s4-dns: Ignore duplicate dns zones from multiple locations in dlz_bind9

BIND DLZ module currently loads DNS zones from DNS partitions and domain
partitions using following prefixes:

   CN=MicrosoftDNS,DC=DomainDnsZones
   CN=MicrosoftDNS,DC=ForestDNSZones
   CN=MicrosoftDNS,CN=System

Windows supports DNS zones duplicated in DNS partitions and domain
partition and updates both of them simultaneously.

BIND DLZ module can handle DNS zones stored either in DNS partitions
or domain partition, but not both.  This patch ignores duplicate zones
from domain partition and allows BIND9 to work with AD with duplicate
DNS zones.

Signed-off-by: Amitay Isaacs <amitay@gmail.com>
Reviewed-by: Kai Blin <kai@samba.org>

1 files changed, 55 insertions, 0 deletions

diff --git a/source4/dns_server/dlz_bind9.c b/source4/dns_server/dlz_bind9.c
index ac41dd02aa..ea00cfd8b7 100644
--- a/source4/dns_server/dlz_bind9.c
+++ b/source4/dns_server/dlz_bind9.c
@@ -36,6 +36,7 @@
 #include "gen_ndr/server_id.h"
 #include "messaging/messaging.h"
 #include "lib/cmdline/popt_common.h"
+#include "lib/util/dlinklist.h"
 #include "dlz_minimal.h"
 
 
@@ -44,6 +45,11 @@ struct b9_options {
 	const char *debug;
 };
 
+struct b9_zone {
+	char *name;
+	struct b9_zone *prev, *next;
+};
+
 struct dlz_bind9_data {
 	struct b9_options options;
 	struct ldb_context *samdb;
@@ -51,6 +57,7 @@ struct dlz_bind9_data {
 	struct loadparm_context *lp;
 	int *transaction_token;
 	uint32_t soa_serial;
+	struct b9_zone *zonelist;
 
 	/* Used for dynamic update */
 	struct smb_krb5_context *smb_krb5_ctx;
@@ -1099,6 +1106,42 @@ static bool b9_has_soa(struct dlz_bind9_data *state, struct ldb_dn *dn, const ch
 	return false;
 }
 
+static bool b9_zone_add(struct dlz_bind9_data *state, const char *name)
+{
+	struct b9_zone *zone;
+
+	zone = talloc_zero(state, struct b9_zone);
+	if (zone == NULL) {
+		return false;
+	}
+
+	zone->name = talloc_strdup(zone, name);
+	if (zone->name == NULL) {
+		talloc_free(zone);
+		return false;
+	}
+
+	DLIST_ADD(state->zonelist, zone);
+	return true;
+}
+
+static bool b9_zone_exists(struct dlz_bind9_data *state, const char *name)
+{
+	struct b9_zone *zone = state->zonelist;
+	bool found = false;
+
+	while (zone != NULL) {
+		if (strcasecmp(name, zone->name) == 0) {
+			found = true;
+			break;
+		}
+		zone = zone->next;
+	}
+
+	return found;
+}
+
+
 /*
   configure a writeable zone
  */
@@ -1161,6 +1204,18 @@ _PUBLIC_ isc_result_t dlz_configure(dns_view_t *view, void *dbdata)
 			if (!b9_has_soa(state, zone_dn, zone)) {
 				continue;
 			}
+
+			if (b9_zone_exists(state, zone)) {
+				state->log(ISC_LOG_WARNING, "samba_dlz: Ignoring duplicate zone '%s' from '%s'",
+					   zone, ldb_dn_get_linearized(zone_dn));
+				continue;
+			}
+
+			if (!b9_zone_add(state, zone)) {
+				talloc_free(tmp_ctx);
+				return ISC_R_NOMEMORY;
+			}
+
 			result = state->writeable_zone(view, zone);
 			if (result != ISC_R_SUCCESS) {
 				state->log(ISC_LOG_ERROR, "samba_dlz: Failed to configure zone '%s'",