ovsdb/log.c

   1 /* Copyright (c) 2009, 2010, 2011, 2012, 2013 Nicira, Inc.
   2  *
   3  * Licensed under the Apache License, Version 2.0 (the "License");
   4  * you may not use this file except in compliance with the License.
   5  * You may obtain a copy of the License at:
   6  *
   7  *     http://www.apache.org/licenses/LICENSE-2.0
   8  *
   9  * Unless required by applicable law or agreed to in writing, software
  10  * distributed under the License is distributed on an "AS IS" BASIS,
  11  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  12  * See the License for the specific language governing permissions and
  13  * limitations under the License.
  14  */
  15
  16 #include <config.h>
  17
  18 #include "log.h"
  19
  20 #include <errno.h>
  21 #include <fcntl.h>
  22 #include <stdlib.h>
  23 #include <string.h>
  24 #include <sys/stat.h>
  25 #include <unistd.h>
  26
  27 #include "json.h"
  28 #include "lockfile.h"
  29 #include "ovsdb.h"
  30 #include "ovsdb-error.h"
  31 #include "sha1.h"
  32 #include "socket-util.h"
  33 #include "transaction.h"
  34 #include "util.h"
  35
  36 enum ovsdb_log_mode {
  37     OVSDB_LOG_READ,
  38     OVSDB_LOG_WRITE
  39 };
  40
  41 struct ovsdb_log {
  42     off_t prev_offset;
  43     off_t offset;
  44     char *name;
  45     struct lockfile *lockfile;
  46     FILE *stream;
  47     struct ovsdb_error *read_error;
  48     bool write_error;
  49     enum ovsdb_log_mode mode;
  50 };
  51
  52 /* Attempts to open 'name' with the specified 'open_mode'.  On success, stores
  53  * the new log into '*filep' and returns NULL; otherwise returns NULL and
  54  * stores NULL into '*filep'.
  55  *
  56  * Whether the file will be locked using lockfile_lock() depends on 'locking':
  57  * use true to lock it, false not to lock it, or -1 to lock it only if
  58  * 'open_mode' is a mode that allows writing.
  59  */
  60 struct ovsdb_error *
  61 ovsdb_log_open(const char *name, enum ovsdb_log_open_mode open_mode,
  62                int locking, struct ovsdb_log **filep)
  63 {
  64     struct lockfile *lockfile;
  65     struct ovsdb_error *error;
  66     struct ovsdb_log *file;
  67     struct stat s;
  68     FILE *stream;
  69     int flags;
  70     int fd;
  71
  72     *filep = NULL;
  73
  74     ovs_assert(locking == -1 || locking == false || locking == true);
  75     if (locking < 0) {
  76         locking = open_mode != OVSDB_LOG_READ_ONLY;
  77     }
  78     if (locking) {
  79         int retval = lockfile_lock(name, &lockfile);
  80         if (retval) {
  81             error = ovsdb_io_error(retval, "%s: failed to lock lockfile",
  82                                    name);
  83             goto error;
  84         }
  85     } else {
  86         lockfile = NULL;
  87     }
  88
  89     if (open_mode == OVSDB_LOG_READ_ONLY) {
  90         flags = O_RDONLY;
  91     } else if (open_mode == OVSDB_LOG_READ_WRITE) {
  92         flags = O_RDWR;
  93     } else if (open_mode == OVSDB_LOG_CREATE) {
  94 #ifndef _WIN32
  95         if (stat(name, &s) == -1 && errno == ENOENT
  96             && lstat(name, &s) == 0 && S_ISLNK(s.st_mode)) {
  97             /* 'name' is a dangling symlink.  We want to create the file that
  98              * the symlink points to, but POSIX says that open() with O_EXCL
  99              * must fail with EEXIST if the named file is a symlink.  So, we
 100              * have to leave off O_EXCL and accept the race. */
 101             flags = O_RDWR | O_CREAT;
 102         } else {
 103             flags = O_RDWR | O_CREAT | O_EXCL;
 104         }
 105 #else
 106         flags = O_RDWR | O_CREAT | O_EXCL;
 107 #endif
 108     } else {
 109         OVS_NOT_REACHED();
 110     }
 111     fd = open(name, flags, 0666);
 112     if (fd < 0) {
 113         const char *op = open_mode == OVSDB_LOG_CREATE ? "create" : "open";
 114         error = ovsdb_io_error(errno, "%s: %s failed", op, name);
 115         goto error_unlock;
 116     }
 117
 118     if (!fstat(fd, &s) && s.st_size == 0) {
 119         /* It's (probably) a new file so fsync() its parent directory to ensure
 120          * that its directory entry is committed to disk. */
 121         fsync_parent_dir(name);
 122     }
 123
 124     stream = fdopen(fd, open_mode == OVSDB_LOG_READ_ONLY ? "rb" : "w+b");
 125     if (!stream) {
 126         error = ovsdb_io_error(errno, "%s: fdopen failed", name);
 127         goto error_close;
 128     }
 129
 130     file = xmalloc(sizeof *file);
 131     file->name = xstrdup(name);
 132     file->lockfile = lockfile;
 133     file->stream = stream;
 134     file->prev_offset = 0;
 135     file->offset = 0;
 136     file->read_error = NULL;
 137     file->write_error = false;
 138     file->mode = OVSDB_LOG_READ;
 139     *filep = file;
 140     return NULL;
 141
 142 error_close:
 143     close(fd);
 144 error_unlock:
 145     lockfile_unlock(lockfile);
 146 error:
 147     return error;
 148 }
 149
 150 void
 151 ovsdb_log_close(struct ovsdb_log *file)
 152 {
 153     if (file) {
 154         free(file->name);
 155         fclose(file->stream);
 156         lockfile_unlock(file->lockfile);
 157         ovsdb_error_destroy(file->read_error);
 158         free(file);
 159     }
 160 }
 161
 162 static const char magic[] = "OVSDB JSON ";
 163
 164 static bool
 165 parse_header(char *header, unsigned long int *length,
 166              uint8_t sha1[SHA1_DIGEST_SIZE])
 167 {
 168     char *p;
 169
 170     /* 'header' must consist of a magic string... */
 171     if (strncmp(header, magic, strlen(magic))) {
 172         return false;
 173     }
 174
 175     /* ...followed by a length in bytes... */
 176     *length = strtoul(header + strlen(magic), &p, 10);
 177     if (!*length || *length == ULONG_MAX || *p != ' ') {
 178         return false;
 179     }
 180     p++;
 181
 182     /* ...followed by a SHA-1 hash... */
 183     if (!sha1_from_hex(sha1, p)) {
 184         return false;
 185     }
 186     p += SHA1_HEX_DIGEST_LEN;
 187
 188     /* ...and ended by a new-line. */
 189     if (*p != '\n') {
 190         return false;
 191     }
 192
 193     return true;
 194 }
 195
 196 struct ovsdb_log_read_cbdata {
 197     char input[4096];
 198     struct ovsdb_log *file;
 199     int error;
 200     unsigned long length;
 201 };
 202
 203 static struct ovsdb_error *
 204 parse_body(struct ovsdb_log *file, off_t offset, unsigned long int length,
 205            uint8_t sha1[SHA1_DIGEST_SIZE], struct json **jsonp)
 206 {
 207     struct json_parser *parser;
 208     struct sha1_ctx ctx;
 209
 210     sha1_init(&ctx);
 211     parser = json_parser_create(JSPF_TRAILER);
 212
 213     while (length > 0) {
 214         char input[BUFSIZ];
 215         int chunk;
 216
 217         chunk = MIN(length, sizeof input);
 218         if (fread(input, 1, chunk, file->stream) != chunk) {
 219             json_parser_abort(parser);
 220             return ovsdb_io_error(ferror(file->stream) ? errno : EOF,
 221                                   "%s: error reading %lu bytes "
 222                                   "starting at offset %lld", file->name,
 223                                   length, (long long int) offset);
 224         }
 225         sha1_update(&ctx, input, chunk);
 226         json_parser_feed(parser, input, chunk);
 227         length -= chunk;
 228     }
 229
 230     sha1_final(&ctx, sha1);
 231     *jsonp = json_parser_finish(parser);
 232     return NULL;
 233 }
 234
 235 struct ovsdb_error *
 236 ovsdb_log_read(struct ovsdb_log *file, struct json **jsonp)
 237 {
 238     uint8_t expected_sha1[SHA1_DIGEST_SIZE];
 239     uint8_t actual_sha1[SHA1_DIGEST_SIZE];
 240     struct ovsdb_error *error;
 241     off_t data_offset;
 242     unsigned long data_length;
 243     struct json *json;
 244     char header[128];
 245
 246     *jsonp = json = NULL;
 247
 248     if (file->read_error) {
 249         return ovsdb_error_clone(file->read_error);
 250     } else if (file->mode == OVSDB_LOG_WRITE) {
 251         return OVSDB_BUG("reading file in write mode");
 252     }
 253
 254     if (!fgets(header, sizeof header, file->stream)) {
 255         if (feof(file->stream)) {
 256             error = NULL;
 257         } else {
 258             error = ovsdb_io_error(errno, "%s: read failed", file->name);
 259         }
 260         goto error;
 261     }
 262
 263     if (!parse_header(header, &data_length, expected_sha1)) {
 264         error = ovsdb_syntax_error(NULL, NULL, "%s: parse error at offset "
 265                                    "%lld in header line \"%.*s\"",
 266                                    file->name, (long long int) file->offset,
 267                                    (int) strcspn(header, "\n"), header);
 268         goto error;
 269     }
 270
 271     data_offset = file->offset + strlen(header);
 272     error = parse_body(file, data_offset, data_length, actual_sha1, &json);
 273     if (error) {
 274         goto error;
 275     }
 276
 277     if (memcmp(expected_sha1, actual_sha1, SHA1_DIGEST_SIZE)) {
 278         error = ovsdb_syntax_error(NULL, NULL, "%s: %lu bytes starting at "
 279                                    "offset %lld have SHA-1 hash "SHA1_FMT" "
 280                                    "but should have hash "SHA1_FMT,
 281                                    file->name, data_length,
 282                                    (long long int) data_offset,
 283                                    SHA1_ARGS(actual_sha1),
 284                                    SHA1_ARGS(expected_sha1));
 285         goto error;
 286     }
 287
 288     if (json->type == JSON_STRING) {
 289         error = ovsdb_syntax_error(NULL, NULL, "%s: %lu bytes starting at "
 290                                    "offset %lld are not valid JSON (%s)",
 291                                    file->name, data_length,
 292                                    (long long int) data_offset,
 293                                    json->u.string);
 294         goto error;
 295     }
 296
 297     file->prev_offset = file->offset;
 298     file->offset = data_offset + data_length;
 299     *jsonp = json;
 300     return NULL;
 301
 302 error:
 303     file->read_error = ovsdb_error_clone(error);
 304     json_destroy(json);
 305     return error;
 306 }
 307
 308 /* Causes the log record read by the previous call to ovsdb_log_read() to be
 309  * effectively discarded.  The next call to ovsdb_log_write() will overwrite
 310  * that previously read record.
 311  *
 312  * Calling this function more than once has no additional effect.
 313  *
 314  * This function is useful when ovsdb_log_read() successfully reads a record
 315  * but that record does not make sense at a higher level (e.g. it specifies an
 316  * invalid transaction). */
 317 void
 318 ovsdb_log_unread(struct ovsdb_log *file)
 319 {
 320     ovs_assert(file->mode == OVSDB_LOG_READ);
 321     file->offset = file->prev_offset;
 322 }
 323
 324 struct ovsdb_error *
 325 ovsdb_log_write(struct ovsdb_log *file, struct json *json)
 326 {
 327     uint8_t sha1[SHA1_DIGEST_SIZE];
 328     struct ovsdb_error *error;
 329     char *json_string;
 330     char header[128];
 331     size_t length;
 332
 333     json_string = NULL;
 334
 335     if (file->mode == OVSDB_LOG_READ || file->write_error) {
 336         file->mode = OVSDB_LOG_WRITE;
 337         file->write_error = false;
 338         if (fseeko(file->stream, file->offset, SEEK_SET)) {
 339             error = ovsdb_io_error(errno, "%s: cannot seek to offset %lld",
 340                                    file->name, (long long int) file->offset);
 341             goto error;
 342         }
 343         if (ftruncate(fileno(file->stream), file->offset)) {
 344             error = ovsdb_io_error(errno, "%s: cannot truncate to length %lld",
 345                                    file->name, (long long int) file->offset);
 346             goto error;
 347         }
 348     }
 349
 350     if (json->type != JSON_OBJECT && json->type != JSON_ARRAY) {
 351         error = OVSDB_BUG("bad JSON type");
 352         goto error;
 353     }
 354
 355     /* Compose content.  Add a new-line (replacing the null terminator) to make
 356      * the file easier to read, even though it has no semantic value.  */
 357     json_string = json_to_string(json, 0);
 358     length = strlen(json_string) + 1;
 359     json_string[length - 1] = '\n';
 360
 361     /* Compose header. */
 362     sha1_bytes(json_string, length, sha1);
 363     snprintf(header, sizeof header, "%s%"PRIuSIZE" "SHA1_FMT"\n",
 364              magic, length, SHA1_ARGS(sha1));
 365
 366     /* Write. */
 367     if (fwrite(header, strlen(header), 1, file->stream) != 1
 368         || fwrite(json_string, length, 1, file->stream) != 1
 369         || fflush(file->stream))
 370     {
 371         error = ovsdb_io_error(errno, "%s: write failed", file->name);
 372
 373         /* Remove any partially written data, ignoring errors since there is
 374          * nothing further we can do. */
 375         ignore(ftruncate(fileno(file->stream), file->offset));
 376
 377         goto error;
 378     }
 379
 380     file->offset += strlen(header) + length;
 381     free(json_string);
 382     return NULL;
 383
 384 error:
 385     file->write_error = true;
 386     free(json_string);
 387     return error;
 388 }
 389
 390 struct ovsdb_error *
 391 ovsdb_log_commit(struct ovsdb_log *file)
 392 {
 393     if (fsync(fileno(file->stream))) {
 394         return ovsdb_io_error(errno, "%s: fsync failed", file->name);
 395     }
 396     return NULL;
 397 }
 398
 399 /* Returns the current offset into the file backing 'log', in bytes.  This
 400  * reflects the number of bytes that have been read or written in the file.  If
 401  * the whole file has been read, this is the file size. */
 402 off_t
 403 ovsdb_log_get_offset(const struct ovsdb_log *log)
 404 {
 405     return log->offset;
 406 }