smbd/statcache.c

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/* 
   Unix SMB/CIFS implementation.
   stat cache code
   Copyright (C) Andrew Tridgell 1992-2000
   Copyright (C) Jeremy Allison 1999-2004
   Copyright (C) Andrew Bartlett <abartlet@samba.org> 2003
   
   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.
*/

#include "includes.h"

/****************************************************************************
 Stat cache code used in unix_convert.
*****************************************************************************/

static TDB_CONTEXT *tdb_stat_cache;

/**
 * Add an entry into the stat cache.
 *
 * @param full_orig_name       The original name as specified by the client
 * @param orig_translated_path The name on our filesystem.
 * 
 * @note Only the first strlen(orig_translated_path) characters are stored 
 *       into the cache.  This means that full_orig_name will be internally
 *       truncated.
 *
 */

void stat_cache_add( const char *full_orig_name, const char *orig_translated_path, BOOL case_sensitive)
{
        char *translated_path;
        size_t translated_path_length;
        TDB_DATA data_val;
        char *original_path;
        size_t original_path_length;
        size_t sc_size = lp_max_stat_cache_size();

        if (!lp_stat_cache())
                return;

        if (sc_size && (tdb_map_size(tdb_stat_cache) > sc_size*1024)) {
                reset_stat_cache();
        }

        ZERO_STRUCT(data_val);

        /*
         * Don't cache trivial valid directory entries such as . and ..
         */

        if((*full_orig_name == '\0') || (full_orig_name[0] == '.' && 
                                ((full_orig_name[1] == '\0') ||
                                 (full_orig_name[1] == '.' && full_orig_name[2] == '\0'))))
                return;

        /*
         * If we are in case insentive mode, we don't need to
         * store names that need no translation - else, it
         * would be a waste.
         */

        if(case_sensitive && (strcmp(full_orig_name, orig_translated_path) == 0))
                return;

        /*
         * Remove any trailing '/' characters from the
         * translated path.
         */

        translated_path = SMB_STRDUP(orig_translated_path);
        if (!translated_path)
                return;

        translated_path_length = strlen(translated_path);

        if(translated_path[translated_path_length-1] == '/') {
                translated_path[translated_path_length-1] = '\0';
                translated_path_length--;
        }

        if(case_sensitive) {
                original_path = SMB_STRDUP(full_orig_name);
        } else {
                original_path = strdup_upper(full_orig_name);
        }

        if (!original_path) {
                SAFE_FREE(translated_path);
                return;
        }

        original_path_length = strlen(original_path);

        if(original_path[original_path_length-1] == '/') {
                original_path[original_path_length-1] = '\0';
                original_path_length--;
        }

        if (original_path_length != translated_path_length) {
                if (original_path_length < translated_path_length) {
                        DEBUG(0, ("OOPS - tried to store stat cache entry for weird length paths [%s] %lu and [%s] %lu)!\n",
                                  original_path, (unsigned long)original_path_length, translated_path, (unsigned long)translated_path_length));
                        SAFE_FREE(original_path);
                        SAFE_FREE(translated_path);
                        return;
                }

                /* we only want to index by the first part of original_path,
                        up to the length of translated_path */

                original_path[translated_path_length] = '\0';
                original_path_length = translated_path_length;
        }

        /*
         * New entry or replace old entry.
         */
  
        data_val.dsize = translated_path_length + 1;
        data_val.dptr = translated_path;

        if (tdb_store_bystring(tdb_stat_cache, original_path, data_val, TDB_REPLACE) != 0) {
                DEBUG(0,("stat_cache_add: Error storing entry %s -> %s\n", original_path, translated_path));
        } else {
                DEBUG(5,("stat_cache_add: Added entry (%lx:size%x) %s -> %s\n",
                        (unsigned long)data_val.dptr, (unsigned int)data_val.dsize, original_path, translated_path));
        }

        SAFE_FREE(original_path);
        SAFE_FREE(translated_path);
}

/**
 * Look through the stat cache for an entry
 *
 * @param conn    A connection struct to do the stat() with.
 * @param name    The path we are attempting to cache, modified by this routine
 *                to be correct as far as the cache can tell us
 * @param dirpath The path as far as the stat cache told us.
 * @param start   A pointer into name, for where to 'start' in fixing the rest of the name up.
 * @param psd     A stat buffer, NOT from the cache, but just a side-effect.
 *
 * @return True if we translated (and did a scuccessful stat on) the entire name.
 *
 */

BOOL stat_cache_lookup(connection_struct *conn, pstring name, pstring dirpath, 
                       char **start, SMB_STRUCT_STAT *pst)
{
        char *chk_name;
        size_t namelen;
        BOOL sizechanged = False;
        unsigned int num_components = 0;

        if (!lp_stat_cache())
                return False;
 
        namelen = strlen(name);

        *start = name;

        DO_PROFILE_INC(statcache_lookups);

        /*
         * Don't lookup trivial valid directory entries.
         */
        if((*name == '\0') || (name[0] == '.' && 
                                ((name[1] == '\0') ||
                                 (name[1] == '.' && name[1] == '\0'))))
                return False;

        if (conn->case_sensitive) {
                chk_name = SMB_STRDUP(name);
                if (!chk_name) {
                        DEBUG(0, ("stat_cache_lookup: strdup failed!\n"));
                        return False;
                }

        } else {
                chk_name = strdup_upper(name);
                if (!chk_name) {
                        DEBUG(0, ("stat_cache_lookup: strdup_upper failed!\n"));
                        return False;
                }

                /*
                 * In some language encodings the length changes
                 * if we uppercase. We need to treat this differently
                 * below.
                 */
                if (strlen(chk_name) != namelen)
                        sizechanged = True;
        }

        while (1) {
                TDB_DATA data_val;
                char *sp;

                data_val = tdb_fetch_bystring(tdb_stat_cache, chk_name);
                if(data_val.dptr == NULL || data_val.dsize == 0) {
                        DEBUG(10,("stat_cache_lookup: lookup failed for name [%s]\n", chk_name ));
                        /*
                         * Didn't find it - remove last component for next try.
                         */
                        sp = strrchr_m(chk_name, '/');
                        if (sp) {
                                *sp = '\0';
                                /*
                                 * Count the number of times we have done this,
                                 * we'll need it when reconstructing the string.
                                 */
                                if (sizechanged)
                                        num_components++;

                        } else {
                                /*
                                 * We reached the end of the name - no match.
                                 */
                                DO_PROFILE_INC(statcache_misses);
                                SAFE_FREE(chk_name);
                                return False;
                        }
                        if((*chk_name == '\0') || (strcmp(chk_name, ".") == 0)
                                        || (strcmp(chk_name, "..") == 0)) {
                                DO_PROFILE_INC(statcache_misses);
                                SAFE_FREE(chk_name);
                                return False;
                        }
                } else {
                        BOOL retval;
                        char *translated_path = data_val.dptr;
                        size_t translated_path_length = data_val.dsize - 1;

                        DEBUG(10,("stat_cache_lookup: lookup succeeded for name [%s] -> [%s]\n", chk_name, translated_path ));
                        DO_PROFILE_INC(statcache_hits);
                        if(SMB_VFS_STAT(conn,translated_path, pst) != 0) {
                                /* Discard this entry - it doesn't exist in the filesystem.  */
                                tdb_delete_bystring(tdb_stat_cache, chk_name);
                                SAFE_FREE(chk_name);
                                SAFE_FREE(data_val.dptr);
                                return False;
                        }

                        if (!sizechanged) {
                                memcpy(name, translated_path, MIN(sizeof(pstring)-1, translated_path_length));
                        } else if (num_components == 0) {
                                pstrcpy(name, translated_path);
                        } else {
                                sp = strnrchr_m(name, '/', num_components);
                                if (sp) {
                                        pstring last_component;
                                        pstrcpy(last_component, sp);
                                        pstrcpy(name, translated_path);
                                        pstrcat(name, last_component);
                                } else {
                                        pstrcpy(name, translated_path);
                                }
                        }

                        /* set pointer for 'where to start' on fixing the rest of the name */
                        *start = &name[translated_path_length];
                        if(**start == '/')
                                ++*start;

                        pstrcpy(dirpath, translated_path);
                        retval = (namelen == translated_path_length) ? True : False;
                        SAFE_FREE(chk_name);
                        SAFE_FREE(data_val.dptr);
                        return retval;
                }
        }
}

/***************************************************************************
 Tell all smbd's to delete an entry.
**************************************************************************/

void send_stat_cache_delete_message(const char *name)
{
#ifdef DEVELOPER
        message_send_all(conn_tdb_ctx(),
                        MSG_SMB_STAT_CACHE_DELETE,
                        name,
                        strlen(name)+1,
                        True,
                        NULL);
#endif
}

/***************************************************************************
 Delete an entry.
**************************************************************************/

void stat_cache_delete(const char *name)
{
        char *lname = strdup_upper(name);

        if (!lname) {
                return;
        }
        DEBUG(10,("stat_cache_delete: deleting name [%s] -> %s\n",
                        lname, name ));

        tdb_delete_bystring(tdb_stat_cache, lname);
        SAFE_FREE(lname);
}

/***************************************************************
 Compute a hash value based on a string key value.
 The function returns the bucket index number for the hashed key.
 JRA. Use a djb-algorithm hash for speed.
***************************************************************/
                                                                                                     
unsigned int fast_string_hash(TDB_DATA *key)
{
        unsigned int n = 0;
        const char *p;
        for (p = key->dptr; *p != '\0'; p++) {
                n = ((n << 5) + n) ^ (unsigned int)(*p);
        }
        return n;
}

/***************************************************************************
 Initializes or clears the stat cache.
**************************************************************************/

BOOL reset_stat_cache( void )
{
        if (!lp_stat_cache())
                return True;

        if (tdb_stat_cache) {
                tdb_close(tdb_stat_cache);
        }

        /* Create the in-memory tdb using our custom hash function. */
        tdb_stat_cache = tdb_open_ex("statcache", 1031, TDB_INTERNAL,
                                    (O_RDWR|O_CREAT), 0644, NULL, fast_string_hash);

        if (!tdb_stat_cache)
                return False;
        return True;
}

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