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

   1 /*
   2     graph.c -- graph algorithms
   3     Copyright (C) 2001-2013 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 "conf.h"
  49 #include "connection.h"
  50 #include "device.h"
  51 #include "edge.h"
  52 #include "graph.h"
  53 #include "logger.h"
  54 #include "netutl.h"
  55 #include "node.h"
  56 #include "process.h"
  57 #include "protocol.h"
  58 #include "subnet.h"
  59 #include "utils.h"
  60 #include "xalloc.h"
  61
  62 static bool graph_changed = true;
  63
  64 /* Implementation of Kruskal's algorithm.
  65    Running time: O(EN)
  66    Please note that sorting on weight is already done by add_edge().
  67 */
  68
  69 static void mst_kruskal(void) {
  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         /* 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 static void sssp_bfs(void) {
 151         avl_node_t *node, *next, *to;
 152         edge_t *e;
 153         node_t *n;
 154         list_t *todo_list;
 155         list_node_t *from, *todonext;
 156         bool indirect;
 157         char *name;
 158         char *address, *port;
 159         char *envp[8] = {NULL};
 160         int i;
 161
 162         todo_list = list_alloc(NULL);
 163
 164         /* Clear visited status on nodes */
 165
 166         for(node = node_tree->head; node; node = node->next) {
 167                 n = node->data;
 168                 n->status.visited = false;
 169                 n->status.indirect = true;
 170         }
 171
 172         /* Begin with myself */
 173
 174         myself->status.visited = true;
 175         myself->status.indirect = false;
 176         myself->nexthop = myself;
 177         myself->prevedge = NULL;
 178         myself->via = myself;
 179         list_insert_head(todo_list, myself);
 180
 181         /* Loop while todo_list is filled */
 182
 183         for(from = todo_list->head; from; from = todonext) {    /* "from" is the node from which we start */
 184                 n = from->data;
 185
 186                 for(to = n->edge_tree->head; to; to = to->next) {       /* "to" is the edge connected to "from" */
 187                         e = to->data;
 188
 189                         if(!e->reverse)
 190                                 continue;
 191
 192                         /* Situation:
 193
 194                                    /
 195                                   /
 196                            ----->(n)---e-->(e->to)
 197                                   \
 198                                    \
 199
 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:
 203
 204                            - If edge e provides for better reachability of e->to, update
 205                              e->to and (re)add it to the todo_list to (re)examine the reachability
 206                              of nodes behind it.
 207                          */
 208
 209                         indirect = n->status.indirect || e->options & OPTION_INDIRECT;
 210
 211                         if(e->to->status.visited
 212                            && (!e->to->status.indirect || indirect))
 213                                 continue;
 214
 215                         e->to->status.visited = true;
 216                         e->to->status.indirect = indirect;
 217                         e->to->nexthop = (n->nexthop == myself) ? e->to : n->nexthop;
 218                         e->to->prevedge = e;
 219                         e->to->via = indirect ? n->via : e->to;
 220                         e->to->options = e->options;
 221
 222                         if(e->to->address.sa.sa_family == AF_UNSPEC && e->address.sa.sa_family != AF_UNKNOWN)
 223                                 update_node_udp(e->to, &e->address);
 224
 225                         list_insert_tail(todo_list, e->to);
 226                 }
 227
 228                 todonext = from->next;
 229                 list_delete_node(todo_list, from);
 230         }
 231
 232         list_free(todo_list);
 233
 234         /* Check reachability status. */
 235
 236         for(node = node_tree->head; node; node = next) {
 237                 next = node->next;
 238                 n = node->data;
 239
 240                 if(n->status.visited != n->status.reachable) {
 241                         n->status.reachable = !n->status.reachable;
 242
 243                         if(n->status.reachable) {
 244                                 ifdebug(TRAFFIC) logger(LOG_DEBUG, "Node %s (%s) became reachable",
 245                                            n->name, n->hostname);
 246                         } else {
 247                                 ifdebug(TRAFFIC) logger(LOG_DEBUG, "Node %s (%s) became unreachable",
 248                                            n->name, n->hostname);
 249                         }
 250
 251                         /* TODO: only clear status.validkey if node is unreachable? */
 252
 253                         n->status.validkey = false;
 254                         n->last_req_key = 0;
 255
 256                         n->maxmtu = MTU;
 257                         n->minmtu = 0;
 258                         n->mtuprobes = 0;
 259
 260                         if(n->mtuevent) {
 261                                 event_del(n->mtuevent);
 262                                 n->mtuevent = NULL;
 263                         }
 264
 265                         xasprintf(&envp[0], "NETNAME=%s", netname ? : "");
 266                         xasprintf(&envp[1], "DEVICE=%s", device ? : "");
 267                         xasprintf(&envp[2], "INTERFACE=%s", iface ? : "");
 268                         xasprintf(&envp[3], "NODE=%s", n->name);
 269                         sockaddr2str(&n->address, &address, &port);
 270                         xasprintf(&envp[4], "REMOTEADDRESS=%s", address);
 271                         xasprintf(&envp[5], "REMOTEPORT=%s", port);
 272                         xasprintf(&envp[6], "NAME=%s", myself->name);
 273
 274                         execute_script(n->status.reachable ? "host-up" : "host-down", envp);
 275
 276                         xasprintf(&name,
 277                                          n->status.reachable ? "hosts/%s-up" : "hosts/%s-down",
 278                                          n->name);
 279                         execute_script(name, envp);
 280
 281                         free(name);
 282                         free(address);
 283                         free(port);
 284
 285                         for(i = 0; i < 7; i++)
 286                                 free(envp[i]);
 287
 288                         subnet_update(n, NULL, n->status.reachable);
 289
 290                         if(!n->status.reachable) {
 291                                 update_node_udp(n, NULL);
 292                                 memset(&n->status, 0, sizeof n->status);
 293                                 n->options = 0;
 294                         } else if(n->connection) {
 295                                 send_ans_key(n);
 296                         }
 297                 }
 298         }
 299 }
 300
 301 void graph(void) {
 302         subnet_cache_flush();
 303         sssp_bfs();
 304         mst_kruskal();
 305         graph_changed = true;
 306 }
 307
 308
 309
 310 /* Dump nodes and edges to a graphviz file.
 311
 312    The file can be converted to an image with
 313    dot -Tpng graph_filename -o image_filename.png -Gconcentrate=true
 314 */
 315
 316 void dump_graph(void) {
 317         avl_node_t *node;
 318         node_t *n;
 319         edge_t *e;
 320         char *filename = NULL, *tmpname = NULL;
 321         FILE *file, *pipe = NULL;
 322
 323         if(!graph_changed || !get_config_string(lookup_config(config_tree, "GraphDumpFile"), &filename))
 324                 return;
 325
 326         graph_changed = false;
 327
 328         ifdebug(PROTOCOL) logger(LOG_NOTICE, "Dumping graph");
 329
 330         if(filename[0] == '|') {
 331                 file = pipe = popen(filename + 1, "w");
 332         } else {
 333                 xasprintf(&tmpname, "%s.new", filename);
 334                 file = fopen(tmpname, "w");
 335         }
 336
 337         if(!file) {
 338                 logger(LOG_ERR, "Unable to open graph dump file %s: %s", filename, strerror(errno));
 339                 free(tmpname);
 340                 return;
 341         }
 342
 343         fprintf(file, "digraph {\n");
 344
 345         /* dump all nodes first */
 346         for(node = node_tree->head; node; node = node->next) {
 347                 n = node->data;
 348                 fprintf(file, " %s [label = \"%s\"];\n", n->name, n->name);
 349         }
 350
 351         /* now dump all edges */
 352         for(node = edge_weight_tree->head; node; node = node->next) {
 353                 e = node->data;
 354                 fprintf(file, " %s -> %s;\n", e->from->name, e->to->name);
 355         }
 356
 357         fprintf(file, "}\n");
 358
 359         if(pipe) {
 360                 pclose(pipe);
 361         } else {
 362                 fclose(file);
 363 #ifdef HAVE_MINGW
 364                 unlink(filename);
 365 #endif
 366                 rename(tmpname, filename);
 367                 free(tmpname);
 368         }
 369 }