Add a benchmark for the SPTPS protocol.
[tinc] / src / graph.c
1 /*
2     graph.c -- graph algorithms
3     Copyright (C) 2001-2013 Guus Sliepen <guus@tinc-vpn.org>,
4                   2001-2005 Ivo Timmermans
5
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.
10
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.
15
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.
19 */
20
21 /* We need to generate two trees from the graph:
22
23    1. A minimum spanning tree for broadcasts,
24    2. A single-source shortest path tree for unicasts.
25
26    Actually, the first one alone would suffice but would make unicast packets
27    take longer routes than necessary.
28
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
35    merge trees.
36
37    For the SSSP algorithm Dijkstra's seems to be a nice choice. Currently a
38    simple breadth-first search is presented here.
39
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.
43 */
44
45 #include "system.h"
46
47 #include "connection.h"
48 #include "device.h"
49 #include "edge.h"
50 #include "graph.h"
51 #include "list.h"
52 #include "logger.h"
53 #include "names.h"
54 #include "netutl.h"
55 #include "node.h"
56 #include "protocol.h"
57 #include "script.h"
58 #include "subnet.h"
59 #include "utils.h"
60 #include "xalloc.h"
61 #include "graph.h"
62
63 /* Implementation of Kruskal's algorithm.
64    Running time: O(EN)
65    Please note that sorting on weight is already done by add_edge().
66 */
67
68 static void mst_kruskal(void) {
69         /* Clear MST status on connections */
70
71         for list_each(connection_t, c, connection_list)
72                 c->status.mst = false;
73
74         logger(DEBUG_SCARY_THINGS, LOG_DEBUG, "Running Kruskal's algorithm:");
75
76         /* Clear visited status on nodes */
77
78         for splay_each(node_t, n, node_tree)
79                 n->status.visited = false;
80
81         /* Starting point */
82
83         for splay_each(edge_t, e, edge_weight_tree) {
84                 if(e->from->status.reachable) {
85                         e->from->status.visited = true;
86                         break;
87                 }
88         }
89
90         /* Add safe edges */
91
92         bool skipped = false;
93
94         for splay_each(edge_t, e, edge_weight_tree) {
95                 if(!e->reverse || (e->from->status.visited == e->to->status.visited)) {
96                         skipped = true;
97                         continue;
98                 }
99
100                 e->from->status.visited = true;
101                 e->to->status.visited = true;
102
103                 if(e->connection)
104                         e->connection->status.mst = true;
105
106                 if(e->reverse->connection)
107                         e->reverse->connection->status.mst = true;
108
109                 logger(DEBUG_SCARY_THINGS, LOG_DEBUG, " Adding edge %s - %s weight %d", e->from->name, e->to->name, e->weight);
110
111                 if(skipped) {
112                         skipped = false;
113                         next = edge_weight_tree->head;
114                 }
115         }
116 }
117
118 /* Implementation of a simple breadth-first search algorithm.
119    Running time: O(E)
120 */
121
122 static void sssp_bfs(void) {
123         list_t *todo_list = list_alloc(NULL);
124
125         /* Clear visited status on nodes */
126
127         for splay_each(node_t, n, node_tree) {
128                 n->status.visited = false;
129                 n->status.indirect = true;
130                 n->distance = -1;
131         }
132
133         /* Begin with myself */
134
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);
142
143         /* Loop while todo_list is filled */
144
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);
147
148                 if(n->distance < 0)
149                         abort();
150
151                 for splay_each(edge_t, e, n->edge_tree) {       /* "e" is the edge connected to "from" */
152                         if(!e->reverse)
153                                 continue;
154
155                         /* Situation:
156
157                                    /
158                                   /
159                            ----->(n)---e-->(e->to)
160                                   \
161                                    \
162
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:
166
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
169                              of nodes behind it.
170                          */
171
172                         bool indirect = n->status.indirect || e->options & OPTION_INDIRECT;
173
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))
177                                 continue;
178
179                         e->to->status.visited = true;
180                         e->to->status.indirect = indirect;
181                         e->to->nexthop = (n->nexthop == myself) ? e->to : n->nexthop;
182                         e->to->prevedge = e;
183                         e->to->via = indirect ? n->via : e->to;
184                         e->to->options = e->options;
185                         e->to->distance = n->distance + 1;
186
187                         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);
189
190                         list_insert_tail(todo_list, e->to);
191                 }
192
193                 next = node->next; /* Because the list_insert_tail() above could have added something extra for us! */
194                 list_delete_node(todo_list, node);
195         }
196
197         list_free(todo_list);
198 }
199
200 static void check_reachability(void) {
201         /* Check reachability status. */
202
203         for splay_each(node_t, n, node_tree) {
204                 if(n->status.visited != n->status.reachable) {
205                         n->status.reachable = !n->status.reachable;
206                         n->last_state_change = now.tv_sec;
207
208                         if(n->status.reachable) {
209                                 logger(DEBUG_TRAFFIC, LOG_DEBUG, "Node %s (%s) became reachable",
210                                            n->name, n->hostname);
211                         } else {
212                                 logger(DEBUG_TRAFFIC, LOG_DEBUG, "Node %s (%s) became unreachable",
213                                            n->name, n->hostname);
214                         }
215
216                         if(experimental && OPTION_VERSION(n->options) >= 2)
217                                 n->status.sptps = true;
218
219                         /* TODO: only clear status.validkey if node is unreachable? */
220
221                         n->status.validkey = false;
222                         if(n->status.sptps) {
223                                 sptps_stop(&n->sptps);
224                                 n->status.waitingforkey = false;
225                         }
226                         n->last_req_key = 0;
227
228                         n->status.udp_confirmed = false;
229                         n->maxmtu = MTU;
230                         n->minmtu = 0;
231                         n->mtuprobes = 0;
232
233                         timeout_del(&n->mtutimeout);
234
235                         char *name;
236                         char *address;
237                         char *port;
238                         char *envp[8] = {NULL};
239
240                         xasprintf(&envp[0], "NETNAME=%s", netname ? : "");
241                         xasprintf(&envp[1], "DEVICE=%s", device ? : "");
242                         xasprintf(&envp[2], "INTERFACE=%s", iface ? : "");
243                         xasprintf(&envp[3], "NODE=%s", n->name);
244                         sockaddr2str(&n->address, &address, &port);
245                         xasprintf(&envp[4], "REMOTEADDRESS=%s", address);
246                         xasprintf(&envp[5], "REMOTEPORT=%s", port);
247                         xasprintf(&envp[6], "NAME=%s", myself->name);
248
249                         execute_script(n->status.reachable ? "host-up" : "host-down", envp);
250
251                         xasprintf(&name, n->status.reachable ? "hosts/%s-up" : "hosts/%s-down", n->name);
252                         execute_script(name, envp);
253
254                         free(name);
255                         free(address);
256                         free(port);
257
258                         for(int i = 0; i < 7; i++)
259                                 free(envp[i]);
260
261                         subnet_update(n, NULL, n->status.reachable);
262
263                         if(!n->status.reachable) {
264                                 update_node_udp(n, NULL);
265                                 memset(&n->status, 0, sizeof n->status);
266                                 n->options = 0;
267                         } else if(n->connection) {
268                                 if(n->status.sptps) {
269                                         if(n->connection->outgoing)
270                                                 send_req_key(n);
271                                 } else {
272                                         send_ans_key(n);
273                                 }
274                         }
275                 }
276         }
277 }
278
279 void graph(void) {
280         subnet_cache_flush();
281         sssp_bfs();
282         check_reachability();
283         mst_kruskal();
284 }