ovsdb/log.c

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