eth, les, light: enforce CHT checkpoints on fast-sync too

This commit is contained in:
Péter Szilágyi 2019-04-16 13:20:38 +03:00
parent 78d90c47f7
commit 38f6b85638
No known key found for this signature in database
GPG Key ID: E9AE538CEDF8293D
11 changed files with 208 additions and 112 deletions

View File

@ -376,7 +376,7 @@ func copyDb(ctx *cli.Context) error {
chain, chainDb := utils.MakeChain(ctx, stack)
syncmode := *utils.GlobalTextMarshaler(ctx, utils.SyncModeFlag.Name).(*downloader.SyncMode)
dl := downloader.New(syncmode, chainDb, new(event.TypeMux), chain, nil, nil)
dl := downloader.New(syncmode, 0, chainDb, new(event.TypeMux), chain, nil, nil)
// Create a source peer to satisfy downloader requests from
db, err := rawdb.NewLevelDBDatabase(ctx.Args().First(), ctx.GlobalInt(utils.CacheFlag.Name), 256, "")

View File

@ -75,6 +75,7 @@ var (
errUnknownPeer = errors.New("peer is unknown or unhealthy")
errBadPeer = errors.New("action from bad peer ignored")
errStallingPeer = errors.New("peer is stalling")
errUnsyncedPeer = errors.New("unsynced peer")
errNoPeers = errors.New("no peers to keep download active")
errTimeout = errors.New("timeout")
errEmptyHeaderSet = errors.New("empty header set by peer")
@ -99,6 +100,7 @@ type Downloader struct {
mode SyncMode // Synchronisation mode defining the strategy used (per sync cycle)
mux *event.TypeMux // Event multiplexer to announce sync operation events
checkpoint uint64 // Checkpoint block number to enforce head against (e.g. fast sync)
genesis uint64 // Genesis block number to limit sync to (e.g. light client CHT)
queue *queue // Scheduler for selecting the hashes to download
peers *peerSet // Set of active peers from which download can proceed
@ -205,15 +207,15 @@ type BlockChain interface {
}
// New creates a new downloader to fetch hashes and blocks from remote peers.
func New(mode SyncMode, stateDb ethdb.Database, mux *event.TypeMux, chain BlockChain, lightchain LightChain, dropPeer peerDropFn) *Downloader {
func New(mode SyncMode, checkpoint uint64, stateDb ethdb.Database, mux *event.TypeMux, chain BlockChain, lightchain LightChain, dropPeer peerDropFn) *Downloader {
if lightchain == nil {
lightchain = chain
}
dl := &Downloader{
mode: mode,
stateDB: stateDb,
mux: mux,
checkpoint: checkpoint,
queue: newQueue(),
peers: newPeerSet(),
rttEstimate: uint64(rttMaxEstimate),
@ -326,7 +328,7 @@ func (d *Downloader) Synchronise(id string, head common.Hash, td *big.Int, mode
case nil:
case errBusy:
case errTimeout, errBadPeer, errStallingPeer,
case errTimeout, errBadPeer, errStallingPeer, errUnsyncedPeer,
errEmptyHeaderSet, errPeersUnavailable, errTooOld,
errInvalidAncestor, errInvalidChain:
log.Warn("Synchronisation failed, dropping peer", "peer", id, "err", err)
@ -578,6 +580,10 @@ func (d *Downloader) fetchHeight(p *peerConnection) (*types.Header, error) {
return nil, errBadPeer
}
head := headers[0]
if d.mode == FastSync && head.Number.Uint64() < d.checkpoint {
p.log.Warn("Remote head below checkpoint", "number", head.Number, "hash", head.Hash())
return nil, errUnsyncedPeer
}
p.log.Debug("Remote head header identified", "number", head.Number, "hash", head.Hash())
return head, nil

View File

@ -26,7 +26,7 @@ import (
"testing"
"time"
ethereum "github.com/ethereum/go-ethereum"
"github.com/ethereum/go-ethereum"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/core/rawdb"
"github.com/ethereum/go-ethereum/core/types"
@ -75,7 +75,7 @@ func newTester() *downloadTester {
tester.stateDb = rawdb.NewMemoryDatabase()
tester.stateDb.Put(testGenesis.Root().Bytes(), []byte{0x00})
tester.downloader = New(FullSync, tester.stateDb, new(event.TypeMux), tester, nil, tester.dropPeer)
tester.downloader = New(FullSync, 0, tester.stateDb, new(event.TypeMux), tester, nil, tester.dropPeer)
return tester
}
@ -1051,6 +1051,7 @@ func testBlockHeaderAttackerDropping(t *testing.T, protocol int) {
{errUnknownPeer, false}, // Peer is unknown, was already dropped, don't double drop
{errBadPeer, true}, // Peer was deemed bad for some reason, drop it
{errStallingPeer, true}, // Peer was detected to be stalling, drop it
{errUnsyncedPeer, true}, // Peer was detected to be unsynced, drop it
{errNoPeers, false}, // No peers to download from, soft race, no issue
{errTimeout, true}, // No hashes received in due time, drop the peer
{errEmptyHeaderSet, true}, // No headers were returned as a response, drop as it's a dead end
@ -1569,3 +1570,39 @@ func TestRemoteHeaderRequestSpan(t *testing.T) {
}
}
}
// Tests that peers below a pre-configured checkpoint block are prevented from
// being fast-synced from, avoiding potential cheap eclipse attacks.
func TestCheckpointEnforcement62(t *testing.T) { testCheckpointEnforcement(t, 62, FullSync) }
func TestCheckpointEnforcement63Full(t *testing.T) { testCheckpointEnforcement(t, 63, FullSync) }
func TestCheckpointEnforcement63Fast(t *testing.T) { testCheckpointEnforcement(t, 63, FastSync) }
func TestCheckpointEnforcement64Full(t *testing.T) { testCheckpointEnforcement(t, 64, FullSync) }
func TestCheckpointEnforcement64Fast(t *testing.T) { testCheckpointEnforcement(t, 64, FastSync) }
func TestCheckpointEnforcement64Light(t *testing.T) { testCheckpointEnforcement(t, 64, LightSync) }
func testCheckpointEnforcement(t *testing.T, protocol int, mode SyncMode) {
t.Parallel()
// Create a new tester with a particular hard coded checkpoint block
tester := newTester()
defer tester.terminate()
tester.downloader.checkpoint = uint64(fsMinFullBlocks) + 256
chain := testChainBase.shorten(int(tester.downloader.checkpoint) - 1)
// Attempt to sync with the peer and validate the result
tester.newPeer("peer", protocol, chain)
var expect error
if mode == FastSync {
expect = errUnsyncedPeer
}
if err := tester.sync("peer", nil, mode); err != expect {
t.Fatalf("block sync error mismatch: have %v, want %v", err, expect)
}
if mode == FastSync {
assertOwnChain(t, tester, 1)
} else {
assertOwnChain(t, tester, chain.len())
}
}

View File

@ -28,7 +28,6 @@ import (
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/consensus"
"github.com/ethereum/go-ethereum/consensus/misc"
"github.com/ethereum/go-ethereum/core"
"github.com/ethereum/go-ethereum/core/types"
"github.com/ethereum/go-ethereum/eth/downloader"
@ -55,7 +54,7 @@ const (
)
var (
daoChallengeTimeout = 15 * time.Second // Time allowance for a node to reply to the DAO handshake challenge
syncChallengeTimeout = 15 * time.Second // Time allowance for a node to reply to the sync progress challenge
)
// errIncompatibleConfig is returned if the requested protocols and configs are
@ -72,6 +71,9 @@ type ProtocolManager struct {
fastSync uint32 // Flag whether fast sync is enabled (gets disabled if we already have blocks)
acceptTxs uint32 // Flag whether we're considered synchronised (enables transaction processing)
checkpointNumber uint64 // Block number for the sync progress validator to cross reference
checkpointHash common.Hash // Block hash for the sync progress validator to cross reference
txpool txPool
blockchain *core.BlockChain
chainconfig *params.ChainConfig
@ -126,6 +128,11 @@ func NewProtocolManager(config *params.ChainConfig, mode downloader.SyncMode, ne
if mode == downloader.FastSync {
manager.fastSync = uint32(1)
}
// If we have trusted checkpoints, enforce them on the chain
if checkpoint, ok := params.TrustedCheckpoints[blockchain.Genesis().Hash()]; ok {
manager.checkpointNumber = (checkpoint.SectionIndex+1)*params.CHTFrequency - 1
manager.checkpointHash = checkpoint.SectionHead
}
// Initiate a sub-protocol for every implemented version we can handle
manager.SubProtocols = make([]p2p.Protocol, 0, len(ProtocolVersions))
for i, version := range ProtocolVersions {
@ -165,7 +172,7 @@ func NewProtocolManager(config *params.ChainConfig, mode downloader.SyncMode, ne
return nil, errIncompatibleConfig
}
// Construct the different synchronisation mechanisms
manager.downloader = downloader.New(mode, chaindb, manager.eventMux, blockchain, nil, manager.removePeer)
manager.downloader = downloader.New(mode, manager.checkpointNumber, chaindb, manager.eventMux, blockchain, nil, manager.removePeer)
validator := func(header *types.Header) error {
return engine.VerifyHeader(blockchain, header, true)
@ -291,22 +298,22 @@ func (pm *ProtocolManager) handle(p *peer) error {
// after this will be sent via broadcasts.
pm.syncTransactions(p)
// If we're DAO hard-fork aware, validate any remote peer with regard to the hard-fork
if daoBlock := pm.chainconfig.DAOForkBlock; daoBlock != nil {
// Request the peer's DAO fork header for extra-data validation
if err := p.RequestHeadersByNumber(daoBlock.Uint64(), 1, 0, false); err != nil {
// If we have a trusted CHT, reject all peers below that (avoid fast sync eclipse)
if pm.checkpointHash != (common.Hash{}) {
// Request the peer's checkpoint header for chain height/weight validation
if err := p.RequestHeadersByNumber(pm.checkpointNumber, 1, 0, false); err != nil {
return err
}
// Start a timer to disconnect if the peer doesn't reply in time
p.forkDrop = time.AfterFunc(daoChallengeTimeout, func() {
p.Log().Debug("Timed out DAO fork-check, dropping")
p.syncDrop = time.AfterFunc(syncChallengeTimeout, func() {
p.Log().Warn("Checkpoint challenge timed out, dropping", "addr", p.RemoteAddr(), "type", p.Name())
pm.removePeer(p.id)
})
// Make sure it's cleaned up if the peer dies off
defer func() {
if p.forkDrop != nil {
p.forkDrop.Stop()
p.forkDrop = nil
if p.syncDrop != nil {
p.syncDrop.Stop()
p.syncDrop = nil
}
}()
}
@ -438,41 +445,33 @@ func (pm *ProtocolManager) handleMsg(p *peer) error {
if err := msg.Decode(&headers); err != nil {
return errResp(ErrDecode, "msg %v: %v", msg, err)
}
// If no headers were received, but we're expending a DAO fork check, maybe it's that
if len(headers) == 0 && p.forkDrop != nil {
// Possibly an empty reply to the fork header checks, sanity check TDs
verifyDAO := true
// If no headers were received, but we're expencting a checkpoint header, consider it that
if len(headers) == 0 && p.syncDrop != nil {
// Stop the timer either way, decide later to drop or not
p.syncDrop.Stop()
p.syncDrop = nil
// If we already have a DAO header, we can check the peer's TD against it. If
// the peer's ahead of this, it too must have a reply to the DAO check
if daoHeader := pm.blockchain.GetHeaderByNumber(pm.chainconfig.DAOForkBlock.Uint64()); daoHeader != nil {
if _, td := p.Head(); td.Cmp(pm.blockchain.GetTd(daoHeader.Hash(), daoHeader.Number.Uint64())) >= 0 {
verifyDAO = false
}
}
// If we're seemingly on the same chain, disable the drop timer
if verifyDAO {
p.Log().Debug("Seems to be on the same side of the DAO fork")
p.forkDrop.Stop()
p.forkDrop = nil
return nil
// If we're doing a fast sync, we must enforce the checkpoint block to avoid
// eclipse attacks. Unsynced nodes are welcome to connect after we're done
// joining the network
if atomic.LoadUint32(&pm.fastSync) == 1 {
p.Log().Warn("Dropping unsynced node during fast sync", "addr", p.RemoteAddr(), "type", p.Name())
return errors.New("unsynced node cannot serve fast sync")
}
}
// Filter out any explicitly requested headers, deliver the rest to the downloader
filter := len(headers) == 1
if filter {
// If it's a potential DAO fork check, validate against the rules
if p.forkDrop != nil && pm.chainconfig.DAOForkBlock.Cmp(headers[0].Number) == 0 {
// Disable the fork drop timer
p.forkDrop.Stop()
p.forkDrop = nil
// If it's a potential sync progress check, validate the content and advertised chain weight
if p.syncDrop != nil && headers[0].Number.Uint64() == pm.checkpointNumber {
// Disable the sync drop timer
p.syncDrop.Stop()
p.syncDrop = nil
// Validate the header and either drop the peer or continue
if err := misc.VerifyDAOHeaderExtraData(pm.chainconfig, headers[0]); err != nil {
p.Log().Debug("Verified to be on the other side of the DAO fork, dropping")
return err
if headers[0].Hash() != pm.checkpointHash {
return errors.New("checkpoint hash mismatch")
}
p.Log().Debug("Verified to be on the same side of the DAO fork")
return nil
}
// Otherwise if it's a whitelisted block, validate against the set

View File

@ -453,48 +453,95 @@ func testGetReceipt(t *testing.T, protocol int) {
}
}
// Tests that post eth protocol handshake, DAO fork-enabled clients also execute
// a DAO "challenge" verifying each others' DAO fork headers to ensure they're on
// compatible chains.
func TestDAOChallengeNoVsNo(t *testing.T) { testDAOChallenge(t, false, false, false) }
func TestDAOChallengeNoVsPro(t *testing.T) { testDAOChallenge(t, false, true, false) }
func TestDAOChallengeProVsNo(t *testing.T) { testDAOChallenge(t, true, false, false) }
func TestDAOChallengeProVsPro(t *testing.T) { testDAOChallenge(t, true, true, false) }
func TestDAOChallengeNoVsTimeout(t *testing.T) { testDAOChallenge(t, false, false, true) }
func TestDAOChallengeProVsTimeout(t *testing.T) { testDAOChallenge(t, true, true, true) }
// Tests that post eth protocol handshake, clients perform a mutual checkpoint
// challenge to validate each other's chains. Hash mismatches, or missing ones
// during a fast sync should lead to the peer getting dropped.
func TestCheckpointChallenge(t *testing.T) {
tests := []struct {
syncmode downloader.SyncMode
checkpoint bool
timeout bool
empty bool
match bool
drop bool
}{
// If checkpointing is not enabled locally, don't challenge and don't drop
{downloader.FullSync, false, false, false, false, false},
{downloader.FastSync, false, false, false, false, false},
{downloader.LightSync, false, false, false, false, false},
func testDAOChallenge(t *testing.T, localForked, remoteForked bool, timeout bool) {
// Reduce the DAO handshake challenge timeout
if timeout {
defer func(old time.Duration) { daoChallengeTimeout = old }(daoChallengeTimeout)
daoChallengeTimeout = 500 * time.Millisecond
// If checkpointing is enabled locally and remote response is empty, only drop during fast sync
{downloader.FullSync, true, false, true, false, false},
{downloader.FastSync, true, false, true, false, true}, // Special case, fast sync, unsynced peer
{downloader.LightSync, true, false, true, false, false},
// If checkpointing is enabled locally and remote response mismatches, always drop
{downloader.FullSync, true, false, false, false, true},
{downloader.FastSync, true, false, false, false, true},
{downloader.LightSync, true, false, false, false, true},
// If checkpointing is enabled locally and remote response matches, never drop
{downloader.FullSync, true, false, false, true, false},
{downloader.FastSync, true, false, false, true, false},
{downloader.LightSync, true, false, false, true, false},
// If checkpointing is enabled locally and remote times out, always drop
{downloader.FullSync, true, true, false, true, true},
{downloader.FastSync, true, true, false, true, true},
{downloader.LightSync, true, true, false, true, true},
}
// Create a DAO aware protocol manager
for _, tt := range tests {
t.Run(fmt.Sprintf("sync %v checkpoint %v timeout %v empty %v match %v", tt.syncmode, tt.checkpoint, tt.timeout, tt.empty, tt.match), func(t *testing.T) {
testCheckpointChallenge(t, tt.syncmode, tt.checkpoint, tt.timeout, tt.empty, tt.match, tt.drop)
})
}
}
func testCheckpointChallenge(t *testing.T, syncmode downloader.SyncMode, checkpoint bool, timeout bool, empty bool, match bool, drop bool) {
// Reduce the checkpoint handshake challenge timeout
defer func(old time.Duration) { syncChallengeTimeout = old }(syncChallengeTimeout)
syncChallengeTimeout = 250 * time.Millisecond
// Initialize a chain and generate a fake CHT if checkpointing is enabled
var (
evmux = new(event.TypeMux)
pow = ethash.NewFaker()
db = rawdb.NewMemoryDatabase()
config = &params.ChainConfig{DAOForkBlock: big.NewInt(1), DAOForkSupport: localForked}
gspec = &core.Genesis{Config: config}
genesis = gspec.MustCommit(db)
config = new(params.ChainConfig)
genesis = (&core.Genesis{Config: config}).MustCommit(db)
)
blockchain, err := core.NewBlockChain(db, nil, config, pow, vm.Config{}, nil)
// If checkpointing is enabled, create and inject a fake CHT and the corresponding
// chllenge response.
var response *types.Header
if checkpoint {
index := uint64(rand.Intn(500))
number := (index+1)*params.CHTFrequency - 1
response = &types.Header{Number: big.NewInt(int64(number)), Extra: []byte("valid")}
cht := &params.TrustedCheckpoint{
SectionIndex: index,
SectionHead: response.Hash(),
}
params.TrustedCheckpoints[genesis.Hash()] = cht
defer delete(params.TrustedCheckpoints, genesis.Hash())
}
// Create a checkpoint aware protocol manager
blockchain, err := core.NewBlockChain(db, nil, config, ethash.NewFaker(), vm.Config{}, nil)
if err != nil {
t.Fatalf("failed to create new blockchain: %v", err)
}
pm, err := NewProtocolManager(config, downloader.FullSync, DefaultConfig.NetworkId, evmux, new(testTxPool), pow, blockchain, db, nil)
pm, err := NewProtocolManager(config, syncmode, DefaultConfig.NetworkId, new(event.TypeMux), new(testTxPool), ethash.NewFaker(), blockchain, db, nil)
if err != nil {
t.Fatalf("failed to start test protocol manager: %v", err)
}
pm.Start(1000)
defer pm.Stop()
// Connect a new peer and check that we receive the DAO challenge
// Connect a new peer and check that we receive the checkpoint challenge
peer, _ := newTestPeer("peer", eth63, pm, true)
defer peer.close()
if checkpoint {
challenge := &getBlockHeadersData{
Origin: hashOrNumber{Number: config.DAOForkBlock.Uint64()},
Origin: hashOrNumber{Number: response.Number.Uint64()},
Amount: 1,
Skip: 0,
Reverse: false,
@ -504,28 +551,33 @@ func testDAOChallenge(t *testing.T, localForked, remoteForked bool, timeout bool
}
// Create a block to reply to the challenge if no timeout is simulated
if !timeout {
blocks, _ := core.GenerateChain(&params.ChainConfig{}, genesis, ethash.NewFaker(), db, 1, func(i int, block *core.BlockGen) {
if remoteForked {
block.SetExtra(params.DAOForkBlockExtra)
}
})
if err := p2p.Send(peer.app, BlockHeadersMsg, []*types.Header{blocks[0].Header()}); err != nil {
if empty {
if err := p2p.Send(peer.app, BlockHeadersMsg, []*types.Header{}); err != nil {
t.Fatalf("failed to answer challenge: %v", err)
}
time.Sleep(100 * time.Millisecond) // Sleep to avoid the verification racing with the drops
} else {
// Otherwise wait until the test timeout passes
time.Sleep(daoChallengeTimeout + 500*time.Millisecond)
}
// Verify that depending on fork side, the remote peer is maintained or dropped
if localForked == remoteForked && !timeout {
if peers := pm.peers.Len(); peers != 1 {
t.Fatalf("peer count mismatch: have %d, want %d", peers, 1)
} else if match {
if err := p2p.Send(peer.app, BlockHeadersMsg, []*types.Header{response}); err != nil {
t.Fatalf("failed to answer challenge: %v", err)
}
} else {
if err := p2p.Send(peer.app, BlockHeadersMsg, []*types.Header{{Number: response.Number}}); err != nil {
t.Fatalf("failed to answer challenge: %v", err)
}
}
}
}
// Wait until the test timeout passes to ensure proper cleanup
time.Sleep(syncChallengeTimeout + 100*time.Millisecond)
// Verify that the remote peer is maintained or dropped
if drop {
if peers := pm.peers.Len(); peers != 0 {
t.Fatalf("peer count mismatch: have %d, want %d", peers, 0)
}
} else {
if peers := pm.peers.Len(); peers != 1 {
t.Fatalf("peer count mismatch: have %d, want %d", peers, 1)
}
}
}

View File

@ -79,7 +79,7 @@ type peer struct {
rw p2p.MsgReadWriter
version int // Protocol version negotiated
forkDrop *time.Timer // Timed connection dropper if forks aren't validated in time
syncDrop *time.Timer // Timed connection dropper if sync progress isn't validated in time
head common.Hash
td *big.Int

View File

@ -188,14 +188,12 @@ func (pm *ProtocolManager) synchronise(peer *peer) {
atomic.StoreUint32(&pm.fastSync, 1)
mode = downloader.FastSync
}
if mode == downloader.FastSync {
// Make sure the peer's total difficulty we are synchronizing is higher.
if pm.blockchain.GetTdByHash(pm.blockchain.CurrentFastBlock().Hash()).Cmp(pTd) >= 0 {
return
}
}
// Run the sync cycle, and disable fast sync if we've went past the pivot block
if err := pm.downloader.Synchronise(peer.id, pHead, pTd, mode); err != nil {
return

View File

@ -174,9 +174,12 @@ func NewProtocolManager(
if disableClientRemovePeer {
removePeer = func(id string) {}
}
if lightSync {
manager.downloader = downloader.New(downloader.LightSync, chainDb, manager.eventMux, nil, blockchain, removePeer)
var checkpoint uint64
if cht, ok := params.TrustedCheckpoints[blockchain.Genesis().Hash()]; ok {
checkpoint = (cht.SectionIndex+1)*params.CHTFrequency - 1
}
manager.downloader = downloader.New(downloader.LightSync, checkpoint, chainDb, manager.eventMux, nil, blockchain, removePeer)
manager.peers.notify((*downloaderPeerNotify)(manager))
manager.fetcher = newLightFetcher(manager)
}

View File

@ -101,7 +101,7 @@ func NewLightChain(odr OdrBackend, config *params.ChainConfig, engine consensus.
if bc.genesisBlock == nil {
return nil, core.ErrNoGenesis
}
if cp, ok := trustedCheckpoints[bc.genesisBlock.Hash()]; ok {
if cp, ok := params.TrustedCheckpoints[bc.genesisBlock.Hash()]; ok {
bc.addTrustedCheckpoint(cp)
}
if err := bc.loadLastState(); err != nil {

View File

@ -97,14 +97,6 @@ var (
}
)
// trustedCheckpoints associates each known checkpoint with the genesis hash of the chain it belongs to
var trustedCheckpoints = map[common.Hash]*params.TrustedCheckpoint{
params.MainnetGenesisHash: params.MainnetTrustedCheckpoint,
params.TestnetGenesisHash: params.TestnetTrustedCheckpoint,
params.RinkebyGenesisHash: params.RinkebyTrustedCheckpoint,
params.GoerliGenesisHash: params.GoerliTrustedCheckpoint,
}
var (
ErrNoTrustedCht = errors.New("no trusted canonical hash trie")
ErrNoTrustedBloomTrie = errors.New("no trusted bloom trie")

View File

@ -31,6 +31,15 @@ var (
GoerliGenesisHash = common.HexToHash("0xbf7e331f7f7c1dd2e05159666b3bf8bc7a8a3a9eb1d518969eab529dd9b88c1a")
)
// TrustedCheckpoints associates each known checkpoint with the genesis hash of
// the chain it belongs to.
var TrustedCheckpoints = map[common.Hash]*TrustedCheckpoint{
MainnetGenesisHash: MainnetTrustedCheckpoint,
TestnetGenesisHash: TestnetTrustedCheckpoint,
RinkebyGenesisHash: RinkebyTrustedCheckpoint,
GoerliGenesisHash: GoerliTrustedCheckpoint,
}
var (
// MainnetChainConfig is the chain parameters to run a node on the main network.
MainnetChainConfig = &ChainConfig{