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 2002/05/02 11:50:07 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.
52 #if defined(HAVE_FREEBSD) || defined(HAVE_OPENBSD)
53 #include <sys/param.h>
55 #include <netinet/in.h>
64 #include "connection.h"
69 /* Implementation of Kruskal's algorithm.
71 Please note that sorting on weight is already done by add_edge().
74 void mst_kruskal(void)
76 avl_node_t *node, *next;
84 /* Clear MST status on connections */
86 for(node = connection_tree->head; node; node = node->next)
88 c = (connection_t *)node->data;
92 /* Do we have something to do at all? */
94 if(!edge_weight_tree->head)
97 if(debug_lvl >= DEBUG_SCARY_THINGS)
98 syslog(LOG_DEBUG, "Running Kruskal's algorithm:");
100 /* Clear visited status on nodes */
102 for(node = node_tree->head; node; node = node->next)
104 n = (node_t *)node->data;
105 n->status.visited = 0;
111 ((edge_t *)edge_weight_tree->head->data)->from.node->status.visited = 1;
115 for(skipped = 0, node = edge_weight_tree->head; node; node = next)
118 e = (edge_t *)node->data;
120 if(e->from.node->status.visited == e->to.node->status.visited)
126 e->from.node->status.visited = 1;
127 e->to.node->status.visited = 1;
129 e->connection->status.mst = 1;
133 if(debug_lvl >= DEBUG_SCARY_THINGS)
134 syslog(LOG_DEBUG, " Adding edge %s - %s weight %d", e->from.node->name, e->to.node->name, e->weight);
138 next = edge_weight_tree->head;
143 if(debug_lvl >= DEBUG_SCARY_THINGS)
144 syslog(LOG_DEBUG, "Done, counted %d nodes and %d safe edges.", nodes, safe_edges);
147 /* Implementation of a simple breadth-first search algorithm.
153 avl_node_t *node, *from, *next, *to;
156 halfconnection_t to_hc, from_hc;
157 avl_tree_t *todo_tree;
160 todo_tree = avl_alloc_tree(NULL, NULL);
162 /* Clear visited status on nodes */
164 for(node = node_tree->head; node; node = node->next)
166 n = (node_t *)node->data;
167 n->status.visited = 0;
168 n->status.indirect = 1;
171 /* Begin with myself */
173 myself->status.visited = 1;
174 myself->status.indirect = 0;
175 myself->nexthop = myself;
176 myself->via = myself;
177 node = avl_alloc_node();
179 avl_insert_top(todo_tree, node);
181 /* Loop while todo_tree is filled */
183 while(todo_tree->head)
185 for(from = todo_tree->head; from; from = next) /* "from" is the node from which we start */
188 n = (node_t *)from->data;
190 for(to = n->edge_tree->head; to; to = to->next) /* "to" is the edge connected to "from" */
192 e = (edge_t *)to->data;
194 if(e->from.node == n) /* "from_hc" is the halfconnection with .node == from */
195 to_hc = e->to, from_hc = e->from;
197 to_hc = e->from, from_hc = e->to;
203 ------(n)from_hc-----to_hc
207 n->address is set to the to_hc.udpaddress of the edge left of n.
208 We are currently examining the edge right of n:
210 - If from_hc.udpaddress != n->address, then to_hc.node is probably
211 not reachable for the nodes left of n. We do as if the indirectdata
212 flag is set on edge e.
213 - If edge e provides for better reachability of to_hc.node, update
214 to_hc.node and (re)add it to the todo_tree to (re)examine the reachability
218 indirect = n->status.indirect || e->options & OPTION_INDIRECT || ((n != myself) && sockaddrcmp(&n->address, &from_hc.udpaddress));
220 if(to_hc.node->status.visited && (!to_hc.node->status.indirect || indirect))
223 to_hc.node->status.visited = 1;
224 to_hc.node->status.indirect = indirect;
225 to_hc.node->nexthop = (n->nexthop == myself) ? to_hc.node : n->nexthop;
226 to_hc.node->via = indirect ? n->via : to_hc.node;
227 to_hc.node->options = e->options;
228 if(sockaddrcmp(&to_hc.node->address, &to_hc.udpaddress))
230 node = avl_unlink(node_udp_tree, to_hc.node);
231 to_hc.node->address = to_hc.udpaddress;
232 if(to_hc.node->hostname)
233 free(to_hc.node->hostname);
234 to_hc.node->hostname = sockaddr2hostname(&to_hc.udpaddress);
235 avl_insert_node(node_udp_tree, node);
237 node = avl_alloc_node();
238 node->data = to_hc.node;
239 avl_insert_before(todo_tree, from, node);
242 avl_delete_node(todo_tree, from);
246 avl_free_tree(todo_tree);
248 /* Check reachability status. */
250 for(node = node_tree->head; node; node = next)
253 n = (node_t *)node->data;
255 if(n->status.visited)
257 if(!n->status.reachable)
259 if(debug_lvl >= DEBUG_TRAFFIC)
260 syslog(LOG_DEBUG, _("Node %s (%s) became reachable"), n->name, n->hostname);
261 n->status.reachable = 1;
262 run_hooks("node-visible", n);
267 if(n->status.reachable)
269 if(debug_lvl >= DEBUG_TRAFFIC)
270 syslog(LOG_DEBUG, _("Node %s (%s) became unreachable"), n->name, n->hostname);
271 n->status.reachable = 0;
272 n->status.validkey = 0;
273 n->status.waitingforkey = 0;
275 run_hooks("node-invisible", n);