12343072627

Committed 15 Dec 2024 11:09PM UTC coverage: 57.504% (-1.1%) from 58.636%

Build # 12343072627

Build Type

Pull #9315

github

Committed by

yyforyongyu

Commit Message

contractcourt: offer outgoing htlc one block earlier before its expiry

We need to offer the outgoing htlc one block earlier to make sure when
the expiry height hits, the sweeper will not miss sweeping it in the
same block. This also means the outgoing contest resolver now only does
one thing - watch for preimage spend till height expiry-1, which can
easily be moved into the timeout resolver instead in the future.

Pull Request Pull Request #9315: Implement `blockbeat`

Run Details

1445 of 2007 new or added lines in 26 files covered. (72.0%)

19246 existing lines in 249 files now uncovered.

102342 of 177975 relevant lines covered (57.5%)

24772.24 hits per line

Source File
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0.28

/server.go

package lnd

import (
        "bytes"
        "context"
        "crypto/rand"
        "encoding/hex"
        "fmt"
        "math/big"
        prand "math/rand"
        "net"
        "strconv"
        "strings"
        "sync"
        "sync/atomic"
        "time"

        "github.com/btcsuite/btcd/btcec/v2"
        "github.com/btcsuite/btcd/btcec/v2/ecdsa"
        "github.com/btcsuite/btcd/btcutil"
        "github.com/btcsuite/btcd/chaincfg"
        "github.com/btcsuite/btcd/chaincfg/chainhash"
        "github.com/btcsuite/btcd/connmgr"
        "github.com/btcsuite/btcd/txscript"
        "github.com/btcsuite/btcd/wire"
        "github.com/go-errors/errors"
        sphinx "github.com/lightningnetwork/lightning-onion"
        "github.com/lightningnetwork/lnd/aliasmgr"
        "github.com/lightningnetwork/lnd/autopilot"
        "github.com/lightningnetwork/lnd/brontide"
        "github.com/lightningnetwork/lnd/chainio"
        "github.com/lightningnetwork/lnd/chainreg"
        "github.com/lightningnetwork/lnd/chanacceptor"
        "github.com/lightningnetwork/lnd/chanbackup"
        "github.com/lightningnetwork/lnd/chanfitness"
        "github.com/lightningnetwork/lnd/channeldb"
        "github.com/lightningnetwork/lnd/channelnotifier"
        "github.com/lightningnetwork/lnd/clock"
        "github.com/lightningnetwork/lnd/cluster"
        "github.com/lightningnetwork/lnd/contractcourt"
        "github.com/lightningnetwork/lnd/discovery"
        "github.com/lightningnetwork/lnd/feature"
        "github.com/lightningnetwork/lnd/fn/v2"
        "github.com/lightningnetwork/lnd/funding"
        "github.com/lightningnetwork/lnd/graph"
        graphdb "github.com/lightningnetwork/lnd/graph/db"
        "github.com/lightningnetwork/lnd/graph/db/models"
        "github.com/lightningnetwork/lnd/graph/graphsession"
        "github.com/lightningnetwork/lnd/healthcheck"
        "github.com/lightningnetwork/lnd/htlcswitch"
        "github.com/lightningnetwork/lnd/htlcswitch/hop"
        "github.com/lightningnetwork/lnd/input"
        "github.com/lightningnetwork/lnd/invoices"
        "github.com/lightningnetwork/lnd/keychain"
        "github.com/lightningnetwork/lnd/kvdb"
        "github.com/lightningnetwork/lnd/lncfg"
        "github.com/lightningnetwork/lnd/lnencrypt"
        "github.com/lightningnetwork/lnd/lnpeer"
        "github.com/lightningnetwork/lnd/lnrpc"
        "github.com/lightningnetwork/lnd/lnrpc/routerrpc"
        "github.com/lightningnetwork/lnd/lnwallet"
        "github.com/lightningnetwork/lnd/lnwallet/chainfee"
        "github.com/lightningnetwork/lnd/lnwallet/chanfunding"
        "github.com/lightningnetwork/lnd/lnwallet/rpcwallet"
        "github.com/lightningnetwork/lnd/lnwire"
        "github.com/lightningnetwork/lnd/nat"
        "github.com/lightningnetwork/lnd/netann"
        "github.com/lightningnetwork/lnd/peer"
        "github.com/lightningnetwork/lnd/peernotifier"
        "github.com/lightningnetwork/lnd/pool"
        "github.com/lightningnetwork/lnd/queue"
        "github.com/lightningnetwork/lnd/routing"
        "github.com/lightningnetwork/lnd/routing/localchans"
        "github.com/lightningnetwork/lnd/routing/route"
        "github.com/lightningnetwork/lnd/subscribe"
        "github.com/lightningnetwork/lnd/sweep"
        "github.com/lightningnetwork/lnd/ticker"
        "github.com/lightningnetwork/lnd/tor"
        "github.com/lightningnetwork/lnd/walletunlocker"
        "github.com/lightningnetwork/lnd/watchtower/blob"
        "github.com/lightningnetwork/lnd/watchtower/wtclient"
        "github.com/lightningnetwork/lnd/watchtower/wtpolicy"
        "github.com/lightningnetwork/lnd/watchtower/wtserver"
)

const (
        // defaultMinPeers is the minimum number of peers nodes should always be
        // connected to.
        defaultMinPeers = 3

        // defaultStableConnDuration is a floor under which all reconnection
        // attempts will apply exponential randomized backoff. Connections
        // durations exceeding this value will be eligible to have their
        // backoffs reduced.
        defaultStableConnDuration = 10 * time.Minute

        // numInstantInitReconnect specifies how many persistent peers we should
        // always attempt outbound connections to immediately. After this value
        // is surpassed, the remaining peers will be randomly delayed using
        // maxInitReconnectDelay.
        numInstantInitReconnect = 10

        // maxInitReconnectDelay specifies the maximum delay in seconds we will
        // apply in attempting to reconnect to persistent peers on startup. The
        // value used or a particular peer will be chosen between 0s and this
        // value.
        maxInitReconnectDelay = 30

        // multiAddrConnectionStagger is the number of seconds to wait between
        // attempting to a peer with each of its advertised addresses.
        multiAddrConnectionStagger = 10 * time.Second
)

var (
        // ErrPeerNotConnected signals that the server has no connection to the
        // given peer.
        ErrPeerNotConnected = errors.New("peer is not connected")

        // ErrServerNotActive indicates that the server has started but hasn't
        // fully finished the startup process.
        ErrServerNotActive = errors.New("server is still in the process of " +
                "starting")

        // ErrServerShuttingDown indicates that the server is in the process of
        // gracefully exiting.
        ErrServerShuttingDown = errors.New("server is shutting down")

        // MaxFundingAmount is a soft-limit of the maximum channel size
        // currently accepted within the Lightning Protocol. This is
        // defined in BOLT-0002, and serves as an initial precautionary limit
        // while implementations are battle tested in the real world.
        //
        // At the moment, this value depends on which chain is active. It is set
        // to the value under the Bitcoin chain as default.
        //
        // TODO(roasbeef): add command line param to modify.
        MaxFundingAmount = funding.MaxBtcFundingAmount

        // EndorsementExperimentEnd is the time after which nodes should stop
        // propagating experimental endorsement signals.
        //
        // Per blip04: January 1, 2026 12:00:00 AM UTC in unix seconds.
        EndorsementExperimentEnd = time.Unix(1767225600, 0)
)

// errPeerAlreadyConnected is an error returned by the server when we're
// commanded to connect to a peer, but they're already connected.
type errPeerAlreadyConnected struct {
        peer *peer.Brontide
}

// Error returns the human readable version of this error type.
//
// NOTE: Part of the error interface.
func (e *errPeerAlreadyConnected) Error() string {
        return fmt.Sprintf("already connected to peer: %v", e.peer)
}

// server is the main server of the Lightning Network Daemon. The server houses
// global state pertaining to the wallet, database, and the rpcserver.
// Additionally, the server is also used as a central messaging bus to interact
// with any of its companion objects.
type server struct {
        active   int32 // atomic
        stopping int32 // atomic

        start sync.Once
        stop  sync.Once

        cfg *Config

        implCfg *ImplementationCfg

        // identityECDH is an ECDH capable wrapper for the private key used
        // to authenticate any incoming connections.
        identityECDH keychain.SingleKeyECDH

        // identityKeyLoc is the key locator for the above wrapped identity key.
        identityKeyLoc keychain.KeyLocator

        // nodeSigner is an implementation of the MessageSigner implementation
        // that's backed by the identity private key of the running lnd node.
        nodeSigner *netann.NodeSigner

        chanStatusMgr *netann.ChanStatusManager

        // listenAddrs is the list of addresses the server is currently
        // listening on.
        listenAddrs []net.Addr

        // torController is a client that will communicate with a locally
        // running Tor server. This client will handle initiating and
        // authenticating the connection to the Tor server, automatically
        // creating and setting up onion services, etc.
        torController *tor.Controller

        // natTraversal is the specific NAT traversal technique used to
        // automatically set up port forwarding rules in order to advertise to
        // the network that the node is accepting inbound connections.
        natTraversal nat.Traversal

        // lastDetectedIP is the last IP detected by the NAT traversal technique
        // above. This IP will be watched periodically in a goroutine in order
        // to handle dynamic IP changes.
        lastDetectedIP net.IP

        mu sync.RWMutex

        // peersByPub is a map of the active peers.
        //
        // NOTE: The key used here is the raw bytes of the peer's public key to
        // string conversion, which means it cannot be printed using `%s` as it
        // will just print the binary.
        //
        // TODO(yy): Use the hex string instead.
        peersByPub map[string]*peer.Brontide

        inboundPeers  map[string]*peer.Brontide
        outboundPeers map[string]*peer.Brontide

        peerConnectedListeners    map[string][]chan<- lnpeer.Peer
        peerDisconnectedListeners map[string][]chan<- struct{}

        // TODO(yy): the Brontide.Start doesn't know this value, which means it
        // will continue to send messages even if there are no active channels
        // and the value below is false. Once it's pruned, all its connections
        // will be closed, thus the Brontide.Start will return an error.
        persistentPeers        map[string]bool
        persistentPeersBackoff map[string]time.Duration
        persistentPeerAddrs    map[string][]*lnwire.NetAddress
        persistentConnReqs     map[string][]*connmgr.ConnReq
        persistentRetryCancels map[string]chan struct{}

        // peerErrors keeps a set of peer error buffers for peers that have
        // disconnected from us. This allows us to track historic peer errors
        // over connections. The string of the peer's compressed pubkey is used
        // as a key for this map.
        peerErrors map[string]*queue.CircularBuffer

        // ignorePeerTermination tracks peers for which the server has initiated
        // a disconnect. Adding a peer to this map causes the peer termination
        // watcher to short circuit in the event that peers are purposefully
        // disconnected.
        ignorePeerTermination map[*peer.Brontide]struct{}

        // scheduledPeerConnection maps a pubkey string to a callback that
        // should be executed in the peerTerminationWatcher the prior peer with
        // the same pubkey exits.  This allows the server to wait until the
        // prior peer has cleaned up successfully, before adding the new peer
        // intended to replace it.
        scheduledPeerConnection map[string]func()

        // pongBuf is a shared pong reply buffer we'll use across all active
        // peer goroutines. We know the max size of a pong message
        // (lnwire.MaxPongBytes), so we can allocate this ahead of time, and
        // avoid allocations each time we need to send a pong message.
        pongBuf []byte

        cc *chainreg.ChainControl

        fundingMgr *funding.Manager

        graphDB *graphdb.ChannelGraph

        chanStateDB *channeldb.ChannelStateDB

        addrSource channeldb.AddrSource

        // miscDB is the DB that contains all "other" databases within the main
        // channel DB that haven't been separated out yet.
        miscDB *channeldb.DB

        invoicesDB invoices.InvoiceDB

        aliasMgr *aliasmgr.Manager

        htlcSwitch *htlcswitch.Switch

        interceptableSwitch *htlcswitch.InterceptableSwitch

        invoices *invoices.InvoiceRegistry

        invoiceHtlcModifier *invoices.HtlcModificationInterceptor

        channelNotifier *channelnotifier.ChannelNotifier

        peerNotifier *peernotifier.PeerNotifier

        htlcNotifier *htlcswitch.HtlcNotifier

        witnessBeacon contractcourt.WitnessBeacon

        breachArbitrator *contractcourt.BreachArbitrator

        missionController *routing.MissionController
        defaultMC         *routing.MissionControl

        graphBuilder *graph.Builder

        chanRouter *routing.ChannelRouter

        controlTower routing.ControlTower

        authGossiper *discovery.AuthenticatedGossiper

        localChanMgr *localchans.Manager

        utxoNursery *contractcourt.UtxoNursery

        sweeper *sweep.UtxoSweeper

        chainArb *contractcourt.ChainArbitrator

        sphinx *hop.OnionProcessor

        towerClientMgr *wtclient.Manager

        connMgr *connmgr.ConnManager

        sigPool *lnwallet.SigPool

        writePool *pool.Write

        readPool *pool.Read

        tlsManager *TLSManager

        // featureMgr dispatches feature vectors for various contexts within the
        // daemon.
        featureMgr *feature.Manager

        // currentNodeAnn is the node announcement that has been broadcast to
        // the network upon startup, if the attributes of the node (us) has
        // changed since last start.
        currentNodeAnn *lnwire.NodeAnnouncement

        // chansToRestore is the set of channels that upon starting, the server
        // should attempt to restore/recover.
        chansToRestore walletunlocker.ChannelsToRecover

        // chanSubSwapper is a sub-system that will ensure our on-disk channel
        // backups are consistent at all times. It interacts with the
        // channelNotifier to be notified of newly opened and closed channels.
        chanSubSwapper *chanbackup.SubSwapper

        // chanEventStore tracks the behaviour of channels and their remote peers to
        // provide insights into their health and performance.
        chanEventStore *chanfitness.ChannelEventStore

        hostAnn *netann.HostAnnouncer

        // livenessMonitor monitors that lnd has access to critical resources.
        livenessMonitor *healthcheck.Monitor

        customMessageServer *subscribe.Server

        // txPublisher is a publisher with fee-bumping capability.
        txPublisher *sweep.TxPublisher

        // blockbeatDispatcher is a block dispatcher that notifies subscribers
        // of new blocks.
        blockbeatDispatcher *chainio.BlockbeatDispatcher

        quit chan struct{}

        wg sync.WaitGroup
}

// updatePersistentPeerAddrs subscribes to topology changes and stores
// advertised addresses for any NodeAnnouncements from our persisted peers.
func (s *server) updatePersistentPeerAddrs() error {
        graphSub, err := s.graphBuilder.SubscribeTopology()
        if err != nil {
                return err
        }

        s.wg.Add(1)
        go func() {
                defer func() {
                        graphSub.Cancel()
                        s.wg.Done()
                }()

                for {
                        select {
                        case <-s.quit:
                                return

                        case topChange, ok := <-graphSub.TopologyChanges:
                                // If the router is shutting down, then we will
                                // as well.
                                if !ok {
                                        return
                                }

                                for _, update := range topChange.NodeUpdates {
                                        pubKeyStr := string(
                                                update.IdentityKey.
                                                        SerializeCompressed(),
                                        )

                                        // We only care about updates from
                                        // our persistentPeers.
                                        s.mu.RLock()
                                        _, ok := s.persistentPeers[pubKeyStr]
                                        s.mu.RUnlock()
                                        if !ok {
                                                continue
                                        }

                                        addrs := make([]*lnwire.NetAddress, 0,
                                                len(update.Addresses))

                                        for _, addr := range update.Addresses {
                                                addrs = append(addrs,
                                                        &lnwire.NetAddress{
                                                                IdentityKey: update.IdentityKey,
                                                                Address:     addr,
                                                                ChainNet:    s.cfg.ActiveNetParams.Net,
                                                        },
                                                )
                                        }

                                        s.mu.Lock()

                                        // Update the stored addresses for this
                                        // to peer to reflect the new set.
                                        s.persistentPeerAddrs[pubKeyStr] = addrs

                                        // If there are no outstanding
                                        // connection requests for this peer
                                        // then our work is done since we are
                                        // not currently trying to connect to
                                        // them.
                                        if len(s.persistentConnReqs[pubKeyStr]) == 0 {
                                                s.mu.Unlock()
                                                continue
                                        }

                                        s.mu.Unlock()

                                        s.connectToPersistentPeer(pubKeyStr)
                                }
                        }
                }
        }()

        return nil
}

// CustomMessage is a custom message that is received from a peer.
type CustomMessage struct {
        // Peer is the peer pubkey
        Peer [33]byte

        // Msg is the custom wire message.
        Msg *lnwire.Custom
}

// parseAddr parses an address from its string format to a net.Addr.
func parseAddr(address string, netCfg tor.Net) (net.Addr, error) {
        var (
                host string
                port int
        )

        // Split the address into its host and port components.
        h, p, err := net.SplitHostPort(address)
        if err != nil {
                // If a port wasn't specified, we'll assume the address only
                // contains the host so we'll use the default port.
                host = address
                port = defaultPeerPort
        } else {
                // Otherwise, we'll note both the host and ports.
                host = h
                portNum, err := strconv.Atoi(p)
                if err != nil {
                        return nil, err
                }
                port = portNum
        }

        if tor.IsOnionHost(host) {
                return &tor.OnionAddr{OnionService: host, Port: port}, nil
        }

        // If the host is part of a TCP address, we'll use the network
        // specific ResolveTCPAddr function in order to resolve these
        // addresses over Tor in order to prevent leaking your real IP
        // address.
        hostPort := net.JoinHostPort(host, strconv.Itoa(port))
        return netCfg.ResolveTCPAddr("tcp", hostPort)
}

// noiseDial is a factory function which creates a connmgr compliant dialing
// function by returning a closure which includes the server's identity key.
func noiseDial(idKey keychain.SingleKeyECDH,
        netCfg tor.Net, timeout time.Duration) func(net.Addr) (net.Conn, error) {

        return func(a net.Addr) (net.Conn, error) {
                lnAddr := a.(*lnwire.NetAddress)
                return brontide.Dial(idKey, lnAddr, timeout, netCfg.Dial)
        }
}

// newServer creates a new instance of the server which is to listen using the
// passed listener address.
func newServer(cfg *Config, listenAddrs []net.Addr,
        dbs *DatabaseInstances, cc *chainreg.ChainControl,
        nodeKeyDesc *keychain.KeyDescriptor,
        chansToRestore walletunlocker.ChannelsToRecover,
        chanPredicate chanacceptor.ChannelAcceptor,
        torController *tor.Controller, tlsManager *TLSManager,
        leaderElector cluster.LeaderElector,
        implCfg *ImplementationCfg) (*server, error) {

        var (
                err         error
                nodeKeyECDH = keychain.NewPubKeyECDH(*nodeKeyDesc, cc.KeyRing)

                // We just derived the full descriptor, so we know the public
                // key is set on it.
                nodeKeySigner = keychain.NewPubKeyMessageSigner(
                        nodeKeyDesc.PubKey, nodeKeyDesc.KeyLocator, cc.KeyRing,
                )
        )

        listeners := make([]net.Listener, len(listenAddrs))
        for i, listenAddr := range listenAddrs {
                // Note: though brontide.NewListener uses ResolveTCPAddr, it
                // doesn't need to call the general lndResolveTCP function
                // since we are resolving a local address.
                listeners[i], err = brontide.NewListener(
                        nodeKeyECDH, listenAddr.String(),
                )
                if err != nil {
                        return nil, err
                }
        }

        var serializedPubKey [33]byte
        copy(serializedPubKey[:], nodeKeyDesc.PubKey.SerializeCompressed())

        netParams := cfg.ActiveNetParams.Params

        // Initialize the sphinx router.
        replayLog := htlcswitch.NewDecayedLog(
                dbs.DecayedLogDB, cc.ChainNotifier,
        )
        sphinxRouter := sphinx.NewRouter(nodeKeyECDH, replayLog)

        writeBufferPool := pool.NewWriteBuffer(
                pool.DefaultWriteBufferGCInterval,
                pool.DefaultWriteBufferExpiryInterval,
        )

        writePool := pool.NewWrite(
                writeBufferPool, cfg.Workers.Write, pool.DefaultWorkerTimeout,
        )

        readBufferPool := pool.NewReadBuffer(
                pool.DefaultReadBufferGCInterval,
                pool.DefaultReadBufferExpiryInterval,
        )

        readPool := pool.NewRead(
                readBufferPool, cfg.Workers.Read, pool.DefaultWorkerTimeout,
        )

        // If the taproot overlay flag is set, but we don't have an aux funding
        // controller, then we'll exit as this is incompatible.
        if cfg.ProtocolOptions.TaprootOverlayChans &&
                implCfg.AuxFundingController.IsNone() {

                return nil, fmt.Errorf("taproot overlay flag set, but not " +
                        "aux controllers")
        }

        //nolint:ll
        featureMgr, err := feature.NewManager(feature.Config{
                NoTLVOnion:                cfg.ProtocolOptions.LegacyOnion(),
                NoStaticRemoteKey:         cfg.ProtocolOptions.NoStaticRemoteKey(),
                NoAnchors:                 cfg.ProtocolOptions.NoAnchorCommitments(),
                NoWumbo:                   !cfg.ProtocolOptions.Wumbo(),
                NoScriptEnforcementLease:  cfg.ProtocolOptions.NoScriptEnforcementLease(),
                NoKeysend:                 !cfg.AcceptKeySend,
                NoOptionScidAlias:         !cfg.ProtocolOptions.ScidAlias(),
                NoZeroConf:                !cfg.ProtocolOptions.ZeroConf(),
                NoAnySegwit:               cfg.ProtocolOptions.NoAnySegwit(),
                CustomFeatures:            cfg.ProtocolOptions.CustomFeatures(),
                NoTaprootChans:            !cfg.ProtocolOptions.TaprootChans,
                NoTaprootOverlay:          !cfg.ProtocolOptions.TaprootOverlayChans,
                NoRouteBlinding:           cfg.ProtocolOptions.NoRouteBlinding(),
                NoExperimentalEndorsement: cfg.ProtocolOptions.NoExperimentalEndorsement(),
                NoQuiescence:              cfg.ProtocolOptions.NoQuiescence(),
        })
        if err != nil {
                return nil, err
        }

        invoiceHtlcModifier := invoices.NewHtlcModificationInterceptor()
        registryConfig := invoices.RegistryConfig{
                FinalCltvRejectDelta:        lncfg.DefaultFinalCltvRejectDelta,
                HtlcHoldDuration:            invoices.DefaultHtlcHoldDuration,
                Clock:                       clock.NewDefaultClock(),
                AcceptKeySend:               cfg.AcceptKeySend,
                AcceptAMP:                   cfg.AcceptAMP,
                GcCanceledInvoicesOnStartup: cfg.GcCanceledInvoicesOnStartup,
                GcCanceledInvoicesOnTheFly:  cfg.GcCanceledInvoicesOnTheFly,
                KeysendHoldTime:             cfg.KeysendHoldTime,
                HtlcInterceptor:             invoiceHtlcModifier,
        }

        addrSource := channeldb.NewMultiAddrSource(dbs.ChanStateDB, dbs.GraphDB)

        s := &server{
                cfg:            cfg,
                implCfg:        implCfg,
                graphDB:        dbs.GraphDB,
                chanStateDB:    dbs.ChanStateDB.ChannelStateDB(),
                addrSource:     addrSource,
                miscDB:         dbs.ChanStateDB,
                invoicesDB:     dbs.InvoiceDB,
                cc:             cc,
                sigPool:        lnwallet.NewSigPool(cfg.Workers.Sig, cc.Signer),
                writePool:      writePool,
                readPool:       readPool,
                chansToRestore: chansToRestore,

                blockbeatDispatcher: chainio.NewBlockbeatDispatcher(
                        cc.ChainNotifier,
                ),
                channelNotifier: channelnotifier.New(
                        dbs.ChanStateDB.ChannelStateDB(),
                ),

                identityECDH:   nodeKeyECDH,
                identityKeyLoc: nodeKeyDesc.KeyLocator,
                nodeSigner:     netann.NewNodeSigner(nodeKeySigner),

                listenAddrs: listenAddrs,

                // TODO(roasbeef): derive proper onion key based on rotation
                // schedule
                sphinx: hop.NewOnionProcessor(sphinxRouter),

                torController: torController,

                persistentPeers:         make(map[string]bool),
                persistentPeersBackoff:  make(map[string]time.Duration),
                persistentConnReqs:      make(map[string][]*connmgr.ConnReq),
                persistentPeerAddrs:     make(map[string][]*lnwire.NetAddress),
                persistentRetryCancels:  make(map[string]chan struct{}),
                peerErrors:              make(map[string]*queue.CircularBuffer),
                ignorePeerTermination:   make(map[*peer.Brontide]struct{}),
                scheduledPeerConnection: make(map[string]func()),
                pongBuf:                 make([]byte, lnwire.MaxPongBytes),

                peersByPub:                make(map[string]*peer.Brontide),
                inboundPeers:              make(map[string]*peer.Brontide),
                outboundPeers:             make(map[string]*peer.Brontide),
                peerConnectedListeners:    make(map[string][]chan<- lnpeer.Peer),
                peerDisconnectedListeners: make(map[string][]chan<- struct{}),

                invoiceHtlcModifier: invoiceHtlcModifier,

                customMessageServer: subscribe.NewServer(),

                tlsManager: tlsManager,

                featureMgr: featureMgr,
                quit:       make(chan struct{}),
        }

        // Start the low-level services once they are initialized.
        //
        // TODO(yy): break the server startup into four steps,
        // 1. init the low-level services.
        // 2. start the low-level services.
        // 3. init the high-level services.
        // 4. start the high-level services.
        if err := s.startLowLevelServices(); err != nil {
                return nil, err
        }

        currentHash, currentHeight, err := s.cc.ChainIO.GetBestBlock()
        if err != nil {
                return nil, err
        }

        expiryWatcher := invoices.NewInvoiceExpiryWatcher(
                clock.NewDefaultClock(), cfg.Invoices.HoldExpiryDelta,
                uint32(currentHeight), currentHash, cc.ChainNotifier,
        )
        s.invoices = invoices.NewRegistry(
                dbs.InvoiceDB, expiryWatcher, &registryConfig,
        )

        s.htlcNotifier = htlcswitch.NewHtlcNotifier(time.Now)

        thresholdSats := btcutil.Amount(cfg.MaxFeeExposure)
        thresholdMSats := lnwire.NewMSatFromSatoshis(thresholdSats)

        linkUpdater := func(shortID lnwire.ShortChannelID) error {
                link, err := s.htlcSwitch.GetLinkByShortID(shortID)
                if err != nil {
                        return err
                }

                s.htlcSwitch.UpdateLinkAliases(link)

                return nil
        }

        s.aliasMgr, err = aliasmgr.NewManager(dbs.ChanStateDB, linkUpdater)
        if err != nil {
                return nil, err
        }

        s.htlcSwitch, err = htlcswitch.New(htlcswitch.Config{
                DB:                   dbs.ChanStateDB,
                FetchAllOpenChannels: s.chanStateDB.FetchAllOpenChannels,
                FetchAllChannels:     s.chanStateDB.FetchAllChannels,
                FetchClosedChannels:  s.chanStateDB.FetchClosedChannels,
                LocalChannelClose: func(pubKey []byte,
                        request *htlcswitch.ChanClose) {

                        peer, err := s.FindPeerByPubStr(string(pubKey))
                        if err != nil {
                                srvrLog.Errorf("unable to close channel, peer"+
                                        " with %v id can't be found: %v",
                                        pubKey, err,
                                )
                                return
                        }

                        peer.HandleLocalCloseChanReqs(request)
                },
                FwdingLog:              dbs.ChanStateDB.ForwardingLog(),
                SwitchPackager:         channeldb.NewSwitchPackager(),
                ExtractErrorEncrypter:  s.sphinx.ExtractErrorEncrypter,
                FetchLastChannelUpdate: s.fetchLastChanUpdate(),
                Notifier:               s.cc.ChainNotifier,
                HtlcNotifier:           s.htlcNotifier,
                FwdEventTicker:         ticker.New(htlcswitch.DefaultFwdEventInterval),
                LogEventTicker:         ticker.New(htlcswitch.DefaultLogInterval),
                AckEventTicker:         ticker.New(htlcswitch.DefaultAckInterval),
                AllowCircularRoute:     cfg.AllowCircularRoute,
                RejectHTLC:             cfg.RejectHTLC,
                Clock:                  clock.NewDefaultClock(),
                MailboxDeliveryTimeout: cfg.Htlcswitch.MailboxDeliveryTimeout,
                MaxFeeExposure:         thresholdMSats,
                SignAliasUpdate:        s.signAliasUpdate,
                IsAlias:                aliasmgr.IsAlias,
        }, uint32(currentHeight))
        if err != nil {
                return nil, err
        }
        s.interceptableSwitch, err = htlcswitch.NewInterceptableSwitch(
                &htlcswitch.InterceptableSwitchConfig{
                        Switch:             s.htlcSwitch,
                        CltvRejectDelta:    lncfg.DefaultFinalCltvRejectDelta,
                        CltvInterceptDelta: lncfg.DefaultCltvInterceptDelta,
                        RequireInterceptor: s.cfg.RequireInterceptor,
                        Notifier:           s.cc.ChainNotifier,
                },
        )
        if err != nil {
                return nil, err
        }

        s.witnessBeacon = newPreimageBeacon(
                dbs.ChanStateDB.NewWitnessCache(),
                s.interceptableSwitch.ForwardPacket,
        )

        chanStatusMgrCfg := &netann.ChanStatusConfig{
                ChanStatusSampleInterval: cfg.ChanStatusSampleInterval,
                ChanEnableTimeout:        cfg.ChanEnableTimeout,
                ChanDisableTimeout:       cfg.ChanDisableTimeout,
                OurPubKey:                nodeKeyDesc.PubKey,
                OurKeyLoc:                nodeKeyDesc.KeyLocator,
                MessageSigner:            s.nodeSigner,
                IsChannelActive:          s.htlcSwitch.HasActiveLink,
                ApplyChannelUpdate:       s.applyChannelUpdate,
                DB:                       s.chanStateDB,
                Graph:                    dbs.GraphDB,
        }

        chanStatusMgr, err := netann.NewChanStatusManager(chanStatusMgrCfg)
        if err != nil {
                return nil, err
        }
        s.chanStatusMgr = chanStatusMgr

        // If enabled, use either UPnP or NAT-PMP to automatically configure
        // port forwarding for users behind a NAT.
        if cfg.NAT {
                srvrLog.Info("Scanning local network for a UPnP enabled device")

                discoveryTimeout := time.Duration(10 * time.Second)

                ctx, cancel := context.WithTimeout(
                        context.Background(), discoveryTimeout,
                )
                defer cancel()
                upnp, err := nat.DiscoverUPnP(ctx)
                if err == nil {
                        s.natTraversal = upnp
                } else {
                        // If we were not able to discover a UPnP enabled device
                        // on the local network, we'll fall back to attempting
                        // to discover a NAT-PMP enabled device.
                        srvrLog.Errorf("Unable to discover a UPnP enabled "+
                                "device on the local network: %v", err)

                        srvrLog.Info("Scanning local network for a NAT-PMP " +
                                "enabled device")

                        pmp, err := nat.DiscoverPMP(discoveryTimeout)
                        if err != nil {
                                err := fmt.Errorf("unable to discover a "+
                                        "NAT-PMP enabled device on the local "+
                                        "network: %v", err)
                                srvrLog.Error(err)
                                return nil, err
                        }

                        s.natTraversal = pmp
                }
        }

        // If we were requested to automatically configure port forwarding,
        // we'll use the ports that the server will be listening on.
        externalIPStrings := make([]string, len(cfg.ExternalIPs))
        for idx, ip := range cfg.ExternalIPs {
                externalIPStrings[idx] = ip.String()
        }
        if s.natTraversal != nil {
                listenPorts := make([]uint16, 0, len(listenAddrs))
                for _, listenAddr := range listenAddrs {
                        // At this point, the listen addresses should have
                        // already been normalized, so it's safe to ignore the
                        // errors.
                        _, portStr, _ := net.SplitHostPort(listenAddr.String())
                        port, _ := strconv.Atoi(portStr)

                        listenPorts = append(listenPorts, uint16(port))
                }

                ips, err := s.configurePortForwarding(listenPorts...)
                if err != nil {
                        srvrLog.Errorf("Unable to automatically set up port "+
                                "forwarding using %s: %v",
                                s.natTraversal.Name(), err)
                } else {
                        srvrLog.Infof("Automatically set up port forwarding "+
                                "using %s to advertise external IP",
                                s.natTraversal.Name())
                        externalIPStrings = append(externalIPStrings, ips...)
                }
        }

        // If external IP addresses have been specified, add those to the list
        // of this server's addresses.
        externalIPs, err := lncfg.NormalizeAddresses(
                externalIPStrings, strconv.Itoa(defaultPeerPort),
                cfg.net.ResolveTCPAddr,
        )
        if err != nil {
                return nil, err
        }

        selfAddrs := make([]net.Addr, 0, len(externalIPs))
        selfAddrs = append(selfAddrs, externalIPs...)

        // We'll now reconstruct a node announcement based on our current
        // configuration so we can send it out as a sort of heart beat within
        // the network.
        //
        // We'll start by parsing the node color from configuration.
        color, err := lncfg.ParseHexColor(cfg.Color)
        if err != nil {
                srvrLog.Errorf("unable to parse color: %v\n", err)
                return nil, err
        }

        // If no alias is provided, default to first 10 characters of public
        // key.
        alias := cfg.Alias
        if alias == "" {
                alias = hex.EncodeToString(serializedPubKey[:10])
        }
        nodeAlias, err := lnwire.NewNodeAlias(alias)
        if err != nil {
                return nil, err
        }
        selfNode := &models.LightningNode{
                HaveNodeAnnouncement: true,
                LastUpdate:           time.Now(),
                Addresses:            selfAddrs,
                Alias:                nodeAlias.String(),
                Features:             s.featureMgr.Get(feature.SetNodeAnn),
                Color:                color,
        }
        copy(selfNode.PubKeyBytes[:], nodeKeyDesc.PubKey.SerializeCompressed())

        // Based on the disk representation of the node announcement generated
        // above, we'll generate a node announcement that can go out on the
        // network so we can properly sign it.
        nodeAnn, err := selfNode.NodeAnnouncement(false)
        if err != nil {
                return nil, fmt.Errorf("unable to gen self node ann: %w", err)
        }

        // With the announcement generated, we'll sign it to properly
        // authenticate the message on the network.
        authSig, err := netann.SignAnnouncement(
                s.nodeSigner, nodeKeyDesc.KeyLocator, nodeAnn,
        )
        if err != nil {
                return nil, fmt.Errorf("unable to generate signature for "+
                        "self node announcement: %v", err)
        }
        selfNode.AuthSigBytes = authSig.Serialize()
        nodeAnn.Signature, err = lnwire.NewSigFromECDSARawSignature(
                selfNode.AuthSigBytes,
        )
        if err != nil {
                return nil, err
        }

        // Finally, we'll update the representation on disk, and update our
        // cached in-memory version as well.
        if err := dbs.GraphDB.SetSourceNode(selfNode); err != nil {
                return nil, fmt.Errorf("can't set self node: %w", err)
        }
        s.currentNodeAnn = nodeAnn

        // The router will get access to the payment ID sequencer, such that it
        // can generate unique payment IDs.
        sequencer, err := htlcswitch.NewPersistentSequencer(dbs.ChanStateDB)
        if err != nil {
                return nil, err
        }

        // Instantiate mission control with config from the sub server.
        //
        // TODO(joostjager): When we are further in the process of moving to sub
        // servers, the mission control instance itself can be moved there too.
        routingConfig := routerrpc.GetRoutingConfig(cfg.SubRPCServers.RouterRPC)

        // We only initialize a probability estimator if there's no custom one.
        var estimator routing.Estimator
        if cfg.Estimator != nil {
                estimator = cfg.Estimator
        } else {
                switch routingConfig.ProbabilityEstimatorType {
                case routing.AprioriEstimatorName:
                        aCfg := routingConfig.AprioriConfig
                        aprioriConfig := routing.AprioriConfig{
                                AprioriHopProbability: aCfg.HopProbability,
                                PenaltyHalfLife:       aCfg.PenaltyHalfLife,
                                AprioriWeight:         aCfg.Weight,
                                CapacityFraction:      aCfg.CapacityFraction,
                        }

                        estimator, err = routing.NewAprioriEstimator(
                                aprioriConfig,
                        )
                        if err != nil {
                                return nil, err
                        }

                case routing.BimodalEstimatorName:
                        bCfg := routingConfig.BimodalConfig
                        bimodalConfig := routing.BimodalConfig{
                                BimodalNodeWeight: bCfg.NodeWeight,
                                BimodalScaleMsat: lnwire.MilliSatoshi(
                                        bCfg.Scale,
                                ),
                                BimodalDecayTime: bCfg.DecayTime,
                        }

                        estimator, err = routing.NewBimodalEstimator(
                                bimodalConfig,
                        )
                        if err != nil {
                                return nil, err
                        }

                default:
                        return nil, fmt.Errorf("unknown estimator type %v",
                                routingConfig.ProbabilityEstimatorType)
                }
        }

        mcCfg := &routing.MissionControlConfig{
                OnConfigUpdate:          fn.Some(s.UpdateRoutingConfig),
                Estimator:               estimator,
                MaxMcHistory:            routingConfig.MaxMcHistory,
                McFlushInterval:         routingConfig.McFlushInterval,
                MinFailureRelaxInterval: routing.DefaultMinFailureRelaxInterval,
        }

        s.missionController, err = routing.NewMissionController(
                dbs.ChanStateDB, selfNode.PubKeyBytes, mcCfg,
        )
        if err != nil {
                return nil, fmt.Errorf("can't create mission control "+
                        "manager: %w", err)
        }
        s.defaultMC, err = s.missionController.GetNamespacedStore(
                routing.DefaultMissionControlNamespace,
        )
        if err != nil {
                return nil, fmt.Errorf("can't create mission control in the "+
                        "default namespace: %w", err)
        }

        srvrLog.Debugf("Instantiating payment session source with config: "+
                "AttemptCost=%v + %v%%, MinRouteProbability=%v",
                int64(routingConfig.AttemptCost),
                float64(routingConfig.AttemptCostPPM)/10000,
                routingConfig.MinRouteProbability)

        pathFindingConfig := routing.PathFindingConfig{
                AttemptCost: lnwire.NewMSatFromSatoshis(
                        routingConfig.AttemptCost,
                ),
                AttemptCostPPM: routingConfig.AttemptCostPPM,
                MinProbability: routingConfig.MinRouteProbability,
        }

        sourceNode, err := dbs.GraphDB.SourceNode()
        if err != nil {
                return nil, fmt.Errorf("error getting source node: %w", err)
        }
        paymentSessionSource := &routing.SessionSource{
                GraphSessionFactory: graphsession.NewGraphSessionFactory(
                        dbs.GraphDB,
                ),
                SourceNode:        sourceNode,
                MissionControl:    s.defaultMC,
                GetLink:           s.htlcSwitch.GetLinkByShortID,
                PathFindingConfig: pathFindingConfig,
        }

        paymentControl := channeldb.NewPaymentControl(dbs.ChanStateDB)

        s.controlTower = routing.NewControlTower(paymentControl)

        strictPruning := cfg.Bitcoin.Node == "neutrino" ||
                cfg.Routing.StrictZombiePruning

        s.graphBuilder, err = graph.NewBuilder(&graph.Config{
                SelfNode:            selfNode.PubKeyBytes,
                Graph:               dbs.GraphDB,
                Chain:               cc.ChainIO,
                ChainView:           cc.ChainView,
                Notifier:            cc.ChainNotifier,
                ChannelPruneExpiry:  graph.DefaultChannelPruneExpiry,
                GraphPruneInterval:  time.Hour,
                FirstTimePruneDelay: graph.DefaultFirstTimePruneDelay,
                AssumeChannelValid:  cfg.Routing.AssumeChannelValid,
                StrictZombiePruning: strictPruning,
                IsAlias:             aliasmgr.IsAlias,
        })
        if err != nil {
                return nil, fmt.Errorf("can't create graph builder: %w", err)
        }

        s.chanRouter, err = routing.New(routing.Config{
                SelfNode:           selfNode.PubKeyBytes,
                RoutingGraph:       graphsession.NewRoutingGraph(dbs.GraphDB),
                Chain:              cc.ChainIO,
                Payer:              s.htlcSwitch,
                Control:            s.controlTower,
                MissionControl:     s.defaultMC,
                SessionSource:      paymentSessionSource,
                GetLink:            s.htlcSwitch.GetLinkByShortID,
                NextPaymentID:      sequencer.NextID,
                PathFindingConfig:  pathFindingConfig,
                Clock:              clock.NewDefaultClock(),
                ApplyChannelUpdate: s.graphBuilder.ApplyChannelUpdate,
                ClosedSCIDs:        s.fetchClosedChannelSCIDs(),
                TrafficShaper:      implCfg.TrafficShaper,
        })
        if err != nil {
                return nil, fmt.Errorf("can't create router: %w", err)
        }

        chanSeries := discovery.NewChanSeries(s.graphDB)
        gossipMessageStore, err := discovery.NewMessageStore(dbs.ChanStateDB)
        if err != nil {
                return nil, err
        }
        waitingProofStore, err := channeldb.NewWaitingProofStore(dbs.ChanStateDB)
        if err != nil {
                return nil, err
        }

        scidCloserMan := discovery.NewScidCloserMan(s.graphDB, s.chanStateDB)

        s.authGossiper = discovery.New(discovery.Config{
                Graph:                 s.graphBuilder,
                ChainIO:               s.cc.ChainIO,
                Notifier:              s.cc.ChainNotifier,
                ChainHash:             *s.cfg.ActiveNetParams.GenesisHash,
                Broadcast:             s.BroadcastMessage,
                ChanSeries:            chanSeries,
                NotifyWhenOnline:      s.NotifyWhenOnline,
                NotifyWhenOffline:     s.NotifyWhenOffline,
                FetchSelfAnnouncement: s.getNodeAnnouncement,
                UpdateSelfAnnouncement: func() (lnwire.NodeAnnouncement,
                        error) {

                        return s.genNodeAnnouncement(nil)
                },
                ProofMatureDelta:        0,
                TrickleDelay:            time.Millisecond * time.Duration(cfg.TrickleDelay),
                RetransmitTicker:        ticker.New(time.Minute * 30),
                RebroadcastInterval:     time.Hour * 24,
                WaitingProofStore:       waitingProofStore,
                MessageStore:            gossipMessageStore,
                AnnSigner:               s.nodeSigner,
                RotateTicker:            ticker.New(discovery.DefaultSyncerRotationInterval),
                HistoricalSyncTicker:    ticker.New(cfg.HistoricalSyncInterval),
                NumActiveSyncers:        cfg.NumGraphSyncPeers,
                NoTimestampQueries:      cfg.ProtocolOptions.NoTimestampQueryOption, //nolint:ll
                MinimumBatchSize:        10,
                SubBatchDelay:           cfg.Gossip.SubBatchDelay,
                IgnoreHistoricalFilters: cfg.IgnoreHistoricalGossipFilters,
                PinnedSyncers:           cfg.Gossip.PinnedSyncers,
                MaxChannelUpdateBurst:   cfg.Gossip.MaxChannelUpdateBurst,
                ChannelUpdateInterval:   cfg.Gossip.ChannelUpdateInterval,
                IsAlias:                 aliasmgr.IsAlias,
                SignAliasUpdate:         s.signAliasUpdate,
                FindBaseByAlias:         s.aliasMgr.FindBaseSCID,
                GetAlias:                s.aliasMgr.GetPeerAlias,
                FindChannel:             s.findChannel,
                IsStillZombieChannel:    s.graphBuilder.IsZombieChannel,
                ScidCloser:              scidCloserMan,
        }, nodeKeyDesc)

        selfVertex := route.Vertex(nodeKeyDesc.PubKey.SerializeCompressed())
        //nolint:ll
        s.localChanMgr = &localchans.Manager{
                SelfPub:              nodeKeyDesc.PubKey,
                DefaultRoutingPolicy: cc.RoutingPolicy,
                ForAllOutgoingChannels: func(cb func(*models.ChannelEdgeInfo,
                        *models.ChannelEdgePolicy) error) error {

                        return s.graphDB.ForEachNodeChannel(selfVertex,
                                func(_ kvdb.RTx, c *models.ChannelEdgeInfo,
                                        e *models.ChannelEdgePolicy,
                                        _ *models.ChannelEdgePolicy) error {

                                        // NOTE: The invoked callback here may
                                        // receive a nil channel policy.
                                        return cb(c, e)
                                },
                        )
                },
                PropagateChanPolicyUpdate: s.authGossiper.PropagateChanPolicyUpdate,
                UpdateForwardingPolicies:  s.htlcSwitch.UpdateForwardingPolicies,
                FetchChannel:              s.chanStateDB.FetchChannel,
                AddEdge: func(edge *models.ChannelEdgeInfo) error {
                        return s.graphBuilder.AddEdge(edge)
                },
        }

        utxnStore, err := contractcourt.NewNurseryStore(
                s.cfg.ActiveNetParams.GenesisHash, dbs.ChanStateDB,
        )
        if err != nil {
                srvrLog.Errorf("unable to create nursery store: %v", err)
                return nil, err
        }

        sweeperStore, err := sweep.NewSweeperStore(
                dbs.ChanStateDB, s.cfg.ActiveNetParams.GenesisHash,
        )
        if err != nil {
                srvrLog.Errorf("unable to create sweeper store: %v", err)
                return nil, err
        }

        aggregator := sweep.NewBudgetAggregator(
                cc.FeeEstimator, sweep.DefaultMaxInputsPerTx,
                s.implCfg.AuxSweeper,
        )

        s.txPublisher = sweep.NewTxPublisher(sweep.TxPublisherConfig{
                Signer:     cc.Wallet.Cfg.Signer,
                Wallet:     cc.Wallet,
                Estimator:  cc.FeeEstimator,
                Notifier:   cc.ChainNotifier,
                AuxSweeper: s.implCfg.AuxSweeper,
        })

        s.sweeper = sweep.New(&sweep.UtxoSweeperConfig{
                FeeEstimator: cc.FeeEstimator,
                GenSweepScript: newSweepPkScriptGen(
                        cc.Wallet, s.cfg.ActiveNetParams.Params,
                ),
                Signer:               cc.Wallet.Cfg.Signer,
                Wallet:               newSweeperWallet(cc.Wallet),
                Mempool:              cc.MempoolNotifier,
                Notifier:             cc.ChainNotifier,
                Store:                sweeperStore,
                MaxInputsPerTx:       sweep.DefaultMaxInputsPerTx,
                MaxFeeRate:           cfg.Sweeper.MaxFeeRate,
                Aggregator:           aggregator,
                Publisher:            s.txPublisher,
                NoDeadlineConfTarget: cfg.Sweeper.NoDeadlineConfTarget,
        })

        s.utxoNursery = contractcourt.NewUtxoNursery(&contractcourt.NurseryConfig{
                ChainIO:             cc.ChainIO,
                ConfDepth:           1,
                FetchClosedChannels: s.chanStateDB.FetchClosedChannels,
                FetchClosedChannel:  s.chanStateDB.FetchClosedChannel,
                Notifier:            cc.ChainNotifier,
                PublishTransaction:  cc.Wallet.PublishTransaction,
                Store:               utxnStore,
                SweepInput:          s.sweeper.SweepInput,
                Budget:              s.cfg.Sweeper.Budget,
        })

        // Construct a closure that wraps the htlcswitch's CloseLink method.
        closeLink := func(chanPoint *wire.OutPoint,
                closureType contractcourt.ChannelCloseType) {
                // TODO(conner): Properly respect the update and error channels
                // returned by CloseLink.

                // Instruct the switch to close the channel.  Provide no close out
                // delivery script or target fee per kw because user input is not
                // available when the remote peer closes the channel.
                s.htlcSwitch.CloseLink(chanPoint, closureType, 0, 0, nil)
        }

        // We will use the following channel to reliably hand off contract
        // breach events from the ChannelArbitrator to the BreachArbitrator,
        contractBreaches := make(chan *contractcourt.ContractBreachEvent, 1)

        s.breachArbitrator = contractcourt.NewBreachArbitrator(
                &contractcourt.BreachConfig{
                        CloseLink: closeLink,
                        DB:        s.chanStateDB,
                        Estimator: s.cc.FeeEstimator,
                        GenSweepScript: newSweepPkScriptGen(
                                cc.Wallet, s.cfg.ActiveNetParams.Params,
                        ),
                        Notifier:           cc.ChainNotifier,
                        PublishTransaction: cc.Wallet.PublishTransaction,
                        ContractBreaches:   contractBreaches,
                        Signer:             cc.Wallet.Cfg.Signer,
                        Store: contractcourt.NewRetributionStore(
                                dbs.ChanStateDB,
                        ),
                        AuxSweeper: s.implCfg.AuxSweeper,
                },
        )

        //nolint:ll
        s.chainArb = contractcourt.NewChainArbitrator(contractcourt.ChainArbitratorConfig{
                ChainHash:              *s.cfg.ActiveNetParams.GenesisHash,
                IncomingBroadcastDelta: lncfg.DefaultIncomingBroadcastDelta,
                OutgoingBroadcastDelta: lncfg.DefaultOutgoingBroadcastDelta,
                NewSweepAddr: func() ([]byte, error) {
                        addr, err := newSweepPkScriptGen(
                                cc.Wallet, netParams,
                        )().Unpack()
                        if err != nil {
                                return nil, err
                        }

                        return addr.DeliveryAddress, nil
                },
                PublishTx: cc.Wallet.PublishTransaction,
                DeliverResolutionMsg: func(msgs ...contractcourt.ResolutionMsg) error {
                        for _, msg := range msgs {
                                err := s.htlcSwitch.ProcessContractResolution(msg)
                                if err != nil {
                                        return err
                                }
                        }
                        return nil
                },
                IncubateOutputs: func(chanPoint wire.OutPoint,
                        outHtlcRes fn.Option[lnwallet.OutgoingHtlcResolution],
                        inHtlcRes fn.Option[lnwallet.IncomingHtlcResolution],
                        broadcastHeight uint32,
                        deadlineHeight fn.Option[int32]) error {

                        return s.utxoNursery.IncubateOutputs(
                                chanPoint, outHtlcRes, inHtlcRes,
                                broadcastHeight, deadlineHeight,
                        )
                },
                PreimageDB:   s.witnessBeacon,
                Notifier:     cc.ChainNotifier,
                Mempool:      cc.MempoolNotifier,
                Signer:       cc.Wallet.Cfg.Signer,
                FeeEstimator: cc.FeeEstimator,
                ChainIO:      cc.ChainIO,
                MarkLinkInactive: func(chanPoint wire.OutPoint) error {
                        chanID := lnwire.NewChanIDFromOutPoint(chanPoint)
                        s.htlcSwitch.RemoveLink(chanID)
                        return nil
                },
                IsOurAddress: cc.Wallet.IsOurAddress,
                ContractBreach: func(chanPoint wire.OutPoint,
                        breachRet *lnwallet.BreachRetribution) error {

                        // processACK will handle the BreachArbitrator ACKing
                        // the event.
                        finalErr := make(chan error, 1)
                        processACK := func(brarErr error) {
                                if brarErr != nil {
                                        finalErr <- brarErr
                                        return
                                }

                                // If the BreachArbitrator successfully handled
                                // the event, we can signal that the handoff
                                // was successful.
                                finalErr <- nil
                        }

                        event := &contractcourt.ContractBreachEvent{
                                ChanPoint:         chanPoint,
                                ProcessACK:        processACK,
                                BreachRetribution: breachRet,
                        }

                        // Send the contract breach event to the
                        // BreachArbitrator.
                        select {
                        case contractBreaches <- event:
                        case <-s.quit:
                                return ErrServerShuttingDown
                        }

                        // We'll wait for a final error to be available from
                        // the BreachArbitrator.
                        select {
                        case err := <-finalErr:
                                return err
                        case <-s.quit:
                                return ErrServerShuttingDown
                        }
                },
                DisableChannel: func(chanPoint wire.OutPoint) error {
                        return s.chanStatusMgr.RequestDisable(chanPoint, false)
                },
                Sweeper:                       s.sweeper,
                Registry:                      s.invoices,
                NotifyClosedChannel:           s.channelNotifier.NotifyClosedChannelEvent,
                NotifyFullyResolvedChannel:    s.channelNotifier.NotifyFullyResolvedChannelEvent,
                OnionProcessor:                s.sphinx,
                PaymentsExpirationGracePeriod: cfg.PaymentsExpirationGracePeriod,
                IsForwardedHTLC:               s.htlcSwitch.IsForwardedHTLC,
                Clock:                         clock.NewDefaultClock(),
                SubscribeBreachComplete:       s.breachArbitrator.SubscribeBreachComplete,
                PutFinalHtlcOutcome:           s.chanStateDB.PutOnchainFinalHtlcOutcome,
                HtlcNotifier:                  s.htlcNotifier,
                Budget:                        *s.cfg.Sweeper.Budget,

                // TODO(yy): remove this hack once PaymentCircuit is interfaced.
                QueryIncomingCircuit: func(
                        circuit models.CircuitKey) *models.CircuitKey {

                        // Get the circuit map.
                        circuits := s.htlcSwitch.CircuitLookup()

                        // Lookup the outgoing circuit.
                        pc := circuits.LookupOpenCircuit(circuit)
                        if pc == nil {
                                return nil
                        }

                        return &pc.Incoming
                },
                AuxLeafStore: implCfg.AuxLeafStore,
                AuxSigner:    implCfg.AuxSigner,
                AuxResolver:  implCfg.AuxContractResolver,
        }, dbs.ChanStateDB)

        // Select the configuration and funding parameters for Bitcoin.
        chainCfg := cfg.Bitcoin
        minRemoteDelay := funding.MinBtcRemoteDelay
        maxRemoteDelay := funding.MaxBtcRemoteDelay

        var chanIDSeed [32]byte
        if _, err := rand.Read(chanIDSeed[:]); err != nil {
                return nil, err
        }

        // Wrap the DeleteChannelEdges method so that the funding manager can
        // use it without depending on several layers of indirection.
        deleteAliasEdge := func(scid lnwire.ShortChannelID) (
                *models.ChannelEdgePolicy, error) {

                info, e1, e2, err := s.graphDB.FetchChannelEdgesByID(
                        scid.ToUint64(),
                )
                if errors.Is(err, graphdb.ErrEdgeNotFound) {
                        // This is unlikely but there is a slim chance of this
                        // being hit if lnd was killed via SIGKILL and the
                        // funding manager was stepping through the delete
                        // alias edge logic.
                        return nil, nil
                } else if err != nil {
                        return nil, err
                }

                // Grab our key to find our policy.
                var ourKey [33]byte
                copy(ourKey[:], nodeKeyDesc.PubKey.SerializeCompressed())

                var ourPolicy *models.ChannelEdgePolicy
                if info != nil && info.NodeKey1Bytes == ourKey {
                        ourPolicy = e1
                } else {
                        ourPolicy = e2
                }

                if ourPolicy == nil {
                        // Something is wrong, so return an error.
                        return nil, fmt.Errorf("we don't have an edge")
                }

                err = s.graphDB.DeleteChannelEdges(
                        false, false, scid.ToUint64(),
                )
                return ourPolicy, err
        }

        // For the reservationTimeout and the zombieSweeperInterval different
        // values are set in case we are in a dev environment so enhance test
        // capacilities.
        reservationTimeout := chanfunding.DefaultReservationTimeout
        zombieSweeperInterval := lncfg.DefaultZombieSweeperInterval

        // Get the development config for funding manager. If we are not in
        // development mode, this would be nil.
        var devCfg *funding.DevConfig
        if lncfg.IsDevBuild() {
                devCfg = &funding.DevConfig{
                        ProcessChannelReadyWait: cfg.Dev.ChannelReadyWait(),
                }

                reservationTimeout = cfg.Dev.GetReservationTimeout()
                zombieSweeperInterval = cfg.Dev.GetZombieSweeperInterval()

                srvrLog.Debugf("Using the dev config for the fundingMgr: %v, "+
                        "reservationTimeout=%v, zombieSweeperInterval=%v",
                        devCfg, reservationTimeout, zombieSweeperInterval)
        }

        //nolint:ll
        s.fundingMgr, err = funding.NewFundingManager(funding.Config{
                Dev:                devCfg,
                NoWumboChans:       !cfg.ProtocolOptions.Wumbo(),
                IDKey:              nodeKeyDesc.PubKey,
                IDKeyLoc:           nodeKeyDesc.KeyLocator,
                Wallet:             cc.Wallet,
                PublishTransaction: cc.Wallet.PublishTransaction,
                UpdateLabel: func(hash chainhash.Hash, label string) error {
                        return cc.Wallet.LabelTransaction(hash, label, true)
                },
                Notifier:     cc.ChainNotifier,
                ChannelDB:    s.chanStateDB,
                FeeEstimator: cc.FeeEstimator,
                SignMessage:  cc.MsgSigner.SignMessage,
                CurrentNodeAnnouncement: func() (lnwire.NodeAnnouncement,
                        error) {

                        return s.genNodeAnnouncement(nil)
                },
                SendAnnouncement:     s.authGossiper.ProcessLocalAnnouncement,
                NotifyWhenOnline:     s.NotifyWhenOnline,
                TempChanIDSeed:       chanIDSeed,
                FindChannel:          s.findChannel,
                DefaultRoutingPolicy: cc.RoutingPolicy,
                DefaultMinHtlcIn:     cc.MinHtlcIn,
                NumRequiredConfs: func(chanAmt btcutil.Amount,
                        pushAmt lnwire.MilliSatoshi) uint16 {
                        // For large channels we increase the number
                        // of confirmations we require for the
                        // channel to be considered open. As it is
                        // always the responder that gets to choose
                        // value, the pushAmt is value being pushed
                        // to us. This means we have more to lose
                        // in the case this gets re-orged out, and
                        // we will require more confirmations before
                        // we consider it open.

                        // In case the user has explicitly specified
                        // a default value for the number of
                        // confirmations, we use it.
                        defaultConf := uint16(chainCfg.DefaultNumChanConfs)
                        if defaultConf != 0 {
                                return defaultConf
                        }

                        minConf := uint64(3)
                        maxConf := uint64(6)

                        // If this is a wumbo channel, then we'll require the
                        // max amount of confirmations.
                        if chanAmt > MaxFundingAmount {
                                return uint16(maxConf)
                        }

                        // If not we return a value scaled linearly
                        // between 3 and 6, depending on channel size.
                        // TODO(halseth): Use 1 as minimum?
                        maxChannelSize := uint64(
                                lnwire.NewMSatFromSatoshis(MaxFundingAmount))
                        stake := lnwire.NewMSatFromSatoshis(chanAmt) + pushAmt
                        conf := maxConf * uint64(stake) / maxChannelSize
                        if conf < minConf {
                                conf = minConf
                        }
                        if conf > maxConf {
                                conf = maxConf
                        }
                        return uint16(conf)
                },
                RequiredRemoteDelay: func(chanAmt btcutil.Amount) uint16 {
                        // We scale the remote CSV delay (the time the
                        // remote have to claim funds in case of a unilateral
                        // close) linearly from minRemoteDelay blocks
                        // for small channels, to maxRemoteDelay blocks
                        // for channels of size MaxFundingAmount.

                        // In case the user has explicitly specified
                        // a default value for the remote delay, we
                        // use it.
                        defaultDelay := uint16(chainCfg.DefaultRemoteDelay)
                        if defaultDelay > 0 {
                                return defaultDelay
                        }

                        // If this is a wumbo channel, then we'll require the
                        // max value.
                        if chanAmt > MaxFundingAmount {
                                return maxRemoteDelay
                        }

                        // If not we scale according to channel size.
                        delay := uint16(btcutil.Amount(maxRemoteDelay) *
                                chanAmt / MaxFundingAmount)
                        if delay < minRemoteDelay {
                                delay = minRemoteDelay
                        }
                        if delay > maxRemoteDelay {
                                delay = maxRemoteDelay
                        }
                        return delay
                },
                WatchNewChannel: func(channel *channeldb.OpenChannel,
                        peerKey *btcec.PublicKey) error {

                        // First, we'll mark this new peer as a persistent peer
                        // for re-connection purposes. If the peer is not yet
                        // tracked or the user hasn't requested it to be perm,
                        // we'll set false to prevent the server from continuing
                        // to connect to this peer even if the number of
                        // channels with this peer is zero.
                        s.mu.Lock()
                        pubStr := string(peerKey.SerializeCompressed())
                        if _, ok := s.persistentPeers[pubStr]; !ok {
                                s.persistentPeers[pubStr] = false
                        }
                        s.mu.Unlock()

                        // With that taken care of, we'll send this channel to
                        // the chain arb so it can react to on-chain events.
                        return s.chainArb.WatchNewChannel(channel)
                },
                ReportShortChanID: func(chanPoint wire.OutPoint) error {
                        cid := lnwire.NewChanIDFromOutPoint(chanPoint)
                        return s.htlcSwitch.UpdateShortChanID(cid)
                },
                RequiredRemoteChanReserve: func(chanAmt,
                        dustLimit btcutil.Amount) btcutil.Amount {

                        // By default, we'll require the remote peer to maintain
                        // at least 1% of the total channel capacity at all
                        // times. If this value ends up dipping below the dust
                        // limit, then we'll use the dust limit itself as the
                        // reserve as required by BOLT #2.
                        reserve := chanAmt / 100
                        if reserve < dustLimit {
                                reserve = dustLimit
                        }

                        return reserve
                },
                RequiredRemoteMaxValue: func(chanAmt btcutil.Amount) lnwire.MilliSatoshi {
                        // By default, we'll allow the remote peer to fully
                        // utilize the full bandwidth of the channel, minus our
                        // required reserve.
                        reserve := lnwire.NewMSatFromSatoshis(chanAmt / 100)
                        return lnwire.NewMSatFromSatoshis(chanAmt) - reserve
                },
                RequiredRemoteMaxHTLCs: func(chanAmt btcutil.Amount) uint16 {
                        if cfg.DefaultRemoteMaxHtlcs > 0 {
                                return cfg.DefaultRemoteMaxHtlcs
                        }

                        // By default, we'll permit them to utilize the full
                        // channel bandwidth.
                        return uint16(input.MaxHTLCNumber / 2)
                },
                ZombieSweeperInterval:         zombieSweeperInterval,
                ReservationTimeout:            reservationTimeout,
                MinChanSize:                   btcutil.Amount(cfg.MinChanSize),
                MaxChanSize:                   btcutil.Amount(cfg.MaxChanSize),
                MaxPendingChannels:            cfg.MaxPendingChannels,
                RejectPush:                    cfg.RejectPush,
                MaxLocalCSVDelay:              chainCfg.MaxLocalDelay,
                NotifyOpenChannelEvent:        s.channelNotifier.NotifyOpenChannelEvent,
                OpenChannelPredicate:          chanPredicate,
                NotifyPendingOpenChannelEvent: s.channelNotifier.NotifyPendingOpenChannelEvent,
                EnableUpfrontShutdown:         cfg.EnableUpfrontShutdown,
                MaxAnchorsCommitFeeRate: chainfee.SatPerKVByte(
                        s.cfg.MaxCommitFeeRateAnchors * 1000).FeePerKWeight(),
                DeleteAliasEdge:      deleteAliasEdge,
                AliasManager:         s.aliasMgr,
                IsSweeperOutpoint:    s.sweeper.IsSweeperOutpoint,
                AuxFundingController: implCfg.AuxFundingController,
                AuxSigner:            implCfg.AuxSigner,
                AuxResolver:          implCfg.AuxContractResolver,
        })
        if err != nil {
                return nil, err
        }

        // Next, we'll assemble the sub-system that will maintain an on-disk
        // static backup of the latest channel state.
        chanNotifier := &channelNotifier{
                chanNotifier: s.channelNotifier,
                addrs:        s.addrSource,
        }
        backupFile := chanbackup.NewMultiFile(cfg.BackupFilePath)
        startingChans, err := chanbackup.FetchStaticChanBackups(
                s.chanStateDB, s.addrSource,
        )
        if err != nil {
                return nil, err
        }
        s.chanSubSwapper, err = chanbackup.NewSubSwapper(
                startingChans, chanNotifier, s.cc.KeyRing, backupFile,
        )
        if err != nil {
                return nil, err
        }

        // Assemble a peer notifier which will provide clients with subscriptions
        // to peer online and offline events.
        s.peerNotifier = peernotifier.New()

        // Create a channel event store which monitors all open channels.
        s.chanEventStore = chanfitness.NewChannelEventStore(&chanfitness.Config{
                SubscribeChannelEvents: func() (subscribe.Subscription, error) {
                        return s.channelNotifier.SubscribeChannelEvents()
                },
                SubscribePeerEvents: func() (subscribe.Subscription, error) {
                        return s.peerNotifier.SubscribePeerEvents()
                },
                GetOpenChannels: s.chanStateDB.FetchAllOpenChannels,
                Clock:           clock.NewDefaultClock(),
                ReadFlapCount:   s.miscDB.ReadFlapCount,
                WriteFlapCount:  s.miscDB.WriteFlapCounts,
                FlapCountTicker: ticker.New(chanfitness.FlapCountFlushRate),
        })

        if cfg.WtClient.Active {
                policy := wtpolicy.DefaultPolicy()
                policy.MaxUpdates = cfg.WtClient.MaxUpdates

                // We expose the sweep fee rate in sat/vbyte, but the tower
                // protocol operations on sat/kw.
                sweepRateSatPerVByte := chainfee.SatPerKVByte(
                        1000 * cfg.WtClient.SweepFeeRate,
                )

                policy.SweepFeeRate = sweepRateSatPerVByte.FeePerKWeight()

                if err := policy.Validate(); err != nil {
                        return nil, err
                }

                // authDial is the wrapper around the btrontide.Dial for the
                // watchtower.
                authDial := func(localKey keychain.SingleKeyECDH,
                        netAddr *lnwire.NetAddress,
                        dialer tor.DialFunc) (wtserver.Peer, error) {

                        return brontide.Dial(
                                localKey, netAddr, cfg.ConnectionTimeout, dialer,
                        )
                }

                // buildBreachRetribution is a call-back that can be used to
                // query the BreachRetribution info and channel type given a
                // channel ID and commitment height.
                buildBreachRetribution := func(chanID lnwire.ChannelID,
                        commitHeight uint64) (*lnwallet.BreachRetribution,
                        channeldb.ChannelType, error) {

                        channel, err := s.chanStateDB.FetchChannelByID(
                                nil, chanID,
                        )
                        if err != nil {
                                return nil, 0, err
                        }

                        br, err := lnwallet.NewBreachRetribution(
                                channel, commitHeight, 0, nil,
                                implCfg.AuxLeafStore,
                                implCfg.AuxContractResolver,
                        )
                        if err != nil {
                                return nil, 0, err
                        }

                        return br, channel.ChanType, nil
                }

                fetchClosedChannel := s.chanStateDB.FetchClosedChannelForID

                // Copy the policy for legacy channels and set the blob flag
                // signalling support for anchor channels.
                anchorPolicy := policy
                anchorPolicy.BlobType |= blob.Type(blob.FlagAnchorChannel)

                // Copy the policy for legacy channels and set the blob flag
                // signalling support for taproot channels.
                taprootPolicy := policy
                taprootPolicy.TxPolicy.BlobType |= blob.Type(
                        blob.FlagTaprootChannel,
                )

                s.towerClientMgr, err = wtclient.NewManager(&wtclient.Config{
                        FetchClosedChannel:     fetchClosedChannel,
                        BuildBreachRetribution: buildBreachRetribution,
                        SessionCloseRange:      cfg.WtClient.SessionCloseRange,
                        ChainNotifier:          s.cc.ChainNotifier,
                        SubscribeChannelEvents: func() (subscribe.Subscription,
                                error) {

                                return s.channelNotifier.
                                        SubscribeChannelEvents()
                        },
                        Signer: cc.Wallet.Cfg.Signer,
                        NewAddress: func() ([]byte, error) {
                                addr, err := newSweepPkScriptGen(
                                        cc.Wallet, netParams,
                                )().Unpack()
                                if err != nil {
                                        return nil, err
                                }

                                return addr.DeliveryAddress, nil
                        },
                        SecretKeyRing:      s.cc.KeyRing,
                        Dial:               cfg.net.Dial,
                        AuthDial:           authDial,
                        DB:                 dbs.TowerClientDB,
                        ChainHash:          *s.cfg.ActiveNetParams.GenesisHash,
                        MinBackoff:         10 * time.Second,
                        MaxBackoff:         5 * time.Minute,
                        MaxTasksInMemQueue: cfg.WtClient.MaxTasksInMemQueue,
                }, policy, anchorPolicy, taprootPolicy)
                if err != nil {
                        return nil, err
                }
        }

        if len(cfg.ExternalHosts) != 0 {
                advertisedIPs := make(map[string]struct{})
                for _, addr := range s.currentNodeAnn.Addresses {
                        advertisedIPs[addr.String()] = struct{}{}
                }

                s.hostAnn = netann.NewHostAnnouncer(netann.HostAnnouncerConfig{
                        Hosts:         cfg.ExternalHosts,
                        RefreshTicker: ticker.New(defaultHostSampleInterval),
                        LookupHost: func(host string) (net.Addr, error) {
                                return lncfg.ParseAddressString(
                                        host, strconv.Itoa(defaultPeerPort),
                                        cfg.net.ResolveTCPAddr,
                                )
                        },
                        AdvertisedIPs: advertisedIPs,
                        AnnounceNewIPs: netann.IPAnnouncer(
                                func(modifier ...netann.NodeAnnModifier) (
                                        lnwire.NodeAnnouncement, error) {

                                        return s.genNodeAnnouncement(
                                                nil, modifier...,
                                        )
                                }),
                })
        }

        // Create liveness monitor.
        s.createLivenessMonitor(cfg, cc, leaderElector)

        // Create the connection manager which will be responsible for
        // maintaining persistent outbound connections and also accepting new
        // incoming connections
        cmgr, err := connmgr.New(&connmgr.Config{
                Listeners:      listeners,
                OnAccept:       s.InboundPeerConnected,
                RetryDuration:  time.Second * 5,
                TargetOutbound: 100,
                Dial: noiseDial(
                        nodeKeyECDH, s.cfg.net, s.cfg.ConnectionTimeout,
                ),
                OnConnection: s.OutboundPeerConnected,
        })
        if err != nil {
                return nil, err
        }
        s.connMgr = cmgr

        // Finally, register the subsystems in blockbeat.
        s.registerBlockConsumers()

        return s, nil
}

// UpdateRoutingConfig is a callback function to update the routing config
// values in the main cfg.
func (s *server) UpdateRoutingConfig(cfg *routing.MissionControlConfig) {
        routerCfg := s.cfg.SubRPCServers.RouterRPC

        switch c := cfg.Estimator.Config().(type) {
        case routing.AprioriConfig:
                routerCfg.ProbabilityEstimatorType =
                        routing.AprioriEstimatorName

                targetCfg := routerCfg.AprioriConfig
                targetCfg.PenaltyHalfLife = c.PenaltyHalfLife
                targetCfg.Weight = c.AprioriWeight
                targetCfg.CapacityFraction = c.CapacityFraction
                targetCfg.HopProbability = c.AprioriHopProbability

        case routing.BimodalConfig:
                routerCfg.ProbabilityEstimatorType =
                        routing.BimodalEstimatorName

                targetCfg := routerCfg.BimodalConfig
                targetCfg.Scale = int64(c.BimodalScaleMsat)
                targetCfg.NodeWeight = c.BimodalNodeWeight
                targetCfg.DecayTime = c.BimodalDecayTime
        }

        routerCfg.MaxMcHistory = cfg.MaxMcHistory
}

// registerBlockConsumers registers the subsystems that consume block events.
// By calling `RegisterQueue`, a list of subsystems are registered in the
// blockbeat for block notifications. When a new block arrives, the subsystems
// in the same queue are notified sequentially, and different queues are
// notified concurrently.
//
// NOTE: To put a subsystem in a different queue, create a slice and pass it to
// a new `RegisterQueue` call.
func (s *server) registerBlockConsumers() {
        // In this queue, when a new block arrives, it will be received and
        // processed in this order: chainArb -> sweeper -> txPublisher.
        consumers := []chainio.Consumer{
                s.chainArb,
                s.sweeper,
                s.txPublisher,
        }
        s.blockbeatDispatcher.RegisterQueue(consumers)
}

// signAliasUpdate takes a ChannelUpdate and returns the signature. This is
// used for option_scid_alias channels where the ChannelUpdate to be sent back
// may differ from what is on disk.
func (s *server) signAliasUpdate(u *lnwire.ChannelUpdate1) (*ecdsa.Signature,
        error) {

        data, err := u.DataToSign()
        if err != nil {
                return nil, err
        }

        return s.cc.MsgSigner.SignMessage(s.identityKeyLoc, data, true)
}

// createLivenessMonitor creates a set of health checks using our configured
// values and uses these checks to create a liveness monitor. Available
// health checks,
//   - chainHealthCheck (will be disabled for --nochainbackend mode)
//   - diskCheck
//   - tlsHealthCheck
//   - torController, only created when tor is enabled.
//
// If a health check has been disabled by setting attempts to 0, our monitor
// will not run it.
func (s *server) createLivenessMonitor(cfg *Config, cc *chainreg.ChainControl,
        leaderElector cluster.LeaderElector) {

        chainBackendAttempts := cfg.HealthChecks.ChainCheck.Attempts
        if cfg.Bitcoin.Node == "nochainbackend" {
                srvrLog.Info("Disabling chain backend checks for " +
                        "nochainbackend mode")

                chainBackendAttempts = 0
        }

        chainHealthCheck := healthcheck.NewObservation(
                "chain backend",
                cc.HealthCheck,
                cfg.HealthChecks.ChainCheck.Interval,
                cfg.HealthChecks.ChainCheck.Timeout,
                cfg.HealthChecks.ChainCheck.Backoff,
                chainBackendAttempts,
        )

        diskCheck := healthcheck.NewObservation(
                "disk space",
                func() error {
                        free, err := healthcheck.AvailableDiskSpaceRatio(
                                cfg.LndDir,
                        )
                        if err != nil {
                                return err
                        }

                        // If we have more free space than we require,
                        // we return a nil error.
                        if free > cfg.HealthChecks.DiskCheck.RequiredRemaining {
                                return nil
                        }

                        return fmt.Errorf("require: %v free space, got: %v",
                                cfg.HealthChecks.DiskCheck.RequiredRemaining,
                                free)
                },
                cfg.HealthChecks.DiskCheck.Interval,
                cfg.HealthChecks.DiskCheck.Timeout,
                cfg.HealthChecks.DiskCheck.Backoff,
                cfg.HealthChecks.DiskCheck.Attempts,
        )

        tlsHealthCheck := healthcheck.NewObservation(
                "tls",
                func() error {
                        expired, expTime, err := s.tlsManager.IsCertExpired(
                                s.cc.KeyRing,
                        )
                        if err != nil {
                                return err
                        }
                        if expired {
                                return fmt.Errorf("TLS certificate is "+
                                        "expired as of %v", expTime)
                        }

                        // If the certificate is not outdated, no error needs
                        // to be returned
                        return nil
                },
                cfg.HealthChecks.TLSCheck.Interval,
                cfg.HealthChecks.TLSCheck.Timeout,
                cfg.HealthChecks.TLSCheck.Backoff,
                cfg.HealthChecks.TLSCheck.Attempts,
        )

        checks := []*healthcheck.Observation{
                chainHealthCheck, diskCheck, tlsHealthCheck,
        }

        // If Tor is enabled, add the healthcheck for tor connection.
        if s.torController != nil {
                torConnectionCheck := healthcheck.NewObservation(
                        "tor connection",
                        func() error {
                                return healthcheck.CheckTorServiceStatus(
                                        s.torController,
                                        s.createNewHiddenService,
                                )
                        },
                        cfg.HealthChecks.TorConnection.Interval,
                        cfg.HealthChecks.TorConnection.Timeout,
                        cfg.HealthChecks.TorConnection.Backoff,
                        cfg.HealthChecks.TorConnection.Attempts,
                )
                checks = append(checks, torConnectionCheck)
        }

        // If remote signing is enabled, add the healthcheck for the remote
        // signing RPC interface.
        if s.cfg.RemoteSigner != nil && s.cfg.RemoteSigner.Enable {
                // Because we have two cascading timeouts here, we need to add
                // some slack to the "outer" one of them in case the "inner"
                // returns exactly on time.
                overhead := time.Millisecond * 10

                remoteSignerConnectionCheck := healthcheck.NewObservation(
                        "remote signer connection",
                        rpcwallet.HealthCheck(
                                s.cfg.RemoteSigner,

                                // For the health check we might to be even
                                // stricter than the initial/normal connect, so
                                // we use the health check timeout here.
                                cfg.HealthChecks.RemoteSigner.Timeout,
                        ),
                        cfg.HealthChecks.RemoteSigner.Interval,
                        cfg.HealthChecks.RemoteSigner.Timeout+overhead,
                        cfg.HealthChecks.RemoteSigner.Backoff,
                        cfg.HealthChecks.RemoteSigner.Attempts,
                )
                checks = append(checks, remoteSignerConnectionCheck)
        }

        // If we have a leader elector, we add a health check to ensure we are
        // still the leader. During normal operation, we should always be the
        // leader, but there are circumstances where this may change, such as
        // when we lose network connectivity for long enough expiring out lease.
        if leaderElector != nil {
                leaderCheck := healthcheck.NewObservation(
                        "leader status",
                        func() error {
                                // Check if we are still the leader. Note that
                                // we don't need to use a timeout context here
                                // as the healthcheck observer will handle the
                                // timeout case for us.
                                timeoutCtx, cancel := context.WithTimeout(
                                        context.Background(),
                                        cfg.HealthChecks.LeaderCheck.Timeout,
                                )
                                defer cancel()

                                leader, err := leaderElector.IsLeader(
                                        timeoutCtx,
                                )
                                if err != nil {
                                        return fmt.Errorf("unable to check if "+
                                                "still leader: %v", err)
                                }

                                if !leader {
                                        srvrLog.Debug("Not the current leader")
                                        return fmt.Errorf("not the current " +
                                                "leader")
                                }

                                return nil
                        },
                        cfg.HealthChecks.LeaderCheck.Interval,
                        cfg.HealthChecks.LeaderCheck.Timeout,
                        cfg.HealthChecks.LeaderCheck.Backoff,
                        cfg.HealthChecks.LeaderCheck.Attempts,
                )

                checks = append(checks, leaderCheck)
        }

        // If we have not disabled all of our health checks, we create a
        // liveness monitor with our configured checks.
        s.livenessMonitor = healthcheck.NewMonitor(
                &healthcheck.Config{
                        Checks:   checks,
                        Shutdown: srvrLog.Criticalf,
                },
        )
}

// Started returns true if the server has been started, and false otherwise.
// NOTE: This function is safe for concurrent access.
func (s *server) Started() bool {
        return atomic.LoadInt32(&s.active) != 0
}

// cleaner is used to aggregate "cleanup" functions during an operation that
// starts several subsystems. In case one of the subsystem fails to start
// and a proper resource cleanup is required, the "run" method achieves this
// by running all these added "cleanup" functions.
type cleaner []func() error

// add is used to add a cleanup function to be called when
// the run function is executed.
func (c cleaner) add(cleanup func() error) cleaner {
        return append(c, cleanup)
}

// run is used to run all the previousely added cleanup functions.
func (c cleaner) run() {
        for i := len(c) - 1; i >= 0; i-- {
                if err := c[i](); err != nil {
                        srvrLog.Infof("Cleanup failed: %v", err)
                }
        }
}

// startLowLevelServices starts the low-level services of the server. These
// services must be started successfully before running the main server. The
// services are,
// 1. the chain notifier.
//
// TODO(yy): identify and add more low-level services here.
func (s *server) startLowLevelServices() error {
        var startErr error

        cleanup := cleaner{}

        cleanup = cleanup.add(s.cc.ChainNotifier.Stop)
        if err := s.cc.ChainNotifier.Start(); err != nil {
                startErr = err
        }

        if startErr != nil {
                cleanup.run()
        }

        return startErr
}

// Start starts the main daemon server, all requested listeners, and any helper
// goroutines.
// NOTE: This function is safe for concurrent access.
//
//nolint:funlen
func (s *server) Start() error {
        // Get the current blockbeat.
        beat, err := s.getStartingBeat()
        if err != nil {
                return err
        }

        var startErr error

        // If one sub system fails to start, the following code ensures that the
        // previous started ones are stopped. It also ensures a proper wallet
        // shutdown which is important for releasing its resources (boltdb, etc...)
        cleanup := cleaner{}

        s.start.Do(func() {
                cleanup = cleanup.add(s.customMessageServer.Stop)
                if err := s.customMessageServer.Start(); err != nil {
                        startErr = err
                        return
                }

                if s.hostAnn != nil {
                        cleanup = cleanup.add(s.hostAnn.Stop)
                        if err := s.hostAnn.Start(); err != nil {
                                startErr = err
                                return
                        }
                }

                if s.livenessMonitor != nil {
                        cleanup = cleanup.add(s.livenessMonitor.Stop)
                        if err := s.livenessMonitor.Start(); err != nil {
                                startErr = err
                                return
                        }
                }

                // Start the notification server. This is used so channel
                // management goroutines can be notified when a funding
                // transaction reaches a sufficient number of confirmations, or
                // when the input for the funding transaction is spent in an
                // attempt at an uncooperative close by the counterparty.
                cleanup = cleanup.add(s.sigPool.Stop)
                if err := s.sigPool.Start(); err != nil {
                        startErr = err
                        return
                }

                cleanup = cleanup.add(s.writePool.Stop)
                if err := s.writePool.Start(); err != nil {
                        startErr = err
                        return
                }

                cleanup = cleanup.add(s.readPool.Stop)
                if err := s.readPool.Start(); err != nil {
                        startErr = err
                        return
                }

                cleanup = cleanup.add(s.cc.BestBlockTracker.Stop)
                if err := s.cc.BestBlockTracker.Start(); err != nil {
                        startErr = err
                        return
                }

                cleanup = cleanup.add(s.channelNotifier.Stop)
                if err := s.channelNotifier.Start(); err != nil {
                        startErr = err
                        return
                }

                cleanup = cleanup.add(func() error {
                        return s.peerNotifier.Stop()
                })
                if err := s.peerNotifier.Start(); err != nil {
                        startErr = err
                        return
                }

                cleanup = cleanup.add(s.htlcNotifier.Stop)
                if err := s.htlcNotifier.Start(); err != nil {
                        startErr = err
                        return
                }

                if s.towerClientMgr != nil {
                        cleanup = cleanup.add(s.towerClientMgr.Stop)
                        if err := s.towerClientMgr.Start(); err != nil {
                                startErr = err
                                return
                        }
                }

                cleanup = cleanup.add(s.txPublisher.Stop)
                if err := s.txPublisher.Start(beat); err != nil {
                        startErr = err
                        return
                }

                cleanup = cleanup.add(s.sweeper.Stop)
                if err := s.sweeper.Start(beat); err != nil {
                        startErr = err
                        return
                }

                cleanup = cleanup.add(s.utxoNursery.Stop)
                if err := s.utxoNursery.Start(); err != nil {
                        startErr = err
                        return
                }

                cleanup = cleanup.add(s.breachArbitrator.Stop)
                if err := s.breachArbitrator.Start(); err != nil {
                        startErr = err
                        return
                }

                cleanup = cleanup.add(s.fundingMgr.Stop)
                if err := s.fundingMgr.Start(); err != nil {
                        startErr = err
                        return
                }

                // htlcSwitch must be started before chainArb since the latter
                // relies on htlcSwitch to deliver resolution message upon
                // start.
                cleanup = cleanup.add(s.htlcSwitch.Stop)
                if err := s.htlcSwitch.Start(); err != nil {
                        startErr = err
                        return
                }

                cleanup = cleanup.add(s.interceptableSwitch.Stop)
                if err := s.interceptableSwitch.Start(); err != nil {
                        startErr = err
                        return
                }

                cleanup = cleanup.add(s.invoiceHtlcModifier.Stop)
                if err := s.invoiceHtlcModifier.Start(); err != nil {
                        startErr = err
                        return
                }

                cleanup = cleanup.add(s.chainArb.Stop)
                if err := s.chainArb.Start(beat); err != nil {
                        startErr = err
                        return
                }

                cleanup = cleanup.add(s.graphBuilder.Stop)
                if err := s.graphBuilder.Start(); err != nil {
                        startErr = err
                        return
                }

                cleanup = cleanup.add(s.chanRouter.Stop)
                if err := s.chanRouter.Start(); err != nil {
                        startErr = err
                        return
                }
                // The authGossiper depends on the chanRouter and therefore
                // should be started after it.
                cleanup = cleanup.add(s.authGossiper.Stop)
                if err := s.authGossiper.Start(); err != nil {
                        startErr = err
                        return
                }

                cleanup = cleanup.add(s.invoices.Stop)
                if err := s.invoices.Start(); err != nil {
                        startErr = err
                        return
                }

                cleanup = cleanup.add(s.sphinx.Stop)
                if err := s.sphinx.Start(); err != nil {
                        startErr = err
                        return
                }

                cleanup = cleanup.add(s.chanStatusMgr.Stop)
                if err := s.chanStatusMgr.Start(); err != nil {
                        startErr = err
                        return
                }

                cleanup = cleanup.add(s.chanEventStore.Stop)
                if err := s.chanEventStore.Start(); err != nil {
                        startErr = err
                        return
                }

                cleanup.add(func() error {
                        s.missionController.StopStoreTickers()
                        return nil
                })
                s.missionController.RunStoreTickers()

                // Before we start the connMgr, we'll check to see if we have
                // any backups to recover. We do this now as we want to ensure
                // that have all the information we need to handle channel
                // recovery _before_ we even accept connections from any peers.
                chanRestorer := &chanDBRestorer{
                        db:         s.chanStateDB,
                        secretKeys: s.cc.KeyRing,
                        chainArb:   s.chainArb,
                }
                if len(s.chansToRestore.PackedSingleChanBackups) != 0 {
                        _, err := chanbackup.UnpackAndRecoverSingles(
                                s.chansToRestore.PackedSingleChanBackups,
                                s.cc.KeyRing, chanRestorer, s,
                        )
                        if err != nil {
                                startErr = fmt.Errorf("unable to unpack single "+
                                        "backups: %v", err)
                                return
                        }
                }
                if len(s.chansToRestore.PackedMultiChanBackup) != 0 {
                        _, err := chanbackup.UnpackAndRecoverMulti(
                                s.chansToRestore.PackedMultiChanBackup,
                                s.cc.KeyRing, chanRestorer, s,
                        )
                        if err != nil {
                                startErr = fmt.Errorf("unable to unpack chan "+
                                        "backup: %v", err)
                                return
                        }
                }

                // chanSubSwapper must be started after the `channelNotifier`
                // because it depends on channel events as a synchronization
                // point.
                cleanup = cleanup.add(s.chanSubSwapper.Stop)
                if err := s.chanSubSwapper.Start(); err != nil {
                        startErr = err
                        return
                }

                if s.torController != nil {
                        cleanup = cleanup.add(s.torController.Stop)
                        if err := s.createNewHiddenService(); err != nil {
                                startErr = err
                                return
                        }
                }

                if s.natTraversal != nil {
                        s.wg.Add(1)
                        go s.watchExternalIP()
                }

                // Start connmgr last to prevent connections before init.
                cleanup = cleanup.add(func() error {
                        s.connMgr.Stop()
                        return nil
                })
                s.connMgr.Start()

                // If peers are specified as a config option, we'll add those
                // peers first.
                for _, peerAddrCfg := range s.cfg.AddPeers {
                        parsedPubkey, parsedHost, err := lncfg.ParseLNAddressPubkey(
                                peerAddrCfg,
                        )
                        if err != nil {
                                startErr = fmt.Errorf("unable to parse peer "+
                                        "pubkey from config: %v", err)
                                return
                        }
                        addr, err := parseAddr(parsedHost, s.cfg.net)
                        if err != nil {
                                startErr = fmt.Errorf("unable to parse peer "+
                                        "address provided as a config option: "+
                                        "%v", err)
                                return
                        }

                        peerAddr := &lnwire.NetAddress{
                                IdentityKey: parsedPubkey,
                                Address:     addr,
                                ChainNet:    s.cfg.ActiveNetParams.Net,
                        }

                        err = s.ConnectToPeer(
                                peerAddr, true,
                                s.cfg.ConnectionTimeout,
                        )
                        if err != nil {
                                startErr = fmt.Errorf("unable to connect to "+
                                        "peer address provided as a config "+
                                        "option: %v", err)
                                return
                        }
                }

                // Subscribe to NodeAnnouncements that advertise new addresses
                // our persistent peers.
                if err := s.updatePersistentPeerAddrs(); err != nil {
                        startErr = err
                        return
                }

                // With all the relevant sub-systems started, we'll now attempt
                // to establish persistent connections to our direct channel
                // collaborators within the network. Before doing so however,
                // we'll prune our set of link nodes found within the database
                // to ensure we don't reconnect to any nodes we no longer have
                // open channels with.
                if err := s.chanStateDB.PruneLinkNodes(); err != nil {
                        startErr = err
                        return
                }
                if err := s.establishPersistentConnections(); err != nil {
                        startErr = err
                        return
                }

                // setSeedList is a helper function that turns multiple DNS seed
                // server tuples from the command line or config file into the
                // data structure we need and does a basic formal sanity check
                // in the process.
                setSeedList := func(tuples []string, genesisHash chainhash.Hash) {
                        if len(tuples) == 0 {
                                return
                        }

                        result := make([][2]string, len(tuples))
                        for idx, tuple := range tuples {
                                tuple = strings.TrimSpace(tuple)
                                if len(tuple) == 0 {
                                        return
                                }

                                servers := strings.Split(tuple, ",")
                                if len(servers) > 2 || len(servers) == 0 {
                                        srvrLog.Warnf("Ignoring invalid DNS "+
                                                "seed tuple: %v", servers)
                                        return
                                }

                                copy(result[idx][:], servers)
                        }

                        chainreg.ChainDNSSeeds[genesisHash] = result
                }

                // Let users overwrite the DNS seed nodes. We only allow them
                // for bitcoin mainnet/testnet/signet.
                if s.cfg.Bitcoin.MainNet {
                        setSeedList(
                                s.cfg.Bitcoin.DNSSeeds,
                                chainreg.BitcoinMainnetGenesis,
                        )
                }
                if s.cfg.Bitcoin.TestNet3 {
                        setSeedList(
                                s.cfg.Bitcoin.DNSSeeds,
                                chainreg.BitcoinTestnetGenesis,
                        )
                }
                if s.cfg.Bitcoin.SigNet {
                        setSeedList(
                                s.cfg.Bitcoin.DNSSeeds,
                                chainreg.BitcoinSignetGenesis,
                        )
                }

                // If network bootstrapping hasn't been disabled, then we'll
                // configure the set of active bootstrappers, and launch a
                // dedicated goroutine to maintain a set of persistent
                // connections.
                if shouldPeerBootstrap(s.cfg) {
                        bootstrappers, err := initNetworkBootstrappers(s)
                        if err != nil {
                                startErr = err
                                return
                        }

                        s.wg.Add(1)
                        go s.peerBootstrapper(defaultMinPeers, bootstrappers)
                } else {
                        srvrLog.Infof("Auto peer bootstrapping is disabled")
                }

                // Start the blockbeat after all other subsystems have been
                // started so they are ready to receive new blocks.
                cleanup = cleanup.add(func() error {
                        s.blockbeatDispatcher.Stop()
                        return nil
                })
                if err := s.blockbeatDispatcher.Start(); err != nil {
                        startErr = err
                        return
                }

                // Set the active flag now that we've completed the full
                // startup.
                atomic.StoreInt32(&s.active, 1)
        })

        if startErr != nil {
                cleanup.run()
        }
        return startErr
}

// Stop gracefully shutsdown the main daemon server. This function will signal
// any active goroutines, or helper objects to exit, then blocks until they've
// all successfully exited. Additionally, any/all listeners are closed.
// NOTE: This function is safe for concurrent access.
func (s *server) Stop() error {
        s.stop.Do(func() {
                atomic.StoreInt32(&s.stopping, 1)

                close(s.quit)

                // Shutdown connMgr first to prevent conns during shutdown.
                s.connMgr.Stop()

                // Stop dispatching blocks to other systems immediately.
                s.blockbeatDispatcher.Stop()

                // Shutdown the wallet, funding manager, and the rpc server.
                if err := s.chanStatusMgr.Stop(); err != nil {
                        srvrLog.Warnf("failed to stop chanStatusMgr: %v", err)
                }
                if err := s.htlcSwitch.Stop(); err != nil {
                        srvrLog.Warnf("failed to stop htlcSwitch: %v", err)
                }
                if err := s.sphinx.Stop(); err != nil {
                        srvrLog.Warnf("failed to stop sphinx: %v", err)
                }
                if err := s.invoices.Stop(); err != nil {
                        srvrLog.Warnf("failed to stop invoices: %v", err)
                }
                if err := s.interceptableSwitch.Stop(); err != nil {
                        srvrLog.Warnf("failed to stop interceptable "+
                                "switch: %v", err)
                }
                if err := s.invoiceHtlcModifier.Stop(); err != nil {
                        srvrLog.Warnf("failed to stop htlc invoices "+
                                "modifier: %v", err)
                }
                if err := s.chanRouter.Stop(); err != nil {
                        srvrLog.Warnf("failed to stop chanRouter: %v", err)
                }
                if err := s.graphBuilder.Stop(); err != nil {
                        srvrLog.Warnf("failed to stop graphBuilder %v", err)
                }
                if err := s.chainArb.Stop(); err != nil {
                        srvrLog.Warnf("failed to stop chainArb: %v", err)
                }
                if err := s.fundingMgr.Stop(); err != nil {
                        srvrLog.Warnf("failed to stop fundingMgr: %v", err)
                }
                if err := s.breachArbitrator.Stop(); err != nil {
                        srvrLog.Warnf("failed to stop breachArbitrator: %v",
                                err)
                }
                if err := s.utxoNursery.Stop(); err != nil {
                        srvrLog.Warnf("failed to stop utxoNursery: %v", err)
                }
                if err := s.authGossiper.Stop(); err != nil {
                        srvrLog.Warnf("failed to stop authGossiper: %v", err)
                }
                if err := s.sweeper.Stop(); err != nil {
                        srvrLog.Warnf("failed to stop sweeper: %v", err)
                }
                if err := s.txPublisher.Stop(); err != nil {
                        srvrLog.Warnf("failed to stop txPublisher: %v", err)
                }
                if err := s.channelNotifier.Stop(); err != nil {
                        srvrLog.Warnf("failed to stop channelNotifier: %v", err)
                }
                if err := s.peerNotifier.Stop(); err != nil {
                        srvrLog.Warnf("failed to stop peerNotifier: %v", err)
                }
                if err := s.htlcNotifier.Stop(); err != nil {
                        srvrLog.Warnf("failed to stop htlcNotifier: %v", err)
                }

                // Update channel.backup file. Make sure to do it before
                // stopping chanSubSwapper.
                singles, err := chanbackup.FetchStaticChanBackups(
                        s.chanStateDB, s.addrSource,
                )
                if err != nil {
                        srvrLog.Warnf("failed to fetch channel states: %v",
                                err)
                } else {
                        err := s.chanSubSwapper.ManualUpdate(singles)
                        if err != nil {
                                srvrLog.Warnf("Manual update of channel "+
                                        "backup failed: %v", err)
                        }
                }

                if err := s.chanSubSwapper.Stop(); err != nil {
                        srvrLog.Warnf("failed to stop chanSubSwapper: %v", err)
                }
                if err := s.cc.ChainNotifier.Stop(); err != nil {
                        srvrLog.Warnf("Unable to stop ChainNotifier: %v", err)
                }
                if err := s.cc.BestBlockTracker.Stop(); err != nil {
                        srvrLog.Warnf("Unable to stop BestBlockTracker: %v",
                                err)
                }
                if err := s.chanEventStore.Stop(); err != nil {
                        srvrLog.Warnf("Unable to stop ChannelEventStore: %v",
                                err)
                }
                s.missionController.StopStoreTickers()

                // Disconnect from each active peers to ensure that
                // peerTerminationWatchers signal completion to each peer.
                for _, peer := range s.Peers() {
                        err := s.DisconnectPeer(peer.IdentityKey())
                        if err != nil {
                                srvrLog.Warnf("could not disconnect peer: %v"+
                                        "received error: %v", peer.IdentityKey(),
                                        err,
                                )
                        }
                }

                // Now that all connections have been torn down, stop the tower
                // client which will reliably flush all queued states to the
                // tower. If this is halted for any reason, the force quit timer
                // will kick in and abort to allow this method to return.
                if s.towerClientMgr != nil {
                        if err := s.towerClientMgr.Stop(); err != nil {
                                srvrLog.Warnf("Unable to shut down tower "+
                                        "client manager: %v", err)
                        }
                }

                if s.hostAnn != nil {
                        if err := s.hostAnn.Stop(); err != nil {
                                srvrLog.Warnf("unable to shut down host "+
                                        "annoucner: %v", err)
                        }
                }

                if s.livenessMonitor != nil {
                        if err := s.livenessMonitor.Stop(); err != nil {
                                srvrLog.Warnf("unable to shutdown liveness "+
                                        "monitor: %v", err)
                        }
                }

                // Wait for all lingering goroutines to quit.
                srvrLog.Debug("Waiting for server to shutdown...")
                s.wg.Wait()

                srvrLog.Debug("Stopping buffer pools...")
                s.sigPool.Stop()
                s.writePool.Stop()
                s.readPool.Stop()
        })

        return nil
}

// Stopped returns true if the server has been instructed to shutdown.
// NOTE: This function is safe for concurrent access.
func (s *server) Stopped() bool {
        return atomic.LoadInt32(&s.stopping) != 0
}

// configurePortForwarding attempts to set up port forwarding for the different
// ports that the server will be listening on.
//
// NOTE: This should only be used when using some kind of NAT traversal to
// automatically set up forwarding rules.
func (s *server) configurePortForwarding(ports ...uint16) ([]string, error) {
        ip, err := s.natTraversal.ExternalIP()
        if err != nil {
                return nil, err
        }
        s.lastDetectedIP = ip

        externalIPs := make([]string, 0, len(ports))
        for _, port := range ports {
                if err := s.natTraversal.AddPortMapping(port); err != nil {
                        srvrLog.Debugf("Unable to forward port %d: %v", port, err)
                        continue
                }

                hostIP := fmt.Sprintf("%v:%d", ip, port)
                externalIPs = append(externalIPs, hostIP)
        }

        return externalIPs, nil
}

// removePortForwarding attempts to clear the forwarding rules for the different
// ports the server is currently listening on.
//
// NOTE: This should only be used when using some kind of NAT traversal to
// automatically set up forwarding rules.
func (s *server) removePortForwarding() {
        forwardedPorts := s.natTraversal.ForwardedPorts()
        for _, port := range forwardedPorts {
                if err := s.natTraversal.DeletePortMapping(port); err != nil {
                        srvrLog.Errorf("Unable to remove forwarding rules for "+
                                "port %d: %v", port, err)
                }
        }
}

// watchExternalIP continuously checks for an updated external IP address every
// 15 minutes. Once a new IP address has been detected, it will automatically
// handle port forwarding rules and send updated node announcements to the
// currently connected peers.
//
// NOTE: This MUST be run as a goroutine.
func (s *server) watchExternalIP() {
        defer s.wg.Done()

        // Before exiting, we'll make sure to remove the forwarding rules set
        // up by the server.
        defer s.removePortForwarding()

        // Keep track of the external IPs set by the user to avoid replacing
        // them when detecting a new IP.
        ipsSetByUser := make(map[string]struct{})
        for _, ip := range s.cfg.ExternalIPs {
                ipsSetByUser[ip.String()] = struct{}{}
        }

        forwardedPorts := s.natTraversal.ForwardedPorts()

        ticker := time.NewTicker(15 * time.Minute)
        defer ticker.Stop()
out:
        for {
                select {
                case <-ticker.C:
                        // We'll start off by making sure a new IP address has
                        // been detected.
                        ip, err := s.natTraversal.ExternalIP()
                        if err != nil {
                                srvrLog.Debugf("Unable to retrieve the "+
                                        "external IP address: %v", err)
                                continue
                        }

                        // Periodically renew the NAT port forwarding.
                        for _, port := range forwardedPorts {
                                err := s.natTraversal.AddPortMapping(port)
                                if err != nil {
                                        srvrLog.Warnf("Unable to automatically "+
                                                "re-create port forwarding using %s: %v",
                                                s.natTraversal.Name(), err)
                                } else {
                                        srvrLog.Debugf("Automatically re-created "+
                                                "forwarding for port %d using %s to "+
                                                "advertise external IP",
                                                port, s.natTraversal.Name())
                                }
                        }

                        if ip.Equal(s.lastDetectedIP) {
                                continue
                        }

                        srvrLog.Infof("Detected new external IP address %s", ip)

                        // Next, we'll craft the new addresses that will be
                        // included in the new node announcement and advertised
                        // to the network. Each address will consist of the new
                        // IP detected and one of the currently advertised
                        // ports.
                        var newAddrs []net.Addr
                        for _, port := range forwardedPorts {
                                hostIP := fmt.Sprintf("%v:%d", ip, port)
                                addr, err := net.ResolveTCPAddr("tcp", hostIP)
                                if err != nil {
                                        srvrLog.Debugf("Unable to resolve "+
                                                "host %v: %v", addr, err)
                                        continue
                                }

                                newAddrs = append(newAddrs, addr)
                        }

                        // Skip the update if we weren't able to resolve any of
                        // the new addresses.
                        if len(newAddrs) == 0 {
                                srvrLog.Debug("Skipping node announcement " +
                                        "update due to not being able to " +
                                        "resolve any new addresses")
                                continue
                        }

                        // Now, we'll need to update the addresses in our node's
                        // announcement in order to propagate the update
                        // throughout the network. We'll only include addresses
                        // that have a different IP from the previous one, as
                        // the previous IP is no longer valid.
                        currentNodeAnn := s.getNodeAnnouncement()

                        for _, addr := range currentNodeAnn.Addresses {
                                host, _, err := net.SplitHostPort(addr.String())
                                if err != nil {
                                        srvrLog.Debugf("Unable to determine "+
                                                "host from address %v: %v",
                                                addr, err)
                                        continue
                                }

                                // We'll also make sure to include external IPs
                                // set manually by the user.
                                _, setByUser := ipsSetByUser[addr.String()]
                                if setByUser || host != s.lastDetectedIP.String() {
                                        newAddrs = append(newAddrs, addr)
                                }
                        }

                        // Then, we'll generate a new timestamped node
                        // announcement with the updated addresses and broadcast
                        // it to our peers.
                        newNodeAnn, err := s.genNodeAnnouncement(
                                nil, netann.NodeAnnSetAddrs(newAddrs),
                        )
                        if err != nil {
                                srvrLog.Debugf("Unable to generate new node "+
                                        "announcement: %v", err)
                                continue
                        }

                        err = s.BroadcastMessage(nil, &newNodeAnn)
                        if err != nil {
                                srvrLog.Debugf("Unable to broadcast new node "+
                                        "announcement to peers: %v", err)
                                continue
                        }

                        // Finally, update the last IP seen to the current one.
                        s.lastDetectedIP = ip
                case <-s.quit:
                        break out
                }
        }
}

// initNetworkBootstrappers initializes a set of network peer bootstrappers
// based on the server, and currently active bootstrap mechanisms as defined
// within the current configuration.
func initNetworkBootstrappers(s *server) ([]discovery.NetworkPeerBootstrapper, error) {
        srvrLog.Infof("Initializing peer network bootstrappers!")

        var bootStrappers []discovery.NetworkPeerBootstrapper

        // First, we'll create an instance of the ChannelGraphBootstrapper as
        // this can be used by default if we've already partially seeded the
        // network.
        chanGraph := autopilot.ChannelGraphFromDatabase(s.graphDB)
        graphBootstrapper, err := discovery.NewGraphBootstrapper(chanGraph)
        if err != nil {
                return nil, err
        }
        bootStrappers = append(bootStrappers, graphBootstrapper)

        // If this isn't simnet mode, then one of our additional bootstrapping
        // sources will be the set of running DNS seeds.
        if !s.cfg.Bitcoin.SimNet {
                dnsSeeds, ok := chainreg.ChainDNSSeeds[*s.cfg.ActiveNetParams.GenesisHash]

                // If we have a set of DNS seeds for this chain, then we'll add
                // it as an additional bootstrapping source.
                if ok {
                        srvrLog.Infof("Creating DNS peer bootstrapper with "+
                                "seeds: %v", dnsSeeds)

                        dnsBootStrapper := discovery.NewDNSSeedBootstrapper(
                                dnsSeeds, s.cfg.net, s.cfg.ConnectionTimeout,
                        )
                        bootStrappers = append(bootStrappers, dnsBootStrapper)
                }
        }

        return bootStrappers, nil
}

// createBootstrapIgnorePeers creates a map of peers that the bootstrap process
// needs to ignore, which is made of three parts,
//   - the node itself needs to be skipped as it doesn't make sense to connect
//     to itself.
//   - the peers that already have connections with, as in s.peersByPub.
//   - the peers that we are attempting to connect, as in s.persistentPeers.
func (s *server) createBootstrapIgnorePeers() map[autopilot.NodeID]struct{} {
        s.mu.RLock()
        defer s.mu.RUnlock()

        ignore := make(map[autopilot.NodeID]struct{})

        // We should ignore ourselves from bootstrapping.
        selfKey := autopilot.NewNodeID(s.identityECDH.PubKey())
        ignore[selfKey] = struct{}{}

        // Ignore all connected peers.
        for _, peer := range s.peersByPub {
                nID := autopilot.NewNodeID(peer.IdentityKey())
                ignore[nID] = struct{}{}
        }

        // Ignore all persistent peers as they have a dedicated reconnecting
        // process.
        for pubKeyStr := range s.persistentPeers {
                var nID autopilot.NodeID
                copy(nID[:], []byte(pubKeyStr))
                ignore[nID] = struct{}{}
        }

        return ignore
}

// peerBootstrapper is a goroutine which is tasked with attempting to establish
// and maintain a target minimum number of outbound connections. With this
// invariant, we ensure that our node is connected to a diverse set of peers
// and that nodes newly joining the network receive an up to date network view
// as soon as possible.
func (s *server) peerBootstrapper(numTargetPeers uint32,
        bootstrappers []discovery.NetworkPeerBootstrapper) {

        defer s.wg.Done()

        // Before we continue, init the ignore peers map.
        ignoreList := s.createBootstrapIgnorePeers()

        // We'll start off by aggressively attempting connections to peers in
        // order to be a part of the network as soon as possible.
        s.initialPeerBootstrap(ignoreList, numTargetPeers, bootstrappers)

        // Once done, we'll attempt to maintain our target minimum number of
        // peers.
        //
        // We'll use a 15 second backoff, and double the time every time an
        // epoch fails up to a ceiling.
        backOff := time.Second * 15

        // We'll create a new ticker to wake us up every 15 seconds so we can
        // see if we've reached our minimum number of peers.
        sampleTicker := time.NewTicker(backOff)
        defer sampleTicker.Stop()

        // We'll use the number of attempts and errors to determine if we need
        // to increase the time between discovery epochs.
        var epochErrors uint32 // To be used atomically.
        var epochAttempts uint32

        for {
                select {
                // The ticker has just woken us up, so we'll need to check if
                // we need to attempt to connect our to any more peers.
                case <-sampleTicker.C:
                        // Obtain the current number of peers, so we can gauge
                        // if we need to sample more peers or not.
                        s.mu.RLock()
                        numActivePeers := uint32(len(s.peersByPub))
                        s.mu.RUnlock()

                        // If we have enough peers, then we can loop back
                        // around to the next round as we're done here.
                        if numActivePeers >= numTargetPeers {
                                continue
                        }

                        // If all of our attempts failed during this last back
                        // off period, then will increase our backoff to 5
                        // minute ceiling to avoid an excessive number of
                        // queries
                        //
                        // TODO(roasbeef): add reverse policy too?

                        if epochAttempts > 0 &&
                                atomic.LoadUint32(&epochErrors) >= epochAttempts {

                                sampleTicker.Stop()

                                backOff *= 2
                                if backOff > bootstrapBackOffCeiling {
                                        backOff = bootstrapBackOffCeiling
                                }

                                srvrLog.Debugf("Backing off peer bootstrapper to "+
                                        "%v", backOff)
                                sampleTicker = time.NewTicker(backOff)
                                continue
                        }

                        atomic.StoreUint32(&epochErrors, 0)
                        epochAttempts = 0

                        // Since we know need more peers, we'll compute the
                        // exact number we need to reach our threshold.
                        numNeeded := numTargetPeers - numActivePeers

                        srvrLog.Debugf("Attempting to obtain %v more network "+
                                "peers", numNeeded)

                        // With the number of peers we need calculated, we'll
                        // query the network bootstrappers to sample a set of
                        // random addrs for us.
                        //
                        // Before we continue, get a copy of the ignore peers
                        // map.
                        ignoreList = s.createBootstrapIgnorePeers()

                        peerAddrs, err := discovery.MultiSourceBootstrap(
                                ignoreList, numNeeded*2, bootstrappers...,
                        )
                        if err != nil {
                                srvrLog.Errorf("Unable to retrieve bootstrap "+
                                        "peers: %v", err)
                                continue
                        }

                        // Finally, we'll launch a new goroutine for each
                        // prospective peer candidates.
                        for _, addr := range peerAddrs {
                                epochAttempts++

                                go func(a *lnwire.NetAddress) {
                                        // TODO(roasbeef): can do AS, subnet,
                                        // country diversity, etc
                                        errChan := make(chan error, 1)
                                        s.connectToPeer(
                                                a, errChan,
                                                s.cfg.ConnectionTimeout,
                                        )
                                        select {
                                        case err := <-errChan:
                                                if err == nil {
                                                        return
                                                }

                                                srvrLog.Errorf("Unable to "+
                                                        "connect to %v: %v",
                                                        a, err)
                                                atomic.AddUint32(&epochErrors, 1)
                                        case <-s.quit:
                                        }
                                }(addr)
                        }
                case <-s.quit:
                        return
                }
        }
}

// bootstrapBackOffCeiling is the maximum amount of time we'll wait between
// failed attempts to locate a set of bootstrap peers. We'll slowly double our
// query back off each time we encounter a failure.
const bootstrapBackOffCeiling = time.Minute * 5

// initialPeerBootstrap attempts to continuously connect to peers on startup
// until the target number of peers has been reached. This ensures that nodes
// receive an up to date network view as soon as possible.
func (s *server) initialPeerBootstrap(ignore map[autopilot.NodeID]struct{},
        numTargetPeers uint32,
        bootstrappers []discovery.NetworkPeerBootstrapper) {

        srvrLog.Debugf("Init bootstrap with targetPeers=%v, bootstrappers=%v, "+
                "ignore=%v", numTargetPeers, len(bootstrappers), len(ignore))

        // We'll start off by waiting 2 seconds between failed attempts, then
        // double each time we fail until we hit the bootstrapBackOffCeiling.
        var delaySignal <-chan time.Time
        delayTime := time.Second * 2

        // As want to be more aggressive, we'll use a lower back off celling
        // then the main peer bootstrap logic.
        backOffCeiling := bootstrapBackOffCeiling / 5

        for attempts := 0; ; attempts++ {
                // Check if the server has been requested to shut down in order
                // to prevent blocking.
                if s.Stopped() {
                        return
                }

                // We can exit our aggressive initial peer bootstrapping stage
                // if we've reached out target number of peers.
                s.mu.RLock()
                numActivePeers := uint32(len(s.peersByPub))
                s.mu.RUnlock()

                if numActivePeers >= numTargetPeers {
                        return
                }

                if attempts > 0 {
                        srvrLog.Debugf("Waiting %v before trying to locate "+
                                "bootstrap peers (attempt #%v)", delayTime,
                                attempts)

                        // We've completed at least one iterating and haven't
                        // finished, so we'll start to insert a delay period
                        // between each attempt.
                        delaySignal = time.After(delayTime)
                        select {
                        case <-delaySignal:
                        case <-s.quit:
                                return
                        }

                        // After our delay, we'll double the time we wait up to
                        // the max back off period.
                        delayTime *= 2
                        if delayTime > backOffCeiling {
                                delayTime = backOffCeiling
                        }
                }

                // Otherwise, we'll request for the remaining number of peers
                // in order to reach our target.
                peersNeeded := numTargetPeers - numActivePeers
                bootstrapAddrs, err := discovery.MultiSourceBootstrap(
                        ignore, peersNeeded, bootstrappers...,
                )
                if err != nil {
                        srvrLog.Errorf("Unable to retrieve initial bootstrap "+
                                "peers: %v", err)
                        continue
                }

                // Then, we'll attempt to establish a connection to the
                // different peer addresses retrieved by our bootstrappers.
                var wg sync.WaitGroup
                for _, bootstrapAddr := range bootstrapAddrs {
                        wg.Add(1)
                        go func(addr *lnwire.NetAddress) {
                                defer wg.Done()

                                errChan := make(chan error, 1)
                                go s.connectToPeer(
                                        addr, errChan, s.cfg.ConnectionTimeout,
                                )

                                // We'll only allow this connection attempt to
                                // take up to 3 seconds. This allows us to move
                                // quickly by discarding peers that are slowing
                                // us down.
                                select {
                                case err := <-errChan:
                                        if err == nil {
                                                return
                                        }
                                        srvrLog.Errorf("Unable to connect to "+
                                                "%v: %v", addr, err)
                                // TODO: tune timeout? 3 seconds might be *too*
                                // aggressive but works well.
                                case <-time.After(3 * time.Second):
                                        srvrLog.Tracef("Skipping peer %v due "+
                                                "to not establishing a "+
                                                "connection within 3 seconds",
                                                addr)
                                case <-s.quit:
                                }
                        }(bootstrapAddr)
                }

                wg.Wait()
        }
}

// createNewHiddenService automatically sets up a v2 or v3 onion service in
// order to listen for inbound connections over Tor.
func (s *server) createNewHiddenService() error {
        // Determine the different ports the server is listening on. The onion
        // service's virtual port will map to these ports and one will be picked
        // at random when the onion service is being accessed.
        listenPorts := make([]int, 0, len(s.listenAddrs))
        for _, listenAddr := range s.listenAddrs {
                port := listenAddr.(*net.TCPAddr).Port
                listenPorts = append(listenPorts, port)
        }

        encrypter, err := lnencrypt.KeyRingEncrypter(s.cc.KeyRing)
        if err != nil {
                return err
        }

        // Once the port mapping has been set, we can go ahead and automatically
        // create our onion service. The service's private key will be saved to
        // disk in order to regain access to this service when restarting `lnd`.
        onionCfg := tor.AddOnionConfig{
                VirtualPort: defaultPeerPort,
                TargetPorts: listenPorts,
                Store: tor.NewOnionFile(
                        s.cfg.Tor.PrivateKeyPath, 0600, s.cfg.Tor.EncryptKey,
                        encrypter,
                ),
        }

        switch {
        case s.cfg.Tor.V2:
                onionCfg.Type = tor.V2
        case s.cfg.Tor.V3:
                onionCfg.Type = tor.V3
        }

        addr, err := s.torController.AddOnion(onionCfg)
        if err != nil {
                return err
        }

        // Now that the onion service has been created, we'll add the onion
        // address it can be reached at to our list of advertised addresses.
        newNodeAnn, err := s.genNodeAnnouncement(
                nil, func(currentAnn *lnwire.NodeAnnouncement) {
                        currentAnn.Addresses = append(currentAnn.Addresses, addr)
                },
        )
        if err != nil {
                return fmt.Errorf("unable to generate new node "+
                        "announcement: %v", err)
        }

        // Finally, we'll update the on-disk version of our announcement so it
        // will eventually propagate to nodes in the network.
        selfNode := &models.LightningNode{
                HaveNodeAnnouncement: true,
                LastUpdate:           time.Unix(int64(newNodeAnn.Timestamp), 0),
                Addresses:            newNodeAnn.Addresses,
                Alias:                newNodeAnn.Alias.String(),
                Features: lnwire.NewFeatureVector(
                        newNodeAnn.Features, lnwire.Features,
                ),
                Color:        newNodeAnn.RGBColor,
                AuthSigBytes: newNodeAnn.Signature.ToSignatureBytes(),
        }
        copy(selfNode.PubKeyBytes[:], s.identityECDH.PubKey().SerializeCompressed())
        if err := s.graphDB.SetSourceNode(selfNode); err != nil {
                return fmt.Errorf("can't set self node: %w", err)
        }

        return nil
}

// findChannel finds a channel given a public key and ChannelID. It is an
// optimization that is quicker than seeking for a channel given only the
// ChannelID.
func (s *server) findChannel(node *btcec.PublicKey, chanID lnwire.ChannelID) (
        *channeldb.OpenChannel, error) {

        nodeChans, err := s.chanStateDB.FetchOpenChannels(node)
        if err != nil {
                return nil, err
        }

        for _, channel := range nodeChans {
                if chanID.IsChanPoint(&channel.FundingOutpoint) {
                        return channel, nil
                }
        }

        return nil, fmt.Errorf("unable to find channel")
}

// getNodeAnnouncement fetches the current, fully signed node announcement.
func (s *server) getNodeAnnouncement() lnwire.NodeAnnouncement {
        s.mu.Lock()
        defer s.mu.Unlock()

        return *s.currentNodeAnn
}

// genNodeAnnouncement generates and returns the current fully signed node
// announcement. The time stamp of the announcement will be updated in order
// to ensure it propagates through the network.
func (s *server) genNodeAnnouncement(features *lnwire.RawFeatureVector,
        modifiers ...netann.NodeAnnModifier) (lnwire.NodeAnnouncement, error) {

        s.mu.Lock()
        defer s.mu.Unlock()

        // First, try to update our feature manager with the updated set of
        // features.
        if features != nil {
                proposedFeatures := map[feature.Set]*lnwire.RawFeatureVector{
                        feature.SetNodeAnn: features,
                }
                err := s.featureMgr.UpdateFeatureSets(proposedFeatures)
                if err != nil {
                        return lnwire.NodeAnnouncement{}, err
                }

                // If we could successfully update our feature manager, add
                // an update modifier to include these new features to our
                // set.
                modifiers = append(
                        modifiers, netann.NodeAnnSetFeatures(features),
                )
        }

        // Always update the timestamp when refreshing to ensure the update
        // propagates.
        modifiers = append(modifiers, netann.NodeAnnSetTimestamp)

        // Apply the requested changes to the node announcement.
        for _, modifier := range modifiers {
                modifier(s.currentNodeAnn)
        }

        // Sign a new update after applying all of the passed modifiers.
        err := netann.SignNodeAnnouncement(
                s.nodeSigner, s.identityKeyLoc, s.currentNodeAnn,
        )
        if err != nil {
                return lnwire.NodeAnnouncement{}, err
        }

        return *s.currentNodeAnn, nil
}

// updateAndBroadcastSelfNode generates a new node announcement
// applying the giving modifiers and updating the time stamp
// to ensure it propagates through the network. Then it broadcasts
// it to the network.
func (s *server) updateAndBroadcastSelfNode(features *lnwire.RawFeatureVector,
        modifiers ...netann.NodeAnnModifier) error {

        newNodeAnn, err := s.genNodeAnnouncement(features, modifiers...)
        if err != nil {
                return fmt.Errorf("unable to generate new node "+
                        "announcement: %v", err)
        }

        // Update the on-disk version of our announcement.
        // Load and modify self node istead of creating anew instance so we
        // don't risk overwriting any existing values.
        selfNode, err := s.graphDB.SourceNode()
        if err != nil {
                return fmt.Errorf("unable to get current source node: %w", err)
        }

        selfNode.HaveNodeAnnouncement = true
        selfNode.LastUpdate = time.Unix(int64(newNodeAnn.Timestamp), 0)
        selfNode.Addresses = newNodeAnn.Addresses
        selfNode.Alias = newNodeAnn.Alias.String()
        selfNode.Features = s.featureMgr.Get(feature.SetNodeAnn)
        selfNode.Color = newNodeAnn.RGBColor
        selfNode.AuthSigBytes = newNodeAnn.Signature.ToSignatureBytes()

        copy(selfNode.PubKeyBytes[:], s.identityECDH.PubKey().SerializeCompressed())

        if err := s.graphDB.SetSourceNode(selfNode); err != nil {
                return fmt.Errorf("can't set self node: %w", err)
        }

        // Finally, propagate it to the nodes in the network.
        err = s.BroadcastMessage(nil, &newNodeAnn)
        if err != nil {
                rpcsLog.Debugf("Unable to broadcast new node "+
                        "announcement to peers: %v", err)
                return err
        }

        return nil
}

type nodeAddresses struct {
        pubKey    *btcec.PublicKey
        addresses []net.Addr
}

// establishPersistentConnections attempts to establish persistent connections
// to all our direct channel collaborators. In order to promote liveness of our
// active channels, we instruct the connection manager to attempt to establish
// and maintain persistent connections to all our direct channel counterparties.
func (s *server) establishPersistentConnections() error {
        // nodeAddrsMap stores the combination of node public keys and addresses
        // that we'll attempt to reconnect to. PubKey strings are used as keys
        // since other PubKey forms can't be compared.
        nodeAddrsMap := map[string]*nodeAddresses{}

        // Iterate through the list of LinkNodes to find addresses we should
        // attempt to connect to based on our set of previous connections. Set
        // the reconnection port to the default peer port.
        linkNodes, err := s.chanStateDB.LinkNodeDB().FetchAllLinkNodes()
        if err != nil && err != channeldb.ErrLinkNodesNotFound {
                return err
        }
        for _, node := range linkNodes {
                pubStr := string(node.IdentityPub.SerializeCompressed())
                nodeAddrs := &nodeAddresses{
                        pubKey:    node.IdentityPub,
                        addresses: node.Addresses,
                }
                nodeAddrsMap[pubStr] = nodeAddrs
        }

        // After checking our previous connections for addresses to connect to,
        // iterate through the nodes in our channel graph to find addresses
        // that have been added via NodeAnnouncement messages.
        sourceNode, err := s.graphDB.SourceNode()
        if err != nil {
                return err
        }

        // TODO(roasbeef): instead iterate over link nodes and query graph for
        // each of the nodes.
        selfPub := s.identityECDH.PubKey().SerializeCompressed()
        err = s.graphDB.ForEachNodeChannel(sourceNode.PubKeyBytes, func(
                tx kvdb.RTx,
                chanInfo *models.ChannelEdgeInfo,
                policy, _ *models.ChannelEdgePolicy) error {

                // If the remote party has announced the channel to us, but we
                // haven't yet, then we won't have a policy. However, we don't
                // need this to connect to the peer, so we'll log it and move on.
                if policy == nil {
                        srvrLog.Warnf("No channel policy found for "+
                                "ChannelPoint(%v): ", chanInfo.ChannelPoint)
                }

                // We'll now fetch the peer opposite from us within this
                // channel so we can queue up a direct connection to them.
                channelPeer, err := s.graphDB.FetchOtherNode(
                        tx, chanInfo, selfPub,
                )
                if err != nil {
                        return fmt.Errorf("unable to fetch channel peer for "+
                                "ChannelPoint(%v): %v", chanInfo.ChannelPoint,
                                err)
                }

                pubStr := string(channelPeer.PubKeyBytes[:])

                // Add all unique addresses from channel
                // graph/NodeAnnouncements to the list of addresses we'll
                // connect to for this peer.
                addrSet := make(map[string]net.Addr)
                for _, addr := range channelPeer.Addresses {
                        switch addr.(type) {
                        case *net.TCPAddr:
                                addrSet[addr.String()] = addr

                        // We'll only attempt to connect to Tor addresses if Tor
                        // outbound support is enabled.
                        case *tor.OnionAddr:
                                if s.cfg.Tor.Active {
                                        addrSet[addr.String()] = addr
                                }
                        }
                }

                // If this peer is also recorded as a link node, we'll add any
                // additional addresses that have not already been selected.
                linkNodeAddrs, ok := nodeAddrsMap[pubStr]
                if ok {
                        for _, lnAddress := range linkNodeAddrs.addresses {
                                switch lnAddress.(type) {
                                case *net.TCPAddr:
                                        addrSet[lnAddress.String()] = lnAddress

                                // We'll only attempt to connect to Tor
                                // addresses if Tor outbound support is enabled.
                                case *tor.OnionAddr:
                                        if s.cfg.Tor.Active {
                                                addrSet[lnAddress.String()] = lnAddress
                                        }
                                }
                        }
                }

                // Construct a slice of the deduped addresses.
                var addrs []net.Addr
                for _, addr := range addrSet {
                        addrs = append(addrs, addr)
                }

                n := &nodeAddresses{
                        addresses: addrs,
                }
                n.pubKey, err = channelPeer.PubKey()
                if err != nil {
                        return err
                }

                nodeAddrsMap[pubStr] = n
                return nil
        })
        if err != nil && !errors.Is(err, graphdb.ErrGraphNoEdgesFound) {
                return err
        }

        srvrLog.Debugf("Establishing %v persistent connections on start",
                len(nodeAddrsMap))

        // Acquire and hold server lock until all persistent connection requests
        // have been recorded and sent to the connection manager.
        s.mu.Lock()
        defer s.mu.Unlock()

        // Iterate through the combined list of addresses from prior links and
        // node announcements and attempt to reconnect to each node.
        var numOutboundConns int
        for pubStr, nodeAddr := range nodeAddrsMap {
                // Add this peer to the set of peers we should maintain a
                // persistent connection with. We set the value to false to
                // indicate that we should not continue to reconnect if the
                // number of channels returns to zero, since this peer has not
                // been requested as perm by the user.
                s.persistentPeers[pubStr] = false
                if _, ok := s.persistentPeersBackoff[pubStr]; !ok {
                        s.persistentPeersBackoff[pubStr] = s.cfg.MinBackoff
                }

                for _, address := range nodeAddr.addresses {
                        // Create a wrapper address which couples the IP and
                        // the pubkey so the brontide authenticated connection
                        // can be established.
                        lnAddr := &lnwire.NetAddress{
                                IdentityKey: nodeAddr.pubKey,
                                Address:     address,
                        }

                        s.persistentPeerAddrs[pubStr] = append(
                                s.persistentPeerAddrs[pubStr], lnAddr)
                }

                // We'll connect to the first 10 peers immediately, then
                // randomly stagger any remaining connections if the
                // stagger initial reconnect flag is set. This ensures
                // that mobile nodes or nodes with a small number of
                // channels obtain connectivity quickly, but larger
                // nodes are able to disperse the costs of connecting to
                // all peers at once.
                if numOutboundConns < numInstantInitReconnect ||
                        !s.cfg.StaggerInitialReconnect {

                        go s.connectToPersistentPeer(pubStr)
                } else {
                        go s.delayInitialReconnect(pubStr)
                }

                numOutboundConns++
        }

        return nil
}

// delayInitialReconnect will attempt a reconnection to the given peer after
// sampling a value for the delay between 0s and the maxInitReconnectDelay.
//
// NOTE: This method MUST be run as a goroutine.
func (s *server) delayInitialReconnect(pubStr string) {
        delay := time.Duration(prand.Intn(maxInitReconnectDelay)) * time.Second
        select {
        case <-time.After(delay):
                s.connectToPersistentPeer(pubStr)
        case <-s.quit:
        }
}

// prunePersistentPeerConnection removes all internal state related to
// persistent connections to a peer within the server. This is used to avoid
// persistent connection retries to peers we do not have any open channels with.
func (s *server) prunePersistentPeerConnection(compressedPubKey [33]byte) {
        pubKeyStr := string(compressedPubKey[:])

        s.mu.Lock()
        if perm, ok := s.persistentPeers[pubKeyStr]; ok && !perm {
                delete(s.persistentPeers, pubKeyStr)
                delete(s.persistentPeersBackoff, pubKeyStr)
                delete(s.persistentPeerAddrs, pubKeyStr)
                s.cancelConnReqs(pubKeyStr, nil)
                s.mu.Unlock()

                srvrLog.Infof("Pruned peer %x from persistent connections, "+
                        "peer has no open channels", compressedPubKey)

                return
        }
        s.mu.Unlock()
}

// BroadcastMessage sends a request to the server to broadcast a set of
// messages to all peers other than the one specified by the `skips` parameter.
// All messages sent via BroadcastMessage will be queued for lazy delivery to
// the target peers.
//
// NOTE: This function is safe for concurrent access.
func (s *server) BroadcastMessage(skips map[route.Vertex]struct{},
        msgs ...lnwire.Message) error {

        // Filter out peers found in the skips map. We synchronize access to
        // peersByPub throughout this process to ensure we deliver messages to
        // exact set of peers present at the time of invocation.
        s.mu.RLock()
        peers := make([]*peer.Brontide, 0, len(s.peersByPub))
        for pubStr, sPeer := range s.peersByPub {
                if skips != nil {
                        if _, ok := skips[sPeer.PubKey()]; ok {
                                srvrLog.Tracef("Skipping %x in broadcast with "+
                                        "pubStr=%x", sPeer.PubKey(), pubStr)
                                continue
                        }
                }

                peers = append(peers, sPeer)
        }
        s.mu.RUnlock()

        // Iterate over all known peers, dispatching a go routine to enqueue
        // all messages to each of peers.
        var wg sync.WaitGroup
        for _, sPeer := range peers {
                srvrLog.Debugf("Sending %v messages to peer %x", len(msgs),
                        sPeer.PubKey())

                // Dispatch a go routine to enqueue all messages to this peer.
                wg.Add(1)
                s.wg.Add(1)
                go func(p lnpeer.Peer) {
                        defer s.wg.Done()
                        defer wg.Done()

                        p.SendMessageLazy(false, msgs...)
                }(sPeer)
        }

        // Wait for all messages to have been dispatched before returning to
        // caller.
        wg.Wait()

        return nil
}

// NotifyWhenOnline can be called by other subsystems to get notified when a
// particular peer comes online. The peer itself is sent across the peerChan.
//
// NOTE: This function is safe for concurrent access.
func (s *server) NotifyWhenOnline(peerKey [33]byte,
        peerChan chan<- lnpeer.Peer) {

        s.mu.Lock()

        // Compute the target peer's identifier.
        pubStr := string(peerKey[:])

        // Check if peer is connected.
        peer, ok := s.peersByPub[pubStr]
        if ok {
                // Unlock here so that the mutex isn't held while we are
                // waiting for the peer to become active.
                s.mu.Unlock()

                // Wait until the peer signals that it is actually active
                // rather than only in the server's maps.
                select {
                case <-peer.ActiveSignal():
                case <-peer.QuitSignal():
                        // The peer quit, so we'll add the channel to the slice
                        // and return.
                        s.mu.Lock()
                        s.peerConnectedListeners[pubStr] = append(
                                s.peerConnectedListeners[pubStr], peerChan,
                        )
                        s.mu.Unlock()
                        return
                }

                // Connected, can return early.
                srvrLog.Debugf("Notifying that peer %x is online", peerKey)

                select {
                case peerChan <- peer:
                case <-s.quit:
                }

                return
        }

        // Not connected, store this listener such that it can be notified when
        // the peer comes online.
        s.peerConnectedListeners[pubStr] = append(
                s.peerConnectedListeners[pubStr], peerChan,
        )
        s.mu.Unlock()
}

// NotifyWhenOffline delivers a notification to the caller of when the peer with
// the given public key has been disconnected. The notification is signaled by
// closing the channel returned.
func (s *server) NotifyWhenOffline(peerPubKey [33]byte) <-chan struct{} {
        s.mu.Lock()
        defer s.mu.Unlock()

        c := make(chan struct{})

        // If the peer is already offline, we can immediately trigger the
        // notification.
        peerPubKeyStr := string(peerPubKey[:])
        if _, ok := s.peersByPub[peerPubKeyStr]; !ok {
                srvrLog.Debugf("Notifying that peer %x is offline", peerPubKey)
                close(c)
                return c
        }

        // Otherwise, the peer is online, so we'll keep track of the channel to
        // trigger the notification once the server detects the peer
        // disconnects.
        s.peerDisconnectedListeners[peerPubKeyStr] = append(
                s.peerDisconnectedListeners[peerPubKeyStr], c,
        )

        return c
}

// FindPeer will return the peer that corresponds to the passed in public key.
// This function is used by the funding manager, allowing it to update the
// daemon's local representation of the remote peer.
//
// NOTE: This function is safe for concurrent access.
func (s *server) FindPeer(peerKey *btcec.PublicKey) (*peer.Brontide, error) {
        s.mu.RLock()
        defer s.mu.RUnlock()

        pubStr := string(peerKey.SerializeCompressed())

        return s.findPeerByPubStr(pubStr)
}

// FindPeerByPubStr will return the peer that corresponds to the passed peerID,
// which should be a string representation of the peer's serialized, compressed
// public key.
//
// NOTE: This function is safe for concurrent access.
func (s *server) FindPeerByPubStr(pubStr string) (*peer.Brontide, error) {
        s.mu.RLock()
        defer s.mu.RUnlock()

        return s.findPeerByPubStr(pubStr)
}

// findPeerByPubStr is an internal method that retrieves the specified peer from
// the server's internal state using.
func (s *server) findPeerByPubStr(pubStr string) (*peer.Brontide, error) {
        peer, ok := s.peersByPub[pubStr]
        if !ok {
                return nil, ErrPeerNotConnected
        }

        return peer, nil
}

// nextPeerBackoff computes the next backoff duration for a peer's pubkey using
// exponential backoff. If no previous backoff was known, the default is
// returned.
func (s *server) nextPeerBackoff(pubStr string,
        startTime time.Time) time.Duration {

        // Now, determine the appropriate backoff to use for the retry.
        backoff, ok := s.persistentPeersBackoff[pubStr]
        if !ok {
                // If an existing backoff was unknown, use the default.
                return s.cfg.MinBackoff
        }

        // If the peer failed to start properly, we'll just use the previous
        // backoff to compute the subsequent randomized exponential backoff
        // duration. This will roughly double on average.
        if startTime.IsZero() {
                return computeNextBackoff(backoff, s.cfg.MaxBackoff)
        }

        // The peer succeeded in starting. If the connection didn't last long
        // enough to be considered stable, we'll continue to back off retries
        // with this peer.
        connDuration := time.Since(startTime)
        if connDuration < defaultStableConnDuration {
                return computeNextBackoff(backoff, s.cfg.MaxBackoff)
        }

        // The peer succeed in starting and this was stable peer, so we'll
        // reduce the timeout duration by the length of the connection after
        // applying randomized exponential backoff. We'll only apply this in the
        // case that:
        //   reb(curBackoff) - connDuration > cfg.MinBackoff
        relaxedBackoff := computeNextBackoff(backoff, s.cfg.MaxBackoff) - connDuration
        if relaxedBackoff > s.cfg.MinBackoff {
                return relaxedBackoff
        }

        // Lastly, if reb(currBackoff) - connDuration <= cfg.MinBackoff, meaning
        // the stable connection lasted much longer than our previous backoff.
        // To reward such good behavior, we'll reconnect after the default
        // timeout.
        return s.cfg.MinBackoff
}

// shouldDropLocalConnection determines if our local connection to a remote peer
// should be dropped in the case of concurrent connection establishment. In
// order to deterministically decide which connection should be dropped, we'll
// utilize the ordering of the local and remote public key. If we didn't use
// such a tie breaker, then we risk _both_ connections erroneously being
// dropped.
func shouldDropLocalConnection(local, remote *btcec.PublicKey) bool {
        localPubBytes := local.SerializeCompressed()
        remotePubPbytes := remote.SerializeCompressed()

        // The connection that comes from the node with a "smaller" pubkey
        // should be kept. Therefore, if our pubkey is "greater" than theirs, we
        // should drop our established connection.
        return bytes.Compare(localPubBytes, remotePubPbytes) > 0
}

// InboundPeerConnected initializes a new peer in response to a new inbound
// connection.
//
// NOTE: This function is safe for concurrent access.
func (s *server) InboundPeerConnected(conn net.Conn) {
        // Exit early if we have already been instructed to shutdown, this
        // prevents any delayed callbacks from accidentally registering peers.
        if s.Stopped() {
                return
        }

        nodePub := conn.(*brontide.Conn).RemotePub()
        pubSer := nodePub.SerializeCompressed()
        pubStr := string(pubSer)

        var pubBytes [33]byte
        copy(pubBytes[:], pubSer)

        s.mu.Lock()
        defer s.mu.Unlock()

        // If the remote node's public key is banned, drop the connection.
        shouldDc, dcErr := s.authGossiper.ShouldDisconnect(nodePub)
        if dcErr != nil {
                srvrLog.Errorf("Unable to check if we should disconnect "+
                        "peer: %v", dcErr)
                conn.Close()

                return
        }

        if shouldDc {
                srvrLog.Debugf("Dropping connection for %v since they are "+
                        "banned.", pubSer)

                conn.Close()

                return
        }

        // If we already have an outbound connection to this peer, then ignore
        // this new connection.
        if p, ok := s.outboundPeers[pubStr]; ok {
                srvrLog.Debugf("Already have outbound connection for %v, "+
                        "ignoring inbound connection from local=%v, remote=%v",
                        p, conn.LocalAddr(), conn.RemoteAddr())

                conn.Close()
                return
        }

        // If we already have a valid connection that is scheduled to take
        // precedence once the prior peer has finished disconnecting, we'll
        // ignore this connection.
        if p, ok := s.scheduledPeerConnection[pubStr]; ok {
                srvrLog.Debugf("Ignoring connection from %v, peer %v already "+
                        "scheduled", conn.RemoteAddr(), p)
                conn.Close()
                return
        }

        srvrLog.Infof("New inbound connection from %v", conn.RemoteAddr())

        // Check to see if we already have a connection with this peer. If so,
        // we may need to drop our existing connection. This prevents us from
        // having duplicate connections to the same peer. We forgo adding a
        // default case as we expect these to be the only error values returned
        // from findPeerByPubStr.
        connectedPeer, err := s.findPeerByPubStr(pubStr)
        switch err {
        case ErrPeerNotConnected:
                // We were unable to locate an existing connection with the
                // target peer, proceed to connect.
                s.cancelConnReqs(pubStr, nil)
                s.peerConnected(conn, nil, true)

        case nil:
                // We already have a connection with the incoming peer. If the
                // connection we've already established should be kept and is
                // not of the same type of the new connection (inbound), then
                // we'll close out the new connection s.t there's only a single
                // connection between us.
                localPub := s.identityECDH.PubKey()
                if !connectedPeer.Inbound() &&
                        !shouldDropLocalConnection(localPub, nodePub) {

                        srvrLog.Warnf("Received inbound connection from "+
                                "peer %v, but already have outbound "+
                                "connection, dropping conn", connectedPeer)
                        conn.Close()
                        return
                }

                // Otherwise, if we should drop the connection, then we'll
                // disconnect our already connected peer.
                srvrLog.Debugf("Disconnecting stale connection to %v",
                        connectedPeer)

                s.cancelConnReqs(pubStr, nil)

                // Remove the current peer from the server's internal state and
                // signal that the peer termination watcher does not need to
                // execute for this peer.
                s.removePeer(connectedPeer)
                s.ignorePeerTermination[connectedPeer] = struct{}{}
                s.scheduledPeerConnection[pubStr] = func() {
                        s.peerConnected(conn, nil, true)
                }
        }
}

// OutboundPeerConnected initializes a new peer in response to a new outbound
// connection.
// NOTE: This function is safe for concurrent access.
func (s *server) OutboundPeerConnected(connReq *connmgr.ConnReq, conn net.Conn) {
        // Exit early if we have already been instructed to shutdown, this
        // prevents any delayed callbacks from accidentally registering peers.
        if s.Stopped() {
                return
        }

        nodePub := conn.(*brontide.Conn).RemotePub()
        pubSer := nodePub.SerializeCompressed()
        pubStr := string(pubSer)

        var pubBytes [33]byte
        copy(pubBytes[:], pubSer)

        s.mu.Lock()
        defer s.mu.Unlock()

        // If the remote node's public key is banned, drop the connection.
        shouldDc, dcErr := s.authGossiper.ShouldDisconnect(nodePub)
        if dcErr != nil {
                srvrLog.Errorf("Unable to check if we should disconnect "+
                        "peer: %v", dcErr)
                conn.Close()

                return
        }

        if shouldDc {
                srvrLog.Debugf("Dropping connection for %v since they are "+
                        "banned.", pubSer)

                if connReq != nil {
                        s.connMgr.Remove(connReq.ID())
                }

                conn.Close()

                return
        }

        // If we already have an inbound connection to this peer, then ignore
        // this new connection.
        if p, ok := s.inboundPeers[pubStr]; ok {
                srvrLog.Debugf("Already have inbound connection for %v, "+
                        "ignoring outbound connection from local=%v, remote=%v",
                        p, conn.LocalAddr(), conn.RemoteAddr())

                if connReq != nil {
                        s.connMgr.Remove(connReq.ID())
                }
                conn.Close()
                return
        }
        if _, ok := s.persistentConnReqs[pubStr]; !ok && connReq != nil {
                srvrLog.Debugf("Ignoring canceled outbound connection")
                s.connMgr.Remove(connReq.ID())
                conn.Close()
                return
        }

        // If we already have a valid connection that is scheduled to take
        // precedence once the prior peer has finished disconnecting, we'll
        // ignore this connection.
        if _, ok := s.scheduledPeerConnection[pubStr]; ok {
                srvrLog.Debugf("Ignoring connection, peer already scheduled")

                if connReq != nil {
                        s.connMgr.Remove(connReq.ID())
                }

                conn.Close()
                return
        }

        srvrLog.Infof("Established connection to: %x@%v", pubStr,
                conn.RemoteAddr())

        if connReq != nil {
                // A successful connection was returned by the connmgr.
                // Immediately cancel all pending requests, excluding the
                // outbound connection we just established.
                ignore := connReq.ID()
                s.cancelConnReqs(pubStr, &ignore)
        } else {
                // This was a successful connection made by some other
                // subsystem. Remove all requests being managed by the connmgr.
                s.cancelConnReqs(pubStr, nil)
        }

        // If we already have a connection with this peer, decide whether or not
        // we need to drop the stale connection. We forgo adding a default case
        // as we expect these to be the only error values returned from
        // findPeerByPubStr.
        connectedPeer, err := s.findPeerByPubStr(pubStr)
        switch err {
        case ErrPeerNotConnected:
                // We were unable to locate an existing connection with the
                // target peer, proceed to connect.
                s.peerConnected(conn, connReq, false)

        case nil:
                // We already have a connection with the incoming peer. If the
                // connection we've already established should be kept and is
                // not of the same type of the new connection (outbound), then
                // we'll close out the new connection s.t there's only a single
                // connection between us.
                localPub := s.identityECDH.PubKey()
                if connectedPeer.Inbound() &&
                        shouldDropLocalConnection(localPub, nodePub) {

                        srvrLog.Warnf("Established outbound connection to "+
                                "peer %v, but already have inbound "+
                                "connection, dropping conn", connectedPeer)
                        if connReq != nil {
                                s.connMgr.Remove(connReq.ID())
                        }
                        conn.Close()
                        return
                }

                // Otherwise, _their_ connection should be dropped. So we'll
                // disconnect the peer and send the now obsolete peer to the
                // server for garbage collection.
                srvrLog.Debugf("Disconnecting stale connection to %v",
                        connectedPeer)

                // Remove the current peer from the server's internal state and
                // signal that the peer termination watcher does not need to
                // execute for this peer.
                s.removePeer(connectedPeer)
                s.ignorePeerTermination[connectedPeer] = struct{}{}
                s.scheduledPeerConnection[pubStr] = func() {
                        s.peerConnected(conn, connReq, false)
                }
        }
}

// UnassignedConnID is the default connection ID that a request can have before
// it actually is submitted to the connmgr.
// TODO(conner): move into connmgr package, or better, add connmgr method for
// generating atomic IDs
const UnassignedConnID uint64 = 0

// cancelConnReqs stops all persistent connection requests for a given pubkey.
// Any attempts initiated by the peerTerminationWatcher are canceled first.
// Afterwards, each connection request removed from the connmgr. The caller can
// optionally specify a connection ID to ignore, which prevents us from
// canceling a successful request. All persistent connreqs for the provided
// pubkey are discarded after the operationjw.
func (s *server) cancelConnReqs(pubStr string, skip *uint64) {
        // First, cancel any lingering persistent retry attempts, which will
        // prevent retries for any with backoffs that are still maturing.
        if cancelChan, ok := s.persistentRetryCancels[pubStr]; ok {
                close(cancelChan)
                delete(s.persistentRetryCancels, pubStr)
        }

        // Next, check to see if we have any outstanding persistent connection
        // requests to this peer. If so, then we'll remove all of these
        // connection requests, and also delete the entry from the map.
        connReqs, ok := s.persistentConnReqs[pubStr]
        if !ok {
                return
        }

        for _, connReq := range connReqs {
                srvrLog.Tracef("Canceling %s:", connReqs)

                // Atomically capture the current request identifier.
                connID := connReq.ID()

                // Skip any zero IDs, this indicates the request has not
                // yet been schedule.
                if connID == UnassignedConnID {
                        continue
                }

                // Skip a particular connection ID if instructed.
                if skip != nil && connID == *skip {
                        continue
                }

                s.connMgr.Remove(connID)
        }

        delete(s.persistentConnReqs, pubStr)
}

// handleCustomMessage dispatches an incoming custom peers message to
// subscribers.
func (s *server) handleCustomMessage(peer [33]byte, msg *lnwire.Custom) error {
        srvrLog.Debugf("Custom message received: peer=%x, type=%d",
                peer, msg.Type)

        return s.customMessageServer.SendUpdate(&CustomMessage{
                Peer: peer,
                Msg:  msg,
        })
}

// SubscribeCustomMessages subscribes to a stream of incoming custom peer
// messages.
func (s *server) SubscribeCustomMessages() (*subscribe.Client, error) {
        return s.customMessageServer.Subscribe()
}

// peerConnected is a function that handles initialization a newly connected
// peer by adding it to the server's global list of all active peers, and
// starting all the goroutines the peer needs to function properly. The inbound
// boolean should be true if the peer initiated the connection to us.
func (s *server) peerConnected(conn net.Conn, connReq *connmgr.ConnReq,
        inbound bool) {

        brontideConn := conn.(*brontide.Conn)
        addr := conn.RemoteAddr()
        pubKey := brontideConn.RemotePub()

        srvrLog.Infof("Finalizing connection to %x@%s, inbound=%v",
                pubKey.SerializeCompressed(), addr, inbound)

        peerAddr := &lnwire.NetAddress{
                IdentityKey: pubKey,
                Address:     addr,
                ChainNet:    s.cfg.ActiveNetParams.Net,
        }

        // With the brontide connection established, we'll now craft the feature
        // vectors to advertise to the remote node.
        initFeatures := s.featureMgr.Get(feature.SetInit)
        legacyFeatures := s.featureMgr.Get(feature.SetLegacyGlobal)

        // Lookup past error caches for the peer in the server. If no buffer is
        // found, create a fresh buffer.
        pkStr := string(peerAddr.IdentityKey.SerializeCompressed())
        errBuffer, ok := s.peerErrors[pkStr]
        if !ok {
                var err error
                errBuffer, err = queue.NewCircularBuffer(peer.ErrorBufferSize)
                if err != nil {
                        srvrLog.Errorf("unable to create peer %v", err)
                        return
                }
        }

        // If we directly set the peer.Config TowerClient member to the
        // s.towerClientMgr then in the case that the s.towerClientMgr is nil,
        // the peer.Config's TowerClient member will not evaluate to nil even
        // though the underlying value is nil. To avoid this gotcha which can
        // cause a panic, we need to explicitly pass nil to the peer.Config's
        // TowerClient if needed.
        var towerClient wtclient.ClientManager
        if s.towerClientMgr != nil {
                towerClient = s.towerClientMgr
        }

        thresholdSats := btcutil.Amount(s.cfg.MaxFeeExposure)
        thresholdMSats := lnwire.NewMSatFromSatoshis(thresholdSats)

        // Now that we've established a connection, create a peer, and it to the
        // set of currently active peers. Configure the peer with the incoming
        // and outgoing broadcast deltas to prevent htlcs from being accepted or
        // offered that would trigger channel closure. In case of outgoing
        // htlcs, an extra block is added to prevent the channel from being
        // closed when the htlc is outstanding and a new block comes in.
        pCfg := peer.Config{
                Conn:                    brontideConn,
                ConnReq:                 connReq,
                Addr:                    peerAddr,
                Inbound:                 inbound,
                Features:                initFeatures,
                LegacyFeatures:          legacyFeatures,
                OutgoingCltvRejectDelta: lncfg.DefaultOutgoingCltvRejectDelta,
                ChanActiveTimeout:       s.cfg.ChanEnableTimeout,
                ErrorBuffer:             errBuffer,
                WritePool:               s.writePool,
                ReadPool:                s.readPool,
                Switch:                  s.htlcSwitch,
                InterceptSwitch:         s.interceptableSwitch,
                ChannelDB:               s.chanStateDB,
                ChannelGraph:            s.graphDB,
                ChainArb:                s.chainArb,
                AuthGossiper:            s.authGossiper,
                ChanStatusMgr:           s.chanStatusMgr,
                ChainIO:                 s.cc.ChainIO,
                FeeEstimator:            s.cc.FeeEstimator,
                Signer:                  s.cc.Wallet.Cfg.Signer,
                SigPool:                 s.sigPool,
                Wallet:                  s.cc.Wallet,
                ChainNotifier:           s.cc.ChainNotifier,
                BestBlockView:           s.cc.BestBlockTracker,
                RoutingPolicy:           s.cc.RoutingPolicy,
                Sphinx:                  s.sphinx,
                WitnessBeacon:           s.witnessBeacon,
                Invoices:                s.invoices,
                ChannelNotifier:         s.channelNotifier,
                HtlcNotifier:            s.htlcNotifier,
                TowerClient:             towerClient,
                DisconnectPeer:          s.DisconnectPeer,
                GenNodeAnnouncement: func(...netann.NodeAnnModifier) (
                        lnwire.NodeAnnouncement, error) {

                        return s.genNodeAnnouncement(nil)
                },

                PongBuf: s.pongBuf,

                PrunePersistentPeerConnection: s.prunePersistentPeerConnection,

                FetchLastChanUpdate: s.fetchLastChanUpdate(),

                FundingManager: s.fundingMgr,

                Hodl:                    s.cfg.Hodl,
                UnsafeReplay:            s.cfg.UnsafeReplay,
                MaxOutgoingCltvExpiry:   s.cfg.MaxOutgoingCltvExpiry,
                MaxChannelFeeAllocation: s.cfg.MaxChannelFeeAllocation,
                CoopCloseTargetConfs:    s.cfg.CoopCloseTargetConfs,
                MaxAnchorsCommitFeeRate: chainfee.SatPerKVByte(
                        s.cfg.MaxCommitFeeRateAnchors * 1000).FeePerKWeight(),
                ChannelCommitInterval:  s.cfg.ChannelCommitInterval,
                PendingCommitInterval:  s.cfg.PendingCommitInterval,
                ChannelCommitBatchSize: s.cfg.ChannelCommitBatchSize,
                HandleCustomMessage:    s.handleCustomMessage,
                GetAliases:             s.aliasMgr.GetAliases,
                RequestAlias:           s.aliasMgr.RequestAlias,
                AddLocalAlias:          s.aliasMgr.AddLocalAlias,
                DisallowRouteBlinding:  s.cfg.ProtocolOptions.NoRouteBlinding(),
                DisallowQuiescence:     s.cfg.ProtocolOptions.NoQuiescence(),
                MaxFeeExposure:         thresholdMSats,
                Quit:                   s.quit,
                AuxLeafStore:           s.implCfg.AuxLeafStore,
                AuxSigner:              s.implCfg.AuxSigner,
                MsgRouter:              s.implCfg.MsgRouter,
                AuxChanCloser:          s.implCfg.AuxChanCloser,
                AuxResolver:            s.implCfg.AuxContractResolver,
                AuxTrafficShaper:       s.implCfg.TrafficShaper,
                ShouldFwdExpEndorsement: func() bool {
                        if s.cfg.ProtocolOptions.NoExperimentalEndorsement() {
                                return false
                        }

                        return clock.NewDefaultClock().Now().Before(
                                EndorsementExperimentEnd,
                        )
                },
        }

        copy(pCfg.PubKeyBytes[:], peerAddr.IdentityKey.SerializeCompressed())
        copy(pCfg.ServerPubKey[:], s.identityECDH.PubKey().SerializeCompressed())

        p := peer.NewBrontide(pCfg)

        // TODO(roasbeef): update IP address for link-node
        //  * also mark last-seen, do it one single transaction?

        s.addPeer(p)

        // Once we have successfully added the peer to the server, we can
        // delete the previous error buffer from the server's map of error
        // buffers.
        delete(s.peerErrors, pkStr)

        // Dispatch a goroutine to asynchronously start the peer. This process
        // includes sending and receiving Init messages, which would be a DOS
        // vector if we held the server's mutex throughout the procedure.
        s.wg.Add(1)
        go s.peerInitializer(p)
}

// addPeer adds the passed peer to the server's global state of all active
// peers.
func (s *server) addPeer(p *peer.Brontide) {
        if p == nil {
                return
        }

        pubBytes := p.IdentityKey().SerializeCompressed()

        // Ignore new peers if we're shutting down.
        if s.Stopped() {
                srvrLog.Infof("Server stopped, skipped adding peer=%x",
                        pubBytes)
                p.Disconnect(ErrServerShuttingDown)

                return
        }

        // Track the new peer in our indexes so we can quickly look it up either
        // according to its public key, or its peer ID.
        // TODO(roasbeef): pipe all requests through to the
        // queryHandler/peerManager

        // NOTE: This pubStr is a raw bytes to string conversion and will NOT
        // be human-readable.
        pubStr := string(pubBytes)

        s.peersByPub[pubStr] = p

        if p.Inbound() {
                s.inboundPeers[pubStr] = p
        } else {
                s.outboundPeers[pubStr] = p
        }

        // Inform the peer notifier of a peer online event so that it can be reported
        // to clients listening for peer events.
        var pubKey [33]byte
        copy(pubKey[:], pubBytes)

        s.peerNotifier.NotifyPeerOnline(pubKey)
}

// peerInitializer asynchronously starts a newly connected peer after it has
// been added to the server's peer map. This method sets up a
// peerTerminationWatcher for the given peer, and ensures that it executes even
// if the peer failed to start. In the event of a successful connection, this
// method reads the negotiated, local feature-bits and spawns the appropriate
// graph synchronization method. Any registered clients of NotifyWhenOnline will
// be signaled of the new peer once the method returns.
//
// NOTE: This MUST be launched as a goroutine.
func (s *server) peerInitializer(p *peer.Brontide) {
        defer s.wg.Done()

        pubBytes := p.IdentityKey().SerializeCompressed()

        // Avoid initializing peers while the server is exiting.
        if s.Stopped() {
                srvrLog.Infof("Server stopped, skipped initializing peer=%x",
                        pubBytes)
                return
        }

        // Create a channel that will be used to signal a successful start of
        // the link. This prevents the peer termination watcher from beginning
        // its duty too early.
        ready := make(chan struct{})

        // Before starting the peer, launch a goroutine to watch for the
        // unexpected termination of this peer, which will ensure all resources
        // are properly cleaned up, and re-establish persistent connections when
        // necessary. The peer termination watcher will be short circuited if
        // the peer is ever added to the ignorePeerTermination map, indicating
        // that the server has already handled the removal of this peer.
        s.wg.Add(1)
        go s.peerTerminationWatcher(p, ready)

        // Start the peer! If an error occurs, we Disconnect the peer, which
        // will unblock the peerTerminationWatcher.
        if err := p.Start(); err != nil {
                srvrLog.Warnf("Starting peer=%x got error: %v", pubBytes, err)

                p.Disconnect(fmt.Errorf("unable to start peer: %w", err))
                return
        }

        // Otherwise, signal to the peerTerminationWatcher that the peer startup
        // was successful, and to begin watching the peer's wait group.
        close(ready)

        s.mu.Lock()
        defer s.mu.Unlock()

        // Check if there are listeners waiting for this peer to come online.
        srvrLog.Debugf("Notifying that peer %v is online", p)

        // TODO(guggero): Do a proper conversion to a string everywhere, or use
        // route.Vertex as the key type of peerConnectedListeners.
        pubStr := string(pubBytes)
        for _, peerChan := range s.peerConnectedListeners[pubStr] {
                select {
                case peerChan <- p:
                case <-s.quit:
                        return
                }
        }
        delete(s.peerConnectedListeners, pubStr)
}

// peerTerminationWatcher waits until a peer has been disconnected unexpectedly,
// and then cleans up all resources allocated to the peer, notifies relevant
// sub-systems of its demise, and finally handles re-connecting to the peer if
// it's persistent. If the server intentionally disconnects a peer, it should
// have a corresponding entry in the ignorePeerTermination map which will cause
// the cleanup routine to exit early. The passed `ready` chan is used to
// synchronize when WaitForDisconnect should begin watching on the peer's
// waitgroup. The ready chan should only be signaled if the peer starts
// successfully, otherwise the peer should be disconnected instead.
//
// NOTE: This MUST be launched as a goroutine.
func (s *server) peerTerminationWatcher(p *peer.Brontide, ready chan struct{}) {
        defer s.wg.Done()

        p.WaitForDisconnect(ready)

        srvrLog.Debugf("Peer %v has been disconnected", p)

        // If the server is exiting then we can bail out early ourselves as all
        // the other sub-systems will already be shutting down.
        if s.Stopped() {
                srvrLog.Debugf("Server quitting, exit early for peer %v", p)
                return
        }

        // Next, we'll cancel all pending funding reservations with this node.
        // If we tried to initiate any funding flows that haven't yet finished,
        // then we need to unlock those committed outputs so they're still
        // available for use.
        s.fundingMgr.CancelPeerReservations(p.PubKey())

        pubKey := p.IdentityKey()

        // We'll also inform the gossiper that this peer is no longer active,
        // so we don't need to maintain sync state for it any longer.
        s.authGossiper.PruneSyncState(p.PubKey())

        // Tell the switch to remove all links associated with this peer.
        // Passing nil as the target link indicates that all links associated
        // with this interface should be closed.
        //
        // TODO(roasbeef): instead add a PurgeInterfaceLinks function?
        links, err := s.htlcSwitch.GetLinksByInterface(p.PubKey())
        if err != nil && err != htlcswitch.ErrNoLinksFound {
                srvrLog.Errorf("Unable to get channel links for %v: %v", p, err)
        }

        for _, link := range links {
                s.htlcSwitch.RemoveLink(link.ChanID())
        }

        s.mu.Lock()
        defer s.mu.Unlock()

        // If there were any notification requests for when this peer
        // disconnected, we can trigger them now.
        srvrLog.Debugf("Notifying that peer %v is offline", p)
        pubStr := string(pubKey.SerializeCompressed())
        for _, offlineChan := range s.peerDisconnectedListeners[pubStr] {
                close(offlineChan)
        }
        delete(s.peerDisconnectedListeners, pubStr)

        // If the server has already removed this peer, we can short circuit the
        // peer termination watcher and skip cleanup.
        if _, ok := s.ignorePeerTermination[p]; ok {
                delete(s.ignorePeerTermination, p)

                pubKey := p.PubKey()
                pubStr := string(pubKey[:])

                // If a connection callback is present, we'll go ahead and
                // execute it now that previous peer has fully disconnected. If
                // the callback is not present, this likely implies the peer was
                // purposefully disconnected via RPC, and that no reconnect
                // should be attempted.
                connCallback, ok := s.scheduledPeerConnection[pubStr]
                if ok {
                        delete(s.scheduledPeerConnection, pubStr)
                        connCallback()
                }
                return
        }

        // First, cleanup any remaining state the server has regarding the peer
        // in question.
        s.removePeer(p)

        // Next, check to see if this is a persistent peer or not.
        if _, ok := s.persistentPeers[pubStr]; !ok {
                return
        }

        // Get the last address that we used to connect to the peer.
        addrs := []net.Addr{
                p.NetAddress().Address,
        }

        // We'll ensure that we locate all the peers advertised addresses for
        // reconnection purposes.
        advertisedAddrs, err := s.fetchNodeAdvertisedAddrs(pubKey)
        switch {
        // We found advertised addresses, so use them.
        case err == nil:
                addrs = advertisedAddrs

        // The peer doesn't have an advertised address.
        case err == errNoAdvertisedAddr:
                // If it is an outbound peer then we fall back to the existing
                // peer address.
                if !p.Inbound() {
                        break
                }

                // Fall back to the existing peer address if
                // we're not accepting connections over Tor.
                if s.torController == nil {
                        break
                }

                // If we are, the peer's address won't be known
                // to us (we'll see a private address, which is
                // the address used by our onion service to dial
                // to lnd), so we don't have enough information
                // to attempt a reconnect.
                srvrLog.Debugf("Ignoring reconnection attempt "+
                        "to inbound peer %v without "+
                        "advertised address", p)
                return

        // We came across an error retrieving an advertised
        // address, log it, and fall back to the existing peer
        // address.
        default:
                srvrLog.Errorf("Unable to retrieve advertised "+
                        "address for node %x: %v", p.PubKey(),
                        err)
        }

        // Make an easy lookup map so that we can check if an address
        // is already in the address list that we have stored for this peer.
        existingAddrs := make(map[string]bool)
        for _, addr := range s.persistentPeerAddrs[pubStr] {
                existingAddrs[addr.String()] = true
        }

        // Add any missing addresses for this peer to persistentPeerAddr.
        for _, addr := range addrs {
                if existingAddrs[addr.String()] {
                        continue
                }

                s.persistentPeerAddrs[pubStr] = append(
                        s.persistentPeerAddrs[pubStr],
                        &lnwire.NetAddress{
                                IdentityKey: p.IdentityKey(),
                                Address:     addr,
                                ChainNet:    p.NetAddress().ChainNet,
                        },
                )
        }

        // Record the computed backoff in the backoff map.
        backoff := s.nextPeerBackoff(pubStr, p.StartTime())
        s.persistentPeersBackoff[pubStr] = backoff

        // Initialize a retry canceller for this peer if one does not
        // exist.
        cancelChan, ok := s.persistentRetryCancels[pubStr]
        if !ok {
                cancelChan = make(chan struct{})
                s.persistentRetryCancels[pubStr] = cancelChan
        }

        // We choose not to wait group this go routine since the Connect
        // call can stall for arbitrarily long if we shutdown while an
        // outbound connection attempt is being made.
        go func() {
                srvrLog.Debugf("Scheduling connection re-establishment to "+
                        "persistent peer %x in %s",
                        p.IdentityKey().SerializeCompressed(), backoff)

                select {
                case <-time.After(backoff):
                case <-cancelChan:
                        return
                case <-s.quit:
                        return
                }

                srvrLog.Debugf("Attempting to re-establish persistent "+
                        "connection to peer %x",
                        p.IdentityKey().SerializeCompressed())

                s.connectToPersistentPeer(pubStr)
        }()
}

// connectToPersistentPeer uses all the stored addresses for a peer to attempt
// to connect to the peer. It creates connection requests if there are
// currently none for a given address and it removes old connection requests
// if the associated address is no longer in the latest address list for the
// peer.
func (s *server) connectToPersistentPeer(pubKeyStr string) {
        s.mu.Lock()
        defer s.mu.Unlock()

        // Create an easy lookup map of the addresses we have stored for the
        // peer. We will remove entries from this map if we have existing
        // connection requests for the associated address and then any leftover
        // entries will indicate which addresses we should create new
        // connection requests for.
        addrMap := make(map[string]*lnwire.NetAddress)
        for _, addr := range s.persistentPeerAddrs[pubKeyStr] {
                addrMap[addr.String()] = addr
        }

        // Go through each of the existing connection requests and
        // check if they correspond to the latest set of addresses. If
        // there is a connection requests that does not use one of the latest
        // advertised addresses then remove that connection request.
        var updatedConnReqs []*connmgr.ConnReq
        for _, connReq := range s.persistentConnReqs[pubKeyStr] {
                lnAddr := connReq.Addr.(*lnwire.NetAddress).Address.String()

                switch _, ok := addrMap[lnAddr]; ok {
                // If the existing connection request is using one of the
                // latest advertised addresses for the peer then we add it to
                // updatedConnReqs and remove the associated address from
                // addrMap so that we don't recreate this connReq later on.
                case true:
                        updatedConnReqs = append(
                                updatedConnReqs, connReq,
                        )
                        delete(addrMap, lnAddr)

                // If the existing connection request is using an address that
                // is not one of the latest advertised addresses for the peer
                // then we remove the connecting request from the connection
                // manager.
                case false:
                        srvrLog.Info(
                                "Removing conn req:", connReq.Addr.String(),
                        )
                        s.connMgr.Remove(connReq.ID())
                }
        }

        s.persistentConnReqs[pubKeyStr] = updatedConnReqs

        cancelChan, ok := s.persistentRetryCancels[pubKeyStr]
        if !ok {
                cancelChan = make(chan struct{})
                s.persistentRetryCancels[pubKeyStr] = cancelChan
        }

        // Any addresses left in addrMap are new ones that we have not made
        // connection requests for. So create new connection requests for those.
        // If there is more than one address in the address map, stagger the
        // creation of the connection requests for those.
        go func() {
                ticker := time.NewTicker(multiAddrConnectionStagger)
                defer ticker.Stop()

                for _, addr := range addrMap {
                        // Send the persistent connection request to the
                        // connection manager, saving the request itself so we
                        // can cancel/restart the process as needed.
                        connReq := &connmgr.ConnReq{
                                Addr:      addr,
                                Permanent: true,
                        }

                        s.mu.Lock()
                        s.persistentConnReqs[pubKeyStr] = append(
                                s.persistentConnReqs[pubKeyStr], connReq,
                        )
                        s.mu.Unlock()

                        srvrLog.Debugf("Attempting persistent connection to "+
                                "channel peer %v", addr)

                        go s.connMgr.Connect(connReq)

                        select {
                        case <-s.quit:
                                return
                        case <-cancelChan:
                                return
                        case <-ticker.C:
                        }
                }
        }()
}

// removePeer removes the passed peer from the server's state of all active
// peers.
func (s *server) removePeer(p *peer.Brontide) {
        if p == nil {
                return
        }

        srvrLog.Debugf("removing peer %v", p)

        // As the peer is now finished, ensure that the TCP connection is
        // closed and all of its related goroutines have exited.
        p.Disconnect(fmt.Errorf("server: disconnecting peer %v", p))

        // If this peer had an active persistent connection request, remove it.
        if p.ConnReq() != nil {
                s.connMgr.Remove(p.ConnReq().ID())
        }

        // Ignore deleting peers if we're shutting down.
        if s.Stopped() {
                return
        }

        pKey := p.PubKey()
        pubSer := pKey[:]
        pubStr := string(pubSer)

        delete(s.peersByPub, pubStr)

        if p.Inbound() {
                delete(s.inboundPeers, pubStr)
        } else {
                delete(s.outboundPeers, pubStr)
        }

        // Copy the peer's error buffer across to the server if it has any items
        // in it so that we can restore peer errors across connections.
        if p.ErrorBuffer().Total() > 0 {
                s.peerErrors[pubStr] = p.ErrorBuffer()
        }

        // Inform the peer notifier of a peer offline event so that it can be
        // reported to clients listening for peer events.
        var pubKey [33]byte
        copy(pubKey[:], pubSer)

        s.peerNotifier.NotifyPeerOffline(pubKey)
}

// ConnectToPeer requests that the server connect to a Lightning Network peer
// at the specified address. This function will *block* until either a
// connection is established, or the initial handshake process fails.
//
// NOTE: This function is safe for concurrent access.
func (s *server) ConnectToPeer(addr *lnwire.NetAddress,
        perm bool, timeout time.Duration) error {

        targetPub := string(addr.IdentityKey.SerializeCompressed())

        // Acquire mutex, but use explicit unlocking instead of defer for
        // better granularity.  In certain conditions, this method requires
        // making an outbound connection to a remote peer, which requires the
        // lock to be released, and subsequently reacquired.
        s.mu.Lock()

        // Ensure we're not already connected to this peer.
        peer, err := s.findPeerByPubStr(targetPub)
        if err == nil {
                s.mu.Unlock()
                return &errPeerAlreadyConnected{peer: peer}
        }

        // Peer was not found, continue to pursue connection with peer.

        // If there's already a pending connection request for this pubkey,
        // then we ignore this request to ensure we don't create a redundant
        // connection.
        if reqs, ok := s.persistentConnReqs[targetPub]; ok {
                srvrLog.Warnf("Already have %d persistent connection "+
                        "requests for %v, connecting anyway.", len(reqs), addr)
        }

        // If there's not already a pending or active connection to this node,
        // then instruct the connection manager to attempt to establish a
        // persistent connection to the peer.
        srvrLog.Debugf("Connecting to %v", addr)
        if perm {
                connReq := &connmgr.ConnReq{
                        Addr:      addr,
                        Permanent: true,
                }

                // Since the user requested a permanent connection, we'll set
                // the entry to true which will tell the server to continue
                // reconnecting even if the number of channels with this peer is
                // zero.
                s.persistentPeers[targetPub] = true
                if _, ok := s.persistentPeersBackoff[targetPub]; !ok {
                        s.persistentPeersBackoff[targetPub] = s.cfg.MinBackoff
                }
                s.persistentConnReqs[targetPub] = append(
                        s.persistentConnReqs[targetPub], connReq,
                )
                s.mu.Unlock()

                go s.connMgr.Connect(connReq)

                return nil
        }
        s.mu.Unlock()

        // If we're not making a persistent connection, then we'll attempt to
        // connect to the target peer. If the we can't make the connection, or
        // the crypto negotiation breaks down, then return an error to the
        // caller.
        errChan := make(chan error, 1)
        s.connectToPeer(addr, errChan, timeout)

        select {
        case err := <-errChan:
                return err
        case <-s.quit:
                return ErrServerShuttingDown
        }
}

// connectToPeer establishes a connection to a remote peer. errChan is used to
// notify the caller if the connection attempt has failed. Otherwise, it will be
// closed.
func (s *server) connectToPeer(addr *lnwire.NetAddress,
        errChan chan<- error, timeout time.Duration) {

        conn, err := brontide.Dial(
                s.identityECDH, addr, timeout, s.cfg.net.Dial,
        )
        if err != nil {
                srvrLog.Errorf("Unable to connect to %v: %v", addr, err)
                select {
                case errChan <- err:
                case <-s.quit:
                }
                return
        }

        close(errChan)

        srvrLog.Tracef("Brontide dialer made local=%v, remote=%v",
                conn.LocalAddr(), conn.RemoteAddr())

        s.OutboundPeerConnected(nil, conn)
}

// DisconnectPeer sends the request to server to close the connection with peer
// identified by public key.
//
// NOTE: This function is safe for concurrent access.
func (s *server) DisconnectPeer(pubKey *btcec.PublicKey) error {
        pubBytes := pubKey.SerializeCompressed()
        pubStr := string(pubBytes)

        s.mu.Lock()
        defer s.mu.Unlock()

        // Check that were actually connected to this peer. If not, then we'll
        // exit in an error as we can't disconnect from a peer that we're not
        // currently connected to.
        peer, err := s.findPeerByPubStr(pubStr)
        if err == ErrPeerNotConnected {
                return fmt.Errorf("peer %x is not connected", pubBytes)
        }

        srvrLog.Infof("Disconnecting from %v", peer)

        s.cancelConnReqs(pubStr, nil)

        // If this peer was formerly a persistent connection, then we'll remove
        // them from this map so we don't attempt to re-connect after we
        // disconnect.
        delete(s.persistentPeers, pubStr)
        delete(s.persistentPeersBackoff, pubStr)

        // Remove the peer by calling Disconnect. Previously this was done with
        // removePeer, which bypassed the peerTerminationWatcher.
        peer.Disconnect(fmt.Errorf("server: DisconnectPeer called"))

        return nil
}

// OpenChannel sends a request to the server to open a channel to the specified
// peer identified by nodeKey with the passed channel funding parameters.
//
// NOTE: This function is safe for concurrent access.
func (s *server) OpenChannel(
        req *funding.InitFundingMsg) (chan *lnrpc.OpenStatusUpdate, chan error) {

        // The updateChan will have a buffer of 2, since we expect a ChanPending
        // + a ChanOpen update, and we want to make sure the funding process is
        // not blocked if the caller is not reading the updates.
        req.Updates = make(chan *lnrpc.OpenStatusUpdate, 2)
        req.Err = make(chan error, 1)

        // First attempt to locate the target peer to open a channel with, if
        // we're unable to locate the peer then this request will fail.
        pubKeyBytes := req.TargetPubkey.SerializeCompressed()
        s.mu.RLock()
        peer, ok := s.peersByPub[string(pubKeyBytes)]
        if !ok {
                s.mu.RUnlock()

                req.Err <- fmt.Errorf("peer %x is not online", pubKeyBytes)
                return req.Updates, req.Err
        }
        req.Peer = peer
        s.mu.RUnlock()

        // We'll wait until the peer is active before beginning the channel
        // opening process.
        select {
        case <-peer.ActiveSignal():
        case <-peer.QuitSignal():
                req.Err <- fmt.Errorf("peer %x disconnected", pubKeyBytes)
                return req.Updates, req.Err
        case <-s.quit:
                req.Err <- ErrServerShuttingDown
                return req.Updates, req.Err
        }

        // If the fee rate wasn't specified at this point we fail the funding
        // because of the missing fee rate information. The caller of the
        // `OpenChannel` method needs to make sure that default values for the
        // fee rate are set beforehand.
        if req.FundingFeePerKw == 0 {
                req.Err <- fmt.Errorf("no FundingFeePerKw specified for " +
                        "the channel opening transaction")

                return req.Updates, req.Err
        }

        // Spawn a goroutine to send the funding workflow request to the funding
        // manager. This allows the server to continue handling queries instead
        // of blocking on this request which is exported as a synchronous
        // request to the outside world.
        go s.fundingMgr.InitFundingWorkflow(req)

        return req.Updates, req.Err
}

// Peers returns a slice of all active peers.
//
// NOTE: This function is safe for concurrent access.
func (s *server) Peers() []*peer.Brontide {
        s.mu.RLock()
        defer s.mu.RUnlock()

        peers := make([]*peer.Brontide, 0, len(s.peersByPub))
        for _, peer := range s.peersByPub {
                peers = append(peers, peer)
        }

        return peers
}

// computeNextBackoff uses a truncated exponential backoff to compute the next
// backoff using the value of the exiting backoff. The returned duration is
// randomized in either direction by 1/20 to prevent tight loops from
// stabilizing.
func computeNextBackoff(currBackoff, maxBackoff time.Duration) time.Duration {
        // Double the current backoff, truncating if it exceeds our maximum.
        nextBackoff := 2 * currBackoff
        if nextBackoff > maxBackoff {
                nextBackoff = maxBackoff
        }

        // Using 1/10 of our duration as a margin, compute a random offset to
        // avoid the nodes entering connection cycles.
        margin := nextBackoff / 10

        var wiggle big.Int
        wiggle.SetUint64(uint64(margin))
        if _, err := rand.Int(rand.Reader, &wiggle); err != nil {
                // Randomizing is not mission critical, so we'll just return the
                // current backoff.
                return nextBackoff
        }

        // Otherwise add in our wiggle, but subtract out half of the margin so
        // that the backoff can tweaked by 1/20 in either direction.
        return nextBackoff + (time.Duration(wiggle.Uint64()) - margin/2)
}

// errNoAdvertisedAddr is an error returned when we attempt to retrieve the
// advertised address of a node, but they don't have one.
var errNoAdvertisedAddr = errors.New("no advertised address found")

// fetchNodeAdvertisedAddrs attempts to fetch the advertised addresses of a node.
func (s *server) fetchNodeAdvertisedAddrs(pub *btcec.PublicKey) ([]net.Addr, error) {
        vertex, err := route.NewVertexFromBytes(pub.SerializeCompressed())
        if err != nil {
                return nil, err
        }

        node, err := s.graphDB.FetchLightningNode(vertex)
        if err != nil {
                return nil, err
        }

        if len(node.Addresses) == 0 {
                return nil, errNoAdvertisedAddr
        }

        return node.Addresses, nil
}

// fetchLastChanUpdate returns a function which is able to retrieve our latest
// channel update for a target channel.
func (s *server) fetchLastChanUpdate() func(lnwire.ShortChannelID) (
        *lnwire.ChannelUpdate1, error) {

        ourPubKey := s.identityECDH.PubKey().SerializeCompressed()
        return func(cid lnwire.ShortChannelID) (*lnwire.ChannelUpdate1, error) {
                info, edge1, edge2, err := s.graphBuilder.GetChannelByID(cid)
                if err != nil {
                        return nil, err
                }

                return netann.ExtractChannelUpdate(
                        ourPubKey[:], info, edge1, edge2,
                )
        }
}

// applyChannelUpdate applies the channel update to the different sub-systems of
// the server. The useAlias boolean denotes whether or not to send an alias in
// place of the real SCID.
func (s *server) applyChannelUpdate(update *lnwire.ChannelUpdate1,
        op *wire.OutPoint, useAlias bool) error {

        var (
                peerAlias    *lnwire.ShortChannelID
                defaultAlias lnwire.ShortChannelID
        )

        chanID := lnwire.NewChanIDFromOutPoint(*op)

        // Fetch the peer's alias from the lnwire.ChannelID so it can be used
        // in the ChannelUpdate if it hasn't been announced yet.
        if useAlias {
                foundAlias, _ := s.aliasMgr.GetPeerAlias(chanID)
                if foundAlias != defaultAlias {
                        peerAlias = &foundAlias
                }
        }

        errChan := s.authGossiper.ProcessLocalAnnouncement(
                update, discovery.RemoteAlias(peerAlias),
        )
        select {
        case err := <-errChan:
                return err
        case <-s.quit:
                return ErrServerShuttingDown
        }
}

// SendCustomMessage sends a custom message to the peer with the specified
// pubkey.
func (s *server) SendCustomMessage(peerPub [33]byte, msgType lnwire.MessageType,
        data []byte) error {

        peer, err := s.FindPeerByPubStr(string(peerPub[:]))
        if err != nil {
                return err
        }

        // We'll wait until the peer is active.
        select {
        case <-peer.ActiveSignal():
        case <-peer.QuitSignal():
                return fmt.Errorf("peer %x disconnected", peerPub)
        case <-s.quit:
                return ErrServerShuttingDown
        }

        msg, err := lnwire.NewCustom(msgType, data)
        if err != nil {
                return err
        }

        // Send the message as low-priority. For now we assume that all
        // application-defined message are low priority.
        return peer.SendMessageLazy(true, msg)
}

// newSweepPkScriptGen creates closure that generates a new public key script
// which should be used to sweep any funds into the on-chain wallet.
// Specifically, the script generated is a version 0, pay-to-witness-pubkey-hash
// (p2wkh) output.
func newSweepPkScriptGen(
        wallet lnwallet.WalletController,
        netParams *chaincfg.Params) func() fn.Result[lnwallet.AddrWithKey] {

        return func() fn.Result[lnwallet.AddrWithKey] {
                sweepAddr, err := wallet.NewAddress(
                        lnwallet.TaprootPubkey, false,
                        lnwallet.DefaultAccountName,
                )
                if err != nil {
                        return fn.Err[lnwallet.AddrWithKey](err)
                }

                addr, err := txscript.PayToAddrScript(sweepAddr)
                if err != nil {
                        return fn.Err[lnwallet.AddrWithKey](err)
                }

                internalKeyDesc, err := lnwallet.InternalKeyForAddr(
                        wallet, netParams, addr,
                )
                if err != nil {
                        return fn.Err[lnwallet.AddrWithKey](err)
                }

                return fn.Ok(lnwallet.AddrWithKey{
                        DeliveryAddress: addr,
                        InternalKey:     internalKeyDesc,
                })
        }
}

// shouldPeerBootstrap returns true if we should attempt to perform peer
// bootstrapping to actively seek our peers using the set of active network
// bootstrappers.
func shouldPeerBootstrap(cfg *Config) bool {
        isSimnet := cfg.Bitcoin.SimNet
        isSignet := cfg.Bitcoin.SigNet
        isRegtest := cfg.Bitcoin.RegTest
        isDevNetwork := isSimnet || isSignet || isRegtest

        // TODO(yy): remove the check on simnet/regtest such that the itest is
        // covering the bootstrapping process.
        return !cfg.NoNetBootstrap && !isDevNetwork
}

// fetchClosedChannelSCIDs returns a set of SCIDs that have their force closing
// finished.
func (s *server) fetchClosedChannelSCIDs() map[lnwire.ShortChannelID]struct{} {
        // Get a list of closed channels.
        channels, err := s.chanStateDB.FetchClosedChannels(false)
        if err != nil {
                srvrLog.Errorf("Failed to fetch closed channels: %v", err)
                return nil
        }

        // Save the SCIDs in a map.
        closedSCIDs := make(map[lnwire.ShortChannelID]struct{}, len(channels))
        for _, c := range channels {
                // If the channel is not pending, its FC has been finalized.
                if !c.IsPending {
                        closedSCIDs[c.ShortChanID] = struct{}{}
                }
        }

        // Double check whether the reported closed channel has indeed finished
        // closing.
        //
        // NOTE: There are misalignments regarding when a channel's FC is
        // marked as finalized. We double check the pending channels to make
        // sure the returned SCIDs are indeed terminated.
        //
        // TODO(yy): fix the misalignments in `FetchClosedChannels`.
        pendings, err := s.chanStateDB.FetchPendingChannels()
        if err != nil {
                srvrLog.Errorf("Failed to fetch pending channels: %v", err)
                return nil
        }

        for _, c := range pendings {
                if _, ok := closedSCIDs[c.ShortChannelID]; !ok {
                        continue
                }

                // If the channel is still reported as pending, remove it from
                // the map.
                delete(closedSCIDs, c.ShortChannelID)

                srvrLog.Warnf("Channel=%v is prematurely marked as finalized",
                        c.ShortChannelID)
        }

        return closedSCIDs
}

// getStartingBeat returns the current beat. This is used during the startup to
// initialize blockbeat consumers.
func (s *server) getStartingBeat() (*chainio.Beat, error) {
        // beat is the current blockbeat.
        var beat *chainio.Beat

        // We should get a notification with the current best block immediately
        // by passing a nil block.
        blockEpochs, err := s.cc.ChainNotifier.RegisterBlockEpochNtfn(nil)
        if err != nil {
                return beat, fmt.Errorf("register block epoch ntfn: %w", err)
        }
        defer blockEpochs.Cancel()

        // We registered for the block epochs with a nil request. The notifier
        // should send us the current best block immediately. So we need to
        // wait for it here because we need to know the current best height.
        select {
        case bestBlock := <-blockEpochs.Epochs:
                srvrLog.Infof("Received initial block %v at height %d",
                        bestBlock.Hash, bestBlock.Height)

                // Update the current blockbeat.
                beat = chainio.NewBeat(*bestBlock)

        case <-s.quit:
                srvrLog.Debug("LND shutting down")
        }

        return beat, nil
}

lightningnetwork / lnd / 12343072627

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