/*
 * Copyright (C) Internet Systems Consortium, Inc. ("ISC")
 *
 * SPDX-License-Identifier: MPL-2.0 and 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 https://mozilla.org/MPL/2.0/.
 */

/*
 * Copyright (C) Stichting NLnet, Netherlands, stichting@nlnet.nl.
 *
 * The development of Dynamically Loadable Zones (DLZ) for Bind 9 was
 * conceived and contributed by Rob Butler.
 *
 * Permission to use, copy, modify, and distribute this software for any purpose
 * with or without fee is hereby granted, provided that the above copyright
 * notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
 * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
 * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
 * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
 * OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
 * PERFORMANCE OF THIS SOFTWARE.
 */

/*
 * This provides the externally loadable SQLitee DLZ module, without
 * update support. Based in part on SQLite code contributed by Tim Tessier.
 */

#include <sqlite3.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <dlz_dbi.h>
#include <dlz_list.h>
#include <dlz_minimal.h>
#include <dlz_pthread.h>

#define dbc_search_limit 30
#define ALLNODES	 1
#define ALLOWXFR	 2
#define AUTHORITY	 3
#define FINDZONE	 4
#define COUNTZONE	 5
#define LOOKUP		 6

#define safeGet(in) in == NULL ? "" : in

/*%
 * Structure to hold everything needed by this "instance" of the SQLite3
 * module remember, the module code is only loaded once, but may have
 * many separate instances.
 */
typedef struct {
	db_list_t *db; /*%< handle to a list of DB */
	int dbcount;

	char *dbname;

	/* Helper functions from the dlz_dlopen driver */
	log_t *log;
	dns_sdlz_putrr_t *putrr;
	dns_sdlz_putnamedrr_t *putnamedrr;
	dns_dlz_writeablezone_t *writeable_zone;
} sqlite3_instance_t;

/*
 * SQLite3 result set
 */
typedef struct {
	char **pazResult; /* Result of the query */
	int pnRow;	  /* Number of result rows */
	int pnColumn;	  /* Number of result columns */
	int curRow;	  /* Current row */
	char *pzErrmsg;	  /* Error message */
} sqlite3_res_t;

/* forward references */
isc_result_t
dlz_findzonedb(void *dbdata, const char *name, dns_clientinfomethods_t *methods,
	       dns_clientinfo_t *clientinfo);

void
dlz_destroy(void *dbdata);

static void
b9_add_helper(sqlite3_instance_t *db, const char *helper_name, void *ptr);

/*
 * Private methods
 */

static void
dlz_sqlite3_destroy(dbinstance_t *db) {
	/* release DB connection */
	if (db->dbconn != NULL) {
		sqlite3_close((sqlite3 *)db->dbconn);
	}
	sqlite3_shutdown();

	/* destroy DB instance */
	destroy_dbinstance(db);
}

/*%
 * Properly cleans up a list of database instances.
 * This function is only used when the module is compiled for
 * multithreaded operation.
 */
static void
dlz_sqlite3_destroy_dblist(db_list_t *dblist) {
	dbinstance_t *ndbi = NULL;
	dbinstance_t *dbi = NULL;

	ndbi = DLZ_LIST_HEAD(*dblist);
	while (ndbi != NULL) {
		dbi = ndbi;
		ndbi = DLZ_LIST_NEXT(dbi, link);

		dlz_sqlite3_destroy(dbi);
	}

	/* release memory for the list structure */
	free(dblist);
}

/*%
 * 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 module is compiled for
 * multithreaded operation.
 */
static dbinstance_t *
sqlite3_find_avail(sqlite3_instance_t *sqlite3) {
	dbinstance_t *dbi = NULL, *head;
	int count = 0;

	/* get top of list */
	head = dbi = DLZ_LIST_HEAD(*(sqlite3->db));

	/* loop through list */
	while (count < dbc_search_limit) {
		/* try to lock on the mutex */
		if (dlz_mutex_trylock(&dbi->lock) == 0) {
			return (dbi); /* success, return the DBI for use. */
		}
		/* not successful, keep trying */
		dbi = DLZ_LIST_NEXT(dbi, link);

		/* check to see if we have gone to the top of the list. */
		if (dbi == NULL) {
			count++;
			dbi = head;
		}
	}

	sqlite3->log(ISC_LOG_INFO,
		     "SQLite3 module: 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 *
escape_string(const char *instr) {
	char *outstr;
	char *ptr;
	unsigned int len;
	unsigned int tlen = 0;
	unsigned int atlen = 0;
	unsigned int i;

	if (instr == NULL) {
		return (NULL);
	}
	len = strlen(instr);
	atlen = (2 * len * sizeof(char)) + 1;
	outstr = malloc(atlen);
	if (outstr == NULL) {
		return (NULL);
	}

	ptr = outstr;
	for (i = 0; i < len; i++) {
		if (tlen > atlen || instr[i] == '\0') {
			break;
		}

		if (instr[i] == '\'') {
			*ptr++ = '\'';
			tlen++;
		}

		*ptr++ = instr[i];
		tlen++;
	}
	*ptr = '\0';

	return (outstr);
}

/*%
 * This function is the real core of the module.   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 too.  dbdata really holds a single database instance.
 * The function will construct and run the query, hopefully getting
 * a result set.
 */
static isc_result_t
sqlite3_get_resultset(const char *zone, const char *record, const char *client,
		      unsigned int query, void *dbdata, sqlite3_res_t **rsp) {
	isc_result_t result;
	dbinstance_t *dbi = NULL;
	sqlite3_instance_t *db = (sqlite3_instance_t *)dbdata;
	char *querystring = NULL;
	sqlite3_res_t *rs = NULL;
	int qres = 0;

	if ((query == COUNTZONE && rsp != NULL) ||
	    (query != COUNTZONE && (rsp == NULL || *rsp != NULL)))
	{
		db->log(ISC_LOG_DEBUG(2), "Invalid result set pointer.");
		result = ISC_R_FAILURE;
		goto cleanup;
	}

	/* find an available DBI from the list */
	dbi = sqlite3_find_avail(db);

	if (dbi == NULL) {
		return (ISC_R_FAILURE);
	}

	/* what type of query are we going to run? */
	switch (query) {
	case ALLNODES:
		if (dbi->allnodes_q == NULL) {
			result = ISC_R_NOTIMPLEMENTED;
			goto cleanup;
		}
		break;
	case ALLOWXFR:
		if (dbi->allowxfr_q == NULL) {
			result = ISC_R_NOTIMPLEMENTED;
			goto cleanup;
		}
		break;
	case AUTHORITY:
		if (dbi->authority_q == NULL) {
			result = ISC_R_NOTIMPLEMENTED;
			goto cleanup;
		}
		break;
	case FINDZONE:
		if (dbi->findzone_q == NULL) {
			db->log(ISC_LOG_DEBUG(2), "No query specified for "
						  "findzone.  "
						  "Findzone requires a query");
			result = ISC_R_FAILURE;
			goto cleanup;
		}
		break;
	case COUNTZONE:
		if (dbi->countzone_q == NULL) {
			result = ISC_R_NOTIMPLEMENTED;
			goto cleanup;
		}
		break;
	case LOOKUP:
		if (dbi->lookup_q == NULL) {
			db->log(ISC_LOG_DEBUG(2), "No query specified for "
						  "lookup.  "
						  "Lookup requires a query");
			result = ISC_R_FAILURE;
			goto cleanup;
		}
		break;
	default:
		db->log(ISC_LOG_ERROR, "Incorrect query flag passed to "
				       "sqlite3_get_resultset");
		result = ISC_R_UNEXPECTED;
		goto cleanup;
	}

	if (zone != NULL) {
		if (dbi->zone != NULL) {
			free(dbi->zone);
		}

		dbi->zone = escape_string(zone);
		if (dbi->zone == NULL) {
			result = ISC_R_NOMEMORY;
			goto cleanup;
		}
	} else {
		dbi->zone = NULL;
	}

	if (record != NULL) {
		if (dbi->record != NULL) {
			free(dbi->record);
		}

		dbi->record = escape_string(record);
		if (dbi->record == NULL) {
			result = ISC_R_NOMEMORY;
			goto cleanup;
		}
	} else {
		dbi->record = NULL;
	}

	if (client != NULL) {
		if (dbi->client != NULL) {
			free(dbi->client);
		}

		dbi->client = escape_string(client);
		if (dbi->client == NULL) {
			result = ISC_R_NOMEMORY;
			goto cleanup;
		}
	} else {
		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(dbi->allnodes_q);
		break;
	case ALLOWXFR:
		querystring = build_querystring(dbi->allowxfr_q);
		break;
	case AUTHORITY:
		querystring = build_querystring(dbi->authority_q);
		break;
	case FINDZONE:
		querystring = build_querystring(dbi->findzone_q);
		break;
	case COUNTZONE:
		querystring = build_querystring(dbi->countzone_q);
		break;
	case LOOKUP:
		querystring = build_querystring(dbi->lookup_q);
		break;
	default:
		db->log(ISC_LOG_ERROR, "Incorrect query flag passed to "
				       "sqlite3_get_resultset");
		result = ISC_R_UNEXPECTED;
		goto cleanup;
	}

	if (querystring == NULL) {
		result = ISC_R_NOMEMORY;
		goto cleanup;
	}

	/* output the full query string when debugging */
	db->log(ISC_LOG_DEBUG(1), "\nQuery String: %s\n", querystring);

	rs = malloc(sizeof(sqlite3_res_t));
	if (rs == NULL) {
		db->log(ISC_LOG_ERROR, "Failed to allocate result set");
		result = ISC_R_NOMEMORY;
		goto cleanup;
	}
	memset(rs, 0, sizeof(sqlite3_res_t));

	qres = sqlite3_get_table(dbi->dbconn, querystring, &rs->pazResult,
				 &rs->pnRow, &rs->pnColumn, &rs->pzErrmsg);
	if (qres != SQLITE_OK) {
		db->log(ISC_LOG_DEBUG(1), "SQLite3 query failed; %s",
			rs->pzErrmsg != NULL ? rs->pzErrmsg : "unknown error");
		sqlite3_free(rs->pzErrmsg);
		rs->pzErrmsg = NULL;
		result = ISC_R_FAILURE;
		goto cleanup;
	}

	result = ISC_R_SUCCESS;
	if (query == COUNTZONE) {
		sqlite3_free_table(rs->pazResult);
	}

	if (rsp != NULL) {
		*rsp = rs;
	}

cleanup:
	if (dbi->zone != NULL) {
		free(dbi->zone);
		dbi->zone = NULL;
	}
	if (dbi->record != NULL) {
		free(dbi->record);
		dbi->record = NULL;
	}
	if (dbi->client != NULL) {
		free(dbi->client);
		dbi->client = NULL;
	}

	/* release the lock so another thread can use this dbi */
	(void)dlz_mutex_unlock(&dbi->lock);

	if (querystring != NULL) {
		free(querystring);
	}

	return (result);
}

/*%
 * 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 char **
dlz_sqlite3_fetch_row(sqlite3_res_t *rs) {
	char **retval = NULL;
	if (rs != NULL) {
		if (rs->pnRow > 0 && rs->curRow < rs->pnRow) {
			int index = (rs->curRow + 1) * rs->pnColumn;
			retval = &rs->pazResult[index];
			rs->curRow++;
		}
	}
	return (retval);
}

static unsigned int
dlz_sqlite3_num_fields(sqlite3_res_t *rs) {
	unsigned int retval = 0;
	if (rs != NULL) {
		retval = rs->pnColumn;
	}
	return (retval);
}

static unsigned int
dlz_sqlite3_num_rows(sqlite3_res_t *rs) {
	unsigned int retval = 0;
	if (rs != NULL) {
		retval = rs->pnRow;
	}
	return (retval);
}

static void
dlz_sqlite3_free_result(sqlite3_res_t *rs) {
	if (rs != NULL) {
		sqlite3_free_table(rs->pazResult);
		free(rs);
	}
}

static isc_result_t
dlz_sqlite3_process_rs(sqlite3_instance_t *db, dns_sdlzlookup_t *lookup,
		       sqlite3_res_t *rs) {
	isc_result_t result = ISC_R_NOTFOUND;
	char **row;
	unsigned int fields;
	unsigned int j;
	char *tmpString;
	char *endp;
	int ttl;

	row = dlz_sqlite3_fetch_row(rs);     /* get a row from the result set */
	fields = dlz_sqlite3_num_fields(rs); /* how many columns in result set
					      */
	while (row != NULL) {
		unsigned int len = 0;

		switch (fields) {
		case 1:
			/*
			 * one column in rs, it's the data field.  use
			 * default type of A record, and default TTL
			 * of 86400
			 */
			result = db->putrr(lookup, "a", 86400, safeGet(row[0]));
			break;
		case 2:
			/*
			 * two columns, data field, and data type.
			 * use default TTL of 86400.
			 */
			result = db->putrr(lookup, safeGet(row[0]), 86400,
					   safeGet(row[1]));
			break;
		case 3:
			/*
			 * three columns, all data no defaults.
			 * convert text to int, make sure it worked
			 * right.
			 */
			ttl = strtol(safeGet(row[0]), &endp, 10);
			if (*endp != '\0' || ttl < 0) {
				db->log(ISC_LOG_ERROR, "SQLite3 module: TTL "
						       "must be "
						       "a positive number");
				return (ISC_R_FAILURE);
			}

			result = db->putrr(lookup, safeGet(row[1]), ttl,
					   safeGet(row[2]));
			break;
		default:
			/*
			 * more than 3 fields, concatenate the last
			 * ones together.  figure out how long to make
			 * string.
			 */
			for (j = 2; j < fields; j++) {
				len += strlen(safeGet(row[j])) + 1;
			}

			/*
			 * allocate string memory, allow for NULL to
			 * term string
			 */
			tmpString = malloc(len + 1);
			if (tmpString == NULL) {
				db->log(ISC_LOG_ERROR, "SQLite3 module: unable "
						       "to allocate "
						       "memory for temporary "
						       "string");
				dlz_sqlite3_free_result(rs);
				return (ISC_R_FAILURE);
			}

			strcpy(tmpString, safeGet(row[2]));
			for (j = 3; j < fields; j++) {
				strcat(tmpString, " ");
				strcat(tmpString, safeGet(row[j]));
			}

			ttl = strtol(safeGet(row[0]), &endp, 10);
			if (*endp != '\0' || ttl < 0) {
				db->log(ISC_LOG_ERROR, "SQLite3 module: TTL "
						       "must be "
						       "a positive number");
				free(tmpString);
				return (ISC_R_FAILURE);
			}

			result = db->putrr(lookup, safeGet(row[1]), ttl,
					   tmpString);
			free(tmpString);
		}

		if (result != ISC_R_SUCCESS) {
			dlz_sqlite3_free_result(rs);
			db->log(ISC_LOG_ERROR, "putrr returned error: %d",
				result);
			return (ISC_R_FAILURE);
		}

		row = dlz_sqlite3_fetch_row(rs);
	}

	dlz_sqlite3_free_result(rs);
	return (result);
}

/*
 * DLZ methods
 */

/*% determine if the zone is supported by (in) the database */
isc_result_t
dlz_findzonedb(void *dbdata, const char *name, dns_clientinfomethods_t *methods,
	       dns_clientinfo_t *clientinfo) {
	isc_result_t result;
	sqlite3_res_t *rs = NULL;
	sqlite3_uint64 rows;
	sqlite3_instance_t *db = (sqlite3_instance_t *)dbdata;

	UNUSED(methods);
	UNUSED(clientinfo);

	result = sqlite3_get_resultset(name, NULL, NULL, FINDZONE, dbdata, &rs);
	if (result != ISC_R_SUCCESS || rs == NULL) {
		if (rs != NULL) {
			dlz_sqlite3_free_result(rs);
		}

		db->log(ISC_LOG_ERROR, "SQLite3 module: unable to return "
				       "result set for FINDZONE query");

		return (ISC_R_FAILURE);
	}

	/*
	 * if we returned any rows, the zone is supported.
	 */
	rows = dlz_sqlite3_num_rows(rs);
	dlz_sqlite3_free_result(rs);
	if (rows > 0) {
		sqlite3_get_resultset(name, NULL, NULL, COUNTZONE, dbdata,
				      NULL);
		return (ISC_R_SUCCESS);
	}

	return (ISC_R_NOTFOUND);
}

/*% Determine if the client is allowed to perform a zone transfer */
isc_result_t
dlz_allowzonexfr(void *dbdata, const char *name, const char *client) {
	isc_result_t result;
	sqlite3_instance_t *db = (sqlite3_instance_t *)dbdata;
	sqlite3_res_t *rs = NULL;
	sqlite3_uint64 rows;

	/* first check if the zone is supported by the database. */
	result = dlz_findzonedb(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.
	 */
	result = sqlite3_get_resultset(name, NULL, client, ALLOWXFR, dbdata,
				       &rs);
	if (result == ISC_R_NOTIMPLEMENTED) {
		return (result);
	}

	if (result != ISC_R_SUCCESS || rs == NULL) {
		if (rs != NULL) {
			dlz_sqlite3_free_result(rs);
		}
		db->log(ISC_LOG_ERROR, "SQLite3 module: unable to return "
				       "result set for ALLOWXFR query");
		return (ISC_R_FAILURE);
	}

	/*
	 * count how many rows in result set; if we returned any,
	 * zone xfr is allowed.
	 */
	rows = dlz_sqlite3_num_rows(rs);
	dlz_sqlite3_free_result(rs);
	if (rows > 0) {
		return (ISC_R_SUCCESS);
	}

	return (ISC_R_NOPERM);
}

/*%
 * 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.
 */
isc_result_t
dlz_allnodes(const char *zone, void *dbdata, dns_sdlzallnodes_t *allnodes) {
	isc_result_t result;
	sqlite3_instance_t *db = (sqlite3_instance_t *)dbdata;
	sqlite3_res_t *rs = NULL;
	char **row;
	unsigned int fields;
	unsigned int j;
	char *tmpString;
	char *endp;
	int ttl;

	result = sqlite3_get_resultset(zone, NULL, NULL, ALLNODES, dbdata, &rs);
	if (result == ISC_R_NOTIMPLEMENTED) {
		return (result);
	}

	/* if we didn't get a result set, log an err msg. */
	if (result != ISC_R_SUCCESS) {
		db->log(ISC_LOG_ERROR, "SQLite3 module: unable to return "
				       "result set for all nodes query");
		goto cleanup;
	}

	result = ISC_R_NOTFOUND;

	fields = dlz_sqlite3_num_fields(rs);
	row = dlz_sqlite3_fetch_row(rs);
	while (row != NULL) {
		if (fields < 4) {
			db->log(ISC_LOG_ERROR, "SQLite3 module: too few fields "
					       "returned "
					       "by ALLNODES query");
			result = ISC_R_FAILURE;
			goto cleanup;
		}

		ttl = strtol(safeGet(row[0]), &endp, 10);
		if (*endp != '\0' || ttl < 0) {
			db->log(ISC_LOG_ERROR, "SQLite3 module: TTL must be "
					       "a positive number");
			result = ISC_R_FAILURE;
			goto cleanup;
		}

		if (fields == 4) {
			result = db->putnamedrr(allnodes, safeGet(row[2]),
						safeGet(row[1]), ttl,
						safeGet(row[3]));
		} else {
			unsigned int len = 0;

			/*
			 * more than 4 fields, concatenate the last
			 * ones together.
			 */
			for (j = 3; j < fields; j++) {
				len += strlen(safeGet(row[j])) + 1;
			}

			tmpString = malloc(len + 1);
			if (tmpString == NULL) {
				db->log(ISC_LOG_ERROR, "SQLite3 module: unable "
						       "to allocate "
						       "memory for temporary "
						       "string");
				result = ISC_R_FAILURE;
				goto cleanup;
			}

			strcpy(tmpString, safeGet(row[3]));
			for (j = 4; j < fields; j++) {
				strcat(tmpString, " ");
				strcat(tmpString, safeGet(row[j]));
			}

			result = db->putnamedrr(allnodes, safeGet(row[2]),
						safeGet(row[1]), ttl,
						tmpString);
			free(tmpString);
		}

		if (result != ISC_R_SUCCESS) {
			db->log(ISC_LOG_ERROR, "putnamedrr returned error: %s",
				result);
			result = ISC_R_FAILURE;
			break;
		}

		row = dlz_sqlite3_fetch_row(rs);
	}

cleanup:
	if (rs != NULL) {
		dlz_sqlite3_free_result(rs);
	}

	return (result);
}

/*%
 * If the lookup function does not return SOA or NS records for the zone,
 * use this function to get that information for named.
 */
isc_result_t
dlz_authority(const char *zone, void *dbdata, dns_sdlzlookup_t *lookup) {
	isc_result_t result;
	sqlite3_res_t *rs = NULL;
	sqlite3_instance_t *db = (sqlite3_instance_t *)dbdata;

	result = sqlite3_get_resultset(zone, NULL, NULL, AUTHORITY, dbdata,
				       &rs);
	if (result == ISC_R_NOTIMPLEMENTED) {
		return (result);
	}

	if (result != ISC_R_SUCCESS) {
		if (rs != NULL) {
			dlz_sqlite3_free_result(rs);
		}
		db->log(ISC_LOG_ERROR, "SQLite3 module: unable to return "
				       "result set for AUTHORITY query");
		return (ISC_R_FAILURE);
	}

	/*
	 * lookup and authority result sets are processed in the same
	 * manner: dlz_sqlite3_process_rs does the job for both functions.
	 */
	return (dlz_sqlite3_process_rs(db, lookup, rs));
}

/*% If zone is supported, lookup up a (or multiple) record(s) in it */
isc_result_t
dlz_lookup(const char *zone, const char *name, void *dbdata,
	   dns_sdlzlookup_t *lookup, dns_clientinfomethods_t *methods,
	   dns_clientinfo_t *clientinfo) {
	isc_result_t result;
	sqlite3_res_t *rs = NULL;
	sqlite3_instance_t *db = (sqlite3_instance_t *)dbdata;

	UNUSED(methods);
	UNUSED(clientinfo);

	result = sqlite3_get_resultset(zone, name, NULL, LOOKUP, dbdata, &rs);

	/* if we didn't get a result set, log an err msg. */
	if (result != ISC_R_SUCCESS) {
		if (rs != NULL) {
			dlz_sqlite3_free_result(rs);
		}
		db->log(ISC_LOG_ERROR, "SQLite3 module: unable to return "
				       "result set for LOOKUP query");
		return (ISC_R_FAILURE);
	}

	/*
	 * lookup and authority result sets are processed in the same
	 * manner: dlz_sqlite3_process_rs does the job for both functions.
	 */
	return (dlz_sqlite3_process_rs(db, lookup, rs));
}

/*%
 * Create an instance of the module.
 */
isc_result_t
dlz_create(const char *dlzname, unsigned int argc, char *argv[], void **dbdata,
	   ...) {
	isc_result_t result = ISC_R_FAILURE;
	sqlite3_instance_t *s3 = NULL;
	dbinstance_t *dbi = NULL;
	sqlite3 *dbc = NULL;
	char *tmp = NULL;
	char *endp = NULL;
	const char *helper_name;
	int dbcount, i, ret;
	va_list ap;

	UNUSED(dlzname);

	/* allocate memory for SQLite3 instance */
	s3 = calloc(1, sizeof(sqlite3_instance_t));
	if (s3 == NULL) {
		return (ISC_R_NOMEMORY);
	}
	memset(s3, 0, sizeof(sqlite3_instance_t));

	/* Fill in the helper functions */
	va_start(ap, dbdata);
	while ((helper_name = va_arg(ap, const char *)) != NULL) {
		b9_add_helper(s3, helper_name, va_arg(ap, void *));
	}
	va_end(ap);

	/* if debugging, let user know we are multithreaded. */
	s3->log(ISC_LOG_DEBUG(1), "SQLite3 module: running multithreaded");

	/* verify we have at least 4 arg's passed to the module */
	if (argc < 4) {
		s3->log(ISC_LOG_ERROR, "SQLite3 module requires "
				       "at least 4 command line args.");
		return (ISC_R_FAILURE);
	}

	/* no more than 8 arg's should be passed to the module */
	if (argc > 8) {
		s3->log(ISC_LOG_ERROR, "SQLite3 module cannot accept "
				       "more than 8 command line args.");
		return (ISC_R_FAILURE);
	}

	/* get db name - required */
	s3->dbname = get_parameter_value(argv[1], "dbname=");
	if (s3->dbname == NULL) {
		s3->log(ISC_LOG_ERROR, "SQLite3 module requires a dbname "
				       "parameter.");
		result = ISC_R_FAILURE;
		goto cleanup;
	}

	/* multithreaded build can have multiple DB connections */
	tmp = get_parameter_value(argv[1], "threads=");
	if (tmp == NULL) {
		dbcount = 1;
	} else {
		dbcount = strtol(tmp, &endp, 10);
		if (*endp != '\0' || dbcount < 1) {
			s3->log(ISC_LOG_ERROR, "SQLite3 module: database "
					       "connection count "
					       "must be positive.");
			free(tmp);
			result = ISC_R_FAILURE;
			goto cleanup;
		}
		free(tmp);
	}

	/* allocate memory for database connection list */
	s3->db = calloc(1, sizeof(db_list_t));
	if (s3->db == NULL) {
		result = ISC_R_NOMEMORY;
		goto cleanup;
	}

	/* initialize DB connection list */
	DLZ_LIST_INIT(*(s3->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++) {
		switch (argc) {
		case 4:
			result = build_dbinstance(NULL, NULL, NULL, argv[2],
						  argv[3], NULL, &dbi, s3->log);
			break;
		case 5:
			result = build_dbinstance(NULL, NULL, argv[4], argv[2],
						  argv[3], NULL, &dbi, s3->log);
			break;
		case 6:
			result = build_dbinstance(argv[5], NULL, argv[4],
						  argv[2], argv[3], NULL, &dbi,
						  s3->log);
			break;
		case 7:
			result = build_dbinstance(argv[5], argv[6], argv[4],
						  argv[2], argv[3], NULL, &dbi,
						  s3->log);
			break;
		case 8:
			result = build_dbinstance(argv[5], argv[6], argv[4],
						  argv[2], argv[3], argv[7],
						  &dbi, s3->log);
			break;
		default:
			result = ISC_R_FAILURE;
		}

		if (result != ISC_R_SUCCESS) {
			s3->log(ISC_LOG_ERROR, "SQLite3 module: could not "
					       "create "
					       "database instance object.");
			result = ISC_R_FAILURE;
			goto cleanup;
		}

		/* create and set db connection */
		ret = sqlite3_initialize();
		if (ret != SQLITE_OK) {
			s3->log(ISC_LOG_ERROR, "SQLite3 module: could not "
					       "initialize database object.");
			result = ISC_R_FAILURE;
			goto cleanup;
		}

		ret = sqlite3_open(s3->dbname, &dbc);
		if (ret != SQLITE_OK) {
			s3->log(ISC_LOG_ERROR,
				"SQLite3 module: could not "
				"open '%s'.",
				s3->dbname);
			result = ISC_R_FAILURE;
			goto cleanup;
		}

		/* when multithreaded, build a list of DBI's */
		DLZ_LINK_INIT(dbi, link);
		DLZ_LIST_APPEND(*(s3->db), dbi, link);

		dbi->dbconn = dbc;
		dbc = NULL;
		/* set DBI = null for next loop through. */
		dbi = NULL;
	}

	*dbdata = s3;
	return (ISC_R_SUCCESS);

cleanup:
	dlz_destroy(s3);

	return (result);
}

/*%
 * Destroy the module.
 */
void
dlz_destroy(void *dbdata) {
	sqlite3_instance_t *db = (sqlite3_instance_t *)dbdata;
	/* cleanup the list of DBI's */
	if (db->db != NULL) {
		dlz_sqlite3_destroy_dblist((db_list_t *)(db->db));
	}

	if (db->dbname != NULL) {
		free(db->dbname);
	}
}

/*
 * Return the version of the API
 */
int
dlz_version(unsigned int *flags) {
	*flags |= (DNS_SDLZFLAG_RELATIVEOWNER | DNS_SDLZFLAG_RELATIVERDATA |
		   DNS_SDLZFLAG_THREADSAFE);
	return (DLZ_DLOPEN_VERSION);
}

/*
 * Register a helper function from the bind9 dlz_dlopen driver
 */
static void
b9_add_helper(sqlite3_instance_t *db, const char *helper_name, void *ptr) {
	if (strcmp(helper_name, "log") == 0) {
		db->log = (log_t *)ptr;
	}
	if (strcmp(helper_name, "putrr") == 0) {
		db->putrr = (dns_sdlz_putrr_t *)ptr;
	}
	if (strcmp(helper_name, "putnamedrr") == 0) {
		db->putnamedrr = (dns_sdlz_putnamedrr_t *)ptr;
	}
	if (strcmp(helper_name, "writeable_zone") == 0) {
		db->writeable_zone = (dns_dlz_writeablezone_t *)ptr;
	}
}