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 "stdio-util.h"
  28 #include "udev.h"
  29
  30 static int inotify_fd = -1;
  31
  32 /* inotify descriptor, will be shared with rules directory;
  33  * set to cloexec since we need our children to be able to add
  34  * watches for us
  35  */
  36 int udev_watch_init(struct udev *udev) {
  37         inotify_fd = inotify_init1(IN_CLOEXEC);
  38         if (inotify_fd < 0)
  39                 log_error_errno(errno, "inotify_init failed: %m");
  40         return inotify_fd;
  41 }
  42
  43 /* move any old watches directory out of the way, and then restore
  44  * the watches
  45  */
  46 void udev_watch_restore(struct udev *udev) {
  47         if (inotify_fd < 0)
  48                 return;
  49
  50         if (rename("/run/udev/watch", "/run/udev/watch.old") == 0) {
  51                 DIR *dir;
  52                 struct dirent *ent;
  53
  54                 dir = opendir("/run/udev/watch.old");
  55                 if (dir == NULL) {
  56                         log_error_errno(errno, "unable to open old watches dir /run/udev/watch.old; old watches will not be restored: %m");
  57                         return;
  58                 }
  59
  60                 for (ent = readdir(dir); ent != NULL; ent = readdir(dir)) {
  61                         char device[UTIL_PATH_SIZE];
  62                         ssize_t len;
  63                         struct udev_device *dev;
  64
  65                         if (ent->d_name[0] == '.')
  66                                 continue;
  67
  68                         len = readlinkat(dirfd(dir), ent->d_name, device, sizeof(device));
  69                         if (len <= 0 || len == (ssize_t)sizeof(device))
  70                                 goto unlink;
  71                         device[len] = '\0';
  72
  73                         dev = udev_device_new_from_device_id(udev, device);
  74                         if (dev == NULL)
  75                                 goto unlink;
  76
  77                         log_debug("restoring old watch on '%s'", udev_device_get_devnode(dev));
  78                         udev_watch_begin(udev, dev);
  79                         udev_device_unref(dev);
  80 unlink:
  81                         unlinkat(dirfd(dir), ent->d_name, 0);
  82                 }
  83
  84                 closedir(dir);
  85                 rmdir("/run/udev/watch.old");
  86
  87         } else if (errno != ENOENT)
  88                 log_error_errno(errno, "unable to move watches dir /run/udev/watch; old watches will not be restored: %m");
  89 }
  90
  91 void udev_watch_begin(struct udev *udev, struct udev_device *dev) {
  92         char filename[sizeof("/run/udev/watch/") + DECIMAL_STR_MAX(int)];
  93         int wd;
  94         int r;
  95
  96         if (inotify_fd < 0)
  97                 return;
  98
  99         log_debug("adding watch on '%s'", udev_device_get_devnode(dev));
 100         wd = inotify_add_watch(inotify_fd, udev_device_get_devnode(dev), IN_CLOSE_WRITE);
 101         if (wd < 0) {
 102                 log_error_errno(errno, "inotify_add_watch(%d, %s, %o) failed: %m",
 103                                 inotify_fd, udev_device_get_devnode(dev), IN_CLOSE_WRITE);
 104                 return;
 105         }
 106
 107         xsprintf(filename, "/run/udev/watch/%d", wd);
 108         mkdir_parents(filename, 0755);
 109         unlink(filename);
 110         r = symlink(udev_device_get_id_filename(dev), filename);
 111         if (r < 0)
 112                 log_error_errno(errno, "Failed to create symlink %s: %m", filename);
 113
 114         udev_device_set_watch_handle(dev, wd);
 115 }
 116
 117 void udev_watch_end(struct udev *udev, struct udev_device *dev) {
 118         int wd;
 119         char filename[sizeof("/run/udev/watch/") + DECIMAL_STR_MAX(int)];
 120
 121         if (inotify_fd < 0)
 122                 return;
 123
 124         wd = udev_device_get_watch_handle(dev);
 125         if (wd < 0)
 126                 return;
 127
 128         log_debug("removing watch on '%s'", udev_device_get_devnode(dev));
 129         inotify_rm_watch(inotify_fd, wd);
 130
 131         xsprintf(filename, "/run/udev/watch/%d", wd);
 132         unlink(filename);
 133
 134         udev_device_set_watch_handle(dev, -1);
 135 }
 136
 137 struct udev_device *udev_watch_lookup(struct udev *udev, int wd) {
 138         char filename[sizeof("/run/udev/watch/") + DECIMAL_STR_MAX(int)];
 139         char device[UTIL_NAME_SIZE];
 140         ssize_t len;
 141
 142         if (inotify_fd < 0 || wd < 0)
 143                 return NULL;
 144
 145         xsprintf(filename, "/run/udev/watch/%d", wd);
 146         len = readlink(filename, device, sizeof(device));
 147         if (len <= 0 || (size_t)len == sizeof(device))
 148                 return NULL;
 149         device[len] = '\0';
 150
 151         return udev_device_new_from_device_id(udev, device);
 152 }