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 #ifdef HAVE_INOTIFY
  30 #include <sys/inotify.h>
  31 #endif
  32
  33 #include "udev.h"
  34
  35 int inotify_fd = -1;
  36
  37 /* inotify descriptor, will be shared with rules directory;
  38  * set to cloexec since we need our children to be able to add
  39  * watches for us
  40  */
  41 void udev_watch_init(struct udev *udev)
  42 {
  43         inotify_fd = inotify_init();
  44         if (inotify_fd >= 0)
  45                 util_set_fd_cloexec(inotify_fd);
  46         else if (errno == ENOSYS)
  47                 info(udev, "unable to use inotify, udevd will not monitor rule files changes\n");
  48         else
  49                 err(udev, "inotify_init failed: %m\n");
  50 }
  51
  52 /* move any old watches directory out of the way, and then restore
  53  * the watches
  54  */
  55 void udev_watch_restore(struct udev *udev)
  56 {
  57         char filename[UTIL_PATH_SIZE], oldname[UTIL_PATH_SIZE];
  58
  59         if (inotify_fd < 0)
  60                 return;
  61
  62         util_strlcpy(oldname, udev_get_dev_path(udev), sizeof(oldname));
  63         util_strlcat(oldname, "/.udev/watch.old", sizeof(oldname));
  64
  65         util_strlcpy(filename, udev_get_dev_path(udev), sizeof(filename));
  66         util_strlcat(filename, "/.udev/watch", sizeof(filename));
  67
  68         if (rename(filename, oldname) == 0) {
  69                 DIR *dir;
  70                 struct dirent *ent;
  71
  72                 dir = opendir(oldname);
  73                 if (dir == NULL) {
  74                         err(udev, "unable to open old watches dir '%s', old watches will not be restored: %m", oldname);
  75                         return;
  76                 }
  77
  78                 while ((ent = readdir(dir)) != NULL) {
  79                         char path[UTIL_PATH_SIZE];
  80                         char buf[UTIL_PATH_SIZE];
  81                         ssize_t syslen;
  82                         ssize_t len;
  83                         struct udev_device *dev;
  84
  85                         if (ent->d_name[0] < '0' || ent->d_name[0] > '9')
  86                                 continue;
  87
  88                         util_strlcpy(path, oldname, sizeof(path));
  89                         util_strlcat(path, "/", sizeof(path));
  90                         util_strlcat(path, ent->d_name, sizeof(path));
  91
  92                         syslen = util_strlcpy(buf, udev_get_sys_path(udev), sizeof(buf));
  93                         len = readlink(path, &buf[syslen], sizeof(buf)-syslen);
  94                         if (len <= 0 || len >= (ssize_t)(sizeof(buf)-syslen)) {
  95                                 unlink(path);
  96                                 continue;
  97                         }
  98                         buf[syslen + len] = '\0';
  99                         dbg(udev, "old watch to '%s' found\n", buf);
 100                         dev = udev_device_new_from_syspath(udev, buf);
 101                         if (dev == NULL) {
 102                                 unlink(path);
 103                                 continue;
 104                         }
 105
 106                         info(udev, "restoring old watch on '%s'\n", udev_device_get_devnode(dev));
 107                         udev_watch_begin(udev, dev);
 108
 109                         udev_device_unref(dev);
 110                         unlink(path);
 111                 }
 112
 113                 closedir(dir);
 114                 rmdir(oldname);
 115
 116         } else if (errno != ENOENT) {
 117                 err(udev, "unable to move watches dir '%s', old watches will not be restored: %m", filename);
 118         }
 119 }
 120
 121 void udev_watch_begin(struct udev *udev, struct udev_device *dev)
 122 {
 123         char filename[UTIL_PATH_SIZE];
 124         int wd;
 125
 126         if (inotify_fd < 0)
 127                 return;
 128
 129         info(udev, "adding watch on '%s'\n", udev_device_get_devnode(dev));
 130         wd = inotify_add_watch(inotify_fd, udev_device_get_devnode(dev), IN_CLOSE_WRITE);
 131         if (wd < 0) {
 132                 err(udev, "inotify_add_watch(%d, %s, %o) failed: %m\n",
 133                     inotify_fd, udev_device_get_devnode(dev), IN_CLOSE_WRITE);
 134         }
 135
 136         snprintf(filename, sizeof(filename), "%s/.udev/watch/%d", udev_get_dev_path(udev), wd);
 137         util_create_path(udev, filename);
 138         unlink(filename);
 139         symlink(udev_device_get_devpath(dev), filename);
 140
 141         udev_device_set_watch_handle(dev, wd);
 142 }
 143
 144 void udev_watch_end(struct udev *udev, struct udev_device *dev)
 145 {
 146         int wd;
 147         char filename[UTIL_PATH_SIZE];
 148
 149         if (inotify_fd < 0)
 150                 return;
 151
 152         wd = udev_device_get_watch_handle(dev);
 153         if (wd < 0)
 154                 return;
 155
 156         info(udev, "removing watch on '%s'\n", udev_device_get_devnode(dev));
 157         inotify_rm_watch(inotify_fd, wd);
 158
 159         snprintf(filename, sizeof(filename), "%s/.udev/watch/%d", udev_get_dev_path(udev), wd);
 160         unlink(filename);
 161
 162         udev_device_set_watch_handle(dev, -1);
 163 }
 164
 165 struct udev_device *udev_watch_lookup(struct udev *udev, int wd)
 166 {
 167         char filename[UTIL_PATH_SIZE];
 168         char buf[UTIL_PATH_SIZE];
 169         ssize_t syslen;
 170         ssize_t len;
 171
 172         if (inotify_fd < 0 || wd < 0)
 173                 return NULL;
 174
 175         snprintf(filename, sizeof(filename), "%s/.udev/watch/%d", udev_get_dev_path(udev), wd);
 176         syslen = util_strlcpy(buf, udev_get_sys_path(udev), sizeof(buf));
 177         len = readlink(filename, &buf[syslen], sizeof(buf)-syslen);
 178         if (len > 0 || len < (ssize_t)(sizeof(buf)-syslen)) {
 179                 buf[syslen + len] = '\0';
 180                 return udev_device_new_from_syspath(udev, buf);
 181         }
 182
 183         return NULL;
 184 }