src/udev/udev-watch.c

   1 /*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
   2
   3 /*
   4  * Copyright (C) 2004-2012 Kay Sievers <kay@vrfy.org>
   5  * Copyright (C) 2009 Canonical Ltd.
   6  * Copyright (C) 2009 Scott James Remnant <scott@netsplit.com>
   7  *
   8  * This program is free software: you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License as published by
  10  * the Free Software Foundation, either version 2 of the License, or
  11  * (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License
  19  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  20  */
  21
  22 #include <dirent.h>
  23 #include <errno.h>
  24 #include <stddef.h>
  25 #include <stdio.h>
  26 #include <sys/inotify.h>
  27 #include <unistd.h>
  28
  29 #include "stdio-util.h"
  30 #include "udev.h"
  31
  32 static int inotify_fd = -1;
  33
  34 /* inotify descriptor, will be shared with rules directory;
  35  * set to cloexec since we need our children to be able to add
  36  * watches for us
  37  */
  38 int udev_watch_init(struct udev *udev) {
  39         inotify_fd = inotify_init1(IN_CLOEXEC);
  40         if (inotify_fd < 0)
  41                 log_error_errno(errno, "inotify_init failed: %m");
  42         return inotify_fd;
  43 }
  44
  45 /* move any old watches directory out of the way, and then restore
  46  * the watches
  47  */
  48 void udev_watch_restore(struct udev *udev) {
  49         if (inotify_fd < 0)
  50                 return;
  51
  52         if (rename("/run/udev/watch", "/run/udev/watch.old") == 0) {
  53                 DIR *dir;
  54                 struct dirent *ent;
  55
  56                 dir = opendir("/run/udev/watch.old");
  57                 if (dir == NULL) {
  58                         log_error_errno(errno, "unable to open old watches dir /run/udev/watch.old; old watches will not be restored: %m");
  59                         return;
  60                 }
  61
  62                 for (ent = readdir(dir); ent != NULL; ent = readdir(dir)) {
  63                         char device[UTIL_PATH_SIZE];
  64                         ssize_t len;
  65                         struct udev_device *dev;
  66
  67                         if (ent->d_name[0] == '.')
  68                                 continue;
  69
  70                         len = readlinkat(dirfd(dir), ent->d_name, device, sizeof(device));
  71                         if (len <= 0 || len == (ssize_t)sizeof(device))
  72                                 goto unlink;
  73                         device[len] = '\0';
  74
  75                         dev = udev_device_new_from_device_id(udev, device);
  76                         if (dev == NULL)
  77                                 goto unlink;
  78
  79                         log_debug("restoring old watch on '%s'", udev_device_get_devnode(dev));
  80                         udev_watch_begin(udev, dev);
  81                         udev_device_unref(dev);
  82 unlink:
  83                         unlinkat(dirfd(dir), ent->d_name, 0);
  84                 }
  85
  86                 closedir(dir);
  87                 rmdir("/run/udev/watch.old");
  88
  89         } else if (errno != ENOENT)
  90                 log_error_errno(errno, "unable to move watches dir /run/udev/watch; old watches will not be restored: %m");
  91 }
  92
  93 void udev_watch_begin(struct udev *udev, struct udev_device *dev) {
  94         char filename[UTIL_PATH_SIZE];
  95         int wd;
  96         int r;
  97
  98         if (inotify_fd < 0)
  99                 return;
 100
 101         log_debug("adding watch on '%s'", udev_device_get_devnode(dev));
 102         wd = inotify_add_watch(inotify_fd, udev_device_get_devnode(dev), IN_CLOSE_WRITE);
 103         if (wd < 0) {
 104                 log_error_errno(errno, "inotify_add_watch(%d, %s, %o) failed: %m",
 105                                 inotify_fd, udev_device_get_devnode(dev), IN_CLOSE_WRITE);
 106                 return;
 107         }
 108
 109         xsprintf(filename, "/run/udev/watch/%d", wd);
 110         mkdir_parents(filename, 0755);
 111         unlink(filename);
 112         r = symlink(udev_device_get_id_filename(dev), filename);
 113         if (r < 0)
 114                 log_error_errno(errno, "Failed to create symlink %s: %m", filename);
 115
 116         udev_device_set_watch_handle(dev, wd);
 117 }
 118
 119 void udev_watch_end(struct udev *udev, struct udev_device *dev) {
 120         int wd;
 121         char filename[UTIL_PATH_SIZE];
 122
 123         if (inotify_fd < 0)
 124                 return;
 125
 126         wd = udev_device_get_watch_handle(dev);
 127         if (wd < 0)
 128                 return;
 129
 130         log_debug("removing watch on '%s'", udev_device_get_devnode(dev));
 131         inotify_rm_watch(inotify_fd, wd);
 132
 133         xsprintf(filename, "/run/udev/watch/%d", wd);
 134         unlink(filename);
 135
 136         udev_device_set_watch_handle(dev, -1);
 137 }
 138
 139 struct udev_device *udev_watch_lookup(struct udev *udev, int wd) {
 140         char filename[UTIL_PATH_SIZE];
 141         char device[UTIL_NAME_SIZE];
 142         ssize_t len;
 143
 144         if (inotify_fd < 0 || wd < 0)
 145                 return NULL;
 146
 147         xsprintf(filename, "/run/udev/watch/%d", wd);
 148         len = readlink(filename, device, sizeof(device));
 149         if (len <= 0 || (size_t)len == sizeof(device))
 150                 return NULL;
 151         device[len] = '\0';
 152
 153         return udev_device_new_from_device_id(udev, device);
 154 }