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Diffstat (limited to 'source3/lib')
| -rw-r--r-- | source3/lib/wins_srv.c | 218 |
1 files changed, 218 insertions, 0 deletions
diff --git a/source3/lib/wins_srv.c b/source3/lib/wins_srv.c new file mode 100644 index 0000000000..e84ac342f5 --- /dev/null +++ b/source3/lib/wins_srv.c @@ -0,0 +1,218 @@ +/* + Unix SMB/Netbios implementation. + Version 1.9. + Samba utility functions + Copyright (C) Andrew Tridgell 1992-1998 + + 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 greater than current time server is dead, Jim. */ + char *server; /* DNS name or IP of NBNS server to query. */ + } 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. + */ + { + 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 )) ) + { + if( entry->server ) + free( entry->server ); + 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: 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 )) ) + { + free( entry ); + DEBUG( 0, ("wins_srv_load_list(): strdup(\"%s\") failed.\n", wins_id_bufr) ); + } + else + { + /* Add server to list. */ + (void)ubi_slAddTail( wins_srv_list, entry ); + DEBUGADD( 4, ("\t\t%s,\n", wins_id_bufr) ); + } + } + } + + count = ubi_slCount( wins_srv_list ); + DEBUGADD( 4, ( "\t\t%d WINS server%s listed.\n", count, (1==count)?"":"s" ) ); + + return( (count > 0) ? True : False ); + } /* wins_srv_load_list */ + + +char *wins_srv( void ) + /* ------------------------------------------------------------------------ ** + */ + { + time_t now = time(NULL); + list_entry *entry = (list_entry *)ubi_slFirst( wins_srv_list ); + list_entry *coldest = entry; + + /* Go through the list. Look for the first live entry. */ + while( (NULL != entry) && (now < entry->mourning) ) + { + entry = (list_entry *)ubi_slNext( entry ); + if( entry->mourning < coldest->mourning ) + coldest = entry; + } + + /* If they were all dead, then return the one that's been dead longest. */ + if( NULL == entry ) + { + entry = coldest; + DEBUG( 4, ("wins_srv: All WINS servers appear to have failed.\n") ); + } + + /* The list could be empty. Check it. */ + if( NULL == entry ) + return( NULL ); + return( entry->server ); + } /* wins_srv */ + + +void wins_srv_died( char *boothill ) + /* ------------------------------------------------------------------------ ** + * Called to indicate that a specific WINS server has died. + */ + { + list_entry *entry = (list_entry *)ubi_slFirst( wins_srv_list ); + + while( NULL != entry ) + { + /* Match based on server ID [DNS name or IP]. */ + if( 0 == strcmp( boothill, entry->server ) ) + { + entry->mourning = time(NULL) + NECROMANCYCLE; + DEBUG( 2, ("wins_srv: WINS server %s appears to be down.\n", boothill) ); + return; + } + entry = (list_entry *)ubi_slNext( entry ); + } + } /* wins_srv_died */ + + +unsigned long wins_srv_count( void ) + /* ------------------------------------------------------------------------ ** + * Return the total number of entries in the list, dead or alive. + */ + { + return( ubi_slCount( wins_srv_list ) ); + } /* wins_srv_count */ + +/* ========================================================================== */ |