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 1.1.2.8 2002/03/12 13:42:23 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
37 For the SSSP algorithm Dijkstra's seems to be a nice choice. Currently a
38 simple breadth-first search is presented here.
40 The SSSP algorithm will also be used to determine whether nodes are directly,
41 indirectly or not reachable from the source. It will also set the correct
42 destination address and port of a node if possible.
48 #if defined(HAVE_FREEBSD) || defined(HAVE_OPENBSD)
49 #include <sys/param.h>
51 #include <netinet/in.h>
59 #include "connection.h"
63 /* Kruskal's minimum spanning tree algorithm.
65 Edges are already sorted on weight.
68 void mst_kruskal(void)
75 /* Clear MST status on connections */
77 for(node = connection_tree->head; node; node = node->next)
79 c = (connection_t *)node->data;
83 /* Do we have something to do at all? */
85 if(!edge_weight_tree->head)
88 /* Clear visited status on nodes */
90 for(node = node_tree->head; node; node = node->next)
92 n = (node_t *)node->data;
93 n->status.visited = 0;
98 ((edge_t *)edge_weight_tree->head->data)->from.node->status.visited = 1;
102 for(node = edge_weight_tree->head; node; node = node->next)
104 e = (edge_t *)node->data;
106 if(e->from.node->status.visited && e->to.node->status.visited)
109 e->from.node->status.visited = 1;
110 e->to.node->status.visited = 1;
112 e->connection->status.mst = 1;
116 /* Implementation of a simple breadth-first search algorithm.
122 avl_node_t *node, *from, *next, *to;
125 halfconnection_t to_hc, from_hc;
126 avl_tree_t *todo_tree;
128 todo_tree = avl_alloc_tree(NULL, NULL);
130 /* Clear visited status on nodes */
132 for(node = node_tree->head; node; node = node->next)
134 n = (node_t *)node->data;
135 n->status.visited = 0;
138 /* Begin with myself */
140 myself->status.visited = 1;
141 myself->nexthop = myself;
142 myself->via = myself;
143 node = avl_alloc_node();
145 avl_insert_top(todo_tree, node);
147 /* Loop while todo_tree is filled */
149 while(todo_tree->head)
151 for(from = todo_tree->head; from; from = next) /* "from" is the node from which we start */
154 n = (node_t *)from->data;
156 for(to = n->edge_tree->head; to; to = to->next) /* "to" is the edge connected to "from" */
158 e = (edge_t *)to->data;
160 if(e->from.node == n) /* "from_hc" is the halfconnection with .node == from */
161 to_hc = e->to, from_hc = e->from;
163 to_hc = e->from, from_hc = e->to;
165 if(!to_hc.node->status.visited)
167 to_hc.node->status.visited = 1;
168 to_hc.node->nexthop = (n->nexthop == myself) ? to_hc.node : n->nexthop;
169 to_hc.node->via = (e->options & OPTION_INDIRECT || n->via != n) ? n->via : to_hc.node;
170 to_hc.node->options = e->options;
171 if(sockaddrcmp(&to_hc.node->address, &to_hc.udpaddress))
173 node = avl_unlink(node_udp_tree, to_hc.node);
174 to_hc.node->address = to_hc.udpaddress;
175 if(to_hc.node->hostname)
176 free(to_hc.node->hostname);
177 to_hc.node->hostname = sockaddr2hostname(&to_hc.udpaddress);
178 avl_insert_node(node_udp_tree, node);
180 node = avl_alloc_node();
181 node->data = to_hc.node;
182 avl_insert_before(todo_tree, from, node);
186 avl_delete_node(todo_tree, from);
190 avl_free_tree(todo_tree);
192 /* Check reachability status. */
194 for(node = node_tree->head; node; node = next)
197 n = (node_t *)node->data;
199 if(n->status.visited)
201 if(!n->status.reachable)
203 if(debug_lvl >= DEBUG_TRAFFIC)
204 syslog(LOG_DEBUG, _("Node %s (%s) became reachable"), n->name, n->hostname);
205 n->status.reachable = 1;
210 if(n->status.reachable)
212 if(debug_lvl >= DEBUG_TRAFFIC)
213 syslog(LOG_DEBUG, _("Node %s (%s) became unreachable"), n->name, n->hostname);
214 n->status.reachable = 0;
215 n->status.validkey = 0;
216 n->status.waitingforkey = 0;