cnct: pre-confirmation anchor sweep

Start anchor sweep attempts immediately after the commitment transaction
has been published. This makes the anchor known to the sweeper and
allows the user to bump the fee on it to get their commitment
transaction confirmed in case the fee committed too is insufficient for
timely confirmation.

lntest/itest/lnd_test.go

@@ -8604,13 +8604,19 @@ func assertNumPendingChannels(t *harnessTest, node *lntest.HarnessNode,
 // on chain as he has no funds in the channel.
 func assertDLPExecuted(net *lntest.NetworkHarness, t *harnessTest,
 	carol *lntest.HarnessNode, carolStartingBalance int64,
-	dave *lntest.HarnessNode, daveStartingBalance int64) {
+	dave *lntest.HarnessNode, daveStartingBalance int64,
+	anchors bool) {
 
 	// Upon reconnection, the nodes should detect that Dave is out of sync.
 	// Carol should force close the channel using her latest commitment.
+	expectedTxes := 1
+	if anchors {
+		expectedTxes = 2
+	}
+
 	ctxb := context.Background()
-	forceClose, err := waitForTxInMempool(
-		net.Miner.Node, minerMempoolTimeout,
+	_, err := waitForNTxsInMempool(
+		net.Miner.Node, expectedTxes, minerMempoolTimeout,
 	)
 	if err != nil {
 		t.Fatalf("unable to find Carol's force close tx in mempool: %v",
@@ -8633,12 +8639,13 @@ func assertDLPExecuted(net *lntest.NetworkHarness, t *harnessTest,
 	}
 
 	// Generate a single block, which should confirm the closing tx.
-	block := mineBlocks(t, net, 1, 1)[0]
-	assertTxInBlock(t, block, forceClose)
+	block := mineBlocks(t, net, 1, expectedTxes)[0]
 
 	// Dave should sweep his funds immediately, as they are not timelocked.
-	daveSweep, err := waitForTxInMempool(
-		net.Miner.Node, minerMempoolTimeout,
+	// We also expect Dave to sweep his anchor, if present.
+
+	_, err = waitForNTxsInMempool(
+		net.Miner.Node, expectedTxes, minerMempoolTimeout,
 	)
 	if err != nil {
 		t.Fatalf("unable to find Dave's sweep tx in mempool: %v", err)
@@ -8653,8 +8660,7 @@ func assertDLPExecuted(net *lntest.NetworkHarness, t *harnessTest,
 	assertNumPendingChannels(t, carol, 0, 1)
 
 	// Mine the sweep tx.
-	block = mineBlocks(t, net, 1, 1)[0]
-	assertTxInBlock(t, block, daveSweep)
+	block = mineBlocks(t, net, 1, expectedTxes)[0]
 
 	// Now Dave should consider the channel fully closed.
 	assertNumPendingChannels(t, dave, 0, 0)
@@ -8925,6 +8931,7 @@ func testDataLossProtection(net *lntest.NetworkHarness, t *harnessTest) {
 	// on chain, and both of them properly carry out the DLP protocol.
 	assertDLPExecuted(
 		net, t, carol, carolStartingBalance, dave, daveStartingBalance,
+		false,
 	)
 
 	// As a second part of this test, we will test the scenario where a
@@ -14048,9 +14055,14 @@ func testChanRestoreScenario(t *harnessTest, net *lntest.NetworkHarness,
 	}
 	defer shutdownAndAssert(net, t, carol)
 
-	// Now that our new node is created, we'll give him some coins it can
-	// use to open channels with Carol.
+	// Now that our new nodes are created, we'll give them some coins for
+	// channel opening and anchor sweeping.
 	ctxt, _ := context.WithTimeout(ctxb, defaultTimeout)
+	err = net.SendCoins(ctxt, btcutil.SatoshiPerBitcoin, carol)
+	if err != nil {
+		t.Fatalf("unable to send coins to dave: %v", err)
+	}
+	ctxt, _ = context.WithTimeout(ctxb, defaultTimeout)
 	err = net.SendCoins(ctxt, btcutil.SatoshiPerBitcoin, dave)
 	if err != nil {
 		t.Fatalf("unable to send coins to dave: %v", err)
@@ -14216,6 +14228,7 @@ func testChanRestoreScenario(t *harnessTest, net *lntest.NetworkHarness,
 	// end of the protocol.
 	assertDLPExecuted(
 		net, t, carol, carolStartingBalance, dave, daveStartingBalance,
+		testCase.anchorCommit,
 	)
 }