lnwallet: add CommitFee field to OpenChannel

In order to cleanly handle shutdowns and restarts during state machine operation, the fee for the current
commitment transaction must be persisted. This allows the fee to be
reapplied when the current state is reloaded.

lnwallet/channel.go

@@ -232,6 +232,11 @@ type commitment struct {
 	ourBalance   btcutil.Amount
 	theirBalance btcutil.Amount
 
+	// 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
+
 	// htlcs is the set of HTLCs which remain unsettled within this
 	// commitment.
 	outgoingHTLCs []PaymentDescriptor
@@ -251,6 +256,7 @@ func (c *commitment) toChannelDelta(ourCommit bool) (*channeldb.ChannelDelta, er
 		LocalBalance:  c.ourBalance,
 		RemoteBalance: c.theirBalance,
 		UpdateNum:     c.height,
+		CommitFee:     c.fee,
 		Htlcs:         make([]*channeldb.HTLC, 0, numHtlcs),
 	}
 
@@ -1181,6 +1187,8 @@ func (lc *LightningChannel) restoreStateLogs() error {
 	lc.localCommitChain.tail().theirMessageIndex = theirCounter
 	lc.remoteCommitChain.tail().ourMessageIndex = ourCounter
 	lc.remoteCommitChain.tail().theirMessageIndex = theirCounter
+	lc.localCommitChain.tail().fee = lc.channelState.CommitFee
+	lc.remoteCommitChain.tail().fee = lc.channelState.CommitFee
 
 	return nil
 }
@@ -1245,12 +1253,13 @@ func (lc *LightningChannel) fetchCommitmentView(remoteChain bool,
 
 	// TODO(roasbeef): don't assume view is always fetched from tip?
 	var ourBalance, theirBalance btcutil.Amount
-	if commitChain.tip() == nil {
-		ourBalance = lc.channelState.OurBalance
-		theirBalance = lc.channelState.TheirBalance
-	} else {
-		ourBalance = commitChain.tip().ourBalance
-		theirBalance = commitChain.tip().theirBalance
+	ourBalance = commitChain.tip().ourBalance
+	theirBalance = commitChain.tip().theirBalance
+
+	if lc.channelState.IsInitiator {
+		ourBalance = ourBalance + commitChain.tip().fee
+	} else if !lc.channelState.IsInitiator {
+		theirBalance = theirBalance + commitChain.tip().fee
 	}
 
 	nextHeight := commitChain.tip().height + 1

lnwallet/reservation.go

@@ -215,6 +215,7 @@ func NewChannelReservation(capacity, fundingAmt btcutil.Amount, minFeeRate btcut
 			TheirBalance: theirBalance,
 			MinFeePerKb:  minFeeRate,
 			Db:           wallet.ChannelDB,
+			CommitFee:    commitFee,
 		},
 		numConfsToOpen: numConfs,
 		pushSat:        pushSat,