etc/services - sync with NetBSD-8

[minix.git] / external / bsd / bind / dist / contrib / dlz / drivers / dlz_odbc_driver.c

/*      $NetBSD: dlz_odbc_driver.c,v 1.5 2014/12/10 04:37:55 christos Exp $     */

/*
 * Copyright (C) 2002 Stichting NLnet, Netherlands, stichting@nlnet.nl.
 *
 * 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 STICHTING NLNET
 * DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL
 * STICHTING NLNET 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.
 *
 * 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 ROB BUTLER
 * DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL
 * ROB BUTLER 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.
 */

/*
 * Copyright (C) 1999-2001  Internet Software Consortium.
 *
 * 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 INTERNET SOFTWARE CONSORTIUM
 * DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL
 * INTERNET SOFTWARE CONSORTIUM 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.
 */

#ifdef DLZ_ODBC

#include <config.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>

#include <dns/log.h>
#include <dns/sdlz.h>
#include <dns/result.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 <named/globals.h>

#include <dlz/sdlz_helper.h>
#include <dlz/dlz_odbc_driver.h>

#include <sql.h>
#include <sqlext.h>
#include <sqltypes.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 everthing needed by this "instance" of the odbc driver
 * remember, the driver code is only loaded once, but may have many separate
 * instances
 */

typedef struct {

#ifdef ISC_PLATFORM_USETHREADS

    db_list_t    *db;       /* handle to a list of DB */

#else

    dbinstance_t *db;       /* handle to db */

#endif

    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);
}

/*% propertly cleans up an odbc_instance_t */

static void
destroy_odbc_instance(odbc_instance_t *odbc_inst) {

#ifdef ISC_PLATFORM_USETHREADS

        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(ns_g_mctx, dbi->dbconn);
                }
                /* release all memory that comprised a DBI */
                destroy_sqldbinstance(dbi);
        }
        /* release memory for the list structure */
        isc_mem_put(ns_g_mctx, odbc_inst->db, sizeof(db_list_t));

#else /* ISC_PLATFORM_USETHREADS */

        /* free statement handle */
        if (((odbc_db_t *) (odbc_inst->db->dbconn))->stmnt != NULL) {
                SQLFreeHandle(SQL_HANDLE_STMT,
                              ((odbc_db_t *) (odbc_inst->db->dbconn))->stmnt);
                ((odbc_db_t *) (odbc_inst->db->dbconn))->stmnt = NULL;
        }

        /* disconnect from database, free connection handle */
        if (((odbc_db_t *) (odbc_inst->db->dbconn))->dbc != NULL) {
                SQLDisconnect(((odbc_db_t *) (odbc_inst->db->dbconn))->dbc);
                SQLFreeHandle(SQL_HANDLE_DBC,
                              ((odbc_db_t *) (odbc_inst->db->dbconn))->dbc);
                ((odbc_db_t *) (odbc_inst->db->dbconn))->dbc = NULL;
        }
        /*      free mem for the odbc_db_t structure held in db */
        if (((odbc_db_t *) odbc_inst->db->dbconn) != NULL) {
                isc_mem_free(ns_g_mctx, odbc_inst->db->dbconn);
                odbc_inst->db->dbconn = NULL;
        }

        if (odbc_inst->db != NULL)
                destroy_sqldbinstance(odbc_inst->db);

#endif /* ISC_PLATFORM_USETHREADS */


        /* 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(ns_g_mctx, odbc_inst->dsn);
        if (odbc_inst->pass != NULL)
                isc_mem_free(ns_g_mctx, odbc_inst->pass);
        if (odbc_inst->user != NULL)
                isc_mem_free(ns_g_mctx, odbc_inst->user);

        /* free memory for odbc_inst */
        if (odbc_inst != NULL)
                isc_mem_put(ns_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(ns_g_mctx, sizeof(odbc_db_t));
                if (ndb == NULL) {
                        isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE,
                                      DNS_LOGMODULE_DLZ, ISC_LOG_ERROR,
                                      "Odbc driver unable to allocate memory");
                        return ISC_R_NOMEMORY;
                }
                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(ns_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.
 */

#ifdef ISC_PLATFORM_USETHREADS

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;
}

#endif /* ISC_PLATFORM_USETHREADS */

/*% 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(ns_g_mctx ,(2 * len * sizeof(char)) + 1);
        if (outstr == NULL)
                return NULL;

        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 successfull, 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 successfull, 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 */
#ifdef ISC_PLATFORM_USETHREADS

        /* find an available DBI from the list */
        dbi = odbc_find_avail_conn(((odbc_instance_t *) dbdata)->db);

#else /* ISC_PLATFORM_USETHREADS */

        /*
         * only 1 DBI - no need to lock instance lock either
         * only 1 thread in the whole process, no possible contention.
         */
        dbi =  (dbinstance_t *) ((odbc_instance_t *) dbdata)->db;

#endif /* ISC_PLATFORM_USETHREADS */

        /* if DBI is null, can't do anything else */
        if (dbi == NULL) {
                result = ISC_R_FAILURE;
                goto cleanup;
        }

        /* 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(ns_g_mctx, dbi->allnodes_q);
                break;
        case ALLOWXFR:
                querystring = build_querystring(ns_g_mctx, dbi->allowxfr_q);
                break;
        case AUTHORITY:
                querystring = build_querystring(ns_g_mctx, dbi->authority_q);
                break;
        case FINDZONE:
                querystring = build_querystring(ns_g_mctx, dbi->findzone_q);
                break;
        case LOOKUP:
                querystring = build_querystring(ns_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;
                        /* incase 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 */

                /* if we couldn't even allocate DBI, just return NULL */
        if (dbi == NULL)
                return ISC_R_FAILURE;

        /* free dbi->zone string */
        if (dbi->zone != NULL)
                isc_mem_free(ns_g_mctx, dbi->zone);

        /* free dbi->record string */
        if (dbi->record != NULL)
                isc_mem_free(ns_g_mctx, dbi->record);

        /* free dbi->client string */
        if (dbi->client != NULL)
                isc_mem_free(ns_g_mctx, dbi->client);

#ifdef ISC_PLATFORM_USETHREADS

        /* if we are done using this dbi, release the lock */
        if (result != ISC_R_SUCCESS)
                isc_mutex_unlock(&dbi->instance_lock);

#endif /* ISC_PLATFORM_USETHREADS */

        /* release query string */
        if (querystring  != NULL)
                isc_mem_free(ns_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 reponsibility of the caller to free the memory using
 * isc_mem_free(ns_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(ns_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(ns_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 reponsibility of the caller to free the memory using
 * isc_mem_free(ns_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(ns_g_mctx, ++totSize);
        if (data == NULL)
                return ISC_R_NOMEMORY;

        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(ns_g_mctx, data);
                        return ISC_R_FAILURE;
                }
        }

        if (result != ISC_R_SUCCESS) {
                isc_mem_free(ns_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 postive 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(ns_g_mctx, ttl_s);
                if (type != NULL)
                        isc_mem_free(ns_g_mctx, type);
                if (data != NULL)
                        isc_mem_free(ns_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);

#ifdef ISC_PLATFORM_USETHREADS

        /* free lock on dbi so someone else can use it. */
        isc_mutex_unlock(&dbi->instance_lock);

#endif

        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);

#ifdef ISC_PLATFORM_USETHREADS

                /* free lock on dbi so someone else can use it. */
                isc_mutex_unlock(&dbi->instance_lock);
#endif
        }

        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);

#ifdef ISC_PLATFORM_USETHREADS

                /* free lock on dbi so someone else can use it. */
                isc_mutex_unlock(&dbi->instance_lock);
#endif

        }

        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 postive 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(ns_g_mctx, ttl_s);
                if (type != NULL)
                        isc_mem_free(ns_g_mctx, type);
                if (host != NULL)
                        isc_mem_free(ns_g_mctx, host);
                if (data != NULL)
                        isc_mem_free(ns_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);

#ifdef ISC_PLATFORM_USETHREADS

        /* free lock on dbi so someone else can use it. */
        isc_mutex_unlock(&dbi->instance_lock);

#endif

        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;

#ifdef ISC_PLATFORM_USETHREADS
        /* if multi-threaded, we need a few extra variables. */
        int dbcount;
        int i;
        char *endp;

#endif /* ISC_PLATFORM_USETHREADS */

        UNUSED(dlzname);
        UNUSED(driverarg);

#ifdef ISC_PLATFORM_USETHREADS
        /* 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");
#else /* ISC_PLATFORM_USETHREADS */
        /* if debugging, let user know we are single threaded. */
        isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE,
                      DNS_LOGMODULE_DLZ, ISC_LOG_DEBUG(1),
                      "Odbc driver running single threaded");
#endif /* ISC_PLATFORM_USETHREADS */

        /* 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 */
#ifdef ISC_PLATFORM_USETHREADS

        /* 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);
        }

#endif /* ISC_PLATFORM_USETHREADS */

        /* allocate memory for odbc instance */
        odbc_inst = isc_mem_get(ns_g_mctx, sizeof(odbc_instance_t));
        if (odbc_inst == NULL)
                return (ISC_R_NOMEMORY);
        memset(odbc_inst, 0, sizeof(odbc_instance_t));

        /* parse connection string and get paramters. */

        /* 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;
                }
        }

#ifdef ISC_PLATFORM_USETHREADS

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


        /* 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++) {

#endif /* ISC_PLATFORM_USETHREADS */

                /* how many queries were passed in from config file? */
                switch(argc) {
                case 5:
                        result = build_sqldbinstance(ns_g_mctx, NULL, NULL,
                                                     NULL, argv[3], argv[4],
                                                     NULL, &db);
                        break;
                case 6:
                        result = build_sqldbinstance(ns_g_mctx, NULL, NULL,
                                                     argv[5], argv[3], argv[4],
                                                     NULL, &db);
                        break;
                case 7:
                        result = build_sqldbinstance(ns_g_mctx, argv[6], NULL,
                                                     argv[5], argv[3], argv[4],
                                                     NULL, &db);
                        break;
                case 8:
                        result = build_sqldbinstance(ns_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;
                }

#ifdef ISC_PLATFORM_USETHREADS

                /* when multithreaded, build a list of DBI's */
                ISC_LINK_INIT(db, link);
                ISC_LIST_APPEND(*odbc_inst->db, db, link);

#endif

                result = odbc_connect(odbc_inst, (odbc_db_t **) &(db->dbconn));

                if (result != ISC_R_SUCCESS) {

#ifdef ISC_PLATFORM_USETHREADS

                        /*
                         * 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);
#else
                        isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE,
                                      DNS_LOGMODULE_DLZ, ISC_LOG_ERROR,
                                      "Odbc driver failed to create database "
                                      "connection after 3 attempts");
#endif
                        goto cleanup;
                }

#ifdef ISC_PLATFORM_USETHREADS

                /* set DB = null for next loop through. */
                db = NULL;

        }       /* end for loop */

#else
        /* tell odbc_inst about the db connection we just created. */
        odbc_inst->db = db;

#endif

        /* 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,
                                  ns_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