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_strscpyl(oldname, sizeof(oldname), udev_get_dev_path(udev), "/.udev/watch.old", NULL);
  63         util_strscpyl(filename, sizeof(filename), udev_get_dev_path(udev), "/.udev/watch", NULL);
  64         if (rename(filename, oldname) == 0) {
  65                 DIR *dir;
  66                 struct dirent *ent;
  67
  68                 dir = opendir(oldname);
  69                 if (dir == NULL) {
  70                         err(udev, "unable to open old watches dir '%s', old watches will not be restored: %m", oldname);
  71                         return;
  72                 }
  73
  74                 for (ent = readdir(dir); ent != NULL; ent = readdir(dir)) {
  75                         char device[UTIL_PATH_SIZE];
  76                         char *s;
  77                         size_t l;
  78                         ssize_t len;
  79                         struct udev_device *dev;
  80
  81                         if (ent->d_name[0] < '0' || ent->d_name[0] > '9')
  82                                 continue;
  83
  84                         s = device;
  85                         l = util_strpcpy(&s, sizeof(device), udev_get_sys_path(udev));
  86                         len = readlinkat(dirfd(dir), ent->d_name, s, l);
  87                         if (len <= 0 || len >= (ssize_t)l) {
  88                                 unlinkat(dirfd(dir), ent->d_name, 0);
  89                                 continue;
  90                         }
  91                         s[len] = '\0';
  92                         dbg(udev, "old watch to '%s' found\n", device);
  93                         dev = udev_device_new_from_syspath(udev, device);
  94                         if (dev == NULL) {
  95                                 unlinkat(dirfd(dir), ent->d_name, 0);
  96                                 continue;
  97                         }
  98
  99                         info(udev, "restoring old watch on '%s'\n", udev_device_get_devnode(dev));
 100                         udev_watch_begin(udev, dev);
 101
 102                         udev_device_unref(dev);
 103                         unlinkat(dirfd(dir), ent->d_name, 0);
 104                 }
 105
 106                 closedir(dir);
 107                 rmdir(oldname);
 108
 109         } else if (errno != ENOENT) {
 110                 err(udev, "unable to move watches dir '%s', old watches will not be restored: %m", filename);
 111         }
 112 }
 113
 114 void udev_watch_begin(struct udev *udev, struct udev_device *dev)
 115 {
 116         char filename[UTIL_PATH_SIZE];
 117         int wd;
 118
 119         if (inotify_fd < 0)
 120                 return;
 121
 122         info(udev, "adding watch on '%s'\n", udev_device_get_devnode(dev));
 123         wd = inotify_add_watch(inotify_fd, udev_device_get_devnode(dev), IN_CLOSE_WRITE);
 124         if (wd < 0) {
 125                 err(udev, "inotify_add_watch(%d, %s, %o) failed: %m\n",
 126                     inotify_fd, udev_device_get_devnode(dev), IN_CLOSE_WRITE);
 127         }
 128
 129         snprintf(filename, sizeof(filename), "%s/.udev/watch/%d", udev_get_dev_path(udev), wd);
 130         util_create_path(udev, filename);
 131         unlink(filename);
 132         symlink(udev_device_get_devpath(dev), filename);
 133
 134         udev_device_set_watch_handle(dev, wd);
 135 }
 136
 137 void udev_watch_end(struct udev *udev, struct udev_device *dev)
 138 {
 139         int wd;
 140         char filename[UTIL_PATH_SIZE];
 141
 142         if (inotify_fd < 0)
 143                 return;
 144
 145         wd = udev_device_get_watch_handle(dev);
 146         if (wd < 0)
 147                 return;
 148
 149         info(udev, "removing watch on '%s'\n", udev_device_get_devnode(dev));
 150         inotify_rm_watch(inotify_fd, wd);
 151
 152         snprintf(filename, sizeof(filename), "%s/.udev/watch/%d", udev_get_dev_path(udev), wd);
 153         unlink(filename);
 154
 155         udev_device_set_watch_handle(dev, -1);
 156 }
 157
 158 struct udev_device *udev_watch_lookup(struct udev *udev, int wd)
 159 {
 160         char filename[UTIL_PATH_SIZE];
 161         char syspath[UTIL_PATH_SIZE];
 162         char *s;
 163         size_t l;
 164         ssize_t len;
 165
 166         if (inotify_fd < 0 || wd < 0)
 167                 return NULL;
 168
 169         snprintf(filename, sizeof(filename), "%s/.udev/watch/%d", udev_get_dev_path(udev), wd);
 170         s = syspath;
 171         l = util_strpcpy(&s, sizeof(syspath), udev_get_sys_path(udev));
 172         len = readlink(filename, s, l);
 173         if (len < 0 || (size_t)len >= l)
 174                 return NULL;
 175         s[len] = '\0';
 176         return udev_device_new_from_syspath(udev, syspath);
 177 }