test: add comprehensive integration tests for on-chain HTLC handling

In this commit, we add 6 new integration tests to test the various
actions that may need to be performed when either side goes on-chain to
fully resolve HTLC’s. Many of the tests are mirrors of each other as
they test sweeping/resolving HTLC’s from both commitment transactions.

config.go

@@ -42,6 +42,8 @@ const (
 	defaultNoEncryptWallet    = false
 	defaultTrickleDelay       = 30 * 1000
 
+	defaultBroadcastDelta = 10
+
 	// minTimeLockDelta is the minimum timelock we require for incoming
 	// HTLCs on our channels.
 	minTimeLockDelta = 4

contractcourt/contract_resolvers.go

@@ -1345,7 +1345,7 @@ func (c *commitSweepResolver) Resolve() (ContractResolver, error) {
 			return nil, fmt.Errorf("quitting")
 		}
 
-		log.Infof("ChannelPoint(%v) is fully closed, at height: %v",
+		log.Infof("ChannelPoint(%v) commit tx is fully resolved, at height: %v",
 			c.chanPoint, confInfo.BlockHeight)
 
 	case <-c.Quit:

htlcswitch/link.go

@@ -941,9 +941,13 @@ func (l *channelLink) handleUpstreamMsg(msg lnwire.Message) {
 		// add it to to our preimage cache. By doing this, we ensure
 		// any contested contracts watched by any on-chain arbitrators
 		// can now sweep this HTLC on-chain.
-		if err := l.cfg.PreimageCache.AddPreimage(pre[:]); err != nil {
-			log.Errorf("unable to add preimage=%x to cache", pre[:])
-		}
+		go func() {
+			err := l.cfg.PreimageCache.AddPreimage(pre[:])
+			if err != nil {
+				log.Errorf("unable to add preimage=%x to "+
+					"cache", pre[:])
+			}
+		}()
 
 	case *lnwire.UpdateFailMalformedHTLC:
 		// Convert the failure type encoded within the HTLC fail

peer_test.go

@@ -238,7 +238,8 @@ func TestPeerChannelClosureFeeNegotiationsResponder(t *testing.T) {
 	broadcastTxChan := make(chan *wire.MsgTx)
 
 	responder, responderChan, initiatorChan, cleanUp, err := createTestPeer(
-		notifier, broadcastTxChan)
+		notifier, broadcastTxChan,
+	)
 	if err != nil {
 		t.Fatalf("unable to create test channels: %v", err)
 	}