git.meshlink.io Git - meshlink/blob - src/graph.c

   1 /*
   2     graph.c -- graph algorithms
   3     Copyright (C) 2001-2010 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 "protocol.h"
  57 #include "subnet.h"
  58 #include "utils.h"
  59 #include "xalloc.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         avl_node_t *node, *next;
  70         edge_t *e;
  71         node_t *n;
  72         connection_t *c;
  73         int nodes = 0;
  74         int safe_edges = 0;
  75         bool skipped;
  76
  77         /* Clear MST status on connections */
  78
  79         for(node = connection_tree->head; node; node = node->next) {
  80                 c = node->data;
  81                 c->status.mst = false;
  82         }
  83
  84         /* Do we have something to do at all? */
  85
  86         if(!edge_weight_tree->head)
  87                 return;
  88
  89         ifdebug(SCARY_THINGS) logger(LOG_DEBUG, "Running Kruskal's algorithm:");
  90
  91         /* Clear visited status on nodes */
  92
  93         for(node = node_tree->head; node; node = node->next) {
  94                 n = node->data;
  95                 n->status.visited = false;
  96                 nodes++;
  97         }
  98
  99         /* Starting point */
 100
 101         for(node = edge_weight_tree->head; node; node = node->next) {
 102                 e = node->data;
 103                 if(e->from->status.reachable) {
 104                         e->from->status.visited = true;
 105                         break;
 106                 }
 107         }
 108
 109         /* Add safe edges */
 110
 111         for(skipped = false, node = edge_weight_tree->head; node; node = next) {
 112                 next = node->next;
 113                 e = node->data;
 114
 115                 if(!e->reverse || e->from->status.visited == e->to->status.visited) {
 116                         skipped = true;
 117                         continue;
 118                 }
 119
 120                 e->from->status.visited = true;
 121                 e->to->status.visited = true;
 122
 123                 if(e->connection)
 124                         e->connection->status.mst = true;
 125
 126                 if(e->reverse->connection)
 127                         e->reverse->connection->status.mst = true;
 128
 129                 safe_edges++;
 130
 131                 ifdebug(SCARY_THINGS) logger(LOG_DEBUG, " Adding edge %s - %s weight %d", e->from->name,
 132                                    e->to->name, e->weight);
 133
 134                 if(skipped) {
 135                         skipped = false;
 136                         next = edge_weight_tree->head;
 137                         continue;
 138                 }
 139         }
 140
 141         ifdebug(SCARY_THINGS) logger(LOG_DEBUG, "Done, counted %d nodes and %d safe edges.", nodes,
 142                            safe_edges);
 143 }
 144
 145 /* Implementation of a simple breadth-first search algorithm.
 146    Running time: O(E)
 147 */
 148
 149 void sssp_bfs(void) {
 150         avl_node_t *node, *next, *to;
 151         edge_t *e;
 152         node_t *n;
 153         list_t *todo_list;
 154         list_node_t *from, *todonext;
 155         bool indirect;
 156         char *name;
 157         char *address, *port;
 158         char *envp[7];
 159         int i;
 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 edge e provides for better reachability of e->to, update
 203                              e->to and (re)add it to the todo_list to (re)examine the reachability
 204                              of nodes behind it.
 205                          */
 206
 207                         indirect = n->status.indirect || e->options & OPTION_INDIRECT;
 208
 209                         if(e->to->status.visited
 210                            && (!e->to->status.indirect || indirect))
 211                                 continue;
 212
 213                         e->to->status.visited = true;
 214                         e->to->status.indirect = indirect;
 215                         e->to->nexthop = (n->nexthop == myself) ? e->to : n->nexthop;
 216                         e->to->via = indirect ? n->via : e->to;
 217                         e->to->options = e->options;
 218
 219                         if(e->to->address.sa.sa_family == AF_UNSPEC && e->address.sa.sa_family != AF_UNKNOWN)
 220                                 update_node_udp(e->to, &e->address);
 221
 222                         list_insert_tail(todo_list, e->to);
 223                 }
 224
 225                 todonext = from->next;
 226                 list_delete_node(todo_list, from);
 227         }
 228
 229         list_free(todo_list);
 230
 231         /* Check reachability status. */
 232
 233         for(node = node_tree->head; node; node = next) {
 234                 next = node->next;
 235                 n = node->data;
 236
 237                 if(n->status.visited != n->status.reachable) {
 238                         n->status.reachable = !n->status.reachable;
 239
 240                         if(n->status.reachable) {
 241                                 ifdebug(TRAFFIC) logger(LOG_DEBUG, "Node %s (%s) became reachable",
 242                                            n->name, n->hostname);
 243                         } else {
 244                                 ifdebug(TRAFFIC) logger(LOG_DEBUG, "Node %s (%s) became unreachable",
 245                                            n->name, n->hostname);
 246                         }
 247
 248                         /* TODO: only clear status.validkey if node is unreachable? */
 249
 250                         n->status.validkey = false;
 251                         n->last_req_key = 0;
 252
 253                         n->maxmtu = MTU;
 254                         n->minmtu = 0;
 255                         n->mtuprobes = 0;
 256
 257                         if(n->mtuevent) {
 258                                 event_del(n->mtuevent);
 259                                 n->mtuevent = NULL;
 260                         }
 261
 262                         xasprintf(&envp[0], "NETNAME=%s", netname ? : "");
 263                         xasprintf(&envp[1], "DEVICE=%s", device ? : "");
 264                         xasprintf(&envp[2], "INTERFACE=%s", iface ? : "");
 265                         xasprintf(&envp[3], "NODE=%s", n->name);
 266                         sockaddr2str(&n->address, &address, &port);
 267                         xasprintf(&envp[4], "REMOTEADDRESS=%s", address);
 268                         xasprintf(&envp[5], "REMOTEPORT=%s", port);
 269                         envp[6] = NULL;
 270
 271                         execute_script(n->status.reachable ? "host-up" : "host-down", envp);
 272
 273                         xasprintf(&name,
 274                                          n->status.reachable ? "hosts/%s-up" : "hosts/%s-down",
 275                                          n->name);
 276                         execute_script(name, envp);
 277
 278                         free(name);
 279                         free(address);
 280                         free(port);
 281
 282                         for(i = 0; i < 6; i++)
 283                                 free(envp[i]);
 284
 285                         subnet_update(n, NULL, n->status.reachable);
 286
 287                         if(!n->status.reachable)
 288                                 update_node_udp(n, NULL);
 289                         else if(n->connection)
 290                                 send_ans_key(n);
 291                 }
 292         }
 293 }
 294
 295 void graph(void) {
 296         subnet_cache_flush();
 297         sssp_bfs();
 298         mst_kruskal();
 299         graph_changed = true;
 300 }
 301
 302
 303
 304 /* Dump nodes and edges to a graphviz file.
 305
 306    The file can be converted to an image with
 307    dot -Tpng graph_filename -o image_filename.png -Gconcentrate=true
 308 */
 309
 310 void dump_graph(void) {
 311         avl_node_t *node;
 312         node_t *n;
 313         edge_t *e;
 314         char *filename = NULL, *tmpname = NULL;
 315         FILE *file;
 316
 317         if(!graph_changed || !get_config_string(lookup_config(config_tree, "GraphDumpFile"), &filename))
 318                 return;
 319
 320         graph_changed = false;
 321
 322         ifdebug(PROTOCOL) logger(LOG_NOTICE, "Dumping graph");
 323
 324         if(filename[0] == '|') {
 325                 file = popen(filename + 1, "w");
 326         } else {
 327                 xasprintf(&tmpname, "%s.new", filename);
 328                 file = fopen(tmpname, "w");
 329         }
 330
 331         if(!file) {
 332                 logger(LOG_ERR, "Unable to open graph dump file %s: %s", filename, strerror(errno));
 333                 free(tmpname);
 334                 return;
 335         }
 336
 337         fprintf(file, "digraph {\n");
 338
 339         /* dump all nodes first */
 340         for(node = node_tree->head; node; node = node->next) {
 341                 n = node->data;
 342                 fprintf(file, " %s [label = \"%s\"];\n", n->name, n->name);
 343         }
 344
 345         /* now dump all edges */
 346         for(node = edge_weight_tree->head; node; node = node->next) {
 347                 e = node->data;
 348                 fprintf(file, " %s -> %s;\n", e->from->name, e->to->name);
 349         }
 350
 351         fprintf(file, "}\n");
 352
 353         if(filename[0] == '|') {
 354                 pclose(file);
 355         } else {
 356                 fclose(file);
 357 #ifdef HAVE_MINGW
 358                 unlink(filename);
 359 #endif
 360                 rename(tmpname, filename);
 361                 free(tmpname);
 362         }
 363 }