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 #define FD_PENDING_SIZE 20
  27 static SIG_ATOMIC_T fd_pending_array[FD_PENDING_SIZE];
  28 static SIG_ATOMIC_T signals_received;
  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 (SIGRTMIN+2)
  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
  58 struct change_data {
  59         int directory_handle;
  60 };
  61
  62 /****************************************************************************
  63  The signal handler for change notify.
  64  The Linux kernel has a bug in that we should be able to block any
  65  further delivery of RT signals until the kernel_check_notify() function
  66  unblocks them, but it seems that any signal mask we're setting here is
  67  being overwritten on exit from this handler. I should create a standalone
  68  test case for the kernel hackers. JRA.
  69 *****************************************************************************/
  70
  71 static void signal_handler(int sig, siginfo_t *info, void *unused)
  72 {
  73         if (signals_received < FD_PENDING_SIZE - 1) {
  74                 fd_pending_array[signals_received] = (SIG_ATOMIC_T)info->si_fd;
  75                 signals_received++;
  76         } /* Else signal is lost. */
  77         sys_select_signal();
  78 }
  79
  80 /****************************************************************************
  81  Check if a change notify should be issued.
  82  time non-zero means timeout check (used for hash). Ignore this (async method
  83  where time is zero will be used instead).
  84 *****************************************************************************/
  85
  86 static BOOL kernel_check_notify(connection_struct *conn, uint16 vuid, char *path, uint32 flags, void *datap, time_t t)
  87 {
  88         struct change_data *data = (struct change_data *)datap;
  89         int i;
  90         BOOL ret = False;
  91
  92         if (t)
  93                 return False;
  94
  95         BlockSignals(True, RT_SIGNAL_NOTIFY);
  96         for (i = 0; i < signals_received; i++) {
  97                 if (data->directory_handle == (int)fd_pending_array[i]) {
  98                         DEBUG(3,("kernel_check_notify: kernel change notify on %s fd[%d]=%d (signals_received=%d)\n",
  99                                                 path, i, (int)fd_pending_array[i], (int)signals_received ));
 100
 101                         close((int)fd_pending_array[i]);
 102                         fd_pending_array[i] = (SIG_ATOMIC_T)-1;
 103                         if (signals_received - i - 1) {
 104                                 memmove(CONST_DISCARD(void *, &fd_pending_array[i]),
 105                                         CONST_DISCARD(void *, &fd_pending_array[i+1]),
 106                                         sizeof(SIG_ATOMIC_T)*(signals_received-i-1));
 107                         }
 108                         data->directory_handle = -1;
 109                         signals_received--;
 110                         ret = True;
 111                         break;
 112                 }
 113         }
 114         BlockSignals(False, RT_SIGNAL_NOTIFY);
 115         return ret;
 116 }
 117
 118 /****************************************************************************
 119  Remove a change notify data structure.
 120 *****************************************************************************/
 121
 122 static void kernel_remove_notify(void *datap)
 123 {
 124         struct change_data *data = (struct change_data *)datap;
 125         int fd = data->directory_handle;
 126         if (fd != -1) {
 127                 int i;
 128                 BlockSignals(True, RT_SIGNAL_NOTIFY);
 129                 for (i = 0; i < signals_received; i++) {
 130                         if (fd == (int)fd_pending_array[i]) {
 131                                 fd_pending_array[i] = (SIG_ATOMIC_T)-1;
 132                                 if (signals_received - i - 1) {
 133                                         memmove(CONST_DISCARD(void *, &fd_pending_array[i]),
 134                                                 CONST_DISCARD(void *, &fd_pending_array[i+1]),
 135                                                 sizeof(SIG_ATOMIC_T)*(signals_received-i-1));
 136                                 }
 137                                 data->directory_handle = -1;
 138                                 signals_received--;
 139                                 break;
 140                         }
 141                 }
 142                 close(fd);
 143                 BlockSignals(False, RT_SIGNAL_NOTIFY);
 144         }
 145         SAFE_FREE(data);
 146         DEBUG(3,("kernel_remove_notify: fd=%d\n", fd));
 147 }
 148
 149 /****************************************************************************
 150  Register a change notify request.
 151 *****************************************************************************/
 152
 153 static void *kernel_register_notify(connection_struct *conn, char *path, uint32 flags)
 154 {
 155         struct change_data data;
 156         int fd;
 157         unsigned long kernel_flags;
 158
 159         fd = sys_open(path,O_RDONLY, 0);
 160
 161         if (fd == -1) {
 162                 DEBUG(3,("Failed to open directory %s for change notify\n", path));
 163                 return NULL;
 164         }
 165
 166         if (sys_fcntl_long(fd, F_SETSIG, RT_SIGNAL_NOTIFY) == -1) {
 167                 DEBUG(3,("Failed to set signal handler for change notify\n"));
 168                 return NULL;
 169         }
 170
 171         kernel_flags = DN_CREATE|DN_DELETE|DN_RENAME; /* creation/deletion changes everything! */
 172         if (flags & FILE_NOTIFY_CHANGE_FILE)        kernel_flags |= DN_MODIFY;
 173         if (flags & FILE_NOTIFY_CHANGE_DIR_NAME)    kernel_flags |= DN_RENAME|DN_DELETE;
 174         if (flags & FILE_NOTIFY_CHANGE_ATTRIBUTES)  kernel_flags |= DN_ATTRIB;
 175         if (flags & FILE_NOTIFY_CHANGE_SIZE)        kernel_flags |= DN_MODIFY;
 176         if (flags & FILE_NOTIFY_CHANGE_LAST_WRITE)  kernel_flags |= DN_MODIFY;
 177         if (flags & FILE_NOTIFY_CHANGE_LAST_ACCESS) kernel_flags |= DN_ACCESS;
 178         if (flags & FILE_NOTIFY_CHANGE_CREATION)    kernel_flags |= DN_CREATE;
 179         if (flags & FILE_NOTIFY_CHANGE_SECURITY)    kernel_flags |= DN_ATTRIB;
 180         if (flags & FILE_NOTIFY_CHANGE_EA)          kernel_flags |= DN_ATTRIB;
 181         if (flags & FILE_NOTIFY_CHANGE_FILE_NAME)   kernel_flags |= DN_RENAME|DN_DELETE;
 182
 183         if (sys_fcntl_long(fd, F_NOTIFY, kernel_flags) == -1) {
 184                 DEBUG(3,("Failed to set async flag for change notify\n"));
 185                 return NULL;
 186         }
 187
 188         data.directory_handle = fd;
 189
 190         DEBUG(3,("kernel change notify on %s (ntflags=0x%x flags=0x%x) fd=%d\n",
 191                  path, (int)flags, (int)kernel_flags, fd));
 192
 193         return (void *)memdup(&data, sizeof(data));
 194 }
 195
 196 /****************************************************************************
 197  See if the kernel supports change notify.
 198 ****************************************************************************/
 199
 200 static BOOL kernel_notify_available(void)
 201 {
 202         int fd, ret;
 203         fd = open("/tmp", O_RDONLY);
 204         if (fd == -1)
 205                 return False; /* uggh! */
 206         ret = sys_fcntl_long(fd, F_NOTIFY, 0);
 207         close(fd);
 208         return ret == 0;
 209 }
 210
 211 /****************************************************************************
 212  Setup kernel based change notify.
 213 ****************************************************************************/
 214
 215 struct cnotify_fns *kernel_notify_init(void)
 216 {
 217         static struct cnotify_fns cnotify;
 218         struct sigaction act;
 219
 220         ZERO_STRUCT(act);
 221
 222         act.sa_handler = NULL;
 223         act.sa_sigaction = signal_handler;
 224         act.sa_flags = SA_SIGINFO;
 225         sigemptyset( &act.sa_mask );
 226         if (sigaction(RT_SIGNAL_NOTIFY, &act, NULL) != 0) {
 227                 DEBUG(0,("Failed to setup RT_SIGNAL_NOTIFY handler\n"));
 228                 return NULL;
 229         }
 230
 231         if (!kernel_notify_available())
 232                 return NULL;
 233
 234         cnotify.register_notify = kernel_register_notify;
 235         cnotify.check_notify = kernel_check_notify;
 236         cnotify.remove_notify = kernel_remove_notify;
 237         cnotify.select_time = -1;
 238
 239         /* the signal can start off blocked due to a bug in bash */
 240         BlockSignals(False, RT_SIGNAL_NOTIFY);
 241
 242         return &cnotify;
 243 }
 244
 245 #else
 246  void notify_kernel_dummy(void) {}
 247 #endif /* HAVE_KERNEL_CHANGE_NOTIFY */