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 <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         if (inotify_fd < 0)
  53                 return;
  54
  55         if (rename("/run/udev/watch", "/run/udev/watch.old") == 0) {
  56                 DIR *dir;
  57                 struct dirent *ent;
  58
  59                 dir = opendir("/run/udev/watch.old");
  60                 if (dir == NULL) {
  61                         log_error("unable to open old watches dir /run/udev/watch.old; old watches will not be restored: %m");
  62                         return;
  63                 }
  64
  65                 for (ent = readdir(dir); ent != NULL; ent = readdir(dir)) {
  66                         char device[UTIL_PATH_SIZE];
  67                         ssize_t len;
  68                         struct udev_device *dev;
  69
  70                         if (ent->d_name[0] == '.')
  71                                 continue;
  72
  73                         len = readlinkat(dirfd(dir), ent->d_name, device, sizeof(device));
  74                         if (len <= 0 || len == (ssize_t)sizeof(device))
  75                                 goto unlink;
  76                         device[len] = '\0';
  77
  78                         dev = udev_device_new_from_device_id(udev, device);
  79                         if (dev == NULL)
  80                                 goto unlink;
  81
  82                         log_debug("restoring old watch on '%s'\n", udev_device_get_devnode(dev));
  83                         udev_watch_begin(udev, dev);
  84                         udev_device_unref(dev);
  85 unlink:
  86                         unlinkat(dirfd(dir), ent->d_name, 0);
  87                 }
  88
  89                 closedir(dir);
  90                 rmdir("/run/udev/watch.old");
  91
  92         } else if (errno != ENOENT) {
  93                 log_error("unable to move watches dir /run/udev/watch; old watches will not be restored: %m");
  94         }
  95 }
  96
  97 void udev_watch_begin(struct udev *udev, struct udev_device *dev)
  98 {
  99         char filename[UTIL_PATH_SIZE];
 100         int wd;
 101         int r;
 102
 103         if (inotify_fd < 0)
 104                 return;
 105
 106         log_debug("adding watch on '%s'\n", udev_device_get_devnode(dev));
 107         wd = inotify_add_watch(inotify_fd, udev_device_get_devnode(dev), IN_CLOSE_WRITE);
 108         if (wd < 0) {
 109                 log_error("inotify_add_watch(%d, %s, %o) failed: %m\n",
 110                     inotify_fd, udev_device_get_devnode(dev), IN_CLOSE_WRITE);
 111                 return;
 112         }
 113
 114         snprintf(filename, sizeof(filename), "/run/udev/watch/%d", wd);
 115         mkdir_parents(filename, 0755);
 116         unlink(filename);
 117         r = symlink(udev_device_get_id_filename(dev), filename);
 118         if (r < 0)
 119                 log_error("Failed to create symlink: %m");
 120
 121         udev_device_set_watch_handle(dev, wd);
 122 }
 123
 124 void udev_watch_end(struct udev *udev, struct udev_device *dev)
 125 {
 126         int wd;
 127         char filename[UTIL_PATH_SIZE];
 128
 129         if (inotify_fd < 0)
 130                 return;
 131
 132         wd = udev_device_get_watch_handle(dev);
 133         if (wd < 0)
 134                 return;
 135
 136         log_debug("removing watch on '%s'\n", udev_device_get_devnode(dev));
 137         inotify_rm_watch(inotify_fd, wd);
 138
 139         snprintf(filename, sizeof(filename), "/run/udev/watch/%d", wd);
 140         unlink(filename);
 141
 142         udev_device_set_watch_handle(dev, -1);
 143 }
 144
 145 struct udev_device *udev_watch_lookup(struct udev *udev, int wd)
 146 {
 147         char filename[UTIL_PATH_SIZE];
 148         char device[UTIL_NAME_SIZE];
 149         ssize_t len;
 150
 151         if (inotify_fd < 0 || wd < 0)
 152                 return NULL;
 153
 154         snprintf(filename, sizeof(filename), "/run/udev/watch/%d", wd);
 155         len = readlink(filename, device, sizeof(device));
 156         if (len <= 0 || (size_t)len == sizeof(device))
 157                 return NULL;
 158         device[len] = '\0';
 159
 160         return udev_device_new_from_device_id(udev, device);
 161 }