1 /*++
2 /* NAME
3 /* mkmap_db 3
4 /* SUMMARY
5 /* create or open database, DB style
6 /* SYNOPSIS
7 /* #include <mkmap.h>
8 /*
9 /* MKMAP *mkmap_hash_open(path)
10 /* const char *path;
11 /*
12 /* MKMAP *mkmap_btree_open(path)
13 /* const char *path;
14 /* DESCRIPTION
15 /* This module implements support for creating DB databases.
16 /*
17 /* mkmap_hash_open() and mkmap_btree_open() take a file name,
18 /* append the ".db" suffix, and do whatever initialization is
19 /* required before the Berkeley DB open routine is called.
20 /*
21 /* All errors are fatal.
22 /* SEE ALSO
23 /* dict_db(3), DB dictionary interface.
24 /* LICENSE
25 /* .ad
26 /* .fi
27 /* The Secure Mailer license must be distributed with this software.
28 /* AUTHOR(S)
29 /* Wietse Venema
30 /* IBM T.J. Watson Research
31 /* P.O. Box 704
32 /* Yorktown Heights, NY 10598, USA
33 /*--*/
34
35 /* System library. */
36
37 #include <sys_defs.h>
38 #include <sys/stat.h>
39 #include <unistd.h>
40 #include <errno.h>
41
42 /* Utility library. */
43
44 #include <msg.h>
45 #include <mymalloc.h>
46 #include <stringops.h>
47 #include <dict.h>
48 #include <dict_db.h>
49 #include <myflock.h>
50 #include <warn_stat.h>
51
52 /* Global library. */
53
54 #include <mail_params.h>
55
56 /* Application-specific. */
57
58 #include "mkmap.h"
59
60 #ifdef HAS_DB
61 #ifdef PATH_DB_H
62 #include PATH_DB_H
63 #else
64 #include <db.h>
65 #endif
66
67 typedef struct MKMAP_DB {
68 MKMAP mkmap; /* parent class */
69 char *lock_file; /* path name */
70 int lock_fd; /* -1 or open locked file */
71 } MKMAP_DB;
72
73 /* mkmap_db_after_close - clean up after closing database */
74
mkmap_db_after_close(MKMAP * mp)75 static void mkmap_db_after_close(MKMAP *mp)
76 {
77 MKMAP_DB *mkmap = (MKMAP_DB *) mp;
78
79 if (mkmap->lock_fd >= 0 && close(mkmap->lock_fd) < 0)
80 msg_warn("close %s: %m", mkmap->lock_file);
81 myfree(mkmap->lock_file);
82 }
83
84 /* mkmap_db_after_open - lock newly created database */
85
mkmap_db_after_open(MKMAP * mp)86 static void mkmap_db_after_open(MKMAP *mp)
87 {
88 MKMAP_DB *mkmap = (MKMAP_DB *) mp;
89
90 if (mkmap->lock_fd < 0) {
91 if ((mkmap->lock_fd = open(mkmap->lock_file, O_RDWR, 0644)) < 0)
92 msg_fatal("open lockfile %s: %m", mkmap->lock_file);
93 if (myflock(mkmap->lock_fd, INTERNAL_LOCK, MYFLOCK_OP_EXCLUSIVE) < 0)
94 msg_fatal("lock %s: %m", mkmap->lock_file);
95 }
96 }
97
98 /* mkmap_db_before_open - lock existing database */
99
mkmap_db_before_open(const char * path,DICT * (* db_open)(const char *,int,int))100 static MKMAP *mkmap_db_before_open(const char *path,
101 DICT *(*db_open) (const char *, int, int))
102 {
103 MKMAP_DB *mkmap = (MKMAP_DB *) mymalloc(sizeof(*mkmap));
104 struct stat st;
105
106 /*
107 * Override the default per-table cache size for map (re)builds.
108 *
109 * db_cache_size" is defined in util/dict_db.c and defaults to 128kB, which
110 * works well for the lookup code.
111 *
112 * We use a larger per-table cache when building ".db" files. For "hash"
113 * files performance degrades rapidly unless the memory pool is O(file
114 * size).
115 *
116 * For "btree" files performance is good with sorted input even for small
117 * memory pools, but with random input degrades rapidly unless the memory
118 * pool is O(file size).
119 *
120 * XXX This should be specified via the DICT interface so that the buffer
121 * size becomes an object property, instead of being specified by poking
122 * a global variable so that it becomes a class property.
123 */
124 dict_db_cache_size = var_db_create_buf;
125
126 /*
127 * Fill in the generic members.
128 */
129 mkmap->lock_file = concatenate(path, ".db", (char *) 0);
130 mkmap->mkmap.open = db_open;
131 mkmap->mkmap.after_open = mkmap_db_after_open;
132 mkmap->mkmap.after_close = mkmap_db_after_close;
133
134 /*
135 * Unfortunately, not all systems that might support db databases do
136 * support locking on open(), so we open the file before updating it.
137 *
138 * XXX Berkeley DB 4.1 refuses to open a zero-length file. This means we can
139 * open and lock only an existing file, and that we must not truncate it.
140 */
141 if ((mkmap->lock_fd = open(mkmap->lock_file, O_RDWR, 0644)) < 0) {
142 if (errno != ENOENT)
143 msg_fatal("open %s: %m", mkmap->lock_file);
144 }
145
146 /*
147 * Get an exclusive lock - we're going to change the database so we can't
148 * have any spectators.
149 *
150 * XXX Horror. Berkeley DB 4.1 refuses to open a zero-length file. This
151 * means that we must examine the size while the file is locked, and that
152 * we must unlink a zero-length file while it is locked. Avoid a race
153 * condition where two processes try to open the same zero-length file
154 * and where the second process ends up deleting the wrong file.
155 */
156 else {
157 if (myflock(mkmap->lock_fd, INTERNAL_LOCK, MYFLOCK_OP_EXCLUSIVE) < 0)
158 msg_fatal("lock %s: %m", mkmap->lock_file);
159 if (fstat(mkmap->lock_fd, &st) < 0)
160 msg_fatal("fstat %s: %m", mkmap->lock_file);
161 if (st.st_size == 0) {
162 if (st.st_nlink > 0) {
163 if (unlink(mkmap->lock_file) < 0)
164 msg_fatal("cannot remove zero-length database file %s: %m",
165 mkmap->lock_file);
166 msg_warn("removing zero-length database file: %s",
167 mkmap->lock_file);
168 }
169 close(mkmap->lock_fd);
170 mkmap->lock_fd = -1;
171 }
172 }
173
174 return (&mkmap->mkmap);
175 }
176
177 /* mkmap_hash_open - create or open hashed DB file */
178
mkmap_hash_open(const char * path)179 MKMAP *mkmap_hash_open(const char *path)
180 {
181 return (mkmap_db_before_open(path, dict_hash_open));
182 }
183
184 /* mkmap_btree_open - create or open btree DB file */
185
mkmap_btree_open(const char * path)186 MKMAP *mkmap_btree_open(const char *path)
187 {
188 return (mkmap_db_before_open(path, dict_btree_open));
189 }
190
191 #endif
192