2 graph.c -- graph algorithms
3 Copyright (C) 2001-2012 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.
48 #include "connection.h"
63 /* Implementation of Kruskal's algorithm.
65 Please note that sorting on weight is already done by add_edge().
68 static void mst_kruskal(void) {
69 /* Clear MST status on connections */
71 for(list_node_t *node = connection_list->head; node; node = node->next) {
72 connection_t *c = node->data;
73 c->status.mst = false;
76 logger(DEBUG_SCARY_THINGS, LOG_DEBUG, "Running Kruskal's algorithm:");
78 /* Clear visited status on nodes */
80 for(splay_node_t *node = node_tree->head; node; node = node->next) {
81 node_t *n = node->data;
82 n->status.visited = false;
87 for(splay_node_t *node = edge_weight_tree->head, *next; node; node = next) {
89 edge_t *e = node->data;
91 if(!e->reverse || (e->from->status.visited && e->to->status.visited))
94 e->from->status.visited = true;
95 e->to->status.visited = true;
98 e->connection->status.mst = true;
100 if(e->reverse->connection)
101 e->reverse->connection->status.mst = true;
103 logger(DEBUG_SCARY_THINGS, LOG_DEBUG, " Adding edge %s - %s weight %d", e->from->name,
104 e->to->name, e->weight);
108 /* Implementation of a simple breadth-first search algorithm.
112 static void sssp_bfs(void) {
113 splay_node_t *node, *to;
117 list_node_t *from, *todonext;
120 todo_list = list_alloc(NULL);
122 /* Clear visited status on nodes */
124 for(node = node_tree->head; node; node = node->next) {
126 n->status.visited = false;
127 n->status.indirect = true;
131 /* Begin with myself */
133 myself->status.visited = true;
134 myself->status.indirect = false;
135 myself->nexthop = myself;
136 myself->prevedge = NULL;
137 myself->via = myself;
138 myself->distance = 0;
139 list_insert_head(todo_list, myself);
141 /* Loop while todo_list is filled */
143 for(from = todo_list->head; from; from = todonext) { /* "from" is the node from which we start */
148 for(to = n->edge_tree->head; to; to = to->next) { /* "to" is the edge connected to "from" */
158 ----->(n)---e-->(e->to)
162 Where e is an edge, (n) and (e->to) are nodes.
163 n->address is set to the e->address of the edge left of n to n.
164 We are currently examining the edge e right of n from n:
166 - If edge e provides for better reachability of e->to, update
167 e->to and (re)add it to the todo_list to (re)examine the reachability
171 indirect = n->status.indirect || e->options & OPTION_INDIRECT;
173 if(e->to->status.visited
174 && (!e->to->status.indirect || indirect)
175 && (e->to->distance != n->distance + 1 || e->weight >= e->to->prevedge->weight))
178 e->to->status.visited = true;
179 e->to->status.indirect = indirect;
180 e->to->nexthop = (n->nexthop == myself) ? e->to : n->nexthop;
182 e->to->via = indirect ? n->via : e->to;
183 e->to->options = e->options;
184 e->to->distance = n->distance + 1;
186 if(!e->to->status.reachable || (e->to->address.sa.sa_family == AF_UNSPEC && e->address.sa.sa_family != AF_UNKNOWN)
188 update_node_udp(e->to, &e->address);
190 list_insert_tail(todo_list, e->to);
193 todonext = from->next;
194 list_delete_node(todo_list, from);
197 list_free(todo_list);
200 static void check_reachability(void) {
201 splay_node_t *node, *next;
204 char *address, *port;
208 /* Check reachability status. */
210 for(node = node_tree->head; node; node = next) {
214 if(n->status.visited != n->status.reachable) {
215 n->status.reachable = !n->status.reachable;
216 n->last_state_change = time(NULL);
218 if(n->status.reachable) {
219 logger(DEBUG_TRAFFIC, LOG_DEBUG, "Node %s (%s) became reachable",
220 n->name, n->hostname);
222 logger(DEBUG_TRAFFIC, LOG_DEBUG, "Node %s (%s) became unreachable",
223 n->name, n->hostname);
226 if(experimental && OPTION_VERSION(n->options) >= 2)
227 n->status.sptps = true;
229 /* TODO: only clear status.validkey if node is unreachable? */
231 n->status.validkey = false;
232 if(n->status.sptps) {
233 sptps_stop(&n->sptps);
234 n->status.waitingforkey = false;
242 if(timeout_initialized(&n->mtuevent))
243 event_del(&n->mtuevent);
245 xasprintf(&envp[0], "NETNAME=%s", netname ? : "");
246 xasprintf(&envp[1], "DEVICE=%s", device ? : "");
247 xasprintf(&envp[2], "INTERFACE=%s", iface ? : "");
248 xasprintf(&envp[3], "NODE=%s", n->name);
249 sockaddr2str(&n->address, &address, &port);
250 xasprintf(&envp[4], "REMOTEADDRESS=%s", address);
251 xasprintf(&envp[5], "REMOTEPORT=%s", port);
254 execute_script(n->status.reachable ? "host-up" : "host-down", envp);
257 n->status.reachable ? "hosts/%s-up" : "hosts/%s-down",
259 execute_script(name, envp);
265 for(i = 0; i < 6; i++)
268 subnet_update(n, NULL, n->status.reachable);
270 if(!n->status.reachable) {
271 update_node_udp(n, NULL);
272 } else if(n->connection) {
273 if(n->status.sptps) {
274 if(n->connection->outgoing)
285 subnet_cache_flush();
287 check_reachability();