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_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->reverse || (e->from->status.visited && e->to->status.visited))
87 e->from->status.visited = true;
88 e->to->status.visited = true;
91 e->connection->status.mst = true;
93 if(e->reverse->connection)
94 e->reverse->connection->status.mst = true;
96 logger(DEBUG_SCARY_THINGS, LOG_DEBUG, " Adding edge %s - %s weight %d", e->from->name,
97 e->to->name, e->weight);
101 /* Implementation of a simple breadth-first search algorithm.
105 static void sssp_bfs(void) {
106 list_t *todo_list = list_alloc(NULL);
108 /* Clear visited status on nodes */
110 for splay_each(node_t, n, node_tree) {
111 n->status.visited = false;
112 n->status.indirect = true;
116 /* Begin with myself */
118 myself->status.visited = true;
119 myself->status.indirect = false;
120 myself->nexthop = myself;
121 myself->prevedge = NULL;
122 myself->via = myself;
123 myself->distance = 0;
124 list_insert_head(todo_list, myself);
126 /* Loop while todo_list is filled */
128 for list_each(node_t, n, todo_list) { /* "n" is the node from which we start */
129 logger(DEBUG_SCARY_THINGS, LOG_DEBUG, " Examining edges from %s", n->name);
134 for splay_each(edge_t, e, n->edge_tree) { /* "e" is the edge connected to "from" */
142 ----->(n)---e-->(e->to)
146 Where e is an edge, (n) and (e->to) are nodes.
147 n->address is set to the e->address of the edge left of n to n.
148 We are currently examining the edge e right of n from n:
150 - If edge e provides for better reachability of e->to, update
151 e->to and (re)add it to the todo_list to (re)examine the reachability
155 bool indirect = n->status.indirect || e->options & OPTION_INDIRECT;
157 if(e->to->status.visited
158 && (!e->to->status.indirect || indirect)
159 && (e->to->distance != n->distance + 1 || e->weight >= e->to->prevedge->weight))
162 e->to->status.visited = true;
163 e->to->status.indirect = indirect;
164 e->to->nexthop = (n->nexthop == myself) ? e->to : n->nexthop;
166 e->to->via = indirect ? n->via : e->to;
167 e->to->options = e->options;
168 e->to->distance = n->distance + 1;
170 if(!e->to->status.reachable || (e->to->address.sa.sa_family == AF_UNSPEC && e->address.sa.sa_family != AF_UNKNOWN))
171 update_node_udp(e->to, &e->address);
173 list_insert_tail(todo_list, e->to);
176 next = node->next; /* Because the list_insert_tail() above could have added something extra for us! */
177 list_delete_node(todo_list, node);
180 list_free(todo_list);
183 static void check_reachability(void) {
184 /* Check reachability status. */
186 for splay_each(node_t, n, node_tree) {
187 if(n->status.visited != n->status.reachable) {
188 n->status.reachable = !n->status.reachable;
189 n->last_state_change = time(NULL);
191 if(n->status.reachable) {
192 logger(DEBUG_TRAFFIC, LOG_DEBUG, "Node %s (%s) became reachable",
193 n->name, n->hostname);
195 logger(DEBUG_TRAFFIC, LOG_DEBUG, "Node %s (%s) became unreachable",
196 n->name, n->hostname);
199 if(experimental && OPTION_VERSION(n->options) >= 2)
200 n->status.sptps = true;
202 /* TODO: only clear status.validkey if node is unreachable? */
204 n->status.validkey = false;
205 if(n->status.sptps) {
206 sptps_stop(&n->sptps);
207 n->status.waitingforkey = false;
211 n->status.udp_confirmed = false;
216 if(timeout_initialized(&n->mtuevent))
217 event_del(&n->mtuevent);
224 xasprintf(&envp[0], "NETNAME=%s", netname ? : "");
225 xasprintf(&envp[1], "DEVICE=%s", device ? : "");
226 xasprintf(&envp[2], "INTERFACE=%s", iface ? : "");
227 xasprintf(&envp[3], "NODE=%s", n->name);
228 sockaddr2str(&n->address, &address, &port);
229 xasprintf(&envp[4], "REMOTEADDRESS=%s", address);
230 xasprintf(&envp[5], "REMOTEPORT=%s", port);
233 execute_script(n->status.reachable ? "host-up" : "host-down", envp);
235 xasprintf(&name, n->status.reachable ? "hosts/%s-up" : "hosts/%s-down", n->name);
236 execute_script(name, envp);
242 for(int i = 0; i < 6; i++)
245 subnet_update(n, NULL, n->status.reachable);
247 if(!n->status.reachable) {
248 update_node_udp(n, NULL);
249 } else if(n->connection) {
250 if(n->status.sptps) {
251 if(n->connection->outgoing)
262 subnet_cache_flush();
264 check_reachability();