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                         // Only update nexthop the first time we visit this node.
 216
 217                         if(!e->to->status.visited)
 218                                 e->to->nexthop = (n->nexthop == myself) ? e->to : n->nexthop;
 219
 220                         e->to->status.visited = true;
 221                         e->to->status.indirect = indirect;
 222                         e->to->prevedge = e;
 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->last_req_key = 0;
 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                         xasprintf(&envp[6], "NAME=%s", myself->name);
 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 < 7; i++)
 290                                 free(envp[i]);
 291
 292                         subnet_update(n, NULL, n->status.reachable);
 293
 294                         if(!n->status.reachable) {
 295                                 update_node_udp(n, NULL);
 296                                 memset(&n->status, 0, sizeof n->status);
 297                                 n->options = 0;
 298                         } else if(n->connection) {
 299                                 send_ans_key(n);
 300                         }
 301                 }
 302         }
 303 }
 304
 305 void graph(void) {
 306         subnet_cache_flush();
 307         sssp_bfs();
 308         mst_kruskal();
 309         graph_changed = true;
 310 }
 311
 312
 313
 314 /* Dump nodes and edges to a graphviz file.
 315
 316    The file can be converted to an image with
 317    dot -Tpng graph_filename -o image_filename.png -Gconcentrate=true
 318 */
 319
 320 void dump_graph(void) {
 321         avl_node_t *node;
 322         node_t *n;
 323         edge_t *e;
 324         char *filename = NULL, *tmpname = NULL;
 325         FILE *file, *pipe = NULL;
 326
 327         if(!graph_changed || !get_config_string(lookup_config(config_tree, "GraphDumpFile"), &filename))
 328                 return;
 329
 330         graph_changed = false;
 331
 332         ifdebug(PROTOCOL) logger(LOG_NOTICE, "Dumping graph");
 333
 334         if(filename[0] == '|') {
 335                 file = pipe = popen(filename + 1, "w");
 336         } else {
 337                 xasprintf(&tmpname, "%s.new", filename);
 338                 file = fopen(tmpname, "w");
 339         }
 340
 341         if(!file) {
 342                 logger(LOG_ERR, "Unable to open graph dump file %s: %s", filename, strerror(errno));
 343                 free(filename);
 344                 free(tmpname);
 345                 return;
 346         }
 347
 348         fprintf(file, "digraph {\n");
 349
 350         /* dump all nodes first */
 351         for(node = node_tree->head; node; node = node->next) {
 352                 n = node->data;
 353                 fprintf(file, " %s [label = \"%s\"];\n", n->name, n->name);
 354         }
 355
 356         /* now dump all edges */
 357         for(node = edge_weight_tree->head; node; node = node->next) {
 358                 e = node->data;
 359                 fprintf(file, " %s -> %s;\n", e->from->name, e->to->name);
 360         }
 361
 362         fprintf(file, "}\n");
 363
 364         if(pipe) {
 365                 pclose(pipe);
 366         } else {
 367                 fclose(file);
 368 #ifdef HAVE_MINGW
 369                 unlink(filename);
 370 #endif
 371                 if(rename(tmpname, filename))
 372                         logger(LOG_ERR, "Could not rename %s to %s: %s\n", tmpname, filename, strerror(errno));
 373                 free(tmpname);
 374         }
 375
 376         free(filename);
 377 }