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
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.
49 #include "splay_tree.h"
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) {
67 splay_node_t *node, *next;
74 /* Clear MST status on connections */
76 for(node = connection_tree->head; node; node = node->next) {
78 c->status.mst = false;
81 ifdebug(SCARY_THINGS) logger(LOG_DEBUG, "Running Kruskal's algorithm:");
83 /* Clear visited status on nodes */
85 for(node = node_tree->head; node; node = node->next) {
87 n->status.visited = false;
92 for(node = edge_weight_tree->head; node; node = next) {
96 if(!e->reverse || (e->from->status.visited && e->to->status.visited))
99 e->from->status.visited = true;
100 e->to->status.visited = true;
103 e->connection->status.mst = true;
105 if(e->reverse->connection)
106 e->reverse->connection->status.mst = true;
108 ifdebug(SCARY_THINGS) logger(LOG_DEBUG, " Adding edge %s - %s weight %d", e->from->name,
109 e->to->name, e->weight);
113 /* Implementation of Dijkstra's algorithm.
117 void sssp_dijkstra(void) {
118 splay_node_t *node, *to;
122 list_node_t *lnode, *nnode;
127 todo_list = list_alloc(NULL);
129 ifdebug(SCARY_THINGS) logger(LOG_DEBUG, "Running Dijkstra's algorithm:");
131 /* Clear visited status on nodes */
133 for(node = node_tree->head; node; node = node->next) {
135 n->status.visited = false;
136 n->status.indirect = true;
140 /* Begin with myself */
142 myself->status.indirect = false;
143 myself->nexthop = myself;
144 myself->via = myself;
145 myself->distance = 0;
146 list_insert_head(todo_list, myself);
148 /* Loop while todo_list is filled */
150 while(todo_list->head) {
154 /* Select node from todo_list with smallest distance */
156 for(lnode = todo_list->head; lnode; lnode = lnode->next) {
158 if(!n || m->status.indirect < n->status.indirect || m->distance < n->distance) {
164 /* Mark this node as visited and remove it from the todo_list */
166 n->status.visited = true;
167 list_unlink_node(todo_list, nnode);
169 /* Update distance of neighbours and add them to the todo_list */
171 for(to = n->edge_tree->head; to; to = to->next) { /* "to" is the edge connected to "from" */
174 if(e->to->status.visited || !e->reverse)
181 ----->(n)---e-->(e->to)
185 Where e is an edge, (n) and (e->to) are nodes.
186 n->address is set to the e->address of the edge left of n to n.
187 We are currently examining the edge e right of n from n:
189 - If e->reverse->address != n->address, then e->to is probably
190 not reachable for the nodes left of n. We do as if the indirectdata
191 flag is set on edge e.
192 - If edge e provides for better reachability of e->to, update e->to.
195 if(e->to->distance < 0)
196 list_insert_tail(todo_list, e->to);
198 indirect = n->status.indirect || e->options & OPTION_INDIRECT || ((n != myself) && sockaddrcmp(&n->address, &e->reverse->address));
200 if(e->to->distance >= 0 && (!e->to->status.indirect || indirect) && e->to->distance <= n->distance + e->weight)
203 e->to->distance = n->distance + e->weight;
204 e->to->status.indirect = indirect;
205 e->to->nexthop = (n->nexthop == myself) ? e->to : n->nexthop;
206 e->to->via = indirect ? n->via : e->to;
207 e->to->options = e->options;
209 if(sockaddrcmp(&e->to->address, &e->address)) {
210 node = splay_unlink(node_udp_tree, e->to);
211 sockaddrfree(&e->to->address);
212 sockaddrcpy(&e->to->address, &e->address);
215 free(e->to->hostname);
217 e->to->hostname = sockaddr2hostname(&e->to->address);
220 splay_insert_node(node_udp_tree, node);
222 if(e->to->options & OPTION_PMTU_DISCOVERY) {
223 e->to->mtuprobes = 0;
226 if(e->to->status.validkey)
227 send_mtu_probe(e->to);
231 ifdebug(SCARY_THINGS) logger(LOG_DEBUG, " Updating edge %s - %s weight %d distance %d", e->from->name,
232 e->to->name, e->weight, e->to->distance);
236 list_free(todo_list);
239 /* Implementation of a simple breadth-first search algorithm.
243 void sssp_bfs(void) {
244 splay_node_t *node, *to;
248 list_node_t *from, *todonext;
253 todo_list = list_alloc(NULL);
255 /* Clear visited status on nodes */
257 for(node = node_tree->head; node; node = node->next) {
259 n->status.visited = false;
260 n->status.indirect = true;
263 /* Begin with myself */
265 myself->status.visited = true;
266 myself->status.indirect = false;
267 myself->nexthop = myself;
268 myself->via = myself;
269 list_insert_head(todo_list, myself);
271 /* Loop while todo_list is filled */
273 for(from = todo_list->head; from; from = todonext) { /* "from" is the node from which we start */
276 for(to = n->edge_tree->head; to; to = to->next) { /* "to" is the edge connected to "from" */
286 ----->(n)---e-->(e->to)
290 Where e is an edge, (n) and (e->to) are nodes.
291 n->address is set to the e->address of the edge left of n to n.
292 We are currently examining the edge e right of n from n:
294 - If e->reverse->address != n->address, then e->to is probably
295 not reachable for the nodes left of n. We do as if the indirectdata
296 flag is set on edge e.
297 - If edge e provides for better reachability of e->to, update
298 e->to and (re)add it to the todo_list to (re)examine the reachability
302 indirect = n->status.indirect || e->options & OPTION_INDIRECT
303 || ((n != myself) && sockaddrcmp(&n->address, &e->reverse->address));
305 if(e->to->status.visited
306 && (!e->to->status.indirect || indirect))
309 e->to->status.visited = true;
310 e->to->status.indirect = indirect;
311 e->to->nexthop = (n->nexthop == myself) ? e->to : n->nexthop;
312 e->to->via = indirect ? n->via : e->to;
313 e->to->options = e->options;
315 if(e->to->address.sa.sa_family == AF_UNSPEC && e->address.sa.sa_family != AF_UNKNOWN)
316 update_node_udp(e->to, &e->address);
318 list_insert_tail(todo_list, e->to);
321 todonext = from->next;
322 list_delete_node(todo_list, from);
325 list_free(todo_list);
328 void check_reachability() {
329 splay_node_t *node, *next;
332 char *address, *port;
336 /* Check reachability status. */
338 for(node = node_tree->head; node; node = next) {
342 if(n->status.visited != n->status.reachable) {
343 n->status.reachable = !n->status.reachable;
345 if(n->status.reachable) {
346 ifdebug(TRAFFIC) logger(LOG_DEBUG, _("Node %s (%s) became reachable"),
347 n->name, n->hostname);
349 ifdebug(TRAFFIC) logger(LOG_DEBUG, _("Node %s (%s) became unreachable"),
350 n->name, n->hostname);
353 /* TODO: only clear status.validkey if node is unreachable? */
355 n->status.validkey = false;
356 n->status.waitingforkey = false;
362 asprintf(&envp[0], "NETNAME=%s", netname ? : "");
363 asprintf(&envp[1], "DEVICE=%s", device ? : "");
364 asprintf(&envp[2], "INTERFACE=%s", iface ? : "");
365 asprintf(&envp[3], "NODE=%s", n->name);
366 sockaddr2str(&n->address, &address, &port);
367 asprintf(&envp[4], "REMOTEADDRESS=%s", address);
368 asprintf(&envp[5], "REMOTEPORT=%s", port);
371 execute_script(n->status.reachable ? "host-up" : "host-down", envp);
374 n->status.reachable ? "hosts/%s-up" : "hosts/%s-down",
376 execute_script(name, envp);
382 for(i = 0; i < 6; i++)
385 subnet_update(n, NULL, n->status.reachable);
390 /* Dump nodes and edges to a graphviz file.
392 The file can be converted to an image with
393 dot -Tpng graph_filename -o image_filename.png -Gconcentrate=true
396 int dump_graph(struct evbuffer *out) {
401 if(evbuffer_add_printf(out, "digraph {\n") == -1)
404 /* dump all nodes first */
405 for(node = node_tree->head; node; node = node->next) {
407 if(evbuffer_add_printf(out, " %s [label = \"%s\"];\n",
408 n->name, n->name) == -1)
412 /* now dump all edges */
413 for(node = edge_weight_tree->head; node; node = node->next) {
415 if(evbuffer_add_printf(out, " %s -> %s;\n",
416 e->from->name, e->to->name) == -1)
420 if(evbuffer_add_printf(out, "}\n") == -1)
427 subnet_cache_flush();
429 check_reachability();