Simplified implementation of Kruskal's minimum spanning tree algorithm.

[tinc] / src / graph.c

diff --git a/src/graph.c b/src/graph.c
index c7ca8af..6aac6f2 100644 (file)
--- a/src/graph.c
+++ b/src/graph.c
@@ -1,7 +1,7 @@
 /*
     graph.c -- graph algorithms
 /*
     graph.c -- graph algorithms

-    Copyright (C) 2001 Guus Sliepen <guus@sliepen.warande.net>,
-                  2001 Ivo Timmermans <itimmermans@bigfoot.com>
+    Copyright (C) 2001-2002 Guus Sliepen <guus@sliepen.warande.net>,
+                  2001-2002 Ivo Timmermans <itimmermans@bigfoot.com>

 
     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
 
     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


@@ -17,41 +17,52 @@
     along with this program; if not, write to the Free Software
     Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 
     along with this program; if not, write to the Free Software
     Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 

-    $Id: graph.c,v 1.1.2.2 2001/10/28 22:42:49 guus Exp $
+    $Id: graph.c,v 1.1.2.8 2002/03/12 13:42:23 guus Exp $

 */
 
 /* We need to generate two trees from the graph:
 
    1. A minimum spanning tree for broadcasts,
    2. A single-source shortest path tree for unicasts.
 */
 
 /* We need to generate two trees from the graph:
 
    1. A minimum spanning tree for broadcasts,
    2. A single-source shortest path tree for unicasts.

-   
+

    Actually, the first one alone would suffice but would make unicast packets
    take longer routes than necessary.
    Actually, the first one alone would suffice but would make unicast packets
    take longer routes than necessary.

-   
+

    For the MST algorithm we can choose from Prim's or Kruskal's. I personally
    favour Kruskal's, because we make an extra AVL tree of edges sorted on
    weights (metric). That tree only has to be updated when an edge is added or
    removed, and during the MST algorithm we just have go linearly through that
    For the MST algorithm we can choose from Prim's or Kruskal's. I personally
    favour Kruskal's, because we make an extra AVL tree of edges sorted on
    weights (metric). That tree only has to be updated when an edge is added or
    removed, and during the MST algorithm we just have go linearly through that

-   tree, adding safe edges until #edges = #nodes - 1.
+   tree.

 
    For the SSSP algorithm Dijkstra's seems to be a nice choice. Currently a
    simple breadth-first search is presented here.
 
    For the SSSP algorithm Dijkstra's seems to be a nice choice. Currently a
    simple breadth-first search is presented here.

+
+   The SSSP algorithm will also be used to determine whether nodes are directly,
+   indirectly or not reachable from the source. It will also set the correct
+   destination address and port of a node if possible.

 */
 
 #include <syslog.h>
 #include "config.h"
 */
 
 #include <syslog.h>
 #include "config.h"

+#include <string.h>
+#if defined(HAVE_FREEBSD) || defined(HAVE_OPENBSD)
+ #include <sys/param.h>
+#endif
+#include <netinet/in.h>

 
 #include <avl_tree.h>
 
 #include <avl_tree.h>

+#include <utils.h>

 
 

+#include "netutl.h"

 #include "node.h"
 #include "edge.h"
 #include "connection.h"
 
 #include "system.h"
 
 #include "node.h"
 #include "edge.h"
 #include "connection.h"
 
 #include "system.h"
 

-/* Implementation of Kruskal's algorithm.
+/* Kruskal's minimum spanning tree algorithm.

    Running time: O(E)
    Running time: O(E)

-   Please note that sorting on weight is already done by add_edge().
+   Edges are already sorted on weight.

 */
 
 void mst_kruskal(void)
 */
 
 void mst_kruskal(void)


@@ -60,10 +71,19 @@ void mst_kruskal(void)
   edge_t *e;
   node_t *n;
   connection_t *c;
   edge_t *e;
   node_t *n;
   connection_t *c;

-  int nodes = 0;
-  int safe_edges = 0;
+
+  /* Clear MST status on connections */
+
+  for(node = connection_tree->head; node; node = node->next)
+    {
+      c = (connection_t *)node->data;
+      c->status.mst = 0;
+    }
+
+  /* Do we have something to do at all? */

   
   

-  syslog(LOG_DEBUG, _("Running Kruskal's algorithm:"));
+  if(!edge_weight_tree->head)
+    return;

 
   /* Clear visited status on nodes */
 
 
   /* Clear visited status on nodes */
 


@@ -71,45 +91,25 @@ void mst_kruskal(void)
     {
       n = (node_t *)node->data;
       n->status.visited = 0;
     {
       n = (node_t *)node->data;
       n->status.visited = 0;

-      nodes++;

     }
 
     }
 

-  /* Clear MST status on connections */
-
-  for(node = connection_tree->head; node; node = node->next)
-    {
-      c = (connection_t *)node->data;
-      c->status.mst = 0;
-    }
+  /* Starting point */
+  
+  ((edge_t *)edge_weight_tree->head->data)->from.node->status.visited = 1;

 
   /* Add safe edges */
 
   for(node = edge_weight_tree->head; node; node = node->next)
     {
 
   /* Add safe edges */
 
   for(node = edge_weight_tree->head; node; node = node->next)
     {

-// Algorithm should work without this:
-//      if(safe_edges = nodes - 1)
-//        break;
-

       e = (edge_t *)node->data;
       e = (edge_t *)node->data;

-      
-      if(e->from->status.visited && e->to->status.visited)
+
+      if(e->from.node->status.visited && e->to.node->status.visited)

         continue;
 
         continue;
 

-      e->from->status.visited = 1;
-      e->to->status.visited = 1;
+      e->from.node->status.visited = 1;
+      e->to.node->status.visited = 1;

       if(e->connection)
         e->connection->status.mst = 1;
       if(e->connection)
         e->connection->status.mst = 1;

-
-      safe_edges++;      
-
-      syslog(LOG_DEBUG, _("Adding safe edge %s - %s weight %d"), e->from->name, e->to->name, e->weight);
-    }
-
-  syslog(LOG_DEBUG, _("Done."));
-
-  if(safe_edges != nodes - 1)
-    {
-      syslog(LOG_ERR, _("Implementation of Kruskal's algorithm is screwed: %d nodes, found %d safe edges"), nodes, safe_edges);

     }
 }
 
     }
 }
 


@@ -121,12 +121,9 @@ void sssp_bfs(void)
 {
   avl_node_t *node, *from, *next, *to;
   edge_t *e;
 {
   avl_node_t *node, *from, *next, *to;
   edge_t *e;

-  node_t *n, *check;
-  int nodes = 0;
-  int visited = 0;
+  node_t *n;
+  halfconnection_t to_hc, from_hc;

   avl_tree_t *todo_tree;
   avl_tree_t *todo_tree;

-  
-  syslog(LOG_DEBUG, _("Running BFS algorithm:"));

 
   todo_tree = avl_alloc_tree(NULL, NULL);
 
 
   todo_tree = avl_alloc_tree(NULL, NULL);
 


@@ -136,7 +133,6 @@ void sssp_bfs(void)
     {
       n = (node_t *)node->data;
       n->status.visited = 0;
     {
       n = (node_t *)node->data;
       n->status.visited = 0;

-      nodes++;

     }
 
   /* Begin with myself */
     }
 
   /* Begin with myself */


@@ -147,44 +143,85 @@ void sssp_bfs(void)
   node = avl_alloc_node();
   node->data = myself;
   avl_insert_top(todo_tree, node);
   node = avl_alloc_node();
   node->data = myself;
   avl_insert_top(todo_tree, node);

-  visited++;

 
   /* Loop while todo_tree is filled */
 
   while(todo_tree->head)
     {
 
   /* Loop while todo_tree is filled */
 
   while(todo_tree->head)
     {

-      for(from = todo_tree->head; from; from = next)
+      for(from = todo_tree->head; from; from = next)             /* "from" is the node from which we start */

         {
           next = from->next;
           n = (node_t *)from->data;
         {
           next = from->next;
           n = (node_t *)from->data;

-          
-          for(to = n->edge_tree->head; to; to = to->next)
+
+          for(to = n->edge_tree->head; to; to = to->next)        /* "to" is the edge connected to "from" */

             {
               e = (edge_t *)to->data;
 
             {
               e = (edge_t *)to->data;
 

-              if(e->from == n)
-                check = e->to;
+              if(e->from.node == n)                              /* "from_hc" is the halfconnection with .node == from */
+                to_hc = e->to, from_hc = e->from;

               else
               else

-                check = e->from;
+                to_hc = e->from, from_hc = e->to;

 
 

-              if(!check->status.visited)
+              if(!to_hc.node->status.visited)

                 {
                 {

-                  check->status.visited = 1;
-                  check->nexthop = (n->nexthop == myself)?n:n->nexthop;
-                  check->via = check; /* FIXME: only if !(e->options & INDIRECT), otherwise use n->via */
-                  avl_insert_before(todo_tree, todo_tree->head, to);
-                  visited++;
+                  to_hc.node->status.visited = 1;
+                  to_hc.node->nexthop = (n->nexthop == myself) ? to_hc.node : n->nexthop;
+                  to_hc.node->via = (e->options & OPTION_INDIRECT || n->via != n) ? n->via : to_hc.node;
+                 to_hc.node->options = e->options;
+                  if(sockaddrcmp(&to_hc.node->address, &to_hc.udpaddress))
+                 {
+                    node = avl_unlink(node_udp_tree, to_hc.node);
+                    to_hc.node->address = to_hc.udpaddress;
+                   if(to_hc.node->hostname)
+                     free(to_hc.node->hostname);
+                   to_hc.node->hostname = sockaddr2hostname(&to_hc.udpaddress);
+                    avl_insert_node(node_udp_tree, node);
+                 }
+                  node = avl_alloc_node();
+                  node->data = to_hc.node;
+                  avl_insert_before(todo_tree, from, node);

                 }
             }
 
                 }
             }
 

-           avl_delete_node(todo_tree, from);
+          avl_delete_node(todo_tree, from);

         }
     }
 
         }
     }
 

-  syslog(LOG_DEBUG, _("Done."));
+  avl_free_tree(todo_tree);
+  
+  /* Check reachability status. */

 
 

-  if(visited != nodes)
+  for(node = node_tree->head; node; node = next)

     {
     {

-      syslog(LOG_ERR, _("Implementation of BFS algorithm is screwed: %d nodes, visited %d"), nodes, visited);
+      next = node->next;
+      n = (node_t *)node->data;
+
+      if(n->status.visited)
+      {
+        if(!n->status.reachable)
+       {
+          if(debug_lvl >= DEBUG_TRAFFIC)
+            syslog(LOG_DEBUG, _("Node %s (%s) became reachable"), n->name, n->hostname);
+          n->status.reachable = 1;
+       }
+      }
+      else
+      {
+        if(n->status.reachable)
+       {
+          if(debug_lvl >= DEBUG_TRAFFIC)
+            syslog(LOG_DEBUG, _("Node %s (%s) became unreachable"), n->name, n->hostname);
+          n->status.reachable = 0;
+         n->status.validkey = 0;
+         n->status.waitingforkey = 0;
+         n->sent_seqno = 0;
+       }
+      }

     }
 }
     }
 }

+
+void graph(void)
+{
+  mst_kruskal();
+  sssp_bfs();
+}