src/udev/udev-watch.c

   1 /* SPDX-License-Identifier: GPL-2.0+ */
   2 /*
   3  * Copyright (C) 2004-2012 Kay Sievers <kay@vrfy.org>
   4  * Copyright (C) 2009 Canonical Ltd.
   5  * Copyright (C) 2009 Scott James Remnant <scott@netsplit.com>
   6  *
   7  * This program is free software: you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License as published by
   9  * the Free Software Foundation, either version 2 of the License, or
  10  * (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  19  */
  20
  21 #include <errno.h>
  22 #include <stddef.h>
  23 #include <stdio.h>
  24 #include <sys/inotify.h>
  25 #include <unistd.h>
  26
  27 #include "dirent-util.h"
  28 #include "stdio-util.h"
  29 #include "udev.h"
  30
  31 static int inotify_fd = -1;
  32
  33 /* inotify descriptor, will be shared with rules directory;
  34  * set to cloexec since we need our children to be able to add
  35  * watches for us
  36  */
  37 int udev_watch_init(struct udev *udev) {
  38         inotify_fd = inotify_init1(IN_CLOEXEC);
  39         if (inotify_fd < 0)
  40                 log_error_errno(errno, "inotify_init failed: %m");
  41         return inotify_fd;
  42 }
  43
  44 /* move any old watches directory out of the way, and then restore
  45  * the watches
  46  */
  47 void udev_watch_restore(struct udev *udev) {
  48         if (inotify_fd < 0)
  49                 return;
  50
  51         if (rename("/run/udev/watch", "/run/udev/watch.old") == 0) {
  52                 DIR *dir;
  53                 struct dirent *ent;
  54
  55                 dir = opendir("/run/udev/watch.old");
  56                 if (dir == NULL) {
  57                         log_error_errno(errno, "unable to open old watches dir /run/udev/watch.old; old watches will not be restored: %m");
  58                         return;
  59                 }
  60
  61                 FOREACH_DIRENT_ALL(ent, dir, break) {
  62                         char device[UTIL_PATH_SIZE];
  63                         ssize_t len;
  64                         struct udev_device *dev;
  65
  66                         if (ent->d_name[0] == '.')
  67                                 continue;
  68
  69                         len = readlinkat(dirfd(dir), ent->d_name, device, sizeof(device));
  70                         if (len <= 0 || len == (ssize_t)sizeof(device))
  71                                 goto unlink;
  72                         device[len] = '\0';
  73
  74                         dev = udev_device_new_from_device_id(udev, device);
  75                         if (dev == NULL)
  76                                 goto unlink;
  77
  78                         log_debug("restoring old watch on '%s'", udev_device_get_devnode(dev));
  79                         udev_watch_begin(udev, dev);
  80                         udev_device_unref(dev);
  81 unlink:
  82                         (void) unlinkat(dirfd(dir), ent->d_name, 0);
  83                 }
  84
  85                 closedir(dir);
  86                 rmdir("/run/udev/watch.old");
  87
  88         } else if (errno != ENOENT)
  89                 log_error_errno(errno, "unable to move watches dir /run/udev/watch; old watches will not be restored: %m");
  90 }
  91
  92 void udev_watch_begin(struct udev *udev, struct udev_device *dev) {
  93         char filename[sizeof("/run/udev/watch/") + DECIMAL_STR_MAX(int)];
  94         int wd;
  95         int r;
  96
  97         if (inotify_fd < 0)
  98                 return;
  99
 100         log_debug("adding watch on '%s'", udev_device_get_devnode(dev));
 101         wd = inotify_add_watch(inotify_fd, udev_device_get_devnode(dev), IN_CLOSE_WRITE);
 102         if (wd < 0) {
 103                 log_error_errno(errno, "inotify_add_watch(%d, %s, %o) failed: %m",
 104                                 inotify_fd, udev_device_get_devnode(dev), IN_CLOSE_WRITE);
 105                 return;
 106         }
 107
 108         xsprintf(filename, "/run/udev/watch/%d", wd);
 109         mkdir_parents(filename, 0755);
 110         unlink(filename);
 111         r = symlink(udev_device_get_id_filename(dev), filename);
 112         if (r < 0)
 113                 log_error_errno(errno, "Failed to create symlink %s: %m", filename);
 114
 115         udev_device_set_watch_handle(dev, wd);
 116 }
 117
 118 void udev_watch_end(struct udev *udev, struct udev_device *dev) {
 119         int wd;
 120         char filename[sizeof("/run/udev/watch/") + DECIMAL_STR_MAX(int)];
 121
 122         if (inotify_fd < 0)
 123                 return;
 124
 125         wd = udev_device_get_watch_handle(dev);
 126         if (wd < 0)
 127                 return;
 128
 129         log_debug("removing watch on '%s'", udev_device_get_devnode(dev));
 130         inotify_rm_watch(inotify_fd, wd);
 131
 132         xsprintf(filename, "/run/udev/watch/%d", wd);
 133         unlink(filename);
 134
 135         udev_device_set_watch_handle(dev, -1);
 136 }
 137
 138 struct udev_device *udev_watch_lookup(struct udev *udev, int wd) {
 139         char filename[sizeof("/run/udev/watch/") + DECIMAL_STR_MAX(int)];
 140         char device[UTIL_NAME_SIZE];
 141         ssize_t len;
 142
 143         if (inotify_fd < 0 || wd < 0)
 144                 return NULL;
 145
 146         xsprintf(filename, "/run/udev/watch/%d", wd);
 147         len = readlink(filename, device, sizeof(device));
 148         if (len <= 0 || (size_t)len == sizeof(device))
 149                 return NULL;
 150         device[len] = '\0';
 151
 152         return udev_device_new_from_device_id(udev, device);
 153 }