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.
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;
77 /* Clear MST status on connections */
79 for(node = connection_tree->head; node; node = node->next) {
81 c->status.mst = false;
84 /* Do we have something to do at all? */
86 if(!edge_weight_tree->head)
89 ifdebug(SCARY_THINGS) logger(LOG_DEBUG, "Running Kruskal's algorithm:");
91 /* Clear visited status on nodes */
93 for(node = node_tree->head; node; node = node->next) {
95 n->status.visited = false;
101 for(node = edge_weight_tree->head; node; node = node->next) {
103 if(e->from->status.reachable) {
104 e->from->status.visited = true;
111 for(skipped = false, node = edge_weight_tree->head; node; node = next) {
115 if(!e->reverse || e->from->status.visited == e->to->status.visited) {
120 e->from->status.visited = true;
121 e->to->status.visited = true;
124 e->connection->status.mst = true;
126 if(e->reverse->connection)
127 e->reverse->connection->status.mst = true;
131 ifdebug(SCARY_THINGS) logger(LOG_DEBUG, " Adding edge %s - %s weight %d", e->from->name,
132 e->to->name, e->weight);
136 next = edge_weight_tree->head;
141 ifdebug(SCARY_THINGS) logger(LOG_DEBUG, "Done, counted %d nodes and %d safe edges.", nodes,
145 /* Implementation of a simple breadth-first search algorithm.
149 void sssp_bfs(void) {
150 splay_node_t *node, *next, *to;
154 list_node_t *from, *todonext;
157 char *address, *port;
163 todo_list = list_alloc(NULL);
165 /* Clear visited status on nodes */
167 for(node = node_tree->head; node; node = node->next) {
169 n->status.visited = false;
170 n->status.indirect = true;
173 /* Begin with myself */
175 myself->status.visited = true;
176 myself->status.indirect = false;
177 myself->nexthop = myself;
178 myself->via = myself;
179 list_insert_head(todo_list, myself);
181 /* Loop while todo_list is filled */
183 for(from = todo_list->head; from; from = todonext) { /* "from" is the node from which we start */
186 for(to = n->edge_tree->head; to; to = to->next) { /* "to" is the edge connected to "from" */
196 ----->(n)---e-->(e->to)
200 Where e is an edge, (n) and (e->to) are nodes.
201 n->address is set to the e->address of the edge left of n to n.
202 We are currently examining the edge e right of n from n:
204 - If e->reverse->address != n->address, then e->to is probably
205 not reachable for the nodes left of n. We do as if the indirectdata
206 flag is set on edge e.
207 - If edge e provides for better reachability of e->to, update
208 e->to and (re)add it to the todo_list to (re)examine the reachability
212 indirect = n->status.indirect || e->options & OPTION_INDIRECT
213 || ((n != myself) && sockaddrcmp(&n->address, &e->reverse->address));
215 if(e->to->status.visited
216 && (!e->to->status.indirect || indirect))
219 e->to->status.visited = true;
220 e->to->status.indirect = indirect;
221 e->to->nexthop = (n->nexthop == myself) ? e->to : n->nexthop;
222 e->to->via = indirect ? n->via : e->to;
223 e->to->options = e->options;
225 if(sockaddrcmp(&e->to->address, &e->address)) {
226 node = splay_unlink(node_udp_tree, e->to);
227 sockaddrfree(&e->to->address);
228 sockaddrcpy(&e->to->address, &e->address);
231 free(e->to->hostname);
233 e->to->hostname = sockaddr2hostname(&e->to->address);
236 splay_insert_node(node_udp_tree, node);
238 if(e->to->options & OPTION_PMTU_DISCOVERY) {
239 e->to->mtuprobes = 0;
242 if(e->to->status.validkey)
243 send_mtu_probe(e->to);
247 list_insert_tail(todo_list, e->to);
250 todonext = from->next;
251 list_delete_node(todo_list, from);
254 list_free(todo_list);
256 /* Check reachability status. */
258 for(node = node_tree->head; node; node = next) {
262 if(n->status.visited != n->status.reachable) {
263 n->status.reachable = !n->status.reachable;
265 if(n->status.reachable) {
266 ifdebug(TRAFFIC) logger(LOG_DEBUG, _("Node %s (%s) became reachable"),
267 n->name, n->hostname);
268 splay_insert(node_udp_tree, n);
270 ifdebug(TRAFFIC) logger(LOG_DEBUG, _("Node %s (%s) became unreachable"),
271 n->name, n->hostname);
272 splay_delete(node_udp_tree, n);
275 n->status.validkey = false;
276 n->status.waitingforkey = false;
282 asprintf(&envp[0], "NETNAME=%s", netname ? : "");
283 asprintf(&envp[1], "DEVICE=%s", device ? : "");
284 asprintf(&envp[2], "INTERFACE=%s", iface ? : "");
285 asprintf(&envp[3], "NODE=%s", n->name);
286 sockaddr2str(&n->address, &address, &port);
287 asprintf(&envp[4], "REMOTEADDRESS=%s", address);
288 asprintf(&envp[5], "REMOTEPORT=%s", port);
291 execute_script(n->status.reachable ? "host-up" : "host-down", envp);
294 n->status.reachable ? "hosts/%s-up" : "hosts/%s-down",
296 execute_script(name, envp);
302 for(i = 0; i < 6; i++)
305 subnet_update(n, NULL, n->status.reachable);
310 /* Dump nodes and edges to a graphviz file.
312 The file can be converted to an image with
313 dot -Tpng graph_filename -o image_filename.png -Gconcentrate=true
316 int dump_graph(struct evbuffer *out) {
321 if(evbuffer_add_printf(out, "digraph {\n") == -1)
324 /* dump all nodes first */
325 for(node = node_tree->head; node; node = node->next) {
327 if(evbuffer_add_printf(out, " %s [label = \"%s\"];\n",
328 n->name, n->name) == -1)
332 /* now dump all edges */
333 for(node = edge_weight_tree->head; node; node = node->next) {
335 if(evbuffer_add_printf(out, " %s -> %s;\n",
336 e->from->name, e->to->name) == -1)
340 if(evbuffer_add_printf(out, "}\n") == -1)