rpcserver+fundingmanager: thread remote_max_htlcs to channel opening

lntest/harness.go

@@ -855,6 +855,11 @@ type OpenChannelParams struct {
 	// MinHtlc is the htlc_minimum_msat value set when opening the channel.
 	MinHtlc lnwire.MilliSatoshi
 
+	// RemoteMaxHtlcs is the remote_max_htlcs value set when opening the
+	// channel, restricting the number of concurrent HTLCs the remote party
+	// can add to a commitment.
+	RemoteMaxHtlcs uint16
+
 	// FundingShim is an optional funding shim that the caller can specify
 	// in order to modify the channel funding workflow.
 	FundingShim *lnrpc.FundingShim
@@ -893,6 +898,7 @@ func (n *NetworkHarness) OpenChannel(ctx context.Context,
 		MinConfs:           minConfs,
 		SpendUnconfirmed:   p.SpendUnconfirmed,
 		MinHtlcMsat:        int64(p.MinHtlc),
+		RemoteMaxHtlcs:     uint32(p.RemoteMaxHtlcs),
 		FundingShim:        p.FundingShim,
 	}
 

lntest/itest/lnd_test.go

@@ -4848,9 +4848,7 @@ func testListChannels(net *lntest.NetworkHarness, t *harnessTest) {
 	const bobRemoteMaxHtlcs = 100
 
 	// Create two fresh nodes and open a channel between them.
-	alice, err := net.NewNode("Alice", []string{
+	alice, err := net.NewNode("Alice", nil)
-		fmt.Sprintf("--default-remote-max-htlcs=%v", aliceRemoteMaxHtlcs),
-	})
 	if err != nil {
 		t.Fatalf("unable to create new node: %v", err)
 	}
@@ -4889,6 +4887,7 @@ func testListChannels(net *lntest.NetworkHarness, t *harnessTest) {
 		lntest.OpenChannelParams{
 			Amt:            chanAmt,
 			MinHtlc:        customizedMinHtlc,
+			RemoteMaxHtlcs: aliceRemoteMaxHtlcs,
 		},
 	)
 

rpcserver.go

@@ -1742,6 +1742,7 @@ func (r *rpcServer) parseOpenChannelReq(in *lnrpc.OpenChannelRequest,
 	minHtlcIn := lnwire.MilliSatoshi(in.MinHtlcMsat)
 	remoteCsvDelay := uint16(in.RemoteCsvDelay)
 	maxValue := lnwire.MilliSatoshi(in.RemoteMaxValueInFlightMsat)
+	maxHtlcs := uint16(in.RemoteMaxHtlcs)
 
 	globalFeatureSet := r.server.featureMgr.Get(feature.SetNodeAnn)
 
@@ -1774,6 +1775,13 @@ func (r *rpcServer) parseOpenChannelReq(in *lnrpc.OpenChannelRequest,
 			"channel size is: %v SAT", int64(minChanFundingSize))
 	}
 
+	// Prevent users from submitting a max-htlc value that would exceed the
+	// protocol maximum.
+	if maxHtlcs > input.MaxHTLCNumber/2 {
+		return nil, fmt.Errorf("remote-max-htlcs (%v) cannot be "+
+			"greater than %v", maxHtlcs, input.MaxHTLCNumber/2)
+	}
+
 	// Then, we'll extract the minimum number of confirmations that each
 	// output we use to fund the channel's funding transaction should
 	// satisfy.
@@ -1862,6 +1870,7 @@ func (r *rpcServer) parseOpenChannelReq(in *lnrpc.OpenChannelRequest,
 		minConfs:         minConfs,
 		shutdownScript:   script,
 		maxValueInFlight: maxValue,
+		maxHtlcs:         maxHtlcs,
 	}, nil
 }