2 graph.c -- graph algorithms
3 Copyright (C) 2001-2002 Guus Sliepen <guus@sliepen.eu.org>,
4 2001-2002 Ivo Timmermans <ivo@o2w.nl>
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 1.1.2.19 2002/09/09 21:24:34 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.
53 #ifdef HAVE_SYS_PARAM_H
54 #include <sys/param.h>
56 #include <netinet/in.h>
64 #include "connection.h"
70 /* Implementation of Kruskal's algorithm.
72 Please note that sorting on weight is already done by add_edge().
75 void mst_kruskal(void)
77 avl_node_t *node, *next;
87 /* Clear MST status on connections */
89 for(node = connection_tree->head; node; node = node->next) {
90 c = (connection_t *) node->data;
94 /* Do we have something to do at all? */
96 if(!edge_weight_tree->head)
99 if(debug_lvl >= DEBUG_SCARY_THINGS)
100 syslog(LOG_DEBUG, "Running Kruskal's algorithm:");
102 /* Clear visited status on nodes */
104 for(node = node_tree->head; node; node = node->next) {
105 n = (node_t *) node->data;
106 n->status.visited = 0;
112 ((edge_t *) edge_weight_tree->head->data)->from->status.visited = 1;
116 for(skipped = 0, node = edge_weight_tree->head; node; node = next) {
118 e = (edge_t *) node->data;
120 if(!e->reverse || e->from->status.visited == e->to->status.visited) {
125 e->from->status.visited = 1;
126 e->to->status.visited = 1;
129 e->connection->status.mst = 1;
131 if(e->reverse->connection)
132 e->reverse->connection->status.mst = 1;
136 if(debug_lvl >= DEBUG_SCARY_THINGS)
137 syslog(LOG_DEBUG, " Adding edge %s - %s weight %d", e->from->name,
138 e->to->name, e->weight);
142 next = edge_weight_tree->head;
147 if(debug_lvl >= DEBUG_SCARY_THINGS)
148 syslog(LOG_DEBUG, "Done, counted %d nodes and %d safe edges.", nodes,
152 /* Implementation of a simple breadth-first search algorithm.
158 avl_node_t *node, *from, *next, *to;
161 avl_tree_t *todo_tree;
164 char *address, *port;
170 todo_tree = avl_alloc_tree(NULL, NULL);
172 /* Clear visited status on nodes */
174 for(node = node_tree->head; node; node = node->next) {
175 n = (node_t *) node->data;
176 n->status.visited = 0;
177 n->status.indirect = 1;
180 /* Begin with myself */
182 myself->status.visited = 1;
183 myself->status.indirect = 0;
184 myself->nexthop = myself;
185 myself->via = myself;
186 node = avl_alloc_node();
188 avl_insert_top(todo_tree, node);
190 /* Loop while todo_tree is filled */
192 while(todo_tree->head) {
193 for(from = todo_tree->head; from; from = next) { /* "from" is the node from which we start */
195 n = (node_t *) from->data;
197 for(to = n->edge_tree->head; to; to = to->next) { /* "to" is the edge connected to "from" */
198 e = (edge_t *) to->data;
207 ------(n)-----(e->to)
211 n->address is set to the e->address of the edge left of n to n.
212 We are currently examining the edge e right of n from n:
214 - If e->reverse->address != n->address, then e->to is probably
215 not reachable for the nodes left of n. We do as if the indirectdata
216 flag is set on edge e.
217 - If edge e provides for better reachability of e->to, update
218 e->to and (re)add it to the todo_tree to (re)examine the reachability
222 indirect = n->status.indirect || e->options & OPTION_INDIRECT
224 && sockaddrcmp(&n->address, &e->reverse->address));
226 if(e->to->status.visited
227 && (!e->to->status.indirect || indirect))
230 e->to->status.visited = 1;
231 e->to->status.indirect = indirect;
232 e->to->nexthop = (n->nexthop == myself) ? e->to : n->nexthop;
233 e->to->via = indirect ? n->via : e->to;
234 e->to->options = e->options;
236 if(sockaddrcmp(&e->to->address, &e->address)) {
237 node = avl_unlink(node_udp_tree, e->to);
238 e->to->address = e->address;
241 free(e->to->hostname);
243 e->to->hostname = sockaddr2hostname(&e->to->address);
244 avl_insert_node(node_udp_tree, node);
247 node = avl_alloc_node();
249 avl_insert_before(todo_tree, from, node);
252 avl_delete_node(todo_tree, from);
256 avl_free_tree(todo_tree);
258 /* Check reachability status. */
260 for(node = node_tree->head; node; node = next) {
262 n = (node_t *) node->data;
264 if(n->status.visited != n->status.reachable) {
265 n->status.reachable = !n->status.reachable;
267 if(debug_lvl >= DEBUG_TRAFFIC)
268 if(n->status.reachable)
269 syslog(LOG_DEBUG, _("Node %s (%s) became reachable"),
270 n->name, n->hostname);
272 syslog(LOG_DEBUG, _("Node %s (%s) became unreachable"),
273 n->name, n->hostname);
275 n->status.validkey = 0;
276 n->status.waitingforkey = 0;
278 asprintf(&envp[0], "NETNAME=%s", netname ? : "");
279 asprintf(&envp[1], "DEVICE=%s", device ? : "");
280 asprintf(&envp[2], "INTERFACE=%s", interface ? : "");
281 asprintf(&envp[3], "NODE=%s", n->name);
282 sockaddr2str(&n->address, &address, &port);
283 asprintf(&envp[4], "REMOTEADDRESS=%s", address);
284 asprintf(&envp[5], "REMOTEPORT=%s", port);
288 n->status.reachable ? "hosts/%s-up" : "hosts/%s-down",
290 execute_script(name, envp);
296 for(i = 0; i < 7; i++)