source/lib/wins_srv.c

   1 /*
   2    Unix SMB/CIFS implementation.
   3    Samba utility functions
   4    Copyright (C) Andrew Tridgell 1992-1998
   5    Copyright (C) Christopher R. Hertel 2000
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 2 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program; if not, write to the Free Software
  19    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  20 */
  21
  22 #include "includes.h"
  23
  24 /* -------------------------------------------------------------------------- **
  25  * Discussion...
  26  *
  27  * This module implements WINS failover.
  28  *
  29  * Microsoft's WINS servers provide a feature called WINS replication,
  30  * which synchronises the WINS name databases between two or more servers.
  31  * This means that the two servers can be used interchangably (more or
  32  * less). WINS replication is particularly useful if you are trying to
  33  * synchronise the WINS namespace between servers in remote locations, or
  34  * if your WINS servers tend to crash a lot.
  35  *
  36  * WINS failover allows the client to 'switch' to a different WINS server
  37  * if the current WINS server mysteriously disappears.  On Windows
  38  * systems, this is typically represented as 'primary' and 'secondary'
  39  * WINS servers.
  40  *
  41  * Failover only works if the WINS servers are synced.  If they are not,
  42  * then
  43  *   a) if the primary WINS server never fails the client will never 'see'
  44  *      the secondary (or tertiary or...) WINS server name space.
  45  *   b) if the primary *does* fail, the client will be entering an
  46  *      unfamiliar namespace.  The client itself will not be registered in
  47  *      that namespace and any names which match names in the previous
  48  *      space will likely resolve to different host IP addresses.
  49  *
  50  * One key thing to remember regarding WINS failover is that Samba does
  51  * not (yet) implement WINS replication.  For those interested, sniff port
  52  * 42 (TCP? UDP? ...dunno off hand) and see what two MS WINS servers do.
  53  *
  54  * At this stage, only failover is implemented.  The next thing is to add
  55  * support for multi-WINS server registration and query (multi-membership).
  56  *
  57  * Multi-membership is a little wierd.  The idea is that the client can
  58  * register itself with multiple non-replicated WINS servers, and query
  59  * all of those servers (in a prescribed sequence) to resolve a name.
  60  *
  61  * The implications of multi-membership are not quite clear.  Worth
  62  * trying, I suppose.  Changes will be needed in the name query and
  63  * registration code to accomodate this feature.  Also, there will need to
  64  * be some sort of syntax extension for the 'wins server' parameter in
  65  * smb.conf.  I'm thinking that a colon could be used as a separator.
  66  *
  67  * Of course, for each WINS namespace there might be multiple, synced WINS
  68  * servers.  The change to this module would likely be the addition of a
  69  * linked list of linked lists.
  70  *
  71  * crh@samba.org
  72  */
  73
  74 /* -------------------------------------------------------------------------- **
  75  * Defines...
  76  *
  77  *   NECROMANCYCLE - The dead server retry period, in seconds.  When a WINS
  78  *                   server is declared dead, wait this many seconds before
  79  *                   attempting to communicate with it.
  80  */
  81
  82 #define NECROMANCYCLE 600   /* 600 seconds == 10 minutes. */
  83
  84 /* -------------------------------------------------------------------------- **
  85  * Typedefs...
  86  */
  87
  88 typedef struct
  89   {
  90   ubi_slNode     node;      /* Linked list node structure.                  */
  91   time_t         mourning;  /* If > current time then server is dead, Jim.  */
  92   char          *server;    /* DNS name or IP of NBNS server to query.      */
  93   struct in_addr ip_addr;   /* Cache translated IP.                         */
  94   } list_entry;
  95
  96 /* -------------------------------------------------------------------------- **
  97  * Private, static variables.
  98  */
  99
 100 static ubi_slNewList( wins_srv_list );
 101
 102 /* -------------------------------------------------------------------------- **
 103  * Functions...
 104  */
 105
 106
 107 BOOL wins_srv_load_list( char *src )
 108   /* ------------------------------------------------------------------------ **
 109    * Create or recreate the linked list of failover WINS servers.
 110    *
 111    *  Input:  src - String of DNS names and/or IP addresses delimited by the
 112    *                characters listed in LIST_SEP (see include/local.h).
 113    *
 114    *  Output: True if at least one name or IP could be parsed out of the
 115    *          list, else False.
 116    *
 117    *  Notes:  There is no syntax checking done on the names or IPs.  We do
 118    *          check to see if the field is an IP, in which case we copy it
 119    *          to the ip_addr field of the entry.  Don't bother to to a host
 120    *          name lookup on all names now.  They're done as needed in
 121    *          wins_srv_ip().
 122    * ------------------------------------------------------------------------ **
 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       /* Create a copy of the server name and store it in the list. */
 151       if( NULL == (entry->server = strdup( wins_id_bufr )) )
 152         {
 153         SAFE_FREE( entry );
 154         DEBUG( 0,
 155           ("wins_srv_load_list(): strdup(\"%s\") failed.\n", wins_id_bufr) );
 156         }
 157       else
 158         {
 159         /* Add server to list.
 160          * If the server name was actually an IP address we will store that
 161          * too.  It it was a DNS name, we will wait until we need to use
 162          * the WINS server before doing the DNS lookup.  Since this may be
 163          * a list, and since we will reload the list whenever smb.conf is
 164          * reloaded, there's no point in trying to look up names until we
 165          * need them.  ...of course, once we do the lookup we will cache
 166          * the result.  See wins_srv_ip().
 167          */
 168         if( is_ipaddress( wins_id_bufr ) )
 169           entry->ip_addr = *interpret_addr2( wins_id_bufr );
 170         else
 171           entry->ip_addr = *interpret_addr2( "0.0.0.0" );
 172         (void)ubi_slAddTail( wins_srv_list, entry );
 173         DEBUGADD( 4, ("%s,\n", wins_id_bufr) );
 174         }
 175       }
 176     }
 177
 178   count = ubi_slCount( wins_srv_list );
 179   DEBUGADD( 4,
 180     ( "%d WINS server%s listed.\n", (int)count, (1==count)?"":"s" ) );
 181
 182   return( (count > 0) ? True : False );
 183   } /* wins_srv_load_list */
 184
 185
 186 struct in_addr wins_srv_ip( void )
 187   /* ------------------------------------------------------------------------ **
 188    * Return the IP address of an NBNS (WINS) server thought to be active.
 189    *
 190    *  Input:  none.
 191    *
 192    *  Output: An IP address in struct in_addr form.
 193    *
 194    *  Notes:  This function will return the IP address of the first available
 195    *          NBNS (WINS) server.  The order of the list is determined in
 196    *          smb.conf.  If all of the WINS servers have been marked 'dead'
 197    *          then the zero IP (0.0.0.0) is returned.  The zero IP is not a
 198    *          valid Unicast address on any system.
 199    *
 200    * ------------------------------------------------------------------------ **
 201    */
 202   {
 203   time_t      now     = time(NULL);
 204   list_entry *entry   = (list_entry *)ubi_slFirst( wins_srv_list );
 205
 206   while( NULL != entry )
 207     {
 208     if( now >= entry->mourning )        /* Found a live one. */
 209       {
 210       /* If we don't have the IP, look it up. */
 211       if( is_zero_ip( entry->ip_addr ) )
 212         entry->ip_addr = *interpret_addr2( entry->server );
 213
 214       /* If we still don't have the IP then kill it, else return it. */
 215       if( is_zero_ip( entry->ip_addr ) )
 216         entry->mourning = now + NECROMANCYCLE;
 217       else
 218         return( entry->ip_addr );
 219       }
 220     entry = (list_entry *)ubi_slNext( entry );
 221     }
 222
 223   /* If there are no live entries, return the zero IP. */
 224   return( *interpret_addr2( "0.0.0.0" ) );
 225   } /* wins_srv_ip */
 226
 227
 228 char *wins_srv_name( void )
 229   /* ------------------------------------------------------------------------ **
 230    * Return the name of first live WINS server in the list.
 231    *
 232    *  Input:  none.
 233    *
 234    *  Output: A pointer to a string containing either the DNS name or IP
 235    *          address of the WINS server as given in the WINS SERVER
 236    *          parameter in smb.conf, or NULL if no (live) WINS servers are
 237    *          in the list.
 238    *
 239    *  Notes:  This function will return the name of the first available
 240    *          NBNS (WINS) server.  The order of the list is determined in
 241    *          smb.conf.  If all of the WINS servers have been marked 'dead'
 242    *          then NULL is returned.
 243    *
 244    *        - This function does not verify that the name can be mapped to
 245    *          an IP address, or that the WINS server is running.
 246    *
 247    * ------------------------------------------------------------------------ **
 248    */
 249   {
 250   time_t      now     = time(NULL);
 251   list_entry *entry   = (list_entry *)ubi_slFirst( wins_srv_list );
 252
 253   while( NULL != entry )
 254     {
 255     if( now >= entry->mourning )
 256       return( entry->server );          /* Found a live one. */
 257     entry = (list_entry *)ubi_slNext( entry );
 258     }
 259
 260   /* If there are no live entries, return NULL. */
 261   return( NULL );
 262   } /* wins_srv_name */
 263
 264
 265 void wins_srv_died( struct in_addr boothill_ip )
 266   /* ------------------------------------------------------------------------ **
 267    * Called to indicate that a specific WINS server has died.
 268    *
 269    *  Input:  boothill_ip - IP address of an NBNS (WINS) server that has
 270    *                        failed.
 271    *
 272    *  Notes:  This function marks the record 'dead' for NECROMANCYCLE
 273    *          seconds.
 274    *
 275    * ------------------------------------------------------------------------ **
 276    */
 277   {
 278   list_entry *entry;
 279
 280   if( is_zero_ip( boothill_ip ) )
 281     {
 282     DEBUG( 4, ("wins_srv_died(): Invalid request to mark zero IP down.\n") );
 283     return;
 284     }
 285
 286   entry = (list_entry *)ubi_slFirst( wins_srv_list );
 287   while( NULL != entry )
 288     {
 289     /* Match based on IP. */
 290     if( ip_equal( boothill_ip, entry->ip_addr ) )
 291       {
 292       entry->mourning = time(NULL) + NECROMANCYCLE;
 293       entry->ip_addr.s_addr = 0;  /* Force a re-lookup at re-birth. */
 294       DEBUG( 2, ( "wins_srv_died(): WINS server %s appears to be down.\n",
 295                   entry->server ) );
 296       return;
 297       }
 298     entry = (list_entry *)ubi_slNext( entry );
 299     }
 300
 301   if( DEBUGLVL( 1 ) )
 302     {
 303     dbgtext( "wins_srv_died(): Could not mark WINS server %s down.\n",
 304               inet_ntoa( boothill_ip ) );
 305     dbgtext( "Address not found in server list.\n" );
 306     }
 307   } /* wins_srv_died */
 308
 309
 310 unsigned long wins_srv_count( void )
 311   /* ------------------------------------------------------------------------ **
 312    * Return the total number of entries in the list, dead or alive.
 313    * ------------------------------------------------------------------------ **
 314    */
 315   {
 316   unsigned long count = ubi_slCount( wins_srv_list );
 317
 318   if( DEBUGLVL( 8 ) )
 319     {
 320     list_entry *entry = (list_entry *)ubi_slFirst( wins_srv_list );
 321     time_t      now   = time(NULL);
 322
 323     dbgtext( "wins_srv_count: WINS status: %ld servers.\n", count );
 324     while( NULL != entry )
 325       {
 326       dbgtext( "  %s <%s>: ", entry->server, inet_ntoa( entry->ip_addr ) );
 327       if( now >= entry->mourning )
 328         dbgtext( "alive\n" );
 329       else
 330         dbgtext( "dead for %d more seconds\n", (int)(entry->mourning - now) );
 331
 332       entry = (list_entry *)ubi_slNext( entry );
 333       }
 334     }
 335
 336   return( count );
 337   } /* wins_srv_count */
 338
 339 /* ========================================================================== */