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

   1 /*
   2     graph.c -- graph algorithms
   3     Copyright (C) 2001-2011 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 "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[7];
 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->via = myself;
 178         list_insert_head(todo_list, myself);
 179
 180         /* Loop while todo_list is filled */
 181
 182         for(from = todo_list->head; from; from = todonext) {    /* "from" is the node from which we start */
 183                 n = from->data;
 184
 185                 for(to = n->edge_tree->head; to; to = to->next) {       /* "to" is the edge connected to "from" */
 186                         e = to->data;
 187
 188                         if(!e->reverse)
 189                                 continue;
 190
 191                         /* Situation:
 192
 193                                    /
 194                                   /
 195                            ----->(n)---e-->(e->to)
 196                                   \
 197                                    \
 198
 199                            Where e is an edge, (n) and (e->to) are nodes.
 200                            n->address is set to the e->address of the edge left of n to n.
 201                            We are currently examining the edge e right of n from n:
 202
 203                            - If edge e provides for better reachability of e->to, update
 204                              e->to and (re)add it to the todo_list to (re)examine the reachability
 205                              of nodes behind it.
 206                          */
 207
 208                         indirect = n->status.indirect || e->options & OPTION_INDIRECT;
 209
 210                         if(e->to->status.visited
 211                            && (!e->to->status.indirect || indirect))
 212                                 continue;
 213
 214                         e->to->status.visited = true;
 215                         e->to->status.indirect = indirect;
 216                         e->to->nexthop = (n->nexthop == myself) ? e->to : n->nexthop;
 217                         e->to->via = indirect ? n->via : e->to;
 218                         e->to->options = e->options;
 219
 220                         if(e->to->address.sa.sa_family == AF_UNSPEC && e->address.sa.sa_family != AF_UNKNOWN)
 221                                 update_node_udp(e->to, &e->address);
 222
 223                         list_insert_tail(todo_list, e->to);
 224                 }
 225
 226                 todonext = from->next;
 227                 list_delete_node(todo_list, from);
 228         }
 229
 230         list_free(todo_list);
 231
 232         /* Check reachability status. */
 233
 234         for(node = node_tree->head; node; node = next) {
 235                 next = node->next;
 236                 n = node->data;
 237
 238                 if(n->status.visited != n->status.reachable) {
 239                         n->status.reachable = !n->status.reachable;
 240
 241                         if(n->status.reachable) {
 242                                 ifdebug(TRAFFIC) logger(LOG_DEBUG, "Node %s (%s) became reachable",
 243                                            n->name, n->hostname);
 244                         } else {
 245                                 ifdebug(TRAFFIC) logger(LOG_DEBUG, "Node %s (%s) became unreachable",
 246                                            n->name, n->hostname);
 247                         }
 248
 249                         /* TODO: only clear status.validkey if node is unreachable? */
 250
 251                         n->status.validkey = false;
 252                         n->last_req_key = 0;
 253
 254                         n->maxmtu = MTU;
 255                         n->minmtu = 0;
 256                         n->mtuprobes = 0;
 257
 258                         if(n->mtuevent) {
 259                                 event_del(n->mtuevent);
 260                                 n->mtuevent = NULL;
 261                         }
 262
 263                         xasprintf(&envp[0], "NETNAME=%s", netname ? : "");
 264                         xasprintf(&envp[1], "DEVICE=%s", device ? : "");
 265                         xasprintf(&envp[2], "INTERFACE=%s", iface ? : "");
 266                         xasprintf(&envp[3], "NODE=%s", n->name);
 267                         sockaddr2str(&n->address, &address, &port);
 268                         xasprintf(&envp[4], "REMOTEADDRESS=%s", address);
 269                         xasprintf(&envp[5], "REMOTEPORT=%s", port);
 270                         envp[6] = NULL;
 271
 272                         execute_script(n->status.reachable ? "host-up" : "host-down", envp);
 273
 274                         xasprintf(&name,
 275                                          n->status.reachable ? "hosts/%s-up" : "hosts/%s-down",
 276                                          n->name);
 277                         execute_script(name, envp);
 278
 279                         free(name);
 280                         free(address);
 281                         free(port);
 282
 283                         for(i = 0; i < 6; i++)
 284                                 free(envp[i]);
 285
 286                         subnet_update(n, NULL, n->status.reachable);
 287
 288                         if(!n->status.reachable)
 289                                 update_node_udp(n, NULL);
 290                         else if(n->connection)
 291                                 send_ans_key(n);
 292                 }
 293         }
 294 }
 295
 296 void graph(void) {
 297         subnet_cache_flush();
 298         sssp_bfs();
 299         mst_kruskal();
 300         graph_changed = true;
 301 }
 302
 303
 304
 305 /* Dump nodes and edges to a graphviz file.
 306
 307    The file can be converted to an image with
 308    dot -Tpng graph_filename -o image_filename.png -Gconcentrate=true
 309 */
 310
 311 void dump_graph(void) {
 312         avl_node_t *node;
 313         node_t *n;
 314         edge_t *e;
 315         char *filename = NULL, *tmpname = NULL;
 316         FILE *file;
 317
 318         if(!graph_changed || !get_config_string(lookup_config(config_tree, "GraphDumpFile"), &filename))
 319                 return;
 320
 321         graph_changed = false;
 322
 323         ifdebug(PROTOCOL) logger(LOG_NOTICE, "Dumping graph");
 324
 325         if(filename[0] == '|') {
 326                 file = popen(filename + 1, "w");
 327         } else {
 328                 xasprintf(&tmpname, "%s.new", filename);
 329                 file = fopen(tmpname, "w");
 330         }
 331
 332         if(!file) {
 333                 logger(LOG_ERR, "Unable to open graph dump file %s: %s", filename, strerror(errno));
 334                 free(tmpname);
 335                 return;
 336         }
 337
 338         fprintf(file, "digraph {\n");
 339
 340         /* dump all nodes first */
 341         for(node = node_tree->head; node; node = node->next) {
 342                 n = node->data;
 343                 fprintf(file, " %s [label = \"%s\"];\n", n->name, n->name);
 344         }
 345
 346         /* now dump all edges */
 347         for(node = edge_weight_tree->head; node; node = node->next) {
 348                 e = node->data;
 349                 fprintf(file, " %s -> %s;\n", e->from->name, e->to->name);
 350         }
 351
 352         fprintf(file, "}\n");
 353
 354         if(filename[0] == '|') {
 355                 pclose(file);
 356         } else {
 357                 fclose(file);
 358 #ifdef HAVE_MINGW
 359                 unlink(filename);
 360 #endif
 361                 rename(tmpname, filename);
 362                 free(tmpname);
 363         }
 364 }