lnd.xprv/routing/route/route.go

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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
}