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 ((edge_t *) edge_weight_tree->head->data)->from->status.visited = true;
108 for(skipped = false, node = edge_weight_tree->head; node; node = next) {
112 if(!e->reverse || e->from->status.visited == e->to->status.visited) {
117 e->from->status.visited = true;
118 e->to->status.visited = true;
121 e->connection->status.mst = true;
123 if(e->reverse->connection)
124 e->reverse->connection->status.mst = true;
128 ifdebug(SCARY_THINGS) logger(LOG_DEBUG, " Adding edge %s - %s weight %d", e->from->name,
129 e->to->name, e->weight);
133 next = edge_weight_tree->head;
138 ifdebug(SCARY_THINGS) logger(LOG_DEBUG, "Done, counted %d nodes and %d safe edges.", nodes,
142 /* Implementation of a simple breadth-first search algorithm.
148 avl_node_t *node, *next, *to;
152 list_node_t *from, *todonext;
155 char *address, *port;
161 todo_list = list_alloc(NULL);
163 /* Clear visited status on nodes */
165 for(node = node_tree->head; node; node = node->next) {
167 n->status.visited = false;
168 n->status.indirect = true;
171 /* Begin with myself */
173 myself->status.visited = true;
174 myself->status.indirect = false;
175 myself->nexthop = myself;
176 myself->via = myself;
177 list_insert_head(todo_list, myself);
179 /* Loop while todo_list is filled */
181 for(from = todo_list->head; from; from = todonext) { /* "from" is the node from which we start */
184 for(to = n->edge_tree->head; to; to = to->next) { /* "to" is the edge connected to "from" */
194 ----->(n)---e-->(e->to)
198 Where e is an edge, (n) and (e->to) are nodes.
199 n->address is set to the e->address of the edge left of n to n.
200 We are currently examining the edge e right of n from n:
202 - If e->reverse->address != n->address, then e->to is probably
203 not reachable for the nodes left of n. We do as if the indirectdata
204 flag is set on edge e.
205 - If edge e provides for better reachability of e->to, update
206 e->to and (re)add it to the todo_list to (re)examine the reachability
210 indirect = n->status.indirect || e->options & OPTION_INDIRECT
211 || ((n != myself) && sockaddrcmp(&n->address, &e->reverse->address));
213 if(e->to->status.visited
214 && (!e->to->status.indirect || indirect))
217 e->to->status.visited = true;
218 e->to->status.indirect = indirect;
219 e->to->nexthop = (n->nexthop == myself) ? e->to : n->nexthop;
220 e->to->via = indirect ? n->via : e->to;
221 e->to->options = e->options;
223 if(sockaddrcmp(&e->to->address, &e->address)) {
224 node = avl_unlink(node_udp_tree, e->to);
225 sockaddrfree(&e->to->address);
226 sockaddrcpy(&e->to->address, &e->address);
229 free(e->to->hostname);
231 e->to->hostname = sockaddr2hostname(&e->to->address);
234 avl_insert_node(node_udp_tree, node);
236 if(e->to->options & OPTION_PMTU_DISCOVERY) {
237 e->to->mtuprobes = 0;
240 if(e->to->status.validkey)
241 send_mtu_probe(e->to);
245 list_insert_tail(todo_list, e->to);
248 todonext = from->next;
249 list_delete_node(todo_list, from);
252 list_free(todo_list);
254 /* Check reachability status. */
256 for(node = node_tree->head; node; node = next) {
260 if(n->status.visited != n->status.reachable) {
261 n->status.reachable = !n->status.reachable;
263 if(n->status.reachable) {
264 ifdebug(TRAFFIC) logger(LOG_DEBUG, _("Node %s (%s) became reachable"),
265 n->name, n->hostname);
266 avl_insert(node_udp_tree, n);
268 ifdebug(TRAFFIC) logger(LOG_DEBUG, _("Node %s (%s) became unreachable"),
269 n->name, n->hostname);
270 avl_delete(node_udp_tree, n);
273 n->status.validkey = false;
274 n->status.waitingforkey = false;
280 asprintf(&envp[0], "NETNAME=%s", netname ? : "");
281 asprintf(&envp[1], "DEVICE=%s", device ? : "");
282 asprintf(&envp[2], "INTERFACE=%s", iface ? : "");
283 asprintf(&envp[3], "NODE=%s", n->name);
284 sockaddr2str(&n->address, &address, &port);
285 asprintf(&envp[4], "REMOTEADDRESS=%s", address);
286 asprintf(&envp[5], "REMOTEPORT=%s", port);
289 execute_script(n->status.reachable ? "host-up" : "host-down", envp);
292 n->status.reachable ? "hosts/%s-up" : "hosts/%s-down",
294 execute_script(name, envp);
300 for(i = 0; i < 6; i++)
303 subnet_update(n, NULL, n->status.reachable);
312 graph_changed = true;
317 /* Dump nodes and edges to a graphviz file.
319 The file can be converted to an image with
320 dot -Tpng graph_filename -o image_filename.png -Gconcentrate=true
323 void dump_graph(void)
328 char *filename = NULL, *tmpname = NULL;
331 if(!graph_changed || !get_config_string(lookup_config(config_tree, "GraphDumpFile"), &filename))
334 graph_changed = false;
336 ifdebug(PROTOCOL) logger(LOG_NOTICE, "Dumping graph");
338 if(filename[0] == '|') {
339 file = popen(filename + 1, "w");
341 asprintf(&tmpname, "%s.new", filename);
342 file = fopen(tmpname, "w");
346 logger(LOG_ERR, "Unable to open graph dump file %s: %s", filename, strerror(errno));
351 fprintf(file, "digraph {\n");
353 /* dump all nodes first */
354 for(node = node_tree->head; node; node = node->next) {
356 fprintf(file, " %s [label = \"%s\"];\n", n->name, n->name);
359 /* now dump all edges */
360 for(node = edge_weight_tree->head; node; node = node->next) {
362 fprintf(file, " %s -> %s;\n", e->from->name, e->to->name);
365 fprintf(file, "}\n");
369 if(filename[0] != '|') {
370 rename(tmpname, filename);