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 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 {
  70         avl_node_t *node, *next;
  71         edge_t *e;
  72         node_t *n;
  73         connection_t *c;
  74         int nodes = 0;
  75         int safe_edges = 0;
  76         bool skipped;
  77
  78         cp();
  79
  80         /* Clear MST status on connections */
  81
  82         for(node = connection_tree->head; node; node = node->next) {
  83                 c = node->data;
  84                 c->status.mst = false;
  85         }
  86
  87         /* Do we have something to do at all? */
  88
  89         if(!edge_weight_tree->head)
  90                 return;
  91
  92         ifdebug(SCARY_THINGS) logger(LOG_DEBUG, "Running Kruskal's algorithm:");
  93
  94         /* Clear visited status on nodes */
  95
  96         for(node = node_tree->head; node; node = node->next) {
  97                 n = node->data;
  98                 n->status.visited = false;
  99                 nodes++;
 100         }
 101
 102         /* Starting point */
 103
 104         for(node = edge_weight_tree->head; node; node = next) {
 105                 e = node->data;
 106                 if(e->from->status.reachable) {
 107                         e->from->status.visited = true;
 108                         break;
 109                 }
 110         }
 111
 112         /* Add safe edges */
 113
 114         for(skipped = false, node = edge_weight_tree->head; node; node = next) {
 115                 next = node->next;
 116                 e = node->data;
 117
 118                 if(!e->reverse || e->from->status.visited == e->to->status.visited) {
 119                         skipped = true;
 120                         continue;
 121                 }
 122
 123                 e->from->status.visited = true;
 124                 e->to->status.visited = true;
 125
 126                 if(e->connection)
 127                         e->connection->status.mst = true;
 128
 129                 if(e->reverse->connection)
 130                         e->reverse->connection->status.mst = true;
 131
 132                 safe_edges++;
 133
 134                 ifdebug(SCARY_THINGS) logger(LOG_DEBUG, " Adding edge %s - %s weight %d", e->from->name,
 135                                    e->to->name, e->weight);
 136
 137                 if(skipped) {
 138                         skipped = false;
 139                         next = edge_weight_tree->head;
 140                         continue;
 141                 }
 142         }
 143
 144         ifdebug(SCARY_THINGS) logger(LOG_DEBUG, "Done, counted %d nodes and %d safe edges.", nodes,
 145                            safe_edges);
 146 }
 147
 148 /* Implementation of a simple breadth-first search algorithm.
 149    Running time: O(E)
 150 */
 151
 152 void sssp_bfs(void)
 153 {
 154         avl_node_t *node, *next, *to;
 155         edge_t *e;
 156         node_t *n;
 157         list_t *todo_list;
 158         list_node_t *from, *todonext;
 159         bool indirect;
 160         char *name;
 161         char *address, *port;
 162         char *envp[7];
 163         int i;
 164
 165         cp();
 166
 167         todo_list = list_alloc(NULL);
 168
 169         /* Clear visited status on nodes */
 170
 171         for(node = node_tree->head; node; node = node->next) {
 172                 n = node->data;
 173                 n->status.visited = false;
 174                 n->status.indirect = true;
 175         }
 176
 177         /* Begin with myself */
 178
 179         myself->status.visited = true;
 180         myself->status.indirect = false;
 181         myself->nexthop = myself;
 182         myself->via = myself;
 183         list_insert_head(todo_list, myself);
 184
 185         /* Loop while todo_list is filled */
 186
 187         for(from = todo_list->head; from; from = todonext) {    /* "from" is the node from which we start */
 188                 n = from->data;
 189
 190                 for(to = n->edge_tree->head; to; to = to->next) {       /* "to" is the edge connected to "from" */
 191                         e = to->data;
 192
 193                         if(!e->reverse)
 194                                 continue;
 195
 196                         /* Situation:
 197
 198                                    /
 199                                   /
 200                            ----->(n)---e-->(e->to)
 201                                   \
 202                                    \
 203
 204                            Where e is an edge, (n) and (e->to) are nodes.
 205                            n->address is set to the e->address of the edge left of n to n.
 206                            We are currently examining the edge e right of n from n:
 207
 208                            - If e->reverse->address != n->address, then e->to is probably
 209                              not reachable for the nodes left of n. We do as if the indirectdata
 210                              flag is set on edge e.
 211                            - If edge e provides for better reachability of e->to, update
 212                              e->to and (re)add it to the todo_list to (re)examine the reachability
 213                              of nodes behind it.
 214                          */
 215
 216                         indirect = n->status.indirect || e->options & OPTION_INDIRECT
 217                                 || ((n != myself) && sockaddrcmp(&n->address, &e->reverse->address));
 218
 219                         if(e->to->status.visited
 220                            && (!e->to->status.indirect || indirect))
 221                                 continue;
 222
 223                         e->to->status.visited = true;
 224                         e->to->status.indirect = indirect;
 225                         e->to->nexthop = (n->nexthop == myself) ? e->to : n->nexthop;
 226                         e->to->via = indirect ? n->via : e->to;
 227                         e->to->options = e->options;
 228
 229                         if(sockaddrcmp(&e->to->address, &e->address)) {
 230                                 node = avl_unlink(node_udp_tree, e->to);
 231                                 sockaddrfree(&e->to->address);
 232                                 sockaddrcpy(&e->to->address, &e->address);
 233
 234                                 if(e->to->hostname)
 235                                         free(e->to->hostname);
 236
 237                                 e->to->hostname = sockaddr2hostname(&e->to->address);
 238
 239                                 if(node)
 240                                         avl_insert_node(node_udp_tree, node);
 241
 242                                 if(e->to->options & OPTION_PMTU_DISCOVERY) {
 243                                         e->to->mtuprobes = 0;
 244                                         e->to->minmtu = 0;
 245                                         e->to->maxmtu = MTU;
 246                                         if(e->to->status.validkey)
 247                                                 send_mtu_probe(e->to);
 248                                 }
 249                         }
 250
 251                         list_insert_tail(todo_list, e->to);
 252                 }
 253
 254                 todonext = from->next;
 255                 list_delete_node(todo_list, from);
 256         }
 257
 258         list_free(todo_list);
 259
 260         /* Check reachability status. */
 261
 262         for(node = node_tree->head; node; node = next) {
 263                 next = node->next;
 264                 n = node->data;
 265
 266                 if(n->status.visited != n->status.reachable) {
 267                         n->status.reachable = !n->status.reachable;
 268
 269                         if(n->status.reachable) {
 270                                 ifdebug(TRAFFIC) logger(LOG_DEBUG, _("Node %s (%s) became reachable"),
 271                                            n->name, n->hostname);
 272                                 avl_insert(node_udp_tree, n);
 273                         } else {
 274                                 ifdebug(TRAFFIC) logger(LOG_DEBUG, _("Node %s (%s) became unreachable"),
 275                                            n->name, n->hostname);
 276                                 avl_delete(node_udp_tree, n);
 277                         }
 278
 279                         n->status.validkey = false;
 280                         n->status.waitingforkey = false;
 281
 282                         n->maxmtu = MTU;
 283                         n->minmtu = 0;
 284                         n->mtuprobes = 0;
 285
 286                         asprintf(&envp[0], "NETNAME=%s", netname ? : "");
 287                         asprintf(&envp[1], "DEVICE=%s", device ? : "");
 288                         asprintf(&envp[2], "INTERFACE=%s", iface ? : "");
 289                         asprintf(&envp[3], "NODE=%s", n->name);
 290                         sockaddr2str(&n->address, &address, &port);
 291                         asprintf(&envp[4], "REMOTEADDRESS=%s", address);
 292                         asprintf(&envp[5], "REMOTEPORT=%s", port);
 293                         envp[6] = NULL;
 294
 295                         execute_script(n->status.reachable ? "host-up" : "host-down", envp);
 296
 297                         asprintf(&name,
 298                                          n->status.reachable ? "hosts/%s-up" : "hosts/%s-down",
 299                                          n->name);
 300                         execute_script(name, envp);
 301
 302                         free(name);
 303                         free(address);
 304                         free(port);
 305
 306                         for(i = 0; i < 6; i++)
 307                                 free(envp[i]);
 308
 309                         subnet_update(n, NULL, n->status.reachable);
 310                 }
 311         }
 312 }
 313
 314 void graph(void)
 315 {
 316         sssp_bfs();
 317         mst_kruskal();
 318         graph_changed = true;
 319 }
 320
 321
 322
 323 /* Dump nodes and edges to a graphviz file.
 324
 325    The file can be converted to an image with
 326    dot -Tpng graph_filename -o image_filename.png -Gconcentrate=true
 327 */
 328
 329 void dump_graph(void)
 330 {
 331         avl_node_t *node;
 332         node_t *n;
 333         edge_t *e;
 334         char *filename = NULL, *tmpname = NULL;
 335         FILE *file;
 336
 337         if(!graph_changed || !get_config_string(lookup_config(config_tree, "GraphDumpFile"), &filename))
 338                 return;
 339
 340         graph_changed = false;
 341
 342         ifdebug(PROTOCOL) logger(LOG_NOTICE, "Dumping graph");
 343
 344         if(filename[0] == '|') {
 345                 file = popen(filename + 1, "w");
 346         } else {
 347                 asprintf(&tmpname, "%s.new", filename);
 348                 file = fopen(tmpname, "w");
 349         }
 350
 351         if(!file) {
 352                 logger(LOG_ERR, "Unable to open graph dump file %s: %s", filename, strerror(errno));
 353                 free(tmpname);
 354                 return;
 355         }
 356
 357         fprintf(file, "digraph {\n");
 358
 359         /* dump all nodes first */
 360         for(node = node_tree->head; node; node = node->next) {
 361                 n = node->data;
 362                 fprintf(file, " %s [label = \"%s\"];\n", n->name, n->name);
 363         }
 364
 365         /* now dump all edges */
 366         for(node = edge_weight_tree->head; node; node = node->next) {
 367                 e = node->data;
 368                 fprintf(file, " %s -> %s;\n", e->from->name, e->to->name);
 369         }
 370
 371         fprintf(file, "}\n");
 372
 373         if(filename[0] == '|') {
 374                 pclose(file);
 375         } else {
 376                 fclose(file);
 377                 rename(tmpname, filename);
 378                 free(tmpname);
 379         }
 380 }