akovalenko/lnd.xprv
1
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

lnwallet/channel: break up availableBalance

Browse Source
This commit is contained in:
Johan T. Halseth 2020-02-19 12:27:41 +01:00
parent 0d9a1b8656
commit 58dec10680
No known key found for this signature in database
GPG Key ID: 15BAADA29DA20D26
1 changed files with 46 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

58
lnwallet/channel.go
View File

@ -5997,11 +5997,14 @@ func (lc *LightningChannel) CompleteCooperativeClose(localSig, remoteSig []byte,
return closeTx, ourBalance, nil
}
// AvailableBalance returns the current available balance within the channel.
// By available balance, we mean that if at this very instance s new commitment
// were to be created which evals all the log entries, what would our available
// balance me. This method is useful when deciding if a given channel can
// accept an HTLC in the multi-hop forwarding scenario.
// AvailableBalance returns the current balance available for sending within
// the channel. By available balance, we mean that if at this very instance a
// new commitment were to be created which evals all the log entries, what
// would our available balance for adding an additional HTLC be. It takes into
// account the fee that must be paid for adding this HTLC (if we're the
// initiator), and that we cannot spend from the channel reserve. This method
// is useful when deciding if a given channel can accept an HTLC in the
// multi-hop forwarding scenario.
func (lc *LightningChannel) AvailableBalance() lnwire.MilliSatoshi {
lc.RLock()
defer lc.RUnlock()
@ -6021,19 +6024,50 @@ func (lc *LightningChannel) availableBalance() (lnwire.MilliSatoshi, int64) {
htlcView := lc.fetchHTLCView(remoteACKedIndex,
lc.localUpdateLog.logIndex)
// Then compute our current balance for that view.
ourBalance, _, commitWeight, filteredView, err :=
lc.computeView(htlcView, false, false)
// Calculate our available balance from our local commitment.
//
// NOTE: This is not always accurate, since the remote node can always
// add updates concurrently, causing our balance to go down if we're
// the initiator, but this is a problem on the protocol level.
ourLocalCommitBalance, commitWeight := lc.availableCommitmentBalance(
htlcView,
)
return ourLocalCommitBalance, commitWeight
}
// availableCommitmentBalance attempts to calculate the balance we have
// available for HTLCs on the local/remote commitment given the htlcView. To
// account for sending HTLCs of different sizes, it will report the balance
// available for sending non-dust HTLCs, which will be manifested on the
// commitment, increasing the commitment fee we must pay as an initiator,
// eating into our balance. It will make sure we won't violate the channel
// reserve constraints for this amount.
func (lc *LightningChannel) availableCommitmentBalance(view *htlcView) (
lnwire.MilliSatoshi, int64) {
// Compute the current balances for this commitment. This will take
// into account HTLCs to determine the commit weight, which the
// initiator must pay the fee for.
ourBalance, _, commitWeight, filteredView, err := lc.computeView(
view, false, false,
)
if err != nil {
lc.log.Errorf("Unable to fetch available balance: %v", err)
return 0, 0
}
// If we are the channel initiator, we must remember to subtract the
// commitment fee from our available balance.
commitFee := filteredView.feePerKw.FeeForWeight(commitWeight)
// Given the commitment weight, find the commitment fee in case of no
// added HTLC output.
feePerKw := filteredView.feePerKw
baseCommitFee := lnwire.NewMSatFromSatoshis(
feePerKw.FeeForWeight(commitWeight),
)
// If we are the channel initiator, we must to subtract the commitment
// fee from our available balance.
if lc.channelState.IsInitiator {
ourBalance -= lnwire.NewMSatFromSatoshis(commitFee)
ourBalance -= baseCommitFee
}
return ourBalance, commitWeight