2 graph.c -- graph algorithms
3 Copyright (C) 2001-2011 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"
62 static bool graph_changed = true;
64 /* Implementation of Kruskal's algorithm.
66 Please note that sorting on weight is already done by add_edge().
69 static void mst_kruskal(void) {
70 avl_node_t *node, *next;
78 /* Clear MST status on connections */
80 for(node = connection_tree->head; node; node = node->next) {
82 c->status.mst = false;
85 /* Do we have something to do at all? */
87 if(!edge_weight_tree->head)
90 ifdebug(SCARY_THINGS) logger(LOG_DEBUG, "Running Kruskal's algorithm:");
92 /* Clear visited status on nodes */
94 for(node = node_tree->head; node; node = node->next) {
96 n->status.visited = false;
102 for(node = edge_weight_tree->head; node; node = node->next) {
104 if(e->from->status.reachable) {
105 e->from->status.visited = true;
112 for(skipped = false, node = edge_weight_tree->head; node; node = next) {
116 if(!e->reverse || e->from->status.visited == e->to->status.visited) {
121 e->from->status.visited = true;
122 e->to->status.visited = true;
125 e->connection->status.mst = true;
127 if(e->reverse->connection)
128 e->reverse->connection->status.mst = true;
132 ifdebug(SCARY_THINGS) logger(LOG_DEBUG, " Adding edge %s - %s weight %d", e->from->name,
133 e->to->name, e->weight);
137 next = edge_weight_tree->head;
142 ifdebug(SCARY_THINGS) logger(LOG_DEBUG, "Done, counted %d nodes and %d safe edges.", nodes,
146 /* Implementation of a simple breadth-first search algorithm.
150 static void sssp_bfs(void) {
151 avl_node_t *node, *next, *to;
155 list_node_t *from, *todonext;
158 char *address, *port;
162 todo_list = list_alloc(NULL);
164 /* Clear visited status on nodes */
166 for(node = node_tree->head; node; node = node->next) {
168 n->status.visited = false;
169 n->status.indirect = true;
172 /* Begin with myself */
174 myself->status.visited = true;
175 myself->status.indirect = false;
176 myself->nexthop = myself;
177 myself->via = myself;
178 list_insert_head(todo_list, myself);
180 /* Loop while todo_list is filled */
182 for(from = todo_list->head; from; from = todonext) { /* "from" is the node from which we start */
185 for(to = n->edge_tree->head; to; to = to->next) { /* "to" is the edge connected to "from" */
195 ----->(n)---e-->(e->to)
199 Where e is an edge, (n) and (e->to) are nodes.
200 n->address is set to the e->address of the edge left of n to n.
201 We are currently examining the edge e right of n from n:
203 - If edge e provides for better reachability of e->to, update
204 e->to and (re)add it to the todo_list to (re)examine the reachability
208 indirect = n->status.indirect || e->options & OPTION_INDIRECT;
210 if(e->to->status.visited
211 && (!e->to->status.indirect || indirect))
214 e->to->status.visited = true;
215 e->to->status.indirect = indirect;
216 e->to->nexthop = (n->nexthop == myself) ? e->to : n->nexthop;
217 e->to->via = indirect ? n->via : e->to;
218 e->to->options = e->options;
220 if(e->to->address.sa.sa_family == AF_UNSPEC && e->address.sa.sa_family != AF_UNKNOWN)
221 update_node_udp(e->to, &e->address);
223 list_insert_tail(todo_list, e->to);
226 todonext = from->next;
227 list_delete_node(todo_list, from);
230 list_free(todo_list);
232 /* Check reachability status. */
234 for(node = node_tree->head; node; node = next) {
238 if(n->status.visited != n->status.reachable) {
239 n->status.reachable = !n->status.reachable;
241 if(n->status.reachable) {
242 ifdebug(TRAFFIC) logger(LOG_DEBUG, "Node %s (%s) became reachable",
243 n->name, n->hostname);
245 ifdebug(TRAFFIC) logger(LOG_DEBUG, "Node %s (%s) became unreachable",
246 n->name, n->hostname);
249 /* TODO: only clear status.validkey if node is unreachable? */
251 n->status.validkey = false;
259 event_del(n->mtuevent);
263 xasprintf(&envp[0], "NETNAME=%s", netname ? : "");
264 xasprintf(&envp[1], "DEVICE=%s", device ? : "");
265 xasprintf(&envp[2], "INTERFACE=%s", iface ? : "");
266 xasprintf(&envp[3], "NODE=%s", n->name);
267 sockaddr2str(&n->address, &address, &port);
268 xasprintf(&envp[4], "REMOTEADDRESS=%s", address);
269 xasprintf(&envp[5], "REMOTEPORT=%s", port);
272 execute_script(n->status.reachable ? "host-up" : "host-down", envp);
275 n->status.reachable ? "hosts/%s-up" : "hosts/%s-down",
277 execute_script(name, envp);
283 for(i = 0; i < 6; i++)
286 subnet_update(n, NULL, n->status.reachable);
288 if(!n->status.reachable)
289 update_node_udp(n, NULL);
290 else if(n->connection)
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);