13566028875

Committed 27 Feb 2025 12:09PM UTC coverage: 49.396% (-9.4%) from 58.748%

Build # 13566028875

Build Type

Pull #9555

github

Committed by

ellemouton

Commit Message

graph/db: populate the graph cache in Start instead of during construction

In this commit, we move the graph cache population logic out of the
ChannelGraph constructor and into its Start method instead.

Pull Request Pull Request #9555: graph: extract cache from CRUD [6]

Run Details

34 of 54 new or added lines in 4 files covered. (62.96%)

27464 existing lines in 436 files now uncovered.

101095 of 204664 relevant lines covered (49.4%)

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Source File
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68.98

/discovery/gossiper.go

package discovery

import (
        "bytes"
        "errors"
        "fmt"
        "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/chainhash"
        "github.com/btcsuite/btcd/wire"
        "github.com/davecgh/go-spew/spew"
        "github.com/lightninglabs/neutrino/cache"
        "github.com/lightninglabs/neutrino/cache/lru"
        "github.com/lightningnetwork/lnd/batch"
        "github.com/lightningnetwork/lnd/chainntnfs"
        "github.com/lightningnetwork/lnd/channeldb"
        "github.com/lightningnetwork/lnd/fn/v2"
        "github.com/lightningnetwork/lnd/graph"
        graphdb "github.com/lightningnetwork/lnd/graph/db"
        "github.com/lightningnetwork/lnd/graph/db/models"
        "github.com/lightningnetwork/lnd/input"
        "github.com/lightningnetwork/lnd/keychain"
        "github.com/lightningnetwork/lnd/lnpeer"
        "github.com/lightningnetwork/lnd/lnutils"
        "github.com/lightningnetwork/lnd/lnwallet"
        "github.com/lightningnetwork/lnd/lnwallet/btcwallet"
        "github.com/lightningnetwork/lnd/lnwallet/chanvalidate"
        "github.com/lightningnetwork/lnd/lnwire"
        "github.com/lightningnetwork/lnd/multimutex"
        "github.com/lightningnetwork/lnd/netann"
        "github.com/lightningnetwork/lnd/routing/route"
        "github.com/lightningnetwork/lnd/ticker"
        "golang.org/x/time/rate"
)

const (
        // DefaultMaxChannelUpdateBurst is the default maximum number of updates
        // for a specific channel and direction that we'll accept over an
        // interval.
        DefaultMaxChannelUpdateBurst = 10

        // DefaultChannelUpdateInterval is the default interval we'll use to
        // determine how often we should allow a new update for a specific
        // channel and direction.
        DefaultChannelUpdateInterval = time.Minute

        // maxPrematureUpdates tracks the max amount of premature channel
        // updates that we'll hold onto.
        maxPrematureUpdates = 100

        // maxFutureMessages tracks the max amount of future messages that
        // we'll hold onto.
        maxFutureMessages = 1000

        // DefaultSubBatchDelay is the default delay we'll use when
        // broadcasting the next announcement batch.
        DefaultSubBatchDelay = 5 * time.Second

        // maxRejectedUpdates tracks the max amount of rejected channel updates
        // we'll maintain. This is the global size across all peers. We'll
        // allocate ~3 MB max to the cache.
        maxRejectedUpdates = 10_000

        // DefaultProofMatureDelta specifies the default value used for
        // ProofMatureDelta, which is the number of confirmations needed before
        // processing the announcement signatures.
        DefaultProofMatureDelta = 6
)

var (
        // ErrGossiperShuttingDown is an error that is returned if the gossiper
        // is in the process of being shut down.
        ErrGossiperShuttingDown = errors.New("gossiper is shutting down")

        // ErrGossipSyncerNotFound signals that we were unable to find an active
        // gossip syncer corresponding to a gossip query message received from
        // the remote peer.
        ErrGossipSyncerNotFound = errors.New("gossip syncer not found")

        // ErrNoFundingTransaction is returned when we are unable to find the
        // funding transaction described by the short channel ID on chain.
        ErrNoFundingTransaction = errors.New(
                "unable to find the funding transaction",
        )

        // ErrInvalidFundingOutput is returned if the channel funding output
        // fails validation.
        ErrInvalidFundingOutput = errors.New(
                "channel funding output validation failed",
        )

        // ErrChannelSpent is returned when we go to validate a channel, but
        // the purported funding output has actually already been spent on
        // chain.
        ErrChannelSpent = errors.New("channel output has been spent")

        // emptyPubkey is used to compare compressed pubkeys against an empty
        // byte array.
        emptyPubkey [33]byte
)

// optionalMsgFields is a set of optional message fields that external callers
// can provide that serve useful when processing a specific network
// announcement.
type optionalMsgFields struct {
        capacity      *btcutil.Amount
        channelPoint  *wire.OutPoint
        remoteAlias   *lnwire.ShortChannelID
        tapscriptRoot fn.Option[chainhash.Hash]
}

// apply applies the optional fields within the functional options.
func (f *optionalMsgFields) apply(optionalMsgFields ...OptionalMsgField) {
        for _, optionalMsgField := range optionalMsgFields {
                optionalMsgField(f)
        }
}

// OptionalMsgField is a functional option parameter that can be used to provide
// external information that is not included within a network message but serves
// useful when processing it.
type OptionalMsgField func(*optionalMsgFields)

// ChannelCapacity is an optional field that lets the gossiper know of the
// capacity of a channel.
func ChannelCapacity(capacity btcutil.Amount) OptionalMsgField {
        return func(f *optionalMsgFields) {
                f.capacity = &capacity
        }
}

// ChannelPoint is an optional field that lets the gossiper know of the outpoint
// of a channel.
func ChannelPoint(op wire.OutPoint) OptionalMsgField {
        return func(f *optionalMsgFields) {
                f.channelPoint = &op
        }
}

// TapscriptRoot is an optional field that lets the gossiper know of the root of
// the tapscript tree for a custom channel.
func TapscriptRoot(root fn.Option[chainhash.Hash]) OptionalMsgField {
        return func(f *optionalMsgFields) {
                f.tapscriptRoot = root
        }
}

// RemoteAlias is an optional field that lets the gossiper know that a locally
// sent channel update is actually an update for the peer that should replace
// the ShortChannelID field with the remote's alias. This is only used for
// channels with peers where the option-scid-alias feature bit was negotiated.
// The channel update will be added to the graph under the original SCID, but
// will be modified and re-signed with this alias.
func RemoteAlias(alias *lnwire.ShortChannelID) OptionalMsgField {
        return func(f *optionalMsgFields) {
                f.remoteAlias = alias
        }
}

// networkMsg couples a routing related wire message with the peer that
// originally sent it.
type networkMsg struct {
        peer              lnpeer.Peer
        source            *btcec.PublicKey
        msg               lnwire.Message
        optionalMsgFields *optionalMsgFields

        isRemote bool

        err chan error
}

// chanPolicyUpdateRequest is a request that is sent to the server when a caller
// wishes to update a particular set of channels. New ChannelUpdate messages
// will be crafted to be sent out during the next broadcast epoch and the fee
// updates committed to the lower layer.
type chanPolicyUpdateRequest struct {
        edgesToUpdate []EdgeWithInfo
        errChan       chan error
}

// PinnedSyncers is a set of node pubkeys for which we will maintain an active
// syncer at all times.
type PinnedSyncers map[route.Vertex]struct{}

// Config defines the configuration for the service. ALL elements within the
// configuration MUST be non-nil for the service to carry out its duties.
type Config struct {
        // ChainHash is a hash that indicates which resident chain of the
        // AuthenticatedGossiper. Any announcements that don't match this
        // chain hash will be ignored.
        //
        // TODO(roasbeef): eventually make into map so can de-multiplex
        // incoming announcements
        //   * also need to do same for Notifier
        ChainHash chainhash.Hash

        // Graph is the subsystem which is responsible for managing the
        // topology of lightning network. After incoming channel, node, channel
        // updates announcements are validated they are sent to the router in
        // order to be included in the LN graph.
        Graph graph.ChannelGraphSource

        // ChainIO represents an abstraction over a source that can query the
        // blockchain.
        ChainIO lnwallet.BlockChainIO

        // ChanSeries is an interfaces that provides access to a time series
        // view of the current known channel graph. Each GossipSyncer enabled
        // peer will utilize this in order to create and respond to channel
        // graph time series queries.
        ChanSeries ChannelGraphTimeSeries

        // Notifier is used for receiving notifications of incoming blocks.
        // With each new incoming block found we process previously premature
        // announcements.
        //
        // TODO(roasbeef): could possibly just replace this with an epoch
        // channel.
        Notifier chainntnfs.ChainNotifier

        // Broadcast broadcasts a particular set of announcements to all peers
        // that the daemon is connected to. If supplied, the exclude parameter
        // indicates that the target peer should be excluded from the
        // broadcast.
        Broadcast func(skips map[route.Vertex]struct{},
                msg ...lnwire.Message) error

        // NotifyWhenOnline is a function that allows the gossiper to be
        // notified when a certain peer comes online, allowing it to
        // retry sending a peer message.
        //
        // NOTE: The peerChan channel must be buffered.
        NotifyWhenOnline func(peerPubKey [33]byte, peerChan chan<- lnpeer.Peer)

        // NotifyWhenOffline is a function that allows the gossiper to be
        // notified when a certain peer disconnects, allowing it to request a
        // notification for when it reconnects.
        NotifyWhenOffline func(peerPubKey [33]byte) <-chan struct{}

        // FetchSelfAnnouncement retrieves our current node announcement, for
        // use when determining whether we should update our peers about our
        // presence in the network.
        FetchSelfAnnouncement func() lnwire.NodeAnnouncement

        // UpdateSelfAnnouncement produces a new announcement for our node with
        // an updated timestamp which can be broadcast to our peers.
        UpdateSelfAnnouncement func() (lnwire.NodeAnnouncement, error)

        // ProofMatureDelta the number of confirmations which is needed before
        // exchange the channel announcement proofs.
        ProofMatureDelta uint32

        // TrickleDelay the period of trickle timer which flushes to the
        // network the pending batch of new announcements we've received since
        // the last trickle tick.
        TrickleDelay time.Duration

        // RetransmitTicker is a ticker that ticks with a period which
        // indicates that we should check if we need re-broadcast any of our
        // personal channels.
        RetransmitTicker ticker.Ticker

        // RebroadcastInterval is the maximum time we wait between sending out
        // channel updates for our active channels and our own node
        // announcement. We do this to ensure our active presence on the
        // network is known, and we are not being considered a zombie node or
        // having zombie channels.
        RebroadcastInterval time.Duration

        // WaitingProofStore is a persistent storage of partial channel proof
        // announcement messages. We use it to buffer half of the material
        // needed to reconstruct a full authenticated channel announcement.
        // Once we receive the other half the channel proof, we'll be able to
        // properly validate it and re-broadcast it out to the network.
        //
        // TODO(wilmer): make interface to prevent channeldb dependency.
        WaitingProofStore *channeldb.WaitingProofStore

        // MessageStore is a persistent storage of gossip messages which we will
        // use to determine which messages need to be resent for a given peer.
        MessageStore GossipMessageStore

        // AnnSigner is an instance of the MessageSigner interface which will
        // be used to manually sign any outgoing channel updates. The signer
        // implementation should be backed by the public key of the backing
        // Lightning node.
        //
        // TODO(roasbeef): extract ann crafting + sign from fundingMgr into
        // here?
        AnnSigner lnwallet.MessageSigner

        // ScidCloser is an instance of ClosedChannelTracker that helps the
        // gossiper cut down on spam channel announcements for already closed
        // channels.
        ScidCloser ClosedChannelTracker

        // NumActiveSyncers is the number of peers for which we should have
        // active syncers with. After reaching NumActiveSyncers, any future
        // gossip syncers will be passive.
        NumActiveSyncers int

        // NoTimestampQueries will prevent the GossipSyncer from querying
        // timestamps of announcement messages from the peer and from replying
        // to timestamp queries.
        NoTimestampQueries bool

        // RotateTicker is a ticker responsible for notifying the SyncManager
        // when it should rotate its active syncers. A single active syncer with
        // a chansSynced state will be exchanged for a passive syncer in order
        // to ensure we don't keep syncing with the same peers.
        RotateTicker ticker.Ticker

        // HistoricalSyncTicker is a ticker responsible for notifying the
        // syncManager when it should attempt a historical sync with a gossip
        // sync peer.
        HistoricalSyncTicker ticker.Ticker

        // ActiveSyncerTimeoutTicker is a ticker responsible for notifying the
        // syncManager when it should attempt to start the next pending
        // activeSyncer due to the current one not completing its state machine
        // within the timeout.
        ActiveSyncerTimeoutTicker ticker.Ticker

        // MinimumBatchSize is minimum size of a sub batch of announcement
        // messages.
        MinimumBatchSize int

        // SubBatchDelay is the delay between sending sub batches of
        // gossip messages.
        SubBatchDelay time.Duration

        // IgnoreHistoricalFilters will prevent syncers from replying with
        // historical data when the remote peer sets a gossip_timestamp_range.
        // This prevents ranges with old start times from causing us to dump the
        // graph on connect.
        IgnoreHistoricalFilters bool

        // PinnedSyncers is a set of peers that will always transition to
        // ActiveSync upon connection. These peers will never transition to
        // PassiveSync.
        PinnedSyncers PinnedSyncers

        // MaxChannelUpdateBurst specifies the maximum number of updates for a
        // specific channel and direction that we'll accept over an interval.
        MaxChannelUpdateBurst int

        // ChannelUpdateInterval specifies the interval we'll use to determine
        // how often we should allow a new update for a specific channel and
        // direction.
        ChannelUpdateInterval time.Duration

        // IsAlias returns true if a given ShortChannelID is an alias for
        // option_scid_alias channels.
        IsAlias func(scid lnwire.ShortChannelID) bool

        // SignAliasUpdate is used to re-sign a channel update using the
        // remote's alias if the option-scid-alias feature bit was negotiated.
        SignAliasUpdate func(u *lnwire.ChannelUpdate1) (*ecdsa.Signature,
                error)

        // FindBaseByAlias finds the SCID stored in the graph by an alias SCID.
        // This is used for channels that have negotiated the option-scid-alias
        // feature bit.
        FindBaseByAlias func(alias lnwire.ShortChannelID) (
                lnwire.ShortChannelID, error)

        // GetAlias allows the gossiper to look up the peer's alias for a given
        // ChannelID. This is used to sign updates for them if the channel has
        // no AuthProof and the option-scid-alias feature bit was negotiated.
        GetAlias func(lnwire.ChannelID) (lnwire.ShortChannelID, error)

        // FindChannel allows the gossiper to find a channel that we're party
        // to without iterating over the entire set of open channels.
        FindChannel func(node *btcec.PublicKey, chanID lnwire.ChannelID) (
                *channeldb.OpenChannel, error)

        // IsStillZombieChannel takes the timestamps of the latest channel
        // updates for a channel and returns true if the channel should be
        // considered a zombie based on these timestamps.
        IsStillZombieChannel func(time.Time, time.Time) bool

        // AssumeChannelValid toggles whether the gossiper will check for
        // spent-ness of channel outpoints. For neutrino, this saves long
        // rescans from blocking initial usage of the daemon.
        AssumeChannelValid bool
}

// processedNetworkMsg is a wrapper around networkMsg and a boolean. It is
// used to let the caller of the lru.Cache know if a message has already been
// processed or not.
type processedNetworkMsg struct {
        processed bool
        msg       *networkMsg
}

// cachedNetworkMsg is a wrapper around a network message that can be used with
// *lru.Cache.
type cachedNetworkMsg struct {
        msgs []*processedNetworkMsg
}

// Size returns the "size" of an entry. We return the number of items as we
// just want to limit the total amount of entries rather than do accurate size
// accounting.
func (c *cachedNetworkMsg) Size() (uint64, error) {
        return uint64(len(c.msgs)), nil
}

// rejectCacheKey is the cache key that we'll use to track announcements we've
// recently rejected.
type rejectCacheKey struct {
        pubkey [33]byte
        chanID uint64
}

// newRejectCacheKey returns a new cache key for the reject cache.
func newRejectCacheKey(cid uint64, pub [33]byte) rejectCacheKey {
        k := rejectCacheKey{
                chanID: cid,
                pubkey: pub,
        }

        return k
}

// sourceToPub returns a serialized-compressed public key for use in the reject
// cache.
func sourceToPub(pk *btcec.PublicKey) [33]byte {
        var pub [33]byte
        copy(pub[:], pk.SerializeCompressed())
        return pub
}

// cachedReject is the empty value used to track the value for rejects.
type cachedReject struct {
}

// Size returns the "size" of an entry. We return 1 as we just want to limit
// the total size.
func (c *cachedReject) Size() (uint64, error) {
        return 1, nil
}

// AuthenticatedGossiper is a subsystem which is responsible for receiving
// announcements, validating them and applying the changes to router, syncing
// lightning network with newly connected nodes, broadcasting announcements
// after validation, negotiating the channel announcement proofs exchange and
// handling the premature announcements. All outgoing announcements are
// expected to be properly signed as dictated in BOLT#7, additionally, all
// incoming message are expected to be well formed and signed. Invalid messages
// will be rejected by this struct.
type AuthenticatedGossiper struct {
        // Parameters which are needed to properly handle the start and stop of
        // the service.
        started sync.Once
        stopped sync.Once

        // bestHeight is the height of the block at the tip of the main chain
        // as we know it. Accesses *MUST* be done with the gossiper's lock
        // held.
        bestHeight uint32

        quit chan struct{}
        wg   sync.WaitGroup

        // cfg is a copy of the configuration struct that the gossiper service
        // was initialized with.
        cfg *Config

        // blockEpochs encapsulates a stream of block epochs that are sent at
        // every new block height.
        blockEpochs *chainntnfs.BlockEpochEvent

        // prematureChannelUpdates is a map of ChannelUpdates we have received
        // that wasn't associated with any channel we know about.  We store
        // them temporarily, such that we can reprocess them when a
        // ChannelAnnouncement for the channel is received.
        prematureChannelUpdates *lru.Cache[uint64, *cachedNetworkMsg]

        // banman tracks our peer's ban status.
        banman *banman

        // networkMsgs is a channel that carries new network broadcasted
        // message from outside the gossiper service to be processed by the
        // networkHandler.
        networkMsgs chan *networkMsg

        // futureMsgs is a list of premature network messages that have a block
        // height specified in the future. We will save them and resend it to
        // the chan networkMsgs once the block height has reached. The cached
        // map format is,
        //   {msgID1: msg1, msgID2: msg2, ...}
        futureMsgs *futureMsgCache

        // chanPolicyUpdates is a channel that requests to update the
        // forwarding policy of a set of channels is sent over.
        chanPolicyUpdates chan *chanPolicyUpdateRequest

        // selfKey is the identity public key of the backing Lightning node.
        selfKey *btcec.PublicKey

        // selfKeyLoc is the locator for the identity public key of the backing
        // Lightning node.
        selfKeyLoc keychain.KeyLocator

        // channelMtx is used to restrict the database access to one
        // goroutine per channel ID. This is done to ensure that when
        // the gossiper is handling an announcement, the db state stays
        // consistent between when the DB is first read until it's written.
        channelMtx *multimutex.Mutex[uint64]

        recentRejects *lru.Cache[rejectCacheKey, *cachedReject]

        // syncMgr is a subsystem responsible for managing the gossip syncers
        // for peers currently connected. When a new peer is connected, the
        // manager will create its accompanying gossip syncer and determine
        // whether it should have an activeSync or passiveSync sync type based
        // on how many other gossip syncers are currently active. Any activeSync
        // gossip syncers are started in a round-robin manner to ensure we're
        // not syncing with multiple peers at the same time.
        syncMgr *SyncManager

        // reliableSender is a subsystem responsible for handling reliable
        // message send requests to peers. This should only be used for channels
        // that are unadvertised at the time of handling the message since if it
        // is advertised, then peers should be able to get the message from the
        // network.
        reliableSender *reliableSender

        // chanUpdateRateLimiter contains rate limiters for each direction of
        // a channel update we've processed. We'll use these to determine
        // whether we should accept a new update for a specific channel and
        // direction.
        //
        // NOTE: This map must be synchronized with the main
        // AuthenticatedGossiper lock.
        chanUpdateRateLimiter map[uint64][2]*rate.Limiter

        // vb is used to enforce job dependency ordering of gossip messages.
        vb *ValidationBarrier

        sync.Mutex
}

// New creates a new AuthenticatedGossiper instance, initialized with the
// passed configuration parameters.
func New(cfg Config, selfKeyDesc *keychain.KeyDescriptor) *AuthenticatedGossiper {
        gossiper := &AuthenticatedGossiper{
                selfKey:           selfKeyDesc.PubKey,
                selfKeyLoc:        selfKeyDesc.KeyLocator,
                cfg:               &cfg,
                networkMsgs:       make(chan *networkMsg),
                futureMsgs:        newFutureMsgCache(maxFutureMessages),
                quit:              make(chan struct{}),
                chanPolicyUpdates: make(chan *chanPolicyUpdateRequest),
                prematureChannelUpdates: lru.NewCache[uint64, *cachedNetworkMsg]( //nolint: ll
                        maxPrematureUpdates,
                ),
                channelMtx: multimutex.NewMutex[uint64](),
                recentRejects: lru.NewCache[rejectCacheKey, *cachedReject](
                        maxRejectedUpdates,
                ),
                chanUpdateRateLimiter: make(map[uint64][2]*rate.Limiter),
                banman:                newBanman(),
        }

        gossiper.vb = NewValidationBarrier(1000, gossiper.quit)

        gossiper.syncMgr = newSyncManager(&SyncManagerCfg{
                ChainHash:               cfg.ChainHash,
                ChanSeries:              cfg.ChanSeries,
                RotateTicker:            cfg.RotateTicker,
                HistoricalSyncTicker:    cfg.HistoricalSyncTicker,
                NumActiveSyncers:        cfg.NumActiveSyncers,
                NoTimestampQueries:      cfg.NoTimestampQueries,
                IgnoreHistoricalFilters: cfg.IgnoreHistoricalFilters,
                BestHeight:              gossiper.latestHeight,
                PinnedSyncers:           cfg.PinnedSyncers,
                IsStillZombieChannel:    cfg.IsStillZombieChannel,
        })

        gossiper.reliableSender = newReliableSender(&reliableSenderCfg{
                NotifyWhenOnline:  cfg.NotifyWhenOnline,
                NotifyWhenOffline: cfg.NotifyWhenOffline,
                MessageStore:      cfg.MessageStore,
                IsMsgStale:        gossiper.isMsgStale,
        })

        return gossiper
}

// EdgeWithInfo contains the information that is required to update an edge.
type EdgeWithInfo struct {
        // Info describes the channel.
        Info *models.ChannelEdgeInfo

        // Edge describes the policy in one direction of the channel.
        Edge *models.ChannelEdgePolicy
}

// PropagateChanPolicyUpdate signals the AuthenticatedGossiper to perform the
// specified edge updates. Updates are done in two stages: first, the
// AuthenticatedGossiper ensures the update has been committed by dependent
// sub-systems, then it signs and broadcasts new updates to the network. A
// mapping between outpoints and updated channel policies is returned, which is
// used to update the forwarding policies of the underlying links.
func (d *AuthenticatedGossiper) PropagateChanPolicyUpdate(
        edgesToUpdate []EdgeWithInfo) error {

        errChan := make(chan error, 1)
        policyUpdate := &chanPolicyUpdateRequest{
                edgesToUpdate: edgesToUpdate,
                errChan:       errChan,
        }

        select {
        case d.chanPolicyUpdates <- policyUpdate:
                err := <-errChan
                return err
        case <-d.quit:
                return fmt.Errorf("AuthenticatedGossiper shutting down")
        }
}

// Start spawns network messages handler goroutine and registers on new block
// notifications in order to properly handle the premature announcements.
func (d *AuthenticatedGossiper) Start() error {
        var err error
        d.started.Do(func() {
                log.Info("Authenticated Gossiper starting")
                err = d.start()
        })
        return err
}

func (d *AuthenticatedGossiper) start() error {
        // First we register for new notifications of newly discovered blocks.
        // We do this immediately so we'll later be able to consume any/all
        // blocks which were discovered.
        blockEpochs, err := d.cfg.Notifier.RegisterBlockEpochNtfn(nil)
        if err != nil {
                return err
        }
        d.blockEpochs = blockEpochs

        height, err := d.cfg.Graph.CurrentBlockHeight()
        if err != nil {
                return err
        }
        d.bestHeight = height

        // Start the reliable sender. In case we had any pending messages ready
        // to be sent when the gossiper was last shut down, we must continue on
        // our quest to deliver them to their respective peers.
        if err := d.reliableSender.Start(); err != nil {
                return err
        }

        d.syncMgr.Start()

        d.banman.start()

        // Start receiving blocks in its dedicated goroutine.
        d.wg.Add(2)
        go d.syncBlockHeight()
        go d.networkHandler()

        return nil
}

// syncBlockHeight syncs the best block height for the gossiper by reading
// blockEpochs.
//
// NOTE: must be run as a goroutine.
func (d *AuthenticatedGossiper) syncBlockHeight() {
        defer d.wg.Done()

        for {
                select {
                // A new block has arrived, so we can re-process the previously
                // premature announcements.
                case newBlock, ok := <-d.blockEpochs.Epochs:
                        // If the channel has been closed, then this indicates
                        // the daemon is shutting down, so we exit ourselves.
                        if !ok {
                                return
                        }

                        // Once a new block arrives, we update our running
                        // track of the height of the chain tip.
                        d.Lock()
                        blockHeight := uint32(newBlock.Height)
                        d.bestHeight = blockHeight
                        d.Unlock()

                        log.Debugf("New block: height=%d, hash=%s", blockHeight,
                                newBlock.Hash)

                        // Resend future messages, if any.
                        d.resendFutureMessages(blockHeight)

                case <-d.quit:
                        return
                }
        }
}

// futureMsgCache embeds a `lru.Cache` with a message counter that's served as
// the unique ID when saving the message.
type futureMsgCache struct {
        *lru.Cache[uint64, *cachedFutureMsg]

        // msgID is a monotonically increased integer.
        msgID atomic.Uint64
}

// nextMsgID returns a unique message ID.
func (f *futureMsgCache) nextMsgID() uint64 {
        return f.msgID.Add(1)
}

// newFutureMsgCache creates a new future message cache with the underlying lru
// cache being initialized with the specified capacity.
func newFutureMsgCache(capacity uint64) *futureMsgCache {
        // Create a new cache.
        cache := lru.NewCache[uint64, *cachedFutureMsg](capacity)

        return &futureMsgCache{
                Cache: cache,
        }
}

// cachedFutureMsg is a future message that's saved to the `futureMsgCache`.
type cachedFutureMsg struct {
        // msg is the network message.
        msg *networkMsg

        // height is the block height.
        height uint32
}

// Size returns the size of the message.
func (c *cachedFutureMsg) Size() (uint64, error) {
        // Return a constant 1.
        return 1, nil
}

// resendFutureMessages takes a block height, resends all the future messages
// found below and equal to that height and deletes those messages found in the
// gossiper's futureMsgs.
func (d *AuthenticatedGossiper) resendFutureMessages(height uint32) {
        var (
                // msgs are the target messages.
                msgs []*networkMsg

                // keys are the target messages' caching keys.
                keys []uint64
        )

        // filterMsgs is the visitor used when iterating the future cache.
        filterMsgs := func(k uint64, cmsg *cachedFutureMsg) bool {
                if cmsg.height <= height {
                        msgs = append(msgs, cmsg.msg)
                        keys = append(keys, k)
                }

                return true
        }

        // Filter out the target messages.
        d.futureMsgs.Range(filterMsgs)

        // Return early if no messages found.
        if len(msgs) == 0 {
                return
        }

        // Remove the filtered messages.
        for _, key := range keys {
                d.futureMsgs.Delete(key)
        }

        log.Debugf("Resending %d network messages at height %d",
                len(msgs), height)

        for _, msg := range msgs {
                select {
                case d.networkMsgs <- msg:
                case <-d.quit:
                        msg.err <- ErrGossiperShuttingDown
                }
        }
}

// Stop signals any active goroutines for a graceful closure.
func (d *AuthenticatedGossiper) Stop() error {
        d.stopped.Do(func() {
                log.Info("Authenticated gossiper shutting down...")
                defer log.Debug("Authenticated gossiper shutdown complete")

                d.stop()
        })
        return nil
}

func (d *AuthenticatedGossiper) stop() {
        log.Debug("Authenticated Gossiper is stopping")
        defer log.Debug("Authenticated Gossiper stopped")

        // `blockEpochs` is only initialized in the start routine so we make
        // sure we don't panic here in the case where the `Stop` method is
        // called when the `Start` method does not complete.
        if d.blockEpochs != nil {
                d.blockEpochs.Cancel()
        }

        d.syncMgr.Stop()

        d.banman.stop()

        close(d.quit)
        d.wg.Wait()

        // We'll stop our reliable sender after all of the gossiper's goroutines
        // have exited to ensure nothing can cause it to continue executing.
        d.reliableSender.Stop()
}

// TODO(roasbeef): need method to get current gossip timestamp?
//  * using mtx, check time rotate forward is needed?

// ProcessRemoteAnnouncement sends a new remote announcement message along with
// the peer that sent the routing message. The announcement will be processed
// then added to a queue for batched trickled announcement to all connected
// peers.  Remote channel announcements should contain the announcement proof
// and be fully validated.
func (d *AuthenticatedGossiper) ProcessRemoteAnnouncement(msg lnwire.Message,
        peer lnpeer.Peer) chan error {

        log.Debugf("Processing remote msg %T from peer=%x", msg, peer.PubKey())

        errChan := make(chan error, 1)

        // For messages in the known set of channel series queries, we'll
        // dispatch the message directly to the GossipSyncer, and skip the main
        // processing loop.
        switch m := msg.(type) {
        case *lnwire.QueryShortChanIDs,
                *lnwire.QueryChannelRange,
                *lnwire.ReplyChannelRange,
                *lnwire.ReplyShortChanIDsEnd:

                syncer, ok := d.syncMgr.GossipSyncer(peer.PubKey())
                if !ok {
                        log.Warnf("Gossip syncer for peer=%x not found",
                                peer.PubKey())

                        errChan <- ErrGossipSyncerNotFound
                        return errChan
                }

                // If we've found the message target, then we'll dispatch the
                // message directly to it.
                err := syncer.ProcessQueryMsg(m, peer.QuitSignal())
                if err != nil {
                        log.Errorf("Process query msg from peer %x got %v",
                                peer.PubKey(), err)
                }

                errChan <- err
                return errChan

        // If a peer is updating its current update horizon, then we'll dispatch
        // that directly to the proper GossipSyncer.
        case *lnwire.GossipTimestampRange:
                syncer, ok := d.syncMgr.GossipSyncer(peer.PubKey())
                if !ok {
                        log.Warnf("Gossip syncer for peer=%x not found",
                                peer.PubKey())

                        errChan <- ErrGossipSyncerNotFound
                        return errChan
                }

                // If we've found the message target, then we'll dispatch the
                // message directly to it.
                if err := syncer.ApplyGossipFilter(m); err != nil {
                        log.Warnf("Unable to apply gossip filter for peer=%x: "+
                                "%v", peer.PubKey(), err)

                        errChan <- err
                        return errChan
                }

                errChan <- nil
                return errChan

        // To avoid inserting edges in the graph for our own channels that we
        // have already closed, we ignore such channel announcements coming
        // from the remote.
        case *lnwire.ChannelAnnouncement1:
                ownKey := d.selfKey.SerializeCompressed()
                ownErr := fmt.Errorf("ignoring remote ChannelAnnouncement1 " +
                        "for own channel")

                if bytes.Equal(m.NodeID1[:], ownKey) ||
                        bytes.Equal(m.NodeID2[:], ownKey) {

                        log.Warn(ownErr)
                        errChan <- ownErr
                        return errChan
                }
        }

        nMsg := &networkMsg{
                msg:      msg,
                isRemote: true,
                peer:     peer,
                source:   peer.IdentityKey(),
                err:      errChan,
        }

        select {
        case d.networkMsgs <- nMsg:

        // If the peer that sent us this error is quitting, then we don't need
        // to send back an error and can return immediately.
        case <-peer.QuitSignal():
                return nil
        case <-d.quit:
                nMsg.err <- ErrGossiperShuttingDown
        }

        return nMsg.err
}

// ProcessLocalAnnouncement sends a new remote announcement message along with
// the peer that sent the routing message. The announcement will be processed
// then added to a queue for batched trickled announcement to all connected
// peers.  Local channel announcements don't contain the announcement proof and
// will not be fully validated. Once the channel proofs are received, the
// entire channel announcement and update messages will be re-constructed and
// broadcast to the rest of the network.
func (d *AuthenticatedGossiper) ProcessLocalAnnouncement(msg lnwire.Message,
        optionalFields ...OptionalMsgField) chan error {

        optionalMsgFields := &optionalMsgFields{}
        optionalMsgFields.apply(optionalFields...)

        nMsg := &networkMsg{
                msg:               msg,
                optionalMsgFields: optionalMsgFields,
                isRemote:          false,
                source:            d.selfKey,
                err:               make(chan error, 1),
        }

        select {
        case d.networkMsgs <- nMsg:
        case <-d.quit:
                nMsg.err <- ErrGossiperShuttingDown
        }

        return nMsg.err
}

// channelUpdateID is a unique identifier for ChannelUpdate messages, as
// channel updates can be identified by the (ShortChannelID, ChannelFlags)
// tuple.
type channelUpdateID struct {
        // channelID represents the set of data which is needed to
        // retrieve all necessary data to validate the channel existence.
        channelID lnwire.ShortChannelID

        // Flags least-significant bit must be set to 0 if the creating node
        // corresponds to the first node in the previously sent channel
        // announcement and 1 otherwise.
        flags lnwire.ChanUpdateChanFlags
}

// msgWithSenders is a wrapper struct around a message, and the set of peers
// that originally sent us this message. Using this struct, we can ensure that
// we don't re-send a message to the peer that sent it to us in the first
// place.
type msgWithSenders struct {
        // msg is the wire message itself.
        msg lnwire.Message

        // isLocal is true if this was a message that originated locally. We'll
        // use this to bypass our normal checks to ensure we prioritize sending
        // out our own updates.
        isLocal bool

        // sender is the set of peers that sent us this message.
        senders map[route.Vertex]struct{}
}

// mergeSyncerMap is used to merge the set of senders of a particular message
// with peers that we have an active GossipSyncer with. We do this to ensure
// that we don't broadcast messages to any peers that we have active gossip
// syncers for.
func (m *msgWithSenders) mergeSyncerMap(syncers map[route.Vertex]*GossipSyncer) {
        for peerPub := range syncers {
                m.senders[peerPub] = struct{}{}
        }
}

// deDupedAnnouncements de-duplicates announcements that have been added to the
// batch. Internally, announcements are stored in three maps
// (one each for channel announcements, channel updates, and node
// announcements). These maps keep track of unique announcements and ensure no
// announcements are duplicated. We keep the three message types separate, such
// that we can send channel announcements first, then channel updates, and
// finally node announcements when it's time to broadcast them.
type deDupedAnnouncements struct {
        // channelAnnouncements are identified by the short channel id field.
        channelAnnouncements map[lnwire.ShortChannelID]msgWithSenders

        // channelUpdates are identified by the channel update id field.
        channelUpdates map[channelUpdateID]msgWithSenders

        // nodeAnnouncements are identified by the Vertex field.
        nodeAnnouncements map[route.Vertex]msgWithSenders

        sync.Mutex
}

// Reset operates on deDupedAnnouncements to reset the storage of
// announcements.
func (d *deDupedAnnouncements) Reset() {
        d.Lock()
        defer d.Unlock()

        d.reset()
}

// reset is the private version of the Reset method. We have this so we can
// call this method within method that are already holding the lock.
func (d *deDupedAnnouncements) reset() {
        // Storage of each type of announcement (channel announcements, channel
        // updates, node announcements) is set to an empty map where the
        // appropriate key points to the corresponding lnwire.Message.
        d.channelAnnouncements = make(map[lnwire.ShortChannelID]msgWithSenders)
        d.channelUpdates = make(map[channelUpdateID]msgWithSenders)
        d.nodeAnnouncements = make(map[route.Vertex]msgWithSenders)
}

// addMsg adds a new message to the current batch. If the message is already
// present in the current batch, then this new instance replaces the latter,
// and the set of senders is updated to reflect which node sent us this
// message.
func (d *deDupedAnnouncements) addMsg(message networkMsg) {
        log.Tracef("Adding network message: %v to batch", message.msg.MsgType())

        // Depending on the message type (channel announcement, channel update,
        // or node announcement), the message is added to the corresponding map
        // in deDupedAnnouncements. Because each identifying key can have at
        // most one value, the announcements are de-duplicated, with newer ones
        // replacing older ones.
        switch msg := message.msg.(type) {

        // Channel announcements are identified by the short channel id field.
        case *lnwire.ChannelAnnouncement1:
                deDupKey := msg.ShortChannelID
                sender := route.NewVertex(message.source)

                mws, ok := d.channelAnnouncements[deDupKey]
                if !ok {
                        mws = msgWithSenders{
                                msg:     msg,
                                isLocal: !message.isRemote,
                                senders: make(map[route.Vertex]struct{}),
                        }
                        mws.senders[sender] = struct{}{}

                        d.channelAnnouncements[deDupKey] = mws

                        return
                }

                mws.msg = msg
                mws.senders[sender] = struct{}{}
                d.channelAnnouncements[deDupKey] = mws

        // Channel updates are identified by the (short channel id,
        // channelflags) tuple.
        case *lnwire.ChannelUpdate1:
                sender := route.NewVertex(message.source)
                deDupKey := channelUpdateID{
                        msg.ShortChannelID,
                        msg.ChannelFlags,
                }

                oldTimestamp := uint32(0)
                mws, ok := d.channelUpdates[deDupKey]
                if ok {
                        // If we already have seen this message, record its
                        // timestamp.
                        update, ok := mws.msg.(*lnwire.ChannelUpdate1)
                        if !ok {
                                log.Errorf("Expected *lnwire.ChannelUpdate1, "+
                                        "got: %T", mws.msg)

                                return
                        }

                        oldTimestamp = update.Timestamp
                }

                // If we already had this message with a strictly newer
                // timestamp, then we'll just discard the message we got.
                if oldTimestamp > msg.Timestamp {
                        log.Debugf("Ignored outdated network message: "+
                                "peer=%v, msg=%s", message.peer, msg.MsgType())
                        return
                }

                // If the message we just got is newer than what we previously
                // have seen, or this is the first time we see it, then we'll
                // add it to our map of announcements.
                if oldTimestamp < msg.Timestamp {
                        mws = msgWithSenders{
                                msg:     msg,
                                isLocal: !message.isRemote,
                                senders: make(map[route.Vertex]struct{}),
                        }

                        // We'll mark the sender of the message in the
                        // senders map.
                        mws.senders[sender] = struct{}{}

                        d.channelUpdates[deDupKey] = mws

                        return
                }

                // Lastly, if we had seen this exact message from before, with
                // the same timestamp, we'll add the sender to the map of
                // senders, such that we can skip sending this message back in
                // the next batch.
                mws.msg = msg
                mws.senders[sender] = struct{}{}
                d.channelUpdates[deDupKey] = mws

        // Node announcements are identified by the Vertex field.  Use the
        // NodeID to create the corresponding Vertex.
        case *lnwire.NodeAnnouncement:
                sender := route.NewVertex(message.source)
                deDupKey := route.Vertex(msg.NodeID)

                // We do the same for node announcements as we did for channel
                // updates, as they also carry a timestamp.
                oldTimestamp := uint32(0)
                mws, ok := d.nodeAnnouncements[deDupKey]
                if ok {
                        oldTimestamp = mws.msg.(*lnwire.NodeAnnouncement).Timestamp
                }

                // Discard the message if it's old.
                if oldTimestamp > msg.Timestamp {
                        return
                }

                // Replace if it's newer.
                if oldTimestamp < msg.Timestamp {
                        mws = msgWithSenders{
                                msg:     msg,
                                isLocal: !message.isRemote,
                                senders: make(map[route.Vertex]struct{}),
                        }

                        mws.senders[sender] = struct{}{}

                        d.nodeAnnouncements[deDupKey] = mws

                        return
                }

                // Add to senders map if it's the same as we had.
                mws.msg = msg
                mws.senders[sender] = struct{}{}
                d.nodeAnnouncements[deDupKey] = mws
        }
}

// AddMsgs is a helper method to add multiple messages to the announcement
// batch.
func (d *deDupedAnnouncements) AddMsgs(msgs ...networkMsg) {
        d.Lock()
        defer d.Unlock()

        for _, msg := range msgs {
                d.addMsg(msg)
        }
}

// msgsToBroadcast is returned by Emit() and partitions the messages we'd like
// to broadcast next into messages that are locally sourced and those that are
// sourced remotely.
type msgsToBroadcast struct {
        // localMsgs is the set of messages we created locally.
        localMsgs []msgWithSenders

        // remoteMsgs is the set of messages that we received from a remote
        // party.
        remoteMsgs []msgWithSenders
}

// addMsg adds a new message to the appropriate sub-slice.
func (m *msgsToBroadcast) addMsg(msg msgWithSenders) {
        if msg.isLocal {
                m.localMsgs = append(m.localMsgs, msg)
        } else {
                m.remoteMsgs = append(m.remoteMsgs, msg)
        }
}

// isEmpty returns true if the batch is empty.
func (m *msgsToBroadcast) isEmpty() bool {
        return len(m.localMsgs) == 0 && len(m.remoteMsgs) == 0
}

// length returns the length of the combined message set.
func (m *msgsToBroadcast) length() int {
        return len(m.localMsgs) + len(m.remoteMsgs)
}

// Emit returns the set of de-duplicated announcements to be sent out during
// the next announcement epoch, in the order of channel announcements, channel
// updates, and node announcements. Each message emitted, contains the set of
// peers that sent us the message. This way, we can ensure that we don't waste
// bandwidth by re-sending a message to the peer that sent it to us in the
// first place. Additionally, the set of stored messages are reset.
func (d *deDupedAnnouncements) Emit() msgsToBroadcast {
        d.Lock()
        defer d.Unlock()

        // Get the total number of announcements.
        numAnnouncements := len(d.channelAnnouncements) + len(d.channelUpdates) +
                len(d.nodeAnnouncements)

        // Create an empty array of lnwire.Messages with a length equal to
        // the total number of announcements.
        msgs := msgsToBroadcast{
                localMsgs:  make([]msgWithSenders, 0, numAnnouncements),
                remoteMsgs: make([]msgWithSenders, 0, numAnnouncements),
        }

        // Add the channel announcements to the array first.
        for _, message := range d.channelAnnouncements {
                msgs.addMsg(message)
        }

        // Then add the channel updates.
        for _, message := range d.channelUpdates {
                msgs.addMsg(message)
        }

        // Finally add the node announcements.
        for _, message := range d.nodeAnnouncements {
                msgs.addMsg(message)
        }

        d.reset()

        // Return the array of lnwire.messages.
        return msgs
}

// calculateSubBatchSize is a helper function that calculates the size to break
// down the batchSize into.
func calculateSubBatchSize(totalDelay, subBatchDelay time.Duration,
        minimumBatchSize, batchSize int) int {
        if subBatchDelay > totalDelay {
                return batchSize
        }

        subBatchSize := (batchSize*int(subBatchDelay) +
                int(totalDelay) - 1) / int(totalDelay)

        if subBatchSize < minimumBatchSize {
                return minimumBatchSize
        }

        return subBatchSize
}

// batchSizeCalculator maps to the function `calculateSubBatchSize`. We create
// this variable so the function can be mocked in our test.
var batchSizeCalculator = calculateSubBatchSize

// splitAnnouncementBatches takes an exiting list of announcements and
// decomposes it into sub batches controlled by the `subBatchSize`.
func (d *AuthenticatedGossiper) splitAnnouncementBatches(
        announcementBatch []msgWithSenders) [][]msgWithSenders {

        subBatchSize := batchSizeCalculator(
                d.cfg.TrickleDelay, d.cfg.SubBatchDelay,
                d.cfg.MinimumBatchSize, len(announcementBatch),
        )

        var splitAnnouncementBatch [][]msgWithSenders

        for subBatchSize < len(announcementBatch) {
                // For slicing with minimal allocation
                // https://github.com/golang/go/wiki/SliceTricks
                announcementBatch, splitAnnouncementBatch =
                        announcementBatch[subBatchSize:],
                        append(splitAnnouncementBatch,
                                announcementBatch[0:subBatchSize:subBatchSize])
        }
        splitAnnouncementBatch = append(
                splitAnnouncementBatch, announcementBatch,
        )

        return splitAnnouncementBatch
}

// splitAndSendAnnBatch takes a batch of messages, computes the proper batch
// split size, and then sends out all items to the set of target peers. Locally
// generated announcements are always sent before remotely generated
// announcements.
func (d *AuthenticatedGossiper) splitAndSendAnnBatch(
        annBatch msgsToBroadcast) {

        // delayNextBatch is a helper closure that blocks for `SubBatchDelay`
        // duration to delay the sending of next announcement batch.
        delayNextBatch := func() {
                select {
                case <-time.After(d.cfg.SubBatchDelay):
                case <-d.quit:
                        return
                }
        }

        // Fetch the local and remote announcements.
        localBatches := d.splitAnnouncementBatches(annBatch.localMsgs)
        remoteBatches := d.splitAnnouncementBatches(annBatch.remoteMsgs)

        d.wg.Add(1)
        go func() {
                defer d.wg.Done()

                log.Debugf("Broadcasting %v new local announcements in %d "+
                        "sub batches", len(annBatch.localMsgs),
                        len(localBatches))

                // Send out the local announcements first.
                for _, annBatch := range localBatches {
                        d.sendLocalBatch(annBatch)
                        delayNextBatch()
                }

                log.Debugf("Broadcasting %v new remote announcements in %d "+
                        "sub batches", len(annBatch.remoteMsgs),
                        len(remoteBatches))

                // Now send the remote announcements.
                for _, annBatch := range remoteBatches {
                        d.sendRemoteBatch(annBatch)
                        delayNextBatch()
                }
        }()
}

// sendLocalBatch broadcasts a list of locally generated announcements to our
// peers. For local announcements, we skip the filter and dedup logic and just
// send the announcements out to all our coonnected peers.
func (d *AuthenticatedGossiper) sendLocalBatch(annBatch []msgWithSenders) {
        msgsToSend := lnutils.Map(
                annBatch, func(m msgWithSenders) lnwire.Message {
                        return m.msg
                },
        )

        err := d.cfg.Broadcast(nil, msgsToSend...)
        if err != nil {
                log.Errorf("Unable to send local batch announcements: %v", err)
        }
}

// sendRemoteBatch broadcasts a list of remotely generated announcements to our
// peers.
func (d *AuthenticatedGossiper) sendRemoteBatch(annBatch []msgWithSenders) {
        syncerPeers := d.syncMgr.GossipSyncers()

        // We'll first attempt to filter out this new message for all peers
        // that have active gossip syncers active.
        for pub, syncer := range syncerPeers {
                log.Tracef("Sending messages batch to GossipSyncer(%s)", pub)
                syncer.FilterGossipMsgs(annBatch...)
        }

        for _, msgChunk := range annBatch {
                msgChunk := msgChunk

                // With the syncers taken care of, we'll merge the sender map
                // with the set of syncers, so we don't send out duplicate
                // messages.
                msgChunk.mergeSyncerMap(syncerPeers)

                err := d.cfg.Broadcast(msgChunk.senders, msgChunk.msg)
                if err != nil {
                        log.Errorf("Unable to send batch "+
                                "announcements: %v", err)
                        continue
                }
        }
}

// networkHandler is the primary goroutine that drives this service. The roles
// of this goroutine includes answering queries related to the state of the
// network, syncing up newly connected peers, and also periodically
// broadcasting our latest topology state to all connected peers.
//
// NOTE: This MUST be run as a goroutine.
func (d *AuthenticatedGossiper) networkHandler() {
        defer d.wg.Done()

        // Initialize empty deDupedAnnouncements to store announcement batch.
        announcements := deDupedAnnouncements{}
        announcements.Reset()

        d.cfg.RetransmitTicker.Resume()
        defer d.cfg.RetransmitTicker.Stop()

        trickleTimer := time.NewTicker(d.cfg.TrickleDelay)
        defer trickleTimer.Stop()

        // To start, we'll first check to see if there are any stale channel or
        // node announcements that we need to re-transmit.
        if err := d.retransmitStaleAnns(time.Now()); err != nil {
                log.Errorf("Unable to rebroadcast stale announcements: %v", err)
        }

        for {
                select {
                // A new policy update has arrived. We'll commit it to the
                // sub-systems below us, then craft, sign, and broadcast a new
                // ChannelUpdate for the set of affected clients.
                case policyUpdate := <-d.chanPolicyUpdates:
                        log.Tracef("Received channel %d policy update requests",
                                len(policyUpdate.edgesToUpdate))

                        // First, we'll now create new fully signed updates for
                        // the affected channels and also update the underlying
                        // graph with the new state.
                        newChanUpdates, err := d.processChanPolicyUpdate(
                                policyUpdate.edgesToUpdate,
                        )
                        policyUpdate.errChan <- err
                        if err != nil {
                                log.Errorf("Unable to craft policy updates: %v",
                                        err)
                                continue
                        }

                        // Finally, with the updates committed, we'll now add
                        // them to the announcement batch to be flushed at the
                        // start of the next epoch.
                        announcements.AddMsgs(newChanUpdates...)

                case announcement := <-d.networkMsgs:
                        log.Tracef("Received network message: "+
                                "peer=%v, msg=%s, is_remote=%v",
                                announcement.peer, announcement.msg.MsgType(),
                                announcement.isRemote)

                        switch announcement.msg.(type) {
                        // Channel announcement signatures are amongst the only
                        // messages that we'll process serially.
                        case *lnwire.AnnounceSignatures1:
                                emittedAnnouncements, _ := d.processNetworkAnnouncement(
                                        announcement,
                                )
                                log.Debugf("Processed network message %s, "+
                                        "returned len(announcements)=%v",
                                        announcement.msg.MsgType(),
                                        len(emittedAnnouncements))

                                if emittedAnnouncements != nil {
                                        announcements.AddMsgs(
                                                emittedAnnouncements...,
                                        )
                                }
                                continue
                        }

                        // If this message was recently rejected, then we won't
                        // attempt to re-process it.
                        if announcement.isRemote && d.isRecentlyRejectedMsg(
                                announcement.msg,
                                sourceToPub(announcement.source),
                        ) {

                                announcement.err <- fmt.Errorf("recently " +
                                        "rejected")
                                continue
                        }

                        // We'll set up any dependent, and wait until a free
                        // slot for this job opens up, this allow us to not
                        // have thousands of goroutines active.
                        annJobID, err := d.vb.InitJobDependencies(
                                announcement.msg,
                        )
                        if err != nil {
                                announcement.err <- err
                                continue
                        }

                        d.wg.Add(1)
                        go d.handleNetworkMessages(
                                announcement, &announcements, annJobID,
                        )

                // The trickle timer has ticked, which indicates we should
                // flush to the network the pending batch of new announcements
                // we've received since the last trickle tick.
                case <-trickleTimer.C:
                        // Emit the current batch of announcements from
                        // deDupedAnnouncements.
                        announcementBatch := announcements.Emit()

                        // If the current announcements batch is nil, then we
                        // have no further work here.
                        if announcementBatch.isEmpty() {
                                continue
                        }

                        // At this point, we have the set of local and remote
                        // announcements we want to send out. We'll do the
                        // batching as normal for both, but for local
                        // announcements, we'll blast them out w/o regard for
                        // our peer's policies so we ensure they propagate
                        // properly.
                        d.splitAndSendAnnBatch(announcementBatch)

                // The retransmission timer has ticked which indicates that we
                // should check if we need to prune or re-broadcast any of our
                // personal channels or node announcement. This addresses the
                // case of "zombie" channels and channel advertisements that
                // have been dropped, or not properly propagated through the
                // network.
                case tick := <-d.cfg.RetransmitTicker.Ticks():
                        if err := d.retransmitStaleAnns(tick); err != nil {
                                log.Errorf("unable to rebroadcast stale "+
                                        "announcements: %v", err)
                        }

                // The gossiper has been signalled to exit, to we exit our
                // main loop so the wait group can be decremented.
                case <-d.quit:
                        return
                }
        }
}

// handleNetworkMessages is responsible for waiting for dependencies for a
// given network message and processing the message. Once processed, it will
// signal its dependants and add the new announcements to the announce batch.
//
// NOTE: must be run as a goroutine.
func (d *AuthenticatedGossiper) handleNetworkMessages(nMsg *networkMsg,
        deDuped *deDupedAnnouncements, jobID JobID) {

        defer d.wg.Done()
        defer d.vb.CompleteJob()

        // We should only broadcast this message forward if it originated from
        // us or it wasn't received as part of our initial historical sync.
        shouldBroadcast := !nMsg.isRemote || d.syncMgr.IsGraphSynced()

        // If this message has an existing dependency, then we'll wait until
        // that has been fully validated before we proceed.
        err := d.vb.WaitForParents(jobID, nMsg.msg)
        if err != nil {
                log.Debugf("Validating network message %s got err: %v",
                        nMsg.msg.MsgType(), err)

                if errors.Is(err, ErrVBarrierShuttingDown) {
                        log.Warnf("unexpected error during validation "+
                                "barrier shutdown: %v", err)
                }
                nMsg.err <- err

                return
        }

        // Process the network announcement to determine if this is either a
        // new announcement from our PoV or an edges to a prior vertex/edge we
        // previously proceeded.
        newAnns, allow := d.processNetworkAnnouncement(nMsg)

        log.Tracef("Processed network message %s, returned "+
                "len(announcements)=%v, allowDependents=%v",
                nMsg.msg.MsgType(), len(newAnns), allow)

        // If this message had any dependencies, then we can now signal them to
        // continue.
        err = d.vb.SignalDependents(nMsg.msg, jobID)
        if err != nil {
                // Something is wrong if SignalDependents returns an error.
                log.Errorf("SignalDependents returned error for msg=%v with "+
                        "JobID=%v", spew.Sdump(nMsg.msg), jobID)

                nMsg.err <- err

                return
        }

        // If the announcement was accepted, then add the emitted announcements
        // to our announce batch to be broadcast once the trickle timer ticks
        // gain.
        if newAnns != nil && shouldBroadcast {
                // TODO(roasbeef): exclude peer that sent.
                deDuped.AddMsgs(newAnns...)
        } else if newAnns != nil {
                log.Trace("Skipping broadcast of announcements received " +
                        "during initial graph sync")
        }
}

// TODO(roasbeef): d/c peers that send updates not on our chain

// InitSyncState is called by outside sub-systems when a connection is
// established to a new peer that understands how to perform channel range
// queries. We'll allocate a new gossip syncer for it, and start any goroutines
// needed to handle new queries.
func (d *AuthenticatedGossiper) InitSyncState(syncPeer lnpeer.Peer) {
        d.syncMgr.InitSyncState(syncPeer)
}

// PruneSyncState is called by outside sub-systems once a peer that we were
// previously connected to has been disconnected. In this case we can stop the
// existing GossipSyncer assigned to the peer and free up resources.
func (d *AuthenticatedGossiper) PruneSyncState(peer route.Vertex) {
        d.syncMgr.PruneSyncState(peer)
}

// isRecentlyRejectedMsg returns true if we recently rejected a message, and
// false otherwise, This avoids expensive reprocessing of the message.
func (d *AuthenticatedGossiper) isRecentlyRejectedMsg(msg lnwire.Message,
        peerPub [33]byte) bool {

        var scid uint64
        switch m := msg.(type) {
        case *lnwire.ChannelUpdate1:
                scid = m.ShortChannelID.ToUint64()

        case *lnwire.ChannelAnnouncement1:
                scid = m.ShortChannelID.ToUint64()

        default:
                return false
        }

        _, err := d.recentRejects.Get(newRejectCacheKey(scid, peerPub))
        return err != cache.ErrElementNotFound
}

// retransmitStaleAnns examines all outgoing channels that the source node is
// known to maintain to check to see if any of them are "stale". A channel is
// stale iff, the last timestamp of its rebroadcast is older than the
// RebroadcastInterval. We also check if a refreshed node announcement should
// be resent.
func (d *AuthenticatedGossiper) retransmitStaleAnns(now time.Time) error {
        // Iterate over all of our channels and check if any of them fall
        // within the prune interval or re-broadcast interval.
        type updateTuple struct {
                info *models.ChannelEdgeInfo
                edge *models.ChannelEdgePolicy
        }

        var (
                havePublicChannels bool
                edgesToUpdate      []updateTuple
        )
        err := d.cfg.Graph.ForAllOutgoingChannels(func(
                info *models.ChannelEdgeInfo,
                edge *models.ChannelEdgePolicy) error {

                // If there's no auth proof attached to this edge, it means
                // that it is a private channel not meant to be announced to
                // the greater network, so avoid sending channel updates for
                // this channel to not leak its
                // existence.
                if info.AuthProof == nil {
                        log.Debugf("Skipping retransmission of channel "+
                                "without AuthProof: %v", info.ChannelID)
                        return nil
                }

                // We make a note that we have at least one public channel. We
                // use this to determine whether we should send a node
                // announcement below.
                havePublicChannels = true

                // If this edge has a ChannelUpdate that was created before the
                // introduction of the MaxHTLC field, then we'll update this
                // edge to propagate this information in the network.
                if !edge.MessageFlags.HasMaxHtlc() {
                        // We'll make sure we support the new max_htlc field if
                        // not already present.
                        edge.MessageFlags |= lnwire.ChanUpdateRequiredMaxHtlc
                        edge.MaxHTLC = lnwire.NewMSatFromSatoshis(info.Capacity)

                        edgesToUpdate = append(edgesToUpdate, updateTuple{
                                info: info,
                                edge: edge,
                        })
                        return nil
                }

                timeElapsed := now.Sub(edge.LastUpdate)

                // If it's been longer than RebroadcastInterval since we've
                // re-broadcasted the channel, add the channel to the set of
                // edges we need to update.
                if timeElapsed >= d.cfg.RebroadcastInterval {
                        edgesToUpdate = append(edgesToUpdate, updateTuple{
                                info: info,
                                edge: edge,
                        })
                }

                return nil
        })
        if err != nil && !errors.Is(err, graphdb.ErrGraphNoEdgesFound) {
                return fmt.Errorf("unable to retrieve outgoing channels: %w",
                        err)
        }

        var signedUpdates []lnwire.Message
        for _, chanToUpdate := range edgesToUpdate {
                // Re-sign and update the channel on disk and retrieve our
                // ChannelUpdate to broadcast.
                chanAnn, chanUpdate, err := d.updateChannel(
                        chanToUpdate.info, chanToUpdate.edge,
                )
                if err != nil {
                        return fmt.Errorf("unable to update channel: %w", err)
                }

                // If we have a valid announcement to transmit, then we'll send
                // that along with the update.
                if chanAnn != nil {
                        signedUpdates = append(signedUpdates, chanAnn)
                }

                signedUpdates = append(signedUpdates, chanUpdate)
        }

        // If we don't have any public channels, we return as we don't want to
        // broadcast anything that would reveal our existence.
        if !havePublicChannels {
                return nil
        }

        // We'll also check that our NodeAnnouncement is not too old.
        currentNodeAnn := d.cfg.FetchSelfAnnouncement()
        timestamp := time.Unix(int64(currentNodeAnn.Timestamp), 0)
        timeElapsed := now.Sub(timestamp)

        // If it's been a full day since we've re-broadcasted the
        // node announcement, refresh it and resend it.
        nodeAnnStr := ""
        if timeElapsed >= d.cfg.RebroadcastInterval {
                newNodeAnn, err := d.cfg.UpdateSelfAnnouncement()
                if err != nil {
                        return fmt.Errorf("unable to get refreshed node "+
                                "announcement: %v", err)
                }

                signedUpdates = append(signedUpdates, &newNodeAnn)
                nodeAnnStr = " and our refreshed node announcement"

                // Before broadcasting the refreshed node announcement, add it
                // to our own graph.
                if err := d.addNode(&newNodeAnn); err != nil {
                        log.Errorf("Unable to add refreshed node announcement "+
                                "to graph: %v", err)
                }
        }

        // If we don't have any updates to re-broadcast, then we'll exit
        // early.
        if len(signedUpdates) == 0 {
                return nil
        }

        log.Infof("Retransmitting %v outgoing channels%v",
                len(edgesToUpdate), nodeAnnStr)

        // With all the wire announcements properly crafted, we'll broadcast
        // our known outgoing channels to all our immediate peers.
        if err := d.cfg.Broadcast(nil, signedUpdates...); err != nil {
                return fmt.Errorf("unable to re-broadcast channels: %w", err)
        }

        return nil
}

// processChanPolicyUpdate generates a new set of channel updates for the
// provided list of edges and updates the backing ChannelGraphSource.
func (d *AuthenticatedGossiper) processChanPolicyUpdate(
        edgesToUpdate []EdgeWithInfo) ([]networkMsg, error) {

        var chanUpdates []networkMsg
        for _, edgeInfo := range edgesToUpdate {
                // Now that we've collected all the channels we need to update,
                // we'll re-sign and update the backing ChannelGraphSource, and
                // retrieve our ChannelUpdate to broadcast.
                _, chanUpdate, err := d.updateChannel(
                        edgeInfo.Info, edgeInfo.Edge,
                )
                if err != nil {
                        return nil, err
                }

                // We'll avoid broadcasting any updates for private channels to
                // avoid directly giving away their existence. Instead, we'll
                // send the update directly to the remote party.
                if edgeInfo.Info.AuthProof == nil {
                        // If AuthProof is nil and an alias was found for this
                        // ChannelID (meaning the option-scid-alias feature was
                        // negotiated), we'll replace the ShortChannelID in the
                        // update with the peer's alias. We do this after
                        // updateChannel so that the alias isn't persisted to
                        // the database.
                        chanID := lnwire.NewChanIDFromOutPoint(
                                edgeInfo.Info.ChannelPoint,
                        )

                        var defaultAlias lnwire.ShortChannelID
                        foundAlias, _ := d.cfg.GetAlias(chanID)
                        if foundAlias != defaultAlias {
                                chanUpdate.ShortChannelID = foundAlias

                                sig, err := d.cfg.SignAliasUpdate(chanUpdate)
                                if err != nil {
                                        log.Errorf("Unable to sign alias "+
                                                "update: %v", err)
                                        continue
                                }

                                lnSig, err := lnwire.NewSigFromSignature(sig)
                                if err != nil {
                                        log.Errorf("Unable to create sig: %v",
                                                err)
                                        continue
                                }

                                chanUpdate.Signature = lnSig
                        }

                        remotePubKey := remotePubFromChanInfo(
                                edgeInfo.Info, chanUpdate.ChannelFlags,
                        )
                        err := d.reliableSender.sendMessage(
                                chanUpdate, remotePubKey,
                        )
                        if err != nil {
                                log.Errorf("Unable to reliably send %v for "+
                                        "channel=%v to peer=%x: %v",
                                        chanUpdate.MsgType(),
                                        chanUpdate.ShortChannelID,
                                        remotePubKey, err)
                        }
                        continue
                }

                // We set ourselves as the source of this message to indicate
                // that we shouldn't skip any peers when sending this message.
                chanUpdates = append(chanUpdates, networkMsg{
                        source:   d.selfKey,
                        isRemote: false,
                        msg:      chanUpdate,
                })
        }

        return chanUpdates, nil
}

// remotePubFromChanInfo returns the public key of the remote peer given a
// ChannelEdgeInfo that describe a channel we have with them.
func remotePubFromChanInfo(chanInfo *models.ChannelEdgeInfo,
        chanFlags lnwire.ChanUpdateChanFlags) [33]byte {

        var remotePubKey [33]byte
        switch {
        case chanFlags&lnwire.ChanUpdateDirection == 0:
                remotePubKey = chanInfo.NodeKey2Bytes
        case chanFlags&lnwire.ChanUpdateDirection == 1:
                remotePubKey = chanInfo.NodeKey1Bytes
        }

        return remotePubKey
}

// processRejectedEdge examines a rejected edge to see if we can extract any
// new announcements from it.  An edge will get rejected if we already added
// the same edge without AuthProof to the graph. If the received announcement
// contains a proof, we can add this proof to our edge.  We can end up in this
// situation in the case where we create a channel, but for some reason fail
// to receive the remote peer's proof, while the remote peer is able to fully
// assemble the proof and craft the ChannelAnnouncement.
func (d *AuthenticatedGossiper) processRejectedEdge(
        chanAnnMsg *lnwire.ChannelAnnouncement1,
        proof *models.ChannelAuthProof) ([]networkMsg, error) {

        // First, we'll fetch the state of the channel as we know if from the
        // database.
        chanInfo, e1, e2, err := d.cfg.Graph.GetChannelByID(
                chanAnnMsg.ShortChannelID,
        )
        if err != nil {
                return nil, err
        }

        // The edge is in the graph, and has a proof attached, then we'll just
        // reject it as normal.
        if chanInfo.AuthProof != nil {
                return nil, nil
        }

        // Otherwise, this means that the edge is within the graph, but it
        // doesn't yet have a proper proof attached. If we did not receive
        // the proof such that we now can add it, there's nothing more we
        // can do.
        if proof == nil {
                return nil, nil
        }

        // We'll then create then validate the new fully assembled
        // announcement.
        chanAnn, e1Ann, e2Ann, err := netann.CreateChanAnnouncement(
                proof, chanInfo, e1, e2,
        )
        if err != nil {
                return nil, err
        }
        err = netann.ValidateChannelAnn(chanAnn, d.fetchPKScript)
        if err != nil {
                err := fmt.Errorf("assembled channel announcement proof "+
                        "for shortChanID=%v isn't valid: %v",
                        chanAnnMsg.ShortChannelID, err)
                log.Error(err)
                return nil, err
        }

        // If everything checks out, then we'll add the fully assembled proof
        // to the database.
        err = d.cfg.Graph.AddProof(chanAnnMsg.ShortChannelID, proof)
        if err != nil {
                err := fmt.Errorf("unable add proof to shortChanID=%v: %w",
                        chanAnnMsg.ShortChannelID, err)
                log.Error(err)
                return nil, err
        }

        // As we now have a complete channel announcement for this channel,
        // we'll construct the announcement so they can be broadcast out to all
        // our peers.
        announcements := make([]networkMsg, 0, 3)
        announcements = append(announcements, networkMsg{
                source: d.selfKey,
                msg:    chanAnn,
        })
        if e1Ann != nil {
                announcements = append(announcements, networkMsg{
                        source: d.selfKey,
                        msg:    e1Ann,
                })
        }
        if e2Ann != nil {
                announcements = append(announcements, networkMsg{
                        source: d.selfKey,
                        msg:    e2Ann,
                })

        }

        return announcements, nil
}

// fetchPKScript fetches the output script for the given SCID.
func (d *AuthenticatedGossiper) fetchPKScript(chanID *lnwire.ShortChannelID) (
        []byte, error) {

        return lnwallet.FetchPKScriptWithQuit(d.cfg.ChainIO, chanID, d.quit)
}

// addNode processes the given node announcement, and adds it to our channel
// graph.
func (d *AuthenticatedGossiper) addNode(msg *lnwire.NodeAnnouncement,
        op ...batch.SchedulerOption) error {

        if err := netann.ValidateNodeAnn(msg); err != nil {
                return fmt.Errorf("unable to validate node announcement: %w",
                        err)
        }

        return d.cfg.Graph.AddNode(models.NodeFromWireAnnouncement(msg), op...)
}

// isPremature decides whether a given network message has a block height+delta
// value specified in the future. If so, the message will be added to the
// future message map and be processed when the block height as reached.
//
// NOTE: must be used inside a lock.
func (d *AuthenticatedGossiper) isPremature(chanID lnwire.ShortChannelID,
        delta uint32, msg *networkMsg) bool {

        // The channel is already confirmed at chanID.BlockHeight so we minus
        // one block. For instance, if the required confirmation for this
        // channel announcement is 6, we then only need to wait for 5 more
        // blocks once the funding tx is confirmed.
        if delta > 0 {
                delta--
        }

        msgHeight := chanID.BlockHeight + delta

        // The message height is smaller or equal to our best known height,
        // thus the message is mature.
        if msgHeight <= d.bestHeight {
                return false
        }

        // Add the premature message to our future messages which will be
        // resent once the block height has reached.
        //
        // Copy the networkMsgs since the old message's err chan will be
        // consumed.
        copied := &networkMsg{
                peer:              msg.peer,
                source:            msg.source,
                msg:               msg.msg,
                optionalMsgFields: msg.optionalMsgFields,
                isRemote:          msg.isRemote,
                err:               make(chan error, 1),
        }

        // Create the cached message.
        cachedMsg := &cachedFutureMsg{
                msg:    copied,
                height: msgHeight,
        }

        // Increment the msg ID and add it to the cache.
        nextMsgID := d.futureMsgs.nextMsgID()
        _, err := d.futureMsgs.Put(nextMsgID, cachedMsg)
        if err != nil {
                log.Errorf("Adding future message got error: %v", err)
        }

        log.Debugf("Network message: %v added to future messages for "+
                "msgHeight=%d, bestHeight=%d", msg.msg.MsgType(),
                msgHeight, d.bestHeight)

        return true
}

// processNetworkAnnouncement processes a new network relate authenticated
// channel or node announcement or announcements proofs. If the announcement
// didn't affect the internal state due to either being out of date, invalid,
// or redundant, then nil is returned. Otherwise, the set of announcements will
// be returned which should be broadcasted to the rest of the network. The
// boolean returned indicates whether any dependents of the announcement should
// attempt to be processed as well.
func (d *AuthenticatedGossiper) processNetworkAnnouncement(
        nMsg *networkMsg) ([]networkMsg, bool) {

        // If this is a remote update, we set the scheduler option to lazily
        // add it to the graph.
        var schedulerOp []batch.SchedulerOption
        if nMsg.isRemote {
                schedulerOp = append(schedulerOp, batch.LazyAdd())
        }

        switch msg := nMsg.msg.(type) {
        // A new node announcement has arrived which either presents new
        // information about a node in one of the channels we know about, or a
        // updating previously advertised information.
        case *lnwire.NodeAnnouncement:
                return d.handleNodeAnnouncement(nMsg, msg, schedulerOp)

        // A new channel announcement has arrived, this indicates the
        // *creation* of a new channel within the network. This only advertises
        // the existence of a channel and not yet the routing policies in
        // either direction of the channel.
        case *lnwire.ChannelAnnouncement1:
                return d.handleChanAnnouncement(nMsg, msg, schedulerOp...)

        // A new authenticated channel edge update has arrived. This indicates
        // that the directional information for an already known channel has
        // been updated.
        case *lnwire.ChannelUpdate1:
                return d.handleChanUpdate(nMsg, msg, schedulerOp)

        // A new signature announcement has been received. This indicates
        // willingness of nodes involved in the funding of a channel to
        // announce this new channel to the rest of the world.
        case *lnwire.AnnounceSignatures1:
                return d.handleAnnSig(nMsg, msg)

        default:
                err := errors.New("wrong type of the announcement")
                nMsg.err <- err
                return nil, false
        }
}

// processZombieUpdate determines whether the provided channel update should
// resurrect a given zombie edge.
//
// NOTE: only the NodeKey1Bytes and NodeKey2Bytes members of the ChannelEdgeInfo
// should be inspected.
func (d *AuthenticatedGossiper) processZombieUpdate(
        chanInfo *models.ChannelEdgeInfo, scid lnwire.ShortChannelID,
        msg *lnwire.ChannelUpdate1) error {

        // The least-significant bit in the flag on the channel update tells us
        // which edge is being updated.
        isNode1 := msg.ChannelFlags&lnwire.ChanUpdateDirection == 0

        // Since we've deemed the update as not stale above, before marking it
        // live, we'll make sure it has been signed by the correct party. If we
        // have both pubkeys, either party can resurrect the channel. If we've
        // already marked this with the stricter, single-sided resurrection we
        // will only have the pubkey of the node with the oldest timestamp.
        var pubKey *btcec.PublicKey
        switch {
        case isNode1 && chanInfo.NodeKey1Bytes != emptyPubkey:
                pubKey, _ = chanInfo.NodeKey1()
        case !isNode1 && chanInfo.NodeKey2Bytes != emptyPubkey:
                pubKey, _ = chanInfo.NodeKey2()
        }
        if pubKey == nil {
                return fmt.Errorf("incorrect pubkey to resurrect zombie "+
                        "with chan_id=%v", msg.ShortChannelID)
        }

        err := netann.VerifyChannelUpdateSignature(msg, pubKey)
        if err != nil {
                return fmt.Errorf("unable to verify channel "+
                        "update signature: %v", err)
        }

        // With the signature valid, we'll proceed to mark the
        // edge as live and wait for the channel announcement to
        // come through again.
        err = d.cfg.Graph.MarkEdgeLive(scid)
        switch {
        case errors.Is(err, graphdb.ErrZombieEdgeNotFound):
                log.Errorf("edge with chan_id=%v was not found in the "+
                        "zombie index: %v", err)

                return nil

        case err != nil:
                return fmt.Errorf("unable to remove edge with "+
                        "chan_id=%v from zombie index: %v",
                        msg.ShortChannelID, err)

        default:
        }

        log.Debugf("Removed edge with chan_id=%v from zombie "+
                "index", msg.ShortChannelID)

        return nil
}

// fetchNodeAnn fetches the latest signed node announcement from our point of
// view for the node with the given public key.
func (d *AuthenticatedGossiper) fetchNodeAnn(
        pubKey [33]byte) (*lnwire.NodeAnnouncement, error) {

        node, err := d.cfg.Graph.FetchLightningNode(pubKey)
        if err != nil {
                return nil, err
        }

        return node.NodeAnnouncement(true)
}

// isMsgStale determines whether a message retrieved from the backing
// MessageStore is seen as stale by the current graph.
func (d *AuthenticatedGossiper) isMsgStale(msg lnwire.Message) bool {
        switch msg := msg.(type) {
        case *lnwire.AnnounceSignatures1:
                chanInfo, _, _, err := d.cfg.Graph.GetChannelByID(
                        msg.ShortChannelID,
                )

                // If the channel cannot be found, it is most likely a leftover
                // message for a channel that was closed, so we can consider it
                // stale.
                if errors.Is(err, graphdb.ErrEdgeNotFound) {
                        return true
                }
                if err != nil {
                        log.Debugf("Unable to retrieve channel=%v from graph: "+
                                "%v", chanInfo.ChannelID, err)
                        return false
                }

                // If the proof exists in the graph, then we have successfully
                // received the remote proof and assembled the full proof, so we
                // can safely delete the local proof from the database.
                return chanInfo.AuthProof != nil

        case *lnwire.ChannelUpdate1:
                _, p1, p2, err := d.cfg.Graph.GetChannelByID(msg.ShortChannelID)

                // If the channel cannot be found, it is most likely a leftover
                // message for a channel that was closed, so we can consider it
                // stale.
                if errors.Is(err, graphdb.ErrEdgeNotFound) {
                        return true
                }
                if err != nil {
                        log.Debugf("Unable to retrieve channel=%v from graph: "+
                                "%v", msg.ShortChannelID, err)
                        return false
                }

                // Otherwise, we'll retrieve the correct policy that we
                // currently have stored within our graph to check if this
                // message is stale by comparing its timestamp.
                var p *models.ChannelEdgePolicy
                if msg.ChannelFlags&lnwire.ChanUpdateDirection == 0 {
                        p = p1
                } else {
                        p = p2
                }

                // If the policy is still unknown, then we can consider this
                // policy fresh.
                if p == nil {
                        return false
                }

                timestamp := time.Unix(int64(msg.Timestamp), 0)
                return p.LastUpdate.After(timestamp)

        default:
                // We'll make sure to not mark any unsupported messages as stale
                // to ensure they are not removed.
                return false
        }
}

// updateChannel creates a new fully signed update for the channel, and updates
// the underlying graph with the new state.
func (d *AuthenticatedGossiper) updateChannel(info *models.ChannelEdgeInfo,
        edge *models.ChannelEdgePolicy) (*lnwire.ChannelAnnouncement1,
        *lnwire.ChannelUpdate1, error) {

        // Parse the unsigned edge into a channel update.
        chanUpdate := netann.UnsignedChannelUpdateFromEdge(info, edge)

        // We'll generate a new signature over a digest of the channel
        // announcement itself and update the timestamp to ensure it propagate.
        err := netann.SignChannelUpdate(
                d.cfg.AnnSigner, d.selfKeyLoc, chanUpdate,
                netann.ChanUpdSetTimestamp,
        )
        if err != nil {
                return nil, nil, err
        }

        // Next, we'll set the new signature in place, and update the reference
        // in the backing slice.
        edge.LastUpdate = time.Unix(int64(chanUpdate.Timestamp), 0)
        edge.SigBytes = chanUpdate.Signature.ToSignatureBytes()

        // To ensure that our signature is valid, we'll verify it ourself
        // before committing it to the slice returned.
        err = netann.ValidateChannelUpdateAnn(
                d.selfKey, info.Capacity, chanUpdate,
        )
        if err != nil {
                return nil, nil, fmt.Errorf("generated invalid channel "+
                        "update sig: %v", err)
        }

        // Finally, we'll write the new edge policy to disk.
        if err := d.cfg.Graph.UpdateEdge(edge); err != nil {
                return nil, nil, err
        }

        // We'll also create the original channel announcement so the two can
        // be broadcast along side each other (if necessary), but only if we
        // have a full channel announcement for this channel.
        var chanAnn *lnwire.ChannelAnnouncement1
        if info.AuthProof != nil {
                chanID := lnwire.NewShortChanIDFromInt(info.ChannelID)
                chanAnn = &lnwire.ChannelAnnouncement1{
                        ShortChannelID:  chanID,
                        NodeID1:         info.NodeKey1Bytes,
                        NodeID2:         info.NodeKey2Bytes,
                        ChainHash:       info.ChainHash,
                        BitcoinKey1:     info.BitcoinKey1Bytes,
                        Features:        lnwire.NewRawFeatureVector(),
                        BitcoinKey2:     info.BitcoinKey2Bytes,
                        ExtraOpaqueData: info.ExtraOpaqueData,
                }
                chanAnn.NodeSig1, err = lnwire.NewSigFromECDSARawSignature(
                        info.AuthProof.NodeSig1Bytes,
                )
                if err != nil {
                        return nil, nil, err
                }
                chanAnn.NodeSig2, err = lnwire.NewSigFromECDSARawSignature(
                        info.AuthProof.NodeSig2Bytes,
                )
                if err != nil {
                        return nil, nil, err
                }
                chanAnn.BitcoinSig1, err = lnwire.NewSigFromECDSARawSignature(
                        info.AuthProof.BitcoinSig1Bytes,
                )
                if err != nil {
                        return nil, nil, err
                }
                chanAnn.BitcoinSig2, err = lnwire.NewSigFromECDSARawSignature(
                        info.AuthProof.BitcoinSig2Bytes,
                )
                if err != nil {
                        return nil, nil, err
                }
        }

        return chanAnn, chanUpdate, err
}

// SyncManager returns the gossiper's SyncManager instance.
func (d *AuthenticatedGossiper) SyncManager() *SyncManager {
        return d.syncMgr
}

// IsKeepAliveUpdate determines whether this channel update is considered a
// keep-alive update based on the previous channel update processed for the same
// direction.
func IsKeepAliveUpdate(update *lnwire.ChannelUpdate1,
        prev *models.ChannelEdgePolicy) bool {

        // Both updates should be from the same direction.
        if update.ChannelFlags&lnwire.ChanUpdateDirection !=
                prev.ChannelFlags&lnwire.ChanUpdateDirection {

                return false
        }

        // The timestamp should always increase for a keep-alive update.
        timestamp := time.Unix(int64(update.Timestamp), 0)
        if !timestamp.After(prev.LastUpdate) {
                return false
        }

        // None of the remaining fields should change for a keep-alive update.
        if update.ChannelFlags.IsDisabled() != prev.ChannelFlags.IsDisabled() {
                return false
        }
        if lnwire.MilliSatoshi(update.BaseFee) != prev.FeeBaseMSat {
                return false
        }
        if lnwire.MilliSatoshi(update.FeeRate) != prev.FeeProportionalMillionths {
                return false
        }
        if update.TimeLockDelta != prev.TimeLockDelta {
                return false
        }
        if update.HtlcMinimumMsat != prev.MinHTLC {
                return false
        }
        if update.MessageFlags.HasMaxHtlc() && !prev.MessageFlags.HasMaxHtlc() {
                return false
        }
        if update.HtlcMaximumMsat != prev.MaxHTLC {
                return false
        }
        if !bytes.Equal(update.ExtraOpaqueData, prev.ExtraOpaqueData) {
                return false
        }
        return true
}

// latestHeight returns the gossiper's latest height known of the chain.
func (d *AuthenticatedGossiper) latestHeight() uint32 {
        d.Lock()
        defer d.Unlock()
        return d.bestHeight
}

// handleNodeAnnouncement processes a new node announcement.
func (d *AuthenticatedGossiper) handleNodeAnnouncement(nMsg *networkMsg,
        nodeAnn *lnwire.NodeAnnouncement,
        ops []batch.SchedulerOption) ([]networkMsg, bool) {

        timestamp := time.Unix(int64(nodeAnn.Timestamp), 0)

        log.Debugf("Processing NodeAnnouncement: peer=%v, timestamp=%v, "+
                "node=%x, source=%x", nMsg.peer, timestamp, nodeAnn.NodeID,
                nMsg.source.SerializeCompressed())

        // We'll quickly ask the router if it already has a newer update for
        // this node so we can skip validating signatures if not required.
        if d.cfg.Graph.IsStaleNode(nodeAnn.NodeID, timestamp) {
                log.Debugf("Skipped processing stale node: %x", nodeAnn.NodeID)
                nMsg.err <- nil
                return nil, true
        }

        if err := d.addNode(nodeAnn, ops...); err != nil {
                log.Debugf("Adding node: %x got error: %v", nodeAnn.NodeID,
                        err)

                if !graph.IsError(
                        err,
                        graph.ErrOutdated,
                        graph.ErrIgnored,
                ) {

                        log.Error(err)
                }

                nMsg.err <- err
                return nil, false
        }

        // In order to ensure we don't leak unadvertised nodes, we'll make a
        // quick check to ensure this node intends to publicly advertise itself
        // to the network.
        isPublic, err := d.cfg.Graph.IsPublicNode(nodeAnn.NodeID)
        if err != nil {
                log.Errorf("Unable to determine if node %x is advertised: %v",
                        nodeAnn.NodeID, err)
                nMsg.err <- err
                return nil, false
        }

        var announcements []networkMsg

        // If it does, we'll add their announcement to our batch so that it can
        // be broadcast to the rest of our peers.
        if isPublic {
                announcements = append(announcements, networkMsg{
                        peer:     nMsg.peer,
                        isRemote: nMsg.isRemote,
                        source:   nMsg.source,
                        msg:      nodeAnn,
                })
        } else {
                log.Tracef("Skipping broadcasting node announcement for %x "+
                        "due to being unadvertised", nodeAnn.NodeID)
        }

        nMsg.err <- nil
        // TODO(roasbeef): get rid of the above

        log.Debugf("Processed NodeAnnouncement: peer=%v, timestamp=%v, "+
                "node=%x, source=%x", nMsg.peer, timestamp, nodeAnn.NodeID,
                nMsg.source.SerializeCompressed())

        return announcements, true
}

// handleChanAnnouncement processes a new channel announcement.
func (d *AuthenticatedGossiper) handleChanAnnouncement(nMsg *networkMsg,
        ann *lnwire.ChannelAnnouncement1,
        ops ...batch.SchedulerOption) ([]networkMsg, bool) {

        scid := ann.ShortChannelID

        log.Debugf("Processing ChannelAnnouncement1: peer=%v, short_chan_id=%v",
                nMsg.peer, scid.ToUint64())

        // We'll ignore any channel announcements that target any chain other
        // than the set of chains we know of.
        if !bytes.Equal(ann.ChainHash[:], d.cfg.ChainHash[:]) {
                err := fmt.Errorf("ignoring ChannelAnnouncement1 from chain=%v"+
                        ", gossiper on chain=%v", ann.ChainHash,
                        d.cfg.ChainHash)
                log.Errorf(err.Error())

                key := newRejectCacheKey(
                        scid.ToUint64(),
                        sourceToPub(nMsg.source),
                )
                _, _ = d.recentRejects.Put(key, &cachedReject{})

                nMsg.err <- err
                return nil, false
        }

        // If this is a remote ChannelAnnouncement with an alias SCID, we'll
        // reject the announcement. Since the router accepts alias SCIDs,
        // not erroring out would be a DoS vector.
        if nMsg.isRemote && d.cfg.IsAlias(scid) {
                err := fmt.Errorf("ignoring remote alias channel=%v", scid)
                log.Errorf(err.Error())

                key := newRejectCacheKey(
                        scid.ToUint64(),
                        sourceToPub(nMsg.source),
                )
                _, _ = d.recentRejects.Put(key, &cachedReject{})

                nMsg.err <- err
                return nil, false
        }

        // If the advertised inclusionary block is beyond our knowledge of the
        // chain tip, then we'll ignore it for now.
        d.Lock()
        if nMsg.isRemote && d.isPremature(scid, 0, nMsg) {
                log.Warnf("Announcement for chan_id=(%v), is premature: "+
                        "advertises height %v, only height %v is known",
                        scid.ToUint64(), scid.BlockHeight, d.bestHeight)
                d.Unlock()
                nMsg.err <- nil
                return nil, false
        }
        d.Unlock()

        // At this point, we'll now ask the router if this is a zombie/known
        // edge. If so we can skip all the processing below.
        if d.cfg.Graph.IsKnownEdge(scid) {
                nMsg.err <- nil
                return nil, true
        }

        // Check if the channel is already closed in which case we can ignore
        // it.
        closed, err := d.cfg.ScidCloser.IsClosedScid(scid)
        if err != nil {
                log.Errorf("failed to check if scid %v is closed: %v", scid,
                        err)
                nMsg.err <- err

                return nil, false
        }

        if closed {
                err = fmt.Errorf("ignoring closed channel %v", scid)
                log.Error(err)

                // If this is an announcement from us, we'll just ignore it.
                if !nMsg.isRemote {
                        nMsg.err <- err
                        return nil, false
                }

                // Increment the peer's ban score if they are sending closed
                // channel announcements.
                d.banman.incrementBanScore(nMsg.peer.PubKey())

                // If the peer is banned and not a channel peer, we'll
                // disconnect them.
                shouldDc, dcErr := d.ShouldDisconnect(nMsg.peer.IdentityKey())
                if dcErr != nil {
                        log.Errorf("failed to check if we should disconnect "+
                                "peer: %v", dcErr)
                        nMsg.err <- dcErr

                        return nil, false
                }

                if shouldDc {
                        nMsg.peer.Disconnect(ErrPeerBanned)
                }

                nMsg.err <- err

                return nil, false
        }

        // If this is a remote channel announcement, then we'll validate all
        // the signatures within the proof as it should be well formed.
        var proof *models.ChannelAuthProof
        if nMsg.isRemote {
                err := netann.ValidateChannelAnn(ann, d.fetchPKScript)
                if err != nil {
                        err := fmt.Errorf("unable to validate announcement: "+
                                "%v", err)

                        key := newRejectCacheKey(
                                scid.ToUint64(),
                                sourceToPub(nMsg.source),
                        )
                        _, _ = d.recentRejects.Put(key, &cachedReject{})

                        log.Error(err)
                        nMsg.err <- err
                        return nil, false
                }

                // If the proof checks out, then we'll save the proof itself to
                // the database so we can fetch it later when gossiping with
                // other nodes.
                proof = &models.ChannelAuthProof{
                        NodeSig1Bytes:    ann.NodeSig1.ToSignatureBytes(),
                        NodeSig2Bytes:    ann.NodeSig2.ToSignatureBytes(),
                        BitcoinSig1Bytes: ann.BitcoinSig1.ToSignatureBytes(),
                        BitcoinSig2Bytes: ann.BitcoinSig2.ToSignatureBytes(),
                }
        }

        // With the proof validated (if necessary), we can now store it within
        // the database for our path finding and syncing needs.
        var featureBuf bytes.Buffer
        if err := ann.Features.Encode(&featureBuf); err != nil {
                log.Errorf("unable to encode features: %v", err)
                nMsg.err <- err
                return nil, false
        }

        edge := &models.ChannelEdgeInfo{
                ChannelID:        scid.ToUint64(),
                ChainHash:        ann.ChainHash,
                NodeKey1Bytes:    ann.NodeID1,
                NodeKey2Bytes:    ann.NodeID2,
                BitcoinKey1Bytes: ann.BitcoinKey1,
                BitcoinKey2Bytes: ann.BitcoinKey2,
                AuthProof:        proof,
                Features:         featureBuf.Bytes(),
                ExtraOpaqueData:  ann.ExtraOpaqueData,
        }

        // If there were any optional message fields provided, we'll include
        // them in its serialized disk representation now.
        var tapscriptRoot fn.Option[chainhash.Hash]
        if nMsg.optionalMsgFields != nil {
                if nMsg.optionalMsgFields.capacity != nil {
                        edge.Capacity = *nMsg.optionalMsgFields.capacity
                }
                if nMsg.optionalMsgFields.channelPoint != nil {
                        cp := *nMsg.optionalMsgFields.channelPoint
                        edge.ChannelPoint = cp
                }

                // Optional tapscript root for custom channels.
                tapscriptRoot = nMsg.optionalMsgFields.tapscriptRoot
        }

        // Before we start validation or add the edge to the database, we obtain
        // the mutex for this channel ID. We do this to ensure no other
        // goroutine has read the database and is now making decisions based on
        // this DB state, before it writes to the DB. It also ensures that we
        // don't perform the expensive validation check on the same channel
        // announcement at the same time.
        d.channelMtx.Lock(scid.ToUint64())

        // If AssumeChannelValid is present, then we are unable to perform any
        // of the expensive checks below, so we'll short-circuit our path
        // straight to adding the edge to our graph. If the passed
        // ShortChannelID is an alias, then we'll skip validation as it will
        // not map to a legitimate tx. This is not a DoS vector as only we can
        // add an alias ChannelAnnouncement from the gossiper.
        if !(d.cfg.AssumeChannelValid || d.cfg.IsAlias(scid)) { //nolint:nestif
                op, capacity, script, err := d.validateFundingTransaction(
                        ann, tapscriptRoot,
                )
                if err != nil {
                        defer d.channelMtx.Unlock(scid.ToUint64())

                        switch {
                        case errors.Is(err, ErrNoFundingTransaction),
                                errors.Is(err, ErrInvalidFundingOutput):

                                key := newRejectCacheKey(
                                        scid.ToUint64(),
                                        sourceToPub(nMsg.source),
                                )
                                _, _ = d.recentRejects.Put(
                                        key, &cachedReject{},
                                )

                                // Increment the peer's ban score. We check
                                // isRemote so we don't actually ban the peer in
                                // case of a local bug.
                                if nMsg.isRemote {
                                        d.banman.incrementBanScore(
                                                nMsg.peer.PubKey(),
                                        )
                                }

                        case errors.Is(err, ErrChannelSpent):
                                key := newRejectCacheKey(
                                        scid.ToUint64(),
                                        sourceToPub(nMsg.source),
                                )
                                _, _ = d.recentRejects.Put(key, &cachedReject{})

                                // Since this channel has already been closed,
                                // we'll add it to the graph's closed channel
                                // index such that we won't attempt to do
                                // expensive validation checks on it again.
                                // TODO: Populate the ScidCloser by using closed
                                // channel notifications.
                                dbErr := d.cfg.ScidCloser.PutClosedScid(scid)
                                if dbErr != nil {
                                        log.Errorf("failed to mark scid(%v) "+
                                                "as closed: %v", scid, dbErr)

                                        nMsg.err <- dbErr

                                        return nil, false
                                }

                                // Increment the peer's ban score. We check
                                // isRemote so we don't accidentally ban
                                // ourselves in case of a bug.
                                if nMsg.isRemote {
                                        d.banman.incrementBanScore(
                                                nMsg.peer.PubKey(),
                                        )
                                }

                        default:
                                // Otherwise, this is just a regular rejected
                                // edge.
                                key := newRejectCacheKey(
                                        scid.ToUint64(),
                                        sourceToPub(nMsg.source),
                                )
                                _, _ = d.recentRejects.Put(key, &cachedReject{})
                        }

                        if !nMsg.isRemote {
                                log.Errorf("failed to add edge for local "+
                                        "channel: %v", err)
                                nMsg.err <- err

                                return nil, false
                        }

                        shouldDc, dcErr := d.ShouldDisconnect(
                                nMsg.peer.IdentityKey(),
                        )
                        if dcErr != nil {
                                log.Errorf("failed to check if we should "+
                                        "disconnect peer: %v", dcErr)
                                nMsg.err <- dcErr

                                return nil, false
                        }

                        if shouldDc {
                                nMsg.peer.Disconnect(ErrPeerBanned)
                        }

                        nMsg.err <- err

                        return nil, false
                }

                edge.FundingScript = fn.Some(script)

                // TODO(roasbeef): this is a hack, needs to be removed after
                //  commitment fees are dynamic.
                edge.Capacity = capacity
                edge.ChannelPoint = op
        }

        log.Debugf("Adding edge for short_chan_id: %v", scid.ToUint64())

        // We will add the edge to the channel router. If the nodes present in
        // this channel are not present in the database, a partial node will be
        // added to represent each node while we wait for a node announcement.
        err = d.cfg.Graph.AddEdge(edge, ops...)
        if err != nil {
                log.Debugf("Graph rejected edge for short_chan_id(%v): %v",
                        scid.ToUint64(), err)

                defer d.channelMtx.Unlock(scid.ToUint64())

                // If the edge was rejected due to already being known, then it
                // may be the case that this new message has a fresh channel
                // proof, so we'll check.
                if graph.IsError(err, graph.ErrIgnored) {
                        // Attempt to process the rejected message to see if we
                        // get any new announcements.
                        anns, rErr := d.processRejectedEdge(ann, proof)
                        if rErr != nil {
                                key := newRejectCacheKey(
                                        scid.ToUint64(),
                                        sourceToPub(nMsg.source),
                                )
                                cr := &cachedReject{}
                                _, _ = d.recentRejects.Put(key, cr)

                                nMsg.err <- rErr

                                return nil, false
                        }

                        log.Debugf("Extracted %v announcements from rejected "+
                                "msgs", len(anns))

                        // If while processing this rejected edge, we realized
                        // there's a set of announcements we could extract,
                        // then we'll return those directly.
                        //
                        // NOTE: since this is an ErrIgnored, we can return
                        // true here to signal "allow" to its dependants.
                        nMsg.err <- nil

                        return anns, true
                }

                // Otherwise, this is just a regular rejected edge.
                key := newRejectCacheKey(
                        scid.ToUint64(),
                        sourceToPub(nMsg.source),
                )
                _, _ = d.recentRejects.Put(key, &cachedReject{})

                if !nMsg.isRemote {
                        log.Errorf("failed to add edge for local channel: %v",
                                err)
                        nMsg.err <- err

                        return nil, false
                }

                shouldDc, dcErr := d.ShouldDisconnect(nMsg.peer.IdentityKey())
                if dcErr != nil {
                        log.Errorf("failed to check if we should disconnect "+
                                "peer: %v", dcErr)
                        nMsg.err <- dcErr

                        return nil, false
                }

                if shouldDc {
                        nMsg.peer.Disconnect(ErrPeerBanned)
                }

                nMsg.err <- err

                return nil, false
        }

        // If err is nil, release the lock immediately.
        d.channelMtx.Unlock(scid.ToUint64())

        log.Debugf("Finish adding edge for short_chan_id: %v", scid.ToUint64())

        // If we earlier received any ChannelUpdates for this channel, we can
        // now process them, as the channel is added to the graph.
        var channelUpdates []*processedNetworkMsg

        earlyChanUpdates, err := d.prematureChannelUpdates.Get(scid.ToUint64())
        if err == nil {
                // There was actually an entry in the map, so we'll accumulate
                // it. We don't worry about deletion, since it'll eventually
                // fall out anyway.
                chanMsgs := earlyChanUpdates
                channelUpdates = append(channelUpdates, chanMsgs.msgs...)
        }

        // Launch a new goroutine to handle each ChannelUpdate, this is to
        // ensure we don't block here, as we can handle only one announcement
        // at a time.
        for _, cu := range channelUpdates {
                // Skip if already processed.
                if cu.processed {
                        continue
                }

                // Mark the ChannelUpdate as processed. This ensures that a
                // subsequent announcement in the option-scid-alias case does
                // not re-use an old ChannelUpdate.
                cu.processed = true

                d.wg.Add(1)
                go func(updMsg *networkMsg) {
                        defer d.wg.Done()

                        switch msg := updMsg.msg.(type) {
                        // Reprocess the message, making sure we return an
                        // error to the original caller in case the gossiper
                        // shuts down.
                        case *lnwire.ChannelUpdate1:
                                log.Debugf("Reprocessing ChannelUpdate for "+
                                        "shortChanID=%v", scid.ToUint64())

                                select {
                                case d.networkMsgs <- updMsg:
                                case <-d.quit:
                                        updMsg.err <- ErrGossiperShuttingDown
                                }

                        // We don't expect any other message type than
                        // ChannelUpdate to be in this cache.
                        default:
                                log.Errorf("Unsupported message type found "+
                                        "among ChannelUpdates: %T", msg)
                        }
                }(cu.msg)
        }

        // Channel announcement was successfully processed and now it might be
        // broadcast to other connected nodes if it was an announcement with
        // proof (remote).
        var announcements []networkMsg

        if proof != nil {
                announcements = append(announcements, networkMsg{
                        peer:     nMsg.peer,
                        isRemote: nMsg.isRemote,
                        source:   nMsg.source,
                        msg:      ann,
                })
        }

        nMsg.err <- nil

        log.Debugf("Processed ChannelAnnouncement1: peer=%v, short_chan_id=%v",
                nMsg.peer, scid.ToUint64())

        return announcements, true
}

// handleChanUpdate processes a new channel update.
func (d *AuthenticatedGossiper) handleChanUpdate(nMsg *networkMsg,
        upd *lnwire.ChannelUpdate1,
        ops []batch.SchedulerOption) ([]networkMsg, bool) {

        log.Debugf("Processing ChannelUpdate: peer=%v, short_chan_id=%v, ",
                nMsg.peer, upd.ShortChannelID.ToUint64())

        // We'll ignore any channel updates that target any chain other than
        // the set of chains we know of.
        if !bytes.Equal(upd.ChainHash[:], d.cfg.ChainHash[:]) {
                err := fmt.Errorf("ignoring ChannelUpdate from chain=%v, "+
                        "gossiper on chain=%v", upd.ChainHash, d.cfg.ChainHash)
                log.Errorf(err.Error())

                key := newRejectCacheKey(
                        upd.ShortChannelID.ToUint64(),
                        sourceToPub(nMsg.source),
                )
                _, _ = d.recentRejects.Put(key, &cachedReject{})

                nMsg.err <- err
                return nil, false
        }

        blockHeight := upd.ShortChannelID.BlockHeight
        shortChanID := upd.ShortChannelID.ToUint64()

        // If the advertised inclusionary block is beyond our knowledge of the
        // chain tip, then we'll put the announcement in limbo to be fully
        // verified once we advance forward in the chain. If the update has an
        // alias SCID, we'll skip the isPremature check. This is necessary
        // since aliases start at block height 16_000_000.
        d.Lock()
        if nMsg.isRemote && !d.cfg.IsAlias(upd.ShortChannelID) &&
                d.isPremature(upd.ShortChannelID, 0, nMsg) {

                log.Warnf("Update announcement for short_chan_id(%v), is "+
                        "premature: advertises height %v, only height %v is "+
                        "known", shortChanID, blockHeight, d.bestHeight)
                d.Unlock()
                nMsg.err <- nil
                return nil, false
        }
        d.Unlock()

        // Before we perform any of the expensive checks below, we'll check
        // whether this update is stale or is for a zombie channel in order to
        // quickly reject it.
        timestamp := time.Unix(int64(upd.Timestamp), 0)

        // Fetch the SCID we should be using to lock the channelMtx and make
        // graph queries with.
        graphScid, err := d.cfg.FindBaseByAlias(upd.ShortChannelID)
        if err != nil {
                // Fallback and set the graphScid to the peer-provided SCID.
                // This will occur for non-option-scid-alias channels and for
                // public option-scid-alias channels after 6 confirmations.
                // Once public option-scid-alias channels have 6 confs, we'll
                // ignore ChannelUpdates with one of their aliases.
                graphScid = upd.ShortChannelID
        }

        if d.cfg.Graph.IsStaleEdgePolicy(
                graphScid, timestamp, upd.ChannelFlags,
        ) {

                log.Debugf("Ignored stale edge policy for short_chan_id(%v): "+
                        "peer=%v, msg=%s, is_remote=%v", shortChanID,
                        nMsg.peer, nMsg.msg.MsgType(), nMsg.isRemote,
                )

                nMsg.err <- nil
                return nil, true
        }

        // Check that the ChanUpdate is not too far into the future, this could
        // reveal some faulty implementation therefore we log an error.
        if time.Until(timestamp) > graph.DefaultChannelPruneExpiry {
                log.Errorf("Skewed timestamp (%v) for edge policy of "+
                        "short_chan_id(%v), timestamp too far in the future: "+
                        "peer=%v, msg=%s, is_remote=%v", timestamp.Unix(),
                        shortChanID, nMsg.peer, nMsg.msg.MsgType(),
                        nMsg.isRemote,
                )

                nMsg.err <- fmt.Errorf("skewed timestamp of edge policy, "+
                        "timestamp too far in the future: %v", timestamp.Unix())

                return nil, false
        }

        // Get the node pub key as far since we don't have it in the channel
        // update announcement message. We'll need this to properly verify the
        // message's signature.
        //
        // We make sure to obtain the mutex for this channel ID before we
        // access the database. This ensures the state we read from the
        // database has not changed between this point and when we call
        // UpdateEdge() later.
        d.channelMtx.Lock(graphScid.ToUint64())
        defer d.channelMtx.Unlock(graphScid.ToUint64())

        chanInfo, e1, e2, err := d.cfg.Graph.GetChannelByID(graphScid)
        switch {
        // No error, break.
        case err == nil:
                break

        case errors.Is(err, graphdb.ErrZombieEdge):
                err = d.processZombieUpdate(chanInfo, graphScid, upd)
                if err != nil {
                        log.Debug(err)
                        nMsg.err <- err
                        return nil, false
                }

                // We'll fallthrough to ensure we stash the update until we
                // receive its corresponding ChannelAnnouncement. This is
                // needed to ensure the edge exists in the graph before
                // applying the update.
                fallthrough
        case errors.Is(err, graphdb.ErrGraphNotFound):
                fallthrough
        case errors.Is(err, graphdb.ErrGraphNoEdgesFound):
                fallthrough
        case errors.Is(err, graphdb.ErrEdgeNotFound):
                // If the edge corresponding to this ChannelUpdate was not
                // found in the graph, this might be a channel in the process
                // of being opened, and we haven't processed our own
                // ChannelAnnouncement yet, hence it is not not found in the
                // graph. This usually gets resolved after the channel proofs
                // are exchanged and the channel is broadcasted to the rest of
                // the network, but in case this is a private channel this
                // won't ever happen. This can also happen in the case of a
                // zombie channel with a fresh update for which we don't have a
                // ChannelAnnouncement for since we reject them. Because of
                // this, we temporarily add it to a map, and reprocess it after
                // our own ChannelAnnouncement has been processed.
                //
                // The shortChanID may be an alias, but it is fine to use here
                // since we don't have an edge in the graph and if the peer is
                // not buggy, we should be able to use it once the gossiper
                // receives the local announcement.
                pMsg := &processedNetworkMsg{msg: nMsg}

                earlyMsgs, err := d.prematureChannelUpdates.Get(shortChanID)
                switch {
                // Nothing in the cache yet, we can just directly insert this
                // element.
                case err == cache.ErrElementNotFound:
                        _, _ = d.prematureChannelUpdates.Put(
                                shortChanID, &cachedNetworkMsg{
                                        msgs: []*processedNetworkMsg{pMsg},
                                })

                // There's already something in the cache, so we'll combine the
                // set of messages into a single value.
                default:
                        msgs := earlyMsgs.msgs
                        msgs = append(msgs, pMsg)
                        _, _ = d.prematureChannelUpdates.Put(
                                shortChanID, &cachedNetworkMsg{
                                        msgs: msgs,
                                })
                }

                log.Debugf("Got ChannelUpdate for edge not found in graph"+
                        "(shortChanID=%v), saving for reprocessing later",
                        shortChanID)

                // NOTE: We don't return anything on the error channel for this
                // message, as we expect that will be done when this
                // ChannelUpdate is later reprocessed.
                return nil, false

        default:
                err := fmt.Errorf("unable to validate channel update "+
                        "short_chan_id=%v: %v", shortChanID, err)
                log.Error(err)
                nMsg.err <- err

                key := newRejectCacheKey(
                        upd.ShortChannelID.ToUint64(),
                        sourceToPub(nMsg.source),
                )
                _, _ = d.recentRejects.Put(key, &cachedReject{})

                return nil, false
        }

        // The least-significant bit in the flag on the channel update
        // announcement tells us "which" side of the channels directed edge is
        // being updated.
        var (
                pubKey       *btcec.PublicKey
                edgeToUpdate *models.ChannelEdgePolicy
        )
        direction := upd.ChannelFlags & lnwire.ChanUpdateDirection
        switch direction {
        case 0:
                pubKey, _ = chanInfo.NodeKey1()
                edgeToUpdate = e1
        case 1:
                pubKey, _ = chanInfo.NodeKey2()
                edgeToUpdate = e2
        }

        log.Debugf("Validating ChannelUpdate: channel=%v, for node=%x, has "+
                "edge policy=%v", chanInfo.ChannelID,
                pubKey.SerializeCompressed(), edgeToUpdate != nil)

        // Validate the channel announcement with the expected public key and
        // channel capacity. In the case of an invalid channel update, we'll
        // return an error to the caller and exit early.
        err = netann.ValidateChannelUpdateAnn(pubKey, chanInfo.Capacity, upd)
        if err != nil {
                rErr := fmt.Errorf("unable to validate channel update "+
                        "announcement for short_chan_id=%v: %v",
                        spew.Sdump(upd.ShortChannelID), err)

                log.Error(rErr)
                nMsg.err <- rErr
                return nil, false
        }

        // If we have a previous version of the edge being updated, we'll want
        // to rate limit its updates to prevent spam throughout the network.
        if nMsg.isRemote && edgeToUpdate != nil {
                // If it's a keep-alive update, we'll only propagate one if
                // it's been a day since the previous. This follows our own
                // heuristic of sending keep-alive updates after the same
                // duration (see retransmitStaleAnns).
                timeSinceLastUpdate := timestamp.Sub(edgeToUpdate.LastUpdate)
                if IsKeepAliveUpdate(upd, edgeToUpdate) {
                        if timeSinceLastUpdate < d.cfg.RebroadcastInterval {
                                log.Debugf("Ignoring keep alive update not "+
                                        "within %v period for channel %v",
                                        d.cfg.RebroadcastInterval, shortChanID)
                                nMsg.err <- nil
                                return nil, false
                        }
                } else {
                        // If it's not, we'll allow an update per minute with a
                        // maximum burst of 10. If we haven't seen an update
                        // for this channel before, we'll need to initialize a
                        // rate limiter for each direction.
                        //
                        // Since the edge exists in the graph, we'll create a
                        // rate limiter for chanInfo.ChannelID rather then the
                        // SCID the peer sent. This is because there may be
                        // multiple aliases for a channel and we may otherwise
                        // rate-limit only a single alias of the channel,
                        // instead of the whole channel.
                        baseScid := chanInfo.ChannelID
                        d.Lock()
                        rls, ok := d.chanUpdateRateLimiter[baseScid]
                        if !ok {
                                r := rate.Every(d.cfg.ChannelUpdateInterval)
                                b := d.cfg.MaxChannelUpdateBurst
                                rls = [2]*rate.Limiter{
                                        rate.NewLimiter(r, b),
                                        rate.NewLimiter(r, b),
                                }
                                d.chanUpdateRateLimiter[baseScid] = rls
                        }
                        d.Unlock()

                        if !rls[direction].Allow() {
                                log.Debugf("Rate limiting update for channel "+
                                        "%v from direction %x", shortChanID,
                                        pubKey.SerializeCompressed())
                                nMsg.err <- nil
                                return nil, false
                        }
                }
        }

        // We'll use chanInfo.ChannelID rather than the peer-supplied
        // ShortChannelID in the ChannelUpdate to avoid the router having to
        // lookup the stored SCID. If we're sending the update, we'll always
        // use the SCID stored in the database rather than a potentially
        // different alias. This might mean that SigBytes is incorrect as it
        // signs a different SCID than the database SCID, but since there will
        // only be a difference if AuthProof == nil, this is fine.
        update := &models.ChannelEdgePolicy{
                SigBytes:                  upd.Signature.ToSignatureBytes(),
                ChannelID:                 chanInfo.ChannelID,
                LastUpdate:                timestamp,
                MessageFlags:              upd.MessageFlags,
                ChannelFlags:              upd.ChannelFlags,
                TimeLockDelta:             upd.TimeLockDelta,
                MinHTLC:                   upd.HtlcMinimumMsat,
                MaxHTLC:                   upd.HtlcMaximumMsat,
                FeeBaseMSat:               lnwire.MilliSatoshi(upd.BaseFee),
                FeeProportionalMillionths: lnwire.MilliSatoshi(upd.FeeRate),
                ExtraOpaqueData:           upd.ExtraOpaqueData,
        }

        if err := d.cfg.Graph.UpdateEdge(update, ops...); err != nil {
                if graph.IsError(
                        err, graph.ErrOutdated,
                        graph.ErrIgnored,
                ) {

                        log.Debugf("Update edge for short_chan_id(%v) got: %v",
                                shortChanID, err)
                } else {
                        // Since we know the stored SCID in the graph, we'll
                        // cache that SCID.
                        key := newRejectCacheKey(
                                chanInfo.ChannelID,
                                sourceToPub(nMsg.source),
                        )
                        _, _ = d.recentRejects.Put(key, &cachedReject{})

                        log.Errorf("Update edge for short_chan_id(%v) got: %v",
                                shortChanID, err)
                }

                nMsg.err <- err
                return nil, false
        }

        // If this is a local ChannelUpdate without an AuthProof, it means it
        // is an update to a channel that is not (yet) supposed to be announced
        // to the greater network. However, our channel counter party will need
        // to be given the update, so we'll try sending the update directly to
        // the remote peer.
        if !nMsg.isRemote && chanInfo.AuthProof == nil {
                if nMsg.optionalMsgFields != nil {
                        remoteAlias := nMsg.optionalMsgFields.remoteAlias
                        if remoteAlias != nil {
                                // The remoteAlias field was specified, meaning
                                // that we should replace the SCID in the
                                // update with the remote's alias. We'll also
                                // need to re-sign the channel update. This is
                                // required for option-scid-alias feature-bit
                                // negotiated channels.
                                upd.ShortChannelID = *remoteAlias

                                sig, err := d.cfg.SignAliasUpdate(upd)
                                if err != nil {
                                        log.Error(err)
                                        nMsg.err <- err
                                        return nil, false
                                }

                                lnSig, err := lnwire.NewSigFromSignature(sig)
                                if err != nil {
                                        log.Error(err)
                                        nMsg.err <- err
                                        return nil, false
                                }

                                upd.Signature = lnSig
                        }
                }

                // Get our peer's public key.
                remotePubKey := remotePubFromChanInfo(
                        chanInfo, upd.ChannelFlags,
                )

                log.Debugf("The message %v has no AuthProof, sending the "+
                        "update to remote peer %x", upd.MsgType(), remotePubKey)

                // Now we'll attempt to send the channel update message
                // reliably to the remote peer in the background, so that we
                // don't block if the peer happens to be offline at the moment.
                err := d.reliableSender.sendMessage(upd, remotePubKey)
                if err != nil {
                        err := fmt.Errorf("unable to reliably send %v for "+
                                "channel=%v to peer=%x: %v", upd.MsgType(),
                                upd.ShortChannelID, remotePubKey, err)
                        nMsg.err <- err
                        return nil, false
                }
        }

        // Channel update announcement was successfully processed and now it
        // can be broadcast to the rest of the network. However, we'll only
        // broadcast the channel update announcement if it has an attached
        // authentication proof. We also won't broadcast the update if it
        // contains an alias because the network would reject this.
        var announcements []networkMsg
        if chanInfo.AuthProof != nil && !d.cfg.IsAlias(upd.ShortChannelID) {
                announcements = append(announcements, networkMsg{
                        peer:     nMsg.peer,
                        source:   nMsg.source,
                        isRemote: nMsg.isRemote,
                        msg:      upd,
                })
        }

        nMsg.err <- nil

        log.Debugf("Processed ChannelUpdate: peer=%v, short_chan_id=%v, "+
                "timestamp=%v", nMsg.peer, upd.ShortChannelID.ToUint64(),
                timestamp)
        return announcements, true
}

// handleAnnSig processes a new announcement signatures message.
func (d *AuthenticatedGossiper) handleAnnSig(nMsg *networkMsg,
        ann *lnwire.AnnounceSignatures1) ([]networkMsg, bool) {

        needBlockHeight := ann.ShortChannelID.BlockHeight +
                d.cfg.ProofMatureDelta
        shortChanID := ann.ShortChannelID.ToUint64()

        prefix := "local"
        if nMsg.isRemote {
                prefix = "remote"
        }

        log.Infof("Received new %v announcement signature for %v", prefix,
                ann.ShortChannelID)

        // By the specification, channel announcement proofs should be sent
        // after some number of confirmations after channel was registered in
        // bitcoin blockchain. Therefore, we check if the proof is mature.
        d.Lock()
        premature := d.isPremature(
                ann.ShortChannelID, d.cfg.ProofMatureDelta, nMsg,
        )
        if premature {
                log.Warnf("Premature proof announcement, current block height"+
                        "lower than needed: %v < %v", d.bestHeight,
                        needBlockHeight)
                d.Unlock()
                nMsg.err <- nil
                return nil, false
        }
        d.Unlock()

        // Ensure that we know of a channel with the target channel ID before
        // proceeding further.
        //
        // We must acquire the mutex for this channel ID before getting the
        // channel from the database, to ensure what we read does not change
        // before we call AddProof() later.
        d.channelMtx.Lock(ann.ShortChannelID.ToUint64())
        defer d.channelMtx.Unlock(ann.ShortChannelID.ToUint64())

        chanInfo, e1, e2, err := d.cfg.Graph.GetChannelByID(
                ann.ShortChannelID,
        )
        if err != nil {
                _, err = d.cfg.FindChannel(nMsg.source, ann.ChannelID)
                if err != nil {
                        err := fmt.Errorf("unable to store the proof for "+
                                "short_chan_id=%v: %v", shortChanID, err)
                        log.Error(err)
                        nMsg.err <- err

                        return nil, false
                }

                proof := channeldb.NewWaitingProof(nMsg.isRemote, ann)
                err := d.cfg.WaitingProofStore.Add(proof)
                if err != nil {
                        err := fmt.Errorf("unable to store the proof for "+
                                "short_chan_id=%v: %v", shortChanID, err)
                        log.Error(err)
                        nMsg.err <- err
                        return nil, false
                }

                log.Infof("Orphan %v proof announcement with short_chan_id=%v"+
                        ", adding to waiting batch", prefix, shortChanID)
                nMsg.err <- nil
                return nil, false
        }

        nodeID := nMsg.source.SerializeCompressed()
        isFirstNode := bytes.Equal(nodeID, chanInfo.NodeKey1Bytes[:])
        isSecondNode := bytes.Equal(nodeID, chanInfo.NodeKey2Bytes[:])

        // Ensure that channel that was retrieved belongs to the peer which
        // sent the proof announcement.
        if !(isFirstNode || isSecondNode) {
                err := fmt.Errorf("channel that was received doesn't belong "+
                        "to the peer which sent the proof, short_chan_id=%v",
                        shortChanID)
                log.Error(err)
                nMsg.err <- err
                return nil, false
        }

        // If proof was sent by a local sub-system, then we'll send the
        // announcement signature to the remote node so they can also
        // reconstruct the full channel announcement.
        if !nMsg.isRemote {
                var remotePubKey [33]byte
                if isFirstNode {
                        remotePubKey = chanInfo.NodeKey2Bytes
                } else {
                        remotePubKey = chanInfo.NodeKey1Bytes
                }

                // Since the remote peer might not be online we'll call a
                // method that will attempt to deliver the proof when it comes
                // online.
                err := d.reliableSender.sendMessage(ann, remotePubKey)
                if err != nil {
                        err := fmt.Errorf("unable to reliably send %v for "+
                                "channel=%v to peer=%x: %v", ann.MsgType(),
                                ann.ShortChannelID, remotePubKey, err)
                        nMsg.err <- err
                        return nil, false
                }
        }

        // Check if we already have the full proof for this channel.
        if chanInfo.AuthProof != nil {
                // If we already have the fully assembled proof, then the peer
                // sending us their proof has probably not received our local
                // proof yet. So be kind and send them the full proof.
                if nMsg.isRemote {
                        peerID := nMsg.source.SerializeCompressed()
                        log.Debugf("Got AnnounceSignatures for channel with " +
                                "full proof.")

                        d.wg.Add(1)
                        go func() {
                                defer d.wg.Done()

                                log.Debugf("Received half proof for channel "+
                                        "%v with existing full proof. Sending"+
                                        " full proof to peer=%x",
                                        ann.ChannelID, peerID)

                                ca, _, _, err := netann.CreateChanAnnouncement(
                                        chanInfo.AuthProof, chanInfo, e1, e2,
                                )
                                if err != nil {
                                        log.Errorf("unable to gen ann: %v",
                                                err)
                                        return
                                }

                                err = nMsg.peer.SendMessage(false, ca)
                                if err != nil {
                                        log.Errorf("Failed sending full proof"+
                                                " to peer=%x: %v", peerID, err)
                                        return
                                }

                                log.Debugf("Full proof sent to peer=%x for "+
                                        "chanID=%v", peerID, ann.ChannelID)
                        }()
                }

                log.Debugf("Already have proof for channel with chanID=%v",
                        ann.ChannelID)
                nMsg.err <- nil
                return nil, true
        }

        // Check that we received the opposite proof. If so, then we're now
        // able to construct the full proof, and create the channel
        // announcement. If we didn't receive the opposite half of the proof
        // then we should store this one, and wait for the opposite to be
        // received.
        proof := channeldb.NewWaitingProof(nMsg.isRemote, ann)
        oppProof, err := d.cfg.WaitingProofStore.Get(proof.OppositeKey())
        if err != nil && err != channeldb.ErrWaitingProofNotFound {
                err := fmt.Errorf("unable to get the opposite proof for "+
                        "short_chan_id=%v: %v", shortChanID, err)
                log.Error(err)
                nMsg.err <- err
                return nil, false
        }

        if err == channeldb.ErrWaitingProofNotFound {
                err := d.cfg.WaitingProofStore.Add(proof)
                if err != nil {
                        err := fmt.Errorf("unable to store the proof for "+
                                "short_chan_id=%v: %v", shortChanID, err)
                        log.Error(err)
                        nMsg.err <- err
                        return nil, false
                }

                log.Infof("1/2 of channel ann proof received for "+
                        "short_chan_id=%v, waiting for other half",
                        shortChanID)

                nMsg.err <- nil
                return nil, false
        }

        // We now have both halves of the channel announcement proof, then
        // we'll reconstruct the initial announcement so we can validate it
        // shortly below.
        var dbProof models.ChannelAuthProof
        if isFirstNode {
                dbProof.NodeSig1Bytes = ann.NodeSignature.ToSignatureBytes()
                dbProof.NodeSig2Bytes = oppProof.NodeSignature.ToSignatureBytes()
                dbProof.BitcoinSig1Bytes = ann.BitcoinSignature.ToSignatureBytes()
                dbProof.BitcoinSig2Bytes = oppProof.BitcoinSignature.ToSignatureBytes()
        } else {
                dbProof.NodeSig1Bytes = oppProof.NodeSignature.ToSignatureBytes()
                dbProof.NodeSig2Bytes = ann.NodeSignature.ToSignatureBytes()
                dbProof.BitcoinSig1Bytes = oppProof.BitcoinSignature.ToSignatureBytes()
                dbProof.BitcoinSig2Bytes = ann.BitcoinSignature.ToSignatureBytes()
        }

        chanAnn, e1Ann, e2Ann, err := netann.CreateChanAnnouncement(
                &dbProof, chanInfo, e1, e2,
        )
        if err != nil {
                log.Error(err)
                nMsg.err <- err
                return nil, false
        }

        // With all the necessary components assembled validate the full
        // channel announcement proof.
        err = netann.ValidateChannelAnn(chanAnn, d.fetchPKScript)
        if err != nil {
                err := fmt.Errorf("channel announcement proof for "+
                        "short_chan_id=%v isn't valid: %v", shortChanID, err)

                log.Error(err)
                nMsg.err <- err
                return nil, false
        }

        // If the channel was returned by the router it means that existence of
        // funding point and inclusion of nodes bitcoin keys in it already
        // checked by the router. In this stage we should check that node keys
        // attest to the bitcoin keys by validating the signatures of
        // announcement. If proof is valid then we'll populate the channel edge
        // with it, so we can announce it on peer connect.
        err = d.cfg.Graph.AddProof(ann.ShortChannelID, &dbProof)
        if err != nil {
                err := fmt.Errorf("unable add proof to the channel chanID=%v:"+
                        " %v", ann.ChannelID, err)
                log.Error(err)
                nMsg.err <- err
                return nil, false
        }

        err = d.cfg.WaitingProofStore.Remove(proof.OppositeKey())
        if err != nil {
                err := fmt.Errorf("unable to remove opposite proof for the "+
                        "channel with chanID=%v: %v", ann.ChannelID, err)
                log.Error(err)
                nMsg.err <- err
                return nil, false
        }

        // Proof was successfully created and now can announce the channel to
        // the remain network.
        log.Infof("Fully valid channel proof for short_chan_id=%v constructed"+
                ", adding to next ann batch", shortChanID)

        // Assemble the necessary announcements to add to the next broadcasting
        // batch.
        var announcements []networkMsg
        announcements = append(announcements, networkMsg{
                peer:   nMsg.peer,
                source: nMsg.source,
                msg:    chanAnn,
        })
        if src, err := chanInfo.NodeKey1(); err == nil && e1Ann != nil {
                announcements = append(announcements, networkMsg{
                        peer:   nMsg.peer,
                        source: src,
                        msg:    e1Ann,
                })
        }
        if src, err := chanInfo.NodeKey2(); err == nil && e2Ann != nil {
                announcements = append(announcements, networkMsg{
                        peer:   nMsg.peer,
                        source: src,
                        msg:    e2Ann,
                })
        }

        // We'll also send along the node announcements for each channel
        // participant if we know of them. To ensure our node announcement
        // propagates to our channel counterparty, we'll set the source for
        // each announcement to the node it belongs to, otherwise we won't send
        // it since the source gets skipped. This isn't necessary for channel
        // updates and announcement signatures since we send those directly to
        // our channel counterparty through the gossiper's reliable sender.
        node1Ann, err := d.fetchNodeAnn(chanInfo.NodeKey1Bytes)
        if err != nil {
                log.Debugf("Unable to fetch node announcement for %x: %v",
                        chanInfo.NodeKey1Bytes, err)
        } else {
                if nodeKey1, err := chanInfo.NodeKey1(); err == nil {
                        announcements = append(announcements, networkMsg{
                                peer:   nMsg.peer,
                                source: nodeKey1,
                                msg:    node1Ann,
                        })
                }
        }

        node2Ann, err := d.fetchNodeAnn(chanInfo.NodeKey2Bytes)
        if err != nil {
                log.Debugf("Unable to fetch node announcement for %x: %v",
                        chanInfo.NodeKey2Bytes, err)
        } else {
                if nodeKey2, err := chanInfo.NodeKey2(); err == nil {
                        announcements = append(announcements, networkMsg{
                                peer:   nMsg.peer,
                                source: nodeKey2,
                                msg:    node2Ann,
                        })
                }
        }

        nMsg.err <- nil
        return announcements, true
}

// isBanned returns true if the peer identified by pubkey is banned for sending
// invalid channel announcements.
func (d *AuthenticatedGossiper) isBanned(pubkey [33]byte) bool {
        return d.banman.isBanned(pubkey)
}

// ShouldDisconnect returns true if we should disconnect the peer identified by
// pubkey.
func (d *AuthenticatedGossiper) ShouldDisconnect(pubkey *btcec.PublicKey) (
        bool, error) {

        pubkeySer := pubkey.SerializeCompressed()

        var pubkeyBytes [33]byte
        copy(pubkeyBytes[:], pubkeySer)

        // If the public key is banned, check whether or not this is a channel
        // peer.
        if d.isBanned(pubkeyBytes) {
                isChanPeer, err := d.cfg.ScidCloser.IsChannelPeer(pubkey)
                if err != nil {
                        return false, err
                }

                // We should only disconnect non-channel peers.
                if !isChanPeer {
                        return true, nil
                }
        }

        return false, nil
}

// validateFundingTransaction fetches the channel announcements claimed funding
// transaction from chain to ensure that it exists, is not spent and matches
// the channel announcement proof. The transaction's outpoint and value are
// returned if we can glean them from the work done in this method.
func (d *AuthenticatedGossiper) validateFundingTransaction(
        ann *lnwire.ChannelAnnouncement1,
        tapscriptRoot fn.Option[chainhash.Hash]) (wire.OutPoint, btcutil.Amount,
        []byte, error) {

        scid := ann.ShortChannelID

        // Before we can add the channel to the channel graph, we need to obtain
        // the full funding outpoint that's encoded within the channel ID.
        fundingTx, err := lnwallet.FetchFundingTxWrapper(
                d.cfg.ChainIO, &scid, d.quit,
        )
        if err != nil {
                //nolint:ll
                //
                // In order to ensure we don't erroneously mark a channel as a
                // zombie due to an RPC failure, we'll attempt to string match
                // for the relevant errors.
                //
                // * btcd:
                //    * https://github.com/btcsuite/btcd/blob/master/rpcserver.go#L1316
                //    * https://github.com/btcsuite/btcd/blob/master/rpcserver.go#L1086
                // * bitcoind:
                //    * https://github.com/bitcoin/bitcoin/blob/7fcf53f7b4524572d1d0c9a5fdc388e87eb02416/src/rpc/blockchain.cpp#L770
                //     * https://github.com/bitcoin/bitcoin/blob/7fcf53f7b4524572d1d0c9a5fdc388e87eb02416/src/rpc/blockchain.cpp#L954
                switch {
                case strings.Contains(err.Error(), "not found"):
                        fallthrough

                case strings.Contains(err.Error(), "out of range"):
                        // If the funding transaction isn't found at all, then
                        // we'll mark the edge itself as a zombie so we don't
                        // continue to request it. We use the "zero key" for
                        // both node pubkeys so this edge can't be resurrected.
                        zErr := d.cfg.Graph.MarkZombieEdge(scid.ToUint64())
                        if zErr != nil {
                                return wire.OutPoint{}, 0, nil, zErr
                        }

                default:
                }

                return wire.OutPoint{}, 0, nil, fmt.Errorf("%w: %w",
                        ErrNoFundingTransaction, err)
        }

        // Recreate witness output to be sure that declared in channel edge
        // bitcoin keys and channel value corresponds to the reality.
        fundingPkScript, err := makeFundingScript(
                ann.BitcoinKey1[:], ann.BitcoinKey2[:], ann.Features,
                tapscriptRoot,
        )
        if err != nil {
                return wire.OutPoint{}, 0, nil, err
        }

        // Next we'll validate that this channel is actually well formed. If
        // this check fails, then this channel either doesn't exist, or isn't
        // the one that was meant to be created according to the passed channel
        // proofs.
        fundingPoint, err := chanvalidate.Validate(
                &chanvalidate.Context{
                        Locator: &chanvalidate.ShortChanIDChanLocator{
                                ID: scid,
                        },
                        MultiSigPkScript: fundingPkScript,
                        FundingTx:        fundingTx,
                },
        )
        if err != nil {
                // Mark the edge as a zombie so we won't try to re-validate it
                // on start up.
                zErr := d.cfg.Graph.MarkZombieEdge(scid.ToUint64())
                if zErr != nil {
                        return wire.OutPoint{}, 0, nil, zErr
                }

                return wire.OutPoint{}, 0, nil, fmt.Errorf("%w: %w",
                        ErrInvalidFundingOutput, err)
        }

        // Now that we have the funding outpoint of the channel, ensure
        // that it hasn't yet been spent. If so, then this channel has
        // been closed so we'll ignore it.
        chanUtxo, err := d.cfg.ChainIO.GetUtxo(
                fundingPoint, fundingPkScript, scid.BlockHeight, d.quit,
        )
        if err != nil {
                if errors.Is(err, btcwallet.ErrOutputSpent) {
                        zErr := d.cfg.Graph.MarkZombieEdge(scid.ToUint64())
                        if zErr != nil {
                                return wire.OutPoint{}, 0, nil, zErr
                        }
                }

                return wire.OutPoint{}, 0, nil, fmt.Errorf("%w: unable to "+
                        "fetch utxo for chan_id=%v, chan_point=%v: %w",
                        ErrChannelSpent, scid.ToUint64(), fundingPoint, err)
        }

        return *fundingPoint, btcutil.Amount(chanUtxo.Value), fundingPkScript,
                nil
}

// makeFundingScript is used to make the funding script for both segwit v0 and
// segwit v1 (taproot) channels.
func makeFundingScript(bitcoinKey1, bitcoinKey2 []byte,
        features *lnwire.RawFeatureVector,
        tapscriptRoot fn.Option[chainhash.Hash]) ([]byte, error) {

        legacyFundingScript := func() ([]byte, error) {
                witnessScript, err := input.GenMultiSigScript(
                        bitcoinKey1, bitcoinKey2,
                )
                if err != nil {
                        return nil, err
                }
                pkScript, err := input.WitnessScriptHash(witnessScript)
                if err != nil {
                        return nil, err
                }

                return pkScript, nil
        }

        if features.IsEmpty() {
                return legacyFundingScript()
        }

        chanFeatureBits := lnwire.NewFeatureVector(features, lnwire.Features)
        if chanFeatureBits.HasFeature(
                lnwire.SimpleTaprootChannelsOptionalStaging,
        ) {

                pubKey1, err := btcec.ParsePubKey(bitcoinKey1)
                if err != nil {
                        return nil, err
                }
                pubKey2, err := btcec.ParsePubKey(bitcoinKey2)
                if err != nil {
                        return nil, err
                }

                fundingScript, _, err := input.GenTaprootFundingScript(
                        pubKey1, pubKey2, 0, tapscriptRoot,
                )
                if err != nil {
                        return nil, err
                }

                // TODO(roasbeef): add tapscript root to gossip v1.5

                return fundingScript, nil
        }

        return legacyFundingScript()
}

lightningnetwork / lnd / 13566028875

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