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// OpenVPN -- An application to securely tunnel IP networks
// over a single port, with support for SSL/TLS-based
// session authentication and key exchange,
// packet encryption, packet authentication, and
// packet compression.
//
// Copyright (C) 2012- OpenVPN Inc.
//
// SPDX-License-Identifier: MPL-2.0 OR AGPL-3.0-only WITH openvpn3-openssl-exception
//
#ifndef OPENVPN_COMPRESS_LZ4_H
#define OPENVPN_COMPRESS_LZ4_H
// Implement LZ4 compression.
// Should only be included by compress.hpp
#include <algorithm> // for std::max
#include <openvpn/common/numeric_util.hpp>
#include <lz4.h>
namespace openvpn {
class CompressLZ4Base : public Compress
{
protected:
CompressLZ4Base(const Frame::Ptr &frame, const SessionStats::Ptr &stats)
: Compress(frame, stats)
{
}
bool do_decompress(BufferAllocated &buf)
{
auto prepRes = frame->prepare(Frame::DECOMPRESS_WORK, work);
if (!numeric_util::is_safe_conversion<const int>(prepRes))
return false;
// initialize work buffer
auto payload_size = static_cast<const int>(prepRes);
// do uncompress
const int decomp_size = LZ4_decompress_safe((const char *)buf.c_data(),
(char *)work.data(),
(int)buf.size(),
payload_size);
if (decomp_size < 0)
{
error(buf);
return false;
}
OVPN_LOG_VERBOSE("LZ4 uncompress " << buf.size() << " -> " << decomp_size);
work.set_size(decomp_size);
buf.swap(work);
return true;
}
bool do_compress(BufferAllocated &buf)
{
// initialize work buffer
frame->prepare(Frame::COMPRESS_WORK, work);
// verify that input data length is not too large
if (lz4_extra_buffer(buf.size()) > work.max_size())
{
error(buf);
return false;
}
// do compress
const unsigned int comp_size = LZ4_compress_default((const char *)buf.c_data(),
(char *)work.data(),
(int)buf.size(),
(int)work.capacity());
// did compression actually reduce data length?
if (comp_size < buf.size())
{
if (comp_size <= 0)
{
error(buf);
return false;
}
OVPN_LOG_VERBOSE("LZ4 compress " << buf.size() << " -> " << comp_size);
work.set_size(comp_size);
buf.swap(work);
return true;
}
else
return false;
}
// Worst case size expansion on compress.
// Official LZ4 worst-case size expansion alg is
// LZ4_COMPRESSBOUND macro in lz4.h.
// However we optimize it slightly here to lose the integer division
// when len < 65535.
size_t lz4_extra_buffer(const size_t len)
{
if (likely(len < 65535))
return len + len / 256 + 17;
else
return len + len / 255 + 16;
}
BufferAllocated work;
};
class CompressLZ4 : public CompressLZ4Base
{
// magic number for LZ4 compression
enum
{
LZ4_COMPRESS = 0x69,
};
public:
CompressLZ4(const Frame::Ptr &frame, const SessionStats::Ptr &stats, const bool asym_arg)
: CompressLZ4Base(frame, stats),
asym(asym_arg)
{
OVPN_LOG_INFO("LZ4 init asym=" << asym_arg);
}
const char *name() const override
{
return "lz4";
}
void compress(BufferAllocated &buf, const bool hint) override
{
// skip null packets
if (!buf.size())
return;
if (hint && !asym)
{
if (do_compress(buf))
{
do_swap(buf, LZ4_COMPRESS);
return;
}
}
// indicate that we didn't compress
do_swap(buf, NO_COMPRESS_SWAP);
}
void decompress(BufferAllocated &buf) override
{
// skip null packets
if (!buf.size())
return;
const unsigned char c = buf.pop_front();
switch (c)
{
case NO_COMPRESS_SWAP:
do_unswap(buf);
break;
case LZ4_COMPRESS:
do_unswap(buf);
do_decompress(buf);
break;
default:
error(buf); // unknown op
}
}
private:
const bool asym;
};
class CompressLZ4v2 : public CompressLZ4Base
{
public:
CompressLZ4v2(const Frame::Ptr &frame, const SessionStats::Ptr &stats, const bool asym_arg)
: CompressLZ4Base(frame, stats),
asym(asym_arg)
{
OVPN_LOG_INFO("LZ4v2 init asym=" << asym_arg);
}
const char *name() const override
{
return "lz4v2";
}
void compress(BufferAllocated &buf, const bool hint) override
{
// skip null packets
if (!buf.size())
return;
if (hint && !asym)
{
if (do_compress(buf))
{
v2_push(buf, OVPN_COMPv2_LZ4);
return;
}
}
// indicate that we didn't compress
v2_push(buf, OVPN_COMPv2_NONE);
}
void decompress(BufferAllocated &buf) override
{
// skip null packets
if (!buf.size())
return;
const int c = v2_pull(buf);
switch (c)
{
case OVPN_COMPv2_NONE:
break;
case OVPN_COMPv2_LZ4:
do_decompress(buf);
break;
default:
error(buf); // unknown op
}
}
private:
const bool asym;
};
} // namespace openvpn
#endif
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