ovsdb/log.c

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