Adding upstream version 1:9.16.44.upstream/1%9.16.44upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1406 insertions, 0 deletions

diff --git a/contrib/dlz/drivers/dlz_odbc_driver.c b/contrib/dlz/drivers/dlz_odbc_driver.c
new file mode 100644
index 0000000..dae5510
--- /dev/null
+++ b/contrib/dlz/drivers/dlz_odbc_driver.c
@@ -0,0 +1,1406 @@
+/*
+ * Copyright (C) 2002 Stichting NLnet, Netherlands, stichting@nlnet.nl.
+ * Copyright (C) Internet Systems Consortium, Inc. ("ISC")
+ *
+ * SPDX-License-Identifier: MPL-2.0
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0.  If a copy of the MPL was not distributed with this
+ * file, you can obtain one at https://mozilla.org/MPL/2.0/.
+ *
+ * See the COPYRIGHT file distributed with this work for additional
+ * information regarding copyright ownership.
+ */
+
+/*
+ * Copyright (C) 1999-2001, 2016  Internet Systems Consortium, Inc. ("ISC")
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#ifdef DLZ_ODBC
+#include <sql.h>
+#include <sqlext.h>
+#include <sqltypes.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <isc/mem.h>
+#include <isc/platform.h>
+#include <isc/print.h>
+#include <isc/result.h>
+#include <isc/string.h>
+#include <isc/util.h>
+
+#include <dns/log.h>
+#include <dns/result.h>
+#include <dns/sdlz.h>
+
+#include <dlz/dlz_odbc_driver.h>
+#include <dlz/sdlz_helper.h>
+#include <named/globals.h>
+
+static dns_sdlzimplementation_t *dlz_odbc = NULL;
+
+#define dbc_search_limit 30
+#define ALLNODES	 1
+#define ALLOWXFR	 2
+#define AUTHORITY	 3
+#define FINDZONE	 4
+#define LOOKUP		 5
+
+#define sqlOK(a) ((a == SQL_SUCCESS || a == SQL_SUCCESS_WITH_INFO) ? -1 : 0)
+
+/*
+ * Private Structures
+ */
+
+/*
+ * structure to hold ODBC connection & statement
+ */
+
+typedef struct {
+	SQLHDBC dbc;
+	SQLHSTMT stmnt;
+} odbc_db_t;
+
+/*
+ * Structure to hold everything needed by this "instance" of the odbc driver
+ * remember, the driver code is only loaded once, but may have many separate
+ * instances
+ */
+
+typedef struct {
+	db_list_t *db;	 /* handle to a list of DB */
+	SQLHENV sql_env; /* handle to SQL environment */
+	SQLCHAR *dsn;
+	SQLCHAR *user;
+	SQLCHAR *pass;
+} odbc_instance_t;
+
+/* forward reference */
+
+static size_t
+odbc_makesafe(char *to, const char *from, size_t length);
+
+/*
+ * Private methods
+ */
+
+static SQLSMALLINT
+safeLen(void *a) {
+	if (a == NULL) {
+		return (0);
+	}
+	return (strlen((char *)a));
+}
+
+/*% properly cleans up an odbc_instance_t */
+
+static void
+destroy_odbc_instance(odbc_instance_t *odbc_inst) {
+	dbinstance_t *ndbi = NULL;
+	dbinstance_t *dbi = NULL;
+
+	/* get the first DBI in the list */
+	ndbi = ISC_LIST_HEAD(*odbc_inst->db);
+
+	/* loop through the list */
+	while (ndbi != NULL) {
+		dbi = ndbi;
+		/* get the next DBI in the list */
+		ndbi = ISC_LIST_NEXT(dbi, link);
+
+		/* if we have a connection / statement object in memory */
+		if (dbi->dbconn != NULL) {
+			/* free statement handle */
+			if (((odbc_db_t *)(dbi->dbconn))->stmnt != NULL) {
+				SQLFreeHandle(
+					SQL_HANDLE_STMT,
+					((odbc_db_t *)(dbi->dbconn))->stmnt);
+				((odbc_db_t *)(dbi->dbconn))->stmnt = NULL;
+			}
+
+			/* disconnect from database & free connection handle */
+			if (((odbc_db_t *)(dbi->dbconn))->dbc != NULL) {
+				SQLDisconnect(((odbc_db_t *)dbi->dbconn)->dbc);
+				SQLFreeHandle(
+					SQL_HANDLE_DBC,
+					((odbc_db_t *)(dbi->dbconn))->dbc);
+				((odbc_db_t *)(dbi->dbconn))->dbc = NULL;
+			}
+
+			/* free memory that held connection & statement. */
+			isc_mem_free(named_g_mctx, dbi->dbconn);
+		}
+		/* release all memory that comprised a DBI */
+		destroy_sqldbinstance(dbi);
+	}
+	/* release memory for the list structure */
+	isc_mem_put(named_g_mctx, odbc_inst->db, sizeof(db_list_t));
+
+	/* free sql environment */
+	if (odbc_inst->sql_env != NULL) {
+		SQLFreeHandle(SQL_HANDLE_ENV, odbc_inst->sql_env);
+	}
+
+	/* free ODBC instance strings */
+	if (odbc_inst->dsn != NULL) {
+		isc_mem_free(named_g_mctx, odbc_inst->dsn);
+	}
+	if (odbc_inst->pass != NULL) {
+		isc_mem_free(named_g_mctx, odbc_inst->pass);
+	}
+	if (odbc_inst->user != NULL) {
+		isc_mem_free(named_g_mctx, odbc_inst->user);
+	}
+
+	/* free memory for odbc_inst */
+	if (odbc_inst != NULL) {
+		isc_mem_put(named_g_mctx, odbc_inst, sizeof(odbc_instance_t));
+	}
+}
+
+/*% Connects to database, and creates ODBC statements */
+
+static isc_result_t
+odbc_connect(odbc_instance_t *dbi, odbc_db_t **dbc) {
+	odbc_db_t *ndb = *dbc;
+	SQLRETURN sqlRes;
+	isc_result_t result = ISC_R_SUCCESS;
+
+	if (ndb != NULL) {
+		/*
+		 * if db != null, we have to do some cleanup
+		 * if statement handle != null free it
+		 */
+		if (ndb->stmnt != NULL) {
+			SQLFreeHandle(SQL_HANDLE_STMT, ndb->stmnt);
+			ndb->stmnt = NULL;
+		}
+
+		/* if connection handle != null free it */
+		if (ndb->dbc != NULL) {
+			SQLFreeHandle(SQL_HANDLE_DBC, ndb->dbc);
+			ndb->dbc = NULL;
+		}
+	} else {
+		ndb = isc_mem_allocate(named_g_mctx, sizeof(odbc_db_t));
+		memset(ndb, 0, sizeof(odbc_db_t));
+	}
+
+	sqlRes = SQLAllocHandle(SQL_HANDLE_DBC, dbi->sql_env, &(ndb->dbc));
+	if (!sqlOK(sqlRes)) {
+		isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE,
+			      DNS_LOGMODULE_DLZ, ISC_LOG_ERROR,
+			      "Odbc driver unable to allocate memory");
+		result = ISC_R_NOMEMORY;
+		goto cleanup;
+	}
+
+	sqlRes = SQLConnect(ndb->dbc, dbi->dsn, safeLen(dbi->dsn), dbi->user,
+			    safeLen(dbi->user), dbi->pass, safeLen(dbi->pass));
+	if (!sqlOK(sqlRes)) {
+		isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE,
+			      DNS_LOGMODULE_DLZ, ISC_LOG_ERROR,
+			      "Odbc driver unable to connect");
+		result = ISC_R_FAILURE;
+		goto cleanup;
+	}
+
+	sqlRes = SQLAllocHandle(SQL_HANDLE_STMT, ndb->dbc, &(ndb->stmnt));
+	if (!sqlOK(sqlRes)) {
+		isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE,
+			      DNS_LOGMODULE_DLZ, ISC_LOG_ERROR,
+			      "Odbc driver unable to allocate memory");
+		result = ISC_R_NOMEMORY;
+		goto cleanup;
+	}
+
+	*dbc = ndb;
+
+	return (ISC_R_SUCCESS);
+
+cleanup:
+
+	if (ndb != NULL) {
+		/* if statement handle != null free it */
+		if (ndb->stmnt != NULL) {
+			SQLFreeHandle(SQL_HANDLE_STMT, ndb->stmnt);
+			ndb->stmnt = NULL;
+		}
+
+		/* if connection handle != null free it */
+		if (ndb->dbc != NULL) {
+			SQLDisconnect(ndb->dbc);
+			SQLFreeHandle(SQL_HANDLE_DBC, ndb->dbc);
+			ndb->dbc = NULL;
+		}
+		/* free memory holding ndb */
+		isc_mem_free(named_g_mctx, ndb);
+	}
+
+	return (result);
+}
+
+/*%
+ * Loops through the list of DB instances, attempting to lock
+ * on the mutex.  If successful, the DBI is reserved for use
+ * and the thread can perform queries against the database.
+ * If the lock fails, the next one in the list is tried.
+ * looping continues until a lock is obtained, or until
+ * the list has been searched dbc_search_limit times.
+ * This function is only used when the driver is compiled for
+ * multithreaded operation.
+ */
+
+static dbinstance_t *
+odbc_find_avail_conn(db_list_t *dblist) {
+	dbinstance_t *dbi = NULL;
+	dbinstance_t *head;
+	int count = 0;
+
+	/* get top of list */
+	head = dbi = ISC_LIST_HEAD(*dblist);
+
+	/* loop through list */
+	while (count < dbc_search_limit) {
+		/* try to lock on the mutex */
+		if (isc_mutex_trylock(&dbi->instance_lock) == ISC_R_SUCCESS) {
+			return (dbi); /* success, return the DBI for use. */
+		}
+		/* not successful, keep trying */
+		dbi = ISC_LIST_NEXT(dbi, link);
+
+		/* check to see if we have gone to the top of the list. */
+		if (dbi == NULL) {
+			count++;
+			dbi = head;
+		}
+	}
+	isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE, DNS_LOGMODULE_DLZ,
+		      ISC_LOG_INFO,
+		      "Odbc driver unable to find available "
+		      "connection after searching %d times",
+		      count);
+	return (NULL);
+}
+
+/*% Allocates memory for a new string, and then constructs the new
+ * string by "escaping" the input string.  The new string is
+ * safe to be used in queries.  This is necessary because we cannot
+ * be sure of what types of strings are passed to us, and we don't
+ * want special characters in the string causing problems.
+ */
+
+static char *
+odbc_escape_string(const char *instr) {
+	char *outstr;
+	unsigned int len;
+
+	if (instr == NULL) {
+		return (NULL);
+	}
+
+	len = strlen(instr);
+
+	outstr = isc_mem_allocate(named_g_mctx, (2 * len * sizeof(char)) + 1);
+
+	odbc_makesafe(outstr, instr, len);
+
+	return (outstr);
+}
+
+/* ---------------
+ * Escaping arbitrary strings to get valid SQL strings/identifiers.
+ *
+ * Replaces "\\" with "\\\\" and "'" with "''".
+ * length is the length of the buffer pointed to by
+ * from.  The buffer at to must be at least 2*length + 1 characters
+ * long.  A terminating NUL character is written.
+ *
+ * NOTICE!!!
+ * This function was borrowed directly from PostgreSQL's libpq.
+ *
+ * The copyright statements from the original file containing this
+ * function are included below:
+ * Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ * ---------------
+ */
+
+static size_t
+odbc_makesafe(char *to, const char *from, size_t length) {
+	const char *source = from;
+	char *target = to;
+	unsigned int remaining = length;
+
+	while (remaining > 0) {
+		switch (*source) {
+		case '\\':
+			*target = '\\';
+			target++;
+			*target = '\\';
+			/* target and remaining are updated below. */
+			break;
+
+		case '\'':
+			*target = '\'';
+			target++;
+			*target = '\'';
+			/* target and remaining are updated below. */
+			break;
+
+		default:
+			*target = *source;
+			/* target and remaining are updated below. */
+		}
+		source++;
+		target++;
+		remaining--;
+	}
+
+	/* Write the terminating NUL character. */
+	*target = '\0';
+
+	return (target - to);
+}
+
+/*%
+ * This function is the real core of the driver.   Zone, record
+ * and client strings are passed in (or NULL is passed if the
+ * string is not available).  The type of query we want to run
+ * is indicated by the query flag, and the dbdata object is passed
+ * passed in to.  dbdata really holds either:
+ *		1) a list of database instances (in multithreaded mode) OR
+ *		2) a single database instance (in single threaded mode)
+ * The function will construct the query and obtain an available
+ * database instance (DBI).  It will then run the query and hopefully
+ * obtain a result set.  The data base instance that is used is returned
+ * to the caller so they can get the data from the result set from it.
+ * If successful, it will be the responsibility of the caller to close
+ * the cursor, and unlock the mutex of the DBI when they are done with it.
+ * If not successful, this function will perform all the cleanup.
+ */
+
+static isc_result_t
+odbc_get_resultset(const char *zone, const char *record, const char *client,
+		   unsigned int query, void *dbdata, dbinstance_t **r_dbi) {
+	isc_result_t result;
+	dbinstance_t *dbi = NULL;
+	char *querystring = NULL;
+	unsigned int j = 0;
+	SQLRETURN sqlRes;
+
+	REQUIRE(*r_dbi == NULL);
+
+	/* get db instance / connection */
+
+	/* find an available DBI from the list */
+	dbi = odbc_find_avail_conn(((odbc_instance_t *)dbdata)->db);
+
+	/* if DBI is null, can't do anything else */
+	if (dbi == NULL) {
+		return (ISC_R_FAILURE);
+	}
+
+	/* what type of query are we going to run? */
+	switch (query) {
+	case ALLNODES:
+		/*
+		 * if the query was not passed in from the config file
+		 * then we can't run it.  return not_implemented, so
+		 * it's like the code for that operation was never
+		 * built into the driver.... AHHH flexibility!!!
+		 */
+		if (dbi->allnodes_q == NULL) {
+			result = ISC_R_NOTIMPLEMENTED;
+			goto cleanup;
+		}
+		break;
+	case ALLOWXFR:
+		/* same as comments as ALLNODES */
+		if (dbi->allowxfr_q == NULL) {
+			result = ISC_R_NOTIMPLEMENTED;
+			goto cleanup;
+		}
+		break;
+	case AUTHORITY:
+		/* same as comments as ALLNODES */
+		if (dbi->authority_q == NULL) {
+			result = ISC_R_NOTIMPLEMENTED;
+			goto cleanup;
+		}
+		break;
+	case FINDZONE:
+		/* this is required.  It's the whole point of DLZ! */
+		if (dbi->findzone_q == NULL) {
+			isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE,
+				      DNS_LOGMODULE_DLZ, ISC_LOG_DEBUG(2),
+				      "No query specified for findzone.  "
+				      "Findzone requires a query");
+			result = ISC_R_FAILURE;
+			goto cleanup;
+		}
+		break;
+	case LOOKUP:
+		/* this is required.  It's also a major point of DLZ! */
+		if (dbi->lookup_q == NULL) {
+			isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE,
+				      DNS_LOGMODULE_DLZ, ISC_LOG_DEBUG(2),
+				      "No query specified for lookup.  "
+				      "Lookup requires a query");
+			result = ISC_R_FAILURE;
+			goto cleanup;
+		}
+		break;
+	default:
+		/*
+		 * this should never happen.  If it does, the code is
+		 * screwed up!
+		 */
+		UNEXPECTED_ERROR(__FILE__, __LINE__,
+				 "Incorrect query flag passed to "
+				 "odbc_get_resultset");
+		result = ISC_R_UNEXPECTED;
+		goto cleanup;
+	}
+
+	/*
+	 * was a zone string passed?  If so, make it safe for use in
+	 * queries.
+	 */
+	if (zone != NULL) {
+		dbi->zone = odbc_escape_string(zone);
+		if (dbi->zone == NULL) {
+			result = ISC_R_NOMEMORY;
+			goto cleanup;
+		}
+	} else { /* no string passed, set the string pointer to NULL */
+		dbi->zone = NULL;
+	}
+
+	/*
+	 * was a record string passed?  If so, make it safe for use in
+	 * queries.
+	 */
+	if (record != NULL) {
+		dbi->record = odbc_escape_string(record);
+		if (dbi->record == NULL) {
+			result = ISC_R_NOMEMORY;
+			goto cleanup;
+		}
+	} else { /* no string passed, set the string pointer to NULL */
+		dbi->record = NULL;
+	}
+
+	/*
+	 * was a client string passed?  If so, make it safe for use in
+	 * queries.
+	 */
+	if (client != NULL) {
+		dbi->client = odbc_escape_string(client);
+		if (dbi->client == NULL) {
+			result = ISC_R_NOMEMORY;
+			goto cleanup;
+		}
+	} else { /* no string passed, set the string pointer to NULL */
+		dbi->client = NULL;
+	}
+
+	/*
+	 * what type of query are we going to run?
+	 * this time we build the actual query to run.
+	 */
+	switch (query) {
+	case ALLNODES:
+		querystring = build_querystring(named_g_mctx, dbi->allnodes_q);
+		break;
+	case ALLOWXFR:
+		querystring = build_querystring(named_g_mctx, dbi->allowxfr_q);
+		break;
+	case AUTHORITY:
+		querystring = build_querystring(named_g_mctx, dbi->authority_q);
+		break;
+	case FINDZONE:
+		querystring = build_querystring(named_g_mctx, dbi->findzone_q);
+		break;
+	case LOOKUP:
+		querystring = build_querystring(named_g_mctx, dbi->lookup_q);
+		break;
+	default:
+		/*
+		 * this should never happen.  If it does, the code is
+		 * screwed up!
+		 */
+		UNEXPECTED_ERROR(__FILE__, __LINE__,
+				 "Incorrect query flag passed to "
+				 "odbc_get_resultset");
+		result = ISC_R_UNEXPECTED;
+		goto cleanup;
+	}
+
+	/* if the querystring is null, Bummer, outta RAM.  UPGRADE TIME!!!   */
+	if (querystring == NULL) {
+		result = ISC_R_NOMEMORY;
+		goto cleanup;
+	}
+
+	/* output the full query string during debug so we can see */
+	/* what lame error the query has. */
+	isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE, DNS_LOGMODULE_DLZ,
+		      ISC_LOG_DEBUG(1), "\nQuery String: %s\n", querystring);
+
+	/* attempt query up to 3 times. */
+	for (j = 0; j < 3; j++) {
+		/* try to get result set */
+		sqlRes = SQLExecDirect(((odbc_db_t *)dbi->dbconn)->stmnt,
+				       (SQLCHAR *)querystring,
+				       (SQLINTEGER)strlen(querystring));
+
+		/* if error, reset DB connection */
+		if (!sqlOK(sqlRes)) {
+			/* close cursor */
+			SQLCloseCursor(((odbc_db_t *)dbi->dbconn)->stmnt);
+			/* attempt to reconnect */
+			result = odbc_connect((odbc_instance_t *)dbdata,
+					      (odbc_db_t **)&(dbi->dbconn));
+			/* check if we reconnected */
+			if (result != ISC_R_SUCCESS) {
+				break;
+			}
+			/* in case this is the last time through the loop */
+			result = ISC_R_FAILURE;
+		} else {
+			result = ISC_R_SUCCESS;
+			/* return dbi */
+			*r_dbi = dbi;
+			/* result set ok, break loop */
+			break;
+		}
+	} /* end for loop */
+
+cleanup: /* it's always good to cleanup after yourself */
+
+	/* free dbi->zone string */
+	if (dbi->zone != NULL) {
+		isc_mem_free(named_g_mctx, dbi->zone);
+	}
+
+	/* free dbi->record string */
+	if (dbi->record != NULL) {
+		isc_mem_free(named_g_mctx, dbi->record);
+	}
+
+	/* free dbi->client string */
+	if (dbi->client != NULL) {
+		isc_mem_free(named_g_mctx, dbi->client);
+	}
+
+	/* if we are done using this dbi, release the lock */
+	if (result != ISC_R_SUCCESS) {
+		isc_mutex_unlock(&dbi->instance_lock);
+	}
+
+	/* release query string */
+	if (querystring != NULL) {
+		isc_mem_free(named_g_mctx, querystring);
+	}
+
+	/* return result */
+	return (result);
+}
+
+/*%
+ * Gets a single field from the ODBC statement.  The memory for the
+ * returned data is dynamically allocated.  If this method is successful
+ * it is the responsibility of the caller to free the memory using
+ * isc_mem_free(named_g_mctx, *ptr);
+ */
+
+static isc_result_t
+odbc_getField(SQLHSTMT *stmnt, SQLSMALLINT field, char **data) {
+	SQLLEN size;
+
+	REQUIRE(data != NULL && *data == NULL);
+
+	if (sqlOK(SQLColAttribute(stmnt, field, SQL_DESC_DISPLAY_SIZE, NULL, 0,
+				  NULL, &size)) &&
+	    size > 0)
+	{
+		*data = isc_mem_allocate(named_g_mctx, size + 1);
+		if (data != NULL) {
+			if (sqlOK(SQLGetData(stmnt, field, SQL_C_CHAR, *data,
+					     size + 1, &size)))
+			{
+				return (ISC_R_SUCCESS);
+			}
+			isc_mem_free(named_g_mctx, *data);
+		}
+	}
+	return (ISC_R_FAILURE);
+}
+
+/*%
+ * Gets multiple fields from the ODBC statement.  The memory for the
+ * returned data is dynamically allocated.  If this method is successful
+ * it is the responsibility of the caller to free the memory using
+ * isc_mem_free(named_g_mctx, *ptr);
+ */
+
+static isc_result_t
+odbc_getManyFields(SQLHSTMT *stmnt, SQLSMALLINT startField,
+		   SQLSMALLINT endField, char **retData) {
+	isc_result_t result;
+	SQLLEN size;
+	int totSize = 0;
+	SQLSMALLINT i;
+	int j = 0;
+	char *data;
+
+	REQUIRE(retData != NULL && *retData == NULL);
+	REQUIRE(startField > 0 && startField <= endField);
+
+	/* determine how large the data is */
+	for (i = startField; i <= endField; i++) {
+		if (sqlOK(SQLColAttribute(stmnt, i, SQL_DESC_DISPLAY_SIZE, NULL,
+					  0, NULL, &size)) &&
+		    size > 0)
+		{
+			{
+				/* always allow for a " " (space) character */
+				totSize += (size + 1);
+				/* after the data item */
+			}
+		}
+	}
+
+	if (totSize < 1) {
+		return (ISC_R_FAILURE);
+	}
+
+	/* allow for a "\n" at the end of the string/ */
+	data = isc_mem_allocate(named_g_mctx, ++totSize);
+
+	result = ISC_R_FAILURE;
+
+	/* get the data and concat all fields into a large string */
+	for (i = startField; i <= endField; i++) {
+		if (sqlOK(SQLGetData(stmnt, i, SQL_C_CHAR, &(data[j]),
+				     totSize - j, &size)))
+		{
+			if (size > 0) {
+				j += size;
+				data[j++] = ' ';
+				data[j] = '\0';
+				result = ISC_R_SUCCESS;
+			}
+		} else {
+			isc_mem_free(named_g_mctx, data);
+			return (ISC_R_FAILURE);
+		}
+	}
+
+	if (result != ISC_R_SUCCESS) {
+		isc_mem_free(named_g_mctx, data);
+		return (result);
+	}
+
+	*retData = data;
+	return (ISC_R_SUCCESS);
+}
+
+/*%
+ * The processing of result sets for lookup and authority are
+ * exactly the same.  So that functionality has been moved
+ * into this function to minimize code.
+ */
+
+static isc_result_t
+odbc_process_rs(dns_sdlzlookup_t *lookup, dbinstance_t *dbi) {
+	isc_result_t result;
+	SQLSMALLINT fields;
+	SQLHSTMT *stmnt;
+	char *ttl_s;
+	char *type;
+	char *data;
+	char *endp;
+	int ttl;
+
+	REQUIRE(dbi != NULL);
+
+	stmnt = ((odbc_db_t *)(dbi->dbconn))->stmnt;
+
+	/* get number of columns */
+	if (!sqlOK(SQLNumResultCols(stmnt, &fields))) {
+		isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE,
+			      DNS_LOGMODULE_DLZ, ISC_LOG_ERROR,
+			      "Odbc driver unable to process result set");
+		result = ISC_R_FAILURE;
+		goto process_rs_cleanup;
+	}
+
+	/* get things ready for processing */
+	result = ISC_R_FAILURE;
+
+	while (sqlOK(SQLFetch(stmnt))) {
+		/* set to null for next pass through */
+		data = type = ttl_s = NULL;
+
+		switch (fields) {
+		case 1:
+			/*
+			 * one column in rs, it's the data field.  use
+			 * default type of A record, and default TTL
+			 * of 86400.  attempt to get data, & tell bind
+			 * about it.
+			 */
+			if ((result = odbc_getField(stmnt, 1, &data)) ==
+			    ISC_R_SUCCESS)
+			{
+				result = dns_sdlz_putrr(lookup, "a", 86400,
+							data);
+			}
+			break;
+		case 2:
+			/*
+			 * two columns, data field, and data type.
+			 * use default TTL of 86400.  attempt to get
+			 * DNS type & data, then tell bind about it.
+			 */
+			if ((result = odbc_getField(stmnt, 1, &type)) ==
+				    ISC_R_SUCCESS &&
+			    (result = odbc_getField(stmnt, 2, &data)) ==
+				    ISC_R_SUCCESS)
+			{
+				result = dns_sdlz_putrr(lookup, type, 86400,
+							data);
+			}
+			break;
+		default:
+			/*
+			 * 3 fields or more, concatenate the last ones
+			 * together.  attempt to get DNS ttl, type,
+			 * data then tell Bind about them.
+			 */
+			if ((result = odbc_getField(stmnt, 1, &ttl_s)) ==
+				    ISC_R_SUCCESS &&
+			    (result = odbc_getField(stmnt, 2, &type)) ==
+				    ISC_R_SUCCESS &&
+			    (result = odbc_getManyFields(
+				     stmnt, 3, fields, &data)) == ISC_R_SUCCESS)
+			{
+				/* try to convert ttl string to int */
+				ttl = strtol(ttl_s, &endp, 10);
+				/* failure converting ttl. */
+				if (*endp != '\0' || ttl < 0) {
+					isc_log_write(dns_lctx,
+						      DNS_LOGCATEGORY_DATABASE,
+						      DNS_LOGMODULE_DLZ,
+						      ISC_LOG_ERROR,
+						      "Odbc driver ttl must "
+						      "be a positive number");
+					result = ISC_R_FAILURE;
+				} else {
+					/*
+					 * successful converting TTL,
+					 * tell Bind everything
+					 */
+					result = dns_sdlz_putrr(lookup, type,
+								ttl, data);
+				}
+			} /* closes bid if () */
+		}	  /* closes switch(fields) */
+
+		/* clean up mem */
+		if (ttl_s != NULL) {
+			isc_mem_free(named_g_mctx, ttl_s);
+		}
+		if (type != NULL) {
+			isc_mem_free(named_g_mctx, type);
+		}
+		if (data != NULL) {
+			isc_mem_free(named_g_mctx, data);
+		}
+
+		/* I sure hope we were successful */
+		if (result != ISC_R_SUCCESS) {
+			isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE,
+				      DNS_LOGMODULE_DLZ, ISC_LOG_ERROR,
+				      "dns_sdlz_putrr returned error. "
+				      "Error code was: %s",
+				      isc_result_totext(result));
+			result = ISC_R_FAILURE;
+			goto process_rs_cleanup;
+		}
+	} /* closes while loop */
+
+process_rs_cleanup:
+
+	/* close cursor */
+	SQLCloseCursor(((odbc_db_t *)(dbi->dbconn))->stmnt);
+
+	/* free lock on dbi so someone else can use it. */
+	isc_mutex_unlock(&dbi->instance_lock);
+
+	return (result);
+}
+
+/*
+ * SDLZ interface methods
+ */
+
+/*% determine if the zone is supported by (in) the database */
+
+static isc_result_t
+odbc_findzone(void *driverarg, void *dbdata, const char *name,
+	      dns_clientinfomethods_t *methods, dns_clientinfo_t *clientinfo) {
+	isc_result_t result;
+	dbinstance_t *dbi = NULL;
+
+	UNUSED(driverarg);
+	UNUSED(methods);
+	UNUSED(clientinfo);
+
+	/* run the query and get the result set from the database. */
+	/* if result != ISC_R_SUCCESS cursor and mutex already cleaned up. */
+	/* so we don't have to do it here. */
+	result = odbc_get_resultset(name, NULL, NULL, FINDZONE, dbdata, &dbi);
+
+	/* Check that we got a result set with data */
+	if (result == ISC_R_SUCCESS &&
+	    !sqlOK(SQLFetch(((odbc_db_t *)(dbi->dbconn))->stmnt)))
+	{
+		result = ISC_R_NOTFOUND;
+	}
+
+	if (dbi != NULL) {
+		/* get rid of result set, we are done with it. */
+		SQLCloseCursor(((odbc_db_t *)(dbi->dbconn))->stmnt);
+
+		/* free lock on dbi so someone else can use it. */
+		isc_mutex_unlock(&dbi->instance_lock);
+	}
+
+	return (result);
+}
+
+/*% Determine if the client is allowed to perform a zone transfer */
+static isc_result_t
+odbc_allowzonexfr(void *driverarg, void *dbdata, const char *name,
+		  const char *client) {
+	isc_result_t result;
+	dbinstance_t *dbi = NULL;
+
+	UNUSED(driverarg);
+
+	/* first check if the zone is supported by the database. */
+	result = odbc_findzone(driverarg, dbdata, name, NULL, NULL);
+	if (result != ISC_R_SUCCESS) {
+		return (ISC_R_NOTFOUND);
+	}
+
+	/*
+	 * if we get to this point we know the zone is supported by
+	 * the database.  the only questions now are is the zone
+	 * transfer is allowed for this client and did the config file
+	 * have an allow zone xfr query
+	 *
+	 * Run our query, and get a result set from the database.  if
+	 * result != ISC_R_SUCCESS cursor and mutex already cleaned
+	 * up, so we don't have to do it here.
+	 */
+	result = odbc_get_resultset(name, NULL, client, ALLOWXFR, dbdata, &dbi);
+
+	/* if we get "not implemented", send it along. */
+	if (result == ISC_R_NOTIMPLEMENTED) {
+		return (result);
+	}
+
+	/* Check that we got a result set with data */
+	if (result == ISC_R_SUCCESS &&
+	    !sqlOK(SQLFetch(((odbc_db_t *)(dbi->dbconn))->stmnt)))
+	{
+		result = ISC_R_NOPERM;
+	}
+
+	if (dbi != NULL) {
+		/* get rid of result set, we are done with it. */
+		SQLCloseCursor(((odbc_db_t *)(dbi->dbconn))->stmnt);
+
+		/* free lock on dbi so someone else can use it. */
+		isc_mutex_unlock(&dbi->instance_lock);
+	}
+
+	return (result);
+}
+
+/*%
+ * If the client is allowed to perform a zone transfer, the next order of
+ * business is to get all the nodes in the zone, so bind can respond to the
+ * query.
+ */
+
+static isc_result_t
+odbc_allnodes(const char *zone, void *driverarg, void *dbdata,
+	      dns_sdlzallnodes_t *allnodes) {
+	isc_result_t result;
+	dbinstance_t *dbi = NULL;
+	SQLHSTMT *stmnt;
+	SQLSMALLINT fields;
+	char *data;
+	char *type;
+	char *ttl_s;
+	int ttl;
+	char *host;
+	char *endp;
+
+	UNUSED(driverarg);
+
+	/* run the query and get the result set from the database. */
+	result = odbc_get_resultset(zone, NULL, NULL, ALLNODES, dbdata, &dbi);
+
+	/* if we get "not implemented", send it along */
+	if (result == ISC_R_NOTIMPLEMENTED) {
+		return (result);
+	}
+
+	/* if we didn't get a result set, log an err msg. */
+	if (result != ISC_R_SUCCESS) {
+		isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE,
+			      DNS_LOGMODULE_DLZ, ISC_LOG_ERROR,
+			      "Odbc driver unable to return "
+			      "result set for all nodes query");
+		return (ISC_R_FAILURE);
+	}
+
+	stmnt = ((odbc_db_t *)(dbi->dbconn))->stmnt;
+
+	/* get number of columns */
+	if (!sqlOK(SQLNumResultCols(stmnt, &fields))) {
+		isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE,
+			      DNS_LOGMODULE_DLZ, ISC_LOG_ERROR,
+			      "Odbc driver unable to process result set");
+		result = ISC_R_FAILURE;
+		goto allnodes_cleanup;
+	}
+
+	if (fields < 4) { /* gotta have at least 4 columns */
+		isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE,
+			      DNS_LOGMODULE_DLZ, ISC_LOG_ERROR,
+			      "Odbc driver too few fields returned by "
+			      "all nodes query");
+		result = ISC_R_FAILURE;
+		goto allnodes_cleanup;
+	}
+
+	/* get things ready for processing */
+	result = ISC_R_FAILURE;
+
+	while (sqlOK(SQLFetch(stmnt))) {
+		/* set to null for next pass through */
+		data = host = type = ttl_s = NULL;
+
+		/*
+		 * attempt to get DNS ttl, type, host, data then tell
+		 * Bind about them
+		 */
+		if ((result = odbc_getField(stmnt, 1, &ttl_s)) ==
+			    ISC_R_SUCCESS &&
+		    (result = odbc_getField(stmnt, 2, &type)) ==
+			    ISC_R_SUCCESS &&
+		    (result = odbc_getField(stmnt, 3, &host)) ==
+			    ISC_R_SUCCESS &&
+		    (result = odbc_getManyFields(stmnt, 4, fields, &data)) ==
+			    ISC_R_SUCCESS)
+		{
+			/* convert ttl string to int */
+			ttl = strtol(ttl_s, &endp, 10);
+			/* failure converting ttl. */
+			if (*endp != '\0' || ttl < 0) {
+				isc_log_write(dns_lctx,
+					      DNS_LOGCATEGORY_DATABASE,
+					      DNS_LOGMODULE_DLZ, ISC_LOG_ERROR,
+					      "Odbc driver ttl must be "
+					      "a positive number");
+				result = ISC_R_FAILURE;
+			} else {
+				/* successful converting TTL, tell Bind  */
+				result = dns_sdlz_putnamedrr(allnodes, host,
+							     type, ttl, data);
+			}
+		} /* closes big if () */
+
+		/* clean up mem */
+		if (ttl_s != NULL) {
+			isc_mem_free(named_g_mctx, ttl_s);
+		}
+		if (type != NULL) {
+			isc_mem_free(named_g_mctx, type);
+		}
+		if (host != NULL) {
+			isc_mem_free(named_g_mctx, host);
+		}
+		if (data != NULL) {
+			isc_mem_free(named_g_mctx, data);
+		}
+
+		/* if we weren't successful, log err msg */
+		if (result != ISC_R_SUCCESS) {
+			isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE,
+				      DNS_LOGMODULE_DLZ, ISC_LOG_ERROR,
+				      "dns_sdlz_putnamedrr returned error. "
+				      "Error code was: %s",
+				      isc_result_totext(result));
+			result = ISC_R_FAILURE;
+			goto allnodes_cleanup;
+		}
+	} /* closes while loop */
+
+allnodes_cleanup:
+
+	/* close cursor */
+	SQLCloseCursor(((odbc_db_t *)(dbi->dbconn))->stmnt);
+
+	/* free lock on dbi so someone else can use it. */
+	isc_mutex_unlock(&dbi->instance_lock);
+
+	return (result);
+}
+
+/*%
+ * if the lookup function does not return SOA or NS records for the zone,
+ * use this function to get that information for Bind.
+ */
+
+static isc_result_t
+odbc_authority(const char *zone, void *driverarg, void *dbdata,
+	       dns_sdlzlookup_t *lookup) {
+	isc_result_t result;
+	dbinstance_t *dbi = NULL;
+
+	UNUSED(driverarg);
+
+	/* run the query and get the result set from the database. */
+	result = odbc_get_resultset(zone, NULL, NULL, AUTHORITY, dbdata, &dbi);
+	/* if we get "not implemented", send it along */
+	if (result == ISC_R_NOTIMPLEMENTED) {
+		return (result);
+	}
+	/* if we didn't get a result set, log an err msg. */
+	if (result != ISC_R_SUCCESS) {
+		isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE,
+			      DNS_LOGMODULE_DLZ, ISC_LOG_ERROR,
+			      "Odbc driver unable to return "
+			      "result set for authority query");
+		return (ISC_R_FAILURE);
+	}
+	/* lookup and authority result sets are processed in the same manner */
+	/* odbc_process_rs does the job for both functions. */
+	return (odbc_process_rs(lookup, dbi));
+}
+
+/*% if zone is supported, lookup up a (or multiple) record(s) in it */
+
+static isc_result_t
+odbc_lookup(const char *zone, const char *name, void *driverarg, void *dbdata,
+	    dns_sdlzlookup_t *lookup, dns_clientinfomethods_t *methods,
+	    dns_clientinfo_t *clientinfo) {
+	isc_result_t result;
+	dbinstance_t *dbi = NULL;
+
+	UNUSED(driverarg);
+	UNUSED(methods);
+	UNUSED(clientinfo);
+
+	/* run the query and get the result set from the database. */
+	result = odbc_get_resultset(zone, name, NULL, LOOKUP, dbdata, &dbi);
+	/* if we didn't get a result set, log an err msg. */
+	if (result != ISC_R_SUCCESS) {
+		isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE,
+			      DNS_LOGMODULE_DLZ, ISC_LOG_ERROR,
+			      "Odbc driver unable to return "
+			      "result set for lookup query");
+		return (ISC_R_FAILURE);
+	}
+	/* lookup and authority result sets are processed in the same manner */
+	/* odbc_process_rs does the job for both functions. */
+	return (odbc_process_rs(lookup, dbi));
+}
+
+/*%
+ * create an instance of the driver.  Remember, only 1 copy of the driver's
+ * code is ever loaded, the driver has to remember which context it's
+ * operating in.  This is done via use of the dbdata argument which is
+ * passed into all query functions.
+ */
+static isc_result_t
+odbc_create(const char *dlzname, unsigned int argc, char *argv[],
+	    void *driverarg, void **dbdata) {
+	isc_result_t result;
+	odbc_instance_t *odbc_inst = NULL;
+	dbinstance_t *db = NULL;
+	SQLRETURN sqlRes;
+	int dbcount;
+	int i;
+	char *endp;
+
+	UNUSED(dlzname);
+	UNUSED(driverarg);
+
+	/* if debugging, let user know we are multithreaded. */
+	isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE, DNS_LOGMODULE_DLZ,
+		      ISC_LOG_DEBUG(1), "Odbc driver running multithreaded");
+
+	/* verify we have at least 5 arg's passed to the driver */
+	if (argc < 5) {
+		isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE,
+			      DNS_LOGMODULE_DLZ, ISC_LOG_ERROR,
+			      "Odbc driver requires at least "
+			      "4 command line args.");
+		return (ISC_R_FAILURE);
+	}
+
+	/* no more than 8 arg's should be passed to the driver */
+	if (argc > 8) {
+		isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE,
+			      DNS_LOGMODULE_DLZ, ISC_LOG_ERROR,
+			      "Odbc driver cannot accept more than "
+			      "7 command line args.");
+		return (ISC_R_FAILURE);
+	}
+
+	/* multithreaded build can have multiple DB connections */
+	/* check how many db connections we should create */
+	dbcount = strtol(argv[1], &endp, 10);
+	if (*endp != '\0' || dbcount < 0) {
+		isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE,
+			      DNS_LOGMODULE_DLZ, ISC_LOG_ERROR,
+			      "Odbc driver database connection count "
+			      "must be positive.");
+		return (ISC_R_FAILURE);
+	}
+
+	/* allocate memory for odbc instance */
+	odbc_inst = isc_mem_get(named_g_mctx, sizeof(odbc_instance_t));
+	memset(odbc_inst, 0, sizeof(odbc_instance_t));
+
+	/* parse connection string and get parameters. */
+
+	/* get odbc database dsn - required */
+	odbc_inst->dsn = (SQLCHAR *)getParameterValue(argv[2], "dsn=");
+	if (odbc_inst->dsn == NULL) {
+		isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE,
+			      DNS_LOGMODULE_DLZ, ISC_LOG_ERROR,
+			      "odbc driver requires a dns parameter.");
+		result = ISC_R_FAILURE;
+		goto cleanup;
+	}
+	/* get odbc database username */
+	/* if no username was passed, set odbc_inst.user = NULL; */
+	odbc_inst->user = (SQLCHAR *)getParameterValue(argv[2], "user=");
+
+	/* get odbc database password */
+	/* if no password was passed, set odbc_inst.pass = NULL; */
+	odbc_inst->pass = (SQLCHAR *)getParameterValue(argv[2], "pass=");
+
+	/* create odbc environment & set environment to ODBC V3 */
+	if (odbc_inst->sql_env == NULL) {
+		/* create environment handle */
+		sqlRes = SQLAllocHandle(SQL_HANDLE_ENV, SQL_NULL_HANDLE,
+					&(odbc_inst->sql_env));
+		if (!sqlOK(sqlRes)) {
+			isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE,
+				      DNS_LOGMODULE_DLZ, ISC_LOG_INFO,
+				      "Odbc driver unable to allocate memory");
+			result = ISC_R_NOMEMORY;
+			goto cleanup;
+		}
+		/*set ODBC version = 3 */
+		sqlRes = SQLSetEnvAttr(odbc_inst->sql_env,
+				       SQL_ATTR_ODBC_VERSION,
+				       (void *)SQL_OV_ODBC3, 0);
+		if (!sqlOK(sqlRes)) {
+			isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE,
+				      DNS_LOGMODULE_DLZ, ISC_LOG_INFO,
+				      "Unable to configure ODBC environment");
+			result = ISC_R_NOMEMORY;
+			goto cleanup;
+		}
+	}
+
+	/* allocate memory for database connection list */
+	odbc_inst->db = isc_mem_get(named_g_mctx, sizeof(db_list_t));
+
+	/* initialize DB connection list */
+	ISC_LIST_INIT(*odbc_inst->db);
+
+	/* create the appropriate number of database instances (DBI) */
+	/* append each new DBI to the end of the list */
+	for (i = 0; i < dbcount; i++) {
+		/* how many queries were passed in from config file? */
+		switch (argc) {
+		case 5:
+			result = build_sqldbinstance(named_g_mctx, NULL, NULL,
+						     NULL, argv[3], argv[4],
+						     NULL, &db);
+			break;
+		case 6:
+			result = build_sqldbinstance(named_g_mctx, NULL, NULL,
+						     argv[5], argv[3], argv[4],
+						     NULL, &db);
+			break;
+		case 7:
+			result = build_sqldbinstance(named_g_mctx, argv[6],
+						     NULL, argv[5], argv[3],
+						     argv[4], NULL, &db);
+			break;
+		case 8:
+			result = build_sqldbinstance(named_g_mctx, argv[6],
+						     argv[7], argv[5], argv[3],
+						     argv[4], NULL, &db);
+			break;
+		default:
+			/* not really needed, should shut up compiler. */
+			result = ISC_R_FAILURE;
+		}
+
+		/* unsuccessful?, log err msg and cleanup. */
+		if (result != ISC_R_SUCCESS) {
+			isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE,
+				      DNS_LOGMODULE_DLZ, ISC_LOG_ERROR,
+				      "Odbc driver could not create "
+				      "database instance object.");
+			goto cleanup;
+		}
+
+		/* when multithreaded, build a list of DBI's */
+		ISC_LINK_INIT(db, link);
+		ISC_LIST_APPEND(*odbc_inst->db, db, link);
+
+		result = odbc_connect(odbc_inst, (odbc_db_t **)&(db->dbconn));
+
+		if (result != ISC_R_SUCCESS) {
+			/*
+			 * if multi threaded, let user know which
+			 * connection failed.  user could be
+			 * attempting to create 10 db connections and
+			 * for some reason the db backend only allows
+			 * 9.
+			 */
+			isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE,
+				      DNS_LOGMODULE_DLZ, ISC_LOG_ERROR,
+				      "Odbc driver failed to create database "
+				      "connection number %u after 3 attempts",
+				      i + 1);
+			goto cleanup;
+		}
+
+		/* set DB = null for next loop through. */
+		db = NULL;
+	} /* end for loop */
+
+	/* set dbdata to the odbc_instance we created. */
+	*dbdata = odbc_inst;
+
+	/* hey, we got through all of that ok, return success. */
+	return (ISC_R_SUCCESS);
+
+cleanup:
+
+	destroy_odbc_instance(odbc_inst);
+
+	return (result);
+}
+
+/*%
+ * destroy an instance of the driver.  Remember, only 1 copy of the driver's
+ * code is ever loaded, the driver has to remember which context it's
+ * operating in.  This is done via use of the dbdata argument.
+ * so we really only need to clean it up since we are not using driverarg.
+ */
+
+static void
+odbc_destroy(void *driverarg, void *dbdata) {
+	UNUSED(driverarg);
+
+	destroy_odbc_instance((odbc_instance_t *)dbdata);
+}
+
+/* pointers to all our runtime methods. */
+/* this is used during driver registration */
+/* i.e. in dlz_odbc_init below. */
+static dns_sdlzmethods_t dlz_odbc_methods = {
+	odbc_create,
+	odbc_destroy,
+	odbc_findzone,
+	odbc_lookup,
+	odbc_authority,
+	odbc_allnodes,
+	odbc_allowzonexfr,
+	NULL,
+	NULL,
+	NULL,
+	NULL,
+	NULL,
+	NULL,
+	NULL,
+};
+
+/*%
+ * Wrapper around dns_sdlzregister().
+ */
+isc_result_t
+dlz_odbc_init(void) {
+	isc_result_t result;
+
+	/*
+	 * Write debugging message to log
+	 */
+	isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE, DNS_LOGMODULE_DLZ,
+		      ISC_LOG_DEBUG(2), "Registering DLZ odbc driver.");
+
+	/*
+	 * Driver is always threadsafe.  When multithreaded all
+	 * functions use multithreaded code.  When not multithreaded,
+	 * all functions can only be entered once, but only 1 thread
+	 * of operation is available in Bind.  So everything is still
+	 * threadsafe.
+	 */
+	result = dns_sdlzregister("odbc", &dlz_odbc_methods, NULL,
+				  DNS_SDLZFLAG_RELATIVEOWNER |
+					  DNS_SDLZFLAG_RELATIVERDATA |
+					  DNS_SDLZFLAG_THREADSAFE,
+				  named_g_mctx, &dlz_odbc);
+	/* if we can't register the driver, there are big problems. */
+	if (result != ISC_R_SUCCESS) {
+		UNEXPECTED_ERROR(__FILE__, __LINE__,
+				 "dns_sdlzregister() failed: %s",
+				 isc_result_totext(result));
+		result = ISC_R_UNEXPECTED;
+	}
+
+	return (result);
+}
+
+/*%
+ * Wrapper around dns_sdlzunregister().
+ */
+void
+dlz_odbc_clear(void) {
+	/*
+	 * Write debugging message to log
+	 */
+	isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE, DNS_LOGMODULE_DLZ,
+		      ISC_LOG_DEBUG(2), "Unregistering DLZ odbc driver.");
+
+	/* unregister the driver. */
+	if (dlz_odbc != NULL) {
+		dns_sdlzunregister(&dlz_odbc);
+	}
+}
+
+#endif /* ifdef DLZ_ODBC */