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                         dev = udev_device_new_from_syspath(udev, buf);
 106                         if (dev == NULL) {
 107                                 unlink(path);
 108                                 continue;
 109                         }
 110
 111                         info(udev, "restoring old watch on '%s'\n", udev_device_get_devnode(dev));
 112                         udev_watch_begin(udev, dev);
 113
 114                         udev_device_unref(dev);
 115                         unlink(path);
 116                 }
 117
 118                 closedir(dir);
 119                 rmdir(oldname);
 120
 121         } else if (errno != ENOENT) {
 122                 err(udev, "unable to move watches dir '%s', old watches will not be restored: %m", filename);
 123         }
 124 }
 125
 126 static const char *udev_watch_filename(struct udev *udev, int wd)
 127 {
 128         static char filename[UTIL_PATH_SIZE];
 129         char str[32];
 130
 131         sprintf(str, "%d", wd);
 132         util_strlcpy(filename, udev_get_dev_path(udev), sizeof(filename));
 133         util_strlcat(filename, "/.udev/watch/", sizeof(filename));
 134         util_strlcat(filename, str, sizeof(filename));
 135
 136         return filename;
 137 }
 138
 139 void udev_watch_begin(struct udev *udev, struct udev_device *dev)
 140 {
 141         const char *filename;
 142         int wd;
 143
 144         if (inotify_fd < 0)
 145                 return;
 146
 147         wd = inotify_add_watch(inotify_fd, udev_device_get_devnode(dev), IN_CLOSE_WRITE);
 148         if (wd < 0) {
 149                 err(udev, "inotify_add_watch(%d, %s, %o) failed: %m\n",
 150                     inotify_fd, udev_device_get_devnode(dev), IN_CLOSE_WRITE);
 151         }
 152
 153         filename = udev_watch_filename(udev, wd);
 154         util_create_path(udev, filename);
 155         unlink(filename);
 156         symlink(udev_device_get_syspath(dev), filename);
 157 }
 158
 159 void udev_watch_clear(struct udev *udev, struct udev_device *dev)
 160 {
 161         static char filename[UTIL_PATH_SIZE];
 162         DIR *dir;
 163         struct dirent *ent;
 164
 165         util_strlcpy(filename, udev_get_dev_path(udev), sizeof(filename));
 166         util_strlcat(filename, "/.udev/watch", sizeof(filename));
 167
 168         dir = opendir(filename);
 169         if (dir == NULL)
 170                 return;
 171
 172         while ((ent = readdir(dir)) != NULL) {
 173                 char path[UTIL_PATH_SIZE];
 174                 char buf[UTIL_PATH_SIZE];
 175                 ssize_t len;
 176
 177                 if (ent->d_name[0] < '0' || ent->d_name[0] > '9')
 178                         continue;
 179
 180                 util_strlcpy(path, filename, sizeof(path));
 181                 util_strlcat(path, "/", sizeof(path));
 182                 util_strlcat(path, ent->d_name, sizeof(path));
 183
 184                 len = readlink(path, buf, sizeof(buf));
 185                 if (len <= 0)
 186                         continue;
 187
 188                 buf[len] = '\0';
 189                 if (strcmp(buf, udev_device_get_syspath(dev)))
 190                         continue;
 191
 192                 /* this is the watch we're looking for */
 193                 info(udev, "clearing existing watch on '%s'\n", udev_device_get_devnode(dev));
 194                 udev_watch_end(udev, atoi(ent->d_name));
 195         }
 196
 197         closedir(dir);
 198 }
 199
 200 void udev_watch_end(struct udev *udev, int wd)
 201 {
 202         const char *filename;
 203
 204         if (inotify_fd < 0 || wd < 0)
 205                 return;
 206
 207         inotify_rm_watch(inotify_fd, wd);
 208
 209         filename = udev_watch_filename(udev, wd);
 210         unlink(filename);
 211 }
 212
 213 const char *udev_watch_lookup(struct udev *udev, int wd)
 214 {
 215         const char *filename;
 216         static char buf[UTIL_PATH_SIZE];
 217         ssize_t len;
 218
 219         if (inotify_fd < 0 || wd < 0)
 220                 return NULL;
 221
 222         filename = udev_watch_filename(udev, wd);
 223         len = readlink(filename, buf, sizeof(buf));
 224         if (len > 0) {
 225                 buf[len] = '\0';
 226
 227                 return buf;
 228         }
 229
 230         return NULL;
 231 }