First cut toward adding WINS server failover.

*Note: failover doesn't actually work yet!*  It's just that the code I'm
adding provides all of the pieces necessary.

I do have one big question.  Something that I'll have to ask Jeremy, I'm
thinkin'.  In nmbd/nmbd_subnetdb.c the IP of the WINS server is used to
set up the Unicast subnet.

...so what happens if the WINS server changes?

My guess is either:
  a) nothing.
  b) I'd have to change the unicast subnet entry whenever the WINS server
     changes.

Urq.

BTW, the lp_wins_server() function no longer returns the WINS server name
or IP.  It returns the list of WINS servers entered in smb.conf.  To get
the currently 'live' WINS server, use the wins_srv() function.

Fun, eh?

Chris -)-----
(This used to be commit cc08bdc74f4cd111fdc582ee7babef47ed8a950d)

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 */
+
+/* ========================================================================== */