package htlcswitch import ( "bytes" "crypto/sha256" "fmt" "math" prand "math/rand" "sync" "sync/atomic" "time" "github.com/btcsuite/btcd/wire" "github.com/btcsuite/btclog" "github.com/davecgh/go-spew/spew" "github.com/go-errors/errors" "github.com/lightningnetwork/lnd/build" "github.com/lightningnetwork/lnd/channeldb" "github.com/lightningnetwork/lnd/contractcourt" "github.com/lightningnetwork/lnd/htlcswitch/hodl" "github.com/lightningnetwork/lnd/htlcswitch/hop" "github.com/lightningnetwork/lnd/invoices" "github.com/lightningnetwork/lnd/lnpeer" "github.com/lightningnetwork/lnd/lntypes" "github.com/lightningnetwork/lnd/lnwallet" "github.com/lightningnetwork/lnd/lnwallet/chainfee" "github.com/lightningnetwork/lnd/lnwire" "github.com/lightningnetwork/lnd/queue" "github.com/lightningnetwork/lnd/ticker" ) func init() { prand.Seed(time.Now().UnixNano()) } const ( // DefaultMaxOutgoingCltvExpiry is the maximum outgoing time lock that // the node accepts for forwarded payments. The value is relative to the // current block height. The reason to have a maximum is to prevent // funds getting locked up unreasonably long. Otherwise, an attacker // willing to lock its own funds too, could force the funds of this node // to be locked up for an indefinite (max int32) number of blocks. // // The value 2016 corresponds to on average two weeks worth of blocks // and is based on the maximum number of hops (20), the default CLTV // delta (40), and some extra margin to account for the other lightning // implementations and past lnd versions which used to have a default // CLTV delta of 144. DefaultMaxOutgoingCltvExpiry = 2016 // DefaultMinLinkFeeUpdateTimeout represents the minimum interval in // which a link should propose to update its commitment fee rate. DefaultMinLinkFeeUpdateTimeout = 10 * time.Minute // DefaultMaxLinkFeeUpdateTimeout represents the maximum interval in // which a link should propose to update its commitment fee rate. DefaultMaxLinkFeeUpdateTimeout = 60 * time.Minute // DefaultMaxLinkFeeAllocation is the highest allocation we'll allow // a channel's commitment fee to be of its balance. This only applies to // the initiator of the channel. DefaultMaxLinkFeeAllocation float64 = 0.5 ) // ForwardingPolicy describes the set of constraints that a given ChannelLink // is to adhere to when forwarding HTLC's. For each incoming HTLC, this set of // constraints will be consulted in order to ensure that adequate fees are // paid, and our time-lock parameters are respected. In the event that an // incoming HTLC violates any of these constraints, it is to be _rejected_ with // the error possibly carrying along a ChannelUpdate message that includes the // latest policy. type ForwardingPolicy struct { // MinHTLC is the smallest HTLC that is to be forwarded. MinHTLCOut lnwire.MilliSatoshi // MaxHTLC is the largest HTLC that is to be forwarded. MaxHTLC lnwire.MilliSatoshi // BaseFee is the base fee, expressed in milli-satoshi that must be // paid for each incoming HTLC. This field, combined with FeeRate is // used to compute the required fee for a given HTLC. BaseFee lnwire.MilliSatoshi // FeeRate is the fee rate, expressed in milli-satoshi that must be // paid for each incoming HTLC. This field combined with BaseFee is // used to compute the required fee for a given HTLC. FeeRate lnwire.MilliSatoshi // TimeLockDelta is the absolute time-lock value, expressed in blocks, // that will be subtracted from an incoming HTLC's timelock value to // create the time-lock value for the forwarded outgoing HTLC. The // following constraint MUST hold for an HTLC to be forwarded: // // * incomingHtlc.timeLock - timeLockDelta = fwdInfo.OutgoingCTLV // // where fwdInfo is the forwarding information extracted from the // per-hop payload of the incoming HTLC's onion packet. TimeLockDelta uint32 // TODO(roasbeef): add fee module inside of switch } // ExpectedFee computes the expected fee for a given htlc amount. The value // returned from this function is to be used as a sanity check when forwarding // HTLC's to ensure that an incoming HTLC properly adheres to our propagated // forwarding policy. // // TODO(roasbeef): also add in current available channel bandwidth, inverse // func func ExpectedFee(f ForwardingPolicy, htlcAmt lnwire.MilliSatoshi) lnwire.MilliSatoshi { return f.BaseFee + (htlcAmt*f.FeeRate)/1000000 } // ChannelLinkConfig defines the configuration for the channel link. ALL // elements within the configuration MUST be non-nil for channel link to carry // out its duties. type ChannelLinkConfig struct { // FwrdingPolicy is the initial forwarding policy to be used when // deciding whether to forwarding incoming HTLC's or not. This value // can be updated with subsequent calls to UpdateForwardingPolicy // targeted at a given ChannelLink concrete interface implementation. FwrdingPolicy ForwardingPolicy // Circuits provides restricted access to the switch's circuit map, // allowing the link to open and close circuits. Circuits CircuitModifier // Switch provides a reference to the HTLC switch, we only use this in // testing to access circuit operations not typically exposed by the // CircuitModifier. // // TODO(conner): remove after refactoring htlcswitch testing framework. Switch *Switch // ForwardPackets attempts to forward the batch of htlcs through the // switch, any failed packets will be returned to the provided // ChannelLink. The link's quit signal should be provided to allow // cancellation of forwarding during link shutdown. ForwardPackets func(chan struct{}, ...*htlcPacket) chan error // DecodeHopIterators facilitates batched decoding of HTLC Sphinx onion // blobs, which are then used to inform how to forward an HTLC. // // NOTE: This function assumes the same set of readers and preimages // are always presented for the same identifier. DecodeHopIterators func([]byte, []hop.DecodeHopIteratorRequest) ( []hop.DecodeHopIteratorResponse, error) // ExtractErrorEncrypter function is responsible for decoding HTLC // Sphinx onion blob, and creating onion failure obfuscator. ExtractErrorEncrypter hop.ErrorEncrypterExtracter // FetchLastChannelUpdate retrieves the latest routing policy for a // target channel. This channel will typically be the outgoing channel // specified when we receive an incoming HTLC. This will be used to // provide payment senders our latest policy when sending encrypted // error messages. FetchLastChannelUpdate func(lnwire.ShortChannelID) (*lnwire.ChannelUpdate, error) // Peer is a lightning network node with which we have the channel link // opened. Peer lnpeer.Peer // Registry is a sub-system which responsible for managing the invoices // in thread-safe manner. Registry InvoiceDatabase // PreimageCache is a global witness beacon that houses any new // preimages discovered by other links. We'll use this to add new // witnesses that we discover which will notify any sub-systems // subscribed to new events. PreimageCache contractcourt.WitnessBeacon // OnChannelFailure is a function closure that we'll call if the // channel failed for some reason. Depending on the severity of the // error, the closure potentially must force close this channel and // disconnect the peer. // // NOTE: The method must return in order for the ChannelLink to be able // to shut down properly. OnChannelFailure func(lnwire.ChannelID, lnwire.ShortChannelID, LinkFailureError) // UpdateContractSignals is a function closure that we'll use to update // outside sub-systems with the latest signals for our inner Lightning // channel. These signals will notify the caller when the channel has // been closed, or when the set of active HTLC's is updated. UpdateContractSignals func(*contractcourt.ContractSignals) error // ChainEvents is an active subscription to the chain watcher for this // channel to be notified of any on-chain activity related to this // channel. ChainEvents *contractcourt.ChainEventSubscription // FeeEstimator is an instance of a live fee estimator which will be // used to dynamically regulate the current fee of the commitment // transaction to ensure timely confirmation. FeeEstimator chainfee.Estimator // hodl.Mask is a bitvector composed of hodl.Flags, specifying breakpoints // for HTLC forwarding internal to the switch. // // NOTE: This should only be used for testing. HodlMask hodl.Mask // SyncStates is used to indicate that we need send the channel // reestablishment message to the remote peer. It should be done if our // clients have been restarted, or remote peer have been reconnected. SyncStates bool // BatchTicker is the ticker that determines the interval that we'll // use to check the batch to see if there're any updates we should // flush out. By batching updates into a single commit, we attempt to // increase throughput by maximizing the number of updates coalesced // into a single commit. BatchTicker ticker.Ticker // FwdPkgGCTicker is the ticker determining the frequency at which // garbage collection of forwarding packages occurs. We use a // time-based approach, as opposed to block epochs, as to not hinder // syncing. FwdPkgGCTicker ticker.Ticker // PendingCommitTicker is a ticker that allows the link to determine if // a locally initiated commitment dance gets stuck waiting for the // remote party to revoke. PendingCommitTicker ticker.Ticker // BatchSize is the max size of a batch of updates done to the link // before we do a state update. BatchSize uint32 // UnsafeReplay will cause a link to replay the adds in its latest // commitment txn after the link is restarted. This should only be used // in testing, it is here to ensure the sphinx replay detection on the // receiving node is persistent. UnsafeReplay bool // MinFeeUpdateTimeout represents the minimum interval in which a link // will propose to update its commitment fee rate. A random timeout will // be selected between this and MaxFeeUpdateTimeout. MinFeeUpdateTimeout time.Duration // MaxFeeUpdateTimeout represents the maximum interval in which a link // will propose to update its commitment fee rate. A random timeout will // be selected between this and MinFeeUpdateTimeout. MaxFeeUpdateTimeout time.Duration // OutgoingCltvRejectDelta defines the number of blocks before expiry of // an htlc where we don't offer an htlc anymore. This should be at least // the outgoing broadcast delta, because in any case we don't want to // risk offering an htlc that triggers channel closure. OutgoingCltvRejectDelta uint32 // TowerClient is an optional engine that manages the signing, // encrypting, and uploading of justice transactions to the daemon's // configured set of watchtowers. TowerClient TowerClient // MaxOutgoingCltvExpiry is the maximum outgoing timelock that the link // should accept for a forwarded HTLC. The value is relative to the // current block height. MaxOutgoingCltvExpiry uint32 // MaxFeeAllocation is the highest allocation we'll allow a channel's // commitment fee to be of its balance. This only applies to the // initiator of the channel. MaxFeeAllocation float64 // NotifyActiveLink allows the link to tell the ChannelNotifier when a // link is first started. NotifyActiveLink func(wire.OutPoint) // NotifyActiveChannel allows the link to tell the ChannelNotifier when // channels becomes active. NotifyActiveChannel func(wire.OutPoint) // NotifyInactiveChannel allows the switch to tell the ChannelNotifier // when channels become inactive. NotifyInactiveChannel func(wire.OutPoint) // HtlcNotifier is an instance of a htlcNotifier which we will pipe htlc // events through. HtlcNotifier htlcNotifier } // 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 // switch. Additionally, the link encapsulate logic of commitment protocol // message ordering and updates. type channelLink struct { // The following fields are only meant to be used *atomically* started int32 reestablished int32 shutdown int32 // failed should be set to true in case a link error happens, making // sure we don't process any more updates. failed bool // keystoneBatch represents a volatile list of keystones that must be // written before attempting to sign the next commitment txn. These // represent all the HTLC's forwarded to the link from the switch. Once // we lock them into our outgoing commitment, then the circuit has a // keystone, and is fully opened. keystoneBatch []Keystone // openedCircuits is the set of all payment circuits that will be open // once we make our next commitment. After making the commitment we'll // ACK all these from our mailbox to ensure that they don't get // re-delivered if we reconnect. openedCircuits []CircuitKey // closedCircuits is the set of all payment circuits that will be // closed once we make our next commitment. After taking the commitment // we'll ACK all these to ensure that they don't get re-delivered if we // reconnect. closedCircuits []CircuitKey // channel is a lightning network channel to which we apply htlc // updates. channel *lnwallet.LightningChannel // shortChanID is the most up to date short channel ID for the link. shortChanID lnwire.ShortChannelID // cfg is a structure which carries all dependable fields/handlers // which may affect behaviour of the service. cfg ChannelLinkConfig // mailBox is the main interface between the outside world and the // link. All incoming messages will be sent over this mailBox. Messages // include new updates from our connected peer, and new packets to be // forwarded sent by the switch. mailBox MailBox // upstream is a channel that new messages sent from the remote peer to // the local peer will be sent across. upstream chan lnwire.Message // downstream is a channel in which new multi-hop HTLC's to be // forwarded will be sent across. Messages from this channel are sent // by the HTLC switch. downstream chan *htlcPacket // 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 // updateFeeTimer is the timer responsible for updating the link's // commitment fee every time it fires. updateFeeTimer *time.Timer // uncommittedPreimages stores a list of all preimages that have been // learned since receiving the last CommitSig from the remote peer. The // batch will be flushed just before accepting the subsequent CommitSig // or on shutdown to avoid doing a write for each preimage received. uncommittedPreimages []lntypes.Preimage sync.RWMutex // hodlQueue is used to receive exit hop htlc resolutions from invoice // registry. hodlQueue *queue.ConcurrentQueue // hodlMap stores related htlc data for a circuit key. It allows // resolving those htlcs when we receive a message on hodlQueue. hodlMap map[channeldb.CircuitKey]hodlHtlc // log is a link-specific logging instance. log btclog.Logger wg sync.WaitGroup quit chan struct{} } // hodlHtlc contains htlc data that is required for resolution. type hodlHtlc struct { pd *lnwallet.PaymentDescriptor obfuscator hop.ErrorEncrypter } // NewChannelLink creates a new instance of a ChannelLink given a configuration // and active channel that will be used to verify/apply updates to. func NewChannelLink(cfg ChannelLinkConfig, channel *lnwallet.LightningChannel) ChannelLink { logPrefix := fmt.Sprintf("ChannelLink(%v):", channel.ShortChanID()) return &channelLink{ cfg: cfg, 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{}), } } // A compile time check to ensure channelLink implements the ChannelLink // interface. var _ ChannelLink = (*channelLink)(nil) // Start starts all helper goroutines required for the operation of the channel // link. // // NOTE: Part of the ChannelLink interface. func (l *channelLink) Start() error { if !atomic.CompareAndSwapInt32(&l.started, 0, 1) { err := errors.Errorf("channel link(%v): already started", l) l.log.Warn("already started") return err } l.log.Info("starting") // If the config supplied watchtower client, ensure the channel is // registered before trying to use it during operation. // TODO(halseth): support anchor types for watchtower. state := l.channel.State() if l.cfg.TowerClient != nil && state.ChanType.HasAnchors() { l.log.Warnf("Skipping tower registration for anchor " + "channel type") } else if l.cfg.TowerClient != nil && !state.ChanType.HasAnchors() { err := l.cfg.TowerClient.RegisterChannel(l.ChanID()) if err != nil { return err } } l.mailBox.ResetMessages() l.hodlQueue.Start() // Before launching the htlcManager messages, revert any circuits that // were marked open in the switch's circuit map, but did not make it // into a commitment txn. We use the next local htlc index as the cut // off point, since all indexes below that are committed. This action // is only performed if the link's final short channel ID has been // assigned, otherwise we would try to trim the htlcs belonging to the // all-zero, hop.Source ID. if l.ShortChanID() != hop.Source { localHtlcIndex, err := l.channel.NextLocalHtlcIndex() if err != nil { return fmt.Errorf("unable to retrieve next local "+ "htlc index: %v", err) } // NOTE: This is automatically done by the switch when it // starts up, but is necessary to prevent inconsistencies in // the case that the link flaps. This is a result of a link's // life-cycle being shorter than that of the switch. chanID := l.ShortChanID() err = l.cfg.Circuits.TrimOpenCircuits(chanID, localHtlcIndex) if err != nil { return fmt.Errorf("unable to trim circuits above "+ "local htlc index %d: %v", localHtlcIndex, err) } // Since the link is live, before we start the link we'll update // the ChainArbitrator with the set of new channel signals for // this channel. // // TODO(roasbeef): split goroutines within channel arb to avoid go func() { signals := &contractcourt.ContractSignals{ HtlcUpdates: l.htlcUpdates, ShortChanID: l.channel.ShortChanID(), } err := l.cfg.UpdateContractSignals(signals) if err != nil { l.log.Errorf("unable to update signals") } }() } l.updateFeeTimer = time.NewTimer(l.randomFeeUpdateTimeout()) l.wg.Add(1) go l.htlcManager() return nil } // Stop gracefully stops all active helper goroutines, then waits until they've // exited. // // NOTE: Part of the ChannelLink interface. func (l *channelLink) Stop() { if !atomic.CompareAndSwapInt32(&l.shutdown, 0, 1) { l.log.Warn("already stopped") return } l.log.Info("stopping") // As the link is stopping, we are no longer interested in htlc // resolutions coming from the invoice registry. l.cfg.Registry.HodlUnsubscribeAll(l.hodlQueue.ChanIn()) if l.cfg.ChainEvents.Cancel != nil { l.cfg.ChainEvents.Cancel() } l.updateFeeTimer.Stop() l.hodlQueue.Stop() close(l.quit) l.wg.Wait() // Now that the htlcManager has completely exited, reset the packet // courier. This allows the mailbox to revaluate any lingering Adds that // were delivered but didn't make it on a commitment to be failed back // if the link is offline for an extended period of time. The error is // ignored since it can only fail when the daemon is exiting. _ = l.mailBox.ResetPackets() // As a final precaution, we will attempt to flush any uncommitted // preimages to the preimage cache. The preimages should be re-delivered // after channel reestablishment, however this adds an extra layer of // protection in case the peer never returns. Without this, we will be // unable to settle any contracts depending on the preimages even though // we had learned them at some point. err := l.cfg.PreimageCache.AddPreimages(l.uncommittedPreimages...) if err != nil { l.log.Errorf("unable to add preimages=%v to cache: %v", l.uncommittedPreimages, err) } } // WaitForShutdown blocks until the link finishes shutting down, which includes // termination of all dependent goroutines. func (l *channelLink) WaitForShutdown() { l.wg.Wait() } // EligibleToForward returns a bool indicating if the channel is able to // actively accept requests to forward HTLC's. We're able to forward HTLC's if // we know the remote party's next revocation point. Otherwise, we can't // initiate new channel state. We also require that the short channel ID not be // the all-zero source ID, meaning that the channel has had its ID finalized. func (l *channelLink) EligibleToForward() bool { return l.channel.RemoteNextRevocation() != nil && l.ShortChanID() != hop.Source && l.isReestablished() } // isReestablished returns true if the link has successfully completed the // channel reestablishment dance. func (l *channelLink) isReestablished() bool { return atomic.LoadInt32(&l.reestablished) == 1 } // markReestablished signals that the remote peer has successfully exchanged // channel reestablish messages and that the channel is ready to process // subsequent messages. func (l *channelLink) markReestablished() { atomic.StoreInt32(&l.reestablished, 1) } // sampleNetworkFee samples the current fee rate on the network to get into the // chain in a timely manner. The returned value is expressed in fee-per-kw, as // this is the native rate used when computing the fee for commitment // transactions, and the second-level HTLC transactions. func (l *channelLink) sampleNetworkFee() (chainfee.SatPerKWeight, error) { // We'll first query for the sat/kw recommended to be confirmed within 3 // blocks. feePerKw, err := l.cfg.FeeEstimator.EstimateFeePerKW(3) if err != nil { return 0, err } l.log.Debugf("sampled fee rate for 3 block conf: %v sat/kw", int64(feePerKw)) return feePerKw, nil } // shouldAdjustCommitFee returns true if we should update our commitment fee to // match that of the network fee. We'll only update our commitment fee if the // network fee is +/- 10% to our network fee. func shouldAdjustCommitFee(netFee, chanFee chainfee.SatPerKWeight) bool { switch { // If the network fee is greater than the commitment fee, then we'll // switch to it if it's at least 10% greater than the commit fee. case netFee > chanFee && netFee >= (chanFee+(chanFee*10)/100): return true // If the network fee is less than our commitment fee, then we'll // switch to it if it's at least 10% less than the commitment fee. case netFee < chanFee && netFee <= (chanFee-(chanFee*10)/100): return true // Otherwise, we won't modify our fee. default: return false } } // createFailureWithUpdate retrieves this link's last channel update message and // passes it into the callback. It expects a fully populated failure message. func (l *channelLink) createFailureWithUpdate( cb func(update *lnwire.ChannelUpdate) lnwire.FailureMessage) lnwire.FailureMessage { update, err := l.cfg.FetchLastChannelUpdate(l.ShortChanID()) if err != nil { return &lnwire.FailTemporaryNodeFailure{} } return cb(update) } // syncChanState attempts to synchronize channel states with the remote party. // This method is to be called upon reconnection after the initial funding // flow. We'll compare out commitment chains with the remote party, and re-send // either a danging commit signature, a revocation, or both. func (l *channelLink) syncChanStates() error { l.log.Info("attempting to re-resynchronize") // First, we'll generate our ChanSync message to send to the other // side. Based on this message, the remote party will decide if they // need to retransmit any data or not. chanState := l.channel.State() localChanSyncMsg, err := chanState.ChanSyncMsg() if err != nil { return fmt.Errorf("unable to generate chan sync message for "+ "ChannelPoint(%v)", l.channel.ChannelPoint()) } if err := l.cfg.Peer.SendMessage(true, localChanSyncMsg); err != nil { return fmt.Errorf("unable to send chan sync message for "+ "ChannelPoint(%v): %v", l.channel.ChannelPoint(), err) } var msgsToReSend []lnwire.Message // Next, we'll wait indefinitely to receive the ChanSync message. The // first message sent MUST be the ChanSync message. select { case msg := <-l.upstream: remoteChanSyncMsg, ok := msg.(*lnwire.ChannelReestablish) if !ok { return fmt.Errorf("first message sent to sync "+ "should be ChannelReestablish, instead "+ "received: %T", msg) } // If the remote party indicates that they think we haven't // done any state updates yet, then we'll retransmit the // funding locked message first. We do this, as at this point // we can't be sure if they've really received the // FundingLocked message. if remoteChanSyncMsg.NextLocalCommitHeight == 1 && localChanSyncMsg.NextLocalCommitHeight == 1 && !l.channel.IsPending() { l.log.Infof("resending FundingLocked message to peer") nextRevocation, err := l.channel.NextRevocationKey() if err != nil { return fmt.Errorf("unable to create next "+ "revocation: %v", err) } fundingLockedMsg := lnwire.NewFundingLocked( l.ChanID(), nextRevocation, ) err = l.cfg.Peer.SendMessage(false, fundingLockedMsg) if err != nil { return fmt.Errorf("unable to re-send "+ "FundingLocked: %v", err) } } // In any case, we'll then process their ChanSync message. l.log.Info("received re-establishment message from remote side") var ( openedCircuits []CircuitKey closedCircuits []CircuitKey ) // We've just received a ChanSync message from the remote // party, so we'll process the message in order to determine // if we need to re-transmit any messages to the remote party. msgsToReSend, openedCircuits, closedCircuits, err = l.channel.ProcessChanSyncMsg(remoteChanSyncMsg) if err != nil { return err } // Repopulate any identifiers for circuits that may have been // opened or unclosed. This may happen if we needed to // retransmit a commitment signature message. l.openedCircuits = openedCircuits l.closedCircuits = closedCircuits // Ensure that all packets have been have been removed from the // link's mailbox. if err := l.ackDownStreamPackets(); err != nil { return err } if len(msgsToReSend) > 0 { l.log.Infof("sending %v updates to synchronize the "+ "state", len(msgsToReSend)) } // If we have any messages to retransmit, we'll do so // immediately so we return to a synchronized state as soon as // possible. for _, msg := range msgsToReSend { l.cfg.Peer.SendMessage(false, msg) } case <-l.quit: return ErrLinkShuttingDown } return nil } // resolveFwdPkgs loads any forwarding packages for this link from disk, and // reprocesses them in order. The primary goal is to make sure that any HTLCs // we previously received are reinstated in memory, and forwarded to the switch // if necessary. After a restart, this will also delete any previously // completed packages. func (l *channelLink) resolveFwdPkgs() error { fwdPkgs, err := l.channel.LoadFwdPkgs() if err != nil { return err } l.log.Debugf("loaded %d fwd pks", len(fwdPkgs)) for _, fwdPkg := range fwdPkgs { if err := l.resolveFwdPkg(fwdPkg); err != nil { return err } } // If any of our reprocessing steps require an update to the commitment // txn, we initiate a state transition to capture all relevant changes. if l.channel.PendingLocalUpdateCount() > 0 { return l.updateCommitTx() } return nil } // resolveFwdPkg interprets the FwdState of the provided package, either // reprocesses any outstanding htlcs in the package, or performs garbage // collection on the package. func (l *channelLink) resolveFwdPkg(fwdPkg *channeldb.FwdPkg) error { // Remove any completed packages to clear up space. if fwdPkg.State == channeldb.FwdStateCompleted { l.log.Debugf("removing completed fwd pkg for height=%d", fwdPkg.Height) err := l.channel.RemoveFwdPkg(fwdPkg.Height) if err != nil { l.log.Errorf("unable to remove fwd pkg for height=%d: "+ "%v", fwdPkg.Height, err) return err } } // Otherwise this is either a new package or one has gone through // processing, but contains htlcs that need to be restored in memory. // We replay this forwarding package to make sure our local mem state // is resurrected, we mimic any original responses back to the remote // party, and re-forward the relevant HTLCs to the switch. // If the package is fully acked but not completed, it must still have // settles and fails to propagate. if !fwdPkg.SettleFailFilter.IsFull() { settleFails, err := lnwallet.PayDescsFromRemoteLogUpdates( fwdPkg.Source, fwdPkg.Height, fwdPkg.SettleFails, ) if err != nil { l.log.Errorf("unable to process remote log updates: %v", err) return err } l.processRemoteSettleFails(fwdPkg, settleFails) } // Finally, replay *ALL ADDS* in this forwarding package. The // downstream logic is able to filter out any duplicates, but we must // shove the entire, original set of adds down the pipeline so that the // batch of adds presented to the sphinx router does not ever change. if !fwdPkg.AckFilter.IsFull() { adds, err := lnwallet.PayDescsFromRemoteLogUpdates( fwdPkg.Source, fwdPkg.Height, fwdPkg.Adds, ) if err != nil { l.log.Errorf("unable to process remote log updates: %v", err) return err } l.processRemoteAdds(fwdPkg, adds) // If the link failed during processing the adds, we must // return to ensure we won't attempted to update the state // further. if l.failed { return fmt.Errorf("link failed while " + "processing remote adds") } } return nil } // fwdPkgGarbager periodically reads all forwarding packages from disk and // removes those that can be discarded. It is safe to do this entirely in the // background, since all state is coordinated on disk. This also ensures the // link can continue to process messages and interleave database accesses. // // NOTE: This MUST be run as a goroutine. func (l *channelLink) fwdPkgGarbager() { defer l.wg.Done() l.cfg.FwdPkgGCTicker.Resume() defer l.cfg.FwdPkgGCTicker.Stop() for { select { case <-l.cfg.FwdPkgGCTicker.Ticks(): fwdPkgs, err := l.channel.LoadFwdPkgs() if err != nil { l.log.Warnf("unable to load fwdpkgs for gc: %v", err) continue } // TODO(conner): batch removal of forward packages. for _, fwdPkg := range fwdPkgs { if fwdPkg.State != channeldb.FwdStateCompleted { continue } err = l.channel.RemoveFwdPkg(fwdPkg.Height) if err != nil { l.log.Warnf("unable to remove fwd pkg "+ "for height=%d: %v", fwdPkg.Height, err) } } case <-l.quit: return } } } // htlcManager is the primary goroutine which drives a channel's commitment // update state-machine in response to messages received via several channels. // This goroutine reads messages from the upstream (remote) peer, and also from // downstream channel managed by the channel link. In the event that an htlc // needs to be forwarded, then send-only forward handler is used which sends // htlc packets to the switch. Additionally, the this goroutine handles acting // upon all timeouts for any active HTLCs, manages the channel's revocation // window, and also the htlc trickle queue+timer for this active channels. // // NOTE: This MUST be run as a goroutine. func (l *channelLink) htlcManager() { defer func() { l.cfg.BatchTicker.Stop() l.wg.Done() l.log.Infof("exited") }() l.log.Infof("HTLC manager started, bandwidth=%v", l.Bandwidth()) // Notify any clients that the link is now in the switch via an // ActiveLinkEvent. l.cfg.NotifyActiveLink(*l.ChannelPoint()) // TODO(roasbeef): need to call wipe chan whenever D/C? // If this isn't the first time that this channel link has been // created, then we'll need to check to see if we need to // re-synchronize state with the remote peer. settledHtlcs is a map of // HTLC's that we re-settled as part of the channel state sync. if l.cfg.SyncStates { err := l.syncChanStates() if err != nil { l.log.Warnf("error when syncing channel states: %v", err) errDataLoss, localDataLoss := err.(*lnwallet.ErrCommitSyncLocalDataLoss) switch { case err == ErrLinkShuttingDown: l.log.Debugf("unable to sync channel states, " + "link is shutting down") return // We failed syncing the commit chains, probably // because the remote has lost state. We should force // close the channel. case err == lnwallet.ErrCommitSyncRemoteDataLoss: fallthrough // The remote sent us an invalid last commit secret, we // should force close the channel. // TODO(halseth): and permanently ban the peer? case err == lnwallet.ErrInvalidLastCommitSecret: fallthrough // The remote sent us a commit point different from // what they sent us before. // TODO(halseth): ban peer? case err == lnwallet.ErrInvalidLocalUnrevokedCommitPoint: // We'll fail the link and tell the peer to // force close the channel. Note that the // database state is not updated here, but will // be updated when the close transaction is // ready to avoid that we go down before // storing the transaction in the db. l.fail( LinkFailureError{ code: ErrSyncError, ForceClose: true, }, "unable to synchronize channel "+ "states: %v", err, ) return // We have lost state and cannot safely force close the // channel. Fail the channel and wait for the remote to // hopefully force close it. The remote has sent us its // latest unrevoked commitment point, and we'll store // it in the database, such that we can attempt to // recover the funds if the remote force closes the // channel. case localDataLoss: err := l.channel.MarkDataLoss( errDataLoss.CommitPoint, ) if err != nil { l.log.Errorf("unable to mark channel "+ "data loss: %v", err) } // We determined the commit chains were not possible to // sync. We cautiously fail the channel, but don't // force close. // TODO(halseth): can we safely force close in any // cases where this error is returned? case err == lnwallet.ErrCannotSyncCommitChains: if err := l.channel.MarkBorked(); err != nil { l.log.Errorf("unable to mark channel "+ "borked: %v", err) } // Other, unspecified error. default: } l.fail( LinkFailureError{ code: ErrRecoveryError, ForceClose: false, }, "unable to synchronize channel "+ "states: %v", err, ) return } } // We've successfully reestablished the channel, mark it as such to // allow the switch to forward HTLCs in the outbound direction. l.markReestablished() // Now that we've received both funding locked and channel reestablish, // we can go ahead and send the active channel notification. We'll also // defer the inactive notification for when the link exits to ensure // that every active notification is matched by an inactive one. l.cfg.NotifyActiveChannel(*l.ChannelPoint()) defer l.cfg.NotifyInactiveChannel(*l.ChannelPoint()) // With the channel states synced, we now reset the mailbox to ensure // we start processing all unacked packets in order. This is done here // to ensure that all acknowledgments that occur during channel // resynchronization have taken affect, causing us only to pull unacked // packets after starting to read from the downstream mailbox. l.mailBox.ResetPackets() // After cleaning up any memory pertaining to incoming packets, we now // replay our forwarding packages to handle any htlcs that can be // processed locally, or need to be forwarded out to the switch. We will // only attempt to resolve packages if our short chan id indicates that // the channel is not pending, otherwise we should have no htlcs to // reforward. if l.ShortChanID() != hop.Source { if err := l.resolveFwdPkgs(); err != nil { l.fail(LinkFailureError{code: ErrInternalError}, "unable to resolve fwd pkgs: %v", err) return } // With our link's in-memory state fully reconstructed, spawn a // goroutine to manage the reclamation of disk space occupied by // completed forwarding packages. l.wg.Add(1) go l.fwdPkgGarbager() } for { // We must always check if we failed at some point processing // the last update before processing the next. if l.failed { l.log.Errorf("link failed, exiting htlcManager") return } // If the previous event resulted in a non-empty batch, resume // the batch ticker so that it can be cleared. Otherwise pause // the ticker to prevent waking up the htlcManager while the // batch is empty. if l.channel.PendingLocalUpdateCount() > 0 { l.cfg.BatchTicker.Resume() } else { l.cfg.BatchTicker.Pause() } select { // Our update fee timer has fired, so we'll check the network // fee to see if we should adjust our commitment fee. case <-l.updateFeeTimer.C: l.updateFeeTimer.Reset(l.randomFeeUpdateTimeout()) // If we're not the initiator of the channel, don't we // don't control the fees, so we can ignore this. if !l.channel.IsInitiator() { continue } // If we are the initiator, then we'll sample the // current fee rate to get into the chain within 3 // blocks. netFee, err := l.sampleNetworkFee() if err != nil { l.log.Errorf("unable to sample network fee: %v", err) continue } // We'll check to see if we should update the fee rate // based on our current set fee rate. We'll cap the new // fee rate to our max fee allocation. commitFee := l.channel.CommitFeeRate() maxFee := l.channel.MaxFeeRate(l.cfg.MaxFeeAllocation) newCommitFee := chainfee.SatPerKWeight( math.Min(float64(netFee), float64(maxFee)), ) if !shouldAdjustCommitFee(newCommitFee, commitFee) { continue } // If we do, then we'll send a new UpdateFee message to // the remote party, to be locked in with a new update. if err := l.updateChannelFee(newCommitFee); err != nil { l.log.Errorf("unable to update fee rate: %v", err) continue } // The underlying channel has notified us of a unilateral close // carried out by the remote peer. In the case of such an // event, we'll wipe the channel state from the peer, and mark // the contract as fully settled. Afterwards we can exit. // // TODO(roasbeef): add force closure? also breach? case <-l.cfg.ChainEvents.RemoteUnilateralClosure: l.log.Warnf("remote peer has closed on-chain") // TODO(roasbeef): remove all together go func() { chanPoint := l.channel.ChannelPoint() l.cfg.Peer.WipeChannel(chanPoint) }() return case <-l.cfg.BatchTicker.Ticks(): // Attempt to extend the remote commitment chain // including all the currently pending entries. If the // send was unsuccessful, then abandon the update, // waiting for the revocation window to open up. if err := l.updateCommitTx(); err != nil { l.fail(LinkFailureError{code: ErrInternalError}, "unable to update commitment: %v", err) return } case <-l.cfg.PendingCommitTicker.Ticks(): l.fail(LinkFailureError{code: ErrRemoteUnresponsive}, "unable to complete dance") return // A message from the switch was just received. This indicates // that the link is an intermediate hop in a multi-hop HTLC // circuit. case pkt := <-l.downstream: l.handleDownstreamPkt(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. case msg := <-l.upstream: l.handleUpstreamMsg(msg) // A htlc resolution is received. This means that we now have a // resolution for a previously accepted htlc. case hodlItem := <-l.hodlQueue.ChanOut(): htlcResolution := hodlItem.(invoices.HtlcResolution) err := l.processHodlQueue(htlcResolution) if err != nil { l.fail(LinkFailureError{code: ErrInternalError}, fmt.Sprintf("process hodl queue: %v", err.Error()), ) return } case <-l.quit: return } } } // processHodlQueue processes a received htlc resolution and continues reading // from the hodl queue until no more resolutions remain. When this function // returns without an error, the commit tx should be updated. func (l *channelLink) processHodlQueue( firstResolution invoices.HtlcResolution) error { // Try to read all waiting resolution messages, so that they can all be // processed in a single commitment tx update. htlcResolution := firstResolution loop: for { // Lookup all hodl htlcs that can be failed or settled with this event. // The hodl htlc must be present in the map. circuitKey := htlcResolution.CircuitKey() hodlHtlc, ok := l.hodlMap[circuitKey] if !ok { return fmt.Errorf("hodl htlc not found: %v", circuitKey) } if err := l.processHtlcResolution(htlcResolution, hodlHtlc); err != nil { return err } // Clean up hodl map. delete(l.hodlMap, circuitKey) select { case item := <-l.hodlQueue.ChanOut(): htlcResolution = item.(invoices.HtlcResolution) default: break loop } } // Update the commitment tx. if err := l.updateCommitTx(); err != nil { return fmt.Errorf("unable to update commitment: %v", err) } return nil } // processHtlcResolution applies a received htlc resolution to the provided // htlc. When this function returns without an error, the commit tx should be // updated. func (l *channelLink) processHtlcResolution(resolution invoices.HtlcResolution, htlc hodlHtlc) error { circuitKey := resolution.CircuitKey() // Determine required action for the resolution based on the type of // resolution we have received. switch res := resolution.(type) { // Settle htlcs that returned a settle resolution using the preimage // in the resolution. case *invoices.HtlcSettleResolution: l.log.Debugf("received settle resolution for %v "+ "with outcome: %v", circuitKey, res.Outcome) return l.settleHTLC(res.Preimage, htlc.pd) // For htlc failures, we get the relevant failure message based // on the failure resolution and then fail the htlc. case *invoices.HtlcFailResolution: l.log.Debugf("received cancel resolution for "+ "%v with outcome: %v", circuitKey, res.Outcome) // Get the lnwire failure message based on the resolution // result. failure := getResolutionFailure(res, htlc.pd.Amount) l.sendHTLCError( htlc.pd, failure, htlc.obfuscator, true, ) return nil // Fail if we do not get a settle of fail resolution, since we // are only expecting to handle settles and fails. default: return fmt.Errorf("unknown htlc resolution type: %T", resolution) } } // getResolutionFailure returns the wire message that a htlc resolution should // be failed with. func getResolutionFailure(resolution *invoices.HtlcFailResolution, amount lnwire.MilliSatoshi) *LinkError { // If the resolution has been resolved as part of a MPP timeout, // we need to fail the htlc with lnwire.FailMppTimeout. if resolution.Outcome == invoices.ResultMppTimeout { return NewDetailedLinkError( &lnwire.FailMPPTimeout{}, resolution.Outcome, ) } // If the htlc is not a MPP timeout, we fail it with // FailIncorrectDetails. This error is sent for invoice payment // failures such as underpayment/ expiry too soon and hodl invoices // (which return FailIncorrectDetails to avoid leaking information). incorrectDetails := lnwire.NewFailIncorrectDetails( amount, uint32(resolution.AcceptHeight), ) return NewDetailedLinkError(incorrectDetails, resolution.Outcome) } // randomFeeUpdateTimeout returns a random timeout between the bounds defined // within the link's configuration that will be used to determine when the link // should propose an update to its commitment fee rate. func (l *channelLink) randomFeeUpdateTimeout() time.Duration { lower := int64(l.cfg.MinFeeUpdateTimeout) upper := int64(l.cfg.MaxFeeUpdateTimeout) return time.Duration(prand.Int63n(upper-lower) + lower) } // handleDownstreamPkt processes an HTLC packet sent from the downstream HTLC // Switch. Possible messages sent by the switch include requests to forward new // HTLCs, timeout previously cleared HTLCs, and finally to settle currently // cleared HTLCs with the upstream peer. // // TODO(roasbeef): add sync ntfn to ensure switch always has consistent view? func (l *channelLink) handleDownstreamPkt(pkt *htlcPacket) { var isSettle bool switch htlc := pkt.htlc.(type) { case *lnwire.UpdateAddHTLC: // If hodl.AddOutgoing mode is active, we exit early to simulate // arbitrary delays between the switch adding an ADD to the // mailbox, and the HTLC being added to the commitment state. if l.cfg.HodlMask.Active(hodl.AddOutgoing) { l.log.Warnf(hodl.AddOutgoing.Warning()) l.mailBox.AckPacket(pkt.inKey()) return } // A new payment has been initiated via the downstream channel, // so we add the new HTLC to our local log, then update the // commitment chains. htlc.ChanID = l.ChanID() openCircuitRef := pkt.inKey() index, err := l.channel.AddHTLC(htlc, &openCircuitRef) if err != nil { // The HTLC was unable to be added to the state machine, // as a result, we'll signal the switch to cancel the // pending payment. l.log.Warnf("Unable to handle downstream add HTLC: %v", err) // Remove this packet from the link's mailbox, this // prevents it from being reprocessed if the link // restarts and resets it mailbox. If this response // doesn't make it back to the originating link, it will // be rejected upon attempting to reforward the Add to // the switch, since the circuit was never fully opened, // and the forwarding package shows it as // unacknowledged. l.mailBox.FailAdd(pkt) return } l.log.Tracef("received downstream htlc: payment_hash=%x, "+ "local_log_index=%v, pend_updates=%v", htlc.PaymentHash[:], index, l.channel.PendingLocalUpdateCount()) pkt.outgoingChanID = l.ShortChanID() pkt.outgoingHTLCID = index htlc.ID = index l.log.Debugf("queueing keystone of ADD open circuit: %s->%s", pkt.inKey(), pkt.outKey()) l.openedCircuits = append(l.openedCircuits, pkt.inKey()) l.keystoneBatch = append(l.keystoneBatch, pkt.keystone()) l.cfg.Peer.SendMessage(false, htlc) // Send a forward event notification to htlcNotifier. l.cfg.HtlcNotifier.NotifyForwardingEvent( newHtlcKey(pkt), HtlcInfo{ IncomingTimeLock: pkt.incomingTimeout, IncomingAmt: pkt.incomingAmount, OutgoingTimeLock: htlc.Expiry, OutgoingAmt: htlc.Amount, }, getEventType(pkt), ) case *lnwire.UpdateFulfillHTLC: // If hodl.SettleOutgoing mode is active, we exit early to // simulate arbitrary delays between the switch adding the // SETTLE to the mailbox, and the HTLC being added to the // commitment state. if l.cfg.HodlMask.Active(hodl.SettleOutgoing) { l.log.Warnf(hodl.SettleOutgoing.Warning()) l.mailBox.AckPacket(pkt.inKey()) return } // An HTLC we forward to the switch has just settled somewhere // upstream. Therefore we settle the HTLC within the our local // state machine. inKey := pkt.inKey() err := l.channel.SettleHTLC( htlc.PaymentPreimage, pkt.incomingHTLCID, pkt.sourceRef, pkt.destRef, &inKey, ) if err != nil { l.log.Errorf("unable to settle incoming HTLC for "+ "circuit-key=%v: %v", inKey, err) // If the HTLC index for Settle response was not known // to our commitment state, it has already been // cleaned up by a prior response. We'll thus try to // clean up any lingering state to ensure we don't // continue reforwarding. if _, ok := err.(lnwallet.ErrUnknownHtlcIndex); ok { l.cleanupSpuriousResponse(pkt) } // Remove the packet from the link's mailbox to ensure // it doesn't get replayed after a reconnection. l.mailBox.AckPacket(inKey) return } l.log.Debugf("queueing removal of SETTLE closed circuit: "+ "%s->%s", pkt.inKey(), pkt.outKey()) l.closedCircuits = append(l.closedCircuits, pkt.inKey()) // With the HTLC settled, we'll need to populate the wire // message to target the specific channel and HTLC to be // canceled. htlc.ChanID = l.ChanID() htlc.ID = pkt.incomingHTLCID // Then we send the HTLC settle message to the connected peer // so we can continue the propagation of the settle message. l.cfg.Peer.SendMessage(false, htlc) isSettle = true // Send a settle event notification to htlcNotifier. l.cfg.HtlcNotifier.NotifySettleEvent( newHtlcKey(pkt), getEventType(pkt), ) case *lnwire.UpdateFailHTLC: // If hodl.FailOutgoing mode is active, we exit early to // simulate arbitrary delays between the switch adding a FAIL to // the mailbox, and the HTLC being added to the commitment // state. if l.cfg.HodlMask.Active(hodl.FailOutgoing) { l.log.Warnf(hodl.FailOutgoing.Warning()) l.mailBox.AckPacket(pkt.inKey()) return } // An HTLC cancellation has been triggered somewhere upstream, // we'll remove then HTLC from our local state machine. inKey := pkt.inKey() err := l.channel.FailHTLC( pkt.incomingHTLCID, htlc.Reason, pkt.sourceRef, pkt.destRef, &inKey, ) if err != nil { l.log.Errorf("unable to cancel incoming HTLC for "+ "circuit-key=%v: %v", inKey, err) // If the HTLC index for Fail response was not known to // our commitment state, it has already been cleaned up // by a prior response. We'll thus try to clean up any // lingering state to ensure we don't continue // reforwarding. if _, ok := err.(lnwallet.ErrUnknownHtlcIndex); ok { l.cleanupSpuriousResponse(pkt) } // Remove the packet from the link's mailbox to ensure // it doesn't get replayed after a reconnection. l.mailBox.AckPacket(inKey) return } l.log.Debugf("queueing removal of FAIL closed circuit: %s->%s", pkt.inKey(), pkt.outKey()) l.closedCircuits = append(l.closedCircuits, pkt.inKey()) // With the HTLC removed, we'll need to populate the wire // message to target the specific channel and HTLC to be // canceled. The "Reason" field will have already been set // within the switch. htlc.ChanID = l.ChanID() htlc.ID = pkt.incomingHTLCID // We send the HTLC message to the peer which initially created // the HTLC. l.cfg.Peer.SendMessage(false, htlc) isSettle = true // If the packet does not have a link failure set, it failed // further down the route so we notify a forwarding failure. // Otherwise, we notify a link failure because it failed at our // node. if pkt.linkFailure != nil { l.cfg.HtlcNotifier.NotifyLinkFailEvent( newHtlcKey(pkt), newHtlcInfo(pkt), getEventType(pkt), pkt.linkFailure, false, ) } else { l.cfg.HtlcNotifier.NotifyForwardingFailEvent( newHtlcKey(pkt), getEventType(pkt), ) } } // If this newly added update exceeds the min batch size for adds, or // this is a settle request, then initiate an update. if l.channel.PendingLocalUpdateCount() >= uint64(l.cfg.BatchSize) || isSettle { if err := l.updateCommitTx(); err != nil { l.fail(LinkFailureError{code: ErrInternalError}, "unable to update commitment: %v", err) return } } } // cleanupSpuriousResponse attempts to ack any AddRef or SettleFailRef // associated with this packet. If successful in doing so, it will also purge // the open circuit from the circuit map and remove the packet from the link's // mailbox. func (l *channelLink) cleanupSpuriousResponse(pkt *htlcPacket) { inKey := pkt.inKey() l.log.Debugf("cleaning up spurious response for incoming "+ "circuit-key=%v", inKey) // If the htlc packet doesn't have a source reference, it is unsafe to // proceed, as skipping this ack may cause the htlc to be reforwarded. if pkt.sourceRef == nil { l.log.Errorf("uanble to cleanup response for incoming "+ "circuit-key=%v, does not contain source reference", inKey) return } // If the source reference is present, we will try to prevent this link // from resending the packet to the switch. To do so, we ack the AddRef // of the incoming HTLC belonging to this link. err := l.channel.AckAddHtlcs(*pkt.sourceRef) if err != nil { l.log.Errorf("unable to ack AddRef for incoming "+ "circuit-key=%v: %v", inKey, err) // If this operation failed, it is unsafe to attempt removal of // the destination reference or circuit, so we exit early. The // cleanup may proceed with a different packet in the future // that succeeds on this step. return } // Now that we know this link will stop retransmitting Adds to the // switch, we can begin to teardown the response reference and circuit // map. // // If the packet includes a destination reference, then a response for // this HTLC was locked into the outgoing channel. Attempt to remove // this reference, so we stop retransmitting the response internally. // Even if this fails, we will proceed in trying to delete the circuit. // When retransmitting responses, the destination references will be // cleaned up if an open circuit is not found in the circuit map. if pkt.destRef != nil { err := l.channel.AckSettleFails(*pkt.destRef) if err != nil { l.log.Errorf("unable to ack SettleFailRef "+ "for incoming circuit-key=%v: %v", inKey, err) } } l.log.Debugf("deleting circuit for incoming circuit-key=%x", inKey) // With all known references acked, we can now safely delete the circuit // from the switch's circuit map, as the state is no longer needed. err = l.cfg.Circuits.DeleteCircuits(inKey) if err != nil { l.log.Errorf("unable to delete circuit for "+ "circuit-key=%v: %v", inKey, err) } } // handleUpstreamMsg processes wire messages related to commitment state // updates from the upstream peer. The upstream peer is the peer whom we have a // direct channel with, updating our respective commitment chains. func (l *channelLink) handleUpstreamMsg(msg lnwire.Message) { switch msg := msg.(type) { case *lnwire.UpdateAddHTLC: // We just received an add request from an upstream peer, so we // add it to our state machine, then add the HTLC to our // "settle" list in the event that we know the preimage. index, err := l.channel.ReceiveHTLC(msg) if err != nil { l.fail(LinkFailureError{code: ErrInvalidUpdate}, "unable to handle upstream add HTLC: %v", err) return } l.log.Tracef("receive upstream htlc with payment hash(%x), "+ "assigning index: %v", msg.PaymentHash[:], index) case *lnwire.UpdateFulfillHTLC: pre := msg.PaymentPreimage idx := msg.ID if err := l.channel.ReceiveHTLCSettle(pre, idx); err != nil { l.fail( LinkFailureError{ code: ErrInvalidUpdate, ForceClose: true, }, "unable to handle upstream settle HTLC: %v", err, ) return } settlePacket := &htlcPacket{ outgoingChanID: l.ShortChanID(), outgoingHTLCID: idx, htlc: &lnwire.UpdateFulfillHTLC{ PaymentPreimage: pre, }, } // Add the newly discovered preimage to our growing list of // uncommitted preimage. These will be written to the witness // cache just before accepting the next commitment signature // from the remote peer. l.uncommittedPreimages = append(l.uncommittedPreimages, pre) // Pipeline this settle, send it to the switch. go l.forwardBatch(settlePacket) case *lnwire.UpdateFailMalformedHTLC: // Convert the failure type encoded within the HTLC fail // message to the proper generic lnwire error code. var failure lnwire.FailureMessage switch msg.FailureCode { case lnwire.CodeInvalidOnionVersion: failure = &lnwire.FailInvalidOnionVersion{ OnionSHA256: msg.ShaOnionBlob, } case lnwire.CodeInvalidOnionHmac: failure = &lnwire.FailInvalidOnionHmac{ OnionSHA256: msg.ShaOnionBlob, } case lnwire.CodeInvalidOnionKey: failure = &lnwire.FailInvalidOnionKey{ OnionSHA256: msg.ShaOnionBlob, } default: l.log.Warnf("unexpected failure code received in "+ "UpdateFailMailformedHTLC: %v", msg.FailureCode) // We don't just pass back the error we received from // our successor. Otherwise we might report a failure // that penalizes us more than needed. If the onion that // we forwarded was correct, the node should have been // able to send back its own failure. The node did not // send back its own failure, so we assume there was a // problem with the onion and report that back. We reuse // the invalid onion key failure because there is no // specific error for this case. failure = &lnwire.FailInvalidOnionKey{ OnionSHA256: msg.ShaOnionBlob, } } // With the error parsed, we'll convert the into it's opaque // form. var b bytes.Buffer if err := lnwire.EncodeFailure(&b, failure, 0); err != nil { l.log.Errorf("unable to encode malformed error: %v", err) return } // If remote side have been unable to parse the onion blob we // have sent to it, than we should transform the malformed HTLC // message to the usual HTLC fail message. err := l.channel.ReceiveFailHTLC(msg.ID, b.Bytes()) if err != nil { l.fail(LinkFailureError{code: ErrInvalidUpdate}, "unable to handle upstream fail HTLC: %v", err) return } case *lnwire.UpdateFailHTLC: idx := msg.ID err := l.channel.ReceiveFailHTLC(idx, msg.Reason[:]) if err != nil { l.fail(LinkFailureError{code: ErrInvalidUpdate}, "unable to handle upstream fail HTLC: %v", err) return } case *lnwire.CommitSig: // Since we may have learned new preimages for the first time, // we'll add them to our preimage cache. By doing this, we // ensure any contested contracts watched by any on-chain // arbitrators can now sweep this HTLC on-chain. We delay // committing the preimages until just before accepting the new // remote commitment, as afterwards the peer won't resend the // Settle messages on the next channel reestablishment. Doing so // allows us to more effectively batch this operation, instead // of doing a single write per preimage. err := l.cfg.PreimageCache.AddPreimages( l.uncommittedPreimages..., ) if err != nil { l.fail( LinkFailureError{code: ErrInternalError}, "unable to add preimages=%v to cache: %v", l.uncommittedPreimages, err, ) return } // Instead of truncating the slice to conserve memory // allocations, we simply set the uncommitted preimage slice to // nil so that a new one will be initialized if any more // witnesses are discovered. We do this maximum size of the // slice can occupy 15KB, and want to ensure we release that // memory back to the runtime. l.uncommittedPreimages = nil // We just received a new updates to our local commitment // chain, validate this new commitment, closing the link if // invalid. err = l.channel.ReceiveNewCommitment(msg.CommitSig, msg.HtlcSigs) if err != nil { // If we were unable to reconstruct their proposed // commitment, then we'll examine the type of error. If // it's an InvalidCommitSigError, then we'll send a // direct error. var sendData []byte switch err.(type) { case *lnwallet.InvalidCommitSigError: sendData = []byte(err.Error()) case *lnwallet.InvalidHtlcSigError: sendData = []byte(err.Error()) } l.fail( LinkFailureError{ code: ErrInvalidCommitment, ForceClose: true, SendData: sendData, }, "ChannelPoint(%v): unable to accept new "+ "commitment: %v", l.channel.ChannelPoint(), err, ) return } // As we've just accepted a new state, we'll now // immediately send the remote peer a revocation for our prior // state. nextRevocation, currentHtlcs, err := l.channel.RevokeCurrentCommitment() if err != nil { l.log.Errorf("unable to revoke commitment: %v", err) return } l.cfg.Peer.SendMessage(false, nextRevocation) // Since we just revoked our commitment, we may have a new set // of HTLC's on our commitment, so we'll send them over our // HTLC update channel so any callers can be notified. select { case l.htlcUpdates <- &contractcourt.ContractUpdate{ HtlcKey: contractcourt.LocalHtlcSet, Htlcs: currentHtlcs, }: case <-l.quit: return } // If both commitment chains are fully synced from our PoV, // then we don't need to reply with a signature as both sides // already have a commitment with the latest accepted. if !l.channel.OweCommitment(true) { return } // Otherwise, the remote party initiated the state transition, // so we'll reply with a signature to provide them with their // version of the latest commitment. if err := l.updateCommitTx(); err != nil { l.fail(LinkFailureError{code: ErrInternalError}, "unable to update commitment: %v", err) return } case *lnwire.RevokeAndAck: // We've received a revocation from the remote chain, if valid, // this moves the remote chain forward, and expands our // revocation window. fwdPkg, adds, settleFails, remoteHTLCs, err := l.channel.ReceiveRevocation( msg, ) if err != nil { // TODO(halseth): force close? l.fail(LinkFailureError{code: ErrInvalidRevocation}, "unable to accept revocation: %v", err) return } // The remote party now has a new primary commitment, so we'll // update the contract court to be aware of this new set (the // prior old remote pending). select { case l.htlcUpdates <- &contractcourt.ContractUpdate{ HtlcKey: contractcourt.RemoteHtlcSet, Htlcs: remoteHTLCs, }: case <-l.quit: return } // If we have a tower client, we'll proceed in backing up the // state that was just revoked. // TODO(halseth): support anchor types for watchtower. state := l.channel.State() if l.cfg.TowerClient != nil && state.ChanType.HasAnchors() { l.log.Warnf("Skipping tower backup for anchor " + "channel type") } else if l.cfg.TowerClient != nil && !state.ChanType.HasAnchors() { breachInfo, err := lnwallet.NewBreachRetribution( state, state.RemoteCommitment.CommitHeight-1, 0, ) if err != nil { l.fail(LinkFailureError{code: ErrInternalError}, "failed to load breach info: %v", err) return } chanType := l.channel.State().ChanType chanID := l.ChanID() err = l.cfg.TowerClient.BackupState( &chanID, breachInfo, chanType.IsTweakless(), ) if err != nil { l.fail(LinkFailureError{code: ErrInternalError}, "unable to queue breach backup: %v", err) return } } l.processRemoteSettleFails(fwdPkg, settleFails) l.processRemoteAdds(fwdPkg, adds) // If the link failed during processing the adds, we must // return to ensure we won't attempted to update the state // further. if l.failed { return } // The revocation window opened up. If there are pending local // updates, try to update the commit tx. Pending updates could // already have been present because of a previously failed // update to the commit tx or freshly added in by // processRemoteAdds. Also in case there are no local updates, // but there are still remote updates that are not in the remote // commit tx yet, send out an update. if l.channel.OweCommitment(true) { if err := l.updateCommitTx(); err != nil { l.fail(LinkFailureError{code: ErrInternalError}, "unable to update commitment: %v", err) return } } case *lnwire.UpdateFee: // We received fee update from peer. If we are the initiator we // will fail the channel, if not we will apply the update. fee := chainfee.SatPerKWeight(msg.FeePerKw) if err := l.channel.ReceiveUpdateFee(fee); err != nil { l.fail(LinkFailureError{code: ErrInvalidUpdate}, "error receiving fee update: %v", err) return } case *lnwire.Error: // Error received from remote, MUST fail channel, but should // only print the contents of the error message if all // characters are printable ASCII. l.fail(LinkFailureError{code: ErrRemoteError}, "ChannelPoint(%v): received error from peer: %v", l.channel.ChannelPoint(), msg.Error()) default: l.log.Warnf("received unknown message of type %T", msg) } } // ackDownStreamPackets is responsible for removing htlcs from a link's mailbox // for packets delivered from server, and cleaning up any circuits closed by // signing a previous commitment txn. This method ensures that the circuits are // removed from the circuit map before removing them from the link's mailbox, // otherwise it could be possible for some circuit to be missed if this link // flaps. func (l *channelLink) ackDownStreamPackets() error { // First, remove the downstream Add packets that were included in the // previous commitment signature. This will prevent the Adds from being // replayed if this link disconnects. for _, inKey := range l.openedCircuits { // In order to test the sphinx replay logic of the remote // party, unsafe replay does not acknowledge the packets from // the mailbox. We can then force a replay of any Add packets // held in memory by disconnecting and reconnecting the link. if l.cfg.UnsafeReplay { continue } l.log.Debugf("removing Add packet %s from mailbox", inKey) l.mailBox.AckPacket(inKey) } // Now, we will delete all circuits closed by the previous commitment // signature, which is the result of downstream Settle/Fail packets. We // batch them here to ensure circuits are closed atomically and for // performance. err := l.cfg.Circuits.DeleteCircuits(l.closedCircuits...) switch err { case nil: // Successful deletion. default: l.log.Errorf("unable to delete %d circuits: %v", len(l.closedCircuits), err) return err } // With the circuits removed from memory and disk, we now ack any // Settle/Fails in the mailbox to ensure they do not get redelivered // after startup. If forgive is enabled and we've reached this point, // the circuits must have been removed at some point, so it is now safe // to un-queue the corresponding Settle/Fails. for _, inKey := range l.closedCircuits { l.log.Debugf("removing Fail/Settle packet %s from mailbox", inKey) l.mailBox.AckPacket(inKey) } // Lastly, reset our buffers to be empty while keeping any acquired // growth in the backing array. l.openedCircuits = l.openedCircuits[:0] l.closedCircuits = l.closedCircuits[:0] return nil } // updateCommitTx signs, then sends an update to the remote peer adding a new // commitment to their commitment chain which includes all the latest updates // we've received+processed up to this point. func (l *channelLink) updateCommitTx() error { // Preemptively write all pending keystones to disk, just in case the // HTLCs we have in memory are included in the subsequent attempt to // sign a commitment state. err := l.cfg.Circuits.OpenCircuits(l.keystoneBatch...) if err != nil { return err } // Reset the batch, but keep the backing buffer to avoid reallocating. l.keystoneBatch = l.keystoneBatch[:0] // If hodl.Commit mode is active, we will refrain from attempting to // commit any in-memory modifications to the channel state. Exiting here // permits testing of either the switch or link's ability to trim // circuits that have been opened, but unsuccessfully committed. if l.cfg.HodlMask.Active(hodl.Commit) { l.log.Warnf(hodl.Commit.Warning()) return nil } theirCommitSig, htlcSigs, pendingHTLCs, err := l.channel.SignNextCommitment() if err == lnwallet.ErrNoWindow { l.cfg.PendingCommitTicker.Resume() l.log.Tracef("revocation window exhausted, unable to send: "+ "%v, pend_updates=%v, dangling_closes%v", l.channel.PendingLocalUpdateCount(), newLogClosure(func() string { return spew.Sdump(l.openedCircuits) }), newLogClosure(func() string { return spew.Sdump(l.closedCircuits) }), ) return nil } else if err != nil { return err } if err := l.ackDownStreamPackets(); err != nil { return err } l.cfg.PendingCommitTicker.Pause() // The remote party now has a new pending commitment, so we'll update // the contract court to be aware of this new set (the prior old remote // pending). select { case l.htlcUpdates <- &contractcourt.ContractUpdate{ HtlcKey: contractcourt.RemotePendingHtlcSet, Htlcs: pendingHTLCs, }: case <-l.quit: return ErrLinkShuttingDown } commitSig := &lnwire.CommitSig{ ChanID: l.ChanID(), CommitSig: theirCommitSig, HtlcSigs: htlcSigs, } l.cfg.Peer.SendMessage(false, commitSig) return nil } // Peer returns the representation of remote peer with which we have the // channel link opened. // // NOTE: Part of the ChannelLink interface. func (l *channelLink) Peer() lnpeer.Peer { return l.cfg.Peer } // ChannelPoint returns the channel outpoint for the channel link. // NOTE: Part of the ChannelLink interface. func (l *channelLink) ChannelPoint() *wire.OutPoint { return l.channel.ChannelPoint() } // ShortChanID returns the short channel ID for the channel link. The short // channel ID encodes the exact location in the main chain that the original // funding output can be found. // // NOTE: Part of the ChannelLink interface. func (l *channelLink) ShortChanID() lnwire.ShortChannelID { l.RLock() defer l.RUnlock() return l.shortChanID } // UpdateShortChanID updates the short channel ID for a link. This may be // required in the event that a link is created before the short chan ID for it // is known, or a re-org occurs, and the funding transaction changes location // within the chain. // // NOTE: Part of the ChannelLink interface. func (l *channelLink) UpdateShortChanID() (lnwire.ShortChannelID, error) { chanID := l.ChanID() // Refresh the channel state's short channel ID by loading it from disk. // This ensures that the channel state accurately reflects the updated // short channel ID. err := l.channel.State().RefreshShortChanID() if err != nil { l.log.Errorf("unable to refresh short_chan_id for chan_id=%v: "+ "%v", chanID, err) return hop.Source, err } sid := l.channel.ShortChanID() l.log.Infof("updating to short_chan_id=%v for chan_id=%v", sid, chanID) l.Lock() l.shortChanID = sid l.Unlock() go func() { err := l.cfg.UpdateContractSignals(&contractcourt.ContractSignals{ HtlcUpdates: l.htlcUpdates, ShortChanID: sid, }) if err != nil { l.log.Errorf("unable to update signals") } }() // Now that the short channel ID has been properly updated, we can begin // garbage collecting any forwarding packages we create. l.wg.Add(1) go l.fwdPkgGarbager() return sid, nil } // ChanID returns the channel ID for the channel link. The channel ID is a more // compact representation of a channel's full outpoint. // // NOTE: Part of the ChannelLink interface. func (l *channelLink) ChanID() lnwire.ChannelID { return lnwire.NewChanIDFromOutPoint(l.channel.ChannelPoint()) } // Bandwidth returns the total amount that can flow through the channel link at // this given instance. The value returned is expressed in millisatoshi and can // be used by callers when making forwarding decisions to determine if a link // can accept an HTLC. // // NOTE: Part of the ChannelLink interface. func (l *channelLink) Bandwidth() lnwire.MilliSatoshi { // Get the balance available on the channel for new HTLCs. This takes // the channel reserve into account so HTLCs up to this value won't // violate it. return l.channel.AvailableBalance() } // AttachMailBox updates the current mailbox used by this link, and hooks up // the mailbox's message and packet outboxes to the link's upstream and // downstream chans, respectively. func (l *channelLink) AttachMailBox(mailbox MailBox) { l.Lock() l.mailBox = mailbox l.upstream = mailbox.MessageOutBox() l.downstream = mailbox.PacketOutBox() l.Unlock() } // UpdateForwardingPolicy updates the forwarding policy for the target // ChannelLink. Once updated, the link will use the new forwarding policy to // govern if it an incoming HTLC should be forwarded or not. We assume that // fields that are zero are intentionally set to zero, so we'll use newPolicy to // update all of the link's FwrdingPolicy's values. // // NOTE: Part of the ChannelLink interface. func (l *channelLink) UpdateForwardingPolicy(newPolicy ForwardingPolicy) { l.Lock() defer l.Unlock() l.cfg.FwrdingPolicy = newPolicy } // CheckHtlcForward should return a nil error if the passed HTLC details // satisfy the current forwarding policy fo the target link. Otherwise, // a LinkError with a valid protocol failure message should be returned // in order to signal to the source of the HTLC, the policy consistency // issue. // // NOTE: Part of the ChannelLink interface. func (l *channelLink) CheckHtlcForward(payHash [32]byte, incomingHtlcAmt, amtToForward lnwire.MilliSatoshi, incomingTimeout, outgoingTimeout uint32, heightNow uint32) *LinkError { l.RLock() policy := l.cfg.FwrdingPolicy l.RUnlock() // First check whether the outgoing htlc satisfies the channel policy. err := l.canSendHtlc( policy, payHash, amtToForward, outgoingTimeout, heightNow, ) if err != nil { return err } // Next, using the amount of the incoming HTLC, we'll calculate the // expected fee this incoming HTLC must carry in order to satisfy the // constraints of the outgoing link. expectedFee := ExpectedFee(policy, amtToForward) // If the actual fee is less than our expected fee, then we'll reject // this HTLC as it didn't provide a sufficient amount of fees, or the // values have been tampered with, or the send used incorrect/dated // information to construct the forwarding information for this hop. In // any case, we'll cancel this HTLC. actualFee := incomingHtlcAmt - amtToForward if incomingHtlcAmt < amtToForward || actualFee < expectedFee { l.log.Errorf("outgoing htlc(%x) has insufficient fee: "+ "expected %v, got %v", payHash[:], int64(expectedFee), int64(actualFee)) // As part of the returned error, we'll send our latest routing // policy so the sending node obtains the most up to date data. failure := l.createFailureWithUpdate( func(upd *lnwire.ChannelUpdate) lnwire.FailureMessage { return lnwire.NewFeeInsufficient( amtToForward, *upd, ) }, ) return NewLinkError(failure) } // Finally, we'll ensure that the time-lock on the outgoing HTLC meets // the following constraint: the incoming time-lock minus our time-lock // delta should equal the outgoing time lock. Otherwise, whether the // sender messed up, or an intermediate node tampered with the HTLC. timeDelta := policy.TimeLockDelta if incomingTimeout < outgoingTimeout+timeDelta { l.log.Errorf("incoming htlc(%x) has incorrect time-lock value: "+ "expected at least %v block delta, got %v block delta", payHash[:], timeDelta, incomingTimeout-outgoingTimeout) // Grab the latest routing policy so the sending node is up to // date with our current policy. failure := l.createFailureWithUpdate( func(upd *lnwire.ChannelUpdate) lnwire.FailureMessage { return lnwire.NewIncorrectCltvExpiry( incomingTimeout, *upd, ) }, ) return NewLinkError(failure) } return nil } // CheckHtlcTransit should return a nil error if the passed HTLC details // satisfy the current channel policy. Otherwise, a LinkError with a // valid protocol failure message should be returned in order to signal // the violation. This call is intended to be used for locally initiated // payments for which there is no corresponding incoming htlc. func (l *channelLink) CheckHtlcTransit(payHash [32]byte, amt lnwire.MilliSatoshi, timeout uint32, heightNow uint32) *LinkError { l.RLock() policy := l.cfg.FwrdingPolicy l.RUnlock() return l.canSendHtlc( policy, payHash, amt, timeout, heightNow, ) } // htlcSatifiesPolicyOutgoing checks whether the given htlc parameters satisfy // the channel's amount and time lock constraints. func (l *channelLink) canSendHtlc(policy ForwardingPolicy, payHash [32]byte, amt lnwire.MilliSatoshi, timeout uint32, heightNow uint32) *LinkError { // As our first sanity check, we'll ensure that the passed HTLC isn't // too small for the next hop. If so, then we'll cancel the HTLC // directly. if amt < policy.MinHTLCOut { l.log.Errorf("outgoing htlc(%x) is too small: min_htlc=%v, "+ "htlc_value=%v", payHash[:], policy.MinHTLCOut, amt) // As part of the returned error, we'll send our latest routing // policy so the sending node obtains the most up to date data. failure := l.createFailureWithUpdate( func(upd *lnwire.ChannelUpdate) lnwire.FailureMessage { return lnwire.NewAmountBelowMinimum( amt, *upd, ) }, ) return NewLinkError(failure) } // Next, ensure that the passed HTLC isn't too large. If so, we'll // cancel the HTLC directly. if policy.MaxHTLC != 0 && amt > policy.MaxHTLC { l.log.Errorf("outgoing htlc(%x) is too large: max_htlc=%v, "+ "htlc_value=%v", payHash[:], policy.MaxHTLC, amt) // As part of the returned error, we'll send our latest routing // policy so the sending node obtains the most up-to-date data. failure := l.createFailureWithUpdate( func(upd *lnwire.ChannelUpdate) lnwire.FailureMessage { return lnwire.NewTemporaryChannelFailure(upd) }, ) return NewDetailedLinkError(failure, OutgoingFailureHTLCExceedsMax) } // We want to avoid offering an HTLC which will expire in the near // future, so we'll reject an HTLC if the outgoing expiration time is // too close to the current height. if timeout <= heightNow+l.cfg.OutgoingCltvRejectDelta { l.log.Errorf("htlc(%x) has an expiry that's too soon: "+ "outgoing_expiry=%v, best_height=%v", payHash[:], timeout, heightNow) failure := l.createFailureWithUpdate( func(upd *lnwire.ChannelUpdate) lnwire.FailureMessage { return lnwire.NewExpiryTooSoon(*upd) }, ) return NewLinkError(failure) } // Check absolute max delta. if timeout > l.cfg.MaxOutgoingCltvExpiry+heightNow { l.log.Errorf("outgoing htlc(%x) has a time lock too far in "+ "the future: got %v, but maximum is %v", payHash[:], timeout-heightNow, l.cfg.MaxOutgoingCltvExpiry) return NewLinkError(&lnwire.FailExpiryTooFar{}) } // Check to see if there is enough balance in this channel. if amt > l.Bandwidth() { failure := l.createFailureWithUpdate( func(upd *lnwire.ChannelUpdate) lnwire.FailureMessage { return lnwire.NewTemporaryChannelFailure(upd) }, ) return NewDetailedLinkError( failure, OutgoingFailureInsufficientBalance, ) } return nil } // Stats returns the statistics of channel link. // // NOTE: Part of the ChannelLink interface. func (l *channelLink) Stats() (uint64, lnwire.MilliSatoshi, lnwire.MilliSatoshi) { snapshot := l.channel.StateSnapshot() return snapshot.ChannelCommitment.CommitHeight, snapshot.TotalMSatSent, snapshot.TotalMSatReceived } // String returns the string representation of channel link. // // NOTE: Part of the ChannelLink interface. func (l *channelLink) String() string { return l.channel.ChannelPoint().String() } // HandleSwitchPacket handles the switch packets. This packets which might be // forwarded to us from another channel link in case the htlc update came from // another peer or if the update was created by user // // NOTE: Part of the ChannelLink interface. func (l *channelLink) HandleSwitchPacket(pkt *htlcPacket) error { l.log.Tracef("received switch packet inkey=%v, outkey=%v", pkt.inKey(), pkt.outKey()) return l.mailBox.AddPacket(pkt) } // HandleChannelUpdate handles the htlc requests as settle/add/fail which sent // to us from remote peer we have a channel with. // // NOTE: Part of the ChannelLink interface. func (l *channelLink) HandleChannelUpdate(message lnwire.Message) { l.mailBox.AddMessage(message) } // updateChannelFee updates the commitment fee-per-kw on this channel by // committing to an update_fee message. func (l *channelLink) updateChannelFee(feePerKw chainfee.SatPerKWeight) error { l.log.Infof("updating commit fee to %v sat/kw", feePerKw) // We skip sending the UpdateFee message if the channel is not // currently eligible to forward messages. if !l.EligibleToForward() { l.log.Debugf("skipping fee update for inactive channel") return nil } // First, we'll update the local fee on our commitment. if err := l.channel.UpdateFee(feePerKw); err != nil { return err } // We'll then attempt to send a new UpdateFee message, and also lock it // in immediately by triggering a commitment update. msg := lnwire.NewUpdateFee(l.ChanID(), uint32(feePerKw)) if err := l.cfg.Peer.SendMessage(false, msg); err != nil { return err } return l.updateCommitTx() } // processRemoteSettleFails accepts a batch of settle/fail payment descriptors // after receiving a revocation from the remote party, and reprocesses them in // the context of the provided forwarding package. Any settles or fails that // have already been acknowledged in the forwarding package will not be sent to // the switch. func (l *channelLink) processRemoteSettleFails(fwdPkg *channeldb.FwdPkg, settleFails []*lnwallet.PaymentDescriptor) { if len(settleFails) == 0 { return } l.log.Debugf("settle-fail-filter %v", fwdPkg.SettleFailFilter) var switchPackets []*htlcPacket for i, pd := range settleFails { // Skip any settles or fails that have already been // acknowledged by the incoming link that originated the // forwarded Add. if fwdPkg.SettleFailFilter.Contains(uint16(i)) { continue } // TODO(roasbeef): rework log entries to a shared // interface. switch pd.EntryType { // A settle for an HTLC we previously forwarded HTLC has been // received. So we'll forward the HTLC to the switch which will // handle propagating the settle to the prior hop. case lnwallet.Settle: // If hodl.SettleIncoming is requested, we will not // forward the SETTLE to the switch and will not signal // a free slot on the commitment transaction. if l.cfg.HodlMask.Active(hodl.SettleIncoming) { l.log.Warnf(hodl.SettleIncoming.Warning()) continue } settlePacket := &htlcPacket{ outgoingChanID: l.ShortChanID(), outgoingHTLCID: pd.ParentIndex, destRef: pd.DestRef, htlc: &lnwire.UpdateFulfillHTLC{ PaymentPreimage: pd.RPreimage, }, } // Add the packet to the batch to be forwarded, and // notify the overflow queue that a spare spot has been // freed up within the commitment state. switchPackets = append(switchPackets, settlePacket) // A failureCode message for a previously forwarded HTLC has // been received. As a result a new slot will be freed up in // our commitment state, so we'll forward this to the switch so // the backwards undo can continue. case lnwallet.Fail: // If hodl.SettleIncoming is requested, we will not // forward the FAIL to the switch and will not signal a // free slot on the commitment transaction. if l.cfg.HodlMask.Active(hodl.FailIncoming) { l.log.Warnf(hodl.FailIncoming.Warning()) continue } // Fetch the reason the HTLC was canceled so we can // continue to propagate it. This failure originated // from another node, so the linkFailure field is not // set on the packet. failPacket := &htlcPacket{ outgoingChanID: l.ShortChanID(), outgoingHTLCID: pd.ParentIndex, destRef: pd.DestRef, htlc: &lnwire.UpdateFailHTLC{ Reason: lnwire.OpaqueReason( pd.FailReason, ), }, } // If the failure message lacks an HMAC (but includes // the 4 bytes for encoding the message and padding // lengths, then this means that we received it as an // UpdateFailMalformedHTLC. As a result, we'll signal // that we need to convert this error within the switch // to an actual error, by encrypting it as if we were // the originating hop. convertedErrorSize := lnwire.FailureMessageLength + 4 if len(pd.FailReason) == convertedErrorSize { failPacket.convertedError = true } // Add the packet to the batch to be forwarded, and // notify the overflow queue that a spare spot has been // freed up within the commitment state. switchPackets = append(switchPackets, failPacket) } } // Only spawn the task forward packets we have a non-zero number. if len(switchPackets) > 0 { go l.forwardBatch(switchPackets...) } } // processRemoteAdds serially processes each of the Add payment descriptors // which have been "locked-in" by receiving a revocation from the remote party. // The forwarding package provided instructs how to process this batch, // indicating whether this is the first time these Adds are being processed, or // whether we are reprocessing as a result of a failure or restart. Adds that // have already been acknowledged in the forwarding package will be ignored. func (l *channelLink) processRemoteAdds(fwdPkg *channeldb.FwdPkg, lockedInHtlcs []*lnwallet.PaymentDescriptor) { l.log.Tracef("processing %d remote adds for height %d", len(lockedInHtlcs), fwdPkg.Height) decodeReqs := make( []hop.DecodeHopIteratorRequest, 0, len(lockedInHtlcs), ) for _, pd := range lockedInHtlcs { switch pd.EntryType { // TODO(conner): remove type switch? case lnwallet.Add: // Before adding the new htlc to the state machine, // parse the onion object in order to obtain the // routing information with DecodeHopIterator function // which process the Sphinx packet. onionReader := bytes.NewReader(pd.OnionBlob) req := hop.DecodeHopIteratorRequest{ OnionReader: onionReader, RHash: pd.RHash[:], IncomingCltv: pd.Timeout, } decodeReqs = append(decodeReqs, req) } } // Atomically decode the incoming htlcs, simultaneously checking for // replay attempts. A particular index in the returned, spare list of // channel iterators should only be used if the failure code at the // same index is lnwire.FailCodeNone. decodeResps, sphinxErr := l.cfg.DecodeHopIterators( fwdPkg.ID(), decodeReqs, ) if sphinxErr != nil { l.fail(LinkFailureError{code: ErrInternalError}, "unable to decode hop iterators: %v", sphinxErr) return } var switchPackets []*htlcPacket for i, pd := range lockedInHtlcs { idx := uint16(i) if fwdPkg.State == channeldb.FwdStateProcessed && fwdPkg.AckFilter.Contains(idx) { // If this index is already found in the ack filter, // the response to this forwarding decision has already // been committed by one of our commitment txns. ADDs // in this state are waiting for the rest of the fwding // package to get acked before being garbage collected. continue } // An incoming HTLC add has been full-locked in. As a result we // can now examine the forwarding details of the HTLC, and the // HTLC itself to decide if: we should forward it, cancel it, // or are able to settle it (and it adheres to our fee related // constraints). // Fetch the onion blob that was included within this processed // payment descriptor. var onionBlob [lnwire.OnionPacketSize]byte copy(onionBlob[:], pd.OnionBlob) // Before adding the new htlc to the state machine, parse the // onion object in order to obtain the routing information with // DecodeHopIterator function which process the Sphinx packet. chanIterator, failureCode := decodeResps[i].Result() if failureCode != lnwire.CodeNone { // If we're unable to process the onion blob than we // should send the malformed htlc error to payment // sender. l.sendMalformedHTLCError(pd.HtlcIndex, failureCode, onionBlob[:], pd.SourceRef) l.log.Errorf("unable to decode onion hop "+ "iterator: %v", failureCode) continue } // Retrieve onion obfuscator from onion blob in order to // produce initial obfuscation of the onion failureCode. obfuscator, failureCode := chanIterator.ExtractErrorEncrypter( l.cfg.ExtractErrorEncrypter, ) if failureCode != lnwire.CodeNone { // If we're unable to process the onion blob than we // should send the malformed htlc error to payment // sender. l.sendMalformedHTLCError( pd.HtlcIndex, failureCode, onionBlob[:], pd.SourceRef, ) l.log.Errorf("unable to decode onion "+ "obfuscator: %v", failureCode) continue } heightNow := l.cfg.Switch.BestHeight() pld, err := chanIterator.HopPayload() if err != nil { // If we're unable to process the onion payload, or we // received invalid onion payload failure, then we // should send an error back to the caller so the HTLC // can be canceled. var failedType uint64 if e, ok := err.(hop.ErrInvalidPayload); ok { failedType = uint64(e.Type) } // TODO: currently none of the test unit infrastructure // is setup to handle TLV payloads, so testing this // would require implementing a separate mock iterator // for TLV payloads that also supports injecting invalid // payloads. Deferring this non-trival effort till a // later date failure := lnwire.NewInvalidOnionPayload(failedType, 0) l.sendHTLCError( pd, NewLinkError(failure), obfuscator, false, ) l.log.Errorf("unable to decode forwarding "+ "instructions: %v", err) continue } fwdInfo := pld.ForwardingInfo() switch fwdInfo.NextHop { case hop.Exit: err := l.processExitHop( pd, obfuscator, fwdInfo, heightNow, pld, ) if err != nil { l.fail(LinkFailureError{code: ErrInternalError}, err.Error(), ) return } // There are additional channels left within this route. So // we'll simply do some forwarding package book-keeping. default: // If hodl.AddIncoming is requested, we will not // validate the forwarded ADD, nor will we send the // packet to the htlc switch. if l.cfg.HodlMask.Active(hodl.AddIncoming) { l.log.Warnf(hodl.AddIncoming.Warning()) continue } switch fwdPkg.State { case channeldb.FwdStateProcessed: // This add was not forwarded on the previous // processing phase, run it through our // validation pipeline to reproduce an error. // This may trigger a different error due to // expiring timelocks, but we expect that an // error will be reproduced. if !fwdPkg.FwdFilter.Contains(idx) { break } // Otherwise, it was already processed, we can // can collect it and continue. addMsg := &lnwire.UpdateAddHTLC{ Expiry: fwdInfo.OutgoingCTLV, Amount: fwdInfo.AmountToForward, PaymentHash: pd.RHash, } // Finally, we'll encode the onion packet for // the _next_ hop using the hop iterator // decoded for the current hop. buf := bytes.NewBuffer(addMsg.OnionBlob[0:0]) // We know this cannot fail, as this ADD // was marked forwarded in a previous // round of processing. chanIterator.EncodeNextHop(buf) updatePacket := &htlcPacket{ incomingChanID: l.ShortChanID(), incomingHTLCID: pd.HtlcIndex, outgoingChanID: fwdInfo.NextHop, sourceRef: pd.SourceRef, incomingAmount: pd.Amount, amount: addMsg.Amount, htlc: addMsg, obfuscator: obfuscator, incomingTimeout: pd.Timeout, outgoingTimeout: fwdInfo.OutgoingCTLV, } switchPackets = append( switchPackets, updatePacket, ) continue } // TODO(roasbeef): ensure don't accept outrageous // timeout for htlc // With all our forwarding constraints met, we'll // create the outgoing HTLC using the parameters as // specified in the forwarding info. addMsg := &lnwire.UpdateAddHTLC{ Expiry: fwdInfo.OutgoingCTLV, Amount: fwdInfo.AmountToForward, PaymentHash: pd.RHash, } // Finally, we'll encode the onion packet for the // _next_ hop using the hop iterator decoded for the // current hop. buf := bytes.NewBuffer(addMsg.OnionBlob[0:0]) err := chanIterator.EncodeNextHop(buf) if err != nil { l.log.Errorf("unable to encode the "+ "remaining route %v", err) failure := l.createFailureWithUpdate( func(upd *lnwire.ChannelUpdate) lnwire.FailureMessage { return lnwire.NewTemporaryChannelFailure( upd, ) }, ) l.sendHTLCError( pd, NewLinkError(failure), obfuscator, false, ) continue } // Now that this add has been reprocessed, only append // it to our list of packets to forward to the switch // this is the first time processing the add. If the // fwd pkg has already been processed, then we entered // the above section to recreate a previous error. If // the packet had previously been forwarded, it would // have been added to switchPackets at the top of this // section. if fwdPkg.State == channeldb.FwdStateLockedIn { updatePacket := &htlcPacket{ incomingChanID: l.ShortChanID(), incomingHTLCID: pd.HtlcIndex, outgoingChanID: fwdInfo.NextHop, sourceRef: pd.SourceRef, incomingAmount: pd.Amount, amount: addMsg.Amount, htlc: addMsg, obfuscator: obfuscator, incomingTimeout: pd.Timeout, outgoingTimeout: fwdInfo.OutgoingCTLV, } fwdPkg.FwdFilter.Set(idx) switchPackets = append(switchPackets, updatePacket) } } } // Commit the htlcs we are intending to forward if this package has not // been fully processed. if fwdPkg.State == channeldb.FwdStateLockedIn { err := l.channel.SetFwdFilter(fwdPkg.Height, fwdPkg.FwdFilter) if err != nil { l.fail(LinkFailureError{code: ErrInternalError}, "unable to set fwd filter: %v", err) return } } if len(switchPackets) == 0 { return } l.log.Debugf("forwarding %d packets to switch", len(switchPackets)) // NOTE: This call is made synchronous so that we ensure all circuits // are committed in the exact order that they are processed in the link. // Failing to do this could cause reorderings/gaps in the range of // opened circuits, which violates assumptions made by the circuit // trimming. l.forwardBatch(switchPackets...) } // processExitHop handles an htlc for which this link is the exit hop. It // returns a boolean indicating whether the commitment tx needs an update. func (l *channelLink) processExitHop(pd *lnwallet.PaymentDescriptor, obfuscator hop.ErrorEncrypter, fwdInfo hop.ForwardingInfo, heightNow uint32, payload invoices.Payload) error { // If hodl.ExitSettle is requested, we will not validate the final hop's // ADD, nor will we settle the corresponding invoice or respond with the // preimage. if l.cfg.HodlMask.Active(hodl.ExitSettle) { l.log.Warnf(hodl.ExitSettle.Warning()) return nil } // As we're the exit hop, we'll double check the hop-payload included in // the HTLC to ensure that it was crafted correctly by the sender and // matches the HTLC we were extended. if pd.Amount != fwdInfo.AmountToForward { l.log.Errorf("onion payload of incoming htlc(%x) has incorrect "+ "value: expected %v, got %v", pd.RHash, pd.Amount, fwdInfo.AmountToForward) failure := NewLinkError( lnwire.NewFinalIncorrectHtlcAmount(pd.Amount), ) l.sendHTLCError(pd, failure, obfuscator, true) return nil } // We'll also ensure that our time-lock value has been computed // correctly. if pd.Timeout != fwdInfo.OutgoingCTLV { l.log.Errorf("onion payload of incoming htlc(%x) has incorrect "+ "time-lock: expected %v, got %v", pd.RHash[:], pd.Timeout, fwdInfo.OutgoingCTLV) failure := NewLinkError( lnwire.NewFinalIncorrectCltvExpiry(pd.Timeout), ) l.sendHTLCError(pd, failure, obfuscator, true) return nil } // Notify the invoiceRegistry of the exit hop htlc. If we crash right // after this, this code will be re-executed after restart. We will // receive back a resolution event. invoiceHash := lntypes.Hash(pd.RHash) circuitKey := channeldb.CircuitKey{ ChanID: l.ShortChanID(), HtlcID: pd.HtlcIndex, } event, err := l.cfg.Registry.NotifyExitHopHtlc( invoiceHash, pd.Amount, pd.Timeout, int32(heightNow), circuitKey, l.hodlQueue.ChanIn(), payload, ) if err != nil { return err } // Create a hodlHtlc struct and decide either resolved now or later. htlc := hodlHtlc{ pd: pd, obfuscator: obfuscator, } // If the event is nil, the invoice is being held, so we save payment // descriptor for future reference. if event == nil { l.hodlMap[circuitKey] = htlc return nil } // Process the received resolution. return l.processHtlcResolution(event, htlc) } // settleHTLC settles the HTLC on the channel. func (l *channelLink) settleHTLC(preimage lntypes.Preimage, pd *lnwallet.PaymentDescriptor) error { hash := preimage.Hash() l.log.Infof("settling htlc %v as exit hop", hash) err := l.channel.SettleHTLC( preimage, pd.HtlcIndex, pd.SourceRef, nil, nil, ) if err != nil { return fmt.Errorf("unable to settle htlc: %v", err) } // If the link is in hodl.BogusSettle mode, replace the preimage with a // fake one before sending it to the peer. if l.cfg.HodlMask.Active(hodl.BogusSettle) { l.log.Warnf(hodl.BogusSettle.Warning()) preimage = [32]byte{} copy(preimage[:], bytes.Repeat([]byte{2}, 32)) } // HTLC was successfully settled locally send notification about it // remote peer. l.cfg.Peer.SendMessage(false, &lnwire.UpdateFulfillHTLC{ ChanID: l.ChanID(), ID: pd.HtlcIndex, PaymentPreimage: preimage, }) // Once we have successfully settled the htlc, notify a settle event. l.cfg.HtlcNotifier.NotifySettleEvent( HtlcKey{ IncomingCircuit: channeldb.CircuitKey{ ChanID: l.ShortChanID(), HtlcID: pd.HtlcIndex, }, }, HtlcEventTypeReceive, ) return nil } // forwardBatch forwards the given htlcPackets to the switch, and waits on the // err chan for the individual responses. This method is intended to be spawned // as a goroutine so the responses can be handled in the background. func (l *channelLink) forwardBatch(packets ...*htlcPacket) { // Don't forward packets for which we already have a response in our // mailbox. This could happen if a packet fails and is buffered in the // mailbox, and the incoming link flaps. var filteredPkts = make([]*htlcPacket, 0, len(packets)) for _, pkt := range packets { if l.mailBox.HasPacket(pkt.inKey()) { continue } filteredPkts = append(filteredPkts, pkt) } errChan := l.cfg.ForwardPackets(l.quit, filteredPkts...) go handleBatchFwdErrs(errChan, l.log) } // sendHTLCError functions cancels HTLC and send cancel message back to the // peer from which HTLC was received. func (l *channelLink) sendHTLCError(pd *lnwallet.PaymentDescriptor, failure *LinkError, e hop.ErrorEncrypter, isReceive bool) { reason, err := e.EncryptFirstHop(failure.WireMessage()) if err != nil { l.log.Errorf("unable to obfuscate error: %v", err) return } err = l.channel.FailHTLC(pd.HtlcIndex, reason, pd.SourceRef, nil, nil) if err != nil { l.log.Errorf("unable cancel htlc: %v", err) return } l.cfg.Peer.SendMessage(false, &lnwire.UpdateFailHTLC{ ChanID: l.ChanID(), ID: pd.HtlcIndex, Reason: reason, }) // Notify a link failure on our incoming link. Outgoing htlc information // is not available at this point, because we have not decrypted the // onion, so it is excluded. var eventType HtlcEventType if isReceive { eventType = HtlcEventTypeReceive } else { eventType = HtlcEventTypeForward } l.cfg.HtlcNotifier.NotifyLinkFailEvent( HtlcKey{ IncomingCircuit: channeldb.CircuitKey{ ChanID: l.ShortChanID(), HtlcID: pd.HtlcIndex, }, }, HtlcInfo{ IncomingTimeLock: pd.Timeout, IncomingAmt: pd.Amount, }, eventType, failure, true, ) } // sendMalformedHTLCError helper function which sends the malformed HTLC update // to the payment sender. func (l *channelLink) sendMalformedHTLCError(htlcIndex uint64, code lnwire.FailCode, onionBlob []byte, sourceRef *channeldb.AddRef) { shaOnionBlob := sha256.Sum256(onionBlob) err := l.channel.MalformedFailHTLC(htlcIndex, code, shaOnionBlob, sourceRef) if err != nil { l.log.Errorf("unable cancel htlc: %v", err) return } l.cfg.Peer.SendMessage(false, &lnwire.UpdateFailMalformedHTLC{ ChanID: l.ChanID(), ID: htlcIndex, ShaOnionBlob: shaOnionBlob, FailureCode: code, }) } // fail is a function which is used to encapsulate the action necessary for // properly failing the link. It takes a LinkFailureError, which will be passed // to the OnChannelFailure closure, in order for it to determine if we should // force close the channel, and if we should send an error message to the // remote peer. func (l *channelLink) fail(linkErr LinkFailureError, format string, a ...interface{}) { reason := errors.Errorf(format, a...) // Return if we have already notified about a failure. if l.failed { l.log.Warnf("ignoring link failure (%v), as link already "+ "failed", reason) return } l.log.Errorf("failing link: %s with error: %v", reason, linkErr) // Set failed, such that we won't process any more updates, and notify // the peer about the failure. l.failed = true l.cfg.OnChannelFailure(l.ChanID(), l.ShortChanID(), linkErr) }