src/udev/udev-watch.c

   1 /*
   2  * Copyright (C) 2004-2012 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 #include <sys/inotify.h>
  30
  31 #include "udev.h"
  32
  33 static int inotify_fd = -1;
  34
  35 /* inotify descriptor, will be shared with rules directory;
  36  * set to cloexec since we need our children to be able to add
  37  * watches for us
  38  */
  39 int udev_watch_init(struct udev *udev)
  40 {
  41         inotify_fd = inotify_init1(IN_CLOEXEC);
  42         if (inotify_fd < 0)
  43                 log_error("inotify_init failed: %m\n");
  44         return inotify_fd;
  45 }
  46
  47 /* move any old watches directory out of the way, and then restore
  48  * the watches
  49  */
  50 void udev_watch_restore(struct udev *udev)
  51 {
  52         char filename[UTIL_PATH_SIZE], oldname[UTIL_PATH_SIZE];
  53
  54         if (inotify_fd < 0)
  55                 return;
  56
  57         util_strscpyl(oldname, sizeof(oldname), udev_get_run_path(udev), "/watch.old", NULL);
  58         util_strscpyl(filename, sizeof(filename), udev_get_run_path(udev), "/watch", NULL);
  59         if (rename(filename, oldname) == 0) {
  60                 DIR *dir;
  61                 struct dirent *ent;
  62
  63                 dir = opendir(oldname);
  64                 if (dir == NULL) {
  65                         log_error("unable to open old watches dir '%s', old watches will not be restored: %m", oldname);
  66                         return;
  67                 }
  68
  69                 for (ent = readdir(dir); ent != NULL; ent = readdir(dir)) {
  70                         char device[UTIL_PATH_SIZE];
  71                         char *s;
  72                         size_t l;
  73                         ssize_t len;
  74                         struct udev_device *dev;
  75
  76                         if (ent->d_name[0] == '.')
  77                                 continue;
  78
  79                         s = device;
  80                         l = util_strpcpy(&s, sizeof(device), udev_get_sys_path(udev));
  81                         len = readlinkat(dirfd(dir), ent->d_name, s, l);
  82                         if (len <= 0 || len == (ssize_t)l)
  83                                 goto unlink;
  84                         s[len] = '\0';
  85
  86                         dev = udev_device_new_from_id_filename(udev, s);
  87                         if (dev == NULL)
  88                                 goto unlink;
  89
  90                         log_debug("restoring old watch on '%s'\n", udev_device_get_devnode(dev));
  91                         udev_watch_begin(udev, dev);
  92                         udev_device_unref(dev);
  93 unlink:
  94                         unlinkat(dirfd(dir), ent->d_name, 0);
  95                 }
  96
  97                 closedir(dir);
  98                 rmdir(oldname);
  99
 100         } else if (errno != ENOENT) {
 101                 log_error("unable to move watches dir '%s', old watches will not be restored: %m", filename);
 102         }
 103 }
 104
 105 void udev_watch_begin(struct udev *udev, struct udev_device *dev)
 106 {
 107         char filename[UTIL_PATH_SIZE];
 108         int wd;
 109
 110         if (inotify_fd < 0)
 111                 return;
 112
 113         log_debug("adding watch on '%s'\n", udev_device_get_devnode(dev));
 114         wd = inotify_add_watch(inotify_fd, udev_device_get_devnode(dev), IN_CLOSE_WRITE);
 115         if (wd < 0) {
 116                 log_error("inotify_add_watch(%d, %s, %o) failed: %m\n",
 117                     inotify_fd, udev_device_get_devnode(dev), IN_CLOSE_WRITE);
 118                 return;
 119         }
 120
 121         snprintf(filename, sizeof(filename), "%s/watch/%d", udev_get_run_path(udev), wd);
 122         util_create_path(udev, filename);
 123         unlink(filename);
 124         symlink(udev_device_get_id_filename(dev), filename);
 125
 126         udev_device_set_watch_handle(dev, wd);
 127 }
 128
 129 void udev_watch_end(struct udev *udev, struct udev_device *dev)
 130 {
 131         int wd;
 132         char filename[UTIL_PATH_SIZE];
 133
 134         if (inotify_fd < 0)
 135                 return;
 136
 137         wd = udev_device_get_watch_handle(dev);
 138         if (wd < 0)
 139                 return;
 140
 141         log_debug("removing watch on '%s'\n", udev_device_get_devnode(dev));
 142         inotify_rm_watch(inotify_fd, wd);
 143
 144         snprintf(filename, sizeof(filename), "%s/watch/%d", udev_get_run_path(udev), wd);
 145         unlink(filename);
 146
 147         udev_device_set_watch_handle(dev, -1);
 148 }
 149
 150 struct udev_device *udev_watch_lookup(struct udev *udev, int wd)
 151 {
 152         char filename[UTIL_PATH_SIZE];
 153         char majmin[UTIL_PATH_SIZE];
 154         char *s;
 155         size_t l;
 156         ssize_t len;
 157
 158         if (inotify_fd < 0 || wd < 0)
 159                 return NULL;
 160
 161         snprintf(filename, sizeof(filename), "%s/watch/%d", udev_get_run_path(udev), wd);
 162         s = majmin;
 163         l = util_strpcpy(&s, sizeof(majmin), udev_get_sys_path(udev));
 164         len = readlink(filename, s, l);
 165         if (len <= 0 || (size_t)len == l)
 166                 return NULL;
 167         s[len] = '\0';
 168
 169         return udev_device_new_from_id_filename(udev, s);
 170 }