lnd.xprv/lnwallet/channel.go

5377 lines
186 KiB
Go

package lnwallet
import (
"bytes"
"container/list"
"crypto/sha256"
"fmt"
"runtime"
"sort"
"sync"
"sync/atomic"
"github.com/davecgh/go-spew/spew"
"github.com/lightningnetwork/lnd/chainntnfs"
"github.com/lightningnetwork/lnd/channeldb"
"github.com/lightningnetwork/lnd/lnwire"
"github.com/roasbeef/btcd/blockchain"
"github.com/roasbeef/btcd/chaincfg/chainhash"
"github.com/roasbeef/btcd/btcec"
"github.com/roasbeef/btcd/txscript"
"github.com/roasbeef/btcd/wire"
"github.com/roasbeef/btcutil"
"github.com/roasbeef/btcutil/txsort"
)
var zeroHash chainhash.Hash
var (
// ErrChanClosing is returned when a caller attempts to close a channel
// that has already been closed or is in the process of being closed.
ErrChanClosing = fmt.Errorf("channel is being closed, operation disallowed")
// ErrNoWindow is returned when revocation window is exhausted.
ErrNoWindow = fmt.Errorf("unable to sign new commitment, the current" +
" revocation window is exhausted")
// ErrMaxWeightCost is returned when the cost/weight (see segwit)
// exceeds the widely used maximum allowed policy weight limit. In this
// case the commitment transaction can't be propagated through the
// network.
ErrMaxWeightCost = fmt.Errorf("commitment transaction exceed max " +
"available cost")
// ErrMaxHTLCNumber is returned when a proposed HTLC would exceed the
// maximum number of allowed HTLC's if committed in a state transition
ErrMaxHTLCNumber = fmt.Errorf("commitment transaction exceed max " +
"htlc number")
// ErrInsufficientBalance is returned when a proposed HTLC would
// exceed the available balance.
ErrInsufficientBalance = fmt.Errorf("insufficient local balance")
// ErrCannotSyncCommitChains is returned if, upon receiving a ChanSync
// message, the state machine deems that is unable to properly
// synchronize states with the remote peer.
ErrCannotSyncCommitChains = fmt.Errorf("unable to sync commit chains")
// ErrInvalidLastCommitSecret is returned in the case that the
// commitment secret sent by the remote party in their
// ChannelReestablish message doesn't match the last secret we sent.
ErrInvalidLastCommitSecret = fmt.Errorf("commit secret is incorrect")
// ErrCommitSyncDataLoss is returned in the case that we receive a
// valid commit secret within the ChannelReestablish message from the
// remote node AND they advertise a RemoteCommitTailHeight higher than
// our current known height.
ErrCommitSyncDataLoss = fmt.Errorf("possible commitment state data " +
"loss")
)
// channelState is an enum like type which represents the current state of a
// particular channel.
// TODO(roasbeef): actually update state
type channelState uint8
const (
// channelPending indicates this channel is still going through the
// funding workflow, and isn't yet open.
channelPending channelState = iota
// channelOpen represents an open, active channel capable of
// sending/receiving HTLCs.
channelOpen
// channelClosing represents a channel which is in the process of being
// closed.
channelClosing
// channelClosed represents a channel which has been fully closed. Note
// that before a channel can be closed, ALL pending HTLCs must be
// settled/removed.
channelClosed
// channelDispute indicates that an un-cooperative closure has been
// detected within the channel.
channelDispute
// channelPendingPayment indicates that there a currently outstanding
// HTLCs within the channel.
channelPendingPayment
)
// PaymentHash represents the sha256 of a random value. This hash is used to
// uniquely track incoming/outgoing payments within this channel, as well as
// payments requested by the wallet/daemon.
type PaymentHash [32]byte
// updateType is the exact type of an entry within the shared HTLC log.
type updateType uint8
const (
// Add is an update type that adds a new HTLC entry into the log.
// Either side can add a new pending HTLC by adding a new Add entry
// into their update log.
Add updateType = iota
// Fail is an update type which removes a prior HTLC entry from the
// log. Adding a Fail entry to ones log will modify the _remote_
// parties update log once a new commitment view has been evaluated
// which contains the Fail entry.
Fail
// MalformedFail is an update type which removes a prior HTLC entry
// from the log. Adding a MalformedFail entry to ones log will modify
// the _remote_ parties update log once a new commitment view has been
// evaluated which contains the MalformedFail entry. The difference
// from Fail type lie in
// the different data we have to store.
MalformedFail
// Settle is an update type which settles a prior HTLC crediting the
// balance of the receiving node. Adding a Settle entry to a log will
// result in the settle entry being removed on the log as well as the
// original add entry from the remote party's log after the next state
// transition.
Settle
)
// String returns a human readable string that uniquely identifies the target
// update type.
func (u updateType) String() string {
switch u {
case Add:
return "Add"
case Fail:
return "Fail"
case MalformedFail:
return "MalformedFail"
case Settle:
return "Settle"
default:
return "<unknown type>"
}
}
// PaymentDescriptor represents a commitment state update which either adds,
// settles, or removes an HTLC. PaymentDescriptors encapsulate all necessary
// metadata w.r.t to an HTLC, and additional data pairing a settle message to
// the original added HTLC.
//
// TODO(roasbeef): LogEntry interface??
// * need to separate attrs for cancel/add/settle
type PaymentDescriptor struct {
// RHash is the payment hash for this HTLC. The HTLC can be settled iff
// the preimage to this hash is presented.
RHash PaymentHash
// RPreimage is the preimage that settles the HTLC pointed to within the
// log by the ParentIndex.
RPreimage PaymentHash
// Timeout is the absolute timeout in blocks, after which this HTLC
// expires.
Timeout uint32
// Amount is the HTLC amount in milli-satoshis.
Amount lnwire.MilliSatoshi
// LogIndex is the log entry number that his HTLC update has within the
// log. Depending on if IsIncoming is true, this is either an entry the
// remote party added, or one that we added locally.
LogIndex uint64
// HtlcIndex is the index within the main update log for this HTLC.
// Entries within the log of type Add will have this field populated,
// as other entries will point to the entry via this counter.
//
// NOTE: This field will only be populate if EntryType is Add.
HtlcIndex uint64
// ParentIndex is the HTLC index of the entry that this update settles or
// times out.
//
// NOTE: This field will only be populate if EntryType is Fail or
// Settle.
ParentIndex uint64
// localOutputIndex is the output index of this HTLc output in the
// commitment transaction of the local node.
//
// NOTE: If the output is dust from the PoV of the local commitment
// chain, then this value will be -1.
localOutputIndex int32
// remoteOutputIndex is the output index of this HTLC output in the
// commitment transaction of the remote node.
//
// NOTE: If the output is dust from the PoV of the remote commitment
// chain, then this value will be -1.
remoteOutputIndex int32
// sig is the signature for the second-level HTLC transaction that
// spends the version of this HTLC on the commitment transaction of the
// local node. This signature is generated by the remote node and
// stored by the local node in the case that local node needs to
// broadcast their commitment transaction.
sig *btcec.Signature
// addCommitHeight[Remote|Local] encodes the height of the commitment
// which included this HTLC on either the remote or local commitment
// chain. This value is used to determine when an HTLC is fully
// "locked-in".
addCommitHeightRemote uint64
addCommitHeightLocal uint64
// removeCommitHeight[Remote|Local] encodes the height of the
// commitment which removed the parent pointer of this
// PaymentDescriptor either due to a timeout or a settle. Once both
// these heights are below the tail of both chains, the log entries can
// safely be removed.
removeCommitHeightRemote uint64
removeCommitHeightLocal uint64
// OnionBlob is an opaque blob which is used to complete multi-hop
// routing.
//
// NOTE: Populated only on add payment descriptor entry types.
OnionBlob []byte
// ShaOnionBlob is a sha of the onion blob.
//
// NOTE: Populated only in payment descriptor with MalfromedFail type.
ShaOnionBlob [sha256.Size]byte
// FailReason stores the reason why a particular payment was cancelled.
//
// NOTE: Populate only in fail payment descriptor entry types.
FailReason []byte
// FailCode stores the code why a particular payment was cancelled.
//
// NOTE: Populated only in payment descriptor with MalfromedFail type.
FailCode lnwire.FailCode
// [our|their|]PkScript are the raw public key scripts that encodes the
// redemption rules for this particular HTLC. These fields will only be
// populated iff the EntryType of this PaymentDescriptor is Add.
// ourPkScript is the ourPkScript from the context of our local
// commitment chain. theirPkScript is the latest pkScript from the
// context of the remote commitment chain.
//
// NOTE: These values may change within the logs themselves, however,
// they'll stay consistent within the commitment chain entries
// themselves.
ourPkScript []byte
ourWitnessScript []byte
theirPkScript []byte
theirWitnessScript []byte
// EntryType denotes the exact type of the PaymentDescriptor. In the
// case of a Timeout, or Settle type, then the Parent field will point
// into the log to the HTLC being modified.
EntryType updateType
// isForwarded denotes if an incoming HTLC has been forwarded to any
// possible upstream peers in the route.
isForwarded bool
}
// commitment represents a commitment to a new state within an active channel.
// New commitments can be initiated by either side. Commitments are ordered
// into a commitment chain, with one existing for both parties. Each side can
// independently extend the other side's commitment chain, up to a certain
// "revocation window", which once reached, disallows new commitments until
// the local nodes receives the revocation for the remote node's chain tail.
type commitment struct {
// height represents the commitment height of this commitment, or the
// update number of this commitment.
height uint64
// isOurs indicates whether this is the local or remote node's version
// of the commitment.
isOurs bool
// [our|their]MessageIndex are indexes into the HTLC log, up to which
// this commitment transaction includes. These indexes allow both sides
// to independently, and concurrent send create new commitments. Each
// new commitment sent to the remote party includes an index in the
// shared log which details which of their updates we're including in
// this new commitment.
ourMessageIndex uint64
theirMessageIndex uint64
// [our|their]HtlcIndex are the current running counters for the HTLC's
// offered by either party. This value is incremented each time a party
// offers a new HTLC. The log update methods that consume HTLC's will
// reference these counters, rather than the running cumulative message
// counters.
ourHtlcIndex uint64
theirHtlcIndex uint64
// txn is the commitment transaction generated by including any HTLC
// updates whose index are below the two indexes listed above. If this
// commitment is being added to the remote chain, then this txn is
// their version of the commitment transactions. If the local commit
// chain is being modified, the opposite is true.
txn *wire.MsgTx
// sig is a signature for the above commitment transaction.
sig []byte
// [our|their]Balance represents the settled balances at this point
// within the commitment chain. This balance is computed by properly
// evaluating all the add/remove/settle log entries before the listed
// indexes.
ourBalance lnwire.MilliSatoshi
theirBalance lnwire.MilliSatoshi
// fee is the amount that will be paid as fees for this commitment
// transaction. The fee is recorded here so that it can be added back
// and recalculated for each new update to the channel state.
fee btcutil.Amount
// feePerKw is the fee per kw used to calculate this commitment
// transaction's fee.
feePerKw btcutil.Amount
// dustLimit is the limit on the commitment transaction such that no
// output values should be below this amount.
dustLimit btcutil.Amount
// outgoingHTLCs is a slice of all the outgoing HTLC's (from our PoV)
// on this commitment transaction.
outgoingHTLCs []PaymentDescriptor
// incomingHTLCs is a slice of all the incoming HTLC's (from our PoV)
// on this commitment transaction.
incomingHTLCs []PaymentDescriptor
// [outgoing|incoming]HTLCIndex is an index that maps an output index
// on the commitment transaction to the payment descriptor that
// represents the HTLC output.
//
// NOTE: that these fields are only populated if this commitment state
// belongs to the local node. These maps are used when validating any
// HTLC signatures which are part of the local commitment state. We use
// this map in order to locate the details needed to validate an HTLC
// signature while iterating of the outputs in the local commitment
// view.
outgoingHTLCIndex map[int32]*PaymentDescriptor
incomingHTLCIndex map[int32]*PaymentDescriptor
}
// locateOutputIndex is a small helper function to locate the output index of a
// particular HTLC within the current commitment transaction. The duplicate map
// massed in is to be retained for each output within the commitment
// transition. This ensures that we don't assign multiple HTLC's to the same
// index within the commitment transaction.
func locateOutputIndex(p *PaymentDescriptor, tx *wire.MsgTx, ourCommit bool,
dups map[PaymentHash][]int32) (int32, error) {
// Checks to see if element (e) exists in slice (s).
contains := func(s []int32, e int32) bool {
for _, a := range s {
if a == e {
return true
}
}
return false
}
// If this their commitment transaction, we'll be trying to locate
// their pkScripts, otherwise we'll be looking for ours. This is
// required as the commitment states are asymmetric in order to ascribe
// blame in the case of a contract breach.
pkScript := p.theirPkScript
if ourCommit {
pkScript = p.ourPkScript
}
for i, txOut := range tx.TxOut {
if bytes.Equal(txOut.PkScript, pkScript) &&
txOut.Value == int64(p.Amount.ToSatoshis()) {
// If this payment hash and index has already been
// found, then we'll continue in order to avoid any
// duplicate indexes.
if contains(dups[p.RHash], int32(i)) {
continue
}
idx := int32(i)
dups[p.RHash] = append(dups[p.RHash], idx)
return idx, nil
}
}
return 0, fmt.Errorf("unable to find htlc: script=%x, value=%v",
pkScript, p.Amount)
}
// populateHtlcIndexes modifies the set of HTLC's locked-into the target view
// to have full indexing information populated. This information is required as
// we need to keep track of the indexes of each HTLC in order to properly write
// the current state to disk, and also to locate the PaymentDescriptor
// corresponding to HTLC outputs in the commitment transaction.
func (c *commitment) populateHtlcIndexes() error {
// First, we'll set up some state to allow us to locate the output
// index of the all the HTLC's within the commitment transaction. We
// must keep this index so we can validate the HTLC signatures sent to
// us.
dups := make(map[PaymentHash][]int32)
c.outgoingHTLCIndex = make(map[int32]*PaymentDescriptor)
c.incomingHTLCIndex = make(map[int32]*PaymentDescriptor)
// populateIndex is a helper function that populates the necessary
// indexes within the commitment view for a particular HTLC.
populateIndex := func(htlc *PaymentDescriptor, incoming bool) error {
isDust := htlcIsDust(incoming, c.isOurs, c.feePerKw,
htlc.Amount.ToSatoshis(), c.dustLimit)
var err error
switch {
// If this is our commitment transaction, and this is a dust
// output then we mark it as such using a -1 index.
case c.isOurs && isDust:
htlc.localOutputIndex = -1
// If this is the commitment transaction of the remote party,
// and this is a dust output then we mark it as such using a -1
// index.
case !c.isOurs && isDust:
htlc.remoteOutputIndex = -1
// If this is our commitment transaction, then we'll need to
// locate the output and the index so we can verify an HTLC
// signatures.
case c.isOurs:
htlc.localOutputIndex, err = locateOutputIndex(
htlc, c.txn, c.isOurs, dups,
)
if err != nil {
return err
}
// As this is our commitment transactions, we need to
// keep track of the locations of each output on the
// transaction so we can verify any HTLC signatures
// sent to us after we construct the HTLC view.
if incoming {
c.incomingHTLCIndex[htlc.localOutputIndex] = htlc
} else {
c.outgoingHTLCIndex[htlc.localOutputIndex] = htlc
}
// Otherwise, this is there remote party's commitment
// transaction and we only need to populate the remote output
// index within the HTLC index.
case !c.isOurs:
htlc.remoteOutputIndex, err = locateOutputIndex(
htlc, c.txn, c.isOurs, dups,
)
if err != nil {
return err
}
default:
return fmt.Errorf("invalid commitment configuration")
}
return nil
}
// Finally, we'll need to locate the index within the commitment
// transaction of all the HTLC outputs. This index will be required
// later when we write the commitment state to disk, and also when
// generating signatures for each of the HTLC transactions.
for i := 0; i < len(c.outgoingHTLCs); i++ {
htlc := &c.outgoingHTLCs[i]
if err := populateIndex(htlc, false); err != nil {
return nil
}
}
for i := 0; i < len(c.incomingHTLCs); i++ {
htlc := &c.incomingHTLCs[i]
if err := populateIndex(htlc, true); err != nil {
return nil
}
}
return nil
}
// toDiskCommit converts the target commitment into a format suitable to be
// written to disk after an accepted state transition.
func (c *commitment) toDiskCommit(ourCommit bool) *channeldb.ChannelCommitment {
numHtlcs := len(c.outgoingHTLCs) + len(c.incomingHTLCs)
commit := &channeldb.ChannelCommitment{
CommitHeight: c.height,
LocalLogIndex: c.ourMessageIndex,
LocalHtlcIndex: c.ourHtlcIndex,
RemoteLogIndex: c.theirMessageIndex,
RemoteHtlcIndex: c.theirHtlcIndex,
LocalBalance: c.ourBalance,
RemoteBalance: c.theirBalance,
CommitFee: c.fee,
FeePerKw: c.feePerKw,
CommitTx: c.txn,
CommitSig: c.sig,
Htlcs: make([]channeldb.HTLC, 0, numHtlcs),
}
for _, htlc := range c.outgoingHTLCs {
outputIndex := htlc.localOutputIndex
if !ourCommit {
outputIndex = htlc.remoteOutputIndex
}
h := channeldb.HTLC{
RHash: htlc.RHash,
Amt: htlc.Amount,
RefundTimeout: htlc.Timeout,
OutputIndex: outputIndex,
HtlcIndex: htlc.HtlcIndex,
LogIndex: htlc.LogIndex,
Incoming: false,
}
h.OnionBlob = make([]byte, len(htlc.OnionBlob))
copy(h.OnionBlob[:], htlc.OnionBlob)
if ourCommit && htlc.sig != nil {
h.Signature = htlc.sig.Serialize()
}
commit.Htlcs = append(commit.Htlcs, h)
}
for _, htlc := range c.incomingHTLCs {
outputIndex := htlc.localOutputIndex
if !ourCommit {
outputIndex = htlc.remoteOutputIndex
}
h := channeldb.HTLC{
RHash: htlc.RHash,
Amt: htlc.Amount,
RefundTimeout: htlc.Timeout,
OutputIndex: outputIndex,
HtlcIndex: htlc.HtlcIndex,
LogIndex: htlc.LogIndex,
Incoming: true,
}
h.OnionBlob = make([]byte, len(htlc.OnionBlob))
copy(h.OnionBlob[:], htlc.OnionBlob)
if ourCommit && htlc.sig != nil {
h.Signature = htlc.sig.Serialize()
}
commit.Htlcs = append(commit.Htlcs, h)
}
return commit
}
// diskHtlcToPayDesc converts an HTLC previously written to disk within a
// commitment state to the form required to manipulate in memory within the
// commitment struct and updateLog. This function is used when we need to
// restore commitment state written do disk back into memory once we need to
// restart a channel session.
func (lc *LightningChannel) diskHtlcToPayDesc(feeRate btcutil.Amount,
commitHeight uint64, isPendingCommit bool, htlc *channeldb.HTLC,
localCommitKeys, remoteCommitKeys *CommitmentKeyRing) (PaymentDescriptor, error) {
// The proper pkScripts for this PaymentDescriptor must be
// generated so we can easily locate them within the commitment
// transaction in the future.
var (
ourP2WSH, theirP2WSH []byte
ourWitnessScript, theirWitnessScript []byte
pd PaymentDescriptor
err error
)
// If the either outputs is dust from the local or remote node's
// perspective, then we don't need to generate the scripts as we only
// generate them in order to locate the outputs within the commitment
// transaction. As we'll mark dust with a special output index in the
// on-disk state snapshot.
isDustLocal := htlcIsDust(htlc.Incoming, true, feeRate,
htlc.Amt.ToSatoshis(), lc.channelState.LocalChanCfg.DustLimit)
if !isDustLocal && localCommitKeys != nil {
ourP2WSH, ourWitnessScript, err = genHtlcScript(
htlc.Incoming, true, htlc.RefundTimeout, htlc.RHash,
localCommitKeys)
if err != nil {
return pd, err
}
}
isDustRemote := htlcIsDust(htlc.Incoming, false, feeRate,
htlc.Amt.ToSatoshis(), lc.channelState.RemoteChanCfg.DustLimit)
if !isDustRemote && remoteCommitKeys != nil {
theirP2WSH, theirWitnessScript, err = genHtlcScript(
htlc.Incoming, false, htlc.RefundTimeout, htlc.RHash,
remoteCommitKeys)
if err != nil {
return pd, err
}
}
// With the scripts reconstructed (depending on if this is our commit
// vs theirs or a pending commit for the remote party), we can now
// re-create the original payment descriptor.
pd = PaymentDescriptor{
RHash: htlc.RHash,
Timeout: htlc.RefundTimeout,
Amount: htlc.Amt,
EntryType: Add,
HtlcIndex: htlc.HtlcIndex,
LogIndex: htlc.LogIndex,
OnionBlob: htlc.OnionBlob,
ourPkScript: ourP2WSH,
ourWitnessScript: ourWitnessScript,
theirPkScript: theirP2WSH,
theirWitnessScript: theirWitnessScript,
}
// If this is a pending commit, then the HTLC was only included in the
// commitment of the remote party, so we only set that commit height.
// Otherwise, we'll set the commit height for both chains as the HTLC
// was written to disk after it was fully locked in.
if isPendingCommit {
pd.addCommitHeightRemote = commitHeight
} else {
pd.addCommitHeightRemote = commitHeight
pd.addCommitHeightLocal = commitHeight
}
return pd, nil
}
// extractPayDescs will convert all HTLC's present within a disk commit state
// to a set of incoming and outgoing payment descriptors. Once reconstructed,
// these payment descriptors can be re-inserted into the in-memory updateLog
// for each side.
func (lc *LightningChannel) extractPayDescs(commitHeight uint64,
isPendingCommit bool, feeRate btcutil.Amount,
htlcs []channeldb.HTLC, localCommitKeys *CommitmentKeyRing,
remoteCommitKeys *CommitmentKeyRing) ([]PaymentDescriptor, []PaymentDescriptor, error) {
var (
incomingHtlcs []PaymentDescriptor
outgoingHtlcs []PaymentDescriptor
)
// For each included HTLC within this commitment state, we'll convert
// the disk format into our in memory PaymentDescriptor format,
// partitioning based on if we offered or received the HTLC.
for _, htlc := range htlcs {
// TODO(roasbeef): set isForwarded to false for all? need to
// persist state w.r.t to if forwarded or not, or can
// inadvertently trigger replays
payDesc, err := lc.diskHtlcToPayDesc(
feeRate, commitHeight, isPendingCommit, &htlc,
localCommitKeys, remoteCommitKeys,
)
if err != nil {
return incomingHtlcs, outgoingHtlcs, err
}
if htlc.Incoming {
incomingHtlcs = append(incomingHtlcs, payDesc)
} else {
outgoingHtlcs = append(outgoingHtlcs, payDesc)
}
}
return incomingHtlcs, outgoingHtlcs, nil
}
// diskCommitToMemCommit converts tthe on-disk commitment format to our
// in-memory commitment format which is needed in order to properly resume
// channel operations after a restart.
func (lc *LightningChannel) diskCommitToMemCommit(isLocal, isPendingCommit bool,
diskCommit *channeldb.ChannelCommitment,
localCommitPoint, remoteCommitPoint *btcec.PublicKey) (*commitment, error) {
// First, we'll need to re-derive the commitment key ring for each
// party used within this particular state. If this is a pending commit
// (we extended but weren't able to complete the commitment dance
// before shutdown), then the localCommitPoint won't be set as we
// haven't yet received a responding commitment from the remote party.
var localCommitKeys, remoteCommitKeys *CommitmentKeyRing
if localCommitPoint != nil {
localCommitKeys = deriveCommitmentKeys(localCommitPoint, true,
lc.localChanCfg, lc.remoteChanCfg)
}
if remoteCommitPoint != nil {
remoteCommitKeys = deriveCommitmentKeys(remoteCommitPoint, false,
lc.localChanCfg, lc.remoteChanCfg)
}
// With the key rings re-created, we'll now convert all the on-disk
// HTLC"s into PaymentDescriptor's so we can re-insert them into our
// update log.
incomingHtlcs, outgoingHtlcs, err := lc.extractPayDescs(
diskCommit.CommitHeight, isPendingCommit,
diskCommit.FeePerKw, diskCommit.Htlcs,
localCommitKeys, remoteCommitKeys,
)
if err != nil {
return nil, err
}
// With the necessary items generated, we'll now re-construct the
// commitment state as it was originally present in memory.
commit := &commitment{
height: diskCommit.CommitHeight,
isOurs: isLocal,
ourBalance: diskCommit.LocalBalance,
theirBalance: diskCommit.RemoteBalance,
ourMessageIndex: diskCommit.LocalLogIndex,
ourHtlcIndex: diskCommit.LocalHtlcIndex,
theirMessageIndex: diskCommit.RemoteLogIndex,
theirHtlcIndex: diskCommit.RemoteHtlcIndex,
txn: diskCommit.CommitTx,
sig: diskCommit.CommitSig,
fee: diskCommit.CommitFee,
feePerKw: diskCommit.FeePerKw,
incomingHTLCs: incomingHtlcs,
outgoingHTLCs: outgoingHtlcs,
}
if isLocal {
commit.dustLimit = lc.channelState.LocalChanCfg.DustLimit
} else {
commit.dustLimit = lc.channelState.RemoteChanCfg.DustLimit
}
// Finally, we'll re-populate the HTLC index for this state so we can
// properly locate each HTLC within the commitment transaction.
if err := commit.populateHtlcIndexes(); err != nil {
return nil, err
}
return commit, nil
}
// CommitmentKeyRing holds all derived keys needed to construct commitment and
// HTLC transactions. The keys are derived differently depending whether the
// commitment transaction is ours or the remote peer's. Private keys associated
// with each key may belong to the commitment owner or the "other party" which
// is referred to in the field comments, regardless of which is local and which
// is remote.
type CommitmentKeyRing struct {
// commitPoint is the "per commitment point" used to derive the tweak
// for each base point.
CommitPoint *btcec.PublicKey
// LocalCommitKeyTweak is the tweak used to derive the local public key
// from the local payment base point or the local private key from the
// base point secret. This may be included in a SignDescriptor to
// generate signatures for the local payment key.
LocalCommitKeyTweak []byte
// TODO(roasbeef): need delay tweak as well?
// LocalHtlcKeyTweak is the teak used to derive the local HTLC key from
// the local HTLC base point point. This value is needed in order to
// derive the final key used within the HTLC scripts in the commitment
// transaction.
LocalHtlcKeyTweak []byte
// LocalHtlcKey is the key that will be used in the "to self" clause of
// any HTLC scripts within the commitment transaction for this key ring
// set.
LocalHtlcKey *btcec.PublicKey
// RemoteHtlcKey is the key that will be used in clauses within the
// HTLC script that send money to the remote party.
RemoteHtlcKey *btcec.PublicKey
// DelayKey is the commitment transaction owner's key which is included
// in HTLC success and timeout transaction scripts.
DelayKey *btcec.PublicKey
// NoDelayKey is the other party's payment key in the commitment tx.
// This is the key used to generate the unencumbered output within the
// commitment transaction.
NoDelayKey *btcec.PublicKey
// RevocationKey is the key that can be used by the other party to
// redeem outputs from a revoked commitment transaction if it were to
// be published.
RevocationKey *btcec.PublicKey
}
// deriveCommitmentKey generates a new commitment key set using the base points
// and commitment point. The keys are derived differently depending whether the
// commitment transaction is ours or the remote peer's.
func deriveCommitmentKeys(commitPoint *btcec.PublicKey, isOurCommit bool,
localChanCfg, remoteChanCfg *channeldb.ChannelConfig) *CommitmentKeyRing {
// First, we'll derive all the keys that don't depend on the context of
// whose commitment transaction this is.
keyRing := &CommitmentKeyRing{
CommitPoint: commitPoint,
LocalCommitKeyTweak: SingleTweakBytes(commitPoint,
localChanCfg.PaymentBasePoint),
LocalHtlcKeyTweak: SingleTweakBytes(commitPoint,
localChanCfg.HtlcBasePoint),
LocalHtlcKey: TweakPubKey(localChanCfg.HtlcBasePoint,
commitPoint),
RemoteHtlcKey: TweakPubKey(remoteChanCfg.HtlcBasePoint,
commitPoint),
}
// We'll now compute the delay, no delay, and revocation key based on
// the current commitment point. All keys are tweaked each state in
// order to ensure the keys from each state are unlinkable. To create
// the revocation key, we take the opposite party's revocation base
// point and combine that with the current commitment point.
var (
delayBasePoint *btcec.PublicKey
noDelayBasePoint *btcec.PublicKey
revocationBasePoint *btcec.PublicKey
)
if isOurCommit {
delayBasePoint = localChanCfg.DelayBasePoint
noDelayBasePoint = remoteChanCfg.PaymentBasePoint
revocationBasePoint = remoteChanCfg.RevocationBasePoint
} else {
delayBasePoint = remoteChanCfg.DelayBasePoint
noDelayBasePoint = localChanCfg.PaymentBasePoint
revocationBasePoint = localChanCfg.RevocationBasePoint
}
// With the base points assigned, we can now derive the actual keys
// using the base point, and the current commitment tweak.
keyRing.DelayKey = TweakPubKey(delayBasePoint, commitPoint)
keyRing.NoDelayKey = TweakPubKey(noDelayBasePoint, commitPoint)
keyRing.RevocationKey = DeriveRevocationPubkey(
revocationBasePoint, commitPoint,
)
return keyRing
}
// commitmentChain represents a chain of unrevoked commitments. The tail of the
// chain is the latest fully signed, yet unrevoked commitment. Two chains are
// tracked, one for the local node, and another for the remote node. New
// commitments we create locally extend the remote node's chain, and vice
// versa. Commitment chains are allowed to grow to a bounded length, after
// which the tail needs to be "dropped" before new commitments can be received.
// The tail is "dropped" when the owner of the chain sends a revocation for the
// previous tail.
type commitmentChain struct {
// commitments is a linked list of commitments to new states. New
// commitments are added to the end of the chain with increase height.
// Once a commitment transaction is revoked, the tail is incremented,
// freeing up the revocation window for new commitments.
commitments *list.List
// startingHeight is the starting height of this commitment chain on a
// session basis.
startingHeight uint64
}
// newCommitmentChain creates a new commitment chain from an initial height.
func newCommitmentChain(initialHeight uint64) *commitmentChain {
return &commitmentChain{
commitments: list.New(),
startingHeight: initialHeight,
}
}
// addCommitment extends the commitment chain by a single commitment. This
// added commitment represents a state update proposed by either party. Once
// the commitment prior to this commitment is revoked, the commitment becomes
// the new defacto state within the channel.
func (s *commitmentChain) addCommitment(c *commitment) {
s.commitments.PushBack(c)
}
// advanceTail reduces the length of the commitment chain by one. The tail of
// the chain should be advanced once a revocation for the lowest unrevoked
// commitment in the chain is received.
func (s *commitmentChain) advanceTail() {
s.commitments.Remove(s.commitments.Front())
}
// tip returns the latest commitment added to the chain.
func (s *commitmentChain) tip() *commitment {
return s.commitments.Back().Value.(*commitment)
}
// tail returns the lowest unrevoked commitment transaction in the chain.
func (s *commitmentChain) tail() *commitment {
return s.commitments.Front().Value.(*commitment)
}
// hasUnackedCommitment returns true if the commitment chain has more than one
// entry. The tail of the commitment chain has been ACKed by revoking all prior
// commitments, but any subsequent commitments have not yet been ACKed.
func (s *commitmentChain) hasUnackedCommitment() bool {
return s.commitments.Front() != s.commitments.Back()
}
// updateLog is an append-only log that stores updates to a node's commitment
// chain. This structure can be seen as the "mempool" within Lightning where
// changes are stored before they're committed to the chain. Once an entry has
// been committed in both the local and remote commitment chain, then it can be
// removed from this log.
//
// TODO(roasbeef): create lightning package, move commitment and update to
// package?
// * also move state machine, separate from lnwallet package
// * possible embed updateLog within commitmentChain.
type updateLog struct {
// logIndex is a monotonically increasing integer that tracks the total
// number of update entries ever applied to the log. When sending new
// commitment states, we include all updates up to this index.
logIndex uint64
// htlcCounter is a monotonically increasing integer that tracks the
// total number of offered HTLC's by the owner of this update log. We
// use a distinct index for this purpose, as update's that remove
// entries from the log will be indexed using this counter.
htlcCounter uint64
// List is the updatelog itself, we embed this value so updateLog has
// access to all the method of a list.List.
*list.List
// updateIndex is an index that maps a particular entries index to the
// list element within the list.List above.
updateIndex map[uint64]*list.Element
// offerIndex is an index that maps the counter for offered HTLC's to
// their list element within the main list.List.
htlcIndex map[uint64]*list.Element
}
// newUpdateLog creates a new updateLog instance.
func newUpdateLog(logIndex, htlcCounter uint64) *updateLog {
return &updateLog{
List: list.New(),
updateIndex: make(map[uint64]*list.Element),
htlcIndex: make(map[uint64]*list.Element),
logIndex: logIndex,
htlcCounter: htlcCounter,
}
}
// restoreHtlc will "restore" a prior HTLC to the updateLog. We say restore as
// this method is intended to be used when re-covering a prior commitment
// state. This function differs from appendHtlc in that it won't increment
// either of log's counters. If the HTLC is already present, then it is
// ignored.
func (u *updateLog) restoreHtlc(pd *PaymentDescriptor) {
if _, ok := u.htlcIndex[pd.HtlcIndex]; ok {
return
}
u.htlcIndex[pd.HtlcIndex] = u.PushBack(pd)
}
// appendUpdate appends a new update to the tip of the updateLog. The entry is
// also added to index accordingly.
func (u *updateLog) appendUpdate(pd *PaymentDescriptor) {
u.updateIndex[u.logIndex] = u.PushBack(pd)
u.logIndex++
}
// appendHtlc appends a new HTLC offer to the tip of the update log. The entry
// is also added to the offer index accordingly.
func (u *updateLog) appendHtlc(pd *PaymentDescriptor) {
u.htlcIndex[u.htlcCounter] = u.PushBack(pd)
u.htlcCounter++
u.logIndex++
}
// lookupHtlc attempts to look up an offered HTLC according to its offer
// index. If the entry isn't found, then a nil pointer is returned.
func (u *updateLog) lookupHtlc(i uint64) *PaymentDescriptor {
htlc, ok := u.htlcIndex[i]
if !ok {
return nil
}
return htlc.Value.(*PaymentDescriptor)
}
// remove attempts to remove an entry from the update log. If the entry is
// found, then the entry will be removed from the update log and index.
func (u *updateLog) removeUpdate(i uint64) {
entry := u.updateIndex[i]
u.Remove(entry)
delete(u.updateIndex, i)
}
// removeHtlc attempts to remove an HTLC offer form the update log. If the
// entry is found, then the entry will be removed from both the main log and
// the offer index.
func (u *updateLog) removeHtlc(i uint64) {
entry := u.htlcIndex[i]
u.Remove(entry)
delete(u.htlcIndex, i)
}
// compactLogs performs garbage collection within the log removing HTLCs which
// have been removed from the point-of-view of the tail of both chains. The
// entries which timeout/settle HTLCs are also removed.
func compactLogs(ourLog, theirLog *updateLog,
localChainTail, remoteChainTail uint64) {
compactLog := func(logA, logB *updateLog) {
var nextA *list.Element
for e := logA.Front(); e != nil; e = nextA {
// Assign next iteration element at top of loop because
// we may remove the current element from the list,
// which can change the iterated sequence.
nextA = e.Next()
htlc := e.Value.(*PaymentDescriptor)
if htlc.EntryType == Add {
continue
}
// If the HTLC hasn't yet been removed from either
// chain, the skip it.
if htlc.removeCommitHeightRemote == 0 ||
htlc.removeCommitHeightLocal == 0 {
continue
}
// Otherwise if the height of the tail of both chains
// is at least the height in which the HTLC was
// removed, then evict the settle/timeout entry along
// with the original add entry.
if remoteChainTail >= htlc.removeCommitHeightRemote &&
localChainTail >= htlc.removeCommitHeightLocal {
logA.removeUpdate(htlc.LogIndex)
logB.removeHtlc(htlc.ParentIndex)
}
}
}
compactLog(ourLog, theirLog)
compactLog(theirLog, ourLog)
}
// LightningChannel implements the state machine which corresponds to the
// current commitment protocol wire spec. The state machine implemented allows
// for asynchronous fully desynchronized, batched+pipelined updates to
// commitment transactions allowing for a high degree of non-blocking
// bi-directional payment throughput.
//
// In order to allow updates to be fully non-blocking, either side is able to
// create multiple new commitment states up to a pre-determined window size.
// This window size is encoded within InitialRevocationWindow. Before the start
// of a session, both side should send out revocation messages with nil
// preimages in order to populate their revocation window for the remote party.
//
// The state machine has for main methods:
// * .SignNextCommitment()
// * Called one one wishes to sign the next commitment, either initiating a
// new state update, or responding to a received commitment.
// * .ReceiveNewCommitment()
// * Called upon receipt of a new commitment from the remote party. If the
// new commitment is valid, then a revocation should immediately be
// generated and sent.
// * .RevokeCurrentCommitment()
// * Revokes the current commitment. Should be called directly after
// receiving a new commitment.
// * .ReceiveRevocation()
// * Processes a revocation from the remote party. If successful creates a
// new defacto broadcastable state.
//
// See the individual comments within the above methods for further details.
type LightningChannel struct {
// signer is the main signer instances that will be responsible for
// signing any HTLC and commitment transaction generated by the state
// machine.
signer Signer
// signDesc is the primary sign descriptor that is capable of signing
// the commitment transaction that spends the multi-sig output.
signDesc *SignDescriptor
channelEvents chainntnfs.ChainNotifier
status channelState
// ChanPoint is the funding outpoint of this channel.
ChanPoint *wire.OutPoint
// sigPool is a pool of workers that are capable of signing and
// validating signatures in parallel. This is utilized as an
// optimization to void serially signing or validating the HTLC
// signatures, of which there may be hundreds.
sigPool *sigPool
// pCache is the global preimage cache shared across all other
// LightningChannel instance. We'll use this cache either when we force
// close, or we detect that the remote party has force closed. If the
// preimage for an incoming HTLC is found in the cache, then we'll try
// to claim it on chain.
pCache PreimageCache
// Capacity is the total capacity of this channel.
Capacity btcutil.Amount
// stateHintObfuscator is a 48-bit state hint that's used to obfuscate
// the current state number on the commitment transactions.
stateHintObfuscator [StateHintSize]byte
// currentHeight is the current height of our local commitment chain.
// This is also the same as the number of updates to the channel we've
// accepted.
currentHeight uint64
// remoteCommitChain is the remote node's commitment chain. Any new
// commitments we initiate are added to the tip of this chain.
remoteCommitChain *commitmentChain
// localCommitChain is our local commitment chain. Any new commitments
// received are added to the tip of this chain. The tail (or lowest
// height) in this chain is our current accepted state, which we are
// able to broadcast safely.
localCommitChain *commitmentChain
channelState *channeldb.OpenChannel
localChanCfg *channeldb.ChannelConfig
remoteChanCfg *channeldb.ChannelConfig
// [local|remote]Log is a (mostly) append-only log storing all the HTLC
// updates to this channel. The log is walked backwards as HTLC updates
// are applied in order to re-construct a commitment transaction from a
// commitment. The log is compacted once a revocation is received.
localUpdateLog *updateLog
remoteUpdateLog *updateLog
// pendingFeeUpdate is set to the fee-per-kw we last sent (if we are
// channel initiator) or received (if non-initiator) in an update fee
// message, which haven't yet been included in a commitment. It will
// be nil if no fee update is un-committed.
pendingFeeUpdate *btcutil.Amount
// pendingAckFeeUpdate is set to the last committed fee update which is
// not yet ACKed. This value will be nil if a fee update hasn't been
// initiated.
pendingAckFeeUpdate *btcutil.Amount
// LocalFundingKey is the public key under control by the wallet that
// was used for the 2-of-2 funding output which created this channel.
LocalFundingKey *btcec.PublicKey
// RemoteFundingKey is the public key for the remote channel counter
// party which used for the 2-of-2 funding output which created this
// channel.
RemoteFundingKey *btcec.PublicKey
sync.RWMutex
cowg sync.WaitGroup
wg sync.WaitGroup
shutdown int32
quit chan struct{}
}
// NewLightningChannel creates a new, active payment channel given an
// implementation of the chain notifier, channel database, and the current
// settled channel state. Throughout state transitions, then channel will
// automatically persist pertinent state to the database in an efficient
// manner.
func NewLightningChannel(signer Signer, pCache PreimageCache,
state *channeldb.OpenChannel) (*LightningChannel, error) {
localCommit := state.LocalCommitment
remoteCommit := state.RemoteCommitment
// First, initialize the update logs with their current counter values
// from the local and remote commitments.
localUpdateLog := newUpdateLog(
localCommit.LocalLogIndex, localCommit.LocalHtlcIndex,
)
remoteUpdateLog := newUpdateLog(
remoteCommit.RemoteLogIndex, remoteCommit.RemoteHtlcIndex,
)
lc := &LightningChannel{
// TODO(roasbeef): tune num sig workers?
sigPool: newSigPool(runtime.NumCPU(), signer),
signer: signer,
pCache: pCache,
currentHeight: localCommit.CommitHeight,
remoteCommitChain: newCommitmentChain(remoteCommit.CommitHeight),
localCommitChain: newCommitmentChain(localCommit.CommitHeight),
channelState: state,
localChanCfg: &state.LocalChanCfg,
remoteChanCfg: &state.RemoteChanCfg,
localUpdateLog: localUpdateLog,
remoteUpdateLog: remoteUpdateLog,
ChanPoint: &state.FundingOutpoint,
Capacity: state.Capacity,
LocalFundingKey: state.LocalChanCfg.MultiSigKey,
RemoteFundingKey: state.RemoteChanCfg.MultiSigKey,
quit: make(chan struct{}),
}
// With the main channel struct reconstructed, we'll now restore the
// commitment state in memory and also the update logs themselves.
err := lc.restoreCommitState(
&localCommit, &remoteCommit, localUpdateLog, remoteUpdateLog,
)
if err != nil {
return nil, err
}
// Create the sign descriptor which we'll be using very frequently to
// request a signature for the 2-of-2 multi-sig from the signer in
// order to complete channel state transitions.
err = lc.createSignDesc()
if err != nil {
return nil, err
}
lc.createStateHintObfuscator()
// Finally, we'll kick of the signature job pool to handle any upcoming
// commitment state generation and validation.
if err := lc.sigPool.Start(); err != nil {
return nil, err
}
return lc, nil
}
// createSignDesc derives the SignDescriptor for commitment transactions from
// other fields on the LightningChannel.
func (lc *LightningChannel) createSignDesc() error {
localKey := lc.localChanCfg.MultiSigKey.SerializeCompressed()
remoteKey := lc.remoteChanCfg.MultiSigKey.SerializeCompressed()
multiSigScript, err := genMultiSigScript(localKey, remoteKey)
if err != nil {
return err
}
fundingPkScript, err := witnessScriptHash(multiSigScript)
if err != nil {
return err
}
lc.signDesc = &SignDescriptor{
PubKey: lc.localChanCfg.MultiSigKey,
WitnessScript: multiSigScript,
Output: &wire.TxOut{
PkScript: fundingPkScript,
Value: int64(lc.channelState.Capacity),
},
HashType: txscript.SigHashAll,
InputIndex: 0,
}
return nil
}
// createStateHintObfuscator derives and assigns the state hint obfuscator for
// the channel, which is used to encode the commitment height in the sequence
// number of commitment transaction inputs.
func (lc *LightningChannel) createStateHintObfuscator() {
state := lc.channelState
if state.IsInitiator {
lc.stateHintObfuscator = DeriveStateHintObfuscator(
state.LocalChanCfg.PaymentBasePoint,
state.RemoteChanCfg.PaymentBasePoint,
)
} else {
lc.stateHintObfuscator = DeriveStateHintObfuscator(
state.RemoteChanCfg.PaymentBasePoint,
state.LocalChanCfg.PaymentBasePoint,
)
}
}
// Stop gracefully shuts down any active goroutines spawned by the
// LightningChannel during regular duties.
func (lc *LightningChannel) Stop() {
if !atomic.CompareAndSwapInt32(&lc.shutdown, 0, 1) {
return
}
lc.sigPool.Stop()
close(lc.quit)
}
// WaitForClose blocks until the channel's close observer has terminated.
func (lc *LightningChannel) WaitForClose() {
lc.cowg.Wait()
}
// ResetState resets the state of the channel back to the default state. This
// ensures that any active goroutines which need to act based on on-chain
// events do so properly.
func (lc *LightningChannel) ResetState() {
lc.Lock()
lc.status = channelOpen
lc.Unlock()
}
// logUpdateToPayDesc converts a LogUpdate into a matching PaymentDescriptor
// entry that can be re-inserted into the update log. This method is used when
// we extended a state to the remote party, but the connection was obstructed
// before we could finish the commitment dance. In this case, we need to
// re-insert the original entries back into the update log so we can resume as
// if nothing happened.
func (lc *LightningChannel) logUpdateToPayDesc(logUpdate *channeldb.LogUpdate,
remoteUpdateLog *updateLog, commitHeight uint64,
feeRate btcutil.Amount, remoteCommitKeys *CommitmentKeyRing,
remoteDustLimit btcutil.Amount) (*PaymentDescriptor, error) {
// Depending on the type of update message we'll map that to a distinct
// PaymentDescriptor instance.
var pd *PaymentDescriptor
switch wireMsg := logUpdate.UpdateMsg.(type) {
// For offered HTLC's, we'll map that to a PaymentDescriptor with the
// type Add, ensuring we restore the necessary fields. From the PoV of
// the commitment chain, this HTLC was included in the remote chain,
// but not the local chain.
case *lnwire.UpdateAddHTLC:
// First, we'll map all the relevant fields in the
// UpdateAddHTLC message to their corresponding fields in the
// PaymentDescriptor struct. We also set addCommitHeightRemote
// as we've included this HTLC in our local commitment chain
// for the remote party.
pd = &PaymentDescriptor{
RHash: wireMsg.PaymentHash,
Timeout: wireMsg.Expiry,
Amount: wireMsg.Amount,
EntryType: Add,
HtlcIndex: wireMsg.ID,
LogIndex: logUpdate.LogIndex,
addCommitHeightRemote: commitHeight,
}
pd.OnionBlob = make([]byte, len(wireMsg.OnionBlob))
copy(pd.OnionBlob[:], wireMsg.OnionBlob[:])
isDustRemote := htlcIsDust(false, false, feeRate,
wireMsg.Amount.ToSatoshis(), remoteDustLimit)
if !isDustRemote {
theirP2WSH, theirWitnessScript, err := genHtlcScript(
false, false, wireMsg.Expiry, wireMsg.PaymentHash,
remoteCommitKeys)
if err != nil {
return nil, err
}
pd.theirPkScript = theirP2WSH
pd.theirWitnessScript = theirWitnessScript
}
// For HTLC's we we're offered we'll fetch the original offered HTLc
// from the remote party's update log so we can retrieve the same
// PaymentDescriptor that SettleHTLC would produce.
case *lnwire.UpdateFulfillHTLC:
ogHTLC := remoteUpdateLog.lookupHtlc(wireMsg.ID)
pd = &PaymentDescriptor{
Amount: ogHTLC.Amount,
RPreimage: wireMsg.PaymentPreimage,
LogIndex: logUpdate.LogIndex,
ParentIndex: ogHTLC.HtlcIndex,
EntryType: Settle,
removeCommitHeightRemote: commitHeight,
}
// If we sent a failure for a prior incoming HTLC, then we'll consult
// the update log of the remote party so we can retrieve the
// information of the original HTLC we're failing. We also set the
// removal height for the remote commitment.
case *lnwire.UpdateFailHTLC:
ogHTLC := remoteUpdateLog.lookupHtlc(wireMsg.ID)
pd = &PaymentDescriptor{
Amount: ogHTLC.Amount,
RHash: ogHTLC.RHash,
ParentIndex: ogHTLC.HtlcIndex,
LogIndex: logUpdate.LogIndex,
EntryType: Fail,
FailReason: wireMsg.Reason[:],
removeCommitHeightRemote: commitHeight,
}
// HTLC fails due to malformed onion blobs are treated the exact same
// way as regular HTLC fails.
case *lnwire.UpdateFailMalformedHTLC:
ogHTLC := remoteUpdateLog.lookupHtlc(wireMsg.ID)
// TODO(roasbeef): err if nil?
pd = &PaymentDescriptor{
Amount: ogHTLC.Amount,
RHash: ogHTLC.RHash,
ParentIndex: ogHTLC.HtlcIndex,
LogIndex: logUpdate.LogIndex,
EntryType: MalformedFail,
FailCode: wireMsg.FailureCode,
ShaOnionBlob: wireMsg.ShaOnionBlob,
removeCommitHeightRemote: commitHeight,
}
}
return pd, nil
}
// restoreCommitState will restore the local commitment chain and updateLog
// state to a consistent in-memory representation of the passed dis commitment.
// This method is to be used upon reconnection to our channel counter party.
// Once the connection has been established, we'll prepare our in memory state
// to re-sync states with the remote party, and also verify/extend new proposed
// commitment states.
func (lc *LightningChannel) restoreCommitState(
localCommitState, remoteCommitState *channeldb.ChannelCommitment,
localUpdateLog, remoteUpdateLog *updateLog) error {
// In order to reconstruct the pkScripts on each of the pending HTLC
// outputs (if any) we'll need to regenerate the current revocation for
// this current un-revoked state as well as retrieve the current
// revocation for the remote party.
ourRevPreImage, err := lc.channelState.RevocationProducer.AtIndex(
lc.currentHeight,
)
if err != nil {
return err
}
localCommitPoint := ComputeCommitmentPoint(ourRevPreImage[:])
remoteCommitPoint := lc.channelState.RemoteCurrentRevocation
// With the revocation state reconstructed, we can now convert the disk
// commitment into our in-memory commitment format, inserting it into
// the local commitment chain.
localCommit, err := lc.diskCommitToMemCommit(
true, false, localCommitState, localCommitPoint,
remoteCommitPoint,
)
if err != nil {
return err
}
lc.localCommitChain.addCommitment(localCommit)
walletLog.Debugf("ChannelPoint(%v), starting local commitment: %v",
lc.channelState.FundingOutpoint, newLogClosure(func() string {
return spew.Sdump(lc.localCommitChain.tail())
}),
)
// We'll also do the same for the remote commitment chain.
remoteCommit, err := lc.diskCommitToMemCommit(
false, false, remoteCommitState, localCommitPoint,
remoteCommitPoint,
)
if err != nil {
return err
}
lc.remoteCommitChain.addCommitment(remoteCommit)
walletLog.Debugf("ChannelPoint(%v), starting remote commitment: %v",
lc.channelState.FundingOutpoint, newLogClosure(func() string {
return spew.Sdump(lc.remoteCommitChain.tail())
}),
)
var (
pendingRemoteCommit *commitment
pendingRemoteCommitDiff *channeldb.CommitDiff
pendingRemoteKeyChain *CommitmentKeyRing
)
// Next, we'll check to see if we have an un-acked commitment state we
// extended to the remote party but which was never ACK'd.
pendingRemoteCommitDiff, err = lc.channelState.RemoteCommitChainTip()
if err != nil && err != channeldb.ErrNoPendingCommit {
return nil
}
if pendingRemoteCommitDiff != nil {
// If we have a pending remote commitment, then we'll also
// reconstruct the original commitment for that state,
// inserting it into the remote party's commitment chain. We
// don't pass our commit point as we don't have the
// corresponding state for the local commitment chain.
pendingCommitPoint := lc.channelState.RemoteNextRevocation
pendingRemoteCommit, err = lc.diskCommitToMemCommit(
false, true, &pendingRemoteCommitDiff.Commitment,
nil, pendingCommitPoint,
)
if err != nil {
return err
}
lc.remoteCommitChain.addCommitment(pendingRemoteCommit)
// We'll also re-create the set of commitment keys needed to
// fully re-derive the state.
pendingRemoteKeyChain = deriveCommitmentKeys(
pendingCommitPoint, false, lc.localChanCfg,
lc.remoteChanCfg,
)
}
// Finally, with the commitment states restored, we'll now restore the
// state logs based on the current local+remote commit, and any pending
// remote commit that exists.
err = lc.restoreStateLogs(localCommit, remoteCommit, pendingRemoteCommit,
pendingRemoteCommitDiff, pendingRemoteKeyChain,
)
if err != nil {
return err
}
return nil
}
// restoreStateLogs runs through the current locked-in HTLCs from the point of
// view of the channel and insert corresponding log entries (both local and
// remote) for each HTLC read from disk. This method is required to sync the
// in-memory state of the state machine with that read from persistent storage.
func (lc *LightningChannel) restoreStateLogs(
localCommitment, remoteCommitment, pendingRemoteCommit *commitment,
pendingRemoteCommitDiff *channeldb.CommitDiff,
pendingRemoteKeys *CommitmentKeyRing) error {
// For each HTLC within the local commitment, we add it to the relevant
// update logc based on if it's incoming vs outgoing. For any incoming
// HTLC's, we also re-add it to the rHashMap so we can quickly look it
// up.
for i := range localCommitment.incomingHTLCs {
htlc := localCommitment.incomingHTLCs[i]
lc.remoteUpdateLog.restoreHtlc(&htlc)
}
for i := range localCommitment.outgoingHTLCs {
htlc := localCommitment.outgoingHTLCs[i]
lc.localUpdateLog.restoreHtlc(&htlc)
}
// We'll also do the same for the HTLC"s within the remote commitment
// party. We also insert these HTLC's as it's possible our state has
// diverged slightly in the case of a congruent update from both sides.
// The restoreHtlc method will de-dup the HTLC's to handle this case.
for i := range remoteCommitment.incomingHTLCs {
htlc := remoteCommitment.incomingHTLCs[i]
lc.remoteUpdateLog.restoreHtlc(&htlc)
}
for i := range remoteCommitment.outgoingHTLCs {
htlc := remoteCommitment.outgoingHTLCs[i]
lc.localUpdateLog.restoreHtlc(&htlc)
}
// If we didn't have a dangling (un-acked) commit for the remote party,
// then we can exit here.
if pendingRemoteCommit == nil {
return nil
}
// If we do have a dangling commitment for the remote party, then we'll
// also restore into the log any incoming HTLC's offered by them. Any
// outgoing HTLC's that were initially committed in this new state will
// be restored below.
for i := range pendingRemoteCommit.incomingHTLCs {
htlc := pendingRemoteCommit.incomingHTLCs[i]
lc.remoteUpdateLog.restoreHtlc(&htlc)
}
// We'll also update the log counters to match the latest known
// counters in this dangling commitment. Otherwise, our updateLog would
// have dated counters as it was initially created using their lowest
// unrevoked commitment.
lc.remoteUpdateLog.logIndex = pendingRemoteCommit.theirMessageIndex
lc.remoteUpdateLog.htlcCounter = pendingRemoteCommit.theirHtlcIndex
pendingCommit := pendingRemoteCommitDiff.Commitment
pendingHeight := pendingCommit.CommitHeight
// If we did have a dangling commit, then we'll examine which updates
// we included in that state and re-insert them into our update log.
for _, logUpdate := range pendingRemoteCommitDiff.LogUpdates {
// If the log update is a fee update, then it doesn't need an
// entry within the updateLog, so we'll just apply it and move
// on.
if feeUpdate, ok := logUpdate.UpdateMsg.(*lnwire.UpdateFee); ok {
newFeeRate := btcutil.Amount(feeUpdate.FeePerKw)
lc.pendingAckFeeUpdate = &newFeeRate
continue
}
payDesc, err := lc.logUpdateToPayDesc(
&logUpdate, lc.remoteUpdateLog, pendingHeight,
pendingCommit.FeePerKw, pendingRemoteKeys,
lc.channelState.RemoteChanCfg.DustLimit,
)
if err != nil {
return err
}
if payDesc.EntryType == Add {
lc.localUpdateLog.appendHtlc(payDesc)
} else {
lc.localUpdateLog.appendUpdate(payDesc)
}
}
return nil
}
// HtlcRetribution contains all the items necessary to seep a revoked HTLC
// transaction from a revoked commitment transaction broadcast by the remote
// party.
type HtlcRetribution struct {
// SignDesc is a design descriptor capable of generating the necessary
// signatures to satisfy the revocation clause of the HTLC's public key
// script.
SignDesc SignDescriptor
// OutPoint is the target outpoint of this HTLC pointing to the
// breached commitment transaction.
OutPoint wire.OutPoint
// SecondLevelWitnessScript is the witness script that will be created
// if the second level HTLC transaction for this output is
// broadcast/confirmed. We provide this as if the remote party attempts
// to to go the second level to claim the HTLC then we'll need to
// update the SignDesc above accordingly to sweep properly.
SecondLevelWitnessScript []byte
// IsIncoming is a boolean flag that indicates whether or not this
// HTLC was accepted from the counterparty. A false value indicates that
// this HTLC was offered by us. This flag is used determine the exact
// witness type should be used to sweep the output.
IsIncoming bool
}
// BreachRetribution contains all the data necessary to bring a channel
// counterparty to justice claiming ALL lingering funds within the channel in
// the scenario that they broadcast a revoked commitment transaction. A
// BreachRetribution is created by the closeObserver if it detects an
// uncooperative close of the channel which uses a revoked commitment
// transaction. The BreachRetribution is then sent over the ContractBreach
// channel in order to allow the subscriber of the channel to dispatch justice.
type BreachRetribution struct {
// BreachTransaction is the transaction which breached the channel
// contract by spending from the funding multi-sig with a revoked
// commitment transaction.
BreachTransaction *wire.MsgTx
// BreachHeight records the block height confirming the breach
// transaction, used as a height hint when registering for
// confirmations.
BreachHeight uint32
// ChainHash is the chain that the contract beach was identified
// within. This is also the resident chain of the contract (the chain
// the contract was created on).
ChainHash chainhash.Hash
// RevokedStateNum is the revoked state number which was broadcast.
RevokedStateNum uint64
// PendingHTLCs is a slice of the HTLCs which were pending at this
// point within the channel's history transcript.
PendingHTLCs []channeldb.HTLC
// LocalOutputSignDesc is a SignDescriptor which is capable of
// generating the signature necessary to sweep the output within the
// BreachTransaction that pays directly us.
//
// NOTE: A nil value indicates that the local output is considered dust
// according to the remote party's dust limit.
LocalOutputSignDesc *SignDescriptor
// LocalOutpoint is the outpoint of the output paying to us (the local
// party) within the breach transaction.
LocalOutpoint wire.OutPoint
// RemoteOutputSignDesc is a SignDescriptor which is capable of
// generating the signature required to claim the funds as described
// within the revocation clause of the remote party's commitment
// output.
//
// NOTE: A nil value indicates that the local output is considered dust
// according to the remote party's dust limit.
RemoteOutputSignDesc *SignDescriptor
// RemoteOutpoint is the outpoint of the output paying to the remote
// party within the breach transaction.
RemoteOutpoint wire.OutPoint
// HtlcRetributions is a slice of HTLC retributions for each output
// active HTLC output within the breached commitment transaction.
HtlcRetributions []HtlcRetribution
}
// NewBreachRetribution creates a new fully populated BreachRetribution for the
// passed channel, at a particular revoked state number, and one which targets
// the passed commitment transaction.
func NewBreachRetribution(chanState *channeldb.OpenChannel, stateNum uint64,
broadcastCommitment *wire.MsgTx,
breachHeight uint32) (*BreachRetribution, error) {
commitHash := broadcastCommitment.TxHash()
// Query the on-disk revocation log for the snapshot which was recorded
// at this particular state num.
revokedSnapshot, err := chanState.FindPreviousState(stateNum)
if err != nil {
return nil, err
}
// With the state number broadcast known, we can now derive/restore the
// proper revocation preimage necessary to sweep the remote party's
// output.
revocationPreimage, err := chanState.RevocationStore.LookUp(stateNum)
if err != nil {
return nil, err
}
commitmentSecret, commitmentPoint := btcec.PrivKeyFromBytes(btcec.S256(),
revocationPreimage[:])
// With the commitment point generated, we can now generate the four
// keys we'll need to reconstruct the commitment state,
keyRing := deriveCommitmentKeys(commitmentPoint, false,
&chanState.LocalChanCfg, &chanState.RemoteChanCfg)
// Next, reconstruct the scripts as they were present at this state
// number so we can have the proper witness script to sign and include
// within the final witness.
remoteDelay := uint32(chanState.RemoteChanCfg.CsvDelay)
remotePkScript, err := commitScriptToSelf(remoteDelay, keyRing.DelayKey,
keyRing.RevocationKey)
if err != nil {
return nil, err
}
remoteWitnessHash, err := witnessScriptHash(remotePkScript)
if err != nil {
return nil, err
}
localPkScript, err := commitScriptUnencumbered(keyRing.NoDelayKey)
if err != nil {
return nil, err
}
// In order to fully populate the breach retribution struct, we'll need
// to find the exact index of the local+remote commitment outputs.
localOutpoint := wire.OutPoint{
Hash: commitHash,
}
remoteOutpoint := wire.OutPoint{
Hash: commitHash,
}
for i, txOut := range broadcastCommitment.TxOut {
switch {
case bytes.Equal(txOut.PkScript, localPkScript):
localOutpoint.Index = uint32(i)
case bytes.Equal(txOut.PkScript, remoteWitnessHash):
remoteOutpoint.Index = uint32(i)
}
}
// Conditionally instantiate a sign descriptor for each of the
// commitment outputs. If either is considered dust using the remote
// party's dust limit, the respective sign descriptor will be nil.
var (
localSignDesc *SignDescriptor
remoteSignDesc *SignDescriptor
)
// Compute the local and remote balances in satoshis.
localAmt := revokedSnapshot.LocalBalance.ToSatoshis()
remoteAmt := revokedSnapshot.RemoteBalance.ToSatoshis()
// If the local balance exceeds the remote party's dust limit,
// instantiate the local sign descriptor.
if localAmt >= chanState.RemoteChanCfg.DustLimit {
localSignDesc = &SignDescriptor{
SingleTweak: keyRing.LocalCommitKeyTweak,
PubKey: chanState.LocalChanCfg.PaymentBasePoint,
WitnessScript: localPkScript,
Output: &wire.TxOut{
PkScript: localPkScript,
Value: int64(localAmt),
},
HashType: txscript.SigHashAll,
}
}
// Similarly, if the remote balance exceeds the remote party's dust
// limit, assemble the remote sign descriptor.
if remoteAmt >= chanState.RemoteChanCfg.DustLimit {
remoteSignDesc = &SignDescriptor{
PubKey: chanState.LocalChanCfg.RevocationBasePoint,
DoubleTweak: commitmentSecret,
WitnessScript: remotePkScript,
Output: &wire.TxOut{
PkScript: remoteWitnessHash,
Value: int64(remoteAmt),
},
HashType: txscript.SigHashAll,
}
}
// With the commitment outputs located, we'll now generate all the
// retribution structs for each of the HTLC transactions active on the
// remote commitment transaction.
htlcRetributions := make([]HtlcRetribution, len(revokedSnapshot.Htlcs))
for i, htlc := range revokedSnapshot.Htlcs {
var (
htlcScript []byte
err error
)
// We'll generate the original second level witness script now,
// as we'll need it if we're revoking an HTLC output on the
// remote commitment transaction, and *they* go to the second
// level.
secondLevelWitnessScript, err := secondLevelHtlcScript(
keyRing.RevocationKey, keyRing.DelayKey, remoteDelay,
)
if err != nil {
return nil, err
}
// If this is an incoming HTLC, then this means that they were
// the sender of the HTLC (relative to us). So we'll
// re-generate the sender HTLC script.
if htlc.Incoming {
htlcScript, err = senderHTLCScript(
keyRing.LocalHtlcKey, keyRing.RemoteHtlcKey,
keyRing.RevocationKey, htlc.RHash[:],
)
if err != nil {
return nil, err
}
// Otherwise, is this was an outgoing HTLC that we sent, then
// from the PoV of the remote commitment state, they're the
// receiver of this HTLC.
} else {
htlcScript, err = receiverHTLCScript(
htlc.RefundTimeout, keyRing.LocalHtlcKey,
keyRing.RemoteHtlcKey, keyRing.RevocationKey,
htlc.RHash[:],
)
if err != nil {
return nil, err
}
}
htlcRetributions[i] = HtlcRetribution{
SignDesc: SignDescriptor{
PubKey: chanState.LocalChanCfg.RevocationBasePoint,
DoubleTweak: commitmentSecret,
WitnessScript: htlcScript,
Output: &wire.TxOut{
Value: int64(htlc.Amt.ToSatoshis()),
},
HashType: txscript.SigHashAll,
},
OutPoint: wire.OutPoint{
Hash: commitHash,
Index: uint32(htlc.OutputIndex),
},
SecondLevelWitnessScript: secondLevelWitnessScript,
IsIncoming: htlc.Incoming,
}
}
// Finally, with all the necessary data constructed, we can create the
// BreachRetribution struct which houses all the data necessary to
// swiftly bring justice to the cheating remote party.
return &BreachRetribution{
ChainHash: chanState.ChainHash,
BreachTransaction: broadcastCommitment,
BreachHeight: breachHeight,
RevokedStateNum: stateNum,
PendingHTLCs: revokedSnapshot.Htlcs,
LocalOutpoint: localOutpoint,
LocalOutputSignDesc: localSignDesc,
RemoteOutpoint: remoteOutpoint,
RemoteOutputSignDesc: remoteSignDesc,
HtlcRetributions: htlcRetributions,
}, nil
}
// htlcTimeoutFee returns the fee in satoshis required for an HTLC timeout
// transaction based on the current fee rate.
func htlcTimeoutFee(feePerKw btcutil.Amount) btcutil.Amount {
return (feePerKw * HtlcTimeoutWeight) / 1000
}
// htlcSuccessFee returns the fee in satoshis required for an HTLC success
// transaction based on the current fee rate.
func htlcSuccessFee(feePerKw btcutil.Amount) btcutil.Amount {
return (feePerKw * HtlcSuccessWeight) / 1000
}
// htlcIsDust determines if an HTLC output is dust or not depending on two
// bits: if the HTLC is incoming and if the HTLC will be placed on our
// commitment transaction, or theirs. These two pieces of information are
// require as we currently used second-level HTLC transactions ass off-chain
// covenants. Depending on the two bits, we'll either be using a timeout or
// success transaction which have different weights.
func htlcIsDust(incoming, ourCommit bool,
feePerKw, htlcAmt, dustLimit btcutil.Amount) bool {
// First we'll determine the fee required for this HTLC based on if this is
// an incoming HTLC or not, and also on whose commitment transaction it
// will be placed on.
var htlcFee btcutil.Amount
switch {
// If this is an incoming HTLC on our commitment transaction, then the
// second-level transaction will be a success transaction.
case incoming && ourCommit:
htlcFee = htlcSuccessFee(feePerKw)
// If this is an incoming HTLC on their commitment transaction, then
// we'll be using a second-level timeout transaction as they've added
// this HTLC.
case incoming && !ourCommit:
htlcFee = htlcTimeoutFee(feePerKw)
// If this is an outgoing HTLC on our commitment transaction, then
// we'll be using a timeout transaction as we're the sender of the
// HTLC.
case !incoming && ourCommit:
htlcFee = htlcTimeoutFee(feePerKw)
// If this is an outgoing HTLC on their commitment transaction, then
// we'll be using an HTLC success transaction as they're the receiver
// of this HTLC.
case !incoming && !ourCommit:
htlcFee = htlcSuccessFee(feePerKw)
}
return (htlcAmt - htlcFee) < dustLimit
}
// htlcView represents the "active" HTLCs at a particular point within the
// history of the HTLC update log.
type htlcView struct {
ourUpdates []*PaymentDescriptor
theirUpdates []*PaymentDescriptor
}
// fetchHTLCView returns all the candidate HTLC updates which should be
// considered for inclusion within a commitment based on the passed HTLC log
// indexes.
func (lc *LightningChannel) fetchHTLCView(theirLogIndex, ourLogIndex uint64) *htlcView {
var ourHTLCs []*PaymentDescriptor
for e := lc.localUpdateLog.Front(); e != nil; e = e.Next() {
htlc := e.Value.(*PaymentDescriptor)
// This HTLC is active from this point-of-view iff the log
// index of the state update is below the specified index in
// our update log.
if htlc.LogIndex < ourLogIndex {
ourHTLCs = append(ourHTLCs, htlc)
}
}
var theirHTLCs []*PaymentDescriptor
for e := lc.remoteUpdateLog.Front(); e != nil; e = e.Next() {
htlc := e.Value.(*PaymentDescriptor)
// If this is an incoming HTLC, then it is only active from
// this point-of-view if the index of the HTLC addition in
// their log is below the specified view index.
if htlc.LogIndex < theirLogIndex {
theirHTLCs = append(theirHTLCs, htlc)
}
}
return &htlcView{
ourUpdates: ourHTLCs,
theirUpdates: theirHTLCs,
}
}
// fetchCommitmentView returns a populated commitment which expresses the state
// of the channel from the point of view of a local or remote chain, evaluating
// the HTLC log up to the passed indexes. This function is used to construct
// both local and remote commitment transactions in order to sign or verify new
// commitment updates. A fully populated commitment is returned which reflects
// the proper balances for both sides at this point in the commitment chain.
func (lc *LightningChannel) fetchCommitmentView(remoteChain bool,
ourLogIndex, ourHtlcIndex, theirLogIndex, theirHtlcIndex uint64,
keyRing *CommitmentKeyRing) (*commitment, error) {
commitChain := lc.localCommitChain
if remoteChain {
commitChain = lc.remoteCommitChain
}
ourBalance := commitChain.tip().ourBalance
theirBalance := commitChain.tip().theirBalance
// Add the fee from the previous commitment state back to the
// initiator's balance, so that the fee can be recalculated and
// re-applied in case fee estimation parameters have changed or the
// number of outstanding HTLCs has changed.
if lc.channelState.IsInitiator {
ourBalance += lnwire.NewMSatFromSatoshis(commitChain.tip().fee)
} else if !lc.channelState.IsInitiator {
theirBalance += lnwire.NewMSatFromSatoshis(commitChain.tip().fee)
}
nextHeight := commitChain.tip().height + 1
// Run through all the HTLCs that will be covered by this transaction
// in order to update their commitment addition height, and to adjust
// the balances on the commitment transaction accordingly.
htlcView := lc.fetchHTLCView(theirLogIndex, ourLogIndex)
filteredHTLCView := lc.evaluateHTLCView(htlcView, &ourBalance,
&theirBalance, nextHeight, remoteChain)
// Initiate feePerKw to the last committed fee for this chain as we'll
// need this to determine which HTLC's are dust, and also the final fee
// rate.
feePerKw := commitChain.tail().feePerKw
// Check if any fee updates have taken place since that last
// commitment.
if lc.channelState.IsInitiator {
switch {
// We've sent an update_fee message since our last commitment,
// and now are now creating a commitment that reflects the new
// fee update.
case remoteChain && lc.pendingFeeUpdate != nil:
feePerKw = *lc.pendingFeeUpdate
// We've created a new commitment for the remote chain that
// includes a fee update, and have not received a commitment
// after the fee update has been ACKed.
case !remoteChain && lc.pendingAckFeeUpdate != nil:
feePerKw = *lc.pendingAckFeeUpdate
}
} else {
switch {
// We've received a fee update since the last local commitment,
// so we'll include the fee update in the current view.
case !remoteChain && lc.pendingFeeUpdate != nil:
feePerKw = *lc.pendingFeeUpdate
// Earlier we received a commitment that signed an earlier fee
// update, and now we must ACK that update.
case remoteChain && lc.pendingAckFeeUpdate != nil:
feePerKw = *lc.pendingAckFeeUpdate
}
}
// Determine how many current HTLCs are over the dust limit, and should
// be counted for the purpose of fee calculation.
var dustLimit btcutil.Amount
if remoteChain {
dustLimit = lc.remoteChanCfg.DustLimit
} else {
dustLimit = lc.localChanCfg.DustLimit
}
c := &commitment{
ourBalance: ourBalance,
theirBalance: theirBalance,
ourMessageIndex: ourLogIndex,
ourHtlcIndex: ourHtlcIndex,
theirMessageIndex: theirLogIndex,
theirHtlcIndex: theirHtlcIndex,
height: nextHeight,
feePerKw: feePerKw,
dustLimit: dustLimit,
isOurs: !remoteChain,
}
// Actually generate unsigned commitment transaction for this view.
if err := lc.createCommitmentTx(c, filteredHTLCView, keyRing); err != nil {
return nil, err
}
// In order to ensure _none_ of the HTLC's associated with this new
// commitment are mutated, we'll manually copy over each HTLC to its
// respective slice.
c.outgoingHTLCs = make([]PaymentDescriptor, len(filteredHTLCView.ourUpdates))
for i, htlc := range filteredHTLCView.ourUpdates {
c.outgoingHTLCs[i] = *htlc
}
c.incomingHTLCs = make([]PaymentDescriptor, len(filteredHTLCView.theirUpdates))
for i, htlc := range filteredHTLCView.theirUpdates {
c.incomingHTLCs[i] = *htlc
}
// Finally, we'll populate all the HTLC indexes so we can track the
// locations of each HTLC in the commitment state.
if err := c.populateHtlcIndexes(); err != nil {
return nil, err
}
return c, nil
}
func (lc *LightningChannel) fundingTxIn() wire.TxIn {
return *wire.NewTxIn(&lc.channelState.FundingOutpoint, nil, nil)
}
// createCommitmentTx generates the unsigned commitment transaction for a
// commitment view and assigns to txn field.
func (lc *LightningChannel) createCommitmentTx(c *commitment,
filteredHTLCView *htlcView, keyRing *CommitmentKeyRing) error {
ourBalance := c.ourBalance
theirBalance := c.theirBalance
numHTLCs := int64(0)
for _, htlc := range filteredHTLCView.ourUpdates {
if htlcIsDust(false, c.isOurs, c.feePerKw,
htlc.Amount.ToSatoshis(), c.dustLimit) {
continue
}
numHTLCs++
}
for _, htlc := range filteredHTLCView.theirUpdates {
if htlcIsDust(true, c.isOurs, c.feePerKw,
htlc.Amount.ToSatoshis(), c.dustLimit) {
continue
}
numHTLCs++
}
// Next, we'll calculate the fee for the commitment transaction based
// on its total weight. Once we have the total weight, we'll multiply
// by the current fee-per-kw, then divide by 1000 to get the proper
// fee.
totalCommitWeight := CommitWeight + (HtlcWeight * numHTLCs)
// With the weight known, we can now calculate the commitment fee,
// ensuring that we account for any dust outputs trimmed above.
commitFee := btcutil.Amount((int64(c.feePerKw) * totalCommitWeight) / 1000)
// Currently, within the protocol, the initiator always pays the fees.
// So we'll subtract the fee amount from the balance of the current
// initiator.
if lc.channelState.IsInitiator {
ourBalance -= lnwire.NewMSatFromSatoshis(commitFee)
} else if !lc.channelState.IsInitiator {
theirBalance -= lnwire.NewMSatFromSatoshis(commitFee)
}
var (
delay uint32
delayBalance, p2wkhBalance btcutil.Amount
)
if c.isOurs {
delay = uint32(lc.localChanCfg.CsvDelay)
delayBalance = ourBalance.ToSatoshis()
p2wkhBalance = theirBalance.ToSatoshis()
} else {
delay = uint32(lc.remoteChanCfg.CsvDelay)
delayBalance = theirBalance.ToSatoshis()
p2wkhBalance = ourBalance.ToSatoshis()
}
// Generate a new commitment transaction with all the latest
// unsettled/un-timed out HTLCs.
commitTx, err := CreateCommitTx(lc.fundingTxIn(), keyRing, delay,
delayBalance, p2wkhBalance, c.dustLimit)
if err != nil {
return err
}
// We'll now add all the HTLC outputs to the commitment transaction.
// Each output includes an off-chain 2-of-2 covenant clause, so we'll
// need the objective local/remote keys for this particular commitment
// as well.
for _, htlc := range filteredHTLCView.ourUpdates {
if htlcIsDust(false, c.isOurs, c.feePerKw,
htlc.Amount.ToSatoshis(), c.dustLimit) {
continue
}
err := lc.addHTLC(commitTx, c.isOurs, false, htlc, keyRing)
if err != nil {
return err
}
}
for _, htlc := range filteredHTLCView.theirUpdates {
if htlcIsDust(true, c.isOurs, c.feePerKw,
htlc.Amount.ToSatoshis(), c.dustLimit) {
continue
}
err := lc.addHTLC(commitTx, c.isOurs, true, htlc, keyRing)
if err != nil {
return err
}
}
// Set the state hint of the commitment transaction to facilitate
// quickly recovering the necessary penalty state in the case of an
// uncooperative broadcast.
err = SetStateNumHint(commitTx, c.height, lc.stateHintObfuscator)
if err != nil {
return err
}
// Sort the transactions according to the agreed upon canonical
// ordering. This lets us skip sending the entire transaction over,
// instead we'll just send signatures.
txsort.InPlaceSort(commitTx)
c.txn = commitTx
c.fee = commitFee
c.ourBalance = ourBalance
c.theirBalance = theirBalance
return nil
}
// evaluateHTLCView processes all update entries in both HTLC update logs,
// producing a final view which is the result of properly applying all adds,
// settles, and timeouts found in both logs. The resulting view returned
// reflects the current state of HTLCs within the remote or local commitment
// chain.
func (lc *LightningChannel) evaluateHTLCView(view *htlcView, ourBalance,
theirBalance *lnwire.MilliSatoshi, nextHeight uint64, remoteChain bool) *htlcView {
newView := &htlcView{}
// We use two maps, one for the local log and one for the remote log to
// keep track of which entries we need to skip when creating the final
// htlc view. We skip an entry whenever we find a settle or a timeout
// modifying an entry.
skipUs := make(map[uint64]struct{})
skipThem := make(map[uint64]struct{})
// First we run through non-add entries in both logs, populating the
// skip sets and mutating the current chain state (crediting balances,
// etc) to reflect the settle/timeout entry encountered.
for _, entry := range view.ourUpdates {
if entry.EntryType == Add {
continue
}
// If we're settling an inbound HTLC, and it hasn't been
// processed yet, then increment our state tracking the total
// number of satoshis we've received within the channel.
if entry.EntryType == Settle && !remoteChain &&
entry.removeCommitHeightLocal == 0 {
lc.channelState.TotalMSatReceived += entry.Amount
}
addEntry := lc.remoteUpdateLog.lookupHtlc(entry.ParentIndex)
skipThem[addEntry.HtlcIndex] = struct{}{}
processRemoveEntry(entry, ourBalance, theirBalance,
nextHeight, remoteChain, true)
}
for _, entry := range view.theirUpdates {
if entry.EntryType == Add {
continue
}
// If the remote party is settling one of our outbound HTLC's,
// and it hasn't been processed, yet, the increment our state
// tracking the total number of satoshis we've sent within the
// channel.
if entry.EntryType == Settle && !remoteChain &&
entry.removeCommitHeightLocal == 0 {
lc.channelState.TotalMSatSent += entry.Amount
}
addEntry := lc.localUpdateLog.lookupHtlc(entry.ParentIndex)
skipUs[addEntry.HtlcIndex] = struct{}{}
processRemoveEntry(entry, ourBalance, theirBalance,
nextHeight, remoteChain, false)
}
// Next we take a second pass through all the log entries, skipping any
// settled HTLCs, and debiting the chain state balance due to any newly
// added HTLCs.
for _, entry := range view.ourUpdates {
isAdd := entry.EntryType == Add
if _, ok := skipUs[entry.HtlcIndex]; !isAdd || ok {
continue
}
processAddEntry(entry, ourBalance, theirBalance, nextHeight,
remoteChain, false)
newView.ourUpdates = append(newView.ourUpdates, entry)
}
for _, entry := range view.theirUpdates {
isAdd := entry.EntryType == Add
if _, ok := skipThem[entry.HtlcIndex]; !isAdd || ok {
continue
}
processAddEntry(entry, ourBalance, theirBalance, nextHeight,
remoteChain, true)
newView.theirUpdates = append(newView.theirUpdates, entry)
}
return newView
}
// processAddEntry evaluates the effect of an add entry within the HTLC log.
// If the HTLC hasn't yet been committed in either chain, then the height it
// was committed is updated. Keeping track of this inclusion height allows us to
// later compact the log once the change is fully committed in both chains.
func processAddEntry(htlc *PaymentDescriptor, ourBalance, theirBalance *lnwire.MilliSatoshi,
nextHeight uint64, remoteChain bool, isIncoming bool) {
// If we're evaluating this entry for the remote chain (to create/view
// a new commitment), then we'll may be updating the height this entry
// was added to the chain. Otherwise, we may be updating the entry's
// height w.r.t the local chain.
var addHeight *uint64
if remoteChain {
addHeight = &htlc.addCommitHeightRemote
} else {
addHeight = &htlc.addCommitHeightLocal
}
if *addHeight != 0 {
return
}
if isIncoming {
// If this is a new incoming (un-committed) HTLC, then we need
// to update their balance accordingly by subtracting the
// amount of the HTLC that are funds pending.
*theirBalance -= htlc.Amount
} else {
// Similarly, we need to debit our balance if this is an out
// going HTLC to reflect the pending balance.
*ourBalance -= htlc.Amount
}
*addHeight = nextHeight
}
// processRemoveEntry processes a log entry which settles or times out a
// previously added HTLC. If the removal entry has already been processed, it
// is skipped.
func processRemoveEntry(htlc *PaymentDescriptor, ourBalance,
theirBalance *lnwire.MilliSatoshi, nextHeight uint64,
remoteChain bool, isIncoming bool) {
var removeHeight *uint64
if remoteChain {
removeHeight = &htlc.removeCommitHeightRemote
} else {
removeHeight = &htlc.removeCommitHeightLocal
}
// Ignore any removal entries which have already been processed.
if *removeHeight != 0 {
return
}
switch {
// If an incoming HTLC is being settled, then this means that we've
// received the preimage either from another subsystem, or the
// upstream peer in the route. Therefore, we increase our balance by
// the HTLC amount.
case isIncoming && htlc.EntryType == Settle:
*ourBalance += htlc.Amount
// Otherwise, this HTLC is being failed out, therefore the value of the
// HTLC should return to the remote party.
case isIncoming && (htlc.EntryType == Fail || htlc.EntryType == MalformedFail):
*theirBalance += htlc.Amount
// If an outgoing HTLC is being settled, then this means that the
// downstream party resented the preimage or learned of it via a
// downstream peer. In either case, we credit their settled value with
// the value of the HTLC.
case !isIncoming && htlc.EntryType == Settle:
*theirBalance += htlc.Amount
// Otherwise, one of our outgoing HTLC's has timed out, so the value of
// the HTLC should be returned to our settled balance.
case !isIncoming && (htlc.EntryType == Fail || htlc.EntryType == MalformedFail):
*ourBalance += htlc.Amount
}
*removeHeight = nextHeight
}
// generateRemoteHtlcSigJobs generates a series of HTLC signature jobs for the
// sig pool, along with a channel that if closed, will cancel any jobs after
// they have been submitted to the sigPool. This method is to be used when
// generating a new commitment for the remote party. The jobs generated by the
// signature can be submitted to the sigPool to generate all the signatures
// asynchronously and in parallel.
func genRemoteHtlcSigJobs(keyRing *CommitmentKeyRing,
localChanCfg, remoteChanCfg *channeldb.ChannelConfig,
remoteCommitView *commitment) ([]signJob, chan struct{}, error) {
txHash := remoteCommitView.txn.TxHash()
dustLimit := localChanCfg.DustLimit
feePerKw := remoteCommitView.feePerKw
// With the keys generated, we'll make a slice with enough capacity to
// hold potentially all the HTLC's. The actual slice may be a bit
// smaller (than its total capacity) an some HTLC's may be dust.
numSigs := (len(remoteCommitView.incomingHTLCs) +
len(remoteCommitView.outgoingHTLCs))
sigBatch := make([]signJob, 0, numSigs)
var err error
cancelChan := make(chan struct{})
// For ech outgoing and incoming HTLC, if the HTLC isn't considered a
// dust output after taking into account second-level HTLC fees, then a
// sigJob will be generated and appended to the current batch.
for _, htlc := range remoteCommitView.incomingHTLCs {
if htlcIsDust(true, false, feePerKw, htlc.Amount.ToSatoshis(),
dustLimit) {
continue
}
// If the HTLC isn't dust, then we'll create an empty sign job
// to add to the batch momentarily.
sigJob := signJob{}
sigJob.cancel = cancelChan
sigJob.resp = make(chan signJobResp, 1)
// As this is an incoming HTLC and we're sinning the commitment
// transaction of the remote node, we'll need to generate an
// HTLC timeout transaction for them. The output of the timeout
// transaction needs to account for fees, so we'll compute the
// required fee and output now.
htlcFee := htlcTimeoutFee(feePerKw)
outputAmt := htlc.Amount.ToSatoshis() - htlcFee
// With the fee calculate, we can properly create the HTLC
// timeout transaction using the HTLC amount minus the fee.
op := wire.OutPoint{
Hash: txHash,
Index: uint32(htlc.remoteOutputIndex),
}
sigJob.tx, err = createHtlcTimeoutTx(op, outputAmt,
htlc.Timeout, uint32(remoteChanCfg.CsvDelay),
keyRing.RevocationKey, keyRing.DelayKey)
if err != nil {
return nil, nil, err
}
// Finally, we'll generate a sign descriptor to generate a
// signature to give to the remote party for this commitment
// transaction. Note we use the raw HTLC amount.
sigJob.signDesc = SignDescriptor{
PubKey: localChanCfg.HtlcBasePoint,
SingleTweak: keyRing.LocalHtlcKeyTweak,
WitnessScript: htlc.theirWitnessScript,
Output: &wire.TxOut{
Value: int64(htlc.Amount.ToSatoshis()),
},
HashType: txscript.SigHashAll,
SigHashes: txscript.NewTxSigHashes(sigJob.tx),
InputIndex: 0,
}
sigJob.outputIndex = htlc.remoteOutputIndex
sigBatch = append(sigBatch, sigJob)
}
for _, htlc := range remoteCommitView.outgoingHTLCs {
if htlcIsDust(false, false, feePerKw, htlc.Amount.ToSatoshis(),
dustLimit) {
continue
}
sigJob := signJob{}
sigJob.cancel = cancelChan
sigJob.resp = make(chan signJobResp, 1)
// As this is an outgoing HTLC and we're signing the commitment
// transaction of the remote node, we'll need to generate an
// HTLC success transaction for them. The output of the timeout
// transaction needs to account for fees, so we'll compute the
// required fee and output now.
htlcFee := htlcSuccessFee(feePerKw)
outputAmt := htlc.Amount.ToSatoshis() - htlcFee
// With the proper output amount calculated, we can now
// generate the success transaction using the remote party's
// CSV delay.
op := wire.OutPoint{
Hash: txHash,
Index: uint32(htlc.remoteOutputIndex),
}
sigJob.tx, err = createHtlcSuccessTx(op, outputAmt,
uint32(remoteChanCfg.CsvDelay), keyRing.RevocationKey,
keyRing.DelayKey)
if err != nil {
return nil, nil, err
}
// Finally, we'll generate a sign descriptor to generate a
// signature to give to the remote party for this commitment
// transaction. Note we use the raw HTLC amount.
sigJob.signDesc = SignDescriptor{
PubKey: localChanCfg.HtlcBasePoint,
SingleTweak: keyRing.LocalHtlcKeyTweak,
WitnessScript: htlc.theirWitnessScript,
Output: &wire.TxOut{
Value: int64(htlc.Amount.ToSatoshis()),
},
HashType: txscript.SigHashAll,
SigHashes: txscript.NewTxSigHashes(sigJob.tx),
InputIndex: 0,
}
sigJob.outputIndex = htlc.remoteOutputIndex
sigBatch = append(sigBatch, sigJob)
}
return sigBatch, cancelChan, nil
}
// createCommitDiff will create a commit diff given a new pending commitment
// for the remote party and the necessary signatures for the remote party to
// validate this new state. This function is called right before sending the
// new commitment to the remote party. The commit diff returned contains all
// information necessary for retransmission.
func (lc *LightningChannel) createCommitDiff(
newCommit *commitment, commitSig lnwire.Sig,
htlcSigs []lnwire.Sig) (*channeldb.CommitDiff, error) {
// First, we need to convert the funding outpoint into the ID that's
// used on the wire to identify this channel. We'll use this shortly
// when recording the exact CommitSig message that we'll be sending
// out.
chanID := lnwire.NewChanIDFromOutPoint(&lc.channelState.FundingOutpoint)
// If we have a fee update that we're waiting on an ACK of, then we'll
// create an entry so this is properly retransmitted. Note that we can
// only send an UpdateFee message if we're the initiator of the
// channel.
var logUpdates []channeldb.LogUpdate
if lc.channelState.IsInitiator && lc.pendingFeeUpdate != nil {
logUpdates = append(logUpdates, channeldb.LogUpdate{
UpdateMsg: &lnwire.UpdateFee{
ChanID: chanID,
FeePerKw: uint32(*lc.pendingFeeUpdate),
},
})
}
// We'll now run through our local update log to locate the items which
// were only just committed within this pending state. This will be the
// set of items we need to retransmit if we reconnect and find that
// they didn't process this new state fully.
for e := lc.localUpdateLog.Front(); e != nil; e = e.Next() {
pd := e.Value.(*PaymentDescriptor)
// If this entry wasn't committed at the exact height of this
// remote commitment, then we'll skip it as it was already
// lingering in the log.
if pd.addCommitHeightRemote != newCommit.height &&
pd.removeCommitHeightRemote != newCommit.height {
continue
}
// Knowing that this update is a part of this new commitment,
// we'll create a log update and not its index in the log so
// we can later restore it properly if a restart occurs.
logUpdate := channeldb.LogUpdate{
LogIndex: pd.LogIndex,
}
// We'll map the type of the PaymentDescriptor to one of the
// four messages that it corresponds to. With this set of
// messages obtained, we can simply read from disk and re-send
// them in the case of a needed channel sync.
switch pd.EntryType {
case Add:
htlc := &lnwire.UpdateAddHTLC{
ChanID: chanID,
ID: pd.HtlcIndex,
Amount: pd.Amount,
Expiry: pd.Timeout,
PaymentHash: pd.RHash,
}
copy(htlc.OnionBlob[:], pd.OnionBlob)
logUpdate.UpdateMsg = htlc
case Settle:
logUpdate.UpdateMsg = &lnwire.UpdateFulfillHTLC{
ChanID: chanID,
ID: pd.ParentIndex,
PaymentPreimage: pd.RPreimage,
}
case Fail:
logUpdate.UpdateMsg = &lnwire.UpdateFailHTLC{
ChanID: chanID,
ID: pd.ParentIndex,
Reason: pd.FailReason,
}
case MalformedFail:
logUpdate.UpdateMsg = &lnwire.UpdateFailMalformedHTLC{
ChanID: chanID,
ID: pd.ParentIndex,
ShaOnionBlob: pd.ShaOnionBlob,
FailureCode: pd.FailCode,
}
}
logUpdates = append(logUpdates, logUpdate)
}
// With the set of log updates mapped into wire messages, we'll now
// convert the in-memory commit into a format suitable for writing to
// disk.
diskCommit := newCommit.toDiskCommit(false)
return &channeldb.CommitDiff{
Commitment: *diskCommit,
CommitSig: &lnwire.CommitSig{
ChanID: lnwire.NewChanIDFromOutPoint(
&lc.channelState.FundingOutpoint,
),
CommitSig: commitSig,
HtlcSigs: htlcSigs,
},
LogUpdates: logUpdates,
}, nil
}
// SignNextCommitment signs a new commitment which includes any previous
// unsettled HTLCs, any new HTLCs, and any modifications to prior HTLCs
// committed in previous commitment updates. Signing a new commitment
// decrements the available revocation window by 1. After a successful method
// call, the remote party's commitment chain is extended by a new commitment
// which includes all updates to the HTLC log prior to this method invocation.
// The first return parameter is the signature for the commitment transaction
// itself, while the second parameter is a slice of all HTLC signatures (if
// any). The HTLC signatures are sorted according to the BIP 69 order of the
// HTLC's on the commitment transaction.
func (lc *LightningChannel) SignNextCommitment() (lnwire.Sig, []lnwire.Sig, error) {
lc.Lock()
defer lc.Unlock()
var (
sig lnwire.Sig
htlcSigs []lnwire.Sig
)
// If we're awaiting for an ACK to a commitment signature, or if we
// don't yet have the initial next revocation point of the remote
// party, then we're unable to create new states. Each time we create a
// new state, we consume a prior revocation point.
commitPoint := lc.channelState.RemoteNextRevocation
if lc.remoteCommitChain.hasUnackedCommitment() || commitPoint == nil {
return sig, htlcSigs, ErrNoWindow
}
// Determine the last update on the remote log that has been locked in.
remoteACKedIndex := lc.localCommitChain.tail().theirMessageIndex
remoteHtlcIndex := lc.localCommitChain.tail().theirHtlcIndex
// Before we extend this new commitment to the remote commitment chain,
// ensure that we aren't violating any of the constraints the remote
// party set up when we initially set up the channel. If we are, then
// we'll abort this state transition.
err := lc.validateCommitmentSanity(remoteACKedIndex,
lc.localUpdateLog.logIndex, false, true, true)
if err != nil {
return sig, htlcSigs, err
}
// Grab the next commitment point for the remote party. This will be
// used within fetchCommitmentView to derive all the keys necessary to
// construct the commitment state.
keyRing := deriveCommitmentKeys(commitPoint, false, lc.localChanCfg,
lc.remoteChanCfg)
// Create a new commitment view which will calculate the evaluated
// state of the remote node's new commitment including our latest added
// HTLCs. The view includes the latest balances for both sides on the
// remote node's chain, and also update the addition height of any new
// HTLC log entries. When we creating a new remote view, we include
// _all_ of our changes (pending or committed) but only the remote
// node's changes up to the last change we've ACK'd.
newCommitView, err := lc.fetchCommitmentView(
true, lc.localUpdateLog.logIndex, lc.localUpdateLog.htlcCounter,
remoteACKedIndex, remoteHtlcIndex, keyRing,
)
if err != nil {
return sig, htlcSigs, err
}
walletLog.Tracef("ChannelPoint(%v): extending remote chain to height %v, "+
"local_log=%v, remote_log=%v",
lc.channelState.FundingOutpoint, newCommitView.height,
lc.localUpdateLog.logIndex, remoteACKedIndex)
walletLog.Tracef("ChannelPoint(%v): remote chain: our_balance=%v, "+
"their_balance=%v, commit_tx: %v",
lc.channelState.FundingOutpoint, newCommitView.ourBalance,
newCommitView.theirBalance,
newLogClosure(func() string {
return spew.Sdump(newCommitView.txn)
}),
)
// With the commitment view constructed, if there are any HTLC's, we'll
// need to generate signatures of each of them for the remote party's
// commitment state. We do so in two phases: first we generate and
// submit the set of signature jobs to the worker pool.
sigBatch, cancelChan, err := genRemoteHtlcSigJobs(keyRing,
lc.localChanCfg, lc.remoteChanCfg, newCommitView,
)
if err != nil {
return sig, htlcSigs, err
}
lc.sigPool.SubmitSignBatch(sigBatch)
// While the jobs are being carried out, we'll Sign their version of
// the new commitment transaction while we're waiting for the rest of
// the HTLC signatures to be processed.
lc.signDesc.SigHashes = txscript.NewTxSigHashes(newCommitView.txn)
rawSig, err := lc.signer.SignOutputRaw(newCommitView.txn, lc.signDesc)
if err != nil {
close(cancelChan)
return sig, htlcSigs, err
}
sig, err = lnwire.NewSigFromRawSignature(rawSig)
if err != nil {
close(cancelChan)
return sig, htlcSigs, err
}
// We'll need to send over the signatures to the remote party in the
// order as they appear on the commitment transaction after BIP 69
// sorting.
sort.Slice(sigBatch, func(i, j int) bool {
return sigBatch[i].outputIndex < sigBatch[j].outputIndex
})
// With the jobs sorted, we'll now iterate through all the responses to
// gather each of the signatures in order.
htlcSigs = make([]lnwire.Sig, 0, len(sigBatch))
for _, htlcSigJob := range sigBatch {
select {
case jobResp := <-htlcSigJob.resp:
// If an error occurred, then we'll cancel any other
// active jobs.
if jobResp.err != nil {
close(cancelChan)
return sig, htlcSigs, err
}
htlcSigs = append(htlcSigs, jobResp.sig)
case <-lc.quit:
return sig, htlcSigs, fmt.Errorf("channel shutting down")
}
}
// As we're about to proposer a new commitment state for the remote
// party, we'll write this pending state to disk before we exit, so we
// can retransmit it if necessary.
commitDiff, err := lc.createCommitDiff(newCommitView, sig, htlcSigs)
if err != nil {
return sig, htlcSigs, err
}
if lc.channelState.AppendRemoteCommitChain(commitDiff); err != nil {
return sig, htlcSigs, err
}
// TODO(roasbeef): check that one eclair bug
// * need to retransmit on first state still?
// * after initial reconnect
// Extend the remote commitment chain by one with the addition of our
// latest commitment update.
lc.remoteCommitChain.addCommitment(newCommitView)
// If we are the channel initiator then we would have signed any sent
// fee update at this point, so mark this update as pending ACK, and
// set pendingFeeUpdate to nil. We can do this since we know we won't
// sign any new commitment before receiving a RevokeAndAck, because of
// the revocation window of 1.
if lc.channelState.IsInitiator {
lc.pendingAckFeeUpdate = lc.pendingFeeUpdate
lc.pendingFeeUpdate = nil
}
return sig, htlcSigs, nil
}
// ProcessChanSyncMsg processes a ChannelReestablish message sent by the remote
// connection upon re establishment of our connection with them. This method
// will return a single message if we are currently out of sync, otherwise a
// nil lnwire.Message will be returned. If it is decided that our level of
// de-synchronization is irreconcilable, then an error indicating the issue
// will be returned. In this case that an error is returned, the channel should
// be force closed, as we cannot continue updates.
//
// One of two message sets will be returned:
//
// * CommitSig+Updates: if we have a pending remote commit which they claim to
// have not received
// * RevokeAndAck: if we sent a revocation message that they claim to have
// not received
func (lc *LightningChannel) ProcessChanSyncMsg(msg *lnwire.ChannelReestablish) ([]lnwire.Message, error) {
// We owe them a commitment if they have an un-acked commitment and the
// tip of their chain (from our Pov) is equal to what they think their
// next commit height should be.
remoteChainTip := lc.remoteCommitChain.tip()
oweCommitment := (lc.remoteCommitChain.hasUnackedCommitment() &&
msg.NextLocalCommitHeight == remoteChainTip.height)
// We owe them a revocation if the tail of our current commitment is
// one greater than what they _think_ our commitment tail is.
localChainTail := lc.localCommitChain.tail()
oweRevocation := localChainTail.height == msg.RemoteCommitTailHeight+1
// Now we'll examine the state we have, vs what was contained in the
// chain sync message. If we're de-synchronized, then we'll send a
// batch of messages which when applied will kick start the chain
// resync.
var updates []lnwire.Message
// If the remote party included the optional fields, then we'll verify
// their correctness first, as it will influence our decisions below.
hasRecoveryOptions := msg.LocalUnrevokedCommitPoint != nil
commitSecretCorrect := true
if hasRecoveryOptions && msg.RemoteCommitTailHeight != 0 {
// We'll check that they've really sent a valid commit
// secret from our shachain for our prior height, but only if
// this isn't the first state.
heightSecret, err := lc.channelState.RevocationProducer.AtIndex(
msg.RemoteCommitTailHeight - 1,
)
if err != nil {
return nil, err
}
commitSecretCorrect = bytes.Equal(
heightSecret[:], msg.LastRemoteCommitSecret[:],
)
}
// TODO(roasbeef): check validity of commitment point after the fact
// If the commit secret they sent is incorrect then we'll fail the
// channel as the remote node has an inconsistent state.
if !commitSecretCorrect {
// In this case, we'll return an error to indicate the remote
// node sent us the wrong values. This will let the caller act
// accordingly.
return nil, ErrInvalidLastCommitSecret
}
switch {
// If we owe the remote party a revocation message, then we'll re-send
// the last revocation message that we sent. This will be the
// revocation message for our prior chain tail.
case oweRevocation:
revocationMsg, err := lc.generateRevocation(
localChainTail.height - 1,
)
if err != nil {
return nil, err
}
updates = append(updates, revocationMsg)
// Next, as a precaution, we'll check a special edge case. If
// they initiated a state transition, we sent the revocation,
// but died before the signature was sent. We re-transmit our
// revocation, but also initiate a state transition to re-sync
// them.
if lc.localCommitChain.tip().height >
lc.remoteCommitChain.tip().height {
commitSig, htlcSigs, err := lc.SignNextCommitment()
switch {
// If we signed this state, then we'll accumulate
// another update to send over.
case err == nil:
updates = append(updates, &lnwire.CommitSig{
ChanID: lnwire.NewChanIDFromOutPoint(
&lc.channelState.FundingOutpoint,
),
CommitSig: commitSig,
HtlcSigs: htlcSigs,
})
// If we get a failure due to not knowing their next
// point, then this is fine as they'll either send
// FundingLocked, or revoke their next state to allow
// us to continue forwards.
case err == ErrNoWindow:
// Otherwise, this is an error and we'll treat it as
// such.
default:
return nil, err
}
}
// If we don't owe the remote party a revocation, but their value for
// what our remote chain tail should be doesn't match up, and their
// purported commitment secrete matches up, then we'll behind!
case (msg.RemoteCommitTailHeight > localChainTail.height &&
hasRecoveryOptions && commitSecretCorrect):
// In this case, we've likely lost data and shouldn't proceed
// with channel updates. So we'll return the appropriate error
// to signal to the caller the current state.
return nil, ErrCommitSyncDataLoss
// If we don't owe them a revocation, and the height of our commitment
// chain reported by the remote party is not equal to our chain tail,
// then we cannot sync.
case !oweRevocation && localChainTail.height != msg.RemoteCommitTailHeight:
if err := lc.channelState.MarkBorked(); err != nil {
return nil, err
}
return nil, ErrCannotSyncCommitChains
}
// If we owe them a commitment, then we'll read from disk our
// commitment diff, so we can re-send them to the remote party.
if oweCommitment {
// Grab the current remote chain tip from the database. This
// commit diff contains all the information required to re-sync
// our states.
commitDiff, err := lc.channelState.RemoteCommitChainTip()
if err != nil {
return nil, err
}
// Next, we'll need to send over any updates we sent as part of
// this new proposed commitment state.
for _, logUpdate := range commitDiff.LogUpdates {
updates = append(updates, logUpdate.UpdateMsg)
}
// With the batch of updates accumulated, we'll now re-send the
// original CommitSig message required to re-sync their remote
// commitment chain with our local version of their chain.
updates = append(updates, commitDiff.CommitSig)
} else if !oweCommitment && remoteChainTip.height+1 !=
msg.NextLocalCommitHeight {
if err := lc.channelState.MarkBorked(); err != nil {
return nil, err
}
// If we don't owe them a commitment, yet the tip of their
// chain isn't one more than the next local commit height they
// report, we'll fail the channel.
return nil, ErrCannotSyncCommitChains
}
return updates, nil
}
// ChanSyncMsg returns the ChannelReestablish message that should be sent upon
// reconnection with the remote peer that we're maintaining this channel with.
// The information contained within this message is necessary to re-sync our
// commitment chains in the case of a last or only partially processed message.
// When the remote party receiver this message one of three things may happen:
//
// 1. We're fully synced and no messages need to be sent.
// 2. We didn't get the last CommitSig message they sent, to they'll re-send
// it.
// 3. We didn't get the last RevokeAndAck message they sent, so they'll
// re-send it.
func (lc *LightningChannel) ChanSyncMsg() (*lnwire.ChannelReestablish, error) {
// The remote commitment height that we we'll send in the
// ChannelReestablish message is our current commitment height plus
// one. If the receiver thinks that our commitment height is actually
// *equal* to this value, then they'll re-send the last commitment that
// they sent but we never fully processed.
localHeight := lc.localCommitChain.tip().height
nextLocalCommitHeight := localHeight + 1
// The second value we'll send is the height of the remote commitment
// from our PoV. If the receiver thinks that their height is actually
// *one plus* this value, then they'll re-send their last revocation.
remoteChainTipHeight := lc.remoteCommitChain.tail().height
// If this channel has undergone a commitment update, then in order to
// prove to the remote party our knowledge of their prior commitment
// state, we'll also send over the last commitment secret that the
// remote party sent.
var lastCommitSecret [32]byte
if remoteChainTipHeight != 0 {
remoteSecret, err := lc.channelState.RevocationStore.LookUp(
remoteChainTipHeight - 1,
)
if err != nil {
return nil, err
}
lastCommitSecret = [32]byte(*remoteSecret)
}
// Additionally, we'll send over the current unrevoked commitment on
// our local commitment transaction.
currentCommitSecret, err := lc.channelState.RevocationProducer.AtIndex(
localHeight,
)
if err != nil {
return nil, err
}
return &lnwire.ChannelReestablish{
ChanID: lnwire.NewChanIDFromOutPoint(
&lc.channelState.FundingOutpoint,
),
NextLocalCommitHeight: nextLocalCommitHeight,
RemoteCommitTailHeight: remoteChainTipHeight,
LastRemoteCommitSecret: lastCommitSecret,
LocalUnrevokedCommitPoint: ComputeCommitmentPoint(
currentCommitSecret[:],
),
}, nil
}
// validateCommitmentSanity is used to validate that on current state the commitment
// transaction is valid in terms of propagating it over Bitcoin network, and
// also that all outputs are meet Bitcoin spec requirements and they are
// spendable.
func (lc *LightningChannel) validateCommitmentSanity(theirLogCounter,
ourLogCounter uint64, prediction bool, local bool, remote bool) error {
// TODO(roasbeef): verify remaining sanity requirements
htlcCount := 0
// If we adding or receiving the htlc we increase the number of htlcs
// by one in order to not overflow the commitment transaction by
// insertion.
if prediction {
htlcCount++
}
// TODO(roasbeef): call availableBalance in here re-using htlcView
// Run through all the HTLCs that will be covered by this transaction
// in order to calculate theirs count.
view := lc.fetchHTLCView(theirLogCounter, ourLogCounter)
if remote {
for _, entry := range view.theirUpdates {
if entry.EntryType == Add {
htlcCount++
}
}
for _, entry := range view.ourUpdates {
if entry.EntryType != Add {
htlcCount--
}
}
}
if local {
for _, entry := range view.ourUpdates {
if entry.EntryType == Add {
htlcCount++
}
}
for _, entry := range view.theirUpdates {
if entry.EntryType != Add {
htlcCount--
}
}
}
// If we're validating the commitment sanity for HTLC _log_ update by a
// particular side, then we'll only consider half of the available HTLC
// bandwidth. However, if we're validating the _creation_ of a new
// commitment state, then we'll use the full value as the sum of the
// contribution of both sides shouldn't exceed the max number.
var maxHTLCNumber int
if local && remote {
maxHTLCNumber = MaxHTLCNumber
} else {
maxHTLCNumber = MaxHTLCNumber / 2
}
if htlcCount > maxHTLCNumber {
return ErrMaxHTLCNumber
}
return nil
}
// genHtlcSigValidationJobs generates a series of signatures verification jobs
// meant to verify all the signatures for HTLC's attached to a newly created
// commitment state. The jobs generated are fully populated, and can be sent
// directly into the pool of workers.
func genHtlcSigValidationJobs(localCommitmentView *commitment,
keyRing *CommitmentKeyRing, htlcSigs []lnwire.Sig,
localChanCfg, remoteChanCfg *channeldb.ChannelConfig) ([]verifyJob, error) {
// If this new commitment state doesn't have any HTLC's that are to be
// signed, then we'll return a nil slice.
if len(htlcSigs) == 0 {
return nil, nil
}
txHash := localCommitmentView.txn.TxHash()
feePerKw := localCommitmentView.feePerKw
// With the required state generated, we'll create a slice with large
// enough capacity to hold verification jobs for all HTLC's in this
// view. In the case that we have some dust outputs, then the actual
// length will be smaller than the total capacity.
numHtlcs := (len(localCommitmentView.incomingHTLCs) +
len(localCommitmentView.outgoingHTLCs))
verifyJobs := make([]verifyJob, 0, numHtlcs)
// We'll iterate through each output in the commitment transaction,
// populating the sigHash closure function if it's detected to be an
// HLTC output. Given the sighash, and the signing key, we'll be able
// to validate each signature within the worker pool.
i := 0
for index := range localCommitmentView.txn.TxOut {
var (
sigHash func() ([]byte, error)
sig *btcec.Signature
err error
)
outputIndex := int32(index)
switch {
// If this output index is found within the incoming HTLC index,
// then this means that we need to generate an HTLC success
// transaction in order to validate the signature.
case localCommitmentView.incomingHTLCIndex[outputIndex] != nil:
htlc := localCommitmentView.incomingHTLCIndex[outputIndex]
sigHash = func() ([]byte, error) {
op := wire.OutPoint{
Hash: txHash,
Index: uint32(htlc.localOutputIndex),
}
htlcFee := htlcSuccessFee(feePerKw)
outputAmt := htlc.Amount.ToSatoshis() - htlcFee
successTx, err := createHtlcSuccessTx(op,
outputAmt, uint32(localChanCfg.CsvDelay),
keyRing.RevocationKey, keyRing.DelayKey)
if err != nil {
return nil, err
}
hashCache := txscript.NewTxSigHashes(successTx)
sigHash, err := txscript.CalcWitnessSigHash(
htlc.ourWitnessScript, hashCache,
txscript.SigHashAll, successTx, 0,
int64(htlc.Amount.ToSatoshis()),
)
if err != nil {
return nil, err
}
return sigHash, nil
}
// With the sighash generated, we'll also store the
// signature so it can be written to disk if this state
// is valid.
sig, err = htlcSigs[i].ToSignature()
if err != nil {
return nil, err
}
htlc.sig = sig
// Otherwise, if this is an outgoing HTLC, then we'll need to
// generate a timeout transaction so we can verify the
// signature presented.
case localCommitmentView.outgoingHTLCIndex[outputIndex] != nil:
htlc := localCommitmentView.outgoingHTLCIndex[outputIndex]
sigHash = func() ([]byte, error) {
op := wire.OutPoint{
Hash: txHash,
Index: uint32(htlc.localOutputIndex),
}
htlcFee := htlcTimeoutFee(feePerKw)
outputAmt := htlc.Amount.ToSatoshis() - htlcFee
timeoutTx, err := createHtlcTimeoutTx(op,
outputAmt, htlc.Timeout,
uint32(localChanCfg.CsvDelay),
keyRing.RevocationKey, keyRing.DelayKey,
)
if err != nil {
return nil, err
}
hashCache := txscript.NewTxSigHashes(timeoutTx)
sigHash, err := txscript.CalcWitnessSigHash(
htlc.ourWitnessScript, hashCache,
txscript.SigHashAll, timeoutTx, 0,
int64(htlc.Amount.ToSatoshis()),
)
if err != nil {
return nil, err
}
return sigHash, nil
}
// With the sighash generated, we'll also store the
// signature so it can be written to disk if this state
// is valid.
sig, err = htlcSigs[i].ToSignature()
if err != nil {
return nil, err
}
htlc.sig = sig
default:
continue
}
verifyJobs = append(verifyJobs, verifyJob{
pubKey: keyRing.RemoteHtlcKey,
sig: sig,
sigHash: sigHash,
})
i++
}
return verifyJobs, nil
}
// InvalidCommitSigError is a struct that implements the error interface to
// report a failure to validation a commitment signature for a remote peer.
// We'll use the items in this struct to generate a rich error message for the
// remote peer when we receive an invalid signature from it. Doing so can
// greatly aide in debugging cross implementation issues.
type InvalidCommitSigError struct {
commitHeight uint64
commitSig []byte
sigHash []byte
commitTx []byte
}
// Error returns a detailed error string including the exact transaction that
// caused an invalid commitment signature.
func (i *InvalidCommitSigError) Error() string {
return fmt.Sprintf("rejected commitment: commit_height=%v, "+
"invalid_sig=%x, commit_tx=%x, sig_hash=%x", i.commitHeight,
i.commitSig[:], i.commitTx, i.sigHash[:])
}
// A compile time flag to ensure that InvalidCommitSigError implements the
// error interface.
var _ error = (*InvalidCommitSigError)(nil)
// ReceiveNewCommitment process a signature for a new commitment state sent by
// the remote party. This method should be called in response to the
// remote party initiating a new change, or when the remote party sends a
// signature fully accepting a new state we've initiated. If we are able to
// successfully validate the signature, then the generated commitment is added
// to our local commitment chain. Once we send a revocation for our prior
// state, then this newly added commitment becomes our current accepted channel
// state.
func (lc *LightningChannel) ReceiveNewCommitment(commitSig lnwire.Sig,
htlcSigs []lnwire.Sig) error {
lc.Lock()
defer lc.Unlock()
// Determine the last update on the local log that has been locked in.
localACKedIndex := lc.remoteCommitChain.tail().ourMessageIndex
localHtlcIndex := lc.remoteCommitChain.tail().ourHtlcIndex
// Ensure that this new local update from the remote node respects all
// the constraints we specified during initial channel setup. If not,
// then we'll abort the channel as they've violated our constraints.
err := lc.validateCommitmentSanity(lc.remoteUpdateLog.logIndex,
localACKedIndex, false, true, true)
if err != nil {
return err
}
// We're receiving a new commitment which attempts to extend our local
// commitment chain height by one, so fetch the proper commitment point
// as this will be needed to derive the keys required to construct the
// commitment.
nextHeight := lc.currentHeight + 1
commitSecret, err := lc.channelState.RevocationProducer.AtIndex(nextHeight)
if err != nil {
return err
}
commitPoint := ComputeCommitmentPoint(commitSecret[:])
keyRing := deriveCommitmentKeys(commitPoint, true, lc.localChanCfg,
lc.remoteChanCfg)
// With the current commitment point re-calculated, construct the new
// commitment view which includes all the entries we know of in their
// HTLC log, and up to ourLogIndex in our HTLC log.
localCommitmentView, err := lc.fetchCommitmentView(
false, localACKedIndex, localHtlcIndex,
lc.remoteUpdateLog.logIndex, lc.remoteUpdateLog.htlcCounter,
keyRing,
)
if err != nil {
return err
}
walletLog.Tracef("ChannelPoint(%v): extending local chain to height %v, "+
"local_log=%v, remote_log=%v",
lc.channelState.FundingOutpoint, localCommitmentView.height,
localACKedIndex, lc.remoteUpdateLog.logIndex)
walletLog.Tracef("ChannelPoint(%v): local chain: our_balance=%v, "+
"their_balance=%v, commit_tx: %v", lc.channelState.FundingOutpoint,
localCommitmentView.ourBalance, localCommitmentView.theirBalance,
newLogClosure(func() string {
return spew.Sdump(localCommitmentView.txn)
}),
)
// Construct the sighash of the commitment transaction corresponding to
// this newly proposed state update.
localCommitTx := localCommitmentView.txn
multiSigScript := lc.signDesc.WitnessScript
hashCache := txscript.NewTxSigHashes(localCommitTx)
sigHash, err := txscript.CalcWitnessSigHash(multiSigScript, hashCache,
txscript.SigHashAll, localCommitTx, 0,
int64(lc.channelState.Capacity))
if err != nil {
// TODO(roasbeef): fetchview has already mutated the HTLCs...
// * need to either roll-back, or make pure
return err
}
// As an optimization, we'll generate a series of jobs for the worker
// pool to verify each of the HTLc signatures presented. Once
// generated, we'll submit these jobs to the worker pool.
verifyJobs, err := genHtlcSigValidationJobs(
localCommitmentView, keyRing, htlcSigs, lc.localChanCfg,
lc.remoteChanCfg,
)
if err != nil {
return err
}
cancelChan := make(chan struct{})
verifyResps := lc.sigPool.SubmitVerifyBatch(verifyJobs, cancelChan)
// While the HTLC verification jobs are proceeding asynchronously,
// we'll ensure that the newly constructed commitment state has a valid
// signature.
verifyKey := btcec.PublicKey{
X: lc.remoteChanCfg.MultiSigKey.X,
Y: lc.remoteChanCfg.MultiSigKey.Y,
Curve: btcec.S256(),
}
cSig, err := commitSig.ToSignature()
if err != nil {
return err
}
if !cSig.Verify(sigHash, &verifyKey) {
close(cancelChan)
// If we fail to validate their commitment signature, we'll
// generate a special error to send over the protocol. We'll
// include the exact signature and commitment we failed to
// verify against in order to aide debugging.
var txBytes bytes.Buffer
localCommitTx.Serialize(&txBytes)
return &InvalidCommitSigError{
commitHeight: nextHeight,
commitSig: commitSig.ToSignatureBytes(),
sigHash: sigHash,
commitTx: txBytes.Bytes(),
}
}
// With the primary commitment transaction validated, we'll check each
// of the HTLC validation jobs.
for i := 0; i < len(verifyJobs); i++ {
// In the case that a single signature is invalid, we'll exit
// early and cancel all the outstanding verification jobs.
select {
case err := <-verifyResps:
if err != nil {
close(cancelChan)
return fmt.Errorf("invalid htlc signature: %v", err)
}
case <-lc.quit:
return fmt.Errorf("channel shutting down")
}
}
// The signature checks out, so we can now add the new commitment to
// our local commitment chain.
localCommitmentView.sig = commitSig.ToSignatureBytes()
lc.localCommitChain.addCommitment(localCommitmentView)
// If we are not channel initiator, then the commitment just received
// would've signed any received fee update since last commitment. Mark
// any such fee update as pending ACK (so we remember to ACK it on our
// next commitment), and set pendingFeeUpdate to nil. We can do this
// since we won't receive any new commitment before ACKing.
if !lc.channelState.IsInitiator {
lc.pendingAckFeeUpdate = lc.pendingFeeUpdate
lc.pendingFeeUpdate = nil
}
return nil
}
// FullySynced returns a boolean value reflecting if both commitment chains
// (remote+local) are fully in sync. Both commitment chains are fully in sync
// if the tip of each chain includes the latest committed changes from both
// sides.
func (lc *LightningChannel) FullySynced() bool {
lc.RLock()
defer lc.RUnlock()
lastLocalCommit := lc.localCommitChain.tip()
lastRemoteCommit := lc.remoteCommitChain.tip()
oweCommitment := lastLocalCommit.height > lastRemoteCommit.height
localUpdatesSynced := (lastLocalCommit.ourMessageIndex ==
lastRemoteCommit.ourMessageIndex)
remoteUpdatesSynced := (lastLocalCommit.theirMessageIndex ==
lastRemoteCommit.theirMessageIndex)
return !oweCommitment && localUpdatesSynced && remoteUpdatesSynced
}
// RevokeCurrentCommitment revokes the next lowest unrevoked commitment
// transaction in the local commitment chain. As a result the edge of our
// revocation window is extended by one, and the tail of our local commitment
// chain is advanced by a single commitment. This now lowest unrevoked
// commitment becomes our currently accepted state within the channel. This
// method also returns the set of HTLC's currently active within the commitment
// transaction. This return value allows callers to act once an HTLC has been
// locked into our commitment transaction.
func (lc *LightningChannel) RevokeCurrentCommitment() (*lnwire.RevokeAndAck, []channeldb.HTLC, error) {
lc.Lock()
defer lc.Unlock()
revocationMsg, err := lc.generateRevocation(lc.currentHeight)
if err != nil {
return nil, nil, err
}
walletLog.Tracef("ChannelPoint(%v): revoking height=%v, now at height=%v",
lc.channelState.FundingOutpoint, lc.localCommitChain.tail().height,
lc.currentHeight+1)
// Advance our tail, as we've revoked our previous state.
lc.localCommitChain.advanceTail()
lc.currentHeight++
// Additionally, generate a channel delta for this state transition for
// persistent storage.
chainTail := lc.localCommitChain.tail()
newCommitment := chainTail.toDiskCommit(true)
err = lc.channelState.UpdateCommitment(newCommitment)
if err != nil {
return nil, nil, err
}
walletLog.Tracef("ChannelPoint(%v): state transition accepted: "+
"our_balance=%v, their_balance=%v",
lc.channelState.FundingOutpoint, chainTail.ourBalance,
chainTail.theirBalance)
revocationMsg.ChanID = lnwire.NewChanIDFromOutPoint(
&lc.channelState.FundingOutpoint,
)
return revocationMsg, newCommitment.Htlcs, nil
}
// ReceiveRevocation processes a revocation sent by the remote party for the
// lowest unrevoked commitment within their commitment chain. We receive a
// revocation either during the initial session negotiation wherein revocation
// windows are extended, or in response to a state update that we initiate. If
// successful, then the remote commitment chain is advanced by a single
// commitment, and a log compaction is attempted. In addition, a slice of
// HTLC's which can be forwarded upstream are returned.
func (lc *LightningChannel) ReceiveRevocation(revMsg *lnwire.RevokeAndAck) ([]*PaymentDescriptor, error) {
lc.Lock()
defer lc.Unlock()
// Ensure that the new pre-image can be placed in preimage store.
store := lc.channelState.RevocationStore
revocation, err := chainhash.NewHash(revMsg.Revocation[:])
if err != nil {
return nil, err
}
if err := store.AddNextEntry(revocation); err != nil {
return nil, err
}
// Verify that if we use the commitment point computed based off of the
// revealed secret to derive a revocation key with our revocation base
// point, then it matches the current revocation of the remote party.
currentCommitPoint := lc.channelState.RemoteCurrentRevocation
derivedCommitPoint := ComputeCommitmentPoint(revMsg.Revocation[:])
if !derivedCommitPoint.IsEqual(currentCommitPoint) {
return nil, fmt.Errorf("revocation key mismatch")
}
// Now that we've verified that the prior commitment has been properly
// revoked, we'll advance the revocation state we track for the remote
// party: the new current revocation is what was previously the next
// revocation, and the new next revocation is set to the key included
// in the message.
lc.channelState.RemoteCurrentRevocation = lc.channelState.RemoteNextRevocation
lc.channelState.RemoteNextRevocation = revMsg.NextRevocationKey
walletLog.Tracef("ChannelPoint(%v): remote party accepted state transition, "+
"revoked height %v, now at %v", lc.channelState.FundingOutpoint,
lc.remoteCommitChain.tail().height,
lc.remoteCommitChain.tail().height+1)
// At this point, the revocation has been accepted, and we've rotated
// the current revocation key+hash for the remote party. Therefore we
// sync now to ensure the revocation producer state is consistent with
// the current commitment height and also to advance the on-disk
// commitment chain.
if err := lc.channelState.AdvanceCommitChainTail(); err != nil {
return nil, err
}
// Since they revoked the current lowest height in their commitment
// chain, we can advance their chain by a single commitment.
lc.remoteCommitChain.advanceTail()
remoteChainTail := lc.remoteCommitChain.tail().height
localChainTail := lc.localCommitChain.tail().height
// Now that we've verified the revocation update the state of the HTLC
// log as we may be able to prune portions of it now, and update their
// balance.
var htlcsToForward []*PaymentDescriptor
for e := lc.remoteUpdateLog.Front(); e != nil; e = e.Next() {
htlc := e.Value.(*PaymentDescriptor)
if htlc.isForwarded {
continue
}
uncommitted := (htlc.addCommitHeightRemote == 0 ||
htlc.addCommitHeightLocal == 0)
if htlc.EntryType == Add && uncommitted {
continue
}
// We'll only forward any new HTLC additions iff, it's "freshly
// locked in". Meaning that the HTLC was only *just* considered
// locked-in at this new state. By doing this we ensure that we
// don't re-forward any already processed HTLC's after a
// restart.
if htlc.EntryType == Add &&
remoteChainTail == htlc.addCommitHeightRemote &&
localChainTail >= htlc.addCommitHeightLocal {
htlc.isForwarded = true
htlcsToForward = append(htlcsToForward, htlc)
continue
}
if htlc.EntryType != Add &&
remoteChainTail >= htlc.removeCommitHeightRemote &&
localChainTail >= htlc.removeCommitHeightLocal {
htlc.isForwarded = true
htlcsToForward = append(htlcsToForward, htlc)
continue
}
}
// As we've just completed a new state transition, attempt to see if we
// can remove any entries from the update log which have been removed
// from the PoV of both commitment chains.
compactLogs(lc.localUpdateLog, lc.remoteUpdateLog,
localChainTail, remoteChainTail)
return htlcsToForward, nil
}
// NextRevocationKey returns the commitment point for the _next_ commitment
// height. The pubkey returned by this function is required by the remote party
// along with their revocation base to to extend our commitment chain with a
// new commitment.
func (lc *LightningChannel) NextRevocationKey() (*btcec.PublicKey, error) {
lc.RLock()
defer lc.RUnlock()
nextHeight := lc.currentHeight + 1
revocation, err := lc.channelState.RevocationProducer.AtIndex(nextHeight)
if err != nil {
return nil, err
}
return ComputeCommitmentPoint(revocation[:]), nil
}
// InitNextRevocation inserts the passed commitment point as the _next_
// revocation to be used when creating a new commitment state for the remote
// party. This function MUST be called before the channel can accept or propose
// any new states.
func (lc *LightningChannel) InitNextRevocation(revKey *btcec.PublicKey) error {
lc.Lock()
defer lc.Unlock()
return lc.channelState.InsertNextRevocation(revKey)
}
// AddHTLC adds an HTLC to the state machine's local update log. This method
// should be called when preparing to send an outgoing HTLC.
func (lc *LightningChannel) AddHTLC(htlc *lnwire.UpdateAddHTLC) (uint64, error) {
lc.Lock()
defer lc.Unlock()
if err := lc.validateCommitmentSanity(lc.remoteUpdateLog.logIndex,
lc.localUpdateLog.logIndex, true, true, false); err != nil {
return 0, err
}
// To ensure that we can actually fully accept this new HTLC, we'll
// calculate the current available bandwidth, and subtract the value of
// the HTLC from it.
initialBalance, _ := lc.availableBalance()
availableBalance := initialBalance
availableBalance -= htlc.Amount
feePerKw := lc.channelState.LocalCommitment.FeePerKw
dustLimit := lc.channelState.LocalChanCfg.DustLimit
htlcIsDust := htlcIsDust(
false, true, feePerKw, htlc.Amount.ToSatoshis(), dustLimit,
)
// If this HTLC is not dust, and we're the initiator, then we'll also
// subtract the amount we'll need to pay in fees for this HTLC.
if !htlcIsDust && lc.channelState.IsInitiator {
htlcFee := lnwire.NewMSatFromSatoshis(
btcutil.Amount((int64(feePerKw) * HtlcWeight) / 1000),
)
availableBalance -= htlcFee
}
// If this value is negative, then we can't accept the HTLC, so we'll
// reject it with an error.
if availableBalance < 0 {
// TODO(roasbeef): also needs to respect reservation
// * expand to add context err msg
walletLog.Errorf("Unable to carry added HTLC: amt=%v, bal=%v",
htlc.Amount, availableBalance)
return 0, ErrInsufficientBalance
}
pd := &PaymentDescriptor{
EntryType: Add,
RHash: PaymentHash(htlc.PaymentHash),
Timeout: htlc.Expiry,
Amount: htlc.Amount,
LogIndex: lc.localUpdateLog.logIndex,
HtlcIndex: lc.localUpdateLog.htlcCounter,
OnionBlob: htlc.OnionBlob[:],
}
lc.localUpdateLog.appendHtlc(pd)
return pd.HtlcIndex, nil
}
// ReceiveHTLC adds an HTLC to the state machine's remote update log. This
// method should be called in response to receiving a new HTLC from the remote
// party.
func (lc *LightningChannel) ReceiveHTLC(htlc *lnwire.UpdateAddHTLC) (uint64, error) {
lc.Lock()
defer lc.Unlock()
if htlc.ID != lc.remoteUpdateLog.htlcCounter {
return 0, fmt.Errorf("ID %d on HTLC add does not match expected next "+
"ID %d", htlc.ID, lc.remoteUpdateLog.htlcCounter)
}
if err := lc.validateCommitmentSanity(lc.remoteUpdateLog.logIndex,
lc.localUpdateLog.logIndex, true, false, true); err != nil {
return 0, err
}
pd := &PaymentDescriptor{
EntryType: Add,
RHash: PaymentHash(htlc.PaymentHash),
Timeout: htlc.Expiry,
Amount: htlc.Amount,
LogIndex: lc.remoteUpdateLog.logIndex,
HtlcIndex: lc.remoteUpdateLog.htlcCounter,
OnionBlob: htlc.OnionBlob[:],
}
lc.remoteUpdateLog.appendHtlc(pd)
return pd.HtlcIndex, nil
}
// SettleHTLC attempts to settle an existing outstanding received HTLC. The
// remote log index of the HTLC settled is returned in order to facilitate
// creating the corresponding wire message. In the case the supplied preimage
// is invalid, an error is returned. Additionally, the value of the settled
// HTLC is also returned.
func (lc *LightningChannel) SettleHTLC(preimage [32]byte, htlcIndex uint64,
) error {
lc.Lock()
defer lc.Unlock()
htlc := lc.remoteUpdateLog.lookupHtlc(htlcIndex)
if htlc == nil {
return fmt.Errorf("No HTLC with ID %d in channel %v", htlcIndex,
lc.channelState.ShortChanID)
}
if htlc.RHash != sha256.Sum256(preimage[:]) {
return fmt.Errorf("Invalid payment preimage %x for hash %x",
preimage[:], htlc.RHash[:])
}
pd := &PaymentDescriptor{
Amount: htlc.Amount,
RPreimage: preimage,
LogIndex: lc.localUpdateLog.logIndex,
ParentIndex: htlcIndex,
EntryType: Settle,
}
lc.localUpdateLog.appendUpdate(pd)
return nil
}
// ReceiveHTLCSettle attempts to settle an existing outgoing HTLC indexed by an
// index into the local log. If the specified index doesn't exist within the
// log, and error is returned. Similarly if the preimage is invalid w.r.t to
// the referenced of then a distinct error is returned.
func (lc *LightningChannel) ReceiveHTLCSettle(preimage [32]byte, htlcIndex uint64) error {
lc.Lock()
defer lc.Unlock()
htlc := lc.localUpdateLog.lookupHtlc(htlcIndex)
if htlc == nil {
return fmt.Errorf("No HTLC with ID %d in channel %v", htlcIndex,
lc.channelState.ShortChanID)
}
if htlc.RHash != sha256.Sum256(preimage[:]) {
return fmt.Errorf("Invalid payment preimage %x for hash %x",
preimage[:], htlc.RHash[:])
}
pd := &PaymentDescriptor{
Amount: htlc.Amount,
RPreimage: preimage,
ParentIndex: htlc.HtlcIndex,
RHash: htlc.RHash,
LogIndex: lc.remoteUpdateLog.logIndex,
EntryType: Settle,
}
lc.remoteUpdateLog.appendUpdate(pd)
return nil
}
// FailHTLC attempts to fail a targeted HTLC by its payment hash, inserting an
// entry which will remove the target log entry within the next commitment
// update. This method is intended to be called in order to cancel in
// _incoming_ HTLC.
func (lc *LightningChannel) FailHTLC(htlcIndex uint64, reason []byte) error {
lc.Lock()
defer lc.Unlock()
htlc := lc.remoteUpdateLog.lookupHtlc(htlcIndex)
if htlc == nil {
return fmt.Errorf("No HTLC with ID %d in channel %v", htlcIndex,
lc.channelState.ShortChanID)
}
pd := &PaymentDescriptor{
Amount: htlc.Amount,
RHash: htlc.RHash,
ParentIndex: htlcIndex,
LogIndex: lc.localUpdateLog.logIndex,
EntryType: Fail,
FailReason: reason,
}
lc.localUpdateLog.appendUpdate(pd)
return nil
}
// MalformedFailHTLC attempts to fail a targeted HTLC by its payment hash,
// inserting an entry which will remove the target log entry within the next
// commitment update. This method is intended to be called in order to cancel
// in _incoming_ HTLC.
func (lc *LightningChannel) MalformedFailHTLC(htlcIndex uint64,
failCode lnwire.FailCode, shaOnionBlob [sha256.Size]byte) error {
lc.Lock()
defer lc.Unlock()
htlc := lc.remoteUpdateLog.lookupHtlc(htlcIndex)
if htlc == nil {
return fmt.Errorf("No HTLC with ID %d in channel %v", htlcIndex,
lc.channelState.ShortChanID)
}
pd := &PaymentDescriptor{
Amount: htlc.Amount,
RHash: htlc.RHash,
ParentIndex: htlcIndex,
LogIndex: lc.localUpdateLog.logIndex,
EntryType: MalformedFail,
FailCode: failCode,
ShaOnionBlob: shaOnionBlob,
}
lc.localUpdateLog.appendUpdate(pd)
return nil
}
// ReceiveFailHTLC attempts to cancel a targeted HTLC by its log index,
// inserting an entry which will remove the target log entry within the next
// commitment update. This method should be called in response to the upstream
// party cancelling an outgoing HTLC. The value of the failed HTLC is returned
// along with an error indicating success.
func (lc *LightningChannel) ReceiveFailHTLC(htlcIndex uint64, reason []byte,
) error {
lc.Lock()
defer lc.Unlock()
htlc := lc.localUpdateLog.lookupHtlc(htlcIndex)
if htlc == nil {
return fmt.Errorf("No HTLC with ID %d in channel %v", htlcIndex,
lc.channelState.ShortChanID)
}
pd := &PaymentDescriptor{
Amount: htlc.Amount,
RHash: htlc.RHash,
ParentIndex: htlc.HtlcIndex,
LogIndex: lc.remoteUpdateLog.logIndex,
EntryType: Fail,
FailReason: reason,
}
lc.remoteUpdateLog.appendUpdate(pd)
return nil
}
// ChannelPoint returns the outpoint of the original funding transaction which
// created this active channel. This outpoint is used throughout various
// subsystems to uniquely identify an open channel.
func (lc *LightningChannel) ChannelPoint() *wire.OutPoint {
lc.RLock()
defer lc.RUnlock()
return &lc.channelState.FundingOutpoint
}
// ShortChanID returns the short channel ID for the channel. The short channel
// ID encodes the exact location in the main chain that the original
// funding output can be found.
func (lc *LightningChannel) ShortChanID() lnwire.ShortChannelID {
lc.RLock()
defer lc.RUnlock()
return lc.channelState.ShortChanID
}
// genHtlcScript generates the proper P2WSH public key scripts for the HTLC
// output modified by two-bits denoting if this is an incoming HTLC, and if the
// HTLC is being applied to their commitment transaction or ours.
func genHtlcScript(isIncoming, ourCommit bool, timeout uint32, rHash [32]byte,
keyRing *CommitmentKeyRing) ([]byte, []byte, error) {
var (
witnessScript []byte
err error
)
// Generate the proper redeem scripts for the HTLC output modified by
// two-bits denoting if this is an incoming HTLC, and if the HTLC is
// being applied to their commitment transaction or ours.
switch {
// The HTLC is paying to us, and being applied to our commitment
// transaction. So we need to use the receiver's version of HTLC the
// script.
case isIncoming && ourCommit:
witnessScript, err = receiverHTLCScript(timeout,
keyRing.RemoteHtlcKey, keyRing.LocalHtlcKey,
keyRing.RevocationKey, rHash[:])
// We're being paid via an HTLC by the remote party, and the HTLC is
// being added to their commitment transaction, so we use the sender's
// version of the HTLC script.
case isIncoming && !ourCommit:
witnessScript, err = senderHTLCScript(keyRing.RemoteHtlcKey,
keyRing.LocalHtlcKey, keyRing.RevocationKey, rHash[:])
// We're sending an HTLC which is being added to our commitment
// transaction. Therefore, we need to use the sender's version of the
// HTLC script.
case !isIncoming && ourCommit:
witnessScript, err = senderHTLCScript(keyRing.LocalHtlcKey,
keyRing.RemoteHtlcKey, keyRing.RevocationKey, rHash[:])
// Finally, we're paying the remote party via an HTLC, which is being
// added to their commitment transaction. Therefore, we use the
// receiver's version of the HTLC script.
case !isIncoming && !ourCommit:
witnessScript, err = receiverHTLCScript(timeout, keyRing.LocalHtlcKey,
keyRing.RemoteHtlcKey, keyRing.RevocationKey, rHash[:])
}
if err != nil {
return nil, nil, err
}
// Now that we have the redeem scripts, create the P2WSH public key
// script for the output itself.
htlcP2WSH, err := witnessScriptHash(witnessScript)
if err != nil {
return nil, nil, err
}
return htlcP2WSH, witnessScript, nil
}
// addHTLC adds a new HTLC to the passed commitment transaction. One of four
// full scripts will be generated for the HTLC output depending on if the HTLC
// is incoming and if it's being applied to our commitment transaction or that
// of the remote node's. Additionally, in order to be able to efficiently
// locate the added HTLC on the commitment transaction from the
// PaymentDescriptor that generated it, the generated script is stored within
// the descriptor itself.
func (lc *LightningChannel) addHTLC(commitTx *wire.MsgTx, ourCommit bool,
isIncoming bool, paymentDesc *PaymentDescriptor,
keyRing *CommitmentKeyRing) error {
timeout := paymentDesc.Timeout
rHash := paymentDesc.RHash
p2wsh, witnessScript, err := genHtlcScript(isIncoming, ourCommit,
timeout, rHash, keyRing)
if err != nil {
return err
}
// Add the new HTLC outputs to the respective commitment transactions.
amountPending := int64(paymentDesc.Amount.ToSatoshis())
commitTx.AddTxOut(wire.NewTxOut(amountPending, p2wsh))
// Store the pkScript of this particular PaymentDescriptor so we can
// quickly locate it within the commitment transaction later.
if ourCommit {
paymentDesc.ourPkScript = p2wsh
paymentDesc.ourWitnessScript = witnessScript
} else {
paymentDesc.theirPkScript = p2wsh
paymentDesc.theirWitnessScript = witnessScript
}
return nil
}
// getSignedCommitTx function take the latest commitment transaction and
// populate it with witness data.
func (lc *LightningChannel) getSignedCommitTx() (*wire.MsgTx, error) {
// Fetch the current commitment transaction, along with their signature
// for the transaction.
localCommit := lc.channelState.LocalCommitment
commitTx := localCommit.CommitTx
theirSig := append(localCommit.CommitSig, byte(txscript.SigHashAll))
// With this, we then generate the full witness so the caller can
// broadcast a fully signed transaction.
lc.signDesc.SigHashes = txscript.NewTxSigHashes(commitTx)
ourSigRaw, err := lc.signer.SignOutputRaw(commitTx, lc.signDesc)
if err != nil {
return nil, err
}
ourSig := append(ourSigRaw, byte(txscript.SigHashAll))
// With the final signature generated, create the witness stack
// required to spend from the multi-sig output.
ourKey := lc.localChanCfg.MultiSigKey.SerializeCompressed()
theirKey := lc.remoteChanCfg.MultiSigKey.SerializeCompressed()
commitTx.TxIn[0].Witness = SpendMultiSig(
lc.signDesc.WitnessScript, ourKey,
ourSig, theirKey, theirSig,
)
return commitTx, nil
}
// CommitOutputResolution carries the necessary information required to allow
// us to sweep our direct commitment output in the case that either party goes
// to chain.
type CommitOutputResolution struct {
// SelfOutPoint is the full outpoint that points to out pay-to-self
// output within the closing commitment transaction.
SelfOutPoint wire.OutPoint
// SelfOutputSignDesc is a fully populated sign descriptor capable of
// generating a valid signature to sweep the output paying to us.
SelfOutputSignDesc SignDescriptor
// MaturityDelay is the relative time-lock, in blocks for all outputs
// that pay to the local party within the broadcast commitment
// transaction. This value will be non-zero iff, this output was on our
// commitment transaction.
MaturityDelay uint32
}
// UnilateralCloseSummary describes the details of a detected unilateral
// channel closure. This includes the information about with which
// transactions, and block the channel was unilaterally closed, as well as
// summarization details concerning the _state_ of the channel at the point of
// channel closure. Additionally, if we had a commitment output above dust on
// the remote party's commitment transaction, the necessary a SignDescriptor
// with the material necessary to seep the output are returned. Finally, if we
// had any outgoing HTLC's within the commitment transaction, then an
// OutgoingHtlcResolution for each output will included.
type UnilateralCloseSummary struct {
// SpendDetail is a struct that describes how and when the commitment
// output was spent.
*chainntnfs.SpendDetail
// ChannelCloseSummary is a struct describing the final state of the
// channel and in which state is was closed.
channeldb.ChannelCloseSummary
// CommitResolution contains all the data required to sweep the output
// to ourselves. If this is our commitment transaction, then we'll need
// to wait a time delay before we can sweep the output.
//
// NOTE: If our commitment delivery output is below the dust limit,
// then this will be nil.
CommitResolution *CommitOutputResolution
// HtlcResolutions contains a fully populated HtlcResolutions struct
// which contains all the data required to sweep any outgoing HTLC's,
// and also any incoming HTLC's that we know the pre-image to.
HtlcResolutions *HtlcResolutions
// RemoteCommit is the exact commitment state that the remote party
// broadcast.
RemoteCommit channeldb.ChannelCommitment
}
// NewUnilateralCloseSummary creates a new summary that provides the caller
// with all the information required to claim all funds on chain in the event
// that the remote party broadcasts their commitment.
func NewUnilateralCloseSummary(chanState *channeldb.OpenChannel, signer Signer,
pCache PreimageCache, commitSpend *chainntnfs.SpendDetail,
remoteCommit channeldb.ChannelCommitment) (*UnilateralCloseSummary, error) {
// First, we'll generate the commitment point and the revocation point
// so we can re-construct the HTLC state and also our payment key.
commitPoint := chanState.RemoteCurrentRevocation
keyRing := deriveCommitmentKeys(
commitPoint, false, &chanState.LocalChanCfg,
&chanState.RemoteChanCfg,
)
// Next, we'll obtain HTLC resolutions for all the outgoing HTLC's we
// had on their commitment transaction.
htlcResolutions, err := extractHtlcResolutions(
remoteCommit.FeePerKw, false, signer, remoteCommit.Htlcs,
keyRing, &chanState.LocalChanCfg, &chanState.RemoteChanCfg,
*commitSpend.SpenderTxHash, pCache,
)
if err != nil {
return nil, fmt.Errorf("unable to create htlc resolutions: %v", err)
}
commitTxBroadcast := commitSpend.SpendingTx
// Before we can generate the proper sign descriptor, we'll need to
// locate the output index of our non-delayed output on the commitment
// transaction.
selfP2WKH, err := commitScriptUnencumbered(keyRing.NoDelayKey)
if err != nil {
return nil, fmt.Errorf("unable to create self commit script: %v", err)
}
var selfPoint *wire.OutPoint
for outputIndex, txOut := range commitTxBroadcast.TxOut {
if bytes.Equal(txOut.PkScript, selfP2WKH) {
selfPoint = &wire.OutPoint{
Hash: *commitSpend.SpenderTxHash,
Index: uint32(outputIndex),
}
break
}
}
// With the HTLC's taken care of, we'll generate the sign descriptor
// necessary to sweep our commitment output, but only if we had a
// non-trimmed balance.
var commitResolution *CommitOutputResolution
if selfPoint != nil {
localPayBase := chanState.LocalChanCfg.PaymentBasePoint
localBalance := remoteCommit.LocalBalance.ToSatoshis()
commitResolution = &CommitOutputResolution{
SelfOutPoint: *selfPoint,
SelfOutputSignDesc: SignDescriptor{
PubKey: localPayBase,
SingleTweak: keyRing.LocalCommitKeyTweak,
WitnessScript: selfP2WKH,
Output: &wire.TxOut{
Value: int64(localBalance),
PkScript: selfP2WKH,
},
HashType: txscript.SigHashAll,
},
MaturityDelay: 0,
}
}
localBalance := remoteCommit.LocalBalance.ToSatoshis()
closeSummary := channeldb.ChannelCloseSummary{
ChanPoint: chanState.FundingOutpoint,
ChainHash: chanState.ChainHash,
ClosingTXID: *commitSpend.SpenderTxHash,
CloseHeight: uint32(commitSpend.SpendingHeight),
RemotePub: chanState.IdentityPub,
Capacity: chanState.Capacity,
SettledBalance: localBalance,
CloseType: channeldb.ForceClose,
IsPending: true,
}
return &UnilateralCloseSummary{
SpendDetail: commitSpend,
ChannelCloseSummary: closeSummary,
CommitResolution: commitResolution,
HtlcResolutions: htlcResolutions,
RemoteCommit: remoteCommit,
}, nil
}
// IncomingHtlcResolution houses the information required to sweep any incoming
// HTLC's that we know the preimage to. We'll need to sweep an HTLC manually
// using this struct if we need to go on-chain for any reason, or if we detect
// that the remote party broadcasts their commitment transaction.
type IncomingHtlcResolution struct {
// Preimage is the preimage that will be used to satisfy the contract
// of the HTLC.
//
// NOTE: This field will only be populated if we know the preimage at
// the time a unilateral or force close occurs.
Preimage [32]byte
// SignedSuccessTx is the fully signed HTLC success transaction. This
// transaction (if non-nil) can be broadcast immediately. After a csv
// delay (included below), then the output created by this transactions
// can be swept on-chain.
//
// NOTE: If this field is nil, then this indicates that we don't need
// to go to the second level to claim this HTLC. Instead, it can be
// claimed directly from the outpoint listed below.
SignedSuccessTx *wire.MsgTx
// CsvDelay is the relative time lock (expressed in blocks) that must
// pass after the SignedSuccessTx is confirmed in the chain before the
// output can be swept.
//
// NOTE: If SignedSuccessTx is nil, then this field isn't needed.
CsvDelay uint32
// ClaimOutpoint is the final outpoint that needs to be spent in order
// to fully sweep the HTLC. The SignDescriptor below should be used to
// spend this outpoint. In the case of a second-level HTLC (non-nil
// SignedTimeoutTx), then we'll be spending a new transaction.
// Otherwise, it'll be an output in the commitment transaction.
ClaimOutpoint wire.OutPoint
// SweepSignDesc is a sign descriptor that has been populated with the
// necessary items required to spend the sole output of the above
// transaction.
SweepSignDesc SignDescriptor
}
// OutgoingHtlcResolution houses the information necessary to sweep any
// outgoing HTLC's after their contract has expired. This struct will be needed
// in one of two cases: the local party force closes the commitment transaction
// or the remote party unilaterally closes with their version of the commitment
// transaction.
type OutgoingHtlcResolution struct {
// Expiry the absolute timeout of the HTLC. This value is expressed in
// block height, meaning after this height the HLTC can be swept.
Expiry uint32
// SignedTimeoutTx is the fully signed HTLC timeout transaction. This
// must be broadcast immediately after timeout has passed. Once this
// has been confirmed, the HTLC output will transition into the
// delay+claim state.
//
// NOTE: If this field is nil, then this indicates that we don't need
// to go to the second level to claim this HTLC. Instead, it can be
// claimed directly from the outpoint listed below.
SignedTimeoutTx *wire.MsgTx
// CsvDelay is the relative time lock (expressed in blocks) that must
// pass after the SignedTimeoutTx is confirmed in the chain before the
// output can be swept.
//
// NOTE: If SignedTimeoutTx is nil, then this field isn't needed.
CsvDelay uint32
// ClaimOutpoint is the final outpoint that needs to be spent in order
// to fully sweep the HTLC. The SignDescriptor below should be used to
// spend this outpoint. In the case of a second-level HTLC (non-nil
// SignedTimeoutTx), then we'll be spending a new transaction.
// Otherwise, it'll be an output in the commitment transaction.
ClaimOutpoint wire.OutPoint
// SweepSignDesc is a sign descriptor that has been populated with the
// necessary items required to spend the sole output of the above
// transaction.
SweepSignDesc SignDescriptor
}
// HtlcResolutions contains the items necessary to sweep HTLC's on chain
// directly from a commitment transaction. We'll use this in case either party
// goes broadcasts a commitment transaction with live HTLC's.
type HtlcResolutions struct {
// IncomingHTLCs contains a set of structs that can be used to sweep
// all the incoming HTL'C that we know the preimage to.
IncomingHTLCs []IncomingHtlcResolution
// OutgoingHTLCs contains a set of structs that contains all the info
// needed to sweep an outgoing HTLC we've sent to the remote party
// after an absolute delay has expired.
OutgoingHTLCs []OutgoingHtlcResolution
}
// newOutgoingHtlcResolution generates a new HTLC resolution capable of
// allowing the caller to sweep an outgoing HTLC present on either their, or
// the remote party's commitment transaction.
func newOutgoingHtlcResolution(signer Signer, localChanCfg *channeldb.ChannelConfig,
commitHash chainhash.Hash, htlc *channeldb.HTLC, keyRing *CommitmentKeyRing,
feePewKw, dustLimit btcutil.Amount, csvDelay uint32, localCommit bool,
) (*OutgoingHtlcResolution, error) {
op := wire.OutPoint{
Hash: commitHash,
Index: uint32(htlc.OutputIndex),
}
// If we're spending this HTLC output from the remote node's
// commitment, then we won't need to go to the second level as our
// outputs don't have a CSV delay.
if !localCommit {
// First, we'll re-generate the script used to send the HTLC to
// the remote party within their commitment transaction.
htlcReceiverScript, err := receiverHTLCScript(htlc.RefundTimeout,
keyRing.LocalHtlcKey, keyRing.RemoteHtlcKey,
keyRing.RevocationKey, htlc.RHash[:],
)
if err != nil {
return nil, err
}
htlcScriptHash, err := witnessScriptHash(htlcReceiverScript)
if err != nil {
return nil, err
}
// With the script generated, we can completely populated the
// SignDescriptor needed to sweep the output.
return &OutgoingHtlcResolution{
Expiry: htlc.RefundTimeout,
ClaimOutpoint: op,
SweepSignDesc: SignDescriptor{
PubKey: localChanCfg.HtlcBasePoint,
SingleTweak: keyRing.LocalHtlcKeyTweak,
WitnessScript: htlcReceiverScript,
Output: &wire.TxOut{
PkScript: htlcScriptHash,
Value: int64(htlc.Amt.ToSatoshis()),
},
HashType: txscript.SigHashAll,
},
}, nil
}
// Otherwise, we'll need to craft a second level HTLC transaction, as
// well as a sign desc to sweep after the CSV delay.
// In order to properly reconstruct the HTLC transaction, we'll need to
// re-calculate the fee required at this state, so we can add the
// correct output value amount to the transaction.
htlcFee := htlcTimeoutFee(feePewKw)
secondLevelOutputAmt := htlc.Amt.ToSatoshis() - htlcFee
// With the fee calculated, re-construct the second level timeout
// transaction.
timeoutTx, err := createHtlcTimeoutTx(
op, secondLevelOutputAmt, htlc.RefundTimeout, csvDelay,
keyRing.RevocationKey, keyRing.DelayKey,
)
if err != nil {
return nil, err
}
// With the transaction created, we can generate a sign descriptor
// that's capable of generating the signature required to spend the
// HTLC output using the timeout transaction.
htlcCreationScript, err := senderHTLCScript(keyRing.LocalHtlcKey,
keyRing.RemoteHtlcKey, keyRing.RevocationKey, htlc.RHash[:])
if err != nil {
return nil, err
}
timeoutSignDesc := SignDescriptor{
PubKey: localChanCfg.HtlcBasePoint,
SingleTweak: keyRing.LocalHtlcKeyTweak,
WitnessScript: htlcCreationScript,
Output: &wire.TxOut{
Value: int64(htlc.Amt.ToSatoshis()),
},
HashType: txscript.SigHashAll,
SigHashes: txscript.NewTxSigHashes(timeoutTx),
InputIndex: 0,
}
// With the sign desc created, we can now construct the full witness
// for the timeout transaction, and populate it as well.
timeoutWitness, err := senderHtlcSpendTimeout(
htlc.Signature, signer, &timeoutSignDesc, timeoutTx)
if err != nil {
return nil, err
}
timeoutTx.TxIn[0].Witness = timeoutWitness
// Finally, we'll generate the script output that the timeout
// transaction creates so we can generate the signDesc required to
// complete the claim process after a delay period.
htlcSweepScript, err := secondLevelHtlcScript(
keyRing.RevocationKey, keyRing.DelayKey, csvDelay,
)
if err != nil {
return nil, err
}
htlcScriptHash, err := witnessScriptHash(htlcSweepScript)
if err != nil {
return nil, err
}
localDelayTweak := SingleTweakBytes(keyRing.CommitPoint,
localChanCfg.DelayBasePoint)
return &OutgoingHtlcResolution{
Expiry: htlc.RefundTimeout,
SignedTimeoutTx: timeoutTx,
CsvDelay: csvDelay,
ClaimOutpoint: wire.OutPoint{
Hash: timeoutTx.TxHash(),
Index: 0,
},
SweepSignDesc: SignDescriptor{
PubKey: localChanCfg.DelayBasePoint,
SingleTweak: localDelayTweak,
WitnessScript: htlcSweepScript,
Output: &wire.TxOut{
PkScript: htlcScriptHash,
Value: int64(secondLevelOutputAmt),
},
HashType: txscript.SigHashAll,
},
}, nil
}
// newIncomingHtlcResolution creates a new HTLC resolution capable of allowing
// the caller to sweep an incoming HTLC. If the HTLC is on the caller's
// commitment transaction, then they'll need to broadcast a second-level
// transaction before sweeping the output (and incur a CSV delay). Otherwise,
// they can just sweep the output immediately with knowledge of the pre-image.
//
// TODO(roasbeef) consolidate code with above func
func newIncomingHtlcResolution(signer Signer, localChanCfg *channeldb.ChannelConfig,
commitHash chainhash.Hash, htlc *channeldb.HTLC, keyRing *CommitmentKeyRing,
feePewKw, dustLimit btcutil.Amount, csvDelay uint32, localCommit bool,
preimage [32]byte,
) (*IncomingHtlcResolution, error) {
op := wire.OutPoint{
Hash: commitHash,
Index: uint32(htlc.OutputIndex),
}
// If we're spending this output from the remote node's commitment,
// then we can skip the second layer and spend the output directly.
if !localCommit {
// First, we'll re-generate the script the remote party used to
// send the HTLC to us in their commitment transaction.
htlcSenderScript, err := senderHTLCScript(
keyRing.RemoteHtlcKey, keyRing.LocalHtlcKey,
keyRing.RevocationKey, htlc.RHash[:],
)
if err != nil {
return nil, err
}
htlcScriptHash, err := witnessScriptHash(htlcSenderScript)
if err != nil {
return nil, err
}
// With the script generated, we can completely populated the
// SignDescriptor needed to sweep the output.
return &IncomingHtlcResolution{
Preimage: preimage,
ClaimOutpoint: op,
CsvDelay: csvDelay,
SweepSignDesc: SignDescriptor{
PubKey: localChanCfg.HtlcBasePoint,
SingleTweak: keyRing.LocalHtlcKeyTweak,
WitnessScript: htlcSenderScript,
Output: &wire.TxOut{
PkScript: htlcScriptHash,
Value: int64(htlc.Amt.ToSatoshis()),
},
HashType: txscript.SigHashAll,
},
}, nil
}
// Otherwise, we'll need to go to the second level to sweep this HTLC.
// First, we'll reconstruct the original HTLC success transaction,
// taking into account the fee rate used.
htlcFee := htlcSuccessFee(feePewKw)
secondLevelOutputAmt := htlc.Amt.ToSatoshis() - htlcFee
successTx, err := createHtlcSuccessTx(
op, secondLevelOutputAmt, csvDelay,
keyRing.RevocationKey, keyRing.DelayKey,
)
if err != nil {
return nil, err
}
// Once we've created the second-level transaction, we'll generate the
// SignDesc needed spend the HTLC output using the success transaction.
htlcCreationScript, err := receiverHTLCScript(htlc.RefundTimeout,
keyRing.RemoteHtlcKey, keyRing.LocalHtlcKey,
keyRing.RevocationKey, htlc.RHash[:],
)
if err != nil {
return nil, err
}
successSignDesc := SignDescriptor{
PubKey: localChanCfg.HtlcBasePoint,
SingleTweak: keyRing.LocalHtlcKeyTweak,
WitnessScript: htlcCreationScript,
Output: &wire.TxOut{
Value: int64(htlc.Amt.ToSatoshis()),
},
HashType: txscript.SigHashAll,
SigHashes: txscript.NewTxSigHashes(successTx),
InputIndex: 0,
}
// Next, we'll construct the full witness needed to satisfy the input
// of the success transaction.
successWitness, err := receiverHtlcSpendRedeem(
htlc.Signature, preimage[:], signer, &successSignDesc, successTx,
)
if err != nil {
return nil, err
}
successTx.TxIn[0].Witness = successWitness
// Finally, we'll generate the script that the second-level transaction
// creates so we can generate the proper signDesc to sweep it after the
// CSV delay has passed.
htlcSweepScript, err := secondLevelHtlcScript(
keyRing.RevocationKey, keyRing.DelayKey, csvDelay,
)
if err != nil {
return nil, err
}
htlcScriptHash, err := witnessScriptHash(htlcSweepScript)
if err != nil {
return nil, err
}
localDelayTweak := SingleTweakBytes(
keyRing.CommitPoint, localChanCfg.DelayBasePoint,
)
return &IncomingHtlcResolution{
Preimage: preimage,
SignedSuccessTx: successTx,
CsvDelay: csvDelay,
ClaimOutpoint: wire.OutPoint{
Hash: successTx.TxHash(),
Index: 0,
},
SweepSignDesc: SignDescriptor{
PubKey: localChanCfg.DelayBasePoint,
SingleTweak: localDelayTweak,
WitnessScript: htlcSweepScript,
Output: &wire.TxOut{
PkScript: htlcScriptHash,
Value: int64(secondLevelOutputAmt),
},
HashType: txscript.SigHashAll,
},
}, nil
}
// extractHtlcResolutions creates a series of outgoing HTLC resolutions, and
// the local key used when generating the HTLC scrips. This function is to be
// used in two cases: force close, or a unilateral close.
func extractHtlcResolutions(feePerKw btcutil.Amount, ourCommit bool,
signer Signer, htlcs []channeldb.HTLC, keyRing *CommitmentKeyRing,
localChanCfg, remoteChanCfg *channeldb.ChannelConfig,
commitHash chainhash.Hash, pCache PreimageCache) (*HtlcResolutions, error) {
// TODO(roasbeef): don't need to swap csv delay?
dustLimit := remoteChanCfg.DustLimit
csvDelay := remoteChanCfg.CsvDelay
if ourCommit {
dustLimit = localChanCfg.DustLimit
csvDelay = localChanCfg.CsvDelay
}
incomingResolutions := make([]IncomingHtlcResolution, 0, len(htlcs))
outgoingResolutions := make([]OutgoingHtlcResolution, 0, len(htlcs))
for _, htlc := range htlcs {
// We'll skip any HTLC's which were dust on the commitment
// transaction, as these don't have a corresponding output
// within the commitment transaction.
if htlcIsDust(htlc.Incoming, ourCommit, feePerKw,
htlc.Amt.ToSatoshis(), dustLimit) {
continue
}
// If the HTLC is incoming, then we'll attempt to see if we
// know the pre-image to the HTLC.
if htlc.Incoming {
// We'll now query the preimage cache for the preimage
// for this HTLC. If it's present then we can fully
// populate this resolution.
preimage, _ := pCache.LookupPreimage(htlc.RHash[:])
// Otherwise, we'll create an incoming HTLC resolution
// as we can satisfy the contract.
var pre [32]byte
copy(pre[:], preimage)
ihr, err := newIncomingHtlcResolution(
signer, localChanCfg, commitHash, &htlc, keyRing,
feePerKw, dustLimit, uint32(csvDelay), ourCommit,
pre,
)
if err != nil {
return nil, err
}
incomingResolutions = append(incomingResolutions, *ihr)
continue
}
ohr, err := newOutgoingHtlcResolution(
signer, localChanCfg, commitHash, &htlc, keyRing,
feePerKw, dustLimit, uint32(csvDelay), ourCommit,
)
if err != nil {
return nil, err
}
outgoingResolutions = append(outgoingResolutions, *ohr)
}
return &HtlcResolutions{
IncomingHTLCs: incomingResolutions,
OutgoingHTLCs: outgoingResolutions,
}, nil
}
// ForceCloseSummary describes the final commitment state before the channel is
// locked-down to initiate a force closure by broadcasting the latest state
// on-chain. The summary includes all the information required to claim all
// rightfully owned outputs.
type ForceCloseSummary struct {
// ChanPoint is the outpoint that created the channel which has been
// force closed.
ChanPoint wire.OutPoint
// CloseTx is the transaction which closed the channel on-chain. If we
// initiate the force close, then this will be our latest commitment
// state. Otherwise, this will be the state that the remote peer
// broadcasted on-chain.
CloseTx *wire.MsgTx
// CommitResolution contains all the data required to sweep the output
// to ourselves. If this is our commitment transaction, then we'll need
// to wait a time delay before we can sweep the output.
//
// NOTE: If our commitment delivery output is below the dust limit,
// then this will be nil.
CommitResolution *CommitOutputResolution
// HtlcResolutions contains all the data required to sweep any outgoing
// HTLC's and incoming HTLc's we now the preimage to. For each of these
// HTLC's, we'll need to go to the second level to sweep them fully.
HtlcResolutions *HtlcResolutions
// ChanSnapshot is a snapshot of the final state of the channel at the
// time it was closed.
ChanSnapshot channeldb.ChannelSnapshot
}
// ForceClose executes a unilateral closure of the transaction at the current
// lowest commitment height of the channel. Following a force closure, all
// state transitions, or modifications to the state update logs will be
// rejected. Additionally, this function also returns a ForceCloseSummary which
// includes the necessary details required to sweep all the time-locked within
// the commitment transaction.
//
// TODO(roasbeef): all methods need to abort if in dispute state
// TODO(roasbeef): method to generate CloseSummaries for when the remote peer
// does a unilateral close
func (lc *LightningChannel) ForceClose() (*ForceCloseSummary, error) {
lc.Lock()
defer lc.Unlock()
// Set the channel state to indicate that the channel is now in a
// contested state.
lc.status = channelDispute
commitTx, err := lc.getSignedCommitTx()
if err != nil {
return nil, err
}
// Re-derive the original pkScript for to-self output within the
// commitment transaction. We'll need this to find the corresponding
// output in the commitment transaction and potentially for creating
// the sign descriptor.
csvTimeout := uint32(lc.localChanCfg.CsvDelay)
unusedRevocation, err := lc.channelState.RevocationProducer.AtIndex(
lc.currentHeight,
)
if err != nil {
return nil, err
}
commitPoint := ComputeCommitmentPoint(unusedRevocation[:])
keyRing := deriveCommitmentKeys(commitPoint, true, lc.localChanCfg,
lc.remoteChanCfg)
selfScript, err := commitScriptToSelf(csvTimeout, keyRing.DelayKey,
keyRing.RevocationKey)
if err != nil {
return nil, err
}
payToUsScriptHash, err := witnessScriptHash(selfScript)
if err != nil {
return nil, err
}
// Locate the output index of the delayed commitment output back to us.
// We'll return the details of this output to the caller so they can
// sweep it once it's mature.
var (
delayIndex uint32
delayScript []byte
)
for i, txOut := range commitTx.TxOut {
if !bytes.Equal(payToUsScriptHash, txOut.PkScript) {
continue
}
delayIndex = uint32(i)
delayScript = txOut.PkScript
break
}
localCommitment := lc.channelState.LocalCommitment
// With the necessary information gathered above, create a new sign
// descriptor which is capable of generating the signature the caller
// needs to sweep this output. The hash cache, and input index are not
// set as the caller will decide these values once sweeping the output.
// If the output is non-existent (dust), have the sign descriptor be
// nil.
var commitResolution *CommitOutputResolution
if len(delayScript) != 0 {
singleTweak := SingleTweakBytes(commitPoint,
lc.localChanCfg.DelayBasePoint)
localBalance := localCommitment.LocalBalance
commitResolution = &CommitOutputResolution{
SelfOutPoint: wire.OutPoint{
Hash: commitTx.TxHash(),
Index: delayIndex,
},
SelfOutputSignDesc: SignDescriptor{
PubKey: lc.localChanCfg.DelayBasePoint,
SingleTweak: singleTweak,
WitnessScript: selfScript,
Output: &wire.TxOut{
PkScript: delayScript,
Value: int64(localBalance.ToSatoshis()),
},
HashType: txscript.SigHashAll,
},
MaturityDelay: csvTimeout,
}
}
// Once the delay output has been found (if it exists), then we'll also
// need to create a series of sign descriptors for any lingering
// outgoing HTLC's that we'll need to claim as well.
txHash := commitTx.TxHash()
htlcResolutions, err := extractHtlcResolutions(
localCommitment.FeePerKw, true, lc.signer, localCommitment.Htlcs,
keyRing, lc.localChanCfg, lc.remoteChanCfg, txHash, lc.pCache)
if err != nil {
return nil, err
}
return &ForceCloseSummary{
ChanPoint: lc.channelState.FundingOutpoint,
CloseTx: commitTx,
CommitResolution: commitResolution,
HtlcResolutions: htlcResolutions,
ChanSnapshot: *lc.channelState.Snapshot(),
}, nil
}
// CreateCloseProposal is used by both parties in a cooperative channel close
// workflow to generate proposed close transactions and signatures. This method
// should only be executed once all pending HTLCs (if any) on the channel have
// been cleared/removed. Upon completion, the source channel will shift into
// the "closing" state, which indicates that all incoming/outgoing HTLC
// requests should be rejected. A signature for the closing transaction is
// returned.
//
// TODO(roasbeef): caller should initiate signal to reject all incoming HTLCs,
// settle any in flight.
func (lc *LightningChannel) CreateCloseProposal(proposedFee btcutil.Amount,
localDeliveryScript []byte,
remoteDeliveryScript []byte) ([]byte, *chainhash.Hash, btcutil.Amount, error) {
lc.Lock()
defer lc.Unlock()
// If we've already closed the channel, then ignore this request.
if lc.status == channelClosed {
// TODO(roasbeef): check to ensure no pending payments
return nil, nil, 0, ErrChanClosing
}
// Subtract the proposed fee from the appropriate balance, taking care
// not to persist the adjusted balance, as the feeRate may change
// during the channel closing process.
localCommit := lc.channelState.LocalCommitment
ourBalance := localCommit.LocalBalance.ToSatoshis()
theirBalance := localCommit.RemoteBalance.ToSatoshis()
// We'll make sure we account for the complete balance by adding the
// current dangling commitment fee to the balance of the initiator.
commitFee := localCommit.CommitFee
if lc.channelState.IsInitiator {
ourBalance = ourBalance - proposedFee + commitFee
} else {
theirBalance = theirBalance - proposedFee + commitFee
}
closeTx := CreateCooperativeCloseTx(lc.fundingTxIn(),
lc.localChanCfg.DustLimit, lc.remoteChanCfg.DustLimit,
ourBalance, theirBalance, localDeliveryScript,
remoteDeliveryScript, lc.channelState.IsInitiator)
// Ensure that the transaction doesn't explicitly violate any
// consensus rules such as being too big, or having any value with a
// negative output.
tx := btcutil.NewTx(closeTx)
if err := blockchain.CheckTransactionSanity(tx); err != nil {
return nil, nil, 0, err
}
// Finally, sign the completed cooperative closure transaction. As the
// initiator we'll simply send our signature over to the remote party,
// using the generated txid to be notified once the closure transaction
// has been confirmed.
lc.signDesc.SigHashes = txscript.NewTxSigHashes(closeTx)
sig, err := lc.signer.SignOutputRaw(closeTx, lc.signDesc)
if err != nil {
return nil, nil, 0, err
}
// As everything checks out, indicate in the channel status that a
// channel closure has been initiated.
lc.status = channelClosing
closeTXID := closeTx.TxHash()
return sig, &closeTXID, ourBalance, nil
}
// CompleteCooperativeClose completes the cooperative closure of the target
// active lightning channel. A fully signed closure transaction as well as the
// signature itself are returned. Additionally, we also return our final
// settled balance, which reflects any fees we may have paid.
//
// NOTE: The passed local and remote sigs are expected to be fully complete
// signatures including the proper sighash byte.
func (lc *LightningChannel) CompleteCooperativeClose(localSig, remoteSig []byte,
localDeliveryScript, remoteDeliveryScript []byte,
proposedFee btcutil.Amount) (*wire.MsgTx, btcutil.Amount, error) {
lc.Lock()
defer lc.Unlock()
// If the channel is already closed, then ignore this request.
if lc.status == channelClosed {
// TODO(roasbeef): check to ensure no pending payments
return nil, 0, ErrChanClosing
}
// Subtract the proposed fee from the appropriate balance, taking care
// not to persist the adjusted balance, as the feeRate may change
// during the channel closing process.
localCommit := lc.channelState.LocalCommitment
ourBalance := localCommit.LocalBalance.ToSatoshis()
theirBalance := localCommit.RemoteBalance.ToSatoshis()
// We'll make sure we account for the complete balance by adding the
// current dangling commitment fee to the balance of the initiator.
commitFee := localCommit.CommitFee
if lc.channelState.IsInitiator {
ourBalance = ourBalance - proposedFee + commitFee
} else {
theirBalance = theirBalance - proposedFee + commitFee
}
// Create the transaction used to return the current settled balance
// on this active channel back to both parties. In this current model,
// the initiator pays full fees for the cooperative close transaction.
closeTx := CreateCooperativeCloseTx(lc.fundingTxIn(),
lc.localChanCfg.DustLimit, lc.remoteChanCfg.DustLimit,
ourBalance, theirBalance, localDeliveryScript,
remoteDeliveryScript, lc.channelState.IsInitiator)
// Ensure that the transaction doesn't explicitly validate any
// consensus rules such as being too big, or having any value with a
// negative output.
tx := btcutil.NewTx(closeTx)
if err := blockchain.CheckTransactionSanity(tx); err != nil {
return nil, 0, err
}
hashCache := txscript.NewTxSigHashes(closeTx)
// Finally, construct the witness stack minding the order of the
// pubkeys+sigs on the stack.
ourKey := lc.localChanCfg.MultiSigKey.SerializeCompressed()
theirKey := lc.remoteChanCfg.MultiSigKey.SerializeCompressed()
witness := SpendMultiSig(lc.signDesc.WitnessScript, ourKey,
localSig, theirKey, remoteSig)
closeTx.TxIn[0].Witness = witness
// Validate the finalized transaction to ensure the output script is
// properly met, and that the remote peer supplied a valid signature.
prevOut := lc.signDesc.Output
vm, err := txscript.NewEngine(prevOut.PkScript, closeTx, 0,
txscript.StandardVerifyFlags, nil, hashCache, prevOut.Value)
if err != nil {
return nil, 0, err
}
if err := vm.Execute(); err != nil {
return nil, 0, err
}
// As the transaction is sane, and the scripts are valid we'll mark the
// channel now as closed as the closure transaction should get into the
// chain in a timely manner and possibly be re-broadcast by the wallet.
lc.status = channelClosed
return closeTx, ourBalance, nil
}
// DeleteState deletes all state concerning the channel from the underlying
// database, only leaving a small summary describing metadata of the
// channel's lifetime.
func (lc *LightningChannel) DeleteState(c *channeldb.ChannelCloseSummary) error {
return lc.channelState.CloseChannel(c)
}
// AvailableBalance returns the current available balance within the channel.
// By available balance, we mean that if at this very instance s new commitment
// were to be created which evals all the log entries, what would our available
// balance me. This method is useful when deciding if a given channel can
// accept an HTLC in the multi-hop forwarding scenario.
func (lc *LightningChannel) AvailableBalance() lnwire.MilliSatoshi {
lc.RLock()
defer lc.RUnlock()
bal, _ := lc.availableBalance()
return bal
}
// availableBalance is the private, non mutexed version of AvailableBalance.
// This method is provided so methods that already hold the lock can access
// this method. Additionally, the total weight of the next to be created
// commitment is returned for accounting purposes.
func (lc *LightningChannel) availableBalance() (lnwire.MilliSatoshi, int64) {
// First, we'll grab the current local balance. If we're the initiator
// of the channel then we paid the fees on the last commitment state,
// so we'll re-apply those.
settledBalance := lc.channelState.LocalCommitment.LocalBalance
if lc.channelState.IsInitiator {
settledBalance += lnwire.NewMSatFromSatoshis(
lc.localCommitChain.tip().fee,
)
}
// Next we'll grab the current set of log updates that are still active
// and haven't been garbage collected.
remoteACKedIndex := lc.localCommitChain.tip().theirMessageIndex
htlcView := lc.fetchHTLCView(remoteACKedIndex,
lc.localUpdateLog.logIndex)
feePerKw := lc.channelState.LocalCommitment.FeePerKw
dustLimit := lc.channelState.LocalChanCfg.DustLimit
// We'll now re-compute the current weight of all the active HTLC's. We
// make sure to skip any HTLC's that would be dust on our version of
// the commitment transaction.
var totalHtlcWeight int64
for _, htlc := range lc.channelState.LocalCommitment.Htlcs {
if htlcIsDust(false, true, feePerKw, htlc.Amt.ToSatoshis(),
dustLimit) {
continue
}
totalHtlcWeight += HtlcWeight
}
// Next we'll run through our set of updates and modify the
// settledBalance and totalHtlcWeight fields accordingly.
for _, entry := range htlcView.ourUpdates {
switch {
// For any new HTLC's added as a part of this state, we'll
// subtract the total balance, and tally the weight increase if
// it isn't dust.
case entry.EntryType == Add && entry.addCommitHeightLocal == 0:
settledBalance -= entry.Amount
if htlcIsDust(false, true, feePerKw, entry.Amount.ToSatoshis(),
dustLimit) {
continue
}
totalHtlcWeight += HtlcWeight
// For any new HTLC's we newly settled as part of this state,
// we'll subtract the HTLC weight and increase our balance
// accordingly.
case entry.EntryType == Settle && entry.removeCommitHeightLocal == 0:
totalHtlcWeight -= HtlcWeight
settledBalance += entry.Amount
// For any new fails added as a part of this state, we'll
// subtract the weight of the HTLC we're failing.
case entry.EntryType == Fail && entry.removeCommitHeightLocal == 0:
fallthrough
case entry.EntryType == MalformedFail && entry.removeCommitHeightLocal == 0:
totalHtlcWeight -= HtlcWeight
}
}
for _, entry := range htlcView.theirUpdates {
switch {
// If the remote party has an HTLC that will be included as
// part of this state, then we'll account for the additional
// weight of the HTLC.
case entry.EntryType == Add && entry.addCommitHeightLocal == 0:
if htlcIsDust(true, true, feePerKw, entry.Amount.ToSatoshis(),
dustLimit) {
continue
}
totalHtlcWeight += HtlcWeight
// If the remote party is settling one of our HTLC's for the
// first time as part of this state, then we'll subtract the
// weight of the HTLC.
case entry.EntryType == Settle && entry.removeCommitHeightLocal == 0:
totalHtlcWeight -= HtlcWeight
// For any HTLC's that they're failing as a part of the next,
// state, we'll subtract the weight of the HTLC and also credit
// ourselves back the value of the HTLC.
case entry.EntryType == Fail && entry.removeCommitHeightLocal == 0:
fallthrough
case entry.EntryType == MalformedFail && entry.removeCommitHeightLocal == 0:
totalHtlcWeight -= HtlcWeight
settledBalance += entry.Amount
}
}
// If we subtracted dust HTLC's, then we'll need to reset the weight of
// the HTLCs back to zero.
if totalHtlcWeight < 0 {
totalHtlcWeight = 0
}
// If we're the initiator then we need to pay fees for this state, so
// taking into account the number of active HTLC's we'll calculate the
// fee that must be paid.
totalCommitWeight := CommitWeight + totalHtlcWeight
if lc.channelState.IsInitiator {
additionalFee := lnwire.NewMSatFromSatoshis(
btcutil.Amount((int64(feePerKw) * totalCommitWeight) / 1000),
)
settledBalance -= additionalFee
}
return settledBalance, totalCommitWeight
}
// StateSnapshot returns a snapshot of the current fully committed state within
// the channel.
func (lc *LightningChannel) StateSnapshot() *channeldb.ChannelSnapshot {
lc.RLock()
defer lc.RUnlock()
return lc.channelState.Snapshot()
}
// validateFeeRate ensures that if the passed fee is applied to the channel,
// and a new commitment is created (which evaluates this fee), then the
// initiator of the channel does not dip below their reserve.
func (lc *LightningChannel) validateFeeRate(feePerKw btcutil.Amount) error {
// We'll ensure that we can accommodate this new fee change, yet still
// be above our reserve balance. Otherwise, we'll reject the fee
// update.
availableBalance, txWeight := lc.availableBalance()
// Using the weight of the commitment transaction if we were to create
// a commitment now, we'll compute our remaining balance if we apply
// this new fee update.
newFee := lnwire.NewMSatFromSatoshis(
btcutil.Amount((int64(feePerKw) * txWeight) / 1000),
)
balanceAfterFee := availableBalance - newFee
// If this new balance is below our reserve, then we can't accommodate
// the fee change, so we'll reject it.
if balanceAfterFee.ToSatoshis() < lc.channelState.LocalChanCfg.ChanReserve {
return fmt.Errorf("cannot apply fee_update=%v sat/kw, "+
"insufficient balance: start=%v, end=%v",
int64(feePerKw),
availableBalance, balanceAfterFee)
}
// TODO(halseth): should fail if fee update is unreasonable,
// as specified in BOLT#2.
// * COMMENT(roasbeef): can cross-check with our ideal fee rate
return nil
}
// UpdateFee initiates a fee update for this channel. Must only be called by
// the channel initiator, and must be called before sending update_fee to
// the remote.
func (lc *LightningChannel) UpdateFee(feePerKw btcutil.Amount) error {
lc.Lock()
defer lc.Unlock()
// Only initiator can send fee update, so trying to send one as
// non-initiator will fail.
if !lc.channelState.IsInitiator {
return fmt.Errorf("local fee update as non-initiator")
}
// Ensure that the passed fee rate meets our current requirements.
if err := lc.validateFeeRate(feePerKw); err != nil {
return err
}
lc.pendingFeeUpdate = &feePerKw
return nil
}
// ReceiveUpdateFee handles an updated fee sent from remote. This method will
// return an error if called as channel initiator.
func (lc *LightningChannel) ReceiveUpdateFee(feePerKw btcutil.Amount) error {
lc.Lock()
defer lc.Unlock()
// Only initiator can send fee update, and we must fail if we receive
// fee update as initiator
if lc.channelState.IsInitiator {
return fmt.Errorf("received fee update as initiator")
}
// TODO(roasbeef): or just modify to use the other balance?
lc.pendingFeeUpdate = &feePerKw
return nil
}
// generateRevocation generates the revocation message for a given height.
func (lc *LightningChannel) generateRevocation(height uint64) (*lnwire.RevokeAndAck,
error) {
// Now that we've accept a new state transition, we send the remote
// party the revocation for our current commitment state.
revocationMsg := &lnwire.RevokeAndAck{}
commitSecret, err := lc.channelState.RevocationProducer.AtIndex(height)
if err != nil {
return nil, err
}
copy(revocationMsg.Revocation[:], commitSecret[:])
// Along with this revocation, we'll also send the _next_ commitment
// point that the remote party should use to create our next commitment
// transaction. We use a +2 here as we already gave them a look ahead
// of size one after the FundingLocked message was sent:
//
// 0: current revocation, 1: their "next" revocation, 2: this revocation
//
// We're revoking the current revocation. Once they receive this
// message they'll set the "current" revocation for us to their stored
// "next" revocation, and this revocation will become their new "next"
// revocation.
//
// Put simply in the window slides to the left by one.
nextCommitSecret, err := lc.channelState.RevocationProducer.AtIndex(
height + 2,
)
if err != nil {
return nil, err
}
revocationMsg.NextRevocationKey = ComputeCommitmentPoint(nextCommitSecret[:])
revocationMsg.ChanID = lnwire.NewChanIDFromOutPoint(
&lc.channelState.FundingOutpoint)
return revocationMsg, nil
}
// CreateCommitTx creates a commitment transaction, spending from specified
// funding output. The commitment transaction contains two outputs: one paying
// to the "owner" of the commitment transaction which can be spent after a
// relative block delay or revocation event, and the other paying the
// counterparty within the channel, which can be spent immediately.
func CreateCommitTx(fundingOutput wire.TxIn,
keyRing *CommitmentKeyRing, csvTimeout uint32,
amountToSelf, amountToThem, dustLimit btcutil.Amount) (*wire.MsgTx, error) {
// First, we create the script for the delayed "pay-to-self" output.
// This output has 2 main redemption clauses: either we can redeem the
// output after a relative block delay, or the remote node can claim
// the funds with the revocation key if we broadcast a revoked
// commitment transaction.
ourRedeemScript, err := commitScriptToSelf(csvTimeout, keyRing.DelayKey,
keyRing.RevocationKey)
if err != nil {
return nil, err
}
payToUsScriptHash, err := witnessScriptHash(ourRedeemScript)
if err != nil {
return nil, err
}
// Next, we create the script paying to them. This is just a regular
// P2WPKH output, without any added CSV delay.
theirWitnessKeyHash, err := commitScriptUnencumbered(keyRing.NoDelayKey)
if err != nil {
return nil, err
}
// Now that both output scripts have been created, we can finally create
// the transaction itself. We use a transaction version of 2 since CSV
// will fail unless the tx version is >= 2.
commitTx := wire.NewMsgTx(2)
commitTx.AddTxIn(&fundingOutput)
// Avoid creating dust outputs within the commitment transaction.
if amountToSelf >= dustLimit {
commitTx.AddTxOut(&wire.TxOut{
PkScript: payToUsScriptHash,
Value: int64(amountToSelf),
})
}
if amountToThem >= dustLimit {
commitTx.AddTxOut(&wire.TxOut{
PkScript: theirWitnessKeyHash,
Value: int64(amountToThem),
})
}
return commitTx, nil
}
// CreateCooperativeCloseTx creates a transaction which if signed by both
// parties, then broadcast cooperatively closes an active channel. The creation
// of the closure transaction is modified by a boolean indicating if the party
// constructing the channel is the initiator of the closure. Currently it is
// expected that the initiator pays the transaction fees for the closing
// transaction in full.
func CreateCooperativeCloseTx(fundingTxIn wire.TxIn,
localDust, remoteDust, ourBalance, theirBalance btcutil.Amount,
ourDeliveryScript, theirDeliveryScript []byte,
initiator bool) *wire.MsgTx {
// Construct the transaction to perform a cooperative closure of the
// channel. In the event that one side doesn't have any settled funds
// within the channel then a refund output for that particular side can
// be omitted.
closeTx := wire.NewMsgTx(2)
closeTx.AddTxIn(&fundingTxIn)
// Create both cooperative closure outputs, properly respecting the
// dust limits of both parties.
if ourBalance >= localDust {
closeTx.AddTxOut(&wire.TxOut{
PkScript: ourDeliveryScript,
Value: int64(ourBalance),
})
}
if theirBalance >= remoteDust {
closeTx.AddTxOut(&wire.TxOut{
PkScript: theirDeliveryScript,
Value: int64(theirBalance),
})
}
txsort.InPlaceSort(closeTx)
return closeTx
}
// CalcFee returns the commitment fee to use for the given
// fee rate (fee-per-kw).
func (lc *LightningChannel) CalcFee(feeRate uint64) uint64 {
return (feeRate * uint64(CommitWeight)) / 1000
}
// RemoteNextRevocation returns the channelState's RemoteNextRevocation.
func (lc *LightningChannel) RemoteNextRevocation() *btcec.PublicKey {
lc.RLock()
defer lc.RUnlock()
return lc.channelState.RemoteNextRevocation
}
// IsInitiator returns true if we were the ones that initiated the funding
// workflow which led to the creation of this channel. Otherwise, it returns
// false.
func (lc *LightningChannel) IsInitiator() bool {
lc.RLock()
defer lc.RUnlock()
return lc.channelState.IsInitiator
}
// CommitFeeRate returns the current fee rate of the commitment transaction in
// units of sat-per-kw.
func (lc *LightningChannel) CommitFeeRate() btcutil.Amount {
lc.RLock()
defer lc.RUnlock()
return lc.channelState.LocalCommitment.FeePerKw
}
// IsPending returns true if the channel's funding transaction has been fully
// confirmed, and false otherwise.
func (lc *LightningChannel) IsPending() bool {
lc.RLock()
defer lc.RUnlock()
return lc.channelState.IsPending
}
// State provides access to the channel's internal state for testing.
func (lc *LightningChannel) State() *channeldb.OpenChannel {
return lc.channelState
}
// ActiveHtlcs returns a slice of HTLC's which are currently active on *both*
// commitment transactions.
func (lc *LightningChannel) ActiveHtlcs() []channeldb.HTLC {
lc.RLock()
defer lc.RUnlock()
// We'll only return HTLC's that are locked into *both* commitment
// transactions. So we'll iterate through their set of HTLC's to note
// which ones are present on their commitment.
remoteHtlcs := make(map[[32]byte]struct{})
for _, htlc := range lc.channelState.RemoteCommitment.Htlcs {
onionHash := sha256.Sum256(htlc.OnionBlob[:])
remoteHtlcs[onionHash] = struct{}{}
}
// Now that we know which HTLC's they have, we'll only mark the HTLC's
// as active if *we* know them as well.
activeHtlcs := make([]channeldb.HTLC, 0, len(remoteHtlcs))
for _, htlc := range lc.channelState.LocalCommitment.Htlcs {
if _, ok := remoteHtlcs[sha256.Sum256(htlc.OnionBlob[:])]; !ok {
continue
}
activeHtlcs = append(activeHtlcs, htlc)
}
return activeHtlcs
}