udev/udev-watch.c

   1 /*
   2  * Copyright (C) 2004-2008 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 #ifdef HAVE_INOTIFY
  30 #include <sys/inotify.h>
  31 #endif
  32
  33 #include "udev.h"
  34
  35 int inotify_fd = -1;
  36
  37 /* inotify descriptor, will be shared with rules directory;
  38  * set to cloexec since we need our children to be able to add
  39  * watches for us
  40  */
  41 void udev_watch_init(struct udev *udev)
  42 {
  43         inotify_fd = inotify_init();
  44         if (inotify_fd >= 0) {
  45                 int flags;
  46
  47                 flags = fcntl(inotify_fd, F_GETFD);
  48                 if (flags < 0)
  49                         flags = FD_CLOEXEC;
  50                 else
  51                         flags |= FD_CLOEXEC;
  52                 fcntl(inotify_fd, F_SETFD, flags);
  53         } else if (errno == ENOSYS)
  54                 info(udev, "unable to use inotify, udevd will not monitor rule files changes\n");
  55         else
  56                 err(udev, "inotify_init failed: %m\n");
  57 }
  58
  59 /* move any old watches directory out of the way, and then restore
  60  * the watches
  61  */
  62 void udev_watch_restore(struct udev *udev)
  63 {
  64         char filename[UTIL_PATH_SIZE], oldname[UTIL_PATH_SIZE];
  65
  66         if (inotify_fd < 0)
  67                 return;
  68
  69         util_strlcpy(oldname, udev_get_dev_path(udev), sizeof(oldname));
  70         util_strlcat(oldname, "/.udev/watch.old", sizeof(oldname));
  71
  72         util_strlcpy(filename, udev_get_dev_path(udev), sizeof(filename));
  73         util_strlcat(filename, "/.udev/watch", sizeof(filename));
  74
  75         if (rename(filename, oldname) == 0) {
  76                 DIR *dir;
  77                 struct dirent *ent;
  78
  79                 dir = opendir(oldname);
  80                 if (dir == NULL) {
  81                         err(udev, "unable to open old watches dir '%s', old watches will not be restored: %m", oldname);
  82                         return;
  83                 }
  84
  85                 while ((ent = readdir(dir)) != NULL) {
  86                         char path[UTIL_PATH_SIZE];
  87                         char buf[UTIL_PATH_SIZE];
  88                         ssize_t len;
  89                         struct udev_device *dev;
  90
  91                         if (ent->d_name[0] < '0' || ent->d_name[0] > '9')
  92                                 continue;
  93
  94                         util_strlcpy(path, oldname, sizeof(path));
  95                         util_strlcat(path, "/", sizeof(path));
  96                         util_strlcat(path, ent->d_name, sizeof(path));
  97
  98                         len = readlink(path, buf, sizeof(buf));
  99                         if (len <= 0) {
 100                                 unlink(path);
 101                                 continue;
 102                         }
 103
 104                         buf[len] = '\0';
 105                         dbg(udev, "old watch to '%s' found\n", buf);
 106                         dev = udev_device_new_from_syspath(udev, buf);
 107                         if (dev == NULL) {
 108                                 unlink(path);
 109                                 continue;
 110                         }
 111
 112                         info(udev, "restoring old watch on '%s'\n", udev_device_get_devnode(dev));
 113                         udev_watch_begin(udev, dev);
 114
 115                         udev_device_unref(dev);
 116                         unlink(path);
 117                 }
 118
 119                 closedir(dir);
 120                 rmdir(oldname);
 121
 122         } else if (errno != ENOENT) {
 123                 err(udev, "unable to move watches dir '%s', old watches will not be restored: %m", filename);
 124         }
 125 }
 126
 127 static const char *udev_watch_filename(struct udev *udev, int wd)
 128 {
 129         static char filename[UTIL_PATH_SIZE];
 130         char str[32];
 131
 132         sprintf(str, "%d", wd);
 133         util_strlcpy(filename, udev_get_dev_path(udev), sizeof(filename));
 134         util_strlcat(filename, "/.udev/watch/", sizeof(filename));
 135         util_strlcat(filename, str, sizeof(filename));
 136
 137         return filename;
 138 }
 139
 140 void udev_watch_begin(struct udev *udev, struct udev_device *dev)
 141 {
 142         const char *filename;
 143         int wd;
 144
 145         if (inotify_fd < 0)
 146                 return;
 147
 148         wd = inotify_add_watch(inotify_fd, udev_device_get_devnode(dev), IN_CLOSE_WRITE);
 149         if (wd < 0) {
 150                 err(udev, "inotify_add_watch(%d, %s, %o) failed: %m\n",
 151                     inotify_fd, udev_device_get_devnode(dev), IN_CLOSE_WRITE);
 152         }
 153
 154         filename = udev_watch_filename(udev, wd);
 155         util_create_path(udev, filename);
 156         unlink(filename);
 157         symlink(udev_device_get_syspath(dev), filename);
 158 }
 159
 160 void udev_watch_clear(struct udev *udev, struct udev_device *dev)
 161 {
 162         static char filename[UTIL_PATH_SIZE];
 163         DIR *dir;
 164         struct dirent *ent;
 165
 166         util_strlcpy(filename, udev_get_dev_path(udev), sizeof(filename));
 167         util_strlcat(filename, "/.udev/watch", sizeof(filename));
 168
 169         dir = opendir(filename);
 170         if (dir == NULL)
 171                 return;
 172
 173         while ((ent = readdir(dir)) != NULL) {
 174                 char path[UTIL_PATH_SIZE];
 175                 char buf[UTIL_PATH_SIZE];
 176                 ssize_t len;
 177
 178                 if (ent->d_name[0] < '0' || ent->d_name[0] > '9')
 179                         continue;
 180
 181                 util_strlcpy(path, filename, sizeof(path));
 182                 util_strlcat(path, "/", sizeof(path));
 183                 util_strlcat(path, ent->d_name, sizeof(path));
 184
 185                 len = readlink(path, buf, sizeof(buf));
 186                 if (len <= 0)
 187                         continue;
 188
 189                 buf[len] = '\0';
 190                 if (strcmp(buf, udev_device_get_syspath(dev)))
 191                         continue;
 192
 193                 /* this is the watch we're looking for */
 194                 info(udev, "clearing existing watch on '%s'\n", udev_device_get_devnode(dev));
 195                 udev_watch_end(udev, atoi(ent->d_name));
 196         }
 197
 198         closedir(dir);
 199 }
 200
 201 void udev_watch_end(struct udev *udev, int wd)
 202 {
 203         const char *filename;
 204
 205         if (inotify_fd < 0 || wd < 0)
 206                 return;
 207
 208         inotify_rm_watch(inotify_fd, wd);
 209
 210         filename = udev_watch_filename(udev, wd);
 211         unlink(filename);
 212 }
 213
 214 const char *udev_watch_lookup(struct udev *udev, int wd)
 215 {
 216         const char *filename;
 217         static char buf[UTIL_PATH_SIZE];
 218         ssize_t len;
 219
 220         if (inotify_fd < 0 || wd < 0)
 221                 return NULL;
 222
 223         filename = udev_watch_filename(udev, wd);
 224         len = readlink(filename, buf, sizeof(buf));
 225         if (len > 0) {
 226                 buf[len] = '\0';
 227
 228                 return buf;
 229         }
 230
 231         return NULL;
 232 }