itest+lncfg: test the quiescence timeout behaivor

itest/lnd_quiescence_test.go

@@ -14,9 +14,16 @@ import (
 // channel. We initiate quiescence via RPC and if it succeeds we verify that
 // the expected initiator is the resulting initiator.
 func testQuiescence(ht *lntest.HarnessTest) {
-	cfg := node.CfgAnchor
+	aCfg := node.CfgAnchor
+	bCfg := node.CfgAnchor
+
+	// Use different minbackoff values for Alice and Bob to avoid connection
+	// race. See https://github.com/lightningnetwork/lnd/issues/6788.
+	aCfg = append(aCfg, "--minbackoff=1s")
+	bCfg = append(bCfg, "--minbackoff=60s")
+
 	chanPoints, nodes := ht.CreateSimpleNetwork(
-		[][]string{cfg, cfg}, lntest.OpenChannelParams{
+		[][]string{aCfg, bCfg}, lntest.OpenChannelParams{
 			Amt: btcutil.Amount(1000000),
 		})
 
@@ -60,4 +67,48 @@ func testQuiescence(ht *lntest.HarnessTest) {
 		alice, req,
 		lnrpc.PaymentFailureReason_FAILURE_REASON_INSUFFICIENT_BALANCE,
 	)
+
+	// Bob now subscribes the peer events, which will be used to assert the
+	// connection updates.
+	client := bob.RPC.SubscribePeerEvents(&lnrpc.PeerEventSubscription{})
+
+	// Alice now restarts with an extremely short quiescence timeout.
+	ht.RestartNodeWithExtraArgs(
+		alice, []string{"--htlcswitch.quiescencetimeout=1ms"},
+	)
+
+	// Bob should be reconnected to Alice.
+	ht.AssertPeerReconnected(client)
+
+	// Once restarted, the channel is no longer quiescent so Alice can
+	// finish the payment for invoice2.
+	ht.SendPaymentAssertSettled(alice, req)
+
+	// Bob adds another invoice.
+	invoice3 := bob.RPC.AddInvoice(invReq)
+
+	// Alice now requires the channel to be quiescent again. Since we are
+	// using a short timeout (1ms) for the quiescence, Alice should
+	// disconnect from Bob immediately.
+	res = alice.RPC.Quiesce(&devrpc.QuiescenceRequest{
+		ChanId: chanPoint,
+	})
+	require.True(ht, res.Initiator)
+
+	// The above quiescence timeout will cause Alice to disconnect with Bob.
+	// However, since the connection has an open channel, Alice and Bob will
+	// be reconnected shortly.
+	ht.AssertPeerReconnected(client)
+
+	// Make sure Alice has finished the connection too before attempting the
+	// payment below.
+	ht.AssertConnected(alice, bob)
+
+	// Assert that Alice can pay invoice3. This implicitly checks that the
+	// above quiescence is terminated.
+	req = &routerrpc.SendPaymentRequest{
+		PaymentRequest: invoice3.PaymentRequest,
+		FeeLimitMsat:   noFeeLimitMsat,
+	}
+	ht.SendPaymentAssertSettled(alice, req)
 }

lncfg/htlcswitch.go

@@ -40,7 +40,9 @@ func (h *Htlcswitch) Validate() error {
 			MaxMailboxDeliveryTimeout)
 	}
 
-	if h.QuiescenceTimeout < minQuiescenceTimeout {
+	// Skip the validation for integration tests so we can use a smaller
+	// timeout value to check the timeout behavior.
+	if !IsDevBuild() && h.QuiescenceTimeout < minQuiescenceTimeout {
 		return fmt.Errorf("quiescencetimeout: %v below minimal: %v",
 			h.QuiescenceTimeout, minQuiescenceTimeout)
 	}