X-Git-Url: http://git.samba.org/samba.git/?p=nivanova%2Fsamba-autobuild%2F.git;a=blobdiff_plain;f=lib%2Faddns%2Fdnsquery.c;h=87ae97e3d0ba6ab53f65bc63e1e798853bf36a63;hp=57ef8d92f4ac7b9dff4b170c860bc88d50cbc00b;hb=HEAD;hpb=f087a8e2b81fae82fa571ef09d2d1cb682cc8ff8;ds=sidebyside

diff --git a/lib/addns/dnsquery.c b/lib/addns/dnsquery.c
index 57ef8d92f4a..87ae97e3d0b 100644
--- a/lib/addns/dnsquery.c
+++ b/lib/addns/dnsquery.c
@@ -21,245 +21,11 @@
 #include "includes.h"
 #include "lib/util/util_net.h"
 #include "lib/util/tsort.h"
+#include "librpc/gen_ndr/dns.h"
+#include "libcli/dns/dns_lookup.h"
+#include "lib/util/tevent_ntstatus.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.
 *********************************************************************/
@@ -285,104 +51,146 @@ static int dnssrvcmp( struct dns_rr_srv *a, struct dns_rr_srv *b )
 	return 1;
 }
 
-/*********************************************************************
- Simple wrapper for a DNS query
-*********************************************************************/
+struct ads_dns_lookup_srv_state {
+	struct dns_rr_srv *srvs;
+	size_t num_srvs;
+};
 
-#define DNS_FAILED_WAITTIME          30
+static void ads_dns_lookup_srv_done(struct tevent_req *subreq);
 
-static NTSTATUS dns_send_req( TALLOC_CTX *ctx, const char *name, int q_type,
-                              uint8_t **buf, int *resp_length )
+struct tevent_req *ads_dns_lookup_srv_send(TALLOC_CTX *mem_ctx,
+					   struct tevent_context *ev,
+					   const char *name)
 {
-	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,("dns_send_req: last dns check returning cached status (%s)\n",
-			  nt_errstr(last_dns_status) ));
-		return last_dns_status;
+	struct tevent_req *req, *subreq;
+	struct ads_dns_lookup_srv_state *state;
+
+	req = tevent_req_create(mem_ctx, &state,
+				struct ads_dns_lookup_srv_state);
+	if (req == NULL) {
+		return NULL;
 	}
 
-	/* 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,("dns_send_req: "
-					"talloc() failed!\n"));
-				last_dns_status = NT_STATUS_NO_MEMORY;
-				last_dns_check = time_mono(NULL);
-				return last_dns_status;
-			}
+	subreq = dns_lookup_send(
+		state,
+		ev,
+		NULL,
+		name,
+		DNS_QCLASS_IN,
+		DNS_QTYPE_SRV);
+
+	if (tevent_req_nomem(subreq, req)) {
+		return tevent_req_post(req, ev);
+	}
+	tevent_req_set_callback(subreq, ads_dns_lookup_srv_done, req);
+	return req;
+}
+
+static void ads_dns_lookup_srv_done(struct tevent_req *subreq)
+{
+	struct tevent_req *req = tevent_req_callback_data(
+		subreq, struct tevent_req);
+	struct ads_dns_lookup_srv_state *state = tevent_req_data(
+		req, struct ads_dns_lookup_srv_state);
+	int ret;
+	struct dns_name_packet *reply;
+	uint16_t i, idx;
+
+	ret = dns_lookup_recv(subreq, state, &reply);
+	TALLOC_FREE(subreq);
+	if (ret != 0) {
+		tevent_req_nterror(req, map_nt_error_from_unix_common(ret));
+		return;
+	}
+
+	for (i=0; i<reply->ancount; i++) {
+		if (reply->answers[i].rr_type == DNS_QTYPE_SRV) {
+			state->num_srvs += 1;
 		}
+	}
 
-		if ((resp_len = res_query(name, C_IN, q_type, buffer, buf_len))
-				< 0 ) {
-			DEBUG(3,("dns_send_req: "
-				"Failed to resolve %s (%s)\n",
-				name, strerror(errno)));
-			TALLOC_FREE( buffer );
-			last_dns_status = NT_STATUS_UNSUCCESSFUL;
+	state->srvs = talloc_array(state, struct dns_rr_srv, state->num_srvs);
+	if (tevent_req_nomem(state->srvs, req)) {
+		return;
+	}
 
-			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;
+	idx = 0;
+
+	for (i=0; i<reply->ancount; i++) {
+		struct dns_res_rec *an = &reply->answers[i];
+		struct dns_rr_srv *dst = &state->srvs[idx];
+		struct dns_srv_record *src;
+
+		if (an->rr_type != DNS_QTYPE_SRV) {
+			continue;
+		}
+		src = &an->rdata.srv_record;
+
+		*dst = (struct dns_rr_srv) {
+			.hostname = talloc_move(state->srvs, &src->target),
+			.priority = src->priority,
+			.weight = src->weight,
+			.port = src->port,
+		};
+		idx += 1;
+	}
+
+	for (i=0; i<reply->arcount; i++) {
+		struct dns_res_rec *ar = &reply->additional[i];
+		struct sockaddr_storage addr;
+		bool ok;
+		size_t j;
+
+		ok = dns_res_rec_get_sockaddr(ar, &addr);
+		if (!ok) {
+			continue;
 		}
 
-		/* 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;
+		for (j=0; j<state->num_srvs; j++) {
+			struct dns_rr_srv *srv = &state->srvs[j];
+			struct sockaddr_storage *tmp;
+
+			if (strcmp(srv->hostname, ar->name) != 0) {
+				continue;
 			}
 
-			resp_len = MIN(resp_len*2, MAX_DNS_PACKET_SIZE);
+			tmp = talloc_realloc(
+				state->srvs,
+				srv->ss_s,
+				struct sockaddr_storage,
+				srv->num_ips+1);
+
+			if (tevent_req_nomem(tmp, req)) {
+				return;
+			}
+			srv->ss_s = tmp;
+
+			srv->ss_s[srv->num_ips] = addr;
+			srv->num_ips += 1;
 		}
+	}
 
+	TYPESAFE_QSORT(state->srvs, state->num_srvs, dnssrvcmp);
 
-	} while ( buf_len < resp_len && resp_len <= MAX_DNS_PACKET_SIZE );
+	tevent_req_done(req);
+}
 
-	*buf = buffer;
-	*resp_length = resp_len;
+NTSTATUS ads_dns_lookup_srv_recv(struct tevent_req *req,
+				 TALLOC_CTX *mem_ctx,
+				 struct dns_rr_srv **srvs,
+				 size_t *num_srvs)
+{
+	struct ads_dns_lookup_srv_state *state = tevent_req_data(
+		req, struct ads_dns_lookup_srv_state);
+	NTSTATUS status;
 
-	last_dns_check = time_mono(NULL);
-	last_dns_status = NT_STATUS_OK;
-	return last_dns_status;
+	if (tevent_req_is_nterror(req, &status)) {
+		return status;
+	}
+	*srvs = talloc_move(mem_ctx, &state->srvs);
+	*num_srvs = state->num_srvs;
+	tevent_req_received(req);
+	return NT_STATUS_OK;
 }
 
 /*********************************************************************
@@ -390,194 +198,142 @@ static NTSTATUS dns_send_req( TALLOC_CTX *ctx, const char *name, int q_type,
 *********************************************************************/
 
 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;
+	struct tevent_context *ev;
+	struct tevent_req *req;
+	NTSTATUS status = NT_STATUS_NO_MEMORY;
+	size_t num_srvs;
+
+	ev = samba_tevent_context_init(ctx);
+	if (ev == NULL) {
+		goto fail;
+	}
+	req = ads_dns_lookup_srv_send(ev, ev, name);
+	if (req == NULL) {
+		goto fail;
+	}
+	if (!tevent_req_poll_ntstatus(req, ev, &status)) {
+		goto fail;
+	}
+	status = ads_dns_lookup_srv_recv(req, ctx, dclist, &num_srvs);
+	*numdcs = num_srvs;	/* size_t->int */
+fail:
+	TALLOC_FREE(ev);
+	return status;
+}
 
-	if ( !ctx || !name || !dclist ) {
-		return NT_STATUS_INVALID_PARAMETER;
-	}
+struct ads_dns_lookup_ns_state {
+	struct dns_rr_ns *nss;
+	size_t num_nss;
+};
 
-	if (dns_hosts_file) {
-		return resolve_dns_hosts_file_as_dns_rr(dns_hosts_file,
-							name, true, ctx,
-							dclist, numdcs);
-	}
+static void ads_dns_lookup_ns_done(struct tevent_req *subreq);
 
-	/* Send the request.  May have to loop several times in case
-	   of large replies */
+struct tevent_req *ads_dns_lookup_ns_send(TALLOC_CTX *mem_ctx,
+					  struct tevent_context *ev,
+					  const char *name)
+{
+	struct tevent_req *req, *subreq;
+	struct ads_dns_lookup_ns_state *state;
 
-	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;
+	req = tevent_req_create(mem_ctx, &state,
+				struct ads_dns_lookup_ns_state);
+	if (req == NULL) {
+		return NULL;
 	}
-	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;
+	subreq = dns_lookup_send(state, ev, NULL, name, DNS_QCLASS_IN,
+				 DNS_QTYPE_NS);
+	if (tevent_req_nomem(subreq, req)) {
+		return tevent_req_post(req, ev);
+	}
+	tevent_req_set_callback(subreq, ads_dns_lookup_ns_done, req);
+	return req;
+}
 
-		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;
+static void ads_dns_lookup_ns_done(struct tevent_req *subreq)
+{
+	struct tevent_req *req = tevent_req_callback_data(
+		subreq, struct tevent_req);
+	struct ads_dns_lookup_ns_state *state = tevent_req_data(
+		req, struct ads_dns_lookup_ns_state);
+	int ret;
+	struct dns_name_packet *reply;
+	uint16_t i, idx;
+
+	ret = dns_lookup_recv(subreq, state, &reply);
+	TALLOC_FREE(subreq);
+	if (ret != 0) {
+		tevent_req_nterror(req, map_nt_error_from_unix_common(ret));
+		return;
+	}
+
+	for (i=0; i<reply->ancount; i++) {
+		if (reply->answers[i].rr_type == DNS_QTYPE_NS) {
+			state->num_nss += 1;
 		}
 	}
 
-	/* 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;
-		}
+	state->nss = talloc_array(state, struct dns_rr_ns, state->num_nss);
+	if (tevent_req_nomem(state->nss, req)) {
+		return;
 	}
-	idx = rrnum;
 
-	/* Parse the authority section */
-	/* just skip these for now */
+	idx = 0;
 
-	for ( rrnum=0; rrnum<auth_count; rrnum++ ) {
-		struct dns_rr rr;
+	for (i=0; i<reply->ancount; i++) {
+		struct dns_res_rec *an = &reply->answers[i];
 
-		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;
+		if (an->rr_type != DNS_QTYPE_NS) {
+			continue;
 		}
-	}
 
-	/* Parse the additional records section */
+		state->nss[idx].hostname = talloc_move(state->nss,
+						       &an->rdata.ns_record);
+		idx += 1;
+	}
 
-	for ( rrnum=0; rrnum<additional_count; rrnum++ ) {
-		struct dns_rr rr;
-		int i;
+	for (i=0; i<reply->arcount; i++) {
+		struct dns_res_rec *ar = &reply->additional[i];
+		struct sockaddr_storage addr;
+		bool ok;
+		size_t j;
 
-		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;
+		ok = dns_res_rec_get_sockaddr(ar, &addr);
+		if (!ok) {
+			continue;
 		}
 
-		/* 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 (j=0; j<state->num_nss; j++) {
+			struct dns_rr_ns *ns = &state->nss[j];
 
-		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
+			if (strcmp(ns->hostname, ar->name) == 0) {
+				ns->ss = addr;
 			}
 		}
 	}
 
-	TYPESAFE_QSORT(dcs, idx, dnssrvcmp );
+	tevent_req_done(req);
+}
 
-	*dclist = dcs;
-	*numdcs = idx;
+NTSTATUS ads_dns_lookup_ns_recv(struct tevent_req *req,
+				TALLOC_CTX *mem_ctx,
+				struct dns_rr_ns **nss,
+				size_t *num_nss)
+{
+	struct ads_dns_lookup_ns_state *state = tevent_req_data(
+		req, struct ads_dns_lookup_ns_state);
+	NTSTATUS status;
 
+	if (tevent_req_is_nterror(req, &status)) {
+		return status;
+	}
+	*nss = talloc_move(mem_ctx, &state->nss);
+	*num_nss = state->num_nss;
+	tevent_req_received(req);
 	return NT_STATUS_OK;
 }
 
@@ -586,168 +342,39 @@ NTSTATUS ads_dns_lookup_srv(TALLOC_CTX *ctx,
 *********************************************************************/
 
 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;
+	struct tevent_context *ev;
+	struct tevent_req *req;
+	NTSTATUS status = NT_STATUS_NO_MEMORY;
+	size_t num_ns = 0;
+
+	ev = samba_tevent_context_init(ctx);
+	if (ev == NULL) {
+		goto fail;
+	}
+	req = ads_dns_lookup_ns_send(ev, ev, dnsdomain);
+	if (req == NULL) {
+		goto fail;
+	}
+	if (!tevent_req_poll_ntstatus(req, ev, &status)) {
+		goto fail;
+	}
+	status = ads_dns_lookup_ns_recv(req, ctx, nslist, &num_ns);
+	*numns = num_ns;
+fail:
+	TALLOC_FREE(ev);
+	return status;
 }
 
+
 /********************************************************************
  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,
@@ -756,18 +383,41 @@ static NTSTATUS ads_dns_query_internal(TALLOC_CTX *ctx,
 				       int *numdcs )
 {
 	char *name;
-	if (sitename && strlen(sitename)) {
+	NTSTATUS status;
+	int num_srvs = 0;
+
+	if ((sitename != NULL) && (strlen(sitename) != 0)) {
 		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 == NULL) {
+			return NT_STATUS_NO_MEMORY;
+		}
+
+		status = ads_dns_lookup_srv(ctx, name, dclist, &num_srvs);
+
+		TALLOC_FREE(name);
+
+		if (NT_STATUS_EQUAL(status, NT_STATUS_IO_TIMEOUT) ||
+		    NT_STATUS_EQUAL(status, NT_STATUS_CONNECTION_REFUSED)) {
+			return status;
+		}
+
+		if (NT_STATUS_IS_OK(status) && (num_srvs != 0)) {
+			goto done;
+		}
 	}
-	if (!name) {
+
+	name = talloc_asprintf(ctx, "%s._tcp.%s._msdcs.%s",
+			       servicename, dc_pdc_gc_domains, realm);
+	if (name == NULL) {
 		return NT_STATUS_NO_MEMORY;
 	}
-	return ads_dns_lookup_srv(ctx, dns_hosts_file, name, dclist, numdcs);
+	status = ads_dns_lookup_srv(ctx, name, dclist, &num_srvs);
+
+done:
+	*numdcs = num_srvs; /* automatic conversion size_t->int */
+	return status;
 }
 
 /********************************************************************
@@ -775,7 +425,6 @@ static NTSTATUS ads_dns_query_internal(TALLOC_CTX *ctx,
 ********************************************************************/
 
 NTSTATUS ads_dns_query_dcs(TALLOC_CTX *ctx,
-			   const char *dns_hosts_file,
 			   const char *realm,
 			   const char *sitename,
 			   struct dns_rr_srv **dclist,
@@ -783,22 +432,13 @@ NTSTATUS ads_dns_query_dcs(TALLOC_CTX *ctx,
 {
 	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);
-	}
+	status = ads_dns_query_internal(ctx,
+					"_ldap",
+					"dc",
+					realm,
+					sitename,
+					dclist,
+					numdcs);
 	return status;
 }
 
@@ -807,7 +447,6 @@ NTSTATUS ads_dns_query_dcs(TALLOC_CTX *ctx,
 ********************************************************************/
 
 NTSTATUS ads_dns_query_gcs(TALLOC_CTX *ctx,
-			   const char *dns_hosts_file,
 			   const char *realm,
 			   const char *sitename,
 			   struct dns_rr_srv **dclist,
@@ -815,22 +454,13 @@ NTSTATUS ads_dns_query_gcs(TALLOC_CTX *ctx,
 {
 	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);
-	}
+	status = ads_dns_query_internal(ctx,
+					"_ldap",
+					"gc",
+					realm,
+					sitename,
+					dclist,
+					numdcs);
 	return status;
 }
 
@@ -841,7 +471,6 @@ NTSTATUS ads_dns_query_gcs(TALLOC_CTX *ctx,
 ********************************************************************/
 
 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,
@@ -849,24 +478,13 @@ NTSTATUS ads_dns_query_kdcs(TALLOC_CTX *ctx,
 {
 	NTSTATUS status;
 
-	status = ads_dns_query_internal(ctx, dns_hosts_file, "_kerberos", "dc",
-					dns_forest_name, sitename, dclist,
+	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, dns_hosts_file,
-						"_kerberos", "dc",
-						dns_forest_name, NULL,
-						dclist, numdcs);
-	}
 	return status;
 }
 
@@ -875,13 +493,17 @@ NTSTATUS ads_dns_query_kdcs(TALLOC_CTX *ctx,
 ********************************************************************/
 
 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);
+	return ads_dns_query_internal(ctx,
+				      "_ldap",
+				      "pdc",
+				      dns_domain_name,
+				      NULL,
+				      dclist,
+				      numdcs);
 }
 
 /********************************************************************
@@ -889,7 +511,6 @@ NTSTATUS ads_dns_query_pdc(TALLOC_CTX *ctx,
 ********************************************************************/
 
 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,
@@ -905,6 +526,11 @@ NTSTATUS ads_dns_query_dcs_guid(TALLOC_CTX *ctx,
 		return NT_STATUS_NO_MEMORY;
 	}
 
-	return ads_dns_query_internal(ctx, dns_hosts_file, "_ldap", domains,
-				      dns_forest_name, NULL, dclist, numdcs);
+	return ads_dns_query_internal(ctx,
+				      "_ldap",
+				      domains,
+				      dns_forest_name,
+				      NULL,
+				      dclist,
+				      numdcs);
 }