package route import ( "encoding/binary" "fmt" "github.com/btcsuite/btcd/btcec" sphinx "github.com/lightningnetwork/lightning-onion" "github.com/lightningnetwork/lnd/lnwire" ) // ErrNoRouteHopsProvided is returned when a caller attempts to construct a new // sphinx packet, but provides an empty set of hops for each route. var ErrNoRouteHopsProvided = fmt.Errorf("empty route hops provided") // Vertex is a simple alias for the serialization of a compressed Bitcoin // public key. type Vertex [33]byte // NewVertex returns a new Vertex given a public key. func NewVertex(pub *btcec.PublicKey) Vertex { var v Vertex copy(v[:], pub.SerializeCompressed()) return v } // String returns a human readable version of the Vertex which is the // hex-encoding of the serialized compressed public key. func (v Vertex) String() string { return fmt.Sprintf("%x", v[:]) } // Hop represents an intermediate or final node of the route. This naming // is in line with the definition given in BOLT #4: Onion Routing Protocol. // The struct houses the channel along which this hop can be reached and // the values necessary to create the HTLC that needs to be sent to the // next hop. It is also used to encode the per-hop payload included within // the Sphinx packet. type Hop struct { // PubKeyBytes is the raw bytes of the public key of the target node. PubKeyBytes Vertex // ChannelID is the unique channel ID for the channel. The first 3 // bytes are the block height, the next 3 the index within the block, // and the last 2 bytes are the output index for the channel. ChannelID uint64 // OutgoingTimeLock is the timelock value that should be used when // crafting the _outgoing_ HTLC from this hop. OutgoingTimeLock uint32 // AmtToForward is the amount that this hop will forward to the next // hop. This value is less than the value that the incoming HTLC // carries as a fee will be subtracted by the hop. AmtToForward lnwire.MilliSatoshi } // Route represents a path through the channel graph which runs over one or // more channels in succession. This struct carries all the information // required to craft the Sphinx onion packet, and send the payment along the // first hop in the path. A route is only selected as valid if all the channels // have sufficient capacity to carry the initial payment amount after fees are // accounted for. type Route struct { // TotalTimeLock is the cumulative (final) time lock across the entire // route. This is the CLTV value that should be extended to the first // hop in the route. All other hops will decrement the time-lock as // advertised, leaving enough time for all hops to wait for or present // the payment preimage to complete the payment. TotalTimeLock uint32 // TotalAmount is the total amount of funds required to complete a // payment over this route. This value includes the cumulative fees at // each hop. As a result, the HTLC extended to the first-hop in the // route will need to have at least this many satoshis, otherwise the // route will fail at an intermediate node due to an insufficient // amount of fees. TotalAmount lnwire.MilliSatoshi // SourcePubKey is the pubkey of the node where this route originates // from. SourcePubKey Vertex // Hops contains details concerning the specific forwarding details at // each hop. Hops []*Hop } // HopFee returns the fee charged by the route hop indicated by hopIndex. func (r *Route) HopFee(hopIndex int) lnwire.MilliSatoshi { var incomingAmt lnwire.MilliSatoshi if hopIndex == 0 { incomingAmt = r.TotalAmount } else { incomingAmt = r.Hops[hopIndex-1].AmtToForward } // Fee is calculated as difference between incoming and outgoing amount. return incomingAmt - r.Hops[hopIndex].AmtToForward } // TotalFees is the sum of the fees paid at each hop within the final route. In // the case of a one-hop payment, this value will be zero as we don't need to // pay a fee to ourself. func (r *Route) TotalFees() lnwire.MilliSatoshi { return r.TotalAmount - r.Hops[len(r.Hops)-1].AmtToForward } // NewRouteFromHops creates a new Route structure from the minimally required // information to perform the payment. It infers fee amounts and populates the // node, chan and prev/next hop maps. func NewRouteFromHops(amtToSend lnwire.MilliSatoshi, timeLock uint32, sourceVertex Vertex, hops []*Hop) (*Route, error) { if len(hops) == 0 { return nil, ErrNoRouteHopsProvided } // First, we'll create a route struct and populate it with the fields // for which the values are provided as arguments of this function. // TotalFees is determined based on the difference between the amount // that is send from the source and the final amount that is received // by the destination. route := &Route{ SourcePubKey: sourceVertex, Hops: hops, TotalTimeLock: timeLock, TotalAmount: amtToSend, } return route, nil } // ToSphinxPath converts a complete route into a sphinx PaymentPath that // contains the per-hop paylods used to encoding the HTLC routing data for each // hop in the route. func (r *Route) ToSphinxPath() (*sphinx.PaymentPath, error) { var path sphinx.PaymentPath // For each hop encoded within the route, we'll convert the hop struct // to an OnionHop with matching per-hop payload within the path as used // by the sphinx package. for i, hop := range r.Hops { pub, err := btcec.ParsePubKey( hop.PubKeyBytes[:], btcec.S256(), ) if err != nil { return nil, err } path[i] = sphinx.OnionHop{ NodePub: *pub, HopData: sphinx.HopData{ // TODO(roasbeef): properly set realm, make // sphinx type an enum actually? Realm: [1]byte{0}, ForwardAmount: uint64(hop.AmtToForward), OutgoingCltv: hop.OutgoingTimeLock, }, } // As a base case, the next hop is set to all zeroes in order // to indicate that the "last hop" as no further hops after it. nextHop := uint64(0) // If we aren't on the last hop, then we set the "next address" // field to be the channel that directly follows it. if i != len(r.Hops)-1 { nextHop = r.Hops[i+1].ChannelID } binary.BigEndian.PutUint64( path[i].HopData.NextAddress[:], nextHop, ) } return &path, nil }