path: root/light/postprocess.go

// Copyright 2017 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library 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 Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.

package light

import (
    "context"
    "encoding/binary"
    "errors"
    "fmt"
    "math/big"
    "time"

    "github.com/ethereum/go-ethereum/common"
    "github.com/ethereum/go-ethereum/common/bitutil"
    "github.com/ethereum/go-ethereum/core"
    "github.com/ethereum/go-ethereum/core/rawdb"
    "github.com/ethereum/go-ethereum/core/types"
    "github.com/ethereum/go-ethereum/ethdb"
    "github.com/ethereum/go-ethereum/log"
    "github.com/ethereum/go-ethereum/params"
    "github.com/ethereum/go-ethereum/rlp"
    "github.com/ethereum/go-ethereum/trie"
)

const (
    // CHTFrequencyClient is the block frequency for creating CHTs on the client side.
    CHTFrequencyClient = 32768

    // CHTFrequencyServer is the block frequency for creating CHTs on the server side.
    // Eventually this can be merged back with the client version, but that requires a
    // full database upgrade, so that should be left for a suitable moment.
    CHTFrequencyServer = 4096

    HelperTrieConfirmations        = 2048 // number of confirmations before a server is expected to have the given HelperTrie available
    HelperTrieProcessConfirmations = 256  // number of confirmations before a HelperTrie is generated
)

// TrustedCheckpoint represents a set of post-processed trie roots (CHT and BloomTrie) associated with
// the appropriate section index and head hash. It is used to start light syncing from this checkpoint
// and avoid downloading the entire header chain while still being able to securely access old headers/logs.
type TrustedCheckpoint struct {
    name                            string
    SectionIdx                      uint64
    SectionHead, CHTRoot, BloomRoot common.Hash
}

var (
    mainnetCheckpoint = TrustedCheckpoint{
        name:        "mainnet",
        SectionIdx:  179,
        SectionHead: common.HexToHash("ae778e455492db1183e566fa0c67f954d256fdd08618f6d5a393b0e24576d0ea"),
        CHTRoot:     common.HexToHash("646b338f9ca74d936225338916be53710ec84020b89946004a8605f04c817f16"),
        BloomRoot:   common.HexToHash("d0f978f5dbc86e5bf931d8dd5b2ecbebbda6dc78f8896af6a27b46a3ced0ac25"),
    }

    ropstenCheckpoint = TrustedCheckpoint{
        name:        "ropsten",
        SectionIdx:  107,
        SectionHead: common.HexToHash("e1988f95399debf45b873e065e5cd61b416ef2e2e5deec5a6f87c3127086e1ce"),
        CHTRoot:     common.HexToHash("15cba18e4de0ab1e95e202625199ba30147aec8b0b70384b66ebea31ba6a18e0"),
        BloomRoot:   common.HexToHash("e00fa6389b2e597d9df52172cd8e936879eed0fca4fa59db99e2c8ed682562f2"),
    }
)

// trustedCheckpoints associates each known checkpoint with the genesis hash of the chain it belongs to
var trustedCheckpoints = map[common.Hash]TrustedCheckpoint{
    params.MainnetGenesisHash: mainnetCheckpoint,
    params.TestnetGenesisHash: ropstenCheckpoint,
}

var (
    ErrNoTrustedCht       = errors.New("No trusted canonical hash trie")
    ErrNoTrustedBloomTrie = errors.New("No trusted bloom trie")
    ErrNoHeader           = errors.New("Header not found")
    chtPrefix             = []byte("chtRoot-") // chtPrefix + chtNum (uint64 big endian) -> trie root hash
    ChtTablePrefix        = "cht-"
)

// ChtNode structures are stored in the Canonical Hash Trie in an RLP encoded format
type ChtNode struct {
    Hash common.Hash
    Td   *big.Int
}

// GetChtRoot reads the CHT root assoctiated to the given section from the database
// Note that sectionIdx is specified according to LES/1 CHT section size
func GetChtRoot(db ethdb.Database, sectionIdx uint64, sectionHead common.Hash) common.Hash {
    var encNumber [8]byte
    binary.BigEndian.PutUint64(encNumber[:], sectionIdx)
    data, _ := db.Get(append(append(chtPrefix, encNumber[:]...), sectionHead.Bytes()...))
    return common.BytesToHash(data)
}

// GetChtV2Root reads the CHT root assoctiated to the given section from the database
// Note that sectionIdx is specified according to LES/2 CHT section size
func GetChtV2Root(db ethdb.Database, sectionIdx uint64, sectionHead common.Hash) common.Hash {
    return GetChtRoot(db, (sectionIdx+1)*(CHTFrequencyClient/CHTFrequencyServer)-1, sectionHead)
}

// StoreChtRoot writes the CHT root assoctiated to the given section into the database
// Note that sectionIdx is specified according to LES/1 CHT section size
func StoreChtRoot(db ethdb.Database, sectionIdx uint64, sectionHead, root common.Hash) {
    var encNumber [8]byte
    binary.BigEndian.PutUint64(encNumber[:], sectionIdx)
    db.Put(append(append(chtPrefix, encNumber[:]...), sectionHead.Bytes()...), root.Bytes())
}

// ChtIndexerBackend implements core.ChainIndexerBackend
type ChtIndexerBackend struct {
    diskdb, trieTable    ethdb.Database
    odr                  OdrBackend
    triedb               *trie.Database
    section, sectionSize uint64
    lastHash             common.Hash
    trie                 *trie.Trie
}

// NewBloomTrieIndexer creates a BloomTrie chain indexer
func NewChtIndexer(db ethdb.Database, clientMode bool, odr OdrBackend) *core.ChainIndexer {
    var sectionSize, confirmReq uint64
    if clientMode {
        sectionSize = CHTFrequencyClient
        confirmReq = HelperTrieConfirmations
    } else {
        sectionSize = CHTFrequencyServer
        confirmReq = HelperTrieProcessConfirmations
    }
    idb := ethdb.NewTable(db, "chtIndex-")
    trieTable := ethdb.NewTable(db, ChtTablePrefix)
    backend := &ChtIndexerBackend{
        diskdb:      db,
        odr:         odr,
        trieTable:   trieTable,
        triedb:      trie.NewDatabase(trieTable),
        sectionSize: sectionSize,
    }
    return core.NewChainIndexer(db, idb, backend, sectionSize, confirmReq, time.Millisecond*100, "cht")
}

// fetchMissingNodes tries to retrieve the last entry of the latest trusted CHT from the
// ODR backend in order to be able to add new entries and calculate subsequent root hashes
func (c *ChtIndexerBackend) fetchMissingNodes(ctx context.Context, section uint64, root common.Hash) error {
    batch := c.trieTable.NewBatch()
    r := &ChtRequest{ChtRoot: root, ChtNum: section - 1, BlockNum: section*c.sectionSize - 1}
    for {
        err := c.odr.Retrieve(ctx, r)
        switch err {
        case nil:
            r.Proof.Store(batch)
            return batch.Write()
        case ErrNoPeers:
            // if there are no peers to serve, retry later
            select {
            case <-ctx.Done():
                return ctx.Err()
            case <-time.After(time.Second * 10):
                // stay in the loop and try again
            }
        default:
            return err
        }
    }
}

// Reset implements core.ChainIndexerBackend
func (c *ChtIndexerBackend) Reset(ctx context.Context, section uint64, lastSectionHead common.Hash) error {
    var root common.Hash
    if section > 0 {
        root = GetChtRoot(c.diskdb, section-1, lastSectionHead)
    }
    var err error
    c.trie, err = trie.New(root, c.triedb)

    if err != nil && c.odr != nil {
        err = c.fetchMissingNodes(ctx, section, root)
        if err == nil {
            c.trie, err = trie.New(root, c.triedb)
        }
    }

    c.section = section
    return err
}

// Process implements core.ChainIndexerBackend
func (c *ChtIndexerBackend) Process(ctx context.Context, header *types.Header) error {
    hash, num := header.Hash(), header.Number.Uint64()
    c.lastHash = hash

    td := rawdb.ReadTd(c.diskdb, hash, num)
    if td == nil {
        panic(nil)
    }
    var encNumber [8]byte
    binary.BigEndian.PutUint64(encNumber[:], num)
    data, _ := rlp.EncodeToBytes(ChtNode{hash, td})
    c.trie.Update(encNumber[:], data)
    return nil
}

// Commit implements core.ChainIndexerBackend
func (c *ChtIndexerBackend) Commit() error {
    root, err := c.trie.Commit(nil)
    if err != nil {
        return err
    }
    c.triedb.Commit(root, false)

    if ((c.section+1)*c.sectionSize)%CHTFrequencyClient == 0 {
        log.Info("Storing CHT", "section", c.section*c.sectionSize/CHTFrequencyClient, "head", fmt.Sprintf("%064x", c.lastHash), "root", fmt.Sprintf("%064x", root))
    }
    StoreChtRoot(c.diskdb, c.section, c.lastHash, root)
    return nil
}

const (
    BloomTrieFrequency  = 32768
    ethBloomBitsSection = 4096
)

var (
    bloomTriePrefix      = []byte("bltRoot-") // bloomTriePrefix + bloomTrieNum (uint64 big endian) -> trie root hash
    BloomTrieTablePrefix = "blt-"
)

// GetBloomTrieRoot reads the BloomTrie root assoctiated to the given section from the database
func GetBloomTrieRoot(db ethdb.Database, sectionIdx uint64, sectionHead common.Hash) common.Hash {
    var encNumber [8]byte
    binary.BigEndian.PutUint64(encNumber[:], sectionIdx)
    data, _ := db.Get(append(append(bloomTriePrefix, encNumber[:]...), sectionHead.Bytes()...))
    return common.BytesToHash(data)
}

// StoreBloomTrieRoot writes the BloomTrie root assoctiated to the given section into the database
func StoreBloomTrieRoot(db ethdb.Database, sectionIdx uint64, sectionHead, root common.Hash) {
    var encNumber [8]byte
    binary.BigEndian.PutUint64(encNumber[:], sectionIdx)
    db.Put(append(append(bloomTriePrefix, encNumber[:]...), sectionHead.Bytes()...), root.Bytes())
}

// BloomTrieIndexerBackend implements core.ChainIndexerBackend
type BloomTrieIndexerBackend struct {
    diskdb, trieTable                          ethdb.Database
    odr                                        OdrBackend
    triedb                                     *trie.Database
    section, parentSectionSize, bloomTrieRatio uint64
    trie                                       *trie.Trie
    sectionHeads                               []common.Hash
}

// NewBloomTrieIndexer creates a BloomTrie chain indexer
func NewBloomTrieIndexer(db ethdb.Database, clientMode bool, odr OdrBackend) *core.ChainIndexer {
    trieTable := ethdb.NewTable(db, BloomTrieTablePrefix)
    backend := &BloomTrieIndexerBackend{
        diskdb:    db,
        odr:       odr,
        trieTable: trieTable,
        triedb:    trie.NewDatabase(trieTable),
    }
    idb := ethdb.NewTable(db, "bltIndex-")

    if clientMode {
        backend.parentSectionSize = BloomTrieFrequency
    } else {
        backend.parentSectionSize = ethBloomBitsSection
    }
    backend.bloomTrieRatio = BloomTrieFrequency / backend.parentSectionSize
    backend.sectionHeads = make([]common.Hash, backend.bloomTrieRatio)
    return core.NewChainIndexer(db, idb, backend, BloomTrieFrequency, 0, time.Millisecond*100, "bloomtrie")
}

// fetchMissingNodes tries to retrieve the last entries of the latest trusted bloom trie from the
// ODR backend in order to be able to add new entries and calculate subsequent root hashes
func (b *BloomTrieIndexerBackend) fetchMissingNodes(ctx context.Context, section uint64, root common.Hash) error {
    indexCh := make(chan uint, types.BloomBitLength)
    type res struct {
        nodes *NodeSet
        err   error
    }
    resCh := make(chan res, types.BloomBitLength)
    for i := 0; i < 20; i++ {
        go func() {
            for bitIndex := range indexCh {
                r := &BloomRequest{BloomTrieRoot: root, BloomTrieNum: section - 1, BitIdx: bitIndex, SectionIdxList: []uint64{section - 1}}
                for {
                    if err := b.odr.Retrieve(ctx, r); err == ErrNoPeers {
                        // if there are no peers to serve, retry later
                        select {
                        case <-ctx.Done():
                            resCh <- res{nil, ctx.Err()}
                            return
                        case <-time.After(time.Second * 10):
                            // stay in the loop and try again
                        }
                    } else {
                        resCh <- res{r.Proofs, err}
                        break
                    }
                }
            }
        }()
    }

    for i := uint(0); i < types.BloomBitLength; i++ {
        indexCh <- i
    }
    close(indexCh)
    batch := b.trieTable.NewBatch()
    for i := uint(0); i < types.BloomBitLength; i++ {
        res := <-resCh
        if res.err != nil {
            return res.err
        }
        res.nodes.Store(batch)
    }
    return batch.Write()
}

// Reset implements core.ChainIndexerBackend
func (b *BloomTrieIndexerBackend) Reset(ctx context.Context, section uint64, lastSectionHead common.Hash) error {
    var root common.Hash
    if section > 0 {
        root = GetBloomTrieRoot(b.diskdb, section-1, lastSectionHead)
    }
    var err error
    b.trie, err = trie.New(root, b.triedb)
    if err != nil && b.odr != nil {
        err = b.fetchMissingNodes(ctx, section, root)
        if err == nil {
            b.trie, err = trie.New(root, b.triedb)
        }
    }
    b.section = section
    return err
}

// Process implements core.ChainIndexerBackend
func (b *BloomTrieIndexerBackend) Process(ctx context.Context, header *types.Header) error {
    num := header.Number.Uint64() - b.section*BloomTrieFrequency
    if (num+1)%b.parentSectionSize == 0 {
        b.sectionHeads[num/b.parentSectionSize] = header.Hash()
    }
    return nil
}

// Commit implements core.ChainIndexerBackend
func (b *BloomTrieIndexerBackend) Commit() error {
    var compSize, decompSize uint64

    for i := uint(0); i < types.BloomBitLength; i++ {
        var encKey [10]byte
        binary.BigEndian.PutUint16(encKey[0:2], uint16(i))
        binary.BigEndian.PutUint64(encKey[2:10], b.section)
        var decomp []byte
        for j := uint64(0); j < b.bloomTrieRatio; j++ {
            data, err := rawdb.ReadBloomBits(b.diskdb, i, b.section*b.bloomTrieRatio+j, b.sectionHeads[j])
            if err != nil {
                return err
            }
            decompData, err2 := bitutil.DecompressBytes(data, int(b.parentSectionSize/8))
            if err2 != nil {
                return err2
            }
            decomp = append(decomp, decompData...)
        }
        comp := bitutil.CompressBytes(decomp)

        decompSize += uint64(len(decomp))
        compSize += uint64(len(comp))
        if len(comp) > 0 {
            b.trie.Update(encKey[:], comp)
        } else {
            b.trie.Delete(encKey[:])
        }
    }
    root, err := b.trie.Commit(nil)
    if err != nil {
        return err
    }
    b.triedb.Commit(root, false)

    sectionHead := b.sectionHeads[b.bloomTrieRatio-1]
    log.Info("Storing bloom trie", "section", b.section, "head", fmt.Sprintf("%064x", sectionHead), "root", fmt.Sprintf("%064x", root), "compression", float64(compSize)/float64(decompSize))
    StoreBloomTrieRoot(b.diskdb, b.section, sectionHead, root)

    return nil
}