1 /***
2 This file is part of avahi.
3
4 avahi is free software; you can redistribute it and/or modify it
5 under the terms of the GNU Lesser General Public License as
6 published by the Free Software Foundation; either version 2.1 of the
7 License, or (at your option) any later version.
8
9 avahi is distributed in the hope that it will be useful, but WITHOUT
10 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
11 or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General
12 Public License for more details.
13
14 You should have received a copy of the GNU Lesser General Public
15 License along with avahi; if not, write to the Free Software
16 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
17 USA.
18 ***/
19
20 #ifdef HAVE_CONFIG_H
21 #include <config.h>
22 #endif
23
24 #include <fcntl.h>
25 #include <unistd.h>
26 #include <sys/select.h>
27 #include <sys/socket.h>
28 #include <sys/un.h>
29 #include <errno.h>
30 #include <string.h>
31 #include <stdio.h>
32 #include <sys/ioctl.h>
33 #include <net/if.h>
34 #include <signal.h>
35 #include <sys/wait.h>
36 #include <getopt.h>
37 #include <assert.h>
38 #include <inttypes.h>
39 #include <stdlib.h>
40
41 #include <avahi-common/llist.h>
42 #include "avahi-common/avahi-malloc.h"
43 #include <avahi-common/address.h>
44
45 #include <libdaemon/dfork.h>
46 #include <libdaemon/dsignal.h>
47 #include <libdaemon/dlog.h>
48 #include <libdaemon/dpid.h>
49 #include <libdaemon/dexec.h>
50
51 #define BROWSE_DNS_SERVERS "BROWSE-DNS-SERVERS\n"
52
53 #define ENV_INTERFACE_DNS_SERVERS "AVAHI_INTERFACE_DNS_SERVERS"
54 #define ENV_DNS_SERVERS "AVAHI_DNS_SERVERS"
55 #define ENV_INTERFACE "AVAHI_INTERFACE"
56
57 static enum {
58 ACKWAIT,
59 BROWSING
60 } state = ACKWAIT;
61
62 static enum {
63 DAEMON_RUN,
64 DAEMON_KILL,
65 DAEMON_REFRESH,
66 DAEMON_VERSION,
67 DAEMON_HELP,
68 DAEMON_CHECK
69 } command = DAEMON_RUN;
70
71 static int quit = 0;
72 static int daemonize = 0;
73 static int use_syslog = 0;
74
75 #if !HAVE_DECL_ENVIRON
76 extern char **environ;
77 #endif
78
79 typedef struct DNSServerInfo DNSServerInfo;
80
81 struct DNSServerInfo {
82 AvahiIfIndex interface;
83 AvahiProtocol protocol;
84 char *address;
85 AVAHI_LLIST_FIELDS(DNSServerInfo, servers);
86 };
87
88 static AVAHI_LLIST_HEAD(DNSServerInfo, servers);
89
server_info_free(DNSServerInfo * i)90 static void server_info_free(DNSServerInfo *i) {
91 assert(i);
92
93 avahi_free(i->address);
94
95 AVAHI_LLIST_REMOVE(DNSServerInfo, servers, servers, i);
96 avahi_free(i);
97 }
98
get_server_info(AvahiIfIndex interface,AvahiProtocol protocol,const char * address)99 static DNSServerInfo* get_server_info(AvahiIfIndex interface, AvahiProtocol protocol, const char *address) {
100 DNSServerInfo *i;
101 assert(address);
102
103 for (i = servers; i; i = i->servers_next)
104 if (i->interface == interface &&
105 i->protocol == protocol &&
106 strcmp(i->address, address) == 0)
107 return i;
108
109 return NULL;
110 }
111
new_server_info(AvahiIfIndex interface,AvahiProtocol protocol,const char * address)112 static DNSServerInfo* new_server_info(AvahiIfIndex interface, AvahiProtocol protocol, const char *address) {
113 DNSServerInfo *i;
114
115 assert(address);
116
117 i = avahi_new(DNSServerInfo, 1);
118 i->interface = interface;
119 i->protocol = protocol;
120 i->address = avahi_strdup(address);
121
122 AVAHI_LLIST_PREPEND(DNSServerInfo, servers, servers, i);
123
124 return i;
125 }
126
set_cloexec(int fd)127 static int set_cloexec(int fd) {
128 int n;
129
130 assert(fd >= 0);
131
132 if ((n = fcntl(fd, F_GETFD)) < 0)
133 return -1;
134
135 if (n & FD_CLOEXEC)
136 return 0;
137
138 return fcntl(fd, F_SETFD, n|FD_CLOEXEC);
139 }
140
open_socket(void)141 static int open_socket(void) {
142 int fd = -1;
143 struct sockaddr_un sa;
144
145 if ((fd = socket(AF_UNIX, SOCK_STREAM, 0)) < 0) {
146 daemon_log(LOG_ERR, "socket(): %s", strerror(errno));
147 goto fail;
148 }
149
150 if (set_cloexec(fd) < 0) {
151 daemon_log(LOG_ERR, "fcntl(): %s", strerror(errno));
152 goto fail;
153 }
154
155 memset(&sa, 0, sizeof(sa));
156 sa.sun_family = AF_UNIX;
157 strncpy(sa.sun_path, AVAHI_SOCKET, sizeof(sa.sun_path)-1);
158 sa.sun_path[sizeof(sa.sun_path)-1] = 0;
159
160 if (connect(fd, (struct sockaddr*) &sa, sizeof(sa)) < 0) {
161 daemon_log(LOG_ERR, "connect(): %s", strerror(errno));
162 daemon_log(LOG_INFO, "Failed to connect to the daemon. This probably means that you");
163 daemon_log(LOG_INFO, "didn't start avahi-daemon before avahi-dnsconfd.");
164 goto fail;
165 }
166
167 return fd;
168
169 fail:
170 if (fd >= 0)
171 close(fd);
172
173 return -1;
174 }
175
loop_write(int fd,const void * data,size_t size)176 static ssize_t loop_write(int fd, const void*data, size_t size) {
177
178 ssize_t ret = 0;
179 assert(fd >= 0 && data && size);
180
181 while (size > 0) {
182 ssize_t r;
183
184 if ((r = write(fd, data, size)) < 0)
185 return r;
186
187 if (r == 0)
188 break;
189
190 ret += r;
191 data = (const uint8_t*) data + r;
192 size -= r;
193 }
194
195 return ret;
196 }
197
concat_dns_servers(AvahiIfIndex interface)198 static char *concat_dns_servers(AvahiIfIndex interface) {
199 DNSServerInfo *i;
200 char *r = NULL;
201
202 for (i = servers; i; i = i->servers_next)
203 if (i->interface == interface || interface <= 0) {
204 DNSServerInfo *j;
205 char *t;
206
207 /* Filter out double entries */
208 for (j = servers; j != i; j = j->servers_next)
209 if (j->interface == interface || interface <= 0)
210 if (strcmp(i->address, j->address) == 0)
211 break;
212
213 if (j != i)
214 continue;
215
216 if (!r)
217 t = avahi_strdup(i->address);
218 else
219 t = avahi_strdup_printf("%s %s", r, i->address);
220
221 avahi_free(r);
222 r = t;
223 }
224
225 return r;
226 }
227
set_env(const char * name,const char * value)228 static void set_env(const char *name, const char *value) {
229 char **e;
230 size_t l;
231
232 assert(name);
233 assert(value);
234
235 l = strlen(name);
236
237 for (e = environ; *e; e++) {
238 /* Search for the variable */
239 if (strlen(*e) < l+1)
240 continue;
241
242 if (strncmp(*e, name, l) != 0 || (*e)[l] != '=')
243 continue;
244
245 /* We simply free the record, sicne we know that we created it previously */
246 avahi_free(*e);
247 *e = avahi_strdup_printf("%s=%s", name, value);
248 return;
249 }
250
251 assert(0);
252 }
253
run_script(int new,AvahiIfIndex interface,AvahiProtocol protocol,const char * address)254 static void run_script(int new, AvahiIfIndex interface, AvahiProtocol protocol, const char *address) {
255 char *p;
256 int ret;
257 char ia[16], pa[16];
258 char name[IF_NAMESIZE];
259
260 assert(interface > 0);
261
262 if (!if_indextoname(interface, name))
263 return;
264
265 p = concat_dns_servers(interface);
266 set_env(ENV_INTERFACE_DNS_SERVERS, p ? p : "");
267 avahi_free(p);
268
269 p = concat_dns_servers(-1);
270 set_env(ENV_DNS_SERVERS, p ? p : "");
271 avahi_free(p);
272
273 set_env(ENV_INTERFACE, name);
274
275 snprintf(ia, sizeof(ia), "%i", (int) interface);
276 snprintf(pa, sizeof(pa), "%i", (int) protocol);
277
278 if (daemon_exec("/", &ret, AVAHI_DNSCONF_SCRIPT, AVAHI_DNSCONF_SCRIPT, new ? "+" : "-", address, ia, pa, avahi_proto_to_string(protocol), NULL) < 0)
279 daemon_log(LOG_WARNING, "Failed to run script");
280 else if (ret != 0)
281 daemon_log(LOG_WARNING, "Script returned with non-zero exit code %i", ret);
282 }
283
new_line(const char * l)284 static int new_line(const char *l) {
285 assert(l);
286
287 if (state == ACKWAIT) {
288 if (*l != '+') {
289 daemon_log(LOG_ERR, "Avahi command failed: %s", l);
290 return -1;
291 }
292
293 daemon_log(LOG_INFO, "Successfully connected to Avahi daemon.");
294 state = BROWSING;
295 } else {
296 AvahiIfIndex interface;
297 AvahiProtocol protocol;
298 int i_interface, i_protocol, port;
299 char a[AVAHI_ADDRESS_STR_MAX];
300
301 assert(state == BROWSING);
302
303 if (*l != '<' && *l != '>') {
304 daemon_log(LOG_ERR, "Avahi sent us an invalid browsing line: %s", l);
305 return -1;
306 }
307
308 if (sscanf(l+1, "%i %i %39s %i", &i_interface, &i_protocol, a, &port) != 4) {
309 daemon_log(LOG_ERR, "Failed to parse browsing line: %s", l);
310 return -1;
311 }
312
313 interface = (AvahiIfIndex) i_interface;
314 protocol = (AvahiProtocol) i_protocol;
315
316 if (*l == '>') {
317 if (port != 53)
318 daemon_log(LOG_WARNING, "DNS server with port address != 53 found, ignoring");
319 else {
320 daemon_log(LOG_INFO, "New DNS Server %s (interface: %i.%s)", a, interface, avahi_proto_to_string(protocol));
321 new_server_info(interface, protocol, a);
322 run_script(1, interface, protocol, a);
323 }
324 } else {
325 DNSServerInfo *i;
326
327 if (port == 53)
328 if ((i = get_server_info(interface, protocol, a))) {
329 daemon_log(LOG_INFO, "DNS Server %s removed (interface: %i.%s)", a, interface, avahi_proto_to_string(protocol));
330 server_info_free(i);
331 run_script(0, interface, protocol, a);
332 }
333 }
334
335 }
336
337 return 0;
338 }
339
do_connect(void)340 static int do_connect(void) {
341 int fd = -1;
342
343 if ((fd = open_socket()) < 0)
344 goto fail;
345
346 if (loop_write(fd, BROWSE_DNS_SERVERS, sizeof(BROWSE_DNS_SERVERS)-1) < 0) {
347 daemon_log(LOG_ERR, "write(): %s", strerror(errno));
348 goto fail;
349 }
350
351 state = ACKWAIT;
352 return fd;
353
354 fail:
355 if (fd >= 0)
356 close(fd);
357
358 return -1;
359 }
360
free_dns_server_info_list(void)361 static void free_dns_server_info_list(void) {
362 while (servers) {
363 AvahiIfIndex interface = servers->interface;
364 AvahiProtocol protocol = servers->protocol;
365 char *address = avahi_strdup(servers->address);
366 server_info_free(servers);
367
368 run_script(0, interface, protocol, address);
369 avahi_free(address);
370 }
371 }
372
help(FILE * f,const char * argv0)373 static void help(FILE *f, const char *argv0) {
374 fprintf(f,
375 "%s [options]\n"
376 " -h --help Show this help\n"
377 " -D --daemonize Daemonize after startup\n"
378 " -s --syslog Write log messages to syslog(3) instead of STDERR\n"
379 " -k --kill Kill a running daemon\n"
380 " -r --refresh Request a running daemon to refresh DNS server data\n"
381 " -c --check Return 0 if a daemon is already running\n"
382 " -V --version Show version\n",
383 argv0);
384 }
385
parse_command_line(int argc,char * argv[])386 static int parse_command_line(int argc, char *argv[]) {
387 int c;
388
389 static const struct option long_options[] = {
390 { "help", no_argument, NULL, 'h' },
391 { "daemonize", no_argument, NULL, 'D' },
392 { "syslog", no_argument, NULL, 's' },
393 { "kill", no_argument, NULL, 'k' },
394 { "version", no_argument, NULL, 'V' },
395 { "refresh", no_argument, NULL, 'r' },
396 { "check", no_argument, NULL, 'c' },
397 { NULL, 0, NULL, 0 }
398 };
399
400 while ((c = getopt_long(argc, argv, "hDkVrcs", long_options, NULL)) >= 0) {
401
402 switch(c) {
403 case 'h':
404 command = DAEMON_HELP;
405 break;
406 case 'D':
407 daemonize = 1;
408 break;
409 case 's':
410 use_syslog = 1;
411 break;
412 case 'k':
413 command = DAEMON_KILL;
414 break;
415 case 'V':
416 command = DAEMON_VERSION;
417 break;
418 case 'r':
419 command = DAEMON_REFRESH;
420 break;
421 case 'c':
422 command = DAEMON_CHECK;
423 break;
424 default:
425 return -1;
426 }
427 }
428
429 if (optind < argc) {
430 fprintf(stderr, "Too many arguments\n");
431 return -1;
432 }
433
434 return 0;
435 }
436
run_daemon(void)437 static int run_daemon(void) {
438 int fd = -1, ret = -1;
439 char buf[1024];
440 size_t buflen = 0;
441
442 AVAHI_LLIST_HEAD_INIT(DNSServerInfo, servers);
443
444 daemon_signal_init(SIGINT, SIGTERM, SIGCHLD, SIGHUP, 0);
445
446 /* Allocate some memory for our environment variables */
447 putenv(avahi_strdup(ENV_INTERFACE"="));
448 putenv(avahi_strdup(ENV_DNS_SERVERS"="));
449 putenv(avahi_strdup(ENV_INTERFACE_DNS_SERVERS"="));
450
451 if ((fd = do_connect()) < 0)
452 goto finish;
453
454 if (daemonize)
455 daemon_retval_send(0);
456
457 ret = 0;
458
459 while (!quit) {
460 fd_set rfds, wfds;
461
462 FD_ZERO(&rfds);
463 FD_ZERO(&wfds);
464
465 FD_SET(fd, &rfds);
466 FD_SET(daemon_signal_fd(), &rfds);
467
468 for (;;) {
469 if (select(fd+1, &rfds, NULL, NULL, NULL) < 0) {
470 if (errno == EINTR)
471 continue;
472
473 daemon_log(LOG_ERR, "select(): %s", strerror(errno));
474 goto finish;
475 }
476
477 break;
478 }
479
480 if (FD_ISSET(daemon_signal_fd(), &rfds)) {
481
482 int sig;
483
484 if ((sig = daemon_signal_next()) <= 0) {
485 daemon_log(LOG_ERR, "daemon_signal_next() failed");
486 goto finish;
487 }
488
489 switch(sig) {
490 case SIGINT:
491 case SIGTERM:
492 daemon_log(LOG_INFO, "Got %s, quitting.", sig == SIGINT ? "SIGINT" : "SIGTERM");
493 ret = 0;
494 goto finish;
495
496 case SIGCHLD:
497 waitpid(-1, NULL, WNOHANG);
498 break;
499
500 case SIGHUP:
501 daemon_log(LOG_INFO, "Refreshing DNS Server list");
502
503 close(fd);
504 free_dns_server_info_list();
505
506 if ((fd = do_connect()) < 0)
507 goto finish;
508
509 break;
510 }
511
512 } else if (FD_ISSET(fd, &rfds)) {
513 ssize_t r;
514 char *n;
515
516 if ((r = read(fd, buf, sizeof(buf) - buflen - 1)) <= 0) {
517 daemon_log(LOG_ERR, "read(): %s", r < 0 ? strerror(errno) : "EOF");
518 goto finish;
519 }
520
521 buflen += r;
522 assert(buflen <= sizeof(buf)-1);
523
524 while ((n = memchr(buf, '\n', buflen))) {
525 *(n++) = 0;
526
527 if (new_line(buf) < 0)
528 goto finish;
529
530 buflen -= (n - buf);
531 memmove(buf, n, buflen);
532 }
533
534 if (buflen >= sizeof(buf)-1) {
535 /* The incoming line is horribly long */
536 buf[sizeof(buf)-1] = 0;
537
538 if (new_line(buf) < 0)
539 goto finish;
540
541 buflen = 0;
542 }
543 }
544 }
545
546 finish:
547
548 free_dns_server_info_list();
549
550 if (fd >= 0)
551 close(fd);
552
553 daemon_signal_done();
554
555 if (ret != 0 && daemonize)
556 daemon_retval_send(1);
557
558 return ret;
559 }
560
pid_file_proc(void)561 static const char* pid_file_proc(void) {
562 return AVAHI_RUNTIME_DIR"/avahi-dnsconfd.pid";
563 }
564
main(int argc,char * argv[])565 int main(int argc, char *argv[]) {
566 char *argv0;
567 int r = 1;
568 int wrote_pid_file = 0;
569
570 if ((argv0 = strrchr(argv[0], '/')))
571 argv0++;
572 else
573 argv0 = argv[0];
574
575 daemon_pid_file_ident = daemon_log_ident = argv0;
576 daemon_pid_file_proc = pid_file_proc;
577
578 if (parse_command_line(argc, argv) < 0)
579 goto finish;
580
581 if (command == DAEMON_RUN) {
582 pid_t pid;
583
584 if (getuid() != 0) {
585 daemon_log(LOG_ERR, "This program is intended to be run as root.");
586 goto finish;
587 }
588
589 if ((pid = daemon_pid_file_is_running()) >= 0) {
590 daemon_log(LOG_ERR, "Daemon already running on PID %u", pid);
591 goto finish;
592 }
593
594 if (daemonize) {
595 daemon_retval_init();
596
597 if ((pid = daemon_fork()) < 0)
598 goto finish;
599 else if (pid != 0) {
600 int ret;
601 /** Parent **/
602
603 if ((ret = daemon_retval_wait(20)) < 0) {
604 daemon_log(LOG_ERR, "Could not receive return value from daemon process.");
605 goto finish;
606 }
607
608 r = ret;
609 goto finish;
610 }
611
612 /* Child */
613 }
614
615 if (use_syslog || daemonize)
616 daemon_log_use = DAEMON_LOG_SYSLOG;
617
618 chdir("/");
619
620 if (daemon_pid_file_create() < 0) {
621 daemon_log(LOG_ERR, "Failed to create PID file: %s", strerror(errno));
622
623 if (daemonize)
624 daemon_retval_send(1);
625 goto finish;
626 } else
627 wrote_pid_file = 1;
628
629 if (run_daemon() < 0)
630 goto finish;
631
632 r = 0;
633 } else if (command == DAEMON_HELP) {
634 help(stdout, argv0);
635
636 r = 0;
637 } else if (command == DAEMON_VERSION) {
638 printf("%s "PACKAGE_VERSION"\n", argv0);
639
640 r = 0;
641 } else if (command == DAEMON_KILL) {
642 if (daemon_pid_file_kill_wait(SIGTERM, 5) < 0) {
643 daemon_log(LOG_WARNING, "Failed to kill daemon: %s", strerror(errno));
644 goto finish;
645 }
646
647 r = 0;
648 } else if (command == DAEMON_REFRESH) {
649 if (daemon_pid_file_kill(SIGHUP) < 0) {
650 daemon_log(LOG_WARNING, "Failed to kill daemon: %s", strerror(errno));
651 goto finish;
652 }
653
654 r = 0;
655 } else if (command == DAEMON_CHECK)
656 r = (daemon_pid_file_is_running() >= 0) ? 0 : 1;
657
658
659 finish:
660
661 if (daemonize)
662 daemon_retval_done();
663
664 if (wrote_pid_file)
665 daemon_pid_file_remove();
666
667 return r;
668 }
669