src/udev/udev-watch.c

   1 /*
   2  * Copyright (C) 2004-2012 Kay Sievers <kay@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 <dirent.h>
  21 #include <errno.h>
  22 #include <stddef.h>
  23 #include <stdio.h>
  24 #include <sys/inotify.h>
  25 #include <unistd.h>
  26
  27 #include "udev.h"
  28
  29 static int inotify_fd = -1;
  30
  31 /* inotify descriptor, will be shared with rules directory;
  32  * set to cloexec since we need our children to be able to add
  33  * watches for us
  34  */
  35 int udev_watch_init(struct udev *udev) {
  36         inotify_fd = inotify_init1(IN_CLOEXEC);
  37         if (inotify_fd < 0)
  38                 log_error_errno(errno, "inotify_init failed: %m");
  39         return inotify_fd;
  40 }
  41
  42 /* move any old watches directory out of the way, and then restore
  43  * the watches
  44  */
  45 void udev_watch_restore(struct udev *udev) {
  46         if (inotify_fd < 0)
  47                 return;
  48
  49         if (rename("/run/udev/watch", "/run/udev/watch.old") == 0) {
  50                 DIR *dir;
  51                 struct dirent *ent;
  52
  53                 dir = opendir("/run/udev/watch.old");
  54                 if (dir == NULL) {
  55                         log_error_errno(errno, "unable to open old watches dir /run/udev/watch.old; old watches will not be restored: %m");
  56                         return;
  57                 }
  58
  59                 for (ent = readdir(dir); ent != NULL; ent = readdir(dir)) {
  60                         char device[UTIL_PATH_SIZE];
  61                         ssize_t len;
  62                         struct udev_device *dev;
  63
  64                         if (ent->d_name[0] == '.')
  65                                 continue;
  66
  67                         len = readlinkat(dirfd(dir), ent->d_name, device, sizeof(device));
  68                         if (len <= 0 || len == (ssize_t)sizeof(device))
  69                                 goto unlink;
  70                         device[len] = '\0';
  71
  72                         dev = udev_device_new_from_device_id(udev, device);
  73                         if (dev == NULL)
  74                                 goto unlink;
  75
  76                         log_debug("restoring old watch on '%s'", udev_device_get_devnode(dev));
  77                         udev_watch_begin(udev, dev);
  78                         udev_device_unref(dev);
  79 unlink:
  80                         unlinkat(dirfd(dir), ent->d_name, 0);
  81                 }
  82
  83                 closedir(dir);
  84                 rmdir("/run/udev/watch.old");
  85
  86         } else if (errno != ENOENT)
  87                 log_error_errno(errno, "unable to move watches dir /run/udev/watch; old watches will not be restored: %m");
  88 }
  89
  90 void udev_watch_begin(struct udev *udev, struct udev_device *dev) {
  91         char filename[UTIL_PATH_SIZE];
  92         int wd;
  93         int r;
  94
  95         if (inotify_fd < 0)
  96                 return;
  97
  98         log_debug("adding watch on '%s'", udev_device_get_devnode(dev));
  99         wd = inotify_add_watch(inotify_fd, udev_device_get_devnode(dev), IN_CLOSE_WRITE);
 100         if (wd < 0) {
 101                 log_error_errno(errno, "inotify_add_watch(%d, %s, %o) failed: %m",
 102                                 inotify_fd, udev_device_get_devnode(dev), IN_CLOSE_WRITE);
 103                 return;
 104         }
 105
 106         snprintf(filename, sizeof(filename), "/run/udev/watch/%d", wd);
 107         mkdir_parents(filename, 0755);
 108         unlink(filename);
 109         r = symlink(udev_device_get_id_filename(dev), filename);
 110         if (r < 0)
 111                 log_error_errno(errno, "Failed to create symlink %s: %m", filename);
 112
 113         udev_device_set_watch_handle(dev, wd);
 114 }
 115
 116 void udev_watch_end(struct udev *udev, struct udev_device *dev) {
 117         int wd;
 118         char filename[UTIL_PATH_SIZE];
 119
 120         if (inotify_fd < 0)
 121                 return;
 122
 123         wd = udev_device_get_watch_handle(dev);
 124         if (wd < 0)
 125                 return;
 126
 127         log_debug("removing watch on '%s'", udev_device_get_devnode(dev));
 128         inotify_rm_watch(inotify_fd, wd);
 129
 130         snprintf(filename, sizeof(filename), "/run/udev/watch/%d", wd);
 131         unlink(filename);
 132
 133         udev_device_set_watch_handle(dev, -1);
 134 }
 135
 136 struct udev_device *udev_watch_lookup(struct udev *udev, int wd) {
 137         char filename[UTIL_PATH_SIZE];
 138         char device[UTIL_NAME_SIZE];
 139         ssize_t len;
 140
 141         if (inotify_fd < 0 || wd < 0)
 142                 return NULL;
 143
 144         snprintf(filename, sizeof(filename), "/run/udev/watch/%d", wd);
 145         len = readlink(filename, device, sizeof(device));
 146         if (len <= 0 || (size_t)len == sizeof(device))
 147                 return NULL;
 148         device[len] = '\0';
 149
 150         return udev_device_new_from_device_id(udev, device);
 151 }