Improvements for PMTU discovery and IPv4 packet fragmentation.
[tinc] / src / net.c
1 /*
2     net.c -- most of the network code
3     Copyright (C) 1998-2003 Ivo Timmermans <ivo@o2w.nl>,
4                   2000-2003 Guus Sliepen <guus@sliepen.eu.org>
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
17     along with this program; if not, write to the Free Software
18     Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
19
20     $Id: net.c,v 1.35.4.203 2003/12/20 19:47:52 guus Exp $
21 */
22
23 #include "system.h"
24
25 #include <openssl/rand.h>
26
27 #include "utils.h"
28 #include "avl_tree.h"
29 #include "conf.h"
30 #include "connection.h"
31 #include "device.h"
32 #include "event.h"
33 #include "graph.h"
34 #include "logger.h"
35 #include "meta.h"
36 #include "net.h"
37 #include "netutl.h"
38 #include "process.h"
39 #include "protocol.h"
40 #include "route.h"
41 #include "subnet.h"
42 #include "xalloc.h"
43
44 bool do_purge = false;
45 volatile bool running = false;
46
47 time_t now = 0;
48
49 /* Purge edges and subnets of unreachable nodes. Use carefully. */
50
51 static void purge(void)
52 {
53         avl_node_t *nnode, *nnext, *enode, *enext, *snode, *snext;
54         node_t *n;
55         edge_t *e;
56         subnet_t *s;
57
58         cp();
59
60         ifdebug(PROTOCOL) logger(LOG_DEBUG, _("Purging unreachable nodes"));
61
62         /* Remove all edges and subnets owned by unreachable nodes. */
63
64         for(nnode = node_tree->head; nnode; nnode = nnext) {
65                 nnext = nnode->next;
66                 n = nnode->data;
67
68                 if(!n->status.reachable) {
69                         ifdebug(SCARY_THINGS) logger(LOG_DEBUG, _("Purging node %s (%s)"), n->name,
70                                            n->hostname);
71
72                         for(snode = n->subnet_tree->head; snode; snode = snext) {
73                                 snext = snode->next;
74                                 s = snode->data;
75                                 if(!tunnelserver)
76                                         send_del_subnet(broadcast, s);
77                                 subnet_del(n, s);
78                         }
79
80                         for(enode = n->edge_tree->head; enode; enode = enext) {
81                                 enext = enode->next;
82                                 e = enode->data;
83                                 if(!tunnelserver)
84                                         send_del_edge(broadcast, e);
85                                 edge_del(e);
86                         }
87                 }
88         }
89
90         /* Check if anyone else claims to have an edge to an unreachable node. If not, delete node. */
91
92         for(nnode = node_tree->head; nnode; nnode = nnext) {
93                 nnext = nnode->next;
94                 n = nnode->data;
95
96                 if(!n->status.reachable) {
97                         for(enode = edge_weight_tree->head; enode; enode = enext) {
98                                 enext = enode->next;
99                                 e = enode->data;
100
101                                 if(e->to == n)
102                                         break;
103                         }
104
105                         if(!enode)
106                                 node_del(n);
107                 }
108         }
109 }
110
111 /*
112   put all file descriptors in an fd_set array
113   While we're at it, purge stuff that needs to be removed.
114 */
115 static int build_fdset(fd_set * fs)
116 {
117         avl_node_t *node, *next;
118         connection_t *c;
119         int i, max = 0;
120
121         cp();
122
123         FD_ZERO(fs);
124
125         for(node = connection_tree->head; node; node = next) {
126                 next = node->next;
127                 c = node->data;
128
129                 if(c->status.remove) {
130                         connection_del(c);
131                         if(!connection_tree->head)
132                                 purge();
133                 } else {
134                         FD_SET(c->socket, fs);
135                         if(c->socket > max)
136                                 max = c->socket;
137                 }
138         }
139
140         for(i = 0; i < listen_sockets; i++) {
141                 FD_SET(listen_socket[i].tcp, fs);
142                 if(listen_socket[i].tcp > max)
143                         max = listen_socket[i].tcp;
144                 FD_SET(listen_socket[i].udp, fs);
145                 if(listen_socket[i].udp > max)
146                         max = listen_socket[i].udp;
147         }
148
149         FD_SET(device_fd, fs);
150         if(device_fd > max)
151                 max = device_fd;
152         
153         return max;
154 }
155
156 /*
157   Terminate a connection:
158   - Close the socket
159   - Remove associated edge and tell other connections about it if report = true
160   - Check if we need to retry making an outgoing connection
161   - Deactivate the host
162 */
163 void terminate_connection(connection_t *c, bool report)
164 {
165         cp();
166
167         if(c->status.remove)
168                 return;
169
170         ifdebug(CONNECTIONS) logger(LOG_NOTICE, _("Closing connection with %s (%s)"),
171                            c->name, c->hostname);
172
173         c->status.remove = true;
174         c->status.active = false;
175
176         if(c->node)
177                 c->node->connection = NULL;
178
179         if(c->socket)
180                 closesocket(c->socket);
181
182         if(c->edge) {
183                 if(report && !tunnelserver)
184                         send_del_edge(broadcast, c->edge);
185
186                 edge_del(c->edge);
187
188                 /* Run MST and SSSP algorithms */
189
190                 graph();
191
192                 /* If the node is not reachable anymore but we remember it had an edge to us, clean it up */
193
194                 if(report && !c->node->status.reachable) {
195                         edge_t *e;
196                         e = lookup_edge(c->node, myself);
197                         if(e) {
198                                 if(!tunnelserver)
199                                         send_del_edge(broadcast, e);
200                                 edge_del(e);
201                         }
202                 }
203         }
204
205         /* Check if this was our outgoing connection */
206
207         if(c->outgoing) {
208                 retry_outgoing(c->outgoing);
209                 c->outgoing = NULL;
210         }
211 }
212
213 /*
214   Check if the other end is active.
215   If we have sent packets, but didn't receive any,
216   then possibly the other end is dead. We send a
217   PING request over the meta connection. If the other
218   end does not reply in time, we consider them dead
219   and close the connection.
220 */
221 static void check_dead_connections(void)
222 {
223         avl_node_t *node, *next;
224         connection_t *c;
225
226         cp();
227
228         for(node = connection_tree->head; node; node = next) {
229                 next = node->next;
230                 c = node->data;
231
232                 if(c->last_ping_time + pingtimeout < now) {
233                         if(c->status.active) {
234                                 if(c->status.pinged) {
235                                         ifdebug(CONNECTIONS) logger(LOG_INFO, _("%s (%s) didn't respond to PING"),
236                                                            c->name, c->hostname);
237                                         c->status.timeout = true;
238                                         terminate_connection(c, true);
239                                 } else {
240                                         send_ping(c);
241                                 }
242                         } else {
243                                 if(c->status.remove) {
244                                         logger(LOG_WARNING, _("Old connection_t for %s (%s) status %04x still lingering, deleting..."),
245                                                    c->name, c->hostname, *(uint32_t *)&c->status);
246                                         connection_del(c);
247                                         continue;
248                                 }
249                                 ifdebug(CONNECTIONS) logger(LOG_WARNING, _("Timeout from %s (%s) during authentication"),
250                                                    c->name, c->hostname);
251                                 terminate_connection(c, false);
252                         }
253                 }
254         }
255 }
256
257 /*
258   check all connections to see if anything
259   happened on their sockets
260 */
261 static void check_network_activity(fd_set * f)
262 {
263         connection_t *c;
264         avl_node_t *node;
265         int result, i;
266         int len = sizeof(result);
267         vpn_packet_t packet;
268
269         cp();
270
271         if(FD_ISSET(device_fd, f)) {
272                 if(read_packet(&packet))
273                         route(myself, &packet);
274         }
275
276         for(node = connection_tree->head; node; node = node->next) {
277                 c = node->data;
278
279                 if(c->status.remove)
280                         continue;
281
282                 if(FD_ISSET(c->socket, f)) {
283                         if(c->status.connecting) {
284                                 c->status.connecting = false;
285                                 getsockopt(c->socket, SOL_SOCKET, SO_ERROR, &result, &len);
286
287                                 if(!result)
288                                         finish_connecting(c);
289                                 else {
290                                         ifdebug(CONNECTIONS) logger(LOG_DEBUG,
291                                                            _("Error while connecting to %s (%s): %s"),
292                                                            c->name, c->hostname, strerror(result));
293                                         closesocket(c->socket);
294                                         do_outgoing_connection(c);
295                                         continue;
296                                 }
297                         }
298
299                         if(!receive_meta(c)) {
300                                 terminate_connection(c, c->status.active);
301                                 continue;
302                         }
303                 }
304         }
305
306         for(i = 0; i < listen_sockets; i++) {
307                 if(FD_ISSET(listen_socket[i].udp, f))
308                         handle_incoming_vpn_data(listen_socket[i].udp);
309
310                 if(FD_ISSET(listen_socket[i].tcp, f))
311                         handle_new_meta_connection(listen_socket[i].tcp);
312         }
313 }
314
315 /*
316   this is where it all happens...
317 */
318 int main_loop(void)
319 {
320         fd_set fset;
321         struct timeval tv;
322         int r, maxfd;
323         time_t last_ping_check, last_config_check;
324         event_t *event;
325
326         cp();
327
328         last_ping_check = now;
329         last_config_check = now;
330         srand(now);
331
332         running = true;
333
334         while(running) {
335                 now = time(NULL);
336
337         //      tv.tv_sec = 1 + (rand() & 7);   /* Approx. 5 seconds, randomized to prevent global synchronisation effects */
338                 tv.tv_sec = 1;
339                 tv.tv_usec = 0;
340
341                 maxfd = build_fdset(&fset);
342
343                 r = select(maxfd + 1, &fset, NULL, NULL, &tv);
344
345                 if(r < 0) {
346                         if(errno != EINTR && errno != EAGAIN) {
347                                 logger(LOG_ERR, _("Error while waiting for input: %s"),
348                                            strerror(errno));
349                                 cp_trace();
350                                 dump_connections();
351                                 return 1;
352                         }
353
354                         continue;
355                 }
356
357                 check_network_activity(&fset);
358
359                 if(do_purge) {
360                         purge();
361                         do_purge = false;
362                 }
363
364                 /* Let's check if everybody is still alive */
365
366                 if(last_ping_check + pingtimeout < now) {
367                         check_dead_connections();
368                         last_ping_check = now;
369
370                         if(routing_mode == RMODE_SWITCH)
371                                 age_subnets();
372
373                         age_past_requests();
374
375                         /* Should we regenerate our key? */
376
377                         if(keyexpires < now) {
378                                 ifdebug(STATUS) logger(LOG_INFO, _("Regenerating symmetric key"));
379
380                                 RAND_pseudo_bytes(myself->key, myself->keylength);
381                                 if(myself->cipher)
382                                         EVP_DecryptInit_ex(&packet_ctx, myself->cipher, NULL, myself->key, myself->key + myself->cipher->key_len);
383                                 send_key_changed(broadcast, myself);
384                                 keyexpires = now + keylifetime;
385                         }
386                 }
387
388
389                 while((event = get_expired_event())) {
390                         event->handler(event->data);
391                         free(event);
392                 }
393
394                 if(sigalrm) {
395                         logger(LOG_INFO, _("Flushing event queue"));
396
397                         while(event_tree->head) {
398                                 event = event_tree->head->data;
399                                 event->handler(event->data);
400                                 event_del(event);
401                         }
402                         sigalrm = false;
403                 }
404
405                 if(sighup) {
406                         connection_t *c;
407                         avl_node_t *node;
408                         char *fname;
409                         struct stat s;
410                         
411                         sighup = false;
412                         
413                         /* Reread our own configuration file */
414
415                         exit_configuration(&config_tree);
416                         init_configuration(&config_tree);
417
418                         if(!read_server_config()) {
419                                 logger(LOG_ERR, _("Unable to reread configuration file, exitting."));
420                                 return 1;
421                         }
422
423                         /* Close connections to hosts that have a changed or deleted host config file */
424                         
425                         for(node = connection_tree->head; node; node = node->next) {
426                                 c = node->data;
427                                 
428                                 if(c->outgoing) {
429                                         free(c->outgoing->name);
430                                         freeaddrinfo(c->outgoing->ai);
431                                         free(c->outgoing);
432                                         c->outgoing = NULL;
433                                 }
434                                 
435                                 asprintf(&fname, "%s/hosts/%s", confbase, c->name);
436                                 if(stat(fname, &s) || s.st_mtime > last_config_check)
437                                         terminate_connection(c, c->status.active);
438                                 free(fname);
439                         }
440
441                         last_config_check = now;
442
443                         /* Try to make outgoing connections */
444                         
445                         try_outgoing_connections();
446                 }
447         }
448
449         return 0;
450 }