lnd.xprv/chainregistry.go

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package main
import (
"encoding/hex"
"fmt"
"io/ioutil"
"net"
"os"
"path/filepath"
"strconv"
"strings"
"sync"
"time"
"github.com/lightninglabs/neutrino"
"github.com/lightningnetwork/lnd/chainntnfs"
"github.com/lightningnetwork/lnd/chainntnfs/bitcoindnotify"
"github.com/lightningnetwork/lnd/chainntnfs/btcdnotify"
"github.com/lightningnetwork/lnd/chainntnfs/neutrinonotify"
"github.com/lightningnetwork/lnd/channeldb"
"github.com/lightningnetwork/lnd/htlcswitch"
"github.com/lightningnetwork/lnd/keychain"
"github.com/lightningnetwork/lnd/lnwallet"
"github.com/lightningnetwork/lnd/lnwallet/btcwallet"
"github.com/lightningnetwork/lnd/lnwire"
"github.com/lightningnetwork/lnd/routing/chainview"
"github.com/roasbeef/btcd/chaincfg/chainhash"
"github.com/roasbeef/btcd/rpcclient"
"github.com/roasbeef/btcutil"
"github.com/roasbeef/btcwallet/chain"
"github.com/roasbeef/btcwallet/walletdb"
)
const (
defaultBitcoinMinHTLCMSat = lnwire.MilliSatoshi(1000)
defaultBitcoinBaseFeeMSat = lnwire.MilliSatoshi(1000)
defaultBitcoinFeeRate = lnwire.MilliSatoshi(1)
defaultBitcoinTimeLockDelta = 144
defaultBitcoinStaticFeeRate = lnwallet.SatPerVByte(50)
defaultLitecoinMinHTLCMSat = lnwire.MilliSatoshi(1000)
defaultLitecoinBaseFeeMSat = lnwire.MilliSatoshi(1000)
defaultLitecoinFeeRate = lnwire.MilliSatoshi(1)
defaultLitecoinTimeLockDelta = 576
defaultLitecoinStaticFeeRate = lnwallet.SatPerVByte(200)
defaultLitecoinMinRelayFee = btcutil.Amount(1000)
)
// defaultBtcChannelConstraints is the default set of channel constraints that are
// meant to be used when initially funding a Bitcoin channel.
//
// TODO(halseth): make configurable at startup?
var defaultBtcChannelConstraints = channeldb.ChannelConstraints{
DustLimit: lnwallet.DefaultDustLimit(),
MaxAcceptedHtlcs: lnwallet.MaxHTLCNumber / 2,
}
// defaultLtcChannelConstraints is the default set of channel constraints that are
// meant to be used when initially funding a Litecoin channel.
var defaultLtcChannelConstraints = channeldb.ChannelConstraints{
DustLimit: defaultLitecoinMinRelayFee,
MaxAcceptedHtlcs: lnwallet.MaxHTLCNumber / 2,
}
// chainCode is an enum-like structure for keeping track of the chains
// currently supported within lnd.
type chainCode uint32
const (
// bitcoinChain is Bitcoin's testnet chain.
bitcoinChain chainCode = iota
// litecoinChain is Litecoin's testnet chain.
litecoinChain
)
// String returns a string representation of the target chainCode.
func (c chainCode) String() string {
switch c {
case bitcoinChain:
return "bitcoin"
case litecoinChain:
return "litecoin"
default:
return "kekcoin"
}
}
// chainControl couples the three primary interfaces lnd utilizes for a
// particular chain together. A single chainControl instance will exist for all
// the chains lnd is currently active on.
type chainControl struct {
chainIO lnwallet.BlockChainIO
feeEstimator lnwallet.FeeEstimator
signer lnwallet.Signer
msgSigner lnwallet.MessageSigner
chainNotifier chainntnfs.ChainNotifier
chainView chainview.FilteredChainView
wallet *lnwallet.LightningWallet
routingPolicy htlcswitch.ForwardingPolicy
}
// newChainControlFromConfig attempts to create a chainControl instance
// according to the parameters in the passed lnd configuration. Currently two
// branches of chainControl instances exist: one backed by a running btcd
// full-node, and the other backed by a running neutrino light client instance.
func newChainControlFromConfig(cfg *config, chanDB *channeldb.DB,
privateWalletPw, publicWalletPw []byte) (*chainControl, func(), error) {
// Set the RPC config from the "home" chain. Multi-chain isn't yet
// active, so we'll restrict usage to a particular chain for now.
homeChainConfig := cfg.Bitcoin
if registeredChains.PrimaryChain() == litecoinChain {
homeChainConfig = cfg.Litecoin
}
ltndLog.Infof("Primary chain is set to: %v",
registeredChains.PrimaryChain())
cc := &chainControl{}
switch registeredChains.PrimaryChain() {
case bitcoinChain:
cc.routingPolicy = htlcswitch.ForwardingPolicy{
MinHTLC: cfg.Bitcoin.MinHTLC,
BaseFee: cfg.Bitcoin.BaseFee,
FeeRate: cfg.Bitcoin.FeeRate,
TimeLockDelta: cfg.Bitcoin.TimeLockDelta,
}
cc.feeEstimator = lnwallet.StaticFeeEstimator{
FeeRate: defaultBitcoinStaticFeeRate,
}
case litecoinChain:
cc.routingPolicy = htlcswitch.ForwardingPolicy{
MinHTLC: cfg.Litecoin.MinHTLC,
BaseFee: cfg.Litecoin.BaseFee,
FeeRate: cfg.Litecoin.FeeRate,
TimeLockDelta: cfg.Litecoin.TimeLockDelta,
}
cc.feeEstimator = lnwallet.StaticFeeEstimator{
FeeRate: defaultLitecoinStaticFeeRate,
}
default:
return nil, nil, fmt.Errorf("Default routing policy for "+
"chain %v is unknown", registeredChains.PrimaryChain())
}
walletConfig := &btcwallet.Config{
PrivatePass: privateWalletPw,
PublicPass: publicWalletPw,
DataDir: homeChainConfig.ChainDir,
NetParams: activeNetParams.Params,
FeeEstimator: cc.feeEstimator,
CoinType: activeNetParams.CoinType,
}
var (
err error
cleanUp func()
btcdConn *chain.RPCClient
bitcoindConn *chain.BitcoindClient
)
// If spv mode is active, then we'll be using a distinct set of
// chainControl interfaces that interface directly with the p2p network
// of the selected chain.
switch homeChainConfig.Node {
case "neutrino":
// First we'll open the database file for neutrino, creating
// the database if needed. We append the normalized network name
// here to match the behavior of btcwallet.
neutrinoDbPath := filepath.Join(homeChainConfig.ChainDir,
normalizeNetwork(activeNetParams.Name))
// Ensure that the neutrino db path exists.
if err := os.MkdirAll(neutrinoDbPath, 0700); err != nil {
return nil, nil, err
}
dbName := filepath.Join(neutrinoDbPath, "neutrino.db")
nodeDatabase, err := walletdb.Create("bdb", dbName)
if err != nil {
return nil, nil, err
}
// With the database open, we can now create an instance of the
// neutrino light client. We pass in relevant configuration
// parameters required.
config := neutrino.Config{
DataDir: neutrinoDbPath,
Database: nodeDatabase,
ChainParams: *activeNetParams.Params,
AddPeers: cfg.NeutrinoMode.AddPeers,
ConnectPeers: cfg.NeutrinoMode.ConnectPeers,
Dialer: func(addr net.Addr) (net.Conn, error) {
return cfg.net.Dial(addr.Network(), addr.String())
},
NameResolver: func(host string) ([]net.IP, error) {
addrs, err := cfg.net.LookupHost(host)
if err != nil {
return nil, err
}
ips := make([]net.IP, 0, len(addrs))
for _, strIP := range addrs {
ip := net.ParseIP(strIP)
if ip == nil {
continue
}
ips = append(ips, ip)
}
return ips, nil
},
}
neutrino.WaitForMoreCFHeaders = time.Second * 1
neutrino.MaxPeers = 8
neutrino.BanDuration = 5 * time.Second
svc, err := neutrino.NewChainService(config)
if err != nil {
return nil, nil, fmt.Errorf("unable to create neutrino: %v", err)
}
svc.Start()
// Next we'll create the instances of the ChainNotifier and
// FilteredChainView interface which is backed by the neutrino
// light client.
cc.chainNotifier, err = neutrinonotify.New(svc)
if err != nil {
return nil, nil, err
}
cc.chainView, err = chainview.NewCfFilteredChainView(svc)
if err != nil {
return nil, nil, err
}
// Finally, we'll set the chain source for btcwallet, and
// create our clean up function which simply closes the
// database.
walletConfig.ChainSource = chain.NewNeutrinoClient(svc)
cleanUp = func() {
nodeDatabase.Close()
}
case "bitcoind", "litecoind":
var bitcoindMode *bitcoindConfig
switch {
case cfg.Bitcoin.Active:
bitcoindMode = cfg.BitcoindMode
case cfg.Litecoin.Active:
bitcoindMode = cfg.LitecoindMode
}
// Otherwise, we'll be speaking directly via RPC and ZMQ to a
// bitcoind node. If the specified host for the btcd/ltcd RPC
// server already has a port specified, then we use that
// directly. Otherwise, we assume the default port according to
// the selected chain parameters.
var bitcoindHost string
if strings.Contains(bitcoindMode.RPCHost, ":") {
bitcoindHost = bitcoindMode.RPCHost
} else {
// The RPC ports specified in chainparams.go assume
// btcd, which picks a different port so that btcwallet
// can use the same RPC port as bitcoind. We convert
// this back to the btcwallet/bitcoind port.
rpcPort, err := strconv.Atoi(activeNetParams.rpcPort)
if err != nil {
return nil, nil, err
}
rpcPort -= 2
bitcoindHost = fmt.Sprintf("%v:%d",
bitcoindMode.RPCHost, rpcPort)
if cfg.Bitcoin.Active && cfg.Bitcoin.RegTest {
conn, err := net.Dial("tcp", bitcoindHost)
if err != nil || conn == nil {
rpcPort = 18443
bitcoindHost = fmt.Sprintf("%v:%d",
bitcoindMode.RPCHost,
rpcPort)
} else {
conn.Close()
}
}
}
bitcoindUser := bitcoindMode.RPCUser
bitcoindPass := bitcoindMode.RPCPass
rpcConfig := &rpcclient.ConnConfig{
Host: bitcoindHost,
User: bitcoindUser,
Pass: bitcoindPass,
DisableConnectOnNew: true,
DisableAutoReconnect: false,
DisableTLS: true,
HTTPPostMode: true,
}
cc.chainNotifier, err = bitcoindnotify.New(rpcConfig,
bitcoindMode.ZMQPath, *activeNetParams.Params)
if err != nil {
return nil, nil, err
}
// Next, we'll create an instance of the bitcoind chain view to
// be used within the routing layer.
cc.chainView, err = chainview.NewBitcoindFilteredChainView(
*rpcConfig, bitcoindMode.ZMQPath,
*activeNetParams.Params)
if err != nil {
srvrLog.Errorf("unable to create chain view: %v", err)
return nil, nil, err
}
// Create a special rpc+ZMQ client for bitcoind which will be
// used by the wallet for notifications, calls, etc.
bitcoindConn, err = chain.NewBitcoindClient(
activeNetParams.Params, bitcoindHost, bitcoindUser,
bitcoindPass, bitcoindMode.ZMQPath,
time.Millisecond*100)
if err != nil {
return nil, nil, err
}
walletConfig.ChainSource = bitcoindConn
// If we're not in regtest mode, then we'll attempt to use a
// proper fee estimator for testnet.
if cfg.Bitcoin.Active && !cfg.Bitcoin.RegTest {
ltndLog.Infof("Initializing bitcoind backed fee estimator")
// Finally, we'll re-initialize the fee estimator, as
// if we're using bitcoind as a backend, then we can
// use live fee estimates, rather than a statically
// coded value.
fallBackFeeRate := lnwallet.SatPerVByte(25)
cc.feeEstimator, err = lnwallet.NewBitcoindFeeEstimator(
*rpcConfig, fallBackFeeRate,
)
if err != nil {
return nil, nil, err
}
if err := cc.feeEstimator.Start(); err != nil {
return nil, nil, err
}
} else if cfg.Litecoin.Active {
ltndLog.Infof("Initializing litecoind backed fee estimator")
// Finally, we'll re-initialize the fee estimator, as
// if we're using litecoind as a backend, then we can
// use live fee estimates, rather than a statically
// coded value.
fallBackFeeRate := lnwallet.SatPerVByte(25)
cc.feeEstimator, err = lnwallet.NewBitcoindFeeEstimator(
*rpcConfig, fallBackFeeRate,
)
if err != nil {
return nil, nil, err
}
if err := cc.feeEstimator.Start(); err != nil {
return nil, nil, err
}
}
case "btcd", "ltcd":
// Otherwise, we'll be speaking directly via RPC to a node.
//
// So first we'll load btcd/ltcd's TLS cert for the RPC
// connection. If a raw cert was specified in the config, then
// we'll set that directly. Otherwise, we attempt to read the
// cert from the path specified in the config.
var btcdMode *btcdConfig
switch {
case cfg.Bitcoin.Active:
btcdMode = cfg.BtcdMode
case cfg.Litecoin.Active:
btcdMode = cfg.LtcdMode
}
var rpcCert []byte
if btcdMode.RawRPCCert != "" {
rpcCert, err = hex.DecodeString(btcdMode.RawRPCCert)
if err != nil {
return nil, nil, err
}
} else {
certFile, err := os.Open(btcdMode.RPCCert)
if err != nil {
return nil, nil, err
}
rpcCert, err = ioutil.ReadAll(certFile)
if err != nil {
return nil, nil, err
}
if err := certFile.Close(); err != nil {
return nil, nil, err
}
}
// If the specified host for the btcd/ltcd RPC server already
// has a port specified, then we use that directly. Otherwise,
// we assume the default port according to the selected chain
// parameters.
var btcdHost string
if strings.Contains(btcdMode.RPCHost, ":") {
btcdHost = btcdMode.RPCHost
} else {
btcdHost = fmt.Sprintf("%v:%v", btcdMode.RPCHost,
activeNetParams.rpcPort)
}
btcdUser := btcdMode.RPCUser
btcdPass := btcdMode.RPCPass
rpcConfig := &rpcclient.ConnConfig{
Host: btcdHost,
Endpoint: "ws",
User: btcdUser,
Pass: btcdPass,
Certificates: rpcCert,
DisableTLS: false,
DisableConnectOnNew: true,
DisableAutoReconnect: false,
}
cc.chainNotifier, err = btcdnotify.New(rpcConfig)
if err != nil {
return nil, nil, err
}
// Finally, we'll create an instance of the default chain view to be
// used within the routing layer.
cc.chainView, err = chainview.NewBtcdFilteredChainView(*rpcConfig)
if err != nil {
srvrLog.Errorf("unable to create chain view: %v", err)
return nil, nil, err
}
// Create a special websockets rpc client for btcd which will be used
// by the wallet for notifications, calls, etc.
2017-06-06 05:44:54 +03:00
chainRPC, err := chain.NewRPCClient(activeNetParams.Params, btcdHost,
btcdUser, btcdPass, rpcCert, false, 20)
if err != nil {
return nil, nil, err
}
2017-06-06 05:44:54 +03:00
walletConfig.ChainSource = chainRPC
btcdConn = chainRPC
// If we're not in simnet or regtest mode, then we'll attempt
// to use a proper fee estimator for testnet.
if !cfg.Bitcoin.SimNet && !cfg.Litecoin.SimNet &&
!cfg.Bitcoin.RegTest && !cfg.Litecoin.RegTest {
ltndLog.Infof("Initializing btcd backed fee estimator")
// Finally, we'll re-initialize the fee estimator, as
// if we're using btcd as a backend, then we can use
// live fee estimates, rather than a statically coded
// value.
fallBackFeeRate := lnwallet.SatPerVByte(25)
cc.feeEstimator, err = lnwallet.NewBtcdFeeEstimator(
*rpcConfig, fallBackFeeRate,
)
if err != nil {
return nil, nil, err
}
if err := cc.feeEstimator.Start(); err != nil {
return nil, nil, err
}
}
default:
return nil, nil, fmt.Errorf("unknown node type: %s",
homeChainConfig.Node)
}
wc, err := btcwallet.New(*walletConfig)
if err != nil {
fmt.Printf("unable to create wallet controller: %v\n", err)
return nil, nil, err
}
cc.msgSigner = wc
cc.signer = wc
cc.chainIO = wc
// Select the default channel constraints for the primary chain.
channelConstraints := defaultBtcChannelConstraints
if registeredChains.PrimaryChain() == litecoinChain {
channelConstraints = defaultLtcChannelConstraints
}
keyRing := keychain.NewBtcWalletKeyRing(
wc.InternalWallet(), activeNetParams.CoinType,
)
// Create, and start the lnwallet, which handles the core payment
// channel logic, and exposes control via proxy state machines.
walletCfg := lnwallet.Config{
Database: chanDB,
Notifier: cc.chainNotifier,
WalletController: wc,
Signer: cc.signer,
FeeEstimator: cc.feeEstimator,
SecretKeyRing: keyRing,
ChainIO: cc.chainIO,
DefaultConstraints: channelConstraints,
NetParams: *activeNetParams.Params,
}
wallet, err := lnwallet.NewLightningWallet(walletCfg)
if err != nil {
fmt.Printf("unable to create wallet: %v\n", err)
return nil, nil, err
}
if err := wallet.Startup(); err != nil {
fmt.Printf("unable to start wallet: %v\n", err)
return nil, nil, err
}
ltndLog.Info("LightningWallet opened")
cc.wallet = wallet
// As a final check, if we're using the RPC backend, we'll ensure that
// the btcd node has the txindex set. Atm, this is required in order to
// properly perform historical confirmation+spend dispatches.
if homeChainConfig.Node != "neutrino" {
// In order to check to see if we have the txindex up to date
// and active, we'll try to fetch the first transaction in the
// latest block via the index. If this doesn't succeed, then we
// know it isn't active (or just not yet up to date).
bestHash, _, err := cc.chainIO.GetBestBlock()
if err != nil {
return nil, nil, fmt.Errorf("unable to get current "+
"best hash: %v", err)
}
bestBlock, err := cc.chainIO.GetBlock(bestHash)
if err != nil {
return nil, nil, fmt.Errorf("unable to get current "+
"block hash: %v", err)
}
firstTxHash := bestBlock.Transactions[0].TxHash()
switch homeChainConfig.Node {
case "btcd":
_, err = btcdConn.GetRawTransaction(&firstTxHash)
case "bitcoind":
_, err = bitcoindConn.GetRawTransactionVerbose(&firstTxHash)
}
if err != nil {
// If the node doesn't have the txindex set, then we'll
// halt startup, as we can't proceed in this state.
return nil, nil, fmt.Errorf("%s detected to not "+
"have --txindex active, cannot proceed",
homeChainConfig.Node)
}
}
return cc, cleanUp, nil
}
var (
// bitcoinTestnetGenesis is the genesis hash of Bitcoin's testnet
// chain.
bitcoinTestnetGenesis = chainhash.Hash([chainhash.HashSize]byte{
0x43, 0x49, 0x7f, 0xd7, 0xf8, 0x26, 0x95, 0x71,
0x08, 0xf4, 0xa3, 0x0f, 0xd9, 0xce, 0xc3, 0xae,
0xba, 0x79, 0x97, 0x20, 0x84, 0xe9, 0x0e, 0xad,
0x01, 0xea, 0x33, 0x09, 0x00, 0x00, 0x00, 0x00,
})
// bitcoinMainnetGenesis is the genesis hash of Bitcoin's main chain.
bitcoinMainnetGenesis = chainhash.Hash([chainhash.HashSize]byte{
0x6f, 0xe2, 0x8c, 0x0a, 0xb6, 0xf1, 0xb3, 0x72,
0xc1, 0xa6, 0xa2, 0x46, 0xae, 0x63, 0xf7, 0x4f,
0x93, 0x1e, 0x83, 0x65, 0xe1, 0x5a, 0x08, 0x9c,
0x68, 0xd6, 0x19, 0x00, 0x00, 0x00, 0x00, 0x00,
})
// litecoinTestnetGenesis is the genesis hash of Litecoin's testnet4
// chain.
litecoinTestnetGenesis = chainhash.Hash([chainhash.HashSize]byte{
0xa0, 0x29, 0x3e, 0x4e, 0xeb, 0x3d, 0xa6, 0xe6,
0xf5, 0x6f, 0x81, 0xed, 0x59, 0x5f, 0x57, 0x88,
0x0d, 0x1a, 0x21, 0x56, 0x9e, 0x13, 0xee, 0xfd,
0xd9, 0x51, 0x28, 0x4b, 0x5a, 0x62, 0x66, 0x49,
})
// litecoinMainnetGenesis is the genesis hash of Litecoin's main chain.
litecoinMainnetGenesis = chainhash.Hash([chainhash.HashSize]byte{
0xe2, 0xbf, 0x04, 0x7e, 0x7e, 0x5a, 0x19, 0x1a,
0xa4, 0xef, 0x34, 0xd3, 0x14, 0x97, 0x9d, 0xc9,
0x98, 0x6e, 0x0f, 0x19, 0x25, 0x1e, 0xda, 0xba,
0x59, 0x40, 0xfd, 0x1f, 0xe3, 0x65, 0xa7, 0x12,
})
// chainMap is a simple index that maps a chain's genesis hash to the
// chainCode enum for that chain.
chainMap = map[chainhash.Hash]chainCode{
bitcoinTestnetGenesis: bitcoinChain,
litecoinTestnetGenesis: litecoinChain,
bitcoinMainnetGenesis: bitcoinChain,
litecoinMainnetGenesis: litecoinChain,
}
// chainDNSSeeds is a map of a chain's hash to the set of DNS seeds
// that will be use to bootstrap peers upon first startup.
//
// The first item in the array is the primary host we'll use to attempt
// the SRV lookup we require. If we're unable to receive a response
// over UDP, then we'll fall back to manual TCP resolution. The second
// item in the array is a special A record that we'll query in order to
// receive the IP address of the current authoritative DNS server for
// the network seed.
//
// TODO(roasbeef): extend and collapse these and chainparams.go into
// struct like chaincfg.Params
chainDNSSeeds = map[chainhash.Hash][][2]string{
bitcoinMainnetGenesis: {
{
"nodes.lightning.directory",
"soa.nodes.lightning.directory",
},
},
bitcoinTestnetGenesis: {
{
"test.nodes.lightning.directory",
"soa.nodes.lightning.directory",
},
},
litecoinMainnetGenesis: {
{
"ltc.nodes.lightning.directory",
"soa.nodes.lightning.directory",
},
},
}
)
// chainRegistry keeps track of the current chains
type chainRegistry struct {
sync.RWMutex
activeChains map[chainCode]*chainControl
netParams map[chainCode]*bitcoinNetParams
primaryChain chainCode
}
// newChainRegistry creates a new chainRegistry.
func newChainRegistry() *chainRegistry {
return &chainRegistry{
activeChains: make(map[chainCode]*chainControl),
netParams: make(map[chainCode]*bitcoinNetParams),
}
}
// RegisterChain assigns an active chainControl instance to a target chain
// identified by its chainCode.
func (c *chainRegistry) RegisterChain(newChain chainCode, cc *chainControl) {
c.Lock()
c.activeChains[newChain] = cc
c.Unlock()
}
// LookupChain attempts to lookup an active chainControl instance for the
// target chain.
func (c *chainRegistry) LookupChain(targetChain chainCode) (*chainControl, bool) {
c.RLock()
cc, ok := c.activeChains[targetChain]
c.RUnlock()
return cc, ok
}
// LookupChainByHash attempts to look up an active chainControl which
// corresponds to the passed genesis hash.
func (c *chainRegistry) LookupChainByHash(chainHash chainhash.Hash) (*chainControl, bool) {
c.RLock()
defer c.RUnlock()
targetChain, ok := chainMap[chainHash]
if !ok {
return nil, ok
}
cc, ok := c.activeChains[targetChain]
return cc, ok
}
// RegisterPrimaryChain sets a target chain as the "home chain" for lnd.
func (c *chainRegistry) RegisterPrimaryChain(cc chainCode) {
c.Lock()
defer c.Unlock()
c.primaryChain = cc
}
// PrimaryChain returns the primary chain for this running lnd instance. The
// primary chain is considered the "home base" while the other registered
// chains are treated as secondary chains.
func (c *chainRegistry) PrimaryChain() chainCode {
c.RLock()
defer c.RUnlock()
return c.primaryChain
}
// ActiveChains returns the total number of active chains.
func (c *chainRegistry) ActiveChains() []chainCode {
c.RLock()
defer c.RUnlock()
chains := make([]chainCode, 0, len(c.activeChains))
for activeChain := range c.activeChains {
chains = append(chains, activeChain)
}
return chains
}
// NumActiveChains returns the total number of active chains.
func (c *chainRegistry) NumActiveChains() uint32 {
c.RLock()
defer c.RUnlock()
return uint32(len(c.activeChains))
}