path: root/src/util/dict_db.c

/*++
/* NAME
/*	dict_db 3
/* SUMMARY
/*	dictionary manager interface to DB files
/* SYNOPSIS
/*	#include <dict_db.h>
/*
/*	extern int dict_db_cache_size;
/*
/*	DEFINE_DICT_DB_CACHE_SIZE;
/*
/*	DICT	*dict_hash_open(path, open_flags, dict_flags)
/*	const char *path;
/*	int	open_flags;
/*	int	dict_flags;
/*
/*	DICT	*dict_btree_open(path, open_flags, dict_flags)
/*	const char *path;
/*	int	open_flags;
/*	int	dict_flags;
/* DESCRIPTION
/*	dict_XXX_open() opens the specified DB database.  The result is
/*	a pointer to a structure that can be used to access the dictionary
/*	using the generic methods documented in dict_open(3).
/*
/*	The dict_db_cache_size variable specifies a non-default per-table
/*	I/O buffer size.  The default buffer size is adequate for reading.
/*	For better performance while creating a large table, specify a large
/*	buffer size before opening the file.
/*
/*	This variable cannot be exported via the dict(3) API and
/*	must therefore be defined in the calling program by invoking
/*	the DEFINE_DICT_DB_CACHE_SIZE macro at the global level.
/*
/*	Arguments:
/* .IP path
/*	The database pathname, not including the ".db" suffix.
/* .IP open_flags
/*	Flags passed to dbopen().
/* .IP dict_flags
/*	Flags used by the dictionary interface.
/* SEE ALSO
/*	dict(3) generic dictionary manager
/* DIAGNOSTICS
/*	Fatal errors: cannot open file, write error, out of memory.
/* LICENSE
/* .ad
/* .fi
/*	The Secure Mailer license must be distributed with this software.
/* AUTHOR(S)
/*	Wietse Venema
/*	IBM T.J. Watson Research
/*	P.O. Box 704
/*	Yorktown Heights, NY 10598, USA
/*
/*	Wietse Venema
/*	Google, Inc.
/*	111 8th Avenue
/*	New York, NY 10011, USA
/*--*/

#include "sys_defs.h"

#ifdef HAS_DB

/* System library. */

#include <sys/stat.h>
#include <limits.h>
#ifdef PATH_DB_H
#include PATH_DB_H
#else
#include <db.h>
#endif
#include <string.h>
#include <unistd.h>
#include <errno.h>

#if defined(_DB_185_H_) && defined(USE_FCNTL_LOCK)
#error "Error: this system must not use the db 1.85 compatibility interface"
#endif

#ifndef DB_VERSION_MAJOR
#define DB_VERSION_MAJOR 1
#define DICT_DB_GET(db, key, val, flag)	db->get(db, key, val, flag)
#define DICT_DB_PUT(db, key, val, flag)	db->put(db, key, val, flag)
#define DICT_DB_DEL(db, key, flag)	db->del(db, key, flag)
#define DICT_DB_SYNC(db, flag)		db->sync(db, flag)
#define DICT_DB_CLOSE(db)		db->close(db)
#define DONT_CLOBBER			R_NOOVERWRITE
#endif

#if DB_VERSION_MAJOR > 1
#define DICT_DB_GET(db, key, val, flag)	sanitize(db->get(db, 0, key, val, flag))
#define DICT_DB_PUT(db, key, val, flag)	sanitize(db->put(db, 0, key, val, flag))
#define DICT_DB_DEL(db, key, flag)	sanitize(db->del(db, 0, key, flag))
#define DICT_DB_SYNC(db, flag)		((errno = db->sync(db, flag)) ? -1 : 0)
#define DICT_DB_CLOSE(db)		((errno = db->close(db, 0)) ? -1 : 0)
#define DONT_CLOBBER			DB_NOOVERWRITE
#endif

#if (DB_VERSION_MAJOR == 2 && DB_VERSION_MINOR < 6)
#define DICT_DB_CURSOR(db, curs)	(db)->cursor((db), NULL, (curs))
#else
#define DICT_DB_CURSOR(db, curs)	(db)->cursor((db), NULL, (curs), 0)
#endif

#ifndef DB_FCNTL_LOCKING
#define DB_FCNTL_LOCKING		0
#endif

/* Utility library. */

#include "msg.h"
#include "mymalloc.h"
#include "vstring.h"
#include "stringops.h"
#include "iostuff.h"
#include "myflock.h"
#include "dict.h"
#include "dict_db.h"
#include "warn_stat.h"

/* Application-specific. */

typedef struct {
    DICT    dict;			/* generic members */
    DB     *db;				/* open db file */
#if DB_VERSION_MAJOR > 2
    DB_ENV *dbenv;
#endif
#if DB_VERSION_MAJOR > 1
    DBC    *cursor;			/* dict_db_sequence() */
#endif
    VSTRING *key_buf;			/* key result */
    VSTRING *val_buf;			/* value result */
} DICT_DB;

#define SCOPY(buf, data, size) \
    vstring_str(vstring_strncpy(buf ? buf : (buf = vstring_alloc(10)), data, size))

#define DICT_DB_NELM		4096

#if DB_VERSION_MAJOR > 1

/* sanitize - sanitize db_get/put/del result */

static int sanitize(int status)
{

    /*
     * XXX This is unclean but avoids a lot of clutter elsewhere. Categorize
     * results into non-fatal errors (i.e., errors that we can deal with),
     * success, or fatal error (i.e., all other errors).
     */
    switch (status) {

	case DB_NOTFOUND:		/* get, del */
	case DB_KEYEXIST:		/* put */
	return (1);			/* non-fatal */

    case 0:
	return (0);				/* success */

    case DB_KEYEMPTY:				/* get, others? */
	status = EINVAL;
	/* FALLTHROUGH */
    default:
	errno = status;
	return (-1);				/* fatal */
    }
}

#endif

/* dict_db_lookup - find database entry */

static const char *dict_db_lookup(DICT *dict, const char *name)
{
    DICT_DB *dict_db = (DICT_DB *) dict;
    DB     *db = dict_db->db;
    DBT     db_key;
    DBT     db_value;
    int     status;
    const char *result = 0;

    dict->error = 0;

    /*
     * Sanity check.
     */
    if ((dict->flags & (DICT_FLAG_TRY1NULL | DICT_FLAG_TRY0NULL)) == 0)
	msg_panic("dict_db_lookup: no DICT_FLAG_TRY1NULL | DICT_FLAG_TRY0NULL flag");

    memset(&db_key, 0, sizeof(db_key));
    memset(&db_value, 0, sizeof(db_value));

    /*
     * Optionally fold the key.
     */
    if (dict->flags & DICT_FLAG_FOLD_FIX) {
	if (dict->fold_buf == 0)
	    dict->fold_buf = vstring_alloc(10);
	vstring_strcpy(dict->fold_buf, name);
	name = lowercase(vstring_str(dict->fold_buf));
    }

    /*
     * Acquire a shared lock.
     */
    if ((dict->flags & DICT_FLAG_LOCK)
	&& myflock(dict->lock_fd, INTERNAL_LOCK, MYFLOCK_OP_SHARED) < 0)
	msg_fatal("%s: lock dictionary: %m", dict_db->dict.name);

    /*
     * See if this DB file was written with one null byte appended to key and
     * value.
     */
    if (dict->flags & DICT_FLAG_TRY1NULL) {
	db_key.data = (void *) name;
	db_key.size = strlen(name) + 1;
	if ((status = DICT_DB_GET(db, &db_key, &db_value, 0)) < 0)
	    msg_fatal("error reading %s: %m", dict_db->dict.name);
	if (status == 0) {
	    dict->flags &= ~DICT_FLAG_TRY0NULL;
	    result = SCOPY(dict_db->val_buf, db_value.data, db_value.size);
	}
    }

    /*
     * See if this DB file was written with no null byte appended to key and
     * value.
     */
    if (result == 0 && (dict->flags & DICT_FLAG_TRY0NULL)) {
	db_key.data = (void *) name;
	db_key.size = strlen(name);
	if ((status = DICT_DB_GET(db, &db_key, &db_value, 0)) < 0)
	    msg_fatal("error reading %s: %m", dict_db->dict.name);
	if (status == 0) {
	    dict->flags &= ~DICT_FLAG_TRY1NULL;
	    result = SCOPY(dict_db->val_buf, db_value.data, db_value.size);
	}
    }

    /*
     * Release the shared lock.
     */
    if ((dict->flags & DICT_FLAG_LOCK)
	&& myflock(dict->lock_fd, INTERNAL_LOCK, MYFLOCK_OP_NONE) < 0)
	msg_fatal("%s: unlock dictionary: %m", dict_db->dict.name);

    return (result);
}

/* dict_db_update - add or update database entry */

static int dict_db_update(DICT *dict, const char *name, const char *value)
{
    DICT_DB *dict_db = (DICT_DB *) dict;
    DB     *db = dict_db->db;
    DBT     db_key;
    DBT     db_value;
    int     status;

    dict->error = 0;

    /*
     * Sanity check.
     */
    if ((dict->flags & (DICT_FLAG_TRY1NULL | DICT_FLAG_TRY0NULL)) == 0)
	msg_panic("dict_db_update: no DICT_FLAG_TRY1NULL | DICT_FLAG_TRY0NULL flag");

    /*
     * Optionally fold the key.
     */
    if (dict->flags & DICT_FLAG_FOLD_FIX) {
	if (dict->fold_buf == 0)
	    dict->fold_buf = vstring_alloc(10);
	vstring_strcpy(dict->fold_buf, name);
	name = lowercase(vstring_str(dict->fold_buf));
    }
    memset(&db_key, 0, sizeof(db_key));
    memset(&db_value, 0, sizeof(db_value));
    db_key.data = (void *) name;
    db_value.data = (void *) value;
    db_key.size = strlen(name);
    db_value.size = strlen(value);

    /*
     * If undecided about appending a null byte to key and value, choose a
     * default depending on the platform.
     */
    if ((dict->flags & DICT_FLAG_TRY1NULL)
	&& (dict->flags & DICT_FLAG_TRY0NULL)) {
#ifdef DB_NO_TRAILING_NULL
	dict->flags &= ~DICT_FLAG_TRY1NULL;
#else
	dict->flags &= ~DICT_FLAG_TRY0NULL;
#endif
    }

    /*
     * Optionally append a null byte to key and value.
     */
    if (dict->flags & DICT_FLAG_TRY1NULL) {
	db_key.size++;
	db_value.size++;
    }

    /*
     * Acquire an exclusive lock.
     */
    if ((dict->flags & DICT_FLAG_LOCK)
	&& myflock(dict->lock_fd, INTERNAL_LOCK, MYFLOCK_OP_EXCLUSIVE) < 0)
	msg_fatal("%s: lock dictionary: %m", dict_db->dict.name);

    /*
     * Do the update.
     */
    if ((status = DICT_DB_PUT(db, &db_key, &db_value,
	     (dict->flags & DICT_FLAG_DUP_REPLACE) ? 0 : DONT_CLOBBER)) < 0)
	msg_fatal("error writing %s: %m", dict_db->dict.name);
    if (status) {
	if (dict->flags & DICT_FLAG_DUP_IGNORE)
	     /* void */ ;
	else if (dict->flags & DICT_FLAG_DUP_WARN)
	    msg_warn("%s: duplicate entry: \"%s\"", dict_db->dict.name, name);
	else
	    msg_fatal("%s: duplicate entry: \"%s\"", dict_db->dict.name, name);
    }
    if (dict->flags & DICT_FLAG_SYNC_UPDATE)
	if (DICT_DB_SYNC(db, 0) < 0)
	    msg_fatal("%s: flush dictionary: %m", dict_db->dict.name);

    /*
     * Release the exclusive lock.
     */
    if ((dict->flags & DICT_FLAG_LOCK)
	&& myflock(dict->lock_fd, INTERNAL_LOCK, MYFLOCK_OP_NONE) < 0)
	msg_fatal("%s: unlock dictionary: %m", dict_db->dict.name);

    return (status);
}

/* delete one entry from the dictionary */

static int dict_db_delete(DICT *dict, const char *name)
{
    DICT_DB *dict_db = (DICT_DB *) dict;
    DB     *db = dict_db->db;
    DBT     db_key;
    int     status = 1;
    int     flags = 0;

    dict->error = 0;

    /*
     * Sanity check.
     */
    if ((dict->flags & (DICT_FLAG_TRY1NULL | DICT_FLAG_TRY0NULL)) == 0)
	msg_panic("dict_db_delete: no DICT_FLAG_TRY1NULL | DICT_FLAG_TRY0NULL flag");

    /*
     * Optionally fold the key.
     */
    if (dict->flags & DICT_FLAG_FOLD_FIX) {
	if (dict->fold_buf == 0)
	    dict->fold_buf = vstring_alloc(10);
	vstring_strcpy(dict->fold_buf, name);
	name = lowercase(vstring_str(dict->fold_buf));
    }
    memset(&db_key, 0, sizeof(db_key));

    /*
     * Acquire an exclusive lock.
     */
    if ((dict->flags & DICT_FLAG_LOCK)
	&& myflock(dict->lock_fd, INTERNAL_LOCK, MYFLOCK_OP_EXCLUSIVE) < 0)
	msg_fatal("%s: lock dictionary: %m", dict_db->dict.name);

    /*
     * See if this DB file was written with one null byte appended to key and
     * value.
     */
    if (dict->flags & DICT_FLAG_TRY1NULL) {
	db_key.data = (void *) name;
	db_key.size = strlen(name) + 1;
	if ((status = DICT_DB_DEL(db, &db_key, flags)) < 0)
	    msg_fatal("error deleting from %s: %m", dict_db->dict.name);
	if (status == 0)
	    dict->flags &= ~DICT_FLAG_TRY0NULL;
    }

    /*
     * See if this DB file was written with no null byte appended to key and
     * value.
     */
    if (status > 0 && (dict->flags & DICT_FLAG_TRY0NULL)) {
	db_key.data = (void *) name;
	db_key.size = strlen(name);
	if ((status = DICT_DB_DEL(db, &db_key, flags)) < 0)
	    msg_fatal("error deleting from %s: %m", dict_db->dict.name);
	if (status == 0)
	    dict->flags &= ~DICT_FLAG_TRY1NULL;
    }
    if (dict->flags & DICT_FLAG_SYNC_UPDATE)
	if (DICT_DB_SYNC(db, 0) < 0)
	    msg_fatal("%s: flush dictionary: %m", dict_db->dict.name);

    /*
     * Release the exclusive lock.
     */
    if ((dict->flags & DICT_FLAG_LOCK)
	&& myflock(dict->lock_fd, INTERNAL_LOCK, MYFLOCK_OP_NONE) < 0)
	msg_fatal("%s: unlock dictionary: %m", dict_db->dict.name);

    return status;
}

/* dict_db_sequence - traverse the dictionary */

static int dict_db_sequence(DICT *dict, int function,
			            const char **key, const char **value)
{
    const char *myname = "dict_db_sequence";
    DICT_DB *dict_db = (DICT_DB *) dict;
    DB     *db = dict_db->db;
    DBT     db_key;
    DBT     db_value;
    int     status = 0;
    int     db_function;

    dict->error = 0;

#if DB_VERSION_MAJOR > 1

    /*
     * Initialize.
     */
    memset(&db_key, 0, sizeof(db_key));
    memset(&db_value, 0, sizeof(db_value));

    /*
     * Determine the function.
     */
    switch (function) {
    case DICT_SEQ_FUN_FIRST:
	if (dict_db->cursor == 0)
	    DICT_DB_CURSOR(db, &(dict_db->cursor));
	db_function = DB_FIRST;
	break;
    case DICT_SEQ_FUN_NEXT:
	if (dict_db->cursor == 0)
	    msg_panic("%s: no cursor", myname);
	db_function = DB_NEXT;
	break;
    default:
	msg_panic("%s: invalid function %d", myname, function);
    }

    /*
     * Acquire a shared lock.
     */
    if ((dict->flags & DICT_FLAG_LOCK)
	&& myflock(dict->lock_fd, INTERNAL_LOCK, MYFLOCK_OP_SHARED) < 0)
	msg_fatal("%s: lock dictionary: %m", dict_db->dict.name);

    /*
     * Database lookup.
     */
    status =
	dict_db->cursor->c_get(dict_db->cursor, &db_key, &db_value, db_function);
    if (status != 0 && status != DB_NOTFOUND)
	msg_fatal("error [%d] seeking %s: %m", status, dict_db->dict.name);

    /*
     * Release the shared lock.
     */
    if ((dict->flags & DICT_FLAG_LOCK)
	&& myflock(dict->lock_fd, INTERNAL_LOCK, MYFLOCK_OP_NONE) < 0)
	msg_fatal("%s: unlock dictionary: %m", dict_db->dict.name);

    if (status == 0) {

	/*
	 * Copy the result so it is guaranteed null terminated.
	 */
	*key = SCOPY(dict_db->key_buf, db_key.data, db_key.size);
	*value = SCOPY(dict_db->val_buf, db_value.data, db_value.size);
    }
    return (status);
#else

    /*
     * determine the function
     */
    switch (function) {
    case DICT_SEQ_FUN_FIRST:
	db_function = R_FIRST;
	break;
    case DICT_SEQ_FUN_NEXT:
	db_function = R_NEXT;
	break;
    default:
	msg_panic("%s: invalid function %d", myname, function);
    }

    /*
     * Acquire a shared lock.
     */
    if ((dict->flags & DICT_FLAG_LOCK)
	&& myflock(dict->lock_fd, INTERNAL_LOCK, MYFLOCK_OP_SHARED) < 0)
	msg_fatal("%s: lock dictionary: %m", dict_db->dict.name);

    if ((status = db->seq(db, &db_key, &db_value, db_function)) < 0)
	msg_fatal("error seeking %s: %m", dict_db->dict.name);

    /*
     * Release the shared lock.
     */
    if ((dict->flags & DICT_FLAG_LOCK)
	&& myflock(dict->lock_fd, INTERNAL_LOCK, MYFLOCK_OP_NONE) < 0)
	msg_fatal("%s: unlock dictionary: %m", dict_db->dict.name);

    if (status == 0) {

	/*
	 * Copy the result so that it is guaranteed null terminated.
	 */
	*key = SCOPY(dict_db->key_buf, db_key.data, db_key.size);
	*value = SCOPY(dict_db->val_buf, db_value.data, db_value.size);
    }
    return status;
#endif
}

/* dict_db_close - close data base */

static void dict_db_close(DICT *dict)
{
    DICT_DB *dict_db = (DICT_DB *) dict;

#if DB_VERSION_MAJOR > 1
    if (dict_db->cursor)
	dict_db->cursor->c_close(dict_db->cursor);
#endif
    if (DICT_DB_SYNC(dict_db->db, 0) < 0)
	msg_fatal("flush database %s: %m", dict_db->dict.name);

    /*
     * With some Berkeley DB implementations, close fails with a bogus ENOENT
     * error, while it reports no errors with put+sync, no errors with
     * del+sync, and no errors with the sync operation just before this
     * comment. This happens in programs that never fork and that never share
     * the database with other processes. The bogus close error has been
     * reported for programs that use the first/next iterator. Instead of
     * making Postfix look bad because it reports errors that other programs
     * ignore, I'm going to report the bogus error as a non-error.
     */
    if (DICT_DB_CLOSE(dict_db->db) < 0)
	msg_info("close database %s: %m (possible Berkeley DB bug)",
		 dict_db->dict.name);
#if DB_VERSION_MAJOR > 2
    dict_db->dbenv->close(dict_db->dbenv, 0);
#endif
    if (dict_db->key_buf)
	vstring_free(dict_db->key_buf);
    if (dict_db->val_buf)
	vstring_free(dict_db->val_buf);
    if (dict->fold_buf)
	vstring_free(dict->fold_buf);
    dict_free(dict);
}

#if DB_VERSION_MAJOR > 2

/* dict_db_new_env - workaround for undocumented ./DB_CONFIG read */

static DB_ENV *dict_db_new_env(const char *db_path)
{
    VSTRING *db_home_buf;
    DB_ENV *dbenv;
    u_int32_t cache_size_gbytes;
    u_int32_t cache_size_bytes;
    int     ncache;

    if ((errno = db_env_create(&dbenv, 0)) != 0)
	msg_fatal("create DB environment: %m");
#if DB_VERSION_MAJOR > 4 || (DB_VERSION_MAJOR == 4 && DB_VERSION_MINOR >= 7)
    if ((errno = dbenv->get_cachesize(dbenv, &cache_size_gbytes,
				      &cache_size_bytes, &ncache)) != 0)
	msg_fatal("get DB cache size: %m");
    if (cache_size_gbytes == 0 && cache_size_bytes < dict_db_cache_size) {
	if ((errno = dbenv->set_cache_max(dbenv, cache_size_gbytes,
					  dict_db_cache_size)) != 0)
	    msg_fatal("set DB max cache size %d: %m", dict_db_cache_size);
	if ((errno = dbenv->set_cachesize(dbenv, cache_size_gbytes,
					  dict_db_cache_size, ncache)) != 0)
	    msg_fatal("set DB cache size %d: %m", dict_db_cache_size);
    }
#endif
    /* XXX db_home is also the default directory for the .db file. */
    db_home_buf = vstring_alloc(100);
    if ((errno = dbenv->open(dbenv, sane_dirname(db_home_buf, db_path),
			   DB_INIT_MPOOL | DB_CREATE | DB_PRIVATE, 0)) != 0)
	msg_fatal("open DB environment: %m");
    vstring_free(db_home_buf);
    return (dbenv);
}

#endif

/* dict_db_open - open data base */

static DICT *dict_db_open(const char *class, const char *path, int open_flags,
			          int type, void *tweak, int dict_flags)
{
    DICT_DB *dict_db;
    struct stat st;
    DB     *db = 0;
    char   *db_path = 0;
    VSTRING *db_base_buf = 0;
    int     lock_fd = -1;
    int     dbfd;

#if DB_VERSION_MAJOR > 1
    int     db_flags;

#endif
#if DB_VERSION_MAJOR > 2
    DB_ENV *dbenv = 0;

#endif

    /*
     * Mismatches between #include file and library are a common cause for
     * trouble.
     */
#if DB_VERSION_MAJOR > 1
    int     major_version;
    int     minor_version;
    int     patch_version;

    (void) db_version(&major_version, &minor_version, &patch_version);
    if (major_version != DB_VERSION_MAJOR || minor_version != DB_VERSION_MINOR)
	return (dict_surrogate(class, path, open_flags, dict_flags,
			       "incorrect version of Berkeley DB: "
	      "compiled against %d.%d.%d, run-time linked against %d.%d.%d",
		       DB_VERSION_MAJOR, DB_VERSION_MINOR, DB_VERSION_PATCH,
			       major_version, minor_version, patch_version));
    if (msg_verbose) {
	msg_info("Compiled against Berkeley DB: %d.%d.%d\n",
		 DB_VERSION_MAJOR, DB_VERSION_MINOR, DB_VERSION_PATCH);
	msg_info("Run-time linked against Berkeley DB: %d.%d.%d\n",
		 major_version, minor_version, patch_version);
    }
#else
    if (msg_verbose)
	msg_info("Compiled against Berkeley DB version 1");
#endif

    db_path = concatenate(path, ".db", (char *) 0);

    /*
     * Note: DICT_FLAG_LOCK is used only by programs that do fine-grained (in
     * the time domain) locking while accessing individual database records.
     * 
     * Programs such as postmap/postalias use their own large-grained (in the
     * time domain) locks while rewriting the entire file.
     * 
     * XXX DB version 4.1 will not open a zero-length file. This means we must
     * open an existing file without O_CREAT|O_TRUNC, and that we must let
     * db_open() create a non-existent file for us.
     */
#define LOCK_OPEN_FLAGS(f) ((f) & ~(O_CREAT|O_TRUNC))
#if DB_VERSION_MAJOR <= 2
#define FREE_RETURN(e) do { \
	DICT *_dict = (e); if (db) DICT_DB_CLOSE(db); \
	if (lock_fd >= 0) (void) close(lock_fd); \
	if (db_base_buf) vstring_free(db_base_buf); \
	if (db_path) myfree(db_path); return (_dict); \
    } while (0)
#else
#define FREE_RETURN(e) do { \
	DICT *_dict = (e); if (db) DICT_DB_CLOSE(db); \
	if (dbenv) dbenv->close(dbenv, 0); \
	if (lock_fd >= 0) (void) close(lock_fd); \
	if (db_base_buf) vstring_free(db_base_buf); \
	if (db_path) myfree(db_path); return (_dict); \
    } while (0)
#endif

    if (dict_flags & DICT_FLAG_LOCK) {
	if ((lock_fd = open(db_path, LOCK_OPEN_FLAGS(open_flags), 0644)) < 0) {
	    if (errno != ENOENT)
		FREE_RETURN(dict_surrogate(class, path, open_flags, dict_flags,
					   "open database %s: %m", db_path));
	} else {
	    if (myflock(lock_fd, INTERNAL_LOCK, MYFLOCK_OP_SHARED) < 0)
		msg_fatal("shared-lock database %s for open: %m", db_path);
	}
    }

    /*
     * Use the DB 1.x programming interface. This is the default interface
     * with 4.4BSD systems. It is also available via the db_185 compatibility
     * interface, but that interface does not have the undocumented feature
     * that we need to make file locking safe with POSIX fcntl() locking.
     */
#if DB_VERSION_MAJOR < 2
    if ((db = dbopen(db_path, open_flags, 0644, type, tweak)) == 0)
	FREE_RETURN(dict_surrogate(class, path, open_flags, dict_flags,
				   "open database %s: %m", db_path));
    dbfd = db->fd(db);
#endif

    /*
     * Use the DB 2.x programming interface. Jump a couple extra hoops.
     */
#if DB_VERSION_MAJOR == 2
    db_flags = DB_FCNTL_LOCKING;
    if (open_flags == O_RDONLY)
	db_flags |= DB_RDONLY;
    if (open_flags & O_CREAT)
	db_flags |= DB_CREATE;
    if (open_flags & O_TRUNC)
	db_flags |= DB_TRUNCATE;
    if ((errno = db_open(db_path, type, db_flags, 0644, 0, tweak, &db)) != 0)
	FREE_RETURN(dict_surrogate(class, path, open_flags, dict_flags,
				   "open database %s: %m", db_path));
    if (db == 0)
	msg_panic("db_open null result");
    if ((errno = db->fd(db, &dbfd)) != 0)
	msg_fatal("get database file descriptor: %m");
#endif

    /*
     * Use the DB 3.x programming interface. Jump even more hoops.
     */
#if DB_VERSION_MAJOR > 2
    db_flags = DB_FCNTL_LOCKING;
    if (open_flags == O_RDONLY)
	db_flags |= DB_RDONLY;
    if (open_flags & O_CREAT)
	db_flags |= DB_CREATE;
    if (open_flags & O_TRUNC)
	db_flags |= DB_TRUNCATE;
    if ((errno = db_create(&db, dbenv = dict_db_new_env(db_path), 0)) != 0)
	msg_fatal("create DB database: %m");
    if (db == 0)
	msg_panic("db_create null result");
    if (type == DB_HASH && db->set_h_nelem(db, DICT_DB_NELM) != 0)
	msg_fatal("set DB hash element count %d: %m", DICT_DB_NELM);
    db_base_buf = vstring_alloc(100);
#if DB_VERSION_MAJOR == 18 || DB_VERSION_MAJOR == 6 || DB_VERSION_MAJOR == 5 || \
	(DB_VERSION_MAJOR == 4 && DB_VERSION_MINOR > 0)
    if ((errno = db->open(db, 0, sane_basename(db_base_buf, db_path),
			  0, type, db_flags, 0644)) != 0)
	FREE_RETURN(dict_surrogate(class, path, open_flags, dict_flags,
				   "open database %s: %m", db_path));
#elif (DB_VERSION_MAJOR == 3 || DB_VERSION_MAJOR == 4)
    if ((errno = db->open(db, sane_basename(db_base_buf, db_path), 0,
			  type, db_flags, 0644)) != 0)
	FREE_RETURN(dict_surrogate(class, path, open_flags, dict_flags,
				   "open database %s: %m", db_path));
#else
#error "Unsupported Berkeley DB version"
#endif
    vstring_free(db_base_buf);
    if ((errno = db->fd(db, &dbfd)) != 0)
	msg_fatal("get database file descriptor: %m");
#endif
    if ((dict_flags & DICT_FLAG_LOCK) && lock_fd >= 0) {
	if (myflock(lock_fd, INTERNAL_LOCK, MYFLOCK_OP_NONE) < 0)
	    msg_fatal("unlock database %s for open: %m", db_path);
	if (close(lock_fd) < 0)
	    msg_fatal("close database %s: %m", db_path);
	lock_fd = -1;
    }
    dict_db = (DICT_DB *) dict_alloc(class, db_path, sizeof(*dict_db));
    dict_db->dict.lookup = dict_db_lookup;
    dict_db->dict.update = dict_db_update;
    dict_db->dict.delete = dict_db_delete;
    dict_db->dict.sequence = dict_db_sequence;
    dict_db->dict.close = dict_db_close;
    dict_db->dict.lock_fd = dbfd;
    dict_db->dict.stat_fd = dbfd;
    if (fstat(dict_db->dict.stat_fd, &st) < 0)
	msg_fatal("dict_db_open: fstat: %m");
    dict_db->dict.mtime = st.st_mtime;
    dict_db->dict.owner.uid = st.st_uid;
    dict_db->dict.owner.status = (st.st_uid != 0);

    /*
     * Warn if the source file is newer than the indexed file, except when
     * the source file changed only seconds ago.
     */
    if ((dict_flags & DICT_FLAG_LOCK) != 0
	&& stat(path, &st) == 0
	&& st.st_mtime > dict_db->dict.mtime
	&& st.st_mtime < time((time_t *) 0) - 100)
	msg_warn("database %s is older than source file %s", db_path, path);

    close_on_exec(dict_db->dict.lock_fd, CLOSE_ON_EXEC);
    close_on_exec(dict_db->dict.stat_fd, CLOSE_ON_EXEC);
    dict_db->dict.flags = dict_flags | DICT_FLAG_FIXED;
    if ((dict_flags & (DICT_FLAG_TRY1NULL | DICT_FLAG_TRY0NULL)) == 0)
	dict_db->dict.flags |= (DICT_FLAG_TRY1NULL | DICT_FLAG_TRY0NULL);
    if (dict_flags & DICT_FLAG_FOLD_FIX)
	dict_db->dict.fold_buf = vstring_alloc(10);
    dict_db->db = db;
#if DB_VERSION_MAJOR > 2
    dict_db->dbenv = dbenv;
#endif
#if DB_VERSION_MAJOR > 1
    dict_db->cursor = 0;
#endif
    dict_db->key_buf = 0;
    dict_db->val_buf = 0;

    myfree(db_path);
    return (DICT_DEBUG (&dict_db->dict));
}

/* dict_hash_open - create association with data base */

DICT   *dict_hash_open(const char *path, int open_flags, int dict_flags)
{
#if DB_VERSION_MAJOR < 2
    HASHINFO tweak;

    memset((void *) &tweak, 0, sizeof(tweak));
    tweak.nelem = DICT_DB_NELM;
    tweak.cachesize = dict_db_cache_size;
#endif
#if DB_VERSION_MAJOR == 2
    DB_INFO tweak;

    memset((void *) &tweak, 0, sizeof(tweak));
    tweak.h_nelem = DICT_DB_NELM;
    tweak.db_cachesize = dict_db_cache_size;
#endif
#if DB_VERSION_MAJOR > 2
    void   *tweak;

    tweak = 0;
#endif
    return (dict_db_open(DICT_TYPE_HASH, path, open_flags, DB_HASH,
			 (void *) &tweak, dict_flags));
}

/* dict_btree_open - create association with data base */

DICT   *dict_btree_open(const char *path, int open_flags, int dict_flags)
{
#if DB_VERSION_MAJOR < 2
    BTREEINFO tweak;

    memset((void *) &tweak, 0, sizeof(tweak));
    tweak.cachesize = dict_db_cache_size;
#endif
#if DB_VERSION_MAJOR == 2
    DB_INFO tweak;

    memset((void *) &tweak, 0, sizeof(tweak));
    tweak.db_cachesize = dict_db_cache_size;
#endif
#if DB_VERSION_MAJOR > 2
    void   *tweak;

    tweak = 0;
#endif

    return (dict_db_open(DICT_TYPE_BTREE, path, open_flags, DB_BTREE,
			 (void *) &tweak, dict_flags));
}

#endif