source/lib/wins_srv.c

   1 /*
   2    Unix SMB/Netbios implementation.
   3    Version 2.
   4    Samba utility functions
   5    Copyright (C) Andrew Tridgell 1992-1998
   6    Copyright (C) Christopher R. Hertel 2000
   7
   8    This program is free software; you can redistribute it and/or modify
   9    it under the terms of the GNU General Public License as published by
  10    the Free Software Foundation; either version 2 of the License, or
  11    (at your option) any later version.
  12
  13    This program is distributed in the hope that it will be useful,
  14    but WITHOUT ANY WARRANTY; without even the implied warranty of
  15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16    GNU General Public License for more details.
  17
  18    You should have received a copy of the GNU General Public License
  19    along with this program; if not, write to the Free Software
  20    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  21 */
  22
  23 #include "includes.h"
  24
  25 /* -------------------------------------------------------------------------- **
  26  * Discussion...
  27  *
  28  * This module implements WINS failover.
  29  *
  30  * Microsoft's WINS servers provide a feature called WINS replication,
  31  * which synchronises the WINS name databases between two or more servers.
  32  * This means that the two servers can be used interchangably (more or
  33  * less). WINS replication is particularly useful if you are trying to
  34  * synchronise the WINS namespace between servers in remote locations, or
  35  * if your WINS servers tend to crash a lot.
  36  *
  37  * WINS failover allows the client to 'switch' to a different WINS server
  38  * if the current WINS server mysteriously disappears.  On Windows
  39  * systems, this is typically represented as 'primary' and 'secondary'
  40  * WINS servers.
  41  *
  42  * Failover only works if the WINS servers are synced.  If they are not,
  43  * then
  44  *   a) if the primary WINS server never fails the client will never 'see'
  45  *      the secondary (or tertiary or...) WINS server name space.
  46  *   b) if the primary *does* fail, the client will be entering an
  47  *      unfamiliar namespace.  The client itself will not be registered in
  48  *      that namespace and any names which match names in the previous
  49  *      space will likely resolve to different host IP addresses.
  50  *
  51  * One key thing to remember regarding WINS failover is that Samba does
  52  * not (yet) implement WINS replication.  For those interested, sniff port
  53  * 42 (TCP? UDP? ...dunno off hand) and see what two MS WINS servers do.
  54  *
  55  * At this stage, only failover is implemented.  The next thing is to add
  56  * support for multi-WINS server registration and query (multi-membership).
  57  *
  58  * Multi-membership is a little wierd.  The idea is that the client can
  59  * register itself with multiple non-replicated WINS servers, and query
  60  * all of those servers (in a prescribed sequence) to resolve a name.
  61  *
  62  * The implications of multi-membership are not quite clear.  Worth
  63  * trying, I suppose.  Changes will be needed in the name query and
  64  * registration code to accomodate this feature.  Also, there will need to
  65  * be some sort of syntax extension for the 'wins server' parameter in
  66  * smb.conf.  I'm thinking that a colon could be used as a separator.
  67  *
  68  * Of course, for each WINS namespace there might be multiple, synced WINS
  69  * servers.  The change to this module would likely be the addition of a
  70  * linked list of linked lists.
  71  *
  72  * crh@samba.org
  73  */
  74
  75 /* -------------------------------------------------------------------------- **
  76  * Defines...
  77  *
  78  *   NECROMANCYCLE - The dead server retry period, in seconds.  When a WINS
  79  *                   server is declared dead, wait this many seconds before
  80  *                   attempting to communicate with it.
  81  */
  82
  83 #define NECROMANCYCLE 600   /* 600 seconds == 10 minutes. */
  84
  85 /* -------------------------------------------------------------------------- **
  86  * Typedefs...
  87  */
  88
  89 typedef struct
  90   {
  91   ubi_slNode     node;      /* Linked list node structure.                  */
  92   time_t         mourning;  /* If > current time then  server is dead, Jim. */
  93   char          *server;    /* DNS name or IP of NBNS server to query.      */
  94   struct in_addr ip_addr;   /* Cache translated IP.                         */
  95   } list_entry;
  96
  97 /* -------------------------------------------------------------------------- **
  98  * Private, static variables.
  99  */
 100
 101 static ubi_slNewList( wins_srv_list );
 102
 103 /* -------------------------------------------------------------------------- **
 104  * Functions...
 105  */
 106
 107
 108 BOOL wins_srv_load_list( char *src )
 109   /* ------------------------------------------------------------------------ **
 110    * Create or recreate the linked list of failover WINS servers.
 111    *
 112    *  Input:  src - String of DNS names and/or IP addresses delimited by the
 113    *                characters listed in LIST_SEP (see include/local.h).
 114    *
 115    *  Output: True if at least one name or IP could be parsed out of the
 116    *          list, else False.
 117    *
 118    *  Notes:  There is no syntax checking done on the names or IPs.  We do
 119    *          check to see if the field is an IP, in which case we copy it
 120    *          to the ip_addr field of the entry.  Don't bother to to a host
 121    *          name lookup on all names now.  They're done as needed in
 122    *          wins_srv_ip().
 123    */
 124   {
 125   list_entry   *entry;
 126   char         *p = src;
 127   pstring       wins_id_bufr;
 128   unsigned long count;
 129
 130   /* Empty the list. */
 131   while( NULL != (entry =(list_entry *)ubi_slRemHead( wins_srv_list )) )
 132     {
 133     SAFE_FREE( entry->server );
 134     SAFE_FREE( entry );
 135     }
 136   (void)ubi_slInitList( wins_srv_list );  /* shouldn't be needed */
 137
 138   /* Parse out the DNS names or IP addresses of the WINS servers. */
 139   DEBUG( 4, ("wins_srv_load_list(): Building WINS server list:\n") );
 140   while( next_token( &p, wins_id_bufr, LIST_SEP, sizeof( wins_id_bufr ) ) )
 141     {
 142     entry = (list_entry *)malloc( sizeof( list_entry ) );
 143     if( NULL == entry )
 144       {
 145       DEBUG( 0, ("wins_srv_load_list(): malloc(list_entry) failed.\n") );
 146       }
 147     else
 148       {
 149       entry->mourning = 0;
 150       if( NULL == (entry->server = strdup( wins_id_bufr )) )
 151         {
 152         SAFE_FREE( entry );
 153         DEBUG( 0, ("wins_srv_load_list(): strdup(\"%s\") failed.\n", wins_id_bufr) );
 154         }
 155       else
 156         {
 157         /* Add server to list. */
 158         if( is_ipaddress( wins_id_bufr ) )
 159           entry->ip_addr = *interpret_addr2( wins_id_bufr );
 160         else
 161           entry->ip_addr = *interpret_addr2( "0.0.0.0" );
 162         (void)ubi_slAddTail( wins_srv_list, entry );
 163         DEBUGADD( 4, ("%s,\n", wins_id_bufr) );
 164         }
 165       }
 166     }
 167
 168   count = ubi_slCount( wins_srv_list );
 169   DEBUGADD( 4, ( "%d WINS server%s listed.\n", (int)count, (1==count)?"":"s" ) );
 170
 171   return( (count > 0) ? True : False );
 172   } /* wins_srv_load_list */
 173
 174
 175 struct in_addr wins_srv_ip( void )
 176   /* ------------------------------------------------------------------------ **
 177    */
 178   {
 179   time_t      now     = time(NULL);
 180   list_entry *entry   = (list_entry *)ubi_slFirst( wins_srv_list );
 181
 182   while( NULL != entry )
 183     {
 184     if( now >= entry->mourning )        /* Found a live one. */
 185       {
 186       /* If we don't have the IP, look it up. */
 187       if( is_zero_ip( entry->ip_addr ) )
 188         entry->ip_addr = *interpret_addr2( entry->server );
 189
 190       /* If we still don't have the IP then kill it, else return it. */
 191       if( is_zero_ip( entry->ip_addr ) )
 192         entry->mourning = now + NECROMANCYCLE;
 193       else
 194         return( entry->ip_addr );
 195       }
 196     entry = (list_entry *)ubi_slNext( entry );
 197     }
 198
 199   /* If there are no live entries, return the zero IP. */
 200   return( *interpret_addr2( "0.0.0.0" ) );
 201   } /* wins_srv_ip */
 202
 203
 204 void wins_srv_died( struct in_addr boothill_ip )
 205   /* ------------------------------------------------------------------------ **
 206    * Called to indicate that a specific WINS server has died.
 207    */
 208   {
 209   list_entry *entry;
 210
 211   if( is_zero_ip( boothill_ip ) )
 212     {
 213     DEBUG( 4, ("wins_srv_died(): Got request to mark zero IP down.\n") );
 214     return;
 215     }
 216
 217   entry = (list_entry *)ubi_slFirst( wins_srv_list );
 218   while( NULL != entry )
 219     {
 220     /* Match based on IP. */
 221     if( ip_equal( boothill_ip, entry->ip_addr ) )
 222       {
 223       entry->mourning = time(NULL) + NECROMANCYCLE;
 224       entry->ip_addr.s_addr = 0;  /* Force a re-lookup at re-birth. */
 225       DEBUG( 2, ( "wins_srv_died(): WINS server %s appears to be down.\n",
 226                   entry->server ) );
 227       return;
 228       }
 229     entry = (list_entry *)ubi_slNext( entry );
 230     }
 231
 232   if( DEBUGLVL( 1 ) )
 233     {
 234     dbgtext( "wins_srv_died(): Could not mark WINS server %s down.\n",
 235               inet_ntoa( boothill_ip ) );
 236     dbgtext( "Address not found in server list.\n" );
 237     }
 238   } /* wins_srv_died */
 239
 240
 241 unsigned long wins_srv_count( void )
 242   /* ------------------------------------------------------------------------ **
 243    * Return the total number of entries in the list, dead or alive.
 244    */
 245   {
 246   unsigned long count = ubi_slCount( wins_srv_list );
 247
 248   if( DEBUGLVL( 8 ) )
 249     {
 250     list_entry *entry = (list_entry *)ubi_slFirst( wins_srv_list );
 251     time_t      now   = time(NULL);
 252
 253     dbgtext( "wins_srv_count: WINS status: %ld servers.\n", count );
 254     while( NULL != entry )
 255       {
 256       dbgtext( "  %s <%s>: ", entry->server, inet_ntoa( entry->ip_addr ) );
 257       if( now >= entry->mourning )
 258         dbgtext( "alive\n" );
 259       else
 260         dbgtext( "dead for %d more seconds\n", (int)(entry->mourning - now) );
 261
 262       entry = (list_entry *)ubi_slNext( entry );
 263       }
 264     }
 265
 266   return( count );
 267   } /* wins_srv_count */
 268
 269 /* ========================================================================== */