/*
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 1.1.2.1 2001/10/28 10:16:18 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.
-
+
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
- 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.
+ 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(V)
- Please note that sorting on weight is already done by add_vertex().
+/* Kruskal's minimum spanning tree algorithm.
+ Running time: O(E)
+ Edges are already sorted on weight.
*/
-void kruskal(void)
+void mst_kruskal(void)
{
avl_node_t *node;
edge_t *e;
node_t *n;
connection_t *c;
- int nodes;
- int safe_edges = 0;
-
- syslog(LOG_DEBUG, _("Running Kruskal's algorithm:"));
- /* Clear MST status on nodes */
+ /* Clear MST status on connections */
- for(node = node_tree->head; node; node = node->next)
+ for(node = connection_tree->head; node; node = node->next)
{
- n = (node_t *)node->data;
- n->status.mst = 0;
- node++;
+ c = (connection_t *)node->data;
+ c->status.mst = 0;
}
- /* Clear MST status on connections */
+ /* Do we have something to do at all? */
+
+ if(!edge_weight_tree->head)
+ return;
- for(node = connection_tree->head; node; node = node->next)
+ /* Clear visited status on nodes */
+
+ for(node = node_tree->head; node; node = node->next)
{
- c = (edge_t *)node->data;
- c->status.mst = 0;
+ n = (node_t *)node->data;
+ n->status.visited = 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)
{
-// Algorithm should work without this:
-// if(safe_edges = nodes - 1)
-// break;
-
e = (edge_t *)node->data;
-
- if(e->from->status.mst && e->to->status.mst)
+
+ if(e->from.node->status.visited && e->to.node->status.visited)
continue;
- e->from->status.mst = 1;
- e->to->status.mst = 1;
+ e->from.node->status.visited = 1;
+ e->to.node->status.visited = 1;
if(e->connection)
e->connection->status.mst = 1;
+ }
+}
- safe_edges++;
+/* Implementation of a simple breadth-first search algorithm.
+ Running time: O(E)
+*/
+
+void sssp_bfs(void)
+{
+ avl_node_t *node, *from, *next, *to;
+ edge_t *e;
+ node_t *n;
+ halfconnection_t to_hc, from_hc;
+ avl_tree_t *todo_tree;
+
+ todo_tree = avl_alloc_tree(NULL, NULL);
+
+ /* Clear visited status on nodes */
+
+ for(node = node_tree->head; node; node = node->next)
+ {
+ n = (node_t *)node->data;
+ n->status.visited = 0;
+ }
+
+ /* Begin with myself */
+
+ myself->status.visited = 1;
+ myself->nexthop = myself;
+ myself->via = myself;
+ node = avl_alloc_node();
+ node->data = myself;
+ avl_insert_top(todo_tree, node);
- syslog(LOG_DEBUG, _("Adding safe edge %s - %s weight %d"), e->from->name, e->to->name, e->weight);
+ /* Loop while todo_tree is filled */
+
+ while(todo_tree->head)
+ {
+ 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) /* "to" is the edge connected to "from" */
+ {
+ e = (edge_t *)to->data;
+
+ if(e->from.node == n) /* "from_hc" is the halfconnection with .node == from */
+ to_hc = e->to, from_hc = e->from;
+ else
+ to_hc = e->from, from_hc = e->to;
+
+ if(!to_hc.node->status.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);
+ }
}
- syslog(LOG_DEBUG, _("Done."));
+ avl_free_tree(todo_tree);
+
+ /* Check reachability status. */
- if(safe_edges != nodes - 1)
+ for(node = node_tree->head; node; node = next)
{
- syslog(LOG_ERR, _("Implementation of Kruskal's algorithm is screwed: %d nodes, found %d safe edges"), nodes, safe_edges);
+ 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();
+}
projects / tinc / blobdiff