package routing import ( "fmt" "github.com/lightningnetwork/lnd/channeldb" "github.com/lightningnetwork/lnd/lnwire" "github.com/lightningnetwork/lnd/routing/route" ) // PaymentSession is used during SendPayment attempts to provide routes to // attempt. It also defines methods to give the PaymentSession additional // information learned during the previous attempts. type PaymentSession interface { // RequestRoute returns the next route to attempt for routing the // specified HTLC payment to the target node. RequestRoute(payment *LightningPayment, height uint32, finalCltvDelta uint16) (*route.Route, error) } // paymentSession is used during an HTLC routings session to prune the local // chain view in response to failures, and also report those failures back to // MissionControl. The snapshot copied for this session will only ever grow, // and will now be pruned after a decay like the main view within mission // control. We do this as we want to avoid the case where we continually try a // bad edge or route multiple times in a session. This can lead to an infinite // loop if payment attempts take long enough. An additional set of edges can // also be provided to assist in reaching the payment's destination. type paymentSession struct { additionalEdges map[route.Vertex][]*channeldb.ChannelEdgePolicy bandwidthHints map[uint64]lnwire.MilliSatoshi sessionSource *SessionSource preBuiltRoute *route.Route preBuiltRouteTried bool pathFinder pathFinder } // RequestRoute returns a route which is likely to be capable for successfully // routing the specified HTLC payment to the target node. Initially the first // set of paths returned from this method may encounter routing failure along // the way, however as more payments are sent, mission control will start to // build an up to date view of the network itself. With each payment a new area // will be explored, which feeds into the recommendations made for routing. // // NOTE: This function is safe for concurrent access. // NOTE: Part of the PaymentSession interface. func (p *paymentSession) RequestRoute(payment *LightningPayment, height uint32, finalCltvDelta uint16) (*route.Route, error) { switch { // If we have a pre-built route, use that directly. case p.preBuiltRoute != nil && !p.preBuiltRouteTried: p.preBuiltRouteTried = true return p.preBuiltRoute, nil // If the pre-built route has been tried already, the payment session is // over. case p.preBuiltRoute != nil: return nil, fmt.Errorf("pre-built route already tried") } // If a route cltv limit was specified, we need to subtract the final // delta before passing it into path finding. The optimal path is // independent of the final cltv delta and the path finding algorithm is // unaware of this value. var cltvLimit *uint32 if payment.CltvLimit != nil { limit := *payment.CltvLimit - uint32(finalCltvDelta) cltvLimit = &limit } // TODO(roasbeef): sync logic amongst dist sys // Taking into account this prune view, we'll attempt to locate a path // to our destination, respecting the recommendations from // MissionControl. ss := p.sessionSource restrictions := &RestrictParams{ ProbabilitySource: ss.MissionControl.GetEdgeProbability, FeeLimit: payment.FeeLimit, OutgoingChannelID: payment.OutgoingChannelID, CltvLimit: cltvLimit, PaymentAttemptPenalty: ss.PaymentAttemptPenalty, MinProbability: ss.MinRouteProbability, } path, err := p.pathFinder( &graphParams{ graph: ss.Graph, additionalEdges: p.additionalEdges, bandwidthHints: p.bandwidthHints, }, restrictions, ss.SelfNode.PubKeyBytes, payment.Target, payment.Amount, ) if err != nil { return nil, err } // With the next candidate path found, we'll attempt to turn this into // a route by applying the time-lock and fee requirements. sourceVertex := route.Vertex(ss.SelfNode.PubKeyBytes) route, err := newRoute( payment.Amount, sourceVertex, path, height, finalCltvDelta, ) if err != nil { // TODO(roasbeef): return which edge/vertex didn't work // out return nil, err } return route, err } // nodeChannel is a combination of the node pubkey and one of its channels. type nodeChannel struct { node route.Vertex channel uint64 }