/*
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
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
- $Id: graph.c,v 1.1.2.5 2001/10/31 12:50:24 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:
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. The implementation here
- however is not so fast, because I tried to avoid having to make a forest and
- merge trees.
+ tree.
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 <string.h>
+#if defined(HAVE_FREEBSD) || defined(HAVE_OPENBSD)
+ #include <sys/param.h>
+#endif
+#include <netinet/in.h>
#include <avl_tree.h>
+#include <utils.h>
+#include "netutl.h"
#include "node.h"
#include "edge.h"
#include "connection.h"
#include "system.h"
-/* Implementation of Kruskal's algorithm.
- Running time: O(EN)
- Please note that sorting on weight is already done by add_edge().
+/* Kruskal's minimum spanning tree algorithm.
+ Running time: O(E)
+ Edges are already sorted on weight.
*/
void mst_kruskal(void)
{
- avl_node_t *node, *next;
+ avl_node_t *node;
edge_t *e;
node_t *n;
connection_t *c;
- int nodes = 0;
- int safe_edges = 0;
- int skipped;
+
+ /* 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? */
+
+ if(!edge_weight_tree->head)
+ return;
/* Clear visited status on nodes */
{
n = (node_t *)node->data;
n->status.visited = 0;
- nodes++;
}
/* Starting point */
- ((edge_t *)edge_weight_tree->head->data)->from->status.visited = 1;
-
- /* Clear MST status on connections */
-
- for(node = connection_tree->head; node; node = node->next)
- {
- c = (connection_t *)node->data;
- c->status.mst = 0;
- }
+ ((edge_t *)edge_weight_tree->head->data)->from.node->status.visited = 1;
/* Add safe edges */
- for(skipped = 0, node = edge_weight_tree->head; node; node = next)
+ for(node = edge_weight_tree->head; node; node = node->next)
{
- next = node->next;
e = (edge_t *)node->data;
- if(e->from->status.visited == e->to->status.visited)
- {
- skipped = 1;
- continue;
- }
+ if(e->from.node->status.visited && e->to.node->status.visited)
+ 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;
-
- safe_edges++;
-
- if(skipped)
- {
- next = edge_weight_tree->head;
- continue;
- }
}
}
Running time: O(E)
*/
-void sssp_bfs(int prune)
+void sssp_bfs(void)
{
avl_node_t *node, *from, *next, *to;
edge_t *e;
- node_t *n, *check;
+ node_t *n;
+ halfconnection_t to_hc, from_hc;
avl_tree_t *todo_tree;
todo_tree = avl_alloc_tree(NULL, NULL);
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;
- 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;
- 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
- 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) ? check : n->nexthop;
- check->via = (e->options & OPTION_INDIRECT || n->via != n) ? n->via : check;
+ 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 = check;
+ node->data = to_hc.node;
avl_insert_before(todo_tree, from, node);
}
}
- avl_delete_node(todo_tree, from);
+ avl_delete_node(todo_tree, from);
}
}
avl_free_tree(todo_tree);
- /* Nodes we haven't visited are unreachable, prune them. */
+ /* Check reachability status. */
- if(prune)
- for(node = node_tree->head; node; node = next)
- {
- next = node->next;
- n = (node_t *)node->data;
+ for(node = node_tree->head; node; node = next)
+ {
+ next = node->next;
+ n = (node_t *)node->data;
- if(n->status.visited == 0)
- node_del(n);
+ 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();
}
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