summaryrefslogtreecommitdiff
path: root/source3/libads/dns.c
blob: d5c851d5ca8dd100457f99f156d6e3d4a2e17793 (plain)
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
/* 
   Unix SMB/CIFS implementation.
   DNS utility library
   Copyright (C) Gerald (Jerry) Carter           2006.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.
   
   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.
   
   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/

#include "includes.h"

/* AIX resolv.h uses 'class' in struct ns_rr */

#if defined(AIX)
#  if defined(class)
#    undef class
#  endif
#endif	/* AIX */

/* resolver headers */

#include <sys/types.h>
#include <netinet/in.h>
#include <arpa/nameser.h>
#include <resolv.h>
#include <netdb.h>

#define MAX_DNS_PACKET_SIZE 0xffff

#ifdef NS_HFIXEDSZ	/* Bind 8/9 interface */
#if !defined(C_IN)	/* AIX 5.3 already defines C_IN */
#  define C_IN		ns_c_in
#endif
#if !defined(T_A)	/* AIX 5.3 already defines T_A */
#  define T_A   	ns_t_a
#endif
#  define T_SRV 	ns_t_srv
#  define T_NS 		ns_t_ns
#else
#  ifdef HFIXEDSZ
#    define NS_HFIXEDSZ HFIXEDSZ
#  else
#    define NS_HFIXEDSZ sizeof(HEADER)
#  endif	/* HFIXEDSZ */
#  ifdef PACKETSZ
#    define NS_PACKETSZ	PACKETSZ
#  else	/* 512 is usually the default */
#    define NS_PACKETSZ	512
#  endif	/* PACKETSZ */
#  define T_SRV 	33
#endif

/*********************************************************************
*********************************************************************/

static BOOL ads_dns_parse_query( TALLOC_CTX *ctx, uint8 *start, uint8 *end,
                          uint8 **ptr, struct dns_query *q )
{
	uint8 *p = *ptr;
	pstring hostname;
	int namelen;

	ZERO_STRUCTP( q );
	
	if ( !start || !end || !q || !*ptr)
		return False;

	/* See RFC 1035 for details. If this fails, then return. */

	namelen = dn_expand( start, end, p, hostname, sizeof(hostname) );
	if ( namelen < 0 ) {
		return False;
	}
	p += namelen;
	q->hostname = talloc_strdup( ctx, hostname );

	/* check that we have space remaining */

	if ( PTR_DIFF(p+4, end) > 0 )
		return False;

	q->type     = RSVAL( p, 0 );
	q->in_class = RSVAL( p, 2 );
	p += 4;

	*ptr = p;

	return True;
}

/*********************************************************************
*********************************************************************/

static BOOL ads_dns_parse_rr( TALLOC_CTX *ctx, uint8 *start, uint8 *end,
                       uint8 **ptr, struct dns_rr *rr )
{
	uint8 *p = *ptr;
	pstring hostname;
	int namelen;

	if ( !start || !end || !rr || !*ptr)
		return -1;

	ZERO_STRUCTP( rr );
	/* pull the name from the answer */

	namelen = dn_expand( start, end, p, hostname, sizeof(hostname) );
	if ( namelen < 0 ) {
		return -1;
	}
	p += namelen;
	rr->hostname = talloc_strdup( ctx, hostname );

	/* check that we have space remaining */

	if ( PTR_DIFF(p+10, end) > 0 )
		return False;

	/* pull some values and then skip onto the string */

	rr->type     = RSVAL(p, 0);
	rr->in_class = RSVAL(p, 2);
	rr->ttl      = RIVAL(p, 4);
	rr->rdatalen = RSVAL(p, 8);
	
	p += 10;

	/* sanity check the available space */

	if ( PTR_DIFF(p+rr->rdatalen, end ) > 0 ) {
		return False;

	}

	/* save a point to the rdata for this section */

	rr->rdata = p;
	p += rr->rdatalen;

	*ptr = p;

	return True;
}

/*********************************************************************
*********************************************************************/

static BOOL ads_dns_parse_rr_srv( TALLOC_CTX *ctx, uint8 *start, uint8 *end,
                       uint8 **ptr, struct dns_rr_srv *srv )
{
	struct dns_rr rr;
	uint8 *p;
	pstring dcname;
	int namelen;

	if ( !start || !end || !srv || !*ptr)
		return -1;

	/* Parse the RR entry.  Coming out of the this, ptr is at the beginning 
	   of the next record */

	if ( !ads_dns_parse_rr( ctx, start, end, ptr, &rr ) ) {
		DEBUG(1,("ads_dns_parse_rr_srv: Failed to parse RR record\n"));
		return False;
	}

	if ( rr.type != T_SRV ) {
		DEBUG(1,("ads_dns_parse_rr_srv: Bad answer type (%d)\n", rr.type));
		return False;
	}

	p = rr.rdata;

	srv->priority = RSVAL(p, 0);
	srv->weight   = RSVAL(p, 2);
	srv->port     = RSVAL(p, 4);

	p += 6;

	namelen = dn_expand( start, end, p, dcname, sizeof(dcname) );
	if ( namelen < 0 ) {
		DEBUG(1,("ads_dns_parse_rr_srv: Failed to uncompress name!\n"));
		return False;
	}
	srv->hostname = talloc_strdup( ctx, dcname );

	return True;
}

/*********************************************************************
*********************************************************************/

static BOOL ads_dns_parse_rr_ns( TALLOC_CTX *ctx, uint8 *start, uint8 *end,
                       uint8 **ptr, struct dns_rr_ns *nsrec )
{
	struct dns_rr rr;
	uint8 *p;
	pstring nsname;
	int namelen;

	if ( !start || !end || !nsrec || !*ptr)
		return -1;

	/* Parse the RR entry.  Coming out of the this, ptr is at the beginning 
	   of the next record */

	if ( !ads_dns_parse_rr( ctx, start, end, ptr, &rr ) ) {
		DEBUG(1,("ads_dns_parse_rr_ns: Failed to parse RR record\n"));
		return False;
	}

	if ( rr.type != T_NS ) {
		DEBUG(1,("ads_dns_parse_rr_ns: Bad answer type (%d)\n", rr.type));
		return False;
	}

	p = rr.rdata;

	/* ame server hostname */
	
	namelen = dn_expand( start, end, p, nsname, sizeof(nsname) );
	if ( namelen < 0 ) {
		DEBUG(1,("ads_dns_parse_rr_ns: Failed to uncompress name!\n"));
		return False;
	}
	nsrec->hostname = talloc_strdup( ctx, nsname );

	return True;
}

/*********************************************************************
 Sort SRV record list based on weight and priority.  See RFC 2782.
*********************************************************************/

static int dnssrvcmp( struct dns_rr_srv *a, struct dns_rr_srv *b )
{
	if ( a->priority == b->priority ) {

		/* randomize entries with an equal weight and priority */
		if ( a->weight == b->weight ) 
			return 0;

		/* higher weights should be sorted lower */ 
		if ( a->weight > b->weight )
			return -1;
		else
			return 1;
	}
		
	if ( a->priority < b->priority )
		return -1;

	return 1;
}

/*********************************************************************
 Simple wrapper for a DNS query
*********************************************************************/

static NTSTATUS dns_send_req( TALLOC_CTX *ctx, const char *name, int q_type, 
                              uint8 **buf, int *resp_length )
{
	uint8 *buffer = NULL;
	size_t buf_len;
	int resp_len = NS_PACKETSZ;	
	
	do {
		if ( buffer )
			TALLOC_FREE( buffer );
		
		buf_len = resp_len * sizeof(uint8);

		if ( (buffer = TALLOC_ARRAY(ctx, uint8, buf_len)) == NULL ) {
			DEBUG(0,("ads_dns_lookup_srv: talloc() failed!\n"));
			return NT_STATUS_NO_MEMORY;
		}

		if ( (resp_len = res_query(name, C_IN, q_type, buffer, buf_len)) < 0 ) {
			DEBUG(1,("ads_dns_lookup_srv: Failed to resolve %s (%s)\n", name, strerror(errno)));
			TALLOC_FREE( buffer );
			return NT_STATUS_UNSUCCESSFUL;
		}
	} while ( buf_len < resp_len && resp_len < MAX_DNS_PACKET_SIZE );
	
	*buf = buffer;
	*resp_length = resp_len;

	return NT_STATUS_OK;
}

/*********************************************************************
 Simple wrapper for a DNS SRV query
*********************************************************************/

static NTSTATUS ads_dns_lookup_srv( TALLOC_CTX *ctx, const char *name, struct dns_rr_srv **dclist, int *numdcs )
{
	uint8 *buffer = NULL;
	int resp_len = 0;
	struct dns_rr_srv *dcs = NULL;
	int query_count, answer_count, auth_count, additional_count;
	uint8 *p = buffer;
	int rrnum;
	int idx = 0;
	NTSTATUS status;

	if ( !ctx || !name || !dclist ) {
		return NT_STATUS_INVALID_PARAMETER;
	}
	
	/* Send the request.  May have to loop several times in case 
	   of large replies */

	status = dns_send_req( ctx, name, T_SRV, &buffer, &resp_len );
	if ( !NT_STATUS_IS_OK(status) ) {
		DEBUG(0,("ads_dns_lookup_srv: Failed to send DNS query (%s)\n",
			nt_errstr(status)));
		return status;
	}
	p = buffer;

	/* For some insane reason, the ns_initparse() et. al. routines are only
	   available in libresolv.a, and not the shared lib.  Who knows why....
	   So we have to parse the DNS reply ourselves */

	/* Pull the answer RR's count from the header.  Use the NMB ordering macros */

	query_count      = RSVAL( p, 4 );
	answer_count     = RSVAL( p, 6 );
	auth_count       = RSVAL( p, 8 );
	additional_count = RSVAL( p, 10 );

	DEBUG(4,("ads_dns_lookup_srv: %d records returned in the answer section.\n", 
		answer_count));
		
	if ( (dcs = TALLOC_ZERO_ARRAY(ctx, struct dns_rr_srv, answer_count)) == NULL ) {
		DEBUG(0,("ads_dns_lookup_srv: talloc() failure for %d char*'s\n", 
			answer_count));
		return NT_STATUS_NO_MEMORY;
	}

	/* now skip the header */

	p += NS_HFIXEDSZ;

	/* parse the query section */

	for ( rrnum=0; rrnum<query_count; rrnum++ ) {
		struct dns_query q;

		if ( !ads_dns_parse_query( ctx, buffer, buffer+resp_len, &p, &q ) ) {
			DEBUG(1,("ads_dns_lookup_srv: Failed to parse query record!\n"));
			return NT_STATUS_UNSUCCESSFUL;
		}
	}

	/* now we are at the answer section */

	for ( rrnum=0; rrnum<answer_count; rrnum++ ) {
		if ( !ads_dns_parse_rr_srv( ctx, buffer, buffer+resp_len, &p, &dcs[rrnum] ) ) {
			DEBUG(1,("ads_dns_lookup_srv: Failed to parse answer record!\n"));
			return NT_STATUS_UNSUCCESSFUL;
		}		
	}
	idx = rrnum;

	/* Parse the authority section */
	/* just skip these for now */

	for ( rrnum=0; rrnum<auth_count; rrnum++ ) {
		struct dns_rr rr;

		if ( !ads_dns_parse_rr( ctx, buffer, buffer+resp_len, &p, &rr ) ) {
			DEBUG(1,("ads_dns_lookup_srv: Failed to parse authority record!\n"));
			return NT_STATUS_UNSUCCESSFUL;
		}
	}

	/* Parse the additional records section */

	for ( rrnum=0; rrnum<additional_count; rrnum++ ) {
		struct dns_rr rr;
		int i;

		if ( !ads_dns_parse_rr( ctx, buffer, buffer+resp_len, &p, &rr ) ) {
			DEBUG(1,("ads_dns_lookup_srv: Failed to parse additional records section!\n"));
			return NT_STATUS_UNSUCCESSFUL;
		}

		/* only interested in A records as a shortcut for having to come 
		   back later and lookup the name.  For multi-homed hosts, the 
		   number of additional records and exceed the number of answer 
		   records. */
		  

		if ( (rr.type != T_A) || (rr.rdatalen != 4) ) 
			continue;

		for ( i=0; i<idx; i++ ) {
			if ( strcmp( rr.hostname, dcs[i].hostname ) == 0 ) {
				int num_ips = dcs[i].num_ips;
				uint8 *buf;
				struct in_addr *tmp_ips;

				/* allocate new memory */
				
				if ( dcs[i].num_ips == 0 ) {
					if ( (dcs[i].ips = TALLOC_ARRAY( dcs, 
						struct in_addr, 1 )) == NULL ) 
					{
						return NT_STATUS_NO_MEMORY;
					}
				} else {
					if ( (tmp_ips = TALLOC_REALLOC_ARRAY( dcs, dcs[i].ips,
						struct in_addr, dcs[i].num_ips+1)) == NULL ) 
					{
						return NT_STATUS_NO_MEMORY;
					}
					
					dcs[i].ips = tmp_ips;
				}
				dcs[i].num_ips++;
				
				/* copy the new IP address */
				
				buf = (uint8*)&dcs[i].ips[num_ips].s_addr;
				memcpy( buf, rr.rdata, 4 );
			}
		}
	}

	qsort( dcs, idx, sizeof(struct dns_rr_srv), QSORT_CAST dnssrvcmp );
	
	*dclist = dcs;
	*numdcs = idx;
	
	return NT_STATUS_OK;
}

/*********************************************************************
 Simple wrapper for a DNS NS query
*********************************************************************/

NTSTATUS ads_dns_lookup_ns( TALLOC_CTX *ctx, const char *dnsdomain, struct dns_rr_ns **nslist, int *numns )
{
	uint8 *buffer = NULL;
	int resp_len = 0;
	struct dns_rr_ns *nsarray = NULL;
	int query_count, answer_count, auth_count, additional_count;
	uint8 *p;
	int rrnum;
	int idx = 0;
	NTSTATUS status;

	if ( !ctx || !dnsdomain || !nslist ) {
		return NT_STATUS_INVALID_PARAMETER;
	}
	
	/* Send the request.  May have to loop several times in case 
	   of large replies */
	   
	status = dns_send_req( ctx, dnsdomain, T_NS, &buffer, &resp_len );
	if ( !NT_STATUS_IS_OK(status) ) {
		DEBUG(0,("ads_dns_lookup_ns: Failed to send DNS query (%s)\n",
			nt_errstr(status)));
		return status;
	}
	p = buffer;

	/* For some insane reason, the ns_initparse() et. al. routines are only
	   available in libresolv.a, and not the shared lib.  Who knows why....
	   So we have to parse the DNS reply ourselves */

	/* Pull the answer RR's count from the header.  Use the NMB ordering macros */

	query_count      = RSVAL( p, 4 );
	answer_count     = RSVAL( p, 6 );
	auth_count       = RSVAL( p, 8 );
	additional_count = RSVAL( p, 10 );

	DEBUG(4,("ads_dns_lookup_ns: %d records returned in the answer section.\n", 
		answer_count));
		
	if ( (nsarray = TALLOC_ARRAY(ctx, struct dns_rr_ns, answer_count)) == NULL ) {
		DEBUG(0,("ads_dns_lookup_ns: talloc() failure for %d char*'s\n", 
			answer_count));
		return NT_STATUS_NO_MEMORY;
	}

	/* now skip the header */

	p += NS_HFIXEDSZ;

	/* parse the query section */

	for ( rrnum=0; rrnum<query_count; rrnum++ ) {
		struct dns_query q;

		if ( !ads_dns_parse_query( ctx, buffer, buffer+resp_len, &p, &q ) ) {
			DEBUG(1,("ads_dns_lookup_ns: Failed to parse query record!\n"));
			return NT_STATUS_UNSUCCESSFUL;
		}
	}

	/* now we are at the answer section */

	for ( rrnum=0; rrnum<answer_count; rrnum++ ) {
		if ( !ads_dns_parse_rr_ns( ctx, buffer, buffer+resp_len, &p, &nsarray[rrnum] ) ) {
			DEBUG(1,("ads_dns_lookup_ns: Failed to parse answer record!\n"));
			return NT_STATUS_UNSUCCESSFUL;
		}		
	}
	idx = rrnum;

	/* Parse the authority section */
	/* just skip these for now */

	for ( rrnum=0; rrnum<auth_count; rrnum++ ) {
		struct dns_rr rr;

		if ( !ads_dns_parse_rr( ctx, buffer, buffer+resp_len, &p, &rr ) ) {
			DEBUG(1,("ads_dns_lookup_ns: Failed to parse authority record!\n"));
			return NT_STATUS_UNSUCCESSFUL;
		}
	}

	/* Parse the additional records section */

	for ( rrnum=0; rrnum<additional_count; rrnum++ ) {
		struct dns_rr rr;
		int i;

		if ( !ads_dns_parse_rr( ctx, buffer, buffer+resp_len, &p, &rr ) ) {
			DEBUG(1,("ads_dns_lookup_ns: Failed to parse additional records section!\n"));
			return NT_STATUS_UNSUCCESSFUL;
		}

		/* only interested in A records as a shortcut for having to come 
		   back later and lookup the name */

		if ( (rr.type != T_A) || (rr.rdatalen != 4) ) 
			continue;

		for ( i=0; i<idx; i++ ) {
			if ( strcmp( rr.hostname, nsarray[i].hostname ) == 0 ) {
				uint8 *buf = (uint8*)&nsarray[i].ip.s_addr;
				memcpy( buf, rr.rdata, 4 );
			}
		}
	}
	
	*nslist = nsarray;
	*numns = idx;
	
	return NT_STATUS_OK;
}

/****************************************************************************
 Store and fetch the AD client sitename.
****************************************************************************/

#define SITENAME_KEY	"AD_SITENAME"

/****************************************************************************
 Store the AD client sitename.
 We store indefinately as every new CLDAP query will re-write this.
 If the sitename is "Default-First-Site-Name" we don't store it
 as this isn't a valid DNS name.
****************************************************************************/

BOOL sitename_store(const char *sitename)
{
	time_t expire;
	BOOL ret = False;

	if (!gencache_init()) {
		return False;
	}
	
	if (!sitename || (sitename && !*sitename)) {
		DEBUG(5,("sitename_store: deleting empty sitename!\n"));
		return gencache_del(SITENAME_KEY);
	}

	expire = get_time_t_max(); /* Store indefinately. */
	
	DEBUG(10,("sitename_store: sitename = [%s], expire = [%u]\n",
		sitename, (unsigned int)expire ));

	ret = gencache_set( SITENAME_KEY, sitename, expire );
	return ret;
}

/****************************************************************************
 Fetch the AD client sitename.
 Caller must free.
****************************************************************************/

char *sitename_fetch(void)
{
	char *sitename = NULL;
	time_t timeout;
	BOOL ret = False;
	
	if (!gencache_init()) {
		return False;
	}
	
	ret = gencache_get( SITENAME_KEY, &sitename, &timeout );
	if ( !ret ) {
		DEBUG(5,("sitename_fetch: No stored sitename\n"));
	} else {
		DEBUG(5,("sitename_fetch: Returning sitename \"%s\"\n",
			sitename ));
	}
	return sitename;
}

/****************************************************************************
 Did the sitename change ?
****************************************************************************/

BOOL stored_sitename_changed(const char *sitename)
{
	BOOL ret = False;
	char *new_sitename = sitename_fetch();

	if (sitename && new_sitename && !strequal(sitename, new_sitename)) {
		ret = True;
	} else if ((sitename && !new_sitename) ||
			(!sitename && new_sitename)) {
		ret = True;
	}
	SAFE_FREE(new_sitename);
	return ret;
}

/********************************************************************
 Query with optional sitename.
********************************************************************/

NTSTATUS ads_dns_query_internal(TALLOC_CTX *ctx,
				const char *servicename,
				const char *realm,
				const char *sitename,
				struct dns_rr_srv **dclist,
				int *numdcs )
{
	char *name;
	if (sitename) {
		name = talloc_asprintf(ctx, "%s._tcp.%s._sites.dc._msdcs.%s",
				servicename, sitename, realm );
	} else {
		name = talloc_asprintf(ctx, "%s._tcp.dc._msdcs.%s",
				servicename, realm );
	}
	if (!name) {
		return NT_STATUS_NO_MEMORY;
	}
	return ads_dns_lookup_srv( ctx, name, dclist, numdcs );
}

/********************************************************************
 Query for AD DC's. Transparently use sitename.
********************************************************************/

NTSTATUS ads_dns_query_dcs(TALLOC_CTX *ctx,
			const char *realm,
			struct dns_rr_srv **dclist,
			int *numdcs )
{
	NTSTATUS status;
	char *sitename = sitename_fetch();

	status = ads_dns_query_internal(ctx, "_ldap", realm, sitename,
					dclist, numdcs);
	if (sitename && !NT_STATUS_IS_OK(status)) {
		/* Sitename DNS query may have failed. Try without. */
		status = ads_dns_query_internal(ctx, "_ldap", realm, NULL,
						dclist, numdcs);
	}
	SAFE_FREE(sitename);
	return status;
}

/********************************************************************
 Query for AD KDC's. Transparently use sitename.
 Even if our underlying kerberos libraries are UDP only, this
 is pretty safe as it's unlikely that a KDC supports TCP and not UDP.
********************************************************************/

NTSTATUS ads_dns_query_kdcs(TALLOC_CTX *ctx,
			const char *realm,
			struct dns_rr_srv **dclist,
			int *numdcs )
{
	NTSTATUS status;
	char *sitename = sitename_fetch();

	status = ads_dns_query_internal(ctx, "_kerberos", realm, sitename,
					dclist, numdcs);
	if (sitename && !NT_STATUS_IS_OK(status)) {
		/* Sitename DNS query may have failed. Try without. */
		status = ads_dns_query_internal(ctx, "_kerberos", realm, NULL,
						dclist, numdcs);
	}
	SAFE_FREE(sitename);
	return status;
}