2 graph.c -- graph algorithms
3 Copyright (C) 2001-2013 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 "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_each(connection_t, c, connection_list)
72 c->status.mst = false;
74 logger(DEBUG_SCARY_THINGS, LOG_DEBUG, "Running Kruskal's algorithm:");
76 /* Clear visited status on nodes */
78 for splay_each(node_t, n, node_tree)
79 n->status.visited = false;
83 for splay_each(edge_t, e, edge_weight_tree) {
84 if(e->from->status.reachable) {
85 e->from->status.visited = true;
94 for splay_each(edge_t, e, edge_weight_tree) {
95 if(!e->reverse || (e->from->status.visited == e->to->status.visited)) {
100 e->from->status.visited = true;
101 e->to->status.visited = true;
104 e->connection->status.mst = true;
106 if(e->reverse->connection)
107 e->reverse->connection->status.mst = true;
109 logger(DEBUG_SCARY_THINGS, LOG_DEBUG, " Adding edge %s - %s weight %d", e->from->name, e->to->name, e->weight);
113 next = edge_weight_tree->head;
118 /* Implementation of a simple breadth-first search algorithm.
122 static void sssp_bfs(void) {
123 list_t *todo_list = list_alloc(NULL);
125 /* Clear visited status on nodes */
127 for splay_each(node_t, n, node_tree) {
128 n->status.visited = false;
129 n->status.indirect = true;
133 /* Begin with myself */
135 myself->status.visited = true;
136 myself->status.indirect = false;
137 myself->nexthop = myself;
138 myself->prevedge = NULL;
139 myself->via = myself;
140 myself->distance = 0;
141 list_insert_head(todo_list, myself);
143 /* Loop while todo_list is filled */
145 for list_each(node_t, n, todo_list) { /* "n" is the node from which we start */
146 logger(DEBUG_SCARY_THINGS, LOG_DEBUG, " Examining edges from %s", n->name);
151 for splay_each(edge_t, e, n->edge_tree) { /* "e" is the edge connected to "from" */
152 if(!e->reverse || e->to == myself)
159 ----->(n)---e-->(e->to)
163 Where e is an edge, (n) and (e->to) are nodes.
164 n->address is set to the e->address of the edge left of n to n.
165 We are currently examining the edge e right of n from n:
167 - If edge e provides for better reachability of e->to, update
168 e->to and (re)add it to the todo_list to (re)examine the reachability
172 bool indirect = n->status.indirect || e->options & OPTION_INDIRECT;
174 if(e->to->status.visited
175 && (!e->to->status.indirect || indirect)
176 && (e->to->distance != n->distance + 1 || e->weight >= e->to->prevedge->weight))
179 // Only update nexthop if it doesn't increase the path length
181 if(!e->to->status.visited || (e->to->distance == n->distance + 1 && e->weight >= e->to->prevedge->weight))
182 e->to->nexthop = (n->nexthop == myself) ? e->to : n->nexthop;
184 e->to->status.visited = true;
185 e->to->status.indirect = indirect;
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->status.reachable || (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 next = node->next; /* Because the list_insert_tail() above could have added something extra for us! */
198 list_delete_node(todo_list, node);
201 list_free(todo_list);
204 static void check_reachability(void) {
205 /* Check reachability status. */
207 int reachable_count = 0;
208 int became_reachable_count = 0;
209 int became_unreachable_count = 0;
210 for splay_each(node_t, n, node_tree) {
211 if(n->status.visited != n->status.reachable) {
212 n->status.reachable = !n->status.reachable;
213 n->last_state_change = now.tv_sec;
215 if(n->status.reachable) {
216 logger(DEBUG_TRAFFIC, LOG_DEBUG, "Node %s (%s) became reachable",
217 n->name, n->hostname);
219 became_reachable_count++;
221 logger(DEBUG_TRAFFIC, LOG_DEBUG, "Node %s (%s) became unreachable",
222 n->name, n->hostname);
224 became_unreachable_count++;
227 if(experimental && OPTION_VERSION(n->options) >= 2)
228 n->status.sptps = true;
230 /* TODO: only clear status.validkey if node is unreachable? */
232 n->status.validkey = false;
233 if(n->status.sptps) {
234 sptps_stop(&n->sptps);
235 n->status.waitingforkey = false;
239 n->status.udp_confirmed = false;
245 timeout_del(&n->udp_ping_timeout);
250 char *envp[8] = {NULL};
252 xasprintf(&envp[0], "NETNAME=%s", netname ? : "");
253 xasprintf(&envp[1], "DEVICE=%s", device ? : "");
254 xasprintf(&envp[2], "INTERFACE=%s", iface ? : "");
255 xasprintf(&envp[3], "NODE=%s", n->name);
256 sockaddr2str(&n->address, &address, &port);
257 xasprintf(&envp[4], "REMOTEADDRESS=%s", address);
258 xasprintf(&envp[5], "REMOTEPORT=%s", port);
259 xasprintf(&envp[6], "NAME=%s", myself->name);
261 execute_script(n->status.reachable ? "host-up" : "host-down", envp);
263 xasprintf(&name, n->status.reachable ? "hosts/%s-up" : "hosts/%s-down", n->name);
264 execute_script(name, envp);
270 for(int i = 0; i < 7; i++)
273 subnet_update(n, NULL, n->status.reachable);
275 if(!n->status.reachable) {
276 update_node_udp(n, NULL);
277 memset(&n->status, 0, sizeof n->status);
279 } else if(n->connection) {
280 // Speed up UDP probing by sending our key.
286 if(n->status.reachable && n != myself)
290 if (device_standby) {
291 if (reachable_count == 0 && became_unreachable_count > 0)
293 else if (reachable_count > 0 && reachable_count == became_reachable_count)
299 subnet_cache_flush();
301 check_reachability();