2 graph.c -- graph algorithms
3 Copyright (C) 2001-2004 Guus Sliepen <guus@tinc-vpn.org>,
4 2001-2004 Ivo Timmermans <ivo@tinc-vpn.org>
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
17 along with this program; if not, write to the Free Software
18 Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
23 /* We need to generate two trees from the graph:
25 1. A minimum spanning tree for broadcasts,
26 2. A single-source shortest path tree for unicasts.
28 Actually, the first one alone would suffice but would make unicast packets
29 take longer routes than necessary.
31 For the MST algorithm we can choose from Prim's or Kruskal's. I personally
32 favour Kruskal's, because we make an extra AVL tree of edges sorted on
33 weights (metric). That tree only has to be updated when an edge is added or
34 removed, and during the MST algorithm we just have go linearly through that
35 tree, adding safe edges until #edges = #nodes - 1. The implementation here
36 however is not so fast, because I tried to avoid having to make a forest and
39 For the SSSP algorithm Dijkstra's seems to be a nice choice. Currently a
40 simple breadth-first search is presented here.
42 The SSSP algorithm will also be used to determine whether nodes are directly,
43 indirectly or not reachable from the source. It will also set the correct
44 destination address and port of a node if possible.
50 #include "connection.h"
60 /* Implementation of Kruskal's algorithm.
62 Please note that sorting on weight is already done by add_edge().
65 void mst_kruskal(void)
67 avl_node_t *node, *next;
77 /* Clear MST status on connections */
79 for(node = connection_tree->head; node; node = node->next) {
81 c->status.mst = false;
84 /* Do we have something to do at all? */
86 if(!edge_weight_tree->head)
89 ifdebug(SCARY_THINGS) logger(LOG_DEBUG, "Running Kruskal's algorithm:");
91 /* Clear visited status on nodes */
93 for(node = node_tree->head; node; node = node->next) {
95 n->status.visited = false;
101 ((edge_t *) edge_weight_tree->head->data)->from->status.visited = true;
105 for(skipped = false, node = edge_weight_tree->head; node; node = next) {
109 if(!e->reverse || e->from->status.visited == e->to->status.visited) {
114 e->from->status.visited = true;
115 e->to->status.visited = true;
118 e->connection->status.mst = true;
120 if(e->reverse->connection)
121 e->reverse->connection->status.mst = true;
125 ifdebug(SCARY_THINGS) logger(LOG_DEBUG, " Adding edge %s - %s weight %d", e->from->name,
126 e->to->name, e->weight);
130 next = edge_weight_tree->head;
135 ifdebug(SCARY_THINGS) logger(LOG_DEBUG, "Done, counted %d nodes and %d safe edges.", nodes,
139 /* Implementation of a simple breadth-first search algorithm.
145 avl_node_t *node, *next, *to;
149 list_node_t *from, *todonext;
152 char *address, *port;
158 todo_list = list_alloc(NULL);
160 /* Clear visited status on nodes */
162 for(node = node_tree->head; node; node = node->next) {
164 n->status.visited = false;
165 n->status.indirect = true;
168 /* Begin with myself */
170 myself->status.visited = true;
171 myself->status.indirect = false;
172 myself->nexthop = myself;
173 myself->via = myself;
174 list_insert_head(todo_list, myself);
176 /* Loop while todo_list is filled */
178 for(from = todo_list->head; from; from = todonext) { /* "from" is the node from which we start */
181 for(to = n->edge_tree->head; to; to = to->next) { /* "to" is the edge connected to "from" */
191 ----->(n)---e-->(e->to)
195 Where e is an edge, (n) and (e->to) are nodes.
196 n->address is set to the e->address of the edge left of n to n.
197 We are currently examining the edge e right of n from n:
199 - If e->reverse->address != n->address, then e->to is probably
200 not reachable for the nodes left of n. We do as if the indirectdata
201 flag is set on edge e.
202 - If edge e provides for better reachability of e->to, update
203 e->to and (re)add it to the todo_list to (re)examine the reachability
207 indirect = n->status.indirect || e->options & OPTION_INDIRECT
208 || ((n != myself) && sockaddrcmp(&n->address, &e->reverse->address));
210 if(e->to->status.visited
211 && (!e->to->status.indirect || indirect))
214 e->to->status.visited = true;
215 e->to->status.indirect = indirect;
216 e->to->nexthop = (n->nexthop == myself) ? e->to : n->nexthop;
217 e->to->via = indirect ? n->via : e->to;
218 e->to->options = e->options;
220 if(sockaddrcmp(&e->to->address, &e->address)) {
221 node = avl_unlink(node_udp_tree, e->to);
222 sockaddrfree(&e->to->address);
223 sockaddrcpy(&e->to->address, &e->address);
226 free(e->to->hostname);
228 e->to->hostname = sockaddr2hostname(&e->to->address);
229 avl_insert_node(node_udp_tree, node);
231 if(e->to->options & OPTION_PMTU_DISCOVERY) {
232 e->to->mtuprobes = 0;
235 if(e->to->status.validkey)
236 send_mtu_probe(e->to);
240 list_insert_tail(todo_list, e->to);
243 todonext = from->next;
244 list_delete_node(todo_list, from);
247 list_free(todo_list);
249 /* Check reachability status. */
251 for(node = node_tree->head; node; node = next) {
255 if(n->status.visited != n->status.reachable) {
256 n->status.reachable = !n->status.reachable;
258 if(n->status.reachable) {
259 ifdebug(TRAFFIC) logger(LOG_DEBUG, _("Node %s (%s) became reachable"),
260 n->name, n->hostname);
262 ifdebug(TRAFFIC) logger(LOG_DEBUG, _("Node %s (%s) became unreachable"),
263 n->name, n->hostname);
266 n->status.validkey = false;
267 n->status.waitingforkey = false;
273 asprintf(&envp[0], "NETNAME=%s", netname ? : "");
274 asprintf(&envp[1], "DEVICE=%s", device ? : "");
275 asprintf(&envp[2], "INTERFACE=%s", iface ? : "");
276 asprintf(&envp[3], "NODE=%s", n->name);
277 sockaddr2str(&n->address, &address, &port);
278 asprintf(&envp[4], "REMOTEADDRESS=%s", address);
279 asprintf(&envp[5], "REMOTEPORT=%s", port);
283 n->status.reachable ? "hosts/%s-up" : "hosts/%s-down",
285 execute_script(name, envp);
291 for(i = 0; i < 6; i++)
294 subnet_update(n, NULL, n->status.reachable);