github.com/insight-chain/inb-go@v1.1.3-0.20191221022159-da049980ae38/eth/backend.go (about)

     1  // Copyright 2014 The go-ethereum Authors
     2  // This file is part of the go-ethereum library.
     3  //
     4  // The go-ethereum library is free software: you can redistribute it and/or modify
     5  // it under the terms of the GNU Lesser General Public License as published by
     6  // the Free Software Foundation, either version 3 of the License, or
     7  // (at your option) any later version.
     8  //
     9  // The go-ethereum library is distributed in the hope that it will be useful,
    10  // but WITHOUT ANY WARRANTY; without even the implied warranty of
    11  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
    12  // GNU Lesser General Public License for more details.
    13  //
    14  // You should have received a copy of the GNU Lesser General Public License
    15  // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
    16  
    17  // Package eth implements the Ethereum protocol.
    18  package eth
    19  
    20  import (
    21  	"errors"
    22  	"fmt"
    23  	"github.com/insight-chain/inb-go/consensus/vdpos"
    24  	"math/big"
    25  	"runtime"
    26  	"sync"
    27  	"sync/atomic"
    28  
    29  	"github.com/insight-chain/inb-go/accounts"
    30  	"github.com/insight-chain/inb-go/common"
    31  	"github.com/insight-chain/inb-go/common/hexutil"
    32  	"github.com/insight-chain/inb-go/consensus"
    33  	"github.com/insight-chain/inb-go/consensus/clique"
    34  	"github.com/insight-chain/inb-go/consensus/ethash"
    35  	"github.com/insight-chain/inb-go/core"
    36  	"github.com/insight-chain/inb-go/core/bloombits"
    37  	"github.com/insight-chain/inb-go/core/rawdb"
    38  	"github.com/insight-chain/inb-go/core/types"
    39  	"github.com/insight-chain/inb-go/core/vm"
    40  	"github.com/insight-chain/inb-go/eth/downloader"
    41  	"github.com/insight-chain/inb-go/eth/filters"
    42  	"github.com/insight-chain/inb-go/eth/gasprice"
    43  	"github.com/insight-chain/inb-go/ethdb"
    44  	"github.com/insight-chain/inb-go/event"
    45  	"github.com/insight-chain/inb-go/internal/ethapi"
    46  	"github.com/insight-chain/inb-go/log"
    47  	"github.com/insight-chain/inb-go/miner"
    48  	"github.com/insight-chain/inb-go/node"
    49  	"github.com/insight-chain/inb-go/p2p"
    50  	"github.com/insight-chain/inb-go/params"
    51  	"github.com/insight-chain/inb-go/rlp"
    52  	"github.com/insight-chain/inb-go/rpc"
    53  )
    54  
    55  type LesServer interface {
    56  	Start(srvr *p2p.Server)
    57  	Stop()
    58  	Protocols() []p2p.Protocol
    59  	SetBloomBitsIndexer(bbIndexer *core.ChainIndexer)
    60  }
    61  
    62  // Ethereum implements the Ethereum full node service.
    63  type Ethereum struct {
    64  	config      *Config
    65  	chainConfig *params.ChainConfig
    66  
    67  	// Channel for shutting down the service
    68  	shutdownChan chan bool // Channel for shutting down the Ethereum
    69  
    70  	// Handlers
    71  	txPool          *core.TxPool
    72  	blockchain      *core.BlockChain
    73  	protocolManager *ProtocolManager
    74  	lesServer       LesServer
    75  
    76  	// DB interfaces
    77  	chainDb ethdb.Database // Block chain database
    78  
    79  	eventMux       *event.TypeMux
    80  	engine         consensus.Engine
    81  	accountManager *accounts.Manager
    82  
    83  	bloomRequests chan chan *bloombits.Retrieval // Channel receiving bloom data retrieval requests
    84  	bloomIndexer  *core.ChainIndexer             // Bloom indexer operating during block imports
    85  
    86  	APIBackend *EthAPIBackend
    87  
    88  	miner     *miner.Miner
    89  	gasPrice  *big.Int
    90  	etherbase common.Address
    91  
    92  	networkID     uint64
    93  	netRPCService *ethapi.PublicNetAPI
    94  
    95  	lock sync.RWMutex // Protects the variadic fields (e.g. gas price and etherbase)
    96  }
    97  
    98  func (s *Ethereum) AddLesServer(ls LesServer) {
    99  	s.lesServer = ls
   100  	ls.SetBloomBitsIndexer(s.bloomIndexer)
   101  }
   102  
   103  // New creates a new Ethereum object (including the
   104  // initialisation of the common Ethereum object)
   105  func New(ctx *node.ServiceContext, config *Config) (*Ethereum, error) {
   106  	// Ensure configuration values are compatible and sane
   107  	if config.SyncMode == downloader.LightSync {
   108  		return nil, errors.New("can't run eth.Ethereum in light sync mode, use les.LightEthereum")
   109  	}
   110  	if !config.SyncMode.IsValid() {
   111  		return nil, fmt.Errorf("invalid sync mode %d", config.SyncMode)
   112  	}
   113  	if config.MinerGasPrice == nil || config.MinerGasPrice.Cmp(common.Big0) <= 0 {
   114  		log.Warn("Sanitizing invalid miner gas price", "provided", config.MinerGasPrice, "updated", DefaultConfig.MinerGasPrice)
   115  		config.MinerGasPrice = new(big.Int).Set(DefaultConfig.MinerGasPrice)
   116  	}
   117  	// Assemble the Ethereum object
   118  	chainDb, err := CreateDB(ctx, config, "chaindata")
   119  	if err != nil {
   120  		return nil, err
   121  	}
   122  	chainConfig, genesisHash, genesisErr := core.SetupGenesisBlockWithOverride(chainDb, config.Genesis, config.ConstantinopleOverride)
   123  	if _, ok := genesisErr.(*params.ConfigCompatError); genesisErr != nil && !ok {
   124  		return nil, genesisErr
   125  	}
   126  	log.Info("Initialised chain configuration", "config", chainConfig)
   127  
   128  	//vdpos by ssh begin
   129  	if chainConfig.Vdpos != nil {
   130  		log.Info("Initialised vdpos configuration", "config", *chainConfig.Vdpos)
   131  		if config.NetworkId == 1 { //eth.DefaultConfig.NetworkId
   132  			// change default eth networkid  to default inb networkid
   133  			config.NetworkId = chainConfig.ChainID.Uint64()
   134  		}
   135  	}
   136  	//vdpos by ssh end
   137  
   138  	eth := &Ethereum{
   139  		config:         config,
   140  		chainDb:        chainDb,
   141  		chainConfig:    chainConfig,
   142  		eventMux:       ctx.EventMux,
   143  		accountManager: ctx.AccountManager,
   144  		engine:         CreateConsensusEngine(ctx, chainConfig, &config.Ethash, config.MinerNotify, config.MinerNoverify, chainDb),
   145  		shutdownChan:   make(chan bool),
   146  		networkID:      config.NetworkId,
   147  		gasPrice:       config.MinerGasPrice,
   148  		etherbase:      config.Etherbase,
   149  		bloomRequests:  make(chan chan *bloombits.Retrieval),
   150  		bloomIndexer:   NewBloomIndexer(chainDb, params.BloomBitsBlocks, params.BloomConfirms),
   151  	}
   152  
   153  	log.Info("Initialising INB protocol", "versions", ProtocolVersions, "network", config.NetworkId)
   154  
   155  	if !config.SkipBcVersionCheck {
   156  		bcVersion := rawdb.ReadDatabaseVersion(chainDb)
   157  		if bcVersion != core.BlockChainVersion && bcVersion != 0 {
   158  			return nil, fmt.Errorf("Blockchain DB version mismatch (%d / %d).\n", bcVersion, core.BlockChainVersion)
   159  		}
   160  		rawdb.WriteDatabaseVersion(chainDb, core.BlockChainVersion)
   161  	}
   162  	var (
   163  		vmConfig = vm.Config{
   164  			EnablePreimageRecording: config.EnablePreimageRecording,
   165  			EWASMInterpreter:        config.EWASMInterpreter,
   166  			EVMInterpreter:          config.EVMInterpreter,
   167  		}
   168  		cacheConfig = &core.CacheConfig{Disabled: config.NoPruning, TrieCleanLimit: config.TrieCleanCache, TrieDirtyLimit: config.TrieDirtyCache, TrieTimeLimit: config.TrieTimeout}
   169  	)
   170  	eth.blockchain, err = core.NewBlockChain(chainDb, cacheConfig, eth.chainConfig, eth.engine, vmConfig, eth.shouldPreserve)
   171  	if err != nil {
   172  		return nil, err
   173  	}
   174  	// Rewind the chain in case of an incompatible config upgrade.
   175  	if compat, ok := genesisErr.(*params.ConfigCompatError); ok {
   176  		log.Warn("Rewinding chain to upgrade configuration", "err", compat)
   177  		eth.blockchain.SetHead(compat.RewindTo)
   178  		rawdb.WriteChainConfig(chainDb, genesisHash, chainConfig)
   179  	}
   180  	eth.bloomIndexer.Start(eth.blockchain)
   181  
   182  	if config.TxPool.Journal != "" {
   183  		config.TxPool.Journal = ctx.ResolvePath(config.TxPool.Journal)
   184  	}
   185  	eth.txPool = core.NewTxPool(config.TxPool, eth.chainConfig, eth.blockchain)
   186  
   187  	if eth.protocolManager, err = NewProtocolManager(eth.chainConfig, config.SyncMode, config.NetworkId, eth.eventMux, eth.txPool, eth.engine, eth.blockchain, chainDb, config.Whitelist); err != nil {
   188  		return nil, err
   189  	}
   190  
   191  	eth.miner = miner.New(eth, eth.chainConfig, eth.EventMux(), eth.engine, config.MinerRecommit, config.MinerGasFloor, config.MinerGasCeil, eth.isLocalBlock)
   192  	eth.miner.SetExtra(makeExtraData(config.MinerExtraData))
   193  
   194  	eth.APIBackend = &EthAPIBackend{eth, nil}
   195  	gpoParams := config.GPO
   196  	if gpoParams.Default == nil {
   197  		gpoParams.Default = config.MinerGasPrice
   198  	}
   199  	eth.APIBackend.gpo = gasprice.NewOracle(eth.APIBackend, gpoParams)
   200  
   201  	return eth, nil
   202  }
   203  
   204  func makeExtraData(extra []byte) []byte {
   205  	if len(extra) == 0 {
   206  		// create default extradata
   207  		extra, _ = rlp.EncodeToBytes([]interface{}{
   208  			uint(params.VersionMajor<<16 | params.VersionMinor<<8 | params.VersionPatch),
   209  			"ginb",
   210  			runtime.Version(),
   211  			runtime.GOOS,
   212  		})
   213  	}
   214  	if uint64(len(extra)) > params.MaximumExtraDataSize {
   215  		log.Warn("Miner extra data exceed limit", "extra", hexutil.Bytes(extra), "limit", params.MaximumExtraDataSize)
   216  		extra = nil
   217  	}
   218  	return extra
   219  }
   220  
   221  // CreateDB creates the chain database.
   222  func CreateDB(ctx *node.ServiceContext, config *Config, name string) (ethdb.Database, error) {
   223  	db, err := ctx.OpenDatabase(name, config.DatabaseCache, config.DatabaseHandles)
   224  	if err != nil {
   225  		return nil, err
   226  	}
   227  	if db, ok := db.(*ethdb.LDBDatabase); ok {
   228  		db.Meter("eth/db/chaindata/")
   229  	}
   230  	return db, nil
   231  }
   232  
   233  // CreateConsensusEngine creates the required type of consensus engine instance for an Ethereum service
   234  func CreateConsensusEngine(ctx *node.ServiceContext, chainConfig *params.ChainConfig, config *ethash.Config, notify []string, noverify bool, db ethdb.Database) consensus.Engine {
   235  	// If proof-of-authority is requested, set it up
   236  	if chainConfig.Clique != nil {
   237  		return clique.New(chainConfig.Clique, db)
   238  	} else if chainConfig.Vdpos != nil {
   239  		return vdpos.New(chainConfig.Vdpos, db)
   240  	}
   241  	// Otherwise assume proof-of-work
   242  	switch config.PowMode {
   243  	case ethash.ModeFake:
   244  		log.Warn("Ethash used in fake mode")
   245  		return ethash.NewFaker()
   246  	case ethash.ModeTest:
   247  		log.Warn("Ethash used in test mode")
   248  		return ethash.NewTester(nil, noverify)
   249  	case ethash.ModeShared:
   250  		log.Warn("Ethash used in shared mode")
   251  		return ethash.NewShared()
   252  	default:
   253  		engine := ethash.New(ethash.Config{
   254  			CacheDir:       ctx.ResolvePath(config.CacheDir),
   255  			CachesInMem:    config.CachesInMem,
   256  			CachesOnDisk:   config.CachesOnDisk,
   257  			DatasetDir:     config.DatasetDir,
   258  			DatasetsInMem:  config.DatasetsInMem,
   259  			DatasetsOnDisk: config.DatasetsOnDisk,
   260  		}, notify, noverify)
   261  		engine.SetThreads(-1) // Disable CPU mining
   262  		return engine
   263  	}
   264  }
   265  
   266  // APIs return the collection of RPC services the ethereum package offers.
   267  // NOTE, some of these services probably need to be moved to somewhere else.
   268  func (s *Ethereum) APIs() []rpc.API {
   269  	apis := ethapi.GetAPIs(s.APIBackend)
   270  
   271  	// Append any APIs exposed explicitly by the consensus engine
   272  	apis = append(apis, s.engine.APIs(s.BlockChain())...)
   273  
   274  	// Append all the local APIs and return
   275  	return append(apis, []rpc.API{
   276  		{
   277  			Namespace: "inb",
   278  			Version:   "1.0",
   279  			Service:   NewPublicEthereumAPI(s),
   280  			Public:    true,
   281  		}, {
   282  			Namespace: "inb",
   283  			Version:   "1.0",
   284  			Service:   NewPublicMinerAPI(s),
   285  			Public:    true,
   286  		}, {
   287  			Namespace: "inb",
   288  			Version:   "1.0",
   289  			Service:   downloader.NewPublicDownloaderAPI(s.protocolManager.downloader, s.eventMux),
   290  			Public:    true,
   291  		}, {
   292  			Namespace: "miner",
   293  			Version:   "1.0",
   294  			Service:   NewPrivateMinerAPI(s),
   295  			Public:    false,
   296  		}, {
   297  			Namespace: "inb",
   298  			Version:   "1.0",
   299  			Service:   filters.NewPublicFilterAPI(s.APIBackend, false),
   300  			Public:    true,
   301  		}, {
   302  			Namespace: "admin",
   303  			Version:   "1.0",
   304  			Service:   NewPrivateAdminAPI(s),
   305  		}, {
   306  			Namespace: "debug",
   307  			Version:   "1.0",
   308  			Service:   NewPublicDebugAPI(s),
   309  			Public:    true,
   310  		}, {
   311  			Namespace: "debug",
   312  			Version:   "1.0",
   313  			Service:   NewPrivateDebugAPI(s.chainConfig, s),
   314  		}, {
   315  			Namespace: "net",
   316  			Version:   "1.0",
   317  			Service:   s.netRPCService,
   318  			Public:    true,
   319  		},
   320  	}...)
   321  }
   322  
   323  func (s *Ethereum) ResetWithGenesisBlock(gb *types.Block) {
   324  	s.blockchain.ResetWithGenesisBlock(gb)
   325  }
   326  
   327  func (s *Ethereum) Etherbase() (eb common.Address, err error) {
   328  	s.lock.RLock()
   329  	etherbase := s.etherbase
   330  	s.lock.RUnlock()
   331  
   332  	if etherbase != (common.Address{}) {
   333  		return etherbase, nil
   334  	}
   335  	if wallets := s.AccountManager().Wallets(); len(wallets) > 0 {
   336  		if accounts := wallets[0].Accounts(); len(accounts) > 0 {
   337  			etherbase := accounts[0].Address
   338  
   339  			s.lock.Lock()
   340  			s.etherbase = etherbase
   341  			s.lock.Unlock()
   342  
   343  			log.Info("Etherbase automatically configured", "address", etherbase)
   344  			return etherbase, nil
   345  		}
   346  	}
   347  	return common.Address{}, fmt.Errorf("etherbase must be explicitly specified")
   348  }
   349  
   350  // isLocalBlock checks whether the specified block is mined
   351  // by local miner accounts.
   352  //
   353  // We regard two types of accounts as local miner account: etherbase
   354  // and accounts specified via `txpool.locals` flag.
   355  func (s *Ethereum) isLocalBlock(block *types.Block) bool {
   356  	author, err := s.engine.Author(block.Header())
   357  	if err != nil {
   358  		log.Warn("Failed to retrieve block author", "number", block.NumberU64(), "hash", block.Hash(), "err", err)
   359  		return false
   360  	}
   361  	// Check whether the given address is etherbase.
   362  	s.lock.RLock()
   363  	etherbase := s.etherbase
   364  	s.lock.RUnlock()
   365  	if author == etherbase {
   366  		return true
   367  	}
   368  	// Check whether the given address is specified by `txpool.local`
   369  	// CLI flag.
   370  	for _, account := range s.config.TxPool.Locals {
   371  		if account == author {
   372  			return true
   373  		}
   374  	}
   375  	return false
   376  }
   377  
   378  // shouldPreserve checks whether we should preserve the given block
   379  // during the chain reorg depending on whether the author of block
   380  // is a local account.
   381  func (s *Ethereum) shouldPreserve(block *types.Block) bool {
   382  	// The reason we need to disable the self-reorg preserving for clique
   383  	// is it can be probable to introduce a deadlock.
   384  	//
   385  	// e.g. If there are 7 available signers
   386  	//
   387  	// r1   A
   388  	// r2     B
   389  	// r3       C
   390  	// r4         D
   391  	// r5   A      [X] F G
   392  	// r6    [X]
   393  	//
   394  	// In the round5, the inturn signer E is offline, so the worst case
   395  	// is A, F and G sign the block of round5 and reject the block of opponents
   396  	// and in the round6, the last available signer B is offline, the whole
   397  	// network is stuck.
   398  	if _, ok := s.engine.(*clique.Clique); ok {
   399  		return false
   400  	}
   401  	return s.isLocalBlock(block)
   402  }
   403  
   404  // SetEtherbase sets the mining reward address.
   405  func (s *Ethereum) SetEtherbase(etherbase common.Address) {
   406  	s.lock.Lock()
   407  	s.etherbase = etherbase
   408  	s.lock.Unlock()
   409  
   410  	s.miner.SetEtherbase(etherbase)
   411  }
   412  
   413  // StartMining starts the miner with the given number of CPU threads. If mining
   414  // is already running, this method adjust the number of threads allowed to use
   415  // and updates the minimum price required by the transaction pool.
   416  func (s *Ethereum) StartMining(threads int) error {
   417  	// Update the thread count within the consensus engine
   418  	type threaded interface {
   419  		SetThreads(threads int)
   420  	}
   421  	if th, ok := s.engine.(threaded); ok {
   422  		log.Info("Updated mining threads", "threads", threads)
   423  		if threads == 0 {
   424  			threads = -1 // Disable the miner from within
   425  		}
   426  		th.SetThreads(threads)
   427  	}
   428  	// If the miner was not running, initialize it
   429  	if !s.IsMining() {
   430  		// Propagate the initial price point to the transaction pool
   431  		s.lock.RLock()
   432  		price := s.gasPrice
   433  		s.lock.RUnlock()
   434  		s.txPool.SetGasPrice(price)
   435  
   436  		// Configure the local mining address
   437  		eb, err := s.Etherbase()
   438  		if err != nil {
   439  			log.Error("Cannot start mining without etherbase", "err", err)
   440  			return fmt.Errorf("etherbase missing: %v", err)
   441  		}
   442  		if clique, ok := s.engine.(*clique.Clique); ok {
   443  			wallet, err := s.accountManager.Find(accounts.Account{Address: eb})
   444  			if wallet == nil || err != nil {
   445  				log.Error("Etherbase account unavailable locally", "err", err)
   446  				return fmt.Errorf("signer missing: %v", err)
   447  			}
   448  			clique.Authorize(eb, wallet.SignHash)
   449  		}
   450  
   451  		//vdpos by ssh begin
   452  		if vdpos, ok := s.engine.(*vdpos.Vdpos); ok {
   453  			wallet, err := s.accountManager.Find(accounts.Account{Address: eb})
   454  			if wallet == nil || err != nil {
   455  				log.Error("Inbbase account unavailable locally", "err", err)
   456  				return fmt.Errorf("signer missing: %v", err)
   457  			}
   458  			vdpos.Authorize(eb, wallet.SignHash, wallet.SignTx)
   459  		}
   460  		//vdpos by ssh end
   461  
   462  		// If mining is started, we can disable the transaction rejection mechanism
   463  		// introduced to speed sync times.
   464  		atomic.StoreUint32(&s.protocolManager.acceptTxs, 1)
   465  
   466  		go s.miner.Start(eb)
   467  	}
   468  	return nil
   469  }
   470  
   471  // StopMining terminates the miner, both at the consensus engine level as well as
   472  // at the block creation level.
   473  func (s *Ethereum) StopMining() {
   474  	// Update the thread count within the consensus engine
   475  	type threaded interface {
   476  		SetThreads(threads int)
   477  	}
   478  	if th, ok := s.engine.(threaded); ok {
   479  		th.SetThreads(-1)
   480  	}
   481  	// Stop the block creating itself
   482  	s.miner.Stop()
   483  }
   484  
   485  func (s *Ethereum) IsMining() bool      { return s.miner.Mining() }
   486  func (s *Ethereum) Miner() *miner.Miner { return s.miner }
   487  
   488  func (s *Ethereum) AccountManager() *accounts.Manager  { return s.accountManager }
   489  func (s *Ethereum) BlockChain() *core.BlockChain       { return s.blockchain }
   490  func (s *Ethereum) TxPool() *core.TxPool               { return s.txPool }
   491  func (s *Ethereum) EventMux() *event.TypeMux           { return s.eventMux }
   492  func (s *Ethereum) Engine() consensus.Engine           { return s.engine }
   493  func (s *Ethereum) ChainDb() ethdb.Database            { return s.chainDb }
   494  func (s *Ethereum) IsListening() bool                  { return true } // Always listening
   495  func (s *Ethereum) EthVersion() int                    { return int(s.protocolManager.SubProtocols[0].Version) }
   496  func (s *Ethereum) NetVersion() uint64                 { return s.networkID }
   497  func (s *Ethereum) Downloader() *downloader.Downloader { return s.protocolManager.downloader }
   498  
   499  // Protocols implements node.Service, returning all the currently configured
   500  // network protocols to start.
   501  func (s *Ethereum) Protocols() []p2p.Protocol {
   502  	if s.lesServer == nil {
   503  		return s.protocolManager.SubProtocols
   504  	}
   505  	return append(s.protocolManager.SubProtocols, s.lesServer.Protocols()...)
   506  }
   507  
   508  // Start implements node.Service, starting all internal goroutines needed by the
   509  // Ethereum protocol implementation.
   510  func (s *Ethereum) Start(srvr *p2p.Server) error {
   511  	// Start the bloom bits servicing goroutines
   512  	s.startBloomHandlers(params.BloomBitsBlocks)
   513  
   514  	// Start the RPC service
   515  	s.netRPCService = ethapi.NewPublicNetAPI(srvr, s.NetVersion())
   516  
   517  	// Figure out a max peers count based on the server limits
   518  	maxPeers := srvr.MaxPeers
   519  	if s.config.LightServ > 0 {
   520  		if s.config.LightPeers >= srvr.MaxPeers {
   521  			return fmt.Errorf("invalid peer config: light peer count (%d) >= total peer count (%d)", s.config.LightPeers, srvr.MaxPeers)
   522  		}
   523  		maxPeers -= s.config.LightPeers
   524  	}
   525  	// Start the networking layer and the light server if requested
   526  	s.protocolManager.Start(maxPeers)
   527  	if s.lesServer != nil {
   528  		s.lesServer.Start(srvr)
   529  	}
   530  	return nil
   531  }
   532  
   533  // Stop implements node.Service, terminating all internal goroutines used by the
   534  // Ethereum protocol.
   535  func (s *Ethereum) Stop() error {
   536  	s.bloomIndexer.Close()
   537  	s.blockchain.Stop()
   538  	s.engine.Close()
   539  	s.protocolManager.Stop()
   540  	if s.lesServer != nil {
   541  		s.lesServer.Stop()
   542  	}
   543  	s.txPool.Stop()
   544  	s.miner.Stop()
   545  	s.eventMux.Stop()
   546  
   547  	s.chainDb.Close()
   548  	close(s.shutdownChan)
   549  	return nil
   550  }