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.
47 #include "splay_tree.h"
49 #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 splay_node_t *node, *next;
74 /* Clear MST status on connections */
76 for(node = connection_tree->head; node; node = node->next) {
78 c->status.mst = false;
81 logger(DEBUG_SCARY_THINGS, LOG_DEBUG, "Running Kruskal's algorithm:");
83 /* Clear visited status on nodes */
85 for(node = node_tree->head; node; node = node->next) {
87 n->status.visited = false;
92 for(node = edge_weight_tree->head; node; node = next) {
96 if(!e->reverse || (e->from->status.visited && e->to->status.visited))
99 e->from->status.visited = true;
100 e->to->status.visited = true;
103 e->connection->status.mst = true;
105 if(e->reverse->connection)
106 e->reverse->connection->status.mst = true;
108 logger(DEBUG_SCARY_THINGS, LOG_DEBUG, " Adding edge %s - %s weight %d", e->from->name,
109 e->to->name, e->weight);
113 /* Implementation of a simple breadth-first search algorithm.
117 static void sssp_bfs(void) {
118 splay_node_t *node, *to;
122 list_node_t *from, *todonext;
125 todo_list = list_alloc(NULL);
127 /* Clear visited status on nodes */
129 for(node = node_tree->head; node; node = node->next) {
131 n->status.visited = false;
132 n->status.indirect = true;
136 /* Begin with myself */
138 myself->status.visited = true;
139 myself->status.indirect = false;
140 myself->nexthop = myself;
141 myself->prevedge = NULL;
142 myself->via = myself;
143 myself->distance = 0;
144 list_insert_head(todo_list, myself);
146 /* Loop while todo_list is filled */
148 for(from = todo_list->head; from; from = todonext) { /* "from" is the node from which we start */
153 for(to = n->edge_tree->head; to; to = to->next) { /* "to" is the edge connected to "from" */
163 ----->(n)---e-->(e->to)
167 Where e is an edge, (n) and (e->to) are nodes.
168 n->address is set to the e->address of the edge left of n to n.
169 We are currently examining the edge e right of n from n:
171 - If edge e provides for better reachability of e->to, update
172 e->to and (re)add it to the todo_list to (re)examine the reachability
176 indirect = n->status.indirect || e->options & OPTION_INDIRECT;
178 if(e->to->status.visited
179 && (!e->to->status.indirect || indirect)
180 && (e->to->distance != n->distance + 1 || e->weight >= e->to->prevedge->weight))
183 e->to->status.visited = true;
184 e->to->status.indirect = indirect;
185 e->to->nexthop = (n->nexthop == myself) ? e->to : n->nexthop;
187 e->to->via = indirect ? n->via : e->to;
188 e->to->options = e->options;
189 e->to->distance = n->distance + 1;
191 if(e->to->address.sa.sa_family == AF_UNSPEC && e->address.sa.sa_family != AF_UNKNOWN)
192 update_node_udp(e->to, &e->address);
194 list_insert_tail(todo_list, e->to);
197 todonext = from->next;
198 list_delete_node(todo_list, from);
201 list_free(todo_list);
204 static void check_reachability(void) {
205 splay_node_t *node, *next;
208 char *address, *port;
212 /* Check reachability status. */
214 for(node = node_tree->head; node; node = next) {
218 if(n->status.visited != n->status.reachable) {
219 n->status.reachable = !n->status.reachable;
221 if(n->status.reachable) {
222 logger(DEBUG_TRAFFIC, LOG_DEBUG, "Node %s (%s) became reachable",
223 n->name, n->hostname);
225 logger(DEBUG_TRAFFIC, LOG_DEBUG, "Node %s (%s) became unreachable",
226 n->name, n->hostname);
229 if(experimental && OPTION_VERSION(n->options) >= 2)
230 n->status.sptps = true;
232 /* TODO: only clear status.validkey if node is unreachable? */
234 n->status.validkey = false;
241 if(timeout_initialized(&n->mtuevent))
242 event_del(&n->mtuevent);
244 xasprintf(&envp[0], "NETNAME=%s", netname ? : "");
245 xasprintf(&envp[1], "DEVICE=%s", device ? : "");
246 xasprintf(&envp[2], "INTERFACE=%s", iface ? : "");
247 xasprintf(&envp[3], "NODE=%s", n->name);
248 sockaddr2str(&n->address, &address, &port);
249 xasprintf(&envp[4], "REMOTEADDRESS=%s", address);
250 xasprintf(&envp[5], "REMOTEPORT=%s", port);
253 execute_script(n->status.reachable ? "host-up" : "host-down", envp);
256 n->status.reachable ? "hosts/%s-up" : "hosts/%s-down",
258 execute_script(name, envp);
264 for(i = 0; i < 6; i++)
267 subnet_update(n, NULL, n->status.reachable);
269 if(!n->status.reachable) {
270 update_node_udp(n, NULL);
271 } else if(n->connection) {
272 if(n->status.sptps) {
273 if(n->connection->outgoing)
284 subnet_cache_flush();
286 check_reachability();