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+/*
+ Unix SMB/CIFS implementation.
+ 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;
+ /* Create a copy of the server name and store it in the list. */
+ 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 the server name was actually an IP address we will store that
+ * too. It it was a DNS name, we will wait until we need to use
+ * the WINS server before doing the DNS lookup. Since this may be
+ * a list, and since we will reload the list whenever smb.conf is
+ * reloaded, there's no point in trying to look up names until we
+ * need them. ...of course, once we do the lookup we will cache
+ * the result. See wins_srv_ip().
+ */
+ 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 )
+ /* ------------------------------------------------------------------------ **
+ * Return the IP address of an NBNS (WINS) server thought to be active.
+ *
+ * Input: none.
+ *
+ * Output: An IP address in struct in_addr form.
+ *
+ * Notes: This function will return the IP address of the first available
+ * NBNS (WINS) server. The order of the list is determined in
+ * smb.conf. If all of the WINS servers have been marked 'dead'
+ * then the zero IP (0.0.0.0) is returned. The zero IP is not a
+ * valid Unicast address on any system.
+ *
+ * ------------------------------------------------------------------------ **
+ */
+ {
+ 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( is_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( is_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 */
+
+
+char *wins_srv_name( void )
+ /* ------------------------------------------------------------------------ **
+ * Return the name of first live WINS server in the list.
+ *
+ * Input: none.
+ *
+ * Output: A pointer to a string containing either the DNS name or IP
+ * address of the WINS server as given in the WINS SERVER
+ * parameter in smb.conf, or NULL if no (live) WINS servers are
+ * in the list.
+ *
+ * Notes: This function will return the name of the first available
+ * NBNS (WINS) server. The order of the list is determined in
+ * smb.conf. If all of the WINS servers have been marked 'dead'
+ * then NULL is returned.
+ *
+ * - This function does not verify that the name can be mapped to
+ * an IP address, or that the WINS server is running.
+ *
+ * ------------------------------------------------------------------------ **
+ */
+ {
+ time_t now = time(NULL);
+ list_entry *entry = (list_entry *)ubi_slFirst( wins_srv_list );
+
+ while( NULL != entry )
+ {
+ if( now >= entry->mourning )
+ return( entry->server ); /* Found a live one. */
+ entry = (list_entry *)ubi_slNext( entry );
+ }
+
+ /* If there are no live entries, return NULL. */
+ return( NULL );
+ } /* wins_srv_name */
+
+
+void wins_srv_died( struct in_addr boothill_ip )
+ /* ------------------------------------------------------------------------ **
+ * Called to indicate that a specific WINS server has died.
+ *
+ * Input: boothill_ip - IP address of an NBNS (WINS) server that has
+ * failed.
+ *
+ * Notes: This function marks the record 'dead' for NECROMANCYCLE
+ * seconds.
+ *
+ * ------------------------------------------------------------------------ **
+ */
+ {
+ list_entry *entry;
+
+ if( is_zero_ip( boothill_ip ) )
+ {
+ DEBUG( 4, ("wins_srv_died(): Invalid 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 */
+
+/* ========================================================================== */
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