r15462: replace the use of OpenLDAP's ldap_domain2hostlist() for

locating AD DC's with out own DNS SRV queries.
Testing on Linux and Solaris.
(This used to be commit cf71f88a3cdcabf99c0798ef4cf8c978397a57eb)

1 files changed, 353 insertions, 0 deletions

diff --git a/source3/libads/dns.c b/source3/libads/dns.c
new file mode 100644
index 0000000000..0119ae9130
--- /dev/null
+++ b/source3/libads/dns.c
@@ -0,0 +1,353 @@
+/* 
+   Unix SMB/CIFS implementation.
+   DNS utility library
+   Copyright (C) Gerald (Jerry) Carter           2006.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2 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, write to the Free Software
+   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+*/
+
+#include "includes.h"
+
+/* AIX resolv.h uses 'class' in struct ns_rr */
+
+#if defined(AIX)
+#  if defined(class)
+#    undef class
+#  endif
+#endif	/* AIX */
+
+/* resolver headers */
+
+#include <sys/types.h>
+#include <netinet/in.h>
+#include <arpa/nameser.h>
+#include <resolv.h>
+#include <netdb.h>
+
+#define MAX_DNS_PACKET_SIZE 0xffff
+
+/*********************************************************************
+*********************************************************************/
+
+static BOOL ads_dns_parse_query( TALLOC_CTX *ctx, uint8 *start, uint8 *end,
+                          uint8 **ptr, struct dns_query *q )
+{
+	uint8 *p = *ptr;
+	pstring hostname;
+	int namelen;
+
+	ZERO_STRUCTP( q );
+	
+	if ( !start || !end || !q || !*ptr)
+		return False;
+
+	/* See RFC 1035 for details. If this fails, then return. */
+
+	namelen = dn_expand( start, end, p, hostname, sizeof(hostname) );
+	if ( namelen < 0 ) {
+		return False;
+	}
+	p += namelen;
+	q->hostname = talloc_strdup( ctx, hostname );
+
+	/* check that we have space remaining */
+
+	if ( PTR_DIFF(p+4, end) > 0 )
+		return False;
+
+	q->type     = RSVAL( p, 0 );
+	q->in_class = RSVAL( p, 2 );
+	p += 4;
+
+	*ptr = p;
+
+	return True;
+}
+
+/*********************************************************************
+*********************************************************************/
+
+static BOOL ads_dns_parse_rr( TALLOC_CTX *ctx, uint8 *start, uint8 *end,
+                       uint8 **ptr, struct dns_rr *rr )
+{
+	uint8 *p = *ptr;
+	pstring hostname;
+	int namelen;
+
+	if ( !start || !end || !rr || !*ptr)
+		return -1;
+
+	ZERO_STRUCTP( rr );
+	/* pull the name from the answer */
+
+	namelen = dn_expand( start, end, p, hostname, sizeof(hostname) );
+	if ( namelen < 0 ) {
+		return -1;
+	}
+	p += namelen;
+	rr->hostname = talloc_strdup( ctx, hostname );
+
+	/* check that we have space remaining */
+
+	if ( PTR_DIFF(p+10, end) > 0 )
+		return False;
+
+	/* pull some values and then skip onto the string */
+
+	rr->type     = RSVAL(p, 0);
+	rr->in_class = RSVAL(p, 2);
+	rr->ttl      = RIVAL(p, 4);
+	rr->rdatalen = RSVAL(p, 8);
+	
+	p += 10;
+
+	/* sanity check the available space */
+
+	if ( PTR_DIFF(p+rr->rdatalen, end ) > 0 ) {
+		return False;
+
+	}
+
+	/* save a point to the rdata for this section */
+
+	rr->rdata = p;
+	p += rr->rdatalen;
+
+	*ptr = p;
+
+	return True;
+}
+
+/*********************************************************************
+*********************************************************************/
+
+static BOOL ads_dns_parse_rr_srv( TALLOC_CTX *ctx, uint8 *start, uint8 *end,
+                       uint8 **ptr, struct dns_rr_srv *srv )
+{
+	struct dns_rr rr;
+	uint8 *p;
+	pstring dcname;
+	int namelen;
+
+	if ( !start || !end || !srv || !*ptr)
+		return -1;
+
+	/* Parse the RR entry.  Coming out of the this, ptr is at the beginning 
+	   of the next record */
+
+	if ( !ads_dns_parse_rr( ctx, start, end, ptr, &rr ) ) {
+		DEBUG(1,("ads_dns_parse_rr_srv: Failed to parse RR record\n"));
+		return False;
+	}
+
+	if ( rr.type != ns_t_srv ) {
+		DEBUG(1,("ads_dns_parse_rr_srv: Bad answer type (%d)\n", rr.type));
+		return False;
+	}
+
+	p = rr.rdata;
+
+	srv->priority = RSVAL(p, 0);
+	srv->weight   = RSVAL(p, 2);
+	srv->port     = RSVAL(p, 4);
+
+	p += 6;
+
+	namelen = dn_expand( start, end, p, dcname, sizeof(dcname) );
+	if ( namelen < 0 ) {
+		DEBUG(1,("ads_dns_parse_rr_srv: Failed to uncompress name!\n"));
+		return False;
+	}
+	srv->hostname = talloc_strdup( ctx, dcname );
+
+	return True;
+}
+
+
+/*********************************************************************
+ 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 )
+{
+	BOOL init = False;
+
+	if ( !init ) {
+		srand( (uint32)time(NULL) );
+	}
+
+	if ( a->priority == b->priority ) {
+
+		/* randomize entries with an equal weight and priority */
+		if ( a->weight == b->weight ) 
+			return rand() % 2 ? -1 : 1;
+
+		/* 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 SRV query
+*********************************************************************/
+
+NTSTATUS ads_dns_lookup_srv( TALLOC_CTX *ctx, const char *name, struct dns_rr_srv **dclist, int *numdcs )
+{
+	uint8 *buffer = NULL;
+	size_t buf_len;
+	int resp_len = NS_PACKETSZ;
+	struct dns_rr_srv *dcs = NULL;
+	int query_count, answer_count, auth_count, additional_count;
+	uint8 *p = buffer;
+	int rrnum;
+	int idx = 0;
+
+	if ( !ctx || !name || !dclist ) {
+		return NT_STATUS_INVALID_PARAMETER;
+	}
+	
+	/* Send the request.  May have to loop several times in case 
+	   of large replies */
+
+	do {
+		if ( buffer )
+			TALLOC_FREE( buffer );
+		
+		buf_len = resp_len * sizeof(uint8);
+
+		if ( (buffer = TALLOC_ARRAY(ctx, uint8, buf_len)) == NULL ) {
+			DEBUG(0,("ads_dns_lookup_srv: talloc() failed!\n"));
+			return NT_STATUS_NO_MEMORY;
+		}
+
+		if ( (resp_len = res_query(name, ns_c_in, ns_t_srv, buffer, buf_len)) < 0 ) {
+			DEBUG(1,("ads_dns_lookup_srv: Failed to resolve %s (%s)\n", name, strerror(errno)));
+			TALLOC_FREE( buffer );
+			return NT_STATUS_UNSUCCESSFUL;
+		}
+	} while ( buf_len < resp_len && resp_len < MAX_DNS_PACKET_SIZE );
+
+	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 ( (dcs = TALLOC_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;
+	}
+
+	/* now skip the header */
+
+	p += NS_HFIXEDSZ;
+
+	/* parse the query section */
+
+	for ( rrnum=0; rrnum<query_count; rrnum++ ) {
+		struct dns_query q;
+
+		if ( !ads_dns_parse_query( ctx, buffer, buffer+resp_len, &p, &q ) ) {
+			DEBUG(1,("ads_dns_lookup_srv: Failed to parse query record!\n"));
+			return NT_STATUS_UNSUCCESSFUL;
+		}
+	}
+
+	/* now we are at the answer section */
+
+	for ( rrnum=0; rrnum<answer_count; rrnum++ ) {
+		if ( !ads_dns_parse_rr_srv( ctx, buffer, buffer+resp_len, &p, &dcs[rrnum] ) ) {
+			DEBUG(1,("ads_dns_lookup_srv: Failed to parse answer record!\n"));
+			return NT_STATUS_UNSUCCESSFUL;
+		}		
+	}
+	idx = rrnum;
+
+	/* Parse the authority section */
+	/* just skip these for now */
+
+	for ( rrnum=0; rrnum<auth_count; rrnum++ ) {
+		struct dns_rr rr;
+
+		if ( !ads_dns_parse_rr( ctx, buffer, buffer+resp_len, &p, &rr ) ) {
+			DEBUG(1,("ads_dns_lookup_srv: Failed to parse authority record!\n"));
+			return NT_STATUS_UNSUCCESSFUL;
+		}
+	}
+
+	/* Parse the additional records section */
+
+	for ( rrnum=0; rrnum<additional_count; rrnum++ ) {
+		struct dns_rr rr;
+		int i;
+
+		if ( !ads_dns_parse_rr( ctx, buffer, buffer+resp_len, &p, &rr ) ) {
+			DEBUG(1,("ads_dns_lookup_srv: Failed to parse additional records section!\n"));
+			return NT_STATUS_UNSUCCESSFUL;
+		}
+
+		/* only interested in A records as a shortcut for having to come 
+		   back later and lookup the name */
+
+		if ( (rr.type != ns_t_a) || (rr.rdatalen != 4) ) 
+			continue;
+
+		for ( i=0; i<idx; i++ ) {
+			if ( strcmp( rr.hostname, dcs[i].hostname ) == 0 ) {
+				uint8 *buf = (uint8*)&dcs[i].ip.s_addr;
+				memcpy( buf, rr.rdata, 4 );
+			}
+		}
+	}
+
+	qsort( dcs, idx, sizeof(struct dns_rr_srv), QSORT_CAST dnssrvcmp );
+	
+	*dclist = dcs;
+	*numdcs = idx;
+	
+	return NT_STATUS_OK;
+}
+
+/********************************************************************
+********************************************************************/
+
+NTSTATUS ads_dns_query_dcs( TALLOC_CTX *ctx, const char *domain, struct dns_rr_srv **dclist, int *numdcs )
+{
+	pstring name;
+
+	snprintf( name, sizeof(name), "_ldap._tcp.dc._msdcs.%s", domain );
+
+	return ads_dns_lookup_srv( ctx, name, dclist, numdcs );
+}
+