plugeth/les/sync.go

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// Copyright 2016 The go-ethereum Authors
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// 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 les
import (
"context"
"errors"
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"time"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/core/rawdb"
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"github.com/ethereum/go-ethereum/eth/downloader"
"github.com/ethereum/go-ethereum/light"
"github.com/ethereum/go-ethereum/log"
)
var errInvalidCheckpoint = errors.New("invalid advertised checkpoint")
const (
// lightSync starts syncing from the current highest block.
// If the chain is empty, syncing the entire header chain.
lightSync = iota
// legacyCheckpointSync starts syncing from a hardcoded checkpoint.
legacyCheckpointSync
// checkpointSync starts syncing from a checkpoint signed by trusted
// signer or hardcoded checkpoint for compatibility.
checkpointSync
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)
// validateCheckpoint verifies the advertised checkpoint by peer is valid or not.
//
// Each network has several hard-coded checkpoint signer addresses. Only the
// checkpoint issued by the specified signer is considered valid.
//
// In addition to the checkpoint registered in the registrar contract, there are
// several legacy hardcoded checkpoints in our codebase. These checkpoints are
// also considered as valid.
func (h *clientHandler) validateCheckpoint(peer *peer) error {
ctx, cancel := context.WithTimeout(context.Background(), time.Second*10)
defer cancel()
// Fetch the block header corresponding to the checkpoint registration.
cp := peer.checkpoint
header, err := light.GetUntrustedHeaderByNumber(ctx, h.backend.odr, peer.checkpointNumber, peer.id)
if err != nil {
return err
}
// Fetch block logs associated with the block header.
logs, err := light.GetUntrustedBlockLogs(ctx, h.backend.odr, header)
if err != nil {
return err
}
events := h.backend.oracle.contract.LookupCheckpointEvents(logs, cp.SectionIndex, cp.Hash())
if len(events) == 0 {
return errInvalidCheckpoint
}
var (
index = events[0].Index
hash = events[0].CheckpointHash
signatures [][]byte
)
for _, event := range events {
signatures = append(signatures, append(event.R[:], append(event.S[:], event.V)...))
}
valid, signers := h.backend.oracle.verifySigners(index, hash, signatures)
if !valid {
return errInvalidCheckpoint
}
log.Warn("Verified advertised checkpoint", "peer", peer.id, "signers", len(signers))
return nil
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}
// synchronise tries to sync up our local chain with a remote peer.
func (h *clientHandler) synchronise(peer *peer) {
// Short circuit if the peer is nil.
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if peer == nil {
return
}
// Make sure the peer's TD is higher than our own.
latest := h.backend.blockchain.CurrentHeader()
currentTd := rawdb.ReadTd(h.backend.chainDb, latest.Hash(), latest.Number.Uint64())
if currentTd != nil && peer.headBlockInfo().Td.Cmp(currentTd) < 0 {
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return
}
// Recap the checkpoint.
//
// The light client may be connected to several different versions of the server.
// (1) Old version server which can not provide stable checkpoint in the handshake packet.
// => Use hardcoded checkpoint or empty checkpoint
// (2) New version server but simple checkpoint syncing is not enabled(e.g. mainnet, new testnet or private network)
// => Use hardcoded checkpoint or empty checkpoint
// (3) New version server but the provided stable checkpoint is even lower than the hardcoded one.
// => Use hardcoded checkpoint
// (4) New version server with valid and higher stable checkpoint
// => Use provided checkpoint
var checkpoint = &peer.checkpoint
var hardcoded bool
if h.checkpoint != nil && h.checkpoint.SectionIndex >= peer.checkpoint.SectionIndex {
checkpoint = h.checkpoint // Use the hardcoded one.
hardcoded = true
}
// Determine whether we should run checkpoint syncing or normal light syncing.
//
// Here has four situations that we will disable the checkpoint syncing:
//
// 1. The checkpoint is empty
// 2. The latest head block of the local chain is above the checkpoint.
// 3. The checkpoint is hardcoded(recap with local hardcoded checkpoint)
// 4. For some networks the checkpoint syncing is not activated.
mode := checkpointSync
switch {
case checkpoint.Empty():
mode = lightSync
log.Debug("Disable checkpoint syncing", "reason", "empty checkpoint")
case latest.Number.Uint64() >= (checkpoint.SectionIndex+1)*h.backend.iConfig.ChtSize-1:
mode = lightSync
log.Debug("Disable checkpoint syncing", "reason", "local chain beyond the checkpoint")
case hardcoded:
mode = legacyCheckpointSync
log.Debug("Disable checkpoint syncing", "reason", "checkpoint is hardcoded")
case h.backend.oracle == nil || !h.backend.oracle.isRunning():
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if h.checkpoint == nil {
mode = lightSync // Downgrade to light sync unfortunately.
} else {
checkpoint = h.checkpoint
mode = legacyCheckpointSync
}
log.Debug("Disable checkpoint syncing", "reason", "checkpoint syncing is not activated")
}
// Notify testing framework if syncing has completed(for testing purpose).
defer func() {
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if h.syncDone != nil {
h.syncDone()
}
}()
start := time.Now()
if mode == checkpointSync || mode == legacyCheckpointSync {
// Validate the advertised checkpoint
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if mode == checkpointSync {
if err := h.validateCheckpoint(peer); err != nil {
log.Debug("Failed to validate checkpoint", "reason", err)
h.removePeer(peer.id)
return
}
h.backend.blockchain.AddTrustedCheckpoint(checkpoint)
}
log.Debug("Checkpoint syncing start", "peer", peer.id, "checkpoint", checkpoint.SectionIndex)
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// Fetch the start point block header.
//
// For the ethash consensus engine, the start header is the block header
// of the checkpoint.
//
// For the clique consensus engine, the start header is the block header
// of the latest epoch covered by checkpoint.
ctx, cancel := context.WithTimeout(context.Background(), time.Second*5)
defer cancel()
if !checkpoint.Empty() && !h.backend.blockchain.SyncCheckpoint(ctx, checkpoint) {
log.Debug("Sync checkpoint failed")
h.removePeer(peer.id)
return
}
}
// Fetch the remaining block headers based on the current chain header.
if err := h.downloader.Synchronise(peer.id, peer.Head(), peer.Td(), downloader.LightSync); err != nil {
log.Debug("Synchronise failed", "reason", err)
return
}
log.Debug("Synchronise finished", "elapsed", common.PrettyDuration(time.Since(start)))
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}