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/*
* OpenVPN -- An application to securely tunnel IP networks
* over a single UDP port, with support for SSL/TLS-based
* session authentication and key exchange,
* packet encryption, packet authentication, and
* packet compression.
*
* Copyright (C) 2002-2012 OpenVPN Technologies, Inc. <sales@openvpn.net>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2
* as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program (see the file COPYING included with this
* distribution); if not, write to the Free Software Foundation, Inc.,
* 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#ifdef HAVE_CONFIG_H
#include "config.h"
#elif defined(_MSC_VER)
#include "config-msvc.h"
#endif
#include "syshead.h"
#if defined(ENABLE_SNAPPY)
#include "snappy-c.h"
#include "comp.h"
#include "error.h"
#include "otime.h"
#include "memdbg.h"
/* Initial command byte to tell our peer if we compressed */
#define SNAPPY_COMPRESS_BYTE 0x68
static void
snap_compress_init (struct compress_context *compctx)
{
msg (D_INIT_MEDIUM, "Snappy compression initializing");
ASSERT(compctx->flags & COMP_F_SWAP);
}
static void
snap_compress_uninit (struct compress_context *compctx)
{
}
static void
snap_compress (struct buffer *buf, struct buffer work,
struct compress_context *compctx,
const struct frame* frame)
{
snappy_status status;
bool compressed = false;
if (buf->len <= 0)
return;
/*
* In order to attempt compression, length must be at least COMPRESS_THRESHOLD.
*/
if (buf->len >= COMPRESS_THRESHOLD)
{
const size_t ps = PAYLOAD_SIZE (frame);
size_t zlen = ps + COMP_EXTRA_BUFFER (ps);
ASSERT (buf_init (&work, FRAME_HEADROOM (frame)));
ASSERT (buf_safe (&work, zlen));
if (buf->len > ps)
{
dmsg (D_COMP_ERRORS, "Snappy compression buffer overflow");
buf->len = 0;
return;
}
status = snappy_compress((const char *)BPTR(buf), (size_t)BLEN(buf), (char *)BPTR(&work), &zlen);
if (status != SNAPPY_OK)
{
dmsg (D_COMP_ERRORS, "Snappy compression error: %d", status);
buf->len = 0;
return;
}
ASSERT (buf_safe (&work, zlen));
work.len = zlen;
compressed = true;
dmsg (D_COMP, "Snappy compress %d -> %d", buf->len, work.len);
compctx->pre_compress += buf->len;
compctx->post_compress += work.len;
}
/* did compression save us anything? */
{
uint8_t comp_head_byte = NO_COMPRESS_BYTE_SWAP;
if (compressed && work.len < buf->len)
{
*buf = work;
comp_head_byte = SNAPPY_COMPRESS_BYTE;
}
{
uint8_t *head = BPTR (buf);
uint8_t *tail = BEND (buf);
ASSERT (buf_safe (buf, 1));
++buf->len;
/* move head byte of payload to tail */
*tail = *head;
*head = comp_head_byte;
}
}
}
static void
snap_decompress (struct buffer *buf, struct buffer work,
struct compress_context *compctx,
const struct frame* frame)
{
size_t zlen = EXPANDED_SIZE (frame);
snappy_status status;
uint8_t c; /* flag indicating whether or not our peer compressed */
if (buf->len <= 0)
return;
ASSERT (buf_init (&work, FRAME_HEADROOM (frame)));
/* do unframing/swap (assumes buf->len > 0) */
{
uint8_t *head = BPTR (buf);
c = *head;
--buf->len;
*head = *BEND (buf);
}
if (c == SNAPPY_COMPRESS_BYTE) /* packet was compressed */
{
ASSERT (buf_safe (&work, zlen));
status = snappy_uncompress((const char *)BPTR(buf), (size_t)BLEN(buf), (char *)BPTR(&work), &zlen);
if (status != SNAPPY_OK)
{
dmsg (D_COMP_ERRORS, "Snappy decompression error: %d", status);
buf->len = 0;
return;
}
ASSERT (buf_safe (&work, zlen));
work.len = zlen;
dmsg (D_COMP, "Snappy decompress %d -> %d", buf->len, work.len);
compctx->pre_decompress += buf->len;
compctx->post_decompress += work.len;
*buf = work;
}
else if (c == NO_COMPRESS_BYTE_SWAP) /* packet was not compressed */
{
;
}
else
{
dmsg (D_COMP_ERRORS, "Bad Snappy decompression header byte: %d", c);
buf->len = 0;
}
}
const struct compress_alg snappy_alg = {
"snappy",
snap_compress_init,
snap_compress_uninit,
snap_compress,
snap_decompress
};
#else
static void dummy(void) {}
#endif /* ENABLE_SNAPPY */
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