source: trunk/server/source4/ntvfs/sysdep/inotify.c

/* 
   Unix SMB/CIFS implementation.

   Copyright (C) Andrew Tridgell 2006
   
   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.
   
   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.
   
   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

/*
  notify implementation using inotify
*/

#include "includes.h"
#include "system/filesys.h"
#include <tevent.h>
#include "ntvfs/sysdep/sys_notify.h"
#include "../lib/util/dlinklist.h"
#include "libcli/raw/smb.h"
#include "param/param.h"

#if HAVE_SYS_INOTIFY_H
#include <sys/inotify.h>
#else
/* for older glibc varients - we can remove this eventually */
#include <linux/inotify.h>
#include <asm/unistd.h>

#ifndef HAVE_INOTIFY_INIT
/*
  glibc doesn't define these functions yet (as of March 2006)
*/
static int inotify_init(void)
{
        return syscall(__NR_inotify_init);
}

static int inotify_add_watch(int fd, const char *path, __u32 mask)
{
        return syscall(__NR_inotify_add_watch, fd, path, mask);
}

static int inotify_rm_watch(int fd, int wd)
{
        return syscall(__NR_inotify_rm_watch, fd, wd);
}
#endif
#endif


/* older glibc headers don't have these defines either */
#ifndef IN_ONLYDIR
#define IN_ONLYDIR 0x01000000
#endif
#ifndef IN_MASK_ADD
#define IN_MASK_ADD 0x20000000
#endif

struct inotify_private {
        struct sys_notify_context *ctx;
        int fd;
        struct inotify_watch_context *watches;
};

struct inotify_watch_context {
        struct inotify_watch_context *next, *prev;
        struct inotify_private *in;
        int wd;
        sys_notify_callback_t callback;
        void *private_data;
        uint32_t mask; /* the inotify mask */
        uint32_t filter; /* the windows completion filter */
        const char *path;
};


/*
  see if a particular event from inotify really does match a requested
  notify event in SMB
*/
static bool filter_match(struct inotify_watch_context *w,
                         struct inotify_event *e)
{
        if ((e->mask & w->mask) == 0) {
                /* this happens because inotify_add_watch() coalesces watches on the same
                   path, oring their masks together */
                return false;
        }

        /* SMB separates the filters for files and directories */
        if (e->mask & IN_ISDIR) {
                if ((w->filter & FILE_NOTIFY_CHANGE_DIR_NAME) == 0) {
                        return false;
                }
        } else {
                if ((e->mask & IN_ATTRIB) &&
                    (w->filter & (FILE_NOTIFY_CHANGE_ATTRIBUTES|
                                  FILE_NOTIFY_CHANGE_LAST_WRITE|
                                  FILE_NOTIFY_CHANGE_LAST_ACCESS|
                                  FILE_NOTIFY_CHANGE_EA|
                                  FILE_NOTIFY_CHANGE_SECURITY))) {
                        return true;
                }
                if ((e->mask & IN_MODIFY) && 
                    (w->filter & FILE_NOTIFY_CHANGE_ATTRIBUTES)) {
                        return true;
                }
                if ((w->filter & FILE_NOTIFY_CHANGE_FILE_NAME) == 0) {
                        return false;
                }
        }

        return true;
}
        


/*
  dispatch one inotify event
  
  the cookies are used to correctly handle renames
*/
static void inotify_dispatch(struct inotify_private *in, 
                             struct inotify_event *e, 
                             uint32_t prev_cookie,
                             struct inotify_event *e2)
{
        struct inotify_watch_context *w, *next;
        struct notify_event ne;

        /* ignore extraneous events, such as unmount and IN_IGNORED events */
        if ((e->mask & (IN_ATTRIB|IN_MODIFY|IN_CREATE|IN_DELETE|
                        IN_MOVED_FROM|IN_MOVED_TO)) == 0) {
                return;
        }

        /* map the inotify mask to a action. This gets complicated for
           renames */
        if (e->mask & IN_CREATE) {
                ne.action = NOTIFY_ACTION_ADDED;
        } else if (e->mask & IN_DELETE) {
                ne.action = NOTIFY_ACTION_REMOVED;
        } else if (e->mask & IN_MOVED_FROM) {
                if (e2 != NULL && e2->cookie == e->cookie) {
                        ne.action = NOTIFY_ACTION_OLD_NAME;
                } else {
                        ne.action = NOTIFY_ACTION_REMOVED;
                }
        } else if (e->mask & IN_MOVED_TO) {
                if (e->cookie == prev_cookie) {
                        ne.action = NOTIFY_ACTION_NEW_NAME;
                } else {
                        ne.action = NOTIFY_ACTION_ADDED;
                }
        } else {
                ne.action = NOTIFY_ACTION_MODIFIED;
        }
        ne.path = e->name;

        /* find any watches that have this watch descriptor */
        for (w=in->watches;w;w=next) {
                next = w->next;
                if (w->wd == e->wd && filter_match(w, e)) {
                        w->callback(in->ctx, w->private_data, &ne);
                }
        }

        /* SMB expects a file rename to generate three events, two for
           the rename and the other for a modify of the
           destination. Strange! */
        if (ne.action != NOTIFY_ACTION_NEW_NAME ||
            (e->mask & IN_ISDIR) != 0) {
                return;
        }

        ne.action = NOTIFY_ACTION_MODIFIED;
        e->mask = IN_ATTRIB;
        
        for (w=in->watches;w;w=next) {
                next = w->next;
                if (w->wd == e->wd && filter_match(w, e) &&
                    !(w->filter & FILE_NOTIFY_CHANGE_CREATION)) {
                        w->callback(in->ctx, w->private_data, &ne);
                }
        }
}

/*
  called when the kernel has some events for us
*/
static void inotify_handler(struct tevent_context *ev, struct tevent_fd *fde,
                            uint16_t flags, void *private_data)
{
        struct inotify_private *in = talloc_get_type(private_data,
                                                     struct inotify_private);
        int bufsize = 0;
        struct inotify_event *e0, *e;
        uint32_t prev_cookie=0;

        /*
          we must use FIONREAD as we cannot predict the length of the
          filenames, and thus can't know how much to allocate
          otherwise
        */
        if (ioctl(in->fd, FIONREAD, &bufsize) != 0 || 
            bufsize == 0) {
                DEBUG(0,("No data on inotify fd?!\n"));
                return;
        }

        e0 = e = talloc_size(in, bufsize);
        if (e == NULL) return;

        if (read(in->fd, e0, bufsize) != bufsize) {
                DEBUG(0,("Failed to read all inotify data\n"));
                talloc_free(e0);
                return;
        }

        /* we can get more than one event in the buffer */
        while (bufsize >= sizeof(*e)) {
                struct inotify_event *e2 = NULL;
                bufsize -= e->len + sizeof(*e);
                if (bufsize >= sizeof(*e)) {
                        e2 = (struct inotify_event *)(e->len + sizeof(*e) + (char *)e);
                }
                inotify_dispatch(in, e, prev_cookie, e2);
                prev_cookie = e->cookie;
                e = e2;
        }

        talloc_free(e0);
}

/*
  setup the inotify handle - called the first time a watch is added on
  this context
*/
static NTSTATUS inotify_setup(struct sys_notify_context *ctx)
{
        struct inotify_private *in;
        struct tevent_fd *fde;

        in = talloc(ctx, struct inotify_private);
        NT_STATUS_HAVE_NO_MEMORY(in);

        in->fd = inotify_init();
        if (in->fd == -1) {
                DEBUG(0,("Failed to init inotify - %s\n", strerror(errno)));
                talloc_free(in);
                return map_nt_error_from_unix(errno);
        }
        in->ctx = ctx;
        in->watches = NULL;

        ctx->private_data = in;

        /* add a event waiting for the inotify fd to be readable */
        fde = tevent_add_fd(ctx->ev, in, in->fd,
                           TEVENT_FD_READ, inotify_handler, in);
        if (!fde) {
                if (errno == 0) {
                        errno = ENOMEM;
                }
                DEBUG(0,("Failed to tevent_add_fd() - %s\n", strerror(errno)));
                talloc_free(in);
                return map_nt_error_from_unix(errno);
        }

        tevent_fd_set_auto_close(fde);

        return NT_STATUS_OK;
}


/*
  map from a change notify mask to a inotify mask. Remove any bits
  which we can handle
*/
static const struct {
        uint32_t notify_mask;
        uint32_t inotify_mask;
} inotify_mapping[] = {
        {FILE_NOTIFY_CHANGE_FILE_NAME,   IN_CREATE|IN_DELETE|IN_MOVED_FROM|IN_MOVED_TO},
        {FILE_NOTIFY_CHANGE_DIR_NAME,    IN_CREATE|IN_DELETE|IN_MOVED_FROM|IN_MOVED_TO},
        {FILE_NOTIFY_CHANGE_ATTRIBUTES,  IN_ATTRIB|IN_MOVED_TO|IN_MOVED_FROM|IN_MODIFY},
        {FILE_NOTIFY_CHANGE_LAST_WRITE,  IN_ATTRIB},
        {FILE_NOTIFY_CHANGE_LAST_ACCESS, IN_ATTRIB},
        {FILE_NOTIFY_CHANGE_EA,          IN_ATTRIB},
        {FILE_NOTIFY_CHANGE_SECURITY,    IN_ATTRIB}
};

static uint32_t inotify_map(struct notify_entry *e)
{
        int i;
        uint32_t out=0;
        for (i=0;i<ARRAY_SIZE(inotify_mapping);i++) {
                if (inotify_mapping[i].notify_mask & e->filter) {
                        out |= inotify_mapping[i].inotify_mask;
                        e->filter &= ~inotify_mapping[i].notify_mask;
                }
        }
        return out;
}

/*
  destroy a watch
*/
static int watch_destructor(struct inotify_watch_context *w)
{
        struct inotify_private *in = w->in;
        int wd = w->wd;
        DLIST_REMOVE(w->in->watches, w);

        /* only rm the watch if its the last one with this wd */
        for (w=in->watches;w;w=w->next) {
                if (w->wd == wd) break;
        }
        if (w == NULL) {
                inotify_rm_watch(in->fd, wd);
        }
        return 0;
}


/*
  add a watch. The watch is removed when the caller calls
  talloc_free() on *handle
*/
static NTSTATUS inotify_watch(struct sys_notify_context *ctx,
                              struct notify_entry *e,
                              sys_notify_callback_t callback,
                              void *private_data, 
                              void *handle_p)
{
        struct inotify_private *in;
        int wd;
        uint32_t mask;
        struct inotify_watch_context *w;
        uint32_t filter = e->filter;
        void **handle = (void **)handle_p;

        /* maybe setup the inotify fd */
        if (ctx->private_data == NULL) {
                NTSTATUS status;
                status = inotify_setup(ctx);
                NT_STATUS_NOT_OK_RETURN(status);
        }

        in = talloc_get_type(ctx->private_data, struct inotify_private);

        mask = inotify_map(e);
        if (mask == 0) {
                /* this filter can't be handled by inotify */
                return NT_STATUS_INVALID_PARAMETER;
        }

        /* using IN_MASK_ADD allows us to cope with inotify() returning the same
           watch descriptor for muliple watches on the same path */
        mask |= (IN_MASK_ADD | IN_ONLYDIR);

        /* get a new watch descriptor for this path */
        wd = inotify_add_watch(in->fd, e->path, mask);
        if (wd == -1) {
                e->filter = filter;
                return map_nt_error_from_unix(errno);
        }

        w = talloc(in, struct inotify_watch_context);
        if (w == NULL) {
                inotify_rm_watch(in->fd, wd);
                e->filter = filter;
                return NT_STATUS_NO_MEMORY;
        }

        w->in = in;
        w->wd = wd;
        w->callback = callback;
        w->private_data = private_data;
        w->mask = mask;
        w->filter = filter;
        w->path = talloc_strdup(w, e->path);
        if (w->path == NULL) {
                inotify_rm_watch(in->fd, wd);
                e->filter = filter;
                return NT_STATUS_NO_MEMORY;
        }

        (*handle) = w;

        DLIST_ADD(in->watches, w);

        /* the caller frees the handle to stop watching */
        talloc_set_destructor(w, watch_destructor);
        
        return NT_STATUS_OK;
}


static struct sys_notify_backend inotify = {
        .name = "inotify",
        .notify_watch = inotify_watch
};

/*
  initialialise the inotify module
 */
NTSTATUS sys_notify_inotify_init(void)
{
        /* register ourselves as a system inotify module */
        return sys_notify_register(&inotify);
}