2 graph.c -- graph algorithms
3 Copyright (C) 2001-2002 Guus Sliepen <guus@sliepen.warande.net>,
4 2001-2002 Ivo Timmermans <itimmermans@bigfoot.com>
6 This program is free software; you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation; either version 2 of the License, or
9 (at your option) any later version.
11 This program is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with this program; if not, write to the Free Software
18 Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
20 $Id: graph.c,v 1.1.2.6 2002/02/10 21:57:54 guus Exp $
23 /* We need to generate two trees from the graph:
25 1. A minimum spanning tree for broadcasts,
26 2. A single-source shortest path tree for unicasts.
28 Actually, the first one alone would suffice but would make unicast packets
29 take longer routes than necessary.
31 For the MST algorithm we can choose from Prim's or Kruskal's. I personally
32 favour Kruskal's, because we make an extra AVL tree of edges sorted on
33 weights (metric). That tree only has to be updated when an edge is added or
34 removed, and during the MST algorithm we just have go linearly through that
35 tree, adding safe edges until #edges = #nodes - 1. The implementation here
36 however is not so fast, because I tried to avoid having to make a forest and
39 For the SSSP algorithm Dijkstra's seems to be a nice choice. Currently a
40 simple breadth-first search is presented here.
42 The SSSP algorithm will also be used to determine whether nodes are directly,
43 indirectly or not reachable from the source. It will also set the correct
44 destination address and port of a node if possible.
50 #if defined(HAVE_FREEBSD) || defined(HAVE_OPENBSD)
51 #include <sys/param.h>
53 #include <netinet/in.h>
61 #include "connection.h"
65 /* Implementation of Kruskal's algorithm.
67 Please note that sorting on weight is already done by add_edge().
70 void mst_kruskal(void)
72 avl_node_t *node, *next;
80 /* Do we have something to do at all? */
82 if(!edge_weight_tree->head)
85 /* Clear visited status on nodes */
87 for(node = node_tree->head; node; node = node->next)
89 n = (node_t *)node->data;
90 n->status.visited = 0;
96 ((edge_t *)edge_weight_tree->head->data)->from.node->status.visited = 1;
98 /* Clear MST status on connections */
100 for(node = connection_tree->head; node; node = node->next)
102 c = (connection_t *)node->data;
108 for(skipped = 0, node = edge_weight_tree->head; node; node = next)
111 e = (edge_t *)node->data;
113 if(e->from.node->status.visited == e->to.node->status.visited)
119 e->from.node->status.visited = 1;
120 e->to.node->status.visited = 1;
122 e->connection->status.mst = 1;
128 next = edge_weight_tree->head;
134 /* Implementation of a simple breadth-first search algorithm.
140 avl_node_t *node, *from, *next, *to;
143 halfconnection_t to_hc, from_hc;
144 avl_tree_t *todo_tree;
146 todo_tree = avl_alloc_tree(NULL, NULL);
148 /* Clear visited status on nodes */
150 for(node = node_tree->head; node; node = node->next)
152 n = (node_t *)node->data;
153 n->status.visited = 0;
156 /* Begin with myself */
158 myself->status.visited = 1;
159 myself->nexthop = myself;
160 myself->via = myself;
161 node = avl_alloc_node();
163 avl_insert_top(todo_tree, node);
165 /* Loop while todo_tree is filled */
167 while(todo_tree->head)
169 for(from = todo_tree->head; from; from = next) /* "from" is the node from which we start */
172 n = (node_t *)from->data;
174 for(to = n->edge_tree->head; to; to = to->next) /* "to" is the edge connected to "from" */
176 e = (edge_t *)to->data;
178 if(e->from.node == n) /* "from_hc" is the halfconnection with .node == from */
179 to_hc = e->to, from_hc = e->from;
181 to_hc = e->from, from_hc = e->to;
183 if(!to_hc.node->status.visited)
185 to_hc.node->status.visited = 1;
186 to_hc.node->nexthop = (n->nexthop == myself) ? to_hc.node : n->nexthop;
187 to_hc.node->via = (e->options & OPTION_INDIRECT || n->via != n) ? n->via : to_hc.node;
188 to_hc.node->options = e->options;
189 if(to_hc.node->address != to_hc.address || to_hc.node->port != to_hc.port)
191 node = avl_unlink(node_udp_tree, to_hc.node);
192 to_hc.node->address = to_hc.address;
193 to_hc.node->port = to_hc.port;
194 if(to_hc.node->hostname)
195 free(to_hc.node->hostname);
196 to_hc.node->hostname = hostlookup(htonl(to_hc.address));
197 avl_insert_node(node_udp_tree, node);
199 to_hc.node->port = to_hc.port;
200 node = avl_alloc_node();
201 node->data = to_hc.node;
202 avl_insert_before(todo_tree, from, node);
206 avl_delete_node(todo_tree, from);
210 avl_free_tree(todo_tree);
212 /* Check reachability status. */
214 for(node = node_tree->head; node; node = next)
217 n = (node_t *)node->data;
219 if(n->status.visited)
221 if(!n->status.reachable)
223 if(debug_lvl >= DEBUG_TRAFFIC)
224 syslog(LOG_DEBUG, _("Node %s (%s) became reachable"), n->name, n->hostname);
225 n->status.reachable = 1;
230 if(n->status.reachable)
232 if(debug_lvl >= DEBUG_TRAFFIC)
233 syslog(LOG_DEBUG, _("Node %s (%s) became unreachable"), n->name, n->hostname);
234 n->status.reachable = 0;
235 n->status.validkey = 0;
236 n->status.waitingforkey = 0;