breacharbiter: introduce new sub-system to watch for breaches

This commit introduces a new sub-system into the daemon whose job it is
to vigilantly watch for any potential channel breaches throughout the
up-time of the daemon. The logic which was moved from the utxoNursery
in a prior commit now resides within the breachArbiter.

Upon start-up the breachArbiter will query the database for all active
channels, launching a goroutine for each channel in order to be able to
take action if a channel breach is detected. The breachArbiter is also
responsible for notifying the htlcSwitch about channel breaches in
order to black-list the breached linked during any multi-hop forwarding
decisions.

lnwallet/channel.go

@@ -467,7 +467,7 @@ func NewLightningChannel(signer Signer, bio BlockChainIO,
 		FundingWitnessScript:  state.FundingWitnessScript,
 		ForceCloseSignal:      make(chan struct{}),
 		UnilateralCloseSignal: make(chan struct{}),
-		ContractBreach:        make(chan *BreachRetribution),
+		ContractBreach:        make(chan *BreachRetribution, 1),
 	}
 
 	// Initialize both of our chains the current un-revoked commitment for
@@ -692,6 +692,7 @@ func (lc *LightningChannel) closeObserver(channelCloseNtfn *chainntnfs.SpendEven
 	lc.Lock()
 	defer lc.Unlock()
 
+	// TODO(roasbeef): logs duplicated due to breachArbiter...
 	walletLog.Warnf("Unprompted commitment broadcast for ChannelPoint(%v) "+
 		"detected!", lc.channelState.ChanID)
 
@@ -704,7 +705,11 @@ func (lc *LightningChannel) closeObserver(channelCloseNtfn *chainntnfs.SpendEven
 	obsfucator := lc.channelState.StateHintObsfucator
 	broadcastStateNum := uint64(GetStateNumHint(commitTxBroadcast, obsfucator))
 
-	currentStateNum := lc.remoteCommitChain.tail().height
+	currentStateNum, err := lc.channelState.CommitmentHeight()
+	if err != nil {
+		walletLog.Errorf("unable to obtain commitment height: %v", err)
+		return
+	}
 
 	switch {
 	// If state number spending transaction matches the current latest
@@ -713,7 +718,7 @@ func (lc *LightningChannel) closeObserver(channelCloseNtfn *chainntnfs.SpendEven
 	// necessary.
 	case broadcastStateNum == currentStateNum:
 		walletLog.Infof("Unilateral close of ChannelPoint(%v) "+
-			"detected: %v", lc.channelState.ChanID)
+			"detected", lc.channelState.ChanID)
 		close(lc.UnilateralCloseSignal)
 
 	// If the state number broadcast is lower than the remote node's
@@ -736,7 +741,7 @@ func (lc *LightningChannel) closeObserver(channelCloseNtfn *chainntnfs.SpendEven
 			return
 		}
 
-		walletLog.Infof("Punishment breach retribution created: %#v",
+		walletLog.Debugf("Punishment breach retribution created: %#v",
 			retribution)
 
 		// Finally, send the retribution struct over the contract beach

lnwallet/size.go

@@ -5,7 +5,7 @@ import (
 )
 
 const (
-	WitnessFactor = blockchain.WitnessScaleFactor
+	WitnessFactor              = blockchain.WitnessScaleFactor
 	MaxTransactionWeightPolicy = blockchain.MaxBlockCost / 10
 
 	// The weight(cost), which is different from the !size! (see BIP-141),
@@ -21,7 +21,7 @@ const (
 	//	- WitnessScriptSHA256: 32 bytes
 	P2WSHSize = 1 + 1 + 32
 
-	// P2PKH: 22 bytes
+	// P2WPKH: 22 bytes
 	//	- OP_0: 1 byte
 	//	- OP_DATA: 1 byte (PublicKeyHASH160 length)
 	//	- PublicKeyHASH160: 20 bytes
@@ -117,7 +117,6 @@ const (
 	MaxHTLCNumber = 1253
 )
 
-
 // estimateCommitTxCost estimate commitment transaction cost depending on the
 // precalculated cost of base transaction, witness data, which is needed for
 // paying for funding tx, and htlc cost multiplied by their count.
@@ -133,4 +132,4 @@ func estimateCommitTxCost(count int, prediction bool) int64 {
 	witnessCost := int64(WitnessCommitmentTxCost)
 
 	return htlcCost + baseCost + witnessCost
-}
+}