Move source3/libads/dns.c to lib/addns

3 files changed, 976 insertions, 0 deletions

diff --git a/lib/addns/dnsquery.c b/lib/addns/dnsquery.c
new file mode 100644
index 0000000000..f680d63258
--- /dev/null
+++ b/lib/addns/dnsquery.c
@@ -0,0 +1,910 @@
+/*
+   Unix SMB/CIFS implementation.
+   DNS utility library
+   Copyright (C) Gerald (Jerry) Carter           2006.
+   Copyright (C) Jeremy Allison                  2007.
+
+   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"
+#include "lib/util/util_net.h"
+#include "lib/util/tsort.h"
+#include "dnsquery.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
+
+#if defined(HAVE_IPV6)
+#if !defined(T_AAAA)
+#  define T_AAAA	ns_t_aaaa
+#endif
+#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_t *start, uint8_t *end,
+                          uint8_t **ptr, struct dns_query *q )
+{
+	uint8_t *p = *ptr;
+	char hostname[MAX_DNS_NAME_LENGTH];
+	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_t *start, uint8_t *end,
+                       uint8_t **ptr, struct dns_rr *rr )
+{
+	uint8_t *p = *ptr;
+	char hostname[MAX_DNS_NAME_LENGTH];
+	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_t *start, uint8_t *end,
+                       uint8_t **ptr, struct dns_rr_srv *srv )
+{
+	struct dns_rr rr;
+	uint8_t *p;
+	char dcname[MAX_DNS_NAME_LENGTH];
+	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 );
+
+	DEBUG(10,("ads_dns_parse_rr_srv: Parsed %s [%u, %u, %u]\n",
+		  srv->hostname,
+		  srv->priority,
+		  srv->weight,
+		  srv->port));
+
+	return true;
+}
+
+/*********************************************************************
+*********************************************************************/
+
+static bool ads_dns_parse_rr_ns( TALLOC_CTX *ctx, uint8_t *start, uint8_t *end,
+                       uint8_t **ptr, struct dns_rr_ns *nsrec )
+{
+	struct dns_rr rr;
+	uint8_t *p;
+	char nsname[MAX_DNS_NAME_LENGTH];
+	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_t **buf, int *resp_length )
+{
+	uint8_t *buffer = NULL;
+	size_t buf_len = 0;
+	int resp_len = NS_PACKETSZ;
+	static time_t last_dns_check = 0;
+	static NTSTATUS last_dns_status = NT_STATUS_OK;
+	time_t now = time_mono(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_t);
+
+		if (buf_len) {
+			if ((buffer = talloc_array(ctx, uint8_t, buf_len))
+					== NULL ) {
+				DEBUG(0,("ads_dns_lookup_srv: "
+					"talloc() failed!\n"));
+				last_dns_status = NT_STATUS_NO_MEMORY;
+				last_dns_check = time_mono(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_mono(NULL);
+			return last_dns_status;
+		}
+
+		/* On AIX, Solaris, and possibly some older glibc systems (e.g. SLES8)
+		   truncated replies never give back a resp_len > buflen
+		   which ends up causing DNS resolve failures on large tcp DNS replies */
+
+		if (buf_len == resp_len) {
+			if (resp_len == MAX_DNS_PACKET_SIZE) {
+				DEBUG(1,("dns_send_req: DNS reply too large when resolving %s\n",
+					name));
+				TALLOC_FREE( buffer );
+				last_dns_status = NT_STATUS_BUFFER_TOO_SMALL;
+				last_dns_check = time_mono(NULL);
+				return last_dns_status;
+			}
+
+			resp_len = MIN(resp_len*2, MAX_DNS_PACKET_SIZE);
+		}
+
+
+	} while ( buf_len < resp_len && resp_len <= MAX_DNS_PACKET_SIZE );
+
+	*buf = buffer;
+	*resp_length = resp_len;
+
+	last_dns_check = time_mono(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 *dns_hosts_file,
+				const char *name,
+				struct dns_rr_srv **dclist,
+				int *numdcs)
+{
+	uint8_t *buffer = NULL;
+	int resp_len = 0;
+	struct dns_rr_srv *dcs = NULL;
+	int query_count, answer_count, auth_count, additional_count;
+	uint8_t *p = buffer;
+	int rrnum;
+	int idx = 0;
+	NTSTATUS status;
+
+	if ( !ctx || !name || !dclist ) {
+		return NT_STATUS_INVALID_PARAMETER;
+	}
+
+	if (dns_hosts_file) {
+		return resolve_dns_hosts_file_as_dns_rr(dns_hosts_file,
+							name, true, ctx,
+							dclist, numdcs);
+	}
+
+	/* 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 [%d]!\n", rrnum));
+			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 recordi [%d]!\n", rrnum));
+			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! [%d]\n", rrnum));
+			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! [%d]\n", rrnum));
+			return NT_STATUS_UNSUCCESSFUL;
+		}
+
+		/* Only interested in A or AAAA 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) {
+#if defined(HAVE_IPV6)
+			/* RFC2874 defines A6 records. This
+			 * requires recusive and horribly complex lookups.
+			 * Bastards. Ignore this for now.... JRA.
+			 * Luckily RFC3363 reprecates A6 records.
+			 */
+			if (rr.type != T_AAAA || rr.rdatalen != 16)
+#endif
+				continue;
+		}
+
+		for ( i=0; i<idx; i++ ) {
+			if ( strcmp( rr.hostname, dcs[i].hostname ) == 0 ) {
+				int num_ips = dcs[i].num_ips;
+				struct sockaddr_storage *tmp_ss_s;
+
+				/* allocate new memory */
+
+				if (dcs[i].num_ips == 0) {
+					if ((dcs[i].ss_s = talloc_array(dcs,
+						struct sockaddr_storage, 1 ))
+							== NULL ) {
+						return NT_STATUS_NO_MEMORY;
+					}
+				} else {
+					if ((tmp_ss_s = talloc_realloc(dcs,
+							dcs[i].ss_s,
+							struct sockaddr_storage,
+							dcs[i].num_ips+1))
+								== NULL ) {
+						return NT_STATUS_NO_MEMORY;
+					}
+
+					dcs[i].ss_s = tmp_ss_s;
+				}
+				dcs[i].num_ips++;
+
+				/* copy the new IP address */
+				if (rr.type == T_A) {
+					struct in_addr ip;
+					memcpy(&ip, rr.rdata, 4);
+					in_addr_to_sockaddr_storage(
+							&dcs[i].ss_s[num_ips],
+							ip);
+				}
+#if defined(HAVE_IPV6)
+				if (rr.type == T_AAAA) {
+					struct in6_addr ip6;
+					memcpy(&ip6, rr.rdata, rr.rdatalen);
+					in6_addr_to_sockaddr_storage(
+							&dcs[i].ss_s[num_ips],
+							ip6);
+				}
+#endif
+			}
+		}
+	}
+
+	TYPESAFE_QSORT(dcs, idx, 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 *dns_hosts_file,
+				const char *dnsdomain,
+				struct dns_rr_ns **nslist,
+				int *numns)
+{
+	uint8_t *buffer = NULL;
+	int resp_len = 0;
+	struct dns_rr_ns *nsarray = NULL;
+	int query_count, answer_count, auth_count, additional_count;
+	uint8_t *p;
+	int rrnum;
+	int idx = 0;
+	NTSTATUS status;
+
+	if ( !ctx || !dnsdomain || !nslist ) {
+		return NT_STATUS_INVALID_PARAMETER;
+	}
+
+	if (dns_hosts_file) {
+		DEBUG(1, ("NO 'NS' lookup available when using resolv:host file"));
+		return NT_STATUS_OBJECT_NAME_NOT_FOUND;
+	}
+
+	/* 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) {
+#if defined(HAVE_IPV6)
+			if (rr.type != T_AAAA || rr.rdatalen != 16)
+#endif
+				continue;
+		}
+
+		for ( i=0; i<idx; i++ ) {
+			if (strcmp(rr.hostname, nsarray[i].hostname) == 0) {
+				if (rr.type == T_A) {
+					struct in_addr ip;
+					memcpy(&ip, rr.rdata, 4);
+					in_addr_to_sockaddr_storage(
+							&nsarray[i].ss,
+							ip);
+				}
+#if defined(HAVE_IPV6)
+				if (rr.type == T_AAAA) {
+					struct in6_addr ip6;
+					memcpy(&ip6, rr.rdata, rr.rdatalen);
+					in6_addr_to_sockaddr_storage(
+							&nsarray[i].ss,
+							ip6);
+				}
+#endif
+			}
+		}
+	}
+
+	*nslist = nsarray;
+	*numns = idx;
+
+	return NT_STATUS_OK;
+}
+
+/********************************************************************
+ Query with optional sitename.
+********************************************************************/
+
+static NTSTATUS ads_dns_query_internal(TALLOC_CTX *ctx,
+				       const char *dns_hosts_file,
+				       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 && strlen(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, dns_hosts_file, name, dclist, numdcs);
+}
+
+/********************************************************************
+ Query for AD DC's.
+********************************************************************/
+
+NTSTATUS ads_dns_query_dcs(TALLOC_CTX *ctx,
+			   const char *dns_hosts_file,
+			   const char *realm,
+			   const char *sitename,
+			   struct dns_rr_srv **dclist,
+			   int *numdcs )
+{
+	NTSTATUS status;
+
+	status = ads_dns_query_internal(ctx, dns_hosts_file, "_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, dns_hosts_file,
+						"_ldap", "dc", realm,
+						NULL, dclist, numdcs);
+	}
+	return status;
+}
+
+/********************************************************************
+ Query for AD GC's.
+********************************************************************/
+
+NTSTATUS ads_dns_query_gcs(TALLOC_CTX *ctx,
+			   const char *dns_hosts_file,
+			   const char *realm,
+			   const char *sitename,
+			   struct dns_rr_srv **dclist,
+			   int *numdcs )
+{
+	NTSTATUS status;
+
+	status = ads_dns_query_internal(ctx, dns_hosts_file, "_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, dns_hosts_file,
+						"_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_hosts_file,
+			    const char *dns_forest_name,
+			    const char *sitename,
+			    struct dns_rr_srv **dclist,
+			    int *numdcs )
+{
+	NTSTATUS status;
+
+	status = ads_dns_query_internal(ctx, dns_hosts_file, "_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, dns_hosts_file,
+						"_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_hosts_file,
+			   const char *dns_domain_name,
+			   struct dns_rr_srv **dclist,
+			   int *numdcs )
+{
+	return ads_dns_query_internal(ctx, dns_hosts_file, "_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_hosts_file,
+				const char *dns_forest_name,
+				const char *domain_guid,
+				struct dns_rr_srv **dclist,
+				int *numdcs )
+{
+	/*_ldap._tcp.DomainGuid.domains._msdcs.DnsForestName */
+
+	const char *domains;
+
+	/* little hack */
+	domains = talloc_asprintf(ctx, "%s.domains", domain_guid);
+	if (!domains) {
+		return NT_STATUS_NO_MEMORY;
+	}
+
+	return ads_dns_query_internal(ctx, dns_hosts_file, "_ldap", domains,
+				      dns_forest_name, NULL, dclist, numdcs);
+}
diff --git a/lib/addns/dnsquery.h b/lib/addns/dnsquery.h
new file mode 100644
index 0000000000..a3ea47a04e
--- /dev/null
+++ b/lib/addns/dnsquery.h
@@ -0,0 +1,61 @@
+/*
+ *  Unix SMB/CIFS implementation.
+ *  Internal DNS query structures
+ *  Copyright (C) Gerald 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/>.
+ */
+
+#ifndef _ADS_DNS_H
+#define _ADS_DNS_H
+
+#include "libcli/dns/dns.h"
+
+/* The following definitions come from libads/dns.c  */
+
+NTSTATUS ads_dns_lookup_ns(TALLOC_CTX *ctx,
+				const char *dns_hosts_file,
+				const char *dnsdomain,
+				struct dns_rr_ns **nslist,
+				int *numns);
+NTSTATUS ads_dns_query_dcs(TALLOC_CTX *ctx,
+			   const char *dns_hosts_file,
+			   const char *realm,
+			   const char *sitename,
+			   struct dns_rr_srv **dclist,
+			   int *numdcs );
+NTSTATUS ads_dns_query_gcs(TALLOC_CTX *ctx,
+			   const char *dns_hosts_file,
+			   const char *realm,
+			   const char *sitename,
+			   struct dns_rr_srv **dclist,
+			   int *numdcs );
+NTSTATUS ads_dns_query_kdcs(TALLOC_CTX *ctx,
+			    const char *dns_hosts_file,
+			    const char *dns_forest_name,
+			    const char *sitename,
+			    struct dns_rr_srv **dclist,
+			    int *numdcs );
+NTSTATUS ads_dns_query_pdc(TALLOC_CTX *ctx,
+			   const char *dns_hosts_file,
+			   const char *dns_domain_name,
+			   struct dns_rr_srv **dclist,
+			   int *numdcs );
+NTSTATUS ads_dns_query_dcs_guid(TALLOC_CTX *ctx,
+				const char *dns_hosts_file,
+				const char *dns_forest_name,
+				const char *domain_guid,
+				struct dns_rr_srv **dclist,
+				int *numdcs );
+#endif	/* _ADS_DNS_H */
diff --git a/lib/addns/wscript_build b/lib/addns/wscript_build
index 69a4716245..a7010531a0 100644..100755
--- a/lib/addns/wscript_build
+++ b/lib/addns/wscript_build
@@ -5,3 +5,8 @@ bld.SAMBA_LIBRARY('addns',
                    public_deps='talloc krb5 k5crypto com_err gssapi gssapi_krb5 uuid',
                    private_library=True,
                    vars=locals())
+
+bld.SAMBA_SUBSYSTEM('DNSQUERY',
+	source='dnsquery.c',
+	deps='samba-util lmhosts resolv'
+	)