package routing import ( "fmt" "time" "github.com/lightningnetwork/lnd/channeldb" "github.com/lightningnetwork/lnd/lnwire" ) // 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 { pruneViewSnapshot graphPruneView additionalEdges map[Vertex][]*channeldb.ChannelEdgePolicy bandwidthHints map[uint64]lnwire.MilliSatoshi // errFailedFeeChans is a map of the short channel IDs that were the // source of policy related routing failures during this payment attempt. // We'll use this map to prune out channels when the first error may not // require pruning, but any subsequent ones do. errFailedPolicyChans map[edgeLocator]struct{} mc *missionControl haveRoutes bool preBuiltRoutes []*Route } // ReportVertexFailure adds a vertex to the graph prune view after a client // reports a routing failure localized to the vertex. The time the vertex was // added is noted, as it'll be pruned from the shared view after a period of // vertexDecay. However, the vertex will remain pruned for the *local* session. // This ensures we don't retry this vertex during the payment attempt. func (p *paymentSession) ReportVertexFailure(v Vertex) { log.Debugf("Reporting vertex %v failure to Mission Control", v) // First, we'll add the failed vertex to our local prune view snapshot. p.pruneViewSnapshot.vertexes[v] = struct{}{} // With the vertex added, we'll now report back to the global prune // view, with this new piece of information so it can be utilized for // new payment sessions. p.mc.Lock() p.mc.failedVertexes[v] = time.Now() p.mc.Unlock() } // ReportChannelFailure adds a channel to the graph prune view. The time the // channel was added is noted, as it'll be pruned from the global view after a // period of edgeDecay. However, the edge will remain pruned for the duration // of the *local* session. This ensures that we don't flap by continually // retrying an edge after its pruning has expired. // // TODO(roasbeef): also add value attempted to send and capacity of channel func (p *paymentSession) ReportEdgeFailure(e *edgeLocator) { log.Debugf("Reporting edge %v failure to Mission Control", e) // First, we'll add the failed edge to our local prune view snapshot. p.pruneViewSnapshot.edges[*e] = struct{}{} // With the edge added, we'll now report back to the global prune view, // with this new piece of information so it can be utilized for new // payment sessions. p.mc.Lock() p.mc.failedEdges[*e] = time.Now() p.mc.Unlock() } // ReportChannelPolicyFailure handles a failure message that relates to a // channel policy. For these types of failures, the policy is updated and we // want to keep it included during path finding. This function does mark the // edge as 'policy failed once'. The next time it fails, the whole node will be // pruned. This is to prevent nodes from keeping us busy by continuously sending // new channel updates. func (p *paymentSession) ReportEdgePolicyFailure( errSource Vertex, failedEdge *edgeLocator) { // Check to see if we've already reported a policy related failure for // this channel. If so, then we'll prune out the vertex. _, ok := p.errFailedPolicyChans[*failedEdge] if ok { // TODO(joostjager): is this aggresive pruning still necessary? // Just pruning edges may also work unless there is a huge // number of failing channels from that node? p.ReportVertexFailure(errSource) return } // Finally, we'll record a policy failure from this node and move on. p.errFailedPolicyChans[*failedEdge] = struct{}{} } // 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. func (p *paymentSession) RequestRoute(payment *LightningPayment, height uint32, finalCltvDelta uint16) (*Route, error) { switch { // If we have a set of pre-built routes, then we'll just pop off the // next route from the queue, and use it directly. case p.haveRoutes && len(p.preBuiltRoutes) > 0: nextRoute := p.preBuiltRoutes[0] p.preBuiltRoutes[0] = nil // Set to nil to avoid GC leak. p.preBuiltRoutes = p.preBuiltRoutes[1:] return nextRoute, nil // If we were instantiated with a set of pre-built routes, and we've // run out, then we'll return a terminal error. case p.haveRoutes && len(p.preBuiltRoutes) == 0: return nil, fmt.Errorf("pre-built routes exhausted") } // Otherwise we actually need to perform path finding, so we'll obtain // our current prune view snapshot. This view will only ever grow // during the duration of this payment session, never shrinking. pruneView := p.pruneViewSnapshot log.Debugf("Mission Control session using prune view of %v "+ "edges, %v vertexes", len(pruneView.edges), len(pruneView.vertexes)) // 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. path, err := findPath( &graphParams{ graph: p.mc.graph, additionalEdges: p.additionalEdges, bandwidthHints: p.bandwidthHints, }, &restrictParams{ ignoredNodes: pruneView.vertexes, ignoredEdges: pruneView.edges, feeLimit: payment.FeeLimit, }, p.mc.selfNode, 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 := Vertex(p.mc.selfNode.PubKeyBytes) route, err := newRoute( payment.Amount, payment.FeeLimit, sourceVertex, path, height, finalCltvDelta, ) if err != nil { // TODO(roasbeef): return which edge/vertex didn't work // out return nil, err } return route, err }