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         ((edge_t *) edge_weight_tree->head->data)->from->status.visited = true;
 105
 106         /* Add safe edges */
 107
 108         for(skipped = false, node = edge_weight_tree->head; node; node = next) {
 109                 next = node->next;
 110                 e = node->data;
 111
 112                 if(!e->reverse || e->from->status.visited == e->to->status.visited) {
 113                         skipped = true;
 114                         continue;
 115                 }
 116
 117                 e->from->status.visited = true;
 118                 e->to->status.visited = true;
 119
 120                 if(e->connection)
 121                         e->connection->status.mst = true;
 122
 123                 if(e->reverse->connection)
 124                         e->reverse->connection->status.mst = true;
 125
 126                 safe_edges++;
 127
 128                 ifdebug(SCARY_THINGS) logger(LOG_DEBUG, " Adding edge %s - %s weight %d", e->from->name,
 129                                    e->to->name, e->weight);
 130
 131                 if(skipped) {
 132                         skipped = false;
 133                         next = edge_weight_tree->head;
 134                         continue;
 135                 }
 136         }
 137
 138         ifdebug(SCARY_THINGS) logger(LOG_DEBUG, "Done, counted %d nodes and %d safe edges.", nodes,
 139                            safe_edges);
 140 }
 141
 142 /* Implementation of a simple breadth-first search algorithm.
 143    Running time: O(E)
 144 */
 145
 146 void sssp_bfs(void)
 147 {
 148         avl_node_t *node, *next, *to;
 149         edge_t *e;
 150         node_t *n;
 151         list_t *todo_list;
 152         list_node_t *from, *todonext;
 153         bool indirect;
 154         char *name;
 155         char *address, *port;
 156         char *envp[7];
 157         int i;
 158
 159         cp();
 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(sockaddrcmp(&e->to->address, &e->address)) {
 224                                 node = avl_unlink(node_udp_tree, e->to);
 225                                 sockaddrfree(&e->to->address);
 226                                 sockaddrcpy(&e->to->address, &e->address);
 227
 228                                 if(e->to->hostname)
 229                                         free(e->to->hostname);
 230
 231                                 e->to->hostname = sockaddr2hostname(&e->to->address);
 232
 233                                 if(node)
 234                                         avl_insert_node(node_udp_tree, node);
 235
 236                                 if(e->to->options & OPTION_PMTU_DISCOVERY) {
 237                                         e->to->mtuprobes = 0;
 238                                         e->to->minmtu = 0;
 239                                         e->to->maxmtu = MTU;
 240                                         if(e->to->status.validkey)
 241                                                 send_mtu_probe(e->to);
 242                                 }
 243                         }
 244
 245                         list_insert_tail(todo_list, e->to);
 246                 }
 247
 248                 todonext = from->next;
 249                 list_delete_node(todo_list, from);
 250         }
 251
 252         list_free(todo_list);
 253
 254         /* Check reachability status. */
 255
 256         for(node = node_tree->head; node; node = next) {
 257                 next = node->next;
 258                 n = node->data;
 259
 260                 if(n->status.visited != n->status.reachable) {
 261                         n->status.reachable = !n->status.reachable;
 262
 263                         if(n->status.reachable) {
 264                                 ifdebug(TRAFFIC) logger(LOG_DEBUG, _("Node %s (%s) became reachable"),
 265                                            n->name, n->hostname);
 266                                 avl_insert(node_udp_tree, n);
 267                         } else {
 268                                 ifdebug(TRAFFIC) logger(LOG_DEBUG, _("Node %s (%s) became unreachable"),
 269                                            n->name, n->hostname);
 270                                 avl_delete(node_udp_tree, n);
 271                         }
 272
 273                         n->status.validkey = false;
 274                         n->status.waitingforkey = false;
 275
 276                         n->maxmtu = MTU;
 277                         n->minmtu = 0;
 278                         n->mtuprobes = 0;
 279
 280                         asprintf(&envp[0], "NETNAME=%s", netname ? : "");
 281                         asprintf(&envp[1], "DEVICE=%s", device ? : "");
 282                         asprintf(&envp[2], "INTERFACE=%s", iface ? : "");
 283                         asprintf(&envp[3], "NODE=%s", n->name);
 284                         sockaddr2str(&n->address, &address, &port);
 285                         asprintf(&envp[4], "REMOTEADDRESS=%s", address);
 286                         asprintf(&envp[5], "REMOTEPORT=%s", port);
 287                         envp[6] = NULL;
 288
 289                         execute_script(n->status.reachable ? "host-up" : "host-down", envp);
 290
 291                         asprintf(&name,
 292                                          n->status.reachable ? "hosts/%s-up" : "hosts/%s-down",
 293                                          n->name);
 294                         execute_script(name, envp);
 295
 296                         free(name);
 297                         free(address);
 298                         free(port);
 299
 300                         for(i = 0; i < 6; i++)
 301                                 free(envp[i]);
 302
 303                         subnet_update(n, NULL, n->status.reachable);
 304                 }
 305         }
 306 }
 307
 308 void graph(void)
 309 {
 310         mst_kruskal();
 311         sssp_bfs();
 312         graph_changed = true;
 313 }
 314
 315
 316
 317 /* Dump nodes and edges to a graphviz file.
 318
 319    The file can be converted to an image with
 320    dot -Tpng graph_filename -o image_filename.png -Gconcentrate=true
 321 */
 322
 323 void dump_graph(void)
 324 {
 325         avl_node_t *node;
 326         node_t *n;
 327         edge_t *e;
 328         char *filename = NULL, *tmpname = NULL;
 329         FILE *file;
 330
 331         if(!graph_changed || !get_config_string(lookup_config(config_tree, "GraphDumpFile"), &filename))
 332                 return;
 333
 334         graph_changed = false;
 335
 336         ifdebug(PROTOCOL) logger(LOG_NOTICE, "Dumping graph");
 337
 338         if(filename[0] == '|') {
 339                 file = popen(filename + 1, "w");
 340         } else {
 341                 asprintf(&tmpname, "%s.new", filename);
 342                 file = fopen(tmpname, "w");
 343         }
 344
 345         if(!file) {
 346                 logger(LOG_ERR, "Unable to open graph dump file %s: %s", filename, strerror(errno));
 347                 free(tmpname);
 348                 return;
 349         }
 350
 351         fprintf(file, "digraph {\n");
 352
 353         /* dump all nodes first */
 354         for(node = node_tree->head; node; node = node->next) {
 355                 n = node->data;
 356                 fprintf(file, " %s [label = \"%s\"];\n", n->name, n->name);
 357         }
 358
 359         /* now dump all edges */
 360         for(node = edge_weight_tree->head; node; node = node->next) {
 361                 e = node->data;
 362                 fprintf(file, " %s -> %s;\n", e->from->name, e->to->name);
 363         }
 364
 365         fprintf(file, "}\n");
 366
 367         fclose(file);
 368
 369         if(filename[0] != '|') {
 370                 rename(tmpname, filename);
 371                 free(tmpname);
 372         }
 373 }