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

   1 /*
   2     graph.c -- graph algorithms
   3     Copyright (C) 2001-2009 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 "subnet.h"
  57 #include "utils.h"
  58 #include "xalloc.h"
  59
  60 static bool graph_changed = true;
  61
  62 /* Implementation of Kruskal's algorithm.
  63    Running time: O(EN)
  64    Please note that sorting on weight is already done by add_edge().
  65 */
  66
  67 void mst_kruskal(void) {
  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         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[7];
 160         int i;
 161
 162         cp();
 163
 164         todo_list = list_alloc(NULL);
 165
 166         /* Clear visited status on nodes */
 167
 168         for(node = node_tree->head; node; node = node->next) {
 169                 n = node->data;
 170                 n->status.visited = false;
 171                 n->status.indirect = true;
 172         }
 173
 174         /* Begin with myself */
 175
 176         myself->status.visited = true;
 177         myself->status.indirect = false;
 178         myself->nexthop = myself;
 179         myself->via = myself;
 180         list_insert_head(todo_list, myself);
 181
 182         /* Loop while todo_list is filled */
 183
 184         for(from = todo_list->head; from; from = todonext) {    /* "from" is the node from which we start */
 185                 n = from->data;
 186
 187                 for(to = n->edge_tree->head; to; to = to->next) {       /* "to" is the edge connected to "from" */
 188                         e = to->data;
 189
 190                         if(!e->reverse)
 191                                 continue;
 192
 193                         /* Situation:
 194
 195                                    /
 196                                   /
 197                            ----->(n)---e-->(e->to)
 198                                   \
 199                                    \
 200
 201                            Where e is an edge, (n) and (e->to) are nodes.
 202                            n->address is set to the e->address of the edge left of n to n.
 203                            We are currently examining the edge e right of n from n:
 204
 205                            - If e->reverse->address != n->address, then e->to is probably
 206                              not reachable for the nodes left of n. We do as if the indirectdata
 207                              flag is set on edge e.
 208                            - If edge e provides for better reachability of e->to, update
 209                              e->to and (re)add it to the todo_list to (re)examine the reachability
 210                              of nodes behind it.
 211                          */
 212
 213                         indirect = n->status.indirect || e->options & OPTION_INDIRECT
 214                                 || ((n != myself) && sockaddrcmp(&n->address, &e->reverse->address));
 215
 216                         if(e->to->status.visited
 217                            && (!e->to->status.indirect || indirect))
 218                                 continue;
 219
 220                         e->to->status.visited = true;
 221                         e->to->status.indirect = indirect;
 222                         e->to->nexthop = (n->nexthop == myself) ? e->to : n->nexthop;
 223                         e->to->via = indirect ? n->via : e->to;
 224                         e->to->options = e->options;
 225
 226                         if(e->to->address.sa.sa_family == AF_UNSPEC && e->address.sa.sa_family != AF_UNKNOWN)
 227                                 update_node_udp(e->to, &e->address);
 228
 229                         list_insert_tail(todo_list, e->to);
 230                 }
 231
 232                 todonext = from->next;
 233                 list_delete_node(todo_list, from);
 234         }
 235
 236         list_free(todo_list);
 237
 238         /* Check reachability status. */
 239
 240         for(node = node_tree->head; node; node = next) {
 241                 next = node->next;
 242                 n = node->data;
 243
 244                 if(n->status.visited != n->status.reachable) {
 245                         n->status.reachable = !n->status.reachable;
 246
 247                         if(n->status.reachable) {
 248                                 ifdebug(TRAFFIC) logger(LOG_DEBUG, _("Node %s (%s) became reachable"),
 249                                            n->name, n->hostname);
 250                         } else {
 251                                 ifdebug(TRAFFIC) logger(LOG_DEBUG, _("Node %s (%s) became unreachable"),
 252                                            n->name, n->hostname);
 253                         }
 254
 255                         /* TODO: only clear status.validkey if node is unreachable? */
 256
 257                         n->status.validkey = false;
 258                         n->status.waitingforkey = false;
 259
 260                         n->maxmtu = MTU;
 261                         n->minmtu = 0;
 262                         n->mtuprobes = 0;
 263
 264                         if(n->mtuevent) {
 265                                 event_del(n->mtuevent);
 266                                 n->mtuevent = NULL;
 267                         }
 268
 269                         xasprintf(&envp[0], "NETNAME=%s", netname ? : "");
 270                         xasprintf(&envp[1], "DEVICE=%s", device ? : "");
 271                         xasprintf(&envp[2], "INTERFACE=%s", iface ? : "");
 272                         xasprintf(&envp[3], "NODE=%s", n->name);
 273                         sockaddr2str(&n->address, &address, &port);
 274                         xasprintf(&envp[4], "REMOTEADDRESS=%s", address);
 275                         xasprintf(&envp[5], "REMOTEPORT=%s", port);
 276                         envp[6] = NULL;
 277
 278                         execute_script(n->status.reachable ? "host-up" : "host-down", envp);
 279
 280                         xasprintf(&name,
 281                                          n->status.reachable ? "hosts/%s-up" : "hosts/%s-down",
 282                                          n->name);
 283                         execute_script(name, envp);
 284
 285                         free(name);
 286                         free(address);
 287                         free(port);
 288
 289                         for(i = 0; i < 6; i++)
 290                                 free(envp[i]);
 291
 292                         subnet_update(n, NULL, n->status.reachable);
 293                 }
 294         }
 295 }
 296
 297 void graph(void) {
 298         subnet_cache_flush();
 299         sssp_bfs();
 300         mst_kruskal();
 301         graph_changed = true;
 302 }
 303
 304
 305
 306 /* Dump nodes and edges to a graphviz file.
 307
 308    The file can be converted to an image with
 309    dot -Tpng graph_filename -o image_filename.png -Gconcentrate=true
 310 */
 311
 312 void dump_graph(void) {
 313         avl_node_t *node;
 314         node_t *n;
 315         edge_t *e;
 316         char *filename = NULL, *tmpname = NULL;
 317         FILE *file;
 318
 319         if(!graph_changed || !get_config_string(lookup_config(config_tree, "GraphDumpFile"), &filename))
 320                 return;
 321
 322         graph_changed = false;
 323
 324         ifdebug(PROTOCOL) logger(LOG_NOTICE, "Dumping graph");
 325
 326         if(filename[0] == '|') {
 327                 file = popen(filename + 1, "w");
 328         } else {
 329                 xasprintf(&tmpname, "%s.new", filename);
 330                 file = fopen(tmpname, "w");
 331         }
 332
 333         if(!file) {
 334                 logger(LOG_ERR, "Unable to open graph dump file %s: %s", filename, strerror(errno));
 335                 free(tmpname);
 336                 return;
 337         }
 338
 339         fprintf(file, "digraph {\n");
 340
 341         /* dump all nodes first */
 342         for(node = node_tree->head; node; node = node->next) {
 343                 n = node->data;
 344                 fprintf(file, " %s [label = \"%s\"];\n", n->name, n->name);
 345         }
 346
 347         /* now dump all edges */
 348         for(node = edge_weight_tree->head; node; node = node->next) {
 349                 e = node->data;
 350                 fprintf(file, " %s -> %s;\n", e->from->name, e->to->name);
 351         }
 352
 353         fprintf(file, "}\n");
 354
 355         if(filename[0] == '|') {
 356                 pclose(file);
 357         } else {
 358                 fclose(file);
 359 #ifdef HAVE_MINGW
 360                 unlink(filename);
 361 #endif
 362                 rename(tmpname, filename);
 363                 free(tmpname);
 364         }
 365 }