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 2002/04/28 12:46:26 zarq 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.
49 #if defined(HAVE_FREEBSD) || defined(HAVE_OPENBSD)
50 #include <sys/param.h>
52 #include <netinet/in.h>
58 #include "interface.h"
62 #include "connection.h"
67 /* Implementation of Kruskal's algorithm.
69 Please note that sorting on weight is already done by add_edge().
72 void mst_kruskal(void)
74 avl_node_t *node, *next;
82 /* Clear MST status on connections */
84 for(node = connection_tree->head; node; node = node->next)
86 c = (connection_t *)node->data;
90 /* Do we have something to do at all? */
92 if(!edge_weight_tree->head)
95 log(DEBUG_SCARY_THINGS, TLOG_DEBUG,
96 _("Running Kruskal's algorithm:"));
98 /* Clear visited status on nodes */
100 for(node = node_tree->head; node; node = node->next)
102 n = (node_t *)node->data;
103 n->status.visited = 0;
109 ((edge_t *)edge_weight_tree->head->data)->from.node->status.visited = 1;
113 for(skipped = 0, node = edge_weight_tree->head; node; node = next)
116 e = (edge_t *)node->data;
118 if(e->from.node->status.visited == e->to.node->status.visited)
124 e->from.node->status.visited = 1;
125 e->to.node->status.visited = 1;
127 e->connection->status.mst = 1;
131 if(debug_lvl >= DEBUG_SCARY_THINGS)
132 syslog(LOG_DEBUG, " Adding edge %s - %s weight %d", e->from.node->name, e->to.node->name, e->weight);
136 next = edge_weight_tree->head;
141 if(debug_lvl >= DEBUG_SCARY_THINGS)
142 syslog(LOG_DEBUG, "Done, counted %d nodes and %d safe edges.", nodes, safe_edges);
145 /* Implementation of a simple breadth-first search algorithm.
151 avl_node_t *node, *from, *next, *to;
154 halfconnection_t to_hc, from_hc;
155 avl_tree_t *todo_tree;
158 todo_tree = avl_alloc_tree(NULL, NULL);
160 /* Clear visited status on nodes */
162 for(node = node_tree->head; node; node = node->next)
164 n = (node_t *)node->data;
165 n->status.visited = 0;
166 n->status.indirect = 1;
169 /* Begin with myself */
171 myself->status.visited = 1;
172 myself->status.indirect = 0;
173 myself->nexthop = myself;
174 myself->via = myself;
175 node = avl_alloc_node();
177 avl_insert_top(todo_tree, node);
179 /* Loop while todo_tree is filled */
181 while(todo_tree->head)
183 for(from = todo_tree->head; from; from = next) /* "from" is the node from which we start */
186 n = (node_t *)from->data;
188 for(to = n->edge_tree->head; to; to = to->next) /* "to" is the edge connected to "from" */
190 e = (edge_t *)to->data;
192 if(e->from.node == n) /* "from_hc" is the halfconnection with .node == from */
193 to_hc = e->to, from_hc = e->from;
195 to_hc = e->from, from_hc = e->to;
201 ------(n)from_hc-----to_hc
205 n->address is set to the to_hc.udpaddress of the edge left of n.
206 We are currently examining the edge right of n:
208 - If from_hc.udpaddress != n->address, then to_hc.node is probably
209 not reachable for the nodes left of n. We do as if the indirectdata
210 flag is set on edge e.
211 - If edge e provides for better reachability of to_hc.node, update
212 to_hc.node and (re)add it to the todo_tree to (re)examine the reachability
216 indirect = n->status.indirect || e->options & OPTION_INDIRECT || ((n != myself) && sockaddrcmp(&n->address, &from_hc.udpaddress));
218 if(to_hc.node->status.visited && (!to_hc.node->status.indirect || indirect))
221 to_hc.node->status.visited = 1;
222 to_hc.node->status.indirect = indirect;
223 to_hc.node->nexthop = (n->nexthop == myself) ? to_hc.node : n->nexthop;
224 to_hc.node->via = indirect ? n->via : to_hc.node;
225 to_hc.node->options = e->options;
226 if(sockaddrcmp(&to_hc.node->address, &to_hc.udpaddress))
228 node = avl_unlink(node_udp_tree, to_hc.node);
229 to_hc.node->address = to_hc.udpaddress;
230 if(to_hc.node->hostname)
231 free(to_hc.node->hostname);
232 to_hc.node->hostname = sockaddr2hostname(&to_hc.udpaddress);
233 avl_insert_node(node_udp_tree, node);
235 node = avl_alloc_node();
236 node->data = to_hc.node;
237 avl_insert_before(todo_tree, from, node);
240 avl_delete_node(todo_tree, from);
244 avl_free_tree(todo_tree);
246 /* Check reachability status. */
248 for(node = node_tree->head; node; node = next)
251 n = (node_t *)node->data;
253 if(n->status.visited)
255 if(!n->status.reachable)
257 if(debug_lvl >= DEBUG_TRAFFIC)
258 syslog(LOG_ERR, _("Node %s (%s) became reachable"), n->name, n->hostname);
259 n->status.reachable = 1;
260 run_hooks("node-visible", n);
265 if(n->status.reachable)
267 if(debug_lvl >= DEBUG_TRAFFIC)
268 syslog(LOG_DEBUG, _("Node %s (%s) became unreachable"), n->name, n->hostname);
269 n->status.reachable = 0;
270 n->status.validkey = 0;
271 n->status.waitingforkey = 0;
273 run_hooks("node-invisible", n);