cnct: define separate broadcast delta for outgoing htlcs

This commits exposes the various parameters around going to chain and
accepting htlcs in a clear way.

In addition to this, it reverts those parameters to what they were
before the merge of commit d107627145.

contractcourt/chain_arbitrator.go

@@ -53,13 +53,20 @@ type ChainArbitratorConfig struct {
 	// ChainHash is the chain that this arbitrator is to operate within.
 	ChainHash chainhash.Hash
 
-	// BroadcastDelta is the delta that we'll use to decide when to
-	// broadcast our commitment transaction.  This value should be set
-	// based on our current fee estimation of the commitment transaction.
-	// We use this to determine when we should broadcast instead of the
-	// just the HTLC timeout, as we want to ensure that the commitment
-	// transaction is already confirmed, by the time the HTLC expires.
-	BroadcastDelta uint32
+	// IncomingBroadcastDelta is the delta that we'll use to decide when to
+	// broadcast our commitment transaction if we have incoming htlcs. This
+	// value should be set based on our current fee estimation of the
+	// commitment transaction. We use this to determine when we should
+	// broadcast instead of the just the HTLC timeout, as we want to ensure
+	// that the commitment transaction is already confirmed, by the time the
+	// HTLC expires. Otherwise we may end up not settling the htlc on-chain
+	// because the other party managed to time it out.
+	IncomingBroadcastDelta uint32
+
+	// OutgoingBroadcastDelta is the delta that we'll use to decide when to
+	// broadcast our commitment transaction if there are active outgoing
+	// htlcs. This value can be lower than the incoming broadcast delta.
+	OutgoingBroadcastDelta uint32
 
 	// NewSweepAddr is a function that returns a new address under control
 	// by the wallet. We'll use this to sweep any no-delay outputs as a

contractcourt/channel_arbitrator.go

@@ -1106,7 +1106,8 @@ func (c *ChannelArbitrator) checkChainActions(height uint32,
 		// We'll need to go on-chain for an outgoing HTLC if it was
 		// never resolved downstream, and it's "close" to timing out.
 		haveChainActions = haveChainActions || c.shouldGoOnChain(
-			htlc.RefundTimeout, c.cfg.BroadcastDelta, height,
+			htlc.RefundTimeout, c.cfg.OutgoingBroadcastDelta,
+			height,
 		)
 	}
 	for _, htlc := range c.activeHTLCs.incomingHTLCs {
@@ -1124,7 +1125,8 @@ func (c *ChannelArbitrator) checkChainActions(height uint32,
 			continue
 		}
 		haveChainActions = haveChainActions || c.shouldGoOnChain(
-			htlc.RefundTimeout, c.cfg.BroadcastDelta, height,
+			htlc.RefundTimeout, c.cfg.IncomingBroadcastDelta,
+			height,
 		)
 	}
 
@@ -1162,7 +1164,8 @@ func (c *ChannelArbitrator) checkChainActions(height uint32,
 		// until the HTLC times out to see if we can also redeem it
 		// on-chain.
 		case !c.shouldGoOnChain(
-			htlc.RefundTimeout, c.cfg.BroadcastDelta, height,
+			htlc.RefundTimeout, c.cfg.OutgoingBroadcastDelta,
+			height,
 		):
 			// TODO(roasbeef): also need to be able to query
 			// circuit map to see if HTLC hasn't been fully

contractcourt/channel_arbitrator_test.go

@@ -165,7 +165,8 @@ func createTestChannelArbitrator(log ArbitratorLog) (*ChannelArbitrator,
 		DeliverResolutionMsg: func(...ResolutionMsg) error {
 			return nil
 		},
-		BroadcastDelta: 5,
+		OutgoingBroadcastDelta: 5,
+		IncomingBroadcastDelta: 5,
 		Notifier: &mockNotifier{
 			epochChan: make(chan *chainntnfs.BlockEpoch),
 			spendChan: make(chan *chainntnfs.SpendDetail),