source: branches/samba-3.5.x/source3/libsmb/trustdom_cache.c

/* 
   Unix SMB/CIFS implementation.

   Trusted domain names cache on top of gencache.

   Copyright (C) Rafal Szczesniak       2002

   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/>.
*/

#include "includes.h"

#undef DBGC_CLASS
#define DBGC_CLASS DBGC_ALL     /* there's no proper class yet */

#define TDOMKEY_FMT  "TDOM/%s"
#define TDOMTSKEY    "TDOMCACHE/TIMESTAMP"


/**
 * @file trustdom_cache.c
 *
 * Implementation of trusted domain names cache useful when
 * samba acts as domain member server. In such case, caching
 * domain names currently trusted gives a performance gain
 * because there's no need to query PDC each time we need
 * list of trusted domains
 **/

/**
 * Initialise trustdom name caching system. Call gencache
 * initialisation routine to perform necessary activities.
 *
 * @return true upon successful cache initialisation or
 *         false if cache init failed
 **/

bool trustdom_cache_enable(void)
{
        return True;
}


/**
 * Shutdown trustdom name caching system. Calls gencache
 * shutdown function.
 *
 * @return true upon successful cache close or
 *         false if it failed
 **/

bool trustdom_cache_shutdown(void)
{
        return True;
}


/**
 * Form up trustdom name key. It is based only
 * on domain name now.
 *
 * @param name trusted domain name
 * @return cache key for use in gencache mechanism
 **/

static char* trustdom_cache_key(const char* name)
{
        char* keystr = NULL;
        asprintf_strupper_m(&keystr, TDOMKEY_FMT, name);

        return keystr;
}


/**
 * Store trusted domain in gencache as the domain name (key)
 * and trusted domain's SID (value)
 *
 * @param name trusted domain name
 * @param alt_name alternative trusted domain name (used in ADS domains)
 * @param sid trusted domain's SID
 * @param timeout cache entry expiration time
 * @return true upon successful value storing or
 *         false if store attempt failed
 **/
 
bool trustdom_cache_store(char* name, char* alt_name, const DOM_SID *sid,
                          time_t timeout)
{
        char *key, *alt_key;
        fstring sid_string;
        bool ret;

        DEBUG(5, ("trustdom_store: storing SID %s of domain %s\n",
                  sid_string_dbg(sid), name));

        key = trustdom_cache_key(name);
        alt_key = alt_name ? trustdom_cache_key(alt_name) : NULL;

        /* Generate string representation domain SID */
        sid_to_fstring(sid_string, sid);

        /*
         * try to put the names in the cache
         */
        if (alt_key) {
                ret = gencache_set(alt_key, sid_string, timeout);
                if ( ret ) {
                        ret = gencache_set(key, sid_string, timeout);
                }
                SAFE_FREE(alt_key);
                SAFE_FREE(key);
                return ret;
        }

        ret = gencache_set(key, sid_string, timeout);
        SAFE_FREE(key);
        return ret;
}


/**
 * Fetch trusted domain's SID from the gencache.
 * This routine can also be used to check whether given
 * domain is currently trusted one.
 *
 * @param name trusted domain name
 * @param sid trusted domain's SID to be returned
 * @return true if entry is found or
 *         false if has expired/doesn't exist
 **/

bool trustdom_cache_fetch(const char* name, DOM_SID* sid)
{
        char *key = NULL, *value = NULL;
        time_t timeout;

        /* exit now if null pointers were passed as they're required further */
        if (!sid)
                return False;

        /* prepare a key and get the value */
        key = trustdom_cache_key(name);
        if (!key)
                return False;

        if (!gencache_get(key, &value, &timeout)) {
                DEBUG(5, ("no entry for trusted domain %s found.\n", name));
                SAFE_FREE(key);
                return False;
        } else {
                SAFE_FREE(key);
                DEBUG(5, ("trusted domain %s found (%s)\n", name, value));
        }

        /* convert sid string representation into DOM_SID structure */
        if(! string_to_sid(sid, value)) {
                sid = NULL;
                SAFE_FREE(value);
                return False;
        }

        SAFE_FREE(value);
        return True;
}


/*******************************************************************
 fetch the timestamp from the last update 
*******************************************************************/

uint32 trustdom_cache_fetch_timestamp( void )
{
        char *value = NULL;
        time_t timeout;
        uint32 timestamp;

        if (!gencache_get(TDOMTSKEY, &value, &timeout)) {
                DEBUG(5, ("no timestamp for trusted domain cache located.\n"));
                SAFE_FREE(value);
                return 0;
        } 

        timestamp = atoi(value);

        SAFE_FREE(value);
        return timestamp;
}

/*******************************************************************
 store the timestamp from the last update 
*******************************************************************/

bool trustdom_cache_store_timestamp( uint32 t, time_t timeout )
{
        fstring value;

        fstr_sprintf(value, "%d", t );

        if (!gencache_set(TDOMTSKEY, value, timeout)) {
                DEBUG(5, ("failed to set timestamp for trustdom_cache\n"));
                return False;
        } 

        return True;
}


/**
 * Delete single trustdom entry. Look at the
 * gencache_iterate definition.
 *
 **/

static void flush_trustdom_name(const char* key, const char *value, time_t timeout, void* dptr)
{
        gencache_del(key);
        DEBUG(5, ("Deleting entry %s\n", key));
}


/**
 * Flush all the trusted domains entries from the cache.
 **/

void trustdom_cache_flush(void)
{
        /* 
         * iterate through each TDOM cache's entry and flush it
         * by flush_trustdom_name function
         */
        gencache_iterate(flush_trustdom_name, NULL, trustdom_cache_key("*"));
        DEBUG(5, ("Trusted domains cache flushed\n"));
}

/********************************************************************
 update the trustdom_cache if needed 
********************************************************************/
#define TRUSTDOM_UPDATE_INTERVAL        600

void update_trustdom_cache( void )
{
        char **domain_names;
        DOM_SID *dom_sids;
        uint32 num_domains;
        uint32 last_check;
        int time_diff;
        TALLOC_CTX *mem_ctx = NULL;
        time_t now = time(NULL);
        int i;

        /* get the timestamp.  We have to initialise it if the last timestamp == 0 */   
        if ( (last_check = trustdom_cache_fetch_timestamp()) == 0 ) 
                trustdom_cache_store_timestamp(0, now+TRUSTDOM_UPDATE_INTERVAL);

        time_diff = (int) (now - last_check);

        if ( (time_diff > 0) && (time_diff < TRUSTDOM_UPDATE_INTERVAL) ) {
                DEBUG(10,("update_trustdom_cache: not time to update trustdom_cache yet\n"));
                return;
        }

        /* note that we don't lock the timestamp. This prevents this
           smbd from blocking all other smbd daemons while we
           enumerate the trusted domains */
        trustdom_cache_store_timestamp(now, now+TRUSTDOM_UPDATE_INTERVAL);

        if ( !(mem_ctx = talloc_init("update_trustdom_cache")) ) {
                DEBUG(0,("update_trustdom_cache: talloc_init() failed!\n"));
                goto done;
        }

        /* get the domains and store them */

        if ( enumerate_domain_trusts(mem_ctx, lp_workgroup(), &domain_names, 
                &num_domains, &dom_sids)) {
                for ( i=0; i<num_domains; i++ ) {
                        trustdom_cache_store( domain_names[i], NULL, &dom_sids[i], 
                                now+TRUSTDOM_UPDATE_INTERVAL);
                }               
        } else {
                /* we failed to fetch the list of trusted domains - restore the old
                   timestamp */
                trustdom_cache_store_timestamp(last_check, 
                                               last_check+TRUSTDOM_UPDATE_INTERVAL);
        }

done:   
        talloc_destroy( mem_ctx );

        return;
}