ovsdb/log.c

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