package routing import ( "bytes" "crypto/sha256" "fmt" "runtime" "sort" "sync" "sync/atomic" "time" "github.com/btcsuite/btcd/btcec" "github.com/btcsuite/btcd/wire" "github.com/btcsuite/btcutil" "github.com/coreos/bbolt" "github.com/davecgh/go-spew/spew" "github.com/go-errors/errors" sphinx "github.com/lightningnetwork/lightning-onion" "github.com/lightningnetwork/lnd/channeldb" "github.com/lightningnetwork/lnd/htlcswitch" "github.com/lightningnetwork/lnd/input" "github.com/lightningnetwork/lnd/lnwallet" "github.com/lightningnetwork/lnd/lnwire" "github.com/lightningnetwork/lnd/multimutex" "github.com/lightningnetwork/lnd/routing/chainview" "github.com/lightningnetwork/lnd/routing/route" "github.com/lightningnetwork/lnd/zpay32" ) const ( // defaultPayAttemptTimeout is a duration that we'll use to determine // if we should give up on a payment attempt. This will be used if a // value isn't specified in the LightningNode struct. 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) ) var ( // ErrNoRouteHopsProvided is returned when a caller attempts to // construct a new sphinx packet, but provides an empty set of hops for // each route. ErrNoRouteHopsProvided = fmt.Errorf("empty route hops provided") // 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) 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) 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) 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 } // 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 } // 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 // SendToSwitch 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. SendToSwitch func(firstHop lnwire.ShortChannelID, htlcAdd *lnwire.UpdateAddHTLC, circuit *sphinx.Circuit) ([sha256.Size]byte, error) // 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 // 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 // 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 } // routeTuple is an entry within the ChannelRouter's route cache. We cache // prospective routes based on first the destination, and then the target // amount. We required the target amount as that will influence the available // set of paths for a payment. type routeTuple struct { amt lnwire.MilliSatoshi dest [33]byte } // newRouteTuple creates a new route tuple from the target and amount. func newRouteTuple(amt lnwire.MilliSatoshi, dest []byte) routeTuple { r := routeTuple{ amt: amt, } copy(r.dest[:], dest) return r } // 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 } // newEdgeLocatorByPubkeys returns an edgeLocator based on its end point // pubkeys. func newEdgeLocatorByPubkeys(channelID uint64, fromNode, toNode *route.Vertex) *EdgeLocator { // Determine direction based on lexicographical ordering of both // pubkeys. var direction uint8 if bytes.Compare(fromNode[:], toNode[:]) == 1 { direction = 1 } return &EdgeLocator{ ChannelID: channelID, Direction: direction, } } // newEdgeLocator extracts an edgeLocator based for a full edge policy // structure. func newEdgeLocator(edge *channeldb.ChannelEdgePolicy) *EdgeLocator { return &EdgeLocator{ ChannelID: edge.ChannelID, Direction: uint8(edge.ChannelFlags & lnwire.ChanUpdateDirection), } } // 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 // 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 *missionControl // 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 rejectMtx sync.RWMutex rejectCache map[uint64]struct{} 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, rejectCache: make(map[uint64]struct{}), quit: make(chan struct{}), } r.missionControl = newMissionControl( cfg.Graph, selfNode, cfg.QueryBandwidth, ) 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. if r.cfg.AssumeChannelValid { if err := r.pruneZombieChans(); err != nil { return 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 } } 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 numChansClosed uint32 for nextHeight := pruneHeight + 1; nextHeight <= uint32(bestHeight); nextHeight++ { // 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. var spentOutputs []*wire.OutPoint 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 hash+height of the block // being pruned so the prune tip can be updated. closedChans, err := r.cfg.Graph.PruneGraph(spentOutputs, nextHash, nextHeight) if err != nil { return err } numClosed := uint32(len(closedChans)) log.Infof("Block %v (height=%v) closed %v channels", nextHash, nextHeight, numClosed) numChansClosed += numClosed } log.Infof("Graph pruning complete: %v channels were closed since "+ "height %v", numChansClosed, 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 { var chansToPrune []uint64 chanExpiry := r.cfg.ChannelPruneExpiry log.Infof("Examining channel graph for zombie channels") // 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 { // 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 info.NodeKey1Bytes == r.selfNode.PubKeyBytes || info.NodeKey2Bytes == r.selfNode.PubKeyBytes { 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) } } isZombieChan := e1Zombie && e2Zombie // If AssumeChannelValid is present and we've determined the // channel is not a zombie, 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 && !isZombieChan { var e1Disabled, e2Disabled bool if e1 != nil { e1Disabled = e1.IsDisabled() log.Tracef("Edge #1 of ChannelID(%v) "+ "disabled=%v", info.ChannelID, e1Disabled) } if e2 != nil { e2Disabled = e2.IsDisabled() log.Tracef("Edge #2 of ChannelID(%v) "+ "disabled=%v", info.ChannelID, e2Disabled) } isZombieChan = e1Disabled && e2Disabled } // If the channel is not considered zombie, we can move on to // the next. if !isZombieChan { return nil } log.Debugf("ChannelID(%v) is a zombie, collecting to prune", info.ChannelID) // TODO(roasbeef): add ability to delete single directional edge chansToPrune = append(chansToPrune, info.ChannelID) // As we're detecting this as a zombie channel, we'll add this // to the set of recently rejected items so we don't re-accept // it shortly after. r.rejectCache[info.ChannelID] = struct{}{} return nil } r.rejectMtx.Lock() defer r.rejectMtx.Unlock() err := r.cfg.Graph.ForEachChannel(filterPruneChans) if err != nil { return fmt.Errorf("unable to filter local zombie channels: "+ "%v", err) } log.Infof("Pruning %v zombie channels", len(chansToPrune)) // With the set of zombie-like channels obtained, we'll do another pass // to delete them from the channel graph. for _, chanID := range chansToPrune { log.Tracef("Pruning zombie channel with ChannelID(%v)", chanID) } if err := r.cfg.Graph.DeleteChannelEdges(chansToPrune...); 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() // We'll use this validation barrier to ensure that we process all jobs // in the proper order during parallel validation. validationBarrier := NewValidationBarrier(runtime.NumCPU()*4, r.quit) for { 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 { 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.err <- err // If this message had any dependencies, then // we can now signal them to continue. validationBarrier.SignalDependants(update.msg) 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) } // 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{}) 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); err != nil { return errors.Errorf("unable to add node %v to the "+ "graph: %v", msg.PubKeyBytes, err) } log.Infof("Updated vertex data for node=%x", msg.PubKeyBytes) case *channeldb.ChannelEdgeInfo: // If we recently rejected this channel edge, then we won't // attempt to re-process it. r.rejectMtx.RLock() if _, ok := r.rejectCache[msg.ChannelID]; ok { r.rejectMtx.RUnlock() return newErrf(ErrRejected, "recently rejected "+ "chan_id=%v", msg.ChannelID) } r.rejectMtx.RUnlock() // 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); err != nil { return fmt.Errorf("unable to add edge: %v", err) } log.Infof("New channel discovered! Link "+ "connects %x and %x with ChannelID(%v)", msg.NodeKey1Bytes, msg.NodeKey2Bytes, msg.ChannelID) 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) fundingPoint, _, err := r.fetchChanPoint(&channelID) if err != nil { r.rejectMtx.Lock() r.rejectCache[msg.ChannelID] = struct{}{} r.rejectMtx.Unlock() return errors.Errorf("unable to fetch chan point 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 } fundingPkScript, err := input.WitnessScriptHash(witnessScript) 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. chanUtxo, err := r.cfg.Chain.GetUtxo( fundingPoint, fundingPkScript, channelID.BlockHeight, ) if err != nil { r.rejectMtx.Lock() r.rejectCache[msg.ChannelID] = struct{}{} r.rejectMtx.Unlock() return fmt.Errorf("unable to fetch utxo "+ "for chan_id=%v, chan_point=%v: %v", msg.ChannelID, fundingPoint, err) } // By checking the equality of witness pkscripts we checks that // funding witness script is multisignature lock which contains // both local and remote public keys which was declared in // channel edge and also that the announced channel value is // right. if !bytes.Equal(fundingPkScript, chanUtxo.PkScript) { return errors.Errorf("pkScript mismatch: expected %x, "+ "got %x", fundingPkScript, chanUtxo.PkScript) } // 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); err != nil { return errors.Errorf("unable to add edge: %v", err) } log.Infof("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) // 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: // If we recently rejected this channel edge, then we won't // attempt to re-process it. r.rejectMtx.RLock() if _, ok := r.rejectCache[msg.ChannelID]; ok { r.rejectMtx.RUnlock() return newErrf(ErrRejected, "recently rejected "+ "chan_id=%v", msg.ChannelID) } r.rejectMtx.RUnlock() // 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); 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) })) default: return errors.Errorf("wrong routing update message type") } return nil } // fetchChanPoint retrieves the original outpoint which is encoded within the // channelID. This method also return the public key script for the target // transaction. // // TODO(roasbeef): replace with call to GetBlockTransaction? (would allow to // later use getblocktxn) func (r *ChannelRouter) fetchChanPoint( chanID *lnwire.ShortChannelID) (*wire.OutPoint, *wire.TxOut, 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, nil, err } fundingBlock, err := r.cfg.Chain.GetBlock(blockHash) if err != nil { return nil, 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, nil, fmt.Errorf("tx_index=#%v is out of range "+ "(max_index=%v), network_chan_id=%v\n", chanID.TxIndex, numTxns-1, spew.Sdump(chanID)) } // Finally once we have the block itself, we seek to the targeted // transaction index to obtain the funding output and txout. fundingTx := fundingBlock.Transactions[chanID.TxIndex] outPoint := &wire.OutPoint{ Hash: fundingTx.TxHash(), Index: uint32(chanID.TxPosition), } txOut := fundingTx.TxOut[chanID.TxPosition] return outPoint, txOut, nil } // routingMsg couples a routing related routing topology update to the // error channel. type routingMsg struct { msg interface{} err chan error } // pathsToFeeSortedRoutes takes a set of paths, and returns a corresponding set // of routes. A route differs from a path in that it has full time-lock and // fee information attached. The set of routes returned may be less than the // initial set of paths as it's possible we drop a route if it can't handle the // total payment flow after fees are calculated. func pathsToFeeSortedRoutes(source route.Vertex, paths [][]*channeldb.ChannelEdgePolicy, finalCLTVDelta uint16, amt lnwire.MilliSatoshi, currentHeight uint32) ([]*route.Route, error) { validRoutes := make([]*route.Route, 0, len(paths)) for _, path := range paths { // Attempt to make the path into a route. We snip off the first // hop in the path as it contains a "self-hop" that is inserted // by our KSP algorithm. route, err := newRoute( amt, source, path[1:], currentHeight, finalCLTVDelta, ) if err != nil { // TODO(roasbeef): report straw breaking edge? continue } // If the path as enough total flow to support the computed // route, then we'll add it to our set of valid routes. validRoutes = append(validRoutes, route) } // If all our perspective routes were eliminating during the transition // from path to route, then we'll return an error to the caller if len(validRoutes) == 0 { return nil, newErr(ErrNoPathFound, "unable to find a path to "+ "destination") } // Finally, we'll sort the set of validate routes to optimize for // lowest total fees, using the required time-lock within the route as // a tie-breaker. sort.Slice(validRoutes, func(i, j int) bool { // To make this decision we first check if the total fees // required for both routes are equal. If so, then we'll let // the total time lock be the tie breaker. Otherwise, we'll put // the route with the lowest total fees first. if validRoutes[i].TotalFees == validRoutes[j].TotalFees { timeLockI := validRoutes[i].TotalTimeLock timeLockJ := validRoutes[j].TotalTimeLock return timeLockI < timeLockJ } return validRoutes[i].TotalFees < validRoutes[j].TotalFees }) return validRoutes, nil } // FindRoutes attempts to query the ChannelRouter for a bounded number // available paths to a particular target destination which is able to send // `amt` after factoring in channel capacities and cumulative fees along each // route. To `numPaths eligible paths, we use a modified version of // Yen's algorithm which itself uses a modified version of Dijkstra's algorithm // within its inner loop. Once we have a set of candidate routes, we calculate // the required fee and time lock values running backwards along the route. The // route that will be ranked the highest is the one with the lowest cumulative // fee along the route. func (r *ChannelRouter) FindRoutes(source, target route.Vertex, amt lnwire.MilliSatoshi, restrictions *RestrictParams, numPaths uint32, finalExpiry ...uint16) ([]*route.Route, error) { var finalCLTVDelta uint16 if len(finalExpiry) == 0 { finalCLTVDelta = zpay32.DefaultFinalCLTVDelta } else { finalCLTVDelta = finalExpiry[0] } log.Debugf("Searching for path to %x, sending %v", target, amt) // If we don't have a set of routes cached, we'll query the graph for a // set of potential routes to the destination node that can support our // payment amount. If no such routes can be found then an error will be // returned. // We can short circuit the routing by opportunistically checking to // see if the target vertex event exists in the current graph. if _, exists, err := r.cfg.Graph.HasLightningNode(target); err != nil { return nil, err } else if !exists { log.Debugf("Target %x is not in known graph", target) return nil, newErrf(ErrTargetNotInNetwork, "target not found") } // 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 nil, err } // Before we open the db transaction below, 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 } tx, err := r.cfg.Graph.Database().Begin(false) if err != nil { tx.Rollback() return nil, err } // Now that we know the destination is reachable within the graph, // we'll execute our KSP algorithm to find the k-shortest paths from // our source to the destination. shortestPaths, err := findPaths( tx, r.cfg.Graph, source, target, amt, restrictions, numPaths, bandwidthHints, ) if err != nil { tx.Rollback() return nil, err } tx.Rollback() // Now that we have a set of paths, we'll need to turn them into // *routes* by computing the required time-lock and fee information for // each path. During this process, some paths may be discarded if they // aren't able to support the total satoshis flow once fees have been // factored in. sourceVertex := route.Vertex(r.selfNode.PubKeyBytes) validRoutes, err := pathsToFeeSortedRoutes( sourceVertex, shortestPaths, finalCLTVDelta, amt, uint32(currentHeight), ) if err != nil { return nil, err } go log.Tracef("Obtained %v paths sending %v to %x: %v", len(validRoutes), amt, target, newLogClosure(func() string { return spew.Sdump(validRoutes) }), ) return validRoutes, nil } // 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) ([]byte, *sphinx.Circuit, error) { // As a sanity check, we'll ensure that the set of hops has been // properly filled in, otherwise, we won't actually be able to // construct a route. if len(rt.Hops) == 0 { return nil, nil, route.ErrNoRouteHopsProvided } // 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 { return spew.Sdump(sphinxPath[:sphinxPath.TrueRouteLength()]) }), ) // Generate a new random session key to ensure that we don't trigger // any replay. // // TODO(roasbeef): add more sources of randomness? sessionKey, err := btcec.NewPrivateKey(btcec.S256()) if err != nil { return nil, nil, err } // 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, ) 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 unset the internal curve here in order to keep // the logs from getting noisy. sphinxPacket.EphemeralKey.Curve = nil return spew.Sdump(sphinxPacket) }), ) 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. If this value is // unspecified, then a default value of DefaultFinalCLTVDelta will be // used. 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. 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 // OutgoingChannelID is the channel that needs to be taken to the first // hop. If nil, any channel may be used. OutgoingChannelID *uint64 // TODO(roasbeef): add e2e message? } // 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) { // 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.missionControl.NewPaymentSession( payment.RouteHints, payment.Target, ) if err != nil { return [32]byte{}, nil, err } return r.sendPayment(payment, paySession) } // SendToRoute attempts to send a payment as described within the passed // LightningPayment through the provided routes. This function is blocking // and will return either: when the payment is successful, or all 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) SendToRoute(routes []*route.Route, payment *LightningPayment) ([32]byte, *route.Route, error) { paySession := r.missionControl.NewPaymentSessionFromRoutes( routes, ) return r.sendPayment(payment, paySession) } // 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, paySession *paymentSession) ([32]byte, *route.Route, error) { log.Tracef("Dispatching route for lightning payment: %v", newLogClosure(func() string { for _, routeHint := range payment.RouteHints { for _, hopHint := range routeHint { hopHint.NodeID.Curve = nil } } return spew.Sdump(payment) }), ) // 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 } var finalCLTVDelta uint16 if payment.FinalCLTVDelta == nil { finalCLTVDelta = zpay32.DefaultFinalCLTVDelta } else { finalCLTVDelta = *payment.FinalCLTVDelta } var payAttemptTimeout time.Duration if payment.PayAttemptTimeout == time.Duration(0) { payAttemptTimeout = defaultPayAttemptTimeout } else { payAttemptTimeout = payment.PayAttemptTimeout } timeoutChan := time.After(payAttemptTimeout) // We'll continue until either our payment succeeds, or we encounter a // critical error during path finding. var lastError error for { // Before we attempt this next payment, we'll check to see if // either we've gone past the payment attempt timeout, or the // router is exiting. In either case, we'll stop this payment // attempt short. select { case <-timeoutChan: errStr := fmt.Sprintf("payment attempt not completed "+ "before timeout of %v", payAttemptTimeout) return [32]byte{}, nil, newErr( ErrPaymentAttemptTimeout, errStr, ) case <-r.quit: return [32]byte{}, nil, ErrRouterShuttingDown default: // Fall through if we haven't hit our time limit, or // are expiring. } route, err := paySession.RequestRoute( payment, uint32(currentHeight), finalCLTVDelta, ) if err != nil { // If we're unable to successfully make a payment using // any of the routes we've found, then return an error. if lastError != nil { return [32]byte{}, nil, fmt.Errorf("unable to "+ "route payment to destination: %v", lastError) } return [32]byte{}, nil, err } // Send payment attempt. It will return a final boolean // indicating if more attempts are needed. preimage, final, err := r.sendPaymentAttempt( paySession, route, payment.PaymentHash, ) if final { return preimage, route, err } lastError = err } } // sendPaymentAttempt tries to send the payment via the specified route. If // successful, it returns the obtained preimage. If an error occurs, the last // bool parameter indicates whether this is a final outcome or more attempts // should be made. func (r *ChannelRouter) sendPaymentAttempt(paySession *paymentSession, route *route.Route, paymentHash [32]byte) ([32]byte, bool, error) { log.Tracef("Attempting to send payment %x, using route: %v", paymentHash, newLogClosure(func() string { return spew.Sdump(route) }), ) preimage, err := r.sendToSwitch(route, paymentHash) if err == nil { return preimage, true, nil } log.Errorf("Attempt to send payment %x failed: %v", paymentHash, err) finalOutcome := r.processSendError(paySession, route, err) return [32]byte{}, finalOutcome, err } // sendToSwitch sends a payment along the specified route and returns the // obtained preimage. func (r *ChannelRouter) sendToSwitch(route *route.Route, paymentHash [32]byte) ( [32]byte, error) { // Generate the raw encoded sphinx packet to be included along // with the htlcAdd message that we send directly to the // switch. onionBlob, circuit, err := generateSphinxPacket( route, paymentHash[:], ) if err != nil { return [32]byte{}, err } // Craft an HTLC packet to send to the layer 2 switch. The // metadata within this packet will be used to route the // payment through the network, starting with the first-hop. htlcAdd := &lnwire.UpdateAddHTLC{ Amount: route.TotalAmount, Expiry: route.TotalTimeLock, PaymentHash: paymentHash, } copy(htlcAdd.OnionBlob[:], onionBlob) // Attempt to send this payment through the network to complete // the payment. If this attempt fails, then we'll continue on // to the next available route. firstHop := lnwire.NewShortChanIDFromInt( route.Hops[0].ChannelID, ) return r.cfg.SendToSwitch( firstHop, htlcAdd, circuit, ) } // 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. This is indicated by the boolean // return value. func (r *ChannelRouter) processSendError(paySession *paymentSession, rt *route.Route, err error) bool { fErr, ok := err.(*htlcswitch.ForwardingError) if !ok { return true } errSource := fErr.ErrorSource errVertex := route.NewVertex(errSource) log.Tracef("node=%x reported failure when sending htlc", errVertex) // Always determine chan id ourselves, because a channel // update with id may not be available. failedEdge, err := getFailedEdge(rt, route.Vertex(errVertex)) if err != nil { return true } // processChannelUpdateAndRetry is a closure that // handles a failure message containing a channel // update. This function always tries to apply the // channel update and passes on the result to the // payment session to adjust its view on the reliability // of the network. // // As channel id, the locally determined channel id is // used. It does not rely on the channel id that is part // of the channel update message, because the remote // node may lie to us or the update may be corrupt. processChannelUpdateAndRetry := func( update *lnwire.ChannelUpdate, pubKey *btcec.PublicKey) { // Try to apply the channel update. updateOk := r.applyChannelUpdate(update, pubKey) // If the update could not be applied, prune the // edge. There is no reason to continue trying // this channel. // // TODO: Could even prune the node completely? // Or is there a valid reason for the channel // update to fail? if !updateOk { paySession.ReportEdgeFailure( failedEdge, ) } paySession.ReportEdgePolicyFailure( route.NewVertex(errSource), failedEdge, ) } switch onionErr := fErr.FailureMessage.(type) { // If the end destination didn't know the payment // hash or we sent the wrong payment amount to the // destination, then we'll terminate immediately. case *lnwire.FailUnknownPaymentHash: return true // If we sent the wrong amount to the destination, then // we'll exit early. case *lnwire.FailIncorrectPaymentAmount: return true // If the time-lock that was extended to the final node // was incorrect, then we can't proceed. case *lnwire.FailFinalIncorrectCltvExpiry: return true // If we crafted an invalid onion payload for the final // node, then we'll exit early. case *lnwire.FailFinalIncorrectHtlcAmount: return true // Similarly, if the HTLC expiry that we extended to // the final hop expires too soon, then will fail the // payment. // // TODO(roasbeef): can happen to to race condition, try // again with recent block height case *lnwire.FailFinalExpiryTooSoon: return true // If we erroneously attempted to cross a chain border, // then we'll cancel the payment. case *lnwire.FailInvalidRealm: return true // If we get a notice that the expiry was too soon for // an intermediate node, then we'll prune out the node // that sent us this error, as it doesn't now what the // correct block height is. case *lnwire.FailExpiryTooSoon: r.applyChannelUpdate(&onionErr.Update, errSource) paySession.ReportVertexFailure(errVertex) return false // If we hit an instance of onion payload corruption or // an invalid version, then we'll exit early as this // shouldn't happen in the typical case. case *lnwire.FailInvalidOnionVersion: return true case *lnwire.FailInvalidOnionHmac: return true case *lnwire.FailInvalidOnionKey: return true // If we get a failure due to violating the minimum // amount, we'll apply the new minimum amount and retry // routing. case *lnwire.FailAmountBelowMinimum: processChannelUpdateAndRetry( &onionErr.Update, errSource, ) return false // If we get a failure due to a fee, we'll apply the // new fee update, and retry our attempt using the // newly updated fees. case *lnwire.FailFeeInsufficient: processChannelUpdateAndRetry( &onionErr.Update, errSource, ) return false // If we get the failure for an intermediate node that // disagrees with our time lock values, then we'll // apply the new delta value and try it once more. case *lnwire.FailIncorrectCltvExpiry: processChannelUpdateAndRetry( &onionErr.Update, errSource, ) return false // The outgoing channel that this node was meant to // forward one is currently disabled, so we'll apply // the update and continue. case *lnwire.FailChannelDisabled: r.applyChannelUpdate(&onionErr.Update, errSource) paySession.ReportEdgeFailure(failedEdge) return false // It's likely that the outgoing channel didn't have // sufficient capacity, so we'll prune this edge for // now, and continue onwards with our path finding. case *lnwire.FailTemporaryChannelFailure: r.applyChannelUpdate(onionErr.Update, errSource) paySession.ReportEdgeFailure(failedEdge) return false // If the send fail due to a node not having the // required features, then we'll note this error and // continue. case *lnwire.FailRequiredNodeFeatureMissing: paySession.ReportVertexFailure(errVertex) return false // If the send fail due to a node not having the // required features, then we'll note this error and // continue. case *lnwire.FailRequiredChannelFeatureMissing: paySession.ReportVertexFailure(errVertex) return false // If the next hop in the route wasn't known or // offline, we'll only the channel which we attempted // to route over. This is conservative, and it can // handle faulty channels between nodes properly. // Additionally, this guards against routing nodes // returning errors in order to attempt to black list // another node. case *lnwire.FailUnknownNextPeer: paySession.ReportEdgeFailure(failedEdge) return false // If the node wasn't able to forward for which ever // reason, then we'll note this and continue with the // routes. case *lnwire.FailTemporaryNodeFailure: paySession.ReportVertexFailure(errVertex) return false case *lnwire.FailPermanentNodeFailure: paySession.ReportVertexFailure(errVertex) return false // If we crafted a route that contains a too long time // lock for an intermediate node, we'll prune the node. // As there currently is no way of knowing that node's // maximum acceptable cltv, we cannot take this // constraint into account during routing. // // TODO(joostjager): Record the rejected cltv and use // that as a hint during future path finding through // that node. case *lnwire.FailExpiryTooFar: paySession.ReportVertexFailure(errVertex) return false // If we get a permanent channel or node failure, then // we'll prune the channel in both directions and // continue with the rest of the routes. case *lnwire.FailPermanentChannelFailure: paySession.ReportEdgeFailure(&EdgeLocator{ ChannelID: failedEdge.ChannelID, Direction: 0, }) paySession.ReportEdgeFailure(&EdgeLocator{ ChannelID: failedEdge.ChannelID, Direction: 1, }) return false default: return true } } // getFailedEdge tries to locate the failing channel given a route and the // pubkey of the node that sent the error. It will assume that the error is // associated with the outgoing channel of the error node. func getFailedEdge(route *route.Route, errSource route.Vertex) ( *EdgeLocator, error) { hopCount := len(route.Hops) fromNode := route.SourcePubKey for i, hop := range route.Hops { toNode := hop.PubKeyBytes // Determine if we have a failure from the final hop. // // TODO(joostjager): In this case, certain types of errors are // not expected. For example FailUnknownNextPeer. This could be // a reason to prune the node? finalHopFailing := i == hopCount-1 && errSource == toNode // As this error indicates that the target channel was unable to // carry this HTLC (for w/e reason), we'll return the _outgoing_ // channel that the source of the error was meant to pass the // HTLC along to. // // If the errSource is the final hop, we assume that the failing // channel is the incoming channel. if errSource == fromNode || finalHopFailing { return newEdgeLocatorByPubkeys( hop.ChannelID, &fromNode, &toNode, ), nil } fromNode = toNode } return nil, fmt.Errorf("cannot find error source node in route") } // 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 { // If we get passed a nil channel update (as it's optional with some // onion errors), then we'll exit early with a success result. if msg == nil { return true } 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) error { rMsg := &routingMsg{ msg: node, 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) error { rMsg := &routingMsg{ msg: edge, 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) error { rMsg := &routingMsg{ msg: update, 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) { pubKey, err := btcec.ParsePubKey(node[:], btcec.S256()) if err != nil { return nil, fmt.Errorf("unable to parse raw public key: %v", err) } return r.cfg.Graph.FetchLightningNode(pubKey) } // 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(nil, func(_ *bbolt.Tx, 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(_ *bbolt.Tx, 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()) }