source: trunk/samba-3.0.25pre1/source/libads/dns.c@ 5

Last change on this file since 5 was 1, checked in by Paul Smedley, 18 years ago

Initial code import
File size: 19.7 KB
Line 
1/*
2 Unix SMB/CIFS implementation.
3 DNS utility library
4 Copyright (C) Gerald (Jerry) Carter 2006.
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
21#include "includes.h"
22
23/* AIX resolv.h uses 'class' in struct ns_rr */
24
25#if defined(AIX)
26# if defined(class)
27# undef class
28# endif
29#endif /* AIX */
30
31/* resolver headers */
32
33#include <sys/types.h>
34#include <netinet/in.h>
35#include <arpa/nameser.h>
36#include <resolv.h>
37#include <netdb.h>
38
39#define MAX_DNS_PACKET_SIZE 0xffff
40
41#ifdef NS_HFIXEDSZ /* Bind 8/9 interface */
42#if !defined(C_IN) /* AIX 5.3 already defines C_IN */
43# define C_IN ns_c_in
44#endif
45#if !defined(T_A) /* AIX 5.3 already defines T_A */
46# define T_A ns_t_a
47#endif
48# define T_SRV ns_t_srv
49#if !defined(T_NS) /* AIX 5.3 already defines T_NS */
50# define T_NS ns_t_ns
51#endif
52#else
53# ifdef HFIXEDSZ
54# define NS_HFIXEDSZ HFIXEDSZ
55# else
56# define NS_HFIXEDSZ sizeof(HEADER)
57# endif /* HFIXEDSZ */
58# ifdef PACKETSZ
59# define NS_PACKETSZ PACKETSZ
60# else /* 512 is usually the default */
61# define NS_PACKETSZ 512
62# endif /* PACKETSZ */
63# define T_SRV 33
64#endif
65
66/*********************************************************************
67*********************************************************************/
68
69static BOOL ads_dns_parse_query( TALLOC_CTX *ctx, uint8 *start, uint8 *end,
70 uint8 **ptr, struct dns_query *q )
71{
72 uint8 *p = *ptr;
73 pstring hostname;
74 int namelen;
75
76 ZERO_STRUCTP( q );
77
78 if ( !start || !end || !q || !*ptr)
79 return False;
80
81 /* See RFC 1035 for details. If this fails, then return. */
82
83 namelen = dn_expand( start, end, p, hostname, sizeof(hostname) );
84 if ( namelen < 0 ) {
85 return False;
86 }
87 p += namelen;
88 q->hostname = talloc_strdup( ctx, hostname );
89
90 /* check that we have space remaining */
91
92 if ( PTR_DIFF(p+4, end) > 0 )
93 return False;
94
95 q->type = RSVAL( p, 0 );
96 q->in_class = RSVAL( p, 2 );
97 p += 4;
98
99 *ptr = p;
100
101 return True;
102}
103
104/*********************************************************************
105*********************************************************************/
106
107static BOOL ads_dns_parse_rr( TALLOC_CTX *ctx, uint8 *start, uint8 *end,
108 uint8 **ptr, struct dns_rr *rr )
109{
110 uint8 *p = *ptr;
111 pstring hostname;
112 int namelen;
113
114 if ( !start || !end || !rr || !*ptr)
115 return -1;
116
117 ZERO_STRUCTP( rr );
118 /* pull the name from the answer */
119
120 namelen = dn_expand( start, end, p, hostname, sizeof(hostname) );
121 if ( namelen < 0 ) {
122 return -1;
123 }
124 p += namelen;
125 rr->hostname = talloc_strdup( ctx, hostname );
126
127 /* check that we have space remaining */
128
129 if ( PTR_DIFF(p+10, end) > 0 )
130 return False;
131
132 /* pull some values and then skip onto the string */
133
134 rr->type = RSVAL(p, 0);
135 rr->in_class = RSVAL(p, 2);
136 rr->ttl = RIVAL(p, 4);
137 rr->rdatalen = RSVAL(p, 8);
138
139 p += 10;
140
141 /* sanity check the available space */
142
143 if ( PTR_DIFF(p+rr->rdatalen, end ) > 0 ) {
144 return False;
145
146 }
147
148 /* save a point to the rdata for this section */
149
150 rr->rdata = p;
151 p += rr->rdatalen;
152
153 *ptr = p;
154
155 return True;
156}
157
158/*********************************************************************
159*********************************************************************/
160
161static BOOL ads_dns_parse_rr_srv( TALLOC_CTX *ctx, uint8 *start, uint8 *end,
162 uint8 **ptr, struct dns_rr_srv *srv )
163{
164 struct dns_rr rr;
165 uint8 *p;
166 pstring dcname;
167 int namelen;
168
169 if ( !start || !end || !srv || !*ptr)
170 return -1;
171
172 /* Parse the RR entry. Coming out of the this, ptr is at the beginning
173 of the next record */
174
175 if ( !ads_dns_parse_rr( ctx, start, end, ptr, &rr ) ) {
176 DEBUG(1,("ads_dns_parse_rr_srv: Failed to parse RR record\n"));
177 return False;
178 }
179
180 if ( rr.type != T_SRV ) {
181 DEBUG(1,("ads_dns_parse_rr_srv: Bad answer type (%d)\n", rr.type));
182 return False;
183 }
184
185 p = rr.rdata;
186
187 srv->priority = RSVAL(p, 0);
188 srv->weight = RSVAL(p, 2);
189 srv->port = RSVAL(p, 4);
190
191 p += 6;
192
193 namelen = dn_expand( start, end, p, dcname, sizeof(dcname) );
194 if ( namelen < 0 ) {
195 DEBUG(1,("ads_dns_parse_rr_srv: Failed to uncompress name!\n"));
196 return False;
197 }
198 srv->hostname = talloc_strdup( ctx, dcname );
199
200 return True;
201}
202
203/*********************************************************************
204*********************************************************************/
205
206static BOOL ads_dns_parse_rr_ns( TALLOC_CTX *ctx, uint8 *start, uint8 *end,
207 uint8 **ptr, struct dns_rr_ns *nsrec )
208{
209 struct dns_rr rr;
210 uint8 *p;
211 pstring nsname;
212 int namelen;
213
214 if ( !start || !end || !nsrec || !*ptr)
215 return -1;
216
217 /* Parse the RR entry. Coming out of the this, ptr is at the beginning
218 of the next record */
219
220 if ( !ads_dns_parse_rr( ctx, start, end, ptr, &rr ) ) {
221 DEBUG(1,("ads_dns_parse_rr_ns: Failed to parse RR record\n"));
222 return False;
223 }
224
225 if ( rr.type != T_NS ) {
226 DEBUG(1,("ads_dns_parse_rr_ns: Bad answer type (%d)\n", rr.type));
227 return False;
228 }
229
230 p = rr.rdata;
231
232 /* ame server hostname */
233
234 namelen = dn_expand( start, end, p, nsname, sizeof(nsname) );
235 if ( namelen < 0 ) {
236 DEBUG(1,("ads_dns_parse_rr_ns: Failed to uncompress name!\n"));
237 return False;
238 }
239 nsrec->hostname = talloc_strdup( ctx, nsname );
240
241 return True;
242}
243
244/*********************************************************************
245 Sort SRV record list based on weight and priority. See RFC 2782.
246*********************************************************************/
247
248static int dnssrvcmp( struct dns_rr_srv *a, struct dns_rr_srv *b )
249{
250 if ( a->priority == b->priority ) {
251
252 /* randomize entries with an equal weight and priority */
253 if ( a->weight == b->weight )
254 return 0;
255
256 /* higher weights should be sorted lower */
257 if ( a->weight > b->weight )
258 return -1;
259 else
260 return 1;
261 }
262
263 if ( a->priority < b->priority )
264 return -1;
265
266 return 1;
267}
268
269/*********************************************************************
270 Simple wrapper for a DNS query
271*********************************************************************/
272
273static NTSTATUS dns_send_req( TALLOC_CTX *ctx, const char *name, int q_type,
274 uint8 **buf, int *resp_length )
275{
276 uint8 *buffer = NULL;
277 size_t buf_len;
278 int resp_len = NS_PACKETSZ;
279
280 do {
281 if ( buffer )
282 TALLOC_FREE( buffer );
283
284 buf_len = resp_len * sizeof(uint8);
285
286 if ( (buffer = TALLOC_ARRAY(ctx, uint8, buf_len)) == NULL ) {
287 DEBUG(0,("ads_dns_lookup_srv: talloc() failed!\n"));
288 return NT_STATUS_NO_MEMORY;
289 }
290
291 if ( (resp_len = res_query(name, C_IN, q_type, buffer, buf_len)) < 0 ) {
292 DEBUG(3,("ads_dns_lookup_srv: Failed to resolve %s (%s)\n", name, strerror(errno)));
293 TALLOC_FREE( buffer );
294 if (errno == ETIMEDOUT) {
295 return NT_STATUS_IO_TIMEOUT;
296 }
297 if (errno == ECONNREFUSED) {
298 return NT_STATUS_CONNECTION_REFUSED;
299 }
300 return NT_STATUS_UNSUCCESSFUL;
301 }
302 } while ( buf_len < resp_len && resp_len < MAX_DNS_PACKET_SIZE );
303
304 *buf = buffer;
305 *resp_length = resp_len;
306
307 return NT_STATUS_OK;
308}
309
310/*********************************************************************
311 Simple wrapper for a DNS SRV query
312*********************************************************************/
313
314static NTSTATUS ads_dns_lookup_srv( TALLOC_CTX *ctx, const char *name, struct dns_rr_srv **dclist, int *numdcs )
315{
316 uint8 *buffer = NULL;
317 int resp_len = 0;
318 struct dns_rr_srv *dcs = NULL;
319 int query_count, answer_count, auth_count, additional_count;
320 uint8 *p = buffer;
321 int rrnum;
322 int idx = 0;
323 NTSTATUS status;
324
325 if ( !ctx || !name || !dclist ) {
326 return NT_STATUS_INVALID_PARAMETER;
327 }
328
329 /* Send the request. May have to loop several times in case
330 of large replies */
331
332 status = dns_send_req( ctx, name, T_SRV, &buffer, &resp_len );
333 if ( !NT_STATUS_IS_OK(status) ) {
334 DEBUG(3,("ads_dns_lookup_srv: Failed to send DNS query (%s)\n",
335 nt_errstr(status)));
336 return status;
337 }
338 p = buffer;
339
340 /* For some insane reason, the ns_initparse() et. al. routines are only
341 available in libresolv.a, and not the shared lib. Who knows why....
342 So we have to parse the DNS reply ourselves */
343
344 /* Pull the answer RR's count from the header. Use the NMB ordering macros */
345
346 query_count = RSVAL( p, 4 );
347 answer_count = RSVAL( p, 6 );
348 auth_count = RSVAL( p, 8 );
349 additional_count = RSVAL( p, 10 );
350
351 DEBUG(4,("ads_dns_lookup_srv: %d records returned in the answer section.\n",
352 answer_count));
353
354 if ( (dcs = TALLOC_ZERO_ARRAY(ctx, struct dns_rr_srv, answer_count)) == NULL ) {
355 DEBUG(0,("ads_dns_lookup_srv: talloc() failure for %d char*'s\n",
356 answer_count));
357 return NT_STATUS_NO_MEMORY;
358 }
359
360 /* now skip the header */
361
362 p += NS_HFIXEDSZ;
363
364 /* parse the query section */
365
366 for ( rrnum=0; rrnum<query_count; rrnum++ ) {
367 struct dns_query q;
368
369 if ( !ads_dns_parse_query( ctx, buffer, buffer+resp_len, &p, &q ) ) {
370 DEBUG(1,("ads_dns_lookup_srv: Failed to parse query record!\n"));
371 return NT_STATUS_UNSUCCESSFUL;
372 }
373 }
374
375 /* now we are at the answer section */
376
377 for ( rrnum=0; rrnum<answer_count; rrnum++ ) {
378 if ( !ads_dns_parse_rr_srv( ctx, buffer, buffer+resp_len, &p, &dcs[rrnum] ) ) {
379 DEBUG(1,("ads_dns_lookup_srv: Failed to parse answer record!\n"));
380 return NT_STATUS_UNSUCCESSFUL;
381 }
382 }
383 idx = rrnum;
384
385 /* Parse the authority section */
386 /* just skip these for now */
387
388 for ( rrnum=0; rrnum<auth_count; rrnum++ ) {
389 struct dns_rr rr;
390
391 if ( !ads_dns_parse_rr( ctx, buffer, buffer+resp_len, &p, &rr ) ) {
392 DEBUG(1,("ads_dns_lookup_srv: Failed to parse authority record!\n"));
393 return NT_STATUS_UNSUCCESSFUL;
394 }
395 }
396
397 /* Parse the additional records section */
398
399 for ( rrnum=0; rrnum<additional_count; rrnum++ ) {
400 struct dns_rr rr;
401 int i;
402
403 if ( !ads_dns_parse_rr( ctx, buffer, buffer+resp_len, &p, &rr ) ) {
404 DEBUG(1,("ads_dns_lookup_srv: Failed to parse additional records section!\n"));
405 return NT_STATUS_UNSUCCESSFUL;
406 }
407
408 /* only interested in A records as a shortcut for having to come
409 back later and lookup the name. For multi-homed hosts, the
410 number of additional records and exceed the number of answer
411 records. */
412
413
414 if ( (rr.type != T_A) || (rr.rdatalen != 4) )
415 continue;
416
417 for ( i=0; i<idx; i++ ) {
418 if ( strcmp( rr.hostname, dcs[i].hostname ) == 0 ) {
419 int num_ips = dcs[i].num_ips;
420 uint8 *buf;
421 struct in_addr *tmp_ips;
422
423 /* allocate new memory */
424
425 if ( dcs[i].num_ips == 0 ) {
426 if ( (dcs[i].ips = TALLOC_ARRAY( dcs,
427 struct in_addr, 1 )) == NULL )
428 {
429 return NT_STATUS_NO_MEMORY;
430 }
431 } else {
432 if ( (tmp_ips = TALLOC_REALLOC_ARRAY( dcs, dcs[i].ips,
433 struct in_addr, dcs[i].num_ips+1)) == NULL )
434 {
435 return NT_STATUS_NO_MEMORY;
436 }
437
438 dcs[i].ips = tmp_ips;
439 }
440 dcs[i].num_ips++;
441
442 /* copy the new IP address */
443
444 buf = (uint8*)&dcs[i].ips[num_ips].s_addr;
445 memcpy( buf, rr.rdata, 4 );
446 }
447 }
448 }
449
450 qsort( dcs, idx, sizeof(struct dns_rr_srv), QSORT_CAST dnssrvcmp );
451
452 *dclist = dcs;
453 *numdcs = idx;
454
455 return NT_STATUS_OK;
456}
457
458/*********************************************************************
459 Simple wrapper for a DNS NS query
460*********************************************************************/
461
462NTSTATUS ads_dns_lookup_ns( TALLOC_CTX *ctx, const char *dnsdomain, struct dns_rr_ns **nslist, int *numns )
463{
464 uint8 *buffer = NULL;
465 int resp_len = 0;
466 struct dns_rr_ns *nsarray = NULL;
467 int query_count, answer_count, auth_count, additional_count;
468 uint8 *p;
469 int rrnum;
470 int idx = 0;
471 NTSTATUS status;
472
473 if ( !ctx || !dnsdomain || !nslist ) {
474 return NT_STATUS_INVALID_PARAMETER;
475 }
476
477 /* Send the request. May have to loop several times in case
478 of large replies */
479
480 status = dns_send_req( ctx, dnsdomain, T_NS, &buffer, &resp_len );
481 if ( !NT_STATUS_IS_OK(status) ) {
482 DEBUG(3,("ads_dns_lookup_ns: Failed to send DNS query (%s)\n",
483 nt_errstr(status)));
484 return status;
485 }
486 p = buffer;
487
488 /* For some insane reason, the ns_initparse() et. al. routines are only
489 available in libresolv.a, and not the shared lib. Who knows why....
490 So we have to parse the DNS reply ourselves */
491
492 /* Pull the answer RR's count from the header. Use the NMB ordering macros */
493
494 query_count = RSVAL( p, 4 );
495 answer_count = RSVAL( p, 6 );
496 auth_count = RSVAL( p, 8 );
497 additional_count = RSVAL( p, 10 );
498
499 DEBUG(4,("ads_dns_lookup_ns: %d records returned in the answer section.\n",
500 answer_count));
501
502 if ( (nsarray = TALLOC_ARRAY(ctx, struct dns_rr_ns, answer_count)) == NULL ) {
503 DEBUG(0,("ads_dns_lookup_ns: talloc() failure for %d char*'s\n",
504 answer_count));
505 return NT_STATUS_NO_MEMORY;
506 }
507
508 /* now skip the header */
509
510 p += NS_HFIXEDSZ;
511
512 /* parse the query section */
513
514 for ( rrnum=0; rrnum<query_count; rrnum++ ) {
515 struct dns_query q;
516
517 if ( !ads_dns_parse_query( ctx, buffer, buffer+resp_len, &p, &q ) ) {
518 DEBUG(1,("ads_dns_lookup_ns: Failed to parse query record!\n"));
519 return NT_STATUS_UNSUCCESSFUL;
520 }
521 }
522
523 /* now we are at the answer section */
524
525 for ( rrnum=0; rrnum<answer_count; rrnum++ ) {
526 if ( !ads_dns_parse_rr_ns( ctx, buffer, buffer+resp_len, &p, &nsarray[rrnum] ) ) {
527 DEBUG(1,("ads_dns_lookup_ns: Failed to parse answer record!\n"));
528 return NT_STATUS_UNSUCCESSFUL;
529 }
530 }
531 idx = rrnum;
532
533 /* Parse the authority section */
534 /* just skip these for now */
535
536 for ( rrnum=0; rrnum<auth_count; rrnum++ ) {
537 struct dns_rr rr;
538
539 if ( !ads_dns_parse_rr( ctx, buffer, buffer+resp_len, &p, &rr ) ) {
540 DEBUG(1,("ads_dns_lookup_ns: Failed to parse authority record!\n"));
541 return NT_STATUS_UNSUCCESSFUL;
542 }
543 }
544
545 /* Parse the additional records section */
546
547 for ( rrnum=0; rrnum<additional_count; rrnum++ ) {
548 struct dns_rr rr;
549 int i;
550
551 if ( !ads_dns_parse_rr( ctx, buffer, buffer+resp_len, &p, &rr ) ) {
552 DEBUG(1,("ads_dns_lookup_ns: Failed to parse additional records section!\n"));
553 return NT_STATUS_UNSUCCESSFUL;
554 }
555
556 /* only interested in A records as a shortcut for having to come
557 back later and lookup the name */
558
559 if ( (rr.type != T_A) || (rr.rdatalen != 4) )
560 continue;
561
562 for ( i=0; i<idx; i++ ) {
563 if ( strcmp( rr.hostname, nsarray[i].hostname ) == 0 ) {
564 uint8 *buf = (uint8*)&nsarray[i].ip.s_addr;
565 memcpy( buf, rr.rdata, 4 );
566 }
567 }
568 }
569
570 *nslist = nsarray;
571 *numns = idx;
572
573 return NT_STATUS_OK;
574}
575
576/****************************************************************************
577 Store and fetch the AD client sitename.
578****************************************************************************/
579
580#define SITENAME_KEY "AD_SITENAME/DOMAIN/%s"
581
582static char *sitename_key(const char *realm)
583{
584 char *keystr;
585
586 if (asprintf(&keystr, SITENAME_KEY, strupper_static(realm)) == -1) {
587 return NULL;
588 }
589
590 return keystr;
591}
592
593
594/****************************************************************************
595 Store the AD client sitename.
596 We store indefinately as every new CLDAP query will re-write this.
597 If the sitename is "Default-First-Site-Name" we don't store it
598 as this isn't a valid DNS name.
599****************************************************************************/
600
601BOOL sitename_store(const char *realm, const char *sitename)
602{
603 time_t expire;
604 BOOL ret = False;
605 char *key;
606
607 if (!gencache_init()) {
608 return False;
609 }
610
611 if (!realm || (strlen(realm) == 0)) {
612 DEBUG(0,("no realm\n"));
613 return False;
614 }
615
616 key = sitename_key(realm);
617
618 if (!sitename || (sitename && !*sitename)) {
619 DEBUG(5,("sitename_store: deleting empty sitename!\n"));
620 ret = gencache_del(key);
621 SAFE_FREE(key);
622 return ret;
623 }
624
625 expire = get_time_t_max(); /* Store indefinately. */
626
627 DEBUG(10,("sitename_store: realm = [%s], sitename = [%s], expire = [%u]\n",
628 realm, sitename, (unsigned int)expire ));
629
630 ret = gencache_set( key, sitename, expire );
631 SAFE_FREE(key);
632 return ret;
633}
634
635/****************************************************************************
636 Fetch the AD client sitename.
637 Caller must free.
638****************************************************************************/
639
640char *sitename_fetch(const char *realm)
641{
642 char *sitename = NULL;
643 time_t timeout;
644 BOOL ret = False;
645 const char *query_realm;
646 char *key;
647
648 if (!gencache_init()) {
649 return False;
650 }
651
652 if (!realm || (strlen(realm) == 0)) {
653 query_realm = lp_realm();
654 } else {
655 query_realm = realm;
656 }
657
658 key = sitename_key(query_realm);
659
660 ret = gencache_get( key, &sitename, &timeout );
661 SAFE_FREE(key);
662 if ( !ret ) {
663 DEBUG(5,("sitename_fetch: No stored sitename for %s\n",
664 query_realm));
665 } else {
666 DEBUG(5,("sitename_fetch: Returning sitename for %s: \"%s\"\n",
667 query_realm, sitename ));
668 }
669 return sitename;
670}
671
672/****************************************************************************
673 Did the sitename change ?
674****************************************************************************/
675
676BOOL stored_sitename_changed(const char *realm, const char *sitename)
677{
678 BOOL ret = False;
679
680 char *new_sitename;
681
682 if (!realm || (strlen(realm) == 0)) {
683 DEBUG(0,("no realm\n"));
684 return False;
685 }
686
687 new_sitename = sitename_fetch(realm);
688
689 if (sitename && new_sitename && !strequal(sitename, new_sitename)) {
690 ret = True;
691 } else if ((sitename && !new_sitename) ||
692 (!sitename && new_sitename)) {
693 ret = True;
694 }
695 SAFE_FREE(new_sitename);
696 return ret;
697}
698
699/********************************************************************
700 Query with optional sitename.
701********************************************************************/
702
703NTSTATUS ads_dns_query_internal(TALLOC_CTX *ctx,
704 const char *servicename,
705 const char *realm,
706 const char *sitename,
707 struct dns_rr_srv **dclist,
708 int *numdcs )
709{
710 char *name;
711 if (sitename) {
712 name = talloc_asprintf(ctx, "%s._tcp.%s._sites.dc._msdcs.%s",
713 servicename, sitename, realm );
714 } else {
715 name = talloc_asprintf(ctx, "%s._tcp.dc._msdcs.%s",
716 servicename, realm );
717 }
718 if (!name) {
719 return NT_STATUS_NO_MEMORY;
720 }
721 return ads_dns_lookup_srv( ctx, name, dclist, numdcs );
722}
723
724/********************************************************************
725 Query for AD DC's.
726********************************************************************/
727
728NTSTATUS ads_dns_query_dcs(TALLOC_CTX *ctx,
729 const char *realm,
730 const char *sitename,
731 struct dns_rr_srv **dclist,
732 int *numdcs )
733{
734 NTSTATUS status;
735
736 status = ads_dns_query_internal(ctx, "_ldap", realm, sitename,
737 dclist, numdcs);
738
739 if (NT_STATUS_EQUAL(status, NT_STATUS_IO_TIMEOUT) ||
740 NT_STATUS_EQUAL(status, NT_STATUS_CONNECTION_REFUSED)) {
741 return status;
742 }
743
744 if (sitename && !NT_STATUS_IS_OK(status)) {
745 /* Sitename DNS query may have failed. Try without. */
746 status = ads_dns_query_internal(ctx, "_ldap", realm, NULL,
747 dclist, numdcs);
748 }
749 return status;
750}
751
752/********************************************************************
753 Query for AD KDC's.
754 Even if our underlying kerberos libraries are UDP only, this
755 is pretty safe as it's unlikely that a KDC supports TCP and not UDP.
756********************************************************************/
757
758NTSTATUS ads_dns_query_kdcs(TALLOC_CTX *ctx,
759 const char *realm,
760 const char *sitename,
761 struct dns_rr_srv **dclist,
762 int *numdcs )
763{
764 NTSTATUS status;
765
766 status = ads_dns_query_internal(ctx, "_kerberos", realm, sitename,
767 dclist, numdcs);
768
769 if (NT_STATUS_EQUAL(status, NT_STATUS_IO_TIMEOUT) ||
770 NT_STATUS_EQUAL(status, NT_STATUS_CONNECTION_REFUSED)) {
771 return status;
772 }
773
774 if (sitename && !NT_STATUS_IS_OK(status)) {
775 /* Sitename DNS query may have failed. Try without. */
776 status = ads_dns_query_internal(ctx, "_kerberos", realm, NULL,
777 dclist, numdcs);
778 }
779 return status;
780}
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