/* Copyright (c) 2008, 2009, 2010, 2011, 2013 Nicira, Inc.

 *

 * 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 "entropy.h"

#include <errno.h>

#include <fcntl.h>

#include <unistd.h>

#include "util.h"

#include "socket-util.h"

#include "openvswitch/vlog.h"

VLOG_DEFINE_THIS_MODULE(entropy);

static const char urandom[] = "/dev/urandom";

/* Initializes 'buffer' with 'n' bytes of high-quality random numbers.  Returns

 * 0 if successful, otherwise a positive errno value or EOF on error. */

int

get_entropy(void *buffer, size_t n)

{

    size_t bytes_read;

    int error;

    int fd;

    fd = open(urandom, O_RDONLY);

    if (fd < 0) {

        VLOG_ERR("%s: open failed (%s)", urandom, ovs_strerror(errno));

        return errno ? errno : EINVAL;

    }

    error = read_fully(fd, buffer, n, &bytes_read);

    close(fd);

    if (error) {

        VLOG_ERR("%s: read error (%s)", urandom, ovs_retval_to_string(error));

    }

    return error;

}

/* Initializes 'buffer' with 'n' bytes of high-quality random numbers.  Exits

 * if an error occurs. */

void

get_entropy_or_die(void *buffer, size_t n)

{

    int error = get_entropy(buffer, n);

    if (error) {

        VLOG_FATAL("%s: read error (%s)",

                   urandom, ovs_retval_to_string(error));

    }

}