-
Notifications
You must be signed in to change notification settings - Fork 120
/
mdns.c
1263 lines (1108 loc) · 44.3 KB
/
mdns.c
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
#ifdef _WIN32
#define _CRT_SECURE_NO_WARNINGS 1
#endif
#include <stdio.h>
#include <errno.h>
#include <signal.h>
#ifdef _WIN32
#include <winsock2.h>
#include <iphlpapi.h>
#define sleep(x) Sleep(x * 1000)
#else
#include <netdb.h>
#include <ifaddrs.h>
#include <net/if.h>
#include <sys/time.h>
#endif
// Alias some things to simulate recieving data to fuzz library
#if defined(MDNS_FUZZING)
#define recvfrom(sock, buffer, capacity, flags, src_addr, addrlen) ((mdns_ssize_t)capacity)
#define printf
#endif
#include "mdns.h"
#if defined(MDNS_FUZZING)
#undef recvfrom
#endif
static char addrbuffer[64];
static char entrybuffer[256];
static char namebuffer[256];
static char sendbuffer[1024];
static mdns_record_txt_t txtbuffer[128];
static struct sockaddr_in service_address_ipv4;
static struct sockaddr_in6 service_address_ipv6;
static int has_ipv4;
static int has_ipv6;
volatile sig_atomic_t running = 1;
// Data for our service including the mDNS records
typedef struct {
mdns_string_t service;
mdns_string_t hostname;
mdns_string_t service_instance;
mdns_string_t hostname_qualified;
struct sockaddr_in address_ipv4;
struct sockaddr_in6 address_ipv6;
int port;
mdns_record_t record_ptr;
mdns_record_t record_srv;
mdns_record_t record_a;
mdns_record_t record_aaaa;
mdns_record_t txt_record[2];
} service_t;
static mdns_string_t
ipv4_address_to_string(char* buffer, size_t capacity, const struct sockaddr_in* addr,
size_t addrlen) {
char host[NI_MAXHOST] = {0};
char service[NI_MAXSERV] = {0};
int ret = getnameinfo((const struct sockaddr*)addr, (socklen_t)addrlen, host, NI_MAXHOST,
service, NI_MAXSERV, NI_NUMERICSERV | NI_NUMERICHOST);
int len = 0;
if (ret == 0) {
if (addr->sin_port != 0)
len = snprintf(buffer, capacity, "%s:%s", host, service);
else
len = snprintf(buffer, capacity, "%s", host);
}
if (len >= (int)capacity)
len = (int)capacity - 1;
mdns_string_t str;
str.str = buffer;
str.length = len;
return str;
}
static mdns_string_t
ipv6_address_to_string(char* buffer, size_t capacity, const struct sockaddr_in6* addr,
size_t addrlen) {
char host[NI_MAXHOST] = {0};
char service[NI_MAXSERV] = {0};
int ret = getnameinfo((const struct sockaddr*)addr, (socklen_t)addrlen, host, NI_MAXHOST,
service, NI_MAXSERV, NI_NUMERICSERV | NI_NUMERICHOST);
int len = 0;
if (ret == 0) {
if (addr->sin6_port != 0)
len = snprintf(buffer, capacity, "[%s]:%s", host, service);
else
len = snprintf(buffer, capacity, "%s", host);
}
if (len >= (int)capacity)
len = (int)capacity - 1;
mdns_string_t str;
str.str = buffer;
str.length = len;
return str;
}
static mdns_string_t
ip_address_to_string(char* buffer, size_t capacity, const struct sockaddr* addr, size_t addrlen) {
if (addr->sa_family == AF_INET6)
return ipv6_address_to_string(buffer, capacity, (const struct sockaddr_in6*)addr, addrlen);
return ipv4_address_to_string(buffer, capacity, (const struct sockaddr_in*)addr, addrlen);
}
// Callback handling parsing answers to queries sent
static int
query_callback(int sock, const struct sockaddr* from, size_t addrlen, mdns_entry_type_t entry,
uint16_t query_id, uint16_t rtype, uint16_t rclass, uint32_t ttl, const void* data,
size_t size, size_t name_offset, size_t name_length, size_t record_offset,
size_t record_length, void* user_data) {
(void)sizeof(sock);
(void)sizeof(query_id);
(void)sizeof(name_length);
(void)sizeof(user_data);
mdns_string_t fromaddrstr = ip_address_to_string(addrbuffer, sizeof(addrbuffer), from, addrlen);
const char* entrytype = (entry == MDNS_ENTRYTYPE_ANSWER) ?
"answer" :
((entry == MDNS_ENTRYTYPE_AUTHORITY) ? "authority" : "additional");
mdns_string_t entrystr =
mdns_string_extract(data, size, &name_offset, entrybuffer, sizeof(entrybuffer));
if (rtype == MDNS_RECORDTYPE_PTR) {
mdns_string_t namestr = mdns_record_parse_ptr(data, size, record_offset, record_length,
namebuffer, sizeof(namebuffer));
printf("%.*s : %s %.*s PTR %.*s rclass 0x%x ttl %u length %d\n",
MDNS_STRING_FORMAT(fromaddrstr), entrytype, MDNS_STRING_FORMAT(entrystr),
MDNS_STRING_FORMAT(namestr), rclass, ttl, (int)record_length);
} else if (rtype == MDNS_RECORDTYPE_SRV) {
mdns_record_srv_t srv = mdns_record_parse_srv(data, size, record_offset, record_length,
namebuffer, sizeof(namebuffer));
printf("%.*s : %s %.*s SRV %.*s priority %d weight %d port %d\n",
MDNS_STRING_FORMAT(fromaddrstr), entrytype, MDNS_STRING_FORMAT(entrystr),
MDNS_STRING_FORMAT(srv.name), srv.priority, srv.weight, srv.port);
} else if (rtype == MDNS_RECORDTYPE_A) {
struct sockaddr_in addr;
mdns_record_parse_a(data, size, record_offset, record_length, &addr);
mdns_string_t addrstr =
ipv4_address_to_string(namebuffer, sizeof(namebuffer), &addr, sizeof(addr));
printf("%.*s : %s %.*s A %.*s\n", MDNS_STRING_FORMAT(fromaddrstr), entrytype,
MDNS_STRING_FORMAT(entrystr), MDNS_STRING_FORMAT(addrstr));
} else if (rtype == MDNS_RECORDTYPE_AAAA) {
struct sockaddr_in6 addr;
mdns_record_parse_aaaa(data, size, record_offset, record_length, &addr);
mdns_string_t addrstr =
ipv6_address_to_string(namebuffer, sizeof(namebuffer), &addr, sizeof(addr));
printf("%.*s : %s %.*s AAAA %.*s\n", MDNS_STRING_FORMAT(fromaddrstr), entrytype,
MDNS_STRING_FORMAT(entrystr), MDNS_STRING_FORMAT(addrstr));
} else if (rtype == MDNS_RECORDTYPE_TXT) {
size_t parsed = mdns_record_parse_txt(data, size, record_offset, record_length, txtbuffer,
sizeof(txtbuffer) / sizeof(mdns_record_txt_t));
for (size_t itxt = 0; itxt < parsed; ++itxt) {
if (txtbuffer[itxt].value.length) {
printf("%.*s : %s %.*s TXT %.*s = %.*s\n", MDNS_STRING_FORMAT(fromaddrstr),
entrytype, MDNS_STRING_FORMAT(entrystr),
MDNS_STRING_FORMAT(txtbuffer[itxt].key),
MDNS_STRING_FORMAT(txtbuffer[itxt].value));
} else {
printf("%.*s : %s %.*s TXT %.*s\n", MDNS_STRING_FORMAT(fromaddrstr), entrytype,
MDNS_STRING_FORMAT(entrystr), MDNS_STRING_FORMAT(txtbuffer[itxt].key));
}
}
} else {
printf("%.*s : %s %.*s type %u rclass 0x%x ttl %u length %d\n",
MDNS_STRING_FORMAT(fromaddrstr), entrytype, MDNS_STRING_FORMAT(entrystr), rtype,
rclass, ttl, (int)record_length);
}
return 0;
}
// Callback handling questions incoming on service sockets
static int
service_callback(int sock, const struct sockaddr* from, size_t addrlen, mdns_entry_type_t entry,
uint16_t query_id, uint16_t rtype, uint16_t rclass, uint32_t ttl, const void* data,
size_t size, size_t name_offset, size_t name_length, size_t record_offset,
size_t record_length, void* user_data) {
(void)sizeof(ttl);
if (entry != MDNS_ENTRYTYPE_QUESTION)
return 0;
const char dns_sd[] = "_services._dns-sd._udp.local.";
const service_t* service = (const service_t*)user_data;
mdns_string_t fromaddrstr = ip_address_to_string(addrbuffer, sizeof(addrbuffer), from, addrlen);
size_t offset = name_offset;
mdns_string_t name = mdns_string_extract(data, size, &offset, namebuffer, sizeof(namebuffer));
const char* record_name = 0;
if (rtype == MDNS_RECORDTYPE_PTR)
record_name = "PTR";
else if (rtype == MDNS_RECORDTYPE_SRV)
record_name = "SRV";
else if (rtype == MDNS_RECORDTYPE_A)
record_name = "A";
else if (rtype == MDNS_RECORDTYPE_AAAA)
record_name = "AAAA";
else if (rtype == MDNS_RECORDTYPE_TXT)
record_name = "TXT";
else if (rtype == MDNS_RECORDTYPE_ANY)
record_name = "ANY";
else
return 0;
printf("Query %s %.*s\n", record_name, MDNS_STRING_FORMAT(name));
if ((name.length == (sizeof(dns_sd) - 1)) &&
(strncmp(name.str, dns_sd, sizeof(dns_sd) - 1) == 0)) {
if ((rtype == MDNS_RECORDTYPE_PTR) || (rtype == MDNS_RECORDTYPE_ANY)) {
// The PTR query was for the DNS-SD domain, send answer with a PTR record for the
// service name we advertise, typically on the "<_service-name>._tcp.local." format
// Answer PTR record reverse mapping "<_service-name>._tcp.local." to
// "<hostname>.<_service-name>._tcp.local."
mdns_record_t answer = {
.name = name, .type = MDNS_RECORDTYPE_PTR, .data.ptr.name = service->service};
// Send the answer, unicast or multicast depending on flag in query
uint16_t unicast = (rclass & MDNS_UNICAST_RESPONSE);
printf(" --> answer %.*s (%s)\n", MDNS_STRING_FORMAT(answer.data.ptr.name),
(unicast ? "unicast" : "multicast"));
if (unicast) {
mdns_query_answer_unicast(sock, from, addrlen, sendbuffer, sizeof(sendbuffer),
query_id, rtype, name.str, name.length, answer, 0, 0, 0,
0);
} else {
mdns_query_answer_multicast(sock, sendbuffer, sizeof(sendbuffer), answer, 0, 0, 0,
0);
}
}
} else if ((name.length == service->service.length) &&
(strncmp(name.str, service->service.str, name.length) == 0)) {
if ((rtype == MDNS_RECORDTYPE_PTR) || (rtype == MDNS_RECORDTYPE_ANY)) {
// The PTR query was for our service (usually "<_service-name._tcp.local"), answer a PTR
// record reverse mapping the queried service name to our service instance name
// (typically on the "<hostname>.<_service-name>._tcp.local." format), and add
// additional records containing the SRV record mapping the service instance name to our
// qualified hostname (typically "<hostname>.local.") and port, as well as any IPv4/IPv6
// address for the hostname as A/AAAA records, and two test TXT records
// Answer PTR record reverse mapping "<_service-name>._tcp.local." to
// "<hostname>.<_service-name>._tcp.local."
mdns_record_t answer = service->record_ptr;
mdns_record_t additional[5] = {0};
size_t additional_count = 0;
// SRV record mapping "<hostname>.<_service-name>._tcp.local." to
// "<hostname>.local." with port. Set weight & priority to 0.
additional[additional_count++] = service->record_srv;
// A/AAAA records mapping "<hostname>.local." to IPv4/IPv6 addresses
if (service->address_ipv4.sin_family == AF_INET)
additional[additional_count++] = service->record_a;
if (service->address_ipv6.sin6_family == AF_INET6)
additional[additional_count++] = service->record_aaaa;
// Add two test TXT records for our service instance name, will be coalesced into
// one record with both key-value pair strings by the library
additional[additional_count++] = service->txt_record[0];
additional[additional_count++] = service->txt_record[1];
// Send the answer, unicast or multicast depending on flag in query
uint16_t unicast = (rclass & MDNS_UNICAST_RESPONSE);
printf(" --> answer %.*s (%s)\n",
MDNS_STRING_FORMAT(service->record_ptr.data.ptr.name),
(unicast ? "unicast" : "multicast"));
if (unicast) {
mdns_query_answer_unicast(sock, from, addrlen, sendbuffer, sizeof(sendbuffer),
query_id, rtype, name.str, name.length, answer, 0, 0,
additional, additional_count);
} else {
mdns_query_answer_multicast(sock, sendbuffer, sizeof(sendbuffer), answer, 0, 0,
additional, additional_count);
}
}
} else if ((name.length == service->service_instance.length) &&
(strncmp(name.str, service->service_instance.str, name.length) == 0)) {
if ((rtype == MDNS_RECORDTYPE_SRV) || (rtype == MDNS_RECORDTYPE_ANY)) {
// The SRV query was for our service instance (usually
// "<hostname>.<_service-name._tcp.local"), answer a SRV record mapping the service
// instance name to our qualified hostname (typically "<hostname>.local.") and port, as
// well as any IPv4/IPv6 address for the hostname as A/AAAA records, and two test TXT
// records
// Answer PTR record reverse mapping "<_service-name>._tcp.local." to
// "<hostname>.<_service-name>._tcp.local."
mdns_record_t answer = service->record_srv;
mdns_record_t additional[5] = {0};
size_t additional_count = 0;
// A/AAAA records mapping "<hostname>.local." to IPv4/IPv6 addresses
if (service->address_ipv4.sin_family == AF_INET)
additional[additional_count++] = service->record_a;
if (service->address_ipv6.sin6_family == AF_INET6)
additional[additional_count++] = service->record_aaaa;
// Add two test TXT records for our service instance name, will be coalesced into
// one record with both key-value pair strings by the library
additional[additional_count++] = service->txt_record[0];
additional[additional_count++] = service->txt_record[1];
// Send the answer, unicast or multicast depending on flag in query
uint16_t unicast = (rclass & MDNS_UNICAST_RESPONSE);
printf(" --> answer %.*s port %d (%s)\n",
MDNS_STRING_FORMAT(service->record_srv.data.srv.name), service->port,
(unicast ? "unicast" : "multicast"));
if (unicast) {
mdns_query_answer_unicast(sock, from, addrlen, sendbuffer, sizeof(sendbuffer),
query_id, rtype, name.str, name.length, answer, 0, 0,
additional, additional_count);
} else {
mdns_query_answer_multicast(sock, sendbuffer, sizeof(sendbuffer), answer, 0, 0,
additional, additional_count);
}
}
} else if ((name.length == service->hostname_qualified.length) &&
(strncmp(name.str, service->hostname_qualified.str, name.length) == 0)) {
if (((rtype == MDNS_RECORDTYPE_A) || (rtype == MDNS_RECORDTYPE_ANY)) &&
(service->address_ipv4.sin_family == AF_INET)) {
// The A query was for our qualified hostname (typically "<hostname>.local.") and we
// have an IPv4 address, answer with an A record mappiing the hostname to an IPv4
// address, as well as any IPv6 address for the hostname, and two test TXT records
// Answer A records mapping "<hostname>.local." to IPv4 address
mdns_record_t answer = service->record_a;
mdns_record_t additional[5] = {0};
size_t additional_count = 0;
// AAAA record mapping "<hostname>.local." to IPv6 addresses
if (service->address_ipv6.sin6_family == AF_INET6)
additional[additional_count++] = service->record_aaaa;
// Add two test TXT records for our service instance name, will be coalesced into
// one record with both key-value pair strings by the library
additional[additional_count++] = service->txt_record[0];
additional[additional_count++] = service->txt_record[1];
// Send the answer, unicast or multicast depending on flag in query
uint16_t unicast = (rclass & MDNS_UNICAST_RESPONSE);
mdns_string_t addrstr = ip_address_to_string(
addrbuffer, sizeof(addrbuffer), (struct sockaddr*)&service->record_a.data.a.addr,
sizeof(service->record_a.data.a.addr));
printf(" --> answer %.*s IPv4 %.*s (%s)\n", MDNS_STRING_FORMAT(service->record_a.name),
MDNS_STRING_FORMAT(addrstr), (unicast ? "unicast" : "multicast"));
if (unicast) {
mdns_query_answer_unicast(sock, from, addrlen, sendbuffer, sizeof(sendbuffer),
query_id, rtype, name.str, name.length, answer, 0, 0,
additional, additional_count);
} else {
mdns_query_answer_multicast(sock, sendbuffer, sizeof(sendbuffer), answer, 0, 0,
additional, additional_count);
}
} else if (((rtype == MDNS_RECORDTYPE_AAAA) || (rtype == MDNS_RECORDTYPE_ANY)) &&
(service->address_ipv6.sin6_family == AF_INET6)) {
// The AAAA query was for our qualified hostname (typically "<hostname>.local.") and we
// have an IPv6 address, answer with an AAAA record mappiing the hostname to an IPv6
// address, as well as any IPv4 address for the hostname, and two test TXT records
// Answer AAAA records mapping "<hostname>.local." to IPv6 address
mdns_record_t answer = service->record_aaaa;
mdns_record_t additional[5] = {0};
size_t additional_count = 0;
// A record mapping "<hostname>.local." to IPv4 addresses
if (service->address_ipv4.sin_family == AF_INET)
additional[additional_count++] = service->record_a;
// Add two test TXT records for our service instance name, will be coalesced into
// one record with both key-value pair strings by the library
additional[additional_count++] = service->txt_record[0];
additional[additional_count++] = service->txt_record[1];
// Send the answer, unicast or multicast depending on flag in query
uint16_t unicast = (rclass & MDNS_UNICAST_RESPONSE);
mdns_string_t addrstr =
ip_address_to_string(addrbuffer, sizeof(addrbuffer),
(struct sockaddr*)&service->record_aaaa.data.aaaa.addr,
sizeof(service->record_aaaa.data.aaaa.addr));
printf(" --> answer %.*s IPv6 %.*s (%s)\n",
MDNS_STRING_FORMAT(service->record_aaaa.name), MDNS_STRING_FORMAT(addrstr),
(unicast ? "unicast" : "multicast"));
if (unicast) {
mdns_query_answer_unicast(sock, from, addrlen, sendbuffer, sizeof(sendbuffer),
query_id, rtype, name.str, name.length, answer, 0, 0,
additional, additional_count);
} else {
mdns_query_answer_multicast(sock, sendbuffer, sizeof(sendbuffer), answer, 0, 0,
additional, additional_count);
}
}
}
return 0;
}
// Callback handling questions and answers dump
static int
dump_callback(int sock, const struct sockaddr* from, size_t addrlen, mdns_entry_type_t entry,
uint16_t query_id, uint16_t rtype, uint16_t rclass, uint32_t ttl, const void* data,
size_t size, size_t name_offset, size_t name_length, size_t record_offset,
size_t record_length, void* user_data) {
mdns_string_t fromaddrstr = ip_address_to_string(addrbuffer, sizeof(addrbuffer), from, addrlen);
size_t offset = name_offset;
mdns_string_t name = mdns_string_extract(data, size, &offset, namebuffer, sizeof(namebuffer));
const char* record_name = 0;
if (rtype == MDNS_RECORDTYPE_PTR)
record_name = "PTR";
else if (rtype == MDNS_RECORDTYPE_SRV)
record_name = "SRV";
else if (rtype == MDNS_RECORDTYPE_A)
record_name = "A";
else if (rtype == MDNS_RECORDTYPE_AAAA)
record_name = "AAAA";
else if (rtype == MDNS_RECORDTYPE_TXT)
record_name = "TXT";
else if (rtype == MDNS_RECORDTYPE_ANY)
record_name = "ANY";
else
record_name = "<UNKNOWN>";
const char* entry_type = "Question";
if (entry == MDNS_ENTRYTYPE_ANSWER)
entry_type = "Answer";
else if (entry == MDNS_ENTRYTYPE_AUTHORITY)
entry_type = "Authority";
else if (entry == MDNS_ENTRYTYPE_ADDITIONAL)
entry_type = "Additional";
printf("%.*s: %s %s %.*s rclass 0x%x ttl %u\n", MDNS_STRING_FORMAT(fromaddrstr), entry_type,
record_name, MDNS_STRING_FORMAT(name), (unsigned int)rclass, ttl);
return 0;
}
// Open sockets for sending one-shot multicast queries from an ephemeral port
static int
open_client_sockets(int* sockets, int max_sockets, int port) {
// When sending, each socket can only send to one network interface
// Thus we need to open one socket for each interface and address family
int num_sockets = 0;
#ifdef _WIN32
IP_ADAPTER_ADDRESSES* adapter_address = 0;
ULONG address_size = 8000;
unsigned int ret;
unsigned int num_retries = 4;
do {
adapter_address = (IP_ADAPTER_ADDRESSES*)malloc(address_size);
ret = GetAdaptersAddresses(AF_UNSPEC, GAA_FLAG_SKIP_MULTICAST | GAA_FLAG_SKIP_ANYCAST, 0,
adapter_address, &address_size);
if (ret == ERROR_BUFFER_OVERFLOW) {
free(adapter_address);
adapter_address = 0;
address_size *= 2;
} else {
break;
}
} while (num_retries-- > 0);
if (!adapter_address || (ret != NO_ERROR)) {
free(adapter_address);
printf("Failed to get network adapter addresses\n");
return num_sockets;
}
int first_ipv4 = 1;
int first_ipv6 = 1;
for (PIP_ADAPTER_ADDRESSES adapter = adapter_address; adapter; adapter = adapter->Next) {
if (adapter->TunnelType == TUNNEL_TYPE_TEREDO)
continue;
if (adapter->OperStatus != IfOperStatusUp)
continue;
for (IP_ADAPTER_UNICAST_ADDRESS* unicast = adapter->FirstUnicastAddress; unicast;
unicast = unicast->Next) {
if (unicast->Address.lpSockaddr->sa_family == AF_INET) {
struct sockaddr_in* saddr = (struct sockaddr_in*)unicast->Address.lpSockaddr;
if ((saddr->sin_addr.S_un.S_un_b.s_b1 != 127) ||
(saddr->sin_addr.S_un.S_un_b.s_b2 != 0) ||
(saddr->sin_addr.S_un.S_un_b.s_b3 != 0) ||
(saddr->sin_addr.S_un.S_un_b.s_b4 != 1)) {
int log_addr = 0;
if (first_ipv4) {
service_address_ipv4 = *saddr;
first_ipv4 = 0;
log_addr = 1;
}
has_ipv4 = 1;
if (num_sockets < max_sockets) {
saddr->sin_port = htons((unsigned short)port);
int sock = mdns_socket_open_ipv4(saddr);
if (sock >= 0) {
sockets[num_sockets++] = sock;
log_addr = 1;
} else {
log_addr = 0;
}
}
if (log_addr) {
char buffer[128];
mdns_string_t addr = ipv4_address_to_string(buffer, sizeof(buffer), saddr,
sizeof(struct sockaddr_in));
printf("Local IPv4 address: %.*s\n", MDNS_STRING_FORMAT(addr));
}
}
} else if (unicast->Address.lpSockaddr->sa_family == AF_INET6) {
struct sockaddr_in6* saddr = (struct sockaddr_in6*)unicast->Address.lpSockaddr;
// Ignore link-local addresses
if (saddr->sin6_scope_id)
continue;
static const unsigned char localhost[] = {0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 1};
static const unsigned char localhost_mapped[] = {0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0xff, 0xff, 0x7f, 0, 0, 1};
if ((unicast->DadState == NldsPreferred) &&
memcmp(saddr->sin6_addr.s6_addr, localhost, 16) &&
memcmp(saddr->sin6_addr.s6_addr, localhost_mapped, 16)) {
int log_addr = 0;
if (first_ipv6) {
service_address_ipv6 = *saddr;
first_ipv6 = 0;
log_addr = 1;
}
has_ipv6 = 1;
if (num_sockets < max_sockets) {
saddr->sin6_port = htons((unsigned short)port);
int sock = mdns_socket_open_ipv6(saddr);
if (sock >= 0) {
sockets[num_sockets++] = sock;
log_addr = 1;
} else {
log_addr = 0;
}
}
if (log_addr) {
char buffer[128];
mdns_string_t addr = ipv6_address_to_string(buffer, sizeof(buffer), saddr,
sizeof(struct sockaddr_in6));
printf("Local IPv6 address: %.*s\n", MDNS_STRING_FORMAT(addr));
}
}
}
}
}
free(adapter_address);
#else
struct ifaddrs* ifaddr = 0;
struct ifaddrs* ifa = 0;
if (getifaddrs(&ifaddr) < 0)
printf("Unable to get interface addresses\n");
int first_ipv4 = 1;
int first_ipv6 = 1;
for (ifa = ifaddr; ifa; ifa = ifa->ifa_next) {
if (!ifa->ifa_addr)
continue;
if (!(ifa->ifa_flags & IFF_UP) || !(ifa->ifa_flags & IFF_MULTICAST))
continue;
if ((ifa->ifa_flags & IFF_LOOPBACK) || (ifa->ifa_flags & IFF_POINTOPOINT))
continue;
if (ifa->ifa_addr->sa_family == AF_INET) {
struct sockaddr_in* saddr = (struct sockaddr_in*)ifa->ifa_addr;
if (saddr->sin_addr.s_addr != htonl(INADDR_LOOPBACK)) {
int log_addr = 0;
if (first_ipv4) {
service_address_ipv4 = *saddr;
first_ipv4 = 0;
log_addr = 1;
}
has_ipv4 = 1;
if (num_sockets < max_sockets) {
saddr->sin_port = htons(port);
int sock = mdns_socket_open_ipv4(saddr);
if (sock >= 0) {
sockets[num_sockets++] = sock;
log_addr = 1;
} else {
log_addr = 0;
}
}
if (log_addr) {
char buffer[128];
mdns_string_t addr = ipv4_address_to_string(buffer, sizeof(buffer), saddr,
sizeof(struct sockaddr_in));
printf("Local IPv4 address: %.*s\n", MDNS_STRING_FORMAT(addr));
}
}
} else if (ifa->ifa_addr->sa_family == AF_INET6) {
struct sockaddr_in6* saddr = (struct sockaddr_in6*)ifa->ifa_addr;
// Ignore link-local addresses
if (saddr->sin6_scope_id)
continue;
static const unsigned char localhost[] = {0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 1};
static const unsigned char localhost_mapped[] = {0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0xff, 0xff, 0x7f, 0, 0, 1};
if (memcmp(saddr->sin6_addr.s6_addr, localhost, 16) &&
memcmp(saddr->sin6_addr.s6_addr, localhost_mapped, 16)) {
int log_addr = 0;
if (first_ipv6) {
service_address_ipv6 = *saddr;
first_ipv6 = 0;
log_addr = 1;
}
has_ipv6 = 1;
if (num_sockets < max_sockets) {
saddr->sin6_port = htons(port);
int sock = mdns_socket_open_ipv6(saddr);
if (sock >= 0) {
sockets[num_sockets++] = sock;
log_addr = 1;
} else {
log_addr = 0;
}
}
if (log_addr) {
char buffer[128];
mdns_string_t addr = ipv6_address_to_string(buffer, sizeof(buffer), saddr,
sizeof(struct sockaddr_in6));
printf("Local IPv6 address: %.*s\n", MDNS_STRING_FORMAT(addr));
}
}
}
}
freeifaddrs(ifaddr);
#endif
return num_sockets;
}
// Open sockets to listen to incoming mDNS queries on port 5353
static int
open_service_sockets(int* sockets, int max_sockets) {
// When recieving, each socket can recieve data from all network interfaces
// Thus we only need to open one socket for each address family
int num_sockets = 0;
// Call the client socket function to enumerate and get local addresses,
// but not open the actual sockets
open_client_sockets(0, 0, 0);
if (num_sockets < max_sockets) {
struct sockaddr_in sock_addr;
memset(&sock_addr, 0, sizeof(struct sockaddr_in));
sock_addr.sin_family = AF_INET;
#ifdef _WIN32
sock_addr.sin_addr = in4addr_any;
#else
sock_addr.sin_addr.s_addr = INADDR_ANY;
#endif
sock_addr.sin_port = htons(MDNS_PORT);
#ifdef __APPLE__
sock_addr.sin_len = sizeof(struct sockaddr_in);
#endif
int sock = mdns_socket_open_ipv4(&sock_addr);
if (sock >= 0)
sockets[num_sockets++] = sock;
}
if (num_sockets < max_sockets) {
struct sockaddr_in6 sock_addr;
memset(&sock_addr, 0, sizeof(struct sockaddr_in6));
sock_addr.sin6_family = AF_INET6;
sock_addr.sin6_addr = in6addr_any;
sock_addr.sin6_port = htons(MDNS_PORT);
#ifdef __APPLE__
sock_addr.sin6_len = sizeof(struct sockaddr_in6);
#endif
int sock = mdns_socket_open_ipv6(&sock_addr);
if (sock >= 0)
sockets[num_sockets++] = sock;
}
return num_sockets;
}
// Send a DNS-SD query
static int
send_dns_sd(void) {
int sockets[32];
int num_sockets = open_client_sockets(sockets, sizeof(sockets) / sizeof(sockets[0]), 0);
if (num_sockets <= 0) {
printf("Failed to open any client sockets\n");
return -1;
}
printf("Opened %d socket%s for DNS-SD\n", num_sockets, num_sockets > 1 ? "s" : "");
printf("Sending DNS-SD discovery\n");
for (int isock = 0; isock < num_sockets; ++isock) {
if (mdns_discovery_send(sockets[isock]))
printf("Failed to send DNS-DS discovery: %s\n", strerror(errno));
}
size_t capacity = 2048;
void* buffer = malloc(capacity);
void* user_data = 0;
size_t records;
// This is a simple implementation that loops for 5 seconds or as long as we get replies
int res;
printf("Reading DNS-SD replies\n");
do {
struct timeval timeout;
timeout.tv_sec = 5;
timeout.tv_usec = 0;
int nfds = 0;
fd_set readfs;
FD_ZERO(&readfs);
for (int isock = 0; isock < num_sockets; ++isock) {
if (sockets[isock] >= nfds)
nfds = sockets[isock] + 1;
FD_SET(sockets[isock], &readfs);
}
records = 0;
res = select(nfds, &readfs, 0, 0, &timeout);
if (res > 0) {
for (int isock = 0; isock < num_sockets; ++isock) {
if (FD_ISSET(sockets[isock], &readfs)) {
records += mdns_discovery_recv(sockets[isock], buffer, capacity, query_callback,
user_data);
}
}
}
} while (res > 0);
free(buffer);
for (int isock = 0; isock < num_sockets; ++isock)
mdns_socket_close(sockets[isock]);
printf("Closed socket%s\n", num_sockets > 1 ? "s" : "");
return 0;
}
// Send a mDNS query
static int
send_mdns_query(mdns_query_t* query, size_t count) {
int sockets[32];
int query_id[32];
int num_sockets = open_client_sockets(sockets, sizeof(sockets) / sizeof(sockets[0]), 0);
if (num_sockets <= 0) {
printf("Failed to open any client sockets\n");
return -1;
}
printf("Opened %d socket%s for mDNS query\n", num_sockets, num_sockets > 1 ? "s" : "");
size_t capacity = 2048;
void* buffer = malloc(capacity);
void* user_data = 0;
printf("Sending mDNS query");
for (size_t iq = 0; iq < count; ++iq) {
const char* record_name = "PTR";
if (query[iq].type == MDNS_RECORDTYPE_SRV)
record_name = "SRV";
else if (query[iq].type == MDNS_RECORDTYPE_A)
record_name = "A";
else if (query[iq].type == MDNS_RECORDTYPE_AAAA)
record_name = "AAAA";
else
query[iq].type = MDNS_RECORDTYPE_PTR;
printf(" : %s %s", query[iq].name, record_name);
}
printf("\n");
for (int isock = 0; isock < num_sockets; ++isock) {
query_id[isock] =
mdns_multiquery_send(sockets[isock], query, count, buffer, capacity, 0);
if (query_id[isock] < 0)
printf("Failed to send mDNS query: %s\n", strerror(errno));
}
// This is a simple implementation that loops for 5 seconds or as long as we get replies
int res;
printf("Reading mDNS query replies\n");
int records = 0;
do {
struct timeval timeout;
timeout.tv_sec = 10;
timeout.tv_usec = 0;
int nfds = 0;
fd_set readfs;
FD_ZERO(&readfs);
for (int isock = 0; isock < num_sockets; ++isock) {
if (sockets[isock] >= nfds)
nfds = sockets[isock] + 1;
FD_SET(sockets[isock], &readfs);
}
res = select(nfds, &readfs, 0, 0, &timeout);
if (res > 0) {
for (int isock = 0; isock < num_sockets; ++isock) {
if (FD_ISSET(sockets[isock], &readfs)) {
size_t rec = mdns_query_recv(sockets[isock], buffer, capacity, query_callback,
user_data, query_id[isock]);
if (rec > 0)
records += rec;
}
FD_SET(sockets[isock], &readfs);
}
}
} while (res > 0);
printf("Read %d records\n", records);
free(buffer);
for (int isock = 0; isock < num_sockets; ++isock)
mdns_socket_close(sockets[isock]);
printf("Closed socket%s\n", num_sockets > 1 ? "s" : "");
return 0;
}
// Provide a mDNS service, answering incoming DNS-SD and mDNS queries
static int
service_mdns(const char* hostname, const char* service_name, int service_port) {
int sockets[32];
int num_sockets = open_service_sockets(sockets, sizeof(sockets) / sizeof(sockets[0]));
if (num_sockets <= 0) {
printf("Failed to open any client sockets\n");
return -1;
}
printf("Opened %d socket%s for mDNS service\n", num_sockets, num_sockets > 1 ? "s" : "");
size_t service_name_length = strlen(service_name);
if (!service_name_length) {
printf("Invalid service name\n");
return -1;
}
char* service_name_buffer = malloc(service_name_length + 2);
memcpy(service_name_buffer, service_name, service_name_length);
if (service_name_buffer[service_name_length - 1] != '.')
service_name_buffer[service_name_length++] = '.';
service_name_buffer[service_name_length] = 0;
service_name = service_name_buffer;
printf("Service mDNS: %s:%d\n", service_name, service_port);
printf("Hostname: %s\n", hostname);
size_t capacity = 2048;
void* buffer = malloc(capacity);
mdns_string_t service_string = (mdns_string_t){service_name, strlen(service_name)};
mdns_string_t hostname_string = (mdns_string_t){hostname, strlen(hostname)};
// Build the service instance "<hostname>.<_service-name>._tcp.local." string
char service_instance_buffer[256] = {0};
snprintf(service_instance_buffer, sizeof(service_instance_buffer) - 1, "%.*s.%.*s",
MDNS_STRING_FORMAT(hostname_string), MDNS_STRING_FORMAT(service_string));
mdns_string_t service_instance_string =
(mdns_string_t){service_instance_buffer, strlen(service_instance_buffer)};
// Build the "<hostname>.local." string
char qualified_hostname_buffer[256] = {0};
snprintf(qualified_hostname_buffer, sizeof(qualified_hostname_buffer) - 1, "%.*s.local.",
MDNS_STRING_FORMAT(hostname_string));
mdns_string_t hostname_qualified_string =
(mdns_string_t){qualified_hostname_buffer, strlen(qualified_hostname_buffer)};
service_t service = {0};
service.service = service_string;
service.hostname = hostname_string;
service.service_instance = service_instance_string;
service.hostname_qualified = hostname_qualified_string;
service.address_ipv4 = service_address_ipv4;
service.address_ipv6 = service_address_ipv6;
service.port = service_port;
// Setup our mDNS records
// PTR record reverse mapping "<_service-name>._tcp.local." to
// "<hostname>.<_service-name>._tcp.local."
service.record_ptr = (mdns_record_t){.name = service.service,
.type = MDNS_RECORDTYPE_PTR,
.data.ptr.name = service.service_instance,
.rclass = 0,
.ttl = 0};
// SRV record mapping "<hostname>.<_service-name>._tcp.local." to
// "<hostname>.local." with port. Set weight & priority to 0.
service.record_srv = (mdns_record_t){.name = service.service_instance,
.type = MDNS_RECORDTYPE_SRV,
.data.srv.name = service.hostname_qualified,
.data.srv.port = service.port,
.data.srv.priority = 0,
.data.srv.weight = 0,
.rclass = 0,
.ttl = 0};
// A/AAAA records mapping "<hostname>.local." to IPv4/IPv6 addresses
service.record_a = (mdns_record_t){.name = service.hostname_qualified,
.type = MDNS_RECORDTYPE_A,
.data.a.addr = service.address_ipv4,
.rclass = 0,
.ttl = 0};
service.record_aaaa = (mdns_record_t){.name = service.hostname_qualified,
.type = MDNS_RECORDTYPE_AAAA,
.data.aaaa.addr = service.address_ipv6,
.rclass = 0,
.ttl = 0};
// Add two test TXT records for our service instance name, will be coalesced into
// one record with both key-value pair strings by the library
service.txt_record[0] = (mdns_record_t){.name = service.service_instance,
.type = MDNS_RECORDTYPE_TXT,
.data.txt.key = {MDNS_STRING_CONST("test")},
.data.txt.value = {MDNS_STRING_CONST("1")},
.rclass = 0,
.ttl = 0};
service.txt_record[1] = (mdns_record_t){.name = service.service_instance,
.type = MDNS_RECORDTYPE_TXT,
.data.txt.key = {MDNS_STRING_CONST("other")},
.data.txt.value = {MDNS_STRING_CONST("value")},
.rclass = 0,
.ttl = 0};
// Send an announcement on startup of service
{
printf("Sending announce\n");
mdns_record_t additional[5] = {0};
size_t additional_count = 0;
additional[additional_count++] = service.record_srv;
if (service.address_ipv4.sin_family == AF_INET)
additional[additional_count++] = service.record_a;
if (service.address_ipv6.sin6_family == AF_INET6)
additional[additional_count++] = service.record_aaaa;
additional[additional_count++] = service.txt_record[0];
additional[additional_count++] = service.txt_record[1];
for (int isock = 0; isock < num_sockets; ++isock)
mdns_announce_multicast(sockets[isock], buffer, capacity, service.record_ptr, 0, 0,
additional, additional_count);
}
// This is a crude implementation that checks for incoming queries
while (running) {
int nfds = 0;
fd_set readfs;
FD_ZERO(&readfs);
for (int isock = 0; isock < num_sockets; ++isock) {
if (sockets[isock] >= nfds)
nfds = sockets[isock] + 1;
FD_SET(sockets[isock], &readfs);
}
struct timeval timeout;
timeout.tv_sec = 0;
timeout.tv_usec = 100000;
if (select(nfds, &readfs, 0, 0, &timeout) >= 0) {
for (int isock = 0; isock < num_sockets; ++isock) {
if (FD_ISSET(sockets[isock], &readfs)) {
mdns_socket_listen(sockets[isock], buffer, capacity, service_callback,
&service);
}
FD_SET(sockets[isock], &readfs);
}
} else {
break;
}
}
// Send a goodbye on end of service
{
printf("Sending goodbye\n");
mdns_record_t additional[5] = {0};
size_t additional_count = 0;
additional[additional_count++] = service.record_srv;
if (service.address_ipv4.sin_family == AF_INET)
additional[additional_count++] = service.record_a;