tinc-vpn.org Git - tinc/blob - src/graph.c

   1 /*
   2     graph.c -- graph algorithms
   3     Copyright (C) 2001-2006 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
  17     along with this program; if not, write to the Free Software
  18     Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  19
  20     $Id$
  21 */
  22
  23 /* We need to generate two trees from the graph:
  24
  25    1. A minimum spanning tree for broadcasts,
  26    2. A single-source shortest path tree for unicasts.
  27
  28    Actually, the first one alone would suffice but would make unicast packets
  29    take longer routes than necessary.
  30
  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
  37    merge trees.
  38
  39    For the SSSP algorithm Dijkstra's seems to be a nice choice. Currently a
  40    simple breadth-first search is presented here.
  41
  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.
  45 */
  46
  47 #include "system.h"
  48
  49 #include "avl_tree.h"
  50 #include "config.h"
  51 #include "connection.h"
  52 #include "device.h"
  53 #include "edge.h"
  54 #include "logger.h"
  55 #include "netutl.h"
  56 #include "node.h"
  57 #include "process.h"
  58 #include "subnet.h"
  59 #include "utils.h"
  60
  61 /* Implementation of Kruskal's algorithm.
  62    Running time: O(EN)
  63    Please note that sorting on weight is already done by add_edge().
  64 */
  65
  66 void mst_kruskal(void)
  67 {
  68         avl_node_t *node, *next;
  69         edge_t *e;
  70         node_t *n;
  71         connection_t *c;
  72         int nodes = 0;
  73         int safe_edges = 0;
  74         bool skipped;
  75
  76         cp();
  77
  78         /* Clear MST status on connections */
  79
  80         for(node = connection_tree->head; node; node = node->next) {
  81                 c = node->data;
  82                 c->status.mst = false;
  83         }
  84
  85         /* Do we have something to do at all? */
  86
  87         if(!edge_weight_tree->head)
  88                 return;
  89
  90         ifdebug(SCARY_THINGS) logger(LOG_DEBUG, "Running Kruskal's algorithm:");
  91
  92         /* Clear visited status on nodes */
  93
  94         for(node = node_tree->head; node; node = node->next) {
  95                 n = node->data;
  96                 n->status.visited = false;
  97                 nodes++;
  98         }
  99
 100         /* Starting point */
 101
 102         for(node = edge_weight_tree->head; node; node = node->next) {
 103                 e = node->data;
 104                 if(e->from->status.reachable) {
 105                         e->from->status.visited = true;
 106                         break;
 107                 }
 108         }
 109
 110         /* Add safe edges */
 111
 112         for(skipped = false, node = edge_weight_tree->head; node; node = next) {
 113                 next = node->next;
 114                 e = node->data;
 115
 116                 if(!e->reverse || e->from->status.visited == e->to->status.visited) {
 117                         skipped = true;
 118                         continue;
 119                 }
 120
 121                 e->from->status.visited = true;
 122                 e->to->status.visited = true;
 123
 124                 if(e->connection)
 125                         e->connection->status.mst = true;
 126
 127                 if(e->reverse->connection)
 128                         e->reverse->connection->status.mst = true;
 129
 130                 safe_edges++;
 131
 132                 ifdebug(SCARY_THINGS) logger(LOG_DEBUG, " Adding edge %s - %s weight %d", e->from->name,
 133                                    e->to->name, e->weight);
 134
 135                 if(skipped) {
 136                         skipped = false;
 137                         next = edge_weight_tree->head;
 138                         continue;
 139                 }
 140         }
 141
 142         ifdebug(SCARY_THINGS) logger(LOG_DEBUG, "Done, counted %d nodes and %d safe edges.", nodes,
 143                            safe_edges);
 144 }
 145
 146 /* Implementation of a simple breadth-first search algorithm.
 147    Running time: O(E)
 148 */
 149
 150 void sssp_bfs(void)
 151 {
 152         avl_node_t *node, *next, *to;
 153         edge_t *e;
 154         node_t *n;
 155         list_t *todo_list;
 156         list_node_t *from, *todonext;
 157         bool indirect;
 158         char *name;
 159         char *address, *port;
 160         char *envp[7];
 161         int i;
 162
 163         cp();
 164
 165         todo_list = list_alloc(NULL);
 166
 167         /* Clear visited status on nodes */
 168
 169         for(node = node_tree->head; node; node = node->next) {
 170                 n = node->data;
 171                 n->status.visited = false;
 172                 n->status.indirect = true;
 173         }
 174
 175         /* Begin with myself */
 176
 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);
 182
 183         /* Loop while todo_list is filled */
 184
 185         for(from = todo_list->head; from; from = todonext) {    /* "from" is the node from which we start */
 186                 n = from->data;
 187
 188                 for(to = n->edge_tree->head; to; to = to->next) {       /* "to" is the edge connected to "from" */
 189                         e = to->data;
 190
 191                         if(!e->reverse)
 192                                 continue;
 193
 194                         /* Situation:
 195
 196                                    /
 197                                   /
 198                            ----->(n)---e-->(e->to)
 199                                   \
 200                                    \
 201
 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:
 205
 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
 211                              of nodes behind it.
 212                          */
 213
 214                         indirect = n->status.indirect || e->options & OPTION_INDIRECT
 215                                 || ((n != myself) && sockaddrcmp(&n->address, &e->reverse->address));
 216
 217                         if(e->to->status.visited
 218                            && (!e->to->status.indirect || indirect))
 219                                 continue;
 220
 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;
 226
 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);
 231
 232                                 if(e->to->hostname)
 233                                         free(e->to->hostname);
 234
 235                                 e->to->hostname = sockaddr2hostname(&e->to->address);
 236
 237                                 if(node)
 238                                         avl_insert_node(node_udp_tree, node);
 239
 240                                 if(e->to->options & OPTION_PMTU_DISCOVERY) {
 241                                         e->to->mtuprobes = 0;
 242                                         e->to->minmtu = 0;
 243                                         e->to->maxmtu = MTU;
 244                                         if(e->to->status.validkey)
 245                                                 send_mtu_probe(e->to);
 246                                 }
 247                         }
 248
 249                         list_insert_tail(todo_list, e->to);
 250                 }
 251
 252                 todonext = from->next;
 253                 list_delete_node(todo_list, from);
 254         }
 255
 256         list_free(todo_list);
 257
 258         /* Check reachability status. */
 259
 260         for(node = node_tree->head; node; node = next) {
 261                 next = node->next;
 262                 n = node->data;
 263
 264                 if(n->status.visited != n->status.reachable) {
 265                         n->status.reachable = !n->status.reachable;
 266
 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);
 271                         } else {
 272                                 ifdebug(TRAFFIC) logger(LOG_DEBUG, _("Node %s (%s) became unreachable"),
 273                                            n->name, n->hostname);
 274                                 avl_delete(node_udp_tree, n);
 275                         }
 276
 277                         n->status.validkey = false;
 278                         n->status.waitingforkey = false;
 279
 280                         n->maxmtu = MTU;
 281                         n->minmtu = 0;
 282                         n->mtuprobes = 0;
 283
 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);
 291                         envp[6] = NULL;
 292
 293                         execute_script(n->status.reachable ? "host-up" : "host-down", envp);
 294
 295                         asprintf(&name,
 296                                          n->status.reachable ? "hosts/%s-up" : "hosts/%s-down",
 297                                          n->name);
 298                         execute_script(name, envp);
 299
 300                         free(name);
 301                         free(address);
 302                         free(port);
 303
 304                         for(i = 0; i < 6; i++)
 305                                 free(envp[i]);
 306
 307                         subnet_update(n, NULL, n->status.reachable);
 308                 }
 309         }
 310 }
 311
 312 /* Dump nodes and edges to a graphviz file.
 313
 314    The file can be converted to an image with
 315    dot -Tpng graph_filename -o image_filename.png -Gconcentrate=true
 316 */
 317
 318 static void dump_graph(int fd, short events, void *data)
 319 {
 320         avl_node_t *node;
 321         node_t *n;
 322         edge_t *e;
 323         char *filename = NULL, *tmpname = NULL;
 324         FILE *file;
 325
 326         if(!get_config_string(lookup_config(config_tree, "GraphDumpFile"), &filename))
 327                 return;
 328
 329         ifdebug(PROTOCOL) logger(LOG_NOTICE, "Dumping graph");
 330
 331         if(filename[0] == '|') {
 332                 file = popen(filename + 1, "w");
 333         } else {
 334                 asprintf(&tmpname, "%s.new", filename);
 335                 file = fopen(tmpname, "w");
 336         }
 337
 338         if(!file) {
 339                 logger(LOG_ERR, "Unable to open graph dump file %s: %s", filename, strerror(errno));
 340                 free(tmpname);
 341                 return;
 342         }
 343
 344         fprintf(file, "digraph {\n");
 345
 346         /* dump all nodes first */
 347         for(node = node_tree->head; node; node = node->next) {
 348                 n = node->data;
 349                 fprintf(file, " %s [label = \"%s\"];\n", n->name, n->name);
 350         }
 351
 352         /* now dump all edges */
 353         for(node = edge_weight_tree->head; node; node = node->next) {
 354                 e = node->data;
 355                 fprintf(file, " %s -> %s;\n", e->from->name, e->to->name);
 356         }
 357
 358         fprintf(file, "}\n");
 359
 360         if(filename[0] == '|') {
 361                 pclose(file);
 362         } else {
 363                 fclose(file);
 364 #ifdef HAVE_MINGW
 365                 unlink(filename);
 366 #endif
 367                 rename(tmpname, filename);
 368                 free(tmpname);
 369         }
 370 }
 371
 372 void graph(void)
 373 {
 374         static struct event ev;
 375
 376         sssp_bfs();
 377         mst_kruskal();
 378
 379         if(!timeout_initialized(&ev))
 380                 timeout_set(&ev, dump_graph, NULL);
 381         event_add(&ev, &(struct timeval){5, 0});
 382 }