lnd.xprv/htlcswitch/htlcnotifier.go
carla fc0ee06a99
htlcswitch: add notifications for forwards
This commit adds notifications for htlcs which are forwarded through
our node. Forwards are notified when the htlc is added on our ougoing
link, settles when we send a settle message to the downstream peer.
If a failure occurs, we check whether it occurred at our node, then
notify a link or forwarding failure accordingly.

Note that this change also adds forward event notifications for sends
which are initiated by our node because the handling code for adding
a htlc which originates from our node is the same as that for handling
forwards. Htlcs for our locally initiated sends have our internal pid
set in the incoming htlcs id field, so we extract this value and notify
with a zero htlc id to be consistent with receives (which have zero
outgoing circuits). Subsequent settles or failures are not noitfied
for local sends in this commit, and will be handled in a follow up.
2020-02-19 18:03:22 +02:00

430 lines
14 KiB
Go

package htlcswitch
import (
"fmt"
"strings"
"sync"
"time"
"github.com/lightningnetwork/lnd/channeldb"
"github.com/lightningnetwork/lnd/htlcswitch/hop"
"github.com/lightningnetwork/lnd/lnwire"
"github.com/lightningnetwork/lnd/subscribe"
)
// HtlcNotifier notifies clients of htlc forwards, failures and settles for
// htlcs that the switch handles. It takes subscriptions for its events and
// notifies them when htlc events occur. These are served on a best-effort
// basis; events are not persisted, delivery is not guaranteed (in the event
// of a crash in the switch, forward events may be lost) and some events may
// be replayed upon restart. Events consumed from this package should be
// de-duplicated by the htlc's unique combination of incoming+outgoing circuit
// and not relied upon for critical operations.
//
// The htlc notifier sends the following kinds of events:
// Forwarding Event:
// - Represents a htlc which is forwarded onward from our node.
// - Present for htlc forwards through our node and local sends.
//
// Link Failure Event:
// - Indicates that a htlc has failed on our incoming or outgoing link,
// with an incoming boolean which indicates where the failure occurred.
// - Incoming link failures are present for failed attempts to pay one of
// our invoices (insufficient amount or mpp timeout, for example) and for
// forwards that we cannot decode to forward onwards.
// - Outgoing link failures are present for forwards or local payments that
// do not meet our outgoing link's policy (insufficient fees, for example)
// and when we fail to forward the payment on (insufficient outgoing
// capacity, or an unknown outgoing link).
//
// Forwarding Failure Event:
// - Forwarding failures indicate that a htlc we forwarded has failed at
// another node down the route.
// - Present for local sends and htlc forwards which fail after they left
// our node.
//
// Settle event:
// - Settle events are present when a htlc which we added is settled through
// the release of a preimage.
// - Present for local receives, and successful local sends or forwards.
//
// Each htlc is identified by its incoming and outgoing circuit key. Htlcs,
// and their subsequent settles or fails, can be identified by the combination
// of incoming and outgoing circuits. Note that receives to our node will
// have a zero outgoing circuit key because the htlc terminates at our
// node, and sends from our node will have a zero incoming circuit key because
// the send originates at our node.
type HtlcNotifier struct {
started sync.Once
stopped sync.Once
// now returns the current time, it is set in the htlcnotifier to allow
// for timestamp mocking in tests.
now func() time.Time
ntfnServer *subscribe.Server
}
// NewHtlcNotifier creates a new HtlcNotifier which gets htlc forwarded,
// failed and settled events from links our node has established with peers
// and sends notifications to subscribing clients.
func NewHtlcNotifier(now func() time.Time) *HtlcNotifier {
return &HtlcNotifier{
now: now,
ntfnServer: subscribe.NewServer(),
}
}
// Start starts the HtlcNotifier and all goroutines it needs to consume
// events and provide subscriptions to clients.
func (h *HtlcNotifier) Start() error {
var err error
h.started.Do(func() {
log.Trace("HtlcNotifier starting")
err = h.ntfnServer.Start()
})
return err
}
// Stop signals the notifier for a graceful shutdown.
func (h *HtlcNotifier) Stop() {
h.stopped.Do(func() {
if err := h.ntfnServer.Stop(); err != nil {
log.Warnf("error stopping htlc notifier: %v", err)
}
})
}
// SubscribeHtlcEvents returns a subscribe.Client that will receive updates
// any time the server is made aware of a new event.
func (h *HtlcNotifier) SubscribeHtlcEvents() (*subscribe.Client, error) {
return h.ntfnServer.Subscribe()
}
// HtlcKey uniquely identifies the htlc.
type HtlcKey struct {
// IncomingCircuit is the channel an htlc id of the incoming htlc.
IncomingCircuit channeldb.CircuitKey
// OutgoingCircuit is the channel and htlc id of the outgoing htlc.
OutgoingCircuit channeldb.CircuitKey
}
// String returns a string representation of a htlc key.
func (k HtlcKey) String() string {
switch {
case k.IncomingCircuit.ChanID == hop.Source:
return k.OutgoingCircuit.String()
case k.OutgoingCircuit.ChanID == hop.Exit:
return k.IncomingCircuit.String()
default:
return fmt.Sprintf("%v -> %v", k.IncomingCircuit,
k.OutgoingCircuit)
}
}
// HtlcInfo provides the details of a htlc that our node has processed. For
// forwards, incoming and outgoing values are set, whereas sends and receives
// will only have outgoing or incoming details set.
type HtlcInfo struct {
// IncomingTimelock is the time lock of the htlc on our incoming
// channel.
IncomingTimeLock uint32
// OutgoingTimelock is the time lock the htlc on our outgoing channel.
OutgoingTimeLock uint32
// IncomingAmt is the amount of the htlc on our incoming channel.
IncomingAmt lnwire.MilliSatoshi
// OutgoingAmt is the amount of the htlc on our outgoing channel.
OutgoingAmt lnwire.MilliSatoshi
}
// String returns a string representation of a htlc.
func (h HtlcInfo) String() string {
var details []string
// If the incoming information is not zero, as is the case for a send,
// we include the incoming amount and timelock.
if h.IncomingAmt != 0 || h.IncomingTimeLock != 0 {
str := fmt.Sprintf("incoming amount: %v, "+
"incoming timelock: %v", h.IncomingAmt,
h.IncomingTimeLock)
details = append(details, str)
}
// If the outgoing information is not zero, as is the case for a
// receive, we include the outgoing amount and timelock.
if h.OutgoingAmt != 0 || h.OutgoingTimeLock != 0 {
str := fmt.Sprintf("outgoing amount: %v, "+
"outgoing timelock: %v", h.OutgoingAmt,
h.OutgoingTimeLock)
details = append(details, str)
}
return strings.Join(details, ", ")
}
// HtlcEventType represents the type of event that a htlc was part of.
type HtlcEventType int
const (
// HtlcEventTypeSend represents a htlc that was part of a send from
// our node.
HtlcEventTypeSend HtlcEventType = iota
// HtlcEventTypeReceive represents a htlc that was part of a receive
// to our node.
HtlcEventTypeReceive
// HtlcEventTypeForward represents a htlc that was forwarded through
// our node.
HtlcEventTypeForward
)
// String returns a string representation of a htlc event type.
func (h HtlcEventType) String() string {
switch h {
case HtlcEventTypeSend:
return "send"
case HtlcEventTypeReceive:
return "receive"
case HtlcEventTypeForward:
return "forward"
default:
return "unknown"
}
}
// ForwardingEvent represents a htlc that was forwarded onwards from our node.
// Sends which originate from our node will report forward events with zero
// incoming circuits in their htlc key.
type ForwardingEvent struct {
// HtlcKey uniquely identifies the htlc, and can be used to match the
// forwarding event with subsequent settle/fail events.
HtlcKey
// HtlcInfo contains details about the htlc.
HtlcInfo
// HtlcEventType classifies the event as part of a local send or
// receive, or as part of a forward.
HtlcEventType
// Timestamp is the time when this htlc was forwarded.
Timestamp time.Time
}
// LinkFailEvent describes a htlc that failed on our incoming or outgoing
// link. The incoming bool is true for failures on incoming links, and false
// for failures on outgoing links. The failure reason is provided by a lnwire
// failure message which is enriched with a failure detail in the cases where
// the wire failure message does not contain full information about the
// failure.
type LinkFailEvent struct {
// HtlcKey uniquely identifies the htlc.
HtlcKey
// HtlcInfo contains details about the htlc.
HtlcInfo
// HtlcEventType classifies the event as part of a local send or
// receive, or as part of a forward.
HtlcEventType
// LinkError is the reason that we failed the htlc.
LinkError *LinkError
// Incoming is true if the htlc was failed on an incoming link.
// If it failed on the outgoing link, it is false.
Incoming bool
// Timestamp is the time when the link failure occurred.
Timestamp time.Time
}
// ForwardingFailEvent represents a htlc failure which occurred down the line
// after we forwarded a htlc onwards. An error is not included in this event
// because errors returned down the route are encrypted. HtlcInfo is not
// reliably available for forwarding failures, so it is omitted. These events
// should be matched with their corresponding forward event to obtain this
// information.
type ForwardingFailEvent struct {
// HtlcKey uniquely identifies the htlc, and can be used to match the
// htlc with its corresponding forwarding event.
HtlcKey
// HtlcEventType classifies the event as part of a local send or
// receive, or as part of a forward.
HtlcEventType
// Timestamp is the time when the forwarding failure was received.
Timestamp time.Time
}
// SettleEvent represents a htlc that was settled. HtlcInfo is not reliably
// available for forwarding failures, so it is omitted. These events should
// be matched with corresponding forward events or invoices (for receives)
// to obtain additional information about the htlc.
type SettleEvent struct {
// HtlcKey uniquely identifies the htlc, and can be used to match
// forwards with their corresponding forwarding event.
HtlcKey
// HtlcEventType classifies the event as part of a local send or
// receive, or as part of a forward.
HtlcEventType
// Timestamp is the time when this htlc was settled.
Timestamp time.Time
}
// NotifyForwardingEvent notifies the HtlcNotifier than a htlc has been
// forwarded.
//
// Note this is part of the htlcNotifier interface.
func (h *HtlcNotifier) NotifyForwardingEvent(key HtlcKey, info HtlcInfo,
eventType HtlcEventType) {
event := &ForwardingEvent{
HtlcKey: key,
HtlcInfo: info,
HtlcEventType: eventType,
Timestamp: h.now(),
}
log.Tracef("Notifying forward event: %v over %v, %v", eventType, key,
info)
if err := h.ntfnServer.SendUpdate(event); err != nil {
log.Warnf("Unable to send forwarding event: %v", err)
}
}
// NotifyLinkFailEvent notifies that a htlc has failed on our incoming
// or outgoing link.
//
// Note this is part of the htlcNotifier interface.
func (h *HtlcNotifier) NotifyLinkFailEvent(key HtlcKey, info HtlcInfo,
eventType HtlcEventType, linkErr *LinkError, incoming bool) {
event := &LinkFailEvent{
HtlcKey: key,
HtlcInfo: info,
HtlcEventType: eventType,
LinkError: linkErr,
Incoming: incoming,
Timestamp: h.now(),
}
log.Tracef("Notifying link failure event: %v over %v, %v", eventType,
key, info)
if err := h.ntfnServer.SendUpdate(event); err != nil {
log.Warnf("Unable to send link fail event: %v", err)
}
}
// NotifyForwardingFailEvent notifies the HtlcNotifier that a htlc we
// forwarded has failed down the line.
//
// Note this is part of the htlcNotifier interface.
func (h *HtlcNotifier) NotifyForwardingFailEvent(key HtlcKey,
eventType HtlcEventType) {
event := &ForwardingFailEvent{
HtlcKey: key,
HtlcEventType: eventType,
Timestamp: h.now(),
}
log.Tracef("Notifying forwarding failure event: %v over %v", eventType,
key)
if err := h.ntfnServer.SendUpdate(event); err != nil {
log.Warnf("Unable to send forwarding fail event: %v", err)
}
}
// NotifySettleEvent notifies the HtlcNotifier that a htlc that we committed
// to as part of a forward or a receive to our node has been settled.
//
// Note this is part of the htlcNotifier interface.
func (h *HtlcNotifier) NotifySettleEvent(key HtlcKey, eventType HtlcEventType) {
event := &SettleEvent{
HtlcKey: key,
HtlcEventType: eventType,
Timestamp: h.now(),
}
log.Tracef("Notifying settle event: %v over %v", eventType, key)
if err := h.ntfnServer.SendUpdate(event); err != nil {
log.Warnf("Unable to send settle event: %v", err)
}
}
// newHtlc key returns a htlc key for the packet provided. If the packet
// has a zero incoming channel ID, the packet is for one of our own sends,
// which has the payment id stashed in the incoming htlc id. If this is the
// case, we replace the incoming htlc id with zero so that the notifier
// consistently reports zero circuit keys for events that terminate or
// originate at our node.
func newHtlcKey(pkt *htlcPacket) HtlcKey {
htlcKey := HtlcKey{
IncomingCircuit: channeldb.CircuitKey{
ChanID: pkt.incomingChanID,
HtlcID: pkt.incomingHTLCID,
},
OutgoingCircuit: CircuitKey{
ChanID: pkt.outgoingChanID,
HtlcID: pkt.outgoingHTLCID,
},
}
// If the packet has a zero incoming channel ID, it is a send that was
// initiated at our node. If this is the case, our internal pid is in
// the incoming htlc ID, so we overwrite it with 0 for notification
// purposes.
if pkt.incomingChanID == hop.Source {
htlcKey.IncomingCircuit.HtlcID = 0
}
return htlcKey
}
// newHtlcInfo returns HtlcInfo for the packet provided.
func newHtlcInfo(pkt *htlcPacket) HtlcInfo {
return HtlcInfo{
IncomingTimeLock: pkt.incomingTimeout,
OutgoingTimeLock: pkt.outgoingTimeout,
IncomingAmt: pkt.incomingAmount,
OutgoingAmt: pkt.amount,
}
}
// getEventType returns the htlc type based on the fields set in the htlc
// packet. Sends that originate at our node have the source (zero) incoming
// channel ID. Receives to our node have the exit (zero) outgoing channel ID
// and forwards have both fields set.
func getEventType(pkt *htlcPacket) HtlcEventType {
switch {
case pkt.incomingChanID == hop.Source:
return HtlcEventTypeSend
case pkt.outgoingChanID == hop.Exit:
return HtlcEventTypeReceive
default:
return HtlcEventTypeForward
}
}