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 /* Implementation of Kruskal's algorithm.
63 Please note that sorting on weight is already done by add_edge().
66 void mst_kruskal(void)
68 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.
152 avl_node_t *node, *next, *to;
156 list_node_t *from, *todonext;
159 char *address, *port;
165 todo_list = list_alloc(NULL);
167 /* Clear visited status on nodes */
169 for(node = node_tree->head; node; node = node->next) {
171 n->status.visited = false;
172 n->status.indirect = true;
175 /* Begin with myself */
177 myself->status.visited = true;
178 myself->status.indirect = false;
179 myself->nexthop = myself;
180 myself->via = myself;
181 list_insert_head(todo_list, myself);
183 /* Loop while todo_list is filled */
185 for(from = todo_list->head; from; from = todonext) { /* "from" is the node from which we start */
188 for(to = n->edge_tree->head; to; to = to->next) { /* "to" is the edge connected to "from" */
198 ----->(n)---e-->(e->to)
202 Where e is an edge, (n) and (e->to) are nodes.
203 n->address is set to the e->address of the edge left of n to n.
204 We are currently examining the edge e right of n from n:
206 - If e->reverse->address != n->address, then e->to is probably
207 not reachable for the nodes left of n. We do as if the indirectdata
208 flag is set on edge e.
209 - If edge e provides for better reachability of e->to, update
210 e->to and (re)add it to the todo_list to (re)examine the reachability
214 indirect = n->status.indirect || e->options & OPTION_INDIRECT
215 || ((n != myself) && sockaddrcmp(&n->address, &e->reverse->address));
217 if(e->to->status.visited
218 && (!e->to->status.indirect || indirect))
221 e->to->status.visited = true;
222 e->to->status.indirect = indirect;
223 e->to->nexthop = (n->nexthop == myself) ? e->to : n->nexthop;
224 e->to->via = indirect ? n->via : e->to;
225 e->to->options = e->options;
227 if(sockaddrcmp(&e->to->address, &e->address)) {
228 node = avl_unlink(node_udp_tree, e->to);
229 sockaddrfree(&e->to->address);
230 sockaddrcpy(&e->to->address, &e->address);
233 free(e->to->hostname);
235 e->to->hostname = sockaddr2hostname(&e->to->address);
238 avl_insert_node(node_udp_tree, node);
240 if(e->to->options & OPTION_PMTU_DISCOVERY) {
241 e->to->mtuprobes = 0;
244 if(e->to->status.validkey)
245 send_mtu_probe(e->to);
249 list_insert_tail(todo_list, e->to);
252 todonext = from->next;
253 list_delete_node(todo_list, from);
256 list_free(todo_list);
258 /* Check reachability status. */
260 for(node = node_tree->head; node; node = next) {
264 if(n->status.visited != n->status.reachable) {
265 n->status.reachable = !n->status.reachable;
267 if(n->status.reachable) {
268 ifdebug(TRAFFIC) logger(LOG_DEBUG, _("Node %s (%s) became reachable"),
269 n->name, n->hostname);
270 avl_insert(node_udp_tree, n);
272 ifdebug(TRAFFIC) logger(LOG_DEBUG, _("Node %s (%s) became unreachable"),
273 n->name, n->hostname);
274 avl_delete(node_udp_tree, n);
277 n->status.validkey = false;
278 n->status.waitingforkey = false;
284 asprintf(&envp[0], "NETNAME=%s", netname ? : "");
285 asprintf(&envp[1], "DEVICE=%s", device ? : "");
286 asprintf(&envp[2], "INTERFACE=%s", iface ? : "");
287 asprintf(&envp[3], "NODE=%s", n->name);
288 sockaddr2str(&n->address, &address, &port);
289 asprintf(&envp[4], "REMOTEADDRESS=%s", address);
290 asprintf(&envp[5], "REMOTEPORT=%s", port);
293 execute_script(n->status.reachable ? "host-up" : "host-down", envp);
296 n->status.reachable ? "hosts/%s-up" : "hosts/%s-down",
298 execute_script(name, envp);
304 for(i = 0; i < 6; i++)
307 subnet_update(n, NULL, n->status.reachable);
312 /* Dump nodes and edges to a graphviz file.
314 The file can be converted to an image with
315 dot -Tpng graph_filename -o image_filename.png -Gconcentrate=true
318 static void dump_graph(int fd, short events, void *data)
323 char *filename = NULL, *tmpname = NULL;
326 if(!get_config_string(lookup_config(config_tree, "GraphDumpFile"), &filename))
329 ifdebug(PROTOCOL) logger(LOG_NOTICE, "Dumping graph");
331 if(filename[0] == '|') {
332 file = popen(filename + 1, "w");
334 asprintf(&tmpname, "%s.new", filename);
335 file = fopen(tmpname, "w");
339 logger(LOG_ERR, "Unable to open graph dump file %s: %s", filename, strerror(errno));
344 fprintf(file, "digraph {\n");
346 /* dump all nodes first */
347 for(node = node_tree->head; node; node = node->next) {
349 fprintf(file, " %s [label = \"%s\"];\n", n->name, n->name);
352 /* now dump all edges */
353 for(node = edge_weight_tree->head; node; node = node->next) {
355 fprintf(file, " %s -> %s;\n", e->from->name, e->to->name);
358 fprintf(file, "}\n");
360 if(filename[0] == '|') {
367 rename(tmpname, filename);
374 static struct event ev;
379 if(!timeout_initialized(&ev))
380 timeout_set(&ev, dump_graph, NULL);
381 event_add(&ev, &(struct timeval){5, 0});