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 1.1.2.14 2002/07/10 11:27:06 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;
85 /* Clear MST status on connections */
87 for(node = connection_tree->head; node; node = node->next)
89 c = (connection_t *)node->data;
93 /* Do we have something to do at all? */
95 if(!edge_weight_tree->head)
98 if(debug_lvl >= DEBUG_SCARY_THINGS)
99 syslog(LOG_DEBUG, "Running Kruskal's algorithm:");
101 /* Clear visited status on nodes */
103 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.node->status.visited = 1;
116 for(skipped = 0, node = edge_weight_tree->head; node; node = next)
119 e = (edge_t *)node->data;
121 if(e->from.node->status.visited == e->to.node->status.visited)
127 e->from.node->status.visited = 1;
128 e->to.node->status.visited = 1;
130 e->connection->status.mst = 1;
134 if(debug_lvl >= DEBUG_SCARY_THINGS)
135 syslog(LOG_DEBUG, " Adding edge %s - %s weight %d", e->from.node->name, e->to.node->name, e->weight);
139 next = edge_weight_tree->head;
144 if(debug_lvl >= DEBUG_SCARY_THINGS)
145 syslog(LOG_DEBUG, "Done, counted %d nodes and %d safe edges.", nodes, safe_edges);
148 /* Implementation of a simple breadth-first search algorithm.
154 avl_node_t *node, *from, *next, *to;
157 halfconnection_t to_hc, from_hc;
158 avl_tree_t *todo_tree;
161 char *address, *port;
165 todo_tree = avl_alloc_tree(NULL, NULL);
167 /* Clear visited status on nodes */
169 for(node = node_tree->head; node; node = node->next)
171 n = (node_t *)node->data;
172 n->status.visited = 0;
173 n->status.indirect = 1;
176 /* Begin with myself */
178 myself->status.visited = 1;
179 myself->status.indirect = 0;
180 myself->nexthop = myself;
181 myself->via = myself;
182 node = avl_alloc_node();
184 avl_insert_top(todo_tree, node);
186 /* Loop while todo_tree is filled */
188 while(todo_tree->head)
190 for(from = todo_tree->head; from; from = next) /* "from" is the node from which we start */
193 n = (node_t *)from->data;
195 for(to = n->edge_tree->head; to; to = to->next) /* "to" is the edge connected to "from" */
197 e = (edge_t *)to->data;
199 if(e->from.node == n) /* "from_hc" is the halfconnection with .node == from */
200 to_hc = e->to, from_hc = e->from;
202 to_hc = e->from, from_hc = e->to;
208 ------(n)from_hc-----to_hc
212 n->address is set to the to_hc.udpaddress of the edge left of n.
213 We are currently examining the edge right of n:
215 - If from_hc.udpaddress != n->address, then to_hc.node is probably
216 not reachable for the nodes left of n. We do as if the indirectdata
217 flag is set on edge e.
218 - If edge e provides for better reachability of to_hc.node, update
219 to_hc.node and (re)add it to the todo_tree to (re)examine the reachability
223 indirect = n->status.indirect || e->options & OPTION_INDIRECT || ((n != myself) && sockaddrcmp(&n->address, &from_hc.udpaddress));
225 if(to_hc.node->status.visited && (!to_hc.node->status.indirect || indirect))
228 to_hc.node->status.visited = 1;
229 to_hc.node->status.indirect = indirect;
230 to_hc.node->nexthop = (n->nexthop == myself) ? to_hc.node : n->nexthop;
231 to_hc.node->via = indirect ? n->via : to_hc.node;
232 to_hc.node->options = e->options;
233 if(sockaddrcmp(&to_hc.node->address, &to_hc.udpaddress))
235 node = avl_unlink(node_udp_tree, to_hc.node);
236 to_hc.node->address = to_hc.udpaddress;
237 if(to_hc.node->hostname)
238 free(to_hc.node->hostname);
239 to_hc.node->hostname = sockaddr2hostname(&to_hc.udpaddress);
240 avl_insert_node(node_udp_tree, node);
242 node = avl_alloc_node();
243 node->data = to_hc.node;
244 avl_insert_before(todo_tree, from, node);
247 avl_delete_node(todo_tree, from);
251 avl_free_tree(todo_tree);
253 /* Check reachability status. */
255 for(node = node_tree->head; node; node = next)
258 n = (node_t *)node->data;
260 if(n->status.visited ^ n->status.reachable)
262 n->status.reachable = !n->status.reachable;
263 if(debug_lvl >= DEBUG_TRAFFIC)
264 if(n->status.reachable)
265 syslog(LOG_DEBUG, _("Node %s (%s) became reachable"), n->name, n->hostname);
267 syslog(LOG_DEBUG, _("Node %s (%s) became unreachable"), n->name, n->hostname);
269 if(!n->status.reachable)
271 n->status.reachable = 0;
272 n->status.validkey = 0;
273 n->status.waitingforkey = 0;
277 asprintf(&envp[0], "NETNAME=%s", netname?netname:"");
278 asprintf(&envp[1], "DEVICE=%s", device?device:"");
279 asprintf(&envp[2], "INTERFACE=%s", interface?interface:"");
280 asprintf(&envp[3], "NODE=%s", n->name);
281 sockaddr2str(&n->address, &address, &port);
282 asprintf(&envp[4], "REMOTEADDRESS=%s", address);
283 asprintf(&envp[5], "REMOTEPORT=%s", port);
286 asprintf(&name, n->status.reachable?"hosts/%s-up":"hosts/%s-down", n->name);
287 execute_script(name, envp);
292 for(i = 0; i < 7; i++)