udev/udev-watch.c

   1 /*
   2  * Copyright (C) 2004-2008 Kay Sievers <kay.sievers@vrfy.org>
   3  * Copyright (C) 2009 Canonical Ltd.
   4  * Copyright (C) 2009 Scott James Remnant <scott@netsplit.com>
   5  *
   6  * This program is free software: you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation, either version 2 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  18  */
  19
  20 #include <sys/types.h>
  21 #include <errno.h>
  22 #include <fcntl.h>
  23 #include <stdio.h>
  24 #include <dirent.h>
  25 #include <stddef.h>
  26 #include <stdlib.h>
  27 #include <string.h>
  28 #include <unistd.h>
  29 #include <sys/inotify.h>
  30
  31 #include "udev.h"
  32
  33 static int inotify_fd = -1;
  34
  35 /* inotify descriptor, will be shared with rules directory;
  36  * set to cloexec since we need our children to be able to add
  37  * watches for us
  38  */
  39 int udev_watch_init(struct udev *udev)
  40 {
  41         inotify_fd = inotify_init();
  42         if (inotify_fd >= 0)
  43                 util_set_fd_cloexec(inotify_fd);
  44         else
  45                 err(udev, "inotify_init failed: %m\n");
  46         return inotify_fd;
  47 }
  48
  49 /* move any old watches directory out of the way, and then restore
  50  * the watches
  51  */
  52 void udev_watch_restore(struct udev *udev)
  53 {
  54         char filename[UTIL_PATH_SIZE], oldname[UTIL_PATH_SIZE];
  55
  56         if (inotify_fd < 0)
  57                 return;
  58
  59         util_strscpyl(oldname, sizeof(oldname), udev_get_dev_path(udev), "/.udev/watch.old", NULL);
  60         util_strscpyl(filename, sizeof(filename), udev_get_dev_path(udev), "/.udev/watch", NULL);
  61         if (rename(filename, oldname) == 0) {
  62                 DIR *dir;
  63                 struct dirent *ent;
  64
  65                 dir = opendir(oldname);
  66                 if (dir == NULL) {
  67                         err(udev, "unable to open old watches dir '%s', old watches will not be restored: %m", oldname);
  68                         return;
  69                 }
  70
  71                 for (ent = readdir(dir); ent != NULL; ent = readdir(dir)) {
  72                         char device[UTIL_PATH_SIZE];
  73                         char *s;
  74                         size_t l;
  75                         ssize_t len;
  76                         struct udev_device *dev;
  77
  78                         if (ent->d_name[0] < '0' || ent->d_name[0] > '9')
  79                                 continue;
  80
  81                         s = device;
  82                         l = util_strpcpy(&s, sizeof(device), udev_get_sys_path(udev));
  83                         len = readlinkat(dirfd(dir), ent->d_name, s, l);
  84                         if (len <= 0 || len >= (ssize_t)l) {
  85                                 unlinkat(dirfd(dir), ent->d_name, 0);
  86                                 continue;
  87                         }
  88                         s[len] = '\0';
  89                         dbg(udev, "old watch to '%s' found\n", device);
  90                         dev = udev_device_new_from_syspath(udev, device);
  91                         if (dev == NULL) {
  92                                 unlinkat(dirfd(dir), ent->d_name, 0);
  93                                 continue;
  94                         }
  95
  96                         info(udev, "restoring old watch on '%s'\n", udev_device_get_devnode(dev));
  97                         udev_watch_begin(udev, dev);
  98
  99                         udev_device_unref(dev);
 100                         unlinkat(dirfd(dir), ent->d_name, 0);
 101                 }
 102
 103                 closedir(dir);
 104                 rmdir(oldname);
 105
 106         } else if (errno != ENOENT) {
 107                 err(udev, "unable to move watches dir '%s', old watches will not be restored: %m", filename);
 108         }
 109 }
 110
 111 void udev_watch_begin(struct udev *udev, struct udev_device *dev)
 112 {
 113         char filename[UTIL_PATH_SIZE];
 114         int wd;
 115
 116         if (inotify_fd < 0)
 117                 return;
 118
 119         info(udev, "adding watch on '%s'\n", udev_device_get_devnode(dev));
 120         wd = inotify_add_watch(inotify_fd, udev_device_get_devnode(dev), IN_CLOSE_WRITE);
 121         if (wd < 0) {
 122                 err(udev, "inotify_add_watch(%d, %s, %o) failed: %m\n",
 123                     inotify_fd, udev_device_get_devnode(dev), IN_CLOSE_WRITE);
 124                 return;
 125         }
 126
 127         snprintf(filename, sizeof(filename), "%s/.udev/watch/%d", udev_get_dev_path(udev), wd);
 128         util_create_path(udev, filename);
 129         unlink(filename);
 130         symlink(udev_device_get_devpath(dev), filename);
 131
 132         udev_device_set_watch_handle(dev, wd);
 133 }
 134
 135 void udev_watch_end(struct udev *udev, struct udev_device *dev)
 136 {
 137         int wd;
 138         char filename[UTIL_PATH_SIZE];
 139
 140         if (inotify_fd < 0)
 141                 return;
 142
 143         wd = udev_device_get_watch_handle(dev);
 144         if (wd < 0)
 145                 return;
 146
 147         info(udev, "removing watch on '%s'\n", udev_device_get_devnode(dev));
 148         inotify_rm_watch(inotify_fd, wd);
 149
 150         snprintf(filename, sizeof(filename), "%s/.udev/watch/%d", udev_get_dev_path(udev), wd);
 151         unlink(filename);
 152
 153         udev_device_set_watch_handle(dev, -1);
 154 }
 155
 156 struct udev_device *udev_watch_lookup(struct udev *udev, int wd)
 157 {
 158         char filename[UTIL_PATH_SIZE];
 159         char syspath[UTIL_PATH_SIZE];
 160         char *s;
 161         size_t l;
 162         ssize_t len;
 163
 164         if (inotify_fd < 0 || wd < 0)
 165                 return NULL;
 166
 167         snprintf(filename, sizeof(filename), "%s/.udev/watch/%d", udev_get_dev_path(udev), wd);
 168         s = syspath;
 169         l = util_strpcpy(&s, sizeof(syspath), udev_get_sys_path(udev));
 170         len = readlink(filename, s, l);
 171         if (len < 0 || (size_t)len >= l)
 172                 return NULL;
 173         s[len] = '\0';
 174         return udev_device_new_from_syspath(udev, syspath);
 175 }