package routing import ( "sync" "time" "github.com/btcsuite/btcd/btcec" "github.com/coreos/bbolt" "github.com/lightningnetwork/lnd/channeldb" "github.com/lightningnetwork/lnd/lnwire" ) const ( // vertexDecay is the decay period of colored vertexes added to // missionControl. Once vertexDecay passes after an entry has been // added to the prune view, it is garbage collected. This value is // larger than edgeDecay as an edge failure typical indicates an // unbalanced channel, while a vertex failure indicates a node is not // online and active. vertexDecay = time.Duration(time.Minute * 5) // edgeDecay is the decay period of colored edges added to // missionControl. Once edgeDecay passed after an entry has been added, // it is garbage collected. This value is smaller than vertexDecay as // an edge related failure during payment sending typically indicates // that a channel was unbalanced, a condition which may quickly change. // // TODO(roasbeef): instead use random delay on each? edgeDecay = time.Duration(time.Second * 5) ) // missionControl contains state which summarizes the past attempts of HTLC // routing by external callers when sending payments throughout the network. // missionControl remembers the outcome of these past routing attempts (success // and failure), and is able to provide hints/guidance to future HTLC routing // attempts. missionControl maintains a decaying network view of the // edges/vertexes that should be marked as "pruned" during path finding. This // graph view acts as a shared memory during HTLC payment routing attempts. // With each execution, if an error is encountered, based on the type of error // and the location of the error within the route, an edge or vertex is added // to the view. Later sending attempts will then query the view for all the // vertexes/edges that should be ignored. Items in the view decay after a set // period of time, allowing the view to be dynamic w.r.t network changes. type missionControl struct { // failedEdges maps a short channel ID to be pruned, to the time that // it was added to the prune view. Edges are added to this map if a // caller reports to missionControl a failure localized to that edge // when sending a payment. failedEdges map[EdgeLocator]time.Time // failedVertexes maps a node's public key that should be pruned, to // the time that it was added to the prune view. Vertexes are added to // this map if a caller reports to missionControl a failure localized // to that particular vertex. failedVertexes map[Vertex]time.Time graph *channeldb.ChannelGraph selfNode *channeldb.LightningNode queryBandwidth func(*channeldb.ChannelEdgeInfo) lnwire.MilliSatoshi sync.Mutex // TODO(roasbeef): further counters, if vertex continually unavailable, // add to another generation // TODO(roasbeef): also add favorable metrics for nodes } // newMissionControl returns a new instance of missionControl. // // TODO(roasbeef): persist memory func newMissionControl(g *channeldb.ChannelGraph, selfNode *channeldb.LightningNode, qb func(*channeldb.ChannelEdgeInfo) lnwire.MilliSatoshi) *missionControl { return &missionControl{ failedEdges: make(map[EdgeLocator]time.Time), failedVertexes: make(map[Vertex]time.Time), selfNode: selfNode, queryBandwidth: qb, graph: g, } } // graphPruneView is a filter of sorts that path finding routines should // consult during the execution. Any edges or vertexes within the view should // be ignored during path finding. The contents of the view reflect the current // state of the wider network from the PoV of mission control compiled via HTLC // routing attempts in the past. type graphPruneView struct { edges map[EdgeLocator]struct{} vertexes map[Vertex]struct{} } // GraphPruneView returns a new graphPruneView instance which is to be // consulted during path finding. If a vertex/edge is found within the returned // prune view, it is to be ignored as a goroutine has had issues routing // through it successfully. Within this method the main view of the // missionControl is garbage collected as entries are detected to be "stale". func (m *missionControl) GraphPruneView() graphPruneView { // First, we'll grab the current time, this value will be used to // determine if an entry is stale or not. now := time.Now() m.Lock() // For each of the vertexes that have been added to the prune view, if // it is now "stale", then we'll ignore it and avoid adding it to the // view we'll return. vertexes := make(map[Vertex]struct{}) for vertex, pruneTime := range m.failedVertexes { if now.Sub(pruneTime) >= vertexDecay { log.Tracef("Pruning decayed failure report for vertex %v "+ "from Mission Control", vertex) delete(m.failedVertexes, vertex) continue } vertexes[vertex] = struct{}{} } // We'll also do the same for edges, but use the edgeDecay this time // rather than the decay for vertexes. edges := make(map[EdgeLocator]struct{}) for edge, pruneTime := range m.failedEdges { if now.Sub(pruneTime) >= edgeDecay { log.Tracef("Pruning decayed failure report for edge %v "+ "from Mission Control", edge) delete(m.failedEdges, edge) continue } edges[edge] = struct{}{} } m.Unlock() log.Debugf("Mission Control returning prune view of %v edges, %v "+ "vertexes", len(edges), len(vertexes)) return graphPruneView{ edges: edges, vertexes: vertexes, } } // NewPaymentSession creates a new payment session backed by the latest prune // view from Mission Control. 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. func (m *missionControl) NewPaymentSession(routeHints [][]HopHint, target Vertex) (*paymentSession, error) { viewSnapshot := m.GraphPruneView() edges := make(map[Vertex][]*channeldb.ChannelEdgePolicy) // Traverse through all of the available hop hints and include them in // our edges map, indexed by the public key of the channel's starting // node. for _, routeHint := range routeHints { // If multiple hop hints are provided within a single route // hint, we'll assume they must be chained together and sorted // in forward order in order to reach the target successfully. for i, hopHint := range routeHint { // In order to determine the end node of this hint, // we'll need to look at the next hint's start node. If // we've reached the end of the hints list, we can // assume we've reached the destination. endNode := &channeldb.LightningNode{} if i != len(routeHint)-1 { endNode.AddPubKey(routeHint[i+1].NodeID) } else { targetPubKey, err := btcec.ParsePubKey( target[:], btcec.S256(), ) if err != nil { return nil, err } endNode.AddPubKey(targetPubKey) } // Finally, create the channel edge from the hop hint // and add it to list of edges corresponding to the node // at the start of the channel. edge := &channeldb.ChannelEdgePolicy{ Node: endNode, ChannelID: hopHint.ChannelID, FeeBaseMSat: lnwire.MilliSatoshi( hopHint.FeeBaseMSat, ), FeeProportionalMillionths: lnwire.MilliSatoshi( hopHint.FeeProportionalMillionths, ), TimeLockDelta: hopHint.CLTVExpiryDelta, } v := NewVertex(hopHint.NodeID) edges[v] = append(edges[v], edge) } } // We'll also obtain a set of bandwidthHints from the lower layer for // each of our outbound channels. This will allow the path finding to // skip any links that aren't active or just don't have enough // bandwidth to carry the payment. sourceNode, err := m.graph.SourceNode() if err != nil { return nil, err } bandwidthHints, err := generateBandwidthHints( sourceNode, m.queryBandwidth, ) if err != nil { return nil, err } return &paymentSession{ pruneViewSnapshot: viewSnapshot, additionalEdges: edges, bandwidthHints: bandwidthHints, errFailedPolicyChans: make(map[EdgeLocator]struct{}), mc: m, }, nil } // NewPaymentSessionFromRoutes creates a new paymentSession instance that will // skip all path finding, and will instead utilize a set of pre-built routes. // This constructor allows callers to specify their own routes which can be // used for things like channel rebalancing, and swaps. func (m *missionControl) NewPaymentSessionFromRoutes(routes []*Route) *paymentSession { return &paymentSession{ pruneViewSnapshot: m.GraphPruneView(), haveRoutes: true, preBuiltRoutes: routes, errFailedPolicyChans: make(map[EdgeLocator]struct{}), mc: m, } } // 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 *bbolt.Tx, 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 } // ResetHistory resets the history of missionControl returning it to a state as // if no payment attempts have been made. func (m *missionControl) ResetHistory() { m.Lock() m.failedEdges = make(map[EdgeLocator]time.Time) m.failedVertexes = make(map[Vertex]time.Time) m.Unlock() }