lnd.xprv/lnwallet/channel.go

3957 lines
137 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"
"encoding/hex"
"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 exausted.
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")
)
// 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
// 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 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 wthin 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
// Index 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.
Index uint64
// ParentIndex is the index of the log entry that this HTLC update
// settles or times out.
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 comimtnet
// 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 above the tail of both chains, the log entries can
// safely be removed.
removeCommitHeightRemote uint64
removeCommitHeightLocal uint64
// Payload is an opaque blob which is used to complete multi-hop
// routing.
Payload []byte
// [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
// [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
// 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
// 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 int he local commitment view.
outgoignHTLCIndex 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) {
// 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(ourCommitTx bool,
dustLimit btcutil.Amount) 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.outgoignHTLCIndex = 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, ourCommitTx, c.feePerKw,
htlc.Amount.ToSatoshis(), 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 ourCommitTx && 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 !ourCommitTx && 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 ourCommitTx:
htlc.localOutputIndex, err = locateOutputIndex(htlc, c.txn,
ourCommitTx, 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.outgoignHTLCIndex[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 !ourCommitTx:
htlc.remoteOutputIndex, err = locateOutputIndex(htlc, c.txn,
ourCommitTx, 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
}
// toChannelDelta converts the target commitment into a format suitable to be
// written to disk after an accepted state transition.
func (c *commitment) toChannelDelta(ourCommit bool) (*channeldb.ChannelDelta, error) {
numHtlcs := len(c.outgoingHTLCs) + len(c.incomingHTLCs)
delta := &channeldb.ChannelDelta{
LocalBalance: c.ourBalance,
RemoteBalance: c.theirBalance,
UpdateNum: c.height,
CommitFee: c.fee,
FeePerKw: c.feePerKw,
Htlcs: make([]*channeldb.HTLC, 0, numHtlcs),
}
for _, htlc := range c.outgoingHTLCs {
outputIndex := htlc.localOutputIndex
if !ourCommit {
outputIndex = htlc.remoteOutputIndex
}
h := &channeldb.HTLC{
Incoming: false,
Amt: htlc.Amount,
RHash: htlc.RHash,
RefundTimeout: htlc.Timeout,
OutputIndex: outputIndex,
}
if ourCommit && htlc.sig != nil {
h.Signature = htlc.sig.Serialize()
}
delta.Htlcs = append(delta.Htlcs, h)
}
for _, htlc := range c.incomingHTLCs {
outputIndex := htlc.localOutputIndex
if !ourCommit {
outputIndex = htlc.remoteOutputIndex
}
h := &channeldb.HTLC{
Incoming: true,
Amt: htlc.Amount,
RHash: htlc.RHash,
RefundTimeout: htlc.Timeout,
OutputIndex: outputIndex,
}
if ourCommit && htlc.sig != nil {
h.Signature = htlc.sig.Serialize()
}
delta.Htlcs = append(delta.Htlcs, h)
}
return delta, nil
}
// 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 propsed 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)
}
// 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
// ackIndex is a special "pointer" index into the log that tracks the
// position which, up to, all changes have been ACK'd by the remote
// party. When receiving new commitment states, we include all of our
// updates up to this index to restore the commitment view.
ackedIndex uint64
// pendingACKIndex is another special "pointer" index into the log that
// tracks our logIndex value right before we extend the remote party's
// commitment chain. Once we receive an ACK for this changes, then we
// set ackedIndex=pendingAckIndex.
//
// TODO(roasbeef): eventually expand into list when we go back to a
// sliding window format
pendingAckIndex 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
}
// newUpdateLog creates a new updateLog instance.
func newUpdateLog() *updateLog {
return &updateLog{
List: list.New(),
updateIndex: make(map[uint64]*list.Element),
}
}
// 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++
}
// lookup attempts to look up an update entry according to it's index value. In
// the case that the entry isn't found, a nil pointer is returned.
func (u *updateLog) lookup(i uint64) *PaymentDescriptor {
return u.updateIndex[i].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) remove(i uint64) {
entry := u.updateIndex[i]
u.Remove(entry)
delete(u.updateIndex, i)
}
// initiateTransition marks that the caller has extended the commitment chain
// of the remote party with the contents of the updateLog. This function will
// mark the log index value at this point so it can later be marked as ACK'd.
func (u *updateLog) initiateTransition() {
u.pendingAckIndex = u.logIndex
}
// ackTransition updates the internal indexes of the updateLog to mark that the
// last pending state transition has been accepted by the remote party. To do
// so, we mark the prior pendingAckIndex as fully ACK'd.
func (u *updateLog) ackTransition() {
u.ackedIndex = u.pendingAckIndex
u.pendingAckIndex = 0
}
// 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 {
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.remove(htlc.Index)
logB.remove(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.
// Ths method .ExtendRevocationWindow() is used to extend the revocation window
// by a single revocation.
//
// 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
// pendingACk denotes if we have an outstanding commitment transaction
// and are waiting for a revocation to be received. Until the
// revocation is received, we're unable to propose a new commitment
// state.
pendingACK bool
status channelState
// 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
// feeEstimator is used to calculate the fee rate for the channel's
// commitment and cooperative close transactions.
feeEstimator FeeEstimator
// Capcity is the total capacity of this channel.
Capacity btcutil.Amount
// stateHintObsfucator is a 48-bit state hint that's used to obfsucate
// the current state number on the commitment transactions.
stateHintObsfucator [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
// rHashMap is a map with PaymentHashes pointing to their respective
// PaymentDescriptors. We insert *PaymentDescriptors whenever we
// receive HTLCs. When a state transition happens (settling or
// canceling the HTLC), rHashMap will provide an efficient
// way to lookup the original PaymentDescriptor.
rHashMap map[PaymentHash][]*PaymentDescriptor
// FundingWitnessScript is the witness script for the 2-of-2 multi-sig
// that opened the channel.
FundingWitnessScript []byte
fundingTxIn *wire.TxIn
fundingP2WSH []byte
// ForceCloseSignal is a channel that is closed to indicate that a
// local system has initiated a force close by broadcasting the current
// commitment transaction directly on-chain.
ForceCloseSignal chan struct{}
// UnilateralCloseSignal is a channel that is closed to indicate that
// the remote party has performed a unilateral close by broadcasting
// their version of the commitment transaction on-chain.
UnilateralCloseSignal chan struct{}
// UnilateralClose is a channel that will be sent upon by the close
// observer once the unilateral close of a channel is detected.
UnilateralClose chan *UnilateralCloseSummary
// ContractBreach is a channel that is used to communicate the data
// necessary to fully resolve the channel in the case that a contract
// breach is detected. A contract breach occurs it is detected that the
// counterparty has broadcast a prior *revoked* state.
ContractBreach chan *BreachRetribution
// 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
// availableLocalBalance represent the amount of available money which
// might be processed by this channel at the specific point of time.
availableLocalBalance lnwire.MilliSatoshi
sync.RWMutex
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, events chainntnfs.ChainNotifier,
fe FeeEstimator, state *channeldb.OpenChannel) (*LightningChannel, error) {
localKey := state.LocalChanCfg.MultiSigKey.SerializeCompressed()
remoteKey := state.RemoteChanCfg.MultiSigKey.SerializeCompressed()
multiSigScript, err := genMultiSigScript(localKey, remoteKey)
if err != nil {
return nil, err
}
var stateHint [StateHintSize]byte
if state.IsInitiator {
stateHint = deriveStateHintObfuscator(
state.LocalChanCfg.PaymentBasePoint,
state.RemoteChanCfg.PaymentBasePoint,
)
} else {
stateHint = deriveStateHintObfuscator(
state.RemoteChanCfg.PaymentBasePoint,
state.LocalChanCfg.PaymentBasePoint,
)
}
lc := &LightningChannel{
// TODO(roasbeef): tune num sig workers?
sigPool: newSigPool(runtime.NumCPU(), signer),
signer: signer,
channelEvents: events,
feeEstimator: fe,
stateHintObsfucator: stateHint,
currentHeight: state.NumUpdates,
remoteCommitChain: newCommitmentChain(state.NumUpdates),
localCommitChain: newCommitmentChain(state.NumUpdates),
channelState: state,
localChanCfg: &state.LocalChanCfg,
remoteChanCfg: &state.RemoteChanCfg,
localUpdateLog: newUpdateLog(),
remoteUpdateLog: newUpdateLog(),
rHashMap: make(map[PaymentHash][]*PaymentDescriptor),
Capacity: state.Capacity,
FundingWitnessScript: multiSigScript,
ForceCloseSignal: make(chan struct{}),
UnilateralClose: make(chan *UnilateralCloseSummary, 1),
UnilateralCloseSignal: make(chan struct{}),
ContractBreach: make(chan *BreachRetribution, 1),
LocalFundingKey: state.LocalChanCfg.MultiSigKey,
RemoteFundingKey: state.RemoteChanCfg.MultiSigKey,
quit: make(chan struct{}),
}
// Initialize both of our chains using current un-revoked commitment
// for each side.
lc.localCommitChain.addCommitment(&commitment{
height: lc.currentHeight,
ourBalance: state.LocalBalance,
ourMessageIndex: 0,
theirBalance: state.RemoteBalance,
theirMessageIndex: 0,
fee: state.CommitFee,
feePerKw: state.FeePerKw,
})
walletLog.Debugf("ChannelPoint(%v), starting local commitment: %v",
state.FundingOutpoint, newLogClosure(func() string {
return spew.Sdump(lc.localCommitChain.tail())
}),
)
// To obtain the proper height for the remote node's commitment state,
// we'll need to fetch the tail end of their revocation log from the
// database.
logTail, err := state.RevocationLogTail()
if err != nil && err != channeldb.ErrNoActiveChannels &&
err != channeldb.ErrNoPastDeltas {
return nil, err
}
remoteCommitment := &commitment{
ourBalance: state.LocalBalance,
ourMessageIndex: 0,
theirBalance: state.RemoteBalance,
theirMessageIndex: 0,
fee: state.CommitFee,
feePerKw: state.FeePerKw,
}
if logTail == nil {
remoteCommitment.height = 0
} else {
remoteCommitment.height = logTail.UpdateNum + 1
}
lc.remoteCommitChain.addCommitment(remoteCommitment)
walletLog.Debugf("ChannelPoint(%v), starting remote commitment: %v",
state.FundingOutpoint, newLogClosure(func() string {
return spew.Sdump(lc.remoteCommitChain.tail())
}),
)
// If we're restarting from a channel with history, then restore the
// update in-memory update logs to that of the prior state.
if lc.currentHeight != 0 {
lc.restoreStateLogs()
}
// 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.
fundingPkScript, err := witnessScriptHash(multiSigScript)
if err != nil {
return nil, err
}
lc.fundingTxIn = wire.NewTxIn(&state.FundingOutpoint, nil, nil)
lc.fundingP2WSH = fundingPkScript
lc.signDesc = &SignDescriptor{
PubKey: lc.localChanCfg.MultiSigKey,
WitnessScript: multiSigScript,
Output: &wire.TxOut{
PkScript: lc.fundingP2WSH,
Value: int64(lc.channelState.Capacity),
},
HashType: txscript.SigHashAll,
InputIndex: 0,
}
// We'll only launch a close observer if the ChainNotifier
// implementation is non-nil. Passing a nil value indicates that the
// channel shouldn't be actively watched for.
if lc.channelEvents != nil {
// Register for a notification to be dispatched if the funding
// outpoint has been spent. This indicates that either us or
// the remote party has broadcasted a commitment transaction
// on-chain.
fundingOut := &lc.fundingTxIn.PreviousOutPoint
// As a height hint, we'll try to use the opening height, but
// if the channel isn't yet open, then we'll use the height it
// was broadcast at.
heightHint := lc.channelState.ShortChanID.BlockHeight
if heightHint == 0 {
heightHint = lc.channelState.FundingBroadcastHeight
}
channelCloseNtfn, err := lc.channelEvents.RegisterSpendNtfn(
fundingOut, heightHint,
)
if err != nil {
return nil, err
}
// Launch the close observer which will vigilantly watch the
// network for any broadcasts the current or prior commitment
// transactions, taking action accordingly.
lc.wg.Add(1)
go lc.closeObserver(channelCloseNtfn)
}
// Initialize the available local balance
s := lc.StateSnapshot()
lc.availableLocalBalance = s.LocalBalance
// Finally, we'll kick of the signature job pool to handle any upcoming
// commitment state generation and validation.
if lc.sigPool.Start(); err != nil {
return nil, err
}
return lc, nil
}
// 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
}
// TODO(roasbeef): ensure that when channel links and breach arbs exit,
// that they call Stop?
lc.sigPool.Stop()
close(lc.quit)
lc.wg.Wait()
}
// HtlcRetribution contains all the items necessary to seep a revoked HTLC
// transaction from a revoked commitment transaction broadcast by the remot
// 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
}
// 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
// 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.
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.
RemoteOutputSignDesc SignDescriptor
// RemoteOutpoint is the output 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) (*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,
localKey := TweakPubKey(chanState.LocalChanCfg.PaymentBasePoint,
commitmentPoint)
remoteKey := TweakPubKey(chanState.RemoteChanCfg.PaymentBasePoint,
commitmentPoint)
remoteDelayKey := TweakPubKey(chanState.RemoteChanCfg.DelayBasePoint,
commitmentPoint)
// Once we derive the revocation leaf, we can then re-create the
// revocation public key used within this state. This is needed in
// order to create the proper script below.
revocationKey := DeriveRevocationPubkey(
chanState.LocalChanCfg.RevocationBasePoint,
commitmentPoint,
)
// 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, remoteDelayKey,
revocationKey)
if err != nil {
return nil, err
}
remoteWitnessHash, err := witnessScriptHash(remotePkScript)
if err != nil {
return nil, err
}
localPkScript, err := commitScriptUnencumbered(localKey)
if err != nil {
return nil, err
}
localWitnessHash, err := witnessScriptHash(localPkScript)
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)
}
}
// 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(chanState.Htlcs))
for i, htlc := range revokedSnapshot.Htlcs {
var (
htlcScript []byte
err error
)
// 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(localKey, remoteKey,
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, localKey, remoteKey,
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),
},
}
}
// We'll need to reconstruct the single tweak so we can sweep our
// non-delayed pay-to-self output self.
singleTweak := SingleTweakBytes(commitmentPoint,
chanState.LocalChanCfg.PaymentBasePoint)
// 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{
BreachTransaction: broadcastCommitment,
RevokedStateNum: stateNum,
PendingHTLCs: revokedSnapshot.Htlcs,
LocalOutpoint: localOutpoint,
LocalOutputSignDesc: SignDescriptor{
SingleTweak: singleTweak,
PubKey: chanState.LocalChanCfg.PaymentBasePoint,
WitnessScript: localPkScript,
Output: &wire.TxOut{
PkScript: localWitnessHash,
Value: int64(revokedSnapshot.LocalBalance.ToSatoshis()),
},
HashType: txscript.SigHashAll,
},
RemoteOutpoint: remoteOutpoint,
RemoteOutputSignDesc: SignDescriptor{
PubKey: chanState.LocalChanCfg.RevocationBasePoint,
DoubleTweak: commitmentSecret,
WitnessScript: remotePkScript,
Output: &wire.TxOut{
PkScript: remoteWitnessHash,
Value: int64(revokedSnapshot.RemoteBalance.ToSatoshis()),
},
HashType: txscript.SigHashAll,
},
HtlcRetributions: htlcRetributions,
}, nil
}
// closeObserver is a goroutine which watches the network for any spends of the
// multi-sig funding output. A spend from the multi-sig output may occur under
// the following three scenarios: a cooperative close, a unilateral close, and
// a uncooperative contract breaching close. In the case of the last scenario a
// BreachRetribution struct is created and sent over the ContractBreach channel
// notifying subscribers that the counterparty has violated the condition of
// the channel by broadcasting a revoked prior state.
//
// NOTE: This MUST be run as a goroutine.
func (lc *LightningChannel) closeObserver(channelCloseNtfn *chainntnfs.SpendEvent) {
defer lc.wg.Done()
walletLog.Infof("Close observer for ChannelPoint(%v) active",
lc.channelState.FundingOutpoint)
var (
commitSpend *chainntnfs.SpendDetail
ok bool
)
select {
// If the daemon is shutting down, then this notification channel will
// be closed, so check the second read-value to avoid a false positive.
case commitSpend, ok = <-channelCloseNtfn.Spend:
if !ok {
return
}
// Otherwise, we've beeen signalled to bail out early by the
// caller/maintainer of this channel.
case <-lc.quit:
// As we're exiting before the spend notification has been
// triggered, we'll cancel the notification intent so the
// ChainNotiifer can free up the resources.
channelCloseNtfn.Cancel()
return
}
// If we've already initiated a local cooperative or unilateral close
// locally, then we have nothing more to do.
lc.RLock()
if lc.status == channelClosed || lc.status == channelDispute ||
lc.status == channelClosing {
lc.RUnlock()
return
}
lc.RUnlock()
// Otherwise, the remote party might have broadcast a prior revoked
// state...!!!
commitTxBroadcast := commitSpend.SpendingTx
// If this is our commitment transaction, then we can exit here as we
// don't have any further processing we need to do (we can't cheat
// ourselves :p).
commitmentHash := lc.channelState.CommitTx.TxHash()
isOurCommitment := commitSpend.SpenderTxHash.IsEqual(&commitmentHash)
if isOurCommitment {
return
}
lc.Lock()
defer lc.Unlock()
walletLog.Warnf("Unprompted commitment broadcast for ChannelPoint(%v) "+
"detected!", lc.channelState.FundingOutpoint)
// Decode the state hint encoded within the commitment transaction to
// determine if this is a revoked state or not.
obsfucator := lc.stateHintObsfucator
broadcastStateNum := GetStateNumHint(commitTxBroadcast, obsfucator)
currentStateNum := lc.currentHeight
// TODO(roasbeef): track heights distinctly?
switch {
// If state number spending transaction matches the current latest
// state, then they've initiated a unilateral close. So we'll trigger
// the unilateral close signal so subscribers can clean up the state as
// necessary.
//
// We'll also handle the case of the remote party broadcasting their
// commitment transaction which is one height above ours. This case an
// arise when we initiate a state transition, but the remote party has
// a fail crash _after_ accepting the new state, but _before_ sending
// their signature to us.
case broadcastStateNum >= currentStateNum:
walletLog.Infof("Unilateral close of ChannelPoint(%v) "+
"detected", lc.channelState.FundingOutpoint)
// As we've detected that the channel has been closed,
// immediately delete the state from disk, creating a close
// summary for future usage by related sub-systems.
//
// TODO(roasbeef): include HTLC's
// * and time-locked balance, NEED TO???
closeSummary := channeldb.ChannelCloseSummary{
ChanPoint: lc.channelState.FundingOutpoint,
ClosingTXID: *commitSpend.SpenderTxHash,
RemotePub: lc.channelState.IdentityPub,
Capacity: lc.Capacity,
SettledBalance: lc.channelState.LocalBalance.ToSatoshis(),
CloseType: channeldb.ForceClose,
IsPending: true,
}
if err := lc.DeleteState(&closeSummary); err != nil {
walletLog.Errorf("unable to delete channel state: %v",
err)
}
// 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 := lc.channelState.RemoteCurrentRevocation
revokeKey := DeriveRevocationPubkey(
lc.localChanCfg.RevocationBasePoint,
commitPoint,
)
// Next, we'll obtain HTLC resolutions for all the outgoing
// HTLC's we had on their commitment transaction.
htlcResolutions, localKey, err := extractHtlcResolutions(
lc.channelState.FeePerKw, false, lc.signer,
lc.channelState.Htlcs, commitPoint,
revokeKey, lc.localChanCfg, lc.remoteChanCfg,
*commitSpend.SpenderTxHash)
if err != nil {
walletLog.Errorf("unable to create htlc "+
"resolutions: %v", err)
return
}
// 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(localKey)
if err != nil {
walletLog.Errorf("unable to create self commit "+
"script: %v", err)
return
}
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 selfSignDesc *SignDescriptor
if selfPoint != nil {
localPayBase := lc.localChanCfg.PaymentBasePoint
selfSignDesc = &SignDescriptor{
PubKey: localPayBase,
SingleTweak: SingleTweakBytes(commitPoint, localPayBase),
WitnessScript: selfP2WKH,
Output: &wire.TxOut{
Value: int64(lc.channelState.LocalBalance.ToSatoshis()),
PkScript: selfP2WKH,
},
HashType: txscript.SigHashAll,
}
}
// TODO(roasbeef): send msg before writing to disk
// * need to ensure proper fault tolerance in all cases
// * get ACK from the consumer of the ntfn before writing to disk?
// * no harm in repeated ntfns: at least once semantics
// Notify any subscribers that we've detected a unilateral
// commitment transaction broadcast.
close(lc.UnilateralCloseSignal)
// We'll also send all the details necessary to re-claim funds
// that are suspended within any contracts.
lc.UnilateralClose <- &UnilateralCloseSummary{
SpendDetail: commitSpend,
ChannelCloseSummary: closeSummary,
SelfOutPoint: selfPoint,
SelfOutputSignDesc: selfSignDesc,
HtlcResolutions: htlcResolutions,
}
// If the state number broadcast is lower than the remote node's
// current un-revoked height, then THEY'RE ATTEMPTING TO VIOLATE THE
// CONTRACT LAID OUT WITHIN THE PAYMENT CHANNEL. Therefore we close
// the signal indicating a revoked broadcast to allow subscribers to
// swiftly dispatch justice!!!
case broadcastStateNum < currentStateNum:
walletLog.Warnf("Remote peer has breached the channel "+
"contract for ChannelPoint(%v). Revoked state #%v was "+
"broadcast!!!", lc.channelState.FundingOutpoint,
broadcastStateNum)
// Create a new reach retribution struct which contains all the
// data needed to swiftly bring the cheating peer to justice.
retribution, err := newBreachRetribution(lc.channelState,
broadcastStateNum, commitTxBroadcast)
if err != nil {
walletLog.Errorf("unable to create breach retribution: %v", err)
return
}
walletLog.Debugf("Punishment breach retribution created: %v",
spew.Sdump(retribution))
// Finally, send the retribution struct over the contract beach
// channel to allow the observer the use the breach retribution
// to sweep ALL funds.
lc.ContractBreach <- retribution
}
}
// 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 = htlcTimeoutFee(feePerKw)
}
return (htlcAmt - htlcFee) < dustLimit
}
// 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() error {
var pastHeight uint64
if lc.currentHeight > 0 {
pastHeight = lc.currentHeight - 1
}
// Obtain the local and remote channel configurations. These house all
// the relevant public keys and points we'll need in order to restore
// the state log.
localChanCfg := lc.localChanCfg
remoteChanCfg := lc.remoteChanCfg
// 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.
ourRevPreImage, err := lc.channelState.RevocationProducer.AtIndex(lc.currentHeight)
if err != nil {
return err
}
// With the commitment secret recovered, we'll generate the revocation
// used on the *local* commitment transaction. This is computed using
// the point derived from the commitment secret at the remote party's
// revocation based.
localCommitPoint := ComputeCommitmentPoint(ourRevPreImage[:])
localRevocation := DeriveRevocationPubkey(
remoteChanCfg.RevocationBasePoint,
localCommitPoint,
)
remoteCommitPoint := lc.channelState.RemoteCurrentRevocation
remoteRevocation := DeriveRevocationPubkey(
localChanCfg.RevocationBasePoint,
remoteCommitPoint,
)
// Additionally, we'll fetch the current payment base points which are
// required to fully generate the scripts.
localCommitLocalKey := TweakPubKey(localChanCfg.PaymentBasePoint,
localCommitPoint)
localCommitRemoteKey := TweakPubKey(remoteChanCfg.PaymentBasePoint,
localCommitPoint)
remoteCommitLocalKey := TweakPubKey(localChanCfg.PaymentBasePoint,
remoteCommitPoint)
remoteCommitRemoteKey := TweakPubKey(remoteChanCfg.PaymentBasePoint,
remoteCommitPoint)
var ourCounter, theirCounter uint64
// Grab the current fee rate as we'll need this to determine if the
// prior HTLC's were considered dust or not at this particular
// commitment sate.
feeRate := lc.channelState.FeePerKw
// TODO(roasbeef): partition entries added based on our current review
// an our view of them from the log?
for _, htlc := range lc.channelState.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
// 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, ourWitnessScript, theirWitnessScript []byte
// 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(), localChanCfg.DustLimit)
isDustRemote := htlcIsDust(htlc.Incoming, false, feeRate,
htlc.Amt.ToSatoshis(), remoteChanCfg.DustLimit)
if !isDustLocal {
ourP2WSH, ourWitnessScript, err = lc.genHtlcScript(
htlc.Incoming, true, htlc.RefundTimeout, htlc.RHash,
localCommitLocalKey, localCommitRemoteKey,
localRevocation)
if err != nil {
return err
}
}
if !isDustRemote {
theirP2WSH, theirWitnessScript, err = lc.genHtlcScript(
htlc.Incoming, false, htlc.RefundTimeout, htlc.RHash,
remoteCommitLocalKey, remoteCommitRemoteKey,
remoteRevocation)
if err != nil {
return err
}
}
pd := &PaymentDescriptor{
RHash: htlc.RHash,
Timeout: htlc.RefundTimeout,
Amount: htlc.Amt,
EntryType: Add,
addCommitHeightRemote: pastHeight,
addCommitHeightLocal: pastHeight,
ourPkScript: ourP2WSH,
ourWitnessScript: ourWitnessScript,
theirPkScript: theirP2WSH,
theirWitnessScript: theirWitnessScript,
}
if !htlc.Incoming {
pd.Index = ourCounter
lc.localUpdateLog.appendUpdate(pd)
ourCounter++
} else {
pd.Index = theirCounter
lc.remoteUpdateLog.appendUpdate(pd)
lc.rHashMap[pd.RHash] = append(lc.rHashMap[pd.RHash], pd)
theirCounter++
}
}
lc.localCommitChain.tail().ourMessageIndex = ourCounter
lc.localCommitChain.tail().theirMessageIndex = theirCounter
lc.remoteCommitChain.tail().ourMessageIndex = ourCounter
lc.remoteCommitChain.tail().theirMessageIndex = theirCounter
return nil
}
// 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.Index < 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.Index < 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.
//
// TODO(roasbeef): update commit to to have all keys?
func (lc *LightningChannel) fetchCommitmentView(remoteChain bool,
ourLogIndex, theirLogIndex uint64,
commitPoint *btcec.PublicKey) (*commitment, error) {
commitChain := lc.localCommitChain
if remoteChain {
commitChain = lc.remoteCommitChain
}
ourCommitTx := !remoteChain
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.
// TODO(roasbeef): error if log empty?
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
}
numHTLCs := int64(0)
for _, htlc := range filteredHTLCView.ourUpdates {
if htlcIsDust(false, ourCommitTx, feePerKw,
htlc.Amount.ToSatoshis(), dustLimit) {
continue
}
numHTLCs++
}
for _, htlc := range filteredHTLCView.theirUpdates {
if htlcIsDust(true, ourCommitTx, feePerKw,
htlc.Amount.ToSatoshis(), 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(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 (
delayKey, paymentKey, revocationKey *btcec.PublicKey
delay uint32
delayBalance, p2wkhBalance btcutil.Amount
)
// We'll now compute the delay, payment 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.
if remoteChain {
delayKey = TweakPubKey(lc.remoteChanCfg.DelayBasePoint,
commitPoint)
paymentKey = TweakPubKey(lc.localChanCfg.PaymentBasePoint,
commitPoint)
revocationKey = DeriveRevocationPubkey(
lc.localChanCfg.RevocationBasePoint,
commitPoint,
)
delay = uint32(lc.remoteChanCfg.CsvDelay)
delayBalance = theirBalance.ToSatoshis()
p2wkhBalance = ourBalance.ToSatoshis()
} else {
delayKey = TweakPubKey(lc.localChanCfg.DelayBasePoint,
commitPoint)
paymentKey = TweakPubKey(lc.remoteChanCfg.PaymentBasePoint,
commitPoint)
revocationKey = DeriveRevocationPubkey(
lc.remoteChanCfg.RevocationBasePoint,
commitPoint,
)
delay = uint32(lc.localChanCfg.CsvDelay)
delayBalance = ourBalance.ToSatoshis()
p2wkhBalance = theirBalance.ToSatoshis()
}
// TODO(roasbeef); create all keys unconditionally within commitment
// store in commitment, will need all when doing HTLC's
// Generate a new commitment transaction with all the latest
// unsettled/un-timed out HTLCs.
commitTx, err := CreateCommitTx(lc.fundingTxIn, delayKey, paymentKey,
revocationKey, delay, delayBalance, p2wkhBalance, dustLimit)
if err != nil {
return nil, 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.
// TODO(roasbeef): could avoid computing them both here
localKey := TweakPubKey(lc.localChanCfg.PaymentBasePoint, commitPoint)
remoteKey := TweakPubKey(lc.remoteChanCfg.PaymentBasePoint, commitPoint)
for _, htlc := range filteredHTLCView.ourUpdates {
if htlcIsDust(false, !remoteChain, feePerKw,
htlc.Amount.ToSatoshis(), dustLimit) {
continue
}
err := lc.addHTLC(commitTx, ourCommitTx, false, htlc, localKey,
remoteKey, revocationKey)
if err != nil {
return nil, err
}
}
for _, htlc := range filteredHTLCView.theirUpdates {
if htlcIsDust(true, !remoteChain, feePerKw,
htlc.Amount.ToSatoshis(), dustLimit) {
continue
}
err := lc.addHTLC(commitTx, ourCommitTx, true, htlc, localKey,
remoteKey, revocationKey)
if err != nil {
return nil, err
}
}
// Set the state hint of the commitment transaction to facilitate
// quickly recovering the necessary penalty state in the case of an
// uncooperative broadcast.
obsfucator := lc.stateHintObsfucator
stateNum := nextHeight
if err := SetStateNumHint(commitTx, stateNum, obsfucator); err != nil {
return nil, 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 := &commitment{
txn: commitTx,
height: nextHeight,
ourBalance: ourBalance,
ourMessageIndex: ourLogIndex,
theirMessageIndex: theirLogIndex,
theirBalance: theirBalance,
fee: commitFee,
feePerKw: feePerKw,
}
// 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(ourCommitTx, dustLimit); err != nil {
return nil, err
}
return c, 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 in inbound HTLC, and it hasn't been
// processed, yet, the 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.lookup(entry.ParentIndex)
skipThem[addEntry.Index] = 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.lookup(entry.ParentIndex)
skipUs[addEntry.Index] = 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.Index]; !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.Index]; !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 timesout 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:
*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:
*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.
//
// TODO(roasbeef): all keys will eventually be generated within the commitment
// itself
func genRemoteHtlcSigJobs(commitPoint *btcec.PublicKey,
localChanCfg, remoteChanCfg *channeldb.ChannelConfig,
remoteCommitView *commitment) ([]signJob, chan struct{}, error) {
// First, we'll generate all the keys required to generate the scripts
// for each HTLC output and transaction.
//
// TODO(roabseef): avoid re-calculating, put in commitment struct?
commitTweak := SingleTweakBytes(commitPoint,
localChanCfg.PaymentBasePoint)
revocationKey := DeriveRevocationPubkey(
localChanCfg.RevocationBasePoint,
commitPoint,
)
remoteDelayKey := TweakPubKey(remoteChanCfg.DelayBasePoint,
commitPoint)
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),
revocationKey, remoteDelayKey)
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.PaymentBasePoint,
SingleTweak: commitTweak,
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), revocationKey,
remoteDelayKey)
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.PaymentBasePoint,
SingleTweak: commitTweak,
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
}
// 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 it he 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() (*btcec.Signature, []*btcec.Signature, error) {
lc.Lock()
defer lc.Unlock()
// If we're awaiting an ACK to a commitment signature, then we're
// unable to create new states as we don't have any revocations we can
// use.
if lc.pendingACK {
return nil, nil, ErrNoWindow
}
// 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(lc.remoteUpdateLog.ackedIndex,
lc.localUpdateLog.logIndex, false, true, true)
if err != nil {
return nil, nil, err
}
// Grab the next commitment point for the remote party. This well be
// used within fetchCommitmentView to derive all the keys necessary to
// construct the commitment state.
commitPoint := lc.channelState.RemoteNextRevocation
// 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.remoteUpdateLog.ackedIndex,
commitPoint)
if err != nil {
return nil, nil, err
}
walletLog.Tracef("ChannelPoint(%v): extending remote chain to height %v",
lc.channelState.FundingOutpoint, newCommitView.height)
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(commitPoint,
lc.localChanCfg, lc.remoteChanCfg, newCommitView,
)
if err != nil {
return nil, nil, 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 nil, nil, err
}
sig, err := btcec.ParseSignature(rawSig, btcec.S256())
if err != nil {
close(cancelChan)
return nil, nil, 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.
sortedSigs := sortableSignBatch(sigBatch)
sort.Sort(sortedSigs)
// With the jobs sorted, we'll now iterate through all the responses to
// gather each of the signatures in order.
htlcSigs := make([]*btcec.Signature, 0, len(sigBatch))
for _, htlcSigJob := range sortedSigs {
jobResp := <-htlcSigJob.resp
// If an error occurred, then we'll cancel any other active
// jobs.
if jobResp.err != nil {
close(cancelChan)
return nil, nil, err
}
htlcSigs = append(htlcSigs, jobResp.sig)
}
// 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 revoke_and_ack, because
// of the revocation window of 1.
if lc.channelState.IsInitiator {
lc.pendingAckFeeUpdate = lc.pendingFeeUpdate
lc.pendingFeeUpdate = nil
}
// As we've just created a new update for the remote commitment chain,
// we set the bool indicating that we're waiting for an ACK to our new
// changes.
lc.pendingACK = true
// Additionally, we'll remember our log index at this point, so we can
// properly track which changes have been ACK'd.
lc.localUpdateLog.initiateTransition()
return sig, htlcSigs, 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++
}
// 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,
commitPoint *btcec.PublicKey, htlcSigs []*btcec.Signature,
localChanCfg, remoteChanCfg *channeldb.ChannelConfig) []verifyJob {
// 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
}
// First, we'll re-derive the keys necessary to reconstruct the HTLC
// output and transaction state.
remoteKey := TweakPubKey(remoteChanCfg.PaymentBasePoint, commitPoint)
revocationKey := DeriveRevocationPubkey(
remoteChanCfg.RevocationBasePoint,
commitPoint,
)
localDelayKey := TweakPubKey(localChanCfg.DelayBasePoint,
commitPoint)
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)
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),
revocationKey, localDelayKey)
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.
htlc.sig = htlcSigs[i]
// 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.outgoignHTLCIndex[outputIndex] != nil:
htlc := localCommitmentView.outgoignHTLCIndex[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),
revocationKey, localDelayKey,
)
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.
htlc.sig = htlcSigs[i]
default:
continue
}
verifyJobs = append(verifyJobs, verifyJob{
pubKey: remoteKey,
sig: htlcSigs[i],
sigHash: sigHash,
})
i++
}
return verifyJobs
}
// ReceiveNewCommitment process a signature for a new commitment state sent by
// the remote party. This method will 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 *btcec.Signature,
htlcSigs []*btcec.Signature) error {
lc.Lock()
defer lc.Unlock()
// 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,
lc.localUpdateLog.ackedIndex, 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 well 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[:])
// 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,
lc.localUpdateLog.ackedIndex, lc.remoteUpdateLog.logIndex,
commitPoint)
if err != nil {
return err
}
walletLog.Tracef("ChannelPoint(%v): extending local chain to height %v",
lc.channelState.FundingOutpoint, localCommitmentView.height)
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.FundingWitnessScript
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 := genHtlcSigValidationJobs(localCommitmentView,
commitPoint,
htlcSigs, lc.localChanCfg, lc.remoteChanCfg)
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(),
}
if !commitSig.Verify(sigHash, &verifyKey) {
close(cancelChan)
return fmt.Errorf("invalid commitment signature")
}
// 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.
if err := <-verifyResps; err != nil {
close(cancelChan)
return fmt.Errorf("invalid htlc signature: %v", err)
}
}
// The signature checks out, so we can now add the new commitment to
// our local commitment chain.
localCommitmentView.sig = commitSig.Serialize()
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
}
// Finally we'll keep track of the current pending index for the remote
// party so we can ACK up to this value once we revoke our current
// commitment.
lc.remoteUpdateLog.initiateTransition()
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()
oweCommitment := (lc.localCommitChain.tip().height >
lc.remoteCommitChain.tip().height)
localUpdatesSynced := (lc.localCommitChain.tip().ourMessageIndex ==
lc.remoteCommitChain.tip().ourMessageIndex)
remoteUpdatesSynced := (lc.localCommitChain.tip().theirMessageIndex ==
lc.remoteCommitChain.tip().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.
func (lc *LightningChannel) RevokeCurrentCommitment() (*lnwire.RevokeAndAck, error) {
lc.Lock()
defer lc.Unlock()
// 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(
lc.currentHeight,
)
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(
lc.currentHeight + 2,
)
if err != nil {
return nil, err
}
revocationMsg.NextRevocationKey = ComputeCommitmentPoint(
nextCommitSecret[:],
)
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.
tail := lc.localCommitChain.tail()
delta, err := tail.toChannelDelta(true)
if err != nil {
return nil, err
}
err = lc.channelState.UpdateCommitment(tail.txn, tail.sig, delta)
if err != nil {
return nil, err
}
walletLog.Tracef("ChannelPoint(%v): state transition accepted: "+
"our_balance=%v, their_balance=%v",
lc.channelState.FundingOutpoint, tail.ourBalance,
tail.theirBalance)
// In the process of revoking our current commitment, we've also
// implicitly ACK'd their set of pending changes that arrived before
// the signature the triggered this revocation. So we'll move up their
// ACK'd index within the log to right at this set of pending changes.
lc.remoteUpdateLog.ackTransition()
revocationMsg.ChanID = lnwire.NewChanIDFromOutPoint(
&lc.channelState.FundingOutpoint,
)
return revocationMsg, nil
}
// LocalAvailableBalance returns the amount of available money which might be
// proceed by this channel at the specific point of time.
func (lc *LightningChannel) LocalAvailableBalance() lnwire.MilliSatoshi {
lc.Lock()
defer lc.Unlock()
return lc.availableLocalBalance
}
// 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()
// Now that we've received a new revocation from the remote party,
// we'll toggle our pendingACk bool to indicate that we can create a
// new commitment state after we finish processing this revocation.
lc.pendingACK = false
// 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.
tail := lc.remoteCommitChain.tail()
delta, err := tail.toChannelDelta(false)
if err != nil {
return nil, err
}
if err := lc.channelState.AppendToRevocationLog(delta); 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
}
// TODO(roasbeef): re-visit after adding persistence to HTLCs
// * either record add height, or set to N - 1
uncomitted := (htlc.addCommitHeightRemote == 0 ||
htlc.addCommitHeightLocal == 0)
if htlc.EntryType == Add && uncomitted {
continue
}
if htlc.EntryType == Add &&
remoteChainTail >= htlc.addCommitHeightRemote &&
localChainTail >= htlc.addCommitHeightLocal {
htlc.isForwarded = true
htlcsToForward = append(htlcsToForward, htlc)
} else if htlc.EntryType != Add &&
remoteChainTail >= htlc.removeCommitHeightRemote &&
localChainTail >= htlc.removeCommitHeightLocal {
htlc.isForwarded = true
htlcsToForward = append(htlcsToForward, htlc)
}
}
// 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)
// As a final step, now that we've received an ACK for our last batch
// of pending changes, we'll update our local ACK'd index to the now
// commitment index, and reset our pendingACKIndex.
lc.localUpdateLog.ackTransition()
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 created 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
}
if lc.availableLocalBalance < htlc.Amount {
return 0, ErrInsufficientBalance
}
lc.availableLocalBalance -= htlc.Amount
pd := &PaymentDescriptor{
EntryType: Add,
RHash: PaymentHash(htlc.PaymentHash),
Timeout: htlc.Expiry,
Amount: htlc.Amount,
Index: lc.localUpdateLog.logIndex,
}
lc.localUpdateLog.appendUpdate(pd)
return pd.Index, 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 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,
Index: lc.remoteUpdateLog.logIndex,
}
lc.remoteUpdateLog.appendUpdate(pd)
lc.rHashMap[pd.RHash] = append(lc.rHashMap[pd.RHash], pd)
return pd.Index, 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.
func (lc *LightningChannel) SettleHTLC(preimage [32]byte) (uint64, error) {
lc.Lock()
defer lc.Unlock()
paymentHash := sha256.Sum256(preimage[:])
targetHTLCs, ok := lc.rHashMap[paymentHash]
if !ok {
return 0, fmt.Errorf("invalid payment hash(%v)",
hex.EncodeToString(paymentHash[:]))
}
targetHTLC := targetHTLCs[0]
pd := &PaymentDescriptor{
Amount: targetHTLC.Amount,
RPreimage: preimage,
Index: lc.localUpdateLog.logIndex,
ParentIndex: targetHTLC.Index,
EntryType: Settle,
}
lc.localUpdateLog.appendUpdate(pd)
lc.rHashMap[paymentHash][0] = nil
lc.rHashMap[paymentHash] = lc.rHashMap[paymentHash][1:]
if len(lc.rHashMap[paymentHash]) == 0 {
delete(lc.rHashMap, paymentHash)
}
lc.availableLocalBalance += pd.Amount
return targetHTLC.Index, 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, logIndex uint64) error {
lc.Lock()
defer lc.Unlock()
paymentHash := sha256.Sum256(preimage[:])
htlc := lc.localUpdateLog.lookup(logIndex)
if htlc == nil {
return fmt.Errorf("non existant log entry")
}
if !bytes.Equal(htlc.RHash[:], paymentHash[:]) {
return fmt.Errorf("invalid payment hash(%v)",
hex.EncodeToString(paymentHash[:]))
}
pd := &PaymentDescriptor{
Amount: htlc.Amount,
RPreimage: preimage,
ParentIndex: htlc.Index,
RHash: htlc.RHash,
Index: 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(rHash [32]byte) (uint64, error) {
lc.Lock()
defer lc.Unlock()
addEntries, ok := lc.rHashMap[rHash]
if !ok {
return 0, fmt.Errorf("unable to find HTLC to fail")
}
addEntry := addEntries[0]
pd := &PaymentDescriptor{
Amount: addEntry.Amount,
RHash: addEntry.RHash,
ParentIndex: addEntry.Index,
Index: lc.localUpdateLog.logIndex,
EntryType: Fail,
}
lc.localUpdateLog.appendUpdate(pd)
lc.rHashMap[rHash][0] = nil
lc.rHashMap[rHash] = lc.rHashMap[rHash][1:]
if len(lc.rHashMap[rHash]) == 0 {
delete(lc.rHashMap, rHash)
}
return addEntry.Index, 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.
func (lc *LightningChannel) ReceiveFailHTLC(logIndex uint64) error {
lc.Lock()
defer lc.Unlock()
htlc := lc.localUpdateLog.lookup(logIndex)
if htlc == nil {
return fmt.Errorf("unable to find HTLC to fail")
}
pd := &PaymentDescriptor{
Amount: htlc.Amount,
RHash: htlc.RHash,
ParentIndex: htlc.Index,
Index: lc.remoteUpdateLog.logIndex,
EntryType: Fail,
}
lc.remoteUpdateLog.appendUpdate(pd)
lc.availableLocalBalance += pd.Amount
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 (lc *LightningChannel) genHtlcScript(isIncoming, ourCommit bool,
timeout uint32, rHash [32]byte, localKey, remoteKey *btcec.PublicKey,
revocationKey *btcec.PublicKey) ([]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, remoteKey,
localKey, 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(remoteKey, localKey,
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(localKey, remoteKey,
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, localKey,
remoteKey, 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,
localKey, remoteKey, revocationKey *btcec.PublicKey) error {
timeout := paymentDesc.Timeout
rHash := paymentDesc.RHash
p2wsh, witnessScript, err := lc.genHtlcScript(isIncoming,
ourCommit, timeout, rHash, localKey, remoteKey, revocationKey)
if err != nil {
return err
}
// Add the new HTLC outputs to the respective commitment transactions.
amountPending := int64(paymentDesc.Amount)
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.
commitTx := lc.channelState.CommitTx
theirSig := append(lc.channelState.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.FundingWitnessScript, ourKey,
ourSig, theirKey, theirSig)
return &commitTx, nil
}
// 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
// SelfOutPoint is the full outpoint that points to our non-delayed
// pay-to-self output within the commitment transaction of the remote
// party.
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
// HtlcResolutions is a slice of HTLC resolutions which allows the
// local node to sweep any outgoing HTLC"s after the timeout period has
// passed.
HtlcResolutions []OutgoingHtlcResolution
}
// OutgoingHtlcResolution houses the information necessary to sweep any outging
// HTLC's after their contract has expired. This struct will be needed in one
// of tow 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.
SignedTimeoutTx *wire.MsgTx
// 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
}
// newHtlcResolution 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 newHtlcResolution(signer Signer, localChanCfg *channeldb.ChannelConfig,
commitHash chainhash.Hash, htlc *channeldb.HTLC, commitTweak []byte,
delayKey, localKey, remoteKey *btcec.PublicKey, revokeKey *btcec.PublicKey,
feePewKw, dustLimit btcutil.Amount) (*OutgoingHtlcResolution, error) {
op := wire.OutPoint{
Hash: commitHash,
Index: uint32(htlc.OutputIndex),
}
// 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, uint32(localChanCfg.CsvDelay),
revokeKey, localKey,
)
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(localKey, remoteKey,
revokeKey, htlc.RHash[:])
if err != nil {
return nil, err
}
timeoutSignDesc := SignDescriptor{
PubKey: localChanCfg.PaymentBasePoint,
SingleTweak: commitTweak,
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(revokeKey,
delayKey, uint32(localChanCfg.CsvDelay))
if err != nil {
return nil, err
}
return &OutgoingHtlcResolution{
Expiry: htlc.RefundTimeout,
SignedTimeoutTx: timeoutTx,
SweepSignDesc: SignDescriptor{
PubKey: localChanCfg.DelayBasePoint,
SingleTweak: commitTweak,
WitnessScript: htlcSweepScript,
Output: &wire.TxOut{
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,
commitPoint, revokeKey *btcec.PublicKey,
localChanCfg, remoteChanCfg *channeldb.ChannelConfig,
commitHash chainhash.Hash) ([]OutgoingHtlcResolution, *btcec.PublicKey, error) {
// As uusal, we start by re-generating the key-ring required to
// reconstruct the pkScripts used, and sign any transactions or inputs
// required to sweep all funds.
commitTweak := SingleTweakBytes(commitPoint,
localChanCfg.PaymentBasePoint)
localKey := TweakPubKey(localChanCfg.PaymentBasePoint, commitPoint)
delayKey := TweakPubKey(localChanCfg.DelayBasePoint, commitPoint)
remoteKey := TweakPubKey(remoteChanCfg.PaymentBasePoint, commitPoint)
dustLimit := remoteChanCfg.DustLimit
if ourCommit {
dustLimit = localChanCfg.DustLimit
}
htlcResolutions := make([]OutgoingHtlcResolution, len(htlcs))
for i, htlc := range htlcs {
// Skip any incoming HTLC's, as unless we have the pre-image to
// spend them, they'll eventually be swept by the party that
// offered the HTLC after the timeout.
if htlc.Incoming {
continue
}
// We'll also 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
}
ohr, err := newHtlcResolution(signer, localChanCfg, commitHash,
htlc, commitTweak, delayKey, localKey, remoteKey,
revokeKey, feePerKw, dustLimit)
if err != nil {
return nil, nil, err
}
// TODO(roasbeef): needs to point to proper amount including
htlcResolutions[i] = *ohr
}
return htlcResolutions, localKey, 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
// SelfOutpoint is the output created by the above close tx which is
// spendable by us after a relative time delay.
SelfOutpoint wire.OutPoint
// CloseTx is the transaction which closed the channel on-chain. If we
// initiate the force close, then this'll be our latest commitment
// state. Otherwise, this'll be the state that the remote peer
// broadcasted on-chain.
CloseTx *wire.MsgTx
// SelfOutputSignDesc is a fully populated sign descriptor capable of
// generating a valid signature to sweep the self output.
//
// NOTE: If the commitment delivery output of the force closing party
// is below the dust limit, then this will be nil.
SelfOutputSignDesc *SignDescriptor
// SelfOutputMaturity is the relative maturity period before the above
// output can be claimed.
SelfOutputMaturity uint32
// HtlcResolutions is a slice of HTLC resolutions which allows the
// local node to sweep any outgoing HTLC"s after the timeout period has
// passed.
HtlcResolutions []OutgoingHtlcResolution
}
// 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[:])
revokeKey := DeriveRevocationPubkey(
lc.remoteChanCfg.RevocationBasePoint,
commitPoint,
)
delayKey := TweakPubKey(lc.localChanCfg.DelayBasePoint, commitPoint)
selfScript, err := commitScriptToSelf(csvTimeout, delayKey, revokeKey)
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
selfSignDesc *SignDescriptor
)
for i, txOut := range commitTx.TxOut {
if !bytes.Equal(payToUsScriptHash, txOut.PkScript) {
continue
}
delayIndex = uint32(i)
delayScript = txOut.PkScript
break
}
// 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.
if len(delayScript) != 0 {
singleTweak := SingleTweakBytes(commitPoint,
lc.localChanCfg.DelayBasePoint)
selfSignDesc = &SignDescriptor{
PubKey: lc.localChanCfg.DelayBasePoint,
SingleTweak: singleTweak,
WitnessScript: selfScript,
Output: &wire.TxOut{
PkScript: delayScript,
Value: int64(lc.channelState.LocalBalance.ToSatoshis()),
},
HashType: txscript.SigHashAll,
}
}
// 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(
lc.channelState.FeePerKw, true, lc.signer, lc.channelState.Htlcs,
commitPoint, revokeKey, lc.localChanCfg, lc.remoteChanCfg, txHash)
if err != nil {
return nil, err
}
// Finally, close the channel force close signal which notifies any
// subscribers that the channel has now been forcibly closed. This
// allows callers to begin to carry out any post channel closure
// activities.
close(lc.ForceCloseSignal)
return &ForceCloseSummary{
ChanPoint: lc.channelState.FundingOutpoint,
SelfOutpoint: wire.OutPoint{
Hash: commitTx.TxHash(),
Index: delayIndex,
},
CloseTx: commitTx,
SelfOutputSignDesc: selfSignDesc,
SelfOutputMaturity: csvTimeout,
HtlcResolutions: htlcResolutions,
}, 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 uint64,
localDeliveryScript, remoteDeliveryScript []byte) ([]byte, uint64, 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, 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.
ourBalance := lc.channelState.LocalBalance.ToSatoshis()
theirBalance := lc.channelState.RemoteBalance.ToSatoshis()
if lc.channelState.IsInitiator {
ourBalance = ourBalance - btcutil.Amount(proposedFee)
} else {
theirBalance = theirBalance - btcutil.Amount(proposedFee)
}
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, 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, 0, err
}
// As everything checks out, indicate in the channel status that a
// channel closure has been initiated.
lc.status = channelClosing
return sig, proposedFee, 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.
//
// 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,
localDeliveryScript, remoteDeliveryScript []byte,
proposedFee uint64) (*wire.MsgTx, 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, 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.
ourBalance := lc.channelState.LocalBalance.ToSatoshis()
theirBalance := lc.channelState.RemoteBalance.ToSatoshis()
if lc.channelState.IsInitiator {
ourBalance = ourBalance - btcutil.Amount(proposedFee)
} else {
theirBalance = theirBalance - btcutil.Amount(proposedFee)
}
// 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, 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.
vm, err := txscript.NewEngine(lc.fundingP2WSH, closeTx, 0,
txscript.StandardVerifyFlags, nil, hashCache,
int64(lc.channelState.Capacity))
if err != nil {
return nil, err
}
if err := vm.Execute(); err != nil {
return nil, 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, 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)
}
// 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()
}
// 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")
}
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(halseth): should fail if fee update is unreasonable,
// as specified in BOLT#2.
lc.pendingFeeUpdate = &feePerKw
return 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, delayKey, paymentKey *btcec.PublicKey,
revokeKey *btcec.PublicKey, 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, delayKey,
revokeKey)
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(paymentKey)
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
}