udev/udev-watch.c

   1 /*
   2  * Copyright (C) 2004-2008 Kay Sievers <kay.sievers@vrfy.org>
   3  * Copyright (C) 2009 Canonical Ltd.
   4  *
   5  * This program is free software: you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation, either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License
  16  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  17  */
  18
  19 #include <sys/types.h>
  20 #include <errno.h>
  21 #include <fcntl.h>
  22 #include <stdio.h>
  23 #include <dirent.h>
  24 #include <stddef.h>
  25 #include <stdlib.h>
  26 #include <string.h>
  27 #include <unistd.h>
  28 #ifdef HAVE_INOTIFY
  29 #include <sys/inotify.h>
  30 #endif
  31
  32 #include "udev.h"
  33
  34 int inotify_fd = -1;
  35
  36 /* inotify descriptor, will be shared with rules directory;
  37  * set to cloexec since we need our children to be able to add
  38  * watches for us
  39  */
  40 void udev_watch_init(struct udev *udev)
  41 {
  42         inotify_fd = inotify_init();
  43         if (inotify_fd >= 0) {
  44                 int flags;
  45
  46                 flags = fcntl(inotify_fd, F_GETFD);
  47                 if (flags < 0)
  48                         flags = FD_CLOEXEC;
  49                 else
  50                         flags |= FD_CLOEXEC;
  51                 fcntl(inotify_fd, F_SETFD, flags);
  52         } else if (errno == ENOSYS)
  53                 info(udev, "unable to use inotify, udevd will not monitor rule files changes\n");
  54         else
  55                 err(udev, "inotify_init failed: %m\n");
  56 }
  57
  58 /* move any old watches directory out of the way, and then restore
  59  * the watches
  60  */
  61 void udev_watch_restore(struct udev *udev)
  62 {
  63         char filename[UTIL_PATH_SIZE], oldname[UTIL_PATH_SIZE];
  64
  65         if (inotify_fd < 0)
  66                 return;
  67
  68         util_strlcpy(oldname, udev_get_dev_path(udev), sizeof(oldname));
  69         util_strlcat(oldname, "/.udev/watch.old", sizeof(oldname));
  70
  71         util_strlcpy(filename, udev_get_dev_path(udev), sizeof(filename));
  72         util_strlcat(filename, "/.udev/watch", sizeof(filename));
  73
  74         if (rename(filename, oldname) == 0) {
  75                 DIR *dir;
  76                 struct dirent *ent;
  77
  78                 dir = opendir(oldname);
  79                 if (dir == NULL) {
  80                         err(udev, "unable to open old watches dir '%s', old watches will not be restored: %m", oldname);
  81                         return;
  82                 }
  83
  84                 while ((ent = readdir(dir)) != NULL) {
  85                         char path[UTIL_PATH_SIZE];
  86                         char buf[UTIL_PATH_SIZE];
  87                         ssize_t len;
  88                         struct udev_device *dev;
  89
  90                         if (ent->d_name[0] < '0' || ent->d_name[0] > '9')
  91                                 continue;
  92
  93                         util_strlcpy(path, oldname, sizeof(path));
  94                         util_strlcat(path, "/", sizeof(path));
  95                         util_strlcat(path, ent->d_name, sizeof(path));
  96
  97                         len = readlink(path, buf, sizeof(buf));
  98                         if (len <= 0) {
  99                                 unlink(path);
 100                                 continue;
 101                         }
 102
 103                         buf[len] = '\0';
 104                         dbg(udev, "old watch to '%s' found\n", buf);
 105
 106                         dev = udev_device_new_from_syspath(udev, buf);
 107                         if (dev == NULL) {
 108                                 unlink(path);
 109                                 continue;
 110                         }
 111
 112                         udev_device_read_db(dev);
 113                         udev_device_set_info_loaded(dev);
 114
 115                         info(udev, "restoring old watch on '%s'\n", udev_device_get_devnode(dev));
 116                         udev_watch_begin(udev, dev);
 117
 118                         udev_device_unref(dev);
 119
 120                         unlink(path);
 121                 }
 122
 123                 closedir(dir);
 124                 rmdir(oldname);
 125
 126         } else if (errno != ENOENT) {
 127                 err(udev, "unable to move watches dir '%s', old watches will not be restored: %m", filename);
 128         }
 129 }
 130
 131 static const char *udev_watch_filename(struct udev *udev, int wd)
 132 {
 133         static char filename[UTIL_PATH_SIZE];
 134         char str[32];
 135
 136         sprintf(str, "%d", wd);
 137         util_strlcpy(filename, udev_get_dev_path(udev), sizeof(filename));
 138         util_strlcat(filename, "/.udev/watch/", sizeof(filename));
 139         util_strlcat(filename, str, sizeof(filename));
 140
 141         return filename;
 142 }
 143
 144 void udev_watch_begin(struct udev *udev, struct udev_device *dev)
 145 {
 146         const char *filename;
 147         int wd;
 148
 149         if (inotify_fd < 0)
 150                 return;
 151
 152         wd = inotify_add_watch (inotify_fd, udev_device_get_devnode(dev), IN_CLOSE_WRITE);
 153         if (wd < 0) {
 154                 err(udev, "inotify_add_watch(%d, %s, %o) failed: %m\n",
 155                     inotify_fd, udev_device_get_devnode(dev), IN_CLOSE_WRITE);
 156         }
 157
 158         filename = udev_watch_filename(udev, wd);
 159         util_create_path(udev, filename);
 160         unlink(filename);
 161         symlink(udev_device_get_syspath(dev), filename);
 162 }
 163
 164 void udev_watch_clear(struct udev *udev, struct udev_device *dev)
 165 {
 166         static char filename[UTIL_PATH_SIZE];
 167         DIR *dir;
 168         struct dirent *ent;
 169
 170         util_strlcpy(filename, udev_get_dev_path(udev), sizeof(filename));
 171         util_strlcat(filename, "/.udev/watch", sizeof(filename));
 172
 173         dir = opendir(filename);
 174         if (dir == NULL)
 175                 return;
 176
 177         while ((ent = readdir(dir)) != NULL) {
 178                 char path[UTIL_PATH_SIZE];
 179                 char buf[UTIL_PATH_SIZE];
 180                 ssize_t len;
 181
 182                 if (ent->d_name[0] < '0' || ent->d_name[0] > '9')
 183                         continue;
 184
 185                 util_strlcpy(path, filename, sizeof(path));
 186                 util_strlcat(path, "/", sizeof(path));
 187                 util_strlcat(path, ent->d_name, sizeof(path));
 188
 189                 len = readlink(path, buf, sizeof(buf));
 190                 if (len <= 0)
 191                         continue;
 192
 193                 buf[len] = '\0';
 194                 if (strcmp(buf, udev_device_get_syspath(dev)))
 195                         continue;
 196
 197                 /* this is the watch we're looking for */
 198                 info(udev, "clearing existing watch on '%s'\n", udev_device_get_devnode(dev));
 199                 udev_watch_end(udev, atoi(ent->d_name));
 200         }
 201
 202         closedir(dir);
 203 }
 204
 205 void udev_watch_end(struct udev *udev, int wd)
 206 {
 207         const char *filename;
 208
 209         if (inotify_fd < 0 || wd < 0)
 210                 return;
 211
 212         inotify_rm_watch(inotify_fd, wd);
 213
 214         filename = udev_watch_filename(udev, wd);
 215         unlink(filename);
 216 }
 217
 218 const char *udev_watch_lookup(struct udev *udev, int wd)
 219 {
 220         const char *filename;
 221         static char buf[UTIL_PATH_SIZE];
 222         ssize_t len;
 223
 224         if (inotify_fd < 0 || wd < 0)
 225                 return NULL;
 226
 227         filename = udev_watch_filename(udev, wd);
 228         len = readlink(filename, buf, sizeof(buf));
 229         if (len > 0) {
 230                 buf[len] = '\0';
 231
 232                 return buf;
 233         }
 234
 235         return NULL;
 236 }