12430728843

Committed 20 Dec 2024 11:36AM UTC coverage: 61.336% (+2.6%) from 58.716%

Build # 12430728843

Build Type

Pull #8777

github

Committed by

ziggie1984

Commit Message

channeldb: fix typo.

Pull Request Pull Request #8777: multi: make reassignment of alias channel edge atomic

Run Details

161 of 213 new or added lines in 7 files covered. (75.59%)

70 existing lines in 17 files now uncovered.

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Source File
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80.6

/discovery/gossiper.go

package discovery

import (
        "bytes"
        "errors"
        "fmt"
        "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/keychain"
        "github.com/lightningnetwork/lnd/lnpeer"
        "github.com/lightningnetwork/lnd/lnutils"
        "github.com/lightningnetwork/lnd/lnwallet"
        "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
)

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")

        // 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
}

// 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

        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.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 {

        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.
                syncer.ProcessQueryMsg(m, peer.QuitSignal())

                errChan <- nil
                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)
        }

        // We'll use this validation to ensure that we process jobs in their
        // dependency order during parallel validation.
        validationBarrier := graph.NewValidationBarrier(1000, d.quit)

        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.
                        validationBarrier.InitJobDependencies(announcement.msg)

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

                // 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, vb *graph.ValidationBarrier) {

        defer d.wg.Done()
        defer 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 := vb.WaitForDependants(nMsg.msg)
        if err != nil {
                log.Debugf("Validating network message %s got err: %v",
                        nMsg.msg.MsgType(), err)

                if !graph.IsError(
                        err,
                        graph.ErrVBarrierShuttingDown,
                        graph.ErrParentValidationFailed,
                ) {

                        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.
        vb.SignalDependants(nMsg.msg, allow)

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

        timestamp := time.Unix(int64(msg.Timestamp), 0)
        features := lnwire.NewFeatureVector(msg.Features, lnwire.Features)
        node := &models.LightningNode{
                HaveNodeAnnouncement: true,
                LastUpdate:           timestamp,
                Addresses:            msg.Addresses,
                PubKeyBytes:          msg.NodeID,
                Alias:                msg.Alias.String(),
                AuthSigBytes:         msg.Signature.ToSignatureBytes(),
                Features:             features,
                Color:                msg.RGBColor,
                ExtraOpaqueData:      msg.ExtraOpaqueData,
        }

        return d.cfg.Graph.AddNode(node, 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 {
        // TODO(roasbeef) make height delta 6
        //  * or configurable

        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", nMsg.peer, timestamp, nodeAnn.NodeID)

        // 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,
                        graph.ErrVBarrierShuttingDown,
                ) {

                        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", nMsg.peer, timestamp, nodeAnn.NodeID)

        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.
        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.
                edge.TapscriptRoot = nMsg.optionalMsgFields.tapscriptRoot
        }

        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.
        //
        // Before we 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.
        d.channelMtx.Lock(scid.ToUint64())
        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.
                switch {
                case 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

                case graph.IsError(
                        err, graph.ErrNoFundingTransaction,
                        graph.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 graph.IsError(err, graph.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
        }

        // 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, from node=%x, has "+
                "edge=%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,
                        graph.ErrVBarrierShuttingDown,
                ) {

                        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
}

lightningnetwork / lnd / 12430728843

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