go-ethereum/cmd/devp2p/internal/ethtest/helpers.go

750 lines
23 KiB
Go

// Copyright 2020 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 ethtest
import (
"fmt"
"net"
"reflect"
"strings"
"time"
"github.com/davecgh/go-spew/spew"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/core/types"
"github.com/ethereum/go-ethereum/crypto"
"github.com/ethereum/go-ethereum/eth/protocols/eth"
"github.com/ethereum/go-ethereum/internal/utesting"
"github.com/ethereum/go-ethereum/p2p"
"github.com/ethereum/go-ethereum/p2p/rlpx"
)
var (
pretty = spew.ConfigState{
Indent: " ",
DisableCapacities: true,
DisablePointerAddresses: true,
SortKeys: true,
}
timeout = 20 * time.Second
)
// Is_66 checks if the node supports the eth66 protocol version,
// and if not, exists the test suite
func (s *Suite) Is_66(t *utesting.T) {
conn, err := s.dial66()
if err != nil {
t.Fatalf("dial failed: %v", err)
}
if err := conn.handshake(); err != nil {
t.Fatalf("handshake failed: %v", err)
}
if conn.negotiatedProtoVersion < 66 {
t.Fail()
}
}
// dial attempts to dial the given node and perform a handshake,
// returning the created Conn if successful.
func (s *Suite) dial() (*Conn, error) {
// dial
fd, err := net.Dial("tcp", fmt.Sprintf("%v:%d", s.Dest.IP(), s.Dest.TCP()))
if err != nil {
return nil, err
}
conn := Conn{Conn: rlpx.NewConn(fd, s.Dest.Pubkey())}
// do encHandshake
conn.ourKey, _ = crypto.GenerateKey()
_, err = conn.Handshake(conn.ourKey)
if err != nil {
conn.Close()
return nil, err
}
// set default p2p capabilities
conn.caps = []p2p.Cap{
{Name: "eth", Version: 64},
{Name: "eth", Version: 65},
}
conn.ourHighestProtoVersion = 65
return &conn, nil
}
// dial66 attempts to dial the given node and perform a handshake,
// returning the created Conn with additional eth66 capabilities if
// successful
func (s *Suite) dial66() (*Conn, error) {
conn, err := s.dial()
if err != nil {
return nil, fmt.Errorf("dial failed: %v", err)
}
conn.caps = append(conn.caps, p2p.Cap{Name: "eth", Version: 66})
conn.ourHighestProtoVersion = 66
return conn, nil
}
// peer performs both the protocol handshake and the status message
// exchange with the node in order to peer with it.
func (c *Conn) peer(chain *Chain, status *Status) error {
if err := c.handshake(); err != nil {
return fmt.Errorf("handshake failed: %v", err)
}
if _, err := c.statusExchange(chain, status); err != nil {
return fmt.Errorf("status exchange failed: %v", err)
}
return nil
}
// handshake performs a protocol handshake with the node.
func (c *Conn) handshake() error {
defer c.SetDeadline(time.Time{})
c.SetDeadline(time.Now().Add(10 * time.Second))
// write hello to client
pub0 := crypto.FromECDSAPub(&c.ourKey.PublicKey)[1:]
ourHandshake := &Hello{
Version: 5,
Caps: c.caps,
ID: pub0,
}
if err := c.Write(ourHandshake); err != nil {
return fmt.Errorf("write to connection failed: %v", err)
}
// read hello from client
switch msg := c.Read().(type) {
case *Hello:
// set snappy if version is at least 5
if msg.Version >= 5 {
c.SetSnappy(true)
}
c.negotiateEthProtocol(msg.Caps)
if c.negotiatedProtoVersion == 0 {
return fmt.Errorf("unexpected eth protocol version")
}
return nil
default:
return fmt.Errorf("bad handshake: %#v", msg)
}
}
// negotiateEthProtocol sets the Conn's eth protocol version to highest
// advertised capability from peer.
func (c *Conn) negotiateEthProtocol(caps []p2p.Cap) {
var highestEthVersion uint
for _, capability := range caps {
if capability.Name != "eth" {
continue
}
if capability.Version > highestEthVersion && capability.Version <= c.ourHighestProtoVersion {
highestEthVersion = capability.Version
}
}
c.negotiatedProtoVersion = highestEthVersion
}
// statusExchange performs a `Status` message exchange with the given node.
func (c *Conn) statusExchange(chain *Chain, status *Status) (Message, error) {
defer c.SetDeadline(time.Time{})
c.SetDeadline(time.Now().Add(20 * time.Second))
// read status message from client
var message Message
loop:
for {
switch msg := c.Read().(type) {
case *Status:
if have, want := msg.Head, chain.blocks[chain.Len()-1].Hash(); have != want {
return nil, fmt.Errorf("wrong head block in status, want: %#x (block %d) have %#x",
want, chain.blocks[chain.Len()-1].NumberU64(), have)
}
if have, want := msg.TD.Cmp(chain.TD()), 0; have != want {
return nil, fmt.Errorf("wrong TD in status: have %v want %v", have, want)
}
if have, want := msg.ForkID, chain.ForkID(); !reflect.DeepEqual(have, want) {
return nil, fmt.Errorf("wrong fork ID in status: have %v, want %v", have, want)
}
if have, want := msg.ProtocolVersion, c.ourHighestProtoVersion; have != uint32(want) {
return nil, fmt.Errorf("wrong protocol version: have %v, want %v", have, want)
}
message = msg
break loop
case *Disconnect:
return nil, fmt.Errorf("disconnect received: %v", msg.Reason)
case *Ping:
c.Write(&Pong{}) // TODO (renaynay): in the future, this should be an error
// (PINGs should not be a response upon fresh connection)
default:
return nil, fmt.Errorf("bad status message: %s", pretty.Sdump(msg))
}
}
// make sure eth protocol version is set for negotiation
if c.negotiatedProtoVersion == 0 {
return nil, fmt.Errorf("eth protocol version must be set in Conn")
}
if status == nil {
// default status message
status = &Status{
ProtocolVersion: uint32(c.negotiatedProtoVersion),
NetworkID: chain.chainConfig.ChainID.Uint64(),
TD: chain.TD(),
Head: chain.blocks[chain.Len()-1].Hash(),
Genesis: chain.blocks[0].Hash(),
ForkID: chain.ForkID(),
}
}
if err := c.Write(status); err != nil {
return nil, fmt.Errorf("write to connection failed: %v", err)
}
return message, nil
}
// createSendAndRecvConns creates two connections, one for sending messages to the
// node, and one for receiving messages from the node.
func (s *Suite) createSendAndRecvConns(isEth66 bool) (*Conn, *Conn, error) {
var (
sendConn *Conn
recvConn *Conn
err error
)
if isEth66 {
sendConn, err = s.dial66()
if err != nil {
return nil, nil, fmt.Errorf("dial failed: %v", err)
}
recvConn, err = s.dial66()
if err != nil {
sendConn.Close()
return nil, nil, fmt.Errorf("dial failed: %v", err)
}
} else {
sendConn, err = s.dial()
if err != nil {
return nil, nil, fmt.Errorf("dial failed: %v", err)
}
recvConn, err = s.dial()
if err != nil {
sendConn.Close()
return nil, nil, fmt.Errorf("dial failed: %v", err)
}
}
return sendConn, recvConn, nil
}
// readAndServe serves GetBlockHeaders requests while waiting
// on another message from the node.
func (c *Conn) readAndServe(chain *Chain, timeout time.Duration) Message {
start := time.Now()
for time.Since(start) < timeout {
c.SetReadDeadline(time.Now().Add(5 * time.Second))
switch msg := c.Read().(type) {
case *Ping:
c.Write(&Pong{})
case *GetBlockHeaders:
req := *msg
headers, err := chain.GetHeaders(req)
if err != nil {
return errorf("could not get headers for inbound header request: %v", err)
}
if err := c.Write(headers); err != nil {
return errorf("could not write to connection: %v", err)
}
default:
return msg
}
}
return errorf("no message received within %v", timeout)
}
// readAndServe66 serves eth66 GetBlockHeaders requests while waiting
// on another message from the node.
func (c *Conn) readAndServe66(chain *Chain, timeout time.Duration) (uint64, Message) {
start := time.Now()
for time.Since(start) < timeout {
c.SetReadDeadline(time.Now().Add(10 * time.Second))
reqID, msg := c.Read66()
switch msg := msg.(type) {
case *Ping:
c.Write(&Pong{})
case *GetBlockHeaders:
headers, err := chain.GetHeaders(*msg)
if err != nil {
return 0, errorf("could not get headers for inbound header request: %v", err)
}
resp := &eth.BlockHeadersPacket66{
RequestId: reqID,
BlockHeadersPacket: eth.BlockHeadersPacket(headers),
}
if err := c.Write66(resp, BlockHeaders{}.Code()); err != nil {
return 0, errorf("could not write to connection: %v", err)
}
default:
return reqID, msg
}
}
return 0, errorf("no message received within %v", timeout)
}
// headersRequest executes the given `GetBlockHeaders` request.
func (c *Conn) headersRequest(request *GetBlockHeaders, chain *Chain, isEth66 bool, reqID uint64) (BlockHeaders, error) {
defer c.SetReadDeadline(time.Time{})
c.SetReadDeadline(time.Now().Add(20 * time.Second))
// if on eth66 connection, perform eth66 GetBlockHeaders request
if isEth66 {
return getBlockHeaders66(chain, c, request, reqID)
}
if err := c.Write(request); err != nil {
return nil, err
}
switch msg := c.readAndServe(chain, timeout).(type) {
case *BlockHeaders:
return *msg, nil
default:
return nil, fmt.Errorf("invalid message: %s", pretty.Sdump(msg))
}
}
// getBlockHeaders66 executes the given `GetBlockHeaders` request over the eth66 protocol.
func getBlockHeaders66(chain *Chain, conn *Conn, request *GetBlockHeaders, id uint64) (BlockHeaders, error) {
// write request
packet := eth.GetBlockHeadersPacket(*request)
req := &eth.GetBlockHeadersPacket66{
RequestId: id,
GetBlockHeadersPacket: &packet,
}
if err := conn.Write66(req, GetBlockHeaders{}.Code()); err != nil {
return nil, fmt.Errorf("could not write to connection: %v", err)
}
// wait for response
msg := conn.waitForResponse(chain, timeout, req.RequestId)
headers, ok := msg.(BlockHeaders)
if !ok {
return nil, fmt.Errorf("unexpected message received: %s", pretty.Sdump(msg))
}
return headers, nil
}
// headersMatch returns whether the received headers match the given request
func headersMatch(expected BlockHeaders, headers BlockHeaders) bool {
return reflect.DeepEqual(expected, headers)
}
// waitForResponse reads from the connection until a response with the expected
// request ID is received.
func (c *Conn) waitForResponse(chain *Chain, timeout time.Duration, requestID uint64) Message {
for {
id, msg := c.readAndServe66(chain, timeout)
if id == requestID {
return msg
}
}
}
// sendNextBlock broadcasts the next block in the chain and waits
// for the node to propagate the block and import it into its chain.
func (s *Suite) sendNextBlock(isEth66 bool) error {
// set up sending and receiving connections
sendConn, recvConn, err := s.createSendAndRecvConns(isEth66)
if err != nil {
return err
}
defer sendConn.Close()
defer recvConn.Close()
if err = sendConn.peer(s.chain, nil); err != nil {
return fmt.Errorf("peering failed: %v", err)
}
if err = recvConn.peer(s.chain, nil); err != nil {
return fmt.Errorf("peering failed: %v", err)
}
// create new block announcement
nextBlock := s.fullChain.blocks[s.chain.Len()]
blockAnnouncement := &NewBlock{
Block: nextBlock,
TD: s.fullChain.TotalDifficultyAt(s.chain.Len()),
}
// send announcement and wait for node to request the header
if err = s.testAnnounce(sendConn, recvConn, blockAnnouncement); err != nil {
return fmt.Errorf("failed to announce block: %v", err)
}
// wait for client to update its chain
if err = s.waitForBlockImport(recvConn, nextBlock, isEth66); err != nil {
return fmt.Errorf("failed to receive confirmation of block import: %v", err)
}
// update test suite chain
s.chain.blocks = append(s.chain.blocks, nextBlock)
return nil
}
// testAnnounce writes a block announcement to the node and waits for the node
// to propagate it.
func (s *Suite) testAnnounce(sendConn, receiveConn *Conn, blockAnnouncement *NewBlock) error {
if err := sendConn.Write(blockAnnouncement); err != nil {
return fmt.Errorf("could not write to connection: %v", err)
}
return s.waitAnnounce(receiveConn, blockAnnouncement)
}
// waitAnnounce waits for a NewBlock or NewBlockHashes announcement from the node.
func (s *Suite) waitAnnounce(conn *Conn, blockAnnouncement *NewBlock) error {
for {
switch msg := conn.readAndServe(s.chain, timeout).(type) {
case *NewBlock:
if !reflect.DeepEqual(blockAnnouncement.Block.Header(), msg.Block.Header()) {
return fmt.Errorf("wrong header in block announcement: \nexpected %v "+
"\ngot %v", blockAnnouncement.Block.Header(), msg.Block.Header())
}
if !reflect.DeepEqual(blockAnnouncement.TD, msg.TD) {
return fmt.Errorf("wrong TD in announcement: expected %v, got %v", blockAnnouncement.TD, msg.TD)
}
return nil
case *NewBlockHashes:
hashes := *msg
if blockAnnouncement.Block.Hash() != hashes[0].Hash {
return fmt.Errorf("wrong block hash in announcement: expected %v, got %v", blockAnnouncement.Block.Hash(), hashes[0].Hash)
}
return nil
case *NewPooledTransactionHashes:
// ignore tx announcements from previous tests
continue
default:
return fmt.Errorf("unexpected: %s", pretty.Sdump(msg))
}
}
}
func (s *Suite) waitForBlockImport(conn *Conn, block *types.Block, isEth66 bool) error {
defer conn.SetReadDeadline(time.Time{})
conn.SetReadDeadline(time.Now().Add(20 * time.Second))
// create request
req := &GetBlockHeaders{
Origin: eth.HashOrNumber{
Hash: block.Hash(),
},
Amount: 1,
}
// loop until BlockHeaders response contains desired block, confirming the
// node imported the block
for {
var (
headers BlockHeaders
err error
)
if isEth66 {
requestID := uint64(54)
headers, err = conn.headersRequest(req, s.chain, eth66, requestID)
} else {
headers, err = conn.headersRequest(req, s.chain, eth65, 0)
}
if err != nil {
return fmt.Errorf("GetBlockHeader request failed: %v", err)
}
// if headers response is empty, node hasn't imported block yet, try again
if len(headers) == 0 {
time.Sleep(100 * time.Millisecond)
continue
}
if !reflect.DeepEqual(block.Header(), headers[0]) {
return fmt.Errorf("wrong header returned: wanted %v, got %v", block.Header(), headers[0])
}
return nil
}
}
func (s *Suite) oldAnnounce(isEth66 bool) error {
sendConn, receiveConn, err := s.createSendAndRecvConns(isEth66)
if err != nil {
return err
}
defer sendConn.Close()
defer receiveConn.Close()
if err := sendConn.peer(s.chain, nil); err != nil {
return fmt.Errorf("peering failed: %v", err)
}
if err := receiveConn.peer(s.chain, nil); err != nil {
return fmt.Errorf("peering failed: %v", err)
}
// create old block announcement
oldBlockAnnounce := &NewBlock{
Block: s.chain.blocks[len(s.chain.blocks)/2],
TD: s.chain.blocks[len(s.chain.blocks)/2].Difficulty(),
}
if err := sendConn.Write(oldBlockAnnounce); err != nil {
return fmt.Errorf("could not write to connection: %v", err)
}
// wait to see if the announcement is propagated
switch msg := receiveConn.readAndServe(s.chain, time.Second*8).(type) {
case *NewBlock:
block := *msg
if block.Block.Hash() == oldBlockAnnounce.Block.Hash() {
return fmt.Errorf("unexpected: block propagated: %s", pretty.Sdump(msg))
}
case *NewBlockHashes:
hashes := *msg
for _, hash := range hashes {
if hash.Hash == oldBlockAnnounce.Block.Hash() {
return fmt.Errorf("unexpected: block announced: %s", pretty.Sdump(msg))
}
}
case *Error:
errMsg := *msg
// check to make sure error is timeout (propagation didn't come through == test successful)
if !strings.Contains(errMsg.String(), "timeout") {
return fmt.Errorf("unexpected error: %v", pretty.Sdump(msg))
}
default:
return fmt.Errorf("unexpected: %s", pretty.Sdump(msg))
}
return nil
}
func (s *Suite) maliciousHandshakes(t *utesting.T, isEth66 bool) error {
var (
conn *Conn
err error
)
if isEth66 {
conn, err = s.dial66()
if err != nil {
return fmt.Errorf("dial failed: %v", err)
}
} else {
conn, err = s.dial()
if err != nil {
return fmt.Errorf("dial failed: %v", err)
}
}
defer conn.Close()
// write hello to client
pub0 := crypto.FromECDSAPub(&conn.ourKey.PublicKey)[1:]
handshakes := []*Hello{
{
Version: 5,
Caps: []p2p.Cap{
{Name: largeString(2), Version: 64},
},
ID: pub0,
},
{
Version: 5,
Caps: []p2p.Cap{
{Name: "eth", Version: 64},
{Name: "eth", Version: 65},
},
ID: append(pub0, byte(0)),
},
{
Version: 5,
Caps: []p2p.Cap{
{Name: "eth", Version: 64},
{Name: "eth", Version: 65},
},
ID: append(pub0, pub0...),
},
{
Version: 5,
Caps: []p2p.Cap{
{Name: "eth", Version: 64},
{Name: "eth", Version: 65},
},
ID: largeBuffer(2),
},
{
Version: 5,
Caps: []p2p.Cap{
{Name: largeString(2), Version: 64},
},
ID: largeBuffer(2),
},
}
for i, handshake := range handshakes {
t.Logf("Testing malicious handshake %v\n", i)
if err := conn.Write(handshake); err != nil {
return fmt.Errorf("could not write to connection: %v", err)
}
// check that the peer disconnected
for i := 0; i < 2; i++ {
switch msg := conn.readAndServe(s.chain, 20*time.Second).(type) {
case *Disconnect:
case *Error:
case *Hello:
// Discard one hello as Hello's are sent concurrently
continue
default:
return fmt.Errorf("unexpected: %s", pretty.Sdump(msg))
}
}
// dial for the next round
if isEth66 {
conn, err = s.dial66()
if err != nil {
return fmt.Errorf("dial failed: %v", err)
}
} else {
conn, err = s.dial()
if err != nil {
return fmt.Errorf("dial failed: %v", err)
}
}
}
return nil
}
func (s *Suite) maliciousStatus(conn *Conn) error {
if err := conn.handshake(); err != nil {
return fmt.Errorf("handshake failed: %v", err)
}
status := &Status{
ProtocolVersion: uint32(conn.negotiatedProtoVersion),
NetworkID: s.chain.chainConfig.ChainID.Uint64(),
TD: largeNumber(2),
Head: s.chain.blocks[s.chain.Len()-1].Hash(),
Genesis: s.chain.blocks[0].Hash(),
ForkID: s.chain.ForkID(),
}
// get status
msg, err := conn.statusExchange(s.chain, status)
if err != nil {
return fmt.Errorf("status exchange failed: %v", err)
}
switch msg := msg.(type) {
case *Status:
default:
return fmt.Errorf("expected status, got: %#v ", msg)
}
// wait for disconnect
switch msg := conn.readAndServe(s.chain, timeout).(type) {
case *Disconnect:
return nil
case *Error:
return nil
default:
return fmt.Errorf("expected disconnect, got: %s", pretty.Sdump(msg))
}
}
func (s *Suite) hashAnnounce(isEth66 bool) error {
// create connections
sendConn, recvConn, err := s.createSendAndRecvConns(isEth66)
if err != nil {
return fmt.Errorf("failed to create connections: %v", err)
}
defer sendConn.Close()
defer recvConn.Close()
if err := sendConn.peer(s.chain, nil); err != nil {
return fmt.Errorf("peering failed: %v", err)
}
if err := recvConn.peer(s.chain, nil); err != nil {
return fmt.Errorf("peering failed: %v", err)
}
// create NewBlockHashes announcement
type anno struct {
Hash common.Hash // Hash of one particular block being announced
Number uint64 // Number of one particular block being announced
}
nextBlock := s.fullChain.blocks[s.chain.Len()]
announcement := anno{Hash: nextBlock.Hash(), Number: nextBlock.Number().Uint64()}
newBlockHash := &NewBlockHashes{announcement}
if err := sendConn.Write(newBlockHash); err != nil {
return fmt.Errorf("failed to write to connection: %v", err)
}
// Announcement sent, now wait for a header request
var (
id uint64
msg Message
blockHeaderReq GetBlockHeaders
)
if isEth66 {
id, msg = sendConn.Read66()
switch msg := msg.(type) {
case GetBlockHeaders:
blockHeaderReq = msg
default:
return fmt.Errorf("unexpected %s", pretty.Sdump(msg))
}
if blockHeaderReq.Amount != 1 {
return fmt.Errorf("unexpected number of block headers requested: %v", blockHeaderReq.Amount)
}
if blockHeaderReq.Origin.Hash != announcement.Hash {
return fmt.Errorf("unexpected block header requested. Announced:\n %v\n Remote request:\n%v",
pretty.Sdump(announcement),
pretty.Sdump(blockHeaderReq))
}
if err := sendConn.Write66(&eth.BlockHeadersPacket66{
RequestId: id,
BlockHeadersPacket: eth.BlockHeadersPacket{
nextBlock.Header(),
},
}, BlockHeaders{}.Code()); err != nil {
return fmt.Errorf("failed to write to connection: %v", err)
}
} else {
msg = sendConn.Read()
switch msg := msg.(type) {
case *GetBlockHeaders:
blockHeaderReq = *msg
default:
return fmt.Errorf("unexpected %s", pretty.Sdump(msg))
}
if blockHeaderReq.Amount != 1 {
return fmt.Errorf("unexpected number of block headers requested: %v", blockHeaderReq.Amount)
}
if blockHeaderReq.Origin.Hash != announcement.Hash {
return fmt.Errorf("unexpected block header requested. Announced:\n %v\n Remote request:\n%v",
pretty.Sdump(announcement),
pretty.Sdump(blockHeaderReq))
}
if err := sendConn.Write(&BlockHeaders{nextBlock.Header()}); err != nil {
return fmt.Errorf("failed to write to connection: %v", err)
}
}
// wait for block announcement
msg = recvConn.readAndServe(s.chain, timeout)
switch msg := msg.(type) {
case *NewBlockHashes:
hashes := *msg
if len(hashes) != 1 {
return fmt.Errorf("unexpected new block hash announcement: wanted 1 announcement, got %d", len(hashes))
}
if nextBlock.Hash() != hashes[0].Hash {
return fmt.Errorf("unexpected block hash announcement, wanted %v, got %v", nextBlock.Hash(),
hashes[0].Hash)
}
case *NewBlock:
// node should only propagate NewBlock without having requested the body if the body is empty
nextBlockBody := nextBlock.Body()
if len(nextBlockBody.Transactions) != 0 || len(nextBlockBody.Uncles) != 0 {
return fmt.Errorf("unexpected non-empty new block propagated: %s", pretty.Sdump(msg))
}
if msg.Block.Hash() != nextBlock.Hash() {
return fmt.Errorf("mismatched hash of propagated new block: wanted %v, got %v",
nextBlock.Hash(), msg.Block.Hash())
}
// check to make sure header matches header that was sent to the node
if !reflect.DeepEqual(nextBlock.Header(), msg.Block.Header()) {
return fmt.Errorf("incorrect header received: wanted %v, got %v", nextBlock.Header(), msg.Block.Header())
}
default:
return fmt.Errorf("unexpected: %s", pretty.Sdump(msg))
}
// confirm node imported block
if err := s.waitForBlockImport(recvConn, nextBlock, isEth66); err != nil {
return fmt.Errorf("error waiting for node to import new block: %v", err)
}
// update the chain
s.chain.blocks = append(s.chain.blocks, nextBlock)
return nil
}