2 graph.c -- graph algorithms
3 Copyright (C) 2001-2009 Guus Sliepen <guus@tinc-vpn.org>,
4 2001-2005 Ivo Timmermans
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.
21 /* We need to generate two trees from the graph:
23 1. A minimum spanning tree for broadcasts,
24 2. A single-source shortest path tree for unicasts.
26 Actually, the first one alone would suffice but would make unicast packets
27 take longer routes than necessary.
29 For the MST algorithm we can choose from Prim's or Kruskal's. I personally
30 favour Kruskal's, because we make an extra AVL tree of edges sorted on
31 weights (metric). That tree only has to be updated when an edge is added or
32 removed, and during the MST algorithm we just have go linearly through that
33 tree, adding safe edges until #edges = #nodes - 1. The implementation here
34 however is not so fast, because I tried to avoid having to make a forest and
37 For the SSSP algorithm Dijkstra's seems to be a nice choice. Currently a
38 simple breadth-first search is presented here.
40 The SSSP algorithm will also be used to determine whether nodes are directly,
41 indirectly or not reachable from the source. It will also set the correct
42 destination address and port of a node if possible.
49 #include "connection.h"
60 static bool graph_changed = true;
62 /* Implementation of Kruskal's algorithm.
64 Please note that sorting on weight is already done by add_edge().
67 void mst_kruskal(void)
69 avl_node_t *node, *next;
79 /* Clear MST status on connections */
81 for(node = connection_tree->head; node; node = node->next) {
83 c->status.mst = false;
86 /* Do we have something to do at all? */
88 if(!edge_weight_tree->head)
91 ifdebug(SCARY_THINGS) logger(LOG_DEBUG, "Running Kruskal's algorithm:");
93 /* Clear visited status on nodes */
95 for(node = node_tree->head; node; node = node->next) {
97 n->status.visited = false;
103 for(node = edge_weight_tree->head; node; node = node->next) {
105 if(e->from->status.reachable) {
106 e->from->status.visited = true;
113 for(skipped = false, node = edge_weight_tree->head; node; node = next) {
117 if(!e->reverse || e->from->status.visited == e->to->status.visited) {
122 e->from->status.visited = true;
123 e->to->status.visited = true;
126 e->connection->status.mst = true;
128 if(e->reverse->connection)
129 e->reverse->connection->status.mst = true;
133 ifdebug(SCARY_THINGS) logger(LOG_DEBUG, " Adding edge %s - %s weight %d", e->from->name,
134 e->to->name, e->weight);
138 next = edge_weight_tree->head;
143 ifdebug(SCARY_THINGS) logger(LOG_DEBUG, "Done, counted %d nodes and %d safe edges.", nodes,
147 /* Implementation of a simple breadth-first search algorithm.
153 avl_node_t *node, *next, *to;
157 list_node_t *from, *todonext;
160 char *address, *port;
166 todo_list = list_alloc(NULL);
168 /* Clear visited status on nodes */
170 for(node = node_tree->head; node; node = node->next) {
172 n->status.visited = false;
173 n->status.indirect = true;
176 /* Begin with myself */
178 myself->status.visited = true;
179 myself->status.indirect = false;
180 myself->nexthop = myself;
181 myself->via = myself;
182 list_insert_head(todo_list, myself);
184 /* Loop while todo_list is filled */
186 for(from = todo_list->head; from; from = todonext) { /* "from" is the node from which we start */
189 for(to = n->edge_tree->head; to; to = to->next) { /* "to" is the edge connected to "from" */
199 ----->(n)---e-->(e->to)
203 Where e is an edge, (n) and (e->to) are nodes.
204 n->address is set to the e->address of the edge left of n to n.
205 We are currently examining the edge e right of n from n:
207 - If e->reverse->address != n->address, then e->to is probably
208 not reachable for the nodes left of n. We do as if the indirectdata
209 flag is set on edge e.
210 - If edge e provides for better reachability of e->to, update
211 e->to and (re)add it to the todo_list to (re)examine the reachability
215 indirect = n->status.indirect || e->options & OPTION_INDIRECT
216 || ((n != myself) && sockaddrcmp(&n->address, &e->reverse->address));
218 if(e->to->status.visited
219 && (!e->to->status.indirect || indirect))
222 e->to->status.visited = true;
223 e->to->status.indirect = indirect;
224 e->to->nexthop = (n->nexthop == myself) ? e->to : n->nexthop;
225 e->to->via = indirect ? n->via : e->to;
226 e->to->options = e->options;
228 if(e->to->address.sa.sa_family == AF_UNSPEC && e->address.sa.sa_family != AF_UNKNOWN)
229 update_node_udp(e->to, &e->address);
231 list_insert_tail(todo_list, e->to);
234 todonext = from->next;
235 list_delete_node(todo_list, from);
238 list_free(todo_list);
240 /* Check reachability status. */
242 for(node = node_tree->head; node; node = next) {
246 if(n->status.visited != n->status.reachable) {
247 n->status.reachable = !n->status.reachable;
249 if(n->status.reachable) {
250 ifdebug(TRAFFIC) logger(LOG_DEBUG, _("Node %s (%s) became reachable"),
251 n->name, n->hostname);
253 ifdebug(TRAFFIC) logger(LOG_DEBUG, _("Node %s (%s) became unreachable"),
254 n->name, n->hostname);
257 /* TODO: only clear status.validkey if node is unreachable? */
259 n->status.validkey = false;
260 n->status.waitingforkey = false;
267 event_del(n->mtuevent);
271 xasprintf(&envp[0], "NETNAME=%s", netname ? : "");
272 xasprintf(&envp[1], "DEVICE=%s", device ? : "");
273 xasprintf(&envp[2], "INTERFACE=%s", iface ? : "");
274 xasprintf(&envp[3], "NODE=%s", n->name);
275 sockaddr2str(&n->address, &address, &port);
276 xasprintf(&envp[4], "REMOTEADDRESS=%s", address);
277 xasprintf(&envp[5], "REMOTEPORT=%s", port);
280 execute_script(n->status.reachable ? "host-up" : "host-down", envp);
283 n->status.reachable ? "hosts/%s-up" : "hosts/%s-down",
285 execute_script(name, envp);
291 for(i = 0; i < 6; i++)
294 subnet_update(n, NULL, n->status.reachable);
301 subnet_cache_flush();
304 graph_changed = true;
309 /* Dump nodes and edges to a graphviz file.
311 The file can be converted to an image with
312 dot -Tpng graph_filename -o image_filename.png -Gconcentrate=true
315 void dump_graph(void)
320 char *filename = NULL, *tmpname = NULL;
323 if(!graph_changed || !get_config_string(lookup_config(config_tree, "GraphDumpFile"), &filename))
326 graph_changed = false;
328 ifdebug(PROTOCOL) logger(LOG_NOTICE, "Dumping graph");
330 if(filename[0] == '|') {
331 file = popen(filename + 1, "w");
333 xasprintf(&tmpname, "%s.new", filename);
334 file = fopen(tmpname, "w");
338 logger(LOG_ERR, "Unable to open graph dump file %s: %s", filename, strerror(errno));
343 fprintf(file, "digraph {\n");
345 /* dump all nodes first */
346 for(node = node_tree->head; node; node = node->next) {
348 fprintf(file, " %s [label = \"%s\"];\n", n->name, n->name);
351 /* now dump all edges */
352 for(node = edge_weight_tree->head; node; node = node->next) {
354 fprintf(file, " %s -> %s;\n", e->from->name, e->to->name);
357 fprintf(file, "}\n");
359 if(filename[0] == '|') {
366 rename(tmpname, filename);