source/smbd/notify_kernel.c

   1 /*
   2    Unix SMB/Netbios implementation.
   3    Version 3.0
   4    change notify handling - linux kernel based implementation
   5    Copyright (C) Andrew Tridgell 2000
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 2 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program; if not, write to the Free Software
  19    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  20 */
  21
  22 #include "includes.h"
  23
  24 #if HAVE_KERNEL_CHANGE_NOTIFY
  25
  26 static VOLATILE sig_atomic_t fd_pending;
  27 static VOLATILE sig_atomic_t signals_received;
  28 static VOLATILE sig_atomic_t signals_processed;
  29
  30 #ifndef DN_ACCESS
  31 #define DN_ACCESS       0x00000001      /* File accessed in directory */
  32 #define DN_MODIFY       0x00000002      /* File modified in directory */
  33 #define DN_CREATE       0x00000004      /* File created in directory */
  34 #define DN_DELETE       0x00000008      /* File removed from directory */
  35 #define DN_RENAME       0x00000010      /* File renamed in directory */
  36 #define DN_ATTRIB       0x00000020      /* File changed attribute */
  37 #define DN_MULTISHOT    0x80000000      /* Don't remove notifier */
  38 #endif
  39
  40
  41 #ifndef RT_SIGNAL_NOTIFY
  42 #define RT_SIGNAL_NOTIFY 34
  43 #endif
  44
  45 #ifndef F_SETSIG
  46 #define F_SETSIG 10
  47 #endif
  48
  49 #ifndef F_NOTIFY
  50 #define F_NOTIFY 1026
  51 #endif
  52
  53 /****************************************************************************
  54  This is the structure to keep the information needed to
  55  determine if a directory has changed.
  56 *****************************************************************************/
  57 struct change_data {
  58         int directory_handle;
  59 };
  60
  61 /****************************************************************************
  62 the signal handler for change notify
  63 *****************************************************************************/
  64 static void signal_handler(int sig, siginfo_t *info, void *unused)
  65 {
  66         BlockSignals(True, sig);
  67         fd_pending = (sig_atomic_t)info->si_fd;
  68         signals_received++;
  69         sys_select_signal();
  70 }
  71
  72
  73
  74 /****************************************************************************
  75  Check if a change notify should be issued.
  76  time non-zero means timeout check (used for hash). Ignore this (async method
  77  where time is zero will be used instead).
  78 *****************************************************************************/
  79 static BOOL kernel_check_notify(connection_struct *conn, uint16 vuid, char *path, uint32 flags, void *datap, time_t t)
  80 {
  81         struct change_data *data = (struct change_data *)datap;
  82
  83         if (t)
  84                 return False;
  85
  86         if (data->directory_handle != (int)fd_pending) return False;
  87
  88         DEBUG(3,("kernel change notify on %s fd=%d\n", path, (int)fd_pending));
  89
  90         close((int)fd_pending);
  91         fd_pending = (sig_atomic_t)-1;
  92         data->directory_handle = -1;
  93         signals_processed++;
  94         BlockSignals(False, RT_SIGNAL_NOTIFY);
  95         return True;
  96 }
  97
  98 /****************************************************************************
  99 remove a change notify data structure
 100 *****************************************************************************/
 101 static void kernel_remove_notify(void *datap)
 102 {
 103         struct change_data *data = (struct change_data *)datap;
 104         int fd = data->directory_handle;
 105         if (fd != -1) {
 106                 if (fd == (int)fd_pending) {
 107                         fd_pending = (sig_atomic_t)-1;
 108                         signals_processed++;
 109                         BlockSignals(False, RT_SIGNAL_NOTIFY);
 110                 }
 111                 close(fd);
 112         }
 113         SAFE_FREE(data);
 114         DEBUG(3,("removed kernel change notify fd=%d\n", fd));
 115 }
 116
 117
 118 /****************************************************************************
 119 register a change notify request
 120 *****************************************************************************/
 121 static void *kernel_register_notify(connection_struct *conn, char *path, uint32 flags)
 122 {
 123         struct change_data data;
 124         int fd;
 125         unsigned long kernel_flags;
 126
 127         fd = conn->vfs_ops.open(conn, path, O_RDONLY, 0);
 128
 129         if (fd == -1) {
 130                 DEBUG(3,("Failed to open directory %s for change notify\n", path));
 131                 return NULL;
 132         }
 133
 134         if (fcntl(fd, F_SETSIG, RT_SIGNAL_NOTIFY) == -1) {
 135                 DEBUG(3,("Failed to set signal handler for change notify\n"));
 136                 return NULL;
 137         }
 138
 139         kernel_flags = DN_CREATE|DN_DELETE|DN_RENAME; /* creation/deletion changes everything! */
 140         if (flags & FILE_NOTIFY_CHANGE_FILE)        kernel_flags |= DN_MODIFY;
 141         if (flags & FILE_NOTIFY_CHANGE_DIR_NAME)    kernel_flags |= DN_RENAME|DN_DELETE;
 142         if (flags & FILE_NOTIFY_CHANGE_ATTRIBUTES)  kernel_flags |= DN_ATTRIB;
 143         if (flags & FILE_NOTIFY_CHANGE_SIZE)        kernel_flags |= DN_MODIFY;
 144         if (flags & FILE_NOTIFY_CHANGE_LAST_WRITE)  kernel_flags |= DN_MODIFY;
 145         if (flags & FILE_NOTIFY_CHANGE_LAST_ACCESS) kernel_flags |= DN_ACCESS;
 146         if (flags & FILE_NOTIFY_CHANGE_CREATION)    kernel_flags |= DN_CREATE;
 147         if (flags & FILE_NOTIFY_CHANGE_SECURITY)    kernel_flags |= DN_ATTRIB;
 148         if (flags & FILE_NOTIFY_CHANGE_EA)          kernel_flags |= DN_ATTRIB;
 149         if (flags & FILE_NOTIFY_CHANGE_FILE_NAME)   kernel_flags |= DN_RENAME|DN_DELETE;
 150
 151         if (fcntl(fd, F_NOTIFY, kernel_flags) == -1) {
 152                 DEBUG(3,("Failed to set async flag for change notify\n"));
 153                 return NULL;
 154         }
 155
 156         data.directory_handle = fd;
 157
 158         DEBUG(3,("kernel change notify on %s (ntflags=0x%x flags=0x%x) fd=%d\n",
 159                  path, (int)flags, (int)kernel_flags, fd));
 160
 161         return (void *)memdup(&data, sizeof(data));
 162 }
 163
 164 /****************************************************************************
 165 see if the kernel supports change notify
 166 ****************************************************************************/
 167 static BOOL kernel_notify_available(void)
 168 {
 169         int fd, ret;
 170         fd = open("/tmp", O_RDONLY);
 171         if (fd == -1) return False; /* uggh! */
 172         ret = fcntl(fd, F_NOTIFY, 0);
 173         close(fd);
 174         return ret == 0;
 175 }
 176
 177
 178 /****************************************************************************
 179 setup kernel based change notify
 180 ****************************************************************************/
 181 struct cnotify_fns *kernel_notify_init(void)
 182 {
 183         static struct cnotify_fns cnotify;
 184         struct sigaction act;
 185
 186         act.sa_handler = NULL;
 187         act.sa_sigaction = signal_handler;
 188         act.sa_flags = SA_SIGINFO;
 189         if (sigaction(RT_SIGNAL_NOTIFY, &act, NULL) != 0) {
 190                 DEBUG(0,("Failed to setup RT_SIGNAL_NOTIFY handler\n"));
 191                 return NULL;
 192         }
 193
 194         if (!kernel_notify_available()) return NULL;
 195
 196         cnotify.register_notify = kernel_register_notify;
 197         cnotify.check_notify = kernel_check_notify;
 198         cnotify.remove_notify = kernel_remove_notify;
 199         cnotify.select_time = -1;
 200
 201         return &cnotify;
 202 }
 203
 204
 205 #else
 206  void notify_kernel_dummy(void) {}
 207 #endif /* HAVE_KERNEL_CHANGE_NOTIFY */