b..1bc0570517 100644
--- a/src/logind-seat.c
+++ b/src/logind-seat.c
@@ -449,6 +449,9 @@ int seat_get_idle_hint(Seat *s, dual_timestamp *t) {
 int seat_check_gc(Seat *s) {
         assert(s);
 
+        if (!s->started)
+                return 0;
+
         if (seat_is_vtconsole(s))
                 return 1;
 
diff --git a/src/logind-session.c b/src/logind-session.c
index d68423bdcf..7671850003 100644
--- a/src/logind-session.c
+++ b/src/logind-session.c
@@ -23,6 +23,7 @@
 #include <string.h>
 #include <unistd.h>
 #include <sys/epoll.h>
+#include <fcntl.h>
 
 #include "logind-session.h"
 #include "strv.h"
@@ -56,7 +57,7 @@ Session* session_new(Manager *m, User *u, const char *id) {
         }
 
         s->manager = m;
-        s->pipe_fd = -1;
+        s->fifo_fd = -1;
         s->user = u;
 
         LIST_PREPEND(Session, sessions_by_user, u->sessions, s);
@@ -98,7 +99,7 @@ void session_free(Session *s) {
 
         hashmap_remove(s->manager->sessions, s->id);
 
-        session_unset_pipe_fd(s);
+        session_remove_fifo(s);
 
         free(s->state_file);
         free(s);
@@ -149,6 +150,11 @@ int session_save(Session *s) {
                         "CGROUP=%s\n",
                         s->cgroup_path);
 
+        if (s->fifo_path)
+                fprintf(f,
+                        "FIFO=%s\n",
+                        s->fifo_path);
+
         if (s->seat)
                 fprintf(f,
                         "SEAT=%s\n",
@@ -229,6 +235,7 @@ int session_load(Session *s) {
                            "REMOTE",         &remote,
                            "KILL_PROCESSES", &kill_processes,
                            "CGROUP",         &s->cgroup_path,
+                           "FIFO",           &s->fifo_path,
                            "SEAT",           &seat,
                            "TTY",            &s->tty,
                            "DISPLAY",        &s->display,
@@ -290,6 +297,8 @@ int session_load(Session *s) {
                         s->type = t;
         }
 
+        session_open_fifo(s);
+
 finish:
         free(remote);
         free(kill_processes);
@@ -746,43 +755,77 @@ void session_set_idle_hint(Session *s, bool b) {
                              "IdleSinceHintMonotonic\0");
 }
 
-int session_set_pipe_fd(Session *s, int fd) {
+int session_open_fifo(Session *s) {
         struct epoll_event ev;
         int r;
 
         assert(s);
-        assert(fd >= 0);
-        assert(s->pipe_fd < 0);
 
-        r = hashmap_put(s->manager->pipe_fds, INT_TO_PTR(fd + 1), s);
+        if (s->fifo_fd >= 0)
+                return 0;
+
+        if (!s->fifo_path)
+                return -EINVAL;
+
+        s->fifo_fd = open(s->fifo_path, O_RDONLY|O_CLOEXEC|O_NDELAY);
+        if (s->fifo_fd < 0)
+                return -errno;
+
+        r = hashmap_put(s->manager->fifo_fds, INT_TO_PTR(s->fifo_fd + 1), s);
         if (r < 0)
                 return r;
 
         zero(ev);
         ev.events = 0;
-        ev.data.u32 = FD_PIPE_BASE + fd;
+        ev.data.u32 = FD_FIFO_BASE + s->fifo_fd;
 
-        if (epoll_ctl(s->manager->epoll_fd, EPOLL_CTL_ADD, fd, &ev) < 0) {
-                assert_se(hashmap_remove(s->manager->pipe_fds, INT_TO_PTR(fd + 1)) == s);
+        if (epoll_ctl(s->manager->epoll_fd, EPOLL_CTL_ADD, s->fifo_fd, &ev) < 0)
                 return -errno;
-        }
 
-        s->pipe_fd = fd;
         return 0;
 }
 
-void session_unset_pipe_fd(Session *s) {
+int session_create_fifo(Session *s) {
+        int r;
+
         assert(s);
 
-        if (s->pipe_fd < 0)
-                return;
+        if (!s->fifo_path) {
+                if (asprintf(&s->fifo_path, "/run/systemd/sessions/%s.ref", s->id) < 0)
+                        return -ENOMEM;
 
-        assert_se(hashmap_remove(s->manager->pipe_fds, INT_TO_PTR(s->pipe_fd + 1)) == s);
+                if (mkfifo(s->fifo_path, 0600) < 0 && errno != EEXIST)
+                        return -errno;
+        }
 
-        assert_se(epoll_ctl(s->manager->epoll_fd, EPOLL_CTL_DEL, s->pipe_fd, NULL) == 0);
+        /* Open reading side */
+        r = session_open_fifo(s);
+        if (r < 0)
+                return r;
+
+        /* Open writing side */
+        r = open(s->fifo_path, O_WRONLY|O_CLOEXEC|O_NDELAY);
+        if (r < 0)
+                return -errno;
 
-        close_nointr_nofail(s->pipe_fd);
-        s->pipe_fd = -1;
+        return r;
+}
+
+void session_remove_fifo(Session *s) {
+        assert(s);
+
+        if (s->fifo_fd >= 0) {
+                assert_se(hashmap_remove(s->manager->fifo_fds, INT_TO_PTR(s->fifo_fd + 1)) == s);
+                assert_se(epoll_ctl(s->manager->epoll_fd, EPOLL_CTL_DEL, s->fifo_fd, NULL) == 0);
+                close_nointr_nofail(s->fifo_fd);
+                s->fifo_fd = -1;
+        }
+
+        if (s->fifo_path) {
+                unlink(s->fifo_path);
+                free(s->fifo_path);
+                s->fifo_path = NULL;
+        }
 }
 
 int session_check_gc(Session *s) {
@@ -790,9 +833,12 @@ int session_check_gc(Session *s) {
 
         assert(s);
 
-        if (s->pipe_fd >= 0) {
+        if (!s->started)
+                return 0;
+
+        if (s->fifo_fd >= 0) {
 
-                r = pipe_eof(s->pipe_fd);
+                r = pipe_eof(s->fifo_fd);
                 if (r < 0)
                         return r;
 
diff --git a/src/logind-session.h b/src/logind-session.h
index 72f85caaaf..d0cf0ed886 100644
--- a/src/logind-session.h
+++ b/src/logind-session.h
@@ -65,7 +65,8 @@ struct Session {
         pid_t leader;
         uint32_t audit_id;
 
-        int pipe_fd;
+        int fifo_fd;
+        char *fifo_path;
 
         char *cgroup_path;
         char **controllers, **reset_controllers;
@@ -91,8 +92,9 @@ int session_activate(Session *s);
 bool session_is_active(Session *s);
 int session_get_idle_hint(Session *s, dual_timestamp *t);
 void session_set_idle_hint(Session *s, bool b);
-int session_set_pipe_fd(Session *s, int fd);
-void session_unset_pipe_fd(Session *s);
+int session_open_fifo(Session *s);
+int session_create_fifo(Session *s);
+void session_remove_fifo(Session *s);
 int session_start(Session *s);
 int session_stop(Session *s);
 int session_save(Session *s);
diff --git a/src/logind-user.c b/src/logind-user.c
index 177e88200a..4335bf6462 100644
--- a/src/logind-user.c
+++ b/src/logind-user.c
@@ -459,6 +459,9 @@ int user_check_gc(User *u) {
 
         assert(u);
 
+        if (!u->started)
+                return 0;
+
         if (u->sessions)
                 return 1;
 
diff --git a/src/logind.c b/src/logind.c
index a0a89c0689..d38d7d51c3 100644
--- a/src/logind.c
+++ b/src/logind.c
@@ -52,7 +52,7 @@ Manager *manager_new(void) {
         m->sessions = hashmap_new(string_hash_func, string_compare_func);
         m->users = hashmap_new(trivial_hash_func, trivial_compare_func);
         m->cgroups = hashmap_new(string_hash_func, string_compare_func);
-        m->pipe_fds = hashmap_new(trivial_hash_func, trivial_compare_func);
+        m->fifo_fds = hashmap_new(trivial_hash_func, trivial_compare_func);
 
         if (!m->devices || !m->seats || !m->sessions || !m->users) {
                 manager_free(m);
@@ -98,7 +98,7 @@ void manager_free(Manager *m) {
         hashmap_free(m->devices);
         hashmap_free(m->seats);
         hashmap_free(m->cgroups);
-        hashmap_free(m->pipe_fds);
+        hashmap_free(m->fifo_fds);
 
         if (m->console_active_fd >= 0)
                 close_nointr_nofail(m->console_active_fd);
@@ -802,9 +802,9 @@ static void manager_pipe_notify_eof(Manager *m, int fd) {
         assert_se(m);
         assert_se(fd >= 0);
 
-        assert_se(s = hashmap_get(m->pipe_fds, INT_TO_PTR(fd + 1)));
-        assert(s->pipe_fd == fd);
-        session_unset_pipe_fd(s);
+        assert_se(s = hashmap_get(m->fifo_fds, INT_TO_PTR(fd + 1)));
+        assert(s->fifo_fd == fd);
+        session_remove_fifo(s);
 
         session_stop(s);
 }
@@ -1081,9 +1081,6 @@ int manager_startup(Manager *m) {
         manager_enumerate_users(m);
         manager_enumerate_sessions(m);
 
-        /* Get rid of objects that are no longer used */
-        manager_gc(m);
-
         /* And start everything */
         HASHMAP_FOREACH(seat, m->seats, i)
                 seat_start(seat);
@@ -1139,8 +1136,8 @@ int manager_run(Manager *m) {
                         break;
 
                 default:
-                        if (event.data.u32 >= FD_PIPE_BASE)
-                                manager_pipe_notify_eof(m, event.data.u32 - FD_PIPE_BASE);
+                        if (event.data.u32 >= FD_FIFO_BASE)
+                                manager_pipe_notify_eof(m, event.data.u32 - FD_FIFO_BASE);
                 }
         }
 
diff --git a/src/logind.h b/src/logind.h
index 309541415d..9b9f38bb80 100644
--- a/src/logind.h
+++ b/src/logind.h
@@ -37,15 +37,14 @@
  * spawn user systemd
  * direct client API
  * add configuration file
- * D-Bus method: AttachDevices(seat, devices[]);
- * use named pipes to detect when a session dies
  * verify access to SetIdleHint
+ *
+ * udev:
  * drop redundant udev_device_get_is_initialized() use as soon as libudev is fixed
  * properly escape/remove : and . from seat names in udev rules
  * use device_has_tag() as soon as it is available
  * trigger based on libudev if available
  * enumerate recursively with libudev when triggering
- * make sure IMPORT{parent}="ID_SEAT" works between usb hub and sound card
  *
  * non-local X11 server
  * reboot/shutdown halt management
@@ -94,7 +93,7 @@ struct Manager {
         unsigned long session_counter;
 
         Hashmap *cgroups;
-        Hashmap *pipe_fds;
+        Hashmap *fifo_fds;
 };
 
 enum {
@@ -102,7 +101,7 @@ enum {
         FD_VCSA_UDEV,
         FD_CONSOLE,
         FD_BUS,
-        FD_PIPE_BASE
+        FD_FIFO_BASE
 };
 
 Manager *manager_new(void);