smbd/notify_internal.c

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/* 
   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 2 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, write to the Free Software
   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/

/*
  this is the change notify database. It implements mechanisms for
  storing current change notify waiters in a tdb, and checking if a
  given event matches any of the stored notify waiiters.
*/

#include "includes.h"
#include "librpc/gen_ndr/ndr_notify.h"

struct notify_context {
        struct tdb_wrap *w;
        struct server_id server;
        struct messaging_context *messaging_ctx;
        struct notify_list *list;
        struct notify_array *array;
        int seqnum;
        struct sys_notify_context *sys_notify_ctx;
};


struct notify_list {
        struct notify_list *next, *prev;
        void *private_data;
        void (*callback)(void *, const struct notify_event *);
        void *sys_notify_handle;
        int depth;
};

#define NOTIFY_KEY "notify array"

#define NOTIFY_ENABLE           "notify:enable"
#define NOTIFY_ENABLE_DEFAULT   True

static NTSTATUS notify_remove_all(struct notify_context *notify,
                                  const struct server_id *server);
static void notify_handler(struct messaging_context *msg_ctx, void *private_data, 
                           uint32_t msg_type, struct server_id server_id, DATA_BLOB *data);

/*
  destroy the notify context
*/
static int notify_destructor(struct notify_context *notify)
{
        messaging_deregister(notify->messaging_ctx, MSG_PVFS_NOTIFY, notify);

        if (notify->list != NULL) {
                notify_remove_all(notify, &notify->server);
        }

        return 0;
}

/*
  Open up the notify.tdb database. You should close it down using
  talloc_free(). We need the messaging_ctx to allow for notifications
  via internal messages
*/
struct notify_context *notify_init(TALLOC_CTX *mem_ctx, struct server_id server, 
                                   struct messaging_context *messaging_ctx,
                                   struct event_context *ev,
                                   connection_struct *conn)
{
        struct notify_context *notify;

        if (!lp_change_notify(conn->params)) {
                return NULL;
        }

        notify = talloc(mem_ctx, struct notify_context);
        if (notify == NULL) {
                return NULL;
        }

        notify->w = tdb_wrap_open(notify, lock_path("notify.tdb"),
                                  0, TDB_SEQNUM|TDB_CLEAR_IF_FIRST,
                                  O_RDWR|O_CREAT, 0644);
        if (notify->w == NULL) {
                talloc_free(notify);
                return NULL;
        }

        notify->server = server;
        notify->messaging_ctx = messaging_ctx;
        notify->list = NULL;
        notify->array = NULL;
        notify->seqnum = tdb_get_seqnum(notify->w->tdb);

        talloc_set_destructor(notify, notify_destructor);

        /* register with the messaging subsystem for the notify
           message type */
        messaging_register(notify->messaging_ctx, notify, 
                           MSG_PVFS_NOTIFY, notify_handler);

        notify->sys_notify_ctx = sys_notify_context_create(conn, notify, ev);

        return notify;
}


/*
  lock the notify db
*/
static NTSTATUS notify_lock(struct notify_context *notify)
{
        if (tdb_lock_bystring(notify->w->tdb, NOTIFY_KEY) != 0) {
                return NT_STATUS_INTERNAL_DB_CORRUPTION;
        }
        return NT_STATUS_OK;
}

/*
  unlock the notify db
*/
static void notify_unlock(struct notify_context *notify)
{
        tdb_unlock_bystring(notify->w->tdb, NOTIFY_KEY);
}

/*
  load the notify array
*/
static NTSTATUS notify_load(struct notify_context *notify)
{
        TDB_DATA dbuf;
        DATA_BLOB blob;
        NTSTATUS status;
        int seqnum;

        seqnum = tdb_get_seqnum(notify->w->tdb);

        if (seqnum == notify->seqnum && notify->array != NULL) {
                return NT_STATUS_OK;
        }

        notify->seqnum = seqnum;

        talloc_free(notify->array);
        notify->array = TALLOC_ZERO_P(notify, struct notify_array);
        NT_STATUS_HAVE_NO_MEMORY(notify->array);

        dbuf = tdb_fetch_bystring(notify->w->tdb, NOTIFY_KEY);
        if (dbuf.dptr == NULL) {
                return NT_STATUS_OK;
        }

        blob.data = (uint8 *)dbuf.dptr;
        blob.length = dbuf.dsize;

        status = ndr_pull_struct_blob(&blob, notify->array, notify->array, 
                                      (ndr_pull_flags_fn_t)ndr_pull_notify_array);

        if (DEBUGLEVEL >= 10) {
                DEBUG(10, ("notify_load:\n"));
                NDR_PRINT_DEBUG(notify_array, notify->array);
        }

        free(dbuf.dptr);

        return status;
}

/*
  compare notify entries for sorting
*/
static int notify_compare(const void *p1, const void *p2)
{
        const struct notify_entry *e1 = (const struct notify_entry *)p1;
        const struct notify_entry *e2 = (const struct notify_entry *)p2;
        return strcmp(e1->path, e2->path);
}

/*
  save the notify array
*/
static NTSTATUS notify_save(struct notify_context *notify)
{
        TDB_DATA dbuf;
        DATA_BLOB blob;
        NTSTATUS status;
        int ret;
        TALLOC_CTX *tmp_ctx;

        /* if possible, remove some depth arrays */
        while (notify->array->num_depths > 0 &&
               notify->array->depth[notify->array->num_depths-1].num_entries == 0) {
                notify->array->num_depths--;
        }

        /* we might just be able to delete the record */
        if (notify->array->num_depths == 0) {
                ret = tdb_delete_bystring(notify->w->tdb, NOTIFY_KEY);
                if (ret != 0) {
                        return NT_STATUS_INTERNAL_DB_CORRUPTION;
                }
                return NT_STATUS_OK;
        }

        tmp_ctx = talloc_new(notify);
        NT_STATUS_HAVE_NO_MEMORY(tmp_ctx);

        status = ndr_push_struct_blob(&blob, tmp_ctx, notify->array, 
                                      (ndr_push_flags_fn_t)ndr_push_notify_array);
        if (!NT_STATUS_IS_OK(status)) {
                talloc_free(tmp_ctx);
                return status;
        }

        if (DEBUGLEVEL >= 10) {
                DEBUG(10, ("notify_save:\n"));
                NDR_PRINT_DEBUG(notify_array, notify->array);
        }

        dbuf.dptr = (char *)blob.data;
        dbuf.dsize = blob.length;
                
        ret = tdb_store_bystring(notify->w->tdb, NOTIFY_KEY, dbuf, TDB_REPLACE);
        talloc_free(tmp_ctx);
        if (ret != 0) {
                return NT_STATUS_INTERNAL_DB_CORRUPTION;
        }

        return NT_STATUS_OK;
}


/*
  handle incoming notify messages
*/
static void notify_handler(struct messaging_context *msg_ctx, void *private_data, 
                           uint32_t msg_type, struct server_id server_id, DATA_BLOB *data)
{
        struct notify_context *notify = talloc_get_type(private_data, struct notify_context);
        NTSTATUS status;
        struct notify_event ev;
        TALLOC_CTX *tmp_ctx = talloc_new(notify);
        struct notify_list *listel;

        if (tmp_ctx == NULL) {
                return;
        }

        status = ndr_pull_struct_blob(data, tmp_ctx, &ev, 
                                      (ndr_pull_flags_fn_t)ndr_pull_notify_event);
        if (!NT_STATUS_IS_OK(status)) {
                talloc_free(tmp_ctx);
                return;
        }

        for (listel=notify->list;listel;listel=listel->next) {
                if (listel->private_data == ev.private_data) {
                        listel->callback(listel->private_data, &ev);
                        break;
                }
        }

        talloc_free(tmp_ctx);   
}

/*
  callback from sys_notify telling us about changes from the OS
*/
static void sys_notify_callback(struct sys_notify_context *ctx, 
                                void *ptr, struct notify_event *ev)
{
        struct notify_list *listel = talloc_get_type(ptr, struct notify_list);
        ev->private_data = listel;
        DEBUG(10, ("sys_notify_callback called with action=%d, for %s\n",
                   ev->action, ev->path));
        listel->callback(listel->private_data, ev);
}

/*
  add an entry to the notify array
*/
static NTSTATUS notify_add_array(struct notify_context *notify, struct notify_entry *e,
                                 void *private_data, int depth)
{
        int i;
        struct notify_depth *d;
        struct notify_entry *ee;

        /* possibly expand the depths array */
        if (depth >= notify->array->num_depths) {
                d = talloc_realloc(notify->array, notify->array->depth, 
                                   struct notify_depth, depth+1);
                NT_STATUS_HAVE_NO_MEMORY(d);
                for (i=notify->array->num_depths;i<=depth;i++) {
                        ZERO_STRUCT(d[i]);
                }
                notify->array->depth = d;
                notify->array->num_depths = depth+1;
        }
        d = &notify->array->depth[depth];

        /* expand the entries array */
        ee = talloc_realloc(notify->array->depth, d->entries, struct notify_entry,
                            d->num_entries+1);
        NT_STATUS_HAVE_NO_MEMORY(ee);
        d->entries = ee;

        d->entries[d->num_entries] = *e;
        d->entries[d->num_entries].private_data = private_data;
        d->entries[d->num_entries].server = notify->server;
        d->entries[d->num_entries].path_len = strlen(e->path);
        d->num_entries++;

        d->max_mask |= e->filter;
        d->max_mask_subdir |= e->subdir_filter;

        if (d->num_entries > 1) {
                qsort(d->entries, d->num_entries, sizeof(d->entries[0]), notify_compare);
        }

        /* recalculate the maximum masks */
        d->max_mask = 0;
        d->max_mask_subdir = 0;

        for (i=0;i<d->num_entries;i++) {
                d->max_mask |= d->entries[i].filter;
                d->max_mask_subdir |= d->entries[i].subdir_filter;
        }

        return notify_save(notify);
}

/*
  add a notify watch. This is called when a notify is first setup on a open
  directory handle.
*/
NTSTATUS notify_add(struct notify_context *notify, struct notify_entry *e0,
                    void (*callback)(void *, const struct notify_event *), 
                    void *private_data)
{
        struct notify_entry e = *e0;
        NTSTATUS status;
        char *tmp_path = NULL;
        struct notify_list *listel;
        size_t len;
        int depth;

        /* see if change notify is enabled at all */
        if (notify == NULL) {
                return NT_STATUS_NOT_IMPLEMENTED;
        }

        status = notify_lock(notify);
        NT_STATUS_NOT_OK_RETURN(status);

        status = notify_load(notify);
        if (!NT_STATUS_IS_OK(status)) {
                goto done;
        }

        /* cope with /. on the end of the path */
        len = strlen(e.path);
        if (len > 1 && e.path[len-1] == '.' && e.path[len-2] == '/') {
                tmp_path = talloc_strndup(notify, e.path, len-2);
                if (tmp_path == NULL) {
                        status = NT_STATUS_NO_MEMORY;
                        goto done;
                }
                e.path = tmp_path;
        }

        depth = count_chars(e.path, '/');

        listel = TALLOC_ZERO_P(notify, struct notify_list);
        if (listel == NULL) {
                status = NT_STATUS_NO_MEMORY;
                goto done;
        }

        listel->private_data = private_data;
        listel->callback = callback;
        listel->depth = depth;
        DLIST_ADD(notify->list, listel);

        /* ignore failures from sys_notify */
        if (notify->sys_notify_ctx != NULL) {
                /*
                  this call will modify e.filter and e.subdir_filter
                  to remove bits handled by the backend
                */
                status = sys_notify_watch(notify->sys_notify_ctx, &e,
                                          sys_notify_callback, listel, 
                                          &listel->sys_notify_handle);
                if (NT_STATUS_IS_OK(status)) {
                        talloc_steal(listel, listel->sys_notify_handle);
                }
        }

        /* if the system notify handler couldn't handle some of the
           filter bits, or couldn't handle a request for recursion
           then we need to install it in the array used for the
           intra-samba notify handling */
        if (e.filter != 0 || e.subdir_filter != 0) {
                status = notify_add_array(notify, &e, private_data, depth);
        }

done:
        notify_unlock(notify);
        talloc_free(tmp_path);

        return status;
}

/*
  remove a notify watch. Called when the directory handle is closed
*/
NTSTATUS notify_remove(struct notify_context *notify, void *private_data)
{
        NTSTATUS status;
        struct notify_list *listel;
        int i, depth;
        struct notify_depth *d;

        /* see if change notify is enabled at all */
        if (notify == NULL) {
                return NT_STATUS_NOT_IMPLEMENTED;
        }

        for (listel=notify->list;listel;listel=listel->next) {
                if (listel->private_data == private_data) {
                        DLIST_REMOVE(notify->list, listel);
                        break;
                }
        }
        if (listel == NULL) {
                return NT_STATUS_OBJECT_NAME_NOT_FOUND;
        }

        depth = listel->depth;

        talloc_free(listel);

        status = notify_lock(notify);
        NT_STATUS_NOT_OK_RETURN(status);

        status = notify_load(notify);
        if (!NT_STATUS_IS_OK(status)) {
                notify_unlock(notify);
                return status;
        }

        if (depth >= notify->array->num_depths) {
                notify_unlock(notify);
                return NT_STATUS_OBJECT_NAME_NOT_FOUND;
        }

        /* we only have to search at the depth of this element */
        d = &notify->array->depth[depth];

        for (i=0;i<d->num_entries;i++) {
                if (private_data == d->entries[i].private_data &&
                    cluster_id_equal(&notify->server, &d->entries[i].server)) {
                        break;
                }
        }
        if (i == d->num_entries) {
                notify_unlock(notify);
                return NT_STATUS_OBJECT_NAME_NOT_FOUND;
        }

        if (i < d->num_entries-1) {
                memmove(&d->entries[i], &d->entries[i+1], 
                        sizeof(d->entries[i])*(d->num_entries-(i+1)));
        }
        d->num_entries--;

        status = notify_save(notify);

        notify_unlock(notify);

        return status;
}

/*
  remove all notify watches for a messaging server
*/
static NTSTATUS notify_remove_all(struct notify_context *notify,
                                  const struct server_id *server)
{
        NTSTATUS status;
        int i, depth, del_count=0;

        status = notify_lock(notify);
        NT_STATUS_NOT_OK_RETURN(status);

        status = notify_load(notify);
        if (!NT_STATUS_IS_OK(status)) {
                notify_unlock(notify);
                return status;
        }

        /* we have to search for all entries across all depths, looking for matches
           for the server id */
        for (depth=0;depth<notify->array->num_depths;depth++) {
                struct notify_depth *d = &notify->array->depth[depth];
                for (i=0;i<d->num_entries;i++) {
                        if (cluster_id_equal(server, &d->entries[i].server)) {
                                if (i < d->num_entries-1) {
                                        memmove(&d->entries[i], &d->entries[i+1], 
                                                sizeof(d->entries[i])*(d->num_entries-(i+1)));
                                }
                                i--;
                                d->num_entries--;
                                del_count++;
                        }
                }
        }

        if (del_count > 0) {
                status = notify_save(notify);
        }

        notify_unlock(notify);

        return status;
}


/*
  send a notify message to another messaging server
*/
static NTSTATUS notify_send(struct notify_context *notify, struct notify_entry *e,
                            const char *path, uint32_t action)
{
        struct notify_event ev;
        DATA_BLOB data;
        NTSTATUS status;
        TALLOC_CTX *tmp_ctx;

        ev.action = action;
        ev.path = path;
        ev.private_data = e->private_data;

        tmp_ctx = talloc_new(notify);

        status = ndr_push_struct_blob(&data, tmp_ctx, &ev, 
                                      (ndr_push_flags_fn_t)ndr_push_notify_event);
        if (!NT_STATUS_IS_OK(status)) {
                talloc_free(tmp_ctx);
                return status;
        }

        status = messaging_send(notify->messaging_ctx, e->server, 
                                MSG_PVFS_NOTIFY, &data);
        talloc_free(tmp_ctx);
        return status;
}


/*
  trigger a notify message for anyone waiting on a matching event

  This function is called a lot, and needs to be very fast. The unusual data structure
  and traversal is designed to be fast in the average case, even for large numbers of
  notifies
*/
void notify_trigger(struct notify_context *notify,
                    uint32_t action, uint32_t filter, const char *path)
{
        NTSTATUS status;
        int depth;
        const char *p, *next_p;

        DEBUG(10, ("notify_trigger called action=0x%x, filter=0x%x, "
                   "path=%s\n", (unsigned)action, (unsigned)filter, path));

        /* see if change notify is enabled at all */
        if (notify == NULL) {
                return;
        }

 again:
        status = notify_load(notify);
        if (!NT_STATUS_IS_OK(status)) {
                return;
        }

        /* loop along the given path, working with each directory depth separately */
        for (depth=0,p=path;
             p && depth < notify->array->num_depths;
             p=next_p,depth++) {
                int p_len = p - path;
                int min_i, max_i, i;
                struct notify_depth *d = &notify->array->depth[depth];
                next_p = strchr(p+1, '/');

                /* see if there are any entries at this depth */
                if (d->num_entries == 0) continue;
                
                /* try to skip based on the maximum mask. If next_p is
                 NULL then we know it will be a 'this directory'
                 match, otherwise it must be a subdir match */
                if (next_p != NULL) {
                        if (0 == (filter & d->max_mask_subdir)) {
                                continue;
                        }
                } else {
                        if (0 == (filter & d->max_mask)) {
                                continue;
                        }
                }

                /* we know there is an entry here worth looking
                 for. Use a bisection search to find the first entry
                 with a matching path */
                min_i = 0;
                max_i = d->num_entries-1;

                while (min_i < max_i) {
                        struct notify_entry *e;
                        int cmp;
                        i = (min_i+max_i)/2;
                        e = &d->entries[i];
                        cmp = strncmp(path, e->path, p_len);
                        if (cmp == 0) {
                                if (p_len == e->path_len) {
                                        max_i = i;
                                } else {
                                        max_i = i-1;
                                }
                        } else if (cmp < 0) {
                                max_i = i-1;
                        } else {
                                min_i = i+1;
                        }
                }

                if (min_i != max_i) {
                        /* none match */
                        continue;
                }

                /* we now know that the entries start at min_i */
                for (i=min_i;i<d->num_entries;i++) {
                        struct notify_entry *e = &d->entries[i];
                        if (p_len != e->path_len ||
                            strncmp(path, e->path, p_len) != 0) break;
                        if (next_p != NULL) {
                                if (0 == (filter & e->subdir_filter)) {
                                        continue;
                                }
                        } else {
                                if (0 == (filter & e->filter)) {
                                        continue;
                                }
                        }
                        status = notify_send(notify, e, path + e->path_len + 1,
                                             action);

                        if (NT_STATUS_EQUAL(
                                    status, NT_STATUS_INVALID_HANDLE)) {
                                struct server_id server = e->server;

                                DEBUG(10, ("Deleting notify entries for "
                                           "process %s because it's gone\n",
                                           procid_str_static(&e->server.id)));
                                notify_remove_all(notify, &server);
                                goto again;
                        }
                }
        }
}

---