/usr/src/openvswitch-1.4.0/ovsdb/log.c is in openvswitch-datapath-dkms 1.4.0-1ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at:
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include <config.h>
#include "log.h"
#include <assert.h>
#include <errno.h>
#include <fcntl.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <unistd.h>
#include "json.h"
#include "lockfile.h"
#include "ovsdb.h"
#include "ovsdb-error.h"
#include "sha1.h"
#include "socket-util.h"
#include "transaction.h"
#include "util.h"
#include "vlog.h"
VLOG_DEFINE_THIS_MODULE(ovsdb_log);
enum ovsdb_log_mode {
OVSDB_LOG_READ,
OVSDB_LOG_WRITE
};
struct ovsdb_log {
off_t prev_offset;
off_t offset;
char *name;
struct lockfile *lockfile;
FILE *stream;
struct ovsdb_error *read_error;
struct ovsdb_error *write_error;
enum ovsdb_log_mode mode;
};
/* Attempts to open 'name' with the specified 'open_mode'. On success, stores
* the new log into '*filep' and returns NULL; otherwise returns NULL and
* stores NULL into '*filep'.
*
* Whether the file will be locked using lockfile_lock() depends on 'locking':
* use true to lock it, false not to lock it, or -1 to lock it only if
* 'open_mode' is a mode that allows writing.
*/
struct ovsdb_error *
ovsdb_log_open(const char *name, enum ovsdb_log_open_mode open_mode,
int locking, struct ovsdb_log **filep)
{
struct lockfile *lockfile;
struct ovsdb_error *error;
struct ovsdb_log *file;
struct stat s;
FILE *stream;
int flags;
int fd;
*filep = NULL;
assert(locking == -1 || locking == false || locking == true);
if (locking < 0) {
locking = open_mode != OVSDB_LOG_READ_ONLY;
}
if (locking) {
int retval = lockfile_lock(name, 0, &lockfile);
if (retval) {
error = ovsdb_io_error(retval, "%s: failed to lock lockfile",
name);
goto error;
}
} else {
lockfile = NULL;
}
if (open_mode == OVSDB_LOG_READ_ONLY) {
flags = O_RDONLY;
} else if (open_mode == OVSDB_LOG_READ_WRITE) {
flags = O_RDWR;
} else if (open_mode == OVSDB_LOG_CREATE) {
flags = O_RDWR | O_CREAT | O_EXCL;
} else {
NOT_REACHED();
}
fd = open(name, flags, 0666);
if (fd < 0) {
const char *op = open_mode == OVSDB_LOG_CREATE ? "create" : "open";
error = ovsdb_io_error(errno, "%s: %s failed", op, name);
goto error_unlock;
}
if (!fstat(fd, &s) && s.st_size == 0) {
/* It's (probably) a new file so fsync() its parent directory to ensure
* that its directory entry is committed to disk. */
fsync_parent_dir(name);
}
stream = fdopen(fd, open_mode == OVSDB_LOG_READ_ONLY ? "rb" : "w+b");
if (!stream) {
error = ovsdb_io_error(errno, "%s: fdopen failed", name);
goto error_close;
}
file = xmalloc(sizeof *file);
file->name = xstrdup(name);
file->lockfile = lockfile;
file->stream = stream;
file->prev_offset = 0;
file->offset = 0;
file->read_error = NULL;
file->write_error = NULL;
file->mode = OVSDB_LOG_READ;
*filep = file;
return NULL;
error_close:
close(fd);
error_unlock:
lockfile_unlock(lockfile);
error:
return error;
}
void
ovsdb_log_close(struct ovsdb_log *file)
{
if (file) {
free(file->name);
fclose(file->stream);
lockfile_unlock(file->lockfile);
ovsdb_error_destroy(file->read_error);
ovsdb_error_destroy(file->write_error);
free(file);
}
}
static const char magic[] = "OVSDB JSON ";
static bool
parse_header(char *header, unsigned long int *length,
uint8_t sha1[SHA1_DIGEST_SIZE])
{
char *p;
/* 'header' must consist of a magic string... */
if (strncmp(header, magic, strlen(magic))) {
return false;
}
/* ...followed by a length in bytes... */
*length = strtoul(header + strlen(magic), &p, 10);
if (!*length || *length == ULONG_MAX || *p != ' ') {
return false;
}
p++;
/* ...followed by a SHA-1 hash... */
if (!sha1_from_hex(sha1, p)) {
return false;
}
p += SHA1_HEX_DIGEST_LEN;
/* ...and ended by a new-line. */
if (*p != '\n') {
return false;
}
return true;
}
struct ovsdb_log_read_cbdata {
char input[4096];
struct ovsdb_log *file;
int error;
unsigned long length;
};
static struct ovsdb_error *
parse_body(struct ovsdb_log *file, off_t offset, unsigned long int length,
uint8_t sha1[SHA1_DIGEST_SIZE], struct json **jsonp)
{
struct json_parser *parser;
struct sha1_ctx ctx;
sha1_init(&ctx);
parser = json_parser_create(JSPF_TRAILER);
while (length > 0) {
char input[BUFSIZ];
int chunk;
chunk = MIN(length, sizeof input);
if (fread(input, 1, chunk, file->stream) != chunk) {
json_parser_abort(parser);
return ovsdb_io_error(ferror(file->stream) ? errno : EOF,
"%s: error reading %lu bytes "
"starting at offset %lld", file->name,
length, (long long int) offset);
}
sha1_update(&ctx, input, chunk);
json_parser_feed(parser, input, chunk);
length -= chunk;
}
sha1_final(&ctx, sha1);
*jsonp = json_parser_finish(parser);
return NULL;
}
struct ovsdb_error *
ovsdb_log_read(struct ovsdb_log *file, struct json **jsonp)
{
uint8_t expected_sha1[SHA1_DIGEST_SIZE];
uint8_t actual_sha1[SHA1_DIGEST_SIZE];
struct ovsdb_error *error;
off_t data_offset;
unsigned long data_length;
struct json *json;
char header[128];
*jsonp = json = NULL;
if (file->read_error) {
return ovsdb_error_clone(file->read_error);
} else if (file->mode == OVSDB_LOG_WRITE) {
return OVSDB_BUG("reading file in write mode");
}
if (!fgets(header, sizeof header, file->stream)) {
if (feof(file->stream)) {
error = NULL;
} else {
error = ovsdb_io_error(errno, "%s: read failed", file->name);
}
goto error;
}
if (!parse_header(header, &data_length, expected_sha1)) {
error = ovsdb_syntax_error(NULL, NULL, "%s: parse error at offset "
"%lld in header line \"%.*s\"",
file->name, (long long int) file->offset,
(int) strcspn(header, "\n"), header);
goto error;
}
data_offset = file->offset + strlen(header);
error = parse_body(file, data_offset, data_length, actual_sha1, &json);
if (error) {
goto error;
}
if (memcmp(expected_sha1, actual_sha1, SHA1_DIGEST_SIZE)) {
error = ovsdb_syntax_error(NULL, NULL, "%s: %lu bytes starting at "
"offset %lld have SHA-1 hash "SHA1_FMT" "
"but should have hash "SHA1_FMT,
file->name, data_length,
(long long int) data_offset,
SHA1_ARGS(actual_sha1),
SHA1_ARGS(expected_sha1));
goto error;
}
if (json->type == JSON_STRING) {
error = ovsdb_syntax_error(NULL, NULL, "%s: %lu bytes starting at "
"offset %lld are not valid JSON (%s)",
file->name, data_length,
(long long int) data_offset,
json->u.string);
goto error;
}
file->prev_offset = file->offset;
file->offset = data_offset + data_length;
*jsonp = json;
return NULL;
error:
file->read_error = ovsdb_error_clone(error);
json_destroy(json);
return error;
}
/* Causes the log record read by the previous call to ovsdb_log_read() to be
* effectively discarded. The next call to ovsdb_log_write() will overwrite
* that previously read record.
*
* Calling this function more than once has no additional effect.
*
* This function is useful when ovsdb_log_read() successfully reads a record
* but that record does not make sense at a higher level (e.g. it specifies an
* invalid transaction). */
void
ovsdb_log_unread(struct ovsdb_log *file)
{
assert(file->mode == OVSDB_LOG_READ);
file->offset = file->prev_offset;
}
struct ovsdb_error *
ovsdb_log_write(struct ovsdb_log *file, struct json *json)
{
uint8_t sha1[SHA1_DIGEST_SIZE];
struct ovsdb_error *error;
char *json_string;
char header[128];
size_t length;
json_string = NULL;
if (file->write_error) {
return ovsdb_error_clone(file->write_error);
} else if (file->mode == OVSDB_LOG_READ) {
file->mode = OVSDB_LOG_WRITE;
if (fseeko(file->stream, file->offset, SEEK_SET)) {
error = ovsdb_io_error(errno, "%s: cannot seek to offset %lld",
file->name, (long long int) file->offset);
goto error;
}
if (ftruncate(fileno(file->stream), file->offset)) {
error = ovsdb_io_error(errno, "%s: cannot truncate to length %lld",
file->name, (long long int) file->offset);
goto error;
}
}
if (json->type != JSON_OBJECT && json->type != JSON_ARRAY) {
error = OVSDB_BUG("bad JSON type");
goto error;
}
/* Compose content. Add a new-line (replacing the null terminator) to make
* the file easier to read, even though it has no semantic value. */
json_string = json_to_string(json, 0);
length = strlen(json_string) + 1;
json_string[length - 1] = '\n';
/* Compose header. */
sha1_bytes(json_string, length, sha1);
snprintf(header, sizeof header, "%s%zu "SHA1_FMT"\n",
magic, length, SHA1_ARGS(sha1));
/* Write. */
if (fwrite(header, strlen(header), 1, file->stream) != 1
|| fwrite(json_string, length, 1, file->stream) != 1
|| fflush(file->stream))
{
error = ovsdb_io_error(errno, "%s: write failed", file->name);
/* Remove any partially written data, ignoring errors since there is
* nothing further we can do. */
ignore(ftruncate(fileno(file->stream), file->offset));
goto error;
}
file->offset += strlen(header) + length;
free(json_string);
return NULL;
error:
file->write_error = ovsdb_error_clone(error);
free(json_string);
return error;
}
struct ovsdb_error *
ovsdb_log_commit(struct ovsdb_log *file)
{
if (fsync(fileno(file->stream))) {
return ovsdb_io_error(errno, "%s: fsync failed", file->name);
}
return NULL;
}
/* Returns the current offset into the file backing 'log', in bytes. This
* reflects the number of bytes that have been read or written in the file. If
* the whole file has been read, this is the file size. */
off_t
ovsdb_log_get_offset(const struct ovsdb_log *log)
{
return log->offset;
}
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