2 graph.c -- graph algorithms
3 Copyright (C) 2001-2006 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.
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.
51 #include "connection.h"
61 static bool graph_changed = true;
63 /* Implementation of Kruskal's algorithm.
65 Please note that sorting on weight is already done by add_edge().
68 void mst_kruskal(void)
70 avl_node_t *node, *next;
80 /* Clear MST status on connections */
82 for(node = connection_tree->head; node; node = node->next) {
84 c->status.mst = false;
87 /* Do we have something to do at all? */
89 if(!edge_weight_tree->head)
92 ifdebug(SCARY_THINGS) logger(LOG_DEBUG, "Running Kruskal's algorithm:");
94 /* Clear visited status on nodes */
96 for(node = node_tree->head; node; node = node->next) {
98 n->status.visited = false;
104 for(node = edge_weight_tree->head; node; node = node->next) {
106 if(e->from->status.reachable) {
107 e->from->status.visited = true;
114 for(skipped = false, node = edge_weight_tree->head; node; node = next) {
118 if(!e->reverse || e->from->status.visited == e->to->status.visited) {
123 e->from->status.visited = true;
124 e->to->status.visited = true;
127 e->connection->status.mst = true;
129 if(e->reverse->connection)
130 e->reverse->connection->status.mst = true;
134 ifdebug(SCARY_THINGS) logger(LOG_DEBUG, " Adding edge %s - %s weight %d", e->from->name,
135 e->to->name, e->weight);
139 next = edge_weight_tree->head;
144 ifdebug(SCARY_THINGS) logger(LOG_DEBUG, "Done, counted %d nodes and %d safe edges.", nodes,
148 /* Implementation of a simple breadth-first search algorithm.
154 avl_node_t *node, *next, *to;
158 list_node_t *from, *todonext;
161 char *address, *port;
167 todo_list = list_alloc(NULL);
169 /* Clear visited status on nodes */
171 for(node = node_tree->head; node; node = node->next) {
173 n->status.visited = false;
174 n->status.indirect = true;
177 /* Begin with myself */
179 myself->status.visited = true;
180 myself->status.indirect = false;
181 myself->nexthop = myself;
182 myself->via = myself;
183 list_insert_head(todo_list, myself);
185 /* Loop while todo_list is filled */
187 for(from = todo_list->head; from; from = todonext) { /* "from" is the node from which we start */
190 for(to = n->edge_tree->head; to; to = to->next) { /* "to" is the edge connected to "from" */
200 ----->(n)---e-->(e->to)
204 Where e is an edge, (n) and (e->to) are nodes.
205 n->address is set to the e->address of the edge left of n to n.
206 We are currently examining the edge e right of n from n:
208 - If e->reverse->address != n->address, then e->to 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 e->to, update
212 e->to and (re)add it to the todo_list to (re)examine the reachability
216 indirect = n->status.indirect || e->options & OPTION_INDIRECT
217 || ((n != myself) && sockaddrcmp(&n->address, &e->reverse->address));
219 if(e->to->status.visited
220 && (!e->to->status.indirect || indirect))
223 e->to->status.visited = true;
224 e->to->status.indirect = indirect;
225 e->to->nexthop = (n->nexthop == myself) ? e->to : n->nexthop;
226 e->to->via = indirect ? n->via : e->to;
227 e->to->options = e->options;
229 if(sockaddrcmp(&e->to->address, &e->address)) {
230 node = avl_unlink(node_udp_tree, e->to);
231 sockaddrfree(&e->to->address);
232 sockaddrcpy(&e->to->address, &e->address);
235 free(e->to->hostname);
237 e->to->hostname = sockaddr2hostname(&e->to->address);
240 avl_insert_node(node_udp_tree, node);
242 if(e->to->options & OPTION_PMTU_DISCOVERY) {
243 e->to->mtuprobes = 0;
246 if(e->to->status.validkey)
247 send_mtu_probe(e->to);
251 list_insert_tail(todo_list, e->to);
254 todonext = from->next;
255 list_delete_node(todo_list, from);
258 list_free(todo_list);
260 /* Check reachability status. */
262 for(node = node_tree->head; node; node = next) {
266 if(n->status.visited != n->status.reachable) {
267 n->status.reachable = !n->status.reachable;
269 if(n->status.reachable) {
270 ifdebug(TRAFFIC) logger(LOG_DEBUG, _("Node %s (%s) became reachable"),
271 n->name, n->hostname);
272 avl_insert(node_udp_tree, n);
274 ifdebug(TRAFFIC) logger(LOG_DEBUG, _("Node %s (%s) became unreachable"),
275 n->name, n->hostname);
276 avl_delete(node_udp_tree, n);
279 n->status.validkey = false;
280 n->status.waitingforkey = false;
286 asprintf(&envp[0], "NETNAME=%s", netname ? : "");
287 asprintf(&envp[1], "DEVICE=%s", device ? : "");
288 asprintf(&envp[2], "INTERFACE=%s", iface ? : "");
289 asprintf(&envp[3], "NODE=%s", n->name);
290 sockaddr2str(&n->address, &address, &port);
291 asprintf(&envp[4], "REMOTEADDRESS=%s", address);
292 asprintf(&envp[5], "REMOTEPORT=%s", port);
295 execute_script(n->status.reachable ? "host-up" : "host-down", envp);
298 n->status.reachable ? "hosts/%s-up" : "hosts/%s-down",
300 execute_script(name, envp);
306 for(i = 0; i < 6; i++)
309 subnet_update(n, NULL, n->status.reachable);
318 graph_changed = true;
323 /* Dump nodes and edges to a graphviz file.
325 The file can be converted to an image with
326 dot -Tpng graph_filename -o image_filename.png -Gconcentrate=true
329 void dump_graph(void)
334 char *filename = NULL, *tmpname = NULL;
337 if(!graph_changed || !get_config_string(lookup_config(config_tree, "GraphDumpFile"), &filename))
340 graph_changed = false;
342 ifdebug(PROTOCOL) logger(LOG_NOTICE, "Dumping graph");
344 if(filename[0] == '|') {
345 file = popen(filename + 1, "w");
347 asprintf(&tmpname, "%s.new", filename);
348 file = fopen(tmpname, "w");
352 logger(LOG_ERR, "Unable to open graph dump file %s: %s", filename, strerror(errno));
357 fprintf(file, "digraph {\n");
359 /* dump all nodes first */
360 for(node = node_tree->head; node; node = node->next) {
362 fprintf(file, " %s [label = \"%s\"];\n", n->name, n->name);
365 /* now dump all edges */
366 for(node = edge_weight_tree->head; node; node = node->next) {
368 fprintf(file, " %s -> %s;\n", e->from->name, e->to->name);
371 fprintf(file, "}\n");
373 if(filename[0] == '|') {
380 rename(tmpname, filename);