/* Unix SMB/Netbios implementation. Version 2. Samba utility functions Copyright (C) Andrew Tridgell 1992-1998 Copyright (C) Christopher R. Hertel 2000 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" /* -------------------------------------------------------------------------- ** * Discussion... * * This module implements WINS failover. * * Microsoft's WINS servers provide a feature called WINS replication, * which synchronises the WINS name databases between two or more servers. * This means that the two servers can be used interchangably (more or * less). WINS replication is particularly useful if you are trying to * synchronise the WINS namespace between servers in remote locations, or * if your WINS servers tend to crash a lot. * * WINS failover allows the client to 'switch' to a different WINS server * if the current WINS server mysteriously disappears. On Windows * systems, this is typically represented as 'primary' and 'secondary' * WINS servers. * * Failover only works if the WINS servers are synced. If they are not, * then * a) if the primary WINS server never fails the client will never 'see' * the secondary (or tertiary or...) WINS server name space. * b) if the primary *does* fail, the client will be entering an * unfamiliar namespace. The client itself will not be registered in * that namespace and any names which match names in the previous * space will likely resolve to different host IP addresses. * * One key thing to remember regarding WINS failover is that Samba does * not (yet) implement WINS replication. For those interested, sniff port * 42 (TCP? UDP? ...dunno off hand) and see what two MS WINS servers do. * * At this stage, only failover is implemented. The next thing is to add * support for multi-WINS server registration and query (multi-membership). * * Multi-membership is a little wierd. The idea is that the client can * register itself with multiple non-replicated WINS servers, and query * all of those servers (in a prescribed sequence) to resolve a name. * * The implications of multi-membership are not quite clear. Worth * trying, I suppose. Changes will be needed in the name query and * registration code to accomodate this feature. Also, there will need to * be some sort of syntax extension for the 'wins server' parameter in * smb.conf. I'm thinking that a colon could be used as a separator. * * Of course, for each WINS namespace there might be multiple, synced WINS * servers. The change to this module would likely be the addition of a * linked list of linked lists. * * crh@samba.org */ /* -------------------------------------------------------------------------- ** * Defines... * * NECROMANCYCLE - The dead server retry period, in seconds. When a WINS * server is declared dead, wait this many seconds before * attempting to communicate with it. */ #define NECROMANCYCLE 600 /* 600 seconds == 10 minutes. */ /* -------------------------------------------------------------------------- ** * Typedefs... */ typedef struct { ubi_slNode node; /* Linked list node structure. */ time_t mourning; /* If > current time then server is dead, Jim. */ char *server; /* DNS name or IP of NBNS server to query. */ struct in_addr ip_addr; /* Cache translated IP. */ } list_entry; /* -------------------------------------------------------------------------- ** * Private, static variables. */ static ubi_slNewList( wins_srv_list ); /* -------------------------------------------------------------------------- ** * Functions... */ BOOL wins_srv_load_list( char *src ) /* ------------------------------------------------------------------------ ** * Create or recreate the linked list of failover WINS servers. * * Input: src - String of DNS names and/or IP addresses delimited by the * characters listed in LIST_SEP (see include/local.h). * * Output: True if at least one name or IP could be parsed out of the * list, else False. * * Notes: There is no syntax checking done on the names or IPs. We do * check to see if the field is an IP, in which case we copy it * to the ip_addr field of the entry. Don't bother to to a host * name lookup on all names now. They're done as needed in * wins_srv_ip(). */ { list_entry *entry; char *p = src; pstring wins_id_bufr; unsigned long count; /* Empty the list. */ while( NULL != (entry =(list_entry *)ubi_slRemHead( wins_srv_list )) ) { SAFE_FREE( entry->server ); SAFE_FREE( entry ); } (void)ubi_slInitList( wins_srv_list ); /* shouldn't be needed */ /* Parse out the DNS names or IP addresses of the WINS servers. */ DEBUG( 4, ("wins_srv_load_list(): Building WINS server list:\n") ); while( next_token( &p, wins_id_bufr, LIST_SEP, sizeof( wins_id_bufr ) ) ) { entry = (list_entry *)malloc( sizeof( list_entry ) ); if( NULL == entry ) { DEBUG( 0, ("wins_srv_load_list(): malloc(list_entry) failed.\n") ); } else { entry->mourning = 0; if( NULL == (entry->server = strdup( wins_id_bufr )) ) { SAFE_FREE( entry ); DEBUG( 0, ("wins_srv_load_list(): strdup(\"%s\") failed.\n", wins_id_bufr) ); } else { /* Add server to list. */ if( is_ipaddress( wins_id_bufr ) ) entry->ip_addr = *interpret_addr2( wins_id_bufr ); else entry->ip_addr = *interpret_addr2( "0.0.0.0" ); (void)ubi_slAddTail( wins_srv_list, entry ); DEBUGADD( 4, ("%s,\n", wins_id_bufr) ); } } } count = ubi_slCount( wins_srv_list ); DEBUGADD( 4, ( "%d WINS server%s listed.\n", (int)count, (1==count)?"":"s" ) ); return( (count > 0) ? True : False ); } /* wins_srv_load_list */ struct in_addr wins_srv_ip( void ) /* ------------------------------------------------------------------------ ** */ { time_t now = time(NULL); list_entry *entry = (list_entry *)ubi_slFirst( wins_srv_list ); while( NULL != entry ) { if( now >= entry->mourning ) /* Found a live one. */ { /* If we don't have the IP, look it up. */ if( zero_ip( entry->ip_addr ) ) entry->ip_addr = *interpret_addr2( entry->server ); /* If we still don't have the IP then kill it, else return it. */ if( zero_ip( entry->ip_addr ) ) entry->mourning = now + NECROMANCYCLE; else return( entry->ip_addr ); } entry = (list_entry *)ubi_slNext( entry ); } /* If there are no live entries, return the zero IP. */ return( *interpret_addr2( "0.0.0.0" ) ); } /* wins_srv_ip */ void wins_srv_died( struct in_addr boothill_ip ) /* ------------------------------------------------------------------------ ** * Called to indicate that a specific WINS server has died. */ { list_entry *entry; if( zero_ip( boothill_ip ) ) { DEBUG( 4, ("wins_srv_died(): Got request to mark zero IP down.\n") ); return; } entry = (list_entry *)ubi_slFirst( wins_srv_list ); while( NULL != entry ) { /* Match based on IP. */ if( ip_equal( boothill_ip, entry->ip_addr ) ) { entry->mourning = time(NULL) + NECROMANCYCLE; entry->ip_addr.s_addr = 0; /* Force a re-lookup at re-birth. */ DEBUG( 2, ( "wins_srv_died(): WINS server %s appears to be down.\n", entry->server ) ); return; } entry = (list_entry *)ubi_slNext( entry ); } if( DEBUGLVL( 1 ) ) { dbgtext( "wins_srv_died(): Could not mark WINS server %s down.\n", inet_ntoa( boothill_ip ) ); dbgtext( "Address not found in server list.\n" ); } } /* wins_srv_died */ unsigned long wins_srv_count( void ) /* ------------------------------------------------------------------------ ** * Return the total number of entries in the list, dead or alive. */ { unsigned long count = ubi_slCount( wins_srv_list ); if( DEBUGLVL( 8 ) ) { list_entry *entry = (list_entry *)ubi_slFirst( wins_srv_list ); time_t now = time(NULL); dbgtext( "wins_srv_count: WINS status: %ld servers.\n", count ); while( NULL != entry ) { dbgtext( " %s <%s>: ", entry->server, inet_ntoa( entry->ip_addr ) ); if( now >= entry->mourning ) dbgtext( "alive\n" ); else dbgtext( "dead for %d more seconds\n", (int)(entry->mourning - now) ); entry = (list_entry *)ubi_slNext( entry ); } } return( count ); } /* wins_srv_count */ /* ========================================================================== */