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                 int flags;
  46
  47                 flags = fcntl(inotify_fd, F_GETFD);
  48                 if (flags < 0)
  49                         flags = FD_CLOEXEC;
  50                 else
  51                         flags |= FD_CLOEXEC;
  52                 fcntl(inotify_fd, F_SETFD, flags);
  53         } else if (errno == ENOSYS)
  54                 info(udev, "unable to use inotify, udevd will not monitor rule files changes\n");
  55         else
  56                 err(udev, "inotify_init failed: %m\n");
  57 }
  58
  59 /* move any old watches directory out of the way, and then restore
  60  * the watches
  61  */
  62 void udev_watch_restore(struct udev *udev)
  63 {
  64         char filename[UTIL_PATH_SIZE], oldname[UTIL_PATH_SIZE];
  65
  66         if (inotify_fd < 0)
  67                 return;
  68
  69         util_strlcpy(oldname, udev_get_dev_path(udev), sizeof(oldname));
  70         util_strlcat(oldname, "/.udev/watch.old", sizeof(oldname));
  71
  72         util_strlcpy(filename, udev_get_dev_path(udev), sizeof(filename));
  73         util_strlcat(filename, "/.udev/watch", sizeof(filename));
  74
  75         if (rename(filename, oldname) == 0) {
  76                 DIR *dir;
  77                 struct dirent *ent;
  78
  79                 dir = opendir(oldname);
  80                 if (dir == NULL) {
  81                         err(udev, "unable to open old watches dir '%s', old watches will not be restored: %m", oldname);
  82                         return;
  83                 }
  84
  85                 while ((ent = readdir(dir)) != NULL) {
  86                         char path[UTIL_PATH_SIZE];
  87                         char buf[UTIL_PATH_SIZE];
  88                         ssize_t syslen;
  89                         ssize_t len;
  90                         struct udev_device *dev;
  91
  92                         if (ent->d_name[0] < '0' || ent->d_name[0] > '9')
  93                                 continue;
  94
  95                         util_strlcpy(path, oldname, sizeof(path));
  96                         util_strlcat(path, "/", sizeof(path));
  97                         util_strlcat(path, ent->d_name, sizeof(path));
  98
  99                         syslen = util_strlcpy(buf, udev_get_sys_path(udev), sizeof(buf));
 100                         len = readlink(path, &buf[syslen], sizeof(buf)-syslen);
 101                         if (len <= 0 || len >= (ssize_t)(sizeof(buf)-syslen)) {
 102                                 unlink(path);
 103                                 continue;
 104                         }
 105                         buf[syslen + len] = '\0';
 106                         dbg(udev, "old watch to '%s' found\n", buf);
 107                         dev = udev_device_new_from_syspath(udev, buf);
 108                         if (dev == NULL) {
 109                                 unlink(path);
 110                                 continue;
 111                         }
 112
 113                         info(udev, "restoring old watch on '%s'\n", udev_device_get_devnode(dev));
 114                         udev_watch_begin(udev, dev);
 115
 116                         udev_device_unref(dev);
 117                         unlink(path);
 118                 }
 119
 120                 closedir(dir);
 121                 rmdir(oldname);
 122
 123         } else if (errno != ENOENT) {
 124                 err(udev, "unable to move watches dir '%s', old watches will not be restored: %m", filename);
 125         }
 126 }
 127
 128 void udev_watch_begin(struct udev *udev, struct udev_device *dev)
 129 {
 130         char filename[UTIL_PATH_SIZE];
 131         int wd;
 132
 133         if (inotify_fd < 0)
 134                 return;
 135
 136         info(udev, "adding watch on '%s'\n", udev_device_get_devnode(dev));
 137         wd = inotify_add_watch(inotify_fd, udev_device_get_devnode(dev), IN_CLOSE_WRITE);
 138         if (wd < 0) {
 139                 err(udev, "inotify_add_watch(%d, %s, %o) failed: %m\n",
 140                     inotify_fd, udev_device_get_devnode(dev), IN_CLOSE_WRITE);
 141         }
 142
 143         snprintf(filename, sizeof(filename), "%s/.udev/watch/%d", udev_get_dev_path(udev), wd);
 144         util_create_path(udev, filename);
 145         unlink(filename);
 146         symlink(udev_device_get_devpath(dev), filename);
 147
 148         udev_device_set_watch_handle(dev, wd);
 149 }
 150
 151 void udev_watch_end(struct udev *udev, struct udev_device *dev)
 152 {
 153         int wd;
 154         char filename[UTIL_PATH_SIZE];
 155
 156         if (inotify_fd < 0)
 157                 return;
 158
 159         wd = udev_device_get_watch_handle(dev);
 160         if (wd < 0)
 161                 return;
 162
 163         info(udev, "removing watch on '%s'\n", udev_device_get_devnode(dev));
 164         inotify_rm_watch(inotify_fd, wd);
 165
 166         snprintf(filename, sizeof(filename), "%s/.udev/watch/%d", udev_get_dev_path(udev), wd);
 167         unlink(filename);
 168
 169         udev_device_set_watch_handle(dev, -1);
 170 }
 171
 172 struct udev_device *udev_watch_lookup(struct udev *udev, int wd)
 173 {
 174         char filename[UTIL_PATH_SIZE];
 175         char buf[UTIL_PATH_SIZE];
 176         ssize_t syslen;
 177         ssize_t len;
 178
 179         if (inotify_fd < 0 || wd < 0)
 180                 return NULL;
 181
 182         snprintf(filename, sizeof(filename), "%s/.udev/watch/%d", udev_get_dev_path(udev), wd);
 183         syslen = util_strlcpy(buf, udev_get_sys_path(udev), sizeof(buf));
 184         len = readlink(filename, &buf[syslen], sizeof(buf)-syslen);
 185         if (len > 0 || len < (ssize_t)(sizeof(buf)-syslen)) {
 186                 buf[syslen + len] = '\0';
 187                 return udev_device_new_from_syspath(udev, buf);
 188         }
 189
 190         return NULL;
 191 }