pyldb: avoid segfault when adding an element with no name
[nivanova/samba-autobuild/.git] / lib / addns / dnsquery.c
index f680d6325817737cddb84904775dc8c941edf288..87ae97e3d0ba6ab53f65bc63e1e798853bf36a63 100644 (file)
 #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.
 *********************************************************************/
@@ -285,299 +51,289 @@ 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,("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,("ads_dns_lookup_srv: "
-                                       "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,("ads_dns_lookup_srv: "
-                               "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;
 }
 
 /*********************************************************************
  Simple wrapper for a DNS SRV query
 *********************************************************************/
 
-static NTSTATUS ads_dns_lookup_srv( TALLOC_CTX *ctx,
-                               const char *dns_hosts_file,
+NTSTATUS ads_dns_lookup_srv(TALLOC_CTX *ctx,
                                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 @@ static 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);
 }