package routing import ( "bytes" "fmt" "runtime" "sync" "sync/atomic" "time" "github.com/btcsuite/btcd/btcec" "github.com/btcsuite/btcd/wire" "github.com/btcsuite/btcutil" "github.com/davecgh/go-spew/spew" "github.com/go-errors/errors" sphinx "github.com/lightningnetwork/lightning-onion" "github.com/lightningnetwork/lnd/batch" "github.com/lightningnetwork/lnd/channeldb" "github.com/lightningnetwork/lnd/channeldb/kvdb" "github.com/lightningnetwork/lnd/clock" "github.com/lightningnetwork/lnd/htlcswitch" "github.com/lightningnetwork/lnd/input" "github.com/lightningnetwork/lnd/lntypes" "github.com/lightningnetwork/lnd/lnwallet" "github.com/lightningnetwork/lnd/lnwallet/chanvalidate" "github.com/lightningnetwork/lnd/lnwire" "github.com/lightningnetwork/lnd/multimutex" "github.com/lightningnetwork/lnd/record" "github.com/lightningnetwork/lnd/routing/chainview" "github.com/lightningnetwork/lnd/routing/route" "github.com/lightningnetwork/lnd/ticker" "github.com/lightningnetwork/lnd/zpay32" ) const ( // DefaultPayAttemptTimeout is the default payment attempt timeout. The // payment attempt timeout defines the duration after which we stop // trying more routes for a payment. DefaultPayAttemptTimeout = time.Duration(time.Second * 60) // DefaultChannelPruneExpiry is the default duration used to determine // if a channel should be pruned or not. DefaultChannelPruneExpiry = time.Duration(time.Hour * 24 * 14) // DefaultFirstTimePruneDelay is the time we'll wait after startup // before attempting to prune the graph for zombie channels. We don't // do it immediately after startup to allow lnd to start up without // getting blocked by this job. DefaultFirstTimePruneDelay = 30 * time.Second // defaultStatInterval governs how often the router will log non-empty // stats related to processing new channels, updates, or node // announcements. defaultStatInterval = time.Minute // MinCLTVDelta is the minimum CLTV value accepted by LND for all // timelock deltas. This includes both forwarding CLTV deltas set on // channel updates, as well as final CLTV deltas used to create BOLT 11 // payment requests. // // NOTE: For payment requests, BOLT 11 stipulates that a final CLTV // delta of 9 should be used when no value is decoded. This however // leads to inflexiblity in upgrading this default parameter, since it // can create inconsistencies around the assumed value between sender // and receiver. Specifically, if the receiver assumes a higher value // than the sender, the receiver will always see the received HTLCs as // invalid due to their timelock not meeting the required delta. // // We skirt this by always setting an explicit CLTV delta when creating // invoices. This allows LND nodes to freely update the minimum without // creating incompatibilities during the upgrade process. For some time // LND has used an explicit default final CLTV delta of 40 blocks for // bitcoin (160 for litecoin), though we now clamp the lower end of this // range for user-chosen deltas to 18 blocks to be conservative. MinCLTVDelta = 18 ) var ( // ErrRouterShuttingDown is returned if the router is in the process of // shutting down. ErrRouterShuttingDown = fmt.Errorf("router shutting down") ) // ChannelGraphSource represents the source of information about the topology // of the lightning network. It's responsible for the addition of nodes, edges, // applying edge updates, and returning the current block height with which the // topology is synchronized. type ChannelGraphSource interface { // AddNode is used to add information about a node to the router // database. If the node with this pubkey is not present in an existing // channel, it will be ignored. AddNode(node *channeldb.LightningNode, op ...batch.SchedulerOption) error // AddEdge is used to add edge/channel to the topology of the router, // after all information about channel will be gathered this // edge/channel might be used in construction of payment path. AddEdge(edge *channeldb.ChannelEdgeInfo, op ...batch.SchedulerOption) error // AddProof updates the channel edge info with proof which is needed to // properly announce the edge to the rest of the network. AddProof(chanID lnwire.ShortChannelID, proof *channeldb.ChannelAuthProof) error // UpdateEdge is used to update edge information, without this message // edge considered as not fully constructed. UpdateEdge(policy *channeldb.ChannelEdgePolicy, op ...batch.SchedulerOption) error // IsStaleNode returns true if the graph source has a node announcement // for the target node with a more recent timestamp. This method will // also return true if we don't have an active channel announcement for // the target node. IsStaleNode(node route.Vertex, timestamp time.Time) bool // IsPublicNode determines whether the given vertex is seen as a public // node in the graph from the graph's source node's point of view. IsPublicNode(node route.Vertex) (bool, error) // IsKnownEdge returns true if the graph source already knows of the // passed channel ID either as a live or zombie edge. IsKnownEdge(chanID lnwire.ShortChannelID) bool // IsStaleEdgePolicy returns true if the graph source has a channel // edge for the passed channel ID (and flags) that have a more recent // timestamp. IsStaleEdgePolicy(chanID lnwire.ShortChannelID, timestamp time.Time, flags lnwire.ChanUpdateChanFlags) bool // MarkEdgeLive clears an edge from our zombie index, deeming it as // live. MarkEdgeLive(chanID lnwire.ShortChannelID) error // ForAllOutgoingChannels is used to iterate over all channels // emanating from the "source" node which is the center of the // star-graph. ForAllOutgoingChannels(cb func(c *channeldb.ChannelEdgeInfo, e *channeldb.ChannelEdgePolicy) error) error // CurrentBlockHeight returns the block height from POV of the router // subsystem. CurrentBlockHeight() (uint32, error) // GetChannelByID return the channel by the channel id. GetChannelByID(chanID lnwire.ShortChannelID) (*channeldb.ChannelEdgeInfo, *channeldb.ChannelEdgePolicy, *channeldb.ChannelEdgePolicy, error) // FetchLightningNode attempts to look up a target node by its identity // public key. channeldb.ErrGraphNodeNotFound is returned if the node // doesn't exist within the graph. FetchLightningNode(route.Vertex) (*channeldb.LightningNode, error) // ForEachNode is used to iterate over every node in the known graph. ForEachNode(func(node *channeldb.LightningNode) error) error // ForEachChannel is used to iterate over every channel in the known // graph. ForEachChannel(func(chanInfo *channeldb.ChannelEdgeInfo, e1, e2 *channeldb.ChannelEdgePolicy) error) error } // PaymentAttemptDispatcher is used by the router to send payment attempts onto // the network, and receive their results. type PaymentAttemptDispatcher interface { // SendHTLC is a function that directs a link-layer switch to // forward a fully encoded payment to the first hop in the route // denoted by its public key. A non-nil error is to be returned if the // payment was unsuccessful. SendHTLC(firstHop lnwire.ShortChannelID, paymentID uint64, htlcAdd *lnwire.UpdateAddHTLC) error // GetPaymentResult returns the the result of the payment attempt with // the given paymentID. The method returns a channel where the payment // result will be sent when available, or an error is encountered // during forwarding. When a result is received on the channel, the // HTLC is guaranteed to no longer be in flight. The switch shutting // down is signaled by closing the channel. If the paymentID is // unknown, ErrPaymentIDNotFound will be returned. GetPaymentResult(paymentID uint64, paymentHash lntypes.Hash, deobfuscator htlcswitch.ErrorDecrypter) ( <-chan *htlcswitch.PaymentResult, error) // CleanStore calls the underlying result store, telling it is safe to // delete all entries except the ones in the keepPids map. This should // be called preiodically to let the switch clean up payment results // that we have handled. // NOTE: New payment attempts MUST NOT be made after the keepPids map // has been created and this method has returned. CleanStore(keepPids map[uint64]struct{}) error } // PaymentSessionSource is an interface that defines a source for the router to // retrive new payment sessions. type PaymentSessionSource interface { // NewPaymentSession creates a new payment session that will produce // routes to the given target. An optional set of routing hints can be // provided in order to populate additional edges to explore when // finding a path to the payment's destination. NewPaymentSession(p *LightningPayment) (PaymentSession, error) // NewPaymentSessionEmpty creates a new paymentSession instance that is // empty, and will be exhausted immediately. Used for failure reporting // to missioncontrol for resumed payment we don't want to make more // attempts for. NewPaymentSessionEmpty() PaymentSession } // MissionController is an interface that exposes failure reporting and // probability estimation. type MissionController interface { // ReportPaymentFail reports a failed payment to mission control as // input for future probability estimates. It returns a bool indicating // whether this error is a final error and no further payment attempts // need to be made. ReportPaymentFail(paymentID uint64, rt *route.Route, failureSourceIdx *int, failure lnwire.FailureMessage) ( *channeldb.FailureReason, error) // ReportPaymentSuccess reports a successful payment to mission control as input // for future probability estimates. ReportPaymentSuccess(paymentID uint64, rt *route.Route) error // GetProbability is expected to return the success probability of a // payment from fromNode along edge. GetProbability(fromNode, toNode route.Vertex, amt lnwire.MilliSatoshi) float64 } // FeeSchema is the set fee configuration for a Lightning Node on the network. // Using the coefficients described within the schema, the required fee to // forward outgoing payments can be derived. type FeeSchema struct { // BaseFee is the base amount of milli-satoshis that will be chained // for ANY payment forwarded. BaseFee lnwire.MilliSatoshi // FeeRate is the rate that will be charged for forwarding payments. // This value should be interpreted as the numerator for a fraction // (fixed point arithmetic) whose denominator is 1 million. As a result // the effective fee rate charged per mSAT will be: (amount * // FeeRate/1,000,000). FeeRate uint32 } // ChannelPolicy holds the parameters that determine the policy we enforce // when forwarding payments on a channel. These parameters are communicated // to the rest of the network in ChannelUpdate messages. type ChannelPolicy struct { // FeeSchema holds the fee configuration for a channel. FeeSchema // TimeLockDelta is the required HTLC timelock delta to be used // when forwarding payments. TimeLockDelta uint32 // MaxHTLC is the maximum HTLC size including fees we are allowed to // forward over this channel. MaxHTLC lnwire.MilliSatoshi // MinHTLC is the minimum HTLC size including fees we are allowed to // forward over this channel. MinHTLC *lnwire.MilliSatoshi } // Config defines the configuration for the ChannelRouter. ALL elements within // the configuration MUST be non-nil for the ChannelRouter to carry out its // duties. type Config struct { // Graph is the channel graph that the ChannelRouter will use to gather // metrics from and also to carry out path finding queries. // TODO(roasbeef): make into an interface Graph *channeldb.ChannelGraph // Chain is the router's source to the most up-to-date blockchain data. // All incoming advertised channels will be checked against the chain // to ensure that the channels advertised are still open. Chain lnwallet.BlockChainIO // ChainView is an instance of a FilteredChainView which is used to // watch the sub-set of the UTXO set (the set of active channels) that // we need in order to properly maintain the channel graph. ChainView chainview.FilteredChainView // Payer is an instance of a PaymentAttemptDispatcher and is used by // the router to send payment attempts onto the network, and receive // their results. Payer PaymentAttemptDispatcher // Control keeps track of the status of ongoing payments, ensuring we // can properly resume them across restarts. Control ControlTower // MissionControl is a shared memory of sorts that executions of // payment path finding use in order to remember which vertexes/edges // were pruned from prior attempts. During SendPayment execution, // errors sent by nodes are mapped into a vertex or edge to be pruned. // Each run will then take into account this set of pruned // vertexes/edges to reduce route failure and pass on graph information // gained to the next execution. MissionControl MissionController // SessionSource defines a source for the router to retrieve new payment // sessions. SessionSource PaymentSessionSource // ChannelPruneExpiry is the duration used to determine if a channel // should be pruned or not. If the delta between now and when the // channel was last updated is greater than ChannelPruneExpiry, then // the channel is marked as a zombie channel eligible for pruning. ChannelPruneExpiry time.Duration // GraphPruneInterval is used as an interval to determine how often we // should examine the channel graph to garbage collect zombie channels. GraphPruneInterval time.Duration // FirstTimePruneDelay is the time we'll wait after startup before // attempting to prune the graph for zombie channels. We don't do it // immediately after startup to allow lnd to start up without getting // blocked by this job. FirstTimePruneDelay time.Duration // QueryBandwidth is a method that allows the router to query the lower // link layer to determine the up to date available bandwidth at a // prospective link to be traversed. If the link isn't available, then // a value of zero should be returned. Otherwise, the current up to // date knowledge of the available bandwidth of the link should be // returned. QueryBandwidth func(edge *channeldb.ChannelEdgeInfo) lnwire.MilliSatoshi // NextPaymentID is a method that guarantees to return a new, unique ID // each time it is called. This is used by the router to generate a // unique payment ID for each payment it attempts to send, such that // the switch can properly handle the HTLC. NextPaymentID func() (uint64, error) // AssumeChannelValid toggles whether or not the router will check for // spentness of channel outpoints. For neutrino, this saves long rescans // from blocking initial usage of the daemon. AssumeChannelValid bool // PathFindingConfig defines global path finding parameters. PathFindingConfig PathFindingConfig // Clock is mockable time provider. Clock clock.Clock } // EdgeLocator is a struct used to identify a specific edge. type EdgeLocator struct { // ChannelID is the channel of this edge. ChannelID uint64 // Direction takes the value of 0 or 1 and is identical in definition to // the channel direction flag. A value of 0 means the direction from the // lower node pubkey to the higher. Direction uint8 } // String returns a human readable version of the edgeLocator values. func (e *EdgeLocator) String() string { return fmt.Sprintf("%v:%v", e.ChannelID, e.Direction) } // ChannelRouter is the layer 3 router within the Lightning stack. Below the // ChannelRouter is the HtlcSwitch, and below that is the Bitcoin blockchain // itself. The primary role of the ChannelRouter is to respond to queries for // potential routes that can support a payment amount, and also general graph // reachability questions. The router will prune the channel graph // automatically as new blocks are discovered which spend certain known funding // outpoints, thereby closing their respective channels. type ChannelRouter struct { ntfnClientCounter uint64 // To be used atomically. started uint32 // To be used atomically. stopped uint32 // To be used atomically. bestHeight uint32 // To be used atomically. // cfg is a copy of the configuration struct that the ChannelRouter was // initialized with. cfg *Config // selfNode is the center of the star-graph centered around the // ChannelRouter. The ChannelRouter uses this node as a starting point // when doing any path finding. selfNode *channeldb.LightningNode // newBlocks is a channel in which new blocks connected to the end of // the main chain are sent over, and blocks updated after a call to // UpdateFilter. newBlocks <-chan *chainview.FilteredBlock // staleBlocks is a channel in which blocks disconnected fromt the end // of our currently known best chain are sent over. staleBlocks <-chan *chainview.FilteredBlock // networkUpdates is a channel that carries new topology updates // messages from outside the ChannelRouter to be processed by the // networkHandler. networkUpdates chan *routingMsg // topologyClients maps a client's unique notification ID to a // topologyClient client that contains its notification dispatch // channel. topologyClients map[uint64]*topologyClient // ntfnClientUpdates is a channel that's used to send new updates to // topology notification clients to the ChannelRouter. Updates either // add a new notification client, or cancel notifications for an // existing client. ntfnClientUpdates chan *topologyClientUpdate // channelEdgeMtx is a mutex we use to make sure we process only one // ChannelEdgePolicy at a time for a given channelID, to ensure // consistency between the various database accesses. channelEdgeMtx *multimutex.Mutex // statTicker is a resumable ticker that logs the router's progress as // it discovers channels or receives updates. statTicker ticker.Ticker // stats tracks newly processed channels, updates, and node // announcements over a window of defaultStatInterval. stats *routerStats sync.RWMutex quit chan struct{} wg sync.WaitGroup } // A compile time check to ensure ChannelRouter implements the // ChannelGraphSource interface. var _ ChannelGraphSource = (*ChannelRouter)(nil) // New creates a new instance of the ChannelRouter with the specified // configuration parameters. As part of initialization, if the router detects // that the channel graph isn't fully in sync with the latest UTXO (since the // channel graph is a subset of the UTXO set) set, then the router will proceed // to fully sync to the latest state of the UTXO set. func New(cfg Config) (*ChannelRouter, error) { selfNode, err := cfg.Graph.SourceNode() if err != nil { return nil, err } r := &ChannelRouter{ cfg: &cfg, networkUpdates: make(chan *routingMsg), topologyClients: make(map[uint64]*topologyClient), ntfnClientUpdates: make(chan *topologyClientUpdate), channelEdgeMtx: multimutex.NewMutex(), selfNode: selfNode, statTicker: ticker.New(defaultStatInterval), stats: new(routerStats), quit: make(chan struct{}), } return r, nil } // Start launches all the goroutines the ChannelRouter requires to carry out // its duties. If the router has already been started, then this method is a // noop. func (r *ChannelRouter) Start() error { if !atomic.CompareAndSwapUint32(&r.started, 0, 1) { return nil } log.Tracef("Channel Router starting") bestHash, bestHeight, err := r.cfg.Chain.GetBestBlock() if err != nil { return err } // If the graph has never been pruned, or hasn't fully been created yet, // then we don't treat this as an explicit error. if _, _, err := r.cfg.Graph.PruneTip(); err != nil { switch { case err == channeldb.ErrGraphNeverPruned: fallthrough case err == channeldb.ErrGraphNotFound: // If the graph has never been pruned, then we'll set // the prune height to the current best height of the // chain backend. _, err = r.cfg.Graph.PruneGraph( nil, bestHash, uint32(bestHeight), ) if err != nil { return err } default: return err } } // If AssumeChannelValid is present, then we won't rely on pruning // channels from the graph based on their spentness, but whether they // are considered zombies or not. We will start zombie pruning after a // small delay, to avoid slowing down startup of lnd. if r.cfg.AssumeChannelValid { time.AfterFunc(r.cfg.FirstTimePruneDelay, func() { select { case <-r.quit: return default: } log.Info("Initial zombie prune starting") if err := r.pruneZombieChans(); err != nil { log.Errorf("Unable to prune zombies: %v", err) } }) } else { // Otherwise, we'll use our filtered chain view to prune // channels as soon as they are detected as spent on-chain. if err := r.cfg.ChainView.Start(); err != nil { return err } // Once the instance is active, we'll fetch the channel we'll // receive notifications over. r.newBlocks = r.cfg.ChainView.FilteredBlocks() r.staleBlocks = r.cfg.ChainView.DisconnectedBlocks() // Before we perform our manual block pruning, we'll construct // and apply a fresh chain filter to the active // FilteredChainView instance. We do this before, as otherwise // we may miss on-chain events as the filter hasn't properly // been applied. channelView, err := r.cfg.Graph.ChannelView() if err != nil && err != channeldb.ErrGraphNoEdgesFound { return err } log.Infof("Filtering chain using %v channels active", len(channelView)) if len(channelView) != 0 { err = r.cfg.ChainView.UpdateFilter( channelView, uint32(bestHeight), ) if err != nil { return err } } // Before we begin normal operation of the router, we first need // to synchronize the channel graph to the latest state of the // UTXO set. if err := r.syncGraphWithChain(); err != nil { return err } // Finally, before we proceed, we'll prune any unconnected nodes // from the graph in order to ensure we maintain a tight graph // of "useful" nodes. err = r.cfg.Graph.PruneGraphNodes() if err != nil && err != channeldb.ErrGraphNodesNotFound { return err } } // If any payments are still in flight, we resume, to make sure their // results are properly handled. payments, err := r.cfg.Control.FetchInFlightPayments() if err != nil { return err } // Before we restart existing payments and start accepting more // payments to be made, we clean the network result store of the // Switch. We do this here at startup to ensure no more payments can be // made concurrently, so we know the toKeep map will be up-to-date // until the cleaning has finished. toKeep := make(map[uint64]struct{}) for _, p := range payments { payment, err := r.cfg.Control.FetchPayment( p.Info.PaymentHash, ) if err != nil { return err } for _, a := range payment.HTLCs { toKeep[a.AttemptID] = struct{}{} } } log.Debugf("Cleaning network result store.") if err := r.cfg.Payer.CleanStore(toKeep); err != nil { return err } for _, payment := range payments { log.Infof("Resuming payment with hash %v", payment.Info.PaymentHash) r.wg.Add(1) go func(payment *channeldb.InFlightPayment) { defer r.wg.Done() // We create a dummy, empty payment session such that // we won't make another payment attempt when the // result for the in-flight attempt is received. paySession := r.cfg.SessionSource.NewPaymentSessionEmpty() // We pass in a zero timeout value, to indicate we // don't need it to timeout. It will stop immediately // after the existing attempt has finished anyway. We // also set a zero fee limit, as no more routes should // be tried. _, _, err := r.sendPayment( payment.Info.Value, 0, payment.Info.PaymentHash, 0, paySession, ) if err != nil { log.Errorf("Resuming payment with hash %v "+ "failed: %v.", payment.Info.PaymentHash, err) return } log.Infof("Resumed payment with hash %v completed.", payment.Info.PaymentHash) }(payment) } r.wg.Add(1) go r.networkHandler() return nil } // Stop signals the ChannelRouter to gracefully halt all routines. This method // will *block* until all goroutines have excited. If the channel router has // already stopped then this method will return immediately. func (r *ChannelRouter) Stop() error { if !atomic.CompareAndSwapUint32(&r.stopped, 0, 1) { return nil } log.Tracef("Channel Router shutting down") // Our filtered chain view could've only been started if // AssumeChannelValid isn't present. if !r.cfg.AssumeChannelValid { if err := r.cfg.ChainView.Stop(); err != nil { return err } } close(r.quit) r.wg.Wait() return nil } // syncGraphWithChain attempts to synchronize the current channel graph with // the latest UTXO set state. This process involves pruning from the channel // graph any channels which have been closed by spending their funding output // since we've been down. func (r *ChannelRouter) syncGraphWithChain() error { // First, we'll need to check to see if we're already in sync with the // latest state of the UTXO set. bestHash, bestHeight, err := r.cfg.Chain.GetBestBlock() if err != nil { return err } r.bestHeight = uint32(bestHeight) pruneHash, pruneHeight, err := r.cfg.Graph.PruneTip() if err != nil { switch { // If the graph has never been pruned, or hasn't fully been // created yet, then we don't treat this as an explicit error. case err == channeldb.ErrGraphNeverPruned: case err == channeldb.ErrGraphNotFound: default: return err } } log.Infof("Prune tip for Channel Graph: height=%v, hash=%v", pruneHeight, pruneHash) switch { // If the graph has never been pruned, then we can exit early as this // entails it's being created for the first time and hasn't seen any // block or created channels. case pruneHeight == 0 || pruneHash == nil: return nil // If the block hashes and heights match exactly, then we don't need to // prune the channel graph as we're already fully in sync. case bestHash.IsEqual(pruneHash) && uint32(bestHeight) == pruneHeight: return nil } // If the main chain blockhash at prune height is different from the // prune hash, this might indicate the database is on a stale branch. mainBlockHash, err := r.cfg.Chain.GetBlockHash(int64(pruneHeight)) if err != nil { return err } // While we are on a stale branch of the chain, walk backwards to find // first common block. for !pruneHash.IsEqual(mainBlockHash) { log.Infof("channel graph is stale. Disconnecting block %v "+ "(hash=%v)", pruneHeight, pruneHash) // Prune the graph for every channel that was opened at height // >= pruneHeight. _, err := r.cfg.Graph.DisconnectBlockAtHeight(pruneHeight) if err != nil { return err } pruneHash, pruneHeight, err = r.cfg.Graph.PruneTip() if err != nil { switch { // If at this point the graph has never been pruned, we // can exit as this entails we are back to the point // where it hasn't seen any block or created channels, // alas there's nothing left to prune. case err == channeldb.ErrGraphNeverPruned: return nil case err == channeldb.ErrGraphNotFound: return nil default: return err } } mainBlockHash, err = r.cfg.Chain.GetBlockHash(int64(pruneHeight)) if err != nil { return err } } log.Infof("Syncing channel graph from height=%v (hash=%v) to height=%v "+ "(hash=%v)", pruneHeight, pruneHash, bestHeight, bestHash) // If we're not yet caught up, then we'll walk forward in the chain // pruning the channel graph with each new block that hasn't yet been // consumed by the channel graph. var spentOutputs []*wire.OutPoint for nextHeight := pruneHeight + 1; nextHeight <= uint32(bestHeight); nextHeight++ { // Break out of the rescan early if a shutdown has been // requested, otherwise long rescans will block the daemon from // shutting down promptly. select { case <-r.quit: return ErrRouterShuttingDown default: } // Using the next height, request a manual block pruning from // the chainview for the particular block hash. nextHash, err := r.cfg.Chain.GetBlockHash(int64(nextHeight)) if err != nil { return err } filterBlock, err := r.cfg.ChainView.FilterBlock(nextHash) if err != nil { return err } // We're only interested in all prior outputs that have been // spent in the block, so collate all the referenced previous // outpoints within each tx and input. for _, tx := range filterBlock.Transactions { for _, txIn := range tx.TxIn { spentOutputs = append(spentOutputs, &txIn.PreviousOutPoint) } } } // With the spent outputs gathered, attempt to prune the channel graph, // also passing in the best hash+height so the prune tip can be updated. closedChans, err := r.cfg.Graph.PruneGraph( spentOutputs, bestHash, uint32(bestHeight), ) if err != nil { return err } log.Infof("Graph pruning complete: %v channels were closed since "+ "height %v", len(closedChans), pruneHeight) return nil } // pruneZombieChans is a method that will be called periodically to prune out // any "zombie" channels. We consider channels zombies if *both* edges haven't // been updated since our zombie horizon. If AssumeChannelValid is present, // we'll also consider channels zombies if *both* edges are disabled. This // usually signals that a channel has been closed on-chain. We do this // periodically to keep a healthy, lively routing table. func (r *ChannelRouter) pruneZombieChans() error { chansToPrune := make(map[uint64]struct{}) chanExpiry := r.cfg.ChannelPruneExpiry log.Infof("Examining channel graph for zombie channels") // A helper method to detect if the channel belongs to this node isSelfChannelEdge := func(info *channeldb.ChannelEdgeInfo) bool { return info.NodeKey1Bytes == r.selfNode.PubKeyBytes || info.NodeKey2Bytes == r.selfNode.PubKeyBytes } // First, we'll collect all the channels which are eligible for garbage // collection due to being zombies. filterPruneChans := func(info *channeldb.ChannelEdgeInfo, e1, e2 *channeldb.ChannelEdgePolicy) error { // Exit early in case this channel is already marked to be pruned if _, markedToPrune := chansToPrune[info.ChannelID]; markedToPrune { return nil } // We'll ensure that we don't attempt to prune our *own* // channels from the graph, as in any case this should be // re-advertised by the sub-system above us. if isSelfChannelEdge(info) { return nil } // If *both* edges haven't been updated for a period of // chanExpiry, then we'll mark the channel itself as eligible // for graph pruning. var e1Zombie, e2Zombie bool if e1 != nil { e1Zombie = time.Since(e1.LastUpdate) >= chanExpiry if e1Zombie { log.Tracef("Edge #1 of ChannelID(%v) last "+ "update: %v", info.ChannelID, e1.LastUpdate) } } if e2 != nil { e2Zombie = time.Since(e2.LastUpdate) >= chanExpiry if e2Zombie { log.Tracef("Edge #2 of ChannelID(%v) last "+ "update: %v", info.ChannelID, e2.LastUpdate) } } // If the channel is not considered zombie, we can move on to // the next. if !e1Zombie || !e2Zombie { return nil } log.Debugf("ChannelID(%v) is a zombie, collecting to prune", info.ChannelID) // TODO(roasbeef): add ability to delete single directional edge chansToPrune[info.ChannelID] = struct{}{} return nil } // If AssumeChannelValid is present we'll look at the disabled bit for both // edges. If they're both disabled, then we can interpret this as the // channel being closed and can prune it from our graph. if r.cfg.AssumeChannelValid { disabledChanIDs, err := r.cfg.Graph.DisabledChannelIDs() if err != nil { return fmt.Errorf("unable to get disabled channels ids "+ "chans: %v", err) } disabledEdges, err := r.cfg.Graph.FetchChanInfos(disabledChanIDs) if err != nil { return fmt.Errorf("unable to fetch disabled channels edges "+ "chans: %v", err) } // Ensuring we won't prune our own channel from the graph. for _, disabledEdge := range disabledEdges { if !isSelfChannelEdge(disabledEdge.Info) { chansToPrune[disabledEdge.Info.ChannelID] = struct{}{} } } } startTime := time.Unix(0, 0) endTime := time.Now().Add(-1 * chanExpiry) oldEdges, err := r.cfg.Graph.ChanUpdatesInHorizon(startTime, endTime) if err != nil { return fmt.Errorf("unable to fetch expired channel updates "+ "chans: %v", err) } for _, u := range oldEdges { filterPruneChans(u.Info, u.Policy1, u.Policy2) } log.Infof("Pruning %v zombie channels", len(chansToPrune)) if len(chansToPrune) == 0 { return nil } // With the set of zombie-like channels obtained, we'll do another pass // to delete them from the channel graph. toPrune := make([]uint64, 0, len(chansToPrune)) for chanID := range chansToPrune { toPrune = append(toPrune, chanID) log.Tracef("Pruning zombie channel with ChannelID(%v)", chanID) } if err := r.cfg.Graph.DeleteChannelEdges(toPrune...); err != nil { return fmt.Errorf("unable to delete zombie channels: %v", err) } // With the channels pruned, we'll also attempt to prune any nodes that // were a part of them. err = r.cfg.Graph.PruneGraphNodes() if err != nil && err != channeldb.ErrGraphNodesNotFound { return fmt.Errorf("unable to prune graph nodes: %v", err) } return nil } // networkHandler is the primary goroutine for the ChannelRouter. The roles of // this goroutine include answering queries related to the state of the // network, pruning the graph on new block notification, applying network // updates, and registering new topology clients. // // NOTE: This MUST be run as a goroutine. func (r *ChannelRouter) networkHandler() { defer r.wg.Done() graphPruneTicker := time.NewTicker(r.cfg.GraphPruneInterval) defer graphPruneTicker.Stop() defer r.statTicker.Stop() r.stats.Reset() // We'll use this validation barrier to ensure that we process all jobs // in the proper order during parallel validation. // // NOTE: For AssumeChannelValid, we bump up the maximum number of // concurrent validation requests since there are no blocks being // fetched. This significantly increases the performance of IGD for // neutrino nodes. // // However, we dial back to use multiple of the number of cores when // fully validating, to avoid fetching up to 1000 blocks from the // backend. On bitcoind, this will empirically cause massive latency // spikes when executing this many concurrent RPC calls. Critical // subsystems or basic rpc calls that rely on calls such as GetBestBlock // will hang due to excessive load. // // See https://github.com/lightningnetwork/lnd/issues/4892. var validationBarrier *ValidationBarrier if r.cfg.AssumeChannelValid { validationBarrier = NewValidationBarrier(1000, r.quit) } else { validationBarrier = NewValidationBarrier( 4*runtime.NumCPU(), r.quit, ) } for { // If there are stats, resume the statTicker. if !r.stats.Empty() { r.statTicker.Resume() } select { // A new fully validated network update has just arrived. As a // result we'll modify the channel graph accordingly depending // on the exact type of the message. case update := <-r.networkUpdates: // We'll set up any dependants, and wait until a free // slot for this job opens up, this allow us to not // have thousands of goroutines active. validationBarrier.InitJobDependencies(update.msg) r.wg.Add(1) go func() { defer r.wg.Done() defer validationBarrier.CompleteJob() // If this message has an existing dependency, // then we'll wait until that has been fully // validated before we proceed. err := validationBarrier.WaitForDependants( update.msg, ) if err != nil { if err != ErrVBarrierShuttingDown && err != ErrParentValidationFailed { log.Warnf("unexpected error "+ "during validation "+ "barrier shutdown: %v", err) } return } // Process the routing update to determine if // this is either a new update from our PoV or // an update to a prior vertex/edge we // previously accepted. err = r.processUpdate(update.msg, update.op...) update.err <- err // If this message had any dependencies, then // we can now signal them to continue. allowDependents := err == nil || IsError(err, ErrIgnored, ErrOutdated) validationBarrier.SignalDependants( update.msg, allowDependents, ) if err != nil { return } // Send off a new notification for the newly // accepted update. topChange := &TopologyChange{} err = addToTopologyChange( r.cfg.Graph, topChange, update.msg, ) if err != nil { log.Errorf("unable to update topology "+ "change notification: %v", err) return } if !topChange.isEmpty() { r.notifyTopologyChange(topChange) } }() // TODO(roasbeef): remove all unconnected vertexes // after N blocks pass with no corresponding // announcements. case chainUpdate, ok := <-r.staleBlocks: // If the channel has been closed, then this indicates // the daemon is shutting down, so we exit ourselves. if !ok { return } // Since this block is stale, we update our best height // to the previous block. blockHeight := uint32(chainUpdate.Height) atomic.StoreUint32(&r.bestHeight, blockHeight-1) // Update the channel graph to reflect that this block // was disconnected. _, err := r.cfg.Graph.DisconnectBlockAtHeight(blockHeight) if err != nil { log.Errorf("unable to prune graph with stale "+ "block: %v", err) continue } // TODO(halseth): notify client about the reorg? // A new block has arrived, so we can prune the channel graph // of any channels which were closed in the block. case chainUpdate, ok := <-r.newBlocks: // If the channel has been closed, then this indicates // the daemon is shutting down, so we exit ourselves. if !ok { return } // We'll ensure that any new blocks received attach // directly to the end of our main chain. If not, then // we've somehow missed some blocks. We don't process // this block as otherwise, we may miss on-chain // events. currentHeight := atomic.LoadUint32(&r.bestHeight) if chainUpdate.Height != currentHeight+1 { log.Errorf("out of order block: expecting "+ "height=%v, got height=%v", currentHeight+1, chainUpdate.Height) continue } // Once a new block arrives, we update our running // track of the height of the chain tip. blockHeight := uint32(chainUpdate.Height) atomic.StoreUint32(&r.bestHeight, blockHeight) log.Infof("Pruning channel graph using block %v (height=%v)", chainUpdate.Hash, blockHeight) // We're only interested in all prior outputs that have // been spent in the block, so collate all the // referenced previous outpoints within each tx and // input. var spentOutputs []*wire.OutPoint for _, tx := range chainUpdate.Transactions { for _, txIn := range tx.TxIn { spentOutputs = append(spentOutputs, &txIn.PreviousOutPoint) } } // With the spent outputs gathered, attempt to prune // the channel graph, also passing in the hash+height // of the block being pruned so the prune tip can be // updated. chansClosed, err := r.cfg.Graph.PruneGraph(spentOutputs, &chainUpdate.Hash, chainUpdate.Height) if err != nil { log.Errorf("unable to prune routing table: %v", err) continue } log.Infof("Block %v (height=%v) closed %v channels", chainUpdate.Hash, blockHeight, len(chansClosed)) if len(chansClosed) == 0 { continue } // Notify all currently registered clients of the newly // closed channels. closeSummaries := createCloseSummaries(blockHeight, chansClosed...) r.notifyTopologyChange(&TopologyChange{ ClosedChannels: closeSummaries, }) // A new notification client update has arrived. We're either // gaining a new client, or cancelling notifications for an // existing client. case ntfnUpdate := <-r.ntfnClientUpdates: clientID := ntfnUpdate.clientID if ntfnUpdate.cancel { r.RLock() client, ok := r.topologyClients[ntfnUpdate.clientID] r.RUnlock() if ok { r.Lock() delete(r.topologyClients, clientID) r.Unlock() close(client.exit) client.wg.Wait() close(client.ntfnChan) } continue } r.Lock() r.topologyClients[ntfnUpdate.clientID] = &topologyClient{ ntfnChan: ntfnUpdate.ntfnChan, exit: make(chan struct{}), } r.Unlock() // The graph prune ticker has ticked, so we'll examine the // state of the known graph to filter out any zombie channels // for pruning. case <-graphPruneTicker.C: if err := r.pruneZombieChans(); err != nil { log.Errorf("Unable to prune zombies: %v", err) } // Log any stats if we've processed a non-empty number of // channels, updates, or nodes. We'll only pause the ticker if // the last window contained no updates to avoid resuming and // pausing while consecutive windows contain new info. case <-r.statTicker.Ticks(): if !r.stats.Empty() { log.Infof(r.stats.String()) } else { r.statTicker.Pause() } r.stats.Reset() // The router has been signalled to exit, to we exit our main // loop so the wait group can be decremented. case <-r.quit: return } } } // assertNodeAnnFreshness returns a non-nil error if we have an announcement in // the database for the passed node with a timestamp newer than the passed // timestamp. ErrIgnored will be returned if we already have the node, and // ErrOutdated will be returned if we have a timestamp that's after the new // timestamp. func (r *ChannelRouter) assertNodeAnnFreshness(node route.Vertex, msgTimestamp time.Time) error { // If we are not already aware of this node, it means that we don't // know about any channel using this node. To avoid a DoS attack by // node announcements, we will ignore such nodes. If we do know about // this node, check that this update brings info newer than what we // already have. lastUpdate, exists, err := r.cfg.Graph.HasLightningNode(node) if err != nil { return errors.Errorf("unable to query for the "+ "existence of node: %v", err) } if !exists { return newErrf(ErrIgnored, "Ignoring node announcement"+ " for node not found in channel graph (%x)", node[:]) } // If we've reached this point then we're aware of the vertex being // advertised. So we now check if the new message has a new time stamp, // if not then we won't accept the new data as it would override newer // data. if !lastUpdate.Before(msgTimestamp) { return newErrf(ErrOutdated, "Ignoring outdated "+ "announcement for %x", node[:]) } return nil } // processUpdate processes a new relate authenticated channel/edge, node or // channel/edge update network update. If the update didn't affect the internal // state of the draft due to either being out of date, invalid, or redundant, // then error is returned. func (r *ChannelRouter) processUpdate(msg interface{}, op ...batch.SchedulerOption) error { switch msg := msg.(type) { case *channeldb.LightningNode: // Before we add the node to the database, we'll check to see // if the announcement is "fresh" or not. If it isn't, then // we'll return an error. err := r.assertNodeAnnFreshness(msg.PubKeyBytes, msg.LastUpdate) if err != nil { return err } if err := r.cfg.Graph.AddLightningNode(msg, op...); err != nil { return errors.Errorf("unable to add node %v to the "+ "graph: %v", msg.PubKeyBytes, err) } log.Tracef("Updated vertex data for node=%x", msg.PubKeyBytes) r.stats.incNumNodeUpdates() case *channeldb.ChannelEdgeInfo: // Prior to processing the announcement we first check if we // already know of this channel, if so, then we can exit early. _, _, exists, isZombie, err := r.cfg.Graph.HasChannelEdge( msg.ChannelID, ) if err != nil && err != channeldb.ErrGraphNoEdgesFound { return errors.Errorf("unable to check for edge "+ "existence: %v", err) } if isZombie { return newErrf(ErrIgnored, "ignoring msg for zombie "+ "chan_id=%v", msg.ChannelID) } if exists { return newErrf(ErrIgnored, "ignoring msg for known "+ "chan_id=%v", msg.ChannelID) } // If AssumeChannelValid is present, then we are unable to // perform any of the expensive checks below, so we'll // short-circuit our path straight to adding the edge to our // graph. if r.cfg.AssumeChannelValid { if err := r.cfg.Graph.AddChannelEdge(msg, op...); err != nil { return fmt.Errorf("unable to add edge: %v", err) } log.Tracef("New channel discovered! Link "+ "connects %x and %x with ChannelID(%v)", msg.NodeKey1Bytes, msg.NodeKey2Bytes, msg.ChannelID) r.stats.incNumEdgesDiscovered() break } // Before we can add the channel to the channel graph, we need // to obtain the full funding outpoint that's encoded within // the channel ID. channelID := lnwire.NewShortChanIDFromInt(msg.ChannelID) fundingTx, err := r.fetchFundingTx(&channelID) if err != nil { return errors.Errorf("unable to fetch funding tx for "+ "chan_id=%v: %v", msg.ChannelID, err) } // Recreate witness output to be sure that declared in channel // edge bitcoin keys and channel value corresponds to the // reality. witnessScript, err := input.GenMultiSigScript( msg.BitcoinKey1Bytes[:], msg.BitcoinKey2Bytes[:], ) if err != nil { return err } pkScript, err := input.WitnessScriptHash(witnessScript) if err != nil { return err } // Next we'll validate that this channel is actually well // formed. If this check fails, then this channel either // doesn't exist, or isn't the one that was meant to be created // according to the passed channel proofs. fundingPoint, err := chanvalidate.Validate(&chanvalidate.Context{ Locator: &chanvalidate.ShortChanIDChanLocator{ ID: channelID, }, MultiSigPkScript: pkScript, FundingTx: fundingTx, }) if err != nil { return err } // Now that we have the funding outpoint of the channel, ensure // that it hasn't yet been spent. If so, then this channel has // been closed so we'll ignore it. fundingPkScript, err := input.WitnessScriptHash(witnessScript) if err != nil { return err } chanUtxo, err := r.cfg.Chain.GetUtxo( fundingPoint, fundingPkScript, channelID.BlockHeight, r.quit, ) if err != nil { return fmt.Errorf("unable to fetch utxo "+ "for chan_id=%v, chan_point=%v: %v", msg.ChannelID, fundingPoint, err) } // TODO(roasbeef): this is a hack, needs to be removed // after commitment fees are dynamic. msg.Capacity = btcutil.Amount(chanUtxo.Value) msg.ChannelPoint = *fundingPoint if err := r.cfg.Graph.AddChannelEdge(msg, op...); err != nil { return errors.Errorf("unable to add edge: %v", err) } log.Tracef("New channel discovered! Link "+ "connects %x and %x with ChannelPoint(%v): "+ "chan_id=%v, capacity=%v", msg.NodeKey1Bytes, msg.NodeKey2Bytes, fundingPoint, msg.ChannelID, msg.Capacity) r.stats.incNumEdgesDiscovered() // As a new edge has been added to the channel graph, we'll // update the current UTXO filter within our active // FilteredChainView so we are notified if/when this channel is // closed. filterUpdate := []channeldb.EdgePoint{ { FundingPkScript: fundingPkScript, OutPoint: *fundingPoint, }, } err = r.cfg.ChainView.UpdateFilter( filterUpdate, atomic.LoadUint32(&r.bestHeight), ) if err != nil { return errors.Errorf("unable to update chain "+ "view: %v", err) } case *channeldb.ChannelEdgePolicy: // We make sure to hold the mutex for this channel ID, // such that no other goroutine is concurrently doing // database accesses for the same channel ID. r.channelEdgeMtx.Lock(msg.ChannelID) defer r.channelEdgeMtx.Unlock(msg.ChannelID) edge1Timestamp, edge2Timestamp, exists, isZombie, err := r.cfg.Graph.HasChannelEdge(msg.ChannelID) if err != nil && err != channeldb.ErrGraphNoEdgesFound { return errors.Errorf("unable to check for edge "+ "existence: %v", err) } // If the channel is marked as a zombie in our database, and // we consider this a stale update, then we should not apply the // policy. isStaleUpdate := time.Since(msg.LastUpdate) > r.cfg.ChannelPruneExpiry if isZombie && isStaleUpdate { return newErrf(ErrIgnored, "ignoring stale update "+ "(flags=%v|%v) for zombie chan_id=%v", msg.MessageFlags, msg.ChannelFlags, msg.ChannelID) } // If the channel doesn't exist in our database, we cannot // apply the updated policy. if !exists { return newErrf(ErrIgnored, "ignoring update "+ "(flags=%v|%v) for unknown chan_id=%v", msg.MessageFlags, msg.ChannelFlags, msg.ChannelID) } // As edges are directional edge node has a unique policy for // the direction of the edge they control. Therefore we first // check if we already have the most up to date information for // that edge. If this message has a timestamp not strictly // newer than what we already know of we can exit early. switch { // A flag set of 0 indicates this is an announcement for the // "first" node in the channel. case msg.ChannelFlags&lnwire.ChanUpdateDirection == 0: // Ignore outdated message. if !edge1Timestamp.Before(msg.LastUpdate) { return newErrf(ErrOutdated, "Ignoring "+ "outdated update (flags=%v|%v) for "+ "known chan_id=%v", msg.MessageFlags, msg.ChannelFlags, msg.ChannelID) } // Similarly, a flag set of 1 indicates this is an announcement // for the "second" node in the channel. case msg.ChannelFlags&lnwire.ChanUpdateDirection == 1: // Ignore outdated message. if !edge2Timestamp.Before(msg.LastUpdate) { return newErrf(ErrOutdated, "Ignoring "+ "outdated update (flags=%v|%v) for "+ "known chan_id=%v", msg.MessageFlags, msg.ChannelFlags, msg.ChannelID) } } // Now that we know this isn't a stale update, we'll apply the // new edge policy to the proper directional edge within the // channel graph. if err = r.cfg.Graph.UpdateEdgePolicy(msg, op...); err != nil { err := errors.Errorf("unable to add channel: %v", err) log.Error(err) return err } log.Tracef("New channel update applied: %v", newLogClosure(func() string { return spew.Sdump(msg) })) r.stats.incNumChannelUpdates() default: return errors.Errorf("wrong routing update message type") } return nil } // fetchFundingTx returns the funding transaction identified by the passed // short channel ID. // // TODO(roasbeef): replace with call to GetBlockTransaction? (would allow to // later use getblocktxn) func (r *ChannelRouter) fetchFundingTx( chanID *lnwire.ShortChannelID) (*wire.MsgTx, error) { // First fetch the block hash by the block number encoded, then use // that hash to fetch the block itself. blockNum := int64(chanID.BlockHeight) blockHash, err := r.cfg.Chain.GetBlockHash(blockNum) if err != nil { return nil, err } fundingBlock, err := r.cfg.Chain.GetBlock(blockHash) if err != nil { return nil, err } // As a sanity check, ensure that the advertised transaction index is // within the bounds of the total number of transactions within a // block. numTxns := uint32(len(fundingBlock.Transactions)) if chanID.TxIndex > numTxns-1 { return nil, fmt.Errorf("tx_index=#%v is out of range "+ "(max_index=%v), network_chan_id=%v", chanID.TxIndex, numTxns-1, chanID) } return fundingBlock.Transactions[chanID.TxIndex], nil } // routingMsg couples a routing related routing topology update to the // error channel. type routingMsg struct { msg interface{} op []batch.SchedulerOption err chan error } // FindRoute attempts to query the ChannelRouter for the optimum path to a // particular target destination to which it is able to send `amt` after // factoring in channel capacities and cumulative fees along the route. func (r *ChannelRouter) FindRoute(source, target route.Vertex, amt lnwire.MilliSatoshi, restrictions *RestrictParams, destCustomRecords record.CustomSet, routeHints map[route.Vertex][]*channeldb.ChannelEdgePolicy, finalExpiry uint16) (*route.Route, error) { log.Debugf("Searching for path to %v, sending %v", target, amt) // We'll attempt to obtain a set of bandwidth hints that can help us // eliminate certain routes early on in the path finding process. bandwidthHints, err := generateBandwidthHints( r.selfNode, r.cfg.QueryBandwidth, ) if err != nil { return nil, err } // We'll fetch the current block height so we can properly calculate the // required HTLC time locks within the route. _, currentHeight, err := r.cfg.Chain.GetBestBlock() if err != nil { return nil, err } // Now that we know the destination is reachable within the graph, we'll // execute our path finding algorithm. finalHtlcExpiry := currentHeight + int32(finalExpiry) routingTx, err := newDbRoutingTx(r.cfg.Graph) if err != nil { return nil, err } defer func() { err := routingTx.close() if err != nil { log.Errorf("Error closing db tx: %v", err) } }() path, err := findPath( &graphParams{ additionalEdges: routeHints, bandwidthHints: bandwidthHints, graph: routingTx, }, restrictions, &r.cfg.PathFindingConfig, source, target, amt, finalHtlcExpiry, ) if err != nil { return nil, err } // Create the route with absolute time lock values. route, err := newRoute( source, path, uint32(currentHeight), finalHopParams{ amt: amt, totalAmt: amt, cltvDelta: finalExpiry, records: destCustomRecords, }, ) if err != nil { return nil, err } go log.Tracef("Obtained path to send %v to %x: %v", amt, target, newLogClosure(func() string { return spew.Sdump(route) }), ) return route, nil } // generateNewSessionKey generates a new ephemeral private key to be used for a // payment attempt. func generateNewSessionKey() (*btcec.PrivateKey, error) { // Generate a new random session key to ensure that we don't trigger // any replay. // // TODO(roasbeef): add more sources of randomness? return btcec.NewPrivateKey(btcec.S256()) } // generateSphinxPacket generates then encodes a sphinx packet which encodes // the onion route specified by the passed layer 3 route. The blob returned // from this function can immediately be included within an HTLC add packet to // be sent to the first hop within the route. func generateSphinxPacket(rt *route.Route, paymentHash []byte, sessionKey *btcec.PrivateKey) ([]byte, *sphinx.Circuit, error) { // Now that we know we have an actual route, we'll map the route into a // sphinx payument path which includes per-hop paylods for each hop // that give each node within the route the necessary information // (fees, CLTV value, etc) to properly forward the payment. sphinxPath, err := rt.ToSphinxPath() if err != nil { return nil, nil, err } log.Tracef("Constructed per-hop payloads for payment_hash=%x: %v", paymentHash[:], newLogClosure(func() string { path := make([]sphinx.OnionHop, sphinxPath.TrueRouteLength()) for i := range path { hopCopy := sphinxPath[i] hopCopy.NodePub.Curve = nil path[i] = hopCopy } return spew.Sdump(path) }), ) // Next generate the onion routing packet which allows us to perform // privacy preserving source routing across the network. sphinxPacket, err := sphinx.NewOnionPacket( sphinxPath, sessionKey, paymentHash, sphinx.DeterministicPacketFiller, ) if err != nil { return nil, nil, err } // Finally, encode Sphinx packet using its wire representation to be // included within the HTLC add packet. var onionBlob bytes.Buffer if err := sphinxPacket.Encode(&onionBlob); err != nil { return nil, nil, err } log.Tracef("Generated sphinx packet: %v", newLogClosure(func() string { // We make a copy of the ephemeral key and unset the // internal curve here in order to keep the logs from // getting noisy. key := *sphinxPacket.EphemeralKey key.Curve = nil packetCopy := *sphinxPacket packetCopy.EphemeralKey = &key return spew.Sdump(packetCopy) }), ) return onionBlob.Bytes(), &sphinx.Circuit{ SessionKey: sessionKey, PaymentPath: sphinxPath.NodeKeys(), }, nil } // LightningPayment describes a payment to be sent through the network to the // final destination. type LightningPayment struct { // Target is the node in which the payment should be routed towards. Target route.Vertex // Amount is the value of the payment to send through the network in // milli-satoshis. Amount lnwire.MilliSatoshi // FeeLimit is the maximum fee in millisatoshis that the payment should // accept when sending it through the network. The payment will fail // if there isn't a route with lower fees than this limit. FeeLimit lnwire.MilliSatoshi // CltvLimit is the maximum time lock that is allowed for attempts to // complete this payment. CltvLimit uint32 // PaymentHash is the r-hash value to use within the HTLC extended to // the first hop. PaymentHash [32]byte // FinalCLTVDelta is the CTLV expiry delta to use for the _final_ hop // in the route. This means that the final hop will have a CLTV delta // of at least: currentHeight + FinalCLTVDelta. FinalCLTVDelta uint16 // PayAttemptTimeout is a timeout value that we'll use to determine // when we should should abandon the payment attempt after consecutive // payment failure. This prevents us from attempting to send a payment // indefinitely. A zero value means the payment will never time out. // // TODO(halseth): make wallclock time to allow resume after startup. PayAttemptTimeout time.Duration // RouteHints represents the different routing hints that can be used to // assist a payment in reaching its destination successfully. These // hints will act as intermediate hops along the route. // // NOTE: This is optional unless required by the payment. When providing // multiple routes, ensure the hop hints within each route are chained // together and sorted in forward order in order to reach the // destination successfully. RouteHints [][]zpay32.HopHint // OutgoingChannelIDs is the list of channels that are allowed for the // first hop. If nil, any channel may be used. OutgoingChannelIDs []uint64 // LastHop is the pubkey of the last node before the final destination // is reached. If nil, any node may be used. LastHop *route.Vertex // DestFeatures specifies the set of features we assume the final node // has for pathfinding. Typically these will be taken directly from an // invoice, but they can also be manually supplied or assumed by the // sender. If a nil feature vector is provided, the router will try to // fallback to the graph in order to load a feature vector for a node in // the public graph. DestFeatures *lnwire.FeatureVector // PaymentAddr is the payment address specified by the receiver. This // field should be a random 32-byte nonce presented in the receiver's // invoice to prevent probing of the destination. PaymentAddr *[32]byte // PaymentRequest is an optional payment request that this payment is // attempting to complete. PaymentRequest []byte // DestCustomRecords are TLV records that are to be sent to the final // hop in the new onion payload format. If the destination does not // understand this new onion payload format, then the payment will // fail. DestCustomRecords record.CustomSet // MaxParts is the maximum number of partial payments that may be used // to complete the full amount. MaxParts uint32 // MaxShardAmt is the largest shard that we'll attempt to split using. // If this field is set, and we need to split, rather than attempting // half of the original payment amount, we'll use this value if half // the payment amount is greater than it. // // NOTE: This field is _optional_. MaxShardAmt *lnwire.MilliSatoshi } // SendPayment attempts to send a payment as described within the passed // LightningPayment. This function is blocking and will return either: when the // payment is successful, or all candidates routes have been attempted and // resulted in a failed payment. If the payment succeeds, then a non-nil Route // will be returned which describes the path the successful payment traversed // within the network to reach the destination. Additionally, the payment // preimage will also be returned. func (r *ChannelRouter) SendPayment(payment *LightningPayment) ([32]byte, *route.Route, error) { paySession, err := r.preparePayment(payment) if err != nil { return [32]byte{}, nil, err } log.Tracef("Dispatching SendPayment for lightning payment: %v", spewPayment(payment)) // Since this is the first time this payment is being made, we pass nil // for the existing attempt. return r.sendPayment( payment.Amount, payment.FeeLimit, payment.PaymentHash, payment.PayAttemptTimeout, paySession, ) } // SendPaymentAsync is the non-blocking version of SendPayment. The payment // result needs to be retrieved via the control tower. func (r *ChannelRouter) SendPaymentAsync(payment *LightningPayment) error { paySession, err := r.preparePayment(payment) if err != nil { return err } // Since this is the first time this payment is being made, we pass nil // for the existing attempt. r.wg.Add(1) go func() { defer r.wg.Done() log.Tracef("Dispatching SendPayment for lightning payment: %v", spewPayment(payment)) _, _, err := r.sendPayment( payment.Amount, payment.FeeLimit, payment.PaymentHash, payment.PayAttemptTimeout, paySession, ) if err != nil { log.Errorf("Payment with hash %x failed: %v", payment.PaymentHash, err) } }() return nil } // spewPayment returns a log closures that provides a spewed string // representation of the passed payment. func spewPayment(payment *LightningPayment) logClosure { return newLogClosure(func() string { // Make a copy of the payment with a nilled Curve // before spewing. var routeHints [][]zpay32.HopHint for _, routeHint := range payment.RouteHints { var hopHints []zpay32.HopHint for _, hopHint := range routeHint { h := hopHint.Copy() h.NodeID.Curve = nil hopHints = append(hopHints, h) } routeHints = append(routeHints, hopHints) } p := *payment p.RouteHints = routeHints return spew.Sdump(p) }) } // preparePayment creates the payment session and registers the payment with the // control tower. func (r *ChannelRouter) preparePayment(payment *LightningPayment) ( PaymentSession, error) { // Before starting the HTLC routing attempt, we'll create a fresh // payment session which will report our errors back to mission // control. paySession, err := r.cfg.SessionSource.NewPaymentSession(payment) if err != nil { return nil, err } // Record this payment hash with the ControlTower, ensuring it is not // already in-flight. // // TODO(roasbeef): store records as part of creation info? info := &channeldb.PaymentCreationInfo{ PaymentHash: payment.PaymentHash, Value: payment.Amount, CreationTime: r.cfg.Clock.Now(), PaymentRequest: payment.PaymentRequest, } err = r.cfg.Control.InitPayment(payment.PaymentHash, info) if err != nil { return nil, err } return paySession, nil } // SendToRoute attempts to send a payment with the given hash through the // provided route. This function is blocking and will return the attempt // information as it is stored in the database. For a successful htlc, this // information will contain the preimage. If an error occurs after the attempt // was initiated, both return values will be non-nil. func (r *ChannelRouter) SendToRoute(hash lntypes.Hash, rt *route.Route) ( *channeldb.HTLCAttempt, error) { // Calculate amount paid to receiver. amt := rt.ReceiverAmt() // If this is meant as a MP payment shard, we set the amount // for the creating info to the total amount of the payment. finalHop := rt.Hops[len(rt.Hops)-1] mpp := finalHop.MPP if mpp != nil { amt = mpp.TotalMsat() } // Record this payment hash with the ControlTower, ensuring it is not // already in-flight. info := &channeldb.PaymentCreationInfo{ PaymentHash: hash, Value: amt, CreationTime: r.cfg.Clock.Now(), PaymentRequest: nil, } err := r.cfg.Control.InitPayment(hash, info) switch { // If this is an MPP attempt and the hash is already registered with // the database, we can go on to launch the shard. case err == channeldb.ErrPaymentInFlight && mpp != nil: // Any other error is not tolerated. case err != nil: return nil, err } log.Tracef("Dispatching SendToRoute for hash %v: %v", hash, newLogClosure(func() string { return spew.Sdump(rt) }), ) // Launch a shard along the given route. sh := &shardHandler{ router: r, paymentHash: hash, } var shardError error attempt, outcome, err := sh.launchShard(rt) // With SendToRoute, it can happen that the route exceeds protocol // constraints. Mark the payment as failed with an internal error. if err == route.ErrMaxRouteHopsExceeded || err == sphinx.ErrMaxRoutingInfoSizeExceeded { log.Debugf("Invalid route provided for payment %x: %v", hash, err) controlErr := r.cfg.Control.Fail( hash, channeldb.FailureReasonError, ) if controlErr != nil { return nil, controlErr } } // In any case, don't continue if there is an error. if err != nil { return nil, err } var htlcAttempt *channeldb.HTLCAttempt switch { // Failed to launch shard. case outcome.err != nil: shardError = outcome.err htlcAttempt = outcome.attempt // Shard successfully launched, wait for the result to be available. default: result, err := sh.collectResult(attempt) if err != nil { return nil, err } // We got a successful result. if result.err == nil { return result.attempt, nil } // The shard failed, break switch to handle it. shardError = result.err htlcAttempt = result.attempt } // Since for SendToRoute we won't retry in case the shard fails, we'll // mark the payment failed with the control tower immediately. Process // the error to check if it maps into a terminal error code, if not use // a generic NO_ROUTE error. reason := r.processSendError( attempt.AttemptID, &attempt.Route, shardError, ) if reason == nil { r := channeldb.FailureReasonNoRoute reason = &r } err = r.cfg.Control.Fail(hash, *reason) if err != nil { return nil, err } return htlcAttempt, shardError } // sendPayment attempts to send a payment to the passed payment hash. This // function is blocking and will return either: when the payment is successful, // or all candidates routes have been attempted and resulted in a failed // payment. If the payment succeeds, then a non-nil Route will be returned // which describes the path the successful payment traversed within the network // to reach the destination. Additionally, the payment preimage will also be // returned. // // The existing attempt argument should be set to nil if this is a payment that // haven't had any payment attempt sent to the switch yet. If it has had an // attempt already, it should be passed such that the result can be retrieved. // // This method relies on the ControlTower's internal payment state machine to // carry out its execution. After restarts it is safe, and assumed, that the // router will call this method for every payment still in-flight according to // the ControlTower. func (r *ChannelRouter) sendPayment( totalAmt, feeLimit lnwire.MilliSatoshi, paymentHash lntypes.Hash, timeout time.Duration, paySession PaymentSession) ([32]byte, *route.Route, error) { // We'll also fetch the current block height so we can properly // calculate the required HTLC time locks within the route. _, currentHeight, err := r.cfg.Chain.GetBestBlock() if err != nil { return [32]byte{}, nil, err } // Now set up a paymentLifecycle struct with these params, such that we // can resume the payment from the current state. p := &paymentLifecycle{ router: r, totalAmount: totalAmt, feeLimit: feeLimit, paymentHash: paymentHash, paySession: paySession, currentHeight: currentHeight, } // If a timeout is specified, create a timeout channel. If no timeout is // specified, the channel is left nil and will never abort the payment // loop. if timeout != 0 { p.timeoutChan = time.After(timeout) } return p.resumePayment() } // tryApplyChannelUpdate tries to apply a channel update present in the failure // message if any. func (r *ChannelRouter) tryApplyChannelUpdate(rt *route.Route, errorSourceIdx int, failure lnwire.FailureMessage) error { // It makes no sense to apply our own channel updates. if errorSourceIdx == 0 { log.Errorf("Channel update of ourselves received") return nil } // Extract channel update if the error contains one. update := r.extractChannelUpdate(failure) if update == nil { return nil } // Parse pubkey to allow validation of the channel update. This should // always succeed, otherwise there is something wrong in our // implementation. Therefore return an error. errVertex := rt.Hops[errorSourceIdx-1].PubKeyBytes errSource, err := btcec.ParsePubKey( errVertex[:], btcec.S256(), ) if err != nil { log.Errorf("Cannot parse pubkey: idx=%v, pubkey=%v", errorSourceIdx, errVertex) return err } // Apply channel update. if !r.applyChannelUpdate(update, errSource) { log.Debugf("Invalid channel update received: node=%v", errVertex) } return nil } // processSendError analyzes the error for the payment attempt received from the // switch and updates mission control and/or channel policies. Depending on the // error type, this error is either the final outcome of the payment or we need // to continue with an alternative route. A final outcome is indicated by a // non-nil return value. func (r *ChannelRouter) processSendError(paymentID uint64, rt *route.Route, sendErr error) *channeldb.FailureReason { internalErrorReason := channeldb.FailureReasonError reportFail := func(srcIdx *int, msg lnwire.FailureMessage) *channeldb.FailureReason { // Report outcome to mission control. reason, err := r.cfg.MissionControl.ReportPaymentFail( paymentID, rt, srcIdx, msg, ) if err != nil { log.Errorf("Error reporting payment result to mc: %v", err) return &internalErrorReason } return reason } if sendErr == htlcswitch.ErrUnreadableFailureMessage { log.Tracef("Unreadable failure when sending htlc") return reportFail(nil, nil) } // If the error is a ClearTextError, we have received a valid wire // failure message, either from our own outgoing link or from a node // down the route. If the error is not related to the propagation of // our payment, we can stop trying because an internal error has // occurred. rtErr, ok := sendErr.(htlcswitch.ClearTextError) if !ok { return &internalErrorReason } // failureSourceIdx is the index of the node that the failure occurred // at. If the ClearTextError received is not a ForwardingError the // payment error occurred at our node, so we leave this value as 0 // to indicate that the failure occurred locally. If the error is a // ForwardingError, it did not originate at our node, so we set // failureSourceIdx to the index of the node where the failure occurred. failureSourceIdx := 0 source, ok := rtErr.(*htlcswitch.ForwardingError) if ok { failureSourceIdx = source.FailureSourceIdx } // Extract the wire failure and apply channel update if it contains one. // If we received an unknown failure message from a node along the // route, the failure message will be nil. failureMessage := rtErr.WireMessage() if failureMessage != nil { err := r.tryApplyChannelUpdate( rt, failureSourceIdx, failureMessage, ) if err != nil { return &internalErrorReason } } log.Tracef("Node=%v reported failure when sending htlc", failureSourceIdx) return reportFail(&failureSourceIdx, failureMessage) } // extractChannelUpdate examines the error and extracts the channel update. func (r *ChannelRouter) extractChannelUpdate( failure lnwire.FailureMessage) *lnwire.ChannelUpdate { var update *lnwire.ChannelUpdate switch onionErr := failure.(type) { case *lnwire.FailExpiryTooSoon: update = &onionErr.Update case *lnwire.FailAmountBelowMinimum: update = &onionErr.Update case *lnwire.FailFeeInsufficient: update = &onionErr.Update case *lnwire.FailIncorrectCltvExpiry: update = &onionErr.Update case *lnwire.FailChannelDisabled: update = &onionErr.Update case *lnwire.FailTemporaryChannelFailure: update = onionErr.Update } return update } // applyChannelUpdate validates a channel update and if valid, applies it to the // database. It returns a bool indicating whether the updates was successful. func (r *ChannelRouter) applyChannelUpdate(msg *lnwire.ChannelUpdate, pubKey *btcec.PublicKey) bool { ch, _, _, err := r.GetChannelByID(msg.ShortChannelID) if err != nil { log.Errorf("Unable to retrieve channel by id: %v", err) return false } if err := ValidateChannelUpdateAnn(pubKey, ch.Capacity, msg); err != nil { log.Errorf("Unable to validate channel update: %v", err) return false } err = r.UpdateEdge(&channeldb.ChannelEdgePolicy{ SigBytes: msg.Signature.ToSignatureBytes(), ChannelID: msg.ShortChannelID.ToUint64(), LastUpdate: time.Unix(int64(msg.Timestamp), 0), MessageFlags: msg.MessageFlags, ChannelFlags: msg.ChannelFlags, TimeLockDelta: msg.TimeLockDelta, MinHTLC: msg.HtlcMinimumMsat, MaxHTLC: msg.HtlcMaximumMsat, FeeBaseMSat: lnwire.MilliSatoshi(msg.BaseFee), FeeProportionalMillionths: lnwire.MilliSatoshi(msg.FeeRate), }) if err != nil && !IsError(err, ErrIgnored, ErrOutdated) { log.Errorf("Unable to apply channel update: %v", err) return false } return true } // AddNode is used to add information about a node to the router database. If // the node with this pubkey is not present in an existing channel, it will // be ignored. // // NOTE: This method is part of the ChannelGraphSource interface. func (r *ChannelRouter) AddNode(node *channeldb.LightningNode, op ...batch.SchedulerOption) error { rMsg := &routingMsg{ msg: node, op: op, err: make(chan error, 1), } select { case r.networkUpdates <- rMsg: select { case err := <-rMsg.err: return err case <-r.quit: return ErrRouterShuttingDown } case <-r.quit: return ErrRouterShuttingDown } } // AddEdge is used to add edge/channel to the topology of the router, after all // information about channel will be gathered this edge/channel might be used // in construction of payment path. // // NOTE: This method is part of the ChannelGraphSource interface. func (r *ChannelRouter) AddEdge(edge *channeldb.ChannelEdgeInfo, op ...batch.SchedulerOption) error { rMsg := &routingMsg{ msg: edge, op: op, err: make(chan error, 1), } select { case r.networkUpdates <- rMsg: select { case err := <-rMsg.err: return err case <-r.quit: return ErrRouterShuttingDown } case <-r.quit: return ErrRouterShuttingDown } } // UpdateEdge is used to update edge information, without this message edge // considered as not fully constructed. // // NOTE: This method is part of the ChannelGraphSource interface. func (r *ChannelRouter) UpdateEdge(update *channeldb.ChannelEdgePolicy, op ...batch.SchedulerOption) error { rMsg := &routingMsg{ msg: update, op: op, err: make(chan error, 1), } select { case r.networkUpdates <- rMsg: select { case err := <-rMsg.err: return err case <-r.quit: return ErrRouterShuttingDown } case <-r.quit: return ErrRouterShuttingDown } } // CurrentBlockHeight returns the block height from POV of the router subsystem. // // NOTE: This method is part of the ChannelGraphSource interface. func (r *ChannelRouter) CurrentBlockHeight() (uint32, error) { _, height, err := r.cfg.Chain.GetBestBlock() return uint32(height), err } // GetChannelByID return the channel by the channel id. // // NOTE: This method is part of the ChannelGraphSource interface. func (r *ChannelRouter) GetChannelByID(chanID lnwire.ShortChannelID) ( *channeldb.ChannelEdgeInfo, *channeldb.ChannelEdgePolicy, *channeldb.ChannelEdgePolicy, error) { return r.cfg.Graph.FetchChannelEdgesByID(chanID.ToUint64()) } // FetchLightningNode attempts to look up a target node by its identity public // key. channeldb.ErrGraphNodeNotFound is returned if the node doesn't exist // within the graph. // // NOTE: This method is part of the ChannelGraphSource interface. func (r *ChannelRouter) FetchLightningNode(node route.Vertex) (*channeldb.LightningNode, error) { return r.cfg.Graph.FetchLightningNode(nil, node) } // ForEachNode is used to iterate over every node in router topology. // // NOTE: This method is part of the ChannelGraphSource interface. func (r *ChannelRouter) ForEachNode(cb func(*channeldb.LightningNode) error) error { return r.cfg.Graph.ForEachNode(func(_ kvdb.RTx, n *channeldb.LightningNode) error { return cb(n) }) } // ForAllOutgoingChannels is used to iterate over all outgoing channels owned by // the router. // // NOTE: This method is part of the ChannelGraphSource interface. func (r *ChannelRouter) ForAllOutgoingChannels(cb func(*channeldb.ChannelEdgeInfo, *channeldb.ChannelEdgePolicy) error) error { return r.selfNode.ForEachChannel(nil, func(_ kvdb.RTx, c *channeldb.ChannelEdgeInfo, e, _ *channeldb.ChannelEdgePolicy) error { if e == nil { return fmt.Errorf("channel from self node has no policy") } return cb(c, e) }) } // ForEachChannel is used to iterate over every known edge (channel) within our // view of the channel graph. // // NOTE: This method is part of the ChannelGraphSource interface. func (r *ChannelRouter) ForEachChannel(cb func(chanInfo *channeldb.ChannelEdgeInfo, e1, e2 *channeldb.ChannelEdgePolicy) error) error { return r.cfg.Graph.ForEachChannel(cb) } // AddProof updates the channel edge info with proof which is needed to // properly announce the edge to the rest of the network. // // NOTE: This method is part of the ChannelGraphSource interface. func (r *ChannelRouter) AddProof(chanID lnwire.ShortChannelID, proof *channeldb.ChannelAuthProof) error { info, _, _, err := r.cfg.Graph.FetchChannelEdgesByID(chanID.ToUint64()) if err != nil { return err } info.AuthProof = proof return r.cfg.Graph.UpdateChannelEdge(info) } // IsStaleNode returns true if the graph source has a node announcement for the // target node with a more recent timestamp. // // NOTE: This method is part of the ChannelGraphSource interface. func (r *ChannelRouter) IsStaleNode(node route.Vertex, timestamp time.Time) bool { // If our attempt to assert that the node announcement is fresh fails, // then we know that this is actually a stale announcement. return r.assertNodeAnnFreshness(node, timestamp) != nil } // IsPublicNode determines whether the given vertex is seen as a public node in // the graph from the graph's source node's point of view. // // NOTE: This method is part of the ChannelGraphSource interface. func (r *ChannelRouter) IsPublicNode(node route.Vertex) (bool, error) { return r.cfg.Graph.IsPublicNode(node) } // IsKnownEdge returns true if the graph source already knows of the passed // channel ID either as a live or zombie edge. // // NOTE: This method is part of the ChannelGraphSource interface. func (r *ChannelRouter) IsKnownEdge(chanID lnwire.ShortChannelID) bool { _, _, exists, isZombie, _ := r.cfg.Graph.HasChannelEdge(chanID.ToUint64()) return exists || isZombie } // IsStaleEdgePolicy returns true if the graph soruce has a channel edge for // the passed channel ID (and flags) that have a more recent timestamp. // // NOTE: This method is part of the ChannelGraphSource interface. func (r *ChannelRouter) IsStaleEdgePolicy(chanID lnwire.ShortChannelID, timestamp time.Time, flags lnwire.ChanUpdateChanFlags) bool { edge1Timestamp, edge2Timestamp, exists, isZombie, err := r.cfg.Graph.HasChannelEdge(chanID.ToUint64()) if err != nil { return false } // If we know of the edge as a zombie, then we'll make some additional // checks to determine if the new policy is fresh. if isZombie { // When running with AssumeChannelValid, we also prune channels // if both of their edges are disabled. We'll mark the new // policy as stale if it remains disabled. if r.cfg.AssumeChannelValid { isDisabled := flags&lnwire.ChanUpdateDisabled == lnwire.ChanUpdateDisabled if isDisabled { return true } } // Otherwise, we'll fall back to our usual ChannelPruneExpiry. return time.Since(timestamp) > r.cfg.ChannelPruneExpiry } // If we don't know of the edge, then it means it's fresh (thus not // stale). if !exists { return false } // As edges are directional edge node has a unique policy for the // direction of the edge they control. Therefore we first check if we // already have the most up to date information for that edge. If so, // then we can exit early. switch { // A flag set of 0 indicates this is an announcement for the "first" // node in the channel. case flags&lnwire.ChanUpdateDirection == 0: return !edge1Timestamp.Before(timestamp) // Similarly, a flag set of 1 indicates this is an announcement for the // "second" node in the channel. case flags&lnwire.ChanUpdateDirection == 1: return !edge2Timestamp.Before(timestamp) } return false } // MarkEdgeLive clears an edge from our zombie index, deeming it as live. // // NOTE: This method is part of the ChannelGraphSource interface. func (r *ChannelRouter) MarkEdgeLive(chanID lnwire.ShortChannelID) error { return r.cfg.Graph.MarkEdgeLive(chanID.ToUint64()) } // generateBandwidthHints is a helper function that's utilized the main // findPath function in order to obtain hints from the lower layer w.r.t to the // available bandwidth of edges on the network. Currently, we'll only obtain // bandwidth hints for the edges we directly have open ourselves. Obtaining // these hints allows us to reduce the number of extraneous attempts as we can // skip channels that are inactive, or just don't have enough bandwidth to // carry the payment. func generateBandwidthHints(sourceNode *channeldb.LightningNode, queryBandwidth func(*channeldb.ChannelEdgeInfo) lnwire.MilliSatoshi) (map[uint64]lnwire.MilliSatoshi, error) { // First, we'll collect the set of outbound edges from the target // source node. var localChans []*channeldb.ChannelEdgeInfo err := sourceNode.ForEachChannel(nil, func(tx kvdb.RTx, edgeInfo *channeldb.ChannelEdgeInfo, _, _ *channeldb.ChannelEdgePolicy) error { localChans = append(localChans, edgeInfo) return nil }) if err != nil { return nil, err } // Now that we have all of our outbound edges, we'll populate the set // of bandwidth hints, querying the lower switch layer for the most up // to date values. bandwidthHints := make(map[uint64]lnwire.MilliSatoshi) for _, localChan := range localChans { bandwidthHints[localChan.ChannelID] = queryBandwidth(localChan) } return bandwidthHints, nil } // ErrNoChannel is returned when a route cannot be built because there are no // channels that satisfy all requirements. type ErrNoChannel struct { position int fromNode route.Vertex } // Error returns a human readable string describing the error. func (e ErrNoChannel) Error() string { return fmt.Sprintf("no matching outgoing channel available for "+ "node %v (%v)", e.position, e.fromNode) } // BuildRoute returns a fully specified route based on a list of pubkeys. If // amount is nil, the minimum routable amount is used. To force a specific // outgoing channel, use the outgoingChan parameter. func (r *ChannelRouter) BuildRoute(amt *lnwire.MilliSatoshi, hops []route.Vertex, outgoingChan *uint64, finalCltvDelta int32, payAddr *[32]byte) (*route.Route, error) { log.Tracef("BuildRoute called: hopsCount=%v, amt=%v", len(hops), amt) var outgoingChans map[uint64]struct{} if outgoingChan != nil { outgoingChans = map[uint64]struct{}{ *outgoingChan: {}, } } // If no amount is specified, we need to build a route for the minimum // amount that this route can carry. useMinAmt := amt == nil // We'll attempt to obtain a set of bandwidth hints that helps us select // the best outgoing channel to use in case no outgoing channel is set. bandwidthHints, err := generateBandwidthHints( r.selfNode, r.cfg.QueryBandwidth, ) if err != nil { return nil, err } // Fetch the current block height outside the routing transaction, to // prevent the rpc call blocking the database. _, height, err := r.cfg.Chain.GetBestBlock() if err != nil { return nil, err } // Allocate a list that will contain the unified policies for this // route. edges := make([]*unifiedPolicy, len(hops)) var runningAmt lnwire.MilliSatoshi if useMinAmt { // For minimum amount routes, aim to deliver at least 1 msat to // the destination. There are nodes in the wild that have a // min_htlc channel policy of zero, which could lead to a zero // amount payment being made. runningAmt = 1 } else { // If an amount is specified, we need to build a route that // delivers exactly this amount to the final destination. runningAmt = *amt } // Open a transaction to execute the graph queries in. routingTx, err := newDbRoutingTx(r.cfg.Graph) if err != nil { return nil, err } defer func() { err := routingTx.close() if err != nil { log.Errorf("Error closing db tx: %v", err) } }() // Traverse hops backwards to accumulate fees in the running amounts. source := r.selfNode.PubKeyBytes for i := len(hops) - 1; i >= 0; i-- { toNode := hops[i] var fromNode route.Vertex if i == 0 { fromNode = source } else { fromNode = hops[i-1] } localChan := i == 0 // Build unified policies for this hop based on the channels // known in the graph. u := newUnifiedPolicies(source, toNode, outgoingChans) err := u.addGraphPolicies(routingTx) if err != nil { return nil, err } // Exit if there are no channels. unifiedPolicy, ok := u.policies[fromNode] if !ok { return nil, ErrNoChannel{ fromNode: fromNode, position: i, } } // If using min amt, increase amt if needed. if useMinAmt { min := unifiedPolicy.minAmt() if min > runningAmt { runningAmt = min } } // Get a forwarding policy for the specific amount that we want // to forward. policy := unifiedPolicy.getPolicy(runningAmt, bandwidthHints) if policy == nil { return nil, ErrNoChannel{ fromNode: fromNode, position: i, } } // Add fee for this hop. if !localChan { runningAmt += policy.ComputeFee(runningAmt) } log.Tracef("Select channel %v at position %v", policy.ChannelID, i) edges[i] = unifiedPolicy } // Now that we arrived at the start of the route and found out the route // total amount, we make a forward pass. Because the amount may have // been increased in the backward pass, fees need to be recalculated and // amount ranges re-checked. var pathEdges []*channeldb.ChannelEdgePolicy receiverAmt := runningAmt for i, edge := range edges { policy := edge.getPolicy(receiverAmt, bandwidthHints) if policy == nil { return nil, ErrNoChannel{ fromNode: hops[i-1], position: i, } } if i > 0 { // Decrease the amount to send while going forward. receiverAmt -= policy.ComputeFeeFromIncoming( receiverAmt, ) } pathEdges = append(pathEdges, policy) } // Build and return the final route. return newRoute( source, pathEdges, uint32(height), finalHopParams{ amt: receiverAmt, totalAmt: receiverAmt, cltvDelta: uint16(finalCltvDelta), records: nil, paymentAddr: payAddr, }, ) }