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 1.1.2.10 2002/03/19 22:48:25 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 /* Clear MST status on connections */
82 for(node = connection_tree->head; node; node = node->next)
84 c = (connection_t *)node->data;
88 /* Do we have something to do at all? */
90 if(!edge_weight_tree->head)
93 if(debug_lvl >= DEBUG_SCARY_THINGS)
94 syslog(LOG_DEBUG, "Running Kruskal's algorithm:");
96 /* Clear visited status on nodes */
98 for(node = node_tree->head; node; node = node->next)
100 n = (node_t *)node->data;
101 n->status.visited = 0;
107 ((edge_t *)edge_weight_tree->head->data)->from.node->status.visited = 1;
111 for(skipped = 0, node = edge_weight_tree->head; node; node = next)
114 e = (edge_t *)node->data;
116 if(e->from.node->status.visited == e->to.node->status.visited)
122 e->from.node->status.visited = 1;
123 e->to.node->status.visited = 1;
125 e->connection->status.mst = 1;
129 if(debug_lvl >= DEBUG_SCARY_THINGS)
130 syslog(LOG_DEBUG, " Adding edge %s - %s weight %d", e->from.node->name, e->to.node->name, e->weight);
134 next = edge_weight_tree->head;
139 if(debug_lvl >= DEBUG_SCARY_THINGS)
140 syslog(LOG_DEBUG, "Done, counted %d nodes and %d safe edges.", nodes, safe_edges);
143 /* Implementation of a simple breadth-first search algorithm.
149 avl_node_t *node, *from, *next, *to;
152 halfconnection_t to_hc, from_hc;
153 avl_tree_t *todo_tree;
156 todo_tree = avl_alloc_tree(NULL, NULL);
158 /* Clear visited status on nodes */
160 for(node = node_tree->head; node; node = node->next)
162 n = (node_t *)node->data;
163 n->status.visited = 0;
164 n->status.indirect = 1;
167 /* Begin with myself */
169 myself->status.visited = 1;
170 myself->status.indirect = 0;
171 myself->nexthop = myself;
172 myself->via = myself;
173 node = avl_alloc_node();
175 avl_insert_top(todo_tree, node);
177 /* Loop while todo_tree is filled */
179 while(todo_tree->head)
181 for(from = todo_tree->head; from; from = next) /* "from" is the node from which we start */
184 n = (node_t *)from->data;
186 for(to = n->edge_tree->head; to; to = to->next) /* "to" is the edge connected to "from" */
188 e = (edge_t *)to->data;
190 if(e->from.node == n) /* "from_hc" is the halfconnection with .node == from */
191 to_hc = e->to, from_hc = e->from;
193 to_hc = e->from, from_hc = e->to;
199 ------(n)from_hc-----to_hc
203 n->address is set to the to_hc.udpaddress of the edge left of n.
204 We are currently examining the edge right of n:
206 - If from_hc.udpaddress != n->address, then to_hc.node is probably
207 not reachable for the nodes left of n. We do as if the indirectdata
208 flag is set on edge e.
209 - If edge e provides for better reachability of to_hc.node, update
210 to_hc.node and (re)add it to the todo_tree to (re)examine the reachability
214 indirect = n->status.indirect || e->options & OPTION_INDIRECT || ((n != myself) && sockaddrcmp(&n->address, &from_hc.udpaddress));
216 if(to_hc.node->status.visited && (!to_hc.node->status.indirect || indirect))
219 to_hc.node->status.visited = 1;
220 to_hc.node->status.indirect = indirect;
221 to_hc.node->nexthop = (n->nexthop == myself) ? to_hc.node : n->nexthop;
222 to_hc.node->via = indirect ? n->via : to_hc.node;
223 to_hc.node->options = e->options;
224 if(sockaddrcmp(&to_hc.node->address, &to_hc.udpaddress))
226 node = avl_unlink(node_udp_tree, to_hc.node);
227 to_hc.node->address = to_hc.udpaddress;
228 if(to_hc.node->hostname)
229 free(to_hc.node->hostname);
230 to_hc.node->hostname = sockaddr2hostname(&to_hc.udpaddress);
231 avl_insert_node(node_udp_tree, node);
233 node = avl_alloc_node();
234 node->data = to_hc.node;
235 avl_insert_before(todo_tree, from, node);
238 avl_delete_node(todo_tree, from);
242 avl_free_tree(todo_tree);
244 /* Check reachability status. */
246 for(node = node_tree->head; node; node = next)
249 n = (node_t *)node->data;
251 if(n->status.visited)
253 if(!n->status.reachable)
255 if(debug_lvl >= DEBUG_TRAFFIC)
256 syslog(LOG_DEBUG, _("Node %s (%s) became reachable"), n->name, n->hostname);
257 n->status.reachable = 1;
262 if(n->status.reachable)
264 if(debug_lvl >= DEBUG_TRAFFIC)
265 syslog(LOG_DEBUG, _("Node %s (%s) became unreachable"), n->name, n->hostname);
266 n->status.reachable = 0;
267 n->status.validkey = 0;
268 n->status.waitingforkey = 0;