source: branches/samba-3.2.x/source/libsmb/conncache.c@ 198

/* 
   Unix SMB/CIFS implementation.

   Winbind daemon connection manager

   Copyright (C) Tim Potter             2001
   Copyright (C) Andrew Bartlett        2002
   Copyright (C) Gerald (Jerry) Carter  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 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"

#define CONNCACHE_ADDR          1
#define CONNCACHE_NAME          2

/* cache entry contains either a server name **or** and IP address as 
   the key.  This means that a server could have two entries (one for each key) */
   
struct failed_connection_cache {
        fstring         domain_name;
        fstring         controller;
        time_t          lookup_time;
        NTSTATUS        nt_status;
        struct failed_connection_cache *prev, *next;
};

static struct failed_connection_cache *failed_connection_cache;

/**********************************************************************
 Check for a previously failed connection.
 failed_cache_timeout is an a absolute number of seconds after which
 we should time this out. If failed_cache_timeout == 0 then time out
 immediately. If failed_cache_timeout == -1 then never time out.
**********************************************************************/

NTSTATUS check_negative_conn_cache_timeout( const char *domain, const char *server, unsigned int failed_cache_timeout )
{
        struct failed_connection_cache *fcc;
        NTSTATUS result = NT_STATUS_UNSUCCESSFUL;
        
        /* can't check if we don't have strings */
        
        if ( !domain || !server )
                return NT_STATUS_OK;

        for (fcc = failed_connection_cache; fcc; fcc = fcc->next) {
        
                if (!(strequal(domain, fcc->domain_name) && strequal(server, fcc->controller))) {
                        continue; /* no match; check the next entry */
                }
                
                /* we have a match so see if it is still current */
                if (failed_cache_timeout != (unsigned int)-1) {
                        if (failed_cache_timeout == 0 ||
                                        (time(NULL) - fcc->lookup_time) > (time_t)failed_cache_timeout) {
                                /* Cache entry has expired, delete it */

                                DEBUG(10, ("check_negative_conn_cache: cache entry expired for %s, %s\n", 
                                        domain, server ));

                                DLIST_REMOVE(failed_connection_cache, fcc);
                                SAFE_FREE(fcc);

                                return NT_STATUS_OK;
                        }
                }

                /* The timeout hasn't expired yet so return false */

                DEBUG(10, ("check_negative_conn_cache: returning negative entry for %s, %s\n", 
                        domain, server ));

                result = fcc->nt_status;
                return result;
        }

        /* end of function means no cache entry */      
        return NT_STATUS_OK;
}

NTSTATUS check_negative_conn_cache( const char *domain, const char *server)
{
        return check_negative_conn_cache_timeout(domain, server, FAILED_CONNECTION_CACHE_TIMEOUT);
}

/**********************************************************************
 Add an entry to the failed conneciton cache (aither a name of dotted 
 decimal IP
**********************************************************************/

void add_failed_connection_entry(const char *domain, const char *server, NTSTATUS result) 
{
        struct failed_connection_cache *fcc;

        SMB_ASSERT(!NT_STATUS_IS_OK(result));

        /* Check we already aren't in the cache.  We always have to have 
           a domain, but maybe not a specific DC name. */

        for (fcc = failed_connection_cache; fcc; fcc = fcc->next) {                     
                if ( strequal(fcc->domain_name, domain) && strequal(fcc->controller, server) ) {
                        DEBUG(10, ("add_failed_connection_entry: domain %s (%s) already tried and failed\n",
                                   domain, server ));
                        /* Update the failed time. */
                        fcc->lookup_time = time(NULL);
                        return;
                }
        }

        /* Create negative lookup cache entry for this domain and controller */

        if ( !(fcc = SMB_MALLOC_P(struct failed_connection_cache)) ) {
                DEBUG(0, ("malloc failed in add_failed_connection_entry!\n"));
                return;
        }
        
        ZERO_STRUCTP(fcc);
        
        fstrcpy( fcc->domain_name, domain );
        fstrcpy( fcc->controller, server );
        fcc->lookup_time = time(NULL);
        fcc->nt_status = result;
        
        DEBUG(10,("add_failed_connection_entry: added domain %s (%s) to failed conn cache\n",
                domain, server ));
        
        DLIST_ADD(failed_connection_cache, fcc);
}

/****************************************************************************
****************************************************************************/
 
void flush_negative_conn_cache( void )
{
        struct failed_connection_cache *fcc;
        
        fcc = failed_connection_cache;

        while (fcc) {
                struct failed_connection_cache *fcc_next;

                fcc_next = fcc->next;
                DLIST_REMOVE(failed_connection_cache, fcc);
                free(fcc);

                fcc = fcc_next;
        }

}

/****************************************************************************
 Remove all negative entries for a domain. Used when going to online state in
 winbindd.
****************************************************************************/
 
void flush_negative_conn_cache_for_domain(const char *domain)
{
        struct failed_connection_cache *fcc;
        
        fcc = failed_connection_cache;

        while (fcc) {
                struct failed_connection_cache *fcc_next;

                fcc_next = fcc->next;

                if (strequal(fcc->domain_name, domain)) {
                        DEBUG(10,("flush_negative_conn_cache_for_domain: removed server %s "
                                " from failed cache for domain %s\n",
                                fcc->controller, domain));
                        DLIST_REMOVE(failed_connection_cache, fcc);
                        free(fcc);
                }

                fcc = fcc_next;
        }
}