samba-mirror/source3/libads/dns.c

/* 
   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 3 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, see <http://www.gnu.org/licenses/>.
*/

#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
#if !defined(T_NS)	/* AIX 5.3 already defines T_NS */
#  define T_NS 		ns_t_ns
#endif
#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
*********************************************************************/

#define DNS_FAILED_WAITTIME          30

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;	
	static time_t last_dns_check = 0;
	static NTSTATUS last_dns_status = NT_STATUS_OK;	
	time_t now = time(NULL);

	/* Try to prevent bursts of DNS lookups if the server is down */

	/* Protect against large clock changes */

	if ( last_dns_check > now )
		last_dns_check = 0;

	/* IF we had a DNS timeout or a bad server and we are still 
	   in the 30 second cache window, just return the previous 
	   status and save the network timeout. */

	if ( (NT_STATUS_EQUAL(last_dns_status,NT_STATUS_IO_TIMEOUT) ||
	      NT_STATUS_EQUAL(last_dns_status,NT_STATUS_CONNECTION_REFUSED)) &&
	     (last_dns_check+DNS_FAILED_WAITTIME) > now ) 
	{
		DEBUG(10,("last_dns_check: Returning cached status (%s)\n",
			  nt_errstr(last_dns_status) ));
		return last_dns_status;
	}

	/* Send the Query */
	do {
		if ( buffer )
			TALLOC_FREE( buffer );
		
		buf_len = resp_len * sizeof(uint8);

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

		if ( (resp_len = res_query(name, C_IN, q_type, buffer, buf_len)) < 0 ) {
			DEBUG(3,("ads_dns_lookup_srv: Failed to resolve %s (%s)\n", name, strerror(errno)));
			TALLOC_FREE( buffer );
			last_dns_status = NT_STATUS_UNSUCCESSFUL;
			
			if (errno == ETIMEDOUT) {
				last_dns_status = NT_STATUS_IO_TIMEOUT;				
			}
			if (errno == ECONNREFUSED) {
				last_dns_status = NT_STATUS_CONNECTION_REFUSED;				
			}
			last_dns_check = time(NULL);
			return last_dns_status;
		}
	} while ( buf_len < resp_len && resp_len < MAX_DNS_PACKET_SIZE );
	
	*buf = buffer;
	*resp_length = resp_len;

	last_dns_check = time(NULL);
	last_dns_status = NT_STATUS_OK;	
	return last_dns_status;
}

/*********************************************************************
 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(3,("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 (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;
		}
	} else {
		dcs = NULL;
	}

	/* 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(3,("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 (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;
		}
	} else {
		nsarray = NULL;
	}

	/* 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/DOMAIN/%s"

static char *sitename_key(const char *realm)
{
	char *keystr;
	
	if (asprintf(&keystr, SITENAME_KEY, strupper_static(realm)) == -1) {
		return NULL;
	}

	return keystr;
}


/****************************************************************************
 Store the AD client sitename.
 We store indefinately as every new CLDAP query will re-write this.
****************************************************************************/

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

	if (!gencache_init()) {
		return False;
	}

	if (!realm || (strlen(realm) == 0)) {
		DEBUG(0,("sitename_store: no realm\n"));
		return False;
	}
	
	key = sitename_key(realm);

	if (!sitename || (sitename && !*sitename)) {
		DEBUG(5,("sitename_store: deleting empty sitename!\n"));
		ret = gencache_del(key);
		SAFE_FREE(key);
		return ret;
	}

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

	ret = gencache_set( key, sitename, expire );
	SAFE_FREE(key);
	return ret;
}

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

char *sitename_fetch(const char *realm)
{
	char *sitename = NULL;
	time_t timeout;
	BOOL ret = False;
	const char *query_realm;
	char *key;
	
	if (!gencache_init()) {
		return False;
	}

	if (!realm || (strlen(realm) == 0)) {
		query_realm = lp_realm(); 
	} else {
		query_realm = realm;
	}

	key = sitename_key(query_realm);

	ret = gencache_get( key, &sitename, &timeout );
	SAFE_FREE(key);
	if ( !ret ) {
		DEBUG(5,("sitename_fetch: No stored sitename for %s\n",
			query_realm));
	} else {
		DEBUG(5,("sitename_fetch: Returning sitename for %s: \"%s\"\n",
			query_realm, sitename ));
	}
	return sitename;
}

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

BOOL stored_sitename_changed(const char *realm, const char *sitename)
{
	BOOL ret = False;

	char *new_sitename;

	if (!realm || (strlen(realm) == 0)) {
		DEBUG(0,("stored_sitename_changed: no realm\n"));
		return False;
	}

	new_sitename = sitename_fetch(realm);

	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.
********************************************************************/

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

/********************************************************************
 Query for AD DC's.
********************************************************************/

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

	status = ads_dns_query_internal(ctx, "_ldap", "dc", realm, sitename,
					dclist, numdcs);

	if (NT_STATUS_EQUAL(status, NT_STATUS_IO_TIMEOUT) ||
	    NT_STATUS_EQUAL(status, NT_STATUS_CONNECTION_REFUSED)) {
		return status;
	}

	if (sitename &&
	    ((!NT_STATUS_IS_OK(status)) ||
	     (NT_STATUS_IS_OK(status) && (numdcs == 0)))) {
		/* Sitename DNS query may have failed. Try without. */
		status = ads_dns_query_internal(ctx, "_ldap", "dc", realm,
						NULL, dclist, numdcs);
	}
	return status;
}

/********************************************************************
 Query for AD GC's.
********************************************************************/

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

	status = ads_dns_query_internal(ctx, "_ldap", "gc", realm, sitename,
					dclist, numdcs);

	if (NT_STATUS_EQUAL(status, NT_STATUS_IO_TIMEOUT) ||
	    NT_STATUS_EQUAL(status, NT_STATUS_CONNECTION_REFUSED)) {
		return status;
	}

	if (sitename &&
	    ((!NT_STATUS_IS_OK(status)) ||
	     (NT_STATUS_IS_OK(status) && (numdcs == 0)))) {
		/* Sitename DNS query may have failed. Try without. */
		status = ads_dns_query_internal(ctx, "_ldap", "gc", realm,
						NULL, dclist, numdcs);
	}
	return status;
}

/********************************************************************
 Query for AD KDC's.
 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 *dns_forest_name,
			    const char *sitename,
			    struct dns_rr_srv **dclist,
			    int *numdcs )
{
	NTSTATUS status;

	status = ads_dns_query_internal(ctx, "_kerberos", "dc",
					dns_forest_name, sitename, dclist,
					numdcs);

	if (NT_STATUS_EQUAL(status, NT_STATUS_IO_TIMEOUT) ||
	    NT_STATUS_EQUAL(status, NT_STATUS_CONNECTION_REFUSED)) {
		return status;
	}

	if (sitename &&
	    ((!NT_STATUS_IS_OK(status)) ||
	     (NT_STATUS_IS_OK(status) && (numdcs == 0)))) {
		/* Sitename DNS query may have failed. Try without. */
		status = ads_dns_query_internal(ctx, "_kerberos", "dc",
						dns_forest_name, NULL,
						dclist, numdcs);
	}
	return status;
}

/********************************************************************
 Query for AD PDC. Sitename is obsolete here.
********************************************************************/

NTSTATUS ads_dns_query_pdc(TALLOC_CTX *ctx,
			   const char *dns_domain_name,
			   struct dns_rr_srv **dclist,
			   int *numdcs )
{
	return ads_dns_query_internal(ctx, "_ldap", "pdc", dns_domain_name,
				      NULL, dclist, numdcs);
}

/********************************************************************
 Query for AD DC by guid. Sitename is obsolete here.
********************************************************************/

NTSTATUS ads_dns_query_dcs_guid(TALLOC_CTX *ctx,
				const char *dns_forest_name,
				const struct GUID *domain_guid,
				struct dns_rr_srv **dclist,
				int *numdcs )
{
	/*_ldap._tcp.DomainGuid.domains._msdcs.DnsForestName */

	const char *domains;
	const char *guid_string;

	guid_string = GUID_string(ctx, domain_guid);
	if (!guid_string) {
		return NT_STATUS_NO_MEMORY;
	}

	/* little hack */
	domains = talloc_asprintf(ctx, "%s.domains", guid_string);
	if (!domains) {
		return NT_STATUS_NO_MEMORY;
	}

	return ads_dns_query_internal(ctx, "_ldap", domains, dns_forest_name,
				      NULL, dclist, numdcs);
}