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// Copyright (C) 2019-2023 Algorand, Inc.
// This file is part of go-algorand
//
// go-algorand is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as
// published by the Free Software Foundation, either version 3 of the
// License, or (at your option) any later version.
//
// go-algorand 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 Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with go-algorand. If not, see <https://www.gnu.org/licenses/>.
package network
import (
"bytes"
"fmt"
"io"
"github.com/DataDog/zstd"
"github.com/algorand/go-algorand/logging"
"github.com/algorand/go-algorand/protocol"
)
var zstdCompressionMagic = [4]byte{0x28, 0xb5, 0x2f, 0xfd}
const zstdCompressionLevel = zstd.BestSpeed
// checkCanCompress checks if there is an proposal payload message and peers supporting compression
func checkCanCompress(request broadcastRequest, peers []*wsPeer) bool {
canCompress := false
hasPP := false
for _, tag := range request.tags {
if tag == protocol.ProposalPayloadTag {
hasPP = true
break
}
}
// if have proposal payload check if there are any peers supporting compression
if hasPP {
for _, peer := range peers {
if peer.pfProposalCompressionSupported() {
canCompress = true
break
}
}
}
return canCompress
}
// zstdCompressMsg returns a concatenation of a tag and compressed data
func zstdCompressMsg(tbytes []byte, d []byte) ([]byte, string) {
bound := zstd.CompressBound(len(d))
if bound < len(d) {
// although CompressBound allocated more than the src size, this is an implementation detail.
// increase the buffer size to always have enough space for the raw data if compression fails.
bound = len(d)
}
mbytesComp := make([]byte, len(tbytes)+bound)
copy(mbytesComp, tbytes)
comp, err := zstd.CompressLevel(mbytesComp[len(tbytes):], d, zstdCompressionLevel)
if err != nil {
// fallback and reuse non-compressed original data
logMsg := fmt.Sprintf("failed to compress into buffer of len %d: %v", len(d), err)
copied := copy(mbytesComp[len(tbytes):], d)
return mbytesComp[:len(tbytes)+copied], logMsg
}
mbytesComp = mbytesComp[:len(tbytes)+len(comp)]
return mbytesComp, ""
}
// MaxDecompressedMessageSize defines a maximum decompressed data size
// to prevent zip bombs. This depends on MaxTxnBytesPerBlock consensus parameter
// and should be larger.
const MaxDecompressedMessageSize = 20 * 1024 * 1024 // some large enough value
// wsPeerMsgDataConverter performs optional incoming messages conversion.
// At the moment it only supports zstd decompression for payload proposal
type wsPeerMsgDataConverter struct {
log logging.Logger
origin string
// actual converter(s)
ppdec zstdProposalDecompressor
}
type zstdProposalDecompressor struct {
active bool
}
func (dec zstdProposalDecompressor) enabled() bool {
return dec.active
}
func (dec zstdProposalDecompressor) accept(data []byte) bool {
return len(data) > 4 && bytes.Equal(data[:4], zstdCompressionMagic[:])
}
func (dec zstdProposalDecompressor) convert(data []byte) ([]byte, error) {
r := zstd.NewReader(bytes.NewReader(data))
defer r.Close()
b := make([]byte, 0, 3*len(data))
for {
if len(b) == cap(b) {
// grow capacity, retain length
b = append(b, 0)[:len(b)]
}
n, err := r.Read(b[len(b):cap(b)])
b = b[:len(b)+n]
if err != nil {
if err == io.EOF {
return b, nil
}
return nil, err
}
if len(b) > MaxDecompressedMessageSize {
return nil, fmt.Errorf("proposal data is too large: %d", len(b))
}
}
}
func (c *wsPeerMsgDataConverter) convert(tag protocol.Tag, data []byte) ([]byte, error) {
if tag == protocol.ProposalPayloadTag {
if c.ppdec.enabled() {
// sender might support compressed payload but fail to compress for whatever reason,
// in this case it sends non-compressed payload - the receiver decompress only if it is compressed.
if c.ppdec.accept(data) {
res, err := c.ppdec.convert(data)
if err != nil {
return nil, fmt.Errorf("peer %s: %w", c.origin, err)
}
return res, nil
}
c.log.Warnf("peer %s supported zstd but sent non-compressed data", c.origin)
}
}
return data, nil
}
func makeWsPeerMsgDataConverter(wp *wsPeer) *wsPeerMsgDataConverter {
c := wsPeerMsgDataConverter{
log: wp.log,
origin: wp.originAddress,
}
if wp.pfProposalCompressionSupported() {
c.ppdec = zstdProposalDecompressor{
active: true,
}
}
return &c
}
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