2 graph.c -- graph algorithms
3 Copyright (C) 2001-2011 Guus Sliepen <guus@tinc-vpn.org>,
4 2001-2005 Ivo Timmermans
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.
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.
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.
21 /* We need to generate two trees from the graph:
23 1. A minimum spanning tree for broadcasts,
24 2. A single-source shortest path tree for unicasts.
26 Actually, the first one alone would suffice but would make unicast packets
27 take longer routes than necessary.
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
37 For the SSSP algorithm Dijkstra's seems to be a nice choice. Currently a
38 simple breadth-first search is presented here.
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.
47 #include "splay_tree.h"
49 #include "connection.h"
62 /* Implementation of Kruskal's algorithm.
64 Please note that sorting on weight is already done by add_edge().
67 void mst_kruskal(void) {
68 splay_node_t *node, *next;
73 /* Clear MST status on connections */
75 for(node = connection_tree->head; node; node = node->next) {
77 c->status.mst = false;
80 ifdebug(SCARY_THINGS) logger(LOG_DEBUG, "Running Kruskal's algorithm:");
82 /* Clear visited status on nodes */
84 for(node = node_tree->head; node; node = node->next) {
86 n->status.visited = false;
91 for(node = edge_weight_tree->head; node; node = next) {
95 if(!e->reverse || (e->from->status.visited && e->to->status.visited))
98 e->from->status.visited = true;
99 e->to->status.visited = true;
102 e->connection->status.mst = true;
104 if(e->reverse->connection)
105 e->reverse->connection->status.mst = true;
107 ifdebug(SCARY_THINGS) logger(LOG_DEBUG, " Adding edge %s - %s weight %d", e->from->name,
108 e->to->name, e->weight);
112 /* Implementation of Dijkstra's algorithm.
116 static void sssp_dijkstra(void) {
117 splay_node_t *node, *to;
121 list_node_t *lnode, *nnode;
124 todo_list = list_alloc(NULL);
126 ifdebug(SCARY_THINGS) logger(LOG_DEBUG, "Running Dijkstra's algorithm:");
128 /* Clear visited status on nodes */
130 for(node = node_tree->head; node; node = node->next) {
132 n->status.visited = false;
133 n->status.indirect = true;
137 /* Begin with myself */
139 myself->status.indirect = false;
140 myself->nexthop = myself;
141 myself->via = myself;
142 myself->distance = 0;
143 list_insert_head(todo_list, myself);
145 /* Loop while todo_list is filled */
147 while(todo_list->head) {
151 /* Select node from todo_list with smallest distance */
153 for(lnode = todo_list->head; lnode; lnode = lnode->next) {
155 if(!n || m->status.indirect < n->status.indirect || m->distance < n->distance) {
161 /* Mark this node as visited and remove it from the todo_list */
163 n->status.visited = true;
164 list_unlink_node(todo_list, nnode);
166 /* Update distance of neighbours and add them to the todo_list */
168 for(to = n->edge_tree->head; to; to = to->next) { /* "to" is the edge connected to "from" */
171 if(e->to->status.visited || !e->reverse)
178 ----->(n)---e-->(e->to)
182 Where e is an edge, (n) and (e->to) are nodes.
183 n->address is set to the e->address of the edge left of n to n.
184 We are currently examining the edge e right of n from n:
186 - If e->reverse->address != n->address, then e->to is probably
187 not reachable for the nodes left of n. We do as if the indirectdata
188 flag is set on edge e.
189 - If edge e provides for better reachability of e->to, update e->to.
192 if(e->to->distance < 0)
193 list_insert_tail(todo_list, e->to);
195 indirect = n->status.indirect || e->options & OPTION_INDIRECT || ((n != myself) && sockaddrcmp(&n->address, &e->reverse->address));
197 if(e->to->distance >= 0 && (!e->to->status.indirect || indirect) && e->to->distance <= n->distance + e->weight)
200 e->to->distance = n->distance + e->weight;
201 e->to->status.indirect = indirect;
202 e->to->nexthop = (n->nexthop == myself) ? e->to : n->nexthop;
203 e->to->via = indirect ? n->via : e->to;
204 e->to->options = e->options;
206 if(sockaddrcmp(&e->to->address, &e->address)) {
207 node = splay_unlink(node_udp_tree, e->to);
208 sockaddrfree(&e->to->address);
209 sockaddrcpy(&e->to->address, &e->address);
212 free(e->to->hostname);
214 e->to->hostname = sockaddr2hostname(&e->to->address);
217 splay_insert_node(node_udp_tree, node);
219 if(e->to->options & OPTION_PMTU_DISCOVERY) {
220 e->to->mtuprobes = 0;
223 if(e->to->status.validkey)
224 send_mtu_probe(e->to);
228 ifdebug(SCARY_THINGS) logger(LOG_DEBUG, " Updating edge %s - %s weight %d distance %d", e->from->name,
229 e->to->name, e->weight, e->to->distance);
233 list_free(todo_list);
236 /* Implementation of a simple breadth-first search algorithm.
240 void sssp_bfs(void) {
241 splay_node_t *node, *to;
245 list_node_t *from, *todonext;
248 todo_list = list_alloc(NULL);
250 /* Clear visited status on nodes */
252 for(node = node_tree->head; node; node = node->next) {
254 n->status.visited = false;
255 n->status.indirect = true;
258 /* Begin with myself */
260 myself->status.visited = true;
261 myself->status.indirect = false;
262 myself->nexthop = myself;
263 myself->via = myself;
264 list_insert_head(todo_list, myself);
266 /* Loop while todo_list is filled */
268 for(from = todo_list->head; from; from = todonext) { /* "from" is the node from which we start */
271 for(to = n->edge_tree->head; to; to = to->next) { /* "to" is the edge connected to "from" */
281 ----->(n)---e-->(e->to)
285 Where e is an edge, (n) and (e->to) are nodes.
286 n->address is set to the e->address of the edge left of n to n.
287 We are currently examining the edge e right of n from n:
289 - If edge e provides for better reachability of e->to, update
290 e->to and (re)add it to the todo_list to (re)examine the reachability
294 indirect = n->status.indirect || e->options & OPTION_INDIRECT;
296 if(e->to->status.visited
297 && (!e->to->status.indirect || indirect))
300 e->to->status.visited = true;
301 e->to->status.indirect = indirect;
302 e->to->nexthop = (n->nexthop == myself) ? e->to : n->nexthop;
303 e->to->via = indirect ? n->via : e->to;
304 e->to->options = e->options;
306 if(e->to->address.sa.sa_family == AF_UNSPEC && e->address.sa.sa_family != AF_UNKNOWN)
307 update_node_udp(e->to, &e->address);
309 list_insert_tail(todo_list, e->to);
312 todonext = from->next;
313 list_delete_node(todo_list, from);
316 list_free(todo_list);
319 static void check_reachability(void) {
320 splay_node_t *node, *next;
323 char *address, *port;
327 /* Check reachability status. */
329 for(node = node_tree->head; node; node = next) {
333 if(n->status.visited != n->status.reachable) {
334 n->status.reachable = !n->status.reachable;
336 if(n->status.reachable) {
337 ifdebug(TRAFFIC) logger(LOG_DEBUG, "Node %s (%s) became reachable",
338 n->name, n->hostname);
340 ifdebug(TRAFFIC) logger(LOG_DEBUG, "Node %s (%s) became unreachable",
341 n->name, n->hostname);
344 /* TODO: only clear status.validkey if node is unreachable? */
346 n->status.validkey = false;
353 if(timeout_initialized(&n->mtuevent))
354 event_del(&n->mtuevent);
356 xasprintf(&envp[0], "NETNAME=%s", netname ? : "");
357 xasprintf(&envp[1], "DEVICE=%s", device ? : "");
358 xasprintf(&envp[2], "INTERFACE=%s", iface ? : "");
359 xasprintf(&envp[3], "NODE=%s", n->name);
360 sockaddr2str(&n->address, &address, &port);
361 xasprintf(&envp[4], "REMOTEADDRESS=%s", address);
362 xasprintf(&envp[5], "REMOTEPORT=%s", port);
365 execute_script(n->status.reachable ? "host-up" : "host-down", envp);
368 n->status.reachable ? "hosts/%s-up" : "hosts/%s-down",
370 execute_script(name, envp);
376 for(i = 0; i < 6; i++)
379 subnet_update(n, NULL, n->status.reachable);
381 if(!n->status.reachable)
382 update_node_udp(n, NULL);
383 else if(n->connection)
390 subnet_cache_flush();
392 check_reachability();