htlcswitch: sync link hand-off

This commit extends the link with a new synchronous delivery point for
local UpdateAddHTLC messages. The switch method SendHTLC is updated to
use this delivery point and thereby becomes a synchronous call.

For MPP payments, synchronous hand-off is important. Otherwise the next
pathfinding round could start without the channel balance updated yet.
This commit is contained in:
Joost Jager 2020-04-13 17:29:52 +02:00
parent de2df5606a
commit c325bf8c57
No known key found for this signature in database
GPG Key ID: A61B9D4C393C59C7
6 changed files with 120 additions and 18 deletions

@ -70,6 +70,10 @@ type ChannelLink interface {
// possible).
HandleSwitchPacket(*htlcPacket) error
// HandleLocalAddPacket handles a locally-initiated UpdateAddHTLC
// packet. It will be processed synchronously.
HandleLocalAddPacket(*htlcPacket) error
// HandleChannelUpdate handles the htlc requests as settle/add/fail
// which sent to us from remote peer we have a channel with.
//

@ -286,6 +286,14 @@ type ChannelLinkConfig struct {
HtlcNotifier htlcNotifier
}
// localUpdateAddMsg contains a locally initiated htlc and a channel that will
// receive the outcome of the link processing. This channel must be buffered to
// prevent the link from blocking.
type localUpdateAddMsg struct {
pkt *htlcPacket
err chan error
}
// channelLink is the service which drives a channel's commitment update
// state-machine. In the event that an HTLC needs to be propagated to another
// link, the forward handler from config is used which sends HTLC to the
@ -346,6 +354,10 @@ type channelLink struct {
// by the HTLC switch.
downstream chan *htlcPacket
// localUpdateAdd is a channel to which locally initiated HTLCs are
// sent across.
localUpdateAdd chan *localUpdateAddMsg
// htlcUpdates is a channel that we'll use to update outside
// sub-systems with the latest set of active HTLC's on our channel.
htlcUpdates chan *contractcourt.ContractUpdate
@ -395,11 +407,12 @@ func NewChannelLink(cfg ChannelLinkConfig,
channel: channel,
shortChanID: channel.ShortChanID(),
// TODO(roasbeef): just do reserve here?
htlcUpdates: make(chan *contractcourt.ContractUpdate),
hodlMap: make(map[channeldb.CircuitKey]hodlHtlc),
hodlQueue: queue.NewConcurrentQueue(10),
log: build.NewPrefixLog(logPrefix, log),
quit: make(chan struct{}),
htlcUpdates: make(chan *contractcourt.ContractUpdate),
hodlMap: make(map[channeldb.CircuitKey]hodlHtlc),
hodlQueue: queue.NewConcurrentQueue(10),
log: build.NewPrefixLog(logPrefix, log),
quit: make(chan struct{}),
localUpdateAdd: make(chan *localUpdateAddMsg),
}
}
@ -1112,6 +1125,10 @@ func (l *channelLink) htlcManager() {
case pkt := <-l.downstream:
l.handleDownstreamPkt(pkt)
// A message containing a locally initiated add was received.
case msg := <-l.localUpdateAdd:
msg.err <- l.handleDownstreamUpdateAdd(msg.pkt)
// A message from the connected peer was just received. This
// indicates that we have a new incoming HTLC, either directly
// for us, or part of a multi-hop HTLC circuit.
@ -1256,8 +1273,11 @@ func (l *channelLink) randomFeeUpdateTimeout() time.Duration {
// handleDownstreamUpdateAdd processes an UpdateAddHTLC packet sent from the
// downstream HTLC Switch.
func (l *channelLink) handleDownstreamUpdateAdd(pkt *htlcPacket) {
htlc := pkt.htlc.(*lnwire.UpdateAddHTLC)
func (l *channelLink) handleDownstreamUpdateAdd(pkt *htlcPacket) error {
htlc, ok := pkt.htlc.(*lnwire.UpdateAddHTLC)
if !ok {
return errors.New("not an UpdateAddHTLC packet")
}
// If hodl.AddOutgoing mode is active, we exit early to simulate
// arbitrary delays between the switch adding an ADD to the
@ -1265,7 +1285,7 @@ func (l *channelLink) handleDownstreamUpdateAdd(pkt *htlcPacket) {
if l.cfg.HodlMask.Active(hodl.AddOutgoing) {
l.log.Warnf(hodl.AddOutgoing.Warning())
l.mailBox.AckPacket(pkt.inKey())
return
return nil
}
// A new payment has been initiated via the downstream channel,
@ -1291,7 +1311,10 @@ func (l *channelLink) handleDownstreamUpdateAdd(pkt *htlcPacket) {
// unacknowledged.
l.mailBox.FailAdd(pkt)
return
return NewDetailedLinkError(
lnwire.NewTemporaryChannelFailure(nil),
OutgoingFailureDownstreamHtlcAdd,
)
}
l.log.Tracef("received downstream htlc: payment_hash=%x, "+
@ -1324,6 +1347,8 @@ func (l *channelLink) handleDownstreamUpdateAdd(pkt *htlcPacket) {
)
l.tryBatchUpdateCommitTx()
return nil
}
// handleDownstreamPkt processes an HTLC packet sent from the downstream HTLC
@ -1335,7 +1360,9 @@ func (l *channelLink) handleDownstreamUpdateAdd(pkt *htlcPacket) {
func (l *channelLink) handleDownstreamPkt(pkt *htlcPacket) {
switch htlc := pkt.htlc.(type) {
case *lnwire.UpdateAddHTLC:
l.handleDownstreamUpdateAdd(pkt)
// Handle add message. The returned error can be ignored,
// because it is also sent through the mailbox.
_ = l.handleDownstreamUpdateAdd(pkt)
case *lnwire.UpdateFulfillHTLC:
// If hodl.SettleOutgoing mode is active, we exit early to
@ -2329,6 +2356,33 @@ func (l *channelLink) HandleSwitchPacket(pkt *htlcPacket) error {
return l.mailBox.AddPacket(pkt)
}
// HandleLocalAddPacket handles a locally-initiated UpdateAddHTLC packet. It
// will be processed synchronously.
//
// NOTE: Part of the ChannelLink interface.
func (l *channelLink) HandleLocalAddPacket(pkt *htlcPacket) error {
l.log.Tracef("received switch packet outkey=%v", pkt.outKey())
// Create a buffered result channel to prevent the link from blocking.
errChan := make(chan error, 1)
select {
case l.localUpdateAdd <- &localUpdateAddMsg{
pkt: pkt,
err: errChan,
}:
case <-l.quit:
return ErrLinkShuttingDown
}
select {
case err := <-errChan:
return err
case <-l.quit:
return ErrLinkShuttingDown
}
}
// HandleChannelUpdate handles the htlc requests as settle/add/fail which sent
// to us from remote peer we have a channel with.
//

@ -702,6 +702,11 @@ func (f *mockChannelLink) HandleSwitchPacket(pkt *htlcPacket) error {
return nil
}
func (f *mockChannelLink) HandleLocalAddPacket(pkt *htlcPacket) error {
_ = f.mailBox.AddPacket(pkt)
return nil
}
func (f *mockChannelLink) HandleChannelUpdate(lnwire.Message) {
}

@ -491,7 +491,7 @@ func (s *Switch) SendHTLC(firstHop lnwire.ShortChannelID, paymentID uint64,
return linkErr
}
return link.HandleSwitchPacket(packet)
return link.HandleLocalAddPacket(packet)
}
// UpdateForwardingPolicies sends a message to the switch to update the

@ -4182,6 +4182,34 @@ func testSphinxReplayPersistence(net *lntest.NetworkHarness, t *harnessTest) {
},
)
// Next, we'll create Fred who is going to initiate the payment and
// establish a channel to from him to Carol. We can't perform this test
// by paying from Carol directly to Dave, because the '--unsafe-replay'
// setup doesn't apply to locally added htlcs. In that case, the
// mailbox, that is responsible for generating the replay, is bypassed.
fred, err := net.NewNode("Fred", nil)
if err != nil {
t.Fatalf("unable to create new nodes: %v", err)
}
defer shutdownAndAssert(net, t, fred)
ctxt, _ = context.WithTimeout(ctxb, defaultTimeout)
if err := net.ConnectNodes(ctxt, fred, carol); err != nil {
t.Fatalf("unable to connect fred to carol: %v", err)
}
ctxt, _ = context.WithTimeout(ctxb, defaultTimeout)
err = net.SendCoins(ctxt, btcutil.SatoshiPerBitcoin, fred)
if err != nil {
t.Fatalf("unable to send coins to fred: %v", err)
}
ctxt, _ = context.WithTimeout(ctxb, channelOpenTimeout)
chanPointFC := openChannelAndAssert(
ctxt, t, net, fred, carol,
lntest.OpenChannelParams{
Amt: chanAmt,
},
)
// Now that the channel is open, create an invoice for Dave which
// expects a payment of 1000 satoshis from Carol paid via a particular
// preimage.
@ -4198,8 +4226,7 @@ func testSphinxReplayPersistence(net *lntest.NetworkHarness, t *harnessTest) {
t.Fatalf("unable to add invoice: %v", err)
}
// Wait for Carol to recognize and advertise the new channel generated
// above.
// Wait for all channels to be recognized and advertized.
ctxt, _ = context.WithTimeout(ctxb, defaultTimeout)
err = carol.WaitForNetworkChannelOpen(ctxt, chanPoint)
if err != nil {
@ -4211,13 +4238,23 @@ func testSphinxReplayPersistence(net *lntest.NetworkHarness, t *harnessTest) {
t.Fatalf("bob didn't advertise channel before "+
"timeout: %v", err)
}
err = carol.WaitForNetworkChannelOpen(ctxt, chanPointFC)
if err != nil {
t.Fatalf("alice didn't advertise channel before "+
"timeout: %v", err)
}
err = fred.WaitForNetworkChannelOpen(ctxt, chanPointFC)
if err != nil {
t.Fatalf("bob didn't advertise channel before "+
"timeout: %v", err)
}
// With the invoice for Dave added, send a payment from Carol paying
// With the invoice for Dave added, send a payment from Fred paying
// to the above generated invoice.
ctx, cancel := context.WithCancel(ctxb)
defer cancel()
payStream, err := carol.SendPayment(ctx)
payStream, err := fred.SendPayment(ctx)
if err != nil {
t.Fatalf("unable to open payment stream: %v", err)
}
@ -4270,12 +4307,12 @@ func testSphinxReplayPersistence(net *lntest.NetworkHarness, t *harnessTest) {
t.Fatalf("unable to receive payment response: %v", err)
}
// Construct the response we expect after sending a duplicate packet
// that fails due to sphinx replay detection.
// Assert that Fred receives the expected failure after Carol sent a
// duplicate packet that fails due to sphinx replay detection.
if resp.PaymentError == "" {
t.Fatalf("expected payment error")
}
assertLastHTLCError(t, carol, lnrpc.Failure_INVALID_ONION_KEY)
assertLastHTLCError(t, fred, lnrpc.Failure_INVALID_ONION_KEY)
// Since the payment failed, the balance should still be left
// unaltered.

@ -24,6 +24,7 @@
<time> [ERR] CRTR: Channel update of ourselves received
<time> [ERR] CRTR: Error collecting result for shard <number> for payment <hex>: shard handler exiting
<time> [ERR] CRTR: Error encountered during rescan: rescan exited
<time> [ERR] CRTR: Failed sending attempt <number> for payment <hex> to switch: could not add downstream htlc
<time> [ERR] CRTR: Failed sending attempt <number> for payment <hex> to switch: insufficient bandwidth to route htlc
<time> [ERR] CRTR: Failed sending attempt <number> for payment <hex> to switch: UnknownNextPeer
<time> [ERR] CRTR: out of order block: expecting height=<height>, got height=<height>
@ -80,6 +81,7 @@
<time> [ERR] HSWC: ChannelLink(<chan>): link failed, exiting htlcManager
<time> [ERR] HSWC: ChannelLink(<chan>): outgoing htlc(<hex>) has insufficient fee: expected 575000, got 1075
<time> [ERR] HSWC: ChannelLink(<chan>): outgoing htlc(<hex>) is too small: min_htlc=<amt>, htlc_value=<amt>
<time> [ERR] HSWC: ChannelLink(<chan>): unable to cancel incoming HTLC for circuit-key=(Chan ID=<chan>, HTLC ID=0): HTLC with ID 0 has already been failed
<time> [ERR] HSWC: ChannelLink(<chan>): unable to decode onion hop iterator: TemporaryChannelFailure
<time> [ERR] HSWC: ChannelLink(<chan>): unhandled error while forwarding htlc packet over htlcswitch: AmountBelowMinimum(amt=4000 mSAT, update=(lnwire.ChannelUpdate) {
<time> [ERR] HSWC: ChannelLink(<chan>): unhandled error while forwarding htlc packet over htlcswitch: circuit has already been closed