1e6043d15cf56b5926f92a0c238208c6e0cb676b
[tinc] / src / graph.c
1 /*
2     graph.c -- graph algorithms
3     Copyright (C) 2001-2010 Guus Sliepen <guus@tinc-vpn.org>,
4                   2001-2005 Ivo Timmermans
5
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.
10
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.
15
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.
19 */
20
21 /* We need to generate two trees from the graph:
22
23    1. A minimum spanning tree for broadcasts,
24    2. A single-source shortest path tree for unicasts.
25
26    Actually, the first one alone would suffice but would make unicast packets
27    take longer routes than necessary.
28
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
35    merge trees.
36
37    For the SSSP algorithm Dijkstra's seems to be a nice choice. Currently a
38    simple breadth-first search is presented here.
39
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.
43 */
44
45 #include "system.h"
46
47 #include "avl_tree.h"
48 #include "config.h"
49 #include "connection.h"
50 #include "device.h"
51 #include "edge.h"
52 #include "logger.h"
53 #include "netutl.h"
54 #include "node.h"
55 #include "process.h"
56 #include "protocol.h"
57 #include "subnet.h"
58 #include "utils.h"
59 #include "xalloc.h"
60
61 static bool graph_changed = true;
62
63 /* Implementation of Kruskal's algorithm.
64    Running time: O(EN)
65    Please note that sorting on weight is already done by add_edge().
66 */
67
68 void mst_kruskal(void) {
69         avl_node_t *node, *next;
70         edge_t *e;
71         node_t *n;
72         connection_t *c;
73         int nodes = 0;
74         int safe_edges = 0;
75         bool skipped;
76
77         /* Clear MST status on connections */
78
79         for(node = connection_tree->head; node; node = node->next) {
80                 c = node->data;
81                 c->status.mst = false;
82         }
83
84         /* Do we have something to do at all? */
85
86         if(!edge_weight_tree->head)
87                 return;
88
89         ifdebug(SCARY_THINGS) logger(LOG_DEBUG, "Running Kruskal's algorithm:");
90
91         /* Clear visited status on nodes */
92
93         for(node = node_tree->head; node; node = node->next) {
94                 n = node->data;
95                 n->status.visited = false;
96                 nodes++;
97         }
98
99         /* Starting point */
100
101         for(node = edge_weight_tree->head; node; node = node->next) {
102                 e = node->data;
103                 if(e->from->status.reachable) {
104                         e->from->status.visited = true;
105                         break;
106                 }
107         }
108
109         /* Add safe edges */
110
111         for(skipped = false, node = edge_weight_tree->head; node; node = next) {
112                 next = node->next;
113                 e = node->data;
114
115                 if(!e->reverse || e->from->status.visited == e->to->status.visited) {
116                         skipped = true;
117                         continue;
118                 }
119
120                 e->from->status.visited = true;
121                 e->to->status.visited = true;
122
123                 if(e->connection)
124                         e->connection->status.mst = true;
125
126                 if(e->reverse->connection)
127                         e->reverse->connection->status.mst = true;
128
129                 safe_edges++;
130
131                 ifdebug(SCARY_THINGS) logger(LOG_DEBUG, " Adding edge %s - %s weight %d", e->from->name,
132                                    e->to->name, e->weight);
133
134                 if(skipped) {
135                         skipped = false;
136                         next = edge_weight_tree->head;
137                         continue;
138                 }
139         }
140
141         ifdebug(SCARY_THINGS) logger(LOG_DEBUG, "Done, counted %d nodes and %d safe edges.", nodes,
142                            safe_edges);
143 }
144
145 /* Implementation of a simple breadth-first search algorithm.
146    Running time: O(E)
147 */
148
149 void sssp_bfs(void) {
150         avl_node_t *node, *next, *to;
151         edge_t *e;
152         node_t *n;
153         list_t *todo_list;
154         list_node_t *from, *todonext;
155         bool indirect;
156         char *name;
157         char *address, *port;
158         char *envp[7];
159         int i;
160
161         todo_list = list_alloc(NULL);
162
163         /* Clear visited status on nodes */
164
165         for(node = node_tree->head; node; node = node->next) {
166                 n = node->data;
167                 n->status.visited = false;
168                 n->status.indirect = true;
169         }
170
171         /* Begin with myself */
172
173         myself->status.visited = true;
174         myself->status.indirect = false;
175         myself->nexthop = myself;
176         myself->via = myself;
177         list_insert_head(todo_list, myself);
178
179         /* Loop while todo_list is filled */
180
181         for(from = todo_list->head; from; from = todonext) {    /* "from" is the node from which we start */
182                 n = from->data;
183
184                 for(to = n->edge_tree->head; to; to = to->next) {       /* "to" is the edge connected to "from" */
185                         e = to->data;
186
187                         if(!e->reverse)
188                                 continue;
189
190                         /* Situation:
191
192                                    /
193                                   /
194                            ----->(n)---e-->(e->to)
195                                   \
196                                    \
197
198                            Where e is an edge, (n) and (e->to) are nodes.
199                            n->address is set to the e->address of the edge left of n to n.
200                            We are currently examining the edge e right of n from n:
201
202                            - If e->reverse->address != n->address, then e->to is probably
203                              not reachable for the nodes left of n. We do as if the indirectdata
204                              flag is set on edge e.
205                            - If edge e provides for better reachability of e->to, update
206                              e->to and (re)add it to the todo_list to (re)examine the reachability
207                              of nodes behind it.
208                          */
209
210                         indirect = n->status.indirect || e->options & OPTION_INDIRECT
211                                 || ((n != myself) && sockaddrcmp(&n->address, &e->reverse->address));
212
213                         if(e->to->status.visited
214                            && (!e->to->status.indirect || indirect))
215                                 continue;
216
217                         e->to->status.visited = true;
218                         e->to->status.indirect = indirect;
219                         e->to->nexthop = (n->nexthop == myself) ? e->to : n->nexthop;
220                         e->to->via = indirect ? n->via : e->to;
221                         e->to->options = e->options;
222
223                         if(e->to->address.sa.sa_family == AF_UNSPEC && e->address.sa.sa_family != AF_UNKNOWN)
224                                 update_node_udp(e->to, &e->address);
225
226                         list_insert_tail(todo_list, e->to);
227                 }
228
229                 todonext = from->next;
230                 list_delete_node(todo_list, from);
231         }
232
233         list_free(todo_list);
234
235         /* Check reachability status. */
236
237         for(node = node_tree->head; node; node = next) {
238                 next = node->next;
239                 n = node->data;
240
241                 if(n->status.visited != n->status.reachable) {
242                         n->status.reachable = !n->status.reachable;
243
244                         if(n->status.reachable) {
245                                 ifdebug(TRAFFIC) logger(LOG_DEBUG, "Node %s (%s) became reachable",
246                                            n->name, n->hostname);
247                         } else {
248                                 ifdebug(TRAFFIC) logger(LOG_DEBUG, "Node %s (%s) became unreachable",
249                                            n->name, n->hostname);
250                         }
251
252                         /* TODO: only clear status.validkey if node is unreachable? */
253
254                         n->status.validkey = false;
255                         n->last_req_key = 0;
256
257                         n->maxmtu = MTU;
258                         n->minmtu = 0;
259                         n->mtuprobes = 0;
260
261                         if(n->mtuevent) {
262                                 event_del(n->mtuevent);
263                                 n->mtuevent = NULL;
264                         }
265
266                         xasprintf(&envp[0], "NETNAME=%s", netname ? : "");
267                         xasprintf(&envp[1], "DEVICE=%s", device ? : "");
268                         xasprintf(&envp[2], "INTERFACE=%s", iface ? : "");
269                         xasprintf(&envp[3], "NODE=%s", n->name);
270                         sockaddr2str(&n->address, &address, &port);
271                         xasprintf(&envp[4], "REMOTEADDRESS=%s", address);
272                         xasprintf(&envp[5], "REMOTEPORT=%s", port);
273                         envp[6] = NULL;
274
275                         execute_script(n->status.reachable ? "host-up" : "host-down", envp);
276
277                         xasprintf(&name,
278                                          n->status.reachable ? "hosts/%s-up" : "hosts/%s-down",
279                                          n->name);
280                         execute_script(name, envp);
281
282                         free(name);
283                         free(address);
284                         free(port);
285
286                         for(i = 0; i < 6; i++)
287                                 free(envp[i]);
288
289                         subnet_update(n, NULL, n->status.reachable);
290
291                         if(!n->status.reachable)
292                                 update_node_udp(n, NULL);
293                         else if(n->connection)
294                                 send_ans_key(n);
295                 }
296         }
297 }
298
299 void graph(void) {
300         subnet_cache_flush();
301         sssp_bfs();
302         mst_kruskal();
303         graph_changed = true;
304 }
305
306
307
308 /* Dump nodes and edges to a graphviz file.
309            
310    The file can be converted to an image with
311    dot -Tpng graph_filename -o image_filename.png -Gconcentrate=true
312 */
313
314 void dump_graph(void) {
315         avl_node_t *node;
316         node_t *n;
317         edge_t *e;
318         char *filename = NULL, *tmpname = NULL;
319         FILE *file;
320         
321         if(!graph_changed || !get_config_string(lookup_config(config_tree, "GraphDumpFile"), &filename))
322                 return;
323
324         graph_changed = false;
325
326         ifdebug(PROTOCOL) logger(LOG_NOTICE, "Dumping graph");
327         
328         if(filename[0] == '|') {
329                 file = popen(filename + 1, "w");
330         } else {
331                 xasprintf(&tmpname, "%s.new", filename);
332                 file = fopen(tmpname, "w");
333         }
334
335         if(!file) {
336                 logger(LOG_ERR, "Unable to open graph dump file %s: %s", filename, strerror(errno));
337                 free(tmpname);
338                 return;
339         }
340
341         fprintf(file, "digraph {\n");
342         
343         /* dump all nodes first */
344         for(node = node_tree->head; node; node = node->next) {
345                 n = node->data;
346                 fprintf(file, " %s [label = \"%s\"];\n", n->name, n->name);
347         }
348
349         /* now dump all edges */
350         for(node = edge_weight_tree->head; node; node = node->next) {
351                 e = node->data;
352                 fprintf(file, " %s -> %s;\n", e->from->name, e->to->name);
353         }
354
355         fprintf(file, "}\n");   
356         
357         if(filename[0] == '|') {
358                 pclose(file);
359         } else {
360                 fclose(file);
361 #ifdef HAVE_MINGW
362                 unlink(filename);
363 #endif
364                 rename(tmpname, filename);
365                 free(tmpname);
366         }
367 }