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Unix SMB/CIFS implementation.
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Copyright (C) Gerald (Jerry) Carter 2006.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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/* AIX resolv.h uses 'class' in struct ns_rr */
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/* resolver headers */
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#include <sys/types.h>
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#include <netinet/in.h>
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#include <arpa/nameser.h>
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#define MAX_DNS_PACKET_SIZE 0xffff
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#ifdef NS_HFIXEDSZ /* Bind 8/9 interface */
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#if !defined(C_IN) /* AIX 5.3 already defines C_IN */
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#if !defined(T_A) /* AIX 5.3 already defines T_A */
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# define T_SRV ns_t_srv
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# define NS_HFIXEDSZ HFIXEDSZ
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# define NS_HFIXEDSZ sizeof(HEADER)
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# endif /* HFIXEDSZ */
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# define NS_PACKETSZ PACKETSZ
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# else /* 512 is usually the default */
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# define NS_PACKETSZ 512
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# endif /* PACKETSZ */
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/*********************************************************************
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*********************************************************************/
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static BOOL ads_dns_parse_query( TALLOC_CTX *ctx, uint8 *start, uint8 *end,
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uint8 **ptr, struct dns_query *q )
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if ( !start || !end || !q || !*ptr)
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/* See RFC 1035 for details. If this fails, then return. */
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namelen = dn_expand( start, end, p, hostname, sizeof(hostname) );
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q->hostname = talloc_strdup( ctx, hostname );
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/* check that we have space remaining */
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if ( PTR_DIFF(p+4, end) > 0 )
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q->type = RSVAL( p, 0 );
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q->in_class = RSVAL( p, 2 );
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/*********************************************************************
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*********************************************************************/
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static BOOL ads_dns_parse_rr( TALLOC_CTX *ctx, uint8 *start, uint8 *end,
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uint8 **ptr, struct dns_rr *rr )
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if ( !start || !end || !rr || !*ptr)
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/* pull the name from the answer */
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namelen = dn_expand( start, end, p, hostname, sizeof(hostname) );
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rr->hostname = talloc_strdup( ctx, hostname );
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/* check that we have space remaining */
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if ( PTR_DIFF(p+10, end) > 0 )
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/* pull some values and then skip onto the string */
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rr->type = RSVAL(p, 0);
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rr->in_class = RSVAL(p, 2);
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rr->ttl = RIVAL(p, 4);
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rr->rdatalen = RSVAL(p, 8);
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/* sanity check the available space */
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if ( PTR_DIFF(p+rr->rdatalen, end ) > 0 ) {
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/* save a point to the rdata for this section */
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/*********************************************************************
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*********************************************************************/
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static BOOL ads_dns_parse_rr_srv( TALLOC_CTX *ctx, uint8 *start, uint8 *end,
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uint8 **ptr, struct dns_rr_srv *srv )
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if ( !start || !end || !srv || !*ptr)
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/* Parse the RR entry. Coming out of the this, ptr is at the beginning
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of the next record */
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if ( !ads_dns_parse_rr( ctx, start, end, ptr, &rr ) ) {
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DEBUG(1,("ads_dns_parse_rr_srv: Failed to parse RR record\n"));
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if ( rr.type != T_SRV ) {
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DEBUG(1,("ads_dns_parse_rr_srv: Bad answer type (%d)\n", rr.type));
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srv->priority = RSVAL(p, 0);
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srv->weight = RSVAL(p, 2);
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srv->port = RSVAL(p, 4);
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namelen = dn_expand( start, end, p, dcname, sizeof(dcname) );
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DEBUG(1,("ads_dns_parse_rr_srv: Failed to uncompress name!\n"));
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srv->hostname = talloc_strdup( ctx, dcname );
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/*********************************************************************
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Sort SRV record list based on weight and priority. See RFC 2782.
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*********************************************************************/
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static int dnssrvcmp( struct dns_rr_srv *a, struct dns_rr_srv *b )
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srand( (uint32)time(NULL) );
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if ( a->priority == b->priority ) {
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/* randomize entries with an equal weight and priority */
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if ( a->weight == b->weight )
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return rand() % 2 ? -1 : 1;
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/* higher weights should be sorted lower */
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if ( a->weight > b->weight )
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if ( a->priority < b->priority )
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/*********************************************************************
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Simple wrapper for a DNS SRV query
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*********************************************************************/
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NTSTATUS ads_dns_lookup_srv( TALLOC_CTX *ctx, const char *name, struct dns_rr_srv **dclist, int *numdcs )
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uint8 *buffer = NULL;
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int resp_len = NS_PACKETSZ;
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struct dns_rr_srv *dcs = NULL;
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int query_count, answer_count, auth_count, additional_count;
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if ( !ctx || !name || !dclist ) {
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return NT_STATUS_INVALID_PARAMETER;
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/* Send the request. May have to loop several times in case
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TALLOC_FREE( buffer );
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buf_len = resp_len * sizeof(uint8);
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if ( (buffer = TALLOC_ARRAY(ctx, uint8, buf_len)) == NULL ) {
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DEBUG(0,("ads_dns_lookup_srv: talloc() failed!\n"));
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return NT_STATUS_NO_MEMORY;
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if ( (resp_len = res_query(name, C_IN, T_SRV, buffer, buf_len)) < 0 ) {
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DEBUG(1,("ads_dns_lookup_srv: Failed to resolve %s (%s)\n", name, strerror(errno)));
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TALLOC_FREE( buffer );
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return NT_STATUS_UNSUCCESSFUL;
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} while ( buf_len < resp_len && resp_len < MAX_DNS_PACKET_SIZE );
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/* For some insane reason, the ns_initparse() et. al. routines are only
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available in libresolv.a, and not the shared lib. Who knows why....
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So we have to parse the DNS reply ourselves */
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/* Pull the answer RR's count from the header. Use the NMB ordering macros */
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query_count = RSVAL( p, 4 );
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answer_count = RSVAL( p, 6 );
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auth_count = RSVAL( p, 8 );
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additional_count = RSVAL( p, 10 );
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DEBUG(4,("ads_dns_lookup_srv: %d records returned in the answer section.\n",
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if ( (dcs = TALLOC_ARRAY(ctx, struct dns_rr_srv, answer_count)) == NULL ) {
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DEBUG(0,("ads_dns_lookup_srv: talloc() failure for %d char*'s\n",
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return NT_STATUS_NO_MEMORY;
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/* now skip the header */
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/* parse the query section */
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for ( rrnum=0; rrnum<query_count; rrnum++ ) {
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if ( !ads_dns_parse_query( ctx, buffer, buffer+resp_len, &p, &q ) ) {
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DEBUG(1,("ads_dns_lookup_srv: Failed to parse query record!\n"));
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return NT_STATUS_UNSUCCESSFUL;
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/* now we are at the answer section */
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for ( rrnum=0; rrnum<answer_count; rrnum++ ) {
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if ( !ads_dns_parse_rr_srv( ctx, buffer, buffer+resp_len, &p, &dcs[rrnum] ) ) {
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DEBUG(1,("ads_dns_lookup_srv: Failed to parse answer record!\n"));
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return NT_STATUS_UNSUCCESSFUL;
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/* Parse the authority section */
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/* just skip these for now */
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for ( rrnum=0; rrnum<auth_count; rrnum++ ) {
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if ( !ads_dns_parse_rr( ctx, buffer, buffer+resp_len, &p, &rr ) ) {
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DEBUG(1,("ads_dns_lookup_srv: Failed to parse authority record!\n"));
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return NT_STATUS_UNSUCCESSFUL;
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/* Parse the additional records section */
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for ( rrnum=0; rrnum<additional_count; rrnum++ ) {
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if ( !ads_dns_parse_rr( ctx, buffer, buffer+resp_len, &p, &rr ) ) {
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DEBUG(1,("ads_dns_lookup_srv: Failed to parse additional records section!\n"));
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return NT_STATUS_UNSUCCESSFUL;
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/* only interested in A records as a shortcut for having to come
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back later and lookup the name */
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if ( (rr.type != T_A) || (rr.rdatalen != 4) )
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for ( i=0; i<idx; i++ ) {
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if ( strcmp( rr.hostname, dcs[i].hostname ) == 0 ) {
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uint8 *buf = (uint8*)&dcs[i].ip.s_addr;
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memcpy( buf, rr.rdata, 4 );
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qsort( dcs, idx, sizeof(struct dns_rr_srv), QSORT_CAST dnssrvcmp );
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/********************************************************************
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********************************************************************/
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NTSTATUS ads_dns_query_dcs( TALLOC_CTX *ctx, const char *domain, struct dns_rr_srv **dclist, int *numdcs )
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snprintf( name, sizeof(name), "_ldap._tcp.dc._msdcs.%s", domain );
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return ads_dns_lookup_srv( ctx, name, dclist, numdcs );
added
removed
source/libads/dns.c
