src/udev/udev-watch.c

   1 /* SPDX-License-Identifier: GPL-2.0+ */
   2 /*
   3  * Copyright © 2009 Canonical Ltd.
   4  * Copyright © 2009 Scott James Remnant <scott@netsplit.com>
   5  */
   6
   7 #include <errno.h>
   8 #include <stddef.h>
   9 #include <stdio.h>
  10 #include <sys/inotify.h>
  11 #include <unistd.h>
  12
  13 #include "dirent-util.h"
  14 #include "stdio-util.h"
  15 #include "udev.h"
  16
  17 static int inotify_fd = -1;
  18
  19 /* inotify descriptor, will be shared with rules directory;
  20  * set to cloexec since we need our children to be able to add
  21  * watches for us
  22  */
  23 int udev_watch_init(struct udev *udev) {
  24         inotify_fd = inotify_init1(IN_CLOEXEC);
  25         if (inotify_fd < 0)
  26                 log_error_errno(errno, "inotify_init failed: %m");
  27         return inotify_fd;
  28 }
  29
  30 /* move any old watches directory out of the way, and then restore
  31  * the watches
  32  */
  33 void udev_watch_restore(struct udev *udev) {
  34         if (inotify_fd < 0)
  35                 return;
  36
  37         if (rename("/run/udev/watch", "/run/udev/watch.old") == 0) {
  38                 DIR *dir;
  39                 struct dirent *ent;
  40
  41                 dir = opendir("/run/udev/watch.old");
  42                 if (dir == NULL) {
  43                         log_error_errno(errno, "unable to open old watches dir /run/udev/watch.old; old watches will not be restored: %m");
  44                         return;
  45                 }
  46
  47                 FOREACH_DIRENT_ALL(ent, dir, break) {
  48                         char device[UTIL_PATH_SIZE];
  49                         ssize_t len;
  50                         struct udev_device *dev;
  51
  52                         if (ent->d_name[0] == '.')
  53                                 continue;
  54
  55                         len = readlinkat(dirfd(dir), ent->d_name, device, sizeof(device));
  56                         if (len <= 0 || len == (ssize_t)sizeof(device))
  57                                 goto unlink;
  58                         device[len] = '\0';
  59
  60                         dev = udev_device_new_from_device_id(udev, device);
  61                         if (dev == NULL)
  62                                 goto unlink;
  63
  64                         log_debug("restoring old watch on '%s'", udev_device_get_devnode(dev));
  65                         udev_watch_begin(udev, dev);
  66                         udev_device_unref(dev);
  67 unlink:
  68                         (void) unlinkat(dirfd(dir), ent->d_name, 0);
  69                 }
  70
  71                 closedir(dir);
  72                 rmdir("/run/udev/watch.old");
  73
  74         } else if (errno != ENOENT)
  75                 log_error_errno(errno, "unable to move watches dir /run/udev/watch; old watches will not be restored: %m");
  76 }
  77
  78 void udev_watch_begin(struct udev *udev, struct udev_device *dev) {
  79         char filename[sizeof("/run/udev/watch/") + DECIMAL_STR_MAX(int)];
  80         int wd;
  81         int r;
  82
  83         if (inotify_fd < 0)
  84                 return;
  85
  86         log_debug("adding watch on '%s'", udev_device_get_devnode(dev));
  87         wd = inotify_add_watch(inotify_fd, udev_device_get_devnode(dev), IN_CLOSE_WRITE);
  88         if (wd < 0) {
  89                 log_error_errno(errno, "inotify_add_watch(%d, %s, %o) failed: %m",
  90                                 inotify_fd, udev_device_get_devnode(dev), IN_CLOSE_WRITE);
  91                 return;
  92         }
  93
  94         xsprintf(filename, "/run/udev/watch/%d", wd);
  95         mkdir_parents(filename, 0755);
  96         unlink(filename);
  97         r = symlink(udev_device_get_id_filename(dev), filename);
  98         if (r < 0)
  99                 log_error_errno(errno, "Failed to create symlink %s: %m", filename);
 100
 101         udev_device_set_watch_handle(dev, wd);
 102 }
 103
 104 void udev_watch_end(struct udev *udev, struct udev_device *dev) {
 105         int wd;
 106         char filename[sizeof("/run/udev/watch/") + DECIMAL_STR_MAX(int)];
 107
 108         if (inotify_fd < 0)
 109                 return;
 110
 111         wd = udev_device_get_watch_handle(dev);
 112         if (wd < 0)
 113                 return;
 114
 115         log_debug("removing watch on '%s'", udev_device_get_devnode(dev));
 116         inotify_rm_watch(inotify_fd, wd);
 117
 118         xsprintf(filename, "/run/udev/watch/%d", wd);
 119         unlink(filename);
 120
 121         udev_device_set_watch_handle(dev, -1);
 122 }
 123
 124 struct udev_device *udev_watch_lookup(struct udev *udev, int wd) {
 125         char filename[sizeof("/run/udev/watch/") + DECIMAL_STR_MAX(int)];
 126         char device[UTIL_NAME_SIZE];
 127         ssize_t len;
 128
 129         if (inotify_fd < 0 || wd < 0)
 130                 return NULL;
 131
 132         xsprintf(filename, "/run/udev/watch/%d", wd);
 133         len = readlink(filename, device, sizeof(device));
 134         if (len <= 0 || (size_t)len == sizeof(device))
 135                 return NULL;
 136         device[len] = '\0';
 137
 138         return udev_device_new_from_device_id(udev, device);
 139 }