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 along
17 with this program; if not, write to the Free Software Foundation, Inc.,
18 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 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) {
68 avl_node_t *node, *next;
76 /* Clear MST status on connections */
78 for(node = connection_tree->head; node; node = node->next) {
80 c->status.mst = false;
83 /* Do we have something to do at all? */
85 if(!edge_weight_tree->head)
88 ifdebug(SCARY_THINGS) logger(LOG_DEBUG, "Running Kruskal's algorithm:");
90 /* Clear visited status on nodes */
92 for(node = node_tree->head; node; node = node->next) {
94 n->status.visited = false;
100 for(node = edge_weight_tree->head; node; node = node->next) {
102 if(e->from->status.reachable) {
103 e->from->status.visited = true;
110 for(skipped = false, node = edge_weight_tree->head; node; node = next) {
114 if(!e->reverse || e->from->status.visited == e->to->status.visited) {
119 e->from->status.visited = true;
120 e->to->status.visited = true;
123 e->connection->status.mst = true;
125 if(e->reverse->connection)
126 e->reverse->connection->status.mst = true;
130 ifdebug(SCARY_THINGS) logger(LOG_DEBUG, " Adding edge %s - %s weight %d", e->from->name,
131 e->to->name, e->weight);
135 next = edge_weight_tree->head;
140 ifdebug(SCARY_THINGS) logger(LOG_DEBUG, "Done, counted %d nodes and %d safe edges.", nodes,
144 /* Implementation of a simple breadth-first search algorithm.
148 void sssp_bfs(void) {
149 avl_node_t *node, *next, *to;
153 list_node_t *from, *todonext;
156 char *address, *port;
160 todo_list = list_alloc(NULL);
162 /* Clear visited status on nodes */
164 for(node = node_tree->head; node; node = node->next) {
166 n->status.visited = false;
167 n->status.indirect = true;
170 /* Begin with myself */
172 myself->status.visited = true;
173 myself->status.indirect = false;
174 myself->nexthop = myself;
175 myself->via = myself;
176 list_insert_head(todo_list, myself);
178 /* Loop while todo_list is filled */
180 for(from = todo_list->head; from; from = todonext) { /* "from" is the node from which we start */
183 for(to = n->edge_tree->head; to; to = to->next) { /* "to" is the edge connected to "from" */
193 ----->(n)---e-->(e->to)
197 Where e is an edge, (n) and (e->to) are nodes.
198 n->address is set to the e->address of the edge left of n to n.
199 We are currently examining the edge e right of n from n:
201 - If e->reverse->address != n->address, then e->to is probably
202 not reachable for the nodes left of n. We do as if the indirectdata
203 flag is set on edge e.
204 - If edge e provides for better reachability of e->to, update
205 e->to and (re)add it to the todo_list to (re)examine the reachability
209 indirect = n->status.indirect || e->options & OPTION_INDIRECT
210 || ((n != myself) && sockaddrcmp(&n->address, &e->reverse->address));
212 if(e->to->status.visited
213 && (!e->to->status.indirect || indirect))
216 e->to->status.visited = true;
217 e->to->status.indirect = indirect;
218 e->to->nexthop = (n->nexthop == myself) ? e->to : n->nexthop;
219 e->to->via = indirect ? n->via : e->to;
220 e->to->options = e->options;
222 if(e->to->address.sa.sa_family == AF_UNSPEC && e->address.sa.sa_family != AF_UNKNOWN)
223 update_node_udp(e->to, &e->address);
225 list_insert_tail(todo_list, e->to);
228 todonext = from->next;
229 list_delete_node(todo_list, from);
232 list_free(todo_list);
234 /* Check reachability status. */
236 for(node = node_tree->head; node; node = next) {
240 if(n->status.visited != n->status.reachable) {
241 n->status.reachable = !n->status.reachable;
243 if(n->status.reachable) {
244 ifdebug(TRAFFIC) logger(LOG_DEBUG, "Node %s (%s) became reachable",
245 n->name, n->hostname);
247 ifdebug(TRAFFIC) logger(LOG_DEBUG, "Node %s (%s) became unreachable",
248 n->name, n->hostname);
251 /* TODO: only clear status.validkey if node is unreachable? */
253 n->status.validkey = false;
261 event_del(n->mtuevent);
265 xasprintf(&envp[0], "NETNAME=%s", netname ? : "");
266 xasprintf(&envp[1], "DEVICE=%s", device ? : "");
267 xasprintf(&envp[2], "INTERFACE=%s", iface ? : "");
268 xasprintf(&envp[3], "NODE=%s", n->name);
269 sockaddr2str(&n->address, &address, &port);
270 xasprintf(&envp[4], "REMOTEADDRESS=%s", address);
271 xasprintf(&envp[5], "REMOTEPORT=%s", port);
274 execute_script(n->status.reachable ? "host-up" : "host-down", envp);
277 n->status.reachable ? "hosts/%s-up" : "hosts/%s-down",
279 execute_script(name, envp);
285 for(i = 0; i < 6; i++)
288 subnet_update(n, NULL, n->status.reachable);
290 if(!n->status.reachable)
291 update_node_udp(n, NULL);
297 subnet_cache_flush();
300 graph_changed = true;
305 /* Dump nodes and edges to a graphviz file.
307 The file can be converted to an image with
308 dot -Tpng graph_filename -o image_filename.png -Gconcentrate=true
311 void dump_graph(void) {
315 char *filename = NULL, *tmpname = NULL;
318 if(!graph_changed || !get_config_string(lookup_config(config_tree, "GraphDumpFile"), &filename))
321 graph_changed = false;
323 ifdebug(PROTOCOL) logger(LOG_NOTICE, "Dumping graph");
325 if(filename[0] == '|') {
326 file = popen(filename + 1, "w");
328 xasprintf(&tmpname, "%s.new", filename);
329 file = fopen(tmpname, "w");
333 logger(LOG_ERR, "Unable to open graph dump file %s: %s", filename, strerror(errno));
338 fprintf(file, "digraph {\n");
340 /* dump all nodes first */
341 for(node = node_tree->head; node; node = node->next) {
343 fprintf(file, " %s [label = \"%s\"];\n", n->name, n->name);
346 /* now dump all edges */
347 for(node = edge_weight_tree->head; node; node = node->next) {
349 fprintf(file, " %s -> %s;\n", e->from->name, e->to->name);
352 fprintf(file, "}\n");
354 if(filename[0] == '|') {
361 rename(tmpname, filename);